| 摘要 |
<p>PROBLEM TO BE SOLVED: To produce a PET bottle prevented from the core shift of a bottle bottom part and capable of obtaining excellent self-stability by two-stage blow molding. SOLUTION: A preform 11 is subjected to blow molding to form a primary molded bottle 17 equipped with a body part 17a and a bottom part 17b, characterized by that the bottom part 17b is equipped with flat parts 29, 30 and a central part 31 protrudes into the bottom part 17a and larger than a final product. The body part 17a is heated to be freely shrunk to form a shrunk bottle 19 equipped with a flat earth part 20 and the recessed part 21 expanded into the body part inside the earth part 20. The shrunk bottle 19 is subjected to blow molding to form a secondary molded bottle 26 as the final product. Blow molding is performed so that the ratio r2 /r1 of the outer diameter r1 of the bottom part 17b of the primary molded bottle 17 to the outer diameter r2 of the max. part connected to the bottom part 17b of the body part 17a rising from the outer periphery of the flat part 30 becomes 1.1-1.8, pref., 1.3-1.6. The flat parts 29, 30 are taper parts inclined toward the center of the bottom part 17b.</p> |
