Particulate water absorbing agent with water-absorbing resin as main component

• US 20070066167A1
• Filed: 03/29/2005
• Published: 03/22/2007
• Est. Priority Date: 03/29/2004
• Status: Abandoned Application

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Wada, Katsuyuki, Kimura, Kazuki, Ueda, Hiroko, Kanto, Teruyuki, Fujimaru, Hirotama
• Application Number:
  US10/570,965
• Publication Number:
  US 20070066167A1
• Time in Patent Office: Days
• US Class Current: 442/101
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 3/12 Powdering or granulating
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
• CPC Class Codes: Y10T 428/249924 Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer
• CPC Class Codes: Y10T 442/2344 Coating or impregnation is anti-slip or friction-increasing other than specified as an abrasive

Abstract

The present invention provides a water absorbing agent which maintains excellent water absorbing properties for a long time, even when urine composition of human urine varies depending. A particulate water absorbing agent comprising a water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer, which exhibits Centrifuge retention capacity in a physiological saline solution of not lower than 32 g/g, mass median particle size (D50) of 200 to 400 μm, ratio of particles with diameter of smaller than 150 μm of 0 to 2% by weight, and increased extractables by deterioration of 0 to 15% by weight and extractables for one hour in deterioration test liquid of 0.1 to 30% by weight.

Claims

1. A particulate water absorbing agent comprising a water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer containing an acid group and/or a salt thereof and said water absorbing agent satisfies the following (a) to (d):

(a) centrifuge retention capacity (CRC) of the water absorbing agent in a physiological saline solution being in the range not lower than 32 g/g;

(b) mass median particle size (D50) of the water absorbing agent being in the range of 200 to 400 μ

m;

(c) ratio of particles of the water absorbing agent having diameter of smaller than 150 μ

m being in the range of 0 to 2% by weight; and

(d) increased extractables of the water absorbing agent by deterioration expressed by the following formula of 0 to 15% by weight and extractables of the water absorbing agent for one hour in deterioration test liquid of 0.1 to 30% by weight, wherein the deterioration test solution means a physiological saline solution containing 0.05% by weight of L-ascorbic acid.

Increased extractables by deterioration (% by weight)=extractables for one hour in deterioration test liquid (% by weight)−

extractables for one hour in a physiological saline solution (% by weight)

4. A particulate water absorbing agent according to claim 1, wherein a water-absorbing resin is further surface crosslinked.

5. A particulate water absorbing agent according to claim 1, wherein further (h) 90 to 100% by weight of a particulate water absorbing agent has diameter in the range of 600 to 150 μ

m.

6. A particulate water absorbing agent according to claim 1, wherein the water absorbing agent satisfies further (i) absorbency against pressure at 1.9 kPa (AAP 1.9 kPa) in a physiological saline solution being not lower than 20 g/g.

7. A particulate water absorbing agent claim 1, wherein the water absorbing agent satisfies further (j) absorption speed with vortex method being not longer than 60 seconds.

8. A particulate water absorbing agent according to claim 1, wherein the water absorbing agent satisfies further (k) fluidity after moisture absorption being in the range of 0 to 20% by weight.

9. A particulate water absorbing agent according to claim 1, wherein the water absorbing agent satisfies further (l) logarithmic standard deviation of particle size distribution being in the range of 0.20 to 0.40.

10. A particulate water absorbing agent according to claim 1, which further comprises, besides a water-absorbing resin as a main component, one or more minor components selected from the group consisting of a chelating agent, a deodorant, a polyvalent metal salt and an inorganic fine particle.

11. A particulate water absorbing agent according to claim 10, wherein the chelating agent is one or more agents selected from the group consisting of aminocarboxylic acid and salt thereof.

12. A particulate water absorbing agent according to claim 10, wherein the deodorant is a component made from a plant.

13. A particulate water absorbing agent according to claim 10, wherein the polyvalent metal salt is a polyvalent metal salt of an organic acid.

14. A particulate water absorbing agent according to claim 10, wherein the inorganic fine particle is a composite hydrated oxide.

15. A particulate water absorbing agent according to claim 1, wherein particle shape of a water-absorbing resin is irregularly pulverized shape.

16. A particulate water absorbing agent according to claim 1, wherein the above (d) increased extractables by deterioration is 0 to 12% by weight.

18. A particulate water absorbing agent according to claim 1, wherein the above (g) absorbency against pressure at 4.8 kPa in a physiological saline solution is not lower than 22 g/g.

19. An absorbing article for excrement, urine or blood, which is molded by comprising a particulate water absorbing agent according to claim 1 and hydrophilic fibers.

20. A method for production of a particulate water absorbing agent according to claim 1, which comprises

a step of crosslinking polymerization of the aqueous solution of an unsaturated monomer containing non-neutralized acrylic acid and/or salts thereof in the presence of a crosslinking agent and a chain transfer agent;

and

a step of surface crosslinking the water-absorbing resin particle obtained by the polymerization and satisfied (a) to (c) described below,

(a) centrifuge retention capacity (CRC) of the resin particle in a physiological saline solution being in the range of not lower than 32 g/g;

(b) mass median particle size (D50) of the resin particle being in the range of 200 to 400 μ

m; and

(c) ratio of particles having diameter of the resin particle of smaller than 150 μ

m being in the range of 0 to 2% by weight.

21. A method for production of a particulate water absorbing agent according to claim 1, which comprises

a step of crosslinking polymerization of the aqueous solution of an unsaturated monomer in concentration of 10 to 30% by weight containing non-neutralized acrylic acid in the presence of a crosslinking agent;

a step of neutralization after the polymerization; and

a step of surface crosslinking the water-absorbing resin particle obtained by the neutralization and satisfied (a) to (c) described below,

(a) centrifuge retention capacity (CRC) of the resin particle in a physiological saline solution being in the range of not lower than 32 g/g;

(b) mass median particle size (D50) of the resin particle being in the range of 200 to 400 μ

m; and

(c) ratio of particles having diameter of the resin particle of smaller than 150 μ

m being in the range of 0 to 2% by weight.

22. A method for production of a particulate water absorbing agent according to claim 1, which comprises,

a step of crosslinking polymerization of the aqueous solution of an unsaturated monomer containing non-neutralized acrylic acid and/or salts thereof the presence of a crosslinking agent;

a step of surface crosslinking the water-absorbing resin particle obtained by the polymerization and satisfied (a) to (c) described below,

(a) centrifuge retention capacity (CRC) of the resin particle in a physiological saline solution being in the range of not lower than 32 g/g;

(b) mass median particle size (D50) of the resin particle being in the range of 200 to 400 μ

m;

(c) ratio of particles having diameter of the resin particle of smaller than 150 μ

m being in the range of 0 to 2% by weight; and

a step of adding a chelating agent with one or more timings selected from the group consisting of

(i) during polymerization

(ii) after the polymerization and before surface crosslinking

(iii) during surface crosslinking

(iv) after surface crosslinking.

2. A particulate water absorbing agent comprising a water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer containing an acid group and/or a salt thereof and said water absorbing agent satisfies the following (a) to (c) and (e):

(a) centrifuge retention capacity (CRC) of the water absorbing agent in a physiological saline solution being in the range of not lower than 32 g/g;

(b) mass median particle size (D50) of the water absorbing agent being in the range of 200 to 400 μ

m;

(c) ratio of particles having diameter of smaller than 150 μ

m being in the range of 0 to 2% by weight; and

(e) increased ratio of extractables of the water absorbing agent by deterioration expressed by the following formula of 1 to 4 times, and extractables of the water absorbing agent for one hour in deterioration test liquid of 0.1 to 30% by weight, wherein the deterioration test solution means a physiological saline solution containing 0.05% by weight of L-ascorbic acid.

Increased ratio of extractables by deterioration=extractables for one hour in deterioration test liquid (% by weight)/extractables for one hour in a physiological saline solution (% by weight)

17. A particulate water absorbing agent according to claim 2, wherein the above (e) increased ratio of extractables by deterioration is 1 to 3.

3. A particulate water absorbing agent comprising a water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer containing an acid group and/or a salt thereof said water absorbing agent satisfies the following (a) to (c), (f) and (g):

(a) centrifuge retention capacity (CRC) of the water absorbing agent in a physiological saline solution being in the range of not lower than 32 g/g;

(b) mass median particle size (D50) of the water absorbing agent being in the range of 200 to 400 μ

m;

(c) ratio of particles having diameter of the water absorbing agent of smaller than 150 μ

m being in the range of 0 to 2% by weight;

(f) extractables of the water absorbing agent for 16 hours in a physiological saline solution being in the range of 0.1 to 10% by weight; and

(g) absorbency against pressure at 4.8 kPa (AAP4.8 kPa) of the absorbent in a physiological saline solution being not lower than 21 g/g.