JP6133000B1 - Totally aromatic polyester amide and method for producing the same - Google Patents

Abstract

Provided is a wholly aromatic polyester amide having a good balance between heat resistance and manufacturability. The wholly aromatic polyester amide according to the present invention comprises the following constituent units (I) to (V) as essential constituent components, and the constituent unit (I) is contained in an amount of 55 to 68 mol% with respect to all constituent units. The unit (II) is 6 to 16.1 mol%, the structural unit (III) is 6.4 to 10 mol%, the structural unit (IV) is 9 to 21.5 mol%, and the structural unit (V) is 1 to 7 Contains mol% and exhibits optical anisotropy upon melting.

Description

  The present invention relates to a wholly aromatic polyester amide and a method for producing the same.

  Since the liquid crystalline polymer has excellent fluidity, mechanical strength, heat resistance, chemical resistance, electrical properties and the like in a well-balanced manner, it is suitably used widely as a high-performance engineering plastic. As the liquid crystalline polymer, a wholly aromatic polyester amide is used together with a wholly aromatic polyester. For example, Patent Document 1 discloses an aromatic polyester amide obtained by reacting p-aminophenol, 4-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, and terephthalic acid.

Japanese Patent Laid-Open No. 02-086623

  However, conventional wholly aromatic polyester amides do not have sufficient heat resistance and are required to have improved heat resistance. Further, the wholly aromatic polyester amide is also required to be excellent in ease of production, that is, excellent in manufacturability, based on the excellent polymerizability of the monomer.

  In view of the above problems, an object of the present invention is to provide a wholly aromatic polyester amide having excellent balance between heat resistance and manufacturability.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it has been found that the above-mentioned problems can be solved by a wholly aromatic polyester amide composed of specific structural units, and the content of each structural unit is in a specific range, and the present invention has been completed. More specifically, the present invention provides the following.

(1) As an essential constituent, it is composed of the following structural units (I) to (V),
Content of structural unit (I) is 55-68 mol% with respect to all the structural units,
The content of the structural unit (II) is 6 to 16.1 mol% with respect to all the structural units,
Content of structural unit (III) is 6.4-10 mol% with respect to all the structural units,
Content of structural unit (IV) is 9-21.5 mol% with respect to all the structural units,
A wholly aromatic polyester amide having an optical anisotropy when melted, wherein the content of the structural unit (V) is 1 to 7 mol% with respect to the total structural units.

  (2) The wholly aromatic polyester amide according to (1), which has a melting point of 300 to 340 ° C.

(3) The wholly aromatic polyester amide according to (1) or (2), wherein the difference between the melting point and the deflection temperature under load is 120 ° C. or less,
The deflection temperature under load was obtained by melt-kneading 60% by mass of the wholly aromatic polyester amide and 40% by mass of milled fiber having an average fiber diameter of 11 μm and an average fiber length of 75 μm at the melting point of the wholly aromatic polyester amide + 20 ° C. A wholly aromatic polyester amide measured in the state of the polyester resin composition obtained in this manner.

(4) A method for producing a wholly aromatic polyester amide exhibiting optical anisotropy when melted,
In the method, 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol are acylated with a fatty acid anhydride in the presence of a fatty acid metal salt to obtain 1,4-phenylenedicarboxylic acid. And transesterifying with 1,3-phenylenedicarboxylic acid,
For all monomers consisting of 4-hydroxybenzoic acid, 1,4-phenylenedicarboxylic acid, 1,3-phenylenedicarboxylic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol,
The amount of 4-hydroxybenzoic acid used is 55 to 68 mol%,
The amount of 1,4-phenylenedicarboxylic acid used is 6 to 16.1 mol%,
The amount of 1,3-phenylenedicarboxylic acid used is 6.4 to 10 mol%,
The amount of 4,4′-dihydroxybiphenyl used is 9 to 21.5 mol%,
The amount of N-acetyl-p-aminophenol used is 1 to 7 mol%.
And
The method wherein the amount of the fatty acid anhydride used is 1.02 to 1.04 times the total hydroxyl equivalent of 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol.

  (5) The method according to (4), wherein the fatty acid metal salt is an acetic acid metal salt and the fatty acid anhydride is acetic anhydride.

  (6) The total number of moles of 1,4-phenylene dicarboxylic acid and 1,3-phenylene dicarboxylic acid is 1 to 1 of the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol. 1.06 times, or the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol is the sum of 1,4-phenylene dicarboxylic acid and 1,3-phenylene dicarboxylic acid The method according to (5), which is 1 to 1.06 times the number of moles.

  According to the present invention, the wholly aromatic polyester amide of the present invention, which consists of a specific structural unit and exhibits optical anisotropy when melted, is excellent in balance between heat resistance and manufacturability.

  Further, the wholly aromatic polyester amide of the present invention does not have a very high molding processing temperature, and therefore can be injection molded, extruded, compressed, etc. without using a molding machine having a special structure.

  As described above, the wholly aromatic polyester amide of the present invention is excellent in moldability and can be molded using various molding machines. As a result, it can be easily processed into various three-dimensional molded products, fibers, films and the like. For this reason, molded products such as connectors, CPU sockets, relay switch parts, bobbins, actuators, noise reduction filter cases or heat fixing rolls for OA equipment, which are suitable uses of the wholly aromatic polyester amide of the present invention, can be easily obtained. It is done.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<Totally aromatic polyester amide>
The wholly aromatic polyester amide of the present invention comprises the following structural unit (I), the following structural unit (II), the following structural unit (III), the following structural unit (IV), and the following structural unit (V).

  The structural unit (I) is derived from 4-hydroxybenzoic acid (hereinafter also referred to as “HBA”). The wholly aromatic polyester amide of the present invention contains 55 to 68 mol% of the structural unit (I) with respect to all the structural units. When the content of the structural unit (I) is less than 55 mol% or exceeds 68 mol%, at least one of heat resistance and manufacturability tends to be insufficient.

  The structural unit (II) is derived from 1,4-phenylenedicarboxylic acid (hereinafter also referred to as “TA”). The wholly aromatic polyester amide of the present invention contains 6 to 16.1 mol% of the structural unit (II) with respect to the total structural units. When the content of the structural unit (II) is less than 6 mol% or exceeds 16.1 mol%, at least one of heat resistance and manufacturability tends to be insufficient.

  The structural unit (III) is derived from 1,3-phenylenedicarboxylic acid (hereinafter also referred to as “IA”). The wholly aromatic polyester amide of the present invention contains 6.4 to 10 mol% of the structural unit (III) with respect to all the structural units. When the content of the structural unit (III) is less than 6.4 mol% or exceeds 10 mol%, at least one of heat resistance and manufacturability tends to be insufficient.

  The structural unit (IV) is derived from 4,4′-dihydroxybiphenyl (hereinafter also referred to as “BP”). The wholly aromatic polyester amide of the present invention contains 9 to 21.5 mol% of the structural unit (IV) with respect to the total structural unit. When the content of the structural unit (IV) is less than 9 mol% or exceeds 21.5 mol%, at least one of heat resistance and manufacturability tends to be insufficient.

  The structural unit (V) is derived from N-acetyl-p-aminophenol (hereinafter also referred to as “APAP”). The wholly aromatic polyester amide of the present invention contains 1 to 7 mol% of the structural unit (V) with respect to all structural units. When the content of the structural unit (V) is less than 1 mol%, the heat resistance is good, but the manufacturability tends to be insufficient. If the content of the structural unit (V) exceeds 7 mol%, at least one of heat resistance and manufacturability tends to be insufficient.

  As described above, the wholly aromatic polyester amide of the present invention contains a specific amount of each of the specific structural units (I) to (V) with respect to the total structural units. Excellent balance.

  As an index representing the heat resistance, a difference between a melting point and a deflection temperature under load (hereinafter also referred to as “DTUL”) can be given. If this difference is 120 ° C. or less, the heat resistance tends to increase, which is preferable. DTUL is obtained by melt-kneading 60% by mass of the wholly aromatic polyester amide and 40% by mass of milled fiber having an average fiber diameter of 11 μm and an average fiber length of 75 μm at the melting point of the wholly aromatic polyester amide + 20 ° C. It is a value measured in the state of the polyester resin composition, and can be measured according to ISO75-1,2.

  Subsequently, the manufacturing method of the wholly aromatic polyester amide of this invention is demonstrated. The wholly aromatic polyester amide of the present invention is polymerized using a direct polymerization method or a transesterification method. In the polymerization, a melt polymerization method, a solution polymerization method, a slurry polymerization method, a solid phase polymerization method, or the like is used.

  In the present invention, at the time of polymerization, an acylating agent for the polymerization monomer or a monomer having terminal activated as an acid chloride derivative can be used. Examples of the acylating agent include fatty acid anhydrides such as acetic anhydride.

In the polymerization, various catalysts can be used. Typical examples include dialkyl tin oxide, diaryl tin oxide, titanium dioxide, alkoxy titanium silicates, titanium alcoholates, fatty acid metal salts, BF ₃ Lewis acid salts such as are mentioned, and fatty acid metal salts are preferred. The amount of the catalyst used is generally about 0.001 to 1% by weight, particularly about 0.003 to 0.2% by weight, based on the total weight of the monomers.

  Moreover, when performing solution polymerization or slurry polymerization, as a solvent, liquid paraffin, a high heat resistant synthetic oil, an inert mineral oil, etc. are used.

  The reaction conditions are, for example, a reaction temperature of 200 to 380 ° C. and a final ultimate pressure of 0.1 to 760 Torr (that is, 13 to 101,080 Pa). Particularly in the melt reaction, for example, the reaction temperature is 260 to 380 ° C., preferably 300 to 360 ° C., the final ultimate pressure is 1 to 100 Torr (that is, 133 to 13,300 Pa), preferably 1 to 50 Torr (that is, 133 to 6,670 Pa). ).

  In the reaction, all the raw material monomers (HBA, TA, IA, BP, and APAP), the acylating agent, and the catalyst can be charged into the same reaction vessel to start the reaction (one-stage system), or the raw material monomers HBA, BP , And the APAP hydroxyl group can be acylated with an acylating agent and then reacted with the carboxyl groups of TA and IA (two-stage system).

  The melt polymerization is performed after the inside of the reaction system reaches a predetermined temperature, and after starting the pressure reduction to a predetermined degree of pressure reduction. After the torque of the stirrer reaches a predetermined value, an inert gas is introduced, and the total aromatic polyester amide is discharged from the reaction system through a normal pressure from a reduced pressure state to a predetermined pressure state.

  The wholly aromatic polyester amide produced by the above polymerization method can be further increased in molecular weight by solid-phase polymerization that is heated in an inert gas at normal pressure or reduced pressure. The preferable conditions for the solid state polymerization reaction are a reaction temperature of 230 to 350 ° C., preferably 260 to 330 ° C., and a final ultimate pressure of 10 to 760 Torr (ie 1,330 to 101,080 Pa).

The process for producing a wholly aromatic polyester amide of the present invention comprises acylating 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol with a fatty acid anhydride in the presence of a fatty acid metal salt. And preferably comprises a step of transesterification with 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid,
For all monomers consisting of 4-hydroxybenzoic acid, 1,4-phenylenedicarboxylic acid, 1,3-phenylenedicarboxylic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol,
The amount of 4-hydroxybenzoic acid used is 55 to 68 mol%,
The amount of 1,4-phenylenedicarboxylic acid used is 6 to 16.1 mol%,
The amount of 1,3-phenylenedicarboxylic acid used is 6.4 to 10 mol%,
The amount of 4,4′-dihydroxybiphenyl used is 9 to 21.5 mol%,
The amount of N-acetyl-p-aminophenol used is 1 to 7 mol%.
It is preferable that
The amount of the fatty acid anhydride used is 1.02 to 1.04 times the total hydroxyl equivalent of 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol. preferable. More preferably, the fatty acid metal salt is an acetic acid metal salt and the fatty acid anhydride is acetic anhydride. The total number of moles of 1,4-phenylene dicarboxylic acid and 1,3-phenylene dicarboxylic acid is 1 to 1 of the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol. 1.06 times, or the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol is 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid. More preferably, it is 1-1.06 times the total number of moles.

  Next, the properties of wholly aromatic polyester amide will be described. The wholly aromatic polyester amide of the present invention exhibits optical anisotropy when melted. An optical anisotropy when melted means that the wholly aromatic polyester amide of the present invention is a liquid crystalline polymer.

  In the present invention, the fact that the wholly aromatic polyester amide is a liquid crystalline polymer is an indispensable element for the wholly aromatic polyester amide to have both heat stability and easy processability. The wholly aromatic polyester amide composed of the structural units (I) to (V) may not form an anisotropic molten phase depending on the constituent components and the sequence distribution in the polymer. Is limited to wholly aromatic polyester amides exhibiting optical anisotropy when melted.

  The property of melt anisotropy can be confirmed by a conventional polarization inspection method using an orthogonal polarizer. More specifically, the melting anisotropy can be confirmed by melting a sample placed on a hot stage manufactured by Linkham Co., Ltd. using a polarizing microscope manufactured by Olympus and observing it at a magnification of 150 times in a nitrogen atmosphere. The liquid crystalline polymer is optically anisotropic and transmits light when inserted between crossed polarizers. If the sample is optically anisotropic, for example, polarized light is transmitted even in a molten stationary liquid state.

  Since a nematic liquid crystalline polymer causes a significant decrease in viscosity at the melting point or higher, generally exhibiting liquid crystallinity at the melting point or higher is an index of workability. The melting point (liquid crystallinity expression temperature) is preferably as high as possible from the viewpoint of heat resistance, but it is 300 to 340 ° C. in consideration of thermal degradation during polymer melt processing, heating capability of the molding machine, and the like. Is a preferred guideline. In addition, More preferably, it is 305-335 degreeC.

<Polyesteramide resin composition>
Various fibrous, granular, and plate-like inorganic and organic fillers can be blended with the wholly aromatic polyester amide of the present invention according to the purpose of use.

  As an inorganic filler mix | blended with the polyesteramide resin composition of this invention, there exist a fibrous form, a granular form, and a plate-shaped thing.

  Silica such as glass fiber, asbestos fiber, silica fiber, silica / alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, wollastonite as fibrous inorganic filler Inorganic fibrous materials such as fibers, magnesium sulfate fibers, aluminum borate fibers, and metal fibrous materials such as stainless steel, aluminum, titanium, copper, and brass. A particularly typical fibrous filler is glass fiber.

  In addition, as the granular inorganic filler, carbon black, graphite, silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium oxalate, aluminum oxalate, kaolin, clay, diatomaceous earth, wollast Silicates such as knight, iron oxide, titanium oxide, zinc oxide, antimony trioxide, metal oxides such as alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate Examples thereof include salts, other ferrites, silicon carbide, silicon nitride, boron nitride, and various metal powders.

  Examples of the plate-like inorganic filler include mica, glass flakes, talc, and various metal foils.

  Examples of organic fillers include heat-resistant high-strength synthetic fibers such as aromatic polyester fibers, liquid crystalline polymer fibers, aromatic polyamides, and polyimide fibers.

  These inorganic and organic fillers can be used alone or in combination of two or more. The combined use of the fibrous inorganic filler and the granular or plate-like inorganic filler is a preferable combination in order to combine mechanical strength, dimensional accuracy, electrical properties, and the like. Particularly preferably, the fibrous filler is glass fiber, and the platy filler is mica and talc. The blending amount thereof is 120 parts by mass or less, preferably 20 to 80 parts by mass with respect to 100 parts by mass of the wholly aromatic polyester amide. Part. By combining the glass fiber with mica or talc, the polyesteramide resin composition is particularly prominent in improving the heat distortion temperature and mechanical properties.

  In using these fillers, if necessary, a sizing agent or a surface treatment agent can be used.

  As described above, the polyesteramide resin composition of the present invention contains the wholly aromatic polyesteramide of the present invention and an inorganic or organic filler as essential components. Ingredients may be included. Here, the other component may be any component, and examples thereof include other resins, antioxidants, stabilizers, pigments, crystal nucleating agents and the like.

  Moreover, the manufacturing method of the polyesteramide resin composition of this invention is not specifically limited, A polyesteramide resin composition can be prepared by a conventionally well-known method.

<Polyesteramide molded product>
The polyesteramide molded article of the present invention is formed by molding the wholly aromatic polyesteramide or the polyesteramide resin composition of the present invention. The molding method is not particularly limited, and a general molding method can be employed. Examples of general molding methods include injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, and the like.

  A polyesteramide molded product obtained by molding the wholly aromatic polyesteramide of the present invention is excellent in heat resistance and toughness. Moreover, since the polyesteramide molded article formed by molding the polyesteramide resin composition of the present invention is excellent in heat resistance and toughness and contains an inorganic or organic filler, mechanical strength and the like are further improved.

  Moreover, since the wholly aromatic polyester amide and the polyester amide resin composition of the present invention are excellent in moldability, a polyester amide molded product having a desired shape can be easily obtained.

  Preferable uses of the polyesteramide molded product of the present invention having the above properties include connectors, CPU sockets, relay switch parts, bobbins, actuators, noise reduction filter cases, heat fixing rolls for OA equipment, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to a following example.

<Example 1>
A polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a decompression / outflow line was charged with the following raw material monomers, fatty acid metal salt catalyst, and acylating agent, and nitrogen substitution was started.
(I) 4-hydroxybenzoic acid 10.6 mol (64 mol%) (HBA)
(II) 1.9 mol (11.2 mol%) terephthalic acid (TA)
(III) 1.1 mol (6.8 mol%) of isophthalic acid (IA)
(IV) 2.7 mol (16 mol%) of 4,4′-dihydroxybiphenyl (BP)
(V) 0.3 mol (2 mol%) of N-acetyl-p-aminophenol (APAP)
Potassium acetate catalyst 110mg
Acetic anhydride 1715 g (1.03 times the total hydroxyl equivalent of APAP of HBA and BP)
After charging the raw materials, the temperature of the reaction system was raised to 140 ° C. and reacted at 140 ° C. for 1 hour. Thereafter, the temperature is further increased to 360 ° C. over 5.5 hours, and then the pressure is reduced to 10 Torr (ie, 1330 Pa) over 20 minutes to melt while distilling acetic acid, excess acetic anhydride, and other low-boiling components. Polymerization was performed. After the stirring torque reached a predetermined value, nitrogen was introduced and the pressure was changed from a reduced pressure state to a normal pressure, and the polymer was discharged from the lower part of the polymerization vessel.

<Evaluation>
About the wholly aromatic polyester amide of Example 1, evaluation of melting | fusing point, DTUL, and manufacturability was performed with the following method. The evaluation results are shown in Tables 1 to 4.

[Melting point]
After observing the endothermic peak temperature (Tm1) observed by DSC (manufactured by TA Instruments) at a temperature rising condition of 20 ° C./min from room temperature, the temperature is 2 at (Tm1 + 40) ° C. After being held for a minute, the sample was once cooled to room temperature under a temperature drop condition of 20 ° C./min, and then the temperature of the endothermic peak observed when measured under a temperature rise condition of 20 ° C./min was measured again.

[DTUL]
60% by mass of polymer and 40% by mass of glass fiber (manufactured by Central Glass Co., Ltd., milled fiber, average fiber diameter 11 μm, average fiber length 75 μm) using a twin screw extruder (TEX30α type, manufactured by Nippon Steel) Then, the mixture was melt-kneaded at a cylinder temperature of polymer melting point + 20 ° C. to obtain polyester resin composition pellets.
The polyester resin composition pellets were molded under the following molding conditions using a molding machine (“SE100DU” manufactured by Sumitomo Heavy Industries, Ltd.) to obtain measurement specimens (4 mm × 10 mm × 80 mm). Using this test piece, the deflection temperature under load was measured by a method based on ISO75-1,2. Note that 1.8 MPa was used as the bending stress. The results are shown in Tables 1-4.
〔Molding condition〕
Cylinder temperature: Polymer melting point + 20 ° C
Mold temperature: 80 ℃
Back pressure: 2MPa
Injection speed: 33mm / sec

[Manufacturability]
The behavior when the polymer was discharged from the lower part of the polymerization vessel was observed, and the manufacturability was evaluated according to the following criteria. The results are shown in Tables 1-4.
○: The polymer was discharged as a strand without any problem, and when this strand could be cut into a pellet, it was evaluated that the manufacturability was good.
X: Manufacturability was evaluated to be poor when solidification or the like was caused in the container during polymerization and the polymer could not be discharged, or when the polymer could be discharged as a strand but the strand could not be cut.

<Examples 2 to 25 and Comparative Examples 1 to 9>
A polymer was obtained in the same manner as in Example 1 except that the type of raw material monomer and the charging ratio (mol%) were as shown in Tables 1 to 4. Moreover, the same evaluation as Example 1 was performed. The evaluation results are shown in Tables 1 to 4.

Claims (5)

It consists of only the following structural units (I) to (V) as essential constituent components,
Content of structural unit (I) is 55-68 mol% with respect to all the structural units,
The content of the structural unit (II) is 6 to 16.1 mol% with respect to all the structural units,
Content of structural unit (III) is 6.4-10 mol% with respect to all the structural units,
Content of structural unit (IV) is 9-21.5 mol% with respect to all the structural units,
The content of the structural unit (V) is 1 to 7 mol% with respect to all the structural units ,
The total number of moles of the structural unit (II) and the structural unit (III) is 1 to 1.06 times the total number of moles of the structural unit (IV) and the structural unit (V), or the structural unit ( IV) and the total number of moles of the structural unit (V) is 1 to 1.06 times the total number of moles of the structural unit (II) and the structural unit (III), and the optical anisotropy during melting Totally aromatic polyester amide shown.

  The wholly aromatic polyester amide according to claim 1, which has a melting point of 300 to 340 ° C. The wholly aromatic polyester amide according to claim 1 or 2, wherein the difference between the melting point and the deflection temperature under load is 120 ° C or less,
The deflection temperature under load was obtained by melt-kneading 60% by mass of the wholly aromatic polyester amide and 40% by mass of milled fiber having an average fiber diameter of 11 μm and an average fiber length of 75 μm at the melting point of the wholly aromatic polyester amide + 20 ° C. A wholly aromatic polyester amide measured in the state of the polyester resin composition obtained in this manner. A process for producing a wholly aromatic polyester amide exhibiting optical anisotropy when melted,
In the method, 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol are acylated with a fatty acid anhydride in the presence of a fatty acid metal salt to obtain 1,4-phenylenedicarboxylic acid. And transesterifying with 1,3-phenylenedicarboxylic acid,
For all monomers consisting only of 4-hydroxybenzoic acid, 1,4-phenylenedicarboxylic acid, 1,3-phenylenedicarboxylic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol,
The amount of 4-hydroxybenzoic acid used is 55 to 68 mol%,
The amount of 1,4-phenylenedicarboxylic acid used is 6 to 16.1 mol%,
The amount of 1,3-phenylenedicarboxylic acid used is 6.4 to 10 mol%,
The amount of 4,4′-dihydroxybiphenyl used is 9 to 21.5 mol%,
The amount of N-acetyl-p-aminophenol used is 1 to 7 mol%.
And
The total number of moles of 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid is 1-1.06 of the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol. Or the total number of moles of 4,4′-dihydroxybiphenyl and N-acetyl-p-aminophenol is the total number of moles of 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid. 1 to 1.06 times,
The method wherein the amount of the fatty acid anhydride used is 1.02 to 1.04 times the total hydroxyl equivalent of 4-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, and N-acetyl-p-aminophenol.   The method according to claim 4, wherein the fatty acid metal salt is an acetic acid metal salt and the fatty acid anhydride is acetic anhydride.