| 摘要 |
PURPOSE: To obtain a biaxially oriented polyester film which is highly elastic, excellent in surface flatness and suitable for magnetic recording medium by using a polyester chip wherein its polyester fine content is small and its intrinsic viscosity is high. CONSTITUTION: A biaxially oriented polyester film is composed of polyester of 0.7-3.0 (dl/g) intrinsic viscosity [3h]. Its rupture elongation A is at most 200%, and the relation between rupture elongation A and elastic modulus satisfies the expression B>=-1110×log (A)+2850. Thereby, after cooling the obtain polyester under nitrogen gas flow, it is charged into methanol. After sufficiently stirring, it is filtered by using a 50mesh filter. By drying chips on the filter, polyester as the target is obtained. |
