Abstract: Hydrogel particles are produced by a drying step followed sequentially by precomminuting, grinding, separating, and further drying of coarse particles.

Abstract: A hydrophilic, highly swellable hydrogel based on (co)polymerized monomers or based on graft (co)polymers and prepared by a) free-radically (co)polymerizing one-or more hydrophilic monomers or graft (co)polymerizing one or more hydrophilic monomers onto a grafting base, the average degree of neutralization of the acid-functional monomers being from 0 to 40 mol %, b) comminuting the acidic hydrogel, c) neutralizing the acidic hydrogel to an ultimate degree of neutralization of 50-85 mol % by adding a neutralizing agent, d) drying, grinding and sieving the hydrogel particles characterized by a centrifuge retention and a vertical absorption swell height, each having a specified minimum.value, coupled with an extractables content having a specified maximum value or a centrifuge retention and a vertical absorption swell height, each having a specified minimum value and an extractables content having a specified maximum value.

Abstract: Water-swellable hydrophilic polymers are prepared by neutralization of the acidic hydrogel having a degree of neutralization of 0-40 mol % to an ultimate degree of neutralization of 60-85 mol % by mixing with a neutralizing agent in a mincer comprising a system of screw, rotating blade, restricted flow zone and breaker plate, wherein the mincer has a power output of from 1000 to 6000 Wh/m3 the hydrogel passes through a zone having-an energy dissipation density of from 400 to 800 W/1 of mixing volume the average residence time of the hydrogel in the mincer is from 5 to 30 seconds the breaker plate has an open area of from 20 to 40%.