Superabsorbent polymer having high absorption rate under load and preparation method thereof

Patent metadata

Field	Value
Publication number	US-2016354757-A1
Application number	US-201515112081-A
Country	US
Kind code	A1
Filing date	Nov 27, 2015
Priority date	Nov 27, 2014
Publication date	Dec 8, 2016
Grant date	—

Abstract

Provided are a superabsorbent polymer and a preparation method thereof. In the superabsorbent polymer according to the present invention, a low-temperature foaming agent are used together with a high-temperature foaming agent to control the size and distribution of internal pores of the superabsorbent polymer, thereby increasing absorption rate under load without reduction in gel strength.

First claim

1 . A superabsorbent polymer comprising a crosslinked polymer resulting from polymerization and internal crosslinking of a monomer composition comprising acrylic acid-based monomers having acidic groups which are at least partially neutralized, and a surface crosslinking layer formed on the surface of the crosslinked polymer,
wherein the superabsorbent polymer has centrifuge retention capacity (CRC) as 29.5 g/g or more, absorbency under load (AUL) as 18 g/g or more, gel bed permeability (GBP) as 60 Darcy or more, and 5-min gel-AUL as 18.0 g/g or more.

2 . The superabsorbent polymer of claim 1 , wherein a ratio (A:B) of a total pore area ratio (A) of pores having a diameter of 5 μm to 100 μm and a total pore area ratio (B) of pores having a diameter of 100 μm to 400 μm in the superabsorbent polymer is 3:7 to 9:1.

3 . The superabsorbent polymer of claim 1 , wherein a ratio (A:B) of a total pore area ratio (A) of pores having a diameter of 5 μm to 100 μm and a total pore area ratio (B) of pores having a diameter of 100 μm to 400 μm in the superabsorbent polymer is 4:6 to 8:2.

4 . The superabsorbent polymer of claim 1 , further comprising a low-temperature foaming agent and a high-temperature foaming agent which are dispersed in the crosslinked polymer.

5 . The superabsorbent polymer of claim 4 , wherein the low-temperature foaming agent is sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, or magnesium carbonate.

6 . The superabsorbent polymer of claim 4 , wherein the high-temperature foaming agent is azodicarbonamide (ADCA), dinitroso pentamethylene tetramine (DPT), p,p′-oxybisbenzenesulfonylhydrazide (OBSH), p-toluenesulfonyl hydrazide (TSH), or sugar ester.

7 . The superabsorbent polymer of claim 1 , wherein the acrylic acid-based monomer is represented by the following Chemical Formula 1:
R 1 —COOM 1   [Chemical Formula 1]
wherein, R 1 is an alkyl group containing an unsaturated bond and having 2 to 5 carbon atoms, and M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

8 . The superabsorbent polymer of claim 1 , wherein the acrylic acid-based monomer comprises one or more selected from the group consisting of acrylic acid, methacrylic acid, and a monovalent metal salt, a divalent metal salt, an ammonium salt, and an organic amine salt thereof.

9 . The superabsorbent polymer of claim 1 , wherein the crosslinked polymer is internally crosslinked by one or more first crosslinking agents selected from the group consisting of N,N′-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene carbonate.

10 . The superabsorbent polymer of claim 1 , wherein the superabsorbent polymer is a particulate polymer having a particle diameter of 150 to 850 μm.

11 . A method of preparing the superabsorbent polymer of claim 1 , the method comprising the steps of:
1) polymerizing or crosslinking a monomer composition comprising acrylic acid-based monomers having acidic groups which are at least partially neutralized, in the presence of a polymerization initiator, a first crosslinking agent, a low-temperature foaming agent, and a high-temperature foaming agent at 25 to 100° C. to form a water-containing gel polymer, 2) coarsely pulverizing the water-containing gel polymer, 3) drying the coarsely pulverized water-containing gel polymer at 150° C. to 250° C., 4) pulverizing the dried polymer, and 5) surface-modifying the pulverized polymer by a second crosslinking agent.

12 . The method of claim 11 , wherein the low-temperature foaming agent is sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, or magnesium carbonate.

13 . The method of claim 11 , wherein the polymerization and crosslinking of step 1 are performed at a temperature of 30° C. to 90° C.

14 . The method of claim 11 , wherein the high-temperature foaming agent is azodicarbonamide (ADCA), dinitroso pentamethylene tetramine (DPT), p,p′-oxybisbenzenesulfonylhydrazide (OBSH), p-toluenesulfonyl hydrazide (TSH), or sugar ester.

15 . The method of claim 14 , wherein the sugar ester is sucrose stearate, sucrose palmitate, or sucrose laurate.

16 . The method of claim 11 , wherein a weight ratio of the low-temperature foaming agent and the high-temperature foaming agent is 50:1 to 2:1.

17 . The method of claim 11 , wherein the drying of Step 3 is performed at a temperature of 150° C. to 200° C.

18 . The method of claim 11 , wherein the second crosslinking agent is one or more compounds selected from the group consisting of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propane diol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, hexanediol, trimethylol propane, pentaerythritol, sorbitol, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, calcium chloride, magnesium chloride, aluminum chloride, and iron chloride.

Assignees

• Lg Chemical Ltd

Inventors

• Lee Sang Gi
• Lee Soo Jin
• Nam Hye Mi
• Hwang Min Ho

Classifications

• C08J9/224

  Surface treatment · CPC title

• C08F20/10 Primary

  Esters · CPC title

• B01J20/3085

  Chemical treatments not covered by groups B01J20/3007 - B01J20/3078 · CPC title

• B01J20/267 Primary

  Cross-linked polymers · CPC title

• C08J2203/02

  CO2-releasing, e.g. NaHCO3 and citric acid · CPC title