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US 4,070,312 AGranted
Closed cell polyimides
AssigneeInternational Harvester Company
InventorsJohn Gagliani, John V. Long
Life of this patent
Estimating the term…
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.
Claims8
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.degree. to 350.degree. 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.degree.-250.degree. 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.degree. to 400.degree. C. for a time sufficiently long to develop a porous, closed cell structure.
1 more element
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.degree. to 150.degree. C.;
- reducing the foamed material to particulate form;
- heating the particulate material under confinement at a temperature in the range of 300.degree. to 350.degree. 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.degree.-250.degree. C. and under a pressure of one to 15 atmospheres;
- and heating the hydrated polyimide at a temperature of 270.degree. to 400.degree. C. for 1 to 4 hours to develop a porous, closed cell structure.
5 more elements
Dependencies are inferred from the claim text.