A thermo-induced reversible color-changing composite coating capable of synergistic modulation of visible and near-infrared spectra and its preparation method

Abstract

This invention discloses a thermotropic reversible color-changing composite coating capable of synergistic modulation of visible-near-infrared spectroscopy and its preparation method. This composite temperature-controlling coating is a multi-layered composite structure consisting of a solar-spectrum high-reflectance base layer, a near-infrared absorption layer, a near-infrared modulation layer, and a thermotropic layer. Each layer is prepared using coatings with rutile titanium dioxide, silica aerogel-modified cesium tungsten bronze, nano-tin antimony oxide-modified vanadium oxide, and thermotropic reversible color-changing microcapsules as fillers. This coating ingeniously achieves high reflectance of the visible-near-infrared spectrum of sunlight under high-temperature conditions and high absorption of the visible-near-infrared spectrum of sunlight under low-temperature conditions through its multi-layered composite structure design, greatly improving the overall modulation performance of the coating's solar reflectance. The excellent performance of this coating contributes to the adaptability of temperature-controlling materials to complex temperature environments and is of great significance for related technological advancements and industrial development.

Description

Technical Field

[0001] This invention belongs to the field of fine polymer materials, specifically relating to the preparation of a thermotropic reversible color-changing composite coating that can achieve synergistic modulation of visible-near-infrared spectra and its application in structural temperature control in transportation, construction, machinery, chemical and other fields. Background Technology

[0002] For engineering and spatial structures operating in exposed environments, atmospheric heat convection and solar heat radiation have a significant impact on structural temperature, resulting in large diurnal or seasonal temperature differences. This can significantly affect the durability of the structure itself and the temperature comfort of the internal space. Therefore, it is essential to use relevant materials and technologies for structural temperature control.

[0003] Solar radiation is one of the main energy sources for heat exchange between structures and the external environment. Different surface structures and materials have different response properties to the solar spectrum. If more spectral energy is reflected, it can effectively prevent temperature rise under sunlight. If more spectral energy is absorbed, it will cause the structure to heat up rapidly after absorbing sunlight. Therefore, it can be seen that the photothermal conversion performance of the structural surface to sunlight is the most important factor affecting the structural temperature. The solar spectrum contains spectral energy in multiple bands, among which the visible light band (300 nm~780 nm) and the near-infrared band (780 nm~2500 nm) account for the highest spectral energy and have the greatest impact on the solar photothermal effect. Therefore, the response performance of the structural surface to these two spectral bands is the key performance of structural temperature control. Conventional structural materials have a single spectral response performance, which is difficult to fully meet the complex temperature control requirements of structures facing different environmental conditions. For example, using high-reflectivity temperature control materials can reduce the energy consumption for cooling the structure under solar radiation in high-temperature environments, but may have a negative impact on the temperature control load of the structure in cold winters. Therefore, developing intelligent temperature control materials with different surface photothermal properties according to different environmental scenarios has important economic and social significance, and also brings new development opportunities for the future application research of surface temperature control materials.

[0004] Researchers have studied various intelligent surface temperature-controlled materials that regulate surface photothermal properties through different methods. Among them, intelligent temperature-controlled materials that regulate temperature have received considerable research attention due to their most direct design concept and application. Patent CN118638296B discloses an intelligent temperature-controlled TPU material for automotive glass films. Through in-situ synthesis technology, a thermosensitive temperature-controlled filler is incorporated into the TPU molecular chain, maintaining its high light transmittance while significantly improving its solar energy regulation efficiency. Patent CN113419580B discloses an intelligent temperature-controlled device based on passive radiation cooling and solar heating. This device is fabricated by sequentially arranging a passive radiation cooling layer, a thermochromic layer, and a solar heating layer from the outside to the inside. It can achieve passive temperature control that changes with ambient temperature and is applicable to a wide range of ambient temperature variations. Patent CN116285442B discloses a carbon-negative, self-temperature-regulating thermochromic coating. By modifying the reversible color-changing microcapsules with titanium sol, its UV aging resistance is improved while enhancing the bonding force of other inorganic carbonized cementitious materials, resulting in excellent coating performance.

[0005] As can be seen from the above description, existing thermochromic intelligent temperature control materials already possess intelligent control characteristics and certain practical value. However, from the perspective of overall technological development, they still face some challenges. Currently, thermochromic intelligent temperature control materials mainly include thermochromic coating materials and thermochromic temperature-controlled glass materials. Among them, thermochromic coating materials that change color at room temperature typically use organic thermochromic materials, which have relatively strong control over the absorption rate in the visible light band. However, due to their molecular structure, they usually have no control effect on the near-infrared band. Therefore, the total solar light modulation rate can usually only reach a maximum of 30%, making further improvement difficult. As for thermochromic temperature-controlled glass, although it can utilize the phase transition of vanadium oxide materials to achieve near-infrared band control, it usually has no control over visible light to ensure light transmittance. Its solar light modulation rate is also within 20%, and it mainly controls transmittance, which is different from the control of reflectance and absorptivity of coatings. Therefore, it can be seen that based on relevant research, further development of novel thermotropic intelligent temperature control materials and improvement of the overall regulation performance of materials in the solar spectrum are of great significance for promoting the further development of related technologies and advancing industry progress. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems and provide a thermo-induced reversible color-changing composite coating that can achieve synergistic modulation of visible and near-infrared spectra and its preparation method.

[0007] The present invention discloses a thermochromic composite coating capable of synergistic modulation of visible and near-infrared spectra. This coating is a multi-layered composite temperature-controlled coating composed of a high solar reflectance layer, a near-infrared absorption layer, a near-infrared modulation layer, and a thermochromic layer. The high solar reflectance layer is prepared using a high-performance solar reflective coating with added rutile titanium dioxide. The near-infrared absorption layer is prepared using a high near-infrared absorption coating with added silica aerogel-modified cesium tungsten bronze. The near-infrared modulation layer is prepared using a near-infrared modulation coating with added nano-tin antimony oxide-modified vanadium dioxide. The thermochromic layer is prepared using a thermochromic coating with added thermochromic microcapsules. The dry film thicknesses of the high solar reflectance layer, near-infrared absorption layer, near-infrared modulation layer, and thermochromic layer are 40 μm~60 μm, 15 μm~25 μm, 10 μm~20 μm, and 30 μm~50 μm, respectively.

[0008] The high-performance solar reflective coating consists of A1 main agent and B1 curing agent; wherein A1 main agent is prepared from matrix resin, rutile titanium dioxide filler, solvent and functional additives; the mass contents of matrix resin, rutile titanium dioxide filler, solvent and functional additives are 55%~72%, 22%~33%, 3%~10% and 1%~4% respectively, based on the total mass of A1 main agent; B1 curing agent is prepared from curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A1 main agent and B1 curing agent is 1:(0.08~0.22).

[0009] The high near-infrared absorption coating consists of A2 main agent and B2 curing agent; wherein A2 main agent is prepared from matrix resin, silica aerogel modified cesium tungsten bronze filler, solvent and functional additives; the mass contents of matrix resin, silica aerogel modified cesium tungsten bronze filler, solvent and functional additives are 70%~80%, 15%~20%, 3%~5% and 1%~3% respectively, based on the total mass of A2 main agent; B2 curing agent is prepared from curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A2 main agent and B2 curing agent is 1:(0.12~0.25).

[0010] The preparation method of silica aerogel modified cesium tungsten bronze in high near-infrared absorption coating is as follows: (1) Tungsten chloride is mixed with anhydrous ethanol and completely dissolved, then cesium hydroxide is added and stirred for 5 min, then acetic acid is added and stirred evenly; (2) The reaction precursor solution is transferred into the reactor and heated at 220℃~240℃ for 24 h. The precipitate is centrifuged, washed and vacuum dried to obtain cesium tungsten bronze powder; (3) The cesium tungsten bronze powder and a certain amount of silica aerogel are mixed evenly in N,N-dimethylformamide and ball-milled at 600 rpm for 30 min to obtain silica aerogel modified cesium tungsten bronze; the mass ratio of cesium tungsten bronze to silica aerogel is 1: (0.3~0.6).

[0011] The near-infrared modulated coating consists of A3 main agent and B3 curing agent. A3 main agent is prepared from matrix resin, nano-tin antimony oxide modified vanadium dioxide filler, solvent and functional additives. The mass contents of matrix resin, nano-tin antimony oxide modified vanadium dioxide filler, solvent and functional additives are 75%~85%, 10%~15%, 3%~5% and 1%~3% respectively, based on the total mass of A3 main agent. B3 curing agent is prepared from curing agent and solvent. The mass contents of curing agent and solvent are 85%~100% and 0~15% respectively. The mass ratio of A3 main agent to B3 curing agent is 1:(0.14~0.25).

[0012] The preparation method of nano-tin-antimony modified vanadium dioxide in near-infrared modulated coating is as follows: (1) Vanadium pentoxide and oxalic acid dihydrate are uniformly dissolved in deionized water at a molar ratio of 1:2. After dissolution, magnesium sulfate is added and stirred for 30 min to obtain a reaction precursor solution; (2) The reaction precursor solution is transferred to a hydrothermal reactor and reacted at 240℃ for 10 h. Then, it is ultrasonically cleaned three times with deionized water and anhydrous ethanol, vacuum filtered at 60℃ and dried for 12 h. The resulting powder is then ground to obtain magnesium-doped vanadium dioxide powder; (3) The vanadium dioxide powder and nano-tin-antimony are mixed evenly in water and ball-milled at a speed of 400 rpm to 600 rpm for 30 min; (4) Under a nitrogen atmosphere, the ball-milled powder is heat-treated at a temperature of 520℃ to 600℃ for 3 minutes. h, nano-tin antimony oxide modified vanadium dioxide can be obtained; wherein the magnesium doping amount is 1.5%~2.3% based on the mass of vanadium oxide; the mass ratio of vanadium dioxide to nano-tin antimony oxide is 1:(0.8~1.4).

[0013] The thermochromic coating consists of A4 main agent and B4 curing agent. A4 main agent is prepared from matrix resin, thermochromic microcapsule filler, solvent and functional additives. The mass contents of matrix resin, thermochromic microcapsule filler, solvent and functional additives are 55%~72%, 20%~35%, 3%~10% and 1%~4% respectively, based on the total mass of A4 main agent. B4 curing agent is prepared from curing agent and solvent. The mass contents of curing agent and solvent are 85%~100% and 0~15% respectively. The mass ratio of A4 main agent to B4 curing agent is 1:(0.09~0.22).

[0014] The preparation method of thermotropic reversible color-changing microcapsules in thermotropic reversible color-changing coatings includes the following steps: (1) Dissolve the ternary thermotropic reversible color-changing core material composed of pigment, color developer and solvent and add it to water containing emulsifier. Emulsify it at high speed under heating conditions of 65°C to obtain thermotropic reversible color-changing emulsion; (2) Add the resin prepolymer to the reversible color-changing emulsion at a constant rate under heating and stirring conditions. After the addition is completed, polymerize in situ at 85°C for 1 hour. Filter and dry the suspension after the reaction to obtain thermotropic reversible color-changing microcapsules; wherein the pigment is crystal violet lactone, 2-phenylamino-3-methyl-6-dibutylaminofluorane, 3',6'-dimethoxyfluorene. At least one of the following: alkanes; at least one of the following: color developer: bisphenol A, bisphenol F, bisphenol S; at least one of the following: tetradecyl alcohol, glyceryl tridecanoate, methyl octadecyl acetate, ethyl octadecyl acetate; the mass concentration of the pigment molecules is 0.8-6%, and the mass ratio of pigment to color developer is 1:(1.5-4) based on the total mass of the color-changing core material; at least one of the following: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium styrene-maleic anhydride copolymer, with a mass concentration of 0.5-1%; at least one of the following: melamine resin prepolymer, urea-formaldehyde resin prepolymer, methyl melamine-formaldehyde resin prepolymer, used in an amount of 5-13% of the total mass of the capsule.

[0015] The preparation methods for high-performance solar reflective coatings, high near-infrared absorption coatings, near-infrared modulation coatings, and thermochromic reversible color-changing coatings are as follows: Weigh appropriate amounts of each component, disperse and mix the matrix resin and filler using a high-speed disperser at 40~60℃ and a linear velocity of 6-10m / s for 15min, followed by ultrasonic treatment for 4~10min, then add the remaining components to the mixture and disperse for 30min until the system is homogeneous and stable to obtain the coating main component; disperse and mix the isocyanate and solvent using a high-speed disperser for 15min until the system is homogeneous and stable to obtain the curing agent component;

[0016] The matrix resin is at least one of silicone resin, fluorocarbon resin, and polyurethane resin; the solvent is at least one of xylene, acetone, ethanol, isopropanol, butyl acetate, and propylene glycol methyl ether acetate; the functional additive is at least one of dispersant, defoamer, leveling agent, adhesion promoter, and thixotropic agent; the isocyanate is at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, phenyl diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate trimer, and hexamethylene diisocyanate biuret; and the solvent is at least one of xylene, acetone, ethanol, isopropanol, butyl acetate, and propylene glycol methyl ether acetate.

[0017] The thermochromic composite coating is prepared by sequentially forming a coating of appropriate thickness on a substrate using a high-performance solar reflective coating, a high near-infrared absorption coating, a near-infrared modulation coating, and a thermochromic coating. The forming method can be any one of screen printing, spraying, casting, or roller coating. Each coating layer needs to be dried at room temperature for 24 hours and then cured at 60°C for 12 hours before the next coating layer is formed.

[0018] The positive effects of the thermotropic reversible color-changing composite coating capable of synergistic modulation of visible and near-infrared spectra in this invention are as follows: This invention ingeniously achieves high reflectivity of the visible and near-infrared spectra of sunlight under high-temperature conditions and high absorption of the visible and near-infrared spectra of sunlight under low-temperature conditions through a multi-layer composite coating structure design, thus realizing a visible and near-infrared spectral synergistic modulation material system suitable for structural facade coating systems. Visible spectral energy modulation is mainly achieved through the thermotropic reversible color-changing coating system, while near-infrared spectral energy modulation mainly relies on a near-infrared modulation layer containing vanadium oxide. To address the problem that the vanadium oxide layer cannot achieve near-infrared spectral absorption at low temperatures, a near-infrared absorption layer containing cesium tungsten bronze is introduced to facilitate the absorption of near-infrared spectral energy transmitted through the vanadium oxide layer under low-temperature conditions.

[0019] Furthermore, to further improve the coating performance, magnesium doping was first introduced to regulate the phase transition point of vanadium oxide, reducing the regulation temperature from the original 68℃ to approximately 40℃, thus achieving suitable transition temperature control. Secondly, addressing the issue of high absorption of vanadium oxide in the visible light band, nano-tin-antimony oxide was introduced to modify the vanadium oxide. Through the construction of a nanocomposite structure and high-temperature thermal annealing, a high tin concentration was achieved at the interface, diffusing into the vanadium oxide, broadening the bandgap of the vanadium oxide, and avoiding unnecessary defects. This effectively improved the visible light transmittance of the film and further enhanced its near-infrared modulation performance. To reduce the absorption of cesium tungsten bronze in the visible light band while enhancing its near-infrared absorption and temperature control effect, silica aerogel was used to modify the cesium tungsten bronze. Ball milling allowed the high surface energy cesium tungsten bronze component to adsorb lightweight silica aerogel particles. Due to the anti-reflection effect of silica, the visible transmittance of the composite particles was higher than that of pure cesium tungsten bronze. Furthermore, the Rayleigh scattering of silica aerogel particles with diameters of 10 nm or even smaller can effectively reduce scattering perpendicular to the incident light direction, thereby allowing the incident near-infrared light to be fully absorbed by cesium tungsten bronze. Combined with the strong heat insulation effect of aerogel particles, this effectively enhances its heat absorption capacity in low-temperature environments.

[0020] In summary, through ingenious design and material modification, this invention has prepared a composite coating structure system that can achieve synergistic regulation of visible and near-infrared sunlight due to temperature self-sensing under appropriate conditions. This system can effectively achieve the effects of low-temperature heat absorption and heat preservation, and high-temperature reflective cooling. This invention patent is of great significance for the preparation, research and development of surface passive temperature control materials with intelligent temperature control function, and for their promotion in related application fields. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments.

[0022] Example 1: A thermotropic reversible color-changing composite coating I capable of achieving synergistic modulation of visible-near-infrared spectra, the preparation process of which is as follows:

[0023] (1) Weigh 65 parts of fluorocarbon resin, 5 parts of xylene, 28.3 parts of rutile titanium dioxide, 0.5 parts of dispersant, 0.5 parts of leveling agent and 0.6 parts of defoamer. Disperse and mix the fluorocarbon resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AIa of the high-performance solar reflective coating.

[0024] (2) Weigh 80 parts of fluorocarbon resin, 3 parts of xylene, 15.3 parts of silica aerogel modified cesium tungsten bronze, 0.5 parts of dispersant, 0.5 parts of leveling agent and 0.6 parts of defoamer, and prepare high near-infrared absorption coating AIb by a similar method as in (1).

[0025] (3) Weigh 79 parts of fluorocarbon resin, 7 parts of xylene, 12.4 parts of nano-tin antimony modified vanadium oxide, 0.5 parts of dispersant, 0.5 parts of leveling agent and 0.6 parts of defoamer, and prepare near-infrared modulated coating AIc by a similar method as in (1).

[0026] (4) Weigh 70 parts of fluorocarbon resin, 5.4 parts of xylene, 23 parts of thermochromic microcapsules, 0.5 parts of dispersant, 0.5 parts of leveling agent and 0.6 parts of defoamer, and prepare thermochromic reversible color-changing coating AId by a similar method to (1).

[0027] (5) Disperse and mix 30 parts toluene diisocyanate, 65 parts toluene diisocyanate trimer and 5 parts xylene using a high-speed disperser for 15 minutes until the system is homogeneous and stable to obtain the curing agent component BI of the above coating.

[0028] (6) Weigh the AIa main agent and BI curing agent according to the mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 60μm by spraying.

[0029] (7) Weigh the AIb main agent and BI curing agent at a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectivity substrate to prepare a near-infrared absorption layer with a dry film thickness of 25μm by spraying.

[0030] (8) Weigh AIc main agent and BI curing agent at a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after drying and curing the near-infrared absorption layer.

[0031] (9) Weigh AId main agent and BI curing agent according to a mass ratio of 1:0.13, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer has dried and cured. This will give you the composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating I.

[0032] Example 2: A thermotropic reversible color-changing composite coating II capable of achieving synergistic modulation of visible-near-infrared spectroscopy, the preparation process of which is as follows:

[0033] (1) Weigh 65 parts of silicone resin, 6 parts of acetone, 28 parts of rutile titanium dioxide, 0.5 parts of dispersant, 0.3 parts of defoamer and 0.2 parts of thixotropic agent. Disperse and mix the silicone resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AIIa of the high-performance solar reflective coating.

[0034] (2) Weigh 80 parts of silicone resin, 3 parts of acetone, 16 parts of silica aerogel modified cesium tungsten bronze, 0.5 parts of dispersant, 0.3 parts of defoamer and 0.2 parts of thixotropic agent, and prepare high near-infrared absorption coating AIIb by a similar method to (1).

[0035] (3) Weigh 79.5 parts of silicone resin, 5.5 parts of acetone, 14 parts of nano-tin antimony modified vanadium oxide, 0.5 parts of dispersant, 0.3 parts of defoamer and 0.2 parts of thixotropic agent, and prepare near-infrared modulated coating AIIc by a similar method to (1).

[0036] (4) Weigh 70 parts of silicone resin, 3 parts of acetone, 26 parts of thermochromic microcapsules, 0.5 parts of dispersant, 0.3 parts of defoamer and 0.2 parts of thixotropic agent, and prepare thermochromic reversible color-changing coating AIId by a method similar to that in (1).

[0037] (5) Use polymethylene polyphenyl polyisocyanate as the curing agent component BII of the above coating.

[0038] (6) Weigh AIIa main agent and BII curing agent at a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 40μm by spraying.

[0039] (7) Weigh AIIb main agent and BII curing agent according to a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate. Then, prepare a near-infrared absorption layer with a dry film thickness of 25μm by spraying.

[0040] (8) Weigh AIIc main agent and BII curing agent according to a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 20μm by spraying after drying and curing the near-infrared absorption layer.

[0041] (9) Weigh AIId main agent and BII curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer has dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating II can be obtained.

[0042] Example 3: A thermotropic reversible color-changing composite coating III capable of achieving synergistic modulation of visible-near-infrared spectroscopy, the preparation process of which is as follows:

[0043] (1) Weigh 67 parts of fluorocarbon resin, 5.5 parts of butyl acetate, 24.5 parts of rutile titanium dioxide, 1 part of dispersant, 1 part of defoamer and 1 part of leveling agent. Disperse and mix the fluorocarbon resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AIIIa of the high-performance solar reflective coating.

[0044] (2) Weigh 74 parts of fluorocarbon resin, 8 parts of butyl acetate, 15 parts of silica aerogel modified cesium tungsten bronze, 1 part of dispersant, 1 part of defoamer and 1 part of leveling agent, and prepare high near-infrared absorption coating AIIIb by a similar method to (1).

[0045] (3) Weigh 75 parts of fluorocarbon resin, 7 parts of butyl acetate, 15 parts of nano-tin oxide antimony modified vanadium oxide, 1 part of dispersant, 1 part of defoamer and 1 part of leveling agent, and prepare near-infrared modulated coating AIIIc by a similar method as in (1).

[0046] (4) Weigh 62 parts of fluorocarbon resin, 4 parts of butyl acetate, 31 parts of thermochromic microcapsules, 1 part of dispersant, 1 part of defoamer and 1 part of leveling agent, and prepare thermochromic reversible color-changing coating AIIId by a similar method as in (1).

[0047] (5) Disperse and mix 85 parts of isophorone diisocyanate and 15 parts of butyl acetate using a high-speed disperser for 15 minutes until the system is homogeneous and stable to obtain the curing agent component BIII of the above coating.

[0048] (6) Weigh AIIIa main agent and BIII curing agent at a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 45μm by spraying.

[0049] (7) Weigh AIIIb main agent and BIII curing agent according to a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate to prepare a near-infrared absorption layer with a dry film thickness of 20μm by spraying.

[0050] (8) Weigh AIIIc main agent and BIII curing agent at a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after drying and curing the near-infrared absorption layer.

[0051] (9) Weigh AIIId main agent and BIII curing agent according to a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 35μm by spraying after the near-infrared modulation layer has dried and cured. This will give you the composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating III.

[0052] Example 4: A thermotropic reversible color-changing composite coating IV capable of achieving synergistic modulation of visible-near-infrared spectroscopy, the preparation process of which is as follows:

[0053] (1) Weigh 66 parts of polyurethane resin, 3.8 parts of ethanol, 29 parts of rutile titanium dioxide, 0.6 parts of dispersant and 0.6 parts of leveling agent. Disperse and mix the polyurethane resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AIVa of the high-performance solar reflective coating.

[0054] (2) Weigh 72.5 parts of polyurethane resin, 6.8 parts of ethanol, 19.5 parts of silica aerogel modified cesium tungsten bronze, 0.6 parts of dispersant and 0.6 parts of leveling agent, and prepare a high near-infrared absorption coating AIVb by a similar method to (1).

[0055] (3) Weigh 84 parts of polyurethane resin, 3.8 parts of ethanol, 11 parts of nano-tin antimony modified vanadium oxide, 0.6 parts of dispersant and 0.6 parts of leveling agent, and prepare near-infrared modulated coating AIVc by a similar method as in (1).

[0056] (4) Weigh 60 parts of polyurethane resin, 6.8 parts of ethanol, 32 parts of thermochromic microcapsules, 0.6 parts of dispersant and 0.6 parts of leveling agent, and prepare thermochromic reversible color-changing coating AIVd by a method similar to that in (1).

[0057] (5) Dicyclohexylmethane diisocyanate was used as the curing agent component BIV of the above coating.

[0058] (6) Weigh AIVa main agent and BIV curing agent at a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 45μm by spraying.

[0059] (7) Weigh AIVb main agent and BIV curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate. Then, prepare a near-infrared absorption layer with a dry film thickness of 18μm by spraying.

[0060] (8) Weigh AIVc main agent and BIV curing agent at a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after drying and curing the near-infrared absorption layer.

[0061] (9) Weigh AIVd main agent and BIV curing agent according to a mass ratio of 1:0.09, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer has dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating IV can be obtained.

[0062] Example 5: A thermotropic reversible color-changing composite coating V capable of achieving synergistic modulation of visible and near-infrared spectra, the preparation process of which is as follows:

[0063] (1) Weigh 60 parts of silicone resin, 8.8 parts of butyl acetate, 30 parts of rutile titanium dioxide, 0.6 parts of defoamer and 0.6 parts of thixotropic agent. Disperse and mix the silicone resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AVA of the high-performance solar reflective coating.

[0064] (2) Weigh 77 parts of silicone resin, 5.8 parts of butyl acetate, 16 parts of silica aerogel modified cesium tungsten bronze, 0.6 parts of defoamer and 0.6 parts of thixotropic agent, and prepare high near-infrared absorption coating AVb by a similar method as in (1).

[0065] (3) Weigh 80 parts of silicone resin, 6.3 parts of butyl acetate, 12.5 parts of nano-tin antimony modified vanadium oxide, 0.6 parts of defoamer and 0.6 parts of thixotropic agent, and prepare near-infrared modulated coating AVC by a similar method as in (1).

[0066] (4) Weigh 70 parts of silicone resin, 5.8 parts of butyl acetate, 23 parts of thermochromic microcapsules, 0.6 parts of defoamer and 0.6 parts of thixotropic agent, and prepare thermochromic reversible color-changing coating AVd by a method similar to that in (1).

[0067] (5) Disperse and mix 35 parts of dicyclohexylmethane diisocyanate, 60 parts of hexamethylene diisocyanate biuret and 5 parts of butyl acetate using a high-speed disperser for 15 minutes until the system is homogeneous and stable to obtain the curing agent component BV of the above coating.

[0068] (6) Weigh AVA main agent and BV curing agent at a mass ratio of 1:0.09, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 50μm by spraying.

[0069] (7) Weigh AVb main agent and BV curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectivity substrate to prepare a near-infrared absorption layer with a dry film thickness of 20μm by spraying.

[0070] (8) Weigh AVC main agent and BV curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after drying and curing the near-infrared absorption layer.

[0071] (9) Weigh AVd main agent and BV curing agent according to a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 50μm by spraying after the near-infrared modulation layer is dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating V can be obtained.

[0072] Example 6: A thermotropic reversible color-changing composite coating VI capable of achieving synergistic modulation of visible-near-infrared spectra, the preparation process of which is as follows:

[0073] (1) Weigh 70 parts of polyurethane resin, 4 parts of isopropanol, 24 parts of rutile titanium dioxide, 1 part of leveling agent and 1 part of adhesion promoter. Use a high-speed disperser to disperse and mix the polyurethane resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AVIa of the high-performance solar reflective coating.

[0074] (2) Weigh 77 parts of polyurethane resin, 5 parts of isopropanol, 16 parts of silica aerogel modified cesium tungsten bronze, 1 part of leveling agent and 1 part of adhesion promoter, and prepare high near-infrared absorption coating AVIb by a similar method as in (1).

[0075] (3) Weigh 76.5 parts of polyurethane resin, 8.5 parts of isopropanol, 13 parts of nano-tin antimony modified vanadium oxide, 1 part of leveling agent and 1 part of adhesion promoter, and prepare near-infrared modulated coating AVIc by a similar method as in (1).

[0076] (4) Weigh 56 parts of polyurethane resin, 9 parts of isopropanol, 33 parts of thermochromic microcapsules, 1 part of leveling agent and 1 part of adhesion promoter, and prepare thermochromic reversible color-changing coating AVId by a similar method to (1).

[0077] (5) Disperse and mix 93 parts of cyclohexanedimethyl diisocyanate and 7 parts of isopropanol using a high-speed disperser for 15 minutes until the system is homogeneous and stable to obtain the curing agent component BVI of the above coating.

[0078] (6) Weigh AVIa main agent and BVI curing agent at a mass ratio of 1:0.13, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 45μm by spraying.

[0079] (7) Weigh AVIb main agent and BVI curing agent at a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate to prepare a near-infrared absorption layer with a dry film thickness of 22μm by spraying.

[0080] (8) Weigh AVIc main agent and BVI curing agent at a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 18μm by spraying after the near-infrared absorption layer has dried and cured.

[0081] (9) Weigh AVId main agent and BVI curing agent according to a mass ratio of 1:0.09, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer is dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible color coating VI can be obtained.

[0082] Example 7: A thermotropic reversible color-changing composite coating VII capable of achieving synergistic modulation of visible-near-infrared spectroscopy, the preparation process of which is as follows:

[0083] (1) Weigh 62 parts of fluorocarbon resin, 4.7 parts of xylene, 32 parts of rutile titanium dioxide, 0.4 parts of dispersant, 0.4 parts of leveling agent and 0.5 parts of defoamer. Disperse and mix the fluorocarbon resin and rutile titanium dioxide at 50℃ and 8 m / s linear velocity for 15 min using a high-speed disperser. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the main component AVIIa of the high-performance solar reflective coating.

[0084] (2) Weigh 80 parts of fluorocarbon resin, 3.7 parts of xylene, 15 parts of silica aerogel modified cesium tungsten bronze, 0.4 parts of dispersant, 0.4 parts of leveling agent and 0.5 parts of defoamer, and prepare high near-infrared absorption coating AVIIb by a similar method to (1).

[0085] (3) Weigh 75 parts of fluorocarbon resin, 9.2 parts of xylene, 14.5 parts of nano-tin antimony modified vanadium oxide, 0.4 parts of dispersant, 0.4 parts of leveling agent and 0.5 parts of defoamer, and prepare near-infrared modulated coating AVIIc by a similar method as in (1).

[0086] (4) Weigh 68 parts of fluorocarbon resin, 6.7 parts of xylene, 24 parts of thermochromic microcapsules, 0.4 parts of dispersant, 0.4 parts of leveling agent and 0.5 parts of defoamer, and prepare thermochromic reversible color-changing coating AVIId by a method similar to that in (1).

[0087] (5) Disperse and mix 92 parts hexamethylene diisocyanate and 8 parts xylene using a high-speed disperser for 15 minutes until the system is homogeneous and stable to obtain the curing agent component BVII of the above coating.

[0088] (6) Weigh AVIIa main agent and BVII curing agent at a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 60μm by spraying.

[0089] (7) Weigh AVIIb main agent and BVII curing agent at a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate to prepare a near-infrared absorption layer with a dry film thickness of 20μm by spraying.

[0090] (8) Weigh AVIIc main agent and BVII curing agent according to a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 12μm by spraying after drying and curing the near-infrared absorption layer.

[0091] (9) Weigh AVIId main agent and BVII curing agent according to a mass ratio of 1:0.13, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 35μm by spraying after the near-infrared modulation layer has dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating VII can be obtained.

[0092] Comparative Example 1: Commercially available reflective heat insulation coatings

[0093] A reflective heat-insulating and temperature-controlling coating was prepared using a commercially available brand of reflective heat-insulating coating and its performance was compared with that of the examples.

[0094] Comparative Example 2: Commercially available thermochromic coatings

[0095] A thermochromic coating was prepared using a commercially available brand of thermochromic paint and its performance was compared with that of the examples.

[0096] Comparative Example 3: Self-made thermochromic temperature-controlled coating VIII, the preparation process of which is as follows:

[0097] (1) Weigh AIIa main agent and BII curing agent according to a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar spectrum high reflectivity base layer with a dry film thickness of 40μm by spraying.

[0098] (2) Weigh AIId main agent and BII curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate. After drying and curing, prepare a thermochromic layer with a dry film thickness of 40μm by spraying to obtain the self-made thermochromic temperature control coating VIII.

[0099] Comparative Example 4: Self-made thermo-responsive coating IX, the preparation process of which is as follows:

[0100] (1) Weigh AIIa main agent and BII curing agent according to a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar spectrum high reflectivity base layer with a dry film thickness of 40μm by spraying.

[0101] (2) Weigh AIIc main agent and BII curing agent according to a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate. Then, prepare a near-infrared modulation layer with a dry film thickness of 20μm by spraying.

[0102] (9) Weigh AIId main agent and BII curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer is dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating IX can be obtained.

[0103] Comparative Example 5: Thermotropic reversible color-changing composite coating X was prepared from aerogel-free modified cesium tungsten bronze. The preparation process is as follows:

[0104] (1) Weigh 72.5 parts of polyurethane resin, 6.8 parts of ethanol, 19.5 parts of cesium tungsten bronze (no silica aerogel was used for ball milling modification during the preparation process), 0.6 parts of dispersant and 0.6 parts of leveling agent. Disperse and mix the polyurethane resin and cesium tungsten bronze using a high-speed disperser at 50°C and a linear velocity of 8 m / s for 15 min. Then, perform ultrasonic treatment for 8 min. Add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the coating main component AXb.

[0105] (2) Weigh AIVa main agent and BIV curing agent at a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 45μm by spraying.

[0106] (7) Weigh AXb main agent and BIV curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate. Then, prepare a near-infrared absorption layer with a dry film thickness of 18μm by spraying.

[0107] (8) Weigh AIVc main agent and BIV curing agent at a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after drying and curing the near-infrared absorption layer.

[0108] (9) Weigh AIVd main agent and BIV curing agent according to a mass ratio of 1:0.09, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 40μm by spraying after the near-infrared modulation layer is dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating X can be obtained.

[0109] Comparative Example 6: Thermotropic reversible color-changing composite coating XI was prepared with no nano-tin oxide antimony modified vanadium oxide content. The preparation process is as follows:

[0110] (1) Weigh 80 parts of silicone resin, 6.3 parts of butyl acetate, 12.5 parts of vanadium oxide (vanadium oxide prepared by modification and annealing without the addition of nano-tin antimony oxide during the preparation process), 0.6 parts of defoamer and 0.6 parts of thixotropic agent. Disperse and mix the silicone resin and vanadium oxide using a high-speed disperser at 50℃ and a linear velocity of 8 m / s for 15 min, followed by ultrasonic treatment for 8 min. Then add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the coating main component AXIc.

[0111] (2) Weigh AVA main agent and BV curing agent according to a mass ratio of 1:0.09, mix them evenly with mechanical stirring, and then prepare a solar spectrum high reflectivity base layer with a dry film thickness of 50μm by spraying.

[0112] (3) Weigh AVb main agent and BV curing agent according to a mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectivity substrate to prepare a near-infrared absorption layer with a dry film thickness of 20μm by spraying.

[0113] (4) Weigh the AXIc main agent and BV curing agent according to the mass ratio of 1:0.12, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 15μm by spraying after the near-infrared absorption layer has dried and cured.

[0114] (5) Weigh AVd main agent and BV curing agent according to a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 50μm by spraying after the near-infrared modulation layer has dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating XI can be obtained.

[0115] Comparative Example 7: Thermotropic reversible color-changing composite coating XII, the preparation process of which is as follows:

[0116] (6) Weigh AVIIa main agent and BVII curing agent at a mass ratio of 1:0.11, mix them evenly with mechanical stirring, and then prepare a solar high reflectivity base layer with a dry film thickness of 20μm by spraying.

[0117] (7) Weigh AVIIb main agent and BVII curing agent according to a mass ratio of 1:0.15, mix them evenly with mechanical stirring, and then dry and cure them on a high solar reflectance substrate to prepare a near-infrared absorption layer with a dry film thickness of 40μm by spraying.

[0118] (8) Weigh AVIIc main agent and BVII curing agent at a mass ratio of 1:0.14, mix them evenly with mechanical stirring, and then prepare a near-infrared modulation layer with a dry film thickness of 40μm by spraying after drying and curing the near-infrared absorption layer.

[0119] (9) Weigh AVIId main agent and BVII curing agent according to a mass ratio of 1:0.13, mix them evenly with mechanical stirring, and then prepare a thermochromic layer with a dry film thickness of 20μm by spraying after the near-infrared modulation layer has dried and cured. The composite visible-near-infrared spectrum synergistic modulation thermochromic reversible coating XII can be obtained.

[0120] Effect description:

[0121] The thermotropic reversible color-changing composite coatings with synergistic visible-near-infrared spectral modulation prepared in Examples 1-7 of this invention were compared with the comparative coatings in Examples 1-7. The solar reflectance spectra of the coatings at 5℃ and 50℃ were tested, and the visible light modulation capability (300 nm~780 nm), near-infrared modulation capability (780 nm~2500 nm), and solar light modulation capability (difference in solar reflectance) of the coatings at 5℃ and 50℃ were calculated. The modulation performance stability after 200 high and low temperature cycles was also tested, and the relevant test results are summarized in Table 1.

[0122] Table 1 Performance test results of thermotropic reversible color-changing composite coating

[0123] sample Visible light band modulation performance Near-infrared band modulation performance Solar reflectance modulation performance Modulation performance retention rate after 200 cycles Example 1 68% 40% 51% 95% Example 2 64% 38% 48% 98% Example 3 65% 45% 46% 97% Example 4 65% 42% 48% 98% Example 5 70% 36% 45% 97% Example 6 72% 38% 52% 96% Example 7 66% 42% 46% 98% Comparative Example 1 0% 0% 0% / Comparative Example 2 65% 1% 25% 68% Comparative Example 3 82% 1% 29% 95% Comparative Example 4 70% 1% 26% 95% Comparative Example 5 50% 23% 30% 96% Comparative Example 6 48% 20% 24% 95% Comparative Example 7 30% 33% 22% 96%

[0124] As shown in Table 1, the visible-near-infrared spectral synergistic modulation thermochromic composite coating prepared in the examples can simultaneously achieve modulation performance of 60%~70% in the visible light band and 35%~40% in the near-infrared band under low-temperature conditions of 5℃ and high-temperature conditions of 50℃. This results in an overall solar reflectance modulation rate approaching 50%, a significant improvement over traditional thermochromic temperature-controlled coatings. This is due to the synergistic effect of a cleverly designed multi-layered functional structure incorporating high reflectance, near-infrared absorption, near-infrared modulation, and thermochromic properties. Furthermore, the system shows no significant degradation in modulation and temperature control performance after 200 color-changing cycles, indicating superior long-term service performance. These experimental results confirm the strong practical value of the embodiments of the present invention.

[0125] Comparative Example 1 is a high-reflectivity heat-insulating coating with no temperature response performance. It has the same spectral performance under different conditions, so it is only suitable for reflective cooling under high-temperature conditions. Comparative Examples 2 and 3 are composite coatings of thermochromic coating and high-reflectivity coating. Since the room-temperature color-changing substance is an organic color-changing material, it can only achieve reflectivity adjustment in the visible light band, and has no adjustment performance in the near-infrared band. Even though the self-made color-changing coating can achieve more than 80% modulation performance in the visible light band, its overall solar reflectivity modulation performance is still far lower than that of the examples.

[0126] Comparative Example 4 lacks a near-infrared absorption layer prepared using cesium tungsten bronze-like raw materials as fillers. Therefore, although the vanadium oxide layer can control the near-infrared transmittance at different temperatures, the increased near-infrared bands are still reflected by the underlying layer. Thus, it also lacks near-infrared modulation performance, and its modulation performance in the visible light band is even lower than that of a pure reversible color-changing coating. This is because the vanadium oxide layer also absorbs a small portion of visible light at high temperatures.

[0127] Comparative Example 5 used cesium tungsten bronze without silica aerogel modification as the filler for the near-infrared absorption layer. It exhibited significant absorption of visible light at high temperatures, but its near-infrared absorption rate was insufficient at low temperatures. Therefore, its modulation performance in both bands was significantly lower than that of the example, and its overall solar reflectance modulation performance was also insufficient. Comparative Example 6 used vanadium oxide without nano-tin antimony oxide modification as the filler for the near-infrared modulation layer. It also showed significant absorption of visible light at high temperatures, and the difference in near-infrared transmittance before and after the phase transition at different temperatures was small. Therefore, its modulation performance in both bands was also significantly lower than that of the example, and its overall solar reflectance modulation performance was insufficient.

[0128] In Comparative Example 7, the high-reflectivity layer and the reversible color-changing layer are relatively thin, while the near-infrared absorption layer and the near-infrared modulation layer are relatively thick. This results in a significant increase in absorption in the visible light band and a significant decrease in modulation performance. The near-infrared modulation performance is also reduced due to the thinning of the reflective layer, so the overall performance is significantly reduced.

[0129] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments without departing from the technical essence of the present invention shall still fall within the scope of the present invention.

Claims

1. A thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible-near-infrared spectra, characterized in that... It is a multi-layered composite temperature-controlled coating composed of a solar high reflectivity layer, a near-infrared absorption layer, a near-infrared modulation layer, and a thermochromic layer. The solar high reflectivity layer is prepared using a high-performance solar reflective coating with rutile titanium dioxide filler. The near-infrared absorption layer is prepared using a high near-infrared absorption coating with silica aerogel-modified cesium tungsten bronze filler. The near-infrared modulation layer is prepared using a near-infrared modulation coating with nano-tin antimony oxide-modified vanadium dioxide filler. The thermochromic layer is prepared using a thermochromic reversible color-changing coating with thermochromic microcapsule filler. The film thicknesses of the solar high reflectivity layer, near-infrared absorption layer, near-infrared modulation layer, and thermochromic layer are 40 μm~60 μm, 15 μm~25 μm, 10 μm~20 μm, and 30 μm~50 μm, respectively.

2. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The high-performance solar reflective coating is composed of A1 main agent and B1 curing agent; wherein A1 main agent is prepared by mixing matrix resin, rutile titanium dioxide filler, solvent and functional additives; the mass contents of matrix resin, rutile titanium dioxide filler, solvent and functional additives are 55%~72%, 22%~33%, 3%~10% and 1%~4% respectively, based on the total mass of A1 main agent; B1 curing agent is prepared by curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A1 main agent and B1 curing agent is 1:(0.08~0.22).

3. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The high near-infrared absorption coating is composed of A2 main agent and B2 curing agent; wherein A2 main agent is prepared from matrix resin, silica aerogel modified cesium tungsten bronze filler, solvent and functional additives; the mass contents of matrix resin, silica aerogel modified cesium tungsten bronze filler, solvent and functional additives are 70%~80%, 15%~20%, 3%~10% and 1%~3% respectively, based on the total mass of A2 main agent; B2 curing agent is prepared from curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A2 main agent and B2 curing agent is 1:(0.12~0.25).

4. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The preparation method of silica aerogel modified cesium tungsten bronze is as follows: (1) Tungsten chloride is mixed with ethanol and completely dissolved, then cesium hydroxide is added and stirred for 5 min, and finally acetic acid is added and stirred evenly to obtain a reaction precursor solution; (2) The reaction precursor solution is transferred into a reactor and heated at 220℃~240℃ for 24 h. The precipitate is centrifuged, washed and vacuum dried to obtain cesium tungsten bronze powder; (3) The cesium tungsten bronze powder and a certain amount of silica aerogel are mixed evenly in N,N-dimethylformamide and ball-milled at 600 rpm for 30 min to obtain silica aerogel modified cesium tungsten bronze; wherein the mass ratio of cesium tungsten bronze to silica aerogel is 1: (0.3~0.6).

5. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The near-infrared modulated coating is composed of A3 main agent and B3 curing agent; wherein A3 main agent is prepared from matrix resin, nano-tin antimony oxide modified vanadium dioxide filler, solvent and functional additives; the mass contents of matrix resin, nano-tin antimony oxide modified vanadium dioxide filler, solvent and functional additives are 75%~85%, 10%~15%, 3%~10% and 1%~3% respectively, based on the total mass of A3 main agent; B3 curing agent is prepared from curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A3 main agent and B3 curing agent is 1:(0.14~0.25).

6. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The preparation method of the nano-tin-antimony modified vanadium dioxide is as follows: (1) Vanadium pentoxide and oxalic acid dihydrate are uniformly dissolved in deionized water at a molar ratio of 1:

2. After dissolution, magnesium sulfate is added and stirred for 30 min to obtain a reaction precursor solution; (2) The reaction precursor solution is transferred to a hydrothermal reactor and reacted at 240℃ for 10 h. Then, it is ultrasonically cleaned three times with water and ethanol respectively, vacuum filtered at 60℃ and dried for 12 h, and ground to obtain magnesium-doped vanadium dioxide powder; (3) The vanadium dioxide powder and nano-tin-antimony are mixed evenly in water and ball-milled at a speed of 400 rpm to 600 rpm for 30 min; (4) Under a nitrogen atmosphere, the ball-milled powder is heat-treated at a temperature of 520 ℃ to 600 ℃ for 3 h to obtain nano-tin-antimony modified vanadium dioxide; wherein the doping amount of magnesium element is 1.5% to 2.3% based on the mass of vanadium dioxide; the mass ratio of vanadium dioxide to nano-tin-antimony is 1: (0.8 to 1.4).

7. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The thermochromic coating is composed of A4 main agent and B4 curing agent; wherein A4 main agent is prepared from matrix resin, thermochromic microcapsule filler, solvent and functional additives; the mass contents of matrix resin, thermochromic microcapsule filler, solvent and functional additives are 55%~72%, 20%~35%, 3%~10% and 1%~4% respectively, based on the total mass of A4 main agent; B4 curing agent is prepared from curing agent and solvent, the mass contents of curing agent and solvent are 85%~100% and 0~15% respectively; the mass ratio of A4 main agent and B4 curing agent is 1:(0.09~0.22).

8. The thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The preparation method of the thermotropic reversible color-changing microcapsules includes the following steps: (1) dissolving the ternary thermotropic reversible color-changing core material composed of pigment, color developer and solvent and adding it to water containing emulsifier, and emulsifying it at high speed under heating conditions at 65°C to obtain a thermotropic reversible color-changing emulsion; (2) adding the resin prepolymer to the reversible color-changing emulsion at a constant rate under heating and stirring conditions, and after the addition is completed, polymerizing in situ at 85°C for 1 hour, filtering and drying the suspension after the reaction to obtain the thermotropic reversible color-changing microcapsules; wherein the pigment is at least one of crystal violet lactone, 2-phenylamino-3-methyl-6-dibutylaminofluorane, and 3',6'-dimethoxyfluorane; The color developer is at least one of bisphenol A, bisphenol F, and bisphenol S; the solvent is at least one of tetradecyl alcohol, glyceryl tridecanoate, methyl octadecanoate, and ethyl octadecanoate; the mass concentration of the pigment molecules is 0.8% to 6%, and the mass ratio of pigment to color developer is 1:(1.5 to 4) based on the total mass of the color-changing core material; the emulsifier is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium salt of styrene-maleic anhydride copolymer, with a mass concentration of 0.5% to 1%; the resin prepolymer is at least one of melamine resin prepolymer, urea-formaldehyde resin prepolymer, and methyl melamine-formaldehyde resin prepolymer, and the amount used is 5% to 13% of the total mass of the thermotropic reversible color-changing microcapsules.

9. A thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible-near-infrared spectra according to any one of claims 2, 3, 5, and 7, characterized in that... The preparation methods for the high-performance solar reflective coating, high near-infrared absorption coating, near-infrared modulation coating, and thermotropic reversible color-changing coating are as follows: Weigh out appropriate amounts of each component, disperse and mix the matrix resin and filler using a high-speed disperser at 40 ℃~60 ℃ and a linear velocity of 6 m / s~10 m / s for 15 min, then perform ultrasonic treatment for 4 min~10 min, and finally add the remaining components to the mixture and disperse for 30 min until the system is homogeneous and stable to obtain the coating main component. The curing agent component is obtained by dispersing and mixing isocyanate and solvent using a high-speed disperser for 15 minutes until the system is homogeneous and stable. The matrix resin is at least one of silicone resin, fluorocarbon resin, and polyurethane resin; the solvent is at least one of xylene, acetone, ethanol, isopropanol, butyl acetate, and propylene glycol methyl ether acetate; the functional additive is at least one of dispersant, defoamer, leveling agent, adhesion promoter, and thixotropic agent; and the isocyanate is at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, phenyl diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate trimer, and hexamethylene diisocyanate biuret.

10. A thermotropic reversible color-changing composite coating capable of achieving synergistic modulation of visible and near-infrared spectra as described in claim 1, characterized in that... The coating is prepared by sequentially forming a film of appropriate thickness on a substrate using high-performance solar reflective coating, high near-infrared absorption coating, near-infrared modulation coating and thermochromic coating. The forming method can be any one of screen printing, spraying, casting, or roller coating; each coating layer needs to be dried at room temperature for 24 hours and then cured at 60°C for 12 hours. The next coating layer is formed after the previous coating layer is completed. This thermotropic reversible color-changing composite coating can be used as a surface temperature control material for buildings, cold storage facilities, industrial storage tanks, and transportation infrastructure structures.