POLYMETHYLENETEREPHTHALATE FILM AND PROCESS FOR THE PREPERATION THEREOF

摘要

PURPOSE: A biaxially oriented poly(trimethylene terephthalate) film and its preparation method are provided, which film is improved in the flex-crack resistance and the gas blocking and is suitable to the food packing material. CONSTITUTION: The biaxially oriented poly(trimethylene terephthalate: formula) film comprises poly(trimethylene terephthalate) resin; and 0.05-0.50 wt.% of inert particles with the mean particle size of 0.5-0.25 micrometers based on the weight of the resin. The one or both sides of poly(trimethylene terephthalate) film are coated by poly(vinylidene chloride) by the thickness of 2-6 micrometer. Preferably the limiting viscosity of the film is 0.95-1.40 g/dl, and the inert particles are selected from the group consisting of silica, calcium carbonate, alumina and zinc oxide. The method comprises the steps of melt extruding the mixture of poly(trimethylene terephthalate) film and inert particles at 275-290 deg.C to make a sheet; stretching the sheet longitudinally by 1.5-3.5 times at 45-75 deg.C; stretching the sheet horizontally by 1.5-3.5 times at 50-85 deg.C; thermal fixing the sheet at 120-180 deg.C; cooling the sheet at 25-40 deg.C; and coating the one or both sides of the film by using poly(vinylidene chloride).