A high-reflectivity-radiation-cooled silica aerogel composite coating, its preparation method and application

Abstract

This invention belongs to the technical field of thermal insulation coating materials, specifically relating to a high-reflectivity-radiation cooling silica aerogel composite coating, its preparation method, and its application. The composite coating includes a silica aerogel aqueous dispersion slurry, a film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber, and mica powder. The preparation method includes: adding hydrophobic silica aerogel to deionized water, adjusting the pH, then adding a dispersant, wetting agent, and defoamer, stirring and dispersing to obtain a silica aerogel aqueous dispersion slurry; then mixing it evenly with the film-forming resin, and then... Hollow glass microspheres, titanium dioxide, glass fiber, and mica powder are added and stirred to prepare a slurry / film-forming resin / filler mixed solution. Dispersant, wetting agent, and defoamer are added to the mixed solution and stirred to prepare a silica aerogel composite coating. Finally, the coating is applied to a substrate and dried to obtain a silica aerogel composite coating material. The composite coating of this invention not only has an ultra-low thermal conductivity but also has high solar visible light reflectivity and infrared emissivity in the mid-infrared atmospheric window, exhibiting excellent radiative cooling performance. It can achieve passive 24-hour uninterrupted all-weather cooling and transfer the Earth's heat away, effectively reducing the energy consumption of air conditioning systems, weakening greenhouse gas emissions, and thus mitigating global warming.

Description

Technical Field

[0001] This invention belongs to the technical field of heat-insulating coating materials, specifically relating to a high-reflectivity-radiation cooling silica aerogel composite coating, its preparation method, and its application. Background Technology

[0002] With the rapid advancement of urbanization and informatization in the 21st century, artificial intelligence has swept the globe in recent years, exacerbating energy shortages and global warming. According to the United Nations Environment Programme's "Global Construction Status Report 2024-2025," in 2023, the global construction industry's carbon emissions surpassed those of the transportation sector, accounting for 34% of total carbon emissions, and its energy consumption accounted for 32% of global energy consumption. Meanwhile, according to the "China Urban and Rural Construction Carbon Emission Research Report (2024 Edition)," in 2022, the annual carbon emissions from building operations in China accounted for 21.7% of total carbon emissions, and its energy consumption accounted for 22% of total national energy consumption. Against the backdrop of green building development, the development of a passive, zero-energy, long-term stable building insulation and cooling technology has become an urgent need for countries around the world.

[0003] Passive daytime radiative cooling (PDRC) has been gradually discovered as a novel, passive, and efficient cooling strategy. It leverages the high reflectivity of solar radiation in the 0.3–2.5 μm band and the high emissivity in the mid-infrared atmospheric window (8–13 μm) to achieve continuous 24-hour cooling and transfer Earth's heat away. Traditional thermal insulation coatings only possess limited insulation properties and cannot efficiently reflect sunlight or emit heat into outer space. Therefore, their cooling capacity is limited in the construction industry, and they cannot effectively reduce energy consumption in air conditioning and other refrigeration and insulation technologies. Summary of the Invention

[0004] To address the problems in existing technologies, this invention provides a high-reflectivity-radiative cooling silica aerogel composite coating, its preparation method, and its application. Using hydrophobic SiO2 aerogel composite hollow glass microspheres, rutile titanium dioxide, glass fiber, and mica powder, and employing a resin emulsion as the film-forming material, a high-reflectivity-radiative cooling SiO2 aerogel composite thermal insulation coating is prepared. This coating not only possesses an ultra-low thermal conductivity but also high solar visible light reflectivity and infrared emissivity in the mid-infrared atmospheric window, exhibiting excellent radiative cooling performance. It can achieve passive 24-hour uninterrupted all-weather cooling and transfer Earth's heat away, effectively reducing the energy consumption of air conditioning systems, mitigating greenhouse gas emissions, and thus alleviating global warming.

[0005] Aerogel materials possess a nanoscale three-dimensional porous network structure, exhibiting characteristics such as high chemical stability, ultra-low density, high porosity, high specific surface area, low refractive index, and extremely low thermal conductivity. Among various aerogels, SiO2 aerogel stands out. Compared to traditional thermal insulation materials such as hollow glass microspheres, expanded vermiculite, diatomaceous earth, and sepiolite, coatings prepared using SiO2 aerogel as a filler not only offer excellent thermal insulation but also possess advantages such as high and medium infrared emissivity and lightweight. Adding SiO2 aerogel to coatings not only enhances their thermal insulation performance but also further enhances light reflection and infrared emission capabilities by utilizing its low refractive index optical properties and molecular structure.

[0006] The technical problem solved by this invention is achieved by the following technical solution:

[0007] The present invention aims to provide a high-reflectivity-radiation cooling silica aerogel composite coating, comprising silica aerogel water dispersion slurry, film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber and mica powder.

[0008] Furthermore, the mass ratio of silica aerogel water dispersion slurry, film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber and mica powder is (36~50):(80~120):(2~5):(1~5):(4~8):(4~8).

[0009] Furthermore, the glass fiber is selected from at least one of the following: alkali-free chopped glass fiber, silane-modified alkali-free chopped glass fiber, ultrafine ground glass fiber powder, chemical-resistant chopped glass fiber, high-silica and high-temperature resistant glass fiber, and high-strength alkali-resistant glass fiber.

[0010] The film-forming resins selected include pure acrylic emulsions (homogeneous or copolymer emulsions of acrylates), silicone-acrylic emulsions (silicone-modified acrylate copolymer emulsions), styrene-acrylic emulsions (copolymer emulsions of styrene and acrylate monomers), vinyl acetate emulsions (copolymer emulsions with vinyl acetate and vinyl tert-carbonate as the main monomers), fluoroacrylic emulsions (fluorocarbon-modified acrylate emulsions), chloroacrylic emulsions, anionic waterborne polyurethanes, cationic waterborne polyurethanes, nonionic waterborne polyurethanes, bisphenol A type epoxy resins, phenolic epoxy resins, alicyclic epoxy resins, and water-soluble epoxy resins. At least one of the following: self-emulsifying alkyd resin, alkyd emulsion, methyl silicone resin, phenyl silicone resin, methylphenyl silicone resin, epoxy modified organosilicon, polyester modified organosilicon, FEVE type fluorocarbon resin (fluoroolefin-vinyl ether copolymer), PTFE type resin (polytetrafluoroethylene), PVDF type resin (polyvinylidene fluoride), PVF type resin (polyvinyl fluoride), thermoplastic phenolic resin, thermosetting phenolic resin, modified phenolic resin (rosin modified, alkyd modified), urea-formaldehyde resin, melamine-formaldehyde resin, and phenyl melamine-formaldehyde resin.

[0011] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0012] S1: Add hydrophobic silica aerogel to deionized water, adjust the pH with dilute hydrochloric acid and ammonia, then add dispersant, wetting agent and defoamer, stir and disperse to obtain silica aerogel water dispersion slurry;

[0013] S2: Mix the silica aerogel water dispersion slurry and film-forming resin of S1 evenly, then add hollow glass microspheres, titanium dioxide, glass fiber and mica powder, and stir to obtain a slurry / film-forming resin / filler mixed solution.

[0014] S3: Add the dispersant, wetting agent, and defoamer to the slurry / film-forming resin / filler mixture solution in S2. Place the mixed solution on a magnetic stirring table and pre-stir at low speed to ensure initial homogenization of the mixture and additives, while preventing splashing due to magnetic instability at the beginning. Then, start high-speed stirring. When the stirring is about to end, slow down the stirring speed until the bubbles completely disappear, thus obtaining the silica aerogel composite coating.

[0015] S4: Apply the silica aerogel composite coating of S3 onto the substrate and dry to obtain the silica aerogel composite coating material.

[0016] Furthermore, in S1, the mass ratio of hydrophobic silica aerogel, deionized water, dispersant, defoamer, and wetting agent is (0.5~4):(36~44):(0.4~2.0):(0.2~2.0):(0.3~2.0).

[0017] Furthermore, in S1, the pH range is adjusted to between 7 and 9. The stirring is first performed at a low speed of 100 to 400 r / min for 5 to 10 min, and then at a high speed of 600 to 1000 r / min for 1 to 3 h. The dispersion includes ultrasonic dispersion at a frequency of 20 to 35 kHz for 10 to 30 min.

[0018] Furthermore, in S2, the stirring rate is 100~400 r / min, and the time is 5~10 min.

[0019] Furthermore, in S3, the mass ratio of dispersant, wetting agent, and defoamer is (1.5~3.0):(1.0~2.5):(1.0~2.0);

[0020] The mixing process includes pre-mixing at a low speed of 100-400 r / min for 5-10 min, then mixing at a high speed of 800-1200 r / min for 1.5-4 h, and then mixing at a low speed of 100-400 r / min for 5-10 min.

[0021] Furthermore, in S4, the coating method is selected from one of the following: brush coating, high-pressure airless spraying, air-assisted airless spraying, scraping coating, trowel coating, curtain coating, roller coating, spraying, flow coating, and dip coating; the number of coatings is 2 to 3, and the drying time at room temperature is 6 to 72 hours based on the coating thickness.

[0022] Application of a high-reflectivity-radiation cooling silica aerogel composite coating or a method for preparing a high-reflectivity-radiation cooling silica aerogel composite coating in the preparation of building materials, textiles, new energy thermal management materials or cold chain transportation materials.

[0023] Preferably, the hydrophobic silica aerogel is selected from at least one of the following: methyl-modified, epoxy-modified, amino-modified, fluoroalkyl-modified, phenyl-modified, ethyl-modified, vinyl-modified, heptadecafluorodecyltrimethoxysilane-modified, perfluorooctyltriethoxysilane-modified, dimethyldiethoxysilane (DMDEOS)-modified, dimethyldiethoxysilane (DMDEOS)-modified, methyltrimethoxysilane (MTMS)-modified, trimethylchlorosilane (TMCS)-modified, hexamethyldisilazane (HMDS)-modified, hexamethyldisiloxane (HMDSO)-modified, octyltrimethoxysilane-modified, hexadecyltrimethoxysilane-modified, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane-modified, and γ-aminopropyltriethoxysilane hydrophobic silica aerogel.

[0024] The dispersant can be selected from at least one of the following: 1124 (ammonium polyacrylate), 8055 (ammonium polyacrylate), 5027 (ammonium polycarboxylate), 5040 (sodium polycarboxylate), W627 dispersant (polymer mixture), BASF Dispex® Ultra PX 4575, Dispex® Ultra CX 4452, KLTL5040, KLTL5030, 8450, HH®2021, WF812, DAPRO ACP-16W, Zhongke Yutian ZKFS-180, DY2698, F108, Ecodisp50, ECODIS P90, Disuper S19, DAPRO ACP-16W, DP-270, DISPERBYK-190, DISPERBYK-110, DISPERBYK-108, UCON LB-400X, and Solsperse 20000.

[0025] The defoamer can be at least one of the following: NXZ, FoamStar® ED 2528, TERGITOL XD, BASF FoamStar® ED2528, BYK-024, TS-100, KMT-100, Wacker 601, BYK-054, Defom 6500, BYK-065, TEGO Foamex 8051, Defom 6800, BYK-A 530, TEGO Airex 900, and Defom 3500.

[0026] The wetting agent can be at least one of the following: PE-100, SURFYNOL 104, TRITON X-405, Hydropalat WE 3110, Hydropalat WE 3475, BYK-DYNWET 800, TEGO Wet 236, DISPERBYK-190, TEGO Dispers 750W, Kaysalor DS 7326, Solsperse 20000, Lutensol AT 25, Triton X-100, Aerosol OT, Hostapur SAS, BYK-333, DISPERBYK-190, and EGO Wet 260.

[0027] Hollow glass microspheres can be selected from at least one of 3M™ K15, 3M™ K20, 3M™ S15, Saint-Lite HL15, Hainuo HN15, Sinosteel H15, 3M™ S22, 3M™ S28, 3M™ S32, 3M™ A20, 3M™ K37, and 3M™ HGS8000X.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] 1. This invention uses hydrophobic silica aerogel as its core, and combines it with hollow glass microspheres, rutile titanium dioxide, flake mica powder, and chopped glass fibers in a five-element compound. The selected hydrophobic silica aerogel provides strong thermal insulation properties while also helping to improve the emissivity of infrared electromagnetic waves within the atmospheric window; the selected hollow glass microspheres effectively support the film-forming resin network, providing excellent thermal insulation properties while also helping to improve the infrared emissivity within the atmospheric window; the selected rutile titanium dioxide effectively improves the light reflection properties of the silica aerogel composite coating; and the selected glass fibers effectively enhance the silica aerogel... The composite coating enhances crack resistance and mechanical properties, significantly improving weather resistance and structural stability. The selected mica powder creates a "maze" effect within the coating, effectively improving the mechanical properties, corrosion resistance, and mid-infrared emissivity of the silica aerogel composite coating. This high-reflectivity-radiative cooling silica aerogel composite thermal insulation coating, through the construction of an integrated synergistic system of "photothermal reflection + atmospheric window radiative heat dissipation + multi-level porous insulation + fiber toughening," differs from traditional single-barrier and single-reflective coatings, possessing ultra-low thermal conductivity, ultra-high solar visible light reflectivity, and mid-infrared atmospheric window infrared emissivity. This composite coating preparation process offers comprehensive advantages such as ease of operation, raw material availability, cost-effectiveness, controllable reaction, and industrial applicability, making it valuable for applications in building energy conservation, industrial insulation, outdoor thermal protection, and new energy thermal management.

[0030] 2. This invention features a directionally designed "radiative heat dissipation functional system" that precisely matches the 8-13 μm atmospheric window. Combined with the synergistic effect of multiple fillers, it achieves the dual benefits of "high daytime reflectivity and heat absorption, and continuous radiative heat dissipation day and night." This overcomes the limitations of traditional coatings that "only block heat but do not dissipate it," and abandons the single-filler design of existing technologies. Instead, it employs a composite radiation system of "hydrophobic silica aerogel + flake mica powder + infrared radiation additive." These two components synergistically enhance the infrared emissivity in the 8-13 μm band and complement the functions of other fillers in the coating (rutile titanium dioxide and hollow glass microspheres). The nanoscale three-dimensional porous structure of the hydrophobic silica aerogel effectively enhances the reflection and refraction of mid-infrared electromagnetic waves, thereby regulating the emissivity of infrared electromagnetic waves in the atmospheric window. Rutile titanium dioxide is almost transparent in the mid-infrared band and does not affect the emission of infrared electromagnetic waves. The hollow structure of the hollow glass microspheres creates a scattering effect, effectively enhancing the infrared emissivity of the coating. The prepared silica aerogel composite coating has excellent radiative cooling performance. It can efficiently block heat transfer while emitting heat from the earth through atmospheric windows, effectively reducing the large amount of energy consumption of air conditioning and refrigeration systems in the construction industry and mitigating global greenhouse gas emissions and global warming effects.

[0031] 3. This invention utilizes hydrophobically modified aerogels adapted to water-based coating systems. By adding dispersants, wetting agents, and defoamers, combined with mechanical and ultrasonic dispersion, a uniform, stable, and high-solid-content silica aerogel aqueous dispersion slurry is prepared. This solves the industry pain points of ordinary hydrophilic or hydrophobic aerogels in film-forming resins, such as difficulty in dispersion, agglomeration, storage stratification, and poor water resistance of the coating film. Simultaneously, it retains the ultra-high specific surface area, ultra-high porosity, and nano-three-dimensional porous network structure characteristics of silica aerogels, meeting the requirements of low thermal conductivity, hydrophobicity, moisture resistance, and dispersion stability in the coating. The selected dispersants, wetting agents, and defoamers are readily available. The dispersant provides excellent dispersion stability for the silica aerogel aqueous dispersion slurry; the selected wetting agent effectively improves the wettability of silica aerogel in aqueous systems; and the selected defoamer effectively eliminates air bubbles in the silica aerogel aqueous dispersion slurry.

[0032] 4. This invention utilizes an interfacial compatibility design of waterborne film-forming resin and highly filled inorganic filler, employing a composite additive system of dispersant, wetting agent, and defoamer. This solves the problems of easy agglomeration, sedimentation, foaming, cratering, and poor adhesion in waterborne coating systems with high solids content inorganic fillers, achieving simultaneous improvement in film density, weather resistance, and mechanical properties under high solids content in waterborne coatings. This silica aerogel composite coating preparation process is simplified, convenient to operate, uses inexpensive and readily available raw materials, significantly reduces overall preparation costs, and ensures stable and controllable reaction parameters throughout the process. The reaction environment is easy to regulate, and the process exhibits good repeatability and adaptability, making it suitable for continuous large-scale industrial production.

[0033] 5. This invention utilizes hydrophobic silica aerogel to prepare a uniformly and stably dispersed silica aerogel aqueous dispersion slurry by adding dispersants, wetting agents, defoamers, and other additives, combined with mechanical and ultrasonic dispersion. Based on this, using acrylic emulsion as the film-forming resin, and adding hollow glass microspheres, rutile titanium dioxide, glass fiber, and mica powder as functional fillers, a high-reflectivity-radiative cooling silica aerogel composite thermal insulation coating is prepared. It not only has an ultra-low thermal conductivity coefficient but also high solar visible light reflectivity and mid-red atmospheric window infrared emissivity, possessing excellent radiative cooling performance. It can effectively provide a passive 24-hour uninterrupted autonomous cooling effect, and has great application prospects in the field of building energy conservation. It is of great significance for reducing greenhouse gas emissions and mitigating global warming.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. Furthermore, in order to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0035] Figure 1 This is an optical image of the methyl-modified hydrophobic silica aerogel aqueous dispersion slurry prepared in Example 1.

[0036] Figure 2 This is an optical image of the high-reflectivity-radiation-cooling silica aerogel coating prepared in Example 1.

[0037] Figure 3 This is an optical image of the high-reflectivity-radiation-cooled silica aerogel composite coating prepared in Example 1.

[0038] Figure 4 This is a microscopic morphology diagram of the high-reflectivity-radiation cooling silica aerogel composite coating prepared in Example 1.

[0039] Figure 5 The image shows the ultraviolet-visible-near-infrared reflectance spectrum of the high-reflectance-radiation-cooled silica aerogel composite coating prepared in Example 1.

[0040] Figure 6 The image shows the mid-infrared emissivity spectrum of the high-reflectivity-radiation-cooling silica aerogel composite coating prepared in Example 1. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0042] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0043] Example 1

[0044] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0045] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ, and wetting agent PE-100 were mixed at a mass ratio of 36.8:3.2:1.5:1:0.6, stirred for 2 h at a stirring speed of 800 r / min, and ultrasonically dispersed for 20 min at a frequency of 20 kHz. The mixture was then allowed to stand for 3 h to stabilize, resulting in a silica aerogel aqueous dispersion slurry. This slurry was a milky white, viscous liquid. An optical image is attached. Figure 1 As shown.

[0046] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:4:3:5:5 and stir at low speed for 5 min at a rate of 200 r / min.

[0047] 3) Dispersant 1124, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.5:1:1 (dispersant 1124 to acrylic emulsion ratio of 1.5:90). The mixture was stirred at high speed for 2 hours at a stirring rate of 800 r / min to obtain a silica aerogel composite coating. The coating is a pure white, homogeneous liquid. The optical image of the coating is attached. Figure 2 As shown.

[0048] 4) The silica aerogel composite coating obtained in step 3) is applied to the substrate in multiple coats and dried at room temperature for 64 h to obtain the silica aerogel composite coating. An optical image of the dried and cured silica aerogel composite coating is attached. Figure 3 As shown.

[0049] The silica aerogel composite coating prepared in Example 1 has a thermal conductivity of 0.049 W / m². -1 K -1 The solar reflectance is 90.44%, and the atmospheric window infrared emissivity is 91.07%. The ultraviolet-visible-near-infrared reflectance spectrum and the mid-infrared emissivity spectrum are attached. Figure 5 and attached Figure 6 As shown.

[0050] Example 2

[0051] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0052] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 5040, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 37.6:2.4:1.1:0.8:0.5, stirred for 2 h at a stirring rate of 800 r / min, ultrasonically dispersed for 20 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0053] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:4:3:5:5 and stir at low speed for 5 min at a rate of 200 r / min.

[0054] 3) Dispersant 5040, wetting agent PE-100 and defoamer NXZ are added to the mixed solution of silica aerogel, acrylic emulsion and filler obtained in step 2) at a mass ratio of 1.5:1:1 (the ratio of dispersant 5040 to acrylic emulsion is 1.5:90). The mixture is stirred at high speed for 2 hours at a stirring rate of 1000 r / min to finally obtain silica aerogel composite coating.

[0055] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 64 h to obtain the silica aerogel composite coating.

[0056] The silica aerogel composite coating prepared in Example 2 has a thermal conductivity of 0.057 W / m. -1 K -1 The solar reflectance is 88.74%, and the atmospheric window infrared emissivity is 90.80%.

[0057] Example 3

[0058] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0059] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 5040, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 38.4:1.6:1.0:0.7:0.5, stirred for 2.5 h at a stirring rate of 800 r / min, ultrasonically dispersed for 25 min at a frequency of 24 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0060] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:4:3:5:5 and stir at low speed for 10 min at a speed of 150 r / min.

[0061] 3) Dispersant 5040, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.4:1:1 (the ratio of dispersant 5040 to acrylic emulsion is 1.4:90). The mixture was stirred at high speed for 2 hours at a stirring rate of 1100 r / min to finally obtain the silica aerogel composite coating.

[0062] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 64 h to obtain the silica aerogel composite coating.

[0063] The silica aerogel composite coating prepared in Example 3 has a thermal conductivity of 0.075 W / m. -1 K -1 The solar reflectance is 86.74%, and the atmospheric window infrared emissivity is 90.78%.

[0064] Example 4

[0065] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0066] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 5027, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 39.2:0.8:0.8:0.5:0.5, stirred for 2 h at a stirring rate of 800 r / min, ultrasonically dispersed for 20 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0067] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:4:3:5:5 and stir at low speed for 5 min at a rate of 200 r / min.

[0068] 3) Dispersant 5027, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.2:1.1:1 (the ratio of dispersant 5027 to acrylic emulsion is 1.2:90). The mixture was stirred at high speed for 2 hours at a stirring rate of 1000 r / min to finally obtain the silica aerogel composite coating.

[0069] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 60 h to obtain the silica aerogel composite coating.

[0070] The silica aerogel composite coating prepared in Example 4 has a thermal conductivity of 0.093 W / m². -1 K -1 The solar reflectance is 86.61%, and the atmospheric window infrared emissivity is 90.76%.

[0071] Example 5

[0072] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0073] 1) Deionized water, phenyl-modified hydrophobic silica aerogel, dispersant 8055, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 36:4:2:1.5:1, stirred for 2.5 h at a stirring rate of 900 r / min, ultrasonically dispersed for 25 min at a frequency of 30 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0074] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), pure acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:110:5:4:5:5 and stir at low speed for 10 min at a rate of 300 r / min.

[0075] 3) Dispersant 8055, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, pure acrylic emulsion, and filler obtained in step 2) at a mass ratio of 2:1.5:1.5 (the ratio of dispersant 8055 to pure acrylic emulsion is 2:110). The mixture was stirred at high speed for 2 hours at a stirring rate of 1200 r / min to finally obtain silica aerogel composite coating.

[0076] 4) The silica aerogel composite coating obtained in step 3) is sprayed onto the substrate in multiple layers and dried at room temperature for 12 h to obtain the silica aerogel composite coating.

[0077] The silica aerogel composite coating prepared in Example 5 has a thermal conductivity of 0.045 W / m. -1 K -1 The solar reflectance is 91.12%, and the atmospheric window infrared emissivity is 91.53%.

[0078] Example 6

[0079] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0080] 1) Deionized water, ethyl-modified hydrophobic silica aerogel, dispersant W627, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 36.5:3.5:1.8:1.2:0.8, stirred for 1.5 h at a stirring rate of 700 r / min, ultrasonically dispersed for 25 min at a frequency of 28 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining a silica aerogel water dispersion slurry.

[0081] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), pure acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:100:4.5:3.5:5:5 and stir at low speed for 8 min at a rate of 300 r / min.

[0082] 3) Dispersant W627, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, pure acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.8:1.3:1 (the ratio of dispersant W627 to pure acrylic emulsion was 1.8:100). The mixture was stirred at high speed for 4 hours at a stirring rate of 900 r / min to finally obtain the silica aerogel composite coating.

[0083] 4) The silica aerogel composite coating obtained in step 3) is sprayed onto the substrate in multiple layers and dried at room temperature for 15 h to obtain the silica aerogel composite coating.

[0084] The silica aerogel composite coating prepared in Example 6 has a thermal conductivity of 0.062 W / m². -1 K -1 The solar reflectance is 90.88%, and the atmospheric window infrared emissivity is 91.23%.

[0085] Example 7

[0086] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0087] 1) Deionized water, epoxy-modified hydrophobic silica aerogel, dispersant W627, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 37:3:1.5:1.1:0.7, stirred for 2.5 h at a stirring rate of 1000 r / min, ultrasonically dispersed for 25 min at a frequency of 30 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0088] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), styrene-acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:100:4:3:5:5 and stir at low speed for 8 min at a rate of 250 r / min.

[0089] 3) Dispersant W627, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, styrene-acrylic emulsion and filler obtained in step 2) at a mass ratio of 1.5:1.2:1 (the ratio of dispersant W627 to styrene-acrylic emulsion is 1.5:90). The mixture was stirred at high speed for 3 hours at a stirring rate of 1200 r / min to finally obtain silica aerogel composite coating.

[0090] 4) Spray the silica aerogel composite coating obtained in step 3) onto the substrate in multiple layers and dry at room temperature for 18 hours.

[0091] The silica aerogel composite coating prepared in Example 7 has a thermal conductivity of 0.084 W / m². -1 K -1 The solar reflectance is 89.65%, and the atmospheric window infrared emissivity is 90.89%.

[0092] Example 8

[0093] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0094] 1) Deionized water, fluoroalkyl modified hydrophobic silica aerogel, dispersant 5040, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 37.4:2.6:1.4:1:0.8, stirred for 2 h at a stirring rate of 800 r / min, ultrasonically dispersed for 20 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0095] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), acetic acid emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:2:5:5:5 and stir at low speed for 5 min at a rate of 200 r / min.

[0096] 3) Dispersant 5040, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, acetic acid emulsion, and filler obtained in step 2) at a mass ratio of 1.5:1.2:1 (the ratio of dispersant 5040 to acetic acid emulsion is 1.5:90). The mixture was stirred at high speed for 3 hours at a stirring rate of 1100 r / min to finally obtain silica aerogel composite coating.

[0097] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 48 h to obtain the silica aerogel composite coating.

[0098] The silica aerogel composite coating prepared in Example 8 has a thermal conductivity of 0.134 W / m².-1 K -1 The solar reflectance is 87.78%, and the atmospheric window infrared emissivity is 90.32%.

[0099] Example 9

[0100] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0101] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 5040, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 38:2:1.5:1:0.5, stirred for 3 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 24 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0102] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), styrene-acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:2:5:6:6 and stir at low speed for 8 min at a rate of 300 r / min.

[0103] 3) Dispersant 5040, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, styrene-acrylic emulsion and filler obtained in step 2) at a mass ratio of 2.0:1.5:1 (the ratio of dispersant 5040 to styrene-acrylic emulsion is 2.0:90). The mixture was stirred at high speed for 3 hours at a stirring rate of 1100 r / min to finally obtain silica aerogel composite coating.

[0104] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 48 h to obtain the silica aerogel composite coating.

[0105] The silica aerogel composite coating prepared in Example 9 has a thermal conductivity of 0.088 W / m². -1 K -1 The solar reflectance is 89.78%, and the atmospheric window infrared emissivity is 87.94%.

[0106] Comparative Example 1

[0107] A method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating includes the following steps:

[0108] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 40:0:0.8:0.5:0.5, stirred for 2.5 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 32 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining an aqueous dispersion slurry.

[0109] 2) Mix the water-dispersible slurry, styrene-acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:2:1:4:4 and stir at low speed for 8 min at a rate of 100 r / min.

[0110] 3) Dispersant 1124, wetting agent PE-100, and defoamer NXZ were added to the mixed solution obtained in step 2) at a mass ratio of 1.2:1:1 (the ratio of dispersant 1124 to styrene-acrylic emulsion is 1.2:90). The mixture was stirred at high speed for 2.5 h at a stirring rate of 1200 r / min to obtain the composite coating.

[0111] 4) Apply the composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 60 h to obtain the composite coating.

[0112] The composite coating prepared in Comparative Example 1 has a thermal conductivity of 0.354 W / m². -1 K -1 The solar reflectance is 64.32%, and the atmospheric window infrared emissivity is 70.37%.

[0113] Comparative Example 2

[0114] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 40:0:0.8:0.5:0.5, stirred for 3 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining an aqueous dispersion slurry.

[0115] 2) Mix the water-dispersible slurry, silicone-acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:1:0.5:4:4 and stir at low speed for 8 min at a rate of 100 r / min.

[0116] 3) Add dispersant 1124, wetting agent PE-100, and defoamer NXZ to the mixed solution obtained in step 2) at a mass ratio of 1.2:1:1 (the ratio of dispersant 1124 to silicone-acrylic emulsion is 1.2:90), stir at high speed for 3 hours at a stirring rate of 1200 r / min, and finally obtain the composite coating.

[0117] 4) Apply the composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 72 h to obtain the composite coating.

[0118] The composite coating prepared in Comparative Example 2 has a thermal conductivity of 0.231 W / m². -1 K -1 The solar reflectance is 45.82%, and the atmospheric window infrared emissivity is 56.91%.

[0119] Comparative Example 3

[0120] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 40:0:0.8:0.5:0.5, stirred for 3 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining an aqueous dispersion slurry.

[0121] 2) Mix the water-dispersible slurry, silicone-acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:0:0:4:2 and stir at low speed for 8 min at a rate of 100 r / min.

[0122] 3) Dispersant 1124, wetting agent PE-100, and defoamer NXZ are added to the mixed solution obtained in step 2) at a mass ratio of 1.4:1:1 (the ratio of dispersant 1124 to silicone-acrylic emulsion is 1.4:90). The mixture is stirred at high speed for 3 hours at a stirring rate of 1200 r / min to obtain the composite coating.

[0123] 4) Apply the composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 72 h to obtain the composite coating.

[0124] The composite coating prepared in Comparative Example 3 has a thermal conductivity of 0.586 W / m². -1 K -1 The solar reflectance is 32.94%, and the atmospheric window infrared emissivity is 40.31%.

[0125] Comparative Example 4

[0126] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 40:0.1:0.8:0.5:0.5, stirred for 3 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0127] 2) Mix the silica aerogel water dispersion slurry, silicone acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:0.5:0:4:2 and stir at low speed for 8 min at a rate of 100 r / min.

[0128] 3) Dispersant 1124, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, silicone acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.5:1:1 (the ratio of dispersant 1124 to silicone acrylic emulsion is 1.5:90). The mixture was stirred at high speed for 3 hours at a stirring rate of 1200 r / min to finally obtain the silica aerogel composite coating.

[0129] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 72 h to obtain the silica aerogel composite coating.

[0130] The silica aerogel composite coating prepared in Comparative Example 4 has a thermal conductivity of 0.875 W / m². -1 K -1 The solar reflectance is 44.43%, and the atmospheric window infrared emissivity is 50.12%.

[0131] Comparative Example 5

[0132] 1) Deionized water, methyl-modified hydrophobic silica aerogel, dispersant 1124, defoamer NXZ and wetting agent PE-100 were mixed in a mass ratio of 40:0.2:0.8:0.5:0.5, stirred for 3 h at a stirring rate of 900 r / min, ultrasonically dispersed for 30 min at a frequency of 20 kHz, and then allowed to stand for 3 h to stabilize, thus obtaining silica aerogel water dispersion slurry.

[0133] 2) Mix the silica aerogel water dispersion slurry obtained in step 1), silicone acrylic emulsion, hollow glass microspheres S15, rutile titanium dioxide, alkali-free chopped glass fiber and mica powder in a mass ratio of 40:90:0.5:0.5:4:1 and stir at low speed for 8 min at a rate of 100 r / min.

[0134] 3) Dispersant 1124, wetting agent PE-100, and defoamer NXZ were added to the mixed solution of silica aerogel, silicone acrylic emulsion, and filler obtained in step 2) at a mass ratio of 1.5:1:1 (the ratio of dispersant 1124 to silicone acrylic emulsion is 1.5:90). The mixture was stirred at high speed for 3 hours at a stirring rate of 1200 r / min to finally obtain the silica aerogel composite coating.

[0135] 4) Apply the silica aerogel composite coating obtained in step 3) onto the substrate in multiple coats and dry at room temperature for 72 h to obtain the silica aerogel composite coating.

[0136] The silica aerogel composite coating prepared in Comparative Example 5 has a thermal conductivity of 0.923 W / m². -1 K -1 The solar reflectance is 48.82%, and the atmospheric window infrared emissivity is 56.31%.

[0137] Effect description:

[0138] The composite coatings prepared in Examples 1-9 and Comparative Examples 1-5 were tested for thermal conductivity, solar visible light (400-780 nm) reflectance, and atmospheric window (8-13 μm) infrared emissivity. The thermal conductivity of the SiO2 aerogel composite coating was determined using a thermal constant analyzer (Hotdisk TPS1500, Kegonas, Sweden). This instrument, based on transient planar heat source technology, can accurately obtain data such as the thermal conductivity and thermal diffusivity of the SiO2 aerogel composite coating. The reflectance of the SiO2 aerogel composite coating in the 0.3-2.5 μm solar wavelength range was tested using a UV-3600 ultraviolet-visible-near-infrared spectrophotometer (lambda750, PETKLin Eimer, England), and the average reflectance of the coating in the 400-780 nm solar wavelength range was calculated as the solar visible light reflectance. A Fourier transform infrared spectrometer (Nicolet6700, Thermo Fisher Scientific, The United States) was used. The instrument (US) measures the infrared emissivity of the coating in the 2.5–25 μm band. It is equipped with an integrating sphere accessory to perform infrared emissivity spectral testing in diffuse reflectance mode. The emissivity of the coating in the 8–13 μm band is calculated as the infrared emissivity of the atmospheric window. The test results are shown in Table 1 below.

[0139] Table 1

[0140]

[0141] This invention introduces hollow glass microspheres, rutile titanium dioxide, glass fiber, and mica powder as functional fillers, using a polymer emulsion as the film-forming resin, in synergy with SiO2 aerogel, to prepare a silica aerogel composite coating with excellent thermal insulation properties. This coating exhibits ultra-low thermal conductivity, high reflectivity in the solar radiation band, and high emissivity within the mid-infrared atmospheric window, demonstrating excellent radiative cooling performance. It can achieve passive, autonomous cooling for 24 hours, effectively emitting heat from the Earth through the atmospheric window, reducing greenhouse gas emissions, and thus mitigating the global greenhouse effect.

[0142] The hydrophobic silica aerogel used in this invention can effectively improve the thermal insulation performance of the coating and help improve the infrared emissivity of the coating in the mid-infrared atmospheric window. The selected hollow glass microspheres can effectively support the film-forming resin network, providing excellent thermal insulation performance, while also helping to improve the infrared emissivity in the atmospheric window. The selected rutile titanium dioxide can improve the solar visible light reflectance performance of the silica aerogel composite coating. The selected glass fiber can effectively improve the mechanical properties of the silica aerogel composite coating. The selected mica powder can effectively improve the mechanical properties, corrosion resistance, and infrared emissivity in the atmospheric window of the silica aerogel composite coating.

[0143] This invention discloses a method for preparing a high-reflectivity-radiation cooling type silica aerogel composite thermal insulation coating. The method uses hydrophobic silica aerogel, deionized water, film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber, and mica powder in a mass ratio of (0.5~4):(36~44):(80~120):(2~5):(1~5):(4~8):(4~8). First, a uniformly and stably dispersed SiO2 aerogel aqueous dispersion slurry is prepared by adding dispersants, wetting agents, defoamers, and other additives, combined with mechanical and ultrasonic dispersion. Based on the preparation of a uniformly and stably dispersed SiO2 aerogel aqueous dispersion slurry, further research was conducted on the process design and performance optimization of SiO2 aerogel composite coating. Acrylic emulsion, silicone acrylic emulsion and other emulsions were used as film-forming resins. Functional fillers such as hollow glass microspheres, rutile titanium dioxide, mica powder, and glass fiber, as well as additives such as dispersants, wetting agents, and defoamers were added to help regulate the thermal insulation, optical, mechanical and water and alkali resistance properties of the composite coating.

[0144] This invention's coating, by constructing an integrated synergistic system of "photothermal reflection + atmospheric window radiative heat dissipation + multi-level nanoporous thermal insulation + fiber toughening," differs from traditional single-barrier and single-reflective coatings. It possesses an ultra-low thermal conductivity, high solar visible light (400~780 nm) reflectivity, and high infrared emissivity through a mid-infrared atmospheric window (8~13 μm). It exhibits superior thermal insulation capabilities and excellent radiative cooling performance, enabling passive 24-hour autonomous cooling and radiating heat from Earth into outer space. This is of great significance for achieving efficient energy conservation and mitigating global warming. This coating has broad application prospects in fields such as building insulation and energy saving, industrial energy saving and thermal protection, functional textiles, new energy thermal management, and cold chain transportation.

[0145] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0146] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A high-reflectivity-radiation cooling silica aerogel composite coating, characterized in that, It includes silica aerogel water dispersion slurry, film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber and mica powder.

2. The high-reflectivity-radiation cooling silica aerogel composite coating as described in claim 1, characterized in that: The mass ratio of silica aerogel water dispersion slurry, film-forming resin, hollow glass microspheres, titanium dioxide, glass fiber and mica powder is (36~50):(80~120):(2~5):(1~5):(4~8):(4~8).

3. The high-reflectivity-radiation cooling silica aerogel composite coating as described in claim 1, characterized in that: The glass fiber is selected from at least one of the following: alkali-free chopped glass fiber, silane-modified alkali-free chopped glass fiber, ultrafine ground glass fiber powder, chemical-resistant chopped glass fiber, high-silica and high-temperature resistant glass fiber, and high-strength alkali-resistant glass fiber. The film-forming resin is selected from at least one of the following: pure acrylic emulsion, silicone acrylic emulsion, styrene acrylic emulsion, acetate emulsion, fluoroacrylic emulsion, chloroacrylic emulsion, anionic waterborne polyurethane, cationic waterborne polyurethane, nonionic waterborne polyurethane, bisphenol A epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, water-soluble epoxy resin, self-emulsifying alkyd resin, alkyd emulsion, methyl silicone resin, phenyl silicone resin, methylphenyl silicone resin, epoxy-modified organosilicon, polyester-modified organosilicon, FEVE-type fluorocarbon resin, PTFE-type resin, PVDF-type resin, PVF-type resin, thermoplastic phenolic resin, thermosetting phenolic resin, modified phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, and phenyl melamine-formaldehyde resin.

4. The method for preparing a high-reflectivity-radiation cooling silica aerogel composite coating as described in any one of claims 1-3, characterized in that: Includes the following steps: S1: Add hydrophobic silica aerogel to deionized water, adjust the pH, then add dispersant, wetting agent and defoamer, stir and disperse to obtain silica aerogel water dispersion slurry; S2: Mix the silica aerogel water dispersion slurry and film-forming resin of S1 evenly, then add hollow glass microspheres, titanium dioxide, glass fiber and mica powder, and stir to obtain a slurry / film-forming resin / filler mixed solution. S3: Add dispersant, wetting agent and defoamer to the slurry / film-forming resin / filler mixture solution of S2 and stir to obtain silica aerogel composite coating; S4: Apply the silica aerogel composite coating of S3 onto the substrate and dry to obtain the silica aerogel composite coating material.

5. The method for preparing a high-reflectivity-radiation cooling silica aerogel composite coating as described in claim 4, characterized in that: In S1, the mass ratio of hydrophobic silica aerogel, deionized water, dispersant, defoamer, and wetting agent is (0.5~4):(36~44):(0.4~2.0):(0.2~2.0):(0.3~2.0).

6. The method for preparing a high-reflectivity-radiation cooling silica aerogel composite coating as described in claim 5, characterized in that: In S1, adjust the pH to 7-9, stir at 600-1000 r / min for 1-3 h, and disperse using ultrasonic dispersion at a frequency of 20-35 kHz for 10-30 min.

7. The method for preparing a high-reflectivity-radiation cooling silica aerogel composite coating as described in claim 4, characterized in that: In S2, the stirring rate is 100~400 r / min, and the time is 5~10 min.

8. The method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating as described in claim 4, characterized in that: In S3, the mass ratio of dispersant, wetting agent, and defoamer is (1.5~3.0):(1.0~2.5):(1.0~2.0); Stir at 800~1200 r / min for 1.5~4 h.

9. The method for preparing a high-reflectivity-radiation-cooling silica aerogel composite coating as described in claim 4, characterized in that: In S4, the coating method can be one of brush coating, high-pressure airless spraying, air-assisted airless spraying, scraping, troweling, curtain coating, roller coating, spraying, flow coating and dip coating; the number of coatings is 2 to 3, and the drying time at room temperature is 6 to 72 hours.

10. The application of the high-reflectivity-radiation cooling silica aerogel composite coating as described in any one of claims 1-3 or the preparation method of the high-reflectivity-radiation cooling silica aerogel composite coating as described in any one of claims 4-9 in the preparation of building materials, textiles, new energy thermal management materials or cold chain transportation materials.

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