초록 ▼

The present invention provides a particulate water absorbing agent for a thin type absorbing substrate suitable for actual use. A particulate water absorbing agent having irregularly pulverized shape, characterized by comprising, a surface crosslinked water-absorbing resin obtained by crosslinking p

The present invention provides a particulate water absorbing agent for a thin type absorbing substrate suitable for actual use. A particulate water absorbing agent having irregularly pulverized shape, characterized by comprising, a surface crosslinked water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer with an acid group and/or salts thereof, which absorbing agent contains agglomerated particles therein and further satisfies (i) centrifuge retention capacity (CRC) in a physiological saline solution of not lower than 32 g/g, (ii) mass median particle size (D50) of 200 to 400 μm, and (iii) particles smaller than 600 μm and not smaller than 150 μm of 95 to 100% by weight. By using the particulate water absorbing agent, such absorbing articles can be obtained as have few rugged surface after water absorption, excellent liquid permeation property.

대표청구항 ▼

The invention claimed is: 1. A particulate water absorbing agent having irregularly pulverized shape, wherein said particulate water absorbing agent comprises a surface crosslinked water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer mainly composed of acrylic aci

The invention claimed is: 1. A particulate water absorbing agent having irregularly pulverized shape, wherein said particulate water absorbing agent comprises a surface crosslinked water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer mainly composed of acrylic acid and/or salts thereof, said particulate water absorbing agent contains agglomerated particles therein, and further said particulate water absorbing agent satisfies (i) to (iii) described below: (i) centrifuge retention capacity (CRC) of the particulate water absorbing agent in a physiological saline solution being not lower than 32 g/g; (ii) mass median particle size (D50) of the particulate water absorbing agent being in the range of 200 to 400 μm; and (iii) particles of the particulate water absorbing agent smaller than 600 μm and not smaller than 150 μm being in the range of 95 to 100% by weight, wherein water content of the particulate water absorbing agent is 1 to 10% by weight. 2. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein decreased ratio of the mass median particle size by impact of the particulate water absorbing agent is 5, to 30%. 3. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein increased ratio of the mass median particle size of the particulate Water absorbing agent due to agglomeration is 5, to 30%. 4. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein liquid permeation time under pressure of the particulate water absorbing agent is not longer than 60 seconds. 5. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein absorbency against pressure at 1.9 kPa of the particulate water absorbing agent in a physiological saline solution is not lower than 20 g/g. 6. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein vortex water absorption speed of the particulate water absorbing agent in a physiological saline solution is not longer than 60 seconds. 7. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein fluidity of the particulate water absorbing agent after moisture absorption is 0 to 20% by weight. 8. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein logarithmic standard deviation of particle size distribution of the particulate water absorbing agent is 0.20 to 0.40. 9. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, wherein bulk density of gel after saturated swelling of the particulate water absorbing agent in a physiological saline solution is in the range of 0.80 to 1.0 (g/cm3). 10. A particulate water absorbing agent having irregularly pulverized shape according to claim 1, which further comprises, besides the water-absorbing resin, one or more component selected from the group consisting of a chelating agent, a deodorant, a polyvalent metal salt and an inorganic fine particle. 11. An absorbing article for excrement, urine or blood, which includes absorbent substrate comprising a particulate water absorbing agent having irregularly pulverized shape according to claim 1 and hydrophilic fiber. 12. An absorbing article according to claim 11, wherein the absorbent substrate is a thin type with thickness of 0.1 to 5 mm. 13. An absorbing article according to claim 11, wherein content of the particulate water absorbing agent having irregularly pulverized shape is 30 to 100% by weight based on total weight of the particulate water absorbing agent and the hydrophilic fiber. 14. A method for production of a particulate water absorbing agent having irregularly pulverized shape, which particulate water absorbing agent comprises a surface crosslinked water-absorbing resin obtained by crosslinking polymerization of an unsaturated monomer mainly composed of acrylic acid and/or salts thereof and further via drying and pulverizing steps, and said particulate water absorbing agent contains agglomerated particles therein, which method comprising: a step of crosslinking polymerization of an aqueous solution of an unsaturated monomer containing a non-neutralized acrylic acid and/or salts thereof in the presence of a crosslinking agent; a step of further surface crosslinking of a water-absorbing resin particle obtained by the polymerization and said water absorbing resin particle satisfying (i) to (iii) described below: (i) centrifuge retention capacity (CRC) of the water-absorbing resin particle in a physiological saline solution being not lower than 32 g/g, (ii) mass median particle size (D50) of the water-absorbing resin particle being in the range of 150 to 380 μm, and (iii) the water-absorbing resin particles smaller than 600 μm and not smaller than 150 μm being in the range of 92 to 100% by weight; and a step of further adding aqueous liquid thereto after the surface crosslinking and heating the resin particles while maintaining water content thereof at 1 to 10% by weight and further controlling particle size. 15. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 14, wherein the step of crosslinking polymerization is conducted in the presence of a chain transfer agent. 16. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 14, wherein the aqueous solution of the unsaturated monomer containing a non-neutralized acrylic acid in concentration of 10 to 30% by weight is crosslinking polymerized in the presence of a crosslinking agent; and the obtained resin is neutralized after polymerization. 17. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 14, which method comprises a step of the addition of a chelating agent at one or more timings selected from the group consisting of (i) during polymerization, (ii) after the polymerization and before surface crosslinking, and (iii) during surface crosslinking. 18. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 14, further comprising a step of recovering and regenerating fine particles of the resin which are excluded from the pulverizing step, thereby obtaining a water-absorbing resin particle at yield of not lower than 90% by weight based on weight of feed monomer to be polymerized as solid content equivalent. 19. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 14, wherein the water-absorbing resin particles are agglomerated so that shortening ratio of liquid permeation time under pressure is not lower than 10%. 20. A method for production of a particulate water absorbing agent having irregularly pulverized shape according to claim 19, further comprising a step of adding and mixing inorganic particles after the agglomeration step.