Casting films of poly(meta-phenylene isophthalamide) and its copolymers
AssigneeUnitika Ltd.
InventorsAkira Miyoshi, Masanori Masuda, Tamihiro Nakayama
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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.degree. 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.
Claims20
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.degree. 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.
Dependencies are inferred from the claim text.