Radiation refrigeration coating and preparation method thereof

Abstract

The invention discloses a radiation refrigeration coating and a preparation method thereof, and belongs to the technical field of coating materials. The radiation refrigeration coating comprises a first reflecting layer and a second reflecting layer arranged on the first reflecting layer, the coating raw materials of the first reflecting layer comprise resin, aluminum powder, a first dispersing agent and a first solvent; the coating raw materials of the second reflecting layer comprise fluorosilicone rubber resin, high-molecular polymer powder, a second solvent and a second dispersing agent. In addition, the invention also provides a preparation method of the radiation refrigeration coating, which comprises the following steps of: spraying or rolling the first reflecting layer coating on the surface of the base material; and after drying, spraying or rolling a second reflecting layer coating on the surface of the first reflecting layer to obtain the radiation refrigeration coating. The radiation refrigeration coating has middle and far infrared spectrum emission selectivity and high sunlight reflectivity, and further has excellent cooling performance.

Description

Technical Field

[0001] The present invention relates to the technical field of coating materials, and in particular to a radiation cooling coating and a preparation method thereof. Background Art

[0002] The cooling capacity of radiation cooling materials comes from the fact that they can emit heat through the atmospheric transparent window to the cold outer space with a temperature of only ~3K, and at the same time they can reflect a large amount of solar radiation heat (i.e., they have high solar emissivity). In recent years, various high-performance radiation cooling materials based on thermal emitters have been developed one after another, mainly used in building energy conservation and personal thermal management. According to the spectral response characteristics of such materials in the mid-infrared band, radiation cooling materials can be mainly divided into two categories: non-selective emitters and selective emitters. Non-selective emitters refer to radiation cooling materials that have high emissivity in the entire mid-infrared band (2.5-25μm). Selective emitters usually refer to radiation cooling materials that only have high selective emissivity in the 8–13μm atmospheric transparent window band and high reflectivity in the rest of the mid-infrared band. Selective emitter radiation cooling materials usually have better cooling performance. At present, radiation cooling coatings usually use metal oxides and non-metallic inorganic powders as reflective media. The indifferent absorption of such materials in the mid- and far-infrared wavelengths leads to high wide-band mid- and far-infrared emissivity and lack of emission selectivity. How to achieve the emission selectivity of materials is a problem that the existing technology needs to solve.

[0003] In addition, the surface of carbon steel substrates, such as color steel roofs, chemical storage tanks, pipelines, equipment, etc., rusts due to the chemical reaction between the iron substrate and water and oxygen in the air. Applying paint on such surfaces usually requires grinding, polishing and rust removal. At present, sandblasting is mostly used to remove foreign matter such as oil and corrosion products on the surface of steel structures. This method not only increases costs, but also the dust and noise during the sandblasting process and the volatilization of harmful substances during the coating process seriously endanger the health of construction workers. In addition, it is difficult to completely clean the working surface of some complex structures. How to achieve refrigeration while preventing corrosion is also a technical problem that needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide a radiation cooling coating and a preparation method thereof, and solve the technical problem of how to achieve the emission selectivity of materials in the prior art.

[0005] In order to achieve the above technical objectives, the technical solution of the present invention provides a radiation cooling coating, including: a first reflective layer and a second reflective layer arranged on the first reflective layer; the coating raw materials of the first reflective layer include resin, aluminum powder, a first dispersant and a first solvent; the coating raw materials of the second reflective layer include fluorosilicone rubber resin, high molecular polymer powder, a second solvent and a second dispersant.

[0006] In any embodiment, the thickness of the first reflective layer is 10-30 μm, and the thickness of the second reflective layer is 60-120 μm.

[0007] In any embodiment, the raw materials of the first reflective layer, calculated by mass percentage, include 20-40% resin, 30-50% aluminum powder, 0.5-2% first dispersant, and the balance is the first solvent.

[0008] In any embodiment, the raw material of the second reflective layer, calculated by mass percentage, includes 20-40% fluorosilicone rubber resin, 10-40% high molecular polymer powder, 0.5-2% second dispersant, and the balance is a second solvent.

[0009] In any embodiment, the resin in the first reflective layer includes one or more of epoxy resin, acrylic resin, fluorocarbon resin and polyurethane resin; and / or, the first solvent is one or more of xylene, DMF, PMA, ethyl acetate, butanone, propylene glycol methyl ether and dibasic acid ester; and / or, the first dispersant is one or more of BYK103, BYK163 and BYK2025.

[0010] In any embodiment, the polymer powder is one or more of POM, PVDF, PTFE and PE, and the diameter of the polymer powder is 50nm-5μm; and / or the second dispersant is one or more of BYK103, BYK163, BYK2025; and / or the second solvent is one or more of xylene, DMF, PMA, ethyl acetate and butanone.

[0011] In any embodiment, it also includes a rust-proofing layer, which is arranged below the first reflecting layer; the raw materials of the rust-proofing layer include component A and component B, and the addition amount of component B is 5-8% of the mass of component A; the component A, calculated by mass percentage, includes 15-30% bisphenol A, 20-40% zinc powder, 5-15% aluminum pyrophosphate, 5-15% aluminum tripolyphosphate, 0.5-2% third dispersant, and the balance is a third solvent; the component B includes curing agent 593 and curing agent D230, and the mass ratio of the curing agent 593 to the curing agent D230 is 3:(2-1).

[0012] In any embodiment, the bisphenol A includes bisphenol AE03 and one of bisphenol AE44, bisphenol A E51 and bisphenol AF; bisphenol AE03 accounts for 5-10% of component A, and one of bisphenol A E44, bisphenol A E51 and bisphenol AF accounts for 10-20% of component A.

[0013] In any embodiment, the thickness of the rust-proofing layer is 10-30 μm.

[0014] In addition, the present invention also proposes a method for preparing the above-mentioned radiation cooling coating, comprising the following steps: spraying or rolling a first reflective layer coating on the surface of a substrate; after drying, spraying or rolling a second reflective layer coating on the surface of the first reflective layer to obtain the radiation cooling coating.

[0015] Compared with the prior art, the beneficial effects of the present invention include: the radiation cooling coating proposed in the present invention includes: a first reflection layer and a second reflection layer arranged on the first reflection layer; the coating raw materials of the first reflection layer include resin, aluminum powder, a first dispersant and a first solvent; the coating raw materials of the second reflection layer include fluorosilicone rubber resin, high molecular polymer powder, a second solvent and a second dispersant, and the radiation cooling coating has mid- and far-infrared spectral emission selectivity and high solar reflectivity, and thus has excellent cooling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the radiation cooling coating of Example 1 of the present invention.

[0017] Figure 2 is the solar reflectivity of the radiative cooling coating of Example 1 of the present invention.

[0018] Figure 3 is the mid- and far-infrared emissivity of the radiation cooling coating of Example 1 of the present invention.

[0019] Explanation of reference numerals: 0, substrate; 1, first reflective layer; 2, second reflective layer; 3, rust-proof and anti-corrosion layer. DETAILED DESCRIPTION

[0020] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0022] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0023] This specific embodiment provides a radiation cooling coating, including: a first reflective layer and a second reflective layer arranged on the first reflective layer; the coating raw materials of the first reflective layer include resin, aluminum powder, a first dispersant and a first solvent; the coating raw materials of the second reflective layer include fluorosilicone rubber resin, high molecular polymer powder, a second solvent and a second dispersant; the thickness of the first reflective layer is 10-30μm, and the thickness of the second reflective layer is 60-120μm.

[0024] In some embodiments, the raw materials of the first reflective layer, calculated by mass percentage, include 20-40% resin, 30-50% aluminum powder, 0.5-2% first dispersant, and the balance is the first solvent; the raw materials of the second reflective layer, calculated by mass percentage, include 20-40% fluorosilicone rubber resin, 10-40% high molecular polymer powder, 0.5-2% second dispersant, and the balance is the second solvent.

[0025] In some embodiments, the resin in the first reflective layer includes one or more of epoxy resin, acrylic resin, fluorocarbon resin and polyurethane resin; the first solvent is one or more of xylene, DMF, PMA, ethyl acetate, butanone, propylene glycol methyl ether and dibasic acid ester; and / or, the first dispersant is one or more of BYK103, BYK163, BYK2025, preferably one or two of POM and PE; the polymer powder is one or more of POM, PVDF, PTFE and PE, and the diameter of the polymer powder is 50nm-5μm; the second dispersant is one or more of BYK103, BYK163, BYK2025; the second solvent is one or more of xylene, DMF, PMA, ethyl acetate and butanone. The polymer powder acts as a white reflective medium, has high emissivity in the atmospheric window, and is infrared transparent in other areas, which is the key to constructing emissivity selectivity.

[0026] In some embodiments, it also includes a rust-proofing layer, which is arranged below the first reflecting layer; the raw materials of the rust-proofing layer include component A and component B, and the addition amount of component B is 5-8% of the mass of component A; the component A, calculated by mass percentage, includes 15-30% bisphenol A, 20-40% zinc powder, 5-15% aluminum pyrophosphate, 5-15% aluminum tripolyphosphate, 0.5-2% third dispersant, and the balance is a third solvent; the component B includes curing agent 593 and curing agent D230, and the mass ratio of the curing agent 593 to the curing agent D230 is 3:(2-1); the thickness of the rust-proofing layer is 10-30μm.

[0027] In some embodiments, the bisphenol A includes bisphenol AE03 and one of bisphenol AE44, bisphenol AE51 and bisphenol AF; bisphenol AE03 accounts for 5-10% in component A, and one of bisphenol AE44, bisphenol AE51 and bisphenol AF accounts for 10-20% in component A.

[0028] Emissivity selectivity of coating: Fluorosilicone rubber resin gives the coating extremely high UV resistance, enabling it to maintain good appearance and performance during long-term outdoor use, excellent weather resistance and durability, and can remain stable even under extreme weather conditions. It has the characteristics of water repellency and oil repellency, which can effectively prevent moisture and oil from damaging the insulation layer, thereby extending its service life and maintenance cycle. 1208cm -1 Yes-CF stretching vibration absorption, 1064cm -1 、1014cm -1 It is the characteristic absorption of Si-O-Si, 896cm -1 It is the characteristic absorption of fluorosilicone rubber. Fluorosilicone rubber absorbs at 766cm -1 -1260cm -1 (i.e. 8-13μm atmospheric window band) has a strong absorption peak and high transmittance in other bands. According to Kirchhoff's law (Kirchhoff's law is a key principle in thermal radiation, which describes the relationship between an object's absorption and emission of thermal radiation. According to Kirchhoff's law, the absorptivity and emissivity of an object are equal), fluorosilicone rubber has high emissivity in the 8-13μm band and low emissivity in other bands, that is, it has good emission selectivity. Therefore, fluorosilicone rubber is used as the film-forming material of the second reflective layer of the outer layer of the coating.

[0029] In addition, polymer powder, especially polyoxymethylene (POM), is a thermoplastic crystalline polymer powder with good comprehensive properties, including high rigidity, high hardness, excellent fatigue resistance and wear resistance, as well as good electrical insulation and chemical stability. The absorption peak of its infrared spectrum is concentrated at 1300cm -1 -650cm -1 (7.7-15μm). In addition, polyvinylidene fluoride (PVDF) is a highly non-reactive thermoplastic fluorinated polymer; it has good chemical corrosion resistance, high temperature resistance, oxidation resistance, weather resistance, and radiation resistance; its infrared spectrum absorption peak is concentrated at 1500cm -1 -760cm -1 (7-13μm); polytetrafluoroethylene (PTFE) has outstanding comprehensive properties, high and low temperature resistance, corrosion resistance, non-stick, self-lubricating, excellent dielectric properties, and very low friction coefficient. The infrared spectrum absorption peak of PTFE is mainly concentrated at 1300cm -1 -1000cm -1 (7.7-10μm); Polyethylene (PE) has excellent corrosion resistance, wear resistance, low temperature resistance and chemical resistance, so it is widely used in various fields. The infrared spectrum absorption peak of PE is mainly concentrated at 1450cm -1 -760cm -1(7-13μm). Therefore, POM, PVDF, PTFE, and PE powders are used as the reflective medium and mid- and far-infrared emitting medium of the second coating.

[0030] Solar reflectivity of coating: The high solar reflectivity of coating mainly comes from 1. The reflection of light by the first reflective layer with low emissivity and enhanced reflection. This functional layer can contribute more than 75% of the solar reflectivity. 2. The scattering and reflection of ultraviolet, visible and near-infrared light by the fluorosilicone rubber resin powder in the second reflective layer with selected emissivity and high solar reflectivity.

[0031] In addition, considering the transmittance of mid-infrared wavelengths of this function, the underlying functional layer does not use metal oxides or inorganic powders containing high emissivity. We found that after the mid-infrared wavelengths are transmitted, they are absorbed by the metal oxides or non-metallic inorganic powders, resulting in increased absorption in the entire band and loss of emission-induced selectivity.

[0032] This specific embodiment also proposes a method for preparing the above-mentioned radiation cooling coating, comprising the following steps: spraying or rolling a first reflective layer coating on the surface of a substrate; after drying, spraying or rolling a second reflective layer coating on the surface of the first reflective layer to obtain the radiation cooling coating.

[0033] In some embodiments, before spraying the first reflective layer coating, the process further includes spraying or rolling a rust-proofing layer on the surface of the substrate.

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] In the present invention, reference is made to “some embodiments”, “this embodiment”, examples, etc., which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0036] If similar descriptions of "first / second" appear in the application documents, the following instructions are added. In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It is understandable that "first\second\third" can be interchanged in a specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0037] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, object A and / or object B may represent three situations: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0038] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0039] It should be noted that the coating materials of the first reflective layer, the second reflective layer or the rust-proof and anti-corrosion layer in the following embodiments or comparative examples are all prepared by mixing various components.

[0040] Example 1

[0041] Combination Figure 1 The present embodiment provides a radiation cooling coating, comprising: a first reflective layer 1 and a second reflective layer 2 arranged on the first reflective layer, and a rust-proofing layer 3 arranged below the first reflective layer 1; the coating raw materials of the first reflective layer, calculated by mass percentage, include 50% acrylic resin, 30% 3μm aluminum powder, 31% BYK16, and 19% ethyl acetate, and the coating thickness of the first reflective layer is set to 20μm; the coating raw materials of the second reflective layer, calculated by mass percentage, include 30% fluorosilicone rubber resin, 30% 1μm PE powder and 1μm POM powder accounts for 30%, dispersant BYK103 accounts for 1%, xylene accounts for 9%, and the coating thickness of the second reflective layer is set to 100μm; the rust-proofing layer includes component A and component B, and the mass of component B is 6% of component A; component A, calculated by mass percentage, includes E5120%, E0310%, zinc powder 40%, aluminum pyrophosphate 10%, aluminum tripolyphosphate 10%, BYK20251%, and dibasic acid ester 9%; the component B includes curing agent 593 and the curing agent D230; the mass ratio of curing agent 593 and the curing agent D23 is 3:2, and the coating thickness of the rust-proofing layer is set to 60μm.

[0042] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, comprising the following steps: spraying the rust-proofing layer 3 on the surface of the substrate 0, and continuing to spray the coating of the first reflective layer 1 after the rust-proofing layer 3 is dried; after the coating of the first reflective layer 1 is dried, spraying the coating of the second reflective layer 2 on the surface of the first reflective layer 1 to obtain the radiation cooling coating.

[0043] Combination Figure 2 and 3The solar reflectivity of the radiation cooling coating in this embodiment is 92%, the emissivity of 8-13μm is 0.94, the emissivity of 2.5-25μm is 0.75, the coating adhesion is 5B, it is resistant to 5% sulfuric acid for 24h without abnormality, 5% sodium hydroxide for 24h without abnormality, and neutral salt spray for 1500h without rust.

[0044] Example 2

[0045] The present embodiment provides a radiant cooling coating, comprising: a first reflecting layer, a second reflecting layer arranged on the first reflecting layer, and a rust-proofing layer arranged below the first reflecting layer; the coating raw materials of the first reflecting layer, calculated by mass percentage, include 50% acrylic resin, 30% 3μm aluminum powder, 31% BYK16, and 19% ethyl acetate, and the coating thickness of the first reflecting layer is set to 60μm; the coating raw materials of the second reflecting layer, calculated by mass percentage, include 30% fluorosilicone rubber resin, 30% 1μm PE powder, and 19% 1μm POM powder 30%, dispersant BYK10 31%, xylene 9%, the coating thickness of the second reflective layer is set to 60μm; the rust-proofing layer includes component A and component B, and the addition amount of component B is 6% of the mass of component A; component A, calculated by mass percentage, includes E51 20%, E03 10%, zinc powder 40%, aluminum pyrophosphate 10%, aluminum tripolyphosphate 10%, BYK20 251% and dibasic acid ester 9%, the component B includes curing agent 593 and the curing agent D230, the mass ratio of curing agent 593 and the curing agent D230 is 3:2, and the coating thickness of the rust-proofing layer is set to 60μm.

[0046] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, which includes the following steps: spraying a rust-proofing layer on the surface of a substrate, and continuing to spray a first reflective layer of paint after the rust-proofing layer is dried; after the first reflective layer of paint is dried, spraying a second reflective layer of paint on the surface of the first reflective layer to obtain the radiation cooling coating.

[0047] The obtained radiation cooling coating has a solar reflectivity of 85%, an emissivity of 0.92 at 8-13 μm, an emissivity of 0.78 at 2.5-25 μm, a coating adhesion of 5B, and no abnormality in resistance to 5% sulfuric acid for 24 hours, 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0048] Example 3

[0049] The present embodiment provides a radiation cooling coating, comprising: a first reflection layer and a second reflection layer arranged on the first reflection layer, and a rust-proofing layer arranged below the first reflection layer; the coating raw materials of the first reflection layer, calculated by mass percentage, include 40% acrylic resin, 40% 10μm aluminum powder, 31% BYK16, 19% ethyl acetate, the coating thickness is set to 20μm, and the coating thickness of the first reflection layer is set to 60μm; the coating raw materials of the second reflection layer, calculated by mass percentage, include 30% fluorosilicone rubber resin, 30% 1μm PE powder, and 10μm POM powder 30%, dispersant BYK10 31%, xylene 9%, the coating thickness of the second reflective layer is set to 100μm; the rust-proofing layer includes component A and component B, and the addition amount of component B is 6% of the mass of component A; component A, calculated by mass percentage, includes E51 20%, E03 10%, zinc powder 40%, aluminum pyrophosphate 10%, aluminum tripolyphosphate 10%, BYK20 251% and dibasic acid ester 9%, the component B includes curing agent 593 and the curing agent D230, the mass ratio of curing agent 593 and the curing agent D230 is 3:1, and the coating thickness of the rust-proofing layer is set to 60μm.

[0050] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, which includes the following steps: spraying a rust-proofing layer on the surface of a substrate, and continuing to spray a first reflective layer of paint after the rust-proofing layer is dried; after the first reflective layer of paint is dried, spraying a second reflective layer of paint on the surface of the first reflective layer to obtain the radiation cooling coating.

[0051] The radiant cooling coating obtained in this embodiment has a solar reflectivity of 93%, an emissivity of 0.91 at 8-13 μm, an emissivity of 0.70 at 2.5-25 μm, a coating adhesion of 5B, and no abnormality in 5% sulfuric acid for 24 hours, no abnormality in 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0052] Example 4

[0053] The present embodiment provides a radiant cooling coating, comprising: a first reflecting layer and a second reflecting layer arranged on the first reflecting layer, and a rust-proofing layer arranged below the first reflecting layer; the coating raw materials of the first reflecting layer, calculated by mass percentage, include 50% acrylic resin, 25% 3μm aluminum powder, 31% BYK16, and 24% ethyl acetate, and the coating thickness is set to 20μm, and the coating thickness of the first reflecting layer is set to 60μm; the coating raw materials of the second reflecting layer, calculated by mass percentage, include 30% fluorosilicone rubber resin, 30% 1μm PVDF powder, and 1μm PTFE powder 30%, dispersant BYK10 31%, xylene 9%, the coating thickness of the second reflective layer is set to 100μm; the rust-proofing layer includes component A and component B, and the addition amount of component B is 6% of the mass of component A; component A, calculated by mass percentage, includes E51 20%, E03 10%, zinc powder 40%, aluminum pyrophosphate 10%, aluminum tripolyphosphate 10%, BYK20 251% and dibasic acid ester 9%, the component B includes curing agent 593 and the curing agent D230, the mass ratio of curing agent 593 and the curing agent D230 is 3:1, and the coating thickness of the rust-proofing layer is set to 60μm.

[0054] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, which includes the following steps: spraying a rust-proofing layer on the surface of a substrate, and continuing to spray a first reflective layer of paint after the rust-proofing layer is dried; after the first reflective layer of paint is dried, spraying a second reflective layer of paint on the surface of the first reflective layer to obtain the radiation cooling coating.

[0055] The radiant cooling coating obtained in this embodiment has a solar reflectivity of 89%, an emissivity of 0.93 at 8-13 μm, an emissivity of 0.78 at 2.5-25 μm, a coating adhesion of 5B, and no abnormality in 5% sulfuric acid for 24 hours, no abnormality in 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0056] Example 5

[0057] The present embodiment provides a radiation cooling coating, comprising: a first reflection layer and a second reflection layer arranged on the first reflection layer, and a rust-proofing layer arranged below the first reflection layer; the coating raw materials of the first reflection layer, calculated by mass percentage, include 50% acrylic resin, 30% 3μm aluminum powder, 31% BYK16, and 24% ethyl acetate, and the coating thickness of the first reflection layer is set to 20μm; the coating raw materials of the second reflection layer, calculated by mass percentage, include 30% fluorosilicone rubber resin, 30% 1μm PE powder, and 1μm PTFE powder 30%, dispersant BYK10 31%, xylene 9%, the coating thickness of the second reflective layer is set to 100μm; the rust-proofing layer includes component A and component B, and the addition amount of component B is 6% of the mass of component A; component A, calculated by mass percentage, includes E51 20%, E03 10%, zinc powder 30%, aluminum pyrophosphate 15%, aluminum tripolyphosphate 15%, BYK20 251% and dibasic acid ester 9%, the component B includes curing agent 593 and the curing agent D230, the mass ratio of curing agent 593 and the curing agent D230 is 3:1, and the coating thickness of the rust-proofing layer is set to 30μm.

[0058] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, which includes the following steps: spraying a rust-proofing layer on the surface of a substrate, and continuing to spray a first reflective layer of paint after the rust-proofing layer is dried; after the first reflective layer of paint is dried, spraying a second reflective layer of paint on the surface of the first reflective layer to obtain the radiation cooling coating.

[0059] The radiant cooling coating obtained in this embodiment has a solar reflectivity of 92%, an emissivity of 0.94 at 8-13 μm, an emissivity of 0.75 at 2.5-25 μm, a coating adhesion of 5B, and no abnormality in 5% sulfuric acid for 24 hours, no abnormality in 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 2000 hours.

[0060] Comparative Example 1

[0061] The difference between the radiation cooling coating of this comparative example and Example 1 is that an equal amount of 30% polyurethane resin is used to replace the fluorosilicone rubber resin in the coating material of the second reflective layer.

[0062] The solar reflectivity of the coating obtained in this comparative example is 91%, the emissivity of 8-13μm is 0.94, the emissivity of 2.5-25μm is 0.93, the coating adhesion is 5B, and there is no abnormality in 5% sulfuric acid for 24h, no abnormality in 5% sodium hydroxide for 24h, and no rust in neutral salt spray for 1500h. The difference between comparative example 1 and example 1 is that the film-forming material of the second reflective layer is polyurethane resin, which may be because polyurethane has a high thermal conductivity at 3500cm -1 -2800cm -1The high absorption rate results in that the selective emission performance of the coating in the mid- and far-infrared spectra is worse than that of Example 1.

[0063] Comparative Example 2

[0064] The difference between the radiation cooling coating of this comparative example and Example 1 is that 1 μm PE powder and 1 μm POM powder are replaced by an equal amount of 60% metal oxide titanium dioxide in the coating material of the second reflective layer.

[0065] The coating obtained in this comparative example has a solar reflectivity of 87%, an emissivity of 0.94 at 8-13 μm, an emissivity of 0.94 at 2.5-25 μm, a coating adhesion of 5B, no abnormality in resistance to 5% sulfuric acid for 24 hours, no abnormality in resistance to 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0066] Comparative Example 3

[0067] The radiation cooling coating of this comparative example is different from that of Example 1 in that it does not have a first reflection layer, but includes a second reflection layer and a rust-proofing layer disposed below the second reflection layer.

[0068] This embodiment also includes a method for preparing the above-mentioned radiation cooling coating, which includes the following steps: spraying a rust-proofing layer on the surface of a substrate, and after the rust-proofing layer is dried, continuing to spray a second reflective layer of coating to obtain the radiation cooling coating.

[0069] The radiation cooling coating obtained in this comparative example has a solar reflectivity of 92%, an emissivity of 0.75 at 8-13 μm, an emissivity of 0.74 at 2.5-25 μm, a coating adhesion of 5B, no abnormality in resistance to 5% sulfuric acid for 24 hours, no abnormality in resistance to 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0070] This comparative example does not have a first reflective layer. Due to the transmission of sunlight through the second reflective layer on the surface, it is absorbed by the rust-proof anti-corrosion layer, resulting in a decrease in the sunlight reflectivity. At the same time, after the mid- and far-infrared is transmitted, it is absorbed by the rust-proof anti-corrosion layer, resulting in an increase in the overall mid- and far-infrared absorptivity of the coating, and the coating loses its emission selectivity.

[0071] Comparative Example 4

[0072] The difference between the radiation cooling coating of this comparative example and Example 1 is that the aluminum powder in the first coating is replaced by the same amount of aluminum oxide. Due to the high emissivity of aluminum oxide in the full band of 2.5-25μm, the low emissivity layer does not play its due role. After the mid- and far-infrared is transmitted through the surface layer, it is absorbed by the aluminum oxide coating, resulting in the absorption of the full band of mid- and far-infrared in the coating, and the coating loses its emission selectivity.

[0073] The coating obtained in this comparative example has a solar reflectivity of 89%, an emissivity of 0.88 at 8-13 μm, an emissivity of 0.89 at 2.5-25 μm, a coating adhesion of 5B, no abnormality in resistance to 5% sulfuric acid for 24 hours, no abnormality in resistance to 5% sodium hydroxide for 24 hours, and no rust in neutral salt spray for 1500 hours.

[0074] Comparative Example 5

[0075] The radiation cooling coating of this comparative example is different from that of Example 1 in that aluminum pyrophosphate and aluminum tripolyphosphate are not added, and component A of the rust-proofing layer, calculated by mass percentage, includes E51 20%, E03 10%, zinc powder 60%, BYK20 251%, and dibasic acid ester 9%.

[0076] The coating obtained in this comparative example has a solar reflectivity of 92%, an emissivity of 0.94 at 8-13 μm, an emissivity of 0.75 at 2.5-25 μm, a coating adhesion of 2B, and is resistant to 5% sulfuric acid for 24 hours, 5% sodium hydroxide for 24 hours, and neutral salt spray for 200 hours without rust, but rust occurs after 860 hours.

[0077] The difference between Comparative Example 5 and Example 1 is that aluminum pyrophosphate and aluminum tripolyphosphate are not added to the rust-proof anti-corrosion layer, resulting in the inability to convert rust into a dense coating, which in turn leads to reduced adhesion and salt spray resistance of the coating.

[0078] Related tests:

[0079] Temperature test method: A water tank test is used. The water tank has a size of 600mm*400mm*40mm, is made of stainless steel, and is filled with water. The probe uses a K-type thermocouple, and the probe is located in the center of the water tank. A data multi-channel data recorder is used to record the temperature data. The probe is calibrated before the test, with a deviation of ±1°C. The water tanks are placed on the same horizontal plane with the same orientation. To prevent the influence of heat transfer from the ground, the water tanks are placed on 8cm thick extruded boards. Atmospheric temperature and solar radiation data are obtained from a meteorological station near the test area. The coated plates coated with Examples 1-5 and Comparative Examples 1-5 are attached to the outer surface of the water tank and sealed with tape all around. A plate without a coating is attached to the outer surface of the water tank as a control group. The ambient temperature is 26°C, and the average solar radiation is 750w / m 2 Under the conditions, the water temperature in the water tank corresponding to the radiation cooling coatings of different embodiments and comparative examples was tested, as shown in Table 1.

[0080] Table 1 Water temperature of the water tank corresponding to the radiation cooling coating of Examples 1-5 and Comparative Examples 1-5

[0081] Water temperature (℃) Example 1 22 Example 2 23 Example 3 22.5 Example 4 24 Example 5 23.5 Comparative Example 1 29 Comparative Example 2 35.5 Comparative Example 3 30.5 Comparative Example 4 32.5 Comparative Example 5 26.5 Control group 55

[0082] The radiant cooling coating proposed in the present invention can be applied to the surface of a metal substrate, such as a steel substrate, and has the following functions: 1. Selective emission of mid- and far-infrared spectra; 2. High solar reflectivity; 3. Rust-to-corrosion protection function, which can eliminate the need for rust-to-rust construction, and has good adhesion, salt spray resistance, and acid and alkali resistance.

[0083] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A radiation cooling coating, characterized in that: include: A first reflective layer and a second reflective layer arranged on the first reflective layer; the coating raw materials of the first reflective layer include resin, aluminum powder, a first dispersant and a first solvent; the coating raw materials of the second reflective layer include fluorosilicone rubber resin, high molecular polymer powder, a second solvent and a second dispersant.

2. The radiative cooling coating according to claim 1, characterized in that: The thickness of the first reflective layer is 10-30 μm, and the thickness of the second reflective layer is 60-120 μm.

3. The radiative cooling coating according to claim 1, characterized in that: The raw materials of the first reflective layer, calculated by mass percentage, include 20-40% resin, 30-50% aluminum powder, 0.5-2% first dispersant, and the balance is the first solvent.

4. The radiative cooling coating according to claim 1, characterized in that: The raw materials of the second reflective layer, calculated by mass percentage, include 20-40% fluorosilicone rubber resin, 10-40% high molecular polymer powder, 0.5-2% second dispersant, and the balance is second solvent.

5. The radiative cooling coating according to claim 1, characterized in that: The resin in the first reflective layer includes one or more of epoxy resin, acrylic resin, fluorocarbon resin and polyurethane resin; and / or the first solvent is one or more of xylene, DMF, PMA, ethyl acetate, butanone, propylene glycol methyl ether and dibasic acid ester; and / or the first dispersant is one or more of BYK103, BYK163 and BYK2025.

6. The radiative cooling coating according to claim 1, characterized in that: The polymer powder is one or more of POM, PVDF, PTFE and PE, and the diameter of the polymer powder is 50nm-5μm; and / or the second dispersant is one or more of BYK103, BYK163, BYK2025; and / or the second solvent is one or more of xylene, DMF, PMA, ethyl acetate and butanone.

7. The radiative cooling coating according to claim 1, characterized in that: It also includes a rust-proofing layer, which is arranged below the first reflecting layer; the raw materials of the rust-proofing layer include component A and component B, and the addition amount of component B is 5-8% of the mass of component A; The component A, calculated by mass percentage, includes 15-30% bisphenol A, 20-40% zinc powder, 5-15% aluminum pyrophosphate, 5-15% aluminum tripolyphosphate, 0.5-2% a third dispersant, and the balance is a third solvent; the component B includes curing agent 593 and curing agent D230, and the mass ratio of the curing agent 593 to the curing agent D230 is 3:(2-1).

8. The radiative cooling coating according to claim 7, characterized in that: The bisphenol A includes bisphenol AE03 and one of bisphenol A E44, bisphenol A E51 and bisphenol AF; bisphenol AE03 accounts for 5-10% of component A, and one of bisphenol A E44, bisphenol AE51 and bisphenol AF accounts for 10-20% of component A.

9. The radiative cooling coating according to claim 7, characterized in that: The thickness of the rust-proofing layer is 10-30 μm.

10. A method for preparing a radiative cooling coating according to any one of claims 1 to 9, characterized in that: The following steps are involved: The first reflective layer coating is sprayed or rolled on the surface of the substrate; after drying, the second reflective layer coating is sprayed or rolled on the surface of the first reflective layer to obtain the radiation cooling coating.

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