NL8102811A - METHOD FOR PREPARING A CONCENTRATED SOLUTION OF AZO DYES AND SOLUTIONS OBTAINED BY SUCH A METHOD - Google Patents

Description

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BRIEF DESCRIPTION: Process for the preparation of a concentrated solution of azo dyes and solutions obtained according to such a process. The invention relates to a process for the preparation of a concentrated solution of azo dyes from diazotizers. bare amines and coupling agents by diazotizing and coupling in the presence of water and at least one solvent miscible with water. The invention further relates to solutions of azo-10 dyes obtained by using such a method.

The anionic dyes, which are soluble in water, are commonly sold and used in the form of powders that can contain a greater or lesser amount of inorganic salts. Some advantages, but also a number of disadvantages are associated with this method.

The main advantage is the great stability in the storage of these products. In particular, there is no change when these products are stored, even below a temperature of 0 ° C, making it possible to store these products in unheated rooms for the entire 20 years. On the other hand, powdered dyes are known to have a marked tendency to release dust when processed. Attempts have been made to overcome this drawback by applying various processes. By using oil or hygroscopic liquids, the release of dust is effectively reduced. On the other hand, it then becomes more difficult to obtain solutions of the dyes. It has also been investigated to give the dyes a less desirable shape for dust formation, by converting the dyes into granules. Since the granules are then obtained in a very compact form, it becomes difficult to dissolve them, especially when the particular dye is less soluble in water. This is the case for the dyes which are processed according to the present method, when they are used in the form of a powder.

The present process concerns a preparation of stable, highly concentrated solutions of azo dyes that are soluble in water and more in particular the dyes described in the "Color Index" under the name Acid Orange 7 and Acid Orange 8.

The solutions obtained according to the invention contain between 40 and 65% dye based on the total weight of the solution.

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The solutions for azo dyes have already been proposed. In U.S. patents 3,898,033 - 4,019,858 - 3,551,088 -3,681,320 - 3-986,827 - 4,082,742 - 4,043,752 and 4,063,880 and in French patents 2,197,951 - 2,216,324 and 2,109 * 806, solutions 5 have been described in which the dye concentration does not exceed 255¾. Other patents such as German Pat. Nos. 2,629,673 and 2,629,674 as well as British Pat. No. 1,355,437 disclose solutions the concentration of which may reach the value of 405¾, but their preparation involves dry dyes. In practice, it is desirable to prepare the dye in water, separate it by filtration, dry the dye, dissolve it in the solvent or solvents required thereby, and separate the insolubles by filtration. This method requires a long processing time and necessitates a number of operations, which makes this method impractical. Other patents describe analogous methods of preparation such as in French Patents 2,193,065 and 2,316,296, German Patents 2,061,760 and 2,341,293 or Belgian Patent 828,876. In some cases, the use of a moist paste of the dye offers advantages, but this only has a certain advantage when it is not necessary to prepare the free acid of the dye as stated in Belgian patent 631,379. In fact, it is often difficult to obtain the free acid of a sulfonated dye, and the resulting product thus obtained is generally difficult to filter off. French Patent 2,110,324 indicates that solutions can contain up to 75% by weight of dye. Nevertheless, and this is also apparent from French Patent 2,174,161, truly concentrated solutions can only be obtained when the diazotization is effected by means of alkyl nitrite, the anhydride of nitric acid or mixtures of nitrogen oxide and air. In fact, it is clear from Examples 10, 11, 15 to 17 of French Pat. No. 2,110,324 that the use of sodium nitrite to diazotize the amines used in the preparation of the dyes results in more dilute solutions. The weight of the solution obtained with a part of β-naphthol is 9 * 136 35 parts in example 10 and 8.819 parts in example 11. In which examples sodium nitrite is used as diazotizing agent, although this weight is only 6.16 parts in examples 15 to 17. However, the use of alkyl nitrites necessitates that the preparation and the separation of the 81 02 8 1 1 I '* -3- 21910 / Vk / mb and thereby the preparation of the dye solution is longer and more complicated and also more difficult to implement.

However, the studies carried out have shown that it is possible to obtain solutions that are at least as concentrated, but considerably easier to obtain by using a method according to the invention and characterized in that diazotization is effected with sodium nitrite in presence of sulfuric acid and the sodium sulfate formed is removed by filtration. Solvents suitable for the coupling medium may be ethers derived from ethylene glycol. Etanolamines can be mentioned as solvent for the coupling medium. The respective percentages of water and solvents can range from 10/90 to 70/30. It is surprising that the sodium sulfate formed is completely or almost completely precipitated and the resulting dye remains almost completely in the solution.

According to this method, solutions are obtained consisting of: 40 to 65/5 dye 10 - 40¾ of a mixture of solvents consisting of 25 to 20 75/5 monoethylene glycol and 75 to 25¾ methyl or ethyl ether of monoethylene glycol, 0-30¾ of a mixture consisting of 0 to 5¾ monoethanolamine, 0 to 5¾ diethanolamine and 100 to 90¾ triethanolamine, 10-30¾ water less than 2¾ sodium sulfate.

The process according to the invention is applicable to the preparation of azo dyes, in particular to the preparation of known dyes mentioned under the name "Acid Orange 7", which is the sodium salt of sulphobenzene - (1-azo ~ 1) - | 2-hydroxynaphthalene and "Acid Orange 30 8" corresponding to the sodium salt of f4-sulfo-2-methylbenzene - (1-azo-1) [2-hydroxynaphthalene] and mixtures thereof.

The solutions obtained have a very high water solubility and are stable even at very low temperatures.

The invention is further elucidated by means of the following examples, wherein the indicated parts are parts by weight if not the contrary is stated.

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Example I

Sulfanilic acid was mixed in an amount of 173 parts with 50 parts of monoethylene glycol, 50 parts of methyl ether of monoethylene glycol, 50 parts of water, 100 parts of ice and 53 parts of 9455 sulfuric acid. Then, 70 parts of sodium nitrite were added within a 30 minute period. The mixture continued to react for 10 minutes until it was no longer possible to decolorize sulfanilic acid and 144 parts of β-naphthol were added over a 30 minute period, then within an hour 210 parts of an industrially available mixture containing 961 triethanol-10 amine , 2% diethanolamine and 2% monoethanolamine. The mixture was reacted for 30 minutes, after which sodium sulfate was separated by filtration. Thus, 772 parts of a solution containing 58,255 triethanolamine salt of the dye "Acid Orange 7" were obtained. By adding 23 parts of water to this solution, 15955 parts of a solution were obtained at a concentration such that 100 parts of the solution corresponded to 70 parts of a commercially available dye in the form of a powder.

This solution can be stored well. After this solution has been stored for a month at a temperature of -20 ° C, it is sufficient to heat the solution to 0 ° C in order to obtain a solution corresponding to the starting product and in which no crystallization product has been effected. The weight of the solution per part β-naphthol is 5.52 parts. The solution contains less than 155 mineral salts.

Example II

The procedure in Example I was repeated but with 150 parts of the mixture of alkanolamines instead of 210 parts, the coupling taking about 6 hours instead of 30 minutes.

After the separation of sodium sulfate by filtration at 40 ° C, 720 parts of a solution containing 62.4¾ of dye were obtained. The concentration of the solution was brought to the desired value by adding water.

Example III

A mixture was prepared of 187 parts of 2-aminotoluene-5-sulfonic acid with 200 parts of monoethylene glycol and 200 parts of methyl ether of monoethylene glycol, after which 100 parts of ice was added and then 53 parts of 94% sulfuric acid. Then, 70 parts of sodium nitrite were added within a 30 minute period. The mixture was left to react for 81 02 8 1 1 (tl -5- 21910 / Vk / mb) until the undiazotized amine could no longer be determined. This suspension was then poured onto the solution at 20 for a period of 20 minutes ° C of 144 parts of β-naphthol in 120 parts of technical triethanolamine containing 2% diethanolamine and 5% 2% monoethanolamine After coupling was completed, sodium sulfate was separated by filtration to obtain 950 parts of a solution containing 48% dye By adding water the concentration was brought to the desired value The solution is completely stable during storage It contained less than 1% mineral salts.

Example IV

When instead of 200 parts of ethylene glycol and 200 parts of ethyl ether of ethylene glycol ^ 100 parts of the first substance and 300 parts of the second substance were used, or otherwise 300 parts of the first substance and 100 parts of the second substance, solutions with the same characteristics.

Example V

The diazo compound was prepared from 173 parts of sulfanilic acid according to the procedure of Example 1, after which the resulting suspension was poured over a period of 30 minutes into the solution of 144 parts of β-naphthol in 210 parts of triethanolamine. After filtration, the same solution as in Example 1 was obtained.

Example VI

The procedure of Example 3 was repeated, but 187 parts of 2-aminotoluene-5-sulfonic acid were replaced by 168.3 parts of this product and 17.3 parts of sulfanilic acid to give a solution containing a mixture of 90%. dye "Acid Orange 8" "and 10 $ of the dye" Acid Orange 7 ".

Example VII

A mixture was prepared of 187 parts of 2-aminotoluene-5-sulfonic acid, 100 parts of monoethylene glycol, 100 parts of methyl ether of monoethylene glycol, 100 parts of ice and 70 parts of sodium nitrite. Within a 15 minute period, 53 parts of 94% sulfuric acid were added and the diazotization reaction was continued until there was no further discoloration of the diazotizable amine. 144 parts of β-naphthol were then added over a 30 minute period, then 210 parts of triethanolamine (industrial product) within an hour. The mixture was reacted for 30 minutes for 81 02 8 1 1 A '-6-21910 / Vk / rab, then heated to MO ° C and sodium sulfate was separated by filtration. Thus, 810 parts of a solution containing 57¾ dye "Acid Orange 8" were obtained.

Example VIII

A mixture was prepared of 173 parts of sulfanilic acid and MO parts of monoethylene glycol, MO parts of methyl ether of monoethylene glycol and 120 parts of water. Within a one hour period, 70 parts of sodium nitrite was added and then 53 parts of 9M $ sulfuric acid within an hour. The diazotization was stopped after which 1MM parts of Q-naphthol were added. Within a period of one hour, 180 parts of pure triethanolamine or the same mixture as in Example 1 was added. The reaction was effected for 30 minutes, after which the temperature was raised to 60 ° C and sodium sulfate was separated by filtration. Thus, 710 parts of a solution containing about 62% of dye was obtained, the concentration of which was adjusted to a value such that 1M0 parts of the solution corresponded to 100 parts of the commercially available powdered product. This operation was carried out by adding water or by adding monoethylene glycol or the methyl ether of monoethylene glycol or by a mixture of these two products in which one of the substances was water.

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Claims (10)

1. A process for preparing a concentrated solution of azo dyes from diazotizable amines and coupling agents by diazotizing and coupling in the presence of water and at least one solvent miscible with water, characterized in that the diazotizing is effected with sodium nitrite in the presence of sulfuric acid and the sodium sulfate formed is removed by filtration. 2. Process according to claim 1, characterized in that the di-drifting is effected in a mixture of water, monoethylene glycol and methyl or ethyl ether of monoethylene glycol. Process according to claim 1 or 2, characterized in that the coupling is effected in the presence of triethanolamine alone or in a mixture of mono, di and triethanolamine. Process according to claims 1-3, characterized in that the coupling agent used is 3-naphthol. Process according to Claims 1 to 4, characterized in that the diazotizable amine is sulfanilic acid. 6. Process according to claims 1-4, characterized in that 2-aminotoluene-5-sulfonic acid is used as diazotizable amine. 7. Process according to claims 1-4, characterized in that the diozotable amine is a mixture of sulfanilic acid and 2-aminotoluene-5-sulfonic acid. 8. Solution obtained according to the method as claimed in claims 1-7, characterized in that the solution consists of: 40 to 65% dye, 10 to 40% of a mixture consisting of 25 to 75% monoethylene glycol, 75 to 25¾ methyl or ethyl ether of monoethylene glycol, 0-30¾ of a mixture consisting of 0-5¾ monoethanolamine, 0-5¾ diethanolamine and 100-90¾ triethanolamine, 10-30¾ water and less than 2¾ sodium sulfate. Solution according to claim 8, characterized in that the dye is "Acid Orange 7". Solution according to claim 8, characterized in that the colorant is "Acid Orange 8" or a mixture thereof with "Acid Orange 7". . 81 02 8 1 1