A high reflectance-high emissivity radiative cooling paint for electrical equipment

Abstract

The present application relates to a kind of high reflection-high emissivity radiation refrigeration coatings for electric power equipment.The coating includes deionized water, styrene-acrylic emulsion, titanium white, hollow glass microsphere, zinc oxide, hexacyclic stone powder, dispersing agent, defoaming agent, film-forming aid, mildew preventive, and optionally added mica powder, calcined kaolin, talc powder, silica powder or block copolymer emulsion.The coating realizes high reflection of sunlight and high emission of middle and far infrared band by optimizing the synergistic effect of multiple infrared functional fillers and emulsion matrix.The coating has excellent cooling capacity, self-cleaning performance and environmental adaptability.

Description

Technical Field

[0001] This invention relates to the technical field of coating preparation, and in particular to a high-reflectivity, high-emissivity radiation cooling coating for power equipment. Background Technology

[0002] With the widespread application of outdoor power equipment in high-temperature and high-radiation environments, surface thermal management has become an increasingly important issue. Due to the unavoidable exposure to direct sunlight and ambient heat radiation during operation, the casing temperature often rises significantly, potentially leading to decreased insulation performance of internal components, reduced operating efficiency, and even the risk of overheating failure. Therefore, researching and developing functional surface materials capable of reducing equipment surface temperature has become a key focus in this field.

[0003] Radiation-cooling coatings are a type of coating material that achieves passive cooling by relying on high solar reflectivity and high infrared emissivity. In recent years, they have been increasingly used in fields such as building energy conservation, vehicle cooling, and thermal control of optoelectronic equipment. These coatings are generally constructed based on a composite system of high-reflectivity pigments and functional inorganic fillers. Their basic design concept is to maximize the reflection of incident solar energy (especially the visible and near-infrared portions) while maintaining good thermal radiation capabilities in the atmospheric transparency window band (8–13 μm), thereby enabling the surface heat to be effectively released into outer space.

[0004] In existing radiation-cooling coating technologies, titanium dioxide is commonly used as the main reflective material. Its high refractive index and stable optical properties give it excellent scattering capabilities in the visible light band. To further improve thermal management performance, some studies have attempted to introduce inorganic fillers of different particle sizes or to compound metal oxide powders with infrared emission capabilities into emulsion systems to enhance their reflection and emission performance over a wider spectral range. Some coatings also optimize the scattering path by controlling surface roughness or microstructure distribution, thereby achieving heat flow regulation.

[0005] While existing radiation-cooling coatings possess some cooling capabilities, they still have limitations in terms of material compatibility, thermal stability, and adaptability to actual power equipment surfaces. For example, some materials have limited emissivity in the mid-infrared region, resulting in insufficient overall cooling effect. In long-term environments, the coating's weather resistance, adhesion, and stain resistance also require further optimization. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-reflectivity, high-emissivity radiation cooling coating for power equipment and its preparation method.

[0007] A high-reflectivity, high-emissivity radiation cooling coating for power equipment comprises the following components in parts by weight:

[0008] 30-45 parts deionized water, 40-60 parts styrene-acrylic emulsion, 20-40 parts titanium dioxide, 5-20 parts hollow glass microspheres, 3-10 parts zinc oxide, 5-15 parts hexagonal stone powder, 0.2-2 parts dispersant, 0.1-1 part defoamer, 1-5 parts film-forming aid, and 0.1-2 parts mildew inhibitor.

[0009] Preferably, the coating further comprises 10-20 parts of mica powder, wherein the mica powder is D... 50 Particle size 5–20 μm.

[0010] Preferably, the coating further comprises 5-15 parts of calcined kaolin, wherein the calcined kaolin D 50 The particle size is 0.2–10 μm, and the weight loss on ignition is less than 0.5–1%.

[0011] Preferably, the coating further comprises 10-30 parts of talc powder, wherein the talc powder has a flake structure. 50 The particle size is 5-15 μm, and the free SiO2 content in the talc powder is 90-98%.

[0012] Preferably, the coating further comprises 3 to 10 parts of silica micro powder, wherein the silica micro powder is spherical or irregular particles with an average particle size of 100 nm to 1 μm and a specific surface area of ​​50 to 300 m² / g.

[0013] Preferably, the hexagonal stone powder is pre-treated with 1-5 wt% aminopropyltriethoxysilane for surface grafting and then coated with 1-3 wt% polyphosphate silane.

[0014] Preferably, the coating further comprises 5 to 15 parts of a polyacrylate-polyether block copolymer emulsion, wherein the mass ratio of the polyether soft segment to the polyacrylate hard segment in the copolymer emulsion is (3 to 5):1, the glass transition temperature is -40 to -10°C, and the number average molecular weight is 30,000 to 80,000.

[0015] A method for preparing a high-reflectivity, high-emissivity radiation-cooling coating for power equipment, as described above, includes the following steps:

[0016] (1) Deionized water, dispersant, defoamer and film-forming aid are mixed under stirring to form a dispersion pre-liquid;

[0017] (2) Add hollow glass microspheres and titanium dioxide (30-60 wt% of the total amount of titanium dioxide) sequentially to the system in step (1), stir and let stand for a short time;

[0018] (3) Add the remaining titanium dioxide and hexagonal stone powder, and introduce one or more of mica powder, calcined kaolin, talc powder, and silica powder. After shearing, stirring and ultrasonic treatment, a filler dispersion system is obtained.

[0019] (4) Add styrene-acrylic emulsion and zinc oxide dropwise under temperature control, and simultaneously add polyacrylate-polyether block copolymer emulsion to form a uniform emulsion-filler system;

[0020] (5) After the addition is complete, perform homogenization and pH adjustment, and then let it stand.

[0021] (6) The coating system obtained in step (5) is subjected to temperature-controlled aging and thermal cycling treatment to form the final coating.

[0022] Preferably, in step (3), the filler dispersion system undergoes the following processes in sequence:

[0023] (A) High-speed stirring at a shear rate of 1500±100 rpm for 4 to 6 minutes;

[0024] (B) Immediately introduce 5-10°C cold air to turbulently cool the gas for 1-2 minutes;

[0025] (C) Continue with ultrasonic treatment at a frequency of 40±5kHz for 2 to 4 minutes, and maintain the system temperature at no higher than 30℃ during the ultrasonic process.

[0026] Preferably, the thermal cycling in step (6) includes maintaining the temperature at 25±2℃, 50±2℃ and then decreasing it to 25±2℃ in a closed environment, with each temperature stage lasting for 4 hours.

[0027] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0028] First, hexagonal stone powder is introduced into the coating as a responsive filler in the mid- and far-infrared band. Its layered structure and moderate particle size distribution form a multi-scale composite reflective system with titanium dioxide, creating an effective optical gradient in the visible to mid-infrared band. In particular, when used in combination with hollow glass microspheres, its interface scattering and bulk refraction mechanisms work synergistically to enhance the multiple reflections and scattering depth of light, thereby improving the overall thermal reflectivity.

[0029] Hexagonal stone powder exhibits a platy or granular-lamellar composite structure, with its particle size range overlapping to some extent with talc and mica powder, but their crystal morphologies differ significantly. Both can form a microscopic multi-level composite orientation arrangement within the same coating system, enhancing the directional infrared reflectivity of the film. Talc, due to its extremely high flake-to-diameter ratio, is advantageous for constructing lateral shielding structures, while hexagonal stone powder is more conducive to the formation of vertical multi-layer interfaces, resulting in a complementary microstructure.

[0030] Mica powder, as a natural multilayered mineral, has a strong ultraviolet-visible light shielding ability. When blended with hexagonal stone powder, they can complement each other in terms of light reaction mechanisms in different wavelength bands: mica is mainly responsible for short-wavelength reflection, while hexagonal stone powder extends the reflection capability to the mid- and far-infrared regions, thereby expanding the radiation modulation efficiency in the overall spectral range.

[0031] In this system, calcined kaolin serves as a thermal stability enhancer, and its small particle size and surface activity also help fill the microporous areas that hexagonal stone powder cannot cover, thereby constructing a high-density, multi-scale composite filler skeleton. When coexisting with hexagonal stone powder, it can form a spatially coupled distribution between the nano- and micro-scales, improving thermal barrier properties and coating consistency.

[0032] Due to its high specific surface area, silica micropowder, when used in conjunction with inorganic materials such as hexagonal stone powder with relatively low specific surface area, can form a fine-particle-large-particle nested structure in the coating, which helps to improve surface roughness and thermal emission efficiency. At the same time, due to its rich surface functional groups, it may also promote interfacial forces with surface-modified hexagonal stone powder, enhancing the stability and weather resistance of the coating.

[0033] Furthermore, after grafting with aminopropyltriethoxysilane and coating with polyphosphate silane, the surface activity and interfacial compatibility of hexagonal stone powder are enhanced, which helps to improve its dispersion stability and the integrity of the network film structure in the styrene-acrylic emulsion matrix. This surface modification treatment not only reduces interfacial energy but also inhibits powder agglomeration, improves system uniformity and coating durability.

[0034] This invention employs a stepwise addition scheme for titanium dioxide in the preparation process. 30-60% is introduced early by blending with hollow microspheres, which helps to initially construct the optical framework. The remaining portion, along with other reflective fillers, forms a stable filler dispersion system under the synergistic effects of shearing, cold air disturbance, and ultrasound. This three-stage processing flow of shearing-cold air-ultrasound not only controls the dispersion efficiency but also effectively regulates the system's temperature rise, dispersion uniformity, and particle stability, providing a favorable foundation for the subsequent formation of the emulsion-filler composite system. Furthermore, the introduction of block polyacrylate-polyether emulsion imparts good flexibility and compatibility to the film layer. Its low glass transition temperature helps improve the integrity of the film layer under thermal expansion and contraction or stress impact, forming a complementary system with the styrene-acrylic emulsion. Attached Figure Description

[0035] Figure 1 The graphs show the solar spectral reflectance R(λ) curves from 0.3 to 2.5 µm for Examples 1, 6, 8, Comparative Example 1, and Comparative Example 2.

[0036] Figure 2The graph shows the hemispherical emissivity ε(λ) curves for the 8–13 µm atmospheric window of Examples 1, 6, 8, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0040] 37.5 parts deionized water, 50 parts styrene-acrylic emulsion (50% solid content), 30 parts titanium dioxide (rutile type), 12.5 parts hollow glass microspheres (particle size D) 50 15–30 μm), 6.5 parts zinc oxide (analytical grade), 10 parts hexagonal stone powder (particle size D) 50 The film-forming agent has a thickness of 5-10 μm. 1.1 parts of dispersant (sodium polycarboxylate dispersant), 0.5 parts of defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 3 parts of film-forming aid (propylene glycol butyl ether), and 1 part of mildew inhibitor (Jiuxin Chemical, model: P803).

[0041] The preparation method is as follows:

[0042] (1) Add 37.5 parts of deionized water to the mixing tank, and then add 1.1 parts of dispersant, 0.5 parts of defoamer and 3 parts of film-forming aid in sequence. Stir at 400 rpm for 5 min under stirring conditions to form a uniform dispersion pre-liquid.

[0043] (2) Add 12.5 parts of hollow glass microspheres and 50% (i.e. 15 parts) of the total amount of titanium dioxide to the above dispersion pre-liquid, stir at 800 rpm for 2 min, and let stand for 1 min.

[0044] (3) Add the remaining 15 parts of titanium dioxide and 10 parts of hexagonal stone powder to the system, stir for 4 min under shearing at 1500 rpm, and then treat with ultrasonic waves at 40 kHz for 3 min to obtain a uniformly dispersed filler system.

[0045] (4) Cool the obtained system to 28°C, and slowly add 50 parts of styrene-acrylic emulsion and 6.5 parts of zinc oxide at this temperature, while maintaining a stirring rate of 600 rpm. Add the mixture at a constant rate for 10 min to form an emulsion-filler composite dispersion system.

[0046] (5) After the addition is complete, stir homogenize at 1000 rpm for 3 min, and adjust the pH to 7.2 with dilute ammonia water, and then let it stand for 1 h.

[0047] (6) The system was aged in a 40℃ constant temperature oven for 24 hours, and then the temperature was maintained at 25±2℃, 50±2℃ and then reduced to 25±2℃ in a sealed container. Each stage lasted for 4 hours to complete the heat cycle treatment and obtain a stable refrigeration coating product.

[0048] Example 2

[0049] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0050] 33 parts deionized water, 42 parts styrene-acrylic emulsion (50% solid content), 25 parts titanium dioxide (rutile type), 10 parts hollow glass microspheres (D 50 Particle size 15–30 μm), 4 parts zinc oxide (analytical grade), 7 parts hexagonal stone powder (particle size D) 50 (5-10 μm), 15 parts mica powder (D) 50 =10μm), 0.5 parts of dispersant (sodium polycarboxylate dispersant), 0.3 parts of defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 2 parts of film-forming aid (propylene glycol butyl ether), 0.5 parts of mildew inhibitor (Jiuxin Chemical, model: P803).

[0051] The preparation method is as follows:

[0052] (1) Add 33 parts of deionized water to the mixing tank, and add 0.5 parts of dispersant, 0.3 parts of defoamer and 2 parts of film-forming aid in sequence. Stir at 380 rpm for 6 minutes under stirring conditions to form a uniform dispersion pre-liquid.

[0053] (2) Add 10 parts of hollow glass microspheres and 50% (i.e. 12.5 parts) of the total amount of titanium dioxide to the above pre-liquid, stir at 750 rpm for 3 min, and let stand for 1 min.

[0054] (3) Add the remaining 12.5 parts of titanium dioxide, 7 parts of hexagonal stone powder and 15 parts of mica powder to the system, stir for 5 min under shearing at 1500 rpm, and then treat with ultrasonic waves at 40 kHz for 3 min to obtain a uniformly dispersed filler system.

[0055] (4) Control the system temperature at 28℃, slowly add 42 parts of styrene-acrylic emulsion and 4 parts of zinc oxide, control the stirring rate at 620 rpm, and add at a constant rate for 9 min to form an emulsion-filler composite system.

[0056] (5) After the addition is complete, stir homogenize at 980 rpm for 3 min, adjust the pH to 7.0, and let stand for 1 h.

[0057] (6) The system was aged at 39°C for 24 hours, and then the temperature was maintained at 25°C, 50°C and then reduced to 25°C for thermal cycling treatment. Each stage lasted for 4 hours. The treatment process was completed under closed conditions.

[0058] Example 3

[0059] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0060] 45 parts deionized water, 60 parts styrene-acrylic emulsion (50% solid content), 40 parts titanium dioxide (rutile type), 18 parts hollow glass microspheres (D 50 Particle size 15-30 μm), 10 parts zinc oxide (analytical grade), 15 parts hexagonal stone powder (D 50 =5~10μm), 10 parts of calcined kaolin (D 50 =2μm, loss on ignition 0.5%), 2 parts dispersant (sodium polycarboxylate dispersant), 1 part defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 5 parts film-forming aid (propylene glycol butyl ether), 2 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0061] The preparation method is as follows:

[0062] (1) Add 45 parts of deionized water to the mixing tank, then add 2 parts of dispersant, 1 part of defoamer and 5 parts of film-forming aid in sequence. Stir at 420 rpm for 5 min under stirring conditions to form a uniform dispersion pre-liquid.

[0063] (2) Add 18 parts of hollow glass microspheres and 50% (i.e. 20 parts) of the total amount of titanium dioxide to the above system, stir at 850 rpm for 2 min, and let stand for 1 min.

[0064] (3) Add the remaining 20 parts of titanium dioxide, 15 parts of hexagonal stone powder and 10 parts of calcined kaolin to the system, shear and stir at 1500 rpm for 5 min, and then sonicate at 40 kHz for 3 min to obtain a uniformly dispersed filler system.

[0065] (4) Control the system temperature at 27℃, add 60 parts of styrene-acrylic emulsion and 10 parts of zinc oxide dropwise at a stirring speed of 600 rpm, and keep the dropwise addition at a constant rate for 10 min to form an emulsion-filler mixture system.

[0066] (5) After the addition is complete, stir homogenize at 1000 rpm for 3 min, adjust the pH to 7.4 with dilute ammonia, and let stand for 1 h.

[0067] (6) The obtained system was aged at 40°C for 24 hours, and then the temperature was maintained at 25°C, 50°C and 25°C in a sealed container for 4 hours at each stage to complete the thermal cycling treatment.

[0068] Example 4

[0069] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0070] 30 parts deionized water, 40 parts styrene-acrylic emulsion (50% solid content), 20 parts titanium dioxide (rutile type), 5 parts hollow glass microspheres (D 50 Particle size 15–30 μm), 3 parts zinc oxide (analytical grade), 5 parts hexagonal stone powder (D 50 =5~10μm), 25 parts of talc powder (flaky structure, D) 50 =10μm, free SiO2 content 94%), dispersant 0.2 parts (sodium polycarboxylate dispersant), defoamer 0.1 parts (Hai'an (Linyi) Guoli Chemical, model: FAG470), film-forming aid 1 part (propylene glycol butyl ether), mildew inhibitor 0.1 parts (Jiuxin Chemical, model: P803).

[0071] The preparation method is as follows:

[0072] (1) Add 30 parts of deionized water to the mixing tank, and add 0.2 parts of dispersant, 0.1 parts of defoamer and 1 part of film-forming aid in sequence. Stir at 400 rpm for 4 min under stirring conditions to form a uniform dispersion pre-liquid.

[0073] (2) Add 5 parts of hollow glass microspheres and 50% (i.e. 10 parts) of the total amount of titanium dioxide to the above system, stir at 700 rpm for 2 min, and let stand for 1 min.

[0074] (3) Add the remaining 10 parts of titanium dioxide, 5 parts of hexagonal stone powder and 25 parts of talc powder. The shear rate is 1500 rpm. After stirring for 5 min, perform ultrasonic treatment at 40 kHz for 3 min to form a filler dispersion system.

[0075] (4) Control the temperature at 28℃, slowly add 40 parts of styrene-acrylic emulsion and 3 parts of zinc oxide, control the stirring rate at 580 rpm, and add at a constant rate for 11 min to form an emulsion-filler mixture system.

[0076] (5) After the addition is complete, stir homogenize at 960 rpm for 3 min, adjust the pH to 7.1 with dilute ammonia, and let stand for 1 h.

[0077] (6) Aging at 38℃ for 22 hours, followed by thermal cycling at 24℃, 49℃ and 24℃ in a closed environment, with each stage lasting 4 hours.

[0078] Example 5

[0079] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0080] 36 parts deionized water, 48 parts styrene-acrylic emulsion (50% solid content), 35 parts titanium dioxide (rutile type), 15 parts hollow glass microspheres (D 50 Particle size 15–30 μm), 8 parts zinc oxide (analytical grade), 12 parts hexagonal stone powder (D 50 =5~10μm), 6 parts of silica micro powder (spherical structure, average particle size of about 500nm, specific surface area of ​​150m²). 2 / g), 1.5 parts dispersant (sodium polycarboxylate dispersant), 0.8 parts defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 4 parts film-forming aid (propylene glycol butyl ether), 1.2 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0081] The preparation method is as follows:

[0082] (1) Add 36 parts of deionized water to the mixing tank, then add 1.5 parts of dispersant, 0.8 parts of defoamer and 4 parts of film-forming aid in sequence. Stir at 390 rpm for 5 min under stirring conditions to form a uniform dispersion pre-liquid.

[0083] (2) Add 15 parts of hollow glass microspheres and 50% of the total amount of titanium dioxide (i.e., 17.5 parts) to the above system, stir at 820 rpm for 3 min, and let stand for 1 min.

[0084] (3) Add the remaining 17.5 parts of titanium dioxide, 12 parts of hexagonal stone powder and 6 parts of silica micro powder, and shear and stir at 1500 rpm for 5 min, then sonicate at 40 kHz for 3 min to form a highly dispersed filler system.

[0085] (4) The system temperature was controlled at 27℃. 48 parts of styrene-acrylic emulsion and 8 parts of zinc oxide were slowly added dropwise at a stirring rate of 640 rpm for 10 min.

[0086] (5) After the addition is complete, stir homogenize at 1000 rpm for 3 min, adjust the pH to 7.3, and let stand for 1 h.

[0087] (6) Aging at 41℃ for 24 hours, followed by thermal cycling treatment at 25℃, 50℃ and 25℃ in sequence, each stage lasting 4 hours, and the process is carried out in a closed environment.

[0088] Example 6

[0089] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0090] 39 parts deionized water, 45 parts styrene-acrylic emulsion (50% solid content), 28 parts titanium dioxide (rutile type), 8 parts hollow glass microspheres (D 50 The product contains: 15-30 μm particle size, 6 parts zinc oxide (analytical grade), 9 parts hexagonal stone powder (grafted with 3 wt% aminopropyltriethoxysilane and further coated with 2 wt% polyphosphate silane), 1.2 parts dispersant (sodium polycarboxylate dispersant), 0.6 parts defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 3 parts film-forming aid (propylene glycol butyl ether), and 0.9 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0091] The pretreatment of hexagonal stone powder is as follows:

[0092] (A) Weigh out the original hexagonal stone powder (D) 50 =5~10μm) 100g, added to 200g anhydrous ethanol, ultrasonically dispersed for 10min, and then slowly added 3wt% (relative to the powder mass) of aminopropyltriethoxysilane (KH-550), adjusted the pH to 4.5~5.0, and stirred at 45℃ for 2h to complete the grafting modification.

[0093] (B) After filtration and drying to constant weight, the obtained surface-grafted powder was redispersed in anhydrous ethanol, and 2 wt% (relative to the powder mass) of polyphosphate silane was added. The reaction was continued at 50°C for 1 hour to complete the composite coating treatment. Finally, the powder was vacuum dried at 70°C for 8 hours to obtain the treated hexagonal stone powder.

[0094] The preparation method is as follows:

[0095] (1) Add 39 parts of deionized water to the mixing tank, and add 1.2 parts of dispersant, 0.6 parts of defoamer and 3 parts of film-forming aid in sequence. Stir at 405 rpm for 6 minutes under stirring conditions to form a uniform dispersion pre-liquid.

[0096] (2) Add 8 parts of hollow glass microspheres and 50% (i.e. 14 parts) of the total amount of titanium dioxide to the above system, stir at 780 rpm for 2 min, and let stand for 1 min.

[0097] (3) Add the remaining 14 parts of titanium dioxide and 9 parts of surface-treated hexagonal stone powder to the system, shear and stir at a speed of 1500 rpm for 5 min, and then perform ultrasonic treatment at 40 kHz for 3 min to form a stable filler system.

[0098] (4) Adjust the system temperature to 27°C, and slowly add 45 parts of styrene-acrylic emulsion and 6 parts of zinc oxide at a stirring speed of 610 rpm. Maintain a constant dropping rate for 9 min to form an emulsion-filler composite dispersion.

[0099] (5) After the addition is complete, stir homogenize at 950 rpm for 3 min, adjust the pH to 7.2 with dilute ammonia, and let stand for 1 h.

[0100] (6) The system was aged at 40°C for 23 hours, and then subjected to closed thermal cycling treatment, maintaining the temperature at 26°C, 51°C and 26°C in sequence, with each stage lasting 4 hours.

[0101] Example 7

[0102] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0103] 32 parts deionized water, 43 parts styrene-acrylic emulsion (50% solid content), 10 parts polyacrylate-polyether block copolymer emulsion (polyether soft segment to polyacrylate hard segment mass ratio 4:1, glass transition temperature -25℃, number average molecular weight 50,000), 32 parts titanium dioxide (rutile type), 12 parts hollow glass microspheres (particle size 15–30 μm), 7 parts zinc oxide (analytical grade), 10 parts hexagonal stone powder (D50=5–10 μm), 0.8 parts dispersant (sodium polycarboxylate dispersant), 0.5 parts defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 2.5 parts film-forming aid (propylene glycol butyl ether), 0.4 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0104] The preparation method is as follows:

[0105] (1) Add 32 parts of deionized water to the mixing tank, and add 0.8 parts of dispersant, 0.5 parts of defoamer and 2.5 parts of film-forming aid in sequence. Stir at 395 rpm for 5 min under stirring conditions to form a uniform dispersion pre-liquid.

[0106] (2) Add 12 parts of hollow glass microspheres and 50% of the total amount of titanium dioxide (i.e., 16 parts) to the above system, stir at 770 rpm for 2 min, and let stand for 1 min.

[0107] (3) Add the remaining 16 parts of titanium dioxide and 10 parts of hexagonal stone powder to the system, shear and stir at 1500 rpm for 5 min, and then treat with ultrasonic waves at 40 kHz for 3 min to form a uniform filler dispersion system.

[0108] (4) Control the temperature at 28℃, add 43 parts of styrene-acrylic emulsion and 7 parts of zinc oxide at a stirring speed of 630 rpm, and simultaneously add 10 parts of copolymer emulsion for 10 min.

[0109] (5) After the addition is complete, stir homogenize at 990 rpm for 3 min, adjust the pH to 7.2, and let stand for 1 h.

[0110] (6) The system was aged at 39°C for 24 hours and then subjected to thermal cycling treatment: the temperature was maintained at 25°C, 50°C and 25°C in a closed state, with each stage lasting 4 hours, to complete the final coating preparation.

[0111] Example 8

[0112] This embodiment discloses a high-reflectivity, high-emissivity radiation-cooling coating for power equipment and its preparation method. The coating comprises the following components in parts by weight:

[0113] 37 parts deionized water, 50 parts styrene-acrylic emulsion (50% solid content), 30 parts titanium dioxide (rutile type), 10 parts hollow glass microspheres (D 50 Particle size 15-30 μm), 6 parts zinc oxide, 10 parts hexagonal stone powder (D 50 =5~10μm), 1.0 part of dispersant (sodium polycarboxylate dispersant), 0.4 part of defoamer (siloxane), 2.5 parts of film-forming aid (propylene glycol butyl ether), and 0.6 parts of mildew inhibitor (Jiuxin Chemical, model: P803).

[0114] The preparation method is as follows.

[0115] (1) Add 37 parts of deionized water to the mixing tank, and add 1.0 part of dispersant, 0.4 parts of defoamer and 2.5 parts of film-forming aid in sequence. Stir at 400 rpm for 5 min under stirring conditions to form a uniform dispersion pre-liquid.

[0116] (2) Add 10 parts of hollow glass microspheres and 50% (i.e. 15 parts) of the total amount of titanium dioxide to the above system, stir at 800 rpm for 2 min, and let stand for 1 min.

[0117] (3) Continue to add the remaining 15 parts of titanium dioxide and 10 parts of hexagonal stone powder, and perform the following three-stage treatment to form a filler dispersion system:

[0118] (A) Shear dispersion: Stir at high speed for 5 min at 1600 rpm;

[0119] (B) Gas disturbance cooling: Immediately introduce a cold air flow of 8°C to disturb and cool the surface of the stirred system for 1.5 min;

[0120] (C) Ultrasonic dispersion: Continue ultrasonic treatment at 40 kHz for 3 min, and maintain the system temperature ≤30℃ during this process.

[0121] (4) Adjust the system temperature to 27°C, and slowly add 50 parts of styrene-acrylic emulsion and 6 parts of zinc oxide at a stirring speed of 610 rpm. Maintain a constant adding rate for 10 min to form a uniform emulsion-filler system.

[0122] (5) After the addition is complete, stir homogenize at 1000 rpm for 3 min, adjust the pH to 7.1 with dilute ammonia, and let stand for 1 h.

[0123] (6) The obtained system was aged at 40°C for 24 hours and subjected to closed thermal cycling treatment at temperatures of 25°C, 50°C and 25°C respectively, with each stage lasting 4 hours.

[0124] Comparative Example 1

[0125] The raw materials used in this comparative example and their quantities are as follows (by weight):

[0126] 35 parts deionized water, 48 parts styrene-acrylic emulsion (50% solid content), 30 parts titanium dioxide, 12 parts hollow glass microspheres, 6 parts zinc oxide (excluding hexagonal stone powder), 1.0 part dispersant (sodium polycarboxylate dispersant), 0.5 parts defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 3 parts film-forming aid (propylene glycol butyl ether), 0.5 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0127] The preparation method was carried out in accordance with steps (1) to (6) described in Example 1.

[0128] Comparative Example 2

[0129] The raw materials used in this comparative example and their quantities are as follows (by weight):

[0130] 35 parts deionized water, 48 parts styrene-acrylic emulsion (50% solid content), 30 parts titanium dioxide (without hollow glass microspheres and zinc oxide), 10 parts hexagonal stone powder, 1.0 part dispersant (sodium polycarboxylate dispersant), 0.5 parts defoamer (Hai'an (Linyi) Guoli Chemical, model: FAG470), 3 parts film-forming aid (propylene glycol butyl ether), 0.5 parts mildew inhibitor (Jiuxin Chemical, model: P803).

[0131] The preparation method is the same as steps (1) to (6) described in Example 1.

[0132] Performance testing

[0133] After the coating samples of the examples and comparative examples were applied to the testing equipment, temperature and humidity data were monitored for 7 days, with a maximum temperature exceeding 50°C and a maximum humidity exceeding 75%. After 7 days, the coating performance was tested, including solar reflectivity, hemispherical emissivity, contact angle, ambient temperature difference, adhesion, and stain resistance. The specific test results for Examples 1, 6, and 8, as well as Comparative Examples 1 and 2, are shown in Tables 1 to 5 below. The test results for Examples 2 to 5 and Example 7 all met the required values.

[0134] Table 1. Detection results of Example 1

[0135]

[0136] Table 2 Detection Results of Example 6

[0137]

[0138] Table 3 Detection results of Example 8

[0139]

[0140] Table 4. Test results of Comparative Example 1

[0141]

[0142] Table 5. Detection results of Comparative Example 2

[0143]

[0144] Figure 1 and Figure 2 The graphs show the solar spectral reflectance R(λ) curves from 0.3 to 2.5 µm and the hemispherical emissivity ε(λ) curves from 8 to 13 µm of the atmospheric window for Examples 1, 6, 8, Comparative Example 1, and Comparative Example 2. Figure 1 and Figure 2 It is evident that the overall solar reflectance and hemispherical emissivity of Example 6 are higher than those of Example 1. In Example 6, the hexagonal stone powder was pre-treated with 1-5 wt% aminopropyltriethoxysilane for surface grafting and then coated with 1-3 wt% polyphosphate silane. This indicates that the synergistic effect between the hexagonal stone powder treated with the two specific silane components of a specific concentration and order is better than that between the hollow glass microspheres, mica powder, and talc powder, thus achieving a further advantage in the final solar reflectance and hemispherical reflectance tests. Secondly, in Example 8, the preparation step (3) specifically involved shearing and stirring followed by ultrasonic treatment. The resulting coating achieved the optimal overall solar reflectance and hemispherical emissivity, indicating that the dispersion operation in the process steps of this application is beneficial to the synergistic effect between the hexagonal stone powder, hollow glass microspheres, and titanium dioxide in the coating, thereby improving the radiative cooling performance of the coating.

[0145] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-reflectivity, high-emissivity radiative cooling coating for power equipment, characterized in that, Includes the following components in parts by weight: 30-45 parts deionized water, 40-60 parts styrene-acrylic emulsion, 20-40 parts titanium dioxide, 5-20 parts hollow glass microspheres, 3-10 parts zinc oxide, 5-15 parts hexagonal stone powder, 0.2-2 parts dispersant, 0.1-1 part defoamer, 1-5 parts film-forming aid, and 0.1-2 parts mildew inhibitor; The coating also includes 10-20 parts of mica powder, wherein the mica powder is D. 50 Particle size 5–20 μm; The coating also includes 10-30 parts of talc powder, which is in a flake-like structure. 50 The talc powder has a particle size of 5–15 μm and a free SiO2 content of 90–98%. The hexagonal stone powder was grafted with 3wt% aminopropyltriethoxysilane and further coated with 2wt% polyphosphate silane.

2. The high-reflectivity, high-emissivity radiative cooling coating for power equipment according to claim 1, characterized in that, The coating also includes 5-15 parts of calcined kaolin, wherein the calcined kaolin D 50 The particle size is 0.2–10 μm, and the weight loss on ignition is less than 0.5–1%.

3. The high-reflectivity-high-emissivity radiative cooling coating for power equipment according to claim 1, characterized in that, The coating also includes 3 to 10 parts of silica micro powder, which is spherical or irregular particles with an average particle size of 100 nm to 1 μm and a specific surface area of ​​50 to 300 m² / g.

4. The high-reflectivity, high-emissivity radiative cooling coating for power equipment according to claim 1, characterized in that, The coating also includes 5 to 15 parts of a polyacrylate-polyether block copolymer emulsion, wherein the mass ratio of the polyether soft segment to the polyacrylate hard segment in the copolymer emulsion is (3 to 5):1, the glass transition temperature is -40 to -10℃, and the number average molecular weight is 30,000 to 80,000.

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