Method for Preparing Superabsorbent Polymer

Patent metadata

Field	Value
Publication number	US-2022111351-A1
Application number	US-202017431527-A
Country	US
Kind code	A1
Filing date	Nov 5, 2020
Priority date	Nov 5, 2019
Publication date	Apr 14, 2022
Grant date	—

Abstract

A method for preparing superabsorbent polymer is disclosed herein. In some embodiments, a method includes polymerizing a monomer composition to form a hydrogel polymer, wherein the monomer composition comprises a water soluble ethylenically unsaturated monomer and a polymerization initiator, drying and grinding the hydrogel polymer to prepare a base resin powder, surface cross-linking the base resin powder using a surface cross-linking agent to prepare surface cross-linked base resin powder, and hydrating the surface cross-linked base resin powder by pulse spraying water to prepare a superabsorbent polymer, wherein a scattering index of droplets generated during the pulse spraying is 5 to 10, and wherein the scattering index is calculated in accordance with the following Mathematical Formula 1. The superabsorbent polymer can have an improved moisture content to prevent surface property change of the superabsorbent polymer, and decreased amount of fine powder which improves processability during manufacture of articles using superabsorbent polymer.

First claim

1 . A method for preparing superabsorbent polymer, comprising:
polymerizing a monomer composition to form a hydrogel polymer, wherein the monomer composition comprises a water soluble ethylenically unsaturated monomer and a polymerization initiator, and wherein the polymerization is thermal polymerization or photopolymerization; drying and grinding the hydrogel polymer to prepare a base resin powder; surface cross-linking the base resin powder using a surface cross-linking agent to prepare surface cross-linked base resin powder; and hydrating the surface cross-linked base resin powder by pulse spraying water to prepare a superabsorbent polymer, wherein a scattering index of droplets generated during the pulse spraying is 5 to 10, and wherein the scattering index is calculated in accordance with the following Mathematical Formula 1:
Scattering index=[(Re droplet)/(Re air)]×100   [Mathematical Formula 1]

in the Mathematical Formula 1, Re droplet is Reynolds number of droplet, and Re air is Reynolds number of air.

2 . The method for preparing superabsorbent polymer according to claim 1 , wherein the pulse spraying comprises:
pulse spraying from a pulse type spray nozzle, wherein a pulse controls a rate at which the pulse type spray nozzle is on or off.

3 . The method for preparing superabsorbent polymer according to claim 2 , wherein the orifice diameter of the pulse type spray nozzle is 1 to 2 mm.

4 . The method for preparing superabsorbent polymer according to claim 1 , wherein, during the pulse spraying, a pulse on rate is 10 to 50% of the total spraying time.

5 . The method for preparing superabsorbent polymer according to claim 1 , wherein, during the pulse spraying, a water introduction flow is 0.02 to 0.05 m 3 /hr.

6 . The method for preparing superabsorbent polymer according to claim 1 , wherein, during the pulse spraying, a pulse cycle is 1 to 2000 Hz.

7 . The method for preparing superabsorbent polymer according to claim 1 , wherein the Reynolds number of droplet is 0.2 to 0.35, and the Reynolds number of air is 2 to 5.

8 . The method for preparing superabsorbent polymer according to claim 1 , wherein the average diameter of the droplets is 400 to 600 μm.

9 . The method for preparing superabsorbent polymer according to claim 1 , wherein an amount of droplets having diameters of 300 μm or less is 5 to 10 wt %, based on the total weight of generated droplets.

10 . The method for preparing superabsorbent polymer according to claim 1 , wherein the surface cross-linking agent comprises a polyhydric alcohol-based compound, an alkylene carbonate-based compound, and a multivalent metal salt.

11 . The method for preparing superabsorbent polymer according to claim 10 , wherein the polyhydric alcohol-based compound comprises ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropyleneglycol, or glycerol.

12 . The method for preparing superabsorbent polymer according to claim 10 , wherein the alkylene carbonate-based compound comprises ethylene carbonate or propylene carbonate.

13 . The method for preparing superabsorbent polymer according to claim 10 , wherein the multivalent metal salt comprises aluminum sulfate, aluminum carboxylate, or a mixture thereof.

14 . The method for preparing superabsorbent polymer according to claim 10 , wherein the surface cross-linking agent further comprises hydrophilic inorganic particles.

15 . The method for preparing superabsorbent polymer according to claim 1 , wherein the superabsorbent polymer has a moisture content of 1 to 5 wt %, and has a content of coarse particles having particle size greater than 850 μm of 5 wt % or less, based on the total weight of the superabsorbent polymer.

Assignees

• Lg Chemical Ltd

Inventors

• Kim Kyu Pal
• Min Kyunghoon
• Kim Gicheul
• Min Yoon Jae
• Kim Ki Hyun

Classifications

• C08K3/30

  Sulfur-, selenium- or tellurium-containing compounds · CPC title

• C08K13/02

  Organic and inorganic ingredients · CPC title

• C08J2333/02

  Homopolymers or copolymers of acids; Metal or ammonium salts thereof · CPC title

• B01J20/3021

  Milling, crushing or grinding · CPC title

• C08J3/075

  Macromolecular gels · CPC title