| 摘要 |
PURPOSE:To produce the title film having an excellent dimensional stability and being useful for industrial materials such as tire cord, photographs, magnetic tapes, etc., by melt-spinning or forming a specified copolymer polyester into a fiber or a film, followed by heat-stretching. CONSTITUTION:A dicarboxylic acid component comprising 65-90mol% 4,4'- diphenyldicarboxylic acid and 35-10mol% monosubstituted terephthalic acid (e.g., methylterephthalic acid) is copolymerized with a diol component based on ethylene glycol to obtain a copolymer polyester having an intrinsic viscosity as measured in o-chlorophenol at 35 deg.C>=0.5. This polyester is molten at a temperature of its melting point -350 deg.C, extruded through a film-formation die and quenched at a temperature of room temperature -100 deg.C. The obtained unstretched film is stretched at 100-180 deg.C at an area stretch ratio >=5 in a uniaxial stretching process.
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