Process for the continuous preparation of water-absorbent polymers

• Main Authors: Rudolph, Henry, Vorholt, Herbert, Reimann, Armin, Jung, Detlef, Becker, Volker, van Stiphoudt, Manfred
• Format: Patent
• Language: English; French; German
• Published: 21.12.2022
• Subjects: AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; BLASTING; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS, ORSURGICAL ARTICLES; CHEMISTRY; COMPOSITIONS BASED THEREON; COMPOSITIONS OF MACROMOLECULAR COMPOUNDS; DISINFECTION, STERILISATION, OR DEODORISATION OF AIR; DRYING; DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM; GENERAL PROCESSES OF COMPOUNDING; HEATING; HUMAN NECESSITIES; HYGIENE; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; LIGHTING; MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVINGCARBON-TO-CARBON UNSATURATED BONDS; MAKING GRANULES OR PREFORMS; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS, OR SURGICALARTICLES; MECHANICAL ENGINEERING; MEDICAL OR VETERINARY SCIENCE; METALLURGY; METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS INGENERAL; ORGANIC MACROMOLECULAR COMPOUNDS; PERFORMING OPERATIONS; PREPARATION OR PRETREATMENT OF THE MATERIAL TO BESHAPED; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIALCONTAINING PLASTICS; THEIR PREPARATION OR CHEMICAL WORKING-UP; TRANSPORTING; WEAPONS; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL; WORKING-UP

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 (±1) and at least one crosslinker (±3); (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 (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 L 0 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. 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.