Heat resistant and biaxially stretched blow-molded plastic container having a base movable to accommodate internal vacuum forces and issued from a double-blow process

A heat-resistant and biaxially stretched blow-molded plastic container issued from a double-blow process, the container comprising a base movable to accommodate vacuum forces generated within the container, thereby decreasing the volume of the container, wherein the base comprises a push-up portion, and first and second parting lines that are separated from one another by a gap, and that are extending on opposite sides of the push-up portion, and at least one or more of the following:

• (i) the distance between each parting line and a center of the base is not more than 20 mm;
• (ii) the distance between the first and second parting lines is not more than 40 mm;
• and/or
• (iii) the distance between the first and second parting lines is less than 50% of the transverse dimension of the base measured between the two outermost points of the parting lines.

A method for double-blow molding a heat-resistant plastic container, comprising:

• (a) providing a plastic preform in the mold cavity of a primary blow mold that includes a mold cavity defined by a pair of mold halves and a base mold, the mold cavity including a bottom wall formed by a bottom part of each mold half, and the base mold including a protruding centering portion that protrudes inside the mold cavity through said bottom wall,
• (b) biaxially stretch blow molding the preform inside the mold cavity to form a primary biaxially stretched container having a base including a pushup portion molded by the protruding centering portion of the primary blow mold and first and second parting lines formed in the contact plane of the two mold halves, separated from one another by a gap, extending on opposite sides of the pushup portion,
• (c) heating the primary biaxially stretched container inside or outside the primary blow mold to make the primary biaxially stretched container shrink and to obtain a secondary shrunk container,
• (d) providing said secondary shrunk container in a secondary blow mold,
• (e) blow molding the secondary shrunk container inside the secondary blow mold to form a final biaxially stretched and heat-resistant container including a base that is movable to accommodate vacuum forces generated within the container thereby decreasing the volume of the container, said base including a movable wall including said pushup portion and said first and second parting lines, and the stretching of the base inside the secondary blow mold being sufficiently small to obtain one or more of the following:
• (i) a distance between each parting line and a center of the base of not more than 20 mm;
• (ii) a distance between the two parting lines of not more than 40 mm;
• or and/or
• (iii) a distance between the two parting lines of less than 50% of the transverse dimension of the base measured between the two outermost points of the parting lines.