Copolymer solution consisting of acrylic resin, process for its manufacture and the use thereof in reactive lacquers

Process for the manufacture, in organic solvents, of copolymers which are soluble in organic solvents, by copolymerisation of alkyl acrylates, hydroxyalkyl acrylates, styrene and an .alpha.,.beta.-unsaturated carboxylic acid with simultaneous esterification by glycidyl esters of .alpha.-alkylalkanemonocarboxylic acids and/or .alpha.,.alpha.-dialkylalkanemonocarboxylic acids, by heating in the presence of polymerisation initiators, characterised in that a mixture consisting of (A) 10 to 30% by weight of inert organic solvents which are customary in the lacquer industry and (B) 90 to 70% by weight of a reaction mixture consisting of the components a, b, c, d.sub.1 and d.sub.2 is reacted, the inert organic solvent and the components to be esterified, that is to say (a) 5-24% by weight of glycidyl esters of .alpha.-alkylalkanemonocarboxylic acids and/or .alpha.,.alpha.-dialkylalkanemonocarboxylic acids of the following empirical formula C.sub.12-14 H.sub.20-26 O.sub.3 +), being heated to 165.degree. to 180.degree. C. and a mixture consisting of (b) 12-30% by weight of hydroxyethyl acrylate and/or hydroxyethyl methacrylate, (c) 1-10% by weight of acrylic acid, (d.sub.1) 20-50% by weight of styrene and (d.sub.2) 5-35% by weight of methyl methacrylate, the components a, b, c, d.sub.1 and d.sub.2 being employed in such quantities that their sum adds up to 100% by weight, being added slowly and uniformly, in the presence of mixtures of diacyl peroxides or peresters and alkyl hydroperoxides or dialkyl peroxides as the polymerisation initiators, and, in the course thereof, the temperature being kept between 165.degree. C. at the start and 180.degree. C. at the end, until the solids content of the solution has reached the theoretical value of between 70 and 80% by weight, the polymerisation and condensation reactions proceeding simultaneously and jointly and the additional condition applying that the components a, b and c are employed in such quantities that the copolymers have a hydroxyl group content of 3.5 to 6.5% by weight. .sup.(+) Preferably a mixture of glycidyl esters of .alpha.,.alpha.-dialkylalkanemonocarboxylic acids having a minor content (up to about 10% by weight of the mixture) of glycidyl esters of .alpha.-alkylalkanemonocarboxylic acids of the said empirical formula, the mixture having an epoxide equivalent of 240 to 250.