POWDER-FORM CROSS-LINKED POLYMERS CAPABLE OF ABSORBING AQUEOUS LIQUIDS AND BODY FLUIDS, METHOD OF PREPARING THEM AND THEIR USE

The invention concerns powder-form, water-swelling cross-linked polymers with a high capacity for absorbing, under pressure, aqueous liquids, in particular body fluids, the polymers being made from (a) monomers containing 55-99.9 % by wt. of acid groups of which at least 50 mole % have been neutralized; (b) 0-40 % by wt. of monomers copolymerizable with (a); (c) 0.1-5.0 % by wt. of at least one cross-linking agent and (d) 0-30 % by wt. of a watersoluble polymer. The cations of the salts covered by (a) include Li+ and Na+ but preferably K+, Cs+ and Rb+ plus primary, secondary or tertiary methylammonium ions, alone or in combination. The polymers are prepared by reacting the monomers together with a carbon dioxide expanding agent, drying the polymer thus formed and then heating it to a temperature of 100-300.degree.C with one or more compounds capable of reacting with the polymer to cross-link the surface layer. Polymers of this kind are suitable for use as components of nappies, sanitary towels and incontinence pads, as components of current- and light-carrying cables, as soil-improvement agents and artificial earth in plant cultivation and as packaging materials.