US3981853A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polytetrafluoroethylene molding powder from polytetrafluoroethylene fine powder
Assignee: EIDP Inc
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Filing: 1974-06-17
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Granted: 1976-09-21
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Expires: 1994-06-17
Abstract
Abstract Polytetrafluoroethylene fine powder is compacted at or near room temperature at a pressure of 8000 psi (562 kg/cm 2 ) to 50,000 psi (3513 kg/cm 2 ), followed by partially decompacting the resultant compacted fine powder to a molding powder having an average particle diameter of less than 100 microns.
Inventors
- 👤 Carl Harding Manwiller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:15
CPC Classifications
C; C08; C08J; C08J3/00; C08J3/12; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
57 words
A process for making polytetrafluoroethylene molding powder from polytetrafluoroethylene fine powder obtained from aqueous dispersion polymerization comprising compacting said fine powder at a temperature of about 20° to 30°C. at a pressure of 8000 psi to 50,000 psi and partially decompacting the resultant compact to said molding powder having an average diameter of less than 100 microns.
Claim 2
Dependent Claim
57 words
A process for making polytetrafluoroethylene molding powder from polytetrafluoroethylene fine powder obtained from aqueous dispersion polymerization comprising compacting said fine powder at a temperature of about 20° to 30°C. at a pressure of 8000 psi to 50,000 psi and partially decompacting the resultant compact to said molding powder having an average diameter of less than 100 microns.
Claim 3
Dependent Claim
15 words
The process of claim 1 wherein the average particle diameter is at least 10 microns.
Claim 4
Dependent Claim
27 words
the process of claim 1 wherein said molding powder has a preform porosity at 1000 psi (70 kg/cm 2 ) preform pressure of no greater than 0.20.
Claim 5
Dependent Claim
89 words
The process of claim 1 wherein said molding powder has an apparent density of at least 500 g/l, with the proviso that the apparent density is at least as great as the value calculated from the equation apparent density ≧ 500 g/l + 3 (Δ SG.sub.5-1) wherein Δ SG 5-1 is 1000 times the difference in specific gravities of sintered moldings made at preform pressures of 1000 psi (70 kg/cm 2 ) and 5000 psi (352 kg/cm 2 ) wherein said Δ SG 5-1 is no greater than 75.
Claim 6
Dependent Claim
15 words
The process of claim 1 wherein said partial decompaction is done by decompacting in gas.
Claim 7
Dependent Claim
15 words
The process of claim 1 wherein said partial decompaction is done by decompacting in liquid.
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) | 1979-09-21 | 1980-03-22 | 1980-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-21 | 1984-03-22 | 1984-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-21 | 1988-03-22 | 1988-09-21 | $7700.00 | Window Closed / Lapsed |