JPH0681700B

PURPOSE:To obtain a biaxially oriented plastic bottle superior in the appearance such as smoothness or glossiness or shape reproducibility, by method wherein a bottom mold is arranged within a split mold in a moving direction of an orientation bar and a gap where circulation of gas is free is formed between the bottom mold and split mold. CONSTITUTION:A core mold is made to support a preform 13, inserted into a cavity position of a split mold, a bottom mold 2 is lowered and fitted closely over the bottom part 16 of the preform 13, under a state where blow molds 1a, 1b are broken, and the bottom mold 2 is at a raising position. Under this condition, a gap 17 enabling free circulation of air is formed between a bottom mold elevating shaft 9 and opening part 11. An orientation bar 3 is inserted into the perform 13 by piercing through the core mold, extension and orientation of the preform are started, a fluid is blown into the preform 13 which is being extended through a passage within an orienting machine or a passage between the orientation bar 3 and core mold and the preform 13 is expanded and oriented in a circumferential direction. Then during this blow molding, air within a cavity 4 is exhausted quickly through the gap 17.