This paper mainly introduces the method of synthesizing acid blue black/0B dye with basic raw materials such as p-nitroaniline, H acid and aniline, discusses the influence of preparation process and reaction conditions on dye performance, and introduces its application in printing and dyeing industry.
Key words: acid dye; blue black 1OB; diazotized I coupling; leather In recent years, with the increasing demand for leather products, the research and development of leather dyes has gradually developed, strong acid dyes are the earliest developed The acid dye can be used to dye protein fibers such as wool and silk and polyamide fibers in an acidic medium, and can also be used for coloring leather and paper foods. The strong acid dye has simple molecular structure, low molecular weight, and has the advantages of simple dyeing method, good leveling property and bright color when dyeing. Acid blue black lOB is a kind of strong acid dye which has a large production quantity and thus plays an important role in dye production.
1 Experimental part
1.1 Reaction principle

1.3 Experimental operation process

1.3.l Diazotization of p-nitroaniline

Put 30 g of crushed ice into a 250 ml four-necked bottle, start the stirrer, and pour the mixture of all dissolved p-nitroaniline, hydrochloric acid and water, which is heated to above 90 °C, and slowly cool down to obtain light blue small particles. When the temperature drops below 5 °C, NaNO will be used. The solution was quickly added, and the starch-KI test paper was used to measure whether it was excessive. If the reaction was normal, the solution was pale yellow, and the temperature was kept for 0.5 h, and suction filtration was performed.

1.3.2 Acid coupling

The diazo filtrate of p-nitroaniline was poured into a 500 ml four-necked flask and stirred. The H acid was added dropwise to the diazo solution for 1.5 h, and the temperature was controlled at 1o-15. After °C, 6 h, the sampling plate was sampled, and the color of the coupling liquid was purple-red.

1.3.3 Aniline diazotization Aqueous hydrochloric acid solution was poured into a 250 ml four-necked flask, and after adding about 30 g of crushed ice, aniline was added. When the temperature was below 5 ° C, NaN was added. 2 Slowly add the reaction bottle to the dropping tube. After the addition, the starch-KI test paper is used to check whether it is excessive, and the temperature is kept for 0 5 h.

L.3.4 Alkaline coupling Add NaOH to the acid coupling solution to neutralize excess HCI, then add 2.6 g NaCO. The coupling solution is made alkaline, the aniline diazonium droplets are kept in the coupling solution, and then an equal amount of Na2CO solution is added to adjust the pH of the coupling solution to 8-9, and the sample is taken after 0.5 h of incubation. Dot plate, the color of the coupling liquid is blue and black.

1.3.5 Add 30 g of NaC1 in the well-maintained alkaline coupling solution, salt out 0.5 la, suction filter, dry the filter cake, weigh, grind and bag. This reaction is a self-coupling reaction and is irreversible. Once the azo compound is formed, even if the acid solution is added, the azo compound cannot be converted into a diazonium salt, so that the diazonium salt solution contains impurities, and the yield Reduce; when the amount of acid is insufficient, the diazonium salt is also easily decomposed, and the higher the temperature, the faster. Therefore, when the diazotization reaction is carried out, the amount of the acid must be controlled so that the pH of the medium is less than 3.

2.1.2 When the amount of nitrous acid and the dropping rate diazotization reaction are carried out, a slight excess of nitrous acid must be maintained from the beginning to the end, otherwise it will cause its own coupling reaction, but too much nitrous acid will be unfavorable for the next coupling reaction, so control The amount of nitrous acid and the dropping rate are the key points of the diazotization reaction.
The rate of diazotization is controlled by the rate of addition of sodium nitrite solution. It must be maintained at a certain rate of feed. If it is too slow, the aromatic amine that is not in effect will undergo a self-coupling reaction with the diazonium salt. The rate of different aromatic amines added with sodium nitrite is different. There are two steps of diazotization in the process of blue black 10B, using two kinds of aromatic amines, p-nitroaniline and aniline, p-nitroaniline A weakly basic aromatic amine containing a strong electron withdrawing group, NO, in the molecule. Alkaline is weak, it is difficult to form a salt with dilute acid. Even if an ammonium salt is formed, it is easily hydrolyzed in water to form a free aromatic amine. The true diazotization reaction is dissolved in the free amine, not the ammonium salt of the aromatic amine. Therefore, the diazotization reaction rate of p-nitroaniline is faster than that of the alkali strong aniline, and therefore in the two diazotization reactions. The reaction control conditions of p-nitroaniline and aniline are different. In the reaction, KI-starch test paper is usually used to check whether the nitrous acid is excessive. If the KI-starch test paper turns blue, it means that the nitrous acid excess aniline belongs to the strong basic aromatic amine, and the molecular water has no electron-withdrawing substituent, which is easy to The inorganic acid forms a stable ammonium salt, and the diazotization reaction rate is slow. Therefore, the addition rate of sodium nitrite does not have to be too fast, and it can be added dropwise. Therefore, when the aniline is diazotized, as long as the slight excess of sodium nitrite and the dropping rate are controlled, the temperature is controlled below 5 ° C, and the reaction can be carried out normally.

2.2 The coupling reaction can be carried out while the side reaction of the diazonium salt can be generated to form a 焦-like substance. It can be seen from many experiments that for every 10 °C increase in temperature, the coupling reaction rate increases by 2 to 2.4 times, and the decomposition rate of diazonium salt increases by 3.1 to 5.3 times. Therefore, the coupling reaction should be at a lower temperature. Through comparative analysis and comparison, it is easier to control the coupling reaction temperature between 8 and 15 °C.
The pH of the two-step coupling reaction differs during the coupling process, and the p-nitroaniline diazo solution needs to be coupled under acidic conditions. The aniline diazo solution needs to be coupled under alkaline conditions, and it is known from the localization effect of H acid that acid coupling must be performed first, then the pH value is adjusted, and then alkaline coupling is performed. Under acidic conditions, a NH of H acid forms a hydrochloride salt. Therefore, the density of an NH-ortho-electron cloud increases, which is beneficial to the attack of a positively charged p-nitrodiazonium salt. Under alkaline conditions, due to an OH Partially ionizes H to increase the density of electron clouds in the vicinity of an OH. When adding aniline diazonium salt, it is easy to attack the position. In the alkaline coupling and the addition, the lye is added twice. It is known from the reaction kinetics that the stability of the aniline diazonium solution is not good. When the pH value is less than 4, the decomposition rate is higher than the coupling speed, and the first alkali is added. Adjusting the pH value to make the pH value greater than 7, when the pH is between 8 and 9, the coupling speed is greater than the decomposition rate, and adding the second alkali liquid makes the aniline diazonium salt completely participate in the coupling reaction.

3 Conclusions In the research of the synthesis process of Blue Black 10B, it has been analyzed several times. The key points of the experiment can be derived: (a) the amount of mineral acid, (b) the amount of nitrous acid and the rate of drop, (c) the holding time of the coupling, and (d) the pH of the reaction medium. As long as the above conditions are controlled, the product can reach the standard in terms of color, power and yield.

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