Water-swellable hydrophilic polymers

A process for the preparation of the water-swellable hydrophilic polymers which comprises free radical (co)polymerizing of one or more hydrophilic monomers of the formula I ##STR7## wherein R.sup.1 is hydrogen, methyl or ethyl,

• R.sup.2 is the group --COOR.sup.4, the sulphonyl group, the phosphonyl group, the phosphonyl group esterified by (C.sub.1 -C.sub.4)-alkanol or a group of the formula ##STR8## R.sup.3 is hydrogen, methyl, ethyl or the carboxyl group, R.sup.4 is hydrogen, amino or hydrogen-(C.sub.1 -C.sub.4)-alkyl and
• R.sup.5 is the sulphonyl group, the phosphonyl group or the carboxyl group, or grafting (co)polymerization of one or more hydrophilic monomers of the formula I onto a grafting base, using a free radical initiator which forms three or more fee radical sites per molecule,
• wherein about 15 to about 50% strength by weight aqueous solution of one or more hydrophilic monomers and, optionally a suitable grafting base is polymerized by the process of gel polymerization in the presence of a free radical initiator which can form di- or poly-radicals.