A lightweight radiant heat-insulating and decorative panel for exterior walls and its preparation method

Abstract

The present invention relates to the field of coatings, and discloses an exterior wall lightweight radiation heat-insulating and decorative board and a preparation method thereof. The radiation cooling layer on the surface of the exterior wall lightweight radiation heat-insulating and decorative board comprises: modified acrylate resin, silicon dioxide, heavy calcium carbonate, talcum powder, modified hollow glass microspheres, and an auxiliary agent; the modified acrylate resin is copolymerized from perfluorooctylethyl acrylate, methyl methacrylate, modified isocyanatoethyl methacrylate, and vinyltriethoxysilane; the modified isocyanatoethyl methacrylate is prepared by reacting salicylaldehyde and benzothiazole-2-carboxaldehyde with the amino groups at both ends of 1,5-naphthalenediamine, then carrying out a nucleophilic addition reaction with DOPO, and then grafting with isocyanatoethyl methacrylate; the modified hollow glass microspheres are prepared by using tetrabutyl titanate as a titanium source by the sol-gel method. The radiation cooling layer prepared by the present invention has a superhydrophobic and superoleophobic self-cleaning effect, good radiation cooling effect, and excellent flame retardant performance and antibacterial effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to an exterior wall lightweight radiation heat-insulating decorative board and a preparation method thereof. Background Art

[0002] With the development of the economy and the improvement of living standards, the consumption of energy is increasing day by day, and the demand for refrigeration is more urgent. As is well known, all objects on the earth continuously absorb various heats such as solar heat and thermal radiation from the outside world; at the same time, all objects are also continuously emitting heat in the form of infrared radiation, which is the principle that an infrared thermometer can measure temperature outside the body and an infrared detector can detect targets. Radiative cooling belongs to passive cooling technology, which neither requires power consumption nor a refrigerant as a heat transfer medium, and can even dissipate the heat in a specific internal space to the cold cosmic space outside the atmosphere in the form of infrared radiation. When the infrared heat radiates heat outward within the "atmospheric window" in the 8-13 μm wavelength band, it can be directly radiated to the cosmic space outside the atmosphere, taking the cosmic space as a radiator.

[0003] As is well known, the heat exchange between the building envelope and the surrounding environment and the sun can greatly affect the thermal comfort of the indoor space. To meet the building thermal comfort requirements, people have adopted various methods to improve the energy efficiency of the building envelope, including reflective materials, heat-insulating materials, etc. Among them, building coatings, as a non-structural solution, have attracted more and more attention due to their construction convenience and large-scale applicability. Among them, radiative cooling coatings have the advantages of no pollution and no emission compared with traditional cooling methods, and are of great significance for energy conservation and emission reduction and achieving carbon neutrality. However, the existing radiative cooling coating technology faces the challenges of wind, rain and dust pollution due to its long-term outdoor working environment, which will cause damage to the spectral performance, thus greatly weakening the radiative cooling performance and even shortening its service life. In addition, most of the radiative cooling coatings prepared based on organic substances have poor flame retardancy, antibacterial property and durability, and it is difficult to achieve refrigeration safely and for a long time. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide an exterior wall lightweight radiation heat-insulating decorative board and a preparation method thereof, and the prepared radiative cooling layer has a super-hydrophobic and super-oleophobic self-cleaning effect, good radiative cooling effect, and excellent flame retardancy and antibacterial effect.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A lightweight radiant heat-insulating and decorative panel for exterior walls, comprising a substrate and a radiant cooling layer on the surface of the substrate. The radiant cooling layer comprises the following components in parts by weight: 40-60 parts of modified acrylate resin, 10-20 parts of silica, 10-20 parts of heavy calcium carbonate, 4-7 parts of talcum powder, 10-20 parts of modified hollow glass microspheres, 1.5-2 parts of film-forming aid, 1-2 parts of defoaming agent, 0.2-0.5 parts of leveling agent, and 5-15 parts of organic solvent;

[0007] The modified acrylate resin is prepared by copolymerizing perfluorooctylethyl acrylate, methyl methacrylate, modified isocyanatoethyl methacrylate, and vinyltriethoxysilane. Among them, the modified isocyanatoethyl methacrylate is prepared by Schiff base reaction of salicylaldehyde and benzothiazole-2-carboxaldehyde with the amino groups at both ends of 1,5-naphthalenediamine to obtain a Schiff base-containing monomer, and then nucleophilic addition reaction of DOPO and the Schiff base-containing monomer followed by grafting with isocyanatoethyl methacrylate; the modified hollow glass microspheres are prepared by sol-gel method using anhydrous ethanol as solvent, tetrabutyl titanate as titanium source, and glacial acetic acid as chelating agent.

[0008] Preferably, the substrate is any one of iron plate, copper plate, stainless steel plate, aluminum plate, asbestos-free fiber cement board, UHPC board, ceramic board, and clay board.

[0009] Preferably, the film-forming aid is any one of propylene glycol methyl ether or ethylene glycol butyl ether; the defoaming agent is any one of fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether; the leveling agent is sodium polyacrylate; the organic solvent is acetone.

[0010] Preferably, the preparation method of the modified acrylate resin comprises the following steps:

[0011] (1) Take salicylaldehyde, 1,5-naphthalenediamine, and benzothiazole-2-carboxaldehyde in a reactor, add anhydrous ethanol solvent, stir evenly, then dropwise add glacial acetic acid, and stir at 65-80°C for 4-5h. After the reaction is completed, filter, wash, and dry to prepare a Schiff base-containing monomer;

[0012] (2) Take the Schiff base-containing monomer in a reactor, add anhydrous ethanol solvent and DOPO, and stir at 75-85°C for 6-8h. After the reaction is completed, filter, wash, and dry to prepare a DOPO derivative;

[0013] (3) Take the DOPO derivative, isocyanatoethyl methacrylate, and dibutyltin dilaurate in a reactor, add acetone solvent, heat to 45-50°C, and stir for 10-12h. After the reaction is completed, perform rotary evaporation, wash, and dry to prepare the modified isocyanatoethyl methacrylate;

[0014] (4)Take perfluorooctylethyl acrylate, methyl methacrylate, modified isocyanatoethyl methacrylate and vinyltriethoxysilane in a reactor, add acetone solvent and stir evenly. React while passing nitrogen, add azobisisobutyronitrile initiator, and place it under stirring reaction at 55 - 70 °C for 6 - 8 h to prepare a modified acrylate resin.

[0015] Preferably, in the step (1), the molar ratio of salicylaldehyde, 1,5 - naphthalenediamine and benzothiazole - 2 - carbaldehyde is 1 - 1.2:1:1 - 1.2.

[0016] Preferably, in the step (2), the molar ratio of the Schiff - base - containing monomer and DOPO is 1:2 - 2.3.

[0017] Preferably, in the step (3), the molar ratio of the DOPO derivative and isocyanatoethyl methacrylate is 1:1 - 1.2.

[0018] Preferably, in the step (4), the molar ratio of perfluorooctylethyl acrylate, methyl methacrylate, modified isocyanatoethyl methacrylate and vinyltriethoxysilane is 2 - 6:2 - 6:1 - 2:1.

[0019] Preferably, the preparation method of the modified hollow glass microspheres includes the following steps: Take anhydrous ethanol, tetrabutyl titanate and glacial acetic acid and mix them evenly to obtain solution one. Take anhydrous ethanol and deionized water and mix them evenly to obtain solution two. Under stirring, drop solution two into solution one, and adjust the pH value of the system to 3 - 4. Stir and react for 0.5 - 1 h, then add hollow glass microspheres, continue to stir for 1 - 1.5 h, stand for aging for 10 - 12 h and then dry, and calcine at 500 - 550 °C for 3 - 4 h to prepare the modified hollow glass microspheres.

[0020] A preparation method of an exterior - wall lightweight radiation - heat - insulating decorative board includes the following steps:

[0021] S1. Weigh each component by weight.

[0022] S2. Disperse the modified acrylate resin in an organic solvent to obtain a dispersion liquid, then add the modified hollow glass microspheres, place it under stirring at 70 - 80 °C to stir evenly, then raise the temperature to 100 - 120 °C, and stir and react for 2 - 4 h to obtain a composite acrylate resin.

[0023] S3. Pour the composite acrylate resin, silica, heavy calcium carbonate, talc powder, film - forming aid, defoaming agent and leveling agent into a mixer, and fully stir and mix evenly to obtain a radiation - cooling layer.

[0024] S4. Uniformly coat the radiation - cooling layer on the surface of the substrate, and after heat - drying and curing, prepare the exterior - wall lightweight radiation - heat - insulating decorative board.

[0025] Advantages of the present invention:

[0026] In the present invention, absolute ethanol is used as a solvent, tetrabutyl titanate is used as a titanium source, and glacial acetic acid is used as a chelating agent. Modified hollow glass microspheres coated with titanium dioxide are prepared by a sol-gel method, which improves the surface roughness of the hollow glass microspheres. The hollow structure of the hollow glass microspheres makes them have the characteristics of low thermal conductivity and good heat insulation effect. Titanium dioxide has the characteristics of large refractive index and high solar reflectivity. Coating titanium dioxide on the surface of the hollow glass microspheres can complement the optical properties and heat insulation functions of the two. At the same time, in the present invention, salicylaldehyde and benzothiazole-2-carboxaldehyde respectively react with the amino groups at both ends of 1,5-naphthalenediamine to undergo a Schiff base reaction to prepare a Schiff base monomer-containing substance. Then, the P-H bond in the DOPO structure undergoes a nucleophilic addition reaction with the two -CH=N- groups formed to prepare a DOPO derivative. After that, the hydroxyl group introduced in the DOPO derivative structure undergoes a nucleophilic addition reaction with the isocyanate group in the structure of isocyanatoethyl methacrylate to prepare a modified isocyanatoethyl methacrylate containing a double bond group.

[0027] In the present invention, perfluorooctylethyl acrylate, methyl methacrylate, modified isocyanatoethyl methacrylate, and vinyltriethoxysilane are used as polymerization monomers to prepare a modified acrylic resin. Among them, perfluorooctylethyl acrylate provides a fluorocarbon chain as a hydrophobic and oleophobic group, methyl methacrylate improves the solubility of the modified acrylic resin in acetone solvent and adjusts the film-forming property of the modified acrylic resin. Modified isocyanatoethyl methacrylate provides a thiazole monomer with antibacterial activity and nitrogen and phosphorus elements with a synergistic flame retardant effect. Vinyltriethoxysilane provides a siloxane group, introducing a reaction binding site, which undergoes a condensation reaction with the hydroxyl groups on the surface of the modified hollow glass microspheres, and grafts and adsorbs the modified acrylic resin on the surface of the modified hollow glass microspheres to prepare a composite acrylate resin, thereby preparing a superhydrophobic and superoleophobic radiative cooling layer, and further generating an antifouling and self-cleaning effect, which can effectively alleviate the problem that the passive radiative cooling performance of the passive radiative cooling coating is reduced due to environmental pollution.

[0028] The radiative cooling layer prepared in the present invention has a passive radiative cooling effect with a surface temperature lower than the ambient air temperature under direct sunlight and a superhydrophobic and superoleophobic self-cleaning effect. The solar reflectivity of the radiative cooling layer can reach 98.6%, the overall infrared emissivity can reach 95.0%, and the selective infrared emissivity in the atmospheric window can reach 99.1%. Therefore, it is very easy to achieve that the heat emitted is greater than the heat absorbed, reaching a cooling phenomenon with a surface temperature lower than the ambient air temperature around, and applying this radiative cooling layer to the surface of an exterior wall lightweight radiative heat insulation and decorative board, thereby preparing a finished board with integrated radiative cooling, heat insulation, and decoration. Description of the Drawings

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is the infrared spectrum diagram of the DOPO derivative prepared in Example 1 of the present invention;

[0031] Figure 2 It is the infrared spectrum diagram of the hollow glass microspheres before and after modification in Example 2 of the present invention. Specific embodiments

[0032] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] Example 1 A preparation method of a modified acrylate resin includes the following steps:

[0034] (1) Take 1.4 g of salicylaldehyde, 1.6 g of 1,5-naphthalenediamine and 1.7 g of benzothiazole-2-carboxaldehyde in a reactor, add 50 mL of anhydrous ethanol solvent, stir evenly, then drop two drops of glacial acetic acid, and place it under stirring at 75 °C for 4 h. After the reaction is completed, filter, wash, and dry to prepare a Schiff base monomer;

[0035] (2) Take 4 g of the Schiff base monomer (Mr = 407.5) in a reactor, add 100 mL of anhydrous ethanol solvent and 4.3 g of DOPO, place it under stirring at 80 °C for 7 h. After the reaction is completed, filter, wash, and dry to prepare a DOPO derivative;

[0036] (3) Take 4.2 g of the DOPO derivative (Mr = 839.8), 1.6 g of isocyanatoethyl methacrylate and one drop of dibutyltin dilaurate in a reactor, add 50 mL of acetone solvent, heat up to 50 °C, and stir for 12 h. After the reaction is completed, perform rotary evaporation, wash, and dry to prepare a modified isocyanatoethyl methacrylate;

[0037] (4) Take 20.7 g of perfluorooctylethyl acrylate, 4 g of methyl methacrylate, 9.9 g of modified isocyanatoethyl methacrylate, and 1.9 g of vinyltriethoxysilane in a reactor. Add 100 mL of acetone solvent and stir evenly. Pass nitrogen during the reaction. Add 0.6 g of azobisisobutyronitrile initiator and place it under stirring at 65 °C for 8 h to prepare a modified acrylate resin.

[0038] The DOPO derivative was subjected to infrared spectroscopy, and the results are as Figure 1 shown. The DOPO infrared spectrum has the following characteristic peaks: 932 cm -1 , 1213 cm -1 (P-O-CAr), 1246 cm -1 (P=O), 1477 cm -1 , 1580 cm -1 (P-CAr), 2436 cm -1 (P-H). The C=N bond of the Schiff base imine structure appears at 1618 cm -1 in the curve of the Schiff base monomer. In the curve of the DOPO derivative, no C=N characteristic peak and P-H characteristic peak were observed, and the 932 cm -1 , 1213 cm -1 (P-O-CAr), 1246 cm -1 (P=O), 1477 cm -1 , 1580 cm -1 (P-CAr) characteristic peaks all exist, indicating that the DOPO derivative was successfully synthesized.

[0039] Example 2 A preparation method of modified hollow glass microspheres includes the following steps:

[0040] Take 40 mL of absolute ethanol, 10 mL of tetrabutyl titanate, and 3 mL of glacial acetic acid and mix them evenly to obtain Solution 1. Take 20 mL of absolute ethanol and 5 mL of deionized water and mix them evenly to obtain Solution 2. Under stirring, add Solution 2 dropwise to Solution 1, and adjust the pH value of the system to 4. Stir and react for 1 h, then add 2 g of hollow glass microspheres, continue to stir for 1 h, stand for aging for 12 h and then dry, and calcine at 550 °C for 4 h to prepare modified hollow glass microspheres.

[0041] The modified hollow glass microspheres were subjected to infrared spectroscopy, and the results are as Figure 2 shown. Among them, the 5 main absorption peaks are located at 463 cm -1 , 793 cm -1 , 1155 cm -1 , 1401 cm -1 , 3445 cm -1At this point, it corresponds to the bending vibration, symmetric expansion vibration, and asymmetric stretching vibration of the silicon-oxygen bond (Si-O-Si), the deformation vibration of the hydroxyl group (O-H), and the stretching vibration of the silanol group (Si-OH). Compared with hollow glass microspheres, new absorption peaks appear in the modified hollow glass microspheres. At 2003 cm -1 The weak peak at this point corresponds to the vibration of the Ti-O-Ti bond. At 2193 cm -1 The vibration of the Si-O-Ti bond at this point indicates that titanium dioxide is bonded to the surface of the hollow glass microspheres through the Si-O-Ti bond, and the modified hollow glass microspheres are successfully prepared.

[0042] Example 3 A radiative cooling layer comprises the following components in parts by weight:

[0043] 42 parts of the modified acrylate resin prepared in Example 1, 10 parts of silica, 10 parts of heavy calcium carbonate, 4 parts of talc powder, 10 parts of the modified hollow glass microspheres prepared in Example 2, 1.5 parts of the film-forming aid propylene glycol methyl ether, 1 part of the defoaming agent fatty alcohol polyoxyethylene ether, 0.2 part of the leveling agent sodium polyacrylate, and 7 parts of the organic solvent acetone.

[0044] A preparation method of an exterior wall lightweight radiative heat-insulating decorative board comprises the following steps:

[0045] S1. Weigh each component according to parts by weight;

[0046] S2. Disperse the modified acrylate resin in acetone to obtain a dispersion liquid, then add the modified hollow glass microspheres, stir evenly at 75 °C, then raise the temperature to 110 °C, and stir and react for 3 h to obtain a composite acrylate resin;

[0047] S3. Pour the composite acrylate resin, silica, heavy calcium carbonate, talc powder, film-forming aid, defoaming agent, and leveling agent into a mixer, and fully stir and mix evenly to obtain a radiative cooling layer;

[0048] S4. Uniformly coat the radiative cooling layer on the surface of the asbestos-free fiber cement board, and after heat drying and curing, prepare the exterior wall lightweight radiative heat-insulating decorative board.

[0049] Example 4 A radiative cooling layer comprises the following components in parts by weight:

[0050] 47 parts of the modified acrylate resin prepared in Example 1, 14 parts of silica, 12 parts of heavy calcium carbonate, 5 parts of talc powder, 15 parts of the modified hollow glass microspheres prepared in Example 2, 2 parts of the film-forming aid ethylene glycol monobutyl ether, 1.5 parts of the defoaming agent alkylphenol polyoxyethylene ether, 0.4 part of the leveling agent sodium polyacrylate, and 10 parts of the organic solvent acetone.

[0051] The preparation method of an exterior wall lightweight radiative heat-insulating decorative board is the same as that in Example 3.

[0052] Example 5 A radiation cooling layer comprises the following components by weight:

[0053] 55 parts of the modified acrylate resin prepared in Example 1, 17 parts of silica, 16 parts of heavy calcium carbonate, 6.5 parts of talcum powder, 18 parts of the modified hollow glass microspheres prepared in Example 2, 2 parts of the film-forming auxiliary propylene glycol methyl ether, 2 parts of the defoaming agent fatty alcohol polyoxyethylene ether, 0.5 part of the leveling agent sodium polyacrylate, and 14 parts of the organic solvent acetone.

[0054] The preparation method of a lightweight external wall radiation heat-insulating decorative board is the same as that in Example 3.

[0055] Comparative Example 1 The preparation method of a modified acrylate resin comprises the following steps:

[0056] Take perfluorooctylethyl acrylate, methyl methacrylate, isocyanatoethyl methacrylate and vinyltriethoxysilane in a reactor, add acetone solvent and stir evenly, introduce nitrogen during the reaction, add azobisisobutyronitrile initiator, and stir and react at 55-70 °C for 6-8 h to prepare the modified acrylate resin.

[0057] Comparative Example 2 A radiation cooling layer comprises the following components by weight:

[0058] 55 parts of the modified acrylate resin prepared in Comparative Example 1, 17 parts of silica, 16 parts of heavy calcium carbonate, 6.5 parts of talcum powder, 18 parts of the modified hollow glass microspheres prepared in Example 2, 2 parts of the film-forming auxiliary propylene glycol methyl ether, 2 parts of the defoaming agent fatty alcohol polyoxyethylene ether, 0.5 part of the leveling agent sodium polyacrylate, and 14 parts of the organic solvent acetone.

[0059] The preparation method of a lightweight external wall radiation heat-insulating decorative board is the same as that in Example 3.

[0060] Comparative Example 3 A radiation cooling layer comprises the following components by weight:

[0061] 55 parts of the modified acrylate resin prepared in Example 1, 17 parts of silica, 16 parts of heavy calcium carbonate, 6.5 parts of talcum powder, 18 parts of hollow glass microspheres, 2 parts of the film-forming auxiliary propylene glycol methyl ether, 2 parts of the defoaming agent fatty alcohol polyoxyethylene ether, 0.5 part of the leveling agent sodium polyacrylate, and 14 parts of the organic solvent acetone.

[0062] The preparation method of a lightweight external wall radiation heat-insulating decorative board is the same as that in Example 3.

[0063] Performance testing

[0064] The radiation cooling layers prepared in Examples 3-5 and Comparative Examples 2-3 were subjected to performance tests: the static water contact angle and the static n-hexadecane contact angle were measured using a contact angle tester; the antibacterial rate was tested with reference to GB / T 21866-2008, and the test strain was Staphylococcus aureus; the flame retardancy was tested by the limiting oxygen index; the solar reflectance, the overall infrared emissivity, and the selective infrared emissivity in the atmospheric window were entrusted to the National Building Materials Testing Center for testing. The higher the solar reflectance, the less solar heat is absorbed during the day, and the higher the values of the overall infrared emissivity or the selective infrared emissivity in the atmospheric window, the stronger the self-cooling ability. The data results are shown in Table 1.

[0065] Table 1 Test Results of Specimen Performance

[0066] ;

[0067] It can be seen from the data in Table 1 that the radiation cooling layers prepared in Examples 3-5 of the present invention have a superhydrophobic and superoleophobic self-cleaning effect. The solar reflectance can reach 98.3-98.6%, the overall infrared emissivity can reach 94.1-95.0%, and the selective infrared emissivity in the atmospheric window can reach 98.7-99.1%. At the same time, the flame retardancy and antibacterial effect are excellent. Among them, in Comparative Example 2, isocyanatoethyl methacrylate was not modified, and the measured antibacterial rate against Escherichia coli and the limiting oxygen index were lower than those in Examples 3-5. The reason is that the antibacterial active thiazole monomer and the nitrogen and phosphorus elements with a synergistic flame retardant effect were not introduced. In Comparative Example 3, the hollow glass microspheres were not coated and modified, and the measured contact angle was lower than that in Examples 3-5, and the double superhydrophobic surface was not achieved. The possible reason is that the coating modification improved the surface roughness of the hollow glass microspheres and was grafted with a modified acrylate resin in the subsequent process, promoting the coating to reach a superhydrophobic and superoleophobic state. Moreover, the measured solar reflectance, overall infrared emissivity, and selective infrared emissivity (8-13 μm) in the atmospheric window were lower than those in Examples 3-5. The reason is that the coated and modified hollow glass microspheres have strong reflection and refraction of sunlight, and the strong absorption of Ti-O bonds and Si-O bonds in the corresponding wavenumber range of the atmospheric window enhances the emissivity of the coating. In addition, the antibacterial rate against Escherichia coli was lower than that in Examples 3-5, indicating that the introduction of titanium dioxide improved the antibacterial effect to a certain extent.

[0068] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0069] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A lightweight radiation thermal insulation decorative panel for exterior walls, characterized in that: The invention comprises a substrate and a radiation cooling layer on the surface of the substrate, wherein the radiation cooling layer comprises the following components in parts by weight: 40-60 parts of modified acrylic resin, 10-20 parts of silicon dioxide, 10-20 parts of heavy calcium carbonate, 4-7 parts of talc, 10-20 parts of modified hollow glass microspheres, 1.5-2 parts of film-forming aid, 1-2 parts of defoaming agent, 0.2-0.5 parts of leveling agent, and 5-15 parts of organic solvent; The modified hollow glass microspheres are prepared by a sol-gel method using anhydrous ethanol as a solvent, n-butyl titanate as a titanium source, and glacial acetic acid as a chelating agent; The preparation method of the modified acrylate resin comprises the following steps: (1) salicylaldehyde, 1,5-naphthalenediamine and benzothiazole-2-carboxaldehyde are placed in a reactor, anhydrous ethanol solvent is added, the mixture is stirred evenly, glacial acetic acid is added dropwise, and the mixture is stirred at 65-80° C. for 4-5 hours. After the reaction is completed, the mixture is filtered, washed and dried to prepare a Schiff base monomer; (2) Putting a Schiff base monomer into a reactor, adding anhydrous ethanol solvent and DOPO, stirring and reacting at 75-85°C for 6-8 hours, filtering, washing and drying after the reaction is completed to prepare a DOPO derivative; (3) Put DOPO derivative, isocyanoethyl methacrylate and dibutyltin dilaurate in a reactor, add acetone solvent, raise the temperature to 45-50°C, stir and react for 10-12 hours, and after the reaction is completed, perform rotary evaporation, wash and dry to prepare modified isocyanoethyl methacrylate; (4) perfluorooctyl ethyl acrylate, methyl methacrylate, modified isocyanoethyl methacrylate and vinyl triethoxysilane are placed in a reactor, acetone solvent is added and stirred evenly, nitrogen is passed through the reaction, azobisisobutyronitrile initiator is added, and the mixture is stirred and reacted at 55-70°C for 6-8h to prepare a modified acrylate resin; The molar ratio of the Schiff base monomer to DOPO in step (2) is 1:2-2.

3.

2. The lightweight radiation thermal insulation decorative panel for exterior walls according to claim 1 is characterized in that: The substrate is any one of an iron plate, a copper plate, a stainless steel plate, an aluminum plate, an asbestos-free fiber cement plate, an UHPC plate, a ceramic plate, and a clay plate.

3. The lightweight radiation thermal insulation decorative panel for exterior walls according to claim 1 is characterized in that: The film-forming aid is any one of propylene glycol methyl ether and ethylene glycol butyl ether; the defoamer is any one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether; the leveling agent is sodium polyacrylate; and the organic solvent is acetone.

4. The exterior wall lightweight radiation thermal insulation decorative panel according to claim 1, characterized in that: In the step (1), the molar ratio of salicylaldehyde, 1,5-naphthalenediamine and benzothiazole-2-carboxaldehyde is 1-1.2:1:1-1.

2.

5. The lightweight radiation thermal insulation decorative panel for exterior walls according to claim 1, characterized in that: In the step (3), the molar ratio of the DOPO derivative to isocyanoethyl methacrylate is 1:1-1.

2.

6. The lightweight radiation thermal insulation decorative panel for exterior walls according to claim 1, characterized in that: In the step (4), the molar ratio of perfluorooctyl ethyl acrylate, methyl methacrylate, modified isocyanoethyl methacrylate and vinyl triethoxysilane is 2-6:2-6:1-2:

1.

7. The exterior wall lightweight radiation thermal insulation decorative panel according to claim 1, characterized in that: The preparation method of the modified hollow glass microspheres comprises the following steps: taking anhydrous ethanol, tetrabutyl titanate and glacial acetic acid and mixing them uniformly to obtain a solution 1; taking anhydrous ethanol and deionized water and mixing them uniformly to obtain a solution 2; adding the solution 2 dropwise into the solution 1 under stirring, adjusting the pH value of the system to 3-4, stirring and reacting for 0.5-1h, then adding the hollow glass microspheres, continuing to stir for 1-1.5h, standing and aging for 10-12h and then drying, and calcining at 500-550°C for 3-4h to prepare the modified hollow glass microspheres.

8. A method for preparing a lightweight radiation thermal insulation decorative panel for an exterior wall according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Weigh each component by weight; S2, dispersing the modified acrylic resin in an organic solvent to obtain a dispersion, then adding the modified hollow glass microspheres, stirring evenly at 70-80° C., then heating to 100-120° C., stirring and reacting for 2-4 hours, to obtain a composite acrylic resin; S3, pouring the composite acrylic resin, silicon dioxide, heavy calcium carbonate, talcum powder, film-forming aid, defoaming agent and leveling agent into a mixer, stirring and mixing thoroughly to obtain a radiation cooling layer; S4. The radiation cooling layer is evenly coated on the surface of the substrate, and after thermal drying and curing, a lightweight radiation thermal insulation decorative panel for the exterior wall is prepared.

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