Self-cleaning lignin super-hydrophobic coating and preparation method and application thereof

Abstract

The application discloses a self-cleaning lignin super-hydrophobic coating and a preparation method and application thereof, which is composed of the following components in parts by weight: lignin / PDA / TiO2 composite particles 1-5 parts, silane reagent 0.1-0.3 parts, epoxy resin 1-5 parts, curing agent 0.1-0.5 parts and solvent 50-100 parts. The lignin is used as a raw material, the utilization rate of the lignin is improved, the problem of surplus treatment and high value of a pulp and paper enterprise is solved, the self-cleaning effect is achieved when the coating is sprayed on the surfaces of various substrates, and the coating has wide applicability to substrates.

Description

Technical Field

[0001] This invention relates to the field of hydrophobic coating technology, specifically to a self-cleaning lignin superhydrophobic coating, its preparation method, and its application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] The self-cleaning technology originates from the "lotus effect." Due to the micro-nano structure and low surface energy of the superhydrophobic surface of a lotus leaf, the interaction between the surface and water droplets is reduced, decreasing water droplet adhesion and causing the droplets to form a spherical shape. When the lotus leaf surface is tilted to a certain degree, the water droplets can roll on its surface, carrying away surface contaminants and achieving a self-cleaning effect. A superhydrophobic surface refers to a lotus leaf-like surface with a static contact angle greater than 150° and a dynamic roll-off angle less than 10°.

[0004] Self-cleaning technology has been applied in textiles, construction, automotive windows, and solar cells. However, manufacturing superhydrophobic surfaces requires the construction of micro- and nano-structures. Early superhydrophobic micro- and nano-structured surfaces were produced using laser etching techniques, including femtosecond, picosecond, and nanosecond lasers. This laser etching technology is expensive, inefficient, requires demanding processing environments, and is difficult to scale up. Currently, methods for preparing superhydrophobic micro- and nano-structured surfaces include sol-gel methods, chemical vapor deposition (CVD), and spraying. While the sol-gel method uses inexpensive inorganic materials such as titanium dioxide, silicon dioxide, and zinc oxide, the preparation process is cumbersome and produces significant solvent pollution. CVD, while achieving quick preparation by causing products to accumulate on the substrate through chemical reactions, requires strict process conditions and exhibits poor coating adhesion. Spraying, on the other hand, is simple to operate, applicable to a wide range of substrates, and produces coatings with good adhesion, making it a significant advantage in preparing superhydrophobic coatings.

[0005] Furthermore, the raw materials for existing self-cleaning superhydrophobic coatings are non-degradable, and their large-scale use will pollute the environment. Therefore, it is of great significance to find a superhydrophobic coating that is simple to operate, environmentally friendly, and has a wide range of applications. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a self-cleaning lignin superhydrophobic coating, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing lignin / PDA / TiO2 composite particles, comprising the following steps:

[0009] Lignin was dispersed in a solvent, and Tris-HCl (tris(hydroxymethyl)aminomethane) buffer was added dropwise to adjust the pH to 8.4. Dopamine hydrochloride was then added, and the mixture was stirred for 12–24 h. Dopamine was deposited on the lignin surface in the solution through an oxidative self-polymerization reaction, resulting in a large number of hydroxyl groups on the lignin surface, thus forming lignin / PDA composite particles. The mass percentage of lignin, dopamine hydrochloride, and Tris-HCl was 10–20:1–3:1, yielding solution A.

[0010] Slowly add 100-200 mL of 0.5 mol / L acid solution to solution A to adjust the pH of the solution to <1. Let it stand for 10-40 min to precipitate lignin and obtain lignin / PDA composite particles.

[0011] The lignin / PDA composite particles were dispersed in a solvent (anhydrous ethanol, deionized water, acetone), and a tetrabutyl titanate solution (an ethanolic solution of tetrabutyl titanate) was added dropwise to the solvent. 、 The lignin / PDA / TiO2 composite particles are obtained by stirring in an aqueous solution or acetone solution at 15-40℃ for 1-12 hours.

[0012] Slowly add acid solution to solution A to ensure the uniformity of the precipitate particles.

[0013] The role of the acid solution: to adjust the pH value, making the solution acidic, so that the composite particles can be precipitated by acid. Standard amount: prepare 100-200 mL of 0.5 mol / L sulfuric acid solution, with the adjusted pH < 1.

[0014] The lignin / PDA / TiO2 composite particles are used as the main component in the coating, giving the coating certain hydrophobic and mechanical properties.

[0015] Compared to existing research, dopamine can provide a large number of hydroxyl functional groups on the lignin surface through self-polymerization deposition. Furthermore, the abundance of hydroxyl functional groups on the lignin surface provides more reaction sites for the TiO2 precursor to be grafted onto the lignin / PDA composite particle surface via condensation reactions, resulting in more uniform dispersion of TiO2 on the lignin / PDA composite particle surface. In addition, using bio-based lignin as a coating material is not only environmentally friendly and biodegradable, but also improves the utilization rate of lignin, solving the problem of waste treatment and high-value utilization in pulp and paper manufacturing enterprises.

[0016] In some embodiments, the solvent is anhydrous ethanol, deionized water, or acetone.

[0017] In some embodiments, the dilute acid solution is a sulfuric acid solution, an oxalic acid solution, or a hydrochloric acid solution.

[0018] Preferably, the concentration of the dilute acid solution is 0.3 to 0.7 mol / L.

[0019] In some embodiments, the lignin is alkali lignin or sulfate lignin.

[0020] Secondly, the present invention provides a lignin / PDA / TiO2 composite particle, which is prepared by the aforementioned preparation method.

[0021] Thirdly, the present invention provides a self-cleaning lignin superhydrophobic coating, which is composed of the following components in parts by weight: 1-5 parts of lignin / PDA / TiO2 composite particles, 0.1-0.3 parts of silane reagent, 1-5 parts of epoxy resin, 0.1-0.5 parts of curing agent, and 50-100 parts of solvent.

[0022] In some embodiments, the silane reagent is 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS).

[0023] In some embodiments, the epoxy resin is E-44 or E-51.

[0024] In some embodiments, the curing agent is ethylenediamine or diethylenetriamine.

[0025] Fourthly, the present invention provides a method for preparing a self-cleaning lignin superhydrophobic coating, comprising the following steps: adding a silane reagent dropwise to a lignin / PDA / TiO2 composite particle solution and mixing it; then adding an epoxy resin dropwise to the solution and mixing it; finally adding an epoxy resin curing agent dropwise to the solution and mixing it to obtain the superhydrophobic coating.

[0026] Fifthly, the present invention provides a self-cleaning lignin superhydrophobic coating, which is obtained by spraying the self-cleaning lignin superhydrophobic coating onto the surface of a substrate and drying and curing it.

[0027] In specific operations, follow these steps: Use 0.001~0.003g / cm³ 2 To apply the superhydrophobic coating, pour the superhydrophobic coating into the spray gun, adjust the nozzle diameter to 0.5 mm, and keep the distance between the spray gun and the substrate 15 cm. After spraying the coating onto the substrate surface, place it in a vacuum drying oven and cure it at 60–90 °C for 1–10 h to obtain the superhydrophobic coating.

[0028] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0029] 1) The coating material is derived from bio-based raw materials, which are green, environmentally friendly, and biodegradable;

[0030] 2) By using lignin as a raw material, the utilization rate of lignin is improved, which solves the problem of waste treatment and high-value utilization in pulp and paper enterprises;

[0031] 3) The coating preparation process is simple, requiring only ordinary chemical processes (weighing, dropping, and stirring) to prepare superhydrophobic coatings;

[0032] 4) The coating process does not have high requirements for equipment, has wide applicability to substrates, and has a self-cleaning effect when sprayed on various substrate surfaces. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a contact angle diagram of the superhydrophobic coating prepared in Example 1;

[0035] Figure 2 These are images showing the self-cleaning effect of the superhydrophobic coating prepared in Example 1 on the paper substrate surface. (a) is a photograph of the distribution of methylene blue powder on the filter paper surface, and (b) is a photograph of water droplets rolling and carrying away methylene blue powder when water is dripped onto the filter paper surface.

[0036] Figure 3 These are wear test diagrams of the superhydrophobic coating prepared in Example 7 on the surface of an aluminum plate. (a) is a schematic diagram of the wear test, and (b) is a diagram showing the changes in contact angle and roll angle of the aluminum plate sample after different friction cycles. Detailed Implementation

[0037] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] The present invention will be further described below with reference to the embodiments.

[0039] Example 1:

[0040] Step 1: Select filter paper (76*26mm) as the substrate, dry it in a vacuum drying oven and set it aside for later use.

[0041] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0042] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0043] Step 4: Use a pipette to draw 0.015 mL of FOTS and add it to solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0044] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the filter paper. After spraying the coating onto the filter paper, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 157° and a dynamic contact angle of 1°.

[0045] Step 6: Cover the surface of the filter paper with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the surface of the filter paper at a flow rate of 20 mL / min. The water droplets roll on the surface of the filter paper and carry away the methylene blue powder, achieving a self-cleaning effect.

[0046] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 6 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0047] Example 2

[0048] Step 1: Select filter paper (76*26mm) as the substrate, dry it in a vacuum drying oven and set it aside for later use.

[0049] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0050] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.2 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0051] Step 4: Use a pipette to draw 0.01 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0052] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the filter paper. After spraying the coating onto the filter paper, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 156° and a dynamic contact angle of 1°.

[0053] Step 6: Cover the surface of the filter paper with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the surface of the filter paper at a flow rate of 20 mL / min. The water droplets roll on the surface of the filter paper and carry away the methylene blue powder, achieving a self-cleaning effect.

[0054] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 5 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0055] Example 3

[0056] Step 1: Select filter paper (76*26mm) as the substrate, dry it in a vacuum drying oven and set it aside for later use.

[0057] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0058] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.4 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0059] Step 4: Use a pipette to draw 0.02 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0060] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the filter paper. After spraying the coating onto the filter paper, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 157° and a dynamic contact angle of 1°.

[0061] Step 6: Cover the cut surface of the filter paper with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the surface of the filter paper at a flow rate of 20 mL / min. The water droplets roll on the surface of the filter paper and carry away the methylene blue powder, achieving a self-cleaning effect.

[0062] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 7 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0063] Example 4

[0064] Step 1: Select glass (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the glass slide, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0065] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0066] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0067] Step 4: Use a pipette to draw 0.015 mL of FOTS and add it to solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0068] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the glass. After spraying onto the glass surface, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 155° and a dynamic contact angle of 2°.

[0069] Step 6: Cover the glass surface with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the glass surface at a flow rate of 20 mL / min. The water droplets roll on the glass surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0070] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 5 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0071] Example 5

[0072] Step 1: Select glass (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the glass slide, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0073] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0074] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.2 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0075] Step 4: Use a pipette to draw 0.01 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0076] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the glass. After spraying onto the glass surface, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 158° and a dynamic contact angle of 1°.

[0077] Step 6: Cover the glass surface with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the glass surface at a flow rate of 20 mL / min. The water droplets roll on the glass surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0078] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 6 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0079] Example 6

[0080] Step 1: Select glass (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the glass slide, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0081] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0082] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.4 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0083] Step 4: Use a pipette to draw 0.02 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0084] Step 5, according to 0.002 g / cm 2The superhydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the glass. After spraying onto the glass surface, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 157° and a dynamic contact angle of 1°.

[0085] Step 6: Cover the glass surface with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the glass surface at a flow rate of 20 mL / min. The water droplets roll on the glass surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0086] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 5 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0087] Example 7

[0088] Step 1: Select aluminum sheet (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the aluminum sheet, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0089] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0090] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0091] Step 4: Use a pipette to draw 0.015 mL of FOTS and add it to solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0092] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the spray gun, the nozzle diameter was adjusted to 0.5 mm, and the distance between the spray gun and the aluminum sheet was 15 cm. After spraying on the surface of the aluminum sheet, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 157° and a dynamic contact angle of 1°.

[0093] Step 6: Cover the prepared aluminum sheet with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the aluminum sheet surface at a flow rate of 20 mL / min. The water droplets roll on the aluminum sheet surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0094] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 6 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0095] Example 8

[0096] Step 1: Select aluminum sheet (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the aluminum sheet, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0097] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0098] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.2 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0099] Step 4: Use a pipette to draw 0.01 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain a superhydrophobic coating with a static contact angle of 154° and a dynamic contact angle of 2°.

[0100] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the spray gun, the nozzle diameter was adjusted to 0.5 mm, and the distance between the spray gun and the aluminum sheet was 15 cm. After spraying on the surface of the aluminum sheet, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain the superhydrophobic coating.

[0101] Step 6: Cover the prepared aluminum sheet with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the aluminum sheet surface at a flow rate of 20 mL / min. The water droplets roll on the aluminum sheet surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0102] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 6 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0103] Example 9

[0104] Step 1: Select aluminum sheet (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the aluminum sheet, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0105] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0106] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.4 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0107] Step 4: Use a pipette to draw 0.04 mL of FOTS and place it into solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the superhydrophobic coating.

[0108] Step 5, according to 0.002 g / cm 2 The superhydrophobic coating was poured into the spray gun, the nozzle diameter was adjusted to 0.5 mm, and the distance between the spray gun and the aluminum sheet was 15 cm. After spraying on the surface of the aluminum sheet, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a superhydrophobic coating with a static contact angle of 155° and a dynamic contact angle of 1°.

[0109] Step 6: Cover the prepared aluminum sheet with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the aluminum sheet surface at a flow rate of 20 mL / min. The water droplets roll on the aluminum sheet surface and carry away the methylene blue powder, achieving a self-cleaning effect.

[0110] Step 7: Test the mechanical durability of the superhydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 150°, and the wear cycle is recorded. The experimental results show that after 5 wear cycles, the coating's contact angle is less than 150°, indicating a loss of superhydrophobicity.

[0111] Comparative Example 1

[0112] Compared to Example 1, this comparative example replaced the components of the coating and replaced the modifying agent with n-octyltrichlorosilane.

[0113] Step 1: Select filter paper (76*26mm) as the substrate, dry it in a vacuum drying oven and set it aside for later use.

[0114] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0115] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0116] Step 4: Use a pipette to take 0.015 mL of n-octyltrichlorosilane and add it to solution D. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the hydrophobic coating.

[0117] Step 5, according to 0.002 g / cm 2 The hydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the filter paper. After spraying the coating onto the filter paper, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a hydrophobic coating with a static contact angle of 139° and a dynamic contact angle of 27°.

[0118] Step 6: Cover the filter paper surface with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the filter paper surface at a flow rate of 20 mL / min. In this comparative example, n-octyltrichlorosilane was used as a modifying agent. The coating did not achieve a superhydrophobic effect; the water droplets could not roll on the coating surface to carry away the methylene blue powder, and the water droplets dissolved the methylene blue powder upon contact with it, thus failing to achieve a self-cleaning effect.

[0119] Step 7: Test the mechanical durability of the hydrophobic coating through an abrasion test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. Abrasion continues until the coating's contact angle is less than 90°, and the abrasion cycle is recorded. The experimental results show that after 12 abrasion cycles, the coating's contact angle is less than 90°, indicating a loss of hydrophobicity.

[0120] Comparative Example 2

[0121] Compared to Example 4, this comparative example changed the method of preparing the coating.

[0122] Step 1: Select glass (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the glass slide, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0123] Step 2: Weigh 60 mg of alkali lignin and add it to 8 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution A. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution B. Add solution B dropwise to solution A and stir at room temperature for 10 h to obtain lignin / TiO2 composite particle solution C.

[0124] Step 3: Use a pipette to draw 0.015 mL of FOTS and place it into solution C. Stir at room temperature for 30 min, add 0.05 g of epoxy resin, stir at room temperature for 15 min, add 0.05 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the hydrophobic coating.

[0125] Step 4, according to 0.002 g / cm 2 The hydrophobic coating was poured into the airbrush, and the nozzle diameter was adjusted to 0.5 mm. The airbrush was held 15 cm away from the glass. After spraying onto the glass surface, it was placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a hydrophobic coating with a static contact angle of 115° and a dynamic contact angle of 46°.

[0126] Step 5: Cover the glass surface with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the glass surface at a flow rate of 20 mL / min. This comparative example lacks the dopamine-induced self-polymerization on the lignin surface to form a secondary reaction platform. Therefore, after adding the titanium dioxide precursor tetrabutyl titanate, the reaction sites decrease, resulting in less titanium dioxide production. Consequently, the hydrophobic effect of the coating decreases, and the coating fails to achieve a superhydrophobic effect. Water droplets cannot roll on the coating surface to carry away the methylene blue powder, and upon contact with the methylene blue powder, they dissolve it, thus failing to achieve a self-cleaning effect.

[0127] Step 6: Test the mechanical durability of the hydrophobic coating through a wear test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. The wear continues until the coating's contact angle is less than 90°, and the wear cycle is recorded. The experimental results show that after 14 wear cycles, the coating's contact angle is less than 90°, indicating a loss of hydrophobicity.

[0128] Comparative Example 3

[0129] Compared to Example 7, this comparative example changed the process parameters for coating preparation and adjusted the amount of epoxy resin and its curing agent diethylenetriamine.

[0130] Step 1: Select aluminum sheet (76*26*1mm) as the substrate, use anhydrous ethanol and acetone to deeply clean the aluminum sheet, rinse with deionized water and then put it into a vacuum drying oven to dry for later use.

[0131] Step 2: Disperse 1g of alkali lignin in 50mL of anhydrous ethanol, then add 0.1mL of Tris-HCl to the solution and stir at room temperature for 10min. Weigh 0.06g of dopamine hydrochloride granules and add them to the solution, stirring at room temperature for 24h to obtain solution A. Slowly pour 0.5mol / L sulfuric acid solution into solution A and let it stand for 30min to precipitate the lignin. Separate the solid and liquid phases by centrifugation for 10min. Place the solid, i.e., the precipitate, in a vacuum drying oven and dry at 60℃ for 10h to obtain lignin / PDA composite particles.

[0132] Step 3: Weigh 60 mg of lignin / PDA composite particles and add them to 8 mL of anhydrous ethanol to obtain solution B. Measure 0.3 mL of tetrabutyl titanate using a graduated cylinder and pour it into 2 mL of anhydrous ethanol. Stir at room temperature for 10 min to obtain solution C. Add solution C dropwise to solution B and stir at room temperature for 10 h to obtain lignin / PDA / TiO2 composite particle solution D.

[0133] Step 4: Use a pipette to draw 0.015 mL of FOTS and add it to solution D. Stir at room temperature for 30 min, add 2 g of epoxy resin, stir at room temperature for 15 min, add 0.5 g of diethylenetriamine, and stir at room temperature for 15 min to obtain the hydrophobic coating.

[0134] Step 5, according to 0.002 g / cm 2The amount of hydrophobic coating to be sprayed is determined by pouring the spray gun into the spray gun, adjusting the nozzle diameter to 0.5 mm, and keeping the distance between the spray gun and the aluminum sheet at 15 cm. After spraying the coating onto the surface of the aluminum sheet, it is placed in a vacuum drying oven and cured at 85°C for 10 hours to obtain a hydrophobic coating with a static contact angle of 102° and a dynamic contact angle of 86°.

[0135] Step 6: Cover the prepared aluminum sheet with a layer of methylene blue powder and place it at an angle on the table. Use a constant flow pump to add deionized water droplets to the aluminum sheet surface at a flow rate of 20 mL / min. Epoxy resin, as a coating component, enhances the mechanical strength of the coating. However, there is a balance point between the amount of epoxy resin added and the hydrophobic properties of the coating. Adding too much epoxy resin will reduce the hydrophobic properties of the coating, failing to achieve a superhydrophobic effect. Water droplets cannot roll on the coating surface to carry away the methylene blue powder, and will dissolve the methylene blue powder upon contact, thus failing to achieve a self-cleaning effect.

[0136] Step 7: Test the mechanical durability of the hydrophobic coating through an abrasion test. Place a 1000# sandpaper (10*2.5cm, length*width) on the sample surface. Apply pressure to the sandpaper using a 100g weight to increase the rolling friction between the sandpaper and the sample surface. Each cycle consists of the sandpaper moving 10cm laterally and longitudinally. After one cycle, the contact angle is measured. Abrasion continues until the coating's contact angle is less than 90°, and the abrasion cycle is recorded. The experimental results show that after 23 abrasion cycles, the coating's contact angle is less than 90°, indicating a loss of hydrophobicity.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-cleaning lignin superhydrophobic coating, characterized in that: It is composed of the following components in parts by weight: 1-5 parts of lignin / PDA / TiO2 composite particles, 0.1-0.3 parts of silane reagent, 1-5 parts of epoxy resin, 0.1-0.5 parts of curing agent, and 50-100 parts of solvent; wherein the silane reagent is 1H,1H,2H,2H-perfluorooctyltrichlorosilane. The preparation method of the lignin / PDA / TiO2 composite particles includes the following steps: Lignin was dispersed in a solvent, Tris-HCl was added dropwise, and dopamine hydrochloride was added. The mixture was stirred for 12-24 hours. The mass percentages of lignin, dopamine hydrochloride, and Tris-HCl were 10-20:1-3:1, resulting in solution A. Slowly add dilute acid solution to solution A to adjust the pH value of the solution to <1, let it stand for 10~40min to precipitate lignin and obtain lignin / PDA composite particles; The lignin / PDA composite particles are dispersed in a solvent, and a tetrabutyl titanate solution is added dropwise. The mixture is stirred at 15-40 °C for 1-12 h. The TiO2 precursor tetrabutyl titanate is grafted onto the surface of the lignin / PDA composite particles through a condensation reaction, thus obtaining the lignin / PDA / TiO2 composite particles.

2. The self-cleaning lignin superhydrophobic coating according to claim 1, characterized in that: The dilute acid solution is a sulfuric acid solution, an oxalic acid solution, or a hydrochloric acid solution.

3. The self-cleaning lignin superhydrophobic coating according to claim 2, characterized in that: The concentration of the dilute acid solution is 0.3~0.7 mol / L.

4. The self-cleaning lignin superhydrophobic coating according to claim 1, characterized in that: The lignin is alkali lignin or sulfate lignin.

5. The self-cleaning lignin superhydrophobic coating according to claim 1, characterized in that: The epoxy resin is either E-44 or E-51.

6. The self-cleaning lignin superhydrophobic coating according to claim 1, characterized in that: The curing agent is ethylenediamine or diethylenetriamine.

7. The method for preparing the self-cleaning lignin superhydrophobic coating according to any one of claims 1-6, characterized in that: The process includes the following steps: adding silane reagent dropwise to a lignin / PDA / TiO2 composite particle solution and mixing well; then adding epoxy resin dropwise and mixing well; finally adding epoxy resin curing agent dropwise and mixing well to obtain a superhydrophobic coating.

8. A self-cleaning lignin superhydrophobic coating, characterized in that: The self-cleaning lignin superhydrophobic coating described in any one of claims 1-6 is sprayed onto the surface of the substrate and dried and cured to obtain the coating.

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