A protective coating containing silica, its preparation method and application

Abstract

This invention relates to a silica-containing protective coating, its preparation method, and its application. The preparation method includes the following steps: treating an alkali-treated substrate with a surfactant, followed by a first reaction with an amino-containing bissilane coupling agent to form a mesoporous silica layer on the substrate. The average thickness of the mesoporous silica layer is 100-300 nm. A second reaction is then performed with a carbon-carbon double-bond monosilane coupling agent to deposit Parylene, resulting in the silica-containing protective coating on the substrate. The silica-containing protective coating provided by this invention exhibits high adhesion to the substrate, good bonding effect, and good batch-to-batch stability.

Description

Technical Field

[0001] This invention relates to the field of coating materials technology, and in particular to a protective coating containing silica, Parylene coating, its preparation method and application. Background Technology

[0002] Parylene (poly(p-xylene), also known as Parylene) coating is a new type of environmentally friendly coating material that provides protective properties such as protection against salt spray, oxidation, and moisture. Parylene coating is made using a vapor deposition process, but because Parylene itself is relatively symmetrical (weakly polar), its adhesion to the substrate is relatively weak during the transition from a gaseous to a solid state.

[0003] In existing technologies, coupling agents are typically applied to the substrate by immersion coating or vapor treatment of the substrate with coupling agents before Parylene film deposition. This allows the coupling agent and Parylene monomers to react simultaneously on the substrate surface, forming a Parylene coating. Introducing a coupling agent can effectively improve the adhesion of the Parylene coating to the substrate.

[0004] CN116641026A discloses an aerospace-grade Parylene-C based thin film and its preparation method. The aerospace-grade Parylene-C based thin film includes a coupling agent layer, a Parylene-C main film layer, an adhesive layer, and a polyimide protective film layer sequentially formed on the device to be coated. The Parylene-C main film layer has a thickness of 10-30 μm, and the polyimide protective film layer has a thickness of 2-5 μm. This technical solution, by using a coupling agent, enables Parylene-C to be deposited more firmly on the surface of the device to be coated.

[0005] In the prior art, the coupling agent vapor treatment of the substrate before Parylene film deposition generally refers to placing the coupling agent in the deposition chamber or introducing the vapor of the coupling agent into the deposition chamber under vacuum conditions, waiting for the coupling agent vapor to react with the substrate for a period of time before depositing the Parylene film. When coupling agent vapor is used to treat the substrate, some coupling agent is adsorbed onto the substrate surface after contact with the vapor. Because the evaporation process occurs under ambient temperature and vacuum conditions, the interaction between the coupling agent and the substrate is mainly physical adsorption, resulting in a weak interaction force. After the Parylene active monomer comes into contact with the substrate surface, the coupling agent and Parylene monomer react simultaneously on the metal substrate surface to form a Parylene coating. This reaction process occurs under ambient temperature and vacuum conditions, which are insufficient to allow the coupling agent adsorbed on the substrate surface to react completely. This results in residual unreacted coupling agent between the Parylene coating and the substrate. If the Parylene coating is damaged during use, these unreacted coupling agents may pose a certain safety risk. Alternatively, a curing period under specific temperature and humidity conditions may be required to allow the silanoxy groups and silanoxy groups on the substrate surface to react fully, thereby enhancing the adhesion of the Parylene coating. In addition, during the evaporation process, the concentration of coupling agent in the deposition chamber, the interaction time between the coupling agent vapor and the substrate, and the system vacuum level and vacuuming capability are all related. This can cause unstable adhesion between batches of products and leave a large amount of coupling agent residue in the deposition chamber.

[0006] The coupling agent used in the preparation of Parylene coatings is usually a monosilane coupling agent, such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane. After hydrolysis, it forms three silanol groups, which can react with the hydroxyl groups on the substrate surface under certain conditions to form stable covalent bonds. Usually, after the first silanol group reacts, the reactivity of the remaining silanol groups is significantly reduced due to steric hindrance, resulting in a low crosslinking density of the formed silane layer. In addition, the reaction between the silanol group and the hydroxyl group on the substrate surface is a reversible reaction, and the formed covalent bonds are easily hydrolyzed. During the dip coating process, the monosilane coupling agent binds to the substrate through weak interactions such as hydrogen bonding. This portion of the monosilane coupling agent may be removed during the washing process, thus affecting the adhesion of the Parylene coating to the substrate.

[0007] When braided metal stents are coated using conventional Parylene coating processes, relative displacement occurs between the metal wires of the braided metal stent and between the braided metal stent and the sheath during loading-release or loading-release-retrieval-release processes. The Parylene coating at the contact points between the metal wires and between the braided metal stent and the sheath is prone to damage, peeling, and detachment. The Parylene coating at these locations no longer provides protection, and the detached Parylene coating can directly enter the human body, easily causing thrombosis or vascular blockage, which poses a very high safety risk.

[0008] Therefore, there is a need to develop a protective coating with good adhesion to the substrate and its preparation method. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a silica-containing protective coating, its preparation method, and its application. The silica-containing protective coating exhibits high adhesion to the substrate, good bonding effect, and good batch-to-batch stability.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a protective coating containing silica, the method comprising the following steps: treating an alkali-treated substrate with a surfactant, then reacting it with an amino-containing bissilane coupling agent to form a mesoporous silica layer on the substrate, the mesoporous silica layer having an average thickness of 100~300 nm (e.g., 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm or 280 nm, etc.), and then reacting it with a monosilane coupling agent containing carbon-carbon double bonds to deposit Parylene, thereby obtaining the protective coating containing silica on the substrate.

[0012] In this invention, the surface of the alkali-treated substrate contains a large number of hydroxyl groups. By employing a soft template method, using a surfactant as a soft template agent and a bissilane coupling agent as a silicon source, a mesoporous silica layer is grown in situ on the substrate surface. The silica is chemically bonded to the substrate, resulting in high adhesion. The mesoporous silica layer can also alter the surface roughness of the substrate, improving its uniformity. After a second reaction with a monosilane coupling agent containing carbon-carbon double bonds, a large number of carbon-carbon double bonds are introduced into the surface and pore structure of the mesoporous silica layer. These bonds can react with Parylene active monomers, serving as reaction sites for Parylene deposition. During Parylene polymerization, the Parylene active monomers penetrate into the mesoporous structure of the mesoporous silica layer and polymerize, causing silica and Parylene to interdope, significantly increasing the contact area between silica and Parylene, forming a silica / Parylene composite layer, which enhances the adhesion to the Parylene layer. The protective coating containing silicon dioxide contains a large number of Si-O-Si bonds, which can effectively improve heat resistance and mechanical strength, and can withstand higher intensity friction when rubbing against the surface of other materials.

[0013] In this invention, the preparation method of the silica-containing protective coating is simple and the modification is easy. Those skilled in the art can also introduce various functional organic functional groups, molecules or polymers into the mesoporous silica layer to further improve the bonding force with the Parylene layer or introduce other functions, such as development performance, near-infrared response performance, etc.

[0014] Preferably, the preparation method includes the following steps: (1) mixing a surfactant, water and optionally a pH adjuster to obtain a surfactant solution; (2) mixing an amino-containing bissilane coupling agent, ethanol, water and optionally a pH adjuster to obtain a bissilane solution; (3) mixing a carbon-carbon double bond-containing monosilane coupling agent, ethanol, water and optionally a pH adjuster to obtain a monosilane solution; (4) immersing the alkali-treated substrate into the surfactant solution obtained in step (1) and stirring, then adding the bissilane solution obtained in step (2) to carry out a first reaction, forming a mesoporous silica layer on the substrate, then adding the monosilane solution obtained in step (3) to carry out a second reaction, and then depositing Parylene to form the silica-containing protective coating; the steps (1), (2) and (3) are performed in any order, or simultaneously.

[0015] In this invention, the preparation method eliminates the need to place the coupling agent in the deposition chamber for evaporation or to introduce coupling agent vapor into the deposition chamber. This shortens the processing time for Parylene deposition. Furthermore, the reaction between the amine-containing bissilane coupling agent and the carbon-carbon double-bond-containing monosilane coupling agent and the substrate is completed before Parylene deposition. Since no coupling agent vapor is used during Parylene deposition, the problem of coupling agent residue in the deposition chamber is effectively avoided. Therefore, changes in the vacuum level and vacuum extraction capability of the deposition system have almost no impact on the adhesion of the protective coating and the substrate, effectively improving the stability of the product across batches. The Parylene layer deposited in this method immediately achieves excellent adhesion after exiting the furnace, eliminating the need for a curing process and significantly reducing the processing time to achieve high adhesion.

[0016] It should be noted that the volume of the surfactant solution used in this invention is related to the shape and volume of the substrate. In step (4), the substrate after alkali treatment is immersed in the surfactant solution prepared in step (1) and stirred. Then, the bissilane solution prepared in step (2) is added to carry out the first reaction, forming a mesoporous silica layer on the substrate. Then, the monosilane solution prepared in step (3) is added to carry out the second reaction. During this process, the substrate needs to be completely immersed in the solution.

[0017] Preferably, the surfactant includes a nonionic surfactant.

[0018] Preferably, the nonionic surfactant comprises any one or a combination of at least two of the following: polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxyethylene sorbitan monooleate, polysorbate, polyoxyethylene fatty alcohol ether, polyethylene glycol fatty acid ester, or polyoxyethylene-polyoxypropylene block copolymer.

[0019] For example, the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer includes P123.

[0020] For example, the polysorbate includes polysorbate 20 (Tween 20) or polysorbate 80 (Tween 80).

[0021] In this invention, the surfactant is a soft template for preparing mesoporous silica. Without the addition of surfactant, a mesoporous silica layer cannot be formed. Instead, an amino-containing bissilane coupling agent and a carbon-carbon double bond monosilane coupling agent are attached to the substrate. However, the amino-containing bissilane coupling agent is usually easily soluble in water, and its amount attached to the substrate is small and easily removed, which makes it impossible to effectively play its role in improving the bonding force.

[0022] Preferably, the amine-containing bissilane coupling agent has the following general formula: (RO)3-Si-(CH2) n-NH-(CH2) n -Si-(OR)3.

[0023] In each of these, R is an alkyl group having 1 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8 or 9), and n is 1 to 10 (e.g., 2, 3, 4, 5, 6, 7, 8 or 9).

[0024] Preferably, each of the carbon-carbon double bond-containing monosilane coupling agents independently has the following general structural formula: YR 1 -Si(R 2 )3 and / or Y-Si(R 2 3.

[0025] Wherein, Y is independently any one of methacryloyloxy, acryloyloxy, or an alkenyl group having 2 to 10 carbon atoms (e.g., 3, 4, 5, 6, 7, 8, or 9, etc.); R 1 It is an alkylene group having 1 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8, or 9, etc.) or an alkene group having 1 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8, or 9, etc.); R 2 Each is an alkoxy group with 1 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8 or 9).

[0026] Preferably, the amine-containing bissilane coupling agent comprises bis[3-(trimethoxysilyl)propyl]amine and / or bis[3-(triethoxysilyl)propyl]amine.

[0027] Preferably, each of the carbon-carbon double bond-containing monosilane coupling agents independently comprises any one or a combination of at least two of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltris(β-methoxyethoxy)silane.

[0028] Preferably, the mass ratio of surfactant to water in step (1) is (0.1~1):100 (e.g. 0.2:100, 0.3:100, 0.4:100, 0.5:100, 0.6:100, 0.7:100, 0.8:100 or 0.9:100, etc.), and more preferably (0.3~7):100.

[0029] Preferably, the volume ratio of the amine-containing bissilane coupling agent in step (2) to the total volume of ethanol and water is (2~5):10, for example, 2.5:10, 3:10, 3.5:10, 4:10 or 4.5:10, etc.

[0030] Preferably, with the total volume of ethanol and water in step (2) being 100%, the volume of ethanol is 85% to 95%, such as 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, or 94%.

[0031] Preferably, the volume ratio of the monosilane coupling agent containing carbon-carbon double bonds in step (3) to the total volume of ethanol and water is (0.1~1):10, for example 0.2:10, 0.3:10, 0.4:10, 0.5:10, 0.6:10, 0.7:10, 0.8:10 or 0.9:10, etc.

[0032] Preferably, with the total volume of ethanol and water in step (3) being 100%, the volume of ethanol is 85% to 95%, such as 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, or 94%.

[0033] Preferably, the absolute value of the pH difference between any two of the surfactant solution, bissilane solution and monosilane solution is ≤0.2, for example, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16 or 0.18.

[0034] In this invention, the absolute value of the pH difference between any two of the surfactant solution, bissilane solution, and monosilane solution is kept ≤0.2, so that the addition of bissilane solution and monosilane solution to the surfactant solution does not cause a significant change in the pH of the system. For example, the pH of the surfactant solution, bissilane solution, and monosilane solution is all 8.

[0035] Preferably, the pH adjuster in steps (1), (2) and (3) each independently includes an acidic solution and / or an alkaline solution.

[0036] Preferably, the acidic solution comprises an aqueous solution of acetic acid.

[0037] Preferably, the volume percentage concentration of the acetic acid aqueous solution is 10% to 40%, such as 15%, 20%, 25%, 30%, or 35%.

[0038] Preferably, the alkaline solution includes a weak alkaline solution and / or a strong alkaline solution.

[0039] Preferably, the weak alkaline solution includes ammonia.

[0040] Preferably, the concentration of the strong alkali solution is 0.5~3 mol / L, for example 0.8 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.1 mol / L, 2.4 mol / L or 2.7 mol / L.

[0041] Preferably, the mixing steps (2) and (3) further include a settling step.

[0042] Preferably, the resting time in steps (2) and (3) is 0 to 24 hours, for example, 3 hours, 6 hours, 9 hours, 12 hours, 15 hours, 18 hours or 21 hours.

[0043] Preferably, the stirring temperature in step (4) is 35~40℃ (e.g., 35.5℃, 36℃, 36.5℃, 37℃, 37.5℃, 38℃, 38.5℃, 39℃ or 39.5℃, etc.), and the stirring time is ≥30 min, e.g., 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc.

[0044] Preferably, the volume ratio of the surfactant solution to the bissilane solution in step (4) is 100:(1~5), for example, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4 or 100:4.5, etc.

[0045] Preferably, the addition of the bissilane solution obtained in step (2) in step (4) is done by adding the bissilane solution obtained in step (2) in batches.

[0046] Preferably, the temperature of the first reaction is 35~40℃ (e.g., 35.5℃, 36℃, 36.5℃, 37℃, 37.5℃, 38℃, 38.5℃, 39℃ or 39.5℃, etc.), and the time of the first reaction is ≥12 h, e.g., 14 h, 16 h, 18 h, 20 h, 22 h or 24 h, etc.

[0047] Preferably, the first reaction of the bissilane solution obtained in step (2) is carried out under stirring or shaking.

[0048] Preferably, the volume ratio of the surfactant solution to the monosilane solution in step (4) is 100:(1~5), for example, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4 or 100:4.5, etc.

[0049] Preferably, the addition of the monosilane solution obtained in step (3) in step (4) is done by adding the monosilane solution obtained in step (3) in batches.

[0050] Preferably, the second reaction includes reacting at 35~40℃ (e.g., 35.5℃, 36℃, 36.5℃, 37℃, 37.5℃, 38℃, 38.5℃, 39℃ or 39.5℃, etc.) for ≥1 h (e.g., 2 h, 3 h, 4 h, 5 h or 6 h, etc.), and then raising the temperature to 60~80℃ (e.g., 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃ or 78℃, etc.) and continuing the reaction for ≥8 h, e.g., 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h, etc.

[0051] Preferably, the second reaction of the monosilane solution obtained in step (3) is carried out under stirring or shaking.

[0052] In this invention, water is mainly used as the reaction medium during the treatment of the substrate with surfactants, amine-containing bissilane coupling agents, and carbon-carbon double-bond monosilane coupling agents. The role of ethanol is mainly to dissolve the amine-containing bissilane coupling agents and carbon-carbon double-bond monosilane coupling agents. Only a small amount of amine-containing bissilane coupling agents, carbon-carbon double-bond monosilane coupling agents, and ethanol are needed in the whole process to improve the adhesion effect to the substrate and effectively reduce the use of chemical reagents.

[0053] Preferably, the second reaction is followed by a washing and drying step.

[0054] Preferably, the cleaning includes ultrasonic cleaning in ethanol for a time of 10-60 seconds, such as 20 seconds, 30 seconds, 40 seconds or 50 seconds.

[0055] Preferably, the drying temperature is 60~100℃ (e.g., 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃, etc.), and the drying time is 20~120 min (e.g., 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min or 110 min, etc.).

[0056] Preferably, the alkali treatment includes immersion in a strong alkali solution.

[0057] Preferably, the temperature of the immersion coating with the strong alkaline solution is 20~90℃, such as 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃.

[0058] Preferably, the immersion time in the strong alkaline solution is 2 to 24 hours, such as 5 hours, 8 hours, 11 hours, 14 hours, 17 hours, 20 hours, or 23 hours.

[0059] Preferably, the strong alkaline solution used in the alkaline treatment includes a strong alkali and water.

[0060] Preferably, the strong base includes alkali metal hydroxides and / or alkaline earth metal hydroxides.

[0061] Preferably, the alkali metal hydroxide includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, or rubidium hydroxide.

[0062] Preferably, the alkaline earth metal hydroxide includes calcium hydroxide and / or barium hydroxide.

[0063] Preferably, the mass percentage concentration of the strong alkali solution used in the alkali treatment is 10% to 30%, such as 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, or 28%.

[0064] For example, the substrate is made of nickel-titanium alloy, which generates a large number of Ti-OH and sodium titanate layers on its surface after alkali treatment. These layers are negatively charged and can be used to adsorb amine-containing bissilane coupling agents in situ on the surface under the action of surfactants.

[0065] Preferably, the conditions for depositing Parylene include: a temperature of 120~180℃ in the evaporation chamber (e.g., 130℃, 140℃, 150℃, 160℃, or 170℃), a temperature of 670~690℃ in the pyrolysis chamber (e.g., 673℃, 676℃, 679℃, 682℃, 685℃, or 688℃), a temperature of 10~30℃ in the deposition chamber (e.g., 12℃, 14℃, 16℃, 18℃, 20℃, 22℃, 24℃, 26℃, or 28℃), and a chamber pressure of 1~13 Pa in the deposition chamber (e.g., 2 Pa, 4 Pa, 6 Pa, 8 Pa, 10 Pa, or 12 Pa).

[0066] Preferably, the thickness of the silica-containing protective coating is 0.5~2 μm, such as 0.7 μm, 0.9 μm, 1.1 μm, 1.3 μm, 1.5 μm, 1.7 μm or 1.9 μm.

[0067] In a second aspect, the present invention provides a protective coating containing silicon dioxide, wherein the protective coating containing silicon dioxide is prepared by the preparation method described in the first aspect.

[0068] Thirdly, the present invention provides the application of a silica-containing protective coating as described in the second aspect in the protection of a substrate surface.

[0069] For example, the substrate includes a nickel-titanium alloy substrate.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] This invention involves treating an alkali-treated substrate with a surfactant, followed by a first reaction with an amine-containing bissilane coupling agent to form a mesoporous silica layer on the substrate. The average thickness of the mesoporous silica layer is 100-300 nm. A second reaction is then performed with a carbon-carbon double-bond monosilane coupling agent to deposit Parylene, resulting in a silica-containing protective coating on the substrate. This silica-containing protective coating exhibits high adhesion to the substrate, good bonding performance, and good batch-to-batch stability. Attached Figure Description

[0072] Figure 1 This is a flowchart of the method for preparing the protective coating provided in Embodiment 1 of the present invention;

[0073] Among them, 1-mesoporous silica layer; 2-carbon-carbon double bond modified mesoporous silica layer; 3-silica / Parylene composite layer; 4-Parylene layer; 5-protective coating. Detailed Implementation

[0074] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0075] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effects of the present invention.

[0076] Example 1

[0077] This embodiment provides a protective coating containing silicon dioxide and its preparation method. The preparation method includes the following steps, and the preparation process is as follows: Figure 1 As shown:

[0078] The preparation method includes the following steps:

[0079] (1) Mix surfactant (P123) with purified water at a mass ratio of 0.5:100, and add sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH to 8 to obtain surfactant solution.

[0080] (2) Dissolve the amine-containing bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine) in anhydrous ethanol until completely dissolved, then add purified water. The volume ratio of the amine-containing bissilane coupling agent, anhydrous ethanol and purified water is 3:9:1. Then add acetic acid aqueous solution with a volume percentage concentration of 20% to adjust the pH to 8. Let stand for hydrolysis for 24 h to obtain a bissilane solution.

[0081] (3) After the carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane) is completely dissolved in anhydrous ethanol, purified water is added. The volume ratio of the carbon-carbon double bond monosilane coupling agent, anhydrous ethanol and purified water is 0.5:9:1. Then, a 1 mol / L sodium hydroxide solution is added to adjust the pH to 8. The mixture is allowed to stand for 4 h to hydrolyze and obtain a monosilane solution.

[0082] (4) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (20% by mass) and treated at 60°C for 8 h. After ultrasonic cleaning with purified water for 3 min, it was dried with compressed air and then dried in an oven at 60°C for 10 min to obtain the alkali-treated substrate. Then the alkali-treated substrate was immersed in the surfactant solution prepared in step (1) and stirred in a water bath at 37°C for 30 min. Then the bissilane solution prepared in step (2) was added in 3 batches, every 15 min. Add the solution once per minute, with the same amount of bissilane solution added each time. The volume ratio of surfactant solution to bissilane solution is 100:3. The reaction is carried out under stirring and a 37°C water bath for 12 hours, forming a mesoporous silica layer 1 on the substrate. Then, add the monosilane solution obtained in step (3) in three batches, once every 15 minutes, with the same amount of monosilane solution added each time. The volume ratio of surfactant solution to monosilane solution is 100:2. The reaction is carried out at 37°C for 1 hour, and then the temperature is raised to 70°C and the reaction continues for 16 hours. The solution is ultrasonically treated in anhydrous ethanol for 60 seconds to remove components with weak surface bonding. The solution is dried at 80°C for 40 minutes, forming a carbon-carbon double bond modified mesoporous silica layer 2 on the substrate. Parylene is deposited. The conditions for Parylene deposition include: the temperature of the evaporation chamber is 150°C, the temperature of the pyrolysis chamber is 680°C, the temperature of the deposition chamber is 25°C, the chamber pressure of the deposition chamber is 2.0 Pa, and the Parylene C powder is 3.5 kJ / kg. g, Part of the Parylene formed by polymerization diffuses into the carbon-carbon double bond modified mesoporous silica layer to form a silica / Parylene composite layer 3, and another part forms a Parylene layer 4, forming a protective coating 5 on the substrate.

[0083] Example 2

[0084] This embodiment provides a protective coating containing silicon dioxide and its preparation method, the preparation method including the following steps:

[0085] The preparation method includes the following steps:

[0086] (1) Mix surfactant (P123) with purified water at a mass ratio of 0.5:100, and add sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH to 8 to obtain surfactant solution.

[0087] (2) Dissolve the amine-containing bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine) in anhydrous ethanol until completely dissolved, then add purified water. The volume ratio of the amine-containing bissilane coupling agent, anhydrous ethanol and purified water is 2:9:1. Then add acetic acid aqueous solution with a volume percentage concentration of 20% to adjust the pH to 8, and let it stand for 24 h to hydrolyze to obtain a bissilane solution.

[0088] (3) After the carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane) is completely dissolved in anhydrous ethanol, purified water is added. The volume ratio of the carbon-carbon double bond monosilane coupling agent, anhydrous ethanol and purified water is 0.1:9:1. Then, a 1 mol / L sodium hydroxide solution is added to adjust the pH to 8. The mixture is allowed to stand for 4 h to hydrolyze and obtain a monosilane solution.

[0089] (4) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (20% by mass) at 25°C for 24 h, ultrasonically cleaned with purified water for 3 min, dried with compressed air, and then dried in an oven at 60°C for 10 min to obtain the alkali-treated substrate; then the alkali-treated substrate was immersed in the surfactant solution prepared in step (1) and stirred in a water bath at 37°C for 30 min; then the bissilane solution prepared in step (2) was added in 3 batches, once every 15 min, with the same amount of bissilane solution added each time, and the volume ratio of surfactant solution to bissilane solution was 100:5. The reaction was carried out under stirring and a water bath at 37°C for 12 min. h, a mesoporous silica layer is formed on the substrate; then add the monosilane solution prepared in step (3) in 3 batches, adding once every 15 min, with the same amount of monosilane solution added each time, the volume ratio of surfactant solution to monosilane solution being 100:5, reacting at 37℃ for 1 h, then raising the temperature to 60℃ and continuing the reaction for 24 h, ultrasonically treating in anhydrous ethanol for 60 s to remove components with weak surface bonding, drying at 80℃ for 40 min, forming a carbon-carbon double bond modified mesoporous silica layer on the substrate, depositing Parylene, the conditions for depositing Parylene include: the temperature of the evaporation chamber is 150℃, the temperature of the pyrolysis chamber is 680℃, the temperature of the deposition chamber is 25℃, the chamber pressure of the deposition chamber is 2.0 Pa, Parylene C powder 3.5 g, part of the Parylene formed by polymerization penetrates into the carbon-carbon double bond modified mesoporous silica layer to form a silica / Parylene composite layer, and the other part forms a Parylene layer, forming a protective coating on the substrate.

[0090] Example 3

[0091] This embodiment provides a protective coating containing silicon dioxide and its preparation method, the preparation method including the following steps:

[0092] The preparation method includes the following steps:

[0093] (1) Mix surfactant (P123) with purified water at a mass ratio of 0.5:100, and add sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH to 8 to obtain surfactant solution.

[0094] (2) Dissolve the amine-containing bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine) in anhydrous ethanol until completely dissolved, then add purified water. The volume ratio of the amine-containing bissilane coupling agent, anhydrous ethanol and purified water is 5:9:1. Then add acetic acid aqueous solution with a volume percentage concentration of 20% to adjust the pH to 8, and let it stand for 24 h to hydrolyze to obtain a bissilane solution.

[0095] (3) After the carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane) is completely dissolved in anhydrous ethanol, purified water is added. The volume ratio of the carbon-carbon double bond monosilane coupling agent, anhydrous ethanol and purified water is 1:9:1. Then, a 1 mol / L sodium hydroxide solution is added to adjust the pH to 8. The mixture is allowed to stand for 4 h to hydrolyze and obtain a monosilane solution.

[0096] (4) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (20% by mass) and treated at 90°C for 2 h. After ultrasonic cleaning with purified water for 3 min, it was dried with compressed air and then dried in an oven at 60°C for 10 min to obtain the alkali-treated substrate. Then the alkali-treated substrate was immersed in the surfactant solution prepared in step (1) and stirred in a water bath at 37°C for 30 min. Then the bissilane solution prepared in step (2) was added in 3 batches, every 15 min. Add the solution once per minute, with the same amount of bissilane solution added each time. The volume ratio of surfactant solution to bissilane solution is 100:1. The reaction is carried out under stirring and a 37°C water bath for 12 hours, forming a mesoporous silica layer on the substrate. Then, add the monosilane solution obtained in step (3) in three batches, once every 15 minutes, with the same amount of monosilane solution added each time. The volume ratio of surfactant solution to monosilane solution is 100:1. The reaction is carried out at 37°C for 1 hour, and then the temperature is raised to 80°C and the reaction continues for 12 hours. The solution is ultrasonically treated in anhydrous ethanol for 60 seconds to remove components with weak surface bonding. The solution is dried at 80°C for 40 minutes, forming a carbon-carbon double bond modified mesoporous silica layer on the substrate. Parylene is deposited. The conditions for Parylene deposition include: the temperature of the evaporation chamber is 150°C, the temperature of the pyrolysis chamber is 680°C, the temperature of the deposition chamber is 25°C, the chamber pressure of the deposition chamber is 2.0 Pa, and the Parylene C powder is 3.5 kJ / kg. g, the portion of Parylene formed by polymerization diffuses into the carbon-carbon double bond modified mesoporous silica layer to form a silica / Parylene composite layer, and the other portion forms a Parylene layer, forming a protective coating on the substrate.

[0097] Example 4

[0098] This embodiment provides a protective coating containing silica and its preparation method. The difference between this embodiment and Embodiment 1 is that the mass ratio of surfactant (P123) and purified water in step (1) is adjusted to 0.7:100, while other conditions are the same as in Embodiment 1.

[0099] Example 5

[0100] This embodiment provides a protective coating containing silica and its preparation method. The difference between this embodiment and Embodiment 1 is that the mass ratio of surfactant (P123) and purified water in step (1) is adjusted to 0.3:100, while other conditions are the same as in Embodiment 1.

[0101] Example 6

[0102] This embodiment provides a protective coating containing silica and its preparation method. The difference between this embodiment and Embodiment 1 is that the surfactant (P123) in step (1) is replaced with the same mass of surfactant (Tween 80), while the other conditions are the same as in Embodiment 1.

[0103] Example 7

[0104] This embodiment provides a protective coating containing silica and its preparation method. The difference between this embodiment and Embodiment 1 is that the amine-containing bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine) in step (2) is replaced with the same volume of amine-containing bissilane coupling agent (bis[3-(triethoxysilyl)propyl]amine), and the other conditions are the same as in Embodiment 1.

[0105] Example 8

[0106] This embodiment provides a protective coating containing silica and its preparation method. The difference between this embodiment and Embodiment 1 is that the monosilane coupling agent containing carbon-carbon double bonds (3-methacryloyloxypropyltrimethoxysilane) in step (3) is replaced with the same volume of monosilane coupling agent containing carbon-carbon double bonds (vinyltriethoxysilane). Other conditions are the same as in Embodiment 1.

[0107] Comparative Example 1

[0108] This comparative example provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0109] (1) Mix 100 mg of water-dispersible silica (particle size of 20 nm, model XFI03, manufacturer: Jiangsu Xianfeng Nanotechnology Co., Ltd.) with 200 mL of anhydrous ethanol, stir vigorously at 1000 rpm for 5 min, sonicate for 30 min, and filter through a 0.1 μm filter membrane to obtain the filtrate.

[0110] (2) Add an aqueous acetic acid solution (40% by mass) to the filtrate obtained in step (1), and then slowly add bis[3-(trimethoxysilyl)propyl]amine. The volume ratio of the filtrate, the aqueous acetic acid solution and the bis[3-(trimethoxysilyl)propyl]amine is 100:0.1:6. Then add an aqueous acetic acid solution with a volume percentage concentration of 20% to adjust the pH to 5.5. After stirring for 8 h, add 3-methacryloyloxypropyltrimethoxysilane. The volume ratio of bis[3-(trimethoxysilyl)propyl]amine and 3-methacryloyloxypropyltrimethoxysilane is 6:2. Add an aqueous acetic acid solution with a volume percentage concentration of 20% again to adjust the pH to 5.5. Continue to react for 4 h to obtain silica sol.

[0111] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (20% by mass) and treated at 60°C for 8 h. After ultrasonic cleaning with purified water for 3 min, it was dried with compressed air and then dried in an oven at 60°C for 10 min to obtain the alkali-treated substrate. Then the alkali-treated substrate was immersed in the silica sol prepared in step (2) for 10 min. After taking it out, it was dried with compressed air and then dried in an oven at 80°C for 40 min to deposit Parylene. The conditions for depositing Parylene included: the temperature of the evaporation chamber was 150°C, the temperature of the pyrolysis chamber was 680°C, the temperature of the deposition chamber was 25°C, the chamber pressure of the deposition chamber was 2.0 Pa, and 3.5 g of Parylene C powder was used to form a protective coating on the substrate.

[0112] Comparative Example 2

[0113] This comparative example provides a protective coating and its preparation method. The difference between this example and Example 1 is that step (2) is adjusted to: dissolving tetraethyl orthosilicate in anhydrous ethanol until completely dissolved, with a volume ratio of tetraethyl orthosilicate to anhydrous ethanol of 3:10, to obtain a tetraethyl orthosilicate solution; replacing the bissilane solution in step (4) with the same volume of tetraethyl orthosilicate solution, with other conditions being the same as in Example 1.

[0114] Comparative Example 3

[0115] This comparative example provides a protective coating and its preparation method. The difference between this example and Example 1 is that step (3) is not included; step (4) does not include the step of adding the monosilane solution obtained in step (3) and reacting at 37°C for 1 h. Other conditions are the same as in Example 1.

[0116] Comparative Example 4

[0117] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that the monosilane coupling agent containing carbon-carbon double bonds (3-methacryloyloxypropyltrimethoxysilane) is replaced with the same volume of γ-glycidoxypropyltrimethoxysilane, while other conditions are the same as in Example 1.

[0118] Comparative Example 5

[0119] This comparative example provides a protective coating and its preparation method. The difference between this example and Example 1 is that the volume ratio of the amine-containing bissilane coupling agent, anhydrous ethanol and purified water in step (2) is adjusted to 5:9:1, and the volume ratio of the surfactant solution and the bissilane solution in step (4) is adjusted to 100:4. Other conditions are the same as in Example 1.

[0120] Comparative Example 6

[0121] This comparative example provides a protective coating and its preparation method. The difference between this example and Example 1 is that the volume ratio of the amine-containing bissilane coupling agent, anhydrous ethanol and purified water in step (2) is adjusted to 0.5:9:1, and the volume ratio of the surfactant solution and the bissilane solution in step (4) is adjusted to 100:2. Other conditions are the same as in Example 1.

[0122] Comparative Example 7

[0123] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that the amine-containing bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine) is replaced with the same volume of 1,2-bistrimethoxysilylethane, while the other conditions are the same as in Example 1.

[0124] Comparative Example 8

[0125] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that step (1) is adjusted to add a 1 mol / L sodium hydroxide solution to purified water to adjust the pH to 8 to obtain an alkaline solution; the surfactant solution in step (4) is replaced with the same volume of alkaline solution, and other conditions are the same as in Example 1.

[0126] Comparative Example 9

[0127] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that step (4) is adjusted to immerse the substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) in a sodium hydroxide solution (20% by mass) and treat it at 60°C for 8 h. Then, it is ultrasonically cleaned with purified water for 3 min and dried by blowing with compressed air at 60°C for 10 min to obtain the alkali-treated substrate. Then, the alkali-treated substrate is immersed in the surfactant solution obtained in step (1) and stirred in a water bath at 37°C for 30 min. Then, the bissilane solution obtained in step (2) is added in 3 batches, once every 15 min, with the same amount of bissilane solution added each time. The volume ratio of surfactant solution to bissilane solution is 100:3. Then, the monosilane solution obtained in step (3) is added in 3 batches, once every 15 min, with the same amount of monosilane solution added each time. The volume ratio of surfactant solution to monosilane solution is 100:2. The reaction is carried out at 37°C for 13 min. h, then the temperature is raised to 70℃ and the reaction continues for 16 h. After ultrasonic treatment in anhydrous ethanol for 60 s, the loosely bonded components are removed. After drying at 80℃ for 40 min, Parylene is deposited. The conditions for Parylene deposition include: the temperature of the evaporation chamber is 150℃, the temperature of the pyrolysis chamber is 680℃, the temperature of the deposition chamber is 25℃, the chamber pressure of the deposition chamber is 2.0 Pa, and 3.5 g of Parylene C powder is used to form a protective coating on the substrate. Other conditions are the same as in Example 1.

[0128] The following performance tests were conducted on the silica-containing protective coatings provided in Examples 1-8 and the protective coatings provided in Comparative Examples 1-9.

[0129] (1) Average thickness: The thickness of the mesoporous silica layer obtained in step (4) of the preparation method provided in Examples 1-8 and Comparative Examples 3-6 was measured at 5 locations using a Filmetrics film thickness tester (model: F20). The average value was taken to obtain the average thickness of the mesoporous silica layer.

[0130] The thickness of the silica-containing protective coatings prepared in Examples 1-8 was measured at five locations using a Filmetrics film thickness tester (model: F20), and the average value was taken to obtain the average thickness of the silica-containing protective coatings.

[0131] The thickness of the protective coatings prepared in Comparative Examples 1 to 9 was measured at 5 locations using a Filmmetrics film thickness tester (model: F20), and the average value was taken to obtain the average thickness of the protective coating.

[0132] (2) Adhesion effect: The test was conducted in accordance with GB / T 9286-2021. The protective coating containing silica was cut directly after it was made, with a blade spacing of 1 mm. Then, tape was used to stick and peel off the coating. The peeling situation was observed and graded according to GB / T 9286-2021. Each time the tape was stuck and peeled off, it was considered as one test. The same position was used to stick and peel off the tape 7 times to check the peeling situation.

[0133] (3) Destructive strength: Tested according to GB / T 5210-2006, 6 samples were selected for testing, and the average value was taken.

[0134] (4) Appearance: The substrates in the preparation methods provided in Examples 1-8 and Comparative Examples 1-9 were replaced with nickel-titanium alloy wire braided supports to prepare protective coatings on nickel-titanium alloy wire braided supports. The appearance of the protective coatings on the nickel-titanium alloy wire braided supports was visually observed under a microscope (magnification of at least 10 times) to check for any abnormalities.

[0135] The aforementioned nickel-titanium alloy wire braided support has a diameter of 10.5 mm and a length of 40 mm, and the nickel-titanium alloy wire used has a diameter of 0.2 mm. Before alkaline treatment, the support is first acid-washed for 10 minutes to remove the surface oxide layer.

[0136] The test results are shown in Table 1.

[0137] Table 1

[0138]

[0139] In Table 1, " / " indicates that the test was not performed.

[0140] According to the test results in Table 1, the protective coatings prepared in Examples 1-8 have high bonding strength with the substrate and good adhesion to the substrate.

[0141] Compared with Example 1, if silica modified by amine-containing bissilane coupling agent and carbon-carbon double bond-containing monosilane coupling agent is coated on the substrate surface to prepare a silica layer (Comparative Example 1), no chemical bond is formed between the silica layer and the substrate, and the silica layer does not have a mesoporous structure, so a silica / Parylene composite layer cannot be formed, and the resulting protective coating has low adhesion to the substrate.

[0142] Compared to Example 1, if the bissilane solution is replaced with the same volume of tetraethyl orthosilicate solution (Comparative Example 2), the hydrolysis products of tetraethyl orthosilicate are not positively charged and cannot displace surfactant molecules on the substrate surface by electrostatic interaction. Instead, they polymerize in the aqueous solution to form silica particles. During ultrasonic cleaning, any silica that may have been adsorbed on the substrate surface is removed, leaving almost no silica. Therefore, a silica / Parylene composite layer cannot be formed, resulting in low adhesion between the protective coating and the substrate.

[0143] Compared with Example 1, if the step of adding the monosilane solution obtained in step (3) is not included (Comparative Example 3), carbon-carbon double bonds cannot be introduced into the mesoporous silica layer, carbon-carbon double bond modified mesoporous silica layer cannot be formed, and the resulting protective coating has low adhesion to the substrate.

[0144] Compared with Example 1, if the monosilane coupling agent containing carbon-carbon double bonds is replaced with the same volume of monosilane coupling agent without carbon-carbon double bonds (Comparative Example 4), carbon-carbon double bonds cannot be introduced into the mesoporous silica layer, and a carbon-carbon double bond modified mesoporous silica layer cannot be formed, resulting in low adhesion between the protective coating and the substrate.

[0145] Compared with Example 1, the average thickness of the mesoporous silica layer formed on the substrate during the preparation process of Comparative Example 5 was too high, resulting in a decrease in the adhesion between the protective coating and the substrate; while the average thickness of the mesoporous silica layer formed on the substrate during the preparation process of Comparative Example 6 was too low, resulting in a decrease in the adhesion between the protective coating and the substrate.

[0146] Compared to Example 1, if the amine-containing bissilane coupling agent is replaced with a non-amine-containing bissilane coupling agent (Comparative Example 7), the hydrolysis products of the non-amine-containing bissilane coupling agent carry a negative charge and cannot displace surfactant molecules on the substrate surface. Instead, they polymerize in aqueous solution to form silica particles. During ultrasonic cleaning, any silica particles that may have been adsorbed on the substrate surface are removed, leaving almost no silica. Therefore, a silica / Parylene composite layer cannot be formed, resulting in low adhesion between the protective coating and the substrate.

[0147] Compared to Example 1, if no surfactant is added (Comparative Example 8), the amine-containing bissilane coupling agent and the carbon-carbon double-bond-containing monosilane coupling agent react directly with the hydroxyl groups on the substrate surface to form a silane-modified layer instead of a mesoporous silica layer. However, due to the low concentration of the amine-containing bissilane coupling agent and the carbon-carbon double-bond-containing monosilane coupling agent in the solution, the degree of crosslinking of the silane in the silane-modified layer is low, resulting in low adhesion between the protective coating and the substrate.

[0148] Compared to Example 1, if a monosilane solution is added immediately after the disilane solution and then the reaction is carried out (Comparative Example 9), a chemical reaction occurs between the two substances because a certain concentration of monosilane and disilane are present in the aqueous solution at the same time. As the system heats up, the reaction intensifies, forming a large amount of amorphous silica, causing the solution to become turbid and failing to effectively improve the adhesion between the protective coating and the substrate. During this reaction, some amine-containing disilanes still form silica structures on the substrate surface, but the uniformity is poor, resulting in numerous spots (bright spots, as the nickel-titanium alloy wire was not treated before use and its surface is glossy).

[0149] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a protective coating containing silica, characterized in that, The preparation method includes the following steps: (1) A surfactant, water and optionally a pH adjuster are mixed, wherein the mass ratio of the surfactant to water is (0.1~1):100, to obtain a surfactant solution; (2) Mix the amine-containing bissilane coupling agent, ethanol, water and optionally a pH adjuster to obtain a bissilane solution; (3) Mix a monosilane coupling agent containing carbon-carbon double bonds, ethanol, water, and optionally a pH adjuster to obtain a monosilane solution; (4) The substrate after alkali treatment is immersed in the surfactant solution prepared in step (1) and stirred. Then, the bissilane solution prepared in step (2) is added to carry out the first reaction to form a mesoporous silica layer on the substrate. The average thickness of the mesoporous silica layer is 100~300 nm. Then, the monosilane solution prepared in step (3) is added to carry out the second reaction. After that, Parylene is deposited to form the silica-containing protective coating. In step (2), the volume ratio of the amine-containing bissilane coupling agent to the total volume of ethanol and water is (2~3):10; in step (4), the volume ratio of the surfactant solution to the bissilane solution is 100:(3~5). or The volume ratio of the amine-containing bissilane coupling agent in step (2) to the total volume of ethanol and water is (3~5):10; the volume ratio of the surfactant solution to the bissilane solution in step (4) is 100:(1~3); Steps (1), (2), and (3) can be performed in any order or simultaneously.

2. The preparation method according to claim 1, characterized in that, The surfactants include nonionic surfactants; The nonionic surfactant includes any one or a combination of at least two of the following: polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxyethylene dehydrated sorbitan monooleate, polysorbate, polyoxyethylene fatty alcohol ether, polyethylene glycol fatty acid ester, or polyoxyethylene-polyoxypropylene block copolymer. The amine-containing bissilane coupling agent has the following general formula: (RO)3-Si-(CH2) n -NH-(CH2) n -Si-(OR)3; Wherein, R is an alkyl group having 1 to 10 carbon atoms, and n is 1 to 10. The monosilane coupling agent containing carbon-carbon double bonds has the following general structural formula: YR 1 -Si(R 2 )3 and / or Y-Si(R 2 3; Wherein, Y is independently any one of methacryloyloxy, acryloyloxy, or an alkenyl group having 2 to 10 carbon atoms; R 1 It is an alkylene group having 1 to 10 carbon atoms or an alkene group having 1 to 10 carbon atoms; R 2 Each is an alkoxy group with 1 to 10 carbon atoms.

3. The preparation method according to claim 1, characterized in that, The amine-containing bissilane coupling agent includes bis[3-(trimethoxysilyl)propyl]amine and / or bis[3-(triethoxysilyl)propyl]amine; Each of the carbon-carbon double bond-containing monosilane coupling agents independently comprises any one or a combination of at least two of 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltri(β-methoxyethoxy)silane.

4. The preparation method according to claim 1, characterized in that, Taking the total volume of ethanol and water in step (2) as 100%, the volume of ethanol is 85%~95%; The volume ratio of the monosilane coupling agent containing carbon-carbon double bonds in step (3) to the total volume of ethanol and water is (0.1~1):10; Taking the total volume of ethanol and water in step (3) as 100%, the volume of ethanol is 85%~95%; The absolute value of the pH difference between any two of the surfactant solution, bissilane solution, and monosilane solution is ≤0.2; The pH adjuster in steps (1), (2) and (3) each independently includes an acidic solution and / or an alkaline solution; The acidic solution includes an aqueous solution of acetic acid; The volume percentage concentration of the acetic acid aqueous solution is 10%~40%; The alkaline solution includes a weak alkaline solution and / or a strong alkaline solution; The weak alkaline solution includes ammonia; The concentration of the strong alkali solution is 0.5~3 mol / L; The mixing process described in steps (2) and (3) also includes a settling step; The resting time described in steps (2) and (3) is 0 to 24 hours, respectively.

5. The preparation method according to claim 1, characterized in that, The stirring temperature in step (4) is 35~40℃, and the stirring time is ≥30 min; The addition of the bissilane solution obtained in step (2) in step (4) is done in batches; The temperature of the first reaction is 35~40℃, and the reaction time is ≥12 h; The first reaction of the bissilane solution obtained in step (2) is carried out under stirring or shaking. The volume ratio of the surfactant solution to the monosilane solution in step (4) is 100:(1~5); The addition of the monosilane solution obtained in step (3) in step (4) is done in batches; The second reaction includes reacting at 35~40℃ for ≥1 h, and then raising the temperature to 60~80℃ to continue the reaction for ≥8 h; The second reaction is carried out by stirring or shaking the monosilane solution obtained in step (3).

6. The preparation method according to claim 1, characterized in that, The second reaction is followed by a washing and drying step; The cleaning process includes ultrasonic cleaning in ethanol for 10-60 seconds. The drying temperature is 60~100℃, and the drying time is 20~120 min; The alkaline treatment includes immersion in a strong alkaline solution; The temperature for impregnation with the strong alkaline solution is 20~90℃; The immersion time in the strong alkaline solution is 2-24 hours. The strong alkaline solution used in the alkaline treatment includes a strong alkali and water; The strong base includes alkali metal hydroxides and / or alkaline earth metal hydroxides; The alkali metal hydroxide includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, or rubidium hydroxide. The alkaline earth metal hydroxides include calcium hydroxide and / or barium hydroxide; The strong alkaline solution used in the alkaline treatment has a mass percentage concentration of 10% to 30%.

7. The preparation method according to claim 1, characterized in that, The conditions for Parylene deposition include: the temperature of the evaporation chamber is 120~180℃, the temperature of the pyrolysis chamber is 670~690℃, the temperature of the deposition chamber is 10~30℃, and the chamber pressure of the deposition chamber is 1~13 Pa. The thickness of the silica-containing protective coating is 0.5~2 μm.

8. A protective coating containing silicon dioxide, characterized in that, The silica-containing protective coating is prepared using the preparation method described in any one of claims 1 to 7.

9. The application of the silica-containing protective coating as described in claim 8 in the protection of a substrate surface.

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