Liquid crystalline resin and liquid crystalline resin composition

Abstract

Provided are: a liquid crystalline resin which has excellent tracking resistance and is suppressed in discoloration; and a liquid crystalline resin composition which contains the same.　The liquid crystalline resin according to the present invention exhibits optical anisotropy when melted, contains constituent units (I) to (IV), and may or may not contain a constituent unit (V). With respect to all the constituent units, the content of the constituent unit (I) is 10-80 mol%, the content of the constituent unit (II) is 1-20 mol%, the content of the constituent unit (III) is 9-44 mol%, the content of the constituent unit (IV) is 10-45 mol%, the content of the constituent unit (V) is 0-35 mol%, and the content of a constituent unit containing a naphthalene ring is 0-40 mol%. In the formulae, Ar1 to Ar3 each independently represent a phenylene group or the like; R represents a cyclohexylene group or a divalent aliphatic chain hydrocarbon group having 4 to 10 carbon atoms; X's each independently represent a hydrogen atom or a monovalent aliphatic chain hydrocarbon group having 1 to 6 carbon atoms; and Y and Z each independently represent an oxygen atom or an imino group.

Description

Liquid crystalline resin and liquid crystalline resin composition

[0001] The present invention relates to a liquid crystalline resin and a liquid crystalline resin composition.

[0002] Liquid crystalline resins have well-balanced excellent mechanical strength, heat resistance, chemical resistance, electrical properties and the like, and also have excellent dimensional stability, so they are widely used as high-performance engineering plastics. For example, liquid crystalline resins are used for resin parts used near power sources of electrical and electronic parts such as relays, switches, and connectors. In such resin parts, when moisture, dust, and the like adhere to the surface during use and microdischarges are repeated, a conductive path is formed on the surface, causing a dielectric breakdown phenomenon (tracking), which may short-circuit between electrodes. Therefore, liquid crystalline resins constituting parts used near power sources of electrical and electronic parts are required to have tracking resistance.

[0003] For example, Patent Document 1 discloses that a molded article excellent in tracking fracture resistance can be obtained from a wholly aromatic polyester resin containing a specific amount of a specific structural unit. Patent Document 2 discloses that a molded article obtained from a specific liquid crystalline resin containing a repeating unit derived from an alicyclic dicarboxylic acid or a derivative thereof has excellent tracking resistance.

[0004] Japanese Patent Application Laid-Open No. 2014-172953Japanese National Publication of International Patent Application No. 2020-522595

[0005] However, according to studies by the present inventors, it has been found that tracking resistance is difficult to improve in liquid crystalline resins that do not have an aliphatic skeleton and consist only of an aromatic skeleton. On the other hand, according to studies by the present inventors, it has also been found that liquid crystalline resins having an aliphatic skeleton are prone to discoloration at high temperatures, while it is difficult to sufficiently improve tracking resistance.

[0006] In view of the above problems, an object of the present invention is to provide a liquid crystalline resin excellent in tracking resistance with suppressed discoloration, and a liquid crystalline resin composition containing the same.

[0007] The inventors of the present invention have diligently conducted research to solve the above problems. As a result, they have found that the above problems can be solved by a liquid crystalline resin containing structural units derived from hydroxyarenecarboxylic acid, structural units derived from hydroquinone substituted with a tert-butyl group, structural units derived from arenediol, arenediamine, or hydroxyarylamine, and structural units derived from cyclohexanedicarboxylic acid or aliphatic chain dicarboxylic acid, and containing or not containing structural units derived from arialedicarboxylic acid, wherein the content of each of the above structural units and structural units containing a naphthalene ring is within a specific range, and have completed the present invention. More specifically, the present invention provides the following.

[0008] (1) A liquid crystalline resin that exhibits optical anisotropy when melted, wherein the liquid crystalline resin contains the following constituent units (I), (II), (III), and (IV), and may or may not contain the following constituent unit (V), the content of constituent unit (I) is 10 to 80 mol% of the total constituent units, the content of constituent unit (II) is 1 to 20 mol% of the total constituent units, the content of constituent unit (III) is 9 to 44 mol% of the total constituent units, the content of constituent unit (IV) is 10 to 45 mol% of the total constituent units, the content of constituent unit (V) is 0 to 35 mol% of the total constituent units, and the content of constituent units containing a naphthalene ring is 0 to 40 mol% of the total constituent units. (In the formula, Ar １ Ar ２ , and Ar ３ Each of these independently represents a phenylene group, a naphthylene group, or a biphenylylene group. R represents a cyclohexylene group or a divalent aliphatic hydrocarbon group having 4 to 10 carbon atoms. Each of these independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 6 carbon atoms. Y and Z independently represent an oxygen atom or an imino group.

[0009] (2) The liquid crystalline resin described in (1), wherein the total content of constituent units (I) to (V) is 100 mol% of the total constituent units.

[0010] (3) The liquid crystalline resin according to (1) or (2), wherein the constituent unit (IV) is a constituent unit selected from one or more of the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, sebacic acid, and derivatives thereof.

[0011] (4) The liquid crystalline resin according to any one of (1) to (3), wherein the constituent unit (IV) is a constituent unit selected from the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and derivatives thereof, one or more of these.

[0012] (5) The liquid crystalline resin according to any one of (1) to (4), wherein the constituent unit (II) is a constituent unit derived from one or more selected from the group consisting of tert-butylhydroquinone and derivatives thereof.

[0013] (6) A liquid crystalline resin composition comprising the liquid crystalline resin described in any of (1) to (5).

[0014] (7) A molded article made of the liquid crystalline resin described in any of (1) to (5).

[0015] (8) A molded article made from the liquid crystalline resin composition described in (6).

[0016] According to the present invention, it is possible to provide a liquid crystalline resin with excellent tracking resistance and suppressed discoloration, and a liquid crystalline resin composition containing the same.

[0017] Embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below.

[0018] <Liquid Crystalline Resin> The liquid crystalline resin of the present invention contains the following constituent units (I), (II), (III), and (IV), and may or may not contain the following constituent unit (V).

[0019]

[0020] In the formula representing the constituent unit (I), Ar １Examples of these groups include 1,2-phenylene groups, 1,3-phenylene groups, 1,4-phenylene groups, 2,6-naphthylene groups, and 4,4'-biphenylene groups. From the viewpoint of reactivity and the stability of the molecular structure of the liquid crystalline resin, 1,4-phenylene groups and 2,6-naphthylene groups are preferred, and from the viewpoint of tracking resistance, 1,4-phenylene groups are more preferred. Therefore, the constituent unit (I) is derived from, for example, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, or 6-hydroxy-2-naphthoic acid (hereinafter also referred to as "2-HBA", "3-HBA", "4-HBA", or "HNA", respectively), and is preferably derived from 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, or a combination of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid from the viewpoint of reactivity and the stability of the molecular structure of the liquid crystalline resin, and is more preferably derived from 4-hydroxybenzoic acid from the viewpoint of tracking resistance. Hereinafter, monomers that derive the constituent unit (I), such as 2-HBA, 3-HBA, 4-HBA, and HNA, are also referred to as monomer (I). In the liquid crystalline resin of the present invention, the constituent unit (I) may be used alone or in combination of two or more types.

[0021] In the liquid crystalline resin of the present invention, the content of constituent unit (I) is 10 to 80 mol% of the total constituent units. If the content of constituent unit (I) is less than 10 mol% or more than 80 mol%, at least one of tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin tends to be insufficient. From the viewpoint of tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin, the content of constituent unit (I) is preferably 15 to 75 mol%, more preferably 18 to 70 mol%, and even more preferably 20 to 65 mol%.

[0022] In the formula representing the constituent unit (II), X independently represents either a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 6 carbon atoms.

[0023] The monovalent aliphatic chain hydrocarbon group having 1 to 6 carbon atoms represented by X is preferably a monovalent aliphatic chain hydrocarbon group having 2 to 5 carbon atoms, and more preferably a monovalent aliphatic chain hydrocarbon group having 3 to 4 carbon atoms, from the viewpoint of improving tracking resistance and suppressing discoloration. Examples of monovalent aliphatic chain hydrocarbon groups having 1 to 6 carbon atoms include alkyl groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, and alkynyl groups having 2 to 6 carbon atoms, with alkyl groups having 1 to 6 carbon atoms being preferred from the viewpoint of improving tracking resistance and suppressing discoloration.

[0024] Regarding X, the alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 2 to 5 carbon atoms, and more preferably an alkyl group having 3 to 4 carbon atoms, from the viewpoint of improving tracking resistance and suppressing discoloration. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, and hexyl group. From the viewpoint of improving tracking resistance and suppressing discoloration, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, and tert-butyl group are preferred, and tert-butyl group is more preferred.

[0025] Regarding X, the alkenyl group having 2 to 6 carbon atoms is preferably an alkenyl group having 2 to 5 carbon atoms, and more preferably an alkenyl group having 3 to 4 carbon atoms, from the viewpoint of improving tracking resistance and suppressing discoloration. Examples of the above alkenyl group include an ethylene group, a propylene group, and a butylene group, and from the viewpoint of improving tracking resistance and suppressing discoloration, the propylene group and the butylene group are preferred.

[0026] Regarding X, the alkynyl group having 2 to 6 carbon atoms is preferably an alkynyl group having 2 to 5 carbon atoms, and more preferably an alkynyl group having 3 to 4 carbon atoms, from the viewpoint of improving tracking resistance and suppressing discoloration. Examples of the above alkynyl group include an ethynyl group and a propargyl group, and the propargyl group is preferred from the viewpoint of improving tracking resistance and suppressing discoloration.

[0027] From the viewpoint of improving tracking resistance and suppressing discoloration, X is preferably a hydrogen atom, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group, more preferably a hydrogen atom and a tert-butyl group, and even more preferably a hydrogen atom.

[0028] From the viewpoint of improving tracking resistance and suppressing discoloration, the constituent unit (II) is preferably derived from 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, or tert-butylhydroquinone (hereinafter also referred to as "TBHQ"), and more preferably derived from tert-butylhydroquinone. That is, as constituent unit (II), from the viewpoint of improving tracking resistance and suppressing discoloration, a constituent unit derived from one or more selected from the group consisting of 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, tert-butylhydroquinone, and their derivatives is preferred, and a constituent unit derived from one or more selected from the group consisting of tert-butylhydroquinone and its derivatives is more preferred. Hereinafter, monomers that derive constituent unit (II), such as 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, and tert-butylhydroquinone, will also be referred to as monomer (II). In the liquid crystalline resin of the present invention, constituent unit (II) may be used alone or in combination of two or more types.

[0029] In the liquid crystalline resin of the present invention, the content of constituent unit (II) is 1 to 20 mol% of the total constituent units. If the content of constituent unit (II) is less than 1 mol% or more than 20 mol%, at least one of the following is likely to be insufficient: tracking resistance, suppression of discoloration, reactivity, and stability of the molecular structure of the liquid crystalline resin. From the viewpoint of improving tracking resistance, suppression of discoloration, reactivity, and stability of the molecular structure of the liquid crystalline resin, the content of constituent unit (II) is preferably 1.5 to 15 mol%, more preferably 2 to 12 mol%, and even more preferably 2.5 to 10 mol%.

[0030] In the formula representing the constituent unit (III), Ar ２ Examples of such groups include 1,2-phenylene groups, 1,3-phenylene groups, 1,4-phenylene groups, 2,6-naphthylene groups, and 4,4'-biphenylylene groups, with 4,4'-biphenyl groups and 1,4-phenylene groups being preferred from the viewpoint of improving tracking resistance and reactivity. Therefore, the constituent unit (III) can be derived from, for example, hydroquinone (hereinafter also referred to as "HQ"), 2,6-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl (hereinafter also referred to as "BP"), and N-acetyl-p-aminophenol (hereinafter also referred to as "APAP"), and is preferably derived from hydroquinone from the viewpoint of improving tracking resistance. Hereinafter, monomers that derive constituent unit (III), such as HQ, BP, and APAP, will also be referred to as monomer (III). In the liquid crystalline resin of the present invention, constituent unit (III) may be used alone or in combination of two or more types.

[0031] In the liquid crystalline resin of the present invention, the content of constituent unit (III) is 9 to 44 mol% of the total constituent units. If the content of constituent unit (III) is less than 9 mol% or more than 44 mol%, at least one of tracking resistance and reactivity tends to be insufficient. From the viewpoint of improving tracking resistance and reactivity, the content of constituent unit (III) is preferably 11 to 40 mol%, more preferably 12 to 37 mol%, and even more preferably 12.5 to 35 mol%.

[0032] In the formula representing the constituent unit (IV), R represents a cyclohexylene group or a divalent aliphatic chain hydrocarbon group having 4 to 10 carbon atoms.

[0033] The cyclohexylene group represented by R is a 1,4-cyclohexylene group, a 1,3-cyclohexylene group, or a 1,2-cyclohexylene group, and from the viewpoint of reactivity and the stability of the molecular structure of the liquid crystalline resin, a 1,4-cyclohexylene group or a 1,3-cyclohexylene group is preferred.

[0034] The divalent aliphatic chain hydrocarbon group having 4 to 10 carbon atoms represented by R is preferably a divalent aliphatic chain hydrocarbon group having 6 to 10 carbon atoms, and more preferably a divalent aliphatic chain hydrocarbon group having 7 to 9 carbon atoms, from the viewpoint of improving tracking resistance. An example of a divalent aliphatic chain hydrocarbon group having 4 to 10 carbon atoms is an alkylene group having 4 to 10 carbon atoms.

[0035] Regarding R, the alkylene group having 4 to 10 carbon atoms is preferably an alkylene group having 6 to 10 carbon atoms, and more preferably an alkylene group having 7 to 9 carbon atoms, from the viewpoint of improving tracking resistance. Examples of the alkylene group include butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene groups. From the viewpoint of improving tracking resistance and suppressing discoloration, hexylene, heptylene, octylene, nonylene, and decylene groups are preferred, hexylene, heptylene, and octylene groups are more preferred, and octylene groups are particularly preferred.

[0036] From the viewpoint of improving tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin, 1,4-cyclohexylene groups, 1,3-cyclohexylene groups, and octylene groups are preferred for R, and 1,4-cyclohexylene groups and 1,3-cyclohexylene groups are more preferred.

[0037] The constituent unit (IV) is derived from, for example, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid (hereinafter also referred to as "1,4-CHDA", "1,3-CHDA", and "1,2-CHDA", respectively), suberic acid (octanedioic acid), azelaic acid (nonanedioic acid), or sebacic acid (decandioic acid). From the viewpoint of improving tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin, it is preferably derived from 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, or sebacic acid. Specifically, the constituent unit (IV) can be one or more selected from the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, suberic acid, azelaic acid, sebacic acid, and their derivatives. From the viewpoint of improving tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin, constituent units derived from one or more selected from the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, sebacic acid, and their derivatives are preferred, and constituent units derived from one or more selected from the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and their derivatives are more preferred. Hereinafter, monomers that derive constituent unit (IV), such as 1,2-CHDA, 1,3-CHDA, 1,4-CHDA, and sebacic acid, will also be referred to as monomer (IV). In the liquid crystalline resin of the present invention, the constituent unit (IV) may be used alone or in combination of two or more types.

[0038] In the liquid crystalline resin of the present invention, the content of constituent units (IV) is 10 to 45 mol% of the total constituent units. If the content of constituent units (IV) is less than 10 mol% or more than 45 mol%, at least one of the following tends to be insufficient: tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin. From the viewpoint of improving tracking resistance, reactivity, and the stability of the molecular structure of the liquid crystalline resin, the content of constituent units (IV) is preferably 12 to 43 mol%, more preferably 14 to 41 mol%, and even more preferably 15 to 40 mol%.

[0039] In the formula representing the structural unit (V), Ar ３ examples of which include 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 2,6-naphthylene group and 4,4'-biphenylylene group. From the viewpoints of improving tracking resistance and reactivity, 1,3-phenylene group and 1,4-phenylene group are preferred, and 1,3-phenylene group is more preferred. Accordingly, the structural unit (V) is derived from, for example, 1,3-phenylenedicarboxylic acid (hereinafter also referred to as "IA"), 1,4-phenylenedicarboxylic acid (hereinafter also referred to as "TA"), and 2,6-naphthalenedicarboxylic acid (hereinafter also referred to as "NDA"). From the viewpoints of improving tracking resistance and reactivity, the structural unit (V) is preferably derived from 1,3-phenylenedicarboxylic acid and 1,4-phenylenedicarboxylic acid, and more preferably derived from 1,3-phenylenedicarboxylic acid. Hereinafter, monomers that derive the structural unit (V), such as IA, TA, and NDA, are also referred to as monomer (V). In the liquid crystalline resin of the present invention, the structural unit (V) may be used alone or in combination of two or more types.

[0040] In the liquid crystalline resin of the present invention, the content of the structural unit (V) is 0 to 35 mol% based on all structural units. When the content of the structural unit (V) exceeds 35 mol%, at least one of tracking resistance and reactivity tends to be insufficient. From the viewpoints of improving tracking resistance and reactivity, the content of the structural unit (V) is preferably 0 to 25 mol%, more preferably 0 to 15 mol%, and still more preferably 0 to 5 mol%.

[0041] In the liquid crystalline resin of the present invention, the content of structural units containing a naphthalene ring is 0 to 40 mol% based on all structural units. When the content of structural units containing a naphthalene ring exceeds 40 mol%, tracking resistance tends to be insufficient. From the viewpoint of improving tracking resistance, the content of structural units containing a naphthalene ring is preferably 0 to 25 mol%, more preferably 0 to 15 mol%, and still more preferably 0 to 5 mol%. Examples of structural units containing a naphthalene ring include 6-hydroxy-2-naphthoic acid, 2,6-dihydroxynaphthalene, and 2,6-naphthalenedicarboxylic acid.

[0042] In the liquid crystalline resin of the present invention, the molar ratio of the content of the structural unit (II) to the content of the structural unit (III) is more than 0.01 and less than 1.00, preferably 0.03 or more and 0.95 or less, more preferably 0.05 or more and 0.90 or less, from the viewpoints of improving tracking resistance, suppressing discoloration, reactivity, and stability of the molecular structure of the liquid crystalline resin.

[0043] As described above, the liquid crystalline resin of the present invention contains the above structural units (I), (II), (III), and (IV), and contains or does not contain the above structural unit (V). Since the content of each of the above structural units (I) to (V) and the content of the structural unit containing a naphthalene ring fall within specific ranges relative to all structural units, the liquid crystalline resin is excellent in tracking resistance and has suppressed discoloration. More specifically, since the liquid crystalline resin of the present invention uses an aliphatic dicarboxylic acid, which is less likely to carbonize when voltage is applied, as a monomer, it is presumed that tracking resistance is easily improved. Further, in the liquid crystalline resin of the present invention, hydroquinone substituted with a tert-butyl group is also used as a monomer. Since the tert-butyl group is presumed to be able to function as a radical scavenger, it is presumed that during polymerization of the liquid crystalline resin, degradation of the aliphatic skeleton is suppressed, and discoloration at high temperatures is suppressed.

[0044] In the liquid crystalline resin of the present invention, from the viewpoints of improving tracking resistance and suppressing discoloration, the total content of structural units (I) to (V) relative to all structural units is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, and most preferably 100 mol%. Therefore, the liquid crystalline resin of the present invention may contain structural units other than the structural units (I) to (V) (hereinafter also referred to as "structural unit (Z)"). In the liquid crystalline resin of the present invention, from the viewpoints of improving tracking resistance and suppressing discoloration, the content of the structural unit (Z) relative to all structural units is preferably 0 to 20 mol%, more preferably 0 to 10 mol%, still more preferably 0 to 5 mol%, and most preferably 0 mol%.

[0045] Examples of constituent units (Z) include those derived from one or more selected from the group consisting of aliphatic chain dicarboxylic acids not included in monomer (IV), alicyclic dicarboxylic acids not included in monomer (IV), aliphatic chain diols, alicyclic diols, and their derivatives. Hereinafter, the monomer that derives constituent unit (Z) will also be referred to as monomer (Z). In the liquid crystalline resin of the present invention, constituent unit (Z) may be used alone or in combination of two or more types.

[0046] Next, the method for producing the liquid crystalline resin of the present invention will be described. The liquid crystalline resin of the present invention is polymerized using methods such as direct polymerization or transesterification. For polymerization, methods such as melt polymerization, solution polymerization, slurry polymerization, solid-phase polymerization, or a combination of two or more of these can be used, with melt polymerization or a combination of melt polymerization and solid-phase polymerization being preferred.

[0047] Various catalysts can be used in these polymerization processes. Examples include metal salt catalysts such as fatty acid metal salt catalysts and organic compound catalysts. Representative examples include metal salt catalysts such as potassium acetate, magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, antimony trioxide, and tris(2,4-pentanedionato)cobalt(III), as well as organic compound catalysts such as 1-methylimidazole and 4-dimethylaminopyridine.

[0048] For example, the reaction conditions are a reaction temperature of 200 to 380°C and a final pressure of 0.1 to 760 Torr (i.e., 13 to 101,080 Pa). In particular, for melting reactions, for example, the reaction temperature is 260 to 380°C, preferably 300 to 360°C, and the final pressure is 1 to 100 Torr (i.e., 133 to 13,300 Pa), preferably 1 to 50 Torr (i.e., 133 to 6,670 Pa).

[0049] The reaction can be initiated by charging all the starting monomers (monomers (I) to (IV), optionally monomer (V), and optionally monomer (Z)), an acylating agent, and a catalyst into the same reaction vessel (single-stage method), or by acylating the hydroxyl groups of monomer (I), monomer (II), optionally monomer (III) having a hydroxyl group, and optionally monomer (Z) having a hydroxyl group with an acylating agent, and then reacting them with the carboxyl groups of monomer (I), monomer (IV), optionally monomer (V), and optionally monomer (Z) having a carboxyl group (two-stage method).

[0050] Melt polymerization is carried out by starting to reduce the pressure after the reaction system reaches a predetermined temperature, and then maintaining a predetermined degree of reduced pressure. After the torque of the stirrer reaches a predetermined value, an inert gas is introduced, and the system is brought from a reduced pressure state through atmospheric pressure to a predetermined pressurized state, and the liquid crystalline resin is discharged from the reaction system.

[0051] The liquid crystalline resin produced by the above polymerization method can be further subjected to solid-phase polymerization by heating under atmospheric pressure or reduced pressure in an inert gas to increase its molecular weight. Preferred conditions for the solid-phase polymerization reaction are a reaction temperature of 230 to 350°C, preferably 260 to 330°C, and a final pressure of 10 to 760 Torr (i.e., 1,330 to 101,080 Pa).

[0052] Next, the properties of the liquid crystalline resin will be described. The liquid crystalline resin of the present invention exhibits liquid crystalline properties, that is, optical anisotropy when melted.

[0053] In the present invention, the liquid crystalline properties of the liquid crystalline resin are essential for the liquid crystalline resin to possess both thermal stability and ease of processing. Resins containing the above-mentioned constituent units (I), (II), (III), and (IV), and containing or not containing the above-mentioned constituent unit (V), may not form an anisotropic molten phase depending on the constituent components and the sequence distribution in the resin, but the liquid crystalline resin of the present invention is limited to resins that exhibit optical anisotropy when melted.

[0054] The property of melt anisotropy can be confirmed by conventional polarization testing methods using orthogonal polarizers. More specifically, melt anisotropy can be confirmed by melting a sample placed on a Linkam hot stage using an Olympus polarizing microscope and observing it at 150x magnification under a nitrogen atmosphere. Liquid crystal resins are optically anisotropic and transmit light when inserted between orthogonal polarizers. If a sample is optically anisotropic, polarized light will be transmitted even in a molten, stationary liquid state.

[0055] Nematic liquid crystalline resins exhibit a significant decrease in viscosity above their melting point; therefore, exhibiting liquid crystalline properties at or above the melting point is generally considered an indicator of processability. While a higher melting point is preferable from the viewpoint of heat resistance, considering the thermal degradation of the liquid crystalline resin during melting and the heating capacity of the molding machine, a melting point of 245°C or higher is a preferable guideline. More preferably, it is 250 to 400°C, and even more preferably 252 to 380°C.

[0056] A temperature 10 to 30°C higher than the melting point of the liquid crystalline resin of the present invention, and a shear rate of 1000 sec. －１ The melt viscosity of the liquid crystalline resin in the above is preferably 500 Pa·s or less, more preferably 0.5 to 300 Pa·s, and even more preferably 1 to 100 Pa·s. When the melt viscosity is within the above range, the liquid crystalline resin itself, or a composition containing the liquid crystalline resin, is more easily able to maintain fluidity during molding, and the filling pressure is less likely to become excessive. In this specification, melt viscosity refers to the melt viscosity measured in accordance with ISO 11443.

[0057] <Liquid Crystalline Resin Composition> The liquid crystalline resin of the present invention described above may be blended with various fibrous, granular, or plate-shaped inorganic and organic fillers depending on the intended use.

[0058] The inorganic fillers incorporated into the liquid crystalline resin composition of the present invention include fibrous, granular, and plate-like forms.

[0059] Examples of fibrous inorganic fillers include glass fibers, milled glass fibers, carbon fibers, asbestos fibers, silica fibers, silica-alumina fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, silicate fibers such as wollastonite, magnesium sulfate fibers, aluminum borate fibers, and inorganic fibrous materials such as stainless steel, aluminum, titanium, copper, and brass. Glass fibers are a particularly representative fibrous filler.

[0060] Furthermore, examples of granular inorganic fillers include carbon black, graphite, silica, quartz powder, glass beads, glass balloons, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite, metal oxides such as iron oxide, titanium oxide, zinc oxide, antimony trioxide, and alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate, as well as ferrite, silicon carbide, silicon nitride, boron nitride, and various metal powders.

[0061] Examples of plate-shaped inorganic fillers include mica, glass flakes, talc, and various metal foils.

[0062] Examples of organic fillers include heat-resistant, high-strength synthetic fibers such as aromatic polyester fibers, liquid crystalline polymer fibers, aromatic polyamides, and polyimide fibers.

[0063] These inorganic and organic fillers can be used individually or in combination of two or more. The combination of fibrous inorganic fillers and granular or plate-shaped inorganic fillers is a preferred combination for achieving a balance of mechanical strength, dimensional accuracy, and electrical properties. Particularly preferred are glass fibers as the fibrous filler and mica and talc as the plate-shaped fillers, with the total amount of these being preferably 120 parts by mass or less, more preferably 20 to 80 parts by mass, per 100 parts by mass of the liquid crystalline resin. By combining glass fibers with mica or talc, the liquid crystalline resin composition shows particularly significant improvements in heat distortion temperature, mechanical properties, and other characteristics.

[0064] When using these fillers, a consolidating agent or surface treatment agent may be used if necessary.

[0065] As described above, the liquid crystalline resin composition of the present invention contains the liquid crystalline resin of the present invention as an essential component and optionally contains inorganic or organic fillers, but other components may be included as long as they do not impair the effects of the present invention. Here, the other components may be any components, and examples include other resins, flame retardants, antioxidants, stabilizers, pigments, crystal nucleating agents, and other additives.

[0066] Furthermore, the method for producing the liquid crystalline resin composition of the present invention is not particularly limited, and the liquid crystalline resin composition of the present invention can be prepared by conventionally known methods.

[0067] <Molded Articles> The molded articles of the present invention consist of the liquid crystalline resin of the present invention or the liquid crystalline resin composition of the present invention. The molded articles of the present invention can be obtained by molding the liquid crystalline resin of the present invention or the liquid crystalline resin composition of the present invention. The molding method is not particularly limited and general molding methods can be used. Examples of general molding methods include injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, and inflation molding. The shape of the molded article is not particularly limited and may be any desired shape.

[0068] Molded articles made from the liquid crystalline resin of the present invention exhibit excellent tracking resistance and suppressed discoloration. Furthermore, molded articles made from the liquid crystalline resin composition of the present invention exhibit excellent tracking resistance and suppressed discoloration, and when inorganic or organic fillers are included, mechanical strength and other properties are further improved.

[0069] Preferred applications for the molded articles of the present invention having the above-described properties include components for electrical and electronic equipment such as relays, switches, connectors, motor insulators, and busbars.

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0071] <Example 1> The following raw materials were charged into a polymerization vessel equipped with a stirrer, reflux column, monomer inlet, nitrogen inlet, and vacuum / outlet line, and nitrogen purging was started. (I) 205.1 g (60 mol%) of 4-hydroxybenzoic acid (4-HBA) (I) 23.3 g (5 mol%) of 6-hydroxy-2-naphthoic acid (HNA) (II) 20.6 g (5 mol%) of tert-butylhydroquinone (TBHQ) (III) 34.1 g (12.5 mol%) of hydroquinone (HQ) (IV) 63.9 g (15 mol%) of 1,4-cyclohexanedicarboxylic acid (1,4-CHDA) (V) 10.3 g (2.5 mol%) of 1,3-phenylenedicarboxylic acid (IA) 45.2 mg of fatty acid metal salt catalyst (potassium acetate catalyst) 263 g of acylating agent (acetic anhydride) After charging the raw materials, the polymerization vessel was purged with nitrogen and the temperature of the reaction system was raised to 140°C. Subsequently, the temperature was further increased to the final polymerization temperature of 320°C over 225 minutes, and then the pressure was reduced to 10 Torr (i.e., 1333 Pa) over 18 minutes to allow molten polymerization to proceed while distilling off acetic acid and other low-boiling components. After the stirring torque reached a predetermined value, nitrogen was introduced to change the pressure from reduced to atmospheric pressure and then to a pressurized state, and the polymer was discharged from the bottom of the polymerization vessel and pelletized to obtain pelletized resin.

[0072] <Examples 2-5, Comparative Examples 1-10> Resins were obtained in the same manner as in Example 1, except that the types of raw material monomers and the charging ratio (mol%) were as shown in Table 1 or Table 2. However, the final polymerization temperature was changed to 340°C for Comparative Examples 1, 8, and 9, and to 325°C for Comparative Examples 2 and 10. In the table, BP represents 4,4'-dihydroxybiphenyl, MeHQ represents methylhydroquinone, and TA represents 1,4-phenylenedicarboxylic acid.

[0073] <Evaluation> The resins of the examples and comparative examples were evaluated for liquid crystalline properties, measured for CTI (comparative tracking index), and evaluated for discoloration using the following methods. The results are shown in Table 1 or Table 2.

[0074] [Evaluation of Liquid Crystallinity] Using a polarizing microscope manufactured by Olympus Corporation, the resin was melted on a hot stage manufactured by Linkam Corporation and observed under a nitrogen atmosphere at 150x magnification and crossed nicols to evaluate liquid crystallinity according to the following criteria. ○ (Good): An optically anisotropic molten phase was formed in the molten resin. × (Poor): An optically anisotropic molten phase was not formed in the molten resin.

[0075] [CTI Measurement] Using the pellets from the examples and comparative examples, a 100 mmφ × 0.3 mmt film was prepared by hot pressing under vacuum. A film of approximately 30 mm × 30 mm was cut from this film for evaluation and used as a test specimen. During measurement, a 3 mmt polybutylene terephthalate resin molded product was placed under the test specimen.

[0076] Based on IEC 60112, 3rd edition, the applied voltage (V: volts) at which tracking occurred in a test specimen was measured using a 0.1% by mass ammonium chloride aqueous solution and a platinum electrode. For test specimens that did not show tracking failure when 450V was applied, the applied voltage was increased by 50V increments, and the maximum voltage at which tracking failure did not occur (up to a maximum of 600V) was evaluated for all test specimens (N=3). For test specimens that showed tracking failure when 450V was applied, the applied voltage was appropriately decreased by 100 to 25V increments, and the maximum voltage at which tracking failure did not occur for all test specimens (N=3) was evaluated. A measured CTI value of 250V or higher was evaluated as good tracking resistance, and a value of less than 250V was evaluated as poor tracking resistance.

[0077] [Evaluation of discoloration] Using the pellets from the examples and comparative examples, films measuring 100 mmφ × 0.3 mmt were prepared by hot pressing under vacuum and used as test specimens. The L value of these test specimens was measured using a spectrophotometer (SE6000, manufactured by Nippon Denshoku Industries Ltd.) and the discoloration was evaluated according to the following criteria. ○ (Good): The L value was 55 or higher, indicating that discoloration was suppressed. × (Poor): The L value was less than 55, indicating that discoloration was not suppressed.

[0078]

[0079]

[0080] As is clear from the results shown in Table 1 or Table 2, the liquid crystalline resin of the example was confirmed to have excellent tracking resistance and suppressed discoloration.

Claims

1. A liquid crystalline resin that exhibits optical anisotropy when melted, wherein the liquid crystalline resin contains the following constituent units (I), (II), (III), and (IV), and may or may not contain the following constituent unit (V), the content of constituent unit (I) is 10 to 80 mol% of the total constituent units, the content of constituent unit (II) is 1 to 20 mol% of the total constituent units, the content of constituent unit (III) is 9 to 44 mol% of the total constituent units, the content of constituent unit (IV) is 10 to 45 mol% of the total constituent units, the content of constituent unit (V) is 0 to 35 mol% of the total constituent units, and the content of constituent units containing a naphthalene ring is 0 to 40 mol% of the total constituent units. (In the formula, Ar １ Ar ２ , and Ar ３ Each of these independently represents a phenylene group, a naphthylene group, or a biphenylylene group. R represents a cyclohexylene group or a divalent aliphatic hydrocarbon group having 4 to 10 carbon atoms. Each of these independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 6 carbon atoms. Y and Z independently represent an oxygen atom or an imino group.

2. The liquid crystalline resin according to claim 1, wherein the total content of constituent units (I) to (V) is 100 mol% of the total constituent units.

3. The liquid crystalline resin according to claim 1 or 2, wherein the constituent unit (IV) is a constituent unit selected from one or more of the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, sebacic acid, and derivatives thereof.

4. The liquid crystalline resin according to claim 1 or 2, wherein the constituent unit (IV) is a constituent unit selected from the group consisting of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and derivatives thereof, one or more of these.

5. The liquid crystalline resin according to claim 1 or 2, wherein the constituent unit (II) is a constituent unit derived from one or more selected from the group consisting of tert-butylhydroquinone and its derivatives.

6. A liquid crystalline resin composition comprising the liquid crystalline resin described in claim 1 or 2.

7. A molded article made of the liquid crystalline resin according to claim 1 or 2.

8. A molded article comprising the liquid crystalline resin composition described in claim 6.

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