Polyacrylic acid (salt) -based water absorbent resin powder and its manufacturing method

Providing except through property and water-absorption rate, impact resistance stability, weather resistance, excellent water-absorbing resin. Provides a polyacrylic acid (salt) -based water absorbent resin powder, wherein the absorption capacity without load (CRC) of 30 ~ 45 [g / g], absorption against pressure (AAP0.3) of 20 to 35 [g / g], the pressurized water absorption ratio (AAP0.7) of 10 ~ 28 [g / g] and a weight average particle diameter (D50) of 300 ~ 500μm, the polyacrylic acid (salt) -based water-absorbing resin powders containing p-methoxyphenol, deteriorated soluble component (0.05% L? a saline-two hours / 60 deg.] C, extracted rinse 1 hour / rT) is 40 wt% or less, of the formula a predetermined internal gas bubbles of 0.1 to 2.5%. (Internal gas bubbles ratio) [%] = {(true density)? (Apparent density)} / (true density) × 100.