Polyacrylic acid (salt) -based water-absorbing agent and a production method thereof

Hardly cause gel blocking, a suitable water-absorbing agent for use in sanitary articles and the absorbent articles of more water-absorbing agent content thin, other physical properties (water absorption capacity, bulk density) of the water-absorbing agent impairs maintain or almost without high water absorption rate (e.g., FSR) and high absorbency against pressure, high liquid permeability, further, compatible and the salt tolerance, provides water-absorbing agent. Water absorbing agent, a surface vicinity of a polyacrylic (salt) -based water-absorbing agent which is crosslinked by an organic surface cross-linking agent, (A) absorption rate (FSR) is 0.28 g / g / s or more, or water time ( Vortex) is 42 seconds or less, (B) absorbency against pressure (AAP) is 20 g / g or more, (C) "salt tolerance index = (CRCdw) / (CRCs)" (CRCdw: water absorption capacity of pure water (unit: g / g), CRCs: 0.9 absorbency weight% brine (unit: salt tolerance index expressed in g / g)) satisfies the "salt tolerance index ≦ 0.49 × CRCs-7.47" , (D) bulk density satisfies 0.55~0.70g / cm