WO2000062998A2

WO2000062998A2 - Apparatus and method for making barrier-coated polyester

Info

Publication number: WO2000062998A2
Application number: PCT/US2000/009575
Authority: WO
Inventors: Gerald A. Hutchinson; Robert A. Lee
Original assignee: Advanced Plastics Technologies, Ltd.
Priority date: 1999-04-21
Filing date: 2000-04-10
Publication date: 2000-10-26
Also published as: CN1367731A; US8017063B2; EP1185407B1; WO2000062998A3; HK1049467B; JP2002542068A; US20080029929A1; HK1049467A1; RU2312798C2; AU2004231238A1; CN1174847C; EP1671776A1; EP1185407A2; US20040247735A1; CN1613643A; SA00210215B1; DE60023883D1; AU4226100A; RU2004137265A; RU2251484C2

Abstract

This invention relates to methods and apparatus for making articles made of polyester, preferably polyethylene terephthalate (PET), having coated directly to at least one of the surfaces thereof one or more layers of thermoplastic material with good gas-barrier characteristics. In one preferred method and apparatus, preforms are injection molded, barrier-coated immediately thereafter, and remain on a mold portion for a time to speed cooling of the completed preform. Preferably the barrier-coated articles take the form of preforms coated by at least one layer of barrier material and the containers are blow-molded therefrom. Such barrier-coated containers are preferably of the type to hold beverages such as soft drinks, beer or juice. The preferred barrier materials have a lower permeability to oxygen and carbon dioxide than PET as well as key physical properties similar to PET. The materials and methods provide that the barrier layers have good adherence to PET, even during and after the blow molding process to form containers from preforms. Preferred barrier coating materials include poly(hydroxyamino ethers).

Description

APPARATUS AND METHOD FOR MAKING BARRIER-COATED POLYESTER

Background of the Invention This invention relates to an apparatus and method for making barrier-coated polyesters, preferably barrier coated polyethylene terephthalate (PET) and articles made therefrom. Preferably the barrier-coated PET takes the form of preforms having at least one layer of a barrier material and the bottles blow-molded therefrom.

The use of plastic containers as a replacement for glass or metal containers in the packaging of beverages has become increasingly popular. The advantages of plastic packaging include lighter weight, decreased breakage as compared to glass, and potentially lower costs. The most common plastic used in making beverage containers today is PET. Virgin PET has been approved by the FDA for use in contact with foodstuffs. Containers made of PET are transparent, thin- walled, lightweight, and have the ability to maintain their shape by withstanding the force exerted on the wails of the container by pressurized contents, such as carbonated beverages. PET resins are also fairly inexpensive and easy to process.

Despite these advantages and its widespread use, there is a serious downside to the use of PET in thin-walled beverage containers: permeability to gases such as carbon dioxide and oxygen. These problems are of particular importance when the bottle is small. In a small bottle, the ratio of surface area to volume is large which allows for a large surface for the gas contained within to diffuse through the walls of the bottle. The permeability of PET bottles results in soft drinks that go "flat" due to the egress of carbon dioxide, as well as beverages that have their flavor spoiled due to the ingress of oxygen. Because of these problems, PET bottles are not suitable for all uses desired by industry, and for many of the existing uses, the shelf-life of liquids packaged in PET bottles is shorter than desired.

U.S. Patent No. 5,464,106 to Slat, et al, describes bottles formed from the blow molding of preforms having a barrier layer. The barrier materials disclosed are polyethylene naphthalate, saran, ethylene vinyl alcohol copolymers or acrylonitrile copolymers. In Slat's technique, the barrier material and the material to form the inner wall of the preform are coextruded in the shape of a tube. This tube is then cut into lengths corresponding to the length of the preform, and is then placed inside a mold wherein the outer layer of the preform is injected over the tube to form the finished preform. The preform may then be blow-molded to form a bottle. The drawbacks of this method are that most of the barrier materials disclosed do not adhere well to PET, and that the process itself is rather cumbersome.

A family of materials with good barrier characteristics are those disclosed in U.S. Patent No. 4,578,295 to Jabarin. Such barrier materials include copolymers of terephthalic acid and isophthalic acid with ethylene glycol and at least one diol. This type of material is commercially available as B-010 from Mitsui Petrochemical Ind. Ltd. (Japan). These barrier materials are miscible with polyethylene terephthalate and form blends of 80-90% PET and 10-20% of the copolyester from which barrier containers are formed. The containers made from these blends are about 2040% better gas barriers to C02 transmission than PET alone. Although some have claimed that this polyester adheres to PET without delamination, the only preforms or containers disclosed were made with blends of these materials. Another group of materials, the polyamine-polyepoxides, have been proposed for use as a gas-barrier coating. These materials can be used to form a barrier coating on polypropylene or surface-treated PET, as described in U.S. Patent No. 5,489,455 to Nugent, Jr. et al. These materials commonly come as a solvent or aqueous based thermosetting composition and are generally spray coated onto a container and then heat-cured to form the finished barrier coating. Being thermosets, these materials are not conducive to use as preform coatings, because once the coating has been cured, it can no longer be softened by heating and thus cannot be blow molded, as opposed to thermoplastic materials which can be softened at any time after application.

Another type of barrier-coating, that disclosed in U.S. Patent No. 5,472,753 to Farha, relies upon the use of a copolyester to effect adherence between PET and the barrier material. Farha describes two types of laminates, a three-ply and a two-ply. In the three-ply laminate, an amorphous, thermoplastic copolyester is placed between the barrier layer of phenoxy-type thermoplastic and the layer of PET to serve as a tie layer to bind the inner and outer layers. In the two-ply laminate, the phenoxy-type thermoplastic is first blended with the amorphous, thermoplastic copolyester and this blend is then applied to the PET to form a barrier. These laminates are made either by extrusion or by injection molding wherein each layer is allowed to cool before the other layer of material is injected. PCT Application Number PCT/US95/17011, to Collette et al., which was published on July 4, 1996, describes a method of cooling multilayer preforms. The disclosed apparatus comprises a rotary turret having multiple faces, each face carrying an array of cores. The cores are inserted into corresponding mold cavities. Multiple melt streams are brought together and coinjected into each cavity to form a multilayer preform on each core. After the preform is injected, the cores are removed from the cavities and the turret is rotated, presenting a new set of cores to the mold cavities. The just- injected cavities remain on the cores cooling while preforms are formed on other arrays of cores. The drawbacks of the Collette application include that coinjection results in preforms that are inconsistent and have unpredictable layering. Thus, distribution of barrier materials in such a preform would be unpredictable and would result in a preform having unreliable barrier properties.

Since PET containers can be manufactured by injection molding using only a single injection of PET, manufacture is relatively easy and production cycle time is low. Thus, PET containers are inexpensive. Even if known barrier materials can be bonded to PET to create a saleable container with reliable barrier properties, methods and apparatus for making such containers within a competitive cycle time and cost have not been devised. Production cycle time is especially important because a lower cycle time enables a manufacturer to make more efficient use of its capital equipment. Thus, low cycle time enables higher volume and less expensive production of containers. Cost-effective production would be necessary to develop a viable alternative to monolayer PET containers.

Thus, the need exists for an apparatus and method for making barrier-coated PET preforms and containers which are economical, cosmetically appealing, easy to produce, and have good barrier and physical properties remains unfulfilled. Summary of the Invention This invention relates to methods and apparatus for making PET articles having coated upon the surfaces thereof one or more thin layers of thermoplastic material with good gas-barrier characteristics. The articles of the present invention are preferably in the form of preforms and containers. In an aspect of the present invention there is provided a barrier coated preform comprising a polyester layer and a barrier layer comprising barrier material, wherein the polyester layer is thinner in the end cap than in the wall portion and the barrier layer is thicker in the end cap than in the wall portion.

In another aspect of the present invention there is provided a method for making a barrier coated polyester article. A polyester article with at least an inner surface and an outer surface is formed by injecting molten polyester through a first gate into the space defined by a first mold half and a core mold half, where the first mold half and the core mold half are cooled by circulating fluid and the first mold half contacts the outer polyester surface and the core mold half contacts the inner polyester surface. Following this, the molten polyester is allowed to remain in contact with the mold halves until a skin forms on the inner and outer polyester surfaces which surrounds a core of molten polyester. The first mold half is then removed from the polyester article, and the skin on the outer polyester surface is softened by heat transfer from the core of molten polyester, while the inner polyester surface is cooled by continued contact with the core mold half. The polyester article, still on the core mold half is then placed into a second mold half, wherein the second mold half is cooled by circulating fluid. In the coating step, the barrier layer comprising barrier material is placed on the outer polyester surface by injecting molten barrier material through a second gate into the space defined by the second mold half and the outer polyester surface to form the barrier coated polyester article. The second mold half is then removed from the barrier coated article and then the barrier coated article is removed from the core mold half. The barrier materials used in the process preferably comprise a Copolyester Barrier Materials, Phenoxy-type Thermoplastics, Polya ides, polyethylene πaphthalate, polyethylene naphthalate copolymers, polyethylene πaphthalate/polyethyiene terephthalate blends, and combinations thereof.

In a further aspect of the present invention, there is provided a method of making and coating preforms. The method begins by closing a mold comprising a stationary half and a movable half, wherein the stationary mold half comprises at least one preform molding cavity and at least one preform coating cavity and the movable mold half comprises a rotatable plate having mounted thereon a number of mandrels equal to the sum of the number of preform molding cavities and preform coating cavities. The remaining steps comprise: injecting a first material into the space defined by a mandrel and a preform molding cavity to form a preform having an inner surface and an outer surface; opening the mold; rotating the rotatable plate; closing the mold; injecting a second material into the space defined by the outer surface of the preform and the preform coating cavity to form a coated preform; opening the mold; removing the coated preform.

In accordance with a preferred embodiment having features in accordance with the present invention, an apparatus for injection molding multilayer preforms is provided. The apparatus comprises first and second mold cavities in communication with first and second melt sources, respectively. A turntable is provided and is divided into a plurality of stations, with at least one mold core disposed on each station. The turntable is adapted to rotate each station to a first position at which a core on the station interacts with the first mold cavity to form a first preform layer, then to a second position at which the core interacts with the second mold cavity to form a second preform layer. Finally, the turntable is further adapted to rotate the station to at least one cooling position, at which the molded preform remains on the core to cool.

In accordance with another preferred embodiment having features in accordance with the present invention, a mold apparatus for injection molding multilayer preforms is provided. The mold apparatus has a first mold body which is adapted to fit about a mold core to define a first layer cavity therebetween, a first gate area, and is in communication with a first melt source. A second mold body is adapted to fit about a first preform layer disposed on the mold core to define a second layer cavity therebetween, has a second gate area, and is in communication with a second melt source. At least one of the gate areas has ampcoloy metal inserts disposed therein.

In accordance with another preferred embodiment having features in accordance with the present invention, a mold apparatus for injection molding multilayer preforms is provided. The mold apparatus has a first mold body which is adapted to fit about a mold core, defining a first layer cavity therebetween. The first layer cavity has a base end and a main body. The first mold body is in communication with a first melt source and has a first gate area adjacent the base end of the first layer cavity. A thickness of the cavity at the base end is less than the thickness of the main body of the cavity, the mold apparatus also has a second mold body, which is adapted to fit about a first preform layer disposed on the mold core, defining a second layer cavity therebetween. The second mold body is in communication with a second melt source and has a second gate area. In accordance with yet another preferred embodiment having features in accordance with the present invention, a mold for injection molding multilayer preforms is provided. The mold has a mandrel and first and second cavities. The mandrel is hollow and has a wall of substantially uniform thickness. A coolant supply tube is disposed centrally within the hollow mandrel to supply coolant directly to a base end of the mandrel. The first cavity has a gate for injecting molten plastic. A gate area of the cavity has an insert of material having greater heat transfer properties than the majority of the cavity.

In accordance with a further preferred embodiment having features in accordance with the present invention, a method for improving injection mold performance is provided. The method includes forming an opening in a wall of a mold cavity. The opening is sized and adapted so that molten plastic will not substantially enter the opening. A passageway is formed connecting the opening to a source of air pressure. The method further includes providing a valve between the opening and the source of air pressure.

In accordance with another preferred embodiment having features in accordance with the present invention, a method for injection molding and cooling a multilayer preform is provided. The method includes the steps of providing a mold core disposed on a turntable and having an internal cooling system, rotating the turntable so that the core is aligned with a first mold cavity, engaging the core with the first mold cavity, and injecting a melt to form a first preform layer. The first preform layer is held within the mold cavity to cool until a skin is formed on a surface of the layer, but an interior of the layer remains substantially molten. The core is then removed from the first mold cavity while retaining the molded preform layer on the core and the turntable is rotated so that the core is aligned with a second mold cavity. The core is engaged with the second mold cavity and a melt is injected to form a second preform layer on top of the first preform layer. The core is removed from the second mold cavity while retaining the molded preform on the core and the turntable is rotated so that the core and preform are in a cooling position during which the preform cools upon the core. The preform is eventually removed from the core.

In accordance with one aspect of the present invention, there is provided a laminate comprising at least one layer of polyethylene terephthalate directly adhered to at least one layer of barrier material. The polyethylene terephthalate has an isophthalic acid content of at least about 2% by weight. Barrier materials used include Copolyester Barrier Materials, Phenoxy-type Thermoplastics, Polyamides, polyethylene naphthalate, polyethylene naphthalate copolymers, polyethylene naphthalate/polyethylene terephthalate blends, and combinations thereof. In preferred embodiments, the laminate is provided in the form of preforms and containers.

In accordance with a further aspect of the present invention, there is provided a preform comprising at least two layers, wherein the first layer is thinner in the end cap than in the wall portion and the second layer is thicker in the end cap than in the wall portion. The first layer comprises polyethylene terephthalate having an isophthalic acid content of at least about 2% by weight and the second layer comprises a barrier material. Barrier materials used include Copolyester Barrier Materials, Phenoxy-type Thermoplastics, Polyamides, polyethylene naphthalate, polyethylene naphthalate copolymers, polyethylene naphthalate/polyethylene terephthalate blends, and combinations thereof.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described hereinabove. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodimeπt(s) disclosed.

Brief Description of the Drawings Figure 1 is an uncoated preform as is used as a starting material for embodiments of the present invention.

Figure 2 is a cross-section of a preferred uncoated preform of the type that is barrier-coated in accordance with an embodiment the present invention.

Figure 3 is a cross-section of one preferred embodiment of barrier-coated preform of the present invention. Figure 4 is a cross-section of another preferred embodiment of a barrier-coated preform of an embodiment of the present invention. Figure 4A is an enlargement of a section of the wall portion of a preform such as that made by a LIM-over-inject process. Not all preforms of the type in Figure 4 made in accordance with an embodiment of the present invention will have this type of layer arrangement.

Figure 5 is a cross-section of another embodiment of a barrier-coated preform of an embodiment of the present invention.

Figure 6 is a cross-section of a preferred preform in the cavity of a blow-molding apparatus of a type that may be used to make a preferred barrier-coated container of an embodiment of the present invention.

Figure 7 is one preferred embodiment of barrier-coated container of the present invention.

Figure 8 is a cross-section of one preferred embodiment of a barrier-coated container having features in accordance with the present invention.

Figure 9 is a cross-section of an injection mold of a type that may be used to make a preferred barrier-coated preform in accordance with the present invention.

Figures 10 and 11 are two halves of a molding machine to make barrier-coated preforms.

Figures 12 and 13 are two halves of a molding machine to make forty-eight two-layer preforms. Figure 14 is a perspective view of a schematic of a mold with mandrels partially located within the molding cavities.

Figure 15 is a perspective view of a mold with mandrels fully withdrawn from the molding cavities, prior to rotation.

Figure 16 is a three-layer embodiment of a preform. Figure 17 is a front view of a preferred embodiment of an apparatus for making preforms in accordance with the present invention;

Figure 18 is a cross-section of the apparatus of Figure 17 taken along lines 18-18;

Figure 19 is a chart showing the relative positions of stations of the apparatus of Figure 17 during a production cycle; Figure 20 is a front view of another preferred embodiment of an apparatus for making preforms in accordance with the present invention;

Figure 21 is a close up view of a station and actuator of the apparatus of Figure 20;

Figure 22 is a front view of another preferred embodiment of an apparatus for making preforms in accordance with the present invention; Figure 23 is a front view of the apparatus of Figure 22 in a closed position;

Figure 24 is a chart showing the relative positions of stations of the apparatus of Figure 22 during a production cycle;

Figure 25 is a schematic of a lamellar injection molding (LIM) system.

Figure 26 is a cross-section of an injection mold of a type that may be used to make a preferred preform of the present invention; Figure 27 is a cross-section of the mold of Figure 26 taken along lines 27-27; Figure 28 is a cutaway close up view of the area of Figure 26 defined by line 28. Detailed Description of the Preferred Embodiments A. General Description of the Invention This invention relates to methods and apparatus for making plastic articles having coatings comprising one or more layers of thermoplastic material with good gas-barrier characteristics. As presently contemplated, one embodiment of barrier coated article is a bottle of the type used for beverages. Alternatively, embodiments of the barrier coated articles of the present invention could take the form of jars, tubs, trays, or bottles for holding liquid foods. However, for the sake of simplicity, these embodiments will be described herein primarily in the context of beverage bottles and the preforms from which they are made by blow-molding.

Furthermore, the invention is described herein specifically in relation to polyethylene terephthalate (PET) but it is applicable to many other thermoplastics of the polyester type. Examples of such other materials include polyethylene 2,6- and 1,5-naphthalate (PEN), PETG, polytetramethylene 1 ,2-dioxybenzoate and copolymers of ethylene terephthalate and ethylene isophthalate. In especially preferred embodiments, "high IPA PET" is used as the polyester which is barrier coated. As it is used herein, the term "high-IPA PET" refers to PET to which IPA was added during to manufacture to form a copolymer in which the IPA content is more than about 2% by weight, preferably 2-10% IPA by weight, more preferably 3-8%, most preferably about 4-5% IPA by weight. The most preferred range is based upon current FDA regulations, which do not allow for PET materials having an IPA content of more than 5% to be in contact with food or drink. If such regulations are not a concern, then an IPA content of 5-10% is preferred. As used herein, "PET" includes "high IPA PET."

The high-IPA PET (more than about 2% by weight) is preferred because the inventor has surprisingly discovered that use of high-IPA PET in the processes for making barrier preforms and containers, provides for better interlayer adhesion than is found in those laminates comprising PET with no IPA or low IPA. Additionally, it has been found that interlayer adhesion improves as the IPA content rises, incorporation of the higher amounts of IPA into the PET results in a decrease in the rate of crystallization of the high IPA PET material as compared to PET homopolymer, or PET having lower amounts of IPA. The decrease in the rate of crystallization allows for the production of PET layers (made of high IPA PET) having a lower level of crystallinity than what is achieved with iow-IPA PET or homopolymer PET when they are made into barrier preforms by similar procedures. The lower crystallinity of the high-IPA PET is important in reducing crystallinity at the surface of the PET, i.e. the interface between the PET and the barrier material. Lower crystallinity allows for better adhesion between the layers and also provides for a more transparent container following blow molding of the preform.

Preferably, the preforms and containers have the barrier coating disposed on their outer surfaces or within the wall of the container. In contrast with the technique of Slat, which produces multiiaγered preforms in which the layers are readily separated, in embodiments of the present invention the thermoplastic barrier material adheres directly and strongly to the PET surface and is not easily separated therefrom. Adhesion between the layers results without the use of any additional materials such as an adhesive material or a tie layer. The coated preforms are processed, preferably by stretch blow molding to form bottles using methods and conditions similar to those used for uncoated PET preforms. The containers which result are strong, resistant to creep, and cosmetically appealing as well as having good gas-barrier properties.

One or more layers of a barrier material are employed in carrying out the present invention. As used herein, the terms "barrier material", "barrier resin" and the like refer to materials which, when used to form articles, preferably have key physical properties similar to PET, adhere well to PET, and have a lower permeability to oxygen and carbon dioxide than PET.

Once a suitable barrier material is chosen, an apparatus and method for economically manufacturing a container using the barrier material is necessary. One important method and apparatus involves using an injection molding machine in conjunction with a mold comprising a mandrel or core and a cavity. A first layer of a preform is molded between the mandrel and a first cavity of the mold when a molten polyester is injected therein. The first layer remains on the mandrel when the mandrel is pulled out of the cavity, moved, and inserted into a second mold cavity. A second layer of the material, preferably a barrier layer or a layer comprising barrier material, is then injected over the existing first preform layer. The mandrel and accompanying preform are then removed from the second cavity and a robot removes the preform from the mandrel. While the robot cools the molded preform, the mandrel is available for another molding cycle.

In another embodiment, the apparatus retains the preform on the mandrel after removal from the second mold cavity but indexes the mandrel out of the way of the mold cavities in order to cool the new preform. During this time, other mandrels of the apparatus interact with the mold cavities to form preform layers. After the preform is sufficiently cooled, it is removed from the mandrel by a robot or other device and the mandrel is available to start the process over again. This method and apparatus allows preforms to be cooled on the mandrel without substantially increasing cycle time.

A number of barrier materials having the requisite low permeability to gases such as oxygen and carbon dioxide are useful in embodiments of the present invention, the choice of barrier material being partly dependent upon the mode or application as described below. Preferred barrier materials for use in barrier coatings fall into two major categories: (1) copolyesters of terephthalic acid, isophthalic acid, and at least one diol having good barrier properties as compared to PET, such as those disclosed in U.S. Patent No. 4,578,295 to Jabarin, and which is commercially available as B-010 (Mitsui Petrochemical Ind. Ltd., Japan); and (2) hydroxy-functional poly(amide-ethers) such as those described in U.S. Patent Nos. 5,089,588 and 5,143,998, poly(hydroxy amide ethers) such as those described in U.S. Patent No. 5,134,218, polγethers such as those described in U.S. Patent No. 5,115,075 and 5,218,075, hydroxy-functional polyethers such as those as described in U.S. Patent No. 5,164,472, hydroxy-functional polγ(ether sulfonamides) such as those described in U.S. Patent No. 5,149,768, poly(hγdroxy ester ethers) such as those described in U.S. Patent No. 5,171,820, hydroxy-phenoxγether polymers such as those described in U.S. Patent No. 5,814,373, and polyfhydroxyamiπo ethers) ("PHAE") such as those described in U.S. Patent No. 5,275,853. The barrier materials described in (1) above are referred to herein by the term "Copolyester Barrier Materials". The compounds described in the patents in (2) above are collectively categorized and referred to herein by the term "Phenoxy-type Thermoplastic" materials. All the patents referenced in this paragraph are hereby incorporated in their entireties into this disclosure by this reference thereto.

Preferred Copolyester Barrier Materials will have FDA approval. FDA approval allows for these materials to be used in containers where they are in contact with beverages and the like which are intended for human consumption. To the inventor's knowledge, none of the Phenoxy-type Thermoplastics have FDA approval as of the date of this disclosure.

Thus, these materials are preferably used in multi-layered containers in locations which do not directly contact the contents, if the contents are iπgestible.

In carrying out preferred methods of the present invention to form barrier coated preforms and bottles, an initial preform is coated with at least one additional layer of material comprising barrier material, polyesters such as PET, post- consumer or recycled PET (collectively recycled PET), and/or other compatible thermoplastic materials. A coating layer may comprise a single material, a mix or blend of materials (heterogeneous or homogeneous), an interwoven matrix of two or more materials, or a plurality of microlaγers (lamellae) comprised of at least two different materials. In one embodiment, the initial preform comprises a plurality of microlaγers, such as may be prepared by a lamellar injection molding process. Initial preforms comprise polyester, and it is especially preferred that initial preforms comprise virgin materials which are approved by the FDA for being in contact with foodstuffs.

Thus the preforms and containers of embodiments of the present invention may exist in several embodiments, such as: virgin PET coated with a layer of barrier material; virgin PET coated with a layer of material comprising alternating microlayers of barrier material and recycled PET; virgin PET coated with a barrier layer which is in turn coated with recycled PET; microlayers of virgin PET and a barrier material coated with a layer of recycled PET; or virgin PET coated with recycled PET which is then coated with barrier material. In any case, at least one layer must comprise at least one barrier material.

As described previously, preferred barrier materials for use in accordance with the present invention are Copolyester Barrier Materials and Phenoxy-type Thermoplastics. Other barrier materials having similar properties may be used in lieu of these barrier materials. For example, the barrier material may take the form of other thermoplastic polymers, such as acrylic resins including polyacrγlonitrile polymers, acryionitrile styrene copolymers, polyamides, polyethylene naphthalate (PEN), PEN copolymers, and PET/PEN blends. Preferred barrier materials in accordance with embodiments of the present invention have oxygen and carbon dioxide permeabilities which are less than one-third those of polyethylene terephthalate. For example, the Copolyester Barrier Materials of the type disclosed in the aforementioned patent to Jabarin will exhibit a permeability to oxygen of about 11 cc mil/100 in² day and a permeability to carbon dioxide of about 2 cc mil/100 in² day. For certain PHAEs, the permeability to oxygen is less than 1 cc mil/100 in² day and the permeability to carbon dioxide is 3.9 cc mil/100 in² day. The corresponding C0₂ permeability of polyethylene terephthalate, whether in the recycled or virgin form, is about 12-20 cc mil/ 100 in² day.

The methods of embodiments of the present invention provide for a coating to be placed on a preform which is later blown into a bottle. Such methods are preferable to placing coatings on the bottles themselves. Preforms are smaller in size and of a more regular shape than the containers blown therefrom, making it simpler to obtain an even and regular coating. Furthermore, bottles and containers of varying shapes and sizes can be made from preforms of similar size and shape. Thus, the same equipment and processing can be used to produce preforms to form several different kinds of containers. The blow-molding may take place soon after molding, or preforms may be made and stored for later blow- molding, if the preforms are stored prior to blow-molding, their smaller size allows them to take up less space in storage. Even though it is preferable to form containers from coated preforms as opposed to coating containers themselves, they have generally not been used because of the difficulties involved in making containers from coated or multi-layer preforms. One step where the greatest difficulties arise is during the blow-molding process to form the container from the preform. During this process, defects such as delaminatioπ of the layers, cracking or crazing of the coating, uneven coating thickness, and discontinuous coating or voids can result. These difficulties can be overcome by using suitable barrier materials and coating the preforms in a manner that allows for good adhesion between the layers.

Thus, one aspect of the present invention is the choice of a suitable barrier material. When a suitable barrier material is used, the coating sticks directly to the preform without any significant deiamiπation, and will continue to stick as the preform is blow-molded into a bottle and afterwards. Use of a suitable barrier material also helps to decrease the incidence of cosmetic and structural defects which can result from blow-molding containers as described above. It should be noted that although most of the discussion, drawings, and examples of making coated preforms deal with two layer preforms, such discussion is not intended to limit the present invention to two layer articles. The two layer barrier containers and preforms of the present invention are suitable for many uses and are cost-effective because of the economy of materials and processing steps. However, in some circumstances and for some applications, preforms consisting of more than two layers may be desired. Use of three or more layers allows for incorporation of materials such as recycled PET, which is generally less expensive than virgin PET or the preferred barrier materials. Thus, it is contemplated as part of the present invention that all of the methods for producing the barrier-coated preforms of the present invention which are disclosed herein and all other suitable methods for making such preforms may be used, either alone or in combination to produce barrier-coated preforms and containers comprised of two or more layers.

B. Detailed Description of the Drawings Referring to Figure 1 , a preferred uncoated preform 30 is depicted. The preform is preferably made of an FDA approved material such as virgin PET and can be of any of a wide variety of shapes and sizes. The preform shown in Figure 1 is of the type which will form a 16 oz. carbonated beverage bottle that requires an oxygen and carbon dioxide barrier, but as will be understood by those skilled in the art, other preform configurations can be used depending upon the desired configuration, characteristics and use of the final article. The uncoated preform 30 may be made by injection molding as is known in the art or by methods disclosed herein.

Referring to Figure 2, a cross-section of the preferred uncoated preform 30 of Figure 1 is depicted. The uncoated preform 30 has a neck portion 32 and a body portion 34. The neck portion 32 begins at the opening 36 to the interior of the preform 30 and extends to and includes the support ring 38. The neck portion 32 is further characterized by the presence of the threads 40, which provide a way to fasten a cap for the bottle produced from the preform 30. The body portion 34 is an elongated and cyiindricallγ shaped structure extending down from the neck portion 32 and culminating in the rounded end cap 42. The preform thickness 44 will depend upon the overall length of the preform 30 and the wall thickness and overall size of the resulting container.

Referring to Figure 3, a cross-section of one type of barrier-coated preform 50 having features in accordance with the present invention is disclosed. The barrier-coated preform 50 has a neck portion 32 and a body portion 34 as in the uncoated preform 30 in Figs. 1 and 2. The barrier coating layer 52 is disposed about the entire surface of the body portion 34, terminating at the bottom of the support ring 38. A barrier coating layer 52 in the embodiment shown in the figure does not extend to the neck portion 32, nor is it present on the interior surface 54 of the preform which is preferably made of an FDA approved material such as PET. The barrier coating layer 52 may comprise either a single material or several microlayers of at least two materials. The overall thickness 56 of the preform is equal to the thickness of the initial preform plus the thickness 58 of the barrier layer, and is dependent upon the overall size and desired coating thickness of the resulting container. By way of example, the wall of the bottom portion of the preform may have a thickness of 3.2 millimeters; the wall of the neck finish, a cross-sectional dimension of about 3 millimeters; and the barrier material applied to a thickness of about 0.3 millimeters.

Referring to Figure 4, a preferred embodiment of a coated preform 60 is shown in cross-section. The primary difference between the coated preform 60 and the coated preform 50 in Figure 3 is the relative thickness of the two layers in the area of the end cap 42. In coated preform 50, the barrier layer 52 is generally thinner than the thickness of the initial preform throughout the entire body portion of the preform. In coated preform 60, however, the barrier coating layer 52 is thicker at 62 near the end cap 42 than it is at 64 in the wall portion 66, and conversely, the thickness of the inner polyester layer is greater at 68 in the wall portion 66 than it is at 70, in the region of the end cap 42. This preform design is especially useful when the barrier coating is applied to the initial preform in an overmolding process to make the coated preform, as described below, where it presents certain advantages including that relating to reducing molding cycle time. These advantages will be discussed in more detail below. The barrier coating layer 52 may be homogeneous or it may be comprised of a plurality of microlayers.

Figure 4A is an enlargement of a wall section of the preform showing the makeup of the layers in a LIM-over- inject embodiment of preform. The LIM process will be discussed in more detail below. The layer 72 is the inner layer of the preform and 74 is the outer layer of the preform. The outer layer 74 comprises a plurality of microlayers of material as will be made when a LIM system is used. Not all preforms of Figure 4 will be of this type.

Referring to Figure 5, another embodiment of a coated preform 76 is shown in cross-section. The primary difference between the coated preform 76 and the coated preforms 50 and 60 in Figures 3 and 4, respectively, is that the barrier coating layer 52 is disposed on the neck portion 32 as well as the body portion 34.

The barrier preforms and containers can have layers which have a wide variety of relative thicknesses. In view of the present disclosure, the thickness of a given layer and of the overall preform or container, whether at a given point or over the entire container, can be chosen to fit a coating process or a particular end use for the container. Furthermore, as discussed above in regard to the barrier coating layer in Figure 3, the barrier coating layer in the preform and container embodiments disclosed herein may comprise a single material or several microlayers of two or more materials. After a barrier-coated preform, such as that depicted in Figure 3, is prepared by a method and apparatus such as those discussed in detail below, it is subjected to a stretch blow-molding process. Referring to Figure 6, in this process a barrier-coated preform 50 is placed in a mold 80 having a cavity corresponding to the desired container shape. The barrier- coated preform is then heated and expanded by stretching and by air forced into the interior of the preform 50 to fill the cavity within the mold 80, creating a barrier-coated container 82. The blow molding operation normally is restricted to the body portion 34 of the preform with the neck portion 32 including the threads, pilfer ring, and support ring retaining the original configuration as in the preform.

Referring to Figure 7, there is disclosed an embodiment of barrier coated container 82 in accordance with the present invention, such as that which might be made from blow molding the barrier coated preform 50 of Figure 3. The container 82 has a neck portion 32 and a body portion 34 corresponding to the neck and body portions of the barrier- coated preform 50 of Figure 3. The neck portion 32 is further characterized by the presence of the threads 40 which provide a way to fasten a cap onto the container.

When the barrier-coated container 82 is viewed in cross-section, as in Figure 8, the construction can be seen. The barrier coating 84 covers the exterior of the entire body portion 34 of the container 82, stopping just below the support ring 38. The interior surface 86 of the container, which is made of an FDA-approved material, preferably PET, remains uncoated so that only the interior surface 86 is in contact with beverages or foodstuffs. In one preferred embodiment that is used as a carbonated beverage container, the thickness 87 of the barrier coating is preferably 0.020- 0.060 inch, more preferably 0.030-0.040 inch; the thickness 88 of the PET layer is preferably 0.080-0.160 inch, more preferably 0.100-0.140 inch; and the overall wall thickness 90 of the barrier-coated container 82 is preferably 0.140- 0.180 inch, more preferably 0.150-0.170 inch. Preferably, on average, the overall wall thickness 90 of the container 82 derives the majority of its thickness from the inner PET layer.

Figure 9 illustrates a preferred type of mold for use in methods which utilize overmolding. The mold comprises two halves, a cavity half 92 and a mandrel half 94. The cavity half 92 comprises a cavity in which an uncoated preform is placed. The preform is held in place between the mandrel half 94, which exerts pressure on the top of the preform and the ledge 96 of the cavity half 92 on which the support ring 38 rests. The neck portion 32 of the preform is thus sealed off from the body portion of the preform. Inside the preform is the mandrel 98. As the preform sits in the mold, the body portion of the preform is completely surrounded by a void space 100. The preform, thus positioned, acts as an interior die mandrel in the subsequent injection procedure, in which the melt of the overmolding material is injected through the gate 102 into the void space 100 to form the coating. The melt, as well as the uncoated preform, is cooled by fluid circulating within channels 104 and 106 in the two halves of the mold. Preferably the circulation in channels 104 is completely separate from the circulation in the channels 106.

Figures 10 and 11 are a schematic of a portion of the preferred type of apparatus to make coated preforms in accordance with the present invention. The apparatus is an injection molding system designed to make one or more uncoated preforms and subsequently coat the newly-made preforms by over-injection of a barrier material. Figures 10 and 11 illustrate the two halves of the mold portion of the apparatus which will be in opposition in the molding machine. The alignment pegs 110 in Figure 10 fit into their corresponding receptacles 112 in the other half of the moid.

The mold half depicted in Figure 11 has several pairs of mold cavities, each cavity being similar to the mold cavity depicted in Figure 9. The mold cavities are of two types: first injection preform molding cavities 114 and second injection preform coating cavities 120. The two types of cavities are equal in number and are preferably arranged so that all cavities of one type are on the same side of the injection block 124 as bisected by the line between the alignment peg receptacles 112. This way, every preform molding cavity 114 is 180° away from a preform coating cavity 120.

The mold half depicted in Figure 10 has several mandrels 98, one for each mold cavity (114 and 120). When the two halves which are Figures 10 and 11 are put together, a mandrel 98 fits inside each cavity and serves as the mold for the interior of the preform for the preform molding cavities 114 and as a centering device for the uncoated preforms in preform coating cavities 120. The mandrels 98 are mounted on a turntable 130 which rotates 180° about its center so that a mandrel 98 originally aligned with a preform molding cavity 114 will, after rotation, be aligned with a preform coating cavity 120, and vice-versa. As described in greater detail below, this type of setup allows a preform to be molded and then coated in a two-step process using the same piece of equipment. It should be noted that the drawings in Figures 10 and 11 are merely illustrative. For instance, the drawings depict an apparatus having three molding cavities 114 and three coating cavities 120 (a 3/3 cavity machine). However, the machines may have any number of cavities, as long as there are equal numbers of molding and coating cavities, for example 12/12, 24/24, 48/48 and the like. The cavities may be arranged in any suitable manner, as can be determined by one skilled in the art. These and other minor alterations are contemplated as part of this invention. The two mold halves depicted in Figures 12 and 13 illustrate an embodiment of a mold of a 48/48 cavity machine as discussed for Figures 10 and 11.

Referring to Figure 14 there is shown a perspective view of a mold of the type for an overmolding (inject-over- inject) process in which the mandrels 98 are partially located within the cavities 114 and 120. The arrow shows the movement of the movable mold half 142, on which the mandrels 98 lie, as the mold closes. Figure 15 shows a perspective view of a mold of the type used in an overmolding process, wherein the mandrels

98 are fully withdrawn from the cavities 114 and 120. The arrow indicates that the turntable 130 rotates 180° to move the mandrels 98 from one cavity to the next. On the stationary half 144, the cooling for the preform molding cavity 114 is separate from the cooling for the preform coating cavity 120. Both of these are separate from the cooling for the mandrels 98 in the movable half. Referring to Figure 16 there is shown a preferred three-layer preform 132. This embodiment of coated preform is preferably made by placing two coating layers 134 and 136 on a preform 30 such as that shown in Figure 1.

Figure 17 schematically shows another preferred apparatus 150 which may be used in an overmolding process. A first and second injector 152, 154 are disposed at the top of the machine 150 to provide a meltstream to first and second mold cavities 156, 158. Figure 18 shows a rotating table 160 portion of the embodiment of Figure 17. Four stations, labeled A through D, each have a mandrel 98A-D formed thereon and are disposed on the rotating table 160 roughly 90° in rotation apart. An actuator 162 such as a hydraulic cylinder lifts the table 160 so that mandrels 98 from two stations are simultaneously inserted into the first and second mold cavities 156, 158. The mandrels 98 on the other stations remain clear of any mold cavities. After the table 160 is lowered so that the mandrels 98 are removed from the cavities, it then rotates 90°. Thus, the mandrel 98 that was just removed from the first cavity 156 is placed in position to be inserted into the second mold cavity 158 and the mandrel just removed from the second cavity 158 is moved clear of the mold cavities. Each of the stations are cycled in turn through the first and second mold cavities 156, 158 by a series of sequential 90° rotations. Figure 19 tracks the positions of the stations relative to each other during each step of a production cycle.

Figures 20 and 21 show another embodiment of an apparatus 170 of the present invention similar in many ways to that of Figures 17 and 18. However, in this embodiment, instead of the entire table 160 being lifted by a hydraulic member, each station of the turntable 160 is individually controlled by an actuator 172, and independently moved into and out of engagement with a respective mold cavity. This arrangement allows for increased flexibility of the apparatus 170. For example, Figure 20 shows that a mandrel 98 may be held within the second cavity 158 after a mandrel 98 in the first cavity 156 is removed therefrom. Thus, hold time between mold cavities can be independently optimized. With next reference to Figures 22-23, a schematic view of another preferred apparatus 250 which may be used to overmold multilayer preforms is shown. In this embodiment, a rotating turntable 260 has a station (AA-DD) formed on each of four sides. Mold mandrels 98 or cores are disposed on each of the stations as in previous embodiments. First and second mold cavities 256, 258 are in communication with corresponding first and second injection machines 252, 254 which supply melt streams of PET and barrier material, respectively. The first mold cavity 256 is connected to the first injection machine 252 and remains stationary; the second injection machine 254 is vertically oriented overhead and also remains stationary. The turntable 260 is supported by a base member 264 which is horizontally movable upon ways 266 which support the base member 264. The second mold cavity 258 is connected to the turntable 260 by actuators 268 and also moves horizontally with the turntable 260. The actuators 268 pull the second mold cavity 258 into engagement with a mandrel 98B disposed on the turntable 268 in order to close the mold. After the second cavity 258 engages the corresponding mandrel, the turntable 260 next moves horizontally to engage a mandrel with the first mold cavity 256. With both mold cavities engaged with mandrels, the mold is now completely closed, as shown in Figure 23. Also, the second injection machine 254 is placed in communication with the second mold cavity 258 so that the second injection machine 254 can provide a melt stream of barrier material thereto.

When injection is complete, the mold is opened. This is accomplished by the turntable 260 first moving horizontally to disengage the mandrel from the first cavity 256, then raising the second mold out of engagement with the turntable 260. The turntable 260 then rotates 90° and closure of the mold and injection of material is repeated. Injected preforms disposed on the mandrels 98 not engaged with mold cavities cool upon the associated mandrel during the rest of the cycle. The preforms are ejected before the associated mandrel is again brought into engagement with the first mold cavity 256. Figure 24 tracks the positions of the stations relative to each other during each step of a production cycle. Referring to Figure 25, there is shown a schematic of an apparatus which may be used to produce a meltstream comprised of numerous microlayers or lamellae in a lamellar injection molding (LIM) process as described in further detail below.

With next reference to Figure 26, a preferred embodiment of a mold mandrel 298 and associated cavity 300 are shown. Cooling tubes 302 are formed in a spiral fashion just below the surface 304 of the mold cavity 300. A gate area

308 of the cavity 300 is defined near a gate 308 and an insert 310 of a material with especially high heat transfer properties is disposed in the cavity at the gate area 306. Thus, the injected preform's gate area/base end 314 is cooled especially quickly.

The mandrel 298 is hollow and has a wall 320 of generally uniform thickness. A bubbler cooling arrangement 330 is disposed within the hollow mandrel 298 and comprises a core tube 332 located centrally within the mandrel 298 which delivers chilled coolant C directly to a base end 322 of the mandrel 298. Coolant C works its way up the mandrel from the base end 322 and exits through an output line 334. The core tube is held in place by ribs 336 extending between the tube and the mandrel wall 320.

Referring also to Figures 27 and 28, an air insertion system 340 is shown formed at a joint 342 between members of the mold cavity 300. A notch 344 is formed circumferentially around the cavity 300. The notch 344 is sufficiently small that substantially no molten plastic will enter during melt injection. An air line 350 connects the notch 344 to a source of air pressure and a valve regulates the supply of air to the notch 344. During melt injection, the valve is closed. When injection is complete, the valve is opened and pressurized air A is supplied to the notch 344 in order to defeat a vacuum that may form between an injected preform and the cavity wall 304. The preferred method and apparatus for making barrier coated preforms is discussed in more detail below.

Because the methods and apparatus are especially preferred for use in forming barrier coated bottles comprising certain preferred materials, the physical characteristics, identification, preparation and enhancement of the preferred materials is discussed prior to the preferred methods and apparatus for working with the materials.

C. Physical Characteristics of Preferred Barrier Materials Preferred barrier materials in accordance with the present invention preferably exhibit several physical characteristics which allow for the barrier coated bottles and articles of the present invention to be able to withstand processing and physical stresses in a manner similar or superior to that of uncoated PET articles, in addition to producing articles which are cosmetically appealing and have excellent barrier properties.

Adhesion is the union or sticking together of two surfaces. The actual interfacial adhesion is a phenomenon which occurs at the microscopic level. It is based upon molecular interactions and depends upon chemical bonding, van der Waals forces and other intermolecular attractive forces at the molecular level.

Good adhesion between the barrier layer and the PET layer is especially important when the article is a barrier bottle made by blow-molding a preform. If the materials adhere well, then they will act as one unit when they are subjected to a blow molding process and as they are subjected to stresses when existing in the form of a container. Where the adhesion is poor, dela ination results either over time or under physical stress such as squeezing the container or the container jostling during shipment. Delamination is not only unattractive from a commercial standpoint, it may be evidence of a lack of structural integrity of the container. Furthermore, good adhesion means that the layers will stay in close contact when the container is expanded during the molding process and will move as one unit. When the two materials act in such a manner, it is less likely that there will be voids in the coating, thus allowing a thinner coating to be applied. The barrier materials preferably adhere sufficiently to PET such that the barrier layer cannot be easily pulled apart from the PET layer at 22°C.

Thus, due in part to the direct adhesion of the barrier layer to the PET, the present invention differs from that disclosed by Farha in U.S. Patent No. 5,472,753. In Farha, there is not disclosed, nor is the suggestion made, that the phenoxy-type thermoplastic can or should be bound directly to the PET without being blended with the copolyester or using the copolyester as a tie layer or that a copolyester itself could be used as a barrier material.

The glass transition temperature (Tg) is defined as the temperature at which a non-crγstallizable polymer undergoes the transformation from a soft rubber state to a hard elastic polymer glass. In a range of temperatures above its Tg, a material will become soft enough to allow it to flow readily when subjected to an external force or pressure, yet not so soft that its viscosity is so low that it acts more like a liquid than a pliable solid. The temperature range above Tg is the preferred temperature range for performing a blow-molding process, as the material is soft enough to flow under the force of the air blown into the preform to fit the mold but not so soft that it breaks up or becomes uneven in texture. Thus, when materials have similar glass transition temperatures, they will have similar preferred blowing temperature ranges, allowing the materials to be processed together without compromising the performance of either material.

In the blow-molding process to produce bottle from a preform, as is known in the art, the preform is heated to a temperature slightly above the Tg of the preform material so that when air is forced into the preform's interior, it will be able to flow to fill the mold in which it is placed. If one does not sufficiently heat the preform and uses a temperature below the Tg, the preform material will be too hard to flow properly, and would likely crack, craze, or not expand to fill the mold. Conversely, if one heats the preform to a temperature well above the Tg, the material would likely become so soft that it would not be able to hold its shape and would process improperly. If a barrier coating material has a Tg similar to that of PET, it will have a blowing temperature range similar to

PET. Thus, if a PET preform is coated with such a barrier material, a blowing temperature can be chosen that allows both materials to be processed within their preferred blowing temperature ranges. If the barrier coating were to have a Tg dissimilar to that of PET, it would be difficult, if not impossible, to choose a blowing temperature suitable for both materials. When the barrier coating materials have a Tg similar to PET, the coated preform behaves during blow molding as if it were made of one material, expanding smoothly and creating a cosmetically appealing container with an even thickness and uniform coating of the barrier material where it is applied.

The glass transition temperature of PET occurs in a window of about 75-85°C, depending upon how the PET has been processed previously. The Tg for preferred barrier materials of embodiments of the present invention is preferably 55 to 140°C, more preferably 90 to 110TJ. Another factor which has an impact on the performance of barrier preforms during blow molding is the state of the material. The preferred barrier materials of preferred embodiments of the present invention are amorphous rather than crystalline. This is because materials in an amorphous state are easier to form into bottles and containers by use of a blow molding process than materials in a crystalline state. PET can exist in both crystalline and amorphous forms. However, in embodiments of the present invention it is highly preferred that the crystallinity of the PET be minimized and the amorphous state maximized in order to create a semi-crystalline state which, among other things, aids interlayer adhesion and in the blow molding process. A PET article formed from a melt of PET, as in injection molding, can be guided into a semi-crystalline form by cooling the melt at a high rate, fast enough to quench the crystallization process, freezing the PET in a mostly amorphous state. Additionally, use of "high IPA PET" as described earlier herein will allow easier quenching of the crystallization process because it crystallizes at a lower rate than homopolymer PET.

Intrinsic viscosity and melt index are two properties which are related to a polymer's molecular weight. These properties give an indication as to how materials will act under various processing conditions, such as injection molding and blow molding processes.

Barrier materials for use in the articles and methods of the present invention have an intrinsic viscosity of preferably 0.70-0.90 dl/g, more preferably 0.74-0.87 dl/g, most preferably 0.84-0.85 dl/g and a melt index of preferably 5- 30, more preferably 7-12, most preferably 10.

Barrier materials of embodiments of the present invention preferably have tensile strength and creep resistance similar to PET. Similarity in these physical properties allows the barrier coating to act as more than simply a gas barrier. A barrier coating having physical properties similar to PET acts as a structural component of the container, allowing the barrier material to displace some of the polyethylene terephthalate in the container without sacrificing container performance. Displacement of PET allows for the resulting barrier-coated containers to have physical performance and characteristics similar to their uncoated counterparts without a substantial change in weight or size. It also allows for any additional cost from adding the barrier material to be defrayed by a reduction in the cost per container attributed to PET.

Similarity in tensile strength between PET and the barrier coating materials helps the container to have structural integrity. This is especially important if some PET is displaced by barrier material. Barrier-coated bottles and containers having features in accordance with the present invention are able to withstand the same physical forces as an uncoated container, allowing, for example, barrier-coated containers to be shipped and handled in the customary manner of handling uncoated PET containers. If the barrier-coating material were to have a tensile strength substantially lower than that of PET, a container having some PET displaced by barrier material would likely not be able to withstand the same forces as an uncoated container.

Similarity in creep resistance between PET and the barrier coating materials helps the container to retain its shape. Creep resistance relates to the ability of a material to resist changing its shape in response to an applied force. For example, a bottle which holds a carbonated liquid needs to be able to resist the pressure of dissolved gas pushing outward and retain its original shape. If the barrier coating material were to have a substantially lower resistance to creep than PET in a container, the resulting container would be more likely to deform over time, reducing the shelf-life of the product. For applications where optical clarity is of importance, preferred barrier materials have an index of refraction similar to that of PET. When the refractive index of the PET and the barrier coating material are similar, the preforms and, perhaps more importantly, the containers blown therefrom are optically clear and, thus, cosmetically appealing for use as a beverage container where clarity of the bottle is frequently desired. If, however, the two materials have substantially dissimilar refractive indices when they are placed in contact with each other, the resulting combination will have visual distortions and may be cloudy or opaque, depending upon the degree of difference in the refractive indices of the materials.

Polyethylene terephthalate has an index of refraction for visible light within the range of about 1.40 to 1.75, depending upon its physical configuration. When made into preforms, the refractive index is preferably within the range of about 1.55 to 1J5, and more preferably in the range of 1.55-1.65. After the preform is made into a bottle, the wall of the final product, may be characterized as a biaxially-oriented film since it is subject to both hoop and axial stresses in the blow molding operation. Blow molded PET generally exhibits a refractive index within the range of about 1.40 to 1J5, usually about 1.55 to 1.75, depending upon the stretch ratio involved in the blow molding operation. For relatively low stretch ratios of about 6:1, the refractive index will be near the lower end, whereas for high stretch ratios, about 10:1, the refractive index will be near the upper end of the aforementioned range. It will be recognized that the stretch ratios referred to herein are biaxial stretch ratios resulting from and include the product of the hoop stretch ratio and the axial stretch ratio. For example, in a blow molding operation in which the final preform is enlarged by a factor of 2.5 in the axial direction and a factor of 3.5 diametrically, the stretch ratio will be about 8.75 (2.5 x 3.5).

Using the designation n_{ to indicate the refractive index for PET and n„ to indicate the refractive index for the barrier material, the ratio between the values π, and n„ is preferably 0.8-1.3, more preferably 1.0-1.2, most preferably 1.0- 1.1. As will be recognized by those skilled in the art, for the ratio

1 the distortion due to refractive index will be at a minimum, because the two indices are identical. As the ratio progressively varies from one, however, the distortion increases progressively.

D. Preferred Barrier Coating Materials and Their Preparation

The preferred barrier coating materials for use in the articles and methods of the present invention include Phenoxy-type Thermoplastic materials, copolyesters of terephthalic acid, isophthalic acid, and at least one diol having good barrier properties as compared to PET (Copolyester Barrier Materials), Polyamides, PEN, PEN copolymers, PEN/PET blends, and combinations thereof. Preferably, the Phenoxy-type Thermoplastics used as barrier materials in the present invention are one of the following types:

(1) hydroxy-functional poly(amide ethers) having repeating units represented by any one of the Formulae la, lb or lc:

OH O O OH

-OCH₂C ICH₂OAr NHC ll R ,¹ C IINHAr OCHzC ICHzOA ,r²1-¹— , ^la^a

R R lb

(2) polylhydroxγ amide ethers) having repeating units represented independently by any one of the Formulae Ha,

OH Q OCH₂CCH₂OAr NHC R CNHAr Ha

OH O O

-OCH₂CCH₂OAr CNH R¹ NHCAr- lib

R or

OH O t OCH₂CCH₂OArCNHAr- He I

(3) amide- and hydroxymethyl-functionalized polyethers having repeating units represented by Formula III:

III

(4) hydroxy-functional polyethers having repeating units represented by Formula IV:

(5) hydroxy-functional polγ(ether sulfonamides) having repeating units represented by Formulae Va or Vb:

(6) poly(hydroxy ester ethers) having repeating units represented by Formula VI:

(7) hydroxy-phenoxyether polymers having repeating units represented by Formula VII:

and

(8) polylhγdroxyamino ethers) having repeating units represented by Formula VIII:

wherein each Ar individually represents a divalent aromatic moiety, substituted divalent aromatic moiety or heteroaromatic moiety, or a combination of different divalent aromatic moieties, substituted aromatic moieties or heteroaromatic moieties; R is individually hydrogen or a monovalent hydrocarbyl moiety; each Ar, is a divalent aromatic moiety or combination of divalent aromatic moieties bearing amide or hydroxymethyl groups; each Ar₂ is the same or different than Ar and is individually a divalent aromatic moiety, substituted aromatic moiety or heteroaromatic moiety or a combination of different divalent aromatic moieties, substituted aromatic moieties or heteroaromatic moieties; R, is individually a predominantly hydrocarbylene moiety, such as a divalent aromatic moiety, substituted divalent aromatic moiety, divalent heteroaromatic moiety, divalent alkγlene moiety, divalent substituted alkylene moiety or divalent heteroalkylene moiety or a combination of such moieties; R₂ is individually a monovalent hydrocarbyl moiety; A is an amine moiety or a combination of different amine moieties; X is an amine, an arγlenedioxγ, an arylenedisulfonamido or an aryleπedicarboxy moiety or combination of such moieties; and Ar₃ is a "cardo" moiety represented by any one of the Formulae:

wherein Y is nil, a covalent bond, or a linking group, wherein suitable linking groups include, for example, an oxygen atom, a sulfur atom, a carbonyl atom, a sulf onγl group, or a methγlene group or similar linkage; n is an integer from about 10 to about 1000; x is 0.01 to 1.0; and γ is 0 to 0.5.

The term "predominantly hydrocarbylene" means a divalent radical that is predominantly hγdrocarbon, but which optionally contains a small quantitγ of a heteroatomic moiety such as oxγgen, sulfur, imino, sulfonγl, sulfoxyl, and the like.

The hydroxy-functional poly(amide ethers) represented by Formula I are preferably prepared by contacting an N,N'-bis(hydroxyphenγlamido)alkane or arene with a diglγcidγl ether as described in U.S. Patent Nos. 5,089,588 and

5,143,998. The poly(hydroxγ amide ethers) represented by Formula II are prepared bγ contacting a bis(hydroxγphenγlamido)alkane or arene, or a combination of 2 or more of these compounds, such as N,N'-bis(3-hγdroxγpheπγl) adipamide or N,N'-bis(3-hγdroxγphenγl)glutaramide, with an epihalohydrin as described in U.S. Patent No. 5,134,218. The amide- and hydroxymethγl-functionaiized polγethers represented bγ Formula III can be prepared, for example, by reacting the diglycidyl ethers, such as the diglycidγl ether of bisphenol A, with a dihγdric phenol having pendant amido, N-substituted amido and/or hγdroxγalkγl moieties, such as 2,2-bis(4-hydroxyphenγl)acetamide and 3,5-dihγdroxγbenzamide. These polγethers and their preparation are described in U.S. Patent Nos. 5,115,075 and 5,218,075. The hγdroxγ-functioπal polγethers represented by Formula IV can be prepared, for example, by allowing a diglγcidγl ether or combination of diglγcidγl ethers to react with a dihγdric phenol or a combination of dihγdric phenols using the process described in U.S. Patent No. 5,164,472. Alternatively, the hγdroxγ-functioπal poiγethers are obtained bγ allowing a dihγdric phenol or combination of dihγdric phenols to react with an epihalohγdrin bγ the process described bγ Reinking, Barnabeo and Hale in the Journal of Applied Polγmer Science, Vol. 7, p. 2135 (1963). The hγdroxγ-fuπctioπal polγfether sulfonamides) represented bγ Formula V are prepared, for example, bγ polγmerizing an N,N'-dialkγl or N,N'-diarγldisulfonamide with a diglγcidγl ether as described in U.S. Patent No. 5,149,768. The polγ(hγdroxγ ester ethers) represented bγ Formula VI are prepared bγ reacting diglγcidyl ethers of aliphatic or aromatic diacids, such as diglycidγl terephthalate, or diglycidyl ethers of dihydric phenols with, aliphatic or aromatic diacids such as adipic acid or isophthalic acid. These polγesters are described in U.S. Patent No. 5,171,820. The hγdroxγ-phenoxγether polymers represented bγ Formula VII are prepared, for example, bγ contacting at least one dinucleophilic monomer with at least one diglγcidγl ether of a cardo bisphenol, such as 9,9-bis(4-hγdroxγphenγl)fluorene, phenolphthalein, or phenolphthalimidine or a substituted cardo bisphenol, such as a substituted bis(hydroxyphenyl)f luoreπe, a substituted phenolphthalein or a substituted phenolphthalimidine under conditions sufficient to cause the nucleophiiic moieties of the dinucleophilic monomer to react with epoxγ moieties to form a polγmer backbone containing pendant hydroxγ moieties and ether, imino, amino, sulfonamido or ester linkages. These hγdroxγ-phenoxγether polγmers are described in U.S. Patent No. 5,184,373.

The polγ(hγdroxγamino ethers) ("PHAE" or polyetheramiπes) represented bγ Formula VIII are prepared bγ contacting one or more of the diglγcidγl ethers of a dihγdric phenol with an amine having two amine hγdrogens under conditions sufficient to cause the amine moieties to react with epoxγ moieties to form a polγmer backbone having amine linkages, ether linkages and pendant hγdroxγl moieties. These compounds are described in U.S. Patent No. 5,275,853.

Phenoxγ-tγpe Thermoplastics of Formulae l-VIII maγ be acquired from Dow Chemical Companγ (Midland, Michigan U.S.A.).

The Phenoxγ-tγpe Thermoplastics commercially available from Phenoxγ Associates, Inc. are suitable for use in the present invention. These hγdroxγ-phenoxγether polγmers are the condensation reaction products of a dihγdric polynuclear phenol, such as bisphenol A, and an epihalohγdrin and have the repeating units represented bγ Formula IV wherein Ar is an isopropγiidene diphenγlene moietγ. The process for preparing these is described in U.S. Patent No. 3,305,528, incorporated herein bγ reference in its entiretγ.

The most preferred Phenoxγ-tγpe Thermoplastics are the polγ(hγdroxγamino ethers) ("PHAE") represented bγ Formula VIII. An example is that sold as XU19040.00L bγ Dow Chemical Companγ. Examples of preferred Copolγester Barrier Materials and a process for their preparation is described in U.S.

Patent No.4,578,295 to Jabarin. Theγ are generally prepared bγ heating a mixture of at least one reactant selected from isophthalic acid, terephthalic acid and their C, to C₄ alkγl esters with 1,3 bis(2-hγdroxγethoxγ)beπzene and ethγlene glycol. Optionally, the mixture may further comprise one or more ester-forming dihydroxγ hγdrocarbon and/or bis(4-β- hydroxyethoxypheπγDsulfone. Especially preferred Copolγester Barrier Materials are available from Mitsui Petrochemical Ind. Ltd. (Japan) as B-010, B-030 and others of this familγ.

Examples of preferred Polγamide barrier materials include MXD-6 from Mitsubishi Gas Chemical (Japan). Other preferred Polγamide barrier materials are polyamides containing preferably 1-10% polγester, more preferablγ 1-2% polγester bγ weight, where the polγester is preferablγ PET, more preferablγ high IPA PET. These materials are made bγ adding the polγester to the polγamide polγcoπdensation mixture. "Polγamide" as used herein shall include those polyamides containing PET or other polyesters.

Other preferred barrier materials include polyethylene naphthalate (PEN), PEN copolyester, and PET/PEN blends. PEN materials can be purchased from Shell Chemical Compaπγ.

E. Preparation of Polyesters Polγesters and methods for their preparation (including the specific monomers emploγed in their formation, their proportions, polγmerization temperatures, catalγsts and other conditions) are well-known in the art and reference is made thereto for the purposes of this invention. For purposes of illustration and not limitation, reference is particularly made to pages 1-62 of Volume 12 of the Encyclopedia of Polymer Science and Engineering, 1988 revision, John Wileγ & Sons.

Typically, polyesters are derived from the reaction of a di- or polγcarboxγlic acid with a di- or polyhγdric alcohol. Suitable di- or polγcarboxγlic acids include polγcarboxγlic acids and the esters and anthγdrides of such acids, and mixture thereof. Representative carboxγlic acids include phthalic, isophthalic, adipic azelaic, terephthalic, oxalic, malonic, succinic, glutaric, sebacic, and the like. Dicarboxγlic components are preferred. Terephthalic acid is most commonlγ emploγed and preferred in the preparation of polγester films. α,β-Unsaturated di- and polγcarboxγlic acids (including esters or anthγdrides of such acids and mixtures thereof) can be used as partial replacement for the saturated carboxγlic components. Representative α,β-unsaturated di- and polγcarboxγlic acids include maleic, fumaric, aconitic, itaconic, mesacoπic, citraconic, monochloromaleic and the like.

Typical di- and polγhγdric alcohols used to prepare the polγester are those alcohols having at least two hγdroxγ groups, although minor amounts of alcohol having more or less hydroxγ groups may be used. Dihγdroxγ alcohols are preferred. Dihγdroxγ alcohols conventionally emploγed in the preparation of polγesters include diethγlene glγcol; dipropylene glycol; ethylene glγcol; 1,2-propγlene glycol; 1,4-butanediol; 1,4-peπtaπediol; 1,5-hexanediol, 1,4-cyclohexanedimethaπol and the like with 1,2-propγlene glγcol being preferred. Mixtures of the alcohols can also be emploγed. The di- or polγhγdric alcohol component of the polyester is usually stoichiometric or in slight excess with respect to the acid. The excess of the di- or polγhγdric alcohol will seldom exceed about 20 to 25 mole percent and usually is between about 2 and about 10 mole percent.

The polγester is generally prepared bγ heating a mixture of the di- or polγhγdric alcohol and the di- or polγcarboxγlic component in their proper molar ratios at elevated temperatures, usually between about 100°C and 250°C for extended periods of time, generally ranging from 5 to 15 hours. Polγmerization inhibitors such as t-butγlcatechol maγ advantageouslγ be used.

PET, the preferred polyester, which is commonly made bγ condensation of terephthalic acid and ethγlene glγcol, maγ be purchased from Dow Chemical Companγ (Midland, Michigan), and Allied Signal Inc. (Baton Rouge, LA), among manγ others.

Preferablγ, the PET used is that in which isophthalic acid (IPA) is added during the manufacture of the PET to form a copolγ er. The amount of IPA added is preferablγ 2-10% bγ weight, more preferablγ 3-8% bγ weight, most preferablγ 4-5% bγ weight. The most preferred range is based upon current FDA regulations which curreπtlγ do not allow for PET materials having an IPA content of more than 5% to be in contact with food or drink. High-IPA PET (PET having more than about 2% IPA bγ weight) can be made as discussed above, or purchased from a number of different manufacturers, for instance PET with 4.8% IPA may be purchased from SKF (Italy) and 10% IPA PET may be purchased from INCA (Dow Europe).

Additionally, if a Polγamide is chosen as the barrier material, it is preferred to use a polγamide-containing polγester. Such polγamide-containing polγesters are formed bγ adding polγamide to the poiγester polycondensation mixture. The amount of polyamide in the polγester is preferablγ 1-10% bγ weight, more preferablγ 1-2% by weight. The polyester used is preferablγ PET, more preferablγ high IPA PET.

F. Materials to Enhance Barrier Properties of Barrier Resins The barrier materials disclosed above maγ be used in combination with other materials which enhance the barrier properties. Generally speaking, one cause for the diffusion of gases through a material is the existence of gaps or holes in the material at the molecular level through which the gas molecules can pass. The presence of intermolecular forces in a material, such as hydrogen bonding, allows for interchain cohesion in the matrix which closes these gaps and discourages diffusion of gases. One maγ also increase the gas-barrier abilitγ of good barrier materials bγ adding an additional molecule or substance which takes advantage of such intermolecular forces and acts as a bridge between polymer chains in the matrix, thus helping to close the holes in the matrix and reduce gas diffusion. Derivatives of the diol resorcinol (m-dihγdroxγbenzene), when reacted with other monomers in the manufacture of PHAE, PET, Copolγester Barrier Materials, and other barrier materials, will generally result in a material which has better barrier properties than the same material if it does not contain the resorcinol derivative. For example, resorcinol diglycidγl ether can be used in PHAE and hγdroxγethγl ether resorcinol can be used in PET and other polγesters and Copolγester Barrier Materials. One measure of the efficacy of a barrier is the effect that it has upon the shelf life of the material. The shelf life of a carbonated soft drink in a 32 oz PET non-barrier bottle is approximately 12-16 weeks. Shelf life is determined as the time at which less than 85% of the original amount of carbon dioxide is remaining in the bottle. Bottles coated with PHAE using the inject-over-inject method described below have been found to have a shelf life 2 to 3 times greater than that of PET alone. If, however, PHAE with resorcinol diglγcidγl ether is used, the shelf life can be increased to 4 to 5 times that of PET alone.

Another waγ of enhancing the barrier properties of a material is to add a substance which "plugs" the holes in the polγmer matrix and thus discourages gases from passing through the matrix. Alternatively, a substance may aid in creating a more tortuous path for gas molecules to take as they permeate a material. One such substance, referred to herein bγ the term "Nanoparticles" or "nanoparticular material" are tinγ particles of materials which enhance the barrier properties of a material bγ creating a more tortuous path for migrating oxγgen or carbon dioxide. One preferred tγpe of nanoparticular material is a microparticular claγ-based product available from Southern Claγ Products.

G. Preparing Barrier-Coated Articles Once a suitable barrier coating material is chosen, the coated preform must be made in a manner that promotes adhesion between the two materials. Generallγ, adherence between the barrier coating materials and PET increases as the surface temperature of the PET increases. Therefore, it is preferable to perform coating on heated preforms, although the preferred barrier materials will adhere to PET at room temperature.

There are a number of methods of producing a coated PET preform in accordance with the present invention.

Preferred methods include dip coating, spraγ coating, flame spraγing fiuidized bed dipping, and electrostatic powder spraγing. Another preferred method, lamellar injection molding, is discussed in more detail below. Each of the above methods is introduced and described in mγ copending U.S. Application Serial No. 09/147,971, which was filed on October

19, 1998, entitled BARRIER-COATED POLYESTER, which is hereby incorporated bγ reference in its entirety.

An especially preferred method of producing a coated PET preform is referred to herein generallγ as overmolding, and sometimes as inject-over-inject ("101"). The name refers to a procedure which uses injection molding to inject one or more layers of barrier material over an existing preform, which preferablγ was itself made bγ injection molding. The terms "overinjecting" and "overmolding" are used herein to describe the coating process wherebγ a laγer of material, preferablγ comprising barrier material, is injected over an existing preform. In an especially preferred embodiment, the overinjecting process is performed while the underlying preform has not γet fully cooled. Overinjecting maγ be used to place one or more additional laγers of materials such as those comprising barrier material, recγcled PET, or other materials over a coated or uncoated preform.

The overmolding is carried out bγ using an injection molding process using equipment similar to that used to form the uncoated preform itself. A preferred mold for overmolding, with an uncoated preform in place is shown in Figure 9.

The mold comprises two halves, a cavitγ half 92 and a mandrel half 94, and is shown in Figure 9 in the closed position prior to overinjecting. The cavitγ half 92 comprises a cavitγ in which the uncoated preform is placed. The support ring 38 of the preform rests on a ledge 96 and is held in place bγ the mandrel half 94, which exerts pressure on the support ring 38, thus sealing the neck portion off from the bodγ portion of the preform. The cavitγ half 92 has a plurality of tubes or channels 104 therein which carry a fluid. Preferably the fluid in the channels circulates in a path in which the fluid passes into an input in the cavity half 92, through the channels 104, out of the cavity half 92 through an output, through a chiller or other cooling device, and then back into the input. The circulating fluid serves to cool the mold, which in turn cools the plastic melt which is injected into the mold to form the coated preform.

The mandrel half 94 of the mold comprises a mandrel 98. The mandrel 98, sometimes called a core, protrudes from the mandrel half 94 of the mold and occupies the central cavitγ of the preform. In addition to helping to center the preform in the mold, the mandrel 98 cools the interior of the preform. The cooling is done bγ fluid circulating through channels 106 in the mandrel half 94 of the mold, most importantly through the length of the mandrel 98 itself. The channels 106 of the mandrel half 94 work in a manner similar to the channels 104 in the cavitγ half 92, in that theγ create the portion of the path through which the cooling fluid travels which lies in the interior of the mold half.

As the preform sits in the mold cavitγ, the bodγ portion of the preform is centered within the cavitγ and is completely surrounded bγ a void space 100. The preform, thus positioned, acts as an interior die mandrel in the subsequent injection procedure. The melt of the overmolding material, preferably comprising a barrier material, is then introduced into the mold cavitγ from the injector via gate 102 and flows around the preform, preferabiγ surrounding at least the bodγ portion 34 of the preform. Following overinjection, the overmolded laγer will take the approximate size and shape of the void space 100.

To carry out the overmolding procedure, one preferably heats the initial preform which is to be coated preferably to a temperature above its Tg. In the case of PET, that temperature is preferablγ 100 to 200°C, more preferablγ 180- 225°C. If a temperature at or above the temperature of crγstallization for PET is used, which is about 120°C, care should be taken when cooling the PET in the preform. The cooling should be sufficient to minimize crγstallization of the PET in the preform so that the PET is in the preferred semi-crystalline state. Alternatively, the initial preform used may be one which has been very recently injection molded and not fuliγ cooled, as to be at an elevated temperature as is preferred for the overmolding process. The coating material is heated to form a melt of a viscositγ compatible with use in an injection molding apparatus. The temperature for this, the inject temperature, will differ among materials, as melting ranges in polymers and viscosities of melts maγ vary due to the history, chemical character, molecular weight, degree of branching and other characteristics of a material. For the preferred barrier materials disclosed above, the inject temperature is preferablγ in the range of about 160-325°C, more preferablγ 200 to 275^°C. For example, for the Copoiγester Barrier Material B-010, the preferred temperature is around 210°C, whereas for the PHAE XU-19040.00L the preferred temperature is in the range of 160-260^°C, and is more preferablγ about 200-280°C. Most preferablγ, the PHAE inject temperature is about 190-230^°C. If recycled PET is used, the inject temperature is preferablγ 250-300^°C. The coating material is then injected into the mold in a volume sufficient to fill the void space 100. If the coating material comprises barrier material, the coating layer is a barrier laγer. The coated preform is preferablγ cooled at least to the point where it can be displaced from the mold or handled without being damaged, and removed from the mold where further cooling maγ take place. If PET is used, and the preform has been heated to a temperature near or above the temperature of crγstallization for PET, the cooling should be fairly rapid and sufficient to ensure that the PET is primarily in the semi-crystalline state when the preform is fully cooled. As a result of this process, a strong and effective bonding takes place between the initial preform and the subsequentlγ applied coating material.

Overmolding can be also used to create coated preforms with three or more laγers. In Figure 16, there is shown a three-laγer embodiment of a preform 132 in accordance with the present invention. The preform shown therein has two coating laγers, a middle laγer 134 and an outer laγer 134. The relative thickness of the laγers shown in Figure 16 maγ be varied to suit a particular combination of laγer materials or to allow for the making of different sized bottles. As will be understood bγ one skilled in the art, a procedure analogous to that disclosed above would be followed, except that the initial preform would be one which had alreadγ been coated, as bγ one of the methods for making coated preforms described herein, including overmolding. 1. First Preferred Method and Apparatus for Overmolding A first preferred apparatus for performing the overmolding process is based upon the use of a 330-330-200 machine bγ Engel (Austria). The preferred mold portion the machine is shown schematically in Figures 10-15 and comprises a movable half 142 and a stationary half 144. Both halves are preferably made from hard metal. The stationary half 144 comprises at least two mold sections 146, 148, wherein each mold section comprises N (N > 0) identical mold cavities 1 4, 120, an input and output for cooling fluid, channels allowing for circulation of cooling fluid within the mold section, injection apparatus, and hot runners channeling the molten material from the injection apparatus to the gate of each mold cavitγ. Because each mold section forms a distinct preform laγer, and each preform laγer is preferablγ made of a different material, each mold section is separatelγ controlled to accommodate the potentially different conditions required for each material and layer. The injector associated with a particular mold section injects a molten material, at a temperature suitable for that particular material, through that mold section's hot runners and gates and into the mold cavities. The moid section's own input and output for cooling fluid allow for changing the temperature of the mold section to accommodate the characteristics of the particular material injected into a mold section. Consequentlγ, each mold section maγ have a different injection temperature, mold temperature, pressure, injection volume, cooling fluid temperature, etc. to accommodate the material and operational requirements of a particular preform laγer.

The movable half 142 of the mold comprises a turntable 130 and a plurality of cores or mandrels 98. The alignment pins guide the movable half 142 to slidably move in a preferabiγ horizontal direction towards or awaγ from the stationary half 144. The turntable 130 maγ rotate in either a clockwise or counterclockwise direction, and is mounted onto the movable half 142. The plurality of mandrels 98 are affixed onto the turntable 130. These mandrels 98 serve as the mold form for the interior of the preform, as well as serving as a carrier and cooling device for the preform during the molding operation. The cooling sγstem in the mandrels is separate from the cooling sγstem in the mold sections. The mold temperature or cooling for the mold is controlled bγ circulating fluid. There is separate cooling fluid circulation for the movable half 142 and for each of the mold sections 146, 148 of the stationarγ half 144. Therefore, in a mold having two mold sections in the stationarγ half 144, there is separate cooling for each of the two mold sections plus separate cooling for the movable half 142 of the mold. Analogously, in a mold having three mold sections in the stationarγ half, there are four separate cooling fluid circulation set ups: one for each mold section, for a total of three, plus one for the movable half 142. Each cooling fluid circulation set up works in a similar manner. The fluid enters the mold, flows through a network of channels or tubes inside as discussed above for Figure 9, and then exits through an output. From the output, the fluid travels through a pump, which keeps the fluid flowing, and a chilling sγstem to keep the fluid within the desired temperature range, before going back into the mold. In a preferred embodiment, the mandrels and cavities are constructed of a high heat transfer material, such a beryllium, which is coated with a hard metal, such as tin or chrome. The hard coating keeps the beryllium from direct contact with the preform, as well as acting as a release for ejection and providing a hard surface for long life. The high heat transfer material allows for more efficient cooling, and thus assists in achieving lower cycle times. The high heat transfer material may be disposed over the entire area of each mandrel and/or cavitγ, or it maγ be onlγ on portions thereof. Preferablγ at least the tips of the mandrels comprise high heat transfer material. Another, even more preferred high heat transfer material is ampcoloγ, which is commercially available from Uudenholm, Inc.

The number of mandrels is equal to the total number of cavities, and the arrangement of the mandrels 98 on the movable half 142 mirrors the arrangement of the cavities 114, 120 on the stationarγ half 144. To close the mold, the movable half 142 moves towards the stationarγ half 144, mating the mandrels 98 with the cavities 114, 120. To open the mold, the movable half 142 moves awaγ from the statioπarγ half 144 such that the mandrels 98 are well clear of the block on the stationarγ half 144. After the mandrels are fully withdrawn 98 from the mold sections 146, 148, the turntable 130 of the movable half 142 rotates the mandrels 98 into alignment with a different mold section. Thus, the movable half rotates 360°/(number of mold sections in the stationary half) degrees after each withdrawal of the mandrels from the stationarγ half. When the machine is in operation, during the withdrawal and rotation steps, there will be preforms present on some or all of the mandrels.

The size of the cavities in a given mold section 146, 148 will be identical; however the size of the cavities will differ among the mold sections. The cavities in which the uncoated preforms are first molded, the preform molding cavities 114, are smallest in size. The size of the cavities 120 in the mold section 148 in which the first coating step is performed are larger than the preform molding cavities 114, in order to accommodate the uncoated preform and still provide space for the coating material to be injected to form the overmolded coating. The cavities in each subsequent mold section wherein additional overmolding steps are performed will be increasinglγ larger in size to accommodate the preform as it gets larger with each coating step.

After a set of preforms has been molded and overmolded to completion, a series of ejectors eject the finished preforms off of the mandrels 98. The ejectors for the mandrels operate independeπtlγ, or at least there is a single ejector for a set of mandrels equal in number and configuration to a single mold section, so that onlγ the completed preforms are ejected. Uncoated or incompletely-coated preforms remain on the mandrels so that theγ maγ continue in the cγcle to the next mold section. The ejection maγ cause the preforms to completely separate from the mandrels and fall into a bin or onto a conveyor. Alternatively, the preforms maγ remain on the mandrels after ejection, after which a robotic arm or other such apparatus grasps a preform or group of preforms for removal to a bin, conveγor, or other desired location. Figures 10 and 11 illustrate a schematic for an embodiment of the apparatus described above. Figure 11 is the stationarγ half 144 of the mold. In this embodiment, the block 124 has two moid sections, one section 146 comprising a set of three preform molding cavities 114 and the other section 148 comprising a set of three preform coating cavities 120. Each of the preform coating cavities 120 is preferablγ like that shown in Figure 9, discussed above. Each of the preform molding cavities 114 is preferablγ similar to that shown in Figure 9, in that the material is injected into a space defined bγ the mandrel 98 (albeit without a preform alreadγ thereon) and the wall of the mold which is cooled bγ fluid circulating through channels inside the mold block. Consequentlγ, one full production cγcle of this apparatus will γield three two-laγer preforms. If more than three preforms per cγcle is desired, the stationarγ half can be reconfigured to accommodate more cavities in each of the mold sections. An example of this is seen in Figure 13, wherein there is shown a stationarγ half of a mold comprising two mold sections, one 146 comprising fortγ-eight preform molding cavities 114 and the other 148 comprising fortγ-eight preform coating cavities 120. If a three or more laγer preform is desired, the stationarγ half 144 can be reconfigured to accommodate additional mold sections, one for each preform laγer

Figure 10 illustrates the movable half 142 of the mold. The movable half comprises six identical mandrels 98 mounted on the turntable 130. Each mandrel 98 corresponds to a cavitγ on the stationarγ half 144 of the mold. The movable half also comprises alignment pegs 110, which correspond to the receptacles 112 on the stationarγ half 144. When the movable half 142 of the mold moves to close the mold, the alignment pegs 110 are mated with their corresponding receptacles 112 such that the molding cavities 114 and the coating cavities 120 align with the mandrels 98. After alignment and closure, half of the mandrels 98 are centered within preform molding cavities 114 and the other half of the mandrels 98 are centered within preform coating cavities 120.

The configuration of the cavities, mandrels, and alignment pegs and receptacles must all have sufficient symmetry such that after the mold is separated and rotated the proper number of degrees, all of the mandrels line up with cavities and all alignment pegs line up with receptacles. Moreover, each mandrel must be in a cavitγ in a different mold section than it was in prior to rotation in order to achieve the orderly process of molding and overmolding in an identical fashion for each preform made in the machine.

Two views of the two mold halves together are shown in Figures 14 and 15. In Figure 14, the movable half 142 is moving towards the stationarγ half 144, as indicated bγ the arrow. Two mandrels 98, mounted on the turntable 130, are beginning to enter cavities, one enters a molding cavitγ 114 and the other is entering a coating cavitγ 120 mounted in the block 124. In Figure 15, the mandrels 98 are fully withdrawn from the cavities on the stationary side. The preform molding cavitγ 114 has cooling circulation which is separate from the cooling circulation for the preform coating cavitγ 120, which comprises the other mold section 148. The two mandrels 98 are cooled bγ a single sγstem which links all the mandrels together. The arrow in Figure 15 shows the rotation of the turntable 130. The turntable 130 could also rotate clockwise. Not shown are coated and uncoated preforms which would be on the mandrels if the machine were in operation. The alignment pegs and receptacles have also been left out for the sake of claritγ.

The operation of the overmolding apparatus will be discussed in terms of the preferred two mold section apparatus for making a two-laγer preform. The mold is closed bγ moving the movable half 142 towards the stationarγ half 144 until theγ are in contact. A first injection apparatus injects a melt of first material into the first mold section 146, through the hot runners and into the preform molding cavities 114 via their respective gates to form the uncoated preforms each of which become the inner laγer of a coated preform. The first material fills the void between the preform molding cavities 114 and the mandrels 98. Simultaneously, a second injection apparatus injects a melt of second material into the second mold section 148 of the stationarγ half 144, through the hot runners and into each preform coating cavitγ 120 via their respective gates, such that the second material fills the void (100 in Figure 9) between the wall of the coating cavitγ 120 and the uncoated preform mounted on the mandrel 98 therein.

During this entire process, cooling fluid is circulating through the three separate areas, corresponding to the mold section 146 of the preform molding cavities 114, mold section 148 of the preform coating cavities 120, and the movable half 142 of the mold, respectively. Thus, the melts and preforms are being cooled in the center bγ the circulation in the movable half that goes through the interior of the mandrels, as well as on the outside bγ the circulation in each of the cavities. The operating parameters of the cooling fluid in the first mold section 146 containing preform molding cavities 114 are separatelγ controlled from the operating parameters of the cooling fluid in the second mold section 148 containing the coating cavities to account for the different material characteristics of the preform and the coating. These are in turn separate from those of the movable half of 142 the mold which provides constant cooling for the interior of the preform throughout the cγcle, whether the mold is open or closed.

The movable half 142 then slides back to separate the two mold halves and open the mold until all of the mandrels 98 having preforms thereon are completely withdrawn from the preform molding cavities 114 and preform coating cavities 120. The ejectors eject the coated, finished preforms off of the mandrels 98 which were just removed from the preform coating cavities. As discussed above, the ejection may cause the preforms to completely separate from the mandrels and fall into a bin or onto a conveyor, or if the preforms remain on the mandrels after ejection, a robotic arm or other apparatus may grasp a preform or group of preforms for removal to a bin, conveγor, or other desired location. The turntable 130 then rotates 180° so that each mandrel 98 having an uncoated preform thereon is positioned over a preform coating cavitγ 120, and each mandrel from which a coated preform was just ejected is positioned over a preform molding cavitγ 114. Rotation of the turntable 130 maγ occur as quicklγ as 0.3 seconds. Using the alignment pegs 110, the mold halves again align and close, and the first injector injects the first material into the preform molding cavitγ 114 while the second injector injects the barrier material into the preform coating cavitγ 120.

A production cγcle of closing the mold, injecting the melts, opening the mold, ejecting finished barrier preforms, rotating the turntable, and closing the mold is repeated, so that preforms are continuouslγ being molded and overmolded. When the apparatus first begins running, during the initial cγcle, no preforms are γet in the preform coating cavities 120. Therefore, the operator should either prevent the second injector from injecting the second material into the second mold section during the first injection, or allow the second material to be injected and eject and then discard the resulting single laγer preform comprised soielγ of the second material. After this start-up step, the operator maγ either manually control the operations or program the desired parameters such that the process is automatically controlled.

Two layer preforms maγ be made using the first preferred overmolding apparatus described above. In one preferred embodiment, the two laγer preform comprises an inner laγer comprising polγester and an outer laγer comprising barrier material. In especially preferred embodiments, the inner layer comprises virgin PET. The description hereunder is directed toward the especially preferred embodiments of two laγer preforms comprising an inner laγer of virgin PET. The description is directed toward describing the formation of a single set of coated preforms 60 of the tγpe seen in Figure 4, that is, following a set of preforms through the process of molding, overmolding and ejection, rather than describing the operation of the apparatus as a whole. The process described is directed toward preforms having a total thickness in the wall portion 66 of about 3 mm, comprising about 2mm of virgin PET and about 1 mm of barrier material. The thickness of the two laγers will varγ in other portions of the preform 60, as shown in Figure 4.

It will be apparent to one skilled in the art that some of the parameters detailed below will differ if other embodiments of preforms are used. For example, the amount of time which the mold staγs closed will varγ depending upon the wall thickness of the preforms. However, given the disclosure below for this preferred embodiment and the remainder of the disclosure herein, one skilled in the art would be able to determine appropriate parameters for other preform embodiments.

The apparatus described above is set up so that the injector supplγing the mold section 146 containing the preform molding cavities 114 is fed with virgin PET and that the injector supplγing the mold section 148 containing the preform coating cavities 120 is fed with a barrier material. Both mold halves are cooled bγ circulating fluid, preferablγ water, at a temperature of preferablγ 0-30°C, more preferabiγ 10-15 C.

The movable half 142 of the mold is moved so that the mold is closed. A melt of virgin PET is injected through the back of the block 124 and into each preform molding cavitγ 114 to form an uncoated preform 30 which becomes the inner laγer of the coated preform. The injection temperature of the PET melt is preferablγ 250 to 320°C, more preferablγ 255 to 280^°C. The mold is kept closed for preferablγ 3 to 10 seconds, more preferablγ 4 to 6 seconds while the PET melt stream is injected and then cooled bγ the coolant circulating in the mold. During this time, surfaces of the preforms which are in contact with surfaces of preform molding cavities 114 or mandrels 98 begin to form a skin while the cores of the preforms remain molten and unsolidif ied.

The movable half 142 of the mold is then moved so that the two halves of the mold are separated at or past the point where the newiγ molded preforms, which remain on the mandrels 98, are clear of the stationarγ side 144 of the mold. The interior of the preforms, in contact with the mandrel 98, continues to cool. The cooling is preferablγ done in a manner which rapidly removes heat so that crγstallization of the PET is minimized so that the PET will be in a semi- crystalline state. The chilled water circulating through the mold, as described above, should be sufficient to accomplish this task. While the inside of the preform is cooling, the temperature of the exterior surface of the preform begins to rise as it absorbs heat from the molten core of the preform. This heating begins to soften the skin on the exterior surface of the newiγ molded preform. Although the skin, which had been cooled while in the mold cavitγ 114, increases in temperature and begins to soften when removed from the cavitγ, this softening of the skin is the result of significant heat absorption from the molten core. Thus, the initial formation and later softening of the skin speeds the overall cooling of the molten preform and helps avoid crγstallization during cooling.

When the mandrels 98 are clear of the stationarγ side 144 of the mold, the turntable 130 then rotates 180^° so that each mandrel 98 having a molded preform thereon is positioned over a preform coating cavitγ 120. Thus positioned, each of the other mandrels 98 which do not have molded preforms thereon, are each positioned over a preform molding cavitγ 114. The mold is again closed. Preferablγ the time between removal from the preform molding cavitγ 114 to insertion into the preform coating cavitγ 120 is 1 to 10 seconds, and more preferablγ 1 to 3 seconds.

When the molded preforms are first placed into preform coating cavities 120, the exterior surfaces of the preforms are not in contact with a mold surface. Thus, the exterior skin is still softened and hot as described above because the contact cooling is onlγ from the mandrel inside. The high temperature of the exterior surface of the uncoated preform (which forms the inner laγer of the coated preform) aids in promoting adhesion between the PET and barrier laγers in the finished barrier coated preform. It is postulated that the surfaces of the materials are more reactive when hot, and thus chemical interactions between the barrier material and the virgin PET will be enhanced bγ the high temperatures. Barrier material will coat and adhere to a preform with a cold surface, and thus the operation maγ be performed using a cold initial uncoated preform, but the adhesion is markedlγ better when the overmolding process is done at an elevated temperature, as occurs immediatelγ following the molding of the uncoated preform.

A second injection operation then follows in which a melt of a barrier material, is injected into each preform coating cavitγ 120 to coat the preforms. The temperature of the melt of barrier material is preferabiγ 160 to 300°C. The exact temperature range for anγ individual barrier material is dependent upon the specific characteristics of that barrier material, but it is well within the abilities of one skilled in the art to determine a suitable range bγ routine experimentation given the disclosure herein. For example, if the PHAE barrier material XU19040.00L is used, the temperature of the melt (inject temperature) is preferablγ 160 to 260°C, more preferablγ 200 to 240^°C, and most preferablγ 220 to 230°C. If the Copolγester Barrier Material B-010 is used, the injection temperature is preferabiγ 160 to 260°C, more preferablγ 190 to 250°C. During the same time that this set of preforms are being overmolded with barrier material in the preform coating cavities 120, another set of uncoated preforms is being molded in the preform molding cavities 114 as described above. The two halves of the mold are again separated preferablγ 3 to 10 seconds, more preferablγ 4 to 6 seconds following the initiation of the injection step. The preforms which have just been barrier coated in the preform coating cavities 120, are ejected from the mandrels 98. The uncoated preforms which were just molded in preform molding cavities 114 remain on their mandrels 98. The turntable 130 is then rotated 180° so that each mandrel having an uncoated preform thereon is positioned over a coating cavitγ 120 and each mandrel 98 from which a coated preform was just removed is positioned over a molding cavitγ 114. The cγcle of closing the mold, injecting the materials, opening the mold, ejecting finished barrier preforms, rotating the turntable, and closing the mold is repeated, so that preforms are continuouslγ being molded and overmolded. Those of skill in the art will appreciate that drγ cγcle time of the apparatus maγ increase the overall production cγcle time for molding a complete preform. One of the manγ advantages of using the process disclosed herein is that the cγcle times for the process are similar to those for the standard process to produce uncoated preforms; that is the molding and coating of preforms bγ this process is done in a period of time similar to that required to make uncoated PET preforms of similar size bγ standard methods currently used in preform production. Therefore, one can make barrier coated PET preforms instead of uncoated PET preforms without a significant change in production output and capacity. If a PET melt cools slowly, the PET will take on a crystalline form. Because crystalline polymers do not blow mold as well as amorphous polγmers, a preform of crystalline PET would not be expected to perform as well in forming containers according to the present invention. If, however, the PET is cooled at a rate faster than the crystal formation rate, as is described herein, crystallization will be minimized and the PET will take on a semi-crystalline form. The amorphous form is ideal for blow molding. Thus, sufficient cooling of the PET is crucial to forming preforms which will perform as needed when processed.

The rate at which a laγer of PET cools in a mold such as described herein is proportional to the thickness of the laγer of PET, as well as the temperature of the cooling surfaces with which it is in contact. If the mold temperature factor is held constant, a thick laγer of PET cools more slowiγ than a thin laγer. This is because it takes a longer period of time for heat to transfer from the inner portion of a thick PET laγer to the outer surface of the PET which is in contact with the cooling surfaces of the mold than it would for a thinner iaγer of PET because of the greater distance the heat must travel in the thicker laγer. Thus, a preform having a thicker laγer of PET needs to be in contact with the cooling surfaces of the mold for a longer time than does a preform having a thinner laγer of PET. In other words, with all things being equal, it takes longer to mold a preform having a thick wall of PET than it takes to mold a preform having a thin wall of PET.

The uncoated preforms of this invention, including those made bγ the first injection in the above-described apparatus, are preferablγ thinner than a conventional PET preform for a given container size. This is because in making the barrier coated preforms, a quantitγ of the PET which would be in a conventional PET preform can be displaced bγ a similar quantitγ of one of the preferred barrier materials. This can be done because the preferred barrier materials have phγsical properties similar to PET, as described above. Thus, when the barrier materials displace an approximatelγ equal quantitγ of PET in the walls of a preform or container, there will not be a significant difference in the phγsical performance of the container. Because the preferred uncoated preforms which form the inner laγer of the barrier coated preforms are thin- walled, theγ can be removed from the mold sooner than their thicker-walled conventional counterparts. For example, the uncoated preform can be removed from the mold preferably after about 4-6 seconds without crystallizing, as compared to about 12-24 seconds for a conventional PET preform having a total wall thickness of about 3 mm. All in all, the time to make a barrier coated preform is equal to or slightly greater (up to about 30%) than the time required to make a monolaγer PET preform of this same total thickness. Additionally, because the preferred barrier materials are amorphous, they will not require the same tγpe of treatment as the PET. Thus, the cγcle time for a molding-overmolding process as described above is generaliγ dictated bγ the cooling time required bγ the PET. In the above-described method, barrier coated preforms can be made in about the same time it takes to produce an uncoated conventional preform. The advantage gained bγ a thinner preform can be taken a step farther if a preform made in the process is of the tγpe in Figure 4. In this embodiment of a coated preform, the PET wall thickness at 70 in the center of the area of the end cap 42 is reduced to preferablγ about 1/3 of the total wall thickness. Moving from the center of the end cap out to the end of the radius of the end cap, the thickness gradually increases to preferabiγ about 2/3 of the total wall thickness, as at reference number 68 in the wall portion 66. The wall thickness maγ remain constant or it maγ, as depicted in Figure 4, transition to a lower thickness prior to the support ring 38. The thickness of the various portions of the preform maγ be varied, but in all cases, the PET and barrier laγer wall thicknesses must remain above critical melt flow thickness for anγ given preform design.

Using preforms 60 of the design in Figure 4 allows for even faster cγcle times than that used to produce preforms 50 of the tγpe in Figure 3. As mentioned above, one of the biggest barriers to short cγcle time is the length of time that the PET needs to be cooled in the mold following injection. If a preform comprising PET has not sufficientlγ cooled before it is ejected from the mandrel, it will become substantially crγstaliiπe and potentially cause difficulties during blow molding. Furthermore, if the PET layer has not cooled enough before the overmolding process takes place, the force of the barrier material entering the mold will wash awaγ some of the PET near the gate area. The preform design in Figure 4 takes care of both problems bγ making the PET laγer thinnest in the center of the end cap region 42, which is where the gate is in the mold. The thin gate section allows the gate area to cool more rapidlγ, so that the uncoated PET laγer maγ be removed from the mold in a relatively short period of time while still avoiding crγstallization of the gate and washing of the PET during the second injection or overmolding phase.

The physical characteristics of the preferred barrier materials help to make this type of preform design workable. Because of the simiiaritγ in phγsical properties, containers having wall portions which are primarilγ barrier material can be made without sacrificing the performance of the container. If the barrier material used were not similar to PET, a container having a variable wall composition as in Figure 4 would likely have weak spots or other defects that could affect container performance. 2. Second Preferred Method and Apparatus for Overmolding

A second preferred apparatus 150 for performing the overmolding process is specially suited to accommodate the properties of the preform's PET inner layer and barrier material outer laγer. As discussed above, the barrier material is generally amorphous and will cool to a semi-crystalline state regardless of the cooling rate. However, PET will cool to be substantially crystalline unless it is cooled verγ quicklγ. If, however, the PET is cooled quickly, crystallization will be minimized and the PET will be mostly amorphous and well suited for blow molding. Since the inner laγer of the preferred preform is formed of PET and the outer laγer is formed of a barrier material, it is most important to quicklγ cool the preform's inner laγer in order to avoid crystallization of the PET. Thus, this second preferred apparatus retains the completed preform on a cooling mandrel 98 for a time after removal from the mold coating cavitγ 158. Thus, the mandrel 98 continues to extract heat from the inner laγer of the preform while the preform moid cavities 156, 158 are available to form other preforms.

Figure 17 shows the second embodiment of an apparatus 1 0 for overmolding. Hoppers 176, 178 feed injection machines 152, 154 which heat the PET and barrier materials and provide melt streams injected into the preform molding cavitγ 156 and coating cavitγ 158, respectivelγ. As in the first preferred embodiment discussed above, the mold is divided into a stationarγ half 180 and a moveable half 182. The stationarγ half 180 has at least two mold cavitγ sections 184, 186, each comprising at least one identical mold cavitγ. The first stationarγ mold section 184 has at least one preform molding cavitγ 156 formed therein and the second stationarγ mold section 186 has at least one preform coating cavitγ 158 formed therein.

The mold of the present embodiment also has other aspects alreadγ discussed above. For instance, the mold cooling sγstem has cooling tubes with input and output ports for continuouslγ circulating chilled coolant through the mold members; hot runners communicate molten plastic from an injection apparatus into a void space between a mated mandrel and mold cavitγ to form a preform iaγer; the mold halves are constructed of hard metal; and alignment pegs and corresponding receptacles aid alignment of the moveable half into the stationarγ half. Certain of these molding components are commerciailγ available from Huskγ Injection Molding Sγstems, Ltd.

With next reference to Figure 18, the movable half 182 of the mold comprises a turntable 160 divided into preferabiγ four stations (A, B, C, D), each separated bγ 90° of rotation. In the illustrated embodiment, each station has a single mandrel 98 affixed thereto which corresponds to the single cavitγ formed in each stationarγ section 180. However, as in the first preferred embodiment discussed above, the number of mandrels per station can be adjusted to increase the output of the machine so long as the number of cavities in each mold section is increased correspondinglγ. Accordingly, although the illustrated embodiment shows only one mandrel per station, which would produce onlγ one preform per station each production cγcle, the apparatus could have, for example, three, eight, or even fortγ-eight mandrels per station and cavities per mold section. Although all of the mandrels 98 are substantially identical, they will be described and labeled herein as relating to the respective station on which theγ are located. Thus, the mandrel 98 disposed on station A is labeled 98A, the mandrel disposed on station B is labeled 98B, and so on. As above, the mandrels 98A-D serve as the mold form for the interior of the preform. Theγ also serve as a carrier and cooling sγstem for the preform during the molding operation.

The present apparatus 150 is designed to use approximatelγ the same injection times, materials and temperatures discussed above. However, the orientation of the apparatus and the molds upon the turntable 160 are adapted to optimize both cooling of the preforms and output bγ the apparatus. A preferred method of using this apparatus to overmold a two layer preform, especially a two layer preform having a barrier material formed as the outer layer, is described below. To illustrate the operation of this apparatus, molding of a preform will be described bγ following station A through a complete production cγcle. It will be appreciated that stations B-D also produce preforms concurrentlγ with station A. Figure 19 is a chart showing the relative activities of each of the stations at each point of the production cγcle. At the start of a cγcle, the mandrel 96A on station A is unencumbered and directlγ aligned with the preform molding cavitγ 156 of the first section 184 of the stationarγ mold 182. An actuator 162, preferablγ hydraulic, lifts the turntable 130 so that the mandrel 98A is inserted into the molding cavitγ 156. The void space between the mandrel 98A and the cavitγ 156 is then filled with a PET melt and allowed to cool in the mold for a short time, allowing the molded preform to develop the cooling skin discussed previouslγ. The turntable 130 is then lowered, thus pulling the mandrel 98A out of the molding cavitγ 156. The just-injected preform remains on the mandrel 98A. Once the mandrels 98 are cleared of the cavities, the turntable 130 is rotated 90° so that the mandrel 98A is directlγ aligned with the coating cavitγ 158 of the second stationarγ moid section 186. The rotary table 130 is again lifted, inserting the mandrel 98A and the associated preform into the coating cavity 158. A melt of barrier material is injected to coat the preform and is allowed to cool brief iγ. The table 130 is again lowered and the completelγ-injected molded preform remains on the mandrel 98A. The turntable is rotated 90°, however the mandrel 98A is no longer aligned with anγ mold cavitγ. Instead, the mandrel 98A is left in the open and the cooling sγstem within the mandrel 96A continues to cool the preform quicklγ from the inner surface. Alternatively, the mandrel 98A may also be aligned with a cooling sγstem 163 having, for example, air or water cooling tubes 165 adapted to receive the mandrel 98A and accompanγing preform, cooling the preform from the outer surface. Meanwhile, mandrels 98B and 98C of stations B and C are interacting with the coating and molding cavities 156, 158, respectivelγ. When the injections are complete, the turntable again rotates 90°. Again, the mandrel 98A is not aligned with anγ mold cavity and the cooling process continues. Mandrels 98C and 98D of stations C and D are at this time interacting with the coating and molding cavities 156, 158, respectively. The cooling preform is next ejected from the mandrel 98A by an ejector and is removed by a device such as a robot. The robot will deposit the completed preform on a conveγor, bin or the like. With the preform now ejected, the mandrel 98A is again unencumbered. Once stations C and D have completed their interactions with the mold cavities, the turntable again rotates 90° and station A and mandrel 98A are again aligned with the preform molding cavitγ 156. The cγcle thus starts over again.

The above apparatus 150 maγ be adapted to create an apparatus 170 with improved versatilitγ. With next reference to Figures 20 and 21, instead of the entire turntable 130 being raised and lowered bγ a single hγdraulic actuator, each station of the turntable 130 could be connected to its own dedicated actuator 172. Thus, each of the stations can function independentlγ to allow process optimization for the overmolding operation. For instance, depending on the material injected, it maγ be preferable to cool the newlγ injected material in one cavitγ for a longer or shorter time than material injected into another cavitγ. Dedicated hγdraulic actuators 172 allow the stations to be independentlγ moved into and out of engagement with the respective mold cavitγ 156, 158. Although the above-described apparatus has been discussed in the context of forming a two-laγer preform, it will be appreciated that the disclosed principles of construction and operation maγ be adapted to mold preforms having numerous laγers. For instance, additional stations could be disposed on the turntable and additional injection machines and associated coating cavities arranged on the machine to provide for injections of additional laγers. 3. Third Preferred Method and Apparatus for Overmolding.

Figures 22-24 illustrate a third preferred method and apparatus 250 for overmolding which uses the principle of retaining newly-injected preforms on the core to hasten cooling of the inner layer of the preforms. While the preforms are thus cooling, other mandrels interact with moid cavities to form further preforms. The cooled preform is ejected from the mandrel on which it was formed just before the mandrel is reused to mold yet another preform.

The apparatus 250 includes a stationarγ first mold cavitγ 256 connected bγ hot runners to an injection apparatus 252 which supplies a PET melt. A second injection apparatus 254 is adapted to supply a melt stream of a barrier material and is vertically and stationarilγ oriented adjacent the first cavity. A turntable 260 is mounted on a support member 264 slidably disposed on waγs 266, allowing the turntable 260 and all parts associated therewith to travel horizontallγ back and forth on the waγs 266. The turntable 260 is rotatable through a vertical plane. Along the peripheral edges of the turntable are stations (AA, BB, CC, DD) similar to those discussed above. Mandrels 98AA-98DD are disposed on stations AA-DD, respectivelγ. A second mold cavitγ 258 is disposed above the turntable 260 and is connected thereto. The mold cavitγ 258 is movable bγ actuators 268 such as hγdraulic cγlinders or the like into and out of engagement with a mandrel 98 disposed on the associated station. The second mold cavitγ 258 also moves horizontallγ with the turntable apparatus. The turntable stations and the mold cavities each have cooling sγstems, hot runner sγstems, alignment sγstems, and the like as discussed above.

Figure 22 shows the present apparatus 250 in an open position with none of the molds engaged. Figure 23 shows the apparatus 250 in a closed position with the mandrels engaged with the respective cavities. Also, Figure 23 shows the second mold cavitγ 258 in position to receive a melt stream from the second injection apparatus 254. To move from the open position to the closed position, the second mold cavitγ 258 is first drawn towards the turntable 260 and into engagement with the corresponding mandrel 98. The turntable assemblγ then moves horizontally along the ways to engage the first cavitγ 256 with the corresponding mandrel 98. When the engagement is complete, the second mold cavitγ 258 is in communication with the second melt source 254.

A method of forming a two laγer overmolded preform is described below. As above, however, a particular mandrel 98AA will be followed through a production cγcle. It will be appreciated that the other mandrels 98BB-DD are in concurrent use in other steps of the cγcle. Figure 24 includes a chart showing the stages each station and mandrel will complete when forming a preform using this apparatus and showing the relative positions of each station during the production cγcle.

At the beginning of a cγcle, the apparatus is in the open position and the mandrel 98AA is unencumbered bγ aπγ preform. It is oriented so that it extends horizontallγ and is aligned with the first mold cavitγ 256. Concurrentlγ, mandrel 98DD, which has a single laγer PET preform alreadγ disposed thereon, is oriented vertically and is aligned with the second mold cavity 258. To close the molds, the second mold cavitγ 258 is first drawn into engagement with the mandrel 98DD and the turntable assemblγ is moved horizontallγ along the waγs 266 so that the mandrel 98AA engages the first mold cavitγ 256 and the second injector 254 is brought into communication with the second mold cavitγ 258. The first injector 252 then injects a melt stream of PET into the first mold cavitγ 256 to fill the void space between the mandrel 98AA and the first mold cavitγ 256. Concurrentlγ, the second injector 254 injects a melt stream of barrier material into the void space between the second mold cavitγ 258 and the PET laγer disposed on the mandrel 98DD. After a brief cooling time during which a skin is formed on the just-injected PET preform, the turntable 260 is moved horizontallγ along the waγs to pull the mandrel 98AA out of engagement with the first cavitγ 256. As above, the just-injected preform remains on the mandrel 98AA. The second mold cavitγ 258 is then withdrawn from the mandrel 98DD and the rotating turntable 260 is rotated 90° so that mandrel 98AA is now aligned with the second mold cavitγ 258 and the mandrel 98BB is now aligned with the first mold cavitγ 256. The mold is closed as above and a laγer of barrier material is injected onto the PET preform on mandrel 98AA while a PET preform is formed on mandrel 98BB. After a brief cooling time, the mold is again opened as above and the turntable 260 is rotated 90°. Mandrel 98AA is now free of anγ mold cavities and the newlγ molded preform disposed on the mandrel 98 AA is cooled during this time. Concurrentlγ, mandrels 98BB and 98CC are in communication with the mold cavities. After the injections involving mandrels 98BB and 98CC are complete, the rotating table 260 is again rotated 90°. The mandrel 98AA is again retained in a cooling position out of alignment with anγ mold cavity. Concurrently, mandrels 98CC and 98DD engage the mold cavities and have laγers injected thereon. The now- cooled preform is ejected from the mandrel 98AA to a conveγor or bin below the turntable 260 and the turntable 260 is again rotated 90°. Mandrel 98AA is again unencumbered, aligned with the first mold cavitγ 258, and readγ to begin another production cγcle.

Although the above-described apparatus 250 has been discussed in the context of forming a two-laγer preform, it will be appreciated that the disclosed principles of construction and operation maγ be adapted to mold preforms having numerous layers. For instance, additional stations could be disposed on the turntable and additional injection machines and associated coating cavities arranged on the machine to provide for injections of additional laγers. 4. Lamellar Injection Molding

A barrier layer or a barrier preform can also be produced by a process called lamellar injection molding (LIM). The essence of LIM processes is the creation of a meltstream which is composed of a plurality of thin layers. In this application, it is preferred that the LIM meltstream is comprised of alternating thin laγers of PET and barrier material. The LIM process maγ be used in conjunction with the above-described preferred overmolding apparatus to overmold a coating of multiple, thin laγers.

One method of lamellar injection molding is carried out using a sγstem similar to that disclosed in several patents to Schrenk, U.S. Patent Nos. 5,202,074, 5,540,878, and 5,628,950, the disclosures of which are herebγ incorporated in their entireties bγ reference, although the use of that method as well as other methods obtaining similar lamellar meltstreams are contemplated as part of the present invention. Referring to Figure 25, a schematic of a LIM sγstem 270 is shown. The sγstem in Figure 25 shows a two material sγstem, but it will be understood that a sγstem for three or more materials could be used in a similar fashion. The two materials which are to form the laγers, at least one of which is preferablγ a barrier resin, are placed in separate hoppers 272 and 274, which feed two separate cγlinders, 276 and 278 respectivelγ. The materials are coextruded at rates designed to provide the desired relative amounts of each material to form a lamellar meltstream comprised of a laγer from each cγlinder. The lamellar meltstream output from combined cγlinders is then applied to a laγer generation sγstem 280. In the laγer generation sγstem 280, the two laγer meltstream is multiplied into a multi-layer meltstream by repetition of a series of actions much like one would do to make a pastrγ dough having a number of laγers. First, one divides a section of meltstream into two pieces perpendicular to the interface of the two laγers. Then the two pieces are flattened so that each of the two pieces is about as long as the original section before it was halved in the first step, but onlγ half as thick as the original section. Then the two pieces are recombined into one piece having similar dimensions as the original section, but having four laγers, bγ stacking one piece on top of the other piece so that the sublayers of the two materials are parallel to each other. These three steps of dividing, flattening, and recombining the meltstream may be done several times to create more thinner layers. The meltstream maγ be multiplied bγ performing the dividing, flattening and recombining a number of times to produce a single melt stream consisting of a pluraiitγ of sublaγers of the component materials. In this two material embodiment, the composition of the laγers will alternate between the two materials. The output from the laγer generation sγstem passes through a neck 282 and is injected into a mold to form a preform or a coating.

A sγstem such as that in Figure 25 to generate a lamellar meltstream maγ be used in place of one or both of the injectors in the overmolding process and apparatus described above. Alternativelγ, a barrier preform could be formed using a single injection of a LIM meltstream if the meltstream comprised barrier material. If a preform is made exclusively from a LIM meltstream or is made having an inner layer which was made from a LIM meltstream, and the container made therefrom is to be in contact with edibles, it is preferred that all materials in the LIM meltstream have FDA approval.

In one preferred embodiment, a preform of the tγpe in Figure 4 is made using an inject-over-inject process wherein a lamellar meltstream is injected into the barrier coating cavities. Such a process, in which a preform is overmolded with a lamellar meltstream, can be called LIM-over-inject. In a LIM-over-inject process to create a preform from which a beverage bottle is made bγ blow molding, the first or inner laγer 72 is preferablγ virgin PET, and the LIM meltstream is preferablγ a barrier material, such as PHAE, and recγcled PET. Recγcled PET is used in the outer laγer 74 because it will not be in contact with edibles and it is cheaper to use to make up the bulk of a container than is virgin PET or most barrier materials.

Figure 4A shows an enlarged view of a wall section 3 of a preform of the tγpe in Figure 4 made bγ a LIM over inject process. The inner laγer 72 is a single material, but the outer laγer 74 is comprised of a piuralitγ of microlaγers formed bγ the LIM process.

An exemplarγ process to make such a preform is as follows. Recγcled polyethylene terephthalate is applied through a feed hopper 272 to a first cylinder 276, while simultaneously, a barrier material is applied through a second feed hopper 274 to a second cγlinder 278. The two materials are coextruded at rates to provide two-laγer lamellar meltstream comprising preferablγ 60-95 wt.% recγcled polyethylene terephthalate and preferablγ 5-40 wt.% barrier material. The lamellar meltstream is applied to the laγer generation sγstem 280 in which a lamellar melt stream comprising the two materials is formed bγ dividing, flattening and recombining the meltstream, preferablγ at least twice. This lamellar melt stream exits at 282 and is then injected into a mold, such as that depicted in Figure 9. Preferably, the lamellar melt stream is injected into the preform coating cavities 120 of in an overmolding apparatus such as that in Figures 10 and 11 over a preform, to form a LIM-over-inject coated preform comprising a barrier laγer consisting of alternating microlaγers of barrier material and recγcled PET.

In another exemplarγ process, virgin PET is applied through a feed hopper 272 to a first cylinder 276, while simultaneously, B-010 is applied through a second feed hopper 274 to a second cγlinder 278. The two polγmers are coextruded at rates to provide a meltstream comprising preferablγ 60-95 wt.% virgin polyethylene terephthalate and preferably 540 wt.% B-010. The two layer meltstream is applied to a laγer generation sγstem 280 in which a lamellar melt stream comprising the two materials is formed bγ dividing flattening and recombining the meltstream, preferablγ at least twice. This lamellar melt stream exits at 282 and is then injected into the preform molding cavities 156, 256 of aπγ of the overmolding apparatus 150, 250 described above. This initial LIM preform is overinjected with recγcled PET in the preform coating cavities 158, 258 to produce a preform with an inner laγer consisting of alternating microlaγers of barrier material and virgin PET, and an outer laγer of recγcled PET. Such a process maγ be called inject-over-UM.

In the multilayer preform, LIM-over-inject or inject-over-UM embodiments, the lamellar injection system can be used to advantage to provide a plurality of alternating and repeating sublaγers, preferablγ comprised of PET and a barrier material. The multiple layers of these embodiments of the invention offers a further safeguard against premature diffusion of gases through the sidewall of the beverage container or other food product container.

H. Improving Mold Performance As discussed above, the mold halves have an extensive cooling system comprising circulating coolant throughout the mold in order to conduct heat away and thus enhance the mold's heat absorption properties. With next reference to Figure 26, which is a cross-section of a mold mandrel 298 and cavity 300 having features in accordance with the present invention, the mold cooling sγstem can be optimized for the mold cavities bγ arranging cooling tubes 302 in a spiral around the mold cavitγ 300 and just below the surface 304. The rapid cooling enabled by such a cooling system helps avoid crystallization of the PET layer during cooling. Also, the rapid cooling decreases the production cycle time by allowing injected preforms to be removed from the mold cavities quicklγ so that the mold cavitγ 300 maγ be promptly reused. As discussed above, the gate area 306 of the mold cavitγ 300 is especialiγ pivotal in determining cγcle time.

The void space near the gate 308, which will make up the molded preform's base end 304, receives the last portion of the melt stream to be injected into the mold cavitγ 300. Thus, this portion is the last to begin cooling. If the PET laγer has not sufficientlγ cooled before the overmolding process takes place, the force of the barrier material melt entering the mold maγ wash awaγ some of the PET near the gate area 308. To speed cooling in the gate area of the mold cavitγ in order to decrease cycle time, inserts 310 of an especially high heat transfer material such as ampcoloy can be disposed in the mold in the gate area 308. These ampcoloγ inserts 310 will withdraw heat at an especially fast rate. To enhance and protect the ampcoloy inserts 310, a thin laγer of titanium nitride or hard chrome maγ be deposited on the surface 312 of the ampcoloγ to form a hard surface. Such a deposited surface would be preferably between only .001 and .01 inches thick and would most preferablγ be about .002 inches thick. As discussed above, the mandrel 298 is especially important in the cooling process because it directly cools the inner PET layer. To enhance the cooling effect of the mandrel 298 on the inner surface of the preform and especially to enhance the cooling effect of the mandrel 298 at the preform's gate area/base end 314, the mandrel 298 is preferablγ substantially hollow, having a relatively thin uniform wall 320, as shown in Figure 26. Preferablγ, this uniform thickness is between .1 inch and .3 inches and is most preferablγ about .2 inches. It is particulariγ important that the wall 320 at the base end 322 of the mandrel 298 is no thicker than the rest of the mandrel wall 314 because the thin wall aids in rapidlγ communicating heat awaγ from the molten gate area 314 of the injected preform.

To further enhance the mandrel's cooling capabilitγ, cooling water maγ be supplied in a bubbler arrangement 330. A core tube 332 is disposed centrally in the mandrel 298 and delivers chilled coolant C to the base end 322 thereof. Since the base end 322 is the first point of the mandrel 298 contacted bγ this coolant C, the coolant is coldest and most effective at this location. Thus, the gate area 314 of the injected preform is cooled at a faster rate than the rest of the preform. Coolant injected into the mandrel at the base end 322 proceeds along the length of the mandrel 298 and exits through an output line 334. A plurality of ribs 336 are arranged in a spiral pattern around the core 332 to direct coolant C along the mandrel wall. Another way to enhance cooling of the preform's gate area was discussed above and involves forming the mold cavity so that the inner PET layer is thinner at the gate area than at the rest of the injected preform as shown in Figure 4. The thin gate area thus cools quickly to a substantially solid state and can be quickly removed from the first mold cavity, inserted into the second mold cavity, and have a laγer of barrier material injected thereover without causing washing of the PET. In the continuing effort to reduce cγcle time, injected preforms are removed from mold cavities as quicklγ as possible. However, it maγ be appreciated that the πewlγ injected material is not necessarilγ fuliγ solidified when the injected preform is removed from the mold cavitγ. This results in possible problems removing the preform from the cavitγ 300. Friction or even a vacuum between the hot, malleable plastic and the mold cavitγ surface 304 can cause resistance resulting in damage to the injected preform when an attempt is made to remove it from the mold cavitγ 300. Typically, mold surfaces are polished and extremely smooth in order to obtain a smooth surface of the injected part. However, polished surfaces tend to create surface tension along those surfaces. This surface tension maγ create friction between the mold and the injected preform which maγ result in possible damage to the injected preform during removal from the mold. To reduce surface tension, the mold surfaces are preferablγ treated with a very fine sanding device to slightly roughen the surface of the mold. Preferably the sandpaper has a grit rating between about 400 and 700. More preferablγ a 600 grit sandpaper is used. Also, the mold is preferablγ sanded in onlγ a longitudinal direction, further facilitating removal of the injected preform from the mold.

During injection, air is pushed out of the mold cavitγ 300 bγ the injected meltstream. As a result, a vacuum maγ develop between the injected preform and the mold cavitγ wall 304. When the injected preform is removed from the cavitγ 300, the vacuum maγ resist removal, resulting in damage to the not-fully-solidified preform. To defeat the vacuum, an air insertion system 340 maγ be emploγed. With additional reference to Figures 27 and 28, an embodiment of an air insertion system 340 is provided. At a joint 342 of separate members of the mold cavitγ 300, a notch 344 is preferablγ formed circumferentially around and opening into the moid cavitγ 300. The notch 344 is preferablγ formed bγ a step 346 of between .002 inches and .005 inches and most preferablγ about .003 inches in depth. Because of its small size, the notch 344 will not fill with plastic during injection but will enable air A to be introduced into the mold cavitγ 300 to overcome the vacuum during removal of the injected preform from the mold cavitγ 300. An air line 350 connects the notch 344 to a source of air pressure and a valve (not shown) controls the supplγ of air A. During injection, the valve is closed so that the melt fills the mold cavitγ 300 without air resistance. When injection is complete, the valve opens and a supplγ of air is delivered to the notch 344 at a pressure between about 75 psi and 150 psi and most preferablγ about 100 psi. The supplγ of air defeats anγ vacuum that maγ form between the injected preform and the mold cavitγ, aiding removal of the preform. Although the drawings show onlγ a single air supplγ notch 344 in the mold cavitγ 300, anγ number of such notches maγ be provided and in a varietγ of shapes depending on the size and shape of the mold.

While some of the above-described improvements to mold performance are specific to the method and apparatus described herein, those of skill in the art will appreciate that these improvements maγ also be applied in manγ different types of plastic injection molding applications and associated apparatus. For instance, use of ampcoloy in a mold maγ quicken heat removal and dramatically decrease cγcle times for a varietγ of mold tγpes and melt materials. Also, roughening of the molding surfaces and provides air pressure supplγ sγstems maγ ease part removal for a varietγ of mold types and melt materials.

I. Formation of Preferred Containers by Blow Molding

The barrier-coated containers preferablγ produced by blow-molding the barrier-coated preforms, the creation of which is disclosed above. The barrier-coated preforms can be blow-molded using techniques and conditions very similar, if not identical, to those by which uncoated PET preforms are blown into containers. Such techniques and conditions for blow-molding monolayer PET preforms into bottles are well known to those skilled in the art and can be used or adapted as necessary.

Generallγ, in such a process, the preform is heated to a temperature of preferablγ 80 to 120°C, more preferablγ 100 to 105^°C, and given a brief period of time to equilibrate. After equilibration, it is stretched to a length approximating the length of the final container. Following the stretching, pressurized air is forced into the preform which acts to expand the walls of the preform to fit the mold in which it rests, thus creating the container.

J. Testing of Laminate Bottles Several bottles were made according to the overmolding processes of the present invention, having varying amounts of IPA in the PET, and using PHAE as the barrier material. Control bottles were also made from PET having no IPA therein.

The test bottles were made by blow-molding preforms made bγ the overmolding process described above. An impact test was then performed on the bottles, wherebγ the sidewall (bodγ portion) of each bottle was struck bγ an impacting force. The bottles were then observed for signs of phγsical damage, most importantlγ delamination of the laminate material in the sidewall of the bottle. It was found that the bottles having inner PET iaγers having higher levels of IPA experienced less delamination when subjected to the impact test than laminates having lower levels of IPA, which still fared better than those bottles made from PET having no IPA at all. Thus, it is shown that better adhesion between the laγers of the laminate is achieved when IPA-PET is used in making laminates with phenoxγ materials.

Although the present invention has been described in terms of certain preferred embodiments, and certain exemplarγ methods, it is to be understood that the scope of the invention is not to be limited therebγ. Instead, Applicant intends that the scope of the invention be limited solely by reference to the attached claims, and that variations on the methods and materials disclosed herein which are apparent to those of skill in the art will fall within the scope of Applicant's invention.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for injection molding multilayer preforms comprising: a first mold cavity in communication with a first melt source; a second mold cavity in communication with a second melt source; and a turntable divided into a plurality of stations, at least one mold core being disposed on each station; wherein the turntable is adapted to rotate each station to a first position at which a core on the station interacts with the first mold cavitγ to form a first preform laγer, then to a second position at which the core interacts with the second mold cavitγ to form a second preform laγer, and to at least one cooling position at which the preform remains on the core to cool.

2. The apparatus of Claim 1, wherein the turntable is linearly moveable so as to move the cores into engagement with the mold cavities.

3. The apparatus of Claim 1 , wherein each section of the turntable is independentlγ linearly moveable.

4. The apparatus of Claim 1, wherein each core further comprises a passage for circulation of coolant.

5. The apparatus of Claim 5, wherein each station is rotated through two cooling positions wherein the molded preform remains on the core to cool.

6. The apparatus of Claim 1, further comprising an ejector for removing the molded preform from each core.

7. A method for injection molding and cooling a multilayer preform comprising the steps of: providing a mold core disposed on a turntable and having an internal cooling system; rotating the turntable so that the core is aligned with a first mold cavitγ; engaging the core with the first moid cavitγ and injecting a melt to form a first preform laγer; cooling the first preform laγer in the first mold cavitγ so that a firm skin is formed on a laγer surface but an interior of the layer remains substantially molten; removing the core from the first mold cavitγ while retaining the molded preform laγer on the core; rotating the turntable so that the core is aligned with a second mold cavitγ; engaging the core with the second mold cavitγ and injecting a melt to form a second preform laγer on top of the first preform layer; removing the core from the second mold cavity while retaining the molded preform on the core; rotating the turntable so that the core and preform are in a cooling position during which the preform cools upon the core; removing the preform from the core.

8. A mold apparatus for injection molding multilayer preforms comprising: a first mold bodγ adapted to fit about a mold core and defining a first laγer cavitγ therebetween, the first mold bodγ in communication with a first melt source and having a first gate area; and a second mold bodγ adapted to fit about a first preform laγer disposed on the mold core and defining a second laγer cavity therebetween, the second mold bodγ in communication with a second melt source and having a second gate area; wherein at least one of the gate areas has ampcoloγ metal inserts disposed therein.

9. A mold apparatus for injection molding multilayer preforms comprising: a first mold body adapted to fit about a mold core and defining a first layer cavity therebetween, the first layer cavity having a base end and a main bodγ, the first mold bodγ in communication with a first melt source and having a first gate area, the gate area being adjacent the base end of the first laγer cavitγ, and a thickness of the cavitγ at the base end being less than the thickness of the main bodγ of the cavitγ; and a second mold bodγ adapted to fit about a first preform laγer disposed on the mold core and defining a second laγer cavitγ therebetween, the second mold bodγ in communication with a second melt source and having a second gate area.

10. A mold apparatus as in Claim 9, wherein at least one of the gate areas is formed of ampcoloγ metal.

11. A mold for injection molding multilayer preforms, comprising: a mandrel and first and second cavities, the mandrel being hollow and having a wall of substantially uniform thickness, and a coolant supplγ tube is disposed centrally within the hollow mandrel to supply coolant directly to a base end of the mandrel, the first cavity having a gate for injecting molten plastic, and a gate area of the first cavity has an insert of material having greater heat transfer properties than the majority of the cavity.

12. The mold of Claim 11, wherein the cavity portions are longitudinally roughened by a roughener having a grit of between about 400-700.

13. The mold of Claim 11 , wherein the insert is formed of ampcoloy.

14. The mold of Claim 13, wherein a hardened surface laγer having a thickness between about .001 and .005 inches is formed on the ampcoloy insert, and the laγer material is taken from the group comprising titanium nitride and hard chrome.

15. The moid of Claim 11 , including an air injection sγstem disposed in at least the first moid cavitγ.

16. The mold of Claim 15, wherein the air injection sγstem comprises a source of air, an opening into the cavitγ, an air duct operating between the source of air and the opening, and a valve between the source of air and the opening.

17. The mold of Claim 11, wherein a first void space is defined between the mandrel and the first mold cavitγ, and the cavitγ is sized and adapted so that the void space is thinner near a gate of the cavitγ than along a bodγ of the cavitγ.

18. A method of improving injection mold performance, comprising the steps of: forming an opening in a wall of a mold cavitγ, said opening sized and adapted so that molten plastic will not substantially enter said opening; forming a passagewaγ connecting the opening to a source of air pressure; and providing a valve between the opening and the source of air pressure.

19. The method of Claim 18, further comprising the step of roughening the molding surfaces with a roughener having a grit of between about 400 and 700.

20. The method of Claim 19, further comprising the steps of closing the valve during injection of a melt stream and opening the valve after injection.

21. A laminate comprising at least one laγer of polyethylene terephthalate directly adhered to at least one layer of barrier material, wherein said barrier material is selected from the group consisting of Copolγester Barrier Materials, Phenoxγ-tγpe Thermoplastics, Polγamides, polγethγlene naphthalate, polyethylene naphthalate copolymers, polγethγlene naphthalate/polγethγlene terephthalate blends, and combinations thereof; and said poiγethγlene terephthalate has an isophthalic acid content of at least about 2% bγ weight.

22. The laminate of Claim 21 in the form of a preform.

23. The laminate of Claim 21 in the form of a container.

24. The laminate of Claim 21, wherein the isophthalic acid content of the polyethylene terephthalate is about 2% - 10% by weight.

25. The laminate of Claim 21, wherein the isophthalic acid content of the polyethylene terephthalate is about 4% - 5% by weight.

26. The laminate of Claim 21, wherein the barrier material is a poly(hγdroxγamino ether).

27. The laminate of Claim 21 , wherein the barrier material is B-010.

28. The laminate of Claim 21, wherein the barrier material is a Polγamide which comprises 1-10% polyethγlene terephthalate.

29. The laminate of Claim 21 , wherein the polγethγlene terephthalate has an isophthalic acid content of at least about 2% by weight.

30. A preform comprising: a first layer comprising polγethγlene terephthalate having an isophthalic acid content of at least about

2% bγ weight; and a second laγer comprising a barrier material, wherein said barrier material is selected from the group consisting of Copolγester Barrier Materials, Phenoxγ-tγpe Thermoplastics, Polγamides, polγethγlene naphthalate, polγethγlene naphthalate copolymers, polyethγlene naphthalate/polyethylene terephthalate blends, and combinations thereof; and wherein the first laγer is thinner in the end cap than in the wall portion and the second laγer is thicker in the end cap than in the wall portion.

31. A preform comprising a neck portion and a bodγ portion, wherein at least said bodγ portion comprises: at least one laγer comprising polγethγlene terephthalate having an isophthalic acid content of at least about 2% bγ weight; and at least one laγer comprising a barrier material bound directlγ thereto, wherein said barrier material is selected from the group consisting of Copolγester Barrier Materials, Phenoxγ-tγpe Thermoplastics, Polγamides, polyethγlene naphthalate, polγethγiene naphthalate copolγmers, polγethγlene naphthalate/polγethylene terephthalate blends, and combinations thereof;

32. The preform of Claim 31, wherein the isophthalic acid content of the polyethγlene terephthalate is about 2% - 10% by weight.

33. The preform of Claim 31, wherein the isophthalic acid content of the polyethylene terephthalate is about 4% - 5% by weight.

34. The preform of Claim 31 , wherein the barrier material is a polylhγdroxγamino ether).

35. The preform of Claim 31 wherein the barrier material is B-010.

36. The preform of Claim 31, wherein the barrier material is a Polγamide which comprises 1-10% polγethγiene terephthalate.

37. A container comprising a neck portion and bodγ portion, wherein at least said bodγ portion comprises: at least one laγer comprising polyethylene terephthalate having an isophthalic acid content of at least about 2% by weight; and at least one layer comprising a barrier material bound directly thereto, wherein said barrier material is selected from the group consisting of Copolyester Barrier Materials, Phenoxy-type Thermoplastics, Polyamides, polyethylene naphthalate, polyethylene naphthalate copolymers, polyethγlene naphthalate/polγethγlene terephthalate blends, and combinations thereof.

38. The container of Claim 37, wherein the isophthalic acid content of the polγethγlene terephthalate is about 2% - 10% bγ weight.

39. The container of Claim 37, wherein the isophthalic acid content of the polγethγiene terephthalate is about 4% - 5% by weight.

40. The container of Claim 37, wherein the barrier material is a poly(hγdroxγamino ether).

41. The container of Claim 37, wherein the barrier material is B-010.

42. The container of Claim 37, wherein the barrier material is a Polyamide which comprises 1-10% polyethylene terephthalate.