Preparation method of multifunctional antifouling self-cleaning cooling paint

Abstract

The application discloses a kind of antifouling self-cleaning cooling multifunctional coating and preparation method thereof.Coating main component has: water-based commercial white paint, alpha phase phosphogypsum (alpha-HPG), water-based polyurethane (WPU), ethyl acetate (EA), stearic acid (SA), N, N-dimethylformamide (DMF).First, water-based commercial white paint and alpha-HPG are modified respectively, then slurry is prepared by using simple blending method at room temperature, and coating is plated by doctor blade method, i.e. the double functional composite coating with excellent hydrophobicity and non-energy consumption cooling effect can be prepared.

Description

Technical Field

[0001] This invention belongs to the field of functional coating technology, specifically relating to a multifunctional anti-fouling, self-cleaning, and cooling coating and its preparation method. Background Technology

[0002] With the intensification of global climate change and the growth in demand for green buildings, the limitations of traditional commercial coatings (such as commercial white paint) in terms of weather resistance, energy efficiency, and environmental friendliness are becoming increasingly apparent. On the one hand, their insufficient hydrophobicity makes the coating prone to absorbing moisture and stains, not only affecting the cleanliness of the appearance but also causing mold and peeling due to long-term dampness, shortening the service life and increasing maintenance costs. On the other hand, white paint has limited heat reflection and heat dissipation capabilities, easily absorbing a large amount of heat in strong sunlight during summer, exacerbating indoor temperature rise and indirectly leading to a surge in air conditioning energy consumption, which contradicts current energy conservation and emission reduction requirements. Therefore, developing anti-fouling, self-cleaning, and cooling multifunctional coatings is an urgent need to address the energy crisis, reduce maintenance costs, and ensure the performance of specific facilities. On the one hand, anti-fouling and self-cleaning cooling coatings can significantly reduce the cooling energy consumption of buildings or power facilities through passive radiation cooling. On the other hand, their anti-fouling and self-cleaning capabilities can greatly reduce surface dust accumulation, maintaining long-term stable cooling performance while significantly reducing the cleaning and maintenance costs of buildings and power facilities, effectively preventing moisture retention and microbial adhesion, inhibiting mold growth, and protecting public health. Therefore, coating technology that integrates multiple functions is a key innovation direction for achieving energy conservation and emission reduction, improving economic efficiency, and ensuring social security.

[0003] However, the core technical bottleneck of antifouling, self-cleaning, and cooling multifunctional coatings lies in the difficulty of synergistically improving cooling performance and hydrophobicity, as well as the challenge of reconciling durability with scalable production. At the performance level, achieving high solar reflectivity (especially for visible and near-infrared light) typically requires wide-bandgap semiconductor materials (such as TiO2, ZnO) or dielectric materials. However, the infrared emission characteristics of these materials, especially their emissivity within atmospheric windows, are not ideal or require fine micro / nano structures for modulation. Although researchers have optimized both reflection and emission spectra simultaneously by designing photonic crystals, random porous structures, or nanocomposite materials, this often involves complex fabrication processes (such as electrospinning, phase separation, and template methods), resulting in high costs and difficulty in scaling up production.

[0004] Polymer-based PDRC materials (such as polyimide (PI), polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), and polymethyl methacrylate (PMMA)) are considered promising radiation cooling materials due to their advantages, including broad-spectrum infrared emission, negligible solar absorption, ease of achieving efficient light scattering through customized micro / nano porous structures, simple preparation, good flexibility, low cost, and scalability. However, these high-performance porous materials still face challenges related to hydrophobicity, large-scale production costs, and durability in outdoor environments.

[0005] To balance optical performance and practicality, researchers have recently begun exploring inorganic-polymer hybrid materials, aiming to combine the high reflectivity and stability of inorganic components with the strong emissivity of polymers. Furthermore, the introduction of inorganic particles not only enhances light scattering and infrared emission but also creates surface roughness, endowing the materials with waterproof and stain-resistant properties. For example, Meng et al. [2023.15(1): p.2256-2266] prepared a fluorinated SiO2 / PVDF-HFP multi-level structured superhydrophobic nanofiber membrane by combining electrospinning and electrospraying. The SiO2 nanoparticles formed a multi-level rough structure on the surface, which not only enhanced the scattering of sunlight but also endowed it with excellent superhydrophobicity (water contact angle >164°). Nie et al. [Compos. Sci. Technol., 2022.230, 109750] developed a PDMS / SiO2 bilayer composite membrane that simultaneously possesses excellent radiative cooling performance (>0.85 reflectivity, >0.95 emissivity, ~15℃ cooling effect) and superhydrophobicity (162° water contact angle).

[0006] However, there are few reports on existing inorganic / organic composite superhydrophobic radiation cooling materials, and the inorganic materials still use high-cost materials such as TiO2 and SiO2, while the organic materials are still traditional radiation cooling materials such as PDMS, PVDF, and PMMA. They still face challenges such as high raw material costs, complex preparation processes, and insufficient polymer durability, which restrict their practical large-scale application. Summary of the Invention

[0007] The purpose of this invention is to address the problems of high cost and insufficient durability of existing inorganic-polymer hybrid waterproof, stain-resistant, and cooling functional materials. This invention provides a novel inorganic-polymer hybrid material and its preparation method, using α-phase hemihydrate gypsum (α-HPG) derived from industrial waste phosphogypsum as the inorganic filler and commercial water-based white paint as the polymer. This material features low cost, good waterproof, stain-resistant, and cooling performance, and excellent durability.

[0008] The technical solution of this invention:

[0009] Commercial waterborne white paint, after modification, forms a robust polymer skeleton core within the coating as the main polymer. α-HPG, after treatment and surface modification, acts as an inorganic particle filler, not only constructing a double-roughened structure to achieve superhydrophobic modification, but also forming a robust inorganic outer shell that provides anti-aging and anti-deformation protection for the inner polymer layer. Waterborne polyurethane penetrates the gaps between α-HPG particles, forming a strong mechanical bond after curing, and also acts as a flexible buffer layer to prevent phosphogypsum from powdering and peeling due to external impacts or scratches. Simultaneously, the white paint polymer skeleton and α-HPG particles form a network of ionic and hydrogen bonds through waterborne polyurethane and stearic acid molecules, creating a dense "force network" across the entire inorganic / organic interface region, ensuring the coating's strength and durability.

[0010] A self-cleaning and cooling anti-fouling coating and its preparation method, comprising the following steps: Step 1: Mix α-PG, NaOH, and Na2SO4 and add them to water. Stir to disperse and obtain a mixed suspension. Then filter, wash and dry to obtain hydroxylated phosphogypsum powder. Step 2: Add hydroxylated phosphogypsum powder to a fluorinated modifier and stir to modify it into hydrophobically modified α-HPG powder; Step 3: The hydrophobically modified α-HPG powder is blended with white paint, stearic acid, and waterborne polyurethane in an organic solvent to obtain a coating. Step 4: Apply the coating to the substrate using a scraper method, and then dry and cure it to obtain the coating.

[0011] In step 1, the mass concentration of α-HPG is 0.2~0.5 g / mL, the mass concentration of NaOH is 0.1~0.25 g / mL, and the mass concentration of Na2SO4 is 0.01~0.02 g / mL.

[0012] In step 2, the fluorination modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

[0013] The fluorination modifier can also be a mixture of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and any one of trifluoroacetic acid, trifluoroethanol, and hexafluoroisopropanol.

[0014] The fluorinated modifier is added to a mixture of water and ethanol, wherein the volume ratio of water to ethanol is 1:1-2, and the mass concentration of 1H,1H,2H,2H-perfluorodecyltriethoxysilane in the mixture is 0.02~0.06 g / mL.

[0015] In a mixture of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and any one of trifluoroacetic acid, trifluoroethanol, and hexafluoroisopropanol, the mass ratio of 1H,1H,2H,2H-perfluorodecyltriethoxysilane to trifluoroacetic acid, trifluoroethanol, and hexafluoroisopropanol is 10:1-5.

[0016] In step 2, the stirring temperature is 60-80℃ and the stirring time is 1-2.5h.

[0017] In step 3, white paint is added to an ethyl acetate solution and stirred to obtain a suspension. The mass concentration of white paint is 0.1 g / mL to 0.2 g / mL, the stirring temperature is 60-80℃, and the stirring time is 0.5-1 h.

[0018] In step 3, SA is added to the DMF solution and stirred to obtain a dispersant. The mass fraction of SA is 0.02-0.1 g / mL, the stirring temperature is room temperature, and the stirring time is 0.5-1 h.

[0019] In step 3, the mass ratio of modified α-HPG powder, dispersant, and waterborne polyurethane is 1:2-4:0.5-1.

[0020] In step 3, the thickness of the film scraped by the scraper method is 300~400μm, and the substrate material includes any one of glass sheet, aluminum sheet, copper sheet, acrylic sheet, and carbon steel sheet.

[0021] Preferably, magnetic stirring is used at 500~700 r / min.

[0022] Preferably, the coating is cured at 80°C for 2-4 hours.

[0023] Another technical solution of the present invention is to apply the coating obtained by the preparation method of the antifouling self-cleaning and cooling coating to coatings with antifouling self-cleaning and radiation cooling functions.

[0024] The beneficial effects of this invention are: The main functional filler in this invention, α-HPG, is derived from solid waste and is inexpensive (approximately 4 CNY / kg). Other raw materials (such as waterborne polyurethane and SA) are all commercially available. The calculated cost of the coating raw materials is approximately 63 CNY / kg, which is significantly lower than that of commercially available high-end multifunctional radiation cooling coating systems.

[0025] The coating of the present invention has excellent water resistance, preventing blistering, cracking and peeling caused by water penetration; The coating formed by the coating of the present invention has excellent radiative cooling properties, and can reduce the surface temperature of an object by 20°C without additional energy input.

[0026] The coating of this invention has excellent anti-fouling and self-cleaning functions, making it difficult for contaminants such as water, ink, dust, and mud to wet and adhere, thus ensuring the long-term stability of the coating performance. Attached Figure Description

[0027] Figure 1 The figures show the water droplet contact angle test results of the coatings in Examples 1, 2, 3, 4, 5, 6, and 8.

[0028] Figure 2 The figures show the water droplet roll-off angle test results for the coatings in Examples 1, 4, 5, and 6.

[0029] Figure 3 The change in water absorption rate with soaking time is shown in Example 1.

[0030] Figure 4 This is a diagram illustrating the self-cleaning effect of Example 1.

[0031] Figure 5 The diagram shows a radiation cooling test setup. Thermocouples are used to record the temperature changes of the sample, and a cavity is set up as a control group (i.e., the sample is removed).

[0032] Figure 6 The graph in 'ac,ef' represents the mechanical performance test results of Example 1. Figure 6 In the image, d is an optical photograph of Example 7. Detailed Implementation

[0033] To further understand the invention's content and features, embodiments of the invention are given below. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] In the waterproof performance test, according to HG / T 3344 The 2012 "Method for Determining Water Absorption Rate of Coating Film" tests the water absorption rate of the coating.

[0035] Mechanical performance tests include sandpaper abrasion, gravel impact, water droplet impact, cross-cut adhesion test, and tape peel test. Sandpaper abrasion ( Figure 6 a): Place the coated side down on 1000-grit sandpaper and press it down with a 200g weight. Then drag the coated surface under load and rub it on the sandpaper for 30cm as one cycle. Measure the WCA and SA of the coating for each cycle; gravel impact ( Figure 6 b) 20 g of quartz sand was dropped from a height of 40 cm onto the sample surface, and the WCA and SA of the coating were measured after each impact. Water droplet impact test: Water droplets were dropped onto the sample surface at a rate of one drop per second from a height of 0.3 m, and the WCA and SA of the coating were measured every two hours; water droplet impact ( Figure 6c): Water droplets are dropped onto the sample surface at a rate of one drop per second from a height of 0.3 m, and the WCA and SA of the coating are measured every two hours; cross-cut adhesion test (C-cut test) Figure 6 e): Using a tool with a 2mm spacing, cut 25mm into the coating surface. 25. A total of 625 squares were formed. Immediately afterwards, 3M tape was applied, and a 200g weight was used to roll the tape back and forth three times. Then, the tape was quickly peeled off at a 60° angle within 90 seconds. The coating peeling area in the grid region was assessed according to the ISO 2409:2013 standard chart. Tape peeling test ( Figure 6 f): Apply 3M transparent tape evenly to the wood surface, then apply a 300g load to the tape and peel it off at a speed of 2cm / s. After peeling, measure WCA and SA every 10 times, for a total of 100 tests, to test the adhesion durability of the surface.

[0036] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0037] Example 1 A method for preparing a multifunctional anti-fouling, self-cleaning, and cooling coating includes the following steps: Step 1: Add 6g α-PG, 3g NaOH, and 0.5g Na2SO4 to 30g deionized water and stir magnetically at room temperature for 30 minutes to obtain a mixed suspension; Step 2: The mixed suspension obtained in Step 1 was filtered, washed three times with deionized water and anhydrous ethanol respectively, and dried at 60°C for 12 hours to obtain 4.2g of hydroxylated α-PG-OH powder; Step 3: Add 0.3g of 1H,1H,2H,2H-perfluorodecyltriethoxysilane to a mixed solvent of 1mL deionized water and 13.4mL anhydrous ethanol, heat at 60℃ and stir magnetically for 10min to obtain a dispersant; Step 4: Grind the 4.2g of α-PG-OH powder obtained in Step 2 into powder and add it to the dispersant obtained in Step 3. Heat at 60℃ and stir magnetically for 2.5h to obtain a mixed suspension of α-PG-OH. Step 5: Filter the mixed suspension obtained in Step 4, wash it three times with deionized water and anhydrous ethanol respectively, and dry it at 60°C for 12 hours to obtain hydrophobic α-PG-OH-FDTS powder. Step 6: Grind the α-PG-OH-FDTS powder obtained in Step 5 and pass it through a 90-mesh sieve to obtain hydrophobic α-PG-OH-FDTS powder with a particle size of 90 mesh. Step 7: Add 2.5g of commercial white paint to 15g of ethyl acetate solution and stir to obtain a suspension; Step 8: Add 1g of stearic acid (SA) to 20ml of DMF solution and stir to obtain a dispersant; Step 9: Add the dispersant from step 8 to the suspension from step 7 and stir to obtain a suspension; Step 10: Take 0.8g of the hydrophobic α-PG-OH-FDTS powder obtained in Step 6 and add it to 2.4g of the suspension obtained in Step 9, and add 0.48g of waterborne polyurethane. Stir at room temperature for 15min to obtain a superhydrophobic coating. Step 11: Place the aluminum substrate in a plasma cleaner for 2 minutes, scrape the film at room temperature using a 400μm high scraper, dry it in an 80℃ oven for 4 hours, and leave it at room temperature for 1 day to obtain a multi-functional anti-fouling, self-cleaning, radiation-cooling coating.

[0038] Through the above steps, the coating prepared on the aluminum sheet achieved a water contact angle of up to 154.1°. Figure 1 The roll angle is 5.3°. Figure 2 At the same time, this coating has excellent water-proof properties. Figure 3 ) and self-cleaning effect ( Figure 4 ).

[0039] The cooling performance of the coating is achieved by means of, for example Figure 5 The test apparatus shown. The maximum temperature drop of the sample compared to the cavity was 21.5°C, and the average temperature drop was 17.8°C. Compared to the commercial white paint coating, the maximum temperature drop and average temperature drop of this sample were 10.7°C and 8.81°C, respectively, indicating that Example 1 has an excellent cooling effect.

[0040] Furthermore, the coating exhibits excellent mechanical properties. In sandpaper abrasion tests, the coating maintains its superhydrophobicity after 50 cycles, with the contact angle remaining around 153° and the roll-off angle decreasing progressively. In gravel impact tests, the coating retains its superhydrophobic properties after 60 gravel impacts. In cross-cut adhesion tests, the coating's adhesion rating is 0. In tape peel tests, the coating retains its superhydrophobic properties after 10 cycles.

[0041] Example 2 The method involves coating a layer of commercial white paint onto an aluminum substrate that has undergone plasma cleaning, then scraping the coating with a 400 μm height blade, drying it in an 80°C oven for 4 hours, and then leaving it at room temperature for 1 day. The tested water contact angle of the coating was 81.5°. Figure 1 It does not reach a superhydrophobic state.

[0042] In the cooling performance test, the sample had a maximum temperature drop of 10.8℃ and an average temperature drop of 9℃ compared to the cavity, indicating a significantly poorer cooling effect.

[0043] Example 3 The method involves coating only the suspension obtained in step 9 of Example 1 onto an aluminum substrate that has undergone plasma cleaning, then applying the coating with a 400 μm high scraper, drying it in an 80°C oven for 4 hours, and then allowing it to stand at room temperature for 1 day. The tested water contact angle of the coating was 101°. Figure 1 It does not reach a superhydrophobic state.

[0044] In the cooling performance test, the sample had a maximum temperature drop of 9.9℃ and an average temperature drop of 6.8℃ compared to the cavity, indicating a significantly poorer cooling effect.

[0045] Example 4 The method and steps are the same as in Example 1, except that in step 10, the amount of α-PG-OH-FDTS powder is 1g, the suspension is 2.5g, and the waterborne polyurethane is 0.5g; the rest is the same as in Example 1. The tested water contact angle of the coating is 155.2°. Figure 1 The roll angle is 4.5°. Figure 2 ).

[0046] In the cooling performance test, the sample experienced a maximum temperature drop of 18°C ​​compared to the cavity, with an average temperature drop of 15°C.

[0047] Example 5 The method and steps are the same as in Example 1, except that in step 10, the amount of α-PG-OH-FDTS powder is 0.7 g, the suspension is 2.8 g, and the waterborne polyurethane is 0.56 g; the rest is the same as in Example 1. The tested water contact angle of the coating is 153.5°. Figure 1 The roll angle is 6.5°. Figure 2 ).

[0048] In the cooling performance test, the sample's maximum temperature drop compared to the cavity was 19.9℃, and the average temperature drop was 15.9℃.

[0049] Example 6 The method and steps are the same as in Example 1, except that in step 10, the amount of α-PG-OH-FDTS powder is 0.6 g, the suspension is 3 g, and the waterborne polyurethane is 0.6 g; the rest is the same as in Example 1. The tested water contact angle of the coating is 152.3°. Figure 1 The roll angle is 7.9°. Figure 2 ).

[0050] In the cooling performance test, the sample's maximum temperature drop compared to the cavity was 17.5℃, and the average temperature drop was 14.2℃.

[0051] Example 7 The method involves dispersing phosphogypsum powder in an aqueous solution, stirring until homogeneous, coating it onto an aluminum substrate that has undergone plasma cleaning, and then applying the coating using a 400 μm high scraper. The coating is then dried in an 80°C oven for 4 hours and left at room temperature for 1 day. Testing revealed that the coating is hydrophilic, has poor adhesion, and is easily cracked. Figure 6 d).

[0052] Example 8 The method and steps are the same as in Example 1, but steps 8 and 9 are omitted. The suspension used in step 10 is the same as in step 7. The rest is the same as in the example. The water contact angle of the coating was tested to be 122.25°, which does not reach the superhydrophobic state.

[0053] In the cooling performance test, the sample had a maximum temperature drop of 13.4℃ and an average temperature drop of 11.6℃ compared to the cavity, indicating poor cooling performance.

[0054] Example 9 The method and steps are the same as in Example 1, except that the hydrophobic modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane in a mass ratio of 10:1 to trifluoroacetic acid.

[0055] The coating was tested and found to have a water contact angle of 155° and a roll-off angle of 7.6°.

[0056] In the cooling performance test, the sample had a maximum temperature drop of 23.8℃ compared to the cavity, and an average temperature drop of 19.8℃.

[0057] Example 10 The method and steps are the same as in Example 1, except that the hydrophobic modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane in a mass ratio of 10:1 to trifluoroethanol.

[0058] The coating was tested and found to have a water contact angle of 154° and a roll-off angle of 7.9°.

[0059] In the cooling performance test, the sample's maximum temperature drop compared to the cavity was 23.5℃, and the average temperature drop was 20.1℃.

Claims

1. A method for preparing a multifunctional anti-fouling, self-cleaning, and cooling coating, characterized in that, Includes the following steps: Step 1: Mix α-HPG, NaOH, and Na2SO4 and add them to water. Stir to disperse and obtain a mixed suspension. Then filter, wash and dry to obtain hydroxylated phosphogypsum powder. Step 2: Add hydroxylated phosphogypsum powder to a fluorinated modifier and stir to modify it into hydrophobically modified α-HPG powder; Step 3: The hydrophobically modified α-HPG powder is blended with white paint, stearic acid, and waterborne polyurethane in an organic solvent to obtain a coating. Step 4: Apply the coating to the substrate using a scraper method, and then dry and cure it to obtain the coating.

2. The preparation method according to claim 1, characterized in that, In step 1, the mass concentration of α-HPG is 0.2~0.5 g / mL, the mass concentration of NaOH is 0.1~0.25 g / mL, and the mass concentration of Na2SO4 is 0.01~0.02 g / mL.

3. The preparation method according to claim 1, characterized in that, In step 2, the fluorination modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or a mixture of 1H,1H,2H,2H-perfluorodecyltriethoxysilane with any one of trifluoroacetic acid, trifluoroethanol, or hexafluoroisopropanol.

4. The preparation method according to claim 3, characterized in that, The fluorinated modifier is added to a mixture of water and ethanol, wherein the volume ratio of water to ethanol is 1:1-2, and the mass concentration of 1H,1H,2H,2H-perfluorodecyltriethoxysilane is 0.02~0.06 g / mL. In a mixture of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and any one of trifluoroacetic acid, trifluoroethanol, and hexafluoroisopropanol, the mass ratio of 1H,1H,2H,2H-perfluorodecyltriethoxysilane to trifluoroacetic acid, trifluoroethanol, and hexafluoroisopropanol is 10:1-5.

5. The preparation method according to claim 4, characterized in that, In step 2, the stirring temperature is 60-80℃ and the stirring time is 1-2.5h.

6. The preparation method according to claim 1, characterized in that, In step 3, white paint is added to an ethyl acetate solution and stirred to obtain a suspension. The mass concentration of white paint is 0.1 g / mL to 0.2 g / mL, the stirring temperature is 60-80℃, and the stirring time is 0.5-1 h.

7. The preparation method according to claim 1, characterized in that, In step 3, SA is added to the DMF solution and stirred to obtain a dispersant. The mass fraction of SA is 0.02-0.1 g / mL, the stirring temperature is room temperature, and the stirring time is 0.5-1 h.

8. The preparation method according to claim 1, characterized in that, In step 3, the mass ratio of modified α-HPG powder, dispersant, and waterborne polyurethane is 1:2-4:0.5-1.

9. The preparation method according to claim 1, characterized in that, In step 3, the thickness of the film scraped by the scraper method is 300~400μm, and the substrate material includes any one of glass sheet, aluminum sheet, copper sheet, acrylic sheet, and carbon steel sheet.

10. The application of a coating obtained by the method of any one of claims 1-9 on the surface of a building exterior, electrical equipment casing, or outdoor facility.

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