The invention discloses a thermoshrinkable
polyester film and a preparation method thereof. The preparation method comprises steps as follows: various
polyester raw materials subjected to dust removal respectively enter storage bins, are respectively metered by an agravic weigher according to the proportion, simultaneously enter an inlet of a double screw extruder, are subjected to
melt extrusion by a sandwich layer double screw extruder and two
surface layer double screw extruders, and form a
casting piece through a three-layer co-
extrusion die head; the
casting piece is respectively subjected to longitudinal stretching and lateral stretching, wherein the longitudinal stretching comprises a preheating zone, a stretching zone, a thermal setting zone and a cooling zone, and the thermal setting zone of the lateral stretching is more than 15m long; and the
casting piece is subjected to traction rolling to obtain the thermoshrinkable
polyester film. By adopting the proportioning mode of directly feeding after accurate metering by people, the instantaneous addition error range of various materials is at most 1%; and the material is biaxially stretched, so that the produced film has the advantages of greatly higher density, strength and uniformity, lower longitudinal shrinkage and lateral low-temperature shrinkage, and especially higher
ductility and thermoshrinkable uniformity.