Preparation method of acid and alkali resistant toluidine red pigment

Abstract

The invention discloses a preparation method of an acid and alkali resistant toluidine red pigment, and belongs to the technical field of pigment synthesis, diprimary amine is introduced to a modified toluidine red pigment, then the modified toluidine red pigment reacts with a dicarboxylic acid compound, and finally the acid and alkali resistant toluidine red pigment is prepared through hydrolysis and self-assembly. The modified toluidine red pigment is prepared by diazotizing 3-amino-4-nitrobenzyl alcohol and then coupling the diazotized 3-amino-4-nitrobenzyl alcohol with 2-naphthol; the acid and alkali resistant toluidine red pigment prepared by the invention not only has bright color, good covering power, higher coloring strength, light resistance, water resistance, oil resistance and dispersity, but also has higher acid and alkali resistance and environmental stability, and the application performance of the pigment is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pigment synthesis, and specifically relates to a preparation method of acid and 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 and 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 and 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 and alkali environments. In addition, toluidine red often has a problem of heavy metal ion elution after long-term exposure to extreme pH environments, which not only affects the product performance but also does not meet the 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. A preparation method of acid and 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; 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: Methane tricarboxylic 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.

[0005] The organic solvent 1 is methanol, ethanol or isopropanol.

[0006] The mass ratio of the methane tricarboxylic acid trimethyl ester, the organic solvent 1 and the sodium hydroxide is 1:5-10:0.3-0.4.

[0007] 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 are beaten for 1 h, then 30% hydrochloric acid is added, and after stirring and mixing, the temperature is lowered to 0-5 DEG C, then 30% sodium nitrite aqueous solution is added dropwise, and diazotization is carried out for 1-3 h until the Congo red test paper is blue and the potassium iodide starch test paper is blue, then the reaction is stopped, and a diazo liquid is obtained; 2) 2-naphthol and water are added into a coupling reactor, then sodium hydroxide is added, and after stirring and mixing, a coupling liquid is obtained, the diazo liquid prepared in step 1) is added dropwise into the coupling liquid, 20-25% sodium hydroxide solution is used to adjust the pH of the system to 8-8.5, stirring is carried out for 1-2 h, heating is carried out to 75-80 DEG C, and then the reaction is continued for 1-1.5 h, filtration is carried out, washing is carried out with water, and drying is carried out, and then a modified toluidine red pigment is obtained.

[0008] In step 1), the mass ratio of water, 3-amino-4-nitrobenzyl alcohol, hydrochloric acid and sodium nitrite aqueous solution is 5-6:1:1.5-1.8:1.4-2.

[0009] In step 2), the mass ratio of 2-naphthol, water, sodium hydroxide and 3-amino-4-nitrobenzyl alcohol in step 1) is 0.9-1.2:10-15:0.1-0.2:1.

[0010] The preparation method of the acid and alkali resistant toluidine red pigment comprises the following steps: ① the modified toluidine red pigment is added into organic solvent 2, then tert-butyl acyl chloride and amine are added, and the reaction is carried out at 30-45 DEG C for 6-12 h, then after the reaction is completed, filtration is carried out, the obtained filtrate is distilled under reduced pressure to remove the solvent, and then a terminal tert-butyl toluidine red pigment is obtained; ② the terminal tert-butyl toluidine red pigment prepared in step ① is added into organic solvent 2, then diethylene triamine is added, and after stirring and dissolving, the temperature is raised to 50-110 DEG C, and the reaction is carried out for 12-24 h, then after the reaction is completed, the solvent is removed by distillation under reduced pressure, the obtained residue is added into organic solvent 1, then a base is added, and the reaction is carried out at 25-45 DEG C for 8-12 h, then filtration is carried out, the obtained filtrate is spin-dried, the obtained residue is washed with water, and drying is carried out, and then a di-primary amine modified toluidine red pigment is obtained; ③ the di-primary amine modified toluidine red pigment prepared in step ② and a dicarboxylic compound are added into organic solvent 3, then 4-dimethylamino pyridine and 1-hydroxybenzotriazole are added, and the reaction is carried out at 25-45 DEG C for 24-48 h, then after the reaction is completed, filtration is carried out, the obtained filter cake is washed with water and dried, then a mixed solution of organic solvent 4 and organic solvent 1 is added, a base is added, and the reaction is carried out at 25-45 DEG C for 12-24 h, then after the reaction is completed, filtration is carried out, the obtained filtrate is distilled under reduced pressure to remove the solvent, washing is carried out with water, and drying is carried out, and then a polymer is obtained. IV. The polymer obtained in step III is added into organic solvent 4, after stirring and dissolving, nitrogen is bubbled into the system at a rate of 5-10 ml / s, and water is added dropwise, until the solution in the system becomes turbid, and is left to stand for 24-48 h, and is centrifuged, to obtain the acid and alkali resistant toluidine red pigment.

[0011] The organic solvent 2 in step I is tetrahydrofuran, acetonitrile, dimethylformamide or acetone; and the amine is triethylamine or N,N-diisopropylethylamine.

[0012] The mass ratio of the modified toluidine red pigment, organic solvent 2, tert-butyl chloride and amine in step I is 1:8-15:0.9-1.5:0.8-1.2.

[0013] The base in step II is sodium hydroxide or potassium hydroxide.

[0014] The mass ratio of the end-tert-butyl toluidine red pigment, organic solvent 2, diethylenetriamine, organic solvent 1 and base in step II is 1:5-10:0.2-0.4:5-10:0.15-0.3.

[0015] The organic solvent 3 in step III is acetone, acetonitrile or tetrahydrofuran.

[0016] The organic solvent 4 in step III is dimethylformamide or dimethyl sulfoxide.

[0017] The volume ratio of organic solvent 4 to organic solvent 1 in the mixed solution of organic solvent 4 and organic solvent 1 in step III is 1:1.5-2.

[0018] The mass ratio of the di-primary amine modified toluidine red pigment, dicarboxylic compound, organic solvent 3, 4-dimethylaminopyridine, 1-hydroxybenzotriazole, mixed solution and base in step III is 1:0.4-0.5:5-10:0.3-0.5:0.35-5:5-10:0.2-0.35.

[0019] The mass ratio of the polymer to organic solvent 4 in step IV is 1:10-15.

[0020] Compared with the prior art, the present application has the following advantages: The acid and alkali resistant toluidine red pigment of the present application firstly introduces a di-primary amine fragment in the toluidine red molecular skeleton, 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 the hydrogen bond effect, forming a dense protective film on the surface of the pigment, effectively preventing the penetration of corrosive substances into the internal pigment, preventing the agglomeration between the pigments, and 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 strongly alkaline, 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.

[0021] 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, which significantly improves the application performance of the pigment. DETAILED DESCRIPTION

[0022] In order to better understand the technical solutions of the present application, the above content of the present application will be further explained in detail through the specific embodiments of the 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.

[0023] Example 1 Preparation of dicarboxylic acid compound: 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).

[0024] Preparation of modified toluidine red pigment: 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; 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.

[0025] Preparation of acid and alkali resistant toluidine red pigment: 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).

[0026] 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 for 12 h, 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).

[0027] ③ Add 0.1 kg of the diprimary amine-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, and react at 25°C for 24 hours. After the reaction is completed, filter the mixture, wash the filter cake with water, dry it, and 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 hours. After the reaction is completed, filter the mixture, and remove the solvent by distillation under reduced pressure from the filtrate. The filtrate is washed with water and dried to obtain a polymer. ④ Add 0.1 kg of the polymer obtained in step ③ to 1 kg of dimethylformamide, stir and dissolve, introduce nitrogen 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 hours, and centrifuge to obtain acid and alkali resistant toluidine red pigment.

[0028] Example 2 Preparation of dicarboxylic acid compound: 0.1 kg of trimethyl methanetricarboxylate was added to 0.6 kg of ethanol, and then 0.032 kg of sodium hydroxide was added thereto. The mixture was reacted at 30° C. for 10 hours. After the reaction was completed, the mixture was filtered. The solvent was removed by distillation under reduced pressure from the filtrate. The residue was washed with water and dried to obtain a dicarboxylic acid compound.

[0029] Preparation of modified toluidine red pigment: 1) Add 5.2 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol to a diazotization reactor and beat for 1 hour. Then add 1.6 kg of 30% hydrochloric acid and stir to mix evenly. Cool to 1°C and then dropwise add 1.5 kg of 30% sodium nitrite aqueous solution. Diazotize for 1.5 hours until Congo red test paper turns blue and potassium iodide starch test paper turns blue. Stop the reaction to obtain a diazo solution. 2) 1 kg of 2-naphthol and 11 kg of water were added to a coupling reactor, and 0.12 kg of sodium hydroxide was added thereto. After stirring and mixing, a coupling solution was obtained. The diazo solution prepared in step 1) was added dropwise to the coupling solution. The pH of the system was adjusted to 8.1 with 20% sodium hydroxide solution. The reaction was stirred for 1.2 hours, heated to 76°C, and the reaction was continued for 1.1 hours. The mixture was filtered, washed with water, and dried to obtain a modified toluidine red pigment.

[0030] Preparation of acid and alkali resistant toluidine red pigment: ① 0.1 kg of modified toluidine red pigment was added to 0.9 kg of acetonitrile, and then 0.1 kg of tert-butyl chloride and 0.09 kg of triethylamine were added. The reaction was carried out at 35°C for 8h. After the reaction was completed, the filtrate was obtained by filtration, and the solvent was removed by distillation under reduced pressure to obtain a tert-butyl-terminated toluidine red pigment; ② 0.1 kg of the tert-butyl-terminated toluidine red pigment prepared in step ① was added to 0.6 kg of acetonitrile, and then 0.025 kg of diethylenetriamine was added. After stirring and dissolving, it was heated to 70°C and reacted for 14h. After the reaction was completed, the solvent was removed by distillation under reduced pressure. The residue was added to 0.6 kg of ethanol, and then 0.018 kg of sodium hydroxide was added. The reaction was carried out at 30°C for 10h. The filtrate was obtained by filtration, and the solvent was removed by rotary evaporation. The residue was washed with water and dried to obtain a di-primary amine modified toluidine red pigment; ③ 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.042 kg of a dicarboxylic acid compound were added to 0.6 kg of acetonitrile, and then 0.035 kg of 4-dimethylaminopyridine and 0.038 kg of 1-hydroxybenzotriazole were added. The reaction was carried out at 30°C for 30h. After the reaction was completed, the filter cake was obtained by filtration, and then washed with water and dried. The filter cake was added to a mixed solution of dimethyl sulfoxide and ethanol, and the volume ratio of dimethyl sulfoxide to ethanol was 1:1.6. Then 0.025 kg of potassium hydroxide was added, and the reaction was carried out at 30°C for 15h. After the reaction was completed, the filtrate was obtained by filtration, and the solvent was removed by distillation under reduced pressure. The residue was washed with water and dried to obtain a polymer; ④ 0.1 kg of the polymer obtained in step ③ was added to 1.1 kg of dimethyl sulfoxide, and then stirred and dissolved. Nitrogen was introduced into the system at a rate of 6 ml / s, and water was added dropwise. When the solution in the system became turbid, it was left to stand for 30h, and then centrifuged to obtain an acid and alkali resistant toluidine red pigment.

[0031] Preparation of a dicarboxylic acid compound: 0.1 kg of methyl methane tricarboxylate was added to 0.7 kg of isopropyl alcohol, and then 0.035 kg of sodium hydroxide was added. The reaction was carried out at 35°C for 11h. After the reaction was completed, the filtrate was obtained by filtration, and the solvent was removed by distillation under reduced pressure. The residue was washed with water and dried to obtain a dicarboxylic acid compound.

[0032] Preparation of a modified toluidine red pigment: 1) 5.5 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added to a diazotization reactor, and then stirred for 1h. 1.6 kg of 30% hydrochloric acid was added, and then stirred until uniform. The temperature was lowered to 2°C, and then 1.7 kg of 30% sodium nitrite aqueous solution was added dropwise. The diazotization reaction was carried out for 2h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped, and a diazonium solution was obtained. 2) 1 kg of 2-naphthol and 12 kg of water were added into a coupling reactor, and then 0.14 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, a 20% sodium hydroxide solution was used to adjust the pH of the system to 8.3, and stirring was performed for 1.4 h; then the reaction was continued at 77°C for 1.2 h; after filtration, washing with water, and drying, a modified toluidine red pigment was obtained.

[0033] Preparation of an acid and alkali resistant toluidine red pigment: ① 0.1 kg of the modified toluidine red pigment was added into 1 kg of dimethylformamide, and then 0.1 kg of tert-butyl chloride and 0.1 kg of triethylamine were added into the dimethylformamide, and the reaction was performed at 38°C for 9 h; after the reaction was completed, filtration was performed, and the obtained filtrate was subjected to distillation under reduced pressure to remove the solvent, so that a tert-butyl-terminated toluidine red pigment was obtained; ② 0.1 kg of the tert-butyl-terminated toluidine red pigment prepared in step ① was added into 0.7 kg of dimethylformamide, and then 0.028 kg of diethylenetriamine was added into the dimethylformamide; after stirring and dissolving, the reaction was performed at 110°C for 18 h; after the reaction was completed, the solvent was removed by distillation under reduced pressure; the obtained residue was added into 0.7 kg of isopropyl alcohol, and then 0.02 kg of sodium hydroxide was added into the isopropyl alcohol; the reaction was performed at 34°C for 10 h; after filtration, the solvent of the obtained filtrate was removed by rotary evaporation; the obtained residue was washed with water, and then dried, so that a di-primary amine modified toluidine red pigment was obtained; ③ 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.045 kg of a dicarboxylic compound were added into 0.7 kg of tetrahydrofuran, and then 0.038 kg of 4-dimethylaminopyridine and 0.04 kg of 1-hydroxybenzotriazole were added into the tetrahydrofuran; the reaction was performed at 32°C for 32 h; after the reaction was completed, filtration was performed; the obtained filter cake was washed with water, and then dried; the obtained filter cake was added into a mixed solution of dimethyl sulfoxide and isopropyl alcohol, and the volume ratio of the dimethyl sulfoxide and the isopropyl alcohol was 1:1.7; then 0.028 kg of sodium hydroxide was added into the mixed solution; the reaction was performed at 35°C for 18 h; after the reaction was completed, filtration was performed; the solvent of the obtained filtrate was removed by distillation under reduced pressure; the obtained residue was washed with water, and then dried, so that a polymer was obtained; ④ 0.1 kg of the polymer obtained in step ③ was added into 1.2 kg of dimethyl sulfoxide; after stirring and dissolving, nitrogen was introduced into the system at a rate of 7 ml / s, and water was added dropwise; after the solution in the system became turbid, the system was allowed to stand for 32 h; centrifugation was performed, so that an acid and alkali resistant toluidine red pigment was obtained.

[0034] Preparation of a dicarboxylic compound: 0.1 kg of trimethyl methane tricarboxylate was added into 0.8 kg of methanol, and then 0.037 kg of sodium hydroxide was added into the methanol; the reaction was performed at 40°C for 11 h; after the reaction was completed, filtration was performed; the solvent of the obtained filtrate was removed by distillation under reduced pressure; the obtained residue was washed with water, and then dried, so that a dicarboxylic compound was obtained.

[0035] Preparation of modified toluidine red pigment: 1) Put 5.7 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol into a diazotization reactor, beat for 1 h, then add 1.7 kg of 30% hydrochloric acid, stir to mix, then cool to 3°C, add 1.8 kg of 30% sodium nitrite aqueous solution dropwise, and diazotize for 2.2 h until the Congo red test paper turns blue and the potassium iodide starch test paper turns blue, then stop the reaction to obtain a diazotized solution; 2) Put 1.1 kg of 2-naphthol and 13 kg of water into a coupling reactor, then add 0.16 kg of sodium hydroxide, stir to mix, and obtain a coupling solution; add the diazotized solution prepared in step 1) dropwise into the coupling solution, adjust the pH of the system to 8.4 with 20% sodium hydroxide solution, stir for 1.6 h, heat to 78°C and continue to react for 1.3 h, filter, wash with water, and dry to obtain a modified toluidine red pigment.

[0036] Preparation of acid and alkali resistant toluidine red pigment: ① Put 0.1 kg of modified toluidine red pigment into 1.2 kg of dimethylformamide, then add 0.12 kg of tert-butyl chloride and 0.11 kg of N,N-diisopropylethylamine, and react at 40°C for 10 h; after the reaction is completed, filter, remove the solvent from the obtained filtrate by reduced pressure distillation, and obtain a tert-butyl-terminated toluidine red pigment; ② Put 0.1 kg of the tert-butyl-terminated toluidine red pigment prepared in step ① into 0.8 kg of acetone, then add 0.03 kg of diethylenetriamine, stir to dissolve, heat to 50°C and react for 12 h; after the reaction is completed, remove the solvent by reduced pressure distillation, put the obtained residue into 0.8 kg of methanol, then add 0.024 kg of potassium hydroxide, react at 38°C for 11 h, filter, spin dry the solvent of the obtained filtrate, wash the obtained residue with water, and dry to obtain a di-primary amine modified toluidine red pigment; ③ Put 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.046 kg of a dicarboxylic acid compound into 0.8 kg of acetonitrile, then add 0.04 kg of 4-dimethylaminopyridine and 0.044 kg of 1-hydroxybenzotriazole, and react at 35°C for 36 h; after the reaction is completed, filter, wash the obtained filter cake with water and dry, then put it into a mixed solution of 0.8 kg of dimethyl sulfoxide and methanol with a volume ratio of 1:1.8; add 0.03 kg of potassium hydroxide, react at 40°C for 20 h, after the reaction is completed, filter, remove the solvent from the obtained filtrate by reduced pressure distillation, wash with water, and dry to obtain a polymer. ④ Put 0.1 kg of the polymer obtained in step ③ into 1.3 kg of dimethyl sulfoxide, after stirring and dissolving, nitrogen gas is introduced into the system at a rate of 8 ml / s, and water is added dropwise. When the solution in the system becomes turbid, stand for 38 h, centrifuge, and obtain the acid and alkali resistant toluidine red pigment.

[0037] Preparation of the dicarboxylic acid compound: Put 0.1 kg of trimethyl methane tricarboxylate into 0.9 kg of ethanol, and then add 0.039 kg of sodium hydroxide thereto. React at 42℃ for 9 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.

[0038] Preparation of the modified toluidine red pigment: 1) Put 5.8 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 hydrochloric acid with a mass concentration of 30%, and stir to mix uniformly. Then cool to 4℃, and then add 1.9 kg of sodium nitrite aqueous solution with a mass concentration of 30% dropwise. Diazotize for 2.5 h until the Congo red test paper turns blue and the potassium iodide starch test paper turns blue. Stop the reaction to obtain a diazotization solution; 2) Put 1.2 kg of 2-naphthol and 14 kg of water into a coupling reactor, and then add 0.18 kg of sodium hydroxide thereto. Stir to mix uniformly to 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 a sodium hydroxide solution with a mass concentration of 20%, stir to react for 1.8 h, heat to 79℃, and continue to react for 1.5 h. Filter, wash with water, and dry to obtain the modified toluidine red pigment.

[0039] Preparation of the acid and alkali resistant toluidine red pigment: ① Put 0.1 kg of the modified toluidine red pigment into 1.4 kg of tetrahydrofuran, and then add 0.14 kg of tert-butyl chloride and 0.11 kg of N,N-diisopropylethylamine thereto. React at 42℃ for 11 h. After the reaction is completed, filter, remove the solvent from the obtained filtrate by distillation under reduced pressure, and obtain the end-tert-butyl toluidine red pigment; ② Put 0.1 kg of the end-tert-butyl toluidine red pigment obtained in step ① into 0.9 kg of acetone, and then add 0.035 kg of diethylenetriamine. Stir to dissolve, heat to 70℃, and react for 20 h. After the reaction is completed, remove the solvent by distillation under reduced pressure. Put the obtained residue into 0.9 kg of methanol, and then add 0.028 kg of sodium hydroxide. React at 40℃ for 11 h. Filter, spin to dry the solvent, wash the obtained residue with water, and dry to obtain the diamine modified toluidine red pigment; ③Into 0.9 kg of acetone, 0.1 kg of the diamine-modified toluidine red pigment prepared in step ② and 0.048 kg of a dicarboxylic compound were added, and then 0.045 kg of 4-dimethylaminopyridine and 0.048 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 40°C for 40 h. After the reaction was completed, the mixture was suction-filtered, and the obtained filter cake was washed with water and dried, and then was added into a mixed solution of 0.9 kg of dimethyl sulfoxide and methanol (volume ratio of dimethyl sulfoxide to methanol: 1:1.9). Then, 0.032 kg of sodium hydroxide was added, and the mixture was reacted at 42°C for 22 h. After the reaction was completed, the mixture was suction-filtered, and the obtained filtrate was distilled under reduced pressure to remove the solvent, and then was washed with water and dried to obtain a polymer; ④Into 1.4 kg of dimethylformamide, 0.1 kg of the polymer obtained in step ③ was added and dissolved by stirring. Then, nitrogen gas was introduced into the system at a rate of 9 ml / s, and water was added dropwise. After the solution in the system became turbid, the mixture was left to stand for 42 h, and then was centrifuged to obtain an acid- and alkali-resistant toluidine red pigment.

[0040] Preparation of a dicarboxylic compound Into 1 kg of isopropyl alcohol, 0.1 kg of trimethyl methane tricarboxylate was added, and then 0.04 kg of sodium hydroxide was added. The mixture was reacted at 45°C for 12 h. After the reaction was completed, the mixture was filtered, and 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 compound.

[0041] Preparation of a modified toluidine red pigment 1) Into a diazotization reactor, 6 kg of water and 1 kg of 3-amino-4-nitrobenzyl alcohol were added and stirred for 1 h. Then, 1.8 kg of 30% hydrochloric acid was added, and the mixture was stirred and mixed uniformly. Then, the temperature of the mixture was lowered to 5°C. Then, 2 kg of 30% sodium nitrite aqueous solution was added dropwise into the mixture, and the mixture was diazotized for 3 h until the Congo red test paper became blue and the potassium iodide starch test paper became blue. Then, the reaction was stopped to obtain a diazotization solution. 2) Into a coupling reactor, 1.2 kg of 2-naphthol and 15 kg of water were added, and then 0.2 kg of sodium hydroxide was added. The mixture was stirred and mixed uniformly to obtain a coupling solution. Then, the diazotization solution prepared in step 1) was added dropwise into the coupling solution. Then, the pH of the system was adjusted to 8.5 using a 20% sodium hydroxide solution. The mixture was stirred and reacted for 2 h, and then was heated to 80°C and reacted for 1.5 h. The mixture was filtered, washed with water, and dried to obtain a modified toluidine red pigment.

[0042] Preparation of an acid- and alkali-resistant toluidine red pigment ①Into 1.5 kg of tetrahydrofuran, 0.1 kg of the modified toluidine red pigment was added, and then 0.15 kg of tert-butyl chloride and 0.12 kg of N,N-diisopropylethylamine were added. The mixture was reacted at 45°C for 12 h. After the reaction was completed, the mixture was suction-filtered, and the obtained filtrate was distilled under reduced pressure to remove the solvent to obtain a tert-butyl-terminated toluidine red pigment. ② 0.1 kg of the tert-butyl-substituted toluidine red pigment prepared in step ① was added into 1 kg of dimethylformamide, and then 0.04 kg of diethylenetriamine was added. After stirring and dissolving, the mixture was heated to 70°C and reacted for 24 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure. The obtained residue was added into 1 kg of methanol, and then 0.03 kg of sodium hydroxide was added. The mixture was reacted at 45°C for 12 h. After filtration, the obtained filtrate was concentrated to dryness. The obtained residue was washed with water and dried to obtain a di-primary amine modified toluidine red pigment; ③ 0.1 kg of the di-primary amine modified toluidine red pigment prepared in step ② and 0.05 kg of a dicarboxylic compound were added into 1 kg of acetone, and then 0.05 kg of 4-dimethylaminopyridine and 0.05 kg of 1-hydroxybenzotriazole were added. The mixture was reacted at 45°C for 48 h. After the reaction was completed, the obtained filter cake was washed with water and dried. The obtained filter cake was added into a mixed solution of 1 kg of dimethyl sulfoxide and methanol (volume ratio of dimethyl sulfoxide to methanol was 1:2). Then, 0.035 kg of sodium hydroxide was added. The mixture was reacted at 45°C for 24 h. After the reaction was completed, the obtained filtrate was concentrated to dryness under reduced pressure, washed with water and dried to obtain a polymer. ④ 0.1 kg of the polymer prepared in step ③ was added into 1.5 kg of dimethylformamide. After stirring and dissolving, nitrogen was introduced into the system at a rate of 10 ml / s, and water was added dropwise. After the solution in the system became turbid, the mixture was allowed to stand for 48 h, and then centrifuged to obtain an acid and alkali resistant toluidine red pigment.

[0043] The acid and alkali resistant toluidine red pigments prepared in Examples 1-6 were detected respectively. The tinting strength was detected according to the method in GB 1708-79; the bulk density was detected according to the method in GB / T 21877-2015, 50 g of the acid and alkali resistant toluidine red pigment was accurately weighed, put into a graduated cylinder, sealed, shaken up and down for 10 times, and then the sample scale in the graduated cylinder was recorded; the light resistance was detected according to the standard GB 1710-79; the water resistance, acid resistance and alkali resistance were detected according to GB 5211.5-2008-T; the comparative example used a toluidine red YS (P.R.3) product of the company, and the detection results are shown in Table 1. As shown in Table 1, the acid and alkali resistant toluidine red pigment prepared in the present application has strong acid and alkali resistance, and also has good tinting strength, light resistance, water resistance, oil resistance and dispersibility.

[0044] Table 1 Performance test results of the pigments prepared in Examples 1-6 and the comparative example

[0045] Although the specific embodiments of the present application are described above, the description is not a limitation on the protection scope of the present application. Various modifications or variations made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A method for preparing an acid- and alkali-resistant toluidine red pigment, characterized in that: The modified toluidine red pigment is prepared by introducing a diprimary amine, reacting with a dicarboxylic acid compound, and finally undergoing hydrolysis and self-assembly. The modified toluidine red pigment is prepared by diazotizing 3-amino-4-nitrobenzyl alcohol and coupling it with 2-naphthol; The dicarboxylic acid compound is prepared according to the following method: Trimethyl methanetricarboxylate is added to organic solvent 1, and then sodium hydroxide is added thereto. The mixture is reacted at 25-45° C. for 8-12 hours. After the reaction is completed, the mixture is filtered, and the solvent is removed by distillation under reduced pressure from the obtained filtrate. The obtained residue is washed with water and dried to obtain a dicarboxylic acid compound.

2. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 1, wherein: The organic solvent 1 is methanol, ethanol or isopropanol.

3. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 1, wherein: The mass ratio of the trimethyl methanetricarboxylate, the organic solvent 1 and the sodium hydroxide is 1:5-10:0.3-0.

4.

4. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 1, wherein: The modified toluidine red pigment is prepared according to the following method: 1) Add water and 3-amino-4-nitrobenzyl alcohol to a diazotization reactor and beat for 1 hour. Then add 30% hydrochloric acid and stir to mix evenly. Cool to 0-5°C and add 30% sodium nitrite aqueous solution dropwise. Diazotization reaction for 1-3 hours until Congo red test paper turns blue and potassium iodide starch test paper turns blue. Stop the reaction to obtain a diazo solution. 2) 2-naphthol and water are added to a coupling reactor, and sodium hydroxide is added thereto. After stirring and mixing, a coupling solution is obtained. The diazo solution prepared in step 1) is added dropwise to the coupling solution. The pH of the system is adjusted to 8-8.5 with a sodium hydroxide solution having a mass concentration of 20-25%. The mixture is stirred for 1-2 hours, heated to 75-80°C, and the reaction is continued for 1-1.5 hours. The mixture is filtered, washed with water, and dried to obtain a modified toluidine red pigment.

5. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 4, wherein: The mass ratio of 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; the mass ratio of 2-naphthol, water and sodium hydroxide in step 2) to 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 the acid and alkali resistant toluidine red pigment according to claim 1, wherein: The preparation method of the acid- and alkali-resistant toluidine red pigment comprises the following steps: ① Add the modified toluidine red pigment to organic solvent 2, then add tert-butylyl chloride and amine thereto, and react at 30-45°C for 6-12 hours. After the reaction is completed, filter and remove the solvent by vacuum distillation of the filtrate to obtain terminal tert-butyltoluidine red pigment; ② Add the tert-butylated toluidine red pigment prepared in step ① to organic solvent 2, then add diethylenetriamine, stir and dissolve, heat to 50-110° C. and react for 12-24 hours. After the reaction, remove the solvent by distillation under reduced pressure, add the resulting residue to organic solvent 1, then add a base, react at 25-45° C. for 8-12 hours, filter with suction, spin-dry the solvent from the resulting filtrate, wash the resulting residue with water, and dry it to obtain a diprimary amine-modified toluidine red pigment; ③ The diprimary amine-modified toluidine red pigment and the dicarboxylic acid compound prepared in step ② are added to organic solvent 3, and then 4-dimethylaminopyridine and 1-hydroxybenzotriazole are added, and the mixture is reacted at 25-45° C. for 24-48 hours. After the reaction is completed, the mixture is filtered, and the resulting filter cake is washed with water and dried. The mixture is then added to a mixed solution of organic solvent 4 and organic solvent 1, and then a base is added. The mixture is reacted at 25-45° C. for 12-24 hours. After the reaction is completed, the mixture is filtered, and the solvent is removed by distillation under reduced pressure from the resulting filtrate, which is then washed with water and dried to obtain a polymer; ④ Add the polymer obtained in step ③ to the organic solvent 4, stir and dissolve, introduce nitrogen into the system at a rate of 5-10 ml / s, and add water dropwise. When the solution in the system becomes turbid, let it stand for 24-48 hours, and centrifuge to obtain acid- and alkali-resistant toluidine red pigment.

7. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 6, wherein: The organic solvent 2 in step ① is tetrahydrofuran, acetonitrile, dimethylformamide or acetone; the amine is triethylamine or N,N-diisopropylethylamine; and the mass ratio of the modified toluidine red pigment, the organic solvent 2, tert-butyryl chloride and the amine in step ① is 1:8-15:0.9-1.5:0.8-1.

2.

8. The method for preparing the acid and alkali resistant toluidine red pigment according to claim 6, wherein: The base in step ② is sodium hydroxide or potassium hydroxide; the mass ratio of the terminal tert-butyltoluidine red color, organic solvent 2, diethylenetriamine, 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 the acid and alkali resistant toluidine red pigment according to claim 6, wherein: 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 to organic solvent 1 in the mixed solution of organic solvent 4 and organic solvent 1 in step ③ is 1:1.5~2; the mass ratio of the diprimary amine-modified toluidine red pigment, dicarboxylic acid compound, organic solvent 3, 4-dimethylaminopyridine, 1-hydroxybenzotriazole, 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 the acid and alkali resistant toluidine red pigment according to claim 6, wherein: The mass ratio of the polymer to the organic solvent 4 in step ④ is 1:10-15.

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