JP6695012B1 - Liquid crystalline resin manufacturing method - Google Patents

Abstract

A method for producing a liquid crystalline resin by reacting a raw material monomer containing at least one selected from the group consisting of an aromatic hydroxycarboxylic acid and a polymerizable derivative thereof, wherein the raw material monomer is B-O (boron- A method for producing a liquid crystalline resin, comprising a step of polycondensing in the presence of an acidic compound having an (oxygen) bond or a compound capable of generating an acidic compound in a reaction system.

Description

  The present invention relates to a method for producing a liquid crystalline resin.

  Liquid crystal resins represented by liquid crystal polyester resins are widely used in various fields because they are excellent in high fluidity, low burr resistance and reflow resistance. Such liquid crystalline resin is selected by appropriately combining raw material monomers such as aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, and aromatic diol so as to obtain a liquid crystalline resin having desired physical properties, and polycondensing them. Obtained. In practice, it is common to pre-acylate a mixture of raw material monomers with an acylating agent (such as acetic anhydride) and then carry out a polycondensation reaction.

In the production of the liquid crystalline resin, various catalysts are used, for example, in order to improve the rate of polycondensation reaction. Above all, when potassium acetate is used as a catalyst, gas tends to be generated more during the reaction. This is due to the presence of a basic serving potassium acetate, the terminal carboxyl group of the liquid crystalline resin (-COOH) is a carboxylic acid ion (-COO ^-) is activated to become a made for easy desorbed as carbon dioxide it is conceivable that. In order to suppress the generation of carbon dioxide gas, it is considered that the polycondensation reaction is carried out under acidic conditions using an acid catalyst. Examples of the acid catalyst include aliphatic sulfonic acid and aromatic sulfonic acid (see Patent Document 1).

International Publication No. 2015/016141

However, according to the studies by the present inventors, when an acid catalyst such as an aliphatic sulfonic acid or an aromatic sulfonic acid is used, the generation of carbon dioxide gas can be suppressed, but the polycondensation rate can be sufficiently improved. It turns out that you can't. When the acid catalyst as described above is used, the terminal carboxyl group of the liquid crystalline resin can exist stably, and the generation of carbon dioxide gas due to the terminal carboxyl group is reduced, but p-hydroxybenzoic acid which is hard to be distilled out of the system. It is considered that this is because an acid is generated and it takes time for polycondensation.
On the other hand, the polycondensation reaction may be performed without a catalyst if only the generation of carbon dioxide is considered, but in the case of no catalyst, the polycondensation rate cannot be improved as a matter of course.
From the above, it is useful in the production of a liquid crystalline resin if it is possible to improve the polycondensation rate while suppressing the generation of carbon dioxide gas by using an acid catalyst.

  The present invention has been made in view of the above conventional problems, and an object thereof is to provide a method for producing a liquid crystalline resin capable of achieving both reduction of carbon dioxide gas generation and improvement of polycondensation rate. To do.

The present inventors carry out a polycondensation reaction for obtaining a liquid crystalline resin in the presence of an acidic compound having a BO (boron-oxygen) bond or a compound capable of generating the acidic compound in the reaction system. The inventors have completed the present invention by finding that the generation of gas can be reduced while improving the polycondensation reaction rate.
One aspect of the present invention for solving the above-mentioned problems is as follows.
(1) A method for producing a liquid crystalline resin by reacting a raw material monomer containing at least one selected from the group consisting of aromatic hydroxycarboxylic acids and their polymerizable derivatives,
A method for producing a liquid crystalline resin, comprising a step of polycondensing the raw material monomer in the presence of an acidic compound having a BO (boron-oxygen) bond or a compound capable of generating the acidic compound in a reaction system.

(2) Before the polycondensation step, the raw material monomer is acylated in the presence of an acidic compound having a BO (boron-oxygen) bond or a compound capable of generating the compound in the reaction system. The method for producing a liquid crystalline resin according to (1) above, further including a step.

(3) The method for producing a liquid crystalline resin according to (1) or (2), wherein a compound having a tertiary amine or an oxide thereof is further present in the polycondensation step.

(4) The acidic compound having a B—O (boron-oxygen) bond is an arylboronic acid having at least one electron-withdrawing group in an aryl group, according to any one of (1) to (3) above. Method for producing liquid crystalline resin.

  According to the present invention, it is possible to provide a method for producing a liquid crystalline resin that can achieve both reduction of carbon dioxide gas generation and improvement of polycondensation rate.

  The method for producing a liquid crystalline resin of the present embodiment is a method for producing a liquid crystalline resin by reacting a raw material monomer containing at least one selected from the group consisting of aromatic hydroxycarboxylic acids and their polymerizable derivatives. .. Then, the raw material monomer is an acidic compound having a BO (boron-oxygen) bond (hereinafter, also referred to as "B-O bond-containing compound"), or a compound capable of generating the acidic compound in the reaction system (hereinafter , Collectively referred to as “B—O bond-containing compound etc.”).

  In the method for producing a liquid crystalline resin of the present embodiment, since the raw material monomer is polycondensed as a catalyst in the presence of a compound containing a BO bond or the like, generation of carbon dioxide gas can be reduced and the polymerization rate can be increased. Can be done. In other words, it is possible to suppress side reactions associated with the polycondensation reaction, and it is possible to reduce the cost because the production can be performed in a shorter time than before. Furthermore, it is preferable that the step of carrying out the acylation reaction is carried out in the presence of the compound having a BO bond. By carrying out both the acylation step and the polycondensation step in the presence of the above-mentioned B—O bond-containing compound and the like, the liquid crystalline resin can be produced in a shorter time.

  In the liquid crystalline resin of the present embodiment, “liquid crystalline” means having a property capable of forming an optically anisotropic molten phase. The properties of the anisotropic molten phase can be confirmed by a conventional polarization inspection method using a crossed polarizer. More specifically, the confirmation of the anisotropic molten phase can be performed by using a Leitz polarization microscope and observing the molten sample placed on the Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. When a resin having liquid crystallinity is inspected between orthogonal polarizers, it normally transmits polarized light even if it is in a molten stationary state, and exhibits optical anisotropy.

(Raw material monomer)
The raw material monomer contains at least one compound selected from the group consisting of aromatic hydroxycarboxylic acids and polymerizable derivatives thereof. The aromatic hydroxycarboxylic acid and the polymerizable derivative thereof are not particularly limited, and examples thereof include p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, m-hydroxybenzoic acid, 6-hydroxy-3-naphthoic acid. , 6-hydroxy-4-naphthoic acid, 4-hydroxy-4'-carboxydiphenyl ether, 2,6-dichloro-p-hydroxybenzoic acid, 2-chloro-p-hydroxybenzoic acid, 2,6-dimethyl-p- Examples thereof include hydroxybenzoic acid, 2,6-difluoro-p-hydroxybenzoic acid, 4-hydroxy-4′-biphenylcarboxylic acid and vanillic acid. At least one compound selected from these can be used. Among them, it is preferable to use at least one selected from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid from the viewpoint of easy availability.

The raw material monomer preferably further satisfies the following (1) or (2).
(1) contains at least one compound selected from the group consisting of aromatic or alicyclic dicarboxylic acids and polymerizable derivatives thereof, or
(2) at least one compound selected from the group consisting of aromatic or alicyclic dicarboxylic acids and their polymerizable derivatives,
At least one compound selected from the group consisting of aromatic or alicyclic diols, aromatic or alicyclic hydroxyamines, aromatic or alicyclic diamines, and polymerizable derivatives thereof.

  The aromatic dicarboxylic acid is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and a compound represented by the following general formula (I). Can be mentioned.

（Ｙ：−（ＣＨ_２）_ｎ−（ｎ＝１〜４）及び−Ｏ（ＣＨ_２）_ｎＯ−（ｎ＝１〜４）より選ばれる基である。）

_{(Y :-( CH 2) n -} (n = 1~4) and _{-O (CH} 2) a n O- (n = 1~4) from the group selected).

  The alicyclic dicarboxylic acid is not particularly limited, and examples thereof include 1,4-cyclohexanedicarboxylic acid and 1,3-cyclopentanedicarboxylic acid. The polymerizable derivative is not particularly limited, and examples thereof include an alkyl ester (having about 1 to 4 carbon atoms) of the above compound, a halide, and the like.

  The aromatic diol is not particularly limited, and examples thereof include 2,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 4,4′-dihydroxybiphenyl, hydroquinone, resorcin, and a compound represented by the following general formula (II). And compounds represented by the following general formula (III).

（Ｘ：アルキレン（Ｃ_１〜Ｃ_４）、アルキリデン、−Ｏ−、−ＳＯ−、−ＳＯ_２−、−Ｓ−、及び−ＣＯ−より選ばれる基である。）

(X: a group selected from alkylene (C _{1 to} C ₄ ), alkylidene, —O—, —SO—, —SO ₂ —, —S—, and —CO—.)

  The alicyclic diol is not particularly limited, and examples thereof include 1,4-cyclohexanedimethanol and 1,4-cyclohexanediol. The polymerizable derivative is not particularly limited, and examples thereof include alkyl esters (having about 1 to 4 carbon atoms) of the above compounds, halides and the like.

  The aromatic hydroxyamine is not particularly limited, and examples thereof include p-aminophenol and (m-aminophenol). The alicyclic hydroxyamine is not particularly limited, and examples thereof include (4-hydroxycyclohexanecarboxylic acid, 3-hydroxycyclopentanecarboxylic acid). The polymerizable derivative is not particularly limited, and examples thereof include alkyl esters (having about 1 to 4 carbon atoms) of the above compounds, halides and the like.

  Examples of aromatic diamines include p-phenylenediamine. The alicyclic diamine is not particularly limited, and examples thereof include 1,4-cyclohexanediamine and 1,3-cyclopentanediamine. The polymerizable derivative is not particularly limited, and examples thereof include alkyl esters (having about 1 to 4 carbon atoms) of the above compounds, halides and the like.

As a specific combination of raw material monomers, for example,
(I) (a) contains at least one compound selected from the group consisting of aromatic hydroxycarboxylic acids and polymerizable derivatives thereof, or
(II) (a) at least one compound selected from the group consisting of aromatic hydroxycarboxylic acids and polymerizable derivatives thereof, and (b) a group consisting of aromatic or alicyclic dicarboxylic acids and polymerizable derivatives thereof And at least one compound selected from the group consisting of (c) an aromatic or alicyclic diol, an aromatic hydroxyamine, an aromatic diamine, and a polymerizable derivative thereof. Can be a combination including. Further, if necessary, a molecular weight modifier may be used in combination with the above constituent components.

[Acylation]
In the production method of the present embodiment, a step of acylating the raw material monomer with an acylating agent can be provided before the polycondensation described later. The acylation is preferably carried out in the presence of the above-mentioned B-O bond-containing compound and the like. As the acylating agent, acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic 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, β-bromopropionic anhydride, etc., but are not particularly limited. Not something. At least one selected from these can be used. Suitable from the viewpoints of price and handleability are carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and isobutyric anhydride. Of these, acetic anhydride is preferable in terms of easy availability. The amount of the acylating agent used is preferably 1.0 to 1.1 equivalents, and more preferably 1.01 to 1.05 equivalents in the total amount of hydroxyl groups of the substance used in the reaction, from the viewpoint of easy reaction control. Is more preferable.

  Acylation can be performed by a known method. For example, a raw material monomer is mixed with an acylating agent, and heated at a temperature range of 120 to 160 ° C. for about 0.5 to 5 hours to cause an acylation reaction to obtain a reaction product containing an acylated product.

[Polycondensation]
Raw material monomers are polycondensed in the presence of a compound containing a BO bond. In addition, when the step of acylating as described above is provided and the above-mentioned BO bond-containing compound or the like is used in the step, the BO bond-containing compound or the like used in the polycondensation is acylated. It may be the same as or different from the one used in.

(Acidic compound having BO bond)
In the production method of the present embodiment, in polycondensing the raw material monomers, an acidic compound having a B—O bond is used as a catalyst, but the use of the B—O bond-containing compound reduces the generation of carbon dioxide gas. It is possible to achieve both improvement of the polycondensation rate. Even if the B-O bond-containing compound is present in the polycondensation reaction, since the B-O bond-containing compound is weakly acidic, the polymerization system can be inclined to be weakly acidic, so that the terminal carboxyl group can stably exist. Like Therefore, the generation of carbon dioxide gas is reduced. In addition, the terminal carboxyl group reacts with the compound containing a BO bond to form a boronic acid ester, and the electron withdrawing property is improved. Therefore, the hydroxyl groups of the raw material monomers are attracted, so that the polycondensation rate is improved.
On the other hand, when a normal acid catalyst such as an aromatic sulfonic acid is used, the ester group is activated preferentially instead of the terminal carboxyl group, so that a side reaction due to strong activation of the ester group is likely to occur. Become. On the other hand, the BO bond-containing compound used in the present embodiment mainly activates the terminal carboxyl group, so that the polycondensation reaction starting from the terminal carboxyl group proceeds and side reactions are unlikely to occur.

  Examples of the B-O bond-containing compound include boronic acid, arylboronic acid, boronic acid derivatives such as fluorine-substituted boronic acid, boric acid, and the like, and among them, arylboronic acid and boric acid are preferable.

  It is preferable to use an arylboronic acid having at least one electron-withdrawing group in the aryl group as the B—O bond-containing compound, since the electron withdrawing property is improved and the polycondensation rate is further improved. Examples of the electron-withdrawing group include halogen such as trifluoromethyl group, fluoro group and chloro group, nitro group, cyano group, keto group and the like.

  Alternatively, in the present embodiment, in addition to using the B—O bond-containing compound as it is, a compound capable of generating the B—O bond-containing compound in the reaction system is used. By generating the BO bond-containing compound in the reaction system, the same effect as that obtained when the BO bond-containing compound is used can be obtained. Examples of the compound include boronic acid anhydride. These compounds can generate the above acid in the reaction system by the presence of carboxylic acid or by heating.

  The acid dissociation constant pKa of the B—O bond-containing compound is preferably 14 or less, more preferably −1.0 to 13, and further preferably 0 to 12. The above pKa means pKa in an aqueous solution at 25 ° C.

  In the present embodiment, the amount of the B—O bond-containing compound or the compound capable of generating the B—O bond-containing compound in the reaction system is not particularly limited as long as it does not adversely affect acylation or polycondensation. Generally, the compound is preferably 50 to 2000 ppm, more preferably 100 to 1000 ppm, based on the theoretical yield of the liquid crystalline resin obtained. The temperature for polycondensation is preferably 300 to 400 ° C.

  In the polycondensation step, it is preferable that a compound having a tertiary amine or an oxide thereof is further present. As described above, in the polycondensation reaction in the present embodiment, first, the terminal carboxyl group is dehydrated and condensed with the B—O bond-containing compound to form a boronic acid ester, but the compound having a tertiary amine or its oxide is When present, the compound replaces the boronic acid moiety and converts it to the more active ester. That is, since the electrophilicity of the terminal carboxyl group is further increased, the polycondensation rate is further improved.

  Examples of the compound having a tertiary amine or its oxide include dimethylaminopyridine oxide (DMAPO), N, N-dimethyl-4-aminopyridine (DMAP), 4-methoxypyridine-N-oxide (MPO), 4- Pyrrolidinopyridine-N-oxide (PPYO), N, N-isopropylethylamine, trimethylamine, triethylamine and the like can be mentioned. Among them, dimethylaminopyridine oxide having stronger nucleophilicity is preferable.

  In the present embodiment, the addition amount of the compound having a tertiary amine or the oxide thereof is generally preferably 50 to 2000 ppm, and preferably 100 to 1000 ppm, with respect to the theoretical yield of the obtained liquid crystalline resin. Is more preferable.

(Solid phase polymerization step)
The method for producing a liquid crystalline resin of the present embodiment may further include a step of solid-phase polymerizing the resin obtained in the melt polymerization step (the above polycondensation step). By the solid-state polymerization, the molecular weight of the raw material resin can be increased, and a liquid crystalline resin excellent in strength and heat resistance can be obtained.

  A conventionally known method can be used for the solid phase polymerization. For example, it can be carried out by heating under reduced pressure or vacuum in an inert gas stream such as nitrogen gas at a temperature 10 to 120 ° C. lower than the liquid crystal forming temperature of the raw material resin. Since the melting point of the liquid crystalline resin rises as the solid-phase polymerization proceeds, it is possible to perform the solid-state polymerization above the original melting point of the raw material resin. The solid phase polymerization may be carried out at a constant temperature or may be increased stepwise. The heating method is not particularly limited, and microwave heating, heater heating, or the like can be used.

[Liquid crystalline resin]
The liquid crystalline resin obtained by the production method of the present embodiment preferably contains at least one selected from liquid crystalline polyester and liquid crystalline polyesteramide. The liquid crystalline polyester and the liquid crystalline polyesteramide are not particularly limited, but aromatic polyester or aromatic polyesteramide is preferable. It is also possible to use a polyester partially containing aromatic polyester or aromatic polyesteramide in the same molecular chain.

More specifically, the aromatic polyester or the aromatic polyester amide includes (1) a polyester mainly composed of (a) one or more aromatic hydroxycarboxylic acids and their derivatives;
(2) Mainly (a) one or more aromatic hydroxycarboxylic acids and their derivatives,
(B) Polyester comprising one or more of aromatic dicarboxylic acid, alicyclic dicarboxylic acid, and derivatives thereof;
(3) Mainly (a) one or more kinds of aromatic hydroxycarboxylic acids and their derivatives, and (b) one or more kinds of aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and their derivatives. And (c) one or more of aromatic diols, alicyclic diols, aliphatic diols, and derivatives thereof, polyesters;
(4) Mainly (a) one or more aromatic hydroxycarboxylic acids and their derivatives, and (c1) one or more aromatic hydroxyamines, aromatic diamines, and their derivatives; c2) a polyesteramide comprising an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, and one or more of their derivatives;
(5) Mainly (a) one or more aromatic hydroxycarboxylic acids and their derivatives, and (b) one or more aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and their derivatives. , (C1) one or more aromatic hydroxyamines, aromatic diamines and their derivatives, and (c2) one or more aromatic diols, alicyclic diols and their derivatives, And a polyester amide and the like.

  The molecular weight (number average molecular weight Mn) of the liquid crystalline resin is not particularly limited, and the resin obtained in the melt polymerization step is preferably 10,000 to 100,000, and more preferably 15,000 to 80,000. The resin obtained in the solid phase polymerization step is preferably 12,000 to 120,000, more preferably 15,000 to 100,000. The number average molecular weight Mn can be measured by gel permeation chromatography.

The melting point of the liquid crystalline resin is not particularly limited and may be 250 to 380 ° C. The melt viscosity of the liquid crystalline resin is not particularly limited, and as the resin obtained by melt polymerization, the melt viscosity measured at a cylinder temperature of 10 to 30 ° C. higher than the melting point of the liquid crystalline resin and a shear rate of 1000 sec ⁻¹ , It is preferably 5 Pa · s or more and 150 Pa · s or less, and more preferably 10 Pa · s or more and 100 Pa · s or less. Further, when the solid phase polymerization step is performed, the resin has a melt viscosity of 5 Pa · s or more and 200 Pa · s or less measured at a cylinder temperature 10 to 30 ° C. higher than the melting point of the liquid crystalline resin and a shear rate of 1000 sec ^−1. It is preferable that the pressure is 10 Pa · s or more and 150 Pa · s or less.

  “Cylinder temperature 10 to 30 ° C. higher than the melting point of the liquid crystalline resin” means a cylinder temperature at which the liquid crystalline resin can be melted to such an extent that the melt viscosity can be measured, and the temperature is higher than the melting point by several degrees Celsius. Whether the cylinder temperature is high depends on the type of the raw material resin within the range of 10 to 30 ° C. The liquid crystalline resin can be in the form of a powder / granular mixture, or in the form of a melt mixture (melt-kneaded product) such as pellets.

  Hereinafter, the present embodiment will be described more specifically by way of examples, but the present embodiment is not limited to the following examples.

[Example 1]
After charging the following raw materials into a polymerization vessel, the temperature of the reaction system was raised to 140 ° C. and the reaction was carried out at 140 ° C. for 3 hours (acylation). After that, the temperature is further raised to 360 ° C. over 4.5 hours, and then the pressure is reduced to 10 Torr (that is, 1330 Pa) over 15 minutes, while distilling out acetic acid, excess acetic anhydride, and other low boiling components. Polycondensation was performed. The time from the start of depressurization until the stirring torque reached a predetermined value was 20 minutes. After the stirring torque reached a predetermined value, nitrogen was introduced, and the polymer was discharged from the lower part of the polymerization container after introducing the polymer from the reduced pressure state to the normal pressure via the normal pressure. Then, the strand was pelletized to obtain a liquid crystalline resin pellet.
(material)
4-Hydroxybenzoic acid (HBA): 184 g (60 mol%)
Terephthalic acid (TA): 52 g (14 mol%)
Isophthalic acid (IA): 22 g (6 mol%)
4,4'-dihydroxybiphenyl (BP): 83 g (20 mol%)
Phenylboronic acid: 54 mg (180 ppm) (catalyst; BO bond-containing compound)
Acylating agent (acetic anhydride): 233 g

[Example 2]
Further, liquid crystalline resin pellets were obtained in the same manner as in Example 1 except that dimethylaminopyridine oxide was added. However, the amount of dimethylaminopyridine oxide used was as shown in Table 1.

[Example 3]
Liquid crystalline resin pellets were obtained in the same manner as in Example 1 except that the B-O bond-containing compound was changed to 3,5-bis (trifluoromethyl) phenylboronic acid. However, the amount of 3,5-bis (trifluoromethyl) phenylboronic acid used was as shown in Table 1.

[Example 4]
Liquid crystal resin pellets were obtained in the same manner as in Example 1 except that the B—O bond-containing compound was changed to boric acid. However, the amount of boric acid used was as shown in Table 1.

[Comparative Example 1]
Liquid crystalline resin pellets were obtained in the same manner as in Example 1 except that potassium acetate was used instead of phenylboronic acid. However, the amount of potassium acetate used was as shown in Table 1.

[Comparative example 2]
Liquid crystal resin pellets were obtained in the same manner as in Example 1 except that phenylboronic acid was not used, that is, no catalyst was used.

[Polycondensation time]
In each of the examples and comparative examples, the time from the start of depressurization until the stirring torque reaches a predetermined value was confirmed. The results are shown in Table 1. The torque value indicated when the target melt viscosity is reached is a predetermined value. Regarding the target melt viscosity, the polymers of Examples 1 to 4 and Comparative Examples 1 and 2 have a melt viscosity of 15 Pa · s at a cylinder temperature of 360 ° C. and a shear rate of 1000 sec ⁻¹ .
The melt viscosity was measured by a capillary rheometer (Capirograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd .: piston diameter 10 mm) at the cylinder temperature and the shear rate, and the apparent melt viscosity was measured according to ISO 11443. An orifice having an inner diameter of 0.5 mm and a length of 30 mm was used for the measurement.

[Melting point]
In each Example and Comparative Example, a differential scanning calorimeter (DSC, manufactured by Hitachi High-Tech Science Co., Ltd.) was used, and an endotherm observed when the liquid crystalline resin was heated from room temperature at a temperature rising rate of 20 ° C./min. The peak temperature (Tm1) was measured. Then, the temperature of (Tm1 + 40) ° C. was maintained for 2 minutes. Further, the temperature was once cooled to room temperature at a temperature decrease rate of 20 ° C./min, and then the endothermic peak temperature (Tm2) observed when heated again at a temperature increase rate of 20 ° C./min was measured as the melting point.

[Amount of carbon dioxide generated]
In each of the examples and comparative examples, a thermogravimetric measuring device (TGA, manufactured by TA Instruments Co., Ltd.) was used, and 10 mg of the liquid crystalline resin was heated at 25 ° C. higher than the melting point of the liquid crystalline resin under a nitrogen stream. At (Tm2 + 25 ° C.), the amount of weight loss after holding for 30 minutes was measured and evaluated as the amount of carbon dioxide gas generated.

From Table 1, it can be seen that in Examples 1 to 4, the time required to reach the predetermined torque after the start of depressurization was short and the carbon dioxide gas generation amount was small. That is, in Examples 1 to 4, it was shown that the reduction of carbon dioxide gas generation and the improvement of the polycondensation rate could both be achieved.
On the other hand, in Comparative Examples 1 and 2, the reduction of carbon dioxide gas generation and the improvement of the polycondensation rate could not be satisfied at the same time.

Claims (4)

A method for producing a liquid crystalline resin by reacting a raw material monomer containing at least one selected from the group consisting of aromatic hydroxycarboxylic acid and its polymerizable derivative,
A method for producing a liquid crystalline resin, comprising the step of polycondensing the raw material monomer using an acidic compound having a BO (boron-oxygen) bond or a compound capable of generating the acidic compound in a reaction system as a catalyst .   Prior to the polycondensation step, a step of acylating the raw material monomer in the presence of an acidic compound having a BO (boron-oxygen) bond or a compound capable of generating the compound in the reaction system is further added. The method for producing a liquid crystalline resin according to claim 1, which comprises.   The method for producing a liquid crystalline resin according to claim 1, wherein a compound having a tertiary amine or an oxide thereof is further present in the polycondensation step.   The liquid crystalline resin according to any one of claims 1 to 3, wherein the acidic compound having a B-O (boron-oxygen) bond is an arylboronic acid having at least one electron-withdrawing group in an aryl group. Production method.