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Publication numberUS20050106970 A1
Publication typeApplication
Application numberUS 10/362,788
PCT numberPCT/US2001/006785
Publication dateMay 19, 2005
Filing dateMar 2, 2001
Priority dateSep 1, 2000
Publication number10362788, 362788, PCT/2001/6785, PCT/US/1/006785, PCT/US/1/06785, PCT/US/2001/006785, PCT/US/2001/06785, PCT/US1/006785, PCT/US1/06785, PCT/US1006785, PCT/US106785, PCT/US2001/006785, PCT/US2001/06785, PCT/US2001006785, PCT/US200106785, US 2005/0106970 A1, US 2005/106970 A1, US 20050106970 A1, US 20050106970A1, US 2005106970 A1, US 2005106970A1, US-A1-20050106970, US-A1-2005106970, US2005/0106970A1, US2005/106970A1, US20050106970 A1, US20050106970A1, US2005106970 A1, US2005106970A1
InventorsGary Stanitis, Frank Cistone, Jin Choi
Original AssigneeStanitis Gary E., Frank Cistone, Jin Choi
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Melt processable perfluoropolymer forms
US 20050106970 A1
Abstract
Melt processable perfluoropolymer forms prepared from melt processable perfluoropolymer fibers and yarns. Filtration media and filtration support media prepared from melt processable perfluoropolymers.
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Claims(61)
1. Textured yarns having 2 to 100 crimps/inch derived from melt processable perfluoropolymers, having individual filament deniers from about 0.5 to about 300 and total yarn deniers of about 10 to 100,000, wherein said perfluoropolymer is selected from the group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of at least one perfluoroalkoxylvinylether where the alkyl group has from 1 to 4 carbon atoms and copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin having from 3 to 8 carbon atoms.
2. Staple Fibers having 0 to 50 crimps/inch derived from melt processable perfluoropolymers having individual filament deniers from about 0.5 to about 300 and total yarn deniers of about 10 to 100,000, wherein said perfluoropolymer is selected from the group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of at least one perfluoroalkoxylvinylether where the alkyl group has from 1 to 4 carbon atoms, and copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin having from 3 to 8 carbon atoms.
3. Yarns and staple fibers according to claims 1 or 2 with individual filaments having a cross-sectional shape selected from the group consisting of circular, elliptical, angular, hollow, multilobal, bi-component or sheath core yarns or staple fibers made from said melt processable perfluoropolymers and any other melt processable polymer as the second component.
4. Yarns and Staple fibers derived from melt processable perfluoropolymers, having individual filament deniers from about 0.5 to about 300, and total yarn deniers of about 10 to 100,000 having cross-sectional geometries of individual filaments other than single component circular, these include elliptical, angular, hollow, multilobal, bi-component, or sheath core.
5. A yam according to claims 3 or 4 having residual elongation of 1 to 50%, better filament uniformity, and less brittleness.
6. A high purity yarn and staple fiber according to claims 3 or 4 suitable for use in semiconductor, pharmaceutical, and other high purity applications.
7. A yarn according to claim 3 or 4 suitable for weaving, knitting, hydroentangling, flame treating, and other textile processes.
8. An air entangled yarn derived from melt processable perfluoropolymers, having individual filament deniers from about 0.5 to about 300, and total yarn deniers of about 10 to 100,000.
9. A twisted yarn having 1 to 20 twists per inch derived from melt processable perfluoropolymers, having individual filament deniers from about 0.5 to about 300, and total yarn deniers of about 10 to 100,000.
10. Yarns made according to claims 3, 4, 5, 6, 8, or 9, or any combination of these claims, suitable for weaving, knitting, hydroentangling, air-jet entangling flame treating, and other textile processes.
11. A woven fabric having a weight per square yard of from about 1 to about 100 ounces per square yard made from yams according to claims 3, 4, 5, 6, 8, 9, or 10, or any combination of these claims, suitable for use in filtration, or as a support scrim in non-woven products.
12. A knitted fabric having a weight per square yard of from about 1 to about 100 ounces per square yard made from yams according to claims 3, 4, 5, 6, 8, 9, or 10, or any combination of these claims, suitable for use in filtration, or as a support scrim in non-woven products.
13. A crimped staple fiber according to claims 3 or 4 wherein the filaments have been crimped to give an angular “saw toothed” shape with 2 to 50 crimps per inch, cut to any length, suitable for use on standard carding equipment to make nonwoven batts which can then be needled into felts or for carding into sliver for making spun yarns or for producing high loft air laid non-woven products.
14. A non-woven perfluoropolymer fabric having a weight per square yard of from about 1 to about 100 ounces per square yard, made from staple fibers according to claim 6, having excellent strength in both the machine and cross-machine directions, and good filtration properties.
15. A non-woven perfluoropolymer fabric having a weight per square yard of from about 1 to about 100 ounces per square yard produced by needlepunching of a continuous, carded staple fiber web, made from staple fibers according to claim 13, having excellent strength in both the machine and cross-machine directions, and good filtration properties.
16. A lightly needled or un-needled carded batt made from melt processable perfluoropolymer which has been densified and/or bonded through a heated calendering process, with smooth, textured, or patterned calender rolls, to yield a fabric with increased strength and stiffness, as compared to its precursor.
17. A fabric, according to claims 14 and 15, further, including a perfluoropolymer woven supporting fabric or scrim for increased strength.
18. A fabric, according to claims 14 and 15, further including a woven supporting fabric or scrim made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or synthetic fibers for increased strength.
19. A fabric according to claims 14, 15, 16, 17, or 18 made from of a blend of melt processable perfluoropolymer staple fibers and fibers selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other synthetic fibers.
20. A fabric according to claims 14, 15, 16, 17, 18, or 19 where the fabric density, air permeability, and mean pore size can be controlled through needling conditions.
21. A calendered fabric according to claims 14, 15, 16, 17, 18, 19, or 20 where the fabric density, air permeability, and mean pore size can be controlled in a continuous fashion through the heated calendering/densification process with smooth, textured, or patterned calender rolls, or in a batch fashion in a plate press.
22. Yarns, staple fibers, or fabrics according to claims 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21 which are thermally bonded to themselves.
23. Yarns, staple fibers and fabrics according to claims 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, or 21 which are thermally bonded to other high temperature plastics, fabrics and other media.
24. Filtration and coalescing media, support layers, drainage layers, and other components produced by winding continuous or spun yarns according to claims 3, 4, 5, 6, or 8, 9, or 10.
25. Filtration and coalescing media, support layers, drainage layers, and other components produced according to claims 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23.
26. Filtration and coalescing components according to claims 24 or 25 with seams formed by thermal fusion.
27. Filtration and coalescing components according to claims 24 or 25 which are melt fused to other components of the filter or the filter housing to form a liquid tight seal.
28. Filtration and coalescing components according to claims 24 or 25 having less tendency to foul and easier cleaning by back-pulsing, rinsing, mechanical means, or other techniques.
29. Filtration and coalescing components according to claims 24 or 25 having high purity suitable for semiconductor, pharmaceutical, and other high purity applications.
30. Pleatable filtration and coalescing components according to claims 24 or 25.
31. Filtration and coalescing components according to claims 24 or 25 thermally bonded to other media, such as membranes, drainage layers, pleat supports and any other component of filter elements or devices.
32. A self-supported non-woven fabric derived from melt processable perfluoropolymers possessing a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi.
33. A scrim-supported non-woven fabric possessing a Mullen burst strength between 10 and 1000 psi wherein said non-woven fabric is derived from melt processable perfluoropolymers.
34. A self-supported or scrim-supported non-woven fabric derived from melt processable perfluoropolymers possessing an air permeability (ASTM D737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.
35. A woven fabric having a weight per square yard of about 1 to about 100 ounces per square yard, made from a blend comprising. 1 to 99 percent by weight of melt processable perfluoropolymer yarns according to claims 3, 4, 5, 6, 8, 9, or 10; and 99 to 1 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyirnide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, suitable for use in filtration, as a support scrim in nonwoven products.
36. A woven fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend of 1 to 99 percent by weight of melt processable perfluoropolyner yams according to claims 3, 4, 5, 6, 8, 9, or 10; and 99 to 1 percent by weight of fibers or yarns made from polytetrafluoroethylene (PTFE), suitable for use in filtration, as a support scrim in nonwoven products.
37. A knitted fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer yarns according to claims 3, 4, 5, 6, 8, 9, or 10; and 99 to 1 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, suitable for use in filtration, or as a support scrim in nonwoven products.
38. A knitted fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend comprising: 1 to 99 percent melt processable perfluoropolymer yarns or fibers according to claims 3, 4, 5, 6, 8, 9, or 10; and 99 to 1 percent PTFE yarns or fibers, suitable for use in filtration, or as a support scrim in nonwoven products.
39. A fabric according to claims 14, 15, 16, 17, or 18 made from a blend comprising: 1 to 99 percent melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers.
40. A fabric, according to claim 39 where the fabric density, air permeability, and mean pore size can be controlled through needling conditions.
41. A calendered fabric according to claims 39 or 40 where the fabric density, air permeability, and mean pore size can be controlled in a continuous fashion through the heated calendering/densification process with smooth, textured, or patterned calender rolls, or in a batch fashion in a plate press.
42. Yams, staple fibers, or fabrics according to claims 35, 36, 37, 38, 39, 40 or 41 which are thermally bonded to themselves.
43. Yarns, staple fibers, or fabrics according to claims 35, 36, 37, 38, 39, 40, or 41 which are thermally bonded to other high temperature plastics, fabrics and other media.
44. Filtration and coalescing media, support layers, drainage layers, and other components produced by winding continuous or spun yams comprising a blend of from 1 to 99 percent melt processable perfluoropolymer yarns or fibers according to claims 3, 4, 5, 6, 8, 9, or 10, and 99 to 1 percent by weight of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers.
45. Filtration and coalescing media, support layers, drainage layers, and other components produced by winding continuous or spun yarns comprising a blend of from 1 to 99 percent melt processable perfluoropolymer yarns or fibers according to claims 3, 4, 5, 6, 8, 9, or 10; and 99 to 1 percent PTFE yarns or fibers.
46. Filtration and coalescing media, support layers, drainage layers, and other components produced according to claims 35, 36, 37, 38, 39, 40, 41, 42, and 43.
47. Filtration and coalescing components according to claims 44, 45, or 46 with seams formed by thermal fusion.
48. Filtration and coalescing components according to claims 44, 45, or 46 which are melt fused to other components of the filter or the filter housing to form a liquid tight seal.
49. Filtration and coalescing components according to claims 44, 45, or 46 having less tendency to foul and easier cleaning by back-pulsing, rinsing, mechanical means, or other techniques.
50. Filtration and coalescing components according to claims 44, 45, or 46 having high purity suitable for serniconductor, pharmaceutical, and other high purity applications.
51. Pleatable filtration and coalescing components according to claims 44, 45, or 46.
52. Filtration and coalescing components according to claims 44, 45, or 46 thermally bonded to other media, such as membranes, drainage layers, pleat supports and any other component of filter elements or devices.
53. A self-supported non-woven fabric derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers and 99 to 1 percent fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, said non-woven fabric possessing a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi.
54. A self-supported non-woven fabric derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers; and from 99 to 1 percent PTFE fibers, said non-woven fabric possessing a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi.
55. A scrim supported non-woven fabric possessing a Mullen burst strength between 10 and 1000 psi wherein said non-woven fabric is derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers; and 99 to 1 percent fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers.
56. A scrim supported non-woven fabric possessing a Mullen burst strength between 10 and 1000 psi wherein said non-woven fabric is derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers.
57. A self-supported or scrim supported non-woven fabric derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers and 99 to 1 percent by weight fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, said self supported or scrim supported non-woven fabric possessing an air permeability (ASTM D737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.
58. A self-supported or scrim supported non-woven fabric derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers, said self-supported or scrim supported non-woven fabric possessing an air permeability (ASTM D737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.
59. Filtration and coalescing components according to claims 24, 25, 44, 45, or 46 with seams formed by sewing, use of an adhesive, or by mechanical fasteners.
60. Filtration and coalescing components according to claims 24, 25, 44, 45, or 46 which are attached to other components of the filter or the filter housing, using an adhesive, to form a liquid tight seal.
61. Filtration and coalescing components according to claims 24, 25, 44, 45, or 46 attached to other media, such as membranes, drainage layers, pleat supports and any other component of filter element devices using an adhesive, by sewing, or by mechanical fasteners.
Description
BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to melt processable perfluoropolymer forms, such as woven, non-woven and knitted forms, and products prepared therefrom, such as filtration and filtration support media. More specifically, the melt processable perfluoropolymer forms of the present invention are prepared from melt processable perfluoropolymer fibers and yarns.

2. Description of the Prior Art

Perfluoropolymers are those polymers with all of their hydrogens substituted with fluorine, the best known of which is polytetrafluoroethylene or PTFE. These perfluoropolymers exhibit extreme chemical inertness to virtually all industrial chemicals, even at elevated temperatures. They also exhibit excellent temperature resistance at constant use temperatures of up to 300° C. They are also useful due to their low surface energy, which causes them to resist wetting and imparts anti-stick and anti-staining properties. In addition, perfluoropolymers are resistant to UV degradation, which makes them suitable for outdoor exposure as well as in applications where artificial UV light is used, such as in water purification. The preparation of continuously extruded, melt spun, multifilament melt processable yarns and staple fibers prepared from melt processable perfluoropolymers are described by Vita et al. In U.S. Pat. Nos. 5,460,882; 5,552,219 and 5,618,481, all of which are incorporated in their entirety by reference. These fibers and yarns can be used to prepare various woven, non-woven and knitted forms. One type of process used to make non-woven product forms is felting, wherein staple fibers are formed into a web by a process known in the industry as carding, followed by needle punching in a continuous or batch mode. The non-woven felt produced by this method can be used as is or can incorporate a woven reinforcing scrim if so desired. Other processes can be used to malce non-woven forms. These include air laying and wet laying, which are done with cut staple fiber, as well as spun bonding and melt blowing processes which create a non-woven web during the fiber production process. A variety of other types of processes may be used on non-wovens, such as calendering, hydro entangling, Air-jet entangling singeing and heat treating. The non-woven forms of the present invention encompass all types, including felts or fiber blends (e.g., glass, PTFE, etc.). Another type of process used for producing non-woven forms is wetlaid or paper maling technology. Yet another standard process type is weaving, which is used to create woven forms (e.g., scrims and clothes) from yarns. Weaving processes may include a number of variants, such as the twisting of the yarn prior to weaving and then application of, for example, either a typical flat weave or a Leno weave. Knitting machines, such as circular units, can be used to produce knitted fabrics. These and other types of processes and units used to produce forms are all applicable for use with the present invention.

The aforementioned forms can further be processed into filtration support media for use in either gas, wet filtration or coalescing apparatus and applications. In some of these applications it is known to use polytetrafluoroethylene (PTFE). For examples of these applications, see U.S. Pat. Nos. 3,986,851 to Rodek, 4,194,041 to Gore, et. al., 4,302,496 to Donovan, 4,361,619 to Forsten, et al., 4,612,237 to Frankenburg, 4,840,838 to Wyss, 4,877,433 to Oshitari, 4,902,423 to Bacino and 4,983,434 to Sassa, all of which are incorporated in their entirety by reference.

Product forms made from multifilament PTFE fibers have been used almost exclusively for these applications because PTFE fibers have been readily available and thought of to have the best balance of properties. It has now been found, however, that product forms made from multifilament melt processable perfluoropolymer fibers have many advantages over those made from PTFE when used in the same or similar applications.

When compared with articles made from melt processable perfiluoropolymer fibers and yarn, articles manufactured from PTFE fibers and yarns carry certain disadvantages which the present invention seeks to overcome. Recited below are eight problems associated with PTFE fibers and yarns. These problems are representative of some of the major disadvantages with PTFE fibers and yarns, and indicative of the great need in industry to find solutions to the problems and/or alternatives to PTFE fibers and yams.

First, PTFE is not a melt processable perfluoropolymer. The fibers, yarns and subsequent forms derived from it often require special or extraordinary handling and do not lend themselves to typical processes used for manufacturing melt processable forms as do say, polyesters, nylons, etc. Those processes include, but are not limited to, calendering, potting, thermally fusing, and thermally laminating. Second, PTFE fibers are not easily crimpable, and cannot accept a high level of crimp. Third, PTFE fibers create forms which are not easily melt fused and have very poor laminating and potting capability. (Potting is a term given to the process of fusing a filter media into a cartridge filter end cap during the manufacturing process of that cartridge). Fourth, PTFE fibers do not have smooth surfaces, which are a source of problems in the production of filtration media. Fifth, yams produced from PTFE by processes such as coextrusion spinning, slit film or slit expanded PTFE membrane processes, contain rough surfaces and diameter and tenacity variations, which are deleterious to their weavability properties. Sixth, filtration media derived from PTFE fibers have relatively low levels of purity. Impurities introduced by PTFE need to be removed, later and, PTFE fibers are brown as a result of decomposed organic matter present in the fibers. The organic matter is necessary in the production of PTFE fibers to allow a processable “paste” to be made, which can then be formed into fiber structures. Although the fiber can be bleached for aesthetic reasons, the impurities left behind from the manufacturing process cannot be fully eliminated. Seventh, PTFE webs are not easily pleated, which can be critical to many cartridge filter applications. Lastly, in order to make PTFE or a modified PTFE (e.g. PTFE which contains a small amount of comonomer) usable for many applications, (in part due to one or more of the above described problems), it is required to impose vigorous and strict processing conditions.

There exists, thus, a need to over these and other known problems in industry and to lessen and remove, if possible, the relatively onerous processing conditions required for PTFE and other perfluoropolymers, and to create better webs, fabrics and other finished forms. The present invention seeks to eliminate these processing requirements and to create forms, and other products prepared therefrom, with improved properties. (It is understood that while fibers and yarns are sometimes discussed separately, the applications described for making inventive forms from one are generally applicable to the other.)

Accordingly, it is an object of the present invention to provide forms which have improved properties over prior art forms.

It is a further object of the present invention to provide melt processable perfluoropolymer forms.

It is yet another object of the present invention to provide relatively relaxed and efficient processing conditions to manufacture melt processable perfluoropolymer forms.

It is still another object of the present invention to provide melt processable perfluoropolymer forms which are easily and inexpensively prepared and maintained, and which have a longer service life than conventional forms.

It is also an object of the present invention to improve the appearance, properties and performance characteristics of melt processable perfluoropolymer forms.

This invention also relates to multilobal fibers having a variety of uses. More particularly, this invention relates to such fibers having at least about two lobes which are useful in such diverse applications as filtering, wicking, insulating and other applications.

It is yet still another object of the present invention to provide products derived from the inventive forms described herein.

It is still a further object of the present invention to provide filtration media with improved properties and performance characteristics.

Another object of the invention is to provide filtration and coalescing components having less tendency to foul and easier cleaning by back-pulsing, rinsing, mechanical means, or other techniques.

An additional object of the invention is filtration and coalescing components having high purity suitable for semiconductor, pharmaceutical, and other high purity applications.

A still further object of the invention is to provide pleatable filtration and coalescing components which are thermally bonded to other media, such as membranes, drainage layers, pleat supports and any other component of filter elements or devices.

Another objective of the invention is to provide filtration and coalescing components with seams formed by thermal fusion

In another object of the invention there is provided filtration and coalescing components with seams formed by sewing, use of an adhesive, or by mechanical fasteners.

In another objective, the invention is directed to filtration and coalescing components which are attached to other components of the filter or the filter housing, using an adhesive, to form a liquid tight seal.

A still further object of the invention is filtration and coalescing components attached to other media, such as membranes, drainage layers, pleat supports and any other component of filter element devices using an adhesive, by sewing, or by mechanical fasteners.

These and other objects of the present invention can be appreciated by referring to the following description.

SUMMARY OF THE INVENTION

The present invention provides melt processable perfluoropolymer forms, and products prepared therefrom, which are manufactured from melt processable perfluoropolymer fibers and yarns. Melt processable perfluoropolymer are preferably subjected to continuously extruded, melt spun, and/or multifilament processes to produce melt processable perfluoropolymer fibers and yarns (e.g. spinning techniques taught in the Vita et al patents discussed above and other similar processes). These melt processable perfluoropolymer fibers and yarns are then subjected to further processing to make a variety of melt processable perfluoropolymer forms, such as woven, non-woven and lcnitted forms. These melt processable perfluoropolymer forms can then be used via conventional techniques to make filtration support media.

The invention also relates to a woven fabric having a weight per square yard of about 1 to about 100 ounces per square yard, made from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer yarns; and 99 to 1 percent of fibers or yarns made from materials selected from the group consisting of glass, ararnid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, suitable for use in filtration, as a support scrim in nonwoven products.

The instant invention is also directed to a woven fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend of 1 to 99 percent by weight of melt processable perfluoropolymer yarns; and 99 to 1 percent by weight of fibers or yarns made from polytetrafluoroethylene (PTFE), suitable for use in filtration, as a support scrim in nonwoven products.

The invention further provides a knitted fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer yarns; and 99 to 1 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, suitable for use in filtration, or as a support scrim in nonwoven products.

Furthermore, the invention is directed to a knitted fabric having a weight per square yard of about 1 to about 100 ounces per square yard made from a blend comprising: 1 to 99 percent melt processable perfluoropolymer yarns or fibers; and 99 to 1 percent PTFE yarns or fibers, suitable for use in filtration, or as a support scrim in nonwoven products.

The invention also describes a fabric made from a blend comprising: 1 to 99 percent melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers.

The invention is also directed to filtration and coalescing media, support layers, drainage layers, and other components produced by winding continuous or spun yarns comprising a blend of from 1 to 99 percent melt processable perfluoropolymer yarns or fibers; and 99 to 1 percent by weight of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers.

Additionally, filtration and coalescing media, support layers, drainage layers, and other components are provided which are produced by winding continuous or spun yarns comprising a blend of from 1 to 99 percent melt processable perfluoropolymer yarns or fibers; and 99 to 1 percent PTFE yarns or fibers.

Additionally, the invention is directed to a self-supported non-wovens fabrics derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers and 99 to 1 percent fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, said non-woven fabric possessing a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi.

The invention also provides a self-supported non-woven fabric derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers; and from 99 to 1 percent PTFE fibers, said non-woven fabric possessing a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi.

In another inventive embodiment, the invention is directed to a scrim supported non-woven fabric possessing a Mullen burst strength between 10 and 1000 psi wherein said non-woven fabric is derived from a blend comprising: from 1 to 99 percent melt processable perfluoropolymer fibers; and 99 to 1 percent fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers.

Also, there is provided a scrim supported non-woven fabric possessing a Mullen burst strength between 10 and 1000 psi wherein said non-woven fabric is derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers.

The instant invention also provides a self-supported or scrim supported non-woven fabric derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers and 99 to 1 percent by weight fibers made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers, said self supported or scrim supported non-woven fabric possessing an air permeability (ASTM D737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.

The present invention further describes a self-supported or scrim supported non-woven fabric derived from a blend comprising: 1 to 99 percent by weight of melt processable perfluoropolymer fibers; and 99 to 1 percent PTFE fibers, said self-supported or scrim supported non-woven fabric possessing an air permeability (ASTM 737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.

The present invention also describes how woven, knit, and non-woven forms made from melt processable perfluoropolymer fibers and blends of melt processable perfluoropolymer fibers with other fibers, can be thermally fused to themselves to form seams. They can also be thermally fused to other media such as membranes, drainage layers, pleat supports and any other component of filter elements or devices.

A further understanding of the invention will be had by referring to the following description of preferred embodiments.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention contemplates the use of any melt processable perfluoropolymer, such as ones taught in the above discussed Vita et al patents perfluoropolymers derived from tetrafluoroethylene (“TFE) and other fluorinated monomers, comonomers, termonomers, etc. Examples include, MFA, PFA, and FEP. More specifically, a representable melt processable perfiluoropolymer which can be utilized in the present invention is Hyflon® MFA 640 perfluoropolymer produced by Ausimont USA, Inc. (New Jersey). The MFA 640 perfluoropolymer is advantageously used to prepare fibers and yarns, which in turn can be converted into non-woven fabric forms by a variety of processes. One common process is for the fibers to be felted, carded or needle punched in a continuous or batch mode. The non-woven form produced by this method can be used as is or can incorporate a woven or knit reinforcing scrim if so desired. This non-woven form may also advantageously contain a blend of perfluoropolymer fibers with other fibers to impart desired properties to the felt. Fibers of different denier can also be made into felts, either with a random distribution, or in a structured or graded fashion to obtain felts with non-homogeneous cross sections. Other processes that can be used to covert the fibers to non-woven forms include Air-Laying techniques, such as with machines made by Rando or Fehrer, and Wetlaid or paper making technology. Additionally, fiber processes other than those taught by Ausimont can produce non-woven forms directly. These include Spun Bonding processes as well as Melt Blowing processes. Preferably, weaving the fibers and yarns will produce woven forms, such as scrims and cloth. The yarn is advantageously twisted prior to flat or Leno weaving. Any normal type of weaving process, with or without a pretreatment of the fiber or yam, can be used. Knitted fabrics can also be advantageously produced with, for example, a circular knitting machine.

A variety of weaving, knitting and non-woven techniques may be applied to convert the melt processable perfluoropolymer fibers and yarns to melt processable perfluoropolymer forms. Unlike the problems mentioned above with respect to PTFE, the fibers, yams and forms according to the present invention do not require any special or extraordinary handling, other than the mitigation of static electricity due to their very high surface resistivity. Well known techniques such as the use of high humidity (60 to 90%), the generation of ionized air, and the application of finish or anti-static compounds are typically used to overcome static problems with PTFE fibers and can also be used with melt processable perfluoropolymer fibers. Forms made from melt processable perfluoropolymer fibers are suitable for typical processes used for polyesters, polyolefins, nylons, etc., including calendering, potting, thermally fusing and thermally laminating.

While on a molecular level, the melt processable fibers are structurally similar to PTFE fibers, it has unexpectedly been found that the melt extruded perfluoropolymer fibers are, unlike PTFE, easily crimpable, and able to accept a high level of crimp, similar to that found in conventional polyester, nylon and polyolefin fibers. These features are both desirable and necessary in order to use standard or normal industry carding and felting equipment.

Unlike PTFE fibers, forms derived from melt processable perfluoropolymer fibers and yarns are easily melt fused and give better laminating and potting capability. The use of melt processable perfluoropolymer fibers and yarns in the manufacture of bearing cloth yields physical property improvements, such as improved lubricity and improved durability over cloths made from PTFE yarn, expanded PTFE yarn or slit film yarns, as a result of the same continuous, uniform filament construction and residual elongation.

The melt processable perfluoropolymer forms can be used to prepare filtration and filtration support media. Melt processable perfluoropolymer yarns and fibers formed by the melt spinning process described in the above discussed Vita et al patents have a much smoother surface than PTFE yarns and fibers, due to their method of manufacture. Filtration media derived from melt processable perfluoropolymer fibers and yarns exhibit superior filtration properties. Improved properties include lower initial pressure drop, reduced tendency to foul leading to continued low pressure drop over the filters life, easier cleaning and powder removal by back-pulsing, vibration, or other means to dislodge particulates, and improved coalescing due to more stable droplet formation.

The melt spinning process used to make melt processable peifluoropolymer fibers and yarns also allows for the production of multilobal fibers. Multilobal fiber forms will advantageously increase the surface area of the individual fibers, leading to even further filtration efficiencies of these forms.

The continuous uniform nature of each filament in melt processable fluoropolymer fibers and yarns allows for improved weavability as compared to the rough surfaces of yarns produced from PTFE by any other process, including coextrusion spinning, slit film or slit expanded PTFE membrane processes. This continuity and uniformity, as well as the residual elongation typical of traditional melt spirning processes, also allow for improved physical property performance of filtration media, if subjected to typical flexing or pulsing stress in dry gas baghouse filter applications or in wet bag or cartridge filters. Filtration media manufactured from melt processable perfluoropolymer fibers and yarns will retain its physical integrity and strength over a longer period of time than filtration media manufactured from PTFE fibers and yarns.

Purity is another property of great concern to the filtration industry, especially in the semiconductor manufacturing area. Filtration media made from melt processable perfluoropolymer fibers and yams have a higher level of purity than media derived from PTFE fibers and yams, as a result of both the processes used to manufacture the fibers and yams and processes used to manufacture the forms. In the manufacture of melt processable perfluoropolymer fibers and yams, a traditional or normal melt spirming process preferably applied to the melt processable perfluoropolymer. This type of process does not require the introduction of any impurities to the extrusion spinning process. In contrast, the manufacturing of PTFE fibers requires the addition of processing impurities, which if possible, need to be removed later.

Furthermore, wet laid webs or filter media can be thermally fused, and therefore, require no bonding agents to form a useful filter or filter support media. Moreover, another concern in industry is pleatability or the ability of a filter support of filtration media material to be folded by a typical pleating machine and retain that pleat. This a critical feature in many cartridge filter applications. Melt processable perfluoropolymer fibers and yarns unexpectedly can be formed into wet laid, thermally fused materials, which can be much mire easily pleated (and will retain that pleat) than do PTFE fibers and yams.

The ability to thermally bond and/or seal a nonwoven fabric is a very important and desirable characteristic. Specifically, in filtration applications, thermal bonding and sealing may be used to form complex shapes, such as filter bags. It may also be used to bond these fabrics to other assemblies, such as flow adapter fittings, mechanical seals, etc. The edges of a cut fabric may be heat sealed in order to reduce dusting and migration of staple fibers cut at that edge.

Bonding and sealing operations may be accomplished with heated air or metal dies; ultrasonic welding or other means may also be used to heat the part and melt the polymer. In any case, energy is applied to very localized areas of the part (at the seam) to partially melt the fabric. Alternative technologies include the use of chemical or polymeric adhesives, or simple mechanical means such as sewing. However, adhesives and other bonding agents are typically expensive, may be hazardous to apply, and often lack the chemical and environmental resistance, and strength, of the base fabric. In the case of fully fluorinated polymers, the surfaces typically require pre-treatment with aggressive solvents in order to permit these adhesives to achieve sufficient bonds. Sewing and other mechanical means are also far from ideal, as the seam is intrinsically non-uniform, and can allow particles to pass through it which would not pass through the fabric itself.

The use of fibers made from melt-processable polymers in fabric manufacture permits the use of thermal sealing. As such, a uniform, strong bond or seal may be formed by partially melting the fabric at the bond point, while maintaining the purity and chemical/ environmental resistance of the base fabric. The ability to bond and seal fabrics produced from melt- processable perfluoropolymer in this manner is a key advantage of these fabrics over those produced from non-melt-processable perfluoropolymers, such as PTFE. Uniform bonds may be achieved if the energy (heat, etc.) applied to the bond is held constant, and the surfaces to be joined are aligned and compressed uniformly.

The present invention is further directed to multilobal fibers having unique properties. More particularly, the invention is directed to multilobal fibers formed from melt processable perfluoropolymers, wherein said fiber has a cross-section comprised of a central core having two or more shaped lobes projecting therefrom, i.e., the fibers of the invention may bilobal, trilobal, quadrilobal, pentalobal, etc.

The fiber of this invention can be manufactured using conventional fiber forming techniques. For example, the fiber can be formed by spinning a “fiber spinning composition” through a spinnerette having a configuration sufficient to provide a fiber having the desired cross-section. As used herein, a “fiber spinning composition” is a melt or solution of a polymer of fiber forming molecular weight. The nature of the spinning composition may vary widely. For example, the spinning composition may be a melt of a polymer or other material used in the formation of the fiber, and may be spun using conventional techniques as for example those melt spinning techniques described in “Man Made Fibers Science and Technology” Vol. 1-3, H. F. Mark et al., Interscience New York, 1968 and “Encyclopedia of Polymer Science and Technology,” Vol. 8. Similarly, the fiber spinning composition may be a solution of the polymer and other material used in the formation of the fiber which may be spun by using conventional solution spinning techniques, as for example those described in U.S. Pat. Nos. 2,967,085; 4,413,110; 3,048,465; 4,551,299 and 4,599,267.

The synthetic fibers of the present invention are generally prepared by melt spinning of the fiber forming polymer through a spinnerette. Various additives may be added to the respective polymer. These include, but are not limited to, lubricants, nucleating agents, antioxidants, ultraviolet light stabilizers, pigments, dyes, anti-static agents, soil resists, stain resists, anti-microbial agents, and flame retardants.

Typically, the polymer is fed into an extruder in form of chips or granules, (indirect) melted and directed via jacketed Dowtherm.RTM. (Dow Chemical, Midland, Mich.) heated polymer distribution lines to the spinning head. The polymer melt may be metered by a high efficiency gear pump to spin pack assembly and extruded through a spinnerette with capillaries having least one multilobal opening, like tris-, tetra-, penta- or hexalobal capillary, preferably tri- and tetralobal capillary.

In another embodiment, the invention is also directed to conjugate multilobal spunbond fiber comprising at least two polymers where the fibers have lobes and each lobe has legs and caps, and the polymers are arranged with a first polymer occupying a portion of the fiber and at least one second polymer having a lower melting point than the first polymer occupying another portion of the fiber. Of course, one of the polymers is a melt processable perfluoropolymer.

As used herein the term “conjugate fibers” refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from each other though conjugate fibers may be monocomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the conjugate fibers and extend continuously along the length of the conjugate fibers. The configuration of such a conjugate fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side by side arrangement, a segmented configuration or an “islands-in-the-sea” arrangement. Conjugate fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. Nos. 5,336,552 and 5,482,772 to Strack et al., and U.S. Pat. No. 5,382,400 to Pike et al., hereby incorporated by reference in their entirety. For two component fibers, the polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios.

In a further embodiment, the invention provides blends comprising 1 to 99 percent by weight of melt processable perfluoropolymer yams; and 99 to 1 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers. The above blends are useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and the fabrics are suitable for use in filtration, as a support scrim in nonwoven products.

In a more preferred embodiment the invention provides blends comprising 10 to 80 percent by weight of melt processable perfluoropolymer yarns; and 90 to 20 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers. The above blends are useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and the fabrics are suitable for use in filtration, as a support scrim in nonwoven products

The most preferred embodiment of the invention provides blends comprising 20 to 50 percent by weight of melt processable perfluoropolymer yarns; and 80 to 50 percent of fibers or yarns made from materials selected from the group consisting of glass, aramid, polyacrylate, polyphenylene sulfide, polyimide, polyester, polyamide, partially fluorinated polymers, carbon, or other natural or other synthetic fibers. The above blends are useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and the fabrics are suitable for use in filtration, as a support scrim in nonwoven products In another embodiment, there is provided a blend comprising 1 to 99 percent by weight of melt processable perfluoropolymer yarns; and 99 to 1 percent by weight of fibers or yarns made from polytetrafluoroethylene (PTFE). The above blend is also useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and are suitable for use in filtration, as a support scrim in nonwoven products

A more preferred embodiment of the invention provides a blend comprising 10 to 80 percent by weight of melt processable perfluoropolymer yarns; and 90 to 20 percent by weight of fibers or yarns made from polytetrafluoroethylene (PTFE). The above blend is also useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and are suitable for use in filtration, as a support scrim in nonwoven products.

The most preferred embodiment provides a blend comprising 20 to 50 percent by weight of melt processable perfluoropolymer yarns; and 80 to 50 percent by weight of fibers or yarns made from polytetrafluoroethylene (PTFE). The above blend is also useful for manufacturing woven fabrics having a weight per square yard of about 1 to about 100 ounces per square yard and are suitable for use in filtration, as a support scrim in nonwoven products

The above described blends are also useful in manufacturing knitted fabrics having a weight per square yard of about 1 to about 100 ounces per square yard, suitable for use in filtration, or as a support scrim in nonwoven products. A further use of the blends of the invention includes filtration and coalescing media, support layers, drainage layers, and other components produced by winding continuous or spun.

These same blends are also useful for providing a self-supported non-woven fabrics as well as a scrim supported non-woven fabrics wherein both the non-woven fabric and the scrim supported non-woven fabric possesses a Mullen burst strength (ASTM-D3776) between 10 and 1000 psi. Additionally, the self supported or scrim supported non-woven fabric derived from the above-described possess an air permeability (ASTM D737) between 1 and 300 cfm/ft2 at 0.5″ water pressure.

The woven, knit, and non-woven forms made from melt processable perfluoropolymer fibers, and from blends of melt processable perfluoropolymer fibers and other fibers, can be to thermally fused to themselves using processes such as hot air heating, ultrasonic heating, infrared or microwave heating, to form seams. They can also be thermally fused to other media such as membranes, drainage layers, pleat supports and any other component of filter elements -or devices using these same processes.

EXAMPLES Example 1

Commercial sample of natural (unbleached) Teflon® PTFE multifilament yam and a sample of multifilament yam produced from Hyflon® MFA melt processable perfluoropolymer were observed by scanning electron microscope. The results are shown as pictures 1 through 4. The fibers in the PTFE yarn show imperfections and roughness which are approximately 10 microns in size (picture 1), and many fractures and fissures which are approximately 0.2 micron in size (picture 2). The melt processable MFA fibers are extremely smooth and regular, with no imperfections measuring 10 microns (picture 3), and have a dramatically reduced number of surface fissures measuring 0.2 micron in size compared with the PTFE.

Example 2

A beam for weaving was produced on a multi-end warping machine using 550 total denier, 109 filament yam that had been pre-twisted with 3 turns per inch in the Z direction. The beam was placed on a Gem loom and a fabric was woven using a plain weave to yield a flat fabric 24 inches wide by 120 feet long with a mesh count of 64 ends per inch by 46 picks per inch. The selvedge was a Leno selvedge (smooth edges, no fraying) Fabric weight was approximately 8.58 ounces per square yard. Filtration and mechanical characteristics are shown in Table 3. It was observed during the weaving process that the yarn was very consistent in diameter and tended to give better tension control than other low tenacity yarns (approximately 1 gram/denier) such as yarns made from PTFE fibers.

Example 3

A beam was produced on a single-end warping machine using 575 total denier, 109 filament yarn that had been pre-twisted with 10 twists per inch in the Z direction. The beam was placed on a Gem loom and a fabric was woven using a Leno weave to yield a fabric 42 inches wide by 21 feet long with 16 ends per inch by 16 picks per inch with a weight of approximately 3.4 ounces per square yard. Characteristics of the resulting scrim fabric are shown in table 1.

Example 4

550 total denier, 109 filament yarn produced from Hyflon® MFA melt processable perfluoropolymer was heated to 100° C. on a heated godet. The heated yarn was fed continuously into a commercial 0.382 inch wide stuffer box with mechanical rolls at 200 meters per minute. The fiber was fed into the stuffer at a faster rate than it was taken away, creating a vertical stack of crimped fiber. The height of the stack was controlled by the take away speed and was adjusted to produce a yarn with a high level of texture or crimp, high bulk, and short crimp leg length.

Example 5

The yarn from example 4 was continuously fed into a commercial air entangler at 200 meters per minute. The entangler intermittently blows cold, compressed air streams through the fiber bundle to make nodes or points of entangled yarns where the individual filaments become nested. This is done to gather and lock the individual strands of parallel filaments, keeping them from opening in subsequent processing steps, making them easier to handle. The MFA yarn air entangled easily and with good inter-fiber entanglement at the nodes. The yarn was later knitted with good results. A hand held air splicer was also used and shown to be effective for splicing two separate pieces of MFA yarn together to form a uniform, strong, uninterrupted single continuous yarn.

Example 6

An 8,000 total denier Hyflon® MFA fiber tow, approximately 9 denier per filament, was heated to 100° C. on a heated godet and fed continuously at 100 meters per minute into the same stuffer box design described in example 4. The stack height was reduced to produce a higher amplitude crimp with a longer leg length in order to be more typical of staple fibers used for carding operations. Good quality crimp was produced, with approximately 20 crimps per inch. The crimped tow was then easily cut using a commercial radial blade tow cutter to achieve a fiber length of approximately 4.5 inches. The staple fiber produced was used in examples 13 through 19.

Example 7

A 12,000 total denier Hyflon® MFA fiber tow, approximately 5 denier per filament, was heated to 200° C. on a heated godet and fed continuously into the same stuffer box design and operating conditions described in Example 6. A more angular and resilient, improved quality crimp was produced under these conditions, with approximately 15 crimps per inch. The crimped tow was suitable for cutting on commercial radial blade tow cutters and was cut to approximately 3.5 inches in length.

Example 8

A 400 total denier Teflon® PTFE fiber tow, approximately 13.3 denier per filament, was heated to 150° C. on a heated godet and fed continuously into the same stuffer box design and conditions used in example 7, at 100 meters per minute. The tow exiting the crimping device had very low amount of crimp and, most of the filaments were broken or damaged, reducing the strength of the tow dramatically, making it difficult to process further. Additionally, the broken filaments would make it impossible to make a consistent cut length required for staple fiber processes

Example 9

Both 550 and 1000 total denier MFA yams were knitted on a single end tubular jersey knitting machine using a weft knitting technique. Flat yams, textured yarns, and air entangled yams were each used. All yarns knitted well.

Example 10

Three inch long, 5.5 denier per filament staple fibers produced from MFA melt processable perfluoropolymer were processed through a laboratory carding process and needle felt device. Good felts were produced; physical properties shown in table 2.

Example 11

Example 10 was repeated, except that one layer of 3.4 ounce per square yard MFA scrim, as described in example 3, was introduced between the carded batts during the needling process.

Example 12

A 50/50 blend of 4.5 denier and 9.0 denier staple fiber produced from MFA perfluoropolymer was pre-opened by standard practice and fed to a standard 18 inch laboratory-scale nonwovens card, producing a continuous carded web. Static electricity was controlled by the use of high humidity, 60 to 90%, as well as the addition of a commercially available finish onto the fibers. The web was manually layered in the machine direction to yield batts of a target basis weight of 850 grams/meter squared. The web was needlepunched according to condition “A” (table 4). Carding and needling procedures typically used to process other synthetic fibers, such as polyester and polypropylene, were used. This process yielded a nonwoven fabric with excellent strength in the machine direction; physical properties are shown in table 3.

Example 13

Example 12 was repeated, except using 100% 5.0 denier fiber of example 7. The felt was later calendered as in example 17. The enhanced crimp and resilience of the fiber led to much improved fiber opening in carding, web uniformity, and overall carding performance. This was even more significant, because no 9.0 denier fiber was needed to be added to improve processing. The improved web quality and cohesion, obtained without the use of a coarse carrier fiber, led to needled felts of higher strength and uniformity, and improved filtration performance.

Example 14

Carded webs produced as in example 12 were manually layered such in the cross-machine direction, simulating a cross-lapped material. The web was needlepunched as in example 12. The resulting fabric possessed a good balance of strengths in the machine and cross-machine directions; results are shown in table 3.

Example 15

Web was produced as in Example 12 except that a woven scrim, as described in example 3, was placed in the middle of the parallel-layered webs. Needling was performed as in Example 12; results in Table 3.

Example 16

The scrim of Example 3 was placed in the middle of webs cross-lapped as in Example 14, yielding a scrim-supported cross lapped product.

Example 17

The needled felt of Example 12 was densified using a heated calendering operation. The felt was continuously pre-heated and pressed between a set of nip rolls, at a temperature of 190° C., yielding fabric with higher density, decreased air permeability, and reduced pore size. Fabric gauge was easily controlled by varying the gap between nip rolls, with minimal expansion after calendering. Nip roll gap was adjusted to obtain a fabric density (target) of 0.275 ounces/inches cubed.

Example 18

A felt produced as in Example 12 was thermally bonded to itself, using 325° C. hot air and pressure exerted by a small set of nip rolls. The resulting bond showed excellent strength, and demonstrated the ease and effectiveness of thermally sealing the fabric to produce leak-proof, unstitched seams, as well as thermally bonding to other surfaces. Products made from PTFE fibers cannot be thermally bonded to itself because it is not melt processable (does not flow under heat and pressure).

Example 19

A parallel, self-supported carded batt was produced as in Example 12, except with reduced needling according to condition “B” of Table 4. As shown in table 3, these results show the ability to control fabric density, air permeability, and pore size through needling conditions, without negatively affecting fabric strength.

Example 20

Three inch long, 5.5 denier per filament staple fibers made from a blend of 50% by weight perfluoropolymer and 50% aramid fibers were processed through a laboratory carding process and needle felt device. Good felts were produced having favorable physical properties and the ability to be thermally fused to themselves or other materials.

Example 21

Three inch long, 5.5 denier per filament staple fibers made from a blend of 40% by weight perfluoropolymer and 60% Nylon 6 fibers were processed through a laboratory carding process and needle felt device. Good felts were produced having favorable physical properties.

Example 22

A blend of 60% by weight 4.5 denier staple fiber produced from MFA perfluoropolymer and 40% 10 denier aramid fibers was pre-opened by standard practice and fed to a standard 18 inch laboratory-scale nonwovens card, producing a continuous carded web. The web was manually layered in the machine direction to yield batts of a target basis weight of 850 grams/meter squared. The web was needlepunched according to condition “A” (table 4). Carding and needling procedures typically used to process other synthetic fibers, such as polyester and polypropylene, were used. This process yielded a nonwoven fabric with excellent strength in the machine direction; and physical properties, and the ability to be thermally fused to itself and other materials.

Example 23

A blend of 50% by weight of 4.5 denier staple fiber produced from MFA perfluoropolymer and 50% PTFE fibers was pre-opened by standard practice and fed to a standard 18 inch laboratory-scale non-wovens card, producing a continuous carded web. Static electricity was controlled by the use of humidity (in the range of 60 to 90%), ionized air generators, as well as the addition of commercially available anti-static solutions where necessary. The web was manually layered in the machine direction to yield batts of a target basis weight of 850 grams/meter squared. The web was needlepunched according to condition “C” (table 4). Carding and needling procedures typically used to process other synthetic fibers, such as polyester and polypropylene, were used. This process yielded a non-woven fabric with excellent strength in the machine direction and good physical properties.

Example 24

A non-woven fabric was produced using 40% by weight MFA fibers and 60% by weight PTFE fibers according to the conditions described in example 23, but with a target basis weight of 660 grams/meter squared. The sample was thermally seamed with good results.

Example 25

A non-woven fabric was produced using 20% by weight MFA fibers and 80% by weight PTFE fibers according to the conditions described in example 23, but with a target basis weight of 660 grams/meter squared. The sample was thermally seamed with good results.

Example 26

A non-woven fabric was produced using 20% by weight MFA fibers and 80% by weight PTFE fibers according to the conditions described in example 23, but with a target basis weight of 330 grams/meter squared. The sample could be seamed thermally.

Example 27

A 40% by weight MFA fiber, 60% by weight PTFE fiber lightly tacked non-woven batt was thermally bonded or fused using a plate press. The plate temperature was between 460° and 540° F., and the pressure was between 500 and 750 psig. Sample weights of 160 to 240 grams/meter squared resulted. The product had an open structure, which allowed the passing of liquids. It also had sufficient rigidity to be used in filtration pleat support and drainage layer applications.

Example 28

A 20% by weight MFA fiber, 80% by weight PTFE fiber lightly tacked non-woven baft was thermally bonded or fused using a plate press. The plate temperature was between 460° and 540° F., and the pressure was between 500 and 750 psig. Sample weights of 146 to 200 grams/meter squared resulted. The product had an open structure, which allowed the passing of liquids. It also had sufficient rigidity to be used in filtration pleat support and drainage layer applications

Example 29

A non-woven needled felt was produced as in Example 12 except that a blend of 70% perfluoroalkoxy fibers, and 30% glass fibers were used. The perfluoroalkoxy fibers were 4.5 denier and the glass fibers were 0.3 denier. The basis weight was 600 grams/meter squared. The product had excellent filtration properties, could be thennally seamed, and could be thermally fused to other components such as membranes, support structures, housings, etc. The non-woven could also be thermally laminated to other forms such as other non-wovens, glass paper, and other woven and knit forms.

Example 30

A non-woven needled felt was produced as in Example 29 except that blend of 35% perfluoroalkoxy fibers, 35% PTFE fibers, and 30% glass fibers were used. The perfluoroalkoxy fibers were 4.5 denier, the PTFE fibers 6.7 denier, and the glass fibers were 0.3 denier. The basis weight was 610 grams/meter squared. The product had excellent filtration properties, could be thermally seamed, and could be thermally fused to other components such as membranes, support structures, housings, etc. The non-woven could also be thermally laminated to other forms such as other non-wovens, glass paper, and other woven and knit forms.

Example 31

A non-woven needled felt was produced as in Example 29 except that a 125 gram/meter squared woven glass scrim was inserted as described in example 15. The final basis weight was 710 grams/meter squared. The product had excellent filtration properties, could be thermally seamed, and could be thermally fused to other components such as membranes, support structures, housings, etc. The non-woven could also be thermally laminated to other forms such as other non-wovens, glass paper, and other woven and knit forms.

Example 32

A non-woven needled felt was produced as in Example 30 except that a 125 gram/meter squared woven glass scrim was inserted as described in example 15. The final basis weight was 700 grams/meter squared. The product had excellent filtration properties, could be thermally seamed, and could be thermally fused to other components such as membranes, support structures, housings, etc. The non-woven could also be thermally laminated to other forms such as other non-wovens, glass paper, and other woven and knit forms.

Example 33

A blend of 80% 5.5 denier MFA fibers and 20% 0.3 denier E-glass fibers were blended and processed on a Rando-Webber air-laying device. The fibers were cut to the appropriate length for use in this type of apparatus. Good quality webs were formed that could be thermally fused to themselves as well as to other components.

Example 34

A blend of 40% 5.5 denier MFA fibers, 40% 6.7 denier PTFE fibers, and 20% 0.3 denier E-glass fibers were blended and processed on a Rando-Webber air-laying device. The fibers were cut to the appropriate length for use in this type of apparatus. Good quality webs were formed that could be thermally fused to themselves as well as to other components.

Example 35

Non-woven webs as described in Example 34 were thermally fused using a spot bonding process to a woven glass support scrim with a basis weight of 100 grams/meter squared to make a non-woven fabric with a basis weight of about 300 grams/meter squared. Good quality webs were formed that could be thermally fused to themselves as well as to other components.

Example 36

Non-woven webs as described in Example 34 were hydraulically entangled to a woven glass support scrim with a basis weight of 100 grams/meter squared to make a non-woven fabric with a basis weight of about 280 grams/meter squared. Good quality webs were formed that could be thermally fused to themselves as well as to other components.

TABLE 1
Number Weight Woven Scrim Properties: Example 3
of per Layer Breaking Load Mullen Burst Strength
Layers oz/yd2 Pounds psi
1 3.4 29.7 45
2 3.4 63 76

TABLE 2
Air Mullen Burst
Layers of Thickness Weight Permeability Strength
Example Scrim In Oz/yd2 ft3/min/ft2 psi
10 0 0.075 19.44 49.5 85.5
11 1 0.074 26.78 73.6 88

TABLE 3
Weight Thickness Permeability Mean Strength, Strength,
g/m2 mm @ 125 Pa Pore kg MD kg CMD
Exam- ASTM ASTM m3/m2-min Size 5.1 cm strip/ASTM
ple D461 D461 ASTM D737 Micron D1682
2 306 0.26 2.3 30.3 38.1 27.7
13 885 2.67 18.4 30.5 35.8 17.5
14 631 2.00 33.8 40.0 16.3 18.3
15 1075 2.87 23.9 30.3 36.2 19.6
16 983 2.49 13.9 28.7 19.9 32.8
17 940 1.86 10.8 23.8 29.9 20.0
19 951 3.01 20.2 35.2 33.2 18.1
23 988 1.81 9.3 9.6 89.5 29.2

TABLE 4
Needlepunch
Conditions Penetration
Frequency Depth
Condition Step Penetrations/cm2 mm
A 1 121 5.9
2 121 7.4
3 121 10.0
4 326 12.0
B 1 121 5.9
2 121 7.4
3 326 9.0
C 1 61 5.9
2 121 7.4
3 121 12
4 163 10
5 163 8

Although the present invention has been described with a certain degree of particularity, it is understood that the present invention has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the subjoined claims.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7640841Jan 2, 2007Jan 5, 2010Saint-Gobain Performance Plastics CorporationAnnular seal and pump including same
US7802796Jan 2, 2007Sep 28, 2010Saint-Gobain Performance Plastics CorporationComposite material and seals formed thereof
US8603411Dec 10, 2012Dec 10, 2013Saint-Gobain Performance Plastics CorporationPolymer material and seals formed thereof for high pressure pump applications
WO2010130412A1 *May 12, 2010Nov 18, 2010Sms Siemag AktiengesellschaftWoven filter fabric for a band filter
Classifications
U.S. Classification442/181
International ClassificationD01F6/12, D03D25/00, D02G3/04
Cooperative ClassificationD02G3/047, D01F6/12
European ClassificationD02G3/04D, D01F6/12
Legal Events
DateCodeEventDescription
Oct 20, 2003ASAssignment
Owner name: LANTOR, INC., MASSACHUSETTS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:STANITIS, GARY E.;CISTONE, FRANK;CHOI, JIN;REEL/FRAME:014603/0664
Effective date: 20030311
Owner name: XTREME FIBERS, INC., PENNSYLVANIA
Nov 13, 2001ASAssignment
Owner name: LANTOR, INC., MASSACHUSETTS
Free format text: CORRECTIVE ASSIGNMENT TO ADD SECOND ASSIGNEE WHICH WAS PREVIOUSLY RECORDED ON REEL 012115, FRAME 0475;ASSIGNORS:CISTONE, FRANK;STANITIS, GARY E.;CHOI, JIN;REEL/FRAME:012349/0838
Effective date: 20010701
Owner name: XTREME FIBERS, INC., PENNSYLVANIA
Aug 27, 2001ASAssignment
Owner name: XTREME FIBERS, INC., PENNSYLVANIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CISTONE, FRANK;STANITIS, GARY E.;CHOI, JIN;REEL/FRAME:012115/0475
Effective date: 20010701