Abstract: This invention is to provide a method for surface-treatment of a water absorbent resin excelling in water absorption properties. This invention relates to a method for the surface-treatment of a water absorbent resin, which comprises: a) mixing 100 parts by weight of a water absorbent resin, 0.01-20 parts by weight of at least one radical polymerization initiator selected from the group consisting of persulfates, hydrogen peroxide, and azo compounds, and a radically polymerizing compound and b) irradiating the resultant mixture with active energy rays. The treatment particularly exalts the absorption ratio against pressure and the saline flow conductivity.

Abstract: An object of the present invention is to provide a particulate water-absorbent resin composition and its production process, wherein the particulate water-absorbent resin composition is an enhanced one in both of the “liquid permeability” and “liquid-sucking-up property” (which have hitherto been antithetical physical properties) of the water-absorbent resin. As a means of achieving this object, a first particulate water-absorbent resin composition according to the present invention is a particulate water-absorbent resin composition comprising a water-absorbent resin (A) of a crosslinked structure obtained by polymerizing an acid-group-containing unsaturated monomer, with the composition being characterized by: having a particle size such that particles in the range of 850 to 150 ?m (but not including 850 ?m) account for not less than 90 weight % of the entirety; and containing a tetra- or more functional polyol (B) at least on surfaces.

Abstract: An object of the present invention is to provide a water absorbent having excellent gel properties and showing excellent properties when used in a water-absorbing material of a sanitary/hygienic material such as paper diaper. Moreover, another object of the present invention is to provide a water absorbent which is safe and excellent in liquid permeability, and in which an amount of liquid permeability improver for improving the liquid permeability is reduced. The water absorbent is made from a water-absorbing resin prepared by a specific polymerization method and having a high degree of cross-linking, a high liquid holding property and a high gel strength (its swelling pressure of gel layer of is 35 kdyne/cm2 or more). This water absorbent is further processed to have a particular particle size distribution (95 wt % or more of its particles are less than 850ƒÊm but not less than 106ƒÊm, and logarithmic standard deviation (ƒĐƒÄ) is in a range of 0.25 to 0.

Abstract: The present invention provides a water absorbing agent that is excellent in a balance between a centrifugal retention capacity (CRC) and a saline flow conductivity (SFC), and a method for producing the water absorbing agent. The method for producing the water absorbing agent, the method comprising mixing (i) a water absorbing resin (A) and (ii) a polymer (B) being a polyamine polymer having a hydroxyl group on a main chain provides a water absorbing agent containing (i) the water absorbing resin (A) and (ii) the polymer (B) being a polyamine polymer having a hydroxyl group on a main chain.

Abstract: An object of the present invention is to provide a water absorbent having excellent gel properties and showing excellent properties when used in a water-absorbing material of a sanitary/hygienic material such as paper diaper. Moreover, another object of the present invention is to provide a water absorbent which is safe and excellent in liquid permeability, and in which an amount of liquid permeability improver for improving the liquid permeability is reduced. The water absorbent is made from a water-absorbing resin prepared by a specific polymerization method and having a high degree of cross-linking, a high liquid holding property and a high gel strength (its swelling pressure of gel layer of is 35 kdyne/cm2 or more). This water absorbent is further processed to have a particular particle size distribution (95 wt % or more of its particles are less than 850ƒÊm but not less than 106ƒÊm, and logarithmic standard deviation (ƒĐƒÄ) is in a range of 0.25 to 0.

Abstract: A water-absorbing agent according to the present invention includes water-absorbent resin particles having an internal cross-linked structure, wherein a vicinity of a surface of the water-absorbent resin particle is cross-linked with a surface cross-linking agent, and the water-absorbent resin particle has therein a sea-island structure having (i) part containing a first water-soluble multivalent metal salt such as aluminum sulfate and (ii) part not containing the first water-soluble multivalent metal salt. With this arrangement, it is possible to provide a water-absorbing agent having less water-soluble component content, more excellent liquid permeability, and more excellent water retention under pressure than the conventional water-absorbing agent.

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, while crushing a cross-linked polymer hydrogel; and (ii) drying the cross-linked polymer hydrogel obtained in the 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: An object of the present invention is to provide a particle-shaped water absorbing agent having a remarkably improved surface color and excellent water-absorbing properties (better water absorption capacity, and lower water soluble content and residual monomer content) at the same time. In order to attain the object, a particle-shaped water absorbing agent according to the present invention is a particle-shaped water absorbing agent whose main component is a polyacrylic acid and/or a salt thereof, the particle-shaped water absorbing agent having a surface color of Hunter b value in a range of ?5 to 10, and having a cross-linking absorption property index (CPI) in a range of 1 to 100, the CPI defined by the following two equations: GEX=(GVs+17)/Ln (water soluble content)??Equation 1; CPI=(GEX/residual monomer content)×100??Equation 3 where GVs is gel volume in saline, Ln (water soluble content) is a logarithm natural of water soluble content.

Abstract: There is disclosed a water-absorbing agent which combines both performances of the capillary suction force and the liquid permeability. This water-absorbing agent is a particulate water-absorbing agent comprising water-absorbent resin particles (?) and a liquid-permeability-enhancing agent (?), wherein the water-absorbent resin particles (?) are surface-crosslink-treated particles of a crosslinked polymer of a monomer including acrylic acid and/or its salt; with the water-absorbing agent being characterized in that the particulate water-absorbing agent has: a mass-average particle diameter (D50) in the range of 234 to 394 gm, a logarithmic standard deviation (??) of a particle diameter distribution in the range of 0.25 to 0.45, an absorption capacity without load (CRC) of not less than 15 g/g, and a water-extractable component content of not higher than 15 mass %; and further a liquid-permeability-enhancing agent (?) content in the range of 0.

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: This invention is to provide a method for producing a modified water absorbent resin excelling in water absorbing properties. This invention relates to a method for producing a modified water absorbent resin, which comprises a) mixing a water absorbent resin and a water-soluble radical polymerization initiator or a heat-degradable radical polymerization initiator without addition of an ethylenically unsaturated monomer and b) irradiating the resultant mixture with active energy rays. The method is particularly capable of exalting the absorbency against pressure and the saline flow conductivity.

Abstract: This invention is to provide a method for surface-treatment of a water absorbent resin excelling in water absorption properties. This invention relates to a method for the surface-treatment of a water absorbent resin, which comprises: a) mixing 100 parts by weight of a water absorbent resin, 0.01-20 parts by weight of at least one radical polymerization initiator selected from the group-consisting of persulfates, hydrogen peroxide, and azo compounds, and a radically polymerizing compound and b) irradiating the resultant mixture with active energy rays. The treatment particularly exalts the absorption ratio against pressure and the saline flow conductivity.

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: The present invention provides: a novel water-absorbing agent, which exhibits an excellent absorption capacity under a load (AAP), gel layer liquid permeation rate under a load (FRUP), saline flow conductivity (SFC), and shape-maintaining property and ball burst strength (BBS) of a swollen water-absorbing agent aggregate, and excellent persistency of these effects for a long time. The water-absorbing agent, which comprises a polymer obtained by a process including the steps of polymerizing and then crosslinking a monomer including acrylic acid and/or a salt thereof, with the water-absorbing agent being characterized by: (1) exhibiting a free swelling capacity of not less than 23 g/g (GV), a gel deformation of not more than 12.5 cm under a short-time load (0.5 hrPT), and a gel deformation deterioration of not more than 3.

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: An object of the present invention is to provide: a water-absorbent resin which can sufficiently overcome the problem of the gel blocking, can manifest sufficient absorption capacity without load and sufficient absorption capacity under load and, at the same time, can also exert excellent liquid permeability under load; and a process for producing the same. As a means of achieving this object, a first production process among the processes according to the present invention for producing a water-absorbent resin having a treated surface is a process comprising: a step of mixing a water-absorbent resin having an internal crosslinked structure obtained by polymerizing a monomer containing acrylic acid and/or a salt thereof as a main component, a complex containing a polyvalent metal atom as a central atom and an organic secondary crosslinking agent in the presence of an aqueous liquid; and a step of crosslinking a surface of the water-absorbent resin with the organic secondary crosslinking agent.

Abstract: An object of the present invention is to provide a particulate water-absorbent resin composition and its production process, wherein the particulate water-absorbent resin composition is an enhanced one in both of the “liquid permeability” and “liquid-sucking-up property” (which have hitherto been antithetical physical properties) of the water-absorbent resin. As a means of achieving this object, a first particulate water-absorbent resin composition according to the present invention is a particulate water-absorbent resin composition comprising a water-absorbent resin (A) of a crosslinked structure obtained by polymerizing an acid-group-containing unsaturated monomer, with the composition being characterized by: having a particle size such that particles in the range of 850 to 150 ?m (but not including 850 ?m) account for not less than 90 weight % of the entirety; and containing a tetra- or more functional polyol (B) at least on surfaces.

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: An object of the present invention is to provide a water absorbent having excellent gel properties and showing excellent properties when used in a water-absorbing material of a sanitary/hygienic material such as paper diaper. Moreover, another object of the present invention is to provide a water absorbent which is safe and excellent in liquid permeability, and in which an amount of liquid permeability improver for improving the liquid permeability is reduced. The water absorbent is made from a water-absorbing resin prepared by a specific polymerization method and having a high degree of cross-linking, a high liquid holding property and a high gel strength (its swelling pressure of gel layer of is 35 kdyne/cm2 or more). This water absorbent is further processed to have a particular particle size distribution (95 wt % or more of its particles are less than 850ƒÊm but not less than 106ƒÊm, and logarithmic standard deviation (ƒĐƒÄ) is in a range of 0.25 to 0.