Abstract

Novel anionic hydrogels, containing acidic groups in their molecular structure, and processes for their preparation are described. These novel hydrogels are stable three-dimensional polymer networks, having good water permeability and mechanical properties, and are obtained by simultaneous polymerization and cross-linking, in the presence of a polymerization catalyst, such as an organic peroxide, azobisisobutyronitrile or other free radical polymerization catalyst, of a mixture of (a) hydroxyalkyl acrylate or methacrylate, (b) a polymerizable acidic monomer containing a sulfonic acid, sulfate or phosphate group in its molecular structure, such as sulfo-ethyl acrylate or methacrylate or a sulfate or phosphate derivative of a hydroxyalkyl- acrylate or methacrylate, and (c) a cross-linking agent, such as a glycol diacrylate or dimethacrylate; if desired there may also be present (d) one or more additional monomers, usually an acryloid monomer such as an alkyl acrylate or methacrylate, acrylamides etc. (although other monomers such as vinyl acetate, styrene, etc. may also be used) which is copolymerizable with (a), (b) and (c). The thus obtained anionic hydrogels are useful for combining, by reaction or complexing, with materials having an opposite charge; such as basic or cationic agricultural chemicals (insecticides, herbicides, fungicides, plant growth regulators, etc.), germicides, pharmaceuticals, cosmetics, hormones, enzymes, flavors, fragrances, antiperspirants, metals and the like, both to recover such basic or cationic materials from an aqueous medium and for purifying water containing them, and also for the preparation of a complex or other combination of the anionic hydrogel with such materials which may be useful per se or from which the complexed or combined basic or cationic material may be slowly or controllably released.