Inorganic radiation refrigeration coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of coatings, in particular to an inorganic radiation refrigeration coating as well as a preparation method and application thereof. The invention relates to an inorganic radiation refrigeration coating, which comprises the following raw materials by weight: 20-40 parts of white sulphoaluminate cement; 30 to 50 parts of inorganic functional filler subjected to surface treatment; 0.1-1 part of a water reducing agent; 0.1-0.5 part of a water retaining agent; 1-2 parts of redispersible latex powder; 0.05 to 0.1 part of a thixotropic agent; 25 to 35 parts of water; the inorganic functional filler subjected to surface treatment is prepared by carrying out surface coating treatment on the inorganic functional filler by adopting a coupling reagent. The inorganic radiation refrigeration coating provided by the invention has good radiation refrigeration, high strength, durability and relatively strong adhesive force.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an inorganic radiation cooling coating, its preparation method, and its application. Background Technology

[0002] Radiation-cooling coatings cool buildings by simultaneously reflecting sunlight and radiating infrared radiation into outer space. Most commercially available radiation-cooling coatings use organic polymers as binders and light-reflecting materials as fillers. While these coatings offer some cooling effect, they have several significant drawbacks: organic polymers are prone to aging under sunlight, especially ultraviolet radiation, leading to a decrease in cooling performance; and most organic resins are flammable, posing a fire hazard.

[0003] Currently, some existing technologies utilize white cement as an inorganic binder for radiative cooling materials. White cement, as an inorganic binder, is not prone to aging or flammability, and it exhibits high compatibility with the concrete mortar substrate widely used in exterior walls. However, a problem exists when using white cement as a binder for radiative cooling coatings: to achieve satisfactory radiative cooling effects, a large proportion of functional fillers needs to be added. However, white cement itself has weak adhesive strength, and there are significant property differences between white cement and functional fillers. This makes the insufficient adhesion and compatibility issues between white cement and functional fillers particularly prominent when the amount of functional fillers added is large. This results in coatings with poor adhesion, easy peeling, and insufficient coating strength. Furthermore, the hydration and hardening process between white cement and raw materials is complex, and the selection of raw materials and preparation methods also has a significant impact on the performance of the prepared coating. Therefore, it is crucial to provide an inorganic radiative cooling coating and its preparation method that combine good radiative cooling, high strength, durability, and adhesion. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an inorganic radiation cooling coating, its preparation method, and its application. The inorganic radiation cooling coating possesses excellent radiation cooling properties, high strength, durability, and adhesion.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an inorganic radiation cooling coating, comprising the following raw materials in parts by weight: 20-40 parts of white sulfoaluminate cement; 30-50 parts of surface-treated inorganic functional filler; Water-reducing agent 0.1-1 part; Water-retaining agent: 0.1–0.5 parts; 1-2 parts of redispersible latex powder; Thixotropic agent 0.05–0.1 parts; 25-35 parts water; The surface-treated inorganic functional filler is prepared by surface coating of inorganic functional filler with coupling reagent.

[0006] The inorganic radiation cooling coating provided in this application uses white sulfoaluminate cement as a binder. White sulfoaluminate cement itself has high solar reflectivity. After hydration and activation, it can form CSH gel and ettringite structure, and has intrinsic high emissivity in the 8-13 μm band. The inorganic functional filler (spherical titanium dioxide or silicon dioxide) used in this application has extremely high refractive index and scattering ability for sunlight. The inorganic functional filler is used as a filler after being surface-coated with coupling agents silane coupling agent and zirconate aluminate coupling agent in sequence. This not only improves the interfacial compatibility and bonding between the inorganic functional filler and white sulfoaluminate cement and redispersible latex powder, but also reduces the interfacial defects of the inorganic functional filler by coating, thereby further improving the radiative cooling effect. Under the optimized formula and dosage, the prepared inorganic radiative cooling coating has good durability, adhesion and crack resistance, and also has good high solar reflectivity and infrared emissivity, thus achieving an effective radiative cooling effect.

[0007] Furthermore, the white sulfoaluminate cement has a Heinz whiteness greater than 92 and a blue light whiteness greater than 87. Higher whiteness indicates better reflectivity to sunlight. White sulfoaluminate cement within the aforementioned whiteness range is readily available and possesses high reflectivity to sunlight, meeting the requirements for radiative cooling effects in coatings. The specific surface area of ​​the white sulfoaluminate cement is 500–580 m² / g. 2 / kg, the white sulfoaluminate cement with the above specific surface area has high hydration activity and strength, and the resulting coating is dense; if the specific surface area is too large or too small, it may lead to insufficient strength or density of the coating.

[0008] Furthermore, the inorganic functional filler is one or both of spherical silicon dioxide and spherical titanium dioxide, preferably spherical titanium dioxide. The particle size of the inorganic functional filler includes fine particles with a particle size of 0.05–0.15 μm and coarse particles with a particle size of 5–15 μm, with a doping ratio of fine particles to coarse particles of 30–40:60–70. This application uses an inorganic functional coating composed of fine and coarse particles with a doping ratio of 30–40:60–70, which can form a nano-microstructure in the coating to avoid uneven accumulation, ensure uniform filler accumulation in the coating, reduce porosity, and achieve better infrared thermal emission effects.

[0009] The choice of treatment reagents and methods for surface coating of inorganic functional fillers is crucial for achieving good radiative cooling, high strength, durability, and adhesion while maintaining high filler content. Specifically, the surface treatment method described in this application involves sequentially coating the inorganic functional filler with a silane coupling agent and a zirconium aluminate coupling agent; the amount of silane coupling agent used is 0.5–1% of the weight of the inorganic functional filler; and the amount of zirconium aluminate coupling agent used is 1–1.5% of the weight of the inorganic functional filler.

[0010] The method of this application involves sequentially coating the surface of inorganic functional fillers with a silane coupling agent and a zirconium aluminate coupling agent. The silane coupling agent forms Si-O-Ti covalent bonds on the surface of the inorganic functional filler, reducing interfacial defects. The zirconium aluminate coupling agent contains zirconium and aluminum, and upon hydrolysis, it generates zirconium aluminum hydroxide on the surface of the inorganic functional filler. This hydroxide reacts with ettringite, a cement hydration product, improving the interfacial adhesion and compatibility between titanium dioxide and white sulfoaluminate cement. The resulting coating exhibits strong adhesion, high strength, and excellent radiative cooling performance. The dosage of the coupling agents is crucial. In this application, the amount of silane coupling agent used is 0.5–1% of the weight of the inorganic functional filler, and the amount of zirconium aluminate coupling agent used is 1–1.5% of the weight of the inorganic functional filler. In this application, if the dosage of silane coupling agent and zirconium aluminate coupling agent is too low, the treatment effect will be poor and the inorganic functional filler particles will not achieve a uniform surface coating effect. If the dosage is too high, the infrared thermal emission performance of the inorganic functional filler will be reduced. Further, the silane coupling agent is selected from one or both of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0011] The use of water-reducing agents can effectively reduce the water consumption of coatings, improve the fluidity and dispersion stability of coatings, ensure that all powder components can be uniformly dispersed, and avoid agglomeration. Furthermore, the water-reducing agent is selected from one or two of polycarboxylate-based high-efficiency water-reducing agents, naphthalene-based high-efficiency water-reducing agents, melamine-based high-efficiency water-reducing agents, aminosulfonate-based high-efficiency water-reducing agents, lignin sulfonate-based water-reducing agents, and aliphatic high-efficiency water-reducing agents. Preferably, the water-reducing agent used in this application is a polycarboxylate-based high-efficiency water-reducing agent. The polycarboxylate-based high-efficiency water-reducing agent selected in this application helps to form a uniform, dense, and highly reflective coating.

[0012] Further, the water-retaining agent is selected from one or two of hydroxypropyl methylcellulose ether, hydroxyethyl methylcellulose ether, sodium carboxymethyl cellulose, and starch ether; preferably, the water-retaining agent is selected from hydroxypropyl methylcellulose ether. Using hydroxypropyl methylcellulose ether as a water-retaining agent can prevent excessive evaporation of moisture in the coating after application and during the cement hydration stage, ensuring that the white sulfoaluminate cement can be fully hydrated. The resulting coating has high strength, good crack resistance, and is easy to apply and maintain.

[0013] Thixotropic agents can impart good thixotropic properties to coatings. Furthermore, the thixotropic agent is selected from one or two of fumed silica, bentonite, and attapulgite. Preferably, the thixotropic agent in this application is fumed silica. Using fumed silica can ensure that the coating thickness is easy to control during construction and ensure uniform coating thickness.

[0014] Further, the redispersible latex powder is selected from one or both of ethylene-vinyl acetate-based or acrylate-based redispersible latex powders. Preferably, the redispersible latex powder used in this application is ethylene-vinyl acetate-based redispersible latex powder. The use of the above-mentioned redispersible latex powder in this application has good compatibility with the system. After addition, it can effectively improve the coating brittleness caused by white sulfoaluminate cement and high proportion of inorganic functional coatings, and improve the coating's toughness, crack resistance and adhesion to the substrate.

[0015] This application also provides a method for preparing the above-mentioned inorganic radiation cooling coating, comprising the following steps: S1. Dilute the silane coupling agent and the zirconium aluminate coupling agent with 5-10 times anhydrous ethanol. Spray the diluted silane coupling agent solution evenly onto the inorganic functional filler, stir and mix at 50-100 rpm for 20-40 min, and dry at 80-100℃ for 1-3 h. Then spray the diluted zirconium aluminate coupling agent solution onto the inorganic functional filler after surface treatment with silane coupling agent, stir and mix at 50-100 rpm for 20-40 min, and dry at 80-100℃ for 1-3 h to obtain the surface-treated inorganic functional filler. S2. According to the formula, put the surface-treated inorganic functional filler, white sulfoaluminate cement, water-reducing agent, water-retaining agent, redispersible latex powder and thixotropic agent into a planetary ball mill and mix them for 20 to 40 minutes at a speed of 100 to 800 rpm and a ball-to-material ratio of 5 to 10:1. S3. Before use, transfer the mixed dry powder into a high-speed mixer, add the amount of water specified in the formula, and mechanically stir at 500-800 rpm for 10-20 minutes to obtain a uniform slurry. S4. Let the uniform slurry stand at room temperature for 5-10 minutes to mature, and the inorganic radiation cooling coating will be obtained.

[0016] This application also provides the application of the inorganic radiation cooling coating or the inorganic radiation cooling coating prepared by the above method in passive cooling of exterior walls; Preferably, the application method involves using a wire bar coater to apply an inorganic radiation cooling coating onto a concrete substrate to prepare a wet film with a thickness of 400–600 μm, and curing it for 7–10 days at a temperature of 15–35°C and a relative humidity of 40–60% to form a cured inorganic radiation cooling coating on the substrate.

[0017] The inorganic radiation cooling coating provided in this application is suitable for a variety of inorganic substrates, especially for concrete substrates. The prepared radiation cooling coating has good durability, good crack resistance, and good radiation cooling effect.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. In this embodiment, white sulfoaluminate cement is selected as the binder. The inorganic functional filler is coated with silane coupling agent and zirconium aluminate coupling agent in sequence. The silane coupling agent can form Si-O-Ti covalent bonds on the surface of the inorganic functional filler to reduce the interfacial defects of the inorganic functional filler. The zirconium aluminate coupling agent contains zirconium and aluminum in its molecules. After hydrolysis, zirconium aluminum hydroxide can be generated on the surface of the inorganic functional filler. It can react with ettringite, a cement hydration product, to improve the interfacial bonding performance and compatibility between titanium dioxide and white sulfoaluminate cement. The auxiliary components, content and preparation method of the coating are optimized. The prepared coating has excellent solar reflectivity and high infrared emissivity. It has the advantages of good radiative cooling, high strength, durability and adhesion, and can achieve efficient, long-lasting and safe radiative cooling effect.

[0019] 2. The coating used in this application is an inorganic system, which has excellent durability, UV resistance and non-flammability. All the raw materials used in this application are readily available and the cost is lower than that of organic resins and functional fillers. It can be applied by traditional construction methods such as spraying and roller coating, and is suitable for large-scale promotion and application. Attached Figure Description

[0020] Figure 1 This is a photograph of the actual product used in the cooling performance test of this invention. Figure 2 The solar reflectance curves of the coatings prepared in Examples 1-3 of this invention are shown. Figure 3 The above are solar reflectance curves of the coatings prepared in Comparative Examples 1 to 5 of this invention. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, all methods described herein are conventional methods, and all raw materials described herein are available from publicly available commercial sources.

[0023] Example 1 This embodiment provides an inorganic radiation-cooling coating, with the following formulation: 30 parts of white sulfoaluminate cement 45 parts of surface-treated spherical titanium dioxide 0.3 parts of polycarboxylate superplasticizer 0.2 parts of hydroxypropyl methylcellulose ether 1.5 parts redispersible latex powder 0.08 parts of fumed silica 30 parts water The white sulfoaluminate cement has a Heinz whiteness of 95, a bluish whiteness of 92, and a specific surface area of ​​526 m². 2 / kg; The preparation method of surface-treated spherical titanium dioxide is as follows: silane coupling agent and zirconium aluminate coupling agent are diluted with 5 times anhydrous ethanol. The diluted silane coupling agent solution is uniformly sprayed onto the inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h. Then, the diluted zirconium aluminate coupling agent solution is sprayed onto the surface-treated inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h to obtain the surface-treated inorganic functional filler. The amount of silane coupling agent is 0.7% of the weight of the inorganic functional filler; the amount of zirconium aluminate coupling agent is 1.2% of the weight of the inorganic functional filler.

[0024] The spherical titanium dioxide is a blend of 0.1μm fine particles and 10μm coarse particles in a ratio of 35:65. The silane coupling agent is γ-aminopropyltriethoxysilane; The redispersible latex powder is an ethylene-vinyl acetate-based redispersible latex powder; The preparation method of the inorganic radiation-cooling coating in this embodiment is as follows: 1. According to the formula, put the surface-treated inorganic functional filler, white sulfoaluminate cement, water-reducing agent, water-retaining agent, redispersible latex powder and thixotropic agent into a planetary ball mill, and ball mill and mix for 30 minutes at a speed of 300 rpm and a ball-to-material ratio of 5:1. 2. Transfer the mixed dry powder into a high-speed mixer, add the amount of water specified in the formula, and mechanically stir at 500 rpm for 20 minutes to obtain a uniform slurry; 3. Allow the obtained slurry to stand at room temperature for 10 minutes to mature, and the inorganic radiation cooling coating will be obtained.

[0025] Example 2 This embodiment provides an inorganic radiation-cooling coating, with the following formulation: 20 parts of white sulfoaluminate cement 30 parts of surface-treated spherical titanium dioxide 0.1 parts of polycarboxylate superplasticizer 0.1 parts of hydroxypropyl methylcellulose ether 1 part redispersible latex powder 0.05 parts of fumed silica 25 parts water The white sulfoaluminate cement has a Heinz whiteness of 95, a bluish whiteness of 92, and a specific surface area of ​​526 m². 2 / kg; The preparation method of surface-treated spherical titanium dioxide is as follows: silane coupling agent and zirconium aluminate coupling agent are diluted with 5 times and 10 times anhydrous ethanol, respectively. The diluted silane coupling agent solution is uniformly sprayed onto the inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 80℃ for 3 h. Then, the diluted zirconium aluminate coupling agent solution is sprayed onto the surface-treated inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 80℃ for 3 h to obtain the surface-treated inorganic functional filler. The amount of silane coupling agent is 1% of the weight of the inorganic functional filler; the amount of zirconium aluminate coupling agent is 1% of the weight of the inorganic functional filler.

[0026] The spherical titanium dioxide is a blend of 0.1μm fine particles and 10μm coarse particles in a ratio of 40:60. The silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane. The redispersible latex powder is an ethylene-vinyl acetate-based redispersible latex powder; The preparation method of the inorganic radiation-cooling coating in this embodiment is as follows: 1. According to the formula, put the surface-treated inorganic functional filler, white sulfoaluminate cement, water-reducing agent, water-retaining agent, redispersible latex powder and thixotropic agent into a planetary ball mill, and ball mill and mix for 30 minutes at a speed of 300 rpm and a ball-to-material ratio of 5:1. 2. Transfer the mixed dry powder into a high-speed mixer, add the amount of water specified in the formula, and mechanically stir at 500 rpm for 20 minutes to obtain a uniform slurry; 3. Allow the obtained slurry to stand at room temperature for 10 minutes to mature, and the inorganic radiation cooling coating will be obtained.

[0027] Example 3 This embodiment provides an inorganic radiation-cooling coating, with the following formulation: 40 parts of white sulfoaluminate cement 50 parts of surface-treated spherical titanium dioxide 1 part of polycarboxylate superplasticizer 0.5 parts of hydroxypropyl methylcellulose ether 2 parts redispersible latex powder 0.1 parts of fumed silica 35 parts water The white sulfoaluminate cement has a Heinz whiteness of 95, a bluish whiteness of 92, and a specific surface area of ​​526 m². 2 / kg; The preparation method of surface-treated spherical titanium dioxide is as follows: silane coupling agent and zirconium aluminate coupling agent are diluted with 10 times anhydrous ethanol. The diluted silane coupling agent solution is uniformly sprayed onto the inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h. Then, the diluted zirconium aluminate coupling agent solution is sprayed onto the surface-treated inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h to obtain the surface-treated inorganic functional filler. The amount of silane coupling agent is 1% of the weight of the inorganic functional filler; the amount of zirconium aluminate coupling agent is 1.5% of the weight of the inorganic functional filler.

[0028] The spherical titanium dioxide is a blend of 0.1μm fine particles and 10μm coarse particles in a ratio of 30:70. The silane coupling agent is γ-aminopropyltriethoxysilane.

[0029] The redispersible latex powder is an ethylene-vinyl acetate-based redispersible latex powder; The preparation method of the inorganic radiation-cooling coating in this embodiment is as follows: 1. According to the formula, put the surface-treated inorganic functional filler, white sulfoaluminate cement, water-reducing agent, water-retaining agent, redispersible latex powder and thixotropic agent into a planetary ball mill, and ball mill and mix for 30 minutes at a speed of 300 rpm and a ball-to-material ratio of 5:1. 2. Transfer the mixed dry powder into a high-speed mixer, add the amount of water specified in the formula, and mechanically stir at 500 rpm for 20 minutes to obtain a uniform slurry; 3. Allow the obtained slurry to stand at room temperature for 10 minutes to mature, and the inorganic radiation cooling coating will be obtained.

[0030] Comparative Example 1 The formulation and preparation method in Example 1 are the same, except that the inorganic functional filler is not coated with a coupling agent for surface treatment.

[0031] Comparative Example 2 The formulation and preparation method in Example 1 are the same, except that the inorganic functional filler is coated with a silane coupling agent only for surface treatment.

[0032] Comparative Example 3 The formulation and preparation method in Example 1 are the same, except that the inorganic functional filler is coated with only zirconate aluminate coupling agent for surface treatment.

[0033] Comparative Example 4 The difference between the formulation and preparation method in Example 1 is that the inorganic functional filler is first treated with zirconate aluminate coupling agent and then treated with silane coupling agent.

[0034] The preparation method of surface-treated spherical titanium dioxide is as follows: silane coupling agent and zirconium aluminate coupling agent are diluted with 5 times anhydrous ethanol. The diluted zirconium aluminate coupling agent solution is sprayed onto the inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h. The diluted silane coupling agent solution is then uniformly sprayed onto the surface-treated inorganic functional filler, stirred and mixed at 100 rpm for 20 min, and dried at 100℃ for 1 h to obtain the surface-treated inorganic functional filler. The amount of silane coupling agent is 0.7% of the weight of the inorganic functional filler; the amount of zirconium aluminate coupling agent is 1.2% of the weight of the inorganic functional filler.

[0035] Comparative Example 5 The formulation and preparation method in Example 1 are the same, except that the amount of zirconium aluminate coupling agent used is 2% of the weight of the inorganic functional filler.

[0036] Comparative Example 6 The formulation and preparation method are the same as in Example 1, except that only 0.1 μm spherical titanium dioxide is used as the inorganic functional filler.

[0037] Comparative Example 7 The formulation and preparation method in Example 1 are the same, except that only 10 μm spherical titanium dioxide is used as the inorganic functional filler.

[0038] Comparative Example 8 The formula and preparation method in Example 1 are the same, except that the specific surface area of ​​the white sulfoaluminate cement is 450 m². 2 / kg.

[0039] Comparative Example 9 The formula and preparation method in Example 1 are the same, except that the specific surface area of ​​the white sulfoaluminate cement is 600 m². 2 / kg.

[0040] Performance testing The inorganic radiation-cooling coatings prepared in the above examples and comparative examples were applied to concrete slabs using a wire bar coater, with a wet film thickness of 500 μm. The coatings were cured for 7 days under standard curing conditions (temperature 23±2℃, relative humidity 50±5%) to prepare a cured coating. The cured coatings were then tested for optical properties, cooling performance, durability, and adhesion. Samples were prepared according to GB / T20472-2006 7.4, and a 7-day flexural strength test was performed. The testing methods for the optical properties, cooling performance, durability, and adhesion of the cured coatings are as follows: 1. Optical performance: The reflectance and emissivity of the coating were tested using a UV-Vis-NIR spectrophotometer and a Fourier transform infrared spectrometer.

[0041] 2. Cooling performance: See Figure 1 On a clear, cloudless midday (solar radiation intensity > 900W / m²) 2 The coated concrete slab was placed outdoors, and its surface temperature was measured using an infrared imager. The difference between the coating surface temperature and the ambient temperature was calculated to evaluate the cooling performance.

[0042] 3. Durability: Conduct QUV accelerated aging test (1000 hours). After the test, observe the appearance of the coating and test the reflectivity of the coating to calculate the percentage reduction in reflectivity.

[0043] 4. Adhesion: Adhesion test shall be performed according to the cross-cut adhesion test as specified in ASTM D3359.

[0044] 5. 7-day flexural strength: Tested in accordance with GB / T 20472-2006 7.4.

[0045] The test results are shown in Table 1 below. The solar reflectance curves of the coatings prepared in Examples 1-3 are shown in the figure below. Figure 2 The solar reflectance curves of the coatings prepared in Comparative Examples 1-5 are shown in the figure. Figure 3 .

[0046] Table 1: Performance Comparison Results of Coatings in Examples and Comparative Examples

[0047] As can be seen from the above, the inorganic radiation cooling coatings provided in Examples 1 to 3 of this application have a solar reflectance of 0.92 to 0.94%, an atmospheric window emissivity of 0.94 to 0.95%, a cooling performance of -4.4 to -5.2℃, an adhesion rating of 0, a 7-day flexural strength of 6.2 to 8.7 MPa, and after 1000 hours of QUV accelerated aging test, the coating showed no chalking or cracking, and the reflectance decreased by less than 0.02%. The inorganic radiation cooling coatings provided in this application combine good radiation cooling, high strength, durability, and adhesion.

[0048] In Comparative Examples 1-5, the inorganic functional fillers were not coated with coupling agents, or only silane coupling agents or zirconium aluminate coupling agents were used, or a combination of zirconium aluminate coupling agent followed by silane coupling agent coating was employed. The high dosage of zirconium aluminate coupling agent significantly impacted the radiation cooling effect, flexural strength, durability, and adhesion of the prepared inorganic radiation cooling coatings. Comparative Examples 6-7 used spherical titanium dioxide particles of a single particle size (fine or coarse), which was not conducive to forming a dense and uniform coating, thus affecting the radiation cooling effect, strength, durability, and adhesion of the coatings. Comparative Examples 8-9 used white sulfoaluminate cement with either a small or large specific surface area, which negatively impacted the radiation cooling effect, durability, and strength of the coatings.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them; although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this application or equivalent substitutions can be made to some technical features, all of which should be covered within the scope of the technical solutions claimed in this application.

Claims

1. An inorganic radiation-cooling coating, characterized in that, The ingredients include the following parts by weight: 20-40 parts of white sulfoaluminate cement; 30-50 parts of surface-treated inorganic functional filler; Water-reducing agent 0.1 to 1 part; Water-retaining agent: 0.1–0.5 parts; 1-2 parts of redispersible latex powder; Thixotropic agent 0.05–0.1 parts; 25-35 parts water; The surface-treated inorganic functional filler is prepared by surface coating of inorganic functional filler with coupling reagent.

2. The inorganic radiation cooling coating according to claim 1, characterized in that, The white sulfoaluminate cement has a Heinz whiteness greater than 92 and a bluish whiteness greater than 87, and its specific surface area is 500–580 m². 2 / kg.

3. The inorganic radiation cooling coating according to claim 1, characterized in that, The inorganic functional filler is one or both of spherical silicon dioxide and spherical titanium dioxide. The particle size of the inorganic functional filler includes fine particles with a particle size of 0.05 to 0.15 μm and coarse particles with a particle size of 5 to 15 μm. The doping ratio of fine particles to coarse particles is 30 to 40: 60 to 70.

4. The inorganic radiation cooling coating according to claim 1, characterized in that, The surface treatment method involves sequentially coating the inorganic functional filler with a silane coupling agent and a zirconium aluminate coupling agent. The amount of the silane coupling agent used is 0.5-1% of the weight of the inorganic functional filler; the amount of the zirconium aluminate coupling agent used is 1-1.5% of the weight of the inorganic functional filler. The silane coupling agent is selected from one or both of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

5. The inorganic radiation cooling coating according to claim 1, characterized in that, The water-reducing agent is selected from one or two of the following: polycarboxylate-based high-efficiency water-reducing agents, naphthalene-based high-efficiency water-reducing agents, melamine-based high-efficiency water-reducing agents, aminosulfonate-based high-efficiency water-reducing agents, lignin sulfonate-based water-reducing agents, and aliphatic high-efficiency water-reducing agents.

6. The inorganic radiation cooling coating according to claim 1, characterized in that, The water-retaining agent is selected from one or two of hydroxypropyl methylcellulose ether, hydroxyethyl methylcellulose ether, sodium carboxymethyl cellulose, and starch ether.

7. The inorganic radiation cooling coating according to claim 1, characterized in that, The thixotropic agent is selected from one or two of fumed silica, bentonite, and attapulgite.

8. The inorganic radiation cooling coating according to claim 1, characterized in that, The redispersible latex powder is selected from one or both of ethylene-vinyl acetate-based or acrylate-based redispersible latex powders.

9. The method for preparing an inorganic radiation-cooling coating according to claims 1-8, characterized in that, Includes the following steps: S1. Dilute the silane coupling agent and the zirconium aluminate coupling agent with 5-10 times anhydrous ethanol. Spray the diluted silane coupling agent solution evenly onto the inorganic functional filler, stir and mix at 50-100 rpm for 20-40 min, and dry at 80-100℃ for 1-3 h. Then spray the diluted zirconium aluminate coupling agent solution onto the inorganic functional filler after surface treatment with silane coupling agent, stir and mix at 50-100 rpm for 20-40 min, and dry at 80-100℃ for 1-3 h to obtain the surface-treated inorganic functional filler. S2. According to the formula, put the surface-treated inorganic functional filler, white sulfoaluminate cement, water-reducing agent, water-retaining agent, redispersible latex powder and thixotropic agent into a planetary ball mill and mix them for 20 to 40 minutes at a speed of 100 to 300 rpm and a ball-to-material ratio of 5 to 10:

1. S3. Transfer the mixed dry powder into a high-speed mixer, add the amount of water specified in the formula, and mechanically stir at 500-800 rpm for 10-20 minutes to obtain a uniform slurry. S4. Allow the obtained slurry to stand at room temperature for 5-10 minutes to mature, and the inorganic radiation cooling coating will be obtained.

10. The application of an inorganic radiative cooling coating according to any one of claims 1 to 8 or an inorganic radiative cooling coating prepared by the method according to claim 9 in passive cooling of exterior walls; Preferably, the application method involves using a wire bar coater to apply an inorganic radiation cooling coating onto a concrete substrate to prepare a wet film with a thickness of 400–600 μm, and curing it for 7–10 days at a temperature of 15–35°C and a relative humidity of 40–60% to form a cured inorganic radiation cooling coating on the substrate.

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