Polyimides

Claim 2

A terpolyimide foam derived from a precursor comprising an essentially stoichiometric mixture of an alkyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid or a mixture of such esters and at least three diamines, one of said diamines being heterocyclic, a second of said diamines being aromatic, a third of said diamines being aliphatic, and there being from 0.05 to 0.5 mole of aliphatic diamine and from 0.05 to 0.9 mole of heterocyclic diamine per mole of benzophenonetetracarboxylic acid ester(s).

Claim 3

A terpolyimide foam derived from a precursor as defined in claim 1 in which the aliphatic diamine has from three to twelve carbon atoms.

Claim 4

A terpolyimide foam derived from a precursor as defined in claim 2 in which the aliphatic diamine has not more than six carbon atoms.

Claim 5

A terpolyimide foam derived from a precursor as defined in either of the preceding claim 2 or 3 in which the aliphatic diamine has an even number of carbon atoms.

Claim 6

A terpolyimide foam derived from a precursor as defined in claim 1 in which the aliphatic diamine has the formula: ##STR3## where x is on the order of 2.6.

Claim 7

A terpolyimide foam derived from a precursor as defined in claim 1 which includes a surface active agent in an amount effective to improve the bubble stability of and produce a more uniform cellular structure in the terpolyimide foam.

Claim 8

A terpolyimide foam derived from a precursor as defined in claim 1 which is a dry powder and which has a maximum particle size of at least 50 microns.

Claim 9

A terpolyimide foam derived from a precursor as defined in claim 1 in which any ester present is a methyl or ethyl half ester of 3,3',4,4'-benzophenonetetracarboxylic acid and the diamines are 2,6-diamino pyridine, p,p'-methylene dianiline, and 1,6-diamino hexane.

Claim 10

A terpolyimide foam derived from a precursor as defined in claim 8 in which the molar ratio of the ester and diamine constituents is: ______________________________________ 3,3',4,4'-benzophenonetetracarboxylic acid ester(s) 1.0 2,6-diamino pyridine 0.3 p,p'-methylene dianiline 0.4-0.65 1,6-diamino hexane 0.05-0.3. ______________________________________

Claim 11

A terpolyimide foam derived from a precursor as defined in claim 1 which includes a filler intimately admixed with the mixture of diamines and tetracarboxylic acid ester(s).

Claim 12

A terpolyimide foam obtained by a process which includes the steps of dissolving a benzophenonetetracarboxylic acid or anhydride in an excess of an alkyl alcohol esterification agent to form a solution of an ester of the acid; adding to and dissolving in said solution in amounts such that the imide forming functionalities are substantially equimolar a heterocyclic diamine, an aromatic diamine, and an aliphatic diamine, there being from 0.05 to 0.5 mole of aliphatic diamine and from 0.05 to 0.9 mole of heterocyclic diamine per mole of 3,3',4,4'-benzophenonetetracarboxylic acid ester; and heating the resulting material to effect first amidization and then imidization of the material existing after the dissolution of said diamines.

Claim 13

A terpolyimide foam obtained by a process which includes the steps of dissolving a benzophenonetetracarboxylic acid or anhydride in an excess of an alkyl alcohol esterification agent to form a solution of an ester of the acid; adding to and dissolving in said solution in amounts such that the imide forming functionalities are substantially equimolar a heterocyclic diamine, an aromatic diamine, and an aliphatic diamine, there being from 0.05 to 0.5 mole of aliphatic diamine and from 0.05 to 0.9 mole of heterocyclic diamine per mole of 3,3',4,4'-benzophenonetetracarboxylic acid ester; and heating the resulting material to effect first amidization and then imidization of the material existing after the dissolution of said diamines.

Claim 14

A terpolyimide foam obtained by a process as defined in claim 11 in which said aromatic diamine is added first to said solution and in which said aromatic diamine is fully dissolved before said heterocyclic and aliphatic diamines are added.

Claim 15

A terpolyimide foam obtained by a process as defined in claim 11 which includes the step of adding to the ester-diamine solution a surfactant in an amount effective to improve the bubble stability of and produce a more homogeneous cellular structure in the terpolyimide foam to which the precursor can be converted.

Claim 16

A terpolyimide foam obtained by a process as defined in claim 11 which includes the step of reducing the material existing after the dissolution of the diamines in the esterification agent to a dry particulate form.

Claim 17

A terpolyimide foam obtained by a process as defined in claim 11 in which the aromatic diamine is completely dissolved in the material existing after the dissolution of the diamines benzophenonetetracarboxylic acid or anhydride in the esterification agent before the heterocyclic and aliphatic diamines are added to said material.

Claim 18

A terpolyimide foam obtained by a process as defined in claim 11 in which the material existing after the dissolution of the diamines in the esterification agent is reduced to a dry particulate form by spray drying.