Process for the continuous preparation of water-absorbent polymers

A process for the preparation of water-absorbent polymer particles, comprising the process steps of

• (i) preparing an aqueous monomer solution comprising at least partially neutralized, monoethylenically unsaturated monomers bearing carboxylic acid groups (α1) and at least one crosslinker (α3);
• (ii) optionally adding fine particles of a water-absorbent polymer to the aqueous monomer solution;
• (iii) adding a polymerization initiator or at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution;
• (iv) decreasing the oxygen content of the aqueous monomer solution;
• (v) charging the aqueous monomer solution into a polymerization reactor;
• (vi) polymerizing the monomers in the aqueous monomer solution in the polymerization reactor;
• (vii) discharging the polymer gel strand out of the polymerization reactor and optionally comminuting the polymer gel thereby obtaining polymer gel particles;
• (viii) drying the polymer gel particles;
• (ix) grinding the dried polymer gel particles thereby obtaining particulate water-absorbent polymer particles;
• (x) sizing the grinded water-absorbent polymer particles;
• and
• (xi) treating the surface of the grinded and sized water-absorbent polymer particles;
• wherein in process step (viii) the gel particles obtained in process step (vii) are charged onto the surface of the belt material of a belt dryer at a position L0 and are subsequently dried on their way through the belt dryer and wherein the belt material has been cooled before coming into contact with the gel particles;
• and
• wherein cooling the surface of the belt material is performed by continuously spraying a cooling liquid onto the surface of the belt material.