WO1981000825A1 - Laminated polymeric articles and process for the production thereof - Google Patents

Abstract

A laminated article and its method of preparation are described. The article comprises two dissimilar and otherwise chemically unbondable layers of resin materials, one thermosetting and one thermoplastic, which are bonded by use of a coating therebetween consisting essentially of urethane resin. The articles have good cold temperature impact resistance and are especially suited for use as laminated pipe.

Description

LAMINATED POLYMERIC ARTICLES AND PROCESS FOR THE PRODUCTION THEREOF

Technical Field This invention relates to the bonding of two dissimilar polymeric resin composition surfaces. In a particular embodiment, the invention relates to a process for bonding an epoxy resin matrix reinforced with glass fibers to the surface of a poly(vinyl chloride) pipe thereby the pipe is reinforced and withstands high delaiπinating forces without rupture of the interface bond between the epoxy resin and the poly(vinyl chloride) surface. The invention also relates to the product of this process vhich in a preferred embodiment comprises a pipe.

Background of the Prior Art For seme time, plastic pipe made of one or more layers each of polymeric olefinic chloride resin ("PVC") and epoxy-impregnated glass fibers has been widely used, in the construction and plumbing industries. Light weight and resistance to corrosion have been among the desirable properties of this type of pipe. Ihe pipe conventionally consists of an inner hollow cylinder of PVC overlayed with a wrapping of epoxy impregnated glass fibers. In seme cases enly a single layer of each material is used; in other cases, however, the first layer of epoxy impregnated glass fibers is overlayed with a second PVC layer which is itself then overlayed with a second layer of epoxy impregnated glass fiber. Any number of such multiple alternating layers may be thus built up.

Bending between each pair of dissimilar surfaces of the alternating layers of epoxy impregnated glass fiber and PVC has, however, been a serious problem, often reaching critical dimensions where the pipe consists solely of a relatively thin PVC inner cylinder overlayed with oily one or two layers of an epoxy impregnated glass fiber wrapping. Since PVC and epoxy do not substantially chemically bond with each other, mechanical forces were depended upon to maintain the integrity between the layers of the pipe. However, these mechanical forces were insufficient to withstand the countervailing forces produced by the fluid pressure within the pipe and the layers of the pipe would become separated or delaminated. This was particularly aggravated

whenever it was necessary to cut into the pipe as with a conventional pipe joint thereby exposing the interface in the cut cross section of the pipe to the full line pressure carried within the pipe.

Pipe manufacturers for some time attempted to overcome the above mentioned problems by seeking various means for creating a strong bond directly between the alternating layers of PVC and epoxy impregnated glass fiber. Those attempts were substantially hindere however, by the characteristic inertness and chemical resistance of PVC and related resins. Since the chemical reactions of those materials are generally substantially confined to those of degradation in heat or strong radioactive environments, conventional attempts to achieve chemical bends of epoxy resins, directly or indirectly, to PVC or related resins were substantially ineffective and failed to overcome the problems noted. Typical of the conventional and/or prior adhesives and surface treatments which had heretofore proven to be unsatisfactory are those described in U.S. Patents Nbs. 2,815,043; 3,002,534 and 3,447,572 as well as British Patent No. 907,763.

Several years ago a process was described in U.S. Patent No. 3,628,991 in which an acrylonitrile-butadiene-styrene ("ABS") co polymer dissolved in a mutual solvent for PVC and ABS was applied to the surface of the PVC pipe to form a surface solution. The epoxy impregnated glass fiber layer was then overwrapped in contact with this ABS containing surface solution and bonded to the ABS, this approach achieved a notable measure of success in creating a satisfactory bond between the PVC inner cylinder ("core") and the epoxy impregnated glass fiber overwrap. Subsequently, an improved process was described in U.S.

Patent No. Re-29,375 in vhich a defined quantity of a solid epoxy resin was incorporated into the ABS containing surface solution. Presence of the solid epoxy resin in the ABS surface solution dramatically improved the bond between the PVC core and the epoxy impregnated glass fiber overwrap layer. This patent also described several other resins which could be used for the core material in place of PVC as well as two resins (solid thermosetting phenolic resins or polyester resins) which could be used in place of the solid epoxy resin in the ABS layer. Critical to the process and products described in this patent, however, was the requirement that the resin incorporated into the butadiene containing layer be chemically the same as the resin used for the fiber glass reinforced overwrap although that resin in the ABS containing layer would normally be in the solid phase while the same resin in the overwrap would be initially in the liquid phase prior to bonding and curing of the entire coated product.

The laminated product described in the reissue patent has enjoyed a marked success in the market place, being sold commercially by Johns -Manville Corporation under the trademark PERMASTRAN. It has been discovered in service, however, that when the pipe is used at low temperatures, such as those on the order of about 0°F (-18°C), the bond formed with the ABS adhesive layer containing the epoxy, phenolic or polyester resin corresponding to the resin in the overwrap has a tendency to weaken and delaminate. Since laminated PVC pipe can frequently be subjected to such temperatures, as when it is being shipped or stored outdoors during the winter, it would be very advantageous to have a bonding medium which would insure that the PVC core and epoxy, phenolic or polyester impregnated fiber glass overwrap remained firmly and securely laminated.

Brief Summary of the Invention The invention herein is a process for bonding together a first layer comprising a thermoplastic poly(vinyl acetate), poly (methyl methacrylate), polystyrene, polybutene, poly(vinyl butyral) or polymeric olefinic chloride resin and a second layer comprising a liquid thermosetting epoxy, phenolic or polyester resin, which layers are substantially chemically unbondable to each other; which process cαπprises applying to the surface of said first layer a coating consisting essentially of urethane resin in such manner that said coating and said first layer become mechanically interengaged at the interface between the two, applying to said coating said second layer in uncured form and thereafter curing said second layer and simulitaneously forming a substantially chemical bond between said coating and said second layer, vhereby a laminated product of improved cold temperature integrity and strength is formed.

In one embodiment the first layer comprises PVC and the second layer comprises epoxy iiηsregnated glass fiber. In another embodiment the coating also contains a butadiene resin . Methods by which the bend between the first layer and the coating can be for include surface roughening and/or solvent washing of the first layer or forming a surface solution at the interface between the first layer and the coating. The invention also comprises a laminated article having a bond between the laminae which has improved cold temperature integrity and strength, said article comprising a first layer containing as the principal component a thermoplastic poly(vinyl acetate), poly(methyl methacrylate), polystyrene, polybutene, poly(vinyl butyral) or polymeric olefinic chloride resin and a second layer containing as the principal component a thermosetting epoxy, phenolic or polyester resin, said layers being bonded into said laminate by a coating therebetween and in intimate contact therewith, said coating consisting essentially of a urethane resin which is mechanically interengaged with said first layer and chemically bonded to said second layer.

In one embodiment the first layer ccrrrprises PVC and the second layer comprises an epoxy impregnated glass fiber material. In another embodiment the abating also contains a butadiene resin. Methods by which the bond between the first layer and the coating can be formed include surface roughening and/or solvent washing of the first layer or forming a surface solution at the interface between the first layer and the coating.

Detailed Description of the Invention This invention is a novel method of bonding two dissimilar and otherwise unbondable resinous compositions. While the process of this invention is applicable to bonding any two of the described classes of materials, the process finds a particularly important use in the bonding of alternate layers of PVC and related resins to layers of epoxy and related polymeric materials. An important specific application of this process lies in a method for producing plastic pipe composed of alternating layers of PVC resin and epoxy impregnated glass fiber.

The process of this invention enables strong bonds to be formed between layers of dissimilar and otherwise generally unbondable resinous oαnpυsitions. Pipe produced by the method described herein has good integrity and substantial resistance to separation at the interfaces within the pipe wall. Where it is necessary to cut into or through the pipe wall and expose one αr more of the interfaces, the method of this invention can be used quite effectively to seal the cut surface and prevent exposure of the interface to the line pressure within the pipe thereby preventing separation of the pipe wall at that interface. A most important property of pipe produced by the process of this invention is its resistance to delamination even under severe cold temperatures, such as those on the order of about 0°F (-18°C). It has, for instance, been discovered that pipe produced according to the present invention shews bond strength which are frequently twice as great as the best previous laminated pipe, i.e., that produced according to the process of the aforementioned reissue patent.

The thermoplastic resin which comprises the principal component of the first layer will be selected frαn the group consisting of poly(vinyl acetate), poly(methyl methacrylate), polystyrene, polybutene, poly(vinyl butyral) and the polymeric olefinic chlorides, notably poly(vinylidene chloride), poly(vinyl chloride) and copolymers thereof. The polymeric olefinic chlorides (which are usually referred to herein collectively as "PVC" resins) are the preferred resins to be used as the first layer of the laminate, particularly when the laminated article is a pipe. PVC pipe cores are noted for their inertness and stability in the presence of a wide variety of different types of fluids which the pipes may be called upon to transport. The thermoplastic resins useful herein are those which are substantially chemically inert but which can form surface solutions with the coatings described below.

The second layer is composed of an initially liquid thermosetting resin selected from the group consisting of epoxy resins, polyester resins and phenolic resins. Of these the epoxy resins are preferred. These resins are reaction products of epoxide compounds with confounds having available hydrogen atoms linked to carbon atoms by oxygen atoms. Examples of the latter are the polyhydric phenols and the polyhydric alcohols. A typical epoxy resin useful in this invention is the reaction product of epichlorohydrin and a polyhydric phenol such a bisphenol-A. Other illustrative epoxy resins typically include reaction products of epihalohydriris and polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylene glycol and the like. Also quite satisfactory in the psrocess of this invention are the epoxy silanes; these are often used as the binding matrix for glass fibers as described, for instance in U.S. Patent No. 3,391,052.

Other suitable epoxy resins include the epoxy novolac resins such as the epoxy phenol novolac resins. These are basically novolac resins vhose phenolic hydroxyl groups have been converted to glycidyl ethers. Other suitable epoxy resins types include ρ-amine phenol epoxys as well as cycloaliphatics in which the epoxide group is directly attached to the cycloaliphatic ring and epoxy ethers.

The phenolic resins include those produced by reacting phenol with an aldehyde. The commercial phenols used are phenol, cresol, xylenols, p-tert.-butylphenol, p-phenyl-phenol, bisphenols and resorcinol. The most important aldehydes are formaldehyde and furfural. Preferred among the phenolic resins are those formed by the reaction of phenol and formaldehyde. The phenolic resin may be formed by either addition or condensation reactions in the presence of either acid or base.

The polyester resins are formed by the reaction of polyfunctional acids or anhydrides and alcohols. A typical polyester resin is prepared by reacting phthallic anhydride or maleic anhydride and propylene glycol.

The polyurethanes which are the basic component of the ooating of the present invention are formed by the reaction of a polyol with a diisocyanate. Typical among the polyols which may be used to form the polyurethanes of the present invention include those derived from glycerol and sorbitol. Typical of the diisocyanates which may be used are toluene diisocyanate (which is usually in the form of mixed isomers of toluene diisocyanate) or diphenyl methane diisocyanate. The reaction to form the polyurethanes is usually catalyzed by amines such as diethylene triamine or dibutyltin dilaurate. In the present invention the polyurethane resin will be in the solid phase after the bond is formed between the coating and the first layer, but will be dissolved or dispsersed in a solvent at the time the coating layer is applied to the thermoplastic first layer, as will be described below.

The coating may also contain a butadiene resin. This include polybutadiene itself or any of a variety of copolymers or terpolymers thereof such as butadiene-styrene resin, acrylcnitrilebutadiene resin, acrylonitrile-butadiene-styrene resin (ABS), mixtures thereof and the like. Praparation methods for all the resins mentioned in the preceding paragraphs are well known and amply described in the art. Any of the known preparation methods are suitable to prepare the resins for use in this invention. The urethane resin will normally initially be in solid form.

In order to form the coating of the present invention, the urethane resin is first dissolved or dispersed in comminuted form in a solvent. It is preferred that the urethane be dissolved in order to obtain the optimum bond. Typical solvents which may be used include tetrahydrofuran, methyl ethyl ketone, cyclohexanone, methylene chloride, acetone, ethyl acetate, iscphorone and the like. When the coating also contains a butadiene resin it is preferred that the solvent be a mutual one for both the urethane and the butadiene resins. Similarly, if the mechanical interengagement of the coating and the first layer is to be obtained by means of formation of a surface solution at the interface thereof, it is preferred that the solvent also be a mutual solvent for the thermoplastic resin in the first layer as well as for the urethane and the thermoplastic resin.

The second layer containing the thermosetting resin impregnated glass fiber, in which the thermosetting resin is initially in liquid form, may if desired also contain a curing agent for the thermosetting resin. Typical curing agents are described in the aforementioned reissue patent.

The exact composition and concentration of the components in the first and second resinous layers are not critical. Each component will be selected primarily because of the particular properties desired in the finished article. Thus in a typical pipe composition the PVC core cylinder will be composed essentially all (i.e., usually about 90% or greater) of PVC with a small amount of conventional additive materials such as stabilizers, antioxidants, colorants, etc. Similarly, the typical overwrap layer of epoxy impregnated glass fiber will consist of a range of concentrations of continuous filament glass fibers in an epoxy matrix and may also include materials such as colorants, antioxidants, stabilizers, curing agents, etc. in small amounts. The various concentrations of epoxy and glass will depend en the properties desired in the finished pipe. In these cases, as in all others involving the various materials which may be in the first and/or second resinous layers, there is much prior art describing the various materials and their properties. Those skilled in the art will have no difficulty selecting suitable compositions frαn the prior art for use in the process of this invention. For the purpose of this invention, therefore, the first and second resinous layers are considered suitable if they are not generally bondable to each other and if they each contain the respective thermoplastic and thermosetting resins as princi components. "Principal component" as used herein is defined to mean a component vhich is present in sufficient quantity so as to contribute substantially to the bonding process of this invention. Generally this will mean that the particular component will comprise 40% to 50% or more by weight, up to 100% by weight, of the particular polymeric composition being considered. Such a component may, however, be present in a smaller concentration if the other components are relatively inert and/or the component in question provides a major part of the bonding function. Thus, for instance, in an epoxy impregnated glass fiber layer, the epoxy resin may vary over wide range en concentrations and yet be considered a principal component for the other important component in the system, glass fiber, is inert and does not participate in the bonding process. It is, of course, important that a "principal component" be present in sufficient amount to materially participate in the bonding function; small or trace amounts of a component which provide only a small amount of bonding are not considered to be within the scope of this invention.

The novel coating layer initially contains two principal components: the urethane resin and a solvent which is a mutual solvent for both the thermoplastic and for the urethane resin. The urethane resin is initially in solid form and is either dissolved or dispersed in the solvent. During the process herein the solvent will evaporate, leaving a solid urethane coating interengaged with the thermoplastic substrate. If desired, the coating may also contain a butadiene resin, in vhich case the solvent is usually also a mutual solvent for the butadiene resin. When a butadiene resin is present, the urethane and butadiene resins will be present in a butadiene:urethane resin weight ratio of up to 85:15, preferably in a range of 20:80 to 80:20, and more preferably in approximately equal amounts. If desired, the coating may also contain a quantity of a thermosetting resin of the same chemical type as the thermosetting epoxy, phenolic or polyester resin of the second layer. The thermosetting resin will, be incorporated into the coating in a manner and quantity analogous to that described in the reissue patent. In this case preferably the mutual solvent for the thermoplastic, butadiene and urethane resins will also be a solvent for the thermosetting resin.

The urethane coating may be interengaged with the thermoplastic substrate (i.e., the first resinous layer) in different ways. In a preferred method, the substrate is first sanded to roughen the surface and the solvent containing the urethane is then sprayed or painted onto the roughened surface. When the solvent subsequently evaporates or is heated to volatilize it, the solid urethane resin left is found to have filled the myriad of minute "valleys" created in the substrate surface by the sanding, thus effecting a firm mechanical interlock of the coating and the substrate.

Alternatively, the substrate can be solvent washed with one of the aforementioned solvents, preferably methyl ethyl ketone or tetrahydrofuran when the substrate is PVC. Solvent washing to roughen the surface may also be combined with sanding, but is not preferred because solvent washing appears to "fill in" the "valleys" created by sanding to seme extent, thus making the subsequent urethane/ substrate bond less strong.

In yet another embodiment, the urethane-containing mutual solvent can be worked into the outer surface of the substrate in a quantity sufficient to dissolve the outer surface portion of the thermoplastic layer and to form a surface solution of that portion with the coating. Care should be taken, however, that the quantity of coating used is not so great as to dissolve a major portion of the first layer and thereby to weaken σr materially change the properties of that composition.

Those skilled in the art of adhesion and bonding will be well aware of the proper amount of coating to be used en a particular resin composition substrate to achieve a good bond without seriously diminishing the desirable properrties of the substrate. The quantity of coating is such as normally to penetrate the surface of the first polymeric resin composition to a depth of about 0.5 to about 8 mils (0.01 to 0.20 mm) and to form a coating thickness of up to about 15 mils (0.38 mm). Some data suggest that the thicker coatings give more consistent results .

The coated first layer is then heated to a temperature of 100°F to 200°F (37°C to 93°C), preferably 100°F to 150º F (37°C to 65ºC), and held for about 1 to 16 hours. This heating serves to precondition the first layer and coating for the final curing step. The volatile solvent is driven off, leaving the urethane resin present as a solid forming the adhesive coating layer. In most cases the surface is not tacky after this heating so that the coated first layer (such as a pipe) may readily be handled and conveyed to the location at which the overwrap is to be applied. In addition, this heating step causes the first layer to undergo shrinkage if the particular thermoplastic resin has a tendency to shrink in the presence of heat. This prevents differential shrinkage from occurring in the subsequent heat curing step after the overwrap has been applied and significantly reduces the possibility that the final laminated product will become delaminated during final curing or that undue delamination stresses will be built up in the bonding adhesive.

Following this heat preconditioning the second layer consisting of the thermosetting resin impregnated glass fiber is applied to and placed in contact with the solid surface of the dried and solidified coating. The thermosetting resin will be in a substantially liquid and uncured state. The concentration of the thermosetting resin in the second layer may, as noted above, vary over quite a wide range, particularly where the layer also contains inert materials such as glass fibers. The layer may be sprayed, painted, wiped or otherwise applied to the hardened surface of the coating, preferably in liquid form. In a preferred embodiment the layer is in the form of resin impregnated filaments which are layed or wrapped en or around the substrate and surface solution. Thus, when pipe is to be formed by the process of this invention the inner cylinder (e.g., the PVC oore) is first coated on its cuter surface with the solvated urethane coating. Thereafter following heating of the solvated coating and inner cylinder, and the resultant solidifying of the urethane coating and mechanical interengagement of the coating and the thermoplastic substrate, epoxy impregnated fiber glass filaments attaining epoxy in the form of a relatively viscous, uncured liquid, are wrapped continuously and tightly around the cylinder bringing the epoxy into intimate contact with the solid coating surface.

Following application of the outer second layer, the thermoplastic resin is cured by conventional curing means. Generally this involves heating the entire assemblage so as to thermally cure the thermosetting resin. The heat applied will, of course, be kept sufficiently low such that other resins in the entire assemblage as well as any fillers or additives or other materials which may be present will not be detrimentally affected. Such curing techniques are well known to those skilled in the art and need not be exemplified here. It has been found that for compositions exemplified below, cure temperatures of about 130°F to about 180°F (54°C to 82°C) maintained for about 0.5 to 16 hours produced entirely satisfactory bonds. Curing of the second or overwrap layer may be expedited by incorporation into the layer of a quantity of curing agent for the thermosetting resin.

The following will illustrate the present invention. In an experimental trial at a commercial pipe plant, samples of pipe made according to the process of U.S. Patent Re-29,375 were compared to pipe made under identical conditions with the exception that urethane was substituted for epoxy in the coating layer. The underlying substrate material was a PVC pipe core and the overwrap was a glass fiber reinforced epoxy resin. The PVC core surfaces were cleaned by washing with methyl ethyl ketone and/or by flap sanding. Both thin (2-4 mils; 0.05-0.10 mm) and thick (10-12 mils; 0.25-0.30 mrn) samples were evaluated. Also the effect of cleaning of the PVC surface was evaluated by making a few samples in which the surface was not cleaned prior to incorporation of the coating layer. Inspection of the pipe samples after production indicated that all samples in which the PVC core had been cleaned were of good quality σr better, while the bonds of the uncleaned samples were uniformly poor. The urethane used was a product designated "Adiprene L-167" available commercially from the DuPont Company. In some cases the coating was sprayed onto the PVC core with commercial spray equipment and in other cases it was handpainted onto the core. Impact testing using the method of ASTM D-2444 produced the results shown in the following Table. In both cases the test felling weight ("tup") was "Tip C."

It will be immediately evident from these data that the materials made in accordance with the present invention are all uniformly stronger than the bonds obtained in the control material made in accordance with the reissue patent process. The improvement is particularly marked at low temperatures (0°F; -18°C) and the thicker the coating the stronger the bond. Data from tests made at the same time indicated that all samples of both the control material and the material of this invention in which the PVC core had been cleaned prior to coating application readily passed the water pressue burst test.

In each case the urethane material contained a conventional amount of a curative material and both were dissolved in a solvent (ethyl acetate).

In another experiment test samples made according to the process of the reissue patent with epoxy were compared to samples similarly formed using "Estane 5716" (trademark) fully reacted urethane resin available commercially from B.F. Goodrich Chemical Co. Results are described in Table II below. Table II

In a subsequent test in which "Estane 5713" (trademark) fully cured urethane resin (available commercially from B.F. Goodrich Chemical Co.) was used in place of the aforementioned "Estane 5716" (trademark) resin because of the former's higher heat resistance, the cold temperature (0°F, -18°C) ASTM D-2444 impact strength was found to be about three times greater than an epxoxy-containing material made according to the reissue patent disclosure.

Statement of Industrial Application The invention herein is applicable to the bonding of any two dissimilar and chemically unbondable resinous materials. It is particularly applicable to the formation of laminated materials such as laminated pipe.

Claims

Claims

1. A process for bonding together a first layer comprising a thermoplastic poly(vinyl acetate), poly(methyl methacrylate), polystyrene, polybutene, poly(vinyl butyral) or polymeric olefinic chloride resin and a second layer comprising a liquid thermosetting epoxy, phenolic or polyester resin, which layers are substantially chemically unbondable to each other; which process comprises applying to the surface of said first layer a coating consisting essentially of urethane resin in such manner that said coating and said first layer become mechanically interengaged at the interface between the two, applying to said coating said second layer in uncured form and thereafter curing said second layer and simultaneously forming a substantially chemical bond between said coating and said second layer whereby a laminated product of improved cold temperature integrity and strength is formed.

2. The process of Claim 1 wherein said first layer comprises a polymeric olefinic chloride resin.

3. A process as in Claim 2 wherein said polymeric olefinic chloride resin is selected from the group consisting of poly(vinylidene diloride), poly(vinyl chloride) and copolymers thereof.

4. A process as in Claim 1 wherein said second layer comprises an espoxy resin.

5. A process as in Claim 1 wherein said ooating further consists essentially of a butadiene resin in a butadiene:urethane resin weight ration of υp to 85:15.

6. A process as in Claim 5 wherein said butadiene resin is selected from the group consisting of polybutadiene, butadienestyrene resin, acrylonitrile-butadiene-styrene resin and mixture thereof.

7. A process as in Claim 5 wherein said ratio is in the range of 20:80 to 80:20.

8. A process as in Claim 7 wherein said urethane and said butadiene resin are present in approximately equal amounts.

9. A process as in CLaim 5 vherein said ooating furt consists essentially of a quantity of a thermosetting resin of the same chemical type as said epoxy, phenolic or polyester resin.

10. A parocess as in Claim 1 wherein said first layer is sanded, solvent washed or both prior to application of the urethane and said urethane is applied in a solvated state, with the solvent subsequently being removed to leave the solid urethane coating mechanically interengaged with said first layer.

11. A process as in Claim 1 wherein said coating and said first layer are mechanically interengaged by forming a surface solution of the two at their interface and subsequently causing the surface solution to be solidified.

12. A process as in Claim 1 wherein said first polymeric resin layer having said surface solution on it is heated for a predetermined time prior to having laminated thereto the second polymeric layer.

13. A laminated article having a bond between the laminae which has improved cold temperature integrity and strength, said article comprising a first layer containing as the principal component a thermoplastic poly(vinyl acetate), poly(methylmethacrylate), a polystyrene, polybutene, poly(vinyl butyral) or polymeric olefinic chloride resin and a second layer containing as the principal component a thermosetting epoxy, phenlic or polyester resin, said layers being bonded into a laminate by a coating therebetween and in intimate contact therewith, said coating consisting essentially of a urethane resin which is mechanically interengaged with said first layer and chemically bonded to said second layer.

14. An article as in Claim 13 wherein said first layer comprises a polymeric olefinic chloride resin.

15. An article as in Claim 14 wherein said polymeric olefinic chloride resin is selected from the group consisting of poly(vinylidene chloride), ρoly(vinyl chloride) and copolymers thereof.

16. An article as in Claim 13 wherein said second layer comprises an epoxy resin.

17. An article as in Claim 13 wherein said coating further consists essentially of a butadiene resin in a butadiene:urethane resin weight ratio of up to 85:15.

18. An article as in Claim 17 wherein said butadiene resin is selected from the group consisting of polybutadiene, butadiene-styrene resin, acryloiitrile-butadiene-styrene resi n and mixture thereof.

19. An article as in Claim 18 wherein said coating further consists essentially of a quantity of a thermosetting resin of the same chemical type as said epoxy, phenolic or polyester resin.

20. An article as in Claim 18 wherein said ratio is in the range of 20:80 to 80:20.

21. An article as in Claim 20 wherein said urethane and said butadiene resin are present in approximately equal amounts.

22. An article as in Claims 13, 17 or 21 comprising a pipe.