Modified polyimide foams and methods of making same

The method of making a modified polyimide foam comprising a mixture of polyimide and polyimide-amide resins with the polyimide-amide predominating which comprises the steps of:

• mixing together an aromatic dianhydride selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and mixtures thereof and an oxoimine having the general formula:
• ##STR8## wherein "x" is an integer from 2 to 4, the mole ratio of oxoimine to dianhydride being from about 1.5:1 to about 0.05:1;
• heating the mixture to a temperature of from about 150.degree. C. to about 200.degree. C. for from about 5 to about 90 minutes ro react said dianhydride with said oxoimine to produce an N-substituted aliphatic imide;
• cooling the mixture to a temperature of from about 40.degree. C. to about 70.degree. C.;
• dissolving said imide in a reactive solvent esterifying agent to esterify said imide;
• heating the imide solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of from about 60 to about 90 minutes to esterify said imide;
• adding thereto about 1.0 M 4,4'-diaminodiphenyl methane per 1.0 M of dianhydride;
• heating the resulting solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of about 2 to about 30 minutes;
• drying the solution at a temperature of from about 60.degree. C. to about 70.degree. C. for a period of about 60 to about 240 minutes to produce a dry material;
• and
• foaming said dry material by heating to a temperature of about 120.degree. C. to about 220.degree. C. in a pre-heated oven for from about 10 to about 40 minutes;
• whereby a resilient, flame resistant modified polyimide foam is produced consisting primarily of polyimide-amide resin.

The method of making a modified polyimide foam comprising a mixture of polyimide and polyimide-amide with the polyimide predominating which comprises the steps of:

• mixing together an aromatic dianhydride selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and mixtures thereof and an oxoimine having the general formula:
• ##STR9## wherein "x" is an integer from 2 to 4, the mole ratio of oxoimine to dianhydride being from about 1.5:1 to about 0.05:1;
• heating the mixture to a temperature of from about 150.degree. C. to about 200.degree. C. for from about 5 to about 90 minutes to react with dianhydride with said oxoimine to produce an N-substituted aliphatic imide;
• cooling the mixture to a temperature of from about 40.degree. C. to about 70.degree. C.;
• dissolving said imide in a reacting solvent esterifying agent to esterify said imide;
• heating the imide solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of from about 60 to about 90 minutes to esterify said imide;
• adding thereto about 1.0 M 4,4'-diaminodiphenyl methane per about 1.0 M of dianhydride;
• heating the resulting solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of about 2 to about 30 minutes;
• drying the solution at a temperature of from about 60.degree. C. to about 70.degree. C. for a period of about 60 to about 240 minutes to produce a dry material;
• and
• foaming said dry material by heating to a temperature of about 230.degree. C. to about 320.degree. C. in a pre-heated oven for about 30 to about 60 minutes;
• whereby a resilient flame resistant modified polyimide foam is produced consisting primarily of polyimide resin.

The method of making a modified polyimide foam comprising a mixture of polyimide and polyimide-amide with significant portions of both polyimide and polyimide-amide which comprises the steps of:

• mixing together an aromatic dianhydride selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and mixtures thereof and an oxoimine having the general formula:
• ##STR10## wherein "x" is an integer from 2 to 4, the mole ratio of oxoimine to dianhydride being from about 1.5:1 to about 0.05:1;
• heating the mixture to a temperature of from about 150.degree. C. to about 200.degree. C. for from about 5 to about 90 minutes to react said dianhyride with said oxoimine to produce an N-substituted aliphatic imide;
• cooling the mixture to a temperature of from about 40.degree. C. to about 70.degree. C.;
• dissolving said imide in a reactive solvent esterifying agent to esterify said imide;
• heating the imide solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of from about 60 to about 90 minutes to esterify said imide;
• adding thereto about 1.0 M 4,4'-diaminodiphenyl methane per about 1.0 M of dianhydride;
• heating the resulting solution to reflux at a temperature of from about 70.degree. C. to about 80.degree. C. for a period of about 2 to about 30 minutes;
• drying the solution at a temperature of from about 60.degree. C. to about 70.degree. C. for a period of about 60 to about 240 minutes to produce a dry material;
• and
• foaming said dry material by heating to a temperature of from about 210.degree. C. to about 250.degree. C. for a period of about 30 to about 45 minutes;
• whereby a resilient flame resistant modified polyimide foam is produced containing significant portions of both polyimide and polyimide-amide resins.