GB839480A - Relating to coating compositions - Google Patents

Abstract

Coating compositions (see Group IV (a)) comprising a liquid carrier and as the predominant resinous component an interpolymer of 50 to 90% by weight of methyl methacrylate and 10 to 50% by weight of another alkyl ester of an ethylenically unsaturated carboxylic acid, said interpolymer having a viscosity of 25 to 320 centistokes when measured at 25 DEG C. as a solution of 25% solids in toluene, may be coated on wood, plastic and metal, e.g. car body panels. The metal may be unprimed, primed and coated with highly pigmented surfacers and undercoats, or with a single primer-surfacer composition comprising nitrocellulose, polyvinyl acetal, alkyd resins or shellac, the base coats being baked before applying top coats according to the invention. Examples describe the application by spraying of (vii) a composition comprising a methyl methacrylate-ethyl acetate copolymer, butyl benzyl phthalate, titanium dioxide, toluene and monoethyl ether of ethylene glycol acetate to primed steel panels; (viii) compositions comprising a methyl methacrylate-ethyl acrylate copolymer, titanium dioxide, polyethylene, butyl benzyl phthalate, toluene and monoethyl ether of ethylene glycol acetate to metal panels which had been "Bonderised" (Registered Trade Mark), primed, coated with a highly pigmented surfacer and a filler prepared from nitrocellulose, a soya oil modified alkyd resin and chlorinated biphenyl; and (ix) compositions comprising a methyl methacrylate-n-butyl methacrylate copolymer, titanium dioxide, phthalocyanine blue, carbon black, butyl benzyl phthalate, toluene and the monoethyl ether of ethylene glycol acetate to primed steel panels.ALSO:Coating compositions comprise a liquid carrier and as the predominant resinous component an interpolymer of 50 to 90% by weight of methyl methacrylate and 10 to 50% by weight of another alkyl ester of an ethylenically unsaturated carboxylic acid, said interpolymer having a viscosity of 25 to 320 centistokes when measured at 25 DEG C. as a solution of 25% solids in toluene. Specified alkyl esters are ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, ethyl methacrylate, n-butyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, mixed octyl and decyl methacrylates, dimethyl itaconate, diethyl itaconate and dibutyl itaconate. Minor amounts of additional comonomers, e.g. N-t.-butyl acrylamide and methacrylic acid (Example VI), may also be used. The interpolymers may be prepared by polymerization in solution, emulsion or suspension, e.g. in the presence of protective colloids such as polyvinyl alcohol, sodium polyacrylate, polyacrylamide, bentonite, starch or magnesium silicate, in the presence of catalysts, e.g. acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetyl benzoyl peroxide, hydroxyheptyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, p-chlorobenzoyl peroxide, cyclohexyl hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, methyl cyclohexyl hydroperoxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl amyl ketone peroxide, peracetic acid, t-butyl peracetate, t-butyl permaleic acid, di-t-butyl perphthalate, t-perphthalic acid, potassium persulphate, ammonium persulphate, a ,a -azo-diisobutyronitrile and p-methoxy phenyl diazo-thio-(2-naphthyl) ether, buffers, e.g. mono- and disodium phospahtes, and chain transfer agents, e.g. dodecyl mercaptan, tertiary dodecyl mercaptan, octyl mercaptan, hexyl mercaptan, carbon tetrachloride, allyl acetate, allyl carbamate, isopropyl benzene, butyl chloride, acetic acid and dioxane. The polymers may be dissolved in solvents, e.g. toluene, xylene, acetone, methyl ethyl ketone, methyl amyl ketone, monoethyl ether of glycol acetate, ethyl acetate, isopropyl acetate, amyl acetate, heptane, octane, methyl alcohol, isopropyl alcohol, amyl alcohol and diacetone alcohol, together with plasticizers, e.g. butyl benzyl phthalate, tricresyl phosphate, dioctyl phthalate, dicyclohexyl phthalate, di-3,5,5-trimethyl hexyl phthalate, butyl cyclohexyl phthalate, epoxidized oils and castor oil acetoacetate, pigments, e.g. carbon black, titanium dioxide, phthalocyanine greens and blues, metal oxides and sulphides and metal, e.g. aluminium, flake pigments, fillers and extenders, e.g. talc, kieselguhr, clays, silicates and diatomaceous earth, silicones, nitrocellulose, polyvinyl acetal resins and polyethylene. The composition may be coated on bare or primed metal, e.g. car bodies, wood and plastics.