Water-absorbing resin and water-blocking material

A water-absorbent resin comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer and a chelating agent having five or more ligands,

• the water-absorbent resin having a median particle size of 100 to 200 μm,
• the water-absorbent resin having 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·s);
• and
• B represents a gel viscosity (mPa·s) after 10 days, and
• the initial gel viscosity A of the water-absorbent resin being 4000 mPa's or more and being measured by the following method:
• 1500 g of distilled water is added to a beaker, and stirred at 600 rpm using a magnetic stirrer bar;
• 1.5 g of a water absorbent resin is placed into a vortex created by this stirring and the mixture is stirred for 1 hour;
• the resulting mixture is then filtered through a 200 mesh wire mesh, and allowed to stand for 15 minutes;
• the gel viscosity of the thus-obtained swollen gel is immediately measured and used as the initial gel viscosity.