JPH05271398A - Production of aromatic liquid crystal polyester - Google Patents

Abstract

PURPOSE:To efficiently and stably obtain the subject polymer having excellent mechanical strength and heat resistance by using a raw material having a high melting point and refluxing part of distilled fatty acids prepared as by- products to a reactor. CONSTITUTION:First, compounds containing a hydroxyl group or its fatty acid ester, having >=80 deg.C melting point as a main raw material are polymerized in a reactor while distilling and removing fatty acids prepared as by-products. In the operation, part of the fatty acids distilled are refluxed to the reactor by using a double tube type inner reflux condenser to give the objective polymer. An aromatic hydroxycarboxylic acid, an aromatic dihydroxy compound, an aromatic dicarboxylic acid, etc., are usually used as the raw material. p- Hydroxybenzoic acid is preferable as the aromatic hydroxycarboxylic acid, 4,4'-dihydroxybiphenyl as the aromatic dihydroxy compound and terephthalic acid as the aromatic dicarboxylic acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for efficiently and stably producing an aromatic liquid crystal polyester having excellent mechanical strength and heat resistance.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher performance of organic polymer materials. For example, strength,
There is a strong demand for the appearance of fibers, films, molded products, etc., which have excellent mechanical strength such as elastic modulus and heat resistance. Polyethylene terephthalate (PET), polybutylene terephthalate (PB) are used as polymer materials that meet the above requirements.
There are aromatic polyesters such as T) and polyethylene-2,6-naphthalate (PEN), and among them, thermotropic liquid crystal polyester (LCP) which forms a melt phase having optical anisotropy is drawing attention.

Conventionally, as a method for producing polyester, for example, in the case of PET, bis (2-hydroxyethyl) terephthalate is first synthesized from terephthalic acid and ethylene glycol or dimethyl terephthalate and ethylene glycol, and then heated under reduced pressure. It is produced by polycondensation while distilling off and removing low-boiling compounds such as ethylene glycol and water by-produced by transesterification. Screw
When synthesizing (2-hydroxyethyl) terephthalate, a distillation column is installed in the kettle, that is, in the reactor, and by-products such as water and low boiling point compounds such as methanol are driven out of the system and excess ethylene glycol is used in the kettle. By returning it, it is possible to increase the yield of bis (2-hydroxyethyl) terephthalate. Further, in Japanese Patent Publication No. 56-38582, rectification is applied even during polycondensation to improve the purity of ethylene glycol produced as a by-product.

On the other hand, LCP is an aromatic hydroxycarboxylic acid such as parahydroxybenzoic acid, an aromatic dihydroxy compound such as 4,4'-dihydroxybiphenyl, an aromatic dicarboxylic acid such as terephthalic acid, and an aliphatic polyester such as PET. It is manufactured using, for example, the following as a main raw material. First, a phenolic hydroxyl group in a raw material is acylated with a fatty acid anhydride such as acetic anhydride, or a fatty acid ester of a phenolic hydroxyl group is used as a raw material, and then by-produced during acylation under heating (in some cases, reduced pressure). It is produced while distilling and removing the fatty acid and / or the fatty acid produced by transesterification (JP-A-2-178323 and JP-A-63).
-1205025, JP 63-1205027, JP 2-15
3922 publication).

Further, a transesterification method with an aromatic dicarboxylic acid and an aliphatic polyester such as PET using a raw material in which a phenolic hydroxyl group contained in an aromatic hydroxycarboxylic acid or an aromatic dihydroxy compound is acylated It is also possible to manufacture in.

[0006]

However, in the conventional method, an aromatic hydroxycarboxylic acid, an aromatic dihydroxy compound or a fatty acid ester thereof (hereinafter, referred to as a raw material) is entrained with a fatty acid distilled during the production of these LCPs. Etc.) is sublimated and dissipated. Since the solubility of the raw materials and the like in fatty acids is not necessarily high, there is a risk of blockage of the distilling pipe, and generally expensive raw materials and the like are dissipated, which requires extra labor for recovery. In order to solve these problems, there is a method of installing a distillation column in the polymerization kettle. However, unlike the case of producing an aliphatic polyester, the reflux liquid at start-up contains a large amount of raw materials and the like, so that it is apt to be clogged, and the amount of the reflux liquid fluctuates, and if it becomes small, it may partially solidify in the tower. .. Further, since the holdup is large, the distillate fatty acid is likely to return to the polymerization kettle, which causes a problem that the substantial speed of the transesterification reaction is reduced.

An object of the present invention is to provide a method for efficiently and stably producing an aromatic liquid crystal polyester having excellent mechanical strength and heat resistance.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the problems in the previous period, the present inventors have found that a part of the fatty acid distilled is refluxed and returned to the reactor to stabilize the accompanying raw materials. It was found that it can be returned to the reactor, and the present invention was completed. That is, a compound having a hydroxyl group or a fatty acid ester thereof in the molecule and having a melting point of 80 ° C. or higher is used as a main raw material, a polymerization reaction is performed in a reactor, and a fatty acid produced as a by-product is distilled off to remove the aromatic liquid crystal polyester. Is a method for producing an aromatic liquid crystal polyester, wherein a part of the fatty acid distilled out is refluxed in a reactor.

[0009]

In the present invention, a part of the distilled fatty acid is refluxed and returned to the reactor to condense or reverse sublimate a raw material or the like that is vaporized or sublimated along with the fatty acid, and is further dissolved in the fatty acid to be dissolved in the reactor. Can be returned to. In this case it is possible to return to the reactor with the fatty acid stream even if it is not completely dissolved. As a means for refluxing a part of the distilled fatty acid, a double-tube internal reflux device with or without a baffle plate can be used. This is because the distilled fatty acid is usually acetic acid, propionic acid, butyric acid, etc., which have a relatively high vapor pressure, but in the present invention, the melting point is usually 80 ° C.
Since the above compounds are used, the vapor pressure (sublimation pressure) is low,
This is to obtain a sufficient rectification effect with one gas-liquid contact. That is, although the principle is exactly the same as that of distillation, when a so-called distillation column is installed side by side, strict design and control of reflux ratio control, liquid dispersion, etc. are required, whereas the present invention is relatively simple. A double-tube internal reflux device with or without baffle structure is sufficient and is extremely easy to design. Further, since the structure is simple, the liquid holdup in the reflux device is extremely small. Therefore, even in the final stage of the polymerization, it is only necessary to reflux the necessary minimum amount of fatty acid, and it is possible to minimize the substantial reduction in the rate of the polymerization reaction (transesterification reaction), which is an equilibrium reaction. However, when a compound having a melting point of less than 80 ° C. is used, a sufficient rectification effect cannot be obtained by the method of the present invention.

The LCP manufacturing apparatus may be either a batch apparatus or a continuous apparatus, and the method of the present invention is applicable to both of them. Examples of the aromatic hydroxycarboxylic acid used in the present invention include p-hydroxybenzoic acid (melting point 215 ° C.), m-hydroxybenzoic acid, 4-hydroxy
-4'-carboxydiphenyl ether, 4-hydroxy-4'-
Carboxyphenyl, 2,6-dichloro-p-hydroxybenzoic acid, 2-chloro-p-hydroxybenzoic acid, 2,6-difluoro-p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy- 3-naphthoic acid, 1-hydroxy-4-
Naphthoic acid and the like can be mentioned, and examples of these fatty acid esters include p-acetoxybenzoic acid (melting point 188 ° C.) and the like. These can be used alone or in combination of two or more. Among these, p-hydroxybenzoic acid, m-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid are preferable from the practical viewpoint.

As an example of the aromatic hydroxy compound used in the present invention, 4,4'-dihydroxybiphenyl (melting point 2
78 ° C), hydroquinone, resorcin, methylhydroquinone, chlorohydroquinone, acetoxyhydroquinone, nitrohydroquinone, dimethylaminohydroquinone, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxy Naphthalene, 2,7-dihydroxynaphthalene, 2,
2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,
2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, bis -(4-hydroxyphenyl) methane, bis-
(4-Hydroxy-3,5-dimethylphenyl) methane, bis-
(4-hydroxy-3,5-dichlorophenyl) methane, bis-
(4-hydroxy-3,5-dibromophenyl) methane, 1,1-
Bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) ketone, bis (4-hydroxy)
-3,5-Dimethylphenyl) ketone, bis (4-hydroxy)
-3,5-dichlorophenyl) ketone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxy-3-chlorophenyl) sulfide, bis (4-hydroxyphenyl)
Sulfone, bis (4-hydroxy-3,5-dichlorophenyl) ether and the like can be mentioned. Examples of these fatty acid esters include 4,4′-diacetoxybiphenyl (melting point 161
℃) and the like. These can be used alone or in combination of two or more. Among these, 4,
4'-Dihydroxybiphenyl, 2,6-dihydroxynaphthalene and 2,2-bis (4-hydroxyphenyl) propane are preferred.

Examples of the aromatic hydroxycarboxylic acid used in the present invention include terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid. Acid, methyl terephthalic acid, methyl isophthalic acid, diphenyl ether-4,4'-
Dicarboxylic acid, diphenyl sulfone-4,4'-dicarboxylic acid, diphenyl ketone-4,4'-dicarboxylic acid, 2,2-diphenylpropane-4,4'-dicarboxylic acid, 1,4-xylylenedicarboxylic acid, 1 , 3-xylylene dicarboxylic acid, and the like. These can be used alone or in combination of two or more. Among these, terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid are preferable because of easy availability.

Other examples of the raw material for the liquid crystal polyesteramide include hydroxyaromatic amines, aromatic diamines, aminoaromatic carboxylic acids, aromatic hydroxy compounds, and aliphatic polyesters such as polyethylene terephthalate. There is no restriction to use one kind or a combination of two or more kinds. In the present invention, a catalyst can be used for the purpose of increasing the rate of esterification and polymerization. Examples of the catalyst include germanium compounds such as germanium oxide, stannous oxalate, stannous acetate, tin compounds such as dialkyltin oxide and diaryltin oxide, titanium dioxide, titanium alcooxides, and alcooxytitanium silicate. Titanium compounds such as acid salts, antimony compounds such as antimony trioxide, metal salts of organic acids such as sodium acetate, potassium acetate, calcium acetate, zinc acetate, ferrous acetate, BF ₃ and AlCl
Examples thereof include Lewis acids such as ₃ , amines, amides, and inorganic acids such as hydrochloric acid and sulfuric acid.

In the present invention, the amount of the carboxylic acid such as the above-mentioned compound and the amount of the phenols and / or amines is reacted in the range of 0.8 times to 1.2 times the equivalent number of the hydroxyl group and / or the amino group with respect to the carboxyl group to react with the polyester. In the reactor, the phenolic hydroxyl group is acylated with an aliphatic acid anhydride such as acetic anhydride, or polymerization is carried out using a raw material in which the phenolic hydroxyl group has already been acylated, that is, a fatty acid ester. The type of the aliphatic acid anhydride is not particularly limited, but acetic anhydride and propionic anhydride are preferable from the viewpoint of price and safety. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.

[0015]

【Example】

(Example 1) 3002.8 g (21.76 mol) of p-hydroxybenzoic acid (melting point 215 ° C.) and 4,4 ′ were placed in an acylation reactor equipped with a stirrer, an argon gas introduction tube, a thermometer and a reflux condenser.
-Dihydroxybiphenyl (melting point 278 ℃) 991.5g (5.27
Mol), terephthalic acid (melting point 425 ° C) 584.2 g (3.52 mol), isophthalic acid (melting point 347 ° C) 53 g (0.32 mol),
Naphthalene-2,6-dicarboxylic acid (decomposition> 300 ℃) 216.4
g (1.28 mol) (these are referred to as raw materials) and acetic anhydride 36
00 g (1.09 times equivalent to hydroxyl group) anhydrous sodium acetate
1.0g was charged. After sufficiently replacing the inside of the acylation reactor with argon gas, it takes about 30 minutes under an argon gas stream.
The temperature was raised to 148 ° C, the temperature was maintained, and the mixture was refluxed for 2 hours.
Then, the entire amount of the content was transferred to a polymerization reactor equipped with a reflux device shown in FIG. 1 equipped with a torque meter, a stirrer, an argon gas introduction tube and a thermometer. Flow nitrogen gas into the reflux device,
While distilling off the by-produced acetic acid and unreacted acetic anhydride, the temperature was raised to 250 ° C. over about 2 hours, and further the temperature was raised to 350 ° C. over about 1 hour. When the temperature of the reaction solution reached 350 ° C., the reactor was gradually depressurized and finally to 15 Torr. Since an increase in torque was observed at the same time as the start of depressurization, the time when the predetermined torque was reached was regarded as the end of the reaction, and the contents (resin) were taken out. When the distilled acetic acid was analyzed, acetic anhydride, unreacted raw materials and acetylated products thereof (these are referred to as unreacted raw materials) were found. Table 1 shows the ratio of the unreacted raw material and its acetylated product to the charged amount and the characteristics of the obtained resin. (Comparative Example 1) FIG. 2 with the reflux reactor removed from the polymerization reactor of FIG.
The polymerization reactor shown in was used. Other conditions are Example 1
An LCP was prepared as in. At this time, crystals of the unreacted raw material and its acetylated product were deposited in the cooler for cooling the distillate, and the torque was not increased to a predetermined value. Table 1 shows the ratio of the unreacted raw material and its acetylated product to the charged amount and the characteristics of the obtained resin. (Comparative Example 2) An LCP was produced in the same manner as in Example except that the polymerization reactor shown in FIG. 2 was used and the temperature from the reaction vessel to the condenser was kept warm. At this time, crystals of the unreacted raw material and its acetylated product were deposited in the cooler for cooling the distillate. Moreover, the torque increased to a predetermined value. Table 1 shows the ratio of the unreacted raw material and its acetylated product to the charged amount and the characteristics of the obtained resin.

The compounds described in the examples and comparative examples were quantified by gas chromatography. In addition, the resins manufactured in this example and the comparative example are injection molding machines
Yamashiro Seisakusho, SAV-60-52), using a mold temperature of 80
℃, injection pressure 150kg / cm ² , the cylinder temperature is adjusted to a temperature at which the resin is sufficiently filled in the mold with this injection pressure,
A 12.7 × 1.27 × 0.32 cm (5 × 1/2 × 1/8 inch) test piece was prepared and then characterized. Characteristic evaluation is ASTM
Standard (HDT; D-648, flexural strength; D-790) was used.

[0017]

[Table 1]

As is clear from Table 1, in the examples of the present invention, since the raw materials charged are directly converted into polymers, there is no loss of the raw materials, and the balance between the carboxylic acid groups and the hydroxyl groups is particularly good as in LCP in terms of synthesis. When important, it has the advantage of being able to produce polymers with good reproducibility. In the comparative example, since a large amount of raw material is distilled out together with acetic acid and acetic anhydride, the distilling pipe is likely to be clogged with trouble, and a slight loss of the raw material due to a change in the heat balance fluctuates. Thus, sufficient resin properties cannot be obtained.

[0019]

Industrial Applicability According to the present invention, it is possible to efficiently and stably produce a liquid crystal polyester having excellent mechanical strength and heat resistance, which is used for precision injection molded articles and electronic parts, with an inexpensive apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a polymerization apparatus used in the present invention.

FIG. 2 is a cross-sectional view showing a conventionally used polymerization apparatus.

[Explanation of symbols]

 1 Heater 2 Polymerization kettle (reactor) 3 Stirrer 4 Thermometer 5 Torque meter motor 6 Cooler 7 Refluxer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Wakui 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] 1. A fragrance while using a compound having a hydroxyl group or a fatty acid ester thereof in the molecule and having a melting point of 80 ° C. or higher as a main raw material to cause a polymerization reaction in a reactor and distilling out and removing a fatty acid produced as a by-product. A method for producing an aromatic liquid crystal polyester, characterized in that, when producing a group liquid crystal polyester, a part of the fatty acid distilled is refluxed to the reactor.