Double-blown PET bottle shaped container having essentially no residual stress and superior heat resistance

A blow-molded biaxially oriented polyethylene terephthalate resin bottle-shaped container made by the following method to have substantially no residual stress and to have high heat resistance, the method comprising the steps of:

• providing a preform with a neck and a body;
• first biaxial-orientation blow-molding the preform in a first mold at a first temperature to biaxially stretch the preform to form a primary intermediate molded bottle-shaped piece that is larger than the bottle-shaped container and having an area magnification of at least 5 times the preform, the primary intermediate molded bottle-shaped piece having residual stress created by the biaxial stretching;
• causing thermal contraction of the primary intermediate molded bottle-shaped piece at a temperature higher than the first temperature to form a secondary intermediate molded bottle-shaped piece that is substantially equal to or smaller than the bottle shaped container to eliminate residual stress caused by the first blow-molding;
• and
• second blow-molding the secondary intermediate molded bottle-shaped piece in a second mold to form the bottle-shaped container, and wherein said bottle-shaped container formed exhibits essentially no residual stress and also exhibits essentially no shrinkage or deformation when said container contains contents having a temperature of 120.degree. C. and wherein the formation of said primary and secondary pieces results in said double-blown container being capable of containing contents heat treated at temperatures up to 120.degree. C. with essentially no container deformation or shrinkage.

A blow-molded biaxially oriented polyethylene terephthalate resin bottle-shaped container made by the following method to have substantially no residual stress and to have high heat resistance, the method comprising the steps of:

• providing a preform with a neck and a body;
• first biaxial-orientation blow-molding the preform in a first mold at a first temperature to biaxially stretch the preform to form a primary intermediate molded bottle-shaped piece that is larger than the bottle-shaped container, the biaxial stretching creating residual stress in the primary intermediate molded bottle-shaped piece;
• causing thermal contraction of the primary intermediate molded bottle-shaped piece at a temperature higher than the first temperature in the range of 200.degree. to 255.degree. C. to form a secondary intermediate molded bottle-shaped piece that is substantially equal to or smaller than the bottle-shaped container to eliminate residual stress caused by the first blow-molding;
• and
• second blow-molding the secondary intermediate molded bottle-shaped piece in a second mold to form the bottle-shaped container, and wherein said bottle-shaped container formed exhibits essentially no residual stress and also exhibits essentially no shrinkage or deformation when said container contains contents having a temperature of 120.degree. C. and wherein the formation of said primary and secondary pieces results in said double-blown container being capable of containing contents heat treated at temperatures up to 120.degree. C. with essentially no container deformation or shrinkage.

A blow-molded biaxially oriented polyethylene terephthalate resin bottle-shaped container, formed by the following method to have high heat resistance, the method comprising the steps of:

• a) forming a preform having a preliminary shape including a neck and a body;
• b) first biaxial-orientation blow-molding the preform in a first mold to form a primary intermediate molded bottle-shaped piece, wherein the primary intermediate molded bottle-shaped piece has an area magnification from the preform in the range of 5-13 times and a density of 1.36 gm/cc or more, by the steps of
• (i) heating the body of the preform to a temperature that approaches but does not reach a thermal crystallization temperature of polyethylene terephthalate resin, and
• (ii) blow-molding the preform in a blow-mold heated to a temperature in the range of 110.degree. C. to 230.degree. C. to form a primary intermediate molded bottle-shaped piece that is larger than the bottle-shaped container;
• c) causing thermal contraction of the primary intermediate molded bottle-shaped piece to form a secondary intermediate molded bottle-shaped piece to eliminate residual stress in the primary intermediate molded bottle-shaped piece resulting from the first blow, wherein the secondary intermediate molded bottle-shaped piece is substantially equal to or smaller than the bottle-shaped container, by the step of
• heating the primary intermediate molded bottle-shaped piece to a temperature of at least 20.degree. C. greater than the temperature of the mold of the first step of blow-molding;
• and
• d) second blow-molding the secondary intermediate molded bottle-shaped piece in a second mold to form the bottle-shaped container having a small orientation magnification from the secondary intermediate molded bottle-shaped piece, wherein substantially no stress is created when the bottle-shaped container is blow-molded, by the steps of
• (i) placing the secondary intermediate molded bottle-shaped piece in a mold heated to a temperature in the range of 100.degree. C. to 150.degree. C., and
• (ii) blow-molding the secondary intermediate molded bottle-shaped piece to form the bottle-shaped container,
• wherein said bottle-shaped container formed exhibits essentially no residual stress and also exhibits essentially no shrinkage or deformation when said container contains contents having a temperature of 120.degree. C. and wherein the formation of said primary and secondary pieces results in said double-blown container being capable of containing contents heat treated at temperatures up to 120.degree. C. with essentially no container deformation or shrinkage.

A blow-molded biaxially oriented polyethylene terephthalate resin bottle-shaped container, formed by the following method to have high heat resistance, the method comprising the steps of:

• biaxial-orientation blow molding a preform in a first mold to biaxially stretch the preform to form a primary intermediate molded bottle-shaped piece that is larger than the bottle-shaped container;
• and
• forming the bottle-shaped container from the primary intermediate molded bottle-shaped piece;
• wherein the primary intermediate molded bottle-shaped piece is heated to be forcibly thermally contracted to form a secondary intermediate molded bottle-shaped piece that is substantially equal to or smaller than the bottle-shaped container;
• and
• further wherein the secondary intermediate molded bottle-shaped piece is blow molded in a second mold to form the bottle-shaped container,
• wherein said bottle-shaped container formed exhibits essentially no residual stress and also exhibits essentially no shrinkage or deformation when said container contains contents having a temperature of 120.degree. C. and wherein the formation of said primary and secondary pieces results in said double-blown container being capable of containing contents heat treated at temperatures up to 120.degree. C. with essentially no container deformation or shrinkage.

A blow-molded biaxially oriented polyethylene terephthalate resin bottle-shaped container, formed by the following method to have high heat resistance, the method comprising the steps of:

• heating a preform at a temperature that approaches but does not reach the thermal crystallization temperature of the polyethylene terephthalate resin;
• biaxial-orientation blow molding the preform in a primary blow mold at a primary blow mold temperature to biaxially stretch the preform to form a primary intermediate molded bottle-shaped piece that is larger than the bottle-shaped container;
• and
• forming the bottle-shaped container from the primary intermediate molded bottle-shaped piece;
• wherein the primary intermediate molded bottle-shaped piece is heated to a temperature higher than the primary blow mold temperature to thermally shrink and eliminate residual stress from the primary intermediate bottle-shaped piece to form a secondary intermediate molded bottle-shaped piece that is substantially equal to or smaller than the bottle-shaped container;
• and
• further wherein the secondary intermediate molded bottle-shaped piece is blow molded in a secondary blow mold to form the bottle-shaped container,
• wherein said bottle-shaped container formed exhibits essentially no residual stress and also exhibits essentially no shrinkage or deformation when said container contains contents having a temperature of 120.degree. C. and wherein the formation of said primary and secondary pieces results in said double-blown container being capable of containing contents heat treated at temperatures up to 120.degree. C. with essentially no container deformation or shrinkage.