PURPOSE: To obtain the subject composite material useful for a cutoff material, a caulking material, etc., having a high coefficient of swelling by water absorption and slight decrease in the coefficient of swelling by water absorption even after repetition of swelling by water absorption and contraction by drying, by mixing a finely granulated water absorbing resin with a non-rigid resin such as rubber.
CONSTITUTION: This water absorbing composite material is obtained by uniformly mixing (A) a water absorbing resin having ≤5μm average particle diameter with (B) a non-rigid resin, preferably natural rubber or synthetic rubber. The blending ratio of both the components is 1-300 pts.wt., preferably 50-200 pts.wt. of the component A per 100 pts.wt. of the component B. The water absorbing resin of the component A is preferably a water-in-oil type water-swelling polymer obtained by emulsifying an aqueous solution of a mixture of a water-soluble vinyl monomer and a crosslinking agent in the presence of a hydrophobic surfactant in an organic dispersion medium and then polymerizing the resultant emulsion.
HASHIMOTO HIRONOBU
EZAKI ATSUSHI
