GB991802A - Coating compositions - Google Patents

Abstract

Coating compositions comprise as predominant resinous component an interpolymer of 50 to 90% by weight of methyl methacrylate and 10 to 50% by weight of an alkyl ester of methacrylic acid wherein the alkyl group contains at least 8 carbon atoms, said interpolymer having a molecular weight above 87,000 and less than 110,000. Specified alkyl methacrylates are n-octyl, 2-ethylhexyl, lauryl, nonyl and decyl methacrylates and mixtures, e.g. of decyl and octyl methacrylates. The compositions may also comprise plasticizers, e.g. tricresyl phosphate, dioctyl phthalate, dicyclohexyl phthalate, di - 3,5,5 - trimethylhexyl phthalate, butyl cyclohexyl phthalate, epoxidized oils and castor oil acetoacetate; pigments, e.g. carbon black, titanium dioxide, metal oxides, metal sulphides, metal flake pigments and phthalocyanines; fillers, e.g. talc, kieselguhr, clays, silicates and diatomaceous earth; silicones, nitrocellulose, polyethylene and polyvinyl acetal resins; and solvents, e.g. toluene, xylene, acetone, methyl ethyl ketone, methyl amyl ketone, glycol ethyl ether acetate, ethyl acetate, amyl acetate, isopropyl acetate, heptane, octane, methanol, isopropanol, amyl alcohol and diacetone alcohol. The interpolymers may be prepared by emulsion, suspension or solution polymerization, in the presence of catalysts and chain transfer agents, many suitable suspending agents, catalysts and chain transfer agents being listed. A small proportion of unsaturated acid, e.g. acrylic or methacrylic acid, may be copolynerized with the alkyl methacrylates. Examples describe (A) the suspension copolymerization of methyl methacrylate and lauryl methacrylate in the presence of benzoyl peroxide, tertiary dodecyl mercaptan, acetylated starch and sodium phosphate buffer; and (B) the solution copolymerization of methyl methacrylate, lauryl methacrylate and methacrylic acid in toluene in in the presence of benzoyl peroxide; and (I) coating compositions comprising copolymer (A), dicyclohexyl phthalate, titanium dioxide, toluene and isopropanol. Specification 901,934 also is referred to.ALSO:Metal substrates, e.g. panels or automobile bodies, which may be primed and/or sealed, are coated, e.g. by spraying with one or more coats of coating compositions comprising as predominant resinous component an interpolymer of 50-90 weight per cent of methyl methacrylate and 10-50 weight per cent of an alkyl ester of methacrylic acid wherein the alkyl group contains at least 8 carbon atoms, said interpolymer having a molecular weight above 87,000 and less than 110,000. Specified alkyl methacrylates are n-octyl, 2-ethylhexyl, lauryl, nonyl and decyl methacrylates. The compositions may also comprise plasticizers, e.g. tricresyl phosphate, dioctyl phthalate, dicyclohexyl phthalate, di-3,5,5-trimethylhexyl phthalate, butyl cyclohexyl phthalate, epoxidized oils and castor oil acetoacetate; pigments, e.g. carbon black, titanium dioxide, metal oxides and sulphides, metal flake pigments and phthalocyanines; fillers, e.g. talc, kieselguhr, clays, silicates and diatomaceous earth; solvents, e.g. toluene, xylene, acetone, methyl ethyl ketone, methyl amyl ketone, glycol ethyl ether acetate, ethyl acetate, amyl acetate, isopropyl acetate, heptane, octane, methanol, isopropanol, amyl alcohol and diacetone alcohol; and resins, e.g. silicones, nitrocellulose, polyethylene and polyacetal resins. The seal coat may comprise a low viscosity nitrocellulose, nitrocelluolse-alkyd or low viscosity polymethyl methacrylate resin. In examples, alkyd resin primed metal surfaces are coated with lacquer comprising methyl methacrylate-lauryl methacrylate copolymers, titanium dioxide, dicyclohexyl phthalate, toluene, xylene, acetone, isopropanol and glycol ethyl ether acetate. Specification 901,934 also is referred to.