Method for producing water-swellable hydorphilic polymers, said polymers and use thereof

A process for preparing a water-swellable hydrophilic polymer, comprising:

• a) free-radically polymerizing or copolymerizing one or more hydrophilic acid-functional monomers to obtain an acidic hydrogel;
• or
• graft polymerizing or copolymerizing one or more hydrophilic acid-functional monomers onto a grafting base to obtain an acidic hydrogel;
• wherein an average degree of neutralization of the acid-functional monomers is from 0 to 40 mol %;
• b) coarsely comminuting said acidic hydrogel;
• c) neutralizing said acidic hydrogel by mixing with a neutralizing agent in a mincer which comprises at least one screw, a rotating blade, a restricted flow zone and a breaker plate, to obtain neutralized, minced hydrogel particles having a final degree of neutralization of 60-85 mol %;
• wherein the mincer has a power output of from 1000 to 6000 Wh/m3;
• wherein the hydrogel passes through a zone having an energy dissipation density of from 400 to 800 W per 1 of mixing volume;
• wherein an average residence time of the acidic hydrogel in the mincer is from 5 to 30 seconds;
• and
• wherein the breaker plate has an open area of from 20 to 40%;
• d) placing the neutralized, minced hydrogel particles without further mechanical shearing stress onto a belt dryer;
• e) drying the neutralized, minced hydrogel particles using said belt dryer, to obtain dried, neutralized hydrogel particles;
• and
• f) grinding and sieving the dried, neutralized hydrogel particles to obtain ground, dried, neutralized hydrogel particles.