US4070433A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Casting films of poly(meta-phenylene isophthalamide) and its copolymers
Assignee: Unitika Ltd
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Filing: 1976-06-16
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Granted: 1978-01-24
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Expires: 1996-06-16
Abstract
Abstract An aromatic polyamide film having a dielectric strength of at least about 150 kv/mm which is useful as an electric insulating material. This film is obtained by casting a solution comprising poly(m-phenylene isophthalamide) or a copolymer thereof and an amide type solvent, drying the cast product to form a film having a residual solvent content of not more than about 60% by weight, immersing the film in an aqueous medium kept at not more than about 20° C, and stretching the resulting wet film containing at least about 5% by weight of the aqueous medium in at least one direction to at least about 1.4 times the original dimension.
Inventors
- 👤 Akira Miyoshi
- 👤 Masanori Masuda
- 👤 Tamihiro Nakayama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:32
CPC Classifications
H; H01; H01B; H01B3/00; H01B3/18; H01B3/30
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
120 words
A process for producing an aromatic polyamide film from a solution comprising an aromatic polyamide in which at least about 50 mol% of its entire structural units are recurring units of the general formula: ##STR3## and an amide type solvent, which comprises casting said solution, drying the cast product to form a film having a residual solvent content of not more than about 60% by weight, immersing the film in an aqueous medium kept at not more than about 20° C, and stretching the resulting wet film containing at least about 5% by weight, based on the weight of the wet film, of the aqueous medium in at least one direction at a stretch ratio of at least about 1.4.
Claim 2
Dependent Claim
120 words
A process for producing an aromatic polyamide film from a solution comprising an aromatic polyamide in which at least about 50 mol% of its entire structural units are recurring units of the general formula: ##STR3## and an amide type solvent, which comprises casting said solution, drying the cast product to form a film having a residual solvent content of not more than about 60% by weight, immersing the film in an aqueous medium kept at not more than about 20° C, and stretching the resulting wet film containing at least about 5% by weight, based on the weight of the wet film, of the aqueous medium in at least one direction at a stretch ratio of at least about 1.4.
Claim 3
Dependent Claim
17 words
The process of claim 1, wherein said amide type solvent is N,N-dimethyl acetamide, N-methyl-2-pyrrolidone, or N,N-dimethyl formamide.
Claim 4
Dependent Claim
14 words
The process of claim 1, wherein said amide type solvent contains an inorganic salt.
Claim 5
Dependent Claim
15 words
The process of claim 3, wherein said inorganic salt is lithium chloride or calcium chloride.
Claim 6
Dependent Claim
17 words
The process of claim 1, wherein said residual solvent content is not more than 50% by weight.
Claim 7
Dependent Claim
16 words
The process of claim 1, wherein said residual solvent content is 20 to 40% by weight.
Claim 8
Dependent Claim
42 words
The process of claim 1, wherein said aqueous medium kept at not more than about 20° C is an aqueous solution containing not more than about 40% by weight, based on the weight of the aqueous solution, of an amide type solvent.
Claim 9
Dependent Claim
17 words
The process of claim 7, wherein said amide type solvent is N,N-dimethyl acetamide, N-methyl-2-pyrrolidone or N,N-dimethyl formamide.
Claim 10
Dependent Claim
19 words
The process of claim 1, wherein said aqueous medium kept at not more than about 20° C is water.
Claim 11
Dependent Claim
24 words
The process of claim 1, wherein the temperature of the aqueous medium in which the film is immersed is not more than 10° C.
Claim 12
Dependent Claim
22 words
The process of claim 1, wherein the content of the aqueous medium in the wet film is at least 20% by weight.
Claim 13
Dependent Claim
38 words
The process of claim 1, wherein said aqueous medium in the wet film is an aqueous solution containing not more than about 40% by weight, based on the weight of the aqueous solution, of an amide type solvent.
Claim 14
Dependent Claim
29 words
The process of claim 12, wherein the amount of the amide type solvent is not more than about 20% by weight based on the weight of the aqueous solution.
Claim 15
Dependent Claim
29 words
The process of claim 12, wherein the amount of the amide type solvent is not more than about 10% by weight based on the weight of the aqueous solution.
Claim 16
Dependent Claim
17 words
The process of claim 12, wherein said amide type solvent is N,N-dimethyl acetamide, N-methyl-2-pyrrolidone or N,N-dimethyl formamide.
Claim 17
Dependent Claim
15 words
The process of claim 1, wherein the aqueous medium in the wet film is water.
Claim 18
Dependent Claim
22 words
The process of claim 1, wherein said wet film is stretched in one direction at a stretch ratio of at least 1.5.
Claim 19
Dependent Claim
22 words
The process of claim 1, wherein said wet film is stretched in one direction at a stretch ratio of at least 2.0.
Claim 20
Dependent Claim
42 words
The process of claim 1, wherein said wet film is biaxially stretched at a stretch ratio of at least 1.3 in one direction and at a stretch ratio of at least 1.5 in another direction at right angles to the first direction.
Claim 21
Dependent Claim
42 words
The process of claim 1, wherein said wet film is stretched axially at a stretch ratio of at least 1.3 in one direction, and at a stretch ratio of at least 2.0 in another direction at right angles to the first direction.
References Cited (Backward Citations)
US3006899A
Cited
US3063966A
Cited
US3094511A
Cited
US3414645A
Cited
US3354127A
Cited
US3696076A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-23 | 1981-07-25 | 1982-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-23 | 1985-07-25 | 1986-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-23 | 1989-07-25 | 1990-01-24 | $7700.00 | Window Closed / Lapsed |