STRETCH BLOW MOLDING PREFORM AND MOLDING METHOD USING THE SAME

PURPOSE: To reduce the using amount of material resin of a plastic bottle and to improve the orientation thickness reduction of the bottom by specifying the ratio of the thickness of a cylindrical and tapered body with a semispherical bottom to that of the bottom and the taper angle of the tapered part. CONSTITUTION: Preform is manufactured by injection molding a thermoplastic resin, and formed of a neck part 1, a body part 2, a closed bottom 3 and a tapered part 4 for connecting the body to the bottom 3. The body 2 is a tapered state in which the diameter is reduced toward the cylindrical bottom as a hole, the body 2 and the bottom 3 are smoothly connected at the inner surface 9 of the preform, and connected via the part 4 in which the outer diameter is reduced toward the bottom at the outer surface of the preform. In this case, the ratio of the thickness 12 d1 of the body 2 to that d2 of the bottom is in the range of 1.0 to 1.5, and the tapered angle θ of the part 4 is in the range of 2 to 12.