US 11,718,694 B2
Super absorbent polymer and preparation method thereof
Hyemin Lee, Daejeon (KR); Tae Young Won, Daejeon (KR); Jungmin Sohn, Daejeon (KR); Junwye Lee, Daejeon (KR); Seongbeom Heo, Daejeon (KR); Kwangin Shin, Daejeon (KR); and Chang Hun Han, Daejeon (KR)
Assigned to LG Chem, Ltd.
Appl. No. 17/271,414
Filed by LG Chem, Ltd., Seoul (KR)
PCT Filed Dec. 20, 2019, PCT No. PCT/KR2019/018228
§ 371(c)(1), (2) Date Feb. 25, 2021,
PCT Pub. No. WO2020/145548, PCT Pub. Date Jul. 16, 2020.
Claims priority of application No. 10-2019-0001977 (KR), filed on Jan. 7, 2019.
Prior Publication US 2021/0309777 A1, Oct. 7, 2021
Int. Cl. C08F 220/06 (2006.01); C08J 3/075 (2006.01); C08J 3/12 (2006.01); C08J 3/24 (2006.01)
CPC C08F 220/06 (2013.01) [C08J 3/075 (2013.01); C08J 3/122 (2013.01); C08J 3/245 (2013.01); C08J 2333/02 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A preparation method of a super absorbent polymer, comprising:
preparing a monomer mixture comprising a water-soluble ethylene-based unsaturated monomer having at least partially neutralized acidic groups and an internal cross-linking agent;
transferring the monomer mixture to a polymerization reactor along a transfer pipe having a diameter that varies from section to section;
cross-linking and polymerizing the monomer mixture transferred to the polymerization reactor to form a hydrogel polymer containing a first cross-linked polymer;
gel-pulverizing, drying, pulverizing and classifying the hydrogel polymer to form a base resin powder containing less than 9.9% by number of base resin powder having an aspect ratio, which is defined as shortest diameter/longest diameter of each base resin powder, of less than 0.5; and
further cross-linking a surface of the base resin powder in the presence of a surface cross-linking agent to form a surface cross-linked layer;
wherein during the transferring of the monomer mixture, the monomer mixture has a maximum transfer rate in a minimum diameter section of the transfer pipe and a minimum transfer rate in a maximum diameter section of the transfer pipe, and the maximum transfer rate is 2.5 times or more compared to the minimum transfer rate.