Gel pulverization device, method for manufacturing polyacrylic acid (polyacrylate) superabsorbent polymer powder, and superabsorbent polymer powder

Patent metadata

Field	Value
Publication number	US-2016199529-A1
Application number	US-201414914150-A
Country	US
Kind code	A1
Filing date	Aug 28, 2014
Priority date	Aug 28, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

Provided is a water absorbent resin that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having a higher liquid permeability and a higher water absorbing speed. Further provided is a water absorbent resin powder that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having increased in absorbency of a liquid and in heat retaining property. A gel grinding device to be used to produce a water absorbent resin, includes: a screw; a feed opening; an extrusion opening; a porous plate; and a barrel, the barrel including a return preventing member provided on an inner surface thereof, and the return preventing member satisfying at least one of specific parameters.

First claim

1 . A gel grinding device to be used to produce a water absorbent resin, comprising:
a screw; a feed opening; an extrusion opening; a porous plate; and a barrel, the barrel including at least one return preventing member provided on an inner surface thereof, and the barrel satisfying at least one of the following (1) and (2): (1) 0.05≦YH/N≦0.25; and (2) 0.05≦YF/N≦0.25 where YH is a height of the at least one return preventing member which height is obtained by cutting the barrel in a direction vertical to a direction in which a gel of the water absorbent resin is extruded; YF is a width of a top surface of the at least one return preventing member, the width being along a direction vertical to a direction in which the at least one return preventing member extends; and N is a diameter of an inner part of the barrel which diameter does not include the at least one return preventing member.

2 . The gel grinding device as set forth in claim 1 , wherein the at least one return preventing member is helically provided on the inner surface of the barrel.

3 . The gel grinding device as set forth in claim 1 , wherein the at least one return preventing member is provided on the inner surface of the barrel so as to be parallel to the screw.

4 . The gel grinding device as set forth in claim 1 , wherein the at least one return preventing member includes return preventing members which are wound from the feed opening to the extrusion opening of the gel grinding device and whose number ranges from one to seven.

5 . The gel grinding device as set forth in claim 1 , wherein the barrel and the porous plate are made of respective different materials.

6 . The gel grinding device as set forth in claim 1 5 , wherein the barrel is made of austenitic stainless steel.

7 . The gel grinding device as set forth in claim 1 , wherein the water absorbent resin is a polyacrylic acid (salt)-based water absorbent resin.

8 . A method for producing a polyacrylic acid (salt)-based water absorbent resin powder, comprising:
a polymerization step of polymerizing an acrylic acid (salt)-based monomer aqueous solution; a gel grinding step, carried out during or after the polymerization, of carrying out gel grinding with respect to a hydrogel-like crosslinked polymer; and a drying step carried out after the gel grinding, in the gel grinding step, the hydrogel-like crosslinked polymer being ground by use of a gel grinding device recited in claim 1 , the hydrogel-like crosslinked polymer having a resin solid content of 10 wt % to 80 wt %.

9 . The method as set forth in claim 8 , wherein T/N 3 ranges from 0.05 to 2.0 where T is an amount [g/hr] in which the gel grinding device treats a hydrogel per hour and T/N 3 is a treatment amount-to-inner diameter ratio [g/hr/mm 3 ] that is a treatment amount per unit time of the gel grinding device.

10 . The method as set forth in claim 8 , wherein the hydrogel-like crosslinked polymer which is obtained in the gel grinding step and is particulate is dried under a condition where a through-flow belt-type dryer is used, a drying temperature is 150° C. to 250° C., and hot air blows in a vertical direction (an up-and-down direction) at an air velocity of 0.8 [m/s] to 2.5 [m/s].

11 . The method as set forth in claim 8 , wherein the barrel of the gel grinding device has a temperature of 40° C. to 120° C. while the gel grinding step is being carried out.

12 . A water absorbent resin powder comprising a polyacrylic acid (salt)-based water absorbent resin as a main component,
the water absorbent resin powder satisfying the following (A) to (C): (A) the water absorbent resin powder containing particles smaller than 150 μm in a ratio of 0 mass % to 4.5 mass % before an impact resistance test, and the water absorbent resin powder containing, in a ratio of 0 mass % to 4.5 mass %, particles smaller than 150 μm and increased by the impact resistance test; (B) the water absorbent resin powder having a saline flow conductivity (SFC) of not less than 10; and (C) the water absorbent resin powder having a thermal conductivity of not more than 125 [mW/(m·K)].

13 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder has an absorption capacity under load (AAP) of not less than 20 [g/g].

14 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder has an internal gas bubbles ratio of 0% to 3.7%, the internal gas bubbles ratio being specified by the following equation:
(internal gas bubbles ratio) [%]={(true density)−(apparent density)}/(true density)×100

15 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder contains at least one of a multivalent metal salt and inorganic microparticles.

16 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder has a mass average particle diameter D50 of 350 μm to 460 μm, or the water absorbent resin powder has a particle size distribution having a logarithmic standard deviation of 0.25 to 0.45.

17 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder contains, in a ratio of not more than 36 mass %, particles that pass through a sieve having a mesh size of 710 μm and do not pass through a sieve having a mesh size of 500 μm.

18 . The water absorbent resin powder as set forth in claim 12 , wherein the water absorbent resin powder has a surface tension of not less than 69.0 [mN/m].

Assignees

• Nippon Catalytic Chem Ind

Inventors

• Torii Kazushi
• Omori Kohei
• Tanaka Nobuya
• Sakamoto Shigeru
• Tada Kenji
• Sato Hironori

Classifications

• B29B7/429

  Screws (B29B7/421 takes precedence) · CPC title

• B29B7/422

  with screw sections co-operating, e.g. intermeshing, with elements on the wall of the surrounding casing · CPC title

• B29B7/428

  Parts or accessories, e.g. casings, feeding or discharging means · CPC title

• C08J3/075

  Macromolecular gels · CPC title

• B01J2220/68

  Superabsorbents · CPC title