Phase change-radiation refrigeration composite energy-saving coating and preparation method thereof

Abstract

The invention discloses a phase change-radiation refrigeration composite energy-saving coating and a preparation method thereof. The coating is prepared from the following components in parts by mass: 30-65 parts of a phase change-radiation refrigeration difunctional filler, 5-30 parts of a high-reflection filler, 3-15 parts of a high-emission filler, 10-60 parts of an emulsion, 3-10 parts of a functional auxiliary agent and 10-25 parts of water. The difunctional filler is of a core-shell structure, a core layer is made of a phase change material, and a shell layer is made of an inorganic material with high sunlight reflectivity and / or high infrared emissivity. According to the invention, radiation refrigeration and a phase change energy storage technology are coupled, so that the coating has the functions of efficient radiation refrigeration and latent heat temperature regulation, the phenomenon of supercooling in a low-temperature environment is effectively inhibited, and self-adaptive heat management is realized.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, specifically to a phase change-radiation cooling composite energy-saving coating and its preparation method. Background Technology

[0002] Against the backdrop of global warming, energy-saving and carbon-reducing technologies have garnered significant attention. Passive cooling technology, with its zero-energy consumption and environmentally friendly characteristics, has become a research hotspot. Among these technologies, radiation-cooling coatings reduce solar heat absorption through high solar reflectivity (0.3-2.5 μm) and radiate heat into outer space via "atmospheric windows" (8-13 μm), achieving a cooling effect below ambient temperature. However, the optical properties of existing radiation-cooling coatings are typically fixed. Continuous heat dissipation in low-temperature environments can easily lead to excessively low temperatures on the coated objects, a phenomenon known as "supercooling." This not only wastes energy but may also cause condensation and other problems, limiting its all-weather, all-climate application.

[0003] Phase change materials (PCMs) can absorb or release a large amount of latent heat during phase change, achieving energy storage and temperature regulation. Combining radiative cooling technology with PCM energy storage technology can theoretically synergistically solve the problems of efficient cooling and temperature buffering. However, existing combined solutions still have many shortcomings: Patent application CN202411484110.X discloses a phase change energy storage-radiative cooling composite material for dynamic thermal management and its preparation method. This technology utilizes liquid gallium metal as the phase change material, bonded to a radiative cooling film via thermally conductive double-sided adhesive. Its main drawbacks are: 1) it is a composite thin-film product and does not involve a coating system; 2) liquid gallium metal has high fluidity, posing a risk of leakage during phase change; 3) the mechanical strength and long-term sealing of the interface bonded with double-sided adhesive are difficult to guarantee, posing a potential for functional failure.

[0004] Patent publication number CN114716865A proposes a radiative heat dissipation phase change coating that uses microcapsules of paraffin encapsulated within silica microspheres. Its main drawback is that while the silica shell has high infrared emissivity in the atmospheric window, its reflectivity in the solar spectrum (especially visible and near-infrared light) is limited, restricting its high reflectivity across the entire wavelength range.

[0005] Patent publication number CN119799088A discloses a heat-buffering phase change microcapsule with a double-layer shell and its preparation method. Coatings prepared using these microcapsules as fillers can provide heat buffering and prevent condensation. However, this technology focuses on passive heat insulation and buffering. Its phase change microcapsules lack optical design to address high solar reflectivity and high atmospheric emission, and therefore do not possess active radiative cooling capabilities. Furthermore, they may even experience temperature increases due to heat absorption under sunlight.

[0006] In summary, there is a lack of a well-designed, stable, and easy-to-apply coating product in the current technology that can organically combine efficient radiative cooling capacity with reliable phase change temperature regulation function at the micro-nano scale, and overcome defects such as "overcooling" to achieve adaptive thermal management. Summary of the Invention

[0007] To address the problems of limited functionality, poor environmental adaptability, susceptibility to overcooling, or insufficient optical performance in existing technologies, the present invention aims to provide a phase change-radiative cooling composite energy-saving coating and its preparation method. This coating introduces a "phase change-radiative cooling dual-functional filler" with a specific core-shell structure, and scientifically blends it with high-reflectivity and high-emissivity fillers. This allows it to simultaneously possess excellent solar reflectivity, atmospheric window emissivity, and significant latent heat storage / release capabilities, thereby achieving a synergistic effect of "high-temperature strong radiative cooling and low-temperature latent heat temperature regulation," effectively broadening the application temperature range and improving energy utilization efficiency.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a phase change-radiation cooling composite energy-saving coating, which is prepared from the following components in parts by mass: 30-65 parts of phase change-radiation cooling dual-function packing material 5-30 parts of high-reflectivity filler 3-15 parts of high-emission filler 10-60 parts of emulsion 3-10 parts of functional additives 10-25 parts water.

[0009] The phase change-radiative cooling bifunctional filler is a core-shell structure particle, with a core layer of phase change material and a shell layer of inorganic material with high solar reflectivity and / or high infrared emissivity, and a particle size between 0.5-1.5 μm to meet the requirements of Mie scattering theory.

[0010] Furthermore, the core phase change material is selected from one or more of alkanes (such as octadecane and eicosane), fatty acids, and alcohols, and its phase change melting temperature range is preferably 15–40°C to adapt to the comfortable temperature environment for the human body or the operating temperature range of conventional equipment. The shell material is one or more combinations of titanium dioxide, zinc oxide, tin dioxide, or silicon dioxide, and can be formed into a single-layer or multi-layer structure by hydrolysis deposition.

[0011] The high-reflectivity filler is one or more of titanium dioxide (such as rutile), zinc oxide, aluminum oxide, barium sulfate, calcium carbonate, zirconium oxide, or yttrium oxide, with a particle size between 300-1000 nm, mainly used to enhance the reflection of sunlight (especially visible and near-infrared light). The high-emissivity filler is one or more of silicon dioxide, silicon nitride, silicon carbide, aluminum nitride, or glass microspheres, with a particle size distribution between 1-20 μm, and its infrared emission peak located within the atmospheric window band of 8-13 μm, used to enhance the ability to radiate heat into space.

[0012] The emulsion is one or a mixture of several of the following: pure acrylic emulsion, styrene-acrylic emulsion, silicone-acrylic emulsion, fluorocarbon emulsion, waterborne polyurethane dispersion, or polyvinyl alcohol, serving as the film-forming substance of the coating. The functional additives are one or more of the following: hydroxyethyl cellulose (thickener), pH adjuster, defoamer, wetting agent, antifreeze, bactericide, or film-forming aids, used to adjust the coating's application performance and storage stability.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned phase change-radiation cooling composite energy-saving coating, comprising the following steps: (1) Weigh out water and some functional additives (such as dispersants, wetting agents, defoamers, pH adjusters, and thickeners) according to the proportion and stir to disperse them to form a uniform mixed solution; (2) The phase change-radiation cooling dual-function filler and the high reflectivity filler are added to the mixed solution in sequence or together according to the ratio, and the mixture is fully dispersed by adjusting the stirring rate to form a uniform and stable filler slurry system; (3) Add emulsion to the slurry system, disperse it evenly at low speed, add high emission filler, continue to disperse, and finally add the remaining functional additives (such as antifreeze, film-forming aid, leveling agent, etc.), stir evenly and filter to obtain the phase change-radiation cooling composite energy-saving coating.

[0014] Thirdly, the present invention provides a method for preparing a phase change-radiative cooling bifunctional filler for the above-mentioned coating, comprising the following steps: (1) The phase change material, inorganic shell precursor (such as tetrabutyl titanate, tetraethyl silicate, zinc acetate, tin chloride, etc.) are mixed with a water-ethanol mixed solvent, and a cationic surfactant (such as hexadecyltrimethylammonium bromide) is added. The mixture is first subjected to high-speed shearing treatment (8000~15000 rpm, 2~10 min), and then subjected to ultrasonic dispersion treatment (400~800 W, 5~30 min) to form a uniform and stable microemulsion system. The mass percentage of each component in the microemulsion is as follows: phase change material 5%~15%, inorganic shell precursor 5%~20%, cationic surfactant 0.5%~3%, and the remainder is a water-ethanol mixed solvent (water to ethanol volume ratio 0.5:1~2:1).

[0015] (2) Adjust the pH value of the microemulsion obtained in step (1) to a suitable range (acidic or alkaline). Under the temperature conditions of 30-70℃, gently stir at a speed of 200-600 rpm to promote the hydrolysis and condensation reaction of the inorganic shell precursor and gradually deposit it on the surface of the phase change material droplets to form a dense inorganic shell. After reacting for several hours to tens of hours, the microcapsule suspension is obtained.

[0016] (3) Solid microcapsules are separated from the suspension by means of filtration, centrifugation, etc., and washed repeatedly with anhydrous ethanol and deionized water to remove residual reactants and surfactants. Finally, they are dried at a suitable temperature (e.g., 50°C) to obtain powdered phase change-radiation cooling bifunctional filler. This process can be carried out once or multiple times to obtain a single-layer or multi-layer shell structure.

[0017] The beneficial effects of this invention are: This invention provides a phase change-radiative cooling composite energy-saving coating and its preparation method. By using a phase change-radiative cooling dual-function filler with a core-shell structure to replace traditional spherical and porous fillers, it can effectively buffer ambient temperature fluctuations and maintain a constant object temperature while achieving radiative cooling and cooling.

[0018] Through theoretical design, two passive cooling technologies, radiation cooling and phase change energy storage, are coupled. By utilizing the latent heat absorption and release during the phase change process, energy can be reversibly stored and released. The passively input energy and excess indoor heat are stored in the form of latent heat, which makes up for the low-temperature continuous scattering defect caused by the inherent optical properties of radiation cooling materials, and achieves the matching of heat supply and demand in time and space.

[0019] The present invention provides a phase change-radiation cooling composite energy-saving coating, which, after being applied, can release the heat absorbed in the high-temperature zone in the low-temperature zone, thereby controlling the indoor environment of the building in an alternating heat environment within a comfortable temperature range, providing all-weather radiation cooling and phase change energy storage, and while achieving radiation cooling, it also has the dynamic thermal management capability of daytime heat buffering and nighttime heat release. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a photograph of the phase change-radiation cooling composite energy-saving coating of Example 1; Figure 3 This is a demonstration of the brushing effect of the phase change-radiation cooling composite energy-saving coating of Example 1. Detailed Implementation

[0021] To make the objectives, advantages, and features of the present invention more apparent, the present invention will be further described in detail below with reference to specific embodiments, the preparation method of which is as follows: Figure 1 As shown.

[0022] Example 1 a. Preparation step one of phase change-radiation cooling bifunctional filler: Octadecylene, tetrabutyl titanate, water-ethanol solvent (volume ratio 1:1), and hexadecyltrimethylammonium bromide are mixed in a mass ratio of 10%:12%:76.8%:1.2%, and then sheared at high speed of 12000 rpm for 4 min by a homogenizer. Subsequently, the mixture is ultrasonically dispersed at 600W power for 15 min by an ultrasonic processor to form a stable emulsion.

[0023] Step 2: Place the emulsion in a reactor and stir slowly at 400 rpm using a mechanical stirrer. Heat in a water bath to a constant temperature of 50 ℃, add hydrochloric acid to adjust the pH to 3.0, and react for 24 h to obtain a microcapsule suspension.

[0024] Step 3: The microcapsules were obtained by filtration of the suspension, washed repeatedly with anhydrous ethanol and deionized water, and then dried in a vacuum oven at a constant temperature of 50°C for 12 h to obtain a single-coated phase change microcapsule powder.

[0025] Step 4: The primary-coated microcapsule powder was added to a solution of zinc acetate dihydrate, water-ethanol solvent (volume ratio 2:1), and octadecyl dimethyl benzyl ammonium chloride. After mixing, the mixture was homogenized at low speed using a homogenizer and ultrasonically dispersed to form a stable turbid liquid. The solution was heated to a constant temperature of 60 °C in a water bath, stirred slowly, and concentrated ammonia was added to adjust the pH to 11.0. After reacting for 12 h, a secondary-coated microcapsule suspension was obtained. After washing and drying, a phase change-radiative cooling bifunctional filler was obtained.

[0026] Actual photos and painting effects are as follows: Figure 2 and Figure 3 As shown.

[0027] b. Preparation of composite energy-saving coatings S1. Weigh 20 parts by weight of deionized water, 1 part of dispersant, 0.1 part of wetting agent, 0.4 parts of defoamer, 0.1 part of pH adjuster, and 0.1 part of hydroxyethyl cellulose and put them into a mixing drum. Stir at 500 r / min for 3-5 min to form a mixed solution.

[0028] S2. Add 35 parts of phase change-radiative cooling bifunctional filler and 15 parts of nano-grade rutile titanium dioxide (add 50% initially, disperse at 700 r / min for 5 min; then add the remaining 50%, disperse at 1000 r / min for 10 min) to form a uniform filler system.

[0029] S3. Adjust the rotation speed to 300 r / min, slowly add 20 parts of silicone-acrylic emulsion and 8 parts of silicon carbide powder, and stir and disperse for 10 min.

[0030] S4. Add 1.5 parts antifreeze, 1.8 parts film-forming aid, 0.1 parts mildew inhibitor, and 0.4 parts leveling agent. Adjust the rotation speed to 400 r / min and stir and disperse for 15 min to obtain the coating.

[0031] S5. Apply the coating to the sample; the dry film thickness is approximately 400 μm. The measured solar reflectance is 91%, the atmospheric window emissivity is 94%, and the phase transition enthalpy is 42 J / g.

[0032] Example 2 a. Preparation of bifunctional packing material: Eicosane, zinc acetate dihydrate, water-ethanol solvent (volume ratio 2:1), and octadecyl dimethyl benzyl ammonium chloride were mixed in a mass ratio of 8%:15%:75.2%:1.8%, and the mixture was sheared at 10000 rpm for 3 min and ultrasonically dispersed at 700 W for 10 min to form an emulsion. The mixture was then stirred at 60℃ and 350 rpm, and concentrated ammonia was added to adjust the pH to 11.0. The reaction was allowed to proceed for 24 h. After filtration, washing, and drying, the bifunctional packing material was obtained.

[0033] b. Coating preparation: The method is the same as in Example 1. The raw material components are: 45 parts of bifunctional filler, 10 parts of zinc oxide, 5 parts of silicon dioxide, and 23 parts of fluorocarbon emulsion. Coating performance: solar reflectance 94%, atmospheric window emissivity 92.5%, phase transition enthalpy 46 J / g.

[0034] Example 3 a. Preparation of bifunctional filler: Fluoride phase change microcapsules, tetraethyl silicate, water-ethanol solvent (volume ratio 0.5:1), and hexadecyltrimethylammonium bromide were mixed in a mass ratio of 12%:10%:77.2%:0.8%, and the mixture was sheared at 12000 rpm for 5 min and ultrasonically dispersed at 450 W for 20 min to form an emulsion. The mixture was then stirred at 40℃ and 500 rpm, and concentrated ammonia was added to adjust the pH to 11. The reaction was carried out for 36 h. After filtration, washing, and drying, the bifunctional filler was obtained.

[0035] b. Coating preparation: The method is the same as in Example 1. The raw material components are: 38 parts of bifunctional filler, 18 parts of barium sulfate, 5 parts of silica, and 20 parts of pure acrylic emulsion. Coating performance: solar reflectance 92%, atmospheric window emissivity 94%, phase transition enthalpy 49 J / g.

[0036] Example 4 a. Preparation of bifunctional packing material: Octadecylane, tin chloride, water-ethanol solvent (volume ratio 1.5:1), and hexadecyltrimethylammonium bromide were mixed in a mass ratio of 7%:8%:84.2%:0.8%, and the mixture was sheared at 10000 rpm for 5 min and ultrasonically dispersed at 550 W for 18 min to form an emulsion. The mixture was then stirred at 55℃ and 450 rpm, and concentrated ammonia was added to adjust the pH to 10.0. The reaction was allowed to proceed for 30 h. After filtration, washing, and drying, the bifunctional packing material was obtained.

[0037] b. Coating preparation: The method is the same as in Example 1. The raw material components are: 52 parts of bifunctional filler, 12 parts of titanium dioxide, 4 parts of glass microspheres, and 25 parts of styrene-acrylic emulsion. Coating performance: solar reflectance 93%, atmospheric window emissivity 91.5%, phase transition enthalpy 62 J / g.

[0038] Example 5 a. Preparation of bifunctional filler: Hexadecane, tetrabutyl titanate, water-ethanol solvent (volume ratio 1.5:1), and octadecyl dimethyl benzyl ammonium chloride were mixed in a mass ratio of 8%:11%:79.5%:1.5%, and the mixture was sheared at 13000 rpm for 3 min and ultrasonically dispersed at 600 W for 10 min to form an emulsion. The mixture was then stirred at 60℃ and 400 rpm, and the pH was adjusted to 3.5 with hydrochloric acid. The reaction was carried out for 24 h. After filtration, washing, and drying, the bifunctional filler was obtained.

[0039] b. Coating preparation: The method is the same as in Example 1. The raw material components are: 50 parts of bifunctional filler, 10 parts of barium sulfate, 5 parts of silicon dioxide, and 20 parts of silicone-acrylic emulsion. Coating performance: solar reflectance 92.5%, atmospheric window emissivity 93%, phase transition enthalpy 61 J / g.

[0040] Comparative Example 1 It does not contain bifunctional fillers. A coating is formed by mixing 20 parts titanium dioxide, 10 parts silica, 40 parts silicone-acrylic emulsion, 25 parts deionized water, and functional additives. The coating has a solar reflectance of 88% and an atmospheric window emissivity of 91%, but does not possess phase change temperature regulation capabilities.

[0041] Effect Analysis Comparative data from Examples 1-5 and Comparative Example 1 show that the phase change-radiative cooling composite energy-saving coating provided by this invention, while maintaining excellent optical performance (high solar reflectance and high atmospheric window emissivity), successfully introduces significant latent heat storage capacity for phase change (phase change enthalpy values ​​are all greater than 40 J / g). This confirms that the technical solution of this invention, which achieves functional integration by introducing a core-shell structured bifunctional filler, is effective. Compared to the single-functional coating of Comparative Example 1, the coating of this invention can achieve dynamic thermal management, efficiently cool at high temperatures, buffer cooling at low temperatures, effectively overcome the "overcooling" phenomenon, and significantly enhance environmental adaptability.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phase change-radiation cooling composite energy-saving coating, characterized in that, It is prepared from the following components in parts by weight: Phase change-radiation cooling dual-function filler 30-65 parts, high reflectivity filler 5-30 parts, high emissivity filler 3-15 parts, emulsion 10-60 parts, functional additives 3-10 parts, water 10-25 parts; The phase change-radiative cooling dual-function filler is a core-shell structure particle, with its core layer being a phase change material and its shell layer being an inorganic material with high solar reflectivity and / or high infrared emissivity.

2. The phase change-radiation cooling composite energy-saving coating according to claim 1, characterized in that, The particle size of the core-shell structured particles is between 0.5 and 1.5 μm.

3. The phase change-radiation cooling composite energy-saving coating according to claim 2, characterized in that, The core phase change material of the phase change-radiation cooling dual-function filler is selected from one or more alkanes, fatty acids, and alcohols, and its phase change melting temperature range is 15 to 40°C.

4. The phase change-radiation cooling composite energy-saving coating according to claim 2, characterized in that, The shell material of the phase change-radiative cooling bifunctional filler is one or more combinations of titanium dioxide, zinc oxide, tin dioxide, or silicon dioxide.

5. The phase change-radiation cooling composite energy-saving coating according to claim 1, characterized in that, The high-reflectivity filler is one or more of titanium dioxide, zinc oxide, aluminum oxide, barium sulfate, calcium carbonate, zirconium oxide, or yttrium oxide, with a particle size between 300 and 1000 nm.

6. The phase change-radiation cooling composite energy-saving coating according to claim 1, characterized in that, The high-emission filler is one or more of silicon dioxide, silicon nitride, silicon carbide, aluminum nitride, or glass microspheres, with a particle size distribution between 1 and 20 μm and an infrared emission peak located in the infrared radiation band of 8 to 13 μm.

7. The phase change-radiation cooling composite energy-saving coating according to claim 1, characterized in that, The emulsion is one or a mixture of several of the following: pure acrylic emulsion, styrene-acrylic emulsion, silicone-acrylic emulsion, fluorocarbon emulsion, aqueous polyurethane dispersion, or polyvinyl alcohol.

8. The phase change-radiation cooling composite energy-saving coating according to claim 1, characterized in that, The functional additives are one or more of hydroxyethyl cellulose, pH adjusters, defoamers, wetting agents, antifreeze agents, bactericides, or film-forming aids, or any combination thereof.

9. A method for preparing energy-saving coatings, used to prepare phase change-radiative cooling composite energy-saving coatings as described in any one of claims 1-8, characterized in that, Includes the following steps: Weigh out the water and functional additives according to the specified ratio, and stir to disperse them to form a mixed solution; The phase change-radiation cooling dual-function filler and the high reflectivity filler were added to the mixed solution according to the specified ratio, and stirred and dispersed to form a uniform mixed system; An emulsion is added to the mixture, and after dispersion, a high-emissivity filler is added. After stirring and dispersing, the remaining additives are added to obtain the phase change-radiation cooling composite energy-saving coating.

10. The method according to claim 9, characterized in that, The preparation method of the phase change-radiation cooling bifunctional packing is as follows: A phase change material, an inorganic shell precursor, and a water-ethanol mixed solvent are mixed and stirred until homogeneous. A cationic surfactant is added, and the mixture is subjected to high-speed shearing at 8000-15000 rpm for 2-10 min, followed by ultrasonic dispersion at 400-800 W for 5-30 min to form a stable microemulsion. The microemulsion contains 5%-15% phase change material, 5%-20% inorganic shell precursor, and 0.5%-3% cationic surfactant by mass, with the remainder being a water-ethanol mixed solvent in a volume ratio of 0.5:1 to 2:

1. The pH value of the microemulsion obtained in the step is adjusted, and the mixture is stirred at a low speed of 200~600 rpm at a temperature of 30-70℃ to cause the inorganic shell precursor to undergo a hydrolysis and deposition reaction, forming an inorganic shell on the surface of the phase change material, thus obtaining a microcapsule suspension. Microcapsules were separated from the microcapsule suspension, washed, and dried to obtain a solid phase change-radiative cooling bifunctional packing material.

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