Hydrophobic coating, preparation method thereof and preparation method of hydrophobic coating

Abstract

The invention discloses a hydrophobic coating, a preparation method thereof and a preparation method of a hydrophobic coating. The hydrophobic coating disclosed by the invention is prepared from the following raw materials in parts by weight: 7 to 13 parts of organic acid solution, 0.05 to 0.9 part of fly ash, 0.005 to 0.1 part of nanofiber and 0.5 to 5 parts of silicon-containing substance, wherein the organic acid solution comprises an alcohol compound containing 1-6 carbon atoms, alkoxy silane, organic acid containing 1-10 carbon atoms and water, and the mass ratio of the alcohol compound to the alkoxy silane to the organic acid to the water is 10: (1-10): (0.005-2): (0.5-2). The hydrophobic coating disclosed by the invention has excellent hydrophobic performance and heat resistance.

Description

Technical Field

[0001] This invention relates to a hydrophobic coating and its preparation method, as well as a method for preparing a hydrophobic coating layer. Background Technology

[0002] The "lotus effect" refers to the superhydrophobicity and self-cleaning phenomenon on the surface of a lotus leaf caused by the combined effect of its micro-nano structure and waxy layer. The wettability of a solid surface is influenced by surface energy and its micro-nano structure. Generally, a solid surface is considered superhydrophobic when the water droplet contact angle is greater than 150° and the roll-off angle is less than 10°. Superhydrophobic coatings have a wide range of applications, including antibacterial, antifouling, self-cleaning, anti-corrosion, oil-water separation, and anti-icing. Fly ash is an industrial solid waste produced after coal combustion. Directly dumping fly ash not only occupies valuable land resources but also causes environmental pollution and ecological damage. Fly ash mainly consists of silicate glass microspheres and a small amount of unburned carbon particles; it is rich in silicate groups, inexpensive, and widely available.

[0003] CN115386251A discloses a method for preparing an inorganic ceramic waterproof coating, comprising 30-40 parts by weight of waste fly ash, 10-20 parts by weight of aluminum tailings waste, 25-35 parts by weight of bauxite, 0.5-1.5 parts by weight of CMC, 0.5-1 parts by weight of leveling agent, 0.5-2 parts by weight of hollow glass microspheres, 6-12 parts by weight of nano-ceramic particles, 1-2 parts by weight of silane coupling agent, 0.5-1.5 parts by weight of pH adjuster, 0.5-2 parts by weight of additives, 8-16 parts by weight of waterborne epoxy resin, 10-15 parts by weight of inorganic pigment, and 45-70 parts by weight of solvent. S2. Waste fly ash, aluminum tailings, bauxite, CMC, nano-ceramic particles, silane coupling agent, additives, inorganic pigments, and solvents are ball-milled to obtain a slurry. S3. The slurry is mixed with water-based epoxy resin and a leveling agent, and milled for at least 20 minutes. It is then filtered through a 20-35 micron filter. Depending on the viscosity, 0.5-5 parts of water are added for dilution, and a pH adjuster is added to adjust the pH to 10-14. Hollow glass microspheres are added, and the mixture is thoroughly stirred to obtain the inorganic ceramic waterproof coating. This waterproof coating exhibits poor hydrophobic properties after high-temperature treatment.

[0004] CN120310433A discloses an environmentally friendly, stain-resistant, and anti-slip formulation, comprising a base liquid component, modified titanium dioxide, modified calcium carbonate, modified fly ash, a dispersant, a defoamer, a curing agent, and deionized water. The base liquid component is prepared by copolymerizing and modifying waterborne epoxy resin with polyurethane. The modified titanium dioxide is prepared by modifying nano-titanium dioxide with the silane coupling agent KH-570. The modified calcium carbonate is prepared by modifying calcium carbonate with sodium stearate. The modified fly ash is prepared by modifying fly ash with ethylene glycol. This formulation exhibits poor hydrophobic properties. Summary of the Invention

[0005] One object of the present invention is to provide a hydrophobic coating having excellent hydrophobic and heat resistance properties. Further, the hydrophobic coating exhibits excellent adhesion. Another object of the present invention is to provide a method for preparing a hydrophobic coating, wherein the hydrophobic coating obtained by the preparation method has excellent hydrophobic and heat resistance properties. Further, the hydrophobic coating obtained by the preparation method exhibits excellent adhesion. A further object of the present invention is to provide a method for preparing a hydrophobic coating layer.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] On one hand, the present invention provides a hydrophobic coating, which is prepared from raw materials comprising the following components: 7-13 parts by weight of organic acid solution; 0.05–0.9 parts by weight of fly ash; Nanofibers: 0.005–0.1 parts by weight; 0.5 to 5 parts by weight of silicon-containing material; The organic acid solution comprises an alcohol compound containing 1 to 6 carbon atoms, an alkoxysilane, an organic acid containing 1 to 10 carbon atoms, and water, wherein the mass ratio of the alcohol compound, alkoxysilane, organic acid, and water is 10:(1 to 10):(0.005 to 2):(0.5 to 2). The alkoxysilane is as shown in formula (I): (I); R1 to R4 are independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens, and at least two of R1 to R4 are C1 to C6 alkoxy groups; The silicon-containing material is selected from one or more compounds represented by formulas (II) to (III); (II); R5 to R8 are independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens, and at least two of R5 to R8 are C1 to C6 alkyl groups; (III); Among them, R9~R 14 Each is independently selected from C1 to C6 alkyl groups, H, and halogens.

[0008] In the hydrophobic coating of the present invention, preferably, the alcohol compound is an aliphatic monohydric alcohol and the organic acid is an aliphatic organic acid.

[0009] In the hydrophobic coating of the present invention, preferably, the nanofibers have a diameter of 4–200 nm and a length of 5–15 μm.

[0010] According to the hydrophobic coating of the present invention, preferably, the fly ash is decarbonized fly ash; The decarbonized fly ash is prepared by the following method: the fly ash is decarbonized at 700-900℃ to obtain the decarbonized fly ash.

[0011] According to the hydrophobic coating of the present invention, preferably, in formula (I), R1 to R4 are independently selected from C1 to C3 alkyl groups and C1 to C3 alkoxy groups; and at least three of R1 to R4 are C1 to C3 alkoxy groups; In formula (II), R5 to R8 are independently selected from C1 to C3 alkyl groups, C1 to C3 alkoxy groups, and halogens, and at least three of R5 to R8 are C1 to C3 alkyl groups; In formula (III), R9~R 14 Alkyl groups selected independently from C1 to C3.

[0012] In the hydrophobic coating of the present invention, preferably, the alcohol compound is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol; The organic acid is selected from one or more of formic acid, acetic acid, propionic acid, citric acid, oxalic acid, malonic acid, succinic acid, and glutaric acid.

[0013] In the hydrophobic coating of the present invention, preferably, the alkoxysilane is selected from one or more of methyltriethoxysilane and tetraethyl orthosilicate; The silicon-containing substance is selected from one or more of hexamethyldisilazane, trimethylethoxysilane, and trimethylchlorosilane.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned hydrophobic coating, comprising the following steps: A hydrophobic coating is obtained by mixing raw materials including organic acid solution, fly ash, nanofibers and silicon-containing substances.

[0015] According to the preparation method of the present invention, preferably, it includes the following steps: An organic acid solution is obtained by stirring an alcohol compound, an alkoxysilane, an organic acid, and water for 2–10 hours. The organic acid solution, fly ash, and nanofibers are then stirred for 0.5–5 hours, followed by the addition of a silicon-containing substance and stirring for another 0.5–5 hours to obtain a hydrophobic coating.

[0016] In another aspect, the present invention provides a method for preparing a hydrophobic coating, comprising the following steps: applying the above-mentioned hydrophobic coating onto the surface of a substrate, and then drying it at 20 to 400°C to obtain a hydrophobic coating.

[0017] The hydrophobic coating of this invention possesses excellent hydrophobic and heat-resistant properties, and can be used in fields such as antibacterial, antifouling, self-cleaning, anti-corrosion, oil-water separation, and anti-icing. Furthermore, the hydrophobic coating of this invention exhibits excellent adhesion. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0019] hydrophobic coatings The hydrophobic coating of the present invention is prepared from raw materials including an organic acid solution, fly ash, nanofibers, and a silicon-containing substance. Preferably, the raw materials of the present invention do not contain resin materials. The resin materials may be selected from one or more of alkyd resins, epoxy resins, acrylic resins, amino resins, and polyurethane resins. In some embodiments, the raw materials consist of an organic acid solution, fly ash, nanofibers, and a silicon-containing substance.

[0020] The hydrophobic coating of this invention is obtained from the aforementioned raw materials through a hydrolysis reaction. Alkoxysilanes in an organic acid solution hydrolyze under appropriate conditions to form chain-like silica sol particles. These silica sol particles adhere to the surface of fly ash, and nanofibers are randomly inserted into the fly ash or silica sol particles. Silicon-containing substances are grafted onto the above structure through hydrolysis and condensation, further reducing the surface energy and achieving superhydrophobic properties.

[0021] The organic acid solution of the present invention comprises an alcohol compound, an alkoxysilane, an organic acid, and water. Preferably, the organic acid solution is composed of an alcohol compound, an alkoxysilane, an organic acid, and water.

[0022] Alcohols contain 1 to 6 carbon atoms; preferably, they contain 1 to 4 carbon atoms. Preferably, the alcohol is a monohydric alcohol. Preferably, the alcohol is an aliphatic compound.

[0023] Examples of alcohol compounds include, but are not limited to, one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol. Preferably, the alcohol compound is selected from one or more of methanol, ethanol, n-propanol, and n-butanol. According to one embodiment of the present invention, the alcohol compound is ethanol.

[0024] Alkoxysilanes are shown in formula (I): (I).

[0025] R1 to R4 are each independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens. Preferably, R1 to R4 are each independently selected from C1 to C3 alkyl groups and C1 to C3 alkoxy groups.

[0026] Examples of halogens include, but are not limited to, fluorine, chlorine, bromine, and iodine.

[0027] Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 2-ethylpropyl, 2,3-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylbutyl, and 2,2-dimethylbutyl.

[0028] Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, 2-methylbutoxy, 3-methylbutoxy, 1-ethylpropoxy, 2-ethylpropoxy, 2,3-dimethylpropoxy, 2,2-dimethylpropoxy, n-hexoxy, 2-methylpentoxy, 3-methylpentoxy, 2,3-dimethylbutoxy, and 2,2-dimethylbutoxy.

[0029] At least two of R1 to R4 are alkoxy groups; preferably, at least three of R1 to R4 are alkoxy groups. In some embodiments, all of R1 to R4 are alkoxy groups.

[0030] The alkoxysilane may be selected from one or more of methyltriethoxysilane and tetraethyl orthosilicate. In some embodiments, the alkoxysilane is methyltriethoxysilane. In other embodiments, the alkoxysilane is tetraethyl orthosilicate.

[0031] The mass ratio of alcohol compound to alkoxysilane is 10:(1-10); preferably 10:(4-9); more preferably 10:(7-8).

[0032] The organic acid contains 1 to 10 carbon atoms; preferably, the organic acid contains 1 to 6 carbon atoms. In some embodiments, the organic acid contains 1 to 3 carbon atoms.

[0033] The organic acid is preferably an aliphatic carboxylic acid. The organic acid can be a monocarboxylic acid or a polycarboxylic acid. For example, dicarboxylic acids and tricarboxylic acids.

[0034] The organic acid may be selected from one or more of formic acid, acetic acid, propionic acid, citric acid, oxalic acid, malonic acid, succinic acid, and glutaric acid. Preferably, the organic acid is selected from one or more of acetic acid, citric acid, and oxalic acid. According to one embodiment of the present invention, the organic acid is acetic acid.

[0035] The mass ratio of alcohol to organic acid can be 10:(0.005-2); preferably 10:(0.02-1.5); more preferably 10:(0.04-1.2). In some embodiments, the mass ratio of alcohol to organic acid is 10:(0.08-1).

[0036] The mass ratio of alcohol to water can be 10: (0.5 to 2); preferably 10: (0.8 to 1.5); more preferably 10: (0.9 to 1.2).

[0037] The organic acid solution described above helps to form a silica sol of appropriate form, thereby improving the hydrophobic properties and high-temperature resistance of the hydrophobic coating.

[0038] The amount of organic acid solution used is 7 to 13 parts by weight; preferably 9 to 12 parts by weight; more preferably 10 to 11 parts by weight.

[0039] The median particle size of fly ash can be 1.0–10.0 μm; preferably 2–8 μm; more preferably 3–7 μm. This helps to improve the hydrophobic properties of the coating.

[0040] The SiO2 content in fly ash is ≥45wt%. According to one embodiment of the present invention, the SiO2 content in fly ash is 47-50wt%. This helps to improve the heat resistance of the coating.

[0041] The fly ash is preferably decarbonized fly ash. The fly ash can be decarbonized at 700–900℃ to obtain decarbonized fly ash. Preferably, the decarbonization treatment is carried out at a temperature of 750–850℃. The decarbonization treatment time can be 2–6 hours; preferably 3–4 hours. The decarbonization treatment is carried out in an air atmosphere.

[0042] The amount of fly ash can be 0.05 to 0.9 parts by weight; preferably 0.08 to 0.6 parts by weight; more preferably 0.1 to 0.4 parts by weight. In some embodiments, the amount of fly ash is 0.12 to 0.2 parts by weight. This helps to improve the hydrophobic and heat-resistant properties of the coating.

[0043] Nanofibers can be selected from one or more of carbon nanofibers and cellulose nanofibers. Preferably, the nanofibers are carbon nanofibers.

[0044] The diameter of the nanofibers can be 4–200 nm; preferably 10–100 nm; more preferably 15–50 nm. The length of the nanofibers can be 5–15 μm; preferably 5–10 μm; more preferably 3–7 μm. This helps to improve the hydrophobic properties of the coating.

[0045] The amount of nanofibers used can be 0.005 to 0.1 parts by weight; preferably 0.01 to 0.08 parts by weight; more preferably 0.02 to 0.05 parts by weight. This helps to improve the hydrophobic and heat-resistant properties of the coating.

[0046] The silicon-containing substance is selected from one or more of the compounds shown in formulas (II) to (III): (II); (III).

[0047] In formula (II), R5 to R8 are each independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens. Preferably, R5 to R8 are each independently selected from C1 to C3 alkyl groups, C1 to C3 alkoxy groups, and halogens.

[0048] At least two of R5 to R8 are alkyl groups; preferably, at least three of R5 to R8 are alkyl groups.

[0049] In formula (III), R9~R 14 Alkyl groups, H, and halogens, each independently selected from C1 to C6; preferably, R9 to R 14 Alkyl groups selected independently from C1 to C3.

[0050] Examples of halogens include, but are not limited to, fluorine, chlorine, bromine, and iodine.

[0051] Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 2-ethylpropyl, 2,3-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylbutyl, and 2,2-dimethylbutyl.

[0052] Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, 2-methylbutoxy, 3-methylbutoxy, 1-ethylpropoxy, 2-ethylpropoxy, 2,3-dimethylpropoxy, 2,2-dimethylpropoxy, n-hexoxy, 2-methylpentoxy, 3-methylpentoxy, 2,3-dimethylbutoxy, and 2,2-dimethylbutoxy.

[0053] The silicon-containing substance may be selected from one or more of hexamethyldisilazane, trimethylethoxysilane, and trimethylchlorosilane. Preferably, the silicon-containing substance is selected from one or more of hexamethyldisilazane and trimethylethoxysilane. More preferably, the silicon-containing substance is hexamethyldisilazane.

[0054] The aforementioned silicon-containing substances help improve the waterproof and heat-resistant properties of coatings.

[0055] The amount of silicon-containing material can be 0.5 to 5 parts by weight; preferably 0.8 to 3 parts by weight; more preferably 1 to 1.2 parts by weight. This helps to improve the waterproof and heat-resistant properties of the coating.

[0056] Preparation method of hydrophobic coating The preparation method of the hydrophobic coating of the present invention includes the following steps: mixing raw materials including organic acid solution, fly ash, nanofibers and silicon-containing substances to obtain the hydrophobic coating. The composition of the raw materials is as described above and will not be repeated here.

[0057] Specifically, the process includes the following steps: stirring an alcohol compound, an alkoxysilane, an organic acid, and water to obtain an organic acid solution; stirring the organic acid solution, fly ash, and nanofibers, and then adding a silicon-containing substance and stirring to obtain a hydrophobic coating.

[0058] The stirring time for alcohol compounds, alkoxysilanes, organic acids and water can be 2 to 10 hours; preferably 3 to 9 hours; more preferably 5 to 8 hours.

[0059] The stirring time for the organic acid solution, fly ash, and nanofibers can be 0.5 to 5 hours; preferably 1 to 3 hours; more preferably 1 to 2 hours.

[0060] The stirring time after adding the silicon-containing substance can be 0.5 to 5 hours; preferably 1 to 4 hours; more preferably 2 to 3 hours.

[0061] Preparation method of hydrophobic coating The method for preparing the hydrophobic coating of the present invention includes the following steps: applying a hydrophobic coating to the surface of a substrate, and then drying it at 20–400°C to obtain the hydrophobic coating. The hydrophobic coating has been described above and will not be repeated here. The hydrophobic coating of the present invention has excellent heat resistance, and the hydrophobic coating formed after drying at high temperatures still retains good hydrophobic properties.

[0062] The substrate can be selected from one or more of glass, fabric, filter paper, aluminum alloy, and plastic. According to one embodiment of the invention, the substrate is glass. The hydrophobic coating of the present invention has a wide range of applications and is universally applicable.

[0063] The drying temperature is 20–400°C; preferably 100–400°C; more preferably 200–400°C. In some embodiments, the drying temperature is 120–200°C.

[0064] The drying time can be 1 to 50 hours; preferably 1 to 20 hours; more preferably 1 to 5 hours. The hydrophobic coating of the present invention can dry rapidly at high temperatures, making it easy to use.

[0065] The test methods used in the following embodiments are as follows: Contact angle: The CA200 contact angle measuring instrument manufactured by Guangdong Beidou Precision Instruments Co., Ltd. was used for testing. The specific method is as follows: A 3 μL water droplet was selected. The coating sample was placed on the lifting platform. After pressing the "droplet" button, the lifting platform with the coating sample was raised so that the coating surface came into contact with the water droplet, and then the lifting platform was lowered. After 3 seconds, the page on the computer was frozen, and the contact angle was measured at this time. The above operation was repeated at 3 different locations on the surface of the coating sample. When the contact angle measurement was completed, the arithmetic mean of the 3 data obtained was taken, and this value was the contact angle value of the coating sample.

[0066] Roll-off angle: Place the coating sample flat on a rotatable platform and calibrate the reference surface with a level; deposit a 3μL water droplet at the center of the coating sample surface; slowly increase the platform tilt angle at a rate of 0.5 to 2° / s; record the platform tilt angle reading immediately when the water droplet begins to roll; repeat the test 3 times at different positions on the coating sample and take the arithmetic mean as the final roll-off angle.

[0067] Maximum heat resistance temperature: Tested according to the method specified in GB / T 1735-2009 Determination of heat resistance of paints and varnishes. A glass slide is used as the substrate, and a muffle furnace is used for the high-temperature test.

[0068] Adhesion rating: Tested according to the method specified in GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method". A glass slide is used as the substrate.

[0069] Preparation Example Fly ash was subjected to decarbonization treatment at 750℃ for 4 hours in air atmosphere to obtain decarbonized fly ash (volume median particle size of 3.4μm and SiO2 content of 47wt%).

[0070] Examples 1-10 An alcohol compound, alkoxysilane, organic acid, and water were stirred and mixed for 6 hours to obtain 10 parts by weight of an organic acid solution. Decarbonized fly ash and carbon nanofibers (50 nm in diameter and 7 μm in length) were added to the organic acid solution and stirred and mixed for 1 hour. Then, a silicon-containing substance was added and stirred and mixed for 2 hours to obtain a hydrophobic coating.

[0071] The types and masses of alcohols, alkoxysilanes, and organic acids are shown in Table 1. The types of silicon-containing substances and the amounts of decarbonized fly ash, carbon nanofibers, and silicon-containing substances are shown in Table 2.

[0072] The maximum heat resistance temperature and adhesion grade of hydrophobic coatings are shown in Table 3.

[0073] Examples 11-20 A hydrophobic coating was applied to the surface of a glass slide using an impregnation method, and then dried at 120°C for 1 hour to obtain the hydrophobic coating. The selection of the hydrophobic coating and the contact angle and roll-off angle of the hydrophobic coating are shown in Table 4.

[0074] As shown in Tables 3 and 4, the hydrophobic coating of the present invention exhibits excellent hydrophobic properties and good heat resistance. Comparing Examples 1 and 2, it is evident that the amount of fly ash significantly affects the contact angle, roll-off angle, and maximum heat resistance temperature of the hydrophobic coating. Comparing Examples 2 and 3, it is evident that the amount of alkoxysilane significantly affects the contact angle, roll-off angle, and maximum heat resistance temperature of the hydrophobic coating. Comparing Examples 4 and 5, it is evident that the amount of organic acid affects the contact angle, roll-off angle, and maximum heat resistance temperature of the hydrophobic coating.

[0075] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A hydrophobic coating, characterized in that, The hydrophobic coating is prepared from raw materials comprising the following components: 7-13 parts by weight of organic acid solution; 0.05–0.9 parts by weight of fly ash; Nanofibers: 0.005–0.1 parts by weight; 0.5 to 5 parts by weight of silicon-containing material; The organic acid solution comprises an alcohol compound containing 1 to 6 carbon atoms, an alkoxysilane, an organic acid containing 1 to 10 carbon atoms, and water, wherein the mass ratio of the alcohol compound, alkoxysilane, organic acid, and water is 10:(1 to 10):(0.005 to 2):(0.5 to 2). The alkoxysilane is as shown in formula (I): （I）； R1 to R4 are independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens, and at least two of R1 to R4 are C1 to C6 alkoxy groups; The silicon-containing material is selected from one or more compounds represented by formulas (II) to (III); (II); R5 to R8 are independently selected from C1 to C6 alkyl groups, C1 to C6 alkoxy groups, H, and halogens, and at least two of R5 to R8 are C1 to C6 alkyl groups; (III); Among them, R9~R 14 Each is independently selected from C1 to C6 alkyl groups, H, and halogens.

2. The hydrophobic coating according to claim 1, characterized in that, The alcohols are aliphatic monohydric alcohols, and the organic acids are aliphatic organic acids.

3. The hydrophobic coating according to claim 1, characterized in that, The nanofibers have a diameter of 4–200 nm and a length of 5–15 μm.

4. The hydrophobic coating according to claim 1, characterized in that, The fly ash is fly ash after carbon removal; The decarbonized fly ash is prepared by the following method: the fly ash is decarbonized at 700-900℃ to obtain the decarbonized fly ash.

5. The hydrophobic coating according to claim 1, characterized in that: In formula (I), R1 to R4 are independently selected from C1 to C3 alkyl groups and C1 to C3 alkoxy groups, respectively; and at least three of R1 to R4 are C1 to C3 alkoxy groups. In formula (II), R5 to R8 are independently selected from C1 to C3 alkyl groups, C1 to C3 alkoxy groups, and halogens, and at least three of R5 to R8 are C1 to C3 alkyl groups; In formula (III), R9~R 14 Alkyl groups selected independently from C1 to C3.

6. The hydrophobic coating according to claim 1, characterized in that, The alcohol compounds are selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol; The organic acid is selected from one or more of formic acid, acetic acid, propionic acid, citric acid, oxalic acid, malonic acid, succinic acid, and glutaric acid.

7. The hydrophobic coating according to claim 1, characterized in that, The alkoxysilane is selected from one or more of methyltriethoxysilane and tetraethyl orthosilicate; The silicon-containing substance is selected from one or more of hexamethyldisilazane, trimethylethoxysilane, and trimethylchlorosilane.

8. The method for preparing the hydrophobic coating according to any one of claims 1 to 7, characterized in that, Includes the following steps: A hydrophobic coating is obtained by mixing raw materials including organic acid solution, fly ash, nanofibers and silicon-containing substances.

9. The preparation method according to claim 8, characterized in that, Includes the following steps: An organic acid solution is obtained by stirring an alcohol compound, an alkoxysilane, an organic acid, and water for 2–10 hours. The organic acid solution, fly ash, and nanofibers are then stirred for 0.5–5 hours, followed by the addition of a silicon-containing substance and stirring for another 0.5–5 hours to obtain a hydrophobic coating.

10. A method for preparing a hydrophobic coating, characterized in that, The process includes the following steps: applying the hydrophobic coating according to any one of claims 1 to 7 to the surface of the substrate, and then drying it at 20 to 400°C to obtain a hydrophobic coating.

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