TWI870448B - Method for producing liquid crystal polyester - Google Patents

Abstract

A liquid crystal polyester having a nitrogen content of 15 to 100 mass ppm.

Description

Method for producing liquid crystal polyester

The present invention relates to liquid crystal polyester (liquid crystalline polyester), molded products and a method for manufacturing liquid crystal polyester.

This patent application claims priority based on Japanese Patent Application No. 2019-157024 filed in Japan on August 29, 2019, and the contents are cited.

In recent years, liquid crystal polyesters composed of aromatic ring skeletons have been used in the electrical and electronic fields as materials with excellent heat resistance and tensile strength. Liquid crystal polyesters can be produced by, for example, the following method: acetic anhydride is added to the phenolic hydroxyl group of aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid and/or aromatic diols such as 4,4'-hydroxybiphenyl to acylate the phenolic hydroxyl group to obtain an acylated product, and then the acylated product is esterified with aromatic dicarboxylic acids such as terephthalic acid.

For example, Patent Document 1 discloses a method for producing liquid crystal polyester by ester exchange in the presence of a specific imidazole compound. The liquid crystal polyester obtained by this production method has excellent heat resistance and mechanical strength, and has less uneven quality, so it is considered suitable as a material for electrical and electronic components.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2004-83778

However, the liquid crystal polyester obtained by the conventional production method as described above becomes thicker during melt retention, and the retention stability is insufficient, which may cause problems such as poor molding during injection molding.

This invention was completed in view of the above situation, and the subject is to provide a liquid crystal polyester with excellent retention stability.

In order to solve the above-mentioned problems, the present invention adopts the following structure.

[1]. A liquid crystal polyester having a nitrogen content of 15 to 100 ppm by mass.

[2]. The liquid crystal polyester as in [1], wherein the nitrogen content is 15 to 50 ppm by mass.

[3]. The liquid crystal polyester as described in [1] or [2], wherein the flow start temperature is above 200°C.

[4]. A molded product comprising a liquid crystal polyester as described in any one of [1] to [3].

[5] A method for producing a liquid crystal polyester, comprising the following steps (i) and (ii): Step (i): in the presence of a component (N), an aromatic hydroxycarboxylic acid represented by the following formula (I) and an aromatic diol represented by the following formula (II) are acylated with a fatty acid anhydride having a carbon number of 9 or less to obtain an acylated product, wherein the component (N) is a heterocyclic organic base compound containing a nitrogen atom; Step (ii): the acylated product is ester-exchanged with an aromatic dicarboxylic acid represented by the following formula (III) to obtain a liquid crystal polyester; wherein the step (i) comprises performing the acylation operation in a manner such that the amount of the component (N) used is set to more than 350 mass ppm and less than 1500 mass ppm relative to the total mass of the aromatic hydroxycarboxylic acid and the aromatic diol, and HO-Ar ¹ -COOH…(I)

HO-Ar ² -OH…(II)

HOOC-Ar ³ -COOH…(III)

[In the formula, ^Ar1 and ^Ar3 each independently represent an arylene group which may be substituted, and ^Ar2 represents an arylene group which may be substituted or a divalent linking group represented by the following formula (IV)]

[wherein, ^R1 and ^R2 independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms, and X represents _{-O-, -S-, -SO2-} , -CO-, _-C6H10- or _an alkylene group].

According to the present invention, a liquid crystal polyester with excellent retention stability can be provided.

[Best form of implementing the invention]

(Liquid crystal polyester)

The liquid crystal polyester of this embodiment has a nitrogen content of 15 to 100 mass ppm.

The nitrogen content is measured for liquid crystal polyester according to JIS-2609: Crude oil and petroleum products - Nitrogen content test method, chemical luminescence method, using a micro-total nitrogen analyzer (Mitsubishi Chemical Analytech, TN-2100H), in which the liquid crystal polyester is thermally decomposed and then oxidized by oxygen combustion under the flow of argon gas. The nitric oxide generated is oxidized with ozone gas under dehydration conditions, and the luminescence intensity at a wavelength of 590~2500nm is measured and detected. The nitrogen content can be obtained from the area value of the luminescence intensity.

The nitrogen content in the liquid crystal polyester of this embodiment is preferably 15 to 50 mass ppm, more preferably 15 to 40 mass ppm, even more preferably 15 to 35 mass ppm, and particularly preferably 15 to 30 mass ppm.

When the nitrogen content in the liquid crystal polyester of this embodiment is above the above-mentioned preferred lower limit, the retention stability is further excellent.

When the nitrogen content in the liquid crystal polyester of this embodiment is below the above-mentioned preferred upper limit, it is easy to produce a liquid crystal polyester with a desired melt viscosity.

As a method for producing a liquid crystal polyester having a nitrogen content within the above range, for example, a method of using a heterocyclic organic alkali compound containing nitrogen atoms as a catalyst when producing the liquid crystal polyester can be cited. According to this, a part of the liquid crystal polyester will be bonded to the heterocyclic organic alkali compound containing nitrogen atoms, and the liquid crystal polyester can be produced in such a way that the nitrogen content in the liquid crystal polyester is within the above range.

The flow start temperature of the liquid crystal polyester of this embodiment is preferably above 200°C, more preferably above 270°C and below 400°C, more preferably above 280°C and below 380°C, and particularly preferably above 300°C and below 350°C.

When the liquid crystal polyester starts to flow at a temperature within the aforementioned range, the heat resistance, strength, and rigidity are good, so it is not easy to be thermally degraded during molding. Also, since the viscosity is not easy to increase during melting, the fluidity tends to be difficult to decrease.

The flow start temperature is also called the reflow temperature or the flow temperature. The flow start temperature is the temperature at which the liquid crystal polyester shows a viscosity of 4800 Pa.s (48,000 ^poise ) when extruded from a nozzle with an inner diameter of 1 mm and a length of 10 mm while the liquid crystal polyester is melted using a capillary rheometer under a load of 9.8 MPa (100 kgf/cm2). The flow start temperature is a standard for the molecular weight of the liquid crystal polyester (reference: Naoyuki Koide, "Liquid Crystal Polymer - Synthesis, Molding, Applications -", CMC Co., Ltd., June 5, 1987, p.95).

The melt viscosity of the liquid crystal polyester of this embodiment after retention at 350°C for 30 seconds is preferably 350 Pa.s to 500 Pa.s, more preferably 400 Pa.s to 500 Pa.s, and even more preferably 440 Pa.s to 500 Pa.s.

The melt viscosity of the liquid crystal polyester of this embodiment after retention at 350°C for 10 minutes is, for example, preferably 350 Pa.s to 600 Pa.s, more preferably 400 Pa.s to 550 Pa.s, and even more preferably 440 Pa.s to 520 Pa.s.

The melt viscosity is for tablet-shaped products of liquid crystal polyester and can be measured using a rheometer.

As the liquid crystal polyester of this embodiment, there can be mentioned a liquid crystal polyester containing a constituent unit represented by the following formula (1) (hereinafter also referred to as constituent unit (1)), a constituent unit represented by the following formula (2) (hereinafter also referred to as constituent unit (2)), and a constituent unit represented by the following formula (3) (hereinafter also referred to as constituent unit (3)), and a compound containing a nitrogen atom is bonded to the main chain terminal of the liquid crystal polyester.

(1)-O-Ar ¹ -CO-

(2) -O-Ar ² -O-

(3)-CO-Ar ³ -CO-

[In formula (1), Ar ¹ represents a phenylene group, a naphthylene group or a biphenylene group, and one or more hydrogen atoms in the above groups represented by Ar ¹ may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

In formula (2), ^Ar2 represents a phenylene group, a naphthylene group, a biphenylene group, or a group represented by the following formula (4). One or more hydrogen atoms contained in ^Ar2 may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

In formula (3), Ar ³ represents a phenylene group, a naphthylene group, a biphenylene group or a group represented by the following formula (4). One or more hydrogen atoms contained in Ar ³ may be substituted by a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

[wherein, ^R1 and ^R2 independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms, and X represents -O-, -S-, _-SO2- , -CO-, _-C6H10- , or an _alkylene group]

<Constituent unit (1)>

The constituent unit (1) is the constituent unit represented by the above formula (1).

In the above formula (1), Ar ¹ represents a phenylene group, a naphthylene group or a biphenylene group, and one or more hydrogen atoms in the above groups represented by Ar ¹ may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

Examples of the halogen atom that can substitute for one or more hydrogen atoms in the above group represented by Ar ¹ include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 10 carbon atoms which can replace one or more hydrogen atoms in the above group represented by ^Ar1 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-nonyl, and n-decyl.

Examples of the aryl group having 6 to 20 carbon atoms which can replace one or more hydrogen atoms in the above group represented by ^Ar1 include monocyclic aromatic groups such as phenyl, o-tolyl, m-tolyl, p-tolyl, and the like; and condensed aromatic groups such as 1-naphthyl, 2-naphthyl, and the like.

When one or more hydrogen atoms in the above groups represented by Ar ¹ are substituted by such groups, the number of substitutions is preferably 1 or 2, more preferably 1.

The constituent unit (1) is a constituent unit derived from a specified aromatic hydroxycarboxylic acid.

Preferred constituent units (1) include those in which Ar ¹ is 1,4-phenylene (a constituent unit derived from 4-hydroxybenzoic acid) and those in which Ar ¹ is 2,6-naphthylene (a constituent unit derived from 6-hydroxy-2-naphthoic acid).

<Constituent units (2)>

The constituent unit (2) is the constituent unit represented by the above formula (2).

In the above formula (2), Ar ² represents a phenylene group, a naphthylene group, a biphenylene group or a group represented by the above formula (4). One or more hydrogen atoms contained in Ar ² may be substituted by a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

The halogen atom, alkyl group and aryl group which can replace one or more hydrogen atoms in the above group represented by ^Ar2 are the same as the halogen atom, alkyl group having 1 to 10 carbon atoms and aryl group having 6 to 20 carbon atoms which can replace one or more hydrogen atoms in the above group represented by ^Ar1 .

When one or more hydrogen atoms in the aforementioned groups represented by Ar ² are substituted by such groups, the number of substitutions is independent of each of the aforementioned groups represented by Ar ² , and is preferably 1 or 2, and more preferably 1. Moreover, Ar ² is more preferably unsubstituted.

The constituent unit (2) is a constituent unit derived from a specified aromatic diol.

As the constituent unit (2), Ar ² is preferably 1,4-phenylene (a constituent unit derived from hydroquinone), Ar ² is 1,3-phenylene (a constituent unit derived from 1,3-benzenediol), Ar ² is 2,6-naphthylene (a constituent unit derived from 2,6-dihydroxynaphthalene), Ar ² is 4,4'-biphenylene (a constituent unit derived from 4,4'-dihydroxybiphenyl), or Ar ² is diphenyl ether-4,4'-diyl (a constituent unit derived from 4,4'-dihydroxydiphenyl ether). Ar ² is more preferably 1,4-phenylene, 1,3-phenylene, 2,6-naphthylene or 4,4'-biphenylene.

<Constituent units (3)>

The constituent unit (3) is the constituent unit represented by the above formula (3).

In the above formula (3), Ar ³ represents a phenylene group, a naphthylene group, a biphenylene group or a group represented by the above formula (4). One or more hydrogen atoms contained in Ar ³ may be substituted by a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms. The halogen atom, the alkyl group and the aryl group capable of replacing one or more hydrogen atoms in the above group represented by Ar ³ are the same as the halogen atom, the alkyl group having 1 to 10 carbon atoms and the aryl group having 6 to 20 carbon atoms capable of replacing one or more hydrogen atoms in the above group represented by Ar ¹ .

When one or more hydrogen atoms in the aforementioned groups represented by Ar ³ are substituted by such groups, the number of substitutions is independent of each of the aforementioned groups represented by Ar ³ , and is preferably 1 or 2, and more preferably 1. Moreover, Ar ³ is more preferably unsubstituted.

Examples of the aforementioned alkylidene group having 1 to 10 carbon atoms include methylene, ethylene, isopropylene, n-butylene and 2-ethylhexylene, and the carbon number is preferably 1 to 10.

The constituent unit (3) is a constituent unit derived from a specified aromatic dicarboxylic acid.

As the constituent unit (3), Ar ³ is preferably 1,4-phenylene (a constituent unit derived from terephthalic acid), Ar ³ is 1,3-phenylene (a constituent unit derived from isophthalic acid), Ar ³ is 2,6-naphthylene (a constituent unit derived from 2,6-naphthalene dicarboxylic acid), Ar ³ is 4,4'-biphenylene (a constituent unit derived from 4,4'-dicarboxylic acid biphenyl), or Ar ³ is diphenyl ether-4,4'-diyl (a constituent unit derived from 4,4'-dicarboxylic acid diphenyl ether). Ar ³ is more preferably 1,4-phenylene, 1,3-phenylene, 2,6-naphthylene or 4,4'-biphenylene.

Relative to the total of all constituent units constituting the liquid crystal polyester (100 mol%), the liquid crystal polyester in this embodiment preferably contains 30 to 80 mol%, more preferably 50 to 70 mol%, and even more preferably 55 to 65 mol%.

Relative to the total of all constituent units constituting the liquid crystal polyester (100 mol%), the liquid crystal polyester in this embodiment preferably contains 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 17.5 to 27.5 mol%.

Relative to the total of all constituent units constituting the liquid crystal polyester (100 mol%), the liquid crystal polyester in this embodiment preferably contains 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 17.5 to 27.5 mol%.

As the compound containing a nitrogen atom bonded to the main chain terminal of the liquid crystal polyester in this embodiment, the (N) component described below can be cited: a heterocyclic organic alkali compound containing a nitrogen atom, etc.

More specifically, the liquid crystal polyester of this embodiment can be obtained by the following production method.

As a method for producing a liquid crystal polyester according to the present embodiment, the following method for producing a liquid crystal polyester can be cited, which comprises the following steps (i) and (ii): Step (i): In the presence of a component (N), an aromatic hydroxycarboxylic acid represented by the following formula (I) and an aromatic diol represented by the following formula (II) are acylated with a fatty acid anhydride having a carbon number of 9 or less to obtain an acylated product, wherein the component (N) is a heterocyclic hydrocarbon containing a nitrogen atom. an organic alkali compound; step (ii): esterifying the acylated product with an aromatic dicarboxylic acid represented by the following formula (III) to obtain a liquid crystal polyester; in the step (i), the acylation operation is performed in such a manner that the amount of the component (N) used is greater than 350 ppm by mass and less than 1500 ppm by mass relative to the total mass of the aromatic hydroxycarboxylic acid and the aromatic diol, HO-Ar ¹ -COOH…(I)

HO-Ar ² -OH…(II)

HOOC-Ar ³ -COOH…(III)

[In the formula, Ar ¹ and Ar ³ each independently represent an arylene group which may be substituted, and Ar ² represents an arylene group which may be substituted or a divalent linking group represented by the following formula (IV)].

[wherein, ^R1 and ^R2 each independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms, and X represents -O-, -S-, _-SO2- , -CO-, _-C6H10- or an _alkylene group].

[Step (i)]

In step (i), an aromatic hydroxycarboxylic acid represented by the following formula (I) (hereinafter also referred to as aromatic hydroxycarboxylic acid (I)) and an aromatic diol represented by the following formula (II) (hereinafter also referred to as aromatic diol (II)) are acylated with a fatty acid anhydride having a carbon number of 9 or less in the presence of a component (N) to obtain an acylated product, wherein the component (N) is a heterocyclic organic base compound containing a nitrogen atom. Thus, an acylated product having an acyl group with high reactivity in an ester exchange reaction can be obtained. Furthermore, the obtained acylated product can contain nitrogen derived from the component (N).

HO-Ar ¹ -COOH…(I)

HO-Ar ² -OH…(II)

[In the formula, Ar ¹ represents an arylene group which may be substituted, and Ar ² represents an arylene group which may be substituted or a divalent linking group represented by the following formula (IV)].

[wherein, ^R1 and ^R2 each independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms, and X represents -O-, -S-, _-SO2- , -CO-, _-C6H10- or an _alkylene group].

． Aromatic hydroxycarboxylic acid represented by the above formula (I)

In the above formula (I), Ar ¹ represents an arylene group which may be substituted.

Examples of the aryl group include phenylene, naphthylene, biphenylene, etc.

The aryl group may be substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, etc. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a t-butyl group.

Specific examples of the aromatic hydroxycarboxylic acid (I) in this embodiment include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-3-naphthoic acid, 1-hydroxy-4-naphthoic acid, 2,6-dichloro-p-hydroxybenzoic acid, 2-chloro-p-hydroxybenzoic acid, 2,6-difluoro-p-hydroxybenzoic acid, and 4-hydroxy-4'-biphenylcarboxylic acid.

Among the above, p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid are preferred in terms of ease of acquisition, and p-hydroxybenzoic acid is particularly preferred.

The aromatic hydroxycarboxylic acid (I) in this embodiment may be a single compound or a combination of two or more compounds.

． Aromatic diol represented by the above formula (II)

In the above formula (II), Ar ² represents an arylene group which may be substituted, or a divalent linking group represented by the above formula (IV).

As the aryl group, there can be mentioned phenylene, naphthylene, biphenylene, etc.

The aryl group can be substituted by a halogen atom, an alkyl group with 1 to 6 carbon atoms, an acyloxy group with 1 to 6 carbon atoms, a phenyl group, a nitro group, etc.

Examples of the halogen atom and the alkyl group having 1 to 6 carbon atoms include the same ones as explained for Ar ¹ in the above formula (I).

Examples of the acyloxy group having 1 to 6 carbon atoms include methyloxy, acetyloxy, and propionyloxy.

In the above formula (IV), ^R1 and ^R2 each independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. Examples of the halogen atom and the alkyl group having 1 to 6 carbon atoms include the same ones as explained for ^Ar1 in the above formula (I).

Examples of the acyloxy group having 1 to 6 carbon atoms include the same ones as explained for Ar ² in the above formula (II).

In the above formula (IV), X represents -O-, -S-, _-SO2- , -CO-, _-C6H10- or an alkylene group. Examples of the alkylene group include branched or linear alkylene groups. Examples of the linear alkylene group include methylene [ _-CH2- ], ethylene [-( _CH2 ) _2- ], propylene _[ -( _CH2 ) _3- ], butylene [-( _CH2 ) _4- ], pentylene [-( _CH2 ) _5- ] and the like. Examples of the branched alkylene group include alkylene methyl groups such as -CH(CH ₃ )-, -CH(CH ₂ CH ₃ )-, and -C(CH ₃ ) ₂ -; alkylene ethyl groups such as -CH(CH ₃ )CH ₂ -, and -C(CH ₂ CH ₃ ) ₂ -CH ₂ -; alkylene propyl groups such as -CH(CH ₃ )CH _{2 CH 2 -, and -CH 2 CH(CH 3 )CH 2 -; and alkylene butyl groups such as -CH(CH 3 )CH 2 CH 2 - , and -CH 2 CH} (CH ₃ )CH ₂ CH ₂ -.

In the above formula (II), Ar ² includes, for example, the following groups:

As the aromatic diol (II) in this embodiment, specifically, 4,4'-dihydroxybiphenyl, hydroquinone, resorcinol, methyl hydroquinone, 2,3,5-trimethyl hydroquinone, chlorohydroquinone, acetyloxy hydroquinone, nitrohydroquinone, 2,2',3,3',5,5'-hexamethyl-4,4'-biphenyl, 1,4-dihydroxynaphthalene, 1, 5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylbenzene)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3-methylbenzene)propane, 2,2-Bis(4-hydroxy-3-chlorophenyl)propane, bis(4-hydroxyphenyl)methane, bis(4-hydroxy-3,5-dimethylbenzene)methane, bis(4-hydroxy-3,5-dichlorophenyl)methane, bis(4-hydroxy-3,5-dibromobenzene)methane, bis(4-hydroxy-3-methylbenzene)methane, bis(4-hydroxy bis-(4-hydroxyphenyl) cyclohexanone, bis-(4-hydroxyphenyl) ketone, bis-(4-hydroxy-3,5-dimethylphenyl) ketone, bis-(4-hydroxy-3,5-dichlorophenyl) ketone, bis-(4-hydroxyphenyl) sulfide, bis-(4-hydroxyphenyl) sulfide, bis-(4-hydroxyphenyl) ether, etc.

Among the above, 4,4'-dihydroxybiphenyl, hydroquinone, resorcinol, 2,6-dihydroxynaphthalene, 2,2-bis(4-hydroxyphenyl)propane, and bis-(4-hydroxyphenyl)sulfone are preferred in terms of ease of acquisition, and 4,4'-dihydroxybiphenyl is particularly preferred.

The aromatic diol (II) in this embodiment may be a single compound or a combination of two or more compounds.

． (N) Component: Heterocyclic organic alkali compound containing nitrogen atoms

The so-called heterocyclic organic alkali compound containing nitrogen atoms refers to a heterocyclic organic compound containing nitrogen atoms that can be used as a base in the chemical structure.

The heterocyclic organic alkali compound may contain heteroatoms (oxygen atoms, sulfur atoms, etc.) other than nitrogen atoms in the ring structure.

The (N) component can be monocyclic or polycyclic.

、吡嗪、嘧啶、三嗪、四嗪、吡咯啶、哌啶等。 Examples of the monocyclic (N) component include pyrrole, pyrazole, imidazole, triazole, tetrazole, oxazole, isoxazole, thiazole, isothiazole, oxadiazole, thiadiazole, pyridine,

, pyrazine, pyrimidine, triazine, tetrazine, pyrrolidine, piperidine, etc.

、喹

啉、喹唑啉、吲哚、吲唑、苯并咪唑、苯并三唑、苯并噁唑、苯并異噁唑、苯并噻唑、苯并異噻唑、苯并噁二唑、苯并噻二唑、1,4-二氮雜雙環[2.2.2]辛烷等。 As the polycyclic (N) component, there can be mentioned quinoline, isoquinoline, cinnoline,

Quin

quinazoline, indole, indazole, benzimidazole, benzotriazole, benzoxazole, benzoisoxazole, benzothiazole, benzoisothiazole, benzoxadiazole, benzothiadiazole, 1,4-diazabicyclo[2.2.2]octane, etc.

Furthermore, the monocyclic and polycyclic (N) components may have a substituent. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, a cyano group, a hydroxymethyl group, a cyanoalkyl group having 2 to 5 carbon atoms, a cyanoalkoxy group having 2 to 5 carbon atoms, a carboxyl group, an amino group, an aminoalkyl group having 1 to 4 carbon atoms, an aminoalkoxy group having 1 to 4 carbon atoms, a phenyl group, a benzyl group, a phenylpropyl group, a methyl group, and the like.

As the alkyl group having 1 to 4 carbon atoms, there can be mentioned methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, etc.

Examples of cyanoalkyl groups having 2 to 5 carbon atoms include cyanomethyl, cyanoethyl, and cyanopropyl.

Examples of the cyanoalkoxy group having 2 to 5 carbon atoms include cyanomethoxy, cyanoethoxy, and cyanobutoxy.

As 1 to 4 aminoalkyl groups, there can be cited aminomethyl, aminoethyl, aminopropyl, etc.

Examples of aminoalkoxy groups having 1 to 4 carbon atoms include aminomethoxy, aminoethoxy, and aminobutoxy.

Among the above, the component (N) in this embodiment is preferably an imidazole compound represented by the following general formula (N-1).

[wherein, ^Rn1 to ^Rn4 independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a hydroxymethyl group, a cyanoalkyl group having 2 to 5 carbon atoms, a cyanoalkoxy group having 2 to 5 carbon atoms, a carboxyl group, an amino group, an aminoalkyl group having 1 to 4 carbon atoms, an aminoalkoxy group having 1 to 4 carbon atoms, a phenyl group, a benzyl group, a phenylpropyl group or a methyl group]

In formula (N-1), ^Rn1 to ^Rn4 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a hydroxymethyl group, a cyanoalkyl group having 2 to 5 carbon atoms, a cyanoalkoxy group having 2 to 5 carbon atoms, a carboxyl group, an amino group, an aminoalkyl group having 1 to 4 carbon atoms, an aminoalkoxy group having 1 to 4 carbon atoms, a phenyl group, a benzyl group, a phenylpropyl group or a formyl group.

Specifically, the same groups as those listed as the substituents that the (N) component may have can be cited.

Specific examples of the imidazole compound represented by the general formula (N-1) include imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 1-ethylimidazole, 2-ethylimidazole, 4-ethylimidazole, 1,2-dimethylimidazole, 1,4-dimethylimidazole, 2,4-dimethylimidazole, 1-methyl-2-ethylimidazole, 1-methyl-4-ethylimidazole, 1-ethyl-2-methylimidazole, 1-ethyl-2-ethylimidazole, 1-ethyl-2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2- -methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 4-cyanoethyl-2-ethyl-4-methylimidazole, 1-aminoethyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 1-aminoethyl-2-ethylimidazole, 4-formylimidazole, 2-methyl-4-formylimidazole, 4-methyl-5-formylimidazole, 2-ethyl-4-methyl-5-formylimidazole, 2-phenyl-4-methyl-4-formylimidazole, etc. Among them, 1-methylimidazole and 2-methylimidazole are preferred from the viewpoint of ease of acquisition and operability.

． Fatty acid anhydrides with carbon number less than 9

Examples of fatty acid anhydrides having carbon numbers of 9 or less in the present embodiment include acetic anhydride, propionic anhydride, butyric anhydride, 2-methylpropionic anhydride, valeric anhydride, 2,2-dimethylpropionic anhydride, 2-ethylhexanoic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, and β-bromopropionic anhydride.

In step (i) of this embodiment, relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II), and aromatic dicarboxylic acid (III), the amount of aromatic hydroxycarboxylic acid (I) used is preferably 30 to 80 mol%, more preferably 40 to 70 mol%, and even more preferably 50 to 65 mol%.

In step (i) of this embodiment, relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II), and aromatic dicarboxylic acid (III), the amount of aromatic diol (II) used is preferably 10-35 mol%, more preferably 15-30 mol%, and even more preferably 17.5-25 mol%.

In step (i) of this embodiment, the amount of fatty acid anhydride with less than 9 carbon atoms used is preferably 1.01 to 1.15 times the equivalent, and more preferably 1.05 to 1.12 times the equivalent, relative to the phenolic hydroxyl group.

When the amount of fatty acid anhydride used is above the above preferred lower limit, the equilibrium during acylation will shift toward the fatty acid anhydride side, making the polymerization into polyester faster.

Furthermore, when the amount of fatty acid anhydride used is below the above-mentioned preferred upper limit, the deterioration of the coloring of the obtained liquid crystal polyester can be further suppressed.

In step (i) of the present embodiment, the acylation is preferably performed with the amount of component (N) being more than 350 mass ppm and less than 1500 mass ppm relative to the total mass of the aromatic hydroxycarboxylic acid (I) and the aromatic diol (II), more preferably 400-1400 mass ppm, more preferably 500-1300 mass ppm, and particularly preferably 600-1300 mass ppm.

When the amount of component (N) used is above the above preferred lower limit, the acylation reaction will proceed sufficiently, and the nitrogen content of the obtained liquid crystal polyester will easily become 15 mass ppm or more.

When the amount of component (N) used is below the above-mentioned preferred upper limit, the reaction control becomes easier.

As long as the (N) component exists during at least one period in step (i), it will be sufficient.

The method of adding component (N) is not particularly limited, and it can be added after mixing it in a solvent that does not affect the reaction and physical properties. Examples of the solvent include acetic acid.

In this embodiment, step (i) is preferably carried out at 120-150°C for 10 minutes to 3 hours, and more preferably at 135-150°C for 20 minutes to 1 hour.

[Step (ii)]

In step (ii), the acylated product obtained in step (i) is ester-exchanged with an aromatic dicarboxylic acid represented by the following formula (III) (hereinafter also referred to as aromatic dicarboxylic acid (III)) to obtain a liquid crystal polyester.

HOOC-Ar ³ -COOH…(III)

[In the formula, Ar ³ represents an aryl group which may be substituted]

Ar ³ in the above formula (III) represents an arylene group which may be substituted.

Examples of the aryl group include phenylene, naphthylene, biphenylene, etc.

The aryl group may be substituted by a halogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and a t-butyl group.

As the aromatic dicarboxylic acid (III) in this embodiment, specifically, terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, methyl terephthalic acid, methyl isophthalic acid, etc. can be cited. Among them, terephthalic acid and isophthalic acid are preferred.

Relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II), and aromatic dicarboxylic acid (III), the amount of aromatic dicarboxylic acid (III) used in this embodiment is preferably 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 17.5 to 25 mol%.

In step (ii) of this embodiment, it is preferred to carry out the reaction while raising the temperature from 120-150°C to 300-350°C at a rate of 0.1-10°C/min, and it is even more preferred to carry out the reaction while raising the temperature from 130-135°C to 280-330°C at a rate of 0.3-5°C/min.

When the acylated fatty acid ester is subjected to an ester exchange reaction with an aromatic dicarboxylic acid, it is preferred to evaporate and distill the by-product fatty acid and the unreacted fatty acid anhydride out of the reaction system in order to shift the equilibrium.

In step (ii) of this embodiment, the above-mentioned component (N) may also be used.

In step (ii), if component (N) is used, relative to the total mass of the aromatic hydroxycarboxylic acid (I) and the aromatic diol (II), it is preferred to set the amount of component (N) to 0-2000 mass ppm or less for the above-mentioned acylation, and it is more preferred to set it to 0-1000 mass ppm for ester exchange, and it is even more preferred to set it to 0-500 mass ppm for ester exchange.

When the amount of component (N) used is above the above preferred lower limit, the transesterification reaction will proceed more easily.

When the amount of component (N) used is below the above-mentioned preferred upper limit, the reaction can be more easily controlled.

[Other steps]

The method for producing the liquid crystal polyester of this embodiment may include the following step (iii): the blocky liquid crystal polyester obtained by the above step (ii) is crushed to obtain a crushed product (powder), and the crushed product is solid-phase polymerized to obtain a powdery liquid crystal polyester.

As a method for pulverizing the bulk of the liquid crystal polyester obtained by the above step (ii), there can be cited a method using an impact compression type pulverizer such as a hammer crusher, a pin crusher, a planetary ball mill, etc.; a compression type pulverizer such as a roller crusher, a disc crusher, etc.; a friction pulverizer such as a ring roller mill; a vibration type pulverizer such as a vibration mill; a pulverizer such as a jet mill, a colloid mill, etc., etc.

The temperature for solid phase polymerization of the above-mentioned pulverized material is preferably 220~350℃, and more preferably 250~320℃.

When the temperature during solid phase polymerization is within the above preferred range, the polymerization will proceed more fully.

As the liquid crystal polyester of this embodiment, specifically, there can be cited a liquid crystal polyester obtained by acylation of p-hydroxybenzoic acid (aromatic hydroxycarboxylic acid (I)) and 4,4'-dihydroxybiphenyl (aromatic diol (II)) with acetic anhydride in the presence of 1-methylimidazole to obtain an acyl compound, and esterification of the acyl compound with terephthalic acid and isophthalic acid (aromatic dicarboxylic acid (III)). That is, there can be cited a liquid crystal polyester having repeating units derived from p-hydroxybenzoic acid, repeating units derived from 4,4'-dihydroxybiphenyl, and repeating units derived from terephthalic acid and isophthalic acid, and containing nitrogen (nitrogen component) derived from 1-methylimidazole.

In the liquid crystal polyester of this embodiment, the ratio of the repeating units derived from the aromatic hydroxycarboxylic acid (I) relative to the total of all constituent units constituting the liquid crystal polyester of this embodiment (100 mol%) is preferably 30 to 80 mol%, more preferably 40 to 70 mol%, and even more preferably 50 to 65 mol%.

In the liquid crystal polyester of this embodiment, the ratio of the repeating units derived from the aromatic diol (II) relative to the total of all constituent units constituting the liquid crystal polyester of this embodiment (100 mol%) is preferably 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 17.5 to 25 mol%.

In the liquid crystal polyester of this embodiment, the ratio of the repeating units derived from the aromatic dicarboxylic acid (III) relative to the total of all constituent units constituting the liquid crystal polyester of this embodiment (100 mol%) is preferably 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 17.5 to 25 mol%.

The liquid crystal polyester of the present embodiment described above has a nitrogen content of 15 to 100 mass ppm. Therefore, the retention stability is excellent. The reason is not clear, but it can be inferred as follows: the compound having a nitrogen atom such as the above-mentioned (N) component will end-cap the end of the liquid crystal polyester, thereby preventing the liquid crystal polyester from bonding to each other and thickening in the retained state of the liquid crystal polyester. In addition, if the nitrogen content of the liquid crystal polyester is within the above range, the compound having a nitrogen atom will not hinder the polymerization reaction, and a liquid crystal polyester with desired characteristics can be obtained.

The present invention has the following side profile.

"1". A liquid crystal polyester, wherein the nitrogen content is 15-100 mass ppm, preferably 15-50 mass ppm, more preferably 15-40 mass ppm, more preferably 15-35 mass ppm, and particularly preferably 15-30 mass ppm, and the melt viscosity after retention at 350°C for 30 seconds is preferably 350 Pa. s to 500 Pa. s, more preferably 400 Pa. s to 500 Pa. s, and more preferably 440 Pa. s to 500 Pa. s.

"2". The liquid crystal polyester as in "1", wherein the flow start temperature is preferably above 200°C, more preferably above 270°C and below 400°C, more preferably above 280°C and below 380°C, and particularly preferably above 300°C and below 350°C.

"3". A liquid crystal polyester as described in "1" or "2", comprising a constituent unit represented by the following formula (1) (hereinafter also referred to as constituent unit (1)), a constituent unit represented by the following formula (2) (hereinafter also referred to as constituent unit (2)) and a constituent unit represented by the following formula (3) (hereinafter also referred to as constituent unit (3)), and a compound containing a nitrogen atom is bonded to the end of the main chain.

(1)-O-Ar ¹ -CO-

(2) -O-Ar ² -O-

(3)-CO-Ar ³ -CO-

[In formula (1), Ar ¹ represents a phenylene group, a naphthylene group or a biphenylene group, and one or more hydrogen atoms in the above groups represented by Ar ¹ may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

In formula (2), ^Ar2 represents a phenylene group, a naphthylene group, a biphenylene group, or a group represented by the following formula (4). One or more hydrogen atoms contained in ^Ar2 may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

In formula (3), Ar ³ represents a phenylene group, a naphthylene group, a biphenylene group or a group represented by the following formula (4). One or more hydrogen atoms contained in Ar ³ may be substituted with a halogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

"4". A liquid crystal polyester as described in any one of "1" to "3", wherein a tablet-shaped molded body having a diameter of 1 cm and a thickness of 2.5 mm produced by hot pressing is melted at 350°C, and the melt viscosity after 30 seconds of retention and the melt viscosity after 10 minutes of retention are measured using a rheometer (manufactured by BOHLIN INSTRUMENTS, trade name: CVO rheometer), and the liquid crystal polyester has a viscosity ratio (melt viscosity after 30 seconds of retention/melt viscosity after 10 minutes of retention) of preferably less than 1.4, more preferably less than 1.3, more preferably less than 1.2, and particularly preferably less than 1.2.

(Molded product)

The molded product of this embodiment uses the above-mentioned liquid crystal polyester as a forming material.

Since the liquid crystal polyester composition containing the above-mentioned liquid crystal polyester is used for production, the retention stability is high and the occurrence of poor molding can be suppressed. In addition, the liquid crystal polyester composition preferably contains the above-mentioned liquid crystal polyester and inorganic fillers such as talc filler, titanium oxide filler, pigment, and glass fiber.

As the molding method of the molded product of this embodiment, the melt molding method is preferred, and examples thereof include injection molding method, T-mold method or inflation method, extrusion molding method, compression molding method, blow molding method, vacuum molding method, and press molding. Among them, the injection molding method is preferred.

Examples of molded parts include optical pickup bobbins, transformer bobbins, and other reels; relay housings, relay bases, relay sprues, relay armatures, and other relay parts; connectors such as RIMM, DDR, CPU sockets, S/O, DIMM, Board to Board connectors, FPC connectors, and card connectors; reflectors such as lamp reflectors and LED reflectors; mounts such as lamp holders and heater holders; diaphragms such as speaker diaphragms; printed wiring boards and printed circuit boards; separation plates such as separation plates for copiers and separation plates for printers; nail); camera module parts; switch parts; motor parts; sensor parts; hard disk drive parts; cooking utensils such as microwave ovens; vehicle parts; aircraft parts; and terminal components such as terminal components for semiconductor components and terminal components for coils.

In addition, other examples include separation nails, heater bases, and other parts related to photocopiers and printers; fan blades, fan gears, gears, bearings, motor parts, and housings; and automotive mechanical parts, fuel-related and exhaust systems. Various intake pipes, exhaust gas, cooling water, various oil temperature sensors, thermostat bases for air conditioners, motor insulators for air conditioners, brush holders for radiator motors, wiper motor related parts, distributors, starter switches, starter relays, transformer wiring harnesses, air conditioner switch substrates, fuel-related solenoid valve coils, fuse connectors, ECU connectors, speaker terminals, electrical parts insulation plates, lamp sockets, lamp reflectors, lamp covers, brake pistons, electromagnetic wire spools, engine oil filters, ignition device housings, etc. Vehicle-related parts; Cooking utensils such as microwave cooking pots and heat-resistant cooking utensils; heat-insulating or sound-insulating materials such as flooring materials and wall materials, supporting materials such as beams or columns, and roofing materials or civil engineering materials; parts for aircraft, spacecraft, and space machinery; radiation facility components such as atomic furnaces; marine facility components; cleaning jigs; optical machine parts; valves; pipes; nozzles; filters; membranes; medical machine parts and medical materials; sensor parts; public health equipment, sports equipment, and entertainment products, etc.

Since the molded product of this embodiment is produced by using a liquid crystal polyester composition containing the above-mentioned liquid crystal polyester with high retention stability, the occurrence of molding defects can be suppressed.

[Implementation example]

The following is a more specific description of the present invention through embodiments, but the present invention is not limited to the following embodiments.

<Manufacturing of liquid crystal polyester>

(Implementation Example 1)

Step (i):

In a 3L reactor equipped with a stirrer, a nitrogen inlet, a thermometer and a reflux cooler, 828.7g (6.0mol) of p-hydroxybenzoic acid, 372.4g (2.0mol) of 4,4'-dihydroxybiphenyl, 249.2g (1.5mol) of terephthalic acid, 83.1g (0.5mol) of isophthalic acid and 1123.0g (11mol) of acetic anhydride were placed. Then, 0.920g of 1-methylimidazole was added to the reactor in a diluted state of acetic acid (the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl was 766ppm). Then, the temperature was raised to 140°C under a nitrogen flow and the temperature was maintained, and the mixture was refluxed for 60 minutes.

Step (ii):

After the above step (i), while distilling off acetic acid and unreacted acetic anhydride, the temperature was raised to 300°C over 4 hours and 8 minutes, and the molten polymer A was taken out when the temperature reached 300°C.

The obtained molten polymer A (resin) was cooled to room temperature, crushed by a coarse crusher, and then heated from room temperature to 240°C in a nitrogen environment for 1 hour, and then heated from 240°C to 285°C in 7 hours and 30 minutes and maintained at 285°C for 5 hours, and polymerized in a solid phase. As a result, the liquid crystal polyester of Example 1 was obtained.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Example 1 using a polarizing microscope shows that a liquid crystal polyester having a melt phase with optical anisotropy is formed.

(Example 2)

Except for changing the addition amount of 1-methylimidazole diluted with acetic acid to 1.53g (relative to the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl is 1274ppm), the rest is the same as the above-mentioned Example 1 to obtain the liquid crystal polyester of Example 2.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Example 2 using a polarizing microscope shows that a liquid crystal polyester having a melt phase with optical anisotropy is formed.

(Implementation Example 3)

Except for changing the addition amount of 1-methylimidazole diluted with acetic acid to 0.612g (relative to the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl being 510ppm), the rest is the same as in the above-mentioned Example 1 to obtain the liquid crystal polyester of Example 3.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Example 3 using a polarizing microscope shows that a liquid crystal polyester having a melt phase with optical anisotropy is formed.

(Comparison Example 1)

Step (a):

In a 3L reactor equipped with a stirrer, a nitrogen inlet pipe, a thermometer and a reflux cooler, 828.7g (6.0mol) of p-hydroxybenzoic acid, 372.4g (2.0mol) of 4,4'-dihydroxybiphenyl, 249.2g (1.5mol) of terephthalic acid, 83.1g (0.5mol) of isophthalic acid and 1123.0g (11mol) of acetic anhydride were placed. Then, the temperature was raised to 140°C and maintained under a nitrogen flow, and the mixture was refluxed for 60 minutes.

Step (b):

After the above step (a), while distilling off acetic acid and unreacted acetic anhydride, the temperature was raised to 300°C over 4 hours and 8 minutes, and the molten polymer B was taken out when the temperature reached 300°C.

The obtained molten polymer B (resin) was cooled to room temperature, crushed by a coarse crusher, and then heated from room temperature to 240°C in 1 hour, and then heated from 240°C to 281°C in 6 hours and 50 minutes in a nitrogen environment, and maintained at 281°C for 5 hours to perform a polymerization reaction in a solid phase. The result was a liquid crystal polyester of Comparative Example 1.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Comparative Example 1 using a polarizing microscope is that a liquid crystal polyester with a melt phase having optical anisotropy is formed.

(Comparison Example 2)

Except that the amount of 1-methylimidazole diluted with acetic acid was changed to 0.383 g (relative to the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl being 319 ppm), the rest was the same as the molten polymer A in the above-mentioned Example 1 to obtain molten polymer C.

The obtained molten polymer C (resin) was cooled to room temperature, crushed by a coarse crusher, and then heated from room temperature to 240°C in 1 hour, and then heated from 240°C to 283°C in 7 hours and 10 minutes in a nitrogen environment, and maintained at 283°C for 5 hours to perform a polymerization reaction in a solid phase. The result was the liquid crystal polyester of Comparative Example 2.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Comparative Example 2 using a polarizing microscope is that a liquid crystal polyester with a melt phase having optical anisotropy is formed.

(Comparison Example 3)

Step (c):

In a 3L reactor equipped with a stirrer, a nitrogen inlet, a thermometer, and a reflux cooler, 828.7g (6.0mol) of p-hydroxybenzoic acid, 372.4g (2.0mol) of 4,4'-dihydroxybiphenyl, 249.2g (1.5mol) of terephthalic acid, 83.1g (0.5mol) of isophthalic acid, and 1123.0g (11mol) of acetic anhydride were placed. Then, 0.153g of 1-methylimidazole (127ppm relative to the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl) was added to the reactor in a diluted state of acetic acid. Then, the temperature was raised to 140°C under a nitrogen flow and the temperature was maintained, and the mixture was refluxed for 60 minutes.

Step (d):

After the above step (c), 0.765 g of 1-methylimidazole was added in a diluted state of acetic acid (relative to the total mass of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl was 637 ppm). While diluting out acetic acid and unreacted acetic anhydride, the temperature was raised to 300°C over 4 hours and 8 minutes, and the molten polymer D was taken out when it reached 300°C.

The obtained molten polymer D (resin) was cooled to room temperature, crushed by a coarse crusher, and then heated from room temperature to 240°C in 1 hour, and then heated from 240°C to 283°C in 7 hours and 10 minutes in a nitrogen environment, and maintained at 283°C for 5 hours, and polymerized in a solid phase. The result was the liquid crystal polyester of Comparative Example 3.

The result of measuring the liquid crystallinity of the liquid crystal polyester of Comparative Example 3 using a polarizing microscope is that a liquid crystal polyester with a melt phase having optical anisotropy is formed.

The addition amount of the (N) component in each of the above-mentioned liquid crystal polyesters is shown in Tables 1 and 2.

[Evaluation of nitrogen content in resin]

For each liquid crystal polyester, according to JIS-2609: Crude oil and petroleum products - Nitrogen content test method, chemical luminescence method, using a micro-total nitrogen analyzer (Mitsubishi Chemical Analytech, TN-2100H), the liquid crystal polyester was thermally decomposed under the flow of argon gas, and then the nitrogen monoxide generated by oxygen combustion oxidation was oxidized with ozone gas under dehydration conditions, and the luminescence intensity at a wavelength of 590~2500nm was measured and detected. The nitrogen content (nitrogen content) was calculated from the area value of the luminescence intensity. The results are shown in Table 3.

[Evaluation of flow start temperature]

The flow start temperature of each liquid crystal polyester was evaluated using a rheometer (manufactured by Shimadzu Corporation, CFT-500 model). Specifically, about 2 g of the liquid crystal polyester of each example was filled in a capillary rheometer equipped with a die nozzle with an inner diameter of 1 mm and a length of 10 mm. Next, for each filled liquid crystal polyester, when it was extruded from the nozzle of the rheometer at a temperature increase rate of 4°C/min and a load of 9.8 MPa (100 kg/ ^cm2 ), the temperature at which the melt viscosity was 4800 Pa.s (48000 poise) was set as the flow start temperature. The results are shown in Table 3.

[Evaluation of melt viscosity]

The liquid crystal polyester of each example was heat-pressed to obtain a tablet-shaped molded product with a diameter of 1 cm and a thickness of 2.5 mm. The tablet-shaped molded product was melted at 350°C using a rheometer (manufactured by BOHLIN INSTRUMENTS, trade name: CVO Rheometer), and the melt viscosity after retention for 30 seconds and after retention for 10 minutes was measured. The results are shown in Table 3.

From the results shown in Table 3, it can be confirmed that the viscosity ratio (after 10 minutes/after 30 seconds) of the liquid crystal polyester of the embodiment with a nitrogen content of 15 to 100 mass ppm is smaller than that of the liquid crystal polyester of the comparative example, so the retention stability is excellent.

In the liquid crystal polyester of Comparative Example 3, although the amount of component (N) added in step (d) (equivalent to the ester exchange reaction step (ii) in this embodiment) is large, the nitrogen content is less than 15 mass ppm. This is speculated as follows: in step (d), when the by-product fatty acid and the unreacted fatty acid anhydride are evaporated and distilled out of the reaction system, the component (N) is also distilled out of the reaction system at the same time.

From the above content, it can be confirmed that the liquid crystal polyester of this embodiment has excellent retention stability.

The above is an explanation of the preferred embodiments of the present invention, but the present invention is not limited to such embodiments. Additions, omissions, substitutions and other changes in the structure can be made within the scope of the purpose of the present invention. The present invention is not limited by the above description, but only by the scope of the attached patent application.

Claims (5)

A method for preparing a liquid crystal polyester comprises the following steps (i) and (ii), wherein the step (i) comprises acylation of an aromatic hydroxycarboxylic acid represented by the following formula (I) and an aromatic diol represented by the following formula (II) with a fatty acid anhydride having a carbon number of 9 or less to obtain an acylated product, wherein the component (N) is a heterocyclic organic base compound containing a nitrogen atom; and the step (ii) comprises ester exchange of the acylated product with an aromatic dicarboxylic acid represented by the following formula (III) to obtain a liquid crystal polyester; wherein the step (i) comprises performing the acylation operation in a manner that the amount of the component (N) used is set to be more than 350 mass ppm and less than 1500 mass ppm relative to the total mass of the aromatic hydroxycarboxylic acid and the aromatic diol, wherein the HO-Ar ¹ -COOH…(I) HO-Ar ² -OH...(II) HOOC-Ar ³ -COOH...(III) [wherein, Ar ¹ and Ar ³ each independently represent an arylene group which may be substituted, and Ar ² represents an arylene group which may be substituted or a divalent linking group represented by the following formula (IV)]

[wherein, ^R1 and ^R2 each independently represent a hydrogen atom, a halogen atom, an acyloxy group having 1 to 6 carbon atoms or an alkyl group having 1 to 6 carbon atoms, and X represents -O-, -S-, _-SO2- , -CO-, _-C6H10- or an _alkylene group]. The method for producing a liquid crystal polyester according to claim 1, wherein the component (N) is an imidazole compound represented by the following formula (N-1),

[wherein, ^Rn1 to ^Rn4 independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a hydroxymethyl group, a cyanoalkyl group having 2 to 5 carbon atoms, a cyanoalkoxy group having 2 to 5 carbon atoms, a carboxyl group, an amino group, an aminoalkyl group having 1 to 4 carbon atoms, an aminoalkoxy group having 1 to 4 carbon atoms, a phenyl group, a benzyl group, a phenylpropyl group or a formyl group]. A method for producing a liquid crystal polyester as claimed in claim 1 or 2, wherein in the aforementioned step (i), the amount of aromatic hydroxycarboxylic acid (I) used is 30-80 mol% relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II) and aromatic dicarboxylic acid (III). A method for producing a liquid crystal polyester as claimed in claim 1 or 2, wherein in the aforementioned step (i), the amount of aromatic diol (II) used is 10-35 mol% relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II) and aromatic dicarboxylic acid (III). A method for producing a liquid crystal polyester as claimed in claim 1 or 2, wherein in the aforementioned step (ii), the amount of aromatic dicarboxylic acid (III) used is 10-35 mol% relative to the total amount of aromatic hydroxycarboxylic acid (I), aromatic diol (II) and aromatic dicarboxylic acid (III).