Wholly aromatic polyester, resin composition, molded article, and method for producing wholly aromatic polyester

Abstract

Provided is a liquid-crystalline wholly aromatic polyester that exhibits a lower flow initiation temperature than heretofore.　The wholly aromatic polyester exhibits optical anisotropy when melted and contains constituent units (I), (II), (III), and (IV) as essential constituent components, wherein the content of the constituent unit (I) is 17.5 to 26 mol% with respect to the total constituent units, the content of the constituent unit (II) is 24 to 32.5 mol% with respect to the total constituent units, the content of the constituent unit (III) is 17.5 to 26 mol% with respect to the total constituent units, the content of the constituent unit (IV) is 24 to 32.5 mol% with respect to the total constituent units, and the content of the total of the constituent units (I), (II), (III), and (IV) with respect to the total constituent units is 100 mol%.

Description

[Technical Field]

[0001] The present invention relates to a wholly aromatic polyester that exhibits optical anisotropy when melted, a resin composition, a molded article, and a method for producing the wholly aromatic polyester. [Background technology]

[0002] Liquid crystalline resins such as wholly aromatic polyesters have a good balance of excellent fluidity, mechanical strength, heat resistance, chemical resistance, electrical properties, etc., and are therefore widely used in various fields as high-performance engineering plastics. Many of the fully aromatic polyesters currently on the market are primarily composed of aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid. However, liquid crystalline resins primarily composed of aromatic hydroxycarboxylic acids have molding temperatures exceeding 350°C, which is too high for melt processing using general-purpose equipment. Patent Document 1 describes an aromatic polyester characterized by containing predetermined amounts of each structural unit represented by a predetermined general formula without using p-hydroxybenzoic acid.

[0003] [Patent Document 1] Patent Publication No. 5-117374 Summary of the Invention

[0004] An object of the present invention is to provide a liquid crystalline wholly aromatic polyester having a lower flow initiation temperature than conventional polyesters.

[0005] The present invention has the following aspects. [1] Essential components include the following structural units (I), (II), (III), and (IV): Contains TIFF0007772914000001.tif98170, the content of the structural unit (I) is 17.5 to 26 mol % based on all structural units, the content of the structural unit (II) is 24 to 32.5 mol % based on all structural units, the content of the structural unit (III) is 17.5 to 26 mol % based on all structural units, the content of the structural unit (IV) is 24 to 32.5 mol % based on all structural units; A wholly aromatic polyester that exhibits optical anisotropy when melted, in which the total content of structural units (I), (II), (III) and (IV) is 100 mol % based on all structural units. [2] The wholly aromatic polyester according to [1], which has a flow initiation temperature of 310°C or less. [3] A resin composition containing the wholly aromatic polyester according to [1] or [2]. [4] A molded article containing the wholly aromatic polyester according to [1] or [2]. [5] A method for producing a wholly aromatic polyester that exhibits optical anisotropy when melted, comprising: The method comprises acylating 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene with a fatty acid anhydride, followed by polycondensation with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid; For all monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene, the amount of 1,4-phenylenedicarboxylic acid used is 17.5 to 26 mol %, the amount of 2,6-naphthalenedicarboxylic acid used is 24 to 32.5 mol %, the amount of 4,4'-dihydroxybiphenyl used is 17.5 to 26 mol %; The amount of 1,4-dihydroxybenzene used is 24 to 32.5 mol %; A method for producing a wholly aromatic polyester, wherein the total amount of 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene used is 100 mol %. [6] The method according to [5], wherein the fatty acid anhydride comprises acetic anhydride.

[0006] According to the present invention, it is possible to provide a liquid crystalline wholly aromatic polyester having a lower flow initiation temperature than conventional polyesters. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiment, and appropriate modifications can be made within the scope that does not impair the effects of the present invention. When a specific description given for one embodiment also applies to other embodiments, that description may be omitted in other embodiments. In this disclosure, the expression "X to Y" for a numerical range means "X or more and Y or less." Furthermore, when multiple upper and lower limit values ​​are given for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range.

[0008] [Fully aromatic polyester] The wholly aromatic polyester according to this embodiment is a wholly aromatic polyester that exhibits optical anisotropy when melted, and contains the following structural units (I), (II), (III), and (IV) as essential structural components: TIFF0007772914000002.tif98170 The content of each structural unit is within a predetermined range as described below. A wholly aromatic polyester having these characteristics exhibits optical anisotropy when melted, has a low resin flow initiation temperature, and can be melt-processed at lower temperatures than conventional methods. Additionally, conventional wholly aromatic polyesters primarily composed of aromatic hydroxycarboxylic acids have the problem of low toughness and brittleness in molded articles. However, the wholly aromatic polyester of the present invention has excellent toughness, making molded articles less susceptible to fracture even when strain is applied. Furthermore, in the present disclosure, the content (mol %) of each structural unit can also be calculated from the monomer charge ratio during polymerization. Alternatively, the proportion (mol %) of each structural unit can also be calculated by pyrolysis gas chromatography, as described in Polymer Degradation and Stability, Vol. 76 (2002), pp. 85-94.

[0009] The structural unit (I) is derived from 1,4-phenylenedicarboxylic acid (hereinafter also referred to as "TA") and its polymerizable derivatives. Examples of polymerizable derivatives include alkyl esters (having approximately 1 to 4 carbon atoms) and halides of 1,4-phenylenedicarboxylic acid. The wholly aromatic polyester contains 17.5 to 26 mol% of the structural unit (I) relative to all structural units. If the content of the structural unit (I) is less than 17.5 mol% or more than 26 mol%, the effect of lowering the flow initiation temperature is insufficient, and low-temperature processability tends to be insufficient. From the viewpoint of achieving both low-temperature processability and toughness, the content of the structural unit (I) relative to all structural units is preferably 18 to 26 mol%, more preferably 19 to 25.5 mol%, and even more preferably 20 to 25 mol%.

[0010] In Patent Document 1, the composition is characterized by containing a predetermined amount of an aromatic dicarboxylic acid represented by a predetermined general formula and an aromatic diol, but the only composition that can lower the melting point Tm to 310° C. or less is a composition that uses, as the aromatic dicarboxylic acid, 2,6-naphthalenedicarboxylic acid in addition to 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid in combination. In the present embodiment, even when no aromatic hydroxycarboxylic acid is used and only 2,6-naphthalenedicarboxylic acid and 1,4-phenylenedicarboxylic acid are used as the aromatic dicarboxylic acids, the resin flow temperature can be lowered compared to conventional compositions by satisfying the requirements of structural units (I) to (IV) and setting the content of each structural unit within a predetermined range.

[0011] The structural unit (II) is derived from 2,6-naphthalenedicarboxylic acid (hereinafter also referred to as "NDA") and its polymerizable derivatives. Examples of the polymerizable derivatives include alkyl esters (having approximately 1 to 4 carbon atoms) and halides of 2,6-naphthalenedicarboxylic acid. The wholly aromatic polyester contains 24 to 32.5 mol% of the structural unit (II) relative to all structural units. If the content of the structural unit (II) is less than 24 mol% or exceeds 32.5 mol%, at least one of low-temperature processability and toughness tends to be insufficient. From the viewpoint of achieving both low-temperature processability and toughness, the content of the structural unit (II) relative to all structural units is preferably 24.5 to 32 mol%, more preferably 24.5 to 31 mol%, and even more preferably 25 to 30 mol%.

[0012] The structural unit (III) is derived from 4,4'-dihydroxybiphenyl (hereinafter also referred to as "BP") and its polymerizable derivatives. Examples of polymerizable derivatives include alkyl esters (having approximately 1 to 4 carbon atoms) and halides of 4,4'-dihydroxybiphenyl. The wholly aromatic polyester contains 17.5 to 26 mol% of the structural unit (III) relative to all structural units. If the content of the structural unit (III) is less than 17.5 mol% or exceeds 26 mol%, at least one of low-temperature processability and toughness tends to be insufficient. From the viewpoint of achieving both low-temperature processability and toughness, the content of the structural unit (III) relative to all structural units is preferably 18 to 26 mol%, more preferably 19 to 25.5 mol%, and even more preferably 20 to 25 mol%.

[0013] The structural unit (IV) is derived from 1,4-dihydroxybenzene (hereinafter also referred to as "HQ") and its polymerizable derivatives. Examples of polymerizable derivatives include alkyl esters (having approximately 1 to 4 carbon atoms) and halides of 1,4-dihydroxybenzene. The wholly aromatic polyester contains 24 to 32.5 mol% of the structural unit (IV) relative to all structural units. If the content of the structural unit (IV) is less than 24 mol% or more than 32.5 mol%, at least one of low-temperature processability and toughness tends to be insufficient. From the viewpoint of achieving both low-temperature processability and toughness, the content of the structural unit (IV) is preferably 24.5 to 32 mol%, more preferably 24.5 to 31 mol%, and even more preferably 25 to 30 mol%.

[0014] The wholly aromatic polyester contains the structural units (I) to (IV) in total at 100 mol % of all the structural units.

[0015] The phrase "exhibiting optical anisotropy when melted" means that the wholly aromatic polyester is a liquid crystalline polymer. Because the wholly aromatic polyester is a liquid crystalline polymer, it can have both low-temperature processability and toughness.

[0016] The optical anisotropy exhibited during melting can be confirmed by a conventional polarization inspection method using crossed polarizers. More specifically, melt anisotropy can be confirmed by melting a sample placed on a Linkam hot stage using an Olympus polarizing microscope and observing it at 150x magnification under a nitrogen atmosphere. Liquid crystal polymers are optically anisotropic and transmit light when inserted between crossed polarizers. If a sample is optically anisotropic, polarized light will transmit even when it is in a molten, static liquid state, for example.

[0017] Nematic liquid crystalline polymers exhibit a significant decrease in viscosity above their melting point, and therefore, the fact that they exhibit liquid crystallinity at or above their melting point is generally an indicator of their processability.

[0018] The melt viscosity of the wholly aromatic polyester at a temperature 10 to 40°C higher than the melting point of the wholly aromatic polyester and at a shear rate of 1000 / sec is preferably 1000 Pa·s or less, more preferably 4 to 500 Pa·s, even more preferably 4 to 250 Pa·s, and particularly preferably 5 to 100 Pa·s. When the melt viscosity is within the above range, the wholly aromatic polyester itself or a composition containing the wholly aromatic polyester is likely to have sufficient fluidity during molding, and excessive filling pressure is unlikely to occur. In the present disclosure, melt viscosity refers to the melt viscosity measured in accordance with ISO 11443.

[0019] The wholly aromatic polyester preferably has a flow initiation temperature of 310°C or less, more preferably 300°C or less, and even more preferably 295°C or less. By setting the flow initiation temperature to 310°C or less, a liquid crystalline wholly aromatic polyester with excellent melt processability at low temperatures can be obtained. In one embodiment, the wholly aromatic polyester may have a flow initiation temperature of 292°C or less. In one embodiment, the wholly aromatic polyester may also have a flow initiation temperature of 290°C or less or 280°C or less.

[0020] The flow initiation temperature is the temperature at which a wholly aromatic polyester becomes fluid when heated under external force, and can be measured by the following method: The flow initiation temperature is measured by using a capillary rheometer (e.g., Flow Tester CFT-500 manufactured by Shimadzu Corporation) to apply a pressure of 100 kg / cm to a sample resin that has been heated and melted at a temperature increase rate of 4°C / min. 2 It is measured as the temperature (°C) at which the melt viscosity is 48,000 poise when extruded from a nozzle with an inner diameter of 1 mm and a length of 10 mm under a load of 1000 kJ / cm.

[0021] [Method of producing wholly aromatic polyester] The method for producing a wholly aromatic polyester according to this embodiment is a method for producing a wholly aromatic polyester that exhibits optical anisotropy when melted, and includes acylation of 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene with a fatty acid anhydride, followed by polycondensation with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid. 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene may each contain a polymerizable derivative thereof. Examples of the polymerizable derivative include alkyl esters (having approximately 1 to 4 carbon atoms) and halides.

[0022] (acylation) The fatty acid anhydride acts as an acylating agent. Examples of the fatty acid anhydride include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, 2-ethylhexanoic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, and β-bromopropionic anhydride. It is preferable to use one or more fatty acid anhydrides selected from these.

[0023] From the viewpoint of cost and ease of handling, preferred examples include carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and isobutyric anhydride, and it is preferable to use one or more selected from these. Among these, from the viewpoint of ease of availability, it is preferable that the fatty acid anhydride contains acetic anhydride.

[0024] From the viewpoint of ease of reaction control, the amount of fatty acid anhydride used is preferably 1.0 to 1.1 equivalents, more preferably 1.01 to 1.05 equivalents, based on the total amount of hydroxyl groups in 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene.

[0025] The amount of 4,4'-dihydroxybiphenyl used is 17.5 to 26 mol %, preferably 18 to 26 mol %, more preferably 19 to 25.5 mol %, and even more preferably 20 to 25 mol %, based on all monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

[0026] The amount of 1,4-dihydroxybenzene used is 24 to 32.5 mol %, preferably 24.5 to 32 mol %, more preferably 24.5 to 31 mol %, and even more preferably 25 to 30 mol %, based on the total amount of monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

[0027] Acylation can be carried out by a known method, for example, by mixing 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene with a fatty acid anhydride and heating the mixture at a temperature in the range of 120 to 160°C for about 0.5 to 5 hours to carry out an acylation reaction, thereby obtaining a reaction product containing an acylated compound.

[0028] (Polycondensation reaction) Next, the acylated product obtained by the above acylation is polycondensed with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.

[0029] The amount of 1,4-phenylenedicarboxylic acid used is 17.5 to 26 mol %, preferably 18 to 26 mol %, more preferably 19 to 25.5 mol %, and even more preferably 20 to 25 mol %, based on the total amount of monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

[0030] The amount of 2,6-naphthalenedicarboxylic acid used is 24 to 32.5 mol %, preferably 24.5 to 32 mol %, more preferably 24.5 to 31 mol %, and even more preferably 25 to 30 mol %, based on the total amount of monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

[0031] The polycondensation reaction can be carried out by a known method, for example, by mixing an acylated product of 4,4'-dihydroxybiphenyl and an acylated product of 1,4-dihydroxybenzene with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, and heating the mixture at a temperature in the range of 200 to 400°C for about 2 to 12 hours to carry out polycondensation.

[0032] In the method for producing a wholly aromatic polyester according to this embodiment, the total amount of 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene used is 100 mol %.

[0033] In the polycondensation reaction, a melt polymerization method, a solution polymerization method, a slurry polymerization method, a solid-phase polymerization method, or a combination of two or more of these methods is used, and a melt polymerization method or a combination of a melt polymerization method and a solid-phase polymerization method is preferably used.

[0034] The wholly aromatic polyester produced by the polycondensation reaction can be further subjected to solid-phase polymerization by heating in an inert gas under normal pressure or reduced pressure to increase the molecular weight. Solid-state polymerization can be performed using conventionally known methods. For example, it can be performed by heating the raw material resin (wholly aromatic polyester obtained by polycondensation reaction) at a temperature 10 to 120°C lower than the liquid crystal formation temperature of the raw material resin (wholly aromatic polyester obtained by polycondensation reaction) under reduced pressure or vacuum in a stream of inert gas such as nitrogen gas. Note that the melting point of the wholly aromatic polyester increases as the solid-state polymerization proceeds, so it is also possible to perform solid-state polymerization at a temperature higher than the original melting point of the raw material resin. Solid-state polymerization can be performed at a constant temperature or by gradually increasing the temperature. The heating method is not particularly limited, and microwave heating, heater heating, etc. can be used.

[0035] A known catalyst can be used in each of the above reactions. Representative examples include metal salt catalysts such as potassium acetate, magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, antimony trioxide, and tris(2,4-pentanedionato)cobalt(III), and organic compound catalysts such as 1-methylimidazole and 4-dimethylaminopyridine. The catalyst preferably contains one or more selected from these. The same catalyst may be used in the acylation reaction and the polycondensation reaction (and, if necessary, the solid-state polymerization reaction).

[0036] In each of the above reactions, all of the raw material monomers (4,4'-dihydroxybiphenyl, 1,4-dihydroxybenzene, 1,4-phenylenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid), fatty acid anhydride, and catalyst can be charged into the same reaction vessel to initiate the reaction (single-stage system), or 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene can be acylated with fatty acid anhydride and then reacted separately with the carboxyl groups of 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid (two-stage system).

[0037] [Resin composition] The resin composition according to this embodiment contains the wholly aromatic polyester described above. Because it contains the wholly aromatic polyester described above, it has a lower flow initiation temperature than conventional resins, and can be melt-processed at a lower temperature. In one embodiment, the wholly aromatic polyester accounts for preferably 80% by mass or more, more preferably 90% by mass or more, of the thermoplastic resin contained in the resin composition. In one embodiment, the thermoplastic resin contained in the resin composition can be composed solely of the wholly aromatic polyester described above.

[0038] The resin composition may be blended with various fibrous, granular, or plate-like inorganic and organic fillers depending on the intended use. Examples of fibrous inorganic fillers include inorganic fibrous materials such as glass fiber, milled glass fiber, carbon fiber, asbestos fiber, silica fiber, silica-alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, silicate fibers such as wollastonite, magnesium sulfate fiber, aluminum borate fiber, and metal fibers such as stainless steel, aluminum, titanium, copper, brass, etc. A particularly representative fibrous filler is glass fiber. Examples of the fibrous organic filler include high-melting organic fibrous materials such as polyamide, fluororesin, polyester resin, and acrylic resin.

[0039] Examples of the powdery inorganic filler include carbon black, graphite, silica, quartz powder, glass beads, glass balloons, glass powder, kaolin, clay, diatomaceous earth, silicates such as wollastonite, metal oxides such as iron oxide, titanium oxide, zinc oxide, antimony trioxide, and alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate, as well as ferrite, 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.

[0040] The amount of the filler to be added is preferably 5 to 150 parts by mass, and more preferably 20 to 80 parts by mass, based on 100 parts by mass of the wholly aromatic polyester. When using the above filler, a sizing agent or a surface treatment agent may be used as needed.

[0041] The resin composition may contain other components, such as other thermoplastic resins, antioxidants, stabilizers, pigments, and additives such as nucleating agents, as long as the effects of the present invention are not impaired.

[0042] The method for producing the resin composition is not particularly limited, and the resin composition can be prepared by a conventionally known method. For example, the resin composition can be prepared by blending the components and melt-kneading them using a single-screw or twin-screw extruder.

[0043] The resin composition has a flow initiation temperature of preferably 310°C or less, more preferably 300°C or less, and even more preferably 295°C or less. In one embodiment, the resin composition may have a flow initiation temperature of 292°C or less. In one embodiment, the resin composition may have a flow initiation temperature of 290°C or less or 280°C or less. A resin composition having a flow initiation temperature of 310°C or less can be melt-processed at a lower temperature than conventional resin compositions.

[0044] [Molded products] The molded article according to the present embodiment is a molded article molded using the wholly aromatic polyester or the resin composition, and contains the wholly aromatic polyester. Because the molded article contains the wholly aromatic polyester, it has excellent toughness and is less likely to break even when deformed.

[0045] The method for producing the molded article is not particularly limited, and any common molding method can be used, such as injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, and inflation molding.

[0046] The molded article according to this embodiment has excellent moldability and can be easily processed into various three-dimensional molded articles, fibers, films, etc. Examples of preferred applications include connectors, CPU sockets, relay switch parts, bobbins, actuators, noise reduction filter cases, electronic circuit boards, and heat fixing rolls for office automation equipment. [Example]

[0047] The present invention will be explained in more detail below by showing examples, but the interpretation of the present invention is not limited to these examples.

[0048] [Example 1] A polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reduction / outlet line was charged with the following raw material monomers, a fatty acid metal salt catalyst, and a fatty acid anhydride, and nitrogen substitution was initiated. (I) 1,4-phenylenedicarboxylic acid (TA) 0.5 moles (25 mole%) (II) 2,6-naphthalenedicarboxylic acid (NDA) 0.5 moles (25 mole%) (III) 4,4'-dihydroxybiphenyl (BP) 0.5 mol (25 mol%) (IV) 1,4-dihydroxybenzene (HQ) 0.5 moles (25 mole%) Potassium acetate catalyst 150 ppm Acetic anhydride 2.08 mol (1.04 equivalents based on the total amount of hydroxyl groups of BP and HQ)

[0049] After the raw materials were charged, the temperature of the reaction system was raised to 140°C and the reaction was carried out at 140°C for 3 hours (acylation step). The temperature was then further raised to 360°C over 4.5 hours, and the pressure was then reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes, and polycondensation was carried out while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction step). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from reduced pressure to normal pressure and then to pressurized, and the polymer was discharged from the bottom of the polymerization vessel. The strands were then pelletized to obtain wholly aromatic polyester pellets.

[0050] [Examples 2 to 4, Comparative Examples 3 to 5] Wholly aromatic polyester pellets were obtained in the same manner as in Example 1, except that the raw material monomers and their blending amounts were as shown in Table 1.

[0051] [Comparative Example 1] A polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reduction / outlet line was charged with the following raw material monomers, a fatty acid metal salt catalyst, and a fatty acid anhydride, and nitrogen substitution was initiated. (I) 1,4-phenylenedicarboxylic acid (TA) 0.46 mol (25 mol%) (III) 4,4'-dihydroxybiphenyl (BP) 0.46 mol (25 mol%) 4-hydroxybenzoic acid (HBA) 0.037 mol (2 mol%) 6-Hydroxy-2-naphthoic acid (HNA) 0.883 mol (48 mol%) Potassium acetate catalyst 150 ppm Acetic anhydride 1.914 mol (1.04 equivalents based on the total amount of hydroxyl groups of BP, HBA, and HNA)

[0052] After the raw materials were charged, the temperature of the reaction system was raised to 140°C and the reaction was carried out at 140°C for 3 hours (acylation step). The temperature was then further raised to 360°C over 4.5 hours, and the pressure was then reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes, and polycondensation was carried out while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction step). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from reduced pressure to normal pressure and then to pressurized, and the polymer was discharged from the bottom of the polymerization vessel. The strands were then pelletized to obtain wholly aromatic polyester pellets.

[0053] Comparative Example 2 A polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reduction / outlet line was charged with the following raw material monomers, a fatty acid metal salt catalyst, and a fatty acid anhydride, and nitrogen substitution was initiated. (I) 1,4-phenylenedicarboxylic acid (TA) 0.8 moles (40 mole%) (III) 4,4'-dihydroxybiphenyl (BP) 0.4 mol (20 mol%) (IV) 1,4-dihydroxybenzene (HQ) 0.4 moles (20 mole%) 6-Hydroxy-2-naphthoic acid (HNA) 0.4 mol (20 mol%) Potassium acetate catalyst 150 ppm Acetic anhydride 2.08 mol (1.04 equivalents based on the total amount of hydroxyl groups of BP, HQ, and HNA)

[0054] After the raw materials were charged, the temperature of the reaction system was raised to 140°C and the reaction was carried out at 140°C for 3 hours (acylation step). The temperature was then further raised to 380°C over 4.5 hours, and the pressure was then reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes, and polycondensation was carried out while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction step). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from reduced pressure to normal pressure and then to pressurized, and the polymer was discharged from the bottom of the polymerization vessel. The strands were then pelletized to obtain wholly aromatic polyester pellets.

[0055] Comparative Example 6 (I) 1,4-phenylenedicarboxylic acid (TA) 0.28 moles (14 mole %) (III) 4,4'-dihydroxybiphenyl (BP) 0.4 mol (20 mol%) 1,3-phenylenedicarboxylic acid (IA) 0.12 mol (6 mol%) 4-hydroxybenzoic acid (HBA) 1.2 moles (60 mole%) Potassium acetate catalyst 150 ppm Acetic anhydride 2.08 mol (1.04 equivalents based on the total amount of hydroxyl groups in BP and HBA)

[0056] After the raw materials were charged, the temperature of the reaction system was raised to 140°C and the reaction was carried out at 140°C for 3 hours (acylation step). The temperature was then further raised to 360°C over 4.5 hours, and the pressure was then reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes, and polycondensation was carried out while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction step). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from reduced pressure to normal pressure and then to pressurized, and the polymer was discharged from the bottom of the polymerization vessel. The strands were then pelletized to obtain wholly aromatic polyester pellets.

[0057] (liquid crystallinity) The wholly aromatic polyesters obtained in the examples and comparative examples were melted on a hot stage manufactured by Linkam Co., Ltd., and observed under a nitrogen atmosphere at a magnification of 150x under crossed Nicols using a polarizing microscope manufactured by Olympus Corporation. Those in which an optically anisotropic molten phase had formed were indicated by "Y" in Table 1.

[0058] (Flow starting temperature) The wholly aromatic polyesters obtained in the examples and comparative examples were heated and melted at a temperature rising rate of 4°C / min using a capillary rheometer (Shimadzu Corporation, Flow Tester CFT-500 model), and then heated to 9.8 MPa (100 kg / cm 2 The temperature at which the melt viscosity reached 4800 Pa·s (48,000 poise) was measured when the material was extruded from a nozzle with an inner diameter of 1 mm and a length of 10 mm under a load of 1000 mbar (200 psi). The results are shown in Table 1.

[0059] (bending test) The wholly aromatic polyester pellets obtained in the Examples and Comparative Examples were molded using a molding machine ("SE30DUZ" manufactured by Sumitomo Heavy Industries, Ltd.) under the following molding conditions to prepare bending test specimens of 50 mm x 4 mm x 0.3 mm. Using these test specimens, the bending strain at the maximum bending stress was measured under the following test conditions. The results are shown in Table 1. [Molding conditions] Cylinder temperature: Examples 1 to 4, Comparative Example 6: 350°C Comparative Examples 1, 3 to 5: 370°C Comparative Example 2: 380°C Mold temperature: 90℃ Injection speed: 33mm / sec Holding pressure: 50MPa [Test conditions] Test speed: 2.0 mm / min Distance between fulcrums 4.8mm Indenter radius: 0.5 mm Support radius: 0.5 mm Elastic modulus: secant method

[0060] [Table 1]

[0061] As shown in Table 1, the wholly aromatic polyesters of Examples 1 to 4 do not contain aromatic hydroxycarboxylic acids, but are composed only of aromatic dicarboxylic acids and aromatic diols. These wholly aromatic polyesters have flow initiation temperatures of 310°C or less, which is lower than conventional polyesters, and therefore have excellent melt processability at low temperatures. Furthermore, the bending strain of the resulting molded articles is 9% or more, so they are less likely to break even when deformed. In contrast, the wholly aromatic polyesters of Comparative Examples 1 to 6 all have flow initiation temperatures exceeding 310°C, requiring melt processing at high temperatures. In addition, the molded articles obtained from the wholly aromatic polyesters of Comparative Examples 1, 2, and 6 have bending strains of less than 9%, making them susceptible to breakage when deformed. [Industrial Applicability]

[0062] The wholly aromatic polyester according to this embodiment has a flow initiation temperature lower than conventional polyesters, and therefore has industrial applicability as a high-performance engineering plastic with excellent melt processability at low temperatures.

Claims

1. The essential components include the following structural units (I), (II), (III), and (IV): Including, the content of the structural unit (I) is 17.5 to 26 mol% based on all structural units; the content of the structural unit (II) is 24 to 32.5 mol% based on all structural units; The content of the structural unit (III) is 17.5 to 26 mol% based on all structural units, The content of the structural unit (IV) is 24 to 32.5 mol% based on all structural units, A wholly aromatic polyester that exhibits optical anisotropy when melted, in which the total content of structural units (I), (II), (III) and (IV) is 100 mol % based on all structural units.

2. The wholly aromatic polyester according to claim 1, which has a flow initiation temperature of 310°C or less.

3. A resin composition comprising the wholly aromatic polyester according to claim 1 or 2.

4. A molded article comprising the wholly aromatic polyester according to claim 1 or 2.

5. A method for producing a wholly aromatic polyester that exhibits optical anisotropy when melted, comprising: The method comprises acylating 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene with a fatty acid anhydride, followed by polycondensation with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid; For all monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene, the amount of 1,4-phenylenedicarboxylic acid used is 17.5 to 26 mol %, The amount of 2,6-naphthalenedicarboxylic acid used is 24 to 32.5 mol %; The amount of 4,4'-dihydroxybiphenyl used is 17.5 to 26 mol %; The amount of 1,4-dihydroxybenzene used is 24 to 32.5 mol %; A method for producing a wholly aromatic polyester, wherein the total amount of 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene used is 100 mol %.

6. 6. The method of claim 5, wherein the fatty acid anhydride comprises acetic anhydride.

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