Patent ID: 8592516
Filing Date: 2013-11-26
Classification: B01J,C08F,F26B

Abstract:
1. A process for drying water-absorbing polymer particles by polymerizing a monomer solution comprising at least one ethylenically unsaturated acid-functional monomer and at least one crosslinker and comminuting a resulting hydrogel to hydrogel particles, then drying the hydrogel particles, said drying comprising use of a heated gas stream, and (a) effecting the drying in two or more temperature zones for which gas inlet temperatures satisfy the condition T (b) the gas stream is flowed against the hydrogel particles upwardly in an upstream sector of a belt dryer and downwardly in a downstream sector of a belt dryer, the direction of flow being reversed at a water content of 15% to 45% by weight for the hydrogel particles, and/or (c) a layer of the hydrogel particles is flowed against in a belt dryer upwardly to some extent at least, a gas velocity being 5% to 30% of a gas velocity required to lift the hydrogel off the belt.