Polyacrylamide-based strengthening agent
View Patent ↗A method for preparing a cationic polyacrylamide composition particularly suitable for making a glyoxylated polyacrylamide composition useful as a temporary wet-strengthening agent and the composition resulting from that method, along with the use of the composition for adding temporary wet strength to paper and the resulting strengthened paper products.
1. A method for producing a cationic polyacrylamide composition comprising (1) initially reacting one portion of an acrylamide monomer mixture in the presence of a cationic monomer and an initiator to produce a cationic polyacrylamide and (2) thereafter reacting a second portion of the acrylamide monomer mixture in the presence of the previously prepared cationic polyacrylamide and an initiator, wherein the acrylamide monomer mixture comprises an acrylamide monomer and wherein a polyacrylamide-adduct made by reacting an amine having active hydrogens with an acrylamide monomer is present during the initially reacting step (1).
2. The method of claim 1 wherein the initially reacting comprises a free radical polymerization of acrylamide monomer in the presence of the cationic monomer.
3. The method of claim 2 wherein the cationic monomer is selected from diallyl dimethyl ammonium chloride, 2-vinylpyridine, 4-vinylpryridine, 2-methyl-5-vinyl pyridine, 2-vinyl-N-methylpyridinium chloride, p-vinylphenyl-trimethyl ammonium chloride, 2-(dimethylamino) ethyl methacrylate, trimethyl(p-vinylbenzyl)ammonium chloride, p-dimethylaminoethylstyrene, dimethylaminopropyl acrylamide, 2-methylacroyloxyethyltrimethyl ammonium methylsulfate, 3-acrylamido-3-methylbutyl trimethyl ammonium chloride, 2-(dimethylamino) ethyl acrylate and mixtures thereof.
4. The method of claim 1 wherein the one portion of the acrylamide monomer mixture comprises from 20 to 75% of the acrylamide monomer and the initially reacting comprises from 40 to 75% of a total reaction period for producing the cationic polyacrylamide composition.
5. The method of claim 4 wherein the second portion of the acrylamide monomer mixture is added for reaction in step (2) at a more rapid rate than the one portion of the acrylamide monomer mixture is added for reaction in step (1).
6. The method of claim 1 wherein the acrylamide monomer is selected from the group consisting of acrylamide, methacrylamide, ethylacrylamide, crotonamide N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide and mixtures thereof.
7. The method of claim 1 wherein the acrylamide monomer mixture comprises an additional component selected from the group consisting of a chain transfer agent, a diluter monomer, a functional monomer and mixtures thereof.
8. The method for producing a cationic polyacrylamide composition according to claim 1 wherein the polyacrylamide-adduct has formula (II):
wherein R 1 , R 2 , and R 3 are independently selected from hydrogen and a residue of an acrylamide monomer resulting from a Michael Addition reaction between an acrylamide monomer and an active hydrogen of the amine, and wherein at least one of R 1 , R 2 , and R 3 is the residue of an acrylamide monomer.
9. The method for producing a cationic polyacrylamide composition according to claim 1 wherein the polyacrylamide-adduct has formula (III)
wherein R 1 , R 2 , R 6 and R 3 are independently selected from hydrogen and a residue of an acrylamide monomer resulting from a Michael Addition reaction between an acrylamide monomer and an active hydrogen of the amine and wherein at least one of R 1 , R 2 , R 6 and R 3 is the residue of an acrylamide monomer; R 4 and R 5 are independently selected from hydrogen and a C 1 to C 4 alkyl; a is an integer independently selected from 1, 2 or 3 and b is an integer reflecting the number of repeating N-alkylene units of the polyacrylamide-adduct.
10. The method for producing a cationic polyacrylamide composition according to claim 1 wherein the polyacrylamide-adduct has formula (IV):
wherein R 1 and R 2 are independently selected from hydrogen and a residue of an acrylamide monomer resulting from a Michael Addition reaction between an acrylamide monomer and an active hydrogen of the amine and wherein at least one of R 1 and R 2 is the residue of an acrylamide monomer; R 4 , R 5 and R 7 are independently selected from hydrogen and a C 1 to C 4 alkyl; a is an integer independently selected from 1, 2 or 3, n is an integer reflecting the number of repeating vinyl amine units indicative of the molecular weight of the polyacrylamide-adduct and Z and Z′ independently are selected from the group consisting of repeating units of another vinyl monomer, hydrogen, and a linear or branched C 1 to C 6 alkyl.
11. The method for producing a cationic polyacrylamide composition according to claim 1 wherein the polyacrylamide-adduct has formula (V):
wherein R 1 and R 8 are independently selected from hydrogen and a residue of an acrylamide monomer resulting from a Michael Addition reaction between an acrylamide monomer and an active hydrogen of the amine and wherein at least one of R 1 and R 8 is the residue of an acrylamide monomer; a and b are integers independently selected from 1, 2 or 3; R 4 , R 5 , R 7 and R 9 are independently selected from the group consisting of hydrogen and a C 1 to C 4 alkyl; n is an integer indicative of the molecular weight of polyacrylamide-adduct and X and X′ independently are selected from the group consisting of —OH, OR, where R is a C 1 to C 4 alkyl and OMe, where Me is a salt-forming metal ion, a residue of a diamine, and a residue of an acrylamide monomer.
12. The method of claim 1 wherein the acrylamide monomer mixture comprises an acrylamide monomer and a polyacrylamide-adduct made by reacting an amine having active hydrogens with an acrylamide monomer.