Preparation method of permanent red pigment for acid and alkali resistant coating

Abstract

The invention discloses a preparation method of a permanent red pigment for acid and alkali resistant coatings, belonging to the technical field of pigment preparation. After diazotization of 2B acid derivatives, they are coupled with 2-hydroxy-3-naphthoic acid, and then an aqueous calcium chloride solution is added for lake formation to obtain pigment particles. Finally, silica is coated on the surface of the pigment particles, and the silica coating layer is subjected to hydrophobic treatment with a fluorosilane coupling agent to prepare the permanent red pigment for acid and alkali resistant coatings. The permanent red pigment for acid and alkali resistant coatings prepared by the invention further enhances the acid and alkali resistance and environmental stability of the pigment while maintaining the excellent properties of the original pigment Red 48:2, and significantly improves the application performance of the pigment.

Description

Technical Field

[0001] The present invention belongs to the technical field of pigment preparation, and specifically relates to a preparation method of a permanent red pigment for acid and alkali resistant coatings. Background Art

[0002] There are many types of permanent reds, such as AF, F2R, FBB, and FGR. Among them, permanent red F5R, also known as pigment red 48:2, is a transparent monoazo calcium salt lake β-naphthol pigment with good color strength and gloss, and good light and heat resistance. It is widely used in the fields of coatings, plastics, and inks.

[0003] No acid and alkali resistant groups are introduced into the chemical structure of pigment red 48:2. Therefore, it is prone to hydrolysis in an acidic or alkaline environment, leading to pigment degradation. In addition, the particle size and surface characteristics of the pigment also affect the stability of the pigment in an acidic or alkaline environment, thus affecting the application of the pigment. Therefore, it is of great significance to modify pigment red 48:2 to improve its acid and alkali resistance and then improve the overall performance of the product. Summary of the Invention

[0004] To solve the above problems, the purpose of the present invention is to provide a preparation method of a permanent red pigment for acid and alkali resistant coatings.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] A preparation method of a permanent red pigment for acid and alkali resistant coatings, after diazotizing the 2B acid derivative, coupling it with 2-hydroxy-3-naphthoic acid, then adding an aqueous calcium chloride solution for lake formation to obtain pigment particles, and finally coating the surface of the pigment particles with silica and performing a hydrophobic treatment on the silica coating layer using a fluorosilane coupling agent to prepare.

[0007] The 2B acid derivative is prepared according to the following steps:

[0008] 1) Add 2-amino-4,6-dichloro-5-methylphenol, concentrated sulfuric acid with a mass concentration of 98%, and trichlorobenzene into a reactor. After stirring and dispersing evenly, evacuate to 0.03 - 0.08 Mpa, heat to 190 - 205 °C and react for 3 - 12 h. After the reaction is completed, filter, and wash the obtained filter cake with methanol 2 - 3 times and dry to obtain a sulfonated product.

[0009] 2) Under nitrogen protection, add the sulfonated product obtained in step 1) into anhydrous pyridine, cool down to 0 - 5 °C, and dropwise add phosphorus oxychloride thereto, controlling the temperature of the system below 10 °C during the dropping process. After the dropping is completed, heat to 60 - 80 °C and react for 5 - 10 h. After the reaction is completed, cool down to 25 - 30 °C, add ice water to quench the reaction, then add 0.1 mol / L hydrochloric acid to adjust the pH of the system to 2 - 3, filter, wash the obtained filter cake with water 3 - 5 times, and dry to obtain the 2B acid derivative.

[0010] In step 1), the mass ratio of 2 - amino - 4,6 - dichloro - 5 - methylphenol, concentrated sulfuric acid and trichlorobenzene is 1:0.45 - 0.5:5 - 10.

[0011] In step 2), the mass ratio of the sulfonated product, anhydrous pyridine, phosphorus oxychloride and ice water is 1:5 - 10:1.7 - 2.5:3 - 5.

[0012] The fluorosilane coupling agent is trifluorooctyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane.

[0013] The preparation method of the permanent red pigment for acid - and alkali - resistant coatings includes the following steps:

[0014] ① Add the 2B acid derivative into ammonia water with a mass concentration of 25%, stir to dissolve, then add hydrochloric acid with a mass concentration of 30%, cool down to 0 - 5 °C, and dropwise add an aqueous solution of sodium nitrite with a mass concentration of 30% thereto, react for 1 - 3 h to obtain a diazo solution;

[0015] ② Add 2 - hydroxy - 3 - naphthoic acid and water into a coupling reactor, then add sodium hydroxide, stir to dissolve, add the diazo solution prepared in step ①, carry out a coupling reaction at 25 - 30 °C for 1 - 2 h, and at the same time adjust the pH of the system to 8 - 9 with sodium carbonate during the reaction. After the coupling reaction is completed, add an aqueous solution of calcium chloride with a mass concentration of 30% to the obtained reaction solution, stir and react for 0.5 - 1 h, then use hydrochloric acid to adjust the pH to 6.0 - 6.5, heat up to 70 - 90 °C and continue to stir and react for 0.5 - 1 h, filter, wash, and dry to obtain pigment particles;

[0016] ③ Add the pigment particles prepared in step ② into ethanol, ultrasonically disperse evenly, then dropwise add tetraethyl orthosilicate thereto, and add ammonia water to adjust the pH of the system to 8 - 10, react at 25 - 40 °C for 12 - 24 h. After the reaction is completed, let it stand for 12 - 24 h, centrifuge, wash the obtained solid with water and ethanol 2 - 3 times, and dry to obtain the silica - coated pigment;

[0017] ④ Add the silica-coated pigment prepared in step ③ to toluene with a water content of less than 10 ppm, then add a fluorosilane coupling agent thereto, heat to 50 °C, stir and react for 5 - 10 h. After the reaction is completed, perform suction filtration, wash the obtained filter cake with toluene 2 - 3 times, and dry to obtain a permanent red pigment for acid- and alkali-resistant coatings.

[0018] In step ①, the mass ratio of the 2B acid derivative, ammonia water, hydrochloric acid, and sodium nitrite solution is 1:2 - 3:0.8 - 1:0.75 - 0.9.

[0019] In step ②, the mass ratio of 2-hydroxy-3-naphthoic acid, water, sodium hydroxide, and calcium chloride aqueous solution is 1:10 - 15:0.25 - 0.35:4 - 6.

[0020] In step ②, the mass ratio of 2-hydroxy-3-naphthoic acid to the 2B acid derivative in step ① is 0.58 - 0.65:1.

[0021] In step ③, the mass ratio of the pigment particles, ethanol, and tetraethyl orthosilicate is 1:10 - 20:1 - 2.5.

[0022] In step ④, the mass ratio of the silica-coated pigment, toluene, and fluorosilane coupling agent is 1:5 - 10:2 - 3.

[0023] The present invention has the following advantages compared with the prior art:

[0024] For the permanent red pigment for acid- and alkali-resistant coatings of the present invention, the 2B acid derivative is used to modify the pigment, introducing a phosphate group into the pigment molecular structure, improving the acid and alkali resistance of the pigment; in addition, silica is used to covalently bond with the pigment particles to achieve the coating of the pigment, forming a protective layer, reducing the contact between the pigment and the external acid-base environment, and further improving the acid and alkali resistance of the pigment; finally, by performing hydrophobic treatment on the silica coating layer, the surface tension of the pigment is reduced, and at the same time, the fluorosilane has an anti-photooxidation effect, improving the light resistance of the pigment.

[0025] For the permanent red pigment for acid- and alkali-resistant coatings of the present invention, silica is used to coat the pigment, reducing the agglomeration of the pigment, increasing the dispersibility and coloring power of the pigment; and the pigment has both hydrophilic phosphate groups and hydrophobic fluorosilane chains, improving the surface tension of the pigment and enhancing the compatibility with various substrates.

[0026] The permanent red pigment for acid- and alkali-resistant coatings prepared by the present invention, while maintaining the excellent properties of the original pigment Red 48:2, further enhances the acid and alkali resistance and environmental stability of the pigment, significantly improving the application performance of the pigment. Specific embodiments

[0027] To better understand the technical solution of the present invention, the following provides a further detailed description of the above content of the present invention in the form of specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Any technology implemented based on the above content of the present invention belongs to the scope of the present invention.

[0028] Example 1 Preparation of 2B acid derivative

[0029] Add 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.45 kg of concentrated sulfuric acid with a mass concentration of 98%, and 5 kg of trichlorobenzene into a reactor. After stirring and dispersing evenly, evacuate to 0.03 Mpa and heat to 190 °C for reaction for 3 h. After the reaction is completed, filter. The obtained filter cake is washed twice with methanol and dried to obtain a sulfonated product. 1 H NMR(300 MHz, DMSO- d 6 , 298 K) δ 9.55 (s, 1H), 8.58(s, 1H), 5.35 (s, 2H), 2.32 (s, 3H).

[0030] Under nitrogen protection, add 1 kg of the sulfonated product into 5 kg of anhydrous pyridine, cool down to 0 °C, and dropwise add 1.7 kg of phosphorus oxychloride thereto, controlling the temperature of the system below 10 °C during the dropping process. After the dropping is completed, heat to 60 °C and react for 5 h. After the reaction ends, cool down to 25 °C, add 3 kg of ice water to quench the reaction, and then add 0.1 mol / L hydrochloric acid to adjust the pH of the system to 2. Filter. The obtained filter cake is washed three times with water and dried to obtain a 2B acid derivative. 1 H NMR(300 MHz, DMSO- d 6 , 298 K) δ 8.55 (s,1H), 5.38(s, 2H), 4.85 (s, 2H), 2.34 (s, 3H).

[0031] Preparation of permanent red pigment for acid and alkali resistant coatings

[0032] Add 1 kg of 2B acid derivative into 2 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, add 0.8 kg of hydrochloric acid with a mass concentration of 30%. Cool down to 0 °C, and dropwise add 0.75 kg of aqueous sodium nitrite solution with a mass concentration of 30% thereto. React for 1 h to obtain a diazo solution.

[0033] Add 0.58 kg of 2-hydroxy-3-naphthoic acid and 5.8 kg of water to a coupling reactor, then add 0.15 kg of sodium hydroxide. After stirring and dissolving, add the diazo solution, and carry out the coupling reaction at 25 °C for 1 h. Meanwhile, adjust the pH of the system to 8 with sodium carbonate during the reaction. After the coupling reaction is completed, add 2.32 kg of an aqueous calcium chloride solution with a mass concentration of 30% to the obtained reaction solution. After stirring and reacting for 0.5 h, adjust the pH to 6 with hydrochloric acid, raise the temperature to 70 °C and continue stirring and reacting for 0.5 h. Filter, wash, and dry to obtain pigment particles;

[0034] Add 1 kg of pigment particles to 10 kg of ethanol. After ultrasonic dispersion, add 1 kg of tetraethyl orthosilicate dropwise thereto, and add ammonia water to adjust the pH of the system to 8. React at 25 °C for 12 h. After the reaction is completed, let it stand for 12 h, centrifuge, and wash the obtained solid twice with water and ethanol, then dry to obtain the pigment coated with silica;

[0035] Add 1 kg of the pigment coated with silica to 5 kg of toluene with a water content of less than 10 ppm, then add 2 kg of trifluorooctyltrimethoxysilane thereto, heat to 50 °C, and stir and react for 5 h. After the reaction is completed, carry out suction filtration, wash the obtained filter cake twice with toluene, and dry to obtain the permanent red pigment for acid and alkali resistant coatings.

[0036] Example 2 Preparation of 2B acid derivative

[0037] Add 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.46 kg of concentrated sulfuric acid with a mass concentration of 98% and 6 kg of trichlorobenzene to a reactor. After stirring and dispersing evenly, evacuate to 0.04 Mpa and heat to 195 °C for reaction for 5 h. After the reaction is completed, filter, and wash the obtained filter cake three times with methanol, then dry to obtain the sulfonated product;

[0038] Under nitrogen protection, add 1 kg of the sulfonated product to 6 kg of anhydrous pyridine, cool down to 2 °C, and add 1.9 kg of phosphorus oxychloride dropwise thereto, controlling the temperature of the system below 10 °C during the dropping process. After the dropping is completed, heat to 65 °C and react for 6 h. After the reaction is completed, cool down to 26 °C, add 3.5 kg of ice water to quench the reaction, then add 0.1 mol / L hydrochloric acid to adjust the pH of the system to 2.5, filter, and wash the obtained filter cake four times with water, then dry to obtain the 2B acid derivative.

[0039] Preparation of permanent red pigment for acid and alkali resistant coatings

[0040] Add 1 kg of 2B acid derivative to 2.2 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, add 0.85 kg of hydrochloric acid with a mass concentration of 30%, cool down to 2 °C, and add 0.8 kg of an aqueous sodium nitrite solution with a mass concentration of 30% dropwise thereto, and react for 1.5 h to obtain the diazo solution;

[0041] Add 0.6 kg of 2-hydroxy-3-naphthoic acid and 6.6 kg of water into the coupling reactor, then add 0.17 kg of sodium hydroxide. After stirring and dissolving, add the diazo solution. Conduct the coupling reaction at 26 °C for 1.2 h. Meanwhile, adjust the pH of the system to 8.2 with sodium carbonate during the reaction. After the coupling reaction is completed, add 2.7 kg of an aqueous calcium chloride solution with a mass concentration of 30% to the obtained reaction solution. After stirring and reacting for 0.6 h, adjust the pH to 6.1 with hydrochloric acid, raise the temperature to 75 °C and continue stirring and reacting for 0.6 h. Filter, wash, and dry to obtain pigment particles;

[0042] Add 1 kg of pigment particles into 12 kg of ethanol. After ultrasonic dispersion, add 1.2 kg of tetraethyl orthosilicate dropwise thereto, and add ammonia water to adjust the pH of the system to 8.5. React at 30 °C for 15 h. After the reaction is completed, let it stand for 15 h, centrifuge, and wash the obtained solid 3 times with water and ethanol, then dry to obtain the pigment coated with silica;

[0043] Add 1 kg of the pigment coated with silica into 6 kg of toluene with a water content of less than 10 ppm, then add 2.2 kg of 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexyltrimethoxysilane, heat to 50 °C, and stir and react for 6 h. After the reaction is completed, conduct suction filtration, wash the obtained filter cake 3 times with toluene, and dry to obtain the permanent red pigment for acid and alkali resistant coatings.

[0044] Example 3 Preparation of 2B acid derivative

[0045] Add 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.47 kg of concentrated sulfuric acid with a mass concentration of 98%, and 7.5 kg of trichlorobenzene into the reactor. After stirring and dispersing evenly, evacuate to 0.05 Mpa and heat to 200 °C for reaction for 8 h. After the reaction is completed, filter, and wash the obtained filter cake 3 times with methanol, then dry to obtain the sulfonated product;

[0046] Under nitrogen protection, add 1 kg of the sulfonated product into 7.5 kg of anhydrous pyridine, cool down to 3 °C, and add 2.1 kg of phosphorus oxychloride dropwise thereto, controlling the temperature of the system below 10 °C during the dropping process. After the dropping is completed, heat to 70 °C and react for 7 h. After the reaction is completed, cool down to 28 °C, add 4 kg of ice water to quench the reaction, then add 0.1 mol / L hydrochloric acid to adjust the pH of the system to 2.5, filter, and wash the obtained filter cake 4 times with water, then dry to obtain the 2B acid derivative.

[0047] Preparation of the permanent red pigment for acid and alkali resistant coatings

[0048] Add 1 kg of 2B acid derivative to 2.5 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, add 0.9 kg of hydrochloric acid with a mass concentration of 30%. Cool down to 3°C, and dropwise add 0.82 kg of sodium nitrite aqueous solution with a mass concentration of 30%. React for 2 h to obtain a diazo solution;

[0049] Add 0.62 kg of 2-hydroxy-3-naphthoic acid and 7.4 kg of water to a coupling reactor, then add 0.19 kg of sodium hydroxide. After stirring and dissolving, add the diazo solution. Conduct a coupling reaction at 28°C for 1.5 h. At the same time, adjust the pH of the system to 8.5 with sodium carbonate during the reaction. After the coupling reaction is completed, add 3 kg of calcium chloride aqueous solution with a mass concentration of 30% to the obtained reaction solution. After stirring and reacting for 0.75 h, adjust the pH to 6.2 with hydrochloric acid, heat up to 80°C and continue stirring and reacting for 0.75 h. Filter, wash, and dry to obtain pigment particles;

[0050] Add 1 kg of pigment particles to 15 kg of ethanol. After ultrasonic dispersion, dropwise add 1.6 kg of tetraethyl orthosilicate, and add ammonia water to adjust the pH of the system to 9. React at 32°C for 18 h. After the reaction is completed, let it stand for 20 h, centrifuge. Wash the obtained solid 3 times with water and ethanol, and dry to obtain silica-coated pigment;

[0051] Add 1 kg of silica-coated pigment to 7 kg of toluene with a water content less than 10 ppm, then add 2.5 kg of 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-heptadecafluorodecyltrimethoxysilane. Heat to 50°C and stir and react for 8 h. After the reaction is completed, perform suction filtration. Wash the obtained filter cake 3 times with toluene and dry to obtain a permanent red pigment for acid and alkali resistant coatings.

[0052] Example 4 Preparation of 2B acid derivative

[0053] Add 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.49 kg of concentrated sulfuric acid with a mass concentration of 98%, and 8.5 kg of trichlorobenzene to a reactor. After stirring and dispersing evenly, evacuate to 0.06 Mpa and heat to 200°C for reaction for 10 h. After the reaction is completed, filter. Wash the obtained filter cake 3 times with methanol and dry to obtain a sulfonated product;

[0054] Under nitrogen protection, add 1 kg of the sulfonated product to 9 kg of anhydrous pyridine. Cool down to 4°C, and dropwise add 2.3 kg of phosphorus oxychloride, controlling the system temperature below 10°C during the dropping process. After the dropping is completed, heat to 75°C and react for 9 h. After the reaction is completed, cool down to 29°C, add 4.5 kg of ice water to quench the reaction, and then add 0.1 mol / L hydrochloric acid to adjust the pH of the system to 2.8. Filter. Wash the obtained filter cake 5 times with water and dry to obtain 2B acid derivative.

[0055] Preparation of Permanent Red Pigment for Acid and Alkali Resistant Coatings

[0056] Add 1 kg of 2B acid derivative into 2.8 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, add 0.95 kg of hydrochloric acid with a mass concentration of 30%. Cool down to 4 °C, and dropwise add 0.85 kg of sodium nitrite aqueous solution with a mass concentration of 30%. React for 2.5 h to obtain a diazo solution;

[0057] Add 0.64 kg of 2-hydroxy-3-naphthoic acid and 8.9 kg of water into a coupling reactor, then add 0.21 kg of sodium hydroxide. After stirring and dissolving, add the diazo solution. Carry out a coupling reaction at 29 °C for 1.8 h. At the same time, adjust the pH of the system to 8.8 with sodium carbonate during the reaction. After the coupling reaction is completed, add 3.5 kg of calcium chloride aqueous solution with a mass concentration of 30% to the obtained reaction solution. Stir and react for 0.9 h, then adjust the pH to 6.4 with hydrochloric acid, heat up to 85 °C and continue to stir and react for 0.9 h. Filter, wash, and dry to obtain pigment particles;

[0058] Add 1 kg of pigment particles into 18 kg of ethanol. After ultrasonic dispersion, dropwise add 2 kg of tetraethyl orthosilicate, and add ammonia water to adjust the pH of the system to 9.5. React at 35 °C for 20 h. After the reaction is completed, let it stand for 22 h, centrifuge. Wash the obtained solid 3 times with water and ethanol, and dry to obtain silica-coated pigment;

[0059] Add 1 kg of silica-coated pigment into 8.5 kg of toluene with a water content less than 10 ppm, then add 2.8 kg of trifluorooctyltrimethoxysilane. Heat to 50 °C and stir and react for 8.5 h. After the reaction is completed, carry out suction filtration. Wash the obtained filter cake 3 times with toluene and dry to obtain the permanent red pigment for acid and alkali resistant coatings.

[0060] Example 5 Preparation of 2B Acid Derivative

[0061] Add 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.5 kg of concentrated sulfuric acid with a mass concentration of 98%, and 10 kg of trichlorobenzene into a reactor. After stirring and dispersing evenly, evacuate to 0.08 Mpa and heat to 205 °C for reaction for 12 h. After the reaction is completed, filter. Wash the obtained filter cake 3 times with methanol and dry to obtain a sulfonated product;

[0062] Under nitrogen protection, 1 kg of sulfide was added to 10 kg of anhydrous pyridine, and the temperature was lowered to 5 °C. 2.5 kg of phosphorus oxychloride was added dropwise thereto, and the temperature of the system was controlled to be lower than 10 °C during the dropping process. After the dropping was completed, the temperature was raised to 80 °C and reacted for 10 h. After the reaction was completed, the temperature was lowered to 30 °C, 5 kg of ice water was added to quench the reaction, and then 0.1 mol / L hydrochloric acid was added to adjust the pH of the system to 3. After filtration, the obtained filter cake was washed with water 5 times and dried to obtain the 2B acid derivative.

[0063] Preparation of Permanent Red Pigment for Acid and Alkali Resistant Coatings

[0064] 1 kg of 2B acid derivative was added to 3 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, 1 kg of hydrochloric acid with a mass concentration of 30% was added. The temperature was lowered to 5 °C, and 0.9 kg of sodium nitrite aqueous solution with a mass concentration of 30% was added dropwise thereto. After reacting for 3 h, a diazo solution was obtained;

[0065] 0.65 kg of 2-hydroxy-3-naphthoic acid and 9.75 kg of water were added to a coupling reactor, and then 0.22 kg of sodium hydroxide was added. After stirring and dissolving, the diazo solution was added. The coupling reaction was carried out at 30 °C for 2 h. At the same time, the pH of the system was adjusted to 9 with sodium carbonate during the reaction. After the coupling reaction was completed, 3.9 kg of calcium chloride aqueous solution with a mass concentration of 30% was added to the obtained reaction solution. After stirring and reacting for 1 h, the pH was adjusted to 6.5 with hydrochloric acid, and the temperature was raised to 90 °C and stirred and reacted for 1 h. After filtration, washing, and drying, pigment particles were obtained;

[0066] 1 kg of pigment particles was added to 20 kg of ethanol. After ultrasonic dispersion, 2.5 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 10. The reaction was carried out at 40 °C for 24 h. After the reaction was completed, it was allowed to stand for 24 h and centrifuged. The obtained solid was washed 3 times with water and ethanol and dried to obtain the pigment coated with silica;

[0067] 1 kg of the pigment coated with silica was added to 10 kg of toluene with a water content of less than 10 ppm, and then 3 kg of 1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-heptadecafluorodecyltrimethoxysilane was added. The temperature was raised to 50 °C and stirred and reacted for 10 h. After the reaction was completed, suction filtration was carried out. The obtained filter cake was washed 3 times with toluene and dried to obtain the permanent red pigment for acid and alkali resistant coatings.

[0068] Example 6 Preparation of 2B Acid Derivative

[0069] 1 kg of 2-amino-4,6-dichloro-5-methylphenol, 0.48 kg of concentrated sulfuric acid with a mass concentration of 98%, and 8 kg of trichlorobenzene were added to a reactor. After stirring and dispersing evenly, the vacuum was pumped to 0.05 Mpa, and the temperature was raised to 205 °C and reacted for 3 h. After the reaction was completed, filtration was carried out. The obtained filter cake was washed 3 times with methanol and dried to obtain the sulfide;

[0070] Under nitrogen protection, 1 kg of sulfide was added to 8 kg of anhydrous pyridine, and the temperature was lowered to 0 °C. Then, 2 kg of phosphorus oxychloride was added dropwise thereto, and the temperature of the system was controlled to be lower than 10 °C during the dropping process. After the dropping was completed, the temperature was raised to 60 °C and the reaction was carried out for 10 h. After the reaction was completed, the temperature was lowered to 30 °C, 5 kg of ice water was added to quench the reaction, and then 0.1 mol / L hydrochloric acid was added to adjust the pH of the system to 2.5. After filtration, the obtained filter cake was washed with water 5 times and dried to obtain the 2B acid derivative.

[0071] Preparation of Permanent Red Pigment for Acid and Alkali Resistant Coatings

[0072] 1 kg of the 2B acid derivative was added to 2.5 kg of ammonia water with a mass concentration of 25%. After stirring and dissolving, 1 kg of hydrochloric acid with a mass concentration of 30% was added. The temperature was lowered to 0 °C, and 0.8 kg of an aqueous sodium nitrite solution with a mass concentration of 30% was added dropwise thereto. The reaction was carried out for 3 h to obtain the diazo solution;

[0073] 0.65 kg of 2-hydroxy-3-naphthoic acid and 6.5 kg of water were added to the coupling reactor, and then 0.17 kg of sodium hydroxide was added. After stirring and dissolving, the diazo solution was added. The coupling reaction was carried out at 30 °C for 1 h, and at the same time, the pH of the system was adjusted to 9 with sodium carbonate during the reaction. After the coupling reaction was completed, 2.6 kg of an aqueous calcium chloride solution with a mass concentration of 30% was added to the obtained reaction solution. After stirring and reacting for 1 h, the pH was adjusted to 6.5 with hydrochloric acid, and the temperature was raised to 90 °C and stirring reaction was continued for 0.5 h. After filtration, washing and drying, pigment particles were obtained;

[0074] 1 kg of the pigment particles was added to 15 kg of ethanol. After ultrasonic dispersion was uniform, 2 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 10. The reaction was carried out at 25 °C for 24 h. After the reaction was completed, it was allowed to stand for 24 h and centrifuged. The obtained solid was washed with water and ethanol 3 times and dried to obtain the pigment coated with silica;

[0075] 1 kg of the pigment coated with silica was added to 8 kg of toluene with a water content of less than 10 ppm, and then 2.5 kg of 1,1,1,3,3,3-heptafluoropropyltrimethoxysilane was added. The temperature was raised to 50 °C and the stirring reaction was carried out for 10 h. After the reaction was completed, suction filtration was carried out. The obtained filter cake was washed with toluene 3 times and dried to obtain the permanent red pigment for acid and alkali resistant coatings.

[0076] The permanent red pigments for acid- and alkali-resistant coatings prepared in Examples 1 to 6 of the present invention were tested. Among them, the coloring power was tested according to the method in GB1708-79; the light fastness was tested according to the method in GB1710-79; the water resistance, acid resistance and alkali resistance were tested according to the method in GB 5211.5-2008-T. The product permanent red F5RS (P.R, 48:2) of the company was used as the comparative example, and the test results are shown in Table 1. It can be seen from the results in Table 1 that the permanent red pigments for acid- and alkali-resistant coatings prepared in the present invention have strong acid and alkali resistance, water resistance and light fastness, improving the application performance of the pigments.

[0077] Table 1 Performance test results of the pigments prepared in Examples 1 to 6 and the comparative example

[0078]

[0079] Although the specific embodiments of the present invention are described above, it is not a limitation on the protection scope of the present invention. Based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A method for preparing a permanent red pigment for acid and alkali resistant coatings, characterized in that: The 2B acid derivative is diazotized, coupled with 2-hydroxy-3-naphthoic acid, and then a calcium chloride aqueous solution is added to obtain pigment particles, and finally the surface of the pigment particles is coated with silica, and the silica coating layer is hydrophobically treated with a fluorine-containing silane coupling agent to prepare the pigment particles; The 2B acid derivative is prepared according to the following steps: 1) Add 2-amino-4,6-dichloro-5-methylphenol, 98% concentrated sulfuric acid and trichlorobenzene into a reactor, stir and disperse them evenly, evacuate to 0.03-0.08Mpa, heat to 190-205°C and react for 3-12 hours. After the reaction is completed, filter and wash the filter cake with methanol for 2-3 times and dry to obtain a sulfonated product; 2) under nitrogen protection, the sulfonated product obtained in step 1) was added to anhydrous pyridine, cooled to 0-5°C, phosphorus oxychloride was added dropwise thereto, and the system temperature was controlled to be below 10°C during the addition. After the addition was completed, the mixture was heated to 60-80°C and reacted for 5-10 hours. After the reaction was completed, the mixture was cooled to 25-30°C, ice water was added to quench the reaction, and 0.1 mol / L hydrochloric acid was added to adjust the pH of the system to 2-3, and the mixture was filtered. The filter cake was washed with water 3-5 times and dried to obtain a 2B acid derivative; The fluorine-containing silane coupling agent is tridecafluorooctyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane.

2. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 1, characterized in that: The mass ratio of 2-amino-4,6-dichloro-5-methylphenol, concentrated sulfuric acid and trichlorobenzene in step 1) is 1:0.45~0.5:5~10.

3. The method for preparing the permanent red pigment for acid and alkali resistant coating according to claim 1, characterized in that: The mass ratio of the sulfonate, anhydrous pyridine, phosphorus oxychloride and ice water in step 2) is 1:5~10:1.7~2.5:3~5.

4. The method for preparing the permanent red pigment for acid and alkali resistant coating according to claim 1, characterized in that: The method for preparing the permanent red pigment for acid and alkali resistant coating comprises the following steps: ① Add the 2B acid derivative to 25% ammonia water, stir and dissolve, then add 30% hydrochloric acid, cool to 0-5°C, add 30% sodium nitrite aqueous solution dropwise, react for 1-3h to obtain diazo solution; ② Add 2-hydroxy-3-naphthoic acid and water to a coupling reactor, then add sodium hydroxide, stir and dissolve, add the diazo solution prepared in step ①, and carry out coupling reaction at 25-30° C. for 1-2 hours. Meanwhile, adjust the pH value of the system to 8-9 with sodium carbonate during the reaction. After the coupling reaction is completed, add a 30% calcium chloride aqueous solution to the obtained reaction solution, stir and react for 0.5-1 hour, then adjust the pH value to 6.0-6.5 with hydrochloric acid, heat to 70-90° C., continue stirring and reacting for 0.5-1 hour, filter, wash, and dry to obtain pigment particles; ③ Add the pigment particles prepared in step ② to ethanol, and after ultrasonic dispersion, add tetraethyl orthosilicate dropwise thereto, and add ammonia water to adjust the pH of the system to 8-10, react at 25-40° C. for 12-24 hours, and after the reaction is completed, stand for 12-24 hours, centrifuge, wash the obtained solid with water and ethanol 2-3 times, and dry to obtain a silica-coated pigment; ④ Add the silica-coated pigment obtained in step ③ to toluene with a water content of less than 10 ppm, then add a fluorinated silane coupling agent thereto, heat to 50°C, stir and react for 5 to 10 hours, and after the reaction is completed, filter and wash the filter cake with toluene 2 to 3 times, and dry to obtain a permanent red pigment for acid and alkali resistant coatings.

5. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 4, characterized in that: The mass ratio of the 2B acid derivative, ammonia water, hydrochloric acid and sodium nitrite solution in step ① is 1:2~3:0.8~1:0.75~0.

9.

6. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 4, characterized in that: The mass ratio of 2-hydroxy-3-naphthoic acid, water, sodium hydroxide and calcium chloride aqueous solution in step ② is 1:10-15:0.25-0.35:4-6.

7. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 4, characterized in that: The mass ratio of the 2-hydroxy-3-naphthoic acid in step ② to the 2B acid derivative in step ① is 0.58-0.65:

1.

8. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 4, characterized in that: The mass ratio of the pigment particles, ethanol and tetraethyl orthosilicate in step ③ is 1:10-20:1-2.

5.

9. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 4, characterized in that: The mass ratio of the silica-coated pigment, toluene and fluorine-containing silane coupling agent in step ④ is 1:5~10:2~3.

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