| 摘要 |
PURPOSE:To obtain polyester film of a high young's modulus by a method wherein polyester having a property providing optically anisotropical molten material is extruded from a slit at a temperature higher than the temperature giving the minimum melting viscosity to make film. CONSTITUTION:Polyester having a property providing optically anistropical molten material is melted and extruded at a temperature higher than the temperature giving the minimum melting viscosity. The preferable melting extruding temperature is at least twenty degrees higher than the temperature indicating the minimum point. Temperature at which melting viscosity inidcates the minimum point differ according to the composition and polymerization of polyester and generally are centered at 330-400 deg.C. The film from the extrusion slit is oriented at first in the direction of machine axis and then in the direction at a right angle to the machine axis. In this way it is possible to obtain the polyester film having a high young's modulus, a high strength, uniform thickness, dimensional stability. |
