Super-hydrophilic-super-oleophobic polyurethane-based coating in air and preparation method thereof

Abstract

The invention belongs to the technical field of super-oleophobic coatings, and particularly relates to a super-hydrophilic-super-oleophobic polyurethane-based coating in air as well as a preparation method and application of the super-hydrophilic-super-oleophobic polyurethane-based coating. Adding dopamine into the boron nitride solution, and dispersing to obtain boron nitride / polydopamine; the preparation method comprises the following steps: dispersing boron nitride / polydopamine in a solvent, then adding ammonia water and an organic silicon source, and carrying out sol-gel reaction to obtain a boron nitride / polydopamine / silicon dioxide solution; adding a fluorine surfactant into the boron nitride / polydopamine / silicon dioxide solution to obtain super-hydrophilic-super-oleophobic composite particles; and adding the super-hydrophilic-super-oleophobic composite particle dispersion liquid into a waterborne polyurethane solution to obtain a spraying solution, and spraying the spraying solution onto a matrix to obtain the super-hydrophilic-super-oleophobic polyurethane-based coating in air. According to the method, the super-hydrophilic and super-oleophobic coating in air is prepared, so that the oleophobicity of the coating can be realized under the condition of no water environment, and the durability of the coating is improved. And meanwhile, various extreme environment conditions can be adapted.

Description

Technical Field

[0001] The present invention belongs to the technical field of superoleophobic coatings, and particularly relates to a superhydrophilic-superoleophobic polyurethane-based coating in air and a preparation method thereof. Background Art

[0002] The superoleophobic performance of superhydrophilic underwater superoleophobic coatings often depends on the presence of a surface water film. Once the water film is damaged and air enters, the direct contact area between the coating and the oil increases, and the oil is likely to adhere to the coating surface, resulting in the rapid oil contamination of the coating and the loss of superoleophobic characteristics, which limits its stability and reliability in practical applications.

[0003] For existing superhydrophilic underwater superoleophobic coatings, for example, Liang et al. designed a superhydrophilic wax-preventing coating with a silica bottom layer. The prepared coating consists of three layers, including an electrodeposited zinc film for improving corrosion resistance, a phosphating film for constructing a fish scale morphology, and a silica film modified by a simple spin coating method, which endows the surface with superhydrophilicity and enhances mechanical properties. The hydrophilicity can be maintained for 20 wear cycles under a 50 g load (Liang W, Zhu L, Li W, et al. Bioinspired Composite Coating with Extreme Underwater Superoleophobicity and Good Stability for Wax Prevention in the Petroleum Industry[J]. Langmuir, 2015: 11058 - 11066. DOI: 10.1021 / acs.langmuir.5b03234.). Li et al. constructed a poly(vinyl alcohol) (PVA) / zeolite composite coating with certain mechanical strength using dopamine, 4A zeolite powder, and poly(vinyl alcohol). Incorporating zeolite into the polymer matrix can improve the mechanical properties of the polymer material. It can not only enhance the mechanical properties of PVA but also enhance the hydrophilicity of the composite coating. The underwater superoleophobicity of this coating can be maintained for 50 wear cycles under a 200 g load and has potential application value for wax prevention (Li S, Song Z, Bai J, et al. Bioinspired poly(vinyl alcohol) / zeolite composite coating with multifunctional integration[J]. Journal of Colloid and Interface Science, 2019, 552. DOI: 10.1016 / j.jcis.2019.04.094.).

[0004] However, after air enters the above-prepared coating, the chemical composition and structure of the coating may be damaged, resulting in oil being easily attached to the surface of the coating, thereby affecting its superhydrophilic and underwater superoleophobic properties. Summary of the Invention

[0005] To solve the above problems, the present invention provides a superhydrophilic-superoleophobic polyurethane-based coating in air and a preparation method thereof. By preparing a superhydrophilic-superoleophobic coating in air, oleophobicity can be achieved even under conditions without a water environment for the coating, improving the durability of the coating. At the same time, it can adapt to the conditions under various extreme environments.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The first object of the present invention is to provide a preparation method of a superhydrophilic-superoleophobic polyurethane-based coating in air, including the following steps: S1. Under alkaline conditions, dopamine is added to a boron nitride solution, dispersed, and stirred at room temperature to form polydopamine on the surface of boron nitride, obtaining boron nitride / polydopamine.

[0008] S2. The boron nitride / polydopamine is dispersed in a solvent, and then ammonia water and an organosilicon source are added in sequence for a sol-gel reaction to obtain a boron nitride / polydopamine / silica solution.

[0009] S3. A fluorosurfactant is added to the boron nitride / polydopamine / silica solution for superhydrophilic-superoleophobic modification to obtain superhydrophilic-superoleophobic composite particles.

[0010] S4. A superhydrophilic-superoleophobic composite particle dispersion liquid is added to an aqueous polyurethane solution to obtain a spraying solution, and the spraying solution is sprayed onto a substrate for in-situ curing to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air.

[0011] Furthermore, the mass ratio of boron nitride to dopamine in the boron nitride solution is 1:0.01 - 0.1, the stirring time is 12h - 24h, and the pH is adjusted to 8 - 9 using tris(hydroxymethyl)aminomethane under alkaline conditions.

[0012] Furthermore, the mass-volume ratio of boron nitride / polydopamine to the organosilicon source is 0.5g:0.2mL - 1mL, the organosilicon source is tetraethyl orthosilicate, the volume ratio of ammonia water to the organosilicon source is 1 - 2:1, and the sol-gel reaction time is 12h - 24h.

[0013] Furthermore, the mass ratio of boron nitride / polydopamine / silica to the fluorosurfactant in the boron nitride / polydopamine / silica solution is 0.5:0.6 - 1, and the superhydrophilic-superoleophobic modification time is 12h - 24h.

[0014] Furthermore, the concentration of the aqueous polyurethane solution is 0.1 g / mL to 0.3 g / mL, the concentration of the superhydrophilic-superoleophobic composite particle dispersion is 0.01 g / mL to 0.04 g / mL, and the volume ratio of the aqueous polyurethane solution to the superhydrophilic-superoleophobic composite particle dispersion is 1 to 4:10.

[0015] Furthermore, the spraying pressure is 6 bar to 7 bar, and the substrate is a metal substrate or a polymer substrate.

[0016] Furthermore, the curing temperature is 110 °C to 130 °C, and the time is 1.5 h to 3 h.

[0017] Furthermore, the thickness of the superhydrophilic-superoleophobic polyurethane-based coating in the air is 50 μm to 70 μm.

[0018] The second object of the present invention is to provide a superhydrophilic-superoleophobic polyurethane-based coating in the air, which is prepared by the above preparation method.

[0019] The third object of the present invention is to provide an application of the superhydrophilic-superoleophobic polyurethane-based coating in the air in the preparation of wax-proof materials.

[0020] The present invention has the following beneficial effects compared with the prior art: The preparation method of the superhydrophilic-superoleophobic polyurethane-based coating provided by the present invention realizes the transformation from hydrophobic to hydrophilic through surface functionalization modification by the combination of boron nitride and polydopamine, and at the same time has oleophobic properties. Then, a sol-gel reaction is carried out. Polydopamine provides a large number of grafting sites, which plays a role in the in-situ growth of silica, and further improves the interfacial bonding effect between silica and boron nitride. Silica is formed on the surface of boron nitride / polydopamine to obtain boron nitride / polydopamine / silica. The interfacial bonding effect between silica and boron nitride is improved by polydopamine. Then, a fluorosurfactant is introduced into boron nitride / polydopamine / silica. The fluorosurfactant has an extremely low dispersive surface free energy component and an extremely high non-dispersive surface free energy component, showing a superhydrophilic-superoleophobic effect to form modified particles. On the one hand, the hydrophilicity of the particles themselves can be significantly improved through chemical modification, so that dense hydrophilic sites are formed in the polyurethane-based coating, strengthening the stability of the surface water film. On the other hand, the introduction of modified particles into the polyurethane-based coating constructs a more complex micro-nano rough structure. Combining with hydrophilic groups, a more firm water film can be formed underwater to prevent oil droplets from directly contacting the coating surface, thereby enhancing oleophobicity. Moreover, an air film can be formed on the air surface relying on the micro-nano rough structure, and then superoleophobicity in the air can be achieved, so that oleophobicity can be realized even under the condition that there is no water environment on the coating, improving the durability of the coating. At the same time, it can adapt to the conditions under various extreme environments.

[0021] The hydrophilic-superoleophobic composite particle modified particles provided by the present invention can be embedded in the coating matrix as a "skeleton" to enhance the abrasion resistance and impact resistance of the coating. The modified particles of the present invention can be directly added to the coating precursor solution by a one-step dispersion method, which simplifies the operation steps and reduces the difficulty of industrial production.

[0022] The hydrophilic-superoleophobic composite particle modified particles provided by the present invention can endow the polyurethane-based coating with excellent adhesion through polydopamine. After the adhesion test, the surface of the coating can still maintain high oleophobicity in the air, and the hydrophilicity remains in a superhydrophilic state. The fluorosurfactant is a short-chain fluorine substance containing a hydrophilic group. The short-chain fluorine can effectively reduce the free energy component of the dispersion force, while the hydrophilic group can increase the free energy component of the polar force. Therefore, when an oil droplet contacts the film surface, it presents a spherical shape, and at this time, the film surface shows an oleophobic state. When water contacts the surface, the hydrophilic groups will attract water molecules through the fluoroalkyl chain to the interior under the action of the polar force, thus showing a hydrophilic state. Description of the Drawings

[0023] Figure 1 It is the wettability diagram of the polyurethane-based coating prepared in Example 1 of the present invention in air and underwater. Figure 1 In it, a is the wettability diagram in air, and b is the wettability diagram underwater.

[0024] Figure 2 It is the oleophobic performance diagram of the polyurethane-based coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention.

[0025] Figure 3 It is the oleophobic performance diagram of the polyurethane-based coatings prepared in Examples 1, 4 to 5 and Comparative Examples 3 to 5 of the present invention.

[0026] Figure 4 It is the hydrophilic and oleophobic performance diagram of the polyurethane-based coatings prepared in Example 1, Comparative Example 6 and Comparative Example 7 of the present invention.

[0027] Figure 5 It is the paraffin prevention performance of the polyurethane-based coating prepared in Example 1 of the present invention at different temperatures.

[0028] Figure 6 It is the physical diagram of the superhydrophilic-superoleophobic polyurethane-based coating in air prepared in Example 1 of the present invention.

[0029] Figure 7 It is the chemical stability diagram of the polyurethane-based coating prepared in Example 1 of the present invention. Figure 7 In it, a is the chemical stability diagram under hydrochloric acid with pH = 1, and b is the chemical stability diagram under 3.5% NaCl.

[0030] Figure 8Adhesion force diagram of the polyurethane-based coating prepared in Example 1 of the present invention Figure 8 In Figure 8 , a is Comparative Example 8, b is Example 1, and b1 is a partial enlarged view of b.

[0031] Figure 9 Wax block adhesion test diagram of the polyurethane-based coating prepared in Example 1 of the present invention in air Figure 9 In Figure 9 , a is the polyurethane-based coating of Example 1, and b is the aluminum plate.

[0032] Figure 10 Maximum wax block adhesion force diagram of the polyurethane-based coatings prepared in Example 1, Examples 4 to 5, and Comparative Examples 3 to 5 of the present invention Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. In the present invention, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. The present invention does not distinguish components by the difference in nouns, but by the difference in the functions of components. As mentioned throughout the specification and claims, "including" is an open-ended term, so it should be understood as "including but not limited to".

[0035] On the one hand, the present invention provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, including the following steps: S1. Under alkaline conditions, dopamine is added to the boron nitride solution, dispersed and stirred at room temperature to form polydopamine on the surface of boron nitride, obtaining boron nitride / polydopamine.

[0036] S2. The boron nitride / polydopamine is dispersed in a solvent, and then ammonia water and an organosilicon source are added in sequence for a sol-gel reaction to obtain a boron nitride / polydopamine / silica solution.

[0037] S3. A fluorosurfactant is added to the boron nitride / polydopamine / silica solution for superhydrophilic-superoleophobic modification to obtain superhydrophilic-superoleophobic composite particles.

[0038] S4. Add a superhydrophilic-superoleophobic composite particle dispersion liquid to the waterborne polyurethane solution to obtain a spraying solution. Spray the spraying solution onto the substrate and perform in-situ curing to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air.

[0039] It should be noted that in the present invention, the combination of boron nitride and polydopamine realizes the transformation from hydrophobic to hydrophilic through surface functionalization modification, and at the same time has oleophobic properties. Then, a sol-gel reaction is carried out. Polydopamine provides a large number of grafting sites, which plays a role in the in-situ growth of silica, and further improves the interfacial bonding effect between silica and boron nitride. Silica is formed on the surface of boron nitride / polydopamine to obtain boron nitride / polydopamine / silica. The interfacial bonding effect between silica and boron nitride is improved by polydopamine. Then, a fluorosurfactant is introduced into boron nitride / polydopamine / silica. The fluorosurfactant has an extremely low dispersive surface free energy component and an extremely high non-dispersive surface free energy component, showing a superhydrophilic-superoleophobic effect, forming modified particles. On the one hand, the hydrophilicity of the particles themselves can be significantly improved through chemical modification, so that dense hydrophilic sites are formed in the polyurethane-based coating, strengthening the stability of the surface water film. On the other hand, when the modified particles are introduced into the polyurethane-based coating, a more complex micro-nano rough structure is constructed. Combining with hydrophilic groups, a more firm water film can be formed underwater, preventing oil droplets from directly contacting the coating surface, thereby enhancing oleophobicity. Moreover, an air film can be formed on the air surface relying on the micro-nano rough structure, and then superoleophobicity in air can be achieved, so that oleophobicity can be realized even under the condition that the coating has no water environment, improving the durability of the coating. At the same time, it can adapt to the conditions under various extreme environments.

[0040] The hydrophilic-superoleophobic composite particle modified particles provided by the present invention can be embedded in the coating matrix as a "skeleton" to enhance the wear resistance and impact resistance of the coating. In the present invention, the modified particles can be directly added to the coating precursor liquid by a one-step dispersion method, simplifying the operation steps and reducing the difficulty of industrial production.

[0041] In some embodiments, the mass ratio of boron nitride to dopamine in the boron nitride solution is 1:0.01 - 0.1, the stirring time is 12h - 24h, and in an alkaline condition, tris(hydroxymethyl)aminomethane is used to adjust the pH to 8 - 9. It should be noted that tris(hydroxymethyl)aminomethane is used to adjust the pH in the present invention, and its purpose is to provide chemical inertness to ensure the stable progress of the reaction.

[0042] In some embodiments, the mass-volume ratio of boron nitride / polydopamine to the organosilicon source is 0.5g:0.2mL - 1mL, the organosilicon source is tetraethyl orthosilicate, the volume ratio of ammonia water to the organosilicon source is 1 - 2:1, and the sol-gel reaction time is 12h - 24h.

[0043] It should be noted that, in the present invention, TEOS is hydrolyzed and condensed under alkaline catalysis to form a SiO2 network, and the PDA-modified h-BN is embedded in the SiO2 network through physical adsorption and chemical bonding to form a BN / PDA / SiO2 three-phase composite system.

[0044] In some embodiments, the mass ratio of boron nitride / polydopamine / silicon dioxide to fluorosurfactant in the boron nitride / polydopamine / silicon dioxide solution is 0.5:0.6-1, and the superhydrophilic-superoleophobic modification time is 12h-24h. Preferably, the model of the fluorosurfactant is F-50.

[0045] The fluorosurfactant F-50 used in the present invention contains polar units in FS-50 that provide extremely strong non-dispersive surface free energy components, and FS-50 contains carbon fluorine short chains with extremely low dispersive surface free energy components, and has extremely low dispersive surface free energy components and extremely high non-dispersive surface free energy components. The carbon fluorine short chains reduce a large amount of dispersive force components on the surface, and the oil droplets belong to the non-polar phase, so when the oil droplets contact the membrane surface, they appear spherical, and the membrane surface is in an oleophobic state at this time. When water contacts the surface, the hydrophilic groups at the end will pull water molecules through the fluoroalkyl chains to the interior under the action of polar forces, thereby showing a hydrophilic state.

[0046] In some embodiments, the concentration of the aqueous polyurethane solution is 0.1 g / mL to 0.3 g / mL, the concentration of the superhydrophilic-superoleophobic composite particle dispersion is 0.01 g / mL to 0.04 g / mL, and the volume ratio of the aqueous polyurethane solution to the superhydrophilic-superoleophobic composite particle dispersion is 1 to 4:10.

[0047] In some embodiments, the spraying pressure is 6 bar to 7 bar, and the substrate is a metal substrate or a polymer substrate.

[0048] In some embodiments, the curing temperature is 110° C. to 130° C., and the curing time is 1.5 h to 3 h.

[0049] In some embodiments, the thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50 μm to 70 μm.

[0050] On the other hand, the present invention also provides a super hydrophilic-super oleophobic polyurethane-based coating in air.

[0051] The present invention also provides the use of the super-hydrophilic-super-oleophobic polyurethane-based coating in air in the preparation of anti-wax materials.

[0052] The invention is further described below through specific examples.

[0053] Example 1 This embodiment provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, comprising the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water, perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution, adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, ultrasonically disperse for 30 min, and then stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction ends, filter, wash with deionized water until neutral, and dry at 80 °C to obtain boron nitride / polydopamine particles, named BN-PDA.

[0054] S2. Disperse 0.5 g of the BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water, with the volume ratio of absolute ethanol to deionized water being 3:1. Ultrasonically disperse for 30 min to make the mixture uniform, obtaining a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and carry out a sol-gel reaction to graft silica particles onto the surface of BN-PDA, obtaining a boron nitride / polydopamine / silica solution with a concentration of 0.025 g / mL, named BN-PDA-SiO2 solution.

[0055] S3. Add 0.6 g of fluorosurfactant FS-50 to 20 mL of the BN-PDA-SiO2 solution obtained in S2, stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification ends, dry to obtain superhydrophilic-superoleophobic composite particles, named F-BN-PDA-SiO2.

[0056] S4. Provide an aluminum sheet substrate with the size of the aluminum sheet substrate being 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate, mechanically polish with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash with ionized water and ethanol in sequence, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0057] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO2 particles in 5 mL of deionized water and perform ultrasonic dispersion to obtain an F-BN-PDA-SiO2 particle dispersion. Add the F-BN-PDA-SiO2 particle dispersion to the waterborne polyurethane solution. The volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion is 1:5 to obtain a spraying solution. Using an air spray gun, spray the spraying solution onto an aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then cure it in situ at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air. The thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50 μm, which is named WPU / F-BN@SiO2.

[0058] Example 2 This example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, including the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water and perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution to adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, perform ultrasonic dispersion for 30 min, and then stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction, perform filtration, washing with deionized water until neutral, and drying at 80 °C in sequence to obtain boron nitride / polydopamine particles, named BN-PDA.

[0059] S2. Disperse 0.5 g of the BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water. The volume ratio of absolute ethanol to deionized water is 3:1, and perform ultrasonic dispersion for 30 min to make the mixture uniform to obtain a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and perform a sol-gel reaction to graft silica particles onto the surface of BN-PDA to obtain a boron nitride / polydopamine / silica solution. The concentration of the boron nitride / polydopamine / silica solution is 0.025 g / mL, named BN-PDA-SiO2 solution.

[0060] S3. Add 0.8 g of fluorosurfactant FS-50 to the 20 mL of the BN-PDA-SiO2 solution obtained in S2, stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification is completed, dry it to obtain superhydrophilic-superoleophobic composite particles, named F-BN-PDA-SiO2.

[0061] S4. Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate. Mechanically polish it with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash it with deionized water and ethanol in sequence, and finally dry it at 80 °C to obtain the treated aluminum sheet substrate.

[0062] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO2 particles in 5 mL of deionized water, perform ultrasonic dispersion to obtain an F-BN-PDA-SiO2 particle dispersion liquid. Add the F-BN-PDA-SiO2 particle dispersion liquid to the waterborne polyurethane solution. The volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion liquid is 1:5 to obtain a spraying solution. Use an air spray gun to spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure it at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air. The thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50 μm, named WPU / F-BN@SiO2.

[0063] Example 3 This example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, including the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water, perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution, adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, perform ultrasonic dispersion for 30 min, and then stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction is completed, filter, wash with deionized water until neutral, and dry at 80 °C in sequence to obtain boron nitride / polydopamine particles, named BN-PDA.

[0064] S2. Disperse 0.5 g of the BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water with a volume ratio of absolute ethanol to deionized water of 3:1, and ultrasonically disperse for 30 min to make the mixture uniform, obtaining a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and carry out a sol-gel reaction to graft silica particles on the surface of BN-PDA, obtaining a boron nitride / polydopamine / silica solution with a concentration of 0.025 g / mL, named BN-PDA-SiO2 solution.

[0065] S3. Add 1.0 g of fluorosurfactant FS-50 to 20 mL of the BN-PDA-SiO2 solution obtained in S2, stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification is completed, carry out drying to obtain superhydrophilic-superoleophobic composite particles, named F-BN-PDA-SiO2.

[0066] S4. Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate, mechanically polish with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash with deionized water and ethanol in sequence, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0067] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO2 particles in 5 mL of deionized water, carry out ultrasonic dispersion to obtain an F-BN-PDA-SiO2 particle dispersion. Add the F-BN-PDA-SiO2 particle dispersion to the waterborne polyurethane solution with a volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion of 1:5 to obtain a spraying solution. Use an air spray gun to spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air with a thickness of 50 μm, named WPU / F-BN@SiO2.

[0068] Example 4 This example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, including the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water, and perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution to adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, and after ultrasonic dispersion for 30 min, stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction, perform filtration, washing with deionized water until neutral, and drying at 80 °C in sequence to obtain boron nitride / polydopamine particles, named BN-PDA.

[0069] S2. Disperse 0.5 g of BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water, and the volume ratio of absolute ethanol to deionized water is 3:1. Perform ultrasonic dispersion for 30 min to make the mixture uniform to obtain a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 0.8 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and carry out a sol-gel reaction to graft silica particles on the surface of BN-PDA to obtain a boron nitride / polydopamine / silica solution. The concentration of the boron nitride / polydopamine / silica solution is 0.025 g / mL, named BN-PDA-SiO2 solution.

[0070] S3. Add 0.6 g of fluorosurfactant FS-50 to 20 mL of the BN-PDA-SiO2 solution obtained in S2, and stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification is completed, perform drying to obtain superhydrophilic-superoleophobic composite particles, named F-BN-PDA-SiO2.

[0071] S4. Provide an aluminum sheet substrate with the size of the aluminum sheet substrate being 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate, mechanically polish with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash with ionized water and ethanol in sequence, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0072] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO₂ particles in 5 mL of deionized water and perform ultrasonic dispersion to obtain an F-BN-PDA-SiO₂ particle dispersion. Add the F-BN-PDA-SiO₂ particle dispersion to the waterborne polyurethane solution. The volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO₂ particle dispersion is 1:5 to obtain a spraying solution. Using an air spray gun, spray the spraying solution onto an aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then perform in-situ curing at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air. The thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50 μm, which is named WPU / F-BN@SiO₂.

[0073] Example 5 This example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air, which includes the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water, perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution to adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, perform ultrasonic dispersion for 30 min, and then stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction ends, perform filtration, washing with deionized water until neutral, and drying at 80 °C in sequence to obtain boron nitride / polydopamine particles, named BN-PDA.

[0074] S2. Disperse 0.5 g of the BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water. The volume ratio of absolute ethanol to deionized water is 3:1. Perform ultrasonic dispersion for 30 min to make the mixture uniform to obtain a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1.2 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and perform a sol-gel reaction to graft silica particles onto the surface of BN-PDA to obtain a boron nitride / polydopamine / silica solution. The concentration of the boron nitride / polydopamine / silica solution is 0.025 g / mL, named BN-PDA-SiO₂ solution.

[0075] S3. Add 0.6 g of fluorosurfactant FS-50 to the 20 mL of the BN-PDA-SiO2 solution obtained in S2, stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification is completed, dry to obtain superhydrophilic-superoleophobic composite particles, named F-BN-PDA-SiO2.

[0076] S4. Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate. Mechanically polish with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash with deionized water and ethanol in sequence, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0077] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO2 particles in 5 mL of deionized water, perform ultrasonic dispersion to obtain an F-BN-PDA-SiO2 particle dispersion liquid. Add the F-BN-PDA-SiO2 particle dispersion liquid to the waterborne polyurethane solution. The volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion liquid is 1:5 to obtain a spraying solution. Use an air spray gun to spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air. The thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50 μm, named WPU / F-BN@SiO2.

[0078] Comparative Example 1 This comparative example provides a preparation method of a superhydrophilic-superoleophobic polyurethane-based coating in air. The basic difference from the preparation method of Example 1 is that the dosage of fluorosurfactant FS-50 in S4 is 0.2 g.

[0079] Comparative Example 2 This comparative example provides a preparation method of a superhydrophilic-superoleophobic polyurethane-based coating in air. The basic difference from the preparation method of Example 1 is that the dosage of fluorosurfactant FS-50 in S4 is 0.4 g.

[0080] Comparative Example 3 This comparative example provides a preparation method of a superhydrophilic-superoleophobic polyurethane-based coating in air. The basic difference from the preparation method of Example 1 is that the dosage of tetraethyl orthosilicate (TEOS) in S2 is 0.2 mL.

[0081] Comparative Example 4 This comparative example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air. The basic difference from the preparation method of Example 1 is that the amount of tetraethyl orthosilicate (TEOS) in S2 is 0.4 mL.

[0082] Comparative Example 5 This comparative example provides a method for preparing a superhydrophilic-superoleophobic polyurethane-based coating in air. The basic difference from the preparation method of Example 1 is that the amount of tetraethyl orthosilicate (TEOS) in S2 is 0.6 mL.

[0083] Comparative Example 6 A method for preparing a polyurethane-based coating includes the following steps: Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate. Mechanically polish it with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash it with ionized water and ethanol in sequence, and finally dry it at 80 °C to obtain the treated aluminum sheet substrate.

[0084] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a spraying solution. Using an air spray gun, spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure it at 120 °C for 2 h to obtain a polyurethane-based coating, named WPU.

[0085] Comparative Example 7 A method for preparing a polyurethane-based coating includes the following steps: S1. Disperse 1 g of boron nitride (BN) particles in 100 mL of deionized water, perform ultrasonic treatment for 10 min to obtain a BN solution; add tris(hydroxymethyl)aminomethane to the BN solution, adjust the pH of the BN solution to about 8.5, then add 0.01 g of dopamine, ultrasonically disperse for 30 min, and then stir at room temperature for 12 h. Dopamine oxidatively self-polymerizes to form polydopamine (PDA), forming a uniform coating on the surface of BN. After the reaction ends, perform filtration, wash with deionized water until neutral, and dry at 80 °C to obtain boron nitride / polydopamine particles, named BN-PDA.

[0086] S2. Disperse 0.5 g of the BN-PDA obtained in S1 in a mixed solvent of 20 mL of absolute ethanol and deionized water, where the volume ratio of absolute ethanol to deionized water is 3:1. Ultrasonically disperse for 30 min to make the mixture uniform, obtaining a BN-PDA dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1.2 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and carry out a sol-gel reaction to graft silica particles onto the surface of BN-PDA, obtaining a boron nitride / polydopamine / silica solution. The concentration of the boron nitride / polydopamine / silica solution is 0.025 g / mL, named BN-PDA-SiO2 solution.

[0087] S3. Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate. Mechanically polish with 400-mesh and 1000-mesh sandpapers in sequence to remove the oxide layer, then wash with ionized water and ethanol in sequence, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0088] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution. Add the BN-PDA-SiO2 solution to the waterborne polyurethane solution, where the volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion is 1:5, obtaining a spraying solution. Use an air spray gun to spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure at 120 °C for 2 h to obtain a polyurethane-based coating, named WPU / BN@SiO2.

[0089] Comparative Example 8 A preparation method of a polyurethane-based coating, comprising the following steps: S1. Disperse 0.5 g of boron nitride in a mixed solvent of 20 mL of absolute ethanol and deionized water, where the volume ratio of absolute ethanol to deionized water is 3:1. Ultrasonically disperse for 30 min to make the mixture uniform, obtaining a BN dispersion. Under magnetic stirring, add 1 mL of ammonia water to the BN-PDA dispersion for hydrolysis, and then slowly dropwise add 1 mL of tetraethyl orthosilicate (TEOS) to form a mixed reaction solution. Magnetically stir the mixed reaction solution for 12 h to ensure that tetraethyl orthosilicate can be completely hydrolyzed, and carry out a sol-gel reaction to graft silica particles onto the surface of BN-PDA, obtaining a boron nitride / polydopamine / silica solution. The concentration of the boron nitride / polydopamine / silica solution is 0.025 g / mL, named BN-SiO2 solution.

[0090] S3. Add 0.6 g of fluorosurfactant FS-50 to the 20 mL of BN-PDA-SiO2 solution obtained in S2, stir for 12 h for superhydrophilic-superoleophobic modification. After the superhydrophilic-superoleophobic modification is completed, dry to obtain superhydrophilic-superoleophobic composite particles, named F-BN-SiO2.

[0091] S4. Provide an aluminum sheet substrate with a size of 80 mm × 80 mm × 1 mm. Pretreat the surface of the aluminum sheet substrate. Mechanically polish with 400-mesh and 1000-mesh sandpapers in turn to remove the oxide layer, then wash with deionized water and ethanol in turn, and finally dry at 80 °C to obtain the treated aluminum sheet substrate.

[0092] Dissolve 5 g of waterborne polyurethane (WPU) in 5 mL of deionized water to obtain a WPU solution; dissolve 0.2 g of F-BN-PDA-SiO2 particles in 5 mL of deionized water, perform ultrasonic dispersion to obtain an F-BN-PDA-SiO2 particle dispersion liquid. Add the F-BN-PDA-SiO2 particle dispersion liquid to the waterborne polyurethane solution. The volume ratio of the waterborne polyurethane solution to the F-BN-PDA-SiO2 particle dispersion liquid is 1:5 to obtain a spraying solution. Use an air spray gun to spray the spraying solution onto the aluminum sheet substrate at a spraying pressure of 6 bar and a distance of about 15 cm from the aluminum sheet substrate, and then in-situ cure at 120 °C for 2 h to obtain a superhydrophilic-superoleophobic polyurethane-based coating in air, named WPU / BN / SiO2.

[0093] Test the structures and properties of the polyurethane-based coatings prepared in Examples 1 to 5 and Comparative Examples 1 to 7. The results are as follows: Figure 1 This is the wettability diagram of the polyurethane-based coating prepared in Example 1 of the present invention in air and underwater. Figure 1 In it, a is the wettability diagram in air, and b is the wettability diagram underwater. As Figure 1 shown, the coating prepared in Example 1 can repel various oil droplets in an air environment, and in a water environment, due to the presence of a water film, it can also keep the underwater oil droplets in a superoleophobic state.

[0094] Figure 2 This is the oleophobic performance diagram of the polyurethane-based coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention. As Figure 2 shown, as the dosage of fluorosurfactant FS-50 increases, the oleophobic angle continuously increases. When the dosage of fluorosurfactant FS-50 is 0.6 g, the coating reaches a superoleophobic state. Thus, it can be seen that with the increase of fluorine-containing groups with low surface energy, the fluorine content on the particle surface increases, and sufficient fluorine can lift the oil droplets, so that the particles can achieve a superoleophobic effect.

[0095] Figure 3 This is the oil-repellent performance diagram of the polyurethane-based coatings prepared in Example 1, Examples 4 to 5, and Comparative Examples 3 to 5 of the present invention. As Figure 3 shown, with the increase in the amount of tetraethyl orthosilicate, the hydrolysis-condensation of TEOS to form SiO2 network increases. In the polyurethane-based coating, a more complex micro-nano rough structure is constructed, and a more firm water film is formed underwater, preventing oil droplets from directly contacting the coating surface, thereby enhancing the oil-repellent property. Moreover, an air film can be formed on the air surface relying on the micro-nano rough structure, and thus super-oleophobicity in air can be achieved.

[0096] Figure 4 This is the hydrophilic and oil-repellent performance diagram of the polyurethane-based coatings prepared in Example 1, Comparative Example 6, and Comparative Example 7 of the present invention. As Figure 4 shown, the single aqueous polyurethane shows a hydrophilic and oleophilic effect. For the modified particles formed without adding the fluorosurfactant FS-50, since the coating does not contain fluorine elements with low surface energy, the oil-repellent angle of the coating cannot be increased. By introducing the F-BN-PDA-SiO2 modified particles into the polyurethane-based coating of the present invention, a more complex micro-nano rough structure is constructed, combined with hydrophilic groups, a more firm water film can be formed underwater, preventing oil droplets from directly contacting the coating surface, thereby enhancing the oil-repellent property. Moreover, an air film can be formed on the air surface relying on the micro-nano rough structure, and thus super-oleophobicity in air can be achieved.

[0097] Using the polyurethane-based coating prepared in Example 1 for wax prevention performance research, it includes the following steps: The cold finger method is used for the experiment. Wax is deposited on the polyurethane-based coating prepared in Example 1 respectively. The wax resistance performance of the coating is characterized by adjusting the circulating water temperature. The circulating water temperature changes in the range of 12°C to 22°C at an interval of 2°C. After 30 minutes, the substrate is slowly taken out and photographed, and the wax prevention rate is calculated.

[0098] Figure 5 This is the wax prevention performance of the polyurethane-based coating prepared in Example 1 of the present invention at different temperatures. Figure 6 This is a physical picture of the super-hydrophilic-super-oleophobic polyurethane-based coating prepared in Example 1 of the present invention. As Figure 5 and Figure 6 shown, a large amount of wax is deposited on the aluminum plate, while for the polyurethane-based coating prepared in Example 1, due to the existence of the water film, almost no wax is deposited on the coating surface. Moreover, the greater the temperature difference, the more wax is deposited on the aluminum plate, while almost no wax adheres to the surface of the polyurethane-based coating prepared in Example 1. It can be seen that the polyurethane-based coating prepared by the present invention can not only repel the adhesion of wax by forming an air film in air, but also isolate the deposition of wax by forming a water film in the wax-containing oil system.

[0099] The polyurethane-based coating prepared in Example 1 was immersed in an acidic solution with pH = 1 and a 3.5% NaCl salt solution for 0 min to 180 min for stability testing to systematically evaluate the long-term stability of the polyurethane-based coating prepared in Example 1. Figure 7 This is the chemical stability diagram of the polyurethane-based coating prepared in Example 1 of the present invention. Figure 7 In it, a is the chemical stability diagram under hydrochloric acid with pH = 1, and b is the chemical stability diagram under 3.5% NaCl. As Figure 7 shown, by immersing the polyurethane-based coating prepared in Example 1 in hydrochloric acid with pH = 1 and a 3.5% NaCl salt solution, it can still maintain its superoleophobic state after a period of time.

[0100] Figure 8 This is the adhesion force diagram of the polyurethane-based coating prepared in Example 1 of the present invention. Figure 8 In it, a is Comparative Example 8, b is Example 1, and b1 is a partial enlarged view of b. The two lower droplets in b1 are an oil droplet and a water droplet respectively, indicating that after the adhesion force test, the coating still has high oleophobicity and the hydrophilicity remains superhydrophilic. The standard test results of the adhesion force are shown in Table 1.

[0101] Table 1 Standard test results of adhesion force As Figure 8 and Table 1 show, for the coating without adding dopamine, the interfacial interaction between the silica formed after TEOS hydrolysis and boron nitride is not good, and the bonding strength between particles is poor. After the modification with dopamine in Example 1, the interfacial strength is increased, and a large number of grafting sites are provided, which provides a role for the in-situ growth of silica. The polyurethane-based coating prepared by modifying the coating with dopamine has excellent adhesion force, and after the adhesion force test, the surface of the coating can still maintain high oleophobicity in the air, and the hydrophilicity remains superhydrophilic.

[0102] Figure 9 This is the wax block adhesion test diagram of the polyurethane-based coating prepared in Example 1 of the present invention in the air. Figure 9 In it, a is the polyurethane-based coating of Example 1, and b is an aluminum plate. As Figure 9 shown, by comparing with the pure aluminum plate, it can be found that a large amount of paraffin adheres to the aluminum plate, while almost none adheres to the coating.

[0103] Figure 10 This is the maximum wax block adhesion force diagram of the polyurethane-based coatings prepared in Example 1, Examples 4 to 5 and Comparative Examples 3 to 5 of the present invention. As Figure 10As shown, for a single aluminum plate, the maximum wax block adhesion force is approximately 5.933 N. As the dosage of tetraethyl orthosilicate gradually increases, the silica generated after hydrolysis increases on the surface of boron nitride / polydopamine, forming a more stable SiO2 network, increasing the micro-nano rough structure of the polyurethane-based coating, thereby enhancing the oil repellency. When the dosage of tetraethyl orthosilicate reaches 1 mL, its oil repellency is the best, resulting in the smallest force on the superoleophobic coating and the maximum wax block adhesion force of approximately 0.785 N. When the dosage of tetraethyl orthosilicate is further increased, the generated silica increases, the stability of the SiO2 network becomes worse, and the wax block adhesion force on the superoleophobic coating increases. When there is only a polyurethane-based coating, that is, without being modified by F-BN-PDA-SiO2 modified particles, the surface shows a hydrophilic and oleophilic effect, so the maximum wax block adhesion force is the largest, and the maximum wax block adhesion force is approximately 9.954 N.

[0104] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and the two endpoints can be selected. Since the steps and methods adopted are the same as those in the embodiments, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0105] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A preparation method of a superhydrophilic-superoleophobic polyurethane-based coating in air, characterized in that, It includes the following steps: Under alkaline conditions, dopamine is added to the boron nitride solution, dispersed and stirred at room temperature to form polydopamine on the surface of boron nitride, obtaining boron nitride / polydopamine; The boron nitride / polydopamine is dispersed in a solvent, and then ammonia water and an organosilicon source are added in sequence to carry out a sol-gel reaction, obtaining a boron nitride / polydopamine / silica solution; A fluorosurfactant is added to the boron nitride / polydopamine / silica solution for superhydrophilic-superoleophobic modification, obtaining superhydrophilic-superoleophobic composite particles; A superhydrophilic-superoleophobic composite particle dispersion is added to the aqueous polyurethane solution to obtain a spraying solution, and the spraying solution is sprayed onto a substrate for in-situ curing, obtaining a superhydrophilic-superoleophobic polyurethane-based coating in air.

2. The preparation method of the superhydrophilic-superoleophobic polyurethane-based coating in the air according to claim 1, characterized in that, The mass ratio of boron nitride to dopamine in the boron nitride solution is 1:0.01 - 0.1, the stirring time is 12h - 24h, and the pH is adjusted to 8 - 9 with tris(hydroxymethyl)aminomethane under alkaline conditions.

3. The preparation method of the superhydrophilic-superoleophobic polyurethane-based coating in air according to claim 1, characterized in that, The mass-volume ratio of boron nitride / polydopamine to the organosilicon source is 0.5g:0.2mL - 1mL, the organosilicon source is tetraethyl orthosilicate, the volume ratio of ammonia water to the organosilicon source is 1 - 2:1, and the sol-gel reaction time is 12h - 24h.

4. The preparation method of the superhydrophilic-superoleophobic polyurethane-based coating in the air according to claim 1, characterized in that, The mass ratio of boron nitride / polydopamine / silica to the fluorosurfactant in the boron nitride / polydopamine / silica solution is 0.5:0.6 - 1, and the superhydrophilic-superoleophobic modification time is 12h - 24h.

5. The preparation method of the super-hydrophilic and super-oleophobic polyurethane-based coating in air according to claim 1, characterized in that, The concentration of the aqueous polyurethane solution is 0.1g / mL - 0.3g / mL, the concentration of the superhydrophilic-superoleophobic composite particle dispersion is 0.01g / mL - 0.04g / mL, and the volume ratio of the aqueous polyurethane solution to the superhydrophilic-superoleophobic composite particle dispersion is 1 - 4:

10.

6. The preparation method of the super-hydrophilic and super-oleophobic polyurethane-based coating in the air according to claim 1, characterized in that, The spraying pressure is 6 bar - 7 bar, and the substrate is a metal substrate or a polymer substrate.

7. The preparation method of the super-hydrophilic and super-oleophobic polyurethane-based coating in the air according to claim 1, characterized in that The curing temperature is 110°C - 130°C, and the time is 1.5h - 3h.

8. The preparation method of the super-hydrophilic and super-oleophobic polyurethane-based coating in the air according to claim 1, wherein, The thickness of the superhydrophilic-superoleophobic polyurethane-based coating in air is 50μm - 70μm.

9. A superhydrophilic-superoleophobic polyurethane-based coating in air, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 8.

10. Use of the superhydrophilic-superoleophobic polyurethane-based coating described in claim 9 in the preparation of a paraffin prevention material.

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