Super-hydrophobic waterborne polyurethane coating capable of realizing friction repair as well as preparation method and application of super-hydrophobic waterborne polyurethane coating

Abstract

The invention discloses a super-hydrophobic waterborne polyurethane coating capable of realizing friction repair as well as a preparation method and application thereof, and relates to the technical field of coatings. The coating comprises the following components in percentage by mass: 5 wt.%-15 wt.% of hydrophobic modified nanoparticles, 15 wt.%-20 wt.% of porous diatomite, 30 wt.%-60 wt.% of waterborne polyurethane and the balance of water, wherein the sum of the mass percentages of the components is 100%; holes of diatomite are filled with hydrophobically modified nanoparticles to form diatomite capsules, and the hydrophobically modified nanoparticles are uniformly dispersed in a waterborne polyurethane emulsion by ingeniously utilizing the hydrophilicity of the surface of the diatomite, so that the uniformly and stably dispersed super-hydrophobic waterborne polyurethane coating is obtained. The super-hydrophobic coating prepared from the coating has friction repair performance.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a super-hydrophobic waterborne polyurethane coating that can be repaired by friction, and a preparation method and application thereof. Background Art

[0002] Green and environmentally friendly water-based paint uses water as a dispersion medium, which can effectively reduce the use of organic solvents and reduce the emission of VOCs. In recent years, water-based emulsion paints have developed rapidly, and their application in the field of coatings has been expanding, showing a trend of gradually replacing traditional solvent-based paints. Among them, water-based polyurethane coatings have the advantages of stable chemical structure and strong adhesion to substrates. They are widely used in home building materials, metal anti-corrosion, floor coatings and other fields. However, due to the introduction of hydrophilic groups in its resin molecules, its coating is not water-resistant and is prone to blistering, cracking and peeling. Super-hydrophobic modification of water-based polyurethane coatings can not only improve the poor water resistance and insufficient weather resistance of its coatings, but also give it more functionalities such as self-cleaning, anti-fouling and anti-corrosion, which is of great significance to its high-performance development.

[0003] Low surface energy substances and surface roughness are two necessary conditions for achieving super hydrophobicity. However, on the one hand, the difference in surface energy between low surface energy substances and water is very large, and it is difficult to disperse in water. This contradiction between low surface energy and water-based coatings seriously limits the water-based development of super hydrophobic coatings. On the other hand, once the surface roughness structure is damaged by external force, the super hydrophobicity of the coating is easily reduced or even lost, resulting in the poor durability of the existing super hydrophobic coating, which is an important factor hindering its commercial application. Through self-repair design, the service life of super hydrophobic coatings can be extended. For example, patents such as CN 110358435A, CN116606590B, and CN 101791608A, by introducing self-repairing polymer materials or thermoplastic resin film-forming agents, the self-repairing of super hydrophobic coatings is achieved. However, this type of super hydrophobic coating must be dissolved and dispersed by organic reagents to self-repairing polymers, and the self-repairing function is limited to the self-repairing of the damaged coating surface chemical substances, and for the surface with severe damage to the rough structure, self-repair cannot be achieved. In response to the above problems, it is urgent to design and prepare a water-based super-hydrophobic coating that is both water-based and environmentally friendly and abrasion-resistant and repairable, which can greatly promote the green and high-performance development of coatings. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned background technology, the present invention provides a kind of super-hydrophobic water-based polyurethane coating and its preparation method and application that can be repaired by friction. The method first fills hydrophobically modified nanoparticles in the holes of diatomite to form diatomite capsules, and cleverly utilizes the hydrophilicity of the diatomite surface to be evenly dispersed in the aqueous polyurethane emulsion to obtain a super-hydrophobic water-based polyurethane coating that can be evenly and stably dispersed. The super-hydrophobic water-based polyurethane coating is applied on the substrate surface, and the hydrophobically modified nanoparticles coated in the holes of diatomite can realize dynamic release by sandpaper friction, so as to realize the construction of surface micro-nano rough structure and the release of low surface energy materials synchronously, and give coating super-hydrophobicity. The method is extremely simple, time-saving, does not require complicated equipment and steps, and more importantly, coating has excellent tolerance for mechanical wear, and when surface super-hydrophobicity decreases due to factors such as light and heat, super-hydrophobicity can be restored by simple friction.

[0005] The first object of the present invention is to provide a super-hydrophobic waterborne polyurethane coating that can be repaired by abrasion, wherein the coating comprises the following components in percentage by mass: 5 wt.% to 15 wt.% of hydrophobically modified nanoparticles, 15 wt.% to 20 wt.% of porous diatomaceous earth, 30 wt.% to 60 wt.% of waterborne polyurethane, and the balance being water, the sum of the mass percentages of the various components being 100%; The hydrophobically modified nanoparticles are prepared by hydrophobically modifying nanoparticles; The nanoparticles are one or more of nano-silicon dioxide, nano-titanium dioxide, nano-calcium hydroxide, nano-calcium carbonate, nano-aluminum oxide, nano-magnesium oxide, nano-magnesium hydroxide, nano-ferroferric oxide particles, silver nanoparticles, polystyrene nanoparticles, polytetrafluoroethylene nanospheres, polyvinylidene fluoride nanospheres, and cellulose nanocrystals.

[0006] Preferably, the particle size of the hydrophobically modified nanoparticles is 10-100 nm; the particle size of the porous diatomaceous earth is 20-60 μm, and the pore size is 500 nm-2 μm.

[0007] Preferably, the hydrophobically modified nanoparticles are prepared according to the following steps: After the nanoparticles are ultrasonically dispersed in a mixed solution containing ethanol, water and ammonia water, a fluorine-containing silane coupling agent is added and stirred for reaction to obtain hydrophobically modified nanoparticles; The volume proportion of ethanol in the mixed solution is 70-90%, the volume proportion of water is 5-20%, and the volume proportion of ammonia water is 2-10%, wherein the sum of the volume proportions of ethanol, water and ammonia water is 100%; During the stirring reaction, the stirring temperature is 20-60°C and the stirring time is 5-10 h.

[0008] Preferably, the fluorinated silane coupling agent is one or more of perfluorinated trimethoxysilane, perfluorinated triethoxysilane, and perfluorinated trichlorosilane; and the added amount of the fluorinated silane coupling agent is 0.5-2 wt.%.

[0009] Preferably, the waterborne polyurethane is anionic waterborne polyurethane, cationic waterborne polyurethane or nonionic waterborne polyurethane.

[0010] The second object of the present invention is to provide a method for preparing a super-hydrophobic waterborne polyurethane coating that can be repaired by friction, comprising the following steps: The hydrophobic nanoparticles are uniformly dispersed in ethyl acetate, porous diatomaceous earth is added and stirred, and centrifuged to obtain diatomaceous earth capsules coated with the hydrophobic nanoparticles; uniformly dispersing waterborne polyurethane in water to obtain waterborne polyurethane emulsion; Add diatomaceous earth capsules into waterborne polyurethane emulsion, stir and mix at room temperature and pressure to obtain a friction-repairable super-hydrophobic waterborne polyurethane coating.

[0011] Preferably, the adding of porous diatomaceous earth and stirring include: stirring temperature is 20-60° C., and stirring time is 2-5 h.

[0012] The third object of the present invention is to provide a super hydrophobic waterborne polyurethane coating that can be repaired by friction and is used in the repair of friction on the surface of a substrate.

[0013] The fourth object of the present invention is to provide a super hydrophobic coating with friction repair performance, which is prepared by coating a friction repairable super hydrophobic waterborne polyurethane coating on a substrate.

[0014] A fifth object of the present invention is to provide a method for preparing a super-hydrophobic coating with friction repair performance, comprising the following steps: A super-hydrophobic water-based polyurethane coating that can be repaired by friction is applied to a substrate by spraying, brushing or dipping. After drying and curing, the coating is polished with sandpaper to expose the hydrophobic modified nanoparticles coated in the diatomaceous earth, thereby obtaining a super-hydrophobic coating with friction-repairing properties; wherein the substrate includes wood, paper, metal, concrete, glass, plastic, rubber or fiber fabric.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a super-hydrophobic water-based polyurethane coating that can be repaired by friction and its preparation method and application, the super-hydrophobic water-based polyurethane coating that can be repaired by friction provided by the present invention has both water-based environmental protection and friction resistance repairability, and its preparation method is simple, and the porous structure of diatomite is cleverly used in the preparation process to coat the hydrophobic nanoparticles therein, and the hydrophilic structure on the surface of diatomite gives it the ability to be uniformly and stably dispersed in an aqueous system, and can achieve uniform mixing with an aqueous polymer emulsion. The prepared super-hydrophobic composite coating has excellent mechanical wear resistance and aging resistance, and not only will not destroy the super-hydrophobic performance after wear, but can enhance the roughness and release the hydrophobic particles, and when the surface super-hydrophobicity is reduced due to force majeure, it can be restored by simple friction, which effectively solves the problem of poor durability of the super-hydrophobic coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The infrared spectra of the hydrophobically modified nanoparticles in Example 1 and the diatomite capsule SiO2@Diatomite in Example 3 are shown.

[0017] Figure 2 This is the SEM image of the diatomite capsule TiO2@Diatomite in Example 4.

[0018] Figure 3 This is the dispersion state of the diatomite capsule SiO2@Diatomite and the hydrophobically modified nanoparticles not coated with diatomite in the aqueous polyurethane emulsion in Example 6.

[0019] Figure 4 These are SEM images of the super-hydrophobic water-based polyurethane coating on the wood surface in Example 8 before and after surface friction.

[0020] Figure 5 The anti-wetting properties of the wood surface in Example 8 to various liquids after the super-hydrophobic water-based polyurethane coating is applied.

[0021] Figure 6 It is the water contact angle after applying super hydrophobic waterborne polyurethane coating on the wood surface in Example 9.

[0022] Figure 7 The change in water contact angle of the super-hydrophobic water-based polyurethane coating on the steel surface in Example 9 during multiple cycles of plasma treatment and friction repair treatment. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0024] The present invention aims to solve the problem that in the prior art, self-repairing of super-hydrophobic coatings is achieved by introducing self-repairing polymer materials or thermoplastic resin film-forming agents, but organic reagents must be used to dissolve and disperse the self-repairing polymers, and the self-repairing function is limited to the self-repairing of chemical substances on the damaged coating surface, and self-repairing cannot be achieved for surfaces with severely damaged rough structures. A super-hydrophobic water-based polyurethane coating that can be repaired by friction and a preparation method and application thereof are provided.

[0025] In order to achieve the above object, the first aspect of the present invention provides a super-hydrophobic waterborne polyurethane coating that can be repaired by abrasion, wherein the coating comprises the following components in percentage by mass: 5 wt.% to 15 wt.% of hydrophobically modified nanoparticles, 15 wt.% to 20 wt.% of porous diatomaceous earth, 30 wt.% to 60 wt.% of waterborne polyurethane, and the balance being water, the sum of the mass percentages of the various components being 100%; The present invention adopts the porous structure of micron diatomite to coat hydrophobic nanoparticles therein, and utilizes the hydrophilic structure on the surface of diatomite to make it uniformly and stably dispersed in an aqueous system, solves the problem that hydrophobic nanoparticles agglomerate in water and are difficult to disperse, reaches the effect of providing micro-nano multi-level structure and low surface energy at the same time, and gives composite coating super-hydrophobicity. Aqueous polyurethane, as the main film-forming material, can provide strong bonding between diatomite, hydrophobically modified nanoparticles and substrate at the same time, so that the super-hydrophobic composite coating formed has excellent mechanical wear resistance, and can realize the dynamic release of hydrophobic nanoparticles and the increase of roughness by wear, with repairability. The coating can realize water-based, super-hydrophobic, mechanical wear resistance and repairability at the same time.

[0026] The hydrophobically modified nanoparticles are prepared by hydrophobically modifying nanoparticles; The nanoparticles are one or more of nano-silicon dioxide, nano-titanium dioxide, nano-calcium hydroxide, nano-calcium carbonate, nano-aluminum oxide, nano-magnesium oxide, nano-magnesium hydroxide, nano-ferroferric oxide particles, silver nanoparticles, polystyrene nanoparticles, polytetrafluoroethylene nanospheres, polyvinylidene fluoride nanospheres, and cellulose nanocrystals.

[0027] The particle size of the hydrophobically modified nanoparticles is 10-100 nm; the particle size of the porous diatomaceous earth is 20-60 μm, and the pore size is 500 nm-2 μm.

[0028] The hydrophobically modified nanoparticles were prepared according to the following steps: After the nanoparticles are ultrasonically dispersed in a mixed solution containing ethanol, water and ammonia, a fluorine-containing silane coupling agent is added and stirred for reaction to obtain hydrophobically modified nanoparticles; The volume proportion of ethanol in the mixed solution is 70-90%, the volume proportion of water is 5-20%, and the volume proportion of ammonia water is 2-10%, wherein the sum of the volume proportions of ethanol, water and ammonia water is 100%; During the stirring reaction, the stirring temperature is 20-60°C and the stirring time is 5-10 h.

[0029] The fluorine-containing silane coupling agent is one or more of perfluorinated trimethoxysilane, perfluorinated triethoxysilane, and perfluorinated trichlorosilane; the addition amount of the fluorine-containing silane coupling agent is 0.5-2 wt.%.

[0030] The waterborne polyurethane is anionic waterborne polyurethane, cationic waterborne polyurethane or nonionic waterborne polyurethane.

[0031] A second aspect of the present invention provides a method for preparing a super-hydrophobic waterborne polyurethane coating that can be repaired by abrasion, comprising the following steps: The hydrophobic nanoparticles are uniformly dispersed in ethyl acetate, porous diatomaceous earth is added and stirred, and centrifuged to obtain diatomaceous earth capsules coated with the hydrophobic nanoparticles; uniformly dispersing waterborne polyurethane in water to obtain waterborne polyurethane emulsion; Add diatomaceous earth capsules into waterborne polyurethane emulsion, stir and mix at room temperature and pressure to obtain a friction-repairable super-hydrophobic waterborne polyurethane coating.

[0032] Wherein, the adding of porous diatomaceous earth and stirring include: the stirring temperature is 20-60° C., and the stirring time is 2-5 hours.

[0033] In one embodiment, a method for preparing a super-hydrophobic waterborne polyurethane coating that can be repaired by abrasion comprises the following steps: Step 1: Preparation of hydrophobically modified nanoparticles. After ultrasonically dispersing the nanoparticles in a mixed solution of ethanol / water / ammonia water, a fluorinated silane coupling agent is added, the reaction is stirred at a certain temperature, and the hydrophobically modified nanoparticles are separated and collected by centrifugation.

[0034] Step 2: Preparation of diatomaceous earth capsules: At room temperature and pressure, the hydrophobic nanoparticles in step 1 are ultrasonically dispersed in ethyl acetate, and a proper amount of porous diatomaceous earth is added and stirred, and the diatomaceous earth capsules coated with the hydrophobic nanoparticles are centrifugally separated and collected.

[0035] Step 3: Preparation of a friction-repairable super-hydrophobic waterborne polyurethane coating. The diatomaceous earth capsules prepared in step 2 are mixed with the waterborne polyurethane emulsion in a certain proportion, and stirred and dispersed evenly at room temperature and pressure to obtain a friction-repairable super-hydrophobic waterborne polyurethane coating.

[0036] The stirring in step 1, step 2 and step 3 adopts one or a combination of mechanical stirring, magnetic stirring, ultrasonic stirring and oscillating stirring. The stirring temperature range in step 1 is 20-60° C. and the stirring time is 5-10 h. The stirring time in step 2 and step 3 is 2-5 h.

[0037] The aqueous polyurethane emulsion in step 3 is one of anionic aqueous polyurethane, cationic aqueous polyurethane and nonionic aqueous polyurethane.

[0038] A third aspect of the present invention provides an application of a friction-repairable super-hydrophobic waterborne polyurethane coating in friction repairing of substrate surfaces.

[0039] A fourth aspect of the present invention provides a super hydrophobic coating with friction repair performance, which is prepared by coating a friction repairable super hydrophobic waterborne polyurethane coating on a substrate.

[0040] A fifth aspect of the present invention provides a method for preparing a super-hydrophobic coating with friction repair performance, comprising the following steps: The super-hydrophobic water-based polyurethane coating that can be repaired by friction is applied to the substrate by spraying, brushing or dipping. After drying and curing, the substrate is polished with sandpaper to expose the hydrophobic modified nanoparticles coated in the diatomaceous earth, thereby obtaining a super-hydrophobic coating with friction-repairing properties.

[0041] In one embodiment, the friction-repairable super-hydrophobic water-based polyurethane coating is applied to a substrate such as wood, paper, metal, concrete, glass, plastic, rubber, fiber fabric, etc. by spraying, brushing or dipping. After drying and curing, the hydrophobic modified nanoparticles coated in the diatomaceous earth are exposed after sandpaper polishing, and a super-hydrophobic coating with friction-repairing performance can be obtained. The curing temperature range is 20-80° C., and the higher the temperature, the shorter the required curing time.

[0042] The super-hydrophobic coating with friction repair performance can be restored to super-hydrophobicity by rubbing the surface with sandpaper after the super-hydrophobicity is reduced or lost due to natural aging, mechanical damage, plasma interference and the like, and is repairable.

[0043] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0044] Example 1 Preparation of hydrophobically modified silica nanoparticles: First, 3.6 g of silica particles with a particle size of about 30 nm were added, followed by 80 mL of ethanol, 8 mL of deionized water, and 4 mL of ammonia water. The mixture was mechanically stirred at 50°C for 10 min, and then 0.48 mL of perfluorinated trichlorosilane was added. The reaction was continued for 5 h, and after centrifugal drying, hydrophobically modified silica nanoparticles with F elements grafted on the surface were obtained.

[0045] Example 2 Preparation of hydrophobically modified titanium dioxide nanoparticles: First, add 1.5 titanium dioxide particles with a particle size of about 30 nm, then add 40 mL of ethanol, 4 mL of deionized water, and 2 mL of ammonia water, and mechanically stir at 50°C for 10 min. Then add 0.25 mL of perfluorodecyltrimethoxysilane and react for 10 hours. After centrifugal drying, hydrophobically modified titanium dioxide nanoparticles with F elements grafted on the surface can be obtained.

[0046] Example 3 Preparation of diatomite capsule SiO2@Diatomite: The whole process is carried out at room temperature and pressure. The hydrophobically modified silica particles in Example 1 are dispersed in 100 mL of ethyl acetate, and 12 g of diatomaceous earth is added for stirring. The reaction is carried out for 3 h. After filtering, ethanol and water are used to wash and dry in turn to prepare the diatomite capsule SiO2@Diatomite. The hydrophobically modified silica particles are filled in the pore structure of diatomite.

[0047] Example 4 Preparation of diatomite capsule TiO2@Diatomite: The whole process is carried out at room temperature and pressure. The hydrophobically modified titanium dioxide particles in Example 2 are dispersed in 100 mL of ethyl acetate, and 12 g of diatomaceous earth is added for stirring. The reaction is carried out for 3 h. After filtering, ethanol and water are used to wash and dry in turn to prepare the diatomite capsule SiO2@Diatomite. The hydrophobically modified titanium dioxide particles are filled in the pore structure of diatomite.

[0048] Example 5 Preparation of diatomite capsule PTFE@Diatomite: Preparation of diatomaceous earth capsules: The whole process was carried out at room temperature and pressure. Polytetrafluoroethylene nanospheres (particle size 50 nm) were directly dispersed in 100 mL of ethyl acetate, and 12 g of diatomaceous earth was added and stirred. The reaction was carried out for 3 h. After filtering, the mixture was washed with ethanol and water in turn and dried.

[0049] Example 6 Preparation of waterborne polyurethane super hydrophobic coating: Take 3.5 g of aqueous polyurethane and disperse it in 3.5 g of water to prepare an aqueous polyurethane emulsion, take the diatomite capsule SiO2@Diatomite 3.0 g prepared in Example 3, add it to the above-mentioned aqueous polyurethane emulsion under mechanical stirring, fully stir and mix at room temperature and pressure, and obtain an aqueous super-hydrophobic coating with a mass proportion of 30% of diatomite capsules, and the coating presents a uniform milky white state, indicating that SiO2@Diatomite capsules are uniformly and stably dispersed in aqueous polyurethane emulsion. The hydrophobically modified silicon dioxide nanoparticles coated with diatomite are not directly agglomerated in aqueous polyurethane emulsion, suspended above the solution, and cannot be dispersed.

[0050] Example 7 Preparation of waterborne polyurethane super hydrophobic coating: Take 4.0 g of aqueous polyurethane and disperse it in 4.0 g of water to prepare an aqueous polyurethane emulsion, take 2.0 g of diatomite capsule PTFE@Diatomite prepared in Example 5, add it to the above aqueous polyurethane emulsion under mechanical stirring, and fully stir and mix at room temperature and pressure to obtain an aqueous super hydrophobic coating in which the mass of diatomite capsule accounts for 20%.

[0051] Example 8 Superhydrophobic waterborne polyurethane coating for wood surface repair by abrasion: The water-based polyurethane super-hydrophobic coating prepared in Example 6 was sprayed on a fir board. After curing at 40°C for 6 h, the surface was polished with 200-mesh sandpaper. After 10 cycles of wear under a load of 100 g, the surface became super-hydrophobic, with a water contact angle of 152.5±1.05°, and exhibited anti-wetting properties to cola, sea water, juice, milk, tea, etc.

[0052] The above coating has excellent abrasion repair performance, which is specifically manifested as follows: after the fir board sprayed with water-based polyurethane superhydrophobic coating is scratched with a carving knife, the surface superhydrophobicity decreases, and it changes from superhydrophobic to hydrophobic state. However, after rubbing the scratched area with sandpaper to make it relatively flat, the surface can restore its superhydrophobicity.

[0053] Example 9 Super hydrophobic waterborne polyurethane coating that can be repaired by abrasion on steel surfaces: The water-based polyurethane super-hydrophobic coating prepared in Example 7 was sprayed on a steel plate, and after curing at 80°C for 2 h, the surface was polished with 100-mesh sandpaper. After 10 cycles of wear under a load of 200 g, the surface had super-hydrophobicity, and the water contact angle could reach 153.7±0.25°.

[0054] The above coating has excellent abrasion repair performance, which is specifically manifested as follows: after the steel plate sprayed with water-based polyurethane superhydrophobic coating is placed in a plasma cleaning device for treatment, the surface wettability changes from superhydrophobic to superhydrophilic, but after a simple friction with sandpaper, the surface can restore the superhydrophobicity.

[0055] In order to illustrate the relevant properties of the super-hydrophobic water-based polyurethane coating for friction repair provided by the present invention, it is described in conjunction with the accompanying drawings.

[0056] Figure 1 The infrared spectra of the hydrophobically modified nanoparticles (F-SiO2) in Example 1 and the algae capsule SiO2@Diatomite in Example 3. Compared with the unmodified silica nanoparticles (SiO2), the silica treated with perfluorotrichlorosilane has a -1 The characteristic peak appears at the CF bond position of the silica nanoparticles, indicating that the fluorosilane is successfully grafted onto the surface of the silica nanoparticles. Compared with the original diatomite (Diatomite), the diatomite capsule SiO2@Diatomite (Diatomite+F-SiO2) filled with hydrophobically modified silica nanoparticles has a peak at 1210 cm -1 The presence of a characteristic peak at the CF bond position indicates the presence of hydrophobically modified silica in diatomite.

[0057] Figure 2 This is the SEM image of the diatomite capsule TiO2@Diatomite in Example 4. Figure 2 (a) is the SEM morphology of the original diatomite, where a porous cavity structure can be observed; Figure 2 (b) is the SEM morphology of diatomite capsule TiO2@Diatomite, where it can be observed that the nanoparticles are filled in the cavity structure.

[0058] Figure 3 This is the dispersion state of the diatomite capsule SiO2@Diatomite and the hydrophobically modified nanoparticles not coated with diatomite in the aqueous polyurethane emulsion in Example 6. Figure 3 (a) is the dispersion state of diatomite capsule SiO2@Diatomite in aqueous polyurethane emulsion, which is uniform milky white as a whole, indicating that the mixture is uniform and stable; Figure 3 (b) The hydrophobic modified nanoparticles are directly dispersed in the aqueous polyurethane emulsion, which has obvious stratification. The hydrophobic nanoparticles agglomerate and suspend in the upper layer of the emulsion, making them difficult to disperse.

[0059] Figure 4 These are SEM images of the super-hydrophobic water-based polyurethane coating on the wood surface in Example 8 before and after surface friction. Figure 4(a) is a SEM image of the surface of a fir board after the water-based polyurethane super-hydrophobic coating was sprayed and cured. The surface is relatively flat, and a small amount of rough particles can be observed. Figure 4 (b) is the SEM morphology image after the surface was polished with 200-grit sandpaper. The surface showed a significant rough structure after polishing.

[0060] Figure 5 The anti-wetting properties of the wood surface to various liquids after the super-hydrophobic water-based polyurethane coating was applied in Example 8. The water-based polyurethane coating after sandpapering showed super-hydrophobicity due to the release of hydrophobic substances and the significant improvement of roughness. Liquids such as cola, salt water, juice, milk, and tea all appeared spherical on its surface without any spreading or wetting.

[0061] Figure 6 It is the water contact angle after applying super hydrophobic waterborne polyurethane coating on the wood surface in Example 9.

[0062] After sandpaper polishing, the water-based polyurethane coating has super hydrophobicity, with a surface water contact angle of up to 153.7±0.25° due to the release of hydrophobic substances and significant improvement in roughness.

[0063] Figure 7 The water contact angle change of the super-hydrophobic water-based polyurethane coating on the surface of the steel in Example 9 during multiple cycles of plasma treatment and friction repair treatment. The steel plate coated with the water-based polyurethane super-hydrophobic coating is placed in a plasma cleaning device for treatment. The high-energy plasma etches the surface and generates polar groups, which will cause the surface water contact angle to be reduced to less than 10 °, from super-hydrophobic to super-hydrophilic and irreversible. However, after simple friction with sandpaper, the surface hydrophobic substance is released and replenished again, and the surface can restore super-hydrophobicity, and can be stably restored to a super-hydrophobic state during five plasma cleaning-friction cycle treatments.

[0064] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0065] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A super-hydrophobic water-based polyurethane coating that can be repaired by friction, characterized in that: The coating comprises the following components in percentage by mass: 5wt.% to 15wt.% of hydrophobically modified nanoparticles, 15wt.% to 20wt.% of porous diatomaceous earth, 30wt.% to 60wt.% of waterborne polyurethane, and the balance being water, the sum of the mass percentages of the various components being 100%; The hydrophobically modified nanoparticles are prepared by hydrophobically modifying nanoparticles; The nanoparticles are one or more of nano-silicon dioxide, nano-titanium dioxide, nano-calcium hydroxide, nano-calcium carbonate, nano-aluminum oxide, nano-magnesium oxide, nano-magnesium hydroxide, nano-ferroferric oxide particles, silver nanoparticles, polystyrene nanoparticles, polytetrafluoroethylene nanospheres, polyvinylidene fluoride nanospheres, and cellulose nanocrystals.

2. The super-hydrophobic water-based polyurethane coating that can be repaired by abrasion according to claim 1, characterized in that: The particle size of the hydrophobically modified nanoparticles is 10-100 nm; the particle size of the porous diatomaceous earth is 20-60 μm, and the pore size is 500 nm-2 μm.

3. The super-hydrophobic water-based polyurethane coating capable of being repaired by abrasion according to claim 1, characterized in that: The hydrophobically modified nanoparticles were prepared according to the following steps: After the nanoparticles are ultrasonically dispersed in a mixed solution containing ethanol, water and ammonia, a fluorine-containing silane coupling agent is added and stirred for reaction to obtain hydrophobically modified nanoparticles; The volume proportion of ethanol in the mixed solution is 70-90%, the volume proportion of water is 5-20%, and the volume proportion of ammonia water is 2-10%, wherein the sum of the volume proportions of ethanol, water and ammonia water is 100%; During the stirring reaction, the stirring temperature is 20-60°C and the stirring time is 5-10 h.

4. The super-hydrophobic water-based polyurethane coating capable of being repaired by abrasion according to claim 3, characterized in that: The fluorine-containing silane coupling agent is one or more of perfluorinated trimethoxysilane, perfluorinated triethoxysilane, and perfluorinated trichlorosilane; the addition amount of the fluorine-containing silane coupling agent is 0.5-2 wt.%.

5. The super-hydrophobic waterborne polyurethane coating capable of being repaired by abrasion according to claim 1, characterized in that: The waterborne polyurethane is anionic waterborne polyurethane, cationic waterborne polyurethane or nonionic waterborne polyurethane.

6. A method for preparing the abrasion-repairable super-hydrophobic waterborne polyurethane coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: The hydrophobic nanoparticles are uniformly dispersed in ethyl acetate, porous diatomaceous earth is added and stirred, and centrifuged to obtain diatomaceous earth capsules coated with the hydrophobic nanoparticles; uniformly dispersing waterborne polyurethane in water to obtain waterborne polyurethane emulsion; The diatomaceous earth capsules are added into the waterborne polyurethane emulsion, and the mixture is stirred at normal temperature and pressure to obtain the super-hydrophobic waterborne polyurethane coating which can be repaired by friction.

7. The method for preparing the super-hydrophobic waterborne polyurethane coating capable of being repaired by abrasion according to claim 6, characterized in that: The adding of porous diatomaceous earth and stirring include: stirring temperature of 20-60° C., and stirring time of 2-5 h.

8. Use of the friction-repairable super-hydrophobic waterborne polyurethane coating according to any one of claims 1 to 5 in friction repairing of substrate surfaces.

9. A super hydrophobic coating with friction repair performance, characterized in that: The super-hydrophobic water-based polyurethane coating capable of being repaired by abrasion according to any one of claims 1 to 5 is coated on a substrate to obtain the coating.

10. A method for preparing the super-hydrophobic coating with friction repair performance according to claim 9, characterized in that: The following steps are involved: A super-hydrophobic water-based polyurethane coating that can be repaired by friction is applied to a substrate by spraying, brushing or dipping. After drying and curing, the coating is polished with sandpaper to expose the hydrophobic modified nanoparticles coated in the diatomaceous earth, thereby obtaining a super-hydrophobic coating with friction-repairing properties; wherein the substrate includes wood, paper, metal, concrete, glass, plastic, rubber or fiber fabric.

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