A protective coating for deep-sea pressure hull and its preparation method

Abstract

This invention relates to the field of coating technology, and discloses a deep-sea pressure-resistant hull protective coating and its preparation method, comprising the following steps: substrate treatment, sequentially adding epoxy resin-modified polyurethane, reinforcing filler, anti-corrosion filler, curing agent and solvent in a predetermined proportion and mixing evenly to obtain a primer, and spraying the primer onto the substrate; then using isoxazole-modified polyurea as a topcoat, spraying the topcoat on the side of the primer away from the substrate to obtain the protective coating. This protective coating has excellent waterproof performance, impact resistance, wear resistance and anti-bioadhesion ability, and can effectively prevent water, various corrosive factors such as ions in seawater, and various polluting organisms in seawater such as barnacles, mussels, oysters and sponges from contacting the substrate surface.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a protective coating for deep-sea pressure hulls and its preparation method. Background Technology

[0002] Marine equipment and facilities, such as offshore platforms, ships, submersibles, and oil and gas development equipment, operate in the marine environment for extended periods, resulting in wear and corrosion. Various organisms and inorganic substances in the deep sea also cause friction and even collisions, affecting the service life and safety of these marine installations. Currently, marine equipment components primarily utilize metallic materials such as titanium alloys and aluminum alloys. These materials have relatively low surface hardness and poor shear resistance. Transmission, sliding, and friction between components, as well as the scouring effect of seawater particles, all contribute to material wear, leading to system damage and failure. Furthermore, the long-term exposure of marine equipment to seawater corrosion behaviors such as chloride ion pitting and oxidation exacerbates friction, adhesion, and even seizing between components, ultimately requiring disassembly and significantly increasing the cost and difficulty of maintenance. Therefore, the coupled damage caused by wear and corrosion has become a major technical challenge for marine equipment components.

[0003] In marine environments, applying organic coatings to metal surfaces is one of the most effective methods of corrosion protection. By adhering tightly to the substrate surface, the organic coating blocks oxygen and slows the penetration of water molecules and other corrosive ions, providing effective protection. However, existing coating materials often have limited functionality and cannot meet the complex and variable performance requirements of deep-sea service environments. For example, epoxy-based anti-corrosion coatings have advantages such as high adhesion, high strength, chemical resistance, and abrasion resistance, but they are brittle and have low heat resistance; polyurethane-based anti-corrosion coatings are hard and have strong adhesion, but poor weather resistance; polyurea-based anti-corrosion coatings have good high-temperature and low-temperature performance, but generally poor mechanical properties. These shortcomings limit the application of protective coatings in deep-sea applications. Therefore, there is a need to provide a deep-sea pressure hull protective coating to address these issues. Summary of the Invention

[0004] Based on the above, the purpose of this invention is to provide a deep-sea pressure-resistant shell protective coating and its preparation method, which provides protection for marine equipment and significantly improves the corrosion resistance, impact resistance, wear resistance and biofouling resistance of marine equipment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A deep-sea pressure-resistant hull protective coating includes a primer and a topcoat, wherein the primer comprises epoxy resin-modified polyurethane and the topcoat comprises isoxazole-modified polyurea.

[0007] As a preferred embodiment of a protective coating for a deep-sea pressure hull, the primer comprises epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler and solvent; the mass ratio of the epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler and solvent is 1: (0.4~1): (0.1~0.2): (0.2~0.45): (1~1.4).

[0008] As a preferred embodiment of a deep-sea pressure-resistant shell protective coating, the curing agent includes an amine curing agent, specifically a mixture of modified triethylenetetramine and T-31 curing agent, wherein the mixing ratio of the modified triethylenetetramine and T-31 curing agent is 1:(2~4).

[0009] As a preferred embodiment of a protective coating for a deep-sea pressure-resistant hull, the solvent includes one or more of xylene and ethyl acetate; the reinforcing filler includes fumed silica; and the anti-corrosion filler includes one or more of zinc phosphate, aluminum tripolyphosphate, and glass flakes.

[0010] As a preferred embodiment of a deep-sea pressure-resistant shell protective coating, the preparation process of the isoxazole-modified polyurea includes: adding ethyl acetate to an alkenyl-terminated polyurea resin, stirring and mixing, filtering to obtain a mixture, and stirring and mixing the mixture with phenylnitrone in a preset ratio to obtain isoxazole-modified polyurea.

[0011] The mass ratio of the alkenyl-terminated polyurea resin to the ethyl acetate is 1:(1~1.5), and the mass ratio of the mixture to the phenylnitrone is (2~2.5):1.

[0012] As a preferred embodiment of a protective coating for a deep-sea pressure-resistant hull, the thickness of the primer is 0.2~0.4 mm, and the thickness of the topcoat is 0.4~0.6 mm.

[0013] A method for preparing a deep-sea pressure-resistant hull protective coating, based on any one of the above-mentioned deep-sea pressure-resistant hull protective coatings, includes the following steps:

[0014] Substrate treatment;

[0015] Epoxy resin modified polyurethane, reinforcing filler, anti-corrosion filler, curing agent and solvent are added in sequence in a predetermined ratio and mixed evenly to obtain a primer. The primer is then sprayed onto the substrate.

[0016] Using the isoxazole-modified polyurea as a topcoat, the topcoat is sprayed onto the side of the primer away from the substrate to obtain a protective coating.

[0017] As a preferred embodiment of the preparation method of a protective coating for a deep-sea pressure hull, the conditions for the primer and topcoat spraying process include: temperature of 22~30℃, humidity of 50~80%, automatic spraying, spraying distance of 10~15 cm, and spraying time interval of 10 min / coat.

[0018] In a preferred embodiment of the preparation method for a protective coating for a deep-sea pressure-resistant hull, the primer and the topcoat are prepared by air drying after spraying and then sanding and finishing.

[0019] As a preferred embodiment of a method for preparing a protective coating for a deep-sea pressure-resistant hull, the specific process of substrate treatment includes:

[0020] Polish the surface of the substrate, clean and dry it, apply a coupling agent to the dried surface of the substrate, and let it air dry naturally;

[0021] The coupling agent includes epoxy silane coupling agents.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention provides a protective coating for deep-sea pressure-resistant hulls. The coating comprises a primer and a topcoat sequentially arranged. The primer comprises epoxy resin-modified polyurethane, and the topcoat comprises isoxazole-modified polyurea. By modifying the polyurethane, the primer can firmly bond to the metal substrate. The polyurea is modified using a nitroketone click reaction, enabling the modified polyurea to bond tightly with the primer. This enhances the waterproof performance, impact resistance, and abrasion resistance of the protective coating, improves its tear strength and elongation at break, and enhances its anti-bioadhesion ability. Isoxazole, obtained by reacting olefins with nitroketones, typically possesses antibacterial and cytotoxic properties. The organic combination of these two substances allows the coating to adhere tightly to the substrate surface, effectively preventing moisture, corrosive agents such as various ions in seawater, and fouling organisms such as barnacles, mussels, oysters, and sponges from contacting the substrate surface. Furthermore, it exhibits excellent impact resistance and abrasion resistance.

[0024] The density of the deep-sea pressure-resistant hull protective coating prepared in this application is less than or equal to 1.1 g / cm³. 3 The thickness is 0.6~1.0 mm, the adhesion strength between the protective coating and the substrate is greater than or equal to 1.5 MPa, and the shear strength of the protective coating is greater than or equal to 2.5 MPa. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the protective coating provided by the present invention;

[0027] Figure 2 This is a flowchart of the method for preparing the protective coating provided by the present invention;

[0028] Figure 3 It is the chemical reaction formula for the preparation process of bisphenol A epoxy resin modified polyurethane;

[0029] Figure 4 yes Figure 3 Chemical structure diagram of R1 in the middle;

[0030] Figure 5 yes Figure 3 Chemical structure diagram of R2 in the middle;

[0031] Figure 6 yes Figure 3 Chemical structure diagram of R3 in the middle;

[0032] Figure 7 It is the chemical reaction formula for the preparation process of isoxazole-modified polyurea;

[0033] Figure 8 yes Figure 7 Chemical structure diagram of R1;

[0034] Figure 9 This is a view of the appearance of the protective coating prepared in Example 1 of the present invention after the primer is sprayed.

[0035] Figure 10 This is a topcoat morphology diagram of the protective coating prepared in Example 1 of the present invention after the topcoat is applied;

[0036] Figure 11 These are ultrasonic flaw detection images of the protective coating prepared in Example 1 of this invention before external pressure fatigue;

[0037] Figure 12 These are ultrasonic flaw detection images of the protective coating prepared in Example 1 of this invention after external pressure fatigue;

[0038] Figure 13 This is a CT scan image of the shell after external pressure fatigue of the protective coating prepared in Example 1 of the present invention;

[0039] Figure 14These are the surface morphology images of the protective coatings prepared in Examples 2, 3, and 4 of this invention after spraying.

[0040] Figure 15 These are the appearance morphology images of the protective coatings prepared in Examples 2, 3, and 4 of this invention after the water absorption test was completed;

[0041] Figure 16 This is a view of the hull surface of the "InSight" unmanned autonomous underwater vehicle after one year of use. Detailed Implementation

[0042] To facilitate understanding of the present invention, a more comprehensive description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Unless otherwise defined, all technical and scientific terms used in this invention pertain to the technical field of the invention.

[0043] This embodiment provides a protective coating for a deep-sea pressure hull. The protective coating includes a primer and a topcoat. The primer comprises epoxy-modified polyurethane, and the topcoat comprises isoxazole-modified polyurea. The thickness of the primer is 0.2~0.4 mm, and the thickness of the topcoat is 0.4~0.6 mm. A schematic diagram of the protective coating structure is shown below. Figure 1 As shown, 1 is the substrate, 2 is the primer, and 3 is the topcoat.

[0044] Specifically, the primer includes epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler, and solvent; the mass ratio of epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler, and solvent is 1:(0.4~1):(0.1~0.2):(0.2~0.45):(1~1.4). In this embodiment, the preferred mass ratio is 1:0.4:0.1:0.32:1.4. Of course, in other embodiments, the mass ratio can also be selected as 1:1:0.2:0.2:1 or 1:0.7:0.15:0.45:1.2, depending on the actual situation. The curing agent includes a compounded amine curing agent, specifically a compound of modified triethylenetetramine and T-31 curing agent, with a compounding ratio of 1:(2~4). In this embodiment, it is preferably 1:3. Of course, in other embodiments, it can also be selected as 1:2 or 1:4, depending on the actual situation. The solvent includes one or more of xylene and ethyl acetate. The reinforcing filler includes fumed silica. The anti-corrosion filler includes one or more of zinc phosphate, aluminum tripolyphosphate, and glass flakes.

[0045] Specifically, epoxy resin modified polyurethane includes bisphenol A epoxy resin modified polyurethane. The preparation process of bisphenol A epoxy resin modified polyurethane includes main reaction 1 and reaction 2, and the chemical reaction formula is as follows: Figure 3 As shown, Figure 3 In the figure, the chemical structural formulas of R1, R2, and R3 are as follows: Figure 4 , Figure 5 , Figure 6 As shown, R1 is 2,6-disubstituted tolyl, R2 is dipentyl ketone, and R3 is bisphenol A epoxy resin. In R3, the group indicated by arrow 1 specifically improves its flexibility, the group indicated by arrow 2 specifically improves its heat resistance and toughness, the group indicated by arrow 3 specifically improves its chemical resistance, and the group indicated by arrow 4 specifically improves its adhesion or reactivity.

[0046] Specifically, the preparation process of isoxazole-modified polyurea includes: adding ethyl acetate to alkenyl-terminated polyurea resin for dilution, stirring and mixing, filtering to obtain a mixture, and stirring and mixing the mixture with phenyl nitrone according to a preset ratio to obtain isoxazole-modified polyurea; wherein, the mass ratio of alkenyl-terminated polyurea resin to ethyl acetate is 1:(1~1.5), preferably 1:1.2 in this embodiment, and can be 1:1 or 1:1.5 in other embodiments, depending on the actual situation; the mass ratio of the mixture to phenyl nitrone is (2~2.5):1, preferably 2.2:1 in this embodiment, and can be 2:1 or 2.5:1 in other embodiments, depending on the actual situation.

[0047] The preparation process of isoxazole-modified polyurea includes main reactions 3, 4, and 5 (click reaction of nitroketone), and the chemical reaction formulas are as follows: Figure 7 As shown, Figure 7 In the diagram, R1 is methylene dicyclohexyl, R2 is polydimethylsiloxane, R3 is CH2, R4 is Bn, and R5 is Ph. The chemical structure of R1 is shown in the figure below. Figure 8 As shown.

[0048] This embodiment also provides a method for preparing a protective coating for a deep-sea pressure-resistant hull, such as... Figure 2 As shown, the specific steps include:

[0049] S100, Substrate treatment;

[0050] Specifically, the substrate treatment process includes: polishing the substrate surface, cleaning and drying, applying a coupling agent to the dried substrate surface, and allowing it to air dry naturally; the coupling agent includes epoxy silane coupling agents, specifically silane coupling agent KH-570.

[0051] S200. Spray primer onto substrate; add epoxy resin modified polyurethane, reinforcing filler, anti-corrosion filler, curing agent and solvent in a predetermined ratio and mix evenly to obtain primer, then spray primer onto substrate.

[0052] Specifically, the conditions for the primer spraying process include: temperature of 22~30℃, humidity of 50~80%, automatic spraying, spraying distance of 10~15 cm, and spraying interval of 10 min / coat; after spraying, allow it to air dry naturally and then sand and finish it.

[0053] Specifically, the primer includes epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler, and solvent; the mass ratio of epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler, and solvent is 1:(0.4~1):(0.1~0.2):(0.2~0.45):(1~1.4). In this embodiment, the preferred mass ratio is 1:0.4:0.1:0.32:1.4. Of course, in other embodiments, the mass ratio can also be selected as 1:1:0.2:0.2:1 or 1:0.7:0.15:0.45:1.2, depending on the actual situation. The curing agent includes a compounded amine curing agent, specifically a compound of modified triethylenetetramine and T-31 curing agent, with a compounding ratio of 1:(2~4). In this embodiment, it is preferably 1:3. Of course, in other embodiments, it can also be selected as 1:2 or 1:4, depending on the actual situation. The solvent includes one or more of xylene and ethyl acetate. The reinforcing filler includes fumed silica. The anti-corrosion filler includes one or more of zinc phosphate, aluminum tripolyphosphate, and glass flakes.

[0054] Preferably, after spraying the primer onto the substrate, a second primer can be sprayed, with the reaction conditions being the same as the first primer spray. After spraying, the primer is allowed to air dry naturally and then sanded and finished.

[0055] S300: Apply topcoat to the side of the primer that is away from the substrate to obtain a protective coating.

[0056] Specifically, the conditions for the topcoat spraying process include: temperature of 22~30℃, humidity of 50~80%, automatic spraying, spraying distance of 10~15 cm (e.g., 10 cm, 11 cm, 12 cm, 13 cm, 14 cm or 15 cm), and a spraying interval of 10 min / coat; after spraying, the topcoat is allowed to air dry naturally and then sanded and repaired.

[0057] The present invention will be further described below through specific embodiments. Example 1

[0058] A method for preparing a protective coating for a deep-sea pressure hull:

[0059] Polish the surface of the shell substrate, clean it with water and ethanol in sequence, and dry it thoroughly. After drying, apply silane coupling agent KH-570 to the surface of the shell substrate and let it air dry naturally.

[0060] To prepare the primer, spray it onto the substrate. First, add 100 g of epoxy-modified polyurethane, 10 g of reinforcing filler fumed silica, and 32.25 g of anti-corrosion filler zinc phosphate sequentially. After each filler is added, stir and mix thoroughly, then knead using a three-roll mill 3-4 times to maintain the fineness of the mixed filler at 10-15 μm. Next, add curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent; the modified triethylenetetramine curing agent should be added first and stirred thoroughly, then the first-generation T-31 curing agent should be added and stirred thoroughly), followed by 142.25 g of xylene solvent, and stir thoroughly. Then, add curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent) again and stir thoroughly to prepare the primer. Then, a primer is sprayed onto the substrate. During the primer spraying process, an automatic spraying system is used in an environment with a temperature of 22~30℃ and a humidity of 50~80%. The spraying distance is controlled at 15 cm, and the spraying interval is 10 minutes per coat. After spraying, the primer is allowed to air dry for 24 hours. The primer spraying process is repeated for the second coat. After spraying, the primer is allowed to air dry and then sanded and finished.

[0061] A topcoat was prepared by spraying it onto the side of the primer facing away from the substrate to obtain a protective coating. 120 g of ethyl acetate was added to 100 g of alkenyl-terminated polyurea resin for dilution, and the mixture was stirred until homogeneous. The mixture was then filtered through a 400-mesh screen under normal pressure to obtain a final product. Subsequently, 1 part of phenyl nitrone was added to every 2.2 parts of the final product, and the mixture was stirred until homogeneous. The topcoat was then prepared. The topcoat was then sprayed onto the side of the primer facing away from the substrate. During the topcoat spraying process, an automatic spraying system was used at a temperature of 22–30°C and a humidity of 50–80%. The spraying distance was controlled at 15 cm, and the spraying interval was 10 min per coat. After spraying, the coating was allowed to air dry for 24 h. The coating was then sanded and finished. The protective coating required in this embodiment was obtained. The appearance morphology of the primer and topcoat after spraying is shown in the figures below. Figure 9 and Figure 10 As shown.

[0062] The protective coating of the casing was subjected to relevant performance tests, and the specific test standards included: GB / T 7124-2008 Adhesives - Tensile Shear Strength Test Standard; GB1040-79 Tensile Strength Test Standard; GB / T 16578.1-2008 Tear Strength Test Standard.

[0063] Tests showed that the shear tensile strength of both the protective coating and the substrate was greater than 3.38 MPa. The primer itself had a tensile strength greater than 21.5 MPa and an elongation at break of less than 18.1%. The topcoat had a tensile strength of approximately 5.2 MPa, an elongation at break of approximately 260%, and a breaking force of approximately 63.5 N, exhibiting excellent toughness and strength. The tensile strength between all components of the protective coating was greater than 1.1 MPa. The adhesion between the primer and intermediate coat, and between the intermediate coat and topcoat, resulted in complete structural damage. The overall surface of the protective coating was smooth and even, without sagging, pinholes, blistering, orange peel, or gaps and pits at the skirt.

[0064] Figure 11 and Figure 12 The images show ultrasonic flaw detection images of the shell before and after 3000 cycles of external pressure fatigue. The comparison shows that there are no obvious debonding defects between the coating and the substrate before and after the external pressure fatigue test, but there are small debonding defects between the coating and the substrate. Figure 13 CT scan images of the casing after 3000 cycles of external pressure fatigue show that the aforementioned debonding defect occurred in the winding layer, while no debonding occurred between the topcoat polyurea coating and the winding layer. The surface coatings are tightly bonded together. Example 2

[0065] A method for preparing a protective coating for a deep-sea pressure hull:

[0066] Polish the surface of the 20x20 cm aluminum alloy substrate, clean it with water and ethanol in sequence, and dry it thoroughly. After drying, apply silane coupling agent KH-570 to the substrate surface and let it air dry naturally.

[0067] To prepare the primer, spray it onto the substrate. First, add 100 g of epoxy-modified polyurethane, 10 g of reinforcing filler fumed silica, and 32.25 g of anti-corrosion filler aluminum tripolyphosphate sequentially. After each filler is added, stir and mix thoroughly, then knead using a three-roll mill 3-4 times to maintain the fineness of the mixed filler at 10-15 μm. Next, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent; the modified triethylenetetramine curing agent should be added first and stirred thoroughly, then the first-generation T-31 curing agent should be added and stirred thoroughly), followed by 142.25 g of xylene solvent, and stir thoroughly. Then, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent) again and stir thoroughly to prepare the primer. Then, a primer is sprayed onto the substrate. During the primer spraying process, an automatic spraying system is used in an environment with a temperature of 22~30℃ and a humidity of 50~80%. The spraying distance is controlled at 14 cm, and the spraying interval is 10 minutes per coat. After spraying, the substrate is allowed to air dry for 24 hours. The primer spraying process is repeated for the second coat. After spraying, the substrate is allowed to air dry and then sanded and finished.

[0068] A topcoat was prepared by spraying it onto the side of the primer facing away from the substrate to obtain a protective coating. 120 g of ethyl acetate was added to 100 g of alkenyl-terminated polyurea for dilution, and the mixture was stirred until homogeneous. The mixture was then filtered through a 400-mesh screen under normal pressure to obtain a final product. Subsequently, 1 part of phenyl nitrone was added to every 2.2 parts of the final product, and the mixture was stirred until homogeneous. The topcoat was then prepared. The topcoat was then sprayed onto the side of the primer facing away from the substrate. During the topcoat spraying process, an automatic spraying system was used at a temperature of 22–30°C and a humidity of 50–80%. The spraying distance was controlled at 13 cm, and the spraying interval was 10 min per coat. After spraying, the coating was allowed to air dry for 24 h. The coating was then sanded and finished. The protective coating required in this embodiment was obtained.

[0069] Performance tests were conducted on the protective coating of the shell. Since the contact angle of the anti-corrosion coating in a seawater environment is greater than or equal to 124.5°, it exhibits hydrophobicity (common polyurea without isoxazole modification has a contact angle of approximately 78-79° with water, exhibiting hydrophilicity). The water absorption rate of the protective coating prepared in this application is less than or equal to 0.3%. The contact angle between the protective coating and water was obtained by taking the average of three measurements using a contact angle tester. The test showed that the average contact angle between the protective coating and water was 124.5°, and the water absorption rate of the latex film was only 0.25%. After immersion in water, the surface was smooth, without loss of gloss, discoloration, bubbles, wrinkling, or peeling. The water absorption rate is lower than that of ordinary polyurea, indicating that the coating material has high density, strong hydrophobicity, and can remain stable for a long time in a deep-sea working environment. Example 3

[0070] A method for preparing a protective coating for a deep-sea pressure hull:

[0071] Polish the surface of the 20x20 cm titanium alloy substrate, clean it with water and ethanol in sequence, and dry it thoroughly. After drying, apply silane coupling agent KH-570 to the substrate surface and let it air dry naturally.

[0072] To prepare the primer, spray it onto the substrate. First, add 100 g of epoxy-modified polyurethane, 10 g of reinforcing filler fumed silica, and 32.25 g of anti-corrosion filler glass flakes sequentially. After each filler is added, stir and mix thoroughly, then knead using a three-roll mill 3-4 times to maintain the fineness of the mixed filler at 10-15 μm. Next, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent; the modified triethylenetetramine curing agent should be added first and stirred thoroughly, then the first-generation T-31 curing agent should be added and stirred thoroughly), followed by 142.25 g of xylene solvent, and stir thoroughly. Then, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent) again and stir thoroughly to prepare the primer. Then, a primer is sprayed onto the substrate. During the primer spraying process, an automatic spraying system is used in an environment with a temperature of 22~30℃ and a humidity of 50~80%. The spraying distance is controlled at 10 cm, and the spraying interval is 10 minutes per coat. After spraying, the substrate is allowed to air dry for 24 hours. The primer spraying process is repeated for the second coat. After spraying, the substrate is allowed to air dry and then sanded and finished.

[0073] A topcoat was prepared by spraying it onto the side of the primer facing away from the substrate to obtain a protective coating. 120 g of ethyl acetate solvent was added to 100 g of alkenyl-terminated polyurea resin for dilution, and the mixture was stirred until homogeneous. The mixture was then filtered through a 400-mesh screen under normal pressure to obtain a final product. Subsequently, 1 part of phenyl nitrone was added to every 2.2 parts of the final product, and the mixture was stirred until homogeneous. The topcoat was then prepared. The topcoat was then sprayed onto the side of the primer facing away from the substrate. During the topcoat spraying process, an automatic spraying system was used at a temperature of 22–30°C and a humidity of 50–80%. The spraying distance was controlled at 10 cm, and the spraying interval was 10 min per coat. After spraying, the coating was allowed to air dry for 24 h. The coating was then sanded and finished. The protective coating required in this embodiment was obtained.

[0074] The protective coating underwent relevant performance testing. Since the contact angle of the anti-corrosion coating in a seawater environment is greater than or equal to 124.5°, it exhibits hydrophobicity (common polyurea without isoxazole modification has a contact angle of approximately 78–79° with water, exhibiting hydrophilicity). The water absorption rate of the protective coating prepared in this application is less than or equal to 0.3%. The contact angle between the protective coating and water was obtained by taking the average of three measurements using a contact angle tester. The test showed that the average contact angle between the protective coating and water was 125.0°, and the water absorption rate of the latex film was only 0.3%. After immersion in water, the surface remained smooth, without loss of gloss, discoloration, bubbling, wrinkling, or peeling. The water absorption rate is lower than that of ordinary polyurea, indicating that the coating material has high density, strong hydrophobicity, and can remain stable for a long time in a deep-sea working environment. Example 4

[0075] A method for preparing a protective coating for a deep-sea pressure hull:

[0076] Polish the surface of the carbon fiber substrate, clean it with water and ethanol in sequence, and dry it thoroughly. After drying, apply silane coupling agent KH-570 to the surface of the substrate and let it air dry naturally.

[0077] To prepare the primer, spray it onto the substrate. First, add 100 g of epoxy-modified polyurethane, 10 g of reinforcing filler fumed silica, and 32.25 g of anti-corrosion filler zinc phosphate sequentially. After each filler is added, stir and mix thoroughly, then knead using a three-roll mill 3-4 times to maintain the fineness of the mixed filler at 10-15 μm. Next, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent; the modified triethylenetetramine curing agent should be added first and stirred thoroughly, then the first-generation T-31 curing agent should be added and stirred thoroughly), followed by 142.25 g of xylene solvent, and stir thoroughly. Then, add the curing agent (4 g of modified triethylenetetramine curing agent and 17.6 g of first-generation T-31 curing agent) again and stir thoroughly to prepare the primer. Then, a primer is sprayed onto the substrate. During the primer spraying process, an automatic spraying system is used in an environment with a temperature of 22~30℃ and a humidity of 50~80%. The spraying distance is controlled at 15 cm, and the spraying interval is 10 minutes per coat. After spraying, the substrate is allowed to air dry for 24 hours. The primer spraying process is repeated for the second coat. After spraying, the substrate is allowed to air dry and then sanded and finished.

[0078] A topcoat was prepared by spraying it onto the side of the primer facing away from the substrate to obtain a protective coating. 120 g of ethyl acetate was added to 100 g of alkenyl-terminated polyurea resin for dilution, and the mixture was stirred until homogeneous. The mixture was then filtered through a 400-mesh screen under normal pressure to obtain a final product. Subsequently, 1 part of phenyl nitrone was added to every 2.2 parts of the final product, and the mixture was stirred until homogeneous to obtain the topcoat. The topcoat was then sprayed onto the side of the primer facing away from the substrate. During the topcoat spraying process, an automatic spraying system was used at a temperature of 22–30°C and a humidity of 50–80%. The spraying distance was controlled at 15 cm, and the spraying interval was 10 min per coat. After spraying, the coating was allowed to air dry for 24 h. The surface was then sanded and finished. The protective coating required in this embodiment was obtained.

[0079] The protective coating underwent relevant performance testing. Since the contact angle of the anti-corrosion coating in a seawater environment is greater than or equal to 124.5°, it exhibits hydrophobicity (common polyurea without isoxazole modification has a contact angle of approximately 78-79° with water, exhibiting hydrophilicity). The water absorption rate of the protective coating prepared in this application is less than or equal to 0.3%. The contact angle between the protective coating and water was obtained by taking the average of three measurements using a contact angle tester. The test showed that the average contact angle between the protective coating and water was 124.0°, and the water absorption rate of the latex film was only 0.28%. After immersion in water, the surface remained smooth, without loss of gloss, discoloration, bubbling, wrinkling, or peeling. The water absorption rate is lower than that of ordinary polyurea, indicating that the coating material has high density, strong hydrophobicity, and can remain stable for a long time in a deep-sea working environment.

[0080] Figure 14 These are images showing the surface morphology of the protective coatings prepared in Examples 2, 3, and 4 after spraying. Figure 15 The images show the appearance morphology of the protective coatings prepared in Examples 2, 3, and 4 after the water absorption test. It can be seen that after the water absorption test, the surface of the protective coating is smooth and there are no phenomena such as loss of gloss, discoloration, bubbles, wrinkles, or peeling. This indicates that the coating material has high density, strong hydrophobicity, and can remain stable for a long time in the deep-sea working environment. Figure 16 This is a picture of the hull surface of the "Insight" unmanned autonomous underwater vehicle after one year of use. The overall appearance of the hull protective coating is smooth and flat, without any runs, pinholes, bubbles, orange peel, etc., and there are no gaps or pits at the skirt end. This indicates that the protective coating has anti-corrosion, anti-collision, wear resistance and anti-bioadhesion properties, and can remain stable for a long time in the deep-sea working environment.

[0081] The above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A protective coating for a deep-sea pressure-resistant hull, characterized in that, It includes a primer and a topcoat, wherein the primer comprises epoxy resin modified polyurethane and the topcoat comprises isoxazole modified polyurea; The primer comprises epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler and solvent; The mass ratio of the epoxy resin modified polyurethane, curing agent, reinforcing filler, anti-corrosion filler, and solvent is 1:(0.4~1):(0.1~0.2):(0.2~0.45):(1~1.4). The curing agent includes an amine curing agent, specifically a mixture of modified triethylenetetramine and T-31 curing agent, wherein the mixing ratio of the modified triethylenetetramine and T-31 curing agent is 1:(2~4). The preparation process of the isoxazole-modified polyurea includes: Ethyl acetate was added to alkenyl-terminated polyurea resin, stirred and mixed, and filtered to obtain a mixture. The mixture was then stirred and mixed with phenylnitrone in a preset ratio to obtain isoxazole-modified polyurea. The mass ratio of the alkenyl-terminated polyurea resin to the ethyl acetate is 1:(1~1.5), and the mass ratio of the mixture to the phenylnitrone is (2~2.5):

1.

2. The deep-sea pressure-resistant hull protective coating according to claim 1, characterized in that, The solvent includes one or more of xylene and ethyl acetate; the reinforcing filler includes fumed silica; and the anti-corrosion filler includes one or more of zinc phosphate, aluminum tripolyphosphate, and glass flakes.

3. The deep-sea pressure-resistant hull protective coating according to claim 1 or 2, characterized in that, The thickness of the primer is 0.2~0.4 mm, and the thickness of the topcoat is 0.4~0.6 mm.

4. A method for preparing a deep-sea pressure-resistant hull protective coating, based on the deep-sea pressure-resistant hull protective coating according to any one of claims 1-2, characterized in that, Includes the following steps: Substrate treatment; Epoxy resin modified polyurethane, reinforcing filler, anti-corrosion filler, curing agent and solvent are added in sequence in a predetermined ratio and mixed evenly to obtain a primer. The primer is then sprayed onto the substrate. Using the isoxazole-modified polyurea as a topcoat, the topcoat is sprayed onto the side of the primer away from the substrate to obtain a protective coating.

5. The method for preparing the protective coating for a deep-sea pressure-resistant hull according to claim 4, characterized in that, The conditions for the primer and topcoat spraying process include: temperature of 22~30℃, humidity of 50~80%, automatic spraying, spraying distance of 10~15 cm, and spraying time interval of 10 min / coat.

6. The method for preparing the protective coating for a deep-sea pressure-resistant hull according to claim 4, characterized in that, During the preparation of the primer and the topcoat, they are allowed to air dry naturally after spraying, and then sanded and finished.

7. The method for preparing the deep-sea pressure-resistant hull protective coating according to claim 4, characterized in that, The specific process of substrate processing includes: Polish the surface of the substrate, clean and dry it, apply a coupling agent to the dried surface of the substrate, and let it air dry naturally; The coupling agent includes epoxy silane coupling agents.

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