Water-Absorbing Polymer Particles with High Free Swell Rate and High Permeability
AssigneeBASF SE
InventorsMatthias Weismantel, Ulrich Riegel, Thomas Gieger, Markus Braun, Michael A. Mitchell
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Abstract
A process for producing water-absorbing polymer particles with high free swell rate and high permeability by polymerization of an aqueous monomer solution or suspension to give an aqueous polymer gel, wherein a thermal blowing agent essentially free of inorganic acid anions is mixed into the polymer gel, and subsequent thermal drying of the polymer gel.
Claims18
A process for producing water-absorbing polymer particles, comprising polymerizing an aqueous monomer solution or suspension comprising
- a) at least one ethylenically unsaturated monomer which bears an acid group and optionally is 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) optionally one or more water-soluble polymer,
- to give an aqueous polymer gel, thermally drying of the polymer gel, comminuting the dried polymer gel to polymer particles, and classifying the resulting polymer particles, which comprises mixing a thermal blowing agent essentially free of inorganic acid anions into the aqueous polymer gel.
Water-absorbing polymer particles having a centrifuge retention capacity (CRC), a free swell rate (FSR), and a permeability (SFC) which meet the conditions
- FSR (g/gs)≧0.01·CRC (g/g)−0.08
- and
- SFC(10−7·cm3s/g)≧11000·exp(−0.18·CRC (g/g)).
Dependencies are inferred from the claim text.