A process of free-radical copolymerization of a monomer composition comprising: a) 70 to 100% by weight of acrylic acid, b) 0 to 30% by weight of at least one hydrophilic nonionic compound, different from a), having a free-radically polymerizable, α,β-ethylenically unsaturated double bond, c) 0 to 1% by weight of at least one free-radically polymerizable crosslinking compound which comprises at least two α,β-ethylenically unsaturated double bonds per molecule, by the method of precipitation polymerization in the presence of an auxiliary composition H) comprising H1) at least one compound with a block structure which comprises at least one hydrophobic group and at least one hydrophilic group, and H2) at least one basic compound different from H1).
