Method Of Controlling Adhesive Build-Up On A Yankee Dryer

Abstract

An improved method of controlling build-up of adhesive coating on a Yankee drying cylinder preferably includes intermittently: (a) increasing the add-on rate of resinous adhesive to the drying cylinder substantially above the steady-state add-on rate; (b) segregating the absorbent sheet product produced while the add-on rate of resinous adhesive to the drying cylinder is elevated above the steady-state add-on rate from absorbent sheet product accumulated during steady-state operation; and (c) while the add-on rate of resinous adhesive to the drying cylinder is increased above the steady-state add-on rate, stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor.

Description

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in detail below with reference to the drawings wherein like numbers designate similar parts and wherein:

FIG. 1 is a schematic diagram of a first papermachine suitable for practicing the process of the present invention;

FIG. 2 is a schematic diagram of a second papermachine suitable for practicing the present invention; and

FIG. 3 is a schematic diagram illustrating the optional use of air foils in connection with the present invention.

Claims

1. In a continuous process of manufacturing absorbent sheet of the class including forming a wet cellulosic web, applying the web onto a drying cylinder of a dryer, which drying cylinder is provided with a resinous adhesive at a substantially constant add-on rate during steady-state operation and accumulating absorbent sheet on a reel, the improvement comprising controlling build-up of an adhesive coating on the drying cylinder by way of intermittently: (a) increasing the add-on rate of resinous adhesive to the drying cylinder above the steady-state add-on rate;(b) segregating absorbent sheet product produced while the add-on rate of resinous adhesive to the drying cylinder is elevated above the steady-state add-on rate from absorbent sheet product accumulated on the reel during steady-state operation; and(c) while the add-on rate of resinous adhesive to the drying cylinder is increased above the steady-state add-on rate, stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor.

2. The improvement according to claim 1, wherein the resinous adhesive comprises a PVOH resin and a polyamide-epihalohydrin resin in substantially fixed proportion during steady-state operation and the increase of resinous adhesive add-on rate to the drying cylinder above the steady-state add-on rate is achieved by increasing the add-on rate of PVOH resin above a steady-state add-on rate of PVOH resin while maintaining the add-on rate of polyamide-epihalohydrin resin substantially at its rate of addition during steady-state operation.

3. The improvement according to claim 1, wherein a major portion of the coating is stripped from the drying cylinder.

4. The improvement according to claim 3, wherein at least about 85% of the coating thickness is stripped from the drying cylinder.

5. The improvement according to claim 1, wherein the resinous adhesive is re-wettable and comprises polyvinyl alcohol.

6. The improvement according to claim 5, wherein the resinous adhesive composition consists essentially of a polyvinyl alcohol resin and a polyamide-epichlorohydrin resin.

7. The improvement according to claim 5, wherein the weight ratio of polyvinyl alcohol resin to polyamide-epichlorohydrin resin is from about 2 to about 4.

8. The improvement according to claim 5, wherein the add-on rate of polyvinyl alcohol rate is increased by at least about 50% with respect to a steady-state add-on rate of polyvinyl alcohol.

9. The improvement according to claim 5, wherein the add-on rate of polyvinyl alcohol rate is increased by at least about 100% with respect to a steady-state add-on rate of polyvinyl alcohol.

10. The improvement according to claim 1, wherein absorbent sheet is peeled from the drying cylinder during steady state operation.

11. The improvement according to claim 1, wherein the dryer is provided with a dryer hood capable of variable temperature and the temperature of the dryer hood is lowered during the step of stripping resinous adhesive from the drying cylinder.

12. The improvement according to claim 11, wherein the hood temperature at a dry-end is lowered by at least about 25° F. during the step of stripping resinous adhesive from the drying cylinder, and the hood temperature at a wet end is lowered by at least about 25° F.

13. The improvement according to claim 11, wherein the hood temperature at a dry-end is lowered by at least about 50° F. during the step of stripping resinous adhesive from the drying cylinder, and the hood temperature at a wet end is lowered by at least about 50° F.

14. The improvement according to claim 11, wherein the hood temperature at a dry-end is lowered by at least about 100° F. during the step of stripping resinous adhesive from the drying cylinder, and the hood temperature at a wet end is lowered by at least about 100° F.

15. The improvement according to claim 1, wherein the resinous adhesive coating composition is employed at an add-on rate of less than about 40 mg/m2 during steady-state operation.

16. The improvement according to claim 1, wherein the resinous adhesive coating composition is employed at an add-on rate of less than about 35 mg/m2 during steady-state operation.

17. The improvement according to claim 1, wherein the resinous adhesive coating composition is employed at an add-on rate of less than about 25 mg/m2 during steady-state operation.

18. The improvement according to claim 1, wherein the resinous adhesive add-on rate is from about 15 mg/m2 to about 60 mg/m2 during steady-state operation.

19. The improvement according to claim 18, wherein the web is peeled from the drying cylinder during steady-state operation of the process.

20. The improvement according to claim 1, wherein the web is creped from the drying cylinder with a creping doctor during steady-state operation of the process.

21. The improvement according to claim 1, wherein the absorbent sheet has a basis weight of from about 10 lbs/3000 ft2 to about 30 lbs/3000 ft2.

22. The improvement according to claim 1, wherein the absorbent sheet has a basis weight of from about 15 lbs/3000 ft2 to about 21 lbs/3000 ft2.

23. The improvement according to claim 1, wherein the resinous adhesive comprises a creping modifier.

24. The improvement according to claim 23, wherein the creping modifier includes a quaternary ammonium complex.

25. The improvement according to claim 23, wherein the creping modifier includes a quaternary ammonium complex and non-cyclic amide functionality.

26. The improvement according to claim 1, wherein at least a portion of the segregated absorbent sheet product is recycled to the process.

27. The improvement according to claim 1, wherein the segregated absorbent sheet product is sent to a broke chute.

28. In a continuous process of manufacturing absorbent sheet of the class including forming a wet cellulosic web, applying the web onto a drying cylinder of a dryer, which drying cylinder is provided with a resinous adhesive comprising a polyvinyl alcohol adhesive resin at a substantially constant add-on rate during steady-state operation, the improvement comprising controlling build-up of an adhesive coating on the drying cylinder by way of intermittently: (a) increasing the add-on rate of polyvinyl alcohol adhesive resin to the drying cylinder above the steady-state add-on rate; and(b) while the add-on rate of polyvinyl alcohol adhesive resin to the drying cylinder is increased above the steady-state add-on rate, stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor.

29. In a continuous process of manufacturing absorbent sheet of the class including forming a wet cellulosic web, applying the web onto a drying cylinder of a dryer, which drying cylinder is provided with a resinous adhesive at a substantially constant add-on rate during steady-state operation, wherein the resin adhesive consists essentially of a PVOH resin and an epihalohydrin resin in substantially fixed proportion in steady-state operation and the dryer is further provided with a dryer hood capable of variable temperature, the improvement comprising controlling build-up of an adhesive coating on the drying cylinder by way of stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor while controlling wet-tack to the drying cylinder by way of a technique selected from the group consisting of: (a) lowering the hood temperature before stripping the coating;(b) changing the resinous adhesive composition before stripping the coating; and(c) increasing the add-on rate of resinous adhesive above the steady-state add-on rate before stripping the coating.

30. The improvement according to claim 29, wherein wet-tack to the drying cylinder is controlled by combinations of two or more of techniques (a), (b) and (c).

31. The improvement according to claim 29, wherein the resinous adhesive composition is from about 60% by weight to about 70% by weight PVOH resin during steady rate operation.

32. The improvement according to claim 29, wherein the resinous adhesive composition is from about 75% by weight to about 90% by weight PVOH resin during steady rate operation.

33. In a continuous process of manufacturing absorbent sheet of the class including forming a wet cellulosic web, applying the web onto a drying cylinder of a Yankee dryer, which drying cylinder is provided with a resinous adhesive at a substantially constant add-on rate during steady-state operation and which Yankee dryer is provided with a dryer hood capable of variable temperature, the improvement comprising controlling build-up of an adhesive coating on the drying cylinder by way of intermittently: (a) stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor; and(b) while stripping at least a portion of the adhesive coating from the drying cylinder, controlling the temperature of the dryer such that the adhesive coating temperature does not exceed about 300° F. contemporaneously with the step of stripping adhesive from the drying cylinder.

34. The improvement according to claim 33, including controlling the temperature of the dryer such that the temperature of the adhesive coating does not exceed about 280° F. contemporaneously with the step of stripping adhesive from the drying cylinder.

35. The improvement according to claim 33, wherein the dryer temperature is controlled by varying the hood temperature.

36. The improvement according to claim 33, wherein the dryer temperature is controlled by varying the drying cylinder steam pressure.

37. The improvement according to claim 33, further comprising segregating product produced contemporaneously with stripping a portion of the coating from the drying cylinder from product produced during steady-state operation.

38. A continuous process for producing absorbent sheet comprising: (a) forming a wet cellulosic web;(b) at least partially dewatering the wet web;(c) adhering the web to a drying cylinder with a resinous adhesive coating composition applied at a substantially constant add-on rate during steady-state operation;(d) drying the web on the drying cylinder;(e) peeling the web from the drying cylinder under steady-state tension; and(f) winding the peeled web under steady-state tension to take up reel operating at a steady-state speed,

39. The method according to claim 38, including the step of reducing tension on the web concurrently with steps (g) and (h) by way of reducing the steady-state speed of the reel.

40. The method according to claim 39, wherein the drying cylinder is provided with a creping doctor which is positioned so that it contacts and crepes the web at reduced tension and does not contact the web during steady-state operation.

41. The method according to claim 39, further including the step of evaluating adhesion of the web to the drying cylinder concurrently with step (g) prior to resuming steady-state operation.

42. The method according to claim 38, wherein the web is at least partially dewatered by way of wet pressing prior to adhering the web to the drying cylinder.

43. The method according to claim 38, wherein the web is at least partially dewatered by way of thermal dewatering prior to adhering the web to the drying cylinder.

44. The method according to claim 43, wherein the web is at least partially dewatered by throughdrying prior to adhering the web to the drying cylinder.

45. The method according to claim 43, wherein the web is at least partially dewatered by impingement-air drying prior to adhering the web to the drying cylinder.

46. The method according to claim 38, further comprising the step of segregating product produced contemporaneously with stripping a portion of the coating from the drying cylinder from product produced during steady-state operation.

47. A continuous process for producing absorbent sheet comprising: (a) forming a wet cellulosic web;(b) at least partially dewatering the wet web;(c) transferring the partially dewatered web to a textured fabric;(d) texturing the wet web by conforming it to the textured fabric;(e) transferring the wet web to a drying cylinder;(f) adhering the web to a drying cylinder with a resinous adhesive coating composition applied at a substantially constant add-on rate during steady-state operation; and(g) drying the wet web on the drying cylinder;

48. The method according to claim 47, further comprising the step of segregating product produced contemporaneously with stripping a portion of the coating from the drying cylinder from product produced during steady-state operation.

49. In a continuous process of manufacturing absorbent sheet of the class including forming a wet cellulosic web, applying the web onto a drying cylinder of a dryer, which drying cylinder is provided with a resinous adhesive at a substantially constant add-on rate during steady-state operation and accumulating the absorbent sheet on a reel, the improvement comprising controlling build-up of an adhesive coating on the drying cylinder by way of intermittently: (a) increasing the add-on rate of resinous adhesive to the drying cylinder above the steady-state add-on rate;(b) segregating the absorbent sheet product produced while the add-on rate of resinous adhesive to the drying cylinder is elevated above the steady-state add-on rate from the absorbent sheet product accumulated on the reel during steady-state operation; and(c) while the add-on rate of resinous adhesive to the drying cylinder is increased above the steady-state add-on rate, stripping at least a portion of the adhesive coating from the drying cylinder with a cleaning doctor; and(d) while the add-on rate of resinous adhesive to the drying cylinder is increased above the steady-state add-on rate, creping the web from the drying cylinder.

50. The improvement according to claim 48, further comprising segregating product produced contemporaneously with stripping a portion of the coating from the drying cylinder from product produced during steady-state operation.

51. The improvement according to claim 48, wherein the dryer is provided with a dryer hood capable of variable temperature and the temperature of the dryer hood is lowered during the step of stripping resinous adhesive from the drying cylinder.