Self-cleaning composite coating, preparation method and construction method

Abstract

The invention discloses a self-cleaning composite coating, a preparation method and a construction method. The self-cleaning composite coating is prepared from the following raw materials in parts by weight: 20-50 parts of fluorosilicone modified epoxy-polyurethane resin; 2-10 parts by weight of a fluorinated graphene-ceramic composite filler; and 10-20 parts by weight of an alkali-resistant filler. The self-cleaning composite coating has excellent self-cleaning property, corrosion resistance and durability.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a self-cleaning composite coating, its preparation method, and its application method. Background Technology

[0002] Soils in Northwest China are rich in Na + Cl-, SO4 2 Corrosive ions, coupled with dry climate and strong ultraviolet radiation, often cause traditional coatings to exhibit the following problems in a short period of time: First, Cl- and SO42-... 2 - Corrosive ions penetrate the coating and reach the metal substrate, causing pitting and stress corrosion cracking; second, a high pH environment (pH>10) causes the hydrolysis of ester bonds in most organic resins (such as ordinary epoxy resin), resulting in coating powdering and loss of strength; third, the expansion stress generated by the crystallization and growth of salt in the coating pores can exceed 20 MPa, which is enough to cause the interfacial bonding of most coatings to fail; fourth, the repeated thermal expansion and contraction caused by the diurnal temperature difference in Northwest China causes shear stress at the interface between the coating and the substrate, ultimately leading to coating peeling.

[0003] CN111808513B discloses a weather-resistant protective coating and its application method. The protective coating comprises component A and component B, with a weight ratio of 100:10-25. Component A comprises the following raw materials in parts by weight: 30-50 parts of fluorosilicone-modified polyurethane resin, 0.1-1 parts of graphene, 0.1-1.5 parts of unsaturated polycarboxylic acid polymer, 0.1-1 parts of organosilicon defoamer, 0.1-1.5 parts of fluorocarbon polymer compound, 0.1-1 parts of polyether siloxane copolymer, 0.1-1 parts of anti-settling agent, and 0.1-0.5 parts of organotin drying agent. Component B comprises the following raw material in parts by weight: 40-60 parts of isocyanate curing agent. The fluorosilicone-modified polyurethane resin is obtained by grafting organosilicon with fluorinated polyurethane resin. Although this application can improve the weather resistance of the coating to some extent, further improvements are needed. Summary of the Invention

[0004] In view of the above, one object of the present invention is to provide a self-cleaning composite coating that exhibits excellent self-cleaning properties, corrosion resistance, and durability. Another object of the present invention is to provide a method for preparing the aforementioned self-cleaning composite coating. A further object of the present invention is to provide a method for applying the aforementioned self-cleaning composite coating.

[0005] The present invention achieves the above objectives using the following technical solutions.

[0006] On one hand, the present invention provides a self-cleaning composite coating, which is prepared from raw materials comprising the following components: 20-50 parts by weight of fluorosilicone modified epoxy-polyurethane resin, 2-10 parts by weight of fluorinated graphene-ceramic composite filler and 10-20 parts by weight of alkali-resistant filler.

[0007] The self-cleaning composite coating of the present invention can be prepared from a mixture comprising: fluorosilicone-modified epoxy-polyurethane resin, fluorinated graphene-ceramic composite filler, and alkali-resistant filler. The amount of fluorosilicone-modified epoxy-polyurethane resin can be 20-50 parts by weight, preferably 25-40 parts by weight, more preferably 30-35 parts by weight. The amount of fluorinated graphene-ceramic composite filler can be 2-10 parts by weight, preferably 3-8 parts by weight, more preferably 4-6 parts by weight. The amount of alkali-resistant filler can be 10-20 parts by weight, preferably 12-18 parts by weight, more preferably 14-16 parts by weight. The fluorosilicone-modified epoxy-polyurethane resin can be obtained by crosslinking a fluorinated polyurethane prepolymer with an epoxy resin. Preferably, an epoxy resin is used as a matrix, which undergoes a silanization reaction and fluorination chain extension to obtain a fluorinated polyurethane prepolymer. The fluorinated polyurethane prepolymer is then crosslinked with an epoxy resin to obtain the fluorosilicone-modified epoxy-polyurethane resin. The resulting resin is suitable for extreme environments and exhibits better tolerance, corrosion resistance, and self-cleaning properties. Fluorinated graphene-ceramic composite fillers are obtained by depositing graphene and fluorinating it with fluorinating agents using ceramic materials as a carrier. The resulting fluorinated graphene-ceramic composite material exhibits excellent self-cleaning properties, corrosion resistance, and mechanical durability. Alkali-resistant fillers ensure the system's self-healing and stability. The resulting coating possesses excellent self-cleaning properties, corrosion resistance, and durability, making it well-suited to the environment of Northwest China.

[0008] According to the self-cleaning composite coating of the present invention, preferably, the raw materials of the fluorosilicone modified epoxy-polyurethane resin include: 30-70 parts by weight of epoxy resin, 2-10 parts by weight of silane coupling agent, 10-25 parts by weight of diisocyanate and 1-5 parts by weight of perfluoroalkyl alcohol.

[0009] In this invention, the epoxy resin can be selected from bisphenol-based epoxy resins, such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, and silicone-modified epoxy resin; preferably selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, and silicone-modified epoxy resin, more preferably bisphenol A type epoxy resin or silicone-modified epoxy resin. The epoxy resin can be 30-70 parts by weight, preferably 40-65 parts by weight, more preferably 45-60 parts by weight.

[0010] The silane coupling agent can be selected from one of aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and bisamino silane coupling agents, preferably one of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and bisamino silane coupling agents, more preferably one of aminopropyltriethoxysilane or bisamino silane coupling agents. The amount of silane coupling agent can be 2 to 10 parts by weight, preferably 3 to 8 parts by weight, more preferably 4 to 6 parts by weight.

[0011] The diisocyanate may be selected from hexamethylene diisocyanate, isoflurane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, phenylenediamine diisocyanate, and tetramethylisophthalimethylene diisocyanate. Preferably, it is selected from hexamethylene diisocyanate, isoflurane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and tetramethylisophthalimethylene diisocyanate; more preferably, it is selected from hexamethylene diisocyanate, isoflurane diisocyanate, and tetramethylisophthalimethylene diisocyanate. In a specific embodiment, the diisocyanate is isoflurane diisocyanate. The amount of diisocyanate used may be 10-25 parts by weight, preferably 12-20 parts by weight, and more preferably 14-18 parts by weight.

[0012] The perfluoroalkyl alcohol can be a C4-C10 perfluoroalkyl alcohol, preferably a C5-C8 perfluoroalkyl alcohol, and more preferably a C6-C8 perfluoroalkyl alcohol. According to a specific embodiment of the present invention, the perfluoroalkyl alcohol is perfluorooctanoic acid. The amount of perfluoroalkyl alcohol used can be 1 to 5 parts by weight, preferably 2 to 5 parts by weight, and more preferably 2.5 to 4 parts by weight.

[0013] In some embodiments, a catalyst may be added. The catalyst may be selected from one of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin oxide, and dimethyltin dimercaptoacetate, preferably one of dibutyltin dilaurate, dioctyltin dilaurate, and dimethyltin dimercaptoacetate, more preferably dibutyltin dilaurate or dimethyltin dimercaptoacetate. The mass of the catalyst may be 0.2 to 0.6 parts by weight, preferably 0.35 to 0.55 parts by weight, more preferably 0.4 to 0.5 parts by weight.

[0014] According to the self-cleaning composite coating of the present invention, preferably, the fluorosilicone modified epoxy-polyurethane resin is prepared by the following method: Epoxy resin and silane coupling agent are reacted under nitrogen protection and stirred at 60-100°C for 1-4 hours; then diisocyanate and perfluoroalkyl alcohol are added and reacted at 40-80°C for 2-5 hours to form fluorinated polyurethane prepolymer; epoxy resin is then added under the condition of a catalyst and the reaction is continued at 60-90°C to obtain fluorosilicone modified epoxy-polyurethane resin.

[0015] In this invention, since the epoxy resin is added in stages and in different amounts, they are described separately and referred to as epoxy resin A and epoxy resin B, respectively. This invention has found that staged epoxy resin reaction is more conducive to the reaction and allows for better utilization of the epoxy resin's properties. The amount of epoxy resin A can be 20-50 parts by weight, preferably 25-45 parts by weight, more preferably 30-40 parts by weight. The amount of catalyst can be 0.2-0.6 parts by weight, preferably 0.35-0.55 parts by weight, more preferably 0.4-0.5 parts by weight. The amount of epoxy resin B can be 10-25 parts by weight, preferably 13-20 parts by weight, more preferably 15-18 parts by weight. The reaction is carried out in stages, which are described below for better explanation: First paragraph: Epoxy resin A reacts with silane coupling agent to obtain the first reaction product; the reaction temperature is recorded as the first reaction temperature, and the reaction time is recorded as the first reaction time.

[0016] Second section: Diisocyanate and perfluoroalkyl alcohol are added to the product of the first reaction and reacted to obtain fluorinated polyurethane prepolymer; wherein, the reaction temperature is recorded as the second reaction temperature and the reaction time is recorded as the second reaction time; The third step: A catalyst and epoxy resin B are added to the fluorinated polyurethane prepolymer to continue the reaction, resulting in fluorosilicone modified epoxy-polyurethane resin; the reaction temperature is referred to as the third reaction temperature. The first reaction temperature can be 70–100°C, preferably 75–90°C, and more preferably 80–85°C. The first reaction time is 1–4 hours, preferably 1.5–3.5 hours, and more preferably 2–3 hours. The second reaction temperature can be 40–80°C, preferably 50–75°C, and more preferably 55–70°C. The second reaction time can be 2–5 hours, preferably 2.5–4 hours, and more preferably 3–3.5 hours. The third reaction temperature can be 60–90°C, preferably 65–80°C, and more preferably 70–75°C.

[0017] The quality of the above components and the reaction conditions are more conducive to the formation of fluorosilicone modified epoxy-polyurethane resin with better high temperature resistance, corrosion resistance, UV resistance, and salt spray resistance.

[0018] According to the self-cleaning composite coating of the present invention, preferably, the fluorinated graphene-ceramic composite filler is prepared by the following method: Ceramic fillers with a particle size of 20–30 μm are etched to form a nanopore array with a diameter of 200–300 nm and a depth of 1–2 μm on the surface of the ceramic fillers. The etched ceramic fillers are then deposited to grow vertically oriented graphene sheets within the nanopores. The graphene sheets are fluorinated with perfluoroiodoalkanes with carbon atoms of C4–C9, and then reacted under ultraviolet light for 4–10 h. After washing and drying, fluorinated graphene-ceramic composite fillers are obtained.

[0019] In this invention, graphene sheets are fluorinated with perfluoroiodoalkanes with carbon atoms ranging from C4 to C9, preferably with perfluoroiodoalkanes with carbon atoms ranging from C5 to C8, and more preferably with perfluoroiodoalkanes with carbon atoms ranging from C7 to C8. A free radical reaction is initiated under ultraviolet light to obtain a superhydrophobic surface with a static contact angle of over 150°. The vertical graphene sheets within the nanopores and the fluorocarbon chains on the surface can form a "nanobrush" structure, reducing the water droplet roll-off angle to below 5° and decreasing salt crystal adhesion by 90%. The ceramic carrier protects the graphene from wear, improving the mechanical durability of the composite material.

[0020] In this invention, deposition is performed using the following steps: etched ceramic particles are loaded into a chemical vapor deposition (PECVD) reaction chamber, a mixture of ammonia and methane gas is introduced, and deposition is carried out at 700–1000°C for 20–60 min. Vertical graphene nanosheets can be grown using PECVD, with a deposition temperature of 700–1000°C, preferably 750–900°C, and more preferably 800–850°C. The deposition time can be 20–60 min, preferably 25–50 min, and more preferably 30–40 min.

[0021] In this invention, nitrogen atoms (N / C atomic ratio of 0.1 to 0.15) are incorporated during the deposition process to form nitrogen-doped graphene sheets. The N / C atomic ratio can be 0.1 to 0.15, preferably 0.11 to 0.13, which can improve the conductivity of graphene and enhance the corrosion protection efficiency of the composite coating.

[0022] In the self-cleaning composite coating of the present invention, preferably, the ceramic filler is selected from one of silicon carbide, silicon nitride, boron nitride, and zirconium boride.

[0023] In this invention, the ceramic filler in the fluorinated graphene-ceramic filler can be one of silicon carbide, silicon nitride, boron nitride, and zirconium boride; preferably one of silicon carbide, silicon nitride, and boron nitride; more preferably silicon carbide or silicon nitride.

[0024] In the self-cleaning composite coating of the present invention, preferably, the alkali-resistant filler is selected from at least one of hollow glass microspheres, nano-cerium oxide, nano-zirconia, and silane-modified cellulose nanocrystals.

[0025] In this invention, the alkali-resistant filler can be selected from at least one of hollow glass microspheres, nano-cerium oxide, nano-zirconia, and silane-modified cellulose nanocrystals; preferably selected from at least one of hollow glass microspheres, nano-cerium oxide, and nano-zirconia; more preferably selected from at least one of hollow glass microspheres and nano-cerium oxide. According to a specific embodiment of the invention, the alkali-resistant filler is selected from hollow glass microspheres and nano-cerium oxide. Hollow glass microspheres can be used to achieve self-repair when the pH of the coating increases due to damage; nano-cerium oxide can convert ultraviolet light into harmless heat energy, and can also form insoluble complexes with alkaline earth metal ions such as calcium and magnesium ions, thus blocking the alkaline corrosion chain reaction.

[0026] The self-cleaning composite coating according to the present invention preferably further includes an additive; the additive is selected from at least one of nano-titanium dioxide, PNIPAM hydrogel, elastic buffer layer, and rheology control agent.

[0027] In this invention, additives may also be included. These additives are mainly used to improve the self-cleaning function of the coating and promote the automatic removal of salt and alkali. The additives may be selected from at least one of nano-titanium dioxide, PNIPAM hydrogel, elastic buffer layer, and rheology control agent; preferably, at least two of these; and more preferably, at least three. According to a specific embodiment of the invention, the additives are nano-titanium dioxide, PNIPAM hydrogel, and rheology control agent. Nano-titanium dioxide can generate electron-hole pairs under visible light, decompose organic pollutants, and reduce the chemical bonding between salt crystals and the substrate; PNIPAM hydrogel is temperature-responsive, shrinking when the temperature exceeds a certain level and recovering when the temperature decreases, and can also cause fatigue peeling at the interface between salt crystals and the coating; the rheology control agent can adjust the rheological properties of the coating, optimizing its processing and performance by changing the material's viscosity, thixotropy, and shear response, for example, it can reduce the coating viscosity at a shear rate of 100 s⁻¹. -1 It reaches 5000-6000 mPa·s and recovers rapidly upon standing (thixotropic index > 3.5), ensuring the stability of the curing process.

[0028] On the other hand, the present invention also provides a method for preparing the self-cleaning composite coating as described above, comprising the following steps: The fluorinated graphene-ceramic composite filler and the alkali-resistant filler are mixed to form a first mixture; then the first mixture is added to the fluorosilicone modified epoxy-polyurethane resin and dispersed; then additives are added and mixed to obtain a second mixture; finally, the second mixture is sealed and aged to obtain a self-cleaning composite coating.

[0029] According to the preparation method of the present invention, preferably: (A) During the formation of the first mixture, the mixing speed is 50-100 rpm and the mixing time is 15-60 min; (B) During the dispersion of the first mixture into the fluorosilicone modified epoxy-polyurethane resin, the dispersion temperature is 30-60℃ and the dispersion time is 30-60 min. (C) During the process of obtaining the second mixture, the stirring speed is 300-600 rpm and the stirring time is 10-40 min.

[0030] In this invention, a mixer can be used for premixing during the formation of the first mixture. The speed can be 50-100 rpm, preferably 55-80 rpm, more preferably 60-70 rpm, and the mixing time can be 15-60 min, preferably 20-50 min, more preferably 25-40 min. This premixing can make the components more uniform.

[0031] During the dispersion process of the first mixture in the fluorosilicone-modified epoxy-polyurethane resin, the rotation speed can be 1500–3000 rpm, preferably 1800–2500 rpm, more preferably 2000–2200 rpm. The dispersion temperature can be 30–60°C, preferably 35–50°C, more preferably 40–45°C. The dispersion time can be 30–60 min, preferably 35–55 min, more preferably 40–50 min. The degree of dispersion can be 90% or more, preferably 93% or more, more preferably 95% or more.

[0032] During the process of obtaining the second mixture, the stirring speed can be 300-600 rpm, preferably 350-550 rpm, and more preferably 400-500 rpm. The stirring time can be 10-40 min, preferably 15-35 min, and more preferably 20-30 min.

[0033] The aging time can be 20 to 30 hours, preferably 22 to 28 hours, and more preferably 24 to 26 hours.

[0034] By controlling the mixing and dispersion parameters at each stage, the self-cleaning, corrosion-resistant, and durable properties of the coating can be guaranteed.

[0035] Furthermore, the present invention also provides a method for applying a self-cleaning composite coating, comprising the following steps: Clean the surface of the substrate and spray the self-cleaning composite coating evenly onto the substrate; cure for 20-30 hours at 15-35℃ and 50-65% relative humidity to complete the initial curing; then keep at an ambient temperature of 15-35℃ for 5-10 days to complete the curing; after complete curing, expose to natural light for 40-60 hours.

[0036] The surface of the substrate needs to be clean, free of oil, dirt and skin. Different cleaning methods are used for different substrates. In this invention, metal substrates or concrete substrates can be selected, with concrete substrates being preferred.

[0037] During the initial curing process: the ambient temperature can be 15–35°C, preferably 20–30°C, more preferably 23–27°C. The relative humidity can be 50–65%, preferably 55–65%, more preferably 58–62%. The curing time can be 20–30 hours, preferably 22–27 hours, more preferably 23–25 hours.

[0038] During the complete curing process: the ambient temperature can be 15–35℃, preferably 20–30℃. During this period, a water contact angle test can be performed (the contact angle should be greater than 150°). If the standard is not met, a fluorosilicone curing agent can be sprayed on. The curing time can be 5–10 days, preferably 6–9 days, and more preferably 7–8 days.

[0039] During the performance activation process after complete curing: the light exposure time can be 40-60 hours, preferably 45-55 hours, and more preferably 48-52 hours.

[0040] The curing process has a significant impact on the performance of coatings. Curing under the above conditions can better ensure the self-cleaning properties, corrosion resistance, and durability of the coatings.

[0041] Compared with the prior art, the self-cleaning composite coating of the present invention has the following advantages: (1) The present invention uses fluorosilicone modified epoxy-polyurethane resin as a low surface energy substrate and adds fluorinated graphene-silicon carbide composite filler. The vertical graphene sheets in the nanopores and the fluorocarbon chains on the surface can form a "nano brush" structure, which enhances the self-cleaning property. The resulting self-cleaning composite coating has a static water contact angle greater than 160°, has superhydrophobicity, and excellent self-cleaning performance.

[0042] (2) The fluorosilicone modified epoxy-polyurethane resin of the present invention, through silanization reaction and fluorination chain extension, introduces silicon-oxygen bonds and carbon-fluorine bonds into the resin molecular chain, which not only endow the coating with extremely low surface energy and form a hydrophobic barrier, but also, through the strong electronegativity of fluorine atoms, stabilizes the chemical bonds and resists the corrosion of salt and alkaline media. The fluorinated graphene-silicon carbide composite filler can neutralize the electrochemical corrosion current, enhance the interfacial bonding force with the resin, and improve the mechanical strength of the formed coating. Through the interaction of the components, the aging of the coating under high salt and alkali conditions and strong light exposure is effectively slowed down, and the coating peeling and failure caused by the accumulation and penetration of pollutants are also mitigated.

[0043] (3) The construction method of the present invention is simple and does not require frequent maintenance, thus reducing the total life cycle cost. Detailed Implementation

[0044] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available.

[0045] Preparation Example 1 35 parts by weight of bisphenol A type epoxy resin and 5 parts by weight of aminopropyltriethoxysilane were reacted under nitrogen protection at 80°C for 2 hours with stirring. Then, 0.3 parts by weight of zinc acetylacetone were added until the epoxy value dropped below 0.12. Next, 15 parts by weight of isophorone diisocyanate and 3 parts by weight of perfluorooctanol (molar ratio of isocyanate to hydroxyl groups (NCO / OH) was 1.2:1) were added, and the mixture was reacted at 60°C for 3 hours to form a fluorinated polyurethane prepolymer. Then, 0.5 parts by weight of dibutyltin dilaurate and 15 parts by weight of bisphenol A type epoxy resin were added, and the reaction was continued at 70°C until the NCO characteristic peak (2270 cm⁻¹) was reached. -1 The fluorine-silicone modified epoxy-polyurethane resin was obtained by completely removing the fluorine and adding acetone to adjust the viscosity to 2500±500mPa·s (25℃).

[0046] Preparation Example 2 Porous silicon carbide particles (20-30 μm in diameter) were placed in a focused ion beam (FIB) system, using Ga... + The ion source operates at an accelerating voltage of 30 kV and an acceleration rate of 2.5 A / cm. 2 Sputter etching at a specific beam current density forms a nanopore array with a diameter of 200–300 nm and a depth of 1–2 μm on the surface of silicon carbide particles (pore density approximately 10⁻⁶). 8 pcs / cm 2 The etched silicon carbide was placed into a chemical vapor deposition (PECVD) reaction chamber, and a mixture of ammonia (20 sccm) and methane (10 sccm) was introduced. The pressure was maintained at 50 Pa, and the radio frequency power (13.56 MHz) was set to 300 W. Deposition was carried out at 800 °C for 30 min. At the same time, nitrogen atoms were doped (the N / C atomic ratio in the system was 0.12) to grow vertically oriented nitrogen-doped graphene sheets in the nanopores. The nitrogen-doped graphene sheets were placed in a Teflon container, and perfluorooctyl iodide (10 mL / 100 g filler) was added. The reaction was carried out under 254 nm ultraviolet light for 6 h. Then, the mixture was washed three times with n-hexane and dried under vacuum at 80 °C to obtain fluorinated graphene-silicon carbide composite filler.

[0047] Preparation Example 3 25 parts by weight of bisphenol A type epoxy resin and 3 parts by weight of aminopropyltriethoxysilane were stirred and reacted at 80°C for 2 hours under nitrogen protection. Then, 0.3 parts by weight of zinc acetylacetonate were added until the epoxy value dropped below 0.12. Then, 13 parts by weight of isophorone diisocyanate and 2.4 parts by weight of perfluorooctyl alcohol were added, and the mixture was reacted at 60°C for 3 hours to form a fluorinated polyurethane prepolymer. Then, 0.1 parts by weight of dibutyltin dilaurate and 10 parts by weight of bisphenol A type epoxy resin were added, and the reaction was continued at 70°C to obtain fluorosilicone modified epoxy-polyurethane resin.

[0048] Example 1 Three parts by weight of the fluorinated graphene-silicon carbide filler obtained in Preparation Example 2, 10 parts by weight of hollow glass microspheres, and three parts by weight of nano-cerium oxide were premixed in a three-dimensional mixer at a speed of 60 rpm for 30 min to obtain the first mixture.

[0049] The first mixture was gradually added to 25 parts by weight of the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1, and dispersed at 40°C for 45 min (2000 rpm) using a high-speed disperser, while applying ultrasonic assistance (800 W power); then 5 parts by weight of HS-PNIPAM (Xi'an Qiyue Biotechnology Co., Ltd.), 2 parts by weight of nano titanium dioxide and 1 part by weight of rheology control agent (fumed silica) were added in sequence, and stirred at 30°C at a low speed of 500 rpm for 20 min to obtain the second mixture.

[0050] The second mixture was sealed and aged at 25°C for 24 hours to obtain the coating. The viscosity of the coating was controlled at 5500±500 mPa·s.

[0051] Example 2 Five parts by weight of the fluorinated graphene-silicon carbide filler obtained in Preparation Example 2, 15 parts by weight of hollow glass microspheres, and 5 parts by weight of nano-cerium oxide were premixed in a three-dimensional mixer at a speed of 60 rpm for 30 min to obtain the first mixture.

[0052] The first mixture was gradually added to 50 parts by weight of the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1, and dispersed at 40°C for 45 min (2000 rpm) using a high-speed disperser, while applying ultrasonic assistance (800 W power) to achieve a filler dispersion of over 95%. Then, 6 parts by weight of HS-PNIPAM (from the same source as in Example 1), 3 parts by weight of nano titanium dioxide and 1 part by weight of rheology control agent (fumed silica) were added sequentially, and stirred at 30°C at a low speed of 500 rpm for 20 min to obtain the second mixture.

[0053] The second mixture was sealed and aged at 25°C for 24 hours to obtain the coating. The viscosity of the coating was controlled at 5500±500 mPa·s.

[0054] Example 3 1.5 parts by weight of the fluorinated graphene-silicon carbide filler obtained in Preparation Example 2, 7 parts by weight of hollow glass microspheres and 3 parts by weight of nano-cerium oxide were premixed in a three-dimensional mixer at a speed of 60 rpm for 30 min to obtain the first mixture.

[0055] The first mixture was gradually added to 20 parts by weight of the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1, and dispersed at 40°C for 45 min (2000 rpm) using a high-speed disperser, while applying ultrasonic assistance (800 W power); then 2.5 parts by weight of HS-PNIPAM (from the same source as in Example 1), 1 part by weight of nano titanium dioxide and 0.5 parts by weight of rheology control agent (fumed silica) were added in sequence, and stirred at 500 rpm at 30°C for 20 min to obtain the second mixture.

[0056] The second mixture was sealed and aged at 25°C for 24 hours to obtain the coating. The viscosity of the coating was controlled at 5500±500 mPa·s.

[0057] Example 4 The only difference from Example 1 is that the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1 is replaced with the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 3.

[0058] Comparative Example 1 The only difference from Example 1 is that the fluorinated graphene-silicon carbide filler obtained in Preparation Example 2 is replaced with graphene.

[0059] Comparative Example 2 The only difference from Example 1 is that the fluorosilicone modified epoxy-polyurethane resin obtained in Example 1 is replaced with silicon carbide filler.

[0060] Comparative Example 3 The only difference from Example 1 is that the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1 is replaced with unfluorinated graphene-silicon carbide filler.

[0061] Comparative Example 4 The only difference from Example 1 is that the fluorosilicone modified epoxy-polyurethane resin obtained in Preparation Example 1 is replaced with the fluorosilicone resin HLR-Si (hydroxyl value 45 mg KOH / g, fluorine content 20%) described in Example 1 of CN111808513B.

[0062] Experimental Example 1 The coating obtained in Example 1 was uniformly sprayed onto a cleaned metal substrate and cured for 24 hours at 25°C and 60% relative humidity to complete the initial curing. Then, it was kept at an ambient temperature of 15-35°C for 7 days to achieve complete curing. After complete curing, it was exposed to natural light for 48 hours to obtain the coating.

[0063] Experimental Example 2 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Example 2.

[0064] Experimental Example 3 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Example 3.

[0065] Experiment Example 4 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Example 4.

[0066] Comparative Experiment Example 1 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Comparative Example 1.

[0067] Comparative Experiment Example 2 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Comparative Example 2.

[0068] Comparative Experiment Example 3 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Comparative Example 3.

[0069] Comparative Experiment Example 4 The difference from Experimental Example 1 is that the paint was replaced with the paint obtained in Comparative Example 4.

[0070] The performance of the coatings in Experimental Examples 1-4 and Comparative Examples 1-4 was tested using the following methods: 1. Static water contact angle: Tested according to the method of GB / T30447-2013.

[0071] 2. Adhesion: Tested according to GB / T 9286-2021, with a spacing of 1mm.

[0072] 3. Pencil hardness: Tested according to the method of GB / T 6739-2022.

[0073] 4. Water resistance: Immerse the coating in boiling water at 98℃ for 168 hours, remove it, wipe the oil clean with gauze, and observe the surface. If there is no peeling, wrinkling, bubbling, or discoloration, it is qualified.

[0074] 5. Oil resistance: Place the coating in 100 °C transformer oil for 24 h, take it out, wipe the oil clean with a gauze, and observe the surface. If there is no peeling, wrinkling, blistering, or color change, it is qualified.

[0075] 6. Acid resistance: Immerse it in 3% sulfuric acid solution for 120 h and then observe the surface. If there is no peeling, wrinkling, blistering, or color change, it is qualified.

[0076] 7. Alkaline resistance: Immerse it in 5% sodium hydroxide solution for 720 h and then observe the surface. If there is no peeling, wrinkling, blistering, or color change, it is qualified.

[0077] 8. Dielectric strength: Detect according to the method of GB / T1408.1 - 2016.

[0078] 9. Salt spray resistance: According to GB / T 1771 - 2007, for 600 h, the unilateral rust width of the scratch ≤ 2 mm, and there are no bubbles, no rust, and no peeling on the rest of the board surface 5 mm away from the scratch. It is qualified.

[0079] 10. Resistance to artificial aging: Detect according to the method of GB / T 1865 - 2009, and detect color difference ΔE, powdering grade, gloss, and phenomena such as peeling, wrinkling, blistering, and color change.

[0080] The test results are shown in Table 1.

[0081] Table 1 As can be seen from Table 1, compared with Comparative Experimental Examples 1 - 4, the coatings formed by applying the self - cleaning composite coatings of Experimental Examples 1 - 4 have high hardness, good mechanical strength, excellent corrosion resistance, salt spray resistance, and durability, and there are no peeling, wrinkling, blistering, or color change phenomena. At the same time, the static water contact angle of the coating > 160°, with excellent self - cleaning performance, good water resistance and oil resistance, and the adhesion between the coating and the substrate is relatively high, and it is not easy to cause peeling. It can be applied to the northwest region with dry climate, large temperature difference between day and night, high salinity, and strong ultraviolet rays.

[0082] The present invention is not limited to the above - mentioned embodiments. Without departing from the essence of the present invention, any deformation, improvement, or replacement that those skilled in the art can think of falls within the scope of the present invention.

Claims

1. A self-cleaning composite coating, characterized by, It is prepared from raw materials including the following components: fluorosilicon modified epoxy-polyurethane resin 20-50 parts by weight; fluorinated graphene-ceramic composite filler 2-10 parts by weight; and alkali-resistant filler 10-20 parts by weight.

2. The self-cleaning composite coating according to claim 1, characterized in that, The raw materials of the fluorosilicon modified epoxy-polyurethane resin include: 30-70 parts by weight of epoxy resin, 2-10 parts by weight of silane coupling agent, 10-25 parts by weight of diisocyanate and 1-5 parts by weight of perfluoroalkyl alcohol.

3. The self-cleaning composite coating according to claim 2, characterized in that, The fluorosilicon modified epoxy-polyurethane resin is prepared by the following method: The epoxy resin and the silane coupling agent are stirred and reacted under nitrogen protection at 60-100℃ for 1-4h; then the diisocyanate and the perfluoroalkyl alcohol are added and reacted at 40-80℃ for 2-5h to form a fluorinated polyurethane prepolymer; then the epoxy resin is added under the condition of a catalyst and the reaction is continued at 60-90℃ to obtain the fluorosilicon modified epoxy-polyurethane resin.

4. The self-cleaning composite coating according to claim 1, wherein, The fluorinated graphene-ceramic composite filler is prepared by the following method: The ceramic filler with a particle size of 20-30μm is etched to form a nanohole array with a diameter of 200-300nm and a depth of 1-2μm on the surface of the ceramic filler; the etched ceramic filler is deposited to grow vertically oriented graphene sheets in the nanoholes; the graphene sheets are fluorinated using perfluoroiodoalkane with carbon atoms C4-C9, and then are placed under ultraviolet light irradiation for 4-10h, washed and dried to obtain the fluorinated graphene-ceramic composite filler.

5. The self-cleaning composite coating according to claim 4, wherein, The ceramic filler is selected from one of silicon carbide, silicon nitride, boron nitride and zirconium boride.

6. The self-cleaning composite coating according to claim 1, wherein, The alkali-resistant filler is selected from at least one of hollow glass microbeads, nano cerium oxide, nano zirconium oxide and silane modified cellulose nanocrystals.

7. The self-cleaning composite coating according to claim 1, wherein, The auxiliary agent is selected from at least one of nano titanium dioxide, PNIPAM hydrogel, elastic buffer layer and rheological control agent.

8. A method of preparing a self-cleaning composite coating as claimed in claim 7, characterized in that, The method comprises the following steps: The fluorinated graphene-ceramic composite filler and the alkali-resistant filler are mixed to form a first mixture; then the first mixture is added to the fluorosilicon modified epoxy-polyurethane resin for dispersion; an auxiliary agent is added for mixing and stirring to obtain a second mixture; finally, the second mixture is sealed and aged to obtain the self-cleaning composite coating.

9. The preparation method according to claim 8, characterized in that: (A) during the formation of the first mixture, the mixing speed is 50-100 rpm and the mixing time is 15-60min; (B) during the dispersion of the first mixture into the fluorosilicon modified epoxy-polyurethane resin, the dispersion temperature is 30-60℃ and the dispersion time is 30-60min; (C) during the obtaining of the second mixture, the stirring speed is 300-600 rpm and the stirring time is 10-40min.

10. A method of applying a self-cleaning composite coating as claimed in any one of claims 1 to 7, characterised in that, The method comprises the following steps: The surface of the substrate is cleaned, and the self-cleaning composite coating is uniformly sprayed on the substrate; initial curing is completed at 15-35 ℃ and relative humidity of 50-65% for 20-30 h; complete curing is performed at ambient temperature of 15-35 ℃ for 5-10 days; and natural light illumination is performed for 40-60 h after complete curing.

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