A double-layer self-cleaning radiant refrigeration coating with high base adhesion and a preparation method and application thereof

Abstract

The present application belongs to the technical field of energy-saving coatings, and particularly relates to a double-layer self-cleaning radiant refrigeration coating with high base adhesion, a preparation method and application thereof. The present application provides excellent base adhesion by the lower base coating, and provides high solar reflectance, high atmospheric window emissivity and self-cleaning function by the upper self-cleaning radiant refrigeration coating. The silane coupling agent in the upper layer enhances the interlayer adhesion and improves the hydrophobic angle of the coating surface. The average reflectivity of the coating in the solar wave band is above 93.8%, the average emissivity in the 8-13 microns band is above 93.1%, the cooling amplitude is above 3.4 DEG C, the base adhesion is grade 1, the water contact angle is 100 DEG, the coating has excellent weather resistance and construction convenience, and is suitable for building exterior wall energy-saving reconstruction.

Description

Technical Field

[0001] This invention belongs to the field of energy-saving coating technology, specifically relating to a double-layer self-cleaning radiation cooling coating with high substrate adhesion, its preparation method, and its application. Background Technology

[0002] With the intensification of the urban heat island effect and the frequent occurrence of extreme heat events, building cooling energy consumption remains high. Radiative cooling technology passively radiates heat to outer space through atmospheric windows (8-13 μm), achieving sub-environmental cooling without additional energy consumption, and is a research hotspot in the field of building energy conservation. Among them, radiative cooling coatings are considered one of the most promising radiative cooling materials due to their advantages such as convenient construction, applicability to irregularly shaped surfaces, and mass production capability.

[0003] However, existing radiative cooling coatings still face two major engineering challenges when applied to building exteriors: first, insufficient adhesion between the coating and substrates such as cement, tiles, and metals, leading to peeling and flaking after prolonged outdoor use; second, the coating surface is prone to dust accumulation and contamination, resulting in decreased optical performance and reduced cooling effect. Therefore, developing a two-layer coating that combines high substrate adhesion, self-cleaning function, and excellent radiative cooling performance is of great significance for promoting the practical application of radiative cooling technology. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a double-layer self-cleaning radiation-cooling coating with high substrate adhesion. The coating formed using this coating achieves an average reflectivity of over 93.8% in the solar radiation band (0.3-2.5 μm) and an average emissivity of over 93.1% in the 8-13 μm atmospheric window. Under strong sunlight at noon in summer, the surface temperature of the coating can be 3.4 ℃ lower than the ambient air temperature, exhibiting a significantly better cooling effect than commercially available ordinary white coatings. Furthermore, it possesses excellent substrate adhesion (Grade 1) and self-cleaning ability (hydrophobic angle 100°).

[0005] An embodiment of the present invention provides a high-adhesion double-layer self-cleaning radiation-cooling coating, comprising: an upper self-cleaning radiation-cooling coating and a lower high-adhesion primer coating;

[0006] The upper self-cleaning radiation cooling coating comprises the following raw materials by weight: 10-200 parts of fluoropolymer, 20-200 parts of first inorganic pigment powder, 10-150 parts of second inorganic pigment powder, 50-500 parts of organic solvent, 2-50 parts of silane coupling agent, and 1-40 parts of hydrophobic additive. The underlying high-adhesion primer, by weight, comprises the following raw materials: 10-200 parts of water-based resin, 20-250 parts of third inorganic pigment powder, 30-400 parts of deionized water, and 1-80 parts of additives.

[0007] Advantages and technical effects of the high substrate adhesion double-layer self-cleaning radiation cooling coating of the present invention: 1. In this embodiment of the invention, the lower high-adhesion primer coating uses an aqueous resin containing polar functional groups (such as hydroxyl, carboxyl, amino, etc.). These polar functional groups can form hydrogen bonds or chemical bonds with active groups on the surface of building substrates such as cement and metal, thereby providing excellent substrate adhesion. At the same time, the addition of additives improves the film-forming properties and application performance of the coating.

[0008] 2. In this embodiment of the invention, the upper self-cleaning radiation-cooling coating uses a fluoropolymer as the film-forming material. The fluorocarbon bond has extremely low surface energy and excellent weather resistance, giving the coating surface hydrophobic properties. Rainwater can wash away dust, achieving self-cleaning. At the same time, the CF bond in the fluoropolymer has characteristic vibrational absorption in the 8-13 micrometer atmospheric window, which can enhance the infrared emissivity of the coating.

[0009] 3. In this embodiment of the invention, a silane coupling agent is added to the upper coating layer. On the one hand, the hydrolyzable groups (such as alkoxy groups) in the silane coupling agent molecule, after hydrolysis, generate silanol groups that can form chemical bonds with the hydroxyl groups on the surface of the lower coating layer and the substrate, significantly enhancing the interlayer adhesion between the upper and lower layers. On the other hand, the hydrophobic organic groups (such as alkyl, fluoroalkyl, or phenyl groups) in the silane coupling agent molecule can reduce the surface energy of the coating, further increasing the water contact angle of the coating surface and enhancing the self-cleaning effect. The silane coupling agent and the hydrophobic additive work synergistically to give the coating surface a higher hydrophobic angle.

[0010] 4. In this embodiment of the invention, the upper coating contains a compound of first inorganic pigment powder and second inorganic pigment powder. These two pigments have different refractive indices and particle size distributions, enabling them to form broadband Mie scattering in the solar light band, thereby achieving high solar reflectivity. Their synergistic effect also enhances the micro-nano rough structure of the coating surface, further improving the hydrophobic and self-cleaning effect. 5. In this embodiment of the invention, all raw materials used are industrially mature products with controllable costs. The coating preparation process is simple, and it can be applied to large areas using methods such as roller coating and spraying, making it suitable for energy-saving renovations of existing buildings and exterior wall coatings of new buildings.

[0011] In some embodiments, the fluoropolymer includes at least one of polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyperfluoroethylene propylene, polyvinyl fluoride, perfluoropropylene, fluorinated polyimide, trifluorochloroethylene-vinyl ether copolymer, or polytetrafluoroethylene powder.

[0012] In some embodiments, the first inorganic pigment powder and the second inorganic pigment powder each independently comprise at least one of silicon oxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide.

[0013] In some embodiments, the particle sizes of the first inorganic pigment powder and the second inorganic pigment powder are different. Preferably, the particle size of the first inorganic pigment powder is 200-1000 nanometers, and the particle size of the second inorganic pigment powder is 100-800 nanometers. The mass ratio of the first inorganic pigment powder to the second inorganic pigment powder is 1:0.2 to 1:2.

[0014] In some embodiments, the organic solvent includes at least one of isopropanol, acetone, ethanol, cyclohexanone, toluene, xylene, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, or propylene carbonate.

[0015] In some embodiments, the silane coupling agent comprises at least one selected from γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, perfluorodecyltrimethoxysilane, or perfluorooctyltriethoxysilane. Preferably, the silane coupling agent is a long-chain alkylsilane or a fluoroalkylsilane to further improve the hydrophobic angle.

[0016] In some embodiments, the hydrophobic additive includes at least one of polysiloxane hydrophobic agents or fluorocarbon surfactants.

[0017] In some embodiments, the waterborne resin in the lower high-adhesion primer includes at least one of waterborne acrylic resin, styrene-acrylic resin, silicone-acrylic resin, polyurethane resin, alkyd resin, epoxy resin, or pure acrylic resin; the waterborne resin contains at least one polar functional group selected from hydroxyl, carboxyl, amino, epoxy, amide, or ether bonds.

[0018] In some embodiments, the third inorganic pigment powder includes at least one of silicon oxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide.

[0019] In some embodiments, the additives include at least one of dispersants, film-forming aids, defoamers, leveling agents, and thickeners.

[0020] This invention provides a method for preparing a double-layer self-cleaning radiation-cooling coating with high substrate adhesion, comprising the following steps: (1) Mix water-based resin, deionized water and additives evenly, add third inorganic pigment powder under stirring conditions, disperse evenly, and obtain a lower layer of high adhesion primer coating. (2) Dissolve the fluoropolymer in an organic solvent, add the first inorganic pigment powder, the second inorganic pigment powder, the silane coupling agent and the hydrophobic additive, disperse evenly, and obtain the upper self-cleaning radiation cooling coating.

[0021] In some embodiments, in step (1) and / or step (2), the dispersion method includes at least one of mechanical stirring, magnetic stirring, ball milling, sand milling or ultrasonic dispersion.

[0022] The present invention also provides the application of the above-mentioned coating, including: applying a lower high-adhesion primer coating to the surface of a building substrate, and drying it to form a lower primer coating; then applying an upper self-cleaning radiation-cooling coating to the lower primer coating, and drying it to form an upper self-cleaning radiation-cooling coating.

[0023] In some embodiments, the coating method includes at least one of roller coating, brush coating, spray coating, squeegee coating, or drip coating.

[0024] In some embodiments, the thickness of the lower base coating layer is not less than 100 micrometers, and the thickness of the upper self-cleaning radiation cooling coating layer is not less than 40 micrometers. Attached Figure Description

[0025] Figure 1 This is the spectral response curve of the double-layer self-cleaning radiation-cooling coating prepared in Example 1; Figure 2 This is a comparison diagram of the cooling effect of the double-layer self-cleaning radiative cooling coating prepared in Example 1 and ordinary white paint; Figure 3 The hydrophobic angle is that of the double-layer self-cleaning radiation cooling coating prepared in Example 1. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] Example 1 (1) Preparation of the lower layer high adhesion primer: 80 parts of water-based acrylic resin (containing hydroxyl group), 120 parts of deionized water, 6 parts of dispersant and 8 parts of film-forming aid are mixed evenly, and 60 parts of titanium dioxide powder are added under stirring. The mixture is dispersed at high speed for 45 minutes to obtain the lower layer primer.

[0028] (2) Preparation of upper self-cleaning radiation cooling coating: 100 parts of polyvinylidene fluoride-hexafluoropropylene copolymer were dissolved in 150 parts of butyl acetate, and 50 parts of titanium dioxide powder, 30 parts of silica powder, 8 parts of γ-aminopropyltriethoxysilane, and 6 parts of polysiloxane hydrophobic additive were added. The mixture was ball-milled and dispersed to a fineness of ≤30 micrometers to obtain the upper self-cleaning radiation cooling coating.

[0029] (3) Application: The lower base coat is applied to the surface of the cement substrate by spraying. After drying, a lower base coat with a thickness of about 100 micrometers is formed. Then, the upper self-cleaning radiation cooling coating is sprayed and dried to form an upper coating with a thickness of about 70 micrometers.

[0030] The double-layer coating prepared in this embodiment has an average reflectivity of 93.9% in the solar radiation band and an average emissivity of 93.2% in the 8-13 micrometer atmospheric window. Figure 1 At midday in summer (solar radiation intensity approximately 900 W / m²), 2 The test showed that the surface temperature of the coating was 3.4°C lower than the ambient air temperature, and its cooling effect was significantly better than that of commercially available ordinary white paint. Figure 2 The surface has a water contact angle of 100°, providing a self-cleaning effect. Figure 3 The adhesion test (cross-cut test) achieved level 1.

[0031] Example 2 (1) Lower layer primer coating: Mix 60 parts of waterborne polyurethane resin (containing carboxyl groups), 100 parts of deionized water, 5 parts of dispersant, and 6 parts of film-forming aid, add 80 parts of zinc oxide powder, and disperse at high speed for 50 minutes.

[0032] (2) Upper self-cleaning coating: Dissolve 80 parts of polychlorotrifluoroethylene in 120 parts of propylene glycol methyl ether acetate, add 40 parts of barium sulfate powder, 25 parts of silicon oxide powder, 10 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 8 parts of fluorocarbon surfactant, and grind to a fineness of ≤30 microns.

[0033] (3) Application: Roller coating, with a lower layer thickness of about 120 micrometers and an upper layer thickness of about 60 micrometers.

[0034] The test results showed a solar reflectance of 93.8%, an atmospheric window emissivity of 93.3%, a temperature drop of 3.3°C, a water contact angle of 99°, and an adhesion rating of 1.

[0035] Example 3 (1) Lower layer primer coating: Mix 100 parts of waterborne epoxy resin (containing epoxy groups), 150 parts of deionized water, 8 parts of dispersant, and 10 parts of film-forming aid, add 50 parts of alumina powder, and disperse at high speed for 40 minutes.

[0036] (2) Upper self-cleaning coating: Dissolve 120 parts of ethylene-tetrafluoroethylene copolymer in 200 parts of xylene, add 60 parts of magnesium oxide powder, 20 parts of zirconium oxide powder, 12 parts of γ-methacryloyloxypropyltrimethoxysilane, and 10 parts of polysiloxane hydrophobic additive, and ball mill and disperse to a fineness of ≤30 micrometers.

[0037] (3) Application: Spraying construction, the lower layer thickness is about 90 micrometers and the upper layer thickness is about 80 micrometers.

[0038] The test results showed a solar reflectance of 94.0%, an atmospheric window emissivity of 93.1%, a temperature drop of 3.5℃, a water contact angle of 101℃, and an adhesion rating of 1.

[0039] Example 4 (1) Lower layer primer coating: Mix 70 parts of waterborne styrene-acrylic resin (containing amide group), 130 parts of deionized water, 7 parts of dispersant, and 9 parts of film-forming aid, add 70 parts of calcium carbonate powder, and disperse at high speed for 60 minutes.

[0040] (2) Upper self-cleaning coating: Dissolve 90 parts of polytetrafluoroethylene propylene in 180 parts of cyclohexanone, add 45 parts of cerium oxide powder, 35 parts of barium sulfate powder, 6 parts of dodecyltrimethoxysilane, and 7 parts of polysiloxane hydrophobic additive, and grind to a fineness of ≤30 microns.

[0041] (3) Application: Scraping application, with a lower layer thickness of about 110 micrometers and an upper layer thickness of about 65 micrometers.

[0042] The test results showed a solar reflectance of 93.8%, an atmospheric window emissivity of 93.2%, a temperature drop of 3.2℃, a water contact angle of 100℃, and an adhesion rating of 1.

[0043] Example 5 (1) Lower layer primer coating: Mix 50 parts of water-based silicone acrylic resin (containing hydroxyl groups), 90 parts of deionized water, 4 parts of dispersant, and 5 parts of film-forming aid, add 90 parts of lithopone powder, and disperse at high speed for 55 minutes.

[0044] (2) Upper self-cleaning coating: Dissolve 110 parts of polyvinylidene fluoride in 160 parts of acetone, add 55 parts of alumina powder, 25 parts of magnesium oxide powder, 9 parts of perfluorodecyltrimethoxysilane, and 9 parts of fluorocarbon surfactant, and ball mill and disperse to a fineness of ≤30 micrometers.

[0045] (3) Application: Spraying construction, the lower layer thickness is about 100 micrometers and the upper layer thickness is about 75 micrometers.

[0046] The test results showed a solar reflectance of 94.1%, an atmospheric window emissivity of 93.4%, a temperature drop of 3.6℃, ​​a water contact angle of 103℃, and an adhesion rating of 1.

[0047] Example 6 (1) Lower layer primer coating: Mix 40 parts of waterborne alkyd resin (containing ester bonds), 80 parts of deionized water, 3 parts of dispersant, and 4 parts of film-forming aid, add 100 parts of silica powder, and disperse at high speed for 70 minutes.

[0048] (2) Upper self-cleaning coating: Dissolve 130 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer in 220 parts of propylene carbonate, add 65 parts of zirconium oxide powder, 15 parts of calcium carbonate powder, 15 parts of phenyltrimethoxysilane, and 12 parts of polysiloxane hydrophobic additive, and grind to a fineness ≤30 microns.

[0049] (3) Application: Roller coating, with a lower layer thickness of about 130 micrometers and an upper layer thickness of about 85 micrometers.

[0050] The test results showed a solar reflectance of 93.9%, an atmospheric window emissivity of 93.1%, a temperature drop of 3.3℃, ​​a water contact angle of 100℃, and an adhesion rating of 1.

[0051] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that no silane coupling agent is added to the upper self-cleaning coating. The test results showed a solar reflectance of 93.8%, an emissivity of 93.1%, a temperature drop of 3.3°C, a water contact angle of 88° (a significant decrease in hydrophobic angle), a decrease in interlayer adhesion, and a grade of 2 in the cross-cut test (slight interlayer peeling occurred).

[0052] Comparative Example 2 The preparation method for this comparative example is the same as that for Example 1, except that no second inorganic pigment powder is added to the upper self-cleaning coating (only 80 parts of titanium dioxide are used). The tested results show a solar reflectance of 91.0%, an emissivity of 90.5%, a temperature drop of 2.5°C, a water contact angle of 85°, and an adhesion rating of 1.

[0053] Comparative Example 3 The preparation method for this comparative example is the same as that for Example 1, except that only the upper self-cleaning coating is directly applied to the cement substrate without a lower base coating. Test results showed: solar reflectivity 93.9%, emissivity 93.2%, temperature drop of 3.4°C, and water contact angle of 100°. However, the substrate adhesion test showed a grade of 3 (significant peeling), making it unsuitable for long-term use.

[0054] Comparative Example 4 The preparation method of this comparative example is the same as that of Example 2, except that the mass ratio of the first inorganic pigment powder to the second inorganic pigment powder in the upper self-cleaning coating is 1:2 (outside the preferred range). Test results: solar reflectivity 90.5%, emissivity 91.0%, temperature drop 2.2℃, water contact angle 90°, and adhesion grade 1.

[0055] Comparative Example 5 The preparation method for this comparative example is the same as that for Example 3, except that the thickness of the lower primer coating is 30 micrometers (below the lower limit of the scope of this invention). Test results showed: solar reflectivity 93.9%, emissivity 93.1%, temperature drop of 3.4°C, and water contact angle of 101°C. However, the substrate adhesion test result was level 3 (insufficient adhesion due to the coating being too thin).

[0056] The coatings obtained in Examples 1-6 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Table 1. The test methods for each property are as follows: (1) Solar reflectance: The reflectance in the 0.3 to 2.5 micrometer band was tested using an ultraviolet / visible / near-infrared spectrophotometer (with integrating sphere) in accordance with relevant standards.

[0057] (2) Atmospheric window emissivity: Fourier transform infrared spectrometer was used to test the emissivity in the 8-13 micrometer band, with a gold mirror as a reference.

[0058] (3) Cooling effect: Place the coated sample in direct sunlight outdoors, attach a thermocouple to the back, record the average temperature from 12:00 to 14:00 noon, and record the ambient air temperature at the same time to calculate the cooling range.

[0059] (4) Adhesion: According to the cross-cut test of GB / T 9286 standard, grade 0 is the best, grade 1 is the second best, grade 2 is acceptable, and grade 3 and above are unqualified.

[0060] (5) Water contact angle: The static contact angle was measured by adding deionized water at room temperature using a contact angle tester.

[0061] Table 1 Performance test results of the examples and comparative examples

[0062] As shown in Table 1, Examples 1-6 of the present invention all exhibit high solar reflectivity (≥0.938) and atmospheric window emissivity (≥0.931), with a temperature reduction of over 3.2°C. They also demonstrate good self-cleaning properties (water contact angle ≥99°) and satisfactory substrate adhesion (Grade 1). Comparative Example 1 shows that the silane coupling agent in the upper layer significantly contributes to interlayer adhesion and hydrophobic angle; without its addition, the water contact angle drops to 88° and the adhesion decreases to Grade 2. Comparative Example 2 shows that the addition of the second inorganic pigment powder not only improves reflectivity but also enhances hydrophobicity. Comparative Example 3 shows that the bottom coating layer in the double-layer structure is crucial for ensuring substrate adhesion. Comparative Example 4 shows that exceeding the preferred mass ratio of the two inorganic pigment powders leads to a significant decrease in optical and hydrophobic properties. Comparative Example 5 shows that an excessively thin lower coating layer severely affects substrate adhesion.

[0063] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A double-layer self-cleaning radiation cooling coating with high substrate adhesion, characterized in that, The product comprises an upper self-cleaning radiation-cooling coating and a lower high-adhesion primer coating. The upper self-cleaning radiation-cooling coating, by weight, comprises the following raw materials: 10-200 parts of fluoropolymer, 20-200 parts of first inorganic pigment powder, 10-150 parts of second inorganic pigment powder, 50-500 parts of organic solvent, 2-50 parts of silane coupling agent, and 1-40 parts of hydrophobic additive. The lower high-adhesion primer coating, by weight, comprises the following raw materials: 10-200 parts of water-based resin, 20-250 parts of third inorganic pigment powder, 30-400 parts of deionized water, and 1-80 parts of additive.

2. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The fluoropolymer includes at least one of polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, perfluoroethylene propylene, polyfluorinated polyimide, perfluoropropylene, fluorinated polyimide, trifluorochloroethylene-vinyl ether copolymer, or polytetrafluoroethylene powder.

3. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The first inorganic pigment powder and the second inorganic pigment powder each independently include at least one of silicon oxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide.

4. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The first inorganic pigment powder and the second inorganic pigment powder have different particle sizes. The particle size of the first inorganic pigment powder is 200-1000 nanometers, and the particle size of the second inorganic pigment powder is 100-800 nanometers. The mass ratio of the first inorganic pigment powder to the second inorganic pigment powder is 1:0.2 to 1:

2.

5. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, dodecyltrimethoxysilane, perfluorodecyltrimethoxysilane, or perfluorooctyltriethoxysilane.

6. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The water-based resin in the lower high-adhesion primer includes at least one of water-based acrylic resin, styrene-acrylic resin, silicone-acrylic resin, polyurethane resin, alkyd resin, epoxy resin, or pure acrylic resin; the water-based resin contains at least one polar functional group selected from hydroxyl, carboxyl, amino, epoxy, amide, or ether bonds.

7. The high substrate adhesion double-layer self-cleaning radiation cooling coating according to claim 1, characterized in that, The additives include at least one of dispersants, film-forming aids, defoamers, leveling agents, and thickeners.

8. The method for preparing a high-substrate-adhesion double-layer self-cleaning radiation-cooling coating according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Mix water-based resin, deionized water and additives evenly, add third inorganic pigment powder, disperse evenly, and obtain a lower layer of high adhesion primer coating. (2) Dissolve the fluoropolymer in an organic solvent, add the first inorganic pigment powder, the second inorganic pigment powder, the silane coupling agent and the hydrophobic additive, disperse evenly, and obtain the upper self-cleaning radiation cooling coating.

9. The preparation method according to claim 8, characterized in that, In step (1) and / or step (2), the dispersion method includes at least one of mechanical stirring, magnetic stirring, ball milling, sand milling or ultrasonic dispersion.

10. The application of the coating according to any one of claims 1 to 7 or the coating prepared by the method according to claim 8 or 9, characterized in that, include: A high-adhesion primer is applied to the surface of the building substrate and dried to form the lower base coat. Then, the upper self-cleaning radiation-cooling coating is applied onto the lower base coating, and after drying, it forms the upper self-cleaning radiation-cooling coating.

11. The application according to claim 10, characterized in that, The coating method includes at least one of roller coating, brush coating, spray coating, scraping coating, or drip coating.

12. The application according to claim 10, characterized in that, The thickness of the lower base coating layer is not less than 100 micrometers, and the thickness of the upper self-cleaning radiation cooling coating layer is not less than 40 micrometers.

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