WATER-ABSORBENT RESIN, SOIL WATER-RETAINING MATERIAL, AND AGRICULTURAL/HORTICULTURAL MATERIAL

摘要

There is provided a water-absorbent resin that exhibits both high water absorbency and high water-discharge capacity. The water-absorbent resin of the present invention is a water-absorbent resin comprising a polymer of a water-soluble ethylenically unsaturated monomer, wherein when a cross-sectional image of the water-absorbent resin is observed using X-ray computed tomography, the water-absorbent resin has a ratio of the area of cavity portions (cavity area ratio) in the cross-sectional image of 5% or more, as calculated according to Equation (I): $\mathrm{cavity}\mathrm{area}\mathrm{ratio}\left[\%\right]=\left\{\mathrm{total}\mathrm{cross-sectional}\mathrm{area}\mathrm{of}\mathrm{cavity}\mathrm{portions}\left(\mathrm{B}\right)\mathrm{in}\mathrm{the}\mathrm{water-absorbent}\mathrm{resin}/\left(\mathrm{total}\mathrm{cross-sectional}\mathrm{area}\mathrm{of}\mathrm{resin}\mathrm{portions}\left(\mathrm{A}\right)\mathrm{in}\mathrm{the}\mathrm{water-absorbent}\mathrm{resin}+\mathrm{total}\mathrm{cross-sectional}\mathrm{area}\mathrm{of}\mathrm{cavity}\mathrm{portions}\left(\mathrm{B}\right)\mathrm{in}\mathrm{the}\mathrm{water-absorbent}\mathrm{resin}\right)\right\}\times 100\mathop{\mathrm{image}}$