Environment-friendly radiation refrigeration self-cleaning coating and preparation method thereof

Abstract

The invention discloses an environment-friendly radiation refrigeration self-cleaning coating and a preparation method thereof, and belongs to the technical field of building coatings. Photocatalyst filler is a zinc oxide-silver oxide composite material; the radiation cooling filler is prepared from nano indium tin oxide, polymethylpentene and a rare earth silicate compound; the nano indium tin oxide is prepared from indium trioxide and tin oxide; the nano material is composed of carbon nanotubes, spinel structure micro powder and rare earth oxide. The base material is prepared from polypropylene glycol, toluene diisocynate and anti-radiation resin; the auxiliary agent is prepared from a flatting agent, a defoaming agent, a neutralizing agent and a flame retardant. According to the present invention, the ratio of the auxiliary agents added to the coating material is appropriate, the coating material has the performance of the auxiliary agents, the influence on the coating material performance due to the excessive addition of the auxiliary agents can be avoided, and the addition of the anti-radiation resin, the polymethylpentene and other materials enables the material to have characteristics of durability and strong adhesion, and the phenomena of cracking, peeling and the like after the material is attached to the substrate surface can be avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of architectural coatings, and in particular relates to an environmentally friendly radiation cooling self-cleaning coating and a preparation method thereof. Background Art

[0002] With the advent of modern society, people have new requirements for living environment. Traditional cement paint has the risk of falling off and peeling after a period of use. Moreover, after being applied to the wall or substrate surface, it has no obvious shielding effect on the radiation in the light. Moreover, it is placed in the outdoor environment for a long time and is affected by dust, rain, snow, sunlight, etc. in the atmosphere, which can easily shorten the effective service life and cannot meet the requirements of today's society. Therefore, with the progress of socialization, modern society has higher performance requirements for exterior wall coatings, such as self-cleaning performance and refrigeration performance.

[0003] At present, there are some coatings with single functions on the market, which have achieved some effects in their application fields, but their comprehensive performance is general and cannot meet the long-term effect. After a period of use, the stain resistance will be significantly reduced. After being exposed to wind and rain for a long time, the coating surface will be seriously contaminated with dust, resulting in a decrease in the radiation cooling effect. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide an environmentally friendly radiation cooling self-cleaning coating and a preparation method thereof, so as to solve the problem that the current coating has a single performance and a short effective time.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The invention discloses an environment-friendly radiation cooling self-cleaning coating, which comprises a photocatalyst filler, a radiation cooling filler, a nano material, a base material and an auxiliary agent; the photocatalyst filler is a zinc oxide-silver oxide composite material; the radiation cooling filler is composed of nano indium tin oxide, polymethylpentene and a rare earth silicate compound; the nano indium tin oxide is prepared from indium trioxide and tin oxide; the nano material is composed of nano carbon tubes, spinel structure micro powder and rare earth oxide; the base material is composed of polypropylene glycol, toluene diisocyanate and radiation-proof resin; the auxiliary agent is composed of a leveling agent, a defoaming agent, a neutralizer and a flame retardant.

[0007] Furthermore, by mass fraction, the photocatalyst filler is 30-50 parts, the radiation cooling filler is 35-60 parts, the nano material is 20-35 parts; the base material is 10-25 parts; and the auxiliary agent is 4-8 parts.

[0008] Furthermore, the mass ratio of the nano-indium tin oxide, polymethylpentene and rare earth silicate compound is 10-20: 5-10: 20-30.

[0009] Furthermore, the radiation protection resin consists of terpene resin and alicyclic epoxy resin SR-2021P.

[0010] Furthermore, the mass ratio of the carbon nanotubes, spinel structure powder and rare earth oxide is 7-12: 5-8: 8-15; the carbon nanotubes are composed of one or more of carbon nanotubes, carbon nanofibers and nanocarbon balls; the rare earth oxides are composed of one or more of yttrium oxide, lanthanum oxide, cerium oxide and praseodymium oxide.

[0011] Furthermore, it also includes a method for preparing an environmentally friendly radiation cooling self-cleaning coating, comprising the following steps:

[0012] S1. After mixing polypropylene glycol and toluene diisocyanate, add radiation protection resin to form a base material;

[0013] S2, adding nano-indium tin oxide, polymethylpentene, and rare earth silicate compound to the zinc oxide-silver oxide composite material in proportion and mixing evenly, and then continuing to add nano-carbon tubes, spinel structure powder, and rare earth oxide and stirring evenly to form a first mixed material;

[0014] S3, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0015] S4. Add a leveling agent, a defoaming agent, a neutralizing agent, and a flame retardant to the second mixture, mix and stir evenly, adjust the pH value, perform heat preservation treatment, and then naturally cool to room temperature to obtain a radiation refrigeration self-cleaning coating.

[0016] Furthermore, the preparation method of the zinc oxide-silver oxide composite material is: using a liquid phase coprecipitation method to prepare a zinc-based precursor, calcining at 500-600°C to prepare porous sponge-like zinc oxide; then using silver nitrate as a precursor, adding sodium hydroxide to react under alkaline environmental conditions, and drying to obtain silver oxide nanoparticles; magnetically stirring the obtained porous sponge-like zinc oxide and silver oxide nanoparticles under alkaline conditions, and mixing them evenly to obtain the zinc oxide-silver oxide composite material.

[0017] Furthermore, the preparation method of the nano indium tin oxide is: electrolysis is performed using metal indium as an anode, an inert electrode as a cathode, and an ammonium salt aqueous solution as an electrolyte; after electrolysis, the electrolyte is heated to a preset temperature, and an ammonia solution is continuously added for stirring, solid-liquid separation is performed, and high-temperature calcination is performed to obtain nano indium tin oxide.

[0018] Furthermore, the preparation method of the rare earth silicate compound is: nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70-80°C to obtain a gel solution; then pre-calcined at 120-150°C for 36 hours; and then heat treated at 600-900°C for 30 hours to obtain a rare earth silicate compound.

[0019] The beneficial effects of the present invention are:

[0020] 1. The coating of the present invention has a significant cooling effect. The zinc oxide-silver oxide composite material of the present invention has the advantages of large specific surface area and high photocatalytic reaction active sites, and has the characteristics of both zinc oxide and silver oxide. It not only reduces the amount of precious metal silver, but also improves the photocatalytic degradation efficiency of the catalyst; and the high reflectivity of the spectral reflective filler to sunlight and the high emissivity of the radiation cooling filler in the infrared band, the coating can significantly reduce the temperature of the surface of the object. The experimental data of the present invention show that under direct sunlight at noon, the coating can reduce the temperature of the contacted object by 10-16°C.

[0021] 2. The coating of the present invention has excellent cooling and radiation protection performance. The nano-indium tin oxide in the coating has good stability, uniform particle size and uniform distribution. It can be used in combination with polymethylpentene and rare earth silicate to have heat insulation, corrosion resistance, sound insulation and other functions. It has low thermal conductivity, strong adhesion and no pollution. It can be applied to the surface of equipment of any shape within -5℃-800℃. The radiation cooling self-cleaning coating prepared by the above materials can effectively reflect the ultraviolet and visible light bands in sunlight, reduce the absorption of sunlight energy, and protect objects from radiation damage.

[0022] 3. The coating of the present invention is environmentally friendly and energy-saving. No harmful substances such as cadmium, lead, chromium, etc. are added to the coating, and there is no volatile substances such as heavy metals and formaldehyde. It is an energy-saving and environmentally friendly product. At the same time, its passive cooling principle does not require additional energy consumption, which helps to save energy and reduce emissions.

[0023] 4. The proportion of additives added to the coating of the present invention is appropriate. The prepared coating has both the performance of the additives and will not affect the performance of the coating due to excessive addition of additives. The addition of radiation-proof resin, polymethylpentene and other materials not only makes the material durable and has strong adhesion, but also does not cause cracks, peeling and other phenomena after being attached to the surface of the substrate. It also makes the coating have radiation-proof effect, and its physical and chemical stability can withstand various harsh climate tests.

[0024] 5. The coating of the present invention has a wide range of applications. The coating can be applied to the surfaces of various materials such as steel, cast iron, galvanized, aluminum, copper, etc., and is suitable for various fields such as building exterior walls, industrial equipment, and transportation. In summary, the cooling and radiation-proof coating of the present invention has excellent performance in material selection, preparation method, and effect, and has broad application prospects and market potential.

[0025] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solution and beneficial effects of the invention clearer, the present invention provides the following drawings for illustration:

[0027] Figure 1 is a preparation flow chart of the present invention;

[0028] Figure 2 This is a comparison chart of temperature suppression between the embodiment of the present invention and common coatings. DETAILED DESCRIPTION

[0029] A method for preparing an environmentally friendly radiation cooling self-cleaning coating.

[0030] Example 1

[0031] S1. Add polypropylene glycol and toluene diisocyanate in a mass ratio of 3:3:4, stir and mix, and then add radiation protection resin to form 10 parts of base material;

[0032] S2. A zinc-based precursor is prepared by a liquid phase coprecipitation method, and a porous sponge-like zinc oxide is prepared after calcination at 500° C. Then, silver nitrate is used as a precursor, sodium hydroxide is added under alkaline environmental conditions to continue the reaction, and silver oxide nanoparticles are obtained after drying; and the porous sponge-like zinc oxide and the silver oxide nanoparticles are magnetically stirred under alkaline conditions to uniformly mix to obtain a zinc oxide-silver oxide composite material;

[0033] 8um nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then pre-calcined at 120°C for 36 hours; and then heat treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0034] Then, nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then, the solution is pre-calcined at 120°C for 36 hours; and then, heat-treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0035] S3, adding 35 parts of radiation cooling fillers composed of nano-indium tin oxide, polymethylpentene, and rare earth silicate compounds in a mass ratio of 10:5:20 to 30 parts of zinc oxide-silver oxide composite materials, mixing the above materials evenly, and then continuing to add 20 parts of nano-materials composed of nano-carbon tubes, spinel structure powder, and rare earth oxides in a mass ratio of 7:5:8, and continue to stir evenly to form a first mixed material;

[0036] S4, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0037] S5. Add a leveling agent, a defoaming agent, a neutralizing agent and a flame retardant in a mass ratio of 1:1:1:1 to the second mixture, mix and stir evenly, adjust the pH value to neutral, and then keep warm at 120°C for 3 hours, and then naturally cool to room temperature to obtain a cooling radiation protection coating.

[0038] Example 2

[0039] S1. Add polypropylene glycol and toluene diisocyanate in a mass ratio of 5:5:7, stir and mix, and then add radiation protection resin to form 17 parts of base material;

[0040] S2. A zinc-based precursor is prepared by a liquid phase coprecipitation method, and a porous sponge-like zinc oxide is prepared after calcination at 500° C. Then, silver nitrate is used as a precursor, sodium hydroxide is added under alkaline environmental conditions to continue the reaction, and silver oxide nanoparticles are obtained after drying; and the porous sponge-like zinc oxide and the silver oxide nanoparticles are magnetically stirred under alkaline conditions to uniformly mix to obtain a zinc oxide-silver oxide composite material;

[0041] 8um nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then pre-calcined at 120°C for 36 hours; and then heat treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0042] Then, nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then, the solution is pre-calcined at 120°C for 36 hours; and then, heat-treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0043] S3, adding 50 parts of radiation cooling fillers composed of nano-indium tin oxide, polymethylpentene, and rare earth silicate compounds in a mass ratio of 15:10:25 to 40 parts of zinc oxide-silver oxide composite materials, mixing the above materials evenly, and then continuing to add 28 parts of nano-materials composed of nano-carbon tubes, spinel structure powder, and rare earth oxides in a mass ratio of 10:8:10, and continue to stir evenly to form a first mixed material;

[0044] S4, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0045] S5. Add a leveling agent, a defoaming agent, a neutralizing agent and a flame retardant in a mass ratio of 1.5:2:1.5:2 to the second mixture, mix and stir evenly, adjust the pH value to neutral, and then keep warm at 120°C for 3 hours, and then naturally cool to room temperature to obtain a cooling radiation protection coating.

[0046] Example 3

[0047] S1. Add polypropylene glycol and toluene diisocyanate in a mass ratio of 7:7:11, stir and mix, and then add radiation protection resin to form 25 parts of base material;

[0048] S2. A zinc-based precursor is prepared by a liquid phase coprecipitation method, and a porous sponge-like zinc oxide is prepared after calcination at 500° C. Then, silver nitrate is used as a precursor, sodium hydroxide is added under alkaline environmental conditions to continue the reaction, and silver oxide nanoparticles are obtained after drying; and the porous sponge-like zinc oxide and the silver oxide nanoparticles are magnetically stirred under alkaline conditions to uniformly mix to obtain a zinc oxide-silver oxide composite material;

[0049] 8um nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then pre-calcined at 120°C for 36 hours; and then heat treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0050] Then, nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then, the solution is pre-calcined at 120°C for 36 hours; and then, heat-treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0051] S3, adding 60 parts of radiation cooling fillers composed of nano-indium tin oxide, polymethylpentene, and rare earth silicate compounds in a mass ratio of 20:10:30 to 50 parts of zinc oxide-silver oxide composite materials, mixing the above materials evenly, and then continuing to add 32 parts of nano-materials composed of nano-carbon tubes, spinel structure powder, and rare earth oxides in a mass ratio of 12:5:15, and continue to stir evenly to form a first mixed material;

[0052] S4, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0053] S5. Add a leveling agent, a defoaming agent, a neutralizing agent and a flame retardant in a mass ratio of 2:2:2:2 to the second mixture, mix and stir evenly, adjust the pH value to neutral, and then keep warm at 120°C for 3 hours, and then naturally cool to room temperature to obtain a cooling radiation protection coating.

[0054] In the material of the present invention, the zinc oxide-silver oxide composite material has the advantages of both zinc oxide and silver oxide, which not only reduces the amount of precious metal silver, but also improves the photocatalytic degradation efficiency by utilizing the material characteristics. Compared with pure silver oxide and zinc oxide, the same amount of composite material shows higher activity and efficiency in the photocatalytic reaction. In the cooling and radiation-proof coating of the present invention, the temperature of the surface of the object can be significantly reduced, and water can be cracked by photocatalytic technology to obtain clean energy hydrogen, degrade organic dyes, and no new harmful substances will be introduced or secondary pollutants will be generated during the process, thereby achieving environmentally friendly treatment. In the present invention, the prepared nano indium tin oxide has the characteristics of high purity, small particle size, large specific surface area, light transmittance, strong reflection of infrared light, low film resistance, high light transmittance, high conductivity, etc. The coating prepared by the method of the present invention in combination with other compatible raw materials can maximize the performance of each material material and make it applicable to industrial applications.

[0055] In order to demonstrate the superiority of the materials and methods of the present invention, comparative examples 1-4 are provided herein.

[0056] Comparative Example 1

[0057] S1. After mixing polypropylene glycol, toluene diisocyanate and radiation protection resin in a mass ratio of 7:7:11, add 25 parts of zinc oxide, 25 parts of silver oxide, and nano-indium tin oxide, polymethylpentene and rare earth silicate compounds in a mass ratio of 20:10:30, nano-carbon tubes, spinel structure powder and rare earth oxide in a mass ratio of 12:5:15, and leveling agent, defoamer, neutralizer and flame retardant in a mass ratio of 2:2:2:2, and continue to stir evenly to form a mixture;

[0058] S2. Let the mixture stand and adjust the pH value to neutral to obtain the coating.

[0059] The difference between this comparative example and Example 1 is that the method specified in the present invention is not followed, and all materials are directly mixed without dividing the steps during preparation, which fails to stimulate the activity of each product and fails to maximize the material effect. The performance of the obtained product coating in all aspects is relatively general and cannot be used for a long time.

[0060] Comparative Example 2

[0061] S1. Add polypropylene glycol and toluene diisocyanate in a mass ratio of 3:3:4, stir and mix, and then add radiation protection resin to form 10 parts of base material;

[0062] S2, adding polymethylpentene and rare earth silicate compound in a mass ratio of 5:20, mixing the above materials evenly, and then adding carbon nanotubes and spinel structure powder in a mass ratio of 7:5, and continuing to stir evenly to form a first mixed material;

[0063] S3, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0064] S4. Add a leveling agent, a defoaming agent, a neutralizing agent and a flame retardant in a mass ratio of 1:1:1:1 to the second mixture, mix and stir evenly, adjust the pH value to neutral, then keep warm at 120°C for 3 hours, and then naturally cool to room temperature to obtain a coating.

[0065] The difference between this comparative example and Example 1 is that no zinc oxide-silver oxide composite material, rare earth silicate compound, or rare earth oxide is added, and the obtained product has no self-cleaning effect, avoids more stains, has poor thermal insulation performance, is coated on the surface of a substrate, has a high surface temperature of the substrate, and has a general radiation protection effect.

[0066] Comparative Example 3

[0067] S1. A zinc-based precursor is prepared by a liquid phase coprecipitation method, and a porous sponge-like zinc oxide is prepared after calcination at 500° C. Then, silver nitrate is used as a precursor, sodium hydroxide is added under alkaline environmental conditions to continue the reaction, and silver oxide nanoparticles are obtained after drying; and the porous sponge-like zinc oxide and the silver oxide nanoparticles are magnetically stirred under alkaline conditions to uniformly mix to obtain a zinc oxide-silver oxide composite material;

[0068] 8um nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then pre-calcined at 120°C for 36 hours; and then heat treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0069] Then, nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70°C to obtain a gel solution; then, the solution is pre-calcined at 120°C for 36 hours; and then, heat-treated at 600°C for 30 hours to obtain a rare earth silicate compound;

[0070] S2, to 30 parts of zinc oxide-silver oxide composite materials, add 35 parts of radiation cooling fillers composed of nano indium tin oxide, polymethylpentene, and rare earth silicate compounds in a mass ratio of 10:5:20, mix the above materials evenly, and then continue to add 20 parts of nano materials composed of nano carbon tubes, spinel structure powder, and rare earth oxides in a mass ratio of 7:5:8, and continue to stir evenly to form a first mixed material;

[0071] S3, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand, and then keeping it warm at 120° C. for 3 hours, and then naturally cooling it to room temperature to obtain a cooling radiation protection coating.

[0072] The difference between this comparative example and Example 1 is that no additives and base materials are added, and the obtained coating has insufficient film-forming properties, insufficient bonding properties, is prone to cracking, and has poor durability.

[0073] Comparative Example 4

[0074] S1. Add polypropylene glycol and toluene diisocyanate in a mass ratio of 5:5:2, stir and mix, and then add radiation protection resin to form a base material;

[0075] S2, adding nano-indium tin oxide, polymethylpentene, and rare earth silicate compound in a mass ratio of 15:15:15 to 30 parts of zinc oxide-silver oxide composite material, mixing the above materials evenly, and then continuing to add nano-carbon tubes, spinel structure powder, and rare earth oxide in a mass ratio of 5:5:5, and continue to stir evenly to form a first mixed material;

[0076] S4, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand;

[0077] S5. Add a leveling agent, a defoaming agent, a neutralizing agent and a flame retardant in a mass ratio of 0.5:0.5:0.5:0.5 to the second mixture, mix and stir evenly, adjust the pH value to neutral, and then keep warm at 120°C for 3 hours, and then naturally cool to room temperature to obtain a cooling radiation protection coating.

[0078] The difference between this comparative example and Example 1 is that the range of each material is not within the scope of the present invention, and the obtained finished product has poor performance. Too much or too little corresponding raw materials will cause the finished product material to fail to exert its maximum performance.

[0079] The present invention provides a comparative example to prove the superiority of the materials and scope of the present invention. In order to prove the performance of the coating of the present invention, the applicant compares the performance of the radiant cooling self-cleaning coating prepared in Examples 1 to 3 and the coatings of Comparative Examples 1 to 4. The results are shown in Table 1:

[0080]

[0081] According to the analysis in Table 1, the radiant cooling self-cleaning coatings prepared by Examples 1 to 3 of the present invention can achieve maximum balance in various aspects of performance, effectively reflect infrared rays in light, and protect the substrate from radiation damage; in addition, after the coating is applied to the surface of the substrate and placed in the sun for a period of time, compared with the same type of substrate not coated with the coating of the present invention, it can be found that the temperature on the back of the substrate is significantly reduced, which has a cooling and heat insulation effect; and the coating of the present invention can also effectively decompose stains after being applied to the surface of the substrate, so that the surface of the substrate remains clean to a certain extent.

[0082] However, when comparative examples 1 to 4 were prepared, they were different from the method of the present invention, had different raw material ranges, or lacked certain raw materials. As a result, the prepared coatings were lacking in various performances, failed to stimulate maximum efficiency, and could not be effectively applied in industrial applications.

[0083] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. An environmentally friendly radiation cooling self-cleaning coating, characterized in that: The coating comprises a photocatalyst filler, a radiation cooling filler, a nano material, a base material and an additive; the photocatalyst filler is a zinc oxide-silver oxide composite material; the radiation cooling filler is composed of nano indium tin oxide, polymethylpentene and a rare earth silicate compound; the nano indium tin oxide is prepared from indium trioxide and tin oxide; the nano material is composed of nano carbon tubes, spinel structure powder and rare earth oxides; the base material is composed of polypropylene glycol, toluene diisocyanate and radiation-proof resin; the additive is composed of a leveling agent, a defoaming agent, a neutralizer and a flame retardant.

2. The environmentally friendly radiation cooling self-cleaning coating according to claim 1, characterized in that: By mass fraction, the photocatalyst filler is 30-50 parts, the radiation cooling filler is 35-60 parts, the nano material is 20-35 parts; the base material is 10-25 parts; and the auxiliary agent is 4-8 parts.

3. The environmentally friendly radiation cooling self-cleaning coating according to claim 1, characterized in that: The mass ratio of the nano-indium tin oxide, polymethylpentene and rare earth silicate compound is 10-20: 5-10: 20-30.

4. The environmentally friendly radiation cooling self-cleaning coating according to claim 1, characterized in that: The mass ratio of the polypropylene glycol, toluene diisocyanate and radiation-proof resin is 3-7:3-7:4-11; the radiation-proof resin is composed of terpene resin and alicyclic epoxy resin SR-2021P.

5. The environmentally friendly radiation cooling self-cleaning coating according to claim 1, characterized in that: The mass ratio of the carbon nanotubes, spinel structure powder and rare earth oxide is 7-12: 5-8: 8-15; the carbon nanotubes are composed of one or more of carbon nanotubes, carbon nanofibers and nanocarbon balls; the rare earth oxides are composed of one or more of yttrium oxide, lanthanum oxide, cerium oxide and praseodymium oxide.

6. A method for preparing an environmentally friendly radiation cooling self-cleaning coating according to any one of claims 1 to 5, characterized in that: The following steps are included: S1. After mixing polypropylene glycol and toluene diisocyanate, add radiation protection resin to form a base material; S2, adding nano-indium tin oxide, polymethylpentene, and rare earth silicate compound to the zinc oxide-silver oxide composite material in proportion and mixing evenly, and then continuing to add nano-carbon tubes, spinel structure powder, and rare earth oxide and stirring evenly to form a first mixed material; S3, mixing the base material and the first mixed material to obtain a second mixed material, and then letting it stand; S4. Add a leveling agent, a defoaming agent, a neutralizing agent, and a flame retardant to the second mixture, mix and stir evenly, adjust the pH value, perform heat preservation treatment, and then naturally cool to room temperature to obtain a radiation refrigeration self-cleaning coating.

7. The method for preparing an environmentally friendly radiation cooling self-cleaning coating according to claim 6, characterized in that: The preparation method of the zinc oxide-silver oxide composite material comprises the following steps: preparing a zinc-based precursor by a liquid phase coprecipitation method, and preparing porous sponge-like zinc oxide by calcining at 500-600° C.; then taking silver nitrate as a precursor, adding sodium hydroxide to react under alkaline environmental conditions, and obtaining silver oxide nanoparticles by drying; and magnetically stirring the obtained porous sponge-like zinc oxide and silver oxide nanoparticles under alkaline conditions to uniformly mix and obtain the zinc oxide-silver oxide composite material.

8. The method for preparing an environmentally friendly radiation cooling self-cleaning coating according to claim 6, characterized in that: The preparation method of nano indium tin oxide is as follows: electrolysis is performed using metal indium as an anode, an inert electrode as a cathode, and an ammonium salt aqueous solution as an electrolyte; After electrolysis, the electrolyte is heated to a preset temperature, and ammonia solution is continuously added for stirring, solid-liquid separation and high-temperature calcination are performed to obtain nano-indium tin oxide.

9. The method for preparing an environmentally friendly radiation cooling self-cleaning coating according to claim 6, characterized in that: The preparation method of the rare earth silicate compound is as follows: nano silicon dioxide, rare earth nitrate and sodium nitrate are mixed and dispersed in an ethanol-water mixed solution, and stirred and mixed at 70-80° C. to obtain a gel solution; then pre-calcined at 120-150° C. for 36 hours; and then heat treated at 600-900° C. for 30 hours to obtain the rare earth silicate compound.

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