Patent ID: 8722796

Claim:
A process for preparing an aqueous dispersion of polymer particles having a number-average particle diameter from 5 to 90 nm by free-radically initiated polymerization of at least one ethylenically unsaturated monomer M in the presence of at least one free-radical initiator and at least one highly branched polymer in an aqueous polymerization medium, the polymerization being carried out using ≦1% by weight, including 0%, of at least one dispersing assistant and ≧5% and ≦60% by weight of the at least one highly branched polymer, based on the total amount of the at least one ethylenically unsaturated monomer M (total monomer amount), and the at least one highly branched polymer containing ≧0.3 mmol of acid groups per gram of highly branched polymer, which process comprises introducing in the aqueous polymerization medium initially only ≧10% by weight of the total amount of the at least one highly branched polymer and optionally ≦50% by weight of the total amount of the at least one ethylenically unsaturated monomer M and subsequently, under polymerization conditions, adding any remainder of the at least one highly branched polymer, and adding the total amount or any remainder of the at least one ethylenically unsaturated monomer M, and carrying out polymerization to a monomer conversion ≧80% by weight.