Polyacrylic acid (salt) water absorbent, and method for producing same

Abstract

Provided is a water-absorbing agent which is less likely to cause gel blocking and is suitable for a sanitary product and an absorbent article each being thin and containing a large amount of a water-absorbing agent, and which, while maintaining or hardly losing the other physical properties (a fluid retention capacity and a bulk specific gravity) of the water-absorbing agent, simultaneously achieves a high water absorbing speed (e.g., FSR), a high fluid retention capacity under load, high liquid permeability, and salt tolerance. The water-absorbing agent is a polyacrylic acid (salt)-based water-absorbing agent whose surface and its vicinity are crosslinked by an organic surface crosslinking agent, characterized by satisfying the following (A)-(D): (A) Free Swell Rate (FSR) of at least 0.28 g/g/s, or Absorption Time (Vortex) of 42 seconds or less; (B) Absorption Against Pressure (AAP) of at least 20 g/g; (C) Salt Tolerance Index represented by 'Salt Tolerance Index=(CRCdw)/(CRCs)' where CRCdw is a centrifuge retention capacity (unit; g/g) for deionized water (dw), and CRCs is a centrifuge retention capacity (unit; g/g) for a 0.9 weight % saline, satisfying 'Salt Tolerance Index≤0.49×CRCs−7.47'; and (D) Bulk Specific Gravity of 0.55 to 0.70 g/cm.