The core/shell particle is excellent in water absorption rate, biodegradability, and water retention and is useful in a hygienic material or soil improver.

The temporal change of water absorption speed (y) is measured by the detector and the measurement unit.

The initial water absorption speed of this polymer preferably ranges from 0.01 to 0.5 ml/g·min.

Provided are: a water adsorbent for an organic electroluminescence display element having hydrophobic properties and no reduction in water-absorption speed; and a production method for same.

A water-absorbing resin which has high water holding capacity, excellent water absorption rate and excellent fluidity after moisture absorption can be produced by the method of the present invention.

At least one reactant preferably reacts more slowly with any one of the other reactants and/or dissolves more slowly in water than any one of the disintegrants absorbs water.

Provided is a water-absorbent resin having excellent liquid permeability, water absorption speed, anti-impact stability, and weather resistance.

  Said water-absorbing polymer preferably has a water uptake rate by the vortex method of 30 seconds or more and a liquid passing rate under a pressure of 2.0 kPa of at least 150 ml/minute.

For example, for lining bath, standard water absorption rate should not exceed 7%, resistance to chemical agents – A, AA.

On the basis of the water absorption speed measured over a predetermined elapsed time, a causative factor or an evaluative factor related to the denseness of a concrete surface layer part is identified or compared.