A process for the preparation of powdery, water-insoluble, cross-linked polymerized resinous particles capable of absorbing aqueous or serous liquids or water, which comprises polymerizing a composition comprising by weight
- (a) 55 to 99.9% of monomeric units of an unsaturated polymerizable monomer containing acid groups, at least 25 mol % of the acid groups being neutralized,
- (b) 0 to 40% of polymerizable unsaturated monomers other than (a),
- (c) 0.1 to 5% of a cross-linking agent, and
- (d) 0 to 30% of a water-soluble polymer, to form resinous particles, coating the particles with 0.1 to 5% their weight on an anhydrous basis of an alkylene carbonate, and heating the coated particles to a temperature of 150.degree. to 300.degree. C.