US4070312A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Closed cell polyimides
Assignee: I M L Corp A CORP OF DE
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Filing: 1975-05-27
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Granted: 1978-01-24
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Expires: 1995-05-27
Abstract
Abstract Closed cell polyimide foams. Methods of making such foams from precursors derived from a benzophenonetetracarboxylic acid diester and a mixture of diamines in which the precursor is molded to shape and cured, hydrated, and heated until a porous, closed cell structure develops.
Inventors
- 👤 John Gagliani
- 👤 John V. Long
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 19:33
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/04; C08J9/12; C08J9/125; C08J2379/00; C08J2379/04; C08J2379/08; Y; Y10; Y10S; Y10S521/00; Y10S521/918
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
160 words
The method of making a strong, thermally stable polyimide with low absorption characteristics and low density comprising the steps of: preparing a moldable material from a diester of 3,3',4,4'-benzophenonetetracarboxylic acid and a mixture of diamines, at least one of said diamines being an aromatic, meta-substituted diamine and any diamine which is not meta-substituted being an aromatic, para-substituted diamine which is free of aliphatic moities; molding such material under confinement at a temperature in the range of 300° to 350° C. and under a pressure of 300 to 2000 psi to cure the material and to impart a selected shape thereto; hydrating the polyimide thus obtained by heating it in an aqueous liquid at a temperature of 25°-250° C. and under a pressure of one to 15 atmospheres for a period of one to 200 hours; and heating the hydrated polyimide at a temperature of 270° to 400° C. for a time sufficiently long to develop a porous, closed cell structure.
Claim 2
Independent Claim
160 words
The method of making a strong, thermally stable polyimide with low absorption characteristics and low density comprising the steps of: preparing a moldable material from a diester of 3,3',4,4'-benzophenonetetracarboxylic acid and a mixture of diamines, at least one of said diamines being an aromatic, meta-substituted diamine and any diamine which is not meta-substituted being an aromatic, para-substituted diamine which is free of aliphatic moities; molding such material under confinement at a temperature in the range of 300° to 350° C. and under a pressure of 300 to 2000 psi to cure the material and to impart a selected shape thereto; hydrating the polyimide thus obtained by heating it in an aqueous liquid at a temperature of 25°-250° C. and under a pressure of one to 15 atmospheres for a period of one to 200 hours; and heating the hydrated polyimide at a temperature of 270° to 400° C. for a time sufficiently long to develop a porous, closed cell structure.
Claim 3
Dependent Claim
19 words
A method as defined in claim 1 in which the liquid in which the polyimide is hydrated is water.
Claim 4
Dependent Claim
31 words
A method as defined in claim 2 in which the aqueous liquid contains an electrolyte in an amount sufficient to increase the rate of absorption of water by the molded polyimide.
Claim 5
Dependent Claim
14 words
A method as defined in claim 3 in which the electrolyte is sodium acetate.
Claim 6
Dependent Claim
32 words
A method as defined in claim 2 in which the aqueous liquid contains an ionic surfactant in an amount sufficient to increase the rate of absorption of water by the molded polyimide.
Claim 7
Dependent Claim
32 words
A method as defined in claim 2 in which the aqueous liquid contains a nonionic surfactant in an amount sufficient to increase the rate of absorption of water by the molded polyimide.
Claim 8
Dependent Claim
42 words
A method as defined in claim 1 in which, in the heating step in which the closed cell structure is developed, the hydrated polyimide is heated at a temperature in the range of 270° to 400° C. for at least 1 hour.
Claim 9
Independent Claim
191 words
The method of making a strong, thermally stable polyimide with low absorption characteristics and low density, comprising the steps of: reacting 3,3',4,4'-benzophenonetetracarboxylic acid or its anhydride with an esterifying agent to produce a 3,3',4,4'-benzophenonetetracarboxylic acid diester; mixing with said diester a mixture of aromatic, primary diamines, at least one of said diamines being a meta-substituted diamine and any diamines which are not meta-substituted being para-substituted and free of aliphatic moities; reducing the resulting mixture to a solid resinoid; foaming said resinoid by heating it to a temperature in the range of 125° to 150° C.; reducing the foamed material to particulate form; heating the particulate material under confinement at a temperature in the range of 300° to 350° C. and under a pressure of 300 to 2000 psi to cure the material and to impart a selected shape thereto; hydrating the polyimide thus obtained by heating it in an aqueous liquid at a temperature of 25°-250° C. and under a pressure of one to 15 atmospheres; and heating the hydrated polyimide at a temperature of 270° to 400° C. for 1 to 4 hours to develop a porous, closed cell structure.
Claim 10
Independent Claim
191 words
The method of making a strong, thermally stable polyimide with low absorption characteristics and low density, comprising the steps of: reacting 3,3',4,4'-benzophenonetetracarboxylic acid or its anhydride with an esterifying agent to produce a 3,3',4,4'-benzophenonetetracarboxylic acid diester; mixing with said diester a mixture of aromatic, primary diamines, at least one of said diamines being a meta-substituted diamine and any diamines which are not meta-substituted being para-substituted and free of aliphatic moities; reducing the resulting mixture to a solid resinoid; foaming said resinoid by heating it to a temperature in the range of 125° to 150° C.; reducing the foamed material to particulate form; heating the particulate material under confinement at a temperature in the range of 300° to 350° C. and under a pressure of 300 to 2000 psi to cure the material and to impart a selected shape thereto; hydrating the polyimide thus obtained by heating it in an aqueous liquid at a temperature of 25°-250° C. and under a pressure of one to 15 atmospheres; and heating the hydrated polyimide at a temperature of 270° to 400° C. for 1 to 4 hours to develop a porous, closed cell structure.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-23 | 1981-07-25 | 1982-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-23 | 1985-07-25 | 1986-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-23 | 1989-07-25 | 1990-01-24 | $7700.00 | Window Closed / Lapsed |