Abstract: One purpose of the present invention is to provide a water-absorbent resin having excellent water absorption characteristics and being capable of improving the shape-retaining characteristics of a water-absorbent material when used in the water-absorbent material. A water-absorbent resin obtained by performing reversed phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, using a radical polymerization initiator, said resin being capable of having both excellent absorption performance and shape retention in a water-absorbent material using the water-absorbent resin, as a result of fulfilling the conditions of: (1) having a water-retention capacity of physiological saline of at least 38 g/g; (2) having a water-absorption capacity of physiological saline under a load of 4.14 kPa of at least 15 ml/g; and (3) having a tan ? of a 50-fold swollen gel of at least 2.10×10?2.

Abstract: The present invention may provide a process for producing a water-absorbent resin by employing a reversed suspension polymerization method, by which a water-absorbent resin having a small particle size and a narrow particle size distribution can be produced. The process for producing a water-absorbent resin may include subjecting a water-soluble ethylenically unsaturated monomer to a reversed phase suspension polymerization in a petroleum hydrocarbon dispersion medium containing a surfactant and a polymeric dispersion agent, wherein the polymeric dispersion agent is a polymeric protective colloid having a weight average molecular weight (Mw) of 2,000 to 15,000 and a molecular weight distribution (Mw/number average molecular weight (Mn)) of 3 to 50.

Abstract: A method for producing a water-absorbent resin includes a polymerization step of polymerizing a polymerizable component containing a water-soluble ethylenically unsaturated monomer dissolved in water using a water-soluble azo-type radical polymerization initiator to obtain a reaction system including a water-absorbent resin precursor, and a dehydration step of removing water from the reaction system by heating. In the dehydration step, a water-soluble radical polymerization initiator is added to the reaction system at any first dehydration stage when the residual water rate calculated by the formula (1) is 50% or more, and a reducing substance is added to the reaction system at any second dehydration stage when the residual water rate decreases from that at the first dehydration stage by 10% or more. According to this production method, a water-absorbent resin having satisfactory water-absorption capacity can be produced while suppressing the content of residual monomers.

Abstract: One purpose of the present invention is to provide a water-absorbent resin having excellent water absorption characteristics and being capable of improving the shape-retaining characteristics of a water-absorbent material when used in the water-absorbent material. A water-absorbent resin obtained by performing reversed phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, using a radical polymerization initiator, said resin being capable of having both excellent absorption performance and shape retention in a water-absorbent material using the water-absorbent resin, as a result of fulfilling the conditions of: (1) having a water-retention capacity of physiological saline of at least 38 g/g; (2) having a water-absorption capacity of physiological saline under a load of 4.14 kPa of at least 15 ml/g; and (3) having a tan ? of a 50-fold swollen gel of at least 2.10×10?2.

Abstract: A method for producing a water-absorbent resin by a reversed-phase suspension polymerization method, includes step 1 of dispersing a first aqueous solution containing a partially neutralized product (A) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule in a petroleum-type hydrocarbon dispersion medium in the presence of a dispersing agent, and then polymerizing the resulting dispersion to obtain a slurry containing primary particles of a polymer, and step 2 of adding a second aqueous solution containing a partially neutralized product (B) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule to the slurry obtained in step 1, and then polymerizing the mixture to obtain a slurry in which the primary particles are agglomerated. In the method, a molar neutralization degree X of the partially neutralized product (A) and a molar neutralization degree Y of the partially neutralized product (B) are defined.

Abstract: The present invention provides a novel water-absorbent resin desirable for use as a hygienic material and the like, and an absorbent material and absorbent article using the water-absorbent resin; the water-absorbent resin having a high gel strength that prevents a reduction in liquid permeation rate by suppressing gel blocking during absorption, and an excellent water-retention capacity at the same time. The water-absorbent resin satisfies the following criteria (1) and (2): (1) having a water-retention capacity of saline solution of 40 g/g or more, and (2) having a total gel strength of 5,500 Pa or greater, the total gel strength being the sum of 30 times swollen gel strength a, 40 times swollen gel strength b, and 50 times swollen gel strength c.

Abstract: A method for producing a water-absorbent resin includes a polymerization step of polymerizing a polymerizable component containing a water-soluble ethylenically unsaturated monomer dissolved in water using a water-soluble azo-type radical polymerization initiator to obtain a reaction system including a water-absorbent resin precursor, and a dehydration step of removing water from the reaction system by heating. In the dehydration step, a water-soluble radical polymerization initiator is added to the reaction system at any first dehydration stage when the residual water rate calculated by the formula (1) is 50% or more, and a reducing substance is added to the reaction system at any second dehydration stage when the residual water rate decreases from that at the first dehydration stage by 10% or more. According to this production method, a water-absorbent resin having satisfactory water-absorption capacity can be produced while suppressing the content of residual monomers.

Abstract: A method for producing a water-absorbent resin by a reversed-phase suspension polymerization method, includes step 1 of dispersing a first aqueous solution containing a partially neutralized product (A) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule in a petroleum-type hydrocarbon dispersion medium in the presence of a dispersing agent, and then polymerizing the resulting dispersion to obtain a slurry containing primary particles of a polymer, and step 2 of adding a second aqueous solution containing a partially neutralized product (B) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule to the slurry obtained in step 1, and then polymerizing the mixture to obtain a slurry in which the primary particles are agglomerated.

Abstract: Object An object of the present invention is to provide a process for producing a water-absorbent resin by employing a reversed suspension polymerization method, by which a water-absorbent resin having a small particle size and a narrow particle size distribution can be produced. Means for Achieving the Object A process for producing a water-absorbent resin comprising subjecting a water-soluble ethylenically unsaturated monomer to a reversed phase suspension polymerization in a petroleum hydrocarbon dispersion medium containing a surfactant and a polymeric dispersion agent, wherein the polymeric dispersion agent is a polymeric protective colloid having a weight average molecular weight (Mw) of 2,000 to 15,000 and a molecular weight distribution (Mw/number average molecular weight (Mn)) of 3 to 50.

Abstract: Object: The main object of the present invention is to provide a water-absorbent resin that has an appropriate absorption capacity and excellent flow-through properties and that is suitably used in an absorbent article applied to a hygienic material, etc. Means for Achieving the Object: A water-absorbent resin formed by agglomerating primary particles according to a reversed-phase suspension polymerization method, the primary particles being obtained by polymerizing at least one water-soluble ethylenically unsaturated monomer in the presence of a dispersion stabilizer according to a reversed-phase suspension polymerization method, the primary particles having a median particle size of 100 to 250 ?m, and the water-absorbent resin having a water-retention capacity of saline solution of 30 g/g or less.

Abstract: A method for production of a water-absorbent resin particle which is excellent in a particle strength, and in which even after mechanical impact, a particle diameter retaining rate and a retaining rate of water absorption capacity under pressure are high, and an absorbent material using the same particle. The method includes the steps of polymerizing a water-soluble ethylenic unsaturated monomer using a water-soluble radical polymerization initiator, optionally in the presence of a crosslinking agent, to obtain a water-absorbent resin particle precursor, adding a post-crosslinking agent to crosslink a surface of the particle, adding an amorphous silica particle and adjusting the resulting particle to a moisture content of less than 10%, and subsequently adding moisture to adjust a final moisture content of the resulting particle to 10 to 20%.

Abstract: The present invention provides a water-absorbent resin particle which is excellent in a particle strength, and in which even after mechanical impact, a particle diameter retaining rate and a retaining rate of water absorption capacity under pressure are high, a method for production thereof, and an absorbent material using the same. More particularly, the present invention provides a water-absorbent resin particle obtained by polymerizing a water-soluble ethylenic unsaturated monomer using a water-soluble radical polymerization initiator, if necessary, in the presence of a crosslinking agent, to obtain a water-absorbent resin particle precursor, adding a post-crosslinking agent to crosslink a surface of the particle, and adding an amorphous silica particle, in which a moisture content is 10 to 20%, and a particle diameter retaining rate after a particle collision test is 90% or more, a method for production thereof, and an absorbent material using the same.

Abstract: A method for producing a highly concentrated aqueous acrylic amide-based polymer dispersion which is inexpensive, good in fluidity and easy to handle is provided. The method comprises polymerizing a water-soluble monomer composition containing an acrylic amide monomer in an aqueous solution of an inorganic salt in the presence of a homopolymer of vinylpyrrolidone and/or a copolymer of vinylpyrrolidone and other monomer(s).