Method of producing biaxially stretched polyester bottles

Abstract

In effecting the stretching by using a stretch rod in a method of producing a biaxially stretched polyester bottle, the air is blown into the preform at such a flow rate that the preform does not come in contact with the stretch rod but the end thereof and does not come in contact with the surfaces of the mold, either. There can be produced a biaxially stretched polyester bottle having an average thickness of about 0.05 to about 0.2 mm or having a further decreased thickness using a resin in decreased amounts and having a decreased weight without developing burst or whitening caused by over-stretching, without forming ring-like thick portion yet maintaining a good yield and efficiency.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of producing biaxially stretched polyester bottles. More specifically, the invention relates to a method of producing biaxially stretched polyester bottles, which is capable of forming thin polyester bottles preventing burst and suppressing the formation of ring-like thick portions maintaining good productivity.BACKGROUND ART

[0002] Biaxially stretched polyester bottles have heretofore been known being obtained by biaxially stretch-blow-forming the preforms made of a polyester resin such as a polyethylene terephthalate, and have been widely used as containers for containing a variety of kinds of beverages, foods, liquid detergents and the like owing to their excellent transparency, surface luster, shock resistance and gas barrier property.

[0003] Biaxially stretched polyester bottles used for containing beverages, usually, have an average thickness of about 0.25 to 0.30 mm. From the standpoint of lowering the cost and decrea...

Examples

example 1

[0057]A preform having a length of 52 mm and a thickness in the body wall of 3.1 mm (resin amount of 19 g) was heated in a heating device (without inner heating device 18b) shown in FIG. 3(B) for 56 seconds, so that the temperature was 115° C. on the outer surface of the preform and 117° C. on the inner surface thereof.

[0058]By using a stretch-blowing apparatus schematically shown in FIG. 2, the thus heated preform was stretched by using a stretch rod at a speed of 200 mm / sec. up to a position of 95% of the distance of from under the support ring down to the grounding surface and, at the same time, the air was blown as a pre-blow, the air being adjusted to possess a temperature of 200° C. and a pressure of 0.07 MPa.

[0059]After the end of stretching by using the stretch rod, the air was blown as a main blow, the air being adjusted to possess a temperature of 200° C. and a pressure of 2 MPa to effect such a stretching that a longitudinal stretching ratio was 4.5 times, a transverse st...

example 2

[0061]A preform having a length of 77 mm and a thickness in the body wall of 2.4 mm (resin amount of 19 g) was heated by the same method as that of Example 1 for 40 seconds, so that the temperature was 105° C. on the outer surface of the preform and 107° C. on the inner surface thereof.

[0062]By using the same stretch-blowing apparatus as that of Example 1 and by effecting the pre-blow and the main blow under the same conditions, the thus heated preform was so stretched that a longitudinal stretching ratio was 3.7 times, a transverse stretching ratio was 4.5 times and a volume ratio was 105 times to obtain the shape of the final article. After the end of stretching, the thermal setting was effected at a temperature of 70° C. followed by cooling. There were produced 1000 polyester bottles each having a capacity of 2000 mL.

[0063]The number of the bottles that developed any one of whitening due to over-stretching, burst, thermal whitening or ring-like thick portion was 0 (occurrence fac...

TECHNICAL FIELD

[0001] The present invention relates to a method of producing biaxially stretched polyester bottles. More specifically, the invention relates to a method of producing biaxially stretched polyester bottles, which is capable of forming thin polyester bottles preventing burst and suppressing the formation of ring-like thick portions maintaining good productivity.BACKGROUND ART

[0002] Biaxially stretched polyester bottles have heretofore been known being obtained by biaxially stretch-blow-forming the preforms made of a polyester resin such as a polyethylene terephthalate, and have been widely used as containers for containing a variety of kinds of beverages, foods, liquid detergents and the like owing to their excellent transparency, surface luster, shock resistance and gas barrier property.

[0003] Biaxially stretched polyester bottles used for containing beverages, usually, have an average thickness of about 0.25 to 0.30 mm. From the standpoint of lowering the cost and decrea...

Examples

example 1

[0057]A preform having a length of 52 mm and a thickness in the body wall of 3.1 mm (resin amount of 19 g) was heated in a heating device (without inner heating device 18b) shown in FIG. 3(B) for 56 seconds, so that the temperature was 115° C. on the outer surface of the preform and 117° C. on the inner surface thereof.

[0058]By using a stretch-blowing apparatus schematically shown in FIG. 2, the thus heated preform was stretched by using a stretch rod at a speed of 200 mm / sec. up to a position of 95% of the distance of from under the support ring down to the grounding surface and, at the same time, the air was blown as a pre-blow, the air being adjusted to possess a temperature of 200° C. and a pressure of 0.07 MPa.

[0059]After the end of stretching by using the stretch rod, the air was blown as a main blow, the air being adjusted to possess a temperature of 200° C. and a pressure of 2 MPa to effect such a stretching that a longitudinal stretching ratio was 4.5 times, a transverse st...

example 2

[0061]A preform having a length of 77 mm and a thickness in the body wall of 2.4 mm (resin amount of 19 g) was heated by the same method as that of Example 1 for 40 seconds, so that the temperature was 105° C. on the outer surface of the preform and 107° C. on the inner surface thereof.

[0062]By using the same stretch-blowing apparatus as that of Example 1 and by effecting the pre-blow and the main blow under the same conditions, the thus heated preform was so stretched that a longitudinal stretching ratio was 3.7 times, a transverse stretching ratio was 4.5 times and a volume ratio was 105 times to obtain the shape of the final article. After the end of stretching, the thermal setting was effected at a temperature of 70° C. followed by cooling. There were produced 1000 polyester bottles each having a capacity of 2000 mL.

[0063]The number of the bottles that developed any one of whitening due to over-stretching, burst, thermal whitening or ring-like thick portion was 0 (occurrence fac...

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