US4482516A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing a high strength porous polytetrafluoroethylene product having a coarse microstructure
Assignee: W.L. Gore and Associates Inc
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Filing: 1982-09-10
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Granted: 1984-11-13
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Expires: 2002-09-10
Abstract
Abstract Porous polytetrafluoroethylene materials having high strength and coarse microstructure are produced by densifying the materials after removal of lubricant and then stretching. The term, "coarse," is used to indicate that the nodes are larger, the fibrils are longer, and the effective pore size is larger than conventional materials of the same matrix tensile strength. Densification can be achieved through the use of such devices as a densification die, a calender machine, or a press. This invention can be used to produce all kinds of shaped articles.
Inventors
- 👤 Jeffery B. Bowman
- 👤 Daniel E. Hubis
- 👤 James D. Lewis
- 👤 Stephen C. Newman
- 👤 Richard A. Staley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 22:59
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; B; B29; B29C; B29C55/00; B29C55/005; D; D01; D01F; D01F6/00; D01F6/02; D01F6/08; D01F6/12; B29K; B29K2027/00; B29K2027/12; B29K2027/18; B29K2105/00; B29K2105/04; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
92 words
A process for producing a porous material of polytetrafluoroethylene polymer, which material is characterized by relatively large nodes interconnected by realtively long fibrils and having relatively high matrix tensile strength, the material having been produced from paste-extruded unsintered polytetrafluoroethylene extrudate, the process comprising the steps: (a) providing an unsintered dry extrudate; (b) increasing the density of the dry extrudate to greater than about 1.80 gm/cc at a temperature below the crystalline melt temperature of PTFE; and (c) stretching said densified dry extrudate at an elevated temperature less than the crystalline melt temperature.
Claim 2
Dependent Claim
92 words
A process for producing a porous material of polytetrafluoroethylene polymer, which material is characterized by relatively large nodes interconnected by realtively long fibrils and having relatively high matrix tensile strength, the material having been produced from paste-extruded unsintered polytetrafluoroethylene extrudate, the process comprising the steps: (a) providing an unsintered dry extrudate; (b) increasing the density of the dry extrudate to greater than about 1.80 gm/cc at a temperature below the crystalline melt temperature of PTFE; and (c) stretching said densified dry extrudate at an elevated temperature less than the crystalline melt temperature.
Claim 3
Dependent Claim
21 words
The process as in claim 1 wherein said densification step increaes the dry extrudate density to greater than about 2.0 gm/cc.
Claim 4
Dependent Claim
21 words
The process as in claim 1 wherein said densification step increases the dry extrudate density to greater than about 2.2 gm/cc.
Claim 5
Dependent Claim
20 words
The process as in claim 1 wherein said densification step increases the dry extrudate density to about its maximum value.
Claim 6
Dependent Claim
20 words
The process as in claim 1 wherein the densification step is accomplished by densifying the dry extrudate in a press.
Claim 7
Dependent Claim
17 words
The process as in claim 1 wherein the densification step is accomplished by calendering the dry extrudate.
Claim 8
Dependent Claim
21 words
The process as in claim 1 wherein the densification step is accomplished by drawing the dry extrudate through a densification die.
Claim 9
Dependent Claim
18 words
The process as in claim 1, 5, 6 or 7 wherein the densified dry extrudate is stretched uniaxially.
Claim 10
Dependent Claim
17 words
The process as in claim 1, 5 or 6 wherein the densified dry extrudate is stretched biaxially.
Claim 11
Dependent Claim
17 words
The process as in claim 1 wherein the stretching step is carried out at about 300° C.
Claim 12
Dependent Claim
23 words
The process as in claim 1 wherein the densification step is carried out at an elevated temperature less than the crystalline melt temperature.
Claim 13
Dependent Claim
17 words
The process as in claim 11 wherein the densification step is carried out at about 300° C.
Claim 14
Dependent Claim
32 words
The process as in claim 1 further including the step of heating the stretched article above the crystalline melt temperature, to sinter the stretched article, while restraining the stretched article from shrinking.
Claim 15
Dependent Claim
19 words
The process as in claim 1, 6 or 7 wherein the densification and stretching steps are carried out continuously.
Claim 16
Dependent Claim
23 words
The process as in claim 1, 2, 3 or 4 further including the step of stretching said dry extrudate before said densification step.
Claim 17
Dependent Claim
43 words
The process as in claim 1 wherein the step of providing a dry extrudate includes the substeps of: (i) mechanically working an extrudate containing an extrusion aid lubricant to obtain a desired shape; and (ii) drying the worked extrudate to remove the lubricant.
Claim 18
Dependent Claim
20 words
The process as in claim 16 wherein said mechanical working substep includes the step of calendering the extrudate containing lubricant.
Claim 19
Dependent Claim
21 words
The process as in claim 16 wherein said mechanical working substep includes the step of stretching the extrudate containing the lubricant.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-11-13 | 1988-05-14 | 1988-11-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-13 | 1992-05-14 | 1992-11-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-13 | 1996-05-14 | 1996-11-13 | $7700.00 | Window Closed / Lapsed |