Method for constructing fluoride-free wear-resistant transparent super-hydrophobic coating

Abstract

The invention relates to the field of coatings, and discloses a method for constructing a fluoride-free wear-resistant transparent super-hydrophobic coating, which comprises the following steps: (1) carrying out surface roughening treatment on wood; (2) wood is immersed in the oil-phase impregnation liquid at 75-85 DEG C, and wood with an uncured hydrophobic layer on the surface is obtained after the wood is taken out; the oil phase impregnation liquid comprises carnauba wax, tung oil and ethyl acetate; (3) the wood is immersed in hydrophobic nano-silica dispersion liquid with the temperature 50-60 DEG C lower than that of the oil-phase impregnation liquid, an uncured hydrophobic layer is cooled and cured into a cured hydrophobic layer with a micron-sized rough surface, and hydrophobic nano-silica is attached to the surface of the cured hydrophobic layer; and taking out, ventilating and drying, enabling the tung oil to permeate into the wood and generate crosslinking, and finally constructing and forming the fluoride-free wear-resistant transparent super-hydrophobic coating on the surface of the wood. According to the method, the super-hydrophobic coating with the micro-nano structure can be constructed on the surface of the wood, and the super-hydrophobic coating has high wear resistance and high transparency.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and particularly to a method for constructing a fluorine-free wear-resistant transparent superhydrophobic coating. Background Art

[0002] As a renewable resource with rich reserves on the earth, wood is widely used in furniture manufacturing, interior decoration and other fields due to its light weight, beauty and other advantages. However, the inherent hydrophilic property of wood makes it prone to problems such as corrosion, aging, and dimensional instability, which greatly limits the scope of wood development and use. Endowing wood with superhydrophobicity can effectively isolate the direct contact between water and wood, thereby improving the stability and durability of wood.

[0003] As an environmentally friendly low surface energy material, carnauba wax can form a hydrophobic coating after being attached to the wood surface. For example, Patent CN200480021651.3 discloses a method including adding a suspension of wood property enhancing substances to a wood product precursor, and specifically discloses a treatment of impregnating in a suspension containing carnauba wax to endow wood with hydrophobicity.

[0004] However, the applicant found in previous experiments that carnauba wax is hard and brittle in nature, and its bonding force with the wood surface is low, which greatly affects the wear resistance of the carnauba wax hydrophobic layer. Therefore, it is necessary to improve the bonding force between carnauba wax and wood. At the same time, the hydrophobicity of the ordinary carnauba wax hydrophobic layer still cannot meet the requirements of superhydrophobicity (hydrophobicity: contact angle greater than 90° and less than 150°; superhydrophobicity: contact angle greater than 150°, rolling angle less than 10°), so it needs to be further modified to obtain excellent superhydrophobicity. In addition, the applicant also found that after treating the wood surface with an impregnating solution with a high carnauba wax content, the formed coating has poor transparency, cannot fully show the original wood color, and will affect the decorative effect of the wood. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for constructing a fluorine-free wear-resistant transparent superhydrophobic coating. The method of the present invention can construct a superhydrophobic coating with a micro-nano structure on the wood surface, and the superhydrophobic coating has high wear resistance and high transparency.

[0006] The specific technical solution of the present invention is: a method for constructing a fluorine-free wear-resistant transparent superhydrophobic coating, comprising the following steps: (1) Roughly treat the wood surface.

[0007] In step (1), the present invention first roughly treats the wood surface. After the above treatment, the wood surface can be in a torn fibrous state, and this primary rough surface is beneficial to the construction of the subsequent superhydrophobic surface.

[0008] (2) Immerse the wood obtained in step (1) into an oil-phase impregnating solution at 75 - 85 °C. After taking it out, wood with an uncured hydrophobic layer on the surface is obtained; the oil-phase impregnating solution includes carnauba wax, tung oil, and ethyl acetate.

[0009] In step (2), after immersing the wood into the oil-phase impregnating solution and taking it out, a layer of uncured hydrophobic layer can be formed on the wood surface, which plays a preliminary hydrophobic modification role and provides a basis for further attaching hydrophobic nano-silica subsequently.

[0010] (3) Immerse the wood obtained in step (2) into a hydrophobic nano-silica dispersion liquid whose temperature is 50 - 60 °C lower than that of the oil-phase impregnating solution when the uncured hydrophobic layer has not cooled. The uncured hydrophobic layer cures upon cooling to form a cured hydrophobic layer with a micron-scale rough surface, and the hydrophobic nano-silica adheres to the surface of the cured hydrophobic layer; take it out and dry it in ventilation. The tung oil penetrates into the interior of the wood and undergoes crosslinking, and finally a fluorine-free wear-resistant transparent superhydrophobic coating is constructed on the wood surface.

[0011] In step (3), immediately immerse it into the hydrophobic nano-silica dispersion liquid with a specific temperature difference before the uncured hydrophobic layer cools. The present invention discovers that if the uncured hydrophobic layer cures upon cooling within a certain temperature difference range, a micron-scale rough surface can be formed. The present invention further discovers that the size of the above-mentioned cooling and curing temperature difference is crucial for whether a micron-scale rough surface can be formed. If the temperature difference is too small, it cannot cure and crystallize into a micron-scale rough surface within an appropriate time; if the temperature difference is too large, the curing and crystallization rate of the hydrophobic layer is too fast.

[0012] During the above impregnation process, the present invention utilizes the viscosity of the uncured hydrophobic layer before complete curing, enabling the hydrophobic nano-silica to firmly adhere to the surface, thereby constructing a coating with a micro-nano surface structure (the micron-scale rough surface of the cured hydrophobic layer + hydrophobic nano-silica), and this micro-nano structure can endow the coating with superhydrophobicity.

[0013] After obtaining the cured hydrophobic layer with hydrophobic nano-silica attached to the surface (i.e., the superhydrophobic with a micro-nano surface structure), conduct ventilation drying on it. Since the oil-phase impregnating solution contains tung oil, the tung oil will penetrate into the interior of the wood. At the same time, the tungolic acid in the tung oil undergoes autoxidation reaction with the oxygen in the air to form a relatively dense crosslinked polymer network structure, which can not only further enhance the hydrophobicity, but also enhance the bonding force between the cured hydrophobic layer and the wood. Meanwhile, compounding with hydrophobic nano-silica can solve the disadvantage of poor wear resistance of a single carnauba wax layer.

[0014] Preferably, in step (2), the mass ratio of carnauba wax to tung oil in the oil-phase impregnating solution is 1:(1 - 4).

[0015] The present invention finds that the tung oil content in the oil-phase impregnating solution has a great influence on the wear resistance and transparency of the finally constructed superhydrophobic layer. Specifically, if the tung oil content is too low, the binding force between the superhydrophobic layer and the wood surface will be weak, resulting in a decrease in wear resistance; at the same time, the lower the tung oil content, the more unfavorable it is to the transparency of the coating.

[0016] Preferably, in step (2), the preparation method of the oil-phase impregnating solution is: adding carnauba wax and tung oil into ethyl acetate, and stirring and dissolving at a rate of 300-500 rpm at 75-85 °C.

[0017] The present invention utilizes the miscibility between ethyl acetate, tung oil, and carnauba wax to prepare an oil-phase impregnating solution.

[0018] Preferably, in step (2), the impregnation time of the wood in the oil-phase impregnating solution is 20-40 s.

[0019] Preferably, in step (3), the particle size of the hydrophobic nano-silica is 20-100 nm.

[0020] The present invention finds that in order to further improve the transparency of the superhydrophobic coating to better present the natural color of the wood, it is necessary to optimize the particle size of the hydrophobic nano-silica. Finally, when the particle size of the hydrophobic nano-silica is in the range of 20-100 nm, a superhydrophobic coating with better transparency can be obtained, and when the particle size of the hydrophobic nano-silica is about 80 nm, it is the best.

[0021] Preferably, in step (3), the hydrophobic nano-silica dispersion is ethanol dispersed with hydrophobic nano-silica, and the mass ratio of hydrophobic nano-silica to ethanol is (3-5):(40-50).

[0022] Preferably, in step (3), the preparation method of the hydrophobic nano-silica dispersion is: dispersing hydrophobic nano-silica in ethanol and ultrasonically dispersing for 5-15 min to obtain a hydrophobic nano-silica dispersion.

[0023] Preferably, in step (3), the impregnation time of the wood in the hydrophobic nano-silica dispersion is 5-10 min, and the ventilation drying time is 6-10 days.

[0024] Preferably, in step (1), the surface roughening treatment is to sand the wood surface, then ultrasonically wash and dry.

[0025] Preferably, the ultrasonic washing is to wash with deionized water and ethanol for 1-10 min each under ultrasonic conditions, and the drying is to dry at 50-70 °C.

[0026] Preferably, in step (1), the sandpaper has a specification of 350 - 450 mesh.

[0027] Preferably, in step (1), the wood is pine.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Based on a cured hydrophobic layer with a micron - scale rough surface (formed by carnauba wax and tung oil) on the wood surface, hydrophobic nano - silica is further adhered to its surface, and a super - hydrophobic coating with a micro - nano structure and better hydrophobicity can be constructed.

[0029] (2) Before the uncured hydrophobic layer cools, it is immediately immersed in a hydrophobic nano - silica dispersion with a specific temperature difference, and the uncured hydrophobic layer can cool and solidify to form a surface with a micron - scale rough surface.

[0030] (3) The present invention uses carnauba wax and tung oil as the main components to compound an oil - phase impregnating solution. When the wood is impregnated with the oil - phase impregnating solution to form a cured hydrophobic layer, tung oil can penetrate into the wood interior and undergo a self - oxidation reaction to form a relatively dense cross - linked polymer network structure. This can not only further enhance the hydrophobicity but also enhance the bonding force between the cured hydrophobic layer and the wood. At the same time, by compounding hydrophobic nano - silica, the disadvantage of poor wear resistance of a single carnauba wax layer can be solved.

[0031] (4) By optimizing the ratio of carnauba wax and tung oil in the oil - phase impregnating solution and the particle size of hydrophobic nano - silica, a super - hydrophobic layer with high transparency can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart for constructing a fluorine - free wear - resistant transparent super - hydrophobic coating on the wood surface of the present invention; Figure 2 is an electron micrograph of a log with a magnification of 200 times; Figure 3 is an electron micrograph of the cured hydrophobic layer obtained in Example 1 with a magnification of 200 times; Figure 4 is an electron micrograph of the cured hydrophobic layer obtained in Example 1 with a magnification of 1000 times; Figure 5 is an electron micrograph of the super - hydrophobic coating obtained in Example 1 with a magnification of 50000 times; Figure 6 is an electron micrograph of the super - hydrophobic coating of Comparative Example 1 with a magnification of 50000 times; Figure 7 is an electron micrograph of the super - hydrophobic coating of Comparative Example 2 with a magnification of 50000 times; Figure 8SEM image of the superhydrophobic coating of Comparative Example 3 at a magnification of 50,000 times; Figure 9 SEM image of the superhydrophobic coating of Comparative Example 4 at a magnification of 50,000 times; Figure 10 SEM image of the superhydrophobic coating of Comparative Example 5 at a magnification of 50,000 times; Figure 11 Contact angle picture of the log; Figure 12 Contact angle picture of Example 1; Figure 13 Contact angle picture of Example 2; Figure 14 Contact angle picture of Example 3; Figure 15 Relationship diagram of contact angle and wear distance of the superhydrophobic coatings prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5; Figure 16 Reflection spectra of the log and the superhydrophobic coatings prepared in Example 1, Example 2, and Example 3; Figure 17 Reflection spectra of the log and the superhydrophobic coatings prepared in Example 1, Example 4, Example 5, and Example 6; Figure 18 Digital photos of the log (a) and the sample of Example 1 (b); Figure 19 Comparison diagram of water absorption rates of the log and the sample of Example 1; Figure 20 Self-cleaning performance diagram of the log (a - b) and the superhydrophobic coating prepared in Example 1 (d - f), and rejection phenomenon diagram of the coating prepared in Example 1 (c) for various liquids. Detailed implementation mode

[0033] The present invention will be further described below in conjunction with the embodiments.

[0034] General embodiment A method for constructing a fluorine-free wear-resistant transparent superhydrophobic coating on the surface of wood, as Figure 1 shown, includes the following steps: (1) Sand the surface of the wood (pine) with 350 - 450 mesh sandpaper, wash it with deionized water and ethanol for 1 - 10 min each under ultrasonic conditions, and dry it at 50 - 70 °C.

[0035] (2)Add carnauba wax and tung oil to ethyl acetate at a mass ratio of 1:(1 - 4):(10 - 50), and stir and dissolve at a rate of 300 - 500 rpm at 75 - 85 °C to obtain an oil - phase impregnating solution; immerse the wood obtained in step (1) in the oil - phase impregnating solution at 75 - 85 °C for 20 - 40 s, and after taking it out, obtain wood with an uncured hydrophobic layer on the surface.

[0036] (3)Disperse hydrophobic nano - silica (particle size 20 - 100 nm) in ethanol at a mass ratio of (3 - 5):(40 - 50), and ultrasonically disperse for 5 - 15 min to obtain a hydrophobic nano - silica dispersion; immediately immerse the wood obtained in step (2) in the hydrophobic nano - silica dispersion whose temperature is 50 - 60 °C lower than that of the oil - phase impregnating solution for 5 - 10 min while the uncured hydrophobic layer has not cooled. The uncured hydrophobic layer cures into a cured hydrophobic layer with a micron - scale rough surface, and the hydrophobic nano - silica adheres to the surface of the cured hydrophobic layer; take it out and ventilate and dry for 6 - 10 days. During this period, the tung oil infiltrating into the wood interior undergoes cross - linking, and finally a fluorine - free wear - resistant transparent super - hydrophobic coating is constructed on the wood surface.

[0037] Example 1 (1)Sand the wooden block (pine, 3 cm×3 cm×1 cm) with 400 - mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0038] (2)Disperse 5 g of hydrophobic nano - silica with an average particle size of 80 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a hydrophobic nano - silica dispersion at 25 °C.

[0039] (3)Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at a rate of 300 rpm at 80 °C, and then immediately immerse the wooden block vertically in the obtained oil - phase impregnating solution. After 30 s, pull it out of the solution.

[0040] (4)Immediately immerse the wooden block obtained in the previous step in the hydrophobic nano - silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a super - hydrophobic coating.

[0041] Example 2 (1)Sand the wooden block (pine, 3 cm×3 cm×1 cm) with 400 - mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0042] (2)Disperse 5 g of hydrophobic nano - silica with an average particle size of 80 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a hydrophobic nano - silica dispersion at 25 °C.

[0043] (3) Add 2.5 g of carnauba wax and 2.5 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm. Then immediately immerse the wooden block vertically into the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0044] (4) Immediately immerse the wooden block obtained in the previous step into the superhydrophobic silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0045] Example 3 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0046] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 80 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a superhydrophobic silica dispersion at 25 °C.

[0047] (3) Add 5 g of carnauba wax to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 500 rpm. Then immediately immerse the wooden block vertically into the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0048] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0049] Example 4 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0050] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 20 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a hydrophobic nano-silica dispersion at 25 °C.

[0051] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm. Then immediately immerse the wooden block vertically into the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0052] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0053] Example 5 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0054] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 50 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a hydrophobic nano-silica dispersion at 25 °C.

[0055] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then vertically immerse the wooden block in the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0056] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0057] Example 6 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0058] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, and ultrasonically disperse for 10 min to obtain a hydrophobic nano-silica dispersion at 25 °C.

[0059] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, and then immediately vertically immerse the wooden block in the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0060] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0061] Comparative Example 1 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0062] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, ultrasonically disperse for 10 min, and cool it in an ice bath to obtain a hydrophobic nano-silica dispersion at 5 °C.

[0063] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then immediately immerse the wooden block vertically in the obtained oil-phase impregnating solution, and pull it out of the solution after 30 s.

[0064] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion liquid, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0065] Comparative Example 2 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0066] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, ultrasonically disperse for 10 min, and place it in an ice bath to cool to obtain a hydrophobic nano-silica dispersion liquid at 15 °C.

[0067] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then immediately immerse the wooden block vertically in the obtained oil-phase impregnating solution, and pull it out of the solution after 30 s.

[0068] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion liquid, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0069] Comparative Example 3 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0070] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, ultrasonically disperse for 10 min, and place it in a warm water bath to obtain a hydrophobic nano-silica dispersion liquid at 40 °C.

[0071] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then immediately immerse the wooden block vertically in the obtained oil-phase impregnating solution, and pull it out of the solution after 30 s.

[0072] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion liquid, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0073] Comparative Example 4 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0074] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, ultrasonically disperse for 10 min, and place it in a warm water bath to obtain a hydrophobic nano-silica dispersion at 50 °C.

[0075] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then immediately immerse the wooden block vertically in the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0076] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0077] Comparative Example 5 (1) Sand the wooden block (pine, 3 cm × 3 cm × 1 cm) with 400-mesh sandpaper, wash it with deionized water and ethanol for 5 min each under ultrasonic conditions, and dry it at 60 °C.

[0078] (2) Disperse 5 g of hydrophobic nano-silica with an average particle size of 100 nm in 45 g of ethanol, ultrasonically disperse for 10 min, and place it in a warm water bath to obtain a hydrophobic nano-silica dispersion at 60 °C.

[0079] (3) Add 1 g of carnauba wax and 4 g of tung oil to 45 g of ethyl acetate, stir and dissolve at 80 °C at a rate of 300 rpm, then immediately immerse the wooden block vertically in the obtained oil-phase impregnation solution, and pull it out of the solution after 30 s.

[0080] (4) Immediately immerse the wooden block obtained in the previous step into the hydrophobic nano-silica dispersion, take it out after soaking for 10 min, and dry it in a fume hood for 8 days to obtain a wooden block with a superhydrophobic coating.

[0081] Performance Test and Characterization Table 1 Contact angle (°) Rolling angle (°) Log 53.1 — Example 1 155.5 3.4 Example 2 155.1 1.7 Example 3 155.5 1.6 Example 4 155.3 3.7 Example 5 155.2 4.2 Example 6 155.5 3.9 Comparative Example 1 152.6 5.1 Comparative Example 2 155.2 4.7 Comparative Example 3 154.6 4.1 Comparative Example 4 153.9 3.7 Comparative Example 5 153.9 3.5 Table 1 and Figures 11 - 13Contact angle and rolling angle parameters of the log and the superhydrophobic coatings prepared in Examples 1-6 and Comparative Examples 1-5. In the present invention, a contact angle measuring instrument was used to measure the products. A water droplet with a volume of 4 μL was taken, and at least 3 points were measured on the surface of each sample to measure the contact angle, and the average value of the results was taken. The platform on which the sample was placed was slowly tilted. When the water droplet slipped from the surface of the sample, the tilt angle of the platform was the rolling angle. A water droplet with a volume of 10 μL was taken, and at least 3 points were measured on the surface of each sample to measure the rolling angle, and the average value of the results was taken. The superhydrophobic surface shows extreme repellency to water, resulting in the bead-like rolling of the liquid droplets. This phenomenon is caused by the reduction of the contact area between the water droplet and the superhydrophobic surface, and the water droplet only contacts a small part of the solid around the top of the rough surface.

[0082] Figure 2 Figure ( Figure 3 and Figure 4 are SEM images of the log at a magnification of 200 times. It can be seen that the wood surface is fibrous after cutting and tearing. This primary rough structure is beneficial to the formation of the superhydrophobic surface. Figure 5 Figure ( Figures 6 - 10 are SEM images of the cured hydrophobic layer obtained in step (3) of Example 1 at magnifications of 200 times and 1000 times, respectively. It can be seen that the microscopic structure of the log is covered by a cured hydrophobic layer with a micron-scale rough structure. The cured hydrophobic layer containing carnauba wax will form numerous micron-scale granular crystals, creating conditions for further constructing the superhydrophobic surface.

[0083] Figure 15Relationship diagram of contact angle and wear distance of superhydrophobic coatings prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. The wear resistance of superhydrophobic materials determines whether they can be widely used. First, lay a piece of 800-mesh sandpaper flat, place the wooden block with the superhydrophobic coating side down on the sandpaper, then place a 100-g weight in the center of the wooden block to apply a force to make it move. The one-way distance is 10 cm, and one round trip is one cycle. The contact angle of the sample is measured every 10 cycles of friction. As shown in the figure, it can be seen that for the sample of Example 1 (the ratio of carnauba wax to tung oil is 1:4), after 600 cm of wear, the contact angle is still above 150°; for the sample of Example 2 (the ratio of carnauba wax to tung oil is 1:1), after 600 cm of wear, the contact angle is still 147°; for the sample of Example 3 (without tung oil), after 600 cm of wear, the contact angle is 127.8°. It can be seen from this that due to the different ratios of carnauba wax and tung oil used in the superhydrophobic coatings of Example 1, Example 2, and Example 3, there are differences in their wear resistance. The ratio used in Example 1 is the best, and the wear resistance is the best. For the sample of Comparative Example 1 (the temperature of the hydrophobic nano-silica dispersion is 5°C), after 600 cm of wear, the contact angle drops to 134.1°. Since the crystallization rate of carnauba wax is too fast at this temperature and the amount of adhered hydrophobic nano-silica decreases, the contact angle decreases significantly as the friction distance increases. For the sample of Comparative Example 2 (the temperature of the hydrophobic nano-silica dispersion is 15°C), after 600 cm of wear, the contact angle drops to 146.8°. For the sample of Comparative Example 3 (the temperature of the hydrophobic nano-silica dispersion is 40°C), after 600 cm of wear, the contact angle drops to 149.6°. For the sample of Comparative Example 4 (the temperature of the hydrophobic nano-silica dispersion is 50°C), after 600 cm of wear, the contact angle drops to 144.1°. For the sample of Comparative Example 5 (the temperature of the hydrophobic nano-silica dispersion is 60°C), after 600 cm of wear, the contact angle drops to 146°. It can be seen from the above that the crystallization temperature of the sample has a certain influence on the wear resistance of the sample. The closer it is to room temperature, the better the wear resistance of the sample. In summary, the wear resistance of Example 1 is the best.

[0084] Figure 16 Reflectance spectra of the log and the superhydrophobic coatings prepared in Example 1, Example 2, and Example 3 Figure 18 Reflectance spectra of the log and the superhydrophobic coatings prepared in Example 1, Example 4, Example 5, and Example 6 Figure 18Digital photos of the log (a) and the superhydrophobic coating (b) prepared in Example 1. As shown in the figure, it can be seen that the reflectance of the superhydrophobic coatings prepared in Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 has increased compared to that of the log. This observation can be understood through Rayleigh scattering (∼λ -4 ), and when the particle size on the coating surface is much smaller than the wavelength of the incident light, the scattering phenomenon will be more obvious. From Figure 17 it can be seen that the reflectance of Example 1 is closer to that of the log because the higher the proportion of carnauba wax in the superhydrophobic coating, the more unfavorable it is to the transparency of the superhydrophobic coating. From Figure 17 it can be seen that when the ratio of carnauba wax to tung oil is constant, the transparencies of the superhydrophobic coatings prepared with hydrophobic nano-silica of different particle sizes are different. Among them, the reflectance of the superhydrophobic coating prepared with hydrophobic nano-silica with a particle size of 80 nm is closer to that of the log, that is, the transparency of Example 1 is the best. Figure 18 (b) is the digital photo of the sample of Example 1, and its chromaticity maintains good consistency compared with Figure 18 the log in (a). The above results show that the superhydrophobic coating prepared in Example 1 has the best transparency.

[0085] Figure 19 Figure for the comparison of the water absorption rates of the log and Example 1. The log and the sample prepared in Example 1 were placed in distilled water, taken out at regular intervals, the surface moisture was blotted with filter paper, and then their weights were measured. The water absorbency (WU) was calculated from the weight change of the sample before and after immersion.

[0086] WU(%)=(W 2 -W 1 ) / W 1 *100 After the log was soaked in water for 5 h, its mass increased sharply by 44.9%. After 288 h of soaking, the mass increased by 109.2%. For the wood with a superhydrophobic coating on its surface, after 5 h of soaking, the mass increased by 3.6%. After 288 h of soaking, the mass increased by 34.7%. The above results show that superhydrophobic modification of wood can significantly reduce the water absorbency of wood.

[0087] Figure 20It is a self-cleaning performance diagram of log (a-b), the superhydrophobic coating prepared in Example 1 (d-f), and a diagram of the rejection phenomenon of the superhydrophobic coating prepared in Example 1 (c) for various liquids. In Figure (a-b), by dripping water droplets, the soil on the log is not completely removed, and the wood surface is wetted by the water droplets. The liquid containing soil adheres to the surface, making the surface dirtier. In Figure (d-f), by dripping water droplets, the soil on the superhydrophobic wood surface is carried away, indicating that the superhydrophobic coating has extremely low adhesion to water and excellent self-cleaning performance. Figure (c) shows that the product of the present invention is also repulsive to common liquids in life such as tea, cola, water, coffee, milk, vinegar, etc., and can be widely used in life.

[0088] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0089] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for constructing a fluorine-free wear-resistant transparent superhydrophobic coating, characterized in that it includes the following steps: (1) Roughly treat the surface of the wood; (2) Immerse the wood obtained in step (1) into an oil-phase impregnating solution at 75-85 °C, and after taking it out, obtain wood with an uncured hydrophobic layer on the surface; the oil-phase impregnating solution includes carnauba wax, tung oil and ethyl acetate; (3) Immerse the wood obtained in step (2) into a hydrophobic nano-silica dispersion whose temperature is 50-60 °C lower than that of the oil-phase impregnating solution before the uncured hydrophobic layer cools down. The uncured hydrophobic layer cures into a cured hydrophobic layer with a micron-level rough surface, and the hydrophobic nano-silica adheres to the surface of the cured hydrophobic layer; take it out and dry it in ventilation. The tung oil penetrates into the interior of the wood and undergoes cross-linking, and finally a fluorine-free wear-resistant transparent superhydrophobic coating is constructed on the wood surface.

2. The method according to claim 1, characterized in that: In step (2), the mass ratio of carnauba wax to tung oil in the oil-phase impregnating solution is 1:(1-4).

3. The method according to claim 1 or 2, characterized in that: In step (2), the preparation method of the oil-phase impregnating solution is: add carnauba wax and tung oil to ethyl acetate, and stir and dissolve at 75-85 °C at a rate of 300-500 rpm.

4. The method according to claim 1 or 2, characterized in that: In step (2), the impregnation time of the wood in the oil-phase impregnating solution is 20-40 s.

5. The method according to claim 1, characterized in that: In step (3), the particle size of the hydrophobic nano-silica is 20-100 nm.

6. The method according to claim 1 or 5, characterized in that: In step (3), the hydrophobic nano-silica dispersion is ethanol dispersed with hydrophobic nano-silica, and the mass ratio of hydrophobic nano-silica to ethanol is (3-5):(40-50).

7. The method according to claim 6, characterized in that: In step (3), the preparation method of the hydrophobic nano-silica dispersion is: disperse the hydrophobic nano-silica in ethanol and ultrasonically disperse it for 5-15 min to obtain the hydrophobic nano-silica dispersion.

8. The method according to claim 1 or 5, characterized in that: In step (3), the impregnation time of the wood in the hydrophobic nano-silica dispersion is 5-10 min, and the ventilation drying time is 6-10 days.

9. The method according to claim 1, characterized in that: In step (1), the surface rough treatment is to polish the wood surface with sandpaper, then ultrasonically wash and dry.

10. The method according to claim 9, characterized in that: In step (1), the specification of the sandpaper is 350-450 mesh.

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