Flash-spun sheet material
View Patent ↗This invention relates to improved plexifilamentary sheet material useful in protective apparel and filtration media, which material is comprised of substantially continuous polyethylene plexifilamentary fiber strands and has a Frazier Permeability, normalized to 1.0 oz/yd 2 basis weight, of at least 2 cfm/ft 2 .
1. A polyethylene plexifilamentary fiber strand produced by a process comprising flash spinning a solution of 12% to 24% by weight polyethylene in spin agent consisting of a mixture of normal pentane and cyclopentane at a spinning temperature from about 205° C. to 220° C. to form said plexifilamentary fiber strand having a surface area of less than 10 m2/g and a crush value of at least 1 mm/g.
2. The plexifilamentary fiber strand of claim 1 wherein the surface area of the strand is less than 8 m2/g.
3. The plexifilamentary fiber strand of claim 1 wherein the surface area of the strand is less than 5 m2/g.
4. The plexifilamentary fiber strand of claim 1 wherein the crush value of the strand is at least 1.5 mm/g.
5. A nonwoven unitary fibrous sheet produced by a process comprising flash spinning a solution of 12% to 24% by weight polyethylene in spin agent consisting of a mixture of normal pentane and cyclopentane at a spinning temperature from about 205° C. to 220° C. to form substantially continuous polyethylene plexifilamentary fiber strands having surface areas of less than 10 m2/g and crush values of at least 1 mm/g; collecting said plexifilamentary fiber strands to form a sheet; and bonding said sheet to form said nonwoven unitary fibrous sheet comprised of substantially continuous polyethylene plexifilamentary fiber strands and having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 2 cfm/ft2.
6. The nonwoven sheet of claim 5 having a hydrostatic head of at least 30 cm.
7. The nonwoven sheet of claim 5 having a hydrostatic head of at least 45 cm.
8. The nonwoven sheet of claim 5 having a hydrostatic head of at least 75 cm.
9. The nonwoven sheet of claim 5 having a hydrostatic head of at least 85 cm.
10. The nonwoven sheet of claim 5 having a hydrostatic head of at least 100 cm.
11. The nonwoven sheet of claim 5 having a hydrostatic head of at least 130 cm.
12. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 4 cfm/ft2.
13. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 8 cfm/ft2.
14. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 10 cfm/ft2.
15. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 15 cfm/ft2.
16. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 20 cfm/ft2.
17. The nonwoven sheet of claim 6 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 25 cfm/ft2.
18. The nonwoven sheet of claim 5 wherein said sheet has a whole surface bonded portion of a first side of the sheet and a point bonded portion on the second side of the sheet, said point bonded portion of the sheet comprising at least 50% by weight of the nonwoven sheet.
19. The nonwoven sheet of claim 18 wherein the point bonded portion of the sheet comprises at least 60% by weight of the nonwoven sheet.
20. The nonwoven sheet of claim 19 wherein the point bonded portion to the sheet is bonded with a ribbed bonding pattern and the whole surface bonded portion of the sheet is bonded with a linen pattern.
21. A garment comprised of the nonwoven sheet of claim 6 .
22. Filter media comprised of the nonwoven sheet of claim 5 .
23. A vacuum bag comprised of the nonwoven sheet of claim 5 .
24. A pillow cover comprised of the nonwoven sheet of claim 5 .
25. A nonwoven sheet produced by a process comprising flash spinning a solution of 12% to 24% by weight polyethylene in spin agent consisting of a mixture of normal pentane and cyclopentane at a spinning temperature from about 205° C. to 220° C. to form substantially continuous polyethylene plexifilamentary fiber strands having surface areas of less than 10 m2/g and crush values of at least 1 mm/g; collecting said plexifilamentary fiber strands to form a sheet; and bonding said sheet to form said nonwoven sheet comprised of substantially continuous polyethylene plexifilamentary fiber strands and having a hydrostatic head of at least 110 cm and a Gurley Hill Porosity of less than 6 seconds.
26. The nonwoven sheet of claim 25 having a hydrostatic head of at least 130 cm.
27. A flash-spun polyethylene plexifilamentary fiber strand having a surface area of less than 10 m2/g and a crush value of at least 1 mm/g.
28. The flash-spun polyethylene plexifilamentary fiber strand of claim 27 , wherein the surface area is less than 8 m2/g.
29. The flash-spun polyethylene plexifilamentary fiber strand of claim 27 , wherein the surface area is less than 5 m2/g.
30. The flash-spun polyethylene plexifilamentary fiber strand of claim 27 , wherein the crush value is at least 1.5 mm/g.
31. A nonwoven sheet comprising substantially continuous, flash-spun polyethylene plexifilamentary fiber strands, the strands having surface areas of less than 10 m2/g and crush values of at least 1 mm/g.
32. The nonwoven sheet of claim 31 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 2 cfm/ft2.
33. The nonwoven sheet of claim 31 having a Gurley Hill Porosity of less than 6 seconds.
34. The nonwoven sheet of claim 32 having a hydrostatic head of at least 30 cm.
35. The nonwoven sheet of claim 32 having a hydrostatic head of at least 75 cm.
36. The nonwoven sheet of claim 32 having a hydrostatic head of at least 100 cm.
37. The nonwoven sheet of claim 32 having a hydrostatic head of at least 130 cm.
38. The nonwoven sheet of claim 31 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 4 cfm/ft2.
39. The nonwoven sheet of claim 31 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 10 cfm/ft2.
40. The nonwoven sheet of claim 31 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 20 cfm/ft2.
41. The nonwoven sheet of claim 31 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 25 cfm/ft2.
42. The nonwoven sheet of claim 31 , wherein the sheet has a whole surface bonded portion of a first side of the sheet and a point bonded portion on the second side of the sheet, the point bonded portion of the sheet comprising at least 50% by weight of the nonwoven sheet.
43. The nonwoven sheet of claim 42 , wherein the point bonded portion of the sheet comprises at least 60% by weight of the nonwoven sheet.
44. The nonwoven sheet of claim 43 , wherein the point bonded portion to the sheet is bonded with a ribbed bonding pattern and the whole surface bonded portion of the sheet is bonded with a linen pattern.
45. A method of forming a polyethylene plexifilamentary fiber strand comprising:
providing a solution of 12% to 24%, by weight of the solution, of polyethylene and a spin agent consisting of a mixture of normal pentane and cyclopentane; and
flash spinning the solution at a spinning temperature from about 205° C. to 220° C. to form the polyethylene plexifilamentary fiber strand; and
wherein the polyethylene plexifilamentary fiber strand has a surface area of less than 10 m2/g and a crush value of at least 1 mm/g.
46. The method of claim 45 , wherein the solution comprises 12% to 17%, by weight of the solution, of polyethylene.
47. The method of claim 45 , wherein the solution comprises 14% to 16%, by weight of the solution, of polyethylene.
48. The method of claim 45 , wherein the solution comprises 15% to 24%, by weight of the solution, of polyethylene.
49. The method of claim 45 , wherein the solution comprises 16% to 20%, by weight of the solution, of polyethylene.
50. The method of claim 45 , wherein the spinning temperature is from 205° C. to 214° C.
51. The method of claim 45 , wherein the spinning temperature is from 208° C. to 212° C.
52. The method of claim 45 , wherein the spinning temperature is from 208° C. to 218° C.
53. The method of claim 45 , wherein the flash spinning step comprises introduction of the solution into a letdown chamber having an entrance angle α of between 10° and 70°.
54. The method of claim 45 , wherein the ratio of normal pentane to cyclopentane is about 60:40.
55. A method of producing a nonwoven unitary fibrous sheet comprising;
providing a solution of 12% to 24%, by weight of the solution, polyethylene and a spin agent consisting of a mixture of normal pentane and cyclopentane;
flash spinning the solution at a spinning temperature from about 205° C. to 220° C. to form substantially continuous polyethylene plexifilamentary fiber strands;
wherein the polyethylene plexifilamentary fiber strand has a surface area of less than 10 m2/g and a crush value of at least 1 mm/g;
collecting the polyethylene plexifilamentary fiber strands to form a sheet; and
bonding the sheet to form the nonwoven unitary fibrous sheet.
56. The method of claim 55 , wherein the sheet is point bonded to form the nonwoven unitary fibrous sheet.
57. The method of claim 56 , wherein the nonwoven unitary fibrous sheet is softened.
58. The method of claim 55 , wherein the sheet is bonded by through-air bonding to form the nonwoven unitary fibrous sheet.
59. A method for producing a nonwoven sheet comprising:
providing a solution of 12% to 24%, by weight of the solution, polyethylene and a spin agent consisting of a mixture of normal pentane and cyclopentane;
flash spinning the solution at a spinning temperature from about 205° C. to 220° C. to form substantially continuous polyethylene plexifilamentary fiber strands;
collecting the plexifilamentary fiber strands to form a sheet; and
bonding the sheet to form the nonwoven sheet;
wherein the substantially continuous polyethylene plexifilamentary fiber strands have surface areas of less than 10 m2/g, crush values of at least 1 mm/g, a hydrostatic head of at least 110 cm, and a Gurley Hill Porosity of less than 6 seconds.
60. The method of claim 59 , wherein the solution comprises 12% to 17%, by weight of the solution, of polyethylene.
61. The method of claim 59 , wherein the solution comprises 14% to 16%, by weight of the solution, of polyethylene.
62. The method of claim 59 , wherein the solution comprises 15% to 24%, by weight of the solution, of polyethylene.
63. The method of claim 59 , wherein the solution comprises 16% to 20%, by weight of the solution, of polyethylene.
64. The method of claim 59 , wherein the spinning temperature is from 205° C. to 214° C.
65. The method of claim 59 , wherein the spinning temperature is from 208° C. to 212° C.
66. The method of claim 59 , wherein the spinning temperature is from 208° C. to 218° C.
67. The method of claim 59 , wherein the flash spinning step comprises introduction of the solution into a letdown chamber having an entrance angle α of between 10° and 70°.
68. The method of claim 59 , wherein the ratio of normal pentane to cyclopentane is about 60:40.
69. The method of claim 59 , wherein the sheet is point bonded to form the nonwoven unitary fibrous sheet.
70. The method of claim 69 , wherein the nonwoven unitary fibrous sheet is softened.
71. The method of claim 59 , wherein the sheet is bonded by through-air bonding to form the nonwoven unitary fibrous sheet.
72. A nonwoven sheet comprising substantially continuous, flash-spun polyethylene plexifilamentary fiber strands and having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 2 cfm/ft2.
73. The nonwoven sheet of claim 72 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 4 cfm/ft2.
74. The nonwoven sheet of claim 72 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 10 cfm/ft2.
75. The nonwoven sheet of claim 72 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 20 cfm/ft2.
76. The nonwoven sheet of claim 72 having a Frazier Permeability, normalized to 1.0 oz/yd2 basis weight, of at least 25 cfm/ft2.
77. The nonwoven sheet of claim 72 having a hydrostatic head of at least 30 cm.
78. The nonwoven sheet of claim 72 having a hydrostatic head of at least 85 cm.
79. The nonwoven sheet of claim 72 having a hydrostatic head of at least 130 cm.
80. The nonwoven sheet of claim 72 having a Gurley Hill Porosity of less than 6 seconds.
81. The nonwoven sheet of claim 72 , wherein the substantially continuous, flash-spun polyethylene plexifilamentary fiber strands are produced by a process comprising flash spinning a solution of 12% to 24% by weight polyethylene in spin agent consisting of a mixture of normal pentane and cyclopentane at a spinning temperature from about 205° C. to 220° C.