Disclosed are water-absorbent resin particles including: a crosslinked polymer having a structural unit derived from an ethylenically unsaturated monomer including at least one compound selected from the group consisting of (meth)acrylic acid and a salt thereof, in which a proportion of (meth)acrylic acid and a salt thereof is 70 to 100 mol % with respect to a total amount of monomer units in the crosslinked polymer, and in a moisture retention test performed under reduced pressure, a moisture retention rate after 6 hours is 55% by mass or more, and a water retention capacity for a physiological saline solution is 32 to 70 g/g.

Water-absorbent resin particles 10a, in which a gel flow rate measured by the following procedures having (1) to (3) is 10 to 70 g/min: (1) mixing 1 part by mass of the water-absorbent resin particles and 199 parts by mass of water to obtain a gel, (2) accommodating the gel in a funnel in a state where a circular lower end opening with a diameter of 8 mm in the funnel is closed, and (3) measuring an outflow amount of the gel per unit time after a lapse of 3 minutes from opening of the lower end opening as the gel flow rate.

Disclosed is water-absorbent resin particles including: a crosslinked polymer having a monomer unit derived from an ethylenically unsaturated monomer including at least one compound selected from the group consisting of (meth)acrylic acid and a salt thereof, in which a proportion of (meth)acrylic acid and a salt thereof is 70 to 100 mol % with respect to a total amount of monomer units in the crosslinked polymer, an artificial urine permeation speed when the water-absorbent resin particles are swollen tenfold is 1.0 g/min or more and 35.0 g/min or less, a water retention capacity for a physiological saline solution is 32 to 60 g/g, and a contact angle measured in a test performed in the order of i) and ii) is 70 degrees or smaller.

An absorber 10 contains water-absorbent resin particles 10a and a fibrous substance, a medium particle diameter of the water-absorbent resin particles 10a is 250 to 600 μm, the water-absorbent resin particles 10a contain small-diameter particles having a particle diameter of 180 μm or less, and a falloff rate of a mixture of the small-diameter particles and the fibrous substance when the mixture is subjected to shaking treatment for 10 minutes is 20% by mass or less.

An absorbent article 100 includes an absorber 10, the absorber 10 contains water-absorbent resin particles 10a, and a swelling height of the water-absorbent resin particles 10a measured by the following procedures (1) to (6) is 10 mm or less.

(1) A container having a recess having a bottom area of 50 cm.sup.2 is disposed in a state where the recess is open in a vertical direction.

(2) 1.00 g of water-absorbent resin particles are disposed in the recess.

(3) A non woven fabric is disposed on the water-absorbent resin particles in the recess.

(4) A weight having a mass of 90 g is disposed on the non-woven fabric.

(5) Physiological saline is supplied into the recess.

(6) A movement distance in a vertical direction of the weight when 300 seconds have passed from the start of swelling of the water-absorbent resin particles is measured as the swelling height.

Water-absorbing resin particles, in which a light transmittance at a wavelength of 425 nm when the water-absorbing resin particles are swollen 30 times with a physiological saline solution is 20% or more, are disclosed.

Provided is a method for producing an absorbent article comprising a water-absorbing resin having an excellent initial water absorption speed under load even substantially without adding a liquid permeability enhancer.

The method steps for producing the water-absorbing resin includes the step of polymerizing a monomer while adding certain polyalkylene glycol thereto so as to generate, during or after the polymerization, a crosslinked hydrogel polymer containing the polyalkylene glycol of a specific molecular weight, wherein the crosslinked hydrogel polymer has a centrifuge retention capacity within a given range and a final water-absorbing resin to be obtained has various physical properties (CRC, AAP, SFC, FSR) being within given ranges.

Disclosed is water-absorbent resin particles including: a crosslinked polymer having a monomer unit derived from an ethylenically unsaturated monomer including at least one compound selected from the group consisting of (meth)acrylic acid and a salt thereof, in which a proportion of (meth)acrylic acid and a salt thereof is 70 to 100 mol % with respect to a total amount of monomer units in the crosslinked polymer, an artificial urine permeation speed when the water-absorbent resin particles are swollen tenfold is 1.0 g/min or more and 35.0 g/min or less, a water retention capacity for a physiological saline solution is 32 to 60 g/g, and a contact angle measured in a test performed in the order of i) and ii) is 70 degrees or smaller.

Provided is a method for producing an absorbent article comprising a water-absorbing resin having an excellent initial water absorption speed under load even substantially without adding a liquid permeability enhancer. The method steps for producing the water-absorbing resin includes the step of polymerizing a monomer while adding certain polyalkylene glycol thereto so as to generate, during or after the polymerization, a crosslinked hydrogel polymer containing the polyalkylene glycol of a specific molecular weight, wherein the crosslinked hydrogel polymer has a centrifuge retention capacity within a given range and a final water-absorbing resin to be obtained has various physical properties (CRC, AAP, SFC, FSR) being within given ranges.

The present invention relates to an absorbent article, comprising a fluid permeable topsheet, a backsheet and an absorbent element disposed between the topsheet and the backsheet wherein the absorbent article has a caliper expansion, measured at 1 minute of at least 150%. The present invention also relates to an absorbent article, comprising a fluid permeable topsheet, a backsheet and an absorbent element disposed between the topsheet and the backsheet wherein the absorbent article has a ratio of dry caliper to the caliper expansion measured at 1 minute of 3 mm/% or less.