Patent ID: 8080620

Claim:
A process for continuously producing water-absorbing polymer particles by polymerizing a monomer solution or suspension comprising a) at least one ethylenically unsaturated monomer which bears acid groups and optionally at least partly neutralized, b) at least one crosslinker, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomers copolymerizable with the monomer a) and e) optionally one or more water-soluble polymers, comprising polymerizing, drying, grinding, classifying and at least partial recycling of undersize particles obtained in the classification, a polymer gel obtained by the polymerization being withdrawn from a polymerization reactor and mixed with the recycled undersize particles in an extruder, wherein a water content of a mixture obtained by mixing the polymer gel withdrawn from the polymerization reactor with the recycled undersize particles is from 40 to 70% by weight, essentially no surfactant is added in the mixing of the polymer gel withdrawn from the polymerization reactor with the recycled undersize particles and/or the surface tension of an aqueous extract of the water-absorbing polymer particles is at least 0.06 N/m, wherein the monomer a) is acrylic acid to an extend of at least 50 mol %.