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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An apparatus (2) includes a neutralization tank (3), a pump (4), a heat exchanger (6), a line mixer (8), a polymerizer (10), a first pipe (12), a second pipe (14), a third pipe (16), a fourth pipe (18), and a fifth pipe (20). Continuously supplied into the neutralization tank (3) 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 (12), the pump (4), the second pipe (14), the heat exchanger (6), and the third pipe (16). The mixture solution is supplied to the polymerizer through the fourth pipe (18).

Abstract: 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.

Abstract: 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.

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.

Abstract: 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° C. to not more than 200° C. and a second or subsequent room at not less than 100° C. to not more than 220° 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).

Abstract: 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.

Abstract: An apparatus (2) includes a neutralization tank (3), a pump (4), a heat exchanger (6), a line mixer (8), a polymerizer (10), a first pipe (12), a second pipe (14), a third pipe (16), a fourth pipe (18), and a fifth pipe (20). Continuously supplied into the neutralization tank (3) 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 (12), the pump (4), the second pipe (14), the heat exchanger (6), and the third pipe (16). The mixture solution is supplied to the polymerizer through the fourth pipe (18).

Abstract: Drying is performed in a continuous fluidized bed having at least two drying rooms. Drying is performed after pulverization is performed between drying in a first drying room and drying in a second or subsequent room. Drying is performed in a continuous fluidized bed whose fluidized bed contains a heat transfer tube. The second or subsequent drying room has a higher drying temperature than the first drying room. Drying is performed with the drying temperature of the first drying room falling within a range of not less than 80° C. to not more than 200° C. and with the drying temperature of the second or subsequent drying room falling within a range of not less than 100° C. to not more than 220° C.

Abstract: 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 “moisture content of 2 to 10% by weight” 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.

Abstract: 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 “moisture content of 2 to 10% by weight” 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.