Batchwise preparation of crosslinked, finely divided polymers

A process for the batchwise preparation of a crosslinked, finely divided, Water-absorbing polymer, which comprises multistage copolymerization in a batchwise mixing apparatus, with constant thorough mixing in all stages, of 100 parts by weight of a monomer from group (a) or of a monomer mixture from groups

• (a) 50-100 parts by weight of acrylic acid or methacrylic acid, each of which has been neutralized with from 0 to 100 mol % of an alkali metal or ammonium base, acrylamide, methacrylamide and N-vinylpyrrolidone,
• (b) 0-30 parts by weight of other water-soluble monoethylenically unsaturated monomers and
• (c) 0-20 parts by weight of water-insoluble monoethylenically unsaturated monomers
• with from 0.01 to 5 parts by weight of, as a crosslinking agent, a monomer containing two or more ethylenically unsaturated double bonds, in 20-80% by weight aqueous solution in the presence of an initiator at above 45.degree. C., in the first stage the aqueous monomer solution being copolymerized at from 45.degree. to 95.degree. C. under from 0.1 to 0.8 bar with removal of some of the water by distillation, in the second stage the copolymerization being completed at from 100.degree. to 170.degree. C. under a pressure up to 8 bar and, in the third stage, after the pressure has been let down, the water content of the resulting finely divided copolymer being reduced to 0.5-10% by weight under reduced pressure at from 70.degree. to 180.degree. C. or under atmospheric pressure at from 120.degree. to 180.degree. C.