KR20240159607A - Wholly aromatic polyester, resin composition, molded article and method for producing wholly aromatic polyester - Google Patents

Abstract

A wholly aromatic polyester having a lower fluidity initiation temperature than conventional ones is provided. The wholly aromatic polyester, which exhibits optical anisotropy when melted, comprises as essential components the following structural units (I), (II), (III) and (IV): , wherein the content of the structural unit (I) is 17.5 to 26 mol% with respect to the entire structural units, the content of the structural unit (II) is 24 to 32.5 mol% with respect to the entire structural units, the content of the structural unit (III) is 17.5 to 26 mol% with respect to the entire structural units, the content of the structural unit (IV) is 24 to 32.5 mol% with respect to the entire structural units, and the content of the sum of the structural units (I), (II), (III) and (IV) is 100 mol% with respect to the entire structural units.

Description

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

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

Liquid crystal resins such as wholly aromatic polyesters have excellent fluidity, mechanical strength, heat resistance, chemical resistance, and electrical properties in a balanced manner, and are therefore widely used in various fields as high-performance engineering plastics.

Most of the wholly aromatic polyesters currently on the market contain aromatic hydroxycarboxylic acids such as 4-hydroxybenzoic acid as their main components. However, liquid crystal resins containing aromatic hydroxycarboxylic acids as their main components have a high molding processing temperature exceeding 350°C, which is too high for melt processing in general-purpose equipment.

Patent Document 1 describes an aromatic polyester characterized by containing a predetermined content of each structural unit represented by a predetermined general formula without using p-hydroxybenzoic acid.

Patent Document 1: Japanese Patent Application Laid-Open No. 5-117374

The present invention aims to provide a liquid crystalline wholly aromatic polyester having a lower flow initiation temperature than conventional polyesters.

The present invention has the following aspects.

[1] As essential components, the following constituent units (I), (II), (III) and (IV):

Including,

The content of the component unit (I) is 17.5 to 26 mol% with respect to the total component unit,

The content of the component unit (II) is 24 to 32.5 mol% with respect to the total component unit,

The content of the component unit (III) is 17.5 to 26 mol% with respect to the total component unit.

The content of the component unit (IV) is 24 to 32.5 mol% with respect to the total component unit.

A wholly aromatic polyester exhibiting optical anisotropy when molten, wherein the total content of the constituent units (I), (II), (III) and (IV) is 100 mol% with respect to the entire constituent units.

[2] The wholly aromatic polyester described in [1] having a flow initiation temperature of 310°C or lower.

[3] A resin composition containing the wholly aromatic polyester described in [1] or [2].

[4] A molded article containing the wholly aromatic polyester described in [1] or [2].

[5] A method for producing a wholly aromatic polyester exhibiting optical anisotropy when melted,

Comprising acylation of 4,4′-dihydroxybiphenyl and 1,4-dihydroxybenzene using a fatty acid anhydride and then polycondensation with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid,

For the entire 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 24-32.5 mol%,

The amount of 4,4′-dihydroxybiphenyl used is 17.5 to 26 mol%,

The amount of 1,4-dihydroxybenzene used is 24-32.5 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 described in [5], wherein the fatty acid anhydride comprises acetic anhydride.

According to the present invention, a liquid crystalline wholly aromatic polyester having a lower flow initiation temperature than conventional ones can be provided.

Hereinafter, an embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments, and may be implemented by making appropriate changes within a range that does not impede the effects of the present invention. If a specific description described for one embodiment also applies to other embodiments, the description may be omitted in other embodiments. In the present disclosure, the expression “X to Y” for a numerical range means “X or more and Y or less.” In addition, if a plurality of upper and lower limits are described for a specific parameter, any of these upper and lower limits can be combined to form a suitable numerical range.

[All-aromatic polyester]

The wholly aromatic polyester according to the present embodiment is a wholly aromatic polyester that exhibits optical anisotropy when melted, and comprises, as essential components, the following structural units (I), (II), (III) and (IV)):

, and the content of each component unit is within a predetermined range described below.

The wholly aromatic polyester having these characteristics exhibits optical anisotropy when melted, and at the same time, the resin has a low flow initiation temperature, and melt processing is possible at lower temperatures than before. In addition, the wholly aromatic polyester mainly composed of a conventional aromatic hydroxycarboxylic acid had the problem that the toughness of the molded product was low, hard, and brittle, but the wholly aromatic polyester according to the present embodiment has excellent toughness, so that the molded product is not easily broken even if deformation is applied. In addition, in the present disclosure, the content (mol%) of each constituent unit can also be calculated from the input ratio of the monomer at the time of polymerization. Alternatively, the ratio (mol%) of each constituent unit can also be calculated by the pyrolysis gas chromatography method described in Polymer Degradation and Stability vol. 76 (2002), 85-94.

The structural unit (I) is derived from 1,4-phenylenedicarboxylic acid (hereinafter also referred to as "TA") and polymerizable derivatives thereof. Examples of the polymerizable derivative include alkyl esters (having about 1 to 4 carbon atoms) of 1,4-phenylenedicarboxylic acid, halides, etc. The wholly aromatic polyester contains the structural unit (I) in an amount of 17.5 to 26 mol% with respect to the total 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 not sufficient, and the low-temperature processability tends to become insufficient. From the viewpoint of achieving compatibility with low-temperature processability and toughness, the content of the structural unit (I) is preferably 18 to 26 mol% with respect to the total structural units, more preferably 19 to 25.5 mol%, and even more preferably 20 to 25 mol%.

Patent Document 1 is characterized by containing a predetermined amount of an aromatic dicarboxylic acid and an aromatic diol represented by a predetermined general formula, but the composition capable of lowering the melting point Tm to 310°C or lower is only a composition that uses, in addition to 2,6-naphthalenedicarboxylic acid, 1,4-phenylenedicarboxylic acid and 1,3-phenylenedicarboxylic acid as the aromatic dicarboxylic acid. In the present embodiment, even when an aromatic hydroxycarboxylic acid is not used and only 2,6-naphthalenedicarboxylic acid and 1,4-phenylenedicarboxylic acid are used as the aromatic dicarboxylic acid, the composition units (I) to (IV) are satisfied and the content of each composition unit is set within a predetermined range, so that the flow initiation temperature of the resin can be lowered than before.

The structural unit (II) is derived from 2,6-naphthalenedicarboxylic acid (hereinafter also referred to as "NDA") and polymerizable derivatives thereof. Examples of the polymerizable derivative include alkyl esters (having about 1 to 4 carbon atoms) of 2,6-naphthalenedicarboxylic acid, halides, etc. The wholly aromatic polyester contains the structural unit (II) in an amount of 24 to 32.5 mol% with respect to the total structural units. If the content of the structural unit (II) is less than 24 mol% or more than 32.5 mol%, at least one of the low-temperature processability and the toughness tends to become insufficient. From the viewpoint of achieving compatibility with low-temperature processability and toughness, the content of the structural unit (II) is preferably 24.5 to 32 mol% with respect to the total structural units, more preferably 24.5 to 31 mol%, and even more preferably 25 to 30 mol%.

The structural unit (III) is derived from 4,4'-dihydroxybiphenyl (hereinafter also referred to as "BP") and polymerizable derivatives thereof. Examples of the polymerizable derivative include 4,4'-dihydroxybiphenyl alkyl esters (having about 1 to 4 carbon atoms), halides, etc. The wholly aromatic polyester contains the structural unit (III) in an amount of 17.5 to 26 mol% with respect to the total structural units. If the content of the structural unit (III) is less than 17.5 mol% or more than 26 mol%, at least one of the low-temperature processability and the toughness tends to become insufficient. From the viewpoint of achieving compatibility with low-temperature processability and toughness, the content of the structural unit (III) is preferably 18 to 26 mol%, more preferably 19 to 25.5 mol%, and even more preferably 20 to 25 mol% with respect to the total structural units.

The structural unit (IV) is derived from 1,4-dihydroxybenzene (hereinafter also referred to as "HQ") and polymerizable derivatives thereof. Examples of the polymerizable derivative include alkyl esters (having about 1 to 4 carbon atoms) of 1,4-dihydroxybenzene, halides, etc. The wholly aromatic polyester contains 24 to 32.5 mol% of the structural unit (IV) with respect to the total 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 the low-temperature processability and the toughness tends to become insufficient. From the viewpoint of compatibility between 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%.

The wholly aromatic polyester contains 100 mol% of the constituent units (I) to (IV) in total with respect to the entire constituent unit.

“Exhibiting optical anisotropy when melted” means that the wholly aromatic polyester is a liquid crystalline polymer. Since the wholly aromatic polyester is a liquid crystalline polymer, it can have both low-temperature processability and toughness.

The optical anisotropy at the time of melting can be confirmed by a conventional polarization inspection method using orthogonal polarizers. More specifically, the melt anisotropy can be confirmed by using an Olympus polarizing microscope, melting a sample placed on a Linkum hot stage, and observing it at a magnification of 150x under a nitrogen atmosphere. Liquid crystal polymers are optically anisotropic and transmit light when inserted between orthogonal polarizers. If the sample is optically anisotropic, polarized light is transmitted even in a molten, still liquid state, for example.

Since nematic liquid crystal polymers exhibit a marked decrease in viscosity above their melting point, the liquid crystallinity exhibited at a temperature at or above the melting point is generally an indicator of processability.

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, further 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 tends to secure fluidity during molding, and the filling pressure is unlikely to become excessive. In addition, in the present disclosure, melt viscosity refers to melt viscosity measured in accordance with ISO 11443.

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

The onset of flow temperature is the temperature at which wholly aromatic polyester exhibits fluidity due to an external force when heated, and can be measured by the following method. That is, the onset of flow temperature is measured as the temperature (℃) at which the melt viscosity exhibits 48000 poise when a sample resin that has been heated and melted at a heating rate of 4℃/min is extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm under a load of 100 kg/cm2 using a capillary type rheometer (e.g., Flow Tester CFT-500 manufactured by Shimadzu Corporation).

[Method for producing wholly aromatic polyester]

The method for producing a wholly aromatic polyester according to the present embodiment is a method for producing a wholly aromatic polyester which exhibits optical anisotropy when melted, comprising: acylating 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene using a fatty acid anhydride, and then polycondensing them 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 include a polymerizable derivative thereof. Examples of the polymerizable derivative include alkyl esters (having about 1 to 4 carbon atoms), halides, and the like.

(acylation)

Fatty acid anhydrides have an action as an acylating agent. Examples of the fatty acid anhydrides 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 at least one selected from these fatty acid anhydrides.

Suitable examples from the viewpoint of price and handling include carboxylic 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 acquisition, it is preferable that the fatty acid anhydride includes acetic anhydride.

The amount of fatty acid anhydride to be used is preferably 1.0 to 1.1 equivalents, more preferably 1.01 to 1.05 equivalents, relative to the total amount of hydroxyl groups of 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene from the viewpoint of easy reaction control.

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 the total monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

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 monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

Acylation can be carried out by a known method. For example, 4,4'-dihydroxybiphenyl and 1,4-dihydroxybenzene are mixed with a fatty acid anhydride and heated at a temperature range of 120 to 160°C for about 0.5 to 5 hours to cause an acylation reaction, thereby obtaining a reaction product containing an acylated product.

(condensation reaction)

Next, the acylation product obtained by the above acylation is polycondensed with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.

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 monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

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 monomers including 1,4-phenylenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-dihydroxybiphenyl, and 1,4-dihydroxybenzene.

The polycondensation reaction can be carried out by a known method. For example, an acylation product of 4,4'-dihydroxybiphenyl and an acylation product of 1,4-dihydroxybenzene are mixed with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, and the mixture is heated at a temperature range of 200 to 400°C for 2 to 12 hours to carry out polycondensation.

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

In the condensation reaction, a melt polymerization method, a solution polymerization method, a slurry polymerization method, a solid-state polymerization method, or a combination of two or more of these are used, and a melt polymerization method or a combination of a melt polymerization method and a solid-state polymerization method is preferably used.

The wholly aromatic polyester manufactured by the above polycondensation reaction can also have its molecular weight increased by solid-state polymerization heated in an inert gas under normal pressure or reduced pressure.

Solid-state polymerization can be performed using a conventionally known method. For example, it can be performed by heating 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) in an inert gas stream such as nitrogen gas under reduced pressure or vacuum. In addition, since the wholly aromatic polyester's melting point also increases as solid-state polymerization progresses, 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 can be performed stepwise at a high temperature. The heating method is not particularly limited, and microwave heating, heater heating, etc. can be used.

In each of the above reactions, a known catalyst can be used. Representative examples thereof 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. It is preferable that the catalyst includes at least one selected from these. The same catalyst may be used in the acylation reaction and the polycondensation reaction (or solid-state polymerization reaction, if necessary).

Each of the above reactions can be initiated by charging all raw material monomers (4,4′-dihydroxybiphenyl, 1,4-dihydroxybenzene, 1,4-phenylenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid), fatty acid anhydride, and catalyst into the same reaction vessel (one-stage method), or by acylating 4,4′-dihydroxybiphenyl and 1,4-dihydroxybenzene with fatty acid anhydride and then reacting them separately with the carboxyl groups of 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid (two-stage method).

[Resin composition]

The resin composition according to the present embodiment contains the wholly aromatic polyester described above. Since it contains the wholly aromatic polyester described above, the fluidity initiation temperature is lower than that of the prior art, and melt processing can be performed at a lower temperature. In one embodiment, among the thermoplastic resins contained in the resin composition, preferably 80 mass% or more, more preferably 90 mass% or more can be the wholly aromatic polyester. In one embodiment, the thermoplastic resin contained in the resin composition can be composed solely of the wholly aromatic polyester described above.

The resin composition can contain various types of inorganic and organic fillers in the form of fibers, granules, and plates, 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 fiber such as wollastonite, magnesium sulfate fiber, aluminum borate fiber, and also fibrous materials of metals such as stainless steel, aluminum, titanium, copper, and brass. A particularly representative fibrous filler is glass fiber.

As fibrous organic fillers, high-melting point organic fibrous materials such as polyamide, fluororesin, polyester resin, and acrylic resin can be mentioned.

Examples of the granular inorganic fillers include silicates such as carbon black, graphite, silica, quartz powder, glass beads, glass balloons, glass powder, kaolin, clay, diatomaceous earth, and 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; other ferrites, silicon carbide, silicon nitride, boron nitride, and various metal powders.

Examples of plate-shaped inorganic fillers include mica, glass flakes, talc, and various metal foils.

The blending amount of the filler is preferably 5 to 150 parts by mass, more preferably 20 to 80 parts by mass, per 100 parts by mass of the wholly aromatic polyester.

When using the above filler, a convergence agent or surface treatment agent may be used as needed.

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

The method for producing the resin composition is not particularly limited, and can be produced by a conventionally known method. For example, the resin composition can be prepared by mixing each component and subjecting them to melt mixing using a single-screw or twin-screw extruder.

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

[Plastic product]

The molded article according to the present embodiment is a molded article molded using the above-described wholly aromatic polyester or the above-described resin composition, and includes the above-described wholly aromatic polyester. Since it includes the above-described wholly aromatic polyester, it has excellent toughness and is difficult to break even when deformed.

The method for manufacturing the molded product is not particularly limited, and a general molding method can be adopted. General molding methods include injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, and inflation molding.

Since the molded article according to the present embodiment has excellent moldability, it can be easily processed into various three-dimensional molded articles, fibers, films, etc. Examples of preferable applications include connectors, CPU sockets, relay switch parts, bobbins, actuators, noise reduction filter cases, electronic circuit boards, or heating fixing rolls for OA devices.

Example

The present invention is described more specifically by way of examples below, but the interpretation of the present invention is not limited by these examples.

[Example 1]

The following raw material monomers, fatty acid metal salt catalysts, and fatty acid anhydrides were introduced into a polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reducing/discharge line, and nitrogen substitution was initiated.

(I) 1,4-phenylenedicarboxylic acid (TA) 0.5 mol (25 mol%)

(II) 2,6-naphthalenedicarboxylic acid (NDA) 0.5 mol (25 mol%)

(III) 4,4′-dihydroxybiphenyl (BP) 0.5 mol (25 mol%)

(IV) 1,4-dihydroxybenzene (HQ) 0.5 mol (25 mol%)

Potassium acetate catalyst 150 ppm

2.08 moles of acetic anhydride (1.04 equivalents based on the total amount of hydroxyl groups in BP and HQ)

After the raw materials were introduced, the temperature of the reaction system was raised to 140°C, and the reaction was performed at 140°C for 3 hours (acylation process). Thereafter, the temperature was raised again to 360°C over 4.5 hours, and the pressure was reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes thereafter, and polycondensation was performed while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction process). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from a reduced pressure state to a normal pressure state and then to a pressurized state, and the polymer was discharged from the lower part of the polymerization vessel. Thereafter, the strand was pelletized to obtain wholly aromatic polyester pellets.

[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 described in Table 1.

[Comparative Example 1]

The following raw material monomers, fatty acid metal salt catalysts, and fatty acid anhydrides were introduced into a polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reducing/discharge line, 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

1.914 moles of acetic anhydride (1.04 equivalents relative to the total amount of hydroxyl groups of BP, HBA, and HNA)

After the raw materials were introduced, the temperature of the reaction system was raised to 140°C, and the reaction was performed at 140°C for 3 hours (acylation process). Thereafter, the temperature was raised again to 360°C over 4.5 hours, and the pressure was reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes thereafter, and polycondensation was performed while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction process). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from a reduced pressure state to a normal pressure state and then to a pressurized state, and the polymer was discharged from the lower part of the polymerization vessel. Thereafter, the strand was pelletized to obtain wholly aromatic polyester pellets.

[Comparative Example 2]

The following raw material monomers, fatty acid metal salt catalysts, and fatty acid anhydrides were introduced into a polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reducing/discharge line, and nitrogen substitution was initiated.

(I) 1,4-phenylenedicarboxylic acid (TA) 0.8 mol (40 mol%)

(III) 4,4′-dihydroxybiphenyl (BP) 0.4 mol (20 mol%)

(IV) 1,4-dihydroxybenzene (HQ) 0.4 mol (20 mol%)

6-Hydroxy-2-naphthoic acid (HNA) 0.4 mol (20 mol%)

Potassium acetate catalyst 150 ppm

2.08 moles of acetic anhydride (1.04 equivalents based on the total hydroxyl groups of BP, HQ, and HNA)

After the raw materials were introduced, the temperature of the reaction system was raised to 140°C, and the reaction was performed at 140°C for 3 hours (acylation process). Thereafter, the temperature was raised again to 380°C over 4.5 hours, and the pressure was reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes thereafter, and polycondensation was performed while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction process). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from a reduced pressure state to a normal pressure state and then to a pressurized state, and the polymer was discharged from the lower part of the polymerization vessel. Thereafter, the strand was pelletized to obtain wholly aromatic polyester pellets.

[Comparative Example 6]

(I) 1,4-phenylenedicarboxylic acid (TA) 0.28 mol (14 mol%)

(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 mol (60 mol%)

Potassium acetate catalyst 150 ppm

2.08 moles of acetic anhydride (1.04 equivalents relative to the total amount of hydroxyl groups in BP and HBA)

After the raw materials were introduced, the temperature of the reaction system was raised to 140°C, and the reaction was performed at 140°C for 3 hours (acylation process). Thereafter, the temperature was raised again to 360°C over 4.5 hours, and the pressure was reduced to 10 Torr (i.e., 1330 Pa) over 15 minutes thereafter, and polycondensation was performed while distilling off acetic acid, excess acetic anhydride, and other low-boiling components (polycondensation reaction process). After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from a reduced pressure state to a normal pressure state and then to a pressurized state, and the polymer was discharged from the lower part of the polymerization vessel. Thereafter, the strand was pelletized to obtain wholly aromatic polyester pellets.

(Liquid crystal)

The wholly aromatic polyesters obtained in the examples and comparative examples were melted by placing them on a hot stage manufactured by Linkom Co., Ltd. using a polarizing microscope manufactured by Olympus Corporation, and observed under cross-Nicol at a magnification of 150 times in a nitrogen atmosphere. The formation of an optically anisotropic melt phase is indicated by "Y" in Table 1.

(Flow initiation temperature)

The wholly aromatic polyesters obtained in the examples and comparative examples were heated and melted at a heating rate of 4°C/min using a capillary rheometer (Flotester CFT-500 manufactured by Shimadzu Corporation), and extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm under a load of 9.8 MPa (100 kg/cm2), and the temperature at which the melt viscosity was 4800 Pa·s (48000 poise) was measured. The results are shown in Table 1.

(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, and a bending test piece measuring 50 mm × 4 mm × 0.3 mm was produced. Using this test piece, the bending deformation when the bending stress reached its maximum was measured under the following test conditions. The results are shown in Table 1.

〔Plastic surgery conditions〕

Cylinder Temperature:

Examples 1 to 4, Comparative Example 6: 350℃

Comparative examples 1, 3∼5: 370℃

Comparative Example 2: 380℃

Mold temperature: 90℃

Injection speed: 33 mm/sec

Pressure: 50 Mpa

[Test conditions]

Test speed: 2.0 mm/min

Point-to-point distance 4.8 mm

Radius of the indenter: 0.5 mm

Radius of support: 0.5 mm

Elasticity: Secant method

As shown in Table 1, the wholly aromatic polyesters of Examples 1 to 4 are composed only of aromatic dicarboxylic acid and aromatic diol without using aromatic hydroxycarboxylic acid. These wholly aromatic polyesters have excellent melt processability at low temperatures because the flow initiation temperature is 310°C or lower, which is lower than that of conventional products. In addition, since the bending deformation of the obtained molded product is 9% or higher, it is difficult to be destroyed even if deformed.

In this regard, the wholly aromatic polyesters of Comparative Examples 1 to 6 all have a flow initiation temperature exceeding 310°C, and thus require melt processing at high temperatures. In addition, the wholly aromatic polyesters of Comparative Examples 1, 2, and 6 have a bending deformation of less than 9% in the obtained molded products, and are easily broken when deformed.

Industrial applicability

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

Claims (6)

As essential components, the following constituent units (I), (II), (III) and (IV):

Including,
The content of the constituent unit (I) is 17.5 to 26 mol% with respect to the total constituent unit,
The content of the component unit (II) is 24 to 32.5 mol% with respect to the total component unit,
The content of the component unit (III) is 17.5 to 26 mol% with respect to the total component unit.
The content of the component unit (IV) is 24 to 32.5 mol% with respect to the total component unit.
A wholly aromatic polyester exhibiting optical anisotropy when molten, wherein the total content of the constituent units (I), (II), (III) and (IV) is 100 mol% with respect to the entire constituent units. In the first paragraph,
A wholly aromatic polyester having a flow initiation temperature of 310°C or less. A resin composition containing the wholly aromatic polyester described in claim 1 or 2. A molded product containing the wholly aromatic polyester described in claim 1 or 2. A method for producing a wholly aromatic polyester exhibiting optical anisotropy when melted,
Comprising acylation of 4,4′-dihydroxybiphenyl and 1,4-dihydroxybenzene using a fatty acid anhydride and then polycondensation with 1,4-phenylenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid,
For the entire 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 24-32.5 mol%,
The amount of 4,4′-dihydroxybiphenyl used is 17.5–26 mol%,
The amount of 1,4-dihydroxybenzene used is 24-32.5 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%. In paragraph 5,
A method for producing a wholly aromatic polyester, wherein the fatty acid anhydride comprises acetic anhydride.