A high-thermal-stability permanent orange pigment for coating and a preparation method thereof

Abstract

The application discloses a high-thermal-stability permanent orange pigment for coating and a preparation method thereof, and belongs to the technical field of pigment synthesis. The permanent orange pigment is composed of 3-5 parts of a folded polymer and 70-100 parts of permanent orange G, wherein the folded polymer is formed by alternately connecting 4,6-di(long ether oxygen) isophthaloyl chloride and 2,7-diaminonaphthalene through an amide bond. The prepared high-thermal-stability permanent orange pigment for coating provides a thermal protection layer for the permanent orange G pigment, improves the thermal stability, significantly improves the dispersibility and durability of the pigment, and expands the application of the pigment in the fields of plastic processing, high-temperature baking coating and engineering plastics with high heat resistance requirements.

Description

Technical Field

[0001] This invention belongs to the field of pigment synthesis technology, specifically a permanent orange pigment for high thermal stability coatings and its preparation method. Background Technology

[0002] Permanent Orange G is a high-performance diazo organic pigment prepared by coupling 3,3'-dichlorobenzidine diazonium salt with 1-phenyl-3-methyl-5-pyrazolone under alkaline conditions. It is widely used in the ink, coating, and plastics industries. This pigment boasts vibrant color, high tinting strength, and excellent lightfastness, water resistance, and acid and alkali resistance. Therefore, it is widely used to replace or partially replace expensive inorganic pigments such as molybdenum chromium red, achieving an optimal balance between color and cost.

[0003] However, the diazo structure of Permanent Orange G is prone to chemical bond breakage at high temperatures, leading to molecular degradation and resulting in a lighter, darker, or even completely faded pigment color. Simultaneously, the pigment produces aromatic amines during high-temperature thermal decomposition, with 3,3'-dichlorobenzidine further forming at temperatures exceeding 240°C. These decomposition products exhibit strong migration properties, easily causing bleeding or blooming in the application medium, severely impacting the coloring effect and quality of the final product. These deficiencies in thermal stability significantly limit the large-scale application of Permanent Orange G in fields requiring high heat resistance, such as plastic processing, high-temperature baking coatings, and engineering plastics. Therefore, improving the thermal stability of Permanent Orange G while maintaining its excellent performance has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a permanent orange pigment for high thermal stability coatings and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A high thermal stability coating permanent orange pigment, by weight, is composed of 3-5 parts of folded polymer and 70-100 parts of permanent orange G; The folded polymer is composed of 4,6-bis(long etheroxy) isophthaloyl chloride and 2,7-diaminonaphthalene linked by alternating amide bonds.

[0006] The folded polymer was prepared according to the following method: 1) 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to organic solvent 1, followed by iodomethane and base 1. The reaction was carried out at 25-60°C for 12-24 h, quenched with water, and the organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with organic solvent 2. The organic phase was then removed by vacuum distillation to obtain compound 1. 2) Add dimethyl 4,6-dihydroxyisophthalate and compound 1 prepared in step 1) to organic solvent 3, stir to dissolve, then add base 2, heat under reflux for 6-12 h, filter the resulting reaction solution, remove the solvent by vacuum distillation of the filtrate, wash the residue with water 3-5 times, and dry to obtain compound 2. 3) Add compound 2 prepared in step 2) to organic solvent 4, stir and mix evenly, then add base 3, and react at 25~40℃ for 6~12h. After the reaction is complete, filter, remove the solvent from the filtrate by vacuum distillation, wash the residue with water 3~5 times, dry, add the product to organic solvent 5, stir and dissolve, then add thionyl chloride and dimethylformamide, and react at 25~40℃ for 12~24h. Remove the solvent by vacuum distillation to obtain compound 3. 4) Add the compound 3 and 2,7-diaminonaphthalene prepared in step 3) to organic solvent 6, stir to dissolve, then add alkali 4, react at 25~40℃ for 24~48h, after the reaction is complete, filter, add the filtrate to organic solvent 4, let stand for 24~48h, filter, wash the filter cake with water 3~5 times, dry, and obtain the folded polymer.

[0007] The organic solvent 1 mentioned in step 1) is tetrahydrofuran, acetone, acetonitrile or dimethylformamide, and the water content of the organic solvent 1 is less than 10 ppm.

[0008] The alkali 1 mentioned in step 1) is sodium hydride, sodium methoxide, sodium ethoxide or sodium tert-butoxide.

[0009] The organic solvent 2 mentioned in step 1) is dichloromethane, ethyl acetate, or diethyl ether.

[0010] In step 1), the mass ratio of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate, organic solvent 1, iodomethane, alkali 1, water, and organic solvent 2 is 1:5~10:0.25~0.4:0.25~0.5:3~5:5~10.

[0011] The organic solvent 3 mentioned in step 2) is acetonitrile, acetone or dimethylformamide.

[0012] The alkali 2 mentioned in step 2) is sodium carbonate or potassium carbonate.

[0013] In step 2), the mass ratio of dimethyl 4,6-dihydroxyisophthalate, compound 1, organic solvent 3, and base 2 is 1:5~8:15~20:1.5~2.5.

[0014] The organic solvent 4 mentioned in step 3) is methanol or ethanol.

[0015] The alkali 3 mentioned in step 3) is sodium hydroxide or potassium hydroxide.

[0016] In step 3), the organic solvent 5 is dichloromethane or tetrahydrofuran; the water content of the organic solvent 5 is less than 10 ppm.

[0017] The mass ratio of compound 2, organic solvent 4, base 3, organic solvent 5, thionyl chloride and dimethylformamide in step 3) is 1:5~10:0.1~0.2:5~10:0.5~1:0.004~0.007.

[0018] The organic solvent 6 mentioned in step 4) is dichloromethane, tetrahydrofuran, acetonitrile, or acetone.

[0019] The base 4 mentioned in step 4) is triethylamine or diisopropylmethylamine.

[0020] In step 4), the mass ratio of compound 3, 2,7-diaminonaphthalene, organic solvent 6, base 4 and organic solvent 4 is 1:0.15~0.2:5~10:0.2~0.4:20~30.

[0021] The preparation method of the permanent orange pigment for the high thermal stability coating includes the following steps: By weight, 3-5 parts of the folded polymer are suspended in 150-300 parts of organic solvent 4, and then 70-100 parts of permanent orange G are added. The mixture is ultrasonically dispersed for 20-30 minutes, stirred at 25-30°C for 24-48 hours, filtered, and the resulting filter cake is dried to obtain permanent orange pigment for high thermal stability coatings.

[0022] The present invention has the following advantages over the prior art: The high thermal stability permanent orange pigment for coatings of this invention is first prepared by amidation polycondensation reaction of 4,6-bis(long etheroxy) isophthaloyl chloride and 2,7-diaminonaphthalene to obtain a folded polymer with a helical folded conformation. The main chain of the folded polymer is an aromatic polyamide backbone, with benzene and naphthalene rings providing a rigid structure, significantly increasing the thermal decomposition temperature of the main chain; amide bonds can form intramolecular hydrogen bonds, and the π-π stacking interaction between aromatic rings and hydrogen bonds synergistically drive the polymer chain to spontaneously fold into an ordered helical conformation. The long ether chains of the side chains prevent aggregation between the folded polymer chains, while simultaneously forming a nanoporous structure with controllable size inside the folded polymer.

[0023] The amide groups on the main chain of the folded polymer prepared in this invention form strong hydrogen bonds with the hydroxyl and amino groups on the pigment surface, achieving tight coating of the pigment. The nanopores inside the folded polymer encapsulate pigment molecules through physical adsorption, adsorbing pigment particles into the pores. Compared with simple coating, the nanopore structure of the folded polymer of this invention provides stronger physical isolation and adsorption stabilization, thereby effectively isolating oxygen and heat, inhibiting oxidative decomposition and azo group breakage under high temperature conditions. The long ether chains of the side chains extend outward to form a steric hindrance layer, further hindering the aggregation of pigment particles and delaying the escape of thermal decomposition products.

[0024] The permanent orange pigment for high thermal stability coatings prepared by this invention provides a thermal protective layer for the permanent orange G pigment through a folded polymer. While improving thermal stability, it also significantly improves the pigment's dispersibility and durability, expanding the pigment's application in fields such as plastic processing, high-temperature baking coatings, and engineering plastics where high heat resistance is required. Detailed Implementation

[0025] To better understand the technical solution of the present invention, the following detailed embodiments further illustrate the above-mentioned content of the present invention. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0026] Example 1: Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 0.5 kg of tetrahydrofuran with a water content of less than 10 ppm, followed by 0.025 kg of iodomethane and 0.025 kg of sodium hydride. The reaction was carried out at 25 °C for 12 h, then quenched with 0.3 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 0.5 kg of dichloromethane. The organic phase was then removed by vacuum distillation to obtain compound 1. 1 H NMR (300 MHz, DMSO-) d 6 , 298 K) δ 7.75 (d, 2H), 7.40 (d, 2H), 3.73 (t, 2H), 3.40-3.55 (m, 37H), 2.41 (s, 3H).

[0027] 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.5 kg of compound 1 were added to 1.5 kg of acetonitrile, stirred and dissolved, and then 0.15 kg of sodium carbonate was added. The mixture was heated under reflux for 6 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed three times with water and dried to obtain compound 2. 1 H NMR (300 MHz, DMSO-) d 6 , 298K) δ 8.01 (s, 1H), 6.93 (s, 1H), 4.30 (t, 4H), 3.93 (s, 6H), 3.71 (t, 4H), 3.40-3.57 (m, 70H).

[0028] 0.1 kg of compound 2 was added to 0.5 kg of methanol and stirred until homogeneous. Then, 0.01 kg of sodium hydroxide was added, and the mixture was reacted at 25 °C for 6 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed three times with water and dried. The product was added to 0.5 kg of dichloromethane with a water content of less than 10 ppm and stirred until dissolved. Then, 0.05 kg of thionyl chloride and 0.0004 kg of dimethylformamide were added, and the mixture was reacted at 25 °C for 12 h. The solvent was removed by vacuum distillation to obtain compound 3. 1 H NMR (300 MHz, DMSO-) d 6 , 298 K) δ 8.20 (s, 1H), 6.95 (s, 1H), 4.32 (t, 4H), 3.73(t, 4H), 3.37-3.55 (m, 70H).

[0029] 0.1 kg of compound 3 and 0.015 kg of 2,7-diaminonaphthalene were added to 0.5 kg of dichloromethane and stirred until dissolved. Then, 0.02 kg of triethylamine was added and the mixture was reacted at 25 °C for 24 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 2 kg of methanol and allowed to stand for 24 h. The mixture was then filtered again. The resulting filter cake was washed three times with water and dried to obtain the folded polymer.

[0030] Preparation of permanent orange pigment for high thermal stability coatings: 0.3 kg of the folded polymer was suspended in 15 kg of methanol, and then 7 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 20 min, stirred at 25 °C for 24 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0031] Example 2: Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 0.6 kg of acetone with a water content of less than 10 ppm, followed by the addition of 0.029 kg of iodomethane and 0.03 kg of sodium methoxide. The reaction was carried out at 35 °C for 14 h, and then quenched by the addition of 0.35 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 0.6 kg of ethyl acetate. The organic phase was then removed by vacuum distillation to obtain compound 1. 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.55 kg of compound 1 were added to 1.6 kg of acetone and stirred to dissolve. Then, 0.17 kg of sodium carbonate was added and the mixture was heated under reflux for 7 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water four times and dried to obtain compound 2. 0.1 kg of compound 2 was added to 0.6 kg of ethanol and stirred until homogeneous. Then, 0.012 kg of potassium hydroxide was added, and the mixture was reacted at 30 °C for 7 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water four times and dried. The product was added to 0.6 kg of tetrahydrofuran with a water content of less than 10 ppm and stirred until dissolved. Then, 0.06 kg of thionyl chloride and 0.0005 kg of dimethylformamide were added, and the mixture was reacted at 30 °C for 15 h. The solvent was removed by vacuum distillation to obtain compound 3. 0.1 kg of compound 3 and 0.016 kg of 2,7-diaminonaphthalene were added to 0.6 kg of tetrahydrofuran and stirred until dissolved. Then, 0.024 kg of triethylamine was added and the mixture was reacted at 28 °C for 30 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 2.2 kg of ethanol and allowed to stand for 30 h. The mixture was then filtered again. The resulting filter cake was washed with water four times and dried to obtain the folded polymer.

[0032] Preparation of permanent orange pigment for high thermal stability coatings: 0.35 kg of the folded polymer was suspended in 20 kg of ethanol, and then 7.5 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 23 min, stirred at 26 °C for 30 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0033] Example 3: Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 0.7 kg of dimethylformamide with a water content of less than 10 ppm, followed by 0.033 kg of iodomethane and 0.035 kg of sodium ethoxide. The reaction was carried out at 45 °C for 17 h, then quenched with 0.4 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 0.7 kg of diethyl ether. The organic phase was then removed by vacuum distillation to obtain compound 1. 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.6 kg of compound 1 were added to 1.7 kg of acetonitrile, stirred and dissolved, and then 0.18 kg of sodium carbonate was added. The mixture was heated under reflux for 8 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water 4 times and dried to obtain compound 2. 0.1 kg of compound 2 was added to 0.7 kg of ethanol and stirred until homogeneous. Then, 0.015 kg of sodium hydroxide was added, and the mixture was reacted at 35 °C for 8 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water five times and dried. The product was added to 0.7 kg of dichloromethane with a water content of less than 10 ppm and stirred until dissolved. Then, 0.07 kg of thionyl chloride and 0.0006 kg of dimethylformamide were added, and the mixture was reacted at 32 °C for 17 h. The solvent was removed by vacuum distillation to obtain compound 3. 0.1 kg of compound 3 and 0.017 kg of 2,7-diaminonaphthalene were added to 0.7 kg of tetrahydrofuran and stirred until dissolved. Then, 0.027 kg of diisopropylmethylamine was added and the mixture was reacted at 30 °C for 32 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 2.4 kg of methanol and allowed to stand for 34 h. The mixture was then filtered again. The resulting filter cake was washed with water five times and dried to obtain the folded polymer.

[0034] Preparation of permanent orange pigment for high thermal stability coatings: 0.4 kg of the folded polymer was suspended in 23 kg of ethanol, and then 8 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 25 min, stirred at 28 °C for 34 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0035] Example 4: Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 0.8 kg of acetonitrile with a water content of less than 10 ppm, followed by the addition of 0.035 kg of iodomethane and 0.04 kg of sodium tert-butoxide. The reaction was carried out at 50 °C for 20 h, then quenched with 0.45 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 0.8 kg of ethyl acetate. The organic phase was then removed by vacuum distillation to obtain compound 1. 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.7 kg of compound 1 were added to 1.8 kg of acetone and stirred to dissolve. Then, 0.2 kg of potassium carbonate was added and the mixture was heated under reflux for 9 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water 5 times and dried to obtain compound 2. 0.1 kg of compound 2 was added to 0.8 kg of methanol and stirred until homogeneous. Then, 0.016 kg of sodium hydroxide was added, and the mixture was reacted at 36 °C for 10 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water five times and dried. The product was added to 0.8 kg of tetrahydrofuran with a water content of less than 10 ppm and stirred until dissolved. Then, 0.08 kg of thionyl chloride and 0.0006 kg of dimethylformamide were added, and the mixture was reacted at 35 °C for 20 h. The solvent was removed by vacuum distillation to obtain compound 3. 0.1 kg of compound 3 and 0.018 kg of 2,7-diaminonaphthalene were added to 0.8 kg of acetonitrile and stirred until dissolved. Then, 0.03 kg of diisopropylmethylamine was added and reacted at 32 °C for 35 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 2.6 kg of ethanol and allowed to stand for 38 h. The mixture was then filtered again. The resulting filter cake was washed with water five times and dried to obtain the folded polymer.

[0036] Preparation of permanent orange pigment for high thermal stability coatings: 0.45 kg of the folded polymer was suspended in 25 kg of ethanol, and then 9 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 28 min, stirred at 28 °C for 40 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0037] Example 5: Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 0.9 kg of acetone with a water content of less than 10 ppm, followed by 0.037 kg of iodomethane and 0.045 kg of sodium methoxide. The reaction was carried out at 55 °C for 22 h, then quenched by adding 0.48 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 0.9 kg of dichloromethane. The organic phase was then removed by vacuum distillation to obtain compound 1. 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.75 kg of compound 1 were added to 1.9 kg of acetone and stirred to dissolve. Then, 0.23 kg of potassium carbonate was added and the mixture was heated under reflux for 10 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water 5 times and dried to obtain compound 2. 0.1 kg of compound 2 was added to 0.9 kg of ethanol and stirred until homogeneous. Then, 0.018 kg of potassium hydroxide was added, and the mixture was reacted at 38 °C for 10 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water five times and dried. The product was added to 0.9 kg of tetrahydrofuran with a water content of less than 10 ppm and stirred until dissolved. Then, 0.09 kg of thionyl chloride and 0.0006 kg of dimethylformamide were added, and the mixture was reacted at 36 °C for 22 h. The solvent was removed by vacuum distillation to obtain compound 3. 0.1 kg of compound 3 and 0.019 kg of 2,7-diaminonaphthalene were added to 0.9 kg of acetone and stirred until dissolved. Then, 0.035 kg of triethylamine was added and the mixture was reacted at 35 °C for 40 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 2.8 kg of methanol and allowed to stand for 41 h. The mixture was then filtered again. The resulting filter cake was washed with water five times and dried to obtain the folded polymer.

[0038] Preparation of permanent orange pigment for high thermal stability coatings: 0.48 kg of the folded polymer was suspended in 27 kg of methanol, and then 9.5 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 29 min, stirred at 29 °C for 45 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0039] Example 6 Preparation of folded polymer: 0.1 kg of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to 1 kg of tetrahydrofuran with a water content of less than 10 ppm, followed by 0.04 kg of iodomethane and 0.05 kg of sodium hydride. The reaction was carried out at 60 °C for 24 h, and then quenched with 0.5 kg of water. The organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with 1 kg of dichloromethane. The organic phase was then removed by vacuum distillation to obtain compound 1. 0.1 kg of dimethyl 4,6-dihydroxyisophthalate and 0.8 kg of compound 1 were added to 2 kg of acetone and stirred to dissolve. Then, 0.25 kg of potassium carbonate was added and the mixture was heated under reflux for 12 h. The resulting reaction solution was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water 5 times and dried to obtain compound 2. 0.1 kg of compound 2 was added to 1 kg of ethanol and stirred until homogeneous. Then, 0.02 kg of potassium hydroxide was added, and the mixture was reacted at 40 °C for 12 h. After the reaction was completed, the mixture was filtered, and the solvent was removed by vacuum distillation of the filtrate. The residue was washed with water five times and dried. The product was added to 1 kg of tetrahydrofuran with a water content of less than 10 ppm and stirred until dissolved. Then, 0.1 kg of thionyl chloride and 0.0007 kg of dimethylformamide were added, and the mixture was reacted at 40 °C for 24 h. The solvent was removed by vacuum distillation to obtain compound 3. 0.1 kg of compound 3 and 0.02 kg of 2,7-diaminonaphthalene were added to 1 kg of tetrahydrofuran and stirred until dissolved. Then, 0.04 kg of triethylamine was added and the mixture was reacted at 40 °C for 48 h. After the reaction was completed, the mixture was filtered. The filtrate was added to 3 kg of methanol and allowed to stand for 48 h. The mixture was then filtered again. The resulting filter cake was washed with water five times and dried to obtain the folded polymer.

[0040] Preparation of permanent orange pigment for high thermal stability coatings: 0.5 kg of the folded polymer was suspended in 30 kg of methanol, and then 10 kg of Permanent Orange G was added. The mixture was ultrasonically dispersed for 30 min, stirred at 30 °C for 48 h, filtered, and the resulting filter cake was dried to obtain Permanent Orange pigment for high thermal stability coatings.

[0041] The folded polymers prepared in Examples 1-6 were tested using a Micromeritics Tristar II 3020 fully automated surface area and porosity analyzer, and the results are shown in Table 1. As can be seen from Table 1, the folded polymers formed abundant mesoporous structures, providing nanoscale spaces for the adsorption and encapsulation of permanent orange G pigment, thereby effectively inhibiting the thermal decomposition of azo groups at high temperatures and improving the thermal stability of the pigment.

[0042] Table 1. Specific surface area parameters of the folded polymers prepared in Examples 1-6

[0043] The high thermal stability coatings prepared in Examples 1-6 were subjected to performance tests using permanent orange pigment. Tinting strength was tested according to the method in GB / T 13451.2-1992; oil absorption was tested according to the method in GB / T 5211.15-2014; heat resistance was tested according to the method in HG / T 3853-2006; lightfastness was tested according to the method in standard GB / T 1710-2008; water resistance, acid resistance, and alkali resistance were tested according to the method in GB 5211.5-2008. The comparative example was our own product, Permanent Orange G (PO13). The test results are shown in Table 2. As can be seen from the results in Table 2, the permanent orange pigment used in the high thermal stability coatings prepared in this invention has strong tinting strength and, compared to the comparative example, exhibits stronger lightfastness, acid and alkali resistance, and heat resistance. The folded polymer in Example 1 has a lower specific surface area, resulting in lower coating efficiency, and therefore lower heat resistance compared to the other examples.

[0044] Table 2 Performance test results of pigments prepared in Examples 1-6

[0045] Thermogravimetric analysis (TGA) was performed on the folded polymer and the high-thermal-stability coating permanent orange pigment prepared in Example 3 of this invention, respectively, under a nitrogen atmosphere. The test temperature ranged from 30 to 600°C, and the heating rate was 10°C / min. The test results are shown in Table 3. As can be seen from the results in Table 3, the high-thermal-stability coating permanent orange pigment prepared in this invention exhibits excellent high-temperature resistance.

[0046] Table 3 Thermogravimetric Analysis Results

[0047] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A permanent orange pigment for high thermal stability coatings, characterized in that: It consists of 3 to 5 parts by weight of folded polymer and 70 to 100 parts of permanent orange G; The folded polymer is composed of 4,6-bis(long etheroxy) isophthaloyl chloride and 2,7-diaminonaphthalene linked alternately by amide bonds; The folded polymer was prepared according to the following method: 1) 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate was added to organic solvent 1, followed by iodomethane and base 1. The reaction was carried out at 25-60°C for 12-24 h, quenched with water, and the organic solvent was removed by vacuum distillation. The residue was filtered, and the filtrate was extracted with organic solvent 2. The organic phase was then removed by vacuum distillation to obtain compound 1. 2) Add dimethyl 4,6-dihydroxyisophthalate and compound 1 prepared in step 1) to organic solvent 3, stir to dissolve, then add base 2, heat under reflux for 6-12 h, filter the resulting reaction solution, remove the solvent by vacuum distillation of the filtrate, wash the residue with water 3-5 times, and dry to obtain compound 2. 3) Add compound 2 prepared in step 2) to organic solvent 4, stir and mix evenly, then add base 3, and react at 25~40℃ for 6~12h. After the reaction is complete, filter, remove the solvent from the filtrate by vacuum distillation, wash the residue with water 3~5 times, dry, add the product to organic solvent 5, stir and dissolve, then add thionyl chloride and dimethylformamide, react at 25~40℃ for 12~24h, remove the solvent by vacuum distillation to obtain compound 3; 4) Add the compound 3 and 2,7-diaminonaphthalene prepared in step 3) to organic solvent 6, stir to dissolve, then add alkali 4, react at 25~40℃ for 24~48h, after the reaction is complete, filter, add the filtrate to organic solvent 4, let stand for 24~48h, filter, wash the filter cake with water 3~5 times, dry, and obtain the folded polymer.

2. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: In step 1), the organic solvent 1 is tetrahydrofuran, acetone, acetonitrile, or dimethylformamide, and the water content of the organic solvent 1 is less than 10 ppm; in step 1), the base 1 is sodium hydride, sodium methoxide, sodium ethoxide, or sodium tert-butoxide; and in step 1), the organic solvent 2 is dichloromethane, ethyl acetate, or diethyl ether.

3. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: In step 1), the mass ratio of 26-hydroxy-3,6,9,12,15,18,21,24-octaoxahexadecyl 4-methylbenzenesulfonate, organic solvent 1, iodomethane, alkali 1, water, and organic solvent 2 is 1:5~10:0.25~0.4:0.25~0.5:3~5:5~10.

4. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: The organic solvent 3 mentioned in step 2) is acetonitrile, acetone or dimethylformamide; the base 2 mentioned in step 2) is sodium carbonate or potassium carbonate.

5. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: In step 2), the mass ratio of dimethyl 4,6-dihydroxyisophthalate, compound 1, organic solvent 3, and base 2 is 1:5~8:15~20:1.5~2.

5.

6. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: In step 3), the organic solvent 4 is methanol or ethanol; in step 3), the base 3 is sodium hydroxide or potassium hydroxide; and in step 3), the organic solvent 5 is dichloromethane or tetrahydrofuran.

7. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: The mass ratio of compound 2, organic solvent 4, base 3, organic solvent 5, thionyl chloride and dimethylformamide in step 3) is 1:5~10:0.1~0.2:5~10:0.5~1:0.004~0.

007.

8. The permanent orange pigment for high thermal stability coatings as described in claim 1, characterized in that: In step 4), the organic solvent 6 is dichloromethane, tetrahydrofuran, acetonitrile, or acetone; in step 4), the base 4 is triethylamine or diisopropylmethylamine; and in step 4), the mass ratio of compound 3, 2,7-diaminonaphthalene, organic solvent 6, base 4, and organic solvent 4 is 1:0.15~0.2:5~10:0.2~0.4:20~30.

9. The method for preparing permanent orange pigment for high thermal stability coatings according to claim 1, characterized in that: Includes the following steps: By weight, 3-5 parts of the folded polymer are suspended in 150-300 parts of organic solvent 4, and then 70-100 parts of permanent orange G are added. The mixture is ultrasonically dispersed for 20-30 minutes, stirred at 25-30°C for 24-48 hours, filtered, and the resulting filter cake is dried to obtain permanent orange pigment for high thermal stability coatings.

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