Process for the preparation of an aqueous copolymer dispersion

A process for the preparation of an aqueous dispersion of a copolymer which can be crosslinked with an aminoplast resin by the action of heat and which is prepared by copolymerization of monomers from the group comprising styrene, esters of acrylic acid, esters of methacrylic acid, vinyl esters, monoolefinic unsaturated monomers having hydroxyl groups, acrylic acid, methacrylic acid, and unsaturated amides, in an aqueous phase in the presence of a radical-forming initiator and an emulsifier, which comprises copolymerizing a mixture of

• 30 to 60 parts by weight of styrene,
• 20 to 50 parts by weight of an ester of acrylic acid or of methacrylic acid, the homopolymer of which has a glass temperature T.sub.G below +50.degree. C., or a mixture of these esters,
• 5 to 30 parts by weight of a vinyl ester of a branched saturated monocarboxylic acid, which has side chains having 8 to 12 carbon atoms and in which the carboxyl group is on a tertiary carbon atom,
• 5 to 15 parts by weight of a hydroxyalkyl ester of a monoolefinic unsaturated monocarboxylic acid,
• 0.5 to 15 parts by weight of an .alpha.,.beta.-unsaturated monocarboxylic acid and/or unsaturated dicarboxylic acid, and
• 0.1 to 8 parts by weight of an addition product of a glycidyl ester of a branched monocarboxylic acid with an unsaturated monocarboxylic or dicarboxylic acid.