A transparent superhydrophobic coating and a method for preparing the same

Abstract

The application relates to the technical field of super-hydrophobic coating, and discloses a transparent super-hydrophobic coating and a preparation method thereof. The method comprises the following steps: S1, coating an organic coating on a glass surface; S2, etching grooves on the coating by using an etching process until the glass base material at the bottom is exposed; S3, coating a silicon oxide sol on the surface, and after a heat treatment process, the organic coating is decomposed and disappears, so that silicon oxide protrusions are formed at the original organic coating groove; S4, removing the excess silicon oxide on the glass surface treated in the step S3 by using a desolvent flushing method, and then drying the glass surface; and S5, after spraying a hydrophobic silicon oxide nanoparticle dispersion liquid on the glass surface, drying is carried out to obtain the required transparent super-hydrophobic coating. Compared with the prior art, the transparent super-hydrophobic coating can realize the adjustment of the haze of the coating, the transparency, the stability and the super-hydrophobicity at the same time, so that the coating can be applied for a longer time, and the maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic coatings, and particularly to a transparent superhydrophobic coating for use on glass surfaces and its preparation method. Background Technology

[0002] Superhydrophobic coatings have attracted considerable attention from researchers due to their anti-fouling, self-cleaning, and anti-counterfeiting properties. However, achieving superhydrophobicity requires the construction of micro- and nano-structures on the surface, but these structures are susceptible to damage due to stress concentration under pressure, leading to a loss of superhydrophobicity. Transparent superhydrophobic coatings, possessing both transparency and superhydrophobicity, have broader application value in fields such as window glass, car windows, greenhouses, and light diffusion panels, and are therefore attracting more research attention. However, the micro- and nano-structures required for superhydrophobic surfaces increase surface light scattering, leading to a decrease in coating transmittance.

[0003] Chinese patent application CN112210272A discloses a method for preparing a superhydrophobic coating with excellent mechanical stability. The method involves mixing nanoparticles, epoxy resin, diglycidyl ether-terminated polydimethylsiloxane, and amino-terminated hyperbranched polysiloxane, followed by coating to obtain a wear-resistant superhydrophobic coating. However, the coating prepared by this method is opaque, limiting its application areas.

[0004] Chinese patent CN111662614A discloses a method for preparing a transparent superhydrophobic coating resistant to water flow impact. The method involves first mixing epoxy resin and silicon dioxide and coating the mixture onto a substrate surface. Then, hydrophobic silicon dioxide nanoparticles are deposited on the semi-cured resin surface to obtain the transparent superhydrophobic coating. The coating prepared by this method exhibits good transparency, superhydrophobicity, and some resistance to water flow impact, but its mechanical stability is poor, limiting its applications.

[0005] Chinese patent CN111454000A discloses a method for preparing a transparent superhydrophobic film with excellent mechanical stability. The method involves first fabricating an inverted triangular pyramid, inverted square pyramid, or inverted hexagonal pyramid structure on the film surface, and then filling the microstructure with hydrophobic nanoparticles to obtain a mechanically stable transparent superhydrophobic coating. However, the film prepared by this method has extremely high haze, limiting its application areas. Summary of the Invention

[0006] To address the problem that existing technologies improve the mechanical stability of superhydrophobic coatings by increasing coating thickness, enhancing adhesion between the coating and the substrate, and adding protective structures, but the continuous large-size rough structure severely increases light scattering, resulting in generally high haze, this invention proposes a transparent superhydrophobic coating and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a transparent superhydrophobic coating includes the following steps: S1, Apply an organic coating to the glass surface; S2, using an etching process to etch trenches on the coating until the underlying glass substrate is exposed; S3, a silica sol is coated on the surface, and after heat treatment, the organic coating decomposes and disappears, leaving silica protrusions at the original organic coating grooves; S4, the glass surface treated in step S3 is rinsed with solvent to remove excess silicon oxide, and then the glass surface is dried; S5. After spraying a hydrophobic silica nanoparticle dispersion onto the glass surface, the desired transparent superhydrophobic coating is obtained by drying.

[0008] Furthermore, the organic coating is an organic material that can be completely decomposed at 500°C, including photoresist and polystyrene.

[0009] Furthermore, the etching process includes photolithography and laser ablation.

[0010] Furthermore, the groove patterns etched by the etching process in step S2 include triangles, quadrilaterals, and hexagons.

[0011] Furthermore, the etching process creates trenches with a width of 10-50 μm.

[0012] Furthermore, the concentration of the silica sol is 30-40%.

[0013] Furthermore, the heat treatment temperature is 500-700℃, the heat treatment time is 2-5h, and the heating rate is 0.5-5℃ / min.

[0014] Furthermore, the heat treatment atmosphere is one or more of air, nitrogen, or other non-reducing gases, or a mixture thereof.

[0015] Furthermore, the solvent used for rinsing is one or more of water, ethanol, or other volatile solvents, or a mixture thereof.

[0016] Furthermore, the drying temperature described in steps S4 and S5 is 20-120℃.

[0017] Furthermore, the surface of the hydrophobic silica nanoparticles in the dispersion can be modified with low surface energy materials, including chlorosilanes, siloxanes, and fluorosilanes.

[0018] Furthermore, the size of the hydrophobic silica nanoparticles in the hydrophobic silica nanoparticle dispersion is 10-100 nm.

[0019] Furthermore, the concentration of the hydrophobic silica nanoparticle dispersion is 5-10 g / L.

[0020] Furthermore, in step S5, the spraying process uses a spraying pressure of 3-4 Bar, a distance of 5-15 cm between the nozzle and the coating surface, and a dosage of 200-800 mL of hydrophobic silica nanoparticle dispersion per square meter.

[0021] A transparent superhydrophobic coating is prepared using the above-described transparent superhydrophobic coating preparation method.

[0022] The present invention has the following beneficial effects: 1. The transparent superhydrophobic coating of the present invention is an inorganic material that is resistant to high temperature, ultraviolet radiation and other environments, and can improve the thermal stability and chemical stability of the transparent superhydrophobic coating of the prior art.

[0023] 2. The silicon oxide protrusion protective structure in this invention can improve the mechanical stability of transparent superhydrophobic coatings in the prior art.

[0024] 3. The transparent superhydrophobic coating of the present invention can provide on-demand control and design of coating haze that is lacking in the prior art through the size and shape design of the raised protective structure, so that the coating can be applied to window glass with low haze requirements and lampshades or greenhouses with high haze requirements.

[0025] 4. The transparent superhydrophobic coating of the present invention has a large flat area, which can solve the problem of decreased optical properties caused by improving the stability of superhydrophobic coatings in the prior art.

[0026] In summary, compared with the prior art, the transparent superhydrophobic coating of the present invention simultaneously achieves adjustable haze, transparency, stability and superhydrophobicity, enabling the coating to be used for a longer period of time and reducing maintenance costs. Attached Figure Description

[0027] Figure 1 The diagram shows three basic structures of the transparent superhydrophobic coating of the present invention. Figure 2 This is a scanning electron microscope image of the surface before rinsing after heat treatment during the preparation process of this invention; Figure 3 This is a scanning electron microscope image of the surface after rinsing in Embodiment 1 of the present invention; Figure 4 This is a scanning electron microscope image of the surface of the transparent superhydrophobic coating of Embodiment 1 of the present invention; Figure 5 The light transmittance curve and haze curve of the hexagonal structure coating of Embodiment 1 of the present invention are shown. Figure 6 This is a schematic diagram of the coating applied to a photovoltaic panel according to Embodiment 1 of the present invention; Figure 7 This is a scanning electron microscope image of the surface of the hexagonal structure coating of Embodiment 2 of the present invention; Figure 8 The light transmittance curve and haze curve of the hexagonal structure coating in Embodiment 2 of the present invention are shown. Figure 9 This is a scanning electron microscope image of the hexagonal structure coating surface of Embodiment 3 of the present invention; Figure 10 This is a scanning electron microscope image of the surface of the quadrilateral structure coating in Embodiment 4 of the present invention; Figure 11 This is a scanning electron microscope image of the surface of the triangular structure coating in Embodiment 5 of the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0029] Please see the appendix Figures 1-11 The present invention provides the following technical solutions: Example 1

[0030] This invention provides a stable, transparent, superhydrophobic coating with adjustable haze. The coating comprises a raised structure constructed by heat treatment of silica sol and a layer of hydrophobic silica nanoparticles sprayed onto it, which together constitute the surface superhydrophobic coating.

[0031] The raised structure on the coating surface has several microstructures in an array, such as Figure 1 As shown, the protrusion is preferably hexagonal, quadrilateral, or triangular. The main function of this protrusion structure is to protect the silica nanoparticles sprayed at the bottom of the pit and to adjust the coating haze. To ensure the performance of the protrusion structure, the thickness is preferably 2-10 μm.

[0032] This transparent superhydrophobic coating is prepared by a combination of template method, sintering process, and spraying process. Specifically, it is prepared by the following method: Take a clean piece of glass and apply a 20 wt.% polystyrene-toluene solution to its surface using a 20 μm scraper. Allow the solvent to evaporate at room temperature for 30 minutes. Then, use a laser engraving machine to ablate hexagonal grooves into the polystyrene-coated glass surface, exposing the glass surface. Next, apply a 30% concentration of silica sol to the surface. Then, heat the glass to 700°C in air at a rate of 5°C / min and hold for 2 hours to allow the residual polystyrene coating to fully decompose. After naturally cooling to room temperature, remove the coated glass. The scanning electron microscope image of the surface at this point is as follows: Figure 2 As shown, residual polystyrene decomposes at high temperatures, causing cracks to form on the silica surface, which can be removed by water jets. However, the silica in the laser-engraved pattern is tightly bonded to the surface without cracks.

[0033] Then, the surface is washed with tap water to remove loosely bonded silicon dioxide. The glass is then dried in an 80℃ oven for 2 hours, resulting in a hexagonal array of raised protective structure glass. The scanning electron microscope image of the surface at this point is as follows: Figure 3 As shown. Its hexagonal structure has a side length of approximately 100 μm and a spacing of 20 μm.

[0034] 1 g of hydrophobic silica nanoparticles with an average size of 20 nm were dispersed in 100 mL of ethanol, and then 100 μL of octadecyltriethoxysilane was added dropwise. The mixture was stirred at 500 rpm for 1 h to obtain an ethanol dispersion of hydrophobic silica nanoparticles. The ethanol dispersion was then sprayed onto the glass surface at a distance of 5 cm from the glass using a spraying pressure of 3 Bar, with a spraying volume of 800 mL per square meter. After drying at 30 °C for 10 min, the resulting transparent superhydrophobic coating was obtained using a scanning electron microscope (SEM) image. Figure 4 As shown, the surface water contact angle is 163° and the roll-off angle is 1°.

[0035] The optical properties of the glass with the transparent superhydrophobic coating were tested using a UV-Vis spectrophotometer, and the results are as follows: Figure 5 As shown, the solid line is the transmittance curve and the dashed line is the haze curve. In the visible light band of 400-800nm, the average transmittance is 93.3% and the average haze is 6.7%.

[0036] The chemical stability of the glass with the transparent superhydrophobic coating was tested using a UV aging test. After 90 days of UV aging, the surface water contact angle was 162° and the roll-off angle was 1.5°, maintaining its superhydrophobicity. The transmittance of the glass with the transparent superhydrophobic coating after 90 days of UV aging was 92.8%, showing little change.

[0037] The glass with the transparent superhydrophobic coating was tested for abrasion resistance using a sandpaper abrasion test. After 2000 cm of abrasion, the surface water contact angle was 156° and the roll-off angle was 9°, and it still maintained superhydrophobicity.

[0038] Adopting such Figure 6 As shown, the lower layer is a photovoltaic panel, the middle layer is glass, and the upper layer is coated with a transparent superhydrophobic coating to achieve its self-cleaning effect. Example 2

[0039] The difference between this embodiment and Embodiment 1 is that the etched hexagonal structure has a side length of 50 μm and a spacing of 15 μm. After the silica sol is coated, the temperature is increased to 600 °C at a rate of 10 °C / min and held for 3 hours in air to allow the residual polystyrene coating to fully decompose. The spraying amount of the ethanol dispersion of silica nanoparticles is 500 mL per square meter. All other steps are the same.

[0040] The surface scanning electron microscope image of the superhydrophobic coating obtained in this embodiment is as follows: Figure 7 As shown, the hexagonal protrusions can be clearly observed. The hexagonal side length is about 50μm and the spacing is about 15μm.

[0041] The optical properties of the glass with the transparent superhydrophobic coating were tested using a UV-Vis spectrophotometer, and the results are as follows: Figure 8 As shown, the solid line is the transmittance curve and the dashed line is the haze curve. In the visible light band of 400-800nm, the average transmittance is 91.0% and the average haze is 31.6%. Example 3

[0042] The difference between this embodiment and Embodiment 1 is as follows: A clean glass piece is taken, photoresist is spin-coated onto its surface, and hexagonal trenches are etched into the photoresist using a photolithography process to expose the glass surface. Then, a layer of 30% concentration silica sol is coated onto the surface, followed by heating to 500°C at a rate of 5°C / min in air and holding at that temperature for 5 hours to allow the residual photoresist to fully decompose. After naturally cooling to room temperature, the coated glass is removed. The spraying amount of the ethanol dispersion of silica nanoparticles is 200 mL per square meter. All other steps are the same.

[0043] The surface scanning electron microscope image of the superhydrophobic coating obtained in this embodiment is as follows: Figure 9 As shown, the hexagonal protrusions can be clearly observed. The hexagonal sides are about 50 μm long and the spacing is about 10 μm. Example 4

[0044] The difference between this embodiment and Embodiment 1 is that the grooves etched by the photolithography process are square. All other steps are the same.

[0045] The surface scanning electron microscope image of the superhydrophobic coating obtained in this embodiment is as follows: Figure 10 As shown, the square structure protrusions can be clearly observed. The square has a side length of about 125 μm and a spacing of about 20 μm. Example 5

[0046] The difference between this embodiment and Embodiment 1 is that the grooves etched by the photolithography process are triangular. All other steps are the same.

[0047] The surface scanning electron microscope image of the superhydrophobic coating obtained in this embodiment is as follows: Figure 11 As shown, the triangular structural protrusions can be clearly observed. The sides of the triangles are about 100 μm long and the spacing is about 20 μm.

[0048] 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 alterations 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 method for preparing a transparent superhydrophobic coating, characterized in that, Includes the following steps: S1, Apply an organic coating to the glass surface; S2, using an etching process to etch trenches on the coating until the underlying glass substrate is exposed; S3, a silica sol is coated on the surface, and after heat treatment, the organic coating decomposes and disappears, leaving silica protrusions at the original organic coating grooves; S4, the glass surface treated in step S3 is rinsed with solvent to remove excess silicon oxide, and then the glass surface is dried; S5. After spraying a hydrophobic silica nanoparticle dispersion onto the glass surface, the desired transparent superhydrophobic coating is obtained by drying.

2. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The organic coating is an organic material that can be completely decomposed at 500°C, including photoresist and polystyrene.

3. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The etching process includes photolithography and laser ablation, and the groove patterns etched by the etching process include triangles, quadrilaterals, and hexagons.

4. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The etching process creates grooves with a width of 10-50 μm.

5. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The concentration of the silica sol is 30-40%.

6. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The heat treatment temperature is 500-700℃, the heat treatment time is 2-5h, and the heating rate is 0.5-5℃ / min.

7. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The heat treatment atmosphere is one or more of air, nitrogen, or other non-reducing gases, and the rinsing solvent is one or more of water, ethanol, or other volatile solvents. The drying temperature in steps S4 and S5 is 20-120°C.

8. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The surface of the hydrophobic silica nanoparticles in the dispersion can be modified with low surface energy materials, including chlorosilanes, siloxanes, and fluorosilanes.

9. The method for preparing a transparent superhydrophobic coating according to claim 1, characterized in that, The hydrophobic silica nanoparticle dispersion has a size of 10-100 nm and a concentration of 5-10 g / L.

10. A transparent superhydrophobic coating, characterized in that, The coating is prepared using the transparent superhydrophobic coating preparation method described in claims 1 to 14.

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