US4439381A
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US
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Methods of preparing polyimides and artifacts composed thereof
Assignee: I M L Corp A CORP OF
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Filing: 1981-05-11
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Granted: 1984-03-27
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Expires: 2001-05-11
Abstract
Abstract Methods of converting essentially unpolymerized precursors into polyimides in which the precursors are exposed to microwave radiation. Preheating, thermal post-curing, and other techniques may be employed to promote the development of optimum properties; and reinforcements can be employed to impart strength and rigidity to the final product. Also disclosed are processes for making various composite artifacts in which non-polymeric precursors are converted to polyimides by using the techniques described above.
Inventors
- 👤 John Gagliani
- 👤 Raymond Lee
- 👤 Anthony L. Wilcoxson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:51
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/02; C08G; C08G73/00; C08G73/06; C08G73/10; C08G73/1003; C08G73/1007; C08G73/1025; C08J2379/00; C08J2379/04; C08J2379/08; Y; Y10; Y10S; Y10S264/00; Y10S264/05; Y10S521/00; Y10S521/915; Y10T; Y10T428/00; Y10T428/249921; Y10T428/249953; Y10T428/249986; Y10T428/249987; Y10T428/24999; Y10T428/249991; Y10T428/249992; Y10T428/31504; Y10T428/31721
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
86 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the step of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, said precursor being supported while it is exposed to microwave radiation on an inflexible, temperature resistant substrate that is compatible with such radiation.
Claim 2
Independent Claim
86 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the step of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, said precursor being supported while it is exposed to microwave radiation on an inflexible, temperature resistant substrate that is compatible with such radiation.
Claim 3
Independent Claim
98 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the steps of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, and precursor being confinded between members which are compatible with microwave radiation as the precursor is exposed to said radiation to thereby control the thickness of the polymeric material to which the precursor is converted.
Claim 4
Independent Claim
98 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the steps of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, and precursor being confinded between members which are compatible with microwave radiation as the precursor is exposed to said radiation to thereby control the thickness of the polymeric material to which the precursor is converted.
Claim 5
Independent Claim
107 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the steps of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, the precursor being converted to a polyimide in a closed mold and said mold being fabricated of a material which is compatible with microwave radiation and has sufficient porosity to allow volatiles evolved in the formation of the polyimide chemical structure to escape therethrough.
Claim 6
Independent Claim
107 words
A method of preparing a polyimide from a non-polymeric precursor comprising an ester of a tetracarboxylic acid and one or more primary diamines which includes the steps of exposing said precursor to microwave radiation having a frequency of at least 915 mHz for periods of sufficient duration to develop a cellular physical structure and to at least partially develop a polyimide chemical structure, the precursor being converted to a polyimide in a closed mold and said mold being fabricated of a material which is compatible with microwave radiation and has sufficient porosity to allow volatiles evolved in the formation of the polyimide chemical structure to escape therethrough.
Claim 7
Independent Claim
45 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3, wherein the member(s) confining and/or supporting said precursor is fabricated of a polypropylene lined with a fluorocarbon polymer coated glass, a glass based crystalline ceramic, or a glass filled polyimide.
Claim 8
Dependent Claim
46 words
A method of preparing a polyimide as defined in any of the preceding claim 1-3 wherein the material produced by exposing the precursor to microwave radiation is thereafter postcured by heating it at a temperature on the order of 250°-550° F. for 40 to 200 minutes.
Claim 9
Independent Claim
31 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor is exposed to microwave radiation for a total of 2 to 55 minutes.
Claim 10
Independent Claim
33 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor is exposed to the microwave radiation at a power output of at least 3.75 kW.
Claim 11
Dependent Claim
28 words
A method of preparing a polyimide as defined in claim 7 wherein the microwave radiation to which the precursor is exposed has a frequency of about 2450 mHz.
Claim 12
Independent Claim
36 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 which employs a microwave radiation power output to unit weight of precursor ratio in the range of 0.6 to 1 kW/kg.
Claim 13
Independent Claim
48 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor is exposed to microwave radiation at a first power output to develop a foam and to microwave energy at a second, higher power output to develop the polyimide chemical structure.
Claim 14
Independent Claim
45 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor is exposed to pulses of microwave radiation, the duration of the pulses and of the intervals therebetween being on the order of 60 to 20 seconds, respectively.
Claim 15
Independent Claim
56 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 in which the precursor is exposed to microwave radiation in a microwave cavity and wherein the cavity is heated to a temperature of at least 250° F. and less than 450° F. while the precursor is exposed to said microwave radiation.
Claim 16
Independent Claim
42 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein a conductive filler is admixed with said precursor prior to exposing it to microwave radiation to promote the conversion of the precursor to a polymeric material.
Claim 17
Dependent Claim
42 words
A method of preparing a polyimide as defined in claim 13 wherein the conductive filler is activated carbon or graphite and wherein said conductive filler is present in said precursor in an amount ranging from 5 to less than 20 weight percent.
Claim 18
Independent Claim
43 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 in which the precursor is preheated at a temperature of not more than 300° F. for 2 to 6 minutes before it is exposed to the microwave radiation.
Claim 19
Dependent Claim
24 words
A method of preparing a polyimide as defined in claim 15 in which the precursor is preheated at a temperature of about 250° F.
Claim 20
Independent Claim
43 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 which includes the step of preheating the members confining and/or supporting said precursor to a temperature of 250°-300° F. prior to exposing said precursor to said microwave radiation.
Claim 21
Independent Claim
27 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor exposed to microwave radiation is a dry particulate solid.
Claim 22
Independent Claim
41 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 which includes the step of reducing the precursor to particles having a size distribution of ca. 300 microns×0 prior to exposing said precursor to microwave radiation.
Claim 23
Independent Claim
66 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor contains a plurality of diamines, one of said diamines being heterocyclic and having nitrogen in the ring, another of said diamines being a para- or meta-substituted aromatic diamine which is free of aliphatic moieties, and any additional diamine being either a heterocyclic or an aromatic diamine as aforesaid.
Claim 24
Dependent Claim
36 words
A method of preparing a polyimide as defined in claim 20 wherein said heterocyclic diamine is present in said precursor in a ratio of 0.3 to 0.6 mole of diamine per mole of 3,3'4,4'-benzophenonetetracarboxylic acid ester.
Claim 25
Dependent Claim
48 words
A method of preparing a polyimide as defined in claim 20 wherein the aromatic and heterocyclic diamines in the precursor are selected from the following group: 2,6-diaminopyridine 3,5-diaminopyridine 3,3'-diaminodiphenyl sulfone 4,4'-diaminodiphenyl sulfone 4,4'-diaminodiphenyl sulfide 3,3'-diaminodiphenyl ether 4,4'-diaminodiphenyl ether meta-phenylene diamine para-phenylene diamine p,p'-methylene dianiline 2,6-diamino toluene 2,4-diamino toluene.
Claim 26
Independent Claim
60 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor contains at least three diamines, one of said diamines being heterocyclic and having nitrogen in the ring, another of said diamines being a para- or meta-substituted aromatic diamine which is free of aliphatic moieties, and a third of said diamines being aliphatic.
Claim 27
Dependent Claim
39 words
A method of preparing a polyimide as defined in claim 23 wherein the liquid resin contains from 0.05 to 0.3 mole of aliphatic diamine and from 0.1 to 0.3 mole of heterocyclic diamine per mole of 3,3'4,4'-benzophenonetetracarboxylic acid ester.
Claim 28
Dependent Claim
26 words
A method of preparing a polyimide as defined in claim 23 wherein the aliphatic diamine in the liquid resin has from three to twelve carbon atoms.
Claim 29
Dependent Claim
48 words
A method of preparing a polyimide as defined in claim 23 wherein the aromatic and heterocyclic diamines in the precursor are selected from the following group: 2,6'diaminopyridine 3,5'-diaminopyridine 3,3'-diaminodiphenyl sulfone 4,4'-diaminodiphenyl sulfone 4,4'-diaminodiphenyl sulfide 3,3'-diaminodiphenyl ether 4,4'-diaminodiphenyl ether meta-phenylene diamine para-phenylene diamine p,p'-methylene dianiline 2,6-diamino toluene 2,4-diamino toluene.
Claim 30
Independent Claim
37 words
A method of preparing a polyimide as defined in any of the preceding claims 1-3 wherein the precursor also contains from 0.015 to 1.5 weight percent of a surfactant capable of enhancing physical properties of the polyimide.
Claim 31
Dependent Claim
28 words
A method of preparing a polyimide as defined in claim 23 wherein the aliphatic diamine in the liquid resin has the formula: ##STR3## where x is approximately 2.6.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-03-27 | 1987-09-26 | 1988-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-27 | 1991-09-26 | 1992-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-27 | 1995-09-26 | 1996-03-27 | $7700.00 | Window Closed / Lapsed |