Low-absorption high-emission radiation refrigeration coating material and preparation method thereof

Abstract

The invention discloses a low-absorption high-emission radiation refrigeration coating material, which comprises a bottom coating and a surface coating, the bottom coating comprises BaSO4 with different particle sizes and a film forming substance, and the surface coating comprises a surface layer filler and a film forming substance. The invention also discloses a preparation method of the material, which comprises the following steps: dispersing and mixing BaSO4 with different particle sizes, a film-forming substance and a solvent to obtain bottom layer slurry, and filtering to obtain a bottom layer coating; dispersing and mixing a surface layer filler, a film-forming substance and a solvent to obtain surface layer slurry, and filtering to obtain a surface layer coating; the prime paint is sprayed on the surface of the base material, and then the surface paint is sprayed on the surface of the prime paint; and curing to obtain the coating. The material has excellent solar spectrum reflection performance, high infrared radiation performance of an atmospheric window and relatively good ultraviolet aging resistance, and can be applied to multiple fields of high-end optical instrument detection, communication electronics, petrochemical engineering, energy-saving buildings and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation refrigeration materials, and in particular to a low-absorption and high-emission radiation refrigeration coating material and a preparation method thereof. Background Art

[0002] Radiative cooling is a passive cooling method that does not consume electricity or other energy. Its principle is that the material has a high reflective performance in the solar spectrum, and at the same time converts the remaining absorbed sunlight and the heat emitted by the surrounding higher temperature objects into its own internal energy and then emits it outward in the form of infrared radiation. The heat is dissipated into the outer space with a cold black background through the atmospheric window (8μm~13μm) to achieve the effect of passive cooling. Existing radiative cooling coatings mostly use single particle size powders, which have poor reflective ability to sunlight and cannot form a synergistic radiation mechanism. The radiative cooling effect is insufficient, and it is easy to discolor after long-term exposure, resulting in performance degradation. Summary of the invention

[0003] The purpose of the present invention is to overcome the above defects, provide a low absorption and high emission radiation refrigeration coating material and its preparation method, and solve the technical problem that the existing radiation refrigeration materials cannot meet the requirements of low absorption and high emission radiation and long life and high stability. The present invention has excellent solar spectrum reflection performance and high infrared radiation performance of the atmospheric window, as well as good resistance to ultraviolet aging, and can be applied to high-end optical instrument detection, communication electronics, petrochemical industry, energy-saving buildings and other fields.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] A low-absorption and high-emission radiation cooling coating material, comprising a base coating and a top coating;

[0006] Taking the total volume fraction of the low coating as 100%, the low coating comprises the following components in volume fractions:

[0007] BaSO4 with a particle size of 0.06μm to 0.16μm 5% to 10%;

[0008] BaSO4 with a particle size of 0.4μm to 0.6μm 20% to 35%;

[0009] Spherical BaSO4 with a particle size of 0.8μm to 1μm 25% to 35%;

[0010] Film-forming substances 20% to 50%;

[0011] Taking the total volume fraction of the top coating as 100%, the top coating comprises the following components in volume fractions:

[0012] Surface filler 50% to 70%;

[0013] Film-forming substances 30% to 50%.

[0014] Furthermore, the material has a reflectivity of 0.90 to 0.92 at 200 nm to 2500 nm and a radiation rate of 0.92 to 0.95 at 8 μm to 13 μm. After 1000 h of UV aging, the reflectivity change is ≤0.01, and the radiation change is ≤0.01. When the ambient temperature is 30° C., the temperature difference with the ambient temperature is 5° C. to 10° C.

[0015] A method for preparing a low-absorption and high-emission radiation cooling coating material, comprising:

[0016] S1: BaSO4 with different particle sizes, film-forming material and solvent are dispersed and mixed to obtain a bottom slurry;

[0017] The bottom layer slurry is filtered to obtain a bottom layer coating;

[0018] S2 disperses and mixes the surface layer filler, the film-forming material and the solvent to obtain a surface layer slurry;

[0019] Filtering the surface layer slurry to obtain the surface layer coating;

[0020] S3 adds curing agent to the base coating and the top coating;

[0021] The base coating with curing agent added is sprayed on the surface of the substrate, and then the top coating with curing agent added is sprayed on the surface of the base coating;

[0022] After spraying, curing is performed to obtain a coating.

[0023] Furthermore, in the bottom slurry, the mass ratio of the film-forming substance to the solvent is 1:2.2 to 1:3.0;

[0024] In the surface layer slurry, the mass ratio of the film-forming substance to the solvent is 1:2.0 to 1:2.8.

[0025] Furthermore, in step S1 and step S2, the film-forming material includes one or more of fluorine-containing acrylic resin, silicone resin or potassium silicate aqueous solution; the solid content of the potassium silicate aqueous solution is 30%;

[0026] The solvent is an oily solvent or an aqueous solvent. The oily solvent includes one or more of butyl acetate, xylene or n-butanol, and the aqueous solvent includes deionized water.

[0027] Further, in step S1, the BaSO4 with different particle sizes includes BaSO4 with a particle size of 0.06 μm to 0.16 μm, BaSO4 with a particle size of 0.4 μm to 0.6 μm, and BaSO4 with a particle size of 0.8 μm to 1 μm;

[0028] In step S2, the surface layer filler is one or more of europium oxide or gadolinium oxide, and the particle size is 3 μm to 5 μm.

[0029] Furthermore, in step S1 and step S2, the method of dispersion and mixing is grinding dispersion, the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 4mm-8mm, the volume fraction of the grinding medium in the entire grinding tank volume is 65%-80%, the rotation speed is 120-220rpm, and the grinding dispersion time is 4h-8h;

[0030] In step S1 or step S2, the bottom layer slurry or the surface layer slurry is filtered using a 120-240 mesh gauze to obtain a bottom layer coating.

[0031] Furthermore, in step S3, when spraying the base coating or the surface coating, the thickness of each spraying is 20 μm to 30 μm, and the next spraying is performed after the surface is dry, until the total thickness of the base coating after spraying is 180 μm to 260 μm, and the total thickness of the surface coating is 50 to 100 μm.

[0032] Further, in step S3, before spraying the primer with the curing agent added thereto on the surface of the substrate, the surface of the substrate is cleaned, specifically comprising:

[0033] Use aviation gasoline, acetone or ethanol to clean the surface, and then perform grinding or sandblasting pretreatment;

[0034] The curing method comprises: curing at room temperature for 10 hours to 20 hours, then baking at 40 to 60 degrees Celsius for 3 hours to 5 hours, and then baking at 70 to 90 degrees Celsius for 20 hours to 32 hours; and naturally cooling to room temperature after baking to obtain a coating.

[0035] Furthermore, the coating obtained in step S3 includes a primer layer and a topcoat layer;

[0036] Taking the total volume fraction of the base coating as 100%, the low coating comprises the following components by volume fraction:

[0037]

[0038] Taking the total volume fraction of the top coating as 100%, the top coating comprises the following components in volume fractions:

[0039] Surface filler 50% to 70%;

[0040] Film-forming substances 30% to 50%.

[0041] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0042] (1) The low-absorption and high-emission radiation refrigeration coating of the present invention has excellent solar spectrum reflection performance and high infrared radiation performance of the atmospheric window, and has good resistance to ultraviolet aging. It can be applied to high-end optical instrument detection, communication electronics, petrochemical industry, energy-saving buildings and other fields;

[0043] (2) The present invention effectively improves the reflectivity in the solar band and the infrared radiation rate of the atmospheric window by designing the particle size distribution of the filler particles and controlling the volume fraction;

[0044] (3) The present invention selects fillers with high bandgap width and spatial binding energy by selecting fillers in the surface layer, thereby effectively avoiding coating performance degradation caused by ultraviolet radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure design for improving the solar spectrum reflection capability of the present invention;

[0046] Figure 2 1 is the optimal reflection particle size curve corresponding to different wavelengths of the solar spectrum of the present invention, wherein (a) is the optimal reflection particle size curve under the far ultraviolet band and the near ultraviolet band, and (b) is the optimal reflection particle size curve under the incident wavelength of 400nm, 1000nm and 2500nm. DETAILED DESCRIPTION

[0047] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0048] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0049] The object of the present invention is to provide a low-absorption and high-emission radiation cooling coating material which realizes high reflection in the solar band and high infrared radiation in the atmospheric window by means of filler particle size distribution design, volume fraction control and coating thickness optimization.

[0050] The present invention provides a low-absorption and high-emission radiation cooling coating material, comprising a base coating and a top coating;

[0051] Combined with the solar spectrum energy distribution and Mie scattering principle, different filler particle sizes correspond to different maximum spectral reflectance capabilities. By using filler particle distributions of different particle sizes, the full spectrum reflectance capability can be improved. The schematic diagram is as follows: Figure 1 and Figure 2 The final scattering result is evaluated by the backscattering coefficient to determine the optimal particle size range.

[0052] In the primer layer, barium sulfate (BaSO4) with different particle sizes is selected as the bottom coating, and the distribution range of different particle sizes is determined by quantitative distribution according to the energy distribution of the solar spectrum. The particle size is 0.06μm-0.16μm, the purity is ≥99.9%, and the volume fraction is 5%-10%; the BaSO4 particle size is 0.4μm-0.6μm, the purity is ≥99.9%, and the volume fraction is 20%-35%; the BaSO4 particle size is 0.8μm-1μm, the purity is ≥99.9%, and the volume fraction is 25%-35%; fluorine-containing acrylic resin, silicone resin or potassium silicate aqueous solution is selected as the film-forming substance in the primer layer, and the volume fraction of the film-forming substance in the bottom layer is 20%-50%.

[0053] In the topcoat layer, one or more of lanthanum hydroxide (La(OH)3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3) are selected as the surface layer filler, with a particle size of 3μm to 5μm, a purity of ≥99.9%, and a volume fraction of the surface layer filler of 50% to 70%. In the topcoat layer, fluorine-containing acrylic resin, organic silicon resin or potassium silicate aqueous solution are selected as the film-forming substance, corresponding to the film-forming substance in the basecoat layer, and the volume fraction of the film-forming substance in the topcoat layer is 30% to 50%.

[0054] Furthermore, the specific thickness of the coating is: the thickness of the base coating is 180 μm to 260 μm, and the thickness of the top coating is 50 to 100 μm.

[0055] (2) The low-absorption and high-emission radiation cooling coating of the present invention has the following characteristics:

[0056] 1) Appearance: The coating is uniformly white, without bubbles, peeling, cracking, falling off, etc.

[0057] 2) Reflectivity of 200nm~2500nm: 0.90~0.92;

[0058] 3) Emissivity of 8μm to 13μm: 0.92 to 0.95;

[0059] 4) UV aging resistance: After 1000h UV aging, the reflectivity change is ≤0.01, and the emissivity change is ≤0.01.

[0060] 5) Temperature difference with ambient temperature: 5℃~10℃.

[0061] The present invention proposes a method for preparing a low-absorption and high-emission radiation cooling coating material, the steps of which are as follows:

[0062] (1) Preparation of base coating: BaSO4 with different particle sizes, film-forming substances and solvents are mixed, and the weight ratio of film-forming substances to solvents is 1:2.2 to 1:3.0, wherein the oily solvent includes one or more of butyl acetate, xylene and n-butanol, and the aqueous solvent is deionized water. Grinding and dispersion are used to disperse and mix the base coating, and the grinding medium is zirconium oxide, which is spherical, has a purity of ≥99.9%, a particle size of 4mm to 8mm, a grinding medium volume of 65% to 80%, a rotation speed of 120 to 220rpm, and a grinding and dispersion time of 4h to 8h. After grinding and dispersion, the slurry is taken out and filtered through a 120-240 mesh gauze to obtain the base coating.

[0063] (2) Preparation of topcoat paint: Mix the topcoat filler, film-forming substance and solvent, the weight ratio of the film-forming substance to the solvent is 1:2.0 to 1:2.8, wherein the oily solvent includes one or more of butyl acetate, xylene and n-butanol, and the aqueous solvent is deionized water. Grinding and dispersing are used to disperse and mix the bottomcoat paint, the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 4mm to 8mm, the grinding medium volume is 65% to 80%, the rotation speed is 120 to 220rpm, and the grinding and dispersing time is 4h to 8h. After the grinding and dispersing is completed, the slurry is taken out and filtered through a 120 to 240 mesh gauze to obtain the topcoat paint.

[0064] (3) Preparation of low-absorption and high-emission radiation cooling coating: Before spraying the substrate, clean the surface with aviation gasoline, acetone and ethanol, perform pre-treatment by grinding or sandblasting, and then spray the coating. Add a curing agent to the coating before spraying, spray the primer first and then the topcoat, and control the thickness of each spraying to 20μm to 30μm. After the surface is dry, spray the next time. After spraying, cure at room temperature for 10h to 20h, bake at 50℃ for 3h to 5h, and bake at 80℃ for 20h to 32h. After baking, naturally cool to room temperature to obtain a low-absorption and high-emission radiation cooling coating. Example:

[0065] Example 1

[0066] (1) Preparation of base coating: BaSO4 with different particle sizes, film-forming substances and solvents are mixed, the particle size is 0.06μm~0.16μm, the purity is ≥99.9%, and the volume fraction is 5%; the BaSO4 particle size is 0.4μm~0.6μm, the purity is ≥99.9%, and the volume fraction is 20%; the BaSO4 particle size is 0.8μm~1μm, the purity is ≥99.9%, and the volume fraction is 25%; in the base coating, fluorinated acrylic resin is selected as the film-forming substance, and the volume fraction of the film-forming substance in the bottom layer is 50%. The weight ratio of the film-forming substance to the solvent is 1:2.2, and the solvent is butyl acetate. Grinding and dispersion are used to disperse and mix the base coating, and the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 4mm, the grinding medium volume is 65%, the rotation speed is 120, and the grinding and dispersion time is 4h. After grinding and dispersion, the slurry is taken out and filtered through a 120-mesh gauze to obtain the base coating.

[0067] (2) Preparation of topcoat coating: Lanthanum hydroxide is selected as the top layer filler, with a particle size of 3 μm, a purity of ≥99.9%, and a volume fraction of 50% for the top layer filler. Fluorine-containing acrylic resin is selected as the film-forming substance in the topcoat, and the volume fraction of the film-forming substance in the topcoat is 50%. The top layer filler, the film-forming substance and the solvent are mixed, and the weight ratio of the film-forming substance to the solvent is 1:2.0. Butyl acetate is selected as the solvent. Grinding and dispersion are used to disperse and mix the base coating. The grinding medium is zirconium oxide, which is spherical, has a purity of ≥99.9%, a particle size of 4 mm, a grinding medium volume of 65%, a rotation speed of 120 rpm, and a grinding and dispersion time of 4 hours. After the grinding and dispersion is completed, the slurry is taken out and filtered through a 120-mesh gauze to obtain the top layer coating.

[0068] (3) Preparation of low-absorption and high-emission radiation cooling coating: Before spraying the substrate, clean the surface with aviation gasoline, acetone and ethanol, perform pre-treatment by grinding or sandblasting, and then spray the coating. Add isocyanate curing agent to the coating before spraying. Spray the primer first and then the topcoat. The thickness of each spray is controlled at 20μm. After the surface is dry, the next spraying is carried out. After spraying, cure at room temperature for 10h, bake at 50℃ for 3h, and bake at 80℃ for 20h. After baking, naturally cool to room temperature to obtain a low-absorption and high-emission radiation cooling coating. The specific thickness of the further coating is: the primer thickness is 180μm, and the topcoat thickness is 50μm.

[0069] The low-absorption and high-emission radiation cooling coating prepared in this embodiment has the following characteristics:

[0070] 1) Appearance: The coating is uniformly white, without bubbles, peeling, cracking, falling off, etc.

[0071] 2) Reflectivity of 200nm~2500nm: 0.90;

[0072] 3) Emissivity of 8μm to 13μm: 0.92;

[0073] 4) UV aging resistance: After 1000h UV aging, the reflectivity change is ≤0.01, and the emissivity change is ≤0.01.

[0074] 5) Temperature difference with ambient temperature: 5℃ (ambient temperature 35℃).

[0075] Example 2

[0076] (1) Preparation of base coating: BaSO4 with different particle sizes, film-forming substances and solvents are mixed, the particle size is 0.06μm to 0.16μm, the purity is ≥99.9%, and the volume fraction is 10%; the BaSO4 particle size is 0.4μm to 0.6μm, the purity is ≥99.9%, and the volume fraction is 35%; the BaSO4 particle size is 0.8μm to 1μm, the purity is ≥99.9%, and the volume fraction is 35%; organic silicon resin is selected as the film-forming substance in the base coating, and the volume fraction of the film-forming substance in the bottom layer is 20%. The weight ratio of the film-forming substance to the solvent is 1:3.0, and the solvent is butyl acetate. Grinding and dispersion are used to disperse and mix the base coating, the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 8mm, the grinding medium volume is 80%, the rotation speed is 220, and the grinding and dispersion time is 8h. After grinding and dispersion, the slurry is taken out and filtered through a 240-mesh gauze to obtain the base coating.

[0077] (2) Preparation of topcoat coating: Lanthanum hydroxide is selected as the top layer filler, with a particle size of 5 μm, a purity of ≥99.9%, and a volume fraction of 70% for the top layer filler. Silicone resin is selected as the film-forming substance in the topcoat, and the volume fraction of the film-forming substance in the topcoat is 30%. The top layer filler, the film-forming substance and the solvent are mixed, and the weight ratio of the film-forming substance to the solvent is 1:2.8, and butyl acetate is selected as the solvent. Grinding and dispersion are used to disperse and mix the bottom layer coating, and the grinding medium is zirconium oxide, which is spherical, has a purity of ≥99.9%, a particle size of 8 mm, a grinding medium volume of 80%, a rotation speed of 240 rpm, and a grinding and dispersion time of 8 hours. After the grinding and dispersion is completed, the slurry is taken out and filtered through a 240-mesh gauze to obtain the top layer coating.

[0078] (3) Preparation of low-absorption and high-emission radiation cooling coating: Before spraying the substrate, use aviation gasoline, acetone and ethanol to clean the surface, grind or sandblast before spraying the coating, add a special curing agent to the coating before spraying, spray the primer first and then the topcoat, and control the thickness of each spraying to 30μm. After the surface is dry, the next spraying is carried out. After spraying, cure at room temperature for 20h, bake at 50℃ for 5h, and bake at 80℃ for 32h. After baking, naturally cool to room temperature to obtain a low-absorption and high-emission radiation cooling coating. The specific thickness of the further coating is: the primer thickness is 260μm and the topcoat thickness is 100μm.

[0079] The low-absorption and high-emission radiation cooling coating prepared in this embodiment has the following characteristics:

[0080] 1) Appearance: The coating is uniformly white, without bubbles, peeling, cracking, falling off, etc.

[0081] 2) Reflectivity of 200nm~2500nm: 0.92;

[0082] 3) Emissivity of 8μm to 13μm: 0.95;

[0083] 4) UV aging resistance: After 1000h UV aging, the reflectivity change is ≤0.01, and the emissivity change is ≤0.01.

[0084] 5) Temperature difference with ambient temperature: 10℃ (ambient temperature 35℃).

[0085] Example 3

[0086] (1) Preparation of base coating: BaSO4 with different particle sizes, film-forming substances and solvents are mixed, the particle size is 0.06μm to 0.16μm, the purity is ≥99.9%, and the volume fraction is 5%; the BaSO4 particle size is 0.4μm to 0.6μm, the purity is ≥99.9%, and the volume fraction is 30%; the BaSO4 particle size is 0.8μm to 1μm, the purity is ≥99.9%, and the volume fraction is 30%; potassium silicate aqueous solution is selected as the film-forming substance in the base coating, and the volume fraction of the film-forming substance in the bottom layer is 35%. The weight ratio of the film-forming substance to the solvent is 1:2.6, and the solvent is deionized water. Grinding and dispersion are used to disperse and mix the base coating, and the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 6mm, the grinding medium volume is 75%, the rotation speed is 180rpm, and the grinding and dispersion time is 6h. After grinding and dispersion, the slurry is taken out and filtered through a 200-mesh gauze to obtain the base coating.

[0087] (2) Preparation of topcoat coating: Lanthanum hydroxide is selected as the top layer filler, with a particle size of 3 μm, a purity of ≥99.9%, and a volume fraction of 60% for the top layer filler. Potassium silicate aqueous solution is selected as the film-forming substance in the topcoat, and the volume fraction of the film-forming substance in the topcoat is 40%. The top layer filler, the film-forming substance and the solvent are mixed, and the weight ratio of the film-forming substance to the solvent is 1:2.4, and deionized water is selected as the solvent. Grinding and dispersion are used to disperse and mix the base coating, and the grinding medium is zirconium oxide, which is spherical, has a purity of ≥99.9%, a particle size of 6 mm, a grinding medium volume of 75%, a rotation speed of 180 rpm, and a grinding and dispersion time of 6 hours. After the grinding and dispersion is completed, the slurry is taken out and filtered with a 200-mesh gauze to obtain the top layer coating.

[0088] (3) Preparation of low-absorption and high-emission radiation cooling coating: Before spraying the substrate, use aviation gasoline, acetone and ethanol to clean the surface, grind or sandblast before spraying the coating, add a special curing agent to the coating before spraying, spray the primer first and then the topcoat, and control the thickness of each spraying to 20μm. After the surface is dry, the next spraying is carried out. After spraying, cure at room temperature for 16h, bake at 50℃ for 4h, and bake at 80℃ for 24h. After baking, naturally cool to room temperature to obtain a low-absorption and high-emission radiation cooling coating. The specific thickness of the further coating is: 200μm for the primer and 60μm for the topcoat.

[0089] The low-absorption and high-emission radiation cooling coating prepared in this embodiment has the following characteristics:

[0090] 1) Appearance: The coating is uniformly white, without bubbles, peeling, cracking, falling off, etc.

[0091] 2) Reflectivity from 200nm to 2500nm: 0.91;

[0092] 3) Emissivity of 8μm to 13μm: 0.93;

[0093] 4) UV aging resistance: After 1000h UV aging, the reflectivity change is ≤0.01, and the emissivity change is ≤0.01.

[0094] 5) Temperature difference with ambient temperature: 7℃ (ambient temperature 35℃).

[0095] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0096] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A low-absorption and high-emission radiation cooling coating material, characterized in that: Includes base coat and top coat; Taking the total volume fraction of the low coating as 100%, the low coating comprises the following components in volume fractions: Taking the total volume fraction of the top coating as 100%, the top coating comprises the following components in volume fractions: Surface filler 50% to 70%; Film-forming substances 30% to 50%.

2. The low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: The reflectivity of the material at 200nm to 2500nm is 0.90 to 0.92; the emissivity at 8μm to 13μm is 0.92 to 0.95; after 1000h of UV aging, the reflectivity changes by ≤0.01, and the emissivity changes by ≤0.01; when the ambient temperature is 30°C, the temperature difference with the ambient temperature is 5°C to 10°C.

3. A method for preparing a low-absorption and high-emission radiation cooling coating material, characterized in that: include: S1: BaSO4 with different particle sizes, film-forming material and solvent are dispersed and mixed to obtain a bottom slurry; The bottom layer slurry is filtered to obtain a bottom layer coating; S2 disperses and mixes the surface layer filler, the film-forming material and the solvent to obtain a surface layer slurry; Filtering the surface layer slurry to obtain the surface layer coating; S3 adds curing agent to the base coating and the top coating; The base coating with curing agent added is sprayed on the surface of the substrate, and then the top coating with curing agent added is sprayed on the surface of the base coating; After spraying, curing is performed to obtain a coating.

4. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In the bottom slurry, the mass ratio of film-forming substance to solvent is 1:2.2 to 1:3.0; In the surface layer slurry, the mass ratio of the film-forming substance to the solvent is 1:2.0 to 1:2.

8.

5. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In step S1 and step S2, the film-forming material includes one or more of fluorine-containing acrylic resin, silicone resin or potassium silicate aqueous solution; the solid content of the potassium silicate aqueous solution is 30%; The solvent is an oily solvent or an aqueous solvent. The oily solvent includes one or more of butyl acetate, xylene or n-butanol, and the aqueous solvent includes deionized water.

6. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In step S1, the BaSO4 with different particle sizes includes BaSO4 with a particle size of 0.06 μm to 0.16 μm, BaSO4 with a particle size of 0.4 μm to 0.6 μm, and BaSO4 with a particle size of 0.8 μm to 1 μm; In step S2, the surface layer filler is one or more of europium oxide or gadolinium oxide, and the particle size is 3 μm to 5 μm.

7. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In step S1 and step S2, the dispersion and mixing method is grinding dispersion, the grinding medium is zirconium oxide, the zirconium oxide is spherical, the zirconium oxide purity is ≥99.9%, the zirconium oxide particle size is 4mm-8mm, the volume fraction of the grinding medium in the entire grinding tank volume is 65%-80%, the rotation speed is 120-220rpm, and the grinding dispersion time is 4h-8h; In step S1 or step S2, the bottom layer slurry or the surface layer slurry is filtered using a 120-240 mesh gauze to obtain a bottom layer coating.

8. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In step S3, when spraying the base coating or the surface coating, the thickness of each spraying is 20 μm to 30 μm, and the next spraying is performed after the surface is dry, until the total thickness of the base coating after spraying is 180 μm to 260 μm, and the total thickness of the surface coating is 50 to 100 μm.

9. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: In step S3, before spraying the primer with the curing agent added thereto on the surface of the substrate, the surface of the substrate is cleaned, which specifically includes: Use aviation gasoline, acetone or ethanol to clean the surface, and then perform grinding or sandblasting pretreatment; The curing method comprises: curing at room temperature for 10 hours to 20 hours, then baking at 40 to 60 degrees Celsius for 3 hours to 5 hours, and then baking at 70 to 90 degrees Celsius for 20 hours to 32 hours; and naturally cooling to room temperature after baking to obtain a coating.

10. The method for preparing a low-absorption and high-emission radiation cooling coating material according to claim 1, characterized in that: The coating obtained in step S3 includes a primer layer and a top coat layer; Taking the total volume fraction of the base coating as 100%, the low coating comprises the following components by volume fraction: Taking the total volume fraction of the top coating as 100%, the top coating comprises the following components in volume fractions: Surface filler 50% to 70%; Film-forming substances 30% to 50%.

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