JPH05186577A - Thermotropic liquid-crystalline polyester and its production - Google Patents

Abstract

PURPOSE:To obtain the title polyester excellent in moldability, oxygen barrier properties, and uniformity by reacting a polyethylene terephthalate polyester, a specific hydroxyarom. carboxylic acid, and a lower fatty and anhydride in a specific manner. CONSTITUTION:A polyethylene terephthalate polyester, a hydroxyarom. carboxylic acid (including 6-hydroxy-2-naphthoic acid), and a lower fatty acid anhydride in an amt. of 1.02-1.50 equivalents based on 1.0 equivalent of the hydroxyarom. carboxylic acid are reacted at 100-150 deg.C in the presence of a solvent until the conversion of the hydroxyarom. carboxylic acid exceeds 95mol%, and the reaction mixture is further reacted at above 150 deg.C to give the title polyester, which can thermally be stretched, contains no foreign matter due to formation of a high-melting polyester, and is esp. suitable for preparing a sheet or film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel copolymerized polyester which forms an optically anisotropic molten phase, a molded article made of the same, and a method for producing the polyester suitable for producing the polyester. The copolyester provided by the present invention is excellent in molding processability and oxygen barrier property, and is excellent in uniformity such as no mixing of high melting point components, and therefore, as a film-like gas barrier material such as a food and drink packaging material. Gives useful molded articles. Further, according to the production method of the present invention, a polyester such as the above-described copolyester of the present invention can be produced in a short reaction time even if it has a high degree of polymerization while suppressing the mixing of high-melting point components. It is possible.

[0002]

2. Description of the Related Art Polyester, especially polyethylene terephthalate (hereinafter sometimes abbreviated as PET),
Because it has excellent properties such as hygiene, aroma retention, and processability, it is widely used as a container for seasonings such as soy sauce and sauces, soft drinks such as juice, cola, and ramune, draft beer, cosmetics, and pharmaceuticals. It's being used. Further, in addition to the above-mentioned properties, it is lighter than glass, and has appropriate pressure resistance and gas barrier properties, and therefore, further expansion as a substitute for glass bottles is expected in the future. However, the shelf life of lager beer, wine, etc., which is expected to be the largest market as a substitute for glass bottles, will be long, and for carbonated drinks, etc., the surface area of the container per unit volume will increase due to the miniaturization of the container. There is a strong demand for improvement of the gas barrier property of the container in order to further reduce the invasion of oxygen and the dissipation of carbon dioxide from the container. It is extremely difficult to improve the gas barrier property of PET itself because it is already at a fairly high level and it is necessary to improve without compromising the mechanical properties such as container molding performance and pressure resistance. It is also a problem.

Conventionally, various methods have been proposed for improving the gas barrier property of PET containers. For example, a method of coating polyvinylidene chloride or the like on the inner and outer layers of the container, or a saponification product of ethylene-vinyl acetate copolymer, etc.
Although a method of forming a multilayer structure of layers (Japanese Patent Laid-Open No. 56-77143) and the like have been proposed, these methods require equipment for coating or a multilayer container in addition to conventional polyester molding equipment, which is industrial. Not only is it disadvantageous in the case of using multi-layer containers due to the use of different types of polymers, but it also has the disadvantages of collecting and reusing used containers and incinerating them. There is. In addition, a method for producing a container from a blend of polyester and a different polymer such as nylon has been proposed (Japanese Patent Publication No. 53-33618 and Japanese Patent Publication No. 56-64839). In this case, it is possible to manufacture the container with the existing equipment, but it is disadvantageous in that the physical property of the container is deteriorated and the recovery and reuse are performed.

On the other hand, in recent years, a method of using a so-called thermotropic liquid crystal polymer which forms an optically anisotropic molten phase as a gas barrier material has been proposed (JP-A-61-61).
-192762, JP-A-62-119265, JP-A-62-187033, JP-A-64-4
No. 5242, JP-A-1-288421). Also, in Polym. Prepr. (Am. Chem. So
c. , Div. Polym. Chem. ), 30
(1), 3-4 (1989), oxygen at 35 ° C. of a melt-extruded film obtained from a thermotropic liquid crystal polyester produced from 40 mol% polyethylene terephthalate and 60 mol% 4-acetoxybenzoic acid. Gas permeation amount is 36ml, 20μm / m ↑ 2 ・ day ・ a
It has been reported to be tm.

However, when the conventionally proposed thermotropic liquid crystal polymer is used as a molded body for oxygen barrier, there are always many problems. That is, the first problem is that molded products obtained from thermotropic liquid crystal polymers that have hitherto been proposed generally have a high degree of crystallinity, a large anisotropy of mechanical properties, and a low elongation. The point is that stretching is substantially impossible.
It is very difficult to mold such polymers into various molded articles for oxygen barriers, such as films, sheets, bottles, cups, trays and bags. A second problem is that it is difficult to say that the oxygen barrier property of the obtained molded product is always sufficiently high. For example, the above-mentioned polyethylene terephthalate and 4
-The thermotropic liquid crystal polyester produced from acetoxybenzoic acid has improved moldability, but the oxygen gas permeation amount of the film obtained from it is 36 ml / 20 μm / m ↑ 2 · day · a as described above.
It is not necessarily a high performance oxygen barrier material as reported as tm.

The thermotropic liquid crystal polyester obtained by the reaction of the above-mentioned polyethylene terephthalate and 4-acetoxybenzoic acid also has a problem in production. Japanese Patent Publication Sho 56
The method for producing polyester disclosed in Japanese Patent Publication No. 18016 has the following problems. That is, first, 4-acetoxybenzoic acid used as a raw material is generally isolated after reacting p-hydroxybenzoic acid with acetic anhydride.
Since it is purified and produced, a complicated production process is required, and it is not a preferable industrial raw material in terms of equipment and cost. Secondly, the polymerization reaction rate is extremely slow, so It is difficult to obtain a sufficiently high polyester, and a thermal liquid crystal polyester capable of giving a molded article having sufficiently high strength cannot be produced with high productivity.

For the purpose of solving such a problem, a method of using a non-acetylated hydroxyaromatic carboxylic acid as one of the raw materials has been proposed. For example, JP-A-62-277427 and JP-A-62-285.
Japanese Patent No. 916 discloses a method for producing a polyester by reacting a raw material polyalkylene terephthalate and a hydroxyaromatic carboxylic acid in the presence of an anhydride of a lower aliphatic acid, and then polycondensing the resulting product. It is described that, compared with the case where an aromatic carboxylic acid is used as a starting material, the polymerization rate is high, the degree of polymerization of the obtained polymer is high, and the color tone is excellent.

On the other hand, in JP-A-62-68813, an acetoxy aromatic carboxylic acid 40 consisting of 6-acetoxy-2-naphthoic acid and p-acetoxybenzoic acid is disclosed.
~ 80 mol% and polyethylene terephthalate 20-60
Copolymerized polyesters obtained by reaction with mol% are disclosed, and p-as the acetoxy aromatic carboxylic acid is disclosed.
It is described that the bending strength, the bending elastic modulus, and the heat distortion temperature are improved as compared with the case where only acetoxybenzoic acid is used.

[0009]

As a result of studies by the present inventors, among the copolyesters described in JP-A-62-68813, a specific polyester having a thermotropic liquid crystallinity in composition is It has been found that it has good moldability and oxygen barrier property and is suitable as a gas barrier material. However, when such a thermotropic liquid crystal polyester is produced by using the acetoxy aromatic carboxylic acid and polyethylene terephthalate according to the method described in JP-A-62-68813, a mixture of these is used at a temperature not lower than the melting point of each raw material compound. It is necessary to react at a temperature, specifically, 270 to 320 ° C., at which time the formation of a homopolymer of acetoxy aromatic carboxylic acid remarkably occurs, and at the same time, the acidolysis reaction of polyethylene terephthalate cannot occur sufficiently, The polymer obtained has a high block property, and the chemical structure and molecular weight of each molecule tend to be inhomogeneous, and when a high melting point polyester rich in acetoxy aromatic carboxylic acid component is mixed, a film is formed. Molded products such as Akira was found that there even be unsatisfactory surface smoothness to be mixed.

Further, according to the study by the present inventors, the above-mentioned JP-A-62-277427 and JP-A-62-28
When 6-hydroxy-2-naphthoic acid is used as one of the starting materials in the method described in Japanese Patent No. 5916, the reaction is carried out in the acylation reaction step of hydroxynaphthoic acid with an anhydride of a lower aliphatic acid. Acyloxynaphthoic acid, which is generated as the reaction proceeds, precipitates in the system, making the reaction system inhomogeneous and making it difficult to proceed the subsequent reaction smoothly. Since the melting point polyester is produced in a large amount, it exists as an infusible foreign substance in the polymer finally obtained,
As a result, it was found that the quality of the polymer was inferior.

[0011]

[Means for Solving the Problems] In view of such a situation,
The present inventors have diligently studied a novel method for producing a polyester in order to provide a high quality thermionic liquid crystal polyester not only having excellent moldability and oxygen barrier property but also free from a high melting point component and a molded article made of the same. As a result, the presence of a solvent in the acylation reaction step of the hydroxynaphthoic acid and the anhydride of the lower aliphatic acid not only achieves the above-mentioned object, but also shortens the reaction time and The inventors have found that it is extremely effective in facilitating reaching the degree of polymerization, and completed the present invention.

That is, the present invention firstly provides a novel thermal liquid crystal polyester, which comprises (A) substantially the following chemical formula 5

[0013]

[Chemical 5]

The structural unit (1) represented by

[0015]

[Chemical 6]

The structural unit (2) represented by

[0017]

[Chemical 7]

The structural unit (3) represented by

[0019]

[Chemical 8]

The constitutional unit (4) represented by the formula (1) and the constitutional unit (1) and the constitutional unit (2) are present in substantially the same number of moles, and the sum of the constitutional unit (1) and the constitutional unit (2). The 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 (3). ) Is 10 mol% or more, and (B) is a polyethylene terephthalate-based polyester substantially composed of the structural unit (1) and the structural unit (2), 6-hydroxy-
In the presence of a solvent, a hydroxyaromatic carboxylic acid consisting of 2-naphthoic acid and p-hydroxybenzoic acid, and an anhydride of a lower aliphatic acid in an amount of 1.02 to 1.50 times equivalent to the hydroxyaromatic carboxylic acid are added. It is obtained by reacting the hydroxyaromatic carboxylic acid at a temperature in the range of 100 to 150 ° C. until the reaction rate of the hydroxyaromatic carboxylic acid becomes 95 mol% or more, and then reacting the obtained reaction mixture at a temperature of more than 150 ° C. A thermal liquid crystalline polyester (hereinafter, such a thermal liquid crystalline polyester may be referred to as a thermal liquid crystalline polyester (P)).

Secondly, the present invention provides a molded article having an improved gas barrier property, in particular, a high oxygen barrier property, which molded article is the novel thermal liquid crystal polyester (P) of the present invention. ) Is a molded product. still,
The term "molded product" used in the present specification means a molded product suitable for packaging such as foods and drinks and pharmaceuticals. Such a molded article includes a sheet obtained by molding the thermal liquid crystal polyester (P) of the present invention; a film; a bottomed container such as a bottle, a tray, a cup or a bag.

Thirdly, the present invention provides a novel method for producing a thermal liquid crystalline polyester suitable for producing the above thermal liquid crystalline polyester (P), which comprises a polyethylene terephthalate type polyester, 6-hydroxy-2. A hydroxyaromatic carboxylic acid containing naphthoic acid and 1.02 to 1.50 with respect to the hydroxyaromatic carboxylic acid
Double equivalents of lower aliphatic acid anhydrides in the presence of solvent are added to 100
To 150 ° C, the reaction is carried out until the reaction rate of the hydroxyaromatic carboxylic acid becomes 95 mol% or more, and then the obtained reaction mixture is reacted at a temperature higher than 150 ° C. It is a method for producing liquid crystal polyester.

The present invention will be described in detail below. The thermal liquid crystal polyester (P) of the present invention contains, as essential constituent units, constituent unit (1), constituent unit (2), constituent unit (3) and constituent unit (4) in the molecule. The structural unit (1) of the thermal liquid crystal polyester (P) of the present invention is a terephthaloyl group. A part of the structural unit (1), preferably 20 mol% or less of the structural unit (1) may be replaced with a structural unit that can be introduced by a dicarboxylic acid other than terephthalic acid or an ester-forming derivative thereof. As the dicarboxylic acid component other than terephthalic acid, for example,
Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,
7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,4-
Cyclohexanedicarboxylic acid, succinic acid, adipic acid,
Sebacic acid etc. are mentioned. Further, if the amount of the obtained thermo-liquid crystalline polyester is within a range capable of being melt-molded, a part of the structural unit (1) is a polyvalent carboxylic acid such as trimellitic acid, trimesic acid, pyromellitic acid or an ester-forming derivative thereof. It is also possible to replace with a structural unit that can be introduced by.

The constitutional unit (2) in the thermal liquid crystal polyester (P) of the present invention is an ethylenedioxy group, but a part thereof, preferably 20 mol% or less of the constitutional unit (2), is due to another glycol. It may be replaced with a structural unit that can be introduced. Examples of glycols other than ethylene glycol include 1,2-propanediol,
1,3-propanediol, 1,4-butanediol,
1,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-
Examples include 1,5-pentanediol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, o-, m- or p-xylylene glycol. Further, if the amount of the obtained thermal liquid crystalline polyester is within a range capable of being melt-molded, a part of the structural unit (2) can be introduced by a polyhydric alcohol such as glycerin, trimethylolpropane, trimethylolpropane and pentaerythritol. It is also possible to replace it with a structural unit.

The constitutional unit (1) and the constitutional unit (2) in the thermal liquid crystal polyester (P) of the present invention is one of the raw materials which is a polyethylene terephthalate type polyester substantially composed of the constitutional unit (1) and the constitutional unit (2). It is introduced into the molecule of the thermal liquid crystal polyester by using as. The polyethylene terephthalate-based polyester is obtained by a reaction using terephthalic acid or its ester-forming derivative as a main starting material and ethylene glycol, which have been conventionally proposed in the production of polyethylene terephthalate. For example, dicarboxylic acid and glycol are obtained. It can be obtained by a method of carrying out an esterification reaction and then polycondensation, a method of transesterifying a dicarboxylic acid ester and a glycol and then polycondensation. The degree of polymerization of the polyethylene terephthalate polyester used as the raw material polyester is not particularly limited, but the intrinsic viscosity measured at 30 ° C. in a mixed solvent of phenol / tetrachloroethane and the like is 0.1 to 1.5 dl /
It is desirable to use g.

The structural unit (1) and the structural unit (2) are
1 in thermionic liquid crystal polyester (P) in the total amount thereof
Within the range of 5 to 90 mol%, preferably 25 to 85 mol%
And more preferably in the range of 30 to 80 mol%.

On the other hand, the thermal liquid crystal polyester (P) of the present invention
The structural unit (3) and the structural unit (4) in 6 are respectively a 6-oxy-2-naphthoyl group introduced by 6-hydroxy-2-naphthoic acid and a 4-oxybenzoyl group introduced by p-hydroxybenzoic acid. Is. A part of the structural unit (3) and the structural unit (4), preferably 10 mol% or less of the total of them may be replaced with a structural unit introduced by another hydroxyaromatic carboxylic acid. Examples of hydroxyaromatic carboxylic acids other than 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid include m-hydroxybenzoic acid, 4-hydroxy-3-chlorobenzoic acid, and 4-hydroxy-3-chlorobenzoic acid.
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 and the like can be mentioned. ..

Further, the thermal liquid crystal polyester (P) of the present invention
In, the total content of the structural unit (3) and the structural unit (4) is in the range of 10 to 85 mol% in the polyester, preferably 15 to 75 mol%, more preferably 20 to 70 mol%. is there. When the total content of the structural unit (3) and the structural unit (4) exceeds 85 mol%, melt polymerization becomes difficult, and the polymer is formed due to the moldability and the mixture of the high-melting point polyester rich in the hydroxyaromatic carboxylic acid component. When the amount is less than 10 mol%, the polyester obtained in many cases does not form a thermal liquid crystal, and the gas barrier property is greatly deteriorated, which is not preferable.

Further, the thermal liquid crystal polyester (P) of the present invention
Then, it is necessary that the ratio of the structural unit (3) to the total amount of the structural unit (3) and the structural unit (4) is 10 mol% or more, which makes it possible to obtain a molding having an extremely excellent oxygen gas barrier property. A product-giving polyester is obtained.

The thermal liquid crystalline polyester (P) of the present invention is based on a hydroxy aromatic carboxylic acid consisting of polyethylene terephthalate polyester, 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid, and the hydroxy aromatic carboxylic acid. 1.02 to 1.50 equivalents of the lower aliphatic acid anhydride in the presence of a solvent of 100 to 15
It is obtained by reacting at a temperature within the range of 0 ° C. until the reaction rate of the hydroxyaromatic carboxylic acid becomes 95 mol% or more, and then reacting the obtained reaction mixture at a temperature exceeding 150 ° C. In the thermal liquid crystalline polyester (P) of the present invention, due to this production method, it is possible to suppress the mixture of high-melting point components such as a homopolymer of hydroxynaphthoic acid and to enhance the randomness of the constitutional unit arrangement in the molecule. As a result, the uniformity becomes good. Furthermore, according to this production method, the reaction time is shortened, and it is easy to increase the degree of polymerization of the polyester. The effect of improving uniformity and shortening of reaction time such as suppression of mixing of these high-melting point components is not limited to the thermal liquid crystal polyester (P) of the present invention, but includes the structural unit (1 ),
Since they commonly appear in the production of thermionic liquid crystal polyesters containing the structural unit (2) and the structural unit (3) as essential structural units, the structural unit (1), the structural unit (2), and the structural unit are described below. The production method of the present invention, which is a production method of a thermal liquid crystal polyester having (3) as an essential constituent unit, will be described.

One of the starting material compounds in the production method of the present invention
6-Hydroxy-2-naphthoic acid is used alone or in combination with other hydroxyaromatic carboxylic acids. As the hydroxyaromatic carboxylic acid other than 6-hydroxy-2-naphthoic acid, use may be made of a hydroxyaromatic carboxylic acid corresponding to a desired oxyaromatic carboxylic acid unit to be introduced into the molecule of the target thermal liquid crystal polyester. Good. For example, the essential hydroxyaromatic carboxylic acid to be used in the production of the thermal liquid crystalline polyester (P) is 6-hydroxy-2.
Naphthoic acid and p-hydroxybenzoic acid.

The composition ratio of each constitutional unit of the thermal liquid crystalline polyester obtained by the production method of the present invention is usually substantially the same as the composition ratio of the raw materials which give these constitutional units. Therefore, the charging ratio of each raw material compound can be appropriately set according to the desired composition ratio of the constituent units.

The lower aliphatic acid anhydride used as one of the starting compounds in the production method of the present invention has 1 to 10 carbon atoms.
8 lower aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, succinic anhydride, glutaric anhydride, maleic anhydride, butyric anhydride, propionic anhydride, anhydrous Examples thereof include valeric acid, and acetic anhydride is particularly preferably used from the viewpoints of price and boiling point suitable for reaction operation. The amount of the lower aliphatic acid anhydride used is 1.02 to 1.50 times the equivalent of the hydroxyaromatic carboxylic acid, that is, 1.02 to 1.50.
The amount is 50 times the molar amount. If the amount of the lower aliphatic acid anhydride used is less than 1.02 times the equivalent of the hydroxyaromatic carboxylic acid, it will take a long time to synthesize the desired thermal liquid crystal polyester, or the degree of polymerization will be sufficient. Will not reach a certain height. On the other hand, when it exceeds 1.50 times the equivalent, coloring of the obtained thermal liquid crystal polyester becomes remarkable.

In the production method of the present invention, a solvent is present in the system when the mixture of the polyethylene terephthalate polyester, the hydroxyaromatic carboxylic acid and the anhydride of the lower aliphatic acid is reacted. Such a solvent does not adversely affect the acylation reaction, the acidolysis reaction and the polycondensation reaction that occur in the system until the desired thermal liquid crystalline polyester is obtained, and the evaporation in the first half step of these series of reactions. It has a boiling point such that it can be distilled off from the system in the polycondensation step under reduced pressure in the latter half without causing scattering from the system or an increase in the pressure of the system, and particularly has a boiling point of 100 to 300 ° C. Also, the solubility of 6-acyloxy-2-naphthoic acid corresponding to the product of the lower aliphatic acid anhydride and 6-hydroxy-2-naphthoic acid used as a solute, and the solubility at a temperature of 25 ° C. is 15 g (solute). An organic compound of 100 g / solvent or more is preferable. Examples of suitable solvents include acetic acid,
Lower aliphatic acids such as propionic acid, butyric acid, isobutyric acid, and trimethylacetic acid; aromatic compounds such as toluene, xylene, pseudocumene, diphenylmethane, biphenyl, diphenyl ether, diphenyl sulfide, diphenyl sulfone, etc., but boiling point, price, recovery Acetic acid is particularly preferably used from the standpoint of ease of use. In the reaction according to the present invention, a solvent is present to suspend the system in the form of a suspension so that the reaction system can be kept under sufficient stirring conditions until the reaction system reaches a temperature at which it can be melted. Or maintain in solution. From this viewpoint, the solvent is usually used in an amount of 0.5 to 5 times the weight of the hydroxyaromatic carboxylic acid. The lower aliphatic acid produced from the anhydride of the lower aliphatic acid used may be a chemical species that can be used as a solvent in the present invention, but in the present invention, the amount of chemical generated in the system is Apart from the seed, it is necessary that a solvent be present in the reaction system.

In the present invention, first, a polyethylene terephthalate polyester, a hydroxyaromatic carboxylic acid, and an anhydride of a lower aliphatic acid are added in the presence of a solvent to obtain 10
The reaction is carried out at a temperature within the range of 0 to 150 ° C. At this stage, mainly, an acylation reaction occurs in which the hydroxyaromatic carboxylic acid reacts with the anhydride of the lower aliphatic acid to be converted into the corresponding acyloxyaromatic carboxylic acid.

In the first step of the acylation reaction step, it is important that the temperature of the system is not substantially higher than 150 ° C. until the reaction rate of the hydroxyaromatic carboxylic acid becomes 95 mol% or more. When the reaction rate of hydroxyaromatic carboxylic acid was raised from a point of less than 95 mol% to a temperature of more than 150 ° C., the acylation reaction no longer proceeded sufficiently, and the reaction rate in the subsequent polycondensation step was increased. Furthermore, it may have an unfavorable influence on the degree of polymerization of the finally obtained thermal liquid crystal polyester. In the acylation reaction step according to the present invention, the reaction time required for the reaction rate of the hydroxyaromatic carboxylic acid to be 95 mol% or more is usually 0.5 to 4 hours, although it varies depending on the reaction conditions such as the reaction temperature. .. The reaction rate of the hydroxyaromatic carboxylic acid can be determined by measuring the residual rate of the unreacted hydroxyaromatic carboxylic acid using, for example, a high performance liquid chromatography method. It can also be determined by ↑ 1H-NMR method.

In the acylation reaction step according to the present invention, it is also important that a solvent be present in the system. If no solvent is added at all, acyloxynaphthoic acid formed along with the progress of the acylation reaction is precipitated, and the inside of the reaction system becomes remarkably heterogeneous, so the reaction may not proceed smoothly from the middle. In such a heterogeneous system, not only the acylation reaction but also the next acidolysis reaction at a temperature of more than 150 ° C. does not proceed smoothly, and at the same time, the homopolyester of acyloxynaphthoic acid remarkably occurs, so that finally The obtained thermal liquid crystal polyester has extremely poor randomness, and a high melting point component is mixed. In the acylation reaction step, it is preferable that the reaction is carried out under stirring at a pressure of around atmospheric pressure or higher in an atmosphere of a gas inert to the reaction such as nitrogen, argon, carbon dioxide and the like.

In the present invention, the reaction mixture obtained by the above-mentioned acylation reaction at 150 ° C. or lower is subjected to a reaction at a temperature higher than 150 ° C. Reactions at temperatures above 150 ° C. are usually
Near normal pressure or higher and 150-230 ℃
The acidolysis reaction step (second stage) in which the temperature is within the range is followed by the polycondensation reaction step (the pressure conditions from the normal pressure to the reduced pressure and the temperature in the range of 250 to 350 ° C.) that are normally followed. It is roughly divided into the third stage).

In the acidolysis reaction step of the second step, a reaction for producing a polyester fragment occurs by the acidolysis (depolymerization) of the polyethylene terephthalate polyester mainly by the acyloxyaromatic carboxylic acid produced. Acidolysis is carried out by reacting under an atmosphere of a gas inert to the reaction such as nitrogen, argon, carbon dioxide, etc., at a temperature of 150 to 230 ° C. and at a pressure of around normal pressure or higher for 30 minutes to 5 hours with stirring. Preferably. By controlling the reaction temperature to 230 ° C or lower, the formation of high melting point polyester rich in the acyloxy aromatic carboxylic acid component is further suppressed, the homogeneity of the resulting thermal liquid crystalline polyester is further improved, and at temperatures above 150 ° C. Reaction time 3
By taking 0 minutes or more, acidolysis (depolymerization) of the polyethylene terephthalate-based polyester sufficiently proceeds, and the randomness of the resulting thermal liquid crystal polyester is enhanced, and as a result, the uniformity and moldability are further improved.

In the polycondensation reaction in the third step, first, nitrogen,
It is desirable to raise the temperature with stirring to a temperature in the range of 230 ° C. to 250 to 350 ° C. under an atmosphere of a gas inert to the reaction such as argon or carbon dioxide. Usually, most of the theoretical amount of the lower aliphatic acid produced at this temperature raising stage is distilled out of the system. Then, preferably the reaction temperature is 260-270 ° C.
From the point when the
Time of 1mmHg, preferably over 2 hours
Hereinafter, it is desirable to further lower the aliphatic acid under a pressure condition of preferably 0.5 mmHg or less to increase the degree of polymerization to a desired logarithmic viscosity, preferably to a logarithmic viscosity of 0.1 dl / g or more. The polymerization temperature for driving under the reduced pressure is preferably 270 ° C. or higher from the viewpoint of reaction rate, and 350 ° C. or lower from the viewpoint of suppressing decomposition of the produced polyester, and particularly preferably 270 to 320 ° C. Further, as a method for further increasing the molecular weight, it is possible in some cases to use a well-known solid phase polymerization method in the industry.

In the present invention, the above-mentioned acylation reaction step in which a pressure of around normal pressure or higher is usually adopted,
In the first half of the acidolysis reaction step and the polycondensation reaction step, a solvent is present to make the system a suspension or solution,
Sufficient stirring and mixing conditions are important for the desired series of reactions to proceed evenly, and for obtaining a highly uniform polyester free of high melting point polyester rich in hydroxyaromatic carboxylic acid components. Is. In addition,
The solvent distills out of the system from the middle of the polycondensation reaction step, but if the temperature reaches a temperature at which the reaction system becomes a molten state, there is no problem because the system can be kept under sufficient stirring conditions. ..

The logarithmic viscosity of the thermal liquid crystal polyester (P) of the present invention measured at 60 ° C. in pentafluorophenol is 0.1 dl / in terms of the mechanical strength of the obtained molded product.
It is desirable that it is g or more, preferably 0.3 dl / g or more, and more preferably 0.5 dl / g or more. Also, although there is no critical upper limit to the logarithmic viscosity, the ease of melt polymerization,
From the viewpoint of moldability, it is preferably 3.0 dl / g or less.

The thermal liquid crystal polyester (P) of the present invention usually has the property of forming a liquid crystal (indicating optical anisotropy) in the melt phase. Confirmation of such anisotropy in the molten phase is carried out by using a polarization microscope equipped with a heating device, as is well known to those skilled in the art, under a crossed Nicols, a thin piece of a sample, preferably a thickness of about 5 to 20 μm. It can be carried out by observing that the thin piece of the above is sandwiched between cover glasses at a constant heating rate and that light is transmitted above a certain temperature.
In this observation, the polarized light transmission 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. This transition temperature is preferably 300 ° C. or lower from the viewpoint of ease of melt molding.

Unlike the conventionally proposed thermal liquid crystal polyester, the transition temperature of the thermally liquid crystal polyester (P) of the present invention to the optically anisotropic molten phase is difficult to determine by a differential scanning calorimeter. .. That is, as is clear from the following examples, the thermal liquid crystal polyester (P) of the present invention
When measured with a differential scanning calorimeter, a clear endothermic peak may not be observed depending on the composition, and even when 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 polyester, the endothermic peak becomes smaller as the proportion of the structural unit (3) increases, and the endothermic peak is often not observed at 35 mol% or more.

With respect to the composition ratio of the structural units (1), (2), (3) and (4) of the thermal liquid crystalline polyester (P) of the present invention, the polymer is dissolved in a suitable solvent and the solution This can be confirmed by measuring the NMR spectrum.

Unlike the conventionally known thermal liquid crystal polymers, the thermal liquid crystal polyester (P) of the present invention has a very low crystallinity in the molded product obtained by quenching from the molten state, and in the usual case, it is determined by X-ray diffraction. The required crystallinity is 20% or less. The crystallinity decreases as the proportion of the structural unit (3) in the polyester increases. Therefore, a molded product such as a film form obtained from the thermal liquid crystalline polyester (P) of the present invention is capable of uniaxially and biaxially hot stretching, unlike the conventionally proposed thermal liquid crystalline polyester, and in many cases. Simultaneous or sequential biaxial stretching of 2 × 2 times or more or 3 × 3 times or more is possible. Moreover, the molded product made of the thermal liquid crystal polyester (P) of the present invention has excellent gas barrier properties. These outstanding properties are not manifested at all in thermotropic polyesters using only p-hydroxybenzoic acid as the hydroxyaromatic carboxylic acid component. Furthermore, by adopting the method for producing a thermo-liquid crystal polyester of the present invention, the surface smoothness, thin-film moldability, film thickness uniformity and the like required for a film-shaped molded product particularly for gas barrier applications are dramatically improved. The obtained thermal liquid crystal polyester is obtained.

The thermo-liquid crystal polyester (P) of the present invention is particularly suitable for the production of a molded product in the form of a sheet or a film, since it can be heat-stretched and does not contain foreign matters due to the formation of high melting point polyester. Further, a hollow molded article can be obtained by extrusion blow molding called direct blow, injection blow molding, biaxial stretch blow molding, or the like.

Further, the thermal liquid crystal polyester (P) of the present invention is another polymer, for example, a polyolefin resin such as polyethylene and polypropylene, a polyester resin such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, a polyamide resin such as nylon and the like. It is also possible to stack with coextrusion,
Laminates such as film, sheet and tube by dry lamination, sandwich lamination, etc., and further by injection molding, blow molding, biaxial stretch blow molding, vacuum molding, compression molding, etc., cup-shaped, bottle-shaped laminated bodies. Can be a container.

A molded product obtained from the thermo-liquid crystal polyester (P) of the present invention has an excellent oxygen barrier property, and is, for example, 20 to 4 of a molded product made of polyethylene terephthalate.
It has the performance of 00 times. Moreover, the excellent oxygen barrier property has very little humidity dependency. For example, the thermal liquid crystalline polyester (P) of the present invention usually has an oxygen permeation amount measured at 20 ° C. of 20 ml · 20 μm / m ↑ 2 · day · a.
Gives a quenched film of tm or less. The oxygen barrier property may be further improved by subjecting the molded product to a heat treatment.

As described above, the thermal liquid crystal polyester (P) of the present invention has dramatically improved moldability as compared with the conventional thermal liquid crystal polyester, and it can be stretched and the oxygen of the molded product can be obtained. Since it also has an extremely excellent barrier property, it can be suitably used as various packaging materials and containers required to have an oxygen barrier property. Therefore, it can be used for a wide variety of applications, for example, as a gas barrier packaging material in the fields of foods, pharmaceuticals, cosmetics, textiles, industrial chemicals and the like. In the container (including the packaging material) made of the thermal liquid crystal polyester (P) of the present invention, the oxygen permeation amount measured at 20 ° C. on the wall surface is usually 20 ml · 20 μm / m ↑.
It is 2 · day · atm or less.

Furthermore, the thermo-liquid crystal polyester (P) of the present invention can be used as a fiber, a coating material, etc., and can also be used as an adhesive agent by utilizing the low temperature fluidity which is uniquely different from the conventional thermo-liquid crystal polymer. It is also possible to use it as such.

[0052]

The present invention will be specifically described with reference to the following examples. The measurement of each physical property value in this example followed the following method.

1) Logarithmic viscosity (η ↓ inh) 0.1 g / dl using pentafluorophenol solvent
The concentration was measured at 60 ° C.

Η ↓ inh = [ln (t ↓ 1 / t ↓ 0)] / c

[Wherein η ↓ inh is logarithmic viscosity (dl / g)
, T ↓ 0 represents the flow down time (seconds) of the solvent, t ↓ 1 represents the flow down time (seconds) in the sample solution, and c represents the concentration of the sample in the solution (0.1 g / dl). .. ]

2) Thermal analysis Differential scanning calorimeter (DSC; manufactured by METTLER CORPORATION, TA-300)
Type 0) for samples that were quenched from the molten state
The melting point (Tm) and the glass transition point (Tg) were measured at a temperature rising rate of 0 ° C./min.

3) Oxygen permeation amount (PO ↓ 2) Gas permeation rate measuring device (MODERN CONTROL)
20 made by S company, OX-TRAN10 / 50A)
The measurement was performed on a hot-pressed film, a stretched film or a laminated stretched film with PET under the conditions of ° C and 65% relative humidity. The unit is ml ・ 20μm / m ↑ 2 ・ day ・ a
tm.

4) Stretchability A heat-pressed film having a thickness of about 100 μm was prepared at a temperature of 260 to 290 ° C., and this film was 3 × 3 at a temperature of 100 to 240 ° C. using a biaxial stretching device manufactured by Shibayama Scientific Instruments Co., Ltd.
It was subjected to double biaxial stretching. Regarding the evaluation of stretchability,
A film with little thickness unevenness and excellent surface smoothness was "good", although stretchability was recognized,
Those with insufficient thickness uniformity or surface smoothness were evaluated as “slightly poor”, and those with no stretchability observed and the film ruptured were evaluated as “unstretchable”.

5) Polymer composition The obtained polymer was used as a trifluoroacetic acid solution, and 500
MHz ↑ 1H-NMR (JEOL, JNM GX-
500 type). As a result of this measurement, it was confirmed that the composition of each structural unit of the thermal liquid crystal polyesters obtained in each of the Examples and Comparative Examples was the same as the composition of the charged raw materials within the analysis accuracy in any case.

6) Reaction Rate of Lower Aliphatic Acid Anhydride It was determined by analyzing the reaction mixture by high performance liquid chromatography and determining the residual rate of unreacted lower aliphatic acid anhydride.

Example 1 1316 g (7.0 mol) of 6-hydroxy-2-naphthoic acid, 138 g (1.0 mol) of p-hydroxybenzoic acid, 918 g (9.0 mol) of acetic anhydride, phenol /
384 g of polyethylene terephthalate having an intrinsic viscosity of 0.70 dl / g (2.0 mol based on the constitutional unit (1)) measured at 30 ° C. using a mixed solvent of tetrachloroethane and the like, and 960 g of acetic acid (16.0) as a solvent. Mol) was charged into a reactor having an internal volume of 8 liters equipped with a stirrer, a distillation column and a nitrogen gas blowing port, and the reaction system was charged with 3 mol.
After replacing the atmosphere with nitrogen twice, the mixture was stirred and heated under a nitrogen stream under reflux conditions (system temperature: about 130 ° C.) for about 2 hours. The reaction rate of acetic anhydride was 100%. 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 inside the system is gradually reduced to 280 ° C. and about 30 mmHg.
As a result of the reaction 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 increased, the reaction was performed at 1 mmHg or less for 1 hour, and then the polyester was taken out. The state of the reaction system is 2
It was in a suspension state until the temperature was raised to 70 ° C., and thereafter, it gradually changed to a molten state as acetic acid was distilled out, and stirring was not hindered throughout the entire reaction process.

The polyester obtained was dissolved in trifluoroacetic acid and the 1 H-NMR spectrum was measured.
The mol% of each structural unit of the polyester is 16.9 mol% / 16.6 mol% / 58 in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). ．
It was found to be 1 mol% / 8.4 mol%. This is substantially the same as the charged raw material composition ratio. A small piece of the obtained polyester is manufactured by Linkam,
In a microscope heating device TH-600 under a nitrogen atmosphere, 10
When the temperature was raised at a rate of ° C / min and observed under a crossed Nicols with a polarizing microscope, light began to pass from around 150 ° C, and then the amount of transmitted light increased further as the temperature rose, finally reaching 350 ° C.
Even when the temperature was raised to ° C, an optically anisotropic molten phase was still formed. A sample obtained by rapidly cooling the polyester from a molten state of 280 ° C. to 30 ° C. was analyzed by DSC in the range of 30 to 400 ° C. at a temperature rising rate of 10 ° C./min.
No endothermic peaks were observed except the glass transition point was observed at ° C. Further, the crystallinity of a sample obtained by rapidly cooling the polyester from the molten state was measured by X-ray wide angle scattering, and as a result, the crystallinity of the sample was 10%.

Next, the oxygen permeation amount of a film having a thickness of about 100 μm obtained by melt-pressing the polyester at 280 ° C. and then rapidly cooling it with a water-cooling type cooling press,
Using a gas permeability measuring device OX-TRAN10 / 50A manufactured by MODERN CONTROLS, 20 ° C,
As a result of measurement under the condition of relative humidity of 65%, the oxygen permeation amount was 0.4 ml · 20 μm / m ↑ 2 · day · atm. Further, the heat-pressed film having a thickness of about 100 μm obtained in the same manner was subjected to simultaneous biaxial stretching of 3 × 3 times at 160 ° C. using a biaxial stretching device manufactured by Shibayama Scientific Instruments Co., resulting in a uniform thickness of about 10 μm. Moreover, a film having excellent surface smoothness was obtained.

Table 1 shows the evaluation results of the logarithmic viscosity of the polyester, the oxygen permeation amount of the pressed film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Example 2 In Example 1, 6-hydroxy-2-naphthoic acid /
A polyester was obtained in the same manner as in Example 1 except that the molar ratio of p-hydroxybenzoic acid / polyethylene terephthalate was 60/10/30 (based on the structural unit (1)).
The mol% of each structural unit of the obtained polyester is 23.5 mol% / 23.3 mol% in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). / 45.
It was found to be 8 mol% / 7.4 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed under a polarizing microscope orthogonal Nicols by the apparatus used in Example 1, it started transmitting light from around 150 ° C., and thereafter, the amount of transmitted light further increased with increasing temperature, and finally 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 Example 1. As a result, no endothermic peak was observed except that a glass transition point was observed at 86 ° C. Further, the crystallinity of this polyester was measured in the same manner as in Example 1, and as a result, the crystallinity was 8%.

Table 1 shows the evaluation results of the logarithmic viscosity of the present polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Example 3 In Example 1, 6-hydroxy-2-naphthoic acid /
A polyester was obtained in the same manner as in Example 1 except that the molar ratio of p-hydroxybenzoic acid / polyethylene terephthalate was 50/10/40 (based on the structural unit (1)).
The mol% of each structural unit of the obtained polyester is 28.5 mol% / 28.8 mol% in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). / 35.
It was found to be 8 mol% / 6.9 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed under a polarizing microscope orthogonal Nicols by the apparatus used in Example 1, it started transmitting light from around 140 ° C., and thereafter, the amount of transmission further increased with increasing temperature, and finally 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 Example 1. As a result, no endothermic peak was observed except that a glass transition point was observed at 82 ° C. Further, the crystallinity of this polyester was measured in the same manner as in Example 1, and as a result, the crystallinity was 11%.

Table 1 shows the evaluation results of the logarithmic viscosity of this polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Example 4 In Example 1, 6-hydroxy-2-naphthoic acid /
A polyester was obtained in the same manner as in Example 1 except that the molar ratio of p-hydroxybenzoic acid / polyethylene terephthalate was 30/30/40 (based on the structural unit (1)).
The mol% of each structural unit of the obtained polyester is 28.4 mol% / 28.6 mol% in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). / 21.
It was found to be 2 mol% / 21.8 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed under a polarizing microscope orthogonal Nicols by the apparatus used in Example 1, it started transmitting light from around 140 ° C., and thereafter, the amount of transmission further increased with increasing temperature, and finally 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 Example 1. As a result, no endothermic peak was observed except that a glass transition point was observed at 76 ° C. Further, the crystallinity of this polyester was measured in the same manner as in Example 1, and as a result, the crystallinity was 13%.

Table 1 shows the evaluation results of the logarithmic viscosity of this polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Comparative Example 1 1610 g (7.0 mol) of 6-acetoxy-2-naphthoic acid and 180 g (1.0 mol) of p-acetoxybenzoic acid.
And polyethylene terephthalate 3 used in Example 1
84 g (2.0 mol based on the structural unit (1)) was used, and the internal volume 8 equipped with a stirrer, a distillation column and a nitrogen gas blowing port was set.
The reaction system was charged in a liter reactor, and the inside of the reaction system was replaced with nitrogen three times. Then, the mixture was stirred and heated under a nitrogen stream at 280 ° C. for about 1 hour. As a result, 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 polyester was taken out.

The polyester obtained was dissolved in trifluoroacetic acid and the 1 H-NMR spectrum was measured.
The mol% of each structural unit of this polyester is 17.1 mol% / 17.2 mol% / 57 in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). ．
It was found to be 7 mol% / 8.0 mol%. This is substantially the same as the charged raw material composition ratio. A small piece of the obtained polyester is manufactured by Linkam,
In a microscope heating device TH-600 under a nitrogen atmosphere, 10
When the temperature was raised at a rate of ° C / min and observed under a crossed Nicols with a polarizing microscope, light began to pass from around 150 ° C, and then the amount of transmitted light increased further as the temperature rose, finally reaching 350 ° C.
Even when the temperature was raised to ° C, an optically anisotropic molten phase was still formed. In addition, a sample obtained by rapidly cooling the polyester from a molten state of 280 ° C. to 30 ° C. was analyzed by DSC in the range of 30 to 400 ° C. at a temperature rising rate of 10 ° C./min.
A glass transition point was observed at 370C and an endothermic peak was observed at 365 ° C. Further, the crystallinity of a sample obtained by rapidly cooling the polyester from the molten state was measured by X-ray wide angle scattering, and as a result, the crystallinity of the sample was 14%.

Next, a film having a thickness of about 100 μm obtained by hot-melt pressing the polyester at 280 ° C. and then rapidly cooling it with a water-cooling type cooling press was used at 160 ° C. using a biaxial stretching device manufactured by Shibayama Scientific Instruments Co., Ltd. As a result of simultaneous biaxial stretching of 3 × 3 times, a stretched film having a thickness of about 10 μm was obtained.
The crystals were mixed, and the surface smoothness was poor.

Table 1 shows the evaluation results of the logarithmic viscosity of the polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Comparative Example 2 In Comparative Example 1, 6-acetoxy-2-naphthoic acid /
A polyester was obtained in the same manner as in Comparative Example 1 except that the molar ratio of p-acetoxybenzoic acid / polyethylene terephthalate was 50/10/40 (based on the structural unit (1)).
The mol% of each structural unit of the obtained polyester is 28.8 mol% / 28.6 mol% in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). / 35.
It was found to be 4 mol% / 7.2 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed under a polarizing microscope orthogonal Nicols by the apparatus used in Example 1, it started to transmit light from around 140 ° C., and thereafter, the amount of transmitted light further increased with increasing temperature, and finally 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 Example 1. As a result, a glass transition point was observed at 80 ° C, and endothermic peaks were observed at 211 ° C and 354 ° C. Further, the crystallinity of this polyester was measured in the same manner as in Example 1, and as a result, the crystallinity was 15%.

Table 1 shows the evaluation results of the logarithmic viscosity of the polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Comparative Example 3 In Comparative Example 1, 6-acetoxy-2-naphthoic acid /
A polyester was obtained in the same manner as in Comparative Example 1 except that the molar ratio of p-acetoxybenzoic acid / polyethylene terephthalate was 30/30/40 (based on the structural unit (1)).
The mol% of each structural unit of the obtained polyester is 28.8 mol% / 28.6 mol% in the order of structural unit (1) / structural unit (2) / structural unit (3) / structural unit (4). / 21.
It was found to be 4 mol% / 21.2 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed under a polarizing microscope orthogonal Nicols by the device used in Example 1, it started to transmit light from around 140 ° C., and then the transmitted light amount further increased with increasing temperature,
Even when the temperature was finally raised to 350 ° C., an optically anisotropic molten phase was still formed. The polyester was analyzed by DSC in the same manner as in Example 1. As a result, a glass transition point was observed at 70 ° C, and endothermic peaks were observed at 200 ° C and 348 ° C. Furthermore, the crystallinity of this polyester was determined according to Example 1.
As a result of the same measurement, the crystallinity was 17%.

Table 1 shows the evaluation results of the logarithmic viscosity of the polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Comparative Example 4 In Comparative Example 2, p-acetoxybenzoic acid was used in place of 6-acetoxy-2-naphthoic acid, that is, all acetoxy aromatic carboxylic acid components (6.0 mol) were used as p-acetoxybenzoic acid. A polyester was obtained in the same manner as in Comparative Example 2 except that an acid was used. The mol% of each structural unit of the obtained polyester is the structural unit (1) / the structural unit (2) /
28.8 mol% / 28.6 mol% in the order of structural unit (4)
It was found to be /42.6 mol%. This is substantially the same as the charged raw material composition ratio. When this polyester was observed by a device used in Example 1 under a crossed Nicols with a polarizing microscope, it started transmitting light at around 200 ° C., and thereafter, the amount of transmitted light increased further 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 analyzing this polyester by DSC in the same manner as in Example 1, a glass transition point was not clearly observed, but an endothermic peak was observed at 205 ° C. Further, the crystallinity of this polyester was measured in the same manner as in Example 1, and as a result, the crystallinity was 25%.

Table 1 shows the evaluation results of the logarithmic viscosity of the polyester, the oxygen permeation amount of the press film, and the stretchability (3 × 3 times simultaneous biaxial stretching).

Comparative Example 5 The oxygen permeation amount and the stretchability (3 ×) of the polyethylene terephthalate press film used as the raw material in Example 1
Table 1 shows the evaluation results of 3 times simultaneous biaxial stretching).

[0082]

[Table 1]

Examples 5 and 6, Comparative Examples 6 and 7 A multilayer sheet was formed using the thermal liquid crystal polyester obtained in Example 1 or Example 2 and polypropylene resin. That is, the thermal liquid crystal polyester and the polypropylene resin were vacuum-dried at 90 ° C. for one day and then coextruded by two extruders to obtain a three-layer sheet of polypropylene / thermal liquid crystal polyester / polypropylene. The thickness of each layer of polypropylene / thermal liquid crystal polyester / polypropylene of the obtained sheet is 280 μm / 20 μm / 20
It was 0 μm. This laminated sheet was simultaneously biaxially stretched at 170 ° C. by 3 × 3 times using the biaxial stretching device used in Example 1 to obtain a laminated stretched film (Examples 5 and 6).

Also, using only polypropylene resin, using only one of the above extruders, the thickness is about 500 μm.
A single layer sheet of was obtained. This sheet was simultaneously biaxially stretched 3 times 3 times at 170 ° C. using the above biaxial stretching device to prepare a stretched film (Comparative Example 6).

The oxygen barrier properties of these laminated stretched films were evaluated by the above-mentioned method. The results are shown in Table 2.

An attempt was also made to form a similar polypropylene / thermal liquid crystal polyester / polypropylene two-layer / three-layer stretched film using the thermal liquid crystal polyester of Comparative Example 4.
The intermediate layer (thermal liquid crystal polyester layer) could not be stretched at any temperature in the range of 140 to 200 ° C., and a good laminated stretched film could not be obtained (Comparative Example 7).

[0087]

[Table 2]

[0088]

EFFECT OF THE INVENTION The thermo-liquid crystalline polyester of the present invention has excellent moldability and, in addition, gives a molded product having extremely excellent gas barrier property, uniformity and surface smoothness.
It is useful as various packaging materials that require high gas barrier properties. Further, according to the production method of the present invention, it is possible to produce a thermal liquid crystal polyester, which gives a molded article excellent in uniformity and surface smoothness, including such a high-performance thermal liquid crystal polyester, in a short reaction time. It becomes possible, and it becomes easy to increase the degree of polymerization.

Claims (3)

[Claims] 1. (A) Substantially the following chemical formula 1 The structural unit (1) represented by the following chemical formula 2 The structural unit (2) represented by the following chemical formula 3 The structural unit (3) represented by and the following chemical formula 4 The structural unit (4) is represented by the formula (1), the structural unit (1) and the structural unit (2) are present in substantially the same number of moles, and the total amount of the structural unit (1) and the structural unit (2) is 15 ~ 90
Mol%, the total amount of the structural unit (3) and the structural unit (4) is 10 to 85 mol%, and the ratio of the structural unit (3) to the total amount of the structural unit (3) and the structural unit (4) is 1
0 mol% or more, and (B) a polyethylene terephthalate-based polyester substantially composed of the structural unit (1) and the structural unit (2), a hydroxy aromatic composed of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid. A carboxylic acid and an anhydride of a lower aliphatic acid in an amount of 1.02 to 1.50 times the equivalent of the hydroxyaromatic carboxylic acid are present in the presence of a solvent at a temperature in the range of 100 to 150 ° C. The reaction was carried out until the reaction rate of the acid became 95 mol% or more, and then the obtained reaction mixture was mixed with 15
Obtained by reacting at a temperature above 0 ° C.,
A thermal liquid crystal polyester characterized in that 2. A molded product made of the thermal liquid crystal polyester according to claim 1. 3. A polyethylene terephthalate-based polyester, a hydroxyaromatic carboxylic acid containing 6-hydroxy-2-naphthoic acid, and 1.02 to 1.50 equivalents of a lower aliphatic acid to the hydroxyaromatic carboxylic acid. The anhydride is reacted in the presence of a solvent at a temperature in the range of 100 to 150 ° C. until the reaction rate of the hydroxyaromatic carboxylic acid is 95 mol% or more, and then the obtained reaction mixture is heated at a temperature of higher than 150 ° C. A method for producing a thermal liquid crystal polyester, which comprises reacting with.