CA1120846A

CA1120846A - Highly reflective multilayer metal/polymer composites

Info

Publication number: CA1120846A
Application number: CA000294464A
Authority: CA
Inventors: Virgil B. Kurfman; Raymond E. Gransden, Jr.
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1977-01-07
Filing date: 1978-01-06
Publication date: 1982-03-30
Also published as: NL185069C; BR7800091A; AU515782B2; DE2800092A1; JPS6011633B2; SE444287B; GB1598364A; JPS53111381A; IT7847554A0; FR2376747B1; MX153480A; AU3197677A; US4115619A; FR2376747A1; NL7800147A; IT1104136B; SE7800157L; DE2800092C2; BE862681A

Abstract

Abstract of the Disclosure A multilayer, metal/organic polymer com-posite exhibiting high specular reflectivity even after substantial elongation is provided by metallizing a layer of thermoplastic organic polymer such as polystyrene or polycarbonate film with a normally solid, soft metal such as indium or an alloy of tin and cadmium. Subsequently the multilayer composite or at least a portion thereof can be stretched or elongated by more than 10 percent in both the longitudinal and transverse directions without losing its initial specular reflectivity. Articles fabricated of the multilayer composite may be structurally reinforced by casting an elastomeric or rigid foam polymer such as polyurethane into a cavity defined by the composite. The multilayer composites are useful in the manufacture of reflective and decorative parts for automobiles and other vehicles of transportation, as well as high barrier packages for foods and electroconductive elements.

Description

Z~8~16 This invention resides in multilayer composites hzving at least one metal layer and at least one layer of thermoplastic organic polymer and to articles formed therefrom.
Metallized plastic articles prepared by ap-plying a metal to a plastic material by vacuum deposition, electrolytic or electroless deposition, foil lamination or similar metallizing techniques are well known. Such articles are widely employed for decorative purposes, particularly the metallized films which are quite flexible and can be shaped to some extent to conform to various contours.
Unfortunately, the degree to which such con-ventional metallized films or sheets or other articles can be shaped without rupture and/or separation of the metal from the polymer is generally limited to those shaping procedures involving localized dimensional changes of less than 25 percent in one direction and less than 20 percent (based on area of the film) if the dimensionàl changes are in two directions. The visual effect of stretching the metallized polymer beyond this limit is a noticeable loss of specular reflectance at the points of excessive elongation. The resulting article has a marred appearance and diminished utility in decorative, electrical and packaging applications.
As a result of the loss of barrier properties caused by actually stretching the metallized polymer beyond the 20 percent limit where the dimensional change is in two directions (based on area of the film), the use of such metallized polymers in many packaging 18,236-F
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~12V8~6 applications is severely reduced, particularly where high barrier to vapor transmission is critical. Likewise, the corresponding loss of electrical conductivity reduces the suitable electrical applications to those involving mini-mal dimensional change.
In addition, the aforementioned limitation on the amount of dimensional change of the metallized polymers significantly hinders their use in the manufacture of reflective parts (often called bright work) for automobiles and other vehicles of transporta-tion as well as for household appliances. Such reflective parts often require biaxial extension such that the stretched article occupies an area more than 50 percent greater than the area of the article prior to stretching.
In view of the aforementioned needs for novel highly extendable, multilayer metal/polymer composites and the deficiencies of existing metallized polymer articles in this regard, the present invention provides a multilayer, metal/organio polymer composite that ex-hibits excellent specular reflectance, electroconductivity and barrier to vapor transmission after substantial dimensional change.
In one aspect the present invention is a formed, multilayer metal/organic polymer composite exhibiting the aforementioned desirable characteristics even though at least a portion of the composite has ;~ been formed such that the portion undergoes a cumulative surface dimensiona} change of at least 20 percent. More specifically, the formed, multilayer composite comprises 18,236-F -2-a normally solid, thermoplastic organic polymer layer having adhered thereto a normally solid, soft metal layer. By "formed multilayer composite" is meant the composite has been formed such that at least a portion undergoes the aforementioned dimensional change, pref-erably by extending at least a portion of the multi-layer composite to an area that is at least 30 percent greater than the area of the portion before forming, without rupturing either the metal layer or the poly-mer layer. In this instance, it is understood thatthe presence of pinholes, i.e., those having an aver-age diameter of less than 1 micrometer, which are often formed during metallizing and/or the extension process, can be tolerated. Such pinholes do not noticeably reduce specular brightness, electroconductivity or bar-rier properties. Generally, a metal or an alloy of metals will be considered a soft metal for the purposes of this invention if it melts at a temperature or over a range of temperatures that is from 80 to 135 percent of the temperature used in forming the composite, said temperatures being in K.

.

The invention resides in a formable metal/-organic polymer composite comprising a layer of a normally solid thermoplastic polymer (as hereinafter defined) and a layer of a normally solid soft metal intimately adhered to at least one surface of the polymer layer, said soft metal melting at a tempera-ture o~ over a range of temperatures that is from 80 to 135 percent of the forming temperature of the thermo-plastic polymer, said temperatures being in degrees K, 18,236-F ~3~

1 ~ ~3~

and said soft metal being indium or an alloy of two or more metals, other than a lead alloy, comprising at least 50 weight percent of a first metal and at least 5 weight percent of at least one second metal, the said composite being capable, when subjected to a forming operation, of undergoing a cumulative sur-face dimensional change of at least 20 percent.
The present invention also resides in a method of making a metal/organic polymer composite by intimately adhering together a layer of a normally solid, soft metal, as hereinafter defined, and at least one surface of a layer of a normally solid form-able thermoplastic polymer as hereinafter defined.
The invention also resides in a method of making a formed metal/organic polymer composite by sub-jecting a metal/organic polymer composite as prepared in accordance with the method of the present invention, to a forming operation during which at least a portion of the composite is modified by its undergoing a cumulative surface dimensional change of at least 20 percent.
The invention further resides in a formed metal/organic polymer composite which has been made by the method according to the present invention.
The present invention also resides in a shaped article comprising the formed composite as made by the method of the present invention and a reinforc-ing material in intimate contact with at least one surface of the formed composite.

,,~. .
~ ~ 18,236-F -4-ilZ~3f~

Surprisingly, the formed multilayer composite of this invention exhibits specular brightness, barrier and/or electrical continuity that are nearly the same as those of the composite prior to forming. In fact, the metal composites of this invention exhibit elec-trical resistivities of less than lOO ohms/square even after forming, preferably less than lO ohms/square.
In contrast, the metal/polymer composites conventional to the art exhibit electrical resistivities greater than 1000 ohms/square after similar forming. Moreover, the metal layer of the formed composite remains strongly adhered to the polymer layer eventhough forming was carried out at temperatures at which most of the metal is in the melted or liquidus state and the polymer layer is heat plastified or nearly so.

18,236-F -4a-As a result of this surprising capability the multilayer composites are usefully formed into articles such as bumpers and other reflective parts for automobiles and other vehicles of transportation, housings and decora-tive parts for appliances and the like with minimal, if any loss, of brightness, barrier properties and electro-conductivity. In addition, these formed composites are usefully employed in electrical applications and as plastic containers exhibiting a high degree of barrier properties to atmospheric gases. Particularly surprising is the fact that multilayer composites of this invention, wherein the polymer layer is polyolefin, exhibit a barrier to oxygen superior to that of conventional metal/polyolefin com-posites wherein the metal layer is aluminum, silver or copper. For purposes of this invention, "high barrier"
means that the formed composite exhibits a permeance to atmospheric gases essentially e~uivalent to metal foil/-polymer laminate films, e~g., an oxygen transmission rate less than about 0.1 cc through a 1 mil thick film having an area of 645 square centimeters (100 square inches) when exposed to a pressure difference of 1 atmosphere at a temperature of 25C (298K) over a 24 hour period (herein-after abbreviated cc/645 cm2/mil/day/atm). Because the formed composites of this invention can withstand wet en-vironments, they are especially desirable for the packaging of oxygen-sensitive wet foods such as, for example, apple-sauce, fruit, or catsup as well as dry foods such as, for example, coffee or potato chips.
In the single drawing, which is a side view in cross-section of a preferred shaped article of the invention 8,236-F ~5-1i~ZC~8f~6 there is depicted a shaped article 1 having a shell 2 of a formed, multilayer metal/organic polymer composite.
The outer layer 3 of the shell 2 comprises a normally solid, thermoplastic polymer and has a surface 4 to which is intimately bonded a layer 5 of a soft metal. The shell 2 defines a cavity 6 which is filled in part with a polymeric filler material which may be either foamed or nonfoamed, rigid or flexible, and elastomeric or non-elas-tomeric. Embedded in the polymeric filler material is a mounting strut 7 for affixing the shaped article to a substrate as desired.
Polymers suitably employed in the polymer layer(s) of the multilayer composites of this in~ention are those normally solid, organic, formable thermoplastic polymers that are readily shaped or molded or otherwise fabricated into desired forms. By the term "formable" is meant that the polymer can be stretched or otherwise extended without rupturing to occupy an area whiah is at least 30 percent greater than its original area, preferably 20~ more than-100 percent and most preferably more than 150 percent. The term "thermoplastic" as used herein is intended to include all synthetic resins that may be softened by heat and then regain their original properties upon cooling. Also included within this term are thermo-setting resins in the B stage, i.e., that stage prior to crosslinking wherein the resin exhibits the heat plastification characteristics of a thermoplastic resin.
In some preferred embodiments, the thermoplastic polymers are also generally transparent.

18,236-F -6-secause of their lower cost and superior struc-tural properties, polymers of particular interest in the practice of this invention include engineering plastics such as polystyrene, styrene/acrylonitrile copolymers, copolymers containing polymerized styrene, acrylon trile and butadiene (often called ABS polymers), styrene/buta-diene copolymers, rubber modified styrene polymers, sty-rene/maleic anhydride copolymers and similar polymers of monovinylidene aromatic carbocyclic monomers; polycarbon-ates including those made from phosgene and bisphenol A
and/or phenolphthalein; polyesters such as polyethylene terephthalate; acrylic resins such as poly(methyl meth-acrylate); polyacetyl resins such as polyformaldehyde resin; nitrile resins such as polyacrylonitrile and other polymers of ~,~-ethylenically unsaturated nitriles such as acrylonitrile/methyl methacrylate copolymers; polyamides such as nylon; polyolefins such as polyethylene and polypropylene; polyvinyl halides such as polyvinylchloride and vinylidene chloride homopolymers and copolymers;
polyurethanes; polyallomers; polyphenylene oxides; polymers of fluorinated olefins such as polytetrafluoroethylene;
and other normally solid polymers which can be formed while in the solid state into the desired shape by conventional forming techniques, such as for example, cold drawing, vacuum drawing, drape molding, pressure thermoforming, or ; scrapless thermoforming procedures. Especially preferred, particularly for polymer layers which must exhibit signi-ficant abrasion resistance as well as a high degree of transparency are the polycarbonates, particularly those derived from the bis(4-hydroxyphenol)alkylidenes (often 18,236-F -7-8'~6 called bisphenol A types) and those derived from the com~ination of such bisphenol A type diols with phenol-phthalein type diols. It is understood that the polymer layer of the multilayered composite may also contain one or more additaments such as, for example, dyes, light stabi-lizers, reinforcement fillers and fibers, pigments, or carbon black.
The thickness of the polymer layer(s) of the multilayer composite is not particularly critical.
Therefore, the polymer layer is of suitable thickness if it can be formed into a continuous layer which will have the necessary strength to survive the conditions normal to its intended use. Accordingly, such properties will often be abrasion resistance, corrosion resistance, tensile or impact strength and other physical properties which will be evident to those skilled in the art of fabricating polymers and metallized polymers. Usually, the thickness of the polymer layer(s) is in the range from 2 to 10,000 micrometers, preferably from 10 to 500 micrometer`s.
The metal layer(s) of the multilayer composite which imparts specular reflectance, as well as high barrier and electroconductivity when such are desired, preferably comprises a metal or an alloy of two or more metals that melts at a temperatuxe or over a range of temperatures that is from 80 to 135 percent of the maximum temperature reached by the metal composite during forming, said tem-peratures being in K. Preferably, the metal or alloy of metals melts at a temperature or over a range of temperatures that is from 90 to 110 percent of the forming temperature.

18,236-F -8-112~8~16 In preferred embodiments, the metal or alloy has a liquidus temperature (Tl-temperature in K at which the metal or alloy is entirely liquid) and a solidus temperature (Ts--t:emperature in K at which the metal or alloy just begins to liquefy) which are within the temperature range of 0.85 Tf to 1.35 Tf wherein Tf is the temperature in K at which the composite is formed.
Typically, such preferred metal alloys can be further characterized as containing at least 50 weight percent, more advantageously from 60 to 87 weight percent, of at least one metal having a melting point below 450C
(723K) and at least 5 weight percent, most advantageously from lO to 47 weight percent, of at least one other metal also having a melting point below 450C (723K). Especially ~5 preferred are alloys similar to the preceding preferred metal alloys which additionally contain at least 0.1 weight percent, most advantageously from 3 to 20 weight percent, of a metal having a melting point above 450C (723K).
An example of a suitable metal is indium, whereas alloys of any two or more of the following metals may be employed: cadmium, indium, tin, antimony, zinc, lead, bismuth, and silver. In addition, other metals may be present in the alloys so long as the melting range of the alloy is within the prescribed range of 80 to 135 percent of the forming temperature. Representative of such alloys are those containing at least 50 weight percent of one or more of antimony, indium, bismuth, tin, zinc, cadmium and lead; from 0 to 10 weight percent of one or more metals such as manganese, nickel, iron, and other metals having melting points greater than 1100C (1373K); and a remaining 18,236-F _g_ amount of one or more of silver, copper, gold, aluminum and magnesium. Of special interest are alloys having a solidus temperature less than 650K, preferably less than 548K, and containing at least 60 welght percent of at least one of indium, bismuth, tin, zinc, cadmium, antimony and lead and not more than 9S, preferably not more than 90 and most preferably not more than 80, weight percent of any one metal.
Illustrative preferred alloys contain at least 5 weight percent of at least two of the following metals: tin, bismuth, lead, zinc, cadmium and antimony.
Examples of preferred alloys are the following alloys comprising metals in the indicated weight percentages:
alloy(l)-from 5 to 95 percent tin, from 5 to 95 percent bismuth, and from 0 to 40 percent copper; alloy(2)-from S to 95 percent tin, from S to 95 percent bismuth and from 0 to 49.9 percent silver; alloy(3)-from 5 to 95 percent zinc, from 5 to 95 percent cadmium and from 0 to 49.9 percent silver; alloy(4)-from 5 to 95 percent zinc, from 5 to 95 percent cadmium and from 0 to 10 percent magnesium; alloy(5)-from about 0.1 to 95 percent tin and from 5 to 99.,9 percent indium; alloy(6)-from 5 to 95 percent tin, from 5 to 95 percent lead and from 0 to 40 percent copper; alloy(7)-from 5 to 95 percent tin, from 5 to 95 percent lead and from 0 to 49.9 percent silver; alloy(8)-from 5 to 95 percent tin, from 5 to 30 percent antimony and from 0 to 40 percent copper; alloy(9~-from 40 to 94 percent tin, from 3 to 30 percent antimony, from 3 to 57 percent bismuth and from 0 to 40 percent copper; alloy(10)-from 90 to 99.9 weight percent indium and from 0.1 to 10 weight percent of 18,236-F -10-at least one of copper, silver, gold, nickel, bismuth, tin, zinc, cadmium, antimony and lead; alloy(ll)-from 75 to 99.9, especially 85 to 98, weight percent o~ at least one of indium, bismuth, tin, zinc, cadmium, antimony and lead and from 0.1 to 25, especially 2 to 15, weight percent of at least one of copper, silver, gold, nickel, magnesium and aluminum, provided that alloy(ll) contain no more than 90 weight percent of any one metal. Also preferred are alloys of tin, silver and indium, alloys of zinc, cadmium and indium, alloys of indium and silver, alloys of tin and cadmium, alloys of silver and indium and alloys of magnesium and aluminum. Of the aforementioned alloys, alloys of tin and bismuth are more preferred with alloys of tin, bismuth and copper being most preferred.
It should be understood, however, that preference for. the different alloys will vary depending on the end use. For example, alloys of tin and copper, alloys of tin and silver and alloys of tin, bismuth and copper show superior corrosion resistance compared to alloys of zinc and cadmium. Similarly, alloys of tin, bismuth and copper and alloys of tin and copper would be more acceptable in food packaging than would be more toxic alloys of tin and lead.
Moreover it is observed that preference for various alloys will vary with the different polymer layers used in the multllayer composite. For example, it is observed that the alloys of tin and copper, the alloys of tin and silver, the alloys of indium and silver, the alloys of tin, bismuth and copper, and the alloys of zinc and cadmium are preferred when the 18,236-F -11-1121~8~i multilayer composite is to be formed at temperatures from 25C (298K) to 175C (448K) as in the case when the polymer layer consists essentially of polycarbonate.
In addition, it has been generally observed t:hat the more concentrated alloys, i.e., those contain-ing larger amounts, e.g., more than 20 weight percent lpreferably 25 weight percent or more) of the minor components of the alloy, are generally more easily extended than the more dilute alloys, i.e., those containing very substantial amounts of the major component of the alloy and minimal amounts of the minor component or components. For example, an alloy of 75 weight percent tin and 25 weight percent silver is superior in regard to plastic character than an alloy of 90 percent tin and 10 percent silver.
Also, an alloy of 50 percent tin and 50 percent indium exhibits extendibility characteristics superior to that of an alloy of 90 percent tin and lO percent indium.
Also it is noted that alloys of tin, bismuth and a higher melting metal such as copper, silver, nickel, magnesium, gold, iron, chromium and manganese, particularly those containing (l) at least 8 weight percent each of tin and bismuth and (2) more bismuth than the higher melting metal, exhibit excellent adhesion and forming characteristics.
For example, composites employing these alloys may be formed at temperatures at which the polymer and most o~ the alloy melt without loss of adhesion or integrity (con-tinuity of the metal layer). These multilayer composites exhibit superior vapor barrier characteristics and may be flexed a number of times without an apparent loss of continuity of the metal layer. Of the alloys of these 18,236-F -12-highly adherent composites, alloys of particular interest consist essentially of from 25 to 90, preferably from 60 to 80, weight percent tin; from 8 to 60, preferably 8 to 30, most preferably 12 to 25, weight percent bismuth; and from 1 to 25, preferably 4 to 12, weight percent of higher melting metal, preferably copper or silver.
Since the normal thermoplastic polymers which will be utilized in the multilayer composites of the present invention are preferably formed at temperatures in the range from 25C (298K) to 200C (473K), preferably 100C (373K) to 200C (473K), it will be generally desirable that the metals and metal alloys advantageously employed in the practice of this invention will have melting points or melting point ranges within the range from 100C (373K) to 400C (673K), preferably from 130C (403K) to 275C (548K). For the purposes of this invention, the melting point of a metal or the melting range of an alloy of metals is defined as the temperature or range of temperatures at which solid and liquid forms of the metal or alloy are in equilibrium.
The alloys typically do not melt entirely at a single tem-perature but will melt gradually over a fairly wide temperature range.
The multilayer composites of the present in-vention are suitably prepared by any conventional method for ma~ing multilayer metal/organic polymer composites wherein the layers of metal and polymer adhere to each other. For example, the metal may be applied as a coating by a conventional metallization technique such as an electroless process described by F. A. Lowenheim in 18,236-F -13-~Z~8fl6 "Metal Coatings of Plastics", Noyes Date Corporation, ~1970), by Pinter, S. H. et al., Plastics S-urface and ~inish, Daniel Davey & Company, Inc., 172-186 (1971) or in U.S. Patent No. 2,464,143. An especially pre-ferred metallization technique in the practice of this invention is a vacuum deposition technique wherein the metal is vacuum evaporated and then deposited onto the polymer layer as described by William Goldie in Metallic ating_of Plastics, Vol. 1, Electrochemical Publications Limited, Chap. 12 (1968). Another preferred metalliæa-tion technique includes sputter coating as described in Chapter 13 of Goldie, supra. Also suitable but less preferred metallization techni~ues include electro-plating and ion plating. In addition, the multilayer composite can be formed by lamination of metal foil to the polymer layer including extrusion coating of the polymer layer onto a metal foil.
In the formation of a multilayer composite wherein the polymer layer comprises a fairly polar polymer such as polycarbonate, polyester, polyvinyl halide or polyvinylidene halide, polyvinyl alcohol, acrylic polymers and other known polar polymers, it is generally not necessary to pretreat the polymer layer prior to application of the metal layer. How-ever, when relatively nonpolar polymers, e.g., poly-styrene or polyethylene are to be employed, it is often desirable to treat the surface of the polymer layers sufficiently to enhance bonding between the metal and the polymer. Such pretreatments can include gas phase sulfonation as described in U.S. Patent No.

18,236-F -14-~2~8~6 3,625,751 to Walles and especially the procedure described in Lindblom et al. in U.S. Patent No.
3,686,018. Other suitable methods for pretreating the polymer include, for example, corona discharge, flame treatment, or liquid phase sulfonation. Alter-natively, the polymer layer may be coated with an adhesive, such as an ethylene/acrylic acid copolymer, an ethylene/vinyl acetate copolymer or similar adhesives, commonly employed in bonding metal layers to relatively nonpolar organic polymer layers.
The quantity or thickness of the metal layer in the multilayer composite is not particularly critical so long as the metal layer forms an essentially con-tinuous film over the desired surface of the polymer layer and thereby provide a highly reflective surface, high barrier to vapor transmission or electroconductivity as the desired end use requires. Preferably, the thickness of the metal layer is in the range from 0.002 to 100 micrometers, more preferably from 0.01 to 100 micrometers and most preferably from 0.01 to 1 micrometer.
While the metal layer may be applied to either or both sides of the polymer layer(s), it is generally desirable to apply the metal layer to only one surface of the polymer layer. Accordingly, in a shaped article as shown in the drawing, the polymer layer provides protection against abrasion of the metal layer which would cause degradation of the highly reflective character of the article. It is understood, however, that when the metal layer is applied to the surfaae of the polymer layer which will be exposed in the final article, such exposed i11!

18,236-F -15-~;11 2~ i6 metal layer can be protected by coating with some other adherent material. Examples of such materials suitably employed as protective coatings for the metal layer include, for example, polycarbonates such as those derived from bisphenol-A and/or phenolphthalein, polyesters such as polyethylene terephthalate, acrylic polymers such as poly(methyl methacrylate), saran polymers such as vinyli-dene chloride copolymers, polyepoxides, alkyd resins, or polyurethanes. An exemplary method for overcoating the metal layer is described in U.S. Patent No. 3,916,048 wherein the protective polymer in the form of a latex is applied to the metal layer and dried to form a continuous film at a temperature below the heat distortion point of the polymer layer. By following this technique it is possible to form the metal composite before or after appli-cation of the protective coating. In cases wherein high barrier characteristics are desirable, it will generally be desirable to overcoat the metal layer with a barrier polymer such as a vinylidene chloride polymer/vinylidene chloride copolymer as described in U.S. Patent No. 3,916,048.
Following adherence of the metal layer to the polymer layer, the multilayer composite is formed by a conventional forming process, e.g., thermoforming or solid phase forming, to the desired shape. Prefer-ably, the forming process is a conven'ional thermo-forming process for shaping sheet stock which process is normally carried out at temperatures from about the second order transition temperature (Tg) of the polymer up to and including temperatures at or above the melting point of the polymer provided that the polymer has sufficient 18,236-F -16-i~2~31!3~i melt strength to undergo the forming operation without rupturing. E~emplary thermoforming processes include, for example, differential air pressure thermoforming, match dye thermoforming, vacuum forming, plug assist-vacuum forming, draw forming, impact forming, rubber pad forming, hydroforming, or drape molding. Since most thermoplastic polymers preferably employed in the practice of this in-vention have melting points less than 200C (473K), it is generally advantageous to thermoform the composite at a temperature from 25C (298K) to 200C (473K), most preferably from 90C (363K) to 180C (453K). Alterna-tively, the composite may be formed by solid phase forming which is carried out at temperatures below the melting point of the polymer. Exemplary solid phase forming methods include cold rolling, impact e~trusion, forging, forward extrusion, cold heading, and rubber-pad forming, e.g., as such methods are further described by P. M.
Coffman in Soc. Plas. Eng. Jo~rnal, Vol. 25, Jan., 1969 (50-54) and Soc. Auto. Eng. Journal, Vol. 76, No. 6, ; 20 36-41 (1968).
In the forming operation performed herein, the entire composite or a portion thereof is formed or shaped in a manner such that at least a portion af the composite undergoes a cumulative surface dimensional change of at least 20 percent, advantageously at least 30 percent.
By cumulative surface dimensional change is meant the combined change of length and width wherein a decrease as well as an increase in a particular dimension is treated as a positive change. Further, only one or both surface dimensions may be changed in the forming operation.

18,236-F -17-l~Z~

Techniques for observing surface dimensional changes are described by A. Nadai in Plasticity, McGraw-Hill (1931).
Preferably, the composite or a portion thereof i9 extended ~stretched) to an area which is at least 30 percent c~reater than its original area, more preferably from 50 to 300 percent, most preferably from lS0 to 300 per-cent. When only a portion of the composite is extended, it is that portion being extended which undergoes the aforementioned increase in area. An example of such portion extension or stretching is in the forming of an automobile bumper, a rimmed cup, blister package, and certain reflectors. While the portion may be as small as 1 mm2, it is usually larger than 1 cm2 and preferably greater than 50 cm2~ The actual degree of extension, of course, will vary with the intended end use.
Following the forming operation, the formed composite may be utilized without further fabrication, as is the case for most packaging and electroconductive applications. In these applications the formed multi-layer composite can be used, for example, as tubs or similar deep drawn containers for various oxygen sensitive foods as described herein, as packaging films, or as printed circuit stock for electrical and electronic equip-ment. In such applications, if the metal layer is not protected on both sides by the polymer layer and/or a protective polymer coating layer as described herein-before, it is desirable to coat the metal layer with a protective coating as described hereinbefore.
In addition to the foregoing uses, a formed composite generally defining a cavity as shown in the 18,236-F -18-drawing is reinforced by filling the enclosed or partially enclosed cavity with a reinforcing material. Alterna-tively, the reinforcing material may be adhered to the surface of the composite outermost from the cavity or concave shape as in the case of the reflector for an automobile headlamp. The type of reinforcing material employed is not particularly critical. For example, the material may be metal such as steel, wood, stone, concrete or plastic, with plastic materials comprising natural and/or synthetic organic polymers being preferred. The reinforcing polymeric filler materials of particular interest may be foamed or nonfoamed, rigid or flexible, elastomeric or non-elastomeric. They may be pure (non-filled) or filled with, for example, pigments, stabilizers, or reinforcing fibers such as glass fibers, or fillers. They may be blends of polymers which may contain crosslinking components.
Examples of suitable rigid polymeric materials include, for example, polyurethane, polystyrene, epoxy polymers, polyvinyl chloride, vinylac resin, silicone polymers, cellulosic polymers, acrylic polymers, satur-ated polyesters and unsaturated polyesters, or asphalt.
Of these materials the polyurethanes are generally pre-ferred. Additional examples of such rigid materials, particularly in the form of foams and methods for pre-paring the same, are more completely described in U.S.
Patent No. 3,703,571. The rigid polymers and rigid polymer foams are particularly useful in the fabrication of articles which are not exposed to significant amounts of impact.

18,236-F -19-1~2~8~i In the production of articles such as bumpers and external trim for automobiles and other vehicles of transportation that are exposed to impact, it is desirable to employ an elastomeric polymer, preferably in the form of a foam, as the reinforcing material. Examples of such elastomeric polymers include, for example, elastomeric polyurethanes, rubbery styrene/butadiene copolymers, poly-butadiene rubber, natural rubber, ethylene polymers, par-ticularly ethylene/propylene copolymer rubber. Such elastomeric polymers, whether solid or foamed, and methods for their preparation are well known to those skilled in the art and therefore will not be discussed in greater detail here. Other suitable reinforcing polymeric materials include polyethylene foam, chlorinated poly-ethylene or blends of two or more of the aforementioned reinforcing materials.
The reinforcing material is readily cast onto the shaped multilayered composite by any of a wide variety of casting techniques. For example, a rein-forcing material may be applied by foamed-in-place or pour-in-place techniques as well as spray applications, slush castings or rotational casting application. Ex-emplary methods are described in more detail in ~.S.
Patent No. 3,414,456~ It is desirable that the condi-tions of the casting technique be employed such that the formed composite does not deform during casting, foaming, and/or curing steps which may be employed. However, if such deforming conditions are employed at this time, a support mold for the thermoformed composite is required.

18,236-F -20-112~84f;

The following examples are given to illustrate some specific embodiments of the invention and should not be construed as limiting the scope thereof. In the Eollowing examples, all parts and percentages are by weight unless otherwise indicated.
Example 1 Metallization . .
A rectangular section (27.94 cm x 12.7 cm) of polystyrene film having a thickness of 127 micrometers and sulfonated to a degree sufficient to render the poly-styrene water wettable is washed with distilled water and dried at 60C for approximately one-half hour. A tungsten wire basket situated in a vacuumizable bell jar and elec-trically attached to a filament control of a 5 kilovolt electron beam power supply is loaded with an indium pellet (0.1 g) and the dried polystyrene film is placed in the jar above the filament. The film is configured to the shape of the partial cylinder having a radius of about 12.7 cm by taping the film to a rigid metal sheet of that configura-tion. The configured film is positioned in the bell jar space such that the axis of the cylinder is proximate to the filament in order to achieve a fairly uniform thickness of the metal to be deposited. The bell jar is closed and the system is evacuated to a pressure of 3 x 10 5 mm Hg.
The electrical current to the filament is turned on and adjusted to a nominal current of 0.8 amps and maintained there for 30 seconds and then turned off for 1 minute. The same cycle is repeated and subsequently the bell jar is opened to atmospheric pressure.

18,236-F -21-i~2~8'a6 Thermoforming The metallized polystyrene film (wherein the metal layer has a thickness of approximately 0.2 micro-meter) is cut into a segment of approximately 12.7 cm x 12.7 cm. The segment is clamped into a thermal forming cup mold having a chamber diameter of 9.5 cm and a mold temp-erature of 93.3C (366.3K). Air is supplied through a connecting air line to the side of the mold facing the metallic layer of the film in an amount sufficient to apply a load of 15 psig (2.09 Kg/cm2). As a result, the sample is drawn to a depth of 2.14 centimeters and with-drawn from the mold. The thermoformed sample is observed to have a brilliant, highly reflective surface when viewed through the polystyrene film layer. The surface is elec-trically conductive from the edge of the thermoformed metallized film to the center.
Comparative Sample For purposes of comparison, a second, similar strip of polystyrene film is metallized in the manner described hereinbefore except that aluminum is substi-tuted for the indium and the deposition conditions are changed to 1 amp for 1.25 minutes. The resulting metallized film is molded by the drawing procedures set forth hereinbefore except that an air pressure of only 11 psig is employed to produce significantly less stretching such that the total depth of the molded article is only l.9 centimeters. The resulting sample is not brilliantly reflective and actually exhibits rather diffused reflection. This sample also did not exhibit electrocon-ductivity from the edge to the center of the sample.

18,236-F -22-112~8~6 Example 2 A rectangular section (33.02 cm x 55.88 cm) of polycarbonate film wherein the polycarbonate is dexived from bisphenol A and phosgene and the film has a thick-ness of 127 micrometers is placed in a bell jar equipped as in Example 1~ A 0.5-g pellet of an alloy of 50 percent tin, 30 percent bismuth and 20 percent copper is evaporated from the tungsten wire basket onto the pcly-carbonate film. The electrical current to the basket is controlled so that complete evaporation of the alloy occurs in two minutes. A segment (12.7 cm x 12.7 cm) of the metallized polycarbonate film is cut from the sample and clamped into a thermoforming mold having a mold tempera-ture of 137.8C (410.8K). Air is supplied to the metal layer surface at sufficient pressure to apply a load of 15 psig (2.09 Kg/cm2). A sample is thereby thermoformed to a depth of 2.5 centimeters and then withdrawn from the mold.
The sample is observed to have a brilliant, highly reflec-tive surface when viewed through the polycarbonate film.
The metallic surface is electrically conductive from the edge of the sample to the center of the sample.
In accordance with the foregoing procedure of this example, several other alloys included within the scope of this invention are deposited on the poly-carbonate film and subsequently thermoformed into cup-like structures that have brilliant, highly re-flective surfaces when viewed through the polycarbonate film and are electrically conductive from the edge to center. These alloys are as follows: 0.7 gram of an alloy of 80 percent tin, 15 percent bismuth and 5 percent -18,236-F -23-1~2~ 4~

copper; 0.6 gram of an alloy of 75 percent tin, 20 percent bismuth and 5 percent silver; 0.6 gram of an alloy of 75 percent tin and 25 percent silver; and 0.7 gram of an alloy of 75 percent tin and 25 percent lead.
For purposes of comparison, other metals and alloys outside the scope of this invention are similarly deposited on polycarbonate film and subsequently thermo-formed into cup-like structures in the manner described hereinbefore which exhibited a loss of electrical con-ductivity in specular reflectance. These metals and alloys include stainless steel, an alloy of 50 percent tin and 50 percent copper, an alloy of 85 percent aluminum and 15 percent magnesium, and metals such as aluminum, tin, copper, silver and chromium which are deposited separately on the polycarbonate.
While it is observed that the alloys of tin and bismuth, alloys of zinc and cadmium, and alloys of tin and lead sometimes exhibited a moderate loss of specular reflectance and electroconductivity when applied to polycarbonate film and thermoformed at temperatures of 137~8C (410.8K), such moderate losses of reflectance and of electrical conductivity are avoided by incorporating a small percentage (preferably from about 2 to about 10 percent) of silver, copper and/or one or more other metals melting above 450C (723K) in the alloy or by depositing a very thin coat (<50 A) of silver or other higher melting (>450C) (>723K) metal or metal alloy on the polycarbonate film prior to depo-sition of the alloy.

18,236-F -24-llzr~6 As an example of such a modified metallization technique, an 0.01-g pellet of silver is deposited on a polycarbonate film by the vacuum metallization technique and then a 0.5-g pellet of an alloy of 50 percent zinc, and 50 percent cadmium is deposited on the silver polycarbonate film. When the resultant metallized film is thermoformed by the aforementioned procedure to prod~ce a cup having a depth of 3.5 centimeters, the resultant cup is highly reflective and electroconductive.
Example 3 A thermoformable, amorphous polyethylene terephthalate film ~polyester film) having a thickness of about 25 micrometers is surface activated by passing the film through a flame in accordance with a con-ventional flame treatment technique. A 1.2-g pellet of an alloy of 55 percent tin, 35 percent bismuth and 10 percent silver is deposited on the flame-treated surface of the polyester film in accordance with the vacuum deposition technique set forth in the preceding examples. The metallized film is then thermoformed into a cup-like structure at a mold temperature of 77C ~350K). The resulting molded part is highly reflective and electroconductive.
Example 4 A polystyrene film having a thickness af about 13 micrometers is flame treated as in the preceding example and the sample is placed in the bell jar which is evacuated~ The evacuated jar is backfilled with a small amount of arg~n gas and a highly negative voltage charge is applied to one connection of the filament 18,236-F -25-:112~8'~6 basket, the other connection being open and the base plate of the vacuum system being grounded. This appli-cation of highly negative voltage set up a glow dis-charge current of 10 milliamps at 0.7 kilovolts and an argon pressure of 0.1 mm Hg. This glow discharge is continued for about 1 minute, and the high voltage is then disconnected. A 0.4-g pellet of indium is then vacuum deposited on the treated polystyrene film by the aforementioned vacuum depositing procedureO
A segment (12.7 cm x 12.7 cm) of the metalli~ed polystyrene sample is coated with a latex of a vinylidene chloride/acrylonitrile/sulfoethyl methacrylate (90/8/2) terpolymer by applying a 50 percent solids latex of the terpolymer to the metal layer to produce a film having a wet thickness of about 5 micrometers. The latex film is dried for 2 hours at 65C (338K) and the resulting dried metallized composite is subsequently thermoformed to a cup having a depth of 3 centimeters. The metal layer is highly reflective and visually continuous.
The thermoformed composite when tested for barrier exhibits an oxygen transmission rate of 0.02 cc/100 in2 (645 cm )/24 hours/atm at 25C (298K). Oxygen trans-mission rate is determined according to the dynamic gas chromatographic method reported by T. L. Caskey in Modern Plastics, December, 1~67.
A similar polystyrene film metallized with aluminum, coated with the terpolymer latex and thermo-formed to a cup depth of 2.5 centimeters is observed to have a visually discontinuous metal film and an oxygen transmission rate of greater than 5 cc/100 in2 (645 cm2)/24 hours/atm.

18,236-F -26-llZ~3fi6 Example 5 A section (12.7 cm x 12.7 cm) of the polycar-bonate film of Example 2 is placed on a steel plate. Fifty grams of indium is melted in a crucible and the molten metal is poured onto the polycarbonate film to provide a coating thickness of about 0.158 centimeter over a 7.62 cm diameter circular portion of the section of poly-carbonate film. The resulting metal/polymer com-posite is thermoformed by the procedure of the foregoing examples to produce a cup having a depth of 2 centi-meters. The cup is observed to have a brilliant re flective surface when viewed through the polycarbonate film and is electrically conductive from the edge to the center of the thermoformed cup.
In the foregoing examples, thermoforming the composit~es to a cup depth of 2 centimeters is com-parable to a biaxial stretching sufficient to in-crease the area of the thermoformed cup to 40 percent greater than the metallized film prior to thermoforming.
; 20 Example 6 Following the procedure of Example 2, a bilayer composite is prepared using the polycarbonate film of Example 2 and an alloy of 50 percent tin, 30 percent bismuth and 20 percent copper. A portion (2.54 cm x 15.24 cm) of the bilayer composite is tested for adhesion by appli-cation and removal of a (1.91 cm x 5.08 cm) portion of pressure sensitive adhesive tape from the alloy layer (1,000 A thickness). No removal o the alloy layer is observed.

18,236-F -27-l~Z~8~16 For purposes of comparison, another portion of the polycarbonate film is coated with aluminum using a ~;imilar procedure. Upon testing the aluminized film ~having an aluminum layer thickness of l,000 A) for ad-hesion in the foregoing manner, the metal appears to be completely removed in the region contacted by the tape.
Example 7 Another portion (2.54 cm x 15.24 cm) of the alloy coated film of Example 6 is heated to 130C (403K~
for 5 minutes. The metal film is then scribed with a razor blade and a pressure sensitive adhesive tape is applied to cover a portion of the scribe marks. A drop of water is applied to the metal tape interface so as to wet the exposed (non-taped) scribe marks. The sample is soaked in this manner for about one minute, and the tape is then slowly pulled off the sample. No removal of alloy is observed.
For purposes of comparison, a portion of the aluminized polycarbonate from the comparative sa~ple of Exampla 6 is heated according to the procedure of Example 7. The sample is scribed, tape tested and wetted with water according to the procedure of Example 7.
Upon removal of the tape, the aluminum coating is peeled cleanly from the polycarbonate film.
Example 8 Following Examples ~ and 7 except that a poly-ethylene terephthalate film is substituted for the poly-carbonate film, alloy/polymer composites and aluminum/-polymer composites are prepared and tested for adhesion as in Examples 6 and 7. The alloy/polymer composites 18,236-F -28-passed both tests whereas the aluminum polymer composites failed both tests.
Example 9 Following Examples 6 and 7 except that an alloy of 75 percent tin and 25 percent silver is substituted for the alloy used in Examples 6 and 7, an alloy/poly-carbonate composite is prepared and tested for adhesion.
The composite passed both tests.
When the polycarbonate film is metallized with tin, silver or an alloy, 99 percent tin and 1 percent silver and tested for adhesion as in Examples 6 and 7, the metal-lized composites failed the adhesion tests.
Example 10 Following the procedure of Example 2, a portion (15.24 cm x 60.96 cm) of polyethylene film is coated with about 0.2 g of a,n alloy of 80 percent tin, 14 percent bismuth and 6 percent copper. When a (15.24 cm x 15.24 cm) portion is tested for barrier to oxygen, it exhibits an oxygen transmission rate of ~1.8 cc/24 hrs.
Similar results are obtained when polyethylene film or other polymer film such as saran film is metallized with other alloys of from 25 to 95 percent tin, 5 to 75 percent of at least one of bismuth, antimony, zinc and lead and up to 25 percent of at least one of copper, silver and nickel.
When a similar polyethylene film portion coated with aluminum is similarly tested for oxygen barrier, an oxygen transmission rate of ~36 cc/24 hrs is observed.
The uncoated polyethylene film exhibits an oxygen trans-mission rate of ~180 cc/24 hrs.

l8,236-F -29-l~Z~3`~
Example 11 Following the procedure of Example 2, a bilayer ~omposite is prepared using the polycarbonate film of Example 2 and an alloy of 84 percent tin, 12 percent bis-muth and 4 percent copper. A sample (12.7 cm x 12.7 cm) of this composite is tested for electrical resistance (ER) by attaching two electrical contacts to the sample and ER is found to be 0.7 ohm/square. The sample is shaped into a cup to a depth of 2 cm as in Example 2, and the ER is again measured by attaching the electrical con-tacts to the sample in the formed area. The ER is found to be 1 ohm/square.
For purposes of comparison, a bilayer composite is prepared as in Example 11 except that aluminum is substituted for the metal alloy. As in Example 11, a sample (12.7 cm x 12.7 cm) of the aluminum composite is tested for ER, formed into a cup shape and retested for ER. The results of these tests are as follows: ER before forming is 0.7 ohm/square, ER after forming is >1000 ohms/-square. ~esults similar to those obtained for the aluminum composite are obtained if silver is substituted for alumi-num in preparing and testing a bilayer composite by the procedure of Example 11.

18,236-F -30-

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A formable metal/organic polymer composite comprising a layer of a normally solid thermoplastic polymer and a layer of a normally solid soft metal inti-mately adhered to at least one surface of the polymer layer, said soft metal melting at a temperature or over a range of temperatures that is from 80 to 135 percent of the forming temperature of the thermoplastic polymer, said temperatures being in degrees K, and said soft metal being indium or an alloy of two or more metals, other than a lead alloy, comprising at least 50 weight percent of a first metal and at least 5 weight percent of at least one second metal, the said composite being capable, when subjected to a forming operation, of undergoing a cumulative surface dimensional change of at least 20 percent.

2. The composite of Claim 1 wherein both the first metal and the second metal(s) have melting points below 450°C (723°K).

3. The composite of Claim 2 wherein the alloy also contains at least 0.1 weight percent of a metal having a melting point above 450°C (723°K).

4. The composite of Claim 1 wherein the alloy has a solidus temperature of less than 650°K
and contains at least 60 weight percent of at least one metal selected from the group consisting of indium, bismuth, tin, zinc, cadmium and antimony.

5. The composite of Claim 1 wherein the alloy does not contain more than 90 weight percent of any one metal.

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6. The composite of Claim 5 wherein the alloy does not contain more than 80 weight percent of any one metal and has a solidus temperature of less than 548°K.

7. The composite of Claim 1 wherein the alloy contains from 85 to 95 weight percent of metal selected from the group consisting of indium, bismuth, tin, zinc, cadmium, antimony and a mixture thereof providing that in any such mixture one of the metals is present in an amount of at least 50 weight percent and from 5 to 15 weight percent of a metal selected from the group consisting of copper, silver, gold, nickel, magnesium, aluminum, and a mixture thereof providing that in any such mixture one of the metals is present in an amount of at least 5 weight percent.

8. The composite of Claim 1 wherein the soft metal is selected from alloys of from 25 to 90 weight percent tin, from 8 to 60 weight percent bis-muth and from 1 to 25 weight percent of at least one metal selected from the group consisting of copper, silver, nickel, magnesium, gold, iron, chromium and manganese, providing that one of the metals selected from the group consisting of tin and bismuth is pres-ent in an amount of at least 50 weight percent.

9. The composite of Claim 1 wherein the soft metal is an alloy selected from the group con-sisting of (i) 50 percent tin, 30 percent bismuth, 20 percent copper; (ii) 80 percent tin, 15 percent bismuth, 5 percent copper; (iii) 75 percent tin, 20 percent copper, 5 percent silver; (iv) 75 percent tin, 25 percent silver; (v) 55 percent tin, 35 percent 18,236-F

bismuth; 10 percent silver; and (vi) 84 percent tin, 12 percent bismuth, 4 percent copper, wherein the indi-cated percentages are weight percentages.

10. The composite of Claim 1 wherein the polymer is selected from the group consisting of poly-styrene, a styrene/acrylonitrile copolymer, a copolymer containing polymerized styrene, acrylonitrile and buta-diene, a styrene/butadiene copolymer, a rubber modi-fied styrene polymer, a styrene/maleic anhydride copolymer, a polymer of a monovinylidene aromatic carbocyclic monomer; a polycarbonate; a polyester; an acrylic resin; a polyacetyl resin; a nitrile resin and another polymer of an .alpha.,.beta.-ethylenically unsaturated nitrile; a polyamide; a polyolefin; a polyvinyl halide;
a polyurethane; a polyallomer; a polyphenylene oxide;
and a polymer of a fluorinated olefin.

11. The composite of Claim 10 wherein the polymer is selected from the group consisting of a polycarbonate made from phosgene and bisphenol A and/or phenolphthalein; polyethylene terephthalate; poly-(methyl methacrylate); polyformaldehyde resin;
polyacrylonitrile; and acrylonitrile/methyl methacrylate copolymer nylon; polyethylene and polypropylene; poly-vinyl chloride and a vinylidene chloride homopolymer and copolymer; and polytetrafluoroethylene.

12. The composite of Claim 1 wherein the soft metal is indium or an alloy of at least two metals selected from the group consisting of cadmium, indium, tin, antimony, bismuth, magnesium, aluminum, zinc, copper and silver, and the thermoplastic polymer is selected from the group consisting of a polycarbonate, 18,236-F

a polyester, an acrylic resin, a monovinylidene aro-matic polymer, a polymer of a vinyl halide or a vinylidene halide, and a polyacetal.

13. The composite of Claim 1 wherein the thermoplastic polymer is selected from the group con-sisting of a polycarbonate, a polyester, and a mono-vinylidene aromatic polymer and the soft metal is selected from the group consisting of 1) indium;
2) an alloy of 55 percent tin, 35 percent bismuth, and 10 percent silver;
3) an alloy of 50 percent zinc and 50 percent cadmium;
4) an alloy of 80 percent tin, 15 percent bismuth and 5 percent copper;
5) an alloy of 75 percent tin, 20 per-cent bismuth and 5 percent silver;
6) an alloy of 75 percent tin and 25 per-cent silver; and 7) an alloy of 50 percent tin, 30 per-cent bismuth and 20 percent copper;
said percentages being in weight percent-ages.

14. The composite of Claim 1 wherein the polymer is selected from the group consisting of poly-ethylene and a vinylidene chloride copolymer and the soft metal is an alloy containing from 50 to 95 weight percent tin, from 5 to 50 weight percent of at least one metal selected from the group consisting of bis-muth, antimony and zinc and up to about 25 weight percent of a metal selected from the group consisting of copper, silver and nickel.

18,236-F

15. The composite of Claim 1 wherein the soft metal layer has a thickness of from 0.01 to 1 micrometer.

16. The composite of Claim 1 wherein the polymer layer contains one or more additives includ-ing dyes, light stabilizers, reinforcement fillers and fibers, pigments, or carbon black.

17. A method of making the metal/organic polymer composite of Claim 1, which method comprises intimately adhering together a layer of said normally solid, soft metal and at least one surface of a layer of the normally solid, formable thermoplastic polymer.

18. The method of Claim 17 wherein the soft metal is applied to the polymer by vacuum deposition, sputter coating, or electroless deposition.

19. A method of making a formed metal/organic polymer composite, which method comprises the step of subjecting the metal/organic polymer composite as claimed in Claim 1 to a forming operation during which at least a portion of the composite is modified by its undergoing a cumulative surface dimensional change of at least 20 percent.

20. The method of Claim 19 wherein the por-tion of the composite undergoes a cumulative surface dimensional change of at least 30 percent.

21. The method of Claim 20 wherein the change is from 50 to 300 percent.

22. The method of Claim 21 wherein the change is from 150 to 300 percent.

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23. The method of Claim 19 in which the forming operation is by cold drawing, vacuum drawing, drape molding, pressure thermo-forming or scrapless thermo-forming.

24. A formed metal/organic polymer composite which has been made by the method of Claim 19.

25. The formed composite of Claim 24 wherein a polymer layer is adhered to each of the surfaces of the soft metal layer.

26. A shaped article comprising the formed composite of Claim 24.

27. A shaped article comprising (1) the formed composite of Claim 24 and (2) a reinforcing material in intimate contact with at least one surface of the formed composite.

28. The shaped article of Claim 27 in which the reinforcing material is a rigid polymeric material selected from the group consisting of polyurethane, polystyrene, an epoxy polymer, polyvinyl chloride, polyvinyl acetate, a silicone polymer, a cellulosic polymer, an acrylic polymer, a saturated polyester, an unsaturated polyester and asphalt.

29. The shaped article of Claim 27 in which the reinforcing material is an elastomeric polymer selected from the group consisting of polyurethane, a rubber styrene/butadiene copolymer, a polybutadiene rubber, natural rubber and an ethylene polymer, par-ticularly as ethylene/propylene copolymer rubber.

18,236-F