# US 7,612,016 B2 · Preparation of superabsorbent polymers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,016 B2 - Document ID: US7612016B2 - Status: Granted - Kind: B2 - Application number: 12/146,688 - Filed: 2008-06-26 - Published: 2008-10-23 - Granted: 2009-11-03 - Earliest claimed: 2001-05-25 - Assignees: Evonik Stockhausen GmbH - Inventors: Richard Mertens; Olaf Höller - Web page: https://patentgrep.com/patent/US7612016B2 ## CPC - C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking} - A61L 15/60: Liquid-swellable gel-forming materials, e.g. super-absorbents - C08B 15/005: {Crosslinking of cellulose derivatives} - C08B 31/006: {Crosslinking of derivatives of starch} - C08B 37/00: Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof (cellulose D21; {microbiological processes C12P}) - C08B 37/0087: {Glucomannans or galactomannans; Tara or tara gum, i.e. D-mannose and D-galactose units, e.g. from Cesalpinia spinosa; Tamarind gum, i.e. D-galactose, D-glucose and D-xylose units, e.g. from Tamarindus indica; Gum Arabic, i.e. L-arabinose, L-rhamnose, D-galactose and D-glucuronic acid units, e.g. from Acacia Senegal or Acacia Seyal; Derivatives thereof} - A61K 47/36: Polysaccharides; Derivatives thereof, e.g. gums, starch, alginate, dextrin, hyaluronic acid, chitosan, inulin, agar or pectin - A61K 47/38: Cellulose; Derivatives thereof - C08J 2300/14: Water soluble or water swellable polymers, e.g. aqueous gels - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K) - C08B: POLYSACCHARIDES; DERIVATIVES THEREOF (polysaccharides containing less than six saccharide radicals attached to each other by glycosidic linkages C07H; fermentation or enzyme-using processes C12P19/00; sugar industry C13; production of cellulose D21) - A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D) ## Abstract The invention describes superabsorbent polymers composed of surface-post crosslinked polycarboxypolysaccharides having excellent age-stable absorption properties, even under load, high attrition resistance and biodegradability and their use for absorbing water, aqueous or serous fluids and also blood. Also disclosed is a method of making which is impervious to changes in raw material quality and which provides consistent product quality. ## Claims ### Claim 1 A process for preparing superabsorbent polymers comprising the steps of: a) forming a hydrogel by mixing an uncrosslinked polycarboxypolysaccharide with water; b) the hydrogel is mechanically comminuted and dried; c) the dried hydrogel is comminuted and classified to form a polymer particles; and d) the polymer particles are coated with a solution of a crosslinker and subjected to a surface post crosslinking wherein said post crosslinked superabsorbent polymer has an absorbency against pressure (AAP0.7) value of 12.5 g/g or more. ### Claim 2 (depends on 1) The process of claim 1 wherein the mixing of polycarboxypolysaccharide and water is carried out in a continuous mixer. ### Claim 3 (depends on 1) The process of claim 1 wherein the mixing of polycarboxypolysaccharide and water is carried out in a batch mixer. ### Claim 4 (depends on 1) The process of claim 1 wherein the mixture of polycarboxypolysaccharide and water has a pH of about 6 or more. ### Claim 5 (depends on 1) The process of claim 1 wherein the mixture of polycarboxypolysaccharide and water has a pH of about 10 or more. ### Claim 6 (depends on 1) The process of claim 1 wherein the mixture of polycarboxypolysaceharide and water includes from about 5 to about 65% by weight of polycarboxypolysaccharide. ### Claim 7 (depends on 1) The process of claim 1 wherein the mixture of polycarboxypolysaccharide and water includes about 0.01 to about 20% by weight, based on the solids content, of one or more water-soluble additives from the group consisting of bases, salts and blowing agents. ### Claim 8 (depends on 1) The process of claim 1 wherein the carboxyl groups of the polycarboxypolysaccharide are 80% neutralized or more. ### Claim 9 (depends on 1) The process of claim 1 wherein up to about 30% by weight of the water in the mixture of polycarboxypolysaccharide and water is replaced by one or more water-miscible organic solvents which do not dissolve the polycarboxypolysaccharide. ### Claim 10 (depends on 1) The process of claim 1 wherein the mixture of polycarboxypolysaccharide and water includes about 0.01 to about 20% by weight, based on the solids content, of one or more antiblocking additives. ### Claim 11 (depends on 1) The process of claim 1 wherein the drying of the hydrogel is effected at temperatures above about 70° C. ### Claim 12 (depends on 1) The process of claim 1 wherein the hydrogel is dried to a moisture content of about 30% by weight or less. ### Claim 13 (depends on 1) The process of claim 1 wherein about 0.01 to about 25% by weight of covalent or ionic surface post crosslinkers or a combination of at least two thereof, based on the polymer powder, is added in the form of about 0.01 to about 80% by weight aqueous solution. ### Claim 14 (depends on 13) The process of claim 13 wherein the aqueous solution of the covalent surface post crosslinker further includes a crosslinking catalyst. ### Claim 15 (depends on 14) The process of claim 14 wherein the weight ration of surface crosslinker to crosslinking catalyst is about 1:0.001 to about 1:1. ### Claim 16 (depends on 1) The process of claim 1 characterized in that the surface post crosslinking is carried out at temperatures of about 40° C. to about 250° C.