Water-absorbing resin and method for manufacturing the same

• US 20070225422A1
• Filed: 03/22/2007
• Published: 09/27/2007
• Est. Priority Date: 03/24/2006
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Machida, Sayaka, Ikeuchi, Hiroyuki, Sakamoto, Shigeru
• Granted Patent: US 9,090,718 B2
• Time in Patent Office: Days
• US Class Current: 524/458
• CPC Class Codes: C08F 2/44 Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 222/102 of dialcohols, e.g. ethylene glycol di(meth)acrylate or 1,4-butanediol dimethacrylate

Abstract

The present invention provides a highly productive method for manufacturing a water-absorbing resin, the amounts of fine powder and dust of which are small, the amount of residual monomer of which is small, and whose absorption rate is high. That is, the method for manufacturing the water-absorbing resin of the present invention is a method for crosslinking and polymerizing an aqueous solution of an acid-group containing unsaturated monomer, and is characterized in that stationary polymerization is carried out in such a manner that a solid matter is added to the monomer aqueous solution, and an initiation temperature of the polymerization is adjusted to 40° C. or more or a maximum temperature of the polymerization is adjusted to 100° C. or more.

Claims

1. A method for manufacturing a water-absorbing resin, comprising the steps of:

carrying out stationary polymerization of an aqueous solution of an acid-group containing unsaturated monomer in the presence of a water-insoluble solid matter; and

adjusting an initiation temperature of the polymerization to 40°

C. or more or adjusting a maximum temperature of the polymerization to 100°

C. or more.

2. The method as set forth in claim 1, wherein the solid matter is a water-insoluble particle.

3. The method as set forth in claim 1, wherein the stationary polymerization is carried out using a continuous belt apparatus.

4. The method as set forth in claim 1, wherein the solid matter is dry powder of a water-absorbing resin or a swollen gel particle of a water-absorbing resin.

5. The method as set forth in claim 1, wherein a content of the solid matter is 0.1 weight % to 50 weight % with respect to the acid-group containing unsaturated monomer, and 90 weight % or more of the solid matter is a matter which has passed through a 5 mm standard sieve.

6. The method as set forth in claim 1, wherein the monomer contains 70 mole % to 99.999 mole % of acrylic acid (salt) and 0.001 mole % to 5 mole % of a crosslinking agent.

7. The method as set forth in claim 1, wherein the solid matter is a water-absorbing resin whose absorption capacity (CRC) with respect to a physiological saline solution is 5 g/g to 20 g/g.

8. The method as set forth in claim 1, wherein a polymerization time is 10 minutes or less.

9. The method as set forth in claim 1, wherein a concentration of the aqueous solution of the monomer is in a range from 40 weight % to 90 weight %.

10. A water-absorbing resin particle whose repeating unit is acrylic acid (salt) of 70 mole % to 99.999 mole % and a crosslinking agent of 0.001 mole % to 5 mole %, the particle satisfying (1) to (6) below,

(1) an absorption capacity (CRC) being 20 g/g to 40 g/g,

(2) an absorption capacity under load (AAP) being 20 g/g to 40 g/g,

(3) an absorption rate (FSR) being 0.25 g/g/sec to 1.0 g/g/sec,

(4) a bulk specific gravity (JIS K 3362) being 0.50 g/ml to 0.80 g/ml,

(5) a residual monomer being 0 ppm to 400 ppm, and

(6) particles (JIS Z8801-1) of 850 μ

m to 150 μ

m being 95 weight % to 100 weight %.

11. The water-absorbing resin particle as set forth in claim 10,

obtained by polymerizing an aqueous solution of an acid-group containing unsaturated monomer, and

containing therein 0.1 weight % to 50 weight % of a water-insoluble particle on the basis of a weight of the acid-group containing unsaturated monomer at the time of the polymerization.