An ultra-weather-resistant hydrophobic self-cleaning fluorocarbon powder coating and a preparation method thereof

Abstract

The application discloses a kind of super weathering hydrophobic self-cleaning fluorocarbon powder coating and preparation method thereof, belong to powder coating technical field.For solving the technical problem that photocatalyst destroys organic resin matrix, leading to poor durability of coating, the application provides a kind of powder coating, raw material includes: surface hydrophobic core-shell structure photocatalytic nanoparticle, hyperbranched fluorosilicon polymer containing reactive end group, fluorocarbon resin and curing agent.The nanoparticle is nanometer titanium dioxide as core, silica as shell, and the shell surface is grafted with fluorine-containing hydrophobic group.The application isolates the damage of titanium dioxide to resin by silica shell layer, and cooperates with two fluorine-containing components to construct a stable super-hydrophobic-photocatalytic dual-functional surface, and the obtained coating has high-efficiency dust removal, oil stain removal and super-long weather resistance.

Description

Technical Field

[0001] This invention belongs to the field of powder coating technology, specifically relating to an ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating and its preparation method. Background Technology

[0002] Fluorocarbon powder coatings are widely used in building curtain walls, transportation facilities, and other areas exposed to the outdoors for extended periods due to their excellent weather resistance and corrosion resistance. To reduce maintenance costs, the development of self-cleaning fluorocarbon coatings has become a hot topic in the industry.

[0003] Currently, there are two main technical approaches to achieving self-cleaning functionality: one is superhydrophobic self-cleaning, which mimics the lotus leaf effect, giving the coating surface an extremely high water contact angle and an extremely low roll-off angle, allowing rainwater to roll off as droplets, carrying away surface dust and other contaminants. This is typically achieved by adding low surface energy materials and constructing micro-nano rough structures in the coating. However, in existing technologies, simple physically blended nanoparticles (such as nano-SiO2) are prone to agglomeration, resulting in poor and unstable hydrophobic effects; simultaneously, the weak bonding between functional fillers and the resin matrix leads to poor durability of the hydrophobic function.

[0004] The second approach is photocatalytic self-cleaning, which utilizes the photocatalytic effect of semiconductor materials such as nano-titanium dioxide (TiO2) to generate reactive oxygen species under ultraviolet light irradiation. These reactive oxygen species decompose organic contaminants (such as oil stains and vehicle exhaust residue) on the coating surface into harmless small molecules, which are then washed away by rainwater. However, photocatalysis has a significant limitation when applied to organic coatings: the highly reactive free radicals generated, while decomposing pollutants, also indiscriminately attack the organic resin matrix of the coating itself, leading to powdering and cracking of the coating and significantly shortening its lifespan. Furthermore, TiO2 itself is hydrophilic, which contradicts the goal of achieving hydrophobic self-cleaning.

[0005] Therefore, how to combine the "active self-cleaning" ability of photocatalytic degradation of organic pollutants with the "passive self-cleaning" ability of superhydrophobic rolling dust removal, and solve the problem of photocatalyst damage to the resin matrix, so as to obtain a self-cleaning coating that can both decompose oil stains and be hydrophobic, is a very challenging and unresolved technical problem in this field. Summary of the Invention

[0006] This invention aims to address the limitations of existing technologies that rely solely on a single self-cleaning function (hydrophobic or photocatalytic), as well as the fundamental contradiction between photocatalytic materials and organic coating systems. This invention is dedicated to providing an ultra-weather-resistant, photophobic-photosensitive dual-effect self-cleaning fluorocarbon powder coating and its preparation method that organically combines photocatalytic active self-cleaning with superhydrophobic passive self-cleaning functions, while simultaneously ensuring ultra-long weather resistance and excellent appearance.

[0007] The objective of this invention can be achieved through the following technical solutions: A super weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating, wherein the raw material components of the powder coating include: film-forming resin, curing agent, surface-hydrophobic core-shell structured photocatalytic nanoparticles, and hyperbranched fluorosilicone polymer containing reactive end groups.

[0008] Furthermore, the surface-hydrophobic core-shell structured photocatalytic nanoparticles comprise a core-shell structure with nano-titanium dioxide as the core and silicon dioxide as the shell, and the surface of the core-shell structure is grafted with fluorinated hydrophobic groups via chemical bonds.

[0009] Furthermore, the fluorinated hydrophobic group is formed by the reaction of the fluorinated silane coupling agent with the hydroxyl groups on the surface of the silica shell.

[0010] Furthermore, the fluorinated silane coupling agent is 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0011] Furthermore, the film-forming resin is a combination of FEVE fluorocarbon resin and hydroxyl polyester resin, and the curing agent is a blocked isocyanate curing agent.

[0012] Furthermore, the ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating comprises, by weight, the following raw material components: FEVE fluorocarbon resin: 40-60 parts; Hydroxy-polymer polyester resin: 5-15 parts; Blocked isocyanate curing agent: 10-20 parts; Surface-hydrophobic core-shell structured photocatalytic nanoparticles: 1-5 parts; Hyperbranched fluorosilicone polymers containing reactive end groups: 1-5 parts; Titanium dioxide: 15-30 parts; Barium sulfate: 5.7-11.3 parts; Leveling agent: 0.5-1.5 parts; Benzoin: 0.2-0.8 parts.

[0013] Furthermore, the preparation method of the ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating includes the following steps: (1) Preparation of surface-hydrophobic core-shell structured photocatalytic nanoparticles; (2) The surface hydrophobic core-shell structure photocatalytic nanoparticles obtained in step (1) are weighed and premixed with FEVE fluorocarbon resin, hydroxyl polyester resin, blocked isocyanate curing agent, hyperbranched fluorosilicone polymer with reactive end groups, titanium dioxide, barium sulfate, leveling agent and benzoin in parts by weight to obtain a mixture. (3) The mixture from step (2) is melt-extruded, cooled and pressed into sheets, coarsely crushed and finely crushed and sieved to obtain the powder coating.

[0014] Furthermore, the method for preparing surface-hydrophobic core-shell structured photocatalytic nanoparticles in step (1) specifically includes: (a) Core-shell coating: Disperse nano-titanium dioxide powder in an alcohol-water mixed solvent, adjust the pH of the system to alkaline, and then add tetraethyl orthosilicate dropwise to carry out hydrolysis and condensation reaction, forming a silica shell layer on the surface of nano-titanium dioxide to obtain core-shell particles; (b) Surface hydrophobic modification: The core-shell particles obtained in step (a) are dispersed in a solvent, and a fluorinated silane coupling agent is added to carry out a grafting reaction to obtain the product; (c) The product of step (b) is centrifuged, washed, dried and depolymerized to obtain the surface hydrophobic core-shell structured photocatalytic nanoparticles.

[0015] Furthermore, in step (a) core-shell coating, the pH value of the reaction system is 10-11 and the reaction temperature is 40-50℃; in step (b) surface hydrophobic modification, the pH value of the reaction system is 9-10 and the reaction temperature is 70-80℃.

[0016] Furthermore, in the melt extrusion process of step (3), the temperature of the twin-screw extruder feed zone is set to 90-100℃, and the temperature of the melt blending zone is set to 110-120℃.

[0017] The beneficial effects of this invention are: This invention provides an ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating and its preparation method, aiming to solve the technical problems of single function, contradictory performance, and poor durability of existing self-cleaning coatings. Through formulation design and material modification, this invention efficiently combines photocatalytic active self-cleaning with superhydrophobic passive self-cleaning functions, and solves the problem of photocatalyst damage to the organic resin matrix, obtaining a product with excellent coating appearance, dual self-cleaning function, and ultra-long weather resistance. The beneficial effects of this invention are specifically analyzed as follows: 1. Achieving efficient synergy between "photocatalytic active self-cleaning" and "superhydrophobic passive self-cleaning" overcomes the functional limitations of existing technologies.

[0018] The core of this invention lies in the synergistic effect of "surface hydrophobic core-shell structured photocatalytic nanoparticles" and "hyperbranched fluorosilicone polymers containing reactive end groups".

[0019] (1) Example 2 is a preferred embodiment of the present invention. Its coating has a smooth and flat appearance, an initial water contact angle of 156.1°, and a roll-off angle as low as 4.5°, reaching the superhydrophobic level. In the self-cleaning test, it can "completely remove" simulated dust and "basically remove" simulated oil stains, showing excellent dual self-cleaning effect.

[0020] (2) Comparative Example 1 (without the two core additives) served as a blank control. Its contact angle was only 85.2° and its roll-off angle was greater than 90°. It had no self-cleaning ability against dust and oil stains, representing the performance level of ordinary fluorocarbon coatings.

[0021] (3) Although Comparative Example 6 (without modified nanoparticles) added hyperbranched fluorosilicone polymer, its contact angle was only 115.2° and its roll-off angle was as high as 32.5°, which is far from superhydrophobic and does not have the ability to remove oil stains by photocatalysis. This proves that "surface hydrophobic core-shell structure photocatalytic nanoparticles" are the core unit for constructing micro-nano rough structures and providing photocatalytic activity, which is a necessary prerequisite for achieving superhydrophobicity and photocatalytic self-cleaning.

[0022] (4) Although Comparative Example 5 (without hyperbranched fluorosilicone polymer) had a high initial contact angle (145.5°), its roll-off angle increased significantly to 10.8°, causing water droplets to not roll off easily, reducing the self-cleaning property of dust to "most of it is carried away", and the coating appearance showed "slight orange peel". This proves that "hyperbranched fluorosilicone polymer with reactive end groups" can not only provide low surface energy, but also synergistically construct a stable hydrophobic structure with nanoparticles, reduce the roll-off angle, and its reactive end groups are conducive to improving the leveling properties of the coating, ensuring excellent coating appearance.

[0023] In summary, only by combining these two key components can the superhydrophobic properties of "high contact angle and low roll-off angle" (passive self-cleaning) and the efficient photocatalytic degradation of oil stains (active self-cleaning) be synergistically achieved, as shown in Examples 1-3, while maintaining a smooth and even coating.

[0024] 2. Through the core-shell structure design, the problem of photocatalyst damage to organic resin is effectively solved, achieving ultra-long durability of the function.

[0025] This is an improvement in the technology of the present invention, which solves the defects of applying photocatalysis technology to organic coatings.

[0026] (1) After 1,000 hours of QUV accelerated aging, the surface condition of the coating in Example 2 was “intact”, and the water contact angle and roll-off angle remained at 151.2° and 6.8° respectively, with minimal performance degradation, demonstrating its excellent weather resistance and functional durability.

[0027] (2) Comparative Example 2 (using untreated nano TiO2) showed "severe powdering and cracking" of the coating after aging, and completely failed.

[0028] (3) Comparative Example 4 (using TiO2 without SiO2 shell, only hydrophobically modified) is the key comparison. Its initial hydrophobic performance is excellent (contact angle 149.1°, roll-off angle 8.2°), but after aging, it also shows "severe powdering and loss of gloss", the coating is destroyed, and the hydrophobic performance is also lost (roll-off angle > 90°).

[0029] The stark contrast between Example 2 and Comparative Examples 2 and 4 demonstrates that the SiO2 core-shell structure plays a crucial role in isolation and protection. This inert SiO2 shell physically isolates the highly catalytically active TiO2 core from the external fluorocarbon resin matrix, effectively preventing the attack of photogenerated highly reactive free radicals on the resin, while not affecting its catalytic degradation of contaminants on the coating surface. This is precisely the key technology enabling the present invention to achieve its function.

[0030] 3. The necessity of surface hydrophobic modification of core-shell particles was clarified, ensuring the realization of superhydrophobic function.

[0031] (1) Comparative Example 3 (using particles coated only with SiO2 but not modified hydrophobically) exhibited strong hydrophilicity (contact angle of only 40.2°) and had no hydrophobic self-cleaning ability.

[0032] (2) This contrasts sharply with the superhydrophobic properties (contact angle 156.1°) of Example 2, demonstrating that grafting fluorinated silane coupling agents onto the SiO2 shell surface to impart low surface energy to the nanoparticles is another necessary step to achieve superhydrophobic properties of the coating.

[0033] In summary, this invention organically combines three key technological innovations—core-shell coating, surface hydrophobic-photosensitive dual-effect modification, and hyperbranched polymer synergy—to address the inherent contradictions and limitations of existing technologies. It not only achieves a synergistic effect of "1+1>2" between superhydrophobicity and photocatalysis in self-cleaning functions, but also ensures an ultra-long service life and functional stability of the coating in harsh outdoor environments through the crucial SiO2 "firewall" technology, providing a solution for the field of high-performance self-cleaning coatings. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels or by existing known methods.

[0035] Example 1 A super weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating and its preparation method: 1. Preparation of surface-hydrophobic core-shell structured photocatalytic nanoparticles (modified product A1): (1) Core-shell coating (TiO2@SiO2): In a 1000 mL beaker, measure 800 parts by weight of a mixture of anhydrous ethanol and deionized water (volume ratio 4:1). Weigh 100 parts by weight of anatase nano-titanium dioxide powder and add it to the mixture. Place the beaker in an ultrasonic cleaner and ultrasonically disperse the powder for 30 minutes at 300 W and 40 kHz to form a homogeneous and stable suspension. Transfer the suspension to a 2000 mL glass reactor equipped with a multi-port stopper, thermometer, stirrer, and dropping funnel. Start mechanical stirring (300 rpm) and add ammonia water dropwise using a dropper, while monitoring the pH with a pH meter, until the pH of the system stabilizes at 10. Weigh 20 parts by weight of tetraethyl orthosilicate (TEOS) and add it to the dropping funnel. Place the reactor in a constant temperature water bath and heat it to 40 °C. Ethyl orthosilicate was added dropwise at a rate of 0.5 mL / min through a dropping funnel under vigorous stirring. After the addition was complete, the reaction was continued at 40 °C for 8 hours.

[0036] (2) Washing and drying: After the reaction was complete, heating and stirring were stopped. The reaction product was transferred to centrifuge tubes and centrifuged at 8000 rpm for 15 minutes using a high-speed centrifuge, discarding the supernatant. 500 parts by weight of anhydrous ethanol were added to the supernatant, and the mixture was ultrasonically dispersed for 10 minutes, followed by centrifugation. This washing process was repeated a total of 3 times. The washed solid product was placed in a vacuum drying oven and dried at 100°C and a vacuum of -0.09 MPa for 12 hours to obtain white powdery core-shell structured nanoparticles (TiO2@SiO2).

[0037] (3) Surface hydrophobic modification: Place 100 parts by weight of TiO2@SiO2 core-shell particles obtained in step (2) into a clean, dry glass reactor of 1000 mL, add 500 parts by weight of anhydrous ethanol, and ultrasonically disperse for 30 minutes to form a uniform suspension. Start mechanical stirring (300 rpm), weigh 5 parts by weight of fluorinated silane coupling agent (1H,1H,2H,2H-perfluorooctyltriethoxysilane), add it to a dropping funnel, and add it dropwise to the suspension.

[0038] (4) Grafting reaction and purification: After the addition was complete, ammonia water was added dropwise using a dropper to adjust the pH of the system to 9. The reaction vessel was placed in a constant-temperature oil bath and heated to 70°C, and the reaction was maintained at this temperature for 6 hours. After the reaction was completed, the product was centrifuged (8000 rpm, 15 minutes) and washed three times with anhydrous ethanol. The washed product was then dried in a vacuum drying oven at 80°C for 12 hours. Finally, the dried powder was depolymerized and pulverized using an air jet mill to obtain the final surface-hydrophobic core-shell structured photocatalytic nanoparticles, denoted as modified product A1.

[0039] 2. Preparation of powder coatings: Weigh each component precisely according to the following weight proportions: FEVE fluorocarbon resin: 40 parts; Hydroxy-coated polyester resin: 15 parts; Blocked isocyanate curing agent: 20 parts; Modified product A1: 1 part; Hyperbranched fluorosilicone polymer with reactive end groups: 1 part; Titanium dioxide: 30 parts; Barium sulfate: 11.3 parts; Leveling agent: 0.5 parts; Benzoin: 0.2 parts; Add all the above components into a high-speed mixer, set the speed to 1500 rpm, and premix for 5 minutes at room temperature to obtain a uniformly shaped mixture.

[0040] The premixed material is fed into a twin-screw melt extruder through a hopper. The temperature of the first zone (feeding zone) of the extruder is set to 90℃, the temperature of the second zone (melt blending zone) is set to 110℃, and the screw speed is set to 300 rpm for melt extrusion.

[0041] The molten material extruded from the die is pressed into thin sheets by a two-roller tablet press and then cooled to room temperature by forced air cooling via a conveyor belt.

[0042] The cooled flaky material is fed into a coarse crusher and crushed into particles with a size of 2-5mm.

[0043] Finally, the coarsely crushed material is ultra-finely crushed using an ACM (Air Classifying Mill) fine pulverizer and then sieved through a 140-mesh (106μm aperture) vibrating screen to collect the fine powder under the screen, thus obtaining the final powder coating of Example 1.

[0044] Example 2 A super weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating and its preparation method: 1. Preparation of surface-hydrophobic core-shell structured photocatalytic nanoparticles (modified product A2): (1) Core-shell coating (TiO2@SiO2): In a 2000 mL beaker, measure 900 parts by weight of a mixture of anhydrous ethanol and deionized water (volume ratio 4:1). Weigh 100 parts by weight of anatase nano-titanium dioxide powder and add it to the mixture. Place the beaker in an ultrasonic cleaner and ultrasonically disperse the powder for 30 minutes at 300 W and 40 kHz to form a homogeneous and stable suspension. Transfer the suspension to a 2000 mL glass reactor equipped with a multi-mouth stopper, thermometer, stirrer, and dropping funnel. Start mechanical stirring (400 rpm) and add ammonia water dropwise using a dropper, while monitoring the pH with a pH meter, until the pH of the system stabilizes at 10.5. Weigh 25 parts by weight of tetraethyl orthosilicate (TEOS) and add it to the dropping funnel. Place the reactor in a constant temperature water bath and heat it to 45°C. Ethyl orthosilicate was added dropwise at a rate of 0.5 mL / min through a dropping funnel under vigorous stirring. After the addition was complete, the reaction was continued at 45 °C for 9 hours.

[0045] (2) Washing and drying: After the reaction was complete, heating and stirring were stopped. The reaction product was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 15 minutes using a high-speed centrifuge, discarding the supernatant. 600 parts by weight of anhydrous ethanol were added to the supernatant, and the mixture was ultrasonically dispersed for 10 minutes, followed by centrifugation. This washing process was repeated a total of 4 times. The washed solid product was placed in a vacuum drying oven and dried at 100°C and a vacuum of -0.09 MPa for 12 hours to obtain white powdery core-shell structured nanoparticles (TiO2@SiO2).

[0046] (3) Surface hydrophobic modification: Place 100 parts by weight of TiO2@SiO2 core-shell particles obtained in step (2) into a clean, dry glass reactor of 2000 mL, add 600 parts by weight of anhydrous ethanol, and ultrasonically disperse for 30 minutes to form a uniform suspension. Start mechanical stirring (400 rpm), weigh 8 parts by weight of fluorinated silane coupling agent (1H,1H,2H,2H-perfluorooctyltriethoxysilane), add it to a dropping funnel, and add it dropwise to the suspension.

[0047] (4) Grafting reaction and purification: After the addition was complete, ammonia water was added dropwise using a dropper to adjust the pH of the system to 9.5. The reaction vessel was placed in a constant-temperature oil bath and heated to 75°C, and the reaction was maintained at this temperature for 7 hours. After the reaction was completed, the product was centrifuged (10,000 rpm, 15 minutes) and washed four times with anhydrous ethanol. The washed product was then dried in a vacuum drying oven at 80°C for 12 hours. Finally, the dried powder was depolymerized and pulverized using an air jet mill to obtain the final surface-hydrophobic core-shell structured photocatalytic nanoparticles, denoted as modified product A2.

[0048] 2. Preparation of powder coatings: Weigh each component precisely according to the following weight proportions: FEVE fluorocarbon resin: 50 parts; Hydroxy-coated polyester resin: 10 parts; Blocked isocyanate curing agent: 16 parts; Modified product A2: 3 parts; Hyperbranched fluorosilicone polymers with reactive end groups: 2 parts; Titanium dioxide: 20 parts; Barium sulfate: 8 parts; Leveling agent: 1.0 part; Benzoin: 0.5 parts; Add all the above components into a high-speed mixer, set the speed to 1500 rpm, and premix for 8 minutes at room temperature to obtain a uniformly shaped mixture.

[0049] The premixed material is fed into a twin-screw melt extruder through a hopper. The temperature of the first zone (feeding zone) of the extruder is set to 95℃, the temperature of the second zone (melt blending zone) is set to 115℃, and the screw speed is set to 350 rpm for melt extrusion.

[0050] The molten material extruded from the die is pressed into thin sheets by a two-roller tablet press and then cooled to room temperature by forced air cooling via a conveyor belt.

[0051] The cooled flaky material is fed into a coarse crusher and crushed into particles with a size of 2-5mm.

[0052] Finally, the coarsely crushed material is ultra-finely crushed using an ACM (Air Classifying Mill) fine pulverizer and then sieved through a 140-mesh (106μm aperture) vibrating screen to collect the fine powder under the screen, thus obtaining the final powder coating product of Example 2.

[0053] Example 3 A super weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating and its preparation method: 1. Preparation of surface-hydrophobic core-shell structured photocatalytic nanoparticles (modified product A3): (1) Core-shell coating (TiO2@SiO2): In a 2000 mL beaker, measure 1000 parts by weight of a mixture of anhydrous ethanol and deionized water (volume ratio 4:1). Weigh 100 parts by weight of anatase nano-titanium dioxide powder and add it to the mixture. Place the beaker in an ultrasonic cleaner and ultrasonically disperse the powder for 30 minutes at 300 W and 40 kHz to form a homogeneous and stable suspension. Transfer the suspension to a 3000 mL glass reactor equipped with a multi-port stopper, thermometer, stirrer, and dropping funnel. Start mechanical stirring (500 rpm) and add ammonia water dropwise using a dropper, while monitoring the pH with a pH meter, until the pH of the system stabilizes at 11. Weigh 30 parts by weight of tetraethyl orthosilicate (TEOS) and add it to the dropping funnel. Place the reactor in a constant temperature water bath and heat it to 50 °C. Ethyl orthosilicate was added dropwise at a rate of 0.5 mL / min through a dropping funnel under vigorous stirring. After the addition was complete, the reaction was continued at 50 °C for 10 hours.

[0054] (2) Washing and drying: After the reaction was complete, heating and stirring were stopped. The reaction product was transferred to centrifuge tubes and centrifuged at 12,000 rpm for 15 minutes using a high-speed centrifuge, discarding the supernatant. 800 parts by weight of anhydrous ethanol were added to the supernatant, and the mixture was ultrasonically dispersed for 10 minutes, followed by centrifugation. This washing process was repeated a total of 5 times. The washed solid product was placed in a vacuum drying oven and dried at 100°C and a vacuum of -0.09 MPa for 12 hours to obtain white powdery core-shell structured nanoparticles (TiO2@SiO2).

[0055] (3) Surface hydrophobic modification: Place 100 parts by weight of TiO2@SiO2 core-shell particles obtained in step (2) into a clean, dry glass reactor of 2000 mL, add 800 parts by weight of anhydrous ethanol, and ultrasonically disperse for 30 minutes to form a uniform suspension. Start mechanical stirring (500 rpm), weigh 10 parts by weight of fluorinated silane coupling agent (1H,1H,2H,2H-perfluorooctyltriethoxysilane), add it to a dropping funnel, and add it dropwise to the suspension.

[0056] (4) Grafting reaction and purification: After the addition was complete, ammonia water was added dropwise using a dropper to adjust the pH of the system to 10. The reaction vessel was placed in a constant-temperature oil bath and heated to 80°C, and the reaction was maintained at this temperature for 8 hours. After the reaction was completed, the product was centrifuged (12000 rpm, 15 minutes) and washed five times with anhydrous ethanol. The washed product was then dried in a vacuum drying oven at 80°C for 12 hours. Finally, the dried powder was depolymerized and pulverized using an air jet mill to obtain the final surface-hydrophobic core-shell structured photocatalytic nanoparticles, denoted as modified product A3.

[0057] 2. Preparation of powder coatings: Weigh each component precisely according to the following weight proportions: FEVE fluorocarbon resin: 60 parts; Hydroxy-coated polyester resin: 5 parts; Blocked isocyanate curing agent: 10 parts; Modified product A3: 5 parts; Hyperbranched fluorosilicone polymers containing reactive end groups: 5 parts; Titanium dioxide: 15 parts; Barium sulfate: 5.7 parts; Leveling agent: 1.5 parts; Benzoin: 0.8 parts; Add all the above components into a high-speed mixer, set the speed to 1500 rpm, and premix for 10 minutes at room temperature to obtain a uniformly shaped mixture.

[0058] The premixed material is fed into a twin-screw melt extruder through a hopper. The temperature of the first zone (feeding zone) of the extruder is set to 100℃, the temperature of the second zone (melt blending zone) is set to 120℃, and the screw speed is set to 400 rpm for melt extrusion.

[0059] The molten material extruded from the die is pressed into thin sheets by a two-roller tablet press and then cooled to room temperature by forced air cooling via a conveyor belt.

[0060] The cooled flaky material is fed into a coarse crusher and crushed into particles with a size of 2-5mm.

[0061] Finally, the coarsely crushed material is ultra-finely crushed using an ACM (Air Classifying Mill) fine pulverizer and then sieved through a 140-mesh (106μm aperture) vibrating screen to collect the fine powder under the screen, thus obtaining the final powder coating product of Example 3.

[0062] Comparative Example 1 Comparative Example 1 served as the control group for Example 2. The difference between Comparative Example 1 and Example 2 was the absence of "modified product A2" and "hyperbranched fluorosilicone polymer with reactive end groups." To maintain a total weight of 100 parts, the missing 5 parts were supplemented with inert filler barium sulfate (i.e., the amount of barium sulfate used was 8 + 5 = 13 parts). The remaining raw materials, amounts, and preparation steps remained consistent with Example 2, ultimately yielding the finished powder coating.

[0063] Comparative Example 2 Comparative Example 2 is the control group of Example 2. The difference between Example 2 and Example 2 is that 3 parts of untreated ordinary anatase nano titanium dioxide were used to replace "modified product A2". The other raw materials, raw material amounts and preparation steps were kept the same as in Example 2, and the final product powder coating was obtained.

[0064] Comparative Example 3 Comparative Example 3 is the control group of Example 2. The difference between Example 2 and Example 3 is that 3 parts of nanoparticles that have only undergone core-shell coating (TiO2@SiO2) but have not undergone hydrophobic modification with fluorinated silane are used to replace "modified product A2". The other raw materials, raw material amounts and preparation steps are kept consistent with those in Example 2, and the final product powder coating is obtained.

[0065] Comparative Example 4 Comparative Example 4 served as the control group for Example 2. The difference between Example 2 and Example 4 was that 3 parts of nano-titanium dioxide, which was directly modified with fluorinated silane but without a SiO2 shell, were used to replace "modified product A2". The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 2, and the final powder coating was obtained.

[0066] Comparative Example 5 Comparative Example 5 served as the control group for Example 2. The difference between Example 2 and Example 5 was that "hyperbranched fluorosilicone polymers with reactive end groups" were not added. To ensure that the total weight remained unchanged at 100 parts, the missing 2 parts were made up by inert filler barium sulfate (i.e., the amount of barium sulfate used was 8+2=10 parts). The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 2, and the final product powder coating was obtained.

[0067] Comparative Example 6 Comparative Example 6 served as the control group for Example 2. The difference between Comparative Example 6 and Example 2 was that "modified product A2" was not added. To ensure that the total weight remained unchanged at 100 parts, the missing 3 parts were made up by inert filler barium sulfate (i.e., the amount of barium sulfate used was 8+3=11 parts). The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 2, and the final product powder coating was obtained.

[0068] Test Example 1 The powder coatings prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The test process is as follows, and the test results are shown in Table 1: 1. Sample preparation: Nine powder coatings from Examples 1-3 and Comparative Examples 1-6 were applied to chromated aluminum plates (100mm × 50mm × 1mm) using the same electrostatic spraying process. The dry film thickness of the coating was controlled at 70 ± 10 μm. All samples were then placed in an oven at 200°C for 15 minutes to cure, and after being removed and allowed to cool naturally at room temperature for 24 hours, performance tests were conducted.

[0069] 2. Testing methods and procedures: (1) Evaluation of coating appearance: Under natural light, at a distance of 30cm from the sample, observe the coating surface with the naked eye from the front and side to see if it is smooth and flat, and whether there are defects such as pinholes, graininess, orange peel. The evaluation is based on four levels: "smooth and flat, no defects", "slight orange peel", "obvious orange peel, with grains" and "severe orange peel, many grains".

[0070] (2) Water contact angle (WCA) and roll-off angle (SA) tests: The Shanghai Zhongchen JC2000D series contact angle measuring instrument was used.

[0071] A. Water Contact Angle: Under ambient temperature of 25℃ and relative humidity of 50%, the sample was placed horizontally on the test platform. A 5μL drop of deionized water was added to the coating surface using a micro-syringe. After the water droplet shape stabilized, the instrument software took a picture, and the static contact angle between the water droplet and the coating surface was automatically calculated using the tangent method. Five different locations were randomly selected for measurement on each sample, and the results were taken as the arithmetic mean.

[0072] B. Roll Angle: Fix the sample on the tiltable platform of the instrument and add a 10μL drop of deionized water. Slowly start tilting the platform at a constant angular velocity of 0.5° / s. Observe in real time through a camera and record the tilt angle of the platform when the water droplet just begins to roll continuously (rolling distance exceeds 20mm), which is the roll angle. Measure at 5 different locations randomly selected for each sample, and take the arithmetic mean of the results.

[0073] (3) Self-cleaning performance test of pollutants: A. Simulated Dust (Passive Self-Cleaning): Place the sample at a 15° angle. Take 1g of dry cement powder that has passed through a 400-mesh sieve and evenly sprinkle it onto the surface of the sample using a powder puff, ensuring complete coverage. Use a dropper to add deionized water to the top of the sample at a flow rate of 2mL / s to simulate rainwater washing. Observe how well the contaminants are carried away by the water flow. Evaluate the results using four levels: "After the water flow, the contaminants are completely carried away, and the surface is as clean as before," "Most of the contaminants are carried away, leaving a small trace," "A small amount is carried away, but a large amount remains," and "Almost no change."

[0074] B. Simulated Oil Stain (Active Self-Cleaning): Place a drop (0.05 mL) of commonly used cooking oil in the center of the sample and gently spread it with your finger to form a thin oil film with a diameter of 1 cm. Place the sample under a 30W ultraviolet lamp (main wavelength 365 nm), with the lamp tube 15 cm away from the sample surface, and irradiate continuously for 4 hours. After irradiation, remove the sample and rinse it with water as described above, observing the water wetting and residue in the oil-stained area.

[0075] (4) Tests on resistance to artificial accelerated aging and photocatalytic damage: Two samples from each group were placed in the QUV accelerated UV aging chamber. Following ASTM G154 standards, UVA-340 lamps were used, and the cyclic conditions were set as follows: UV irradiation (irradiance 0.89 W / m²@340nm, black panel temperature 60℃) for 8 hours, followed by dark condensation (black panel temperature 50℃) for 4 hours. The samples were then removed after 1000 hours of continuous aging.

[0076] A. Appearance evaluation after aging: After the sample is cooled to room temperature, carefully observe the coating surface with the naked eye and a 10x magnifying glass to check for phenomena such as powdering, cracking, blistering, and loss of gloss.

[0077] B. Performance evaluation after aging: The water contact angle (WCA) and roll-off angle (SA) of the aged sample were tested again.

[0078] Table 1 Test Results Analysis of the data in Table 1: 1. Verification of the synergistic effect of the present invention (Example 2 vs. Comparative Examples 1, 5, 6): (1) Example 2 demonstrates excellent overall performance: smooth and flat appearance, contact angle >150° and roll-off angle <5° (superhydrophobic), excellent self-cleaning effect against dust and oil, and extremely high performance retention rate after aging for 1000 hours.

[0079] (2) Comparative Example 1 (blank) was used as the baseline and had no self-cleaning effect.

[0080] (3) Although Comparative Example 5 (lacking hyperbranched polymer) had a higher contact angle, the roll-off angle was significantly increased (10.8°), failing to reach the level of easy roll-off, and the coating appearance deteriorated, proving that the synergistic effect of hyperbranched polymer in constructing hydrophobic structures and improving leveling properties is indispensable.

[0081] (4) Comparative Example 6 (lacking core particles) only exhibited limited hydrophobicity (contact angle 115.2°), far from being superhydrophobic, and did not have the ability to remove oil stains by photocatalysis, which proves the necessity of the core particles of the present invention as the building unit of the rough structure and the core of the photocatalytic function.

[0082] Conclusion: Combining "surface hydrophobic core-shell structured photocatalytic nanoparticles" with "hyperbranched fluorosilicone polymers with reactive end groups" is the only way to achieve a synergistic effect of "superhydrophobicity + photocatalysis + excellent appearance".

[0083] 2. Verification of the critical protective role of the core-shell structure (Example 2 vs. Comparative Examples 2 and 4): Comparative Example 2 (pure TiO2) and Comparative Example 4 (unshelled TiO2) performed poorly in the aging test. Although Comparative Example 4 had good initial hydrophobicity, both of them showed severe powdering and cracking after 1000 hours of QUV testing, and the coating was completely destroyed, and the hydrophobicity was lost.

[0084] Example 2 (TiO2 with shell) The coating remained intact and maintained excellent performance under the same aging conditions.

[0085] Conclusion: This set of comparisons proves that the SiO2 core-shell structure plays a crucial "firewall" role. Without sacrificing photocatalytic activity, it successfully inhibits the damage of TiO2 to organic resins, which is the core technology for achieving long-lasting functionality and is the improvement point of this invention.

[0086] 3. Verification of the necessity of surface hydrophobic modification (Example 2 vs. Comparative Example 3): The coating surface of Comparative Example 3 (coating only, without hydrophobicity) exhibits strong hydrophilicity (contact angle of only 40.2°) and lacks hydrophobic self-cleaning ability.

[0087] Conclusion: This demonstrates that surface hydrophobic modification of core-shell particles is a prerequisite for achieving superhydrophobicity. Without this step, even with a SiO2 shell and hyperbranched polymer, the objectives of this invention cannot be achieved.

[0088] In summary, through the comparative tests of the above embodiments and comparative examples, it can be concluded that the present invention solves the contradictions of the prior art by organically combining the three major improvement points of "core-shell structure", "surface hydrophobic modification" and "hyperbranched polymer" into a single technical solution, and through their synergistic effect, obtains a self-cleaning coating that combines superhydrophobicity, photocatalysis, ultra-long durability and excellent appearance.

[0089] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A super weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating, characterized in that, The raw material components of the powder coating include: film-forming resin, curing agent, surface-hydrophobic core-shell structured photocatalytic nanoparticles, and hyperbranched fluorosilicone polymer with reactive end groups.

2. The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 1, characterized in that, The aforementioned hydrophobic core-shell structure photocatalytic nanoparticles comprise a core-shell structure with nano-titanium dioxide as the core and silicon dioxide as the shell, and the surface of the core-shell structure is grafted with fluorinated hydrophobic groups via chemical bonds.

3. The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 2, characterized in that, The fluorinated hydrophobic groups are formed by the reaction of a fluorinated silane coupling agent with hydroxyl groups on the surface of the silica shell.

4. The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 3, characterized in that, The fluorinated silane coupling agent is 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

5. The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 1, characterized in that, The film-forming resin is a combination of FEVE fluorocarbon resin and hydroxyl polyester resin, and the curing agent is a blocked isocyanate curing agent.

6. The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 1, characterized in that, The ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating comprises, by weight, the following raw material components: FEVE fluorocarbon resin: 40-60 parts; Hydroxy-polymer polyester resin: 5-15 parts; Blocked isocyanate curing agent: 10-20 parts; Surface-hydrophobic core-shell structured photocatalytic nanoparticles: 1-5 parts; Hyperbranched fluorosilicone polymers containing reactive end groups: 1-5 parts; Titanium dioxide: 15-30 parts; Barium sulfate: 5.7-11.3 parts; Leveling agent: 0.5-1.5 parts; Benzoin: 0.2-0.8 parts.

7. A method for preparing an ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Preparation of surface-hydrophobic core-shell structured photocatalytic nanoparticles; (2) The surface hydrophobic core-shell structure photocatalytic nanoparticles obtained in step (1) are weighed and premixed with FEVE fluorocarbon resin, hydroxyl polyester resin, blocked isocyanate curing agent, hyperbranched fluorosilicone polymer with reactive end groups, titanium dioxide, barium sulfate, leveling agent and benzoin in parts by weight to obtain a mixture. (3) The mixture from step (2) is melt-extruded, cooled and pressed into sheets, coarsely crushed and finely crushed and sieved to obtain the powder coating.

8. The method for preparing an ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 7, characterized in that, The method for preparing surface-hydrophobic core-shell structured photocatalytic nanoparticles in step (1) specifically includes: (a) Core-shell coating: Disperse nano-titanium dioxide powder in an alcohol-water mixed solvent, adjust the pH of the system to alkaline, and then add tetraethyl orthosilicate dropwise to carry out hydrolysis and condensation reaction, forming a silica shell layer on the surface of nano-titanium dioxide to obtain core-shell particles; (b) Surface hydrophobic modification: The core-shell particles obtained in step (a) are dispersed in a solvent, and a fluorinated silane coupling agent is added to carry out a grafting reaction to obtain the product; (c) The product of step (b) is centrifuged, washed, dried and depolymerized to obtain the surface hydrophobic core-shell structured photocatalytic nanoparticles.

9. The preparation method of the ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 8, characterized in that, In step (a) core-shell coating, the pH of the reaction system is 10-11 and the reaction temperature is 40-50℃; in step (b) surface hydrophobic modification, the pH of the reaction system is 9-10 and the reaction temperature is 70-80℃.

10. The method for preparing an ultra-weather-resistant, hydrophobic, self-cleaning fluorocarbon powder coating according to claim 7, characterized in that, In step (3), the temperature of the feed zone of the twin-screw extruder is set to 90-100℃ and the temperature of the melt blending zone is set to 110-120℃.

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