Patent ID: 8608096

Claim:
A process for producing water-absorbing polymer particles by polymerizing a monomer solution or suspension comprising at least one ethylenically unsaturated monomer which bears an acid group and may be at least partially neutralized, at least one crosslinker, at least one initiator, optionally one or more ethylenically unsaturated monomer copolymerizable with the monomers mentioned under a), and optionally one or more water-soluble polymer, comprising drying, grinding, and classifying using at least one tumbler screening machine, wherein the tumbler screening machine used for classification is equipped with at least one ball knock cleaning system consisting of a base tray with elastic balls below a screen, the balls have a starting diameter x and the base tray has passage orifices for particles with a maximum particle diameter y, where y is less than x, and entrained elastic balls are removed outside the tumbler screening machine by means of a capture device, said capture device having passage orifices for particles with a maximum particle diameter z, where z is less than y.