US4900762A
Expired / Lapsed
US
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Production of foamed polymer structures
Assignee: Imi Tech Corp
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Filing: 1988-10-11
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Granted: 1990-02-13
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Expires: 2008-10-11
Abstract
Abstract Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, the microwave radiation is directed upon the top, sides and ends of the body of polyimide precursor and of the foam structure as it is developing, but the extent to which such radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure. Mechanisms by which the shields function to provide the improvements of the process are discussed, and methods based thereon are set forth.
Inventors
- 👤 H. Eugene Broemmelsiek
- 👤 Raymond Lee
- 👤 Carroll W. Lanier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:00
CPC Classifications
C; C08; C08J; C08J9/00; B; B01; B01J; B01J19/00; B01J19/08; B01J19/12; B01J19/122; B01J19/126; C08J2379/00; C08J2379/04; C08J2379/08; Y; Y10; Y10S; Y10S521/00; Y10S521/915
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
105 words
A bun of cured polyimide foam produced by directing upon the top, sides and ends of a body of foamable polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, but curtailing the extent to which microwave radiation impinges upwardly into the bottom of said body and said foam structure by maintaining a microwave radiation-curtailing shield underneath said body and said foam structure, and thermally curing the developed foam structure to form cured polyimide foam.
Claim 2
Dependent Claim
105 words
A bun of cured polyimide foam produced by directing upon the top, sides and ends of a body of foamable polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, but curtailing the extent to which microwave radiation impinges upwardly into the bottom of said body and said foam structure by maintaining a microwave radiation-curtailing shield underneath said body and said foam structure, and thermally curing the developed foam structure to form cured polyimide foam.
Claim 3
Dependent Claim
12 words
An article of claim 1 wherein the shield was a metallic shield.
Claim 4
Dependent Claim
15 words
An article of claim 1 wherein the shield was composed primarily or exclusively of aluminum.
Claim 5
Dependent Claim
16 words
An article of claim 1 wherein said precursor was initially in the form of a powder.
Claim 6
Dependent Claim
29 words
An article of claim 1 wherein said precursor was comprised of a lower alkyl ester of an aromatic tetracarboxylic acid and at least one aromatic or heterocyclic primary diamine.
Claim 7
Dependent Claim
19 words
An article of claim 5 wherein said ester was composed predominantly of di-lower alkyl ester of benzophenone tetracarboxylic acid.
Claim 8
Dependent Claim
17 words
An article of claim 5 wherein said diamine was composed predominantly of 4,4'-methylenedianiline or 4,4'-oxydianiline, or both.
Claim 9
Dependent Claim
32 words
An article of claim 5 wherein said ester was composed predominantly of di-lower alkyl ester or benzophenone tetracarboxylic acid and wherein said diamine was composed predominantly of 4,4'-methylenedianiline or 4,4'-oxydianiline, or both.
Claim 10
Dependent Claim
22 words
An article of claim 1 wherein the developed foam structure was subjected to curing into a polyimide foam in a thermal oven.
Claim 11
Dependent Claim
59 words
An article of claim 1 wherein the shield was a metallic shield, wherein said precursor was initially in the form of a powder comprised of a lower alkyl ester of an aromatic tetracarboxylic acid and at least one aromatic or heterocyclic primary diamine, and wherein the developed foam structure was cured into a polyimide foam in a thermal oven.
Claim 12
Dependent Claim
11 words
An article of claim 10 wherein said precursor included a surfactant.
Claim 13
Dependent Claim
41 words
An article of claim 1 wherein the shield was a metallic shield, wherein said precursor was initially in the form of a powder composed predominantly of (i) di-lower alkyl ester of benzophenone tetracarboxylic acid and (ii) 4,4'-methylenedianiline or 4,4'-oxydianiline, or both.
Claim 14
Dependent Claim
28 words
An article of claim 12 wherein said powder was composed predominantly of 3,3',4,4'-benzophenone tetracarboxylic acid dimethyl ester, 4,4'-methylenedianiline and 2,6-diaminopyridine in a mol ratio of approximately 1.0:0.7:0.3, respectively.
Claim 15
Dependent Claim
21 words
An article of claim 13 wherein the metallic shield was an aluminum shield and wherein the polyimide precursor included a surfactant.
Claim 16
Dependent Claim
52 words
An article of claim 1 wherein said shield was preheated such that at least the lower portion of said body of polyimide precursor was preheated to a suitable temperature in the range of about 60° to about 130° C. when commencing exposure of the body of polyimide precursor to such microwave radiation.
Claim 17
Dependent Claim
12 words
An article of claim 15 wherein the shield was a metallic shield.
Claim 18
Dependent Claim
12 words
An article of claim 15 wherein the shield was an aluminum shield.
Claim 19
Dependent Claim
16 words
An article of claim 15 wherein said precursor was initially in the form of a powder.
Claim 20
Dependent Claim
29 words
An article of claim 15 wherein said precursor was comprised of a lower alkyl ester of an aromatic tetracarboxylic acid and at least one aromatic or heterocyclic primary diamine.
Claim 21
Dependent Claim
32 words
An article of claim 19 wherein said ester was composed predominantly of di-lower alkyl ester of benzophenone tetracarboxylic acid and wherein said diamine was composed predominantly of 4,4'-methylenedianiline or 4,4'-oxydianiline, or both.
Claim 22
Dependent Claim
22 words
An article of claim 15 wherein the developed foam structure was subjected to curing into a polyimide foam in a thermal oven.
Claim 23
Dependent Claim
59 words
An article of claim 15 wherein the shield was a metallic shield, wherein said precursor was initially in the form of a powder comprised of a lower alkyl ester of an aromatic tetracarboxylic acid and at least one aromatic or heterocyclic primary diamine, and wherein the developed foam structure was cured into a polyimide foam in a thermal oven.
Claim 24
Dependent Claim
118 words
A bun of cured polyimide foam produced by placing a foamable polyimide precursor in the form of a powder on a heat-stable cloth positioned on a microwave-curtailing shield underneath said heat-stable cloth; directing upon the top, sides and ends of the body of said polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, said microwave-curtailing shield curtailing the extent to which microwave radiation impringes upwardly into the bottom of said body and said foam structure; and thermally curing the developed foam structure to form cured polyimide foam.
Claim 25
Dependent Claim
118 words
A bun of cured polyimide foam produced by placing a foamable polyimide precursor in the form of a powder on a heat-stable cloth positioned on a microwave-curtailing shield underneath said heat-stable cloth; directing upon the top, sides and ends of the body of said polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, said microwave-curtailing shield curtailing the extent to which microwave radiation impringes upwardly into the bottom of said body and said foam structure; and thermally curing the developed foam structure to form cured polyimide foam.
Claim 26
Dependent Claim
16 words
An article of claim 23 wherein the heat stable cloth was positioned on said metallic shield.
Claim 27
Dependent Claim
46 words
An article of claim 24 wherein said metallic shield was preheated such that the temperature of at least the bottom portion of the polyimide precursor was between about 60° and about 130° C. when commencing exposure of the body of polyimide precursor to such microwave radiation.
Claim 28
Dependent Claim
38 words
An article of claim 25 wherein said metallic shield was an aluminum shield and wherein said precursor was comprised of a lower alkyl ester of an aromatic tetracarboxylic acid and at least one aromatic or heterocyclic primary diamine.
Claim 29
Dependent Claim
27 words
An article of claim 26 wherein said precursor was composed predominantly of (i) di-lower alkyl ester of benzophenone tetracarboxylic acid and (ii) 4,4'-methylenedianiline or 4,4'-oxydianiline, or both.
Claim 30
Dependent Claim
28 words
An article of claim 26 wherein said precursor was composed predominantly of 3,3',4,4'-benzophenone tetracarboxylic acid dimethyl ester, 4,4'-methylenedianiline and 2,6-diaminopyridine in a mol ratio of approximately 1.0:0.7:0.3, respectively.
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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) | 1993-02-12 | 1993-08-14 | 1994-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-12 | 1997-08-14 | 1998-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-12 | 2001-08-14 | 2002-02-13 | $7700.00 | Window Closed / Lapsed |