JP2002002651A - Biaxially oriented polyethylene naphthalate product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene naphthalate product having superior transparency, mechanical strength and heat resistance with a gas barrier characteristic so that the same can be effectively used as a gas barrier or a packaging body such as a container or a bag for soda, juice, mineral water, etc. SOLUTION: A biaxially oriented polyethylene naphthalate product (molded container, film) is either heat processed or heat processed while a magnetic field is being applied to impart carbon dioxide permeability of 1.0 (cc.mm/m2.24 hr.atm) or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyethylene naphthalate product having excellent transparency, gas barrier properties, heat resistance and mechanical properties, and more particularly to a food or beverage product having excellent gas barrier properties. The present invention relates to a biaxially oriented polyethylene naphthalate product that can be suitably used as a package or gas barrier in the form of a container, tube, or bag for use.

[0002]

2. Description of the Related Art Polyethylene naphthalate resins have excellent properties such as transparency, mechanical strength, heat resistance and gas barrier properties. Therefore, for example, beverages such as carbonated beverages, juices and mineral waters are available. It is used as a material for molded articles for packaging products. However, in recent years, in order to impart higher gas barrier properties to these molded products of polyethylene naphthalate resin, for example, a gas barrier resin is laminated on polyethylene naphthalate resin and bonded to form a package. A method of processing has been proposed, but the package formed by this method is expensive, and when the used package is recycled, the gas barrier resin is recovered as an impurity in the recovered polyethylene naphthalate resin. When mixed, there is a problem that the purity of the polyethylene naphthalate resin is lowered and the quality of the recycled product is impaired.

[0003]

An object of the present invention is to provide a polyethylene naphthalate resin which has excellent gas barrier properties, can be supplied at a low cost, and has a polyethylene naphthalate resin. It is an object of the present invention to provide a biaxially oriented polyethylene naphthalate product capable of improving the recyclability of a resin, and particularly to provide a biaxially oriented polyethylene naphthalate product suitable for a molded product for packaging.

[0004]

Means for Solving the Problems An object of the present invention is to provide a biaxially oriented polyethylene naphthalate product formed from biaxially oriented polyethylene naphthalate, which has a carbon dioxide gas permeability of 1.0 (cc · mm / m ² · 24 hr · atm) or less, and to provide a biaxially oriented polyethylene naphthalate product characterized by having the following characteristics:

[0005] In the above means for solving the above problems of the present invention, the biaxially oriented polyethylene naphthalate product has a carbon dioxide gas permeability of 0.6 (cc · mm / m ² · 24 hr · atm) or less, especially 0.3 (c
c · mm / m ² · 24 hr · atm) or less. Also,
The biaxially oriented polyethylene naphthalate preferably contains naphthalenedicarboxylic acid as a main acid component and ethylene glycol as a main glycol component.

[0006] carbon dioxide gas transmission rate of polyethylene naphthalate product has a ^{1.0 (cc · mm / m 2} · 24hr · atm) or less is characteristic, carbonated beverages, juice - scan, mineral Walsh - data such beverages It was confirmed that carbon dioxide gas in the product did not escape, and therefore it was practically suitable especially for use as a molded product (container, bag, tube, etc.) for packaging such beverages and gas barrier material.

[0007] Such a low carbon dioxide gas transmission rate can be obtained by promoting the molecular orientation of polyethylene naphthalate. This is achieved by heating the molded product for packaging without applying a magnetic field or while applying a magnetic field. It has been confirmed that this can be achieved by performing. By performing such treatment, the molecular orientation of the polyethylene naphthalate product is favorably promoted, and as a result, carbonated beverages, juices,
Gases in beverages such as mineral water are prevented from permeating through packaging molded articles such as containers and bags, and sufficient gas barrier properties can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. The present invention is directed to a molded product or film for packaging molded from biaxially oriented polyethylene naphthalate. Carbon dioxide gas permeability of 1.0 (ccm
has a ^{m / m 2 · 24hr · atm} ) or less is characteristic, this characteristic is biaxially packaging moldings from oriented polyethylene naphthalate resin (container, after molding the bag, etc.) or a film, a magnetic field this It can be obtained by performing a heat treatment without applying a magnetic field, or performing an additional molecular orientation treatment by applying a heat treatment while applying a magnetic field.

In particular, the biaxially oriented polyethylene naphthalate of this product has a carbon dioxide gas permeability of 0.6 (cc · mm / m ² · 24
hr.atm) or less, and more preferably 0.3 (cc
m ² · 24 hr · atm).

As described above, when a product such as a molded product for packaging (for example, a container) molded with a biaxially oriented polyethylene naphthalate resin is subjected to heat treatment, the gas barrier properties can be greatly improved, and a magnetic field can be further applied. Surprisingly, it has been confirmed that when the heat treatment is performed, excellent gas barrier properties can be imparted even when the heat treatment time is significantly reduced, as compared with the gas barrier properties obtained by simply performing the heat treatment.

More specifically, a molecular orientation treatment method for improving the gas barrier properties of a biaxially oriented polyethylene naphthalate product can be effectively achieved by any of the following three methods. (1) The biaxially oriented polyethylene naphthalate product is used as the glass transition temperature (Tg) of the biaxially oriented polyethylene naphthalate.
℃) is lower than the predetermined temperature range (Tg-5 ℃) ~
(Tg-30 ° C) A method of performing heat treatment at a temperature of 0.1 to 1500 hours. (2) The biaxially oriented polyethylene naphthalate product is used as the glass transition temperature (Tg) of the biaxially oriented polyethylene naphthalate.
° C) higher than the predetermined temperature range (Tg + 25 ° C) ~
A method of performing heat treatment at a temperature of (Tg + 5 ° C.) for 0.5 to 10 minutes and then cooling to room temperature. (3) The biaxially oriented polyethylene naphthalate product is used as the glass transition temperature (Tg) of the biaxially oriented polyethylene naphthalate.
° C) to lower than the melting point (Tm ° C) of the biaxially oriented polyethylene naphthalate (Tm-20).
° C) for 30 seconds to 5 seconds while applying a high magnetic field.
Heat treatment for 00 hours. Here, the glass transition temperature (Tg ° C.) and the melting point (Tm ° C.) of the biaxially oriented polyethylene naphthalate vary depending on film forming conditions such as a stretching temperature, a stretching ratio, and a heat setting temperature. It is about 265 ° C.

The glass transition temperature (Tg) and melting point (Tm) of the polyethylene naphthalate used in the above methods (1) to (3) can be determined by the following method. (Measurement method of glass transition temperature (Tg)) The glass transition temperature (Tg) of a biaxially oriented polyethylene naphthalate product was measured using a differential scanning calorimeter (DSC) using a 10 m partial sample of the product.
g at a rate of 10 ° C./min in a nitrogen stream,
When an endothermic peak appears at Tg, or when the endothermic peak appears at Tg, the temperature indicating the maximum value of this endothermic peak is defined as T
g (° C.). (Measurement method of melting point (Tm)) The melting point (Tm) of the biaxially oriented polyethylene naphthalate product is determined by the glass transition temperature (Tg).
Using a differential scanning calorimeter (DSC) in the same manner as in the above measurement, when a 10 mg portion of the product was heated at 10 ° C./min in a nitrogen stream, the maximum value of the endothermic peak of melting was shown. The temperature is determined as Tm (° C.).

The product of the present invention is preferably molded from biaxially oriented polyethylene naphthalate having naphthalenedicarboxylic acid as the main acid component and ethylene glycol as the main glycol component.

[0014] The term "principal" as used herein means more than 70 mol%, preferably more than 80 mol%.
Accordingly, the biaxially oriented polyethylene naphthalate used in the present invention includes those in which less than 30 mol% of other components are copolymerized or those in which less than 30 mol% of other components are contained as a mixture. .

In the present invention, "naphthalenedicarboxylic acid" includes, for example, 2,6-naphthalenedicarboxylic acid,
2,7-Naphthalenedicarboxylic acid and its ester-forming derivatives are mainly intended, but a part (less than 30 mol%) may be replaced by other dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, Aliphatic dicarboxylic acids such as sebacic acid and dodecanedicarboxylic acid; terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid Acids, aromatic dicarboxylic acids such as diphenyl ether-4,4'-dicarboxylic acid; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and decalin dicarboxylic acid; and oxyacids such as glycolic acid and p-oxybenzoic acid. You may. Examples of the ester-forming derivative of the acid component include lower alkyl esters, phenyl esters, and acid anhydrides.

The "glycol component" is mainly intended for ethylene glycol, and a part (less than 30 mol%) of which is replaced by another glycol such as tetramethylene glycol, propylene glycol or 1,3-butanediol. Diols such as cyclopentimethanol and tricyclodecane dimethylol; bisphenol A, bisphenol S, bishydroxyethoxy bisphenol A;
It may be substituted with an aromatic diol or the like such as tetrabromobisphenol A. Also, as in ordinary polyesters, heat stabilizers such as phosphorus, antioxidants such as hindered phenol, ultraviolet absorbers such as benzotriazole, hydroxybenzophenone and cyanoacrylate, pigments such as terazole blue, dyes, talc and the like. Needless to say, a nucleating agent, a crystallization accelerator such as a higher fatty acid salt, a release agent, a metal oxide or the like may be added.

The polyethylene naphthalate (hereinafter sometimes abbreviated as PEN) used in the present invention is substantially linear and has an amount in a range that does not cause a crosslinking effect, for example, 2 mol% or less based on the total acid component. Also included are copolymers of tricarboxylic or higher functional polycarboxylic acids or polyhydroxy compounds, for example, trimellitic acid, pentaerythritol and the like.

The polyethylene naphthalate used in the present invention can be produced by applying a conventional polyester production method. The transesterification method, that is, the reaction of a lower alkyl ester of naphthalenedicarboxylic acid with ethylene glycol is used. In this reaction, part of the lower alkyl ester of naphthalenedicarboxylic acid (for example, 20 mol% or less) may be substituted with another acid component, or part of the glycol (for example, 20 mol% or less).
Mol% or less) may be replaced with another glycol component.
Examples of the lower alkyl ester of naphthalenedicarboxylic acid include dimethyl ester, diethyl ester, dipropyl ester and the like, and dimethyl ester is particularly preferred.

The polyethylene naphthalate polymer used in the present invention preferably has an intrinsic viscosity of 0.4 to 0.9 (dl / g).
A mixed solvent of 2,2-tetrachloroethane / p-chlorophenol (1: 3 weight ratio, measured at 35 ° C). Since polyethylene naphthalate polymer is used as a material for containers such as carbonated beverages, juices, mineral water, etc., and bags, etc., which require mechanical strength, a PEN polymer having a large intrinsic viscosity is required. A PEN polymer having such a large intrinsic viscosity can be obtained, for example, as follows. That is, the intrinsic viscosity is 0.4 to 0.6 (dl)
/ G) of the polyethylene naphthalate polymer is melt-polymerized by a known method, and thereafter, the polymer pellets obtained by the melt polymerization method are solid-phase polymerized to have an intrinsic viscosity of 0.7 to
0.9 (dl / g) of polyethylene naphthalate polymer can be obtained.

The polymer pellets are prepared in a range from 110 to 130.
C., heated in air for 2-4 hours to crystallize at least the surface layer, dehumidified and dried at 140-170 ° C. for 3-6 hours,
The water content in the pellets is adjusted to 50 ppm or less and supplied to an extruder or a molding machine.

A typical method for producing the biaxially oriented polyethylene naphthalate product of the present invention using the thus obtained polymer will be described below.

One is a method for producing a biaxially oriented polyethylene naphthalate film.

This can be performed by a conventionally known method such as a method of obtaining an unstretched sheet and a method of uniaxially stretching in the longitudinal direction. For example, the raw material polyethylene naphthalate is molded into pellets, dried with hot air or vacuum dried, melt-extruded, extruded into a sheet from a T-die, adhered to a cooling drum by an electrostatic application method or the like, and cooled and solidified. To obtain an unstretched sheet. Next, the obtained unstretched sheet is passed through a plurality of roll groups and / or a heating device such as an infrared heater, and the glass transition temperature Tg ° C. of polyethylene naphthalate.
(Depending on the copolymerization ratio, Tg of homo PEN
Is within about 123 ° C.) to (Tg + 70 ° C.), and is stretched in one or more stages. The stretching ratio is
Usually, it is necessary to set the range of 2.5 times to 6 times so that the subsequent transverse stretching is possible.

Next, the polyethylene naphthalate film uniaxially stretched in the machine direction obtained as described above is
The film is transversely stretched within a temperature range of Tg to (Tg + 70 ° C.), and then heat-set. The transverse stretching ratio is usually 3 to 6 times, and the ratio between the longitudinal and transverse stretching ratios is determined by measuring the physical properties of the obtained biaxially stretched film and appropriately adjusting the film to have preferable characteristics.

The thickness of the polyethylene naphthalate film is not particularly limited depending on the application, but is preferably 50
Those having a thickness of about 500 μm are used. Although the stretching magnification depends on the thickness, an area magnification of about 2 to 16 times is employed.

This polyethylene naphthalate film may or may not be heat-set, but when heat-set, it is usually at 150 to 245 ° C. and usually at 5 to 30 ° C.
Performed for 0 seconds.

The film thus obtained can be used as it is for an appropriate purpose such as a gas partition.
This film can be formed into a molded product for packaging having a predetermined shape and used in the form of a molded product for polyethylene naphthalate packaging (container, bag, or the like).

The other is a method for producing an appropriate product, for example, a bottle, through the biaxially oriented polyethylene naphthalate preform of the present invention.

In this method, the polyethylene naphthalate pellets are injection-molded to form a preform, and the preform is formed, for example, at 130 to 165 ° C., preferably at 135 ° C.
To a molding temperature of ~ 160 ° C and the mold surface is pre-
This is a method of manufacturing a bottle by placing the preform in an axial direction with a stretching rod by placing the preform in a blow-molding mold heated to a predetermined temperature and blowing a high-pressure fluid into the preform to perform biaxial stretching blow molding. The size is set so that the draw ratio of the bottle to the preform is about 6 times or more, preferably 8 to 15 times, in terms of area ratio.

The stretching ratio in two directions is 1.5 to 3.0 times, preferably 2.0 to 2.5 times in the axial direction of the bottle.
The ratio is appropriately set in the range of 3.0 to 5.0 times, preferably 3.5 to 4.5 times in the circumferential direction of the bottle.

This polyethylene naphthalate bottle may or may not be heat-set, but if it is heat-set, it must be kept in a molding die for a long time due to the limitation of high-speed molding. Although there is a problem that it is not possible, after performing both blowing and heat setting with a molding die having a high temperature, cooling air may be blown into the same die to take out the product from the die.

A PEN film produced by any of the above two methods, and a PEN film molded from this PEN film
A PEN product having excellent gas barrier properties by subjecting a molded product for EN packaging (container, bag) or a molded product (bottle) manufactured from a PEN preform to a molecular orientation treatment by one of the three methods described above. can get.

Here, "excellent in gas barrier properties" means that it is difficult to pass gases such as carbon dioxide, oxygen, and water vapor, and has low carbon dioxide gas permeability, oxygen permeability, water vapor permeability (moisture permeability), and the like. It means that it is excellent in impermeability.

By the way, when the stretching area ratio of PEN is larger than that in the unstretched state, the gas barrier property is improved and it becomes difficult to pass gas. When the same stretched PEN film is compared in relation to the presence or absence of heat setting, the stretched PEN film has a slightly improved gas barrier property due to the heat setting. However, the difference between these two is slight. On the other hand, by performing the above-described heat treatment, the gas barrier properties are significantly improved. In particular, when a strong magnetic field is applied to the molded article in addition to the heat treatment, a significant improvement in gas barrier properties and a remarkable reduction in the heat treatment time can be realized. The reason is not clear, but in addition to the heat treatment,
It is considered that the application of a magnetic field in parallel with this further promotes the orientation of the polyethylene naphthalate polymer chains.

The magnitude of the magnetic field applied to the molded product is not particularly limited, but the temperature and time for the heat treatment are influenced by the magnitude of the magnetic field. If the magnitude of the magnetic field is small, it depends on the temperature of the heat treatment. The heat treatment time must be sufficiently long. The magnetic flux density is at most about 30 T (tesla), preferably 0.002 to 20.0 T (tesla), more preferably 0.02 to 20.0 T (tesla), and most preferably 0.1 to 20.0 T (Tesla), 30 seconds to 5
By performing the heat treatment for 00 hours, a molded product of polyethylene naphthalate packaging having desired gas barrier properties, that is, desired carbon dioxide gas permeability, oxygen permeability, and water vapor permeability (moisture permeability) can be obtained.

Heating can be performed while applying a magnetic field using a solenoid coil or the like. In this case, a magnetic field may be applied while transporting the biaxially oriented polyethylene naphthalate product, or the product may be left stationary. Alternatively, a magnetic field may be applied while heating. When a biaxially oriented polyethylene naphthalate product is heat-treated while applying a magnetic field, the direction in which the magnetic field is applied while the product is allowed to stand may be vertical, oblique or horizontal to the product. You may.

The magnetic field generating means is not particularly limited, but may be a permanent magnet or the like in addition to a coil represented by the above-mentioned solenoid coil, or a device for generating a magnetic field intermittently (pulse magnetic field generating device). Etc.).

The mechanism by which the gas barrier property is improved is as follows.
Although it is not clear, when treated with a combination of the heat treatment temperature, heat treatment time, and magnetic field as described above, the crystal and amorphous structure of the biaxially oriented polyethylene naphthalate product before these treatments are mixed and imperfect. This is considered to be due to the fact that the simple structure is more closely packed and changes to a stable structure, so that it changes to a structure that makes gas difficult to permeate. The high magnetic field used in this process is believed to further promote the above phenomenon.

In order to obtain the thermal dimensional stability of the biaxially oriented polyethylene naphthalate product, a product heat-fixed at 150 to 245 ° C. and a product not heat-fixed are each subjected to heat treatment for the purpose of molecular orientation. Experiments have shown that in the relatively short initial stages of the treatment, the gas barrier properties decrease slightly and then improve. Such a phenomenon,
Crystals of biaxially oriented polyethylene naphthalate products,
An incomplete structure with a mixture of amorphous structures is caused by a change to a loose structure in the early stage of heat treatment, and this phenomenon then slowly changes to a more closely packed and stable structure. It is thought that it is canceled by. Therefore, it should be avoided that the treatment is terminated at the beginning of the heat treatment in which the gas barrier property is reduced.

The polyethylene naphthalate product thus biaxially oriented (molded product or film for packaging)
As described above, a method of performing heat treatment for a long time at a temperature lower than the glass transition temperature, a method of performing a heat treatment for a short time at a temperature higher than the glass transition temperature and relatively close to the glass transition temperature, or a method of performing a heat treatment at a temperature lower than the glass transition temperature ( Gas barrier properties are dramatically improved by a method of performing heat treatment while applying a magnetic field in a range from Tg-30 ° C.) to a normal heat setting temperature (Tm-20 ° C.) lower than the melting point. Products suitable for suppressing gas diffusion, such as carbon dioxide permeability,
It was confirmed to be 1.0 (cc · mm / m ² · 24 hr · atm) or less. In particular, the carbon dioxide gas permeability of the biaxially oriented polyethylene naphthalate of this molded product for packaging is 0.6 (cc · mm / m ² · 24
It has been confirmed that the diffusion of gas is further suppressed when the pressure is 0.3 (cc · mm / m ² · 24 hr · atm) or less.

The above heat treatment may be performed after the biaxially oriented polyethylene naphthalate product has been subjected to surface treatment, printing and other surface treatments in advance. In this case, the degree of the combination of the temperature and the magnetic field seems to be slightly different from the case where the heat treatment is performed without performing such a surface treatment. In addition, it is preferable that this surface treatment is performed using components that do not hinder product recycling.

As already mentioned, biaxially oriented polyethylene naphthalate products include both those that have been heat set and those that have not. here,
"Heat setting" refers to applying heat at or above the orientation temperature (longitudinal and transverse stretching temperatures) to obtain dimensional stability after biaxial orientation (biaxial stretching) of a PEN film or a PEN molded product.
set), and the term "heat treatment" means that heat treatment is performed with or without applying a magnetic field under the above conditions for the purpose of molecular orientation.

For products such as PEN molded products and PEN films, the heat treatment temperature is the glass transition temperature of PEN (depending on the copolymerization ratio, but the Tg ° C. of homo-PEN is about 123 ° C.).
There is no particular problem if the temperature is lower than (° C.), but when the heat treatment temperature is Tg ° C. or more, heat shrinkage causes a large change in dimensions, so that the heat treatment was previously performed at 150 to (Tm−20 ° C. = 245 ° C.). Preferably, one is used.

Further, after a PEN molded product, a PEN film or the like is heat-treated at a temperature lower than the glass transition temperature Tg ° C.,
Even if the treatment is performed at a temperature sufficiently higher than the glass transition temperature Tg ° C. for a very short time, heat shrinkage occurs.
It is preferable to heat-set at a temperature of 0 to 245 ° C. and perform a heat treatment.

In recent years, in order to cope with an increase in demand for soft drinks such as juices, teas and sports drinks, the contents are sterilized at a high temperature and then cooled without cooling.
Attempts have been made to improve production efficiency by hot filling while heating to a temperature of ° C. When a biaxially oriented PEN molded product (container) or PEN film is used at such a temperature, the glass transition temperature Tg ° C. of the biaxially oriented PEN resin is used.
Since it is sufficiently lower, no particular problem occurs. Although the method for achieving the characteristic values required for the present invention has been described, the method for treating a product such as a PEN molded product or a PEN film is not limited to these as long as the characteristic values are satisfied. Absent.

[0046]

EXAMPLES Hereinafter, some examples of the present invention will be described together with comparative examples, but the present invention is not limited to these examples.

(Evaluation Method) First, methods for evaluating the physical properties of the polyethylene naphthalate molded article (hereinafter referred to as molded container) and the polyethylene naphthalate film of the present invention are described below.

The carbon dioxide gas permeability measurement and the oxygen permeability measurement were performed at 23 ° C. in accordance with JIS K7126B method. Carbon dioxide gas permeability, the unit of the oxygen permeability, (cc · mm / m ²
・ 24hr ・ atm). In the case of blow-molded containers, for simplicity of measurement, instead of containers with complicated surface shapes, they are molded into capsules, rectangular samples are collected from flat portions of polyethylene naphthalate containers, and averaged from weight, density and surface area. The thickness was calculated and calculated.

(Examples 1 to 5 and Comparative Examples 1 and 2) A homopolyethylene naphthalate (PEN) resin produced from dimethyl-2,6-natalenedicarboxylate and ethylene glycol by a conventional method was solidified. It was used after phase polymerization. The intrinsic viscosity (IV) of the PEN resin is 0.70 (dl /
g). An unstretched sheet having a thickness of 600 μm was formed from this polyethylene naphthalate resin,
After heating for a minute, the film was simultaneously biaxially stretched at a stretching speed of 1000% / min to an area magnification of 6 times, and heat-set at 225 ° C. for 30 seconds to obtain a polyethylene naphthalate film having a thickness of 100 μm.

The polyethylene naphthalate film thus obtained is heat-treated in an air oven.
In Example 1, heat treatment was performed at 108 ° C. for 1 hour. In Example 2, heat treatment was performed at 108 ° C. for 10 hours. In Example 3, heat treatment was performed at 108 ° C. for 50 hours.
Heat treatment was performed at 108 ° C. for 500 hours.
Heat treatment was performed at 08 ° C. for 1500 hours. Comparative Example 1
In Example 2, the film was not heat-treated in an air oven, and in Comparative Example 2, the film was heat-treated in an air oven. This was heat treatment at 108 ° C. for 0.5 hour. The results of measuring the carbon dioxide gas transmission rate and the oxygen gas transmission rate of the products of Examples 1 to 5 and Comparative Examples 1 and 2 are as shown in Table 1 below.

[0051]

[Table 1]

As can be seen from Table 1, the film of Example 1 of the present invention obtained by heating a biaxially oriented polyethylene naphthalate film at 108 ° C. for 1 hour has a carbon dioxide gas permeability of 1.0. (cc · mm / m ² · 24 hr · atm), the oxygen gas permeability is 0.33 (cc · mm / m ² · 24 hr · atm), and the polyethylene naphthalate film of Comparative Example 1 was not heat-treated. Both the carbon dioxide gas permeability and the oxygen gas permeability are smaller than the film, indicating that the film of Example 1 is a biaxially oriented polyethylene naphthalate film having excellent gas barrier properties.

The film of Example 2 of the present invention obtained by heating the biaxially oriented polyethylene naphthalate film at 108 ° C. for 10 hours has a carbon dioxide gas permeability of 0.6.
(cc ・ mm / m ²・ 24hr ・ atm), oxygen gas permeability is 0.23 (c
c ・ mm / m ²・ 24hr ・ atm), both carbon dioxide gas permeability and oxygen gas permeability are smaller than those of Example 1, which means that the film is a biaxially oriented polyethylene naphthalate film having more excellent gas barrier properties. Is shown.

The film of Example 3 of the present invention obtained by heating the biaxially oriented polyethylene naphthalate film at 108 ° C. for 50 hours has a carbon dioxide gas permeability of 0.3.
^{(cc · mm / m 2 ·} 24hr · atm), the oxygen gas permeability 0.10 (c
c · mm / m ² · 24 hr · atm), which is a biaxially oriented polyethylene naphthalate film having a carbon dioxide gas transmission rate and an oxygen gas transmission rate smaller than those of Examples 1 and 2 and further excellent gas barrier properties. Is shown. Similarly,
As shown in Examples 4 and 5, when the heat treatment time is further increased, the carbon dioxide gas permeability and the oxygen gas permeability are further reduced.

(Examples 6 to 10 and Comparative Examples 3 and 4)
A homopolyethylene naphthalate (PEN) resin produced from dimethyl-2,6-natalenedicarboxylate and ethylene glycol by a conventional method was used after solid-phase polymerization. The intrinsic viscosity (IV) of the PEN resin is 0.72 (dl)
/ G). Using this polyethylene naphthalate resin, a preform was molded using an M-100 injection molding machine manufactured by Meiki Seisakusho. Next, this pre-formed body is made of LB-01E manufactured by CORPLAST.
It was biaxially stretched and blown with a molding machine to form a 500 ml container. A piece of polyethylene naphthalate (container piece) having a thickness of 75 μm was cut out from a portion of the side wall of the thus obtained bottle having no unevenness, and a magnetic field having a magnetic flux density of 5.0 T (tesla) was cut in an air oven. Heating was performed in an air oven at a temperature lower than the glass transition temperature of the polyethylene naphthalate bottle (Tg = 123 ° C.) under the following conditions while applying in the thickness direction. In the sixth embodiment, the container piece is set to 113
Heat treatment for 0.25 hours at 113 ° C.
In Example 8, the heat treatment was performed at 113 ° C. for 10 hours. In Example 9, the heat treatment was performed at 113 ° C. for 150 hours. In Example 10, the heat treatment was performed at 113 ° C. for 500 hours. In Comparative Example 3, the container pieces were not heat-treated at all, and in Comparative Example 4, the container pieces were heat-treated at 113 ° C. for 0.1 hour in an air oven. Table 2 shows the results of measuring the carbon dioxide gas transmission rate and the oxygen gas transmission rate of the container pieces of Examples 6 to 10 and Comparative Examples 3 and 4.

[0056]

[Table 2]

As can be seen from Table 2, Example 6 was obtained by subjecting the container pieces to heat treatment at 113 ° C. for 0.25 hours while applying a magnetic field having a magnetic flux density of 5.0 T (tesla) in an air oven. the container pieces, carbon dioxide gas transmission rate is 1.0 (cc · mm / m ²
・ 24hr ・ atm), oxygen gas permeability is 0.34 (cc ・ mm / m ²・
24 hr · atm), compared to the container piece of Comparative Example 3 in which neither the heat treatment nor the application of the magnetic field was applied, the carbon dioxide gas permeability and the oxygen gas permeability were both smaller, and the container of Example 6 was excellent in gas barrier properties. It is a biaxially oriented polyethylene naphthalate container.

Magnetic flux density of the container pieces in an air oven
The container piece of Example 7 obtained by heating for 2 hours at 113 ° C. while applying a magnetic field of 0 T (tesla) had a carbon dioxide gas permeability of 0.5 (cc · mm / m ² · 24 hr · atm), the oxygen gas permeability is 0.25 (cc · mm / m ² · 24 hr · atm), the carbon dioxide gas permeability and the oxygen gas permeability are both smaller than in Example 6, and the container of Example 7 Indicates that the container is a biaxially oriented polyethylene naphthalate container having more excellent gas barrier properties.

The pieces of the container were placed in an air oven, and the magnetic flux density was 5.
The container piece of Example 8 obtained by heating at 113 ° C. for 10 hours longer than Examples 6 and 7 while applying a magnetic field of 0 T (tesla) has a carbon dioxide gas permeability of 0.3 (cc · cm). mm /
m ² · 24hr · atm), the oxygen gas permeability 0.10 (cc · mm / m ²
24 hr · atm), the carbon dioxide gas transmission rate and the oxygen gas transmission rate are both smaller than those in Examples 6 and 7, and the container of Example 8 is a biaxially oriented polyethylene naphthalate container having even more excellent gas barrier properties. Is shown. Similarly, as shown in Examples 9 and 10, when the heat treatment time is further increased, the carbon dioxide gas transmission rate and the oxygen gas transmission rate are further reduced.

When comparing Examples 6 to 10 with Examples 1 to 5, Examples 6 to 10 are similar to Examples 1 to 5 except that a magnetic field is applied and the heat treatment temperature is slightly increased.
It is understood that the processing is performed under substantially the same conditions as in the first embodiment, but that the same effect can be obtained by greatly shortening the time as compared with the first to fifth embodiments in which no magnetic field is applied. Further, as can be seen by comparing Example 4 and Example 10, when the heat treatment temperature and the treatment time are almost the same, the application of a magnetic field greatly improves the gas barrier properties.

(Examples 11 to 13 and Comparative Examples 1 and 5)
A homopolyethylene naphthalate (PEN) resin produced from dimethyl-2,6-natalenedicarboxylate and ethylene glycol by a conventional method was used after solid-phase polymerization. The intrinsic viscosity (IV) of the PEN resin is 0.70 (dl)
/ G). Using this polyethylene naphthalate resin, an unstretched raw material having a thickness of 600 μm was formed.
C. for 1 minute, and simultaneously stretched biaxially at an extension rate of 1000% / min to an area magnification of 6 times.
After heat-setting for 2 seconds, a polyethylene naphthalate film having a thickness of 100 μm was obtained.

In a state where both ends of the film are fixed in an air oven, a magnetic field having a magnetic flux density of 5.0 T (tesla) is applied in the longitudinal direction of the film (the direction in which the unstretched raw material is extruded).
The film was heated at a temperature higher than the glass transition temperature (Tg = 123 ° C.) of the polyethylene naphthalate film under the following conditions. That is, in Example 11, the biaxially oriented polyethylene naphthalate film was heated in an air oven at 150 ° C. for 30 seconds. In Example 12, the biaxially oriented polyethylene naphthalate film was heated at 150 ° C. for 10 minutes. Heat treatment was performed at 150 ° C. for 30 minutes. In Comparative Example 1, the film was not heat-treated at all, and in Comparative Example 5, the film was heat-treated at 150 ° C. for 15 seconds. Table 3 shows the results of measuring the carbon dioxide gas transmission rate and the oxygen gas transmission rate of the films of Examples 11 to 13 and Comparative Examples 1 and 5.

[0063]

[Table 3]

As can be seen from Table 3, the biaxially oriented polyethylene naphthalate film was heated at 150 ° C. for 30 seconds while applying a magnetic field having a magnetic flux density of 5.0 T (tesla) to obtain an eleventh embodiment. film, carbon dioxide gas transmission rate is ^{1.0 (cc · mm / m 2} · 24hr · atm), the oxygen gas transmission rate is ^{0.36 (cc · mm / m 2} · 24hr · atm), and heated Carbon dioxide gas transmission rate,
Both of the oxygen gas transmission rates are small, indicating that the film of Example 11 is a biaxially oriented polyethylene naphthalate film having excellent gas barrier properties.

The film of Example 12 obtained by heating the biaxially oriented polyethylene naphthalate film at 150 ° C. for 10 minutes while applying a magnetic field having a magnetic flux density of 5.0 T (tesla) has a carbon dioxide gas permeability of Is 0.6 (cc ・ mm / m ²
・ 24hr ・ atm), oxygen gas permeability is 0.25 (cc ・ mm / m ²・
24 hr · atm), both of the carbon dioxide gas transmission rate and the oxygen gas transmission rate are smaller than those of Example 11, and it is understood that the gas barrier properties are more excellent.

The film of Example 13 obtained by subjecting the biaxially oriented polyethylene naphthalate film to a heat treatment at 150 ° C. for 30 minutes while applying a magnetic field having a magnetic flux density of 5.0 T (tesla) has a carbon dioxide gas permeability. Is 0.3 (cc ・ mm / m ²
・ 24hr ・ atm), oxygen gas permeability is 0.13 (cc ・ mm / m ²・
24 hr · atm), both of the carbon dioxide gas transmission rate and the oxygen gas transmission rate are smaller than those of Examples 11 and 12, and it can be seen that the gas barrier property is further excellent.

When Examples 11 to 13 are compared with Examples 6 to 10, Examples 11 to 13 are heat-treated at a temperature higher than the glass transition temperature of the biaxially oriented polyethylene naphthalate film while applying a magnetic field. It is understood that the same effect can be obtained by greatly shortening the time as compared with Examples 6 to 10 in which heat treatment is performed at a temperature lower than the glass transition temperature while applying a magnetic field.

[0068]

As described above, the biaxially oriented polyethylene naphthalate product having the characteristics of the present invention has the mechanical properties (mechanical strength), thermal properties (heat resistance), With excellent gas barrier properties while maintaining excellent properties such as optical properties (transparency),
Therefore, it can be effectively used as a package for food or beverage, a package such as a bag, or a gas partition.

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Claims (4)

[Claims] 1. A biaxially oriented polyethylene naphthalate product formed from biaxially oriented polyethylene naphthalate, wherein the biaxially oriented polyethylene naphthalate product has a carbon dioxide gas permeability of 1.0 (cc · mm / m ^A biaxially oriented polyethylene naphthalate product having characteristics of not more than 2.24 hr.atm). 2. The biaxially oriented polyethylene naphthalate product according to claim 1, wherein the biaxially oriented polyethylene naphthalate product has a carbon dioxide gas permeability of 0.6 (cc · mm / m ²
A biaxially oriented polyethylene naphthalate product characterized by having a characteristic of not more than 24 hr · atm). 3. The biaxially oriented polyethylene naphthalate product according to claim 1 or 2, wherein the biaxially oriented polyethylene naphthalate product has a carbon dioxide gas permeability of 0.3 (cc).
A biaxially oriented polyethylene naphthalate product characterized by having a characteristic of not more than mm / m ² · 24 hr · atm). 4. The biaxially oriented polyethylene naphthalate product according to claim 1, wherein the biaxially oriented polyethylene naphthalate of the product comprises naphthalenedicarboxylic acid as a main acid component, and ethylene glycol. A biaxially oriented polyethylene naphthalate product characterized by having a main glycol component.