Glyoxalated inter-copolymers with high and adjustable charge density
View Patent ↗A method for making storage-stable glyoxalated inter-copolymers with higher and adjustable charge density suitable for use as a strengthening agent for paper. The glyoxalated inter-copolymers can be used to enhance the strength of paper, particularly recycled paper and mechanical printing paper.
1. A method for producing a glyoxalated inter-copolymer of high charge density useful for strengthening paper, comprising:
(a) reacting a first portion of glyoxal with a blended composition comprising (1) a polyacrylamide having pendant amide groups and (2) a high charge density polymer having pendant glyoxal-reactive groups selected from the group consisting of (A) a polyamidoamine epichlorohydrin polymer; (B) a Michael addition adduct of a polyamidoamine epichlorohydrin polymer and an acrylamide; (C) an interchange reaction inter-copolymer of primary amine-terminated cationic polyamidoamine and neutral polyacrylamide; (D) a cationic polyamidoamine grafted polyacrylamide; and (E) mixtures thereof, to form a first mixture comprising a glyoxalated inter-copolymer of high charge density having separate segments of the polyacrylamide and the high charge density polymer.
2. The method of claim 1 further comprising:
(b) adding an acid to the first mixture to form a second mixture having reduced pH; and
(c) adding a second portion of the glyoxal to the second mixture to form a stabilized glyoxalated inter-copolymer.
3. The method of claim 1 wherein the high charge density polymer is a polyamidoamine epichlorohydrin polymer.
4. A composition for enhancing the wet strength of paper prepared by the method of claim 1 .
5. Paper strengthened by the composition of claim 4 .
6. A method for producing a glyoxalated inter-copolymer of high charge density useful for strengthening paper, comprising:
(a) reacting a first portion of glyoxal with a blended composition comprising (1) a polyacrylamide having pendant amide groups and (2) a high charge density polymer having pendant glyoxal-reactive groups selected from the group consisting of (A) a polyamidoamine epichlorohydrin polymer; (B) a Michael addition adduct of a polyamidoamine epichlorohydrin polymer and an acrylamide; (C) an interchange reaction inter-copolymer of primary amine-terminated cationic polyamidoamine and neutral polyacrylamide; (D) a cationic polyamidoamine grafted polyacrylamide; (E) a cationic starch; (F) a grafted cationic polyacrylamide cationic starch; and (G) mixtures thereof, to form a first mixture comprising a glyoxalated inter-copolymer of high charge density having separate segments of the polyacrylamide and the high charge density polymer;
(b) adding an acid to the first mixture to form a second mixture having reduced pH; and
(c) adding a second portion of glyoxal to the second mixture to form a stabilized glyoxalated inter-copolymer.
7. The method of claim 6 wherein the polyacrylamide (1) is a non-ionic polyacrylamide.
8. The method of claim 6 wherein the polyacrylamide (1) is a cationic polyacrylamide.
9. The method of claim 8 wherein the cationic polyacrylamide (1) comprises diallyl dimethyl ammonium chloride (DADMAC) in an amount of up to about 0.1 mole percent of the acrylamide monomer.
10. The method of claim 8 further comprising preparing the cationic polyacrylamide (1) by free radical polymerization of an acrylamide monomer in the presence of a cationic co-monomer.
11. The method of claim 10 wherein the cationic co-monomer is selected from DADMAC, 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-methylacroyloxy-ethyltrimethyl ammonium methylsulfate, 3-acrylamido-3-methylbutyl trimethyl ammonium chloride and 2-(dimethylamino) ethyl acrylate.
12. The method of claim 10 wherein the cationic co-monomer is used in a concentration of 1-15 mole percent of the acrylamide monomer.
13. The method of claim 6 wherein the polyacrylamide is prepared by free radical polymerization of an acrylamide monomer and a cationic co-monomer in the presence of an aldehyde scavenger which is an adduct of choline chloride and acrylamide.
14. The method of claim 13 wherein the aldehyde scavenger has the structure:
wherein:
R 1 is hydrogen or C 1 -C 2 alkyl;
R 2 is hydrogen or C 1 -C 4 alkyl; and
A − is a compatible anion.
15. The method of claim 14 wherein R 1 and R 2 are each hydrogen and A − is chloride.
16. The method of claim 6 wherein the polyacrylamide is prepared in the presence of a di-functional monomer to obtain a branched structure.
17. The method of claim 16 wherein the di-functional monomer is selected from the group consisting of N,N′-methylene-bisacrylamide, N,N′-methylene-bismethacrylamide, N-allyl acrylamide, N-allyl methacrylamide and mixtures thereof.
18. The method of claim 16 wherein the di-functional monomer is used in a concentration of 0.01-5.0 mole percent of acrylamide monomer.
19. The method of claim 6 wherein the first portion of glyoxal is provided in an amount of 10 to 60 mole percent of the pendant amide groups.
20. The method of claim 6 wherein the second portion of glyoxal is from about 1 to about 75 weight percent of the first portion of glyoxal.
21. The method of claim 6 wherein the second portion of glyoxal is from about 4 to about 50 weight percent of the first portion of glyoxal.
22. The method of claim 6 further comprising adding an aldehyde scavenger to the first mixture.
23. The method of claim 22 wherein the aldehyde scavenger is selected from the group consisting of lactic acid, malic acid, citric acid, and choline chloride.
24. The method of claim 22 wherein the aldehyde scavenger is added to the first mixture in an amount of 0.0001 to 0.25 mole per mole of total glyoxal.
25. The method of claim 22 wherein the aldehyde scavenger is an adduct of choline chloride and acrylamide.
26. The method of claim 25 wherein the aldehyde scavenger has the structure:
wherein:
R 1 is hydrogen or C 1 -C 2 alkyl;
R 2 is hydrogen or C 1 -C 4 alkyl; and
A − is a compatible anion.
27. The method of claim 26 wherein R 1 and R 2 are each hydrogen and A − is chloride.
28. The method of claim 25 wherein the aldehyde scavenger is present in step (a) in an amount ranging from about 0.1 to about 0.5 mole for each mole of total glyoxal.
29. The method of claim 25 wherein the aldehyde scavenger is present in step (b) in an amount ranging from about 0.01 to about 0.15 mole for each mole of total glyoxal.
30. The method of claim 25 wherein the aldehyde scavenger is present in step (c) in an amount ranging from about 0.01 to about 0.3 mole for each mole of total glyoxal.
31. The method of claim 25 wherein the aldehyde scavenger is added to the stabilized glyoxalated inter-copolymer in an amount ranging from about 0.01 to about 0.3 mole for each mole of total glyoxal.
32. The method of claim 6 further comprising including an aldehyde scavenger in one or more of step (a), step (b), step (c), and the stabilized glyoxalated inter-copolymer.
33. A composition for enhancing the wet strength of paper prepared by the method of claim 6 .
34. Paper strengthened by the composition of claim 33 .
35. The composition of claim 33 wherein the high charge density polymer has a molecular weight of 10,000 to 1,000,000 daltons.
36. The composition of claim 33 wherein the high charge density polymer has a charge density of 2 to 5 meq/g.