	US 11,712,678 B2
	Preparation method of super absorbent polymer
Dong Hyun Kim, Daejeon (KR); Tae Bin Ahn, Daejeon (KR); Jun Wye Lee, Daejeon (KR); and Chang Sun Han, Daejeon (KR)
Assigned to LG Chem, Ltd.
Appl. No. 16/86,244
Filed by LG Chem, Ltd., Seoul (KR)
PCT Filed Dec. 26, 2017, PCT No. PCT/KR2017/015485 § 371(c)(1), (2) Date Sep. 18, 2018, PCT Pub. No. WO2018/139768, PCT Pub. Date Aug. 2, 2018.
Claims priority of application No. 10-2017-0011253 (KR), filed on Jan. 24, 2017.
Prior Publication US 2020/0164344 A1, May 28, 2020
Int. Cl. C08J 3/24 (2006.01); A61L 15/24 (2006.01); C08F 220/06 (2006.01); B01J 20/26 (2006.01); A61L 15/60 (2006.01); B01J 20/28 (2006.01); B01J 20/30 (2006.01); B29B 9/06 (2006.01); B29K 33/00 (2006.01); B29K 105/24 (2006.01); C08J 9/04 (2006.01); C08J 3/12 (2006.01)

CPC B01J 20/267 (2013.01) [A61L 15/24 (2013.01); A61L 15/60 (2013.01); B01J 20/28004 (2013.01); B01J 20/28016 (2013.01); B01J 20/3007 (2013.01); B01J 20/3085 (2013.01); B29B 9/06 (2013.01); C08F 220/06 (2013.01); B29K 2033/08 (2013.01); B29K 2105/24 (2013.01); B29K 2995/0068 (2013.01); C08F 2800/20 (2013.01); C08F 2810/20 (2013.01); C08J 3/12 (2013.01); C08J 3/24 (2013.01); C08J 9/04 (2013.01)]

8 Claims

1. A method for preparing superabsorbent polymer comprising:

conducting crosslinking polymerization of a monomer composition including water soluble ethylenically unsaturated monomers having acid groups of which at least a part are neutralized, in the presence of an internal crosslinking agent and an expanding agent to form a hydrogel polymer comprising a first crosslinked polymer,

chopping the hydrogel polymer to produce a chopped hydrogel polymer,

drying the chopped hydrogel polymer to produce a dried polymer,

chopping the dried polymer to produce a chopped polymer, and

surface-modifying the chopped polymer to obtain the superabsorbent polymer,

wherein the chopping the hydrogel polymer is conducted under a chopping index condition of 20 to 35 (/s) according to the following Mathematical Formula 1, while pushing the hydrogel polymer into a perforated panel having a plurality of holes using a screw extruder equipped inside of a cylindrical mill;

Chopping index=ω×(TSC/A) [Mathematical Formula 1]

in the Mathematical Formula 1,

ω is an angular velocity of a screw in the screw extruder (2π×N/60 s), and N is a rotation number (rpm) of the screw,

TSC is a solid content (%) of the hydrogel polymer introduced into the cylindrical mill, and

A is an aperture ratio (πr²×n/πR²) of the perforated panel, and r is a radius (mm) of the plurality of holes formed on the perforated panel, n is a number of holes formed on the perforated panel, and R is a radius (mm) of the perforated panel,

wherein in the superabsorbent polymer, a rate of expanded particles in which concaves due to expansion occupy ⅓ or more of a particle surface, is 10% or more of a total particle number.