Process for the preparation of a highly water absorptive resin from acrylic resin, epoxy crosslinker and hydrophilic silicate

Claim 1

A process for preparing a highly water absorptive resin comprising the steps of: (a) neutralizing crylic acid with an alkali metal hydroxide to produce an equivalent amount of alkali metal acrylate; (b) mixing about 70-90% by weight of the produced alkali metal acrylate of step (a), about 10-30% by weight of methacrylic acid, a polymerization initiator, and a first crosslinking agent comprising N,N-methylene bisacrylamide to form an initial mixture; (c) dispersing the initial mixture in an aqueous medium and polymerizing the dispersed initial mixture to form a polymerized intermediate aqueous dispersion; (d) removing the water from the polymerized intermediate aqueous dispersion by azeotropic distillation to reduce the water content of the polymerized intermediate aqueous dispersion to about 15-35% by weight, wherein said polymerized intermediate comprised in the aqueous dispersion has an average particle size of about 100-150 μm; (e) adding about 1.2-8% by weight based on the weight of the polymerized intermediate of a second crosslinking agent, said second crosslinking agent having at least two epoxy radicals for increasing the density of the surface thereof; and (f) mixing about 0.1-5% by weight of a silicon dioxide hydrate (SiO 2 . n H 2 O) wherein n is a positive integer based on the polymerized intermediate to produce a highly water absorptive resin.