Nippon Shokubai Co., Ltd.

Toshihiro Takaai

Shinichi Fujino

Hidenori Wada

Yorimichi Dairoku

Satoshi Matsumoto

Kazushi Torii

Katsuyuki Wada

Makoto Matsumoto

Shigeru Sakamoto

Yasuhisa Nakashima

Reiko Nakatsuru

Seiji Kato

Sinichi Fujino

Yorichimi Dairoku

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.)

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

In a method for producing a water absorbent resin by drying a particulate hydrogel having a high solid content concentration (of 45% by weight or more, preferably 50% by weight or more, and more preferably 55% by weight or more), a method for efficient drying water absorbent resin having maintained/improved physical properties is provided. Disclosed is a method for producing a water absorbent resin, comprising: a polymerization step to polymerize an unsaturated monomer, and; a drying step to dry a particulate hydrogel crosslinked polymer, which is obtained by micronization of a hydrogel polymer during or after the polymerization and which has a solid content concentration of 45% by weight or more, wherein, an amount of a peroxide in the particulate hydrogel crosslinked polymer to be dried in the drying step is 1 to 100 ppm relative to the weight of the solid content of the particulate hydrogel crosslinked polymer, and a drying temperature of the particulate hydrogel crosslinked polymer in the drying step is 160&#xb0; C. or more.

Method for producing water absorbent resin

Provided is a method for producing a water absorbent resin, which promotes the formation of interconnected voids (continuous gas bubbles) in a foamed polymer (foam-like water absorbent resin) by a more convenient method, and produces with high efficiency a water absorbent resin which exhibits a high water absorption rate even when stepped into a sheet form or a powder form in hygiene articles and the like. Disclosed is a method for producing a polyacrylic acid-type water absorbent resin, comprising (A) a step of obtaining an aqueous solution of acrylic acid-type monomers containing gas bubbles dispersed therein; (B) a step of polymerizing the aqueous monomer solution and thereby obtaining a foamed polymer; and (C) a step of heating and drying the foamed polymer,

Polyacrylic acid-type water absorbent resin and method for producing same

A production of a water-absorbent resin by which a particle diameter of the water-absorbent resin can be controlled simply and conveniently, and a content of fine powder can be decreased, without necessity of change of raw materials or expensive facility investment is to be provided. The method is a continuous production method of a polyacrylic acid (salt)-based water-absorbent resin, comprising a polymerization step of an aqueous solution containing acrylic acid (salt), a drying step of the resultant hydrogel-like polymer, a pulverization step of the dried substance, a classification step of the pulverized substance, and optionally a surface cross-linking step of the classified substance, wherein (a) the drying step and the pulverization step are connected via a storage step and a transportation step; and (b) a time of holding the dried substance from a time of completing the drying step to a time of starting the pulverization step is set at 3 minutes or longer.

Method for producing particulate water-absorbent resin

Provided is a method for producing a water absorbent resin, which promotes the formation of interconnected voids (continuous gas bubbles) in a foamed polymer (foam-like water absorbent resin) by a more convenient method, and produces with high efficiency a water absorbent resin which exhibits a high water absorption rate even when stepped into a sheet form or a powder form in hygiene articles and the like. Disclosed is a a method for producing a polyacrylic acid-type water absorbent resin, comprising (A) a step of obtaining an aqueous solution of acrylic acid-type monomers containing gas bubbles dispersed therein; (B) a step of polymerizing the aqueous monomer solution and thereby obtaining a foamed polymer; and (C) a step of heating and drying the foamed polymer,

With regard to a method for producing a water absorbent resin by drying a particulate hydrogel crosslinked polymer having a high solid content concentration (of 45% by weight or more, further 50% by weight or more, and particularly 55% by weight or more), to provide a method for efficient drying of a water absorbent resin having maintained/improved physical properties. A production method in which a through-circulation belt type dryer or a through-circulation stationary batch type dryer is used in the drying step and the drop and scatter ratio of a particulate hydrogel crosslinked polymer is set to 1% by weight or less.

An apparatus () includes a neutralization tank (), a pump (), a heat exchanger (), a line mixer (), a polymerizer (), a first pipe (), a second pipe (), a third pipe (), a fourth pipe (), and a fifth pipe (). Continuously supplied into the neutralization tank () are a monomer aqueous solution and a basic aqueous solution, so as to prepare a mixture solution. The mixture solution is circulated through the first pipe (), the pump (), the second pipe (), the heat exchanger (), and the third pipe (). The mixture solution is supplied to the polymerizer through the fourth pipe (). The apparatus () satisfies a requirement that a value X is not more than 200, which value X is found according to the following expression: 'X=(V/F)&#xb7;A', wherein V is a volume of the mixture solution present in a neutralization system, F is a flow volume of the mixture solution to be supplied to a polymerization system, and A is a contact area of the mixture solution present in the neutralization system with a device(s) and a pipe(s) constituting the neutralization system. With this arrangement, it is possible to provide a water absorbent resin having superior whiteness.

Production method and production apparatus of particulate water absorbing agent containing water absorbent resin as main component

A water absorbent resin is dried in a continuous fluidized bed having a heat transfer tube and at least two drying rooms. Pulverization is performed between a first drying room at not less than 80&#xb0; C. to not more than 200&#xb0; C. and a second or subsequent room at not less than 100&#xb0; C. to not more than 220&#xb0; C. A method for producing a water absorbent resin includes: (1) polymerizing a monomer aqueous solution; (2) drying a hydrogel polymer of step (1); (3) performing particle size control of the dry polymer of the step (2); (5) surface crosslinking the water absorbent resin powder of step (3), and step (4) of performing a second heat drying on the water absorbent resin powder of step (3), preceding step (5). The water absorbent resin has a moisture content of 0 wt % to 3 wt % before the step (5).

Process for producing water-absorbing resin

The present invention provides a particulate water absorbing agent for absorbent cores which is excellent in powder conveying property, and achieves sufficient absorption performances for use in absorbent cores in particulate water absorbing agents including a water absorbing resin as a principal component, and which further is suitable for practical applications. In the present invention, characteristics that had not been known conventionally at all, i.e., 'permeability potential under pressure (PPUP)' and 'frictional charge being a positive charge' of the particulate water absorbing agent are regulated at a time, and furthermore, regulation of the &#x201c;moisture content of 2 to 10% by weight&#x201d; is perfected. Also, the particulate water absorbing agent including (A) a water-swelling crosslinked polymer having a constitutional unit derived from an unsaturated monomer containing an acid group and/or a salt thereof; and (B) water fulfills certain requirements.

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Himeji, Japan

Toshihiro Takaai