JP6651383B2 - Method for producing liquid crystal polyester - Google Patents

Description

  The present invention relates to a method for producing a liquid crystal polyester and a catalyst for polycondensation during the production of a liquid crystal polyester.

  Liquid crystal polyester resins that exhibit liquid crystallinity when melted are used in various application fields because of their excellent heat resistance and workability. The liquid crystal polyester is obtained, for example, by polycondensing a derivative of a corresponding monomer such as an aromatic hydroxycarboxylic acid, an aromatic diol, an aromatic dicarboxylic acid, or an ester compound thereof.

  In the polycondensation reaction, when the monomer is a compound in which the reactive group is a phenolic hydroxyl group, such as hydroxycarboxylic acid or aromatic diol, the reactivity may be low and the reaction conversion may not easily increase. Therefore, when such a compound is used as a starting material (raw material), the phenolic hydroxyl group of these compounds is reacted with a fatty acid anhydride prior to polycondensation in order to increase the reactivity, and the phenolic hydroxyl group is reacted. , And a production method of polycondensing an acylated product is known. Further, in order to shorten the reaction time, studies have been made to carry out the reaction in the presence of a catalyst (for example, see Patent Documents 1 and 2).

JP 2003-183373 A JP 2002-146003 A

A common requirement for liquid crystal polyesters is low cost. However, since the raw material of the liquid crystal polyester is usually determined according to the desired physical properties, it is generally difficult to reduce the cost by changing the raw material. Under such circumstances, in order to reduce the cost of the liquid crystal polyester, it is important to rely on a reduction in energy cost due to a lower reaction temperature and an increase in the production amount per unit time due to a reduction in the reaction time.
There is also a need for a liquid crystal polyester product having high whiteness and reduced coloring due to heating.
Under the circumstances described above, in the production of liquid crystal polyester, further reduction in reaction time and reduction in reaction temperature are required.

  The present invention has been made in view of the above problems, and can be used in a method for producing a liquid crystal polyester and a method for producing a liquid crystal polyester, which can shorten the reaction time or lower the reaction temperature. It is intended to provide a catalyst.

  The present inventors have found that the above problem can be solved by the presence of an imidazole compound having a specific structure when polycondensing a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group. Was completed. Specifically, the present invention provides the following.

（式（１）中、Ｒ^１はそれぞれ独立に水素原子もしくは１価の有機基を表し、Ｒ^２は置換基を有してもよい芳香族基を表し、Ｒ^３はそれぞれ独立にハロゲン原子、水酸基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホナト基、又は有機基を表し、ｎは０〜３の整数を表す。前記Ｒ^１は他方のＲ^１又はＲ^２と結合して環状構造を形成してもよい。）
で表されるイミダゾール化合物の存在下で行う、液晶ポリエステルの製造方法である。 The first aspect of the present invention,
A method for producing a liquid crystal polyester, comprising polycondensing a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group,
The polycondensation is performed by the following formula (1):

(In formula (1), R ¹ each independently represents a hydrogen atom or a monovalent organic group, R ² represents an aromatic group which may have a substituent, R ³ each independently represents a halogen atom, A hydroxyl group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonate group, or an organic group, and n represents an integer of 0 to 3. ¹ may combine with the other R ¹ or R ² to form a cyclic structure.)
This is a method for producing a liquid crystal polyester carried out in the presence of an imidazole compound represented by the following formula:

（式（１）中、Ｒ^１はそれぞれ独立に水素原子もしくは１価の有機基を表し、Ｒ^２は置換基を有してもよい芳香族基を表し、Ｒ^３はそれぞれ独立にハロゲン原子、水酸基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホナト基、又は有機基を表し、ｎは０〜３の整数を表す。前記Ｒ^１は他方のＲ^１又はＲ^２と結合して環状構造を形成してもよい。）
で表されるイミダゾール化合物を含む、液晶ポリエステル製造時の重縮合用の触媒である。 According to a second aspect of the present invention, there is provided a compound represented by the following formula (1):

(In formula (1), R ¹ each independently represents a hydrogen atom or a monovalent organic group, R ² represents an aromatic group which may have a substituent, R ³ each independently represents a halogen atom, A hydroxyl group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonate group, or an organic group, and n represents an integer of 0 to 3. ¹ may combine with the other R ¹ or R ² to form a cyclic structure.)
It is a catalyst for polycondensation at the time of producing a liquid crystal polyester, containing the imidazole compound represented by

  Advantageous Effects of Invention According to the present invention, it is possible to provide a method for producing a liquid crystal polyester, which can shorten the reaction time or lower the reaction temperature, and a catalyst suitably used in the method for producing a liquid crystal polyester.

製造 Production method of liquid crystal polyester ポ リ エ ス テ ル
In the invention described in this specification, a liquid crystal polyester is obtained by polycondensing a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group in the presence of an imidazole compound having a specific structure described below. To manufacture.
Hereinafter, the manufacturing process of the imidazole compound, the monomer mixture (A) and the liquid crystal polyester will be described.

<Imidazole compound>
The imidazole compound used as a catalyst in the method for producing a liquid crystal polyester will be described. The imidazole compound is a compound represented by the following formula (1). Hereinafter, the compound represented by the following formula (1) is also simply referred to as “imidazole compound”.

（式（１）中、Ｒ^１はそれぞれ独立に水素原子もしくは１価の有機基を表し、Ｒ^２は置換基を有してもよい芳香族基を表し、Ｒ^３はそれぞれ独立にハロゲン原子、ヒドロキシ基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホナト基、又は有機基を表し、ｎは０〜３の整数を表す。前記Ｒ^１は他方のＲ^１又はＲ^２と結合して環状構造を形成してもよい。）

(In formula (1), R ¹ each independently represents a hydrogen atom or a monovalent organic group, R ² represents an aromatic group which may have a substituent, R ³ each independently represents a halogen atom, And represents a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonate group, or an organic group, and n represents an integer of 0 to 3. R ¹ may combine with the other R ¹ or R ² to form a cyclic structure.)

The imidazole compound catalyzes esterification by elimination of an acid generated between an acyloxy group and a carboxy group in a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group.
For this reason, by using the above-mentioned imidazole compound, the polycondensation at the time of producing the liquid crystal polymer can be reduced in temperature and / or time.

First, if the polycondensation is carried out at a low temperature and / or for a short time, the consumption of fuel, electric power and the like is naturally reduced, which is advantageous in energy consumption.
The liquid crystal polyester is usually produced by a batch reaction. When the polycondensation reaction is shortened, the time required for one batch is reduced, thereby increasing the number of reaction batches per unit time (for example, times / day). As a result, the production amount of the liquid crystal polyester per unit time increases, and the production cost of the liquid crystal polyester can be reduced.

  Further, for example, if a prepolymer to be subjected to solid-state polymerization by melt polycondensation at a low temperature is produced, coloring of the prepolymer is suppressed. By performing solid-phase polymerization using such a prepolymer in which coloring is suppressed, a liquid crystal polyester having high whiteness and less coloring can be obtained.

In the formula (1), R ¹ is a hydrogen atom or a monovalent organic group. The monovalent organic group is not particularly limited, and may be, for example, an alkyl group which may have a substituent, an aromatic group which may have a substituent, and the like. When R ¹ is an alkyl group, the alkyl group may have an ester bond or the like in the chain.

The alkyl groups may be the same as R ⁴ or the like for example in the below equation (1a). The number of carbon atoms of the alkyl group is preferably 1 to 40, more preferably 1 to 30, particularly preferably 1 to 20, and most preferably 1 to 10.
The substituent that the alkyl group may have may be, for example, the same as the substituent that the alkylene group represented by R ⁵ in formula (1a) described below may have.

The aromatic group which may have a substituent group, is the same as R ² in formula (1a) will be described later, the aryl group is preferably a phenyl group is more preferable. The aromatic group which may have a substituent as R ¹ may be the same as or different from R ² .
In the formula (1), one R ¹ is preferably a hydrogen atom, and one R ¹ is a hydrogen atom and the other R ¹ has an alkyl group or a substituent which may have a substituent. More preferably, it is a good aromatic group.
In the formula (1), R ¹ may combine with the other R ¹ or R ² to form a cyclic structure. For example, when at least one R ¹ is an alkyl group which may have a substituent, R ¹ may combine with the other R ¹ or R ² to form a cyclic structure.

  The imidazole compound may be a compound represented by the following formula (1a).

（式（１ａ）中、Ｒ^４は水素原子又はアルキル基であり、Ｒ^２は置換基を有してもよい芳香族基であり、Ｒ^５は置換基を有してもよいアルキレン基であり、Ｒ^３は、ハロゲン原子、ヒドロキシ基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホナト基、又は有機基であり、ｎは０〜３の整数である。Ｒ^５はＲ^２と結合して環状構造を形成してもよい。）

(In the formula (1a), R ⁴ is a hydrogen atom or an alkyl group, R ² is an aromatic group which may have a substituent, and R ⁵ is an alkylene group which may have a substituent. , R ³ are a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonat group, or an organic group; An integer of from 3 to 3. R ⁵ may combine with R ² to form a cyclic structure.)

In the formula (1a), R ⁴ is a hydrogen atom or an alkyl group. When R ⁴ is an alkyl group, the alkyl group may be a straight-chain alkyl group or a branched-chain alkyl group. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 20, preferably 1 to 10, and more preferably 1 to 5.

Specific examples of the alkyl group suitable as R ⁴ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, Isopentyl group, tert-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethyl-n-hexyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl Group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, and n-icosyl group.

In the formula (1a), R ² is an aromatic group which may have a substituent. The aromatic group which may have a substituent may be an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.

  The type of the aromatic hydrocarbon group is not particularly limited as long as the object of the present invention is not hindered. The aromatic hydrocarbon group may be a monocyclic aromatic group, may be formed by condensing two or more aromatic hydrocarbon groups, or may be two or more aromatic hydrocarbon groups. May be formed by bonding with a single bond. As the aromatic hydrocarbon group, a phenyl group, a naphthyl group, a biphenylyl group, an anthryl group, and a phenanthrenyl group are preferable.

  The kind of the aromatic heterocyclic group is not particularly limited as long as the object of the present invention is not hindered. The aromatic heterocyclic group may be a monocyclic group or a polycyclic group. As the aromatic heterocyclic group, a pyridyl group, a furyl group, a thienyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, a thiazolyl group, an isoxazolyl group, an isothiazolyl group, a benzoxazolyl group, a benzothiazolyl group, and a benzimidazolyl group are preferable.

  Examples of the substituent which the phenyl group, polycyclic aromatic hydrocarbon group, or aromatic heterocyclic group may have include a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, and a nitroso group. Group, a sulfino group, a sulfo group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphono group, a phosphonate group, an amino group, an ammonium group, and an organic group. When a phenyl group, a polycyclic aromatic hydrocarbon group, or an aromatic heterocyclic group has a plurality of substituents, the plurality of substituents may be the same or different.

  When the substituent of the aromatic group is an organic group, examples of the organic group include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an aralkyl group. This organic group may include a bond or a substituent other than a hydrocarbon group such as a hetero atom in the organic group. The organic group may be linear, branched, cyclic, or a combination of these structures. This organic group is usually monovalent, but may be a divalent or higher organic group when a cyclic structure is formed.

  When an aromatic group has a substituent on an adjacent carbon atom, the two substituents attached on the adjacent carbon atom may combine to form a cyclic structure. Examples of the cyclic structure include an aliphatic hydrocarbon ring and an aliphatic ring containing a hetero atom.

  When the substituent of the aromatic group is an organic group, the bond contained in the organic group is not particularly limited as long as the effects of the present invention are not impaired, and the organic group may be an oxygen atom, a nitrogen atom, a silicon atom, or the like. May be included. Specific examples of the bond containing a hetero atom include an ether bond, a thioether bond, a carbonyl bond, a thiocarbonyl bond, an ester bond, an amide bond, a urethane bond, an imino bond (-N = C (-R)-, -C (= NR)-: R represents a hydrogen atom or an organic group), a carbonate bond, a sulfonyl bond, a sulfinyl bond, an azo bond and the like.

  As the bond containing a hetero atom that the organic group may have, an ether bond, a thioether bond, a carbonyl bond, and a thiocarbonyl bond from the viewpoint of the heat resistance of the imidazole compound represented by the formula (1) or (1a). , An ester bond, an amide bond, an amino bond (-NR-: R represents a hydrogen atom or a monovalent organic group), a urethane bond, an imino bond (-N = C (-R)-, -C (= NR)- : R represents a hydrogen atom or a monovalent organic group), a carbonate bond, a sulfonyl bond, and a sulfinyl bond.

  When the organic group is a substituent other than a hydrocarbon group, the type of the substituent other than the hydrocarbon group is not particularly limited as long as the object of the present invention is not hindered. Specific examples of the substituent other than a hydrocarbon group include a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a cyano group, an isocyano group, a cyanato group, an isocyanato group, a thiocyanato group, an isothiocyanato group, a silyl group, a silanol group, and an alkoxy group. Group, alkoxycarbonyl group, amino group, monoalkylamino group, dialkylaluminum group, monoarylamino group, diarylamino group, carbamoyl group, thiocarbamoyl group, nitro group, nitroso group, carboxylate group, acyl group, acyloxy group, Examples thereof include a sulfino group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonate group, an alkyl ether group, an alkenyl ether group, an alkylthio ether group, an alkenyl thioether group, an aryl ether group, and an aryl thioether group. The hydrogen atom contained in the above substituent may be substituted by a hydrocarbon group. Further, the hydrocarbon group contained in the substituent may be any of linear, branched, and cyclic.

  Examples of the substituent of the phenyl group, the polycyclic aromatic hydrocarbon group, or the aromatic heterocyclic group include an alkyl group having 1 to 12 carbon atoms, an aryl group having 1 to 12 carbon atoms, and 1 to 12 carbon atoms. Are preferred, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 1 to 12 carbon atoms, an arylamino group having 1 to 12 carbon atoms, and a halogen atom.

As R ² , an imidazole compound represented by the formula (1) or the formula (1a) can be easily synthesized at low cost and the solubility of the imidazole compound in water or an organic solvent is good. Preferred are a phenyl group, a furyl group and a thienyl group.

In the formula (1a), R ⁵ is an alkylene group which may have a substituent. The substituent that the alkylene group may have is not particularly limited as long as the object of the present invention is not impaired. Specific examples of the substituent which the alkylene group may have include a hydroxy group, an alkoxy group, an amino group, a cyano group, and a halogen atom. The alkylene group may be a straight-chain alkylene group or a branched-chain alkylene group, and is preferably a straight-chain alkylene group. The number of carbon atoms of the alkylene group is not particularly limited, preferably 1 to 20, more preferably 1 to 10, and particularly preferably 1 to 5. Note that the number of carbon atoms of the alkylene group does not include the carbon atoms of the substituents bonded to the alkylene group.

  The alkoxy group as a substituent bonded to the alkylene group may be a straight-chain alkoxy group or a branched-chain alkoxy group. The number of carbon atoms of the alkoxy group as a substituent is not particularly limited, and is preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 3.

  The amino group as a substituent bonded to the alkylene group may be a monoalkylamino group or a dialkylamino group. The alkyl group contained in the monoalkylamino group or the dialkylamino group may be a linear alkyl group or a branched alkyl group. The number of carbon atoms of the alkyl group contained in the monoalkylamino group or the dialkylamino group is not particularly limited, and is preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 3.

Specific examples of suitable alkylene groups as R ⁵ are methylene, ethane-1,2-diyl group, n- propane-1,3-diyl group, n- propane-2,2-diyl group, n- butane -1,4-diyl group, n-pentane-1,5-diyl group, n-hexane-1,6-diyl group, n-heptane-1,7-diyl group, n-octane-1,8-diyl Group, n-nonane-1,9-diyl group, n-decane-1,10-diyl group, n-undecane-1,11-diyl group, n-dodecane-1,12-diyl group, n-tridecane- 1,13-diyl group, n-tetradecane-1,14-diyl group, n-pentadecane-1,15-diyl group, n-hexadecane-1,16-diyl group, n-heptadecane-1,17-diyl group N-octadecane-1,18-diyl group, n -Nonadecane-l, 19-diyl group and n-icosane-l, 20-diyl group.

R ³ is a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonat group, or an organic group; It is an integer of 3. When n is an integer of 2 to 3, a plurality of R ³ may be the same or different.

When R ³ is an organic group, the organic group is the same as R ² for the organic group which the aromatic group may have as a substituent.

When R ³ is an organic group, the organic group is preferably an alkyl group, an aromatic hydrocarbon group, or an aromatic heterocyclic group. As the alkyl group, a linear or branched alkyl group having 1 to 8 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, and an isopropyl group are more preferable. As the aromatic hydrocarbon group, a phenyl group, a naphthyl group, a biphenylyl group, an anthryl group, and a phenanthrenyl group are preferable, a phenyl group and a naphthyl group are more preferable, and a phenyl group is particularly preferable. As the aromatic heterocyclic group, a pyridyl group, a furyl group, a thienyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, a thiazolyl group, an isoxazolyl group, an isothiazolyl group, a benzoxazolyl group, a benzothiazolyl group, and a benzimidazolyl group are preferable. A furyl group and a thienyl group are more preferred.

When R ³ is an alkyl group, the bonding position of the alkyl group on the imidazole ring is preferably any of 2-position, 4-position, and 5-position, and more preferably 2-position. When R ³ is an aromatic hydrocarbon group or an aromatic heterocyclic group, the bonding position of these groups on imidazole is preferably the 2-position.

  Among the imidazole compounds represented by the above formula (1), compounds represented by the following formula (1-1a) are preferable because they can be easily synthesized at low cost.

（式（１−１ａ）中、Ｒ^１、Ｒ^３及びｎは、式（１）と同じであり、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０は、それぞれ独立に、水素原子、ハロゲン原子、ヒドロキシ基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルフィノ基、スルホ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホノ基、ホスホナト基、アミノ基、アンモニオ基、又は有機基である。ただし、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０のうち少なくとも１つは水素原子以外の基である。Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０のうち少なくとも２つが結合して環状構造を形成してもよい。Ｒ^１はＲ^８と結合して環状構造を形成してもよい。）

(In the formula (1-1a), R ¹ , R ³ and n are the same as those in the formula (1), and R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom , Halogen atom, hydroxy group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfino group, sulfo group, sulfonato group, phosphino group, phosphinyl group, phosphono group, phosphonate group, amino group, ammonium A group or an organic group, provided that at least one of R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ is a group other than a hydrogen atom, and R ⁶ , R ⁷ , R ⁸ , and R ⁹ , And R ¹⁰ may combine to form a cyclic structure. R ¹ may combine with R ⁸ to form a cyclic structure.)

R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are the same as in the formula (1-1) described later. In the formula (1-1a), R ¹ may be bonded to R ⁸ to form a cyclic structure. For example, when R ¹ is an alkyl group which may have a substituent, R ¹ is R ^{1 It} may combine with ⁸ to form a cyclic structure.

Among the imidazole compounds represented by the above formula (1a) or formula (1-1a), the following formula (1-1) can be easily synthesized at low cost and has excellent solubility in water and organic solvents. Is preferable, and a compound represented by the formula (1-1), wherein R ³ is a methylene group, is more preferable.

（式（１−１）中、Ｒ^３、Ｒ^４、Ｒ^５、及びｎは、式（１ａ）と同様であり、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０は、それぞれ独立に、水素原子、ハロゲン原子、ヒドロキシ基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルフィノ基、スルホ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホノ基、ホスホナト基、アミノ基、アンモニオ基、又は有機基である。ただし、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０のうち少なくとも１つは水素原子以外の基である。Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、及びＲ^１０のうち少なくとも２つが結合して環状構造を形成してもよい。Ｒ^５はＲ^８と結合して環状構造を形成してもよい。）

(In Formula (1-1), R ³ , R ⁴ , R ⁵ , and n are the same as in Formula (1a), and R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are each independently A hydrogen atom, a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfino group, a sulfo group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphono group, a phosphonate group, amino group, ammonio group, or an organic group. ^{However, R 6, R 7, R} 8, R 9, and ^{.R 6, R} 7, at least one is a group other than a hydrogen atom of ^{R 10,} R ^At least two of R ⁸ , R ⁹ and R ¹⁰ may combine to form a cyclic structure. R ⁵ may combine with R ⁸ to form a cyclic structure.)

When R ⁶ , R ⁷ , R ⁸ , R ⁸⁹ , and R ¹⁰ are organic groups, the organic groups are the same as the organic groups that R ² in Formula (1a) has as a substituent. R ⁶ , R ⁷ , R ⁸ , and R ⁹ are preferably hydrogen atoms from the viewpoint of solubility of the imidazole compound in the solvent.

Among them, at least one of R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ is preferably the following substituent, and R ¹⁰ is particularly preferably the following substituent. When R ¹⁰ is the following substituent, R ⁶ , R ⁶⁷ , R ⁸ , and R ⁹ are preferably a hydrogen atom.
-OR ¹¹
(R ¹¹ is a hydrogen atom or an organic group.)

When R ¹¹ is an organic group, the organic group is the same as the organic group that R ² in Formula (1a) has as a substituent. R ¹¹ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.

（式（１−１−１）において、Ｒ^３、Ｒ^４、及びｎは、式（１ａ）と同様であり、Ｒ^１２、Ｒ^１３、Ｒ^１４、Ｒ^１５、及びＲ^１６は、それぞれ独立に、水素原子、ヒドロキシ基、メルカプト基、スルフィド基、シリル基、シラノール基、ニトロ基、ニトロソ基、スルフィノ基、スルホ基、スルホナト基、ホスフィノ基、ホスフィニル基、ホスホノ基、ホスホナト基、アミノ基、アンモニオ基、又は有機基である。ただし、Ｒ^１２、Ｒ^１３、Ｒ^１４、Ｒ^１５、及びＲ^１６のうち少なくとも１つは水素原子以外の基である。） Among the compounds represented by the formula (1-1), a compound represented by the following formula (1-1-1) is preferable.

(In Formula (1-1-1), R ³ , R ⁴ , and n are the same as in Formula (1a), and R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and R ¹⁶ are each independently , Hydrogen atom, hydroxy group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfino group, sulfo group, sulfonato group, phosphino group, phosphinyl group, phosphono group, phosphonate group, amino group, ammonium Or at least one of R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and R ¹⁶ is a group other than a hydrogen atom.)

Among the compounds represented by the formula (1-1-1), at least one of R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and R ¹⁶ is a group represented by the above-described —O—R ^11. It is particularly preferred that R ¹⁶ is a group represented by —O—R ¹¹ . When R ¹⁶ is a group represented by —O—R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are preferably a hydrogen atom.

The method for synthesizing the imidazole compound represented by the above formula (1) is not particularly limited. For example, a halide represented by R ² CR ¹ (Hal) R ¹ (R ¹ and R ² are the same as in the formula (1), and Hal is a halogen atom); The imidazole compound represented by the above formula (1) can be synthesized by reacting the imidazole compound represented by the formula (1) with imidazolylation by a conventional method.

  The method for synthesizing the imidazole compound represented by the above formula (1a) is not particularly limited. For example, by reacting a halogen-containing carboxylic acid derivative represented by the following formula (I) with an imidazole compound represented by the following formula (II) according to a conventional method to perform imidazolylation, the above-mentioned formula (1a) Can be synthesized.

（式（Ｉ）及び式（ＩＩ）中、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５及びｎは、式（１ａ）と同様である。式（Ｉ）において、Ｈａｌはハロゲン原子である。）

(In the formulas (I) and (II), R ² , R ³ , R ⁴ , R ⁵ and n are the same as those in the formula (1a). In the formula (I), Hal is a halogen atom.)

In addition, when the imidazole compound is a compound represented by the formula (1a) and R ⁵ is a methylene group, that is, when the imidazole compound is a compound represented by the following formula (1-2), An imidazole compound can also be synthesized by the method based on the Michael addition reaction described.

（式（１−２）中、Ｒ^２、Ｒ^３、Ｒ^４及びｎは、式（１ａ）と同様である。）

(In the formula (1-2), R ² , R ³ , R ⁴ and n are the same as in the formula (1a).)

  Specifically, for example, mixing a 3-substituted acrylic acid derivative represented by the following formula (III) and an imidazole compound represented by the above formula (II) in a solvent to cause a Michael addition reaction. As a result, an imidazole compound represented by the above formula (1-2) is obtained.

（式（ＩＩＩ）中、Ｒ^２、及びＲ^４は、式（１ａ）と同様である。）

(In the formula (III), R ² and R ⁴ are the same as in the formula (1a).)

  Further, an imidazole compound represented by the following formula (1-3) is obtained by adding a 3-substituted acrylic acid derivative containing an imidazolyl group represented by the following formula (IV) to a solvent containing water. .

（式（ＩＶ）及び式（１−３）中、Ｒ^２、Ｒ^４及びｎは、式（１）と同様である。）

(In the formula (IV) and the formula (1-3), R ² , R ⁴ and n are the same as in the formula (1).)

  In this case, the imidazole compound represented by the above formula (II) and the 3-substituted acrylic acid represented by the following formula (V) are obtained by hydrolysis of the 3-substituted acrylic acid derivative represented by the above formula (IV). And generate. Then, a Michael addition reaction occurs between the 3-substituted acrylic acid represented by the following formula (V) and the imidazole compound represented by the above formula (II), and is represented by the above formula (1-3) An imidazole compound is formed.

（式（Ｖ）中、Ｒ^２は、式（１ａ）と同様である。）

(In the formula (V), R ² is the same as in the formula (1a).)

Preferred specific examples of the imidazole compound represented by the formula (1) or (1a) include the following.

  The amount of the imidazole compound used is not particularly limited. The amount of the imidazole compound used is preferably from 0.001 part by mass to 1 part by mass based on 100 parts by mass of the monomer mixture (A). The lower limit of the amount of the imidazole compound used is more preferably 0.002 parts by mass or more based on 100 parts by mass of the monomer mixture (A). The upper limit of the amount of the imidazole compound used is more preferably 0.8 parts by mass or less based on 100 parts by mass of the monomer mixture (A). That is, the content is more preferably 0.002 parts by mass or more and 0.8 parts by mass or less.

  If the amount of the imidazole compound is too small, it may be difficult to obtain a desired effect by using a catalyst. If the amount of the imidazole compound is too large, the resulting liquid crystal polyester may be colored, or the reaction rate of the melt polycondensation may be too fast to control the polymerization.

The polycondensation may be performed in the presence of another catalyst in addition to the imidazole compound. Examples of other catalysts include magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, metal compounds such as antimony trioxide, and nitrogen-containing heterocyclic compounds such as 1-methylimidazole Is mentioned.
The amount of the other catalyst used is preferably 0.1 part by mass or less based on 100 parts by mass of the monomer mixture (A).

<Monomer mixture (A)>
The monomer mixture (A) is a mixture of monomers including an acylated monomer having a phenolic hydroxyl group. The monomer mixture (A) may contain a monomer having no phenolic hydroxyl group, such as an aromatic dicarboxylic acid represented by terephthalic acid.

  For example, p-acetoxybenzoic acid or a phenolic hydroxyl group-acylated monomer such as hydroquinone diacetate is prepared in advance, and then the phenolic hydroxyl group-acylated monomer is mixed with another monomer to form a phenolic hydroxyl group. A monomer mixture (A) containing an acylated product of a monomer having a hydroxyl group can be prepared.

  However, in terms of cost and production time, the method of acylating the monomer mixture (B) containing a monomer having a phenolic hydroxyl group to obtain a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group is more preferable. It is extremely advantageous over the above method.

As the repeating unit constituting the liquid crystal polyester, an aromatic oxycarbonyl repeating unit, an aromatic dicarbonyl repeating unit, an aromatic dioxy repeating unit, an aromatic aminooxy repeating unit, an aromatic diamino repeating unit, an aromatic aminocarbonyl repeating unit, Examples thereof include an aromatic oxydicarbonyl repeating unit and an aliphatic dioxy repeating unit.
In this specification, the liquid crystal polyester includes a liquid crystal polymer including an amide bond and a thioester bond in addition to the ester bond.

Monomers that provide aromatic oxycarbonyl repeat units are aromatic hydroxycarboxylic acids.
Preferred specific examples of the aromatic hydroxycarboxylic acid include p-hydroxybenzoic acid, m-hydroxybenzoic acid, o-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 5-hydroxy-2-naphthoic acid, -Hydroxy-2-naphthoic acid, 4'-hydroxyphenyl-4-benzoic acid, 3'-hydroxyphenyl-4-benzoic acid, 4'-hydroxyphenyl-3-benzoic acid, alkyl, alkoxy or halogen-substituted products thereof Is mentioned.
Ester-forming derivatives such as ester derivatives of aromatic hydroxycarboxylic acids and acid halides can also be suitably used as monomers for producing liquid crystal polyesters.
Among them, p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferable because the properties and melting point of the liquid crystal polyester obtained can be easily adjusted.

The monomer that provides the aromatic dicarbonyl repeat unit is an aromatic dicarboxylic acid.
Preferred specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, And aromatic dicarboxylic acids such as 4,4'-dicarboxybiphenyl, and alkyl, alkoxy or halogen substituted products thereof.
Ester-forming derivatives such as ester derivatives of aromatic dicarboxylic acids and acid halides can also be suitably used as monomers for producing liquid crystal polyesters.
Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferred because the mechanical properties, heat resistance, melting point temperature and moldability of the resulting liquid crystal polyester can be easily adjusted to appropriate levels.

Monomers that provide aromatic dioxy repeat units are aromatic diols.
Preferred specific examples of the aromatic diol include hydroquinone, resorcin, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, and 4,4′-dihydroxybiphenyl. , 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl ether, and alkyl, alkoxy or halogen substituted products thereof.
Among these, hydroquinone, resorcin, and 4,4′-dihydroxybiphenyl are preferred from the viewpoint of reactivity at the time of polycondensation, properties of the obtained liquid crystal polyester, and the like.

The monomer that provides the aromatic aminooxy repeat unit is an aromatic hydroxyamine.
Preferred specific examples of the aromatic hydroxyamine include p-aminophenol, m-aminophenol, 4-amino-1-naphthol, 5-amino-1-naphthol, 8-amino-2-naphthol, and 4-amino-naphthol. Aromatic hydroxyamines such as 4'-hydroxybiphenyl, and alkyl, alkoxy or halogen-substituted products thereof are exemplified.

The monomer that provides the aromatic diamino repeat unit is an aromatic diamine.
Preferred specific examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 1,5-diaminonaphthalene, aromatic diamines such as 1,8-diaminonaphthalene, and alkyl, alkoxy or halogen-substituted products thereof. No.

Monomers that provide aromatic aminocarbonyl repeat units are aromatic network carboxylic acids.
Preferred specific examples of the aromatic aminocarboxylic acid include aromatic aminocarboxylic acids such as p-aminobenzoic acid, m-aminobenzoic acid and 6-amino-2-naphthoic acid, and alkyl, alkoxy or halogen-substituted products thereof. Is mentioned.
Ester derivatives of aromatic aminocarboxylic acids and ester-forming derivatives such as acid halides can also be suitably used as monomers for producing liquid crystal polyesters.

The monomer that provides the aromatic oxydicarbonyl repeat unit is a hydroxyaromatic dicarboxylic acid.
Preferred specific examples of the hydroxyaromatic dicarboxylic acid include hydroxyaromatic dicarboxylic acids such as 3-hydroxy-2,7-naphthalenedicarboxylic acid, 4-hydroxyisophthalic acid, and 5-hydroxyisophthalic acid; Or a halogen-substituted product.
Ester-forming derivatives such as ester derivatives of hydroxy aromatic dicarboxylic acids and acid halides can also be suitably used as monomers for producing liquid crystal polyesters.

Specific examples of the monomer giving the aliphatic dioxy repeating unit include, for example, aliphatic diols such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, and acylated products thereof.
Further, polyethylene terephthalate or a polymer containing an aliphatic dioxy repeating unit such as polybutylene terephthalate, the aromatic oxycarboxylic acid, the aromatic dicarboxylic acid, the aromatic diol, and their acylated products, ester derivatives, acid halogens A liquid crystal polyester containing an aliphatic dioxy repeating unit can also be obtained by reacting with a compound.

The liquid crystal polyester may include a thioester bond. Examples of monomers that provide such a bond include mercapto aromatic carboxylic acids, aromatic dithiols, and hydroxy aromatic thiols.
The amount of these monomers used is an aromatic oxycarbonyl repeating unit, an aromatic dicarbonyl repeating unit, an aromatic dioxy repeating unit, an aromatic aminooxy repeating unit, an aromatic diamino repeating unit, an aromatic aminocarbonyl repeating unit, It is preferably at most 10 mol% with respect to the total amount of the monomers providing the aromatic oxydicarbonyl repeating unit and the aliphatic dioxy repeating unit.

  Polyesters in which the above repeating units are combined, depending on the monomer composition and composition ratio, depending on the sequence distribution of each repeating unit in the polyester, some may or may not form an anisotropic molten phase. Limited to those that form an anisotropic molten phase.

Preferred examples of the liquid crystal polyester produced in the presence of the imidazole compound include the following 1) to 25).
1) 4-hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid copolymer 2) 4-hydroxybenzoic acid / terephthalic acid / 4,4′-dihydroxybiphenyl copolymer 3) 4-hydroxybenzoic acid / terephthalic acid / Isophthalic acid / 4,4'-dihydroxybiphenyl copolymer 4) 4-hydroxybenzoic acid / terephthalic acid / isophthalic acid / 4,4'-dihydroxybiphenyl / hydroquinone copolymer 5) 4-hydroxybenzoic acid / terephthalic acid / Hydroquinone copolymer 6) 4-Hydroxybenzoic acid / terephthalic acid / 4,4'-dihydroxybiphenyl / hydroquinone copolymer 7) 2-Hydroxy-6-naphthoic acid / terephthalic acid / hydroquinone copolymer 8) 4- Hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid / terephthalic acid / 4,4 ' Dihydroxybiphenyl copolymer 9) 2-hydroxy-6-naphthoic acid / terephthalic acid / 4,4'-dihydroxybiphenyl copolymer 10) 4-hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid / terephthalic acid / hydroquinone Copolymer 11) 4-hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid / terephthalic acid / hydroquinone / 4,4′-dihydroxybiphenyl copolymer 12) 4-hydroxybenzoic acid / 2,6-naphthalenedicarboxylic acid / 4,4'-dihydroxybiphenyl copolymer 13) 4-hydroxybenzoic acid / terephthalic acid / 2,6-naphthalenedicarboxylic acid / hydroquinone copolymer 14) 4-hydroxybenzoic acid / 2,6-naphthalenedicarboxylic acid / Hydroquinone copolymer 15) 4-hydroxybenzoic acid / 2-h Droxy-6-naphthoic acid / 2,6-naphthalenedicarboxylic acid / hydroquinone copolymer 16) 4-hydroxybenzoic acid / terephthalic acid / 2,6-naphthalenedicarboxylic acid / hydroquinone / 4,4'-dihydroxybiphenyl copolymer 17) 4-hydroxybenzoic acid / terephthalic acid / 4-aminophenol copolymer 18) 2-hydroxy-6-naphthoic acid / terephthalic acid / 4-aminophenol copolymer 19) 4-hydroxybenzoic acid / 2-hydroxy -6-naphthoic acid / terephthalic acid / 4-aminophenol copolymer 20) 4-hydroxybenzoic acid / terephthalic acid / 4,4'-dihydroxybiphenyl / 4-aminophenol copolymer 21) 4-hydroxybenzoic acid / Terephthalic acid / ethylene glycol copolymer 22) 4-Hydroxybenzo Acid / terephthalic acid / 4,4'-dihydroxybiphenyl / ethylene glycol copolymer 23) 4-hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid / terephthalic acid / ethylene glycol copolymer 24) 4-hydroxybenzoic acid / 2-hydroxy-6-naphthoic acid / terephthalic acid / 4,4'-dihydroxybiphenyl / ethylene glycol copolymer 25) 4-hydroxybenzoic acid / terephthalic acid / 2,6-naphthalenedicarboxylic acid / 4,4'- Dihydroxybiphenyl copolymer.

<Acylation of monomer mixture (B)>
As described above, the method of acylating the monomer mixture (B) containing a monomer having a phenolic hydroxyl group to obtain a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group in terms of cost and production time. It is advantageous.

  Such an acylation of the monomer mixture (B) is preferably carried out by reacting a phenolic hydroxyl group contained in the monomer mixture (B) with a fatty acid anhydride prior to the polycondensation.

  Examples of the fatty acid anhydride include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, 2-ethylhexanoic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, and trichloroacetic anhydride. Monobromoacetic acid, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, β-bromopropionic anhydride and the like.

  These may be used as a mixture of two or more. Acetic anhydride, propionic anhydride, butyric anhydride, and isobutyric anhydride are preferably used from the viewpoint of price and handleability. Among them, acetic anhydride is more preferably used.

  The amount of the fatty acid anhydride used for the acylation is preferably from 1.0 equivalent to 1.15 equivalent, more preferably from 1.03 equivalent to the amount of the phenolic hydroxyl group contained in the monomer mixture (B). 1.10 equivalent or less is more preferable.

  If the amount of the fatty acid anhydride used is less than 1.0 equivalent of the phenolic hydroxyl group, the unreacted phenolic hydroxyl group remains, so that the conversion rate in polycondensation hardly increases. In addition, when a liquid crystal polyester is produced by polycondensation, unreacted aromatic diol, aromatic hydroxycarboxylic acid, and aromatic dicarboxylic acid tend to sublime and block pipes and the like in a reaction vessel.

When the amount of the fatty acid anhydride exceeds 1.15 equivalents to the phenolic hydroxyl group, the obtained liquid crystal polyester tends to be significantly colored.

  In the acylation reaction in the acylation step, it is usually preferable to carry out the reaction at a temperature of 130 ° C. or more and 180 ° C. or less for 30 minutes or more and 20 hours or less. More preferably, the reaction is performed for a period of time or less.

When the above-mentioned imidazole compound is present during the reaction between the monomer mixture (B) and the fatty acid anhydride, the acylation reaction can be easily performed at a low temperature and / or in a short time.
In this case, the acylation reaction can be carried out at a temperature of 70 to 180 ° C, preferably 80 to 160 ° C, more preferably 80 to 120 ° C.
In this case, the amount of the imidazole compound used is the same as the amount of the imidazole compound used in the polycondensation.

  The acylation of the monomer mixture (B) may be performed in a separate reaction vessel from the reaction vessel for performing the polycondensation reaction. After the acylation of the monomer mixture (B), a polycondensation reaction may be continuously performed in the same reaction solution.

As the material of the surface of the reaction vessel for performing the acylation reaction, which is in contact with the reaction solution, a material having corrosion resistance such as titanium or Hastelloy B is preferable.
When the liquid crystal polyester requires a high color tone (L value), the material of the inner wall of the reaction vessel is preferably glass. If the inner wall of the reaction vessel in contact with the reaction mixture is made of glass, the entire reaction vessel does not need to be made of glass, and for example, a glass-lined SUS-made reaction vessel or the like can be used. For example, in a large-scale production facility, it is preferable to use a glass-lined reaction vessel.

<Molten polycondensation>
The temperature of the polycondensation in the molten state is not particularly limited as long as a liquid crystal polyester having a desired degree of polymerization can be produced. The temperature of the polycondensation may be maintained at a constant temperature after reaching a desired set temperature, or may be changed.

When a liquid crystal polyester is produced only by melt polycondensation, the temperature of the melt polycondensation is preferably from 150 ° C. to 400 ° C., and more preferably from 250 ° C. to 370 ° C.
When a liquid crystal polyester is produced in two stages of melt polycondensation and solid-state polymerization described below, the temperature of the melt polycondensation is preferably from 120 ° C to 350 ° C, more preferably from 200 ° C to 300 ° C.

The time of the polycondensation reaction can be appropriately set from the viewpoint of suppressing a decrease in productivity after selecting reaction conditions such as a temperature condition capable of controlling the reaction and a catalyst amount. For example, the reaction temperature is preferably 30 minutes or more and 5 hours or less at the above-mentioned reaction temperature.

  Melt polycondensation can be carried out under an inert gas, for example, a nitrogen atmosphere, under normal pressure or reduced pressure. For the melt polycondensation, a batch system, a continuous system, or a combination thereof can be adopted, and a batch system is preferable.

  The shape of the reaction vessel used for the polycondensation reaction is not particularly limited, and a known shape of the reaction vessel can be adopted. In the case of a vertical reaction vessel, the stirring blade is preferably a multi-stage paddle blade, turbine blade, Monte blade, or double helical ribbon blade. In a horizontal reaction vessel, it is preferable that various shapes of blades, for example, a lens blade, a spectacle blade, a multi-circular plate blade, and the like are installed perpendicularly to one or two stirring axes. It is also preferable that the blades are twisted to improve the stirring performance and the feed mechanism.

  The heating of the reaction vessel can be performed by a heating medium, a gas, or an electric heater. For the purpose of uniform heating, it is preferable to heat not only the reaction vessel but also members that come into contact with the contents of the reaction vessel, such as a stirring shaft, blades, and baffles.

<Polycondensation in solid phase>
The liquid crystal polyester obtained by subjecting the monomer mixture (A) to polycondensation in a molten state is subjected to polycondensation by heating in a solidified state (solid phase), if necessary, to further increase the molecular weight. May be.

The polymer having a higher molecular weight after the melt polycondensation solidifies when cooled. Therefore, after the polymer obtained by melt polycondensation is withdrawn from the reaction vessel, cooled and solidified, the solid polymer is pulverized to provide a polymer powder to be subjected to solid-state polymerization. Is obtained.
The shape of the powder is not particularly limited as long as it has a certain degree of fluidity, and may be a powder or a flake.
Alternatively, the polymer extracted in a strand form from the reaction vessel in which the melt polycondensation has been performed may be solidified and cut, and the pelletized polymer may be subjected to solid-state polymerization.

When the molecular weight of the liquid crystal polyester is increased to a desired level only by melt polycondensation, the melting point of the liquid crystal polyester is increased with the increase in the molecular weight. Then, the rate of rise of the melting point of the liquid crystal polyester may exceed the rate of temperature rise of the melt polymerization apparatus, and the melting point of the liquid crystal polyester may exceed the internal temperature of the melt polymerization apparatus.
In this case, since the solidification of the liquid crystal polyester proceeds inside the melt polymerization apparatus, it is difficult to take out the polymer from the reaction vessel.

However, as described above, if the molecular weight is increased to a level that can be taken out by melt polycondensation, and then the molecular weight is increased to a desired molecular weight by solid-state polymerization, the polymerization operation is easily performed, and the desired molecular weight is also increased. Easy to manufacture liquid crystal polyester.
In other words, by performing the polycondensation in two stages by dividing the polycondensation into a melt polycondensation and a polycondensation in a solid phase, it is possible to easily produce a high molecular weight liquid crystal polyester having high heat resistance, strength and rigidity.

  The solid-phase polymerization is preferably performed by heating the resin while maintaining a certain temperature range. The temperature condition of the solid phase polymerization is preferably from 150 ° C to 350 ° C, more preferably from 220 ° C to 300 ° C, and even more preferably from 230 ° C to 290 ° C.

  Although the polymerization time of the solid phase polymerization is not particularly limited, it is appropriately determined according to the solid phase polymerization temperature and the target degree of polymerization of the liquid crystal polyester. Typically, the time is preferably from 3 hours to 20 hours.

  As described above, the desired liquid crystal polyester can be obtained.

<Pelletization, filler, additive, etc.>
The liquid crystal polyester produced by the above method is usually a product in the form of pellets.
As a method for producing pellets by granulating liquid crystal polyester particles, melt kneading is performed using a generally used single-screw or twin-screw extruder, and air-cooled or water-cooled as necessary, and then a pelletizer (strand cutter). And shaping into pellets.
A general-purpose extruder can be used for the purpose of melting uniformity and shaping, but it is preferable to use an extruder having a large L / D from the viewpoint of melting uniformity. At the time of melt-kneading, the cylinder set temperature (die head temperature) of the extruder is preferably from 200 ° C to 450 ° C.

  If necessary, an inorganic filler can be added to the liquid crystal polyester obtained by the method described above. Such inorganic fillers include calcium carbonate, talc, clay, silica, magnesium carbonate, barium sulfate, titanium oxide, alumina, montmorillonite, gypsum, glass flake, glass fiber, milled glass fiber, carbon fiber, alumina fiber, silica fiber Examples include alumina fibers, aluminum borate whiskers, and potassium titanate fibers. The amount of the inorganic filler used is appropriately determined depending on the use of the liquid crystal polyester. For example, when a film is formed using liquid crystal polyester, the upper limit of the amount of the inorganic filler to be used is determined as long as the transparency and mechanical strength of the film are not significantly impaired.

  The liquid crystal polyester obtained by the method described above may further include, if necessary, an organic filler, an antioxidant, a heat stabilizer, a light stabilizer, a flame retardant, a lubricant, an antistatic agent, a coloring agent, and a rust inhibitor. Various additives such as a crosslinking agent, a foaming agent, a fluorescent agent, a surface smoothing agent, a surface gloss improving agent, and a mold release improving agent such as a fluororesin can be added during the manufacturing process or in the subsequent processing process.

<Preferred applications of liquid crystal polyester>
In the method for producing a liquid crystal polyester described above, since the temperature polycondensation at a temperature lower than the conventional polycondensation reaction temperature can be advanced, it is easy to obtain a liquid crystal polyester with suppressed coloring. By using a liquid crystal polyester in which coloring is suppressed, a molded article having an excellent color tone can be obtained.

As described above, since the liquid crystal polyester produced by the above-described method has suppressed coloring, it is suitably used for preparing a white liquid crystal polyester composition containing a white pigment such as titanium white.
The white liquid crystal polyester composition is typically suitably used for forming a reflector. By using a white liquid crystal polyester composition, it is easy to obtain a reflector having a high reflectance.

  The method for forming the reflection plate is not particularly limited, but usually, the reflection plate is manufactured by an injection molding method. According to the injection molding method, a reflector having a thin portion or a reflector having a complicated shape can be easily formed. In particular, the thickness of the thin portion is 0.01 mm or more and 3.0 mm or less, preferably 0.02 mm or more. The injection molding method is suitable for obtaining a small reflector of 0 mm or less, more preferably 0.05 mm or more and 1.0 mm or less.

  The white liquid crystal polyester composition obtained by adding a white pigment to the liquid crystal polyester obtained by the method described above has a high whiteness, so that it is light-reflective, particularly visible light-reflective, in the fields of electricity, electronics, automobiles, and machinery. Used as a raw material of a reflection member for the purpose. For example, it is suitably used as a lamp reflector of a light source device such as a halogen lamp or HID, a light emitting device using a light emitting element such as an LED or an organic EL, or a reflector of a display device. In particular, it is suitably used for a reflector of a light emitting device using an LED.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

In Examples, acetylation of a monomer and polycondensation were performed using Compound 1 synthesized according to the following method as a catalyst.
<Compound 1>

1. Synthesis Example of Compound 1 First, 30 g of a cinnamic acid derivative having the structure shown below was dissolved in 200 g of methanol, and 7 g of potassium hydroxide was added to methanol. Then the methanol solution was stirred at 40 ° C. The methanol was distilled off, and the residue was suspended in 200 g of water. 200 g of tetrahydrofuran was mixed and stirred with the obtained suspension, and the aqueous phase was separated. Under ice-cooling, hydrochloric acid (4 g) was added and stirred, and then ethyl acetate (100 g) was mixed and stirred. After allowing the mixture to stand, the oil phase was separated. The target substance was crystallized from the oil phase, and the precipitate was collected to obtain an imidazole compound (Compound 1) having the above structure.

The ¹ H-NMR measurement results of Compound 1 are as follows.
^{1 H-NMR (DMSO):} 11.724 (s, 1H), 7.838 (s, 1H), 7.340 (d, 2H, J = 4.3Hz), 7.321 (d, 1H, J = 7.2 Hz), 6.893 (d, 2H, J = 4.3 Hz), 6.876 (d, 1H, J = 6.1 Hz), 5.695 (dd, 1H, J = 4.3 Hz, 3.2Hz), 3.720 (s, 3H), 3.250 (m, 2H)

[Example 1]
In a reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 994.5 g (7.2 mol) of p-hydroxybenzoic acid, 446.9 g (2.4 mol) of 4, 4'-dihydroxybiphenyl, 239.2 g (1.44 mol) terephthalic acid, 159.5 g (0.96 mol) isophthalic acid, 1298.6 g (12.7 mol) acetic anhydride, and 0.29 g (1.2 mmol) Compound 1) was charged, and the gas in the reactor was replaced with nitrogen gas. Next, the mixture was heated from room temperature to 90 ° C. over 30 minutes while stirring under a nitrogen gas stream, and refluxed at 90 ° C. for 1 hour to perform acetylation.

Next, the temperature was raised from 90 ° C. to 130 ° C. at a rate of 1 ° C./min while distilling off by-produced acetic acid and unreacted acetic anhydride under reduced pressure. At the time when the melt polycondensation was carried out while keeping the temperature at 130 ° C. for 160 minutes, a sharp increase in the torque was recognized with a torque meter. Therefore, the contents were taken out of the reactor and cooled to room temperature. The solid of the polymer obtained by cooling was pulverized to obtain a prepolymer powder.
The color tone of the prepolymer powder was measured using a chromaticity measuring device of MCPD-1000 (manufactured by Otsuka Electronics). The L * value represented by CIE L * a * b * was 90 or more, and the whiteness of the prepolymer powder obtained in Example 1 was good.

[Example 2]
After acetylation of the monomer, melt polycondensation was carried out in the same manner as in Example 1, except that 1.47 g (6.0 mmol) of Compound 1 was further added. At the time when the holding time at 130 ° C. was 40 minutes, a sharp increase in torque was recognized on the torque meter, so the contents were taken out of the reactor and cooled to room temperature. The solid of the polymer obtained by cooling was pulverized to obtain a prepolymer powder.

[Comparative Example 1]
Changing 0.29 g (1.2 mmol) of compound 1 to 0.146 g (1.2 mmol) of 4-dimethylaminopyridine (DMAP) and changing the reaction temperature of acetylation from 130 ° C. to 150 ° C. Otherwise, the monomer was acetylated in the same manner as in Example 1.
Next, the reaction solution was cooled to 130 ° C., and while maintaining the temperature at 130 ° C., melt polycondensation was performed while distilling off acetic acid produced as a by-product and unreacted acetic anhydride under reduced pressure.
However, in Comparative Example 1, even when the holding time at 130 ° C. greatly exceeded 200 minutes, no sharp increase in torque occurred in the torque meter.
That is, when 4-dimethylaminopyridine (DMAP) is used as a catalyst, at 130 ° C., the reaction of melt polycondensation hardly proceeds or the reaction rate of melt polycondensation is considerably slow.
Comparison between Examples 1 and 2 and Comparative Example 1 shows that the imidazole compound represented by the formula (1) exhibits a higher catalytic action than 4-dimethylaminopyridine.

Claims (6)

A method for producing a liquid crystal polyester, comprising polycondensing a monomer mixture (A) containing an acylated product of a monomer having a phenolic hydroxyl group,
The polycondensation is performed according to the following formula (1a) :

(In the formula (1a), R ⁴ represents a hydrogen atom or an alkyl group, R ² represents an aromatic group which may have a substituent , and R ⁵ represents an alkylene group which may have a substituent. , R ³ each independently represents a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonat group, or a heteroatom or a substituent. Represents an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, or an aralkyl group, and n represents an integer of 0 to ^3. R ⁵ is bonded to R ² to form a cyclic structure. May be formed.)
A method for producing a liquid crystal polyester, carried out in the presence of an imidazole compound represented by the formula: Polycondensing the monomer mixture (A) in a molten state;
Withdrawing the polymer obtained by polycondensation in a molten state from the reaction vessel, cooling and solidifying,
The solidified polymer is pulverized or pelletized to obtain polymer particles,
Heating the polymer particles, to promote the polycondensation in the solid phase to increase the degree of polymerization of the polymer,
The method for producing a liquid crystal polyester according to claim 1, comprising:   The method for producing a liquid crystal polyester according to claim 1 or 2, comprising acylating a monomer mixture (B) containing a monomer having a phenolic hydroxyl group to obtain the monomer mixture (A).   The method for producing a liquid crystal polyester according to claim 3, wherein the monomer mixture (B) is acylated by reacting an acid anhydride in an amount of from 1.00 to 1.15 equivalents to the phenolic hydroxyl group.   The method for producing a liquid crystal polyester according to claim 4, wherein the acid anhydride is acetic anhydride. The following formula (1a) :

(In the formula (1a), R ⁴ represents a hydrogen atom or an alkyl group, R ² represents an aromatic group which may have a substituent , and R ⁵ represents an alkylene group which may have a substituent. , R ³ each independently represents a halogen atom, a hydroxy group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, a sulfonato group, a phosphino group, a phosphinyl group, a phosphonat group, or a heteroatom or a substituent. Represents an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, or an aralkyl group, and n represents an integer of 0 to ^3. R ⁵ is bonded to R ² to form a cyclic structure. May be formed.)
A catalyst for polycondensation at the time of producing a liquid crystal polyester, comprising an imidazole compound represented by the formula: