A composite coating for vehicles based on spectral functional partitioning and a method for producing the same

Abstract

The present application belongs to the technical field of functional protective coating materials, and particularly relates to a composite coating for vehicles based on spectral functional zoning and a preparation method thereof. The composite coating for vehicles based on spectral functional zoning is composed of a finish paint and a varnish. The thickness of the finish paint is 15-400 microns, and the thickness of the varnish is 30-70 microns. The present application applies spectral management technology to the automobile body coating to realize radiation refrigeration and energy saving and cooling. In the coating structure, a double-layer structure of 'ultraviolet reflection front, main reflection back and radiation channel through' is designed. In terms of function, the ultraviolet reflection and full-waveband high transmission are realized through the cover light varnish layer, and the strong reflection of visible light and near-infrared light is realized through the finish paint layer. Finally, a lightweight, high-durability and maintenance-free composite coating for vehicles is prepared, which can block the ultraviolet heat generation from the source, efficiently reflect the main solar heat, and keep the radiation heat dissipation channel unblocked, and is suitable for vehicle body cooling.

Description

Technical Field

[0001] This invention belongs to the field of functional protective coating materials technology, specifically relating to a composite coating for automobiles based on spectral functional partitioning and its preparation method. Background Technology

[0002] With the automotive industry's increasing demands for energy conservation, environmental protection, and driving comfort, thermal management of vehicles under intense sunlight has become a critical issue. Summer sun exposure causes a sharp rise in vehicle interior temperature, severely impacting the driving experience and significantly increasing air conditioning energy consumption. For electric vehicles, this directly translates to a shortened driving range. Existing paint technologies aimed at improving heat insulation performance primarily focus on increasing the reflectivity of the coating to visible and near-infrared light from sunlight. However, these technologies have significant limitations: First, they generally lack effective management of ultraviolet (UV) radiation. Traditional clear coats absorb UV rays, leading not only to resin matrix aging but also to the conversion of UV energy into heat, directly exacerbating the vehicle's temperature rise. Second, attempting to simultaneously integrate high solar reflectivity and high infrared radiation within a single coating is technically complex, and fillers with different functions are prone to interference, resulting in performance trade-offs. Most importantly, existing coating materials often have low infrared transmittance in the 8-13μm "atmospheric window" band, severely hindering the vehicle's paint from dissipating heat into outer space through radiative cooling, resulting in coatings that are more effective at heat insulation than at heat dissipation.

[0003] Therefore, developing a novel coating technology that can block ultraviolet heat generation at the source, efficiently reflect the main solar energy, and keep the radiative heat dissipation channel unobstructed has become an important research and development direction in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a spectral functional partitioning-based automotive composite coating and its preparation method. The spectral functional partitioning-based automotive composite coating can block ultraviolet heat generation at the source, efficiently reflect the main solar heat, and maintain unobstructed radiative heat dissipation channels. It also features lightweight, high durability, and maintenance-free operation.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The first aspect of this invention provides an automotive composite coating based on spectral functional partitioning, which consists of a topcoat and a clearcoat, and its structural diagram is shown below. Figure 1 .

[0007] Preferably, the thickness of the topcoat is 15-400 μm; the thickness of the clear coat is 30-70 μm.

[0008] The raw materials for preparing the topcoat, by weight, include 10-30 parts of topcoat filler, 1-10 parts of topcoat additives, 10-60 parts of topcoat base material, and 5-20 parts of topcoat solvent.

[0009] Preferably, the topcoat filler includes at least three of the following: flake alumina, spherical alumina, titanium dioxide, boron nitride, barium sulfate, and hollow glass microspheres.

[0010] Preferably, the particle size of the flake-shaped alumina is 1~10μm; the particle size of the spherical alumina is 0.5~5μm.

[0011] Preferably, the titanium dioxide is rutile titanium dioxide with a particle size of 200~600nm.

[0012] Preferably, the boron nitride is plate-shaped boron nitride with a particle size of 1~10μm.

[0013] Preferably, the barium sulfate particle size is 200~800nm.

[0014] Preferably, the hollow glass microspheres have a particle size of 10-50 μm.

[0015] In some alternative solutions, the topcoat filler is titanium dioxide, hollow glass microspheres, and flake alumina in a mass ratio of (3.5-4.5):(1.5-2.5):1; more preferably, it is 4:2:1.

[0016] In some alternative solutions, the topcoat filler is titanium dioxide, hollow glass microspheres, barium sulfate, and flake alumina, with a mass ratio of (4.5-5.5):(2-3):(1-2):1; more preferably, it is 5:2.5:1.5:1.

[0017] In some alternative solutions, the topcoat filler is titanium dioxide, hollow glass microspheres, and flake boron nitride, with a mass ratio of (3.5-4.5):(1-2):1; more preferably, it is 4:1.6:1.

[0018] Preferably, the topcoat additives include at least one of film-forming aids, wetting and dispersing agents, defoamers, leveling agents, and thickeners.

[0019] Preferably, the mass ratio of the film-forming aid, wetting and dispersing agent, defoamer, leveling agent and thickener is (20-28): (7-11): (6-10): (1-3): (1-3).

[0020] Preferably, the film-forming aid includes at least one of propylene glycol monobutyl ether, diethylene glycol monomethyl ether, dipropylene glycol monobutyl ether, and alcohol ester 12.

[0021] Preferably, the wetting and dispersing agent comprises at least one of polyether-modified polysiloxane, fluoroalkyl ethoxylate, fluorocarbon-modified polyacrylate, 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its ethoxylate, and 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol and its ethoxylate.

[0022] Preferably, the defoamer comprises a polysiloxane-polyether copolymer of fumed silica.

[0023] Preferably, the leveling agent includes at least one of polyether / polyester modified polydimethylsiloxane and hydroxyl-functional acrylic copolymer.

[0024] Preferably, the thickener includes at least one of hydroxyethyl cellulose, carboxymethyl cellulose, and methyl hydroxyethyl cellulose.

[0025] Preferably, the topcoat base material includes at least one of acrylic acid / methacrylic acid copolymer, styrene-acrylate copolymer, silicone-acrylate copolymer, fluorinated acrylate copolymer emulsion, and acrylic emulsion containing hydroxyl functional groups.

[0026] The solvent for the topcoat is water.

[0027] The preparation method of the topcoat includes the following steps:

[0028] A1. Drying the packing material;

[0029] A2. Pre-dispersion: Mix the topcoat solvent, wetting and dispersing agent, and defoamer to obtain a pre-dispersion liquid;

[0030] A3. Powder dispersion: Add topcoat filler to the pre-dispersion liquid in small amounts several times, and stir evenly to obtain a slurry;

[0031] A4. Preparation of main paint: Add slurry to the topcoat base, stir evenly, add the remaining topcoat additives, continue stirring, filter, and the product is obtained.

[0032] Preferably, the specific conditions for step A1 are: temperature of 60~70℃ and time of 1~2 days.

[0033] Preferably, the mixing conditions in step A2 are: a rotation speed of 400~1800 rpm and a time of 5~10 min.

[0034] Preferably, in step A3, during the addition of the topcoat filler, the stirring speed is maintained at 400~600 rpm, and after the addition is completed, the stirring speed is maintained at 400~1800 rpm for 15~60 minutes.

[0035] Preferably, in step A4, before adding the slurry to the topcoat base, the topcoat base is first stirred and dispersed at a stirring speed of 400-600 rpm, then the slurry is added, and the mixture is stirred at 400-1800 rpm for 15-60 minutes. The stirring speed is then adjusted to 400-600 rpm, and the remaining topcoat additives are added gradually. After the addition is complete, the mixture is stirred at a speed of 400-1800 rpm for another 30-60 minutes.

[0036] The raw materials for preparing the varnish, by weight, include 1-20 parts of varnish filler, 40-60 parts of varnish resin, 20-40 parts of curing agent, and 1-15 parts of varnish additives.

[0037] Preferably, the varnish filler includes at least two of the following: magnesium oxide powder, aluminum oxide powder, hydrophobic fumed silica powder, hollow glass microspheres, and zinc oxide.

[0038] Preferably, the particle size of the magnesium oxide powder is 10~400nm.

[0039] Preferably, the zinc oxide includes at least one of silane coupling agent modified zinc oxide and silica-coated zinc oxide.

[0040] Preferably, the zinc oxide in the silane coupling agent modified zinc oxide has a particle size of 20-100 nm, and the silane coupling agent is KH560; the zinc oxide in the silica-coated zinc oxide has a particle size of 10-100 nm.

[0041] In some optional embodiments, the preparation method of the silane coupling agent modified zinc oxide is a conventional method: zinc oxide nanoparticles with a particle size of 20-100 nm are dispersed in a mixed solvent of anhydrous ethanol and deionized water at a material-to-liquid ratio of 1 g:15 mL (the volume ratio of anhydrous ethanol to deionized water is 90-95:5-10), and 1%-3% of the silane coupling agent KH560 is added. The pH of the system is adjusted to 4.0-5.5 with dilute acetic acid. The reaction is stirred at 60-80℃ for 3-5 hours. After the reaction is completed, the mixture is centrifuged, washed 2-3 times with anhydrous ethanol, and dried to obtain the silane coupling agent modified zinc oxide.

[0042] In some alternative solutions, the preparation method of the silica-coated zinc oxide is a conventional method: zinc oxide nanoparticles with a particle size of 10~100nm are dispersed in an ethanol / water mixed solvent, ammonia is added to adjust the pH to 8.0~8.5, and then tetraethyl orthosilicate (TEOS) is slowly added dropwise. The mixture is stirred and reacted at room temperature for 4~6 hours. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain silica-coated zinc oxide.

[0043] Preferably, the alumina powder is flake-shaped alumina powder with a particle size of 20~1000nm.

[0044] Preferably, the hollow glass microspheres have a particle size of 10~50μm.

[0045] Preferably, the particle size of the hydrophobic fumed silica powder is 10 nm to 5 μm.

[0046] In some alternative solutions, the varnish filler is magnesium oxide powder, hollow glass microspheres, and hydrophobic fumed silica powder, with a mass ratio of (6-9):(3-6):(1-3); more preferably, it is 2:2:1.

[0047] In some alternative embodiments, the varnish filler is alumina powder, magnesium oxide powder, hydrophobic fumed silica powder, and hollow glass microspheres, with a mass ratio of 1:(3.5-4.5):(1.5-2.5):(6.5-7.5). A more preferred ratio is 1:4:2:7.

[0048] Preferably, the varnish resin is at least one of MyutoS 929-186 nano ceramic varnish resin, PPG P190-588A varnish resin, and Nippon 2K HD varnish resin.

[0049] Preferably, the curing agent is a curing agent compatible with varnish resin.

[0050] Preferably, the varnish additive is at least one of a diluent, a dispersant, a leveling agent, and a varnish defoamer.

[0051] Preferably, the mass ratio of the diluent, dispersant, leveling agent, and varnish defoamer is (6-8):(1-3):(1-3):(1-7).

[0052] Preferably, the diluent is a diluent for varnish resin.

[0053] Preferably, the dispersant is a high molecular weight block copolymer solution containing pigment affinity groups.

[0054] Preferably, the leveling agent is at least one of polyether-modified polydimethylsiloxane and polyether siloxane copolymer.

[0055] Preferably, the varnish defoamer is a mixture / solution of a defoaming polymer and a polysiloxane.

[0056] The method for preparing the varnish includes the following steps:

[0057] B1. Drying the packing;

[0058] B2. Pre-dispersion: The resin is mixed with the dispersant in the varnish additive to obtain a pre-dispersion;

[0059] B3. Filler dispersion: Add the dried varnish filler from step B1 to the dispersion in small amounts several times, and stir evenly to obtain a slurry.

[0060] B4. Adding additives: Add the remaining varnish additives to the slurry and continue stirring to obtain the main varnish.

[0061] B5. Add hardener: Add hardener to the clear varnish within 6 hours before coating, stir well and filter to obtain the clear varnish.

[0062] Preferably, the specific conditions for step B1 are: temperature of 60~70℃ and time of 1~2 days.

[0063] Preferably, the mixing conditions in step B2 are: a rotation speed of 400~1800 rpm and a time of 1~10 min.

[0064] Preferably, in step B3, during the addition of varnish filler, the pre-dispersion liquid is stirred at a speed of 400-600 rpm, and after the addition is completed, it is stirred at a speed of 400-1800 rpm for 20-60 minutes.

[0065] Preferably, in step B4, the rotation speed is maintained at 400~1800 rpm throughout the process, and after adding the remaining varnish additives, the mixture is stirred for 20~60 minutes.

[0066] Preferably, in step B5, the stirring conditions are: a rotation speed of 300~1000 rpm and a time of 1~10 min.

[0067] Preferably, in step B5, the mesh size of the filter screen is 100-200 mesh.

[0068] A second aspect of the present invention provides a method for preparing the aforementioned automotive composite coating based on spectral functional partitioning, comprising the following steps:

[0069] S1. Apply the topcoat to the pre-treated and qualified car body primer surface, and after obtaining the coating, level it and pre-dry it to obtain the topcoat coating.

[0070] S2. Spray the clear varnish onto the surface of the topcoat coating and bake to obtain the composite coating.

[0071] Preferably, in step S1, the topcoat is applied by spraying or roller coating, and the thickness of the wet film is 20~120μm.

[0072] Preferably, in step S1, the leveling time is 10-30 min, the pre-drying temperature is 60-80℃, and the pre-drying time is 5-20 min.

[0073] Preferably, in step S2, the specific method of spraying is air spraying.

[0074] Preferably, in step S2, the baking temperature is 100~140℃ and the baking time is 10~60min.

[0075] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0076] 1. This invention proposes a spectral functional partitioning-based automotive composite coating. By applying spectral management technology to automotive body coatings, it achieves radiative cooling and energy-saving temperature reduction. Structurally, a two-layer architecture is designed with "pre-UV reflection, post-primary reflection, and unobstructed radiation channels." Functionally, a clear coat layer achieves UV reflection and high transmittance across the entire wavelength range, while a topcoat layer achieves strong reflection of visible and near-infrared light. Ultimately, a lightweight, highly durable, and maintenance-free automotive composite coating is prepared that blocks UV heat generation at its source, efficiently reflects primary solar heat, and maintains unobstructed radiative heat dissipation channels, making it suitable for vehicle body cooling.

[0077] 2. In this invention, by adding powders such as MgO, Al2O3, SiO2, and hollow glass microspheres to the outer clear varnish to reflect ultraviolet rays, high-energy ultraviolet rays are effectively reflected, preventing them from penetrating to the lower layer and being absorbed and converted into heat, while simultaneously protecting the lower resin from ultraviolet aging. By adding modified diamond powder, the clear varnish layer maintains high transmittance to visible light, near-infrared light, and atmospheric window wavelengths, while also imparting superhydrophobicity and high wear resistance to the surface.

[0078] 3. In the inner topcoat, this invention adds highly reflective / high-emissivity powders such as Al2O3, TiO2, and hBN to achieve efficient reflection of visible and near-infrared light that penetrates the clear coat, thereby maximizing the blocking of the main heat source. Attached Figure Description

[0079] Figure 1 This is a structural diagram of the automotive composite coating based on spectral functional partitioning prepared according to the present invention.

[0080] Figure 2 The appearance of the topcoat of the automotive composite coating prepared in Example 1 of the present invention.

[0081] Figure 3 This is a photograph of the hydrophobic angle of the automotive composite coating prepared in Example 2 of the present invention. Detailed Implementation

[0082] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0083] The raw materials used in this invention are partially commercially available, as detailed below:

[0084] The flake-shaped alumina, with a particle size of 1~10μm, comes from Hangzhou Jikang New Materials and has a purity of ≥99.5%.

[0085] Spherical alumina with a particle size of 0.5~5μm, sourced from Shanghai Xiangtian Nanomaterials Technology Co., Ltd., with a purity ≥99.9%.

[0086] Rutile titanium dioxide with a particle size of 200~600nm, sourced from the China Metallurgical Research Institute, with a purity of ≥99.99%.

[0087] The plate-shaped boron nitride, with a particle size of 1~10μm, comes from Beasley New Materials (Suzhou) Co., Ltd., with a purity of >99.0%.

[0088] Barium sulfate, with a particle size of 200~800nm, is a reagent from Shanghai Maclean's Laboratory, with a purity of ≥99.5%.

[0089] Hollow glass microspheres, with a particle size of 10-50 μm, are derived from 3M, with a density > 0.15 g / mL and a strength > 150 MPa.

[0090] Wetting and dispersing agent, polyether-modified polysiloxane, Evonik Industries, Germany, TEGO PREN 5885.

[0091] Defoamer, polysiloxane-polyether copolymer of fumed silica, Evonik, Germany, TEGO Foamex 816.

[0092] Leveling agent, polyether-modified polydimethylsiloxane, BYK 333.

[0093] Thickener, hydroxyethyl cellulose, Dow Chemical, QP-300.

[0094] The topcoat base materials, namely silicone-acrylate copolymer SD-528, styrene-acrylate copolymer SD-588, acrylic / methacrylic acid copolymer SD-688, fluorinated acrylate copolymer emulsion SD-568, and hydroxyl-functionalized acrylic emulsion Steba AW 2F5064, are all from Jiangsu Shengda New Material Technology Co., Ltd.

[0095] Zinc oxide modified with silane coupling agent has a particle size of 20~100nm. The silane coupling agent is KH560, which is self-made.

[0096] Silica-coated zinc oxide with a particle size of 10~100nm, self-made.

[0097] The flake-shaped alumina powder has a particle size of 20~1000nm, comes from Hangzhou Jikang New Materials, and has a purity of ≥99.5%.

[0098] Magnesium oxide powder, with a particle size of 10~400nm, is from Bohuas Nanotechnology (Ningbo) Co., Ltd., with a purity of ≥99.9%.

[0099] Hydrophobic fumed silica powder with a particle size of 10nm~5μm, sourced from Evonik, Germany.

[0100] Varnish resin, PPG P190-588A; Hardener, PPG P190-588A varnish resin matching hardener; Diluent: varnish resin matching diluent.

[0101] Dispersant, high molecular weight block copolymer solution containing pigment affinity groups, Hengcai Nano CX-103.

[0102] Defoamer, a mixture / solution of defoaming polymer and polysiloxane, BYK Chemical, BYK141.

[0103] Example 1:

[0104] This embodiment provides a spectral functional partitioning-based automotive composite coating, which consists of a topcoat and a clear coat.

[0105] The topcoat thickness is 300 μm; the clear coat thickness is 50 μm.

[0106] The raw materials for preparing the topcoat, by weight, are 30 parts topcoat filler, 5 parts topcoat additives, 50 parts topcoat base material, and 15 parts topcoat solvent.

[0107] The topcoat filler consists of titanium dioxide with a particle size of 300 nm, hollow glass microspheres with a particle size of 16 μm, and flake-shaped alumina with a particle size of 1 μm, in a mass ratio of 4:2:1.

[0108] The topcoat additives are film-forming aids, wetting and dispersing agents, defoamers, leveling agents, and thickeners, with a mass ratio of 10:6:4:1:1.

[0109] The film-forming aid is dipropylene glycol monomethyl ether.

[0110] The wetting and dispersing agent is a polyether-modified polysiloxane.

[0111] The defoamer is a polysiloxane-polyether copolymer of fumed silica.

[0112] The leveling agent is polyether-modified polydimethylsiloxane.

[0113] The thickener is hydroxyethyl cellulose.

[0114] The base material for the topcoat is an organosilicon-acrylate copolymer.

[0115] The solvent for the topcoat is deionized water.

[0116] The preparation method of the topcoat includes the following steps:

[0117] A1. Drying the packing material;

[0118] A2. Pre-dispersion: Mix the topcoat solvent, wetting and dispersing agent, and defoamer to obtain a pre-dispersion liquid;

[0119] A3. Powder dispersion: Add topcoat filler to the pre-dispersion liquid in small amounts several times, and stir evenly to obtain a slurry;

[0120] A4. Preparation of main paint: Add slurry to the topcoat base, stir evenly, add the remaining topcoat additives, continue stirring, filter, and the product is obtained.

[0121] The specific conditions for step A1 are: temperature of 60℃ and time of 1 day.

[0122] The mixing conditions for step A2 are: a rotation speed of 1000 rpm and a time of 10 min.

[0123] In step A3, during the addition of the topcoat filler, maintain a stirring speed of 600 rpm, and after the addition is complete, stir at a speed of 1000 rpm for 35 minutes.

[0124] In step A4, before adding the slurry to the topcoat base, the topcoat base is first stirred and dispersed at a stirring speed of 600 rpm, then the slurry is added, and after stirring at 1600 rpm for 35 minutes, the stirring speed is adjusted to 600 rpm, and the remaining topcoat additives are added in batches. After the addition is completed, stirring is continued at a speed of 1600 rpm for 35 minutes.

[0125] The raw materials for preparing the varnish, by weight, are 10 parts varnish filler, 50 parts resin, 25 parts curing agent, and 15 parts varnish additives.

[0126] The varnish filler consists of magnesium oxide powder with a particle size of 100 nm, hollow glass microspheres with a particle size of 16 μm, and hydrophobic fumed silica powder with a particle size of 16 nm, in a mass ratio of 2:2:1.

[0127] The varnish resin is PPG P190-588A varnish resin.

[0128] The curing agent is PPG P190-588A varnish curing agent.

[0129] The varnish additives are diluent, dispersant, leveling agent, and defoamer, with a mass ratio of 8:1:1:1.

[0130] The diluent is a diluent for varnish resin.

[0131] The dispersant is a high molecular weight block copolymer solution containing pigment affinity groups.

[0132] The leveling agent is polyether-modified polydimethylsiloxane.

[0133] The defoamer is a mixture / solution of a defoaming polymer and a polysiloxane.

[0134] The preparation method of the varnish includes the following steps:

[0135] B1. Drying the packing;

[0136] B2. Pre-dispersion: The resin is mixed with the dispersant in the varnish additive to obtain a pre-dispersion;

[0137] B3. Filler dispersion: Add the dried varnish filler from step B1 to the dispersion in small amounts several times, and stir evenly to obtain a slurry.

[0138] B4. Adding additives: Add the remaining varnish additives to the slurry and continue stirring to obtain the main varnish.

[0139] B5. Add hardener: Add hardener to the clear varnish within 6 hours before coating, stir well and filter to obtain the clear varnish.

[0140] The specific conditions for step B1 are: temperature 60℃ and time 1 day.

[0141] The mixing conditions for step B2 are: a rotation speed of 800 rpm and a time of 5 min.

[0142] In step B3, during the addition of varnish filler, the pre-dispersion liquid is stirred at 600 rpm, and after the addition is completed, it is stirred at 800 rpm for 30 minutes.

[0143] In step B4, the rotation speed is maintained at 800 rpm throughout the process. After adding the remaining varnish additives, stir for 30 minutes.

[0144] In step B5, the stirring conditions are: a rotation speed of 500 rpm and a stirring time of 5 min.

[0145] In step B5, the filter screen used for filtration has a mesh size of 100.

[0146] The method for preparing the automotive composite coating based on spectral functional partitioning includes the following steps:

[0147] S1. Apply the topcoat to the pre-treated and qualified car body primer surface, and after obtaining the coating, level it and pre-dry it to obtain the topcoat coating.

[0148] S2. Spray the clear varnish onto the surface of the topcoat coating and bake to obtain the composite coating.

[0149] In step S1, the specific method for applying the topcoat is spraying.

[0150] In step S1, the leveling time is 10 minutes, the pre-drying temperature is 75°C, and the pre-drying time is 10 minutes.

[0151] In step S2, the specific spraying method is air spraying.

[0152] In step S2, the baking temperature is 140℃ and the time is 25 minutes.

[0153] Example 2:

[0154] This embodiment provides a composite coating for automobiles based on spectral functional partitioning. The specific implementation method is the same as that in Embodiment 1, except that:

[0155] The raw materials for preparing the topcoat, by weight, are 30 parts topcoat filler, 5 parts topcoat additives, 50 parts topcoat base material, and 15 parts topcoat solvent.

[0156] The topcoat filler consists of titanium dioxide with a particle size of 300 nm, hollow glass microspheres with a particle size of 16 μm, and boron nitride with a particle size of 1 μm, in a mass ratio of 4:1.6:1.

[0157] Example 3:

[0158] This embodiment provides a composite coating for automobiles based on spectral functional partitioning. The specific implementation method is the same as that in Embodiment 1, except that:

[0159] The raw materials for preparing the varnish, by weight, are 10 parts varnish filler, 50 parts resin, 25 parts curing agent, and 15 parts varnish additives.

[0160] The varnish filler consists of 500nm flake alumina powder, 100nm magnesium oxide powder, 16nm hydrophobic fumed silica powder, and hollow glass microspheres, with a mass ratio of 1:4:2:7.

[0161] Comparative Example 1:

[0162] The only difference between this comparative example and Example 1 is:

[0163] The raw materials for preparing the varnish, by weight, include 5 parts varnish filler, 60 parts resin, 30 parts curing agent, and 5 parts varnish additives.

[0164] The varnish filler is hydrophobic fumed silica with a particle size of 16 nm.

[0165] Comparative Example 2:

[0166] The only difference between this comparative example and Example 1 is:

[0167] The filler in the topcoat is rutile titanium dioxide with a particle size of 300 nm.

[0168] Comparative Example 3:

[0169] The only difference between this comparative example and Example 1 is:

[0170] The filler in the topcoat is barium sulfate with a particle size of 100 nm.

[0171] Comparative Example 4:

[0172] The only difference between this comparative example and Example 1 is:

[0173] The varnish filler is magnesium oxide powder with a particle size of 100 nm.

[0174] Performance testing:

[0175] The solar reflectance and ultraviolet spectral reflectance of the coating were tested according to ISO 22969:2019 "Determination of solar reflectance of paints and varnishes"; the solar irradiance was tested according to ASTM C1371-15 "Standard test method for determination of emissivity of materials near room temperature using a portable radiometer", measuring the 8-13 μm irradiance; and the hydrophobic angle of the coating was tested according to ISO 19403-2:2020 "Wettability of paints and varnishes - Part 2: Determination of surface free energy of solids by contact angle method". The test results are shown in Table 1. Figure 2 and Figure 3 .

[0176] Table 1 Performance Test Results

[0177]

[0178] From Table 1, Figure 2 and Figure 3It can be seen that the automotive composite coatings based on spectral functional partitioning prepared in Examples 1-3 exhibit excellent solar reflectance, ultraviolet spectral reflectance, and 8-13 μm radiative emissivity, while also possessing a high hydrophobic angle number. In Comparative Example 1, the clear coat filler contains only hydrophobic fumed silica with a refractive index of only 1.46 and a particle size much smaller than the ultraviolet wavelength (200-400 nm), resulting in extremely low scattering efficiency. It primarily functions as a thickener, thixotropic agent, and hydrophobic agent, failing to effectively reflect ultraviolet light. Ultraviolet light penetrates the clear coat and reaches the topcoat, thus losing its ultraviolet protection function. In Comparative Example 2, the topcoat filler is rutile titanium dioxide, which only exhibits strong scattering in the visible light band, with a significantly reduced near-infrared scattering ability. This is mainly because a single particle size cannot cover the entire spectrum, resulting in low near-infrared reflectance (which accounts for 53% of the energy in sunlight), making it difficult for the overall solar reflectance to exceed 80%. In Comparative Example 3, the topcoat filler was barium sulfate, which only exhibits high reflectivity in a specific band of the solar spectrum, but its near-infrared scattering efficiency is insufficient. A single batch cannot achieve particle size distribution, resulting in low full-spectrum reflectivity, making it difficult to meet high reflectivity requirements. In Comparative Example 4, the clear varnish filler consisted only of 100nm magnesium oxide powder, which has extremely low scattering efficiency in the ultraviolet band. Furthermore, due to its large addition amount, it is highly hygroscopic and prone to hydration and expansion, leading to coating cracks, poor long-term stability, and inability to achieve continuous ultraviolet reflection.

[0179] Therefore, this invention proposes a composite coating for vehicles based on spectral functional partitioning. The resulting coating is a lightweight, highly durable, and maintenance-free composite coating for vehicles that can block ultraviolet heat generation at the source, efficiently reflect the main solar heat, and keep the radiative heat dissipation channel unobstructed. It is suitable for vehicle body cooling.

[0180] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite coating for automobiles based on spectral functional partitioning, characterized in that, It consists of a topcoat and a clear coat, wherein the thickness of the topcoat is 15-400 μm and the thickness of the clear coat is 30-70 μm. The raw materials for preparing the topcoat, by weight, include 10-30 parts of topcoat filler, 1-10 parts of topcoat additives, 10-60 parts of topcoat base material, and 5-20 parts of topcoat solvent.

2. The automotive composite coating based on spectral functional partitioning according to claim 1, characterized in that, The topcoat filler includes at least three of the following: flake alumina, spherical alumina, titanium dioxide, boron nitride, barium sulfate, and hollow glass microspheres.

3. The automotive composite coating based on spectral functional partitioning according to claim 2, characterized in that, The alumina particles are 1-10 μm in size; the spherical alumina particles are 0.5-5 μm in size; the titanium dioxide is rutile titanium dioxide with a particle size of 200-600 nm; the boron nitride is flake boron nitride with a particle size of 1-10 μm; the barium sulfate particles are 200-800 nm in size; and the hollow glass microspheres have a particle size of 10-50 μm.

4. The automotive composite coating based on spectral functional partitioning according to claim 1, characterized in that, The topcoat additives include at least one of film-forming aids, wetting and dispersing agents, defoamers, leveling agents, and thickeners.

5. The automotive composite coating based on spectral functional partitioning according to claim 4, characterized in that, The preparation method of the topcoat includes the following steps: A1. Drying the packing material; A2. Pre-dispersion: Mix the topcoat solvent, wetting and dispersing agent, and defoamer to obtain a pre-dispersion liquid; A3. Powder dispersion: Add topcoat filler to the pre-dispersion liquid in small amounts several times, and stir evenly to obtain a slurry; A4. Preparation of main paint: Add slurry to the topcoat base, stir evenly, add the remaining topcoat additives, continue stirring, filter, and the product is obtained.

6. The automotive composite coating based on spectral functional partitioning according to claim 1, characterized in that, The raw materials for preparing the varnish, by weight, include 1-20 parts of varnish filler, 40-60 parts of varnish resin, 20-40 parts of curing agent, and 1-15 parts of varnish additives.

7. The automotive composite coating based on spectral functional partitioning according to claim 6, characterized in that, The varnish filler includes at least one of magnesium oxide powder, aluminum oxide powder, hydrophobic fumed silica powder, hollow glass microspheres, and zinc oxide.

8. The automotive composite coating based on spectral functional partitioning according to claim 7, characterized in that, The magnesium oxide powder has a particle size of 10~400nm; the alumina powder is flake-shaped alumina powder with a particle size of 20~1000nm; the hollow glass microspheres have a particle size of 10~50μm; and the hydrophobic fumed silica powder has a particle size of 10nm~5μm.

9. A method for preparing a vehicle composite coating based on spectral functional partitioning according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Apply the topcoat to the pre-treated and qualified body primer surface, and after obtaining the coating, level it and pre-dry it to obtain the topcoat coating. S2. Spray the clear varnish onto the surface of the topcoat coating, and bake to obtain the composite coating.

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