Patent ID: 8378000

Claim:
A process for producing water-absorbent, foam-type polymer structures consisting of the steps of: i) preparing an aqueous composition (A) wherein the aqueous composition (A) comprises (A1) water, (A2) one or more polymers based at least on (α1) from about 55 to about 100 wt. % of a polymerized, monoethylenically unsaturated, acid-group-containing monomer or its salt thereof, wherein said polymerized, monoethylenically unsaturated, acid-group-containing monomer is neutralized from about 50 to about 90 mol %; (α2) from 0 to about 45 wt. % of a polymerized, monoethylenically unsaturated monomer that is copolymerizable with (α1), wherein the sum of the amounts by weight of (α1) and (α2) is 100 wt. % and wherein at least about 31.5 wt. % of the monomers, based on the total weight of the monomers (α1) and (α2), are acrylic acid or salts of acrylic acid, (A3) one or more crosslinkers, (A4) one or more blowing agents, (A5) one or more surfactants, (A6) and optionally further auxiliary substances, ii) foaming the aqueous composition (A) to make a foamed aqueous composition, iii) applying ethylene carbonate to the surface of the foamed aqueous composition of step ii), iv) heating the foamed aqueous composition including ethylene carbonate of step iii) to a temperature in a range of from about 50 to about 300° C., so that the polymer (A2) crosslinks at least partially and the content of water (A1) is adjusted to not more than about 15 wt. %, based on the total weight of the foam-type polymer structure that forms, v) smoothing the surface of the water-absorbent, foam-type polymer structure of step iv) by treating the surface of the water-absorbent, foam-type polymer structure with steam at temperatures in the range of from about 20° C. to 40° C. followed by calendaring wherein the pores in the region of the surface of the foam-type polymer structure are compressed but not closed resulting in the water-absorbent, foam-type polymer structure having nonuniform cell structure.