Water-absorbing resin, absorber, and absorbent article

1 . A water-absorbing resin having an oxidation-reduction potential of a swollen gel of 260 mV or more, as measured by the following oxidation-reduction potential measuring method:

(Oxidation-Reduction Potential Measuring Method)

adding to a beaker, 60 mL of ion exchange water having an oxidation-reduction potential of 390±10 mV;

measuring an oxidation-reduction potential of the ion exchange water after inserting an electrode of a pH meter into the ion exchange water, and

leaving standing for 15 minutes;

next, adding 2.0 g of a water-absorbing resin to the ion exchange water that is being stirred at 400 rpm,

stirring a resultant mixture to obtain the swollen gel;

inserting an electrode of a pH meter into the swollen gel,

leaving standing for 15 minutes, and then

measuring the oxidation-reduction potential;

wherein the oxidation-reduction potential of the swollen gel is 1,000 mV or less.

2 . The water-absorbing resin according to claim 1 , having a physiological-saline absorption amount of 30 g/g or more and 80 g/g or less.

3 . The water-absorbing resin according to claim 1 , having a median particle diameter of 200 μm or more and 600 μm or less.

4 . The water-absorbing resin according to claim 1 , wherein a pH of the swollen gel measured by the pH measuring method below is 8.0 or less:

(pH Measuring Method)

mixing and dissolving 25.0 g of urea, 9.0 g of sodium chloride, 0.6 g of magnesium sulfate heptahydrate, 0.7 g of calcium lactate, 4.0 g of potassium sulfate, and 2.5 g of ammonium sulfate in distilled water, wherein a total of 1,000 g of artificial urine is prepared;

diluting urease (derived from jack bean, 50% glycerol solution, 1,000 U/mL) to prepare a 2-U/mL urease aqueous solution;

preparing a test liquid by mixing 30.0 g of the artificial urine and 1.0 mL of the urease aqueous solution;

placing the test liquid into a petri dish containing 1.0 g of the water-absorbing resin to obtain the swollen gel, and immediately sealing the swollen in a 2-L Tedlar bag, and removing air in the bag;

using a 200-mL glass syringe, 900 mL (total volume) of dry air that has passed through an activated carbon bed is added into the 2-L Tedlar bag;

storing the 2-L Tedlar bag in which the swollen gel is sealed for 24 hours in a tabletop thermo-hygrostat set at a temperature of 35±2° C. and a relative humidity of 60±2%;

removing the swollen gel after storage for 24 hours from the 2-L Tedlar bag,

adding to a beaker together with 200 g of physiological saline, and stirring with a stirrer for 1 minute; and

measuring a pH of the content of the beaker using a pH meter.

5 . An absorber comprising the water-absorbing resin according to claim 1 .

6 . An absorbent article comprising the absorber according to claim 5 .