Process for producing thermally surface postcrosslinked water-absorbing polymer particles

摘要

A process for producing thermally surface postcrosslinked water-absorbing polymer particles, wherein the water-absorbing polymer particles are coated before, during or after the thermal surface postcrosslinking with at least one complex consisting of a polyvalent metal salt and a 2-hydroxycarboxamide.

主权项

1. A process for producing water-absorbing polymer particles by polymerizing a monomer solution or suspension comprising
i) at least one ethylenically unsaturated monomer which bears an acid group and may be at least partly neutralized, ii) at least one crosslinker, iii) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer mentioned under i), and iv) optionally one or more water-soluble polymer, and drying, grinding, and classifying the resulting polymer gel, coating the resulting water-absorbing polymer particles with v) at least one surface postcrosslinkerand thermally surface postcrosslinking, wherein the water-absorbing polymer particles are coated before, during, or after the thermal surface postcrosslinking with at least one complex consisting of a polyvalent metal salt of the general formula (I)
Mn(X)a(OH)b  (I) and a 2-hydroxycarboxamide, in which M is at least one polyvalent metal cation, X is at least one acid anion, a is a number from 0 to n/m, where m is the number of negative charges of the acid anion and n is the number of positive charges of the polyvalent metal cation, and b is a number from 0 to n.