Patent ID: 6552142
Filing Date: 2003-04-22
Classification: C08F

Abstract:
A process for preparing an aqueous copolymer dispersion by free-radical polymerization of ethylenically unsaturated monomers in an aqueous medium comprising(a) from 10 to 90% by weight of at least one hydrophilic monomer A which has and N-vinyl group and whose polymerization rate possesses a maximum at pH level above 7; (b) from 10 to 90% y weight of at least one monoethylenically unsaturated hydrophobic monomer B whose polymerization rate possesses a maximum at pH level below 7; (c) from 0.01 to 20% by weight, based on the total monomers present in the solution, of at least one water-soluble or water-insoluble free-radical initiator or of a mixture of water-soluble with water-insoluble free-radical initiators. wherein the pH is controlled in the course of the polymerization reaction in such a way that in the course of the polymerization it decreases by from 2 to 5 units between start and finish of the reaction.