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US 4,360,604 AGranted
Polyimide foams
AssigneeInternational Harvester Company
InventorsJohn Gagliani, Raymond Lee, Usman A. K. Sorathia
Life of this patent
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Abstract
Copolyimide 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.
Claims10
That method of preparing a polyimide foam precursor which comprises the steps of:
- dissolving 3,3',4,4'-benzophenonetetracarboxylic acid or an anhydride of that acid in one or more alkyl alcohols to form one or more alkyl diesters of the acid;
- dissolving a heterocyclic diamine and a meta- or para-substituted diamine in said alcohol(s) in amounts such that the imide forming functionalities of the diester(s) and the diamines are substantially equimolar and the molar ratio of heterocyclic diamine to tetracarboxylic acid ester(s) is in the ratio of about 0.4-0.42 to 1.0;
- and thereafter evaporating excess alcohol(s) from, and reducing the mixture of ester(s) and diamines to, a dry particulate form.
Dependencies are inferred from the claim text.