Prodn. of aq. self-crosslinking copolymer dispersions for paint binders - by two-stage emulsion polymerisation of acrylic monomer mixt. contg. acetoacetyl and carboxyl gps., followed by neutralisation with poly:amine

A process is claimed for the prodn. of aq., self-crosslinking copolymer dispersions (I) with the following monomer compsn., neutralised with polyamine crosslinkers: (Aa) 3-35 (pref. 8-15) wt.% (meth)acrylate monomers with acetoacetyl gps., (Ab) 1-20 (pref. 3-16) wt.% alpha ,beta -unsatd. carboxylic acid, pref. (meth)acrylic acid, (Ac) 11-96 (pref. 30-70) wt.% alkyl (meth)acrylate and opt. maleate or fumarate diester, and (Ad) 0-40 (pref. 0-25) wt.% other comonomers such as vinylaromatics, vinyl ester, hydroxyalkyl (meth)acrylate or (meth)acrylamide. The process comprises: (A) two-stage radical emulsion polymerisation, comprising (i) copolymerisation of 60-90 wt.% of a mixt. of monomers (Aa)- (Ad) followed by (ii) copolymerisation of 10-40 wt.% of a mixt. of (Ac) and (Ad), to give an acrylate copolymer with an acetoacetyl gp. content of 0.2-1.7 (pref. 0.4-0.8) mole/kg and a COOH gp. content of 0.15-1.6 (pref. 0.4-0.75) mole/kg, the COOH gp. content amounting to 50-95 (pref. 80-90) mole% w.r.t. acetoacetyl gps., and (B) neutralisation of COOH gps. by reaction with 50-100 (pref. 90-100) mole% (w.r.t. total prim. amine gps.) of polyamine contg. at least 2 prim. amino gps.. Also claimed are aq., self-crosslinking copolymer dispersions (I) obtd. by this process. The invention relates to the use of the aqueous, self- crosslinking copolymer dispersions which are prepared in accordance with a two-stage process, are based on acetoacetyl- and carboxyl-containing acrylate polymers and are neutralized with polyamines which act as a crosslinking component as binders, in combination with polyisocyanates of low molecular mass, for two-component coating materials which exhibit a sufficiently long pot life and a markedly reduced tendency toward the yellowing of light-coloured woods.