Patent US4626587A successfully refreshed from Google Patents.
US4626587A
Expired / Lapsed
US
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Extrusion finishing of perfluorinated copolymers
Assignee: EIDP Inc
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Filing: 1985-06-28
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Granted: 1986-12-02
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Expires: 2005-06-28
Abstract
Abstract Unstable backbone links in melt-processible tetrafluoroethylene copolymers can be reduced by subjecting the copolymer to high shear in a twin-screw extruder.
Inventors
- 👤 Richard A. Morgan
- 👤 William H. Sloan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:47
CPC Classifications
C; C08; C08F; C08F8/00; C08F8/50; B; B29; B29C; B29C48/00; B29C48/25; B29C48/36; B29C48/395; B29C48/40; B29C48/405; B29C48/92; B29C2948/00; B29C2948/92; B29C2948/92504; B29C2948/92514; B29C2948/92704; B29C48/022; B29C48/03; B29C48/04; B29C48/50; B29C48/76; B29C48/78; B29C48/80; B29C48/802; B29C48/83; B29C48/834; C08F2810/00; C08F2810/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
136 words
A process for reducing the backbone instability in a raw melt-processible copolymer of 80-99% by weight units of tetrafluorethylene and complementally 20-1% by weight units of hexafluorpropylene which comprises: (a) subjecting said raw melt-processible copolymer, which copolymer has a backbone volatiles index greater than 15 and a melt viscosity between 10 2 and 10 6 Pa.s, to a vacuum of less than 10 5 Pa and to a temperature of between 220° C. and 450° C. while moving the copolymer through a twin screw extruder having intermeshing corotating screws that are self-wiping and which have tight clearance, and subjecting the copolymer to a shear rate between 500 and 7000 reciprocal seconds for a time sufficient to result in the copolymer having a backbone voltailes index less than 10; and (b) removing the copolymer from the extruder.
Claim 2
Dependent Claim
136 words
A process for reducing the backbone instability in a raw melt-processible copolymer of 80-99% by weight units of tetrafluorethylene and complementally 20-1% by weight units of hexafluorpropylene which comprises: (a) subjecting said raw melt-processible copolymer, which copolymer has a backbone volatiles index greater than 15 and a melt viscosity between 10 2 and 10 6 Pa.s, to a vacuum of less than 10 5 Pa and to a temperature of between 220° C. and 450° C. while moving the copolymer through a twin screw extruder having intermeshing corotating screws that are self-wiping and which have tight clearance, and subjecting the copolymer to a shear rate between 500 and 7000 reciprocal seconds for a time sufficient to result in the copolymer having a backbone voltailes index less than 10; and (b) removing the copolymer from the extruder.
Claim 3
Dependent Claim
13 words
The process of claim 1 wherein the twin screw extruder contains kneading blocks.
Claim 4
Dependent Claim
22 words
The process of claim 1 or 2 wherein after step (b), the copolymer is contacted with fluorine gas while agitating the copolymer.
Claim 5
Dependent Claim
25 words
The process of claim 1 or 2 wherein water is added to the extruder in an amount necessary to remove all acid fluoride end groups.
Claim 6
Dependent Claim
40 words
The process of claim 1 or 2 wherein, prior to step (a), the copolymer us contacted with nitrogen for a time sufficient to remove essentially all absorbed and adsorped oxygen from the copolymer immediately prior to carrying out step (a).
References Cited (Backward Citations)
GB829600A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-12-01 | 1990-06-02 | 1990-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-01 | 1994-06-02 | 1994-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-01 | 1998-06-02 | 1998-12-02 | $7700.00 | Window Closed / Lapsed |