Water absorbing, cross-linked acrylate resin copolymers are prepared by aqueous polymerization of (A) acrylic acid neutralized 70 to 100 mole percent for example with ammonia, and/or caustic alkali and/or an amine; with (B) styrene and/or methyl methacrylate in an amount of 1% to 25% based on the weight...http://www.google.es/patents/US4677174?utm_source=gb-gplus-sharePatente US4677174 - Water absorbent styrene-acrylic acid copolymers
