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US4980105A
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Method for extruder devolatilization of spiro(bis)indane polycarbonates
Assignee: General Electric Co
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Filing: 1989-08-28
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Granted: 1990-12-25
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Expires: 2009-08-28
Abstract
Abstract Spiro(bis)indane polycarbonates, including homo- and copolycarbonates, are devolatilized by extrusion under conditions of low viscous dissipation and low residence time. By this method, volatile impurities including spiro(bis)indane cyclic dimer may be removed.
Inventors
- 👤 Lawrence R. Schmidt
- 👤 Joel M. Caraher
- 👤 John L. Maxam
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 16:52
CPC Classifications
C; C08; C08G; C08G64/00; C08G64/40; C08G64/406; B; B29; B29C; B29C48/00; B29C48/25; B29C48/36; B29C48/50; B29C48/76; B29C48/03
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
120 words
A method for removing volatile materials, including spiro(bis)indane carbonate cyclic dimer, from a linear polycarbonate comprising spiro(bis)indane carbonate units which comprises extruding said polycarbonate under conditions of low viscous dissipation, said method comprising the steps of: (A) feeding crude spiro(bis)indane polycarbonate into a solids feed stage of an extruder, said solids feed stage being maintained at a resin temperature of at most about 150° C.; (B) conveying said polycarbonate to a melting stage in said extruder; (C) passing the melted polycarbonate through a first liquid seal to (D) a vacuum vented devolatilizing stage maintained under conditions of high surface area at a resin temperature in the range of about 250-300° C.; and (E) passing the devolatilized polycarbonate through a die.
Claim 2
Independent Claim
120 words
A method for removing volatile materials, including spiro(bis)indane carbonate cyclic dimer, from a linear polycarbonate comprising spiro(bis)indane carbonate units which comprises extruding said polycarbonate under conditions of low viscous dissipation, said method comprising the steps of: (A) feeding crude spiro(bis)indane polycarbonate into a solids feed stage of an extruder, said solids feed stage being maintained at a resin temperature of at most about 150° C.; (B) conveying said polycarbonate to a melting stage in said extruder; (C) passing the melted polycarbonate through a first liquid seal to (D) a vacuum vented devolatilizing stage maintained under conditions of high surface area at a resin temperature in the range of about 250-300° C.; and (E) passing the devolatilized polycarbonate through a die.
Claim 3
Dependent Claim
14 words
A method according to claim 1 wherein the spiro(bis)indane polycarbonate is a 6,6'-dihydroxy-3,3',3'--tetramethyl-1,1'-spiro(bis)indane polycarbonate.
Claim 4
Dependent Claim
13 words
A method according to claim 2 wherein the extruder is a twin-screw extruder.
Claim 5
Dependent Claim
31 words
A method according to claim 3 wherein the temperature of the polycarbonate being extruded is at no point more than about 15° C. greater than the barrel temperature of the extruder.
Claim 6
Dependent Claim
47 words
A method according to claim 4 wherein the temperature of the solids feed stage is up to about 140° C., that of the melting stage is in the range of about 250-275° C. and that of the devolatilizing stage is in the range of about 250-300° C.
Claim 7
Dependent Claim
14 words
A method according to claim 5 wherein the extruder is a corotating, intermeshing extruder.
Claim 8
Dependent Claim
21 words
A method according to claim 6 wherein the devolatilizing stage is maintained at a pressure of about 20 torr or less.
Claim 9
Dependent Claim
41 words
A method according to claim 4 wherein the length of the stages, based on the total length of the stages employed in steps A-E, are as follows: Solids feed stage--about 25-30%; Melting stage--about 30-40%; First liquid seal--about 5-10%; Devolatilizing stage--about 25-35%.
Claim 10
Dependent Claim
16 words
A method according to claim 4 which includes a pre-feed seal preceding the solids feed stage.
Claim 11
Dependent Claim
43 words
A method according to claim 4 which includes, between the devolatilizing stage and the die, a second liquid seal followed by a metering stage, the length of said metering stage being about 20-30% of the length of the stages employed for steps A-E.
Claim 12
Dependent Claim
13 words
A method according to claim 4 wherein the polycarbonate is a spiro(bis)indane homopolycarbonate.
Claim 13
Dependent Claim
14 words
A method according to claim 4 wherein the polycarbonate is a spiro(bis)indane-bisphenol A copolycarbonate.
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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) | 1993-12-24 | 1994-06-25 | 1994-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-24 | 1998-06-25 | 1998-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-24 | 2002-06-25 | 2002-12-25 | $7700.00 | Window Closed / Lapsed |