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 4-hydroxy benzoic 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) 46≤[I]≤49.8; (b) 2≤[II]≤5.5; (c) 6≤[III]≤18; (d) 6≤[IV]≤18; and (e) 20≤[V]≤27. (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 small, thin-walled molded products, molding must be performed at a high injection speed, and the methods described in Patent Documents 1 to 6 have the problem of generating burrs on the sprue, etc. Furthermore, stringiness is likely to occur during molding, and there are issues with high-cycle moldability.

[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 does not produce flash even when molded at a high injection speed and has excellent high-cycle moldability. [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 has excellent high-cycle moldability while suppressing flash (hereinafter referred to as low flash), and thus arrived 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 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.)

[0008] [ka]

[0009] (2) The liquid crystal polyester resin according to (1), further satisfying the following formula (f): 10≦[I] / [II]≦12 (f) (3) The liquid crystal polyester resin according to (1) or (2), further satisfying the following formula (g): 3.9≦[II]≦4.9 (g) (4) The liquid crystal polyester resin according to any one of (1) to (3), further satisfying 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. [Effects of the Invention]

[0010] 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. In particular, it is suitable for use in molding small electrical and electronic parts. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below.

[0012] <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.

[0013] 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.

[0014] 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 of 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 viewpoint of high cycle moldability and low flashing, the structural unit (I) is preferably 49.4 mol% or less, more preferably 49 mol% or less.

[0015] [ka]

[0016] 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 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 less than 2 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 (II) is preferably 3 mol% or more, more preferably 3.5 mol% or more, and even more preferably 3.9 mol% or more.

[0017] On the other hand, the liquid crystal polyester resin of the present invention contains 5.5 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 5.5 mol%, the high cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoint 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.

[0018] [ka]

[0019] In the liquid crystal polyester resin of the present invention, from the viewpoints of high-cycle moldability and low flash, the molar ratio ([I] / [II]) of the contents of the structural units (I) and (II) is preferably 10 or more. On the other hand, from the viewpoints of high-cycle moldability and low flash, [I] / [II] is preferably 12 or less.

[0020] 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.

[0021] 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 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 6 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 (III) is preferably 7 mol % or more, more preferably 8 mol % or more.

[0022] 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 of 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 viewpoint of high cycle moldability and low flashing, the structural unit (III) is preferably 16 mol% or less, more preferably 14 mol% or less.

[0023] [ka]

[0024] 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. The structural unit (IV) is a structural unit derived from hydroquinone. If the structural unit (IV) is less than 6 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 (III) is preferably 8 mol % or more, more preferably 10 mol % or more.

[0025] On the other hand, the liquid crystal polyester resin of the present invention contains 18 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 18 mol%, the high cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoint of high cycle moldability and low flashing, the structural unit (IV) is preferably 17 mol% or less, more preferably 16 mol% or less.

[0026] [ka]

[0027] In the liquid crystal polyester resin of the present invention, from the viewpoints of high-cycle moldability and low flash, the molar ratio ([III] / [IV]) of the contents of the structural units (III) and (IV) is preferably 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.

[0028] 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.

[0029] 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 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 20 mol %, the high cycle performance during molding is significantly reduced and flashing is significantly more likely to occur. From the viewpoint of high cycle moldability and low flashing, the structural unit (V) is preferably 21 mol % or more, more preferably 22 mol % or more.

[0030] On the other hand, the liquid crystal polyester resin of the present invention contains 27 mol% or less of the structural unit (V) relative to 100 mol% of all structural units of 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 viewpoint of high cycle moldability and low flashing, the structural unit (V) is preferably 26 mol% or less, more preferably 25 mol% or less.

[0031] [ka]

[0032] 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.

[0033] 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.

[0034] In order to maintain the high-cycle moldability and low flash effects, the liquid crystal polyester resin of the present invention preferably has a total amount of the structural units (I) to (V) of 98 mol % or more, more preferably 99 mol % or more, and more preferably 100 mol %.

[0035] 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.

[0036] 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.

[0037] 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%.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] <Method of manufacturing liquid crystal polyester resin> The liquid crystal polyester resin of the present invention can be produced by copolymerizing monomers that provide 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, from the viewpoint of achieving excellent high-cycle moldability and low flash without inheriting the properties of the liquid crystal polyester resin before blending, the method of copolymerizing monomers that provide the structural units (I) to (V) in an amount within the above-mentioned range is preferred.

[0042] The method for producing the liquid crystal polyester resin of the present invention is not particularly limited, and can be produced in accordance with a known polyester polycondensation method. Specifically, the following can be mentioned as an example of a liquid crystal polyester resin comprising a structural unit derived from p-hydroxybenzoic acid, a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from 4,4'-dihydroxybiphenyl, a structural unit derived from hydroquinone, and a structural unit derived from terephthalic acid.

[0043] (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.

[0044] (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.

[0045] (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.

[0046] (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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] <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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] <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.

[0059] Molded articles obtained by molding the liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention are suitable for use as electrical and electronic components. Examples of such 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 mobile communication terminal base stations; antenna covers; housings, sensors; actuator parts for camera modules; connectors, relay cases and bases, switches, coil bobbins, and capacitors. Due to their excellent high-cycle moldability and low flash, they are particularly useful for connectors, relays, switches, coil bobbins, and actuator parts for camera modules. [Example]

[0060] 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.

[0061] (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.

[0062] (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).

[0063] (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).

[0064] (4) Evaluation of high-cycle formability 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 10°C above the melting point of the liquid crystal polyester resin, the mold temperature was set at 90°C, and a mold capable of molding a 5.0 mm wide x 40 mm long x 0.2 mm thick molded product was used. Continuous molding was performed at an injection speed of 400 m / s, adjusting the dwell time and cooling time to achieve a cycle time of 20 seconds. The cycle time was shortened by 1 second every 10 shots, and the minimum cycle time was determined as the cycle time at which the average stringiness (length of string extending from the sprue) for 10 shots was 20 mm or more. The shorter the cycle time, the better the high-cycle moldability. If the average stringiness was 20 mm or more at a cycle time of 20 seconds, the cycle time was set to 20 seconds.

[0065] (5) Evaluation of low flash 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 10°C above the melting point of the liquid crystal polyester resin, and the mold temperature was set at 90°C. A mold capable of molding a 5.0 mm wide x 50 mm long x 0.2 mm thick molded product was used. The injection speed was 400 m / s, and the pressure was increased in 5 MPa increments from the minimum pressure required for filling. Ten molded products were molded at each pressure. The maximum pressure at which no flash occurred on the molded product, runner, or sprue (minimum pressure + X (MPa)) was determined. The higher the maximum pressure at which no flash occurred, the better the flash reduction performance. Note that if flash occurred at the minimum pressure required for filling, the pressure was set at 0 MPa.

[0066] [Example 1] A 5-L 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 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).

[0067] [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.

[0068] [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.

[0069] [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 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.

[0070] [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.

[0071] [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.

[0072] [Comparative Example 1] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] [Table 1]

[0078] 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)

[0079] [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.

[0080] [Table 2]

[0081] 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 products with excellent high-cycle moldability and low flash. [Industrial Applicability]

[0082] The liquid crystal polyester resin and liquid crystal polyester resin composition of the present invention have excellent high-cycle moldability and low flash properties, and are therefore suitable for use in electrical and electronic parts and mechanical parts such as connectors, relays, switches, coil bobbins, and actuator parts for camera modules.

Claims

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.) 【Chemical 1】

2. The liquid crystal polyester resin according to claim 1, further satisfying the following formula (f): 10≦[I] / [II]≦12...(f)

3. The liquid crystal polyester resin according to claim 1 or 2, further satisfying the following formula (g): 3.9≦[II]≦4.9...(g)

4. The liquid crystal polyester resin according to any one of claims 1 to 3, further satisfying the following formula (h): 47≦[I]≦49...(h)

5. 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)

6. A method for producing the liquid crystal polyester resin according to any one of claims 1 to 5, comprising copolymerizing monomers that provide the structural units (I) to (V).

7. 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 5.

8. A molded article comprising the liquid crystal polyester resin according to any one of claims 1 to 5 or the liquid crystal polyester resin composition according to claim 7.

9. 9. The molded article according to claim 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.