| 摘要 |
PURPOSE:To produce a film having excellent heat resistance and electrical insulating properties, by casting an optically anisotropic dope contg. a poly(p- phenyleneterephthalamide), rendering it optically isotropic, treating the resulting film with an alkali, washing it with warm water and drying it. CONSTITUTION:An optically anisotropic dope obtd. by dissolving 10-20wt% poly(p-phenyleneterephthalamide) having a relative viscosity of 3.5 or above in 95wt% or higher sulfuric acid is filtered and deaerated. While keeping its optical anisotropy, it is cast on a support and subjected to water absorption and/or heating treatments to render the dope optically isotropic and then coagulated by immering it in a coagulating liquid (e.g., water) at 15 deg.C, thus obtaining a film. The film is treated with an a.q. soln. of 0.1-30wt% alkali, immersed in warm water at 40 deg.C or above, irradiated with ultrasonic wave and washed. If desired, the film is orientated mono- or biaxially at a draw ratio of 1.01-1.4. While preventing the film from shrinking, it is dried to obtain a film having tensile elongation of 8% or above in all, directions, an ash content of 0.03wt% or below and a void content of one void/mm<2> or below.
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