JPH0597770A - Purification of naphthalene tetracarboxylic acid compounds - Google Patents

Abstract

PURPOSE:To readily and stably obtain the subject compound having an excellent hue by bringing the alkali aqueous solution of a naphthalene tetracarboxylic acid into contact with active carbon and a strong basic ion exchange resin and subsequently depositing the compound with an acid. CONSTITUTION:The alkali aqueous solution of a naphthalene tetracarboxylic acid (preferably 1,4,5,8-naphthalene tetracarboxylic acid) is brought into contact with active carbon and a strong basic ion exchange resin, and subsequently preferably deposited with an acid such as hydrochloric acid or sulfuric acid to obtain the objective compound.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying naphthalenetetracarboxylic acids.

[0002]

2. Description of the Related Art Naphthalenetetracarboxylic acids (hereinafter sometimes abbreviated as "NTCA") and their derivatives are
It is useful as an organic dye or pigment, an ultraviolet absorber, etc. (JP-A-63-225650, etc.). However, since naphthalenetetracarboxylic acids are difficult to purify and their storage stability is not so good, those which are usually commercially available are usually gray or dark brown.

Further, the present inventors have already found a naphthalenetetracarboxylic acid diimide compound which is useful as a polyester material having an excellent UV blocking property (Japanese Patent Laid-Open No. HEI 3).
223582), it is difficult to obtain a high-purity product from the diimide compound because the above-mentioned commercially available product must be used as the raw material.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to simply and efficiently purify naphthalenetetracarboxylic acids in view of the above problems of the present situation.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to achieve the object, and as a result, have completed the invention of the following purification method for naphthalenetetracarboxylic acids. That is, the gist of the present invention resides in a method for purifying naphthalenetetracarboxylic acids, which comprises subjecting an alkaline aqueous solution of naphthalenetetracarboxylic acids to contact treatment with activated carbon and a strongly basic ion exchange resin, followed by acid precipitation. Less than,
The present invention will be described in detail. The naphthalene tetracarboxylic acids of the present invention include naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-1,3,5,7-tetracarboxylic acid, or similarly naphthalene-1,2,5.
6-, 2, 3, 6, 7-, 1, 3, 6, 8--and 1,
4,6,7-, 1,2,4,5-, 1,3,4,5-,
Examples thereof include 1,2,3,4-tetracarboxylic acid, and acid anhydrides thereof can also be used. Further, nuclear substitution products of these compounds with alkyl groups, alkoxy groups, halogen groups and the like are also included. Of these, naphthalene-1,4,5,8-tetracarboxylic acid or its acid anhydride is most commonly used.

Commercially available naphthalenetetracarboxylic acids (hereinafter abbreviated as "crude NTCA") are, for example,
The composition of 1,4,5,8-naphthalenetetracarboxylic acid is not always constant depending on its production conditions and storage conditions, but normally its anhydride (monoanhydride, dianhydride) is used.
A few percent to a few tens percent, and in some cases about 0.1% by weight of an alkali metal. Hereinafter, the description will be made on the crude NTCA. In the present invention, by preparing an alkaline aqueous solution of crude NTCA, the subsequent purification treatment such as decolorization is simplified. Although the concentration of the crude NTCA can be arbitrarily selected, it is usually 1 to 30% by weight, preferably 2 to 15% by weight. If the concentration is higher than this, the purification efficiency is lowered, and if the concentration is lower, the productivity is lowered. The alkali used in the present invention becomes alkaline when made into an aqueous solution, and
There is no particular limitation as long as it can dissolve naphthalenetetracarboxylic acids, but hydroxides, carbonates and the like of alkali metals such as lithium, sodium and potassium are usually used.

[0007] The amount of alkali required in the present invention is
It is an amount sufficient to neutralize the carboxylic acid moiety in CA and further ring-opening neutralize the acid anhydride in crude NTCA.
The pH of the alkaline aqueous solution of CA is usually adjusted to 6.9 to 8.5, preferably 7.2 to 8.0. Coarse NTCA
It is estimated that the purification efficiency is improved by opening the acid anhydride in the ring as completely as possible. However, in order to make the ring opening more complete, an excessive amount of alkali is used and the pH is adjusted to the above value. Even if it is higher than the range, the naphthalene tetracarboxylic acid itself is rather decomposed by the alkali, and coloring is caused thereby, which is not preferable. In the present invention, the above-mentioned crude alkaline aqueous solution of NTCA is purified by combining the contact treatment with activated carbon and a strongly basic ion exchange resin. The order of the activated carbon treatment and the ion exchange resin treatment is not particularly limited, and each step may be performed plural times if necessary,
It may be treated with a mixture of activated carbon and an ion exchange resin, but sufficient purification is difficult only by treating each separately. The contact treatment method may be a batch method or a column method, and may be appropriately selected from known treatment methods. The type of activated carbon or strongly basic ion exchange resin used is not particularly limited, and the most suitable one may be selected according to the coloring component and impurities in the crude NTCA, but activated carbon is in powder or crushed form. Among these, the ion exchange resin is preferably a porous type strongly basic ion exchange resin.

Purified NTCA is precipitated and recovered by acid precipitation from the crude alkaline aqueous solution of NTCA after the above purification treatment. The acid used for acid precipitation is usually preferably a strong acid such as hydrochloric acid, sulfuric acid or nitric acid. In the acid precipitation, the acid is usually added to the precipitated NTCA under stirring so that the pH of the solution is usually 3 or less, preferably 1.5 or less. The NTCA acid-precipitated by the excess acid is washed with water and filtered repeatedly as many times as necessary to remove the generated salt and the excess acid in the aqueous solution. At this time, since NTCA itself has a slight dissociation property, at practical washing concentration, p
H does not become higher than about 4. Further, if the number of times of washing with water is excessively large, the yield of purified NTCA becomes low, which is not preferable. The purified NTCA after filtration with water is dried or recovered as it is or after substituting residual water with a water-soluble low boiling point solvent such as acetone or lower alcohol. Although the drying method is not particularly limited, it is not preferable to dry at a temperature of 100 ° C. or higher because it is easily decomposed at a high temperature.

The purified NTCA thus obtained has a high purity and an excellent color tone, and is suitable as a raw material for various NTCA derivatives. In particular, it is useful in the following NTCA diimide compounds, which have hitherto been generally difficult to obtain highly pure products. NTCA diimide compound is NTCA
It can be easily obtained by imidizing an amine with an amine. The amines are not particularly limited, but aliphatic aminocarboxylic acids and their esters such as ammonia, glycine, alanine, valine, and ε-aminocaproic acid and their esters, aminoalcohols and their esters, and aromatic aminocarboxylic acids such as aminobenzoic acid. And its esters and the like. In the imidization reaction, a known synthesis method may be appropriately selected, but one example is shown below.

The charging molar ratio of NTCA and aminocarboxylic acid is set to 1: 2.0 to 3.0 and the mixture is heated and stirred in an acetic acid solvent. However, both NTCA and the produced NTCA diimide compound are substantially insoluble in acetic acid. The reaction proceeds in the suspension system throughout. The reaction temperature can be arbitrarily set between normal temperature and the boiling point of acetic acid. In this case, the reaction time is usually 3
It is 10 hours, and during this time, the water produced by the reaction may be removed to the outside of the reaction system or may be refluxed into the reaction system. The suspension reaction solution obtained by such a reaction is filtered to remove acetic acid, and then washed with a suitable solvent such as water, acetone, alcohol, acetic acid, etc. to remove excess aminocarboxylic acid, and further filtered. The desired NTCA diimide compound is obtained by removing the solvent by drying or the like.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples, "parts" means "parts by weight", and the measuring methods and terms used in the examples are shown below. Crude NTCA: means a commercial product of 1,4,5,8-naphthalenetetracarboxylic acid here. 420 nm absorbance: each sample NT using a UV, visible, and near-infrared spectrophotometer "UV-3100S" manufactured by Shimadzu Corporation, with the alkaline aqueous solution used to dissolve NTCA as a control
The absorbance spectrum of the alkaline aqueous solution of CA was measured, and the degree of NTCA decolorization purification was confirmed by the absorbance at 420 nm. Ion exchange tower: Ion exchange resin 100 in a cylindrical ion exchange resin packed tower in a state of being wet with demineralized water and naturally settling
The part is filled so that the effective height is 30 cm or more, and the alkaline aqueous solution of NTCA is sent from the upper part at an arbitrary liquid sending speed, and the ion-exchange resin passing treatment liquid flows out from the lower part to match it and is received by the receiver. The tower. SV value: The amount of liquid passed through the ion exchange tower is 1 ml of the volume of the ion exchange resin in a state where it is wet with demineralized water and naturally sediments.
In contrast, the passing speed of the treatment liquid, which is shown by how many ml was flowed per hour. Color difference of diimide compound: 5.
0 g was measured and measured using an SM color computer (manufactured by Suga Test Instruments Co., Ltd.), and the color tone expressed in Lab.

Comparative Example 1 50 parts of crude NTCA (manufactured by Hoechst) was dissolved in 1000 parts of demineralized water in which 21.1 parts of sodium hydroxide and 10.1 parts of sodium carbonate were dissolved. This NTCA solution (pH =
Since the absorbance at 420 nm of 7.8) was too high to fall within the measurement range of the measuring instrument, the absorbance was measured by diluting 4 times with demineralized water. The value obtained by quadrupling the absorbance was 13.2. This NTCA solution was temperature controlled to 80 ° C, 30%
N was added dropwise to 129.2 parts of sulfuric acid with stirring over about 1 hour.
TCA was precipitated, further aged for 1 hour with stirring, and then allowed to cool to room temperature. PH of dispersion of this precipitated NTCA
Was 0.9. This dispersion was filtered under reduced pressure using No2C filter paper to collect the deposited NTCA, and further washed with 500 parts of demineralized water for 30 minutes under stirring with stirring and vacuum filtration was repeated 3 times to wash the deposited NTCA. The pH of the last wash water is 3.
It was 9. The deposited NTCA was further washed with 200 parts of acetone with stirring for 30 minutes, filtered under reduced pressure, and dried under reduced pressure at 80 ° C. for 12 hours using a vacuum dryer. Regarding the color tone of the dried and recovered NTCA, the color tone was visually lighter than that of the crude NTCA before the treatment, but it was still dark brown, which was an extremely poor color tone.

Comparative Example 2 50 parts of crude NTCA (manufactured by Sumikin Kako Co., Ltd.), 21.1 parts of sodium hydroxide and 1 part of sodium carbonate in the same manner as in Comparative Example 1.
It was dissolved in 1000 parts of demineralized water in which 0.1 part was dissolved. The 420 nm absorbance of this NTCA solution (pH = 7.8) was 2.3. This NTCA solution was acid-deposited, washed and dried in the same manner as in Comparative Example 1, and the color tone of the NTCA was visually slightly lighter than that of the crude NTCA before the treatment, but it was still gray and unsatisfactory. It was a nice color. Example 1 7.5 parts of activated carbon "Shirasagi KL" (trade name of Takeda Pharmaceutical Co., Ltd.) was added to the NTCA solution of Comparative Example 1 and stirred at room temperature for 3 hours, and then filtered using No. 2 filter paper to obtain a filtrate. Porous strong basic ion exchange resin "Diaion HPA-
25 "(trade name of Mitsubishi Kasei Co., Ltd.) was passed through an ion exchange column at an SV value of 6.0 to obtain 4 of NTCA solution.
The 20 nm absorbance was 0.083. This NTCA solution was subjected to acid precipitation, washing and drying recovery in the same manner as in Comparative Example 1
With respect to the color tone of A, the whiteness was markedly improved visually compared to the crude NTCA before the treatment, and it was a color tone that can be said to be a slightly flesh-colored white color.

Example 2 7.5 parts of activated carbon "DIAHOPE DAC-P" (trade name of Mitsubishi Kasei Co., Ltd.) was further added to the purified NTCA solution of Example 1 and the mixture was stirred at room temperature for 3 hours. The absorbance at 420 nm of the filtrate filtered using the filter paper of No. 4 was 0.027. This NTCA solution was acid-deposited, washed and dried and collected in the same manner as in Comparative Example 1, and the color tone of NTCA was visually observed in Example 1.
The whiteness was improved more than that of the purified NTCA, and the color tone was pure white. Example 3 7.5 parts of activated carbon "Shirasagi KL" (trade name of Takeda Yakuhin Co., Ltd.) was added to the NTCA solution of Comparative Example 2, and the mixture was stirred at room temperature for 3 hours and then filtered using No. 2 filter paper. The NTCA solution obtained by passing the filtrate through the ion exchange column at an SV value of 6.0 in the same manner as in Example 1 had an absorbance at 420 nm of 0.021. The NTCA solution was acid-deposited, washed, and dried and recovered in the same manner as in Comparative Example 1, and the color tone of the NTCA was visually improved to a degree that was significantly whiter than that of the crude NTCA before the treatment, and was a color tone that can be said to be pure white.

Comparative Example 3 7.5 parts of activated carbon "Shirasagi KL" (trade name of Takeda Yakuhin Co., Ltd.) was added to the NTCA solution of Comparative Example 1 and the mixture was stirred at room temperature for 3 hours and then filtered using No. 2 filter paper. Obtained NTCA
The 420 nm absorbance of the solution was 4.60. This NT
The color tone of NTCA obtained by acid precipitation, washing and drying and recovery of the CA solution in the same manner as in Comparative Example 1 was visually lighter than that of the crude NTCA before treatment, and was a light brown color, which is satisfactory. It did not reach the color tone. Comparative Example 4 The NTV solution of Comparative Example 1 was used in an ion exchange column packed with a porous strongly basic ion exchange resin “Diaion HPA-25” (trade name of Mitsubishi Kasei Co., Ltd.) to obtain an SV value = 6.
The 420 nm absorbance of the NTCA solution obtained by passing it at 0 was 0.63. The NTCA solution was acid-deposited, washed and dried and recovered in the same manner as in Comparative Example 1, and the color tone of the NTCA was visually lighter than that of the crude NTCA before the treatment, and was lighter than that of Comparative Example 3. However, the color tone was still unsatisfactory.

Examples 4 to 6 10 parts of each purified NTCA obtained in Examples 1 to 13 and 13 parts of ethyl p-aminobenzoate (Midori Kagaku Co., Ltd.) were stirred in 100 parts of acetic acid under reflux of acetic acid. Temperature (about 120 ° C)
At room temperature for 7 hours to obtain a diimide compound. After washing with water and drying, the color difference of the diimide compound was expressed in Lab and shown in Table 1. In Table 1, L represents the lightness index, and a and b represent the perceived chromaticity index. Each of the diimide compounds had a color tone that was sufficient for practical use. Comparative Examples 5-8 10 parts of each purified NTCA obtained in Comparative Examples 1 to 4 and 13 parts of ethyl p-aminobenzoate were reacted in the same manner as in Examples 4 to 6 to obtain diimide compounds. After washing with water and drying, the color difference of the diimide compound was represented by Lab and shown in Table 1. Each of the diimide compounds had an insufficient color tone and could not be put to practical use.

[0017]

[Table 1]

[0018]

As described above, by using the purification method of the present invention, it becomes possible to easily and stably obtain naphthalenetetracarboxylic acids having excellent color tone. Furthermore, it is possible to easily obtain a derivative of naphthalenetetracarboxylic acid such as a diimide compound which is excellent in quality such as color tone.

Claims (4)

[Claims] 1. A method for purifying naphthalenetetracarboxylic acids, which comprises subjecting an alkaline aqueous solution of naphthalenetetracarboxylic acids to a contact treatment with activated carbon and a strongly basic ion exchange resin, and then subjecting to acid precipitation. 2. The purification method according to claim 1, wherein the pH of the alkaline aqueous solution of naphthalenetetracarboxylic acids is 6.9 to 8.5. 3. The naphthalene tetracarboxylic acid is
The purification method according to claim 1, which is 1,4,5,8-naphthalenetetracarboxylic acid. 4. An imidation reaction of naphthalenetetracarboxylic acids and amines purified by acid treatment after contacting an alkaline aqueous solution of naphthalenetetracarboxylic acids with activated carbon and a strongly basic ion exchange resin. A method for producing a naphthalenetetracarboxylic acid diimide compound, comprising: