VENT TYPE TWO STAGE EXTRUSION EQUIPMENT WITH DIFFERENT BORES

摘要

PURPOSE:To make it possible to stabilize the discharge rate of resin and to extrude resin homogeneously by a method wherein a venting hole is provided in the supplying section of the cylinder of a downstream side extruder and the relation of the cylinder bore of an upstream side or a first extruder and that of the downstream side or a second extruder is put within a specified range. CONSTITUTION:The relation of the bore d1 of a first cylinder 11 and the bore d2 of a second cylinder 21 is d1/d2<1 and d2/d1=1-1.5. The resin which is turned into semi-molten state by a first extruder 10 is supplied from a discharge port 14 through a connecting passage 15 to a feed opening 25 and passed through a supplying section 33 under the state being heated while being conveyed to downstream side in order to remove generated gas through a venting hole 32 by means of a vacuum pump 40. On the other hand, the vented molten resin is further kneaded by a second screw shaft 22 and supplied through an extruding port 26 to a die 30. The amount of resin to supply to the die is set by the rotational frequency of the second screw shaft 22 and kept by changing the rotational frequency of the screw shaft 12 of the first extruder 10 and by regulating a pressure control valve.