Intelligent cooling coating with multi-layer functional gradient structure and preparation method of intelligent cooling coating

Abstract

The invention discloses an intelligent cooling coating with a multi-layer functional gradient structure and a preparation method of the intelligent cooling coating. The coating comprises an infrared reflection-heat conduction blocking bottom layer, a heat insulation middle layer and an anti-pollution high-reflection surface layer. Each layer comprises the following components: hollow glass beads, aerogel powder and a water-based acrylic emulsion, and is used for constructing the low-heat-conductivity and infrared-reflection bottom layer; the metal organic framework material, the polyurethane emulsion, the coupling agent and the dispersing agent are used for constructing a heat-insulation slow-release middle layer; the reflective heat-insulation rare earth powder, the fluorosilicone modified acrylic resin, the flatting agent and the dispersing agent are used for constructing a high-reflection self-cleaning structure of the surface layer. Three-layer step-by-step construction, sequential coating and layered thermocuring are adopted for preparation. The coating is environment-friendly and stable in structure, has the properties of infrared reflection, self-cleaning, thermal buffering and the like, can be used for effectively cooling and improving weather resistance and corrosion resistance, is suitable for high-temperature protection of building outer walls, roofs, storage and transportation equipment and the like, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating, in particular to a multi-layer functional gradient structure intelligent cooling coating and a preparation method thereof. BACKGROUND

[0002] With the acceleration of urbanization process and the continuous intensification of global warming trend, the heat load problem caused by high temperature environment to the infrastructure such as building, transportation and storage is increasingly prominent, especially during the high temperature period in summer, the temperature of the surface of the building outer wall, roof and container can reach above 60℃, which causes the increase of energy consumption, the decline of indoor thermal comfort, and even the intensification of urban heat island effect. Therefore, the development of energy-saving coating materials with high-efficiency cooling function has become a key technical approach to alleviate the influence of high temperature radiation and improve energy utilization efficiency.

[0003] The existing cooling coating mainly relies on high-reflective materials to realize passive temperature control by reflecting the visible light and near-infrared band radiation in sunlight. Among them, inorganic pigments such as TiO2 and ZnO can reduce the surface temperature rise by 5~8℃ in the short term, but their anti-pollution ability is insufficient, and they are easily affected by dust, oil stains and rainwater during long-term outdoor exposure, resulting in the attenuation of reflectivity and the failure of the coating. In addition, the single light reflection mechanism has limited effect in cloudy days, night and other non-strong radiation environments, and the cooling effect is restricted by light conditions, which has obvious application range limitation. In order to make up for the deficiency of single mechanism cooling, researchers try to introduce functional fillers with low thermal conductivity, such as hollow glass beads, aerogel and ceramic particles, to build thermal resistance structure to delay the penetration of heat flow; on the other hand, the phase change heat storage technology is applied to the temperature control coating, which absorbs latent heat to adjust the surface heat fluctuation in a specific temperature range, and has become an important direction to realize composite heat management. However, traditional organic phase change materials have the problems of strong fluidity, poor stability and easy leakage, and need to be improved in weather resistance and encapsulation efficiency through reasonable structure confinement design.

[0004] In recent years, metal-organic framework materials (MOFs) have been used to confine phase change materials due to their high specific surface area, regular pore structure, and good compatibility, achieving the synergistic improvement of high heat of mixing energy storage and structural stability. For example, ZIF-8 materials not only have good thermodynamic stability, but also can inhibit the leakage and deformation of phase change fillers, effectively prolonging the service life of the coating. In addition, to further enhance the cooling efficiency and durability, research has gradually shifted from single reflection to multi-layer gradient structure composite integration strategy, through layered construction of "infrared reflection-thermal resistance-thermal buffering-surface anti-fouling" multifunctional system, to achieve long-lasting cooling and interface heat flow regulation under full sunlight. On the other hand, the long-term service performance of the coating is also affected by surface contamination and water vapor penetration. Traditional TiO2 surface self-cleaning strategies are still prone to failure in complex environments. In contrast, rare earth reflective powder (such as rare earth phosphate and rare earth fluoride) not only has a wider spectrum of visible-near infrared reflection ability, but also has more excellent chemical stability and anti-aging performance, making it suitable for cooling protection needs in various outdoor weather conditions. At the same time, the introduction of fluorosilicon modified acrylic resin helps to construct a low surface energy coating, enhancing the superhydrophobicity and dust adhesion resistance, and prolonging the maintenance period of the actual cooling performance of the coating.

[0005] Among the currently disclosed related patents, the scheme with authorization announcement number CN 119432207A relies on carbon-based material light reflection cooling, but lacks dynamic regulation and conduction blocking ability of heat, and the raw material cost is high and the process is complex; although the scheme with authorization announcement number CN 119192914A adopts a three-layer structure, the middle layer is only bonded by polyurethane and silane coupling agent, lacks efficient heat storage materials, and the surface layer also does not achieve specific reflection and self-cleaning function of solar radiation, which is not suitable for popularization and application. SUMMARY

[0006] To solve the problems described in the background art, the present application provides a multi-layer functional gradient structure intelligent cooling coating and a preparation method thereof.

[0007] To achieve the above-mentioned purposes, the technical solutions of the present application are as follows: In a first aspect, the present application provides a multi-layer functional gradient structure intelligent cooling coating, comprising three layers of structure coated and solidified on the surface of a substrate in turn: Infrared reflection-thermal resistance bottom layer: composed of hollow glass microspheres 14-25 parts, aerogel powder 14-25 parts, and water-based acrylic emulsion 50-60 parts.

[0008] The type of hollow glass microspheres is one or several of K15, VS5500, and IM16K, which can directly reflect part of the infrared heat due to its light weight, low thermal conductivity, and good reflection performance of infrared light; The aerogel powder has an average pore diameter of 30 nm and a specific surface area of 780-820 m² / g, and the nanoscale porous structure (porosity > 90%) can form an excellent static heat barrier by limiting air convection, while enhancing the scattering of infrared light, and cooperates with hollow glass microbeads to improve the infrared reflectivity of the bottom layer (10-15% higher than single material); The water-based acrylic emulsion as the binder firmly bonds the above components to form a stable structure, and together realizes efficient reflection of infrared heat and effective blocking of heat conduction.

[0009] The heat insulation intermediate layer is composed of 5-10 parts of metal organic framework material, 75-85 parts of polyurethane emulsion, 2-5 parts of coupling agent, and 2-5 parts of dispersing agent.

[0010] The metal organic framework material is ZIF-8, which is one or several of models KAR-F01, KAR-F34, and KAR-F42, has a regular three-dimensional pore structure (pore diameter 0.3-1.2 nm), can limit the phase change components in the polyurethane emulsion (avoiding leakage), and has a high specific surface area (1500-2000 m² / g) to enhance the heat absorption and release capacity, so that the overall phase change enthalpy value of the intermediate layer reaches 190-210 J / g. Among them, KAR-F34 has the best limiting effect on phase change materials due to its moderate pore volume (0.6-0.8 cm³ / g), and the phase change enthalpy value retention rate is > 90% after 1000 cold and hot cycles, significantly improving the heat storage adjustment and heat buffering performance, which can buffer the trace heat that penetrates the first two layers and avoid instantaneous accumulation.

[0011] The anti-fouling high-reflective surface layer is composed of 10-15 parts of reflective heat-insulating rare earth powder, 70-80 parts of fluorine-silicon modified acrylic resin, 1-3 parts of leveling agent, and 2-5 parts of dispersing agent.

[0012] The reflective heat-insulating rare earth powder is one or several of rare earth phosphate, rare earth fluoride, and flaky rare earth corrosion-resistant powder, which has a reflectivity of > 85% in the 2-25 μm infrared band due to the 4f electron transition characteristics of rare earth elements, and the flaky structure can form a dense reflective layer. The fluorine-silicon modified acrylic resin gives the surface layer super-hydrophobic self-cleaning properties (water contact angle > 150°, rolling angle < 10°), reduces dirt adhesion (adhesion rate < 5%), and ensures long-term reflection efficiency; The leveling agent and dispersing agent ensure uniform film formation of the surface layer, further optimizing the reflection performance.

[0013] The three-layer structure is coated and cured on the surface of the substrate in turn to form a functional gradient synergistic system: the anti-fouling high-reflection surface layer as the first barrier directly reflects more than 60% of sunlight (especially in the infrared band) back to the outside world; the residual heat that is not completely reflected is reflected again (reflectivity increased by 15-20%) and blocked by the infrared reflection-heat conduction blocking bottom layer; the intermediate layer buffers the small amount of heat that penetrates. The overall coating has a reflectivity of not less than 80% in the 200-2500 nm band of sunlight (more than 85% in the 8-14 μm infrared band), and can reduce the surface temperature of the substrate by 10-15°C compared to the uncoated substrate at noon in summer (35-40°C environment). The reflectivity retention rate is greater than 90% after 50 times of rain washing, and finally a gradient cooling coating with high-efficiency reflection, heat blocking, heat storage regulation and self-cleaning functions is formed.

[0014] In a second aspect, the present application provides a preparation method of a multi-layer functional gradient structure intelligent cooling coating, comprising the following steps: S1) Bottom layer preparation: hollow glass microspheres and aerogel are added to water-based acrylic emulsion in proportion, stirred at high speed for 15 min, and then ultrasonically dispersed for 30 min to obtain a uniform coating; the coating is scraped or sprayed on the surface of the substrate, and dried at room temperature for 24 h or hot air dried at 60°C for 2 h to form a film; S2) Intermediate layer preparation: metal organic framework material is added to polyurethane emulsion, and after adding coupling agent and dispersant, it is high-speed shearing dispersed for 20 min, coated on the surface of the bottom layer, naturally leveled, and dried at 60°C for 4 h; S3) Surface layer preparation: reflective and heat-insulating rare earth powder is added to fluorosilicon modified acrylic resin, and after adding leveling agent and dispersant and high-speed dispersion for 10 min, it is coated on the intermediate layer, pre-cured at room temperature for 2 h, and then heat-cured at 100°C for 1 h to finally form a gradient functional structure coating.

[0015] The multi-layer functional gradient structure intelligent cooling coating obtained by the preparation method has a close combination of each layer structure, has the structural characteristics of the above-mentioned infrared reflection-heat conduction blocking bottom layer, heat-insulating intermediate layer and anti-fouling high-reflection surface layer, and each layer of material is uniformly distributed, thereby realizing the functions of high-efficiency reflection, heat blocking, heat storage regulation and self-cleaning.

[0016] In the step S1), the ultrasonic dispersion uses a power of 250W for 30 min to ensure uniform dispersion and long-term stable suspension of the hollow microspheres and aerogel in the emulsion.

[0017] The metal organic framework material used in step S2) is ZIF-8, which has a framework channel structure for limiting and stabilizing the phase change matrix, improving the heat buffering performance and structural stability of the heat storage release process, and the overall phase change enthalpy value can reach 200 J / g after embedding in the polyurethane emulsion.

[0018] The mass ratio of the reflective heat insulation rare earth powder and the fluorine-silicon modified acrylic resin in the surface layer is 1:5-8, the contact angle of the surface layer is >150°, and the surface layer has super-hydrophobic self-cleaning performance.

[0019] The thicknesses of the three layers are respectively 0.2-0.5 mm for the bottom layer, 0.1-0.3 mm for the intermediate layer, and 0.05-0.2 mm for the surface layer, and the total thickness is not more than 1 mm.

[0020] In the technical scheme of the present application, a three-layer gradient structure of an infrared reflection-heat conduction blocking bottom layer, a heat insulation intermediate layer and a dirt-resistant high-reflection surface layer is constructed to form a multifunctional synergistic system with the functions of reflecting radiant heat, blocking heat conduction and surface self-cleaning, thereby improving the reflection ability of the coating to solar radiant heat and the heat flow inhibition performance, and having the functions of interface anti-pollution and self-cleaning, which is suitable for the energy-saving cooling protection requirements in various high-temperature exposure scenarios such as buildings, transportation and energy equipment.

[0021] In the infrared reflection-heat conduction blocking bottom layer, a porous heat resistance network is constructed by using hollow glass microspheres and aerogel powder. The hollow glass microspheres have a low-density hollow spherical structure, which can effectively reduce the vertical heat flow conduction rate. The aerogel powder has a nano-porous structure with an average pore size of about 30 nm and a specific surface area of up to 800 m² / g, which can uniformly distribute in the emulsion system to form a stable heat insulation layer. The two can synergistically act after being dispersed in the water-based acrylic emulsion to reduce the thermal conductivity and inhibit the heat transfer from the surface to the internal structure, thereby constructing an efficient primary heat insulation barrier.

[0022] In the heat insulation intermediate layer, ZIF-8 type metal organic framework material is introduced as a functional filler, which is mixed in the polyurethane emulsion and dispersed to form a stable system with the aid of coupling agents and dispersants. ZIF-8 has an ordered framework pore structure and a high specific surface area, which can improve the thermal resistance effect of the solid phase interface in the coating and block the formation of continuous heat flow paths. At the same time, the structural rigidity of the MOF material can improve the morphological stability of the coating in a hot environment and enhance the overall heat insulation performance and dimensional stability of the intermediate layer. This layer realizes the integration and coupling of structure and function by adjusting the MOF content and the matrix matching.

[0023] In the anti-fouling high-reflective surface layer, rare earth reflective powder is used to replace traditional inorganic white pigment to construct a wide-band reflection system. It has high solar reflectance and excellent chemical stability, can effectively reflect the radiant energy in the visible and near-infrared spectral range, and inhibit the accumulation of heat absorption. In combination with fluorine-silicon modified acrylic resin, a low surface energy micro-nano rough structure can be constructed on the surface of the coating, thereby imparting super-hydrophobic and self-cleaning functions. The self-cleaning surface can reduce the contact time of external pollutants with the material body, thereby reducing the chemical corrosion and weathering probability from the source, improving the environmental stability and service life of the overall coating, and under the action of rain and wind erosion or gravity, the pollutants can automatically slide down, thereby keeping the coating surface clean, maintaining its original reflectivity and radiation inhibition ability.

[0024] The above three-layer structure is coated on the surface of a pretreated substrate in sequence, and finally forms a gradient functional coating with a total thickness of not more than 1 mm, and the thickness of each layer is controlled as follows: the bottom layer is 0.2-0.5 mm, the intermediate layer is 0.1-0.3 mm, and the surface layer is 0.05-0.2 mm. The structure transitions smoothly between each functional layer, the interface bonding force is strong, the overall coating is dense and stable, and has good thermal expansion compatibility and outdoor service reliability.

[0025] The present application embeds a unique functional material system in the three-layer structure: the intermediate layer innovatively uses metal organic framework material ZIF-8, the pore structure of which can not only limit and stabilize the phase change matrix, but also make the overall phase change enthalpy value reach 200 J / g, realize the dynamic adjustment of "absorption-storage-release" of environmental heat, and make up for the passive cooling defects of traditional coatings relying solely on reflection or heat conduction; the surface layer selects reflective and heat-insulating rare earth powder, which has specific reflection ability for the infrared band in the solar spectrum, and the super-hydrophobic surface formed by the fluorine-silicon modified acrylic resin improves the reflection efficiency and endows the coating with self-cleaning function, solving the problem of easy dust accumulation and failure of existing coatings. The hollow glass beads and aerogel powder in the bottom layer build a low-thermal-conductivity barrier, forming a gradient function synergy of "reflection and barrier-heat storage adjustment-anti-fouling and self-cleaning" with the intermediate layer and the surface layer. This material innovation based on ZIF-8 and reflective and heat-insulating rare earth powder, combined with the system design of three-layer structure, makes the present application not only reflect solar radiation efficiently through rare earth powder in high-temperature environment, but also buffer temperature fluctuations by using the phase change characteristics of ZIF-8, and at the same time maintains long-term stability by virtue of the super-hydrophobic surface, which breaks through the technical limitations of existing patents in terms of function mechanism and material application, and shows better practicality and popularization value in the fields of building and equipment protection.

[0026] The advantages and beneficial effects of the present application are as follows: Compared with the prior art, the multi-layer functional gradient structure intelligent cooling coating provided by the application has significant advantages in structure design and function cooperation. Traditional high-reflection cooling coatings are mainly composed of white inorganic powders such as TiO2 and ZnO, and only rely on a single sunlight reflection mechanism, and lack self-cleaning ability, and are easily polluted by dust and oil after long-term outdoor use, resulting in a rapid decrease in reflectivity and a rapid decrease in cooling effect. In addition, most of the existing coatings are single-layer structures, and the thermal insulation and surface function coupling is insufficient, and cannot effectively cope with the thermal management requirements under complex climate. In contrast, the application introduces rare earth wide-spectrum reflective powder, which significantly enhances the solar heat reflection performance of the coating in the visible-near infrared range, has higher cooling efficiency and excellent aging resistance; the intermediate layer uses ZIF-8 type metal organic framework material, which not only improves the micro thermal insulation performance of the coating, but also enhances the structural rigidity and thermal deformation inhibition capacity; the micro-nano composite self-cleaning structure constructed on the surface layer effectively overcomes the core bottleneck of traditional reflective coatings, i.e., easy pollution and easy decay, and ensures that the coating can still maintain the reflection and protection performance in various environments for a long time. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The anti-fouling high-reflection surface micro-nano structure and water droplet contact schematic diagram of the application are shown in the figure. Figure 2 The temperature comparison curve of the coating in the high-temperature environment cooling test is shown in the figure.

[0028] Figure 3 The structure schematic diagram of the coating of the application is shown in the figure.

[0029] In the figure: 1, substrate; 2, infrared reflection-thermal conduction blocking bottom layer; 3, heat insulation intermediate layer; 4, anti-fouling high-reflection surface layer. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be further described in detail below in combination with the drawings and specific examples.

[0031] Example 1 The intelligent cooling coating I comprises the following components: hollow glass microspheres (K15) 22 g, aerogel powder 21 g, water-based acrylic emulsion 57 g, ZIF-8 (KAR-F01) 9 g, polyurethane emulsion 82 g, coupling agent 5 g, middle layer dispersant 4 g, rare earth powder (rare earth phosphate) 14 g, fluorosilicon modified acrylic resin 80 g, leveling agent 1 g, and surface layer dispersant 5 g.

[0032] The preparation method of the intelligent cooling coating I comprises the following steps: S1) Preparation of the primer coating: Hollow glass microspheres and aerogel powder are added to the water-based acrylic emulsion, and after adding an appropriate amount of dispersant, high-speed stirring is carried out for 15 min, followed by ultrasonic dispersion for 30 min (ultrasonic power 250 W) to form a uniform slurry. The coating is applied to the pretreated substrate surface by scraping, with a wet film thickness of about 0.4 mm, and dried at room temperature for 24 h or at 60°C hot air for 2 h to form a cured film layer; S2) Preparation of the intermediate layer coating: Metal organic framework material is added to the polyurethane emulsion, and after adding KH-550 coupling agent, a high-speed shear machine is used for dispersion for 20 min to prepare the intermediate coating. Uniformly coated on the surface of the primer layer, the thickness is controlled at 0.2~0.3mm, naturally leveled, and dried at 60°C for 4h; S3) Preparation of the surface layer coating: Fluorine-modified nano-TiO2 is added to the fluorosilicon-modified acrylic resin, and a leveling agent is added and uniformly stirred for 10 min to form the surface layer coating. The surface layer coating is applied to the surface of the intermediate layer by spraying, with a wet film thickness of about 0.15 mm, and after pre-curing at room temperature for 2h, it is hot cured at 100°C for 1h to form a self-cleaning surface layer. Complete the overall coating structure: Through the above three layers of construction and curing in turn, a multi-layer functional gradient structure intelligent cooling coating (i.e. Intelligent cooling coating I) with compact structure and synergistic function is finally formed.

[0033] Example 2 Intelligent cooling coating II, including the following components: Hollow glass microspheres (VS5500) 21 g, aerogel powder 22 g, water-based acrylic emulsion 57 g, ZIF-8 (KAR-F34) 10 g, polyurethane emulsion 84 g, coupling agent 2 g, middle layer dispersant 4 g, rare earth powder (fluorinated rare earth) 15 g, fluorosilicon-modified acrylic resin 79 g, leveling agent 2 g, surface layer dispersant 4 g.

[0034] The preparation method and use method of the intelligent cooling coating II are the same as those of Example 1, and an intelligent cooling coating II is obtained.

[0035] Example 3 Intelligent cooling coating III, including the following components: Hollow glass microspheres (IM16K) 16 g, aerogel powder 24 g, water-based acrylic emulsion 60 g, ZIF-8 (KAR-F425) 5 g, polyurethane emulsion 85 g, coupling agent 5 g, middle layer dispersant 5 g, rare earth powder (flaky rare earth) 14 g, fluorosilicon-modified acrylic resin 80 g, leveling agent 1 g, surface layer dispersant 5 g.

[0036] The preparation method and use method of the intelligent cooling coating III are the same as those of Example 1, and an intelligent cooling coating III is obtained.

[0037] Example 4 Intelligent cooling coating IV, comprising the following components: hollow glass microspheres (K15) 21 g, aerogel powder 24 g, water-based acrylic emulsion 55 g, ZIF-8 (KAR-F01) 10 g, polyurethane emulsion 83 g, coupling agent 2 g, middle layer dispersant 5 g, rare earth powder (rare earth phosphate) 14 g, fluorosilicon modified acrylic resin 79 g, leveling agent 2 g, surface layer dispersant 5 g.

[0038] The preparation method and use method of the intelligent cooling coating IV are the same as those of Example 1, and intelligent cooling coating IV is obtained.

[0039] Example 5 Intelligent cooling coating V, comprising the following components: hollow glass microspheres (VS5500) 15 g, aerogel powder 25 g, water-based acrylic emulsion 60 g, ZIF-8 (KAR-F34) 6 g, polyurethane emulsion 85 g, coupling agent 4 g, middle layer dispersant 5 g, rare earth powder (fluorinated rare earth) 13 g, fluorosilicon modified acrylic resin 80 g, leveling agent 3 g, surface layer dispersant 4 g.

[0040] The preparation method and use method of the intelligent cooling coating V are the same as those of Example 1, and intelligent cooling coating V is obtained.

[0041] Example 6 Intelligent cooling coating VI, comprising the following components: hollow glass microspheres (IM16K) 25 g, aerogel powder 25 g, water-based acrylic emulsion 50 g, ZIF-8 (KAR-F42) 10 g, polyurethane emulsion 83 g, coupling agent 2 g, middle layer dispersant 5 g, rare earth powder (rare earth phosphate) 13 g, fluorosilicon modified acrylic resin 80 g, leveling agent 2 g, surface layer dispersant 5 g.

[0042] The preparation method and use method of the intelligent cooling coating VI are the same as those of Example 1, and intelligent cooling coating VI is obtained.

[0043] Example 7 Intelligent cooling coating VII, comprising the following components: hollow glass microspheres (K15) 15 g, aerogel powder 25 g, water-based acrylic emulsion 60 g, ZIF-8 (KAR-F01) 10 g, polyurethane emulsion 81 g, coupling agent 5 g, middle layer dispersant 4 g, rare earth powder (fluorinated rare earth) 14 g, fluorosilicon modified acrylic resin 79 g, leveling agent 3 g, surface layer dispersant 4 g.

[0044] The preparation method and use method of the intelligent cooling coating VII are the same as those of Example 1, and intelligent cooling coating VII is obtained.

[0045] Example 8 Intelligent cooling coating VIII, comprising the following components: hollow glass microspheres (VS5500) 24 g, aerogel powder 24 g, water-based acrylic emulsion 52 g, ZIF-8 (KAR-F34) 9 g, polyurethane emulsion 82 g, coupling agent 5 g, middle layer dispersant 4 g, rare earth powder (flaky rare earth) 18 g, fluorosilicon modified acrylic resin 78 g, leveling agent 2 g, surface layer dispersant 5 g.

[0046] The preparation method and use method of the intelligent cooling coating VIII are the same as those of Example 1, and the intelligent cooling coating VIII is obtained.

[0047] Example 9 Intelligent cooling coating IX, comprising the following components: hollow glass microspheres (IM16K) 20 g, aerogel powder 25 g, water-based acrylic emulsion 55 g, ZIF-8 (KAR-F42) 6 g, polyurethane emulsion 84 g, coupling agent 5 g, middle layer dispersant 5 g, rare earth powder (rare earth phosphate) 15 g, fluorosilicon modified acrylic resin 78 g, leveling agent 2 g, surface layer dispersant 5 g.

[0048] The preparation method and use method of the intelligent cooling coating IX are the same as those of Example 1, and the intelligent cooling coating IX is obtained.

[0049] Example 10 Intelligent cooling coating X, comprising the following components: hollow glass microspheres (K15) 23 g, aerogel powder 22 g, water-based acrylic emulsion 55 g, ZIF-8 (KAR-F01) 9 g, polyurethane emulsion 83 g, coupling agent 4 g, middle layer dispersant 4 g, rare earth powder (fluorinated rare earth) 13 g, fluorosilicon modified acrylic resin 80 g, leveling agent 3 g, surface layer dispersant 4 g.

[0050] The preparation method and use method of the intelligent cooling coating X are the same as those of Example 1, and the intelligent cooling coating X is obtained.

[0051] In the intelligent cooling coating described in the present application, the surface layer of the coating adopts a micro-nano composite rough structure constructed by rare earth reflective powder and fluorosilicon modified acrylic resin. This structure not only has excellent reflection performance, but also endows the coating with super-hydrophobic self-cleaning properties. For example, Figure 1As shown, under magnification, the coating surface exhibits a uniform distribution of spherical protrusions and a multi-level network of gaps between them. This micro-nano structure is naturally formed during the particle size distribution of rare earth powder and the film formation process of fluorosilicone resin, and combines with the low surface energy matrix to construct a stable air interlayer interface. When water droplets come into contact with this surface, the droplets cannot spread out but instead exhibit a highly spherical state, easily rolling off and carrying away attached dust or contaminant particles. This structure effectively inhibits the adhesion and retention of pollutants on the surface, significantly improving the coating's anti-fouling ability and rainwater self-cleaning ability, thereby maintaining the smoothness of the reflective surface and its photothermal regulation efficiency over a long period.

[0052] like Figure 2 As shown, a temperature rise comparison experiment was conducted on the coating of the present invention under natural light conditions. The results show that within a 120-minute solar cycle, the temperature rise curve of the smart coated sample was consistently lower than that of the uncoated substrate. Especially during the period of strongest sunlight radiation (60-90 minutes), the temperature rise rate of the coating tended to level off, and the temperature remained at a relatively stable low level. The comparison showed that the maximum temperature difference between the two could reach 7.8℃, indicating that the coating system can effectively reduce the accumulation efficiency of solar heat on the substrate surface through multiple mechanisms such as infrared reflection, heat blocking, and surface anti-fouling, demonstrating excellent temperature control capabilities. Conversely, the untreated sample, due to its strong surface heat absorption and high thermal conductivity, experienced a continuous temperature rise throughout the test cycle, and the heat was difficult to release, exhibiting a significant temperature rise lag. This verifies that the gradient structure coating of the present invention can not only actively regulate the heat flow path but also achieve a passive and sustained cooling control effect by maintaining the cleanliness of the reflective surface, demonstrating significant energy-saving and thermal protection advantages in practical applications.

[0053] The prepared intelligent cooling coating was tested for water contact angle using a contact angle meter in accordance with the standard GB / T 26490-2011 "Test Method for Superhydrophobic and Amphophobic Properties of Nanomaterials"; a neutral salt spray test was conducted according to GB / T 10125-2012 "Civilized Atmosphere Corrosion Test - Salt Spray Test"; and a simulated exposure test was conducted under high sunlight conditions in midsummer to compare the temperature rise difference between the bare metal plate and the sample treated with the coating of this invention.

[0054] The performance of the intelligent cooling coatings prepared in each embodiment was tested according to the test method described above, and the performance test results are shown in Table 1.

[0055] From the coating performance test results (Table 1), the intelligent cooling coating prepared in Example III performs best in each test. In the composition, the IM16K type glass beads + K15 aerogel + KAR-F42 type ZIF-8 + scale-like rare earth powder forms the optimal synergistic structure. The water contact angle reaches 163.2°, which is much higher than the super-hydrophobic benchmark value of 150°, showing excellent self-cleaning performance; in the GB / T 10125-2012 salt spray test, the coating surface is free of bubbles and corrosion spots after 720h, and is rated as "excellent"; and in the simulated sunlight exposure test, the maximum temperature reduction of the bare substrate surface is 7.8℃, which reflects the excellent cooling performance of the three effects of infrared reflection, heat blocking and phase change regulation.

[0056] The test results fully demonstrate that the multi-layer functional gradient structure intelligent cooling coating constructed by the present application is significantly superior to the existing conventional coating system in terms of key indicators such as cooling efficiency, self-cleaning performance and corrosion resistance, and has technical advantages and application prospects for long-term stable service.

[0057] Table 1 Coating performance test results

Claims

1. A multilayer functional gradient structure intelligent cooling coating, characterized in that: The material includes a substrate, and an infrared reflective-thermal-conducting blocking underlayer, a thermal insulation intermediate layer, and a stain-resistant high-reflectivity surface layer, which are sequentially disposed on the substrate from the inside out. The infrared reflective-thermal-conducting blocking underlayer is in direct contact with the substrate, the thermal insulation intermediate layer is sandwiched between the infrared reflective-thermal-conducting blocking underlayer and the stain-resistant high-reflectivity surface layer, and the stain-resistant high-reflectivity surface layer is exposed to the external environment. The infrared reflective-thermal-conducting blocking underlayer, the thermal insulation intermediate layer, and the stain-resistant high-reflectivity surface layer are sequentially coated and cured to form a functional gradient structure. By weight The components of the infrared reflection-thermal conduction blocking bottom layer include: 14-25 parts of hollow glass microspheres, 14-25 parts of aerogel powder, and 50-60 parts of water-based acrylic emulsion. The components of the thermal insulation intermediate layer include: 5-10 parts of metal-organic framework material, 75-85 parts of polyurethane emulsion, 2-5 parts of coupling agent, and 2-5 parts of dispersant. The components of the anti-fouling and high-reflectivity surface layer include: 10-15 parts of reflective and heat-insulating rare earth powder, 70-80 parts of fluorosilicone modified acrylic resin, 1-3 parts of leveling agent, and 2-5 parts of dispersant.

2. The intelligent cooling coating according to claim 1, characterized in that: The hollow glass microspheres are of one or more of the following types: K15, VS5500, and IM16K.

3. The intelligent cooling coating according to claim 2, characterized in that: The aerogel powder has an average pore size of 30-40 nanometers and a specific surface area of ​​780-820 m² / g.

4. The intelligent cooling coating according to claim 3, characterized in that: The metal-organic framework material is ZIF-8, and its model is one or a combination of KAR-F01, KAR-F34, and KAR-F42.

5. The intelligent cooling coating according to claim 4, characterized in that: The reflective heat-insulating rare earth powder is one or a combination of rare earth phosphate, rare earth fluoride, and flake rare earth corrosion-resistant powder.

6. The intelligent cooling coating according to claim 5, characterized in that: The thicknesses of the three layers are as follows: infrared reflection-thermal conduction blocking bottom layer 0.2-0.5 mm, thermal insulation middle layer 0.1-0.3 mm, and anti-fouling high reflective surface layer 0.05-0.2 mm. The total thickness of the three layers does not exceed 1 mm.

7. A method for preparing a multilayer functionally graded intelligent cooling coating as described in claim 1, characterized in that: Includes the following steps: S1) Substrate preparation: Hollow glass microspheres and aerogel are added to water-based acrylic emulsion at a ratio of 1-1.5:1, stirred at high speed for 15-20 min and then ultrasonically dispersed for 30 min to obtain a uniform coating; it is then scraped or sprayed onto the substrate surface and dried at room temperature for 12-24 h or at 50-60℃ hot air for 2-3 h to cure into a film. S2) Intermediate layer preparation: Add metal-organic framework material to polyurethane emulsion, add coupling agent and dispersant, and then disperse at high speed shear for 20-30 min. Coat it on the bottom surface, let it flow naturally, and dry at 50-60℃ for 4-5 h. S3) Surface preparation: Add reflective heat-insulating rare earth powder to fluorosilicone modified acrylic resin, add leveling agent and dispersant and disperse at high speed for 10-20 min, then coat it on the intermediate layer, pre-cur at room temperature for 2-3 h, and then heat-cur at 90-100℃ for 1-2 h to finally form a gradient functional structure coating, that is, a multi-layer functional gradient structure intelligent cooling coating.

8. The preparation method according to claim 7, characterized in that: In step S1), the ultrasonic dispersion uses a power of 230-260W and a time of 20-30min to ensure that the hollow microspheres and aerogel are uniformly dispersed and stably suspended in the emulsion for a long time.

9. The preparation method according to claim 8, characterized in that: The metal-organic framework material used in step S2) is ZIF-8, whose framework pore structure is used to confine and stabilize the phase change matrix, improve the thermal buffering performance and structural stability of the heat storage and release process, and its overall phase change enthalpy value reaches 180-200 J / g after being embedded in polyurethane emulsion.

10. The preparation method according to claim 9, characterized in that: The surface layer has a reflective and heat-insulating rare earth powder to fluorosilicone modified acrylic resin mass ratio of 1:5-8, a surface contact angle >150°, and superhydrophobic self-cleaning properties.

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