Laminates of asymmetric membranes

• US 6,596,112 B1
• Filed: 10/20/2000
• Issued: 07/22/2003
• Est. Priority Date: 10/20/2000
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: Pall Corporation (Danaher Corporation)
• Inventors: Morris, Richard, Benson, Todd, Lamon, Steve, Gaughan, Mike, Sarabia, Rey, Ditter, Jerry, McDonogh, Richard, Wang, I-fan
• Primary Examiner(s): Crispino, Richard
• Assistant Examiner(s): Hawkins, Cheryl N.
• Application Number:
  US09/694,120
• Time in Patent Office: 1,005 Days
• Field of Search: 156/77, 156/79, 156/182, 156/297, 156/299, 156/306.6, 156/313, 156/90, 156/275.7, 156/275.5, 156/273.3, 156/321, 156/322
• US Class Current: 156/182
• CPC Class Codes: B01D 69/10 Supported membranes; Membrane supports
• CPC Class Codes: B01D 69/1071 Woven, non-woven or net mesh
• CPC Class Codes: B01D 69/12 Composite membranes; Ultra-thin membranes
• CPC Class Codes: B01D 69/1213 Laminated layers
• CPC Class Codes: B01D 69/1216 Three or more layers
• CPC Class Codes: B01D 71/34 Polyvinylidene fluoride
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones
• CPC Class Codes: B32B 2305/20 in the form of a non-woven mat
• CPC Class Codes: B32B 2323/00 Polyalkenes
• CPC Class Codes: B32B 2327/12 containing fluorine
• CPC Class Codes: B32B 2367/00 Polyesters, e.g. PET, i.e. polyethylene terephthalate
• CPC Class Codes: B32B 7/04 Interconnection of layers
• CPC Class Codes: Y10T 156/1089 of discrete laminae to single face of additional lamina
• CPC Class Codes: Y10T 156/1092 All laminae planar and face to face
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet

Abstract

The present invention is directed to composite filters and methods for preparing same. More specifically, it is directed to filter laminates of multiple discreet layers of material bonded together, with at least one of the layers being an asymmetric membrane.

Claims

1. A method of making a filter laminate, comprising the steps of:

1) providing a first plurality of discreet layers of material, wherein at least one of the layers comprises an asymmetric membrane;

2) contacting the layers to form a first stack, wherein each layer is adjacent at least one other layer in the stack;

3) forming a bond between adjacent layers in the first stack, wherein the bond is formed after the formation of the material of the layers, thereby forming a first laminated stack layer;

4) contacting the first laminated stack with a second layer of material; and

5) forming a bond between the first laminated stack layer and the second layer, wherein the bond is formed after the formation of the material of the layers, thereby forming a filter laminate.

2. The method of claim 1, wherein the second layer comprises a plurality of discreet layers.

3. The method of claim 2, further comprising the step of forming a bond between adjacent layers in the second layer, wherein the bond is formed after the formation of the material of the layers, and wherein the bond is formed before the step of forming a bond between the first laminated stack layer and the second layer.

4. The method of claim 2, further comprising the step of forming a bond between adjacent layers in the second layer, wherein the bond is formed after the formation of the material of the layers, and wherein the bond is formed substantially simultaneously with the step of forming a bond between the first laminated stack layer and the second layer.

5. The method of claim 1, wherein a bond is formed by heating a stack or a layer to a temperature of about 200°

F. or less.

6. The method of claim 1, wherein a bond is formed by heating a stack or a layer to a temperature of from about 200°

F. to about 395°

F.

7. The method of claim 1, wherein a bond is formed by heating a stack or a layer to a temperature of from about 396°

F. or higher.

8. The method of claim 1, wherein at least one of the layers comprises an adhesive.

9. The method of claim 1, wherein the asymmetric membrane comprises a first and a second surface, each of the surfaces comprising pores, wherein the pores of the second surface have an average diameter at least about 5 times greater than an average diameter of the pores of the first surface.

10. The method of claim 9, wherein the asymmetric membrane comprises a first and a second surface, each of the surfaces comprising pores, wherein the pores of the second surface have an average diameter at least about 10 times greater than an average diameter of the pores of the first surface.

11. The method of claim 9, wherein the asymmetric membrane further comprises a support structure between the first surface and the second surface, wherein the support structure comprises a reticular network of flow channels connecting the pores of the first surface with the pores of the second surface.

12. The method of claim 11, wherein the flow channels of the asymmetric membrane generally increase gradually in diameter between the first surface and the second surface.

13. The method of claim 11, wherein the asymmetric membrane comprises an isotropic region and an asymmetric region, such that the support region comprises a thickness between the first and second surfaces, wherein the thickness comprises the isotropic region between one of the surfaces and a point within the support region, and an asymmetric region between the point and another of the surfaces, wherein the isotropic region comprises flow channels that are substantially constant in diameter from the surface adjacent the isotropic region to the point between the isotropic region and the asymmetric region, and wherein the asymmetric region comprises flow channels that gradually increase or decrease in diameter from the point to the surface adjacent the asymmetric region.

14. The method of claim 9, wherein the average diameter of the pores of the first surface of the asymmetric membrane is between about 0.01 μ

m and about 10.0 μ

m.

15. The method of claim 9, wherein the average diameter of the pores of the first surface of the asymmetric membrane is less than about 0.01 μ

m.

16. The method of claim 1, wherein the filter laminate comprises at least a first asymmetric membrane and at least a second membrane as distinct layers.

17. The method of claim 16, wherein the first asymmetric membrane is bonded to the second membrane.

18. The method of claim 17, wherein the first surface of the first asymmetric membrane is bonded to the second membrane.

19. The method of claim 17, wherein the second surface of the first asymmetric membrane is bonded to the second membrane.

20. The method of claim 16, wherein the second membrane comprises a second asymmetric membrane having a first and a second surface, each of the surfaces comprising pores, wherein the pores of the second surface have an average diameter at least about 5 times greater than an average diameter of the pores of the first surface.

21. The method of claim 20, wherein the first asymmetric membrane is bonded to the second asymmetric membrane.

22. The method of claim 20, wherein the first surface of the first asymmetric membrane is bonded to the first surface of the second asymmetric membrane.

23. The method of claim 20, wherein the first surface of the first asymmetric membrane is bonded to the second surface of the second asymmetric membrane.

24. The method of claim 20, wherein the second surface of the first asymmetric membrane is bonded to the first surface of the second asymmetric membrane.

25. The method of claim 20, wherein the second surface of the first asymmetric membrane is bonded to the second surface of the second asymmetric membrane.

26. The method of claim 1, wherein the asymmetric membrane comprises a polymer additive on a surface thereof, and wherein the polymer additive contributes to the bond between the asymmetric membrane and another layer.

27. The method of claim 26, wherein the polymer additive comprises polyvinylpyrrolidone or polyethylenevinylacetate.

28. The method of claim 16, wherein the second membrane comprises a polymer additive on a surface thereof, and wherein the polymer additive contributes to the bond between the membrane and another layer.

29. The method of claim 28, wherein the polymer additive comprises polyvinylpyrrolidone or polyethylenevinylacetate.

30. The method of claim 1, wherein the step of forming a bond between adjacent layers in the first stack comprises contacting the asymmetric membrane with an adjacent layer and forming a bond therebetween, wherein the membrane is wet when contacted with the adjacent layer, prior to formation of the bond.

31. The method of claim 1, wherein the step of forming a bond between adjacent layers in the first stack comprises forming a bond in the presence of a temperature higher than a melting point of a component participating in the bond, and lower than a melting point of the asymmetric membrane.

32. The method of claim 1, wherein the step of forming a bond between the first laminated stack and the second layer comprises forming a bond in the presence of a temperature higher than a melting point of a component participating in the bond, and lower than a melting point of the asymmetric membrane.

33. The method of claim 1, wherein the asymmetric membrane comprises a polymer selected from the group consisting of polyvinylidene fluoride, polyarylsulfone, polyethersulfone, polyarylsulfone, polyamides and cellulosic derivatives.

34. The method of claim 1, wherein the material of at least one of the layers is selected from the group consisting of polyester, polypropylene, polyolefin, polyethylene, nylon, paper, cellulose, glass fiber, and acrylic.

35. The method of claim 1, wherein the material of at least one of the layers is selected from the group consisting of nonwoven fibrous material, woven fibrous material, web material, sheet material, calendared material, wet laid material, dry laid material, and extruded material.

36. The method of claim 35, wherein the sheet material is liquid-impermeable.

37. The method of claim 1, wherein the filter laminate has a total thickness of less than about 1000 μ

m.

38. The method of claim 37, wherein the filter laminate has a total thickness of less than about 500 μ

m.

39. The method of claim 38, wherein the filter laminate has a total thickness of between about 75 μ

m and about 350 μ

m.

40. The method of claim 8, wherein the adhesive comprises a hot melt adhesive.

41. The method of claim 40, wherein the hot melt adhesive comprises a thermoplastic.

42. The method of claim 40, wherein the hot melt adhesive comprises a polyester.

43. The method of claim 40, wherein the hot melt adhesive comprises a nylon.

44. The method of claim 40, wherein the hot melt adhesive is selected from the group consisting of ethylenevinylacetate, polypropylene, and polyethylene.

45. The method of claim 40, wherein the hot melt adhesive is selected from the group consisting of web material, nonwoven material, woven material, powder, and solution.

46. The method of claim 1, wherein the asymmetric membrane is cationically charged.

47. The method of claim 1, wherein the asymmetric membrane is anionically charged.

48. The method of claim 1, wherein the asymmetric membrane is hydrophobic.

49. The method of claim 1, wherein the asymmetric membrane is hydrophilic.

50. The method of claim 1, wherein the asymmetric membrane is oleophobic.