Abstract: A process for classifying water-absorbing polymer beads, wherein screens having different mesh sizes are used before and after the postcrosslinking to remove the oversize.

Abstract: The invention relates to a process for producing a water-absorbing resin by polymerization of a reaction mixture comprising at least one hydrophilic monomer and, if appropriate, at least one crosslinker in a reactor, which comprises admixing the reaction mixture with at least one first portion of a particulate additive before the reaction mixture has reached a residence time of 40% of the overall residence time in the reactor and with at least one second portion of a particulate additive when the reaction mixture has reached a residence time of 45% or more of the overall residence time in the reactor, the additive being selected from water-absorbing resin powders, fillers and mixtures thereof, the total solids content of monomer and additive being in the range from 30% to 60% by weight, the amount of additive being in the range from 5% to 50% by weight, based on the monomers, and the weight ratio of the first portion to the second portion of the additive being in the range from 10:1 to 1:5.

Abstract: The present invention relates to a process for continuously preparing water-absorbing polymers by mixing a monomer solution with at least one crosslinker and polymerizing the resulting mixture, wherein the residence time of the mixture between the addition of the at least one crosslinker and the entry into the polymerization reactor is less than 180 seconds, and also to an apparatus for performing the process.

Abstract: The invention relates to a neutralization process in which at least one ethylenically unsaturated carboxylic acid is neutralized at least partly with a base and at least one stream of the neutralization is determined continuously, and also to an apparatus for carrying out the process.

Abstract: The invention relates to a process for continuously preparing water-absorbing polymer particles by mixing a monomer solution with a redox initiator consisting of at least one oxidizing agent and at least one reducing agent and polymerizing it, wherein the monomer solution is mixed with at least one oxidizing agent upstream of the polymerization reactor and the at least one reducing agent is metered into the polymerization reactor, and also to an apparatus for performing the process.

Abstract: The invention relates to a process for preparing water-absorbing polymer particles, comprising the inertization of monomer solutions, wherein the monomer solution, based on the dissolved monomer, comprises from 0.001 to 0.016% by weight of at least one polymerization inhibitor and at least 50% by volume of the inert gas used to inertize the monomer solution is transferred into the polymerization reactor together with the inertized monomer solution, and also to apparatus for performing the process.

Abstract: The invention relates to a continuous neutralization process in which at least one ethylenically unsaturated carboxylic acid is neutralized at least partly with a base and the temperature of the neutralized solution is less than 70° C., and also to an apparatus for carrying out the process.