Water absorbing agent, water absorbent core using the agent, and manufacturing method for water absorbing agent

摘要

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 μm; (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.

主权项

1. A water absorbing agent containing water absorbing resin particles, the agent satisfying conditions (A) to (H) below:
(A) the water absorbing resin particles are, on a surface thereof, either crosslinked or coated with a surface crosslinking agent which has at least one hydroxyl group; (B) the water absorbing resin particles contain, on a surface thereof, a trivalent water-soluble metal salt and water-insoluble inorganic particles that include silicon dioxide; (C) the water absorbing agent has a mass median particle size of 200 μm to 500 μm inclusive; (D) the water absorbing agent contains 0.001 to 0.4 mass % inclusive, of the water-insoluble inorganic particles; (E) the water absorbing resin particles have a size such that no more than 5 mass percent of such particles can pass through a sieve having a mesh opening size of 150 μm; (F) the water absorbing resin particles contain acid groups that are neutralized in a ratio from 50 mol% to 90 mol% inclusive; and (G) the water absorbing resin particles contain 0.001 to 5.0 mass % inclusive, of the trivalent water-soluble metal salt; (H) the water absorbing agent contains dust in an amount that is 355 ppm or less and that contains SiO2 in an amount which is 50 mass % or less.