Method for producing paper

Patent metadata

Field	Value
Publication number	US-10435843-B2
Application number	US-201715649852-A
Country	US
Kind code	B2
Filing date	Jul 14, 2017
Priority date	Feb 16, 2016
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

A method for manufacturing paper is disclosed. A pulp slurry is produced, a paper sheet is formed from the slurry, an aldehyde functionalized polymer or polymers in combination with at least one additional strength additive is added to the slurry before and/or after sheet formation, and a water soluble acid is added on the paper sheet.

First claim

The invention claimed is:

1. A method for manufacturing paper, which comprises:
producing a pulp slurry;
forming a paper sheet from the pulp slurry including cellulose fibers;
adding at least one aldehyde functionalized polymer in combination with at least one additional strength additive to said pulp slurry or to the formed paper sheet, wherein the at least one aldehyde functionalized polymer covalently bonds to the cellulose fibers; and
adding at least one water soluble acid selected from the group consisting of mineral acid, organic acid, acrylic acid containing polymers, conjugate acid of a weak base and amine-containing polymer in protonated form, onto the formed paper sheet.

2. The method according to claim 1 , wherein the water soluble acid has a relative acidity (RA) value greater than 0.05 g/kg dry paper.

3. The method according to claim 1 , wherein the aldehyde functionalized polymer is a glyoxylated polyacrylamide polymer.

4. The method according to claim 1 , wherein the aldehyde functionalized polymer is a charged glyoxylated polyacrylamide polymer.

5. The method according to claim 1 , wherein the aldehyde functionalized polymer is a cationic glyoxylated polyacrylamide polymer.

6. The method according to claim 1 , wherein the additional strength additive comprises cationic polyamines, anionic polyacrylamides (APAM), cationic polyamide epichlorohydrin, polyvinylamine, polyethyleneimine, or mixtures thereof.

7. The method according to claim 1 , wherein the at least one additional strength additive is present in the formed paper sheet in an amount from about 0.1 lb/short tons to about 40 lb/short tons (oven dry paper).

8. The method according to claim 1 , wherein the additional strength additive includes an anionic polyacrylamide.

9. The method according to claim 8 , wherein the weight ratio of aldehyde functionalized polymer and anionic polyacrylamide is from about 1:100 to about 100:1.

10. The method according to claim 1 , wherein the aldehyde functionalized polymer and the additional strength additive are added to said pulp slurry before paper sheet formation.

11. The method according to claim 1 , wherein the aldehyde functionalized polymer is added to said pulp slurry before paper sheet formation and the additional strength additive is added after the paper sheet formation onto the paper surface.

12. The method according to claim 11 , wherein the additional strength additive, and the water soluble acid are added separately onto the surface of the paper sheet.

13. The method according to claim 11 , wherein a mixture of the additional strength additive, and the water soluble acid is added onto the surface of the paper sheet.

14. The method according to claim 1 , wherein the acid is added by spraying, printing, coating, padding, foam application, roller fluid feeding and/or impregnating.

15. The method according to claim 1 , wherein the aldehyde functionalized polymer is added by spraying, printing, coating, padding, foam application, roller fluid feeding and/or impregnating.

16. The method according to claim 1 , wherein the water solubility of the water soluble acid is more than 0.1 g/l at 20° C.

17. The method according to claim 1 , wherein the water soluble acid is a mineral acid, organic acid or a mixture thereof.

18. The method according to claim 17 , wherein the mineral acid is phosphoric acid, boric acid, sulfuric acid, hydrochloric acid, or any mixture thereof.

19. The method according to claim 17 , wherein the organic acid is formic acid, acetic acid, citric acid, lactic acid or malic acid, or any mixture thereof.

20. The method according to claim 1 , wherein the water soluble acid is an acrylic acid-containing polymer, a conjugate acid of a weak base or a mixture thereof.

21. The method according to claim 1 , wherein the acid comprises a mixture of acids.

22. The method according to claim 1 , wherein the pulp is softwood pulp, hardwood pulp, recycled paper, or a mixture thereof.

23. The method according to claim 1 , wherein the pulp comprises precipitated calcium carbonate (PCC), ground calcium carbonate (GCC) and/or recycled paper.

24. The method according to claim 1 , wherein the pulp slurry contains at least one alkaline agent.

25. The method according to claim 1 , wherein at least one alkaline agent is introduced to said pulp slurry before or after sheet forming.

26. The method according to claim 25 , wherein the alkaline agent is dry or encapsulated reagent that is soluble in water.

27. The method according to claim 25 , wherein the alkaline agent dissolves or is released in water over 10 seconds.

28. The method according to claim 25 , wherein the alkaline agent dissolves or is released in water over 30 seconds.

29. The method according to claim 25 , wherein the alkaline agent is selected from the group consisting of magnesium hydroxide, calcium hydroxide, magnesium bisulfite, magnesium oxide, zinc oxide, sodium sulfite, magnesium carbonate, magnesium carbonate-magnesium hydroxide ((MgCO 3 ) 4 Mg(OH) 2 ), sodium oxide-aluminum oxide (Na 2 O Al 2 O 3 ), sodium carbonate, sodium bicarbonate, sodium benzoate, calcium carbonate, calcium bicarbonate, sodium acetate, and combinations thereof.

30. The method according to claim 1 , wherein the water soluble acid is added on the paper sheet in such an amount that the surface of the sheet becomes acidic before entering dryer section.

31. The method according to claim 1 , wherein the water soluble acid is added on the paper sheet web having a solids content of at least 5% by weight.

32. The method according to claim 1 , further comprising:
adding an alkaline agent to said pulp slurry or to the formed paper sheet, unless the pulp slurry already originally contains an alkaline agent;
adding the at least one aldehyde functionalized polymer together with a flocculant including an anionic polyacrylamide before or after the paper sheet formation; and
adding at least one additional strength additive, such as an anionic polyacrylamide and/or polyamidoamine epichlorohydrin, before or after paper sheet formation.

33. A paper produced by the method according to claim 1 .

34. The paper according to claim 33 , wherein the wet to dry tensile strength ratio of the paper product is at least 20%.

Assignees

• Kemira Oyj

Inventors

• Lu Chen
• Chen Junhua
• Campbell Clay
• Rosencrance Scott
• Rabideau Jenna Sue

Classifications

• D21H17/39

  forming ether crosslinkages, e.g. alkylol groups · CPC title

• D21C9/002

  by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives · CPC title

• D21H17/06

  Alcohols; Phenols; Ethers; Aldehydes; Ketones; Acetals; Ketals · CPC title

• D21H17/65

  Acid compounds · CPC title

• D21H17/64

  Alkaline compounds · CPC title