JP3522043B2 - Polyester, preform and biaxially stretched bottle made of polyester, and method for producing polyester biaxially stretched bottle - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester, a preform and a bottle made of the polyester, and a method for producing a polyester biaxially stretched bottle. More specifically, the crystallization rate is high, and the gas barrier property, transparency and The present invention relates to a polyester having excellent heat resistance, a preform made of this polyester, and a biaxially stretched bottle, and a method for producing a polyester biaxially stretched bottle having excellent gas barrier properties, transparency, and heat resistance.

[0002]

BACKGROUND OF THE INVENTION Saturated polyesters such as polyethylene terephthalate are widely used as containers such as bottles because of their excellent gas barrier properties, transparency and mechanical strength. In particular, the bottle obtained by biaxially stretch blow molding polyethylene terephthalate has excellent transparency, mechanical strength, heat resistance, and gas barrier property,
Juice, soft drinks, has been widely used as a beverage Filling containers such as carbonated beverages (PET bottle). Such bottles are generally injection-molded with saturated polyester to form a preform having a spout and a body, and then the preform is inserted into a mold having a predetermined shape and stretch blow-molded. It is manufactured by stretching the barrel to obtain a bottle having a spout and a stretched barrel.

Such polyester bottles, particularly polyester bottles used for beverages such as juices, are required to have heat resistance capable of being subjected to heat sterilization treatment of the contents. Heat set) to improve heat resistance.

[0004] In the polyester bottle obtained as described above, the spout portion is unoriented, it is inferior in mechanical strength and heat resistance when compared to stretched barrel.
For this reason, the cap of the preform is usually heated and crystallized before blow molding, or the cap of the bottle obtained by blow molding is heated and crystallized to obtain mechanical strength and heat resistance of the cap . And so on.

By the way, in recent years, bottles manufactured from polyester resins (particularly polyethylene terephthalate) have tended to be downsized. In the case of such small bottles,
Since the area in contact with the bottle body per unit volume becomes large, the effect on the contents due to gas loss or permeation of oxygen from the outside becomes significant, and the storage period of the contents is reduced. For this reason, the appearance of polyester bottles, which are more excellent in gas barrier properties than before, is desired.

Further, in recent years, it has been required to shorten the production time of bottles produced from polyester resin (particularly polyethylene terephthalate) and improve the productivity.
As a method of shortening the bottle manufacturing time, a method of shortening the crystallization time of the spout and the heat setting time of the bottle are effective.

However, in general, the crystallization time of the spout part ,
When the heat setting time of the bottle body is shortened, the mechanical strength and heat resistance of the obtained bottle are lowered. Therefore, it is necessary to use polyester having a high crystallization rate in order to shorten the crystallization time of the spout and the heat setting time of the bottle body. As such a polyester having a high crystallization rate, a polyester resin composition composed of a raw material polyester and a repropolyester is known. Here, the "raw polyester" refers to a polyester produced from a dicarboxylic acid and a diol and having no history of being molded into a bottle, a preform, etc. by passing through a molding machine in a heating and melting state, and the "repropolyester" is ,
A polyester obtained by passing such a raw material polyester through a molding machine at least once in a heat-melted state and pulverizing the obtained polyester molded body.

However, this polyester resin composition has a high crystallization rate and can perform heat crystallization in a short time, but on the other hand, there is a problem that the transparency of the obtained bottle is lowered.

Therefore, it is desired to develop a polyester capable of obtaining a molded product such as a bottle having a high heat crystallization rate and excellent transparency and gas barrier property, and a preform made of such a polyester. Further, the advent of a biaxially stretched bottle and a method for producing a polyester biaxially stretched bottle using such a polyester is desired.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a polyester having a high crystallization rate and excellent gas barrier properties, transparency and heat resistance. Has an aim.

It is another object of the present invention to provide a preform made of the above polyester and a biaxially stretched bottle having excellent gas barrier properties, transparency and heat resistance.

Further, the present invention is a method for producing a polyester biaxially stretched bottle capable of producing a bottle excellent in gas barrier property, transparency and heat resistance, and excellent in gas barrier property, transparency and heat resistance. It is an object of the present invention to provide a method for producing a polyester biaxially stretched bottle, which can produce such a bottle with high productivity.

[0013]

The polyester according to the present invention comprises a dicarboxylic acid unit containing terephthalic acid and isophthalic acid as main components, and a diol unit containing ethylene glycol and a polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms as main components. Wherein the terephthalic acid unit is 99 to 85% by weight, the isophthalic acid unit is 1 to 15% by weight, the diol structural unit is an ethylene glycol unit 99.999% by weight to 90% by weight, and the carbon number is 0.002 polyalkylene glycol units having 2 to 10 alkylene chains
It is in the range of 1 to 10% by weight.

In the present invention, the polyalkylene glycol preferably has a degree of polymerization (n) of 5 to 50. Further, the polyalkylene glycol is preferably polytetramethylene glycol.

The polyester of the present invention can form a molded article such as a bottle excellent in gas barrier property, transparency and heat resistance. In addition, since the heating crystallization rate is high, it is possible to crystallize the mouth part of the preform or the mouth part of the bottle at a high speed. Therefore, from this polyester, gas barrier properties, transparency and heat resistance are excellent, Moreover, a bottle having excellent mechanical strength and heat resistance of the spout can be manufactured with high productivity.

The preform and the biaxially stretched bottle according to the present invention are characterized by being made of the above polyester. The biaxially stretched bottle of the present invention has a carbon dioxide permeability coefficient of 15.0 cc · mm / m 2 · day · a in the bottle body.
It is desirable that it is tm or less.

The biaxially stretched bottle of the present invention has excellent gas barrier properties, transparency and heat resistance. The method for producing a polyester biaxially stretched bottle according to the present invention, a preform is produced from the polyester as described above, then after heating this preform, a biaxially stretch blow molded to form a stretched bottle, and further The stretched bottle is characterized by being held in a mold at a temperature of 100 ° C. or higher.

In the present invention, the preform mouth plug portion may be heated and crystallized before the biaxial stretch blow molding, or the bottle mouth plug portion may be heated and crystallized after the biaxial stretch blow molding. According to the method for producing a polyester biaxially stretched bottle of the present invention, the carbon dioxide permeability coefficient of the bottle body is 15.0 c.
A polyester biaxially stretched bottle having c · mm / m 2 · day · atm or less is obtained.

The method for producing a polyester biaxially stretched bottle according to the present invention can produce a bottle excellent in gas barrier property, transparency and heat resistance. Further, the method for producing a polyester biaxially stretched bottle according to the present invention, a gas barrier property, excellent transparency and heat resistance, to produce a bottle excellent in mechanical strength and heat resistance of the plug portion with good productivity. You can

[0020]

DETAILED DESCRIPTION OF THE INVENTION The polyester, the preform made of the polyester, the biaxially stretched bottle, and the method for producing the polyester biaxially stretched bottle according to the present invention will be specifically described below.

The polyester according to the present invention comprises a dicarboxylic acid unit containing terephthalic acid and isophthalic acid as main components, and a diol unit containing ethylene glycol and a polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms as a main component. And the terephthalic acid unit in the dicarboxylic acid constitutional unit is 99 to 85% by weight,
Isophthalic acid unit is 1 to 15% by weight and diol constitutional unit is ethylene glycol unit 99.999% by weight
To 90% by weight, and the polyalkylene glycol unit having an alkylene chain having 2 to 10 carbon atoms is in the range of 0.001 to 10% by weight.

The dicarboxylic acid and diol will be described below. Dicarboxylic acid The dicarboxylic acid contains terephthalic acid or its ester derivative (for example, lower alkyl ester, phenyl ester, etc.) as a main component, and contains isophthalic acid in a specific ratio.

Isophthalic Acid In the present invention, the constitutional unit derived from isophthalic acid or its ester derivative in the polyester is 1 to 15% by weight, preferably 2 to 12% by weight, based on the total constitutional units derived from dicarboxylic acid. , And more preferably 4
It is preferably in the range of 10 to 10% by weight from the viewpoint of excellent thermal stability and gas barrier property during molding.

Other Dicarboxylic Acids The polyester of the present invention may contain, as a dicarboxylic acid component, terephthalic acid or its ester derivative and a dicarboxylic acid other than isophthalic acid in an amount of 15 mol% or less. Specific examples of the dicarboxylic acid other than terephthalic acid include phthalic acid, naphthalenedicarboxylic acid,
Aromatic dicarboxylic acids such as diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid; Aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid and decanedicarboxylic acid; Alicyclic rings such as cyclohexanedicarboxylic acid Group dicarboxylic acids and the like.

The dicarboxylic acid other than terephthalic acid may be an ester derivative thereof. Further, these may be a combination of two or more kinds. Diol The diol contains ethylene glycol as a main component and contains polyalkylene glycol having an alkylene chain having 3 to 10 carbon atoms in a specific ratio.

Polyalkylene glycol Polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms is a conventionally known polyalkylene glycol, and such polyalkylene glycol is
It is obtained by cocondensing an alkylene glycol having 2 to 10 carbon atoms by a known method.

The polyalkylene glycol preferably has a degree of polymerization (n) of 5 to 50, preferably 10 to 45. Specific examples of such polyalkylene glycols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyheptamethylene glycol, polyhexamethylene glycol, and polyoctamethylene glycol. Of these, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, and polyoctamethylene glycol are preferable because of their excellent effect of improving gas barrier properties, and polytetramethylene glycol is particularly preferable.

In the present invention, the structural unit derived from the polyalkylene glycol in the polyester is 0.001 to 10% by weight, preferably 0.01 to 8% by weight, based on the total structural units derived from the diol. , And more preferably in the range of 0.1 to 6% by weight.

The amount of polyalkylene glycol is 0.00
If it is less than 1% by weight, the gas barrier property and temperature rising crystallization rate of the polyester may be insufficient, while if it exceeds 10% by weight, the transparency and thermal stability of the polyester may be insufficient. is there.

Other diols diols include ethylene glycol and 2 carbon atoms.
Having an alkylene chain of 10 to 10 and a degree of polymerization (n) of 5 to 50
The diol other than the polyalkylene glycol may be contained in an amount of 15 mol% or less.

Ethylene glycol and the number of carbon atoms is 2
Specific examples of the diol other than the polyalkylene glycol of 10 include diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol (propylene glycol), butanediol, pentanediol, neopentyl glycol, hexamethylene glycol and dodecamethylene. Aliphatic glycols such as glycols; alicyclic glycols such as cyclohexanedimethanol; aromatic diols such as bisphenols and hydroquinone.

These diols may be ester derivatives thereof. Further, these may be a combination of two or more kinds. Furthermore, the polyester according to the present invention optionally contains a small amount of a structural unit derived from a polyfunctional compound such as trimesic acid, pyromellitic acid, trimethylolethane, trimethylolpropane, trimethylolmethane, and pentaerythritol, for example, 2 It may be contained at a ratio of not more than mol%.

The polyester according to the present invention is produced from the above-mentioned dicarboxylic acid and diol by a conventionally known production method. Such polyesters are substantially linear, which is confirmed by the fact that they dissolve in o-chlorophenol.

The polyester of the present invention has an intrinsic viscosity (IV) measured in o-chlorophenol at 25 ° C. of usually 0.3 to 1.5 dl / g, preferably 0.5 to 1.5 d.
It is preferably 1 / g.

The polyester of the present invention has a half-crystallization time of 10 to 400 seconds, preferably 60 to 300 seconds. The semi-crystallization time is measured as described below.

The polyester according to the present invention may contain, if necessary, additives usually added to the polyester, such as a colorant, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant and a lubricant. Good.

The polyester according to the present invention can be used as a material for various molded products such as preforms, bottles, (stretched) films and sheets. Since the polyester according to the present invention has a high crystallization speed, for example, when molding a bottle, the time for heating and crystallizing the mouth part of the preform or the mouth part of the bottle is increased. It is possible to shorten the length and efficiently manufacture a bottle having excellent mechanical strength and heat resistance of the spout .

Preform and Biaxially Stretched Bottle The preform according to the present invention can be obtained by, for example, injection molding or extrusion molding the above polyester.

The bottle according to the present invention is obtained by biaxially stretch blow molding the above polyester and then heat setting. Such a bottle may be a bottle obtained by heating and crystallizing the plug part of the preform and then biaxially stretch-blow molding, or biaxially without heating and crystallizing the plug part of the preform. A bottle obtained by performing stretch blow molding to manufacture a bottle and then heating and crystallizing the mouth plug of the bottle may be used.

In the method for producing a polyester biaxially stretched bottle according to the present invention, a preform is produced from the polyester as described above, and then this preform is heated and biaxially stretch blow molded to form a stretched bottle. Further, the bottle is held in a mold having a temperature of 100 ° C. or higher.

More specifically, first, a preform is produced from the above polyester, and the preform is produced by a conventionally known method such as injection molding or extrusion molding. Next, this preform is 70-150
After heating to 80 ° C., preferably 80 to 140 ° C., biaxial stretch blow molding is performed to mold a stretched bottle.

The draw ratio in the biaxial stretch blow molding is
Area draw ratio (longitudinal draw ratio x horizontal draw ratio) of 6 to 15
It is desirable that the number is twice, preferably 7 to 12 times. Further, the obtained stretched bottle is heat set. Heat set at 100 to 240 ° C., preferably 110 to 22
At a mold temperature of 0 ° C., particularly preferably 140-210 ° C.,
It is desirable to carry out by holding for 1 second or longer, preferably 3 seconds or longer. The heat resistance and the gas barrier property of the stretched bottle are improved by heat setting.

In the present invention, the plug portion of the preform may be heated and crystallized before the biaxial stretch blow molding,
It may be heated and crystallized mouth portion of the stretched bottle after biaxial stretch blow molding the mouth portion of the preform without heating and crystallization.

[0044] heating of the mouth portion of the preform, crystallization and heating and crystallizing the mouth part of the stretched bottle, 100-20
It is carried out at a temperature of 0 ° C, preferably 120-180 ° C.
By this heating and crystallization, the crystallinity of the plug part of the preform or the crystallinity of the plug part of the bottle is 25 to 60%,
It is desirable to set it in the range of preferably 25 to 50%.

The carbon dioxide permeability coefficient of the polyester biaxially stretched bottle body thus obtained is usually 15 cc.
・ Mm / m2 ・ day ・ atm or less, preferably 13c
c ・ mm / m2 ・ day ・ atm or less, especially 11 cc ・
mm / m @ 2 .day.atm or less, and the haze is usually 1.0 to 20%, preferably 5 to 15%.

According to the production method of the present invention, the transparency of the bottle body is less likely to decrease due to the biaxial stretch blow molding and heat setting. Therefore, the polyester resin excellent in transparency, gas barrier property and heat resistance is used. Axial stretched bottles can be manufactured.

Further, according to the present invention, since heating and crystallization of the preform plug portion or the bottle plug portion can be performed at high speed, molding of a bottle including a heating crystallization step of the plug portion is performed. A cycle can be shortened, and a polyester biaxially stretched bottle having excellent gas barrier properties, transparency, and heat resistance can be produced with good productivity.

[0048]

The polyester according to the present invention has an excellent crystallization rate and is excellent in gas barrier property, transparency and heat resistance.

The preform according to the present invention can produce a bottle having excellent gas barrier properties, transparency and heat resistance. The bottle according to the present invention has a gas barrier property,
Excellent transparency and heat resistance.

The method for producing a polyester biaxially stretched bottle according to the present invention can produce a bottle excellent in gas barrier property, transparency and heat resistance. Further, the method for producing a polyester biaxially stretched bottle according to the present invention, a gas barrier property, excellent transparency and heat resistance, to produce a bottle excellent in mechanical strength and heat resistance of the plug portion with good productivity. You can

[0051]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

In the examples, each characteristic was measured as follows. Intrinsic viscosity (IV) A sample solution of 8 g / dl was prepared using an o-chlorophenol solvent, and calculated from the solution viscosity measured at 25 ° C.

Carbon Dioxide Gas Permeability Coefficient (Gas Barrier Property) GL Sciences Inc. Gas Permeability Measurement System GP
It measured using M-250 on condition of 23 degreeC and 60% of relative humidity.

The film used for the measurement was prepared as follows. Stretched film : A film having a thickness of 0.1 mm was prepared using a press molding machine with a mold temperature of 290 ° C., and this film was rapidly cooled under the condition of a cooling mold temperature of 0 ° C. to obtain an amorphous film .
Next, this amorphous film was simultaneously biaxially stretched 3 × 3 times at a temperature 15 ° C. higher than the glass transition temperature (Tg) of the polyester forming the film to obtain a stretched film .

Heat set film : The stretched film was fixed to a metal frame and heat set in an oven at 150 ° C. for 3 minutes to obtain a heat set film . Heat set bottle : A preform is molded at a mold temperature of 10 ° C. using an injection molding machine having a cylinder temperature of 280 ° C., and then this preform is vertically 3 ° C. at a temperature 15 ° C. higher than the Tg of the polyester forming the preform. The bottle was molded by sequentially biaxially stretching it twice and laterally three times, and the bottle body was heat set at 200 ° C. for 1 minute to obtain a biaxially stretched bottle. A body section was cut out from this bottle to obtain a heat set bottle .

Transparency (haze value) The dried polymer was molded into a square plate having a thickness of 5 mm using an injection molding machine having a cylinder temperature of 280 ° C. and a mold temperature of 10 ° C. The diffuse reflectance of light) was compared.

Semi-crystallization time It was measured using a differential scanning calorimeter (DSC) manufactured by Perkin Elmer. 10 mg of dried polymer in a sample pan
Weigh and heat at 290 ° C. for 5 minutes to melt, then 32
Amorphous samples are prepared by quenching to 50 ° C. at a cooling rate of 0 ° C./min and allowing to stand for 5 minutes. This sample was heated to 140 ° C. at a temperature rising rate of 320 ° C./min and kept at that temperature. The sample was crystallized at this temperature to give a time-heating curve, and the total heating value was determined from this time-heating curve. 1 / of total calorific value
The time (second) required to generate the heat of 2 was defined as the half-crystallization time. The shorter the half-crystallization time, the more efficiently the crystallization progresses and the bottle productivity is improved.

Heat resistance of bottles Heat-set bottles = 40 bottles obtained by the method
After leaving it for 1 week under conditions of 90 ° C. and 90% humidity, the bottle was filled with 90 ° C. hot water for 10 minutes, and the capacity before and after filling was measured. The shrinkage rate (%) was calculated from the ratio of the internal volume before and after filling by the following formula.

[0059]

[Equation 1]

From the value of the shrinkage ratio (%) thus obtained, the heat resistance was evaluated according to the following criteria. ○ ... 0 ≦ shrinkage rate (%) <0.5 × ... 0.5 ≦ shrinkage rate (%)

Bottle appearance The bottle appearance was evaluated as follows from the haze value (%) of the bottle obtained by the heat set bottle method. ○ ... 0 ≤ haze value (%) <5 x ... 5 ≤ haze value (%)

[0062]

Example 1 (A) Terephthalic acid (A-1) as a dicarboxylic acid component
148 parts by weight and (A-2) 16 parts by weight of isophthalic acid, (B) 68 parts by weight of ethylene glycol as a diol component, and (B-2) 1.9 parts by weight of polytetramethylene glycol having an average molecular weight of 1000. To obtain a polyester having an intrinsic viscosity (IV) of 0.775 dl / g.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0064]

[Example 2] In Example 1, (B-2) average molecular weight 1
000 polytetramethylene glycol instead of (B
-3) Intrinsic viscosity (I) in the same manner as in Example 1 except that polytetramethylene glycol having an average molecular weight of 2000 was used.
A polyester having a V) of 0.780 dl / g was obtained.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0066]

Example 3 In Example 1, (B-2) average molecular weight 1
000 polytetramethylene glycol instead of (B
-4) Intrinsic viscosity (I) in the same manner as in Example 1 except that polytetramethylene glycol having an average molecular weight of 2900 was used.
A polyester having a V) of 0.778 dl / g was obtained.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0068]

Example 4 (A) Terephthalic acid (A-1) as a dicarboxylic acid component
158 parts by weight and (A-2) 8 parts by weight of isophthalic acid, (B) diol component (B-1) 68 parts by weight of ethylene glycol, and (B-2) 1.9 parts by weight of polytetramethylene glycol having an average molecular weight of 1000. To obtain a polyester having an intrinsic viscosity (IV) of 0.775 dl / g.

[0069]

Comparative Example 1 (A) Terephthalic acid (A-1) as dicarboxylic acid component
166 parts by weight and (B) diol component (B-1) 68 parts by weight of ethylene glycol were used, and the intrinsic viscosity (IV) was 0.775 dl.
/ G of polyester was obtained.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0071]

Comparative Example 2 (A) Terephthalic acid (A-1) as dicarboxylic acid component
Using 166 parts by weight, (B) 68 parts by weight of ethylene glycol (B) as a diol component and 8.5 parts by weight of (B-2) polytetramethylene glycol having an average molecular weight of 1000, the intrinsic viscosity (IV) is 0. A polyester of 0.776 dl / g was obtained.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0073]

Comparative Example 3 (A) Dicarboxylic acid component (A-1) terephthalic acid
133 parts by weight and (A-2) 33 parts by weight of isophthalic acid, (B) 68 parts by weight of ethylene glycol as a diol component, and (B-2) 1.9 parts by weight of polytetramethylene glycol having an average molecular weight of 1000. To obtain a polyester having an intrinsic viscosity (IV) of 0.775 dl / g.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0075]

Reference Example 1 (A) Terephthalic acid (A-1) as dicarboxylic acid component
166 parts by weight, (B) 68 parts by weight of (B-1) ethylene glycol as a diol component, and (B-2) 1.9 parts by weight of polytetramethylene glycol having an average molecular weight of 1000 were used, and the intrinsic viscosity (IV) was 0. A polyester of 0.776 dl / g was obtained.

The haze, Tg, half-crystallization time and carbon dioxide permeability coefficient of the obtained polyester were measured as described above. The results are shown in Table 1.

[0077]

[Table 1]

Claims (12)

(57) [Claims] 1. A dicarboxylic acid composition comprising a dicarboxylic acid unit containing terephthalic acid and isophthalic acid as main components, and a diol unit containing ethylene glycol and a polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms as a main component. In the unit, terephthalic acid unit is 99 to 85% by weight, isophthalic acid unit is 1 to 15% by weight, diol constitutional unit is ethylene glycol unit 99.999% by weight to 90% by weight, and alkylene chain having 2 to 10 carbon atoms. A polyester characterized in that it has a polyalkylene glycol unit in the range of 0.001 to 10% by weight. 2. The polyester according to claim 1, wherein the degree of polymerization (n) of the polyalkylene glycol is in the range of 5 to 50. 3. The polyester according to claim 1, wherein the polyalkylene glycol is polytetramethylene glycol. 4. A preform comprising the polyester according to any one of claims 1 to 3. 5. A biaxially stretched bottle comprising the polyester according to any one of claims 1 to 3. 6. The carbon dioxide permeation coefficient of the bottle body is 15.
The biaxially stretched bottle according to claim 5, which has a density of 0 cc · mm / m 2 · day · atm or less. 7. A dicarboxylic acid composition comprising a dicarboxylic acid unit containing terephthalic acid and isophthalic acid as main components, and a diol unit containing ethylene glycol and a polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms as a main component. In the unit, terephthalic acid unit is 99 to 85% by weight, isophthalic acid unit is 1 to 15% by weight, diol constitutional unit is ethylene glycol unit 99.999% by weight to 90% by weight, and alkylene chain having 2 to 10 carbon atoms. A preform is produced from a polyester having a polyalkylene glycol unit in the range of 0.001 to 10% by weight, and the preform is heated and then biaxially stretch blow molded to form a stretched bottle. Held in a mold at a temperature of 100 ° C or higher A method for producing a biaxially stretched polyester bottle, comprising: 8. The method for producing a polyester biaxially stretched bottle according to claim 7, wherein the preform plug portion is heated and crystallized before the biaxially stretched blow molding. 9. The method for producing a polyester biaxially stretched bottle according to claim 7, wherein the bottle mouth plug part is heated and crystallized after the biaxially stretched blow molding. 10. The method for producing a polyester biaxially stretched bottle according to claim 7, wherein the polyalkylene glycol has a degree of polymerization of 5 to 50. 11. The method for producing a polyester biaxially stretched bottle according to claim 7, wherein the polyalkylene glycol is polytetramethylene glycol. 12. The production of a polyester biaxially stretched bottle according to claim 7, wherein the carbon dioxide gas permeability coefficient of the obtained bottle body is 15.0 cc · mm / m 2 · day · atm or less. Method.