Waterborne polyurethane coating with corrosion-resistant and antifouling characteristics as well as preparation method and application of waterborne polyurethane coating

Abstract

The invention discloses a waterborne polyurethane coating with corrosion-resistant and antifouling characteristics as well as a preparation method and application thereof, and the waterborne polyurethane coating is prepared from the following raw materials in parts by weight: 30 parts of diisocyanate, 15-30 parts of polycarbonate diol, 0.01-0.02 part of a catalyst, 3-5 parts of polydimethylsiloxane, 3-5 parts of a hydrophilic chain extender and 1-3 parts of a micromolecule chain extender. The preparation method comprises the following steps: preparing the following components in parts by weight: 0.5-3 parts of modified silicon dioxide nanoparticles, 1-3 parts of triethylamine, 4-10 parts of acetone and 130-150 parts of water; the modified silicon dioxide nano particles are nano silicon dioxide modified by a silane coupling agent and dodecyl triethoxy silane. The waterborne polyurethane coating can effectively prevent corrosion of seawater to metal equipment and adhesion of marine organisms to the surface of underwater metal equipment, and has important significance in expanding the application of the waterborne polyurethane coating in the field of marine protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne polyurethane coatings, and in particular relates to a waterborne polyurethane coating with corrosion resistance and antifouling properties, and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Underwater metal equipment plays a key role in marine engineering, seabed exploration, and the shipbuilding industry. However, in complex marine environments, high concentrations of chloride ions, dissolved oxygen, and microbial activity in saltwater can accelerate the electrochemical corrosion of metals, leading to material degradation, structural failure, and even safety accidents. Furthermore, the adhesion of marine organisms (such as barnacles, algae, and bacteria) not only increases fluid resistance on the equipment surface, reducing propulsion efficiency, but can also clog sensor apertures or cover critical functional components, ultimately reducing system accuracy and severely impacting the equipment's service reliability and lifespan.

[0004] Polyurethane is a general term for a class of compounds containing repeating carbamate structural units in the molecular chain. It has excellent mechanical properties, water resistance and corrosion resistance, and is widely used in the field of marine equipment protection.

[0005] However, with the introduction of regulations to control volatile organic compound emissions, desolvation of coatings has become a trend, and due to the insufficient hydrophobic properties of traditional solvent-based polyurethane surfaces, it is difficult to prevent the adhesion of marine organisms. In recent years, as traditional solvent-based polyurethanes have gradually been replaced, water-based polyurethanes have emerged. Due to their environmental friendliness, flexibility, and high adhesion, water-based polyurethanes are widely used in the field of protection. However, most water-based polyurethanes have a single-line structure, and in order to ensure good water dispersibility, a large number of hydrophilic groups are introduced during their preparation process. As a result, traditional water-based polyurethane coatings have deficiencies in corrosion resistance and antifouling, making it difficult to meet the protection needs in complex marine environments, limiting the application of water-based polyurethanes in marine engineering. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a water-based polyurethane coating with corrosion resistance and anti-fouling properties, as well as its preparation method and application. The water-based polyurethane coating can effectively prevent the corrosion of metal equipment by seawater and the adhesion of marine organisms to the surface of underwater metal equipment, which is of great significance for expanding the application of water-based polyurethane coatings in the field of marine protection.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a waterborne polyurethane coating having corrosion resistance and antifouling properties, wherein the raw materials include the following components in parts by weight: 30 parts of diisocyanate, 15-30 parts of polycarbonate diol, 0.01-0.02 parts of catalyst, 3-5 parts of polydimethylsiloxane, 3-5 parts of hydrophilic chain extender, 1-3 parts of small molecule chain extender, 0.5-3 parts of modified silica nanoparticles, 1-3 parts of triethylamine, 4-10 parts of acetone, and 130-150 parts of water;

[0009] The modified silicon dioxide nanoparticles are nano silicon dioxide modified by a silane coupling agent and dodecyltriethoxysilane.

[0010] The role of polydimethylsiloxane is to provide hydrophobic siloxane segments, reduce the surface energy of the coating, and enhance the antifouling and barrier properties of the coating.

[0011] The function of the hydrophilic chain extender is to provide hydrophilic groups to help the prepolymer form a stable emulsion in the aqueous phase.

[0012] The role of small molecule chain extenders is to increase the overall strength of the coating by increasing the molecular weight.

[0013] The role of triethylamine is to neutralize the carboxylic acid groups in the system.

[0014] Acetone was used to adjust the viscosity of the system during the reaction.

[0015] In some embodiments, the diisocyanate is at least one of isophorone diisocyanate, diphenylmethane diisocyanate, or hexamethylene diisocyanate.

[0016] In some embodiments, the polycarbonate diol is at least one of adipic acid-ethylene glycol polyester polyol, adipic acid-butylene glycol polyester polyol, or adipic acid-neopentyl glycol polyester polyol.

[0017] In some embodiments, the catalyst is dibutyltin dilaurate.

[0018] In some embodiments, the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid.

[0019] In some embodiments, the small molecule chain extender is 1,4-butanediol.

[0020] In a second aspect, the present invention provides a method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties, comprising the following steps:

[0021] After mixing diisocyanate, polycarbonate diol and polydimethylsiloxane in proportion, heat to 70-80°C, stir and react for a set time, add catalyst, continue stirring and react for a set time, and add acetone to adjust the viscosity during the process. During this process, the hydroxyl group reacts with the isocyanate group to form a urethane bond;

[0022] Then the temperature is lowered to 50-60°C, and a hydrophilic chain extender is added thereto, and the reaction is set for a time (the previous step realizes the prepolymerization of the soft segment and hard segment of the polyurethane. In order to make it dispersed in the aqueous phase, it is necessary to introduce a hydrophilic functional group in this step. The purpose of lowering the temperature is to control the reaction speed and prevent side reactions at high temperatures);

[0023] Then, a small molecule chain extender and modified silica nanoparticles are added thereto, and the reaction is stirred for a set time (to further extend and modify the chain, and the functional groups on the surface of the small molecule chain extender and the modified nano-silica react with the residual isocyanate groups);

[0024] The reaction system was cooled to 40-50°C, triethylamine was added, and the reaction was stirred for a set time (triethylamine was added to neutralize the carboxylic acid groups present due to the introduction of the hydrophilic chain extender. The temperature was lowered to control the reaction rate and reduce the volatilization of triethylamine);

[0025] After the reaction is completed, the temperature is lowered to room temperature, water is added for emulsification, and the acetone is removed to obtain the product.

[0026] In some embodiments, the modified silica nanoparticles are prepared by ultrasonically dispersing 3-6 parts of silica nanoparticles in anhydrous ethanol, adding ammonia and water thereto, heating to 80-90° C., then adding 3-5 parts of a silane coupling agent thereto, stirring and reacting for 2-3 hours, then adding 3-5 parts of dodecyltriethoxysilane, and continuing to stir and react for 2-3 hours;

[0027] After the reaction is completed, the temperature is lowered, the solid and liquid are separated, and the modified silicon dioxide nanoparticles are obtained. The parts mentioned above are all parts by mass. The surface of the prepared modified silicon dioxide nanoparticles has both amino groups and long-chain alkyl groups.

[0028] Preferably, the amount of anhydrous ethanol is 60-80 parts.

[0029] Preferably, the concentration of the ammonia water is 25%-28%, % is mass percentage, and the number of parts of ammonia water is 6-12 parts.

[0030] More preferably, the amount of water is 6-12 parts.

[0031] In some embodiments, diisocyanate, polycarbonate diol, and polydimethylsiloxane are mixed in proportion, heated to 70-80° C., and stirred for 1-2 hours.

[0032] In some embodiments, after the catalyst is added, the reaction is stirred for 1-2 hours.

[0033] In some embodiments, acetone is added during the process to adjust the viscosity to 1500-4000 mPa·s.

[0034] In some embodiments, after the addition of the hydrophilic chain extender, the reaction time is 1-1.5 hours.

[0035] In some embodiments, after adding the small molecule chain extender and the modified silica nanoparticles, the reaction time is 1-2 hours.

[0036] In some embodiments, after adding triethylamine, the stirring reaction time is 1-2 hours.

[0037] In some embodiments, the acetone is removed under reduced pressure.

[0038] In some embodiments, the diisocyanate, polycarbonate diol, polydimethylsiloxane, hydrophilic chain extender, and small molecule chain extender are all dried in advance.

[0039] Preferably, the pre-drying treatment is carried out at a temperature of 90-100° C. and for a time of 5-15 hours.

[0040] In a third aspect, the present invention provides the use of the waterborne polyurethane coating having corrosion resistance and antifouling properties in the protection of underwater metal devices.

[0041] In a fourth aspect, the present invention provides a waterborne polyurethane coating, which is obtained by coating the waterborne polyurethane coating on a substrate to be protected and drying it.

[0042] In a fifth aspect, the present invention provides an underwater metal equipment having the waterborne polyurethane coating attached to its surface.

[0043] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0044] 1. Improved dispersibility of nano-silica in the matrix: The surface of nano-silica particles modified with KH550 has amino groups, which can react with carboxylic acid or isocyanate groups in waterborne polyurethane prepolymers, thereby enhancing the chemical bonding between nano-silica and the polymer matrix and reducing particle agglomeration. However, due to the electrostatic effect of nano-silica and the polarity difference of the chain segments, it will still locally agglomerate in the aqueous system. The nano-silica modified with dodecyltriethoxysilane has long-chain alkyl groups on the surface, which can reduce the surface energy of nano-silica and form a hydrophobic layer on the particle surface. It has good compatibility with the hydrophobic segment of waterborne polyurethane, reduces the electrostatic effect and polarity difference between the segments, and further inhibits the aggregation of particles in the aqueous system. The synergistic effect of the two can make the nano-silica more evenly dispersed in the aqueous matrix and the interface bonding tighter, which is conducive to improving the mechanical properties and corrosion resistance.

[0045] 2. Improved corrosion resistance of the coating: The long chain of dodecyltriethoxysilane forms a directional hydrophobic barrier on the surface of nano-silica, which cooperates with the extremely low surface energy polydimethylsiloxane main chain (-Si-O-Si-) to form a combination of physical and chemical barriers, reducing the penetration of water molecules and chloride ions into the interior of the material and enhancing the coating's resistance to seawater corrosion.

[0046] 3. Improvement of the antifouling performance of the coating: The introduction of hydrophobic long chain segments on the surface of polydimethylsiloxane and nano-silica particles increases the overall hydrophobicity of the coating. In addition, the dynamic migration characteristics of the surface siloxane chains and dodecyl chains can reduce protein adsorption and delay biofilm formation, thereby blocking the initial steps of biofouling and achieving an antifouling effect in the marine environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0048] Figure 1 The figure is a comparison chart of the results after 100 hours of salt spray accelerated corrosion test, wherein a is a single metal copper sheet, and b is a copper sheet with the surface sprayed with the waterborne polyurethane coating of the present invention for protection.

[0049] Figure 2 This is a comparison chart of the results of a Chlorella adhesion experiment. All samples were immersed in a high-concentration Chlorella aqueous solution for one month. Figure a is a single metal copper sheet, and figure b is a copper sheet protected by the waterborne polyurethane coating of the present invention.

[0050] Figure 3The following is a comparison diagram of the water contact angle of the coating surface, where a is a water-based polyurethane coating without the introduction of polydimethylsiloxane and modified silica, and b is a modified water-based polyurethane coating. DETAILED DESCRIPTION

[0051] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0052] The present invention will be further described below with reference to the embodiments.

[0053] Example 1

[0054] The water-based polyurethane coating comprises, in parts by weight, 30 parts of diisocyanate, 30 parts of polycarbonate diol, 0.02 parts of catalyst, 3 parts of polydimethylsiloxane, 4 parts of hydrophilic chain extender, 1 part of small molecule chain extender, 0.5 parts of modified silica nanoparticles, 3 parts of triethylamine, 5 parts of acetone, and 130 parts of water.

[0055] The preparation process of modified silica nanoparticles is as follows: 3 parts of nano-silica particles are added to 80 parts of anhydrous ethanol, ultrasonically dispersed at room temperature for 30 minutes, 6 parts of ammonia water and 6 parts of distilled water are added, and after heating to 80°C, 3 parts of silane coupling agent KH550 are added, stirred and reacted for 2 hours, and then the temperature is kept unchanged. 3 parts of dodecyltriethoxysilane are added, stirred and reacted for 3 hours, and then cooled to room temperature, centrifuged, and dried to obtain modified nano-silica particles.

[0056] The preparation method of a water-based polyurethane emulsion comprises the following steps: before an experiment, diisocyanate, polycarbonate diol, polydimethylsiloxane, a hydrophilic chain extender and a small molecule chain extender are vacuum dried at 90° C. for 10 hours; subsequently, the diisocyanate, polycarbonate diol and polydimethylsiloxane are added to a reaction container, the temperature is raised to 70° C., and stirred for reaction for 1 hour, after which a catalyst is added, and the stirring reaction is continued for 2 hours, during which acetone is added to adjust the viscosity; the temperature is lowered to 60° C., the hydrophilic chain extender is added to the reaction container, the reaction is continued for 1 hour; the small molecule chain extender and modified nano-silica are respectively added to the reaction container, the reaction is stirred for reaction for 1 hour; the temperature is cooled to 50° C., triethylamine is added, and the reaction is stirred for reaction for 1 hour; the temperature is cooled to room temperature, water is added, and high-speed emulsification is performed; and finally, the acetone is removed under reduced pressure.

[0057] The emulsion is evenly sprayed on the metal surface, and the modified waterborne polyurethane coating is obtained after the water is completely dried.

[0058] Example 2

[0059] The waterborne polyurethane coating comprises, by weight, 30 parts diisocyanate, 30 parts polycarbonate diol, 0.01 parts catalyst, 3 parts polydimethylsiloxane, 4 parts hydrophilic chain extender, 1.5 parts small molecule chain extender, 0.5 parts modified silica nanoparticles, 3 parts triethylamine, 5 parts acetone, and 150 parts water.

[0060] The preparation process of modified silica nanoparticles is as follows: 3 parts of nano-silica particles are added to 80 parts of anhydrous ethanol, ultrasonically dispersed at room temperature for 30 minutes, 6 parts of ammonia water and 6 parts of distilled water are added, and after heating to 80°C, 3 parts of silane coupling agent KH550 are added, stirred and reacted for 2 hours, and then the temperature is kept unchanged, 3 parts of dodecyltriethoxysilane are added, stirred and reacted for 3 hours, cooled to room temperature, centrifuged, and dried to obtain modified nano-silica particles.

[0061] The preparation method of a water-based polyurethane emulsion comprises the following steps: before an experiment, diisocyanate, polycarbonate diol, polydimethylsiloxane, a hydrophilic chain extender and a small molecule chain extender are vacuum dried at 90° C. for 5 hours; subsequently, the diisocyanate, polycarbonate diol and polydimethylsiloxane are added to a reaction container, the temperature is raised to 70° C., and stirred for reaction for 1 hour, after which a catalyst is added, and the stirring reaction is continued for 3 hours, during which acetone is added to adjust the viscosity; the temperature is lowered to 60° C., the hydrophilic chain extender is added to the reaction container, the reaction is carried out for 1 hour; the small molecule chain extender and modified nano-silica are respectively added to the reaction container, and the reaction is stirred for 2 hours; the temperature is cooled to 50° C., triethylamine is added, and the reaction is stirred for 1 hour; the temperature is cooled to room temperature, water is added, and high-speed emulsification is performed; and finally, the acetone is removed under reduced pressure.

[0062] The emulsion is evenly sprayed on the metal surface, and the modified waterborne polyurethane coating is obtained after the water is completely dried.

[0063] Example 3

[0064] The waterborne polyurethane coating comprises, by weight, 30 parts of diisocyanate, 30 parts of polycarbonate diol, 0.02 parts of catalyst, 3 parts of polydimethylsiloxane, 4 parts of hydrophilic chain extender, 1 part of small molecule chain extender, 1 part of modified silica nanoparticles, 3 parts of triethylamine, 10 parts of acetone, and 130 parts of water.

[0065] The preparation process of modified silica nanoparticles is as follows: 3 parts of nano-silica particles are added to 80 parts of anhydrous ethanol, ultrasonically dispersed at room temperature for 30 minutes, 6 parts of ammonia water and 6 parts of distilled water are added, and after heating to 80°C, 3 parts of silane coupling agent KH550 are added, stirred and reacted for 2 hours, and then the temperature is kept unchanged, 3 parts of dodecyltriethoxysilane are added, stirred and reacted for 3 hours, cooled to room temperature, centrifuged, and dried to obtain modified nano-silica particles.

[0066] The preparation method of a water-based polyurethane emulsion comprises the following steps: before an experiment, diisocyanate, polycarbonate diol, polydimethylsiloxane, a hydrophilic chain extender and a small molecule chain extender are vacuum dried at 90° C. for 10 hours; subsequently, the diisocyanate, polycarbonate diol and polydimethylsiloxane are added to a reaction container, the temperature is raised to 70° C., and stirred for reaction for 2 hours, after which a catalyst is added, and the stirring reaction is continued for 2 hours, during which acetone is added to adjust the viscosity; the temperature is lowered to 60° C., the hydrophilic chain extender is added to the reaction container, and the reaction is carried out for 1.5 hours; the small molecule chain extender and modified nano-silica are respectively added to the reaction container, and the reaction is carried out with stirring for 1 hour; the temperature is cooled to 50° C., triethylamine is added, and the reaction is carried out with stirring for 1.5 hours; the temperature is cooled to room temperature, water is added, and high-speed emulsification is carried out; and finally, the acetone is removed under reduced pressure.

[0067] The emulsion is evenly sprayed on the metal surface, and the modified waterborne polyurethane coating is obtained after the water is completely dried.

[0068] Example 4

[0069] The water-based polyurethane coating comprises, in parts by weight, 40 parts of diisocyanate, 30 parts of polycarbonate diol, 0.02 parts of catalyst, 3 parts of polydimethylsiloxane, 4 parts of hydrophilic chain extender, 2 parts of small molecule chain extender, 0.5 parts of modified silica nanoparticles, 3 parts of triethylamine, 6 parts of acetone, and 150 parts of water.

[0070] The preparation process of modified silica nanoparticles is as follows: 3 parts of nano-silica particles are added to 80 parts of anhydrous ethanol, ultrasonically dispersed at room temperature for 50 minutes, 6 parts of ammonia water and 6 parts of distilled water are added, and after heating to 80°C, 3 parts of silane coupling agent KH550 are added, stirred and reacted for 2 hours, and then the temperature is kept unchanged. 3 parts of dodecyltriethoxysilane are added, stirred and reacted for 3 hours, and then cooled to room temperature, centrifuged, and dried to obtain modified nano-silica particles.

[0071] The preparation method of a water-based polyurethane emulsion comprises the following steps: before an experiment, diisocyanate, polycarbonate diol, polydimethylsiloxane, a hydrophilic chain extender and a small molecule chain extender are vacuum dried at 90° C. for 10 hours; subsequently, the diisocyanate, polycarbonate diol and polydimethylsiloxane are added to a reaction container, the temperature is raised to 70° C., and stirred for reaction for 1 hour, after which a catalyst is added, and the stirring reaction is continued for 3 hours, during which acetone is added to adjust the viscosity; the temperature is lowered to 60° C., the hydrophilic chain extender is added to the reaction container, and the reaction is carried out for 1.5 hours; the small molecule chain extender and modified nano-silica are respectively added to the reaction container, and the reaction is stirred for 1 hour; the temperature is cooled to 50° C., triethylamine is added, and the reaction is stirred for 1 hour; the temperature is cooled to room temperature, water is added, and high-speed emulsification is performed; and finally, the acetone is removed under reduced pressure.

[0072] The emulsion is evenly sprayed on the metal surface, and the modified waterborne polyurethane coating is obtained after the water is completely dried.

[0073] Example 5

[0074] The amount of modified silicon dioxide nanoparticles was 3 parts, and the other ingredients were the same as in Example 1.

[0075] Comparative Example 1

[0076] The polydimethylsiloxane and modified silicon dioxide nanoparticles are not included, and the other parts are the same as those in Example 1.

[0077] Comparative Example 2

[0078] The modified silicon dioxide nanoparticles are not included, and the other aspects are the same as those in Example 1.

[0079] Comparative Example 3

[0080] Without polydimethylsiloxane, the other steps are the same as those in Example 1.

[0081] Comparative Example 4

[0082] The amount of polydimethylsiloxane is 6 parts, and the other ingredients are the same as in Example 1.

[0083] Comparative Example 5

[0084] During the preparation of modified silica nanoparticles, the silane coupling agent was omitted, and the other steps were the same as in Example 1.

[0085] Comparative Example 6

[0086] During the preparation of modified silica nanoparticles, dodecyltriethoxysilane was omitted, and everything else was the same as in Example 1.

[0087] Comparative Example 7

[0088] During the preparation of modified silica nanoparticles, dodecyltriethoxysilane was replaced with a silane coupling agent, and the rest were the same as in Example 1.

[0089] Comparative Example 8

[0090] During the preparation of modified silica nanoparticles, the silane coupling agent was replaced with dodecyltriethoxysilane, and the other steps were the same as in Example 1.

[0091] Experiments have found that when only dodecyltriethoxysilane is added for modification and the ratio is high, agglomeration easily occurs, turning it into a gel-like state, making subsequent steps impossible. This is because the hydrolysis and polycondensation reactions of the silane form bridge structures between the particles, leading to the formation of a three-dimensional network.

[0092] The performance of different groups of coatings were tested separately, and the results are shown in Table 1.

[0093] Water absorption is measured after the coating is immersed in water for one week.

[0094] The percentage of Chlorella adhesion area was obtained by immersing the coating in a high-concentration Chlorella aqueous solution for one month.

[0095] The corrosion degree grade is tested and rated in accordance with GB / T 10125-2012 "Salt spray test for corrosion in artificial atmosphere" and GB / T6461-2002 "Rating of specimens of metal and other inorganic coatings on metal substrates after corrosion tests".

[0096] Table 1 Test results

[0097]

[0098] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A waterborne polyurethane coating having corrosion resistance and antifouling properties, characterized in that: The raw materials include the following components in parts by weight: 30 parts of diisocyanate, 15-30 parts of polycarbonate diol, 0.01-0.02 parts of catalyst, 3-5 parts of polydimethylsiloxane, 3-5 parts of hydrophilic chain extender, 1-3 parts of small molecule chain extender, 0.5-3 parts of modified silica nanoparticles, 1-3 parts of triethylamine, 4-10 parts of acetone, and 130-150 parts of water; The modified silicon dioxide nanoparticles are nano silicon dioxide modified by a silane coupling agent and dodecyltriethoxysilane.

2. The waterborne polyurethane coating with corrosion resistance and antifouling properties according to claim 1, characterized in that: The diisocyanate is at least one of isophorone diisocyanate, diphenylmethane diisocyanate or hexamethylene diisocyanate; Or, the polycarbonate diol is at least one of adipic acid-ethylene glycol polyester polyol, adipic acid-butylene glycol polyester polyol or adipic acid-neopentyl glycol polyester polyol; Or, the catalyst is dibutyltin dilaurate; Or, the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid; Alternatively, the small molecule chain extender is 1,4-butanediol.

3. The method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties according to claim 1 or 2, characterized in that: The steps include: Mix diisocyanate, polycarbonate diol and polydimethylsiloxane in proportion, heat to 70-80°C, stir and react for a set time, add catalyst, continue stirring and react for a set time, and add acetone to adjust the viscosity; Then the temperature is lowered to 50-60°C and a hydrophilic chain extender is added thereto and the reaction is allowed to proceed for a set time; Then, a small molecule chain extender and modified silica nanoparticles were added thereto and the reaction was stirred for a set time; Cool the reaction system to 40-50°C, add triethylamine, and stir the reaction for the set time; After the reaction is completed, the temperature is lowered to room temperature, water is added for emulsification, and the acetone is removed to obtain the product.

4. The method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties according to claim 3, characterized in that: The modified silica nanoparticles are prepared by ultrasonically dispersing 3-6 parts of silica nanoparticles in anhydrous ethanol, adding ammonia and water, heating the mixture to 80-90° C., adding 3-5 parts of a silane coupling agent, stirring and reacting for 2-3 hours, adding 3-5 parts of dodecyltriethoxysilane, and continuing to stir and react for 2-3 hours. After the reaction is completed, the temperature is lowered, the solid and liquid are separated, and the mixture is dried to obtain modified silicon dioxide nanoparticles.

5. The method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties according to claim 4, characterized in that: The number of parts of the anhydrous ethanol is 60-80 parts; Preferably, the concentration of the ammonia water is 25%-28%, % is the mass percentage, and the number of parts of the ammonia water is 6-12 parts; More preferably, the amount of water is 6-12 parts.

6. The method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties according to claim 3, characterized in that: Mix diisocyanate, polycarbonate diol and polydimethylsiloxane in proportion, heat to 70-80°C, and stir for 1-2 hours; Alternatively, after adding the catalyst, continue stirring the reaction for 1-2 hours; Alternatively, acetone is added during the process to adjust the viscosity to 1500-4000 mPa·s; Alternatively, after adding a hydrophilic chain extender, the reaction time is 1-1.5 h; Alternatively, after adding the small molecule chain extender and modified silica nanoparticles, the reaction time is 1-2 h; Alternatively, after adding triethylamine, the stirring reaction time is 1-2 hours; Alternatively, the acetone can be removed under reduced pressure.

7. The method for preparing the waterborne polyurethane coating having corrosion resistance and antifouling properties according to claim 3, characterized in that: Diisocyanate, polycarbonate diol, polydimethylsiloxane, hydrophilic chain extender and small molecule chain extender are all dried in advance; Preferably, the pre-drying treatment is carried out at a temperature of 90-100° C. and for a time of 5-15 hours.

8. Use of the waterborne polyurethane coating with corrosion resistance and antifouling properties according to claim 1 or 2 in the protection of underwater metal devices.

9. A waterborne polyurethane coating, characterized in that: The waterborne polyurethane coating according to claim 1 or 2 is applied on a substrate to be protected and dried to obtain the product.

10. An underwater metal equipment, characterized in that: The surface of the coating is adhered with the waterborne polyurethane coating according to claim 9.

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