Oriented Polymeric Articles and Method

• US 20080014410A1
• Filed: 06/28/2006
• Published: 01/17/2008
• Est. Priority Date: 06/28/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Johnston, Raymond P., Insley, Thomas I.
• Granted Patent: US 9,134,471 B2
• Time in Patent Office: Days
• US Class Current: 428/141
• CPC Class Codes: B29C 33/62 based on polymers or oligomers
• CPC Class Codes: B29C 43/222 characterised by the shape of the surface
• CPC Class Codes: B29C 55/00 Shaping by stretching, e.g. drawing through a die; Apparatus therefor B29C61/08 takes precedence
• CPC Class Codes: B29C 55/06 parallel with the direction of feed
• CPC Class Codes: B29C 59/04 using rollers or endless belts
• CPC Class Codes: B29C 71/0081 using an electric field, e.g. for electrostatic charging electrostatic pinning of extruded material B29C48/9165; fixing linings by electrostatic charges B29C63/0043
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29L 2031/731 Filamentary material, i.e. comprised of a single element, e.g. filaments, strands, threads, fibres cables B29L2031/707
• CPC Class Codes: C08J 2323/12 Polypropene
• CPC Class Codes: C08J 2367/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds; C08J2367/06 takes precedence
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: D01D 5/423 by fibrillation of films or filaments
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/2457 Parallel ribs and/or grooves
• CPC Class Codes: Y10T 428/249953 Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/2973 Particular cross section
• CPC Class Codes: Y10T 428/2978 Surface characteristic

Abstract

Stretched articles, such as oriented polymeric films or fibers, having microstructure features on at least one surface thereof, and processes for making such articles, are disclosed. A method of making fibers comprises forming a polymeric film having a body having a first surface and a second surface and having a longitudinal dimension. The film also comprises a plurality of elongate microstructure features disposed on the first surface of the body in a direction substantially parallel to the longitudinal dimension of the body, wherein the elongate microstructure features are substantially parallel. The method further comprises stretching the polymeric film in a direction substantially parallel to the longitudinal dimension of the body, and fibrillating the stretched polymeric film along the longitudinal dimension of the body to provide one or more fibers, wherein each fiber has at least one microstructure feature thereon.

Claims

1. A method of making fibers comprising:

forming a polymeric film having

a body having a first surface and a second surface and having a longitudinal dimension, and

a plurality of elongate microstructure features disposed on the first surface of the body in a direction substantially parallel to the longitudinal dimension of the body, wherein the microstructure features are substantially parallel;

stretching the polymeric film in a direction substantially parallel to the longitudinal dimension of the body; and

separating the stretched polymeric film along generally longitudinally disposed separation lines to define a plurality of discrete fiber elements, wherein one or more of the fiber elements have at least one microstructure feature thereon.

2. The method of claim 1, and further comprising:

exposing the polymeric film to an electric field.

3. The method of claim 2 wherein the exposing step defines the film as an electret.

4. The method of claim 3, wherein the forming step further comprises:

defining the shape of at least one of the microstructure features to enhance electrical field effects.

5. The method of claim 2 wherein the exposing step precedes the stretching step.

6. The method of claim 2 wherein the stretching step precedes the exposing step.

7. The method of claim 1, wherein the body has a first thickness and the microstructure features have a second thickness, and wherein after stretching, the ratio of the first thickness to the second thickness is at most 2.

8. The method of claim 1 wherein the forming step further comprises:

defining the longitudinal separation lines on the polymeric film.

9. The method of claim 1, and further comprising:

laterally cutting the fiber elements;

mixing the cut fiber elements; and

forming a filtration layer of mixed fiber elements.

10. The method of claim 1 wherein at least one microstructure feature is continuous along the first surface of the body.

11. The method of claim 1 wherein at least one microstructure feature is discontinuous along the first surface of the body.

12. The method of claim 1 wherein at least two adjacent microstructure features are spaced apart laterally by a separation span of the body.

13. The method of claim 12 wherein at least one of the separation lines extends within one of the separation spans and is spaced laterally from the microstructure features on each side of that separation span.

14. The method of claim 1 wherein at least one of the fiber elements has a plurality of microstructure features thereon.

15. The method of claim 1 wherein at least one microstructure feature has a discontinuity.

16. The method of claim 1 wherein at least one microstructure feature has a plurality of discontinuities.

17. The method of claim 1, wherein the forming step further comprises:

defining at least one generally laterally disposed lateral separation line across the longitudinal dimension of the body; and

separating each fiber element into one or more fiber element segments.

18. The method of claim 17 wherein the film separating and fiber element separating steps occur simultaneously.

19. The method of claim 1, and further comprising:

maintaining the plurality of discrete fiber elements in an array having a substantially parallel fiber element alignment.

20. A method of forming layered arrays of fiber elements comprises:

arranging a first layer defined by an array of fiber elements of claim 19 so that the longitudinal dimensions of the fiber elements of the first layer are aligned in a first direction; and

overlaying the first layer with a second layer of fiber elements defined by another array of fiber elements of claim 19 so that the longitudinal dimensions of the fiber elements of the second layer are aligned in a second direction.

21. The method of claim 20 wherein at least some of the microstructure features on the fiber elements of the first layer engage the second surfaces of the bodies of the fiber elements of the second layer.

22. The method of claim 20 wherein the first and second directions are different.

23. The method of claim 20 wherein the first and second directions are substantially parallel.

24. A method of making fibers comprising:

forming a polymeric film having

a body having a first surface and a second surface and having a longitudinal dimension, and

a plurality of elongate microstructure features disposed on the first surface of the body in a direction substantially parallel to the longitudinal dimension of the body, wherein the elongate microstructure features are substantially parallel;

stretching the polymeric film in a direction substantially parallel to the longitudinal dimension of the body; and

fibrillating the stretched polymeric film along the longitudinal dimension of the body to provide one or more fibers, wherein each fiber has at least one microstructure feature thereon.

25. The method of claim 24, and further comprising:

exposing the polymeric film to an electric field.

26. The method of claim 25 wherein the exposing step defines the film as an electret.

27. The method of claim 26, wherein the forming step further comprises:

defining the shape of at least one of the microstructure features to enhance electrical field effects.

28. The method of claim 25 wherein the exposing step precedes the fibrillating step.

29. The method of claim 25 wherein the fibrillating step precedes the exposing step.

30. The method of claim 24, wherein the body has a first thickness and the microstructure features have a second thickness, and wherein after stretching, the ratio of the first thickness to the second thickness is at most 2.

31. The method of claim 24 wherein the fibrillating step separates the stretched polymeric film into fibers along generally longitudinal separation lines, and wherein the forming step further comprises:

defining the longitudinal separation lines on the polymeric film.

32. The method of claim 24, and further comprising:

laterally cutting the fibers;

mixing the cut fibers; and

forming a filtration layer of mixed fibers.

33. The method of claim 24 wherein at least one microstructure feature is continuous along the first surface of the body.

34. The method of claim 24 wherein at least one microstructure feature is discontinuous along the first surface of the body.

35. The method of claim 24 wherein the fibrillating step separates the stretched polymeric film into fibers along generally longitudinal separation lines, and wherein at least some adjacent microstructure features are spaced apart laterally by a separation span of the body.

36. The method of claim 35 wherein at least one of the separation lines extends within one of the separation spans and is spaced laterally from the microstructure features on each side of that separation span.

37. The method of claim 24 wherein at least one of the fibers has a plurality of microstructure features thereon.

38. The method of claim 24 wherein at least one microstructure feature has a discontinuity.

39. The method of claim 24 wherein at least one microstructure feature has a plurality of discontinuities.

40. The method of claim 24, wherein the forming step further comprises:

defining at least one generally laterally disposed lateral separation line across the longitudinal dimension of the body; and

separating each fiber into one or more fiber segments.

41. The method of claim 40 wherein the film separating and fiber separating steps occur simultaneously.

42. The method of claim 24, and further comprising:

maintaining the fibers in an array having a substantially parallel fiber alignment.

43. A method of forming layered arrays of fiber elements comprises:

arranging a first layer defined by an array of fibers of claim 42 so that the longitudinal dimensions of the fibers of the first layer are aligned in a first direction; and

overlaying the first layer with a second layer of fibers defined by another array of fibers of claim 42 so that the longitudinal dimensions of the fibers of the second layer are aligned in a second direction.

44. The method of claim 43 wherein at least some of the microstructure features on the fibers of the first layer engage the second surfaces of the bodies of the fibers of the second layer.

45. The method of claim 43 wherein the first and second directions are different.

46. The method of claim 43 wherein the first and second directions are substantially parallel.

47. A polymeric film comprising:

a body having a first surface and a second surface, a first thickness and a longitudinal dimension; and

a plurality of elongate microstructure features disposed on the first surface of the body in a direction substantially parallel to the longitudinal dimension of the body, wherein the elongate microstructure features are substantially parallel and have a second thickness,

wherein the film has a stretch ratio of at least 1.5 in the longitudinal dimension of the body, and

wherein the ratio of the first thickness of the body to the second thickness of the microstructure features is at most 2.

48. The film of claim 47 wherein one or more of the microstructure features has a discontinuity.

49. The film of claim 47 wherein one or more of the microstructure features has a plurality of discontinuities.

50. The film of claim 47 wherein at least one microstructure features is continuous along the first surface of the body.

51. The film of claim 47 wherein at least one microstructure feature is discontinuous along the first surface of the body.

52. The film of claim 47 wherein at least two adjacent microstructure features are spaced apart laterally by a separation span of the body.

53. The film of claim 47 wherein the polymeric film is an electret.

54. The film of claim 53 wherein at least one of the microstructure features is shaped to enhance electrical field effects.

55. A film array comprising:

a first film defined by the polymeric film of claim 47, wherein the longitudinal dimension of the body of the film is aligned in a first direction; and

a second polymeric film arranged in an overlaying relation to the first film, wherein the second polymeric film comprises;

a body having a first and a second surface, a first thickness and a longitudinal dimension; and

a plurality of elongate microstructure features disposed on the first surface of the body of the second film in a direction substantially parallel to the longitudinal dimension of the body of the second film, wherein the elongate microstructure features of the second film are substantially parallel and have a second thickness,

wherein the second film has a stretch ratio of at least 1.5 in the longitudinal dimension of the body of the second film, and

wherein the ratio of the first thickness of the body of the second film to the second thickness of the microstructure features of the second film is at least 2.

56. The film array of claim 55 wherein at least some of the microstructure features of the first film engage the second surface of the body of the second film.

57. The film array of claim 55 wherein the longitudinal dimension of the body of the second film is aligned in a second direction that is different from the first direction.

58. The film array of claim 55 wherein the longitudinal dimension of the body of the second film and the longitudinal dimension of the body of the first film are substantially parallel.

59. The film of claim 47, and further comprising:

an adhesive disposed on at least one surface of the body.

60. The film of claim 59 wherein the adhesive is a pressure sensitive adhesive.

61. The film of claim 47 wherein the polymeric film is microporous.

62. The film of claim 61 wherein the microporous polymeric film contains particles.

63. The film of claim 47 wherein the ratio of the first thickness of the body to the second thickness of the microstructure feature is at most 1.

64. The film of claim 47 wherein the ratio of the first thickness of the body to the second thickness of the microstructure feature is at most 0.5.

65. The film of claim 47 wherein the ratio of the first thickness of the body to the second thickness of the microstructure feature is at most 0.1.

66. The film of claim 47 wherein the film is adsorbent.

67. The film of claim 47 wherein the film is absorbent.

68. A polymeric fiber comprising:

a fiber body having a first surface and a second surface, and a longitudinal dimension, and

one or more elongate microstructure features disposed on the first surface of the fiber body in a direction substantially parallel to the longitudinal dimension of the fiber body, wherein any plurality of microstructure features are substantially parallel.

69. The fiber of claim 68 wherein the fiber has a stretch ratio of at least 1.5 in the longitudinal dimension of the fiber body.

70. The fiber of claim 68 wherein the fiber body has a first thickness, wherein the microstructure features have a second thickness, and wherein the ratio of the first thickness to the second thickness is at most 2.

71. The fiber of claim 68 wherein one or more of the microstructure features has a discontinuity.

72. The fiber of claim 68 wherein one or more of the mictrostructure features has a plurality of discontinuities.

73. The fiber of claim 68 wherein at least two adjacent microstructure features are spaced apart laterally by a separation span of the fiber body.

74. The fiber of claim 68 wherein the polymeric fiber is an electret.

75. The fiber of claim 68 wherein at least one of the microstructure features is shaped to enhance electrical field effects.

76. A fiber array comprising a plurality of polymeric fibers of claim 68, wherein the fiber bodies of the fibers in the array are substantially parallel.

77. The invention of claim 76 wherein a first layer of fibers is defined by a fiber array of claim 76 that is aligned in a first direction, wherein a second layer of fibers is defined by a fiber array of claim 76 that is aligned in a second direction, and wherein the second layer overlies the first layer.

78. The invention of claim 77 wherein at least some of the microstructure features on the fibers of the first layer engage the second surfaces of the fiber bodies of the fibers of the second layer.

79. The invention of claim 77 wherein the first and second directions are different.

80. The invention of claim 77 wherein the first and second directions are substantially parallel.

81. The fiber of claim 68 wherein the polymeric fiber is microporous.

82. The fiber of claim 81 wherein the microporous polymeric fiber contains particles.

83. The fiber of claim 68 wherein the fiber body has a first thickness, wherein the microstructure features have a second thickness, and wherein the ratio of the first thickness to the second thickness is at most 1.

84. The fiber of claim 68 wherein the fiber body has a first thickness, wherein the microstructure features have a second thickness, and wherein the ratio of the first thickness to the second thickness is at most 0.5.

85. The fiber of claim 68 wherein the fiber body has a first thickness, wherein the microstructure features have a second thickness, and wherein the ratio of the first thickness to the second thickness is at most 0.1.

86. The fiber of claim 68 wherein the film is adsorbent.

87. The fiber of claim 68 wherein the film is absorbent.