JPH0737417B2 - Method for purifying 4,4'-biphenyldicarboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for purifying 4,4′-biphenyldicarboxylic acid.

[Prior Art] 4,4'-biphenyldicarboxylic acid is a substance that is expected to be in demand as a new polymer raw material.

The 4,4'-biphenyldicarboxylic acid can be synthesized by coupling benzoic acid or its derivative with nickel, palladium, etc. as a catalyst, or oxidizing the 4,4'-biphenyldisubstituted compound by liquid phase oxidation. However, the crude 4,4′-biphenyldicarboxylic acid produced by the former contains impurities such as benzoic acid and catalytic metal, and the crude 4,4′-biphenyldicarboxylic acid produced by the latter contains Include impurities such as oxidation reaction intermediates, catalytic metals, and coloring substances. Therefore, all of them are unsuitable as polymer raw materials that require high purity.
The establishment of a purification method for 4'-biphenyldicarboxylic acid has been an important issue.

Conventionally, as a method for purifying 4,4'-biphenyldicarboxylic acid, as described in JP-A-57-149,244, a method of recrystallizing using dimethyl sulfoxide as a solvent, or JP-A-58-85,841. As described in 1, a method of causing carbon dioxide to act on an aqueous solution of 4,4′-biphenyldicarboxylic acid dialkali salt to precipitate and separate 4,4′-biphenyldicarboxylic acid monoalkali salt, and then disproportionate Are known.

However, in the former purification method, the solubility of 4,4'-biphenyldicarboxylic acid in dimethylsulfoxide was low, a large amount of dimethylsulfoxide was required, and it was an inefficient separation method. Further, the latter purification method also requires a complicated operation using a pressurized pressure vessel, and improvement has been desired.

[Problems to be Solved by the Invention] The present invention aims to provide a purification method capable of obtaining 4,4′-biphenyldicarboxylic acid in high yield and high purity from crude 4,4′-biphenyldicarboxylic acid. To do.

[Means for Solving the Problems] The present inventors have conducted for the purpose of establishing the above-mentioned purification method,
Crude 4,4'-biphenyldicarboxylic acid is made into an aqueous solution of 4,4'-biphenyldicarboxylic acid salt, and then 4,4'-by one or more means selected from concentration, cooling and salting out of the aqueous solution. It was found that high-purity 4,4'-biphenyldicarboxylic acid was obtained in high yield by precipitating and separating a biphenyldicarboxylic acid salt, and then subjecting the obtained salt to acid precipitation or thermal decomposition. Was completed.

The 4,4'-biphenyldicarboxylic acid salt referred to herein is represented by the following formula (I).

(However, in the formula, X and Y represent Li, Na, K, Rb, or NH ₄ , and X and Y may be the same or different). Specifically, 4,4'-biphenyldicarboxylic acid disodium salt, 4,4'-biphenyldicarboxylic acid dipotassium salt, and other 4,4'-biphenyldicarboxylic acid dialkali metal salt or 4,4'-biphenyldicarboxylic acid dipotassium salt. It is an ammonium salt. Also, a mixture of these salts or a salt having different alkali metal or ammonium bonded to one carboxyl group and the other carboxyl group may be used.

The present invention can be carried out, for example, by the steps shown below.

(1) After adding crude 4,4'-biphenyldicarboxylic acid to an aqueous solution of an alkali metal and / or ammonium hydroxide or a weak acid salt to form a dicarboxylic acid salt, or to prepare an aqueous solution of a dicarboxylic acid salt. Process.

(2) A step of adding activated carbon or the like to the aqueous solution for decolorization, and thereafter separating the activated carbon.

(3) A step of precipitating 4,4′-biphenyldicarboxylic acid salt from the aqueous solution.

(4) A step of solid-liquid separating 4,4'-biphenyldicarboxylic acid salt and removing the adhering mother liquor by rinsing.

(5) A step of dissolving 4,4'-biphenyldicarboxylic acid salt in water again.

(6) A step of adding activated carbon or the like to the aqueous solution for decolorization, and then separating the activated carbon.

(7) A step of adding an acid to the aqueous solution and performing acid precipitation to precipitate 4,4′-biphenyldicarboxylic acid.

(8) Solid-liquid separation of 4,4'-biphenyldicarboxylic acid,
A step of removing the attached mother liquor by rinsing and drying.

Both of the steps of the decoloring operation of (2) or (6) may be performed, or only one of them may be performed.

When 4,4'-biphenyldicarboxylic acid is 4,4'-biphenyldicarboxylic acid diammonium salt, (5 ') 4,4'-biphenyldicarboxylic acid diammonium salt is thermally decomposed instead of the fifth step and thereafter. A method of obtaining 4,4′-biphenyldicarboxylic acid is also obtained.

However, in the present invention, the steps (1) and (3) are essential.

Hereinafter, the present invention will be described in detail according to procedures.

The crude 4,4'-biphenyldicarboxylic acid used in the present invention may be one obtained by coupling p-chlorobenzoic acid or the like, or 4,4'-dimethylbiphenyl, 4,4 '.
-Diethylbiphenyl, 4,4'-diisopropylbiphenyl, 4-alkyl-4'-formylbiphenyl, 4-
It may be one obtained by liquid phase oxidation of 4,4'-disubstituted biphenyl such as alkyl-4'-acyl biphenyl. The purity is not particularly limited, but it is preferable to use crude 4,4'-diphenyldicarboxylic acid of about 80 to 99% by weight, preferably about 90 to 98% by weight as a raw material.

Such crude 4,4'-diphenyldicarboxylic acid is first made into an aqueous solution of an alkali salt and / or an ammonium salt. The alkali salt includes lithium salt, sodium salt, potassium salt and rubidium salt, but sodium salt and potassium salt are preferable. As the alkali salt, an aqueous solution of hydroxide, carbonate, hydrogencarbonate or the like is used.
An aqueous solution of hydroxide is particularly preferable. As the ammonium salt, aqueous ammonia, aqueous solution of ammonium carbonate, aqueous solution of ammonium hydrogencarbonate or the like can be used, but aqueous ammonia is particularly preferable. The aqueous ammonia may be brought into contact with the carboxylic acid as an aqueous solution, or the carboxylic acid may be put in water and the ammonia gas may be blown therein. Alkali and /
Alternatively, the amount of ammonium used may be equal to or more than the equivalent of the impurities capable of forming 4,4′-biphenyldicarboxylic acid and a salt, but usually, in order to completely dissolve the crude 4,4′-biphenyldicarboxylic acid. Should be used 1.1 to 1.8 times. Upon dissolution, heating may be carried out if necessary.

When the crude 4,4'-biphenyldicarboxylic acid became an aqueous solution of a dicarboxylic acid salt, activated carbon was added to the crude 4,4'-biphenyldicarboxylic acid in an amount of 1 to 20% by weight, followed by stirring and solid-liquid separation. A decolorizing process can also be performed.

Then, 4,4'-biphenyldicarboxylic acid salt is precipitated from an aqueous solution of 4,4'-biphenyldicarboxylic acid salt. Examples of the precipitation method include the following methods. That is, (a) the aqueous solution is cooled.

(B) Concentrate the aqueous solution.

(C) Salt is added to the aqueous solution for salting out.

Such a method.

The above methods can be used alone, but are more effective when used in combination. For example, a method of concentrating an aqueous solution of 4,4′-biphenyldicarboxylic acid salt to some extent, cooling it to around room temperature, and then adding a salt to precipitate 4,4′-biphenyldicarboxylic acid salt is a highly pure 4,4 ′
Biphenyldicarboxylic acid is obtained in high yield. The salt used for salting out is preferably a chloride, carbonate, hydrogencarbonate or the like, and does not necessarily have to have the same cation as the 4,4'-biphenyldicarboxylic acid salt. That is, sodium chloride may be used for salting out 4,4'-biphenyldicarboxylic acid dipotassium salt.

The 4,4'-biphenyldicarboxylic acid salt thus precipitated is subjected to solid-liquid separation, and rinsed with cold water or an aqueous salt solution to remove the mother liquor adhering to the crystals. The salt used for the rinse liquid may be the same salt as used for salting out. If this rinsing operation is not performed, it becomes difficult to remove impurities in the mother liquor attached to the crystals, and the purity of 4,4'-biphenyldicarboxylic acid finally obtained will be low.

The rinsed 4,4'-biphenyldicarboxylic acid salt is purified or decomposed to give 4,4'-biphenyldicarboxylic acid by a known method. Preferably the 4,4'-biphenyldicarboxylic acid salt is redissolved in water. At this time, heating is effective because it is quickly dissolved. Particularly, in the case of 4,4'-biphenyldicarboxylic acid diammonium salt, the solubility in water is lower than that of other salts, and heating is necessary. If decolorization is necessary at this stage, 1 to 20% by weight of activated carbon is added to 4,4'-biphenyldicarboxylic acid for decolorization, and the activated carbon is removed by solid-liquid separation.

Then, an acid stronger than 4,4'-biphenyldicarboxylic acid such as hydrochloric acid, nitric acid or acetic acid is added to the aqueous solution to precipitate 4,4'-biphenyldicarboxylic acid. Further deposited 4,4'-
By solid-liquid separating the biphenyldicarboxylic acid, washing well with water and drying, highly pure 4,4'-biphenyldicarboxylic acid can be obtained in a high yield.

When the 4,4'-biphenyldicarboxylic acid salt is 4,4'-biphenyldicarboxylic acid diammonium salt, it can be converted to 4,4'-biphenyldicarboxylic acid by thermal decomposition. A suitable temperature for the thermal decomposition is 200 to 400 ° C. When the thermal decomposition temperature exceeds 400 ° C, a coloring substance is present in the 4,4'-biphenyldicarboxylic acid produced, and when the thermal decomposition temperature is less than 200 ° C, the decomposition rate is slow and it is not industrial.

[Examples] Hereinafter, the present invention will be described with reference to Examples. In the examples, "part" is "part by weight", "%" is "% by weight", and the purity is a value measured by a calibration curve method in high performance liquid chromatography.

Example 1 Using 4,4'-diethylbiphenyl as a raw material, cobalt and manganese acetates and sodium bromide as catalysts, the product air-oxidized in an acetic acid solution using an autoclave was filtered off, and the solid content was converted to hot acetic acid. After washing with water and drying, a crude 4,4'-biphenyldicarboxylic acid having a purity of 94.0% was obtained. The obtained crude 4,4'-biphenyldicarboxylic acid contains reaction intermediates such as 4-acetyl-4-carboxybiphenyl and 4-formyl-4-carboxybiphenyl, and catalytic metals such as cobalt and manganese bromine. The powder was colored in a flesh color with the coloring substance.

To 100 parts of this crude 4,4'-biphenyldicarboxylic acid, 1400 parts of a 5% aqueous potassium hydroxide solution was added and dissolved by heating at 80 ° C. The color of the liquid at this time was brownish brown. Then, 70 parts of potassium carbonate was added and concentrated to make the total amount 650 parts. The concentrated liquid was cooled to 50 ° C., and stirring was continued for 1 hour at the same concentration to sufficiently precipitate crystals, which was then separated by filtration.

The obtained crystals of dipotassium salt were rinsed with 95 parts of cold water and once dried to obtain 105 parts of crystals. The color of the crystals at this time was pale yellow. Hot water again to this crystal
Add 2,100 parts, dissolve completely with stirring, and add activated carbon 1
After adding 0 part of the mixture and continuing stirring for 30 minutes under heating at 80 ° C., activated carbon was removed by filtration to obtain a colorless transparent filtrate.

5% Hydrochloric acid was added little by little to this solution under stirring until the pH reached 3, and the precipitated crystals were separated by filtration, washed with water and dried to obtain 75 parts of pure white 4,4'-biphenyldicarboxylic acid crystals. Obtained.
The purity of this crystal was 99.9% and the yield was 79.8%.

Example 2 To 100 parts of the same crude 4,4′-biphenyldicarboxylic acid as in Example 1, 300 parts of 29% ammonia water was added, and further 5,000 parts of water was added and heated to 90 ° C. with stirring to obtain a solution. 3000 this solution
After gradually concentrating to 100 parts and gradually adding 100 parts of potassium chloride, the mixture was gradually cooled to 20 ° C. while continuing stirring to precipitate crystals, which were separated by filtration.

After rinsing the crystals with 95 parts of cold water, hot water at 90 ° C
Ammonia water was added little by little with stirring to maintain the pH at 8.5 or above and redissolved, 15 parts of activated carbon was added, and stirring was continued for 30 minutes, and then the activated carbon was removed by filtration. The color of the solution at this time was colorless and transparent. To this solution, 5% hydrochloric acid was added little by little until the pH became 3, to precipitate crystals, which were separated by filtration, washed with water and dried to give pure white 4,4 '.
84.1 parts of crystals of biphenyldicarboxylic acid were obtained. The purity of this crystal was 99.9% and the yield was 89.5%.

[Effects of the Invention] As described above, according to the present invention, crude 4,4'-biphenyldicarboxylic acid is formed into an aqueous solution of 4,4'-biphenyldicarboxylic acid salt, and then the aqueous solution is concentrated, cooled and salted out. 4, comprising depositing and separating 4,4'-biphenyldicarboxylic acid salt by one or more means selected from
Since it is a method for purifying 4'-biphenyldicarboxylic acid,
High-purity 4,4'-biphenyldicarboxylic acid can be obtained in high yield.

Claims (1)

[Claims] 1. A crude 4,4′-biphenyldicarboxylic acid is formed into an aqueous solution of a 4,4′-biphenyldicarboxylic acid salt represented by the following formula (I), and then the aqueous solution is concentrated, cooled and salted out. A method for purifying 4,4'-biphenyldicarboxylic acid, which comprises a step of depositing and separating 4,4'-biphenyldicarboxylic acid salt by one or more means described above. (However, in the formula, X and Y represent Li, Na, K, Rb, or NH ₄ , and X and Y may be the same or different).