Preparation method of organic pigment for coating based on golden light red

Abstract

The invention discloses a preparation method of an organic pigment for a coating based on golden light red, and belongs to the technical field of pigment synthesis, the preparation method comprises the following steps: diazotizing 2-amino-5-chloro-4-toluene sulfonic acid, coupling with an olefin-terminated modified silicon dioxide-naphthol derivative, adding a barium chloride aqueous solution, and carrying out color lake to obtain an alkenyl-terminated modified golden light red pigment; and finally, reacting with polyvinyl acetate to obtain the product. According to the preparation method disclosed by the invention, the dispersion stability, the moisture resistance, the migration resistance and the solvent resistance of the pigment are remarkably improved, and the application performance of the pigment in the aspect of coatings is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of pigment synthesis, and specifically relates to a preparation method of an organic pigment for coatings based on golden red. Background Art

[0002] Golden red (C.I. PR 53:1) is a barium salt lake pigment, which has good thermal stability, light resistance, acid and alkali resistance, and coloring power, and is widely used in inks, plastics, and rubber products.

[0003] However, due to its structural characteristics, the golden red pigment is prone to moisture absorption, resulting in agglomeration of pigment particles, thus making the pigment unstable during long-term storage; in addition, due to its needle-like particle morphology, the pigment is prone to flocculation, and precipitation or aggregation is likely to occur, with poor dispersion stability, ultimately affecting the uniformity and gloss of the pigment; the golden red pigment has poor tolerance to solvents and is prone to migration, so it is easy to dissolve or discolor in a solvent environment, which will also affect the service life and effect of the product. Therefore, by modifying the golden red pigment to overcome the above defects, it is of great significance to improve the performance of the pigment itself and expand its application scope in different fields. Summary of the Invention

[0004] To solve the above problems, the object of the present invention is to provide a preparation method of an organic pigment for coatings based on golden red.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: A preparation method of an organic pigment for coatings based on golden red, which is prepared by first diazotizing 2-amino-5-chloro-4-methylbenzenesulfonic acid, coupling it with a silica-naphthol derivative modified with terminal olefins, then adding an aqueous barium chloride solution for lake formation to obtain a terminal alkenyl-modified golden red pigment, and finally reacting it with polyvinyl acetate. The silica-naphthol derivative modified with terminal olefins is prepared according to the following steps: 1) Add nano-silica to a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2, soak for 24 - 48 h, then perform suction filtration. The obtained filter cake is washed 2 - 3 times with deionized water, and then dried under nitrogen protection to obtain surface-hydroxylated nano-silica. 2) Add 2-hydroxy-6-naphthoic acid and tert-butyldimethylchlorosilane to an organic solvent, then add imidazole, stir to dissolve, and react at 25 - 30 °C for 10 - 20 h. After the reaction is completed, the solvent is removed by reduced pressure distillation, water is added, and then extracted 2 - 3 times with dichloromethane. The obtained organic phase is distilled under reduced pressure to remove the solvent to obtain a hydroxy-protected naphthoic acid derivative. 3) Add the surface-hydroxylated nano-silica obtained in step 1) into an organic solvent, and then add the hydroxy-protected naphthoic acid derivative prepared in step 2), acrylic acid, 4-dimethylaminopyridine, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide thereto. React at 30~50 °C for 10~24 h. After the reaction is completed, perform suction filtration. The obtained filter cake is washed with acetone 2~3 times, then added into tetrahydrofuran. After stirring and mixing evenly, tetrabutylammonium fluoride is added, and the mixture is stirred and reacted at 25~30 °C for 5~10 h. After the reaction is completed, remove the solvent by distillation under reduced pressure. The obtained residue is extracted with dichloromethane and water. Finally, the obtained organic phase is distilled under reduced pressure to remove the solvent to obtain the terminal-olefin-modified silica-naphthol derivative.

[0006] In step 1), the mass ratio of the nano-silica to the concentrated sulfuric acid-hydrogen peroxide mixture is 1:5~10.

[0007] In step 2), the organic solvent is dichloromethane or tetrahydrofuran.

[0008] In step 2), the mass ratio of 2-hydroxy-6-naphthoic acid, tert-butyldimethylchlorosilane, organic solvent, imidazole, water, and dichloromethane is 1:0.8~1.2:5~10:0.4~0.6:8~15:8~15.

[0009] In step 3), the mass ratio of the surface-hydroxylated nano-silica, organic solvent, hydroxy-protected naphthoic acid derivative, acrylic acid, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, tetrahydrofuran, tetrabutylammonium fluoride, dichloromethane, and water is 1:30~60:8~15:1~3:5~12:8~19:20~40:6.5~13:20~40:20~40.

[0010] The preparation method of the organic pigment for the coating based on Golden Red includes the following steps: ① Add 2-amino-5-chloro-4-methylbenzenesulfonic acid, water, and hydrochloric acid with a mass concentration of 30% into a diazotization reactor. After stirring and dissolving, cool down to 0~10 °C, and then add an aqueous sodium nitrite solution with a mass concentration of 30% thereto. Perform diazotization reaction for 2~4 h to obtain a diazo solution; ② Add the terminal olefin-modified silica-naphthol derivative to ethanol. After stirring and mixing evenly, add it to a coupling reactor, and then dropwise add the diazo solution prepared in step ① thereto. Carry out a coupling reaction at 25-30 °C for 1-2 h. After the coupling reaction is completed, adjust the pH of the system to 7.5-8 with an aqueous sodium hydroxide solution with a mass concentration of 15-20%, stir and react for 20-30 min, then adjust the pH of the system to 1-1.5 with hydrochloric acid, stir and react for 20-30 min, add an aqueous barium chloride solution with a mass concentration of 30% thereto, stir for 20-30 min, then heat to 80-90 °C and react for 1.5-2 h, cool to 25-30 °C, filter, wash the obtained filter cake with water 3-5 times, and dry to obtain a terminal alkenyl-modified C.I. Pigment Red 57:1; ③ Add the terminal alkenyl-modified C.I. Pigment Red 57:1 prepared in step ② and polyvinyl acetate to ethyl acetate, stir and disperse evenly, then add azobisisobutyronitrile, heat to 60-80 °C and react for 5-10 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain an organic pigment for coatings based on C.I. Pigment Red 57:1.

[0011] In step ①, the mass ratio of 2-amino-5-chloro-4-methylbenzenesulfonic acid, water, hydrochloric acid, and aqueous sodium nitrite solution is 1:4.5-6:1-1.5:1.5-2.

[0012] In step ②, the mass ratio of the terminal olefin-modified silica-naphthol derivative, ethanol, and aqueous barium chloride solution to 2-amino-5-chloro-4-methylbenzenesulfonic acid in step ① is 0.5-0.7:5-8:2.4-3:1.

[0013] In step ③, the mass ratio of the terminal alkenyl-modified C.I. Pigment Red 57:1, polyvinyl acetate, ethyl acetate, and azobisisobutyronitrile is 1:0.4-0.8:10-15:0.002-0.02.

[0014] The present invention has the following advantages compared with the prior art: The organic pigment for coatings based on C.I. Pigment Red 57:1 of the present invention fixes the pigment on the silica skeleton by preparing a terminal olefin-modified silica-naphthol derivative, and then reacts with polyvinyl acetate to coat the polymer shell on the outer layer of the composite pigment through chemical bonds, preparing an organic-inorganic hybrid core-shell structure pigment. The steric hindrance effect of the polymer shell prevents the close contact and aggregation between pigment particles, improving the dispersion stability of the pigment; the organic-inorganic hybrid core-shell structure hinders the penetration of water molecules in the environment into the pigment interior, improving the moisture resistance of the pigment and increasing the long-term storage stability of the pigment.

[0015] The organic pigment for coatings based on golden red of the present invention fixes the pigment on the silica skeleton, and then coats the polymer shell layer on the outer layer of the composite pigment through chemical bonds, improving the migration resistance of the pigment; on the other hand, polyvinyl acetate reacts with the vinyl groups on the silica surface to form a cross-linked network, and the pigment is connected to the cross-linked polymer and silica through chemical bonds, reducing the solubility of the pigment in the solvent and improving its solvent resistance.

[0016] The organic pigment for coatings based on golden red of the present invention uses silica as a rigid core, bonds the pigment to its surface through chemical bonds, and finally grafts a polymer shell layer through chemical bonds to prepare an organic-inorganic hybrid core-shell structured pigment, significantly improving the dispersion stability, moisture resistance, migration resistance and solvent resistance of the pigment, and enhancing its application performance in coatings. Detailed implementation manners

[0017] To better understand the technical solution of the present invention, the above content of the present invention will be further described in detail through specific implementation manners in the form of examples below, but this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0018] Example 1 Preparation of silica-naphthol derivative modified with terminal olefins: 1) Add 1 kg of nano-silica into 5 kg of a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2, soak for 24 h, then filter by suction. The obtained filter cake is washed twice with deionized water and then dried under nitrogen protection to obtain surface-hydroxylated nano-silica. 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 0.8 kg of tert-butyldimethylchlorosilane into 5 kg of dichloromethane, then add 0.4 kg of imidazole, stir to dissolve, and react at 25 °C for 10 h. After the reaction is completed, the solvent is removed by vacuum distillation, 8 kg of water is added, and then 8 kg of dichloromethane is added for extraction twice. The obtained organic phase is subjected to vacuum distillation to remove the solvent to obtain a hydroxyl-protected naphthoic acid derivative. 3) Add 1 kg of surface-hydroxylated nano-silica into 30 kg of dichloromethane, then add 8 kg of hydroxyl-protected naphthoic acid derivative, 1 kg of acrylic acid, 5 kg of 4-dimethylaminopyridine, and 8 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide thereto. React at 30 °C for 24 h. After the reaction is completed, perform suction filtration. After the obtained filter cake is washed twice with acetone, add it into 20 kg of tetrahydrofuran. After stirring and mixing evenly, add 6.5 kg of tetrabutylammonium fluoride, and stir and react at 25 °C for 10 h. After the reaction is completed, remove the solvent by distillation under reduced pressure. Add 20 kg of dichloromethane and 20 kg of water to the obtained residue for extraction. Finally, remove the solvent from the obtained organic phase by distillation under reduced pressure to obtain terminal-alkene-modified silica-naphthol derivative.

[0019] Preparation of organic pigment for coatings based on Golden Red ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 4.5 kg of water, and 1 kg of hydrochloric acid with a mass concentration of 30% into a diazotization reactor. After stirring and dissolving, cool down to 0 °C, and then add 1.5 kg of sodium nitrite aqueous solution with a mass concentration of 30% thereto. Perform diazotization reaction for 2 h to obtain a diazo solution. ② Add 0.5 kg of terminal-alkene-modified silica-naphthol derivative into 5 kg of ethanol. After stirring and mixing evenly, add it into a coupling reactor. Then, dropwise add the diazo solution prepared in step ① thereto. Perform coupling reaction at 25 °C for 1 h. After the coupling reaction is completed, adjust the pH of the system to 7.5 with sodium hydroxide aqueous solution with a mass concentration of 15%, stir and react for 20 min, then adjust the pH of the system to 1 with hydrochloric acid, stir and react for 20 min. Add 2.4 kg of barium chloride aqueous solution with a mass concentration of 30% thereto, stir for 20 min, then heat to 80 °C and react for 1.5 h, cool down to 25 °C, filter, wash the obtained filter cake three times with water, and dry to obtain terminal-alkenyl-modified Golden Red pigment. ③ Add 1 kg of the terminal-alkenyl-modified Golden Red pigment prepared in step ② and 0.4 kg of polyvinyl acetate into 10 kg of ethyl acetate. Stir and disperse evenly, then add 0.002 kg of azobisisobutyronitrile, heat to 60 °C and react for 5 h. After the reaction is completed, remove the solvent by distillation under reduced pressure to obtain the organic pigment for coatings based on Golden Red.

[0020] Example 2 Preparation of terminal-alkene-modified silica-naphthol derivative: 1) Add 1 kg of nano-silica into 6 kg of a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2. After soaking for 30 h, perform suction filtration. Wash the obtained filter cake three times with deionized water, and then dry it under nitrogen protection to obtain surface-hydroxylated nano-silica. 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 0.9 kg of tert-butyldimethylchlorosilane to 6 kg of dichloromethane, then add 0.45 kg of imidazole. After stirring and dissolving, react at 26 °C for 12 h. After the reaction is completed, remove the solvent by vacuum distillation. Add 10 kg of water, then add 11 kg of dichloromethane for extraction three times. Remove the solvent from the obtained organic phase by vacuum distillation to obtain a hydroxy-protected naphthoic acid derivative; 3) Add 1 kg of surface-hydroxylated nano-silica to 35 kg of tetrahydrofuran, then add 9 kg of the hydroxy-protected naphthoic acid derivative, 1.5 kg of acrylic acid, 6.5 kg of 4-dimethylaminopyridine, and 10 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide thereto. React at 35 °C for 20 h. After the reaction is completed, perform suction filtration. The obtained filter cake is washed three times with acetone, then added to 25 kg of tetrahydrofuran. After stirring and mixing evenly, add 7.5 kg of tetrabutylammonium fluoride. Stir and react at 26 °C for 8 h. After the reaction is completed, remove the solvent by vacuum distillation. The obtained residue is extracted with 25 kg of dichloromethane and 25 kg of water. Finally, remove the solvent from the obtained organic phase by vacuum distillation to obtain an end-olefin-modified silica-naphthol derivative.

[0021] Preparation of organic pigment for coatings based on Golden Red ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 5 kg of water, and 1.1 kg of hydrochloric acid with a mass concentration of 30% to a diazotization reactor. After stirring and dissolving, cool down to 5 °C, then add 1.6 kg of an aqueous sodium nitrite solution with a mass concentration of 30% thereto. Perform diazotization reaction for 2.5 h to obtain a diazo solution; ② Add 0.55 kg of the end-olefin-modified silica-naphthol derivative to 5.5 kg of ethanol. After stirring and mixing evenly, add it to a coupling reactor, then dropwise add the diazo solution prepared in step ① thereto. Perform coupling reaction at 27 °C for 1.5 h. After the coupling reaction is completed, adjust the pH of the system to 8 with an aqueous sodium hydroxide solution with a mass concentration of 15%. Stir and react for 25 min, then adjust the pH of the system to 1.5 with hydrochloric acid. Stir and react for 25 min. Add 2.6 kg of an aqueous barium chloride solution with a mass concentration of 30% thereto. After stirring for 25 min, heat to 85 °C and react for 1.6 h, then cool down to 26 °C. Filter, and wash the obtained filter cake five times with water and dry it to obtain an end-alkenyl-modified Golden Red pigment; ③ Add 1 kg of the end-alkenyl-modified Golden Red pigment prepared in step ② and 0.5 kg of polyvinyl acetate to 11 kg of ethyl acetate. Stir and disperse evenly, then add 0.005 kg of azobisisobutyronitrile. Heat to 65 °C and react for 9 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain an organic pigment for coatings based on Golden Red.

[0022] Example 3 Preparation of Terminal Olefin-Modified Silica-Naphthol Derivative: 1) Add 1 kg of nano-silica into 8 kg of a sulfuric acid-hydrogen peroxide mixture with a volume ratio of 1:2. After soaking for 35 h, perform suction filtration. The obtained filter cake is washed 3 times with deionized water and then dried under nitrogen protection to obtain surface-hydroxylated nano-silica. 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 1 kg of tert-butyldimethylchlorosilane into 7.5 kg of tetrahydrofuran, then add 0.5 kg of imidazole. After stirring and dissolving, react at 28 °C for 15 h. After the reaction ends, remove the solvent by reduced pressure distillation. Add 11 kg of water, then add 13 kg of dichloromethane for extraction 3 times. The obtained organic phase is distilled under reduced pressure to remove the solvent to obtain a hydroxy-protected naphthoic acid derivative. 3) Add 1 kg of surface-hydroxylated nano-silica into 45 kg of dichloromethane, then add 12 kg of the hydroxy-protected naphthoic acid derivative, 2.2 kg of acrylic acid, 8 kg of 4-dimethylaminopyridine, and 14 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. React at 40 °C for 18 h. After the reaction ends, perform suction filtration. The obtained filter cake is washed 3 times with acetone and then added into 30 kg of tetrahydrofuran. After stirring and mixing evenly, add 9.5 kg of tetrabutylammonium fluoride and stir and react at 28 °C for 7 h. After the reaction ends, remove the solvent by reduced pressure distillation. The obtained residue is added with 30 kg of dichloromethane and 30 kg of water for extraction. Finally, the obtained organic phase is distilled under reduced pressure to remove the solvent to obtain a terminal olefin-modified silica-naphthol derivative.

[0023] Preparation of Organic Pigment for Coating Based on Golden Red ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 5.5 kg of water, and 1.3 kg of hydrochloric acid with a mass concentration of 30% into a diazotization reactor. After stirring and dissolving, cool down to 8 °C, and then add 1.8 kg of an aqueous sodium nitrite solution with a mass concentration of 30%. Perform diazotization reaction for 2.5 h to obtain a diazo solution. ② Add 0.62 kg of the terminal olefin-modified silica-naphthol derivative into 6.5 kg of ethanol. After stirring and mixing evenly, add it into a coupling reactor, and then dropwise add the diazo solution prepared in step ①. Perform coupling reaction at 28 °C for 1.8 h. After the coupling reaction is completed, adjust the pH of the system to 7.5 with an aqueous sodium hydroxide solution with a mass concentration of 15%, stir and react for 25 min, then adjust the pH of the system to 1.5 with hydrochloric acid, stir and react for 25 min. Add 2.8 kg of an aqueous barium chloride solution with a mass concentration of 30%, stir for 25 min, heat to 85 °C and react for 1.8 h, then cool down to 28 °C, filter. The obtained filter cake is washed 5 times with water and dried to obtain a terminal alkenyl-modified golden red pigment. ③ Add 1 kg of the terminal olefin-modified C.I. Pigment Red 57:1 prepared in step ② and 0.6 kg of polyvinyl acetate to 13 kg of ethyl acetate, stir and disperse evenly, then add 0.01 kg of azobisisobutyronitrile, heat to 70 °C and react for 8 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain an organic pigment for coatings based on C.I. Pigment Red 57:1.

[0024] Example 4 Preparation of terminal olefin-modified silica-naphthol derivatives: 1) Add 1 kg of nano-silica to 9 kg of a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2, soak for 40 h, then filter by suction. The obtained filter cake is washed 3 times with deionized water and then dried under nitrogen protection to obtain surface-hydroxylated nano-silica. 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 1.1 kg of tert-butyldimethylchlorosilane to 8.5 kg of tetrahydrofuran, then add 0.52 kg of imidazole, stir to dissolve, and react at 29 °C for 17 h. After the reaction is completed, remove the solvent by vacuum distillation, add 12 kg of water, then add 13 kg of dichloromethane and extract 3 times. The obtained organic phase is distilled under reduced pressure to remove the solvent to obtain a hydroxyl-protected naphthoic acid derivative. 3) Add 1 kg of surface-hydroxylated nano-silica to 50 kg of tetrahydrofuran, then add 13 kg of the hydroxyl-protected naphthoic acid derivative, 2.5 kg of acrylic acid, 10 kg of 4-dimethylaminopyridine, and 16 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and react at 40 °C for 15 h. After the reaction is completed, filter by suction. The obtained filter cake is washed 3 times with acetone and then added to 33 kg of tetrahydrofuran, stirred and mixed evenly, then add 10 kg of tetrabutylammonium fluoride, and stir and react at 26 °C for 8 h. After the reaction is completed, remove the solvent by vacuum distillation. The obtained residue is added to 32 kg of dichloromethane and 35 kg of water for extraction. Finally, the obtained organic phase is distilled under reduced pressure to remove the solvent to obtain terminal olefin-modified silica-naphthol derivatives.

[0025] Preparation of an organic pigment for coatings based on C.I. Pigment Red 57:1: ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 5.6 kg of water, and 1.4 kg of hydrochloric acid with a mass concentration of 30% to a diazotization reactor, stir and dissolve, cool to 5 °C, and then add 1.7 kg of an aqueous sodium nitrite solution with a mass concentration of 30%. Carry out diazotization reaction for 2.5 h to obtain a diazo solution. ② Add 0.65 kg of the terminal olefin-modified silica-naphthol derivative to 7 kg of ethanol. After stirring and mixing evenly, add it to a coupling reactor, and then dropwise add the diazo solution prepared in step ①. Carry out a coupling reaction at 29 °C for 1.8 h. After the coupling reaction is completed, adjust the pH of the system to 8 with a 15% sodium hydroxide aqueous solution, stir and react for 28 min, then adjust the pH of the system to 1 with hydrochloric acid, stir and react for 25 min. Add 2.8 kg of a 30% barium chloride aqueous solution thereto, stir for 30 min, heat to 85 °C and react for 1.5 h, then cool to 28 °C, filter, wash the obtained filter cake with water 4 times, and dry to obtain the terminal alkenyl-modified C.I. Pigment Red 57:1; ③ Add 1 kg of the terminal alkenyl-modified C.I. Pigment Red 57:1 prepared in step ② and 0.7 kg of polyvinyl acetate to 14 kg of ethyl acetate, stir and disperse evenly, then add 0.012 kg of azobisisobutyronitrile, heat to 75 °C and react for 6 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain the organic pigment for coatings based on C.I. Pigment Red 57:1.

[0026] Example 5 Preparation of the terminal olefin-modified silica-naphthol derivative: 1) Add 1 kg of nano-silica to 10 kg of a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2. After soaking for 45 h, carry out suction filtration. Wash the obtained filter cake with deionized water 3 times, and then dry it under nitrogen protection to obtain surface-hydroxylated nano-silica; 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 1.2 kg of tert-butyldimethylchlorosilane to 9 kg of dichloromethane, then add 0.55 kg of imidazole, stir to dissolve, and react at 30 °C for 20 h. After the reaction is completed, remove the solvent by vacuum distillation, add 13 kg of water, and then extract with 15 kg of dichloromethane 3 times. Remove the solvent from the obtained organic phase by vacuum distillation to obtain the hydroxy-protected naphthoic acid derivative; 3) Add 1 kg of surface-hydroxylated nano-silica to 55 kg of tetrahydrofuran, then add 14 kg of the hydroxy-protected naphthoic acid derivative, 2.8 kg of acrylic acid, 11 kg of 4-dimethylaminopyridine, and 18 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide thereto, and react at 45 °C for 13 h. After the reaction is completed, carry out suction filtration. Wash the obtained filter cake with acetone 3 times, then add it to 36 kg of tetrahydrofuran, stir and mix evenly, then add 12 kg of tetrabutylammonium fluoride, stir and react at 28 °C for 6 h. After the reaction is completed, remove the solvent by vacuum distillation. Add 35 kg of dichloromethane and 38 kg of water to the obtained residue for extraction. Finally, remove the solvent from the obtained organic phase by vacuum distillation to obtain the terminal olefin-modified silica-naphthol derivative.

[0027] Preparation of the organic pigment for coatings based on C.I. Pigment Red 57:1: ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 5.8 kg of water, and 1.4 kg of hydrochloric acid with a mass concentration of 30% to a diazotization reactor. After stirring and dissolving, cool the temperature to 10 °C, and then add 1.8 kg of an aqueous sodium nitrite solution with a mass concentration of 30%. Conduct diazotization reaction for 3.5 h to obtain a diazo solution; ② Add 0.68 kg of the terminal olefin-modified silica-naphthol derivative to 7.5 kg of ethanol. After stirring and mixing evenly, add it to a coupling reactor, and then dropwise add the diazo solution prepared in step ① thereto. Conduct coupling reaction at 30 °C for 2 h. After the coupling reaction is completed, adjust the pH of the system to 7.8 with an aqueous sodium hydroxide solution with a mass concentration of 15%, stir and react for 30 min, then adjust the pH of the system to 1.2 with hydrochloric acid, stir and react for 30 min. Add 2.9 kg of an aqueous barium chloride solution with a mass concentration of 30%, stir for 30 min, then heat to 88 °C and react for 1.5 h, then cool to 30 °C, filter, wash the obtained filter cake with water 5 times, and dry to obtain a terminal alkenyl-modified Golden Red pigment; ③ Add 1 kg of the terminal alkenyl-modified Golden Red pigment prepared in step ② and 0.75 kg of polyvinyl acetate to 14 kg of ethyl acetate, stir and disperse evenly, then add 0.015 kg of azobisisobutyronitrile, heat to 78 °C and react for 6 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain an organic pigment for coatings based on Golden Red.

[0028] Example 6 Preparation of the terminal olefin-modified silica-naphthol derivative: 1) Add 1 kg of nano-silica to a mixed solution of 10 kg of concentrated sulfuric acid-hydrogen peroxide with a volume ratio of 1:2. After soaking for 48 h, conduct suction filtration. Wash the obtained filter cake with deionized water 3 times, and then dry it under nitrogen protection to obtain surface-hydroxylated nano-silica; 2) Add 1 kg of 2-hydroxy-6-naphthoic acid and 1 kg of tert-butyldimethylchlorosilane to 10 kg of dichloromethane, then add 0.6 kg of imidazole. After stirring and dissolving, react at 30 °C for 10 h. After the reaction is completed, remove the solvent by vacuum distillation, add 15 kg of water, and then extract 3 times with 15 kg of dichloromethane. Remove the solvent from the obtained organic phase by vacuum distillation to obtain a hydroxyl-protected naphthoic acid derivative; 3) Add 1 kg of surface-hydroxylated nano-silica into 60 kg of tetrahydrofuran, then add 15 kg of hydroxyl-protected naphthoic acid derivative, 3 kg of acrylic acid, 12 kg of 4-dimethylaminopyridine, and 19 kg of 1-ethyl-(3-dimethylaminopropyl) carbodiimide thereto, react at 50 °C for 10 h. After the reaction is completed, perform suction filtration. After the obtained filter cake is washed 3 times with acetone, add it into 40 kg of tetrahydrofuran, stir and mix evenly, then add 13 kg of tetrabutylammonium fluoride, stir and react at 30 °C for 5 h. After the reaction is completed, remove the solvent by distillation under reduced pressure. Add 40 kg of dichloromethane and 40 kg of water to the obtained residue for extraction. Finally, remove the solvent from the obtained organic phase by distillation under reduced pressure to obtain an olefin-terminated silica-naphthol derivative.

[0029] Preparation of organic pigment for coatings based on Golden Red ① Add 1 kg of 2-amino-5-chloro-4-methylbenzenesulfonic acid, 6 kg of water, and 1.5 kg of hydrochloric acid with a mass concentration of 30% into a diazotization reactor, stir to dissolve, cool down to 10 °C, then add 2 kg of sodium nitrite aqueous solution with a mass concentration of 30% thereto, and perform diazotization reaction for 4 h to obtain a diazo solution. ② Add 0.7 kg of olefin-terminated silica-naphthol derivative into 8 kg of ethanol, stir and mix evenly, then add it into a coupling reactor, and then dropwise add the diazo solution prepared in step ① thereto. Perform coupling reaction at 30 °C for 1 h. After the coupling reaction is completed, adjust the pH of the system to 8 with a sodium hydroxide aqueous solution with a mass concentration of 15%, stir and react for 25 min, then adjust the pH of the system to 1 with hydrochloric acid, stir and react for 30 min. Add 3 kg of barium chloride aqueous solution with a mass concentration of 30% thereto, stir for 30 min, then heat to 90 °C and react for 2 h, then cool down to 30 °C, filter. Wash the obtained filter cake 5 times with water and dry it to obtain an olefin-terminated modified Golden Red pigment. ③ Add 1 kg of the olefin-terminated modified Golden Red pigment prepared in step ② and 0.8 kg of polyvinyl acetate into 15 kg of ethyl acetate, stir and disperse evenly, then add 0.02 kg of azobisisobutyronitrile, heat to 80 °C and react for 10 h. After the reaction is completed, remove the solvent by distillation under reduced pressure to obtain an organic pigment for coatings based on Golden Red.

[0030] The organic pigments for coatings based on Golden Red prepared in Examples 1 - 6 were respectively subjected to performance tests. Among them, the lightfastness was detected according to the method in Standard GB1710 - 79; the water resistance, acid resistance, and alkali resistance were detected according to the method in GB 5211.5 - 2008 - T, the oil absorption was detected according to the method in GB / T 5211.15 - 2014, the heat resistance was detected according to the method in HG / T3853 - 2006, and the solvent resistance was detected according to the method in GB / T 23989 - 2009 (Method A, ethanol wiping). For the comparative example, Golden Red C (P.R.53:1) for coatings of the company's product was used. The test results are shown in Table 1. It can be seen from the results in Table 1 that the organic pigments for coatings based on Golden Red prepared in the present invention have strong lightfastness, water resistance, acid and alkali resistance, heat resistance, and solvent resistance.

[0031] Table 1 Performance test results of the pigments prepared in Examples 1 - 6

[0032] By weight, the organic pigments for coatings based on Golden Red prepared in Examples 1 - 6 and 1 part of the comparative - example pigment, 4 parts of alkyd resin, and 5 parts of xylene were mixed evenly. After stirring at 2000 r / min for 30 min, the obtained color paste was coated on a glass plate. After drying, a pigment test plate was obtained. The obtained pigment test plate was covered on a white substrate (with the pigment side facing down). After closely fitting and placing it at 80°C under a pressure of 1 kg / cm 2 for 24 h, the degree of soiling of the white substrate was observed and judged with a standard gray scale. Among them, grade 5 indicates no migration, and grade 1 indicates serious migration. The test results are shown in Table 2. It can be seen from the results in Table 2 that the organic pigments for coatings based on Golden Red prepared in the present invention have higher migration resistance compared with the comparative example.

[0033] Table 2 Results table of the migration resistance of the pigments prepared in Examples 1 - 6

[0034] Although the specific implementation manners 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 efforts are still within the protection scope of the present invention.

Claims

1. A preparation method of an organic pigment for coatings based on golden red, characterized in that: First, 2-amino-5-chloro-4-methylbenzenesulfonic acid is diazotized and then coupled with a silica-naphthol derivative modified with terminal olefins. Then, an aqueous barium chloride solution is added for lake formation to obtain a terminal alkenyl-modified Golden Red pigment. Finally, it is reacted with polyvinyl acetate to prepare the product; The silica-naphthol derivative modified with terminal olefins is prepared according to the following steps: 1) Nano-silica is added to a sulfuric acid-hydrogen peroxide mixed solution with a volume ratio of 1:2, soaked for 24 to 48 h, then filtered by suction. The obtained filter cake is washed 2 to 3 times with deionized water and then dried under nitrogen protection to obtain surface-hydroxylated nano-silica; 2) 2-Hydroxy-6-naphthoic acid and tert-butyldimethylchlorosilane are added to an organic solvent, and then imidazole is added. After stirring and dissolving, the reaction is carried out at 25 to 30 °C for 10 to 20 h. After the reaction is completed, the solvent is removed by vacuum distillation. Water is added, and then dichloromethane is added for extraction 2 to 3 times. The obtained organic phase is subjected to vacuum distillation to remove the solvent to obtain a hydroxy-protected naphthoic acid derivative; 3) The surface-hydroxylated nano-silica obtained in step 1) is added to an organic solvent, and then the hydroxy-protected naphthoic acid derivative, acrylic acid, 4-dimethylaminopyridine, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide prepared in step 2) are added thereto. The reaction is carried out at 30 to 50 °C for 10 to 24 h. After the reaction is completed, filtration by suction is carried out. The obtained filter cake is washed 2 to 3 times with acetone and then added to tetrahydrofuran. After stirring and mixing evenly, tetrabutylammonium fluoride is added, and the reaction is stirred at 25 to 30 °C for 5 to 10 h. After the reaction is completed, the solvent is removed by vacuum distillation. The obtained residue is extracted with dichloromethane and water. Finally, the obtained organic phase is subjected to vacuum distillation to remove the solvent to obtain a silica-naphthol derivative modified with terminal olefins.

2. The preparation method of the organic pigment for coatings based on C.I. Pigment Red 57:1 as claimed in claim 1, wherein: In step 1), the mass ratio of the nano-silica to the sulfuric acid-hydrogen peroxide mixed solution is 1:5 to 10.

3. The preparation method of the organic pigment for coatings based on golden red as claimed in claim 1, characterized in that: In step 2), the organic solvent is dichloromethane or tetrahydrofuran.

4. The preparation method of the organic pigment for coatings based on golden red as claimed in claim 1, characterized in that: In step 2), the mass ratio of 2-hydroxy-6-naphthoic acid, tert-butyldimethylchlorosilane, organic solvent, imidazole, water, and dichloromethane is 1:0.8 to 1.2:5 to 10:0.4 to 0.6:8 to 15:8 to 15.

5. The preparation method of the organic pigment for coatings based on golden red as claimed in claim 1, characterized in that: In step 3), the mass ratio of the surface-hydroxylated nano-silica, organic solvent, hydroxy-protected naphthoic acid derivative, acrylic acid, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, tetrahydrofuran, tetrabutylammonium fluoride, dichloromethane, and water is 1:30 to 60:8 to 15:1 to 3:5 to 12:8 to 19:20 to 40:6.5 to 13:20 to 40:20 to 40.

6. The preparation method of the organic pigment for coatings based on C.I. Pigment Red 57:1 as claimed in claim 1, wherein: It includes the following steps: ① 2-Amino-5-chloro-4-methylbenzenesulfonic acid, water, and hydrochloric acid with a mass concentration of 30% are added to a diazotization reactor. After stirring and dissolving, the temperature is lowered to 0 to 10 °C, and then an aqueous sodium nitrite solution with a mass concentration of 30% is added thereto. The diazotization reaction is carried out for 2 to 4 h to obtain a diazo solution; ② Add the terminal olefin-modified silica-naphthol derivative to ethanol. After stirring and mixing evenly, add it to a coupling reactor. Then, dropwise add the diazonium solution prepared in step ① into it. Conduct a coupling reaction at 25-30 °C for 1-2 h. After the coupling reaction is completed, adjust the pH of the system to 7.5-8 with an aqueous sodium hydroxide solution with a mass concentration of 15-20%. Stir and react for 20-30 min. Then, adjust the pH of the system to 1-1.5 with hydrochloric acid. Stir and react for 20-30 min. Add an aqueous barium chloride solution with a mass concentration of 30% into it. After stirring for 20-30 min, heat to 80-90 °C and react for 1.5-2 h. Then, cool down to 25-30 °C, filter. Wash the obtained filter cake with water 3-5 times and dry it to obtain a terminal alkenyl-modified golden red pigment. ③ Add the terminal alkenyl-modified golden red pigment prepared in step ② and polyvinyl acetate to ethyl acetate. Stir and disperse evenly. Then, add azobisisobutyronitrile. Heat to 60-80 °C and react for 5-10 h. After the reaction is completed, remove the solvent by vacuum distillation to obtain an organic pigment for coatings based on golden red.

7. The preparation method of the organic pigment for coatings based on C.I. Pigment Red 57:1 as claimed in claim 6, wherein: In step ①, the mass ratio of 2-amino-5-chloro-4-methylbenzenesulfonic acid, water, hydrochloric acid, and aqueous sodium nitrite solution is 1:4.5-6:1-1.5:1.5-2.

8. The preparation method of the organic pigment for coatings based on C.I. Pigment Red 57:1 as claimed in claim 6, wherein: In step ②, the mass ratio of the terminal olefin-modified silica-naphthol derivative, ethanol, and aqueous barium chloride solution to 2-amino-5-chloro-4-methylbenzenesulfonic acid in step ① is 0.5-0.7:5-8:2.4-3:

1.

9. The preparation method of the organic pigment for coatings based on golden red as claimed in claim 6, characterized in that: In step ③, the mass ratio of the terminal alkenyl-modified golden red pigment, polyvinyl acetate, ethyl acetate, and azobisisobutyronitrile is 1:0.4-0.8:10-15:0.002-0.02.

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