METHOD OF MOLDING INFLATION FILM

PURPOSE:To enable stable manufacture of a film which has little nonuniform thickness in a circumferential direction and is homogeneous, by a method wherein presetting and control of the temperatures which are different from each other in the circumferential and a longitudinal directions of an annular die are applied to the annular die, a quantity of synthetic resin to be discharged is controlled and control of nonuniform thickness of a synthetic film in the circumferential direction is applied to the film. CONSTITUTION:A mandrel 2 and die 2 body 1 are made presettable and controllable of the temperatures which are different form each other at each of heater parts by heaters 4-10 fitted through division. Molten resin extruded through an extruding machine is dispersed in a circumferential direction of an annular die 12 at a spiral part 30 having a plurality of spiral grooves 3 through an inlet part 11 of a spiral and discharged outside of the die through a lip gap part 13 of the die 12. A nonuniform thickness control bolt 14 controls the lip gap part 13 mechanically. The heaters 7-10 are capable of making presetting and control of the temperatures which are different from each other in the circumferential direction of the die 12 and when a flow of the resin is varied in the circumferential direction, flow control is performed by changing a temperature presetting pattern to uniformize the flow in the circumferential direction.