Method for forming heat-resistant containers

A method of forming a heat-resistant container, comprising the steps of:

• (a) introducing a primary blow molded article into a heating furnace;
• (b) thermally shrinking the primary blow molded article by exposing the entire circumferential surface of a barrel portion of the primary blow molded article to hot air having a temperature high enough to facilitate crystallization of the primary blow molded article by blowing the hot air longitudinally along the primary blow molded article, wherein said thermally shrinking step further includes reforming the outer diameter of the primary blow molded article in a direction parallel to parting surfaces of mold halves of a secondary blow mold to have a diameter smaller than the transverse width of the cavity of the mold halves by pressing facing sidewalls of the barrel portion of the primary blow molded article inwardly;
• and
• (c) secondary blow molding the thermally shrunk primary blow molded article in a cavity of the secondary blow mold thereby shaping the primary blow molded article into the heat-resistant container.

A method of forming a plurality of heat-resistant containers, comprising the steps of:

• (a) introducing a plurality of primary blow molded articles as a set simultaneously into a heating furnace;
• (b) thermally shrinking the set of primary blow molded articles by exposing the entire circumferential surface of a barrel portion of each of the primary blow molded articles to hot air having a temperature high enough to facilitate crystallization of each primary blow molded article by blowing the hot air longitudinally along the primary blow molded article, wherein said thermally shrinking step includes inserting reforming means for pressing the facing sidewalls of the barrel portion of each primary blow molded article inwardly, along opposite sides of each primary blow molded article in the direction of arrangement of one set of primary blow molded articles, and reforming the outer diameter of each of the primary blow molded articles in a direction parallel to parting surfaces of mold halves of a second blow mold to have a diameter smaller than the transverse width of the cavity of the mold halves;
• and
• (c) secondary blow molding the set of thermally shrunk primary blow molded articles in a cavity of the secondary blow mold composed of the mold halves, thereby shaping the set of primary blow molded articles into the heat-resistant containers,
• wherein said thermal shrinking step further includes heating a plurality of sets of primary blow molded articles placed in the heating furnace, introducing each of the primary blow molded articles into the heatinq furnace after said second blow molding step, discharging a leading set of primary blow molded articles out of the heating furnace, and introducing a new set of primary blow molded articles into the heating furnace.