Novel fluoride-free super-hydrophobic nano coating and preparation method thereof

Abstract

The invention provides a novel fluoride-free super-hydrophobic nano coating and a preparation method thereof, and relates to the field of nano materials. The nano coating comprises modified silicon dioxide aerogel, a first solvent, a binder and an auxiliary agent; the modified silicon dioxide aerogel is obtained by carrying out surface modification on silicon dioxide aerogel particles through polyether siloxane. The preparation method comprises the following steps: preparing silicon dioxide aerogel particles and polyether siloxane; the preparation method comprises the following steps: grafting polyether siloxane to the surfaces of silicon dioxide aerogel particles to obtain modified silicon dioxide aerogel; dispersing the modified silicon dioxide aerogel into a first solvent, adding a binder and an auxiliary agent, and uniformly mixing to obtain a nano coating; and uniformly coating the nano coating on the surface of the base material to form the nano coating. The modified silicon dioxide aerogel particles not only endow the coating with excellent super-hydrophobic and oleophobic properties and realize rolling and falling of water drops and oil drops on the surface of the coating, so that the anti-fouling and self-cleaning purposes are achieved, but also the excellent high temperature resistance and insulating properties of the coating are ensured.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials, and particularly to a novel fluorine-free superhydrophobic nanocoating and a preparation method thereof. Background Art

[0002] In today's industrial field, working environments with high temperature, high humidity, and easy contamination pose extremely high requirements for the weather resistance of materials. Traditional coating materials, such as organic coatings, are often prone to aging and decomposition at high temperatures, resulting in a decline in insulation performance, and insufficient hydrophobic and oleophobic properties, being easily contaminated by oil stains and dust, requiring frequent maintenance, and increasing operating costs. Although fluorine-containing coatings have excellent hydrophobic and oleophobic properties, the fluorine-containing compounds generated during their production and use pose a serious threat to the environment and have been increasingly restricted.

[0003] Currently, for insulating, hydrophobic, oleophobic, anti-fouling, and self-cleaning coatings used in high-temperature environments, the following problems mainly exist: insufficient high-temperature stability, many organic coatings are easily decomposed and aged at high temperatures, resulting in performance degradation; poor hydrophobic and oleophobic properties, it is difficult to effectively prevent the adhesion of oil stains and dust, affecting the operating efficiency of equipment; environmental pollution problems, the use of fluorine-containing coatings poses potential hazards to the environment; high preparation costs; the preparation processes of some nanocoating materials are complex and costly, making it difficult to be applied on a large scale.

[0004] Therefore, developing a coating material that can withstand high temperatures, be insulating, hydrophobic, oleophobic, anti-fouling, and self-cleaning, and is also environmentally friendly and non-toxic has become an important direction in current materials science research. Summary of the Invention

[0005] In view of the above problems, embodiments of the present invention are proposed to provide a novel fluorine-free superhydrophobic nanocoating and a preparation method thereof that can overcome the above problems or at least partially solve the above problems.

[0006] A novel fluorine-free superhydrophobic nanocoating includes modified silica aerogel, a first solvent, a binder, and an additive;

[0007] The modified silica aerogel is obtained by surface modification of silica aerogel particles with polyether siloxane.

[0008] Preferably, the additive includes a dispersant, a leveling agent, an antifoaming agent, an ultraviolet absorber, and an antioxidant.

[0009] Preferably, by weight parts, the nanocoating includes 40 - 60 parts of modified silica aerogel, 30 - 40 parts of the first solvent, 5 - 10 parts of the binder, 0.5 - 2 parts of the dispersant, 0.1 - 1 part of the leveling agent, 0.1 - 1 part of the antifoaming agent, 0.1 - 0.5 part of the ultraviolet absorber, and 0.1 - 0.5 part of the antioxidant.

[0010] A preparation method of the nano - coating as described above, comprising the following steps:

[0011] Prepare silica aerogel particles and polyether siloxane;

[0012] Graft polyether siloxane onto the surface of silica aerogel particles to obtain modified silica aerogel;

[0013] Disperse the modified silica aerogel into a first solvent, and add a binder and an auxiliary agent and mix evenly to prepare a nano - coating;

[0014] Uniformly coat the nano - coating on the surface of a substrate to form a nano - coating.

[0015] Preferably, the step of preparing silica aerogel particles includes:

[0016] Dissolve a silane precursor in a second solvent, and add a first catalyst, and carry out hydrolysis and polycondensation reactions at a first reaction temperature and a first reaction time to form a sol;

[0017] Let the sol stand until a gel is formed;

[0018] Carry out aging treatment and drying treatment on the gel to obtain silica aerogel particles.

[0019] Preferably, the volume ratio of the silane precursor to the second solvent is 1:4 - 6; the first reaction temperature is 20 - 50 °C, and the first reaction time is 2 - 6 h.

[0020] Preferably, the particle size of the silica aerogel particles is 10 nm - 10 μm, and the pore size is 2 nm - 50 nm.

[0021] Preferably, the step of grafting polyether siloxane onto the surface of silica aerogel particles to obtain modified silica aerogel includes:

[0022] Disperse silica aerogel particles into a third solvent to obtain a dispersion solution;

[0023] Add a silane coupling agent with a functional group to the dispersion solution to carry out a preliminary reaction to obtain a reaction solution;

[0024] Add polyether siloxane and a second catalyst to the reaction solution and stir at a second reaction temperature for a second reaction time to obtain a modified solution;

[0025] Carry out separation, washing and drying on the modified solution to obtain modified silica aerogel.

[0026] Preferably, the reaction concentration of the silane coupling agent is 1 - 5%; the reaction concentration of the polyether siloxane is 5 - 15%;

[0027] The mass ratio of the silica aerogel particles to the polyether siloxane is 1:0.2 - 0.5;

[0028] The second reaction temperature is 20 - 50 °C, and the second reaction time is 1 - 4 h.

[0029] Preferably, the polyether siloxane is obtained by copolymerizing epoxy long-chain alkanes and polydimethylsiloxane, and the polyether siloxane is a hydroxyl-terminated polyether siloxane or an amino-terminated polyether siloxane.

[0030] The present application specifically includes the following advantages:

[0031] In the embodiments of the present application, the embodiments of the present application surface-modify silica aerogel particles with polyether siloxane to prepare modified silica aerogel and apply it to the coating formulation, thereby endowing the coating with significant performance advantages and achieving breakthroughs in multiple key technical indicators. Specifically, the modified silica aerogel endows the coating with excellent hydrophobic and oleophobic properties, significantly reduces the surface tension, effectively prevents the infiltration and adhesion of liquid contaminants, and thus improves the self-cleaning ability and stain resistance of the coating. In addition, the inherently low thermal conductivity of silica aerogel itself enables the coating to have good high-temperature resistance characteristics, be able to withstand high-temperature environments without easy decomposition or deterioration, and improves the long-term stability of the coating. The addition of aerogel can also enhance the friction resistance performance of the coating, increase its hardness and toughness, and thus extend the service life. Furthermore, silica itself is an excellent insulating material, which helps to improve the electrical insulation performance of the coating and expand its application in the field of electronics and electricity. Compared with traditional fluorine-based hydrophobic and oleophobic materials, the modified silica aerogel used in the present application has the advantages of being fluorine-free and environmentally friendly, meeting the increasingly strict environmental protection regulations and the concept of sustainable development. Finally, by optimizing the formulation and selecting suitable raw materials, the present application strives to reduce the production cost while ensuring excellent performance, making the coating more competitive in the market. Generally speaking, the nano-coating solution proposed in the present application has significant advantages in terms of hydrophobicity and oleophobicity, high temperature resistance, friction resistance, insulation, fluorine-free environmental protection, and low cost, and is expected to promote the development and application of nano-coating technology. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions of the present application, the drawings required for use in the description of the present application will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a process flow chart of the preparation method of the novel fluorine-free superhydrophobic nano-coating of the present invention. Specific Embodiments

[0034] To make the above - mentioned objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0035] Specifically, it may include the following structures: modified silica aerogel, a first solvent, a binder, and an additive.

[0036] The modified silica aerogel is obtained by surface - modifying silica aerogel particles with polyether siloxane.

[0037] In the embodiments of the present application, due to the high specific surface area and low density of silica aerogel, silica aerogel particles form a micro - nano structure in the coating, increasing the surface roughness, thereby enhancing the hydrophobic and oleophobic effects; using polyether siloxane - surface - modified silica aerogel particles as the main functional filler, supplemented with a binder and an additive for compounding, and utilizing the hydrophobicity and weather resistance of polyether siloxane, it has excellent hydrophobic and oleophobic properties and improves the weather resistance of the coating; by combining silica aerogel and polyether siloxane to form a synergistic effect, giving full play to the advantages of both, the performance of the coating is improved. The modified silica aerogel particles not only endow the coating with excellent super - hydrophobic and oleophobic properties, effectively reducing the surface energy and enabling water droplets and oil droplets to roll off on its surface, thus achieving the purpose of anti - fouling and self - cleaning, but also the introduction of modified polyether siloxane ensures good insulation performance of the coating. And this technical solution avoids the use of any fluorine - containing materials, reducing the risk of environmental pollution. Moreover, due to the good high - temperature resistance of silica aerogel itself, the prepared nano - coating can maintain the stability of its structure and performance in a high - temperature environment, achieving a good non - fluorine high - temperature anti - fouling nano - coating effect, having broad application prospects.

[0038] Next, a new non - fluorine super - hydrophobic nano - coating in this exemplary embodiment will be further described.

[0039] It should be noted that silica aerogel has attracted much attention due to its extremely low density, high specific surface area, low thermal conductivity, and good chemical stability. However, the surface of unmodified silica aerogel is rich in hydroxyl groups and has hydrophilicity, which limits its application in the field of hydrophobic and oleophobic.

[0040] Polyether siloxane is a commonly used organosilicon polymer obtained by polymerizing polydimethylsiloxane and alkylene oxide, having good hydrophobicity, weather resistance, and biocompatibility.

[0041] In the embodiments of the present application, surface modification of silica aerogel particles with polyether siloxane to obtain modified silica aerogel can endow it with excellent hydrophobic and oleophobic properties, making it have great application potential in the coating field.

[0042] As an example, the above-mentioned additives include dispersants, leveling agents, defoamers, ultraviolet absorbers, and antioxidants.

[0043] Specifically, the above-mentioned solvent can be ethanol or isopropanol, the binder can be polyurethane resin, the dispersant can be polyvinyl alcohol, the leveling agent can be polydimethylsiloxane or polyacrylic acid, the defoamer can be polyether or silicone defoamer, the ultraviolet absorber can be hydroxybenzoate or benzophenone, and the antioxidant can be butylated hydroxytoluene or tris(hydroxymethyl)aminomethane. Mix the above components evenly to obtain a coating to improve the performance of the coating and the durability of the coating.

[0044] As an example, by weight, the nano-coating includes 40-60 parts of modified silica aerogel, 30-40 parts of the first solvent, 5-10 parts of the binder, 0.5-2 parts of the dispersant, 0.1-1 part of the leveling agent, 0.1-1 part of the defoamer, 0.1-0.5 part of the ultraviolet absorber, and 0.1-0.5 part of the antioxidant.

[0045] Preferably, it includes 50 parts of modified silica aerogel, 40 parts of the first solvent, 5 parts of the binder, 1 part of the dispersant, 0.5 part of the leveling agent, 0.5 part of the defoamer, 0.2 part of the ultraviolet absorber, and 0.3 part of the antioxidant.

[0046] Referring to Figure 1 , the embodiments of the present application also provide a preparation method of a nano-coating, including the following steps:

[0047] S110. Prepare silica aerogel particles and polyether siloxane;

[0048] S120. Graft polyether siloxane onto the surface of silica aerogel particles to obtain modified silica aerogel;

[0049] S130. Disperse the modified silica aerogel into the first solvent, and add a binder and additives and mix evenly to prepare a nano-coating;

[0050] S140. Uniformly coat the nano-coating on the surface of the substrate to form a nano-coating.

[0051] As an example, in step S110, the steps of preparing silica aerogel particles include: dissolving a silane precursor, preferably tetraethoxysilane (TEOS) or tetramethyl orthosilicate (TMOS), in a second solvent, preferably ethanol or isopropanol, where the volume ratio of the silane precursor to the second solvent is 1:4 - 6; and adding a first catalyst, preferably under the catalytic action of a volume ratio of deionized water to a base (ammonia water or diethylamine) of 1:0.1 - 0.3, to carry out hydrolysis and polycondensation reactions at a reaction temperature of 20 - 50 °C for a reaction time of 2 - 6 hours to finally form a sol; allowing the sol to stand for 2 - 24 hours to gelate it; subjecting the gel to an aging treatment to improve its mechanical strength; and removing the solvent in the gel by methods such as supercritical drying or atmospheric drying to obtain silica aerogel particles.

[0052] It should be noted that in the process of preparing silica aerogel particles by the above sol - gel method, by controlling the reaction conditions, including but not limited to the concentration of reactants, the type and concentration of the catalyst, the reaction temperature, the aging time, etc., the particle size and pore structure of the aerogel particles are adjusted so that the particle size range is from 10 nanometers to 10 micrometers and the pore size range is from 2 nanometers to 50 nanometers to obtain the best coating properties, including but not limited to superhydrophobicity, oleophobicity, and mechanical properties.

[0053] As an example, in step S110, the polyether siloxane is prepared by copolymerizing an epoxy long - chain alkane (epoxyoctane or epoxyhexadecane) with polydimethylsiloxane. Under an inert atmosphere (such as nitrogen or argon), the epoxy alkane and polydimethylsiloxane (molar ratio of 1:1) are mixed in a reaction kettle, heated at a high temperature with a reaction temperature of 70 - 100 °C, and the reaction is maintained for 2 - 4 hours to promote the polymerization of the epoxy component and polydimethylsiloxane. A certain amount of catalyst (such as 1 - 5 wt% basic or acidic catalyst) is added to accelerate the reaction, and finally, after reprecipitation purification, the modified polyether siloxane is obtained.

[0054] As an example, in step S120, the step of grafting polyether siloxane onto the surface of silica aerogel particles to obtain modified silica aerogel includes: dispersing silica aerogel particles into a third solvent, preferably toluene or xylene, to obtain a dispersion solution. Adding a silane coupling agent with functional groups, preferably (3-aminopropyl)triethoxysilane or (3-allyl)triethoxysilane, with a reaction concentration of 1-5 wt%, to carry out a preliminary reaction, so that the silane coupling agent is adsorbed on the surface of silica aerogel particles to obtain a reaction solution. Adding polyether siloxane with a reaction concentration of 5-15 wt%, preferably hydroxyl-terminated or amino-terminated polyether siloxane, to the reaction solution, where the mass ratio of silica aerogel to polyether siloxane is 1:0.2-0.5. Under the action of a suitable catalyst (such as stannous octoate or dibutyltin dilaurate or tetrabutyl titanate, with an addition amount of 1-5 wt% of the mass of polyether siloxane), the polyether siloxane reacts with the silane coupling agent, thereby grafting onto the surface of silica aerogel particles. The reaction temperature is 20-50 °C, and stirring is carried out for 1-4 hours. After the reaction, the polyether siloxane-modified silica aerogel particles are separated, washed, and dried.

[0055] It should be noted that the grafting amount of the above polyether siloxane is adjusted by controlling factors such as the ratio of reactants, reaction time, and reaction temperature, so as to form a hydrophobic and oleophobic organic layer on the surface of silica aerogel particles, thereby adjusting the hydrophobic and oleophobic properties of the aerogel particles and ensuring that the coating has good superhydrophobicity and oleophobicity.

[0056] As an example, in step S140, the nano-coating is uniformly coated on the surface of the substrate to form a nano-coating. Specifically, the surface of the substrate is pretreated, such as cleaning, degreasing, sanding, etc., to improve the adhesion of the coating; spraying, dipping, spin-coating, brushing, or scraping processes are used to uniformly coat the coating on the surface of the substrate to form a coating. The coating is cured to firmly bond it to the substrate. Among them, the substrate includes but is not limited to metals, glass, ceramics, plastics, wood, fabrics, etc.

[0057] Preferably, the spraying process uses air spraying, airless spraying, or electrostatic spraying and other methods to control the spraying pressure, the moving speed of the spray gun, and the spraying amount of the coating to obtain a uniform coating thickness.

[0058] The curing process refers to the cross-linking reaction of the binder in the coating at a certain temperature and time to form a firm coating. The curing temperature is selected according to the type of binder, such as room temperature curing, heat curing, or ultraviolet curing, etc.

[0059] Example 1

[0060] The following are the specific experimental steps for the preparation of silica aerogel particles, the synthesis of polyether siloxane, the surface modification of polyether siloxane, the preparation of the coating, and the coating curing:

[0061] Preparation of silica aerogel particles: TEOS is dissolved in anhydrous ethanol to prepare a TEOS solution, where TEOS:ethanol = 1:4 (volume ratio). Deionized water and ammonia water are mixed at a volume ratio of deionized water:ammonia water = 1:0.2 to prepare a catalyst solution. Under stirring conditions, the catalyst solution is slowly added to the TEOS solution for hydrolysis and polycondensation reactions. The reaction temperature is 25°C, and the reaction time is 3 hours. After standing for 12 hours, a gel is formed. The gel is subjected to solvent exchange in ethanol to remove impurities. The gel is dried using supercritical drying or atmospheric drying methods to obtain silica aerogel particles.

[0062] Preparation of polyether siloxane: Under the protection of an inert atmosphere of nitrogen, epoxy octane and polydimethylsiloxane (molar ratio 1:1) are mixed in a reaction kettle, heated at a high temperature of 80°C, and the reaction is maintained for 3 hours to promote the polymerization of the epoxy component and polydimethylsiloxane. A certain amount of catalyst (such as 1 wt% ammonia water) is added to accelerate the reaction. Finally, after reprecipitation purification, modified polyether siloxane is obtained.

[0063] Modification of silica aerogel: The silica aerogel particles are dispersed in toluene and subjected to ultrasonic dispersion. The corresponding silane coupling agent, (3-allyl)triethoxysilane, is added, and the reaction concentration is 2 wt%. Under the catalytic condition of 1 wt% p-toluenesulfonic acid, a preliminary pre-reaction is carried out. Then, polyether siloxane with terminal hydroxyl groups is added, and the reaction concentration is 10 wt%. Under the action of 1 wt% stannous octoate catalyst, the surface modification reaction of silica aerogel particles is carried out again. The polyether siloxane solution is gradually added to the nano-silica aerogel, where the mass ratio of silica aerogel to polyether siloxane is 1:0.2. A mechanical stirrer is used for stirring, the reaction temperature is 25°C, and stirring is carried out for 2 hours to ensure that the polyether siloxane is evenly dispersed on the surface of the aerogel. The polyether siloxane reacts with the hydroxyl groups on the surface of the silica aerogel to form chemical bonding. After the reaction, the modified silica aerogel particles are washed with toluene to remove the unreacted polyether siloxane. Vacuum drying is carried out to obtain the modified silica aerogel particles.

[0064] Coating Preparation: Disperse polyether-siloxane modified silica aerogel particles in a solvent and perform ultrasonic dispersion. Add a binder and other additives, and stir evenly. Adjust the viscosity and solid content of the coating to meet the coating requirements. The specific addition amounts of each component are as follows: polyether-siloxane modified silica aerogel is 50 wt%; solvent (isopropyl alcohol) is 40 wt%; binder (polyurethane resin) is 5 wt%; dispersant (polyvinyl alcohol) is 1 wt%; leveling agent (polydimethylsiloxane) is 0.5 wt%; defoamer (silicone defoamer) is 0.5 wt%; ultraviolet absorber (benzophenone) is 0.2 wt%; antioxidant (butylated hydroxytoluene) is 0.3 wt%.

[0065] Uniformly coat the coating on the surface of the substrate and control the thickness of the coating. Carry out curing treatment on the coating to make it firmly bonded to the substrate. The curing conditions are selected according to the type and characteristics of the binder.

[0066] Example 2

[0067] The following details the specific experimental steps for the preparation of silica aerogel particles, the synthesis of polyether-siloxane, the surface modification of polyether-siloxane, the coating preparation, and the coating curing:

[0068] Preparation of Silica Aerogel Particles: Dissolve TEOS in absolute ethanol to prepare a TEOS solution, where TEOS:ethanol = 1:5 (volume ratio). Mix deionized water and diethylamine according to the volume ratio of deionized water:diethylamine = 1:0.1 to prepare a catalyst solution. Under stirring conditions, slowly add the catalyst solution to the TEOS solution for hydrolysis and polycondensation reactions. The reaction temperature is 30 °C and the reaction time is 4 hours. After standing for 10 hours, a gel is formed. Exchange the solvent of the gel in n-hexane to remove impurities. Dry the gel by atmospheric drying method. The drying temperature is 60 °C and the drying time is 24 hours to obtain silica aerogel particles.

[0069] Preparation of Polyether-Siloxane: Under the protection of an inert atmosphere of argon, mix epoxy hexadecane and polydimethylsiloxane (molar ratio 1:1) in a reaction kettle, heat at a high temperature with a reaction temperature of 90 °C, and maintain the reaction for 4 hours to promote the polymerization of the epoxy component and polydimethylsiloxane. Add a certain amount of catalyst (such as 1 wt% p-toluenesulfonic acid) to accelerate the reaction. Finally, obtain the modified polyether-siloxane through reprecipitation purification.

[0070] Modification of silica aerogel: The silica aerogel particles were dispersed in xylene and subjected to ultrasonic dispersion. The corresponding silane coupling agent (3-aminopropyl) triethoxysilane was added, and its reaction concentration was 3 wt%. Under the catalytic condition of 1 wt% p-toluenesulfonic acid, a preliminary pre-reaction was carried out. Then, a polyether siloxane with terminal hydroxyl groups was added, and its reaction concentration was 12 wt%. Under the action of 1.5 wt% dibutyltin dilaurate catalyst, the surface modification reaction of silica aerogel particles was carried out again. The polyether siloxane solution was gradually added to the nano-silica aerogel, and the mass ratio of silica aerogel to polyether siloxane was 1:0.25. It was stirred with a high-shear disperser at a reaction temperature of 30 °C for 1.5 hours to ensure that the polyether siloxane was evenly dispersed on the surface of the aerogel. The polyether siloxane reacted with the hydroxyl groups on the surface of the silica aerogel to form chemical bonding. After the reaction, the modified silica aerogel particles were washed with xylene to remove the unreacted polyether siloxane. Vacuum drying was carried out to obtain the modified silica aerogel particles.

[0071] Coating preparation: The polyether siloxane-modified silica aerogel particles were dispersed in a solvent and subjected to ultrasonic dispersion. A binder and other additives were added and stirred evenly. The viscosity and solid content of the coating were adjusted to meet the coating requirements. The specific addition amounts of each component were as follows: polyether siloxane-modified silica aerogel was 50 wt%; solvent (isopropyl alcohol) was 40 wt%; binder (polyurethane resin) was 5 wt%; dispersant (polyvinyl alcohol) was 1 wt%; leveling agent (polyacrylic acid) was 0.5 wt%; defoaming agent (polyether defoamer) was 0.5 wt%; ultraviolet absorber (hydroxybenzoate) was 0.2 wt%; antioxidant (butylated hydroxytoluene) was 0.3 wt%.

[0072] Coating curing: The coating was evenly coated on the surface of the substrate, and the thickness of the coating was controlled. The coating was cured to make it firmly bonded to the substrate. The curing condition was drying at room temperature for 24 hours.

[0073] Example 3

[0074] The following details the specific experimental steps for the preparation of silica aerogel particles, the synthesis of polyether siloxane, the surface modification of polyether siloxane, the coating preparation, and the coating curing:

[0075] Preparation of silica aerogel particles: Tetraethyl orthosilicate (TEOS) was dissolved in isopropanol to prepare a TEOS solution, where TEOS:isopropanol = 1:6 (volume ratio). Deionized water and ammonia water were mixed according to the mass ratio of deionized water:ammonia water = 1:0.2 to prepare a catalyst solution. Under stirring conditions, the catalyst solution was slowly added to the TEOS solution for hydrolysis and polycondensation reactions. The reaction temperature was 20 °C and the reaction time was 5 hours. After standing for 8 hours, a gel was formed. The gel was subjected to solvent exchange in acetone to remove impurities. The gel was dried by supercritical CO2 drying method to obtain silica aerogel particles.

[0076] Preparation of polyether siloxane: Under the protection of an inert atmosphere of nitrogen, epoxy octane and polydimethylsiloxane (molar ratio 1:1) were mixed in a reaction kettle, and the high-temperature heating reaction temperature was 100 °C and maintained for 5 hours to promote the polymerization of the epoxy component and polydimethylsiloxane. A certain amount of catalyst (such as 1 wt% triethylamine) was added to accelerate the reaction. Finally, after extraction and washing purification, modified polyether siloxane was obtained.

[0077] Modification of silica aerogel: The silica aerogel particles were dispersed in ethanol and ultrasonically dispersed. The corresponding silane coupling agent (3-aminopropyl)triethoxysilane was added, and the reaction concentration was 4 wt%. Under the catalytic condition of 1 wt% p-toluenesulfonic acid, a preliminary pre-reaction was carried out. Then, polyether siloxane with terminal hydroxyl groups was added, and the reaction concentration was 8 wt%. Under the action of 1 wt% tetrabutyl titanate catalyst, the surface modification reaction of silica aerogel particles was carried out again. The polyether siloxane solution was gradually added to the nano-silica aerogel, where the mass ratio of silica aerogel to polyether siloxane was 1:0.3. A magnetic stirrer was used for stirring, the reaction temperature was 40 °C, and stirring was carried out for 2.5 hours to ensure that the polyether siloxane was evenly dispersed on the surface of the aerogel. The polyether siloxane reacted with the hydroxyl groups on the surface of the silica aerogel to form chemical bonding. After the reaction, the modified silica aerogel particles were washed with ethanol to remove the unreacted polyether siloxane. Vacuum drying was carried out to obtain the modified silica aerogel particles.

[0078] Coating preparation: The polyether siloxane-modified silica aerogel particles were dispersed in a solvent and ultrasonically dispersed. A binder and other additives were added and stirred evenly. The viscosity and solid content of the coating were adjusted to meet the coating requirements. The specific addition amounts of each component were as follows: polyether siloxane-modified silica aerogel was 50 wt%; solvent (isopropanol) was 40 wt%; binder (polyurethane resin) was 5 wt%; dispersant (polyvinyl alcohol) was 1 wt%; leveling agent (polydimethylsiloxane) was 0.5 wt%; defoaming agent (silicone defoaming agent) was 0.5 wt%; ultraviolet absorber (benzophenone) was 0.2 wt%; antioxidant (butylated hydroxytoluene) was 0.3 wt%.

[0079] Coating and curing: The coating is evenly applied on the surface of the substrate, and the thickness of the coating is controlled. The coating is cured to firmly bond it to the substrate. The curing condition is baking at 100 °C for 2 hours.

[0080] Comparative Example 1

[0081] A commercially available hydrophobic and oleophobic nano-coating material contains perfluoropolyether and other components.

[0082] The following multiple performance tests are respectively carried out on the nano-coatings prepared in Examples 1 - 3 and the nano-coating of Comparative Example 1:

[0083] Hydrophobicity test: A contact angle measuring instrument is used to measure the contact angle of water droplets on the coating surface. The larger the contact angle, the better the hydrophobicity. A superhydrophobic surface usually has a contact angle greater than 150°. The rolling angle will also be measured to evaluate the ease of water droplets rolling off the surface.

[0084] Oleophobicity test: A similar method is used to measure the contact angle of oil droplets (such as n-hexadecane) on the coating surface. The larger the contact angle, the better the oleophobicity. A superoleophobic surface usually has a contact angle greater than 150°. The rolling angle will also be measured to evaluate the ease of oil droplets rolling off the surface.

[0085] High-temperature stability test: The coating is placed in a high-temperature environment (such as 100 °C, 150 °C, 200 °C) for a certain period of time (such as 24 hours, 48 hours, 72 hours), and then the changes in its hydrophobicity and oleophobicity are tested. The stability of the coating at high temperatures is evaluated.

[0086] Insulation performance breakdown voltage test: A gradually increasing voltage is applied to the coating until breakdown occurs. The breakdown voltage value is recorded to evaluate the insulation strength and voltage resistance ability of the coating.

[0087] Wear resistance test: A friction testing machine is used to evaluate the wear resistance of the coating. Under a certain load and number of friction cycles, the wear amount of the coating is measured.

[0088] UV aging test: The coating is placed under UV light irradiation to simulate the outdoor exposure environment, and the changes in its hydrophobicity and oleophobicity are regularly tested to evaluate its long-term service life.

[0089] The test results are as follows:

[0090]

[0091] It can be seen from the test results that:

[0092] Hydrophobic and oleophobic properties: The new fluorine-free coating is slightly superior to the fluorine coating in terms of hydrophobic and oleophobic properties, reaching a very excellent level. The data of contact angle and rolling angle indicate that its surface has excellent hydrophobic and oleophobic capabilities.

[0093] High-temperature stability: The high-temperature stability of the new fluorine-free coating is slightly higher than that of the fluorine coating, maintaining good hydrophobicity in an environment of 200 °C.

[0094] Insulating performance: The breakdown voltage of the new fluorine-free coating is slightly higher than that of the fluorine coating, indicating that it has better insulating performance, which may be attributed to the inherent insulating characteristics of silica aerogel.

[0095] Wear resistance: The wear resistance of the new fluorine-free coating is better than that of the fluorine coating. This may be related to the flexibility of polyether siloxane and the hardness of silica aerogel, making its coating more wear-resistant.

[0096] Durability: The durability of the new fluorine-free coating under UV irradiation is comparable to that of the fluorine coating, indicating that the added ultraviolet absorber plays a protective role.

[0097] Toxicity: The greatest advantage of the new fluorine-free coating is its non-toxicity, avoiding the potential toxicity risks that may exist in the fluorine coating and being more in line with environmental protection requirements.

[0098] It can be concluded that the nano-coating in the embodiments of this application uses silica aerogel particles surface-modified with polyether siloxane as the main material, showing more excellent high-temperature stability (higher thermal decomposition temperature), insulating performance (higher breakdown voltage), hydrophobic, oleophobic, anti-fouling and self-cleaning performance (larger water or oil contact angle), and being environmentally friendly and non-toxic (fluorine-free and halogen-free), with a relatively low preparation cost (simple preparation and batch production possible), and having broad application prospects.

[0099] Advantages of the embodiments of this application:

[0100] Silica aerogel particles are prepared by the sol-gel method. By controlling the reaction conditions, the particle size and pore structure of the aerogel particles are adjusted to obtain the best coating performance. The surface modification is carried out by the silanization method, and polyether siloxane is grafted onto the surface of the silica aerogel particles. By controlling the grafting amount of polyether siloxane, the hydrophobic and oleophobic properties of the aerogel particles are adjusted. By optimizing the particle size of the aerogel particles, the surface modification process and the coating method, a superhydrophobic surface with a micro-nano composite structure is successfully constructed. The modified silica aerogel particles not only endow the coating with excellent superhydrophobic and oleophobic properties, effectively reduce the surface energy, and realize the rolling-off of water droplets and oil droplets on its surface, so as to achieve the purpose of anti-fouling and self-cleaning, which can significantly reduce the maintenance cost and cleaning frequency of the substrate and extend its service life. At the same time, the introduction of the modified polyether siloxane also ensures the good insulation performance of the coating. The combination of silica aerogel and polyether siloxane forms a synergistic effect, giving full play to the advantages of both and realizing the improvement of the coating performance. This technical solution avoids the use of any fluorine-containing materials, reduces the environmental pollution risk, and due to the inherent low thermal conductivity of silica aerogel, the coating has excellent high-temperature insulation performance, enabling it to maintain its hydrophobic and oleophobic effects under high-temperature environments, while preventing the substrate from being damaged by heat, achieving a good fluorine-free high-temperature anti-fouling nano-coating effect, and having broad application prospects. And the preparation method of the coating in this application, by precisely controlling each process parameter, ensures the uniformity, adhesion and long-term effectiveness of the coating, laying a foundation for realizing commercial production. The application fields are extensive, including but not limited to the aerospace field (aircraft surface coating, engine component surface treatment), the ship and ocean engineering field (ship hull coating, offshore drilling platform coating), the automotive industry field (body coating, engine and exhaust system coating), the new energy equipment field (solar panel surface coating, lithium battery shell anti-corrosion treatment), the building facade and roof (glass curtain wall coating), bridges and public facilities (metal structure coating), the electronic equipment protection field (mobile phone, display coating, capacitor circuit board nano-coating, PCB, FPC, PCBA, waterproof and moisture-proof coating), the medical and laboratory equipment field (medical device surface antibacterial coating), the cultural relic protection field (ancient building or cultural relic surface coating) and the textile and outdoor equipment (outdoor clothing or tent coating), etc. Its application value is reflected in that it can significantly improve the operation efficiency and safety of related equipment, reduce the maintenance cost, and bring significant economic and environmental benefits to related industries.

[0101] Although the preferred embodiments of the embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

[0102] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or terminal device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or terminal device comprising the said element.

[0103] The above has introduced in detail a novel fluorine-free superhydrophobic nano-coating and its preparation method provided by the present invention. Specific examples are used in this text to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A novel fluorine-free superhydrophobic nano-coating, characterized in that, It includes modified silica aerogel, a first solvent, a binder, and additives; The modified silica aerogel is obtained by surface-modifying silica aerogel particles with polyether siloxane.

2. The novel fluorine-free superhydrophobic nano-coating according to claim 1, wherein The additives include a dispersant, a leveling agent, an antifoaming agent, an ultraviolet absorber, and an antioxidant.

3. The novel fluorine-free superhydrophobic nano-coating according to claim 2, characterized in that, By weight parts, the nano-coating includes 40 - 60 parts of modified silica aerogel, 30 - 40 parts of the first solvent, 5 - 10 parts of the binder, 0.5 - 2 parts of the dispersant, 0.1 - 1 part of the leveling agent, 0.1 - 1 part of the antifoaming agent, 0.1 - 0.5 parts of the ultraviolet absorber, and 0.1 - 0.5 parts of the antioxidant.

4. A method for preparing the nano-coating according to any one of claims 1-3, characterized in that, It includes the following steps: Prepare silica aerogel particles and polyether siloxane; Graft the polyether siloxane onto the surface of the silica aerogel particles to obtain modified silica aerogel; Disperse the modified silica aerogel into the first solvent, and add the binder and additives and mix evenly to prepare a nano-coating; Evenly coat the nano-coating on the surface of the substrate to form a nano-coating.

5. The preparation method according to claim 4, characterized in that, The step of preparing the silica aerogel particles includes: Dissolve the silane precursor in a second solvent, and add a first catalyst, and carry out hydrolysis and polycondensation reactions at a first reaction temperature and a first reaction time to form a sol; Let the sol stand until a gel is formed; Carry out aging treatment and drying treatment on the gel to obtain silica aerogel particles.

6. The preparation method according to claim 5, characterized in that, The volume ratio of the silane precursor to the second solvent is 1:4 - 6; the first reaction temperature is 20 - 50 °C, and the first reaction time is 2 - 6 h.

7. The preparation method according to claim 5, characterized in that, The particle size of the silica aerogel particles is 10 nm - 10 μm, and the pore size is 2 nm - 50 nm.

8. The preparation method according to claim 4, characterized in that, The step of grafting the polyether siloxane onto the surface of the silica aerogel particles to obtain modified silica aerogel includes: Disperse the silica aerogel particles into a third solvent to obtain a dispersion solution; Add a silane coupling agent with functional groups to the dispersion solution for a preliminary reaction to obtain a reaction solution; Add polyether siloxane and a second catalyst to the reaction solution, and stir at a second reaction temperature for a second reaction time to obtain a modified solution; Carry out separation, washing, and drying on the modified solution to obtain modified silica aerogel.

9. The preparation method according to claim 8, wherein The reaction concentration of the silane coupling agent is 1 - 5%; the reaction concentration of the polyether siloxane is 5 - 15%; The mass ratio of the silica aerogel particles to the polyether siloxane is 1:0.2 - 0.5; The second reaction temperature is 20 - 50 °C, and the second reaction time is 1 - 4 h.

10. The preparation method according to claim 4, characterized in that, The polyether siloxane is obtained by copolymerizing epoxy long alkane and polydimethylsiloxane, and the polyether siloxane is a hydroxyl-terminated polyether siloxane or an amino-terminated polyether siloxane.

Images