Abstract: A particulate water absorbing agent of the present invention is a water absorbing agent containing a water absorbing resin as a main component, the particulate water absorbing agent containing a polyvalent metal cation and satisfying: (1) the polyvalent metal cation is contained in an amount between 0.001 wt % and 5 wt % relative to the amount of the water absorbing agent; (2) an absorbency without pressure (CRC) is not less than 28 (g/g) and an absorbency against pressure (AAP 4.83 kPa) is not less than 10 (g/g); (3) the absorbency against pressure and the absorbency without pressure satisfy 77?AAP (4.83 kPa)+1.8×CRC?100; and (4) a moisture content of the water absorbing agent is between 5 wt % and 20 wt %. This provides a water absorbing agent which has blocking resistance after moisture absorption, is excellent in stability to shock and suppresses Re-Wet when used in a diaper.

Abstract: Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production at 1 t/hr or more, the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved.

Abstract: A process for producing a water absorbent resin is provided with which it is possible to efficiently and inexpensively obtain a surface-crosslinked water-absorbing resin having excellent material properties, while ensuring high productivity. In continuous production scaled up to a large scale (in particular, 1 t/hr or more), the physical properties are improved and stabilized (for example, a reduction in standard deviation of the physical properties) by a surface crosslinking treatment to further improve absorption against pressure (AAP) and saline flow conductivity (SFC).

Abstract: A method for producing a polyacrylic water-absorbent resin powder includes the steps of: producing an acrylic monomer solution in which gas is dissolved and/or dispersed; polymerizing the monomer solution in the absence of a surface active agent or in the presence of not more than 300 ppm of a surface active agent; during or after polymerizing, fragmenting the resulting hydrated gel crosslinked polymer; and drying the fragmented hydrated gel crosslinked polymer, the gas being dissolved and/or dispersed in the monomer solution by (a) applying pressure to the acrylic monomer solution and the gas; (b) creating swirling flows of the acrylic monomer solution and the gas; or (c) introducing the gas with the acrylic monomer solution via fine holes. The production method efficiently produces a water-absorbent resin having an excellent water-absorption rate without deteriorating a liquid-absorbent property of a sanitary product or the like.

Abstract: A production method for a water-absorbent resin, comprising a polymerization step for obtaining hydrogel by subjecting a monomer aqueous solution to a polymerization reaction, and a drying step for drying the hydrogel, wherein drying in the drying step is performed using a continuous through-flow belt-type drying machine, the solid content of the hydrogel supplied to the drying step is 35% by weight or more, and thickness variation rate (1) represented by the following EXPRESSION 1 of the hydrogel loaded onto through-flow belt in the continuous through-flow belt, is 1.05 to 5: [MATH. 1] Thickness variation rate (1)=(Maximum thickness of hydrogel in a width direction of the through-flow belt)/(Average thickness of hydrogel in a width direction of the through-flow belt).

Abstract: A production method for a water-absorbent resin, comprising a polymerization step for obtaining hydrogel by subjecting a monomer aqueous solution to a polymerization reaction, and a drying step for drying the hydrogel, wherein drying in the drying step is performed using a continuous through-flow belt-type drying machine, the pore opening rate of the through-flow belt in the continuous through-flow belt-type drying machine is 20 to 50%, the solid content of the hydrogel supplied to the drying step is 35% by weight or more, and the area occupancy rate of the hydrogel is 85 to 100% relative to the through-flow belt.

Abstract: A method for producing a polyacrylic water-absorbent resin powder includes the steps of: producing an acrylic monomer solution in which gas is dissolved and/or dispersed; polymerizing the monomer solution in the absence of a surface active agent or in the presence of not more than 300 ppm of a surface active agent; during or after polymerizing, fragmenting the resulting hydrated gel crosslinked polymer; and drying the fragmented hydrated gel crosslinked polymer, the gas being dissolved and/or dispersed in the monomer solution by (a) applying pressure to the acrylic monomer solution and the gas; (b) creating swirling flows of the acrylic monomer solution and the gas; or (c) introducing the gas with the acrylic monomer solution via fine holes. The production method efficiently produces a water-absorbent resin having an excellent water-absorption rate without deteriorating a liquid-absorbent property of a sanitary product or the like.

Abstract: A method for being capable of sufficiently exerting property improvement effect by the addition of additive particles other than water-absorbing resin to water-absorbing resin particles. The problems can be solved by using additive particles having over cohesive particles in an amount equal to or less than a predetermined amount, or by using the additive particles by crushing or classifying in advance, before mixing with water-absorbing resin particles. Alternatively, the problem can be solved by subjecting a mixture of the water-absorbing resin particles and the additive particles to pneumatic transportation processing, in particular, in a heated state, after mixing or at the same time as mixing. Further, provided is a water-absorbing resin composition, which is capable of stably exerting high-level property. The problems can be solved by a water-absorbing resin composition, where the addition amount of additive particles and amount of free additive particles satisfies a predetermined relation.

Abstract: Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production at 1 t/hr or more, the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved.

Abstract: A water absorbent resin having less fine powder or powdery dust and a controlled particle size is provided, and the water absorption rate of the water absorbent resin is increased by a simple method at low cost, while maintaining or improving other physical properties such as liquid permeability.

Abstract: The purpose of the present invention is to provide a method for producing a water absorbent resin in which a water absorbent resin having excellent properties can be obtained effectively.

Abstract: The present invention provides a method for being capable of sufficiently exerting property improvement effect by the addition of additive particles other than water-absorbing resin to water-absorbing resin particles. The problems can be solved by using additive particles having over cohesive particles in an amount equal to or less than a predetermined amount, or by using the additive particles by crushing or classifying in advance, before mixing with water-absorbing resin particles. Alternatively, the problem can be solved by subjecting a mixture of the water-absorbing resin particles and the additive particles to pneumatic transportation processing, in particular, in a heated state, after mixing or at the same time as mixing. Further, the present invention provides a water-absorbing resin composition, which is capable of stably exerting high-level property.

Abstract: From a view pint of decreasing an out of spec product after surface crosslinking, particularly, when an alkylene carbonate compound is used as a surface crosslinking agent, influence due to an air temperature is great, and it is necessary to reduce ethylene glycol which is produced as a byproduct. There is provided a process for producing a polyacrylic acid (salt)-based water absorbent resin powder, comprising storing a non-polymerized organic compound being a raw material (modified raw material) of a water absorbent resin powder in a heated state, thereafter, mixing the non-polymerized organic compound with other compound at a predetermined ratio and, further, mixing the mixture into a water absorbent resin powder.

Abstract: From a viewpoint of reduction in an out of spec product after surface crosslinking, particularly, when an alkylene carbonate compound is used as a surface crosslinking agent, influence by an air temperature is great, and it is necessary to reduce ethylene glycol which is produced as a byproduct, and there is provided a process for producing a polyacrylic acid (salt)-based water absorbent resin powder, comprising a step of polymerizing an aqueous acrylic acid (salt)-based monomer solution, a step of drying the resulting polymer, an optional grinding•classifying step, and a surface crosslinking step, wherein in the surface crosslinking step, (1) a surface crosslinking agent containing an alkylene carbonate compound and a polyhydric alcohol compound is mixed into a water absorbent resin powder, the mixture is heat-reacted and, further, simultaneously with, or separately from the mixing, an ion reactive surface crosslinking agent is mixed, and/or (2) mixing treatment of mixing a surface crosslinking agent solu

Abstract: A method includes the steps of: adding an organic surface cross-linking agent to a water absorbent resin having a cross-linked structure; adding a liquid permeability improving agent to the water absorbent resin concurrently with or after the addition of the organic surface cross-linking agent; and then adding a lubrication improving agent to the water absorbent resin. This provides a particulate water absorbing agent and a method for producing it, the particulate water absorbing agent being suitable for pneumatic transportation, suffering no decrease in the effect of the liquid permeability improving agent, and excelling in properties such as fluidity and damage resistance after the pneumatic transportation.

Abstract: Provided is a method which does not require alteration of the raw materials or high capital investment, and improves and stabilizes the physical property (for example, liquid permeability) of a water absorbent resin by means of a simple technique. A method for producing a water absorbent resin is disclosed, which method includes a polymerization step of polymerizing an aqueous solution of acrylic acid (salt) to obtain a water-containing gel-like crosslinked polymer; a drying step of drying the water-containing gel-like crosslinked polymer to obtain a water absorbent resin powder; a classification step of classifying the water absorbent resin powder; and a surface crosslinking step of surface crosslinking the water absorbent resin powder, wherein in the classification steps that are carried before the surface crosslinking step and/or after the surface crosslinking step, the stretch tension (tension) of the metal sieve mesh used in the classification step is from 35 [N/cm] to 100 [N/cm].

Abstract: A method for the production of a water-absorbing resin is to be provided which permits enhancement and stabilization of property, for example, liquid permeability, of a water-absorbing resin by a simple and convenient method without requiring change of raw materials or expensive facility investment. The method comprises a polymerization step for polymerizing an aqueous solution of acrylic acid (or salt thereof) to obtain a hydrogel cross-linked polymer; a drying step for drying the hydrogel cross-linked polymer to obtain a water-absorbing resin powder; a classification step for classifying the water-absorbing resin powder; and a surface cross-linking step for surface cross-linking the water-absorbing resin powder before or after the classification step, wherein electricity is eliminated in the classification step.

Abstract: A water absorbent resin having less fine powder or powdery dust and a controlled particle size is provided, and the water absorption rate of the water absorbent resin is increased by a simple method at low cost, while maintaining or improving other physical properties such as liquid permeability.

Abstract: There is provided a production method for a water-absorbing resin for stably and continuously producing the water-absorbing resin with industrially high property, in particular, the water-absorbing resin with high liquid permeation. A method of the present invention relates to a production method for a water-absorbing resin including: a polymerization step of an aqueous solution of an unsaturated monomer; a drying step of the resultant hydrogel polymer; and a surface cross-linking step after drying; characterized by including a pneumatic transportation step for pneumatic transporting the water-absorbing resin powder substance in a pipeline with a surface roughness (Rz) of the inner surface of equal to or smaller than 800 nm, by using gas with a dew point of ?5° C. to ?100° C.

Abstract: A method of enhancing and stabilizing the physical property (for example, liquid permeability) of a water absorbent resin by means of a simple technique without requiring any alteration of the raw materials or high capital investment, is provided. Disclosed is a method for producing a water absorbent resin, which includes a polymerization step of polymerizing an aqueous solution of acrylic acid (salt) to obtain a water-containing gel-like crosslinked polymer; a drying step of drying the water-containing gel-like crosslinked polymer, to obtain a water absorbent resin powder; a classification step of classifying the water absorbent resin powder; and a surface crosslinking step of surface crosslinking the water absorbent resin powder, wherein in the classification step that is carried out before the surface crosslinking step and/or after the surface crosslinking step, a tapping material is installed below the metal sieve mesh used in the classification step, and thereby classification is carried out.