Radiation polymerizable coating composition containing an unsaturated phosphoric ester

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DETAILED DESCRIPTION OF THE INVENTION

I. Radiation Polymerizable Coating Composition

In this application, the term "paint" is meant to include finely divided pigment and/or particulate filler as well as other additives in a film-forming, resin comprising, binder or the binder without pigment, particulate filler, and other additives. Thus, the binder which is ultimately converted to a weather and wear-resistant film can be all or virtually all that is used to form the film, or it can be a vehicle for pigment and other additives.

The radiation polymerizable coating compositions or paints of this invention, which overcome the deficiencies of prior art coatings, on a non-polymerizable solvent, pigment, initiator and particulate filler-free basis, consist essentially of a binder solution of: (1) an alpha-beta olefinically unsaturated organic resin containing between about 0.5 and about 5 units of olefinic unsaturation per 1,000 units of molecular weight; (2) a compound polyermizable with said resin upon exposure to ionizing radiation; and (3) between about 0.05 and about 1.0 parts per 100 parts of the total of said alpha-beta olefinically unsaturated resin and said compound polymerizable therewith of a mono- or diester of phosphoric acid bearing one or more sites of vinyl unsaturation and having the formula: ##STR2## where: R = H, Cl or CH.sub.3

A = c.sub.n H.sub.2n, 2 .ltoreq. n .ltoreq. 6

R' = h, c.sub.1 - c.sub.4 alkyl or C.sub.1 - C.sub.4 bromo- or chloroalkyl

A. Alpha-Beta Olefinically Unsaturated Resins

The term "alpha-beta olefinically unsaturated organic resin" as used herein means an organic resin having olefinic unsaturation provided by an alpha-beta olefinically unsaturated monomer. The term "alpha-beta unsaturation" as used herein includes both the olefinic unsaturation that is between two carbon atoms which are in the alpha and beta positions relative to an activiating group such as a carboxyl group, e.g., the olefinic unsaturation of maleic anhydride, and the olefinic unsaturation between the two carbon atoms which are in the alpha and beta positions with respect to the terminus of an aliphatic carbon-to-carbon chain, e.g., the olefinic unsaturation of acrylic or methacrylic acid or styrene. The binder solution of the coating compositions of this invention preferably includes between about 90 and about 10 parts, preferably between about 80 and about 20 parts of such an alpha-beta olefinically unsaturated resin containing between about 0.5 and about 5 units, preferably between about 0.5 and about 3 units, of unsaturation per 1,000 units of molecular weight. The selection of the particular alpha-beta olefinically unsaturated organic resin will, of course, depend upon the particular selection of the compound polymerizable therewith as well as the type of substrate being coated, the intended use of the end product and the desired viscosity of the binder, keeping in mind the desired mode of application. The following discussion of alpha-beta olefinically unsaturated resins is presented as a summary of the various types of resins which may be employed in radiation curable paints known in the prior art and taught in the above-incorporated prior art patents. Of course, the particular details regarding the various prior art radiation curable compositions are more adequately described in the patent disclosures incorporated herein by reference.

U.S. Pat. No. 3,437,514 to Burlant discloses a number of preferred types of alpha-beta olefinically unsaturated resins useful in this invention, which types are generic to a number of resins disclosed by others of the patents listed above. One of these resins is of the vinyl resin type. The term "vinyl resin" as used in this context is one which is formed from "vinyl monomers" and which includes the requisite amount of alpha-beta olefinic unsaturation. The term "vinyl monomers" is intended to mean monomeric compounds having a ##STR3## terminal group and excludes allylic compounds, resins and modified acrylic resins, the former meaning a resin formed exclusively of acrylic monomers and the latter meaning a resin formed from a major amount of acrylic monomers and a minor amount of non-acrylic monomers. The term "acrylic monomers" means an alpha-beta monounsaturated monocarboxylic acid or esters thereof and includes, but not by way of limitation, acrylic acid, alkyacrylic acids, e.g., methacrylic acids, monohydric and polyhydric alcohol esters of acrylic acid and alkyacrylic acids, eg., glycidyl methacrylate, 2-hydroxethyl methacrylate, etc. These resins have a molecular weight in excess of about 1,000, commonly about 5,000 to about 25,000. Similar alpha-beta olefinically unsaturated vinyl monomer containing polymers are disclosed in U.S. Pat. Nos. 3,528,844; 3,542,586; 3,542,587; 3,577,265; 3,586,527; 3,586,528; 3,586,530; 3,641,210; and 3,642,939. All of these vinyl monomer containing polymers may be prepared by conventional free radical initiated copolymerization using two or more, preferably three or more, vinyl monomers at least one of which has a free or pendant functional group within its molecular structure, e.g., hydroxyethyl methacrylate. This functionality allows the polymer intermediate to then be reacted with various other monomers such as glycidyl methacrylate to provide the desired alpha-beta olefinic unsaturation.

A second type of alpha-beta olefinically unsaturated organic resin disclosed by U.S. Pat. No. 3,437,514 is a polyester having a molecular weight greater than 1,000 and preferably between about 2,000 and about 20,000. The preferred polyester is a copolymerization product of a polyhydric alcohol, and an acyclic, alpha-beta dicarboxylic acid, and a cyclic aliphatic dicarboxylic acid. U.S. Pat. No. 3,577,262 also discloses such an alpha-beta olefinically unsaturated polyester. U.S. Pat. Nos. 3,649,337 and 3,660,371 disclose related unsaturated polyester resins formed by reacting an alpha-beta olefinically unsaturated, monocarboxy termianted, polyester with an epoxy functional, graded-rubber particle.

A third type of unsaturated organic resin useful in this invention and taught by the Burlant patent is a silicone-modified organic resin comprising a polyester having incorporated therein a cyclic or acyclic siloxane which prior to reaction of incorporation has a reactive hydroxyl or hydrocarbonoxy group bonded to at least two of its silicon atoms. Such a resin can also be prepared by reacting a siloxane with a hydroxylated vinyl resin prepared by reacting vinyl monomers, at least one of which is a hydroxylated monomer. Various modifications of resins of this type are taught in U.S. Pat. Nos. 3,437,512; 3,437,513; 3,650,811; 3,650,812; 3,650,813; 3,577,264 and 3,632,399.

A fourth alpha-beta olefinically unsaturated organic resin disclosed by Burlant and useful in this invention is a urethane-modified organic polymer formed by reacting a diisocynate monomer and an organic resin having in its molecular structure a plurality of hydrogen atoms which are labile with respect to an isocyanate group.

A final category of alpha-beta olefinically unsaturated organic resins disclosed by Burlant comprises epoxy resins having requisite amounts of unsaturation. Similar epoxy containing resins are also disclosed in Pat. Nos. 3,577,263 and 3,660,145.

Still other alpha-beta olefinically unsaturated resins are taught by several of the patents enumerated above. For example both U.S. Pat. Nos. 3,660,144 and 3,660,145 teach alpha-beta olefinically unsaturated elastomeric particles of crosslinked acrylic polymer for use in radiation curable paints and U.S. Pat. No. 3,585,065 teaches an alpha-beta olefinically unsaturated siloxane resin for use in a film-forming binder system. Of course, the subject invention is not limited to the types of unsaturated resin summarized above, but may include any alpha-beta olefinically unsaturated organic resin having the requisite unsaturation and being polymerizable upon being subjected to ionizing radiation. It should also be appreciated that the radiation polymerizable paints of this invention may also employ mixtures of the various alpha-beta olefinically unsaturated organic resins where desired for the particular application.

B. Compound Polymerizable with Alpha-Beta Olefinically Unsaturated Resin

The compound polymerizable by exposure to ionizing radiation with the alpha-beta olefinically unsaturated organic resin is included in the paint binder solution in an amount ranging between about 90 and about 10 parts, preferably between about 80 and about 20 parts. The compound is preferably a vinyl monomer as defined above or a mixture of vinyl monomers. The preferred vinyl monomers taught by the above patents are esters of C.sub.1 - C.sub.8 monohydric alcohols and acrylic or methacrylic acids, e.g., methylmethacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, octyl acrylate, 2-ethyl hexylacrylate, etc. Alcohols of higher carbon numbers, e.g., C.sub.9 - C.sub.15 as well as difunctional alcohols can also be used to prepare esters or diesters. Vinyl hydrocarbon monomers, e.g., styrene and alkylated styrenes such as vinyl toluene, alpha-methyl styrene, etc., may also be used separately or in combination with the aforementioned vinyl monomers. In combination with the acrylate monomers and/or vinyl hydrocarbon monomers, where may be used minor amounts of other vinyl monomers such as nitriles, e.g., acrylonitrile, acrylamide or n-methylol carboxylates, e.g., vinyl acetate. Such vinyl monomers are useful in combination with each of the alpha-beta olefinically unsaturated resins discussed previously and taught by the various patents.

Other vinyl containing compounds which may be employed in combination with the alpha-beta olefinically unsaturated resins are divinyl monomers, trivinyl monomers tetravinyl monomers and mixtures thereof. These di-, tri-, and tetravinyl compounds are preferably acrylates, methacrylates or vinyl hydrocarbons. The most preferred are esters of acrylic or methacrylic acids and polyhydric C.sub.2 - C.sub.8 alcohols, e.g. neopentylglycol dimethacrylate, 1,6 hexanedrol diacrylate, 1,3 butylene dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, etc.

Other vinyl containing compounds which are polymerizable with the above-discussed organic resins upon introduction of ionizing radiation, are divinyl and tetravinyl compounds such as those disclosed by U.S. Pat. Nos. 3,586,527; 3,586,528; and 3,586,530. These compounds are formed by first reacting a diepoxide or monoepoxide with acrylic acid and/or methacrylic acid and then subsequently reacting the resultant ester condensation product with a saturated acylhalide. The divinyl and tetravinyl compounds disclosed in these patents are homopolymerizable and copolymerizable with each other and with various monovinyl monomers mentioned above.

Still other compounds polymerizable with the alpha-beta olefinically unsaturated resins may be employed as the second binder component. Included in such compounds are the alpha-beta unsaturated siloxanes taught in U.S. Pat. Nos. 3,577,262 and 3,577,263 as well as the alpha-beta unsaturated diurethanes of U.S. Pat. No. 3,585,065 formed by reacting an unsaturated diisocyanate with an unsaturated polyester.

C. Mono- or Diester of Phosphoric Acid

The coating compositions of the invention include between about 0.05 and about 1.0 parts, preferably between about 0.1 and about 0.6 parts, and more preferably between about 0.2 and about 0.5 parts, per 100 parts of the total of said alpha-beta olefinically unsaturated resin and the compound polymerizable therewith of a mono- or diester of phosphoric acid bearing one or more sites of vinyl unsaturation and having the formula: ##STR4## where: R = H, Cl or CH.sub.3

A = c.sub.n H.sub.2n, 2 .ltoreq. n .ltoreq. 6

R' = h, c.sub.1 to C.sub.4 alkyl or C.sub.1 to C.sub.4 chloro- or bromoalkyl

Representative of the various species of organophosphate esters falling within the above formula are: (1) 2-methacryloyloxyethyl phosphate (R=CH.sub.3, A= --CH.sub.2 CH.sub.2 --, R' = H, m = 1); (2) di-(2-methacryloyloxyethyl) phosphate (R=CH.sub.3, A = --CH.sub.2 CH.sub.2 --, m=2); (3) 2-acryloyloxyethyl phosphate (R=H, A= --CH.sub.2 CH.sub.2, R'=H, m=1); (4) di (2-acryloyloxy-ethyl) phosphate (R=H, A= --CH.sub.2 CH.sub.2 --, m=2); (5) methyl (2-methacryloyloxethyl) phosphate (R=CH.sub.3, A= --CH.sub.2 CH.sub.2 --, R'=CH.sub.3, m=1); (6) ethyl methacryloyloxyethyl phosphate (R=CH.sub.3, A= --CH.sub.2 CH.sub.2 --, R'=CH.sub.3 CH.sub.2 --, m=1; (7) methyl acryloyloxyethyl phosphate (R=H, A= --CH.sub.2 CH.sub.2 --, R'--CH.sub.3, m=1); and (8) ethyl acryloyloxyethyl phosphate (R=H, A= CH.sub.2 CH.sub.2 --, R'= CH.sub.3 CH.sub.2 --, m=1).

The preferred organophosphate esters are 2-methacryloyloxyethyl phosphate, di(2-methacryloyloxyethyl) phosphate, 2-acryloyloxyethyl phosphate and di(2-acryloyloxyethyl) phosphate, with 2-methyacryloyloxyethyl phosphate being most preferred. Exemplary of the many other organophosphate esters which are encompassed by the above formula are those in which the R' groups of (1) through (8) are replaced by propyl, butyl and isobutyl groups or by chloro or bromo substituted ehtyl, propyl, butyl and isobutyl groups.

D. Photoinitiators

When the paint compositions of this invention are polymerized by exposure to ultraviolet radiation it may be desirable to include a photoinitiator or photosensitizer in the paint. The use of such photoinitiators and examples of various ones which may be employed will be discussed hereinafter in greater detail.

E. Inert Solvents and Other Additives

Inert solvents, i.e., solvents that do not enter into the polymerization or crosslinking reactions of the paint binder polyer/monomer system under normal exposure to radiation, can be added to the coating formulation to reduce viscosity and aid in control of application properties. Such solvents are normally selected to be substantially more volatile than the monomeric constituents of the paint formulation, thus allowing them to evaporate prior to irradiation of the coatings. Suitable solvents include, by way of example and not by way of limitation: toluene: butyl acetate; methylethyl ketone; isopropanol; benzene; tetrahydrofuran; dioxane, methylisobutyl ketone; methylene chloride; chloroform; ethylene chloride; trichloroethylene; trichloroethane; and mixtures thereof. Additional materials such as catalysts, pigments, plasticizers, etc., all of which are well known in the formulation of coating compositions and, in particular in the art of radiation polymerizable coating compositions, may be included in the coating compositions of the invention.

II. Coated Articles and Processes for Making Same

The radiation polymerizable paints discussed above diplay unusually good adhesion to a variety of substrates including wood, paper, glass, shaped polymeric surfaces and metal, particularly vapor deposited metal surfaces. In addition to these outstanding adhesion properties, the coatings of the invention also exhibit excellent water resistance and intercoat adhesion. The novel paint compositions of the invention, like prior art radiation polymerizable paints discussed above, may be applied to a variety of substrates by conventional means, e.g., brushing, spraying, roller coating, flow coating, etc., to an average thickness which is preferably in the range of from about 0.1 to about 4.0 mils depending on the substrate and the intended end use of the coated product.

The novel paint compositions of the invention may be cured or polymerized by exposure to radiation, preferably ionizing radiation or ultraviolet light. In either case, the paint compositions may be cured at relatively low temperatures, e.g., between room temperature (20.degree. to 25.degree. C) and the temperature at which significant vaporization of its most volatile component is initiated, (ordinarily between about 20.degree. C and about 70.degree. C).

The term "ionizing radiation" as employed herein means radiation having sufficient energy to remove an electron from a gas atom, forming an ion pair, and hence radiation with energy of, or equivalent to, about 5,000 electron volts. The preferred method of curing paint films of this invention by exposure to ionizing radiation is by subjecting such films to a beam of polymerization-effecting electrons which is at its source of emission within the range of, or equivalent to, 150,000 to 450,000 electron volts. In this method of curing, it is preferred to employ a minimum of 25,000 electron volts per inch of distance between the radiation emitter and the workpiece where the intervening space is occupied by air. Adjustment is made for the resistance of the intervening gas which is preferably an oxygen-free inert gas such as nitrogen, helium, or combustion products of natural gas. It is, however, within the scope of the use of ionizing radiation to effect polymerization using either that which is conventionally termed "high energy particle radiation"or "ionizing electromagnetic radiation".

When such ionizing radiation is employed to cure the paint compositions of this invention, the radiation energy is applied at dose rates of from about 0.1 to about 100 Mrads per second upon a preferably moving workpiece with the coating receiving a total dose in the range of from about 0.1 to about 100, preferably from about 1 to about 25 Mrads. The abbreviation "Mrads" as employed herein means 1 million Rads. The term "Rads" means that dose of radiation which results in the absorption of 100 ergs of energy per gram of absorber, e.g., coating film. The electron emitting means may be a linear electron accelerator capable of producing a direct current potentially in the range hereinbefore set forth. In such a device, electrons are ordinarily emitted from a hot filament and accelerated through a uniform voltage gradient. The electron beam, which may be about 1/8 inch in diameter at this point is scanned in one direction to make a fan-shaped beam and then passed through a metal window, e.g., a magnesium-thorium alloy of about 0.003 inch thickness.

As mentioned above, the radiation polymerizable coating compositions of this invention may also be cured by exposure to ultraviolet light. Preferably, paint conpositions according to this invention which are cured by exposure to ultraviolet light contain little or no pigment. Upon exposure to light of wave lengths less than about 390 m.mu., most of the vinyl monomers employed in the paint compositions of this invention will fragment and produce radicals which can initiate polymerization. However, in order to make more efficient use of the output of high intensity UV sources and thereby attain a commercially feasible rate of cure, it is preferred to include a photoinitiator or photosensitizer in compositions to be cured by ultraviolet radiation.

Photoinitiators (or sensitizers) are substances, generally organic compounds which, upon exposure to light of appropriate wave length, give rise to or promote the production of polymerization initiating species. It is preferred to employ a photoinitiator which decomposes to yield, or otherwise results in the production of, one or more free radical species upon exposure to light having a wavelength of less than about 380 m.mu.. In order for any photochemical reaction to occur, there must be some overlap between the wave length of light incident upon the reaction medium (the coating) and the wave length absorbed by the photoinitiating species. Thus, the selection of an appropriate photoinitiator depends not only upon its efficacy as a polymerization initiator, but also upon the light source(s) used.

Many different types of free-radical initiators and sensitizers have been studied in acrylic systems and these are will known in the art. The rate of cure of the paint compositions of this invention, is, of course, a function of the type of initiator and its concentration, the intensity of incident light of appropriate wavelength and the type and concentration of polymerization inhibitors. Also, the detailed compositions of the coating formulation can have a significant effect on the rate of cure, especially at low exposure levels. Thus, in the end analysis, the amount of ultraviolet radiation which is necessary to achieve the desired properties in the final film formed from the paint compositions of this invention will vary with the composition of the paint itself and one of ordinary skill in this art will be able to determine the optimal exposure to UV light in view of the various factors discussed above with a minimum of experimentation.

Included among the many suitable photoinitiators are: organic carbonyl compounds such as acetone, benzophenone, benzanthrone, benzoin, benzoin methyl ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, benzoin n-butyl ether and benzoin iso-butyl ether; peroxides such as hydrogen peroxide, di-t-butyl peroxide, ergosterol peroxide and benzoyl peroxide organic sulphur compounds such as diphenyl disulfides, dibenzoyl disulfides and dibenzethiazol disulfides; and azo compounds such as 2.2' azobis-(2-methylpropionitrile). .alpha.,.alpha.'-azobisisobutylronitrile, azomethane, azothane, .alpha.-azobis-1-cyclohexane carbonitrile; and other well known initiators such as 2-ethylhexyl-2-cyano-3, 3-diphenylacrylate. Based on availability, solubility in the coating compositions of this invention, freedom from color and efficiency of curing an minimal UV exposure levels, the preferred photoinitiators are 2,2-diethoxyacetophenone, benzophenone and 2-ethylhexyl- 2-cyano -3,3-diphenylacrylate. The amount of each photoinitiator necessary to suitably initiate polymerization in the paint compositions of this invention when curing by exposure to UV light will be apparent to those skilled in the art. It has been found, however, that generally the presence of a photoinitiator in the amount of from about 0.5 to about 5.0 parts per 100 parts of the total reactive vehicle solids in the paint composition will produce adequate curing upon exposure to a low pressure ultraviolet lamp.

A. Coated Articles Including Vapor Deposited Metals

As discussed above, the coating compositions of this invention are particularly suited as abrasion and corrosion resistant protective coatings for surfaces bearing vapor deposited metals. Such coated articles bearing vapor deposited metals are a particularly preferred embodiment of this invention since they are suitable for use as a substitute for plated metal surfaces used for trim or brightwork on the exterior of automobiles.

Vapor deposition of metals, and in particular vacuum metallizing, is a simple and relatively low cost process by which thin layers of metals are deposited on prepared surfaces of substrates such as metal, plastic, glass, paper and other materials. Surfaces bearing vapor deposited metals, and in particular plastic substrates bearing thin deposits of aluminum, have been considered as a substitute for plated metal surfaces used for trim or brightwork on the exterior of automobiles. Since vapor deposition of metals produces very attractive surfaces and is substantially less expensive than processes for metal plating, such as chrome plating, it would appear to be ideally suited for producing such trim or brightwork. However, due to severe abrasion and corrosion problems, articles produced by vapor depositing metals have not been deemed suitable for exterior automotive use. The coating compositions of this invention, when applied over the surface of such vapor deposited metals afford the protection necessary to overcome this problem.

Vapor deposition of metals is well known and the detailed procedures will be apparent to those skilled in the art. Physical vapor deposition, the process most commonly used for decoration of plastics, involves formation of the coating by physical means alone. Two of the most commonly used techniques, i.e., resistive heating and electron beam heating, involve stepwise heating in vacuum, first melting and then vaporizing the material to be deposited. Other well known techniques such as sputtering may also be employed. The choice of methods depends to some extent on the material to be deposited. A review of physical vapor deposition techniques may be found in Vapor Deposition, C. F. Powell, J. H. Oxley and J. M. Blocker, Jr., eds., John Wiley & Sons, Inc. New York (1966), p. 221 ff. Resistive heating of a tungsten filament or basket or of a refractory crucible is commonly used for vapor deposition of aluminum, the most common evaporant for deposition on plastic parts. Electron beam heating of an evaporant contained in a suitable crucible or hearth is recommended for deposition of alloys and metals which have low vapor pressures or which form alloys with conventional filaments or crucibles at normal evaporating tempertures. Iron-chrome alloys can be deposited best using electron-beam heating techniques or sputtering.

Chemical vapor deposition techniques, also discussed in Powell et al, can in principle also be used in the formation of the composite coated articles of this invention. Such techniques involve the transfer of material across temperature or concentration gradients between the substrate and the surrounding atmosphere and formation of coatings by chemical reactions at the surface of the substrate. Chemical vapor deposition techniques often involve heating of the substrate to moderately high temperatures to form the final metallic coating. Application of these techniques is thus restricted to those substrates capable of withstanding the required process conditions.

B. Preferred Plural Coated Embodiment

The preferred coated article of this invention is prepared by: applying a base coat to a substrate and curing the coating; vapor depositing a metal layer on the base coat; applying the coating composition of this invention over the metallized surface; and curing the coating with radiation.

C. Base Coat Compositions

The base coat fills minor surface inperfections of the substrate, provides a high-gloss surface to receive the metal deposit, improves adhesion of the deposit, and reduces the quantity of gas liberated from the substrate at reduced pressures. In selecting a base coat it is thus important that the composition display good intercoat adhesion, i.e., adhere well to both the substrate and the metal layer.

The lacquers and the radiation polymerizable compositions useful as base coats in the process of this invention may be applied by conventional means, e.g., spray coating, dip coating, flow coating, etc., to an average thickness which is preferably in the range of from about 0.1 to about 4.0 mils. The lacquers useful as base coats are well-known in the prior art and may be air dried or heat cured. Most bake-curing lacquers cure in 1-3 hours at temperatures ranging from 140.degree. to 180.degree. F. The radiation polymerizable base coats may be cured at relatively low temperatures, e.g., between room temperature (20.degree. to 25.degree. C) and the temperature at which significant vaporization of its most volatile reactive component is intiated, (ordinarily between about 20.degree. C and about 70.degree. C). The radiation energy is applied at dose rates of from about 0.1 to about 100 Mrads per second upon a preferably moving workpiece with the coating receiving a total dose in the range of from about 0.1 to about 100, preferably from about one to about 25 Mrads. It will be appreciated that the use of radiation polymerizable base coats will substantially lessen the processing time necessary for producing the plural coated articles of the invention.

The lacquer base coats which may be employed are well-known in the art of vapor deposition, and in particular vacuum metallizing, and consist essentially of a cross-linkable or curable resin in a volatile solvent. Representative of the organic resins which may be employed individually or in combination to formulate such a lacquer are: acrylic resins, alkyd resins (pure and modified), polyesters, conventional varnishes, urea-formaldehyde resins, vinyl polymers, acrylonitrile polymers, phenolic resins, cellulosic resins, polyurethanes, butyl rubber and chlorinated butyl rubber, silicone resins, melamine-formaldehyde resins, polyestyrenes, natural rubber, and modified phenolic resins. Numerous base coats employing such organic resins are commercially available.

Radiation polymerizable base coat compositions which may be employed in the process and articles of this invention include the coating formulation including an alpha-beta orefinically unsaturated urethane modified organic resin discussed above and disclosed in U.S. Pat. No. 3,437,514. That composition, exclusive of non-polymerizable solvents, pigments and other non-reactive components consists essentially of: (1)