Patent ID: 8450428
Filing Date: 2013-05-28
Classification: A61L,B01J,B29B,C08F

Abstract:
1. A process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution, comprising a) at least one ethylenically unsaturated monomer which bears an acid group and may be at least partly neutralized, b) at least one crosslinker, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer mentioned under a), and e) water, in a surrounding heated gas phase and flowing the gas cocurrent through a polymerization chamber, wherein a temperature of the gas leaving the polymerization chamber is from 90 to 125° C. and a gas velocity inside the polymerization chamber is from 0.7 to 2.5 m/s to form the water-absorbent polymer particles, followed by thermal postcrosslinking of the water-absorbent polymer particles at a temperature of at least 60° C. with a postcrosslinker comprising groups which can form two covalent bonds with acid groups of the polymer particles in the presence of a gas stream comprising 0.01 to 1 kg of steam per kg of dry gas.