Low compaction, pneumatic dewatering process for producing absorbent sheet

• US 20060000567A1
• Filed: 06/27/2005
• Published: 01/05/2006
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: GPCP IP Holdings LLC
• Original Assignee: Georgia-Pacific Consumer Products LP (KOCH Industries Incorporated)
• Inventors: Murray, Frank C., Wendt, Greg A.
• Granted Patent: US 7,416,637 B2
• Time in Patent Office: Days
• US Class Current: 162/111
• CPC Class Codes: B31F 1/126 including making of the paper to be crêped
• CPC Class Codes: D21F 11/006 Making patterned paper
• CPC Class Codes: D21F 11/14 Making cellulose wadding, filter or blotting paper
• CPC Class Codes: D21F 3/0254 Cluster presses, i.e. presses comprising a press chamber defined by at least three rollers
• CPC Class Codes: D21H 27/002 Tissue paper; Absorbent paper D21H21/22, D21H27/02, D21H27/20 take precedence; toilet paper A47K10/00; absorbent pads for physiological fluids A61L15/16; making on paper-making machines D21F11/00

Abstract

A low-compaction method of making an absorbent cellulosic web includes: forming a nascent web from a papermaking furnish; dewatering the nascent web to a consistency of from about 10 to about 30 percent on a foraminous forming support traveling at a first speed; rush-transferring the web at a consistency of from 10 to about 30 percent to an open texture fabric traveling at a second speed slower than the first speed of the forming support; further dewatering the web on the impression fabric to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane through the web thereby dewatering the web; and drying the web. Preferably the process includes the steps of selecting the papermaking furnish and controlling the process such that the dried web has a void volume fraction of at least 0.7, a hydraulic diameter in the range of from about 3 to about 20 microns and a Wet Springback Ratio of at least about 0.65. Optionally provided is a high solids fabric crepe in a pressure nip.

Claims

1. A low-compaction method of making an absorbent cellulosic web comprising:

a) forming a nascent web from a papermaking furnish;

b) dewatering the nascent web to a consistency of from about 10 to about 30 percent on a foraminous forming support traveling at a first speed;

c) rush-transferring the web at a consistency of from 10 to about 30 percent to an open texture fabric traveling at a second speed slower than the first speed of the forming support;

d) further dewatering the web on the open texture fabric to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane through the web thereby dewatering the web; and

e) drying the web.

2. The method according to claim 1, wherein the web is rush-transferred at a consistency of from about 15 to about 25 percent.

3. The method according to claim 1, wherein the web is rush-transferred at a Rush Transfer Ratio of from about 10 percent to about 30 percent.

4. The method according to claim 3, wherein the web is rush-transferred at a Rush Transfer Ratio of from about 15 percent to about 25 percent.

5. The method according to claim 1, wherein the nascent web is formed on a Fourdrinier former.

6. The method according to claim 5, wherein the nascent web is dewatered to a consistency of from about 20 percent to about 25 percent in the forming section.

7. The method according to claim 1, wherein the dried web is dewatered to a consistency of from about 45 to about 55 percent by application of pneumatic pressure across the web from the distributor membrane to the open texture fabric.

8. The method according to claim 1, wherein the web has a CD stretch of from about 5 percent to about 20 percent.

9. The method according to claim 1, wherein the dried web has a CD stretch of at least about 5 percent and an MD/CD tensile ratio of less than about 1.75.

10. The method according to claim 1, wherein the dried web has a CD stretch of at least about 5 percent and an MD/CD tensile ratio of less than about 1.5.

11. The method according to claim 1, wherein the dried web has a CD stretch of at least about 10 percent and an MD/CD tensile ratio of less than about 2.5.

12. The method according to claim 1, wherein the dried web has a CD stretch of at least about 15 percent and an MD/CD tensile ratio of less than about 3.0.

13. The method according to claim 1, wherein the dried web has a CD stretch of at least about 20 percent and an MD/CD tensile ratio of less than about 3.5.

14. The method according to claim 1, wherein the dried web has a bulk of at least about 6 g/cc.

15. The method according to claim 1, wherein the dried web has a bulk of at least about 7.5 g/cc.

16. The method according to claim 1, wherein the dried web has a bulk of at least about 10 g/cc.

17. The method according to claim 1, wherein the dried web has a bulk of at least about 15 g/cc.

18. The method according to claim 1, wherein the dried web has an absorbency of at least 5 g/g.

19. The method according to claim 1, wherein the dried web has an absorbency of at least about 7 g/g.

20. The method according to claim 1, wherein the dried web has an absorbency of at least about 9 g/g.

21. The method according to claim 1, wherein the dried web has an absorbency of at least about 11 g/g.

22. The method according to claim 1, wherein the dried web has an absorbency of at least about 13 g/g.

23. The method according to claim 1, wherein the dried web has a void volume fraction of from about 0.7 to about 0.9.

24. The method according to claim 1, wherein the dried web has a void volume fraction of from about 0.75 to about 0.85.

25. The method according to claim 1, wherein the dried web has a Wet Springback Ratio of at least about 0.6.

26. The method according to claim 1, wherein the dried web has a Wet Springback Ratio of at least about 0.65.

27. The method according to claim 1, wherein the dried web has a Wet Springback Ratio of from about 0.6 to about 0.8.

28. The method according to claim 1, wherein the dried web has a void volume fraction of at least about 0.7 and exhibits a hydraulic diameter in the range of from about 1.5 microns to about 60 microns.

29. The method according to claim 1, wherein the dried web has a void volume fraction of at least about 0.7 and exhibits a hydraulic diameter in the range of from about 3 microns to about 20 microns.

30. The method according to claim 1, wherein the dried web has a basis weight of from about 30 to about 200 lbs per 3,000 square feet.

31. The method according to claim 1, wherein the dried web has a basis weight of from about 100 to about 150 lbs per 3,000 square feet.

32. A low-compaction method of making an absorbent cellulosic web comprising:

a) forming a nascent web from a papermaking furnish;

b) dewatering the nascent web to a consistency of from about 10 to about 30 percent on a foraminous forming support traveling at a first speed;

c) rush-transferring the web at a consistency of from 10 to about 30 percent to an open texture fabric traveling at a second speed slower than the first speed of the forming support;

d) further dewatering the web on the open texture fabric to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane through the web thereby dewatering the web;

e) drying the web; and

f) selecting the papermaking furnish and controlling steps a-e such that the dried web has a void volume fraction of at least 0.7, a hydraulic diameter in the range of from about 1.5 to about 60 microns and a Wet Springback Ratio of at least about 0.65.

33. The method according to claim 32, wherein the dried web has a hydraulic diameter of from about 3 to about 20 microns.

34. A low-compaction method of making an absorbent cellulosic web comprising:

a) forming a nascent web from a papermaking furnish;

b) dewatering the nascent web to a consistency of from about 10 to about 30 percent on a foraminous forming support traveling at a first speed;

c) transferring the web to an open texture fabric;

d) further dewatering the web on the open texture fabric to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane through the web thereby dewatering the web; and

e) drying the web while it is held in the open texture fabric to a consistency of at least about 90 percent.

35. The method according to claim 34 wherein the web is dried while it is held in the open texture fabric to a consistency of at least about 92 percent.

36. The method according to claim 34, wherein the web is dried while it is held in the open texture fabric to a consistency of at least about 95 percent.

37. The method according to claim 34, wherein the web is dried with a plurality of can dryers while held in the open texture fabric.

38. The method according to claim 37, wherein the web is dried with an impingement-air dryer while held in the open texture fabric.

39. The method according to claim 34, wherein the web is dried with an impingement-air dryer while it is held in the open texture fabric.

40. A low-compaction method of making an absorbent cellulosic web comprising:

a) forming a nascent web from a papermaking furnish;

b) dewatering the nascent web to a consistency of from about 10 to about 30 percent on a foraminous forming support traveling at a first speed;

c) rush-transferring the web at a consistency of from about 10 to about 30 percent to an open texture fabric traveling at a second speed slower than the first a first of the forming support;

d) further dewatering the web on the open texture fabric to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane to the open texture fabric across the web thereby dewatering the web;

e) non-compactively transferring the web to a Yankee dryer; and

f) drying the web.

41. The method according to claim 40, wherein the web is creped from the Yankee dryer.

42. The method according to claim 41, wherein the web is creped from the Yankee dryer with an undulatory creping blade.

43. The method according to claim 40, wherein the web is peeled from the Yankee without a creping blade.

44. The method according to claim 40, wherein the web is applied to the rotating cylinder surface with a creping adhesive.

45. The method according to claim 44, wherein the creping adhesive is predominantly polyvinyl alcohol.

46. A method of making an absorbent cellulosic sheet comprising:

a) forming a nascent web having an apparently random distribution of fiber orientation from a papermaking furnish;

b) rush transferring the web to an open texture fabric;

c) drying the web to a consistency of from about 30 to about 60 percent by way of (i) combining the open texture fabric bearing said web with a fluid distribution membrane and an anti-rewet felt as the three pass through a nip into a pressure chamber defined in part by a plurality of nip rolls, the fluid distribution membrane bearing against the side of the open texture fabric away from the web, with the anti-rewet felt bearing against the web, and (ii) applying a pneumatic pressure gradient from the distributor membrane through the web thereby dewatering the web;

d) thereafter transferring the web to a translating transfer surface moving at a first speed;

e) fabric-creping the web from the transfer surface at a consistency of from about 30 to about 60 percent utilizing a creping fabric, the creping step occurring under pressure in a fabric creping nip defined between the transfer surface and the creping fabric wherein the fabric is traveling at a second speed slower than the speed of said transfer surface, the fabric pattern, nip parameters, velocity delta and web consistency being selected such that the web is creped from the surface and redistributed on the creping fabric to form a web with a reticulum having a plurality of interconnected regions of different fiber orientation including at least (i) a plurality of fiber enriched regions of having an orientation bias in a direction transverse to the machine-direction, interconnected by way of (ii) a plurality of colligating regions whose fiber orientation bias is offset from the fiber orientation of the fiber enriched regions; and

f) drying the web.

47. The method according to claim 46, fabric-creped from the transfer surface at a Fabric Crepe of from about 10 to about 100 percent.

48. The method according to claim 46, fabric-creped from the transfer surface at a Fabric Crepe of at least about 40 percent.

49. The method according to claim 46, fabric-creped from the transfer surface at a Fabric Crepe of at least about 60 percent.

50. The method according to claim 46, fabric-creped from the transfer surface at a Fabric Crepe of at least about 80 percent.

51. The method according to claim 46, wherein the transfer surface is the surface of a rotating cylinder.