Abstract: To provide a disposable diaper enabling reduction in re-wet amount and having an excellent speed of incorporating liquid regardless of concentration and configuration of a water-absorbing agent in an absorbent material. A water-absorbing agent having excellent Gel Capillary Absorption (GCA) and Free Gel Bed Permeability (FGBP) is obtained by crushing a crosslinked hydrogel polymer obtained in a polymerization step to have a specific weight average particle diameter while fluid retention capacity and a surface tension of a water-absorbing agent are adjusted in a specific range, drying the crushed crosslinked hydrogel polymer, and then adding a liquid permeability enhancer thereto during surface crosslinking or after surface crosslinking.

Abstract: Provided is a production method for a water-absorbing resin in which an absorption capacity without pressure of the resulting water-absorbing resin is high and a water-absorbing resin can be efficiently obtained. The production method for a water-absorbing resin including a polymerization step of polymerizing a monomer composition containing an internal crosslinking agent and a monomer to obtain a crosslinked hydrogel polymer, and a drying step of drying the crosslinked hydrogel polymer to obtain a dry polymer, in which the crosslinked hydrogel polymer to be subjected to the drying step contains 50 ppm or more of hydrogen peroxide with respect to the solid content mass of the crosslinked hydrogel polymer, and the crosslinked hydrogel polymer is heated during the drying step so that a maximum reaching temperature of the crosslinked hydrogel polymer exceeds 160° C., and/or the dry polymer is heated after the drying step so that a maximum reaching temperature of the dry polymer exceeds 160° C.

Abstract: [Object] To provide a method for efficiently producing a water-absorbing agent having excellent physical properties. [Solution] The method for producing a water-absorbing agent includes a drying step of drying a particulate crosslinked hydrogel polymer containing a drying aid. The drying aid is (a) a compound having a betaine structure and having a long-chain alkyl group having 8 or more carbon atoms, one quaternary nitrogen, and one acid group within a molecule thereof and/or (b) a compound having a long-chain alkyl group having 8 or more carbon atoms, one tertiary nitrogen, and one or more acid groups within a molecule thereof. An addition amount of the drying aid with respect to a gel solid content of the particulate crosslinked hydrogel polymer is 0.001% by mass to 0.5% by mass. In this production method, surface-crosslinking is performed on water-absorbent resin powder obtained through the drying step.

Abstract: The production method includes a drying step of drying a particulate crosslinked hydrogel polymer obtained by polymerizing a monomer, which is a material of a water-absorbent resin, using a heating device to obtain dried particles. The heating device includes: a rotary container that contains the particulate crosslinked hydrogel polymer therein and rotates; and a plurality of heating tubes that are located within the rotary container, extend in an axial direction of the rotary container, and rotate together with the rotary container. A gel temperature of the particulate crosslinked hydrogel polymer to be subjected to the drying step, the gel temperature being measured by a contact thermometer, is not lower than 50° C.

Abstract: To provide a disposable diaper enabling reduction in re-wet amount and having an excellent speed of incorporating liquid regardless of concentration and configuration of a water-absorbing agent in an absorbent material. A water-absorbing agent having excellent Gel Capillary Absorption (GCA) and Free Gel Bed Permeability (FGBP) is obtained by crushing a crosslinked hydrogel polymer obtained in a polymerization step to have a specific weight average particle diameter while fluid retention capacity and a surface tension of a water-absorbing agent are adjusted in a specific range, drying the crushed crosslinked hydrogel polymer, and then adding a liquid permeability enhancer thereto during surface crosslinking or after surface crosslinking.

Abstract: To provide a disposable diaper enabling reduction in re-wet amount and having an excellent speed of incorporating liquid regardless of concentration and configuration of a water-absorbing agent in an absorbent material. A water-absorbing agent having excellent Gel Capillary Absorption (GCA) and Free Gel Bed Permeability (FGBP) is obtained by crushing a crosslinked hydrogel polymer obtained in a polymerization step to have a specific weight average particle diameter while fluid retention capacity and a surface tension of a water-absorbing agent are adjusted in a specific range, drying the crushed crosslinked hydrogel polymer, and then adding a liquid permeability enhancer thereto during surface crosslinking or after surface crosslinking.

Abstract: The production method includes: a gel-crushing step of grinding a crosslinked hydrogel polymer to obtain a particulate crosslinked hydrogel polymer; a heating drying step of obtaining dried particles from the particulate crosslinked hydrogel polymer by using a continuous stirring drying machine; a post-crosslinking step of post-crosslinking the particulate crosslinked hydrogel polymer or the dried particles; and a sizing step of adjusting a particle size of the dried particles or the post-crosslinked dried particles to obtain water-absorbent resin powder. The particulate crosslinked hydrogel polymer contains a gel fluidizer. A gel temperature of the particulate crosslinked hydrogel polymer containing the gel fluidizer, the gel temperature being measured by a contact thermometer, is not lower than 50° C. In the production method, the dried particles or the post-crosslinked dried particles is forcedly cooled before the sizing step.

Abstract: A production method includes a surface-crosslinking step of heating a mixture of a surface-crosslinking agent and a particulate dried polymer obtained with an acid group-containing unsaturated monomer as a main component. A moisture content of the particulate dried polymer is not greater than 15% by mass. A heating device including a rotary container and a plurality of heating tubes that are located within the rotary container, extend in an axial direction of the rotary container, and rotate together with the rotary container, is used in the surface-crosslinking step. The heating device includes a means for introducing and discharging a gas into and from the rotary container.

Abstract: The present invention addresses the problem of providing; a water absorbent resin powder having a reduced amount of fine powder generated and a reduced amount of fine powder recovered; and a production method for the water absorbent resin. The production method of the present invention includes a drying step and a fine powder granulation step. The drying step is for obtaining a dried polymer by drying a particulate water-containing gel crosslinked polymer which is obtained using an acid group-containing unsaturated monomer as a main component. The fine powder granulation step is for obtaining a fine powder granulated product by adding a binder and an adhesion control agent to a fine powder made of a water absorbent resin. In this production method, the obtained fine powder granulated product is recovered in the drying step or in any step before the drying step.

Abstract: The production method includes a drying step of drying a particulate crosslinked hydrogel polymer obtained by polymerizing a monomer, which is a material of a water-absorbent resin, using a heating device to obtain dried particles. The heating device includes: a rotary container that contains the particulate crosslinked hydrogel polymer therein and rotates; and a plurality of heating tubes that are located within the rotary container, extend in an axial direction of the rotary container, and rotate together with the rotary container. A gel temperature of the particulate crosslinked hydrogel polymer to be subjected to the drying step, the gel temperature being measured by a contact thermometer, is not lower than 50° C.

Abstract: The production method includes: a gel-crushing step of grinding a crosslinked hydrogel polymer to obtain a particulate crosslinked hydrogel polymer; a heating drying step of obtaining dried particles from the particulate crosslinked hydrogel polymer by using a continuous stirring drying machine; a post-crosslinking step of post-crosslinking the particulate crosslinked hydrogel polymer or the dried particles; and a sizing step of adjusting a particle size of the dried particles or the post-crosslinked dried particles to obtain water-absorbent resin powder. The particulate crosslinked hydrogel polymer contains a gel fluidizer. A gel temperature of the particulate crosslinked hydrogel polymer containing the gel fluidizer, the gel temperature being measured by a contact thermometer, is not lower than 50° C. In the production method, the dried particles or the post-crosslinked dried particles is forcedly cooled before the sizing step.

Abstract: [Object] To provide a method for efficiently producing a water-absorbing agent having excellent physical properties. [Solution] The method for producing a water-absorbing agent includes a drying step of drying a particulate crosslinked hydrogel polymer containing a drying aid. The drying aid is (a) a compound having a betaine structure and having a long-chain alkyl group having 8 or more carbon atoms, one quaternary nitrogen, and one acid group within a molecule thereof and/or (b) a compound having a long-chain alkyl group having 8 or more carbon atoms, one tertiary nitrogen, and one or more acid groups within a molecule thereof. An addition amount of the drying aid with respect to a gel solid content of the particulate crosslinked hydrogel polymer is 0.001% by mass to 0.5% by mass. In this production method, surface-crosslinking is performed on water-absorbent resin powder obtained through the drying step.

Abstract: To provide a disposable diaper enabling reduction in re-wet amount and having an excellent speed of incorporating liquid regardless of concentration and configuration of a water-absorbing agent in an absorbent material. A water-absorbing agent having excellent Gel Capillary Absorption (GCA) and Free Gel Bed Permeability (FGBP) is obtained by crushing a crosslinked hydrogel polymer obtained in a polymerization step to have a specific weight average particle diameter while fluid retention capacity and a surface tension of a water-absorbing agent are adjusted in a specific range, drying the crushed crosslinked hydrogel polymer, and then adding a liquid permeability enhancer thereto during surface crosslinking or after surface crosslinking.