Aqueous-Liquid-Absorbing Agent and its Production Process

• US 20070207924A1
• Filed: 03/11/2005
• Published: 09/06/2007
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Sakamoto, Shigeru, Torii, Kazushi, Ikeuchi, Hiroyuki, Iwamura, Taku, Machida, Sayaka
• Granted Patent: US 7,981,833 B2
• Time in Patent Office: Days
• US Class Current: 502/402
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking

Abstract

An object of the present invention is to provide an aqueous-liquid-absorbing agent which comprises water-absorbent resin particles as essential components and is suitable for uses in sanitary materials. As a means of achieving this object, an 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 and have a crosslinked structure in their inside; with the aqueous-liquid-absorbing agent exhibiting an absorption rate (FSR) of not less than 0.2 g/g/s, a water absorption capacity (CRC) of 5 to 25 g/g, a saline flow conductivity (SFC) of not less than 400×10⁻⁷ cm³·s/g, and a wet porosity of not less than 20%. A process according to the present invention for obtaining such an aqueous-liquid-absorbing agent is characterized by comprising the steps of: obtaining a hydrogel from an aqueous monomer solution including a water-soluble ethylenically unsaturated monomer and an internal-crosslinking agent of not less than 0.2 mol % in ratio to the monomer; and then extruding this hydrogel from a perforated structure having perforation diameters in the range of 0.3 to 6.4 mm to thereby pulverize the hydrogel.

Claims

1. An aqueous-liquid-absorbing agent, which 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 steps of polymerizing a water-soluble ethylenically unsaturated monomer and have a crosslinked structure in their inside;

with the aqueous-liquid-absorbing agent exhibiting an absorption rate (FSR) of not less than 0.2 g/g/s, a water absorption capacity (CRC) of 5 to 25 g/g, a saline flow conductivity (SFC) of not less than 400×

10<sup>−

7</sup> cm³·

s/g, and a wet porosity of not less than 20%.

2. 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 600 μ

m.

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

4. An aqueous-liquid-absorbing agent according to claim 1, wherein the water-absorbent particles are surface-crosslinked ones.

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

6. A process for production of an aqueous-liquid-absorbing agent including water-absorbent resin particles as essential components, which process comprises the steps of:

preparing an aqueous monomer solution including a water-soluble ethylenically unsaturated monomer and an internal-crosslinking agent of not less than 0.2 mol % in ratio to the monomer; and

then polymerizing and internal-crosslinking the water-soluble ethylenically unsaturated monomer in the aqueous monomer solution to thereby form a hydrogel; and

then extruding the hydrogel from a perforated structure having perforation diameters in the range of 0.3 to 6.4 mm to thereby pulverize the hydrogel to thus obtain pulverized gel particles; and

then drying the pulverized gel particles to thereby obtain the water-absorbent resin particles.

7. A process for production of an aqueous-liquid-absorbing agent according to claim 6, wherein at least a portion of the pulverized gel particles are agglomerates.

8. A process for production of an aqueous-liquid-absorbing agent according to claim 6, which process further comprises the step of surface-crosslinking the water-absorbent resin particles.

9. A process for production of an aqueous-liquid-absorbing agent according to claim 6, which process further comprises the step of subjecting the water-absorbent resin particles to treatment for liquid permeability enhancement.

10. A process for production of an aqueous-liquid-absorbing agent according to claim 9, wherein the treatment for liquid permeability enhancement is carried out by adding a liquid-permeability-enhancing agent.

11. A process for production of an aqueous-liquid-absorbing agent according to claim 10, wherein the liquid-permeability-enhancing agent is at least one member selected from among polyvalent metal compounds, polycationic compounds, and inorganic fine particles.

12. A process for production of an aqueous-liquid-absorbing agent according to claim 6, wherein the aqueous monomer solution has a monomer concentration of neither lower than 35 weight % nor higher than a saturated concentration.