The present invention provides a water-absorbent resin that has excellent water-absorption performance with respect to salt water; a water-blocking agent including the water-absorbent resin; and a method for producing the water-absorbent resin.

The water-absorbent resin of the present invention includes a partially neutralized polyacrylic acid having a crosslinked structure and has a swelling height of 3.5 mm/0.5 g or more with respect to 3.3 mass % salt water, as determined under the following measurement conditions.

Measurement Conditions for Salt Water Swelling Height

0.5 g of water-absorbent resin particles are sprayed over a circular concave cup having a height of 30 mm and an inner diameter of 80.5 mm. A nonwoven fabric 4 is spread thereon. A circular convex cylinder having an outer diameter of 80 mm is placed on the nonwoven fabric, and 55 g of 3.3 mass % salt water at 20° C. is poured into the circular concave cup. One minute after the start of water absorption by the water-absorbent resin particles, the degree that the circular convex cylinder is pushed up due to swelling of the water-absorbent resin particles is measured as a salt water swelling height of the water-absorbent resin.

Provided are: a water-absorbent resin that has excellent heat resistance, even in a water-absorbed state; and a water-blocking material comprising the water-absorbent resin. The water-absorbent resin according to the present invention includes a crosslinked polymer of a water-soluble ethylenically unsaturated monomer, and has a gel-viscosity retention S of 0.5 or more as calculated by the following formula (I):

Gel-viscosity retention at high temperature S=B/A  (I)

(wherein A represents an initial gel viscosity (mPa.Math.s), and B represents a gel viscosity (mPa.Math.s) after 10 days).

Provided are: a water-absorbent resin that has excellent heat resistance, even in a water-absorbed state; and a water-blocking material comprising the water-absorbent resin. The water-absorbent resin according to the present invention includes a crosslinked polymer of a water-soluble ethylenically unsaturated monomer, and has a gel-viscosity retention S of 0.5 or more as calculated by the following formula (I):

Gel-viscosity retention at high temperature S=B/A  (I)

(wherein A represents an initial gel viscosity (mPa.Math.s), and B represents a gel viscosity (mPa.Math.s) after 10 days).

The invention relates to a method for manufacturing thermoplastic poly(vinyl alcohol) derivative in a melt state reaction and a product thereof, wherein the method thermoplastic poly(vinyl alcohol) that has been dried is heated and admixed with an organic acid anhydride that has a catenated carbon structure which ends into a vinyl group, such that a mixture is obtained which is above the melting point of the mixture, thereby causing an ester bond forming condensation reaction in a melt state, wherein at least some of the organic acid anhydride reacts with hydroxyl groups of the thermoplastic poly(vinyl alcohol), such that reaction product is formed which contains carboxylic acid residue and thermoplastic poly(vinyl alcohol) derivative which contains ester bonded pendant chains of which at least some end into vinyl groups. The invention further relates to a method for manufacturing a paper substrate and a product thereof, which contains a primer layer that contains the reaction product.

The invention relates to a method for manufacturing thermoplastic poly(vinyl alcohol) derivative in a melt state reaction and a product thereof, wherein the method thermoplastic poly(vinyl alcohol) that has been dried is heated and admixed with an organic acid anhydride that has a catenated carbon structure which ends into a vinyl group, such that a mixture is obtained which is above the melting point of the mixture, thereby causing an ester bond forming condensation reaction in a melt state, wherein at least some of the organic acid anhydride reacts with hydroxyl groups of the thermoplastic poly(vinyl alcohol), such that reaction product is formed which contains carboxylic acid residue and thermoplastic poly(vinyl alcohol) derivative which contains ester bonded pendant chains of which at least some end into vinyl groups. The invention further relates to a method for manufacturing a paper substrate and a product thereof, which contains a primer layer that contains the reaction product.

The invention relates to a method for manufacturing thermoplastic poly(vinyl alcohol) derivative in a melt state reaction and a product thereof, wherein the method thermoplastic poly(vinyl alcohol) that has been dried is heated and admixed with an organic acid anhydride that has a catenated carbon structure which ends into a vinyl group, such that a mixture is obtained which is above the melting point of the mixture, thereby causing an ester bond forming condensation reaction in a melt state, wherein at least some of the organic acid anhydride reacts with hydroxyl groups of the thermoplastic poly(vinyl alcohol), such that reaction product is formed which contains carboxylic acid residue and thermoplastic poly(vinyl alcohol) derivative which contains ester bonded pendant chains of which at least some end into vinyl groups. The invention further relates to a method for manufacturing a paper substrate and a product thereof, which contains a primer layer that contains the reaction product.

Water-absorbent resin particles having a degree of gel association of 15 or more are disclosed.

Water-absorbent resin particles having a degree of gel association of 15 or more are disclosed.

An absorber 10 containing water-absorbent resin particles 10a, in which a rate of an amount of change in a water retention amount of physiological saline of the water-absorbent resin particles 10a when the water-absorbent resin particles 10a are irradiated with an ultraviolet ray for 3 hours with respect to a water retention amount of the water-absorbent resin particles 10a of physiological saline before irradiation with an ultraviolet ray is more than 0% and 30% or less.

An absorber 10 containing water-absorbent resin particles 10a, in which a rate of an amount of change in a water retention amount of physiological saline of the water-absorbent resin particles 10a when the water-absorbent resin particles 10a are irradiated with an ultraviolet ray for 3 hours with respect to a water retention amount of the water-absorbent resin particles 10a of physiological saline before irradiation with an ultraviolet ray is more than 0% and 30% or less.