US4710331A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the production of polytetrafluoroethylene porous membranes
Assignee: NIPPON VALQUA KOGYO KK
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Filing: 1986-05-15
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Granted: 1987-12-01
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Expires: 2006-05-15
Abstract
Abstract A process for the production of PTFE porous membranes is provided wherein a PTFE preform is prepared by compression molding a PTFE molding powder of 1-90 μm obtained by suspension polymerization of tetrafluoroethylene, the preform is sintered at a temperature above 327° C., followed by skiving the heated preform into a film form. The thus-obtained film is heat treated at a temperature above 327° C., the heat treated film is slowly cooled at a cooling rate of less than 70° C./hr so as to adjust the crystallinity of PTFE in the sintered film to 60-75% and the film is stretched either uniaxially or biaxially to 1.3 to 6.5 times while heating at a temperature of 100°-320° C.
Inventors
- 👤 Kawahigashi Nobuo
- 👤 Hashida Shigesou
- 👤 Kojima Yasunobu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:13
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0004; B01D67/00041; B01D67/0023; B01D67/0025; B01D67/0027; B01D71/00; B01D71/06; B01D71/30; B01D71/32; B01D71/36; B29; B29C; B29C55/00; B29C55/005; B29D; B29D7/00; B29D7/01; B01D2323/00; B01D2323/08; B01D2323/081; B01D2323/082; B29K; B29K2027/00; B29K2027/12; B29K2027/18; B29K2627/00; B29K2627/12; B29K2627/18; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
116 words
A process for the production of polytetrafluoroethylene porous membranes, which comprises preparing a polytetrafluoroethylene preform by compression molding a polytetrafluoroethylene resin molding powder having an average particle diameter of 1-900 μm obtained by suspension polymerization of tetrafluoroethylene, heating the preform at a temperature above 327° C. followed by skiving the heated preform into a film form, heating the obtained film at a temperature above 327° C., slowly cooling the heated film at a cooling rate of less than 70° C./hr so as to adjust the crystallinity of polytetrafluoroethylene in the heated film to 60-75%, and stretching the heated film either uniaxially or biaxially to 1.3 to 6.5 times while heating at a temperature of 100°-320° C.
Claim 2
Dependent Claim
116 words
A process for the production of polytetrafluoroethylene porous membranes, which comprises preparing a polytetrafluoroethylene preform by compression molding a polytetrafluoroethylene resin molding powder having an average particle diameter of 1-900 μm obtained by suspension polymerization of tetrafluoroethylene, heating the preform at a temperature above 327° C. followed by skiving the heated preform into a film form, heating the obtained film at a temperature above 327° C., slowly cooling the heated film at a cooling rate of less than 70° C./hr so as to adjust the crystallinity of polytetrafluoroethylene in the heated film to 60-75%, and stretching the heated film either uniaxially or biaxially to 1.3 to 6.5 times while heating at a temperature of 100°-320° C.
Claim 3
Dependent Claim
19 words
The process according to claim 1 wherein the particle diameter of the polytetrafluoroethylene resin molding powder is 10-50 μm.
Claim 4
Dependent Claim
20 words
The process according to claim 1 wherein the cooling rate after heated the polytetrafluoroethylene film is less than 10° C./hr.
Claim 5
Dependent Claim
15 words
The process according to claim 1 wherein the crystallinity of polytetrafluoroethylene after cooling is 65-70%.
Claim 6
Dependent Claim
16 words
A process according to claim 1 wherein the streching temperature of polytetrafluoroethylene films is 200°-250° C.
Claim 7
Dependent Claim
17 words
A process according to claim 1 wherein the draw ratio for stretching polytetrafluoroethylene films is 1.8-2.3 times.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-11-30 | 1991-06-01 | 1991-12-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-30 | 1995-06-01 | 1995-12-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-30 | 1999-06-01 | 1999-12-01 | $7700.00 | Window Closed / Lapsed |