JP3136771B2 - Method for producing aromatic copolyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aromatic copolyester having excellent physical properties, especially excellent moldability. More specifically, the present invention can be easily made into a high molecular weight, has excellent heat resistance and mechanical properties, and has good moldability (flowability). The present invention relates to a method for efficiently and operably producing an aromatic copolymer polyester which is also suitable as a molded product, a fiber, or a film material.

[0002]

2. Description of the Related Art Polyester resins, especially aromatic polyester resins, have excellent heat resistance and mechanical properties. With the recent development of office automation equipment, audiovisual equipment, etc., there is a growing demand for higher performance plastics. , Its expectations are increasing. Among them, aromatic polyester resins that exhibit optical anisotropy when melted, that is, liquid crystal polyester resins, combine superfluidity, precision workability, excellent heat resistance, and excellent mechanical properties. As a particular attention.

As an aromatic copolymer polyester which exhibits optical anisotropy when melted, for example, a polyester obtained by polycondensing terephthalic acid, hydroquinone and parahydroxybenzoic acid is disclosed in JP-B-47-47870. However, the polyester having such a rigid and linear structure has a remarkably high softening temperature and has a problem in formability.

In order to solve such a problem, there has been proposed a polyester having a structure in which rigid components are connected by flexible components. That is, a polyester obtained by copolymerizing parahydroxybenzoic acid and polyethylene terephthalate is disclosed in JP-A-49-72393, and such a copolymerized polyester has good flowability and improved moldability. . However, at the same time, they have the drawback that heat resistance is remarkably reduced and mechanical properties are insufficient. Heat resistance and moldability are the reasons for the relationship between front and back.

On the other hand, those obtained by copolymerizing a monomer having a bulky substituent between rigid linear components, or 2,
There have been proposed copolymers of a monomer having a crankshaft structure such as a 6-naphthalene skeleton, and the moldability has been improved. However, considering the balance with moldability, heat resistance is insufficient, and above all, such a special monomer is very expensive, which is a major problem when industrially providing materials. .

Under such circumstances, as another method for improving the moldability and maintaining the balance with the physical properties, a method of introducing a bent structure can be considered. And
As a method for introducing a bent structure, a method of copolymerizing using a meta-oriented aromatic compound, particularly resorcinol, is expected.

The method for producing the aromatic copolymerized polyester includes a solution polycondensation method, an interfacial polycondensation method and a melt polycondensation method. In the solution polycondensation method, the polycondensation reaction proceeds in a solution, but requires a high boiling point and a highly soluble solvent, and requires post-treatment such as solvent removal after the polymerization is completed. It has the disadvantage of being processed. In some solution polycondensation methods and interfacial polycondensation methods, an acid halide, particularly an acid chloride, is used as a raw material monomer corresponding to a carboxylic acid residue while causing a dehydrochlorination reaction with a corresponding hydroxy group in a solvent. The polycondensation reaction proceeds. However, the hydroxy residue is used as a salt in the interfacial polycondensation method. In addition, since a corrosive compound is generated along with the reaction, it is necessary to make the equipment corrosion-resistant and to treat the generated corrosive compound, thereby increasing the cost of the equipment.

On the other hand, in the melt polycondensation method, conventionally, a raw material in which a carboxylic acid residue is used as a phenyl ester is used to carry out a dephenolation reaction by a dephenolation reaction, or a deacetic acid reaction using a monomer having an acetylated hydroxy group. Deacetic acid methods have been used. In the phenol removal method, since the melting point of phenol produced by the reaction is as high as 40 ° C., the equipment for removing phenol becomes large-scale, and the degree of polymerization is not sufficiently increased.

In the acetic acid removal method, the acetylated monomer as a raw material can be easily obtained by reacting a hydroxy residue with acetic anhydride, and it is also possible to continuously proceed to a polycondensation reaction. In addition, since a large-scale facility is not particularly required for removing the generated acetic acid, and no post-treatment of the formed polyester is required, it is possible to use a polyester production apparatus generally conventionally known as it is.

From the above viewpoints, when producing a copolymerized polyester, a melt polycondensation method by a deacetic acid method is considered to be the most advantageous method. Here, the melt polycondensation method by the deacetic acid method will be described in more detail. First, as a raw material monomer, a carboxylic acid residue and an acetylated hydroxy residue are used. The acetylated hydroxy residue can be easily obtained by a known method by reacting the hydroxy residue with acetic anhydride in the presence or absence of a catalyst. These monomers are charged all at once or divided and supplied to a polycondensation reaction. Further, a carboxylic acid residue, a non-acetylated hydroxy residue, and acetic anhydride can be charged at once, and the acetylation reaction and the polycondensation reaction can be continuously performed.

However, in the production of an aromatic copolyester using a melt polycondensation method by a deacetic acid method, a high temperature is required for the reaction, so that a problem arises when a monomer material contains a low-boiling compound. For example, JP-A-63-275
No. 628 discloses an aromatic copolymer polyester comprising a 6-hydroxy-2-naphthalic acid residue, a p-hydroxybenzoyl residue, a 1,4-dihydroxyphenyl residue and a 1,4-dicarboxyphenyl residue. Although disclosed, when hydroquinone is used as a monomer, since the boiling point of acetylated hydroquinone is as low as 228 ° C., the temperature is raised to two or more stages at 230 ° C. or less at the beginning of the reaction, if necessary, preferably at 210 ° C. The need to hold for more than 3 hours is disclosed. When resorcinol is used as a monomer, this problem also falls because the boiling point of acetylated resorcinol is relatively low at 278 ° C. However, JP-A-2-51523 describes that the reaction hardly occurs at 250 ° C. or lower, which is not preferable.

[0012]

Therefore, when resorcinol is to be used as a monomer in order to obtain an aromatic polyester having improved moldability and a good balance of physical properties, the most advantageous method for producing polyester is deacetic acid. The application of the polycondensation method has become extremely difficult, and it has been difficult to obtain a product having a sufficiently high molecular weight and a material giving favorable physical properties.

An object of the present invention is to provide a conventionally known general-purpose aromatic copolymer polyester having a high molecular weight, excellent moldability, and good physical properties by using a low-boiling monomer material called resorcinol. An object of the present invention is to provide a method for efficiently and operably producing a polyester by a melt polycondensation method by a deacetic acid method using a polyester production apparatus.

[0014]

Means for Solving the Problems The present inventors have made intensive studies to solve such problems, and as a result, in a method for producing an aromatic copolymerized polyester by melt polycondensation by a deacetic acid method, specific conditions are required. The present inventors have found that a resin having good moldability and good physical properties can be produced efficiently and with good operability by using a specific raw material charging ratio under the above conditions, and the present invention has been achieved.

That is, the present invention comprises the following repeating structural units (I), (II) and (III), wherein the repeating structural unit (I) is 5 to 95 mol% and (II) is 2.
5 to 47.5 mol%, (III) is 2.5 to 47.5 mol%, and the repeating structural units (II) and (II)
The number of moles of I) is changed to M (II) and M (III), respectively.
Where 0.9 ≦ M (II) / M (III) ≦ 1.
In the method for producing an aromatic copolymer polyester which is 1 by melt polycondensation by a deacetic acid method, the following (1)
The present invention relates to a method for producing an aromatic copolymerized polyester, which comprises sequentially reacting under the conditions shown in (2). (1) Maintain the temperature in the range of 205 to 235 ° C. (2) The temperature is raised to any temperature of 250 to 380 ° C. Repeating structural unit:

[0016]

Embedded image (However, Ar is

[0017]

Embedded image Represents a group selected from the group consisting of R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , R ₆ , R ₇ and R ₈ each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms. R ₉ has 1 carbon atom
And 6 to 6 alkyl groups. X represents a halogen. Y represents hydrogen, halogen or an alkyl group having 1 to 6 carbon atoms),

(III) {CO-Ar "{CO} (where Ar 'is

[0019]

Embedded image Represents a group selected from the group consisting of Z represents hydrogen, halogen, or an alkyl group having 1 to 6 carbon atoms. )

Here, the repeating structural unit (I) is 50 to
80 mol%, (II) is 10 to 25 mol%, (III)
Is preferably from 10 to 25 mol%, because the moldability and physical properties are balanced.

In the repeating structural unit (II), Ar is a preferred repeating structural unit among -O-Ar-O-.

[0022]

Embedded imageOne. Especially R₁, R_Two, R_Three, R_FourAnd
And R_Five, R₆, R₇, R ₈Is preferably hydrogen.

In the repeating structural unit (III), Ar ′ is a preferred repeating structural unit among —CO—Ar′—CO—.

[0024]

Embedded image One. Further, Z is preferably hydrogen. In particular,

[0025]

Embedded image Is preferred.

In the present invention, the number of moles of the starting monomers giving the above-mentioned repeating structural units (II) and (III) is defined as M (2) and M (3), respectively. And when the number of moles of the acetylated monomer component of the hydroxy group that gives the structural unit (II) existing as a sublimate in the reaction system is M ′ (2), then [M (2) −M ′ (2) ] / [M (3)] ≧ 0.9
The present invention relates to a method for producing an aromatic copolymerized polyester, wherein raw material monomers are charged so that the condition 5 is satisfied.

The starting monomers used in the process for producing an aromatic copolymerized polyester of the present invention are preferably the following (A), (B) and (C). In addition, their derivatives are also used. Among the derivatives, acetylated forms are preferred.

[0028]

Embedded image

[0029]

Embedded image HO─Ar─OH, wherein Ar is the same as the above group.

(C) HOOC {Ar '} COOH (where Ar' is the same as the above-mentioned group) Here, in the dihydroxy compound of (B), resorcinol is 40 to 100 mol% , Preferably 50 to 80 mol%.

Although the method for producing the aromatic copolymerized polyester according to the present invention is a melt polycondensation method by a deacetic acid reaction, it is preferably carried out in an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, and helium.
Economically, nitrogen is preferred. In the method for producing an aromatic copolyester according to the present invention, the raw materials may be charged at once or in a divided manner, and the process may be continuous, batch, or a combination thereof.

That is, the starting materials (A), (B) and (C) are charged all at once, and the hydroxy group is acetylated with acetic anhydride and then subjected to deacetic acid polycondensation, or the hydroxy group is previously acetylated. Either a method of preparing raw materials and subjecting them to decondensation polycondensation, or a combination thereof for deacetic acid polycondensation may be used.

Here, the acetylation of the hydroxy group includes:
Equivalent to the hydroxyl group in the raw material monomer-1.2 times equivalent,
Preferably, an equivalent to 1.1-fold equivalent of acetic anhydride is used. If less than the equivalent amount, the degree of polymerization does not sufficiently increase in the subsequent polymerization,
If the ratio exceeds 1.2 times, the color tone of the resin deteriorates, and the fluidity at the time of melting deteriorates. Coloring can be prevented by adding a very small amount of pyridine as a catalyst.

As described above, the raw material monomer, acetic anhydride, and a catalytic amount of pyridine are charged into a reaction vessel, and are heated to 100 ° C. to 150 ° C., preferably 120 ° C. to 14
By reacting at 5 ° C., acetylation of the hydroxy group can be performed.

In the process for producing the aromatic copolymerized polyester of the present invention, an esterification reaction, a transesterification reaction, and a polycondensation reaction are involved, and the reaction is favorably performed without a catalyst.
If necessary, a compound containing cobalt, manganese, tin, titanium, antimony, germanium, phosphorus, an amine compound, or the like can be used alone or in combination as a catalyst for promoting the reaction. The polycondensation reaction proceeds conveniently without a solvent, but if necessary, hydrocarbons having a high boiling point,
Ethers, silicone oil, fluorine oil and the like may be used as the solvent. The polycondensation reaction can be performed at normal pressure, reduced pressure, or a combination thereof.

In the process for producing an aromatic copolymerized polyester according to the present invention, the deacetic acid polycondensation after the hydroxy group of the raw material monomer is acetylated or after the raw material monomer having the acetylated hydroxy group is charged into the reaction vessel. It is characterized in that the reaction conditions and the amount of raw material charged are specified. These conditions will be described below.

Regarding the conditions of the deacetic acid polycondensation reaction, it is preferable to proceed the reaction sequentially under the following conditions. (1) Maintain the temperature in the range of 205 to 235 ° C. (2) The temperature is raised to any temperature of 250 to 380 ° C.

Here, the condition (1) is as follows.
The reaction is carried out while maintaining the temperature in the range of 205 ° C to 235 ° C. Preferably it is kept at 210 ° C to 230 ° C, more preferably at 220 ° C to 225 ° C. The holding time is preferably 30 minutes or more, and more preferably 1 hour to 5 minutes.
The time is good, and more preferably 2 to 3 hours.
The heating rate is preferably 0.5 ° C to 2.0 ° C / min. If the rate of temperature rise is less than 0.5 ° C./min, a large amount of time is required for the polymerization reaction. If the rate exceeds 2.0 ° C./min, not only the control of the reaction becomes difficult, but also the charged amount of the raw material monomer must be increased. It is not preferable because it must be done.

If the holding temperature is lower than 205 ° C. or higher than 235 ° C., the molecular weight cannot be sufficiently increased, and it is not preferable because balanced physical properties cannot be obtained. Further, if the holding time is less than 30 minutes, it is similarly difficult to sufficiently increase the molecular weight, which is not preferable. On the other hand, even if the holding time exceeds 5 hours, no change is observed in the physical properties obtained, and the color tone is rather deteriorated.

Next, the condition of (2) is 250 to 38
To raise the temperature to any temperature in the range of 0 ° C. to continue the reaction. Without this continuation of the reaction at a higher temperature, a high molecular weight resin cannot be obtained. The heating rate is 0.5 ° C ~
2.0 ° C./min is preferred. If the rate of temperature rise is less than 0.5 ° C./min, a large amount of time is required for the polymerization reaction. If the rate exceeds 2.0 ° C./min, not only the control of the reaction becomes difficult, but also the charged amount of the raw material monomer must be increased. It is not preferable because it must be done.

The final temperature is preferably between 250 ° C. and 380
C, more preferably 270C to 330C. If the final temperature is lower than 250 ° C., the reaction does not proceed sufficiently, and if it exceeds 380 ° C., side reactions such as decomposition may occur, which is not preferable. The reaction time after reaching the final temperature is preferably 2 hours or less. If the reaction is continued for more than 2 hours, the color tone may deteriorate, the moldability may deteriorate, and the physical properties may deteriorate.

With respect to the charged amount of the starting monomer, the number of moles of the starting monomer to give the repeating structural units (I), (II) and (III) is defined as M (1), M (2) and M (3). It is determined by the reaction tank and various reaction conditions (temperature, gas flow rate, time, etc.). That is, between the distilling acetic acid at the end of the reaction and the mole number M ′ (2) of the acetylated monomer component of the hydroxy group that gives the repeating structural unit (II) present as a sublimate in the reaction system, [ M (2) −M ′ (2)] / M (3) ≧ 0.95 is preferably determined. When the value of the above formula is less than 0.95, severe conditions are required for increasing the molecular weight, or it is not possible to sufficiently increase the molecular weight, and it is not possible to obtain a resin having well-balanced physical properties. Absent.

More preferably, 1.15 ≧ [M (2)
−M ′ (2)] / M (3) ≧ 0.95. When the value of the above expression is 1.15 or less, problems such as coloring and a loss of the balance of physical properties do not occur, which is preferable.

Here, the term "in the reaction system" means the whole range of the place where the raw material monomer is sublimated or evaporated and then precipitated. Specifically, it depends on what kind of reaction equipment and related equipment are used, but the inside of the reaction tank, the wall of the reaction tank, the lid of the reaction tank, the pipe wall up to the distillate acetic acid recovery tank, the distillate acetic acid recovery A tank wall and the like can be mentioned. The sublimate means a substance precipitated after the raw material monomer is sublimated or evaporated.

The molecular weight of the aromatic copolyester produced by the production method of the present invention can be easily increased by applying a solid phase polymerization method.

The physical property value which is a measure of the molecular weight of the aromatic copolyester produced by the production method of the present invention is a flow temperature defined below. Flow temperature: A polymer heated and melted at a heating rate of 4 ° C./min, measured with a flow tester CFT-500 (capillary rheometer type) manufactured by Shimadzu Corporation and a load of 100 kg / cm ^2.
Is the temperature at the point where the melt viscosity shows 48,000 poise when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm.

The aromatic copolyester produced by the production method of the present invention has good moldability, and can be subjected to general melt molding such as extrusion molding, injection molding, and compression molding, and has various shapes. It can be used after being processed into molded articles, fibers, films and the like. Further, the aromatic copolymerized polyester fiber glass, carbon fiber, potassium titanate whisker, aluminum borate whisker, fibrous or acicular inorganic reinforcing material such as wollastonite, talc, mica, silica, calcium carbonate, quartz, It is also possible to add desired properties to the molded product by adding an inorganic filler such as iron oxide, a solid lubricant such as graphite and polytetrafluoroethylene, an antioxidant, a heat stabilizer or a thermoplastic resin. .

[0048]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, the method of the analysis and physical property measurement in an Example is as follows.

High performance liquid chromatography (hereinafter referred to as HP
LC method): Waters 600E
The measurement was performed by a low-pressure gradient method using methanol / acetic acid (volume ratio: 1000/5) and water / acetic acid (volume ratio: 1000/5) as a mobile phase by a multi-solvent solution sending system. The column used had an inner diameter of 6.0 mm,
It is an octadecylsilyl (ODS) column with a length of 15 cm. Quantitative calculations were performed by the absolute calibration curve method.

Flow temperature (hereinafter sometimes referred to as FT):
Measured with Shimadzu Corporation Flow Tester Model CFT-500 (Capillary Rheometer Type), 4 ° C
The polymer heated and melted at a heating rate of
The temperature at which the melt viscosity shows 48,000 poise when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm at kg / cm ² .

Molded article physical properties: deflection temperature under load (hereinafter TDU)
L), tensile strength, flexural modulus, and Izod impact strength of ASTM D-648, A
STMD-638, ASTM D-790, ASTM D-
It was measured according to 256.

Example 1 Para-hydroxybenzoic acid (hereinafter sometimes referred to as POB), 4,4′-dihydroxydiphenyl (hereinafter sometimes referred to as DOD),
Resorcinol (hereinafter may be referred to as RES) and terephthalic acid (hereinafter may be referred to as TPA) may be used in the form of 70:
It was charged at a molar ratio of 5: 10.9: 15. To this was added 1.1 times equivalent of acetic anhydride with respect to the hydroxy group, and the mixture was stirred for 10 minutes, and then 0.1% by weight of pyridine based on the total amount of POB, DOD, RES, TPA and acetic anhydride was added. Thereafter, the inside of the reaction system was sufficiently purged with nitrogen, and the acetylation reaction was performed for 1 hour at a reaction temperature of 120 ° C. while stirring. Thereafter, the temperature was raised to 220 ° C. at a rate of 1 ° C./min while stirring under a nitrogen atmosphere at normal pressure, and the temperature was maintained for 2 hours. Thereafter, the temperature was further raised to 300 ° C. at a rate of 1 ° C./min, and polymerization was carried out for 1 hour. During this time, acetic acid by-produced by the polycondensation reaction was continuously distilled off.

After the polymer thus obtained is taken out and cooled, it is pulverized with a bantam mill manufactured by Hosokawa Micron Co., Ltd. to particles having an average particle diameter of 200 μm or less, and further treated at a processing temperature of 280 to 300 ° C. under a nitrogen atmosphere at normal pressure. Solid state polymerization was performed for 6 hours. 4,4′-dihydroxydiphenyl present as a sublimate in the distilled acetic acid and in the reaction system;
Resorcinol was quantified by the HPLC method.
Tables 1 and 2 show the analysis results after the polycondensation reaction and the molded article properties of the obtained aromatic copolymerized polyester.

Comparative Example 1 In a polymerization tank similar to that of Example 1, parahydroxybenzoic acid was added.
4,4'-dihydroxydiphenyl, resorcinol and terephthalic acid were charged in a molar ratio of 70: 5: 10.9: 15. After the acetylation reaction was performed in the same manner as in Example 1, the temperature was raised to 300 ° C. at a rate of 1 ° C./min under a normal pressure nitrogen atmosphere.
And the polymerization was carried out for 2 hours. During this time, acetic acid by-produced by the polycondensation reaction was continuously distilled off. Then Example 1
Pulverization and solid-phase polymerization were performed in the same manner as in the above to obtain a polymer. The analysis results and the physical properties of the molded product are shown in Tables 1 and 2.

Example 2 In the same polymerization tank as in Example 1, parahydroxybenzoic acid,
Hydroquinone (hereinafter sometimes referred to as HQ), resorcinol and terephthalic acid were added at 65.0: 5.6: 13.
It was charged at a molar ratio of 0: 17.5. An acetylation reaction and a polymerization reaction were performed in the same manner as in Example 1, and pulverization and solid phase polymerization were performed to obtain a polymer. The analysis results and the physical properties of the molded product are shown in Tables 1 and 2.

Comparative Example 2 In the same polymerization vessel as in Example 1, parahydroxybenzoic acid,
Hydroquinone, resorcinol and terephthalic acid
It was charged at a molar ratio of 5.0: 5.6: 13.0: 17.5. An acetylation reaction and a polymerization reaction were performed in the same manner as in Comparative Example 1, and pulverization and solid phase polymerization were performed to obtain a polymer. The analysis results and the physical properties of the molded product are shown in Tables 1 and 2.

Comparative Examples 3 and 4 In the same polymerization tank as in Example 1, parahydroxybenzoic acid and
Hydroquinone, resorcinol and terephthalic acid
It was charged at a molar ratio of 5.0: 5.6: 13.0: 17.5. After the acetylation reaction was carried out in the same manner as in Example 1, the temperature was increased at a rate of 1 ° C./min while stirring under a nitrogen atmosphere at normal pressure.
The temperature was raised to 40 ° C. and maintained for 2 hours. Then 1 ° C
The temperature was raised to 300 ° C. at a heating rate of 1 minute / minute, and polymerization was carried out for 1 hour. During this time, acetic acid by-produced by the polycondensation reaction was continuously distilled off. Pulverization and solid-phase polymerization were performed in the same manner as in Example 1 to obtain a polymer. Table 1 and Table 2 show the analysis results and physical properties of the molded products.
Shown in

Examples 3 to 7 In the same polymerization vessel as in Example 1, parahydroxybenzoic acid,
4,4'-dihydroxydiphenyl, resorcinol and terephthalic acid were charged at the molar ratios shown in Table 1, and acetylation reaction and polymerization reaction were carried out in the same manner as in Example 1, followed by pulverization and solid phase polymerization to obtain a polymer. The analysis results and the physical properties of the molded product are shown in Tables 1 and 2.

Example 8 In the same polymerization vessel as in Example 1, parahydroxybenzoic acid and
6-hydroxy-2-naphthalenecarboxylic acid, 4,4 ′
-Dihydroxydiphenyl, resorcinol and terephthalic acid are charged, and an aromatic copolymerized polyester can be obtained according to Example 1.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

The aromatic copolymer using resorcinol as a raw material monomer cannot be sufficiently increased in molecular weight by the acetic acid melt polycondensation method due to the low boiling point of the acetylated product. Although a polymer having excellent properties and good physical properties was expected, it could not be produced by this method.

However, according to the present invention, it is possible to obtain an aromatic copolymer polyester having a high molecular weight using resorcinol as a raw material monomer by a deacetic acid melt polycondensation method by using specific temperature conditions and raw material charging conditions. It became. Therefore, according to the present invention, using a resorcinol as a raw material monomer, excellent moldability, an aromatic copolymer polyester excellent in the balance of physical properties, a conventional polyester production apparatus conventionally known by a deacetic acid melt polycondensation method. It has become possible to efficiently and operably manufacture it.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-235922 (JP, A) JP-A-2-69518 (JP, A) JP-A-2-69517 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (2)

(57) [Claims] 1. The following repeating structural units (I) and (II)
And (III), wherein the repeating structural unit (I) is 5-95 mol%, (II) is 2.5-47.5 mol%,
When (III) is 2.5 to 47.5 mol% and the number of moles of the repeating structural units (II) and (III) is represented by M (II) and M (III), respectively, 0.9 ≦ M
In a method for producing an aromatic copolymerized polyester satisfying (II) / M (III) ≦ 1.1 by melt polycondensation by a deacetic acid method, it is desired to sequentially react under the conditions shown in the following (1) and (2). A method for producing an aromatic copolymerized polyester. (1) Maintain the temperature in the range of 205 to 235 ° C. (2) The temperature is raised to any temperature of 250 to 380 ° C. Repeating structural unit: (However, Ar is Represents a group selected from the group consisting of R ₁ , R ₂ , R ₃ ,
R ₄ , R ₅ , R ₆ , R ₇ and R ₈ each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms. R ₉ has 1 carbon atom
And 6 to 6 alkyl groups. X represents a halogen. Y represents hydrogen, halogen, or an alkyl group having 1 to 6 carbon atoms. (III) {CO-Ar '{CO} (where Ar' is Represents a group selected from the group consisting of Z represents hydrogen, halogen, or an alkyl group having 1 to 6 carbon atoms. ) 2. The repeating structural unit (II) according to claim 1.
And M (3) as the charged mole numbers of the raw material monomers giving (III) and (III), respectively, and the repeating structural unit (II) present as distillate in the distilled acetic acid and in the reaction system at the end of the reaction. When the number of moles of the hydroxy-acetylated monomer component is M ′ (2), [M (2) −M ′ (2)] / [M (3)] ≧ 0.9
2. The method for producing an aromatic copolymerized polyester according to claim 1, wherein the raw material monomers are charged so that the condition 5 is satisfied.