Radiation refrigeration coating as well as preparation method and application thereof

Abstract

The invention discloses a radiation refrigeration coating as well as a preparation method and application thereof, and relates to the technical field of material preparation. The preparation method comprises the following steps: sintering hexagonal boron nitride, and removing boron oxide to obtain modified boron nitride powder; the preparation method comprises the following steps: reacting supramolecular polysiloxane with methoxypolyethylene glycol to obtain hyperbranched polysiloxane; the modified boron nitride powder and hyperbranched polysiloxane are subjected to hydrolysis on boron nitride under the alkaline condition, and silane modified boron nitride is obtained; the silane modified boron nitride is added into a polyurethane coating matrix to form the radiation refrigeration coating. The silicon-oxygen modified group is introduced to the surface of the boron nitride, so that the interaction between the boron nitride and the coating group is greatly improved, and the stability of the coating is improved; the coating can be cured under different environmental conditions, and construction on power equipment is facilitated; the formed radiation refrigeration coating is high in sunlight reflectivity, high in mid-infrared emissivity and high in heat dissipation capacity for power equipment.

Description

Technical Field

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

[0002] Heat dissipation is crucial to the safe and stable operation of power equipment and the continuous and reliable power supply of the power grid. Overheating of power equipment is a major cause of failure and lifespan reduction. The insulation and structural conditions of power equipment are closely related to its heat dissipation performance. Excessively high operating temperatures accelerate the aging of insulation materials, thereby shortening the equipment's service life. Therefore, overheating of power equipment has always been a key issue that affects its normal operation and threatens the reliability of the power grid. How to achieve efficient heat dissipation and reduce operating temperatures in power equipment is a key issue in power equipment operation and maintenance. Currently, the most common method of heat dissipation for outdoor power equipment is to transfer internal heat to the equipment surface or heat sink through heat conduction, and then transfer the heat to the surrounding environment through convection. Thermal radiation is not effectively utilized. However, when equipment is exposed to high temperatures, strong sunlight, heavy loads, or even overloads, traditional heat dissipation structures are difficult to optimize and cannot meet the requirements for controlling equipment temperature rise. Furthermore, with the construction of new power systems and the increasing shortage of urban land resources, the problems associated with adding heat dissipation equipment, such as high energy consumption, high noise, large space requirements, and increased maintenance difficulties, need to be urgently addressed. Therefore, there is an urgent need to develop a new type of power equipment heat dissipation technology that is efficient, easy to use, and does not change the equipment structure, so as to improve the heat dissipation capacity of the equipment, improve the reliability of the equipment in extreme environments, ensure the safety of the equipment and the power grid, and ensure reliable power supply.

[0003] Radiative cooling material technology is a new type of passive zero-energy cooling technology. This technology can effectively block the heat input from outdoor sunlight and transmit the heat of power equipment in the form of infrared thermal radiation through the atmospheric window (8-13 microns) to outer space close to absolute zero (3K), thereby achieving excellent cooling effects without requiring any energy and without greenhouse gas emissions. It has great potential in extending equipment life, maintaining stable operation of the power grid, and saving energy and reducing emissions. Among the various complex materials for realizing radiative cooling, polymer-dielectric coatings show great potential due to their easy processing and large-scale production. In addition, they have the advantage of being easy to apply - they can be directly used to transform existing building surfaces and equipment housings with different compositions, particles, and structures.

[0004] Research on radiative cooling coatings for power equipment plays a crucial role in improving the heat dissipation and heat distribution performance of outdoor power equipment, reducing operating temperatures and temperature unevenness, enhancing operational stability, and ensuring grid security and power supply reliability. The research findings are of great significance in promoting the application of new materials in power grids and advancing the deep integration of new materials with advanced power technologies. To improve the performance of radiative cooling coatings and further promote their practical application, it is necessary to develop a new type of radiative cooling coating for power equipment. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a radiative cooling coating that meets the needs of power equipment, so that the coating has an ultra-high sunlight reflectivity, which can significantly reduce the input of sunlight heat. At the same time, the coating has a high and medium infrared emissivity, which improves the heat dissipation effect of the coating.

[0006] To achieve the above object, the present invention provides a method for preparing a radiant cooling coating, which comprises the following steps:

[0007] S1. Sintering hexagonal boron nitride in an air atmosphere and then cooling to obtain a sintered hexagonal boron nitride block;

[0008] S2, dispersing the sintered hexagonal boron nitride block obtained in S1 in a mixed dispersion containing water, isopropyl alcohol, polyvinyl alcohol and sulfuric acid to remove boron oxide, and filtering to obtain modified boron nitride powder;

[0009] S3, mixing a silicon source and anhydride, and adding tetrabutyl titanate to react to obtain supramolecular polysiloxane;

[0010] S4, mixing the supramolecular polysiloxane obtained in S3 with polyethylene glycol monomethyl ether to react to obtain a hyperbranched polysiloxane;

[0011] S5, dispersing the modified boron nitride powder obtained in S2 and the hyperbranched polysiloxane obtained in S4 in a dispersion, adding a pH regulator to hydrolyze the hyperbranched polysiloxane on the boron nitride, and filtering to obtain silane-modified boron nitride;

[0012] S6. Evenly mix the silane-modified boron nitride powder obtained in S5 with a polyurethane coating matrix and a coating thinner to obtain a radiant cooling coating.

[0013] As a further preferred technical solution of the present invention, in step S1: the sintering temperature is 900-1100° C., the sintering time is 0.5-2 hours; and / or the particle size of the hexagonal boron nitride is micron-sized.

[0014] As a further preferred technical solution of the present invention, in step S2, the concentration of sulfuric acid in the mixed dispersion is 0.3 to 1.0 mol / L

[0015] As a further preferred technical solution of the present invention, in step S3: the silicon source is tetraethoxysilane, the acid anhydride is acetic anhydride; and / or the reaction temperature is 100-130° C., and the reaction is stirred at 500-600 rpm for 3-6 hours.

[0016] As a further preferred technical solution of the present invention, in step S4: the molecular weight of polyethylene glycol monomethyl ether is 350, and the molar ratio of supramolecular polysiloxane to polyethylene glycol monomethyl ether is 10:1; and / or, the reaction temperature is 100-130°C, and the reaction is stirred at 500-600 rpm for 3-6 hours.

[0017] As a further preferred technical solution of the present invention, in step S5: the mass ratio of hyperbranched polysiloxane to modified boron nitride powder is 5:2; and / or ammonia water is used as a pH adjuster to adjust the pH value to 8-10.

[0018] As a further preferred technical solution of the present invention, the paint thinner is at least one of xylene and butyl acetate.

[0019] According to another aspect of the present invention, the present invention also provides a radiant cooling coating.

[0020] According to another aspect of the present invention, the present invention further provides an application of a radiation cooling paint, wherein the radiation cooling paint is used to form a radiation cooling coating on the surface of a substrate.

[0021] As a further preferred technical solution of the present invention, the radiant cooling coating is applied to the substrate surface of power equipment. Specifically, the radiant cooling coating is applied to a suitable substrate (such as cold-rolled steel) and allowed to cure under specific conditions to produce a radiant cooling coating for power equipment. Curing conditions include: indoor ambient temperature, outdoor exposure to sunlight, or a forced air oven. The resulting radiant cooling coating has an average solar reflectivity of 97% and an average mid-infrared emissivity of 95%.

[0022] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0023] First, the present invention proposes a method for silanization modification of boron nitride, which significantly increases the sunlight reflectivity by introducing materials with different refractive indices to induce multiple scattering;

[0024] Second, the present invention proposes a method for silanization modification of boron nitride, which increases the mid-infrared emissivity by introducing a silicon oxide compound with a high extinction coefficient in the mid-infrared band;

[0025] Third, the present invention proposes a method for silanization modification of boron nitride, which significantly enhances the interaction between boron nitride and coating groups by introducing silicon-oxygen modified groups on the surface of boron nitride, thereby improving the stability of the coating.

[0026] Fourth, the radiative cooling coating for power equipment prepared by the present invention can be set with different curing conditions according to actual application requirements, facilitating construction on power equipment;

[0027] Fifth, the radiation cooling coating for electric power equipment prepared by the present invention has high sunlight reflectivity and high mid-infrared emissivity, and has strong heat dissipation capability for electric power equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 The SEM image (a) and corresponding elemental energy spectrum (bd) of the modified boron nitride in the radiative cooling coating for power equipment prepared in Example 1 of the present invention;

[0030] Figure 2 (a) The reflection spectrum of the radiation cooling coating for power equipment prepared in Example 1 of the present invention in the sunlight band and (b) the emission spectrum in the mid-infrared band;

[0031] Figure 3 The SEM photograph (a) and corresponding elemental energy spectra (b and c) of the modified boron nitride in the radiation cooling coating for power equipment prepared in Comparative Example 1 of the present invention are shown;

[0032] Figure 4 The reflection spectrum (a) in the sunlight band and the emission spectrum (b) in the mid-infrared band of the radiative cooling coating for power equipment prepared in Example 1 of the present invention are shown in FIG.

[0033] Figure 5 (a) The reflection spectrum of the radiation cooling coating for power equipment prepared in Example 1 of the present invention in the sunlight band and (b) the emission spectrum in the mid-infrared band;

[0034] Figure 6 (a) The reflection spectrum in the sunlight band and (b) the emission spectrum in the mid-infrared band of the radiation cooling coating for power equipment prepared in Example 1 of the present invention.

[0035] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0036] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0037] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0038] The morphology of the modified boron nitride in the radiation cooling coating for electric power equipment prepared in the following examples was observed using a scanning electron microscope (Apreo 2S, Thermo Fisher Scientific, USA) and its equipped energy dispersive spectrometer.

[0039] The spectra of the radiative cooling coatings for power equipment prepared in the following examples were measured using a UV-visible-near infrared spectrophotometer (Lamda 950, PerkinElmer, USA) and a Fourier transform infrared spectrometer (Nicolet 6700, Thermo Fisher, USA).

[0040] Example 1

[0041] A method for preparing a radiative cooling coating for electric power equipment comprises the following steps:

[0042] S1. Add 10 g of hexagonal boron nitride powder with an average particle size of 3 μm into an alumina crucible with a volume of 250 mL, place it in a muffle furnace, and heat it to 1000°C at a rate of 5°C per minute in an air atmosphere, and maintain it for 1 hour. After natural cooling, obtain a sintered hexagonal boron nitride block;

[0043] S2. Disperse the sintered hexagonal boron nitride blocks obtained in S1 in a mixed dispersion containing 100 mL of water, 100 mL of isopropyl alcohol, 0.5 g of polyvinyl alcohol, and sulfuric acid, wherein the concentration of the sulfuric acid is 0.5 mol / L. Stir vigorously for 12 hours to remove the boron oxide, then filter and wash the obtained boron nitride dispersion, and then vacuum dry at 90°C to obtain a modified boron nitride powder.

[0044] S3, mixing tetraethoxysilane and acetic anhydride in a molar ratio of 2.1:1, adding 0.1 mol % of tetrabutyl titanate, heating to 130° C. and stirring at 600 rpm for 6 h to obtain supramolecular polysiloxane;

[0045] S4, mixing polyethylene glycol monomethyl ether with a molecular weight of 350 and the supramolecular polysiloxane obtained in step S3 in a molar ratio of 10:1, heating to 130° C. and stirring at 600 rpm for 6 h to obtain a hyperbranched polysiloxane;

[0046] S5, dispersing the modified boron nitride powder obtained in S2 and the hyperbranched polysiloxane obtained in S4 in an ethanol / water dispersion with a volume ratio of 1:1 at a mass ratio of 1:2.5, adding ammonia water to adjust the pH to 10, stirring at room temperature for 24 hours to hydrolyze the hyperbranched polysiloxane on the boron nitride, and filtering to obtain silane-modified boron nitride;

[0047] S6. Mix 40 parts of the modified boron nitride powder obtained in S5, 100 parts of a polyurethane coating base (Interthane 990 A component from Akzo Nobel), 17 parts of a polyurethane coating base (Interthane 990 curing agent from Akzo Nobel), and 30 parts of a coating thinner (GTA 713 from Akzo Nobel) in a mass ratio, and stir vigorously to mix them evenly to obtain a radiant cooling coating.

[0048] S7. Spray the radiation cooling coating obtained in S6 onto the coating test cold-rolled steel plate with a spraying thickness of 200±10 μm, and let it stand at room temperature for 48 hours to solidify the coating to obtain a radiation cooling coating for power equipment.

[0049] Figure 1 The SEM image and corresponding energy spectrum of the silane-modified boron nitride in the radiative cooling coating for power equipment prepared in Example 1 of the present invention show the presence of a large amount of oxygen and silicon elements in the silane-modified boron nitride, and their distribution is highly consistent with that of nitrogen. This indicates that the silane-modified boron nitride introduces siloxy groups, which helps enhance sunlight scattering and infrared emission properties.

[0050] Figure 2 This is a spectrum picture of the radiation cooling coating for electric power equipment prepared in Example 1 of the present invention. From the picture, it can be calculated that the sunlight reflectivity of the radiation cooling coating for electric power equipment prepared in Example 1 is 97.3%, and the mid-infrared emissivity is 95.2%.

[0051] Comparative Example 1

[0052] As a control experiment of Example 1, the difference is that unmodified boron nitride powder is directly used as filler in the polyurethane matrix. The specific steps are as follows:

[0053] S1. Mix 40 parts of unmodified boron nitride powder, 100 parts of polyurethane coating base (Interthane 990 A component from Akzo Nobel), 17 parts of polyurethane coating base (Interthane 990 curing agent from Akzo Nobel), and 30 parts of coating thinner (GTA 713 from Akzo Nobel) in a mass ratio, and mix them evenly under vigorous stirring to obtain a radiant cooling coating;

[0054] S2. Spray the radiation cooling coating obtained in S1 onto the coating test cold-rolled steel plate with a spraying thickness of 200±10 μm, and let it stand at room temperature for 48 hours to solidify the coating to obtain a radiation cooling coating for power equipment.

[0055] Figure 3 The SEM photograph and corresponding energy spectrum of the modified boron nitride in the radiative cooling coating for power equipment prepared in Comparative Example 1 show that the boron nitride in this example was not modified, which made it difficult to mix evenly in step S2, and the coating eventually exhibited agglomeration and cracking.

[0056] Figure 4 This is a spectral picture of the radiation cooling coating for electric equipment prepared in Comparative Example 1. From the picture, it can be calculated that the sunlight reflectivity of the radiation cooling coating for electric equipment prepared in Comparative Example 1 is 85.0%, and the mid-infrared emissivity is 92.8%. Compared with Example 1, the sunlight reflectivity of the radiation cooling coating for electric equipment prepared in Comparative Example 1 is greatly reduced.

[0057] Comparative Example 2

[0058] As a control experiment of Example 1, the difference is that tetraethoxysilane is used to replace the hyperbranched polysiloxane. The specific steps are as follows:

[0059] S1. Add 10 g of hexagonal boron nitride powder with an average particle size of 3 μm into an alumina crucible with a volume of 250 mL, place it in a muffle furnace, and heat it to 1000°C at a rate of 5°C per minute in an air atmosphere, and maintain it for 1 hour. After natural cooling, obtain a sintered hexagonal boron nitride block;

[0060] S2. Disperse the sintered hexagonal boron nitride blocks obtained in S1 in a mixed dispersion containing 100 mL of water, 100 mL of isopropyl alcohol, 0.5 g of polyvinyl alcohol, and sulfuric acid, where the concentration of the sulfuric acid is 0.5 mol / L. Stir vigorously for 12 hours to remove the boron oxide. Filter and wash the obtained boron nitride dispersion, then vacuum dry at 90°C to obtain a modified boron nitride powder.

[0061] S3, dispersing the modified boron nitride powder obtained in S2 and tetraethoxysilane in a mass ratio of 1:2.5 in an ethanol / water dispersion with a volume ratio of 1:1, adding ammonia water to adjust the pH to 10, stirring at room temperature for 24 hours to hydrolyze the hyperbranched polysiloxane on the boron nitride, and filtering to obtain silane-modified boron nitride;

[0062] S4. Mix 40 parts of unmodified boron nitride powder, 100 parts of polyurethane coating base (Interthane 990 A component from Akzo Nobel), 17 parts of polyurethane coating base (Interthane 990 curing agent from Akzo Nobel), and 30 parts of coating thinner (GTA 713 from Akzo Nobel) in a mass ratio, and mix them evenly under vigorous stirring to obtain a radiant cooling coating.

[0063] S5. Spray the radiation cooling coating obtained in S4 onto the coating test cold-rolled steel plate with a spraying thickness of 200±10 μm, and let it stand at room temperature for 48 hours to solidify the coating, thereby obtaining a radiation cooling coating for power equipment.

[0064] Figure 5 This is a spectrum image of the radiative cooling coating for power equipment prepared in Comparative Example 2. From this image, it can be calculated that the solar reflectivity of the radiative cooling coating for power equipment prepared in Comparative Example 2 is 90.2%, and the mid-infrared emissivity is 94.6%. Compared with Example 1, the solar reflectivity of the radiative cooling coating for power equipment prepared in Comparative Example 2 is lower, indicating that the introduction of small-molecule silane cannot effectively modify the boron nitride. Its hydrolysis products are randomly dispersed in the coating, contributing little to the solar reflectivity.

[0065] Comparative Example 3

[0066] As a control experiment of Example 1, the difference is that the sintering modification step of hexagonal boron nitride is omitted. The specific steps are as follows:

[0067] S1, tetraethoxysilane and acetic anhydride were mixed in a molar ratio of 2.1:1, and 0.1 mol% of tetrabutyl titanate was added, and the mixture was heated to 130° C. and stirred at 600 rpm for 6 h to obtain supramolecular polysiloxane;

[0068] S2, mixing polyethylene glycol monomethyl ether with a molecular weight of 350 and the supramolecular polysiloxane obtained in step S1 in a molar ratio of 10:1, heating to 130° C. and stirring at 600 rpm for 6 h to obtain a hyperbranched polysiloxane;

[0069] S3, dispersing the unmodified hexagonal boron nitride powder and the hyperbranched polysiloxane obtained in S2 in a mass ratio of 1:2.5 in an ethanol / water dispersion with a volume ratio of 1:1, adding ammonia water to adjust the pH to 10, stirring at room temperature for 24 hours to hydrolyze the hyperbranched polysiloxane on the boron nitride, and filtering to obtain silane-modified boron nitride;

[0070] S4. Mix 40 parts of unmodified boron nitride powder, 100 parts of polyurethane coating base (Interthane 990 A component from Akzo Nobel), 17 parts of polyurethane coating base (Interthane 990 curing agent from Akzo Nobel), and 30 parts of coating thinner (GTA 713 from Akzo Nobel) in a mass ratio, and mix them evenly under vigorous stirring to obtain a radiant cooling coating.

[0071] S5. Spray the radiation cooling coating obtained in S4 onto the coating test cold-rolled steel plate with a spraying thickness of 200±10 μm, and let it stand at room temperature for 48 hours to solidify the coating, thereby obtaining a radiation cooling coating for power equipment.

[0072] Figure 6 This is a spectrum image of the radiative cooling coating for power equipment prepared in Comparative Example 3 of the present invention. From this image, it can be calculated that the solar reflectivity of the radiative cooling coating for power equipment prepared in Comparative Example 3 is 93.1%, and the mid-infrared emissivity is 92.3%. Compared with Example 1, the radiative cooling performance of the coating for power equipment prepared in Comparative Example 3 is reduced. This indicates that unmodified BN has difficulty adsorbing hyperbranched polysiloxane, resulting in the hydrolysis products being randomly dispersed in the coating, and their contribution to solar reflectivity is low.

[0073] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a radiant cooling coating, characterized in that: The following steps are involved: S1. Sintering hexagonal boron nitride in an air atmosphere and then cooling to obtain a sintered hexagonal boron nitride block; S2, dispersing the sintered hexagonal boron nitride block obtained in S1 in a mixed dispersion containing water, isopropyl alcohol, polyvinyl alcohol and sulfuric acid to remove boron oxide, and filtering to obtain modified boron nitride powder; S3, mixing a silicon source and anhydride, and adding tetrabutyl titanate to react to obtain supramolecular polysiloxane; S4, mixing the supramolecular polysiloxane obtained in S3 with polyethylene glycol monomethyl ether to react to obtain a hyperbranched polysiloxane; S5, dispersing the modified boron nitride powder obtained in S2 and the hyperbranched polysiloxane obtained in S4 in a dispersion, adding a pH regulator to hydrolyze the hyperbranched polysiloxane on the boron nitride, and filtering to obtain silane-modified boron nitride; S6. Evenly mix the silane-modified boron nitride powder obtained in S5 with a polyurethane coating matrix and a coating thinner to obtain a radiant cooling coating.

2. The method for preparing the radiant cooling coating according to claim 1, characterized in that: In step S1 : the sintering temperature is 900-1100° C., and the sintering time is 0.5-2 hours; and / or the particle size of the hexagonal boron nitride is micron-sized.

3. The method for preparing the radiant cooling coating according to claim 1, characterized in that: In step S2, the concentration of sulfuric acid in the mixed dispersion is 0.3-1.0 mol / L.

4. The method for preparing the radiant cooling coating according to claim 1, characterized in that: In step S3, the silicon source is tetraethoxysilane, the acid anhydride is acetic anhydride; and / or the reaction temperature is 100-130° C., and the reaction is stirred at 500-600 rpm for 3-6 hours.

5. The method for preparing the radiant cooling coating according to claim 1, characterized in that: In step S4: the molecular weight of polyethylene glycol monomethyl ether is 350, and the molar ratio of supramolecular polysiloxane to polyethylene glycol monomethyl ether is 10:1; and / or the reaction temperature is 100-130° C., and the reaction is stirred at 500-600 rpm for 3-6 hours.

6. The method for preparing the radiant cooling coating according to claim 1, characterized in that: In step S5: the mass ratio of hyperbranched polysiloxane to modified boron nitride powder is 5:2; and / or ammonia water is used as a pH adjuster, and the pH value is adjusted to 8-10.

7. The method for preparing the radiant cooling coating according to claim 1, characterized in that: The paint thinner is at least one of xylene and butyl acetate.

8. A radiant cooling coating prepared according to the method according to any one of claims 1 to 7.

9. An application of the radiant cooling coating according to claim 8, characterized in that: The radiation cooling paint is used to form a radiation cooling coating on the surface of a substrate.

10. The use according to claim 9, characterized in that The radiation cooling coating is used for the substrate surface of electric equipment.

Images