Green, low-consumption, high-performance radiative cooling materials, coating preparation methods and applications

Abstract

This invention discloses a green, low-consumption, high-performance radiative cooling material, comprising the following components by mass percentage: 40%~60% bio-based composite matrix, 20%~35% green inorganic radiative cooling filler, 1%~3% bio-based dispersant, 2%~5% bio-based crosslinking agent, 15%~30% deionized water, and 0.5%~2% bio-based additives. The bio-based matrix and green inorganic filler achieve high performance with a solar reflectivity ≥95% and an atmospheric window emissivity ≥96%. The solvent-free material selection eliminates the need for high-temperature calcination during preparation and application, achieving the green goals of no high temperature, no organic solvents, and biodegradability, making it suitable for environmentally friendly applications.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling materials technology, specifically to a green, low-consumption, high-performance radiation cooling material, a coating preparation method, and its application. Background Technology

[0002] Radiation cooling technology achieves passive cooling with zero energy consumption by utilizing the high reflectivity of materials in the solar radiation band and the high emissivity in the atmospheric window band. It is a key technology for addressing the global energy crisis and climate warming. Existing high-performance radiative cooling materials mostly rely on inorganic nanosystems, such as SiO2-TiO2, BN, BaSO4, or organic-inorganic composite systems. However, their preparation processes present significant contradictions: for example, inorganic fillers, such as BN and Al2O3, require high-temperature calcination at 900~1100℃ to form a stable structure. As mentioned in "Radiative Cooling Coatings.docx," BN-based coatings require sintering at 900℃, resulting in energy consumption accounting for 40%~50% of the total coating cost. Organic polymer-based coatings, such as PVDF-HFP and PTFE-based coatings, mostly rely on highly polar organic solvents such as DMF and DCM to dissolve the resin, resulting in VOC emissions of 50~100g / L, far exceeding the requirements in GB18582-2020, and solvent residues can cause indoor air pollution. Traditional coatings, such as epoxy-based and acrylic-based coatings, are mostly non-degradable materials, which easily form white pollution after disposal. Degradable coatings, such as PLA-based coatings, suffer from insufficient cooling performance and poor weather resistance, making them unsuitable for environmental protection requirements.

[0003] The green and low-consumption process for radiation-cooling coatings represents the future direction of development. However, current technologies have not achieved a synergistic effect of high performance, green preparation, and biodegradability. For example, while waterborne polyurethane radiation-cooling films reduce VOCs, they still rely on chemical crosslinking agents, such as isocyanates, and are not biodegradable. Although cellulose nanocrystalline coatings are biodegradable, their solar reflectivity is only 90%–92%, resulting in cooling performance below ideal values. Therefore, developing a radiation-cooling coating that achieves green preparation throughout the entire process, high-performance cooling, and biodegradability has become a core requirement for overcoming the limitations of existing technologies. Summary of the Invention

[0004] This invention provides a green, low-consumption, high-performance radiative cooling material, a coating preparation method, and its application. Addressing the technical problems of existing high-performance radiative cooling coatings that rely on high-temperature calcination, organic solvents, and are non-degradable, this invention achieves high performance with a solar reflectivity of ≥95% and an atmospheric window emissivity of ≥96% by using a bio-based matrix and green inorganic fillers. The solvent-free material selection eliminates the need for high-temperature calcination during preparation and application, achieving the green goals of no high temperature, no organic solvents, and biodegradability, making it suitable for environmentally friendly application scenarios.

[0005] This invention provides a green, low-consumption, high-performance radiative cooling material. Its composition design focuses on the synergistic effect of green components and performance, specifically achieved through the synergistic combination of a bio-based composite matrix, green inorganic refrigeration fillers, bio-based additives, and bio-based crosslinking / dispersing components. The specific technical solution is as follows: by mass percentage, it includes the following components: 40%~60% bio-based composite matrix, 20%~35% green inorganic refrigerated filler, 1%~3% bio-based dispersant, 2%~5% bio-based crosslinking agent, 15%~30% deionized water, and 0.5%~2% bio-based auxiliary agent; the bio-based composite matrix is ​​composed of modified starch and PVA in a mass ratio of 3~5:1; the green inorganic refrigerated filler is SiO2-TiO2-ZnO ternary nanoparticles prepared by hydrothermal method, wherein the mass ratio of SiO2, TiO2, and ZnO is 4~6:2~3:1, and it is modified by a bio-based silane coupling agent; the bio-based dispersant is chitosan quaternary ammonium salt; the bio-based crosslinking agent is citric acid; and the bio-based auxiliary agent is a mixture of tea polyphenols and polyglycerol fatty acid esters in a mass ratio of 1:1~2:1.

[0006] The bio-based composite matrix of this invention is made by blending citric acid-esterified starch and PVA at a mass ratio of 3-5:1. This provides a biodegradable carrier for the coating and enhances the base infrared emission through the vibration of its own CO and OH bonds. Simultaneously, citric acid esterification effectively improves the compatibility of starch and PVA, avoiding delamination during blending and solving the technical pain point of poor compatibility in current biodegradable materials. The ester bonds formed by citric acid crosslinking enhance the mechanical strength of the matrix, giving it a hardness of H-2H. The phenolic hydroxyl groups of tea polyphenols absorb ultraviolet light, causing a UV aging effect of 280° with a reflectance decrease of <5%, preventing photodegradation of starch / PVA. Both starch and PVA are natural biodegradable polymers; microorganisms in the soil can decompose their glycosidic and ester bonds, achieving a degradation rate of >80% within 6 months, with no environmental pollution from the degradation products.

[0007] The green inorganic refrigerated filler in this invention is a SiO2-TiO2-ZnO ternary nanoparticle prepared by hydrothermal method, with a mass ratio of 4~6:2~3:1. It is modified by a bio-based silane coupling agent. SiO2 can enhance visible light scattering to improve solar reflectivity, TiO2 can enhance infrared emission in the 8~11μm band, and ZnO can broaden the emission bandwidth to 11~13.5μm. The three work together to achieve full-band coverage of the 8~13.5μm atmospheric window, meeting the performance requirements of covering the atmospheric window band. At the same time, the hydrothermal preparation process avoids the high energy consumption problem of high-temperature calcination of traditional inorganic fillers, and uses deionized water as solvent, with no organic solvent residue.

[0008] The bio-based additive in this invention is a mixture of tea polyphenols as an anti-UV agent and polyglycerol fatty acid esters as a leveling agent in a mass ratio of 1:1 to 2:1. Tea polyphenols can absorb ultraviolet rays through their own phenolic hydroxyl groups, thereby improving the weather resistance of the coating, while polyglycerol fatty acid esters can optimize the smoothness of the coating. Both meet food-grade safety standards, making up for the poor weather resistance of biodegradable coatings and suitable for scenarios with high environmental protection requirements such as food contact. The crosslinking and dispersing components are citric acid and chitosan quaternary ammonium salt, respectively. Citric acid can undergo esterification with the hydroxyl groups in starch and PVA at room temperature to achieve crosslinking. Chitosan quaternary ammonium salt can form hydrogen bonds with the hydroxyl groups on the surface of ternary nanoparticles through cationic groups. Combined with the steric hindrance effect of its own long-chain structure, it can improve the dispersibility of the filler in the matrix. Both are non-chemically toxic, in line with the concept of green preparation, and solve the environmental pollution problems caused by traditional chemical crosslinking agents and dispersants.

[0009] This application also provides a method for preparing a green, low-consumption, high-performance radiation-cooling coating, comprising: S1, mixing deionized water and a bio-based composite matrix uniformly, then sequentially adding a green inorganic refrigeration filler and a bio-based dispersant for ultrasonic dispersion, followed by adding a bio-based crosslinking agent and stirring to mix uniformly and adjusting the pH to 7-8 to obtain a uniform coating slurry; S2, applying the coating slurry to the substrate surface by scraping, rolling, or spraying, with a wet film thickness of 80-120 μm, allowing it to stand at room temperature for 15-20 min, and then performing microwave-assisted curing at a microwave power of 400-600 W for a curing time of 20-30 min to obtain a green, low-consumption, high-performance radiation-cooling coating. In the coating preparation method of this application, uniform dispersion of the filler is achieved through a room-temperature emulsion self-assembly process: the cationic groups of chitosan quaternary ammonium salt form hydrogen bonds with the hydroxyl groups on the surface of the ternary particles, while its long-chain structure generates steric hindrance, preventing particle aggregation; no high-speed grinding is required, and uniform dispersion can be achieved simply by stirring, making it suitable for continuous production. The coating is cured by microwave-assisted curing with a microwave power of 400~600W and a curing time of 20~30min. It utilizes the volume heating characteristics to promote the esterification and cross-linking of citric acid and matrix hydroxyl groups, avoiding the high energy consumption of traditional thermal curing and reducing curing energy consumption.

[0010] This application also provides an application of a green, low-consumption, high-performance radiation cooling material coating in food contact products, where the amount of tea polyphenols in the bio-based additive is increased to 1%~1.5%, the dry film thickness is 30~50μm, the solar reflectivity is ≥94%, the atmospheric window emissivity is ≥95%, the tensile strength is ≥20MPa, and the elongation at break is ≥150%.

[0011] This application also provides an application of a green, low-consumption, high-performance radiative cooling material coating for use in building interior wall products. The coating has a dry film thickness of 60-80 μm, a solar reflectivity ≥95%, an atmospheric window emissivity ≥96%, and a formaldehyde emission <0.01 mg / m³. 3 .

[0012] This application also provides an application of a coating for a green, low-consumption, high-performance radiation cooling material, which is used in environmentally friendly photovoltaic backsheet products. The dry film thickness is 70~90μm, the solar reflectivity is ≥95%, the atmospheric window emissivity is ≥96%, and the performance degradation is <5% after 280 days of UV aging.

[0013] The present invention has the following beneficial effects:

[0014] 1. This green, low-consumption, high-performance radiation cooling material, after testing, exhibits a solar reflectivity ≥95% in the solar radiation band (0.3~2.5μm) and an emissivity ≥96% in the atmospheric window band (8~13.5μm). It also achieves a cooling temperature difference of 6~8℃ in an environment of 35~40℃. Furthermore, it possesses biodegradability and excellent weather resistance, making it suitable for applications such as building interior walls, grain storage films, and environmentally friendly photovoltaic backsheets. This material achieves a three-in-one integration of high-performance cooling, green preparation, and environmental friendliness, aligning with the technological direction of zero energy consumption and sustainable development in this field.

[0015] 2. This green, low-consumption, high-performance radiative cooling material has a bio-based content of >80% in its raw materials. The selection of materials ensures that the preparation process is free of high temperatures and organic solvents, and the products are biodegradable and meet green requirements. The energy consumption is lower than that of traditional high-temperature processes, VOC <5g / L, which is far below the national standard requirements, and the degradation rate is >80% in 6 months, thus resolving the contradiction between high performance and high pollution.

[0016] 3. The coating prepared from this green, low-consumption, high-performance radiative cooling material has been tested and found to have a solar reflectivity ≥95%, an atmospheric window emissivity ≥96%, a cooling temperature difference of 6~8℃ at 35~40℃, and a cooling power of 100~120W / m. 2 . Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the steps in the preparation method of the green, low-consumption, high-performance radiation-cooling coating of the present invention.

[0018] Figure 2 This is a schematic diagram of the steps in the preparation method of the green, low-consumption, high-performance radiation-cooling coating of Embodiment 1 of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a green, low-consumption, high-performance radiative cooling material, coating, and its application. Addressing the technical pain points of existing high-performance radiative cooling coatings that rely on high-temperature calcination and organic solvents, resulting in high energy consumption, significant environmental pollution, and difficulty in large-scale production, this invention discloses a green, low-consumption, and high-performance synergistic radiative cooling coating and its preparation method. The coating uses a bio-based composite matrix composed of modified starch-polyvinyl alcohol blends as a carrier. A SiO2-TiO2-ZnO ternary nanoparticle green inorganic radiative cooling filler is prepared using a composite hydrothermal method. It is formed through a room-temperature emulsion self-assembly + microwave-assisted curing green process, without high temperatures or organic solvents throughout the entire process; the only solvent is deionized water. The coating exhibits a solar reflectivity of ≥95% in the solar radiation band (0.3~2.5μm) and an emissivity of ≥96% in the atmospheric window band (8~13.5μm). It also achieves a cooling temperature difference of 6~8℃ in environments ranging from 35~40℃. Furthermore, it possesses biodegradability and excellent weather resistance, making it suitable for applications such as building interior walls, grain storage films, and environmentally friendly photovoltaic backsheets. This achieves a three-in-one integration of high-performance cooling, green preparation, and environmental friendliness, aligning with the technological direction of zero energy consumption and sustainable development in this field.

[0021] The green, low-consumption, high-performance radiative cooling material comprises, by mass percentage: 40%–60% bio-based composite matrix, 20%–35% green inorganic refrigeration filler, 1%–3% bio-based dispersant, 2%–5% bio-based crosslinking agent, 15%–30% deionized water, and 0.5%–2% bio-based additives. The bio-based composite matrix is ​​composed of modified starch and PVA in a mass ratio of 3–5:1. The modified starch is citric acid esterified starch with a degree of substitution of 0.3–0.5, and the PVA has a degree of alcoholysis of 88%–92%. The glass transition temperature after blending is 40–50°C. The green inorganic refrigeration filler is water. The SiO2-TiO2-ZnO ternary nanoparticles prepared by thermal method have a SiO2:TiO2:ZnO mass ratio of 4~6:2~3:1 and a particle size of 30~80nm. They are surface modified with a bio-based silane coupling agent, preferably chitosan grafted with KH-570, with a modification degree ≥85%. The bio-based dispersant is chitosan quaternary ammonium salt with a substitution degree of 0.6~0.8. The bio-based crosslinking agent is citric acid with a purity ≥99%. The bio-based adjuvant is a mixture of tea polyphenols and polyglycerol fatty acid esters in a mass ratio of 1:1~2:1. Among them, tea polyphenols are used as UV stabilizers and polyglycerol fatty acid esters are used as leveling agents.

[0022] Preferably, SiO2 particles with a diameter of 50-80 nm enhance visible light scattering, TiO2 particles with a diameter of 30-50 nm strengthen emission in the 8-11 μm band, and ZnO particles with a diameter of 40-60 nm broaden the emission bandwidth to 11-13.5 μm. The three components work synergistically to make the coating emissivity ≥96% in the 8-13.5 μm band.

[0023] like Figure 1As shown, a method for preparing a green, low-consumption, high-performance radiation-cooling coating is also provided, comprising the following steps:

[0024] S1. Preparation of green inorganic refrigerated filler: using tetraethyl orthosilicate, tetrabutyl titanate, and zinc nitrate as raw materials, deionized water as solvent, pH adjusted to 6-7, reaction temperature 80-90℃, reaction time 4-6h, no high-temperature calcination is required, ternary nanoparticles are obtained by direct centrifugation and drying, and energy consumption is reduced by 70%-80% compared with the traditional calcination process;

[0025] S2. Preparation of bio-based composite matrix: Dissolve citric acid esterified starch in deionized water at 80~85℃, stir until completely dissolved, cool to 40~50℃ and add PVA, stir at 500~600r / min for 30~40min to form a uniform bio-based matrix solution with no organic solvent residue.

[0026] S3. Preparation of coating slurry: Add the modified ternary nanoparticles and chitosan quaternary ammonium salt from step S1 as bio-based dispersants to the bio-based matrix solution from step S2, ultrasonically disperse for 20-30 min, then add citric acid as a bio-based crosslinking agent and bio-based auxiliary agent, stir at 700-800 r / min, mix for 25-35 min, adjust the pH to 7-8, and obtain a uniform coating slurry;

[0027] S4. Coating Forming and Curing: Apply the coating slurry to the substrate surface by scraping, rolling or spraying, with a wet film thickness of 80~120μm. Let it stand at room temperature for 15~20min, and then perform microwave-assisted curing with a microwave power of 400~600W and a curing time of 20~30min. No high-temperature heating is required to obtain a green, low-consumption and high-performance synergistic radiation cooling coating.

[0028] Preferably, in S1, tetraethyl orthosilicate, tetrabutyl titanate, and zinc nitrate are dissolved in deionized water at a mass ratio of 5:2.5:1, ultrasonically dispersed for 10-15 min, and the pH is adjusted to 6.5 with dilute hydrochloric acid. The mixture is then transferred to a hydrothermal reactor and reacted at 85°C for 5 h. After cooling, the mixture is centrifuged, and chitosan grafted with KH-570 is added at a rate of 4%-6% of the filler mass. The mixture is stirred at 50-60°C for 2-3 h to modify the material, and then dried to obtain modified ternary nanoparticles.

[0029] Preferably, in S2, citric acid esterified starch with a degree of substitution of 0.4 is dissolved in deionized water at 82°C. After stirring and dissolving, the solution is cooled to 45°C, PVA with a degree of alcoholysis of 90% is added, and the solution is stirred at 550 r / min for 35 min to form a bio-based matrix solution.

[0030] The bio-based composite matrix of this invention is made by blending citric acid esterified starch and PVA at a mass ratio of 3-5:1, wherein the degree of substitution of citric acid esterified starch is 0.3-0.5 and the degree of hydrolysis of PVA is 88%-92%. The glass transition temperature of the blended material is controlled at 40-50℃, which can not only provide a biodegradable carrier for the coating, but also enhance the basic infrared emission through the vibration of its own CO and OH bonds. At the same time, the citric acid esterification modification effectively improves the compatibility between starch and PVA, avoids the problem of stratification during the blending process, and solves the technical pain point of poor compatibility of current biodegradable materials.

[0031] The green inorganic refrigerated filler in this invention is a SiO2-TiO2-ZnO ternary nanoparticle prepared by a hydrothermal method at 80-90℃, with a mass ratio of 4-6:2-3:1 and a particle size controlled at 30-80nm. It is also modified by grafting KH-570 with chitosan, with a modification degree ≥85%. SiO2 can enhance visible light scattering to improve solar reflectivity, TiO2 can enhance infrared emission in the 8-11μm band, and ZnO can broaden the emission bandwidth to 11-13.5μm. The three work together to achieve full-band coverage of the 8-13.5μm atmospheric window, meeting the performance requirements of covering the atmospheric window band. At the same time, the hydrothermal preparation process avoids the high energy consumption problem of high-temperature calcination of traditional inorganic fillers.

[0032] The bio-based additive in this invention is a mixture of tea polyphenols as an anti-UV agent and polyglycerol fatty acid esters as a leveling agent in a mass ratio of 1:1 to 2:1. Tea polyphenols can absorb ultraviolet rays through their own phenolic hydroxyl groups, improving the weather resistance of the coating, while polyglycerol fatty acid esters can optimize the smoothness of the coating. Both meet food-grade safety standards, making up for the poor weather resistance of biodegradable coatings and suitable for scenarios with high environmental protection requirements such as food contact. The crosslinking and dispersing components are citric acid with a purity of ≥99% and chitosan quaternary ammonium salt with a substitution degree of 0.6 to 0.8, respectively. Citric acid can undergo esterification with the hydroxyl groups in starch and PVA at room temperature to achieve crosslinking. Chitosan quaternary ammonium salt can form hydrogen bonds with the hydroxyl groups on the surface of ternary nanoparticles through cationic groups. Combined with the steric hindrance effect of its own long-chain structure, it can improve the dispersibility of the filler in the matrix and avoid agglomeration. Both are non-chemically toxic, in line with the concept of green preparation, and solve the environmental pollution problems caused by traditional chemical crosslinking agents and dispersants.

[0033] The green preparation mechanism mentioned in this invention is as follows: the filler is prepared as SiO2-TiO2-ZnO ternary particles at 80-90℃ using a hydrothermal method, eliminating the need for high-temperature calcination and reducing synthesis energy consumption; and deionized water is used as the solvent, leaving no organic solvent residue. The matrix is ​​prepared by dissolving citric acid esterified starch and PVA in deionized water at 80-85℃, stirring to form a homogeneous solution with VOC < 5g / L; the coating is cured by microwave-assisted curing with a microwave power of 400-600W and a curing time of 20-30min, utilizing the volumetric heating characteristics to promote the esterification and crosslinking of citric acid and matrix hydroxyl groups, avoiding the high energy consumption of traditional thermal curing and reducing curing energy consumption.

[0034] The performance synergy mechanism mentioned in this invention is the use of SiO2 with a particle size of 50~80nm. Since its particle size is close to half the wavelength of visible light, it has the highest scattering efficiency for visible light, which can increase the solar reflectivity to 95%~97%. The phonon resonance of TiO2 generates strong emission in the 8~11μm band, and the lattice vibration of ZnO supplements the 11~13.5μm band. The synergy of the three makes the atmospheric window emissivity ≥96%.

[0035] The mechanical and weather resistance synergy mentioned in this invention refers to the ester bonds formed by the cross-linking of citric acid enhancing the mechanical strength of the matrix, making its hardness reach H~2H. The phenolic hydroxyl groups of tea polyphenols can absorb ultraviolet light, which can cause the reflectivity to decrease by <5% after UV aging 280, thus avoiding the photodegradation of starch / PVA.

[0036] The biodegradable synergy mentioned in this invention refers to the fact that both starch and PVA are natural biodegradable polymers, and microorganisms in the soil can decompose their glycosidic bonds and ester bonds. The effect can reach a degradation rate of >80% in 6 months, and the degradation products have no environmental pollution.

[0037] The green, efficient and scalable preparation process mentioned in this invention refers to the use of room temperature emulsion self-assembly process to achieve uniform dispersion of fillers: the cationic groups of chitosan quaternary ammonium salt form hydrogen bonds with the hydroxyl groups on the surface of ternary particles, while its long chain structure generates steric hindrance to avoid particle agglomeration; no high-speed grinding is required, and uniform dispersion can be achieved by ultrasonic treatment for 20~30 min + medium-speed stirring at 700~800 r / min, which is suitable for continuous production.

[0038] The coating prepared by this method exhibits the following biodegradability: in a natural soil environment at a temperature of 25–30°C and a humidity of 60%–70%, the degradation rate is >80% after 6 months and >90% after 12 months. The degradation products are CO2, H2O, and small-molecule sugars, with no environmental pollutants. At 35–40°C, the coating's cooling power reaches 100–120 W / m². 2The cooling temperature difference is 6~8℃, which is better than the traditional high-temperature prepared SiO2-TiO2 coating with a cooling temperature difference of 4~5℃; and the mechanical properties of the coating meet the requirements of GB / T6739-2021 hardness reaching H~2H, GB / T9286-2021 adhesion reaching level 1, with no cracking or peeling.

[0039] The coating prepared by this method can be applied to substrates including biodegradable polymer substrates, such as PLA, PBAT, paper substrates, or wood substrates. When the substrate is a biodegradable polymer, plasma treatment is required before coating, with a power of 300~400W and a time of 3~5 minutes, to improve the adhesion between the coating and the substrate, achieving a grade of 1~2 according to GB / T9286-2021. The dry film thickness is 30~50μm, with a solar reflectivity ≥94%, an atmospheric window emissivity ≥95%, a tensile strength ≥20MPa, and an elongation at break ≥150%.

[0040] When the coating is applied to food contact scenarios, such as grain storage films, the amount of tea polyphenols in the bio-based additives can be increased to 1%~1.5%, and all components comply with GB4806.1-2016 "General Safety Requirements for Food Contact Materials and Articles" without the release of toxic additives.

[0041] When the coating is applied to the interior walls of buildings: dry film thickness 60~80μm, solar reflectivity ≥95%, atmospheric window emissivity ≥96%, formaldehyde emission <0.01mg / m3, in compliance with GB18582-2020.

[0042] When the coating is applied to environmentally friendly photovoltaic backsheets: dry film thickness 70~90μm, solar reflectivity ≥95%, atmospheric window emissivity ≥96%, and UV aging resistance for 280 days with performance degradation <5%.

[0043] Example 1

[0044] The green, low-consumption, high-performance radiative cooling material of this application is used in a green radiative cooling coating for building interior walls. The raw material ratio, by mass percentage, includes: citric acid esterified starch, degree of substitution 0.4, specific gravity 41%; PVA, degree of hydrolysis 90%, specific gravity 8%; hydrothermal SiO2-TiO2-ZnO, 5:2.5:1, particle size 50nm, specific gravity 25%; chitosan quaternary ammonium salt, degree of substitution 0.7, specific gravity 2%; citric acid 3%; tea polyphenols 0.6%; polyglycerol fatty acid ester 0.4%; and deionized water 20%.

[0045] like Figure 2 As shown, the preparation steps include:

[0046] S1. Tetrabutyl orthosilicate, tetrabutyl titanate, and zinc nitrate were dissolved in deionized water at a mass ratio of 5:2.5:1. The mixture was ultrasonically dispersed for 10-15 min, and the pH was adjusted to 6.5 with dilute hydrochloric acid. The mixture was then transferred to a hydrothermal reactor and reacted at 85℃ for 5 h. After cooling, the mixture was centrifuged and chitosan-grafted KH-570 was added at a rate of 4%-6% of the filler mass. The mixture was stirred at 50-60℃ for 2-3 h to modify the mixture. The modified ternary nanoparticles were then dried.

[0047] S2.30g citric acid esterified starch + 31g deionized water, stir to dissolve at 82℃, cool to 45℃ + 8g PVA, stir at 550r / min for 35min.

[0048] S3. Add 25g modified filler + 2g chitosan quaternary ammonium salt, sonicate for 25min, then add 3g citric acid + 0.6g tea polyphenols + 0.4g polyglycerol fatty acid ester, stir at 750r / min for 30min, pH=7.2.

[0049] S4. Apply to gypsum board substrate, wet film thickness 90μm, stand at room temperature for 18min, microwave at 500W for 25min, dry film thickness 65μm.

[0050] Performance Testing: The cooling coating of this embodiment underwent performance testing, and the results showed the following: Optical Performance: Solar reflectivity 96.5%, 0.3~2.5μm; Atmospheric window emissivity 97.2%, 8~13.5μm; Green and Weather Resistance: VOC=3.2g / L, formaldehyde release 0.008mg / m³, reflectivity decay of 4.3% after 280 days of UV aging, and soil degradation rate of 85% after 6 months. Cooling Effect: At 38℃, the coating surface temperature was 7.5℃ lower than the ambient temperature, and the indoor air temperature decreased by 4.2℃.

[0051] Example 2

[0052] The application of the green, low-consumption, high-performance radiation cooling material of this application in a green radiation cooling coating for grain storage films includes: materials prepared by mass percentage as follows: citric acid esterified starch, degree of substitution 0.35, specific gravity 35%; PVA, degree of hydrolysis 88%, specific gravity 7%; hydrothermal SiO2-TiO2-ZnO, 4:3:1, particle size 40nm, specific gravity 22%; chitosan quaternary ammonium salt, degree of substitution 0.65, specific gravity 1.5%; citric acid 2.5%; tea polyphenols 1.2%; polyglycerol fatty acid ester 0.8%; and deionized water 30%.

[0053] The preparation steps include:

[0054] S1-S3 are the same as in Example 1, with a filler modification degree of 86% and a stirring rate of 700 r / min.

[0055] S4. Molding and curing includes: roller coating onto PLA film, plasma treatment at 400W for 4 min, wet film thickness 60μm, standing at room temperature for 15 min, microwave curing at 450W for 22 min, dry film thickness 40μm.

[0056] Performance testing: Optical performance: solar reflectance 95.2%, atmospheric window emissivity 96.1%; Safety and mechanical performance: conforms to GB4806.1-2016, tensile strength 22MPa, elongation at break 165%, no cracking after 50 folds; Cooling effect: at 36℃, after the grain pile is covered with film, the temperature of the grain pile is 6.8℃ lower than that of the uncovered group, thus preventing grain from becoming moldy.

[0057] Example 3

[0058] The green, low-consumption, high-performance radiation cooling material of this application is used in an environmentally friendly photovoltaic backsheet green radiation cooling coating, comprising: materials prepared by mass percentage as follows: citric acid esterified starch with a degree of substitution of 0.45 and a specific gravity of 32%; PVA with a degree of hydrolysis of 92% and a specific gravity of 9%; hydrothermal SiO2-TiO2-ZnO, 6:2:1, with a particle size of 60nm and a specific gravity of 28%; chitosan quaternary ammonium salt with a degree of substitution of 0.75 and a specific gravity of 2.5%; citric acid 4%; tea polyphenols 0.8%; polyglycerol fatty acid ester 0.7%; and deionized water 23%.

[0059] Preparation steps:

[0060] S1-S3: Same as Example 1, with filler modification degree of 90% and stirring speed of 800 r / min;

[0061] S4. Molding and curing includes: spraying onto PBAT substrate, plasma treatment power of 350W for 5 minutes, wet film thickness of 100μm, standing at room temperature for 20 minutes, microwave curing at 550W for 28 minutes, dry film thickness of 75μm.

[0062] Performance testing: Optical performance: solar reflectance 96.8%, atmospheric window emissivity 97.5%; Weather resistance: reflectance decreases by 3.8% after 280 days of UV aging, resistant to damp heat, 85℃, 85%RH, no bubbling after 500 hours; Cooling effect: at 40℃, the photovoltaic backsheet temperature is 7.2℃ lower than that of traditional backsheets, and the photovoltaic module power generation efficiency is improved by 3.5%.

[0063] Comparative Example

[0064] The traditional high-temperature prepared SiO2-TiO2 coating has the following raw material ratio: 30% acrylic resin, 25% SiO2-TiO2 prepared by calcination at 1000℃, 2% KH-560 coupling agent, 3% IPDI crosslinking agent, and 40% DMF solvent;

[0065] Preparation steps: heat curing at 120℃ for 4 hours, dry film thickness 65μm.

[0066] Performance testing: Optical performance: solar reflectance 93.5%, atmospheric window emissivity 94.2%; Green and weather-resistant: VOC=85g / L, non-degradable, its 12-month degradation rate is <5%, and the reflectance decreases by 7.5% after 280 days of UV aging; Cooling effect: at 38℃, the temperature difference is 4.8℃.

[0067] As can be seen from the comparison of the embodiments and comparative examples, the coating of the present invention is significantly superior to traditional high-temperature coatings in terms of cooling performance, green properties and weather resistance. In particular, it solves the contradiction between high performance and green process, and has outstanding technical innovation and practicality.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A green, low-consumption, high-performance radiative cooling material, characterized in that, By weight percentage, it comprises the following components: 40%–60% bio-based composite matrix, 20%–35% green inorganic cold filler, 1%–3% bio-based dispersant, 2%–5% bio-based crosslinking agent, 15%–30% deionized water, and 0.5%–2% bio-based additives; The bio-based composite matrix is ​​composed of citric acid esterified starch and PVA in a mass ratio of 3~5:1; The green inorganic refrigerated filler is a SiO2-TiO2-ZnO ternary nanoparticle prepared by hydrothermal method, wherein the mass ratio of SiO2, TiO2 and ZnO is 4~6:2~3:1, and it is modified by grafting KH-570 with chitosan. The bio-based dispersant is chitosan quaternary ammonium salt; The bio-based crosslinking agent is citric acid; The bio-based adjuvant is a mixture of tea polyphenols and polyglycerol fatty acid esters in a mass ratio of 1:1 to 2:

1.

2. The green, low-consumption, high-performance radiative cooling material according to claim 1, characterized in that: The degree of substitution of the citric acid esterified starch is 0.3~0.5, the degree of hydrolysis of PVA is 88%~92%, and the glass transition temperature of the blended product is 40~50℃. The green inorganic cold filler has a particle size of 30~80nm; The degree of substitution of the chitosan quaternary ammonium salt is 0.6~0.8; The tea polyphenols are used as UV protectants, and the polyglycerol fatty acid esters are used as leveling agents.

3. A method for preparing a green, low-consumption, high-performance radiation-cooling coating, comprising the green, low-consumption, high-performance radiation-cooling material of claim 1 or 2, characterized in that, include: S1. After mixing deionized water and bio-based composite matrix evenly, green inorganic refrigerated filler and bio-based dispersant are added sequentially and ultrasonically dispersed. Then, bio-based crosslinking agent is added, stirred and mixed evenly, and the pH is adjusted to 7-8 to obtain a uniform coating slurry. S2. Apply the coating slurry to the substrate surface by scraping, rolling or spraying, with a wet film thickness of 80~120μm. Let it stand at room temperature for 15~20min, and then perform microwave-assisted curing with a microwave power of 400~600W and a curing time of 20~30min to obtain a green, low-consumption, high-performance radiation cooling coating.

4. The method for preparing a green, low-consumption, high-performance radiation-cooling coating according to claim 3, characterized in that: The hydrothermal preparation of green inorganic cold fillers includes: dissolving tetraethyl orthosilicate, tetrabutyl titanate, and zinc nitrate in deionized water, ultrasonically dispersing them, adjusting the pH to 6-7, reacting at 80-90℃ for 4-6 hours, and then directly centrifuging and drying to obtain SiO2-TiO2-ZnO ternary nanoparticles.

5. The method for preparing a green, low-consumption, high-performance radiation-cooling coating according to claim 3, characterized in that: The preparation of the bio-based composite matrix includes: dissolving citric acid esterified starch in deionized water at 80~85℃, stirring until completely dissolved, cooling to 40~50℃ and adding PVA, stirring evenly to obtain a bio-based matrix solution.

6. The method for preparing a green, low-consumption, high-performance radiation-cooling coating according to claim 3, characterized in that: The substrate is a biodegradable polymer substrate, which is subjected to plasma treatment before coating. Biodegradable polymer substrates include PLA and PBAT.

7. A food contact product using the green, low-consumption, high-performance radiation cooling material as described in claim 1 or 2, or the green, low-consumption, high-performance radiation cooling coating prepared by any of the methods described in claims 3-6, characterized in that: The amount of tea polyphenols in the bio-based adjuvant is 1%~1.5%, and the dry film thickness is 30~50μm.

8. An interior wall product with a green, low-consumption, high-performance radiative cooling coating prepared by applying the green, low-consumption, high-performance radiative cooling material as described in claim 1 or 2, or the green, low-consumption, high-performance radiative cooling coating preparation method as described in any one of claims 3-6, characterized in that: Dry film thickness 60~80μm.

9. An environmentally friendly photovoltaic backsheet product using the green, low-consumption, high-performance radiation cooling material as described in claim 1 or 2, or the green, low-consumption, high-performance radiation cooling coating prepared by any of the preparation methods described in claims 3-6, characterized in that: Dry film thickness 70~90μm.

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