Patent ID: 7632902

Claim:
A process for preparing an aqueous polymer dispersion by free-radically initiated aqueous emulsion polymerization of a combination of ethylenically unsaturated compounds (monomers), wherein all amounts in parts by weight are based on 100 parts by weight of the monomers, which comprises: a) charging a mixture (i) comprising: an amount of deionized water (portion 1), from 0.001 to 0.5 part by weight of polymer seed having a weight-average particle diameter ≦100 nm, from 0.0001 to 0.1 part by weight of dispersant, and from 0.5 to 10 parts by weight of monomers to a polymerization vessel and polymerizing the monomers to a conversion >80 % [stage A] and b) subsequently supplying to the resultant reaction mixture under polymerization conditions an emulsion (ii) comprising: an amount of deionized water (portion 2), from 0.1 to 5 parts by weight of dispersant, and from 90 to 99.5 parts by weight of monomers, and polymerizing the monomers [stage B], where c) the total amount of monomers is 100 parts by weight, the total amount of deionized water (portion 1+portion 2) is less than 100 parts by weight, and the aqueous polymer dispersion has a polymer solids content of at least 60% by weight.