A high-performance low-temperature curing powder coating for vehicle surfaces and its preparation method

Abstract

The present invention relates to the technical field of powder coatings, and particularly relates to a high-performance low-temperature curing powder coating for vehicle surfaces and a preparation method thereof. The high-performance low-temperature curing powder coating for vehicle surfaces comprises, by weight parts: 45-65 parts of a carboxyl-terminated polyester resin, 30-45 parts of an epoxy resin, 2-5 parts of a curing agent, 0.2-0.5 parts of a curing accelerator, 0.5-1.5 parts of a leveling agent, 2-6 parts of an amino-terminated flame retardant, and 3-8 parts of a modified carbon nanotube. The high-performance low-temperature curing powder coating for vehicle surfaces of the present invention has excellent ultraviolet aging resistance and flame retardant properties, can protect the integrity and aesthetics of the coating, and has broad application prospects in the field of automotive painting.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coatings, and particularly to a high-performance low-temperature curing powder coating for vehicle surfaces and a preparation method thereof. Background Art

[0002] With the development of automotive industrial technology and the upgrading of consumer demands, vehicle surface coatings not only need to have good decorative and protective properties but also need to meet higher functional requirements. Especially for new energy vehicles, for driving safety considerations, their surface coatings must have excellent flame retardant properties to effectively reduce the fire risk. However, the existing methods of improving the flame retardant properties of coatings by adding flame retardants have obvious deficiencies: the flame retardants are prone to migrate or even precipitate from the coating film system, which not only reduces the durability of the flame retardant effect but also affects the overall performance of the coating. At the same time, as a means of transportation that is long-term exposed to outdoor environments, the surface coatings of vehicles must be able to withstand continuous ultraviolet radiation, and such a harsh use environment poses extremely high requirements for the ultraviolet aging resistance of the coatings. Therefore, it is necessary to improve the powder coating formulation to solve the above problems. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a high-performance low-temperature curing powder coating for vehicle surfaces. This powder coating has excellent ultraviolet aging resistance and flame retardant properties, can protect the integrity and aesthetics of the coating, and has broad application prospects in the field of automotive painting.

[0004] Another purpose of the present invention is to provide a preparation method of a high-performance low-temperature curing powder coating for vehicle surfaces. This method has strong operability and is conducive to realizing industrial production.

[0005] One of the purposes of the present invention is achieved by adopting the following technical solutions:

[0006] A high-performance low-temperature curing powder coating for vehicle surfaces, the high-performance low-temperature curing powder coating for vehicle surfaces comprises by weight: 45 - 65 parts of carboxyl-terminated polyester resin, 30 - 45 parts of epoxy resin, 2 - 5 parts of curing agent, 0.2 - 0.5 parts of curing accelerator, 0.5 - 1.5 parts of leveling agent, 2 - 6 parts of amino-terminated flame retardant, 3 - 8 parts of modified carbon nanotubes; the preparation process of the modified carbon nanotubes is as follows:

[0007] (1) Dissolve aureusidin, 4-(chloromethyl)benzaldehyde and acid-binding agent A in solvent A, react under an inert gas, and purify to obtain an intermediate;

[0008] (2) Add amino-functionalized carbon nanotubes to solvent B, add the intermediate and carry out a reflux reaction, and obtain modified carbon nanotubes through filtration, washing, and drying.

[0009] Further, the molar ratio of the aureusidin, 4-(chloromethyl)benzaldehyde and acid-binding agent A is 1:(1~1.5):(1.75~2.25), the concentration of the aureusidin in solvent A is 0.025~0.04 mol / L, the solvent A is N,N-dimethylformamide, and the acid-binding agent A is anhydrous potassium carbonate.

[0010] Further, the mass ratio of the amino-functionalized carbon nanotubes to the intermediate is 1:2.5~7.0, the concentration of the amino-functionalized carbon nanotubes in solvent B is 0.015~0.025 g / mL, and the solvent B is chloroform.

[0011] Further, in step (1), the reaction time is 10~12 h; in step (2), the temperature of the reflux reaction is 60 - 65 °C and the time is 2 - 4 h.

[0012] Further, the preparation process of the terminal amino flame retardant is as follows:

[0013] Add diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-c]pyridin-3-amine and acid-binding agent B into solvent C, and carry out a reflux reaction to obtain the product.

[0014] Further, the molar ratio of the diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-c]pyridin-3-amine and acid-binding agent B is 1:(2~2.2):(2~3), the acid-binding agent B is anhydrous potassium carbonate; the concentration of the diphenyldihydroxysilane in solvent C is 0.2~0.4 mol / L, and the solvent C is N,N-dimethylformamide.

[0015] Further, the temperature of the reflux reaction is 105~135 °C and the time is 8 - 10 h.

[0016] Further, the acid value of the terminal carboxyl polyester resin is 40~60 mgKOH / g; the epoxy resin is bisphenol A type epoxy resin or phenolic epoxy resin; the curing agent is dicyandiamide; the curing accelerator is at least one of 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, heptadecylimidazole, and isopropylimidazole; the leveling agent is isophorone or diacetone alcohol.

[0017] The second object of the present invention is achieved by the following technical solution:

[0018] The preparation method of the above-mentioned high-performance low-temperature curing powder coating for vehicle surfaces includes the following steps:

[0019] According to the said parts by weight, mix the carboxyl-terminated polyester resin, epoxy resin, curing agent, curing accelerator, leveling agent, amino-terminated flame retardant and modified carbon nanotubes evenly, add them into a twin-screw extruder for melt extrusion, and then through crushing, grinding and sieving, a high-performance low-temperature curing powder coating for vehicle surfaces is obtained.

[0020] Furthermore, the temperature of the extrusion is 95 - 105 °C.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The present invention provides a high-performance low-temperature curing powder coating for vehicle surfaces, which has excellent ultraviolet aging resistance and flame retardant properties, can protect the integrity and aesthetics of the coating, and has broad application prospects in the field of automotive painting.

[0023] Specifically, the modified carbon nanotubes added in the coating enhance the anti-ultraviolet aging performance of the coating. Due to its unique conjugated structure, carbon nanotubes can efficiently absorb and disperse ultraviolet light energy, playing a good ultraviolet shielding role; at the same time, the active phenolic hydroxyl groups in the aureolic acid molecules can effectively quench the free radicals induced by ultraviolet rays and inhibit the occurrence of oxidation reactions. The two work together to construct a multi-level protection system, which can not only reflect and scatter part of the ultraviolet radiation but also block the oxygen penetration, thus significantly enhancing the anti-ultraviolet aging performance of the coating.

[0024] The high-performance low-temperature curing powder coating for vehicle surfaces of the present invention also adds an amino-terminated flame retardant, which has a flame retardant structure in the middle and is connected with an amino group at each end. The flame retardant structure forms a heat-insulating protective layer at high temperature relying on the silicon-oxygen structure, and at the same time, the nitrogen-containing heterocycle decomposes to generate non-combustible gases and promotes carbonization, realizing double flame retardancy in the gas phase and condensed phase through the silicon-nitrogen synergistic effect. The two amino groups at both ends can react with the carboxyl-terminated polyester resin and epoxy resin to form strong chemical bonds, so that it can be firmly bonded in the coating film system and is not likely to migrate or precipitate in the coating film during long-term use, affecting the coating performance.

[0025] 2. The amino groups at both ends of the amino-terminated flame retardant added in the high-performance low-temperature curing powder coating for vehicle surfaces of the present invention can not only firmly bond the flame retardant structure in the system but also act as a curing agent, thus reducing the dosage of the curing agent.

[0026] 3. The present invention also provides a preparation method of a high-performance low-temperature curing powder coating for vehicle surfaces. This method has strong operability and is conducive to realizing industrial production. Description of the Drawings

[0027] Figure 1 It is the infrared spectrum diagram of the modified carbon nanotubes of the present invention. Detailed Embodiments

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, under the premise of no conflict, the embodiments described below or the technical features can be arbitrarily combined to form new embodiments. The specific conditions not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0029] The aminated carbon nanotubes of the present invention are aminated multi-walled carbon nanotubes with a purity greater than 95%, a pH value greater than 7, an -NH2 content of 0.45wt%, a length of 55µm, an inner diameter of 2-4nm, and an outer diameter of 8-15nm.

[0030] The acid value of the carboxyl-terminated polyester resin of the present invention is 40-60 mgKOH / g; the model of the bisphenol A epoxy resin of the present invention is E-20; and the model of the phenolic epoxy resin of the present invention is F44.

[0031] Example 1

[0032] A high-performance, low-temperature curing powder coating for a vehicle surface comprises, by weight, 55 parts of a carboxyl-terminated polyester resin, 40 parts of a bisphenol A epoxy resin, 3 parts of dicyandiamide, 0.3 parts of 2,4-dimethylimidazole, 1 part of isophorone, 4 parts of an amino-terminated flame retardant, and 5 parts of modified carbon nanotubes.

[0033] The preparation process of modified carbon nanotubes is as follows:

[0034]

[0035] (1) Chrysopridine, 4-(chloromethyl)benzaldehyde and anhydrous potassium carbonate were added to N,N-dimethylformamide in a molar ratio of 1:1.2:2 to fully dissolve, wherein the concentration of chrysopridine in N,N-dimethylformamide was 0.03 mol / L; under nitrogen protection, the reaction was stirred at room temperature for 11 h. After the reaction was completed, the reaction solution was concentrated under reduced pressure and purified by column chromatography (chloroform / methanol, volume ratio 30:1) to obtain an intermediate (yield 61.3%); the intermediate 1 HNMR: (C 22 H 14 O7, 400MHz, DMSO-d6) δ: 5.85 (s, H), 6.71 (s, H), 7.0-7.02 (d, 2H), 7.35-7.37 (d, 2H), 7 .60-7.62 (d, 2H), 8.01-8.03 (d, 2H), 8.73 (s, H), 9.48 (s, H), 9.89 (s, H), 19.98 (s, H). MS (ESI) m / z=390.07 [M].

[0036] (2) Ultrasonic dispersion of the amino carbon nanotubes in chloroform, adding the intermediate, wherein the mass ratio of the amino carbon nanotubes to the intermediate is 1:5, and the concentration of the amino carbon nanotubes in chloroform is 0.02 g / mL; react at 62 °C under reflux conditions for 3 h, filter to obtain a solid product, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0037] The preparation process of the amino-terminated flame retardant is as follows:

[0038]

[0039] Diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-C]pyridin-3-amine and anhydrous potassium carbonate were added into N,N-dimethylformamide in a molar ratio of 1:2.1:2.5 to fully dissolve, wherein the concentration of diphenyldihydroxysilane in N,N-dimethylformamide was 0.3 mol / L; after reacting at 125°C for 9 h under nitrogen protection, the reaction solution was filtered, and then the filtrate was subjected to reduced pressure distillation to remove the solvent, the remaining product was added to a 5 wt% hydrochloric acid solution for precipitation, and a solid product was obtained by filtration, and the filtrate was washed with deionized water until the filtrate was neutral, and then vacuum dried to obtain an amino-terminated flame retardant (yield 74.6%); 1 HNMR: (C 26 H 22 N6O2Si, 400MHz, DMSO-d6) δ: 5.82 (s, 4H), 6.86 (s, 2H), 7.04-7.08 (d, 2H), 7.35-7.40 (m, 6H), 7.44-7.48 (m, 4H), 7.50 (s, 2H), 9.50 (s, 2H). MS (ESI) m / z=478.16[M].

[0040] This embodiment also provides a method for preparing a high-performance low-temperature curing powder coating for a vehicle surface, comprising the following steps:

[0041] According to the above weight parts, the carboxyl-terminated polyester resin, bisphenol A epoxy resin, dicyandiamide, 2,4-dimethylimidazole, isophorone, amino-terminated flame retardant and modified carbon nanotubes are mixed uniformly, added into a twin-screw extruder for melt extrusion, and the extrusion temperature is controlled at 100° C. After extrusion, it is crushed and ground, and then passed through a 150-mesh sieve to obtain a high-performance low-temperature curing powder coating for vehicle surface.

[0042] Example 2

[0043] A high-performance low-temperature curing powder coating for vehicle surfaces, the high-performance low-temperature curing powder coating for vehicle surfaces comprises by weight: 45 parts of carboxyl-terminated polyester resin, 30 parts of phenolic epoxy resin, 2 parts of dicyandiamide, 0.2 part of 2-ethyl-4-methylimidazole, 0.5 part of diacetone alcohol, 2 parts of amino-terminated flame retardant, and 3 parts of modified carbon nanotubes.

[0044] Among them, the preparation process of the modified carbon nanotubes is as follows:

[0045] (1) Add viola quercetorum, 4-(chloromethyl)benzaldehyde, and anhydrous potassium carbonate into N,N-dimethylformamide in a molar ratio of 1:1:1.75 and dissolve them fully. The concentration of viola quercetorum in N,N-dimethylformamide is 0.03 mol / L; under nitrogen protection, stir and react at room temperature for 10 h. After the reaction is completed, concentrate the reaction solution under reduced pressure and purify it by column chromatography (chloroform / methanol, volume ratio 30:1) to obtain an intermediate (yield 60.7%); the 1 The results of HNMR and MS of the intermediate are the same as those in Example 1;

[0046] (2) Ultrasonically disperse the amino-functionalized carbon nanotubes in chloroform, add the intermediate, where the mass ratio of the amino-functionalized carbon nanotubes to the intermediate is 1:2.5, and the concentration of the amino-functionalized carbon nanotubes in chloroform is 0.02 g / mL; under reflux conditions, react at 60 °C for 4 h, then filter to obtain a solid product, wash it with deionized water, and dry it under vacuum to obtain the modified carbon nanotubes.

[0047] Among them, the preparation process of the amino-terminated flame retardant is as follows:

[0048] Add diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-c]pyridin-3-amine, and anhydrous potassium carbonate into N,N-dimethylformamide in a molar ratio of 1:2:2 and dissolve them fully. The concentration of diphenyldihydroxysilane in N,N-dimethylformamide is 0.3 mol / L; under nitrogen protection, react at 105 °C for 10 h, then filter the reaction solution, and then distill off the solvent under reduced pressure for the filtrate. Add the remaining product to a 5 wt% hydrochloric acid solution to precipitate, filter to obtain a solid product, wash it with deionized water until the filtrate is neutral, and dry it under vacuum to obtain the amino-terminated flame retardant (yield 73.8%); the 1 The results of HNMR and MS of the amino-terminated flame retardant are the same as those in Example 1.

[0049] This example also provides a preparation method of a high-performance low-temperature curing powder coating for vehicle surfaces, comprising the following steps:

[0050] According to the above weight parts, the carboxyl-terminated polyester resin, phenolic epoxy resin, dicyandiamide, 2-ethyl-4-methylimidazole, diacetone alcohol, amino-terminated flame retardant and modified carbon nanotubes are mixed uniformly, added into a twin-screw extruder for melt extrusion, and the extrusion temperature is controlled at 95° C. After extrusion, it is crushed and ground, and then passed through a 150-mesh sieve to obtain a high-performance low-temperature curing powder coating for vehicle surface.

[0051] Example 3

[0052] A high-performance, low-temperature curing powder coating for a vehicle surface comprises, by weight, 65 parts of a carboxyl-terminated polyester resin, 45 parts of a bisphenol A epoxy resin, 5 parts of dicyandiamide, 0.5 parts of 2,4-dimethylimidazole, 1.5 parts of isophorone, 6 parts of an amino-terminated flame retardant, and 8 parts of modified carbon nanotubes.

[0053] The preparation process of modified carbon nanotubes is as follows:

[0054] (1) Chrysopurine, 4-(chloromethyl)benzaldehyde and anhydrous potassium carbonate were added to N,N-dimethylformamide in a molar ratio of 1:1.5:2.25 to fully dissolve, wherein the concentration of chrysopurine in N,N-dimethylformamide was 0.03 mol / L; under nitrogen protection, the reaction was stirred at room temperature for 12 h. After the reaction was completed, the reaction solution was concentrated under reduced pressure and purified by column chromatography (chloroform / methanol, volume ratio 30:1) to obtain an intermediate (yield 61.0%); the intermediate 1 HNMR and MS results are the same as in Example 1;

[0055] (2) Ultrasonic dispersion of the amino carbon nanotubes in chloroform, adding the intermediate, wherein the mass ratio of the amino carbon nanotubes to the intermediate is 1:7.0, and the concentration of the amino carbon nanotubes in chloroform is 0.02 g / mL; react at 65 °C under reflux conditions for 2 h, filter to obtain a solid product, wash with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0056] The preparation process of the amino-terminated flame retardant is as follows:

[0057] Diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-C]pyridine-3-amine and anhydrous potassium carbonate were added into N,N-dimethylformamide in a molar ratio of 1:2.2:3 to fully dissolve, wherein the concentration of diphenyldihydroxysilane in N,N-dimethylformamide was 0.3 mol / L; after reacting at 135°C for 8 h under nitrogen protection, the reaction solution was filtered, and then the filtrate was subjected to reduced pressure distillation to remove the solvent, the remaining product was added to a 5 wt% hydrochloric acid solution for precipitation, and a solid product was obtained by filtration, and the filtrate was washed with deionized water until the filtrate was neutral, and then vacuum dried to obtain an amino-terminated flame retardant (yield 74.5%);1 The results of \(^1H\) NMR and MS were the same as those in Example 1.

[0058] This example also provides a preparation method of a high-performance low-temperature curing powder coating for vehicle surfaces, including the following steps:

[0059] According to the above weight parts, the carboxyl-terminated polyester resin, bisphenol A epoxy resin, dicyandiamide, 2,4-dimethylimidazole, isophorone, amino-terminated flame retardant, and modified carbon nanotubes were mixed evenly, added to a twin-screw extruder for melt extrusion, and the extrusion temperature was controlled at 105 °C. After extrusion, it was crushed and ground, and then passed through a 200-mesh sieve to obtain a high-performance low-temperature curing powder coating for vehicle surfaces.

[0060] Comparative Example 1

[0061] This Comparative Example 1 was basically the same as Example 1, except that the modified carbon nanotubes were replaced with aminated carbon nanotubes.

[0062] Comparative Example 2

[0063] This Comparative Example 2 was basically the same as Example 1, except that the amino-terminated flame retardant was omitted.

[0064] Test Example 1

[0065] The structure of the modified carbon nanotubes was characterized by infrared spectroscopy, and the results were as Figure 1 shown.

[0066] From Figure 1 it can be seen that the infrared spectrum of the modified carbon nanotubes showed characteristic absorption peaks of hydroxyl groups at 3200 - 3600 \(cm^{-1}\), characteristic absorption peaks of \(C = O\) at 1680 \(cm^{-1}\), and characteristic absorption peaks of the benzene ring skeleton at 1564 \(cm^{-1}\), indicating that the carbon nanotubes were successfully grafted with aureusazulene. -1 characteristic absorption peak of hydroxyl groups at 3200 - 3600 \(cm^{-1}\), characteristic absorption peak of \(C = O\) at 1680 \(cm^{-1}\), characteristic absorption peak of the benzene ring skeleton at 1564 \(cm^{-1}\), indicating that the carbon nanotubes were successfully grafted with aureusazulene. -1 characteristic absorption peak of \(C = O\) at 1680 \(cm^{-1}\), characteristic absorption peak of the benzene ring skeleton at 1564 \(cm^{-1}\), indicating that the carbon nanotubes were successfully grafted with aureusazulene. -1 characteristic absorption peak of the benzene ring skeleton at 1564 \(cm^{-1}\), indicating that the carbon nanotubes were successfully grafted with aureusazulene.

[0067] Test Example 2

[0068] The coatings obtained in Examples 1 - 3 and Comparative Examples 1 - 2 were electrostatically sprayed on steel plates, then cured at 120 °C for 30 min to form a coating with a thickness of 60 µm. After standing at room temperature for 20 h, the performance indexes of the coatings of the present invention were tested, and the specific methods were as follows:

[0069] (1) The adhesion was tested according to the test standard of GB / T 9286 - 2021.

[0070] (2) The flame retardant performance of the coating was tested according to Method B - diffusion ignition method in Section 8.2.3 of GB / T 2406.2 - 2009 "Plastics - Determination of burning behavior by the oxygen index method", using Type I specimens.

[0071] (3) The specific test steps for the UV resistance of the coating of the present invention are as follows: Set the UV light intensity to 200 W / m 2 , the temperature to 65 °C, and accelerate the aging for 2000 h in a UV accelerated aging test machine. Observe the changes on the surface of the coating, measure the glossiness of the coating before and after UV aging using a glossmeter, and record the light retention rate (%); Calculate the color difference (ΔE) of the coating before and after UV aging according to the standard of GB / T 11186.3 - 1898. The above test results are all recorded in Table 1.

[0072] Table 1

[0073]

[0074] As can be seen from Table 1: The coatings formed by the coatings of Examples 1 - 3 of the present invention have good adhesion, and after UV accelerated aging treatment, there are basically no phenomena such as blistering, cracking, rusting, and powdering. The light retention rates are all maintained above 90%, the color differences (ΔE) are all less than 3.0, and the color change grade is 0 grade. The light retention rate of Comparative Example 1 is reduced to 72%, and ΔE is 5.8. Its light retention rate is much lower than that of Example 1, and ΔE is higher than that of Example 1. This is because the introduced modified carbon nanotubes enhance the UV aging resistance of the coating. Attributed to the unique conjugated structure of carbon nanotubes, they can efficiently absorb and disperse UV light energy, playing a good UV shielding role; at the same time, the active phenolic hydroxyl groups in the chrysophaeic acid molecule can effectively quench the free radicals induced by ultraviolet rays and inhibit the occurrence of oxidation reactions. The two act synergistically to construct a multi-level protection system, which can not only reflect and scatter part of the UV radiation but also block the penetration of oxygen, thus significantly enhancing the UV aging resistance of the coating.

[0075] In addition, the coatings formed by Examples 1 - 3 also have excellent flame retardant properties, and the oxygen index can reach up to 44.6%. After omitting the end amino flame retardant in Comparative Example 2, the oxygen index is reduced to 24.3%. This phenomenon may be attributed to the special flame retardant structure of the end amino flame retardant. It forms a dense Si - O - C heat insulation protection layer at high temperature relying on the silicon - oxygen structure to isolate the transfer of oxygen and heat. At the same time, the nitrogen - containing heterocycle decomposes to produce non - combustible gases and promotes carbon formation, achieving dual flame retardancy in the gas phase and condensed phase through the silicon - nitrogen synergistic effect. The two amino groups at both ends can react with the end - carboxyl polyester resin and epoxy resin in the coating to form strong chemical bonds, so that it can be firmly bonded in the coating film system and is not likely to migrate or precipitate in the coating film during long - term use, affecting the coating performance.

[0076] The above - mentioned embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non - substantial changes and substitutions made by those skilled in the art based on the present invention belong to the scope of protection required by the present invention.

Claims

1. A high-performance low-temperature curing powder coating for vehicle surfaces, characterized in that, The high-performance low-temperature curing powder coating for vehicle surfaces comprises, by weight parts: 45-65 parts of carboxyl-terminated polyester resin, 30-45 parts of epoxy resin, 2-5 parts of curing agent, 0.2-0.5 parts of curing accelerator, 0.5-1.5 parts of leveling agent, 2-6 parts of amino-terminated flame retardant, and 3-8 parts of modified carbon nanotubes; The preparation process of the modified carbon nanotubes is as follows: (1) Dissolve aurantiamine, 4-(chloromethyl)benzaldehyde and acid-binding agent A in solvent A, react under an inert gas, and purify to obtain an intermediate; (2) Add amino-functionalized carbon nanotubes to solvent B, add the intermediate and carry out a reflux reaction, and obtain modified carbon nanotubes after filtration, washing and drying.

2. The high-performance low-temperature curing powder coating for vehicle surfaces according to claim 1, characterized in that, The molar ratio of aurantiamine, 4-(chloromethyl)benzaldehyde and acid-binding agent A is 1: (1-1.5): (1.75-2.25), the concentration of aurantiamine in solvent A is 0.025-0.04 mol / L, solvent A is N,N-dimethylformamide, and acid-binding agent A is anhydrous potassium carbonate.

3. The high-performance low-temperature curing powder coating for vehicle surface according to claim 1, wherein The mass ratio of amino-functionalized carbon nanotubes to the intermediate is 1: 2.5-7.0, the concentration of amino-functionalized carbon nanotubes in solvent B is 0.015-0.025 g / mL, and solvent B is chloroform.

4. The high-performance low-temperature curing powder coating for vehicle surfaces according to claim 1, characterized in that, In step (1), the reaction time is 10-12 h; in step (2), the temperature of the reflux reaction is 60-65 °C and the time is 2-4 h.

5. The high-performance low-temperature curing powder coating for vehicle surfaces according to claim 1, characterized in that, The preparation process of the amino-terminated flame retardant is as follows: Add diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-c]pyridin-3-amine and acid-binding agent B to solvent C, and carry out a reflux reaction to obtain it.

6. The high-performance low-temperature curing powder coating for vehicle surface according to claim 5, characterized in that, The molar ratio of diphenyldihydroxysilane, 7-chloro-1H-pyrrolo[2,3-c]pyridin-3-amine and acid-binding agent B is 1: (2-2.2): (2-3), acid-binding agent B is anhydrous potassium carbonate; the concentration of diphenyldihydroxysilane in solvent C is 0.2-0.4 mol / L, and solvent C is N,N-dimethylformamide.

7. The high-performance low-temperature curing powder coating for vehicle surfaces according to claim 5, characterized in that, The temperature of the reflux reaction is 105-135 °C and the time is 8-10 h.

8. The high-performance low-temperature curing powder coating for vehicle surface according to claim 1, characterized in that, The acid value of the carboxyl-terminated polyester resin is 40-60 mgKOH / g; the epoxy resin is bisphenol A type epoxy resin or phenolic epoxy resin; the curing agent is dicyandiamide; the curing accelerator is at least one of 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, heptadecylimidazole, and isopropylimidazole; the leveling agent is isophorone or diacetone alcohol.

9. The preparation method of the high-performance low-temperature curing powder coating for vehicle surfaces according to any one of claims 1 to 8, characterized in that, It includes the following steps: According to the said weight parts, mix the carboxyl-terminated polyester resin, epoxy resin, curing agent, curing accelerator, leveling agent, amino-terminated flame retardant and modified carbon nanotubes evenly, add them into a twin-screw extruder for melt extrusion, and then through crushing, grinding and sieving, obtain the high-performance low-temperature curing powder coating for vehicle surfaces.

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