Patent ID: 8697779
Filing Date: 2014-04-15
Classification: A61L,B29B,C08F,Y10T

Abstract:
1. A process for producing water-absorbing polymer particles by (i) polymerizing droplets of a monomer solution comprising a) at least one ethylenically unsaturated monomer, b) optionally a crosslinker, c) at least one initiator, and d) water, in a surrounding gas phase to provide polymer particles having a water content of at least 5% by weight, then (ii) thermally aftertreating the polymer particles in a fluidized state in the presence of a gas stream at a temperature of at least 60° C., the gas stream having a relative moisture content of 20% to 98% at a temperature of less than 100° C. or comprising 0.25 to 10 kg of steam per kg of dry gas at a temperature of 100° C. or more, wherein the thermal aftertreatment is performed for at least 5 minutes, and the thermal aftertreatment temperature and the relative moisture content of the gas stream are selected such that the water content of the polymer particles changes by less than 40% during the thermal aftertreatment.