Aqueous self-curing copolymer dispersions, process for their preparation and their use as binder for paints

Aqueous, self-crosslinking copolymer dispersions are made by (1) copolymerization of unsaturated monomers with carbonyl group(s) (A1), monomers with carboxylic acid groups (A2) and other monomers, (2) addition and polymerization of monomers other than (A1) and (A2), (3) neutralization and (4) addition of a polyfunctional hydrazine or hydrazide. Aqueous, self-crosslinking copolymer dispersions (ABC) obtained by (1) radical-initiated copolymerization of a monomer mixture (A) comprising (A1) 2-55 (preferably 4-50, most preferably 6-45) wt% olefinically unsaturated monomers with at least one carbonyl group, (A2) 0.5-20 (preferably 1-15, most preferably 3-12) wt% alpha , beta -unsaturated carboxylic acids or half-esters thereof with 1-15C linear, branched or cyclic alcohols, (A3) 20-70 (preferably 22-60, most preferably 24-50) wt% monomers selected from vinyl-aromatics, n-butyl methacrylate and (di)alkyl esters of alpha , beta -unsaturated mono- or di-carboxylic acids with 1-3C linear or branched alkanols or 5-15C (poly)cyclic alkanols, (A4) 10-60 (preferably 15-50, most preferably 20-45) wt% (di)alkyl esters as in (A3) with more than 3 carbon atoms in the alkyl groups, not including n-butyl methacrylate and (A5) 0-25 (preferably 2-20, most preferably 5-15) wt% other unsaturated comonomers selected from vinyl esters of 2-18C saturated aliphatic acids and hydroxyalkyl esters, nitriles and amides of alpha , beta -unsaturated acids, followed by (2) the addition and further polymerisation of a mixture (B) containing (B1) 30-90 (preferably 40-80, most preferably 50-75) wt% monomers as defined for (A3), (B2) 10-60 (preferably 20-50, most preferably 25-40) wt% esters as defined for (A4) and (B3) 0-40 (preferably 5-30, most preferably 10-25) wt% other comonomers as for (A5), (3) optional neutralization with ammonia, amines or aqueous alkali and (4) addition of compounds (C) with at least two hydrazine or hydrazide groups per molecule. In this process, the sum of the amounts of (B1)-(B3) must be 100 wt%, the wt. ratio (A):(B) = (50:50)-(95:5) and the amount of compound (C) added is such that the ratio (r) of the total amount of hydrazine groups (n(-NHNH2)) and hydrazide groups (n-(-CONHNH2)) to the amount of carbonyl groups (n-(-CO-)) is 0.5-1.1 mol/mol. Independent claims are also included for (a) the process as described above; (b) binders for 1-component varnish, containing copolymer dispersions as described.