US4595548A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing essentially colorless polyimide film containing phenoxy-linked diamines
Assignee: National Aeronautics and Space Administration
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Filing: 1984-08-23
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Granted: 1986-06-17
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Expires: 2004-08-23
Abstract
Abstract An aromatic condensation polyimide film that is approximately 90% transparent at 500 nm, useful for thermal protective coatings and the like, and the processes for preparing same by thermal and chemical conversion are disclosed. An essential feature of the invention for achieving maximum optical transparency films requires utilizing recrystallized and/or sublimated specific aromatic diamines and dianhydride monomers and introducing phenoxy or thiophenyl separator groups and isomeric m,m'- or o,p'-oriented diamines into the polymer molecular structure. The incorporation of these groups in the polymer structure serves to separate the chromaphoric centers and reduce the formation of inter-chain and intra-chain charge transfer complexes which normally cause absorptions in the UV-visible range. The films may be obtained by hand, brushing, casting or spraying a layer of the polyamic acid solutions onto a surface and thermally converting the applied layer to the polyimide or the polyamic acid solution can be chemically converted to the polyimide, subsequentially dissolved in an organic solvent, and applied as a polyimide film layer with the solvent therein thermally removed.
Inventors
- 👤 Anne K. St. Clair
- 👤 Terry L. St. Clair
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:48
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; C08G; C08G73/00; C08G73/06; C08G73/10; C08G73/1003; C08G73/1007; C08G73/1028; C08J3/00; C08J3/02; C08J3/09; C08J3/091; C08J2379/00; C08J2379/04; C08J2379/08
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
159 words
A method for preparing a high temperature stable, highly optically transparent-to-colorless aromatic polyimide film comprising: chemically reacting equimolar quantities of (1) a highly purified aromatic diamine, and (2) a highly purified aromatic dianhydride in a solvent medium to form a high molecular weight polyamic acid solution, at least one of the reacted diamine and the dianhydride containing a separator linking group in the monomer molecular structure, said separator linking group containing at least one phenoxy or thiophenyl unit, said highly purified aromatic diamine being selected from the group consisting of o,p'- and m,m-oriented aromatic diamines, said highly purified aromatic dianhydride being selected from the group consisting of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-oxydiphthalic anhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, applying a controlled thickness film layer of the polyamic acid solution onto a surface, and thermally curing the applied film layer in the temperature range of 250° C. to 300° C. for at least one hour to yield the optically transparent polyimide film layer.
Claim 2
Independent Claim
159 words
A method for preparing a high temperature stable, highly optically transparent-to-colorless aromatic polyimide film comprising: chemically reacting equimolar quantities of (1) a highly purified aromatic diamine, and (2) a highly purified aromatic dianhydride in a solvent medium to form a high molecular weight polyamic acid solution, at least one of the reacted diamine and the dianhydride containing a separator linking group in the monomer molecular structure, said separator linking group containing at least one phenoxy or thiophenyl unit, said highly purified aromatic diamine being selected from the group consisting of o,p'- and m,m-oriented aromatic diamines, said highly purified aromatic dianhydride being selected from the group consisting of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-oxydiphthalic anhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, applying a controlled thickness film layer of the polyamic acid solution onto a surface, and thermally curing the applied film layer in the temperature range of 250° C. to 300° C. for at least one hour to yield the optically transparent polyimide film layer.
Claim 3
Dependent Claim
25 words
The method of claim 1 wherein the highly purified aromatic diamine is selected from the group consisting of recrystallized: o,p'-diaminodiphenyl ether, m,m'-diaminodiphenyl ether, and 1,3-bis(aminophenoxy)benzene.
Claim 4
Dependent Claim
30 words
The method of claim 1 wherein the solvent is distilled prior to use and is selected from one or more of the group consisting of: N,N-dimethylacetamide, N,N'-dimethylformamide, N-methyl-2-pyrrolidone, and dimethylsulfoxide.
Claim 5
Dependent Claim
33 words
The method of claim 1 wherein the applied polyamic film layer is cast onto a glass plate and the recovered cured optically transparent polyimide film is stripped from the glass for use thereof.
Claim 6
Dependent Claim
43 words
The method of claim 1 wherein the applied polyamic acid film layer is approximately 15% w/w solids and is applied by brush coating onto a surface and the cured optically transparent polyimide film layer serves as a thermal protection coating for the surface.
Claim 7
Dependent Claim
67 words
The method of claim 1 wherein the polyamic acid solution is 15% w/w solids and including the further step of diluting the polyamic acid solution by adding additional solvent thereto prior to applying a film layer thereof onto a surface and wherein the applied film layer is sprayed onto the surface and the cured resulting transparent polyimide serves as a thermal protection coating layer for the surface.
Claim 8
Dependent Claim
18 words
A high temperature stable, highly optically transparent-to-colorless aromatic polyimide film prepared according to the method of claim 1.
Claim 9
Independent Claim
156 words
A method for preparing a high temperature stable, highly optically transparent-to-colorless aromatic polyimide film comprising: chemically reacting equimolar quantities of (1) a highly purified aromatic diamine, and (2) a highly purified aromatic dianhydride in a solvent medium to form a high molecular weight polyamic acid solution, at least one of the highly purified, aromatic diamine and the highly purified aromatic dianhydride containing a separator linking group in the monomer molecular structure, said separator linking group containing at least one of phenoxy or thiophenyl units, said highly purified aromatic diamine being selected from the group consisting of o,p'- and m,m'-oriented aromatic diamines, chemically imidizing the polyamic acid solution to recover a fibrous polyimide precipitate, dissolving the polyimide precipitate in a solvent, preparing a film layer of the polyimide solution, and treating the film layer in the temperature range of 100°-300° C. for at least one hour to remove the solvent and recover a highly optically transparent film.
Claim 10
Independent Claim
156 words
A method for preparing a high temperature stable, highly optically transparent-to-colorless aromatic polyimide film comprising: chemically reacting equimolar quantities of (1) a highly purified aromatic diamine, and (2) a highly purified aromatic dianhydride in a solvent medium to form a high molecular weight polyamic acid solution, at least one of the highly purified, aromatic diamine and the highly purified aromatic dianhydride containing a separator linking group in the monomer molecular structure, said separator linking group containing at least one of phenoxy or thiophenyl units, said highly purified aromatic diamine being selected from the group consisting of o,p'- and m,m'-oriented aromatic diamines, chemically imidizing the polyamic acid solution to recover a fibrous polyimide precipitate, dissolving the polyimide precipitate in a solvent, preparing a film layer of the polyimide solution, and treating the film layer in the temperature range of 100°-300° C. for at least one hour to remove the solvent and recover a highly optically transparent film.
Claim 11
Dependent Claim
28 words
The method of claim 8 wherein the chemical imidizing step includes adding a solution of acetic anhydride and pyridine in an organic solvent to the polyamic acid solution.
Claim 12
Dependent Claim
31 words
The method of claim 9 wherein the ratio of ingredients employed in the chemical imidizing step are 0.003 mole acetic anhydride to 0.003 mole pyridine in one millileter of organic solvent.
Claim 13
Dependent Claim
25 words
The method of claim 10 wherein the organic solvent is selected from one or more of the group consisting of: N,N'-dimethylacetamide, N,N'-dimethylformamide, N-methyl-2-pyrrolidone, and dimethylsulfoxide.
Claim 14
Dependent Claim
34 words
The method of claim 8 wherein the polyimide precipitate is wash blended in freshly distilled water, and thoroughly dried for at least six hours at 120° C. prior to being dissolved in the solvent.
Claim 15
Dependent Claim
17 words
The method of claim 8 wherein the polyimide-to-solvent solutions are in the range of 1-40% solids w/w.
Claim 16
Dependent Claim
29 words
The method of claim 8 wherein the film layer is prepared by casting the polyimide solution onto a glass plate and after solvent removal stripped from the glass plate.
Claim 17
Dependent Claim
34 words
The method of claim 8 wherein the film layer is prepared by hand brushing onto a surface to provide a thermal protection coating layer on the surface after solvent removal from the film layer.
Claim 18
Dependent Claim
32 words
The method of claim 8 wherein the film layer is spray coated onto a surface to provide a thermal protection coating layer on the surface after solvent removal from the film layer.
Claim 19
Dependent Claim
18 words
A high temperature stable, highly optically transparent-to-colorless aromatic polyimide film prepared according to the method of claim 8.
References Cited (Backward Citations)
US4214071A
Cited
US4473523A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-06-16 | 1989-12-16 | 1990-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-16 | 1993-12-16 | 1994-06-17 | $3760.00 | Window Closed / Lapsed |
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