JPH09277358A - Method for producing polyester, preform and biaxially stretched bottle made of polyester, and polyester biaxially stretched bottle - Google Patents

Abstract

(57) [Summary] [Problem] A crystallization rate is high, gas barrier property, transparency,
To provide a polyester having excellent heat resistance, a preform made of the polyester, a biaxially stretched bottle, and a method for producing the same. SOLUTION: (I) terephthalic acid and a dicarboxylic acid component unit containing isophthalic acid as a main component, and (II)
The diol unit derived from ethylene glycol and a polyalkylene glycol having an alkylene chain having 2 to 10 carbon atoms is composed of a diol unit, and the isophthalic acid unit is a dicarboxylic acid. In the range of 1 to 15% by weight, and the proportion of constitutional units derived from polyalkylene glycol is 0.001 to 10% by weight based on all constitutional units derived from diol.
Polyester in the range. A preform and a bottle comprising the polyester. The preform obtained by injection molding from the polyester is biaxially stretch blow-molded to form a stretched bottle, which is then held in a mold at a temperature of 100 ° C. or higher.

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,
It is widely used as a container (PET bottle) for filling beverages such as juice, soft drinks and carbonated drinks. Such a bottle is generally injection-molded with saturated polyester to form a preform having a mouth 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 a barrel to obtain a bottle having a mouth 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.

Further, in the polyester bottle obtained as described above, the mouth portion is unstretched and is inferior in mechanical strength and heat resistance as compared with the stretched body portion. Therefore, the mouth of the preform is usually heated and crystallized before blow molding, or the mouth of the bottle obtained by blow molding is heated and crystallized to obtain mechanical strength and heat resistance of the mouth. 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 influence of the gas loss or the permeation of oxygen from the outside on the contents becomes remarkable, and the storage period of the contents decreases. 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 mouth and the heat setting time of the bottle is effective.

However, in general, the crystallization time at the mouth is
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 in the mouth and the heat setting time in 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. Also, since the heating crystallization rate is fast, the mouth of the preform or the mouth of the bottle can be crystallized at a high speed, and therefore, from this polyester, gas barrier property, transparency and heat resistance are excellent, Moreover, a bottle having excellent mechanical strength and heat resistance at the mouth 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.
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 is to produce a preform from the polyester as described above, then, after heating the preform, form a stretched bottle by biaxially stretch blow molding, and further form It is characterized in that the stretched bottle is held in a mold at a temperature of 100 ° C. or higher.

In the present invention, the preform mouth portion may be heated and crystallized before the biaxially stretch blow molding, and the bottle mouth 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 is to produce a bottle having excellent gas barrier properties, transparency and heat resistance, and excellent mechanical strength and heat resistance at the mouth part 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 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.

Hereinafter, the dicarboxylic acid and the diol will be described. 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 dicarboxylic acid components, terephthalic acid or its ester derivative and dicarboxylic acids 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.

These dicarboxylic acids other than terephthalic acid may be ester derivatives 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 degree of polymerization (n) of the polyalkylene glycol is preferably in the range 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. Among these, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, and polyoctamethylene glycol are preferred because of their excellent gas barrier properties, and polytetramethylene glycol is particularly preferred.

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 the amount is less than 1% by weight, the gas barrier properties of the polyester and the rate of crystallization at elevated temperatures may not be sufficient. On the other hand, if it exceeds 10% by weight, the transparency of the polyester and the heat stability during molding 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
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 diols other than the polyalkylene glycol of No. 10 include diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol (propylene glycol), butanediol, pentanediol, neopentyl glycol, hexamethylene glycol, and dodecamethylene. Aliphatic glycols such as glycol; alicyclic glycols such as cyclohexane dimethanol; 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 rate, for example, when molding a bottle, it is possible to shorten the time for heating and crystallizing the mouth portion of the preform or the mouth portion of the bottle. It is possible to efficiently manufacture bottles with excellent mechanical strength and heat resistance in the finished opening.

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 mouth portion of the preform and then biaxially stretch-blow molding, or biaxially without heating and crystallizing the mouth portion of the preform. A bottle obtained by performing stretch blow molding to produce a bottle and then heating and crystallizing the mouth portion 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, the stretched bottle is formed by biaxial stretch blow molding.

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 setting is 100-240 ° C, preferably 110-22.
At a mold temperature of 0 ° C, particularly preferably 140-210 ° C,
It is desirable to carry out by holding for 1 second or more, preferably 3 seconds or more. The heat resistance and the gas barrier property of the stretched bottle are improved by heat setting.

In the present invention, the mouth portion of the preform may be heated and crystallized before the biaxial stretch blow molding,
It is also possible to heat and crystallize the mouth of the stretched bottle after biaxial stretch blow molding without heating and crystallizing the mouth of the preform.

Heating and crystallization of the preform mouth 〓 and heating and crystallization of the drawn bottle mouth 〓 are 100 to 20
It is carried out at a temperature of 0 ° C, preferably 120-180 ° C.
By this heating and crystallization, the crystallinity of the mouth of the preform or the crystallinity of the mouth 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, in the present invention, since heating and crystallization of the preform mouth portion or the bottle mouth portion can be performed at high speed, the molding cycle of the bottle including the heat crystallization step of the mouth portion can be shortened. Thus, 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 is to produce a bottle having excellent gas barrier properties, transparency and heat resistance, and excellent mechanical strength and heat resistance at the mouth part with good productivity. You can

[0051]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not 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 having a mold temperature of 290 ° C., and this film was rapidly cooled at a cooling mold temperature of 0 ° C. to obtain an amorphous film 〓. Then, the amorphous film 〓 is kept at 15 ° C higher than the glass transition temperature (Tg) of the polyester forming the film.
Simultaneous biaxial stretching was carried out at a high temperature of 3 × 3 times 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 〓: Mold a preform at a mold temperature of 10 ° C using an injection molding machine with a cylinder temperature of 280 ° C.
Next, this preform was bottle-molded by sequentially biaxially stretching the longitudinal direction 3 times and the transverse direction 3 times at a temperature 15 ° C. higher than the Tg of the polyester forming the preform, and the bottle body was further heated at 200 ° C. After heat setting for a minute, a biaxially stretched bottle was obtained. 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.

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

Heat resistance of bottles 40 bottles obtained by the method of heat set bottle
After leaving for 1 week under the condition of 90 ° C. and 90% humidity, the bottle was filled with hot water of 90 ° C. for 10 minutes, and the capacity before and after filling was measured. The shrinkage (%) was determined from the ratio of the contents 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, (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, (B
-4) Except for using polytetramethylene glycol having an average molecular weight of 2900, the intrinsic viscosity (I
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
166 parts by weight, (B) diol component (B-1) 68 parts by weight of ethylene glycol and (B-2) 8.5 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.

[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 are used to obtain an intrinsic viscosity (IV) of 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]

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // B29K 67:00 B29L 22:00

Claims (12)

[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 claim 1. 5. A biaxially stretched bottle comprising the polyester according to claim 1. 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 a main component, 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 mouth 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 portion is heated and crystallized after the biaxially stretch blow molding. 10. The method for producing a polyester biaxially stretched bottle according to claim 7, wherein the degree of polymerization of the polyalkylene glycol is in the range 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 any one of claims 7 to 11, wherein the carbon dioxide permeability coefficient of the obtained bottle body is 15.0 cc · mm / m 2 · day · atm or less. Method.