US 12,403,449 B2
Water-absorbing resin
Tetsuhiro Hinayama, Himeji (JP); and Sok Kiat Cheng, Singapore (SG)
Assigned to SUMITOMO SEIKA CHEMICALS CO., LTD., Hyogo (JP); and SUMITOMO SEIKA SINGAPORE PTE. LTD., Singapore (SG)
Appl. No. 17/291,149
Filed by SUMITOMO SEIKA CHEMICALS CO., LTD., Hyogo (JP); and SUMITOMO SEIKA SINGAPORE PTE. LTD., Singapore (SG)
PCT Filed Oct. 31, 2019, PCT No. PCT/JP2019/042766
§ 371(c)(1), (2) Date May 4, 2021,
PCT Pub. No. WO2020/095811, PCT Pub. Date May 14, 2020.
Claims priority of application No. 2018-208212 (JP), filed on Nov. 5, 2018.
Prior Publication US 2022/0126271 A1, Apr. 28, 2022
Int. Cl. B01J 20/26 (2006.01); A61L 15/24 (2006.01); B01J 20/24 (2006.01)
CPC B01J 20/267 (2013.01) [A61L 15/24 (2013.01); B01J 20/24 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A water-absorbent resin that is a crosslinked polymer of a water-soluble ethylenically unsaturated monomer, the water-absorbent resin having a dry-up index of 2.2 or more, the dry-up index being represented by the following equation (1):
dry-up index=overall absorption capacity term α× water absorption rate term β   (1),
wherein the overall absorption capacity term α and the water absorption rate term β are determined according to the following equations (2) and (3):
overall absorption capacity term α =

OG Complex Work Unit Math
water absorption rate term β =dynamic water absorption rate/static water absorption rate (3),
wherein the degree of neutralization of the water-soluble ethylenically unsaturated monomer is 77 to 80 mol % of all acid groups in the water-soluble ethylenically unsaturated monomer,
the water-soluble ethylenically unsaturated monomer is (meth)acrylic acid,
the overall absorption capacity term α is 0.95 or more,
the water absorption rate term β is 1.56 or more, and
the water-absorbent resin is prepared by a polymerization method satisfying all of conditions (i), (ii), and (iii):
(i) the molar ratio of a water-soluble ethylenically unsaturated monomer and an internal crosslinking agent used in polymerization in the first stage (water-soluble ethylenically unsaturated monomer/internal crosslinking agent) is 10×103 to 15×103;
(ii) the molar ratio of a water-soluble ethylenically unsaturated monomer and an internal crosslinking agent used in polymerization in the second stage (water-soluble ethylenically unsaturated monomer/internal crosslinking agent) is 15×103 to 25×103;
(iii) the molar ratio of the total amount of water-soluble ethylenically unsaturated monomer used in polymerization in which a resin used in a post-crosslinking reaction is prepared and a post-crosslinking agent (water-soluble ethylenically unsaturated monomer/post-crosslinking agent) is 2.5×103 to 4.5×103.