Composite powder enhanced radiation refrigeration coating and preparation method thereof

Abstract

The application discloses a composite powder reinforced radiation refrigeration coating and a preparation method thereof, and relates to the technical field of coating.The multistage surface modification functional powder, the water-based polyurethane resin and the polyisocyanate curing agent are used, the problems of unbalanced radiation refrigeration performance, slow drying speed, poor mechanical performance and environmental stability, and insufficient weather resistance of the existing coating are solved, the application scenarios of efficient cooling, weather resistance, corrosion resistance and long-term stable service are met, and the coating can be widely applied to the fields of building outer walls, metal components, cold chain equipment, outdoor facilities and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional coatings technology, specifically relating to a composite powder-enhanced radiative cooling coating and its preparation method. It is particularly suitable for applications such as building exterior walls, metal components, cold chain equipment, and outdoor facilities that require efficient cooling, weather resistance, corrosion resistance, and long-term stable service. It combines high radiative cooling performance, excellent mechanical properties, environmental stability, and high weather resistance. Background Technology

[0002] Radiative cooling technology dissipates its own heat into space through infrared radiation via an 8-13 μm atmospheric window, while simultaneously reflecting sunlight (0.3-2.5 μm) to reduce heat absorption, achieving passive, energy-free cooling. This is a crucial technological approach for addressing global warming and reducing energy consumption in buildings and industries. Polyurethane-based waterborne radiative cooling coatings have become a current research hotspot due to their environmentally friendly waterborne system, low VOC emissions, and the excellent film-forming properties, adhesion, and weather resistance of polyurethane resin.

[0003] However, existing waterborne polyurethane radiation cooling coatings generally suffer from the following core defects: First, the radiation cooling performance is uneven, making it difficult to simultaneously achieve high solar reflectance, high near-infrared reflectance, and high atmospheric window emissivity, resulting in limited cooling effect; second, the comprehensive physical and chemical properties are insufficient, the drying time is too long, and the mechanical properties, environmental stability, and UV aging resistance cannot meet the requirements for long-term outdoor use; third, the pigments and fillers have poor compatibility with polyurethane resin, easily leading to agglomeration and delamination, and the coating performance degrades rapidly.

[0004] Therefore, developing a waterborne polyurethane radiation cooling coating that combines high radiation cooling performance, rapid drying performance, excellent mechanical properties, environmental stability, and high weather resistance is of great practical significance and application value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a polyurethane-based composite powder-reinforced radiation cooling coating and its preparation method, solving the problems of uneven radiation cooling performance, slow drying speed, poor mechanical properties and environmental stability, and insufficient weather resistance of existing coatings.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A composite powder-reinforced radiation cooling coating, wherein the coating is composed of component A and component B in a mass ratio of 4:1-5:1:

[0008] Component A consists of the following ingredients by mass:

[0009] Multi-level surface-modified functional powder 28–45 parts

[0010] 35–50 parts of waterborne polyurethane resin

[0011] 10–18 parts water

[0012] 4–9 parts of film-forming aid

[0013] Dispersant 1.5–3.5 parts

[0014] Antifreeze 1.5–3.5 parts

[0015] Anti-settling agent 0.3–1 part

[0016] 0.2–0.6 parts of bactericide

[0017] pH adjuster 0.2–0.8 parts

[0018] Defoamer 0.5–1.2 parts

[0019] Wetting agent 0.8–2.5 parts

[0020] Leveling agent 0.8–1.8 parts

[0021] 0.5–1.5 parts of rheology modifier

[0022] Component B is a polyisocyanate curing agent.

[0023] In the technical solution of this invention, the multi-level surface-modified functional powder is prepared by the following method:

[0024] (1) Core-layer plasma activation: Mix 8-12 parts of α-alumina and 4-6 parts of hexagonal boron nitride, add a mixture of deionized water and ethanol in a volume ratio of 1~3:1~3, disperse at high speed of 3000~4000 rpm for 20~30 min, and ultrasonically disperse at 180~220W for 10~20 min; place in a plasma treatment device for activation treatment, then filter and vacuum dry to obtain activated core-layer particles;

[0025] The activation treatment of the plasma equipment is carried out in a mixed atmosphere of N2 with a partial pressure of 80~120 Pa and CO2 with a partial pressure of 80~120 Pa, at a radio frequency of 10~15MHz, a power of 250~350 W, and at 70~80℃ for 10~20 min.

[0026] The conditions for vacuum drying are a temperature of 70~80℃ and vacuum drying for 1~1.5 h;

[0027] (2) Microwave-assisted hydrothermal in-situ coating of the shell layer: The activated core layer particles are added to the composite modified solvent and stirred evenly. Then, 10-15 parts of rutile TiO2, 4-6 parts of zinc oxide, 2-3 parts of scandium-doped gallium oxide and 1-1.5 parts of surfactant are added and stirred at 800-1500 rpm for 10-15 min. The mixture is then transferred to a microwave-assisted hydrothermal reactor for reaction. After the reaction is completed, the mixture is cooled to room temperature, centrifuged, washed and vacuum dried to obtain the "core-shell" powder.

[0028] The composite modified solvent is propylene glycol methyl ether, 1-ethyl-3-methylimidazolium acetate, and supercritical CO2 in a volume ratio of 1~3:1~3:1~3;

[0029] The surfactant is SDBS and Capstone FS-50 in a mass ratio of 1 to 3:1;

[0030] The reaction conditions are 400~500 W microwave power, 170~180℃ for 3~4 h;

[0031] The vacuum drying temperature is 50~60℃, and the time is 1~2 hours;

[0032] (3) Porous network supercritical CO2-assisted grafting modification: The "core-shell" powder was added to a supercritical reactor, along with 2-3 parts of silane coupling agent, 1-1.5 parts of titanate coupling agent NDZ-101, and 0.5-1 parts of aluminate coupling agent DL-411. Supercritical CO2 at 10-15 MPa and 40-45℃ was introduced and stirred at 400-500 rpm for 2-3 h. 6-9 parts of SiO2 aerogel, 2-3 parts of polyvinylidene chloride, and 2-3 parts of ceramic micro powder were added and the reaction continued for 1.5-2 h. The pressure was slowly released at a rate of 0.4-0.5 MPa / min, the sample was taken out, and freeze-dried at -50℃ to -40℃ and 5-10 Pa vacuum for 10-12 h to obtain the grafted modified powder.

[0033] The silane coupling agent is KH-550 and FAS-17 in a mass ratio of 1~3:1~3;

[0034] (4) Compound optimization: The above grafted modified powder is mixed with 2-4 parts of β-zirconia and 2-4 parts of magnesium calcium silicate, and dispersed at high speed of 2000~3000 rpm for 10~15 min to obtain multi-level surface modified functional powder;

[0035] The particle size of β-zirconia is 100-200 nm, and the particle size of magnesium calcium silicate is 0.8-1.5 μm.

[0036] In the technical solution of this invention, the scandium-doped gallium oxide is prepared by the following method:

[0037] (1) Weigh gallium nitrate and scandium nitrate according to the molar fraction of Sc doping 2–5%, add deionized water to prepare a 0.3 mol / L mixed metal salt solution; add urea, stir until completely dissolved, adjust the pH of the solution to 9.0±0.2, and stir to form a uniform and transparent precursor solution; wherein, the total molar ratio of urea to metal ions is 2~4:1;

[0038] (2) The precursor solution was transferred to a microwave hydrothermal reactor and kept at 170-180℃ for 3-4 hours for hydrothermal synthesis. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged and the precipitate was collected. After washing, it was vacuum dried at 50-60℃ and 5-10Pa for 1-2 hours to obtain the precursor powder.

[0039] (3) Place the precursor powder in an alumina crucible and calcine it at 800-850°C for 2-3 hours in an air atmosphere. Then, cool it naturally to room temperature and grind it to obtain scandium-doped gallium oxide powder with a particle size of 200-500 nm.

[0040] In the technical solution of this invention, the waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40 WANEP waterborne polyurethane resin, with a mass ratio of 1:1-3:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent, with a mass ratio of 1:1-1.5:1.

[0041] In the technical solution of this invention, the components are as follows:

[0042] The film-forming aid is one or more of propylene glycol methyl ether and dodecyl alcohol ester;

[0043] The dispersant is a sodium polycarboxylate dispersant, preferably one or more of BYK-194, Evonik TEGO® Dispers 750W, and BYK-191;

[0044] The antifreeze is ethylene glycol;

[0045] The anti-settling agent is organic bentonite;

[0046] The bactericide is an isothiazolinone bactericide, preferably one or more of Lanxess Parmetol A26 and Torr ActiveIDE B20;

[0047] The pH adjuster is one or more of diethanolamine and N,N-dimethylethanolamine;

[0048] The defoamer is an organosilicon defoamer, preferably one or more of Evonik TEGO Foamex 810, BYK-037, and BASF FoamStar SI 2240;

[0049] The wetting agent is a polyether-modified polysiloxane wetting agent, preferably one or more of BYK-349, Air Products Surfynol 420, and Evonik TEGO Wet 270;

[0050] The leveling agent is a polyether-modified silicone leveling agent, preferably one or more of DEUCHEM 432, BYK-361, and TEGOGlide 440;

[0051] The rheology modifier is a polyurethane associative rheology modifier, preferably one or more of Ashland ACRYSOL RM-8W and RHEOLATE® 299.

[0052] A method for preparing the above-mentioned composite powder-reinforced radiation cooling coating includes the following process steps:

[0053] Add waterborne polyurethane resin, multi-stage surface-modified functional powder, water, and dispersant to a dispersion tank according to the specified weight ratio. Disperse at 950-1250 r / min for 15-20 minutes. Then, add film-forming aid, antifreeze, anti-settling agent, and pH adjuster in sequence. Disperse at 1400-1600 r / min for 40-50 minutes. Finally, add bactericide, defoamer, wetting agent, leveling agent, and rheology modifier at 1800-1900 r / min and disperse for 35-45 minutes. After passing the test, filter to obtain component A.

[0054] During construction, components A and B are mixed evenly in a certain proportion to obtain a composite powder-reinforced radiation cooling coating.

[0055] The beneficial effects of this invention are:

[0056] (1) The present invention has excellent and balanced radiation cooling performance: through multi-level surface modified functional powder (containing Sc-doped Ga2O3 novel oxide), it achieves high solar reflectance (≥0.93), high near-infrared reflectance (≥0.94), and high atmospheric window emissivity (≥0.94). The measured outdoor cooling can reach 9~14℃, and the cooling efficiency is significantly better than existing products.

[0057] (2) The present invention has a fast drying speed: by optimizing the film-forming aid ratio and resin compounding, the surface drying time at room temperature (25℃, 50%RH) is ≤60min and the actual drying time is ≤10h, which meets the requirements of rapid construction.

[0058] (3) The mechanical properties of the present invention are excellent: the innovative "core-shell-porous network" multi-level surface modified functional powder has excellent compatibility with water-based polyurethane resin, the coating adhesion reaches level 0 (cross-cut test), the impact strength is 50 kg·cm without abnormality, the wear resistance (1 kg load, 1000 rpm) weight loss is ≤4 mg, the bending performance is 1 mm without cracks, the pencil hardness is ≥2H, and it can withstand outdoor mechanical impact and friction.

[0059] (4) The present invention has outstanding environmental stability: the coating does not crack or peel off after 50 cycles of hot and cold cycling from -40℃ to 80℃; the water resistance (immersion in water for 168h) does not cause blistering, discoloration, or decrease in adhesion; the salt spray resistance (neutral salt spray, 1200h) does not cause rust or peeling; the acid and alkali resistance (pH=2~12 solution, 144h) does not cause corrosion or discoloration; and the UV aging resistance is excellent (after 1000h of xenon lamp aging, there is no chalking or discoloration, and the gloss retention rate is ≥85%), which can adapt to complex outdoor environments.

[0060] (5) The present invention is environmentally friendly and scalable: the water-based system has no VOC emissions, the preparation process is controllable, no extreme equipment is required, the pigments and fillers are uniformly dispersed, the coating performance is stable, it is suitable for large-scale industrial production, and has a wide range of applications, including construction, metal, cold chain, outdoor facilities and other fields. Detailed Implementation

[0061] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0062] The components of this invention are commercially available products, including but not limited to the following sources:

[0063] Covestro Bayhydrol® A 2470 waterborne polyurethane resin:

[0064] https: / / solutions.covestro.com / zh / products / bayhydrol / bayhydrol-a-2470_000000000057821608?SelectedCountry=US

[0065] DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin:

[0066] https: / / allnex.cn / cn / product / c41c925b-d983-4479-900d-adbd1fac3816 / daotan-tw-1225-40wanep-3

[0067] Wanhua Chemical HT-100 Curing Agent:

[0068] https: / / www.whchem.com / search_product.html?name=HT-100

[0069] Wanhua Chemical HT-200 Curing Agent:

[0070] https: / / www.whchem.com / search_product.html?name=HT-200

[0071] BYK-194 dispersant:

[0072] https: / / www.byk.com / zh / products / additive-guide / disperbyk-194-n?search=true

[0073] Evonik TEGO® Dispers 750W:

[0074] https: / / b2b.baidu.com / land?id=feb288b59142c481266c67ec1189daf710

[0075] BYK-191 dispersant:

[0076] https: / / www.byk.com / zh / products / additive-guide / disperbyk-191?search=true

[0077] Lanxess Parmetol A26 fungicide:

[0078] https: / / dxchemical.gys.cn / supply / 4048727055.html

[0079] Tor ACTICIDE B20 fungicide:

[0080] https: / / b2b.baidu.com / land?id=679503ff59ca240fe1335db917e3ee0b10

[0081] Evonik TEGO Foamex 810 defoamer:

[0082] https: / / www.muin.com.cn / TEGO_Foamex_810.html

[0083] BYK-037 Defoamer:

[0084] https: / / www.byk.com / zh / products / additive-guide / byk-037

[0085] BASF FoamStar SI 2240 defoamer:

[0086] https: / / dispersions-resins-products.basf.us / products / foamstar-si-2240

[0087] BYK-349 wetting agent:

[0088] https: / / www.byk.com / zh / products / additive-guide / byk-349?search=true

[0089] Air Products Surfynol 420 wetting agent:

[0090] https: / / nuochen123.gys.cn / supply / 4084158249.html

[0091] Evonik TEGO Wet 270 wetting agent:

[0092] http: / / linshenghua.cn.makepolo.com / product / 101065180500.html

[0093] DEUCHEM 432 leveling agent:

[0094] http: / / www.bnkchem.com / productinfo / 1590158.html

[0095] BYK-361 leveling agent:

[0096] https: / / www.byk.com / zh / products / additive-guide / byk-361-n?search=true

[0097] TEGO Glide 440 leveling agent:

[0098] https: / / www.boochem.com / liupingji / tego / 440.html

[0099] Ashland ACRYSOL RM-8W rheology modifier:

[0100] https: / / hengyuhg.gys.cn / supply / 4700950376.html

[0101] RHEOLATE® 299 rheology modifier:

[0102] https: / / b2b.baidu.com / land?id=da50a988230df4ff63851671854cf32410

[0103] DISEN WATERSOL PU 3110 waterborne polyurethane resin:

[0104] https: / / www.dic.com.cn / cn / products / finder_coating / WATERSOL-PU-3110.html

[0105] The preparation steps of the radiation-cooling coatings in Examples 1-4 and Comparative Examples 1-4 are as follows (test results are shown in Table 1):

[0106] Example 1

[0107] A composite powder-reinforced radiation cooling coating comprises component A and component B, wherein the mass ratio of component A to component B is 4.5:1 and NCO / OH = 1.2:1;

[0108] Component A consists of the following components in parts by weight:

[0109] 35 parts of multi-level surface-modified functional powder

[0110] 42 parts of waterborne polyurethane resin

[0111] 14 parts water

[0112] 6 parts of film-forming aid

[0113] 2.5 parts dispersant

[0114] 2.5 parts antifreeze

[0115] 0.6 parts anti-settling agent

[0116] 0.4 parts of bactericide

[0117] pH adjuster 0.5 parts

[0118] 0.8 parts defoamer

[0119] 1.5 parts wetting agent

[0120] 1.2 parts leveling agent

[0121] 1 part rheology modifier

[0122] Component B is a polyisocyanate curing agent.

[0123] The multi-level surface-modified functional powder is prepared by the following method:

[0124] (1) Mix 10 parts of α-alumina and 5 parts of hexagonal boron nitride, add a mixture of deionized water and ethanol (volume ratio 1:1), disperse at 3500 rpm for 25 min, and ultrasonically disperse at 200 W for 15 min; place in a plasma treatment device, and treat for 20 min under a mixed atmosphere of N2 and CO2 partial pressures of 100 Pa each, a total pressure of 200 Pa, 13.56 MHz radio frequency, 300 W power, and 80 °C; filter and vacuum dry at 80 °C for 1.5 h to obtain activated core layer particles (particle size 0.4-2.5 μm);

[0125] (2) The activated core particles were added to a composite modified solvent (propylene glycol methyl ether, 1-ethyl-3-methylimidazolium acetate, and supercritical CO2 in a volume ratio of 3:1:2), stirred at 800 rpm for 10 min, and 12 parts of rutile TiO2, 5 parts of zinc oxide, 2.5 parts of scandium-doped gallium oxide (Sc-doped Ga2O3) and 1.2 parts of surfactant (SDBS+Capstone FS-50, mass ratio 2:1) were added. The mixture was stirred at 1200 rpm for 15 min. The mixture was then transferred to a microwave-assisted hydrothermal reactor and reacted at 500 W microwave power and 180 °C for 4 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 10 min, washed three times with ethanol, and vacuum dried at 60 °C for 2 h to obtain core-shell powder (particle size 0.6-3 μm).

[0126] (3) The core-shell powder was added to a supercritical reactor, along with 2.5 parts of silane coupling agent (KH-550+FAS-17, mass ratio 1:1), 1.2 parts of titanate coupling agent (NDZ-101), and 0.8 parts of aluminate coupling agent (DL-411). Supercritical CO2 at 15 MPa and 45℃ was introduced and stirred at 500 rpm for 3 h. 8 parts of SiO2 aerogel, 2.5 parts of polyvinylidene chloride, and 2.5 parts of ceramic micro powder were added, and the reaction continued for 2 h. The pressure was slowly released at a rate of 0.5 MPa / min, the sample was removed, and freeze-dried at -50℃ and 10 Pa vacuum for 12 h to obtain grafted modified powder (particle size 1-5 μm, hydrophobic angle 128°).

[0127] (4) The above grafted modified powder is mixed with 3 parts of β-zirconia (100-200 nm) and 3 parts of magnesium calcium silicate (0.8-1.5 μm), and dispersed at 3000 rpm for 15 min to obtain multi-level surface modified functional powder.

[0128] The scandium-doped gallium oxide (Sc-doped Ga2O3) is prepared by the following method:

[0129] (1) Weigh gallium nitrate and scandium nitrate according to 3% molar fraction of Sc doping, add deionized water to prepare a 0.3 mol / L mixed metal salt solution; add urea, stir until completely dissolved, adjust the pH of the solution to 9.0±0.2, and stir to form a uniform and transparent precursor solution; wherein, the total molar ratio of urea to metal ions is 3:1;

[0130] (2) The precursor solution was transferred to a microwave hydrothermal reactor and kept at 175℃ for 3.5h for hydrothermal synthesis. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged and the precipitate was collected. After washing, it was vacuum dried at 60℃ and 10Pa for 2h to obtain the precursor powder.

[0131] (3) The precursor powder was placed in an alumina crucible and calcined at 825°C for 2.5 h in an air atmosphere. It was then naturally cooled to room temperature and ground to obtain scandium-doped gallium oxide powder with a particle size of 200–500 nm.

[0132] The waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin in a mass ratio of 2:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent in a mass ratio of 1.2:1.

[0133] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0134] In a dispersion tank, add 42 parts by weight of waterborne polyurethane resin, 35 parts by weight of multi-stage surface-modified functional powder, 14 parts by weight of water, and 2.5 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 6 parts by weight of dodecyl ester, 2.5 parts by weight of ethylene glycol, 0.6 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE B20 bactericide, 0.8 parts by weight of TEGOFoamex 810 defoamer, 1.5 parts by weight of Surfynol 420 wetting agent, 1.2 parts by weight of BYK-361 leveling agent, and 1 part by weight of RHEOLATE®299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, components A and B are mixed evenly in a certain proportion to obtain a composite powder-reinforced radiation cooling coating.

[0135] Example 2

[0136] A composite powder-reinforced radiation cooling coating comprises component A and component B, wherein the mass ratio of component A to component B is 4:1 and NCO / OH = 1.1:1;

[0137] Component A consists of the following components in parts by weight:

[0138] 30 parts of multi-level surface-modified functional powder

[0139] 38 parts of waterborne polyurethane resin

[0140] 12 parts water

[0141] 5 parts of film-forming aid

[0142] 2 parts dispersant

[0143] 2 parts antifreeze

[0144] 0.5 parts anti-settling agent

[0145] 0.3 parts of bactericide

[0146] pH adjuster 0.4 parts

[0147] 0.6 parts defoamer

[0148] 1.2 parts wetting agent

[0149] 1 part leveling agent

[0150] 0.8 parts rheology modifier

[0151] Component B is a polyisocyanate curing agent.

[0152] The preparation method of the multi-level surface-modified functional powder and scandium-doped gallium oxide (Sc-doped Ga2O3) uses the same types of additives as in Example 1.

[0153] The waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin in a mass ratio of 1:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent in a mass ratio of 1:1.

[0154] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0155] In a dispersion tank, add 38 parts by weight of waterborne polyurethane resin, 30 parts by weight of multi-stage surface-modified functional powder, 12 parts by weight of water, and 2 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 5 parts by weight of dodecyl ester, 2 parts by weight of ethylene glycol, 0.5 parts by weight of organobentonite, and 0.4 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE B20 bactericide, 0.6 parts by weight of TEGO Foamex 810 defoamer, 1.2 parts by weight of Surfynol 420 wetting agent, 1 part by weight of BYK-361 leveling agent, and 0.8 parts by weight of RHEOLATE® 299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, mix component A and component B evenly in the specified proportions to obtain the composite powder-reinforced radiative cooling coating.

[0156] Example 3

[0157] A composite powder-reinforced radiation cooling coating comprises component A and component B, wherein the mass ratio of component A to component B is 5:1 and NCO / OH = 1.3:1;

[0158] Component A consists of the following components in parts by weight:

[0159] 40 parts of multi-level surface-modified functional powder

[0160] 46 parts of waterborne polyurethane resin

[0161] 16 parts water

[0162] 8 parts of film-forming aid

[0163] 3 parts dispersant

[0164] 3 parts antifreeze

[0165] 0.8 parts anti-settling agent

[0166] 0.5 parts of bactericide

[0167] pH adjuster 0.6 parts

[0168] 1 part defoamer

[0169] 2 parts wetting agent

[0170] 1.5 parts leveling agent

[0171] 1.2 parts rheology modifier

[0172] Component B is a polyisocyanate curing agent.

[0173] The preparation method of the multi-level surface-modified functional powder and scandium-doped gallium oxide (Sc-doped Ga2O3) uses the same types of additives as in Example 1.

[0174] The waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin in a mass ratio of 3:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent in a mass ratio of 1.5:1.

[0175] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0176] In a dispersion tank, add 46 parts by weight of waterborne polyurethane resin, 40 parts by weight of multi-stage surface-modified functional powder, 16 parts by weight of water, and 3 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 8 parts by weight of dodecyl ester, 3 parts by weight of ethylene glycol, 0.8 parts by weight of organobentonite, and 0.6 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE B 20 bactericide, 1 part by weight of TEGO Foamex 810 defoamer, 2 parts by weight of Surfynol 420 wetting agent, 1.5 parts by weight of BYK-361 leveling agent, and 1.2 parts by weight of RHEOLATE® 299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, mix component A and component B evenly in the specified proportions to obtain the composite powder-reinforced radiative cooling coating.

[0177] Example 4

[0178] A composite powder-reinforced radiation cooling coating comprises component A and component B, wherein the mass ratio of component A to component B is 4.2:1 and NCO / OH = 1.2:1;

[0179] Component A consists of the following components in parts by weight:

[0180] 32 parts of multi-level surface-modified functional powder

[0181] 40 parts of waterborne polyurethane resin

[0182] 13 parts water

[0183] 7 parts of film-forming aid

[0184] 2.2 parts dispersant

[0185] 2.2 parts antifreeze

[0186] 0.7 parts anti-settling agent

[0187] 0.4 parts of bactericide

[0188] pH adjuster 0.5 parts

[0189] 0.7 parts defoamer

[0190] 1.4 parts wetting agent

[0191] 1.3 parts leveling agent

[0192] 0.9 parts rheology modifier

[0193] Component B is a polyisocyanate curing agent.

[0194] The preparation methods of the multi-level surface-modified functional powder and scandium-doped gallium oxide (Sc-doped Ga2O3), as well as the types of additives used, are the same as in Example 1.

[0195] The waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin in a mass ratio of 2.5:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent in a mass ratio of 1.3:1.

[0196] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0197] In a dispersion tank, add 40 parts by weight of waterborne polyurethane resin, 32 parts by weight of multi-stage surface-modified functional powder, 13 parts by weight of water, and 2.2 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 7 parts by weight of dodecyl ester, 2.2 parts by weight of ethylene glycol, 0.7 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE B20 bactericide, 0.7 parts by weight of TEGOFoamex 810 defoamer, 1.4 parts by weight of Surfynol 420 wetting agent, 1.3 parts by weight of BYK-361 leveling agent, and 0.9 parts by weight of RHEOLATE®299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, components A and B are mixed evenly in a certain proportion to obtain a composite powder-reinforced radiation cooling coating.

[0198] Comparative Example 1

[0199] A radiation-cooling coating was prepared using conventional radiation-cooling functional pigments and fillers, comprising component A and component B, wherein the mass ratio of component A to component B is 4.5:1 and NCO / OH = 1.2:1;

[0200] Component A consists of the following components in parts by weight:

[0201] 35 parts of conventional radiative cooling functional pigments and fillers

[0202] 42 parts of waterborne polyurethane resin

[0203] 14 parts water

[0204] 6 parts of film-forming aid

[0205] 2.5 parts dispersant

[0206] 2.5 parts antifreeze

[0207] 0.6 parts anti-settling agent

[0208] 0.4 parts of bactericide

[0209] pH adjuster 0.5 parts

[0210] 0.8 parts defoamer

[0211] 1.5 parts wetting agent

[0212] 1.2 parts leveling agent

[0213] 1 part rheology modifier

[0214] Component B is a polyisocyanate curing agent.

[0215] The conventional radiative cooling functional pigments and fillers are a mixture of rutile TiO2, ZnO, and SiO2 in a mass ratio of 6:3:1; the proportions of the waterborne polyurethane resin, the proportion of the polyisocyanate curing agent, and the types of additives used are the same as in Example 1.

[0216] The preparation method of the radiation cooling coating described above includes the following process steps:

[0217] In a dispersion tank, add 42 parts by weight of waterborne polyurethane resin, 35 parts by weight of conventional radiative cooling functional pigments and fillers, 14 parts by weight of water, and 2.5 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 6 parts by weight of dodecyl ester, 2.5 parts by weight of ethylene glycol, 0.6 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE BIT 20 bactericide, 0.8 parts by weight of TEGO Foamex 810 defoamer, 1.5 parts by weight of Surfynol 420 wetting agent, 1.2 parts by weight of BYK-361 leveling agent, and 1 part by weight of RHEOLATE® 299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, mix component A and component B evenly in the specified proportions to obtain the radiative cooling coating.

[0218] Comparative Example 2

[0219] A composite powder-reinforced radiation cooling coating was prepared using commercially available waterborne polyurethane resin, comprising component A and component B, wherein the mass ratio of component A to component B is 4.5:1 and NCO / OH = 1.2:1;

[0220] Component A consists of the following components in parts by weight:

[0221] 35 parts of multi-level surface-modified functional powder

[0222] 42 parts of DISEN WATERSOL PU 3110 waterborne polyurethane resin

[0223] 14 parts water

[0224] 6 parts of film-forming aid

[0225] 2.5 parts dispersant

[0226] 2.5 parts antifreeze

[0227] 0.6 parts anti-settling agent

[0228] 0.4 parts of bactericide

[0229] pH adjuster 0.5 parts

[0230] 0.8 parts defoamer

[0231] 1.5 parts wetting agent

[0232] 1.2 parts leveling agent

[0233] 1 part rheology modifier

[0234] Component B is a polyisocyanate curing agent.

[0235] The preparation methods of the multi-level surface-modified functional powder, scandium-doped gallium oxide (Sc-doped Ga2O3), the proportion of polyisocyanate curing agent, and the types of additives used are the same as in Example 1.

[0236] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0237] Add 42 parts by weight of DISRON WATERSOL PU 3110 waterborne polyurethane resin, 35 parts by weight of multi-stage surface-modified functional powder, 14 parts by weight of water, and 2.5 parts by weight of BYK-194 dispersant to a dispersion tank. Disperse at 1000 rpm for 15 minutes. Then add 6 parts by weight of dodecyl ester, 2.5 parts by weight of ethylene glycol, 0.6 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then add 0.3 parts by weight of ACTICIDE BIT20 bactericide, 0.8 parts by weight of TEGO Foamex 810 defoamer, 1.5 parts by weight of Surfynol 420 wetting agent, 1.2 parts by weight of BYK-361 leveling agent, and 1 part by weight of RHEOLATE® 299 rheology modifier to a dispersion tank. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, components A and B are mixed evenly in the specified proportions to obtain the radiation cooling coating.

[0238] Comparative Example 3

[0239] A composite powder-enhanced radiation cooling coating was prepared using a single curing agent, comprising component A and component B, wherein the mass ratio of component A to component B is 4.5:1 and NCO / OH = 1.2:1;

[0240] Component A consists of the following components in parts by weight:

[0241] 35 parts of multi-level surface-modified functional powder

[0242] 42 parts of waterborne polyurethane resin

[0243] 14 parts water

[0244] 6 parts of film-forming aid

[0245] 2.5 parts dispersant

[0246] 2.5 parts antifreeze

[0247] 0.6 parts anti-settling agent

[0248] 0.4 parts of bactericide

[0249] pH adjuster 0.5 parts

[0250] 0.8 parts defoamer

[0251] 1.5 parts wetting agent

[0252] 1.2 parts leveling agent

[0253] 1 part rheology modifier

[0254] Component B is Wanhua Chemical HT-100 curing agent.

[0255] The preparation methods of the multi-level surface-modified functional powder and scandium-doped gallium oxide (Sc-doped Ga2O3), as well as the types of additives used, are the same as in Example 1.

[0256] The preparation method of the composite powder-reinforced radiation cooling coating described above includes the following process steps:

[0257] Add 42 parts by weight of waterborne polyurethane resin, 35 parts by weight of multi-stage surface-modified functional powder, 14 parts by weight of water, and 2.5 parts by weight of BYK-194 dispersant to a dispersion tank and disperse for 15 minutes at 1000 rpm. Then add 6 parts by weight of dodecyl ester, 2.5 parts by weight of ethylene glycol, 0.6 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine and disperse for 45 minutes at 1450 rpm. Then add 0.3 parts by weight of ACTICIDE BIT 20 bactericide, 0.8 parts by weight of TEGOFoamex 810 defoamer, 1.5 parts by weight of Surfynol 420 wetting agent, 1.2 parts by weight of BYK-361 leveling agent, and 1 part by weight of RHEOLATE®299 rheology modifier at 1850 rpm and disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, components A and B are mixed evenly in the specified proportions to obtain the radiation cooling coating.

[0258] Comparative Example 4

[0259] The "core-shell-porous network" modification process of multi-level surface-modified functional powder and the addition of novel oxide (Sc-doped Ga2O3) were cancelled. A radiation cooling coating was prepared using composite functional pigments and fillers, including component A and component B, wherein the mass ratio of component A to component B is 4.5:1 and NCO / OH = 1.2:1.

[0260] Component A consists of the following components in parts by weight:

[0261] 35 parts of composite functional pigments and fillers

[0262] 42 parts of waterborne polyurethane resin

[0263] 14 parts water

[0264] 6 parts of film-forming aid

[0265] 2.5 parts dispersant

[0266] 2.5 parts antifreeze

[0267] 0.6 parts anti-settling agent

[0268] 0.4 parts of bactericide

[0269] pH adjuster 0.5 parts

[0270] 0.8 parts defoamer

[0271] 1.5 parts wetting agent

[0272] 1.2 parts leveling agent

[0273] 1 part rheology modifier

[0274] Component B is a polyisocyanate curing agent.

[0275] The proportion of the polyisocyanate curing agent and the types of additives used are the same as in Example 1.

[0276] The composite functional pigments and fillers are prepared by the following method:

[0277] Ten parts of α-alumina and five parts of hexagonal boron nitride were mixed, and a mixture of deionized water and ethanol (volume ratio 1:1) was added. The mixture was dispersed at 3500 rpm for 25 min and then ultrasonically dispersed at 200 W for 15 min. The above pigment and filler were then mixed with three parts of β-zirconium dioxide (100-200 nm) and three parts of magnesium calcium silicate (0.8-1.5 μm) and dispersed at 3000 rpm for 15 min to obtain a composite functional pigment and filler.

[0278] The preparation method of the radiation cooling coating described above includes the following process steps:

[0279] In a dispersion tank, add 42 parts by weight of waterborne polyurethane resin, 35 parts by weight of composite functional pigments and fillers, 14 parts by weight of water, and 2.5 parts by weight of BYK-194 dispersant. Disperse at 1000 rpm for 15 minutes. Then, add 6 parts by weight of dodecyl ester, 2.5 parts by weight of ethylene glycol, 0.6 parts by weight of organobentonite, and 0.5 parts by weight of N,N-dimethylethanolamine. Disperse at 1450 rpm for 45 minutes. Then, add 0.3 parts by weight of ACTICIDE BIT 20 bactericide, 0.8 parts by weight of TEGO Foamex 810 defoamer, 1.5 parts by weight of Surfynol 420 wetting agent, 1.2 parts by weight of BYK-361 leveling agent, and 1 part by weight of RHEOLATE® 299 rheology modifier at 1850 rpm. Disperse for 40 minutes. After passing the test, filter to obtain component A. During construction, mix component A and component B evenly in the specified proportions to obtain the radiant cooling coating.

[0280] Table 1 Main Technical Indicators of Radiation Cooling Coatings

[0281]

[0282]

[0283] Test results show that Examples 1-4 all yielded polyurethane composite powder-reinforced radiation cooling coatings with high radiation cooling performance, excellent mechanical properties, environmental stability, acid and alkali resistance, salt spray resistance, and high weather resistance.

[0284] To further clarify the beneficial effects of each material component on the coating, this invention discloses Comparative Examples 1-4, which are compared with the test results of Example 1.

[0285] First, the multi-level surface-modified functional powder of this invention adopts a "core-shell-porous network" composite structure. The core layer α-Al2O3+h-BN provides basic reflection and emission properties, while the shell layer rutile TiO2+ZnO+Sc-doped Ga2O3 synergistically enhances solar reflection and infrared emission properties. The porous network (SiO2 aerogel+PVDF+ceramic micropowder) further optimizes light scattering effects. Simultaneously, the introduction of the novel oxide Sc-doped Ga2O3 fills the gap in infrared emission performance of conventional pigments and fillers, achieving a synergistic cooling effect of "high reflection + high emission," which is unattainable with conventional pigments and fillers. Compared with existing conventional pigment and filler systems, the cooling efficiency is significantly improved. Furthermore, the core layer α-Al2O3 provides high hardness, while the shell layers TiO2, ZnO, and Sc-doped Ga2O3 enhance wear resistance. The porous network structure buffers external impacts, and grafting with a composite coupling agent improves compatibility with resins, preventing mechanical property degradation caused by pigment and filler agglomeration. Comparative Example 1 uses conventional radiation-cooling pigments and fillers (TiO2+ZnO+SiO2), which are unmodified and lack novel oxides. They can only achieve basic reflection functions and cannot balance reflection and emission performance. This belongs to the pigment and filler system of conventional particle-filled radiation-cooling coatings currently on the market, and has the shortcoming of single performance.

[0286] Secondly, this invention employs a blend of Bayhydrol® A 2470 waterborne polyurethane resin and DAOTAN® TW 1225 / 40WANEP waterborne polyurethane resin at a ratio of 1:1 to 3:1, a crucial blending scheme. Bayhydrol® A 2470 contains hydroxyl functional groups, exhibiting excellent film-forming properties, solvent resistance, and weather resistance, along with good pigment wettability, thus improving pigment and filler dispersion. DAOTAN® TW 1225 / 40WANEP possesses good shear stability and flexibility, enhancing the mechanical properties of the coating, while its aliphatic polyurethane structure provides some reflectivity. The blending of these two resins creates a synergistic effect in the molecular chains, not only improving film density but also allowing them to combine with the functional groups of multi-level surface-modified functional powders, reducing light absorption and synergistically enhancing radiative cooling performance. Furthermore, the blended resins have a stable pH value and are less prone to viscosity decay during storage, ensuring the stability of the coating performance. If the compounded waterborne polyurethane resin is replaced with conventional waterborne polyurethane resin (Comparative Example 2), problems such as a sharp decrease in coating cooling effect, adhesion, hardness, impact resistance, and abrasion resistance, as well as blistering and rusting due to water, salt spray, and acid / alkali resistance, insufficient UV aging resistance, and excessive coating porosity will occur. This is because conventional resins only have basic film-forming functions and lack radioactive cooling functional groups in their molecular chains, making it impossible to form a synergistic cooling effect with pigments and fillers. Furthermore, the coating density after film formation is insufficient (porosity 2.2%, compared to only 0.7%~0.9% in Examples 1-4), allowing some heat to be conducted through the pores, reducing cooling efficiency. The degree of cross-linking is low, and it is difficult to balance flexibility and hardness. Therefore, the cooling effect and protective performance of the resulting coating are reduced.

[0287] Furthermore, the curing agent compounding scheme of this invention has significant advantages. HT-100 and HT-200 are both hexamethylene diisocyanate-based polyisocyanates, which are colorless to slightly yellow transparent liquids at room temperature. They have good compatibility, and after compounding, the NCO group concentration can be adjusted to keep the NCO / OH ratio stable at 1.1:1~1.3:1, ensuring sufficient reaction with the compounded resin. The compounded curing agent can increase the crosslinking density of the coating, reduce porosity, avoid light scattering loss, and enhance the bonding force between the coating and pigments and fillers, ensuring long-term stable cooling performance. In addition, the compounded curing agent, the compounded resin, and the multi-level surface-modified functional powder form a synergistic system, further optimizing the surface smoothness of the coating and improving light reflection efficiency. If the compounded curing agent is replaced with a single curing agent (Comparative Example 3), problems such as decreased radiation cooling performance, adhesion, hardness, impact resistance, abrasion resistance, salt spray resistance, acid and alkali blistering resistance, and insufficient UV aging resistance will occur. This is because the NCO groups of the single curing agent are not evenly distributed, and the reaction with the hydroxyl groups of the compound resin is incomplete, resulting in a low crosslinking density of the coating (porosity 2.3%). Light is easily scattered and lost in the pores. At the same time, the weather resistance and water resistance of the cured coating are slightly insufficient, and long-term use will lead to a decline in cooling performance.

[0288] Finally, this invention, through a three-step composite modification method involving plasma activation, microwave-assisted hydrothermal coating, and supercritical CO2 grafting, not only solves the problem of pigment and filler agglomeration but also grafts functional groups onto their surfaces, improving compatibility with resins and curing agents. Simultaneously, the "core-shell-porous network" structure optimizes the light transmission path, and the novel oxide further enhances cooling performance. The synergistic effect of these three factors achieves a cooling effect far exceeding that of simply dispersed pigments and fillers. If the "core-shell-porous network" modification and the addition of the novel oxide are omitted (Comparative Example 4), pigment and filler agglomeration occurs, resulting in low light scattering efficiency. Furthermore, the lack of functional group modification on the surface prevents effective synergy with resins and curing agents, leading to a significant decrease in cooling performance. This, in turn, results in problems such as reduced cooling effect, decreased adhesion and hardness, significantly reduced impact resistance and abrasion resistance, severe blistering and rusting due to water / acid / alkali / salt spray, and poor weather resistance.

Claims

1. A composite powder-reinforced radiation cooling coating, characterized in that... This coating is composed of component A and component B in a mass ratio of 4:1 to 5:

1. Component A consists of the following ingredients by mass: Multi-level surface-modified functional powder 28–45 parts 35–50 parts of waterborne polyurethane resin 10–18 parts water 4–9 parts of film-forming aid Dispersant 1.5–3.5 parts Antifreeze 1.5–3.5 parts Anti-settling agent 0.3–1 part 0.2–0.6 parts of bactericide pH adjuster 0.2–0.8 parts Defoamer 0.5–1.2 parts Wetting agent 0.8–2.5 parts Leveling agent 0.8–1.8 parts 0.5–1.5 parts of rheology modifier Component B is a polyisocyanate curing agent.

2. The composite powder-reinforced radiation cooling coating according to claim 1, characterized in that... The multi-level surface-modified functional powder is prepared by the following method: (1) Core-layer plasma activation: Mix 8-12 parts of α-alumina and 4-6 parts of hexagonal boron nitride, add a mixture of deionized water and ethanol in a volume ratio of 1~3:1~3, disperse at high speed of 3000~4000 rpm for 20~30 min, and ultrasonically disperse at 180~220W for 10~20 min; place in a plasma treatment device for activation treatment, then filter and vacuum dry to obtain activated core-layer particles; The activation treatment of the plasma equipment is carried out in a mixed atmosphere of N2 with a partial pressure of 80~120 Pa and CO2 with a partial pressure of 80~120 Pa, at a radio frequency of 10~15MHz, a power of 250~350 W, and at 70~80℃ for 10~20 min. The conditions for vacuum drying are a temperature of 70~80℃ and vacuum drying for 1~1.5 h; (2) Microwave-assisted hydrothermal in-situ coating of the shell layer: The activated core layer particles are added to the composite modified solvent and stirred evenly. Then, 10-15 parts of rutile TiO2, 4-6 parts of zinc oxide, 2-3 parts of scandium-doped gallium oxide and 1-1.5 parts of surfactant are added and stirred at 800-1500 rpm for 10-15 min. The mixture is then transferred to a microwave-assisted hydrothermal reactor for reaction. After the reaction is completed, the mixture is cooled to room temperature, centrifuged, washed and vacuum dried to obtain the "core-shell" powder. The composite modified solvent is propylene glycol methyl ether, 1-ethyl-3-methylimidazolium acetate, and supercritical CO2 in a volume ratio of 1~3:1~3:1~3; The surfactant is SDBS and Capstone FS-50 in a mass ratio of 1 to 3:1; The reaction conditions are 400~500 W microwave power, 170~180℃ for 3~4 h; The vacuum drying temperature is 50~60℃, and the time is 1~2 hours; (3) Porous network supercritical CO2-assisted grafting modification: The "core-shell" powder was added to a supercritical reactor, along with 2-3 parts of silane coupling agent, 1-1.5 parts of titanate coupling agent NDZ-101, and 0.5-1 parts of aluminate coupling agent DL-411. Supercritical CO2 at 10-15 MPa and 40-45℃ was introduced and stirred at 400-500 rpm for 2-3 h. 6-9 parts of SiO2 aerogel, 2-3 parts of polyvinylidene chloride, and 2-3 parts of ceramic micro powder were added and the reaction continued for 1.5-2 h. The pressure was slowly released at a rate of 0.4-0.5 MPa / min, the sample was taken out, and freeze-dried at -50℃ to -40℃ and 5-10 Pa vacuum for 10-12 h to obtain the grafted modified powder. The silane coupling agent is KH-550 and FAS-17 in a mass ratio of 1~3:1~3; (4) Compound optimization: The above grafted modified powder is mixed with 2-4 parts of β-zirconia and 2-4 parts of magnesium calcium silicate, and dispersed at high speed of 2000~3000 rpm for 10~15 min to obtain multi-level surface modified functional powder; The particle size of β-zirconia is 100-200 nm, and the particle size of magnesium calcium silicate is 0.8-1.5 μm.

3. The multi-stage surface-modified functional powder according to claim 2, characterized in that... The scandium-doped gallium oxide was prepared by the following method: (1) Weigh gallium nitrate and scandium nitrate according to the molar fraction of Sc doping 2–5%, add deionized water to prepare a 0.3 mol / L mixed metal salt solution; add urea, stir until completely dissolved, adjust the pH of the solution to 9.0±0.2, and stir to form a uniform and transparent precursor solution; wherein, the total molar ratio of urea to metal ions is 2~4:1; (2) The precursor solution was transferred to a microwave hydrothermal reactor and kept at 170-180℃ for 3-4 hours for hydrothermal synthesis. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged and the precipitate was collected. After washing, it was vacuum dried at 50-60℃ and 5-10Pa for 1-2 hours to obtain the precursor powder. (3) Place the precursor powder in an alumina crucible and calcine it at 800-850°C for 2-3 hours in an air atmosphere. Then, cool it naturally to room temperature and grind it to obtain scandium-doped gallium oxide powder with a particle size of 200-500 nm.

4. The composite powder-reinforced radiation cooling coating according to claim 1, characterized in that... The waterborne polyurethane resin is a mixture of Covestro Bayhydrol® A 2470 waterborne polyurethane resin and Dataon® TW 1225 / 40 WANEP waterborne polyurethane resin, with a mass ratio of 1:1 to 3:1; the polyisocyanate curing agent is a mixture of Wanhua HT-100 curing agent and Wanhua HT-200 curing agent, with a mass ratio of 1:1 to 1.5:

1.

5. The composite powder-reinforced radiation cooling coating according to claim 1, characterized in that: The film-forming aid is one or more of propylene glycol methyl ether and dodecyl alcohol ester; The dispersant is a sodium polycarboxylate dispersant, preferably one or more of BYK-194, Evonik TEGO® Dispers 750W, and BYK-191; The antifreeze is ethylene glycol; The anti-settling agent is organic bentonite; The bactericide is an isothiazolinone bactericide, preferably one or more of Lanxess Parmetol A26 and Torr ActiveIDE B20; The pH adjuster is one or more of diethanolamine and N,N-dimethylethanolamine; The defoamer is an organosilicon defoamer, preferably one or more of Evonik TEGO Foamex 810, BYK-037, and BASF FoamStarSI 2240; The wetting agent is a polyether-modified polysiloxane wetting agent, preferably one or more of BYK-349, Air Products Surfynol 420, and Evonik TEGO Wet 270; The leveling agent is a polyether-modified silicone leveling agent, preferably one or more of DEUCHEM 432, BYK-361, and TEGO Glide440; The rheology modifier is a polyurethane associative rheology modifier, preferably one or more of Ashland ACRYSOL RM-8W and RHEOLATE® 299.

6. A method for preparing a composite powder-reinforced radiation-cooling coating according to any one of claims 1-5, characterized in that, The process includes the following steps: Add waterborne polyurethane resin, multi-stage surface-modified functional powder, water, and dispersant to a dispersion tank according to the specified weight ratio. Disperse at 950-1250 r / min for 15-20 minutes. Then, add film-forming aid, antifreeze, anti-settling agent, and pH adjuster in sequence. Disperse at 1400-1600 r / min for 40-50 minutes. Finally, add bactericide, defoamer, wetting agent, leveling agent, and rheology modifier at 1800-1900 r / min and disperse for 35-45 minutes. After passing the test, filter to obtain component A. During construction, components A and B are mixed evenly in a certain proportion to obtain a composite powder-reinforced radiation cooling coating.

Images