PTFE membranes and gaskets made therefrom

• US 20040173978A1
• Filed: 03/06/2003
• Published: 09/09/2004
• Est. Priority Date: 03/06/2003
• Status: Abandoned Application

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: Minor, Raymond B., Dove, Kevin Edward, Jones, Carl, Bowen, Christopher
• Application Number:
  US10/382,668
• Publication Number:
  US 20040173978A1
• Time in Patent Office: Days
• US Class Current: 277/650
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/475 using pistons, accumulators or press rams
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29L 2031/265 Packings, Gaskets
• CPC Class Codes: B32B 2307/50 having particular mechanical properties
• CPC Class Codes: B32B 2307/54 Yield strength; Tensile strength
• CPC Class Codes: B32B 2307/546 Flexural strength; Flexion stiffness
• CPC Class Codes: B32B 2307/548 Creep
• CPC Class Codes: B32B 2307/552 Fatigue strength
• CPC Class Codes: B32B 2307/714 Inert, i.e. inert to chemical degradation, corrosion
• CPC Class Codes: B32B 2307/72 Density
• CPC Class Codes: B32B 2307/7242 Non-permeable
• CPC Class Codes: B32B 2307/732 Dimensional properties
• CPC Class Codes: B32B 2581/00 Seals; Sealing equipment; Gaskets
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/205 the fillers creating voids or cavities, e.g. by stretching
• CPC Class Codes: B32B 27/322 comprising halogenated polyolefins, e.g. PTFE
• CPC Class Codes: B32B 3/26 characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205; characterised by an apertured layer
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: F16J 15/102 characterised by material
• CPC Class Codes: F16J 15/104 : characterised by structure
• CPC Class Codes: F16J 15/3284 : characterised by their structure; Selection of materials
• CPC Class Codes: F16L 23/22 : made exclusively of a material other than metal
• CPC Class Codes: Y10T 428/215 : Seal, gasket, or packing
• CPC Class Codes: Y10T 428/249978 : Voids specified as micro
• CPC Class Codes: Y10T 428/269 : including synthetic resin or polymer layer or component

Abstract

Improved expanded PTFE materials and improved gasket materials made therefrom, the gaskets being capable of forming a seal with greater bolt load retention than is possible with existing PTFE gaskets. The expanded PTFE membranes of the invention can be tailored to exhibit a matrix tensile strength in at least one direction of at least 25,000 psi, a matrix tensile strength ratio in two orthogonal directions of between 0.025 and 4, an orientation index of 50° or less, and a density of 2.0 g/cc or less. The improved gaskets exhibit improved mechanical properties such as high bolt load retention, low creep, high tensile strength, low stress to seal and high crystallinity index.

Claims

1. A membrane comprising PTFE having a matrix tensile strength in at least one direction of at least 25,000 psi;

a matrix tensile strength ratio in two orthogonal directions of between about 0.25 and 4;

an orientation index of about 50°

or less; and

a density of about 2.0 g/cc or less.

2. The membrane of claim 1 having an orientation index of 40°

or less.

3. The membrane of claim 2 having an orientation index of 30°

or less.

4. The membrane of claim 3 having an orientation index of 20°

or less.

5. The membrane of claim 1 having a crystallinity index of 60% or more.

6. The membrane of claim 5 having a crystallinity index of 65% or more.

7. The membrane of claim 6 having a crystallinity index of 70% or more.

8. The membrane of claim 1 having a density of about 1.0 g/cc or less.

9. The membrane of claim 8 having a density of about 0.5 g/cc or less.

10. The membrane of claim 1 having an enthalpy of at least about 9.0 Joules per gram (J/g).

11. The membrane of claim 10 having an enthalpy of at least 10.0 J/g.

12. The membrane of claim 11 having an enthalpy of at least 11.0 J/g.

13. A membrane comprising PTFE having a matrix tensile strength in at least one direction of at least about 34,000 psi;

a matrix tensile strength ratio in 2 orthogonal directions of between about 0.25 and 4; and

a density of about 2.0 g/cc or less.

14. The membrane of claim 13 having an orientation index of 50°

or less.

15. The membrane of claim 14 having an orientation index of 40°

or less.

16. The membrane of claim 15 having an orientation index of 30°

or less.

17. The membrane of claim 13 having a crystallinity index of 60% or more.

18. The membrane of claim 17 having a crystallinity index of 65% or more.

19. The membrane of claim 18 having a crystallinity index of 70% or more.

20. The membrane of claim 13 having a density of about 1.0 g/cc or less.

21. The membrane of claim 20 having a density of about 0.5 g/cc or less.

22. The membrane of claim 13 having an enthalpy of at least about 9.0 Joules per gram (J/g).

23. The membrane of claim 22 having an enthalpy of at least 10.0 J/g.

24. The membrane of claim 23 having an enthalpy of at least 11.0 J/g.

25. A membrane comprising PTFE having a matrix tensile strength in at least one direction of at least about 44,800 psi;

a matrix tensile strength ratio in 2 orthogonal directions of between about 0.25 and 4; and

a density of about 2 g/cc or less.

26. The membrane of claim 25 having an orientation index of 50°

or less.

27. The membrane of claim 26 having an orientation index of 40°

or less.

28. The membrane of claim 27 having an orientation index of 30°

or less.

29. The membrane of claim 25 having a crystallinity index of 60% or more.

30. The membrane of claim 29 having a crystallinity index of 65% or more.

31. The membrane of claim 30 having a crystallinity index of 70% or more.

32. The membrane of claim 25 having a density of about 1.0 g/cc or less.

34. The membrane of claim 25 having an enthalpy of at least about 9.0 Joules per gram (J/g).

35. The membrane of claim 34 having an enthalpy of at least 10.0 J/g.

36. The membrane of claim 35 having an enthalpy of at least 11.0 J/g.

33. The membrane of claim 332 having a density of about 0.5 g/cc or less.

37. A membrane consisting essentially of a single layer of PTFE having a matrix tensile strength in at least one direction of at least 25,000 psi;

a matrix tensile strength ratio in 2 orthogonal directions of between about 0.25 and 4; and

a density of about 2.0 g/cc or less.

38. The membrane of claim 37 having an orientation index of 50°

or less.

39. The membrane of claim 38 having an orientation index of 40°

or less.

40. The membrane of claim 39 having an orientation index of 30°

or less.

41. The membrane of claim 37 having a crystallinity index of 60% or more.

42. The membrane of claim 41 having a crystallinity index of 65% or more.

43. The membrane of claim 42 having a crystallinity index of 70% or more.

44. The membrane of claim 37 having a density of about 1.0 g/cc or less.

45. The membrane of claim 44 having a density of about 0.5 g/cc or less.

46. The membrane of claim 37 having an enthalpy of at least about 9.0 Joules per gram (J/g).

47. The membrane of claim 46 having an enthalpy of at least 10.0 J/g.

48. The membrane of claim 47 having an enthalpy of at least 11.0 J/g.

49. A gasket comprising PTFE, said gasket having:

a thickness in the range of about 1.5 mm to about 9 mm

a compressibility of at least about 40%,

and a percent bolt load retention versus thickness equal to or greater than the line connecting points A and B in FIG. 18 and defined in the following table;

Point% BLR at RTThicknessA92%1.5 mmB52% 

 

9 mm

50. The gasket of claim 49, wherein said gasket has a crystallinity index of at least about 60%.

51. The gasket of claim 49, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

52. The gasket of claim 49, wherein said gasket has a durometer of about 85 or less.

53. The gasket of claim 49, wherein said gasket has a matrix tensile strength of at least about 22,000 psi (151.7 MPa).

54. The gasket of claim 49, wherein said gasket consists essentially of PTFE.

55. The gasket of claim 49, wherein said gasket has a percent bolt load retention versus thickness equal to or greater than the line connecting the points C and D in FIG. 18 and defined in the following table:

56. The gasket of claim 55, wherein said gasket has a crystallinity index of at least about 60%.

57. The gasket of claim 55, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

58. The gasket of claim 55, wherein said gasket has a durometer of about 85 or less.

59. The gasket of claim 55, wherein said gasket has a matrix tensile strength of at least about 22,000 psi (151.7 MPa).

60. The gasket of claim 55, wherein said gasket consists essentially of PTFE.

61. A gasket comprising PTFE having a nominal thickness of 1.5 mm, a bolt load retention of at least about 91% and a compressibility of at least 40%.

71. The gasket of claim 61, wherein said gasket has a crystallinity index of at least about 60%.

72. The gasket of claim 61, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

62. A gasket comprising PTFE having a nominal thickness of 2 mm, a bolt load retention of at least about 90% and a compressibility of at least 40%.

73. The gasket of claim 62, wherein said gasket has a crystallinity index of at least about 60%.

74. The gasket of claim 62, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

63. A gasket comprising PTFE having a nominal thickness of 3 mm, a bolt load retention of at least about 85% and a compressibility of at least 40%.

75. The gasket of claim 63, wherein said gasket has a crystallinity index of at least about 60%.

76. The gasket of claim 63, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

64. A gasket comprising PTFE having a nominal thickness of 6 mm, a bolt load retention of at least about 65% and a compressibility of at least 40%.

77. The gasket of claim 64, wherein said gasket has a crystallinity index of at least about 60%.

78. The gasket of claim 64, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

65. A gasket comprising PTFE having a nominal thickness of 1.5 mm, a bolt load retention of at least about 91% and a durometer of 85 or less.

79. The gasket of claim 65, wherein said gasket has a crystallinity index of at least about 60%.

80. The gasket of claim 65, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

66. A gasket comprising PTFE having a nominal thickness of 2 mm, a bolt load retention of at least about 90% and a durometer of 85 or less.

81. The gasket of claim 66, wherein said gasket has a crystallinity index of at least about 60%.

82. The gasket of claim 66, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

67. A gasket comprising PTFE having a nominal thickness of 3 mm, a bolt load retention of at least about 85% and a durometer of 85 or less.

83. The gasket of claim 67, wherein said gasket has a crystallinity index of at least about 60%.

84. The gasket of claim 67, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

68. A gasket comprising PTFE having a nominal thickness of 6 mm, a bolt load retention of at least about 65% and a durometer of 85 or less.

85. The gasket of claim 68, wherein said gasket has a crystallinity index of at least about 60%.

86. The gasket of claim 68, wherein said gasket has a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

69. A gasket comprising PTFE having a nominal thickness of 1 mm, a bolt load retention of at least about 93%, a compressibility of at least 40%, and a crystallinity index of at least about 60%.

70. A gasket comprising PTFE having a nominal thickness of 1 mm, a bolt load retention of at least about 93%, a compressibility of at least 40%, and a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa).

87. A gasket comprising PTFE wherein said gasket has

a nominal thickness of 3 mm;

a tensile strength in at least one direction of at least 4,500 psi (31.0 MPa);

a bolt load retention of at least 85%; and

a stress to seal equal to or less than 3500 psi (24.1 MPa).

88. The gasket of claim 87, wherein said tensile strength in at least one direction is at least 5,500 psi (37.9 MPa).

89. The gasket of claim 87, wherein said tensile strength is at least 6,000 psi (41.4 MPa).

90. The gasket of claim 87, wherein said tensile strength is at least 7,000 psi (48.3 MPa).

91. The gasket of claim 87, wherein said gasket comprises multiple PTFE membranes.

92. The gasket of claim 87, wherein said gasket comprises at least one rigid layer.

93. The gasket of claim 87, wherein said rigid layer comprises PTFE.

94. The gasket of claim 87 in the form of a form-in-place tape.

95. A gasket comprising PTFE wherein said gasket has

a nominal thickness of 1.5 mm;

a tensile strength in at least one direction of at least 4,500 psi (31.0 MPa);

a bolt load retention of at least 91%; and

a stress to seal equal to or less than 3500 psi (24.1 MPa).

96. The gasket of claim 95, wherein said tensile strength in at least one direction is at least 5,500 psi (37.9 MPa).

97. The gasket of claim 95, wherein said tensile strength is at least 6,000 psi (41.4 MPa).

98. The gasket of claim 95, wherein said tensile strength is at least 7,000 psi (48.3 MPa).

99. The gasket of claim 95, wherein said gasket comprises multiple PTFE membranes.

100. The gasket of claim 95, wherein said gasket comprises at least one rigid layer.

101. The gasket of claim 95, wherein said rigid layer comprises PTFE.

102. The gasket of claim 95 in the form of a form-in-place tape.

103. A gasket comprising PTFE, said PTFE having a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa) and a compressibility of at least about 40%.

104. The gasket of claim 103, said gasket having a tensile strength in at least one direction of at least about 6,000 psi (41.4 MPa).

105. The gasket of claim 103, said gasket having a tensile strength in at least one direction of at least about 7,000 psi (48.3 MPa).

106. The gasket of claim 103, wherein said gasket comprises multiple PTFE membranes.

107. The gasket of claim 103, wherein said gasket comprises at least one rigid layer.

108. The gasket of claim 107, wherein said rigid layer comprises PTFE.

109. A gasket comprising PTFE, said PTFE having a tensile strength in at least one direction of at least about 5,500 psi (37.9 MPa) and a durometer of 85 or less.

110. The gasket of claim 109, said gasket having a tensile strength in at least one direction of at least about 6,000 psi (41.4 MPa).

111. The gasket of claim 109, said gasket having a tensile strength in at least one direction of at least about 7,000 psi (48.3 MPa).

112. The gasket of claim 109, wherein said gasket comprises multiple PTFE membranes.

113. The gasket of claim 109, wherein said gasket comprises at least one rigid layer.

114. The gasket of claim 109, wherein said rigid layer comprises PTFE.

115. A gasket consisting essentially of PTFE, said gasket having a bolt load retention of at least about 85% for a nominal 3 mm thickness.

116. A gasket consisting essentially of PTFE, said gasket having a bolt load retention of at least about 91% for a nominal 1.5 mm thickness.

117. A gasket consisting essentially of PTFE, said gasket having a matrix tensile strength of at least about 22,000 psi (151.7 MPa).

118. The gasket of claim 117, wherein said matrix tensile strength is at least about 25,000 psi (172.4 MPa).

119. A gasket consisting essentially of PTFE, said gasket having a creep of less than 5.0% and a nominal thickness of 1.5 mm.

120. A gasket comprising PTFE, said gasket having a compressibility of at least about 40%, a creep of less than 5% and a nominal thickness of 1.5 mm.

121. A gasket comprising PTFE, said gasket having a durometer of 85 or less, a creep of less than 5% and a nominal thickness of 1.5 mm.

122. A gasket comprising PTFE, said gasket having a nominal thickness of 1.5 mm, a tensile strength in at least one direction of at least about 5,500 psi ((37.9 MPa) and creep of less than 5%.

123. The gasket of claim 122, said gasket having a tensile strength in at least one direction of at least about 6,000 psi (41.4 MPa).

124. The gasket of claim 122, said gasket having a tensile strength in at least one direction of at least about 7000 psi (48.3 MPa).

125. A gasket comprising PTFE, said gasket having a nominal thickness of 1.5 mm, a bolt load retention of at least about 91% and a stress to seal of less than or equal to 3500 psi (24.1 MPa).

126. A gasket comprising PTFE, said gasket having a nominal thickness of 3 mm, a bolt load retention of at least about 85% and a stress to seal of less than or equal to 3500 psi (24.1 MPa).

127. A gasket comprising PTFE, said gasket having a nominal thickness of 1.5 mm, a bolt load retention of at least about 91% and a stress to seal of less than or equal to 1500 psi (10.3 MPa).

128. A gasket comprising PTFE, said gasket having a nominal thickness of 3 mm, a bolt load retention of at least about 85% and a stress to seal of less than or equal to 1500 psi (10.3 MPa).

129. A gasket comprising PTFE, said gasket having a nominal thickness of 6 mm, a bolt load retention of at least about 65% and a stress to seal of less than or equal to 1500 psi (10.3 MPa).

130. A gasket comprising PTFE, said gasket having a nominal thickness of 1.5 mm, a creep of less than 5% and a stress to seal of less than or equal to 3500 psi (24.1 MPa).

131. The gasket of claim 130, said gasket having a stress to seal of less than or equal to 1500 psi (10.3 MPa).

132. A gasket comprising PTFE, said gasket having a nominal thickness of 3 mm, a tensile strength in at least one direction of at least 5,500 psi (37.9 MPa) and a stress to seal of 3500 psi (24.1 MPa) or less.

133. The gasket of claim 132, said gasket having a tensile strength in at least one direction of at least 6000 psi (41.4 MPa).

134. The gasket of claim 132, said gasket having a tensile strength in at least one direction of at least 7000 psi (48.3 MPa).

135. The gasket of claim 132, said gasket having a stress to seal of 1500 psi (10.3 MPa) or less.