WO2002081172A1 - Injection molding of multi-layer plastic articles - Google Patents

Injection molding of multi-layer plastic articles Download PDF

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Publication number
WO2002081172A1
WO2002081172A1 PCT/IB2001/002015 IB0102015W WO02081172A1 WO 2002081172 A1 WO2002081172 A1 WO 2002081172A1 IB 0102015 W IB0102015 W IB 0102015W WO 02081172 A1 WO02081172 A1 WO 02081172A1
Authority
WO
WIPO (PCT)
Prior art keywords
flow
layer
interior
streams
core
Prior art date
Application number
PCT/IB2001/002015
Other languages
French (fr)
Inventor
Paul Swenson
Original Assignee
Kortec Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kortec Inc. filed Critical Kortec Inc.
Priority to ES01976570.0T priority Critical patent/ES2618804T3/en
Priority to BR0116965-3A priority patent/BR0116965A/en
Priority to JP2002579191A priority patent/JP4283541B2/en
Priority to KR10-2003-7013113A priority patent/KR20030090718A/en
Priority to MXPA03009128A priority patent/MXPA03009128A/en
Priority to EP01976570.0A priority patent/EP1412156B1/en
Priority to CA2442888A priority patent/CA2442888C/en
Publication of WO2002081172A1 publication Critical patent/WO2002081172A1/en
Priority to HK04110160.9A priority patent/HK1067096A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1603Multi-way nozzles specially adapted therefor
    • B29C45/1607Multi-way nozzles specially adapted therefor having at least three different ways
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1642Making multilayered or multicoloured articles having a "sandwich" structure
    • B29C45/1643Making multilayered or multicoloured articles having a "sandwich" structure from at least three different materials or with at least four layers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1642Making multilayered or multicoloured articles having a "sandwich" structure
    • B29C45/1646Injecting parison-like articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1642Making multilayered or multicoloured articles having a "sandwich" structure
    • B29C45/1646Injecting parison-like articles
    • B29C2045/1648Injecting parison-like articles the parison core layer being a barrier material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16Making multilayered or multicoloured articles
    • B29C45/1642Making multilayered or multicoloured articles having a "sandwich" structure
    • B29C45/1646Injecting parison-like articles
    • B29C2045/165Injecting parison-like articles the parison core layer comprising recycled or scrap material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3008Preforms or parisons made of several components at neck portion
    • B29C2949/3009Preforms or parisons made of several components at neck portion partially
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3012Preforms or parisons made of several components at flange portion
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3016Preforms or parisons made of several components at body portion
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/302Preforms or parisons made of several components at bottom portion
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3024Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique
    • B29C2949/3026Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique having two or more components
    • B29C2949/3028Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique having two or more components having three or more components
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3024Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique
    • B29C2949/3026Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique having two or more components
    • B29C2949/3028Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique having two or more components having three or more components
    • B29C2949/303Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique having two or more components having three or more components having more than three components
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3032Preforms or parisons made of several components having components being injected
    • B29C2949/3034Preforms or parisons made of several components having components being injected having two or more components being injected
    • B29C2949/3036Preforms or parisons made of several components having components being injected having two or more components being injected having three or more components being injected
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00Indexing scheme relating to blow-moulding
    • B29C2949/30Preforms or parisons made of several components
    • B29C2949/3032Preforms or parisons made of several components having components being injected
    • B29C2949/3034Preforms or parisons made of several components having components being injected having two or more components being injected
    • B29C2949/3036Preforms or parisons made of several components having components being injected having two or more components being injected having three or more components being injected
    • B29C2949/3038Preforms or parisons made of several components having components being injected having two or more components being injected having three or more components being injected having more than three components being injected
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/25Solid
    • B29K2105/253Preform
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/13Hollow or container type article [e.g., tube, vase, etc.]
    • Y10T428/1352Polymer or resin containing [i.e., natural or synthetic]

Definitions

  • the present invention relates to the co-extrusion of pluralities of flowing polymer plastic streams through nozzle extruders and the like into injection molding and similar apparatus for forming multi-layer plastic articles in which an interior core is encased by inner and outer layers of the article; and, more particularly, to the control of relative volumetric flow rates of the layers for attaining greater flexibility in the properties and relative thickness and positions of the layer sin the ultimate article.
  • the invention is especially, though not exclusively, useful with co-extrusion processes of the type described in my earlier United States patent No. 5,914,138, issued June 22, 1999 For Apparatus ForThrottle-Valving Control For The Co-Extrusion of Plastic Materials As Interior Core Streams Encased by Outer And Inner Streams For Molding And The Like.
  • a common problem in multilayer molding is the maintaining of a uniform penetration of the leading edge of the interior core layer, when that layer is not near the zero gradient of the velocity profile of the flowing polymer stream as it flows through a
  • PCR plastic in a molded article that consists of layers of two other polymers.
  • the present invention is directed to the solution of the above problems, and
  • a principal object of the present invention is to provide a new and
  • volumetric flow rates of the inner and outer layers in such a way as to shift the position of the core and control also the relative thickness of the inner and outer layers of the
  • Another object is to provide novel apparatus and methods to inject the leading edge
  • portion of the interior core flow to be offset from the zero gradient of the combined flow
  • An additional object is to provide novel apparatus and methods to restrict either
  • Still a further object of the present invention is to provide a novel method
  • Another object is to provide in such apparatus, novel operation wherein the
  • leading edge of one of the interior core layers is injected on the zero gradient of the
  • core layer flow from the zero-gradient and to shift the core layer closer to one of the
  • the major portion of the core layer is closer to one of the inner or outer article walls than the other. Preferred and best mode designs and configurations are later described in deta'i
  • Fig. 1 A of which is a schematic longitudinal section of the type of nozzle
  • Fig. IB is a graph illustrating resulting flow
  • Fig. IC is a graph showing the relative timing and proportions of volumetric
  • FIG. ID and IE being similar to Fig.1 A, but showing ; partially and completely filled conditions of the mold cavity fed from the throttled "
  • Figs. 2, 2A, 2B and 2C correspond, respectively, to the showings of Figs. IB, IC,
  • Figs. 3, 3 A, 3B and 3C respectively correspond to Figs. 2, 2A, 2B and 2C, but for
  • Figs. 4 and 5 are velocity profile graphs similar to Fig. 2, for respective ratios of
  • Fig. 6 is a flow fraction and velocity profile similar to Figs. 1 A, 2, 3, and 5, but
  • Figs. 6A, 6B and 6C are similar to respective Figs. 5A, 5B and 5C but describe the
  • Figs. 7, 7A, 7B and 7C correspond to respective Figs. 6, 6A, 6B and 6C,
  • the inner flow-to-outer flow ratio is decreased without shifting the initial core layer leading edge, the core layer being shifted towards the inner
  • Figs. 8 and 9 are graphs similar to Figs. 3A -6A for modifications wherein the
  • Figs. 8E through 81 are respectively similar to Figs. 8 and 8A-8D, but are
  • Figs. 9E through 91 similarly correspond to Figs. 9 and 9A-9D, but relate to
  • Figs. 10A-C are schematic top views of the inner, outer and core flow entry
  • Figs. 11 A and B are similar views with flow restrictor controls disposed in the
  • Figs. 12 A, B and C are schematic views of pin-type flow restriction elements
  • Fig. 13 is a cross-section of a preferred nozzle - flow control apparatus for the
  • FIGs. 14 and 15 are enlarged cross - sections of varying flow control positions of
  • Figs. 16A and B are similar to Figs. 10A-C, but are directed to feed channels for
  • Figs. 17 and 17 A-D ase 19 and 19 A-D illustrated the adaptation of the
  • volumetric flow rate of combined inner and outer layer flow the innermost interior
  • Figs. 18, 18A-D, Figs. 20, and 20A-D are views similar respectively to Figs. 17 and
  • Figs. 21 A, 22D, 23D and 24D show various exemplary types of containers that may be
  • the preferred apparatus employs a multiple-plastic stream co-extruder as for
  • FIG. 1 A a schematic cross-sectional view of a longitudinally
  • extending extruder nozzle N is shown provided with a central longitudinal throttle needle or pin acting as a flow restrictor T downstream of a combining section C,
  • CAV molding cavity
  • molds may also be used for other products, as may a wide variety of plastic materials be
  • core layer is uniformly distributed in the cavity, with the highest point of the velocity
  • Fig. IC a graph is presented plotting as a function of time, the volumetric flov
  • Fig. ID is a longitudinal section similar to Fig.1 A for the
  • Fig. IE shows the completely filled cavity
  • the embodiment uses a non-moving throttle valve pin.
  • a typical injection time-line for such three-layers molded articles is as follows:
  • the core layer flow is thus started on
  • the core material layer is introduced. Shortly after so introducing the core layer to
  • the invention enables the changing of the ratio
  • Fig. IB shows operation with the type of nozzle described in
  • Fig. 2 is an operation showing similar to Fig. IB wherein the throttle pin
  • Fig. 2A presents the same type of volumetric flow rate graph for the operation of
  • FIG. 3 illustrates similar operation but showing the ratio of inner flow-to-outer
  • Fig. 5 shows the case where the inner-to-outer flow is 75:25, again illustrating the
  • Figs. 5A, B and C correspond to Figs. 2A, B and
  • the core layer may indeed be shifted for useful purposes without having the resulting molded article suffer an unacceptable leading edge bias caused by
  • IF-to-outer flow (OF) is in a substantially 50: 50 ratio to place the interior core
  • resulting molded article in this case, having about an 80:20 ratio with the majority of
  • barrier layers One of such purposes for positionable core layers is as barrier layers, where a
  • humidity sensitive barrier layer may be required within the molded article such as a
  • barrier layer and even require less volume of barrier material in order to provide the
  • PET terephthalate
  • vinyl alcohols are useful for barrier properties; scavenger materials include products
  • nylon or ethylene vinyl alcohol, wherein the cobalt makes the nylon or alcohol reactive to oxygen, as in chemical scavenging reaction therewith, rather than allowing oxygen
  • polymer can provide electro-magnetic energy barrier layers, as well.
  • step S 1 in the dash-line curve occurs after the start S of the core flow with 50: 50 inner
  • restrictor is then adjusted to decrease the inner flow-to-outer flow ratio, again without
  • a typical injection time-line for systems of the invention such as those of Figs. 6
  • the invention moreover, provides not only for shifting the core layer to one side
  • the flow starts at zero-gradient velocity profile (I in Fig. 8A ⁇ top curve in Fig.
  • Figs. 8 and 8B-D thus illustrate the shifting of the majority of the core flow
  • FIG. 8E-I illustrate such a flat-shaped molded article
  • Figs. 8 and 8A-8D for a hollow bottle or the like.
  • Figs. 9-9B-D thus illustrate the shifting of the majority of the core flow towards
  • Figs.10A-C are schematic views looking from the top of the nozzle N
  • plastic flow from the source O/IS is split at S 1 into two matched flow streams, and then
  • Fig.12A illustrates the least restricted position with the restrictor pin barely
  • the restrictor insertion and withdrawal control may be automatically
  • Fig. 13 illustrates a cross-section of a preferred hollow nozzle extruder construction of the form described in my said earlier
  • the flat disc structure FD comprises four flat discus surrounding the
  • nozzle inner housing E is shown at R 1 , just at the inner layer feed channel C '. This is a
  • FIG. 10A-C A schematic feed channel diagram similar to Figs. 10A-C, but for the specific
  • plastic streams is illustrated in Figs. 16A and 16B.
  • the inner and outer stream is
  • nozzle entry feed channels but a first interior layer source CS branchfeeds the entry
  • the first interior layer stream (#1) is thus directed within
  • the second interior layer stream (#2) is directed within the nozzle to form the interior annular layer
  • Figs. 20 and 20A-D for flat-shaped articles, respectively.
  • gas barrier and/ or gas other property such as a structural layer or a recycled layer.
  • Fig. 17A shows the flow in the nozzle and partially-filled cavity at time A of Fig.
  • leading edge is on the zero gradient of the combined flow velocity profile, thus assuring
  • Fig. 17 B shows the partially filled cavity
  • Fig. 17C shows the position of the flows in the nozzle
  • Fig. 17D shows the filled cavity
  • the filled cavity shows the first-flowing interior layer closer to the outer wall in the
  • Figs, 19, 19A, 19B, 19C, and 19D are similar to Figs. 17 and 17A-D in concept,
  • the first-flowing interior layer CI is the innermost interior
  • CI may also terminate before or
  • each of the flowing layers is directly proportional to the volumetric flow rate of each layer relative to the total volumetric
  • outer layer be greater or lesser during the time when all layers are simultaneously
  • the chosen position of the gas scavenger layer may typically
  • scavenger layer is to absorb gas permeating from the atmosphere exterior to the
  • a humidity-sensitive gas barrier layer such as the
  • leading edge of the first interior layer is established substantially on the
  • Fig. 21A depicts a plastic molded cylindrical hollow container having an open
  • FIG. 21B shows the cross-section of the container through its
  • Fig. 21D (see Fig. 19B, for example) having a leading edge that does not extend as far as the leading edge of the other interior layer and has a trailing edge that
  • both interior layers terminate approximately at the same distance from the gate.
  • Fig. 22D illustrates a blow-molded hollow container
  • Figs. 22 and 22D are show on enlarged scales in Figs. 22A, 22B and 22C, respectively.
  • Fig. 22 shows a molded preform having the leading edge of its interior layer on the wall
  • container sidewall is shown in Fig. 22B wherein the interior layer is offset from the
  • Fig. 22 C shows the cross-section ⁇ f a
  • the trailing edge of the interior layer is substantially on the wall
  • Figs. 23 A and 23B are similar
  • Fig. 23 C is the cross-section C of a segment of the base of the container of Fig.23 D
  • edge of the first interior layer extends beyond the leading of the second interior layer
  • edge of the second interior layer extends beyond the trailing edge of the first interior

Abstract

A novel technique for molding multi-layer polymer plastic articles having inner, outer and interior or core layers by controlling relative volumetric flow rates of the inner and outer layers to enable relative shifting of the position of the core, and also therelative thickness of the inner and outer layers in the molded articles; and with leading, and, where desired, trailing ends of the interior layer flow into the mold cavity substantially positioned on the zero gradient of the velocity profile of the flowing polymer streams.

Description

Manufacture of Plastic Articles Field
The present invention relates to the co-extrusion of pluralities of flowing polymer plastic streams through nozzle extruders and the like into injection molding and similar apparatus for forming multi-layer plastic articles in which an interior core is encased by inner and outer layers of the article; and, more particularly, to the control of relative volumetric flow rates of the layers for attaining greater flexibility in the properties and relative thickness and positions of the layer sin the ultimate article. More specifically, the invention is especially, though not exclusively, useful with co-extrusion processes of the type described in my earlier United States patent No. 5,914,138, issued June 22, 1999 For Apparatus ForThrottle-Valving Control For The Co-Extrusion of Plastic Materials As Interior Core Streams Encased by Outer And Inner Streams For Molding And The Like.
Background of Invention A common problem in multilayer molding is the maintaining of a uniform penetration of the leading edge of the interior core layer, when that layer is not near the zero gradient of the velocity profile of the flowing polymer stream as it flows through a
hot runner nozzle and/ or into the mold cavity forming the molded article. Unlike the
prior art tapered leading edge flow of, for example, systems of the type disclosed in
United States Patents Nos.4,895,504 and 4,892, 699, my said earlier patent teaches the
combining of the different flow streams of materials to achieve a velocity profile of the
combined streams in the melt delivery system that is similar to the velocity profile of
the combined stream in the injection mold cavity, thereby insuring uniformity in a
resulting molded article.
This problem of maintaining uniform penetration of the leading edge of the
interior core layer when it is not close to the zero gradient of the velocity profile
becomes particularly severe when there is the requirement to form the multilayer article
with the core layer not centered on the midplane of the article.
In two-material, three -layer preform molding, for example, it may be desirable
to have a barrier or scavenger layer closer to either the inner sidewall or outer sidewall
of a blow-molded container article, in order to enhance the barrier property of the
container. In three-material, four-layer preform molding, this leading edge problem
also occurs, particularly when the volumetric flow rate of one of the interior core layers
is greater than that of the other interior core layer. Another common current problem also arises in using post-consumer recycled "
plastic (PCR) in a molded article that consists of layers of two other polymers. Current
art accomplishes this three-material combination by using apparatus and methods that
create a 5-layer article. With such 5-layer technology, however, the molding cycle times
are significantly longer than if the article had been molded of only one material. Such 5-
layer molded articles, moreover, suffer delamination of the layers if the second polymer
has low adhesion to the virgin skin layers and to the central PCR layer.
The present invention is directed to the solution of the above problems, and
limitations, among others, in such prior art systems through a later-described technique
for permitting changed or controlled variation of the relative volumetric flow rates of
the inner and outer layers after the flow of the interior core layer stream has started.
Objects of Invention
A principal object of the present invention, accordingly, is to provide a new and
improved method of and apparatus for molding multi-layer polymer plastic articles
having inner, outer and interior or core layers that shall not be subject to such problems
and limitations; but that, to the contrary, obviate such through the control of relative
volumetric flow rates of the inner and outer layers in such a way as to shift the position of the core and control also the relative thickness of the inner and outer layers of the
article.
Another object is to provide novel apparatus and methods to inject the leading
edge of the interior core layer on the zero gradient of the combined velocity profile
during the initial portion of the interior core layer flow, and then to change the relative
volumetric flow rates of the inner and outer layers to cause the later or subsequent
portion of the interior core flow to be offset from the zero gradient of the combined flow
velocity profile.
An additional object is to provide novel apparatus and methods to restrict either
the flow of the inner or of the outer layer volumetric flow rate in order to shift the
interior core layer trailing portion inside or outside the 50% streamline through the
nozzle and into the molded part.
Still a further object of the present invention is to provide a novel method and
apparatus to produce an article of three materials molded into four layers.
Another object is to provide in such apparatus, novel operation wherein the
leading edge of one of the interior core layers is injected on the zero gradient of the
velocity profile of the combined stream before the start of flow of the other interior core
layer. Other and further objects will be described hereinafter and are more fully -
delineated in the appended claims.
Summary
In summary, however, from one of its important aspects, the invention embraces
a method for co-extruding multiple plastic materials as for injecting through a gate
region into a mold cavity to produce a molded article, that comprises, co-extrusively
flowing streams of plastic materials with at least one interior stream that is to serve as
an interior core of a resulting molded plastic article within inner and outer streams of
plastic material that serve as covering wall plastic material layers for the core; forcing
the flowing streams to flow along concentric annular flow paths within and along a
longitudinally extending tubular extruder nozzle to the cavity gate region; adjusting
the flow streams initially to cause the core stream to start to flow at a region of
substantially zero gradient in the transverse flow velocity profile of the extrusion;
thereupon varying the relative volumetric flow ratio of the inner and outer layer
streams after the zero-gradient flow of the core layer has started in order to offset the
core layer flow from the zero-gradient and to shift the core layer closer to one of the
inner or outer annular flow boundaries, thereby to produce a molded article wherein
the major portion of the core layer is closer to one of the inner or outer article walls than the other. Preferred and best mode designs and configurations are later described in deta'i
Drawings
The invention will now be described in connection with the accompanying
drawings, Fig. 1 A of which is a schematic longitudinal section of the type of nozzle
described in my above-mentioned patent using a central longitudinal restrictor or
throttle pin to force concentric annular flow of the injected plastic thereabout within th
walls of the hollow extruder nozzle; and Fig. IB is a graph illustrating resulting flow
fraction and velocity profile curves across the annular channel within the nozzle of Fig
1 A for an inner flow-to-outer flow ratio of 50: 50 — the ordinate plotting the ratio of
Figure imgf000008_0001
velocity-to-average velocity as a function of the radius of the annulus between the innej
and outer nozzle wall, with the central solid line curve NP plotting said ratio and
showing zero gradient for the core stream CF (shaded vertical strip), and the curve
designated with a circle marker, plotting the flow IF between the radius and the throttle
pin T from the inner to the outer wall, and the curve marked with a triangle, plotting
the flow OF between the outer wall and the annular radius;
Fig. IC is a graph showing the relative timing and proportions of volumetric
flow rate of the combined inner and outer layer flows, the inner layer flow, and the
interior core layer flow, with Figs. ID and IE being similar to Fig.1 A, but showing ; partially and completely filled conditions of the mold cavity fed from the throttled"
nozzle for the conditions of Fig. IB;
Figs. 2, 2A, 2B and 2C correspond, respectively, to the showings of Figs. IB, IC,
ID and IE, but for an inner-to-outer flow ratio of 40:60;
Figs. 3, 3 A, 3B and 3C respectively correspond to Figs. 2, 2A, 2B and 2C, but for
an inner-to-outer flow ration of 60:40;
Figs. 4 and 5 are velocity profile graphs similar to Fig. 2, for respective ratios of
25: 75 and 75:25, with Figs.4A,B and C and Figs. 5A, B and C corresponding to Figs. 2A,
2B and 2C, respectively, but for such 25: 75 and 75:25 ratios, respectively;
Fig. 6 is a flow fraction and velocity profile similar to Figs. 1 A, 2, 3, and 5, but
embodying the methodology of the present invention, with an initial portion of the core
layer flow occurring for a 50: 50 ratio, and the major flow occurring with 80:20 ratio to
shift the core toward the outer wall, but without providing any leading-edge bias;
Figs. 6A, 6B and 6C are similar to respective Figs. 5A, 5B and 5C but describe the
operational conditions of the invention as reflected by Fig. 6;
Figs. 7, 7A, 7B and 7C correspond to respective Figs. 6, 6A, 6B and 6C,
illustrating the operation of the invention for the conditions converse to Fig. 6, wherein,
after the initial 50:50 flow ratio, the inner flow-to-outer flow ratio is decreased without shifting the initial core layer leading edge, the core layer being shifted towards the inner
layer;
Figs. 8 and 9 are graphs similar to Figs. 3A -6A for modifications wherein the
core is shifted back before the end of the flow, as shown in Figs. 8A, B, C and D for
original core shifts towards and away from the inner wall; and, in Figs. 9A, B, C and D,
for original core shifts away from and towards the inner wall, respectively;
Figs. 8E through 81 are respectively similar to Figs. 8 and 8A-8D, but are
designed for producing flat-shaped molded articles;
Figs. 9E through 91 similarly correspond to Figs. 9 and 9A-9D, but relate to
molding flat-shaped articles;
Figs. 10A-C are schematic top views of the inner, outer and core flow entry
channels and flow restrictor controls for varying the inner/ outer channel flow ratios for
the core shifting effects of the invention;
Figs. 11 A and B are similar views with flow restrictor controls disposed in the
most common channel feeding the respective outer and inner layers,
Figs. 12 A, B and C are schematic views of pin-type flow restriction elements;
Fig. 13 is a cross-section of a preferred nozzle - flow control apparatus for the
practice of the invention; Figs. 14 and 15 are enlarged cross - sections of varying flow control positions of
operation of the nozzle of Fig. 13;
Figs. 16A and B are similar to Figs. 10A-C, but are directed to feed channels for
three-material streams to each nozzle to form inner and outer annular covering layers.
Figs. 17 and 17 A-D ase 19 and 19 A-D illustrated the adaptation of the
techniques of the invention for producing three-material, four layered articles, and
illustrating graphs in Figs. 17 and 19 showing relative timing and proportions of
volumetric flow rate of combined inner and outer layer flow, the innermost interior
layer flow and the outermost interior layer flow of two different three-material, four
layer flow systems;
Figs. 18, 18A-D, Figs. 20, and 20A-D are views similar respectively to Figs. 17 and
17A-D and Figs. 19 and 19 A-D, but are directed to the molding of flat-shaped articles
rather than cylindrical-shaped containers and the like.
Figs. 21 A, 22D, 23D and 24D show various exemplary types of containers that may be
formed by the techniques of the invention from respective per-forms 21B-C-D, 22, 23
and 24; respective enlarged cross-sectional segments A, B and C of which are illustrated
in Figs. 22A-C, 23A-C and 24A-C. Preferred Embodiments Of The Invention
In my before-referenced prior co-extrusion patent, at least two-polymer plastic
materials are provided as a 3-layer combined flow stream; a first material L which
forms the ultimate outer and inner molded covering layers of the ultimate molded
product, article or part from the inner and outer flow stream layers (IL and OL),
injected as annular streams; and a second material (I) which forms the middle, inner or
interior core of the product formed from an injected concentric annular interior stream
(I A) encased within the inner and outer annular stream layers of the covering material.
The preferred apparatus employs a multiple-plastic stream co-extruder as for
injection molding cavities in which the extruder is internally provided therewithin and
therealong with a restrictor or throttle pin, rod or element that forces combined plastic
materials streams, formed with an interior core stream encased in outer and inner
stream layers, into corresponding concentric co-extensive annular flow stream layers
that are ultimately split transversely in opposite directions into a cavity gated to the
extruder, and with the core stream at a region of zero gradient in the transverse-flow
velocity profile within the extruder and cavity.
Referring to Fig. 1 A, a schematic cross-sectional view of a longitudinally
extending extruder nozzle N is shown provided with a central longitudinal throttle needle or pin acting as a flow restrictor T downstream of a combining section C,
providing uninterrupted continual annular flow within the extruder of the concentric
inner and outer annular stream layers IL and OL, with the encased interior annular core
stream IA, and into gate G. The combined streams A are then, as before stated, laterally
split and injected transversely in opposite directions into a molding cavity (CAV) —
shown for illustrative purposes of shape suitable for molding cylindrical containers
such as bottles or the like. As described in my said prior patent, other shaped cavity
molds may also be used for other products, as may a wide variety of plastic materials be
used, among them, for example, polyethylene, PET, and other plastic and polymer
compositions/as later more fully described.
As further taught in my prior patent, it is highly desirable in many applications
that, as shown in Fig. IB, the core layer flows substantially on the zero-gradient velocity
profile (O) in order to keep the leading edge of the core layer uniform 360-degrees
around a periphery of the annular flow, to insure, as the flow enters the cavity, that the
core layer is uniformly distributed in the cavity, with the highest point of the velocity
typically on the center line of the flow; and wherein 50 percent of the material is-on the
inside of the streamline and 50 percent is outside the streamline, and the zero gradient
occurs right on the 50-percent streamline. In Fig. IC, a graph is presented plotting as a function of time, the volumetric flov
rate of the combined inner and outer flow (top curve), the inner layer (IL) flow (dash-
line curve) and the interior core layer flow (bottom curve) encompassing the times A
and B, respectively representing a time after the start of the interior core layer flow, and
an intermediate time before the leading-edge of the core layer has left the extruder to
enter the mold cavity. Fig. ID is a longitudinal section similar to Fig.1 A for the
partially filled condition at time B, and Fig. IE shows the completely filled cavity,
demonstrating the distribution of the core layer extending most of the line length of the
flow in the cavity and having a uniform leading edge at a 180-degree section of the
cavity and with the core layer placed on the 50% streamline in the middle of the molded
article.
My earlier patent also provided for moving the throttle or restriction pin to vary
the percentage of the outer layer material in the inner annular flow layer vs. the outer
annular flow layer of the combined flow stream downstream of the combining area.
Changing the relative volumes of the outer layers shifts the position of the core
(interior) layer in the mold cavity to produce a part with controlled outer layer-
thickness on both surfaces of the molded article or part. If the outer layer flow is biased
toward either the inner or outer annular flow layers, the outer layer thickness in the
molded part will be similarly biased on the corresponding surface molded from the biased annular layers. Material from the inner annular flow layer forms the surface
layer of the part molded by the cavity wall opposite the gate into the cavity and the
material from the outer annular flow layer forms the surface layer of the part molded
by the cavity wall adjacent to the gate.
The use of a movable throttle valve pin is typically appropriate in cases where it
is the advantageous to vary, during each injection, the relative percentage of the outer
layers material in the inner annular flow layer vs. the outer annular flow layer. For
cases where the relative thickness of the layer on both surfaces of the molded part can
remain in fixed proportion to each other, the embodiment uses a non-moving throttle valve pin.
A typical injection time-line for such three-layers molded articles is as follows:
Time, Action
Seconds
0 Close mold
0.1 Start injection of inner and outer layer material at substantially 50:50 ratio
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 Start injection of interior layer material on zero-gradient of velocity profile
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1-9
2.0 Finish interior layer injection on zero-gradient of velocity profile
>2.0 Finish injection of inner and outer layer material
It has now been discovered that if, instead of changing the relative percentages of
inner and outer annular layer volumes of materials to obtain unequal covering
thicknesses, as described in my earlier patent, one starts the flow process with the inner
layer-to-outer layer volume flow being equal (ratio of 1), this will start the initial
portion of the interior or core layer flow, along the desired zero-gradient velocity
profile; and then, during the continued flow, the ratio of inner-to-outer layer flow may
be changed to effect core layer shifting as later more fully described.
In accordance with the present invention, the core layer flow is thus started on
the zero-gradient velocity profile, with the inner layer in the combined flow and the
outer layer in the combined flow both having the same volumetric flow rate at the time
the core material layer is introduced. Shortly after so introducing the core layer to
create the leading-edge of the core layer, the invention enables the changing of the ratio
of inner layer-to-outer layer flow, advantageously to place the remaining portion —
preferably about 90 to 95 percent of the core layer that is flowing into the cavity— to be
shifted towards the outside boundary wall or towards the inside boundary wall" of the
molded article. In this way, the advantages of knowledge of the zero-gradient velocity
profile is combined with the advantageous shifting of the position of the core layer to enhance the function of the molded article — the shifting of the volumetric flow of the
inner layer vs. the outer layer, causing the shift of position of the core layer.
As earlier described, Fig. IB shows operation with the type of nozzle described in
my above-referenced patent, employing a throttle pin adjustment such as to produce
substantially a 50: 50 inner flow (IF)-to-outer flow (OF) ratio, placing the leading-edge
of the interior layer flow IL on the zero gradient of the combined velocity profile, and
enabling the absence of any leading edge bias in the molded article due to flow velocity.
Fig. 2 is an operation showing similar to Fig. IB wherein the throttle pin
adjustment has been positioned to achieve an inner flow-to-outer flow ratio of 40: 60,
rather than the 50: 50 ratio of Fig. IB, placing the leading-edge of the interior layer IL
near the zero gradient of the combined velocity profile. This produces a small, but
acceptable leading edge bias in the molded article, as also explained in my earlier
patent.
Fig. 2A presents the same type of volumetric flow rate graph for the operation of
Fig. 2 as described in connection with Fig. IC for the operation of Fig. IB; and Figs. 2B
and 2C illustrate partially filled nozzle-cavity flow conditions at time B and for
complete cavity filling, respectively.
Fig. 3 illustrates similar operation but showing the ratio of inner flow-to-outer
flow as 60: 40, as opposed to Fig. 2. Again, as disclosed in my previous patent, the core layer (CF) remains close to the zero gradient, producing only a small but acceptable
leading edge bias, this time towards the outer wall. Thus, though shifting the core laye
either toward the inner wall or toward the outer wall approximately 10 percent of the
wall thickness, a reasonable and acceptable leading edge bias is still maintained. Figs.
3A, B and C, correspond respectively to Figs. 2A, B and C, above explained, but are
directed to the operation of Fig.3.
In Fig.4, however, a condition is shown for a flow ratio adjustment of 25: 5,
inner flow-to-outer flow, wherein the core layer flow CF is now well offset away from
the zero gradient of the combined velocity profile, resulting in a velocity distribution
bias of the core layer that produces a large leading edge bias that creates an
unacceptable molded article. In Figs. 4 A, B and C, corresponding to the type of
showings in respective Figs. 2A, B and C, the operation for the conditions of Fig. 4 are
similarly presented.
Fig. 5 shows the case where the inner-to-outer flow is 75:25, again illustrating the
bias created in the molded article; and Figs. 5A, B and C correspond to Figs. 2A, B and
C, respectively, but illustrate the conditions of Fig. 5, with a flow Δv (Fig. 5B) producing
a large bias Al (Fig. 5C).
As before stated, however, in accordance with the discovery underlying the
present invention, the core layer may indeed be shifted for useful purposes without having the resulting molded article suffer an unacceptable leading edge bias caused by
the velocity bias. The critical operational requirement for achieving this novel result is
graphically illustrated in Fig. 6, and involves, as earlier discussed, that necessity for
employing an initial throttle pin adjustment or other flow restrictor adjustment that
ensures that the initial portion of the core or interior layer flow occurs when the inner
flow (IF)-to-outer flow (OF) is in a substantially 50: 50 ratio to place the interior core
layer leading edge on the zero gradient of the combined velocity profile, as at region I
in Fig. 6. After that flow is well-established at I - - (of the order of a flow of a few,
preferably about 5, percent (+) of the core material that is to be flowed for the molding
of the article), then it has been found that a subsequent throttle pin adjustment or other
flow-restrictor adjustment at region II, as in the case of Fig. 6, increases the inner flow-
to-outer flow ratio, resulting in shifting the interior core layer leading edge. The
resulting molded article — in this case, having about an 80:20 ratio with the majority of
the core layer flow length III in the molded article extending closer to the outer wall —
will not produce a leading-edge bias caused by velocity bias, and will still enable the
production of the uniform leading edge on the molded article, but with the majority
(say 95%) of the core layer length shifted toward the outer wall, as for purposes earlier
and also hereinafter discussed. One of such purposes for positionable core layers is as barrier layers, where a
humidity sensitive barrier layer may be required within the molded article such as a
cylindrical bottle container or the like. There may be advantage to shifting the barrier
layer towards the outside walls of the container, away from the liquid content and thus
at a lower relative humidity environment that can enhance the performance of the
barrier layer and even require less volume of barrier material in order to provide the
same barrier effect to the contents. Another illustration is for use of oxygen scavenging
layers, the scavenging capacities of which may be increased by being in a higher relative
humidity and/ or being closer to the contents as opposed to being close to the outside
wall. A thicker container outer layer, moreover, would permit less oxygen permeation
than if the outer layer were thinner, slowing down oxygen transfer from the outside to
the scavenging layer. The scavenging capacity of a scavenging layer closer to the
contents would also remove residual oxygen left in the contents of the container during
the filling process.
While the invention is useful with all kinds of polymers, polyethylene
terephthalate (PET) is highly desirable for container skin materials; nylons and ethylene
vinyl alcohols are useful for barrier properties; scavenger materials include products
such as BP- Amoco " Amasorb", and compounds of heavy metals like cobalt with MXD6
nylon, or ethylene vinyl alcohol, wherein the cobalt makes the nylon or alcohol reactive to oxygen, as in chemical scavenging reaction therewith, rather than allowing oxygen
permeation through the materials; and combinations, such as the above, will provide
both barrier and scavenger properties. The incorporation of metal powders in the
polymer can provide electro-magnetic energy barrier layers, as well. Through the
technique of the invention, indeed, any desired position of the core layer and of the
relative thicknesses of the inner and outer layers of the article can readily now be
obtained through this novel control of relative volumetric flow rates of the inner and
outer layers above explained.
This is illustrated in the graph of Fig. 6 A, where the inner layer flow increase
(step S1 in the dash-line curve) occurs after the start S of the core flow with 50: 50 inner
layer-outer layer flow to the left of S1; at time A. As shown in the filled cavity of Fig. 6,
though nearly all the core length is shifted towards the outer wall, no leading-edge bias
exists in the article, and where the leading edge remains on the zero gradient.
The converse of the operation of Figs. 6 A, B and C, is shown in Figs. 7 A, B and
C, where, after the initial portion I of the interior core layer flow occurs during an inner
flow-to-outer flow ratio adjustment of substantially 50: 50,placing the core layerleading
edge on the zero gradient of the combined velocity profile, the throttle pin or other flow
restrictor is then adjusted to decrease the inner flow-to-outer flow ratio, again without
shifting the interior layer leading edge — this time resulting in a molded article with the bulk of the core layer shifted toward the inner wall in the same ratio of 80: 20, and agair
with no leading edge bias caused by velocity bias (Fig. 7C).
A typical injection time-line for systems of the invention such as those of Figs. 6
and 6A-C and 7 and 7A-C is as follows:
Time, Action
Seconds
0 Close mold
0.1 Start injection of inner and outer layer material at substantially 50:50 ratio
0.2
0.3
0.4
0.5
0.6
0.7
0.8 •
0.9
1.0 Start injection of interior layer material substantially on zero-gradient of velocity profile "*
1.1 Change ratio of inner layer: outer layer flow rates 1.2
1.3
1.4
1.5
1.6 .
1.7
1.8
1.9 2.0 Finish interior layer injection (trailing edge offset from zero-gradient of velocity profile)
>20 Finish injection of inner and outer layer material
The invention, moreover, provides not only for shifting the core layer to one side
or the other of the article, such as a hollow container, and for relatively varying the
thickness of the inner and outer layers, but also for enabling the shifting of the core
layer back into another position of the article. Examples of this are shown in Figs. 8A
8B, 8C and 8D for the operation graphically represented in Fig. 8 and in Figs 9A-9D for
the operation graphically represented in Fig. 9.
Turning first to Figs. 8 and 8 A-D, in accordance with this embodiment of the
invention, the flow starts at zero-gradient velocity profile (I in Fig. 8A~top curve in Fig.
8); shifting the core layer toward the inside wall (II-III in Fig. 8B) by decreasing the
inner layer flow (at Si in Fig. 8, between times A and B); and, near the end of the flow
(between times C and D), increasing the inner layer flow back to equality with the outer
layer flow (S2 in Fig. 8) to shift the core layer (at IF in Fig. 8C) back to the zero-gradient
profile (at III' in Fig. 8C), thereby producing the shape shown in Fig. 8D.
A useful purpose for the operation of Fig. 8 resides in structural considerations,
wherein there may be a highly stressed portion of the molded article that can cause
mechanical failure, such as delamination of the article, with the barrier or core layer positioned closer to the inside wall. Secondly, it can be important to control the
thickness and shape of the terminal end of the core flow - -the last portion of the
molded article to freeze or solidify. Injection molding of the hot plastic into the cold
cavity causes the molded article to freeze or solidify from the inner surfaces toward the
interior layer, and it is advantageous to control the final flow of the material entering
the cavity along the 50-percent streamline.
Figs. 8 and 8B-D thus illustrate the shifting of the majority of the core flow
towards the inside boundary wall, with both the leading-edge and also the trailing or
terminal end on the zero gradient.
While the invention has heretofore been illustrated in connection with molding
bottle or cylindrical-shaped container applications, the techniques of the invention are
useful for molding other shaped articles or objects as well, including, as a further
illustration, flat-shaped molded articles. Figs. 8E-I illustrate such a flat-shaped molded
article application, with the views corresponding respectively to the above-described
Figs. 8 and 8A-8D for a hollow bottle or the like.
Similarly, in the embodiment of the invention shown in Figs. 9 and 9A-9D,"the
flow starts at zero-gradient velocity profile (I in Fig. 9A— top curve in the graph of Fig.
9); shifting the core layer toward the outside wall (II-III in Fig. 9B) by increasing the
inner layer flow (at Si1 in Fig. 9, between times A and B); and, near the end of the flow (between times C and D), decreasing the inner layer flow back to equality with the outer
layer flow (S21 in Fig. 9) to shift the core layer (at IF in Fig. 9C) back to the zero-gradient
profile (at III' in Fig. 9C), thereby producing the shape shown in Fig. 9D.
Figs. 9-9B-D thus illustrate the shifting of the majority of the core flow towards
the outside wall, with both the leading-edge and also the trailing or terminal end on the
zero gradient.
A useful injection time-line for the systems of Figs. 8, 8A-D, 9 and 9A-D follows:
Time, Action seconds
0 Close mold
0.1 Start injection of inner and outer layer material at substantially '50:50 ratio
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 Start injection of interior layer material substantially on zero-gradient of velocity profile
1.1 Change ratio of inner layer: outer layer flow rates 1.2
1.3 1.4 1.5 1.6 1.7 1.8 1.9 Return ratio of inner: outer layer flow rates to substantially 50:50
2.0 Finish interior layer injection substantially on zero-gradient of velocity profile
>20 Finish injection of inner and outer layer material
Figs.10A-C are schematic views looking from the top of the nozzle N,
illustrating the entry flow channels or ports feeding the inner, outer and core or interior
layer flows (IE, OE, and CE, respectively) from their respective sources (Figs.10B and
C), and surrounding a central throttle pin entry point TE. This flow channel
arrangement is shown embodied in Figs. 10B and 10C with an array of four nozzles, fed
initially from an outer and inner layer source O/IS and a core or interior layer source
CS, respectively, in a balanced three-layer flow system. The outer and inner layer
plastic flow from the source O/IS is split at S1 into two matched flow streams, and then
branched at B1 to feed the entry channels for the outer layer OE and inner layer IE of
each of the upper and lower pairs of nozzles, in parallel. Similarly, the core layer source
CS branches to feed the core channels CE of the two pairs of nozzles and with balanced
feed.
Flow restrictor controls, such as well-known electrically, hydraulically or even
manually operated valves, are substantially illustrated in Fig. 10B at FR, placed in each
of the outer layer feed channels and synchronously operated to vary the relative ratio of
outer and inner layer flow at preselected times, for the previously described flow shifting purposes of the invention. Similarly, in Fig. IOC, the same controls can be
effected with the flow restrictor controls FR disposed in the inner layer feed channels
within each nozzle or in each final channel feeding material to the inner layer in each
nozzle. Thus, in the embodiments of Figs. 11 A and B, the flow restriction control is
shown inserted in the most common feed channel feeding the outer layer and the inner
layer, respectively, for changing such flow ratios.
Schematic views, showing a simple but effective way of operating pin-type flow
restrictors in a feed channel are shown in Figs. 12A, B and C for three different
positions. Fig.12A illustrates the least restricted position with the restrictor pin barely
inserted into the flow channel; and Figs. 12B and 12C illustrate more and most flow-
restricting positions, respectively. These may be effected, as before indicated, in the
most common channel of the runner system (Figs. 11A and B), or, if desired, in a least
common channel to the nozzle (Figs. 10B and C) and elsewhere, as desired. Again, as
earlier stated, the restrictor insertion and withdrawal control may be automatically
effected in well-known manner, electrically or hydraulically, for example, with timing
control of the position of each with respect to start or the end of the flow — all as"
intended to be schematically represented at FR.
Turning, now, to specific practical designs for such nozzle channel flow and
restriction structures,, reference is made to Fig. 13 which illustrates a cross-section of a preferred hollow nozzle extruder construction of the form described in my said earlier
US patent 5, 914, 138 (Fig. 16 thereof), in which flow from a manifold is effected througl
a flat disc 3-layer flow combining area G-FD surrounding a central longitudinally
movable throttle valve pin T-T1, and wherein annular flow is combined and gated into a
mold cavity .CAV. The flat disc structure FD comprises four flat discus surrounding the
throttle pin T and forming the inner flow channel wall C for the inner layer of the
combined flow stream. Flow channels Ci' , Of, f etc. are created between the three
mating planar surfaces of the discs FD, as also explained in said patent, uniformly to
disperse each flow layer to produce a uniform flow of the respective material flowing
from each channel into the area of combination C. In this manner, each layer of the
combined flow stream is uniformly annularly disposed as it flows from the combining
means through the extruding throttle nozzle and gate G into the cavity CAV. The
movable throttle valve pin T-T1, under control of an upper adjusting restrictor-control
rod R, which is also, in a sense, part of the throttle pin structure as well, varies the
percentage of the outer layer material in the inner annular flow layer versus the outer
annular flow layer of the combined flow stream downstream of the combining area C.
As before explained, changing the relative volume of the outer layers shifts the position
of the core (interior) layer for the previously described purposes of the present invention. In the embodiment above Fig. 13, the restrictor rod R axially movable within the
nozzle inner housing E, is shown at R1, just at the inner layer feed channel C '. This is a
neutral position with disc channels Ci', Of, etc. opened to balance inner layer flow with
respect to the outer layer flow for the purposes of the initial core layer flow in
accordance with the principles of the invention. In the enlarged views of Figs. 14 and
15,the throttle valve T has been adjusted by the rod R to an elevated position R", to
increase the inner flow rate with respect to the outer layer flow rate for the core shifting
control purposes of the invention — the least flow-restricted position; whereas, in Fig.
15, more restriction (most) is illustrated at R'".
A schematic feed channel diagram similar to Figs. 10A-C, but for the specific
annular layer flow of the nozzle of Figs. 13, 14 and 15 when used for 3-material polymer
plastic streams, is illustrated in Figs. 16A and 16B. The inner and outer stream is
divided within the nozzle to form the inner and outer annular covering layers. In this
case, the source O/IS of the inner and outer layer flows, is again branched into the
nozzle entry feed channels, but a first interior layer source CS branchfeeds the entry
channel CEι,and, as shown by the dash lines, a second interior layer source CS2 branch-
feeds the entry channel CE2. The first interior layer stream (#1) is thus directed within
the nozzles N to form the interior annular layer adjacent the inner layer. The second interior layer stream (#2) is directed within the nozzle to form the interior annular layer
adjacent the outer layer.
As earlier mentioned, the techniques of the present invention are not restricted in
the numbers of materials and layers to be molded, though illustrating two-material,
three - layer pre-form molding examples; it having been previously noted that the
invention is also quite useful, for example, in three-material, four-layer pre-form
molding as well. Such an application is shown in Figs. 17 and 17A-D and Figs.19 and
19 A-D for molding hollow container articles or objects, and in Figs. 18 and 18 A-D and
Figs. 20 and 20A-D for flat-shaped articles, respectively.
In connection with the adaptation of the invention for molding of three materials
to form a four-layer object, typical applications would be for a plastic container
composed of two interior layers; one layer would usually be selected for its gas barrier
for gas scavenger properties, and the other interior layer would be selected for some
other property such as a structural layer or a recycled layer. The gas barrier and/ or gas
scavenger property still requires that the leading edge of this one of the two interior
layers be uniform in its penetration around the circumference of the molded object. This
uniform penetration can be achieved by starting the flow of this one interior layer
before starting the flow of the second interior layer, so that the leading edge of this first-
flowing interior layer starts on the zero gradient of the velocity profile. Subsequent initiation of the flow of the second interior layer offsets the later-flowing portions of the
first interior material from the zero gradient, but the uniform leading edge is
established by the initial flow of the first interior layer on the zero gradient.
In Fig. 17, the first-flowing interior layer CI (in this case the outermost interior
layer in the molded object) starts to flow at time SI. The second-flowing interior layer
C2 (in this case the innermost interior layer) starts flowing at time S2 which also
corresponds with the reduction of the flow rate of the combined inner and outer layer
flow. Fig. 17A shows the flow in the nozzle and partially-filled cavity at time A of Fig.
17; this time being between the time SI and S2. The first-flowing interior layer CI
leading edge is on the zero gradient of the combined flow velocity profile, thus assuring
its uniform penetration in the molded object. Fig. 17 B shows the partially filled cavity
at time B of Fig. 17. The leading edge of the first-flowing interior layer CI remains on
the zero gradient, while the later-flowing portions of the first-flowing interior layer are
moved off the zero gradient by the second-flowing interior layer C2, and are closer to
the wall of the extruder. Fig. 17C shows the position of the flows in the nozzle and
cavity at time C of Fig. 17. The second-flowing interior layer has ceased flowing-at time
S3, thereby allowing the final flow portion of the first-flowing interior layer to return to
the zero gradient just before its flow is terminated, S4. Fig. 17D shows the filled cavity
when the trailing edge of the first-flowing interior layer has been injected into the cavity by the continued flow of the combined inner and outer layer flow after time C, of Fig.
17. The filled cavity shows the first-flowing interior layer closer to the outer wall in the
portions of the filled cavity corresponding to the simultaneous flow of the second-
flowing interior layer.
Figs, 19, 19A, 19B, 19C, and 19D are similar to Figs. 17 and 17A-D in concept,
except that, in this example, the first-flowing interior layer CI is the innermost interior
layer and the second-flowing interior layer C2 is the outermost interior layer. All other
features are similar to the case of Figs. 17 and 17 A-D, but in the filled cavity, the first-
flowing interior layer is closer to the inside wall of the molded part in portions of the
cavity corresponding to the simultaneous flow of the second-flowing interior layer.
In both the embodiments of Figs. 17, 17A-D and 19 and 19 A-D, C2 is shown
terminating before the termination of CI in order to allow the final portion of CI to flow-
along the zero gradient of the velocity profile. It should be understood, however, that it
is within the scope of this invention that CI may also terminate before or
simultaneously with the termination of C2 if the desired properties of the molded object
are enhanced by such a termination sequence.
The operational graphs of Figs. 17 and 19 show a reduction in the flow rate of the
combined inner and outer layer flow at time S2, corresponding to the start of the flow of
the second-flowing interior layer. The thickness of each of the flowing layers is directly proportional to the volumetric flow rate of each layer relative to the total volumetric
flow rate of each layer relative to the total volumetric flow rate of all the layers during
the time when all layers are simultaneously flowing. The proximity of the innermost
interior layer and outermost interior layer to the respective inner and outer walls of the
molded article or object is changed by having the flow rate of the combined inner and
outer layer be greater or lesser during the time when all layers are simultaneously
flowing.
Such relative thickness and position of each of the interior layers is chosen to
enhance the properties of the final molded object. For example, if one of the interior
layers is a gas scavenger, the chosen position of the gas scavenger layer may typically
be the innermost interior layer CI of Figs. 19 and 19 A-D in order to reduce the
permeation rate of gas through the outer layers of the container into the scavenger, and
to increase the rate of gas scavenging from the contents of the container. Such a
position, indeed will extend the shelf life of the container contents if the purpose of the
scavenger layer is to absorb gas permeating from the atmosphere exterior to the
container. As another example, the position of outermost interior layer CI of Fig. 17
can enhance the performance of a humidity-sensitive gas barrier layer, such as the
before-mentioned EVOH or MXD6 nylon, by moving such barrier layer away from the
100% relative humidity of the contents of a beverage that is to fill the container to a position in the wall that is closer to the lower relative humidity of the atmosphere
surrounding the container.
A typical injection time-line for molding such three-material, four-layer articles
wherein the leading edge of the first interior layer is established substantially on the
zero-gradient of the velocity profile, and then a second interior layer is injected and its
injection is finished before the first interior layer injection is finished, as shown in Figs.
17, 17A-D and 19 and 19A-D, follows:
Time, Action seconds
0 Close mold
0.1 Start injection of inner and outer layer material at substantially 50:50 ratio
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 Start injection of interior layer material substantially on zero-gradient of velocity profile
1.1 Start injection of second interior layer material and reduce combined flow- rate of inner and outer material
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Finish injection of second interior layer material
2.0 Finish injection of first interior layer material substantially on zero- gradient of velocity profile
>20 Finish injection of inner and outer layer material
As previously described, other-shaped objects or articles may also be molded by
the techniques of the invention, including the flat-shaped articles of earlier mentioned
Figs. 18 and 18A-D and 20 and 20A-D.
Exemplary articles, ports or products formable with the above-described
techniques of the present invention are shown in Figs. 21 A through 24C
Fig. 21A depicts a plastic molded cylindrical hollow container having an open
top and a closed bottom. Fig. 21B shows the cross-section of the container through its
axial center line (shown dashed), wherein the interior layer has a leading edge on the
centerline of the molded wall, this centerline corresponding to the zero-gradient of the
velocity profile during the flow of plastic into the mold cavity which formed the part —
for example as in the forming process of Figs. 7A-C. While the interior layer leading
edge substantially is on the part wall centerline, the other portions of the interior layer
are offset from the centerline toward the inner wall surface of the article.
Variants are illustrated in Figs. 21C and D; with the trailing edge of the interior
layer being substantially on the part centerline in Fig. 21 C, and with an additional
interior layer in Fig. 21D (see Fig. 19B, for example) having a leading edge that does not extend as far as the leading edge of the other interior layer and has a trailing edge that
terminates father from the gate than the other interior layer. What is not depicted, but
is possible, are molded articles wherein the leading edge of one interior layer extends
beyond the leading edge of the other interior layer, and wherein the trailing edges of
both interior layers terminate approximately at the same distance from the gate.
As another example, Fig. 22D illustrates a blow-molded hollow container
formed from the multilayer article of Fig. 22. Cross-sections of segments A, B and C of
Figs. 22 and 22D are show on enlarged scales in Figs. 22A, 22B and 22C, respectively.
Fig. 22 shows a molded preform having the leading edge of its interior layer on the wall
centerline and other portions of its interior layer offset from the centerline toward the
outer wall surface (as in Figs. 6A-C). In the wall section in the finish portion of the
article as illustrated wherein the leading edge of the interior layer is substantially on the
centerline of the wall, and another portion of the interior layer is offset from the
centerline toward the outer wall surface. The wall cross-section of a segment of the
container sidewall is shown in Fig. 22B wherein the interior layer is offset from the
centerline toward the outer wall surface; and Fig. 22 C shows the cross-section σf a
segment of the container base wherein the interior layer trailing edge terminates offset
from the article centerline. In the blow-molded container of Fig. 23 D, the molded pre-form of which is
depicted in Fig. 23, the trailing edge of the interior layer is substantially on the wall
centerline, as distinguished from the pre-form of Fig. 22. Figs. 23 A and 23B are similar
to before-discussed Figs. 22A and 22B, respectively, but with the variations of Fig. 23.
Fig. 23 C is the cross-section C of a segment of the base of the container of Fig.23 D
wherein the trailing edge of the interior layer terminates substantially on the wall
centerline.
Still another modification is presented in the cross-section of a four-layer molded
article and Fig. 24 that can be blow-molded into the container of Fig. 24 D (see Figs. 17-
19). The leading and trailing edges of one interior layer are substantially on the part
centerline and extend beyond the leading and trailing edges of the other interior layer
as shown, more specifically in Figs. 24 A and 24 B, respectively. What is not depicted,
but is possible, are four-layer molded articles for blow-molding wherein the leading
edge of the first interior layer extends beyond the leading of the second interior layer
and wherein the trailing edges of both interior layers terminate approximately the same
distance from the gate. An additional undepicted article is one wherein the trailmg
edge of the second interior layer extends beyond the trailing edge of the first interior
layer and wherein the leading edge of the first interior layer extends beyond the leading
edge of the second interior layer. The previously discussed layer distributions of Figs. 21B, 21C or 21D, moreover,
can also be molded into articles similar to pre-form of Fig. 22 for blow-molding into
containers similar to Fig. 22 D. Similarly, the layer distribution of Figs. 22, 23 and 24 car
also be molded into articles similar to Fig. 21. Additionally, any of these depicted layer
distributions can be molded into articles of other shapes, such as flat plates, (see Figs. 18
and 20), concave discs, lids and closures for containers, and other shapes limited only
by the imagination of one skilled in the art.
Other signs of flow control devices may also be employed, and other further
modifications will also occur to those skilled in this art, such being considered,
however, to fall within the spirit and scope of the invention as defined in the appended
claims.

Claims

What is claimed is:
1. A method for co-extruding multiple polymer plastic materials as for injecting
through a gate region into a mold cavity to produce a molded article, that
comprises, co-extrusively flowing streams of polymer plastic materials with at
least one interior stream that is to serve as an interior core of a resulting molded
plastic article within inner and outer streams of plastic material that serve as
covering wall plastic material layers for the core; forcing the flowing streams to
flow along concentric annular flow paths within and along a longitudinally
extending tubular extruder nozzle to the cavity gate region; adjusting the flow
streams initially to cause the core stream to start to flow at a region of
substantially zero gradient in the transverse flow velocity profile of the
extrusion; thereupon varying the relative volumetric flow ratio of the inner and
outer layer streams after the zero-gradient flow of the core layer has started, in
order to offset the core layer flow from the zero gradient and to shift the core
layer closer to one of the inner or outer annular flow boundaries, thereby to
produce a molded article wherein the major portion of the core layer is closer to
one of the inner or outer article walls than the other.
2. The method of claim 1 wherein the relative thickness of the inner or outer layers
is correspondingly varied substantially in said ratio.
3. The method of claim 1 wherein, prior to the termination of the extrusion, the
flow ratio of the inner and outer layers is varied to shift the terminal end of the
interior core stream back along substantially said zero gradient.
4. The method of claim 1 wherein the inner and outer stream ratio is varied after a
few percent of the core layer stream flow has initially flowed.
5. The method of claim 1 wherein the adjusting of the flow stream initially causes
the inner and outer streams to start to flow with substantially equal volumetric
flow rates.
6. The method of claim 1 wherein said forcing is effected by disposing a
longitudinal pin within and along the extruder to force the combined streams
into said concentric annular flow paths.
7. The method of claim 1 wherein the relative volumetric flow ratio of the inner and
outer streams is controlled by relatively restricting the respective flow channels
of the streams within the extruder.
8. The method of claim 7 wherein the timing of said relative flow restricting is
controlled to coincide with one or both of (1) a short time after the start o'f the
flow of the core stream, and (2) near the termination thereof.
9. The method of claim 7 wherein the timing of said relative flow restricting is
controlled intermediate the flow of the streams to the mold cavity.
10. The method of claim 7 wherein the relative flow restricting is effected by
inserting a flow restrictor into the inner or outer flow stream within the extruder.
11. The method of claim 7 wherein the inner, outer and core layer flow streams are
fed into respective entry channels in the extruder nozzle from respective material
sources, and the flow restrictor is inserted into one of either a source flow
channel, or near a nozzle entry channel.
12. The method of claim 11 wherein a plurality of similar nozzles are similarly
simultaneously fed from respective material sources, with flow restrictors
inserted near corresponding inner or outer layer entry flow channels in each
nozzle or in common feed channels from said sources.
13. The method of claim 1 wherein the inner and outer layer streams are fed from
the same plastic material source and the plastic core material stream from a
different source, and the annular co-extensive streams of the core material stream
encased by the inner and outer layer streams are combined near said gate region
and laterally injected in opposite transverse directions into the mold cavity.
14. The method of claim 13 wherein the molded article thereby formed is a hollow
plastic container in which the interior core layer encased by inner and outer
container walls is of material that serves as a barrier layer for such purposes as resisting the flow of gases through the container walls and/ or scavenging
oxygen.
15. The method of claim 1 wherein a three-material plastic article is to be molded
comprising inner and outer layers and two interior or core layer materials and
wherein the inner and outer layer material streams are divided within the nozzle
to form the inner and outer annular covering wall layers, one of the interior layer
streams being directed within the nozzle to form an interior annular layer
adjacent said inner layer, and the other interior stream being directed within the
nozzle to form an interior annular layer adjacent the outer layer.
16. A method for co-extruding multiple plastic materials as for injecting through a
gate region into a mold cavity to produce a molded article having an interior
core layer encased within inner and outer wall layers, that comprises, co-
extrusively flowing inner and outer layer streams of plastic material encasing an
interior core layer to inject the same though the gate region into the mold cavity;
initially starting the flow with a substantially 50:50 ratio of inner and outer layer
stream volumetric flows to cause the interior core stream to flow at a mid-plane
region of substantially zero gradient in the transverse flow velocity profile of the
extrusion; thereupon, for the major portion of the flow, varying the relative volumetric flow ratio of the inner and outer layer streams to offset the core layer
stream from the mid-plane and shif the core layer closer to one of the inner or
outer flow boundaries, thereby to produce a molded article wherein the major
portion of the core layer within the article is closer to the inner or outer article
wall.
17. The method claimed in claim 16 wherein said flow ratio is varied back to
substantially 50:50 near the terminal end of the flow into the cavity.
18. The method claimed in claim 16 wherein the ratio is varied after a few percent of
the core layer stream flow has initially flowed.
19. The method in claim 16 wherein the ratio is further varied during the continued
flow to the gate region, and into the mold.
20. The method of claim 19 wherein said ratio is varied back to substantially 50:50
near the terminal end of the flow to re-establish the interior core stream flow
back along substantially said zero gradient.
21. The method of claim 16 wherein the core layer stream material is selected for
barrier function characteristics such as at least one of gas permeation control,
gas-scavenging, and electromagnetic shielding.
22. Apparatus for co-extruding multiple plastic materials as for injecting through a
gate region into a mold cavity to produce a molded article having an interior core layer encased within inner and outer wall layers, the apparatus having, in
combination, a longitudinally extending extruder nozzle for receiving plastic
material from sources thereof and co-extrusively flowing the material as inner
and outer layer streams of plastic material encasing an interior core layer to inject
the same through the gate region into the mold cavity; flow control means for
initially starting the flow with a substantially 50:50 ratio of inner and outer layer
stream volumetric flow rates to cause the interior core stream to flow at a mid-
plane region of substantially zero gradient in the transverse flow velocity profile
of the extrusion; means for thereupon, for the major portion of the flow,
adjusting the flow control means to change the relative volumetric flow ratio of
the inner and outer layer streams to offset the core layer stream from the mid-
plane and shift the core layer closer to one of the inner or outer flow boundaries,
thereby to produce a molded article in the cavity wherein the major portion of
the core layer within the article is closer to one of the inner or outer article wall.
23. The apparatus claimed in claim 22 wherein the flow control means is adjusted to
vary the flow ratio back to substantially 50:50 near the terminal end of th flow
into the cavity.
24. The apparatus claimed in claim 22 wherein the flow control means is operated to
change the ratio after a few percent of the core layer stream flow has initially
flowed.
25. The apparatus claimed in claim 22 wherein the flow control is adjusted to further
vary the ratio during the continued flow to the gate region.
26. The apparatus of claim 25 wherein the flow control means is adjusted to vary
said ratio back to substantially 50: 50 near the terminal end of the flow to re¬
establish the interior core stream flow back along substantially said zero
gradient.
27. The apparatus of claim 22 wherein the core layer stream material is selected for
barrier function characteristics such as at least one of humidity control, gas
permeation, gas scavenging and electromagnetic shielding.
28. Apparatus for co-extruding multiple plastic materials as for injecting through a
gate region into a mold cavity to produce a molded article, having, in
combination, a longitudinally extending tubular extrusion nozzle provided with
entry channels for receiving plastic materials from sources thereof and co=- -
extensively flowing the materials as inner and outer layer streams with one
interior strea that is to serve as an interior core of a resulting molded plastic
article within inner and outer streams of plastic material that serve as covering wall plastic material layers for the core; a longitudinal throttle means for forcing
the streams to flow along concentric annular flow paths within and along a
longitudinally extending tubular-extruder nozzle to the cavity gate region;
means for adjusting the flow streams initially to cause the core stream to start to
flow at a region of substantially zero gradient in the transverse flow velocity
profile of the extrusion; means operable thereupon for varying the relative
volumetric flow ratio of the inner and outer layer streams after the zero-gradient
flow of the core layer has started in order to offset the core layer flow from the
zero gradient and to shift the core layer closer to one of. the inner or outer flow-
boundaries, thereby to produce a molded article wherein the major portion of the
core layer is closer to one of the inner or outer article walls than the other.
29. The apparatus of claim 28 wherein the relative thickness of the inner or outer
layers is correspondingly varied substantially in said ratio.
30. The apparatus of claim 28 wherein, prior to the termination of said extrusion, the
adjusting means is controlled to vary the flow ratio of the inner and outer layers
to shift the terminal end of the interior core stream back along substantially said
zero gradient.
31. The apparatus of claim 28 wherein the adjusting means varies the inner and
outer stream ratio after a few percent of the core layer stream flow has initially
started.
32. The apparatus of claim 28 wherein the adjusting means initially causes the inner
and outer streams to start with substantially equal volumetric flow rates.
33. The apparatus of claim 28 wherein said adjusting means comprises an axial pin
or forcing the combined streams into said concentric annular flow paths.
34. The apparatus of claim 28 wherein the relative volumetric flow ratio of the inner
and outer streams is controlled by restrictors disposed in the respective flow
channels of the streams within the extruder.
35. The apparatus of claim 34 wherein means is provided for controlling the timing
of the relative restricting by the restrictors to coincide with one or both of shortly
after the start of the flow of the core stream, and near the termination of the core
stream flow.
36. The apparatus of claim 35 wherein means is provided for controlling the timing
of the relative flow restricting intermediate the flow of the streams to the-mold
cavity.
37. The apparatus of claim 35 wherein the relative flow restricting is effected by
means for inserting a flow restrictor into one of the inner or outer flow streams.
38. The apparatus of claim 28 wherein the inner, outer and core layer flow streams
are fed into respective entry channels in the nozzle from respective material
sources, and the flow restrictor is inserted into one of (1) a source flow channel or
(2) near a nozzle entry channel.
39. The apparatus of claim 28 wherein a plurality of similar nozzles is provided, the
nozzles of which are similarly simultaneously fed from respective material
sources, with flow restrictor means inserted in corresponding inner or outer
layer entry flow channels in each nozzle or in common feed channels from said
sources.
40. The apparatus of claim 28 wherein the inner and outer layer streams are fed from
the same plastic material source and the plastic core material stream from a
different source, and the annular co— extensive streams of the core material
stream encased by the inner and outer layer streams are combined near said gate
region and laterally injected in opposite transverse directions into the mold
cavity.
41. The apparatus of claim 40 wherein the molded article thereby formed is a hollow
plastic container in which the interior core layer is of material that serves as a
barrier layer for such purposes as resisting the flow of humidity and or gases through the container walls and/ or scavenging oxygen through chemical
combination therewith.
42. The apparatus of claim 28 wherein a 3-material plastic article is to be molded
comprising inner and outer layers and two interior or core layer materials, and
wherein the inner and outer layer material streams are divided within the nozzle
to form the inner and outer annular covering wall layers, one of the interior layer
streams is directed within the nozzle to form an interior annular layer adjacent
said inner layer, and the other interior stream is directed within the nozzle to
form an interior annular layer adjacent the outer layer.
43. The method of claim 1 wherein a plurality of similar extruder nozzles is
provided similarly simultaneously fed from respective material sources, and
with flow restriction inserted in corresponding inner and outer layer entry flow
channels into each nozzle or in common feed channels from said sources.
44. The method of claim 1 wherein two interior streams are flowed within said inner
and outer streams, with the flow of one of the interior stream started before the
flow of the other interior stream and with its leading edge starting on said- zero-
gradient, and the subsequent initiation of the flow of said other interior stream
offsetting the later-flowing portions of said one interior stream flow from said
zero gradient, and with the completing of the injecting of the other interior stream before the completion of the injecting of said one interior stream through
said gate region and into said mold cavity, and finishing the injecting of said
interior stream on said zero gradient.
45. The method of claim 44 wherein the materials of the inner, outer and interior
streams constitute three molding materials forming a four-layer molded article.
46. The method of claim 45 wherein the relative thickness and position of each of the
interior streams is chosen to enhance the properties of the molded article.
47. The method of claim 46 wherein the innermost of the interior streams is of gas
scavenging material in order to reduce the permeation rate of gas through said
outer wall of the molded article, and to increase the rate of gas scavenging from
the contents of the article if the scavenger material is intended to absorb gas
permeating from the exterior of the article.
48. The method of claim 46 wherein the outermost of the interior streams is of
humidity sensitive gas barrier material in order to position such barrier at a
position within the molded article that is closer to the exterior atmosphere
surrounding the article.
49. The method of claim 44 wherein the article is one of a cylindrical-shaped hollow
container, such as a bottle, and a flat-shaped article.
50. The apparatus of claim 22 wherein said inner core layer comprises a pair of
interior core streams, with said adjusting means enabling one of the interior
streams to start flow before the other of the pair of interior streams and with its
leading edge starting on said zero gradient, and enabling the subsequent
initiation of the flow of said other interior stream offsetting the later-flowing
portions of said one interior stream through said gate region and into said mold
cavity, with the finishing of the injecting of said one interior stream lying on said
zero gradient.
51. The apparatus of claim 50 wherein the materials of the inner, outer and interior
streams constitute three molding materials forming a four-layer molded article.
52. The apparatus of claim 51 wherein the relative thickness and position of each of
the interior streams is chosen to enhance the properties of the molded article.
53. The apparatus of claim 52 wherein the innermost of the interior streams is of gas
scavenging material in order to reduce the permeation rate of gas through said
outer wall of the molded article, and to increase the rate of gas scavenging from
the contents of the article if the scavenger material is intended to absorb gas
permeating from the exterior of the article.
54. The apparatus of claim 52 wherein the outermost of the interior streams is of
humidity sensitive gas barrier material in order to position such barrier at a position within the molded article that is closer to the exterior atmosphere
surrounding the article.
55. The apparatus of claim 50 wherein the article is one of a cylindrical-shaped
hollow container, such as a bottle, and a flat-shaped article.
56. A molded plastic material article having an interior plastic core layer encased
within inner and outer plastic wall layers wherein the major portion of the core
layer within the article is closer to one of the inner or outer article walls.
57. The molded article of claim 56 wherein the article is hollow and bounded by the
core-encased inner and outer walls.
58. The molded article of claim 57 wherein the initial portion the core layer lies
substantially on the centerline of the core-encased inner and outer article walls.
59. The molded article of claim 58 wherein said initial portion constitutes a few
percent of the length of the core layer.
60. The molded article of claim 59 wherein the core layer near its terminal end again
lies substantially on said centerline.
61. The molded article of claim 59 wherein the core layer material is selected for
barrier function characteristics such as at least one of humidity control, gas
permeation, gas scavenging and electromagnetic shielding.
62. The molded article of claim 59 wherein the inner and outer walls and the core are
of three molding materials forming a four-layer molded article.
63. A pre-form for a hollow molded plastic material article having an interior plastic
core layer encased within inner and outer plastic wall layers wherein the major
portion of the core layer within the pre-form is closer to one of the inner and
outer article walls.
64. The pre-form of claim 63 wherein the initial portion of the core layer lies
substantially on the centerline of the core-encased inner and outer article walls.
65. The pre-form of claim 64 wherein said initial portion constitutes a few percent of
the length of the core layer.
66. The pre-form of claim 65 wherein the core layer near its terminal end again lies
substantially on said centerline.
67. The pre-form of claim 65 wherein the core layer material is selected for barrier
function characteristics such as at leastone of humidity control, gas permeation,
gas scavenging and electromagnetic shielding.
PCT/IB2001/002015 2001-04-06 2001-10-26 Injection molding of multi-layer plastic articles WO2002081172A1 (en)

Priority Applications (8)

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ES01976570.0T ES2618804T3 (en) 2001-04-06 2001-10-26 Injection molding of multilayer plastic items
BR0116965-3A BR0116965A (en) 2001-04-06 2001-10-26 Injection Molding of Multilayer Plastic Articles
JP2002579191A JP4283541B2 (en) 2001-04-06 2001-10-26 Injection molding of multilayer plastic products
KR10-2003-7013113A KR20030090718A (en) 2001-04-06 2001-10-26 Injection molding of multi-layer plastic articles
MXPA03009128A MXPA03009128A (en) 2001-04-06 2001-10-26 Injection molding of multi-layer plastic articles.
EP01976570.0A EP1412156B1 (en) 2001-04-06 2001-10-26 Injection molding of multi-layer plastic articles
CA2442888A CA2442888C (en) 2001-04-06 2001-10-26 Injection molding of multi-layer plastic articles
HK04110160.9A HK1067096A1 (en) 2001-04-06 2004-12-22 Injection molding of multi-layer plastic articles

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US09/828,254 US6596213B2 (en) 2001-04-06 2001-04-06 Method of molding multi-layer polymer plastic articles with control of relative shifting of the core layer
US09/828,254 2001-04-06

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