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: According to the present invention, the manufacturing method for the water absorbing resin involves the step of polymerizing a water-soluble unsaturated monomer, 0.06 of 5 mol % of which is composed of an internal crosslinking agent; and the step of drying a water-containing gel which has a thermally decomposing radical initiator content index of 40 to 100 at 100 to 250° C. The water absorbing resin of the present invention contains a water-soluble unsaturated monomer as a repeat unit for a major chain, 90 mol % of the monomer being composed of an acrylic acid and/or salt thereof, the resin having an internal crosslinking structure and exhibiting a weight-average molecular weight Mw of 360,000 to 1,000,000 daltons and an intrinsic viscosity IV of 2.1 to 6.0 dL/g where the weight-average molecular weight Mw and the intrinsic viscosity IV are measured after treatment under set 2 of hydrolysis conditions.

Abstract: A method for producing a water absorbent resin by (i) polymerizing a monomer including an unsaturated monomer containing a carboxyl group, in the presence of an internal cross-linking agent (A) having two or more radical polymerizable unsaturated groups and in the presence of a non-polymeric internal cross-linking agent (B) having two or more functional groups each allowing formation of an ester bond or an amide bond by reacting with a carboxyl group, while crushing a cross-linked polymer hydrogel; and (ii) drying the cross-linked polymer hydrogel of step (i), wherein: an amount of the internal cross-linking agent (A) is 0.01 mol % or more and 0.2 mol % or less relative to an amount of the unsaturated monomer containing a carboxyl group, and a molar ratio (B)/(A) of the internal cross-linking agent (A) and the non-polymeric internal cross-linking agent (B) is 0.01 or more and 1.8 or less.

Abstract: An object of the present invention is to provide a method for producing water absorbent resin powder in which permeability potential (SFC) is improved while a water absorbing rate (FSR) is being kept. The method is a method for producing water absorbent polyacrylic acid (salt) resin powder including the steps of: (i) polymerizing an acrylic acid (salt) monomer aqueous solution; (ii) during or after the step of (i), performing gel grinding of a hydrogel crosslinked polymer obtained by the polymerization, wherein the hydrogel crosslinked polymer has resin solid content of 10 wt % to 80 wt %, and the gel grinding is carried out with gel grinding energy (GGE) of 18 [J/g] to 60 [J/g]; (iii) drying a particulate hydrogel crosslinked polymer obtained by the gel grinding, wherein the drying is performed at 150° C. to 250° C.; and (iv) carrying out a surface treatment to the particulate hydrogel crosslinked polymer thus dried.

Abstract: A water absorbing agent of the present invention has an internal crosslinking structure obtained by polymerization of a water-soluble unsaturated monomer. The agent satisfies conditions (a) to (d): (a) the agent contains water-insoluble inorganic particles at an amount of from 10 ppm to 1,900 ppm inclusive; (b) the agent contains 5 mass % or less particles which have such a size that they can pass through a sieve having a mesh opening size of 150 ?m; (c) the agent has an absorbency against a pressure of 4.83 kPa (AAP) of 18 g/g or more; and (d) the water-insoluble inorganic particles reside on a surface of the water absorbing resin or near the surface.

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: The present invention provides a water absorbing agent, and a method for producing the water absorbing agent. The water absorbing agent includes water absorbent resin particles, an organic acid and/or salt thereof having carbon number of 10 or more and not more than 30 in its molecule, and a water-soluble polyvalent cation. The method includes the step (i) of mixing the water absorbent resin particles, the organic acid and/or salt thereof having carbon number of 10 or more and not more than 30 in its molecule, and the water-soluble polyvalent cation with one another.

Abstract: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is 1.10 to 1.

Abstract: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is larger than 1.

Abstract: To provide a water absorbing agent which is excellent in balance between absorbency and liquid permeability against pressure and is excellent in flowability at the time of moisture absorption. The water absorbing agent comprises water absorbent resin particles and an organic surface additive, wherein: the organic surface additive having (i) a reactive group for a functional group of a surface of each water absorbent resin particle and (ii) a hydrophobic group exists on the surface of the water absorbent resin particle, and the hydrophobic group has a hydrocarbon group whose carbon number is 8 or more, and a ratio of an oxyalkylene group in a molecular mass of the organic surface additive is 0 or more and 25 mass % or less.

Abstract: There are disclosed a water-absorbent resin composition and its production process, wherein the water-absorbent resin composition causes little gel-blocking and is excellent in the liquid permeability and liquid diffusibility and is high also in the absorption performances and further is strong also against the physical damage; and there are further disclosed a water-absorbent resin composition and its production process, wherein the water-absorbent resin composition has the following further advantages, in addition to the above, of involving little segregation of the metal compound and further having a dust prevention effect.

Abstract: A method for producing a polyacrylic acid (salt)-based water absorbent resin, sequentially including the steps of: storing or producing acrylic acid; mixing acrylic acid containing a polymerization inhibitor with water, a crosslinking agent, and optionally, a basic composition, and/or neutralizing them, to prepare an aqueous monomer solution; polymerizing the aqueous monomer solution; drying an obtained water-containing gel-like crosslinked polymer; and optionally carrying out surface crosslinking, wherein the acrylic acid containing the polymerization inhibitor has a water content of not higher than 1,000 ppm (by mass; the same applies hereinafter), and/or the aqueous monomer solution has a formic acid content of 1 to 700 ppm, relative to the monomer.

Abstract: A water absorbing agent of the present invention has an internal crosslinking structure obtained by polymerization of a water-soluble unsaturated monomer. The agent satisfies conditions (a) to (d): (a) the agent contains water-insoluble inorganic particles at an amount of from 10 ppm to 1,900 ppm inclusive; (b) the agent contains 5 mass % or less particles which have such a size that they can pass through a sieve having a mesh opening size of 150 ?m; (c) the agent has an absorbency against a pressure of 4.83 kPa (AAP) of 18 g/g or more; and (d) the water-insoluble inorganic particles reside on a surface of the water absorbing resin or near the surface.

Abstract: A method for producing a water absorbent resin by (i) polymerizing a monomer including an unsaturated monomer containing a carboxyl group, in the presence of an internal cross-linking agent (A) having two or more radical polymerizable unsaturated groups and in the presence of a non-polymeric internal cross-linking agent (B) having two or more functional groups each allowing formation of an ester bond or an amide bond by reacting with a carboxyl group, while crushing a cross-linked polymer hydrogel; and (ii) drying the cross-linked polymer hydrogel of step (i), wherein: an amount of the internal cross-linking agent (A) is 0.01 mol % or more and 0.2 mol % or less relative to an amount of the unsaturated monomer containing a carboxyl group, and a molar ratio (B)/(A) of the internal cross-linking agent (A) and the non-polymeric internal cross-linking agent (B) is 0.01 or more and 1.8 or less.

Abstract: A method for producing a water absorbent resin comprises the steps of: (i) polymerizing a monomer including an unsaturated monomer containing a carboxyl group, in the presence of an internal cross-linking agent (A) having two or more radical polymerizable unsaturated groups in its single molecule and in the presence of a non-polymeric internal cross-linking agent (B) having in its single molecule two or more functional groups each of which allows formation of an ester bond or an amide bond by reacting with a carboxyl group so as to obtain a cross-linked polymer hydrogel; (ii) crushing the cross-linked polymer hydrogel obtained in the step (i); and (iii) drying crushed cross-linked polymer hydrogel products obtained in the step (ii), wherein: an amount of the internal cross-linking agent (A) is 0.01 mol % or more and 0.

Abstract: The present invention provides a water absorbing agent, including: water absorbent resin particles; and a modified cationic polymer compound containing a primary amino group and/or a secondary amino group, the modified cationic polymer compound being obtained by reacting, with a modifying agent, a cationic polymer compound containing the primary amino group and/or the secondary amino group, and the modifying agent containing two or more carbon atoms continuously linked, and one reactive group which reacts with the primary amino group and/or the secondary amino group. The present invention further provides a method for producing a water absorbing agent including water absorbent resin particles, the method including the step (i) of mixing the water absorbent resin particles with a modified cationic polymer compound.

Abstract: An object of the present invention is to provide an aqueous-liquid-absorbing agent which comprises water-absorbent resin particles as essential components and is suitable for uses in sanitary materials. As a means of achieving this object, an aqueous-liquid-absorbing agent according to the present invention is an aqueous-liquid-absorbing agent comprising water-absorbent resin particles as essential components, wherein the water-absorbent resin particles are obtained by a process including the step of polymerizing a water-soluble ethylenically unsaturated monomer and have a crosslinked structure in their inside; with the aqueous-liquid-absorbing agent exhibiting an absorption rate (FSR) of not less than 0.2 g/g/s, a water absorption capacity (CRC) of 5 to 25 g/g, a saline flow conductivity (SFC) of not less than 400×10?7 cm3·s/g, and a wet porosity of not less than 20%.

Abstract: The production method of a water absorbent resin composition including a particulate water absorbent resin, wherein: 95 wt % or more of particles whose particle diameter is less than 850 ?m and not less, than 106 ?m are contained, and a weight average particle diameter of the particles is less than 500 ?m and not less than 300 ?m and a logarithmic standard deviation (??) of a particle size distribution is 0.45 or less, and a water-soluble component of the water absorbent composition is 35 wt % or less, and a multivalent metal component is contained, and an extraction rate of the multivalent metal component is 5.0 wt % or more and less than 100 wt %, thereby providing the water absorbent resin composition, free from any coagulation of particles in high humidity, which has superior absorbent property in terms of an absorbency and a diffusing absorbency under pressure.

Abstract: The present invention provides a water absorbing agent, and a method for producing the water absorbing agent. The water absorbing agent includes water absorbent resin particles, an organic acid and/or salt thereof having carbon number of 10 or more and not more than 30 in its molecule, and a water-soluble polyvalent cation. The method includes the step (i) of mixing the water absorbent resin particles, the organic acid and/or salt thereof having carbon number of 10 or more and not more than 30 in its molecule, and the water-soluble polyvalent cation with one another.

Abstract: The present invention provides a method for manufacturing a particulate water-absorbing agent which has excellent liquid diffusibility and liquid permeability, and whose amount of residual monomers is reduced. The method for manufacturing the particulate water-absorbing agent of the present invention includes a step of surface-crosslinking, in the presence of an organic crosslinking agent, water-absorbing resin particles obtained through at least a step of polymerizing an aqueous solution of unsaturated monomers, and in or after the polymerizing step, a reaction system is mixed with peroxide. Thus, it is possible to obtain the particulate water-absorbing agent which has excellent liquid diffusibility and liquid permeability and whose amount of residual monomers is small, that is, it is possible to obtain the particulate water-absorbing agent which is highly functional and highly safe.