A color radiative cooling coating based on transparent composite film and a preparation method thereof

Abstract

This invention discloses a colored radiation-cooling coating based on a transparent composite film and its preparation method, belonging to the technical field of colored radiation-cooling coatings for building energy conservation. The colored radiation-cooling coating based on a transparent composite film includes a surface transparent composite film layer and a bottom radiation-cooling composite layer. The bottom layer is prepared from components A and B. Component A includes transparent resin and radiation-functional fillers; the radiation-functional fillers include barium sulfate particles and hollow structured dielectric microspheres. The surface layer is prepared from components A1 and B. Component A1 includes transparent resin, a light stabilizer, and an ultraviolet absorber. The colored radiation-cooling coating based on a transparent composite film allows the radiation-cooling coating to display different colors without affecting its solar reflectivity. Simultaneously, the combination of the radiation-cooling composite layer and the transparent composite film layer improves the radiation reflection performance of the radiation-cooling coating.

Description

Technical Field

[0001] This invention belongs to the technical field of colored radiative cooling coatings for building energy conservation, and particularly relates to a colored radiative cooling coating based on a transparent composite film and its preparation method. Background Technology

[0002] As global warming intensifies, keeping building roofs, walls, and petrochemical storage tanks cool without releasing greenhouse gases has become a challenge, and passive radiative cooling technology holds promise for solving this problem.

[0003] Passive radiation cooling technology is a passive cooling technology that uses materials with high solar reflectivity and emissivity or specially designed structures to cover the surface of an object. The solar heat energy absorbed by the object's surface is mainly transferred to outer space through an 8-13 μm "atmospheric window" (this window coincides with the blackbody radiation peak of an object with a temperature of 230K-300K on Earth, and is therefore the main part of Earth's thermal radiation, which is radiated from this "atmospheric window" to outer space). The object achieves radiative heat transfer with the low temperature of outer space (about 3K) and the external environment through infrared radiation, thereby cooling the object.

[0004] Compared with traditional refrigeration technologies (such as active refrigeration technology based on compressors), radiative refrigeration technology is a passive refrigeration technology that consumes no energy and emits no greenhouse gases, and it has broad application prospects in the field of energy conservation.

[0005] Currently, the colors of almost all radiation-cooling coatings on the commercial market are metallic white or pure white, a single color. This is because minimizing the absorption of sunlight is essential to avoid its thermal effect; therefore, the coating needs a metallic white or pure white surface to reflect sunlight as much as possible. However, for practical applications and architectural aesthetics, passive radiation-cooling coatings with metallic white or pure white surfaces are not the optimal choice. We categorize this issue as a "technical problem of radiation-cooling coatings where color-dependent pigments cause a significant decrease in solar reflectivity."

[0006] From another perspective, we conducted an in-depth study on the traditional radiation cooling materials used in commercial radiation cooling coatings and found that most of them are composed of a single material, and their radiation cooling effect and performance are significantly insufficient. We categorize this type of problem as "the technical problem of insufficient reflection radiation performance of a single radiation cooling material" in radiation cooling coatings. Summary of the Invention

[0007] To address the technical problems of insufficient solar reflectivity and inadequate solar radiation reflectance in existing colored radiation-cooling coatings due to the use of colored pigments, this invention provides a colored radiation-cooling coating based on a transparent composite film and its preparation method. The transparent composite film allows the radiation-cooling coating to display different colors without affecting its solar reflectivity. Furthermore, the combination of the radiation-cooling composite layer and the transparent composite film layer improves the solar radiation reflectance of the radiation-cooling coating.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A colored radiation-cooling coating based on a transparent composite film includes a top layer and a bottom layer, wherein the bottom layer is a radiation-cooling composite layer, and the top layer is a transparent composite film layer with a light transmittance ≥70%.

[0010] The bottom layer preparation raw materials include components A and B, wherein component B is an isocyanate curing agent, and the mass ratio of component A to component B is 1:0.05-0.1; the raw materials for component A include the following components by mass parts:

[0011] Transparent resin……………………………………10-39 parts

[0012] Radiation functional filler………………………………40-80 parts;

[0013] The radiation-functional filler includes barium sulfate particles and hollow structured medium microspheres, with a mass ratio of barium sulfate particles to hollow structured medium microspheres of 2:3-3:2.

[0014] The surface preparation raw materials include components A1 and B, wherein component B is an isocyanate curing agent, and the mass ratio of component A1 to component B is 1:0.05-0.1; the raw materials for component A1 include the following components by mass parts:

[0015] Transparent resin……………………………………80-99 parts

[0016] Light stabilizer……………………………………1-10 parts,

[0017] Ultraviolet light absorber………………………………1-8 parts

[0018] The surface preparation materials also include a transparent composite film, which comprises an upper wavelength beam splitter and a lower dielectric high-reflectivity film. The wavelength beam splitter is a narrowband interference cutoff filter with a visible light transmittance ≥50% in the visible light wavelength range of 380-760nm. The dielectric high-reflectivity film has a visible light reflectance ≥99% in the visible light wavelength range of 380-760nm. The upper part of the transparent composite film can provide different structural colors, while the lower part has a high reflectivity function.

[0019] The wavelength-splitting film can be a single-layer, double-layer, or multi-layer film system, preferably a multi-layer film system; further, the total thickness of the wavelength-splitting film system is no greater than 1.6 mm, and the radial diameter is no greater than 25 mm. The dielectric high-reflectivity film can be a single-layer, double-layer, or multi-layer film system, preferably a multi-layer film system; further, the total thickness of the dielectric high-reflectivity film system is no greater than 1.2 mm, and the radial diameter is no greater than 25 mm. The wavelength-splitting film and the dielectric high-reflectivity film, as well as the individual wavelength-splitting films and the individual dielectric high-reflectivity films, are all physically composited.

[0020] The upper part of the transparent composite film can transmit and / or reflect monochromatic light under sunlight, displaying the color of transmitted light and / or reflected light, as well as mixed monochromatic light colors; its lower part can reflect more than 99% of visible light, and also has the ability to reflect the remaining visible light other than transmitted light, thereby further improving the solar reflectivity of the coating.

[0021] Furthermore, the raw materials for preparing the bottom layer preparation raw material A also include the following components by mass parts:

[0022] Diluent………………………………………………0-10 parts

[0023] Dispersant………………………………………………1-10 parts,

[0024] Wetting agent………………………………………………0.2-6 parts,

[0025] Thickener………………………………………………0.5-5 parts,

[0026] Film-forming aids……………………………………………0.5-8 parts,

[0027] Defoamer………………………………………………0.1-2 parts;

[0028] Furthermore, the surface layer thickness is 0.1-3 mm, and the bottom layer thickness is 0.3-1 mm. Setting the bottom layer thickness to an appropriate level (above 300 μm) ensures that the moderate refractive index of the barium sulfate particles in the bottom layer will not affect its superior solar scattering and reflection performance.

[0029] The hollow structured dielectric microspheres include any one or a combination of two or more of the following: hollow silica microspheres, hollow alumina microspheres, hollow zirconium dioxide microspheres, and hollow white glass microspheres. The outer spherical radius of the hollow structured dielectric microspheres is 0.2-0.8 μm, and the core-shell ratio (equal to the inner spherical radius divided by the outer spherical radius of the microsphere) is 0.2-0.4.

[0030] Furthermore, the hollow structured medium microspheres have a multi-size distribution, and the mass ratio of hollow structured medium microspheres with outer spherical radii in the range of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm is 1-8:20-30:1-5.

[0031] Furthermore, the barium sulfate particles are mainly distributed in two ranges: 375-575 nm and 575-770 nm, with a mass ratio of 1:1-3. The main scientific basis for this two-range distribution is that the peak solar energy is located at a wavelength of 475 nm, and the peak solar photon flux is located at a wavelength of 670 nm. The aim is to achieve the maximum solar reflectivity and emissivity of the coating by selecting a concentrated distribution of barium sulfate particles centered at 475 nm and 670 nm, and using a mixed particle size distribution of 375-770 nm.

[0032] The isocyanate curing agent of component B in the raw materials for preparing the bottom and top layers is selected from any one of Wannate HT-100, HT-300, and HT-600 from Wanhua Chemical Group Co., Ltd., or any one of GB805B-100, GB930-100, GB963A-100, and GB963B-100 from Shenzhen Feiyang Junyan New Materials Co., Ltd. Preferably, it is Wannate HT-300 or GB930-100.

[0033] The transparent resin used in the preparation of the bottom and top layers can be polyaspartic acid ester resin or hydroxyl fluorocarbon resin. The polyaspartic acid ester resin can be commercially available from Shenzhen Feiyang Junyan New Materials Co., Ltd., with grades including F157, F322, F330, F2850, F2872, and the F22X, F42X, and F52X series. The hydroxyl fluorocarbon resin has a solid fluorine content ≥20%.

[0034] The dispersant is a high-efficiency dispersant for inorganic pigments, such as VOK-Disper 4100 from Volker Specialty Chemicals GmbH, Germany.

[0035] The wetting agent is a high-efficiency wetting agent for inorganic pigments, and Tego4100 selected from Evonik Specialty Chemicals AG, Germany, can be used.

[0036] The light stabilizer is a hindered amine-low molecular weight organic compound, and can be selected from Chiguard 101 or 101WB from Chiguard (Shanghai) Chemical Technology Co., Ltd.

[0037] The ultraviolet absorber is a triazine organic compound, and can be Chiguard 5400 or 5400WB selected from Chiguard (Shanghai) Chemical Technology Co., Ltd.

[0038] The thickener can be an organic bentonite, such as Clayminton HC-30 selected from Zhejiang Chang'an Renheng Technology Co., Ltd.

[0039] The diluent is an alkyl aliphatic high-boiling-point organic acid ester solvent with a boiling point of 280-350℃, and LB-300 selected from Guangzhou Chemical Co., Ltd. of the Chinese Academy of Sciences can be used.

[0040] The film-forming aid is a conventionally applicable model, such as Eastman DeuReo 281 from Germany; the defoamer is a conventionally applicable model, such as Tego 825 from Evonik GmbH from Germany.

[0041] The present invention also provides a method for preparing the colored radiation-cooling coating, which specifically includes the following steps:

[0042] (1) Preparation of bottom layer raw material slurry: Mix the raw materials of component A evenly according to the ratio to obtain component A raw material slurry, and then mix it evenly with component B to obtain bottom layer raw material slurry for later use;

[0043] (2) Preparation of surface raw material slurry: Mix all raw materials of component A1 except transparent composite film according to the ratio to obtain component A1 raw material slurry, and then mix it with component B to obtain surface raw material slurry for later use.

[0044] (3) Coating of the base layer slurry: Spray or scrape the base layer slurry onto the substrate, then put it into the oven to bake for 2-4 hours, take it out and let it sit for 4-8 hours to cure the base material, and then use it after it is completely dry.

[0045] (4) Spraying the surface slurry and pasting the transparent composite film: Spray the surface raw material slurry prepared in step (2) onto the substrate coated with the bottom slurry in step (3) until it is moistened. Then paste the transparent composite film, flatten the transparent composite film and put it into the oven to bake for 2-4 hours. Take it out and let it sit for 4-8 hours to allow the base material to cure, and a colored radiation cooling coating is obtained.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The colored radiation-cooling coating prepared by this invention is achieved by setting a transparent composite film on the surface of a radiation-cooling composite layer. The upper part of the transparent composite film has a transparent structural color function, and the lower part of the transparent composite film also has a theoretically 100% visible light reflectance performance, thereby improving the solar reflectance of the entire coating. Through the above settings, the technical problem of the significant decrease in solar reflectance of radiation-cooling coatings caused by traditional reliance on colored pigments is solved.

[0048] 2. Based on the characteristics or variation laws of solar energy distribution (peak wavelength 475nm) and solar photon flux distribution (peak wavelength 670nm), this invention selectively chooses the particle size of barium sulfate particles, especially focusing on 475nm and 670nm for reasonable aggregation and wide particle size distribution. This can significantly increase the number of particles in the coating that reflect solar photons, thereby improving the efficiency of the coating in reflecting solar energy.

[0049] 3. This invention improves the coating’s emission performance in the 8-13μm “atmospheric window” of sunlight by adding a novel transparent functional material, hollow structure medium microspheres, to the radiation-cooling composite layer and by setting the corresponding particle size and core-shell ratio of the hollow structure medium microspheres according to their circular and hollow structural characteristics and their reflection radiation characteristics in the solar energy concentration band.

[0050] 4. This invention effectively combines a novel type of radiative cooling material, hollow-structured dielectric microspheres, with the traditional radiative cooling material, barium sulfate, maximizing the radiative cooling power of the coating. Barium sulfate has a high electronic band gap energy and high insulation properties, resulting in less absorption of solar ultraviolet-visible-infrared light energy. Compared to traditional radiative cooling materials, barium sulfate coatings generate more "multiphonons that absorb infrared photons" under solar energy excitation, thus exhibiting higher thermal conductivity, which facilitates rapid heat transfer, diffusion, and emission. However, using barium sulfate alone has significant drawbacks: while maintaining its inherently high electronic band gap energy, it's impossible to simultaneously achieve a high refractive index, hindering further improvement in the coating's solar emissivity. Hollow-structured dielectric microspheres, with their spherical and hollow structure, exhibit superior radiative solar energy characteristics compared to barium sulfate. Adding an appropriate amount significantly increases the coating's solar emissivity, effectively compensating for the shortcomings of barium sulfate in this aspect. Numerous experiments have also demonstrated that when the two are properly combined and used in combination, they have a higher radiative cooling power than when used as a single material.

[0051] 5. This application improves the filling rate of the radiation cooling coating by rationally matching and distributing the size of barium sulfate and hollow structured medium microspheres. The improved filling rate means that there will be more and denser high-reflection emission fine particles, which will lead to an increase in the number of reflected, refracted or scattered photons, resulting in a significant improvement in the solar thermal efficiency of the reflected, refracted and scattered infrared bands. Detailed Implementation

[0052] The specific embodiments of the present invention are further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention, and the implementation methods are not limited thereto, nor should they be used to limit the scope of protection of the present invention.

[0053] In the embodiments and comparative examples of this invention, the polyaspartic acid ester resin was purchased from Shenzhen Feiyang Junyan New Material Co., Ltd. (F420 and F520), the hydroxyl fluorocarbon resin was purchased from Arkema (China) Ltd., the diluent was purchased from Guangzhou Institute of Chemistry, Chinese Academy of Sciences (LB-300), the light stabilizer was purchased from Chiguard 101 or 101WB (hindered amine-low molecular weight) by Chitai (Shanghai) Chemical Technology Co., Ltd., and the ultraviolet absorber was purchased from Chiguard 5400 or 5400WB (triazine) by Chitai (Shanghai) Chemical Technology Co., Ltd.

[0054] The dispersant was purchased from VOK-Disper 4100 by Volker Specialty Chemicals GmbH, Germany; the wetting agent was purchased from Tego 4100 by Evonik Specialty Chemicals GmbH, Germany; the thickener was purchased from Clayminton HC-30 organic bentonite by Zhejiang Chang'an Renheng Technology Co., Ltd.; the film-forming aid was purchased from Eastman DeuReo 281 by Germany; the defoamer was purchased from Tego 825 by Evonik by Germany; and the curing agent was purchased from Wannate HT-300 by Wanhua Chemical Group Co., Ltd. and GB930-100 by Shenzhen Feiyang Junyan New Materials Co., Ltd.

[0055] The barium sulfate, with a whiteness of over 98%, a purity of over 99%, and a refractive index of approximately 1.64, was purchased from Sahalibn Chemical GmbH, Germany. The hollow silica microspheres were purchased from Hubei Huifu Nanomaterials Co., Ltd.

[0056] Example 1

[0057] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0058] 2. Selection and preparation of transparent composite film sheets:

[0059] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0060] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0061] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0062] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0063] 4. Preparation of the bottom raw material slurry:

[0064] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0065] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0066] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0067] 5. Preparation of surface raw material slurry:

[0068] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0069] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0070] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0071] 6. Preparation of colored radiation-cooling coating:

[0072] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0073] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0074] Example 2

[0075] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0076] 2. Selection and preparation of transparent composite film sheets:

[0077] A transparent composite film with a diameter of 20.5 mm and a thickness of 1.5 mm was selected as the surface film material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 70%, a reflectance of less than 30%, a center wavelength of 575 nm, and a half-bandwidth of 25 nm, with a film thickness of 0.9 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.5%, with a film thickness of 0.6 mm. Under sunlight, this film exhibits a transmissive yellow color and reflects the remaining visible light in other wavelengths. This film is manufactured by Alluxa Corporation, USA.

[0078] 3. Pre-mixing of barium sulfate and hollow zirconium dioxide microspheres:

[0079] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0080] The core-shell ratio of hollow zirconia microspheres was selected as 0.25±0.01, and the mass ratio of the outer spherical radii distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was 8:20:5.

[0081] 4. Preparation of the bottom raw material slurry:

[0082] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 12 parts hydroxyl fluorocarbon resin, 2.5 parts diluent, 22 parts barium sulfate, 22 parts hollow zirconia microspheres, 2.2 parts dispersant, 0.8 parts wetting agent, 0.4 parts thickener, 1.8 parts film-forming aid, and 0.3 parts defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0083] Preparation of raw materials for component B: Prepare 5 parts of GB930-100 curing agent for later use;

[0084] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.05, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0085] 5. Preparation of surface raw material slurry:

[0086] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 80 parts hydroxy fluorocarbon resin, 3.6 parts light stabilizer, and 3 parts ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain A1 component raw material slurry for later use.

[0087] Preparation of raw materials for component B: Prepare 5 parts of GB930-100 curing agent for later use;

[0088] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.05, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0089] 6. Preparation of colored radiation-cooling coating:

[0090] (1) Coating of the base layer slurry: The base layer A and B components of the raw material slurry are sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours to bake. After that, it is taken out and left to cure for another 6 hours.

[0091] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in an oven at 50°C for 3 hours. Take it out and let it stand for 5 hours to allow the base material to cure. The thickness is about 2100μm, and the colored radiation cooling coating is obtained.

[0092] Example 3

[0093] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0094] 2. Selection and preparation of transparent composite film sheets:

[0095] A transparent composite film with a diameter of 24.5 mm and a thickness of 1.8 mm was selected as the surface film material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 77%, a reflectance of less than 23%, a center wavelength of 465 nm, and a half-bandwidth of 25 nm, with a film thickness of 1.0 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.7%, with a film thickness of 0.8 mm. Under sunlight, this film exhibits a transmitted blue color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0096] 3. Pre-mixing of barium sulfate and hollow white glass microspheres by particle size:

[0097] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 60% and 40% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0098] The core-shell ratio of hollow white glass microspheres was selected to be 0.35±0.01, and the mass ratio of the outer spherical radii in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was 3:30:2.

[0099] 4. Preparation of the bottom raw material slurry:

[0100] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 35 parts hydroxyl fluorocarbon resin, 50 parts barium sulfate, 25 parts hollow white glass microspheres, 3.2 parts dispersant, 0.8 parts wetting agent, 1.4 parts thickener, 1.8 parts film-forming aid, and 0.3 parts defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0101] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0102] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0103] 5. Preparation of surface raw material slurry:

[0104] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 93.5 parts hydroxy fluorocarbon resin, 3.6 parts light stabilizer, and 2.9 parts ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain A1 component raw material slurry for later use.

[0105] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0106] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0107] 6. Preparation of colored radiation-cooling coating:

[0108] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 700μm. Then it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0109] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in an oven at 50°C for 4 hours. Take it out and let it stand for 4 hours to allow the base material to cure. The thickness is about 2500μm, and the colored radiation cooling coating is obtained.

[0110] Example 4

[0111] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0112] 2. Selection and preparation of transparent composite film sheets:

[0113] A transparent composite film with a diameter of 20.5 mm and a thickness of 1.5 mm was selected as the surface film material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 80%, a reflectance of less than 20%, a center wavelength of 515 nm, and a half-width of 35 nm, with a film thickness of 0.8 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.4%, with a film thickness of 0.7 mm. Under sunlight, this film exhibits a green transmittance and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0114] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0115] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 60% and 40% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0116] The core-shell ratio of hollow silica microspheres was selected to be 0.3±0.01, and the mass ratio of the outer spherical radii in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was 3:30:2.

[0117] 4. Preparation of the bottom raw material slurry:

[0118] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 26.5 parts hydroxyl fluorocarbon resin, 22 parts barium sulfate, 44 parts hollow silica microspheres, 3.2 parts dispersant, 0.8 parts wetting agent, 1.4 parts thickener, 1.8 parts film-forming aid, and 0.3 parts defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0119] Preparation of raw materials for component B: Prepare 10 parts of GB930-100 curing agent for later use;

[0120] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.08, and disperse it in a high-speed disperser at 500-1200 rpm for 15 minutes to obtain the bottom raw material slurry for later use.

[0121] 5. Preparation of surface raw material slurry:

[0122] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts hydroxyl fluorocarbon resin, 3.6 parts light stabilizer, and 2.4 parts ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain A1 component raw material slurry for later use.

[0123] Preparation of raw materials for component B: Prepare 10 parts of GB930-100 curing agent for later use;

[0124] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.08, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0125] 6. Preparation of colored radiation-cooling coating:

[0126] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 800μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0127] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller, put it in an oven to bake for 2 hours, take it out and let it stand for 8 hours to allow the base material to cure. The thickness is about 1800μm, and the colored radiation cooling coating is obtained.

[0128] Example 5

[0129] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0130] 2. Selection and preparation of transparent composite film sheets:

[0131] A transparent composite film with a diameter of 24.5 mm and a thickness of 1.8 mm was selected as the surface film material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 77%, a reflectance of less than 23%, a center wavelength of 465 nm, and a half-width of 25 nm, with a film thickness of 1.4 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.7%, with a film thickness of 0.4 mm. Under sunlight, this film exhibits a transmitted blue color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0132] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0133] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 40% and 60% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0134] The core-shell ratio of hollow silica microspheres was selected to be 0.3±0.01, and the mass ratio of the outer spherical radii in the range of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was 3:30:2.

[0135] 4. Preparation of the bottom raw material slurry:

[0136] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 26.5 parts hydroxyl fluorocarbon resin, 44 parts barium sulfate, 22 parts hollow silica microspheres, 3.2 parts dispersant, 0.8 parts wetting agent, 1.4 parts thickener, 1.8 parts film-forming aid, and 0.3 parts defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0137] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0138] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0139] 5. Preparation of surface raw material slurry:

[0140] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts hydroxyl fluorocarbon resin, 3.6 parts light stabilizer, and 2.4 parts ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain A1 component raw material slurry for later use.

[0141] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0142] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0143] 6. Preparation of colored radiation-cooling coating:

[0144] (1) Coating of the base layer slurry: The base layer A and B components of the raw material slurry are sprayed onto the white substrate by spraying method. The spraying thickness is about 700μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material for later use.

[0145] (2) Spraying the surface slurry and pasting the transparent composite film: Spray the surface raw material slurry A1 and B onto the substrate coated with the bottom slurry in step (1) until it is wetted. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in an oven at 50°C for 3 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 2400μm, thus obtaining the colored radiation cooling coating.

[0146] Example 6

[0147] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0148] 2. Selection and preparation of transparent composite film sheets:

[0149] A transparent composite film with a diameter of 20.5 mm and a thickness of 1.1 mm was selected as the surface film material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 80%, a reflectivity of less than 20%, a center wavelength of 515 nm, and a half-width of 35 nm, with a film thickness of 0.2 mm. The lower part of the film is a broadband high-pass, high-reflectivity filter with a visible light transmittance of 99.4%, with a film thickness of 0.9 mm. Under sunlight, this film exhibits a green transmittance and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0150] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0151] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 40% and 60% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0152] The core-shell ratio of hollow silica microspheres was selected to be 0.3±0.01, and the mass ratio of the spheres with radii in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was 3:30:2.

[0153] 4. Preparation of the bottom raw material slurry:

[0154] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 26.5 parts hydroxyl fluorocarbon resin, 22 parts barium sulfate, 44 parts hollow silica microspheres, 3.2 parts dispersant, 0.8 parts wetting agent, 1.4 parts thickener, 1.8 parts film-forming aid, and 0.3 parts defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0155] Preparation of raw materials for component B: Prepare 10 parts of GB930-100 curing agent for later use;

[0156] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.08, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0157] 5. Preparation of surface raw material slurry:

[0158] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts hydroxyl fluorocarbon resin, 3.6 parts light stabilizer, and 2.4 parts ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain A1 component raw material slurry for later use.

[0159] Preparation of raw materials for component B: Prepare 10 parts of GB930-100 curing agent for later use;

[0160] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.08, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0161] 6. Preparation of colored radiation-cooling coating:

[0162] (1) Coating of the base layer slurry: The base layer A and B components of the raw material slurry are sprayed onto the white substrate by spraying method. The spraying thickness is about 1000μm. Then, it is placed in a 50℃ oven for 2 hours to bake. After that, it is taken out and left to cure for another 6 hours.

[0163] (2) Spraying of surface slurry and bonding of transparent composite film: Spray surface raw material slurry A1 and B onto the substrate coated with bottom slurry in step (1) and wet it. Then, one side of the transparent composite film is pasted onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller, put it in an oven to bake for 3 hours, take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1400μm, and the colored radiation cooling coating is obtained.

[0164] Example 7

[0165] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0166] 2. Selection and preparation of transparent composite film sheets:

[0167] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0168] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0169] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0170] The mass fraction of hollow silica microspheres with a core-shell ratio of 0.3 ± 0.01 and a spherical radius in the range of 0.2-0.4 μm was selected as 33 parts.

[0171] 4. Preparation of the bottom raw material slurry:

[0172] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0173] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0174] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0175] 5. Preparation of surface raw material slurry:

[0176] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0177] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0178] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0179] 6. Preparation of colored radiation-cooling coating:

[0180] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0181] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0182] Comparative Example 1

[0183] This comparative example is based on Example 1, but differs from Example 1 in that it does not have a surface transparent composite film layer.

[0184] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0185] 2. No pigment or structural color layer was applied.

[0186] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0187] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0188] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0189] 4. Preparation of the bottom raw material slurry:

[0190] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0191] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0192] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0193] 5. Preparation of surface raw material slurry:

[0194] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0195] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0196] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0197] 6. Preparation of colored radiation-cooling coating:

[0198] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0199] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0200] Comparative Example 2

[0201] This comparative example is based on Example 1, but differs from Example 1 in that an organic transparent pigment is used instead of the surface transparent composite film.

[0202] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0203] 2. Selection and preparation of organic transparent pigment DDP254 red pigment

[0204] Select and prepare organic transparent pigment DDP254 red pigment paste for later use.

[0205] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0206] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0207] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0208] 4. Preparation of the bottom raw material slurry:

[0209] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0210] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0211] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0212] 5. Preparation of surface raw material slurry:

[0213] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 45 parts of transparent DDP254 red pigment, 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0214] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0215] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0216] 6. Preparation of colored radiation-cooling coating:

[0217] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0218] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 400μm, and the colored radiation cooling coating is obtained.

[0219] Comparative Example 3

[0220] This comparative example is based on the setup of Example 1, the difference being that hollow silica microspheres were not used, and only barium sulfate was used instead.

[0221] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0222] 2. Selection and preparation of transparent composite film sheets:

[0223] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0224] 3. Preparation of barium sulfate:

[0225] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0226] 4. Preparation of the bottom raw material slurry:

[0227] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 66 parts of barium sulfate, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0228] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0229] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0230] 5. Preparation of surface raw material slurry:

[0231] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0232] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0233] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0234] 6. Preparation of colored radiation-cooling coating:

[0235] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0236] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0237] Comparative Example 4

[0238] This comparative example is based on the setup of Example 1, the difference being that barium sulfate material was not used, and only hollow silica microspheres were used.

[0239] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0240] 2. Selection and preparation of transparent composite film sheets:

[0241] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0242] 3. Pre-mixing of hollow silica microspheres by particle size:

[0243] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0244] 4. Preparation of the bottom raw material slurry:

[0245] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 66 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0246] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0247] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0248] 5. Preparation of surface raw material slurry:

[0249] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0250] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0251] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0252] 6. Preparation of colored radiation-cooling coating:

[0253] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0254] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0255] Comparative Example 5

[0256] This comparative example is based on the setup of Example 1, which differs from Example 1 in that the hollow silica microspheres have a particle radius exceeding the range of 0.2-0.8 μm.

[0257] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0258] 2. Selection and preparation of transparent composite film sheets:

[0259] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0260] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0261] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0262] Hollow silica microspheres with a core-to-shell ratio of 0.3±0.01 and an outer spherical radius ranging from 1.1 to 1.2 were selected.

[0263] 4. Preparation of the bottom raw material slurry:

[0264] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0265] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0266] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0267] 5. Preparation of surface raw material slurry:

[0268] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0269] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0270] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0271] 6. Preparation of colored radiation-cooling coating:

[0272] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0273] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0274] Comparative Example 6

[0275] This comparative example is based on the setup of Example 1, the difference being that the barium sulfate particle size is only distributed in the range of 375-575 nm.

[0276] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0277] 2. Selection and preparation of transparent composite film sheets:

[0278] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0279] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0280] Select barium sulfate white pigment with a particle size of 375-575nm, disperse it for 15 minutes using an ultrasonic disperser, and then set it aside.

[0281] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0282] 4. Preparation of the bottom raw material slurry:

[0283] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0284] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0285] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0286] 5. Preparation of surface raw material slurry:

[0287] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0288] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0289] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0290] 6. Preparation of colored radiation-cooling coating:

[0291] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0292] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0293] Comparative Example 7

[0294] This comparative example is based on Comparative Example 6, but differs from Comparative Example 6 in that the core-shell ratio of the hollow silica microspheres exceeds the range of 0.2-0.4.

[0295] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0296] 2. Selection and preparation of transparent composite film sheets:

[0297] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0298] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0299] Select barium sulfate white pigment with a particle size of 375-575nm, disperse it for 15 minutes using an ultrasonic disperser, and then set it aside.

[0300] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.95±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0301] 4. Preparation of the bottom raw material slurry:

[0302] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 33 parts of barium sulfate, 33 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0303] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0304] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0305] 5. Preparation of surface raw material slurry:

[0306] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0307] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0308] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0309] 6. Preparation of colored radiation-cooling coating:

[0310] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0311] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0312] Comparative Example 8

[0313] This comparative example is based on Example 1, and its difference from Comparative Example 6 is that the ratio of the two radiative cooling materials exceeds the specified range.

[0314] 1. Substrate preparation: Select a 100mm×100mm×1.5mm silicon calcium board as the coating substrate and coat it with white paint for later use.

[0315] 2. Selection and preparation of transparent composite film sheets:

[0316] A transparent composite film with a diameter of 23 mm and a thickness of 0.56 mm was selected as the surface layer material. The upper part of the transparent composite film is a circular, sheet-like narrow-band interference cutoff filter with a visible light transmittance of 75%, a reflectance of less than 25%, a center wavelength of 695 nm, and a half-bandwidth of 55 nm, with a film thickness of 0.3 mm. The lower part of the film is a broadband high-reflectance filter with a visible light reflectance of 99.2%, with a film thickness of 0.26 mm. Under sunlight, this film exhibits a transmitted red color and reflects the remaining visible light in other wavelengths. This optical film is manufactured by Alluxa Corporation, USA.

[0317] 3. Pre-mixing of barium sulfate and hollow silica microspheres by particle size:

[0318] Barium sulfate white pigments with particle sizes of 375-575nm and 575-770nm were selected at mass ratios of 50% and 50% respectively, and dispersed for 15 minutes using an ultrasonic disperser before use.

[0319] The mass ratio of hollow silica microspheres with a core-shell ratio of 0.3±0.01 and an outer spherical radius distributed in the ranges of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm was selected as 3:20:2.

[0320] 4. Preparation of the bottom raw material slurry:

[0321] Preparation of Component A raw material slurry: Prepare the following raw materials by mass percentage: 23.5 parts of polyaspartic acid ester resin (F420 and F520, with mass percentages of 70% and 30% respectively), 5 parts of diluent, 55 parts of barium sulfate, 11 parts of hollow silica microspheres, 2.2 parts of dispersant, 0.8 parts of wetting agent, 0.4 parts of thickener, 1.8 parts of film-forming aid, and 0.3 parts of defoamer; place them in a high-speed disperser at 500-2000 rpm for 120 minutes to obtain the Component A raw material slurry for later use.

[0322] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0323] Preparation of raw materials A and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the bottom raw material slurry for later use.

[0324] 5. Preparation of surface raw material slurry:

[0325] Preparation of A1 component raw material slurry: Prepare the following raw materials by mass percentage: 94 parts of polyaspartic ester resin (F420 and F520 by mass percentages of 70% and 30% respectively), 3.6 parts of light stabilizer, and 2.4 parts of ultraviolet absorber; place them in a high-speed disperser and disperse at 500-1500 rpm for 30 minutes to obtain the A1 component raw material slurry for later use.

[0326] Preparation of raw materials for component B: Prepare 10 parts of Wannate HT-300 curing agent for later use;

[0327] Preparation of raw material slurry of components A1 and B: Before use, prepare the mixture by mass ratio of component A to component B = 1:0.1, put it into a high-speed disperser and disperse it for 15 minutes at 500-1200 rpm to obtain the surface raw material slurry for later use.

[0328] 6. Preparation of colored radiation-cooling coating:

[0329] (1) Coating of the base layer slurry: The base layer slurry is sprayed onto the white substrate by spraying method. The spraying thickness is about 600μm. Then, it is placed in a 50℃ oven for 2 hours and then placed for another 6 hours to cure the base material.

[0330] (2) Spraying the surface slurry and pasting the transparent composite film: First, spray the surface raw material slurry onto the substrate coated with the bottom slurry in step (1) and wet it. Then, paste the bottom side of the transparent composite film onto the wetted substrate one by one. One layer is enough. Press it flat with a rolling roller and bake it in a 50°C oven for 2 hours. Take it out and let it stand for 6 hours to allow the base material to cure. The thickness is about 1000μm, and the colored radiation cooling coating is obtained.

[0331] Performance testing

[0332] Currently, there is no unified standard for testing the comprehensive performance of radiation-cooling coatings. This invention refers to GB / T 2680-2021 "Architectural Glass - Determination of Visible Light Transmittance, Direct Solar Transmittance, Total Solar Transmittance, Ultraviolet Transmittance and Related Window Glass Parameters" to test the "solar reflectivity" performance of samples 1-7 and 1-8 in the 300-2500nm wavelength band; it also refers to GB / T3027-2013 "Detection and Evaluation of Far-Infrared Properties of Textiles" to test the infrared emission performance of samples 1-7 and 1-8 in the 8-13μm "atmospheric window"; it uses equivalent air conditioning cooling power to test the "net cooling power" performance of samples 1-7 and 1-8; and it uses a comparative method to test and calculate the "cooling amplitude" performance of the comparative ambient temperature for samples 1-7 and 1-8, obtaining the test data listed in Table 1.

[0333] Table 1. Test results of radiation cooling coating performance

[0334]

[0335]

[0336] Based on the data in Table 1, comparing Examples 1-7 and Comparative Example 1 illustrates that the "transparent composite film" on the surface not only gives the coating color but also does not weaken the reflective and reflective properties of the underlying layer. At the same time, it has a solar reflectivity of over 99% in the visible light band, which reduces the absorption of ambient heat energy by the coating, reduces the radiative cooling load, and works in conjunction with the underlying layer to achieve the overall solar reflectivity of the coating.

[0337] Comparative Example 1 and Comparative Example 2 illustrate that, compared with pigment pigments, transparent composite film pigments, in addition to having color, also show slight improvements in solar reflectivity, infrared emissivity, and radiative cooling effect. This is because transparent composite films can not only present different colors but also do not affect their solar reflectivity. At the same time, the solar reflectivity of the radiative cooling coating is improved by setting up a radiative cooling composite layer and a transparent composite film layer.

[0338] Comparative Examples 1 and 3-4 illustrate that the solar reflectance and emissivity of the coatings prepared from the two radiative cooling materials and their multi-size mixtures are higher than those of coatings made solely from barium sulfate or hollow microspheres. This is because when opaque barium sulfate is used alone, the refractive index of the barium sulfate material limits the solar reflectance of the coating in the visible-near-infrared band, making it unable to suppress the absorption of solar heat in this band, and the infrared emissivity is also significantly low, resulting in a poorer radiative cooling effect. Similarly, when hollow microspheres are used alone, the transparency of the hollow microspheres limits the solar reflectance of the coating, resulting in insufficient infrared emissivity and a poorer cooling effect.

[0339] Comparative Example 1 and Comparative Example 5 illustrate that when hollow structured dielectric microspheres with radii outside the range of 0.2-0.8 μm are used as radiative cooling materials, their solar reflectivity and emissivity decrease significantly, resulting in a low radiative cooling effect.

[0340] Comparative Example 1 and Comparative Examples 6-7 illustrate that the functional parameter values ​​of the radiation functional material are closely related to the wavelength of sunlight and the distribution range of solar thermal energy. The particle size concentration and distribution range of the radiation functional material corresponding to the wavelength of sunlight are also directly positively correlated with the wavelength range and energy density concentration of sunlight. If they exceed this range, the functional effect will be greatly reduced.

[0341] Comparing Example 1 and Comparative Example 8, it can be seen that the mass ratio of barium sulfate particles to hollow structured medium microspheres is not within the limited range of 2:3-3:2. At this time, the experimental data values ​​of Comparative Example 8 are close to those of Comparative Examples 3-4, and the solar reflectivity, infrared emissivity and radiative cooling effect of the coating are all reduced to varying degrees.

Claims

1. A colored radiation-cooling coating based on a transparent composite film, characterized in that, It includes a surface layer and a bottom layer, wherein the bottom layer is a radiation-cooling composite layer, and the surface layer is made of a surface slurry layer and a transparent composite film, wherein the surface slurry layer is in contact with the bottom layer, and the light transmittance of the surface layer is ≥70%. The bottom layer preparation raw materials include components A and B, wherein component B is an isocyanate curing agent, and the mass ratio of component A to component B is 1:0.05-0.1; the raw materials for component A include the following components by mass parts: Transparent resin……………………………………10-39 parts Radiation functional filler………………………………40-80 parts; The radiation-functional filler includes barium sulfate particles and hollow structured medium microspheres, with a mass ratio of barium sulfate particles to hollow structured medium microspheres of 2:3-3:

2. The raw materials for preparing the surface slurry include components A1 and B, wherein component B is an isocyanate curing agent, and the mass ratio of component A1 to component B is 1:0.05-0.1; the raw materials for preparing component A1 include the following components by mass parts: Transparent resin……………………………………80-99 parts Light stabilizer……………………………………1-10 parts, Ultraviolet light absorber………………………………1-8 parts The transparent composite film comprises an upper wavelength beam-splitting film and a lower dielectric high-reflectivity film; the wavelength beam-splitting film is a narrow-band interference cutoff filter, and the wavelength beam-splitting film has a visible light transmittance ≥50% in the visible light wavelength range of 380-760nm; the dielectric high-reflectivity film has a visible light reflectance ≥99% in the visible light wavelength range of 380-760nm. The hollow structured dielectric microspheres have an outer spherical radius of 0.2-0.8 μm and a core-shell ratio of 0.2-0.

4. The hollow structured medium microspheres have a multi-size distribution, and the mass ratio of hollow structured medium microspheres with outer spherical radii in the range of 0.2-0.4μm, 0.4-0.6μm, and 0.6-0.8μm is 1-8:20-30:1-5; The barium sulfate particles are distributed in two ranges: 375-575nm and 575-770nm, with a mass ratio of 1:1-3.

2. The colored radiation-cooling coating based on a transparent composite film according to claim 1, characterized in that, The raw materials for preparing the bottom layer preparation raw material A also include the following components by mass parts: Diluent………………………………………………0-10 parts Dispersant………………………………………………1-10 parts, Wetting agent………………………………………………0.2-6 parts, Thickener………………………………………………0.5-5 parts, Film-forming aids……………………………………………0.5-8 parts, Defoamer………………………………………………0.1-2 parts.

3. The colored radiation-cooling coating based on a transparent composite film according to claim 1, characterized in that, The surface layer has a thickness of 0.1-3 mm, and the bottom layer has a thickness of 0.3-1 mm.

4. The colored radiation-cooling coating based on a transparent composite film according to claim 1, characterized in that, The hollow structured medium microspheres include any one or a combination of two or more of the following: hollow silica microspheres, hollow alumina microspheres, hollow zirconium dioxide microspheres, and hollow white glass microspheres.

5. The method for preparing the colored radiation-cooling coating based on a transparent composite film according to any one of claims 1-4, characterized in that, Specifically, the steps include the following: (1) Preparation of bottom layer raw material slurry: Mix the raw materials of component A evenly according to the ratio to obtain component A raw material slurry, and then mix it evenly with component B to obtain bottom layer raw material slurry for later use; (2) Preparation of surface raw material slurry: Mix the raw materials of component A1 evenly according to the ratio to obtain component A1 raw material slurry, and then mix it evenly with component B to obtain surface raw material slurry for later use; (3) Coating of the base layer slurry: Spray or scrape the base layer slurry onto the substrate, then put it into the oven to bake for 2-4 hours, take it out and let it sit for 4-8 hours to cure the base material, and then use it after it is completely dry. (4) Spraying the surface slurry and pasting the transparent composite film: Spray the surface raw material slurry prepared in step (2) onto the substrate coated with the bottom slurry in step (3) until it is moistened. Then paste the transparent composite film, flatten the transparent composite film and put it into the oven to bake for 2-4 hours. Take it out and let it sit for 4-8 hours until the base material is cured to obtain the colored radiation cooling coating.

Images