PURPOSE: To improve easiness of cutting and heat-sealing property by melting polyester having specified limiting viscosity and melt viscosity and extruding it through the circular die maintained over the melting point of polyester and thereafter blowing it at blow ratio of more than 1.
CONSTITUTION: Thermoplastic polyester having more than 0.72 limiting viscosity and more than 6,000 poise melt viscosity at 265°C is melted. Molten polyester is extruded from the circular die of which die temperature is maintained over the melting point of thermoplastic polyester, thereafter low-oriented film of less than 50μ thickness is manufactured by being blowed at blow ratio of more than 1 and cooled, taken up. Obtained polyester film has 4W20kg/mm2 tensile strength at break, over 200% elongation, heat-sealing property under 160°C, torsional formability and easiness of cutting.
TAKE TSUGUO
YAMANE YUKIO
KUMADA SABUROU
