PLASTIC PREPARATORY MOLDING AND MANUFACTURE OF CONTAINER USING SAME

摘要

PURPOSE:To enhance the strength of the bottom part of a stretched blow molded product by reducing the non-stretched part thereof by forming a stepped part to the outside surface near to the bottom part of a preformed body for biaxial stretching blow molding and making the diameter of the leading end part of the molded body small. CONSTITUTION:The body part 61 of a bottomed cylindrical preformed body 20 obtained by the injection molding of plastic consists of an upper part 62 and a lower end part 63 having a diameter smaller than that of the upper part and the annular stepped part 64 corresponding to the peripheral edge part of the bottom surface of a completed product after blow molding is formed to the boundary of both parts. The lower end part 63 and bottom part 81 of the preformed body 20 are held to stretching temp. and the mouth part thereof is grasped by a mold 30 to arrange the preformed body in a primary blow mold 32 and heated air is blown from a blowoff port 52 simultaneously with the stretching of the preformed body by a stretching rod 50 to obtain a preformed body 22 wherein the lower end part 63 and the bottom part 81 are stretched. Next, the preformed body 22 is arranged in a secondary blow mold 34 and the body part 61 is held to stretching temp. or higher while the bottom part 81 is cooled to the stretching temp. or lower and the bottom part 81 is pushed by the stretching rod 50 and air is blown out from the blowoff port 52. By this method, the body part 61 is biaxially stretched to obtain a molded container.