A double-layer radiation refrigeration coating, a preparation method and application thereof

Abstract

The application belongs to the technical field of energy-saving coatings, and particularly relates to a double-layer radiation refrigeration coating as well as a preparation method and application thereof. The double-layer radiation refrigeration coating comprises an upper protective coating and a lower reflective coating. The upper protective coating comprises the following raw materials in terms of mass fraction: fluorine-containing polymer 5-100 parts, organic solvent 30-500 parts, and deionized water 5-160 parts. The lower reflective coating comprises the following raw materials in terms of mass fraction: inorganic pigment powder 10-200 parts, water-based resin 5-300 parts, and organic dispersing solvent 30-400 parts.

Description

Technical Field

[0001] This invention belongs to the field of energy-saving coating technology, specifically relating to a double-layer radiative cooling coating, its preparation method, and its application. Background Technology

[0002] Global warming has increased the demand for cooling across all industries. However, traditional cooling technologies (such as air conditioning) consume approximately 15% of the world's electricity while emitting greenhouse gases, exacerbating the greenhouse effect. Radiative cooling is a zero-energy sub-environment (below ambient temperature) cooling technology. It continuously transfers heat through the "atmospheric window" (wavelength 8-13 micrometers) of thermal radiation into outer space (3K), a natural cold bath, thus achieving zero-energy sub-environment cooling.

[0003] However, many radiation cooling coatings currently lack resistance to extreme weather, especially to continuous heavy rainfall. In fact, in areas with frequent precipitation, rainwater erosion severely hinders the long-term, efficient functioning of radiation cooling coatings.

[0004] Therefore, developing a radiation cooling coating with rainwater erosion resistance can fill a major gap in the field of weather-resistant radiation cooling coatings. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a double-layer radiative cooling coating. The radiative cooling coating formed using this coating achieves an average reflectivity of 96% in the solar light band and an average reflectivity of 91% in the 8-13 micrometer range. Its temperature at noon is 6-7°C lower than that of ambient air, and its cooling effect is superior to commercially available white coatings.

[0006] A double-layer radiation cooling coating according to an embodiment of the present invention includes: an upper protective coating and a lower reflective coating;

[0007] The upper protective coating comprises the following raw materials by weight: 5-100 parts of fluoropolymer, 30-500 parts of organic solvent, and 5-160 parts of deionized water.

[0008] The lower reflective coating comprises the following raw materials by weight: 10-200 parts of inorganic pigment powder, 5-300 parts of water-based resin, and 30-400 parts of organic dispersion solvent.

[0009] The advantages and technical effects of the double-layer radiation cooling coating of this invention are as follows: 1. In this invention, the upper protective coating formed by the fluoropolymer, organic solvent and deionized water can separate phases during the film formation process to form a protective coating with a porous structure, which has good resistance to rainwater corrosion, erosion and immersion, and can withstand continuous heavy rain for at least 220 days; 2. In this invention, the water-based resin and pigments used make the coating have good film-forming properties, strong adhesion, and resistance to aging and light exposure; 3. In this invention, the raw materials used are all widely industrialized, inexpensive and easy to purchase, and the coating can obtain an easily applied and tightly bonded radiation cooling coating.

[0010] In some embodiments, the fluoropolymer includes at least one of polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyperfluoroethylene propylene, polyvinyl fluoride, perfluoropropylene, fluorinated polyimide, trichlorotrifluoroethylene-vinyl ether copolymer, or polytetrafluoroethylene powder.

[0011] And / or, the organic solvent includes at least one of isopropanol, acetone, ethanol, cyclohexanone, toluene, dichloromethane, diethyl ether, ethyl acetate, carbon tetrachloride, propylene carbonate, or cyclohexane.

[0012] In some embodiments, the inorganic pigment powder includes at least one of silicon oxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide.

[0013] And / or, the inorganic pigment powder is formed by mixing inorganic pigment powders with a particle size of 10-900 nm and 1-10 μm in a mass ratio of 1-9:9-1.

[0014] In some embodiments, the waterborne resin includes at least one of waterborne acrylic resin, styrene-acrylic resin, melamine resin, silicone-acrylic resin, polyurethane resin, alkyd resin, phenolic resin, amino resin, vinyl acetate-acrylic resin, pure acrylic resin, or epoxy resin.

[0015] In some embodiments, the organic dispersion solvent includes at least one selected from ethanol, acetone, cyclohexanone, ethyl acetate, ethyl butyrate, toluene, styrene, ethylene glycol ether, triethanolamine, or dichloromethane.

[0016] This invention provides a method for preparing a double-layer radiation coating, comprising the following steps:

[0017] (1) Inorganic pigment powder, aqueous resin and organic dispersion solvent are mixed to form a lower reflective coating;

[0018] (2) After mixing the fluoropolymer with the organic solvent, deionized water is added to form the upper protective coating.

[0019] In some embodiments, in step (1) and / or step (2), the mixing method includes at least one of mechanical stirring, magnetic stirring, or ultrasound.

[0020] The present invention also provides the application of the above-described double-layer radiation cooling coating or the double-layer radiation cooling coating prepared by the above-described preparation method, including: coating a lower reflective coating onto a substrate and drying it to form a lower reflective coating layer, and then coating an upper protective coating onto the lower reflective coating layer to form an upper protective coating layer.

[0021] In some embodiments, the coating method includes at least one of drip coating, spin coating, and spray coating.

[0022] In some embodiments, the thickness of the upper protective coating is not less than 30 micrometers, and the thickness of the lower reflective coating is not less than 100 micrometers. Attached Figure Description

[0023] Figure 1 This is a microscopic morphology diagram of the double-layer radiation-cooling coating with rainwater erosion resistance prepared in Example 1;

[0024] Figure 2 This is a spectral response curve of the double-layer radiation-cooled coating with rainwater erosion resistance prepared in Example 1;

[0025] Figure 3 This is a diagram showing the cooling effect of the double-layer radiative cooling coating with rainwater erosion resistance prepared in Example 1. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] A double-layer radiation cooling coating according to an embodiment of the present invention includes: an upper protective coating and a lower reflective coating;

[0028] The upper protective coating comprises the following raw materials by weight: 5-100 parts of fluoropolymer, 30-500 parts of organic solvent, and 5-160 parts of deionized water.

[0029] The lower reflective coating comprises the following raw materials by weight: 10-200 parts of inorganic pigment powder, 5-300 parts of water-based resin, and 30-400 parts of organic dispersion solvent.

[0030] In the double-layer radiative cooling coating of this invention, the upper protective coating formed by the fluoropolymer, organic solvent and deionized water can separate during the film-forming process to form a protective coating with a porous structure, which has good resistance to rainwater corrosion, erosion and immersion, and can withstand continuous rainstorms for at least 220 days; in this invention, the water-based resin and pigments used make the coating have good film-forming properties, strong adhesion, and resistance to aging and light exposure; in this invention, the raw materials used are all widely industrialized, inexpensive and easy to purchase, and the coating can obtain an easily applied and tightly bonded radiative cooling coating.

[0031] In some embodiments, preferably, the fluoropolymer includes at least one of polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyperfluoroethylene propylene, polyvinyl fluoride, perfluoropropylene, fluorinated polyimide, trichlorotrifluoroethylene-vinyl ether copolymer, or polytetrafluoroethylene powder.

[0032] In this embodiment of the invention, the preferred fluoropolymer can be constructed into a porous structure by phase separation and has very good hydrophobic properties, thus achieving a very good protective effect.

[0033] In some embodiments, preferably, the organic solvent includes at least one selected from isopropanol, acetone, ethanol, cyclohexanone, toluene, dichloromethane, diethyl ether, ethyl acetate, carbon tetrachloride, propylene carbonate, or cyclohexane. In these embodiments, no particular limitation is required on the organic solvent, as long as it can dissolve the fluoropolymer.

[0034] In some embodiments, preferably, the inorganic pigment powder includes at least one of silicon oxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide.

[0035] In this embodiment of the invention, an inorganic pigment powder is preferred. This type of inorganic pigment has a good refractive index in the solar radiation band and is suitable for forming high reflectivity coatings.

[0036] In some embodiments, preferably, the inorganic pigment powder is formed by mixing inorganic pigment powders with a particle size of 10-900 nm and a particle size of 1-10 μm in a mass ratio of 1-9:9-1, for example, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, etc.

[0037] In this embodiment of the invention, the use of fillers with mixed particle sizes can provide Mie scattering over a wide range of solar wavelengths compared to fillers with single particle sizes, thereby achieving higher reflectivity.

[0038] In some embodiments, preferably, the waterborne resin includes at least one of waterborne acrylic resin, styrene-acrylic resin, melamine resin, silicone-acrylic resin, polyurethane resin, alkyd resin, phenolic resin, amino resin, vinyl acetate-acrylic resin, pure acrylic resin, or epoxy resin.

[0039] In some embodiments, preferably, the organic dispersion solvent includes at least one selected from ethanol, acetone, cyclohexanone, ethyl acetate, ethyl butyrate, toluene, styrene, ethylene glycol ether, triethanolamine, or dichloromethane.

[0040] This invention provides a method for preparing a double-layer radiation coating, comprising the following steps:

[0041] (1) Inorganic pigment powder, aqueous resin and organic dispersion solvent are mixed to form a lower reflective coating;

[0042] (2) After mixing the fluoropolymer with the organic solvent, deionized water is added to form the upper protective coating.

[0043] In some embodiments, preferably, in step (1) and / or step (2), the mixing method includes at least one of mechanical stirring, magnetic stirring, or ultrasound.

[0044] The present invention also provides the application of the above-described double-layer radiation cooling coating or the double-layer radiation cooling coating prepared by the above-described preparation method, including: coating a lower reflective coating onto a substrate and drying it to form a lower reflective coating layer, and then coating an upper protective coating onto the lower reflective coating layer to form an upper protective coating layer.

[0045] In some embodiments, preferably, the coating method includes at least one of drip coating, spin coating, or spray coating.

[0046] In some embodiments, preferably, the thickness of the upper protective coating is not less than 30 micrometers, and the thickness of the lower reflective coating is not less than 100 micrometers.

[0047] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0048] Example 1

[0049] (1) First, zinc oxide powder with a particle size of 10-900nm and zinc oxide powder with a particle size of 1-10μm are mixed in a mass ratio of 1:1. The mixed zinc oxide powder, silicone propylene resin and acetone are mechanically stirred and mixed evenly in a mass ratio of 25 parts, 60 parts and 80 parts to form a lower reflective coating.

[0050] (2) Mix polyvinylidene fluoride-hexafluoropropylene copolymer and ethyl acetate in a mass ratio of 5 parts and 80 parts respectively, stir evenly, and then add 10 parts of deionized water to form an upper protective coating.

[0051] (3) Apply the lower reflective coating evenly to the substrate using a scraping method to form a lower reflective coating with a thickness of about 100 micrometers; apply the upper protective coating to the lower reflective coating and dry it to form an upper rain protection coating with a thickness of 50 micrometers.

[0052] The double-layer radiation-cooled coating prepared in this embodiment has a measured solar reflectance of 0.96 and an average emissivity of 0.91 for the atmospheric window of 8-13 micrometers. The surface temperature tested on a sunny day is 3°C lower than that of commercial white paint. After 20 hours of rain washing, the surface remains intact, without blistering, peeling, or cracking, equivalent to withstanding approximately 220 rainstorms.

[0053] The double-layer radiation-cooling coating prepared in this embodiment was characterized by SEM, and the results are as follows: Figure 1 As shown, where Figure 1 Image a shows the microstructure of the lower coating layer, which shows a uniform mixture of nano-sized particles and micron-sized ions; image b shows the microstructure of the upper rain protection coating layer, which shows a porous structure; image c shows a cross-sectional microscopic image of the coating layer, which shows that the upper and lower coating layers are tightly bonded together.

[0054] Example 2

[0055] (1) First, mix titanium dioxide powder with a particle size of 10-900nm and a particle size of 1-10μm at a mass ratio of 7:3. Then, mechanically stir and uniformly mix the mixed titanium dioxide powder, styrene-acrylic resin and ethanol at mass ratios of 25 parts, 70 parts and 150 parts to form a lower reflective coating.

[0056] (2) Mix polyvinylidene fluoride and cyclohexane in a mass ratio of 5 parts and 100 parts respectively, stir evenly, and then add 10 parts of deionized water to form an upper rain protection coating.

[0057] (3) Apply the radiation cooling coating evenly to the substrate using a scraping method to form a lower reflective coating with a thickness of 100 micrometers; apply the upper rain protection coating on the lower reflective coating and dry it to form an upper rain protection coating with a thickness of 50 micrometers.

[0058] Example 3

[0059] (1) First, calcium oxide powder with a particle size of 10-900nm and a particle size of 1-10μm are mixed at a mass ratio of 6:4. The mixed calcium oxide powder, epoxy resin and toluene are mechanically stirred and uniformly mixed at a mass ratio of 25 parts, 25 parts and 70 parts to form a lower reflective coating.

[0060] (2) Mix polytetrafluoroethylene and acetone in a mass ratio of 5 parts and 80 parts respectively, stir evenly, and then add 10 parts of deionized water to form an upper layer of rain protection coating.

[0061] (3) Apply the radiation cooling coating evenly to the substrate using a scraping method to form a lower reflective coating with a thickness of 100 micrometers; apply the upper rain protection coating on the lower reflective coating and dry it to form an upper rain protection coating with a thickness of 50 micrometers.

[0062] Example 4

[0063] (1) First, mix alumina powder with a particle size of 10-900nm and a particle size of 1-10μm at a mass ratio of 1:1. Then, mechanically stir and uniformly mix the mixed alumina powder, acrylic resin and ethanol at mass ratios of 40 parts, 40 parts and 50 parts to form a lower reflective coating.

[0064] (2) Mix polyvinylidene fluoride-hexafluoropropylene copolymer and acetone in a mass ratio of 10 parts and 160 parts respectively, stir evenly, and then add 5 parts of deionized water to form an upper protective coating.

[0065] (3) Apply the lower reflective coating evenly to the substrate using a scraping method to form a lower reflective coating with a thickness of about 100 micrometers; apply the upper protective coating to the lower reflective coating and dry it to form an upper rain protection coating with a thickness of 50 micrometers.

[0066] Example 5

[0067] The preparation method of this embodiment is the same as that of Example 1, except that in step (1), the mass ratio of zinc oxide powder with a particle size of 10-900 nm and a particle size of 1-10 μm is 7:3.

[0068] Example 6

[0069] The preparation method of this embodiment is the same as that of Example 1, except that in step (1), the mass ratio of zinc oxide powder with a particle size of 10-900 nm and a particle size of 1-10 μm is 3:7.

[0070] Example 7

[0071] The preparation method of this embodiment is the same as that of Example 1, except that the particle size of the zinc oxide powder used in step (1) is 10-900 nm.

[0072] Example 8

[0073] The preparation method of this embodiment is the same as that of Example 1, except that the particle size of the zinc oxide powder used in step (1) is 1 to 10 μm.

[0074] Comparative Example 1

[0075] The preparation method of this comparative example is the same as that of Example 1, except that the amount of zinc oxide powder used in step (1) is 10 parts.

[0076] Comparative Example 2

[0077] The preparation method of this comparative example is the same as that of Example 1, except that the upper rainwater protective coating is not applied in step (2).

[0078] Comparative Example 3

[0079] The preparation method of this comparative example is the same as that of Example 1, except that: in step (3), after the lower reflective coating and the upper protective coating are mixed evenly, they are applied to the substrate to form a coating with a thickness of 150 μm.

[0080] The coatings obtained in Examples 1-8 and Comparative Examples 1-3 were subjected to performance tests, and the results are shown in Table 1. The test methods for each performance property are as follows:

[0081] (1) Solar reflectance: Solar reflectance was measured according to JIS K 5675 standard using an ultraviolet spectrophotometer (Hitachi UH5700) with an integrating sphere attachment. This method calculates solar reflectance by measuring the reflectance spectrum of the coating sample, multiplying it by the weight factor of the transmission spectrum, and then weighting and averaging the results.

[0082] (2) The average emissivity of the atmospheric window (8-13 micrometers) is calculated using a Fourier transform infrared spectrometer. The inner diameter of the integrating sphere should not be less than 60 mm, and the inner wall should be made of a highly reflective material. The standard plate is a gold mirror used for baseline calibration. The atmospheric window emissivity of the sample can be calculated by performing baseline scanning and sample spectral reflectance scanning within a specified wavelength range.

[0083] (3) Rainwater rinsing time: The time when the reflection of the sample changes significantly after being continuously rinsed under a faucet with a uniform flow rate.

[0084] (4) Spectral images: obtained by ultraviolet spectrophotometer and Fourier transform infrared spectrometer, wherein the optical image of Example 1 is as follows. Figure 2 As shown, from Figure 2As can be seen from this, the double-layer radiation cooling coating prepared in this embodiment has a high reflectivity in the solar band and a high emissivity in the mid- and far-infrared band.

[0085] (5) Cooling effect: This was determined by testing with a designed device composed of insulating styrene foam, aluminum foil, and polyethylene. Thermocouples were placed tightly against the sample inside the device, and their temperature was recorded under strong sunlight. The temperature change in Example 1 is shown below. Figure 3 As shown, from Figure 3 As can be seen, the cooling effect of Example 1 is 3°C lower than that of ordinary white paint and 7°C lower than that of the environment.

[0086] Table 1

[0087]

[0088] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0089] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A double-layer radiative cooling coating, characterized in that, Includes an upper protective coating and a lower reflective coating; The upper protective coating comprises the following raw materials by weight: 5-100 parts of fluoropolymer, 30-500 parts of organic solvent, and 5-160 parts of deionized water; the fluoropolymer includes at least one of polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, polyperfluoroethylene propylene, polyvinyl fluoride, fluorinated polyimide, trifluorochloroethylene-vinyl ether copolymer, or polytetrafluoroethylene powder; the organic solvent includes at least one of isopropanol, acetone, cyclohexanone, toluene, dichloromethane, diethyl ether, ethyl acetate, carbon tetrachloride, or cyclohexane; the upper protective coating formed by the fluoropolymer, organic solvent, and deionized water can undergo phase separation during film formation to form a protective coating with a porous structure. The lower reflective coating comprises the following raw materials by weight: 10-200 parts of inorganic pigment powder, 5-300 parts of water-based resin, and 30-400 parts of organic dispersion solvent.

2. The double-layer radiative cooling coating according to claim 1, characterized in that, The inorganic pigment powder includes at least one of silicon dioxide, calcium oxide, titanium dioxide, barium sulfate, calcium carbonate, zinc oxide, magnesium oxide, lithopone, zirconium oxide, yttrium oxide, or aluminum oxide. And / or, the inorganic pigment powder is formed by mixing inorganic pigment powders with a particle size of 10~900nm and 1~10 μm in a mass ratio of 1~9:9~1.

3. The double-layer radiative cooling coating according to claim 1, characterized in that, The waterborne resin includes at least one of waterborne acrylic resin, styrene-acrylic resin, melamine resin, silicone-acrylic resin, polyurethane resin, alkyd resin, phenolic resin, amino resin, vinyl acetate-acrylic resin, pure acrylic resin, or epoxy resin.

4. The double-layer radiative cooling coating according to claim 1, characterized in that, The organic dispersion solvent includes at least one of ethanol, acetone, cyclohexanone, ethyl acetate, ethyl butyrate, toluene, styrene, ethylene glycol ether, triethanolamine, or dichloromethane.

5. The method for preparing the double-layer radiation-cooling coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Inorganic pigment powder, water-based resin and organic dispersion solvent are mixed to form a lower reflective coating; (2) After mixing the fluoropolymer with the organic solvent, deionized water is added to form the upper protective coating.

6. The method for preparing the double-layer radiation-cooling coating according to claim 5, characterized in that, In step (1) and / or step (2), the mixing method includes at least one of mechanical stirring, magnetic stirring, or ultrasound.

7. The application of the double-layer radiation-cooling coating according to any one of claims 1 to 4 or the double-layer radiation-cooling coating prepared by the preparation method according to claim 5 or 6, characterized in that, include: A lower reflective coating is applied to a substrate and dried to form a lower reflective coating layer. Then, an upper protective coating is applied to the lower reflective coating layer to form an upper protective coating layer.

8. The application according to claim 7, characterized in that, The coating method includes at least one of drip coating, spin coating, or spray coating.

9. The application according to claim 7, characterized in that, The thickness of the upper protective coating is not less than 30 micrometers, and the thickness of the lower reflective coating is not less than 100 micrometers.

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