WO1996027485A1

WO1996027485A1 - Method of recycling polymer materials and sheet article made thereby

Info

Publication number: WO1996027485A1
Application number: PCT/US1996/002987
Authority: WO
Inventors: Marvin R. Havens; Robert F. Jenkins; Makam S. Chetan; Michael L. Becraft
Original assignee: W.R. Grace & Co.-Conn.
Priority date: 1995-03-07
Filing date: 1996-03-01
Publication date: 1996-09-12
Also published as: BR9607194A; EP0758946A1; MX9606240A

Abstract

An extruded sheet and method of forming the sheet from recycled polymeric material having a hygroscopic component, a PVC and/or PVDC component or mixtures or blends of same, and/or a crosslinked polymeric component. The recycled polymeric material is introduced into an extruder to form a melt, and the melt is extruded through a slot die to form the sheet. Also included is an extruded foam sheet incorporating a recycled material having a hygroscopic component in an amount of about 23 percent by weight, a PVC and/or PVDC component or mixtures or blends of same, and/or a crosslinked component, and the method of recycling the material by foam extrusion.

Description

METHOD OF RECYCLING POLYMER MATERIALS AND SHEET ARTICLE MADE THEREBY

Field of the Invention

The invention relates to a method by which polymeric scrap materials are recycled into a sheet material, and to the sheet article formed thereby. More particularly, the invention relates to a method of recycling a material having a hygroscopic component, a PVC or PVDC component or mixtures or blends thereof, and/or a crosslinked component, into the sheet article of the invention.

Background of the Invention

Large quantities of polymer scrap materials are generated in the manufacture of polymeric films and other polymer-containing products. A potential alternative to disposing of the scrap in landfills is the recycling of the scrap in an economically and environmentally feasible manner. Although the recycling approach has been successful in some cases, there are many polymeric materials that have proved difficult to recycle.

Polymeric scrap often contains more than a single polymeric component. Recycling processes applicable to single component materials, for example polyesters such as polyethylene terephthalate, may not be feasible with scrap containing other types of polymeric components. For example, PET can be recycled by glycolysis or other methods into its constituent moieties which can be re-reacted in the primary reactions that produce the end polymer. Such processes, however, prove difficult or infeasible in recycling multi-polymeric component scrap, examples of which include multilayer flexible films and laminates useful in packaging applications. These films or laminates may contain other polymers, such as an alpha-olefin copolymer, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), or a polyamide such as nylon. Other methods have been attempted in recycling these types of films, but with limited success.

In one method, scrap is blended with a virgin or non-recycled material in an extruder and then extruded in the form of a blended polymeric melt. Certain materials, however, are difficult to process and recycle in this manner. For example, it is difficult to recycle films containing a hygroscopic material such as EVOH or nylon. The amount of such recycled material in the blend may be limited and the blend require a high weight proportion of virgin or non-recycled material for successful extrusion. Another material that is difficult to recycle is one containing a crosslinked, or gel, component. Flexible, heat-shrinkable polymeric films are typically subjected to irradiation during manufacturing to induce cross-linking. The crosslinked component can be difficult to melt process and /or blend and therefore prove difficult to recycle. Other materials difficult to recycle by conventional means are those, like

PVC or PVDC-containing materials, having components which upon degradation can evolve harmful gases. Those containing PVC or PVDC tend to release HCL gas upon dissociation.

It is therefore desirable to provide a method of recycling polymeric materials, and a polymeric sheet incorporating same, that can successfully incorporate these difficult to recycle materials.

Summary of the Invention

The present invention in one aspect is directed to a method of recycling a polymeric material comprising a hygroscopic polymeric component to extrude a nonfoamed sheet and also to the sheet formed thereby. The method comprises the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder in which foaming agent is substantially absent; and extruding the melt in the form of a sheet.

The invention is also directed to a method of recycling a polymeric material comprising a hygroscopic polymeric component to extrude a foam sheet, and to the foam sheet thus formed. The method comprises the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder comprising at least about 23 percent by weight of the hygroscopic component; introducing a foaming agent into the melt; and foam extruding the melt in the form of a foam sheet. The foam sheet therefore comprises at least about 23 percent by weight of the hygroscopic component.

The invention is further directed to a method of recycling a polymeric material comprising a component selected from the group consisting of PVC, PVDC, and mixtures or blends thereof, and to the sheet article thus formed. It comprises the steps of: providing a neutralizing compound for blending with the scrap or for introducing into the melt; introducing the polymeric material into an extruder; forming a melt in the extruder; introducing a foaming agent into the melt; and foam extruding the melt in the form of a foam sheet.

In another aspect, the invention is directed to a method of recycling a polymeric material comprising a crosslinked polymeric component and to the sheet thereby formed. The method comprises the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder; and extruding the melt in the form of a sheet. Optionally, the method can further comprise the step of introducing a foaming agent into the melt to extrude a foam sheet comprising the recycled crosslinked polymeric component.

In yet another embodiment, the invention is directed to a method of recycling a polymeric material having a hygroscopic polymeric component and a crosslinked polymeric component, and to the sheet thus formed. The method comprises the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder; and extruding the melt in the form of a sheet. The method can further comprise the step of introducing a foaming agent into the melt to extrude a foam sheet comprising the recycled hygroscopic and crosslinked polymeric components. The method and sheet article of the invention overcome the disadvantages discussed above. Since the recycled scrap of the invention is often generated in significant volumes in manufacturing operations, the invention can produce significant cost savings. The invention allows the recycle of polymeric scrap material that is otherwise difficult to recycle and costly to dispose of. The sheet of the invention is useful in many applications, which include but are not limited to use as a backing material for construction waterproofing materials or use as a substrate or monolayer incorporated into a laminate.

These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from the following detailed description of the preferred embodiments and appended claims.

Definitions

As used herein, the following abbreviations and terms have the meanings defined below:

"Polymer", "polymeric", and the like, unless specifically defined or otherwise limited, generally includes homopolymers, copolymers and terpolymers, and blends and modifications thereof.

"Sheet material" or "Sheet" as used herein designates a web that is extruded from a die slot, e.g. a rectangular die slot, in sheet form, or a tubular foam film extruded through a round die which after extrusion is slit longitudinally into sheet form. When referring herein to sheet material thickness, the term "thickness" shall mean and include average transverse thickness.

"Hygroscopic" indicates the tendency of the specified material to absorb water, as from humidified air.

EVA: designates ethylene vinyl acetate copolymers.

EBA: designates ethylene butyl acrylate copolymers.

EAA: designates ethylene acrylic acid copolymers.

PVDC: designates polyvinylidene chloride copolymers and terpolymers. These include vinylidene chloride /vinyl chloride copolymers (VDC/VC), copolymers of vinylidene chloride and acrylate esters such as methylacrylate (VDC/MA) and methylmethacrylate (VDC/MMA), and vinylidene chloride /acrylonitrile copolymers. Ethylene alpha-olefin copolymer: generally refers to a copolymer of ethylene with one or more comonomers selected from C3 to about C.o alpha olefins. These include: heterogeneous materials such as linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), and ultra low density polyethylene (ULDPE); and homogeneous copolymers such as metallocene catalyzed polymers such as EXACT (TM) materials supplied by Exxon, and TAFMER (TM) materials supplied by Mitsui Petrochemical Corporation. These materials generally include copolymers of ethylene with one or more comonomers selected from C₄ to C₁₀ alpha-olefins such as butene-1 (i.e., 1-butene), hexene-1 , octene-1 , etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts. LLDPE as used herein has a density in the range of from about 0.91 g/cc to about 0.94 g/cc. Other ethylene /alpha- olefins copolymers, such as the long chain branched homogeneous ethylene /alpha-olefin copolymers available from the Dow Chemical Company, known as AFFINITY or ENGAGE (TM) resins, are also included as another type of ethylene alpha-olefin copolymer useful in the present invention.

HDPE: high density polyethylene LDPE: low density polyethylene

EVOH: ethylene vinyl alcohol

EVAL: hydrolyzed ethylene vinyl acetate

PP: polypropylene

Tie: designates when referring to a layer in a multi-layer film or laminate that the layer is provided as an adhesive layer to join the two adjacent layers.

Detailed Description of the Invention

The recycled polymeric materials of the invention include polymeric materials having a hygroscopic polymeric component. These include mono- or multi-layer films having one or more layers containing EVOH, nylon, both such materials, or the like. The method and sheet of the invention can advantageously incorporate recycled materials comprising the hygroscopic polymeric material by conventional extrusion in which foaming agent is substantially absent from the extruder melt. Alternatively, in the foam extrusion embodiment discussed below, the amount of hygroscopic polymeric material comprises at least about 23 percent by weight of the recycled material. Surprisingly, the polymeric hygroscopic scrap can be extruded without blending in additional non-hygroscopic-containing polymeric material, although it may be included if desired. Therefore, the invention includes recycled material that consists essentially of polymeric material comprising a hygroscopic component, but which may include addenda and additives such as are further described below.

The invention also includes polymeric materials having a crosslinked component. Examples of crosslinked polymeric materials are well known and include those in which crosslinking is induced by chemical initiators and also those in which crosslinking is induced by radiation. Flexible heat-shrinkable films, including oriented multilayer films used in diverse packaging applications, are typically subjected to an irradiation step in manufacture to enhance the mechanical properties by polymeric crosslinking in one or more layers. Scrap is generated during the manufacturing process, and this scrap containing a cross¬ linked component can be recycled according to the invention. A preferred amount of recycled crosslinked component by weight of the polymeric material is in the range of from about 10 percent to about 90 percent of gel as determined by ASTM Test D-2765-90. A particularly preferred amount of crosslinked component is from about 15 to about 45 percent of gel.

The present invention also includes the recycling of polymeric materials containing combinations, blends, or mixtures or the like of any of the above-described recycled materials, either together and/ or with other polymeric materials. Such other polymenc materials include but are not limited to ethylene/ alpha-olehns such as LDPE, LLDPE,

VLDPE, ULDPE, HDPE, polypropylene and EPC, PET and PE, polyamides, PVC, PVDC, EVOH, ethylene vinyl esters such as EVA, and ethylene acrylate esters such as EBA. Representative examples of recyclable polymeric scrap articles include used consumer polymenc articles, for example plastic milk bottles, HDPE water bottles, and articles such as tires containing other types of crosslinked polymeric materials, to name but a few. Any of these combinations of matenals can be extruded into the sheet article of the invention. In the extrusion method of the invention, the recycled scrap material as described above is first compressed and/or comminuted into pellets, flakes, powder, or chunks. The comminuted scrap is then fed to an extruder, for example a melt screw extruder. The scrap can be fed into the extruder through a hopper or crammer feeder, either directly on-line from the comminuting means or alternatively batch-fed into the hopper. If desired, the scrap can be mixed or blended in the hopper or the extruder with a virgin or non-recycled polymeric material.

The extruder may comprise either a single stage extruder or a multistage extruder. In a preferred embodiment, the scrap is fed to the primary melt screw extruder of a two stage extruder. The primary extruder functions to melt the thermoplastic material comprising the recycled scrap into a molten mass or "melt", to mix and uniformly disperse any additives into the melt, to increase the bulk density of the melt and to force trapped air from the melt. A typical extruder comprises in sequential order a feed zone for intake of material near the beginning of the screw, a melt zone which melts, mixes, and compresses the molten material, and a metering zone into which further material or additives can be introduced. In a preferred embodiment, a foaming (also termed "blowing") agent such as carbon dioxide is introduced into the extruder, and preferably injected into the melt near the end of the primary extruder. In the case of a foaming agent that is volatile at the pressure and temperature conditions in the extruder, the selection of foaming agent should be such that it can decompose at or below the temperature at which extrusion will be carried out for the particular recycled polymeric scrap material in order to evolve the gas. Examples of foaming agents that decompose at specific temperatures to liberate gases may be found in U.S. Patent No. 4,181,780, issued January 1 , 1980, Brenner et al., which is incorporated herein by reference. Foaming agents useful in the invention are also described in Handbook of

Polymeric Foams and Foam Technology. Chapter 17, "Blowing Agents For Polymer Foams", F. A. Shutov (1991). The amount of chemical foaming agent that is employed is typically in the range of from about 0.25 to about 5 parts per hundred by weight based on the weight of the extruded material. Useful foaming agents also include physical foaming agents, which are well known in the art. Examples of these include butane, pentane, hexane, heptane, carbon dioxide, dichlorodifluoromethane, and nitrogen and the like. The invention also includes foam extrusion in which the foaming agent is introduced into the melt by the generation of a foaming gas as a product of a chemical reaction that takes place in the extruder, a process termed "reactive extrusion". In this method, the scrap is introduced into the extruder with other materials that will react to produce a gaseous reaction product or products. For example, a scrap ethylene /alpha-olefin such as LLDPE is introduced into the extruder with an acid polymer such as EAA and a base material such as a mineral carbonate or bicarbonate. A neutralization reaction takes place in the extruder under pressure. An exemplary reaction is: R-COOH + NaHCO₃ -— > R-COO Na⁺ + CO₂ + H₂O

The reaction of a metal salt and an acid copolymer can therefore produce a reaction product that chemically incorporates a metal ion into the resin, otherwise referred to generically as in "ionomer", while generating a gas. Suitable stoichiometric combinations depend upon the choice of acid and base components and on processing variables, which is within the skill of one of ordinary skill in the art.

The above reaction produces carbon dioxide in the product mix, which upon extrusion and due to the pressure drop across the die is released as a foaming agent in the extrudate. Reactive extrusion thus provides both a process for foam extruding the polymeric scrap and a means for conveniently introducing a foaming agent into the melt. Of course, additional foaming agent may be provided if desired or necessary. Without being bound by theory, it appears that the ionomer of the neutralization reaction provides the additional ahvantage of wetting and binding the scrap together while gases evolve to fill any voids present in the melt and which upon expansion at the die lip produce a foaming effect.

When practicing foam extrusion, it may also be desirable to introduce a nucleating agent to the extruder. The nucleating agent, which functions to provide sites for bubble formation, can be introduced or metered into the same feed stream as the scrap or separately through a port intake downstream of the hopper. The nucleating agent helps produce a foam having small and uniform cells. Typical nucleating agents are citric acid, sodium bicarbonate, and magnesium oxide. Various other additives can be introduced into the extruder or into the materials fed to the extruder. The additives can include fillers or pigments such as carbon black, lubricants and virgin thermoplastics as discussed above, process oils, and mixtures thereof. These or other additives can be employed to improve the physical properties, the appearance, the chemical properties, or the processability of the compositions for foaming. Certain additives or stabilizers may be desirable when recycling PVC and /or

PVDC-containing materials, mixtures or blends of same, or any materials that upon degradation can evolve potentially harmful byproducts such as HCl gas. For example, when recycling PVC and /or PVDC, a neutralizing compound such as a metal carbonate or bicarbonate can be added to the scrap or the melt to neutralize HCl. The evolved acid byproducts can also be reacted with an additive such as a foaming agent to evolve acceptable foaming gases as a reaction product. This can decrease or eliminate the necessity of adding an additional mineral acid component such as a metal carbonate or bicarbonate during foam extrusion. The relative amounts of desired additives, and the technique of their incorporation into the blend composition or extruder, can be readily determined for an intended application by one of ordinary skill in the art.

The melt from the primary extruder next enters the secondary extruder where it is cooled prior to extrusion. The cooling profile of the secondary extruder can be adjusted as desired to optimize the line speed while maintaining the appropriate temperature and melt viscosity for foaming the melt. The extruder configuration can be modified or augmented as desired for a particular application. For example, a screen changer may be positioned in the connecting pipe between the primary and secondary extruders to remove foreign particles that could potentially clog the die. This, however, may not be preferred when recycling some crosslinked materials, which may tend to accumulate on the screen changer and cause clogging. Such modifications are within the skill of one of ordinary skill in the art. The melt is then extruded through the die slot in the form of a sheet. If practicing foam extrusion, the foaming of the extrudate occurs at the die lips to form the foam sheet embodiment of the invention. As referred to above, parameters such as extruder temperature, pressure, and compression can be routinely adjusted to produce the desired or optimal extrusion conditions for a particular recycle material or blend. For example, it may be preferable to extrude a crosslinked thermoplastic material such as polyethylene at a temperature at or above about 350 degrees F. As the amount of crosslinking, i.e. gel content, is increased, the polyethylene melt may prove deformable but not freely flowable in the extruder and thus be difficult to extrude despite increasing the extrusion pressure. Under these conditions, it may be desirable to add uncrosslinked polymeric material, virgin or recycled, and /or resins, plasticizers, lubricants, processing aids, and other materials to the extruder to decrease the melt viscosity and thereby increase flowability and throughput. Under some operating conditions, particles such as compacted foaming agent may form in the melt and accumulate at the die lips. This may cause the formation of undesirable die lines in the extruded foam sheet. Adjustment of parameters such as the extrusion temperature can substantially eliminate the formation of die lines. Accordingly, a preferred extrusion temperature for a particular recycled material or blend of materials is that at which the foam sheet is substantially free of die lines. The die line-free reactive extrusion temperature for a recycled polymeric material can be readily determined without undue experimentation by one of ordinary skill in the art.

The foam sheet of the invention comprises the materials, e.g. recycled polymeric materials, additives, etc., and in the preferred amounts, as discussed above. The foam sheet preferably has a thickness in the range of from about 20- 200 mils, most preferably in the range of from about 20-150 mils. In these thickness', the sheet is Tollable, which facilitates handling, shipping, and storage, thus providing a distinct advantage over friable materials such as polystyrene. The foam sheet can be formed having an irregular or roughened surface, which in certain applications such as for use in a construction waterproofing laminate can impart a desirable impression of toughness and provide increased surface area. Alternatively, the sheet can be formed having a smooth surface and appearance.

The invention is further illustrated by the following examples.

EXAMPLES

In the following examples, the gel content where provided is determined in accordance with ASTM Standard Test Method D-2765-90, wherein a weighed sample is extracted in toluene by boiling the contents for twenty-one hours. The non-soluble species which comprises the gel component is separated and weighed, to provide the percent content by weight of gel of the original weighed sample.

Example 1: Foam extrusion tests were carried out on a number of individual virgin resins: LDPE, HDPE, LLDPE, EVA, and nylon. For each test the resin was combined in the extruder feed with 3 percent by weight Primacor™ 5981 , which is an EAA, and 2 percent by weight sodium bicarbonate. Each extrusion was run with a Brabender 3/4 inch extruder fitted with a two-inch-wide rectangular slot die. In each test, a 60 mil thick foam polymeric sheet material was successfully formed.

Example 2

A monolayer foam sheet material was prepared as in Example 1 but using pelletized scrap resin materials as the extruder feed.

(i) A roll of scrap film having the sequential layer configuration Polypropylene / tie / nylon / EVOH / nylon / tie / LLDPE Thickness (mils) 1.6 0.4 1.04 0.8 1.04 0.64 2.48

(Total thickness- 8.0 mils), with the nylon plus EVOH components comprising a total of 36 percent by weight of the film, was pelletized to form a first pelletized material. The pellets were introduced into a Brabender 3/4 inch extruder fitted with a two-inch -wide rectangular die slot, and successfully foamed into a foam sheet.

(ii) Another roll of heat shrinkable film having the sequential layer configuration

EVA/ LLDPE/ EVA/ LLDPE/ EVA Thickness (mils) 0.1 0.15 0.1 0.15 0.1

(Total thickness 0.6 mils) and crosslinked by electron beam irradiation to a level of 35 percent gel content by weight was pelletized as in Example 1 to form a second pelletized material. Extrusion was carried out as with the first pelletized material to successfully extrude a foam sheet. Without being bound by theory, it is thought that the crosslinked component (35% by weight) and non-crosslinked component (65% by weight) do not form a homogeneous, single phase system but that the crosslinked component comprises a distinct gel phase distributed within the non-crosslinked material.

Example 3

A 20 mil thick two-ply tubular film was formed by coextruding two layers, each layer comprising a blend of EVA and LLDPE, through a circular die. The tubular film was flattened into a tape, which was irradiated by electron beam and thereby crosslinked to a gel content of 45 percent by weight. The film was then extrusion coated with a nonirradiated EVA blend layer to form a 28 mil thick three- ply film having a net gel content of 25 percent by weight. The film was oriented by biaxially stretching to form a shrink film 2.35 mils thick. The tubular film was pelletized and foam extruded as in Example 2 to form a foam sheet.

Example 4

A tubular film was produced as in Example 3 except that an additional PVDC copolymer layer was coextruded between the EVA/LLDPE-blend layers. The film was pelletized and foam extruded as in Example 2 except with 5 percent by weight of sodium bicarbonate. A foam sheet material was successfully formed.

Example 5

A scrap composition having the following composition by weight was pelletized and blended:

(i) 60 percent of the three-ply film of Example 3; (ii) 20 percent of the first pelletized material of Example 2(1); and

(iii) 20 percent of the second pelletized material of Example 2(ii). The net weight percent of gel content in the blend was 22% (15% attributable to (i) and 7% attributable to (iii)). The blend was fed to a tandem extruder at a rate of 172.5 lbs./hr. Once melting and mixing had commenced in the first stage extruder, 2.5 lbs./hr of carbon dioxide under high pressure was injected into the melt. The resultant blend was fed under pressure to the second stage extruder for further mixing and then extruded through a circular die to form a foam sheet material having a thickness of 50 mils and a density of 0.53 g/cc. The test was repeated except that 3.2 lb./hr of carbon dioxide was injected. A foam sheet was formed having a thickness of 100 mils and a density of 0.61 g/cc.

Example 6

The 50 mil sheet material of Example 5 was tested for friability and other mechanical properties. Comparison tests were run on a 250 mil thick polystyrene foam material, with and without outer polyester skin layers. The test for friability consisted of a tensile and elongation test carried out according to ASTM Standard Test Method D-412-87 using an Instron Model 1000 Tensile Tester. As specified in ASTM D-412-87, a specimen was clamped between two grip elements of the Instron testing machine. The machine was then activated to exert an increasing force on the sample. As the sample was stretched (at the rate of 0.5 inches per minute), the change in length was measured and the total change in length at break noted. The load at break (e.g. total force) was also noted. The tensile strength (TS) was computed by dividing the load at break "F" (lbs.) by the original cross section area "A" (sq. inches). Thus, TS = F/A (psi). The percentage elongation at break was calculated as follows:

% Elongation = change in length x 100 /original length It was found that the controls (prior art 250 mil polystyrene foam boards) had essentially no elongation at break and were thus extremely friable.

The tear propagation Strength Test involved a determination of the resistance of a protective board or sheet to tearing forces. Two 3" x 9" strips of the control polystyrene foam board (one with and one without skin layers) were compared to a 3" x 9" strip of the 50 mil sheet material of Example 5. A two-inch longitudinal incision is made in the middle of one of the (3") ends of the strips. The thickness of the strips are measured, and the strips are clamped in the Instron (Model 1000). The Instron grip elements are located a distance of 1 inch on either side of the incision. The load placed on the strip will depend upon materials and thickness'. For the present comparative samples, the crosshead speed was about 0.5 in. /minute. Once the Instron is activated and a tear of 2 inches is propagated from the incision, the peak load is recorded in terms of lbs. and then converted to "Specific Tear Strength" by dividing peak load by the thickness (mils) of the sample.

The results are shown in the following table:

TABLE

Tear Specific Tear

Propagation Strength Tensile at Elongation

Strength (lb.) (lb. /mil) break (psi) at Break (%)

250 mil 22.5 0.09 96 < 1 polystyrene with skin layers

250 mil 13.0 0.05 51.5 < 1 polystyrene without skin layers

50 mil foam 28.5 0.57 720 25 scrap

The data demonstrates that the foam scrap sheet according to the invention is less friable, that is, has higher tear strength properties and substantially stronger tensile properties, and is more extensible than the comparison materials.

Example 7

Recycled scrap was prepared from the following materials:

(a) polymer material as in Example 5 (iii) (highly crosslinked),

(b) polymer material as in Example 3 (moderately crosslinked), and

(c) polymer material as in Example 2(1), as follows. Scrap compositions were pre-blended in the following ratios by weight of materials (a)-(c) and pelletized as in Example 2:

Composition 1: 60% (a) + 20% (b) + 20% (c)

Composition 2: 30% (a) + 30% (b) + 40% (c)

Composition 3: 40% (a) + 40% (b) + 20% (c) Composition 4: 50% (a) + 50% (b)

Composition 5: 100% (a)

Composition 6: 100% (b) For each composition, the pelletized material was metered into an extruder hopper by means of a volumetric feeder, introduced into a 1" single screw extruder having a length:diameter ratio of 24 and fitted with a 4" die, and extruded in accordance with the invention. A 3 roll stack and winder comprised the take-off assembly. Composition 1 was successfully extruded into a sheet having a thickness of 50 mils. Composition 2 was successfully extruded into a sheet having a thickness of 49.5 mils. Composition 3 was successfully extruded into a sheet having a thickness of 49 mils. Composition 4 was successfully extruded into a sheet having a thickness of 38 mils. Composition 5 was successfully extruded into a sheet having a thickness of 45 mils. Composition 6 was successfully extruded into a sheet having a thickness of 38 mils.

Example 8

The following scrap compositions were pre-blended in the indicated ratios by weight using material (a) of Example 7 and pelletized as in Example 2:

Composition 7: 100% material (a) Composition 8: 80% material (a) + 15.6% EAA + 4.4% sodium bicarbonate

Composition 9: 95% material (a) + 3.9% EAA + 1.1% sodium bicarbonate

Composition 7 was successfully extruded into a sheet having a thickness of 60 mils and a density of 0.84 g/cc. Composition 8 was successfully extruded into a foam sheet having a thickness of 70 mils and a density of 0.44 g/cc. Composition 9 was successfully extruded into a foam sheet having a thickness of 70 mils and a density of 0.51 g/cc.

The sheet and method of the invention are useful for recycling polymeric material that is produced in manufacturing operations and material that is present in post-consumer articles. The sheet is useful in numerous applications. For example, the sheet, either foamed or non-foamed, may be used as a component sheet in a waterproofing laminate for sub-grade exterior concrete surfaces and the like. The sheet can also be used as a protective packaging material, e.g. an insert shaped so as to snugly receive and hold a product inside a box. The sheet may also be fabricated such as by thermoforming into various products such as egg cartons. The recycled materials and sheet thickness can be selected or modified as appropriate to suit the intended use.

The invention has been described in detail with reference to particular embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. A method of recycling a polymeric material comprising a hygroscopic polymeric component, comprising the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder in which foaming agent is substantially absent; and extruding the melt in the form of a sheet.

2. A method as in claim 1, wherein the hygroscopic component is selected from the group consisting of ethylene vinyl alcohol, nylon, and mixtures thereof.

3. A method as in claim 2, wherein the hygroscopic component is present in an amount of at least about 23 percent by weight of the polymeric material.

4. A method as in claim 3, wherein the melt further comprises a non- hygroscopic component-containing polymeric material.

5. A method of recycling a polymeric material comprising a hygroscopic polymeric component, comprising the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder comprising at least about 23 percent by weight of the hygroscopic component; introducing a foaming agent into the melt; and foam extruding the melt in the form of a foam sheet.

6. A method as in claim 5, wherein the hygroscopic component is selected from the group consisting of ethylene vinyl alcohol, nylon, and mixtures thereof.

7. A method as in claim 6, wherein the melt further comprises a non- hygroscopic component-containing polymeric material.

8. A method of recycling a polymeric material consisting essentially of material having a hygroscopic polymeric component in an amount of at least about 23 percent by weight, comprising the steps of: comminuting the polymeric material into a comminuted scrap feed; introducing the comminuted scrap feed into an extruder; forming a melt in the extruder; and extruding the melt in the form of a sheet.

9. A method as in claim 8, further comprising the step of introducing a foaming agent into the melt to thereby extrude a foam sheet.

10. A method as in claim 9, wherein the hygroscopic component is selected from the group consisting of ethylene vinyl alcohol, nylon, and mixtures thereof.

11. A method of recycling a polymeric material comprising a crosslinked polymeric component, comprising the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder; and extruding the melt in the form of a sheet.

12. A method as in claim 11, wherein the crosslinked component is present in an amount by weight of the polymeric material of from about 10 percent to about 90 percent of gel as determined by ASTM Test D-2765.

13. A method as in claim 12, wherein the crosslinked component is present in an amount by weight of the polymeric material of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

14. A method as in claim 11 , further comprising the step of introducing a foaming agent into the melt and thereby extruding a foam sheet.

15. A method as in claim 14, wherein the crosslinked component is present in an amount by weight of the polymeric material of from about 10 percent to about 90 percent of gel as determined by ASTM Test D-2765.

16. A method as in claim 15, wherein the crosslinked component is present in an amount by weight of the polymeric material of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

17. A method of recycling a polymeric material having a hygroscopic polymeric component and a crosslinked polymeric component, comprising the steps of: introducing the polymeric material into an extruder; forming a melt in the extruder; and extruding the melt in the form of a sheet.

18. A method as in claim 17, wherein the hygroscopic component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material and the crosslinked component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material.

19. A method as in claim 18, wherein the crosslinked component comprises an amount by weight of the polymeric material of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

20. A method as in claim 17, further comprising the step of introducing a foaming agent into the melt to thereby extrude a foam sheet.

21. A method as in claim 20, wherein the hygroscopic component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material and the crosslinked component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material.

22. A method as in claim 21 , wherein the crosslinked component comprises an amount by weight of the polymeric material of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

23. A method of recycling a polymeric material comprising a component selected from the group consisting of PVC, PVDC, and mixtures or blends thereof, comprising the steps of: providing a neutralizing compound for blending with the scrap or for introducing into the melt; introducing the polymeric material into an extruder; forming a melt in the extruder; introducing a foaming agent into the melt; and foam extruding the melt in the form of a foam sheet.

24. An extruded non-foamed sheet comprising a recycled polymeric material having a hygroscopic component.

25. A sheet as in claim 24, wherein the hygroscopic component is selected from the group consisting of ethylene vinyl alcohol, nylon, and mixtures thereof.

26. A sheet as in claim 25, wherein the hygroscopic component is present in an amount of at least about 23 percent by weight.

27. A sheet as in claim 26, wherein the melt further comprises a non- hygroscopic component-containing polymeric material.

28. An extruded foamed sheet comprising a recycled polymeric material having at least about 23 percent by weight of a hygroscopic component.

29. A sheet as in claim 28, wherein the hygroscopic component is selected from the group consisting of ethylene vinyl alcohol, nylon, and mixtures thereof.

30. A foam sheet consisting essentially of a recycled polymeric material comprising a hygroscopic polymeric component in an amount of at least about 23 percent by weight.

31. An extruded sheet comprising a recycled crosslinked polymeric component.

32. A sheet as in claim 31, wherein the crosslinked component is present in an amount by weight of the foam sheet of from about 10 percent to about 90 percent of gel as determined by ASTM Test D-2765.

33. A sheet as in claim 32, wherein the crosslinked component is present in an amount by weight of the foam sheet of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

34. A sheet as in claim 31 , wherein the sheet is a foam sheet.

35. A sheet as in claim 34, wherein the crosslinked component is present in an amount by weight of the foam sheet of from about 10 percent to about 90 percent of gel as determined by ASTM Test D-2765.

36. A sheet as in claim 35, wherein the crosslinked component is present in an amount by weight of the foam sheet of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

37. A foam sheet comprising a recycled polymeric material having a hygroscopic polymeric component and a crosslinked polymeric component.

38. A foam sheet as in claim 37, wherein the hygroscopic component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material and the crosslinked component is present in an amount of from about 10 to about 90 percent by weight of the polymeric material.

39. A foam sheet as in claim 38, wherein the crosslinked component comprises an amount by weight of the polymeric material of from about 15 to about 45 percent of gel as determined by ASTM Test D-2765.

40. A foam sheet comprising a recycled polymeric material comprising a component selected from the group consisting of PVC, PVDC, and mixtures or blends thereof.