US4332656A
Expired / Lapsed
US
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Polyimide foams
Assignee: I M L Corp A CORP OF
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Filing: 1981-04-10
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Granted: 1982-06-01
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Expires: 2001-04-10
Abstract
Abstract Copolymide foams derived from a diester of 3,3',4,4'-benzophenonetetracarboxylic acid, an aromatic diamine, and a heterocyclic diamine. A molar concentration of the heterocyclic diamine approaching but not exceeding 0.42 is employed. This results in a flexible foam with a homogeneous cellular structure and a reduced compression set loss.
Inventors
- 👤 John Gagliani
- 👤 Raymond Lee
- 👤 Usman A. K. Sorathia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 17:42
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/02; C08J3/00; C08J3/28; C08L; C08L79/00; C08L79/04; C08L79/08; C08J2379/00; C08J2379/04; C08J2379/08
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
87 words
A method of preparing a flexible, resilient polyimide foam with improved compression set properties which comprises the step of foaming and curing a precursor containing at least one alkyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid; a meta- or para-substituted aromatic diamine which is free of aliphatic moieties; and a heterocyclic diamine, said ester(s) and said diamines being present in concentrations such that the imide forming functionalities are substantially equimolar and the molar ratio of heterocyclic diamine to tetracarboxylic acid diester(s) is in the range of about 0.4-0.42 to 1.0.
Claim 2
Independent Claim
87 words
A method of preparing a flexible, resilient polyimide foam with improved compression set properties which comprises the step of foaming and curing a precursor containing at least one alkyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid; a meta- or para-substituted aromatic diamine which is free of aliphatic moieties; and a heterocyclic diamine, said ester(s) and said diamines being present in concentrations such that the imide forming functionalities are substantially equimolar and the molar ratio of heterocyclic diamine to tetracarboxylic acid diester(s) is in the range of about 0.4-0.42 to 1.0.
Claim 3
Dependent Claim
26 words
A method of preparing a polyimide foam as defined in claim 1 wherein the precursor is foamed and cured by the application of microwave energy thereto.
Claim 4
Dependent Claim
64 words
A method of preparing a polyimide foam as defined in claim 2 wherein said precursor is foamed and cured by exposing it to high frequency radiation in an oven operating at a frequency of 915 to 2450 mHz and at 3.75 to 15 kW power and a power output to precursor unit weight ratio of 0.6 to 1 kW/kg for two to 55 minutes.
Claim 5
Dependent Claim
56 words
A method of preparing a polyimide foam as defined in claim 2 in which the polyimide is thermally post cured by heating the product of the microwave foaming and curing steps in a circulating air oven at a temperature of 500° to 550° F. for 30 to 200 minutes to complete the curing of the polyimide.
Claim 6
Dependent Claim
45 words
A method of preparing a polyimide foam as defined in claim 2 wherein the precursor is exposed to microwave radiation at a first power output to develop a foam and to microwave energy at a second, higher power output to develop the polyimide chemical structure.
Claim 7
Dependent Claim
42 words
A method of preparing a polyimide foam as defined in claim 2 wherein the precursor is exposed to pulses of microwave radiation, the duration of the pulses and of the intervals therebetween being on the order of 60 and 20 seconds, respectively.
Claim 8
Dependent Claim
53 words
A method of preparing a polyimide foam as defined in claim 2 in which the precursor is exposed to microwave radiation in a microwave cavity and wherein the cavity is heated to a temperature of at least 250° F. and less than 450° F. while the precursor is exposed to said microwave radiation.
Claim 9
Dependent Claim
39 words
A method of preparing a polyimide foam as defined in claim 2 wherein a conductive filler is admixed with said precursor prior to exposing it to microwave radiation to promote the conversion of the precursor to a polymeric material.
Claim 10
Dependent Claim
40 words
A method of preparing a polyimide foam as defined in claim 2 in which the precursor is preheated at a temperature of not more than 300° F. for 2 to 6 minutes before it is exposed to the microwave radiation.
Claim 11
Dependent Claim
56 words
A method of preparing a polyimide foam as defined in claim 2 wherein said precursor is loaded on a support that is compatible with microwave radiation to a depth of at least 0.5 cm prior to exposing it to said microwave radiation and wherein the loading of the precursor is at least 1.6 kg/m 2 .
Claim 12
Dependent Claim
30 words
A method of preparing a polyimide foam as defined in claim 2 from a precursor which also contains from about 0.00625 to about 0.05 weight percent of an effective surfactant.
Claim 13
Independent Claim
38 words
A method of preparing a polyimide foam as defined in either of the preceding claims 1 or 2 from a precursor in which the diamines that are mixed with the tetracarboxylic acid ester(s) are 2,6-diaminopyridine and p,p'-methylene dianiline.
Claim 14
Dependent Claim
26 words
A method of preparing a polyimide foam as defined in claim 1 wherein said precursor is foamed and cured by the application of thermal energy thereto.
References Cited (Backward Citations)
USRE30213E
Cited
US4241193A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-05-31 | 1985-11-30 | 1986-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-05-31 | 1989-11-30 | 1990-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-05-31 | 1993-11-30 | 1994-06-01 | $7700.00 | Window Closed / Lapsed |