Superabsorbent Polymer Composition and Method for Preparing the Same

Patent metadata

Field	Value
Publication number	US-2021069674-A1
Application number	US-201816771479-A
Country	US
Kind code	A1
Filing date	Dec 7, 2018
Priority date	Dec 11, 2017
Publication date	Mar 11, 2021
Grant date	—

Abstract

The present invention relates to superabsorbent polymer and a method for preparing the same. The present invention can provide a superabsorbent polymer in which a hydrophobic material having an HLB of 0-6 and a surface cross-linking agent are mixed into a base resin prepared in the presence of water dispersible silica, thereby having improved rewetting characteristics and permeability through surface-modification of the base resin.

First claim

1 . A method for preparing superabsorbent polymer comprising:
preparing a base resin in which acrylic acid-based monomers having acid groups, of which at least a part are neutralized, and an internal crosslinking agent are crosslinked, in the presence of colloidal silica; mixing a hydrophobic material having a HLB of 0 or more and 6 or less, and a surface crosslinking agent with the base resin to obtain a mixture; and increasing a temperature of the mixture to conduct surface modification of the base resin.

2 . The method for preparing superabsorbent polymer according to claim 1 , wherein a particle diameter of the colloidal silica is 10 to 100 nm.

3 . The method for preparing superabsorbent polymer according to claim 1 , wherein the colloidal silica is included in a content of 0.01 to 1.0 parts by weight, based on 100 parts by weight of the acrylic acid-based monomers.

4 . The method for preparing superabsorbent polymer according to claim 1 , wherein the hydrophobic material has a melting point below the increased temperature.

5 . The method for preparing superabsorbent polymer according to claim 1 , wherein the hydrophobic material includes one or more of glyceryl stearate, glycol stearate, magnesium stearate, glyceryl laurate, sorbitan stearate, sorbitan trioleate, or PEG-4 dilaurate.

6 . The method for preparing superabsorbent polymer according to claim 5 , wherein the hydrophobic material is glyceryl stearate

7 . The method for preparing superabsorbent polymer according to claim 1 , wherein the hydrophobic material is mixed in a content of 0.02 to 0.5 parts by weight, based on 100 parts by weight of the base resin.

8 . The method for preparing superabsorbent polymer according to claim 1 , wherein during the mixing, the hydrophobic material is dry mixed with the base resin, and then, a surface crosslinking solution comprising the surface crosslinking agent is mixed therewith.

9 . The method for preparing superabsorbent polymer according to claim 1 , wherein the temperature is increased to 80 to 190° C.

10 . The method for preparing superabsorbent polymer according to claim 1 , wherein the preparing the base resin comprises:
polymerizing a monomer composition comprising acrylic acid-based monomers having acid groups, of which at least a part are neutralized, an internal crosslinking agent, colloidal silica, and a polymerization initiator to form a hydrogel polymer; drying the hydrogel polymer; grinding the dried polymer; and sieving the ground polymer.

11 . The method for preparing superabsorbent polymer according to claim 10 , wherein the monomer composition further comprises a foaming agent and a foam stabilizer.

12 . The method for preparing superabsorbent polymer according to claim 11 , wherein the foaming agent includes one or more of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate or magnesium carbonate.

13 . The method for preparing superabsorbent polymer according to claim 11 , wherein the foam stabilizer includes one or more of sodium dodecyl sulfate, sodium stearate, ammonium lauryl sulfate, sodium lauryl ether sulfate (SLES), or sodium myreth sulfate.

14 . The method for preparing superabsorbent polymer according to claim 1 , wherein the superabsorbent polymer has a vortex time of 35 seconds or less.

15 . The method for preparing superabsorbent polymer according to claim 1 , wherein the superabsorbent polymer has a permeability (unit: seconds) measured according to the following Equation 1, of 20 seconds or less:
Permeability (sec)= T 1− B   [Equation 1]
wherein in the Equation 1, T1 is a time taken until the height of a liquid level decreases from 40 ml to 20 ml, after putting 0.2±0.0005 g of a sieved (30 #˜50 #) superabsorbent polymer sample in a chromatography column and adding brine to the volume of 50 ml, and then, leaving it for 30 minutes; and B is a time taken until the height of a liquid level decreases from 40 ml to 20 ml in a chromatography column filled with brine.

16 . A superabsorbent polymer comprising:
a base resin comprising a crosslinked polymer in which acrylic acid-based monomers having acid groups, of which at least a part are neutralized, are crosslinked; and a surface modification layer formed on a surface of base resin particles, in which the crosslinked polymer is additionally crosslinked by a surface crosslinking agent, wherein the surface modification layer comprises a hydrophobic material having a HLB of 0 or more and 6 or less, and a vortex time of the superabsorbent polymer is 35 seconds or less.

17 . The superabsorbent polymer according to claim 16 , wherein the base resin is crosslinked in the presence of colloidal silica.

18 . The superabsorbent polymer according to claim 16 , wherein the superabsorbent polymer has a permeability (unit: seconds) measured according to the following Equation 1, of 20 seconds or less:
Permeability (sec)= T 1− B   [Equation 1]
wherein in the Equation 1, T1 is a time taken until the height of a liquid level decreases from 40 ml to 20 ml, after putting 0.2±0.0005 g of a sieved (30 #˜50 #) superabsorbent polymer sample in a chromatography column and adding brine to the volume of 50 ml, and then, leaving it for 30 minutes; and B is a time taken until the height of a liquid level decreases from 40 ml to 20 ml in a chromatography column filled with brine.

19 . The superabsorbent polymer according to claim 16 , wherein the superabsorbent polymer has a rewet property (tap water long-term rewet under no pressure) of 3.0 g or less, said rewet property being defined by a weight of water exuding from the superabsorbent polymer to a filter paper, after 1 g of the superabsorbent polymer is soaked in 100 g of tap water to swell for 10 minutes to produce a swollen superabsorbent polymer, and then, the swollen superabsorbent polymer is left on the filter paper for 3 hours from a first time point when it is soaked in the tap water.

20 . The superabsorbent polymer according to claim 16 , wherein the superabsorbent polymer has a rewet property (tap water short-term rewet under no pressure) of 1.0 g or less, said rewet property being defined by a weight of water exuding from the superabsorbent polymer to a filter paper, after 1 g of the superabsorbent polymer is soaked in 100 g of tap water to swell for 10 minutes to produce a swollen superabsorbent polymer, and then, the swollen superabsorbent polymer is left on the filter paper for 1 hour from a first time point when it is soaked in the tap water.

Assignees

• Lg Chemical Ltd

Inventors

• Jung Seonjung
• Nam Dae Woo
• Seong Bo Hyun
• Yoon Hyungki

Classifications

• C08J2300/14

  Water soluble or water swellable polymers, e.g. aqueous gels · CPC title

• C08K5/09

  Carboxylic acids; Metal salts thereof; Anhydrides thereof · CPC title

• C08K2201/011

  Nanostructured additives · CPC title

• C08K3/36

  Silica · CPC title

• C08F20/06

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title