JPH107781A - Production of liquid-crystal polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process in which the interval of reactor cleaning can be prolonged and by which a high-quality liquid-crystal polyester having excellent heat resistance is produced and improved productivity is attained. SOLUTION: The process comprises condensation-polymerizing the feedstock therefor under stirring at a given temp. using a polymerizer having feedstock inlets, a stirrer, and a temp. controller. During the reaction, the temps. of at least those parts of the wall of the polymerizer which are located on the surface of the liquid phase and located above and near the surface are regulated to 70-200 deg.C. Alternatively, a distillate resulting from the reaction is continuously sprayed over that part of the polymerizer wall which is in contact with the gas phase inside the polymerizer and over that part of the stirrer shaft which is in contact with the gas phase, whereby the polymerizer wall and the shaft are kept clean in conducting the polycondensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a liquid crystal polyester. More specifically, the present invention relates to a method for producing a liquid crystal polyester having high quality, especially excellent heat resistance, by efficiently cleaning the inside of a can in a melt polycondensation reaction.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher performance of plastics, and a number of polymers having various new properties have been developed and marketed. Above all, attention has been paid to optically anisotropic liquid crystal polymers characterized by parallel arrangement of molecular chains because of their excellent fluidity and mechanical properties.

As a method for producing a liquid crystal polymer, as disclosed in Japanese Patent Application Laid-Open No. 1-149825, when the viscosity increases, the number of agitation is decreased to control the polymerization reaction temperature. As disclosed in the official gazette, after charging the raw materials in a reaction vessel and reacting,
It is known to use a polymerization apparatus that transfers to a polymerization vessel and performs a polycondensation reaction.

[0004]

However, a liquid crystal polymer excellent in quality can be produced by the conventional polymerization method, but the monomer and oligomer remaining in the reaction vessel are repeatedly subjected to batch polymerization after several batch polymerization. Due to the heat history, it becomes a foreign substance that does not melt at a temperature higher than the melting point of the normal polymer, for example, 350 ° C., and is mixed into the polymer when discharged from the can after the polymerization, and adversely affects the physical properties of the obtained liquid crystal polymer. It turned out that the inside of the can had to be cleaned regularly. Accordingly, the present invention provides a method for producing a liquid crystal polyester of high quality, especially excellent in heat resistance, by reducing the amount of monomers and oligomers remaining in the can and improving the productivity by extending the cleaning cycle in the can. Is to do.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention, when a liquid crystal polyester is produced by performing polycondensation while stirring a liquid crystal polyester raw material using a polymerization apparatus having a raw material input port, a stirring device and a temperature control device,
While controlling the temperature of at least the reaction vessel liquid surface during the reaction and the portion located in the vicinity of the reaction liquid surface above it within the range of 70 ° C. to 200 ° C., or controlling the temperature of the gas phase wall surface and the stirring shaft in the reaction vessel. The reaction distillate is sprayed back to the portion located in the phase portion, and the polycondensation is performed while washing the inner wall surface and the stirring shaft of the can. Use
Such a jacket is divided into two or more portions, and the jacket temperature of a portion including at least the reaction vessel liquid level during the reaction and the vicinity of the reaction vessel liquid level above is controlled within the range of 70 ° C. to 200 ° C. The amount of the gaseous phase in the reaction vessel and the amount of the distillate returned to the part located in the gaseous phase part of the stirring shaft, which is sprayed back during one hour, is in the range of 3 to 10% by weight. The method for producing the liquid crystal polyester, wherein the polycondensation is carried out by a deacetic acid reaction, wherein the stirring is carried out at a shear rate of 150 with a stirring blade and a can wall.
The method for producing the liquid crystal polyester, which includes a step performed so as to have a temperature of up to 1000 (1 / sec), after the raw materials are charged, the temperature is raised to a predetermined polycondensation temperature while stirring, and the temperature is started. Thereafter, a shear rate of 150 to 1000 (1) is used for 10% or more of the time until the polycondensation temperature is reached.
/ Sec), wherein the liquid crystal polyester is a liquid crystal polyester having an ethylenedioxy unit, and the liquid crystal polymer is a liquid crystal polyester having an ethylenedioxy unit. Polyester is the following (I), (II), (III), (IV)
The method for producing a liquid crystal polyester according to the above, wherein the liquid crystal polyester comprises a structural unit of

[0006]

Embedded image (However, R1 in the formula is

Embedded image R2 represents one or more groups selected from

Embedded image Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural units (II) and (II)
The sum of I) and the structural units (IV) are substantially equimolar).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal polyester produced in the present invention is a polyester capable of forming anisotropy when melted, for example, an oxycarbonyl unit such as an aromatic oxycarbonyl unit, an aromatic dioxy unit, an ethylenedioxy unit and the like. And polyesters exhibiting melt anisotropy comprising units selected from dioxy units and dicarbonyl units such as aromatic dicarbonyl units. The production method of the present invention is used for producing such a liquid crystal polyester. Among them, a liquid crystal polyester having an ethylenedioxy unit, particularly, the above-mentioned (I), (II), (III) and (I)
The effect is remarkably exerted when producing a liquid crystal polyester comprising the structural unit of V).

The structural unit (I) is a structural unit of a polyester formed from p-hydroxybenzoic acid, and the structural unit (II) is 4,4′-dihydroxybiphenyl,
3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2
-Bis (4-hydroxyphenyl) propane and 4,
A structural unit generated from an aromatic dihydroxy compound selected from 4'-dihydroxydiphenyl ether, a structural unit (III) is a structural unit generated from ethylene glycol, a structural unit (IV) is terephthalic acid, isophthalic acid,
4,4'-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-
Structural units formed from aromatic dicarboxylic acids selected from 4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid and diphenyletherdicarboxylic acid are shown. Of these, R1 is particularly

Embedded image Is at least 70 mol% of the structural unit (II)
But

Embedded image Is more preferably 70% or more of the structural unit (IV).

The above structural units (I), (II), (III),
The copolymerization amount of (IV) is optional. However, the following copolymerization amount is preferred from the viewpoint of fluidity.

That is, from the viewpoint of heat resistance, flame retardancy and mechanical properties, the total of the structural units (I) and (II) is 60 to 95 mol% of the total of (I), (II) and (III). Is preferable, and 82 to 93 mol% is more preferable. The structural units (III) are represented by (I), (II) and (III)
Is preferably 40 to 5 mol%, more preferably 18 to 7 mol%. The molar ratio [(I) / (II)] of the structural units (I) and (II) is preferably 75/25 to 95/5, and more preferably 78 from the viewpoint of the balance between heat resistance and fluidity. / 22 to 93/7. The structural unit (I
V) is substantially equimolar to the sum of structural units (II) and (III).

In the polycondensation of the above-mentioned preferred polyester, 3,3'-diphenyldicarboxylic acid and 2,2'-polyester are used in addition to the components constituting the structural units (I) to (IV).
Aromatic dicarboxylic acids such as aromatic dicarboxylic acids such as diphenyldicarboxylic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone,
Aromatic diols such as methylhydroquinone, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, 1,4-butanediol, 1,6-hexanediol, neopentyl Aliphatic, alicyclic diols such as glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and aromatic hydroxycarboxylic acids such as m-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid; and p-amino Phenol, p
-Aminobenzoic acid and the like can be further copolymerized in such an amount as not to impair the liquid crystallinity.

Some liquid crystal polyesters produced in the present invention can measure the logarithmic viscosity in pentafluorophenol.
It is preferably 0.3 dl / g or more as measured at 0 ° C.
Particularly preferred is 0.5 to 3.0 dl / g.

The melt viscosity of the liquid crystal polyester in the present invention is preferably from 10 to 20,000 poise, more preferably from 20 to 10,000 poise.

The melt viscosity is calculated as melting point (Tm) +10
It is a value measured by Shimadzu Corporation flow tester CFT-500 under conditions of a shear rate of 1,000 (1 / second) under the condition of ° C.

Here, the melting point (Tm) refers to the difference between room temperature and 20 ° C.
After observing the endothermic peak temperature (Tm1) observed when the temperature was measured under the temperature rising condition for 5 minutes, the temperature was maintained at a temperature of Tm1 + 20 ° C. for 5 minutes, and then cooled once to room temperature under the cooling condition of 20 ° C./min. It refers to the endothermic peak temperature (Tm2) observed when the temperature is measured again at a temperature rising condition of 20 ° C./min.

In the present invention, there is no particular limitation on a basic reaction route for producing a liquid crystal polyester by polymerization, and it can be produced by a generally known method. As the raw material, one or more monomers selected from hydroxycarboxylic acids, dihydroxy compounds, dicarboxylic acids, polyesters comprising dioxy and dicarbonyl units, and derivatives thereof can be used.
The reaction can be produced, for example, by subjecting a liquid crystal polyester to deacetic acid polymerization. In the case of performing deacetic acid polymerization, when using a hydroxyl group-containing monomer as a raw material, an acylating agent such as acetic anhydride is usually added together with the raw material.

For example, a method in which a hydroxyl group-acylated compound represented by the following method (1) is used to carry out deacetic acid polycondensation, or together with a hydroxyl group-containing compound represented by the method (2): There is a method in which acetic anhydride is used to acylate the hydroxyl group, followed by deacetic acid polycondensation. In the method (2), there is a method in which a part of the hydroxyl group-containing compound is replaced with an acylated compound. ) Is particularly preferable.

(1) p-acetoxybenzoic acid and 4,
Polyesters and oligomers of diacylated aromatic dihydroxy compounds such as 4'-diacetoxybiphenyl and paradiacetoxybenzene and aromatic dicarboxylic acids such as terephthalic acid, ethylene glycol and aromatic dicarboxylic acids, or bis (β -Hydroxyethyl) ester by a deacetic acid polycondensation reaction. (2) Aromatic dihydroxy compounds such as p-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl and hydroquinone; aromatic dicarboxylic acids such as acetic anhydride and terephthalic acid; and polyesters and oligomers from ethylene glycol and aromatic dicarboxylic acids; A method in which a phenolic hydroxyl group is acylated by reacting with a bis (β-hydroxyethyl) ester of an aromatic dicarboxylic acid and then produced by a deacetic acid polycondensation reaction.

The polymerization proceeds even if this deacetic acid reaction is carried out in the absence of a catalyst, but stannous acetate, tetrabutyl titanate,
In some cases, it may be preferable to add a metal compound such as potassium acetate, antimony trioxide, magnesium, or sodium acetate as a catalyst.

In the present invention, the liquid crystal polyester is produced using a polymerization apparatus having a raw material inlet, a stirrer, and a temperature controller.

Among them, a reaction vessel equipped with a temperature control device such as a material input port, a stirring device, and a jacket, and a discharge port, a condenser for condensing vapor distilled from the reaction vessel during the reaction, a condensate receiving tank, and a decompression tank A vertical reactor comprising a vacuum generator at the time of polymerization is preferably mentioned, and an apparatus having one reaction vessel so as to perform polycondensation in one stage may be used.
An apparatus having two or more reaction vessels for performing polycondensation in two or more stages is preferred. Further, a reactor having a shape in which the ratio of the length to width of the reactor is greater than 1 and less than 3 is preferred.

The reaction apparatus for producing liquid crystal polyester is as described above. When producing by the method (1), generally one reactor is used, and usually, the raw material monomer is charged and the reaction vessel is charged. 200 ° C in a nitrogen atmosphere under pressure or pressure
The temperature is raised to about 400 ° C., stirring is started at the same time as the temperature rise is started, and after sufficiently dissolving the raw material monomers, polycondensation is performed at 200 ° C. to 400 ° C. under reduced pressure and vacuum.

In the case of production by the above method (2), generally, two or more reactors are used.

In the case of using two reactors, usually, the raw material monomer and the acylating agent are charged into the reactor 1 and slurried with stirring, and then the temperature is raised and the acylation is carried out at 130 to 150 ° C. for 1 hour. The temperature is further raised to 200 ° C. to 300 ° C. to distill off the distillate produced by the acylation and the unreacted acylating agent. Next, it is transferred to the reaction vessel 2 equipped with a vacuum generator, and the temperature is further raised to 250 ° C. to 400 ° C., and polycondensation is performed at 250 ° C. to 400 ° C. under reduced pressure and vacuum.

It is important in the present invention that the reaction mixture such as monomers and oligomers reacts with the reaction vessel wall due to lowering of the liquid level due to the distillation of the distillate from the reaction mixture during the polymerization and rising of the liquid level due to stirring. And is subjected to polycondensation while suppressing the occurrence of an undesired reaction due to continued heating. As such a method, at least a method of controlling the temperature of the reaction vessel liquid level and the temperature near the reaction vessel liquid level, specifically, the temperature of the reaction vessel liquid level during the reaction and the temperature of the portion located near the liquid level above it, A method of controlling the temperature in the range of 70 ° C. to 200 ° C., or a method of spraying a reaction distillate on a portion where the reaction mixture adheres, specifically on a portion located in the gas phase wall of the gas chamber in the reactor and the gas phase of the stirring shaft, or There is a method of performing both of them.

Hereinafter, these points will be described in detail.

The above-mentioned method of controlling the temperature at least in the vicinity of the liquid level of the reaction vessel and the liquid level above the same can be achieved, for example, by dividing the jacket of the reaction vessel into two or more parts, and performing the reaction with the liquid level of the reaction vessel and the liquid level above it. The jacket temperature at the position including the vicinity is 70 ° C to 200 ° C, preferably 100 to 2 ° C.
It can be carried out by controlling the temperature within the range of 00 ° C. Such temperature control can be performed by any method of heating, not heating, or cooling while considering heat conduction from the reaction mixture or the reaction vessel.

The temperature of the reaction vessel jacket is the temperature of the heating medium measured by a thermometer attached to the exit of the heating medium circulation line at each of the divided sections of the reaction vessel.
If neither heating nor cooling is required depending on the production conditions of the liquid crystal polyester to be produced, a jacket having no heat circulation line or equipment corresponding thereto can be used.

Preferably, the reaction vessel jacket is divided into three sections so that the liquid level during the reaction is higher than the lower section of the jacket of the reaction vessel and the liquid level during the reaction fluctuates in the middle section of the reaction vessel jacket. Is preferably a gas phase part. At this time, the temperature of the upper stage of the jacket is not particularly limited as long as the production is not hindered. Further, those in which these jackets are further divided can also be used.

The term "in the vicinity of the liquid level above the liquid level in the reaction vessel" as used in the present invention means that the liquid level decreases due to the distillation of the distillate from the reaction mixture, the liquid level rises due to agitation, and other reasons. A portion where a reaction mixture such as a monomer and an oligomer adheres to the reaction vessel wall.

In the above method, it is necessary to control the temperature of the liquid phase portion of the reaction vessel so as to be a desired polycondensation temperature, that is, a necessary temperature in accordance with the progress of the reaction, separately from the temperature near the liquid level. It is. When a jacket is used, the temperature of the reaction vessel jacket in the liquid phase portion is raised independently of the jacket near the liquid level of the reaction vessel to evaporate the reaction distillate as the reaction proceeds, thereby completing the reaction. is important.

Next, a method of spraying the reaction distillate to the portion where the reaction mixture adheres is, for example, a distillate receiving tank which receives the reaction distillate condensed by a condenser in a polymerization apparatus, and a reaction distillate attached thereto. A pump for guiding the liquid into the reaction vessel, and a nozzle provided in the reaction vessel gas phase for spraying the reaction distillate on the gas phase wall of the reaction vessel gas phase wall and the gas phase section of the stirring shaft; The reaction distillate condensed and distilled off from the nozzle is attached to the inner wall of the reaction vessel to which the reaction mixture has adhered and the stirring shaft by the pump, especially the reaction where the distillate distills out due to the reaction and the liquid level drops. This is carried out by spraying back onto the inner wall surface of the can and the stirring shaft and washing the reaction mixture such as monomer and oligomer attached to the inner wall surface of the can and the stirring shaft, while preventing drying.

The amount of the distillate to be sprayed per hour is:
It is preferable to carry out in the range of 3 to 10% by weight, particularly 3 to 7% by weight of the total amount distilled out to the distillate receiving tank per hour.

Particularly preferred is a method in which the temperature near the liquid surface of the reaction vessel is controlled by the above-mentioned method, and a reaction distillate is sprayed on the portion where the reaction mixture adheres by the above-mentioned method.

In the present invention, the whole is heated at the same temperature or the temperature of the liquid surface and the portion located above the liquid surface is set to a temperature exceeding 200 ° C. In addition, if the reaction distillate is not sprayed, the liquid Monomers and oligomers in the reaction mixture adhering to the inner wall surface of the can and the stirrer shaft, which have a reduced surface, dry and stay and receive heat history. For example, foreign matter that does not melt even at 350 ° C. is generated. The cleaning cycle of the can is shortened because it is mixed into the polymer during the cleaning. Further, when the temperature of the liquid surface and a portion located above the liquid surface are set to less than 70 ° C. or when the amount of the reaction distillate to be returned is increased, the monomer adhering to the can wall or the stirring shaft,
Although it does not cause a serious problem in terms of foreign matter such as oligomers, the reaction time in the reaction vessel becomes longer and the productivity is reduced, and the polycondensation reaction becomes insufficient and a polymer of the desired quality cannot be obtained.

In the production method of the present invention, the polycondensation of the liquid crystal polymer is usually carried out with stirring, and at this time, the shear rate between the stirring blade and the wall of the can is 150 to 1000 (1/1).
Second), particularly preferably 200 to 700 (1 / second). In particular, at the time of the initial reaction of polycondensation until the formation of the polyester oligomer, more than 10% of the time from the start of heating to the time of reaching the predetermined polycondensation temperature,
Preferably, the shear rate is 150 to 10 for 50% or more of the time.
It is preferably performed at a rate of 00 (1 / sec), particularly 200 to 700 (1 / sec). Here, the shear rate between the stirring blade and the can wall means a value obtained from the following equation.

Shear rate (1 / sec) = 2 × 2 × 3.14 ×
Stirring number (rotation / second) x can inner diameter x can inner diameter / (can inner diameter x can inner diameter-stirrer outer diameter x stirrer outer diameter) In addition, usually after continuing to a predetermined polycondensation temperature, stirring is continued. However, at this time, it is more preferable that the shear rate is lower than the shear rate during the temperature rise. The predetermined polycondensation temperature refers to a temperature at which polycondensation for increasing the degree of polymerization is started after the initial reaction for producing a polyester oligomer having a degree of polymerization of about 2 to 4, for example, an initial reaction is performed while increasing the temperature, In the method of polycondensation under reduced pressure or vacuum,
The temperature at which polycondensation starts under reduced pressure or vacuum. The predetermined polycondensation temperature is appropriately set to an optimum temperature according to the combination of the liquid crystal polyester raw materials to be used.

Thus, a high-quality liquid crystal polymer having excellent heat resistance can be efficiently produced.

[0039]

The present invention will be described in more detail with reference to the following examples.

Example 1 A reactor 1 having an inner volume of 1.6 m ³ , an inner diameter of the can of 1.2 m, a distance between the inner wall surface of the can and the helical blade stirrer of 1 cm, and a jacket divided into three, and an inner volume of 0.8 m ^3. The inner diameter of the can was 1.1 m, and the distance between the inner wall surface of the can and the stirring blade was 2 cm.

In reaction vessel 1, p-hydroxybenzoic acid 220
kg, 4,4'-dihydroxybiphenyl 27.8k
g, 47.8 kg of polyethylene terephthalate, 24.8 kg of terephthalic acid and 211.8 kg of acetic anhydride. At this time, it was confirmed that the liquid level in the can was in the middle range of the jacket of the reaction vessel 1 divided into three parts. 30 in the can
After stirring at 5 rpm for 5 minutes, the temperature was raised and increased to 60 rpm at the same time, and after the temperature in the can reached 140 ° C in 0.75 hours,
After reacting at 140 ° C. for 1 hour, the temperature in the lower stage of the reactor 1 jacket was raised from 150 ° C. to 270 ° C., and the temperature in the upper stage of the reactor 1 jacket was raised from 150 ° C. to 195 ° C. over 5 hours to raise the internal temperature of the reactor to 250 ° C. In the meantime, the reaction distillate (boiling point 118 ° C.), which is distilled by raising the temperature in the upper stage under the jacket of the reactor 1 while being controlled at 130 ° C. in the middle stage, is passed through the distillate receiving tank, and the diaphragm is pumped by the diaphragm pump. At a pressure of 10 kg / h (corresponding to 4.0% by weight of the total amount of distillate per hour) by a nozzle attached to the reactor, the reaction was performed by spraying back onto the inner wall surface of the can at the middle stage of the jacket of the reaction can 1 and the stirring shaft. I let it. The liquid level in the can at this time was also in the middle range of the jacket of the reaction can 1 as in the preparation. Thereafter, the reactor was moved to the reactor 2 and the stirring speed was changed from 250 ° C. to 320 ° C. over 2 hours while stirring at 30 rpm, the pressure of the polymerization reactor was reduced to 1 Torr, and stirring was continued at 320 ° C. for 2 hours to continue the polycondensation reaction. Completed. After that, the inside of the reaction can 2 was pressurized to 2 kg / cm ² , and then the polymer was discharged in the form of a strand via a die to form pellets. Other operating conditions were as described in Table 1.
The theoretical structural formula of this polymer is shown below.

[0042]

Embedded image k / l / m / n = 80 / 7.5 / 12.5 / 20 When the polymer having the above composition was repeatedly batch-polymerized by the above-described method, it was found that when the polymer was polymerized in 30 batches, the melting point of the polymer was 350 ° C. or more. The phenomenon that foreign matter which did not melt even at ℃ was generated and was mixed in the discharged polymer after the completion of the polymerization appeared, so that the polymerization was repeatedly interrupted and the inside of the can was washed.

COMPARATIVE EXAMPLE 1 Two reactors, the same as in Example 1 but without a jacket and the same as in Example 1, were used for polymerization as follows.

The same amount of the raw material as in Example 1 was charged into the reaction vessel 1, and the temperature was increased while stirring the inside of the vessel at 60 revolutions / minute.
After reacting for 1 hour at 150 ° C, the jacket temperature was increased from 150 ° C to 270 ° C.
The temperature was raised to 5 ° C. over 5 hours to raise the temperature in the can to 250 ° C., and the reaction was carried out. The reaction distillate distilled out after the jacket temperature was raised was all collected in the distillate receiving tank without returning to the reactor. Thereafter, the mixture was transferred to the reactor 2 and polymerized into pellets in the same manner as in Example 1. Other operating conditions were as described in Table 1.

When batch polymerization was repeated with the same polymer composition as in Example 1, a phenomenon in which a substance having a melting point higher than that of the normal polymer mixed into the discharged polymer and became a foreign substance appeared in the 18th batch. Was washed.

COMPARATIVE EXAMPLE 2 Two reactors, the same reactor 1 as in Example 1 and the jacket was not divided and the same reactor 2 as in Example 1, were used, and the polymerization was carried out as follows. The same amount of raw material as in Example 1 was charged into a reaction vessel 1,
The stirring rate of the reaction vessel 1 was set to 20 revolutions / minute, and the following polymerization was carried out in the same manner as in Comparative Example 1. In addition, the shearing speed between the stirring blade and the wall surface of the reactor by stirring the reactor 1 at 20 revolutions / minute is 127.
(1 / sec). Other operating conditions were as described in Table 1.

When repeated batch polymerization was carried out with the same polymer composition as in Example 1, a phenomenon in which a substance having a melting point equal to or higher than that of a normal polymer was mixed into the discharged polymer after the completion of the reaction in the tenth batch to form a foreign substance appeared, and the repeated polymerization was interrupted. Then, the inside of the can was washed.

Example 2 The same reaction vessel 1 as in Example 1 and 2 of reaction vessel 2 as in Example 1
Using a can, polymerization was carried out as follows. The same amount of the raw material as in Example 1 was charged into the reaction vessel 1, and the polymerization was repeated under the same conditions as in Example 1 except that the reaction vessel 1 was stirred at 20 revolutions / minute. Other operating conditions were as shown in Table 1. In the 25th batch, a substance having a melting point higher than the melting point of the normal polymer was mixed into the discharged polymer after polymerization was completed to form a foreign substance. To clean the inside of the can.

Example 3 The same reaction vessel 1 as in Example 1 and the same reaction vessel 2 as in Example 1
Using a can, polymerization was carried out as follows.

The same amount of the raw material as in Example 1 was charged into the reaction vessel 1,
Polymerization was repeated under the same conditions as in Example 1 except that the amount of the reaction distillate returned to the reaction vessel 1 was 3 kg / h (corresponding to 1.2% by weight of the total distillate amount). The other operating conditions were as shown in Table 1. In the 22nd batch, a substance having a melting point higher than the melting point of the normal polymer was mixed into the discharged polymer after the completion of the polymerization to form a foreign substance. To clean the inside of the can.

[0051]

Table 1 Item Example 1 Comparative example 1 Comparative example 2 Example 2 Example 3 Reactor 1 jacket division temperature control 3 division temperature control No division No division Example 1 Example 1 Same as control Discharge amount 10 kg / h No return No return 10 kg / h 3 kg / h Reactor 1 stirring speed (1 / sec) 380 380 127 127 380 Distillation amount (total amount) when transferred to reactor 2 82% by weight 85撹in wt% 83 wt% 80 wt% 82 wt% time 7.0 hours 6.5 hours 6.75 hours 7.2 hours 7.0 hours shear rate from the start to warm to arrival reaches a predetermined polycondensation temperature from 150 to 10 00 (1 / sec) ratio (vs. predetermined polycondensation time to reach the focus temperature) of 100% to 100% 100% 100% 100% foreign materials generated batch number 30 batch 18 batch 10 batch 25 batch 22 batch between拌時

[0052]

According to the present invention, the productivity of liquid crystal polyester is improved, and a high quality polymer having excellent heat resistance can be obtained.

Claims (8)

[Claims] When a liquid crystal polyester is produced by subjecting a liquid crystal polyester material to polycondensation while stirring using a polymerization apparatus having a raw material inlet, a stirring device, and a temperature control device, at least the liquid surface of the reaction vessel during the reaction and the liquid level. While controlling the temperature of the portion located near the upper surface of the reaction solution within the range of 70 ° C. to 200 ° C., or distilling out the reaction gas at the portion located at the gas phase wall in the reactor and the gas phase of the stirring shaft A method for producing a liquid crystal polyester, comprising spraying a liquid back and performing polycondensation while washing an inner wall surface and a stirring shaft of the can. 2. A jacket for a reaction vessel is used as a temperature control device. The jacket is divided into two or more sections, and the jacket temperature of at least a portion including the liquid level of the reaction vessel during reaction and the vicinity of the liquid level of the reaction vessel above it is controlled. The method for producing a liquid crystal polyester according to claim 1, wherein the temperature is controlled within a range of 70C to 200C. 3. The amount of the vapor returned to the wall of the gas phase part in the reaction vessel and the part located in the gas phase part of the stirring shaft is in the range of 3 to 10% by weight of the total distillate distilled out during the reaction. The method for producing a liquid crystal polyester according to claim 1, wherein 4. The method according to claim 1, wherein the polycondensation is carried out by a deacetic acid reaction. 5. The stirring is performed at a shear rate of 15 between the stirring blade and the wall surface of the can.
2. The method for producing a liquid crystal polyester according to claim 1, which comprises a step performed so as to be 0 to 1000 (1 / second). 6. After the raw materials are charged, the temperature is raised to a predetermined polycondensation temperature while stirring, and after the temperature rise is started, the shear rate is set to 150% or more of the time required to reach the polycondensation temperature.
6. The method for producing a liquid crystal polyester according to claim 5, wherein the reaction product is stirred so as to have a flow rate of about 1000 (1 / second). 7. The method according to claim 1, wherein the liquid crystal polyester is a liquid crystal polyester having an ethylenedioxy unit. 8. The liquid crystal polymer according to the following (I), (II) or (II)
The method for producing a liquid crystal polyester according to claim 7, which is a liquid crystal polyester comprising the structural units (I) and (IV). Embedded image (However, R1 in the formula is Wherein R2 represents one or more groups selected from And at least one group selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural units (II) and (II)
The sum of I) and the structural units (IV) are substantially equimolar. )