Abstract:
The invention relates generally to 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 a 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 (i) the preparation of the aqueous monomer solution comprises the step of: (ia) at least partially neutralizing acrylic acid by mixing acrylic acid with an aqueous solution of sodium hydroxide, thereby obtaining an aqueous solution of the at least partially neutralized acrylic acid; (ib) cooling the aqueous solution of the at least partially neutralized acrylic acid with a cooling liquid in a heat exchanger (2), wherein the cooling liquid used in the heat exchanger has been cooled in an absorption chiller (3) in which at least a part of the heat of the heated cooling liquid obtained in the heat exchanger (2) is consumed by the evaporation of a refrigerant liquid in a vacuum that is created by the absorption of a refrigerant vapour into an absorbent. The invention also relates to water-absorbent polymer particles obtainable by such a process, to a composite material, to a process for the preparation of a composite material, to the composite material obtainable by such a process, to chemical products and to the use of the water-absorbent polymer particles or a composite material.
Abstract:
Das erfindungsgemäße Verfahren zur Herstellung eines absorbierenden Polymers umfasst Verfahrensschritte i) Polymerisation einer wässrigen Monomerlösung unter Erhalt eines Polymergels, Zerkleinern des Polymergels unter Erhalt eines Gelgranulates, Trocknen des Gelgranulates, und ist dadurch gekennzeichnet, dass das Gelgranulat nach Schritt ii) ein Spreitverhalten zeigt. Das Herstellungsverfahren eines absorbierenden Polymers zeichnet sich durch einen besonders effizienten Trocknungsschritt iii) aus, der eine besonders schonende und gleichmäßige Trocknung des Gelgranulats ermöglicht. Die so erhaltene absorbierende Polymere und daraus hergestellte Produkte und Erzeugnisse weisen eine besonders gleichmäßige Produktqualität und konstante physikalisch-chemische Eigenschaften auf.