JP2007314591A - Copolyester and polyester filling container produced therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester filling container having a filling heat resistance temperature of 82°C or higher and being endurable in a Pasteur high-temperature sterilization test. <P>SOLUTION: The copolyester comprises ethylene terephthalate, a naphthalene ring composition, and diethylene glycol. The copolyester is characterized in that it contains the naphthalene ring composition in an amount of 0.8-3.0 mol% based on the copolyester and the diethylene glycol in an amount of 1.0-2.0 mol% based on the copolyester, and it has an intrinsic viscosity of 0.76-0.90 dl/g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a copolymer polyester, and more particularly to a copolymer polyester containing a small amount of a naphthalene ring composition and suppressing the content of diethylene glycol.

  For thermoplastic copolyesters containing naphthalene ring structure (hereinafter referred to as copolyester), the glass transition temperature is higher than that of general polyesters, but the naphthalene ring composition of this type of copolyester is high. Is a conventional technique well-known in the polyester technical field. For example, in Patent Document 1, a copolymer polyester containing a 5-15 mol% naphthalene ring composition is present. Is disclosed.

  In particular, when a polyester polyester containing a naphthalene ring structure is used as a material and a polyester filled container is manufactured, the polyester filled container has optimum high temperature resistance and also passes the Pasteur high temperature sterilization test. What can be done is also a conventional technique in the polyester art. For example, Patent Document 2 is a copolymer polyester containing 3 mol% or 5 mol% of a naphthalene ring composition with respect to the copolymer polyester, and a polyester-filled container is produced from the copolymer polyester and is used for a Pasteur high-temperature sterilization test. It is disclosed that it can pass.

  Conventional methods for producing such a copolyester include two types of DMT production process or PTA production process. When such a copolyester is produced in the DMT production process, dimethyl 2,6-naphthalenedicarboxylate (abbreviation NDC) is used as a raw material, and a copolymer containing a naphthalene ring structure is obtained by utilizing a DMT transesterification reaction. Polymerized polyesters are obtained, the cost of which is relatively low and has already been commercialized. When such a copolyester is produced in the PTA production process, 2,6-naphthalenedicarboxylic acid (abbreviation NDA) having a relatively low purity is used as a raw material, and a naphthalene ring is utilized by using a direct esterification reaction of PTA. Although a copolyester having a structure can be obtained, its cost is relatively high.

  However, in the above method for producing a copolyester, when dimethyl 2,6-naphthalenedicarboxylate (NDC) is used as a raw material in the PTA production process, the speed of the melt polycondensation reaction is clearly reduced. By adding a transesterification catalyst in the condensation reaction process to promote the transesterification reaction, a copolyester containing a naphthalene ring structure can be obtained. For example, Patent Document 1 discloses that a copolyester having a naphthalene ring composition containing 5 to 15 mol% is produced by further adding a catalyst for transesterification at the end of the direct esterification reaction. .

  In addition, when producing such a copolyester by the above-mentioned production method, it is possible to produce such copolyester by adding a relatively high content of dimethyl 2,6-naphthalenedicarboxylate (NDC) in the production process. Polyester filled containers can withstand relatively high hot filling temperatures and pass the Pasteur high temperature sterilization test. For this reason, when such a copolyester is used, the production cost is relatively high, and it is relatively increased as an obstacle to commercialization.

Other commonly used polyester-filled containers use a common homopolymer (Homopolymer) or a random polymer containing a copolymer simple substance such as isophthalic acid, diethylene glycol or cyclohexanedimethanol, for example. It is manufactured by a hydrothermal solidification treatment step (Heatsetting) or a non-hydrothermal solidification treatment step. The hot filling temperature of the non-hydrothermal solidification type filling container made of the homopolymer is not 82 ° C. or higher, and the hot filling temperature of the hydrothermal solidification type filling container made of the homopolymer is 92 ° C. or more. Don't be. In particular, a non-hydrothermal solidified filling container made of a homopolymer may be deformed after being filled with a beverage and further passing through a Pasteur pasteurization tunnel, and may be rejected by a beverage supplier. .
US Pat. No. 6,551,675 US Pat. No. 6,284,920

Disclosed in the present invention is a copolyester having a naphthalene ring composition, and the process for producing the polyester is within about 3 mol% of dimethyl 2,6-naphthalenedicarboxylate (NDC) in the direct esterification production process of PTA. In particular, it is not necessary to add a catalyst for transesterification in the polycondensation reaction process, and it is possible to produce a copolyester having a naphthalene ring structure. Is to break through.

What is disclosed in the present invention is a copolyester containing ethylene terephthalate, naphthalene ring composition and diethylene glycol, and the content of naphthalene ring composition is 0.8 to 3.0 mol% with respect to the copolyester. The content of diethylene glycol is 1.0 to 2.0 mol% with respect to the copolymerized polyester, the intrinsic viscosity thereof is 0.76 to 0.90 dl / g, and particularly the heat resistance temperature of filling is 82 ° C. or higher. And it is applied to the polyester filling container which can pass the high temperature sterilization test of Pasteur.

The polyester-filled container produced from the copolymerized polyester of the present invention can be applied to packaging of tea, juice, soft drinks / carbonated drinks or other foods, drinks or nutrients. The filling and packaging method may be a method of hot-filling and capping and further cooling, or a method of pasteurizing and pasteurizing after cold filling.

The polyester-filled container produced from the copolymerized polyester of the present invention can be produced as a polyester-filled container having a single layer or a multi-layer structure. A modifier such as a colorant, an acetaldehyde adsorbent or a coloring material / dye can also be added.

What is disclosed in the present invention is a copolyester having a naphthalene ring composition, and its production method uses dimethyl 2,6-naphthalenedicarboxylate (NDC) as a raw material in the production process of PTA, particularly polycondensation. There is no need to add a transesterification catalyst in the reaction process, and a copolyester having a naphthalene ring structure can be produced.

The copolymerized polyester disclosed in the present invention contains ethylene terephthalate, naphthalene ring composition and diethylene glycol, and the content of naphthalene ring composition is 0.8 to 3.0 mol% with respect to the copolymerized polyester. Is 1.0 to 2.0 mol% with respect to the copolyester, and its intrinsic viscosity is 0.76 to 0.90 dl / g, but 0.80 to 0.86 dl / g is a preferred embodiment. It becomes.

A method for producing the copolyester disclosed in the present invention will be described below.
Ethylene glycol (EG) is poured into a tank provided in a stirrer, and dimethyl 2,6-naphthalenedicarboxylate (NDC) is poured into the paste while stirring with a stirrer to prepare a paste. A high-purity terephthalic acid (PTA) and ethylene glycol (EG) are prepared in advance, and the paste prepared with a metering / feed pump is continuously injected into a tank of paste material that is continuously stirred, These two types of paste are continuously stirred to form dimethyl 2,6-naphthalenedicarboxylate (NDC), high-purity terephthalic acid (PTA) and ethylene glycol (EG) as a uniform paste solution.

In order to ensure that the paste material is uniformly stirred in the paste material tank, the molar ratio of ethylene glycol in the paste material to dimethyl 2,6-naphthalenedicarboxylate and high-purity terephthalic acid is set to 1.05 to 2.0. And the stopping time of the paste material in the paste material tank shall be 30 minutes or more. At the same time, in order to stabilize the concentration of the paste material, it can be continuously controlled by a paste density controller, and in order to stabilize the density of the paste material, the temperature of the paste may preferably be 60 ° C. or less.

Next, the produced paste is continuously transported into two esterification reactors connected in series by a pump to carry out esterification reaction, the conversion rate of the first esterification reactor is about 80 to 92%, The conversion rate of the esterification reactor is about 95-98%. The esterification reaction temperature is 240 to 270 ° C., preferably 250 to 260 ° C., the esterification pressure is 2.0 kg / cm 2 to normal pressure, preferably 1.0 kg / cm 2 to 0.1 kg / cm 2, The esterification reaction time is 3 to 8 hours, preferably 4 to 6 hours.

In the direct esterification reaction process of the present invention, ethylene glycol, water, and a small amount of methanol are formed, so that they enter the distillation tower via a vaporization tube and are separated. The ethylene glycol collected from the bottom of the distillation tower is again refluxed to the esterification reaction tank, and water and a small amount of methanol collected from the top of the distillation tower are led to a wastewater treatment plant for treatment.

The simple substance produced through the above direct esterification reaction is continuously transferred to a prepolymerization tank by a transport pump to perform a prepolymerization reaction. The prepolymerization reaction can be carried out in one or two tanks, the temperature of the prepolymerization is 260 to 280 ° C, preferably 250 to 260 ° C, and the pressure of the prepolymerization reaction is a moderate vacuum negative pressure In the environment, the vacuum pressure is 10 to 200 mmHg. A gas by-product such as ethylene glycol generated by the prepolymerization reaction is extracted with a cooler by vacuum negative pressure, and is converted into a liquid. The time for the prepolymerization reaction is set to 0.5 to 2.0 hours.

In order to raise the viscosity to at least 0.55 dl / g, the low polymer after passing through the above prepolymerization reaction is continuously transported to the main polymerization tank by a pump and subjected to a further polycondensation reaction. The main polymerization tank can be one or two tanks, and the temperature of the main polymerization reaction is 270 to 290 ° C, preferably 270 to 285 ° C. Since the pressure of the main polymerization reaction is a highly vacuum negative pressure environment, the vacuum pressure is reduced to 2 mmHg or less by a multistage injector, and the viscosity value of the final polymer is measured by the degree of vacuum of the main polymerization reaction (unit: Poise). ) Is continuously controlled.

The polymer after completion of the above main polymerization reaction is continuously transported by a pump, passed through a set of filters, sent to a set of perforated die heads (Diehead), and again amorphous by a pellet cutter. Cut into an adhesive polyester resin (Amorphous Resin).

By increasing the molecular weight of the polyester resin in a general continuous solid polymerization apparatus such as a continuous solid polymerization apparatus manufactured by Buhler, Switzerland, Sinco, or Bepex, USA, The intrinsic viscosity of the resin is allowed to reach within the range of 0.76 to 0.90 dl / g, and preferably within the range of 0.80 to 0.86 dl / g.

The polyester resin produced above is used to produce a container preform with an injection blow molding machine under a melting temperature of 270 to 295 ° C., and further, the container preform is heated to a temperature higher than the glass transition temperature with a near infrared lamp. That is, it is stretch-blown into a polyester-filled container (generally called a two-stage bottle manufacturing method). Alternatively, after plasticizing the polyester resin under a melting temperature of 270 to 295 ° C. with a direct injection stretch blow molding machine, it is temporarily cooled, that is, the container preform is blown directly into a polyester filling container (single-stage bottle manufacturing method). To do.

The advantages of polyester filled containers made with the copolyesters disclosed in the present invention include that they can withstand hot filling temperatures of 82 ° C. and higher, have good transparency, and have a relatively low content of regenerated acetaldehyde. . However, the commonly found hot filling temperature of polyester filled containers cannot be higher than 82 ° C.

The polyester-filled container produced from the copolymerized polyester of the present invention can be applied to packaging of tea, juice, soft drinks / carbonated drinks or other foods, drinks or nutrients. The filling and packaging method may be a method of hot-filling and capping and further cooling, or a method of pasteurizing and pasteurizing after cold filling.

The polyester-filled container produced from the copolymerized polyester of the present invention can be produced as a polyester-filled container having a single layer or a multi-layer structure. A modifier such as a colorant, an acetaldehyde adsorbent or a coloring material / dye can also be added.

A polyester filled container made of the copolyester disclosed in the present invention can directly enter the hot filling line, or can enter the hot filling line after several days to complete the beverage filling.

The effect of the copolyester disclosed in the present invention will be described through the following examples, but this method is not intended to limit the scope of the present invention.

Production of Polyester Resin Disclosed in the Present Invention The copolyester disclosed in the present invention is produced using a conventional continuous melt polymerization apparatus and includes one PTA paste preparation tank.

In order to produce a uniformly dispersed pasty liquid, the molar ratio of ethylene glycol (EG) to dimethyl 2,6-naphthalenedicarboxylate and high purity terephthalic acid (PTA + NDC) is controlled to about 1.5. This paste-like liquid is continuously transported to the esterification reaction tank, and the esterification reaction is carried out in the tank connected in series with the two units. The conversion rate of the first esterification reaction tank is about 85%, and the second esterification is performed. The conversion rate of the reaction vessel is about 96%. After the above esterification reaction is completed, the single unit esterified by the transport pump is continuously sent to the pre-polymerization reaction tank with a low vacuum degree, and before being sent to the pre-polymerization reaction tank, the catalyst and coloring material for the polycondensation reaction, etc. Add. In order to continuously transport a prepolymer produced after about 30 to 60 minutes to a main polymerization reactor having a high degree of vacuum with a transport pump, and the maximum degree of vacuum of the main polymerization reactor is usually less than 1 millimeter of mercury, The polymerization reaction is preferably carried out in a reaction tank connected in series, and the main polymerization reaction temperature is 280 to 290 ° C., and the reaction time is about 1.5 to 3 hours. When the intrinsic viscosity of the polymer reaches 0.55 or more, the polymer is transported to a mold having a hole, extruded into an elongated shape, immediately quenched with frozen water, and then sliced to produce a copolyester resin. To do.

The amorphous polyester resin obtained through the melt polymerization production process raises the intrinsic viscosity to a necessary degree of polymerization using a conventional continuous solid polymerization apparatus.

The continuous solid polymerization apparatus referred to herein includes a continuous solid polymerization apparatus manufactured by Bühler, Switzerland, Sinco, Italy, Bepex, or Zimmer, Germany.

Equipment for manufacturing polyester filled containers
The copolyester resin disclosed in the present invention is produced into amorphous transparent bolts having a capacity of about 0.6 liter and about 2.0 liter, respectively, in a one-stage injection blow molding machine manufactured by AOKI Japan. The melt temperature of the injection blow molding machine is 280-295 ° C., and the container preform is manufactured after the molten polymer is injected into the mold, but the temperature after cooling in the polymer mold is still the glass transition Higher than temperature. When the container preform is cooled at a relatively low temperature, the flexibility of the preform becomes relatively stiff so that transparency is also suitable. When the container preform is cooled at a high temperature, the flexibility of the preform becomes relatively soft. However, when the temperature of the preform is too high, there is a possibility that a crystal or whitening phenomenon may occur before the preform is blown.

When producing a polyester-filled container using the copolymerized polyester of the present invention, the preform maintains an appropriate degree of flexibility even before blowing, and also has good transparency.

Inspection method of heat-resistant temperature of filling of polyester filling container
The polyester-filled container produced above is allowed to stand at room temperature for 3 days, filled with hot water at a temperature of 82 ° C or higher, immediately covered, first laid down for 1 minute, and then stood 5 After standing for 10 minutes and then immersing in cold water at 10 ° C. for 10 minutes, the appearance of the polyester-filled container is inspected for the presence of clear deformation and the volume deformation rate is measured.

Furthermore, with the hot water of different temperature, the heat resistance temperature test of filling is conducted on the polyester filling container manufactured as above, and there is no clear change in the appearance of the polyester filling container, and the maximum filling with a volume change rate of 3% or less Let temperature be the heat-resistant temperature of filling of the polyester filling container manufactured above.

Pasteur high temperature sterilization test method
After filling the polyester-filled container manufactured above with carbonated water having a volume ratio of 3.0, the container is covered, placed in a pasteur sterilizing chamber, and the content temperature in the container is about 63 ° C. with 71 ° C. hot water. Inject directly until it reaches. Thereafter, water is sprayed to lower the temperature to 64 ° C., and the content temperature in the container is maintained at 63 ° C. and held for about 15 minutes. Thereafter, water is jetted to lower the temperature to 40 ° C., and when the temperature of the contents in the container is lowered to 40 ° C., the polyester-filled container is placed in brine and rapidly cooled. The appearance and volume change rate of the polyester-filled container after this test are inspected.

There is no clear change in the appearance of the polyester filled container, and the volume change rate should be 3% or less. When the volume change rate is 1.5% or less, it indicates that the quality of the high temperature sterilization resistance of the polyester filled container is good, and when the volume change rate is between 1.5 and 3.0%, the polyester filled container This indicates that the quality of the pasteurized paste is normal but is acceptable, and if the volume change rate is 3.0% or more, the paste-filled container has a poor pasteurized pasteurized quality.

Example 1
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolyester contained 0.8 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.30 mol% diethylene glycol. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.80 dl / g.

As shown in Table 1, the 0.6-liter polyester-filled container produced from this copolyester had a heat resistance temperature of 85.5 ° C. after filling the test, and passed the Pasteur high-temperature sterilization test.

Example 2
The copolymerized polyester obtained in Example 1 was used as a material, and the intrinsic viscosity of the copolymerized polyester increased to 0.84 dl / g.

As shown in Table 1, the 0.6-liter polyester-filled container produced from this copolymerized polyester had a heat resistance temperature of 86.0 ° C. after filling the test, and passed the Pasteur high-temperature sterilization test.

Example 3
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolyester contained 0.8 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.65 mol% diethylene glycol. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.84 dl / g.

As shown in Table 1, the polyester filled container having a capacity of 2.0 liters produced by the copolymer polyester has a heat resistance temperature of 83.5 ° C. after filling the test, and passed the Pasteur high temperature sterilization test.

Example 4
As shown in Table 1, the 0.6-liter polyester-filled container produced from the copolymerized polyester obtained in Example 3 has a heat-resistant temperature of 85.5 ° C. after filling the test and is pasteurized at high temperature. I passed the exam.

Example 5
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolyester contained 0.8 mol%, dimethyl 2,6-naphthalenedicarboxylate, and 2.0 mol% diethylene glycol. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.84 dl / g.

As shown in Table 1, the 0.6 liter polyester-filled container produced from this copolyester had a heat resistance temperature of 84.5 ° C. after filling the test, and passed the Pasteur high-temperature sterilization test.

Example 6
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, it contained 1.5 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.59 mol% diethylene glycol based on the copolyester. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.90 dl / g.

As shown in Table 1, the polyester filled container having a capacity of 2.0 liters produced from this copolymerized polyester had a heat resistance temperature of filling after the test of 85.5 ° C., and passed the Pasteur high temperature sterilization test.

Example 7
According to the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolymer polyester contained 3.0 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.57 mol% diethylene glycol based on the copolyester. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.80 dl / g.

As shown in Table 1, the 0.6 liter polyester-filled container produced from this copolyester had a heat resistance temperature of 85.1 ° C. after filling the test, and passed the Pasteur high-temperature sterilization test.

Example 8
Based on the method for producing a copolyester having a naphthalene ring structure disclosed in the present invention, but the conversion rate of the esterification reaction step is reduced, the content of diethylene glycol is 1.0 mol% with respect to the copolyester, and 2 The copolymer polyester contained 0.0 mol% dimethyl 2,6-naphthalenedicarboxylate and had an intrinsic viscosity of 0.76 dl / gl.

As shown in Table 1, the polyester filled container having a capacity of 2.0 liters produced by the copolymer polyester has a heat resistance temperature of 84.0 ° C. after filling the test, and passed the Pasteur high temperature sterilization test.

Comparative Example 1
According to the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, it contained 5.12 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.50 mol% diethylene glycol based on the copolyester. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.87 dl / g.

As shown in Table 1, the 0.6-liter polyester-filled container produced from this copolyester had a heat resistance temperature of 85.5 ° C. after filling the test, and passed the Pasteur high-temperature sterilization test. However, the raw material cost was clearly higher than that of the copolyester containing the naphthalene ring structure disclosed in the present invention.

Comparative Example 2
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolyester contained 0.8 mol%, dimethyl 2,6-naphthalenedicarboxylate and 1.65 mol% diethylene glycol. A copolyester was obtained, and the intrinsic viscosity of the copolyester was 0.76 dl / g.

As shown in Table 1, the polyester filled container having a capacity of 2.0 liters produced from this copolyester has a heat resistance temperature of only 82.0 ° C. after the test, and a result of undergoing a Pasteur high temperature sterilization test. The volume change rate was 2.5%, which was a little too large. As a result, the intrinsic viscosity value was low, indicating that the heat-resistant temperature of filling was also lowered.

Comparative Example 3
Based on the method for producing a copolyester containing a naphthalene ring structure disclosed in the present invention, the copolyester contained 0.8 mol%, dimethyl 2,6-naphthalenedicarboxylate, and 2.36 mol% diethylene glycol. A copolymer polyester having a naphthalene ring structure was obtained, and the intrinsic viscosity of the copolymer polyester was 0.80 dl / g.

As shown in Table 1, the 0.6-liter polyester-filled container produced from this copolymerized polyester had a heat resistance temperature of only 83.0 ° C. after the test, and the result of the Pasteur high-temperature sterilization test. The volume change rate was 2.8%, which was a little too large. This indicates that the effect of the present invention cannot be satisfied when the content of diethylene glycol exceeds the range of the present invention.

Comparative Example 4
A homopolymer containing only 1.70 mol% diethylene glycol was synthesized, and its intrinsic viscosity was 0.84 dl / g.

As shown in Table 1, the polyester filled container with a capacity of 2.0 liters produced by this homopolymer has a heat resistance temperature of only 81.0 ° C. after the test, and the produced polyester filled container has a high Pasteur temperature. Passed sterilization test.

Comparative Example 5
A copolyester containing 0.5 mol% isophthalic acid and 1.85 mol% diethylene glycol was synthesized and had an intrinsic viscosity of 0.80 dl / g.

As shown in Table 1, the 2.0-liter polyester-filled container manufactured using this copolyester has a heat resistance temperature of only 80.5 ° C. after the test, and the manufactured polyester-filled container The tool high temperature sterilization test could not pass.

Comparative Example 6
A copolyester containing 1.80 mol% isophthalic acid and 1.85 mol% diethylene glycol was synthesized and had an intrinsic viscosity of 0.86 dl / g.

As shown in Table 1, the 0.6-liter polyester-filled container made from this copolyester has a heat resistance temperature of only 82.3 ° C., and the produced polyester-filled container The tool high temperature sterilization test could not pass.

Comparative Example 7
A copolyester containing 1.80 mol% isophthalic acid and 1.85 mol% diethylene glycol was synthesized and had an intrinsic viscosity of 0.86 dl / g.

As shown in Table 1, the polyester filled container with a capacity of 2.0 liters produced from this copolymerized polyester has a heat resistance temperature of only 80.0 ° C. after the test, and the produced polyester filled container has a pass of The tool high temperature sterilization test could not be passed.

表１の個別物質含量は、均しく共重合ポリエステルに対する含量で、且つ、◎＝良好 △＝普通 ×＝不良を示す。
Table 1

The individual substance contents in Table 1 are the contents relative to the copolyester, and ◎ = good △ = normal × = poor.

Claims (7)

  The copolymerized polyester is applied to the production and production of a polyester-filled container having a hot filling temperature of 82 ° C. or more, contains ethylene terephthalate, naphthalene ring composition and diethylene glycol, and the content of naphthalene ring composition is 0. A copolyester having a mol% of 8 to 3.0 and a content of diethylene glycol of 1.0 to 2.0 mol% with respect to the copolyester.   The copolyester according to claim 1, wherein the copolyester has an intrinsic viscosity of 0.76 to 0.90 dl / g.   The copolyester according to claim 1, wherein the copolyester has an intrinsic viscosity of 0.80 to 0.86 dl / g.   The copolyester according to claim 2 or 3, wherein the naphthalene ring composition is dimethyl 2,6-naphthalenedicarboxylate.   The copolyester according to claim 2 or 3, wherein the copolyester is produced by adding dimethyl 2,6-naphthalenedicarboxylate during the production process of high purity terephthalic acid (PTA).   A polyester-filled container, which is manufactured by an injection blow molding machine using the copolyester containing the naphthalene ring structure according to claim 2, and the heat-resistant temperature of filling of the manufactured polyester-filled container is 82 ° C or higher. A polyester filled container.   The polyester-filled container according to claim 6, wherein the polyester-filled container has a single-layer or multi-layer structure and can be applied to packaging of tea, juice, soft drinks / carbonated drinks, food or nutrients, etc. container.