Anionic hydrogels based on heterocyclic N-vinyl monomers

Claim 1

The anionic, polymeric hydrogel produced by simultaneous polymerization and cross-linking in the presence of a free radical polymerization catalyst in an amount of from about 0.05 to about 4 weight percent, based on the total weight of monomers, and at a temperature of from about 20° C. to about 125° C., of a mixture consisting essentially of the following monomers: a. about 20 to about 95 weight percent, based on the total weight of monomers, of a heterocyclic N-vinyl monomer selected from the group consisting of N-vinyl lactams, N-vinyl succinimide, N-vinyl diglycoylimide, N-vinyl glutarimide, N-vinyl-3-morpholinone, N-vinyl-5-methyl-3-morpholinone and N-vinyl imidazole; b. about 50 to 0.05 weight percent, based on the total weight of monomers, of a monoethylenically unsaturated anionic monomer, capable of copolymerizing with (a), and which contains in its molecular structure a sulfonic acid group and is selected from the group consisting of acrylamido aryl sulfonic acids, acrylamido alkyl sulfonic acids, glycidyl acrylate sulfonic acid, glycidyl methacrylate sulfonic acid, and esters of α-methylene carboxylic acids with hydroxysulfonic acids which esters have the formula: R" -- COO -- Q -- SO 3 M, wherein R" represents a member of the group consisting of vinyl and α substituted vinyl, Q represents a divalent hydrocarbon radical having its valence bonds on different carbon atoms, and M is a cation; c. about 0.2 to about 12 weight percent, based on the total weight of monomers, of a polymerizable cross-linking agent, capable of copolymerizing with (a) and (b) and having the formula: ##STR12## wherein R represents a member of the group consisting of hydrogen and alkyl of from about 1 to about 4 carbon atoms; A represents alkylene of from 2 to about 10 carbon atoms or a polyglycol ether group of the formula: ##STR13## in which R' represents a member of the group consisting of hydrogen and alkyl of 1 to 2 carbon atoms, and n represents an integer of from 1 to about 20; and d. from 0 to about 50 weight percent, based on the total weight of monomers, of a monoethylenically unsaturated acrylic monomer capable of copolymerizing with (a), (b) and (c) and capable of polymerizing to a high molecular weight, in excess of 100,000, and selected from the group consisting of acrylamides, methacrylamides, acrylonitrile, methacrylonitrile, alkyl acrylates and methacrylates, and monohydroxy and monoalkoxy polyalkylene glycol acrylates and methacrylates; and provided that (a) ≧ (d) and (a) + (d) = about 40 to about 95 weight percent.