Patent ID: 8865828
Filing Date: 2014-10-21
Classification: C08F,C08J

Abstract:
1. A process for producing permeable water-absorbing 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), e) optionally one or more water-soluble polymer, and f) water, in a surrounding gas phase, the resulting polymer particles being coated with at least one permeability improver comprising an inorganic particulate substance, an inorganic colloidally dissolved substance, and/or a polyvalent cation, and optionally pretreated thermally and/or with steam, the permeable water-absorbing polymer particles having a centrifuge retention capacity of at least 27 g/g, a mean sphericity of at least 0.84, a bulk density of at least 0.55 g/cm or a gel bed permeability which satisfies the condition wherein SFC is saline flow conductivity, GBP is gel bed permeability, and CRC is centrifuge retention capacity.