US20060103045A1

US20060103045A1 - Wet use chopped strand glass as reinforcement in extruded products

Info

Publication number: US20060103045A1
Application number: US10/991,278
Authority: US
Inventors: Frank O'Brien-Bernini; Donn Vermilion; Scott Schweiger; Brian Guhde; William Graham; George Walrath; Leslie Morris
Original assignee: Individual
Current assignee: Owens Corning Intellectual Capital LLC
Priority date: 2004-11-17
Filing date: 2004-11-17
Publication date: 2006-05-18
Also published as: US7222465B2; US20060101768A1; US20070245666A1; MX2007005839A; BRPI0518332A2; CN101068672A; AU2005306758A1; JP2008520471A; WO2006055398A1; EP1812219A1; CA2585911A1; KR20070099562A

Abstract

A method for incorporating wet use chopped strand glass (WUCS) in a screw extrusion process is provided. A polymeric resin is added to an extruder in a polymer feed zone and conveyed to a first compression zone where the resin is at least partially melted. The molten resin is conveyed to a high volume zone where WUCS fibers are added. In the high volume zone, the flights of the screw may have a greater pitch to facilitate the introduction of the WUCS into the extruder. The molten resin/fiber mixture is conveyed to a second compression zone where the resin and fibers are intimately compounded. Next, the molten resin/fiber mass is conveyed to a low pressure zone where moisture evaporated from the fibers is released through an opening. The resin/fiber mixture is then conveyed through a compression/die feed zone to further compound and mix the resin and fibers.

Description

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to the formation of thermoplastic composites, and more particularly, to the incorporation of wet use chopped strand glass (WUCS) in an extrusion process.

BACKGROUND OF THE INVENTION

Typically, glass fibers are formed by drawing molten glass into filaments through a bushing or orifice plate. Normally, a sizing composition is then applied to the drawn filaments, the sizing containing lubricants, coupling agents, and film-forming binder resins. The aqueous sizing composition provides protection to the fibers from interfilament abrasion and promotes compatibility between the glass fibers and any matrix in which the glass fibers are to be used for reinforcement purposes. After the sizing composition is applied, the fibers may be gathered into one or more strands and wound into a package or, alternatively, the fibers may be chopped (typically while wet) and collected. The collected chopped strands can then be dried and cured to form dry use chopped strand glass (DUCS), or they can be packaged in their wet condition as wet use chopped strand glass (WUCS). Such dry chopped glass fiber strands are commonly used as reinforcement materials in thermoplastic articles, and the wet chopped strands are used to manufacture wet-laid mats. It is known in the art that glass fiber reinforced polymer composites possess higher mechanical properties compared to unreinforced polymers. Thus, better dimensional stability, tensile strength and modulus, flexural strength and modulus, impact resistance, and creep resistance can be achieved with glass fiber reinforced composites.
Glass fibers are useful in a variety of technologies. For example, glass fibers are commonly used as reinforcements in polymer matrices to form glass fiber reinforced plastics or composites. Glass fibers have been used in the form of continuous or chopped filaments, strands, rovings, woven fabrics, nonwoven fabrics, meshes, and scrims to reinforce polymers. Dry chopped glass fibers (DUCS) are commonly used as reinforcement materials in reinforced composites (the DUCS may be provided in chopped form as noted above, or chopped from a roving for use in the reinforced composite).
In one conventional method, dry chopped strand segments may be mixed with a polymeric resin and supplied to a compression- or injection-molding machine to be formed into glass fiber reinforced composites. Here, the dry chopped strand segments are mixed with powder, regrind, or pellets of a thermoplastic polymer resin in an extruder. For example, powder, regrind, or polymer pellets are fed into a first port of a twin screw extruder and the dry chopped glass fibers are fed into a second port of the extruder with the melted polymer to form a dry fiber/resin mixture. Alternatively, the polymer resin and dry chopped strand segments are dry mixed and fed together into a single screw extruder where the resin is melted, the integrity of the dry glass fiber strands is broken down, and the dry fiber strands are dispersed throughout the molten resin to form a fiber/resin mixture. The dry fiber/resin mixture may be fed directly into an injection molding machine with or without regrind, or, the dry fiber/resin mixture may be degassed and formed into pellets. The dry fiber strand/resin dispersion pellets are then fed to a molding machine and formed into molded composite articles that have a substantially homogeneous dispersion of dry glass fiber strands throughout the composite article.
In another conventional method, illustrated in FIG. 1, a thermoplastic polymeric resin (not shown) is admixed with dry chopped strand glass (not shown) in a hopper 30 and fed to an extruder 32. The extruder 32 is formed of a barrel 33 and at least one screw 34 that extends substantially along the length of the barrel 33. The screw 34 may be powered by a motor (not shown). Mechanical action and friction generated by the screw 34 melt the polymeric resin and mix the resin and dry fibers into a substantially homogenous mixture. Heaters 37 may be placed on the barrel 33 to facilitate the melting of the polymeric resin. A blowing agent (not shown) may be supplied to the extruder 32 from a blowing agent tank or reservoir 38 through a conduit 39. The blowing agent mixes with the melted polymer/dry fiber blend as it enters the extruder 32. The heat within the extruder 32 causes the blowing agent to dissolve and foam. The polymer/dry fiber/blowing agent mixture is pushed into a shaping die 31 having the shape of the desired final product.
Vinyl siding is formed by extrusion methods similar to those described above, but without the glass reinforcement and without a blowing agent. For example, vinyl chloride resins, such as polyvinyl chloride (PVC), have been used to form siding products. Unfortunately, glass reinforced vinyl siding products made from polymeric resins such as PVC would be too expensive to manufacture, primarily because dry use chopped strand glass (DUCS) requires that the glass be formed, chopped, dried, and cured prior to use in such an extrusion process; each step incurring manufacturing cost.
Conventional PVC-based siding products are typically loaded with inexpensive, inorganic fillers such as calcium carbonate (CaCO₃). Such fillers may increase the modulus or stiffness of the siding product and may decrease the amount of movement that can occur as a result of a change of temperature of the siding. However, conventional PVC siding products are limited in the loading of these fillers due to impact resistance (as required by ASTM D3679) and processing conditions, and, as a result, typically contain only a relatively small amount of inorganic fillers. As a result, conventional siding products may generally thermally distort at approximately 140° F.
Thus, there exists a need in the art for a siding product that has improved resistance to thermal distortion, that has improved crack and puncture resistance, and that is inexpensive to manufacture.

SUMMARY OF THE INVENTION

It is an object of the present invention to utilize wet use chopped strand (WUCS) glass fibers in an extrusion process to form a reinforced extruded thermoplastic product. In at least one exemplary embodiment, a polymeric resin such as polyvinyl chloride (PVC) is fed into the barrel of a screw extruder in a polymer feed zone and conveyed to a first compression region where the polymeric resin is at least partially melted. The polymeric resin may be in the form of a flake, granule, pellet, and/or a powder. A blowing agent may be pre-blended with the resin and fed into the extruder with the polymeric resin. Other additives such as thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers, tackifiers, and reinforcements may be added to the extruder or pre-compounded with the resin. Heaters may be placed on the barrel of the extruder to assist in melting the polymeric resin and/or maintain the molten state of the resin. In the polymer feed zone, flights of the screw have a desired pitch. The molten resin is conveyed downstream to a high volume zone where wet use chopped strand glass fibers are introduced into the barrel of the extruder and mixed with the molten polymeric resin. The flights of the screw in the high volume zone are positioned at a greater pitch and/or greater depth than the flights in the polymer feed zone and first compression zone. This larger pitch and/or greater depth increases the throughput of the high volume zone and allows the wet use chopped strand glass fibers to mix with the molten resin and form a molten resin/fiber mix. An opener may be used to at least partially open the bundles of wet use chopped strand glass fibers prior to their addition into the barrel. In addition, the wet use chopped strand glass fibers may be at least partially dried prior to entering the barrel of the extruder.
The molten resin/fiber mix may then enter a second compression zone where the resin and wet glass fibers are compounded to form a substantially homogenous mass. The flights of the screw in the second compression zone may have a smaller angle, closer spacing, a lower depth, and a closer tolerance to the barrel than the flights located in the previous zones. The shear force caused by the friction between the barrel and the flights and the increased shear within the flights causes the bundles of wet use chopped strand glass fibers to open and separate.
The molten resin/fiber mixture is then passed through a low pressure zone. Heat generated by the process as the molten resin/fiber mixture is conveyed through the barrel causes moisture that was held within the wet fiber bundles to evaporate. The low pressure zone contains flights preferably have a pitch and/or depth that is greater than the flights in the first and second compression zones. An opening located in the high volume zone permits water vapor and other volatiles to exit the barrel of the extruder. Once the water vapor is released, the molten resin/fiber mixture may be passed through a compression/die feed zone to further mix and/or compound the resin and glass fibers. The resin/fiber mixture is then passed out of the extruder and into a shaping die which forms the resin/fiber mixture into a desired shape. In at least one preferred embodiment, the shaping die forms the resin/fiber mixture into a generally flat board or sheet that may be formed into a cladding product.
In at least one other exemplary embodiment, the polymer resin and the wet use chopped strand glass fibers are fed into the barrel of the extruder through a resin/fiber feedthroat at substantially the same time. The resin/feed feedthroat may include baffles or other mixing/feeding devices to blend and mix the WUCS fibers and the polymer resin prior to entering the extruder. The polymeric resin and the wet use chopped strand glass fibers enter the extruder in a polymer feed zone and are conveyed to a compression zone where the resin substantially homogenously mixes with the wet reinforcement fibers. Shear force caused by the mixing and transporting action of the screw as the resin/fiber mixture is conveyed down the barrel of the extruder causes the bundles of WUCS glass fibers to filamentize. As the molten resin/fiber mass is pushed downstream, the heat generated by the rotating process causes the moisture in the WUCS fibers to evaporate. The molten resin/fiber mixture is then passed through a low pressure zone where the flights of the screw have a pitch, depth and/or spacing that is preferably greater than the flights in the compression zone. An opening positioned in the low pressure zone releases water vapor into the air. The viscous resin/fiber mixture may then exit the low pressure zone and enter a compression/die feed zone to further mix and/or compound the resin and glass fibers. Finally, the molten resin/fiber mixture is conveyed out of the extruder and into a shaping die where it is formed into a desired shape (e.g., a siding product).
It is an advantage of the present invention that the extruded siding products reinforced with WUCS glass fibers have improved handleability, improved wind resistance, and are able to withstand long periods of high temperature and sun exposure as well as thermal cycling.
The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art conventional extruder apparatus for extruding a foamed product;
FIG. 2 is a schematic illustration of a screw extruder apparatus according to at least one exemplary embodiment of the present invention;
FIG. 3 is a schematic illustration of a twin screw extruder apparatus according to at least one exemplary embodiment of the present invention;
FIG. 4 is a schematic illustration of a screw extruder apparatus according to at least one other exemplary embodiment of the present invention;
FIG. 5 is a schematic illustration of an extrusion line according to one aspect of the present invention;
FIG. 6 is a schematic illustration of an extrusion line including a second extruder for co-extruding cap stock according to at least one exemplary embodiment of the present invention; and
FIG. 7 is a schematic illustration of an extrusion line including a second extruder for co-extruding a cap stock according to at least other exemplary embodiment of the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. All references cited herein, including published or corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any other references, are each incorporated by reference in their entireties, including all data, tables, figures, and text presented in the cited references. It is to be noted that like numbers found throughout the figures denote like elements.
The invention relates to the use of wet reinforcement fibers, such as wet use chopped strand (WUCS) glass fibers, in applications that may conventionally use dry use chopped strand glass. Accordingly, the invention proposes using WUCS in place of the dry use chopped strand glass in, for example, extrusion, injection molding, compression molding, rotational molding, infusion molding, sheet molding, resin transfer molding (RTM), and in dry laid processes such as is described in U.S. Ser. No. 10/688,013 filed on Oct. 17, 2003 to Enamul Haque (incorporated by reference in its entirety), as well as other known products and processes that conventionally use DUCS. In some instances, the wet reinforcement fibers are agglomerated in the form of a bale, package, or bundle of individual fibers, and, as a result, it may be desirable to first open and/or filamentized the fibers prior to use in the desired application or process. In other instances, the wet reinforcement fibers are used in the desired application process without any initial separation or filamentization. In such an instance, the reinforcement strands may be separated during the process itself.
Unlike dry chopped glass, wet chopped glass contains moisture that may have to be removed from the fibers either prior to the addition of the wet fibers to the process apparatus or during the process itself. Certain modifications to process apparatuses, such as adding a venting device to an existing apparatus, may be used to allow the steam or moisture from the wet reinforcement fibers to escape into the air. In an injection or extrusion processes, the screw(s) may be configured to form a low pressure zone which may be used to vent the moisture with or without vacuum assistance. In compression molding, the charge including the wet fibers may be added to a heated mold, which is then partially closed to spread out and heat the charge, thereby allowing moisture to escape prior to completely closing the mold. Further, reactive or anhydrous fillers, such as Portland cement, CaO, Na₂CO₃, or CaSO₄may be used to bind moisture released during an application process.
One approach to remove water from the wet reinforcement fibers prior to their addition to an existing apparatus is to pass the wet fibers through a heated chamber, optionally in combination with hot air, prior to the fibers entering the processing equipment and/or as part of the conveying equipment for the particular apparatus. Another method to remove water from the wet reinforcement fibers is to pass the wet fibers through a microwave chamber, with or without flowing air, to at least partially dry the fibers prior to use in the apparatus. Another method to remove water from the wet reinforcement fibers is to pass the wet fibers through a condenser chamber, with or without flowing air, to at least partially dry the fibers prior to use in the apparatus.
In dry use chopped strand glass fibers (DUCS), lubricants present in the glass fibers migrate with the water away from the glass strands to the outside of the forming package during the drying process that forms the DUCS glass fibers. However, one advantage obtained by the use wet use chopped strand glass fibers in processes that conventionally use dry glass fibers is that with the wet use chopped strand glass fibers, higher levels of fiber lubricants may be utilized. Higher lubricant levels may aid in dispersion of the fibers and reduce the viscosity at the interface of the resin and fiber, potentially resulting in longer fibers and superior properties (e.g., flexural tensile strength and impact strength), compared to products formed with DUCS glass fibers. In addition, by selecting the proper lubricants for the resin being processed, in combination with a higher level of lubricants achieved with the WUCS, the lubricants will supplement and reduce the amount of resin lubricant needed to lubricate and process the resin in compounding, extrusion, and molding processes. Further, the moisture present in the system may be utilized to supplement and reduce the amount of costly blowing agent(s) needed to foam a product, thereby reducing costs. Moreover, in a pre-blended material, the surface wetness of the glass fibers attracts and sticks to the polymer powder, thereby reducing the tendency of glass fibers to segregate during storage and handling.
Wet reinforcement fibers are less expensive to manufacture than dry chopped fibers because dry fibers are typically dried and packaged in separate steps before being chopped. Therefore, the use of wet use chopped strand glass fibers in processes that conventionally use dry use chopped glass fibers allows the processes and products made therefrom to have lower costs. However, as described herein, in some instances, wet chopped glass fibers may not be simply substituted for dry chopped glass fibers. Some modification of existing processes and/or equipment may be needed to take advantage of the cost benefits provided by the use of wet use chopped strand glass.
One particular example of the use of wet reinforcement fibers in place of dry fibers is in extrusion processes. Thus, in one aspect, the present invention relates to an extrusion process and apparatus for forming thermoplastic composites using wet reinforcement fibers, e.g., wet use chopped strand (WUCS) glass fibers, in a screw extrusion process. A screw extruder for use in the instant invention is generally indicated at reference numeral 100 in FIG. 2. Although the screw extruder for use in the instant invention may equally be a single screw or twin screw extruder, reference is made herein with respect to a single screw extruder.
The extruder 100 contains a screw 102 having helical flights 108 rotating in the direction of arrow 90. The screw 102 extends substantially the length of a barrel 104. The flights cooperate with the cylindrical inner surface of the barrel 104 to define a passage for the advancement of a resin and reinforcement fibers through the barrel 104. In a twin screw extruder embodiment, as illustrated in FIG. 3, the extruder 100 contains a screw 102 and a twin screw 111 that extend substantially the length of the barrel 104. A motor (M) may be used to power the screw 102 and, if present, the twin screw 111.
Turning back to FIG. 2, a resin feed hopper 105 and a wet reinforcement fiber feed hopper 110 are positioned at the end of the extruder 100 opposing the extrusion die 120. In the exemplary embodiment illustrated in FIG. 2, the wet reinforcement feed hopper 110 is positioned downstream from the resin feed hopper 105, but alternatively may be pre-mixed with the resin, or fed into the same hopper or in reverse order. The term “downstream” as used herein refers to the direction of resin and fiber flow through the barrel 104. Feedthroats 101 and 103 interconnect the resin feed hopper 105 and the wet reinforcement fiber feed hopper 110 respectively. An opening 109, such as a vent, is positioned downstream from the wet reinforcement feed hopper 110 between the wet reinforcement feed hopper 110 and extrusion die 120.
In operation, a polymeric resin is fed into barrel 104 of the screw extruder 100 from the resin feed hopper 105 through the feedthroat 101 and into a polymer feed zone 106. The flights 108 in the polymer feed zone 106 may be positioned at a desired pitch that is dependent upon the physical and chemical properties being introduced into the barrel 102. The polymeric resin may be metered into the barrel 104 by a metering mechanism (not shown). The polymeric resin may be in the form of a flake, granule, pellet, and/or powder. If the resin is in the form of a powder or flake, the metering apparatus may be an auger or crammer (not shown) to force the resin into the barrel 104 against the rotating action of the screw 102. Suitable polymeric resins include, but are not limited to, polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polyethylene, polypropylene, polycarbonates, polystyrene, styreneacrylonitrile, acrylonitrile butadiene styrene, ASA (acrylic/styrene/acrylonitrile tripolymer), polysulfone, polyurethane, polyphenylenesulfide, acetal resins, polyamides, polyaramides, polyimides, polyesters, polyester elastomers, acrylic acid esters, copolymers of ethylene and propylene, copolymers of styrene and butadiene, copolymers of vinylacetate and ethylene, and mixtures thereof.
The polymer resin is conveyed from the polymer feed zone 106 to the first compression zone 113, where mechanical action and friction generated by the rotation of the screw 102 at least partially melt the polymeric resin. Optionally, heaters (not shown) may be placed on the barrel 104 at any location to assist in melting the polymeric resin and/or maintaining the molten state of the resin. The extruder 100 may achieve a temperature in the range of from 100-600° F. during the extrusion process, depending on the resin utilized.
A blowing agent may be pre-blended with the polymeric resin and fed into the extruder 100 through the wet reinforcement fiber feed hopper 105 with the polymeric resin. The blowing agent may be added if a lower density product is desired. Typical chemical blowing agents (e.g., materials that undergo decomposition reactions producing gases) include exothermic and endothermic blowing agents. Examples of exothermic chemical blowing agents suitable for use in the present invention include, but are not limited to, azodicarbonate, p,p-oxybis(benzene) sulfonyl hydrazide, p-toluene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, dinitrosopentamethyltetramine, and 5-phenyltetrazole. Non-limiting examples of suitable endothermic chemical blowing agents include sodium bicarbonate and sodium borohydride. Other suitable chemical blowing agents include compounds are those that undergo a change of state at the desired foaming temperature, such as, but not limited to, hydroflouro compounds. Supercritical gases may alternatively be added as blowing agents after the final decompression zone in the extruder 100, e.g., the low pressure zone 115.
In one exemplary embodiment of the invention, approximately 70-90% of the blowing agent is pre-blended with the polymeric resin. The remaining 10-30% of the blowing agent may then be added via inlet 118 in direct communication with feedthroat 101 or via an inlet or conduit (not shown) in direct communication with the barrel 104. By adding a portion of the blowing agent via inlet 118, the amount of blowing agent added to the polymer resin and ultimately into the final product, can be accurately monitored and adjusted as necessary throughout the extrusion process. Alternatively, all of the blowing agent may be added via inlet 118 or an inlet or conduit (not shown) in direct communication with the barrel 104 and may not be pre-blended with the polymer resin. Once the blowing agent has been added to the barrel 104, the heat from the barrel and internal friction causes the blowing agent to at least partially decompose. In a further embodiment, no blowing agent is added.
In addition, other additives and processing aids such as thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers, and/or tackifiers may be pre-blended with the resin and added to the barrel 104 of the extruder 100. The additives and processing aids may also be added to the barrel 104 via the inlet 118 or other feedthroat or inlet (not shown) in direct communication with the barrel 104. Color pellets may be fed into the extruder 100 from a color pellet hopper (not shown) to give the final product a desired color or appearance.
Wet reinforcement fibers are fed from the wet reinforcement fiber feed hopper 110 through the feedthroat 103 and into the barrel 104 of the extruder 100 where they are mixed with the molten polymeric resin in a high volume zone 107. By incorporating the wet reinforcement fibers into the molten resin, there is less wear and tear on the barrel 104 and screw 102 of the extruder 100. In the high volume zone 107, the flights 108 of the screw 102 may be positioned at a greater pitch and/or greater depth than the flights 108 in the polymer feed zone 106 and/or the first compression region 113. In addition, the individual flights 108 in the high volume zone 107 may be spaced farther apart than the flights 108 in the polymer feed zone 106 and/or the first compression zone 113. This larger pitch and/or greater depth of the flights 108 in the high volume zone 107 increases the throughput of the section and allows the wet reinforcement fibers to be introduced into the barrel 104 of the extruder 100, to mix with the molten resin, and to form a molten resin/fiber mix. In one or more exemplary embodiments, the flights 108 in the high volume zone 107 may have a pitch and/or depth that is substantially equal to the flights 108 in the polymer feed zone 106. The wet reinforcement fibers may be metered into the barrel 104 by a metering mechanism such as a vibratory device or screw (not shown) or cram feeder (not shown) that may optionally be mounted within feedthroat 103.
Suitable reinforcement fibers include, but are not limited to, wet use chopped strand glass fibers. Wet reinforcement fibers, such as are used in the present invention, are typically agglomerated in the form of a bale, package, or a bundle of individual fibers. The term “bundle” as used herein is meant to indicate any type of agglomeration of wet reinforcement fibers, which would be easily identified and understood by those of ordinary skill in the art. Any type of glass fibers, such as A-type glass fibers, C-type glass fibers, E-type glass fibers, S-type glass fibers, AR type glass fibers, or modifications thereof can be used as the wet chopped strand glass fibers.
In a preferred embodiment, the reinforcement fibers are wet use chopped strand glass fibers. Wet use chopped strand glass fibers used as the reinforcement fibers may be formed by conventional processes known in the art. The wet use chopped strand glass fibers may have a moisture content of from 1-30%, and preferably have a moisture content of from 5-15%. The chopped strand glass fibers may have a length of from 6-75 mm (and may be longer, depending on the process used). In preferred embodiments, the glass fibers have a length of from 6-12 mm. The diameter of the glass fibers may range from 9-25 microns, and preferably range from 12-16 microns.
Alternatively, the reinforcing fiber material may be strands of one or more synthetic polymers such as polyester, polyamide, aramid, and mixtures thereof. The polymer strands may be used alone as the reinforcing fiber material, or they can be used in combination with wet glass strands such as those described above. Carbon or polyamide fibers may be also used as the wet reinforcing fiber material. In a further alternative embodiment, natural fibers, such as hemp, jute, flax, kenaf, sawdust, or any other known natural fiber may be used alone, or in combination with the glass and/or polymer fibers.
In one exemplary embodiment, the wet reinforcement fibers are fed into an opener (not shown) which at least partially opens and/or filamentizes (e.g., individualizes) the wet reinforcement fibers prior to their addition to the wet reinforcement fiber feed hopper 105. The opener may then dose or feed the wet reinforcement fibers to an evaporator (not shown), where at least a portion of the water is removed from the wet fibers. In exemplary embodiments, greater than 70% of the free water, e.g., water that is external to the reinforcement fibers, is removed. Preferably, however, substantially all of the water is removed by the evaporator. It should be noted that the phrase “substantially all of the water” as it is used herein is meant to denote that all or nearly all of the free water is removed. Optionally, a second opener (not shown) may be used to further filamentize or individualize the wet reinforcement fibers and/or additional evaporators and/or heaters. Such embodiments is considered to be within the purview of this invention. In an alternative embodiment, some or all of the water from the wet glass may remain within the mixture, instead of venting substantially all of the water as described above. In this embodiment, depending on water content, it may be desirable to vent a portion of the water. In these embodiments, the water is used as a foaming agent, or in combination with chemical foaming agents to provide a desired density, or a desiccant may be used to capture excess water in a manner similar to those described in U.S. Pat. No. 6,355,698, which is incorporated herein by reference, to create the desired cell structure and density.
The opener may be any type of opener suitable for opening the bundle of wet reinforcement fibers. The design of the openers depends on the type and physical characteristics of the fiber being opened. Suitable openers for use in the present invention include any conventional standard type bale openers with or without a weighing device. The bale openers may be equipped with various fine openers and may optionally contain one or more licker-in drums or saw-tooth drums. The bale openers may be equipped with feeding rollers or a combination of a feeding roller and a nose bar. The evaporator may be any known drying or water removal device known in the art, such as, but not limited to, an air dryer, an oven, rollers, a suction pump, a heated drum dryer, an infrared heating source, a hot air blower, and a microwave emitting source.
Turning back to FIG. 2, the molten resin/fiber mix is pushed downstream by the screw 102 along the inside of the barrel 104 from the high volume zone 107 to a second compression zone 112 where the molten thermoplastic resin and reinforcing fiber material are mixed and intimately compounded to form a substantially homogenous mass. The flights 108 of the screw 102 may have a smaller angle, smaller pitch, lower depth, closer spacing, and/or a closer tolerance to the barrel 102 than the flights 108 located in the polymer feed zone 106, the first compression zone 113, and the high volume zone 107. As a result, the molten resin/fiber mixture tightly fills the spaces between the flights 108. The shear force caused by the friction between the barrel 104 and the increased shear within the flights 108 as the resin/fiber mixture is forced down the barrel 104 causes the bundles of reinforcement fibers to open and separate (e.g., filamentize). In addition, friction (heat) generated by the rotation of the screw 102 as the molten resin/fiber mix is conveyed downstream causes the moisture that was held within the bundles to evaporate.
In order to reduce the vapor that may build up from water evaporating primarily from the fibers, the molten resin/fiber mixture is preferably conveyed through a low pressure zone 115 that contains flights 108 that preferably have a pitch and/or depth and/or spacing that is greater than the flights in the polymer feed zone 106, high volume zone 107, and first and second compression zones 113, 112. It is preferred that the flights 108 in the low pressure zone 115 have a greater pitch and be spaced apart a greater distance than the flights 108 located in the first compression zone 112. It is also envisioned that the flights 108 in the high volume zone 107 and the flights in the low pressure zone 115 may have a pitch and/or depth that are substantially equal to each other.
An opening 109, such as a vent, positioned in the low pressure zone 115 permits the water vapor and/or other volatiles that may be released from the fibers, additives, and/or processing aids to escape into the air. Releasing the water vapor helps to reduce or prevent degradation of the polymer resin and the occurrence of voids into the final product. It is desirable to volatize substantially all of the moisture from the resin/fiber mixture to achieve a consistent foaming material and/or to control the foaming action. Any moisture that remains in the resin/fiber mixture after passing through the low pressure zone 115 may be used to produce a desired foaming action to lower the product density or to increase the thermal or electrical insulation value of the resulting product.
The viscous resin/fiber mixture then exits the low pressure zone 115 and is conveyed to a compression/die feed zone 116 to further mix and/or compound the resin and glass fibers. The flights 108 in the compression/die feed 116 zone may have a pitch and/or depth that is the same as or smaller than flights in the polymer feed zone 106 and high volume zone 107. The resin/fiber mixture is conveyed from the extruder 100 as a foaming extrudate into a shaping die 120 which shapes the extrudate into a desired shape. A breaker plate, screen or adapter (not shown) may be used to transition the extrudate from the extruder 100 to the shaping die 120. In the adapter, the extrudate is collected as it exits the extruder 100 and is re-shaped so that it may be fed into the die 120 as a solid and continuous slug. The shaping die 120 may be of any shape, such as, for example, a rectangle, sheet, or square. The shaping die 120 may also be configured for use as e.g. a window or door profile. In at least one preferred embodiment, the die 120 forms the extrudate into a generally flat board or sheet that may be formed into a siding product, and the die may comprise a Celuka die. Preferably, the sheet is 30-50 mils in thickness. To form a hollow product, the die 120 may include a mandrel (not shown). In addition, it is within the purview of this invention to include one or more dies arranged in series to achieve the desired shape.
In at least one exemplary embodiment, as illustrated in FIG. 4, the polymer resin and the wet reinforcement fibers are substantially simultaneously fed into the barrel 104 of the extruder 100 through a resin/fiber feedthroat 130. As used herein, the term “substantially simultaneously fed” is meant to indicate that the resin and wet reinforcement fibers are fed into the barrel 104 at the same time or at nearly the same time. The extruder 100 contains at least one screw 102 having flights 108 rotating in the direction of arrow 131. As shown in FIG. 4, the wet reinforcement fiber feed hopper 110 may be connected to resin/feed feedthroat 130 via a wet fiber feedthroat 132. Optionally, the wet fiber feed feedthroat 132 may contain a vibratory device (not shown) or screw 134 to assist in conveying the wet reinforcement fibers from the wet reinforcement fiber feed hopper 110 to the resin/feed feedthroat 130.
An opener (not shown) may be used to at least partially open the bundles of wet reinforcement fibers prior to their addition into the wet reinforcement fiber feed hopper 110. The wet reinforcement fibers may also be at least partially dried, such as by passing the wet reinforcement fibers through a heated chamber or a microwave chamber, prior to entering the opener or the wet reinforcement fiber feed hopper 110. In addition, the resin/feed feedthroat 130 may include baffles (not shown) baffles or other mixing/feeding devices to further blend and mix the wet reinforcement fibers and the polymer resin prior to entering the extruder 100. An embodiment in which the resin and the wet reinforcement fibers are pre-mixed and fed to the extruder by a single hopper (not shown) is also considered to be within the purview of this invention.
In FIG. 4, the resin/fiber mixture enters the barrel 104 of the extruder 100 in a polymer feed zone 133. The resin/fiber mixture is then conveyed downstream to a compression zone 136 where the polymer resin melts due to the mechanical action and friction generated by the rotating action of the screw 102 and substantially homogenously mixes with the wet reinforcement fibers. The flights 108 in the compression zone 136 may have a pitch and/or depth and/or spacing that is smaller than the flights 108 in the polymer feed zone 133. Shear force caused by the mixing and transporting action of the screw as the resin/fiber mixture is conveyed down the barrel of the extruder causes the bundles of reinforcement fibers to filamentize (e.g., open and separate). Heaters (not shown) may be placed at any location on the barrel 104 to assist in melting the polymeric resin and/or maintain the molten/fused state of the resin as the resin/fiber mixture is conveyed through the extruder 100.
As the molten resin/fiber mass is pushed downstream by the screw 102 along the inside of the barrel 104, the heat generated by the extrusion process causes the moisture in the wet reinforcement fibers to evaporate. To release the vapor pressure, the resin/fiber mixture is passed through a low pressure zone 137 that contains flights 108 that may have a greater pitch, depth, and/or spacing than the flights 108 in the polymer feed zone 133 and the compression zone 136. An opening 109 is positioned in the low pressure zone 137 to release water vapor or other vapors that may be released in the compression zone 136 out of the extruder 100 and into the air. The viscous resin/fiber mixture is conveyed from the low pressure zone 137 to a compression/die feed zone 138. The flights 108 in the compression/die feed zone may contains flights 108 that have a smaller pitch, depth, and/or spacing than the flights 108 in the low pressure zone 137 and a pitch, depth, and/or spacing that is the same as or smaller than the flights 108 in the polymer feed zone. Finally, the resin/fiber mix is conveyed from the extruder 100 as an extrudate to the shaping die 120 where it is formed into a desired shape. One or more dies (not shown) may be arranged in series to achieve the desired shape.
It is to be appreciated that the description of the flights and depths of the zones of the screw of the extruder of the various embodiments of the invention are described herein in generalities and are for illustration only. One of skill in the art would understand that the various zones can have various specific pitches and spacings and still provide the function of the particular zone to provide effect of the operation of the invention. It is also to be understood that such varying pitches and spacings for the different zones may also be dependent upon the specific resin chosen. All of such alternative embodiments are considered to be within the purview of this invention.
A schematic illustration of an exemplary extrusion line according to the instant invention is shown in FIG. 6. As the extrudate exits the shaping die 120, it is pulled at a substantially constant speed into a calibrator 140 by a pulling apparatus 145. The pulling apparatus 145 may include a plurality of power driven upper and lower rollers 147,148 that grip and pull the extrudate from the shaping die 120 through at least one calibrator 140 and cooling tank 150. Another example of a suitable pulling apparatus is a track puller (not shown) that contains rubber tracks above and below the extrudate for gripping and pulling the extrudate down the extrusion line.
The molten extrudate exiting the shaping die 120 possesses a foaming pressure that continues to build within the calibrator 140. As the foaming pressure builds, the molten extrudate is forced against a fixed, cooled internal surface which sizes or calibrates the extrudate to a desired shape. In addition, the cooled internal surface cools the surface of the foaming extrudate to form a high-density skin. It is preferred that the skin be of a sufficient density and thickness to prevent molten extrudate in the core from bulging or bursting through the skin as it exits the calibrator(s). The cooled internal surface of the calibrator 140 may be water- or air-cooled channels 142. A vacuum (not shown) may also be used to pull the external surface of the molten extrudate to the cooled surface or surfaces of the cooled channels 142 within the calibrator 140 and calibrate the extrudate.
To further cool the shaped extrudate, it may be passed through at least one cooling tank 150 having a length sufficient to cool the extrudate and set it into its formed shape. Preferably, the cooling tank 150 cools the extrudate with minimal stress on the extrudate. In at least one embodiment, the cooling tank(s) 150 contains waters sprays 155 that spray water onto the shaped extrudate. In another embodiment of the present invention, the cooling tank(s) contain a water bath (not shown) through which the extrudate is passed to cool and set the extrudate.
The cooled, shaped extrudate may be passed through an embosser 160 to give the shaped extrudate a desired surface finish. The embosser may be a two roll device in which at least one of the rolls contains a design. The design may be carved or etched into the roll. The second roll is opposed to the first roll so that pressure may be used to apply the design to the formed extrudate. The rolls may be held at a controlled temperature to assist in the embossing process.
After exiting the embosser 160, the extrudate may be passed through a cut off and trimming apparatus 170. Here, the extrudate may be cut into desired lengths and/or sizes and the lateral edges may be trimmed. The cut off saw may be mounted on a moving carriage that moves with the extrudate to produce a smooth straight cut at a desired angle. It is desirable that the cut-off device be electronically controlled to produce a cut piece having a desired length.
Optionally, the polymer/fiber mixture is co-extruded with a cap stock such as a polyvinyl chloride, acrylic cap stock, ASA (acrylic/styrene/acrylonitrile tripolymer), or other suitable cap materials. As illustrated in FIG. 6, a cap extruder 135 may be positioned in the extrusion line at a location such that a cap formed of the cap stock and a base sheet formed of the extrudate exit the shaping die 120 together. The cap stock is co-extruded in cap extruder 135 in a manner well-known to those of ordinary skill in the thermoplastic extrusion art. The cap may be approximately 2-14 mls in thickness and may or may not be foamed. Alternatively, a film may be applied to the surface of the extrudate.
A schematic illustration of another exemplary extrusion line according to the instant invention is shown in FIG. 7. Wet reinforcement fibers, e.g., WUCS glass fibers, from the wet reinforcement feed hopper 110 and polymer resin from the resin feed hopper 105 are fed into the extruder 100 via resin/fiber feedthroat 130 at substantially the same time. It is to be noted that the phrase “substantially the same time” as used herein is meant to indicate that the wet reinforcement fibers and polymer resin are fed into the extruder 100 at the same time or at nearly the same time. Color pellets may be fed into the extruder 100 via a color pellet hopper (not shown) that may be interconnected with the resin/fiber feedthroat 130 via a conduit (not shown) to give the final product a desired colored appearance.
The extrudate exiting the die 120 is pulled at a substantially constant speed by a pulling apparatus 145 and passed through embossing rolls 172 which place a design on the extrudate so that the final product formed has an aesthetically pleasing surface. One or more of the embossing rollers 172 may include a design. Next, the extrudate is passed through cooling rollers 174 and into the calibrator 140 to size or calibrate the extrudate to the desired shape. After the extrudate is calibrated, the shaped extrudate is further cooled by passing the extrudate through a cooling tank 150.
The extrudate may then pass through a perforator 176 which punches or drills holes in the extruded material to serve as vents, drains, weep holes, and/or nailing slots. After exiting the perforator 176, the extrudate may be cut into discrete lengths by the cut off and trimming apparatus 170 to form the final product, such as a vinyl siding product (not shown). The final product may be stacked on a packing table 175 for packaging and subsequent shipping.
Optionally, a cap extruder 135 may be positioned on the extrusion line to co-extrude a cap. As illustrated in FIG. 7, cap stock (not shown) may be fed from a cap stock feed hopper 180 through a feedthroat 181 and into the cap extruder 135. Color pellets may be fed into the cap extruder 135 from color pellet hopper 182 via feedthroat 183 to give the cap a desired color or appearance. The molten cap stock mixture (not shown) that exits the extruder 135 is conveyed to the die 120. To co-extrude a cap, the cap formed from the cap stock and the base sheet formed from the polymeric resin/fiber mixture from the extruder 100 exit the die 120 at substantially the same time.
It is to be noted that although various embodiments containing different features have been separately described above, individual features of the various embodiments may be combined in any manner and such other embodiments are considered to be within the purview of the invention.
Vinyl siding products such as may be produced by the extrusion processes described herein often contain fillers to increase the modulus or stiffness of the siding product and to decrease the amount of movement that can occur as a result of a change of temperature of the siding. When wet reinforcement fibers such as WUCS are used to reinforce vinyl siding products as in the present invention, a higher loading of fillers may be included in the siding product. Therefore, vinyl siding products reinforced with WUCS glass fibers demonstrate reduced heat distortion. For example, WUCS-reinforced siding products do not thermally distort at a temperature of 160° F. Examples of suitable fillers that may be present in the vinyl siding product include, but are not limited to, calcium carbonate talc, titanium dioxide, aluminum trihydrate, clays, calcium silicate, kaolin, magnesium oxide, molybdenum disulfide, silica, slate powder, zinc salts, zeolites, calcium sulfate, barium salts, Portland cement, CaO, Na₂CO₃, and/or CaSO₄.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples illustrated below which are provided for purposes of illustration only and are not intended to be all inclusive or limiting unless otherwise specified.

EXAMPLES

Example 1

A PVC rigid extrusion compound was metered into the feedthroat of a 130 mm twin screw extruder at the rate of 2200 lb/hr. At the same time, WUCS glass fibers having a 12% moisture content were metered via a side mounted vibrator feeder into the feedthroat of the extruder at 33 lb/hr to give a 5% by weight glass composition. A low pressure zone located approximately 60% of the way down the barrel of the extruder was used to remove the moisture from the glass filled compound. The extruder was fitted with a sheet die to produce a 48 mils thick product. The product was produced on an extrusion line such as is depicted in FIG. 6. The product met the requirements of ASTM D3679 as tested.

Example 2

A polypropylene blended with 2% of a maleic anhydride modified polypropylene was added to a feedthroat of a single screw 60 mm extruder. Approximately 16 inches downstream, wet use chopped strand glass fibers were added via a feedthroat in a high volume zone (e.g., a first low pressure zone). Located approximately another 16 inches down the barrel was a second low pressure zone fitted with a vacuum system set at 15 inches of mercury vacuum to remove moisture from the compound in the extruders. The extruder was fitted with a sheet die to extrude a 125 mils thick product.
Example 3
A compound formed of a polyvinyl chloride (PVC) resin, impact and process modifiers, a tin based stabilizer, a blowing agent, and an inorganic filler such as calcium carbonate was pre-blended with 15% of WUCS glass fibers having a 12% moisture content and fed into the feed throat of an 88 mm twinscrew extruder. The foamed extrudate was calibrated into a board.

Example 4

The compound described above in Example 3 was fed into the feed throat of an 88 mm twinscrew extruder concurrently with WUCS glass fibers having a 12% moisture content at a rate sufficient to result in a foamed extrudate with 15% glass fiber content. The foamed extrudate was formed into a board.

Example 5

The compound described above in Example 3 was fed into the feed throat of an 88 mm twin screw extruder. Wet use chopped strand glass fibers glass fibers having a 12% moisture content was added at a separate location along the barrel of the extruder after the polymer feed zone and initial compression/mixing zone. The foamed extrudate was calibrated into a board.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art (including the contents of the references cited herein), readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance presented herein, in combination with the knowledge of one of ordinary skill in the art. Furthermore, one skilled in the art may apply these teachings to processes other than extrusion, as discussed above.
The invention of this application has been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what is believed to be the preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure. The invention is not otherwise limited, except for the recitation of the claims set forth below.

Claims

1. A method for forming a reinforced extruded thermoplastic product comprising the steps of:

at least partially melting a polymeric resin in a barrel of an extruder in a first compression zone, said barrel encasing at least one rotatable screw having flights and extending substantially along a length of said barrel;

feeding wet reinforcement fibers into said barrel in a high volume zone where said flights are positioned at a greater pitch than said flights located in said first compression zone to facilitate the introduction of said wet reinforcement fibers into said barrel, said wet reinforcement fibers mixing with said molten resin to form a molten resin/fiber mixture;

conveying said resin/fiber mixture downstream along said at least one screw to a low pressure zone where water vapor released from said wet reinforcement fibers exits said barrel through an opening in said barrel; and

passing said resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.

2. The method according to claim 1, wherein said wet reinforcement fibers are wet use chopped strand glass fibers.

3. The method according to claim 2, further comprising the step of:

passing said resin/fiber mixture through a second compression zone where said wet use chopped strand glass fibers are at least partially filamentized prior to said conveying step.

4. The method according to claim 3, wherein said flights in said second compression zone have a pitch that is smaller than the pitch of said flights in said polymer feed zone, said low pressure zone, and said high volume zone.

5. The method according to claim 3, further comprising the step of:

adding said polymeric resin to said barrel in a polymer feed zone prior to said melting step.

6. The method according to claim 5, further comprising the step of:

passing said resin/fiber mixture through a compression/die feed zone to further mix and compound said resin and said wet use chopped strand glass fibers prior to entering said extrusion die.

7. The method according to claim 3, further comprising the step of:

adding a blowing agent to said barrel.

8. The method according to claim 5, further comprising the step of:

pre-blending a blowing agent with said resin prior to adding said resin to said barrel.

9. The method according to claim 2, further comprising the step of:

at least partially opening said wet use chopped strand glass fibers prior to feeding said wet use chopped strand glass fibers into said barrel.

10. The method according to claim 2, further comprising the step of:

removing at least a portion of water located in said wet use chopped strand glass fibers prior to feeding said wet use chopped strand glass fibers into said barrel.

11. The method according to claim 2, further comprising the step of:

embossing said extruded thermoplastic product.

12. The method according to claim 2, further comprising the step of:

co-extruding a cap stock onto said extruded thermoplastic product.

13. An apparatus for extruding a reinforced thermoplastic product comprising:

an elongated barrel having an outlet;

a polymer resin feed hopper to hold a polymer resin;

a wet reinforcement fiber feed hopper to hold wet reinforcement fibers;

an opening in said barrel downstream of said wet reinforcement fiber feed hopper to vent moisture released from said wet reinforcement fibers; and

at least one rotatable screw disposed within said barrel and extending substantially the length of said barrel, said at least one screw having flights in cooperation with an inner surface of said barrel to define a passage for conveying said resin and said wet reinforcement fibers downstream through said barrel to said outlet, said at least one screw including:

a polymer feed zone where said polymer resin is introduced into said barrel;

a high volume zone downstream of said polymer feed zone, said flights in said high volume zone having a pitch sufficient to facilitate the introduction of said wet reinforcement fibers into said barrel;

a first compression zone where said resin and said wet reinforcement fibers are compounded and said wet reinforcement fibers are at least partially filamentized; and

a low pressure zone downstream of said high volume zone, said low pressure zone having flights positioned at a pitch greater than said pitch of said flights in said first compression zone.

14. The apparatus of claim 13, wherein said wet reinforcement fibers are wet use chopped strand glass fibers.

15. The apparatus of claim 14, further comprising:

a first feedthroat interconnecting said polymer resin feed hopper and said barrel; and

a second feedthroat interconnecting said wet reinforcement fiber feed hopper and said barrel.

16. The apparatus of claim 15, further comprising a metering mechanism within said first feedthroat to feed said polymer resin into said barrel.

17. The apparatus of claim 15. further comprising an inlet in direct communication with said first feedthroat to supply at least one member selected from the group consisting of blowing agents, thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers and tackifiers to said first feedthroat.

18. The apparatus of claim 13, further comprising an opener connected to said wet reinforcement fiber feed hopper to at least partially filamentize said wet reinforcement fibers.

19. The apparatus of claim 18, further comprising a condenser interconnecting said opener and said reinforcement fiber feed hopper to at least partially dry said at least partially filamentized wet reinforcement fibers.

20. The apparatus of claim 13, wherein said at least one screw further includes a second compression zone positioned downstream of said polymer feed zone where said polymer resin is at least partially melted.

21. The apparatus of claim 20, wherein said at least one screw further comprises a compression/die feed zone positioned adjacent to said outlet, said flights in said compression/die feed zone having a pitch that is the same as or smaller than the pitch of said polymer feed zone, said first compression zone, said high volume zone, and said low pressure zone.

22. The apparatus of claim 21, wherein said flights in said high volume zone have a pitch that is greater than the pitch of said flights in said first and second compression zones.

23. The apparatus of claim 13, wherein said flights in said first compression zone have a pitch that is less than the pitch of said polymer feed zone, said high volume zone, and said low pressure zone.

24. An apparatus for extruding a reinforced thermoplastic product comprising:

an elongated barrel having an outlet;

a polymer resin feed hopper to hold a polymer resin;

a resin/fiber feedthroat interconnecting said polymer resin feed hopper to said barrel;

a wet reinforcement fiber feed hopper connected to said resin/fiber feedthroat to hold wet reinforcement fibers;

an opening in said barrel downstream of said polymer resin feed hopper and said wet reinforcement fiber feed hopper to vent moisture released from said wet reinforcement fibers; and

a polymer feed zone where said polymer resin is introduced into said barrel;

a compression zone positioned downstream of said polymer feed zone where said polymer resin is at least partially melted;

a low pressure zone having flights positioned at a pitch greater than the pitch of said flights in said compression zone; and

a compression/die feed zone positioned adjacent to said outlet, said flights in said compression/die feed zone having a pitch that is the same as or smaller than the pitch of said polymer feed zone, said compression zone, and said low pressure zone.

25. The apparatus of claim 24, wherein said wet reinforcement fibers are wet use chopped strand glass fibers.

26. The apparatus of claim 25, further comprising a member selected from the group consisting of one or more baffles, a crammer and a vibratory screw positioned in said resin/fiber feedthroat to mix said resin and said wet reinforcement fibers.

27. The apparatus of claim 25, wherein said wet fiber feedthroat interconnects said wet reinforcement fiber feed hopper and said resin/fiber feedthroat, said wet fiber feedthroat including a vibratory screw.

28. The apparatus of claim 25, further comprising an opener connected to said wet reinforcement fiber feed hopper to at least partially filamentize said wet use chopped strand glass fibers.

29. The apparatus of claim 28, further comprising a condenser interconnecting said opener and said reinforcement fiber feed hopper to at least partially dry said filamentized wet use chopped strand glass fibers.

30. A method for forming a reinforced extruded thermoplastic product comprising the steps of:

adding a premix to a barrel of an extruder in a polymer feed zone, said barrel encasing at least one rotatable screw having flights and extending substantially along a length of said barrel;

at least partially melting said premix in a compression zone to form a molten resin/fiber mixture;

conveying said molten resin/fiber mixture downstream along said at least one screw to a low pressure zone where water vapor released from said wet reinforcement fibers as said resin/fiber moisture is conveyed along said at least one screw escapes from said barrel through an opening in said barrel; and

passing said molten resin/fiber mixture through an extrusion die to form said extruded thermoplastic product.

31. The method of claim 30, wherein said wet reinforcement fibers are wet use chopped strand glass fibers.

32. The method according to claim 31, further comprising the step of:

passing said molten resin/fiber mixture through a compression/die feed zone prior to passing said resin/fiber mixture through said die, said flights in said die feed zone having a pitch that is no larger than said flights in said polymer feed zone.

33. The method of claim 32, further comprising the step of:

blending a polymer resin and wet reinforcement fibers to form said resin/fiber premix.

34. The method according to claim 33, further comprising the step of:

adding a member selected from the group consisting of blowing agents, thermostabilizers, UV stabilizers, lubricants, colorants, fillers, compatibilizers, melt strength enhancers, and tackifiers to said barrel.

35. The method according to claim 31, further comprising the steps of:

at least partially opening said wet use chopped strand glass fibers prior to blending said wet use chopped glass fibers and said resin; and

removing at least a portion of water located in said wet use chopped strand glass fibers after said wet use chopped strand glass fibers have been at least partially opened.

36. A method for forming a reinforced extruded thermoplastic product comprising the steps of:

feeding a polymeric resin and wet reinforcement fibers into a barrel of an extruder;

at least partially melting the polymeric resin in the barrel;

mixing said fibers with said molten resin to form a molten resin/fiber mixture;

conveying said resin/fiber mixture downstream along said at least one screw to a zone where water vapor released from said wet reinforcement fibers exits said barrel through an opening in said barrel; and

37. A method for forming a reinforced extruded thermoplastic product comprising the steps of:

at least partially melting the polymeric resin in the barrel;

mixing with said molten resin to form a molten resin/fiber mixture;

conveying said resin/fiber mixture downstream along said at least one screw to a zone where at least a portion of the water vapor released from said wet reinforcement fibers acts as a blowing agent for said resin; and

38. The method according to claim 37, further comprising the step of:

conveying said resin/fiber mixture downstream along said at least one screw to a zone where at least a portion of the water vapor released from said wet reinforcement fibers is removed from said barrel.

39. The method according to claim 37, further comprising the step of:

feeding active or anhydrous fillers to said mixture to bind moisture released during said process.

40. The method according to claim 37, further comprising the step of:

adding a blowing agent to said barrel.