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US 9,790,304 B2Granted
Process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution
AssigneeBASF SE
InventorsThomas Daniel, Norbert Herfert, Stephan Bauer, Katrin Baumann, Birgit Reinhard, Jürgen Freiberg, Rudolf Schliwa
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Abstract
The present invention relates to a process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution comprising less than 0.3% by weight of persulfate and at least 0.05% by weight of azo initiator and thermal aftertreatment of the formed polymer particles at less than 100° C. in a fluidized bed for 60 to 300 minutes.
Claims14
A process for producing water-absorbent polymer particles by polymerizing droplets of
- a) at least one ethylenically unsaturated monomer which bears an acid group and optionally is at least partly neutralized,
- (b) at least one crosslinker,
- cl) from 0.01 to less than 0.3% by weight, based on monomer a), of at least one persulfate,
- c2) at least 0.05% by weight, based on monomer a), of at least one azo 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 heated gas phase in a reaction zone and thermal posttreatment in a fluidized bed, wherein a temperature of a gas leaving the reaction zone is less than 150° C., a temperature of the water-absorbent polymer particles during the thermal posttreatment is less than 100 ° C., and a residence time of the water-absorbent polymer particles in the fluidized bed is from 60 to 300 minutes.
5 more elements
Dependencies are inferred from the claim text.