GB1105561A - Acrylic/hexamethylol melamine hexamethyl ether coating compositions - Google Patents

Abstract

Coating compositions comprise a solution in an organic solvent of (1) an interpolymer of (a) 0-89% by weight of a monovinyl substituted or unsubstituted aromatic hydrocarbon having 8-12 carbon atoms, (b) 10-90% of a compound selected from alkyl acrylates of 4-15 carbon atoms, alkyl methacrylates of 5-16 carbon atoms, cyanoethyl, cyanopropyl or cyanobutyl acrylate, acrylamide and its N,N-dialkyl derivatives wherein the alkyl groups each contain 1-6 carbon atoms, and hydroxyalkyl acrylates or methacrylates wherein the alkyl group has 1-4 carbon atoms, (c) 0-50% of a compound selected from a ,b -olefinically unsaturated nitriles of 3-9 carbon atoms, vinyl acetate, and vinyl or vinylidene chloride or fluoride, and (d) 1-20% of an a ,b -olefinically unsaturated carboxylic acid having 3-10 carbon atoms; said interpolymer having a reduced viscosity of 0.1 to 0.8 (at 25 DEG C. in tetrahydrofuran) and a Tg of at least 25 DEG C.; and (2) 10-40%, based on the weight of the interpolymer, of hexamethylol melamine hexamethyl ether. In a modification, component (d) of the polymer (1) is replaced by hydroxyethyl or hydroxypropyl acrylate or methacrylate, the monoallyl ether of trimethylol propane, acrylamide or methacrylamide. Component (a) of the polymer may be styrene or a substituted derivative thereof or vinyl naphthalene. Suitable nitriles as component (c) include acrylonitrile, a -chloroacrylonitrile and a -trifluoromethyl acrylonitrile. The acid component (d) may be, for example, acrylic, methacrylic, crotonic, cinnamic, atropic, a -chloroacrylic, a -fluoroacrylic, maleic, fumaric or itaconic acid, or monoisopropyl maleate or mono-n-butyl fumarate. Suitable solvents include benzene, xylene, toluene, dioxane, and ethylene glycol monomethyl or monoethyl ether. Additives such as colorants, pigments and fillers may be included in the compositions. Coatings prepared from the compositions are easily cured by baking at 250-350 DEG C. Preparations are illustrated of the polymer component (1) wherein (i) ethyl acrylate, styrene and acrylic acid are copolymerized in 1,4-dioxane in the presence of t.-dodecyl mercaptan using benzoyl peroxide catalyst and (ii) ethyl acrylate and acrylic acid are copolymerized in 1,4-dioxane in the presence of t.-dodecyl mercaptan using di-t.-butyl peroxide catalyst.ALSO:Coatings which can be easily cured by baking at 250-350 DEG C in 10-30 minutes are obtained from compositions comprising a solution in an organic solvent of (1) an interpolymer of (a) 0-89% by weight of a monovinyl aromatic compound (b) 10-90% of a compound selected from alkyl acrylates of 4-15 carbon atoms, alkyl methacrylates of 5-16 carbon atoms, cyano-ethyl, -propyl or -butyl acrylate, acrylamide and its N,N-di-(C1-C6 alkyl) derivatives, and C1-C4-hydroxy alkyl esters of acrylic or methacrylic acid (c) 0-50% of a compound selected from C3-C9 a ,b -olefinically unsaturated nitriles, vinyl acetate, and vinyl or vinylidene chloride or fluoride and (d) 1-20% of an a ,b -olefinically unsaturated carboxylic acid of 3-10 carbon atoms; and (2) 10-40%, based on the weight of the interpolymer, of hexamethylol melamine hexamethyl ether. In a modification, component (d) of the polymer (1) is replaced by hydroxy ethyl or hydroxypropyl acrylate or methacrylate, the monoallyl ether of trimethylol propane, acrylamide or methacrylamide. Suitable solvents include benzene, xylene, toluene, dioxane and ethylene glycol monoethyl or monomethyl ether. Additives such as colourants, pigments and fillers may be included in the compositions. In Examples, coatings are drawn and cured on phosphatised steel; the polymer component being an ethyl acrylate/styrene/acrylic acid or ethyl acrylate/acrylic acid copolymer.