Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom

A water-absorbing agent, comprising 90 wt. % or more of a water-absorbing resin including a partially neutralized polymer of polyacrylic acid, the partially neutralized polymer having a crosslinking structure constructed by polymerization of an acrylic acid (salt) (a monomer other than the acrylic acid (salt) is 0 to 30 mole % relative to the acrylic acid (salt)), wherein

• the water-absorbing agent is surface-treated, and
• the water-absorbing resin contains 10 to 40 mole % of acrylic acid and 90 to 60 mole % of acrylate (the sum should be 100 mole %), and salt-forming neutralization of the water-absorbing resin is (i) performed before polymerization while the water-absorbing resin is in monomer form, or (ii) performed during or after polymerization while the water-absorbing resin is in polymer form, or (iii) performed by a combination of (i) and (ii),
• the water-absorbing agent contains (iv) polyhydric alcohol containing 2 to 10 carbons per molecule or (v) water-insoluble inorganic fine particles,
• the water-absorbing agent meets all of properties (1) through (4):
• (1) heat retention indicator 1 (maximum temperature decrease per minute 5 to 10 minutes after 10 times swelling in a 0.90 wt. % sodium chloride at 50° C.) is from 0 to 3.0° C./min;
• (2) a centrifuge retention capacity in a 0.90 wt. % aqueous solution of sodium chloride (30 minute value) is 34 g/g or less;
• (3) an absorbency in a 0.90 wt. % aqueous solution of sodium chloride against a pressure of 2.0 kPa (60 minute value) is less than 30 g/g;
• and
• (4) a saline flow conductivity (SFC) for a 0.69 wt. % aqueous solution of sodium chloride is less than 20×10−7 cm3 sec/g, wherein
• the water-absorbing agent is particles,
• the water-absorbing agent meets following conditions:
• particles having diameters from 600 to 300 μm as specified by sieve classification account for 60 wt. % or more, and those less than 150 μm account for 3 wt. % or less;
• and
• a standard deviation of logarithm (G) of particle size distribution is from 0.250 to 0.400;
• wherein a mass-average particle diameter (specified by sieve classification) is from 400 to 600 μm.