Patent ID: 7358297

Claim:
A process for preparing aqueous polymer dispersions having an at least bimodal particle size distribution by emulsion-polymerizing at least two ethylenically unsaturated monomers in the presence of polyvinyl alcohol, comprising a) initially introducing from 0.1 to 12% by weight, based on the total weight of all the monomers used to prepare the polymer dispersion, of a molecularly or dispersely water-soluble polymer, whose molecular weight is at least 1.5 times the molecular weight of the polymer of component b), b) initially introducing from 0.1 to 12% by weight, based on the total weight of all the monomers used to prepare the polymer dispersion, of a further molecularly or dispersely water-soluble polymer, having a molecular weight of at least 10,000 g/mol, c) initially introducing from 0.01 to 2% by weight, based on the total weight of all the monomers used to prepare the polymer dispersion, of at least one ionic comonomer, which is an α,β-monoethylenically unsaturated compound containing at least one group derived from a weak acid, and d) adding at least one ethylenically unsaturated, free-radically polymerizable monomer and an initiator of free-radical emulsion polymerization to the mixture comprising components a), b) and c); with the proviso that seed lattices are not employed in said process.