Fibrous Media

• US 20100187171A1
• Filed: 01/27/2010
• Published: 07/29/2010
• Est. Priority Date: 01/28/2009
• Status: Active Grant

• Current Assignee: Donaldson Company Incorporated
• Original Assignee: Donaldson Company Incorporated
• Inventors: Gupta, Hemant
• Granted Patent: US 9,885,154 B2
• Time in Patent Office: Days
• US Class Current: 210/491
• CPC Class Codes: D04H 1/42 characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
• CPC Class Codes: D04H 1/4218 Glass fibres
• CPC Class Codes: D04H 1/435 Polyesters
• CPC Class Codes: D04H 1/43828 sheath-core
• CPC Class Codes: D04H 1/43832 side-by-side
• CPC Class Codes: D04H 1/43835 Mixed fibres, e.g. at least two chemically different fibres or fibre blends
• CPC Class Codes: D04H 1/43838 Ultrafine fibres, e.g. microfibres
• CPC Class Codes: D21F 11/04 paper or board consisting on two or more layers
• CPC Class Codes: D21F 11/14 Making cellulose wadding, filter or blotting paper
• CPC Class Codes: D21F 9/006 paper or board consisting of two or more layers
• CPC Class Codes: D21H 13/24 Polyesters
• CPC Class Codes: D21H 13/40 vitreous, e.g. mineral wool, glass fibres
• CPC Class Codes: D21H 27/08 Filter paper self-supporting filtering material B01D39/14; making on paper-making machines D21F11/14

Abstract

A multi-faceted family of non-woven webs that can take the form of a filter media, an adaptable forming process and a machine capable of making the range of media are disclosed. The filter medium can have a first surface and a second surface defining a thickness. The medium can comprise a region having a gradient. Such a gradient is formed by having a medium wherein the concentration of a fiber, a property or other component varies from one surface to the next surface. The gradient region of the media can comprise the entire thickness of the medium or can comprise a region that comprises a portion of the media thickness. The media are characterized by the presence of a continuous change of the fiber concentration or property within the region. A non-woven web can also be made comprising a planar fiber structure having a gradient. Such a web can comprise fibers having diameters that can range from 1 to 40 microns and a second fiber having a diameter that can range from 0.5 microns to about 5 microns. The gradient can change in the cross machine (x-dimension) or across the thickness (z-dimension) increasing or decreasing in either direction. The media of the invention can be used in a variety of applications for the purpose of removing particulates from a variety of gas use on liquid media. Further, the filtered medium of the invention used in a variety of filter element types including flat media, pleated media, flat panel filters, cylindrical spin-on filters, z media pleated filters and other embodiments wherein the gradient provides useful properties. Methods or processes or an apparatuses for forming a nonwoven medium comprising controllable characteristic within the medium are disclosed. The term medium (plural media) refers to a web made of fiber having variable or controlled structure and physical properties.

Claims

23. A filter medium having a first surface and a second surface defining a thickness, the medium comprising a region comprising a gradient, the region comprising a first fiber having a first fiber composition and a second fiber having a second fiber composition different from the first fiber composition wherein the second fiber varies in concentration in the region such that the concentration of the second fiber increases across the region in a direction from one surface to the other surface.

24. The medium of claim 23 wherein the first fiber has a diameter of at least 1 micron and a second fiber having a diameter of at most 5 microns.

25. The filter medium of claim 23 wherein the region spans a portion of the thickness of the medium.

26. The filter medium of claim 23, wherein the portion of the region comprises a thickness of greater than 10% of the thickness of the medium.

27. The filter medium of claim 23 wherein the first fiber comprises a bicomponent fiber at an amount of at least 30 wt % and at most 80 wt % of the filter medium.

28. The filter medium of claim 23 wherein the second fiber comprises glass or a polyester fiber at an amount of least 30 wt % and at most 70 wt % of the filter medium.

29. The filter medium of claim 23 wherein the filter medium has a β

of greater than 200 for test particles 5 microns and larger when loaded to a pressure drop equal to or greater than 320 kPa as measured under ISO 16889.

30. The filter medium of claim 23 wherein the medium thickness comprises a second region of the thickness that comprises a constant concentration of the first fiber and the second fiber.

31. The filter medium of claim 23 wherein there is at least about 30 wt % and at most about 70 wt % of a first fiber comprising a bicomponent fiber and at least about 30 wt % and at most about 70 wt % of a glass or polyester fiber wherein the concentration of glass or polyester fiber is formed in a continuous gradient that increases from the first surface to the second surface.

32. The medium of claim 23 wherein the first fiber comprises a bicomponent fiber comprising a core and a shell each independently comprising polyester or a polyolefin.

33. The medium of claim 25 wherein the first surface and second surface define the thickness of the medium that ranges from 0.5 to 20 mm and the portion of the region is greater than 0.1 mm.

34. The medium of claim 23 wherein the medium is a depth medium and the second fiber increases from a first upstream surface to a second downstream surface.

35. The medium of claim 23 wherein the medium comprises a loading region and an efficiency region.

36. The medium of claim 23 wherein the medium is combined with a base layer comprising a membrane, a cellulosic medium, a synthetic medium, a scrim or an expanded metal support.

37. The medium of claim 23 wherein any gradient in the medium is nonlinear.

38. The medium of claim 23 wherein the concentration of the second fiber increases in a nonlinear fashion from the upstream surface to the downstream surface.

39. The medium of claim 23 wherein the medium has a gradient in at least one of the group consisting of permeability, pore size, fiber diameter, fiber length, efficiency and solidity.

40. The medium of claim 23 wherein the medium has a gradient in at least one of the group consisting of wettability, chemical resistance, and temperature resistance.

41. The filter medium of claim 23 wherein the medium additionally comprises a uniform bonded fiber region.

42. The medium of claim 41 wherein the first fiber in the bonded region is uniform in concentration.

43. The medium of claim 23 wherein the medium comprises one or more additional fibers.

44. The filter medium of claim 23, wherein the first fiber comprises a cellulosic fiber and the second fiber comprises a glass fiber.

45. The medium of claim 23 wherein a comparison of the first surface with the second surface shows a difference in fiber concentration or fiber composition.

46. A filter medium having a first surface and a second surface, the medium comprising a scaffold fiber, a first fiber having a diameter of at least 1 micron and a second fiber having a diameter of at most 6 microns, the media having a region characterized by a gradient in the concentration of either the first fiber or the second fiber;

and the medium is free of a lamination layer and is free of a laminating adhesive, wherein the first fiber has a first group of fiber characteristics and the second fiber has a second, different group of fiber characteristics.

47. The filter medium of claim 46, wherein the scaffold fiber comprises a bicomponent fiber and both the first and second fiber comprises a glass fiber.

48. The filter medium of claim 46, wherein the scaffold fiber comprises a bicomponent fiber and the first and second fiber comprises a polyester fiber.

49. The filter medium of claim 46, wherein the scaffold fiber comprises a cellulosic fiber and the first and second fiber comprises a glass fiber.

50. The filter medium of claim 46 wherein the first and second fiber comprises a blend of compositionally different fibers and the region characterized by a gradient is a portion of the thickness of the medium.

51. The filter medium of claim 50, wherein the region characterized by a gradient comprises a thickness of greater than 10% of the thickness of the medium.

52. The medium of claim 46 wherein the first surface and second surface define the thickness of the medium that ranges from 0.5 to 20 mm and the portion of the region is greater than 0.1 mm.

53. The filter medium of claim 46 wherein the filter medium has a β

of greater than 200 for test particles 5 microns and larger when loaded to a pressure drop equal to or greater than 320 kPa as measured under ISO 16889.

54. The filter medium of claim 46 wherein at least one region comprises a blend of about 30 wt % to 80 wt % of a first fiber and at least about 20 wt % and at most about 70 wt % of a second fiber having a diameter of at least about 0.6 micron and at most about 5 microns.

55. The filter medium of claim 46 wherein the second fiber comprises a cellulosic fiber having a diameter of at least about 20 microns and at most about 30 microns.

56. The filter medium of claim 46 wherein the glass fiber comprises a blend of a first glass fiber having a diameter of about at least about 0.5 microns and a second glass fiber having a diameter of at least about 2 microns and at most about 5 microns.

57. The filter medium of claim 46 wherein the medium has a gradient that is a nonlinear gradient in pore size or fiber diameter.

58. The filter medium of claim 46 wherein the gradient comprises a filter composition such that the fiber size or the fiber concentration increases in a linear fashion from the first surface to the second surface.

59. The medium of claim 46 wherein at least one region comprises a first fiber bonded with a resin.

60. The medium of claim 59 wherein the fiber bonded with a resin comprises a cellulosic fiber.

61. The medium of claim 59 wherein the fiber bonded with a resin comprises a polyester fiber.

62. The medium of claim 46 further comprising an additive selected from a resin, a crosslinking agent or a combination thereof.

63. The medium of claim 59 wherein the resin comprises a binder resin, an elastomer, a thermoset resin, a gel, a bead, a pellet, a flake, a particle, or a nanostructure.

64. The medium of claim 46 wherein the first fiber and the second fiber are selected from a fiber comprising glass, cellulose, hemp, abacus, a polyolefin, a polyester, a polyamide, a halogenated polymer, a polyurethane, or a combination thereof.

65. The filter medium of claim 46, the second fiber comprising a cellulosic fiber, a synthetic fiber, or blends thereof.

80. The web of claim 61 wherein the web comprises a loading region and an efficiency region.

68. An nonwoven web, the web comprising a planar fibrous structure with a first surface and a second surface, the fibrous structure comprising a first nonwoven region with substantially uniform fiber distribution and a second nonwoven region comprising a first fiber having a diameter of at least 1 micron and a second fiber having a diameter of at most 6 microns wherein the second fiber varies in concentration in the second nonwoven region such that the concentration of the second fiber increases across the second region in a direction from the first surface to the second surface, wherein the first fiber has a first group of fiber characteristics and the second fiber has a second, different group of fiber characteristics.

69. The web of claim 68 wherein the second fiber comprises a blend of fibers of different diameters.

70. The web of claim 68 wherein any change in fiber concentration in the web is a linear change.

71. The web of claim 68 wherein there are two or more of the first nonwoven regions.

72. The web of claim 68 wherein there are two or more of the second nonwoven regions.

73. The web of claim 68 wherein the web comprises a filter medium.

74. The filter medium of claim 73 wherein the filter medium has a β

of greater than 200 for test particles 5 microns and larger when loaded to a pressure drop equal to or greater than 320 kPa as measured under ISO 16889.

76. The medium of claim 73 wherein a comparison of the first surface with the second surface shows a difference in fiber concentration or fiber composition.

77. The web of claim 73 wherein the first nonwoven region is an upstream region.

78. The web of claim 73 wherein the second nonwoven region is an upstream region.

79. The web of claim 73 wherein the web is a depth medium and the second fiber increases from the upstream surface to the downstream surface.

81. The web of claim 68 wherein the concentration of the second fiber increases in a nonlinear fashion from the upstream surface to the downstream surface.

82. A filter medium having a first surface and a second surface defining a thickness, the medium comprising at least one region in the thickness, the region comprising a polyester fiber, a spacer fiber having a diameter of at least 0.3 micron and an efficiency fiber having a diameter of at most 15 microns wherein the polyester fiber does not substantially vary in concentration in the region and the spacer fiber varies in concentration in the region such that the concentration of the spacer fiber increases across the region in a direction from one surface to the other surface.

83. The medium of claim 82 wherein the polyester fiber comprises a bicomponent fiber.

84. The medium of claim 82 wherein the spacer fiber comprises a glass fiber.

85. The medium of claim 82 wherein the efficiency fiber comprises a glass fiber

86. The medium of claim 82 wherein the spacer fiber comprises a single phase polyester fiber.

87. The medium of claim 82 wherein the filter medium has a β

of greater than 200 for test particles 5 microns and larger when loaded to a pressure drop equal to or greater than 320 kPa as measured under ISO 16889.

88. The medium of claim 82 wherein the concentration of the efficiency fiber increases from one surface to the other surface.

89. The medium of claim 82 wherein the medium comprises 30 to 85 wt % polyester fiber, 2 to 45 wt % spacer fiber and 10 to 70 wt % efficiency fiber.

90. The filter medium of claim 82 wherein the medium comprises a second region of the thickness that comprises a constant concentration of the polyester fiber, the spacer fiber and the efficiency fiber.

92. A filter medium having a first edge and a second edge defining a width, each edge parallel to the machine direction of the medium, the medium comprising a first region comprising a first fiber and a second fiber wherein the second fiber varies in concentration in the first region such that the concentration of the second fiber increases from the first edge to the second edge.

1. A filter medium having a first surface and a second surface defining a thickness, the medium comprising a region comprising a gradient, the region comprising a first fiber having a diameter of at least 1 micron and a second fiber having a diameter of at most 6 microns wherein the first fiber is larger in diameter than the second fiber and the second fiber varies in concentration in the region such that the concentration of the second fiber increases across the region in a direction from one surface to the other surface.

2. The filter medium of claim 1 wherein the region spans a portion of the thickness of the medium.

3. The filter medium of claim 2, wherein the portion of the region comprises a thickness of greater than 10% of the thickness of the medium.

4. The filter medium of claim 1 wherein the first fiber comprises a bicomponent fiber at an amount of at least 30 wt % and at most 80 wt % of the filter medium.

5. The filter medium of claim 1 wherein the second fiber comprises glass fiber at an amount of least 30 wt % and at most 70 wt % of the filter medium.

6. The filter medium of claim 1 wherein the filter medium has a β

of greater than 200 for test particles 5 microns and larger when loaded to a pressure drop equal to or greater than 320 kPa as measured under ISO 16889.

7. The filter medium of claim 1 wherein the medium thickness comprises a second region of the thickness that comprises a constant concentration of the first fiber and the second fiber.

8. The filter medium of claim 1 wherein there is at least about 30 wt % and at most about 70 wt % of a bicomponent fiber and at least about 30 wt % and at most about 70 wt % of a second fiber comprising a polyester or a glass fiber wherein the concentration of second fiber is formed in a continuous gradient that increases from the first surface to the second surface.

9. The medium of claim 1 wherein the first fiber comprises a bicomponent fiber comprising a core and a shell each independently comprising a polyester or a polyolefin.

10. The medium of claim 3 wherein the first surface and second surface define the thickness of the medium that ranges from 0.2 to 20 mm and the portion of the region is greater than 0.1 mm.

11. The medium of claim 1 wherein the medium is a depth medium and the second fiber increases from a first upstream surface to a second downstream surface.

12. The medium of claim 11 wherein the medium comprises a loading region and an efficiency region.

13. The medium of claim 1 wherein the medium is combined with a base layer comprising a membrane, a cellulosic medium, a synthetic medium, a scrim or an expanded metal support.

14. The medium of claim 1 wherein any gradient in the medium is nonlinear.

15. The medium of claim 1 wherein the concentration of the second fiber increases in a nonlinear fashion from the upstream surface to the downstream surface.

16. The medium of claim 1 wherein the medium has a gradient in at least one of the group consisting of permeability, pore size, fiber diameter, fiber length, efficiency and solidity.

17. The medium of claim 1 wherein the medium has a gradient in at least one of the group consisting of wettability, chemical resistance and temperature resistance.

18. The filter medium of claim 1 wherein the medium additionally comprises a uniform bonded fiber region.

19. The medium of claim 18 wherein the first fiber in the bonded region is uniform in concentration.

20. The medium of claim 1 wherein the medium comprises one or more additional fibers.

21. The filter medium of claim 1, wherein the first fiber comprises a cellulosic fiber and the second fiber comprises a glass fiber.

22. The medium of claim 1 wherein a comparison of the first surface with the second surface shows a difference in fiber concentration or fiber composition.

66. The medium of claim 1 wherein a comparison of the first surface with the second surface shows a 10% difference in fiber concentration.

67. The medium of claim 1 wherein a comparison of the first surface with the second surface shows a 10% difference in fiber composition.

75. The filter medium of claim 2, wherein the portion of the second non-woven region comprises a thickness of greater than 10% of the thickness of the medium.

91. The medium of claim 1 wherein a comparison of the first surface with the second surface shows a 10% difference in fiber concentration or fiber composition.

93. The filter medium of claim 92 wherein the medium width comprises a second region of the thickness that comprises a constant concentration of the first fiber and the second fiber.

94. The filter medium of claim 92 having a first surface and a second surface defining a thickness, the medium comprising a second region comprising a gradient, the second region wherein the second fiber varies in concentration in the second region such that the concentration of the second fiber increases across the region in a direction from one surface to the other surface.

95. The filter medium of claim 94 wherein the second region spans a portion of the thickness of the medium.

96. The filter medium of claim 92 wherein the first fiber is larger in diameter than the second fiber.

97. The filter medium of claim 92 wherein the filter medium includes a center region of the width and the concentration of the second fiber is highest in the center region.

98. The filter medium of claim 92 wherein the filter medium includes a first edge region adjacent to the first edge and a second edge region adjacent to the second edge, wherein the concentration of the second fiber is higher in the first edge region than in the second edge region.

95-1. The filter medium of claim 92 wherein the first fiber has a first fiber composition and the second fiber having a second fiber composition different from the first fiber composition.