An adaptive radiation cooling coating

Abstract

This invention relates to an adaptive radiation-cooling coating, comprising, from the inside out, a high-reflectivity primer layer, a thermochromic intermediate layer, and a semi-transparent topcoat layer with ultraviolet (UV) blocking and radiation-cooling functions; the thermochromic intermediate layer is colored below a set temperature value and colorless above the set temperature value. This invention combines the semi-transparent topcoat with UV blocking and radiation-cooling functions, the thermochromic intermediate layer, and the primer, placing the thermochromic intermediate layer between the transparent topcoat and the primer. This allows it to resist high temperatures and UV radiation in the environment. At low temperatures, the thermochromic intermediate layer forms a colored intermediate layer that absorbs solar wavelengths to increase the coating temperature; at high temperatures, the thermochromic intermediate layer becomes transparent, allowing solar wavelengths to pass through and be reflected by the high-reflectivity primer layer, thereby reducing the temperature of the coating system.

Description

Technical Field

[0001] This invention relates to the field of thermochromic exterior wall coatings, and more specifically to an adaptive radiation cooling coating. Background Technology

[0002] Thermochromic exterior wall coatings can appear light-colored in high-temperature environments to reflect a large amount of outdoor sunlight, and dark-colored in low-temperature environments to absorb a large amount of outdoor sunlight, achieving reversible color change. This, in turn, regulates the building surface temperature and reduces energy consumption caused by building temperature control. Thermochromic adaptive radiation cooling coatings, in addition to their adaptive adjustment function in the visible light band of sunlight, can also adjust the emissivity of the atmospheric window in the infrared band, further reducing building energy consumption.

[0003] Currently, patent number CN113999585A, entitled "A Thermochromic Radiation-Cooling Coating, a Thermochromic Radiation-Cooling Film, and a Method for Preparing the Same," describes a process where thermochromic resin, radiation-sensitive agents, reflective agents, and other functional materials are mixed and stirred into a coating system to form the thermochromic radiation-cooling coating. This patent tested the film and found that its color-changing and radiation-cooling properties remained stable after 1000 repeated color changes. However, in actual use, ultraviolet light accelerates the decomposition of chemical substances in the thermosensitive layer and the fading of the color. For example, patent number CN115418148A, entitled "An Organic Reversible Thermochromic Exterior Wall Coating and Its Preparation Method," involves adding succinic octanoic acid diimide to bind polyacrylate and L-2-amino-3-indolylpropionic acid to the outside of thermochromic microcapsules as a consumption layer for oxygen free radicals. This prevents the microcapsules from penetrating the core material under light or high temperature conditions, thus causing them to lose their color-changing properties. However, this organic reversible thermochromic exterior wall coating will release VOCs as a result.

[0004] Currently used organic thermochromic coatings employ phenolic substances as color developers or are encapsulated, both of which easily lead to a decrease in the antioxidant, UV resistance, lightfastness, and heat resistance of the color-changing agents. Furthermore, ultraviolet radiation can also affect the color-changing effect of heat-sensitive materials. Therefore, the use of thermochromic coatings in environments with variable external climates is limited. Summary of the Invention

[0005] This invention proposes an adaptive radiation-cooling coating. By combining a semi-transparent topcoat with UV blocking and radiation-cooling functions, a thermochromic intermediate coating, and a primer, the thermochromic intermediate coating is placed between the transparent topcoat and the primer. This allows it to resist high temperatures and UV radiation in the environment. At low temperatures, the thermochromic intermediate coating can form a colored intermediate layer that absorbs solar wavelengths to increase the coating temperature. At high temperatures, the thermochromic intermediate coating becomes transparent, allowing solar wavelengths to pass through the intermediate layer and be reflected by the highly reflective primer layer, thereby reducing the temperature of the coating system.

[0006] This invention is achieved through the following scheme:

[0007] An adaptive radiation cooling coating includes a high-reflectivity primer layer, a thermochromic intermediate layer, and a semi-transparent topcoat layer with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out; the thermochromic intermediate layer is colored when the temperature is below a set temperature value and colorless when the temperature is above the set temperature value.

[0008] The semi-transparent topcoat layer with ultraviolet blocking and radiation cooling functions is prepared from the following components in the following mass proportions: 10-25 parts water, 0.15-0.3 parts cellulose, 35-50 parts barium sulfate filler, 30-40 parts acrylic emulsion, 1.5-3 parts film-forming aid, 1-2 parts dispersant, 0.2-0.5 parts wetting agent, 0.2-0.4 parts defoamer, 0.1-0.3 parts pH adjuster, 0.1-0.3 parts bactericide, and 0.1-0.5 parts ultraviolet absorber.

[0009] The thermochromic intermediate coating is prepared from the following components in the following mass parts: 10-20 parts water, 0.15-0.3 parts cellulose, 50-70 parts acrylic emulsion, 10-30 parts thermochromic capsule powder, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 1-3 parts film-forming aid, 0.1-0.15 parts pH adjuster, 0.2-1 parts light stabilizer, and 0.1-0.5 parts bactericide.

[0010] The high-reflectivity primer coating is prepared from the following components in the following mass proportions: 10-20 parts water, 0.15-0.3 parts cellulose, 30-40 parts acrylic emulsion, 10-30 parts anatase titanium dioxide, 20-30 parts heavy calcium carbonate, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 0.1-0.3 parts pH adjuster, 1-3 parts film-forming aid, and 0.1-0.5 parts bactericide.

[0011] Preferably, in order to make the topcoat film have a high emissivity and achieve its radiation cooling effect: the barium sulfate filler in the semi-transparent topcoat layer with ultraviolet blocking and radiation cooling functions is barium sulfate with a mesh size of 800-1500 and a refractive index range of 1.52-1.65.

[0012] Preferably, the dry film refractive index of the acrylic resin in the semi-transparent topcoat layer with ultraviolet blocking and radiation cooling functions is between 1.56 and 1.66.

[0013] Preferably, the UV absorber in the semi-transparent topcoat layer with UV blocking and radiative cooling functions is hexamethylphosphoric triamine. It has a superior UV absorption capacity, preventing it from penetrating to the thermochromic intermediate coating, thereby improving the product's anti-aging properties.

[0014] Preferably, the thermochromic capsule powder in the thermochromic coating is a heat-decolorizing thermochromic capsule powder. Product number 38 Degree Orange from Guangzhou Jingcai Pigment Technology Co., Ltd. can be used. This invention utilizes a pigment that is colored at low temperatures, changing from colored to colorless when the temperature rises to a set value. The capsule encapsulates an invisible dye, a color-forming agent, and a temperature-regulating agent. The color-forming agent is at least one of spiropyran, fluoranthene, triarylmethane, substituted ethylene, and organic complexes. The pigment particles are spherical with an average diameter of 2–7 micrometers. The interior contains the color-changing substance, and the exterior is a non-infusible transparent shell approximately 0.2–0.5 μm thick. The temperature can be adjusted proportionally.

[0015] Preferably, the light stabilizer in the thermochromic coating is 4-benzoyloxy-2,2,6,6-tetramethylpiperidine. It is a hindered light stabilizer that effectively captures active free radicals generated by polymer materials under ultraviolet light, thereby exerting a light-stabilizing effect.

[0016] The method for preparing the semi-transparent topcoat layer with ultraviolet blocking and radiation cooling functions includes the following steps:

[0017] Pour cellulose into water and stir at 400-600 rpm for 10-15 minutes. Then add dispersant, wetting agent, pH adjuster and half of the defoamer in sequence. Next, increase the speed to 900-1200 rpm and add barium sulfate filler and UV absorber, and stir for 15-20 minutes. Finally, reduce the stirring speed to 400-600 rpm and add film-forming aid, acrylic emulsion, bactericide and the remaining half of the defoamer.

[0018] The method for preparing the thermochromic intermediate coating includes the following steps:

[0019] Pour cellulose into water and stir at 400-600 rpm for 10-15 minutes. Then add dispersant, wetting agent, half of the defoamer, and pH adjuster in sequence. Next, increase the speed to 900-1200 rpm and add thermochromic capsule powder. Stir for 15-20 minutes. Finally, reduce the stirring speed to 400-600 rpm and add film-forming aid, the remaining defoamer, light stabilizer, acrylic emulsion, and bactericide.

[0020] The method for preparing the high-reflectivity primer layer includes the following steps:

[0021] Pour cellulose into water and stir at 400-600 rpm for 10-15 minutes. Then add dispersant, wetting agent, half of the defoamer, and pH adjuster in sequence. Increase the speed to 900-1200 rpm and add anatase titanium dioxide and heavy calcium carbonate. Stir for 15-20 minutes. Finally, reduce the stirring speed to 400-600 rpm and add film-forming aid, the remaining defoamer, acrylic emulsion, and bactericide.

[0022] Compared with the disclosed prior art, the present invention has the following beneficial effects:

[0023] The barium sulfate in the semi-transparent topcoat layer of this invention, which has ultraviolet-blocking and radiation-cooling functions, exhibits an extremely low attenuation coefficient in visible light while possessing a high emissivity to the infrared atmospheric window, thus creating passive cooling. Combined with the ultraviolet absorber hexamethylphosphoric triamine, it forms a semi-transparent protective barrier, safeguarding the temperature-sensitive intermediate layer that is easily damaged by ultraviolet radiation, increasing the topcoat's resistance to artificial aging, and providing higher durability.

[0024] Meanwhile, the color-changing capsules in the thermochromic coating effectively capture the active free radicals generated by the polymer material under ultraviolet light, thus exerting a light-stabilizing effect. At low temperatures, it is in a colored state; when the temperature rises to a set value, the pigment changes from colored to colorless, revealing the primer and highly reflecting sunlight, thereby lowering the temperature of the coating system.

[0025] The system described in this invention has a cooling function for both solar spectral reflection and high infrared emission. At low temperatures, a colored intermediate layer forms, absorbing solar radiation to raise the coating temperature, thus achieving adaptive color change. This coating system is UV resistant, highly weather resistant, can be used for a long time, and is cost-effective. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the thermochromic adaptive radiation cooling coating of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of the invention.

[0028] An adaptive radiation cooling coating includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out; the thermochromic intermediate layer 2 is colored when the temperature is below a set temperature value and colorless when the temperature is above the set temperature value.

[0029] The semi-transparent topcoat layer 3, which has the functions of blocking ultraviolet rays and radiative cooling, is prepared from the following components in the following mass parts: 10-25 parts water, 0.3 parts cellulose, 35-50 parts barium sulfate filler, 30-40 parts acrylic resin, 1.5-3 parts film-forming aid, 1-2 parts dispersant, 0.2-0.5 parts wetting agent, 0.2-0.4 parts defoamer, 0.1-0.15 parts pH adjuster, 0.1-0.3 parts bactericide, and 0.1-0.5 parts ultraviolet absorber.

[0030] The thermochromic intermediate coating 2 is prepared from the following components in the following mass proportions: 10-20 parts water, 0.3 parts cellulose, 50-70 parts acrylic resin, 10-30 parts thermochromic capsule powder, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 1-3 parts film-forming aid, 0.1-0.15 parts pH adjuster, 0.2-1 parts light stabilizer, and 0.1-0.5 parts bactericide.

[0031] The high-reflectivity primer layer 1 is prepared from the following components in the following mass proportions: 10-20 parts water, 0.3 parts cellulose, 30-40 parts acrylic resin, 10-30 parts anatase titanium dioxide, 20-30 parts heavy calcium carbonate, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 0.1-0.3 parts pH adjuster, 1-3 parts film-forming aid, and 0.1-0.5 parts bactericide.

[0032] The barium sulfate filler in the semi-transparent topcoat layer 3, which has the functions of blocking ultraviolet rays and radiative cooling, is barium sulfate with a mesh size of 800-1500 and a refractive index range of 1.52-1.65. In order to make the topcoat have high light transmittance, the barium sulfate is selected to be close to the refractive index of the acrylic resin after drying.

[0033] To achieve a high emissivity in the topcoat film and thus a radiative cooling effect, this invention also incorporates high-infrared-radiation barium sulfate powder, which lowers its own temperature and achieves the radiative cooling effect. The barium sulfate particles have a diameter of 2–7 μm.

[0034] The dry film refractive index of acrylic in the semi-transparent topcoat layer 3, which has the functions of blocking ultraviolet rays and radiative cooling, is between 1.56 and 1.66.

[0035] The UV absorber in the semi-transparent topcoat layer 3, which has UV blocking and radiation cooling functions, is hexamethylphosphoric acid triamine. It has a strong UV absorption capacity, which is used to improve the anti-aging properties of the product.

[0036] The thermochromic capsule powder in the thermochromic intermediate coating 2 is a heat-decolorizing thermochromic capsule powder. This invention utilizes a pigment that is colored at low temperatures, and changes from colored to colorless when the temperature rises to a set value.

[0037] The light stabilizer in the thermochromic intermediate coating 2 is 4-benzoyloxy-2,2,6,6-tetramethylpiperidine. It is a hindered light stabilizer.

[0038] To promote film formation of polymers at low temperatures, film-forming aids are added to the primer, intermediate coat, and topcoat layers of this invention to improve coalescence properties and enable film formation over a wider temperature range. The film-forming aids can be one or more of protein film-forming agents, acrylic resin film-forming agents, polyurethane film-forming agents, butadiene resin film-forming agents, and nitrocellulose film-forming agents.

[0039] The above-mentioned thermochromic radiation cooling coating can be used on the exterior wall facade. The specific operation method includes the following steps: (a) spraying, brushing, rolling and scraping the high reflectivity primer layer on the exterior wall; (b) after the primer has dried, apply the thermochromic intermediate coating layer on the high reflectivity primer layer; (c) after the thermochromic intermediate coating layer has dried to the surface, apply the semi-transparent topcoat layer.

[0040] The present invention will be further described in detail below with reference to specific embodiments.

[0041] Example 1:

[0042] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out. The weight parts of the coating components in each coating are shown in Table 1.

[0043] Table 1 shows the weight parts of the coating components in each coating of this embodiment.

[0044]

[0045] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 35°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0046] Atmospheric window emissivity of the radiation-cooled topcoat: 93.4%; Topcoat transmittance: 72.5%

[0047] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 91.7%.

[0048] Solar reflectivity of the reflective primer: 94.3%

[0049] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0050] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.1.

[0051] Example 2:

[0052] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside to the outside. The weight parts of the coating components in each coating are shown in Table 2.

[0053] Table 2 shows the weight parts of the coating components in each coating of this embodiment.

[0054]

[0055] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 37°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0056] Atmospheric window emissivity of the radiation-cooled topcoat: 92.4%; Topcoat transmittance: 75.5%.

[0057] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 90.7%.

[0058] Solar reflectivity of the reflective primer: 94.1%

[0059] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0060] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.1.

[0061] Example 3:

[0062] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out. The weight parts of the coating components in each coating are shown in Table 3.

[0063] Table 3 shows the weight parts of the coating components in each coating of this embodiment.

[0064]

[0065] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 37°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0066] Atmospheric window emissivity of the radiation-cooled topcoat: 91.1%; Topcoat transmittance: 76.5%.

[0067] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 90.7%.

[0068] Solar reflectivity of the reflective primer: 92.1%

[0069] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0070] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.2.

[0071] Example 4:

[0072] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out. The weight parts of the coating components in each coating are shown in Table 4.

[0073] Table 4. Weight parts of coating components in each coating of this embodiment.

[0074]

[0075] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 38°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0076] Atmospheric window emissivity of the radiation-cooled topcoat: 90.9%; Topcoat transmittance: 77.5%.

[0077] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 89.7%.

[0078] Solar reflectivity of the reflective primer: 91.5%

[0079] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0080] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.6.

[0081] Example 5

[0082] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside to the outside. The weight parts of the coating components in each coating are shown in Table 5.

[0083] Table 5. Weight parts of coating components in each coating of this embodiment.

[0084]

[0085]

[0086] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 38°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0087] Atmospheric window emissivity of the radiation-cooled topcoat: 90.9%; Topcoat transmittance: 77.5%.

[0088] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 89.7%.

[0089] Solar reflectivity of the reflective primer: 91.5%

[0090] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0091] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.6.

[0092] Example 6

[0093] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out. The weight parts of the coating components in each coating are shown in Table 6.

[0094] Table 6. Weight parts of coating components in each coating of this embodiment.

[0095]

[0096]

[0097] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 38°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0098] Atmospheric window emissivity of the radiation-cooled topcoat: 92.9%; Topcoat transmittance: 74.5%.

[0099] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 93.7%.

[0100] Solar reflectivity of the reflective primer: 93.5%

[0101] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0102] Before 500 hours of xenon lamp irradiation, the surface color difference ΔE of the specimen was 0.1.

[0103] Example 7

[0104] The adaptive radiation cooling coating of this embodiment includes a high-reflectivity primer layer 1, a thermochromic intermediate layer 2, and a semi-transparent topcoat layer 3 with ultraviolet blocking and radiation cooling functions, arranged sequentially from the inside out. The weight parts of the coating components in each coating are shown in Table 7.

[0105] Table 7. Weight parts of coating components in each coating of this embodiment.

[0106]

[0107]

[0108] In this embodiment, the color-changing material is designed using crystal violet lactone as the thermochromic developer and bisphenol A as the decolorizing agent, with the solvent type and content adjusted to achieve a color-changing temperature of 38°C. The primer, color-changing intermediate coat, and radiation-cooled topcoat are prepared using the coating formulation shown in the table above. The thickness of each layer is controlled using a wire rod, resulting in the following dry film thicknesses: primer 50 μm, color-changing intermediate coat 80 μm, and radiation-cooled topcoat 50 μm.

[0109] Atmospheric window emissivity of the radiation-cooled topcoat: 92.9%; topcoat transmittance: 73.5%; emissivity: 92%.

[0110] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 89.7%.

[0111] Solar reflectivity of the reflective primer: 91.5%

[0112] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0113] The color difference ΔE on the specimen surface before and after xenon lamp irradiation treatment was 0.1.

[0114] Compared to before xenon lamp irradiation treatment, the surface color difference ΔE of the specimens continuously increased, and the surface color gradually faded. Because the topcoat absorbed a large amount of ultraviolet light and consumed it as heat, it to some extent prevented the photodegradation of the color-changing agent.

[0115] According to Examples 1-5, the emissivity gradually decreases, the transmittance increases, and the reflectivity of the system when it becomes colorless increases from low to high. Examples 6-7 show that when the emissivity and transmittance of the topcoat are both moderate, the reflectivity after color change is better. Examples 1-7 did not have any effect on color difference or color change after 600 hours of artificial aging or xenon lamp irradiation.

[0116] Comparative Example 1

[0117] Table 7 shows the weight parts of the coating components in each coating of this comparative example.

[0118]

[0119]

[0120] The barium sulfate filler in this comparative example topcoat was replaced with 800-mesh heavy calcium carbonate filler, while the rest remained the same as in Example 7.

[0121] Atmospheric window emissivity of the radiation-cooled topcoat: 92.9%; topcoat transmittance: 55.5%; emissivity: 85%.

[0122] When the high-temperature intermediate coating becomes colorless, the system's solar reflectance is 68.7%.

[0123] Solar reflectivity of the reflective primer: 91.5%

[0124] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0125] Color difference ΔE on the specimen surface before and after xenon lamp irradiation treatment: 1.4

[0126] In the comparative example, after changing the filler in the topcoat, its transmittance decreased from 73.5% to 55.5%. After becoming colorless at high temperatures, the system's solar reflectance decreased from 89.7% to 68.7%, and its emissivity decreased from 92% to 85%. This comparative example demonstrates that using barium sulfate in the topcoat results in a more transparent and radiation-efficient coating, leading to a higher solar reflectance ratio for the entire system at high temperatures. The significantly increased color difference before and after xenon lamp treatment indicates that adding barium sulfate to the topcoat increases the system's lifespan.

[0127] Comparative Example 2

[0128] Table 7 shows the weight parts of the coating components in each coating of this comparative example.

[0129]

[0130]

[0131] In this comparative example, the thermochromic capsule powder used in the color-changing coating is converted into a non-color-changing 800-mesh powder with the same lightness value and color. Everything else is the same as in Example 7.

[0132] Atmospheric window emissivity of radiation-cooled topcoat: 92.9%; topcoat transmittance: 73.5%; emissivity: 92%.

[0133] The system's solar reflectance at high temperatures is 58.7%.

[0134] Solar reflectivity of the reflective primer: 91.5%

[0135] System resistance to artificial aging: no blistering, peeling, or cracking after 600 hours.

[0136] The color difference ΔE on the specimen surface before and after xenon lamp irradiation treatment was 0.1.

[0137] After the intermediate paint in Comparative Example 2 was replaced with a non-color-changing filler, the solar reflectance of the system surface was 58.7%, which no longer had excellent reflective performance. Compared with the color-changing system, which had a reflectance of 89.7%, it was obviously difficult to reflect and cool down at high temperatures.

[0138] This invention is not limited to the above embodiments. All equivalent transformations and modifications made based on the principles of this invention are within the scope of protection of this invention.

Claims

1. An adaptive radiation-cooling coating, characterized in that: It includes a high-reflectivity primer layer (1), a thermochromic intermediate layer (2), and a semi-transparent topcoat layer (3) arranged sequentially from the inside out; the thermochromic intermediate layer (2) is colored when the temperature is below the set temperature value and colorless when the temperature is above the set temperature value. The semi-transparent topcoat layer (3) with ultraviolet blocking and radiation cooling functions is prepared from the following components in the following mass parts: 10-25 parts water, 0.15-0.3 parts cellulose, 35-50 parts barium sulfate filler, 30-40 parts acrylic resin, 1.5-3 parts film-forming aid, 1-2 parts dispersant, 0.2-0.5 parts wetting agent, 0.2-0.4 parts defoamer, 0.1-0.3 parts pH adjuster, 0.1-0.3 parts bactericide, and 0.1-0.5 parts ultraviolet absorber; The barium sulfate filler in the semi-transparent topcoat layer (3) with ultraviolet blocking and radiation cooling functions is barium sulfate with a mesh size of 800-1500 and a refractive index range of 1.52-1.65; The dry film refractive index of the acrylic resin in the semi-transparent topcoat layer (3) with ultraviolet blocking and radiation cooling functions is between 1.56 and 1.

66.

2. The adaptive radiation cooling coating according to claim 1, characterized in that: The thermochromic intermediate coating (2) is prepared from the following components in the following mass proportions: 10-20 parts water, 0.15-0.3 parts cellulose, 50-70 parts acrylic resin, 10-30 parts thermochromic capsule powder, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 1-3 parts film-forming aid, 0.1-0.15 parts pH adjuster, 0.2-1 parts light stabilizer, and 0.1-0.5 parts bactericide.

3. The adaptive radiation cooling coating according to claim 1, characterized in that: The high-reflectivity primer layer (1) is prepared from the following components in the following mass proportions: 10-20 parts water, 0.15-0.3 parts cellulose, 30-40 parts acrylic resin, 10-30 parts anatase titanium dioxide, 20-30 parts heavy calcium carbonate, 0.2-0.5 parts defoamer, 0.2-0.5 parts wetting agent, 1-2 parts dispersant, 0.1-0.3 parts pH adjuster, 1-3 parts film-forming aid, and 0.1-0.5 parts bactericide.

4. The adaptive radiation cooling coating according to claim 1, characterized in that: The ultraviolet absorber in the semi-transparent topcoat layer (3) which has the functions of blocking ultraviolet rays and radiative cooling is hexamethylphosphoric triamine.

5. The adaptive radiation cooling coating according to claim 2, characterized in that: The thermochromic capsule powder in the thermochromic intermediate coating (2) is a heat-decolorizing thermochromic capsule powder.

6. The adaptive radiation cooling coating according to claim 2, characterized in that: The light stabilizer in the thermochromic intermediate coating (2) is 4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

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