This article mainly introduces the synthesis of acid blue/Ob dyes from 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.
Keywords: acid dyes; 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 development Acid dyes, which can dye protein fibers and polyamide fibers such as wool and silk in acidic media, can also be used to color leather and paper foods. Strong acid dyes have a simple molecular structure and a low molecular weight. They have the advantages of simple dyeing methods, good level dyeing, and bright color. Acid blue and black lOB is a species with a large amount of production of strong acid dyes, and thus occupies an important position in dye production.
1 Experimental section
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 flask, start the stirrer, and quickly pour the mixture of p-nitroaniline, hydrochloric acid, and water, which have been heated to above 90°C, and quickly cool down to obtain light blue small particles. When the temperature drops below 5°C, NaNO will be added. The solution was quickly added, and the starch-KI test paper was used to determine whether it was excessive. If the reaction was normal, the solution was light yellow, and the solution was incubated for 0.5 h and filtered by suction.
1.3.2 Acid Coupling
The diazo filtrate of p-nitroaniline was poured into a 500 ml four-necked flask and stirring was started. H acid was added dropwise to the diazo solution within 1.5 h, and the heat was maintained for 8 h at a temperature of 1o-15. °C, 6 hours later, the sample point plate, the color of the coupling solution was purple.
1.3.3 Diazotization of Aniline Aqueous hydrochloric acid is poured into a 250 ml four-necked flask, 3Og of crushed ice is added, and then aniline is added. When the temperature is below 5°C, NaN is added. 2 Slowly add the reaction flask to the dropper and add the starch to the KI test paper to check if it is overdose and keep it warm for 0 5 h.
L.3.4 Alkaline Coupling Add NaOH and excess HCI to the acidic coupling solution and add 2.6 g of NaCO. Make the coupling solution alkaline, add a good amount of aniline diazo droplets to the coupling solution, then add the same amount of Na2CO solution, adjust the pH of the coupling solution to 8-9, and sample after 0.5 h of incubation. Point plate, the color of the coupling liquid is blue black.
1.3.5 Add 30 g NaC1 to the well-preserved 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 it is irreversible. Once an azo compound is formed, the azo compound cannot be converted to a diazonium salt even if an additional acid is added. As a result, the diazonium salt solution contains impurities and the yield is high. Lower; when the acid amount is insufficient, the diazonium salt is also easily decomposed, and the higher the temperature, the faster the separation. Therefore, in the diazotization reaction, the amount of acid must be controlled so that the pH of the medium is less than 3.
2.1.2 When the diazotization reaction is carried out with the amount of nitrous acid and the rate of acceleration of the diazotization, a slight excess of nitrous acid must be maintained from beginning to end, otherwise it will cause self-coupling reaction, but too much nitrous acid will adversely affect the next coupling reaction, so the control The amount of nitrous acid and the dropping rate are the key to the diazotization reaction.
Diazotization reaction rate is controlled by the speed of adding sodium nitrite solution, must maintain a certain rate of feed, too slow an aryl amine will react with diazonium salt self-coupling reaction. The rate of different arylamines dropping sodium nitrite is different. There are two steps of diazotization reaction in the process of blue black 10B. They use two kinds of aromatic amines, p-nitroaniline and aniline, and p-nitroaniline. The weaker aromatic amines contain a strong electron-withdrawing group, NO. The alkalinity is weak, and it is difficult to salt with dilute acid. Even if an ammonium salt is formed, it is easily hydrolyzed to form free aromatic amines in water. But the real diazotization reaction is the dissolution of free amine, not the ammonium salt of aromatic amine. Therefore, the rate of diazotization of p-nitroaniline is faster than that of strong aniline, so it is in two diazotization reactions. The reaction control conditions for p-nitroaniline and aniline are different. In the reaction, KI-starch test paper is usually used to test whether nitrous acid is excessive. If KI-starch paper is blue, it indicates that aniline excess aniline is a strong basic arylamine. The molecule does not have an electron-absorbing substituent in the water content. Inorganic acids form stable ammonium salts and the rate of diazotization is slow. Therefore, the addition rate of sodium nitrite is not necessarily too fast, and it can be added dropwise. Therefore, when aniline is diazotized, as long as the sodium nitrite is controlled to have a slight excess and the dropping rate is controlled, the temperature is controlled below 5° C., and the reaction can proceed normally.
2.2 Coupling Reactions Coupling reactions can occur simultaneously with side reactions of diazonium salts to produce coke-like substances. From several experiments, it can be seen that for every 10°C increase in temperature, the coupling reaction rate increases by 2 to 2.4 times and the rate of diazonium salt decomposition increases by 3.1 to 5.3 times. Therefore, the coupling reaction should be at a lower temperature. Through comparative analysis and comparison, the coupling reaction temperature is controlled 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 can be known from the localization effect of H acid that the acid coupling must be performed first, and then the pH is adjusted, and then the basic coupling is performed. Under acidic conditions, an NH of H acid forms the hydrochloride, and therefore, the density of an ortho electron cloud increases, favoring the positively charged attack on the nitrodiazonium salt, due to an OH in alkaline conditions. Part of the ionized H, so that the density of an electron cloud adjacent to an OH increase, when adding aniline diazonium salt, easily attack the position. In the alkaline coupling and in addition, it is necessary to add two lye. According to the reaction kinetics, the stability of aniline diazo solution is not good. When the pH value is less than 4, the decomposition rate is higher than the coupling rate, and the first alkali is added. The pH was adjusted so that the pH was greater than 7. When the pH was between 8 and 9, the coupling rate was greater than the decomposition rate. The addition of the second lye allowed the diazonium salt of aniline to completely participate in the coupling reaction.
3 Conclusions In the study of the synthesis of blue-black 10B, several experiments were performed. The key points of this experiment can be obtained: (a) the amount of inorganic acid, (b) the amount of nitrous acid and the dropping rate, (c) the time of the coupling incubation, and (d) the pH of the reaction medium. As long as the above conditions are properly controlled, the product can meet standards in shade, strength and yield.
This article mainly introduces the synthesis of acid blue/Ob dyes from 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.
Keywords: acid dyes; 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 development Acid dyes, which can dye protein fibers and polyamide fibers such as wool and silk in acidic media, can also be used to color leather and paper foods. Strong acid dyes have a simple molecular structure and a low molecular weight. They have the advantages of simple dyeing methods, good level dyeing, and bright color. Acid blue and black lOB is a species with a large amount of production of strong acid dyes, and thus occupies an important position in dye production.
1 Experimental section
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 flask, start the stirrer, and quickly pour the mixture of p-nitroaniline, hydrochloric acid, and water, which have been heated to above 90°C, and quickly cool down to obtain light blue small particles. When the temperature drops below 5°C, NaNO will be added. The solution was quickly added, and the starch-KI test paper was used to determine whether it was excessive. If the reaction was normal, the solution was light yellow, and the solution was incubated for 0.5 h and filtered by suction.
1.3.2 Acid Coupling
The diazo filtrate of p-nitroaniline was poured into a 500 ml four-necked flask and stirring was started. H acid was added dropwise to the diazo solution within 1.5 h, and the heat was maintained for 8 h at a temperature of 1o-15. °C, 6 hours later, the sample point plate, the color of the coupling solution was purple.
1.3.3 Diazotization of Aniline Aqueous hydrochloric acid is poured into a 250 ml four-necked flask, 3Og of crushed ice is added, and then aniline is added. When the temperature is below 5°C, NaN is added. 2 Slowly add the reaction flask to the dropper and add the starch to the KI test paper to check if it is overdose and keep it warm for 0 5 h.
L.3.4 Alkaline Coupling Add NaOH and excess HCI to the acidic coupling solution and add 2.6 g of NaCO. Make the coupling solution alkaline, add a good amount of aniline diazo droplets to the coupling solution, then add the same amount of Na2CO solution, adjust the pH of the coupling solution to 8-9, and sample after 0.5 h of incubation. Point plate, the color of the coupling liquid is blue black.
1.3.5 Add 30 g NaC1 to the well-preserved 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 it is irreversible. Once an azo compound is formed, the azo compound cannot be converted to a diazonium salt even if an additional acid is added. As a result, the diazonium salt solution contains impurities and the yield is high. Lower; when the acid amount is insufficient, the diazonium salt is also easily decomposed, and the higher the temperature, the faster the separation. Therefore, in the diazotization reaction, the amount of acid must be controlled so that the pH of the medium is less than 3.
2.1.2 When the diazotization reaction is carried out with the amount of nitrous acid and the rate of acceleration of the diazotization, a slight excess of nitrous acid must be maintained from beginning to end, otherwise it will cause self-coupling reaction, but too much nitrous acid will adversely affect the next coupling reaction, so the control The amount of nitrous acid and the dropping rate are the key to the diazotization reaction.
Diazotization reaction rate is controlled by the speed of adding sodium nitrite solution, must maintain a certain rate of feed, too slow an aryl amine will react with diazonium salt self-coupling reaction. The speed of different arylamines dropping sodium nitrite is different. There are two steps of diazotization in the process of blue black 10B. Two kinds of aromatic amines, p-nitroaniline and aniline, and p-nitroaniline are used respectively. The weaker aromatic amines contain a strong electron-withdrawing group, NO. The alkalinity is weak, and it is difficult to salt with dilute acid. Even if an ammonium salt is formed, it is easily hydrolyzed to form free aromatic amines in water. But the real diazotization reaction is the dissolution of free amine, not the ammonium salt of aromatic amine. Therefore, the rate of diazotization of p-nitroaniline is faster than that of strong aniline, so it is in two diazotization reactions. The reaction control conditions for p-nitroaniline and aniline are different. In the reaction, KI-starch test paper is usually used to test whether nitrous acid is excessive. If KI-starch paper is blue, it indicates that aniline excess aniline is a strong basic arylamine. The molecule does not have an electron-absorbing substituent in the water content. Inorganic acids form stable ammonium salts and the rate of diazotization is slow. Therefore, the addition rate of sodium nitrite is not necessarily too fast, and it can be added dropwise. Therefore, when aniline is diazotized, as long as the sodium nitrite is controlled to have a slight excess and the dropping rate is controlled, the temperature is controlled below 5° C., and the reaction can proceed normally.
2.2 Coupling Reactions Coupling reactions can occur simultaneously with side reactions of diazonium salts to produce coke-like substances. From several experiments, it can be seen that for every 10°C increase in temperature, the coupling reaction rate increases by 2 to 2.4 times and the rate of diazonium salt decomposition increases by 3.1 to 5.3 times. Therefore, the coupling reaction should be at a lower temperature. Through comparative analysis and comparison, the coupling reaction temperature is controlled 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 can be known from the localization effect of H acid that the acid coupling must be performed first, and then the pH is adjusted, and then the basic coupling is performed. Under acidic conditions, an NH of H acid forms the hydrochloride, and therefore, the density of an ortho electron cloud increases, favoring the positively charged attack on the nitrodiazonium salt, due to an OH in alkaline conditions. Part of the ionized H, so that the density of an electron cloud adjacent to an OH increase, when adding aniline diazonium salt, easily attack the position. In the alkaline coupling and in addition, it is necessary to add two lye. According to the reaction kinetics, the stability of aniline diazo solution is not good. When the pH value is less than 4, the decomposition rate is greater than the coupling rate, and the first base is added. The pH was adjusted so that the pH was greater than 7. When the pH was between 8 and 9, the coupling rate was greater than the decomposition rate. The addition of the second lye allowed the diazonium salt of aniline to completely participate in the coupling reaction.
3 Conclusions In the study of the synthesis of blue-black 10B, several experiments were performed. The key points of this experiment can be obtained: (a) the amount of inorganic acid, (b) the amount of nitrous acid and the dropping rate, (c) the time of the coupling incubation, and (d) the pH of the reaction medium. As long as the above conditions are properly controlled, the product can meet standards in shade, strength and yield.
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