Aqueous-liquid-absorbing agent and its production process

• US 20090131255A1
• Filed: 09/25/2006
• Published: 05/21/2009
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Sakamoto, Shigeru, Ikeuchi, Hiroyuki, Machida, Sayaka
• Granted Patent: US 7,816,301 B2
• Time in Patent Office: Days
• US Class Current: 502/402
• 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 an aqueous-liquid-absorbing agent which comprises water-absorbent resin particles as essential components and is suitable for uses in sanitary materials. The aqueous-liquid-absorbing agent according to the present invention is an aqueous-liquid-absorbing agent comprising water-absorbent resin particles as essential components, wherein the water-absorbent resin particles are obtained by a process including the step of polymerizing a water-soluble ethylenically unsaturated monomer having a carboxyl group, and have a crosslinked structure in their inside, the aqueous-liquid-absorbing agent exhibiting a water absorption capacity (CRC) of 5 to 25 g/g and a saline flow conductivity (SFC) of not less than 1216 cm³·s·10⁻⁷/g.

Claims

1. An aqueous-liquid-absorbing agent containing water-absorbent resin particles as essential components, wherein the water-absorbent resin particles are obtained by a process including the step of polymerizing a water-soluble ethylenically unsaturated monomer having a carboxyl group, have a crosslinked structure in their inside, and are surface-crosslinked,

the aqueous-liquid-absorbing agent being characterized by exhibiting a water absorption capacity (CRC) of 5 to 25 g/g and a saline flow conductivity (SFC) of not less than 1216 cm³·

s·

10<sup>−

7</sup>/g.

2. An aqueous-liquid-absorbing agent according to claim 1, wherein absorption rate (FSR) is not less than 0.1 g/g/s.

3. An aqueous-liquid-absorbing agent according to claim 1, wherein a wet porosity is not less than 20%.

4. An aqueous-liquid-absorbing agent according to claim 1, which is a particulate shape and of which not less than 90 weight % is in the form of particles having particle diameters in the range of 150 to 850 μ

m.

5. An aqueous-liquid-absorbing agent according to claim 1, wherein at least a portion of the water-absorbent resin particles are agglomerate particles.

6. An aqueous-liquid-absorbing agent according to claim 1, which further comprises a liquid-permeability-enhancing agent.

7. A process for production of an aqueous-liquid-absorbing agent exhibiting a water absorption capacity (CRC) of 5 to 25 g/g and a saline flow conductivity (SFC) of not less than 1216 cm³·

s·

10<sup>−

7</sup>/g,

the process comprising the steps of;

(a) polymerizing a water-soluble ethylenically unsaturated monomer having a carboxyl group in an aqueous monomer solution including the water-soluble ethylenically unsaturated monomer having a carboxyl group, in the presence of an internal-crosslinking agent having at least four functional groups each capable of forming a covalent bond with a carboxyl group to thereby obtain a hydropolymer;

(b) drying the hydropolymer obtained in the step (a) at a temperature of not less than 150°

C. to thereby obtain water-absorbent resin particles; and

(c) surface-crosslinking the water-absorbent resin particles obtained in the step (b),

wherein the amount (Y) (mol %) of the internal-crosslinking agent as used, relative to the water-soluble ethylenically unsaturated monomer having a carboxyl group, is expressed by the following equation (1);

Y≧

0.06/{2−

(2.35X/100)} 

 

(1)

where X is neutralization degree (mol %) of a carboxyl group in the water-absorbent resin particles and is in the range of 45 to 85 mol %.

8. A process for production of an aqueous-liquid-absorbing agent according to claim 7, further comprising the step of pulverizing the obtained hydropolymer or the obtained water-absorbent resin particles at least before or after the step (b).

9. A process for production of an aqueous-liquid-absorbing agent according to claim 8, wherein at least a portion of the water-absorbent resin particles are agglomerate particles.

10. A process for production of an aqueous-liquid-absorbing agent according to claim 7, further comprising the step of subjecting the water-absorbent resin particles to treatment for liquid permeability enhancement before or after the step (c).

11. A process for production of an aqueous-liquid-absorbing agent according to claim 10, wherein the treatment for liquid permeability enhancement is carried out by adding a liquid-permeability-enhancing agent.

12. A process for production of an aqueous-liquid-absorbing agent according to claim 11, wherein the liquid-permeability-enhancing agent is at least one member selected from among water-soluble metal compounds and water-soluble polycationic compounds.

13. A process for production of an aqueous-liquid-absorbing agent according to claim 7, wherein the aqueous monomer solution has a monomer concentration of neither lower than 35 weight % nor higher than a saturated concentration.