Patent ID: 10179185

Abstract:
A process for producing water-absorbing polymer particles is provided, comprising a) a polymerization step in which an aqueous monomer solution comprising at least one ethylenically unsaturated monomer M which bears acid groups and may have been at least partly neutralized and at least one crosslinker is polymerized to obtain an aqueous polymer gel; b) a pelletization step in which the aqueous polymer gel having a solids content of 35 to 70% by weight and a temperature of 75 to 125° C. is forced from a high-pressure zone through a die plate into a low-pressure zone and pellets are obtained, the pressure differential between the high-pressure zone and the low-pressure zone being 4 to less than 14 bar and the orifice ratio of the die plate being 30 to 80%; c) a drying step in which the pellets are dried to a moisture content of less than 10% by weight; d) a grinding step and a classifying step to obtain water-absorbing polymer particles; and e) surface crosslinking of the water-absorbing polymer particles. The water-absorbing polymer particles have a high swell rate and a high retention capacity combined with a favorable ratio of permeability of the swollen gel bed SFC to centrifuge retention capacity CRC.