Method and apparatus for making a laundry detergent sheet

1. A method of making a laundry detergent sheet, said method comprising the steps of:

preparing a first shelf-stable solution;

preparing a second non-shelf-stable solution comprising a portion of said first shelf-stable solution;

applying said second non-shelf-stable solution onto a heated surface; and drying said second non-shelf-stable solution on said surface to form said laundry detergent sheet,

wherein said applying step comprises moving at least a portion of said surface in a rising direction, and contacting said rising portion of said surface with said second non-shelf-stable solution to coat said surface with said second non-shelf-stable solution and allow excess second non-shelf-stable solution to drain off said rising portion of said surface in a direction opposite the rising direction.

2. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution comprises:

a) about 5 to about 20 wt-% of polyvinyl alcohol;

b) about 15 to about 30 wt-% of α-olefin sulfonate;

c) about 1 to about 15 wt-% of glycerin;

d) about 0.01 to about 5 wt-% of preservative; and

e) about 20 to about 80 wt-% of water.

3. The method of making a laundry detergent sheet as claimed in claim 2 wherein said first shelf-stable solution comprises:

a) about 10.1 wt-% of polyvinyl alcohol;

b) about 21.8 wt-% of α-olefin sulfonate;

c) about 10.66 wt-% of glycerin;

d) about 0.14 wt-% of preservative; and

e) about 57.3 wt-% of water.

4. The method of making a laundry detergent sheet as claimed in claim 3 , wherein said preservative comprises methylisothiazolinone (MIT) and chlorotnethylisothiazolinone (CIT).

5. The method of making a laundry detergent sheet as claimed in claim 3 , wherein said α-olefin sulfonate has a concentration of about 36 wt-% to about 42 wt % in water.

6. The method of making a laundry detergent sheet as claimed in claim 5 , wherein said α-olefin sulfonate has a concentration of about 38 wt-% in water.

7. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution has a viscosity in the range of about 45,000 centipoise to about 85,000 centipoise at a temperature of about 14° C. to about 18° C.

8. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution has a viscosity in the range of about 22,000 centipoise to about 67,000 centipoise at a temperature of about 20° C. to about 24° C.

9. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution has a viscosity in the range of about 12,000 centipoise to about 40,000 centipoise at a temperature of about 28° C. to about 32° C.

10. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution has a density of about 1.01 g/ml to about 1.20 g/ml at a temperature of about 20° C. to about 24° C.

11. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said first shelf-stable solution has a useful time of up to at least two months at room temperature.

12. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said second non-shelf-stable solution comprises:

a) about 20 wt-% to about 80 wt-% of said first shelf-stable solution;

b) about 10 wt-% to about 50 wt-% of starch;

c) about 0.10 wt-% to about 5 wt-% of liquid paraffin;

d) about 0.10 wt-% to about 5 wt-% of glycerin; and

e) about 1 wt-% to about 25 wt-% of liquid detergent, wherein said liquid detergent comprises as aqueous solution of one or more of:

sodium laureth sulfate;

sodium borate;

sodium metasilicate;

hexylene glycol;

citric acid;

lauryl glucoside; and

laureth-4.

13. The method of making a laundry detergent sheet as claimed in claim 12 , wherein said second non-shelf-stable solution comprises:

a) about 67.0 wt-% of said first shelf-stable solution;

b) about 19.7 wt-% of starch;

c) about 0.5 wt-% of liquid paraffin.

d) about 1.0 wt-% of glycerin; and

e) about 11.8 wt-% of said liquid detergent.

14. The method of making a laundry detergent sheet as claimed in claim 13 , wherein said liquid detergent comprises:

a) about 5 wt-% to about 90 wt-% of sodium laureth sulfate;

b) about 0.1 - wt-% to about 5 wt-% of sodium borate;

c) about 0.1 wt-% to about 10 wt-% of sodium metasilicate;

d) about 0.1 wt-% to about 10 wt-% of hexylene glycol;

e) about 0.1 wt-% to about 10 wt-% of cocamidopropyl betaine;

f) about 0.1 wt-% to about 10 wt-% of citric acid;

g) about 0.1 wt-% to about 10 wt-% of lauryl glucoside;

h) about 0.1 wt-% to about 20 wt-% of laureth-4; and

i) about 5 wt-% to about 50 wt-% of water.

15. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said second non-shelf-stable solution has a useful time of up to at least 6 hours at room temperature.

16. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said movable surface is a conveyor.

17. The method of making a laundry detergent sheet as claimed in claim 16 , wherein said conveyor has a curved rising portion.

18. The method of making a laundry detergent sheet as claimed in claim 17 , wherein said curved rising portion of said conveyor is a partial cylinder.

19. The method of making a laundry detergent sheet as claimed in claim 16 , wherein said conveyor has a non-curved rising portion.

20. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said movable surface is a cylinder rotatable about a horizontal axis with said rising portion on one side and a descending portion on the other side.

21. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said contacting said rising portion of said surface with said second non-shelf-stable solution comprises positioning an application reservoir, for holding a liquid volume of said second non-shelf-stable solution, against said rising portion of said surface.

22. The method of making a laundry detergent sheet as claimed in claim 21 , further comprising maintaining a liquid level of said second non-shelf-stable solution in said application reservoir by gravity feed from a supply reservoir.

23. The method of making a laundry detergent sheet as claimed in claim 21 , wherein said applying step further comprises adjusting a thickness: of said second non-shelf-stable solution on said surface by varying a viscosity of said second non-shelf-stable solution, varying a slope of the rising portion of said surface, varying a speed of the movable surface, varying a heat of said drying step, varying a position of said application reservoir relative to said rising portion, and/or varying a liquid level of said second non-shelf-stable solution in said application reservoir.

24. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said heated surface conductively heats said second non-shelf-stable solution on said surface.

25. The method of making a laundry detergent sheet as claimed in claim 24 , wherein said heated surface is a conveyor.

26. The method of making a laundry detergent sheet as claimed in claim 24 , wherein said heated surface is a cylinder rotatable about a horizontal axis.

27. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said drying step further comprises applying heat to said second non-shelf-stable solution on said surface.

28. The method of making a laundry detergent sheet as claimed in claim 27 , wherein said step of applying heat to said second non-shelf-stable solution on said surface comprises radiantly heating said second non-shelf-stable solution on said surface.

29. The method of making a laundry detergent sheet as claimed in claim 27 , wherein said step of applying heat to said second non-shelf-stable solution on said surface comprises heating air adjacent to said second non-shelf-stable solution on said surface to convectively heat said second non-shelf-stable solution on said surface.

30. The method of making a laundry detergent sheet as claimed in claim 29 , wherein said step of heating air adjacent to said second non-shelf-stable solution on said surface is carried out in a heated chamber.

31. The method of making a laundry detergent sheet as claimed in claim 30 , further comprising the step of moving said second non-shelf-stable solution on said surface through said heated chamber.

32. The method of making a laundry detergent sheet as claimed in claim 27 , wherein said heat applied to said second non-shelf-stable solution on said surface is about 75° C. to about 85° C.

33. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said drying step is configured to remove about 95% of the water present in the second non-shelf-stable solution.

34. The method of making a laundry detergent sheet as claimed in claim 1 , wherein said laundry detergent sheet has a moisture content of about 3% to about 10% by weight.

35. The method of making a laundry detergent sheet as claimed in claim 34 , wherein said laundry detergent sheet has a thickness of about 0.6 mm to about 1.0 mm.

36. The method of making a laundry detergent sheet as claimed in claim 1 , further comprising removing said laundry detergent sheet from said surface.

37. The method of making a laundry detergent sheet as claimed in claim 36 , wherein said removing said laundry detergent sheet from said surface comprises positioning a scraper member downstream of said drying step.

38. The method of making a laundry detergent sheet as claimed in claim 1 , further comprising cutting the laundry detergent sheet into smaller sheets.

39. The method of making a laundry detergent sheet as claimed in claim 38 , wherein said cutting is by mechanical cutters, laser cutters, or water jet cutters.

40. The method of making a laundry detergent sheet as claimed in claim 38 , wherein at least one of said smaller sheets is sized and shaped for use with one small, medium, large, or extra-large sized load of laundry.

41. The method of making a laundry detergent sheet as claimed in claim 38 , wherein at least one of said smaller sheets has a width of about 5 cm to about 10 cm.

42. The method of making a laundry detergent sheet as claimed in claim 38 , wherein at least one of said smaller sheets has a length of about 10 cm to about 15 cm.

43. A method of making a laundry detergent sheet, said method comprising the steps of:

preparing a first shelf-stable solution;

preparing a second non-shelf-stable solution comprising a portion of said first shelf-stable solution;

contacting a rising portion of a surface on one side of a heated cylinder, rotating in one direction about a horizontal axis, with said second non-shelf-stable solution to coat said surface with said second non-shelf-stable solution and allow excess second non-shelf-stable solution to drain off said rising portion of said surface in a direction opposite the one direction;

drying said second non-shelf-stable solution on said surface of said heated cylinder to form said laundry detergent sheet; and

removing said laundry detergent sheet from said surface of said heated cylinder.

44. The method of making a laundry detergent sheet as claimed in claim 43 , wherein said laundry detergent sheet is capable of dissolving in a laundry cycle of an automatic washing machine.

45. The method of making a laundry detergent sheet as claimed in claim 43 , wherein said removing said laundry detergent sheet from said surface comprises positioning a scraper member downstream of said drying step.

46. The method of making a laundry detergent sheet as claimed in claim 45 , further comprising rutting the laundry detergent sheet into smaller sheets.

47. The method of making a laundry detergent sheet as claimed in claim 46 , wherein at least one of said smaller sheets is sized and shaped for use with one small, medium, large, or extra-large sized load of laundry.

48. The method of making a laundry detergent sheet as claimed in claim 43 , wherein said contacting said rising portion of said surface with said second non-shelf-stable solution comprises positioning an application reservoir, for holding a liquid volume of said second non-shelf-stable solution, against said rising portion of said surface.

49. The method of making a laundry detergent sheet as claimed in claim 48 , further comprising maintaining a liquid level of said second non-shelf-stable solution in said application reservoir by gravity feed from a supply reservoir.

50. The method of making a laundry detergent sheet as claimed in claim 48 , wherein said applying step comprises adjusting a thickness of said second non-shelf-stable solution on said surface by varying a viscosity of said second non-shelf-stable solution, varying a slope of the rising portion of said surface, varying a speed of the rotating cylinder, varying a heat of said drying step, varying a position of said application reservoir relative to said rising portion, and/or varying a liquid level of said second non-shelf-stable solution in said application reservoir.