Water-absorbing agent
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 (α) and a liquid-permeability-enhancing agent (β), wherein the water-absorbent resin particles (α) 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 (σζ) 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 (β) content in the range of 0.01 to 5 mass parts per 100 mass parts of the water-absorbent resin particles (α).
1. A water-absorbing agent, which is a particulate water-absorbing agent comprising water-absorbent resin particles (α) and a liquid-permeability-enhancing agent (β), wherein said water-absorbent resin particles (α) are prepared by crosslinking with a surface-crosslinking agent the surface of irregular-shaped pulverized particles of a crosslinked polymer made from a monomer comprising acrylic acid and/or its salt;
wherein the particulate water-absorbing agent has:
a mass-average particle diameter in the range of 234 to 394 μm, a logarithmic standard deviation (σζ) of a particle diameter distribution in the range of 0.25 to 0.45, an absorption capacity of not less than 15 g/g without load, and a water-extractable component content of not higher than 15 mass %; and further
a liquid-permeability-enhancing agent (β) content in the range of 0.01 to 5 mass parts per 100 mass parts of the water-absorbent resin particles (α).
2. A water-absorbing agent according to claim 1 , wherein the water-absorbent resin particles (α) included in the water-absorbing agent include particles having a porous structure.
3. A water-absorbing agent according to claim 1 or 2 , which includes particles having particle diameters in the range of 100 to 500 μm in an amount of not smaller than 80 mass % relative to the water-absorbing agent.
4. A water-absorbing agent according to claim 1 or 2 , wherein the water-absorbing agent has a mass ratio (particles having particle diameters of not smaller than 300 μm)/(particles having particle diameters of smaller than 300 μm) in the range of 80/20 to 20/80.
5. A water-absorbing agent according to claim 1 or 2 , wherein the water-absorbing agent displays a capillary absorption capacity of not less than 15 g/g for a 0.90 mass % physiological saline solution.
6. A water-absorbing agent according to claim 1 or 2 , wherein the water-absorbing agent displays a saline flow conductivity of not less than 50 (10 −7 ·cm 3 ·s·g −1 ) for a 0.69 mass % physiological saline solution.
7. A water-absorbing agent according to claim 1 or 2 , wherein the absorption capacity of the water-absorbing agent without load is less than 29 g/g.
8. A water-absorbing agent according to claim 1 or 2 , wherein the liquid-permeability-enhancing agent (β) includes water-insoluble hydrophilic inorganic fine particles and/or a water-soluble polyvalent metal salt.
9. A water-absorbing agent according to claim 1 , wherein the water-absorbing agent is obtained by forming the surface-crosslinked water-absorbent resin particles and thereafter mixing the surface-crosslinked water-absorbent resin particles with the liquid-permeability-enhancing agent.
10. A water-absorbing agent according to claim 9 , wherein the liquid-permeability-enhancing agent is added as an aqueous solution, slurry or powder.
11. A water-absorbing agent according to claim 1 , wherein the liquid-permeability-enhancing agent is mixed with the surface-crosslinked water-absorbent resin particles in an amount sufficient to increase the saline flow conductivity of the water-absorbent agent.
12. A water-absorbing agent according to claim 11 , wherein the liquid-permeability-enhancing agent is added as a powder to the surface-crosslinked water-absorbent resin particles.