# US 4,394,464 A · Modified polyimide foams and methods of making same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,464 A - Document ID: US4394464A - Status: Granted - Kind: A - Application number: 06/390,778 - Filed: 1982-06-21 - Granted: 1983-07-19 - Earliest claimed: 1982-06-21 - Inventors: John Gagliani; John V. Long - Web page: https://patentgrep.com/patent/US4394464A ## CPC - C08J 9/02: using blowing gases generated by the reacting monomers or modifying agents during the preparation or modification of macromolecules - C08J 2379/08: Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors - Y10S 264/05: Use of one or more blowing agents together - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract Methods of making modified polyimide/polyimide-amide foams and the resulting compositions. An N-substituted aliphatic imide is prepared by reacting a suitable aromatic dianhydride with a suitable oxoimine. A polyimide forming material is prepared by dissolving the N-substituted aliphatic imide in an esterifying solvent, then adding a suitable aromatic diamine. This material is dried to a powder or film. A foam is produced by heating the material to reaction temperature for a period sufficient to produce a stable foam. The material melts, then spontaneously expands into a foam which becomes self supporting and cures to a resilient flexible foam. Depending upon heating conditions, a polyimide, polyimide-amide or mixture thereof may be produced, resulting in foams having varying physical properties. ## Claims ### Claim 1 The method of making a resilient, flame resistant modified polyimide foam which comprises the steps of: reacting an aromatic dianhydride with an oximine having the general formula: ##STR7## wherein "X" is an integer from 2 to 4, in a mole ratio of oxoimine to dianhydride between about 1.5:1 and about 0.05:1 to produce an N-substituted aliphatic imide; dissolving said imide in a reactive solvent esterifying agent to exterify said imide; adding thereto a diamine; drying the resulting solution; and heating the dry material to a selected foaming temperature of from about 120.degree. C. to about 320.degree. C. for a period of from about 10 to about 60 minutes; whereby a resilient foam having good flame resistance is produced comprising polyimide and polyimide-amide with proportions depending on the selected foaming temperature. ### Claim 2 (depends on 1) The method according to claim 1 wherein said foaming temperature is in the range of from about 230.degree. C. and about 320.degree. C. and the resulting foam comprises primarily a polyimide. ### Claim 3 (depends on 1) The method according to claim 1 wherein said foaming temperature is in the range of from about 120.degree. C. and about 220.degree. C. and the resulting foam is primarily a polyimide-amide. ### Claim 4 (depends on 1) The method according to claim 1 wherein said aromatic dianhydride is pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride or mixtures thereof. ### Claim 5 (depends on 1) The method according to claim 1 wherein said oxoimine is caprolactam. ### Claim 6 (depends on 1) The method according to claim 1 wherein said reactive solvent is methyl alcohol. ### Claim 7 (depends on 1) The method according to claim 1 wherein said diamine is 4,4'-diaminophenyl methane. ### Claim 8 (depends on 1) The method according to claim 1 wherein said diamine comprises at least two different diamines, at least one of which is an aromatic diamine. ### Claim 9 (depends on 1) The method according to claim 1 further including the step of adding from about 0.01 to about 2 wt. % of a surfactant to the solution prior to drying. ### Claim 10 (depends on 1) The method according to claim 1 further including the step of adding fillers or reinforcing materials to the solution prior to drying. ### Claim 11 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. ### Claim 12 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. ### Claim 13 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.