Preparation method of acid and alkali resistant toluidine red pigment

Abstract

The application discloses a preparation method of acid and alkali resistant toluidine red pigment, belongs to the technical field of pigment synthesis, and introduces di-primary amine on a modified toluidine red pigment, then reacts with a dicarboxylic compound, and finally is prepared through hydrolysis and self-assembly; the modified toluidine red pigment is prepared through the following steps that 3-amino-4-nitrobenzyl alcohol is diazotized and then coupled with 2-naphthol; the acid and alkali resistant toluidine red pigment prepared by the application not only has bright color and good hiding power, and also has high coloring strength, light resistance, water resistance, oil resistance and dispersibility, and simultaneously has strong acid and alkali resistance and environmental stability, and significantly improves the application performance of the pigment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pigment synthesis, and specifically relates to a preparation method of acid-alkali-resistant toluidine red pigment. BACKGROUND

[0002] Toluidine red pigment is a common organic pigment and is widely used in the fields of paint, plastic, ink and the like. Although it has bright color and good hiding power and high coloring strength, it has significant defects in acid-alkali resistance.

[0003] The chemical structure of toluidine red contains amine groups and aromatic rings, and these functional groups may be chemically reacted in an acid-alkali environment, thereby causing degradation or discoloration of the pigment; the structure of toluidine red contains an azo group, which is relatively unstable under strong alkali conditions and is prone to hydrolysis and rupture, thereby destroying the chromophore and causing the pigment to fade or discolor, which limits the application of toluidine red in certain acid-alkali environments. In addition, toluidine red often has a problem of heavy metal ion elution after long-term exposure to extreme pH environments, which affects product performance and does not meet increasingly stringent environmental regulations. Therefore, it is necessary to modify toluidine red to improve the durability of toluidine red pigment and expand its application range in various applications. SUMMARY

[0004] To achieve the above-mentioned purpose, the following technical scheme is implemented.

[0005] A preparation method of acid-alkali-resistant toluidine red pigment, in which a di-primary amine is introduced into modified toluidine red pigment, then reacted with a dicarboxylic compound, and finally prepared through hydrolysis and self-assembly;

[0006] The modified toluidine red pigment is prepared by diazotization of 3-amino-4-nitrobenzyl alcohol and coupling with 2-naphthol;

[0007] The dicarboxylic compound is prepared by the following method:

[0008] Methanetricarboxylic acid trimethyl ester is added to an organic solvent 1, and sodium hydroxide is added thereto, and the reaction is carried out at 25-45 DEG C for 8-12 h. After the reaction is completed, the obtained filtrate is distilled under reduced pressure to remove the solvent, and the obtained residue is washed with water and dried to obtain the dicarboxylic compound.

[0009] The organic solvent 1 is methanol, ethanol or isopropanol.

[0010] The mass ratio of the methanetricarboxylic acid trimethyl ester, the organic solvent 1 and the sodium hydroxide is 1:5-10:0.3-0.4.

[0011] The modified toluidine red pigment is prepared by the following method:

[0012] 1) adding water and 3-amino-4-nitrobenzyl alcohol into a diazotization reactor, beating for 1 h, then adding hydrochloric acid with a mass concentration of 30%, stirring and mixing uniformly, cooling to 0-5 DEG C, then adding sodium nitrite aqueous solution with a mass concentration of 30% dropwise, diazotizing for 1-3 h until that a Congo red test paper is blue and a potassium iodide starch test paper is blue, stopping the reaction, and obtaining a diazotization liquid;

[0013] 2) adding 2-naphthol and water into a coupling reactor, then adding sodium hydroxide, stirring and mixing uniformly to obtain a coupling liquid, adding the diazotization liquid obtained in step 1) dropwise into the coupling liquid, adjusting the pH of the system to 8-8.5 by using sodium hydroxide solution with a mass concentration of 20-25%, stirring and reacting for 1-2 h, heating to 75-80 DEG C and continuing to react for 1-1.5 h, filtering, washing with water, and drying to obtain a modified toluidine red pigment.

[0014] The mass ratio of the water, 3-amino-4-nitrobenzyl alcohol, hydrochloric acid and sodium nitrite aqueous solution in step 1) is 5-6:1:1.5-1.8:1.4-2.

[0015] The mass ratio of the 2-naphthol, water and sodium hydroxide in step 2) to the 3-amino-4-nitrobenzyl alcohol in step 1) is 0.9-1.2:10-15:0.1-0.2:1.

[0016] The preparation method of the acid and alkali resistant toluidine red pigment comprises the following steps:

[0017] ① adding the modified toluidine red pigment into organic solvent 2, then adding tert-butyl formic acid chloride and amine, reacting at 30-45 DEG C for 6-12 h, after the reaction is completed, performing suction filtration, removing the solvent from the obtained filtrate by distillation under reduced pressure, and obtaining a tert-butyl-terminated toluidine red pigment;

[0018] ② adding the tert-butyl-terminated toluidine red pigment obtained in step ① into organic solvent 2, then adding diethylenetriamine, stirring and dissolving, heating to 50-110 DEG C and reacting for 12-24 h, after the reaction is completed, removing the solvent by distillation under reduced pressure, adding the obtained residue into organic solvent 1, then adding a base, reacting at 25-45 DEG C for 8-12 h, performing suction filtration, rotating to dry the solvent of the obtained filtrate, washing the obtained residue with water, and drying to obtain a di-primary amine modified toluidine red pigment;

[0019] ③adding the diamine modified toluidine red pigment prepared in step ② and a dicarboxylic compound into the organic solvent 3, adding 4-dimethylaminopyridine and 1-hydroxybenzotriazole, and reacting at 25-45℃ for 24-48h, after the reaction is completed, filtering, washing the obtained filter cake with water, drying, adding a mixed solution of the organic solvent 4 and the organic solvent 1, adding a base, and reacting at 25-45℃ for 12-24h, after the reaction is completed, filtering, removing the solvent from the obtained filtrate by distillation under reduced pressure, washing with water, and drying, to obtain a polymer;

[0020] ④adding the polymer obtained in step ③ into the organic solvent 4, dissolving by stirring, passing nitrogen into the system at a rate of 5-10ml / s, and adding water dropwise, until the solution in the system becomes turbid, standing for 24-48h, centrifuging, to obtain an acid and alkali resistant toluidine red pigment.

[0021] The organic solvent 2 in step ① is tetrahydrofuran, acetonitrile, dimethylformamide or acetone; and the amine is triethylamine or N,N-diisopropylethylamine.

[0022] The mass ratio of the modified toluidine red pigment, the organic solvent 2, the tert-butyl chloride and the amine in step ① is 1:8-15:0.9-1.5:0.8-1.2.

[0023] The base in step ② is sodium hydroxide or potassium hydroxide.

[0024] The mass ratio of the end tert-butyl toluidine red pigment, the organic solvent 2, diethylenetriamine, the organic solvent 1 and the base in step ② is 1:5-10:0.2-0.4:5-10:0.15-0.3.

[0025] The organic solvent 3 in step ③ is acetone, acetonitrile or tetrahydrofuran.

[0026] The organic solvent 4 in step ③ is dimethylformamide or dimethyl sulfoxide.

[0027] The volume ratio of the organic solvent 4 and the organic solvent 1 in the mixed solution of the organic solvent 4 and the organic solvent 1 in step ③ is 1:1.5-2.

[0028] The mass ratio of the diamine modified toluidine red pigment, the dicarboxylic compound, the organic solvent 3, 4-dimethylaminopyridine, 1-hydroxybenzotriazole, the mixed solution and the base in step ③ is 1:0.4-0.5:5-10:0.3-0.5:0.35-5:5-10:0.2-0.35.

[0029] The mass ratio of the polymer and the organic solvent 4 in step ④ is 1:10-15.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] The acid and alkali resistant toluidine red pigment of the present application firstly introduces a di-primary amine fragment in the molecular skeleton of toluidine red, and then introduces the toluidine red molecule into the linear polyamide main chain by the way of amide condensation. There are a large number of hydrogen bonds in the polyamide main chain, so the pigment can be wrapped inside the particle by hydrogen bond action, forming a dense protective film on the surface of the pigment, effectively preventing the penetration of corrosive substances into the internal pigment, while preventing the agglomeration between the pigments, improving the dispersibility of the pigment. On the other hand, the polyamide main chain is rich in a large number of tertiary amines and carboxylic acids. These fragments form an intramolecular buffer system. When the external environment is strongly acidic, the tertiary amine in the polyamide main chain changes the polymer main chain into a proton sponge, which can absorb and neutralize a large number of hydrogen ions in the external environment. When the external environment is a strong alkaline environment, the carboxyl group in the main chain can release protons to neutralize the alkali. Through this buffering mechanism, the toluidine red pigment avoids the interference of the external environment and improves the stability of the pigment.

[0032] The acid and alkali resistant toluidine red pigment prepared by the present application not only has bright color and good hiding power, as well as high coloring strength, light resistance, water resistance, oil resistance and dispersibility, but also has strong acid and alkali resistance and environmental stability, significantly improving the application performance of the pigment. DETAILED DESCRIPTION

[0033] In order to better understand the technical solutions of the present application, the above content of the present application will be further described in detail in the form of examples, but this should not be understood as the scope of the above subject matter of the present application is limited to the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application.

[0034] Example 1 Preparation of dicarboxylic acid compound:

[0035] 0.1 kg of methane tricarboxylic acid trimethyl ester was added to 0.5 kg of methanol, and then 0.03 kg of sodium hydroxide was added. The reaction was carried out at 25℃ for 8h. After the reaction was completed, the filtrate was filtered and the solvent was removed by distillation under reduced pressure. The obtained residue was washed with water and dried to obtain the dicarboxylic acid compound. 1 H NMR (300 MHz, DMSO- d 6 , 298 K) δ 13.25 (s, 2H), 4.05 (s,1H), 3.63 (s, 3H).

[0036] Preparation of modified toluidine red pigment:

[0037] 1) 5 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added into a diazotization reactor, and were beaten for 1 h. Then, 1.5 kg of 30% hydrochloric acid was added, and was stirred and mixed uniformly. After cooling to 0°C, 1.4 kg of 30% sodium nitrite aqueous solution was added dropwise, and was diazotized for 1 h until the Congo red test paper was blue and the potassium iodide starch test paper was blue. The reaction was stopped, and a diazotization solution was obtained;

[0038] 2) 0.9 kg of 2-naphthol and 10 kg of water were added into a coupling reactor. Then, 0.1 kg of sodium hydroxide was added, and was stirred and mixed uniformly to obtain a coupling solution. The diazotization solution obtained in step 1) was added dropwise into the coupling solution. The pH of the system was adjusted to 8 by using 20% sodium hydroxide solution. The stirring reaction was carried out for 1 h, and was heated to 75°C for 1 h. After filtration, washing with water and drying, a modified toluidine red pigment was obtained.

[0039] Preparation of acid and alkali resistant toluidine red pigment:

[0040] ① 0.1 kg of modified toluidine red pigment was added into 0.8 kg of tetrahydrofuran. Then, 0.09 kg of tert-butyl chloride and 0.08 kg of triethylamine were added, and were reacted at 30°C for 6 h. After the reaction was completed, the obtained filtrate was distilled under reduced pressure to remove the solvent, and a tert-butyl-terminated toluidine red pigment was obtained; 1 H NMR (300 MHz, DMSO- d 6 , 298 K) δ 8.45 (d, 1H), 8.15-8.29(m, 4H), 7.73 (d, 1H), 7.55-7.62 (m, 2H), 7.23 (d, 1H), 5.21 (s, 2H), 1.23(s, 9H), 1.33 (s, 9H).

[0041] ② 0.1 kg of the tert-butyl-terminated toluidine red pigment obtained in step ① was added into 0.5 kg of tetrahydrofuran. Then, 0.02 kg of diethylenetriamine was added, and was stirred and dissolved. After heating to 60°C, the reaction was carried out for 12 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure. The obtained residue was added into 0.5 kg of methanol, and 0.015 kg of potassium hydroxide was added. The reaction was carried out at 25°C for 8 h. After filtration, the obtained filtrate was rotary dried. The obtained residue was washed with water and dried to obtain a di-primary amine modified toluidine red pigment; 1 H NMR (300 MHz, DMSO- d 6 , 298 K) δ 9.85 (s, 1H), 8.42 (d, 1H), 8.01-8.32 (m, 5H), 7.35-7.49 (m, 2H), 7.22 (d, 1H) , 3.68 (s, 2H) , 2.55-2.63 (m, 8H), 1.53 (s, 4H).

[0042] ③ Add 0.1 kg of the diamine-modified toluidine red pigment prepared in step ② and 0.04 kg of the dicarboxylic acid compound to 0.5 kg of acetone, then add 0.03 kg of 4-dimethylaminopyridine and 0.035 kg of 1-hydroxybenzotriazole. React at 25 °C for 24 h. After the reaction is complete, filter the mixture. Wash the filter cake with water, dry it, and then add it to a mixed solution of 0.5 kg of dimethylformamide and methanol, wherein the volume ratio of dimethylformamide to methanol is 1:1.5. Then add 0.02 kg of sodium hydroxide and react at 25 °C for 12 h. After the reaction is complete, filter the mixture. Remove the solvent from the filtrate by vacuum distillation, wash it with water, and dry it to obtain the polymer.

[0043] ④ Add 0.1 kg of the polymer obtained in step ③ to 1 kg of dimethylformamide, stir to dissolve, then introduce nitrogen gas into the system at a rate of 5 ml / s and add water dropwise. When the solution in the system becomes turbid, let it stand for 24 h, centrifuge to obtain acid and alkali resistant toluidine red pigment.

[0044] Example 2: Preparation of dicarboxylic acid compounds:

[0045] 0.1 kg of trimethyl methanetricarboxylate was added to 0.6 kg of ethanol, and then 0.032 kg of sodium hydroxide was added. The mixture was reacted at 30 °C for 10 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water and dried to obtain the dicarboxylic acid compound.

[0046] Preparation of modified toluidine red pigment:

[0047] 1) Add 5.2 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol to a diazotization reactor and stir for 1 hour. Then add 1.6 kg of 30% hydrochloric acid and stir until well mixed. Cool down to 1°C and then add 1.5 kg of 30% sodium nitrite aqueous solution dropwise. The diazotization reaction is carried out for 1.5 hours until Congo red test paper turns blue and potassium iodide starch test paper turns blue. Stop the reaction to obtain diazo solution.

[0048] 2) 1 kg of 2-naphthol and 11 kg of water were added into a coupling reactor, and then 0.12 kg of sodium hydroxide was added into the coupling reactor, and after stirring and mixing, a coupling solution was obtained; the diazonium solution prepared in step 1) was added dropwise into the coupling solution, and then the pH of the system was adjusted to 8.1 by using a 20% sodium hydroxide solution; stirring was performed for 1.2 h, and then heating was performed to 76 °C, and the reaction was continued for 1.1 h; filtration was performed, and then washing was performed with water, and drying was performed, to obtain the modified toluidine red pigment.

[0049] Preparation of acid and alkali resistant toluidine red pigment:

[0050] ① 0.1 kg of the modified toluidine red pigment was added into 0.9 kg of acetonitrile, and then 0.1 kg of tert-butyl chloride and 0.09 kg of triethylamine were added into the acetonitrile, and the reaction was performed at 35 °C for 8 h; after the reaction was completed, filtration was performed under suction, and then the solvent was removed from the obtained filtrate by distillation under reduced pressure, to obtain a tert-butyl-terminated toluidine red pigment;

[0051] ② 0.1 kg of the tert-butyl-terminated toluidine red pigment prepared in step ① was added into 0.6 kg of acetonitrile, and then 0.025 kg of diethylenetriamine was added into the acetonitrile; after stirring and dissolving, heating was performed to 70 °C, and the reaction was performed for 14 h; after the reaction was completed, the solvent was removed from the reaction system by distillation under reduced pressure; the obtained residue was added into 0.6 kg of ethanol, and then 0.018 kg of sodium hydroxide was added into the ethanol; the reaction was performed at 30 °C for 10 h; filtration was performed under suction; the solvent was removed from the obtained filtrate by rotary evaporation; the obtained residue was washed with water, and then drying was performed, to obtain a di-primary amine modified toluidine red pigment;

[0052] ③ 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.042 kg of a dicarboxylic compound were added into 0.6 kg of acetonitrile, and then 0.035 kg of 4-dimethylaminopyridine and 0.038 kg of 1-hydroxybenzotriazole were added into the acetonitrile; the reaction was performed at 30 °C for 30 h; after the reaction was completed, filtration was performed under suction; the obtained filter cake was washed with water, and then drying was performed; the obtained filter cake was added into a mixed solution of dimethyl sulfoxide and ethanol, wherein the volume ratio of the dimethyl sulfoxide and the ethanol was 1:1.6; then 0.025 kg of potassium hydroxide was added into the mixed solution; the reaction was performed at 30 °C for 15 h; after the reaction was completed, filtration was performed under suction; the solvent was removed from the obtained filtrate by distillation under reduced pressure; washing was performed with water, and then drying was performed, to obtain a polymer;

[0053] ④ 0.1 kg of the polymer obtained in step ③ was added into 1.1 kg of dimethyl sulfoxide; after stirring and dissolving, nitrogen was introduced into the system at a rate of 6 ml / s, and water was added dropwise; after the solution in the system became turbid, standing was performed for 30 h, and then centrifugation was performed, to obtain an acid and alkali resistant toluidine red pigment.

[0054] Preparation of dicarboxylic compound in Example 3:

[0055] 0.1 kg of methyl tricarboxylic acid trimethyl ester was added to 0.7 kg of isopropyl alcohol, and then 0.035 kg of sodium hydroxide was added thereto, and reacted at 35°C for 11 h. After the reaction was completed, filtration was performed, the obtained filtrate was distilled under reduced pressure to remove the solvent, the obtained residue was washed with water, and dried to obtain a dicarboxylic acid compound.

[0056] Preparation of modified toluidine red pigment:

[0057] 1) 5.5 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added to a diazotization reactor, and beaten for 1 h. Then, 1.6 kg of 30% hydrochloric acid was added, and after being stirred and mixed uniformly, the temperature was lowered to 2°C. Then, 1.7 kg of 30% sodium nitrite aqueous solution was added dropwise, and diazotization was performed for 2 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. Then, the reaction was stopped to obtain a diazonium solution;

[0058] 2) 1 kg of 2-naphthol and 12 kg of water were added to a coupling reactor, and then 0.14 kg of sodium hydroxide was added, and after being stirred and mixed uniformly, a coupling solution was obtained. The diazonium solution prepared in step 1) was added dropwise to the coupling solution, and the pH of the system was adjusted to 8.3 using 20% sodium hydroxide solution. Stirring was performed for 1.4 h, and then heating was performed to 77°C for 1.2 h. Filtration was performed, and then washing with water and drying were performed to obtain a modified toluidine red pigment.

[0059] Preparation of acid and alkali resistant toluidine red pigment:

[0060] ① 0.1 kg of modified toluidine red pigment was added to 1 kg of dimethylformamide, and then 0.1 kg of tert-butyl chloride and 0.1 kg of triethylamine were added thereto, and reacted at 38°C for 9 h. After the reaction was completed, filtration was performed, and then the obtained filtrate was distilled under reduced pressure to remove the solvent to obtain a tert-butyl-terminated toluidine red pigment;

[0061] ② 0.1 kg of the tert-butyl-terminated toluidine red pigment prepared in step ① was added to 0.7 kg of dimethylformamide, and then 0.028 kg of diethylenetriamine was added, and after being stirred and dissolved, heating was performed to 110°C for 18 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and then the obtained residue was added to 0.7 kg of isopropyl alcohol, and then 0.02 kg of sodium hydroxide was added, and reacted at 34°C for 10 h. Filtration was performed, the solvent of the obtained filtrate was removed by rotary evaporation, and then the obtained residue was washed with water and dried to obtain a di-primary amine modified toluidine red pigment.

[0062]

[0063]

[0064] Preparation of the modified toluidine red pigment:

[0065]

[0066] Preparation of the modified toluidine red pigment:

[0067] 1) 5.7 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added into a diazotization reactor, and the mixture was stirred for 1 h. Then, 1.7 kg of 30% hydrochloric acid was added, and the mixture was stirred until uniform. The temperature was then lowered to 3°C, and 1.8 kg of 30% sodium nitrite aqueous solution was added dropwise. The diazotization reaction was carried out for 2.2 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue, and the reaction was stopped. A diazotization solution was obtained.

[0068] 2) 1.1 kg of 2-naphthol and 13 kg of water were added into a coupling reactor, and 0.16 kg of sodium hydroxide was added. The mixture was stirred until uniform, and a coupling solution was obtained. The diazotization solution prepared in step 1) was added dropwise into the coupling solution. The pH of the system was adjusted to 8.4 using a 20% sodium hydroxide solution. The mixture was stirred for 1.6 h, and then heated to 78°C and reacted for another 1.3 h. The mixture was filtered, washed with water, and dried to obtain a modified toluidine red pigment.

[0069] Preparation of the acid- and alkali-resistant toluidine red pigment:

[0070] ​​​① 0.1 kg of modified toluidine red pigment was added to 1.2 kg of dimethylformamide, and then 0.12 kg of tert-butyl chloride and 0.11 kg of N,N-diisopropylethylamine were added thereto, and the mixture was reacted at 40 °C for 10 h. After the reaction was completed, the mixture was filtered under suction, and the obtained filtrate was distilled under reduced pressure to remove the solvent, thereby obtaining a tert-butyl-terminated toluidine red pigment.

[0071] ② 0.1 kg of the tert-butyl-terminated toluidine red pigment obtained in step ① was added to 0.8 kg of acetone, and then 0.03 kg of diethylenetriamine was added thereto. After the mixture was stirred and dissolved, the mixture was heated to 50 °C and reacted for 12 h. After the reaction was completed, the mixture was distilled under reduced pressure to remove the solvent. The obtained residue was added to 0.8 kg of methanol, and then 0.024 kg of potassium hydroxide was added thereto. The mixture was reacted at 38 °C for 11 h, and then filtered under suction. The obtained filtrate was spin-dried to remove the solvent. The obtained residue was washed with water and dried, thereby obtaining a di-primary amine-modified toluidine red pigment.

[0072] ③ 0.1 kg of the di-primary amine-modified toluidine red pigment obtained in step ② and 0.046 kg of a dicarboxylic compound were added to 0.8 kg of acetonitrile, and then 0.04 kg of 4-dimethylaminopyridine and 0.044 kg of 1-hydroxybenzotriazole were added thereto. The mixture was reacted at 35 °C for 36 h. After the reaction was completed, the mixture was filtered under suction. The obtained filter cake was washed with water and dried, and then added to a mixed solution of 0.8 kg of dimethyl sulfoxide and methanol (volume ratio of dimethyl sulfoxide to methanol: 1:1.8). Then, 0.03 kg of potassium hydroxide was added thereto. The mixture was reacted at 40 °C for 20 h. After the reaction was completed, the mixture was filtered under suction. The obtained filtrate was distilled under reduced pressure to remove the solvent, and then washed with water and dried, thereby obtaining a polymer.

[0073] ④ 0.1 kg of the polymer obtained in step ③ was added to 1.3 kg of dimethyl sulfoxide. After the mixture was stirred and dissolved, nitrogen gas was introduced into the system at a rate of 8 ml / s, and water was added dropwise. After the solution in the system became turbid, the mixture was left to stand for 38 h, and then centrifuged, thereby obtaining an acid and alkali resistant toluidine red pigment.

[0074] Example 5: Preparation of a dicarboxylic compound

[0075] 0.1 kg of trimethyl methane tricarboxylate was added to 0.9 kg of ethanol, and then 0.039 kg of sodium hydroxide was added thereto. The mixture was reacted at 42 °C for 9 h. After the reaction was completed, the mixture was filtered. The obtained filtrate was distilled under reduced pressure to remove the solvent. The obtained residue was washed with water and dried, thereby obtaining a dicarboxylic compound.

[0076] Preparation of a modified toluidine red pigment

[0077] 1) 5.8 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added into a diazotization reactor, and were beaten for 1 h. Then, 1.8 kg of 30% hydrochloric acid was added, and after being stirred and mixed uniformly, the temperature was lowered to 4°C. Then, 1.9 kg of 30% sodium nitrite aqueous solution was added dropwise, and diazotization was carried out for 2.5 h until the Congo red test paper showed blue color and the potassium iodide starch test paper showed blue color. The reaction was stopped, and diazotization solution was obtained;

[0078] 2) 1.2 kg of 2-naphthol and 14 kg of water were added into a coupling reactor, and then 0.18 kg of sodium hydroxide was added. After being stirred and mixed uniformly, coupling solution was obtained. The diazotization solution obtained in step 1) was added dropwise into the coupling solution, and the pH of the system was adjusted to 8.5 by using 20% sodium hydroxide solution. Stirring reaction was carried out for 1.8 h, and then heating was carried out at 79°C for 1.5 h. Filtration was carried out, and then washing and drying were carried out, to obtain modified toluidine red pigment.

[0079] Preparation of acid and alkali resistant toluidine red pigment:

[0080] ① 0.1 kg of modified toluidine red pigment was added into 1.4 kg of tetrahydrofuran, and then 0.14 kg of tert-butyl chloride and 0.11 kg of N,N-diisopropylethylamine were added. Reaction was carried out at 42°C for 11 h. After the reaction was completed, filtration was carried out, and then the solvent was removed from the obtained filtrate by distillation under reduced pressure, to obtain a tert-butyl-terminated toluidine red pigment;

[0081] ② 0.1 kg of the tert-butyl-terminated toluidine red pigment obtained in step ① was added into 0.9 kg of acetone, and then 0.035 kg of diethylenetriamine was added. After being stirred and dissolved, the temperature was raised to 70°C, and reaction was carried out for 20 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure. The obtained residue was added into 0.9 kg of methanol, and then 0.028 kg of sodium hydroxide was added. Reaction was carried out at 40°C for 11 h. Filtration was carried out, and then the solvent was removed by rotary evaporation. The obtained residue was washed with water, and then drying was carried out, to obtain a di-primary amine modified toluidine red pigment;

[0082] ③ 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.048 kg of a dicarboxylic compound were added into 0.9 kg of acetone, and then 0.045 kg of 4-dimethylaminopyridine and 0.048 kg of 1-hydroxybenzotriazole were added. Reaction was carried out at 40°C for 40 h. After the reaction was completed, filtration was carried out. The obtained filter cake was washed with water and dried, and then was added into a mixed solution of dimethyl sulfoxide and methanol, wherein the volume ratio of dimethyl sulfoxide and methanol was 1:1.9. Then, 0.032 kg of sodium hydroxide was added. Reaction was carried out at 42°C for 22 h. After the reaction was completed, filtration was carried out. The solvent was removed from the obtained filtrate by distillation under reduced pressure. Washing with water and drying were carried out, to obtain a polymer;

[0083] ④ Put 0.1 kg of the polymer obtained in step ③ into 1.4 kg of dimethylformamide, after stirring and dissolving, nitrogen gas is introduced into the system at a rate of 9 ml / s, and water is added dropwise. When the solution in the system becomes turbid, stand for 42 h, centrifuge, and obtain the acid and alkali resistant toluidine red pigment.

[0084] Preparation of the dicarboxylic acid compound:

[0085] Put 0.1 kg of methane tricarboxylic acid trimethyl ester into 1 kg of isopropyl alcohol, then add 0.04 kg of sodium hydroxide thereto, and react at 45 °C for 12 h. After the reaction is completed, filter, remove the solvent from the obtained filtrate by distillation under reduced pressure, wash the obtained residue with water, and dry to obtain the dicarboxylic acid compound.

[0086] Preparation of the modified toluidine red pigment:

[0087] 1) Put 6 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol into a diazotization reactor, and beat for 1 h. Then add 1.8 kg of 30% hydrochloric acid, stir to mix uniformly, cool to 5 °C, and then add 2 kg of 30% sodium nitrite aqueous solution dropwise. Diazotize for 3 h until the Congo red test paper turns blue and the potassium iodide starch test paper turns blue, and then stop the reaction to obtain a diazotization solution;

[0088] 2) Put 1.2 kg of 2-naphthol and 15 kg of water into a coupling reactor, then add 0.2 kg of sodium hydroxide, stir to mix uniformly, and obtain a coupling solution. Add the diazotization solution obtained in step 1) dropwise into the coupling solution, adjust the pH of the system to 8.5 with 20% sodium hydroxide solution, stir for 2 h, heat to 80 °C, and continue to react for 1.5 h. Filter, wash with water, and dry to obtain the modified toluidine red pigment.

[0089] Preparation of the acid and alkali resistant toluidine red pigment:

[0090] ① Put 0.1 kg of the modified toluidine red pigment into 1.5 kg of tetrahydrofuran, then add 0.15 kg of tert-butyl chloride and 0.12 kg of N,N-diisopropylethylamine, and react at 45 °C for 12 h. After the reaction is completed, filter, remove the solvent from the obtained filtrate by distillation under reduced pressure, and obtain the tert-butyl-terminated toluidine red pigment;

[0091] ② Put 0.1 kg of the tert-butyl-terminated toluidine red pigment obtained in step ① into 1 kg of dimethylformamide, then add 0.04 kg of diethylenetriamine, stir to dissolve, heat to 70 °C, and react for 24 h. After the reaction is completed, remove the solvent by distillation under reduced pressure, add the obtained residue into 1 kg of methanol, then add 0.03 kg of sodium hydroxide, and react at 45 °C for 12 h. Filter, spin to dry the solvent, wash the obtained residue with water, and dry to obtain the diamine-modified toluidine red pigment.

[0092] ③ Add 0.1 kg of the diamine-modified toluidine red pigment prepared in step ② and 0.05 kg of the dicarboxylic acid compound to 1 kg of acetone, then add 0.05 kg of 4-dimethylaminopyridine and 0.05 kg of 1-hydroxybenzotriazole. React at 45 °C for 48 h. After the reaction is complete, filter the mixture. Wash the filter cake with water, dry it, and add it to a mixed solution of 1 kg of dimethyl sulfoxide and methanol, wherein the volume ratio of dimethyl sulfoxide to methanol is 1:2. Then add 0.035 kg of sodium hydroxide and react at 45 °C for 24 h. After the reaction is complete, filter the mixture. Remove the solvent from the filtrate by vacuum distillation, wash it with water, and dry it to obtain the polymer.

[0093] ④ Add 0.1 kg of the polymer obtained in step ③ to 1.5 kg of dimethylformamide, stir to dissolve, then introduce nitrogen gas into the system at a rate of 10 ml / s and add water dropwise. When the solution in the system becomes turbid, let it stand for 48 h, centrifuge, and obtain acid and alkali resistant toluidine red pigment.

[0094] The acid- and alkali-resistant toluidine red pigments prepared in Examples 1-6 were tested respectively. Tinting strength was tested according to the method in GB1708-79; bulk density was tested according to the method in GB / T 21877-2015. 50g of the acid- and alkali-resistant toluidine red pigment was accurately weighed, placed in a graduated cylinder, sealed, and shaken up and down 10 times, with the sample graduations recorded. Lightfastness was tested according to standard GB1710-79; water resistance, acid resistance, and alkali resistance were tested according to GB 5211.5-2008-T. The comparative example used was our company's product, toluidine red YS (PR3). The test results are shown in Table 1. As can be seen from the results in Table 1, the acid- and alkali-resistant toluidine red pigment prepared in this invention has strong acid and alkali resistance, and also exhibits good tinting strength, lightfastness, water resistance, oil resistance, and dispersibility.

[0095] Table 1. Performance test results of pigments prepared in Examples 1-6 and comparative examples.

[0096]

[0097] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A process for the preparation of an acid and base resistant toluidine red pigment, characterized by: After a di-primary amine is introduced into the modified toluidine red pigment, a di-primary amine modified toluidine red pigment is obtained, the di-primary amine modified toluidine red pigment and a dicarboxylic compound are added into an organic solvent 3, 4-dimethylaminopyridine and 1-hydroxybenzotriazole are added, and the mixture is reacted at 25-45℃ for 24-48h, after the reaction is completed, the mixture is filtered, the obtained filter cake is washed with water and dried, and then a mixed solution of the organic solvent 4 and the organic solvent 1 is added, a base is added, and the mixture is reacted at 25-45℃ for 12-24h, after the reaction is completed, the mixture is filtered, the obtained filtrate is distilled under reduced pressure to remove the solvent, washed with water, and dried to obtain a polymer; the obtained polymer is added into the organic solvent 4, the mixture is stirred and dissolved, nitrogen is introduced into the system at a rate of 5-10ml / s, and water is added dropwise, the solution in the system is turbid, and the mixture is placed for 24-48h, centrifuged, and the acid and alkali resistant toluidine red pigment is obtained; The modified toluidine red pigment is prepared by diazotization of 3-amino-4-nitrobenzyl alcohol and coupling with 2-naphthol; The dicarboxylic compound is prepared by the following method: Methanetricarboxylic acid trimethyl ester is added into an organic solvent 1, sodium hydroxide is added, and the mixture is reacted at 25-45℃ for 8-12h, after the reaction is completed, the mixture is filtered, the obtained filtrate is distilled under reduced pressure to remove the solvent, the obtained residue is washed with water and dried to obtain the dicarboxylic compound.

2. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 1, characterized in that: The organic solvent 1 is methanol, ethanol or isopropanol.

3. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 1, characterized in that: The mass ratio of the methanetricarboxylic acid trimethyl ester, the organic solvent 1 and sodium hydroxide is 1:5-10:0.3-0.

4.

4. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 1, characterized in that: The modified toluidine red pigment is prepared by the following method: 1) water and 3-amino-4-nitrobenzyl alcohol are added into a diazotization reactor, and the mixture is beaten for 1h, hydrochloric acid with a mass concentration of 30% is added, the mixture is stirred and mixed uniformly, and then the temperature is lowered to 0-5℃, sodium nitrite aqueous solution with a mass concentration of 30% is added dropwise, and the mixture is diazotized for 1-3h until the Congo red test paper is blue and the potassium iodide starch test paper is blue, the reaction is stopped, and a diazotization solution is obtained; 2) 2-naphthol and water are added into a coupling reactor, sodium hydroxide is added, the mixture is stirred and mixed uniformly, and a coupling solution is obtained, the diazotization solution obtained in step 1) is added dropwise into the coupling solution, the pH of the system is adjusted to 8-8.5 by using sodium hydroxide solution with a mass concentration of 20-25%, the mixture is stirred for 1-2h, heated to 75-80℃, and then the reaction is continued for 1-1.5h, the mixture is filtered, washed with water, and dried to obtain the modified toluidine red pigment.

5. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 4, characterized in that: In step 1), the mass ratio of the water, 3-amino-4-nitrobenzyl alcohol, hydrochloric acid and sodium nitrite aqueous solution is 5-6:1:1.5-1.8:1.4-2; in step 2), the mass ratio of the 2-naphthol, water, sodium hydroxide and the 3-amino-4-nitrobenzyl alcohol in step 1) is 0.9-1.2:10-15:0.1-0.2:

1.

6. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 1, characterized in that: The preparation method of the acid and alkali resistant toluidine red pigment comprises the following steps: The modified toluidine red pigment is added into organic solvent 2, and then tertiary butyl chloride and amine are added, and the reaction is carried out at 30-45℃ for 6-12h, after the reaction is completed, the obtained filtrate is filtered, and the solvent is removed by distillation under reduced pressure to obtain the end-tertiary butyl toluidine red pigment. The end-tertiary butyl toluidine red pigment prepared in step 1 is added into organic solvent 2, and then diethylene triamine is added, and after stirring and dissolving, the system is heated to 50-110℃ and the reaction is carried out for 12-24h, after the reaction is completed, the solvent is removed by distillation under reduced pressure, and the obtained residue is added into organic solvent 1, and then base is added, and the reaction is carried out at 25-45℃ for 8-12h, the obtained filtrate is filtered, and the solvent is removed by rotary evaporation, and then the obtained residue is washed with water and dried to obtain the di-primary amine modified toluidine red pigment. The di-primary amine modified toluidine red pigment prepared in step 2 and dicarboxylic compound are added into organic solvent 3, and then 4-dimethylamino pyridine and 1-hydroxy benzotriazole are added, and the reaction is carried out at 25-45℃ for 24-48h, after the reaction is completed, the obtained filter cake is washed with water and dried, and then the obtained filter cake is added into the mixed solution of organic solvent 4 and organic solvent 1, and then base is added, and the reaction is carried out at 25-45℃ for 12-24h, after the reaction is completed, the obtained filtrate is filtered, and the solvent is removed by distillation under reduced pressure, and then the obtained filtrate is washed with water and dried to obtain the polymer. The polymer obtained in step 3 is added into organic solvent 4, and after stirring and dissolving, nitrogen is introduced into the system at a speed of 5-10ml / s, and water is added dropwise, and after the solution in the system becomes turbid, the system is placed for 24-48h, and then centrifugation is carried out to obtain the acid and alkali resistant toluidine red pigment.

7. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 6, characterized in that: The organic solvent 2 in step 1 is tetrahydrofuran, acetonitrile, dimethylformamide or acetone; the amine is triethylamine or N,N-diisopropyl ethylamine; and the mass ratio of the modified toluidine red pigment, organic solvent 2, tertiary butyl chloride and amine in step 1 is 1:8-15:0.9-1.5:0.8-1.

2.

8. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 6, characterized in that: The base in step 2 is sodium hydroxide or potassium hydroxide; and the mass ratio of the end-tertiary butyl toluidine red pigment, organic solvent 2, diethylene triamine, organic solvent 1 and base in step 2 is 1:5-10:0.2-0.4:5-10:0.15-0.

3.

9. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 6, characterized in that: The organic solvent 3 in step 3 is acetone, acetonitrile or tetrahydrofuran; the organic solvent 4 in step 3 is dimethylformamide or dimethyl sulfoxide; the volume ratio of organic solvent 4 and organic solvent 1 in the mixed solution of organic solvent 4 and organic solvent 1 in step 3 is 1:1.5-2; and the mass ratio of the di-primary amine modified toluidine red pigment, dicarboxylic compound, organic solvent 3, 4-dimethylamino pyridine, 1-hydroxy benzotriazole, mixed solution and base in step 3 is 1:0.4-0.5:5-10:0.3-0.5:0.35-5:5-10:0.2-0.

35.

10. The method for preparing acid and alkali resistant toluidine red pigment as described in claim 6, characterized in that: The mass ratio of the polymer and organic solvent 4 in step 4 is 1:10-15.

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