JPH05186614A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a polyester film excellent in transparency and gas barrier resistance such as for oxygen, useful as a packaging material for various applications by casting, drawing and heat treatment of a hot liquid crystal polyester made up of specific constituents. CONSTITUTION:The objective polyester film can be obtained by casting, drawing and heat treatment of a hot liquid crystal polyester. This film has the following characteristics: (1) oxygen permeability (20 deg.C, RH 65%):<=20cc.20mum/m<2>.day.atm; and (2) light transmittance: >=60%. The polyester can be prepared by acidolysis of e.g. a polyethylene terephthalate-based polyester or polyethylene naphthalate- based polyester with 6-acyloxy-2-naphthoic acid and, as necessary, p- acyloxybenzoic acid followed by raising polymerization degree, being made up of constituents of respective formulas I (Ar is 1,4-phenylene or 2,6- naphthylene) to IV with the following constitution: (a) constituents I and II are equimolar; (b) constituents I and II total 15-90mol%; (c) constituents III and IV total 85-10mol%; and (d) molar ratio of constituent III to a total of constituents III and IV is 0.1-1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film having excellent transparency and gas barrier properties such as oxygen barrier properties.

[0002]

2. Description of the Related Art Recently, a method has been proposed in which a so-called thermotropic (thermal) liquid crystal polymer that forms an optically anisotropic molten phase is used as a gas barrier material (Japanese Patent Laid-Open No. 61-192762). Kaisho 62-119265
JP-A-62-187033, JP-A-64-187033
-45242, JP-A-1-288421). In addition, Polym. Prepr. (Am. Chem. Soc., Div. Po
lym. Chem.), 30 (1), 3-4 (1989), 40 mol%
The melt extruded film obtained from the thermotropic liquid crystal polymer produced from polyethylene terephthalate and 60 mol% 4-acetoxybenzoic acid has an oxygen gas permeation amount at 35 ° C. of 36 ml · 20 μm / m ² · day ·
It has been reported to be atm.

Further, JP-A-62-68813 discloses a copolymer obtained by reacting a mixture of p-acetoxybenzoic acid and 6-acetoxy-2-naphthoic acid with an acetoxy aromatic carboxylic acid with polyethylene terephthalate. Polyesters are disclosed and described to improve flexural strength, flexural modulus, and heat distortion temperature as compared to using p-acetoxybenzoic acid alone as the acetoxyaromatic carboxylic acid.

[0004]

However, there are many problems in using the conventionally proposed thermal liquid crystal polymer as a film for gas barrier. That is, a film obtained from a conventionally proposed thermal liquid crystal polymer generally has a high degree of crystallinity, a large anisotropy of mechanical properties, a small elongation, and is substantially unstretchable. Therefore, it is very difficult to form a film for a gas barrier, and the transparency required in many cases as a gas barrier material is extremely poor.

On the other hand, proposals have been made for a thermal liquid crystal polymer which gives a molded article having a small mechanical property anisotropy. For example, Japanese Unexamined Patent Publication No. 60-28428 proposes a polyester having a terephthaloyl group, a 1,3-dioxyphenylene group and a 2-substituted-1,4-dioxyphenylene group. Thus, the introduction of the iso-skeleton and the substituent improves the moldability of the thermal liquid crystal polymer,
Although not always sufficient, it tends to be easier to produce various molded products. However, according to the studies by the present inventors, the gas barrier properties such as the oxygen barrier properties of the film obtained from the thermotropic liquid crystal polymer by the above method are not necessarily at a high level, and a non-oriented film prepared from the polymer solution is also used. It was also found that the stretchability was not sufficient.

[0006]

[Means for Solving the Problems] In view of such a situation,
The present inventors have earnestly studied to provide a film having excellent transparency which cannot be achieved by a film made of a conventional thermal liquid crystal polymer, and further having a high gas barrier property. Has been completed.

That is, the present invention provides the following formula I:

[0008]

[Chemical 5]

(Wherein Ar represents a 1,4-phenylene group or a 2,6-naphthylene group), a structural unit (1) represented by the following formula II

[0010]

[Chemical 6]

A structural unit (2) represented by the following formula III

[0012]

[Chemical 7]

A structural unit (3) represented by the following formula IV

[0014]

[Chemical 8]

The constitutional unit (4) represented by the formula (1) and the constitutional unit (1) and the constitutional unit (2) are contained in substantially the same number of moles, and the total amount of the constitutional unit (1) and the constitutional unit (2) is 15 to 90 mol%, the total amount of the structural unit (3) and the structural unit (4) is 10 to 85 mol%, and the total amount of the structural unit (3) and the structural unit (4) is less than that of the structural unit (3). It is composed of a thermal liquid crystal polyester [hereinafter, this is referred to as a thermal liquid crystal polyester (I)] having an amount ratio of 10 to 100 mol%, and has an oxygen permeation amount of 20 cc · 20 μm measured at 20 ° C. and a relative humidity of 65%. / M ² · day
-Atm or less, and a light transmittance of 60% or more, relates to a polyester film.

The term "film" used in the present specification includes a sheet-shaped ultrathin film to a thick film, and is in the form of a container such as a sheet, a plate or a bottle. Is also included.

The thermal liquid crystalline polyester (I) used in the present invention comprises the structural unit (1), the structural unit (2) and the structural unit (3) as essential structural units, and within the above range, the structural unit (4) may be included.

The structural unit (1) of the thermal liquid crystal polyester (I) used in the present invention is a terephthaloyl group and / or
Alternatively, it is a 2,6-naphthalenedicarbonyl group, which is a structural unit introduced by terephthalic acid or its ester-forming derivative, or naphthalene-2,6-dicarboxylic acid or its ester-forming derivative. A part of the structural unit (1), for example, up to 20 mol% may be replaced with a structural unit introduced by another dicarboxylic acid or its ester-forming derivative. Other dicarboxylic acid components include, for example, isophthalic acid, 2,7
-Naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-oxydibenzoic acid, 4,4'-methylenedibenzoic acid, 4,4'-sulfonyldibenzoic acid,
Aromatic dicarboxylic acids such as 4,4′-benzophenone dicarboxylic acid and diphenic acid, or 1,4-cyclohexanedicarboxylic acid, succinic acid, glutaric acid, adipic acid,
Examples thereof include alicyclic or aliphatic dicarboxylic acids such as pimelic acid, suberic acid, azelaic acid and sebacic acid. Further, if the amount of the obtained polyester is within the range capable of being melt-molded, it is possible to replace a part of the constitutional unit with one derived from a polyfunctional carboxylic acid having three or more functional groups.

The structural unit (2) in the thermal liquid crystal polyester (I) is an ethylenedioxy group and is introduced with ethylene glycol. Part of it, for example up to 20 mol%, may be replaced by constituent units which can be introduced by other glycols. Examples of glycol components other than ethylene glycol include 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol and 2-methyl-
1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-
Cyclohexanedimethanol, diethylene glycol,
Examples are triethylene glycol, o-, m- or p-xylylene glycol.

If the amount of the thermal liquid crystal polyester (I) is within a range capable of being melt-molded, a part of the structural unit (2) may be 3 parts of glycerin, trimethylolpropane, trimethylolpropane, pentaerythritol and the like. It is also possible to replace it with one derived from a polyhydric alcohol having a valency or more.

The structural unit (1) and the structural unit (2) in the thermal liquid crystalline polyester (I) are usually 2,6-naphthalene, which is a reaction in which terephthalic acid or its ester-forming derivative and ethylene glycol are the main starting materials. Reaction of dicarboxylic acid or its ester-forming derivative with ethylene glycol as a main starting material, or terephthalic acid or its ester-forming derivative with 2,6-
By using as a raw material a polyester obtained by the reaction of naphthalene dicarboxylic acid or its ester-forming derivative and ethylene glycol as a main starting material, it is introduced into the molecule of the thermal liquid crystal polyester (I) used in the present invention. To be done.

The raw material polyester, polyethylene terephthalate polyester, polyethylene naphthalate polyester or a copolymer thereof, can be produced according to the method proposed in the production of ordinary polyesters. Examples thereof include a method in which a dicarboxylic acid and a glycol are subjected to an esterification reaction and then polycondensation, and a method in which a dicarboxylic acid ester and a glycol are transesterified and then polycondensation. At that time, it may sometimes be preferable to use an esterification catalyst, a transesterification catalyst, a polycondensation catalyst, a stabilizer, etc., and these catalysts, stabilizers, etc. are used in the production of polyester, particularly polyethylene terephthalate. What is known as a possible catalyst or stabilizer can be used. For example, as a catalyst for accelerating these reactions, compounds of metals such as sodium, magnesium, calcium, zinc, manganese, tin, tungsten, germanium, titanium and antimony, and as stabilizers phosphoric acid, phosphate ester, Examples thereof include phosphorus compounds such as phosphorous acid and phosphorous acid ester. Further, other additives (colorants, ultraviolet absorbers, light stabilizers, antistatic agents, flame retardants, crystallization accelerators, etc.) can be added as required.

The structural unit (1) and the structural unit (2) are
In the total amount thereof, in the thermal liquid crystal polyester (I),
It is present in the range of 15-90 mol%, preferably in the range of 25-85 mol%, more preferably in the range of 30-80 mol%.

The structural unit (3) and the structural unit (4) are
A structural unit introduced by 6-hydroxy-2-naphthoic acid or its ester-forming derivative and a structural unit introduced by p-hydroxybenzoic acid or its ester-forming derivative, respectively. A part of the structural unit (3) and the structural unit (4), for example, up to 10 mol%, is a structural unit other than the structural unit (3) and the structural unit (4), that is, a 6-oxy-2-naphthoyl group and p-. It may be replaced with an oxyaromatic carbonyl group other than the oxybenzoyl group. Hydroxycarboxylic acid components for forming such groups include m-hydroxybenzoic acid, 4-hydroxy-3-chlorobenzoic acid, 4
-Hydroxy-3,5-dimethylbenzoic acid, 4-hydroxy-3-methylbenzoic acid, 7-hydroxy-2-naphthoic acid, 4-hydroxy-1-naphthoic acid, 5-hydroxy-1-naphthoic acid, p- Examples thereof include hydroxymethylbenzoic acid, p-hydroxyphenylacetic acid, p-hydroxymethoxybenzoic acid, glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid and their ester-forming derivatives. Further, a polyhydric hydroxy acid or the like can be blended as long as the thermal liquid crystal polyester (I) is in an amount within a range capable of being melt-molded.

In the thermal liquid crystal polyester (I), the total content of the structural unit (3) and the structural unit (4) is 1
A range of 0 to 85 mol% is suitable, and preferably 15 to
It is 75 mol%, and more preferably 20 to 70 mol%. When the total content of the structural unit (3) and the structural unit (4) exceeds 85 mol%, disadvantages such as difficulty in melt polymerization and marked deterioration of film moldability occur, and less than 10 mol%. In that case, the obtained polyester does not form a thermal liquid crystal, and the gas barrier property of the film is significantly lowered.

The ratio of the amount of the structural unit (3) to the total amount of the structural unit (3) and the structural unit (4) is 1
0 to 100 mol%, preferably 20 to 100 mol%, more preferably 30 to 100 mol%, which gives a film having excellent film forming processability and extremely excellent gas barrier property. ..

The constitutional unit (3) and the constitutional unit (4) in the thermal liquid crystal polyester (I) are usually used in the polymer molecule by using the corresponding hydroxycarboxylic acid or its ester-forming derivative (eg acyloxycarboxylic acid) as a raw material. Will be introduced to. As the acyloxycarboxylic acid, a lower aliphatic acyloxycarboxylic acid (particularly acetoxycarboxylic acid) obtained by reacting a corresponding hydroxycarboxylic acid with a lower aliphatic acid anhydride (particularly acetic anhydride) is particularly preferable.

Further, if necessary, other additives (colorant, ultraviolet absorber, light stabilizer, antistatic agent, flame retardant,
A crystallization accelerator, etc.) can also be added.

The thermal liquid crystalline polyester (I) forms a liquid crystal in the molten phase (it exhibits optical anisotropy). To confirm such optical anisotropy in the molten phase, a thin piece of a sample, preferably a thin piece of about 5 to 20 μm, is sandwiched between cover glasses under a crossed Nicols using a polarizing microscope equipped with a well-known heating device. This can be done by observing at a constant heating rate and seeing that light is transmitted at a certain temperature or higher. In this observation, the transmission of polarized light can be more reliably observed by applying a light pressure to the sample sandwiched between the cover glasses at high temperature or by sliding the cover glass. In this observation, the temperature at which polarized light starts to transmit is the transition temperature to the optically anisotropic molten phase. From the viewpoint of ease of melt molding, the transition temperature is desirably 350 ° C. or lower, more preferably 300 ° C. or lower.

The transition temperature of the thermally liquid crystal polyester (I) to the optically anisotropic molten phase is difficult to determine by a differential scanning calorimeter, unlike the conventionally proposed thermal liquid crystal polyester. That is, thermal liquid crystal polyester (I)
When measured with a differential scanning calorimeter, a clear endothermic peak may not be observed depending on the composition, and even if an endothermic peak is observed, the peak is not always based on the transition from the crystal to the liquid crystal. Not a thing. In the thermal liquid crystal polyester (I), the endothermic peak becomes smaller as the proportion of the structural unit (3) increases, and the structural unit (3)
When the total of the above ratios is 35 mol% or more, the endothermic peak is often not observed.

The thermal liquid crystalline polyester (I) is produced, for example, by first using polyethylene terephthalate type polyester,
A polyester fragment is prepared by acidolysing a polyethylene naphthalate-based polyester or a copolymer or mixture thereof, preferably with 6-acyloxy-2-naphthoic acid and p-acyloxybenzoic acid, followed by a degree of polymerization of the polyester fragment. Is carried out by a method for preparing the desired thermal liquid crystal polyester (I). The first stage acidolysis is usually carried out at 250 to 300 ° C. in an atmosphere of an inert gas such as nitrogen, argon or carbon dioxide.

As a raw material compound, 6-acyloxy-2
-Naphthoic acid and p-acyloxybenzoic acid, as well as 6-hydroxy-2-naphthoic acid and p-
-Hydroxybenzoic acid can also be used. In that case, the compound is formed by reacting the compound with a lower aliphatic acid anhydride, preferably acetic anhydride, and converting (acylating) substantially all hydroxyl groups into acyloxy groups, preferably acetoxy groups. The thermal liquid crystal polyester (I) used in the present invention is produced by reacting the corresponding acyl ester with the starting polyester without isolation. In this case, the raw material polyester can be added to the system at any time before or after the acylation reaction of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid.

In the acylation reaction step of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid, 6
In the case of a composition having a high content of 2-hydroxy-2-naphthoic acid, 6-acyloxy-2 produced as the reaction proceeds.
-Since naphthoic acid precipitates in the system and makes the system inhomogeneous, it may not be possible to smoothly proceed the subsequent polymerization, and it is not preferable for the randomness of the produced polymer. May have an impact. Therefore,
In order to prevent it, a solvent having a boiling point of about 100 to 300 ° C., particularly preferably acetic acid, which does not adversely affect the desired acylation reaction, is present in the system,
In addition, it is preferable to employ reaction temperature conditions in which acidolysis of the raw material polyester is sufficiently completed.

Next, the acidolysis reaction of 6-acyloxy-2-naphthoic acid with p-acyloxybenzoic acid and the raw material polyester is carried out. At this acidolysis stage, most of the theoretical distillate amount of the lower aliphatic acid derived from the acyl group (eg, acetic acid) goes out of the system. Then, the product of this acidolysis reaction is further subjected to reduced lower aliphatic acid under reduced pressure at 250 to 350 ° C. to obtain a viscosity suitable for forming a desired film, for example, a logarithmic viscosity of 0.1 deciliter / g or more. Increase the degree of polymerization up to. In this case, the polymerization temperature is preferably 270 ° C. or higher from the viewpoint of reaction rate, and 350 ° C. or lower from the viewpoint of stability of the polyester, and particularly preferably 270 to 320 ° C. In this polymerization step, it is desirable that the degree of reduced pressure in the system is gradually raised to finally 1 mmHg or less, preferably 0.5 mmHg or less. Further, in order to further increase the molecular weight, it is possible to use a well-known solid phase polymerization method or the like depending on the composition.

The logarithmic viscosity of the thermal liquid crystalline polyester (I) measured at 60 ° C. in pentafluorophenol is 0.1 deciliter / in terms of the mechanical strength of the resulting molded article.
g or more, preferably 0.3 deciliter / g or more, more preferably 0.4 deciliter / g or more. Also,
Although there is no critical upper limit to the logarithmic viscosity, it is preferably 3.0 deciliter / g or less, more preferably 2.0 deciliter / g or less, from the viewpoint of ease of melt polymerization, moldability and the like.

Unlike conventionally known thermal liquid crystal polymers, the thermal liquid crystal polyester (I) has a very low crystallinity in a film obtained by rapidly cooling it from a molten state, and in the usual case, it is a crystal obtained by X-ray diffraction. The degree of chemical conversion is 20% or less. The crystallinity decreases as the proportion of the structural units (3) and (4) in the polyester increases. For this reason,
Unlike the conventionally proposed thermal liquid crystal polyester, the film obtained from the thermal liquid crystal polyester (I) is capable of being uniaxially and biaxially thermally stretched, and is often 2 × 2 times or more or 3 × 3 times or more. Double or more simultaneous or sequential biaxial stretching is possible.

In producing the film of the present invention,
First, the thermal liquid crystal polyester (I) is cast. At that time, usually, the thermal liquid crystal polyester (I) is dissolved in a solvent before casting. The solvent may be any one that can dissolve the polyester at room temperature or under heating, and examples of such a solvent include pentafluorophenol, trifluoroacetic acid, p-fluorophenol, pentafluoroisopropanol, phenol and the like. Although it can be mentioned, it is preferable to use pentafluorophenol from the viewpoint of boiling point and solubility. It is also possible to mix and use another solvent, for example, chloroform, methylene chloride, tetrachloroethane, etc., in the above-mentioned solvent within the range in which the polyester does not precipitate at the time of casting described later.

The dissolved concentration of the thermal liquid crystal polyester (I) is
There is no particular limitation as long as the concentration of the liquid crystal polyester (I) is transparent and can be uniformly dissolved, but from the viewpoint of workability or economy, it is usually 0.1 to 15% by weight, preferably 1 to 10%.
It is in the range of% by weight.

Then, the above solution is filtered by a filter as needed to remove fine foreign matters contained in the solution, and then the solution is placed on a flat and uniform support made of plastic such as Teflon, metal or glass. A non-oriented film is obtained by casting, then volatilizing the solvent, and then peeling from the support. The non-oriented film thus obtained has a glass transition point lower by about 15 to 30 ° C. than that of a film usually obtained by melt molding. The non-oriented film is preferably dried by heating at a temperature 5 ° C. or more lower than its glass transition point.

The non-oriented film thus obtained is transparent and the molecules of the thermal liquid crystal polyester (I) are not substantially oriented. This is confirmed by, for example, X-ray wide-angle scattering method or observation with a polarizing microscope. Further, the transparency is in the range of 60 to 95% as measured under a visible light region condition with a commercially available spectrophotometer.

The thickness of the above-mentioned non-oriented film is not particularly limited, and can be set according to the thickness required for the film finally obtained after the stretching treatment and heat treatment described below, Usually, the range of 1 to 1000 μm is used. The thickness of such a non-oriented film can be set depending on, for example, the concentration of the solution used or the casting conditions.

Next, the above-mentioned non-oriented transparent film is stretched. Unlike the conventionally proposed thermal liquid crystal polyester, the above-mentioned non-oriented film is usually capable of simultaneous 2x2 times or more or 3x3 times or more simultaneous or sequential biaxial stretching.

The stretching ratio during this stretching treatment is 1.
2 × 1.2 times or more, preferably 1.5 × 1.5 times or more,
It is more preferably 2 × 2 times or more. Draw ratio is 1.2
If it is less than 1.2 times, the transparency of the film may be significantly reduced during the heat treatment described below, which is not preferable.

The temperature at which this stretching treatment is carried out is about 5 ° C. to about 30 ° C. higher than the glass transition point of the obtained non-oriented film.
C., preferably about 10.degree. C. to 25.degree. C. higher temperature range is suitable, when the temperature is lower than this temperature range, the stretchability of the film is not sufficient, and at higher temperature, the transparency of the film is low. It is not preferable because it may be damaged.

After the above stretching treatment, heat treatment is performed. The heating temperature in this case is about 5 to about 50 ° C, preferably about 10 to about 4 than the glass transition point of the non-oriented film used for stretching.
It is preferable to carry out the treatment in a high temperature range of 0 ° C. for 15 minutes to 20 hours, preferably 30 minutes to 15 hours. If the heat treatment temperature is too low, the gas barrier properties of the obtained film may not be sufficiently exhibited, and if it is too high, the transparency of the obtained film may be impaired, which is not preferable.

The film of the present invention is excellent in gas barrier property, for example, the oxygen barrier property is 20 to 400 times or more that of the polyethylene terephthalate film. The oxygen permeability of the film of the present invention measured under the conditions of 20 ° C. and 65% relative humidity is 20 cc · 20 μm /
m ² · day · atm or less. The oxygen permeation amount of the film of the present invention is 15 cc · 20 μm / m ² · day · a.
It is preferably tm or less and 10 cc · 20 μm /
It is more preferably m ² · day · atm or less.

Further, the film of the present invention is excellent in transparency, and the light transmittance thereof measured by ASTM D-1003-61 is 60% or more. The film of the present invention preferably has a light transmittance of 65% or more, and 70%.
The above is more preferable.

The polyester of the present invention has excellent properties such as hygiene, aroma retention and processability.
It can be widely used as a film-like container or packaging material for soy sauce, seasonings such as sauces, soft drinks such as juices, cosmetics, pharmaceuticals and the like.

[0049]

EXAMPLES The present invention will be specifically described below with reference to examples. The physical property values in the examples were measured by the following methods.

1) Logarithmic viscosity (η _inh ) It was measured at 60 ° C. at a concentration of 0.1 g / deciliter using a pentafluorophenol solvent.

Η _inh = ln (t ₁ / t ₀ ) / c

[ _Wherein , η _inh represents logarithmic viscosity (deciliter / g), t ₀ represents flow-down time (second) in the solvent, and t ₁
Represents the flow-down time (second) in the sample solution, and c represents the concentration of the sample in the solution. ]

2) Thermal analysis Differential scanning calorimeter (DSC; manufactured by METTLER CORPORATION, TA-300)
For the sample obtained by rapidly cooling the thermo-liquid crystal polyester from the molten state using the (0 type), 3 at a temperature rising rate of 10 ° C./min.
The measurement was performed in the temperature range of 0 to 300 ° C., and the obtained non-oriented film was measured in the temperature range of 0 to 300 ° C. at a temperature rising rate of 10 ° C./min without once melting.

3) Oxygen transmission rate (PO ₂ ) Gas transmission rate measuring device (MODERN CONTROLS)
20 by using OX-TRAN10 / 50A)
It was measured under the conditions of ° C and 65% relative humidity. Unit is cc ・ 2
It is 0 μm / m ² · day · atm.

4) Transparency of film ASTM using a Poic integrating sphere type light transmittance meter (manufactured by Nippon Seimitsu Optical Co., Ltd., SEP-HS.30D-R type)
It was measured by a method according to D-1003-61.

Synthetic Example 1 1316 g (7.0 mol) of 6-hydroxy-2-naphthoic acid and 138 g of p-hydroxybenzoic acid were placed in a reactor having an internal volume of 8 liter equipped with a stirrer, a distillation column and a nitrogen gas inlet. 1.0 mol), acetic anhydride 918 g (9.0
384 g of polyethylene terephthalate having an intrinsic viscosity of 0.70 deciliter / g measured at 30 ° C. by using a mixed solvent such as phenol / tetrachloroethane.
(2.0 mol) and acetic acid 960 g as a reaction solvent
(16.0 mol) was charged, and the atmosphere in the reaction system was replaced with nitrogen three times, and then the mixture was stirred and heated under a reflux condition under a nitrogen stream for about 2 hours. Next, after stirring and heating at 230 ° C. for about 2 hours and then raising the temperature to 270 ° C. over about 2 hours, the pressure inside the system was gradually reduced and the reaction was performed at 280 ° C. and about 30 mmHg for about 2 hours.
About 95% of the theoretical amount of acetic acid and acetic anhydride were distilled. Next, the degree of vacuum in the reaction system was further raised, and the reaction was carried out at 1 mmHg or less for 1 hour, and then the produced polyester (this is called thermal liquid crystalline polyester A) was taken out.

The obtained polyester micropieces were heated in a microscope heating device (Linkam Co., TH-600) under a nitrogen atmosphere at a rate of 10 ° C./min and under a polarizing microscope orthogonal Nicols. Observation revealed that light started to be transmitted from around 150 ° C., and the amount of transmitted light further increased with increasing temperature, and finally an optically anisotropic molten phase was formed even after increasing the temperature to 350 ° C. It remained. In addition, a sample obtained by rapidly cooling the polyester from a molten state of 280 ° C. to 30 ° C.
DSC in the range of 30 to 400 ° C at a heating rate of 10 ° C / min
As a result of the analysis by 1., no endothermic peak was observed except that a glass transition point was observed at 95 ° C. Furthermore, as a result of measuring the crystallinity of a sample obtained by rapidly cooling the polyester from a molten state by an X-ray wide angle scattering method, the crystallinity of the sample was 1
It was 0%. Furthermore, the logarithmic viscosity of this polyester measured at 60 ° C. in a pentafluorophenol solvent is 1.
It was 02 deciliter / g.

Synthesis Example 2 Polyethylene with an intrinsic viscosity of 0.65 deciliter / g measured at 30 ° C. using 1128 g (6.0 mol) of 6-hydroxy-2-naphthoic acid and a mixed solvent of phenol / tetrachloroethane and the like in weight. Phthalate 975 g (4.0
Mol), 734 g (7.2 mol) of acetic anhydride and 720 g (12.0 mol) of acetic acid as a reaction solvent were used in Synthesis Example 1
The reaction system was charged into the reactor used in 1., and the inside of the reaction system was replaced with nitrogen three times, and then the mixture was stirred and heated under a nitrogen stream under reflux conditions for about 2 hours.
Next, the mixture is heated with stirring at 230 ° C. for about 2 hours, then heated to 270 ° C. over about 2 hours, and then the pressure in the system is gradually reduced,
As a result of reacting at 290 ° C. and about 30 mmHg for about 2 hours, about 95% of the theoretical amount of acetic acid and acetic anhydride were distilled. Next, further increase the degree of vacuum in the reaction system to 1 below 1 mmHg.
After reacting for a period of time, the produced polyester (this is referred to as thermal liquid crystal polyester B) was taken out.

Synthesis Example 1 of the obtained polyester micro pieces
When observed under a crossed Nicols with a polarizing microscope in the same manner as in, the light started to be transmitted from around 150 ° C, and the amount of transmitted light further increased with increasing temperature, and finally reached 350 ° C.
Even when the temperature was raised to, an optically anisotropic molten phase was still formed. Also, this polyester was used in the same manner as in Synthesis Example 1
As a result of SC analysis, no endothermic peak was observed at all, except that a glass transition point was observed at 90 ° C. Further, the crystallinity of a sample obtained by rapidly cooling the polyester from the molten state was measured by the X-ray wide angle scattering method, and as a result, the crystallinity of the sample was 8%. Furthermore, the inherent viscosity of this polyester measured at 60 ° C. in a pentafluorophenol solvent was 1.15 deciliter / g.

Synthesis Example 3 1080 g (6.0 mol) of p-acetoxybenzoic acid and 768 g (4.0 mol) of polyethylene terephthalate similar to that used in Synthesis Example 1 were placed in the same reactor as used in Synthesis Example 1. After charging and purging the reaction system with nitrogen three times, the mixture was stirred and heated under a nitrogen stream at 280 ° C. for about 1 hour, and about 90% of the theoretical amount of acetic acid was distilled. Next, the pressure inside the system was gradually reduced, and after finally reacting at 1 mmHg or less for 5 hours, the produced polyester (this is referred to as thermal liquid crystalline polyester C) was taken out.

Synthesis Example 1 of the obtained polyester micro pieces
When observed under a crossed Nicols with a polarizing microscope in the same manner as in, the light started to be transmitted from around 200 ° C., and the amount of transmitted light was further increased with increasing temperature, and finally 350 ° C.
Even when the temperature was raised to, an optically anisotropic molten phase was still formed. As a result of DSC analysis of this polyester in the same manner as in Synthesis Example 1, a glass transition point was not clearly observed and an endothermic peak was observed at 205 ° C.
Further, the crystallinity of a sample obtained by rapidly cooling the polyester from the molten state was measured by the X-ray wide angle scattering method, and as a result, the crystallinity of the sample was 25%. Furthermore, of this polyester,
The logarithmic viscosity measured at 60 ° C. in a pentafluorophenol solvent was 0.60 deciliter / g.

Synthesis Example 4 166 g (1.0 mol) of terephthalic acid, 100 g (0.52 mol) of resorcinol diacetate, and 104 g (0.5 mol) of methylhydroquinone diacetate.
Was charged into a reactor similar to that used in Synthesis Example 1, the inside of the reaction system was replaced with nitrogen three times, and then 5 while stirring under a nitrogen stream.
The temperature was raised to 200 ° C. to 320 ° C. over time, and about 90% of the theoretical amount of acetic acid was distilled. Then, the degree of vacuum in the reaction system was further raised, and the reaction was carried out at 1 mmHg or less for 1 hour, and then the produced polyester (this is referred to as thermal liquid crystalline polyester D) was taken out.

Synthesis Example 1 of the obtained polyester micro pieces
When observed under a crossed Nicols polarization microscope in the same manner as in, the light transmission started at around 200 ° C, and the amount of transmitted light further increased with increasing temperature, and finally reached 350 ° C.
Even when the temperature was raised to, an optically anisotropic molten phase was still formed. The polyester was analyzed by DSC in the same manner as in Synthesis Example 1, and as a result, a glass transition point at 127 ° C and an endothermic peak at 200 ° C were observed. Further, the crystallinity of a sample obtained by rapidly cooling the polyester from the molten state is X.
As a result of measurement by the line wide-angle scattering method, the crystallinity of the sample was 10
%Met. Furthermore, this polyester has a logarithmic viscosity of 0.5 measured at 60 ° C. in a pentafluorophenol solvent.
It was 5 deciliters / g.

Example 1 The thermal liquid crystal polyester A synthesized in Synthesis Example 1 was mixed with pentafluorophenol / chloroform (30/70 weight ratio).
It was dissolved in a mixed solvent to prepare a solvent having a concentration of about 5%. After this solution was filtered, it was cast on a glass plate and the solvent was volatilized under a nitrogen stream and under reduced pressure at about 50 ° C. to obtain a transparent non-oriented film. The thickness of the obtained film is about 80μ.
It was m. This film was confirmed to be non-oriented by X-ray wide-angle scattering method and observation under a polarizing microscope orthogonal Nicols. Further, as a result of DSC analysis of minute pieces of this film at a temperature rising rate of 10 ° C./min in a temperature range of 0 ° C. to 300 ° C., no endothermic peak was observed except that a glass transition point was observed at 65 ° C. Next, this non-oriented film was simultaneously biaxially stretched 2 × 2 times at 85 ° C. using a biaxial stretching device (manufactured by Shibayama Scientific Instruments Co., Ltd.), and further 100 ° C.
Was heat-treated for 12 hours to obtain a transparent stretched film having a thickness of about 20 μm.

Table 1 shows the evaluation results of the oxygen transmission amount and transparency of this film.

Example 2 A non-oriented film was prepared in the same manner as in Example 1 except that the thermal liquid crystal polyester B synthesized in Synthesis Example 2 was used.
The fine pieces of the film were processed in the same manner as in Example 1, and D
As a result of analysis by SC, no endothermic peak was observed at all except that a glass transition point was observed at 60 ° C. Next, this non-oriented film was simultaneously biaxially stretched at 80 ° C. to 2 × 2 times and further heat-treated at 100 ° C. for 12 hours to obtain a transparent stretched film.

Table 1 shows the evaluation results of the amount of oxygen permeation and the transparency of this film.

Comparative Example 1 A non-oriented film was produced in the same manner as in Example 1 except that the thermal liquid crystal polyester C synthesized in Synthesis Example 3 was used.
The fine pieces of the film were processed in the same manner as in Example 1, and D
As a result of analysis by SC, the glass transition point was 48 ° C and the temperature was 205 ° C.
An endothermic peak was observed at. Next, this non-oriented film was simultaneously biaxially stretched 2 × 2 times at 70 ° C., and then further 80
The heat treatment was tried at each temperature in the range of 100 ° C to 100 ° C, but the whitening and shrinkage of the film were remarkable at any temperature, and a good film could not be obtained.

Comparative Example 2 A non-oriented film was prepared in the same manner as in Example 1 except that the thermal liquid crystal polyester D synthesized in Synthesis Example 4 was used.
The fine pieces of the film were processed in the same manner as in Example 1, and D
As a result of analysis by SC, a glass transition point at 97 ° C, 200 ° C
An endothermic peak was observed at. Next, this non-oriented film was tried to be simultaneously biaxially stretched 2 × 2 times in the range of 95 ° C. to 130 ° C. No stretchability was observed at any temperature, and the film was broken at all. ..

Comparative Example 3 The thermal liquid crystal polyester A used in Synthesis Example 1 was melt hot pressed at 280 ° C. and then rapidly cooled by a water cooling type cooling press to prepare a film having a thickness of about 80 μm. This film was simultaneously biaxially stretched 2 × 2 times at 150 ° C. using the same apparatus as used in Example 1 to obtain a stretched film having a thickness of about 20 μm.

Table 1 shows the evaluation results of the amount of oxygen permeation and the transparency of this film.

Comparative Example 4 The hot liquid crystal polyester B synthesized in Synthesis Example 2 was melt hot pressed at 280 ° C. and then rapidly cooled by a water cooling type cooling press to prepare a film having a thickness of about 80 μm. This film was 2 × 2 at 150 ° C. using the same equipment as used in Example 1.
The film was biaxially stretched twice to obtain a stretched film having a thickness of about 20 μm.

Table 1 shows the evaluation results of the amount of oxygen permeation and the transparency of this film.

[0074]

[Table 1]

[0075]

INDUSTRIAL APPLICABILITY The film of the present invention has excellent transparency and gas barrier properties, and is therefore useful as various packaging materials that require high transparency and gas barrier properties.

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Claims (2)

[Claims] 1. The following formula I: (In the formula, Ar represents a 1,4-phenylene group or a 2,6-naphthylene group.), A structural unit (1) represented by the following formula II: A structural unit (2) represented by the following formula III: A structural unit (3) represented by the following formula IV: Of the structural unit (4), the structural unit (1) and the structural unit (2) are contained in substantially the same number of moles, and the total amount of the structural unit (1) and the structural unit (2) is 15 to 90. Mol%, the total amount of the structural unit (3) and the structural unit (4) is 85 to 10 mol%, and the ratio of the amount of the structural unit (3) to the total amount of the structural unit (3) and the structural unit (4). Is 10 to 100 mol% of the thermal liquid crystalline polyester, the oxygen transmission rate measured under the conditions of 20 ° C. and 65% relative humidity is 20 cc · 20 μm / m ² · day · atm or less, and the light transmittance is A polyester film which is 60% or more. 2. The polyester film according to claim 1, which is produced by drawing a non-oriented film obtained by casting the thermal liquid crystal polyester according to claim 1 and further heat-treating the non-oriented film.