PURPOSE: To prevent the protrusion of the bottom part which spoils the self-standing stability at the time of a heat-sterilization of a container from generating by crystallizing mainly the vicinity of the central part of the bottom part and an area being closer to the central part of trough lines, wherein a creep deformation is easy to generate due to the increase in an internal pressure at the time of heat-sterilization.
CONSTITUTION: After reheating a preform which is obtained by injection-forming of PET, the preform is arranged in a blow-forming die, and is stretched in the peripheral direction by air blowing while stretching in the axial direction to perform a biaxially stretching blow-forming, and a self-standing container of which five leg parts are expanded in the radial directions around a bottom of the central part 3 with an equal interval is formed. For such a self-standing container, the bottom central part 3, its peripheral part 4 and areas 6A of trough line parts being closer to the bottom central part are crystallized by putting the self-standing container in an upper recessed part of a shielding plate 8a, and heating the bottom part of the container by an infrared ray heater. The shielding plate 8a has a slit 9a, and the radiant heat of the infrared ray heater passes through the slit 9a and reaches the bottom part of the container, and crystallizes the desired parts.
URANO TOMOHIRO
NITTA AKIRA
Next Patent: HEAT RESISTANT AND PRESSURE RESISTANT SELF-STANDING CONTAINER