| 摘要 |
PURPOSE:To achieve a high order crystallization and the reduction of residual strain and to enhance heat resistance and dimensional stability, by a method wherein a bottomed preform is subjected to biaxial stretching blow molding in a high temp. mold and the molded one is thermally set at specific temp. before taken out from the mold at temp. higher than the glass transition temp. of the material used in molding. CONSTITUTION:A bottomed preform composed of polyethylene terephthalate (PET) is subjected to biaxial stretching blow molding in a high temp. mold and the molded body is thermally set in the high temp. mold at 135 deg.C or higher, especially, at 140-230 deg.C. Subsequently, the thermally set molded body is taken out of the mold at temp. wherein the surface temp. of said molded body is higher than the glass transition temp. (Tg=69 deg.C) of PET and the shape thereof can be substantially hold, pref., at 75-120 deg.C, most pref., at 80-115 deg.C. At last, the taken out molded body is annealed in a room temp. atmosphere to shrink freely. By this free shrinkage, the residual stress in the wall of the molded body is relaxed and a final container is excellent in dimensional stability and an appearance characteristic. |
