JPH04202158A - Purification of 4,4'-biphenyldicarboxylic acid - Google Patents

Abstract

PURPOSE:To obtain the title high-purity crystalline compound useful as an intermediate raw material for polymers, having excellent heat resistance and strength by making 4,4'-biphenyldicarboxylic acid into an aqueous solution of dialkali salt and precipitating the aqueous solution with an acid at a specific temperature. CONSTITUTION:4,4'-Biphenyldicarboxylic acid (4,4'-BPDA) is dissolved in an alkali aqueous solution, preferably 0.5-1.2N aqueous solution of sodium hydroxide to form an aqueous solution of dialkali salt of 4,4'-BPDA. The aqueous solution is preferably filtered, then treated with active carbon, neutralized with an acid, preferably an aliphatic carboxylic acid at 150-300 deg.C, preferably 160-270 deg.C to maintain the pH at 7-4, thus crystals of 4,4'-BPDA are precipitated and subjected to solid-liquid separation to give the objective compound. The above-mentioned method is especially suitable for purifying crude 4,4'-BPDA obtained by oxidation of 4,4'-disubstituted biphenyl.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the use of 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 5, 3, 5, 4, 5, 4, 5, 4, 5, 4, 5, 5, 5, 5, 4, 4 kinds, etc.
'-Biphenyldicarboxylic acid (hereinafter referred to as 4.4'-BPDA)
). For details, please refer to coarse 4,4°-
BPDA is made into a dialkali salt aqueous solution, and this is acid-precipitated to obtain high-purity 4,4'-BPDA crystals. Crude 4,4"-BP
A method for purifying DA is provided.

[Prior Art] 4.4"-BPDA is obtained by oxidation of 4,4"-disubstituted biphenyl having a substituent at the 4,4°-position that can be easily converted into a carboxyl group by oxidation. However, because it is difficult to obtain 4,4°-disubstituted biphenyl, which is a raw material for oxidation, various methods have been proposed that involve various 4,4°-disubstituted biphenyls.For example,
A method in which p-bromotoluene is debrominized to produce 4,4'-dimethylbiphenyl, which is oxidized, a method in which biphenyl is diethylated or diisopropylated and then oxidized, and 4-ethylbiphenyl is formylated to produce 4-ethylbiphenyl-4. Examples include a method of oxidizing the aldehyde.

In addition to the oxidation of 4,4''-disubstituted biphenyl, there is also a method of isomerizing diphenic acid or its salt, a method of degenomerizing p-halogenobenzoic acid, and 4,4''-disubstituted biphenyl.
A method of carbonylating dihalogenated biphenyl by reacting it with water and carbon monoxide is also known.

However, the 4,4゛-BP obtained by these methods
DA usually contains a large amount of impurities such as reaction intermediates, by-products, unreacted substances, and catalysts used in the reaction.

Therefore, it is not suitable as a polymer raw material as it is and usually requires purification.

As conventional techniques for purifying 4.4"-BPDA,
43 Publication, ■Special Publication No. 1-'33100 (Japanese Unexamined Patent Publication No. 1985-'85841), ■Unexamined Japanese Patent Publication No. 2-26474
The method described in Publication No. 2 and the like are known.

Since 4.4'-BPDA is poorly soluble in ordinary organic solvents, purification by recrystallization is not easy, but a purification method of recrystallization using a specific solvent has been disclosed. For (1) above, dimethyl sulfoxide is used as a solvent, and (2) is N.

A method using No-dimethylformamide has been proposed. However, whether dimethyl sulfoxide or N, N'-dimethylformamide, 4.4'-BPD
The solubility of A is low (, using these solvents ■ or ■
The method described in requires a large amount of expensive solvent;
It is difficult to apply this method to industrial purification.

Further, as a purification method, a so-called acid precipitation method can be applied, in which 4,4''-BPDA is made into a dialkali salt aqueous solution, and this is acid-precipitated to recover crystals of 4,4''-BPDA. However, the 4,4"-BPDA crystals obtained by acid precipitation are very fine and the filterability of the crystals is extremely poor, the solid-liquid separation operation is troublesome, and the separated crystals are also difficult to dry.
Simply carrying out acid precipitation using the usual method will result in crude 4,4"-BP
Various impurities contained in DA cannot always be removed sufficiently. In this way, 4,4'-BPDA by acid precipitation method
There are various problems in the purification of

Items (1) and (2) above disclose improved methods of acid precipitation. In the method described in (2), crude 4,4'-BPDA is dissolved in an alkaline aqueous solution to form a dialkali salt aqueous solution, and carbon dioxide gas is applied to the solution to precipitate 4,4'-BPDA.
Separate the monoalkaline salt crystals. The monoalkaline salt crystals were then purified by disproportionation and acid precipitation into 4,4°-B
This is a PDA. Monoalkali salt crystals obtained by this method are obtained by directly acidifying 4,4
It has better filterability than °-BPDA crystals and can be easily separated into solid and liquid. However, it has the disadvantage that alkali metals cannot be sufficiently removed from the 4,4"BPDA crystals finally obtained through disproportionation and acid precipitation. Furthermore, the monosodium salt of 4,4°-BPDA has a higher solubility than the monopotassium salt. This method also has the disadvantage that potassium hydroxide, which is more expensive than sodium hydroxide, must be used to increase the recovery rate of monoalkali salts. In addition to the disadvantage of being expensive, there are other problems such as high drug costs, complicated processes, and high equipment costs.

In addition, the method described in
4 by adding a water-soluble organic solvent to the dialkali salt aqueous solution of A.
．． 4'-BPDA dialkali salt crystals are precipitated, and then the separated dialkali salt crystals are dissolved in water again to obtain 4.4'-BPDA crystals by acid precipitation. However, this method is not only complicated in that it involves repeating the recrystallization and crystallization operations twice, but also suffers from acid precipitation.
This method has a defect in the acid precipitation method in that the PDA crystals are fine and filterability is poor.

[Problems to be Solved by the Present Invention] The present invention is directed to a technique in which the filterability of purified crystals obtained by acid precipitation is poor (and impurities cannot be sufficiently removed) in the acid precipitation purification of 4,4°-BPDA. The purpose of the present invention is to provide a purification method that solves these problems and makes it possible to produce highly purified 4°4°-BPDA, which is extremely advantageous industrially.

[Means for Solving the Problems] As a result of intensive research to solve the above technical problems in the acid precipitation purification method of 4,4"-BPDA, the present inventors have found that 4,4"-BPDA The present invention was achieved by discovering that 4,4'-BPDA crystals with excellent filterability and high purity can be obtained by acid precipitation of a dialkali salt aqueous solution under specific conditions.

That is, in the present invention, when purifying 4,4°-BPDA by making it into a dialkali salt aqueous solution and then acid precipitation,
4.4”BPD from 4°-BPDA dialkali salt aqueous solution
This is a method for purifying 4,4''-BPDA, which is characterized by acid precipitation of A crystals at a temperature in the range of 1.50 to 3000C.

The present invention will be explained in detail below.

Although the method of the present invention is applicable to any 4,4''-BPDA, it is particularly suitable for purifying crude 4,4°-BPDA obtained by oxidation of 4,4''-disubstituted biphenyl.

4,4'-BPDA can be easily obtained by oxidation of 4,4'-disubstituted biphenyl having a substituent at the 4,4'-position. The substituent at the 4,4'-position may be any substituent that can be oxidized and converted into a carboxyl group, and usually may be an aliphatic hydrocarbon group or one containing an oxygen atom. For example, in methyl, ethyl, propyl, isopropyl, cyclohexyl, formyl, acetyl groups, etc., the two substituents do not necessarily have to be the same (or may be a combination of these). Also, if one of the substituents is already a carboxyl group, It's okay.

The oxidation of 4.4′-disubstituted biphenyl to 4.4″-BPDA is carried out in an acetic acid solvent in the presence of a heavy metal catalyst such as a cobalt compound or a manganese compound with an oxygen-containing gas under high temperature and pressure. Heavy metal compounds such as cobalt compounds and manganese compounds can be used as catalysts, and bromine compounds, aldehydes, and ketones can also be used as promoters.4,4'-BPDA obtained by oxidation contains unreacted products and oxidized intermediates. , by-products, impurities such as catalysts used in the reaction, and other impurities derived from raw materials.

In the method of the present invention, 4,4°-BPDA is first dissolved in an alkaline aqueous solution to form an aqueous solution of 4,4'-BPDA dialkali salt. As the alkali, an alkali metal hydroxide such as sodium, potassium, or lithium, preferably sodium hydroxide or potassium hydroxide, is used in the form of an aqueous solution. 4,4"- compared to potassium hydroxide
Sodium hydroxide, which has a high solubility in BPDA, is more preferable.

The amount of alkali hydroxide used is 4,4”B, which is a dibasic acid.
At least an equivalent amount or more is required as a base to PDA. The concentration of the alkaline aqueous solution is the specified concentration of the base,
1.5N or less, preferably in the range of 0.5 to 1.2N is suitable. When the alkali concentration is below about IN, 4,4°-B P
D and A dissolve almost stoichiometrically, but when the concentration exceeds about IN, the solubility decreases, which is not preferable.

Further, even if the alkali concentration is too low, the amount of solution to be treated increases, which is not preferable.

4,4 in 4.4'-BPDA dialkali salt aqueous solution
'-BPDA concentration can be appropriately selected in the range of 5 to 15% by weight depending on the concentration of the alkaline aqueous solution used.

It is desirable to adsorb the 4.4'-BPDA dialkali salt aqueous solution using activated carbon. Furthermore, prior to the activated carbon treatment, the dialkali salt aqueous solution can be filtered to remove insoluble matter. The activated carbon used may be powder or granule, and 4,4
About 1-50% by weight of activated carbon based on °-BPDA is added to the aqueous dialkali salt solution, heated for about 15 minutes to 5 hours, and then filtered off. The 4.4'-BPDA dialkali salt aqueous solution is treated with activated carbon to remove coloring components, and the final result is high purity 4.4'-BPDA crystals that not only have excellent color quality but also contain virtually no bromine. is obtained. Organic bromides cannot be completely removed simply by acid precipitation purification.

Next, in the method of the present invention, activated carbon-treated 4, 4
'-B PDA dialkali salt aqueous solution is acid-precipitated at high temperature to precipitate 4.4'-B PDA crystals. In order to obtain crystals with excellent filterability during solid-liquid separation by the method of the present invention, the temperature of acid precipitation is particularly important, and the preferred temperature range is 150 to 300C, more preferably 160 to 2700C. If the acid precipitation temperature is lower than the above range, the precipitated crystals will be fine and have poor filterability, making the solid-liquid separation operation in the next step extremely difficult. Moreover, raising the temperature beyond the above range is disadvantageous in terms of energy and is not preferable.

During acid precipitation, the pressure needs to be higher than the saturated vapor pressure of the solution at that temperature. Naturally, the higher the temperature, the higher the pressure required.

Generally, the particle size of fine crystals can be increased by growing the crystals by maintaining them at a high temperature in a solvent, but this effect is not observed at all in 4,4''-BPDA crystals. Crystals with large particle size and excellent filterability can only be obtained by precipitating the crystals at high temperatures.

The type of acid used for acid precipitation may be either an organic acid or an inorganic acid. Inorganic acids include sulfuric acid, nitric acid, phosphoric acid,
Mineral acids such as hydrochloric acid are suitable, and aliphatic carboxylic acids are suitable as organic acids, such as formic acid, acetic acid, and propionic acid. Since the acid precipitation temperature is high, it is desirable that the acid used be one that does not corrode the equipment material.

Although the concentration of acid used for acid precipitation is not particularly limited, it is desirable to avoid high concentrations from the viewpoint of corrosion of equipment materials.

During acid precipitation, the pH is maintained within the range of 7 to 4.

In order to completely acidify and recover 4.4"-E3PDA, it is naturally necessary to neutralize the alkali and lower the pH to 7 or below. However, if the pH is lower than the above range, the crude 4.4"-E3PDA
"- Impurities of aromatic carboxylic acids contained in BPDA as a by-product of the oxidation reaction remain in the purified crystals, making it impossible to obtain high-purity crystals.

In this case, particularly organic acids can be suitably used without worrying about a decrease in pH.

The acid precipitation method can be carried out either batchwise or in a flow manner. A method of adding an acid to a 4.4'-BPDA dialkali salt aqueous solution, or a method of adding a dialkali salt aqueous solution to an acid may be used. A preferable method is to simultaneously supply equivalent amounts of dialkali salt aqueous solution and acid into a high-pressure container to carry out acid precipitation. According to this method, it is possible to avoid extremely high pH or low PR in the high-temperature container, which is desirable from the viewpoint of corrosion resistance of the equipment material.

The slurry liquid of 4,4'-BPDA crystals obtained in the acid precipitation step can be separated into crystals and mother liquor by ordinary solid-liquid separation means. Solid-liquid separation may be performed at elevated temperatures. The mother liquor containing alkali can be removed from the separated crystals by rinsing them with a cleaning liquid such as water or washing them with a slurry, if necessary.

Finally, by drying the crystals, 4,4°-BPDA
High purity purified crystals can be obtained.

[Example] The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these examples.

In the examples, the purity of 4,4"-BPDA and other carboxylic acids were analyzed by gas chromatography, metals were ashed and analyzed by atomic absorption spectroscopy, and bromine was analyzed by tablet-forming and X-ray fluorescence analysis. Ta.

The analysis conditions for gas chromatography analysis are as follows. The sample is subjected to gas chromatography after being methyl esterified using Rinyu trimethyl.

Column °Capillary column (Shimazu C
BPI-325-0, 50) Carrier gas/Nitrogen temperature = 160°C → 270°C (5°C/m1n) Detector/Hydrogen flame ionization detector For grain size measurement, Coulter counter model T
A-IF (Coulter Electronic
s Inc.) and expressed as an average particle size.

Example 1 As crude 4,4°-BPDA as a purified raw material, 4′-ethylbiphenyl-4-aldehyde (EBPAL) produced by formylation of 4-ethylbiphenyl was oxidized by the following method to obtain 4.4” Obtained BPDA.

Acetic acid 800 with the catalyst dissolved in it in a pressure-resistant titanium reactor equipped with a stirring device, a reflux condenser, and a heating device.
Place the weight part in advance at a temperature of 200℃ and a pressure of 1.
6. While blowing air at 5 kg/cm2G, 800 parts by weight of an oxidizing raw material solution in which EBPAL was dissolved at a concentration of 20% by weight in an acetic acid solution of the same catalyst as the charging solution was continuously supplied at a constant rate for 60 minutes. During this time, air was blown in to maintain the oxygen concentration of the exhaust gas at 5%, and even after the feed of the oxidizing raw material solution was stopped, air was blown in for about 20 minutes to complete the oxidation reaction. Here, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and 1. 1, 2.2-tetrabromoethane was dissolved in acetic acid (water 1% by weight), and the solvent was cobalt/manganese/bromine-5001500/1.
The concentration was 000 ppm by weight. Next, the oxidation reaction slurry taken out after the reactor had cooled down was filtered, the separated crystals were washed, and then dried to obtain crude 4,4°-BPD.
A crystal was obtained.

This 4,4"-BPDA has a purity of 96.6%, and the main impurities are terephthalic acid (TPA'), biphenyl-4-carboxylic acid (BPCA), and 4'-ethylbiphenyl-4-carboxylic acid (EBPCA). ), 4'-
Acetyl biphenyl-4-carboxylic acid (AcBPCA)
, organic brominated compounds, etc. (See Table 1) The above crude 4,4''-BPDA crystals were dissolved in an IN-sodium hydroxide aqueous solution to a concentration of 5% by weight.

4. Add 20% by weight of activated carbon powder to this solution, heat under reflux for 60 minutes, cool and filter to remove activated carbon.
A 4'-BPDA disodium salt aqueous solution was prepared.

Next, the activated carbon-treated 4,4"-BPDA disodium salt aqueous solution was subjected to acid precipitation treatment using acetic acid as follows. A 10% by weight acetic acid aqueous solution ( Approximately 1..7N) 750 parts by weight was charged at a temperature of 200°C and a pressure of 20 kg/cm2G.
Then, 750 parts by weight of the above 4°4°-BPDA disodium salt aqueous solution was fed at a constant rate over 30 minutes. The reactor was cooled, and the slurry liquid taken out from inside was filtered under reduced pressure using a glass filter (pore number 4, standard maximum pore diameter 10 to 16 μm) to separate 4.4'-BPDA crystals.

In this case, the filtration mother liquor had a pH of 4.5.

The crystals separated by filtration were washed by repeating the washing operation of reslurrying with pure water and filtration three times.

The washed crystals were heated and dried to obtain purified 11,4”-BPDA.
35.5 parts by weight of was obtained. The recovery rate of purified crystals was 98% considering the purity of crude crystals. The average particle size of the purified crystals was 47 μm, and the filterability of the crystals in a series of solid-liquid separation operations was extremely good. The properties of purified crystals are shown in Table 1 (
It is shown in part l).

Table 1 (Part 1) Batch method acid precipitation Table 1 (Part 2) Batch method acid precipitation Examples 2 to 3 The acid precipitation temperature in Example 1 was set to 25% in Example 2.
Purified crystals were obtained in the same manner as in Example 1 except that the temperature was 0°C and 170°C in Example 3.The filterability of the crystals in the solid-liquid separation operation was good, and the purified crystals obtained were The properties are shown in Table 1 (Part 1).

Comparative Example 1 The same procedure as in Example 1 was carried out except that the acid precipitation temperature in Example 1 was changed to 140°C. However, the particle size of acid-precipitated crystals is small, and the filterability of the slurry liquid taken out is poor.
Vacuum filtration using m) took a long time. Moreover, since the crystals could not be washed sufficiently, the sodium content of the purified crystals was high. The properties of the obtained purified crystals are shown in Table 1 (Part 2).

7. Incidentally, when acid precipitation was performed at room temperature, the resulting slurry liquid became creamy and could not be substantially separated by filtration.

191 Examples 4 to 5 The acid for acid precipitation in Example 1 was 750 parts by weight of formic acid (10% by weight aqueous solution, about 2.2N) in Example 4, and propionic acid (10% by weight in Example 5). Aqueous solution, approx. 1
．． Purified crystals were obtained in exactly the same manner as in Example I except that 750 parts by weight of 4N) was used. The filterability of the crystals in the solid-liquid separation operation was good. The properties of the obtained purified crystals are shown in Table 1 (Part 2).

Example 6 The crude 4,4°-BPI) A of Example 1 was dissolved in an IN-thorium hydroxide aqueous solution to a concentration of 7% by weight, and treated with activated carbon in the same manner as in Example 1 to obtain 4,4°-B- A PDA disodium salt aqueous solution was prepared. Using this 4,4'-BPDA disodium salt aqueous solution and a 10% by weight acetic acid aqueous solution, an acid precipitation reaction was carried out continuously as follows to produce 4,4'-BPD.
Purified crystals of A were obtained.

In a pressure-resistant titanium reactor equipped with a stirring device and a heating device, the above activated carbon-treated disodium salt aqueous solution and 10
A wt% acetic acid aqueous solution is continuously supplied from separate supply ports at a rate of 1,000 parts by weight per hour, while the acid-precipitated crystal slurry is transferred from the discharge port to the crystallization tank with an average residence time of 30 minutes. It was extracted continuously. Obtained 4゜4“
- BPDA slurry liquid is filtered using polypropylene filter cloth (1,
The crystals were separated by filtration using a basket centrifuge (domestic centrifuge, 3.000 rpm, 1,500 G) equipped with a 3.000 mesh centrifuge, and the separated crystals were washed with pure water. This crystal was heated and dried to purify 4.4'-B.
PDA was obtained. The recovery rate of purified crystals was 98% or more. The average particle size of the purified crystals was 48 μm, and the filterability of the crystals in a series of solid-liquid separation operations was extremely good. Table 2 shows the properties of the purified crystals.

Table 2 Flow method acid precipitation Example 7 The activated carbon-treated 4,4''-BPDA disodium salt aqueous solution (4,4''-BPDA concentration 7% by weight) of Example 6 and the IN-hydrochloric acid aqueous solution were used. An acid precipitation reaction was carried out continuously in a titanium reactor as follows at a temperature of 200°C and a pressure of 20 kg/cm2G. At the same time, an IN-hydrochloric acid aqueous solution was supplied at a rate of approximately 930 parts by weight per hour while adjusting the pH of the filtered mother liquor of the acid precipitation slurry to be maintained at 7 or below and 4 or above. On the other hand, the acid precipitation slurry liquid was continuously extracted from the discharge port to the crystallization tank so that the average residence time was 30 minutes. The obtained 4,4''-BPDA slurry liquid was subjected to solid-liquid separation and washing operations in the same manner as in Example 6, and the obtained crystals were dried to obtain purified 4,4°-BPDA.
I got it. Its properties are shown in Table 2.

Comparative Example 2 23- In Example 7, the supply amount of the IN~hydrochloric acid aqueous solution was incorrectly adjusted, and the supply amount increased, causing the pH of the filtered mother liquor of the acid precipitation slurry to change.
became 2. In this case, the filterability of the obtained slurry of acid-precipitated crystals was good, but terephthalic acid (TPA)
), 4'-acetylbiphenyl-4-carboxylic acid (A
cBPCA) and other impurities are not sufficiently purified, resulting in 4.4
'-BPDA had low purity. Its properties are shown in Table 2.

Example 8 Using the activated carbon-treated 4,4'-BPDA disodium salt aqueous solution (4,4'-BPDA concentration 7% by weight) of Example 6 and the IN-sulfuric acid aqueous solution, the same procedure as in Example 7 was carried out to obtain a continuous solution. An acid precipitation reaction was performed to obtain purified crystals of 4°4'-BPDA. Its properties are shown in Table 2.

[Effects of the Invention] According to the method of the present invention, crude 4.4'-BPDA crystals are
．． When purifying the 4'-BPDA dialkali salt aqueous solution by acid precipitation, by acid precipitation at a high temperature of 150 to 300°C, the acid precipitation crystals have excellent filterability that can be applied to solid-liquid separation means. Become. Furthermore, by maintaining the pH during acid precipitation at 7 to 4, crystals containing extremely few impurities can be obtained. Furthermore, by treating the crude 4,4°-BPDA dialkali salt aqueous solution with activated carbon and acid precipitation, we can produce high purity 4,4°-BPDA with excellent color quality and virtually no bromine.
．． 4'-BPDA is obtained.

High purity 4.4'- produced by the method of the present invention
BPDA can be suitably used as a polymer raw material.

By the method of the present invention, high-purity 4.4'-B
PDA can be produced, and the industrial significance of the present invention is extremely large.

Claims (3)

[Claims] (1) 4,4'-biphenyldicarboxylic acid is made into a dialkali salt aqueous solution, and 4,4'-biphenyldicarboxylic acid crystals are extracted from the 4,4'-biphenyldicarboxylic acid dialkali salt aqueous solution at a temperature of 150 to 300°C. A method for purifying 4,4'-biphenyldicarboxylic acid, the method comprising: (2) Claim No. 4 (2) whose pH during acid precipitation is 7 to 4
The method described in section 1). (3) The method according to claim (2), wherein the acid used for acid precipitation is an aliphatic carboxylic acid.