Preparation method of fluorine-free modified super-hydrophobic coating

Abstract

The application provides a preparation method of a fluorine-free modified super-hydrophobic coating, which uses a water-based polyurethane emulsion as an electrolyte to prepare a super-hydrophobic coating on the surface of an electrode material. The preparation method comprises the following steps: 1. preparing a water-based polyurethane emulsion by using an acetone method; 2. using a demulsification-induced rapid curing method to prepare a coating on the surface of a conductive substrate by using the water-based polyurethane emulsion as an electrolyte; and 3. obtaining a super-hydrophobic surface after the coating is dried. By changing the types of isocyanate and polyol and adjusting the voltage and time of power supply, the preparation of the super-hydrophobic coating can be realized in various cases, and a super-hydrophobic coating with a water contact angle of 150-160 degrees can be obtained on the surface of an anode material. The application has the advantages of simple operation, green and safe preparation process, no fluorine pollution, low cost, energy saving and environmental protection, and is suitable for being applied to various conductive substrates and giving the conductive substrates super-hydrophobic functions.

Description

Technical Field

[0001] This invention belongs to the field of superhydrophobic coating preparation technology, specifically relating to a method for preparing fluorine-free modified superhydrophobic coatings using a demulsification-induced rapid curing method. Background Technology

[0002] There are two main approaches to constructing superhydrophobic surfaces: 1. Constructing micro / nano-scale rough surfaces on low surface energy surfaces; 2. Modifying the surface of micro / nano-rough structures with low surface energy materials. Fluorides are commonly used low surface energy materials, often used to modify rough surfaces to obtain hydrophobic properties. However, fluorides are biotoxic and difficult to degrade, severely polluting the environment. Constructing micro / nano structures on substrate surfaces often requires harsh conditions, such as chemical corrosion and physical etching. Modifying low surface energy materials and constructing rough micro / nano structures often need to be done step by step, resulting in a complex process. The addition of fluorine increases costs and also restricts environmental protection. Therefore, a method for preparing superhydrophobic coatings without the need for adding fluorine and without constructing rough surfaces has great development potential. Summary of the Invention

[0003] The purpose of this invention is to provide a simple, rapid, and fluorine-free method for preparing superhydrophobic coatings by utilizing a demulsification-induced rapid curing method. The Chinese abbreviations used in this invention are as follows: WPU stands for waterborne polyurethane emulsion, PBA for polybutylene adipate diol, DMPA for dimethylolpropionic acid, DBTDL for dibutyltin dilaurate, XDI for aromatic diisocyanate, BD for 1,4-butanediol, TEA for triethylamine, and SLS for sodium dodecyl sulfonate.

[0004] The method for preparing a superhydrophobic coating based on demulsification-induced rapid curing as described in this invention comprises the following steps:

[0005] 1. Cleaning the substrate

[0006] The substrates used in this invention are various commonly used conductive substrates, such as copper sheets, iron sheets, aluminum sheets, zinc sheets, ITO or FTO conductive glass, etc. For copper sheets, iron sheets, and aluminum sheets, the surface oxide film is removed by sandpaper and then wiped with ethanol. For zinc sheets, ITO or FTO conductive glass, it is directly wiped with ethanol. This treatment facilitates the preparation of a superhydrophobic coating on the surface of the conductive substrate.

[0007] 2. Preparation of polyol aqueous solutions

[0008] The polyol solution used in this invention is prepared by using water as a solvent to prepare polyol solutions with mass fractions of 0.5wt%, 10wt%, 15wt%, and 30wt%, and then dissolving them uniformly for later use.

[0009] 3. Preparation of waterborne polyurethane emulsions by the acetone method

[0010] Under water bath conditions, PBA, DMPA, and acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser, with a mass ratio of PBA, DMPA, and acetone of 36.65 g: 1.55 g: 60 g. The mixture was in a 60°C water bath at 300 rpm until the solids were completely dissolved. Subsequently, PBA, DBTDL, and XDI were added in a ratio of 36.65 g: 400 μL: 47.55 mmol, and the mixture was in a 60°C water bath at 300 rpm for 3 hours. Finally, BD was added in a PBA to BD mass ratio of 36.65 g: 2.144 g, and the mixture was in a 60°C water bath. The reaction was carried out in a water bath at 300 rpm for 2 hours; TEA was added at a PBA to TEA mass ratio of 36.65 g: 1.15 g, and the reaction was carried out in a 55°C water bath at 700 rpm for 30 minutes; SLS was added at a PBA to SLS mass ratio of 36.65 g: 1.875 g, and the reaction was carried out in a 55°C water bath at 1200 rpm for 30 minutes; and a polyol aqueous solution was added at a PBA to polyol aqueous solution mass ratio of 36.65 g: 40 g, and the reaction was carried out in a 50°C water bath at 1400 rpm for 1 hour to obtain WPU emulsion.

[0011] 4. Preparation of superhydrophobic coatings using a demulsification-induced rapid curing method

[0012] At room temperature, WPU emulsion is used as the electrolyte, electrode material is used as the substrate, the applied voltage is 3 to 4 to 5 to 6 to 10V, the energizing time is 5 to 10 to 20 to 40 to 80 to 120 minutes, after which the electrode is removed, rinsed with deionized water to remove surface adsorbed substances, and after complete drying, a superhydrophobic coating is obtained on the substrate. Attached image description:

[0013] Figure 1 This is a diagram showing the surface and superhydrophobic effect of the superhydrophobic coating in Example 1.

[0014] Figure 2 This is a scanning electron microscope image of the superhydrophobic coating in Example 1.

[0015] Figure 3 This is an X-ray energy dispersive spectroscopy (EDS) analysis diagram of the superhydrophobic coating in Example 1.

[0016] Beneficial Effects: The method for preparing a fluorine-free superhydrophobic coating provided by this invention has the following advantages: It utilizes an emulsion as the electrolyte and employs a demulsification-induced rapid curing method to quickly prepare the superhydrophobic coating without chemical modification. The preparation method is simple and rapid; the shape and size of the coating are determined by the substrate; the surface water contact angle is 150–160°; and the roll-off angle is 5–10°. The raw materials used in this invention are readily available, low in cost, and highly innovative. The superhydrophobic properties of the surface material in the superhydrophobic coating preparation method described in this invention rely on the rough micro / nano structure of the surface and the low surface energy of the surface material. The coating obtained on a conductive substrate through the demulsification-induced rapid curing method has a rough structure, and the selected diisocyanate has hydrophobic groups. Furthermore, the urethane bond formed between the diisocyanate and polyester glycol can block the free hydroxyl groups of water molecules, thus exhibiting a superhydrophobic effect. Detailed Implementation

[0017] The following examples further illustrate the specific implementation and results of the invention, but are not intended to limit the invention.

[0018] Example 1: A method for preparing a fluorine-free modified superhydrophobic coating based on a demulsification-induced rapid curing method, the steps and conditions are as follows:

[0019] 1. Cleaning the substrate

[0020] The substrate used is zinc sheet, which is cleaned with ethanol and dried before use.

[0021] 2. Preparation of polyol aqueous solutions

[0022] In this example, the polyol is an aqueous solution of polyethylene glycol. Weigh 2g of solid polyethylene glycol and add it to 38g of deionized water to obtain a homogeneous polyethylene glycol solution for later use.

[0023] 3. Synthesis of polyurethane emulsions via acetone method

[0024] Under water bath conditions, 36.65 g of PBA, 1.55 g of DMPA, and 60 g of acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser. The mixture was incubated in a 60°C water bath at 300 rpm until the solids were completely dissolved. Then, 40 μL of DBTDL and 47.55 mmol of XDI (in this example, XDI is tetramethylphenyl dimethyl diisocyanate) were added; the reaction was continued at 60°C in a water bath at 300 rpm for 3 hours. 2.144 g of BD was weighed and added; the mixture was then incubated in a 60°C water bath at 300 rpm for 2 hours. Finally, the water bath temperature was set to 55°C, and 1.15 g of TEA was added; the reaction was continued at 700 rpm for 30 minutes. Add 1.875g of SLS, incubate in a 55℃ water bath at 1200rpm for 30min, set the water bath temperature to 50℃, add 40g of polyethylene glycol aqueous solution dropwise, incubate in a 50℃ water bath at 1400rpm for 1h to obtain WPU emulsion, and let the emulsion cool to room temperature for later use.

[0025] 4. Preparation of superhydrophobic coatings using a demulsification-induced rapid curing method

[0026] At room temperature, using the above WPU emulsion as the electrolyte, a clean conductive substrate was used. A voltage of 3V was applied and the substrate was energized for 100 minutes. The substrate was then removed, rinsed with deionized water to remove surface adsorbed substances, and dried completely at room temperature to obtain a superhydrophobic coating. The water contact angle of the coating was measured to be 158°.

[0027] Example 2: A method for preparing a fluorine-free modified superhydrophobic coating based on a demulsification-induced rapid curing method, the steps and conditions of which are as follows:

[0028] 1. Cleaning the substrate

[0029] Choose aluminum sheet as the substrate. Before use, sand it with sandpaper to remove surface oxides, and clean the surface with ethanol and deionized water before use.

[0030] 2. Preparation of polyol aqueous solutions

[0031] In this example, the polyol is an aqueous solution of polypropylene glycol. Weigh 4g of solid polypropylene glycol and add it to 36g of deionized water to obtain a homogeneous polypropylene glycol solution for later use.

[0032] 3. Synthesis of polyurethane emulsions via acetone method

[0033] Under water bath conditions, 36.65 g of PBA, 1.55 g of DMPA, and 60 g of acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser. The mixture was then incubated in a water bath at 60°C and rotated at 300 rpm until the solids were completely dissolved. Subsequently, 40 μL of DBTDL and 47.55 mmol of XDI (in this example, XDI is toluene diisocyanate) were added. The mixture was then incubated in a water bath at 60°C and rotated at 300 rpm for 3 hours. 2.144 g of the mixture was then added to BD and incubated at 60°C. The reaction was carried out in a water bath at 300 rpm for 2 hours. The water bath temperature was then set to 55°C. 1.15 g of TEA was added, and the reaction was carried out at 700 rpm for 30 minutes. 1.875 g of SLS was added, and the reaction was carried out in a water bath at 55°C at 1200 rpm for 30 minutes. The water bath temperature was then set to 50°C. 40 g of polypropylene glycol aqueous solution was added dropwise, and the reaction was carried out in a water bath at 50°C at 1400 rpm for 1 hour to obtain a WPU emulsion. The emulsion was then cooled to room temperature for later use.

[0034] 4. Preparation of superhydrophobic coatings using a demulsification-induced rapid curing method

[0035] At room temperature, using the above WPU emulsion as the electrolyte, a clean conductive substrate was used. A voltage of 4V was applied and the substrate was energized for 80 minutes. The substrate was then removed, rinsed with deionized water to remove surface adsorbed substances, and dried completely at room temperature to obtain a superhydrophobic coating. The water contact angle of the coating was measured to be 157°.

[0036] Example 3: A method for preparing a fluorine-free modified superhydrophobic coating based on a demulsification-induced rapid curing method, the steps and conditions of which are as follows:

[0037] 1. Cleaning the substrate

[0038] The substrate used is an iron sheet. Before use, the surface oxides are removed by sanding with sandpaper, and the surface is cleaned with ethanol and deionized water before use.

[0039] 2. Preparation of polyol aqueous solutions

[0040] In this example, the polyol is an aqueous solution of polyvinyl alcohol. Weigh 0.4g of solid polyvinyl alcohol, add it to 39.6g of deionized water, heat in a 95°C water bath until completely dissolved to obtain a homogeneous polyvinyl alcohol solution, and cool to room temperature for later use.

[0041] 3. Synthesis of polyurethane emulsions via acetone method

[0042] Under water bath conditions, 36.65 g of PBA, 1.55 g of DMPA, and 60 g of acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser. The mixture was then incubated in a 60°C water bath at 300 rpm until the solids were completely dissolved. Subsequently, 40 μL of DBTDL and 47.55 mmol of XDI (in this example, XDI is 1,5-naphthalene diisocyanate) were added. The reaction was continued in a 60°C water bath at 300 rpm for 3 hours. 2.144 g of the mixture was then added to the BD mixture. The reaction was carried out in a 0℃ water bath at 300 rpm for 2 hours. Then, the water bath temperature was set to 55℃, and 1.15 g of TEA was added. The reaction was carried out at 700 rpm for 30 minutes. Then, 1.875 g of SLS was added. The reaction was carried out in a 55℃ water bath at 1200 rpm for 30 minutes. Finally, the water bath temperature was set to 50℃, and 40 g of polyvinyl alcohol aqueous solution was added dropwise. The reaction was carried out in a 50℃ water bath at 1400 rpm for 1 hour to obtain WPU emulsion. The emulsion was then cooled to room temperature for later use.

[0043] 4. Preparation of superhydrophobic coatings using a demulsification-induced rapid curing method

[0044] At room temperature, using the above-mentioned WPU emulsion as the electrolyte and a clean iron sheet with the surface oxide film removed by polishing as the electrode material, a voltage of 5V was applied. After 30 minutes of energizing, the sheet was removed, rinsed with deionized water to remove the surface adsorbed substances, and dried completely at room temperature to obtain a superhydrophobic coating. The water contact angle of the coating was measured to be 155°.

[0045] Example 4: A method for preparing a fluorine-free modified superhydrophobic coating based on a demulsification-induced rapid curing method, the steps and conditions of which are as follows:

[0046] 1. Cleaning the substrate

[0047] The substrate used is ITO conductive glass. The surface is cleaned with ethanol and dried before use.

[0048] 2. Preparation of polyol aqueous solutions

[0049] In this example, the polyol is a mixture of polyethylene glycol and polyvinyl alcohol aqueous solution. 1 wt% polyvinyl alcohol aqueous solution and 15 wt% polyethylene glycol aqueous solution are prepared separately, mixed in equal proportions, and stirred at room temperature to form a homogeneous solution for later use.

[0050] 3. Synthesis of polyurethane emulsions via acetone method

[0051] Under water bath conditions, 36.65 g of PBA, 1.55 g of DMPA, and 60 g of acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser. The mixture was incubated in a 60°C water bath at 300 rpm until the solids were completely dissolved. Then, 40 μL of DBTDL and 47.55 mmol of XDI (in this example, XDI is tetramethylphenyl dimethyl diisocyanate) were added. The reaction was continued at 60°C in a water bath at 300 rpm for 3 hours. Next, 2.144 g of BD was weighed and added to the mixture. The reaction was continued at 60°C in a water bath at 300 rpm for 2 hours. Then, the water bath temperature was set to 55°C, and 1.15 g of TEA was added. The reaction was continued at 700 rpm for 30 minutes. Finally, 1.875 g of SLS was added. The reaction was continued at 55°C in a water bath at 1200 rpm for 30 minutes. Set the water bath temperature to 50℃, add 40g of a mixed aqueous solution of polyethylene glycol and polyvinyl alcohol dropwise, and maintain the water bath at 50℃ with a rotation speed of 1400rpm for 1 hour to obtain a WPU emulsion. Allow the emulsion to cool to room temperature for later use.

[0052] 4. Preparation of superhydrophobic coatings using a demulsification-induced rapid curing method

[0053] At room temperature, using the above WPU emulsion as the electrolyte, a clean conductive substrate was used. A voltage of 10V was applied and the substrate was energized for 15 minutes. The substrate was then removed, rinsed with deionized water to remove surface adsorbed substances, and dried completely at room temperature to obtain a superhydrophobic coating. The water contact angle of the coating was measured to be 159°.

Claims

1. A method for preparing a fluorine-free superhydrophobic coating, characterized in that, The steps are as follows: The acetone method was used to prepare an aqueous polyurethane emulsion. The specific steps were as follows: Under water bath conditions, polybutylene adipate diol, dimethylolpropionic acid, and acetone were added to a three-necked round-bottom flask equipped with a mechanical stirrer and condenser. The mass ratio of polybutylene adipate diol, dimethylolpropionic acid, and acetone was 36.65 g:1.55 g:60 g. The mixture was placed in a water bath at 60°C and rotated at 300 rpm until the solid was completely dissolved. Subsequently, the ratio of polybutylene adipate diol, dibutyltin dilaurate, and diisocyanate was 36.65 g:400 μL:47.55 mmol. The reaction was carried out in a water bath at 60°C and rotated at 300 rpm for 3 hours. The mass ratio of polybutylene adipate diol to 1,4-butanediol was 36.65 g:2.1 g. 44g of polybutylene adipate was added to 1,4-butanediol, and the mixture was reacted in a 60°C water bath at 300 rpm for 2 hours. Triethylamine was added at a mass ratio of 36.65g:1.15g, and the mixture was reacted in a 55°C water bath at 700 rpm for 30 minutes. Sodium dodecyl sulfonate was added at a mass ratio of 36.65g:1.875g, and the mixture was reacted in a 55°C water bath at 1200 rpm for 30 minutes. Finally, an aqueous polyol solution was added at a mass ratio of 36.65g:40g, and the mixture was reacted in a 50°C water bath at 1400 rpm for 1 hour to obtain an aqueous polyurethane emulsion. To prepare a superhydrophobic surface, a conductive material is used as the substrate, the above-mentioned aqueous polyurethane emulsion is used as the electrolyte, a voltage of 3-10V is applied, and the energizing time is 5-120min to prepare a superhydrophobic coating on the substrate surface.

2. The method for preparing a fluorine-free modified superhydrophobic coating as described in claim 1, characterized in that, The acetone method for preparing aqueous polyurethane emulsions uses an aromatic diisocyanate, including 1,5-naphthalene diisocyanate, tetramethylbenzene diisocyanate, phenyl diisocyanate, and combinations thereof in various forms.

3. The method for preparing a fluorine-free modified superhydrophobic coating as described in claim 1, characterized in that, The acetone method for preparing waterborne polyurethane emulsions uses polyols that are miscible with water and contain two or more hydroxyl groups in their molecules, including polyethylene glycol, polypropylene glycol, pentaerythritol, sorbitol, polyvinyl alcohol, and combinations thereof in various forms.

4. The method for preparing a fluorine-free modified superhydrophobic coating as described in claim 1, characterized in that, Conductive substrates are conductive materials that are either metallic or non-metallic, including iron, zinc, aluminum, alloys, ITO, and FTO conductive glass.

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