A fluorine-free transparent self-cleaning solid lubricating coating and a method for preparing the same

Abstract

The present application relates to a kind of fluorine-free transparent self-cleaning solid lubricating coating and its preparation method, solid lubricating coating is formed by being coated on substrate by wax-based suspension and solidification, wax-based suspension is made by dispersing wax micro powder, hydrophobic adhesive and hydrophilic nanosilica in solvent, to provide roughness and hydrophobicity by wax micro powder, to increase coating hardness and certain water contact angle by hydrophilic nanosilica, so that coating has good optical transparency, excellent self-cleaning, hydrophobic, stability and durability, preferably transparency can reach 99%, after sandpaper abrasion, gauze abrasion, sand impact, water impact and acid rain impact, still can maintain the hydrophobic performance of coating, while preparation method is simple and environmental protection, fluorine-free no VOC emission, the addition amount of wax is not limited by preparation, can be flexibly adjusted, can be applied to solar panel, building exterior wall, automobile surface and multiple fields, preferably the power loss of photovoltaic panel after self-cleaning can reach ≤1%, with wide commercial application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating materials, and particularly relates to a fluorine-free transparent self-cleaning solid lubricating coating and a preparation method thereof. BACKGROUND

[0002] Solar photovoltaic power generation is well-known for its inexhaustible, continuous, low-carbon and high-efficiency advantages, and is expected to become a key part of building a new power system to achieve net zero emissions using renewable energy. However, in practical applications, solar photovoltaic panels are seriously polluted every year, especially in some areas where sandstorms are frequent and the wind is strong. Dust accumulation for a month can cause a 18.74% decrease in the efficiency of solar photovoltaic panels, seriously affecting the performance of photovoltaic modules, reducing the photoelectric conversion efficiency, and affecting the power generation benefit. Therefore, researchers are looking for a special functional surface with self-cleaning and high transparency to ensure the power generation capacity of solar photovoltaic panels, reduce the pollution of photovoltaic panels, and reduce maintenance costs.

[0003] In the prior art, researchers are inspired by the water-repellent properties of lotus leaves and design biomimetic functional surfaces, i.e. superhydrophobic surfaces, by imitating the microstructure of lotus leaves and using low-surface-energy materials. Such surfaces have advantages such as anti-pollution, anti-corrosion, anti-icing, anti-ultraviolet, antibacterial, and flame retardant. For example, patent CN118994688A discloses a preparation method of a superhydrophobic self-cleaning layer, a flexible protective assembly, and a preparation method thereof. The self-cleaning coating is designed using a micro-nano hierarchical structure combined with a fluorinated silane-perfluoropolyether mixture. However, on the one hand, the micro-nano structure required by superhydrophobic surfaces is contradictory to the light transmittance required by photovoltaic panels, limiting the application of superhydrophobic coatings on photovoltaic cells. Therefore, it is a problem to be solved to ensure high transparency while giving the surface anti-pollution properties. On the other hand, most superhydrophobic / hydrophobic coatings require the use of fluorine-containing substances to modify the coating in order to achieve hydrophobic lubrication properties, and a large amount of organic reagents are used in the preparation process, which not only increases the cost but also causes harm to the environment. Large amounts of VOC emissions are not conducive to large-scale industrial production. In order to meet the requirements of sustainable development, it is urgent to explore a more environmentally friendly preparation process without fluorine and VOC emissions to reduce the negative impact on the human body and the environment.

[0004] In order to improve the hydrophobicity of the coating surface, hydrophobic silicon dioxide is introduced on the surface of the coating in the prior art, for example: the patent CN118755322A discloses a SiO2 / PVDF hydrophobic self-cleaning coating solution, a preparation method and application thereof, and utilizes OTS to modify nano-SiO2 and introduces PVDF to prepare a PVDF@OTS-SiO2 coating suspension, and sprays to form a transparent hydrophobic coating. Although the hydrophobic silicon dioxide has good hydrophobic effect, silane or fluorinated agent is used to make the silicon dioxide have hydrophobic effect. On the one hand, the preparation process is relatively complex and cumbersome, and the production cost is relatively high. On the other hand, the silane and fluorinated agent will also cause harm to the environment, which will limit its commercial application. SUMMARY

[0005] The present application aims to at least solve one of the above technical problems to a certain extent, and provides a fluorine-free transparent self-cleaning solid lubricating coating and a preparation method thereof. The coating has good optical transparency, excellent self-cleaning, hydrophobicity, stability and durability. The preparation method is simple and environmentally friendly, and has no fluorine and VOC emissions, so it can be applied to solar panels, building exterior walls, automobile surfaces and other fields, and has wide commercial application prospects.

[0006] The technical scheme adopted by the present application to solve the technical problems is:

[0007] A fluorine-free transparent self-cleaning solid lubricating coating, the solid lubricating coating is formed by coating a wax-based suspension on a substrate and solidifying, the wax-based suspension is made by dispersing wax micro powder, hydrophobic adhesive and hydrophilic nano-silicon dioxide in a solvent.

[0008] The transparent self-cleaning lubrication mechanism of the above-mentioned solid lubricating coating includes:

[0009] The hydrophobic adhesive not only plays a role in bonding the substrate, but also provides the hydrophobicity of the coating, enhances the moisture resistance and stain resistance of the coating, the addition of the hydrophilic nano-silicon dioxide not only improves the hardness of the coating, but also enhances the structural stability of the coating through its strong inorganic material properties; in the initial state of the coating, the hydrophilic nano-silicon dioxide and the wax micro powder mainly in the form of micron-sized spherical balls are uniformly dispersed in the coating, without the need for modification of silane and fluorinated agent, a rough surface structure can be formed. This rough structure is covered by the hydrophobic adhesive, forming surface protrusions covered by the hydrophobic adhesive. These surface protrusions provide a relatively rough surface, and the surface energy of the initial coating does not decrease significantly.

[0010] As the coating is heated to the softening or melting temperature of the wax powder, the wax powder begins to soften or melt and spread on the surface, resulting in additional lubrication effect. At this time, the softening or melting of the microcrystalline wax not only fills the micro voids on the surface of the coating, but also reduces the local high surface energy area on the surface, thereby reducing the overall surface energy of the coating. At the same time, as the wax powder softens or melts, the surface roughness of the solid lubricating coating is further optimized, forming a smoother and more transparent coating structure, improving the overall hydrophobic lubrication properties. When the size of the dust, rainwater and other substances falling on the coating surface is much larger than the surface protrusions, they can form a spherical shape under the action of surface tension and slide out of the coating surface, thereby imparting the coating surface with anti-fouling properties and achieving transparent self-cleaning hydrophobic lubrication effect.

[0011] In a preferred embodiment, the particle size of the wax powder is 5-20 μm. The wax powder can be directly added to the solvent without heating and melting the wax, and can be uniformly dispersed by stirring at room temperature, which is beneficial to reducing energy consumption and further improving the simplicity of preparation.

[0012] The wax powder is used to provide a certain roughness and hydrophobicity to the coating. However, the wax powder is in the form of white powder. To further avoid excessive wax powder from affecting the optical transparency of the coating, in a preferred embodiment, the weight concentration of the wax powder in the solvent is 0.3wt%-2wt%, and can be further preferably 0.6wt%-1wt% in consideration of the hydrophobicity and transparency of the coating.

[0013] In a preferred embodiment, the hydrophobic adhesive is PDMS. Polydimethylsiloxane is a high molecular organic silicon compound that can provide a certain hydrophobicity and also act as an adhesive in the coating, so as to form a stable interfacial active system between the wax powder and the hydrophilic nano-silica. Moreover, PDMS itself has high transparency and will not affect the transparency of the coating.

[0014] To balance the hydrophobicity and adhesive effect of PDMS and further avoid excessive PDMS from affecting the smooth spraying, in a preferred embodiment, the weight concentration of the PDMS in the solvent is 5wt%-40wt%, and can be further preferably 20wt%-30wt% in consideration of the hydrophobicity and transparency of the coating.

[0015] To balance the effect of the hydrophilic nano-silica on increasing the hardness and water contact angle of the coating and further avoid excessive hydrophilic nano-silica from affecting the hydrophobicity and optical transparency of the coating, in a preferred embodiment, the weight concentration of the hydrophilic nano-silica in the solvent is 0.3wt%-1wt%, and can be further preferably 0.5wt%-0.7wt% in consideration of the hydrophobicity and transparency of the coating.

[0016] In a preferred embodiment, the hydrophilic nanosilica has a particle size of ≤20 nm, and further preferably 10-20 nm, for further controlling the cost of the material.

[0017] In a preferred embodiment, the solvent is ethyl acetate solution, which has good solubility for PDMS.

[0018] A preparation method of a fluorine-free transparent self-cleaning solid lubricating coating, which preparation method comprises:

[0019] Preparation of a wax-based suspension: take wax powder into a solvent, and then add a hydrophobic binder and hydrophilic nanosilica to uniformly disperse to prepare a wax-based suspension;

[0020] Preparation of a self-cleaning lubricating coating: spray the wax-based suspension on the surface of a substrate, and solidify to obtain a self-cleaning lubricating coating.

[0021] In the above preparation method, the wax powder is directly added into the solvent as an additive, which can avoid the step of heating and melting the wax, can be uniformly dispersed at room temperature, reduces energy consumption, and improves the operation simplicity. Meanwhile, the wax-based suspension is prepared by the hydrophobic binder and the hydrophilic nanosilica, which solves the dispersion problem of traditional wax particles in the solution, avoids the troubles of wax precipitation and spray gun blockage due to rapid temperature drop of the solution after spraying the melted wax, and thus ensures the smooth progress of the spraying process, so that the addition amount is no longer limited and can be flexibly adjusted, which is beneficial to improving the stability and operability of the preparation method.

[0022] In order to quickly obtain wax powder with uniform and small particle size, in a preferred embodiment, the preparation method comprises:

[0023] Preparation of wax powder: heat and dissolve the microcrystalline wax, and then spray it out through a spray gun to collect spherical wax powder.

[0024] In a preferred embodiment, the microcrystalline wax is dissolved by water bath heating during the preparation of the wax powder, which can improve the uniformity and stability of the dissolution.

[0025] In a preferred embodiment, magnetic stirring and ultrasonic dispersion are used during the preparation of the wax-based suspension, which can further improve the uniformity of the wax-based suspension and improve the processing efficiency.

[0026] In a preferred embodiment, the substrate surface is cleaned with anhydrous ethanol before spraying during the preparation of the self-cleaning lubricating coating, which can avoid the influence of stains on the preparation of the coating or the interference of the stains with the performance of the coating.

[0027] In a preferred embodiment, the wax-based suspension is sprayed at a distance of 10-15 cm from the substrate and perpendicular to the substrate at a gas pressure of 0.2-0.5 MPa during the preparation of the self-cleaning lubricating coating, which can form a uniform coating.

[0028] In a preferred embodiment, the self-cleaning lubricating coating is prepared by air blowing drying and curing at 60-80℃, which can improve the curing efficiency.

[0029] The application of the above-mentioned fluorine-free transparent self-cleaning solid lubricating coating includes using the solid lubricating coating on solar panels, building exterior walls, and automobile surfaces.

[0030] Compared with the prior art, the present application has at least the following beneficial effects:

[0031] (1) The solid lubricating coating of the present application provides a certain roughness and hydrophobicity with wax micropowder, enhances the hydrophobicity with a hydrophobic adhesive, acts as an adhesive, allows hydrophilic nanosilica to adhere to the surface of the wax micropowder, increases the hardness and certain water contact angle of the coating, and makes the coating have excellent hydrophobicity and stability. After sandpaper abrasion, gauze abrasion, sand impact, water impact, and acid water impact, the coating can still maintain hydrophobic properties. At the same time, the coating has good optical transparency, which can reach a transparency of >90%, preferably 99%, solving the problem of balancing high transparency and self-cleaning antifouling performance in the prior art.

[0032] (2) The solid lubricating coating of the present application does not need to be modified with silane and fluorinated agents, can be prepared using a fluorine-free method, has no VOC emissions, is simple and environmentally friendly to prepare, is conducive to reducing production costs, and has a wider commercial application prospect.

[0033] (3) The present application directly adds wax micropowder into the solvent, which can be uniformly dispersed at room temperature, thereby effectively reducing energy consumption and improving the simplicity of operation. At the same time, by preparing a wax-based suspension with a hydrophobic adhesive, hydrophilic nanosilica, and a solvent, the dispersion problem of traditional wax particles in the solution is solved, which can avoid the precipitation of wax and the blockage of the spray gun due to rapid temperature drop during spraying, further ensuring the smooth progress of the spraying process. At the same time, the amount of wax added is no longer limited and can be flexibly adjusted, further improving the stability and operability of the preparation method, which is conducive to expanding its application field.

[0034] (4) The solid lubricating coating of the present application applied on the surface of solar panels can effectively reduce the impact of pollution on the efficiency of solar panels, provide protection for photoelectric conversion, thereby improving the use efficiency of solar panels and prolonging their service life, reducing the power loss after self-cleaning after pollution, which can reach a loss of ≤13%, preferably ≤1%, and its excellent self-cleaning, hydrophobicity, and durability lay a foundation for wider commercial application, making it also applicable to building exterior walls, automobile surfaces, and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0036] Figure 1 is a SEM image of the wax micro powder obtained in step S1 of Example 1 of the present application;

[0037] Figure 2 is a water contact angle (WCA) image of the solid lubricating coating obtained in Example 8 of the present application;

[0038] Figure 3 is a transparency test result image of the solid lubricating coating obtained in Example 8 of the present application;

[0039] Figure 4 is a transparency test result image of the solid lubricating coating obtained in Example 8 of the present application under different wavelengths;

[0040] Figure 5 is a hydrophobicity data graph of the solid lubricating coating obtained in Example 8 of the present application after sandpaper abrasion;

[0041] Figure 6 is a hydrophobicity data graph of the solid lubricating coating obtained in Example 8 of the present application after gauze abrasion. DETAILED DESCRIPTION

[0042] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0043] In the following examples and comparative examples, the sources of reagents and test equipment used include:

[0044] Microcrystalline wax (melting point 67-72℃) was purchased from Shanghai Yuan Ye Biotechnology Co., Ltd.; Dow Corning 184 PDMS was purchased from Suzhou Hongyouda E-commerce Co., Ltd.; Hydrophilic nano-silica particles (particle size 10-20 nm) and anhydrous ethanol were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.; Solar photovoltaic panels (parameters: 1 W, 5 V, 200 mA) were purchased from Dongguan Liaobu Hui Xu Trading Company; Spray gun Junshi PS289 (caliber 0.3 mm) was purchased from Jianrui Model E-commerce Co., Ltd.; Victory VC86E multimeter was purchased from Xi'an Beicheng Electronics Co., Ltd.; Illuminance meter (split type TA630B) was purchased from Suzhou Zhaofu Electronics Co., Ltd.; DuPont wire was purchased from Shenzhen Eagle Bean Technology Co., Ltd.; Soldering wire was purchased from Shenzhen Nantian Electronics Co., Ltd.; Glass slides, sandpaper, and flannel were purchased from Henan Anning Electronics Co., Ltd.; Weights were purchased from Shanghai Yanheng Instrument Co., Ltd.; Mud powder was ground from soil on campus, and water was laboratory deionized water; Commercial coating, the main component of which was epoxy resin, had high transparency, about 99%, and was widely used in the photovoltaic field, and was purchased from Taobao.

[0045] In the following examples and comparative examples, the test methods of the coating included:

[0046] (1) Test the hydrophobicity of the solid-state lubricating coating of the sample: use OCA20 contact angle tester to test the hydrophobicity of the surface of the solid-state transparent lubricating coating, and obtain water contact angle WCA and rolling angle WSA.

[0047] (2) Test the optical transparency of the solid-state lubricating coating of the sample: use Shimadzu UV2600 ultraviolet-visible light spectrophotometer to test the optical transparency of the coating.

[0048] (3) Test the change in power of the sample solid-state lubricating coating and the commercial coating after self-cleaning in the same environment: under the conditions of controlling the water consumption of self-cleaning to be 15 mL, the power loss of the photovoltaic panel after being polluted by dust density being about 68% to 75%, and controlling the light intensity to be constant at 26900 lx, use a multimeter to test the power loss of the two after self-cleaning, expressed as the power loss (%) of the photovoltaic panel with the solid-state lubricating coating after self-cleaning, and the power loss (%) of the photovoltaic panel with the commercial coating after self-cleaning.

[0049] (4) Test the hydrophobicity of the sample solid-state lubricating coating after sandpaper abrasion: under the pressure of a 50 g weight, pass the sample solid-state lubricating coating through 1000 mesh sandpaper for 1 time at a friction distance of 10 cm, a total of 30 times, and use OCA20 contact angle tester to test the hydrophobicity of the surface of the solid-state transparent lubricating coating after each two abrasions, and obtain water contact angle WCA and rolling angle WSA.

[0050] (5) Hydrophobicity of the sample solid-state lubricating coating after rubbing with gauze: the sample solid-state lubricating coating was rubbed with gauze under the pressure of 50 g of weight, 1 time for 10 cm of friction distance, a total of 30 times. The hydrophobicity of the solid-state transparent lubricating coating surface after each two rubbings was tested by using an OCA20 contact angle tester to obtain the water contact angle WCA and the rolling angle WSA.

[0051] Example 1:

[0052] A preferred embodiment of the preparation method of the fluorine-free transparent self-cleaning solid-state lubricating coating according to the present application comprises the following steps:

[0053] S1, preparing wax micro powder:

[0054] 20 g of microcrystalline wax was placed in a 50 mL beaker and dissolved by heating in a water bath at 80°C. The dissolved wax was sprayed out through a spray gun with a caliber of 0.5 mm. The spray gun air pressure was provided by a gas pump air compressor with a pressure of 30 L and a power of 980 W. The air pipe connected to the gas pump was preheated. The sprayed wax immediately formed spherical particles in the air. Finally, the wax micro powder was collected using a container. The particle size of the wax micro powder was 5-20 μm.

[0055] S2, preparing wax-based suspension:

[0056] The wax micro powder prepared in step S1 was added to 16 g of ethyl acetate solution. The weight concentration of the wax micro powder in the ethyl acetate solution was 0.3 wt%. Then, PDMS and hydrophilic nano-silica were added. The weight concentration of the PDMS in the ethyl acetate solution was 22 wt%, and the weight concentration of the hydrophilic nano-silica in the ethyl acetate solution was 0.5 wt%. Subsequently, magnetic stirring was performed at room temperature for 2 h, and ultrasonic dispersion was performed for 1 h. The wax-based suspension was uniformly dispersed.

[0057] S3, preparing solid-state lubricating coating:

[0058] A glass slide was used as a substrate and immersed in anhydrous ethanol for 10 min. Then, the substrate was taken out and dried at 60°C to obtain a clean substrate. A spray gun model PS289 was used to spray the wax-based suspension prepared in step S2 at a distance of 10 cm and perpendicular to the clean substrate at an air pressure of 0.2 MPa to prepare a sample. Then, the sample was placed in a forced air drying oven at 60°C and dried and cured for 12 h to obtain a solid-state lubricating coating.

[0059] To investigate the effect of the concentration of the wax micro powder on the solid-state lubricating coating, the weight concentration of the wax micro powder in the ethyl acetate solution in Example 1 was replaced with different concentrations of wax micro powder to prepare coatings. The hydrophobicity, optical transparency, and the change in power after pollution and self-cleaning of the coatings under the same environment were tested. The results are shown in Table 1.

[0060] Table 1. Performance of solid lubricating coating with different concentrations of wax micro powder

[0061]

[0062] From the above Figure 1 It can be seen that the obtained wax micro powder has good spherical morphology. From the comparison results of Examples 1-3 and Comparative Examples 1 and 2, it can be seen that the wax micro powder is used to provide a certain roughness and hydrophobicity of the coating. From the test results of the water contact angle WCA and the rolling angle WSA, it can be seen that the solid lubricating coating has excellent hydrophobicity and lubricating properties. From the transparency results, it can be seen that the solid lubricating coating has good optical transparency. The solid lubricating coating is applied to the surface of a solar panel, and after self-cleaning, the power loss is significantly reduced compared to a commercial coating. It can be seen that the solid lubricating coating has excellent self-cleaning, hydrophobicity and durability, which is beneficial to reduce the power loss of the photovoltaic panel after self-cleaning after pollution. However, the wax micro powder is a white powder. In order to further avoid the loss of coating optical transparency due to excessive wax micro powder, the weight concentration of the wax micro powder in the solvent is preferably 0.3wt%-2wt%, and the weight concentration of the wax micro powder in the solvent is preferably 0.6wt%-1wt% considering the hydrophobicity and transparency of the coating.

[0063] Example 4:

[0064] A preferred embodiment of the preparation method of the fluorine-free transparent self-cleaning solid lubricating coating of the present application comprises the following steps:

[0065] S1, preparing wax micro powder:

[0066] 20g of microcrystalline wax was placed in a 50mL beaker and dissolved by heating in a water bath at 80℃. The dissolved wax was sprayed out through a spray gun with a caliber of 0.5mm. The spray gun air pressure was provided by a 30L air pump air compressor with a power of 980W. The air pipe connected to the air pump was preheated. The sprayed wax immediately formed spherical particles in the air. Finally, a container was used to collect the wax micro powder. The particle size of the wax micro powder was 5-20μm.

[0067] S2, preparing wax-based suspension:

[0068] The wax micro powder prepared in step S1 was added to 16g of ethyl acetate solution. The weight concentration of the wax micro powder in the ethyl acetate solution was 0.8wt%. Then, PDMS and hydrophilic nano-silica were added. The weight concentration of the PDMS in the ethyl acetate solution was 5wt%, and the weight concentration of the hydrophilic nano-silica in the ethyl acetate solution was 0.5wt%. Subsequently, magnetic stirring was performed at room temperature for 2h, and ultrasonic dispersion was performed for 1h. The dispersion was uniform to obtain a wax-based suspension.

[0069] S3, preparing a solid lubricating coating:

[0070] The glass slide is immersed in anhydrous ethanol for 10 min, then the substrate is taken out and dried at 60°C to obtain a clean substrate. A spray gun of model Jiangshi PS289 is used to spray the wax-based suspension of step S2 at a distance of 10 cm and perpendicular to the clean substrate at a gas pressure of 0.2 MPa to form a sample, and then the sample is placed in a blast drying oven at 60°C for 12 h to dry and cure to obtain a solid lubricating coating.

[0071] To investigate the effect of the PDMS concentration on the solid lubricating coating, the weight concentration of the PDMS in the ethyl acetate solution in Example 4 is replaced by different wax powder concentrations to prepare coatings, and the hydrophobicity, optical transparency and change in power after self-cleaning of the coatings in the same environment are tested, and the results are shown in Table 2 below:

[0072] Table 2. Performance of solid lubricating coatings with different PDMS concentrations

[0073]

[0074] As can be seen from the comparison results of Examples 4-6 and Comparative Examples 3 and 4, the PDMS functions to provide hydrophobicity and also functions as an adhesive in the coating, and the PDMS itself has high transparency and does not affect the transparency of the coating. As can be seen from the test results of the water contact angle WCA and the rolling angle WSA, the solid lubricating coating has excellent hydrophobicity and lubricating properties. As can be seen from the transparency results, the solid lubricating coating has good optical transparency. The solid lubricating coating applied to the surface of a solar panel has a significantly reduced power loss after self-cleaning compared to a commercial coating. It can be seen that the solid lubricating coating has excellent self-cleaning, hydrophobicity and durability, which is beneficial to reducing the power loss of the photovoltaic panel after self-cleaning after pollution. However, in order to further avoid the excessive PDMS which is not conducive to smooth spraying or batch manufacturing, the weight concentration of the PDMS in the solvent is preferably 5wt%-40wt%, and considering the hydrophobicity and transparency of the coating, it can be further preferably 20wt%-30wt%.

[0075] Example 7:

[0076] A preferred embodiment of the preparation method of the fluorine-free transparent self-cleaning solid lubricating coating of the present application comprises the following steps:

[0077] S1, preparing wax powder:

[0078] 20 g of microcrystalline wax was put into a 50 mL beaker and dissolved by heating in a water bath at 80 °C. The dissolved wax was sprayed through a 0.5 mm nozzle, and the air pressure was provided by a 30 L, 980 W air pump. The air pipe connected to the air pump was preheated. The sprayed wax immediately formed spherical particles in the air, which were collected in a container to obtain wax micropowder with a particle size of 5-20 μm.

[0079] S2. Preparation of wax-based suspension

[0080] The wax micropowder prepared in step S1 was added to 16 g of ethyl acetate solution, and the weight concentration of the wax micropowder in the ethyl acetate solution was 0.8 wt%. Then, PDMS and hydrophilic nano-silica were added, and the weight concentration of the PDMS in the ethyl acetate solution was 25 wt%, and the weight concentration of the hydrophilic nano-silica in the ethyl acetate solution was 0.3 wt%. Subsequently, magnetic stirring was performed at room temperature for 2 h, and ultrasonic dispersion was performed for 1 h to obtain a uniformly dispersed wax-based suspension.

[0081] S3. Preparation of solid lubricating coating

[0082] A glass slide was used as a substrate and immersed in anhydrous ethanol for 10 min. Then, the substrate was taken out and dried at 60 °C to obtain a clean substrate. A spray gun model PS289 was used to spray the wax-based suspension prepared in step S2 at a distance of 10 cm and perpendicular to the clean substrate at an air pressure of 0.2 MPa to obtain a sample. Then, the sample was placed in a forced air drying oven at 60 °C and dried and cured for 12 h to obtain a solid lubricating coating.

[0083] To investigate the effect of the concentration of hydrophilic nano-silica on the solid lubricating coating, the weight concentration of the hydrophilic nano-silica in the ethyl acetate solution in Example 7 was replaced with different concentrations of wax micropowder to prepare coatings. The hydrophobicity, optical transparency, and change in power after self-cleaning of the coatings in the same environment were tested, and the results are shown in Table 3.

[0084] Table 3. Performance of solid lubricating coatings with different concentrations of hydrophilic nano-silica

[0085]

[0086]

[0087] As can be seen from the comparison results of Examples 7-9 and Comparative Examples 5 and 6, the hydrophilic nano-silica can increase the hardness of the coating and a certain water contact angle. As shown in the photographs in FIG. 1, the solid lubricating coating has excellent hydrophobicity and lubricity. Figure 2 As can be seen from the test results of the water contact angle WCA and the rolling angle WSA, the solid lubricating coating has excellent hydrophobicity and lubricity. As shown in FIG. 2, the solid lubricating coating has excellent optical transparency. Figure 3, attached Figure 4 And the transparency results can see that the solid lubricating coating has good optical transparency under different wavelengths, the solid lubricating coating is applied to the surface of a solar panel, and the power loss after self-cleaning is obviously reduced compared with a commercial coating, so that the solid lubricating coating has excellent self-cleaning, hydrophobicity and durability, is conducive to reducing the power loss of the photovoltaic panel after self-cleaning after pollution, and can long-term guarantee the power generation benefit of the solar photovoltaic panel, but in order to further avoid the loss of hydrophilic nano silicon dioxide in the coating hydrophobicity and optical transparency, the weight concentration of the hydrophilic nano silicon dioxide in the solvent is preferably 0.3wt%-1wt%, and the hydrophobicity and transparency of the coating are further preferably 0.5wt%-0.7wt%.

[0088] Attached Figure 5 And attached Figure 6 It can be seen that the solid lubricating coating obtained by the application can still maintain the hydrophobic property after sandpaper friction and gauze friction, and has excellent hydrophobicity and stability, and the results of examples 1-9 can be seen that the solid lubricating coating obtained by the application has good optical transparency, excellent self-cleaning, hydrophobicity, stability and durability, the preparation method is simple and environmentally friendly, has no fluorine and VOC emission, and an environmentally friendly wax is used to prepare a solid lubricating coating with high transparency, so that it can be applied to solar panels, building outer walls, automobile surfaces and other fields, and has wide commercial application prospects.

[0089] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the application, and are not used to limit the protection scope of the application, for example: the substrate material can be selected as needed, and is not limited to glass slides, and equivalent embodiments or changes made without departing from the spirit of the application should be included in the protection scope of the application.

Claims

1. A fluorine-free transparent self-cleaning solid lubricating coating, characterized in that, The solid-state lubricating coating is formed by coating and curing a wax-based suspension on a substrate, the wax-based suspension is made of wax micro-powder, hydrophobic binder and hydrophilic nano-silica dispersed in a solvent; the particle size of the wax micro-powder is 5-20 μm, the weight concentration of the wax micro-powder in the solvent is 0.3 wt%-2 wt%; the hydrophobic binder is PDMS, the weight concentration of the PDMS in the solvent is 5 wt%-40 wt%; the weight concentration of the hydrophilic nano-silica in the solvent is 0.3 wt%-1 wt%.

2. Fluoride-free transparent self-cleaning solid lubricating coating according to claim 1, characterized in that, The solvent is ethyl acetate solution.

3. The method for producing a fluorine-free transparent self-cleaning solid lubricating coating according to any one of claims 1 to 2, characterized in that, The preparation method comprises: Preparation of the wax-based suspension: take the wax micro-powder and add it to the solvent, then add the hydrophobic binder and the hydrophilic nano-silica and disperse them uniformly to prepare the wax-based suspension; Preparation of the self-cleaning lubricating coating: spray the wax-based suspension on the surface of the substrate, and solidify to obtain the self-cleaning lubricating coating.

4. The method of claim 3, wherein the fluorine-free transparent self-cleaning solid- state lubricating coating is prepared by a process comprising: The preparation method comprises: Preparation of the wax micro-powder: take the microcrystalline wax, heat and dissolve it, then spray it out through a spray gun, and collect the spherical wax micro-powder.

5. The method of claim 3, wherein the fluorine-free transparent self-cleaning solid- state lubricating coating is prepared by a process comprising: Magnetic stirring and ultrasonic dispersion are used when preparing the wax-based suspension.

6. The method of claim 3, wherein the fluorine-free transparent self-cleaning solid- state lubricating coating is prepared by a process comprising: Before spraying, the surface of the substrate is cleaned with anhydrous ethanol, and air blowing drying is used for solidification when preparing the self-cleaning lubricating coating.

7. Use of a fluorine-free transparent self-cleaning solid lubricating coating according to any one of claims 1 to 2, characterized in that, The solid-state lubricating coating is used for solar panels, building exterior walls and automobile surfaces.

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