Water-absorbable polyacrylic acid resin powder, and process for production thereof

Patent metadata

Field	Value
Publication number	US-9334376-B2
Application number	US-201013518438-A
Country	US
Kind code	B2
Filing date	Dec 23, 2010
Priority date	Dec 24, 2009
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A process according to the present invention for production of water-absorbable polyacrylic acid resin powder, including: (a) polymerizing an acrylic acid-based monomer aqueous solution containing bubbles, and (b) drying a hydrogel crosslinked polymer thus obtained in the step of polymerizing, further includes (c) lowering solubility of dissolved gas in a monomer aqueous solution in the presence of a surfactant and/or a dispersing agent, so as to generate the bubbles in the acrylic acid-based monomer aqueous solution. With this arrangement, it is possible to provide white water-absorbable resin with better water absorbing rate, keeping or without significantly losing the other properties (permeability potential, bulk specific gravity, surface tension, absorbency against pressure, impact resistance, etc.)

First claim

The invention claimed is:

1. Water-absorbable resin powder being water-absorbable polyacrylic acid resin powder in which particles having a particle diameter of 850 μm to 150 μm accounts for 95 wt % or more, and having an internal cell rate of 2.8% to 6.6%, the internal cell rate being defined by the following equation:
(internal cell rate [%]={(Real Density [g/cm 3 ])−(Apparent Density [g/cm 3 ])}/(Real Density [g/cm 3 ])×100,

the water-absorbable resin powder having a degree of whiteness of 68 or more [WB value] as measured with use of a spectral colorimeter.

2. The water-absorbable resin powder as set forth in claim 1 , containing a surfactant and/or a dispersing agent inside thereof, wherein:
the water-absorbable resin powder has a surface tension of 60 [mN/m] or greater, and a particle surface being coated with a/the surfactant.

3. The water-absorbable resin powder as set forth in claim 1 , wherein a saline flow conductivity thereof is 20 [×10 −7 ·cm 3 ·sec·g −1 ] or greater, and a water absorbing rate (FSR) thereof is 0.25 [g/g/sec] or greater.

4. The water-absorbable resin powder as set forth in claim 1 , wherein an absorbency without pressure (CRC) thereof is 25 [g/g] or more, and an absorbency against pressure (AAP) under load of 50 [g/cm 2 ] thereof is 15 [g/g] or more.

5. The water-absorbable resin powder as set forth in claim 1 , wherein an absorbency without pressure (CRC) thereof is 25 [g/g] or more, and a saline flow conductivity thereof is 20 [×10 −7 ·cm 3 ·sec·g −1 ] or greater.

6. The water-absorbable resin powder as set forth in claim 1 , further comprising:
one or more kinds of permeability improving agents selected from the group consisting of multivalent metal cations, polyamine polymers and water insoluble fine particles.

7. The water-absorbable resin powder as set forth in claim 1 , further comprising a surfactant.

8. The water-absorbable resin powder as set forth in claim 1 , further comprising p-methoxy phenol by 5 ppm to 60 ppm.

9. The water-absorbable resin powder as set forth in claim 1 , further comprising one or more kinds of additives selected from the group consisting of chelating agents, α-hydroxy carboxylic acids, and inorganic or organic reducing agents.

10. The water-absorbable resin powder as set forth in claim 1 , wherein
a water absorbing rate index there of is 90 or more, water absorbing rate index being defined by the following equation:
(Water Absorbing Rate Index)=(FSR [g/g/sec])×(Bulk Specific Gravity [g/cm 3 ])×(Weight Average Particle Diameter [μm]),

where FSR is a water absorbing rate for saline so as to swell 20-fold, and
a bulk specific gravity thereof is in a range of 0.6 to 0.8 [g/cm 3 ].

11. The water-absorbable resin powder as set forth in claim 1 , wherein a surface tension thereof is 60 [mN/m] or greater.

12. The water-absorbable resin powder as set forth in claim 1 , wherein a bulk specific gravity thereof is in a range of 0.58 to 0.80 [g/cm 3 ].

Assignees

• Nakatsuru Reiko
• Sakamoto Shigeru
• Torii Kazushi
• Takaai Toshihiro
• Nippon Catalytic Chem Ind

Inventors

• Nakatsuru Reiko
• Sakamoto Shigeru
• Torii Kazushi
• Takaai Toshihiro

Classifications

• C08F20/06

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title

• C08F220/06

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title

• C08J2333/08

  Homopolymers or copolymers of acrylic acid esters · CPC title

• C08J2333/10

  Homopolymers or copolymers of methacrylic acid esters · CPC title

• A61L15/60

  Liquid-swellable gel-forming materials, e.g. super-absorbents · CPC title