Layered environmentally friendly waterborne radiative cooling coating composition

Abstract

This application provides a layered, environmentally friendly waterborne radiative cooling coating composition, belonging to the field of radiative cooling. The coating composition includes a waterborne radiative cooling primer, a topcoat, and a clear coat. The primer comprises 20-50 parts of a first waterborne emulsion, 10-20 parts of a narrow bandgap optical scatterer, and 10-20 parts of a wide bandgap optical scatterer. The topcoat comprises 20-50 parts of a second waterborne emulsion and 30-60 parts of a wide bandgap optical scatterer. The clear coat comprises 20-50 parts of a third waterborne emulsion. This coating utilizes a synergistic layering of primer / topcoat / clear coat and optimized wide bandgap filler gradation to achieve high solar reflectivity and mid-infrared emissivity at a thinner film thickness, resulting in significant passive cooling. The all-waterborne system disperses and dries at room temperature, resulting in low energy consumption and no VOC risk. The layered structure enhances adhesion, weather resistance, and self-cleaning properties. Compared to high-filler thick-coating processes, this application saves raw materials, energy consumption, and construction steps, extends maintenance cycles, and reduces total life-cycle costs.

Description

Technical Field

[0001] This invention relates to the field of radiative cooling technology, and more specifically to a layered, environmentally friendly, water-based radiative cooling coating composition. Background Technology

[0002] Global warming is a major challenge facing humanity. With the continuous rise in global average temperature, energy consumption for space cooling is increasing dramatically, severely exacerbating pressure on power grids and carbon dioxide emissions. Passive daytime radiative cooling technology, due to its zero-energy cooling advantage, is considered a sustainable strategy to reduce energy consumption and carbon emissions for space cooling. It primarily achieves passive cooling by using high solar reflectivity (0.3~2.5μm) to block solar energy input, while simultaneously radiating heat to a space cold source (approximately 3K) through atmospheric transparent windows (8~13μm), effectively alleviating grid load and combating global warming.

[0003] Currently, radiative cooling technology has evolved into various product forms, including films, fabrics, glass, and coatings, to meet different application needs. Particularly in the construction field, radiative cooling coating technology is considered an effective strategy for energy-free thermal management, and categories such as solvent-based, water-based, and powder-based radiative cooling coatings have been developed. Among these, water-based radiative cooling coatings are considered a major development direction for environmentally friendly coatings due to their low volatile organic compound (VOC) content and environmental friendliness. However, existing water-based radiative cooling coatings, in pursuit of extremely high solar reflectivity, typically require the addition of large amounts of high-refractive-index nanofillers in the formulation, with filler volume ratios exceeding 70% and coating thicknesses exceeding 300 μm. This not only increases costs but also leads to a decrease in the mechanical properties of the materials.

[0004] In view of this, it is necessary to design a layered, environmentally friendly water-based radiation cooling coating composition to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a layered environmentally friendly waterborne radiation cooling coating composition, which aims to solve the technical problems of high cost and decreased mechanical properties of existing waterborne radiation cooling coatings due to high filler addition and high coating thickness.

[0006] This application provides a layered environmentally friendly waterborne radiation-cooling coating composition, including a waterborne radiation-cooling primer, a waterborne radiation-cooling topcoat, and a waterborne radiation-cooling clear varnish. The water-based radiation cooling primer comprises, by weight: 20-50 parts of a first water-based emulsion, 10-20 parts of a narrow bandgap optical scatterer, 10-20 parts of a wide bandgap optical scatterer, 3-10 parts of a first functional additive, and 15-35 parts of water. The water-based radiation cooling topcoat comprises, by weight: 20-50 parts of a second water-based emulsion, 30-60 parts of a wide bandgap optical scatterer, 3-10 parts of a second functional additive, and 10-40 parts of water. The water-based radiation cooling varnish comprises, by weight, 20-50 parts of a third water-based emulsion, 3-10 parts of a third functional additive, and 30-60 parts of water. Wherein, the narrow bandgap optical scatterer is a material with a bandgap width of less than 4.13 eV; the wide bandgap optical scatterer is a material with a bandgap width of greater than 4.13 eV; The first aqueous emulsion, the second aqueous emulsion, and the third aqueous emulsion are each independently selected from one or more of the following: acrylic emulsion, fluorinated acrylic emulsion, polyurethane emulsion, silicone emulsion, polyvinylidene fluoride emulsion, vinyl chloride / vinyl ether copolymer resin emulsion, polydimethylsiloxane emulsion, polymethyl methacrylate emulsion, perfluoroethylene propylene emulsion, and polyvinyl alcohol emulsion. The first functional additive, the second functional additive, and the third functional additive are each independently selected from one or more of the following: film-forming aids, defoamers, dispersants, wetting agents, pH adjusters, thickeners, leveling agents, bactericides, antifreeze agents, antisettling agents, and anti-flash rust agents.

[0007] As a further improvement to this application, the narrow bandgap optical scatterer is selected from one or more of titanium dioxide, zinc oxide, zinc titanate, barium titanate, and zinc phosphomolybdate.

[0008] As a further improvement to this application, the wide bandgap optical scatterer is selected from one or more of the following: alumina, yttrium oxide, lanthanum oxide, hafnium dioxide, magnesium oxide, zirconium oxide, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, silicon nitride, boron nitride, aluminum nitride, silicon dioxide, wollastonite, talc, kaolin, ceramic microspheres, and hollow glass microspheres.

[0009] As a further improvement of this application, the dry film thickness of the waterborne radiation-cooling primer is 50~100μm, the dry film thickness of the waterborne radiation-cooling topcoat is 70~150μm, and the dry film thickness of the waterborne radiation-cooling clear varnish is 10~20μm.

[0010] As a further improvement to this application, the film-forming method of the layered environmentally friendly water-based radiation cooling coating composition includes one of spraying, brushing, scraping, and rolling.

[0011] As a further improvement of this application, the coating formed by the layered environmentally friendly water-based radiation cooling coating composition has a solar reflectivity of not less than 92% in the 0.28~2.5μm band and an infrared thermal emissivity of not less than 0.93 in the 8~13μm band.

[0012] The beneficial effects of this application are as follows: This application provides a layered environmentally friendly waterborne radiation-cooling coating composition, comprising a waterborne radiation-cooling primer, a waterborne radiation-cooling topcoat, and a waterborne radiation-cooling clear varnish. The waterborne radiation-cooling primer, by weight, comprises: 20-50 parts of a first waterborne emulsion, 10-20 parts of a narrow bandgap optical scatterer, 10-20 parts of a wide bandgap optical scatterer, 3-10 parts of a first functional additive, and 15-35 parts of water. The waterborne radiation-cooling topcoat, by weight, comprises: 20-50 parts of a second waterborne emulsion, 30-60 parts of a wide bandgap optical scatterer, 3-10 parts of a second functional additive, and 10-40 parts of water. The waterborne radiation-cooling clear varnish, by weight, comprises: 20-50 parts of a third waterborne emulsion, 3-10 parts of a third functional additive, and 30-60 parts of water. The optical scatterer is a material with a band gap of less than 4.13 eV; the wide band gap optical scatterer is a material with a band gap of greater than 4.13 eV; the first aqueous emulsion, the second aqueous emulsion, and the third aqueous emulsion are each independently selected from one or more of the following: acrylic emulsion, fluorinated acrylic emulsion, polyurethane emulsion, silicone emulsion, polyvinylidene fluoride emulsion, vinyl chloride / vinyl ether copolymer resin emulsion, polydimethylsiloxane emulsion, polymethyl methacrylate emulsion, perfluoroethylene propylene emulsion, and polyvinyl alcohol emulsion; the first functional additive, the second functional additive, and the third functional additive are each independently selected from one or more of the following: film-forming aid, defoamer, dispersant, wetting agent, pH adjuster, thickener, leveling agent, bactericide, antifreeze, antisettling agent, and anti-flash rust agent. This application employs a layered synergistic design of primer / topcoat / clear coat, and optimizes the gradation using wide-bandgap, high-scattering inorganic fillers. This achieves higher solar reflectivity and mid-infrared emissivity under the same or thinner film thickness, resulting in a significant passive cooling effect. Due to the reduced overall film thickness, raw material consumption per unit area and construction time are simultaneously reduced. The system is entirely water-based, disperses and dries at room temperature, eliminating the need for high-temperature drying and solvent recovery, significantly reducing energy consumption and VOC risk. The layered structure also improves adhesion, weather resistance, and self-cleaning properties: the primer enhances adhesion to various substrates such as concrete, metal, and corrugated steel; the topcoat achieves full-spectrum strong scattering and suppresses UV absorption; and the clear coat, through fluorine-containing / silicon-containing or carbonyl-containing polymers, increases thermal emission in the atmospheric transparency window band (8~13μm) and reduces surface energy, thus providing anti-fouling, anti-aging, and anti-abrasion properties. Compared with existing processes that require high filler and thick coating, this application achieves improvements in yield, quality stability, performance accuracy and application efficiency, substantial savings in energy consumption, raw materials and construction procedures, and extended maintenance cycle and lower total life cycle cost.

[0013] Existing water-based radiation-cooling coatings, in pursuit of high reflectivity, often rely on ultra-high filling and thick coating of high-refractive-index nanoparticles, leading to increased material costs, increased internal stress in the coating, and ultimately, cracking and decreased adhesion. Furthermore, absorption in the UV band limits overall reflectivity, making it difficult to simultaneously achieve high R-values. solar (Reflectivity in the solar radiation band), high ε LWIR This application addresses the need for a balance between thermal emissivity in the atmospheric transparency window band and engineering durability. Its core strategy is "functional layering + particle size / morphology gradient + functional group selection." The primer handles interfacial bonding and primary scattering, the topcoat uses a wide-bandgap inorganic scatterer to construct the main scattering framework and prevent UV absorption, and the clear coat enhances mid-infrared emission and imparts hydrophobic self-cleaning properties through characteristic vibrational groups. This achieves a balance between strong solar scattering and high thermal emissivity with a relatively low total film thickness, while mitigating contamination and aging through surface self-cleaning and top-layer protection. This results in an optimal overall performance in terms of improved cooling efficiency, reduced material and energy consumption, and lower durability and maintenance costs.

[0014] This application directly suppresses UV absorption and forms strong scattering in the 0.28~2.5μm wavelength range through the graded design of wide-bandgap inorganic scatterers, ensuring higher solar reflectivity and greater cooling effect from a mechanistic perspective. The varnish uses polymers containing C=O, CF, or Si-O groups, which enhances the intrinsic vibrations within the 8~13μm atmospheric window, thereby increasing the mid-infrared emissivity. At the same time, the reduced surface energy provides self-cleaning and anti-fouling effects, maintaining high reflectivity over a long period. The primer uses a substrate-friendly emulsion and anti-corrosion system to improve performance on concrete. The coating exhibits improved adhesion and impact resistance on metal and color steel substrates, reducing the risk of cracking and peeling under thermal and humid cycling conditions. A tiered design with a total film thickness controlled between 130 and 270 μm reduces material and labor costs while achieving the same cooling target. The thin coating also improves weather resistance indicators such as salt spray and aging resistance by reducing internal stress and mass load. The all-water-based, room-temperature dispersion, and room-temperature drying process reduces energy consumption and VOC emissions, and is compatible with conventional construction methods such as spraying, brushing, rolling, and scraping, facilitating rapid renovation and large-scale application on large-area roofs and exterior walls. This application achieves verifiable, replicable, and scalable comprehensive advantages in performance, economy, and environmental friendliness through integrated optimization of formulation, process, and application.

[0015] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0017] Figure 1 A schematic diagram of the coating structure formed by the layered environmentally friendly waterborne radiation cooling coating composition provided in the embodiments of this application; Figure 2 This is a graph showing the reflectance spectrum performance of the coating in Example 1 of this application; Explanation of reference numerals in the attached diagram: 1. Water-based radiation-cooled varnish layer; 2. Water-based radiation-cooled topcoat layer; 3. Water-based radiation-cooled primer layer; 4. Wide bandgap optical scatterer; 5. Narrow bandgap optical scatterer. Detailed Implementation

[0018] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0023] To achieve high reflectivity, existing waterborne radiation-cooling coatings often require the addition of large amounts of high-refractive-index fillers, with a volume ratio exceeding 70% and a coating thickness exceeding 300 μm. This not only significantly increases production costs but also leads to a substantial decrease in the material's mechanical properties, limiting its widespread application. The key to further development of this technology lies in balancing the cooling performance with thickness, mechanical properties, and weather resistance.

[0024] To address the technical problem of high filler volume ratio and large coating thickness in existing waterborne radiative cooling coatings in pursuit of high reflectivity, which leads to increased costs and decreased mechanical properties, this application provides a layered environmentally friendly waterborne radiative cooling coating composition. Through layered structural design and formulation component optimization, it is possible to significantly reduce the filler volume ratio and coating thickness while ensuring high cooling performance, effectively improving the mechanical properties of the material and reducing costs.

[0025] This application provides a layered environmentally friendly waterborne radiation-cooling coating composition, including a waterborne radiation-cooling primer, a waterborne radiation-cooling topcoat, and a waterborne radiation-cooling clear varnish. The water-based radiation cooling primer comprises, by weight: 20-50 parts of a first water-based emulsion, 10-20 parts of a narrow bandgap optical scatterer, 10-20 parts of a wide bandgap optical scatterer, 3-10 parts of a first functional additive, and 15-35 parts of water. The water-based radiation cooling topcoat comprises, by weight: 20-50 parts of a second water-based emulsion, 30-60 parts of a wide bandgap optical scatterer, 3-10 parts of a second functional additive, and 10-40 parts of water. The water-based radiation cooling varnish comprises, by weight: 20-50 parts of third water-based emulsion, 3-10 parts of third functional additive, and 30-60 parts of water; Wherein, the narrow bandgap optical scatterer is a material with a bandgap width of less than 4.13 eV; the wide bandgap optical scatterer is a material with a bandgap width of greater than 4.13 eV; The first aqueous emulsion, the second aqueous emulsion, and the third aqueous emulsion are each independently selected from one or more of the following: acrylic emulsion, fluorinated acrylic emulsion, polyurethane emulsion, silicone emulsion, polyvinylidene fluoride (PVDF) emulsion, vinyl chloride / vinyl ether copolymer (FEVE) emulsion, polydimethylsiloxane (PDMS) emulsion, polymethyl methacrylate (PMMA) emulsion, perfluoroethylene propylene (FEP) emulsion, and polyvinyl alcohol (PVA) emulsion. The first functional additive, the second functional additive, and the third functional additive are each independently selected from one or more of the following: film-forming aids, defoamers, dispersants, wetting agents, pH adjusters, thickeners, leveling agents, bactericides, antifreeze agents, antisettling agents, and anti-flash rust agents.

[0026] In the technical solution of this application embodiment, by adopting a tiered design and applying nanomaterials of different sizes and morphologies in each functional layer, a solar reflectivity exceeding 92% can be achieved with a total coating thickness of 130~270μm. Simultaneously, through material-side design, polymers containing abundant C=C, C=O, CF, and other functional groups are applied. The tensile or bending vibrations of these specific functional groups ensure efficient thermal emission of the coating material within the atmospheric transparency window (8~13μm), thereby achieving a thermal emissivity exceeding 93%. The layered design facilitates functional optimization of individual coating layers. While applying high-performance fillers and resins, specially formulated additives are used, and a negative feedback optimization mechanism for individual coating layers is employed to perform directional functional design for each layer. This results in a low-thickness, low-cost radiation-cooling coating with excellent overall performance, overcoming the problem of multifunctional incompatibility in traditional radiation-cooling coatings and further expanding the application range of radiation-cooling coatings. Preferably, the first aqueous emulsion is an acrylic emulsion or a polyurethane emulsion; the second aqueous emulsion is a fluorinated acrylic emulsion; and the third aqueous emulsion is one of a fluorinated acrylic emulsion, a polyvinylidene fluoride emulsion, a vinyl chloride / vinyl ether copolymer resin emulsion, or a polydimethylsiloxane emulsion. Selecting appropriate aqueous emulsions based on the core requirements of different functional layers ensures that each layer achieves optimal performance in terms of mechanical, optical, and durability properties, thereby realizing the synergistic high performance of the overall coating system.

[0027] Furthermore, in some embodiments, the narrow bandgap optical scatterer is selected from one or more of titanium dioxide, zinc oxide, zinc titanate, barium titanate, and zinc phosphomolybdate.

[0028] In the technical solution of this application embodiment, although narrow bandgap optical scatterers have a high refractive index and a certain ability to scatter sunlight, their bandgap width is usually less than 4.13 eV, resulting in strong absorption of sunlight in the ultraviolet band. By placing them at the bottom layer of the coating system and simultaneously introducing wide bandgap scatterers, the insufficient reflection of narrow bandgap materials in the ultraviolet band is compensated, jointly constructing a highly efficient scattering network over a wider spectral range. This composite filler system achieves initial scattering and shielding of sunlight in the primer layer, while maintaining good adhesion and application adaptability of the coating to various substrates, laying the foundation for higher reflectivity in the subsequent topcoat layer.

[0029] Furthermore, in some embodiments, the wide bandgap optical scatterer is selected from one or more of the following: alumina, yttrium oxide, lanthanum oxide, hafnium dioxide, magnesium oxide, zirconium oxide, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, silicon nitride, boron nitride, aluminum nitride, silicon dioxide, wollastonite, talc, kaolin, ceramic microspheres, and hollow glass microspheres.

[0030] In the technical solution of this application embodiment, the wide bandgap optical scatterer has a high refractive index and a bandgap width that is usually greater than 4.13 eV. It has high scattering efficiency for sunlight across the entire wavelength range and works in conjunction with the bottom filler to construct a continuous and efficient scattering network from ultraviolet to infrared. As the core functional filler of the topcoat layer, it directly determines the upper limit of the final solar reflectivity of the coating and is the key material basis for achieving the ultra-high reflectivity (≥92%) described in this application and breaking through the performance bottleneck of traditional narrow bandgap fillers.

[0031] Furthermore, in some embodiments, the dry film thickness of the waterborne radiation-cooling primer is 50~100μm, the dry film thickness of the waterborne radiation-cooling topcoat is 70~150μm, and the dry film thickness of the waterborne radiation-cooling varnish is 10~20μm.

[0032] In the technical solution of this application embodiment, the water-based radiation cooling primer has excellent adhesion to building substrates (concrete, gypsum board, color steel tile, plastic, etc.) and also has a certain scattering effect on sunlight; the water-based radiation cooling topcoat contains a wide bandgap optical scatterer (filler), and the wider bandgap can avoid the absorption of sunlight (ultraviolet light) in the 280~380nm wavelength band by the coating, thereby further reducing the input of solar energy; the water-based radiation cooling clear varnish contains polymer resin with excellent heat emission performance and hydrophobic substances, which can give the material high heat emissivity and self-cleaning ability.

[0033] Furthermore, in some embodiments, the film-forming method of the layered environmentally friendly waterborne radiation cooling coating composition includes one of spraying, brushing, scraping, and rolling.

[0034] In the technical solutions of this application, the layered coating system is highly compatible with existing construction infrastructure and worker skills, without relying on special or expensive specialized equipment. This broad adaptability to common construction methods significantly reduces the application threshold and cost of this application in large-scale building exterior wall energy-saving renovations.

[0035] Furthermore, in some embodiments, the coating formed by the layered environmentally friendly waterborne radiation cooling coating composition has a solar reflectivity of not less than 92% in the 0.28~2.5μm band and an infrared thermal emissivity of not less than 0.93 in the 8~13μm band.

[0036] In the technical solution of this application embodiment, the topcoat uses a wide bandgap high-scattering filler and graded particle size to suppress UV absorption and achieve R... solar ≥92%; the varnish uses polymers containing C=O, CF, and Si-O, along with hydrophobic components, to achieve ε LWIR It exhibits a viscosity of ≥0.93 and self-cleaning and anti-fouling capabilities; the primer utilizes narrow-bandgap scatterers, wide-bandgap optical scatterers, and anti-corrosion additives, making it suitable for various substrates such as concrete and color steel, achieving adhesion rating of 0 and excellent impact resistance. This application employs negative feedback single-layer directional optimization combined with all-waterborne room-temperature preparation, reducing dosage and VOCs, facilitating large-scale construction; the film thickness achieves maximum sub-environmental cooling benefits of ≥10℃, and meets comprehensive performance standards for salt spray resistance for 720 hours and artificial aging for 1000 hours.

[0037] Specifically, the preparation method of the layered environmentally friendly waterborne radiation cooling coating composition provided in this application includes the following steps: S1. Mix narrow bandgap optical scatterer, wide bandgap optical scatterer, anti-settling agent, pH adjuster, dispersant, wetting agent, defoamer and water, stir evenly at 400~600rpm, add the first water-based emulsion, stir evenly again at 400~600rpm, add film-forming aid, defoamer, bactericide, leveling agent, wetting agent, anti-flash rust agent and antifreeze agent, stir evenly at the same speed to obtain water-based radiation cooling primer; S2. Mix the wide bandgap optical scatterer, dispersant, bactericide, thickener, wetting agent, antifreeze, antisettling agent, pH adjuster, and defoamer with water, stir evenly at 400~600 rpm, add the second aqueous emulsion, stir evenly again at 400~600 rpm, add the film-forming aid, defoamer, antifreeze, and leveling agent, and stir evenly at the same speed to obtain the water-based radiation cooling topcoat; S3. Mix water, defoamer, bactericide, pH adjuster, antifreeze and wetting agent, stir evenly at 300~400rpm, add the third water-based emulsion, stir evenly again at 300~400rpm, add film-forming aid, leveling agent, antifreeze and thickener, stir evenly at the same speed to obtain water-based radiation cooling varnish. S4. Pre-treat the substrate to ensure it is flat and clean. Apply the water-based radiation cooling primer to the substrate surface and allow it to dry fully at room temperature and pressure. Then apply the water-based radiation cooling topcoat over the primer and allow it to dry at room temperature and pressure. Finally, apply the water-based radiation cooling clear varnish over the topcoat and allow it to dry completely to obtain a layered environmentally friendly water-based radiation cooling coating sample.

[0038] like Figure 1As shown, the coating sample includes an aqueous radiation-cooled clear varnish layer 1, an aqueous radiation-cooled topcoat layer 2, and an aqueous radiation-cooled primer layer 3; wherein, the aqueous radiation-cooled primer layer 3 contains a narrow bandgap optical scatterer 5 and a wide bandgap optical scatterer 4; the aqueous radiation-cooled topcoat layer 2 contains a wide bandgap optical scatterer 4.

[0039] Both the primer and topcoat employ a step-by-step, orderly mixing and dispersion process to ensure the full deagglomeration and uniform distribution of optical fillers with high solids content, forming a stable scattering network. The clear coat focuses on adjusting surface energy and rheological properties to optimize film quality. This process, by controlling the order of feeding and dispersion parameters, systematically ensures the uniformity of the internal structure and interlayer compatibility of each layer, achieving a synergistic improvement in high optical performance and excellent mechanical durability. Because the primer and topcoat contain a high proportion of solid optical scatterers, medium-to-high-speed stirring helps provide sufficient shear force to fully disperse the fillers, break agglomerates, and ensure their uniform distribution in the emulsion and the construction of the optical scattering network, while avoiding excessive bubbles or emulsion demulsification due to excessive speed. The clear coat, mainly composed of emulsion and liquid additives, uses a lower speed, focusing on gentle mixing, promoting molecular-level homogenization and maintaining emulsion stability, while also facilitating defoaming and achieving good leveling properties, thus ensuring the smoothness and functionality of the final clear coat layer.

[0040] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0041] The reagents used in the following examples or comparative examples are as follows: Anti-settling agent 101, product model GD-101, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Water-based acrylic emulsion 3620, product model MT-3620, purchased from Guangdong Landebao New Materials Co., Ltd. Fungicide 5098, product model GD-5098, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Water-based defoamer 2411, product model GD-2411, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Leveling agent 6038, product model GD-6038, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Anti-flash rust agent 1799, product model GD-1799, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Fluorine-modified acrylic emulsion 802, product model FT-802, was purchased from Anhui Kebang Resin Technology Co., Ltd. Defoamer 2500, product model GD-2500, purchased from Changzhou Judun Anticorrosion Technology Co., Ltd. Fluorine-modified acrylic emulsion 501, product model ZM-501, was purchased from Anhui Kebang Resin Technology Co., Ltd. Thickener 2035, product model GD-2035, was purchased from Changzhou Judun Anticorrosion Technology Co., Ltd.

[0042] Example 1 This embodiment provides a layered environmentally friendly waterborne radiation-cooling coating composition, comprising a waterborne radiation-cooling primer, a waterborne radiation-cooling topcoat, and a waterborne radiation-cooling clear coat, and its preparation method includes the following steps: S1. Add 2g of anti-settling agent 101, 2g of pH adjuster AMP95, 10g of dispersant 4013, 4g of water-based substrate wetting agent 3100, and 3g of defoamer 2500 to 250g of deionized water and disperse evenly. Then add 100g of titanium dioxide R216, 80g of talc XF-1250, 80g of kaolin SX68A, and 50g of zinc phosphomolybdate B906. Stir at 500rpm for 10 minutes until evenly dispersed. Then add 400g of water-based acrylic emulsion 3620 and stir at 500rpm for 10 minutes. Finally, add 20g of film-forming aid alcohol ester twelve and stir at 400rpm for 5 minutes. After stirring for 10 minutes at 400 rpm, add 4g of bactericide 5098, 3g of wetting agent 3105, 3g of water-based defoamer 2411, 1g of defoamer 2500, 3g of leveling agent 6038, 6g of antifreeze propylene glycol, and 4g of anti-flash rust agent 1799. Continue stirring for 10 minutes at 400 rpm. The resulting uniform white mixture is the water-based radiation cooling primer. S2. Add 4g of bactericide 5098, 2g of thickener 30000, 2g of anti-settling agent 101, 2g of pH adjuster AMP95, 6g of antifreeze propylene glycol, 18g of dispersant 4013, 4g of water-based substrate wetting agent 3100, and 5g of defoamer 2500 to 300g of deionized water. After uniform dispersion, add 400g of barium sulfate PLX and stir at 500rpm for 10min until uniformly dispersed. Then add 200g of fluorine-modified acrylic emulsion 802 and stir at 500rpm for 10min. Next, add 24g of film-forming aid alcohol ester twelve and stir at 400rpm for 5min. Finally, add 3g of defoamer 2411, 1g of defoamer 2500, 6g of antifreeze propylene glycol, and 3g of leveling agent 6038 and continue stirring at 400rpm for 10min. The resulting uniform white mixture is the water-based radiation cooling topcoat. S3. Add 2g of bactericide 5098, 1.75g ​​of pH adjuster AMP95, 1.25g of defoamer 2411, 2.5g of antifreeze propylene glycol, and 1.5g of substrate wetting agent 3105 to 300g of deionized water and disperse evenly. Then add 200g of fluorinated modified acrylic emulsion 501 and stir at 400rpm for 10min until evenly dispersed. Continue to add 12g of film-forming aid alcohol ester dodecyl and 5g of leveling agent ethylene glycol butyl ether and stir at 300rpm for 5min. Finally, add 3g of leveling agent 6038 and 1.5g of thickener 2035 and continue to stir at 300rpm for 10min. The resulting uniform milky white mixture is the water-based radiation cooling varnish. S4. For the base (10cm) A 10cm concrete substrate was treated to ensure its flatness and cleanliness. A water-based radiation-cooling primer was applied to the substrate surface using a brush. After complete drying at room temperature and pressure, the primer thickness was 100μm. A water-based radiation-cooling topcoat was then brushed onto the primer. After drying at room temperature and pressure, the topcoat thickness was 140μm. Finally, a water-based radiation-cooling clear varnish was brushed onto the topcoat and allowed to dry completely, resulting in a clear varnish thickness of 10μm. This yielded a layered, environmentally friendly water-based radiation-cooling coating sample with a total coating thickness of 250μm. Figure 2 The figure shows the reflectance spectral performance curve of the coating, where R... solar ε represents the reflectivity in the solar radiation band. LWIR Indicating the thermal emissivity in the atmospheric transparency window band, it can be seen that the coating R obtained in this application... solar The value is 94.12%, which is much higher than that of ordinary white paint.

[0043] Example 2 This embodiment provides a layered environmentally friendly waterborne radiation cooling coating composition. Compared with Example 1, the only difference is that the topcoat thickness is 70 μm, resulting in a layered environmentally friendly waterborne radiation cooling coating sample with a total coating thickness of 180 μm. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0044] Example 3 This embodiment provides a layered environmentally friendly waterborne radiation cooling coating composition. Compared with Example 1, the only difference is that the primer thickness is 50 μm, resulting in a layered environmentally friendly waterborne radiation cooling coating sample with a total coating thickness of 200 μm. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0045] Example 4 This embodiment provides a layered environmentally friendly waterborne radiation cooling coating composition. Compared with Example 1, the only difference is that the varnish thickness is 20 μm, resulting in a layered environmentally friendly waterborne radiation cooling coating sample with a total coating thickness of 260 μm. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0046] Example 5 This embodiment provides a layered environmentally friendly water-based radiation cooling coating composition. Compared with Example 1, the only difference is that in step S2, the amount of barium sulfate added is 300g and the amount of fluorine-modified acrylic emulsion added is 300g. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0047] Example 6 This embodiment provides a layered environmentally friendly water-based radiation cooling coating composition. Compared with Example 1, the only difference is that in step S1, the amount of titanium dioxide added is 80g, the amount of talc added is 40g, the amount of kaolin added is 60g, the amount of zinc phosphomolybdate added is 40g, and the amount of water-based acrylic emulsion added is 300g. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0048] Comparative Example 1 Comparative Example 1 provides a layered environmentally friendly waterborne radiation-cooling coating composition. Compared with Example 1, the only difference is that there is no waterborne radiation-cooling varnish. A double-layer environmentally friendly waterborne radiation-cooling coating sample with a total coating thickness of 240 μm is obtained. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0049] Comparative Example 2 Comparative Example 2 provides a layered environmentally friendly waterborne radiation-cooling coating composition. Compared with Example 1, the only difference is that there is no waterborne radiation-cooling varnish or waterborne radiation-cooling primer. A single-layer environmentally friendly waterborne radiation-cooling coating sample with a coating thickness of 140 μm is obtained. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0050] Comparative Example 3 Comparative Example 3 provides a layered environmentally friendly waterborne radiation-cooling coating composition. Compared with Example 1, the only difference is that there is no waterborne radiation-cooling topcoat or waterborne radiation-cooling clear varnish. A single-layer environmentally friendly waterborne radiation-cooling coating sample with a coating thickness of 100 μm is obtained. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0051] Comparative Example 4 Comparative Example 4 provides a layered environmentally friendly waterborne radiation cooling coating composition. Compared with Example 1, the only difference is that in step S1, 310g of titanium dioxide is added, and talc, kaolin, and zinc phosphomolybdate are not added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0052] Comparative Example 5 Comparative Example 5 provides a layered environmentally friendly water-based radiation cooling coating composition. Compared with Example 1, the only difference is that in step S2, the amount of barium sulfate added is 200g. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0053] The test results of the coating samples obtained in the examples and comparative examples are shown in Table 1.

[0054] Table 1 Test Results (Note 1) Test methods for ultraviolet reflectance and solar reflectance: Place the coating sample into a Shimadzu UV3600 ultraviolet / visible / near-infrared spectrophotometer. The sample size and thickness depend on the requirements of the example. The measurement wavelength range is 0.28~2.5μm. The weighted average reflectance in the 0.28~0.38μm band is the ultraviolet reflectance, and the weighted average reflectance in the 0.28~2.5μm band is the solar reflectance. (Note 2) Mid-infrared thermal emissivity test method: The mid-infrared reflectivity of the coating sample is characterized by Fourier transform spectroscopy (FTIR). With a gold mirror as the background reference, the reflectivity of the sample is tested. For non-special materials, the transmittance is basically 0 when the thickness is in the micrometer range. Therefore, the material absorptivity = 1 - reflectivity - 0. According to Kirchhoff's law, the emissivity of the sample in the mid-infrared band is equal to the absorptivity. Then, the average thermal emissivity of the sample in the atmospheric transparent window band (8~13μm) is calculated by weighting the blackbody radiation spectrum. (Note 3) Cooling test method: On an open rooftop, construct two identical model houses, made of gray concrete slabs, with dimensions of 100×100×50cm; one serves as a blank control group, without any modification, while the other serves as the experimental group. The roof and four exterior walls of the model house are coated with the radiative cooling coating from the embodiments, with the coating thickness conforming to the requirements of each embodiment. After drying for 3 days, the cooling effect is tested. The test method is as follows: On a clear day, before sunrise (5:00 AM), place the thermometer probe in the model house. After sunset (8:00 PM), stop monitoring. The probe is fixed at a height of 25cm above the ground, with the horizontal position at the geometric center of the model house. Read the temperature at 1:00 PM that day (ensuring that the average solar irradiance exceeds 900W / m² during the period from 12:00 PM to 2:00 PM). 2Record the temperatures of the control group and the experimental group. The cooling effect is evaluated by the difference between the temperature of the experimental group and the temperature of the control group. (Note 4) Water contact angle test method: The water contact angle of the characteristic coating sample is measured using the OCA25 video contact angle measuring instrument. First, the sample of the example should be placed on the sample stage of the instrument to ensure that the sample is flat and free of wrinkles and twists, and at the same time, ensure that the needle is directly above the sample. Then, suspend a 1μL water droplet at the end of the needle and move the sample stage upward so that the sample surface contacts the suspended water droplet (the water droplet should be dropped on an area that has not been contacted before). Then, move the sample stage to a suitable position to complete the water droplet transfer process. During the movement, the water droplet should not be deviated. Then, the contact angle value is measured by the goniometric method.

[0055] As shown in Table 1, the three-layer coating provided in this application exhibits a solar reflectivity of 94.12% and an infrared thermal emissivity of 94.01%, achieving a significant temperature reduction of 13.21℃. Simultaneously, it demonstrates a grade 0 adhesion, and passes tests for impact resistance, salt spray resistance (720h), and aging resistance (1000h). Furthermore, it exhibits a water contact angle of 123°, demonstrating excellent hydrophobicity. In contrast, altering the coating structure or component ratio in the comparative examples leads to a decrease in coating performance. This application, through functional layering and material synergistic design of primer-topcoat-clear coat, achieves high cooling efficiency, excellent mechanical strength, and long-term durability with relatively low thickness and filler content, successfully resolving the cost-performance contradiction caused by high-filler, thick-coating methods in existing technologies.

[0056] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A layered, environmentally friendly, water-based radiative cooling coating composition, characterized in that, Including water-based radiation-cooling primer, water-based radiation-cooling topcoat, and water-based radiation-cooling clear coat; The water-based radiation cooling primer comprises, by weight: 20-50 parts of a first water-based emulsion, 10-20 parts of a narrow bandgap optical scatterer, 10-20 parts of a wide bandgap optical scatterer, 3-10 parts of a first functional additive, and 15-35 parts of water. The water-based radiation cooling topcoat comprises, by weight: 20-50 parts of a second water-based emulsion, 30-60 parts of a wide bandgap optical scatterer, 3-10 parts of a second functional additive, and 10-40 parts of water. The water-based radiation cooling varnish comprises, by weight, 20-50 parts of a third water-based emulsion, 3-10 parts of a third functional additive, and 30-60 parts of water. Wherein, the narrow bandgap optical scatterer is a material with a bandgap width of less than 4.13 eV; the wide bandgap optical scatterer is a material with a bandgap width of greater than 4.13 eV; The narrow bandgap optical scatterer is selected from one or more of titanium dioxide, zinc oxide, zinc titanate, barium titanate, and zinc phosphomolybdate; The wide bandgap optical scatterer is selected from one or more of the following: alumina, yttrium oxide, lanthanum oxide, hafnium dioxide, magnesium oxide, zirconium oxide, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, silicon nitride, boron nitride, aluminum nitride, silicon dioxide, wollastonite, talc, kaolin, ceramic microspheres, and hollow glass microspheres. The first aqueous emulsion, the second aqueous emulsion, and the third aqueous emulsion are each independently selected from one or more of the following: acrylic emulsion, fluorinated acrylic emulsion, polyurethane emulsion, silicone emulsion, polyvinylidene fluoride emulsion, vinyl chloride / vinyl ether copolymer resin emulsion, polydimethylsiloxane emulsion, polymethyl methacrylate emulsion, perfluoroethylene propylene emulsion, and polyvinyl alcohol emulsion. The first functional additive, the second functional additive, and the third functional additive are each independently selected from one or more of the following: film-forming aids, defoamers, dispersants, wetting agents, pH adjusters, thickeners, leveling agents, bactericides, antifreeze agents, antisettling agents, and anti-flash rust agents. The coating formed by the layered environmentally friendly water-based radiation cooling coating composition has a solar reflectivity of not less than 92% in the 0.28~2.5μm wavelength band and an infrared thermal emissivity of not less than 0.93 in the 8~13μm wavelength band.

2. The layered environmentally friendly water-based radiative cooling coating composition according to claim 1, characterized in that, The dry film thickness of the water-based radiation-cooling primer is 50~100μm, the dry film thickness of the water-based radiation-cooling topcoat is 70~150μm, and the dry film thickness of the water-based radiation-cooling clear varnish is 10~20μm.

3. The layered environmentally friendly water-based radiative cooling coating composition according to claim 1, characterized in that, The film-forming method of the layered environmentally friendly water-based radiation cooling coating composition includes one of spraying, brushing, scraping, and rolling.

Images