A protective coating, its preparation method and application

Abstract

This invention relates to a protective coating and its preparation method and application. The preparation method of the protective coating includes the following steps: (1) mixing a bissilane coupling agent, a monosilane coupling agent containing carbon-carbon double bonds, ethanol, water and optionally a pH adjuster, wherein the volume ratio of the bissilane coupling agent and the monosilane coupling agent containing carbon-carbon double bonds is (3~10):1, to obtain a composite silane solution; (2) mixing a monosilane coupling agent containing carbon-carbon double bonds, ethanol, water and optionally a pH adjuster to obtain a monosilane solution; (3) immersing the alkali-treated substrate in the composite silane solution obtained in step (1), drying it for the first time, immersing it in the monosilane solution obtained in step (2), drying it for the second time, and then depositing a poly(p-xylene) layer to form a protective coating. The protective coating has high bonding strength with the substrate, good adhesion to the substrate, and good stability between batches.

Description

Technical Field

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

[0002] Parylene, also known as paraxylene, is a new type of environmentally friendly coating material that provides protective properties such as protection against salt spray, oxidation, and moisture. Parylene coatings are produced using a vapor deposition process; however, due to the relatively symmetrical nature of parylene (weak polarity), its adhesion to the substrate is 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 plating a parylene film. This allows the coupling agent and the monomers of parylene 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 to be deposited more firmly on the surface of the device to be coated.

[0005] The process of treating the substrate with coupling agent vapor before depositing a poly(p-xylene) film generally refers to placing the coupling agent in a 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, and then depositing the poly(p-xylene) 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 primarily physical adsorption, resulting in a weak bond. After the active monomer of parylene comes into contact with the substrate surface, the coupling agent and the active monomer of parylene react simultaneously on the metal substrate surface to form a parylene coating. This reaction occurs under ambient temperature and vacuum conditions, which are insufficient to allow the adsorbed coupling agent 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, this unreacted coupling agent poses a safety risk. Alternatively, a curing period under specific temperature and humidity conditions may be necessary to allow sufficient reaction between silanoxy groups and between silanoxy and hydroxyl groups on the substrate surface, 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. However, under normal circumstances, 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, some of 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] Therefore, there is a need to develop a protective coating with good adhesion to the substrate and its preparation method. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a protective coating, its preparation method, and its application. The protective coating exhibits high adhesion to the substrate, good bonding effect, and good batch-to-batch stability.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a protective coating, the method comprising the following steps: (1) mixing a bissilane coupling agent, a monosilane coupling agent containing carbon-carbon double bonds, ethanol, water and optionally a pH adjuster, wherein the volume ratio of the bissilane coupling agent and the monosilane coupling agent containing carbon-carbon double bonds is (3~10):1 (e.g. 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, etc.) to obtain a composite silane solution; (2) mixing the monosilane coupling agent containing carbon-carbon double bonds, ethanol, water and optionally a pH adjuster to obtain a monosilane solution; (3) immersing the alkali-treated substrate in the composite silane solution obtained in step (1), drying it for the first time, immersing it in the monosilane solution obtained in step (2), drying it for the second time, and then depositing a poly(p-xylene) layer to form a protective coating; the steps (1) and (2) are performed in any order, or simultaneously.

[0011] In this invention, the composite silane solution obtained by dip coating step (1) is first dried, then dip coated with the monosilane solution obtained by step (2), and then dried again to form a dense composite silane layer on the substrate surface. Compared with monosilane coupling agent, the bissilane coupling agent in the composite silane solution can generate more silanols after hydrolysis. The number of silanols is twice that of monosilane coupling agent. After the silanol on the first silicon of the bissilane coupling agent reacts, it will not affect the silanol on the second silicon to continue to react. Moreover, the silanol formed after the hydrolysis of the bissilane coupling agent is more acidic than the silanol formed after the hydrolysis of the monosilane coupling agent. It has stronger reactivity. Therefore, more covalent bonds can be formed with the substrate to form more and stronger chemical bonds, resulting in a higher crosslinking density. The chemical bonds are more difficult to hydrolyze, have strong resistance to hydrolysis, and are not easily removed in the subsequent cleaning process. The bonding force between the bissilane coupling agent and the substrate is stronger. The monosilane coupling agent containing carbon-carbon double bonds can introduce a large number of carbon-carbon double bonds, improve the bonding force with the substrate, and improve the density of the composite silane layer.

[0012] In this invention, the monosilane solution obtained in the dip coating step (2) can further introduce a large number of monosilane coupling agents containing carbon-carbon double bonds on the surface of the composite silane layer, and together form a silane layer on the substrate surface. The carbon-carbon double bonds contained therein can react with the active monomer of parylene and connect with the parylene layer through chemical bonds, thereby enhancing the bonding force between the parylene layer and the silane layer. Furthermore, the dip coating monosilane solution can also enhance the processing depth and processing uniformity, reduce the surface difference of the substrate, and improve the batch-to-batch stability.

[0013] 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 of the parylene layer. Furthermore, the reaction between the bissilane coupling agent, the monosilane coupling agent containing carbon-carbon double bonds, and the substrate is completed before the parylene layer is deposited. Since no coupling agent vapor is used during the parylene layer deposition process, 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, thus 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.

[0014] Preferably, the volume ratio of the bissilane coupling agent in step (1) to the total volume of ethanol and water is (3~10):100, for example 4:100, 5:100, 6:100, 7:100, 8:100 or 9:100, etc.

[0015] Preferably, with the total volume of ethanol and water in step (1) being 100%, the volume of ethanol is 85% to 95%, such as 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, or 94%.

[0016] Preferably, the pH of the composite silane solution is 6.5 to 9.5, such as 7, 7.5, 8, 8.5 or 9.

[0017] Preferably, the bissilane coupling agent in step (1) has the following general structural formula: (RO)3-Si-A-Si-(OR)3; wherein R is an alkyl group with 1 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8 or 9), and A is -(CH2). n -NH-(CH2) n - and / or -(CH2) n -, n is independently 1 to 10 (e.g., 2, 3, 4, 5, 6, 7, 8 or 9, etc.).

[0018] Preferably, A is -(CH2). n -

[0019] Preferably, the carbon-carbon double bond-containing monosilane coupling agents described in steps (1) and (2) each independently have the following general structural formula: YR 1 -Si(R 2 )3 and / or Y-Si(R 2 3.

[0020] 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).

[0021] Preferably, the bissilane coupling agent in step (1) includes any one or a combination of at least two of 1,2-bistrimethoxysilyl ethane, 1,2-bistriethoxysilyl ethane, bis[3-(trimethoxysilyl)propyl]amine or bis[3-(triethoxysilyl)propyl]amine.

[0022] Preferably, the carbon-carbon double bond-containing monosilane coupling agents in steps (1) and (2) each independently include any one or a combination of at least two of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltri(β-methoxyethoxy)silane.

[0023] Preferably, the volume ratio of the monosilane coupling agent containing carbon-carbon double bonds in step (2) to the total volume of ethanol and water is (2~10):100, for example, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100 or 9:100, etc.

[0024] 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%.

[0025] Preferably, the pH of the monosilane solution is 6.5 to 9.5 (e.g., 7, 7.5, 8, 8.5 or 9), and more preferably 8.0 to 8.5.

[0026] In this invention, the pH of the monosilane solution affects the hydrolysis and condensation process of the monosilane solution. The optimal pH range is 8.0 to 8.5. As the pH increases, the binding strength decreases slightly. Above 9.5, the binding strength decreases significantly. As the pH decreases, the binding strength decreases slightly. Below 6.5, the binding strength decreases significantly.

[0027] Preferably, the pH adjuster described in steps (1) and (2) each independently comprises an acidic solution and / or an alkaline solution.

[0028] Preferably, the acidic solution comprises an aqueous solution of acetic acid.

[0029] Preferably, the volume percentage concentration of the acetic acid aqueous solution is 10% to 40%, such as 15%, 20%, 25%, 30%, or 35%.

[0030] Preferably, the alkaline solution includes a weak alkaline solution and / or a strong alkaline solution.

[0031] Preferably, the weak alkaline solution includes ammonia.

[0032] Preferably, the strong alkaline solution includes a sodium hydroxide solution.

[0033] Preferably, the concentration of the strong alkali solution is 0.5~3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L or 2.5 mol / L.

[0034] Preferably, steps (2) and (3) each include a settling step after mixing.

[0035] Preferably, the settling time is 0~24 h, such as 3 h, 6 h, 9 h, 12 h, 15 h, 18 h or 21 h.

[0036] Preferably, the alkali treatment includes immersion in a strong alkali solution.

[0037] Preferably, the temperature of the immersion coating with the strong alkaline solution is 20~90℃, such as 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃.

[0038] Preferably, the immersion time in the strong alkaline solution is 1 to 24 hours, such as 3 hours, 6 hours, 9 hours, 12 hours, 15 hours, 18 hours, or 21 hours.

[0039] Preferably, the strong alkaline solution used in the alkaline treatment includes a strong alkali and water.

[0040] Preferably, the strong base includes alkali metal hydroxides and / or alkaline earth metal hydroxides.

[0041] 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.

[0042] Preferably, the alkaline earth metal hydroxide includes calcium hydroxide and / or barium hydroxide.

[0043] 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%.

[0044] Preferably, the time for dipping the composite silane solution obtained in step (1) in step (3) is ≥10 min, such as 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min.

[0045] Preferably, the temperature of the composite silane solution obtained in step (1) of the dip coating step (3) is 10~30℃, such as 12℃, 14℃, 16℃, 18℃, 20℃, 22℃, 24℃, 26℃ or 28℃.

[0046] Preferably, the temperature of the first drying is 80~150℃, such as 90℃, 100℃, 110℃, 120℃, 130℃ or 140℃.

[0047] Preferably, the first drying time is 15 to 60 minutes, such as 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes or 55 minutes.

[0048] Preferably, the dipping time for the monosilane solution obtained in step (2) is ≥10 min, such as 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min.

[0049] Preferably, the temperature of the monosilane solution obtained in step (2) of the dip coating step (3) is 10~30℃, for example 12℃, 14℃, 16℃, 18℃, 20℃, 22℃, 24℃, 26℃ or 28℃.

[0050] Preferably, the temperature of the second drying is 80~150℃, such as 90℃, 100℃, 110℃, 120℃, 130℃ or 140℃.

[0051] Preferably, the second drying time is 15 to 60 minutes, such as 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes or 55 minutes.

[0052] In this invention, during the dip coating process of composite silane solution and monosilane solution, the thickness and composition of the silane layer formed on the substrate surface are related to the composition and concentration of the composite silane solution and monosilane solution, as well as the surface properties of the substrate and the reaction temperature. When the reaction reaches equilibrium, extending the dip coating time will hardly change the silane layer.

[0053] Preferably, the conditions for depositing the poly(p-xylene) layer include: the temperature of the evaporation chamber is 120~180℃ (e.g., 130℃, 140℃, 150℃, 160℃ or 170℃, etc.), the temperature of the pyrolysis chamber is 670~690℃ (e.g., 673℃, 676℃, 679℃, 682℃, 685℃ or 688℃, etc.), the temperature of the deposition chamber is 10~30℃ (e.g., 12℃, 14℃, 16℃, 18℃, 20℃, 22℃, 24℃, 26℃ or 28℃, etc.), and the chamber pressure of the deposition chamber is 1~13 Pa (e.g., 2 Pa, 4 Pa, 6 Pa, 8 Pa, 10 Pa or 12 Pa, etc.).

[0054] Preferably, the raw material for depositing the parylene layer includes parylene dichlorodimethylamine (Parylene C powder).

[0055] In a second aspect, the present invention provides a protective coating comprising a parylene layer and a bissilane coupling agent and a monosilane coupling agent containing carbon-carbon double bonds located between the parylene layer and a substrate, and prepared by the preparation method described in the first aspect.

[0056] Thirdly, the present invention provides an application of the protective coating as described in the second aspect in the protection of a substrate surface.

[0057] For example, the substrate includes a nickel-titanium alloy substrate.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects:

[0059] The preparation method of the present invention involves dipping in a composite silane solution, drying it, then dipping in a monosilane solution, drying it again, and finally depositing a poly(p-xylene) layer. The resulting protective coating has high adhesion to the substrate, good adhesion to the substrate, and good stability of the products produced in each batch. It can effectively avoid the problem of coupling agent residue in the deposition chamber and significantly shorten the processing time to achieve high adhesion. Attached Figure Description

[0060] Figure 1 This is a flowchart of the method for preparing the protective coating provided in Embodiment 1 of the present invention;

[0061] Among them, 1-silane layer; 2-poly(p-xylene) layer; 3-protective coating. Detailed Implementation

[0062] 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.

[0063] 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.

[0064] Example 1

[0065] This embodiment provides a protective coating and its preparation method. The preparation method includes the following steps, and the preparation process is as follows: Figure 1 As shown:

[0066] (1) Mix bissilane coupling agent (1,2-bistrimethoxysilylethane), carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 4:1:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8, and let stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0067] (2) Mix a carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 5:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8. Let stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0068] (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 24 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After removal, it was washed with water and dried. It was then dried at 100°C for 30 min and then immersed in the monosilane solution prepared in step (2) for 60 min. After removal, it was washed with water and dried. It was then dried at 80°C for 40 min to form silane layer 1. After that, parylene layer 2 was deposited. The conditions for depositing parylene layer 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 the dichloro-p-xylene dimer was 3.5. g, forming a protective coating 3 on the substrate.

[0069] Example 2

[0070] This embodiment provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0071] (1) Mix the bissilane coupling agent (1,2-bistrimethoxysilane), the carbon-carbon double bond-containing monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 10:1:95:5. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8.5, and let stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0072] (2) Mix a carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 10:95:5. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8, and let it stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0073] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (mass percentage concentration of 20%) and treated at 60°C for 24 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 100°C for 30 min. After that, it was immersed in the monosilane solution prepared in step (2) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 80°C for 40 min to form a silane layer. Then, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate.

[0074] Example 3

[0075] This embodiment provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0076] (1) Mix the bissilane coupling agent (1,2-bistrimethoxysilane), the carbon-carbon double bond-containing monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 3:1:85:15. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 9, and let it stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0077] (2) Mix a carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 2:85:15. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8, and let it stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0078] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (mass percentage concentration of 20%) and treated at 60°C for 24 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 100°C for 30 min. After that, it was immersed in the monosilane solution prepared in step (2) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 80°C for 40 min to form a silane layer. Then, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate.

[0079] Example 4

[0080] This embodiment provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0081] (1) Mix the bissilane coupling agent (1,2-bistriethoxysilyl ethane), the carbon-carbon double bond-containing monosilane coupling agent (3-methacryloxypropyltriethoxysilane), anhydrous ethanol and water in a volume ratio of 7:1:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 6.5, and let it stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0082] (2) Mix the carbon-carbon double bond-containing monosilane coupling agent (3-methacryloxypropyltriethoxysilane), anhydrous ethanol and water in a volume ratio of 7:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 6.5. Let stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0083] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (mass percentage concentration of 20%) and treated at 60°C for 24 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 100°C for 30 min. After that, it was immersed in the monosilane solution prepared in step (2) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 80°C for 40 min to form a silane layer. Then, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate.

[0084] Example 5

[0085] This embodiment provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0086] (1) Mix bissilane coupling agent (1,2-bistrimethoxysilylethane), carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 4:1:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8, and let stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0087] (2) Mix a carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 5:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8. Let stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0088] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (30% by mass) and treated at 70°C for 4 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 80°C for 60 min. After that, it was immersed in the monosilane solution prepared in step (2) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 100°C for 60 min to form a silane layer. Then, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate.

[0089] Example 6

[0090] This embodiment provides a protective coating and its preparation method, the preparation method comprising the following steps:

[0091] (1) Mix bissilane coupling agent (1,2-bistrimethoxysilylethane), carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 4:1:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8, and let stand in the dark for 24 h to hydrolyze and obtain a composite silane solution.

[0092] (2) Mix a carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane), anhydrous ethanol and water in a volume ratio of 5:90:10. Add sodium hydroxide solution (concentration of 1 mol / L) to adjust the pH to 8. Let stand in the dark for 4 h to hydrolyze and obtain a monosilane solution.

[0093] (3) The substrate (nickel-titanium alloy plate, 20 mm long and 20 mm wide) was immersed in sodium hydroxide solution (10% by mass) and treated at 90°C for 24 h. After ultrasonic cleaning with deionized 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 composite silane solution prepared in step (1) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 120°C for 20 min. After that, it was immersed in the monosilane solution prepared in step (2) for 60 min. After taking it out, it was washed with water and dried. It was then dried at 120°C for 30 min to form a silane layer. Then, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate.

[0094] Example 7

[0095] This embodiment provides a protective coating and its preparation method. The difference between this embodiment and Embodiment 1 is that the carbon-carbon double bond monosilane coupling agent (3-methacryloyloxypropyltrimethoxysilane) in step (1) is replaced with the same volume of carbon-carbon double bond monosilane coupling agent (vinyltriethoxysilane).

[0096] Replace the carbon-carbon double bond monosilane coupling agent (3-methacryloyloxypropyltrimethoxysilane) in step (2) with the same volume of carbon-carbon double bond monosilane coupling agent (vinyltriethoxysilane).

[0097] Other conditions are the same as in Example 1.

[0098] Example 8

[0099] This embodiment provides a protective coating and its preparation method. The difference between this embodiment and Example 1 is that the bissilane coupling agent (1,2-bistrimethoxysilylethane) in step (1) is replaced with the same volume of bissilane coupling agent (bis[3-(trimethoxysilyl)propyl]amine), and the sodium hydroxide solution (concentration of 1 mol / L) is replaced with an acetic acid aqueous solution with a volume percentage concentration of 20% and the pH is adjusted to 8. Other conditions are the same as in Example 1.

[0100] Example 9

[0101] This embodiment provides a protective coating and its preparation method. The difference between this embodiment and Embodiment 1 is that the temperature of the second drying step (3) is adjusted to 60°C, while the other conditions are the same as in Embodiment 1.

[0102] Comparative Example 1

[0103] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that step (2) is not included. Step (3) does not include the step of immersing the coating in the monosilane solution obtained in step (2) for 60 min, washing it with water and drying it after removal, and then drying it at 80°C for 40 min. Other conditions are the same as in Example 1.

[0104] Comparative Example 2

[0105] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that the carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane) in step (1) is replaced with the same volume of 3-aminopropyltriethoxysilane; the carbon-carbon double bond monosilane coupling agent (3-methacryloxypropyltrimethoxysilane) in step (2) is replaced with the same volume of 3-glycidoxypropyltrimethoxysilane, and other conditions are the same as in Example 1.

[0106] Comparative Example 3

[0107] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that the carbon-carbon double bond monosilane coupling agent (3-methacryloyloxypropyltrimethoxysilane) in step (2) is replaced with the same volume of 3-glycidoxypropyltrimethoxysilane. Other conditions are the same as in Example 1.

[0108] Comparative Example 4

[0109] 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 bissilane coupling agent, the monosilane coupling agent containing carbon-carbon double bonds, anhydrous ethanol and water in step (1) is adjusted to 1:4:90:10, while other conditions are the same as in Example 1.

[0110] Comparative Example 5

[0111] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that step (1) is not included. Step (3) 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 24 h. After ultrasonic cleaning with deionized water for 3 min, it is 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 is immersed in the monosilane solution prepared in step (2) for 60 min, taken out, washed with water, dried, and then dried again at 80°C for 40 min. 2 mL of 3-methacryloyloxypropyltrimethoxysilane is placed in a deposition chamber with a chamber pressure of 6 Pa and a temperature of 20°C to treat the substrate after the monosilane solution has been dipped and dried for 60 min. After min, a parylene layer was deposited. The conditions for depositing the parylene layer 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 dichloro-p-xylene dimer was used to form a protective coating on the substrate. Other conditions were the same as in Example 1.

[0112] Comparative Example 6

[0113] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that step (1) is not included. Step (3) does not include the step of immersing the coating in the composite silane solution obtained in step (1) for 60 minutes, washing it with water and drying it after removal, and then drying it at 100°C for 30 minutes. Other conditions are the same as in Example 1.

[0114] Comparative Example 7

[0115] This comparative example provides a protective coating and its preparation method. The difference between this and Example 1 is that the volume ratio of the bissilane coupling agent, the monosilane coupling agent containing carbon-carbon double bonds, anhydrous ethanol and water in step (1) is adjusted to 4:6:90:10; step (2) is not included; step (3) does not include the step of immersing in the monosilane solution obtained in step (2) for 60 min, taking it out, washing it with water, blowing it dry, and performing a second drying at 120°C for 30 min. Other conditions are the same as in Example 1.

[0116] The protective coatings provided in Examples 1-9 and Comparative Examples 1-7 were subjected to the following performance tests.

[0117] (1) Adhesion effect: The test was conducted in accordance with GB / T 9286-2021. After the protective coating was made, it was cut directly with a blade spacing of 1 mm. Then, tape was used to stick and peel off the coating. The peeling of the protective coating was observed and graded in accordance with GB / T 9286-2021. Each time the tape was stuck and peeled off was considered as one test. The same position was used to stick and peel off the tape 7 times to check the peeling of the coating.

[0118] (2) Damaging strength: Tested according to GB / T 5210-2006, 6 samples were selected for testing, and the average value was taken.

[0119] (3) Appearance of protective coating: The substrates in the preparation methods provided in Examples 1-9 and Comparative Examples 1-7 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.

[0120] The aforementioned nickel-titanium alloy wire braided support has a diameter of 10.5 mm and a length of 40 mm. 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 oxide layer on the surface.

[0121] The test results are shown in Table 1.

[0122] Table 1

[0123]

[0124] According to the test results in Table 1, the protective coatings prepared in Examples 1-9 have high bonding strength with the substrate and good adhesion to the substrate.

[0125] Compared to Example 1, if 1,2-bis(trimethoxysilyl)ethane is replaced with the same volume of bis[3-(trimethoxysilyl)propyl]amine (Example 8), the protective coating is prepared using a scaffold woven from nickel-titanium alloy wires. Numerous white spots appear on the scaffold surface. This is likely because the secondary amine groups can form additional coordination bonds with the nickel-titanium metal, resulting in the adsorption of more bissilanes on the nickel-titanium alloy wire surface. Excessive bissilanes solidify and crosslink during drying, forming white spots, especially at the intersections of the nickel-titanium alloy wires in the scaffold. Therefore, the general structural formula of the bissilane coupling agent is (RO)3-Si-A-Si-(OR)3, where A is preferably -(CH2). n - Better results.

[0126] Compared to Example 1, if the second drying temperature is too low (Example 9), the adhesion between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates. This is because a lower temperature affects the degree of crosslinking of the silane layer, thereby affecting the adhesion between the final protective coating and the substrate.

[0127] Compared with Example 1, if the monosilane solution is not used for immersion coating (Comparative Example 1), the content of carbon-carbon double bonds in the silane layer is low, the adhesion between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates.

[0128] Compared with Example 1, if the monosilane coupling agent containing carbon-carbon double bonds in steps (1) and (2) is replaced with a monosilane coupling agent without carbon-carbon double bonds (Comparative Example 2), then the silane layer does not contain carbon-carbon double bonds, the bonding force between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates.

[0129] Compared with Example 1, if the monosilane coupling agent containing carbon-carbon double bonds in step (2) is replaced with a monosilane coupling agent without carbon-carbon double bonds (Comparative Example 3), the content of carbon-carbon double bonds in the silane layer is low, the bonding force between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates.

[0130] Compared with Example 1, if the volume ratio of the bissilane coupling agent and the carbon-carbon double bond monosilane coupling agent in step (1) is too low (Comparative Example 4), and the proportion of the carbon-carbon double bond monosilane coupling agent is high, when the bissilane coupling agent and the carbon-carbon double bond monosilane coupling agent react with the hydroxyl groups on the substrate surface, there is a competitive reaction between the two. Too much carbon-carbon double bond monosilane coupling agent will affect the bonding between the bissilane coupling agent and the substrate, and affect the bonding force between the silane layer and the substrate, thereby reducing the bonding force between the final protective coating and the substrate and worsening the adhesion effect on the substrate.

[0131] Compared with Example 1, if the composite silane solution is not used for dip coating, but 3-methacryloyloxypropyltrimethoxysilane is placed in the deposition chamber to treat the substrate before depositing the parylene layer (Comparative Example 5), the adhesion between the prepared protective coating and the substrate decreases and the adhesion effect on the substrate deteriorates.

[0132] Compared with Example 1, if the composite silane solution is not used for dip coating (Comparative Example 6), the adhesion between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates.

[0133] Compared with Example 1, if only one dip coating is used (Comparative Example 7), the adhesion between the prepared protective coating and the substrate decreases, and the adhesion effect on the substrate deteriorates.

[0134] 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 producing a protective coating, characterized in that The preparation method comprises the following steps: (1) mixing a double silane coupling agent, a single silane coupling agent containing a carbon-carbon double bond, ethanol, water, and optionally a pH adjusting agent, the volume ratio of the double silane coupling agent and the single silane coupling agent containing a carbon-carbon double bond being (3-10):1, to obtain a composite silane solution, the pH of the composite silane solution being 6.5-9.5; (2) mixing a single silane coupling agent containing a carbon-carbon double bond, ethanol, water, and optionally a pH adjusting agent to obtain a single silane solution, the pH of the single silane solution being 6.5-9.5; (3) dip coating the composite silane solution prepared in step (1) after alkali treatment, first drying, then dip coating the single silane solution prepared in step (2), second drying, and then depositing a parylene layer to form a protective coating; Steps (1) and (2) are performed in a step-by-step manner without a specific order or simultaneously; The double silane coupling agent in step (1) has the following general structure: (RO)3-Si-A-Si-(OR)3; wherein R is an alkyl group having 1 to 10 carbon atoms, A is -(CH2) n -NH-(CH2) n - and / or -(CH2) n - and n are each independently 1 to 10; The temperature of the first drying in step (3) is 80-150°C, and the temperature of the second drying is 80-150°C.

2. The production method according to claim 1, characterized by, The volume ratio of the double silane coupling agent in step (1) to the total volume of ethanol and water is (3-10):100; The volume of ethanol in step (1) is 85%-95% based on the total volume of ethanol and water in step (1) being 100%; 3. The preparation method according to claim 1, characterized in that, The carbon-carbon double bond-containing monosilane coupling agents of Step (1) and Step (2) each independently have the following general structure: Y-R 1 -Si(R 2 )3 and / or Y-Si(R 2 )3; wherein each Y is independently any one of a methacryloyloxy group, an acryloyloxy group, or an alkenyl group having 2 to 10 carbon atoms; R 1 is an alkylene group having 1 to 10 carbon atoms or an alkyleneoxy group having 1 to 10 carbon atoms; R 2 each independently is an alkoxy group having 1 to 10 carbon atoms.

4. The preparation method according to claim 1, characterized in that, The double silane coupling agent in step (1) includes any one or a combination of at least two of 1,2-bistrimethoxysilylethane, 1,2-bistrimethoxysilylethane, bis[3-(trimethoxysilyl)propyl]amine, or bis[3-(triethoxysilyl)propyl]amine; The single silane coupling agent containing a carbon-carbon double bond in steps (1) and (2) each independently includes any one or a combination of at least two of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, or vinyltris(β-methoxyethoxy)silane.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the single silane coupling agent containing a carbon-carbon double bond in step (2) to the total volume of ethanol and water is (2-10):100; The volume of ethanol in step (2) is 85%-95% based on the total volume of ethanol and water in step (2) being 100%; The pH adjusting agent in steps (1) and (2) each independently includes an acidic solution and / or a basic solution; The acidic solution includes an aqueous acetic acid solution; The aqueous acetic acid solution has a volume percentage concentration of 10%-40%; The basic solution includes a weak base solution and / or a strong base solution; The weak base solution includes ammonia water; The strong base solution includes a sodium hydroxide solution; The concentration of the strong base solution is 0.5-3 mol / L; The mixing in steps (2) and (3) each independently further comprises a step of standing; The standing time is 3-24 h.

6. The method of claim 1, wherein, The alkali treatment comprises dip coating a strong base solution; The temperature of the dip coating of the strong base solution is 20-90°C; The time of the dip coating of the strong base solution is 1-24 h; The strong base solution used in the alkali treatment includes a strong base and water; The strong base comprises alkali metal hydroxide and / or alkaline earth metal hydroxide; The alkali metal hydroxide comprises any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide or rubidium hydroxide; The alkaline earth metal hydroxide comprises calcium hydroxide and / or barium hydroxide; The mass percentage concentration of the strong base solution used in the alkali treatment is 10% to 30%.

7. The preparation method according to claim 1, characterized in that, The time for the immersion coating of the composite silane solution prepared in step (1) is ≥10 min; The temperature for the immersion coating of the composite silane solution prepared in step (1) is 10 to 30℃; The first drying time is 15 to 60 min; The time for the immersion coating of the single silane solution prepared in step (2) is ≥10 min; The temperature for the immersion coating of the single silane solution prepared in step (2) is 10 to 30℃; The second drying time is 15 to 60 min.

8. The method of any one of claims 1 to 7, wherein the method further comprises the step of: The conditions for the deposition of the parylene layer include: the temperature of the evaporation chamber is 120 to 180℃, the temperature of the cracking chamber is 670 to 690℃, the temperature of the deposition chamber is 10 to 30℃, and the chamber pressure of the deposition chamber is 1 to 13 Pa. ​ 9. A protective coating, characterized in that The protective coating comprises a parylene layer and a bis-silane coupling agent and a single silane coupling agent containing carbon-carbon double bond between the parylene layer and the substrate, and is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the protective coating of claim 9 in the protection of the surface of a substrate.

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