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

Abstract

To provide a liquid crystal polyester resin which is excellent in high cycle moldability while suppressing burrs.SOLUTION: A liquid crystal polyester resin contains a structural unit (I) derived from a p-hydroxybenzoic acid, a structural unit (II) derived from a 6-hydroxy-2-naphthoic acid, a structural unit (III) derived from 4,4'-dihydroxybiphenyl, a structural unit (IV) derived from hydroquinone, and a structural unit (V) derived from a terephthalic acid, and satisfies the following (A) to (E): (A) 36≤[I]≤49.8; (B) 5.5<[II]≤15; (C) 1≤[III]≤9; (D) 14≤[IV]≤25; and (E) 18≤[V]≤29. (I) to (V) represent contents (mol%) of each of the structural units (I) to (V) with respect to 100 mol% of the total structural units of the liquid crystal polyester resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article made thereof, more particularly to a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article obtained using the same. [Background technology]

[0002] 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 smartphones and other devices has led to increased demand for higher integration, thinner walls, lower heights, and other components. For example, liquid crystal polyester resins have been proposed that combine excellent fluidity with high strength and blister resistance by including structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid (e.g., Patent Documents 1 to 6). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-24985 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-137438 [Patent Document 3] International Publication No. 2018 / 101214 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-126842 [Patent Document 5] Patent Publication No. 2015-183159 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-227404 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when molding a thin-walled molded product, it is necessary to perform molding at a high injection pressure, and the methods described in Patent Documents 1 to 6 have the problems of damaging the molding machine or mold, of making it difficult to completely fill the mold due to the tendency for the injection pressure to vary, and of not being able to maintain the shape after heat treatment.

[0005] An object of the present invention is to provide a liquid crystal polyester resin, a liquid crystal polyester resin composition, and a molded article made thereof that can be stably molded at a low injection pressure and have excellent shape stability after heat treatment. [Means for solving the problem]

[0006] 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 can be stably molded at low injection pressure and has excellent shape stability after heat treatment, thereby arriving at the present invention.

[0007] 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 formulae (A) to (E). 36≦[I]≦49.8 (A) 5.5<[II]≦15 (B) 1≦[III]≦9 (C) 14≦[IV]≦25 (D) 18≦[V]≦29 (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.)

[0008] [ka]

[0009] (2) The liquid crystal polyester resin according to (1), further satisfying the following formula (F): 4≦[I] / [II]<7 (F) (3) The liquid crystal polyester resin according to (1) or (2), further satisfying the following formula (G): 46≦[I]≦49.8 (G) (4) A method for producing the liquid crystal polyester resin according to any one of (1) to (3), by copolymerizing monomers that give the structural units (I) to (V). (5) 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 (3). (6) A molded article made of the liquid crystal polyester resin according to any one of (1) to (3) or the liquid crystal polyester resin composition according to (5). (7) The molded article according to (6), 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. [Effects of the Invention]

[0010] The liquid crystal polyester resin of the present invention can be stably molded at low injection pressure and can give molded articles with excellent shape stability after heat treatment. It is particularly suitable for molding small electrical and electronic parts. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are perspective views of a molded connector produced in an example and a conceptual diagram showing the measurement positions of the amount of warpage. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] <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.

[0014] Next, the structural units constituting the liquid crystal polyester resin will be described. The liquid crystal polyester resin of the present invention contains 36 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 36 mol%, the injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. From the viewpoints of being able to be molded stably at a low injection pressure and having excellent shape stability after heat treatment, the structural unit (I) is more preferably 40 mol% or more, even more preferably 43 mol% or more, and particularly preferably 46 mol% or more.

[0015] On the other hand, the liquid crystal polyester resin of the present invention contains 49.8 mol% or less of the 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 injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. In order to enable stable molding at low injection pressure and to achieve excellent shape stability after heat treatment, the structural unit (I) is preferably 49.4 mol% or less, more preferably 49 mol% or less.

[0016] [ka]

[0017] The liquid crystal polyester resin of the present invention contains more than 5.5 mol% of the following structural unit (II) as an oxycarbonyl unit relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (II) is a structural unit derived from 6-hydroxy-2-naphthoic acid. If the structural unit (II) is 5.5 mol% or less, the injection pressure becomes significantly high and unstable, and the shape changes significantly after heat treatment. From the viewpoints of being able to stably mold at low injection pressure and having excellent shape stability after heat treatment, the structural unit (II) is preferably 6 mol% or more, more preferably 7 mol% or more.

[0018] On the other hand, the liquid crystal polyester resin of the present invention contains 15 mol% or less of the structural unit (II) relative to 100 mol% of all structural units of the liquid crystal polyester resin. If the structural unit (II) is more than 15 mol%, the injection pressure becomes unstable and the shape changes significantly after heat treatment. From the viewpoints of being able to be molded stably at a low injection pressure and having excellent shape stability after heat treatment, the structural unit (II) is preferably 13 mol% or less, more preferably 11 mol% or less.

[0019] [ka]

[0020] In view of the fact that the liquid crystal polyester resin of the present invention can be stably molded at a low injection pressure and has excellent shape stability after heat treatment, the molar ratio ([I] / [II]) of the contents of the structural units (I) and (II) is preferably 4 or more, more preferably 4.5 or more, and even more preferably 5 or more. On the other hand, in view of the fact that the liquid crystal polyester resin can be stably molded at a low injection pressure and has excellent shape stability after heat treatment, [I] / [II] is preferably less than 7, more preferably 6.5 or less.

[0021] In addition, structural units derived from m-hydroxybenzoic acid or the like can be used as the oxycarbonyl unit within the range that does not impair the effects of the present invention.

[0022] The liquid crystal polyester resin of the present invention contains 1 mol % or more of the following structural unit (III) as a dioxy unit relative to 100 mol % of all structural units of the liquid crystal polyester resin. The structural unit (III) is a structural unit derived from 4,4'-dihydroxybiphenyl. If the structural unit (III) is less than 1 mol %, the injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. From the viewpoints of enabling stable molding at low injection pressure and excellent shape stability after heat treatment, the structural unit (III) is preferably 2 mol % or more, more preferably 3 mol % or more.

[0023] On the other hand, the liquid crystal polyester resin of the present invention contains 9 mol% or less of the following structural unit (III) relative to 100 mol% of all structural units of the liquid crystal polyester resin. If the structural unit (III) is more than 9 mol%, the injection pressure becomes unstable and the shape changes significantly after heat treatment. From the viewpoints of being able to mold stably at a low injection pressure and having excellent shape stability after heat treatment, the structural unit (III) is preferably 8 mol% or less, more preferably 7 mol% or less.

[0024] [ka]

[0025] The liquid crystal polyester resin of the present invention contains 14 mol% or more of the following structural unit (IV) as dioxy units relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (IV) is a structural unit derived from hydroquinone. If the structural unit (IV) is less than 14 mol%, the injection pressure becomes unstable and the shape changes significantly after heat treatment. From the viewpoints of being able to be molded stably at a low injection pressure and having excellent shape stability after heat treatment, the structural unit (III) is preferably 15 mol% or more, more preferably 16 mol% or more.

[0026] On the other hand, the liquid crystal polyester resin of the present invention contains 25 mol% or less of the structural unit (IV) relative to 100 mol% of all structural units of the liquid crystal polyester resin. If the structural unit (IV) is more than 25 mol%, the injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. In order to enable stable molding at low injection pressure and to achieve excellent shape stability after heat treatment, the structural unit (IV) is preferably 24 mol% or less, more preferably 23 mol% or less.

[0027] [ka]

[0028] In the liquid crystal polyester resin of the present invention, the molar ratio of the contents of the structural units (III) and (IV) ([III] / [IV]) is preferably 0.1 or more, more preferably 0.15 or more, and even more preferably 0.2 or more, from the viewpoints of being able to stably mold at a low injection pressure and having excellent shape stability after heat treatment. On the other hand, in the viewpoints of being able to stably mold at a low injection pressure and having excellent shape stability after heat treatment, [III] / [IV] is preferably 0.6 or less, more preferably 0.55 or less, and even more preferably 0.5 or less.

[0029] Other examples of dioxy units that can be used 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, as long as they do not impair the effects of the present invention.

[0030] The liquid crystal polyester resin of the present invention contains 18 mol% or more of the following structural unit (V) as a dicarbonyl unit relative to 100 mol% of all structural units of the liquid crystal polyester resin. The structural unit (V) is a structural unit derived from terephthalic acid. If the structural unit (V) is less than 18 mol%, the injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. From the viewpoints of enabling stable molding at low injection pressure and excellent shape stability after heat treatment, the structural unit (V) is preferably 19 mol% or more, more preferably 20 mol% or more.

[0031] On the other hand, the liquid crystal polyester resin of the present invention contains 29 mol% or less of the 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 29 mol%, the injection pressure becomes significantly high, resulting in instability, and the shape changes significantly after heat treatment. In order to enable stable molding at low injection pressure and to achieve excellent shape stability after heat treatment, the structural unit (V) is preferably 28 mol% or less, more preferably 27 mol% or less.

[0032] [ka]

[0033] 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, as long as the effects of the present invention are not impaired.

[0034] In addition to the structural units (I) to (V), the liquid crystal polyester resin may contain structural units formed from p-aminobenzoic acid, p-aminophenol, etc., within the range that does not impair the effects of the present invention.

[0035] The liquid crystal polyester resin of the present invention can be stably molded at a low injection pressure and has excellent shape stability after heat treatment. Therefore, 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%.

[0036] Furthermore, 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, more preferably 1.0, from the viewpoint of controlling polymerization.

[0037] The monomers used as raw materials for forming each of the structural units are not particularly limited as long as they have a structure capable of forming each structural unit. In addition, 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.

[0038] The method for calculating the content of each structural unit in a liquid crystal polyester resin is as follows. First, the liquid crystal polyester resin is pulverized, and then tetramethylammonium hydroxide is added. 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%.

[0039] 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.

[0040] 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, from the viewpoint of molding at a stable injection pressure and excellent shape stability after heat treatment. On the other hand, from the viewpoint of low injection pressure, 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.

[0041] The melt viscosity is a value measured by a Koka type flow tester at a temperature of the melting point (Tm) of the liquid crystal polyester resin + 20° C. under the condition of a shear rate of 1000 / sec.

[0042] <Method of manufacturing liquid crystal polyester resin> The liquid crystal polyester resin of the present invention can be produced by copolymerizing the monomers that give the structural units (I) to (V) in an amount within the above-mentioned range, or by blending two or more liquid crystal polyester resins obtained by copolymerizing the structural units (I) to (V) in an amount outside the above-mentioned range, so that the structural units (I) to (V) fall within the above-mentioned range. However, the method of copolymerizing the monomers that give the structural units (I) to (V) in an amount within the above-mentioned range is preferred because it can be molded stably at low injection pressure without inheriting the properties of the liquid crystal polyester resin before blending, and has excellent shape stability after heat treatment.

[0043] The liquid crystal polyester resin of the present invention can be produced by a method similar to a known polyester polycondensation method. Specifically, the following can be mentioned as an example of a liquid crystal polyester resin comprising structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, hydroquinone, and terephthalic acid.

[0044] (1) A method for producing a liquid crystal polyester resin from p-acetoxybenzoic acid, 6-acetoxy-2-naphthoic acid, 4,4'-diacetoxybiphenyl, 1,4-diacetoxybenzene and terephthalic acid by deacetylation condensation polymerization.

[0045] (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.

[0046] (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.

[0047] (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 phenyl esters, respectively, and then 4,4'-dihydroxybiphenyl and hydroquinone are added to produce a liquid crystal polyester resin by dephenolation polycondensation reaction.

[0048] 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 preferably used because it is industrially excellent in controlling the degree of polymerization of the liquid crystal polyester resin.

[0049] 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 treatments using solid-state polymerization include the following: 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 a desired degree of polymerization, thereby completing the reaction. The heating is preferably performed at a temperature within 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) for 1 to 50 hours.

[0050] The polycondensation reaction of the liquid crystal polyester resin proceeds without a catalyst, but stannous acetate, tetrabutyl titanate, potassium acetate, sodium acetate, antimony trioxide, metallic magnesium, or the like can also be used as a catalyst.

[0051] <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 agent. Two or more of the fillers used in the present invention may be used in combination.

[0052] Among the above fillers, glass fiber is preferably used because of its excellent mechanical strength, particularly tensile strength and bending strength, heat resistance, and dimensional stability. The type of glass fiber is not particularly limited as long as it is generally used to reinforce resins, and examples include long fiber type and short fiber type chopped strands and milled fibers. Furthermore, plate-shaped fillers are preferably used because of their excellent thin-wall flowability.

[0053] The surface of the filler may be treated with a known coupling agent (e.g., a silane coupling agent, a titanate coupling agent, etc.) or other surface treatment agent. 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.

[0054] The liquid crystal polyester resin composition of the present invention may further contain conventional additives selected from antioxidants, heat stabilizers (e.g., hindered phenols, hydroquinone, phosphites, thioethers, and their substitution products), ultraviolet absorbers (e.g., resorcinol, salicylate), color inhibitors such as phosphites and hypophosphites, lubricants and mold release agents (montanic acid and its metal salts, its esters, its half esters, stearyl alcohol, stearamide, polyethylene wax, etc.), colorants including dyes or pigments, conductive agents or colorants such as carbon black, crystal nucleating agents, plasticizers, flame retardants (bromine-based flame retardants, phosphorus-based flame retardants, red phosphorus, silicone-based flame retardants, etc.), flame retardant assistants, and antistatic agents, within the range that does not impair the effects of the present invention.

[0055] In the liquid crystal polyester resin composition of the present invention, the content of the filler is preferably 10 to 200 parts by weight per 100 parts by weight of the liquid crystal polyester resin. If the filler content is 10 parts by weight or more, the mechanical strength of the molded article can be improved. 15 parts by weight or more is more preferable, and 20 parts by weight or more is even more preferable. On the other hand, if the filler content is 200 parts by weight or less, a liquid crystal polyester resin composition having excellent moldability and thin-wall flowability and capable of easily injection-molding small, thin-walled molded articles can be obtained, which is preferable. 150 parts by weight or less is more preferable, and 100 parts by weight or less is even more preferable.

[0056] Examples of methods for blending the above-mentioned fillers and additives include a dry blending method in which fillers and other solid additives are blended with a liquid crystal polyester resin, a solution blending method in which fillers and other liquid additives are blended with a 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 a liquid crystal polyester resin, and among these, the melt-kneading method is preferred.

[0057] Known methods can be used for melt-kneading. Examples include a Banbury mixer, a rubber roll machine, a kneader, and a 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.

[0058] Examples of kneading methods include: 1) a method in which the liquid crystal polyester resin, filler, and other additives are all added at once from a bottom feeder and kneaded (lump-mixing method); 2) a method in which the liquid crystal polyester resin and other additives are added from a bottom 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 pellet) containing a high concentration of liquid crystal polyester resin and other additives is prepared, and then the master pellet is kneaded with the liquid crystal polyester resin and filler to a specified concentration (master pellet method). Methods for adding filler and other additives include a bulk kneading method, a sequential addition method, and a method in which a high-concentration composition (master) is added, and any of these methods may be used.

[0059] <Molded products> 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, in order to suppress deterioration of the liquid crystal polyester resin composition and improve its mechanical strength.

[0060] Molded articles obtained by molding the liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention are preferably used as electrical and electronic components. Examples of electrical and electronic components include flexible printed circuit boards, laminated 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; 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 ability to be molded stably at low injection pressure and their excellent shape stability after heat treatment, they are useful for connectors, relays, switches, coil bobbins, and actuator parts for camera modules. [Example]

[0061] The present invention will be described below with reference to 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 by the following methods.

[0062] (1) Composition analysis of liquid crystal 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.

[0063] (2) Melting point (Tm) measurement of liquid crystal polyester Using a differential scanning calorimeter DSC-7 (manufactured by PerkinElmer), the liquid crystal polyester resin was heated from room temperature at a temperature increase rate of 20°C / min, and the endothermic peak temperature (Tm1) was observed.The resin was then held at a temperature of Tm1 + 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 was taken as the melting point (Tm).

[0064] (3) Melt viscosity of liquid crystal polyester resin The melt viscosity of the liquid crystal polyester resin was measured at Tm+20°C and a shear rate of 1000 / s using a high-performance flow tester CFT-500D (orifice 0.5φ×10 mm) (Shimadzu Corporation).

[0065] (4) Evaluation of injection pressure and its stability The liquid crystal polyester resin was dried at 150°C for 3 hours using a hot air dryer and then injected into a Fanuc α30C injection molding machine (manufactured by Fanuc). The cylinder temperature was set at the melting point of the liquid crystal polyester resin + 20°C, the mold temperature was 90°C, and the injection speed was 400 mm / s. The liquid crystal polyester resin was injected through pin gate G1 (gate diameter 0.3 mm) located on one short side 2 of the connector molded product (Figure 1a). The peak pressure during molding was measured to obtain a connector molded product with a terminal pitch of 0.4 mm, a minimum thickness (partition wall 3) of 0.2 mm, and external dimensions of 3 mm wide x 2 mm high x 30 mm long. This process was repeated 100 times. The average peak pressure was used as the injection pressure, and the standard deviation of the peak pressure was used as the stability. Lower average and standard deviations of the peak pressure indicated better performance. Figure 1a is a perspective view of the connector molded product.

[0066] (5) Evaluation of shape stability after heat treatment The liquid crystal polyester resin was dried at 150°C for 3 hours using a hot air dryer and then loaded into a Fanuc α30C injection molding machine (Fanuc). The cylinder temperature was set at 20°C above the melting point of the liquid crystal polyester resin, the mold temperature was 90°C, the injection pressure was 100 MPa, and the speed was set at the minimum filling speed to obtain a connector molded product similar to that described in (4). The resulting connector molded product was placed in an oven heated to 260°C for 3 minutes, and the amount of warpage of the connector molded product after heat treatment was measured. The amount of warpage was measured using a line connecting both ends of the long molded product in the longitudinal direction as the reference line, and the dimensional deviation from this line was measured. Figure 1b is a conceptual diagram showing the measurement points for the amount of warpage on the long molded product. The AB plane was set as reference plane a, and the difference between this and the maximum deformation plane b was defined as the amount of warpage. The smaller the amount of warpage, the better the shape stability.

[0067] [Example 1] A 5-L reactor equipped with a stirring blade and a distillation tube was charged with 792 parts by weight of p-hydroxybenzoic acid (HBA), 198 parts by weight of 6-hydroxy-2-naphthoic acid (HNA), 109 parts by weight of 4,4'-dihydroxybiphenyl (DHB), 206 parts by weight of hydroquinone (HQ), 408 parts by weight of terephthalic acid (TPA), and 1,314 parts by weight of acetic anhydride (1.10 equivalents of total phenolic hydroxyl groups) and reacted at 145°C for 120 minutes with stirring under a nitrogen gas atmosphere. The temperature was then increased from 145°C to 360°C over 4 hours. The polymerization temperature was then maintained at 360°C, the pressure was reduced to 1.0 mmHg (133 Pa) over 1.0 hour, and the reaction was continued until the predetermined stirring torque was reached, at which point the polymerization was completed. 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).

[0068] [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 598 parts by weight of HBA, 330 parts by weight of HNA, 44 parts by weight of DHB, 283 parts by weight of HQ, and 467 parts by weight of TPA.

[0069] [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 792 parts by weight of HBA, 132 parts by weight of HNA, 185 parts by weight of DHB, 180 parts by weight of HQ, and 437 parts by weight of TPA.

[0070] [Example 4] A liquid crystal polyester resin (A-4) was obtained in the same manner as in Example 1, except that the monomer charges were changed to 743 parts by weight of HBA, 176 parts by weight of HNA, 153 parts by weight of DHB, 206 parts by weight of HQ, and 447 parts by weight of TPA.

[0071] [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 663 parts by weight of HBA, 154 parts by weight of HNA, 174 parts by weight of DHB, 232 parts by weight of HQ, and 505 parts by weight of TPA.

[0072] [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 776 parts by weight of HBA, 264 parts by weight of HNA, 65 parts by weight of DHB, 219 parts by weight of HQ, and 389 parts by weight of TPA.

[0073] [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 711 parts by weight of HBA, 176 parts by weight of DHB, 240 parts by weight of HQ, 168 parts by weight of TPA, and 467 parts by weight of TPA.

[0074] 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, 261 parts by weight of DHB, 180 parts by weight of HQ, and 505 parts by weight of TPA.

[0075] 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 517 parts by weight of HBA, 220 parts by weight of HNA, 174 parts by weight of DHB, 271 parts by weight of HQ, and 350 parts by weight of TPA.

[0076] 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 857 parts by weight of HBA, 242 parts by weight of HNA, 65 parts by weight of DHB, 193 parts by weight of HQ, and 350 parts by weight of TPA.

[0077] The liquid crystal polyester resins obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated in the above items (1) to (5). The results are shown in Table 1.

[0078] [Table 1]

[0079] Liquid crystal polyester resin compositions were prepared by further adding a filler 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) Nippon Electric Glass Milled Fiber (40M-10A) (B-2) Yamaguchi Mica (A-21)

[0080] [Example 7, Comparative Example 5] Using 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 fed from the hopper in the amounts shown in Table 2, and the fillers (B-1, B-2) were fed 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.

[0081] [Table 2]

[0082] From the results in Tables 1 and 2, it can be seen that by using a liquid crystal polyester resin containing a predetermined amount of structural units (I) to (V), or a liquid crystal polyester resin composition using such a resin, it is possible to obtain molded articles that can be stably molded at low injection pressure and that have excellent shape stability after heat treatment. [Industrial Applicability]

[0083] The liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention can be stably molded at low injection pressure and have excellent shape stability after heat treatment, and are therefore suitable for use in electrical and electronic components and mechanical components such as connectors, relays, switches, coil bobbins, and actuator components for camera modules. [Explanation of symbols]

[0084] 1 Long plane 2 Short surface 3. Length 30mm 4 Height 2mm 5 Width 3mm 6 Pitch distance 0.4mm 7 Minimum wall thickness 0.2mm 8. Warpage G1 Pin Gate a Reference plane b Maximum deformation surface

Claims

1. A liquid crystal polyester resin containing the following structural units (I) to (V), which satisfies the following formulas (A) to (E). 36≦[I]≦49.8...(A) 5.5<[II]≦15...(B) 1≦[III]≦9...(C) 14≦[IV]≦25...(D) 18≦[V]≦29...(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.) 【Chemical 1】

2. The liquid crystal polyester resin according to claim 1, further satisfying the following formula (F): 4≦[I] / [II]<7...(F)

3. The liquid crystal polyester resin according to claim 1 or 2, further satisfying the following formula (G): 46≦[I]≦49.8...(G)

4. A method for producing the liquid crystal polyester resin according to any one of claims 1 to 3, comprising copolymerizing monomers that provide the structural units (I) to (V).

5. A liquid crystal polyester resin composition comprising 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 claims 1 to 3.

6. A molded article comprising the liquid crystal polyester resin according to any one of claims 1 to 3 or the liquid crystal polyester resin composition according to claim 5.

7. 7. The molded article according to claim 6, 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.

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