CA2550261C - Filler for papermaking process - Google Patents

Abstract

The present invention relates to a filler comprising calcium salt and cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the filler is substantially free from fibres or fibrils of cellulose or lignocellulose. The invention also relates to a filler comprising calcium salt and a cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the cellulose derivative contains cationic groups. The invention further relates to a method of producing a filler which comprises mixing a calcium salt-containing material with a cellulose derivative having a degree of substitution of net ionic groups up to about 0.65 in the substantial absence of fibres or fibrils of cellulose or lignocellulose. The invention also relates to a method of producing a filler which comprises mixing a calcium salt-containing material with a cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the cellulose derivative contains cationic groups. The invention further relates to a filler obtainable by the methods. The invention further relates to a papermaking process which comprises providing an aqueous suspension containing cellulosic fibres, introducing into the suspension a filler comprising calcium salt and cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the filler is substantially free from fibres or fibrils of cellulose or lignocellulose, and dewatering the suspension to form a web or sheet of paper. The invention also relates to a papermaking process which comprises providing an aqueous suspension containing cellulosic fibres, introducing into the suspension a filler calcium salt and cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the cellulose derivative contains cationic groups, and dewatering the suspension to form a web or sheet of paper.

Claims (63)

1. A filler comprising calcium salt and an anionic cellulose derivative having a degree of substitution of net anionic groups up to 0.65, wherein the filler is substantially free from fibres or fibrils of cellulose or lignocellulose.

2. The filler according to claim 1, characterised in that the degree of substitution is from 0.01 to 0.60.

3. The filler according to claim 1 or 2, characterised in that the degree of substitution is from 0.05 to 0.50.

4. The filler according to any one of claims 1 to 3, characterised in that the degree of substitution is from 0.10 to 0.45.

5. The filler according to any one of claims 1 to 4, characterised in that the degree of substitution is from 0.15 to 0.40.

6. The filler according to any one of claims 1 to 5, characterised in that the cellulose derivative is a cellulose ether.

7. The filler according to any one of claims 1 to 6, characterised in that the cellulose derivative contains carboxymethyl groups.

8. The filler according to any one of claims 1 to 7, characterised in that the cellulose derivative is at least partly water soluble.

9. The filler according to any one of claims 1 to 8, characterised in that the filler has a cellulose derivative content from 0.3 to 10 % by weight, based on the weight of the solids of the filler.

10. The filler according to any one of claims 1 to 9, characterised in that the filler has a calcium salt content from 60 to 80 % by weight, based on the weight of the solids of the filler.

11. The filler according to any one of claims 1 to 10, characterised in that the calcium salt is calcium carbonate.

12. The filler according to any one of claims 1 to 11, characterised in that the calcium salt is precipitated calcium carbonate.

13. The filler according to any one of claims 1 to 12, characterised in that the calcium salt is ground calcium carbonate.

14. The filler according to claim 2, characterised in that the filler is free from fibres or fibrils of cellulose or lignocellulose.

15. The filler according to any one of claims 1 to 13, characterised in that at least 10% by weight of the cellulose derivative is adsorbed on or attached to the calcium salt.

16. The filler according to claim 14 or 15, characterized in that at least 60%
by weight of the cellulose derivative is adsorbed on or attached to the calcium salt.

17. The filler according to claim 15, characterised in that at least 45% by weight of the cellulose derivative is adsorbed on or attached to the calcium salt.

18. Paper comprising a filler according to any one of claims 1 to 17.

19. The paper according to claim 18, characterised in that the total filler content of the paper is from 5 to 40 % by weight, based on dry paper.

20. A method of making a filler which comprises mixing a calcium salt-containing material with a cellulose derivative having a degree of substitution of net ionic groups up to 0.65 in the substantial absence of fibres or fibrils of cellulose or lignocellulose.

21. A process for the production of paper which comprises providing an aqueous suspension containing cellulosic fibres, introducing into the suspension a filler according to any one of claims 1 to 16, and dewatering the suspension to form a web or sheet of paper.

22. The process according to claim 21, characterised in that the filler is introduced into the suspension by adding a single composition containing the calcium salt and cellulose derivative to the suspension.

23. The process according to any one of claims 20 to 22, characterised in that the filler is added in an amount of 10 to 30% by weight, based on the weight of dry fibres.

24. The process according to claim 22 or 23, characterised in that the filler is added in an amount of from 5 to 40% by weight, based on the weight of dry fibres.

25. The process according to any one of claims 21 to 24, characterised in that the process further comprises adding a cellulose-reactive sizing agent to the suspension.

26. The process according to any one of claims 21 to 25, characterised in that the process further comprises introducing drainage and retention aids into the cellulosic suspension.

27. The process according to claim 26, characterised in that the drainage and retention aids comprise cationic, anionic or non-ionic polymers.

28. he process according to claim 26 or 27, characterized in that the drainage and retention aids comprise a combination of cationic polymer and anionic microparticulate material.

29. The process of any one of claims 26 to 28, characterised in that the drainage and retention aids comprise a combination of cationic starch and anionic colloidal silica-based particles, a combination of cationic polyacrylamide and anionic colloidal silica-based particles, or a combination of cationic polyacrylamide and butonite or montmorillonite.

30. A filler comprising calcium salt and cellulose derivative having a degree of substitution of net ionic groups up to 0.65, wherein the cellulose derivative contains cationic groups and wherein the net ionic degree of substitution is net anionic, net cationic or net neutral.

31. The filler according to claim 30, characterised in that the cellulose derivative has a degree of substitution of anionic groups up to 0.65.

32. The filler according to claim 30 or 31, characterised in that the degree of substitution is from 0.01 to 0.60.

33. The filler according to any one of claims 30 to 32, characterised in that the degree of substitution is from 0.05 to 0.50.

34. The filler according to any one of claims 30 to 33, characterised in that the degree of substitution is from 0.10 to 0.45.

35. The filler according to any one of claims 30 to 34, characterised in that the degree of substitution is from 0.15 to 0.40.

36. The filler according to any one of claims 30 to 35, characterised in that the cellulose derivative is a cellulose ether.

37. The filler according to any one of claims 30 to 36, characterised in that the cellulose derivative contains carboxymethyl groups.

38. The filler according to any one of claims 30 to 37, characterised in that the cellulose derivative contains quaternary ammonium groups.

39. The filler according to any one of claims 30 to 38, characterised in that the cellulose derivative has a degree of substitution of cationic groups from 0.02 to 0.50.

40. The filler according to any one of claims 30 to 39, characterised in that the cellulose derivative is amphoteric.

41. The filler according to any one of claims 30 to 40, characterised in that the cellulose derivative is at least partly water soluble.

42. The filler according to any one of claims 30 to 41, characterised in that the filler has a cellulose derivative content from 0.3 to 10% by weight, based on the weight of the solids of the filler.

43. The filler according to any one of claims 30 to 42, characterised in that the filler has a calcium salt content from 60 to 80 % by weight, based on the weight of the solids of the filler.

44. The filler according to any one of claims 30 to 43, characterised in that the calcium salt is calcium carbonate.

45. The filler according to any one of claims 30 to 44, characterised in that the calcium salt is precipitated calcium carbonate.

46. The filler according to any one of claims 30 to 45, characterised in that the calcium salt is ground calcium carbonate.

47. The filler according to claim 30, characterised in that the filler further comprises fibres or fibrils of cellulose or lignocellulose.

48. The filler according to claim 30, characterised in that the filler is substantially free from fibres or fibrils of cellulose or lignocellulose.

49. The filler according to any one of claims 30 to 41, characterised in that at least 10% by weight of the cellulose derivative is adsorbed on or attached to the calcium salt.

50. The filler according to claim 49, characterised in that at least 45% by weight of the cellulose derivative is adsorbed on or attached to the calcium salt.

51. Paper comprising a filler according to any one of claims 30 to 50.

52. The paper according to claim 51, characterised in that the filler content of the paper is from 5 to 40 % by weight, based on the weight of dry fibres.

53. The paper according to claim 51 or 52, characterised in that the filler content of the paper is from 10 to 30 % by weight, based on the weight of dry fibres.

54. A method of making a filler which comprises mixing a calcium salt-containing material with a cellulose derivative having a degree of substitution of net ionic groups up to 0.65 wherein the cellulosic derivative contains cationic groups and wherein the net ionic substitution is net anionic, net cationic or net neutral.

55. A process for the production of paper which comprises providing an aqueous suspension containing cellulosic fibres, introducing into the suspension a filler according to any one of claims 30 to 50, and dewatering the suspension to form a web or sheet of paper.

56. The process according to claim 55, characterised in that the filler is introduced into the suspension by adding a single composition containing the calcium salt and cellulose derivative to the suspension.

57. The process according to claim 55 or 56, characterised in that the filler is added in an amount of from 5 to 40 % by weight, based on the weight of dry fibres.

58. The process according to any one of claims 55 to 57, characterised in that the filler is added in an amount of from 10 to 30 % by weight, based on the weight of dry fibres.

59. The process according to any one of claims 56 to 58, characterised in that it further comprises adding a cellulose-reactive sizing agent to the suspension.

60. The process according to any one of claims 56 to 59, characterised in that it further comprises introducing drainage and retention aids into the cellulosic suspension.

61. The process according to claim 60, characterised in that the drainage and retention aids comprise cationic, anionic or non-ionic polymers.

62. The process according to claim 60 or 61, characterised in that it the drainage and retention aids comprise a combination of cationic polymer and anionic microparticulate material.

63. The process according to any one of claims 60 to 62, characterised in that it the drainage and retention aids comprise a combination of cationic starch and anionic colloidal silica-based particles, a combination of cationic polyacrylamide and anionic colloidal silica-based particles, or a combination of cationic polyacrylamide and bentonite or montmorillonite.