JPS6317103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying organic pigments. More specifically, the present invention relates to a method for purifying organic pigments that are excellent in purity, sharpness, chroma, and various resistances such as light resistance, weather resistance, and chemical resistance. Organic pigments produced by chemical reactions often contain trace amounts of unreacted raw materials and reaction by-products, so they must be fully satisfactory in terms of clarity, saturation, light resistance, weather resistance, chemical resistance, etc. I am in a situation where I cannot get it. Generally, methods for purifying organic pigments include a so-called reprecipitation method in which the pigment is once dissolved to a concentrated concentration and then diluted, or a method in which a pigment salt is first formed and then hydrolyzed. An example of the former is a method in which a quinactodone pigment or a phthalocyanine pigment is dissolved in concentrated sulfuric acid and diluted with water or an alcohol, while an example of the latter is a method in which an organic pigment is suspended in a hydrophilic organic solvent and then dissolved in a hydrophilic organic solvent. A method of adding a base capable of forming salts to form an alkali salt of the pigment, and hydrolyzing it using acid or water (Japanese Patent Publication No. 47-39565)
and so on. However, in order to fully utilize the purification effect of this method, it is necessary to use solvents that are expensive, have a high boiling point, and are difficult to recover, such as N-methylpyrrolidone and N,N-dimethylformamide. Furthermore, since the hydrophilic organic solvent used in this method mixes freely with water, complicated equipment and complicated operations are required for its recovery and wastewater treatment. Furthermore, when the crude pigment is produced in a hydrophobic solvent, it has the disadvantage that the solvent must be replaced with a hydrophilic organic solvent. Also,
When forming a pigment salt in a hydrophilic organic solvent as in this method, since the pigment salt is soluble, it is difficult to separate and purify it at the pigment salt stage, and the impurities in the crude pigment are re-purified. It has the disadvantage that it gets mixed into the subsequent pigment. In view of the above-mentioned circumstances, the inventors of the present invention conducted intensive research in search of a method for modifying organic pigments by purification, and as a result, they found that quinacridone pigments, azo pigments, condensed azo pigments, quinophthalone pigments, and perylene pigments. When an organic pigment selected from the group consisting of and flaventhrone pigments is reacted with a base in an aromatic hydrocarbon in the presence of a small amount of alcohol or alcohol and water, when a pigment salt of the pigment is formed, via an intermediate step of dissolving in the aromatic hydrocarbon solvent;
Therefore, pigment salts of extremely high purity are precipitated. When the pigment salt is separated and hydrolyzed, a highly pure pigment with excellent physical properties can be obtained. Furthermore, among the aromatic hydrocarbon solvents used, when using chlorobenzene and nitrobenzene, which have particularly excellent ability to dissolve impurities in pigments, pigments with very high purity and excellent physical properties can be produced without separation. Even if hydrolysis with an acid is carried out in a state in which the pigment salt is completely insoluble (suspended state), the neutralization reaction will proceed sufficiently and there will be no adverse effect on the physical properties of the pigment. Preferably, a pigment with a uniform particle size can be obtained. The present inventors have completed the present invention based on the above knowledge. That is, in the present invention, a crude organic pigment is dispersed in an aromatic hydrocarbon solvent, and an alkali metal or alkaline earth metal alcoholate or hydroxide and alcohol and/or water are added to the alkali salt of the pigment. The present invention provides a method for purifying an organic pigment, which is characterized by forming a pigment, and then hydrolyzing the pigment using an acid or water. Examples of the organic pigments applicable to the present invention include quinacridone pigments, azo or condensed azo pigments, quinophthalone pigments, perylene pigments, and flaventhrone pigments. Examples of the aromatic hydrocarbon solvent include benzene, halogenated benzene, nitrobenzene, and alkylbenzene. Monochlorobenzene, o-dichlorobenzene, 1,2,3-trichlorobenzene, and nitrobenzene are highly soluble as intermediates for forming pigment salts and have excellent ability to dissolve impurities in crude pigments. These solvents can be used alone or as a mixture. The amount of these solvents to be used does not need to be strictly limited, but in consideration of ease of operation and economic efficiency, it is usually used in an amount of about 3 to 20 times the weight of the organic pigment. The base is not limited as long as it reacts with the organic pigment to form a pigment salt, but from the viewpoint of reactivity and ease of availability, alkali metal alcoholates or hydroxides, particularly sodium methylate and sodium ethylate. , caustic potash, caustic soda, etc. are preferred. The amount of these bases used is 1 equivalent or more, preferably 1 to 1.5 equivalents, based on the functional group of the organic pigment used in the present invention. Alcohols include methanol, ethanol, n-propanol, iso-propanol, n
-butanol, sec-butanol, ethylene glycol, etc. are used. Among these, it is preferable to use a combination of the sodium methylate or sodium ethylate and methanol or ethanol in terms of solvent management. Further, instead of these alcohols, alcohols with a portion of water added thereto can also be used. The amount of the alcohol or mixture of alcohol and water to be used varies depending on the crude organic pigment used, the type and amount of aromatic hydrocarbon, or the type and amount of the base, but is usually at least 0.1 times the weight of the crude organic pigment. That's enough. However, if the amount is larger than necessary, some of the generated pigment salt may dissolve and the pigment salt may be lost when separating the pigment salt from the solvent, so some of the alcohol used may be It is necessary to distill it off. In order to omit such a distillation operation, a ratio of 0.1 to 1.0 times by weight is appropriate. When a crude organic pigment is dispersed in an aromatic hydrocarbon at the above-mentioned mixing ratio, and an alkali metal alcoholate or hydroxide and water or alcohol are added, the reaction for forming a pigment salt proceeds rapidly. At this time, before the pigment salt precipitates, as an intermediate step, a state in which the intermediate of the pigment salt is dissolved in the solvent used is observed, and immediately thereafter, precipitation of the pigment salt is observed. This reaction proceeds even at room temperature, but 40
The reaction proceeds more rapidly when heated to ~70°C. If the crude pigment does not contain much impurity, or if a solvent with a high ability to dissolve impurities such as chlorobenzene or nitrobenzene is used as an aromatic hydrocarbon solvent, the pigment salt thus produced can be directly treated with an acid. It may be hydrolyzed using
Preferably, (1) it is separated, washed with an aromatic hydrocarbon solvent if necessary, and dispersed again in the aromatic hydrocarbon solvent. The pigment salt suspension thus obtained is immediately treated with an acid and hydrolyzed to obtain a purified organic pigment. At this time, the acids used include organic acids such as acetic acid, mineral acids, and the like. Using an organic acid such as acetic acid is an effective means because it easily mixes with the solvent used. Another effective method is to blow hydrochloric acid gas, carbon dioxide gas, etc. into the reaction system. (2) Separate it, wash it with a low boiling point solvent in which the pigment salt is insoluble, if necessary, and dry it in an atmosphere that is inert to the pigment salt. Next, the dried pigment salt is treated with a large amount of water or acid to be hydrolyzed to obtain a purified organic pigment. The acid used in this case is sulfuric acid,
Mineral acids such as hydrochloric acid or organic acids such as acetic acid may be used, but mineral acids are preferred from the viewpoint of subsequent treatment, especially wastewater treatment. The amount of these acids used may be any amount sufficient to neutralize the alkali. According to the present invention, the aromatic hydrocarbon solvent used has a high solubility in raw material unreacted substances and reaction by-products contained in the crude organic pigment, and therefore brings about a great purification effect. Furthermore, since the intermediate is once dissolved prior to the precipitation of the pigment salt, impurities inherent in the crude organic pigment particles are also transferred into the solvent used, thereby further enhancing the purification effect. The precipitated pigment salt is insoluble in aromatic hydrocarbon solvents, and its separation operation is easy. In the present invention, there is no mixing of organic solvent with water, and there is no need for complicated solvent recovery or waste water treatment in known methods, which is very economically advantageous. Furthermore, in the present invention, (1) prior to hydrolysis, the pigment salt is once separated and then dispersed again in an aromatic solvent, or (2) the pigment salt is separated, dried, and dispersed in water, and then hydrated. The decomposition method has an even greater purification effect. The organic pigment obtained by the present invention has excellent purity and chroma, as well as other pigment properties such as light resistance and chemical resistance, as is clear from the Examples described below. Hereinafter, the present invention will be explained in detail using examples. In Examples and Reference Examples, all parts and % indicate parts by weight and % by weight. Example 1 30 parts of a crude unsubstituted linear quinacridone pigment was dispersed in 300 parts of nitrobenzene and heated to about 50°C. Then, 80 parts of a 15% caustic potash-methanol solution was added, and the mixture was further heated to 50°C for 1 hour. The produced pigment salt is filtered and the resulting pigment salt nitrobenzene wet cake is re-infused with nitrobenzene.
When the mixture was dispersed in 300 g and 14 parts of acetic acid was added and heated at 50° C. for 1 hour, a very bright red pigment was obtained in a dispersed state. This was filtered, washed successively with methanol and water, and dried (yield: 28.5 parts). A paint was prepared using the pigment obtained in this way, a coating film was created, and when compared with the coating film of the crude pigment that was not subjected to the treatment of this example, the color saturation, sharpness, and coloring power were significantly improved. It was also excellent in various resistances such as light resistance and heat resistance. In addition, the crude pigment had a slightly teal red color, whereas the pigment of this example had a slightly purplish red color. In place of nitrobenzene in this example, o-
The same results as in this example were obtained even when dichlorobenzene or 1,2,3-trichlorobenzene was used. When the pigments shown in Table 1 were used in place of the pigments used in this example and the same treatment as in this example was carried out, pigments of excellent quality and having the color tones shown in Table 1 were obtained.

【table】

[Table] Example 4 The following structural formula 20g of azo pigment and 300g of o-dichlorobenzene
6.6 parts of sodium ethylate and 10 g of ethanol were added, and the mixture was heated to 40°C for 1 hour. The produced yellow pigment salt was filtered, washed successively with o-dichlorobenzene and n-hexane, and dried under reduced pressure. Next, the obtained pigment salt was poured into 1000 parts of 3% sulfuric acid water, dispersed for 2 hours, neutralized and hydrolyzed to obtain a free pigment, filtered, washed with water, and dried to obtain 19 parts of yellow powder. A paint was prepared using the pigment obtained in this way, a coating film was created, and when compared with the coating film of the crude pigment that was not subjected to the treatment of this example, the pigment of this example was It was also excellent in various resistances such as light resistance, heat resistance, and weather resistance. Even when the pigment salt was hydrolyzed using 5% hydrochloric acid or water instead of the 3% sulfuric acid water of this example, a pigment having the same quality as the pigment of this example was obtained. When the pigments shown in Table 2 were used instead of the pigments used in this example and the same treatment as in this example was carried out, pigments of excellent quality and having the color tones shown in Table 2 were obtained.

【table】

Claims (1)

[Claims] 1. An organic pigment selected from the group consisting of quinacridone pigments, azo pigments, condensed azo pigments, quinophthalone pigments, perylene pigments, and flaventhrone pigments is dispersed in an aromatic hydrocarbon solvent, and an alkali metal or alkali is added to the organic pigment. Purification of organic pigments, characterized by adding an alcoholate or hydroxide of an earth metal and alcohol and/or water to form an alkali salt of the pigment, which is then hydrolyzed using acid or water. Law.