JP7732366B2 - Liquid crystal polyester resin, its manufacturing method, liquid crystal polyester resin composition and molded article made from the same - Google Patents

Description

The present invention relates to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article made thereof. More specifically, the present invention relates to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article obtained using the same.

Liquid crystal polyester resins have excellent heat resistance, fluidity, and dimensional stability, and are therefore used in electrical and electronic components that require these properties. In recent years, the miniaturization of devices such as smartphones has led to increased demand for higher integration, thinner walls, and lower heights of components. Liquid crystal polyester resins have been proposed that combine excellent fluidity with high strength and blister resistance by incorporating structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid (see, for example, Patent Documents 1 to 6).

Japanese Patent Application Laid-Open No. 2021-24985 JP 2017-137438 A International Publication No. 2018/101214 JP 2012-126842 A JP 2015-183159 A JP 2015-227404 A

However, when molding small, thin-walled molded products, a high injection speed is required, and the methods described in Patent Documents 1 to 6 posed the problem of burrs forming on the sprue and other areas. Furthermore, stringiness was likely to occur during molding, posing an issue with high-cycle molding.

The objective of the present invention is to provide a liquid crystal polyester resin, a liquid crystal polyester resin composition, and molded articles made therefrom that do not produce flash even when molded at high injection speeds and that have excellent high-cycle moldability.

As a result of extensive research to solve the above problems, the inventors discovered that a liquid crystal polyester resin containing a certain amount of structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid exhibits excellent high-cycle moldability while suppressing flash (hereinafter referred to as "low flash"), leading to the present invention.

That is, the present invention is as follows:
(1) A liquid crystal polyester resin containing the following structural units (I) to (V), which satisfies the following formulas (a) to (e):
46≦[I]≦49.8...(a)
2≦[II]≦5.5...(b)
6≦[III]≦18...(c)
6≦[IV]≦18...(d)
20≦[V]≦27...(e)
([I] to [V] indicate the content (mol %) of each of the structural units (I) to (V) relative to 100 mol % of all structural units in the liquid crystal polyester resin.)

(2) The liquid crystal polyester resin according to (1), which further satisfies the following formula (f):
10≦[I]/[II]≦12...(f)
(3) The liquid crystal polyester resin according to (1) or (2), which further satisfies the following formula (g):
3.9≦[II]≦4.9...(g)
(4) The liquid crystal polyester resin according to any one of (1) to (3), which further satisfies the following formula (h):
47≦[I]≦49...(h)
(5) The liquid crystal polyester resin according to any one of (1) to (4), further satisfying the following formula (i):
98≦[I]+[II]+[III]+[IV]+[V]≦100...(i)
(6) A method for producing the liquid crystal polyester resin according to any one of (1) to (5), by copolymerizing monomers that give the structural units (I) to (V).
(7) A liquid crystal polyester resin composition containing 10 to 200 parts by weight of a filler based on 100 parts by weight of the liquid crystal polyester resin according to any one of (1) to (5).
(8) A molded article made of the liquid crystal polyester resin according to any one of (1) to (5) or the liquid crystal polyester resin composition according to (7).
(9) The molded article according to (8), which is any one selected from the group consisting of a connector, a relay, a switch, a coil bobbin, and an actuator part of a camera module.

The liquid crystal polyester resin of the present invention has excellent high-cycle properties during molding and can produce molded products that are less likely to produce burrs during molding. It is particularly suitable for use in molding small electrical and electronic components.

The present invention is described in detail below.

<Liquid Crystal Polyester Resin>
The liquid crystal polyester resin is a polyester that forms an anisotropic melt phase. Examples of such polyester resins include polyesters composed of structural units selected from the below-described oxycarbonyl unit, dioxy unit, and dicarbonyl unit so as to form an anisotropic melt phase.

Next, the structural units constituting the liquid crystal polyester resin will be described.
The liquid crystal polyester resin of the present invention contains 46 mol% or more of the following structural unit (I) as an oxycarbonyl unit, relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (I) is a structural unit derived from p-hydroxybenzoic acid. If the structural unit (I) is less than 46 mol%, the high cycle performance during molding is significantly reduced and flash is significantly more likely to occur. From the viewpoint of high cycle moldability and low flash, the structural unit (I) is more preferably 46.5 mol% or more, and even more preferably 47 mol% or more.

On the other hand, the liquid crystal polyester resin of the present invention contains 49.8 mol% or less of structural unit (I) relative to 100 mol% of all structural units in the liquid crystal polyester resin. If the structural unit (I) is more than 49.8 mol%, the high-cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flashing, the structural unit (I) is preferably 49.4 mol% or less, and more preferably 49 mol% or less.

The liquid crystal polyester resin of the present invention contains 2 mol% or more of the following structural unit (II) as an oxycarbonyl unit, relative to 100 mol% of all structural units in the liquid crystal polyester resin. Structural unit (II) is a structural unit derived from 6-hydroxy-2-naphthoic acid. If the structural unit (II) is less than 2 mol%, high-cycle performance during molding is significantly reduced and flash is significantly more likely to occur. From the viewpoint of high-cycle moldability and low flash, the structural unit (II) is preferably 3 mol% or more, more preferably 3.5 mol% or more, and even more preferably 3.9 mol% or more.

On the other hand, the liquid crystal polyester resin of the present invention contains 5.5 mol% or less of structural unit (II) relative to 100 mol% of all structural units in the liquid crystal polyester resin. If the structural unit (II) is more than 5.5 mol%, the high-cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flashing, the structural unit (II) is preferably 5.3 mol% or less, more preferably 5.1 mol% or less, and even more preferably 4.9 mol% or less.

From the viewpoint of high-cycle moldability and low flash, the liquid crystal polyester resin of the present invention preferably has a molar ratio ([I]/[II]) of the contents of structural units (I) and (II) of 10 or more. On the other hand, from the viewpoint of high-cycle moldability and low flash, [I]/[II] is preferably 12 or less.

In addition, structural units derived from m-hydroxybenzoic acid, etc., can be used as oxycarbonyl units as long as they do not impair the effects of the present invention.

The liquid crystal polyester resin of the present invention contains 6 mol% or more of the following structural unit (III) as dioxy units, relative to 100 mol% of all structural units in the liquid crystal polyester resin. Structural unit (III) is a structural unit derived from 4,4'-dihydroxybiphenyl. If the structural unit (III) is less than 6 mol%, high-cycle performance during molding is significantly reduced and flash is significantly more likely to occur. From the viewpoint of high-cycle moldability and low flash, the structural unit (III) is preferably 7 mol% or more, and more preferably 8 mol% or more.

On the other hand, the liquid crystal polyester resin of the present invention contains 18 mol% or less of the following structural unit (III) relative to 100 mol% of all structural units in the liquid crystal polyester resin. If the structural unit (III) is more than 18 mol%, the high-cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flashing, the structural unit (III) is preferably 16 mol% or less, more preferably 14 mol% or less.

The liquid crystal polyester resin of the present invention contains 6 mol% or more of the following structural unit (IV) as dioxy units, relative to 100 mol% of all structural units in the liquid crystal polyester resin. Structural unit (IV) is a structural unit derived from hydroquinone. If the structural unit (IV) is less than 6 mol%, high-cycle performance during molding is significantly reduced and flash is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flash, the structural unit (III) is preferably 8 mol% or more, more preferably 10 mol% or more.

On the other hand, the liquid crystal polyester resin of the present invention contains 18 mol% or less of structural unit (IV) relative to 100 mol% of all structural units in the liquid crystal polyester resin. If the structural unit (IV) is more than 18 mol%, the high-cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flashing, the structural unit (IV) is preferably 17 mol% or less, and more preferably 16 mol% or less.

From the viewpoints of high-cycle moldability and low flash, the liquid crystal polyester resin of the present invention preferably has a molar ratio ([III]/[IV]) of the contents of structural units (III) and (IV) of 0.35 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. On the other hand, from the viewpoints of high-cycle moldability and low flash, [III]/[IV] is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less.

Other dioxy units that can be used, as long as they do not impair the effects of the present invention, include structural units derived from aromatic diols such as resorcinol, t-butylhydroquinone, phenylhydroquinone, chlorohydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 3,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, and 4,4'-dihydroxybenzophenone; structural units derived from aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol; and structural units derived from alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol.

The liquid crystal polyester resin of the present invention contains 20 mol% or more of the following structural unit (V) as a dicarbonyl unit, relative to 100 mol% of all structural units in the liquid crystal polyester resin. Structural unit (V) is a structural unit derived from terephthalic acid. If the structural unit (V) is less than 20 mol%, high-cycle performance during molding is significantly reduced and flash is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flash, the structural unit (V) is preferably 21 mol% or more, and more preferably 22 mol% or more.

On the other hand, the liquid crystal polyester resin of the present invention contains 27 mol% or less of structural unit (V) relative to 100 mol% of all structural units in the liquid crystal polyester resin. If the structural unit (V) is more than 27 mol%, the high-cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoints of high-cycle moldability and low flashing, the structural unit (V) is preferably 26 mol% or less, and more preferably 25 mol% or less.

Other dicarbonyl units that can be used include structural units derived from aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid; structural units derived from aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and hexahydroterephthalic acid; and structural units derived from alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid, provided that the effects of the present invention are not impaired.

In addition to the structural units (I) to (V) above, structural units derived from p-aminobenzoic acid, p-aminophenol, etc. can also be used in the liquid crystal polyester resin, as long as the effects of the present invention are not impaired.

In order to maintain the high-cycle moldability and low-burr effects of the liquid crystal polyester resin of the present invention, the total amount of the structural units (I) to (V) is preferably 98 mol% or more, more preferably 99 mol% or more, and more preferably 100 mol%.

Furthermore, from the viewpoint of controlling polymerization property, the ratio of the total amount of the structural units (III) and (IV) to the content of the structural unit (V) (([III] + [IV])/[V]) is preferably 0.9 or more and 1.1 or less, and more preferably 1.0.

The monomers that serve as raw materials for forming each of the structural units described above are not particularly limited as long as they have a structure that can form each structural unit. Furthermore, carboxylic acid derivatives such as acylated products of the hydroxyl groups of such monomers, esterified products of the carboxyl groups, acid halides, and acid anhydrides may also be used.

The method for calculating the content of each structural unit in liquid crystal polyester resin is as follows. First, the liquid crystal polyester resin is pulverized, tetramethylammonium hydroxide is added, and the content can be determined by pyrolysis GC/MS measurement using a Shimadzu GCMS-QP5050A. The content of structural units that are not detected or are below the detection limit is calculated as 0 mol%.

From the viewpoint of heat resistance, the melting point (Tm) of the liquid crystal polyester resin is preferably 280°C or higher, more preferably 300°C or higher, and even more preferably 320°C or higher. On the other hand, from the viewpoint of processability, the melting point (Tm) of the liquid crystal polyester resin is preferably 370°C or lower, more preferably 360°C or lower, and even more preferably 350°C or lower.

From the viewpoint of high-cycle moldability, the melt viscosity of the liquid crystal polyester resin is preferably 3 Pa·s or more, more preferably 5 Pa·s or more, and even more preferably 7 Pa·s or more. On the other hand, from the viewpoint of low flash, the melt viscosity of the liquid crystal polyester resin is preferably 50 Pa·s or less, preferably 30 Pa·s or less, and even more preferably 20 Pa·s or less.

This melt viscosity was measured using a high-speed flow tester at a temperature 20°C above the melting point (Tm) of the liquid crystal polyester resin and at a shear rate of 1000/sec.

<Method of producing liquid crystal polyester resin>
The method for producing the liquid crystal polyester resin of the present invention includes a method of copolymerizing the monomers that give the structural units (I) to (V) in a content within the above-mentioned range, or a method of blending two or more liquid crystal polyester resins obtained by copolymerizing the structural units (I) to (V) in a content outside the above-mentioned range, so that the structural units (I) to (V) fall within the above-mentioned range. However, from the viewpoint of excellent high-cycle moldability and low flash without inheriting the properties of the liquid crystal polyester resin before blending, the method of copolymerizing the monomers that give the structural units (I) to (V) in a content within the above-mentioned range is preferred.

The method for producing the liquid crystal polyester resin of the present invention is not particularly limited, and can be produced in accordance with known polyester polycondensation methods. Specific examples include liquid crystal polyester resins comprising structural units derived from p-hydroxybenzoic acid, structural units derived from 6-hydroxy-2-naphthoic acid, structural units derived from 4,4'-dihydroxybiphenyl, structural units derived from hydroquinone, and structural units derived from terephthalic acid, as follows:

(1) A method for producing a liquid crystal polyester resin by a deacetylation condensation polymerization reaction from p-acetoxybenzoic acid, 6-acetoxy-2-naphthoic acid, 4,4'-diacetoxybiphenyl, 1,4-diacetoxybenzene, and terephthalic acid.

(2) A method for producing a liquid crystal polyester resin by reacting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, 1,4-diacetoxybenzene, and terephthalic acid with acetic anhydride to acetylate the phenolic hydroxyl groups, followed by deacetylation polymerization.

(3) A method for producing a liquid crystal polyester resin by dephenolation polycondensation reaction of phenyl p-hydroxybenzoate, phenyl 6-hydroxy-2-naphthoate, 4,4'-dihydroxybiphenyl, hydroquinone, and diphenyl terephthalate.

(4) A method in which a predetermined amount of diphenyl carbonate is reacted with p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and terephthalic acid to form their respective phenyl esters, and then 4,4'-dihydroxybiphenyl and hydroquinone are added to produce a liquid crystal polyester resin by dephenolation polycondensation reaction.

Among these, (2) the method of producing a liquid crystal polyester resin by reacting p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, 1,4-diacetoxybenzene, and terephthalic acid with acetic anhydride to acetylate the phenolic hydroxyl groups, followed by deacetylation polymerization, is preferred because it offers industrially superior control over the degree of polymerization of the liquid crystal polyester resin.

As a method for producing the liquid crystal polyester resin used in the present invention, it is also possible to complete the polycondensation reaction by solid-state polymerization. Examples of solid-state polymerization treatment include the following method. First, the polymer or oligomer of the liquid crystal polyester resin is pulverized using a pulverizer. The pulverized polymer or oligomer is heated under a nitrogen stream or reduced pressure to polycondense to the desired degree of polymerization, thereby completing the reaction. The heating is preferably carried out for 1 to 50 hours at a temperature in the range of the melting point of the liquid crystal polyester minus 50°C to the melting point minus 5°C (e.g., 200 to 300°C).

The polycondensation reaction of liquid crystal polyester resin proceeds without a catalyst, but catalysts such as stannous acetate, tetrabutyl titanate, potassium acetate, sodium acetate, antimony trioxide, and magnesium metal can also be used.

<Filling material>
The liquid crystal polyester resin of the present invention may contain a filler to impart mechanical strength and other properties to the liquid crystal polyester resin. The filler used in the present invention is not particularly limited, but examples include fibrous, whisker-like, plate-like, powdery, and granular fillers. Specific examples of fibrous and whisker-like fillers include glass fibers, PAN-based and pitch-based carbon fibers, metal fibers such as stainless steel fibers, aluminum fibers, and brass fibers, organic fibers such as aromatic polyamide fibers and liquid crystal polyester fibers, gypsum fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, potassium titanate whiskers, barium titanate whiskers, aluminum borate whiskers, silicon nitride whiskers, and acicular titanium oxide. Examples of plate-like fillers include mica, talc, kaolin, glass flakes, clay, molybdenum disulfide, and wollastonite. Examples of powdery or granular fillers include silica, glass beads, titanium oxide, zinc oxide, calcium polyphosphate, and graphite. The surfaces of the fillers used in the present invention may be treated with a known coupling agent (e.g., a silane-based coupling agent, a titanate-based coupling agent, etc.) or other surface treatment agents. Two or more of the fillers used in the present invention may be used in combination.

Of the above fillers, it is preferable to use glass fiber, as it offers excellent mechanical strength, particularly tensile strength and flexural strength, as well as heat resistance and dimensional stability. There are no particular restrictions on the type of glass fiber, as long as it is one that is generally used to reinforce resins. Examples include chopped strands of long or short fiber types and milled fiber. Furthermore, it is preferable to use a plate-shaped filler, as it has excellent thin-wall flow properties.

The surface of the filler may be treated with a known coupling agent (e.g., a silane-based coupling agent, a titanate-based coupling agent, etc.) or other surface treatment agent. Furthermore, the glass fibers may be coated or bundled with a thermoplastic resin such as an ethylene/vinyl acetate copolymer or a thermosetting resin such as an epoxy resin.

The liquid crystal polyester resin composition of the present invention can further contain conventional additives selected from antioxidants, heat stabilizers (e.g., hindered phenols, hydroquinone, phosphites, thioethers, and their substituted derivatives), ultraviolet absorbers (e.g., resorcinol, salicylate), color inhibitors such as phosphites and hypophosphites, lubricants and mold release agents (e.g., montanic acid and its metal salts, its esters, its half esters, stearyl alcohol, stearamide, and polyethylene wax), colorants including dyes or pigments, conductive agents or colorants such as carbon black, crystal nucleating agents, plasticizers, flame retardants (e.g., bromine-based flame retardants, phosphorus-based flame retardants, red phosphorus, silicone-based flame retardants), flame retardant assistants, and antistatic agents, provided the effects of the present invention are not impaired.

In the liquid crystal polyester resin composition of the present invention, the filler content is preferably 10 to 200 parts by weight per 100 parts by weight of the liquid crystal polyester resin. A filler content of 10 parts by weight or more can improve the mechanical strength of the molded article. 15 parts by weight or more is more preferable, and 20 parts by weight or more is even more preferable. On the other hand, a filler content of 200 parts by weight or less is preferable because it results in a liquid crystal polyester resin composition that has excellent moldability and thin-wall flowability and can be easily injection-molded into small, thin-walled molded articles. 150 parts by weight or less is more preferable, and 100 parts by weight or less is even more preferable.

Methods for blending the above-mentioned fillers and additives include, for example, a dry blending method in which fillers and other solid additives are blended with liquid crystal polyester resin; a solution blending method in which fillers and other liquid additives are blended with liquid crystal polyester resin; a method in which fillers and other additives are added during polymerization of the liquid crystal polyester resin; and a method in which fillers and other additives are melt-kneaded with the liquid crystal polyester resin, with the melt-kneading method being preferred.

Known methods can be used for melt-kneading. Examples include a Banbury mixer, rubber roll machine, kneader, and single-screw or twin-screw extruder. Twin-screw extruders are preferred. The melt-kneading temperature is preferably from the melting point of the liquid crystal polyester resin to the melting point + 50°C.

Kneading methods include: 1) a method in which the liquid crystal polyester resin, filler, and other additives are added all at once from a bottom-loading feeder and kneaded (lump-kneading method); 2) a method in which the liquid crystal polyester resin and other additives are added from a bottom-loading feeder and kneaded, and then the filler and other additives are added from a side feeder and kneaded (side feed method); and 3) a method in which a liquid crystal polyester composition (master pellets) containing a high concentration of liquid crystal polyester resin and other additives is prepared, and then the master pellets are kneaded with the liquid crystal polyester resin and filler to achieve a specified concentration (master pellet method). Methods for adding filler and other additives include bulk kneading, sequential addition, and adding a high-concentration composition (master), and any of these methods is acceptable.

<Molded product>
The liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention can be processed into molded articles having excellent surface appearance (color tone), mechanical properties, and heat resistance by conventional molding methods such as injection molding, extrusion molding, press molding, solution casting, and spinning. Examples of molded articles include injection molded articles, extrusion molded articles, press molded articles, sheets, pipes, various films such as unstretched films, uniaxially stretched films, and biaxially stretched films, and various fibers such as unstretched yarns and ultrastretched yarns. In particular, injection molding is preferred from the viewpoint of processability. When melt molding, melt molding is preferably performed at 370 ° C or less, more preferably 360 ° C or less, from the viewpoint of suppressing deterioration of the liquid crystal polyester resin composition and improving mechanical strength.

Molded articles obtained by molding the liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention can be preferably used as electrical and electronic parts. Examples of electrical and electronic parts include flexible printed circuit boards, laminate circuit boards, printed wiring boards, and three-dimensional circuit boards used in antennas for mobile communication and electronic devices such as personal computers, GPS-equipped devices, mobile phones, and millimeter-wave and quasi-millimeter-wave radars, such as collision prevention radars, tablets, and smartphones; lamp reflectors and lamp sockets for LEDs and the like; small cell and microcell components for communication base stations of mobile communication terminals; antenna covers; housings, sensors; actuator parts for camera modules; connectors, relay cases and bases, switches, coil bobbins, and capacitors. In particular, due to their excellent high-cycle moldability and low flash, they are useful for connectors, relays, switches, coil bobbins, and actuator parts for camera modules.

The present invention will be explained below using examples, but the present invention is not limited to these examples. In the examples, the composition and properties of the liquid crystal polyester resin were measured using the following methods.

(1) Composition Analysis of Liquid Crystalline Polyester Resin 2 μL of a 25% methanol solution of tetramethylammonium hydroxide was added to 0.1 mg of crushed liquid crystal polyester resin pellets, and pyrolysis GC/MS measurement was performed using a Shimadzu GCMS-QP5050A to determine the composition ratio of each component in the liquid crystal polyester resin.

(2) Measurement of melting point (Tm) of liquid crystal polyester Using a differential scanning calorimeter DSC-7 (manufactured by PerkinElmer), a liquid crystal polyester resin was heated from room temperature at a temperature increase rate of 20°C/min, and the endothermic peak temperature (Tm ₁ ) observed was observed. After that, the resin was held at a temperature of Tm ₁ + 20°C for 5 minutes, cooled to room temperature at a temperature decrease rate of 20°C/min, and then heated again at a temperature increase rate of 20°C/min. The endothermic peak temperature observed when this was measured was taken as the melting point (Tm).

(3) Melt Viscosity of Liquid Crystalline Polyester Resin Using a high-speed flow tester CFT-500D (orifice 0.5φ×10 mm) (manufactured by Shimadzu Corporation), the melt viscosity of the liquid crystal polyester resin was measured at Tm+20° C. and a shear rate of 1000/s.

(4) Evaluation of high-cycle moldability The liquid crystal polyester resin was dried at 150 ° C. for 3 hours using a hot air dryer, and then subjected to a FANUC α30C injection molding machine (manufactured by FANUC). The cylinder temperature was set to the melting point of the liquid crystal polyester resin + 10 ° C., the mold temperature was set to 90 ° C., and a mold capable of molding a molded product having a width of 5.0 mm, a length of 40 mm, and a thickness of 0.2 mm was used. Continuous molding was performed under molding conditions of an injection speed of 400 m / s, adjusting the dwell time and cooling time so that the cycle time was 20 seconds. The cycle time was shortened by 1 second every 10 shots, and the cycle time at which the average stringing amount (the length of the string extending from the sprue portion) of 10 shots was 20 mm or more was defined as the minimum cycle time. The shorter the cycle time, the better the high-cycle moldability. Note that if the average stringing amount was 20 mm or more at a cycle time of 20 seconds, the cycle time was set to 20 seconds.

(5) Evaluation of low flash properties The liquid crystal polyester resin was dried at 150 ° C. for 3 hours using a hot air dryer, and then subjected to a FANUC α30C injection molding machine (manufactured by FANUC). The cylinder temperature was set to the melting point of the liquid crystal polyester resin + 10 ° C., the mold temperature was set to 90 ° C., and a mold capable of molding a molded product of 5.0 mm wide x 50 mm long x 0.2 mm thick was used. The injection speed was set to 400 m / s. The pressure was increased by 5 MPa from the lower limit pressure at which the resin could be filled, and 10 molded pieces were molded at each pressure. The maximum pressure at which no flash occurred in the molded product, runner portion, or sprue portion (lower limit pressure + X (MPa)) was determined. The higher the maximum pressure at which no flash occurred, the better the low flash properties. Note that if flash occurred at the lower limit pressure at which the resin could be filled, the pressure was set to 0 MPa.

[Example 1]
A 5L reactor equipped with a stirring blade and a distillation tube was charged with 760 parts by weight of p-hydroxybenzoic acid (HBA), 88 parts by weight of 6-hydroxy-2-naphthoic acid (HNA), 261 parts by weight of 4,4'-dihydroxybiphenyl (DHB), 161 parts by weight of hydroquinone (HQ), 476 parts by weight of terephthalic acid (TPA) and 1314 parts by weight of acetic anhydride (phenolic hydroxyl group total 1.10 equivalents), and then reacted for 120 minutes at 145 ° C. with stirring under a nitrogen gas atmosphere. The temperature was then raised from 145 ° C. to 360 ° C. over 4 hours. Thereafter, the polymerization temperature was maintained at 360 ° C., and the pressure was reduced to 1.0 mmHg (133 Pa) over 1.0 hours. The reaction was continued, and the polymerization was completed when the predetermined stirring torque was reached. Next, the polymer was extruded in the form of strands through a die having one circular discharge port with a diameter of 6 mm, and pelletized with a cutter to obtain a liquid crystal polyester resin (A-1).

[Example 2]
A liquid crystal polyester resin (A-2) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 784 parts by weight of HBA, 99 parts by weight of HNA, 251 parts by weight of DHB, 155 parts by weight of HQ, and 457 parts by weight of TPA.

[Example 3]
A liquid crystal polyester resin (A-3) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 798 parts by weight of HBA, 79 parts by weight of HNA, 261 parts by weight of DHB, 148 parts by weight of HQ, and 457 parts by weight of TPA.

[Example 4]
Liquid crystal polyester resin (A-4) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 752 parts by weight of HBA, 121 parts by weight of HNA, 207 parts by weight of DHB, 187 parts by weight of HQ, and 467 parts by weight of TPA.

[Example 5]
A liquid crystal polyester resin (A-5) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 743 parts by weight of HBA, 66 parts by weight of HNA, 349 parts by weight of DHB, 122 parts by weight of HQ, and 496 parts by weight of TPA.

[Example 6]
A liquid crystal polyester resin (A-6) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 792 parts by weight of HBA, 66 parts by weight of HNA, 305 parts by weight of DHB, 129 parts by weight of HQ, and 467 parts by weight of TPA.

[Comparative Example 1]
A liquid crystal polyester resin (A'-7) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 870 parts by weight of HBA, 352 parts by weight of DHB, 89 parts by weight of HQ, 292 parts by weight of TPA, and 157 parts by weight of isophthalic acid.

[Comparative Example 2]
A liquid crystal polyester resin (A'-8) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 711 parts by weight of HBA, 88 parts by weight of HNA, 272 parts by weight of DHB, 174 parts by weight of HQ, and 505 parts by weight of TPA.

[Comparative Example 3]
A liquid crystal polyester resin (A'-9) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 792 parts by weight of HBA, 220 parts by weight of HNA, 163 parts by weight of DHB, 168 parts by weight of HQ, and 399 parts by weight of TPA.

[Comparative Example 4]
A liquid crystal polyester resin (A'-10) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 889 parts by weight of HBA, 88 parts by weight of HNA, 218 parts by weight of DHB, 135 parts by weight of HQ, and 399 parts by weight of TPA.

The liquid crystal polyester resins obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated in the above (1) to (5), and the results are shown in Table 1.

Liquid crystal polyester resin compositions were prepared by further adding fillers to the liquid crystal polyester resins obtained in Examples 1 to 6 and Comparative Examples 1 to 4. The fillers used in each of the Examples and Comparative Examples are shown below.
Filler (B)
(B-1) Milled fiber (40M-10A) manufactured by Nippon Electric Glass
(B-2) Yamaguchi Mica Mica (A-21)

[Example 7, Comparative Example 5]
In a Toshiba Machine TEM35B twin-screw extruder equipped with a side feeder, the liquid crystal polyester resins (A-1, A'-7) obtained in each production example were added from the hopper in the amounts shown in Table 2, and the fillers (B-1, B-2) were added from the side feeder in the amounts shown in Table 2. The cylinder temperature was set to the melting point of the liquid crystal polyester resin + 10°C, and the mixture was melt-kneaded to form pellets. The resulting pellets of the liquid crystal polyester resin composition were dried with hot air and evaluated in the same manner as in (4) and (5). The results are shown in Table 2.

The results in Tables 1 and 2 show that by using a liquid crystal polyester resin containing the specified amounts of structural units (I) to (V), or a liquid crystal polyester resin composition using such a resin, it is possible to obtain molded articles with excellent high-cycle moldability and low flash.

The liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention have excellent high-cycle moldability and low flash properties, making them suitable for use in electrical and electronic components and mechanical components such as connectors, relays, switches, coil bobbins, and actuator parts for camera modules.

Claims (9)

A liquid crystal polyester resin containing the following structural units (I) to (V), which satisfies the following formulas (a) to (e).
46≦[I]≦49.8...(a)
2≦[II]≦5.5...(b)
6≦[III]≦18...(c)
6≦[IV]≦18...(d)
20≦[V]≦27...(e)
([I] to [V] indicate the content (mol %) of each of the structural units (I) to (V) relative to 100 mol % of all structural units in the liquid crystal polyester resin.)
The liquid crystal polyester resin according to claim 1, further satisfying the following formula (f):
10≦[I]/[II]≦12...(f) The liquid crystal polyester resin according to claim 1 or 2, further satisfying the following formula (g):
3.9≦[II]≦4.9...(g) The liquid crystal polyester resin according to any one of claims 1 to 3, further satisfying the following formula (h):
47≦[I]≦49...(h) The liquid crystal polyester resin according to any one of claims 1 to 4, further satisfying the following formula (i):
98≦[I]+[II]+[III]+[IV]+[V]≦100...(i) A method for producing the liquid crystal polyester resin described in any one of claims 1 to 5 by copolymerizing monomers that provide structural units (I) to (V). A liquid crystal polyester resin composition containing 10 to 200 parts by weight of a filler per 100 parts by weight of the liquid crystal polyester resin described in any one of claims 1 to 5. A molded article made from the liquid crystal polyester resin described in any one of claims 1 to 5, or the liquid crystal polyester resin composition described in claim 7. The molded article according to claim 8, wherein the molded article is any one selected from the group consisting of a connector, a relay, a switch, a coil bobbin, and an actuator component of a camera module.