| 摘要 |
A parison of thermoplastic resin to be particularly used to be subsequently blow molded to become a plastic bottle has an upper portion (H), a middle portion (L) and an end portion (N). The middle portion has, on its lower side near the terminal portion, a lower sub-portion (M) which has a thickness that is variable and smaller with respect to the wall thickness of the parison in the middle portion, with a profile in the shape of a downward narrowing frustum of a cone. Preferably, the thickness in the lower sub-portion (M) is decreased by at least 12% with respect to the thickness of the remaining middle portion of the parison, and the angle between the sides of the profile in the shape of a frustum of a cone and the axis of symmetry is between 5° and 10°. The advantages are broader process tolerances, elimination of heat conditioning treatments, reduction in resin usage.
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