# US 7,745,507 B2 · Absorbent member comprising a modified water absorbent resin > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,745,507 B2 - Document ID: US7745507B2 - Status: Granted - Kind: B2 - Application number: 11/732,589 - Filed: 2007-04-04 - Published: 2007-10-11 - Granted: 2010-06-29 - Earliest claimed: 2006-04-10 - Assignees: The Procter & Gamble Company - Inventors: Yoshiro Mitsukami; Makoto Matsumoto; Taku Iwamura - Web page: https://patentgrep.com/patent/US7745507B2 ## CPC - C08J 3/28: Treatment by wave energy or particle radiation - A61L 15/60: Liquid-swellable gel-forming materials, e.g. super-absorbents - C08J 2300/14: Water soluble or water swellable polymers, e.g. aqueous gels - C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof - Y10T 428/31855: Of addition polymer from unsaturated monomers - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract This invention is to provide an absorbent member and a method for making such an absorbent member. The absorbent member comprises modified water absorbent having good production efficiency, good absorbency against pressure, good absorption speed, gel strength, good liquid permeability, and the like. The modified water absorbent resin is made by a method, which comprises (i) a mixing step comprising mixing a water absorbent resin, water, and a water-soluble radical polymerization initiator without addition of an ethylenically unsaturated monomer, to obtain a water absorbent resin composition, and (ii) an irradiating step comprising irradiating said water absorbent resin composition obtained in the mixing step with active energy rays, wherein the surface water content of said water absorbent resin in said water absorbent resin composition at least at any point of time in the irradiating step (ii) is controlled to a level of not lower than 3.0% by weight based on 100% by weight of the water absorbent resin. Preferably, the amount of water mixed in said step (i) exceeds 20 parts by weight and is not more than 100 parts by weight based on 100 parts by weight of the water absorbent resin. ## Claims ### Claim 1 A method for making an absorbent member comprising modified water absorbent resin, said absorbent member being suitable for use in absorbent articles, said method comprising the steps of: a) providing an absorbent member; and b) providing modified water absorbent resin, said modified water absorbent resin being made by a method comprising: (i) a mixing step comprising mixing water absorbent resin, water, and a heat-degradable radical polymerization initiator without addition of an ethylenically unsaturated monomer, to obtain a water absorbent resin composition, and (ii) an irradiating step comprising irradiating said water absorbent resin composition obtained in the mixing step with active energy rays, and wherein the amount of water mixed in said step (i) exceeds 20 parts by weight and is not more than 100 parts by weight based on 100 parts by weight of the water absorbent resin, and wherein the surface water content of said water absorbent resin in said water absorbent resin composition at least at any point of time in the irradiating step (ii) is controlled to a level of not lower than 3.0% according to the equation: (m)=(1)×((k)/100) wherein m is the surface water content in wt %, 1 is the weight ratio of the amount of water contained in a treating solution in wt % and k is the extraction ratio in wt %; c) furnishing said absorbent member said water absorbent resin, which has been made by the method of step b). ### Claim 2 (depends on 1) The method according to claim 1, wherein said water-soluble radical polymerization initiator is at least one member selected from the group consisting of persulfates, hydrogen peroxide and water-soluble azo compounds. ### Claim 3 (depends on 1) The method according to claim 1, wherein the surface water content at the time of beginning said irradiating step is controlled to a level of not lower than 3.0% by weight. ### Claim 4 (depends on 1) The method according to claim 1, wherein the amount of said radical polymerization initiator in the mixing step is in the range of 0.01 to 20 parts by weight, based on 100 parts by weight of the water absorbent resin. ### Claim 5 (depends on 1) The method according to claim 1, wherein in the mixing step, said radical polymerization initiator is mixed in the form of an aqueous solution. ### Claim 6 (depends on 1) The method according to claim 1, wherein a mixing aid is added to the water absorbent resin simultaneously with carrying out the mixing step (i) or prior to the mixing step (i). ### Claim 7 (depends on 1) The method according to claim 1, wherein said water absorbent resin contains an acid group and has a neutralization ratio in the range of from 50 to 75 mol %. ### Claim 8 (depends on 1) The method according to claim 1, wherein said active energy rays are ultraviolet rays. ### Claim 9 (depends on 1) The method according to claim 1, wherein said water absorbent resin is a powdery water absorbent resin obtained by polymerizing a monomer containing an acrylic acid as a main component. ### Claim 10 (depends on 1) The method according to claim 1, wherein said water absorbent resin contains particles, 90% to 100% by weight of said particles having a particle diameter in the range of from 150 to 850 μm. ### Claim 11 (depends on 1) The method according to claim 1, wherein the absorbency of physiological saline against pressure of 4.83 kPa of the water absorbent resin after the modification is in the range of from 8 to 40 g/g. ### Claim 12 (depends on 1) The method according to claim 1, wherein the saline flow conductivity of the water absorbent resin after the modification is not less than 10×10−7·cm3·s·g−1.