A high-temperature resistant composite coating for tramcars and its preparation method

Abstract

The present invention relates to a high-temperature resistant composite coating for electric vehicles and a preparation method thereof, belonging to the technical field of electric vehicle coatings. The preparation method comprises the following steps: after uniformly mixing methacrylic acid, methyl methacrylate, vinyl acetate and a functional monomer, adding an organic solvent and heating to raise the temperature, adding an initiator and a modified filler, mixing and then performing heat preservation treatment, and cooling to room temperature to obtain a modified acrylic resin; the functional monomer consists of N-methylolacrylamide and isooctyl acrylate; adding a leveling agent, a nano pigment and an auxiliary agent to the modified acrylic resin, stirring at high speed, adding an organic solvent and continuing to stir, and then performing sieving to obtain the product. By introducing high-temperature resistant fillers such as hollow glass microspheres, zirconia, and alumina, and organically modifying them, the present invention increases their compatibility in the composite coating and improves the interfacial bonding force between them and the components, significantly improving the mechanical properties and high-temperature resistance of the acrylic resin composite coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of tram coatings, and relates to a high-temperature resistant composite coating for trams and a preparation method thereof. Background Art

[0002] Tram coatings, as coatings specifically applied to tram bodies and other automotive components, mainly consist of four major components: film-forming substances, pigments, solvents, and additives. Film-forming substances are usually natural resins or synthetic resins, and their key role is to tightly bond other components to form a tough and complete protective film. Pigments serve as the outermost covering and mainly carry the topcoat color of the coating. Solvents and additives together promote the smooth application of the coating on the vehicle body surface, improve the chemical properties of the car paint, and enhance the gloss of the vehicle body.

[0003] Acrylate resin is a resin synthesized mainly from acrylate or methacrylate. Coatings based on this resin are called acrylate coatings. Although acrylate coatings have certain heat resistance, under long-term high-temperature exposure, degradation may gradually occur, such as color change, gloss reduction, hardness decrease, etc., resulting in a decline in coating performance.

[0004] Hollow glass microspheres, whose main component is borosilicate, exhibit a unique hollow thin-walled spherical structure. The particle size range is usually between 10 and 250 microns, and their wall thickness is relatively thin, only about 1 to 2 microns. The thin inner wall makes them prone to breakage. However, due to their low density, high strength, excellent heat insulation performance, and good fluidity and stability, hollow glass microspheres have been widely used in civil fields such as coatings, cement, emulsion explosives, adhesives, etc. However, when hollow glass microspheres are filled into the acrylate resin coating matrix, due to the significant difference in polarity between the two, there are challenges in terms of compatibility. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-temperature resistant composite coating for trams and a preparation method thereof. By adding a variety of high-temperature resistant inorganic fillers to the composite coating and organically modifying them, the mechanical properties and high-temperature resistance of the acrylate resin composite coating are significantly improved.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of a high-temperature resistant composite coating for trams includes the following steps:

[0008] Step 1: Mix methacrylic acid, methyl methacrylate, vinyl acetate and functional monomers evenly, add an organic solvent, heat up the temperature, add an initiator and modified filler, mix them, and then carry out heat preservation treatment. After cooling to room temperature, a modified acrylic resin is obtained. The functional monomers are composed of N-methylolacrylamide and isooctyl acrylate.

[0009] Step 2: Add a leveling agent, nano-pigment and auxiliary agent to the modified acrylic resin, stir at high speed, then add an organic solvent and continue to stir, and then carry out sieving to obtain a high-temperature resistant composite coating.

[0010] As a preferred technical solution of the present invention, in Step 1, the heating and temperature rising is to raise the temperature to 65 - 75 °C; the heat preservation treatment is to carry out heat preservation at 70 - 75 °C for 8 - 10 h; the mass ratio of methacrylic acid, methyl methacrylate, vinyl acetate, functional monomers, organic solvent, initiator and modified filler is 6 - 9:15 - 20:6 - 7:14 - 16:70 - 80:0.8 - 1.0:2.4 - 3.0; the functional monomers are composed of N-methylolacrylamide and isooctyl acrylate mixed according to a mass ratio of 1.0 - 1.5:5 - 6; the organic solvent is ethyl acetate; the initiator is one or both of azobisisobutyronitrile and benzoyl peroxide.

[0011] As a preferred technical solution of the present invention, in Step 2, the high-speed stirring is to stir at a speed of 1000 - 1200 r / min for 30 - 45 min; the continuous stirring is to stir at a speed of 400 - 600 r / min for 10 - 15 min; the sieving is to pass through a 400-mesh sieve; the mass ratio of the modified acrylic resin, leveling agent, nano-pigment, auxiliary agent and organic solvent is 50 - 55:0.5 - 0.8:10 - 12:1 - 3:30 - 40; the nano-pigment is Pigment Red A3B; the leveling agent is one or both of BYK-300 and Evonik TEGO450; the organic solvent is ethyl acetate; the auxiliary agent is silica particles, Therm HPG 6806 or Therm HPG 4000; Therm HPG 4000 is selected for the examples and comparative examples of the present invention. ThermHPG 4000.

[0012] The present invention discloses a preparation method of the modified filler, which includes the following steps:

[0013] 1) Add mixed microspheres to an aqueous sodium hydroxide solution, carry out mechanical stirring, filter out the liquid to obtain solid matter, wash it with deionized water, and place it in an oven for drying to obtain a prefabricated filler;

[0014] 2) Under an inert atmosphere, add the prefabricated filler into deionized water and disperse it by ultrasonic treatment. Add zirconium oxychloride to adjust the pH of the solution to alkaline, then heat it while raising the temperature. Take the solid matter for washing and dry it in an oven to obtain the mixed filler;

[0015] 3) After stirring and mixing alumina, absolute ethanol and p-aminobenzoic acid, add vanillin and stir while heating. After filtering off the filtrate, wash it with ethanol and dry it in an oven to obtain the modified alumina;

[0016] 4) Place the terpolymer, the mixed filler and the modified alumina in a twin-screw extruder, melt and extrude them, and then pelletize to obtain the modified filler; the terpolymer is a styrene-vinyltrimethoxysilane-glycidyl methacrylate copolymer.

[0017] As a preferred technical solution of the present invention, in step 1), the mechanical stirring is carried out at a rotation speed of 400 - 600 r / min for 45 - 60 min; the washing is carried out until neutral; the drying is carried out at a temperature of 60 - 70 °C until constant weight.

[0018] As a preferred technical solution of the present invention, in step 1), the mixed microspheres include the following components by weight: 10 - 20 parts of hollow glass microspheres with a particle size of 30 μm, 18 - 24 parts of hollow glass microspheres with a particle size of 40 μm, and 20 - 30 parts of hollow glass microspheres with a particle size of 60 μm; the concentration of the sodium hydroxide aqueous solution is 20 - 25 g / L; the dosage ratio of the hollow glass microspheres to the sodium hydroxide aqueous solution is 2.0 - 2.4 g: 25 mL; in the solution of the present invention, after the hollow glass microspheres with different particle sizes are treated with sodium hydroxide, while enabling the hollow glass microspheres to incorporate more hydroxyl groups, their surfaces are roughened. The roughened surface of the hollow glass microspheres is more likely to adhere to zirconium oxide. The zirconium oxide fills the rough surface of the hollow glass microspheres, reducing the agglomeration phenomenon and improving the dispersibility and uniformity; the hollow glass microspheres have a unique hollow thin-wall structure and relatively low price. Coating a special functional material on its surface forms a core-shell hollow structure, reducing the self-agglomeration phenomenon of the filler.

[0019] As a preferred technical solution of the present invention, in step 2), the inert atmosphere is a nitrogen atmosphere; the ultrasonic dispersion is carried out at a power of 100 - 200 W for 45 - 60 min; the adjustment of the solution pH to alkaline is to adjust the pH of the solution to 9 - 10 using ammonia water; the heating while raising the temperature is carried out at a temperature of 130 - 150 °C for 3 - 5 h; the washing is carried out with deionized water until neutral; the drying is carried out at a temperature of 70 - 80 °C until constant weight; the mass ratio of the deionized water, the prefabricated filler and zirconium oxychloride is 30: 4 - 5: 2.5 - 3.0.

[0020] As a preferred technical solution of the present invention, in step 3), the stirring and mixing is carried out at a rotation speed of 600 - 800 r / min for 20 - 30 min; the heating and stirring is carried out at a temperature of 60 - 75 °C for 4 - 6 h; the drying is carried out at a temperature of 70 - 80 °C until constant weight; the mass ratio of alumina, absolute ethanol, p-aminobenzoic acid and vanillin is 13 - 15:50 - 55:2.6 - 3.0:4.0 - 4.2; in the solution of the present invention, the imine structure formed by p-aminobenzoic acid and vanillin, combined with the addition of the thermally stable and rigid benzene ring structure, can increase the compatibility and high-temperature resistance between alumina and the acrylate matrix.

[0021] As a preferred technical solution of the present invention, in step 4), the temperature of the melt extrusion is 180 - 210 °C; the mass ratio of the terpolymer, the mixed filler and the modified alumina is 7 - 10:2.8 - 3.2:6 - 8.

[0022] The present invention discloses a preparation method of the terpolymer, comprising the following steps:

[0023] Styrene, vinyltrimethoxysilane and glycidyl methacrylate are placed in ethyl acetate, and after adding an initiator and heating treatment, ethyl acetate is removed to obtain a terpolymer; the terpolymer contains a large number of benzene ring structures, organosilicon structures and epoxy groups, which can be used as a compatibilizer to increase the compatibility of the filler and play a role in reinforcing the composite coating.

[0024] As a preferred technical solution of the present invention, the heating treatment is carried out at a temperature of 70 - 75 °C for 3 - 4 h; the initiator is azobisisobutyronitrile; the mass ratio of styrene, vinyltrimethoxysilane, glycidyl methacrylate, ethyl acetate and the initiator is 10 - 14:3.0 - 3.5:4.0 - 4.3:60 - 70:0.35 - 0.40.

[0025] The beneficial effects of the present invention:

[0026] The present invention introduces high-temperature resistant fillers such as hollow glass microspheres, zirconia, alumina, etc. into the composite coating, and through organic modification thereof, increases their compatibility in the acrylic resin composite coating, improves the interfacial bonding force between them and the components, and significantly improves the mechanical properties and high-temperature resistance of the acrylic resin composite coating. Specific embodiments

[0027] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following examples are provided to illustrate in detail the specific embodiments, structures, features and effects of the present invention.

[0028] Example 1

[0029] A preparation method of a high-temperature resistant composite coating for electric vehicles comprises the following steps:

[0030] Step 1: After mixing methacrylic acid, methyl methacrylate, vinyl acetate and a functional monomer evenly, add an organic solvent and heat to 65 °C, then add an initiator and a modified filler and mix. Keep the mixture at 70 °C for 8 h, and then cool to room temperature to obtain a modified acrylic resin. Among them, the mass ratio of methacrylic acid, methyl methacrylate, vinyl acetate, the functional monomer, the organic solvent, the initiator and the modified filler is 6:15:6:14:70:0.8:2.4; the functional monomer is composed of N-methylolacrylamide and isooctyl acrylate mixed according to a mass ratio of 1.0:5; the organic solvent is ethyl acetate; the initiator is azobisisobutyronitrile;

[0031] Step 2: Add a leveling agent, a nano-pigment and an auxiliary agent to the modified acrylic resin and stir at 1000 r / min for 30 min. Then add an organic solvent and stir at 400 r / min for 10 min, and then pass through a 400-mesh sieve to obtain a high-temperature resistant composite coating. Among them, the mass ratio of the modified acrylic resin, the leveling agent, the nano-pigment, the auxiliary agent and the organic solvent is 50:0.5:10:1:30; the nano-pigment is Pigment Red A3B; the leveling agent is BYK-300; the auxiliary agent is silicon dioxide particles; the organic solvent is ethyl acetate.

[0032] The preparation method of the modified filler comprises the following steps:

[0033] 1) Add mixed microspheres to an aqueous sodium hydroxide solution and stir at 400 r / min for 45 min. Then filter to remove the liquid and take the solid, wash it with deionized water until neutral, place it in an oven, and dry it at 60 °C until constant weight to obtain a prefabricated filler. Among them, the mixed microspheres by weight include the following components: 10 parts of hollow glass microspheres with a particle size of 30 μm, 18 parts of hollow glass microspheres with a particle size of 40 μm, and 20 parts of hollow glass microspheres with a particle size of 60 μm; the concentration of the aqueous sodium hydroxide solution is 20 g / L; the dosage ratio of the hollow glass microspheres to the aqueous sodium hydroxide solution is 2.0 g:25 mL;

[0034] 2) Under a nitrogen atmosphere, add the prefabricated filler to deionized water and ultrasonically treat it at 100 W for 45 min. Add zirconium oxychloride and then adjust the pH of the solution to 9 with ammonia water. Heat it at 130 °C for 3 h, then take the solid and wash it with deionized water until neutral, place it in an oven, and dry it at 70 °C until constant weight to obtain a mixed filler. Among them, the mass ratio of deionized water, the prefabricated filler and zirconium oxychloride is 30:4:2.5;

[0035] 3) After stirring alumina, absolute ethanol, and p-aminobenzoic acid at a rotation speed of 600 r / min for 20 min, vanillin was added and stirred at 60 °C for 4 h. After filtering off the filtrate, it was washed 3 times with absolute ethanol and then placed in an oven and dried at 70 °C to constant weight to obtain modified alumina. Among them, the mass ratio of alumina, absolute ethanol, p-aminobenzoic acid, and vanillin is 13:50:2.6:4.0;

[0036] 4) The terpolymer, mixed filler, and modified alumina were placed in a twin-screw extruder and melt-extruded at 180 °C and then pelletized to obtain a modified filler. Among them, the mass ratio of the terpolymer, mixed filler, and modified alumina is 7:2.8:6.

[0037] The preparation method of the terpolymer includes the following steps:

[0038] Styrene, vinyltrimethoxysilane, and glycidyl methacrylate were placed in ethyl acetate, and azobisisobutyronitrile was added and heated at 70 °C for 3 h. After removing ethyl acetate, a terpolymer was obtained. Among them, the mass ratio of styrene, vinyltrimethoxysilane, glycidyl methacrylate, ethyl acetate, and azobisisobutyronitrile is 10:3.0:4.0:60:0.35.

[0039] Example 2

[0040] A preparation method of a high-temperature resistant composite coating for electric vehicles includes the following steps:

[0041] Step 1: Methacrylic acid, methyl methacrylate, vinyl acetate, and a functional monomer were mixed evenly, then the organic solvent was added and the temperature was raised to 68 °C. An initiator and a modified filler were added and mixed, and then kept warm at 72 °C for 8.5 h and cooled to room temperature to obtain a modified acrylic resin. Among them, the mass ratio of methacrylic acid, methyl methacrylate, vinyl acetate, functional monomer, organic solvent, initiator, and modified filler is 7:17:6.3:14.7:73:0.85:2.6; the functional monomer is composed of N-methylolacrylamide and isooctyl acrylate mixed according to a mass ratio of 1.2:5.3; the organic solvent is ethyl acetate; the initiator is azobisisobutyronitrile;

[0042] Step 2: Add a leveling agent, nano-pigment, and auxiliary agent to the modified acrylic resin. Stir at a speed of 1050 r / min for 35 min, then add an organic solvent and stir at a speed of 460 r / min for 12 min. After passing through a 400-mesh sieve, a high-temperature resistant composite coating is obtained. Among them, the mass ratio of the modified acrylic resin, leveling agent, nano-pigment, auxiliary agent, and organic solvent is 52:0.6:10.7:1.7:33; the nano-pigment is Pigment Red A3B; the leveling agent is BYK-300; the auxiliary agent is silica particles; the organic solvent is ethyl acetate.

[0043] The preparation method of the modified filler includes the following steps:

[0044] 1) Add the mixed microspheres to an aqueous sodium hydroxide solution and stir at a speed of 460 r / min for 50 min. Then filter to remove the liquid and take the solid. Wash it with deionized water until neutral, place it in an oven, and dry it to a constant weight at a temperature of 63 °C to obtain a prefabricated filler. Among them, the mixed microspheres include the following components by weight: 13 parts of hollow glass microspheres with a particle size of 30 μm, 20 parts of hollow glass microspheres with a particle size of 40 μm, and 23 parts of hollow glass microspheres with a particle size of 60 μm; the concentration of the aqueous sodium hydroxide solution is 22 g / L; the dosage ratio of the hollow glass microspheres to the aqueous sodium hydroxide solution is 2.1 g:25 mL;

[0045] 2) Under a nitrogen atmosphere, add the prefabricated filler to deionized water and ultrasonicate at a power of 130 W for 50 min. After adding zirconium oxychloride, adjust the pH of the solution to 9.3 with ammonia water, heat at a temperature of 137 °C for 3.7 h, then take the solid and wash it with deionized water until neutral. Place it in an oven and dry it to a constant weight at a temperature of 73 °C to obtain a mixed filler. Among them, the mass ratio of deionized water, prefabricated filler, and zirconium oxychloride is 30:4.3:2.7;

[0046] 3) Stir alumina, absolute ethanol, and p-aminobenzoic acid at a speed of 660 r / min for 23 min, then add vanillin and stir at a temperature of 65 °C for 4.5 h. After filtering off the filtrate, wash it 3 times with absolute ethanol, place it in an oven, and dry it to a constant weight at a temperature of 73 °C to obtain modified alumina. Among them, the mass ratio of alumina, absolute ethanol, p-aminobenzoic acid, and vanillin is 13.7:52:2.7:4.1;

[0047] 4) Place the terpolymer, mixed filler, and modified alumina in a twin-screw extruder, melt-extrude at 190 °C, and then pelletize to obtain the modified filler. Among them, the mass ratio of the terpolymer, mixed filler, and modified alumina is 8:2.9:6.7.

[0048] The preparation method of the terpolymer includes the following steps:

[0049] Styrene, vinyltrimethoxysilane, and glycidyl methacrylate were placed in ethyl acetate. After adding azobisisobutyronitrile and heating at 72 °C for 3.5 h, the ethyl acetate was removed to obtain a terpolymer. Among them, the mass ratio of styrene, vinyltrimethoxysilane, glycidyl methacrylate, ethyl acetate, and azobisisobutyronitrile was 11:3.2:4.1:63:0.37.

[0050] Example 3

[0051] A preparation method of a high-temperature resistant composite coating for electric vehicles includes the following steps:

[0052] Step 1: Methacrylic acid, methyl methacrylate, vinyl acetate, and a functional monomer were mixed evenly, then the organic solvent was added and heated to 72 °C. After adding an initiator and a modified filler and mixing, it was kept warm at 73 °C for 9.5 h and then cooled to room temperature to obtain a modified acrylic resin. Among them, the mass ratio of methacrylic acid, methyl methacrylate, vinyl acetate, functional monomer, organic solvent, initiator, and modified filler was 8:18:6.7:15.3:77:0.9:2.8; the functional monomer was composed of N-hydroxymethylacrylamide and isooctyl acrylate mixed in a mass ratio of 1.3:5.6; the organic solvent was ethyl acetate; the initiator was azobisisobutyronitrile;

[0053] Step 2: A leveling agent, nano pigment, and auxiliary agent were added to the modified acrylic resin and stirred at 1130 r / min for 40 min. Then the organic solvent was added and stirred at 530 r / min for 13 min, and then passed through a 400-mesh sieve to obtain a high-temperature resistant composite coating. Among them, the mass ratio of the modified acrylic resin, leveling agent, nano pigment, auxiliary agent, and organic solvent was 53:0.7:11.3:2.3:37; the nano pigment was Pigment Red A3B; the leveling agent was BYK-300; the auxiliary agent was silica particles; the organic solvent was ethyl acetate.

[0054] The preparation method of the modified filler includes the following steps:

[0055] 1) The mixed microspheres were added to an aqueous sodium hydroxide solution and stirred at 530 r / min for 55 min. Then the liquid was filtered off and the solid was taken, washed with deionized water until neutral, placed in an oven, and dried to constant weight at 67 °C to obtain a prefabricated filler. Among them, the mixed microspheres included the following components by weight: 17 parts of hollow glass microspheres with a particle size of 30 μm, 22 parts of hollow glass microspheres with a particle size of 40 μm, and 27 parts of hollow glass microspheres with a particle size of 60 μm; the concentration of the aqueous sodium hydroxide solution was 23 g / L; the dosage ratio of the hollow glass microspheres to the aqueous sodium hydroxide solution was 2.3 g:25 mL;

[0056] 2) Under a nitrogen atmosphere, the prefabricated filler was added to deionized water and ultrasonically treated for 55 min at a power of 165 W. After adding zirconium oxychloride, the pH of the solution was adjusted to 9.7 using ammonia water. After heating at 145 °C for 4.5 h, the solid was taken and washed with deionized water until neutral, then placed in an oven and dried to constant weight at 77 °C to obtain a mixed filler; wherein, the mass ratio of the deionized water, prefabricated filler, and zirconium oxychloride is 30:4.7:2.8;

[0057] 3) Alumina, absolute ethanol, and p-aminobenzoic acid were stirred at 730 r / min for 25 min, then vanillin was added and stirred at 70 °C for 5.5 h. After filtering off the filtrate, it was washed 3 times with absolute ethanol and placed in an oven and dried to constant weight at 77 °C to obtain modified alumina; wherein, the mass ratio of the alumina, absolute ethanol, p-aminobenzoic acid, and vanillin is 14.5:53:2.9:4.1;

[0058] 4) The terpolymer, mixed filler, and modified alumina were placed in a twin-screw extruder, melt-extruded at 200 °C, and then pelletized to obtain a modified filler; wherein, the mass ratio of the terpolymer, mixed filler, and modified alumina is 9:3.1:7.3.

[0059] The preparation method of the terpolymer comprises the following steps:

[0060] Styrene, vinyltrimethoxysilane, and glycidyl methacrylate were placed in ethyl acetate, and azobisisobutyronitrile was added and heated at 73 °C for 3.5 h. After removing the ethyl acetate, a terpolymer was obtained; wherein, the mass ratio of the styrene, vinyltrimethoxysilane, glycidyl methacrylate, ethyl acetate, and azobisisobutyronitrile is 13:3.3:4.2:67:0.38.

[0061] Example 4

[0062] A preparation method of a high-temperature resistant composite coating for electric vehicles comprises the following steps:

[0063] Step 1: Methacrylic acid, methyl methacrylate, vinyl acetate, and a functional monomer were mixed evenly, then the organic solvent was added and the temperature was raised to 75 °C. An initiator and a modified filler were added and mixed, and then kept at 75 °C for 10 h and cooled to room temperature to obtain a modified acrylic resin; wherein, the mass ratio of the methacrylic acid, methyl methacrylate, vinyl acetate, functional monomer, organic solvent, initiator, and modified filler is 9:20:7:16:80:1.0:3.0; the functional monomer is composed of N-methylolacrylamide and isooctyl acrylate mixed according to a mass ratio of 1.5:6; the organic solvent is ethyl acetate; the initiator is azobisisobutyronitrile;

[0064] Step 2: Add a leveling agent, nano-pigment, and auxiliary agent to the modified acrylic resin. Stir at a speed of 1200 r / min for 45 min, then add an organic solvent and stir at a speed of 600 r / min for 15 min, and then pass through a 400-mesh sieve to obtain a high-temperature resistant composite coating; wherein, the mass ratio of the modified acrylic resin, leveling agent, nano-pigment, auxiliary agent, and organic solvent is 55:0.8:12:3:40; the nano-pigment is Pigment Red A3B; the leveling agent is BYK-300; the auxiliary agent is silica particles; the organic solvent is ethyl acetate.

[0065] The preparation method of the modified filler includes the following steps:

[0066] 1) Add the mixed microspheres to an aqueous sodium hydroxide solution. Stir at a speed of 600 r / min for 60 min, then filter to remove the liquid and take the solid. Wash with deionized water until neutral, place in an oven, and dry to constant weight at a temperature of 70 °C to obtain a prefabricated filler; wherein, the mixed microspheres include the following components by weight: 20 parts of hollow glass microspheres with a particle size of 30 μm, 24 parts of hollow glass microspheres with a particle size of 40 μm, and 30 parts of hollow glass microspheres with a particle size of 60 μm; the concentration of the aqueous sodium hydroxide solution is 25 g / L; the dosage ratio of the hollow glass microspheres to the aqueous sodium hydroxide solution is 2.4 g:25 mL;

[0067] 2) Under a nitrogen atmosphere, add the prefabricated filler to deionized water and sonicate at a power of 200 W for 60 min. After adding zirconium oxychloride, adjust the pH of the solution to 10 with ammonia water, heat at a temperature of 150 °C for 5 h, then take the solid and wash with deionized water until neutral, place in an oven, and dry to constant weight at a temperature of 80 °C to obtain a mixed filler; wherein, the mass ratio of the deionized water, prefabricated filler, and zirconium oxychloride is 30:5:3.0;

[0068] 3) Stir alumina, absolute ethanol, and p-aminobenzoic acid at a speed of 800 r / min for 30 min, then add vanillin and stir at a temperature of 75 °C for 6 h. After filtering off the filtrate, wash with absolute ethanol 3 times, place in an oven, and dry to constant weight at a temperature of 80 °C to obtain modified alumina; wherein, the mass ratio of the alumina, absolute ethanol, p-aminobenzoic acid, and vanillin is 15:55:3.0:4.2;

[0069] 4) Place the terpolymer, mixed filler, and modified alumina in a twin-screw extruder, melt and extrude at 210 °C, and then pelletize to obtain the modified filler; wherein, the mass ratio of the terpolymer, mixed filler, and modified alumina is 10:3.2:8.

[0070] The preparation method of the terpolymer includes the following steps:

[0071] Styrene, vinyltrimethoxysilane, and glycidyl methacrylate were placed in ethyl acetate. After adding azobisisobutyronitrile and heating at 75 °C for 4 h, the ethyl acetate was removed to obtain a terpolymer. Among them, the mass ratio of styrene, vinyltrimethoxysilane, glycidyl methacrylate, ethyl acetate, and azobisisobutyronitrile was 14:3.5:4.3:70:0.4.

[0072] Comparative Examples 1-3

[0073] Compared with Example 4, the difference in Comparative Examples 1-3 was that the components of the mixed filler were as shown in Table 1; the remaining components, preparation steps, and parameters were the same.

[0074] Table 1

[0075]

[0076] Comparative Example 4

[0077] Compared with Example 4, the difference in Comparative Example 4 was that step 1) was not carried out, and mixed microspheres were used instead of the prefabricated filler; the remaining components, preparation steps, and parameters were the same.

[0078] Comparative Example 5

[0079] Compared with Example 4, the difference in Comparative Example 5 was that step 2) was not carried out, and the prefabricated filler was used instead of the mixed filler; the remaining components, preparation steps, and parameters were the same.

[0080] Comparative Example 6

[0081] Compared with Example 4, the difference in Comparative Example 6 was that p-aminobenzoic acid was not used; the remaining components, preparation steps, and parameters were the same.

[0082] Comparative Example 7

[0083] Compared with Example 4, the difference in Comparative Example 7 was that vanillin was not used; the remaining components, preparation steps, and parameters were the same.

[0084] Comparative Example 8

[0085] Compared with Example 4, the difference in Comparative Example 8 was that vinyltrimethoxysilane was not used; the remaining components, preparation steps, and parameters were the same.

[0086] Comparative Example 9

[0087] Compared with Example 4, the difference in Comparative Example 9 was that glycidyl methacrylate was not used; the remaining components, preparation steps, and parameters were the same.

[0088] Comparative Example 10

[0089] Compared with Example 4, the difference in Comparative Example 10 is that the terpolymer is not used, and the other components, preparation steps and parameters are the same.

[0090] The composite coatings prepared in Examples 1-4 and Comparative Examples 1-10 were respectively subjected to the following performance tests, and the test results are shown in Table 2.

[0091] Impact resistance test: The impact resistance test was carried out according to GB / T 1732-2020.

[0092] High temperature resistance test: After baking at 150 °C for 100 hours, the impact strength of the film was tested;

[0093] Table 2

[0094] Impact strength (kg·cm) Impact strength after baking (kg·cm) Example 1 58 53 Example 2 57 52 Example 3 55 50 Example 4 60 55 Comparative Example 1 42 35 Comparative Example 2 46 38 Comparative Example 3 48 41 Comparative Example 4 46 37 Comparative Example 5 40 33 Comparative Example 6 47 40 Comparative Example 7 48 41 Comparative Example 8 41 34 Comparative Example 9 39 32 Comparative Example 10 35 27

[0095] It can be seen from the test results in Table 2 that compared with Comparative Examples 1-10, the composite coatings prepared by the present invention have excellent mechanical properties and high temperature resistance.

[0096] In the present invention, hollow glass microspheres with different particle sizes reinforce each other to fill the gaps, increasing the compactness of the structure after the coating is cured and improving its mechanical properties and high temperature resistance. After the hollow glass microspheres with different particle sizes are coarsened by sodium hydroxide, their surfaces become rougher, and more active hydroxyl groups are introduced. By generating uniformly distributed zirconia on the surface of the hollow glass microspheres, the rough surface of the hollow glass microspheres plays a role similar to "anchoring" for zirconia, increasing the bonding force between the two. And zirconia can coat the hollow glass microspheres, introducing more hydroxyl groups while reducing the phenomenon of agglomeration between particles, improving its thermal stability and wear resistance, and overcoming the phenomenon of extrusion and crushing of hollow glass microspheres caused by direct addition.

[0097] Then, in the present invention, p-aminobenzoic acid is loaded in the porous structure of alumina. p-Aminobenzoic acid can form a chemical bond connection with vanillin, introducing a thermally stable imine structure and benzene ring structure into the porous alumina, and increasing the dispersibility and compatibility of alumina in the acrylic resin coating through organic modification.

[0098] Finally, in the present invention, the terpolymer, mixed filler and modified alumina are melt-extruded. The organosilicon structure of the terpolymer can further improve the mechanical properties and high temperature resistance of the coating after curing. And the terpolymer can also be used as a compatibilizer. Using its epoxy group, a bridge is formed between the mixed filler and the modified alumina. The combination of carbon-carbon double bonds can significantly increase the compatibility and dispersibility of the mixed filler and the modified alumina in the system, playing a role in reinforcing the composite coating and improving its high temperature resistance.

[0099] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments of equivalent changes within the scope of the technical solution of the present invention by using the above-disclosed technical content. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high temperature resistant composite coating for electric vehicles, characterized in that: The preparation method comprises the following steps: Step 1: after methacrylic acid, methyl methacrylate, vinyl acetate and functional monomers are uniformly mixed, an organic solvent is added and heated, an initiator and a modified filler are added and mixed, and then heat-insulated treatment is performed, and the mixture is cooled to room temperature to obtain a modified acrylic resin; the functional monomers are composed of N-hydroxymethyl acrylamide and isooctyl acrylate; Step 2: adding a leveling agent, a nano pigment and an auxiliary agent to the modified acrylic resin and stirring at high speed, then adding an organic solvent and continuing stirring and sieving to obtain a high temperature resistant composite coating; Wherein, the preparation method of the modified filler comprises the following steps: 1) adding mixed microbeads to a sodium hydroxide aqueous solution for mechanical stirring, filtering out the liquid to obtain solids, washing with deionized water, and drying in an oven to obtain a prefabricated filler; the mixed microbeads include the following components by weight: 10-20 parts of hollow glass microbeads with a particle size of 30 μm, 18-24 parts of hollow glass microbeads with a particle size of 40 μm, and 20-30 parts of hollow glass microbeads with a particle size of 60 μm; 2) under an inert atmosphere, adding the prefabricated filler into deionized water for ultrasonic dispersion, adding zirconium oxychloride to adjust the pH of the solution to alkaline, heating the solution, washing the solid, and drying the solid in an oven to obtain a mixed filler; 3) After mixing alumina, anhydrous ethanol and p-aminobenzoic acid, add vanillin, heat and stir, filter out the filtrate, wash with ethanol, and dry in an oven to obtain modified alumina; the mass ratio of the alumina, anhydrous ethanol, p-aminobenzoic acid and vanillin is 13-15:50-55:2.6-3.0:4.0-4.2; 4) placing the terpolymer, mixed filler and modified alumina in a twin-screw extruder for melt extrusion and then granulating to obtain the modified filler; the terpolymer is styrene-vinyl trimethoxysilane-glycidyl methacrylate copolymer; the mass ratio of the terpolymer, mixed filler and modified alumina is 7-10:2.8-3.2:6-8.

2. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step one, the heating temperature is to heat to 65-75°C; the heat preservation treatment is to keep the temperature at 70-75°C for 8-10h; the mass ratio of methacrylic acid, methyl methacrylate, vinyl acetate, functional monomer, organic solvent, initiator and modified filler is 6-9:15-20:6-7:14-16:70-80:0.8-1.0:2.4-3.0; the functional monomer is a mixture of N-hydroxymethyl acrylamide and isooctyl acrylate in a mass ratio of 1.0-1.5:5-6; the organic solvent is ethyl acetate; the initiator is one or two of azobisisobutyronitrile and benzoyl peroxide.

3. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 2, the high-speed stirring is stirring at a speed of 1000-1200 r / min for 30-45 min; the continued stirring is stirring at a speed of 400-600 r / min for 10-15 min; the screening is through a 400-mesh sieve; the mass ratio of the modified acrylic resin, leveling agent, nano-pigment, auxiliary agent and organic solvent is 50-55:0.5-0.8:10-12:1-3:30-40; the leveling agent is one or two of BYK-300 and Evonik TEGO450; the auxiliary agent is silicon dioxide particles; and the organic solvent is ethyl acetate.

4. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 1), the mechanical stirring is stirring at a speed of 400-600 r / min for 45-60 min; the washing is washing until neutral; The drying step is drying at 60-70° C. to a constant weight.

5. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 1), the concentration of the sodium hydroxide aqueous solution is 20-25 g / L; the usage ratio of the hollow glass microspheres to the sodium hydroxide aqueous solution is 2.0-2.4 g:25 mL.

6. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 2), the inert atmosphere is a nitrogen atmosphere; the ultrasonic dispersion is performed at a power of 100-200 W for 45-60 min; the pH of the solution is adjusted to alkaline by using ammonia water to adjust the pH of the solution to 9-10; the heating is performed at a temperature of 130-150° C. for 3-5 h; the washing is performed using deionized water to wash to neutrality; the drying is performed at a temperature of 70-80° C. to dry to constant weight; the mass ratio of deionized water, prefabricated filler and zirconium oxychloride is 30:4-5:2.5-3.

0.

7. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 3), the stirring and mixing is stirring at a speed of 600-800 r / min for 20-30 min; the heating and stirring is stirring at a temperature of 60-75° C. for 4-6 h; and the drying is drying at a temperature of 70-80° C. to constant weight.

8. The method for preparing a high temperature resistant composite coating for electric vehicles according to claim 1, characterized in that: In step 4), the temperature of the melt extrusion is 180-210°C.

9. A high temperature resistant composite coating for electric vehicles prepared by the preparation method according to any one of claims 1 to 8.

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