Patent ID: 8552071

Claim:
A process for preparing dried hydrogel particles, comprising: polymerizing an olefinically unsaturated carboxylic acid or its salts in a polymerization reaction mixture, to obtain a solid gel containing a polymer; admixing the polymerization reaction mixture before or during the polymerization or admixing said solid gel with an alkali metal silicate of the general formula I M 2 O× n SiO 2 (I), wherein M is an alkali metal and n is from 0.5 to 4; thereby obtaining particles of a gel in which said silicate is evenly distributed; postcrosslinking said particles of the gel; and drying said particles of the gel at an elevated temperature, to obtain said dried hydrogel particles; wherein said postcrosslinking is effected by a crosslinker which is a compound containing two or more groups that form covalent bonds with the carboxyl groups of said particles of the gel; wherein said polymer is prepared by admixing said alkali metal silicate in an amount of from 0.05% by weight to 20% by weight, reckoned on SiO 2 and based on a total monomer weight.