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US4128589A Expired / Lapsed US ⏱️ 0.0 years remaining

Generation of CF4 from Teflon for reactive atmosphere processing and growth of metal fluorides

Assignee: Raytheon Co
•
Filing: 1977-06-22
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Granted: 1978-12-05
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Expires: 1997-06-22
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Abstract

Abstract A tetrafluoromethane (CF 4 ) generator and process is disclosed that facilitates the relatively low temperature production of CF 4 gas via controlled decomposition of polytetrafluoroethylene (Teflon) and tetrafluoroethylene (C 2 F 4 ). CF 4 produced via this process proves to be an excellent OH - scavenger in the processing and growth of metal fluoride single crystals.

Inventors

  • 👤 Ricardo C. Pastor
  • 👤 Morton Robinson

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-05 19:28
CPC Classifications
C; C07; C07C; C07C17/00; C07C17/361; C07C17/367; C30; C30B; C30B11/00; C30B29/00; C30B29/10; C30B29/12

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 193 words
A controllable process for generating CF 4 from commercially available polytetrafluoroethylene comprising the steps of: (a) charging a depolymerization reactor with precisely known quantities of tetrafluoroethylene; (b) selecting a reactor temperature, from a plot of tetrafluoroethylene decay constants versus temperature, which provides for the generation of C 2 F 4 at a desired rate; (c) creating an atmospheric purge by causing an inert carrier gas to flow through said reactor; (d) raising the temperature of said reactor to said selected temperature thereby causing a C 2 F 4 -purge gas mixture to be formed within said reactor; (e) directing said C 2 F 4 -purge gas mixture from said reactor into a pyrolysis chamber, previously heated to a temperature high enough to cause the C 2 F 4 component of said mixture to decompose into known amounts of CF 4 and elemental carbon, at a flow rate sufficient to insure a gas mixture dwell time within said chamber of from 5 to 15 minutes; and (f) removing said CF 4 from said chamber with said carrier gas while allowing said elemental carbon to be trapped along the relatively cool walls of said chamber.
Claim 2
Dependent Claim 193 words
A controllable process for generating CF 4 from commercially available polytetrafluoroethylene comprising the steps of: (a) charging a depolymerization reactor with precisely known quantities of tetrafluoroethylene; (b) selecting a reactor temperature, from a plot of tetrafluoroethylene decay constants versus temperature, which provides for the generation of C 2 F 4 at a desired rate; (c) creating an atmospheric purge by causing an inert carrier gas to flow through said reactor; (d) raising the temperature of said reactor to said selected temperature thereby causing a C 2 F 4 -purge gas mixture to be formed within said reactor; (e) directing said C 2 F 4 -purge gas mixture from said reactor into a pyrolysis chamber, previously heated to a temperature high enough to cause the C 2 F 4 component of said mixture to decompose into known amounts of CF 4 and elemental carbon, at a flow rate sufficient to insure a gas mixture dwell time within said chamber of from 5 to 15 minutes; and (f) removing said CF 4 from said chamber with said carrier gas while allowing said elemental carbon to be trapped along the relatively cool walls of said chamber.
Claim 3
Dependent Claim 43 words
The process of claim 1 wherein said carrier gas is selected from the group consisting of Helium, Argon, Nitrogen and carbon dioxide, said reactor temperature ranges from 425° to 525° C. and said pyrolysis chamber temperature ranges from 800° to about 900° C.
Claim 4
Dependent Claim 28 words
The process of claim 1 wherein said carrier gas is He, said reactor temperature is 482° C. and said pyrolysis chamber temperature is set to approximately 810° C.
Claim 5
Dependent Claim 85 words
A process for generating CF 4 which comprises: (a) depolymerizing polytetrafluoroethylene in the presence of a carrier gas purge at an elevated temperature to form a mixture of C 2 F 4 and said carrier gas; (b) heating said mixture to an elevated temperature and maintaining said mixture at said temperature for a time sufficient to cause said mixture to dissociate into a mixture of inert gas, CF 4 and carbon; and (c) selectively removing said carbon from said mixture of CF 4 and carbon.
Claim 6
Dependent Claim 85 words
A process for generating CF 4 which comprises: (a) depolymerizing polytetrafluoroethylene in the presence of a carrier gas purge at an elevated temperature to form a mixture of C 2 F 4 and said carrier gas; (b) heating said mixture to an elevated temperature and maintaining said mixture at said temperature for a time sufficient to cause said mixture to dissociate into a mixture of inert gas, CF 4 and carbon; and (c) selectively removing said carbon from said mixture of CF 4 and carbon.
Claim 7
Dependent Claim 64 words
The process of claim 4 wherein said carrier gas is selected from the group consisting of He, Ar, N 2 , and CO 2 , said depolymerization temperature is on the order of 450° C. and said C 2 F 4 mixture is heated at an elevated temperature on the order of 850° C. for a time period ranging from 5 to 15 minutes.
Claim 8
Dependent Claim 11 words
The process of claim 5 wherein said carrier gas is He.

References Cited (Backward Citations)

US2933536A Cited
US2978519A Cited
US3223739A Cited
US4076760A Cited
US3832411A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1981-12-04 1982-06-05 1982-12-05 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1985-12-04 1986-06-05 1986-12-05 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1989-12-04 1990-06-05 1990-12-05 $7700.00 Window Closed / Lapsed

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