Patent US4234535A successfully refreshed from Google Patents.
US4234535A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing porous polytetrafluoroethylene tubings
Assignee: Sumitomo Electric Industries Ltd
•
Filing: 1979-06-11
•
Granted: 1980-11-18
•
Expires: 1999-06-11
Abstract
Abstract A porous polytetrafluoroethylene tubing, useful as artificial internal organs or industrial filtering materials for, for example reverse osmosis, ultrafilteration, etc., having a microporous fibrous structure in which the fibrous structure is composed of fibers and nodes connected with each other and the microporous fibrous structure differs between the outer surface portions of the tubing and the inner surface portions of the tubing, and a process for producing the porous resin tubing comprising heating a tubing made of an unsintered polytetrafluoroethylene under conditions in which the tube is stretched at least in the longitudinal direction of the tubing and such that the outer surface of the tubing is heated above about 327° C. and the inner surface of the tubing is heated to a temperature below the temperature of the outer surface.
Inventors
- 👤 Koichi Okita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:37
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/30; B01D71/32; B01D71/36; A; A61; A61F; A61F2/00; A61F2/02; A61F2/04; A61F2/06; B01D39/00; B01D39/14; B01D39/16; B01D39/1692; B01D63/00; B01D63/06; B01D63/061; B29; B29C; B29C48/00; B29C48/022; B29C48/03; B29C48/09; B29C55/00; B29C55/22; B29C67/00; B29C67/0003; B29C67/02; B29C67/04; F; F16; F16L; F16L11/00; F16L11/04; F16L11/06; B01D2239/00; B01D2239/10; B29C48/25; B29C48/36; B29C48/475; B29K; B29K2027/00; B29K2027/12; B29K2027/18
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
109 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that the outer surface of the tube is heated at a temperature higher than about 365° C. and the inner surface of the tube is heated at a temperature lower than the temperature of the outer surface of the tube, and wherein the temperature difference between the center of the heating furnace and the outer surface of the tube is at least 95° C.
Claim 2
Dependent Claim
109 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that the outer surface of the tube is heated at a temperature higher than about 365° C. and the inner surface of the tube is heated at a temperature lower than the temperature of the outer surface of the tube, and wherein the temperature difference between the center of the heating furnace and the outer surface of the tube is at least 95° C.
Claim 3
Dependent Claim
59 words
The process as claimed in claim 1, wherein the tube is heated in a state stretched in at least the longitudinal direction of the tube in a manner such that the outer surface of the tube is heated at a temperature higher than about 365° C. while, in this case, reducing the pressure of the atmosphere surrounding said tube.
Claim 4
Dependent Claim
35 words
The process as claimed in claim 1, wherein the outer surface of the tube is heated to a temperature higher than about 365° C. while supplying cooling air through the inner cavity of the tube.
Claim 5
Dependent Claim
22 words
The process as claimed in claim 1, wherein between said forming and said stretching said liquid lubricant is removed from the tubing.
Claim 6
Dependent Claim
32 words
The process of claim 1, further comprising, after said stretching of the tube in at least the longitudinal direction, a subsequent expansion of the tube in the radial direction of the tube.
Claim 7
Dependent Claim
29 words
The process as claimed in claim 1, wherein said heating of said tube in said stretched state is conducted while preventing shrinkage of said tube in the longitudinal direction.
Claim 8
Dependent Claim
34 words
The process as claimed in claim 6, wherein following said heating of the tube, the tube is fixed in the radial direction before the tube is cooled to a temperature below about 365° C.
Claim 9
Dependent Claim
64 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that only the outer surface of the tube is sintered and the inner surface of the tube remains unsintered.
Claim 10
Dependent Claim
64 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that only the outer surface of the tube is sintered and the inner surface of the tube remains unsintered.
Claim 11
Dependent Claim
60 words
The process as claimed in claim 8, wherein the tube is heated in a state stretched in at least the longitudinal direction of the tube in a manner such that the outer surface of the tube is sintered and the inner surface of the tube remains unsintered while, in this case, reducing the pressure of the atmosphere surrounding said tube.
Claim 12
Dependent Claim
36 words
The process as claimed in claim 8, wherein the outer surface of the tube is sintered and the inner surface of the tube remains unsintered while supplying cooling air through the inner cavity of the tube.
Claim 13
Dependent Claim
113 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that the outer surface of the tube is heated at a temperature higher than about 327° C. and the inner surface of the tube is heated at a temperature lower than the temperature of the outer surface of the tube, said heating being carried out in a manner such that only the outer surface of the tube is sintered and the inner surface of the tube remains unsintered.
Claim 14
Dependent Claim
113 words
A process of producing a porous polytetrafluoroethylene tubing which comprises forming a tubing of a mixture of an unsintered polytetrafluoroethylene containing a liquid lubricant, stretching the tube at least in the longitudinal direction, and heating the tube in a stretched state in such a manner that the outer surface of the tube is heated at a temperature higher than about 327° C. and the inner surface of the tube is heated at a temperature lower than the temperature of the outer surface of the tube, said heating being carried out in a manner such that only the outer surface of the tube is sintered and the inner surface of the tube remains unsintered.
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) | 1983-11-18 | 1984-05-19 | 1984-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-11-18 | 1988-05-19 | 1988-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-11-18 | 1992-05-19 | 1992-11-18 | $7700.00 | Window Closed / Lapsed |