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 an acid and alkali resistant coating, and belongs to the technical field of pigment preparation, a 2B acid derivative is diazotized and then coupled with 2-hydroxy-3-naphthoic acid, then a calcium chloride aqueous solution is added for color lake to obtain pigment particles, and finally the surfaces of the pigment particles are coated with silicon dioxide to obtain the permanent red pigment for the acid and alkali resistant coating. According to the permanent red pigment for the acid and alkali resistant coating prepared by the preparation method disclosed by the invention, the acid and alkali resistance and environmental stability of the pigment are further enhanced while the excellent characteristics of original pigment red 48: 2 are maintained, and the application performance of the pigment is remarkably improved.

Description

Technical Field

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

[0002] There are many types of Permanent Red, including 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 intensity and gloss, and good light and heat resistance. It is widely used in coatings, plastics and inks.

[0003] Pigment Red 48:2 does not have acid and alkali resistant groups in its chemical structure, so it is easy to hydrolyze in an acid or alkaline environment, resulting in pigment degradation; in addition, the particle size and surface characteristics of the pigment will also affect the stability of the pigment in an acid or alkaline environment, thereby affecting the application of the pigment. Therefore, it is of great significance to improve the acid and alkali resistance of Pigment Red 48:2 by modifying it, thereby improving 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 method for preparing a permanent red pigment for acid and alkali resistant coatings.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions: A method for preparing a permanent red pigment for acid- and alkali-resistant coatings, comprising: diazotizing a 2B acid derivative, coupling with 2-hydroxy-3-naphthoic acid, adding a calcium chloride aqueous solution for lake formation to obtain pigment particles, and finally coating the surface of the pigment particles with silicon dioxide, and using a fluorine-containing silane coupling agent to hydrophobically treat the silicon dioxide coating layer to obtain the permanent red pigment; 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) is added to anhydrous pyridine, cooled to 0-5°C, phosphorus oxychloride is added dropwise thereto, and the system temperature is controlled to be lower than 10°C during the dropping process. After the dropping is completed, the mixture is heated to 60-80°C and reacted for 5-10 hours. After the reaction is completed, the mixture is cooled to 25-30°C, ice water is added to quench the reaction, and 0.1 mol / L hydrochloric acid is added to adjust the pH of the system to 2-3, and the mixture is filtered. The filter cake is washed with water 3-5 times and dried to obtain a 2B acid derivative.

[0006] 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.

[0007] 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.

[0008] The fluorine-containing silane coupling agent is tridecafluorooctyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] The mass ratio of the pigment particles, ethanol and tetraethyl orthosilicate in step ③ is 1:10-20:1-2.5.

[0014] The mass ratio of the silica-coated pigment, toluene and fluorine-containing silane coupling agent in step ④ is 1:5~10:2~3.

[0015] Compared with the prior art, the present invention has the following advantages: The permanent red pigment for acid and alkali resistant coating of the present invention uses 2B acid derivatives to modify the pigment, introduces a phosphoric acid group into the molecular structure of the pigment, and improves the acid and alkali resistance of the pigment; in addition, silicon dioxide is covalently bonded to the pigment particles to achieve coating of the pigment to form a protective layer, thereby reducing the contact between the pigment and the external acid and alkali environment and further improving the acid and alkali resistance of the pigment; finally, the silicon dioxide coating layer is hydrophobicized to reduce the surface tension of the pigment, and fluorosilane has an anti-photooxidation effect, thereby improving the light resistance of the pigment.

[0016] The permanent red pigment for acid and alkali resistant coating of the present invention uses silicon dioxide to coat the pigment, which reduces the agglomeration of the pigment and increases the dispersibility and tinting power of the pigment; and the pigment has both hydrophilic phosphate groups and hydrophobic fluorosilane chains, which improves the surface tension of the pigment and enhances the compatibility with various substrates.

[0017] The permanent red pigment for acid and alkali resistant coating prepared by the present 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, thereby significantly improving the application performance of the pigment. DETAILED DESCRIPTION

[0018] In order to better understand the technical solution of the present invention, the above content of the present invention is further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies realized based on the above content of the present invention belong to the scope of the present invention.

[0019] Example 1 Preparation of 2B acid derivatives 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 were added into the reactor, stirred and dispersed evenly, and then evacuated to 0.03 MPa, heated to 190°C and reacted for 3 hours. After the reaction was completed, the reaction was filtered, and the obtained filter cake was washed twice with methanol and dried to obtain a sulfonated product; 1 H NMR (300 MHz, DMSO- d6 , 298 K) δ 9.55 (s, 1H), 8.58 (s, 1H), 5.35 (s, 2H), 2.32 (s, 3H).

[0020] Under nitrogen protection, 1 kg of sulfonate was added to 5 kg of anhydrous pyridine, cooled to 0 ° C, and 1.7 kg of phosphorus oxychloride was added dropwise thereto. The system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 60 ° C and reacted for 5 hours. After the reaction was completed, it was cooled to 25 ° C, 3 kg of 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. Filter, wash the filter cake with water 3 times, and dry 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).

[0021] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 2 kg of 25% ammonia water, stirred and dissolved, then 0.8 kg of 30% hydrochloric acid was added, the temperature was lowered to 0°C, 0.75 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was carried out for 1 hour to obtain a diazo solution; 0.58 kg of 2-hydroxy-3-naphthoic acid and 5.8 kg of water were added to a coupling reactor, and then 0.15 kg of sodium hydroxide was added. After stirring and dissolving, diazo solution was added, and the coupling reaction was carried out at 25° C. for 1 hour. During the reaction, the pH of the system was adjusted to 8 with sodium carbonate. After the coupling reaction was completed, 2.32 kg of a 30% calcium chloride aqueous solution was added to the obtained reaction solution, and the reaction was stirred for 0.5 hour. Then, the pH was adjusted to 6 with hydrochloric acid, and the temperature was raised to 70° C. and the reaction was continued with stirring for 0.5 hour. The reaction was filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 10 kg of ethanol, and after ultrasonic dispersion, 1 kg of ethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 8, and the reaction was carried out at 25°C for 12 hours. After the reaction was completed, the reaction was allowed to stand for 12 hours, and the solid was washed twice with water and ethanol, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 5 kg of toluene with a water content of less than 10 ppm, and then 2 kg of tridecafluorooctyltrimethoxysilane was added thereto, heated to 50°C, and stirred for reaction for 5 hours. After the reaction was completed, the filter was filtered, and the filter cake was washed twice with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0022] Example 2 Preparation of 2B acid derivatives 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 were added into the reactor, stirred and dispersed evenly, and then evacuated to 0.04 MPa, heated to 195°C and reacted for 5 hours. After the reaction was completed, the reaction was filtered, and the obtained filter cake was washed 3 times with methanol and dried to obtain a sulfonated product; Under nitrogen protection, 1 kg of sulfonate was added to 6 kg of anhydrous pyridine, cooled to 2 ° C, 1.9 kg of phosphorus oxychloride was added dropwise thereto, and the system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 65 ° C and reacted for 6 hours. After the reaction was completed, it was cooled to 26 ° C, 3.5 kg of 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 2.5, filtered, and the filter cake was washed with water 4 times and dried to obtain a 2B acid derivative.

[0023] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 2.2 kg of 25% ammonia water, stirred and dissolved, then 0.85 kg of 30% hydrochloric acid was added, the temperature was lowered to 2°C, 0.8 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was carried out for 1.5 hours to obtain a diazo solution; 0.6 kg of 2-hydroxy-3-naphthoic acid and 6.6 kg of water were added to a coupling reactor, and then 0.17 kg of sodium hydroxide was added. After stirring and dissolving, diazo solution was added, and the coupling reaction was carried out at 26° C. for 1.2 hours. Meanwhile, sodium carbonate was used to adjust the pH of the system to 8.2 during the reaction. After the coupling reaction was completed, 2.7 kg of a 30% calcium chloride aqueous solution was added to the obtained reaction solution, and the reaction was stirred for 0.6 hours. Then, hydrochloric acid was used to adjust the pH to 6.1, and the temperature was raised to 75° C. and the stirring reaction was continued for 0.6 hours. The reaction was filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 12 kg of ethanol, and after being uniformly dispersed by ultrasonication, 1.2 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 8.5, and the reaction was carried out at 30°C for 15 hours. After the reaction was completed, the reaction was allowed to stand for 15 hours, and the solid was centrifuged and washed with water and ethanol three times, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 6 kg of toluene with a water content of less than 10 ppm, and then 2.2 kg of heptadecafluorodecyltrimethoxysilane was added thereto, heated to 50°C, and stirred for reaction for 6 hours. After the reaction was completed, it was filtered, and the filter cake was washed 3 times with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0024] Example 3 Preparation of 2B acid derivatives 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 were added into the reactor, stirred and dispersed evenly, and then evacuated to 0.05 MPa, heated to 200°C and reacted for 8 hours. After the reaction was completed, the reaction was filtered, and the obtained filter cake was washed 3 times with methanol and dried to obtain a sulfonated product; Under nitrogen protection, 1 kg of sulfonate was added to 7.5 kg of anhydrous pyridine, cooled to 3 ° C, and 2.1 kg of phosphorus oxychloride was added dropwise thereto. The system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 70 ° C and reacted for 7 hours. After the reaction was completed, it was cooled to 28 ° C, 4 kg of 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 2.5. Filter, wash the filter cake with water 4 times, and dry to obtain a 2B acid derivative.

[0025] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 2.5 kg of 25% ammonia water, stirred and dissolved, then 0.9 kg of 30% hydrochloric acid was added, the temperature was lowered to 3°C, 0.82 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was carried out for 2 hours to obtain a diazo solution; 0.62 kg of 2-hydroxy-3-naphthoic acid and 7.4 kg of water were added to a coupling reactor, and then 0.19 kg of sodium hydroxide was added. After stirring and dissolving, diazo solution was added, and the coupling reaction was carried out at 28° C. for 1.5 hours. Meanwhile, sodium carbonate was used to adjust the pH of the system to 8.5 during the reaction. After the coupling reaction was completed, 3 kg of a 30% calcium chloride aqueous solution was added to the obtained reaction solution, and the reaction was stirred for 0.75 hours. Then, hydrochloric acid was used to adjust the pH to 6.2, and the temperature was raised to 80° C. and the stirring reaction was continued for 0.75 hours. The reaction was filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 15 kg of ethanol, and after being uniformly dispersed by ultrasonication, 1.6 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 9, and the reaction was carried out at 32°C for 18 hours. After the reaction was completed, the reaction was allowed to stand for 20 hours, and the solid was centrifuged. The solid was washed with water and ethanol three times, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 7 kg of toluene with a water content of less than 10 ppm, and then 2.5 kg of heptadecafluorodecyltrimethoxysilane was added thereto, heated to 50°C, stirred and reacted for 8 hours. After the reaction was completed, it was filtered, and the filter cake was washed 3 times with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0026] Example 4 Preparation of 2B acid derivatives 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 were added into the reactor, stirred and dispersed evenly, and then evacuated to 0.06 MPa, heated to 200°C and reacted for 10 hours. After the reaction was completed, the reaction was filtered, and the obtained filter cake was washed 3 times with methanol and dried to obtain a sulfonated product; Under nitrogen protection, 1 kg of sulfonate was added to 9 kg of anhydrous pyridine, cooled to 4 ° C, and 2.3 kg of phosphorus oxychloride was added dropwise thereto. The system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 75 ° C and reacted for 9 hours. After the reaction was completed, it was cooled to 29 ° C, 4.5 kg of 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 2.8. Filter, wash the filter cake with water 5 times, and dry to obtain a 2B acid derivative.

[0027] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 2.8 kg of 25% ammonia water, stirred and dissolved, then 0.95 kg of 30% hydrochloric acid was added, the temperature was lowered to 4°C, 0.85 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was continued for 2.5 hours to obtain a diazo solution; 0.64 kg of 2-hydroxy-3-naphthoic acid and 8.9 kg of water were added to a coupling reactor, and then 0.21 kg of sodium hydroxide was added. After stirring and dissolving, diazo solution was added, and the coupling reaction was carried out at 29° C. for 1.8 hours. During the reaction, sodium carbonate was used to adjust the pH of the system to 8.8. After the coupling reaction was completed, 3.5 kg of a 30% calcium chloride aqueous solution was added to the obtained reaction solution, and the reaction was stirred for 0.9 hours. Then, hydrochloric acid was used to adjust the pH to 6.4, and the temperature was raised to 85° C. and the stirring reaction was continued for 0.9 hours. The reaction was filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 18 kg of ethanol, and after being uniformly dispersed by ultrasonication, 2 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 9.5, and the reaction was carried out at 35°C for 20 hours. After the reaction was completed, the reaction was allowed to stand for 22 hours, and the solid was centrifuged. The solid was washed with water and ethanol three times, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 8.5 kg of toluene with a water content of less than 10 ppm, and then 2.8 kg of tridecafluorooctyltrimethoxysilane was added thereto, heated to 50°C, and stirred for reaction for 8.5 hours. After the reaction was completed, it was filtered, and the filter cake was washed 3 times with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0028] Example 5 Preparation of 2B acid derivatives 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 were added into the reactor, stirred and dispersed evenly, and then evacuated to 0.08 MPa, heated to 205°C and reacted for 12 hours. After the reaction was completed, the reaction was filtered, and the obtained filter cake was washed 3 times with methanol and dried to obtain a sulfonated product; Under nitrogen protection, 1 kg of sulfonate was added to 10 kg of anhydrous pyridine, cooled to 5 ° C, and 2.5 kg of phosphorus oxychloride was added dropwise thereto. The system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 80 ° C and reacted for 10 hours. After the reaction was completed, the temperature was lowered to 30 ° C, 5 kg of 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 3, filtered, and the filter cake was washed with water 5 times and dried to obtain a 2B acid derivative.

[0029] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 3 kg of 25% ammonia water, stirred and dissolved, and then 1 kg of 30% hydrochloric acid was added, the temperature was lowered to 5°C, and 0.9 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was carried out for 3 hours to obtain a diazo solution; 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, diazo solution was added, and coupling reaction was carried out at 30° C. for 2 h. Meanwhile, sodium carbonate was used to adjust the pH of the system to 9 during the reaction. After the coupling reaction was completed, 3.9 kg of 30% calcium chloride aqueous solution was added to the obtained reaction solution, and the reaction was stirred for 1 h. Then, hydrochloric acid was used to adjust the pH to 6.5, and the temperature was raised to 90° C. and the stirring reaction was continued for 1 h. The pigment particles were filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 20 kg of ethanol, and 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, and the reaction was carried out at 40°C for 24 hours. After the reaction was completed, the reaction was allowed to stand for 24 hours, and the solid was washed with water and ethanol three times, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 10 kg of toluene with a water content of less than 10 ppm, and then 3 kg of heptadecafluorodecyltrimethoxysilane was added thereto, heated to 50°C, and stirred for reaction for 10 hours. After the reaction was completed, it was filtered, and the filter cake was washed 3 times with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0030] Example 6 Preparation of 2B acid derivatives 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 into the reactor, stirred and dispersed evenly, then evacuated to 0.05 MPa, heated to 205°C and reacted for 3 hours. After the reaction was completed, the mixture was filtered, and the filter cake was washed 3 times with methanol and dried to obtain a sulfonated product. Under nitrogen protection, 1 kg of sulfonate was added to 8 kg of anhydrous pyridine, cooled to 0 ° C, and 2 kg of phosphorus oxychloride was added dropwise thereto. The system temperature was controlled to be lower than 10 ° C during the addition. After the addition was completed, it was heated to 60 ° C and reacted for 10 hours. After the reaction was completed, it was cooled to 30 ° C, 5 kg of 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 2.5. Filter, wash the filter cake with water 5 times, and dry to obtain a 2B acid derivative.

[0031] Preparation of permanent red pigment for acid and alkali resistant coatings 1 kg of 2B acid derivative was added to 2.5 kg of 25% ammonia water, stirred and dissolved, and then 1 kg of 30% hydrochloric acid was added, the temperature was lowered to 0°C, and 0.8 kg of 30% sodium nitrite aqueous solution was added dropwise thereto, and the reaction was carried out for 3 hours to obtain a diazo solution; 0.65 kg of 2-hydroxy-3-naphthoic acid and 6.5 kg of water were added to a coupling reactor, and then 0.17 kg of sodium hydroxide was added. After stirring and dissolving, diazo solution was added, and coupling reaction was carried out at 30° C. for 1 hour. During the reaction, the pH of the system was adjusted to 9 with sodium carbonate. After the coupling reaction was completed, 2.6 kg of 30% calcium chloride aqueous solution was added to the obtained reaction solution. After stirring and reacting for 1 hour, hydrochloric acid was used to adjust the pH to 6.5, and the temperature was raised to 90° C. and the stirring reaction was continued for 0.5 hour. The reaction was filtered, washed, and dried to obtain pigment particles. 1 kg of pigment particles were added to 15 kg of ethanol, and after ultrasonic dispersion, 2 kg of tetraethyl orthosilicate was added dropwise thereto, and ammonia water was added to adjust the pH of the system to 10, and the reaction was carried out at 25°C for 24 hours. After the reaction was completed, the reaction was allowed to stand for 24 hours, and the solid was washed with water and ethanol three times, and dried to obtain a silica-coated pigment; 1 kg of silica-coated pigment was added to 8 kg of toluene with a water content of less than 10 ppm, and then 2.5 kg of tridecafluorooctyltrimethoxysilane was added thereto, heated to 50°C, and stirred for reaction for 10 hours. After the reaction was completed, it was filtered, and the filter cake was washed 3 times with toluene and dried to obtain a permanent red pigment for acid and alkali resistant coatings.

[0032] The permanent red pigment for acid and alkali resistant coatings prepared in Examples 1 to 6 of the present invention was tested, wherein the tinting strength 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, and the permanent red F5RS (PR, 48:2) of our company was used as a 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 pigment for acid and alkali resistant coatings prepared by the present invention has strong acid and alkali resistance, water resistance and light resistance, and improves the application performance of the pigment.

[0033] Table 1 Performance test results of the pigments prepared in Examples 1 to 6 and the comparative examples

[0034] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection 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) is added to anhydrous pyridine, cooled to 0-5°C, phosphorus oxychloride is added dropwise thereto, and the system temperature is controlled to be lower than 10°C during the dropping process. After the dropping is completed, the mixture is heated to 60-80°C and reacted for 5-10 hours. After the reaction is completed, the mixture is cooled to 25-30°C, ice water is added to quench the reaction, and 0.1 mol / L hydrochloric acid is added to adjust the pH of the system to 2-3, and the mixture is filtered. The filter cake is washed with water 3-5 times and dried to obtain a 2B acid derivative.

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 fluorine-containing silane coupling agent is tridecafluorooctyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane.

5. 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.

6. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 5, 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.

7. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 5, 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.

8. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 5, 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.

9. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 5, characterized in that: The mass ratio of the pigment particles, ethanol and tetraethyl orthosilicate in step ③ is 1:10-20:1-2.

5.

10. The method for preparing the permanent red pigment for acid and alkali resistant coatings according to claim 5, 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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