JPS61185569A - Purification of water-soluble dye - Google Patents

Abstract

PURPOSE:Ammonium carbonate is added to an aqueous solution of a water-soluble dye to effect the salting-out of the dye, and the resulting cake is dissolved in an aqueous medium and kept at elevated temperature to lower the content of inorganic salt readily whereby the dye is purified. CONSTITUTION:Ammonium carbonate, ammonium bicarbonate or ammonium carbamate is added to an aqueous solution of a water-soluble dye (e.g., C, I, Direct Yellow 50) to effect the salting-out of the dye. Then, the precipitate is filtered off and the resultant cake is dissolved or suspended in an aqueous medium, then the solution or suspension is kept over 40 deg.C, preferably at 50-100 deg.C over 0.5hr, preferably for 2-20hr to purify the dye.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for purifying water-soluble dyes.

[Conventional technology]

Since the synthesis of water-soluble dyes is usually carried out in an aqueous solvent, the resulting reaction mixture is a water bath solution of the water-soluble dye. The aqueous solution obtained here contains by-products, salts used in the reaction, and the like. Therefore, it is necessary to separate the desired water-soluble dye from by-products, salts, etc. present in the reaction mixture, and for this purpose, the desired water-soluble dye is usually separated by salting out the reaction aqueous solution. It will be refined.

[Problems that the invention helps solve]

However, the water-soluble dye obtained by this salting-out process contains a large amount of salt used in the salting-out process, so when this salting-out water-soluble dye is dissolved in water, the concentration of The disadvantage was that it was not possible to obtain an aqueous dye solution.

[Means for solving problems]

That is, the gist of the present invention is to add ammonium carbonate, ammonium bicarbonate, or ammonium hacarbamate to an aqueous solution of a water-soluble dye, salt out the water-soluble dye, filter the salting-out mixture, and divide the resulting cake into an aqueous solution. A method for purifying a water-soluble dye, which comprises dissolving or suspending the dye in a medium, and then maintaining the solution or suspension at a temperature of 10° C. or higher for a period of o, r or more.

The present invention will be explained in detail below.

The water-soluble dye of the present invention is not particularly limited, but can include known dyes that usually contain a sulfonic acid group or a carboxylic acid group as a water-soluble group,
For example, water-soluble dyes shown in Table CA) below can be used.

Table [A] In the present invention, a reaction mixture containing the dye obtained by a synthetic reaction is usually used.

The present invention requires the use of ammonium carbonate, ammonium bicarbonate, or ammonium carbamate as the salt when salting out the aqueous solution of the water-soluble dye described above.

The salt used here may be any salt or salt which can salt out substantially all of the water-soluble dye. The salt is usually added directly to the mixture in solid or dissolved form, but optionally it may also be formed in the system, for example by feeding carbon dioxide and ammonia to the reaction mixture. After salting out, the mixture is usually filtered to recover a cake of water-soluble dye, which contains the water-soluble dye as well as the salt added for salting out. Furthermore, most of the counter ions of the water-soluble dye are changed into ammonium salts by salting out with.

In the present invention, the undried wet cake recovered by salting out is dissolved or suspended in an aqueous medium, and
o, s or more at a temperature of ℃ to 100℃, preferably 2 to
It is necessary to thermally decompose the dissolved or suspended ammonium salt in the aqueous solution by holding it for 20 hours.

In this treatment, if the treatment temperature is too low or the treatment time is too short, the decomposition of the ammonium salt added in the above-mentioned step will be insufficient, making it impossible to obtain an aqueous dye solution with a low salt concentration.

The amount of aqueous medium used in this treatment must be at least enough to disperse the dye cake, and is usually 0.3 to 10 times the weight of the wet cake, preferably 0.5 to 3 times the weight of the wet cake.
It is twice the weight.

The aqueous medium used here is usually water or an aqueous solution containing a solubility promoter, such as urea, capro2cutam, ethylene glycol and triethanolamine. In addition, this thermal decomposition treatment is usually carried out under normal pressure,
Depending on the case, it may be carried out under reduced pressure.

In addition, since this treatment thermally decomposes the ammonium salt and generates gases such as carbon dioxide gas and ammonia gas, it is preferable to carry out the treatment in a stirring tank equipped with a processing device for these generated gases.

The aqueous solution of water-soluble dye obtained in the above-mentioned manner can be used as a high-concentration dye aqueous solution as it is, but is post-treated depending on the purpose. For example, if the amount of water is large, an aqueous solution of a water-soluble dye with a desired concentration can be obtained by evaporating and concentrating it or by spray drying it and redissolving it. Moreover, the dye powder obtained by spray drying can also be commercialized as the 11 powder product. In any case, in the present invention, since the content of inorganic salt is small, it is possible to obtain a highly concentrated water-soluble dye.

[For production]

According to the process of the present invention, ammonium carbonate, ammonium bicarbonate, or ammonium carbamate added in the salting out process is thermally decomposed and these inorganic salts are removed, so that the solubility of the dye in water is improved and a high concentration is obtained. An aqueous dye solution is obtained that can be oxidized.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Example/1000rtLl of a reaction solution containing the water-soluble dye of the present invention represented by the following structural formula CI) obtained by a coupling reaction.
Solid content6. Mouth, NaC in solid food! Ammonium bicarbonate/'707/ was gradually added over 7 hours under stirring at a temperature of 1IO° C. to perform salting out.

...... [1] Next, the mixture after salting out was filtered, and the collected wet cake was
701! (Solid content: 30%, including Mail in the solids)
%, ammonium bicarbonate content in solid matter 1I 3%) was suspended in water and heat treated at a temperature of 65° C. for 3 hours. When the amount of ammonium salt in the obtained aqueous solution (lI & OmJ) was measured, the results shown in Table 1 were obtained.

Examples 2 to 3 Table 1 shows the results when the heat treatment conditions were changed from those shown in Table 1 in the method of Example//.

In the method of Example/Example, heat treatment was performed using an aqueous solution containing 3611 urea, 10 g of caprolactam, and triethanolamine/coy. The results are shown in Table 1 when the test was carried out at a temperature of 70° C. for 3 hours in Ord. Note that this dye aqueous solution has 0
Even when cooled to ℃, there was no precipitation of crystals and the product remained stable.

Example Wet cake 1o011 (solid content: 1, Mail content in the solid: 32%) represented by the following structural formula [...] obtained by condensation reaction f 60°C hot water go.

ammonium skate at a temperature of 0°C.
2t1 was gradually added over 30 minutes with stirring to perform salting out.

Then, the mixture after salting out was filtered, and the collected wet cake/
20g (solid content 33%, Mail content in solids u, r
%, ammonium bicarbonate content in solids x, io, o)
was suspended in water and heat treated at a temperature of 60° C. for 6 hours. When the amount of ammonium salt in the obtained aqueous solution (J oml) was measured, the results shown in Table 2 were obtained.

In addition, urea 2711. g') Add ethanolamine//11 ethylene glycol CoJ, F, 70
The mixture was concentrated by evaporation at 100°C and a vacuum of 9°C to -Q-. The dye solid content of this solution was completely dissolved in the IO ratio, and the solution remained stable without precipitation of crystals even when cooled to o'6.

Comparative Example 1 In the evening of the example, the amount of ammonium salt was measured after the aqueous solution in which the wet cake recovered by salting out was suspended was treated at a temperature of 20° C. for 3 hours, as shown in Table 2. I got good results.

Comparative Example The same aqueous solution as Comparative Example/ was heated at a temperature of 50°C for 0.2 S hours (
The amount of ammonium salt after heat treatment (73 minutes) was measured, and the results shown in Table 2 were obtained.

Table 1 Table a [Effects of the Invention] According to the present invention, a wet cake of water-soluble dye recovered by salting out can be easily dispersed or dissolved in water without drying and heat-treated. The content of inorganic salts in aqueous solutions can be reduced. Therefore, the present invention is not only easy to operate, but also has low energy costs for desalination, making it an industrially extremely valuable method.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (7 others)

Claims (1)

[Claims] (1) Adding ammonium carbonate, ammonium bicarbonate or ammonium carbamate to the water-soluble dye aqueous solution,
Salting out the water-soluble dye, filtering the salting out mixture, dissolving or suspending the resulting cake in an aqueous medium, and then heating the solution or suspension at a temperature of 40°C or higher for 0.5 hours or more. A method for purifying water-soluble dyes characterized by the retention of water-soluble dyes.