Directed radiation refrigeration coating, coating composition and preparation and application thereof

Abstract

The invention relates to a directed radiation refrigeration coating, a coating composition and preparation and application thereof, and the heat radiation path of the directed radiation refrigeration coating is changed by adjusting the refractive index between the coatings, so that the heat radiation angle is changed. Furthermore, the heat radiation angle can be accurately controlled by regulating and controlling the thickness of the coating and the proportion of filler components, so that the heat can be greatly exchanged to the outer space through an atmosphere window by changing the heat radiation angle even if the coating is coated on the surface of a base material in the direction perpendicular to the sky, and the refrigeration effect is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of functional coatings and paints, and particularly relates to a directional radiation refrigeration coating, a coating composition, and preparation and application thereof. Background Art

[0002] At present, the world is facing the dual challenges of energy shortage and global warming. The demand for cooling in buildings, electrical and electronic equipment, and rail transportation is increasing, so refrigeration equipment such as air conditioners are widely used. However, traditional refrigeration technology relies on electric drive, has high energy consumption and produces a large amount of greenhouse gases, which seriously affects the environment. Therefore, the development of efficient and energy-saving passive cooling technology has become one of the key directions of global research. Radiative cooling technology is a cooling method that does not require electricity or mechanical drive. It uses the characteristics of the earth's atmospheric window (8-13μm band) that allows objects to radiate heat to outer space, and transfers heat to outer space through radiative heat dissipation, thereby reducing the temperature of the object. Ideally, radiative cooling can achieve significant cooling effects under direct sunlight during the day.

[0003] Based on the principle of radiation cooling, radiation cooling ceramic plates, radiation cooling glass, etc. have been designed and put into practical application one after another. These materials effectively reduce the surface temperature of the substrate through efficient radiation cooling characteristics. CN202311497862.5 discloses a passive radiation cooling ceramic and a preparation method thereof, wherein the passive radiation cooling ceramic includes a first coating, which is formed on the surface of the substrate and reflects visible light, near-infrared light and ultraviolet light in sunlight, and emits mid-infrared light, wherein the metal filler in the coating includes Al2O3, TiO2, ZnO, ZrO2, etc. Compared with commercial ceramic tiles, the temperature of passive radiation cooling ceramics is reduced by 3.1 to 4.9°C under direct sunlight. CN201811324484.X publicly authorized a radiation cooling glass and its preparation method, the radiation cooling glass includes a glass substrate, an oxide layer and a coating layer, the oxide layer mainly includes Al2O3, TiO2, SiO2, HfO2 and the like which have a radiation effect, the infrared emissivity of the radiation cooling glass in the 8-13μm band is ≥93%, and the reflectivity in the 780-2500nm band is ≥90%. However, due to the rigidity and inflexibility of the ceramic and glass materials themselves, their application scope is subject to certain limitations, and they are only suitable for the radiation cooling needs of large flat surfaces.

[0004] In contrast, radiative cooling paint shows obvious advantages. Because it has a variety of coating methods such as brushing, spraying, and rolling, it can flexibly cover the surface of objects in different shapes and environments, thereby significantly expanding its application scenarios. For example, patent CN202310944847.4 publicly authorized a radiative cooling paint and its application. The compound use of CuFe2O4 and La3Ni2O7 greatly improves the emissivity of the radiative cooling paint in the 8-13μm band, thereby improving the radiative cooling effect of the paint. In actual tests, the emissivity of the paint in the 8-13μm band can be as high as 0.98, and the visible light and near-infrared reflectivity are as high as 0.91. The paint and ordinary reflective paint were placed in an insulating temperature difference measuring instrument at an ambient temperature of 25°C to test the cooling performance. The results showed that the cooling effect of the paint was 15°C lower than that of ordinary reflective paint, and it has excellent cooling performance. Patent CN202211593956.8 publicly authorized a radiation cooling coating, its preparation method and radiation cooling coating. The coating uses cage-type polysilsesquioxane modified by silane coupling agent as a radiation filler. Its reflectivity in the 400-2500nm band is 0.93, and its emissivity in the infrared atmospheric window area (wavelength 8-13μm) is 0.96. At the same time, the contact angle between the coating and water is measured using a surface tension / dynamic contact angle meter. The contact angle is 141°, indicating that the coating has excellent radiation cooling performance and hydrophobicity. Patent CN202410041728.2 publicly authorized a high-emission rare earth-based radiation cooling coating, which first applies a reflection enhancement layer with metal powder as filler on the substrate. This layer can promote the reflective performance of the entire paint surface, and then prepares a radiation cooling layer with WO3, Nb2O5, B2O3, etc. as radiation fillers. In actual tests, the temperature drops by 4.2°C. Patent CN202310764406.6 publicly authorizes a radiation cooling paint for construction and its preparation method. It uses tetrahedral radiation cooling fillers instead of traditional spherical, porous and other particles to form a multi-directional reflection and radiation surface convex to the base surface on the surface of the topcoat. It can reflect sunlight and ambient refracted light multiple times, increase the radiation surface and bulge toward the empty outer space. There is no infrared radiation blocking, which enhances the radiation cooling efficiency and can achieve a cooling effect of 17 to 23°C at an ambient temperature of 25°C during the day.Patent 202211634085.X publicly authorizes a passive radiation cooling composite coating and a preparation method. The composite coating includes a top layer and a bottom layer. The top layer is coated on the bottom layer to form a composite coating for reflecting visible light, near-infrared light and ultraviolet light in sunlight, and emitting mid-infrared light. It has high reflectivity in ultraviolet light, visible light and near-infrared bands (solar radiation) to reduce the object's heat absorption of solar radiation. At the same time, it has high emissivity in the mid-infrared band to help the object itself dissipate heat. The filler used in the top layer is one or more of Al2O3, TiO2, BaSO4, Fe2O3, and CuO, and the bottom layer is white latex paint coated on the substrate. The reflectivity of the passive radiation cooling composite coating in the ultraviolet region, visible light and near-infrared region in the 0.1-2.5 μm band is greater than or equal to 0.95, and the emissivity in the mid-infrared region (8-13 μm) is greater than or equal to 0.95. The passive radiation cooling composite coating and the ordinary white coating are simultaneously applied to the upper surfaces of two identical metal iron plates, a thermocouple is connected to the lower surface of the metal iron plate, and a refrigeration performance test is carried out in an outdoor environment. The results show that the temperature of the lower surface of the metal iron plate coated with the passive radiation cooling composite coating is 23.5°C lower than the temperature of the lower surface of the metal iron plate coated with the ordinary white coating.

[0005] However, the data in the above patents all come from the vertical emissivity of the coating, that is, the thermal radiation on the coating surface is perpendicular to the atmospheric window, and the influence of the coating position on the radiative cooling effect is not fully considered. The basic principle of radiative cooling requires that the coating radiate heat to outer space through the atmospheric window, thereby reducing the temperature of the substrate. Therefore, in order to achieve the ideal cooling effect, the coating needs to be directly exposed to the direction of the unobstructed atmospheric window. However, when the coating is applied to the surface of the substrate perpendicular to the sky, since the coating is not directly facing the atmospheric window, the radiated heat is easily blocked by various objects in the surrounding environment of the substrate, the radiation efficiency is greatly reduced, and the cooling effect is therefore limited. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a directional radiation cooling coating, a coating composition and its preparation and application. The coating of the present invention comprises a radiation coating that radiates heat and a reflective coating that reflects sunlight. By adjusting the refractive index between the coatings, the path of the heat radiation of the radiation cooling coating is changed, thereby changing the angle of the heat radiation. Furthermore, by regulating the thickness of the coating and the proportion of the filler component, the heat radiation angle can be accurately controlled, so that even when the coating is applied to the surface of the substrate perpendicular to the sky, the heat can be greatly exchanged to the outer space through the atmospheric window by changing the heat radiation angle, thereby significantly improving the cooling effect.

[0007] The present invention provides a composite coating, which comprises a radiation functional layer and a radiation and reflection dual functional layer, wherein the difference in refractive index between the radiation layer and the functional filler in the radiation and reflection dual functional layer is greater than or equal to 0.3.

[0008] Furthermore, the coating is arranged on the surface of the substrate, and sequentially comprises a substrate, a radiation and reflection dual-functional layer, and a radiation functional layer.

[0009] The refractive index of the radiation functional layer is different from that of the radiation and reflection dual functional layer, and the difference in refractive index is greater than or equal to 0.3. When thermal radiation passes through the interface of materials with different refractive indices, the direction of radiation will change. Furthermore, by adjusting the refractive index between different coatings, the direction of thermal radiation can be precisely controlled.

[0010] Furthermore, the thickness of the radiation functional layer is 150-300 μm; the thickness of the radiation and reflection dual functional layer is 150-300 μm.

[0011] The present invention provides a coating composition used in the composite coating, wherein the coating composition comprises an independent radiation functional layer coating and a radiation and reflection dual functional layer coating;

[0012] The radiation functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming substance, 10 to 50 parts of first radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer, and 1 to 5 parts of thickener;

[0013] The radiation and reflection dual-functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming material, 10 to 50 parts of reflective filler, 10 to 20 parts of second radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer and 1 to 5 parts of thickener.

[0014] Preferably, the radiation functional layer coating comprises, by weight, 3 to 5 parts of dispersant, 10 to 15 parts of water, 35 to 45 parts of film-forming substance, 40 to 50 parts of first radiation filler, 1 to 2 parts of defoamer, 1 to 2 parts of thickener, and 8 to 10 parts of wetting agent.

[0015] Preferably, the radiation and reflection dual-functional layer coating comprises, by weight, 3 to 5 parts of dispersant, 10 to 15 parts of water, 25 to 35 parts of film-forming substance, 30 to 50 parts of reflective filler, 15 to 20 parts of second radiation filler, 8 to 10 parts of wetting agent, 1 to 2 parts of defoaming agent, and 1 to 2 parts of thickener.

[0016] The first radiation filler and the second radiation filler are zero dielectric constant materials (ENZ, epsilon-near-zero). The zero dielectric constant filler can make the thermal radiation on the coating surface more directional (concentrated at a certain angle), which helps to improve radiation efficiency or reduce scattering losses in certain application scenarios.

[0017] Preferably, the first radiation filler is one or more of MgO, AlN, SiO2, Al2O3, and CaO;

[0018] The average particle size of the first radiation filler is 500-1800 nm or a mixture of fillers with different average particle sizes.

[0019] Further preferably, the first radiation filler is a mixture of three fillers with different average particle sizes; wherein the first average particle size in the mixture is 800-1000 nm, the second average particle size is 1100-1200 nm, and the third average particle size is 1300-1400 nm.

[0020] Furthermore, the first average particle size, the second average particle size, and the third average particle size are mixed in a mass ratio of 1-2:2-3:1-2.

[0021] Preferably, the second radiation filler is one or more of CaCO3, BaSO4, ZrO, Si3N4, and ZnS;

[0022] Preferably, the reflective filler is one or more of TiO2, Y2O3, ZnO, MgF2, CaF2, copper powder, silver powder, and aluminum powder;

[0023] Preferably, the average particle size of the second radiation filler is 500-800 nm; the average particle size of the reflective filler is 300-500 nm.

[0024] More preferably, the second radiation filler is CaCO3 with an average particle size of 500-800 nm.

[0025] More preferably, the reflective filler is TiO2 with an average particle size of 300 to 500 nm.

[0026] The dispersant used in the radiation functional layer coating is one or more of polyacrylate, polyacrylate, phosphate, polyacrylamide, polyethylene glycol monomethyl ether, polyethyleneimine, and sodium polystyrene sulfonate; the dispersant in the radiation and reflection dual-functional layer coating is one or more of polyvinyl alcohol, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, polycarboxylate, trimethoxysilane, and polymethacrylate.

[0027] In the radiation functional layer coating and the radiation and reflection dual-functional layer coating, the film-forming substance is one or more of acrylic resin, silicone resin, polyurethane resin, epoxy resin, and fluorocarbon resin; the wetting agent is a non-ionic surfactant; the non-ionic surfactant is one or more of polyether siloxane copolymer, polyether modified polydimethylsiloxane, perfluoropolyether, fatty alcohol polyoxyethylene ether, and ethoxylated fatty acid ester; the defoaming agent is one or more of tributyl phosphate, polyether modified silicone oil, polysiloxane, polydimethylsiloxane, polypropylene glycol, and polyethylene glycol; the thickener is one or more of latex acrylic polymer, polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyethylene copper.

[0028] The present invention provides a method for preparing a composite coating, comprising: mixing a dispersant, water, and a film-forming substance, and then mixing the mixture with a first radiation filler, a wetting agent, a defoaming agent, and a thickener to obtain a radiation functional coating;

[0029] The dispersant, water and film-forming substance are mixed evenly, and then mixed evenly with the second radiation filler, reflective filler, wetting agent, defoamer and thickener to obtain a radiation and reflective dual-function coating;

[0030] The radiation and reflection dual-functional coating is coated on the substrate and cured at room temperature, and then the radiation functional coating is coated and cured at room temperature.

[0031] Furthermore, the radiation functional coating is prepared by dispersing the dispersant, water, and film-forming material at high speed at room temperature for 10 to 15 minutes at a rotation speed of 800 to 1000 r / min to obtain a resin solution; then adding the first radiation filler, wetting agent, defoaming agent, and thickener to the resin solution and dispersing them at room temperature for 1 to 2 hours at a rotation speed of 1000 to 1200 r / min to obtain the radiation functional coating.

[0032] Preparation of radiation and reflection dual-function coating: disperse the dispersant, water and film-forming material at room temperature for 20 to 30 minutes, at a rotation speed of 1000 to 1200 r / min to obtain a resin solution; then add the second radiation filler, reflective filler, wetting agent, defoamer and thickener to the resin solution and disperse them at room temperature for 1 to 2 hours, at a rotation speed of 1600 to 1800 r / min to obtain the radiation and reflection dual-function coating.

[0033] Furthermore, the coating method is one or more of scraping, rolling, and spraying; the substrate is an object that is not directly facing the atmospheric window; and the room temperature curing is more than 3 hours.

[0034] The present invention provides a composite coating, which includes a first radiation functional layer and a reflection functional layer; wherein a second radiation functional layer is arranged between the first radiation functional layer and the reflection functional layer, wherein the difference in refractive index between functional fillers in the first radiation functional layer and the second radiation functional layer is greater than or equal to 0.3.

[0035] Furthermore, the composite coating includes a substrate, which in sequence includes a substrate, a reflective functional layer, a second radiation functional layer and a first radiation functional layer.

[0036] The refractive index of the first radiation functional layer is different from that of the second radiation functional layer, and the difference in refractive index is greater than or equal to 0.3. When thermal radiation passes through the interface of materials with different refractive indices, the direction of radiation changes. Furthermore, by adjusting the refractive index between different coatings, the direction of thermal radiation can be precisely controlled.

[0037] Furthermore, the thickness of the first radiation functional layer is 150-300 μm; the thickness of the reflection functional layer is 150-300 μm; and the thickness of the second radiation functional layer is 150-300 μm.

[0038] The present invention provides a coating composition used in the composite coating, wherein the coating composition comprises an independent first radiation functional layer coating, a second radiation functional layer coating and a reflection functional layer coating;

[0039] The first radiation functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming substance, 10 to 50 parts of first radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer, and 1 to 5 parts of thickener;

[0040] The second radiation functional layer coating comprises, by weight, 1 to 5 parts of a second dispersant, 5 to 15 parts of water, 20 to 50 parts of a film-forming substance, 10 to 50 parts of a second radiation filler, 1 to 12 parts of a wetting agent, 1 to 5 parts of a defoaming agent, and 1 to 5 parts of a thickener;

[0041] The reflective functional layer coating comprises the following components by weight: 5-10 parts of a fourth dispersant, 5-15 parts of water, 20-50 parts of a film-forming substance, 10-60 parts of a reflective filler, 1-12 parts of a wetting agent, 1-5 parts of a defoaming agent, and 1-5 parts of a thickener.

[0042] Preferably, the first radiation functional layer coating comprises the following components by weight: 3 to 5 parts of dispersant, 10 to 15 parts of water, 35 to 45 parts of film-forming substance, 40 to 50 parts of first radiation filler, 1 to 2 parts of defoamer, 1 to 2 parts of thickener, and 8 to 10 parts of wetting agent.

[0043] Preferably, the second radiation functional layer coating comprises, by weight, 3 to 5 parts of dispersant, 10 to 15 parts of water, 35 to 45 parts of film-forming substance, 30 to 50 parts of second radiation filler, 1 to 2 parts of defoamer, 1 to 2 parts of thickener, and 8 to 10 parts of wetting agent.

[0044] Preferably, the reflective functional layer coating comprises, by weight, 5 to 8 parts of dispersant, 5 to 10 parts of water, 35 to 45 parts of film-forming substance, 40 to 50 parts of reflective filler, 1 to 3 parts of wetting agent, 1 to 3 parts of defoaming agent, and 1 to 3 parts of thickener.

[0045] The first radiation filler and the second radiation filler are zero dielectric constant materials (ENZ, epsilon-near-zero). The zero dielectric constant filler can make the thermal radiation on the coating surface more directional (concentrated at a certain angle), which helps to improve radiation efficiency or reduce scattering losses in certain application scenarios.

[0046] Preferably, the first radiation filler is one or more of MgO, AlN, SiO2, Al2O3, and CaO.

[0047] The average particle size of the first radiation filler is 500-1800 nm or a mixture of fillers with different average particle sizes.

[0048] Furthermore, the first radiation filler is a mixture of three fillers with different average particle sizes; wherein the first average particle size in the mixture is 800-1000nm, the second average particle size is 1100-1200nm, and the third average particle size is 1300-1400nm, and the mass ratio of the first average particle size, the second average particle size, and the third average particle size is 1-2:2-3:1-2.

[0049] Furthermore, the first average particle size, the second average particle size, and the third average particle size are mixed in a mass ratio of 1:2:1.

[0050] Preferably, the second radiation filler is one or more of CaCO3, BaSO4, ZrO, Si3N4, and ZnS;

[0051] Preferably, the reflective filler is one or more of TiO2, Y2O3, ZnO, MgF2, CaF2, copper powder, silver powder, and aluminum powder;

[0052] Preferably, the average particle size of the second radiation filler is 500-800 nm; the average particle size of the reflective filler is 300-500 nm.

[0053] More preferably, the second radiation filler is CaCO3 with an average particle size of 500-800 nm.

[0054] More preferably, the reflective filler is TiO2 with an average particle size of 300 to 500 nm.

[0055] The dispersant used in the first and second radiation functional layer coatings is one or more of polyacrylates, polyacrylates, phosphates, polyacrylamides, polyethylene glycol monomethyl ether, polyethyleneimine, and sodium polystyrene sulfonate; the dispersant in the reflective functional layer coating is one or more of polyvinyl alcohol, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, polycarboxylates, trimethoxysilane, and polymethacrylate.

[0056] In the first radiation functional layer coating, the second radiation functional layer coating and the reflective functional layer coating, the film-forming substance is one or more of acrylic resin, silicone resin, polyurethane resin, epoxy resin and fluorocarbon resin; the wetting agent is a non-ionic surfactant, wherein the non-ionic surfactant is one or more of polyether siloxane copolymer, polyether modified polydimethylsiloxane, perfluoropolyether, fatty alcohol polyoxyethylene ether and ethoxylated fatty acid ester; the defoaming agent is one or more of tributyl phosphate, polyether modified silicone oil, polysiloxane, polydimethylsiloxane, polypropylene glycol and polyethylene glycol; the thickener is one or more of latex acrylic polymer, polyvinyl alcohol, polyacrylamide, polyethylene glycol and polyethylene copper.

[0057] The present invention provides a method for preparing the composite coating, comprising: mixing a dispersant, water, and a film-forming substance, and then mixing them with a first radiation filler, a wetting agent, a defoamer, and a thickener to obtain a first radiation functional coating;

[0058] Mixing the dispersant, water and film-forming substance, and then mixing with the second radiation filler, wetting agent, defoamer and thickener to obtain the second radiation functional coating;

[0059] Mix the dispersant, water and film-forming material, and then mix them with the reflective filler, wetting agent, defoamer and thickener to obtain a reflective functional coating;

[0060] The reflective functional coating is sequentially coated on the substrate, and after being cured at room temperature, the second radiation functional coating is coated, and cured at room temperature, and the first radiation functional coating is coated, and cured at room temperature.

[0061] Furthermore, the first radiation functional coating: disperse the dispersant, water, and film-forming material at room temperature for 10 to 15 minutes, at a rotation speed of 800 to 1000 r / min to obtain a resin solution; then add the first radiation filler, wetting agent, defoaming agent, and thickener to the resin solution and disperse them at room temperature for 1 to 2 hours, at a rotation speed of 1000 to 1200 r / min to obtain the first radiation functional coating.

[0062] Furthermore, the second radiation functional coating: disperse the dispersant, water, and film-forming material at room temperature for 10 to 15 minutes, and rotate at 800 to 1000 r / min to obtain a resin solution; then add the second radiation filler, wetting agent, defoaming agent, and thickener to the resin solution and disperse them at room temperature for 1 to 2 hours, and rotate at 1000 to 1200 r / min to obtain the second radiation functional coating.

[0063] Furthermore, the reflective functional coating is prepared by dispersing the dispersant, water and film-forming material at room temperature for 20 to 30 minutes at a rotation speed of 1000 to 1200 r / min to obtain a resin solution, and then adding the reflective filler, wetting agent, defoaming agent and thickener to the resin solution and dispersing them at room temperature for 2 to 3 hours at a rotation speed of 1800 to 2000 r / min to obtain the reflective functional coating.

[0064] Furthermore, the coating method is one or more of scraping, rolling, and spraying; the substrate is an object that is not directly facing the atmospheric window; and the room temperature curing is more than 3 hours.

[0065] The present invention provides applications of the composite coating and the coating composition in urban building exterior walls, energy storage cabinets, containers, mechanical equipment, and public transportation vehicles.

[0066] The present invention aims to fill the gap in the existing radiation cooling coating in terms of heat radiation direction control, so as to improve the overall radiation cooling effect. This method changes the radiation path through the change of the refractive index of different coatings and the special coating structure design, and significantly improves the radiation cooling performance of the coating by precisely controlling the angle of thermal radiation. Even if the coating is not applied to the surface of the substrate directly facing the atmospheric window, the heat can still be effectively radiated to outer space through the atmospheric window by changing the angle of thermal radiation, thereby ensuring excellent cooling effect in a variety of application environments.

[0067] Beneficial Effects

[0068] The present invention adopts a composite coating structure design to prepare a radiation cooling coating with controllable heat radiation direction and excellent cooling performance. Different functional fillers in the composite coating have different refractive indices. By adjusting the refractive index difference between the coatings, the path of heat radiation of the radiation cooling coating is changed, thereby improving the efficiency of radiation cooling. Furthermore, by regulating the thickness of the coating and the filler composition, the angle of heat radiation can be accurately controlled, so that even if the radiation cooling coating is not applied on the top surface of the substrate parallel to the sky atmospheric window, but on the side of the substrate, the heat can be radiated to outer space through the atmospheric window to the maximum extent, thereby ensuring that the coating can achieve excellent cooling performance in different application environments.

[0069] The directional radiation cooling coating of the present invention can achieve a reflectivity of 90% to 95%, an emissivity of 90% to 95%, a maximum temperature difference with the ambient temperature of up to 8.3°C, and has excellent radiation cooling capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram of the double-layer structure of the coating; 1 is the radiation function of the upper layer; 2 is the radiation and reflection dual-function layer;

[0071] Figure 2 Schematic diagram of the three-layer structure of the coating; 1 is the upper radiation function layer; 3 is the middle second radiation function layer; 4 is the reflection function layer;

[0072] Figure 3 The figure is a partial enlarged view of the coating structure of the substrate coated with the directional radiation cooling coating (the coating has a double-layer or triple-layer structure), 2 is the reflective and radiation functional coating, 5 is the directional radiation cooling coating coated on the surface of the substrate, 1 is the upper radiation coating, 3 is the middle radiation coating, and 4 is the lower reflective coating;

[0073] Figure 4 This is a diagram of the angle control mechanism of directional radiation cooling coating (double-layer structure), 6 is heat conduction, 2 is reflection and radiation functional coating, 1 is radiation coating, 7 is thermal radiation, and 8 is the atmospheric window (8-13μm);

[0074] Figure 5 This is a diagram of the angle control mechanism of directional radiation cooling coating (three-layer structure), 4 is the bottom reflective coating, 3 is the middle radiation coating, 1 is the upper radiation coating, 6 is heat conduction, 7 is thermal radiation, and 8 is the atmospheric window (8-13μm);

[0075] Figure 6 It is a test device for directional radiation cooling coating and its internal structure;

[0076] Figure 7 This is a schematic diagram of the performance test process of the radiant cooling coating in Example 1;

[0077] Figure 8 This is a schematic diagram of the performance test process of the directional radiation cooling coating of Example 7;

[0078] Fig. 9 Figure 1 is the radiation mechanism diagram of common radiation cooling coating, 15 and 16 are the surrounding objects, 19 is the thermal radiation of the common radiation cooling coating on the side of the substrate, 17 is the thermal radiation of the surrounding objects, 8 is the atmospheric window (8-13μm), 14 is the sun, 5 is the substrate, and 18 is the thermal radiation of the common radiation cooling coating on the top of the substrate;

[0079] Fig.10Figure 1 is a radiation mechanism diagram of directional radiation cooling coating, 15 and 16 are surrounding objects, 19 is the directional thermal radiation of directional radiation cooling coating on the side of substrate, 8 is the atmospheric window (8-13μm), 14 is the sun, 5 is substrate, and 18 is the thermal radiation of ordinary radiation cooling coating on the top of substrate. DETAILED DESCRIPTION

[0080] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0081] Example 1

[0082] This example provides a single-layer radiant cooling coating, and the preparation method thereof is as follows:

[0083] 1) First, 5 parts of dispersant (polyethylene glycol monomethyl ether), 10 parts of water and 25 parts of film-forming material (acrylic resin) are placed in a high-speed disperser and dispersed at room temperature for 10 minutes at a speed of 1000 r / min to obtain a dispersible resin solution that is easy to disperse reflective and radiative fillers.

[0084] 2) 40 parts of TiO2 with an average particle size of 300 nm, 10 parts of MgO with an average particle size of 800 nm, 8 parts of a wetting agent (polyether-modified polydimethylsiloxane), and 1 part of a defoaming agent (polypropylene glycol) are added to a dispersible resin solution and dispersed at high speed at room temperature for 2 hours at a rotation speed of 1600 r / min to obtain a single-layer radiant cooling coating.

[0085] 3) The prepared single-layer radiation cooling coating is coated on the surface of a metal substrate with a coating thickness of 300 μm and cured at room temperature for more than 8 hours.

[0086] Example 2

[0087] This example provides a double-layer directional radiation cooling coating, including an upper radiation coating and a lower radiation and reflection coating, wherein the preparation methods of the upper coating and the lower coating are as follows:

[0088] 1) Preparation of the upper coating: 5 parts of dispersant (polyethylene glycol monomethyl ether), 10 parts of water and 35 parts of film-forming material (acrylic resin) were placed in a high-speed disperser and dispersed at room temperature for 10 minutes at a speed of 800 r / min to obtain a dispersible resin solution that is easy to disperse the radiation filler. Then 40 parts of MgO with an average particle size of 800 nm, 8 parts of wetting agent (polyether-modified polydimethylsiloxane), 1 part of defoamer (polypropylene glycol) and 1 part of thickener (polyacrylamide) were added to the dispersible resin solution and dispersed at room temperature for 1 hour at a speed of 1000 r / min to obtain the upper coating.

[0089] 2) Preparation of lower coating: 5 parts of dispersant (sodium dodecylbenzene sulfonate), 10 parts of water and 25 parts of film-forming material (acrylic resin) were placed in a high-speed disperser and dispersed at room temperature for 10 minutes at a speed of 1000 r / min to obtain a dispersible resin solution that is easy to disperse reflective fillers. Then 40 parts of TiO2 with an average particle size of 300 nm, 10 parts of CaCO3 with an average particle size of 800 nm, 8 parts of wetting agent (polyether-modified polydimethylsiloxane), 1 part of defoamer (tributyl phosphate), and 1 part of thickener (polyacrylamide) were added to the dispersible resin solution and dispersed at room temperature for 2 hours at a speed of 1600 r / min to obtain the lower coating.

[0090] 3) applying the prepared lower coating to the surface of the metal substrate with a coating thickness of 150 μm, curing at room temperature for more than 8 hours to obtain a lower coating, and then applying the upper coating on the lower coating with a coating thickness of 150 μm, curing at room temperature for more than 8 hours.

[0091] Example 3

[0092] The difference between this example and Example 2 is that the radiation filler used in the upper coating is 40 parts of SiO2 with an average particle size of 800nm, and the rest of this example is the same as Example 2.

[0093] Example 4

[0094] The difference between this example and Example 2 is that the radiation filler used in the upper coating is 50 parts of MgO with an average particle size of 800nm. The rest of this example is the same as Example 2.

[0095] Example 5

[0096] The difference between this example and Example 2 is that the reflective filler and the radiation filler used in the lower coating are 30 parts of TiO2 with an average particle size of 300 nm and 20 parts of CaCO3 with an average particle size of 800 nm. The rest of this example is the same as Example 2.

[0097] Example 6

[0098] The difference between this example and Example 2 is that the coating thickness of the upper coating is 300 μm, and the rest of this example is the same as Example 2.

[0099] Example 7

[0100] Compared with Example 2, the difference between this example and Example 2 is that the coating has a three-layer structure, including an upper radiation coating, a middle radiation coating and a lower reflective coating, and the preparation method is as follows:

[0101] 1) Preparation of the upper coating: First, 5 parts of dispersant (polyethylene glycol monomethyl ether), 10 parts of water and 35 parts of film-forming material (acrylic resin) are placed in a high-speed disperser and dispersed at room temperature for 10 minutes at a speed of 800 r / min to obtain a resin solution that is easy to disperse reflective filler; then 40 parts of MgO with an average particle size of 800 nm, 8 parts of wetting agent (polyether modified polydimethylsiloxane), 1 part of defoaming agent (polypropylene glycol), and 1 part of thickener (polyacrylamide) are added to the dispersed resin solution and dispersed at room temperature for 1 hour at a speed of 1000 r / min to obtain the upper radiation coating.

[0102] 2) Preparation of middle layer coating: First, 5 parts of dispersant (polyethylene glycol monomethyl ether), 10 parts of water and 35 parts of film-forming substance (acrylic resin) are placed in a high-speed disperser and dispersed at room temperature for 10 minutes at a speed of 800 r / min to obtain a resin solution of reflective filler that is easy to disperse; then 40 parts of CaCO3 with an average particle size of 800 nm, 8 parts of wetting agent (polyether modified polydimethylsiloxane), 1 part of defoaming agent (polypropylene glycol), and 1 part of thickener (polyacrylamide) are added to the dispersible resin solution and dispersed at room temperature for 1 hour at a speed of 1000 r / min to obtain the middle layer coating.

[0103] 3) Preparation of the lower coating: First, place 5 parts of dispersant (sodium dodecylbenzene sulfonate), 5 parts of water and 35 parts of film-forming substance (film-forming substance) in a high-speed disperser and disperse them at high speed at room temperature for 30 minutes at a speed of 1000 r / min to obtain a resin solution that is easy to disperse reflective filler; then add 50 parts of TiO2 with an average particle size of 300 nm, 3 parts of wetting agent (polyether modified polydimethylsiloxane), 1 part of defoaming agent (polypropylene glycol), and 1 part of thickener (polyacrylamide) to the dispersed resin solution and disperse them at high speed at room temperature for 3 hours at a speed of 1800 r / min to obtain the lower coating.

[0104] 4) Apply the lower coating to the surface of the metal substrate with a coating thickness of 150 μm, cure at room temperature for more than 8 hours to obtain a lower coating, and then apply the middle coating to the cured lower coating with a coating thickness of 150 μm, cure at room temperature for more than 8 hours. Finally, apply the upper coating to the cured middle coating with a coating thickness of 150 μm, cure at room temperature for more than 8 hours.

[0105] Example 8

[0106] Compared with Example 2, the difference between this example is that the radiation fillers used in the upper coating are 10 parts of MgO with an average particle size of 800nm, 20 parts of MgO with an average particle size of 1100nm and 10 parts of MgO with an average particle size of 1300nm. The rest of this example is the same as Example 2.

[0107] Example 9

[0108] Compared with Example 2, this example differs in that the reflective filler and radiation filler used in the lower coating are 40 parts of Y2O3 with an average particle size of 300nm and 10 parts of CaCO3 with an average particle size of 800nm. The rest of this example is the same as Example 2.

[0109] Example 10

[0110] This example provides a radiation cooling test device and a directional radiation cooling coating cooling performance test method. The test device and test steps are as follows:

[0111] Among them, 13 is a thermocouple, 9 is a transparent film, 10 is a substrate coated with a radiation cooling paint, 11 is aluminum foil, and 12 is foam. The transparent film, aluminum foil, and foam inside the device are used to reduce the influence of heat convection, heat conduction, heat exchange, etc. of the external environment on the test results of the radiation cooling performance of the coating. The thermocouple is used to measure the internal temperature of the device. The metal substrate coated with the directional radiation cooling paint is placed at the opening above the device, and the opening is covered with a transparent film.

[0112] The specific testing process is as follows:

[0113] 1) The metal substrate coated with the radiation cooling coating prepared in Examples 1 and 7 is placed at the upper opening of the testing device.

[0114] 2) The test device was erected and placed outdoors on a sunny day in summer. A cement board was placed in front of the opening of the device to simulate the environmental building. The internal temperature of the device was recorded when the cement board was placed at different positions (1m, 3m, 5m) and after 1 hour of sunlight exposure.

[0115] Experimental tests show that when the cement board is 1m away from the device, after 1h of sunlight exposure, the temperature difference between the inside and outside of the device is 2.6℃; when the cement board is 3m away from the device, the temperature difference between the inside and outside of the device is 2.8℃; when the cement board is 5m away from the device, the temperature difference between the inside and outside of the device is 3.1℃; this shows that when the cement board is 1m, 3m, and 5m away from the test device, the thermal radiation of the single-layer radiation cooling coating is blocked by the cement board and does not radiate to outer space through the atmospheric window. Therefore, the single-layer radiation cooling coating does not have the ability of directional thermal radiation and the cooling effect is average.

[0116] The experimental test shows that when the cement board is 1m away from the device, after 1h of sunlight exposure, the temperature difference between the inside and outside of the device is 4.7℃; when the cement board is 3m away from the device, the temperature difference between the inside and outside of the device is 6.4℃; when the cement board is 5m away from the device, the temperature difference between the inside and outside of the device is 8.3℃; this shows that when the cement board is 1m and 3m away from the test device, part of the heat radiation of the directional radiation cooling coating is blocked, and the coating radiates heat to the cement board instead of the atmospheric window, resulting in poor cooling performance of the coating. When the cement board is 5m away from the test device, the directional radiation cooling coating can effectively radiate heat to outer space through the atmospheric window.

[0117] The reflectivity and emissivity of the directional radiation cooling coatings obtained in Examples 1 to 9 were tested, wherein the test methods for the reflectivity and emissivity were respectively based on GB / T 2680-2021 and GB / T 30127-2013.

[0118] The radiation cooling performance of the coatings in Examples 1 to 9 was tested using the radiation cooling test device, and the test process was as follows:

[0119] 1) Place the metal substrate coated with the radiant cooling coating at the upper opening of the test device. Stand the test device upright and place it outdoors on a sunny day in summer.

[0120] 2) Place a cement board in front of the opening of the device to simulate the environmental building. Place the cement board 5m away from the test device and record the temperature difference between the inside and outside of the device after 1 hour of sunlight exposure.

[0121] The test results are shown in Table 1.

[0122]

[0123]

[0124] The experimental results are analyzed as follows: Comparing Example 1 with Example 2, Example 2 has a better cooling effect, which indicates that the single-layer coating cannot effectively adjust the heat radiation angle. The coating radiates heat to the cement board instead of the atmospheric window, causing the heat to be reflected back by the cement board, and the refrigeration performance deteriorates. Comparing Example 3 with Example 2, it can be found that the coating emissivity of Example 3 is low and the refrigeration performance is poor, indicating that the emissivity of MgO in the radiation filler is higher, so that its refrigeration performance is better. Comparing Example 4 and Example 5 with Example 2, Examples 4 and 5 show better refrigeration effect, indicating that the increase in the content of radiation functional fillers in the coating can further radiate more heat through the atmospheric window to outer space, and the change in the radiation filler also plays a certain role in regulating the angle of heat radiation, and the refrigeration performance is further improved. Comparing Example 6 with Example 2, Example 6 shows a better refrigeration effect, indicating that the increase in coating thickness can effectively adjust the heat radiation angle, so that more heat is radiated to the sky atmospheric window instead of the surrounding environment, thereby improving the refrigeration performance. Comparing Example 7 with Example 2, the results show that the thermal radiation angle of the three-layer coating changes more significantly, so that more heat is radiated to the sky atmospheric window, thereby significantly improving the cooling effect. Comparing Example 8 with Example 2, the coating with a mixture of fillers of different particle sizes has better cooling, indicating that the cooling effect of the coating is improved by mixing functional fillers of different particle sizes. Comparing Example 9 with Example 2, it is found that when the functional filler is replaced by TiO2 (refractive index 2.5-2.7) with Y2O3 (refractive index 1.8-1.9), since the refractive index of Y2O2 is similar to that of MgO (1.7-1.8), the difference in refractive index between the two is less than 0.3, resulting in a decrease in the refractive index difference between the top radiation layer and the lower coating, thereby significantly reducing the thermal radiation angle adjustment effect, and ultimately greatly reducing the cooling effect.

Claims

1. A composite coating, characterized in that: The composite coating comprises a radiation functional layer and a radiation and reflection dual functional layer.

2. The composite coating according to claim 1, characterized in that: The refractive index of the radiation functional layer is different from the refractive index of the radiation and reflection dual functional layer, and the refractive index difference is greater than or equal to 0.

3.

3. A coating composition used in the composite coating according to claim 1, characterized in that: The coating composition includes an independent radiation functional layer coating, a radiation and reflection dual functional layer coating; The radiation functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming substance, 10 to 50 parts of first radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer, and 1 to 5 parts of thickener; The radiation and reflection dual-functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming material, 10 to 50 parts of reflective filler, 10 to 20 parts of second radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer and 1 to 5 parts of thickener.

4. A method for preparing a composite coating, comprising: Mixing the dispersant, water and film-forming material, and then mixing with the first radiation filler, wetting agent, defoamer and thickener to obtain a radiation functional coating; The dispersant, water and film-forming substance are mixed evenly, and then mixed evenly with the second radiation filler, reflective filler, wetting agent, defoamer and thickener to obtain a radiation and reflective dual-function coating; The radiation and reflection dual-functional coating is coated on the substrate and cured at room temperature, and then the radiation functional coating is coated and cured at room temperature.

5. A composite coating, characterized in that: The composite coating comprises a first radiation functional layer and a reflection functional layer, wherein a second radiation functional layer is arranged between the first radiation functional layer and the reflection functional layer.

6. The composite coating according to claim 5, characterized in that: The refractive index of the first radiation functional layer is different from the refractive index of the second radiation functional layer, and the difference between the refractive indices is greater than 0.

3.

7. A coating composition used in the composite coating according to claim 5, characterized in that: The coating composition comprises an independent first radiation functional layer coating, a second radiation functional layer coating and a reflection functional layer coating; The first radiation functional layer coating comprises, by weight, 1 to 5 parts of dispersant, 5 to 15 parts of water, 20 to 50 parts of film-forming substance, 10 to 50 parts of first radiation filler, 1 to 12 parts of wetting agent, 1 to 5 parts of defoamer, and 1 to 5 parts of thickener; The second radiation functional layer coating comprises, by weight, 1 to 5 parts of a second dispersant, 5 to 15 parts of water, 20 to 50 parts of a film-forming substance, 10 to 50 parts of a second radiation filler, 1 to 12 parts of a wetting agent, 1 to 5 parts of a defoaming agent, and 1 to 5 parts of a thickener; The reflective functional layer coating comprises the following components by weight: 5-10 parts of a fourth dispersant, 5-15 parts of water, 20-50 parts of a film-forming substance, 10-60 parts of a reflective filler, 1-12 parts of a wetting agent, 1-5 parts of a defoaming agent, and 1-5 parts of a thickener.

8. The coating composition according to claim 3 or 7, characterized in that: The first radiation filler is one or more of MgO, AlN, SiO2, Al2O3, CaO; the second radiation filler is one or more of CaCO3, BaSO4, ZrO, Si3N4, ZnS; the reflective filler is one or more of TiO2, Y2O3, ZnO, MgF2, CaF2, copper powder, silver powder, aluminum powder; The average particle size of the second radiation filler is 500-800 nm; the average particle size of the reflective filler is 300-500 nm.

9. A method for preparing the composite coating according to claim 5, comprising: Mixing the dispersant, water and film-forming substance, and then mixing with the first radiation filler, wetting agent, defoamer and thickener to obtain the first radiation functional coating; Mixing the dispersant, water and film-forming substance, and then mixing with the second radiation filler, wetting agent, defoamer and thickener to obtain the second radiation functional coating; Mix the dispersant, water and film-forming material, and then mix them with the reflective filler, wetting agent, defoamer and thickener to obtain a reflective functional coating; The reflective functional coating is sequentially coated on the substrate, and after being cured at room temperature, the second radiation functional coating is coated, and cured at room temperature, and the first radiation functional coating is coated, and cured at room temperature.

10. The preparation method according to claim 4 or 9, characterized in that: The coating method is one or more of scraping, rolling and spraying; and the room temperature curing is more than 3 hours.

11. Use of the composite coating according to claim 1 or 5, or the coating composition according to claim 3 or 7 in urban building exterior walls, energy storage cabinets, containers, mechanical equipment, and public transportation.

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