JPH10120624A - Purification of 2-hydroxymephthalene-6-carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply purify a crude product of the subject compound into a high-purity product low in metal ion content by dissolving crude 2- hydroxynaphthalene-6-carboxylic acid in a water-soluble medium by an alkali substance and precipitating with an acid at a pH value in a specific range. SOLUTION: (A) Crude 2-hydroxynaphthalene-6-carboxylic acid is dissolved in (B) a water solvent, for example, water of 2-100 times as much as the component A, by using (C) an alkali substance such as an alkali metal hydroxide, ammonia or a lower aliphatic amine in an amount of 0.8-2.0mol% based on the component A and optionally adding (D) 1-10mol% of an antioxidant based on the component A, and then is precipitated with an acid by adjusting to pH 2.0-5.0 with the acid such as hydrochloric acid, sulfuric acid, formic acid, acetic acid or propionic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying 2-hydroxynaphthalene-6-carboxylic acid (hereinafter abbreviated as "2.6 acid"). More specifically, the crude 2.6 acid (crude 2.6 acid) is added with an antioxidant, if necessary, in an aqueous solvent and dissolved with an alkaline substance. The present invention relates to a method for purifying 2.6 acid, characterized in that it is precipitated.

[0002]

2. Description of the Related Art 2.6 Acid is an important compound as a monomer of a polymer compound for electronic materials. The 2.6 acid used as a monomer of the polymer for electronic materials is not only high in organic composition, but also Na, K, F in order to avoid the influence of metal ions on the performance of electronic materials.
It is required that the content of metal ions such as e be low.
No. 159381 relates to a method for producing 2.6 acids.
No. 6, JP-A-57-95939, etc., a method is generally used in which a potassium salt of 2-hydroxynaphthalene is reacted with carbon dioxide by a Kolbe-Schmit reaction. However, the crude 2.6 acid thus obtained contains raw materials, isomers, tar-like substances, coloring substances, and the like, and it is necessary to improve the purity.

[0003]

SUMMARY OF THE INVENTION From such a problem,
Various methods for purifying the crude 2.6 acid have been proposed.
JP-A-1-216555 and JP-A-2-21863
No. 4 discloses a method in which a crude 2.6 acid (total amount of impurities 0.73%) is prepared from an ether solvent such as a water-miscible linear or cyclic aliphatic ether, aliphatic polyether or aliphatic hydroxy ether. It is recrystallized to obtain a product of high purity (less than 0.2% of total impurities), but its purification yield is as low as 72%, and it is difficult to recover the solvent, which is industrially disadvantageous. In addition, these publications do not describe metal ions, and it is unknown about the content of metal ions in the purified 2.6 acid. The present inventors have conducted intensive studies on the purification method in order to produce a 2.6-acid having a desired high purity. As a result, a 2.6-acid having high purity and a low content of metal ions was obtained in a simple manner. The present invention was completed by finding a method that can be used. That is, an object of the present invention is to provide a method for purifying a 2.6 acid, which is industrially excellent and can obtain a high-purity 2.6 acid.

[0004]

The gist of the present invention made in order to solve the above-mentioned problems is to dissolve a crude 2.6 acid in an aqueous solvent with an alkaline substance, and then to dissolve the crude 2.6 acid in a pH range of 2.0 to 2.0. Purification method of 2.6 acid, characterized by carrying out acid precipitation at 5.0; The above-mentioned method using 2 to 100 times by weight of water to crude 2.6 acid; Alkali metal water as alkaline substance The above or the above-mentioned method, wherein one or two or more selected from oxides, ammonia and lower aliphatic amines are used in an amount of 0.8 to 2.0 mol times based on the crude 2.6 acid; The above or the above-mentioned method, wherein an antioxidant is used in an amount of 1 to 20 mol% with respect to the crude 2.6 acid when dissolving in an alkaline substance; hydrochloric acid, sulfuric acid, formic acid, acetic acid as an acid used for acid precipitation 4. The method according to any one of the above, wherein one or two or more selected from propionic acid are used. Law; it is.

The basic operation of the purification method of the present invention consists of dissolving 2.6 acid in an aqueous solvent with an alkaline substance and then adjusting the pH range to 2.0 to 5.0. And acid precipitation. 2.6 crude used in the present invention
Examples of the acid include a crude product obtained by a Kolbe-Schmit reaction between a potassium salt of 2-hydroxynaphthalene and carbon dioxide, but the acid is not limited to one prepared by such a method. The crude 2.6 acid obtained by the above method is inevitably mixed with raw materials, isomers, decomposition products, and the like. For example, 2-hydroxynaphthalene, 2-hydroxynaphthalene,
It contains raw materials and isomers such as -hydroxynaphthalene-3-carboxylic acid and 2-hydroxynaphthalene-3,6-dicarboxylic acid, metal ions such as Na, K and Fe, coloring components and the like.

In the method of the present invention, the above-mentioned crude 2.6 acid is first dissolved in an aqueous solvent with an alkaline substance. The amount of aqueous solvent used is between 2 and 100 relative to the crude 2.6 acid.
The weight is used, preferably 5 to 50 times by weight. Crude 2.
If the amount of water used is less than 2 times the weight of the 6 acids, it is difficult to sufficiently dissolve the crude 2.6 acid, and if it exceeds 100 times the loss of the 2.6 acids upon acid precipitation increases. And wastewater treatment costs increase. As the water to be used, it is more preferable to use purified water (for example, ion-exchanged water, distilled water, etc.).

The alkaline substance is not particularly limited as long as it is an alkaline substance capable of dissolving 2.6 acid in water.
For example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, lower aliphatic amines such as triethylamine and triethanolamine, aqueous ammonia (and / or ammonia gas) and the like are used, and the operation is particularly simple and It is preferable to use ammonia water and / or ammonia gas since the metal ion content can be reduced.
In addition, you may use 2 or more types of said alkaline substance together. The amount of the alkaline substance used for the crude 2.6 acid is roughly 2.
Any amount may be used as long as the six acids can be dissolved in the solvent, and generally 0.8 to 2.0 moles, preferably 0.9 to 1.3 moles of the alkaline substance is used relative to the crude 2.6 acid. . 0.
If it is less than 8 moles, the 2.6 acid will not be completely dissolved, and if it exceeds 2.0 moles, the economic burden will increase. The temperature for dissolving the crude 2.6 acid is not particularly limited, and the reaction can be carried out at a suitable temperature from room temperature to the boiling point of the solvent or lower. It is carried out at a temperature of about 95 ° C, preferably about 65 to 90 ° C.

In dissolving the above crude 2.6 acid, an antioxidant may be added, if necessary, to prevent oxidation of the 2.6 acid. Examples of the antioxidant include sodium hydrosulfite, Rongalit, acid sulfite, and the like. The amount of the antioxidant to be used is not particularly limited, but is generally used at about 1 to 20 mol% based on the crude 2.6 acid. Further, in order to prevent oxidation of 2.6 acid, it is more preferable to perform the dissolving operation under an inert gas (eg, nitrogen gas, argon gas, etc.) gas stream. The crude 2.6 acid salt aqueous solution thus obtained may be subjected to an activated carbon treatment, if necessary, to be decolorized.

[0009] The aqueous salt solution of the crude 2.6 acid prepared above is then added with an acid, adjusted to a pH range of 2.0 to 5.0, and subjected to acid precipitation to obtain a purified 2.6 acid. . As the acid, various acids can be used, and examples thereof include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as formic acid, acetic acid, propionic acid, and methanesulfonic acid. Particularly, lower aliphatic carboxylic acids soluble in water Acids are preferred, and acetic acid, formic acid and propionic acid are more preferred. In addition, inorganic acids and organic acids may be used in combination. The pH at the time of acid precipitation is adjusted to the range of 2.0 to 5.0, preferably 3.6 to 4.8. pH 2.0
If it is lower, isomers may be mixed, and 5.0
If it is higher, the purification yield may decrease. 2.6 crude
The addition of the acid to the aqueous salt solution of the acid can be performed at an appropriate temperature. However, as described above, it is preferable that the crude 2.6 acid is dissolved under heating. ~ 95 ° C
(Preferably about 65 to 90 ° C.) to precipitate 2.6 acid, and then lower the temperature to room temperature to 0 ° C.
℃ to complete the crystal precipitation. The precipitated crystals are separated by a method such as filtration and centrifugation according to a conventional method, and, if necessary, washed with a small amount of water and dried to purify 2.
Six acids are obtained.

Hereinafter, one procedure of the purification method according to the present invention will be described in more detail. The crude 2.6 acid is dissolved in 2 to 100 times by weight, preferably 5 to 50 times by weight of the crude 2.6 acid. Charge, at least one or two selected from sodium hydroxide, potassium hydroxide, ammonia and lower aliphatic amines such as triethylamine as alkaline substances, in an amount of 0.8 to 2.0 mol based on crude 2.6 acid. Times, preferably 0.9
Room temperature or elevated temperature (less than boiling point) up to 1.3 mol times
To dissolve the crude 2.6 acid. It is advantageous to carry out the treatment under an inert gas atmosphere, particularly nitrogen. At the time of dissolution, if necessary, 1 to 2 or more kinds of antioxidants such as sodium hydrosulfite, Rongalite, and acid sulfite are added in an amount of 1 to 20 mol% based on crude 2.6 acid.
May be used. After dissolution, if necessary, an activated carbon treatment may be performed. Further, if necessary, a salt such as potassium chloride, sodium chloride, ammonium chloride, potassium sulfate, sodium sulfate, or ammonium sulfate is added at this stage, and no salting out to 30% by weight salting out, preferably 5 to 15%. The salting out may be carried out by weight%, separated and purified with an alkali salt of 2.6 acid, and then the salted out salt may be redissolved in water and then subjected to acid precipitation described later. According to this method, the purity of the purified 2.6 acid can be further increased.
The salt used for salting out is preferably the same salt as the base species of the salt of 2.6 acid.

The acid precipitation is carried out in a temperature range of 50 to 95 ° C., preferably 65 to 90 ° C., and in a pH range of 2.0 to 5.0, preferably 3.6.
The reaction is carried out in -4.8, and examples of the acid include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as formic acid, acetic acid, propionic acid and methanesulfonic acid. Particularly, a lower aliphatic carboxylic acid soluble in water is preferable. After the acid precipitation, the precipitation of the crystals is usually completed at a temperature of room temperature to 0 ° C., and the precipitated 2.6 acid crystals are separated from the solvent by, for example, filtration or the like, and are washed and dried if necessary. .

[0012] The purification method of the present invention is not limited to the above description, and can be carried out with appropriate modifications.
For example, a step of adding a precipitation aid such as cellulose powder to an aqueous salt solution of the crude 2.6 acid prepared in the dissolving step, followed by filtration to remove tar-like substances and contaminants may be added. The great advantage of the method according to the present invention is that the obtained 2.6 acid has high purity and can be purified only with an aqueous solvent, which is advantageous not only for removal of metal ions and the like, but also for organic solvents. Because it does not use, it is also excellent in global environment.

[0013]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following examples, three kinds of crude 2.6 acids were used as raw materials, which mainly contained the following impurities. Impurity in crude 2.6 acid (purity: 88.1% by weight) of raw material No. 1. 8.30% by weight of 2-hydroxynaphthalene-3-carboxylic acid 2-hydroxynaphthalene-3,6-dicarboxylic acid 67% by weight 2-hydroxynaphthalene 0.31% by weight Na 87ppm K 417ppm Fe 6ppm

Impurity in raw 2.6 acid (purity: 92.0%) of raw material No. 2. 2-66% by weight of 2-hydroxynaphthalene-3-carboxylic acid 2-hydroxynaphthalene-3,6-dicarboxylic acid 0.70 wt% 2-hydroxynaphthalene 0.48 wt% Na 70 ppm K 315 ppm Fe 15 ppm

Impurity in Raw 2.6 Acid (Purity: 88.1%) of Raw Material No. 3 0.38% by weight of 2-hydroxynaphthalene-3-carboxylic acid 2-hydroxynaphthalene-3,6-dicarboxylic acid 1.62 wt% 2-hydroxynaphthalene 0.20 wt% Na 75 ppm K 320 ppm Fe 4 ppm

Example 1 In a nitrogen stream, 11.3 g of raw material No. 1 crude 2.6 acid (purity: 88.1% by weight) and 0.9 g of 65% ammonium sulfite were added to 150 ml of water and heated to 70 ° C. And 8.2 g of 30% sodium hydroxide were added and dissolved. PH at this time
Was 8.0. The temperature of the solution was raised to 90 ° C., and while keeping the temperature, 35% hydrochloric acid was added dropwise until the pH reached 3.6 to effect acid precipitation. Thereafter, the solution was cooled to room temperature, and the 2.6 acid crystallized from this solution was collected by filtration, washed with 50 ml of ion-exchanged water and dried to obtain 9.5 g of pure 2.6 acid. The purity is 97.
7% and a purification yield of 92.9%.

Example 2 In Example 1, 2% sodium hydroxide was used instead of 30% sodium hydroxide.
The same operation as in Example 1 was carried out except that 3.9 g of 8% aqueous ammonia was used, to obtain 9.4 g of pure 2.6 acid. 99.1% purity
And the purification yield was 93.2%.

Example 3 The procedure of Example 2 was repeated, except that 8.0 g of acetic acid was used instead of 35% hydrochloric acid.
I got The purity was 99.3% and the purification yield was 90.5%. Impurities in the obtained purified 2.6 acid were as follows. 0.21% by weight of 2-hydroxynaphthalene-3-carboxylic acid 0.22% by weight of 2-hydroxynaphthalene-3,6-dicarboxylic acid Less than 0.05% by weight of 2-hydroxynaphthalene Na 1 ppm K 1 ppm Fe 2 ppm

Example 4 In Example 2, 88% formic acid was used instead of 35% hydrochloric acid.
Except that the amount was changed to 4 g, the procedure of Example 2 was repeated to obtain 9.6 g of pure 2.6 acid. The purity was 97.6% and the purification yield was 93.8%.

Example 5 In a nitrogen stream, 15.0 g of raw material No. 2 crude 2.6 acid (purity: 92.0% by weight) was added to 100 ml of water, heated to 70 ° C., and 5.3 g of 28% aqueous ammonia was added. Added and dissolved.
The pH at this time was 7.0. The temperature of the solution was raised to 90 ° C., and acetic acid was added dropwise until the pH reached 4.8. After cooling to room temperature, the 2.6 acid crystallized from this solution was collected by filtration, washed with 67 ml of tap water and dried to obtain 2.6 acid.
2 g were obtained. The purity is 99.7% and the purification yield is 95.
4%. Impurities in the obtained purified 2.6 acid were as follows. 2-hydroxynaphthalene-3-carboxylic acid less than 0.05% by weight 2-hydroxynaphthalene-3,6-dicarboxylic acid 0.28% by weight 2-hydroxynaphthalene less than 0.05% by weight Na 7ppm K 2ppm Fe 5ppm

Example 6 In a nitrogen stream, 22.5 g of raw material No. 3 crude 2.6 acid (purity: 88.1% by weight) was added to 300 ml of water, heated to 70 ° C., and 7.1 g of 28% aqueous ammonia was added. Dissolved. The pH at this time was 7.0. The temperature of the solution was raised to 90 ° C., and acetic acid was added dropwise until the pH reached 4.8. After cooling to room temperature, the 2.6 acid crystallized from this solution was collected by filtration, washed with 100 ml of tap water and dried to obtain 18.4 g of pure 2.6 acid. Purity was 99.4% and purification yield was 91.3%. Impurities in the obtained purified 2.6 acid were as follows. 2-hydroxynaphthalene-3-carboxylic acid less than 0.05% by weight 2-hydroxynaphthalene-3,6-dicarboxylic acid 0.56% by weight 2-hydroxynaphthalene 0.04% by weight Na 9ppm K 4ppm Fe 1ppm

Example 7 In a nitrogen stream, 22.5 g of raw material No. 3 crude 2.6 acid (purity: 88.1% by weight) and 1.7 g of 65% ammonium sulfite were added to 150 ml of water and heated to 70 ° C. Was dissolved in 7.8 g of 28% aqueous ammonia, and salted out by adding 19.5 g of ammonium chloride. After cooling to 15 ° C., the 2.6-acid ammonium salt crystallized from this solution was collected by filtration and 5 wt. %
Washed with 50 ml of aqueous ammonium chloride. The purity of the 2.6 acid at this stage of the 2.6 acid ammonium salt is 99.
9%. Then, the 2.6-acid ammonium salt was dissolved in water, and was subjected to acid precipitation with acetic acid in the same manner as in Example 6 to obtain high-purity purified 2.6-acid.

Comparative Example An additional test of Example 10 described in the above-mentioned Japanese Patent Application Laid-Open No. 1-216955 was conducted. Under nitrogen stream, 25 g of raw material No. 3 crude 2.6 acid (purity: 88.1% by weight) was added to 96 ml of 1.4-dioxane.
And 24 ml of water, and dissolved by heating to 70 ° C. After treating with 1 g of activated carbon, the solution was cooled, and the 2.6 acid crystallized from this solution was collected by filtration, washed with 25% by volume of ethanol and dried to obtain 11.1 g of pure 2.6 acid. Purity 98.6
%, And the purification yield was 55.1%. Thus, the method of the comparative example was found to be industrially disadvantageous because the purification yield was low and the solvent had to be recovered. In addition,
Impurities in the obtained purified 2.6 acid were as follows. 0.02% by weight of 2-hydroxynaphthalene-3-carboxylic acid 0.32% by weight of 2-hydroxynaphthalene-3,6-dicarboxylic acid 0.04% by weight of 2-hydroxynaphthalene

[0024]

As described above, according to the purification method of the present invention, high-purity 2.6 acid can be obtained in high yield, and the purification method is simple. In particular, the process is carried out in an aqueous solvent without using an organic solvent, and the recovery of the solvent is not required, so that the purification cost can be reduced and the content of metal ions such as Na, K, and Fe can be reduced. To play.

Claims (5)

[Claims] 1. Crude 2-hydroxynaphthalene-6
A method for purifying 2-hydroxynaphthalene-6-carboxylic acid, comprising dissolving a carboxylic acid with an alkaline substance in an aqueous solvent, and performing acid precipitation in a pH range of 2.0 to 5.0. 2. Crude 2-hydroxynaphthalene-6
The method according to claim 1, wherein 2 to 100 times by weight of water is used relative to the carboxylic acid. 3. An alkaline substance comprising one or two or more kinds selected from alkali metal hydroxides, ammonia and lower aliphatic amines as crude 2-hydroxynaphthalene-
The method according to claim 1 or 2, wherein the compound is used in an amount of 0.8 to 2.0 moles per 6-carboxylic acid. 4. Crude 2-hydroxynaphthalene-6
4. The method according to claim 1, wherein when dissolving the carboxylic acid in an alkaline substance, the antioxidant is used in an amount of 1 to 20 mol% based on the crude 2-hydroxynaphthalene-6-carboxylic acid. 5. An acid used for acid precipitation, which is selected from the group consisting of hydrochloric acid, sulfuric acid, formic acid, acetic acid and propionic acid.
5. The method according to claim 1, wherein at least one species is used.