Organic-inorganic composite super-hydrophilic self-cleaning coating film, and preparation method and application thereof

Abstract

This invention discloses an organic-inorganic composite superhydrophilic self-cleaning coating, its preparation method, and its application. The organic coating uses a water-based transparent polyurethane resin, whose raw material, the hydroxyl resin, is bio-modified to improve its hydrophilicity, thereby enhancing the adhesion between the coating and the glass substrate and the coating's stability in an aqueous environment. The inorganic nanomaterial used is zinc oxide, which can photocatalytically induce superhydrophilic properties, facilitating self-cleaning through water rinsing while providing hardness and increasing the coating's wear resistance. The coating of this invention employs a dual-spray process, overcoming the problem that traditional single-spray organic-inorganic composite coatings cannot accurately represent the microstructure and roughness of inorganic particles.

Description

Technical Field

[0001] This invention belongs to the field of superhydrophilic self-cleaning materials technology, specifically relating to an organic-inorganic composite superhydrophilic self-cleaning coating, its preparation method, and its application. Background Technology

[0002] Photovoltaic power generation is a major way of utilizing solar energy and plays an important role in long-term energy strategies. Currently, the construction and operation of solar photovoltaic power plants in various countries are at their peak. However, in the operation of photovoltaic power generation systems, in addition to the performance of the photovoltaic modules themselves, contaminants on the surface of the photovoltaic glass have a significant impact on power generation efficiency. Statistics show that every 5g / m³ of dust and other contaminants accumulated significantly affects power generation efficiency. 2 The power generation efficiency of photovoltaic panels decreased by 23.24%. To maintain the efficiency of photovoltaic power generation and extend the lifespan of photovoltaic panels, cleaning is necessary. Existing methods such as manual cleaning, robotic cleaning, and high-pressure water gun cleaning are not only costly but also cause wear and tear on the anti-reflective coating on the surface of the solar photovoltaic panels, thus reducing their lifespan. Therefore, preparing a self-cleaning coating on the photovoltaic panels is the preferred method for preventing contamination.

[0003] Existing self-cleaning coatings are mainly superhydrophobic and superhydrophilic. Superhydrophobic coatings achieve self-cleaning by forming water droplets on the surface, similar to the lotus leaf effect, which carries away dust. However, the formation of water droplets reduces the light transmittance of the photovoltaic panel, and the durability of superhydrophobic self-cleaning coatings is not ideal, failing to guarantee a long self-cleaning lifespan. Superhydrophilic coatings, on the other hand, induce surface hydrophilicity. When water comes into contact with the photovoltaic panel surface, it quickly spreads and forms a water film, carrying away dust while significantly reducing the impact on light transmittance.

[0004] Currently, the most commonly used superhydrophilic coatings are inorganic coatings. Existing technologies mostly use TiO2 nanoparticles to prepare superhydrophilic coatings. However, since TiO2 nanoparticles have a refractive index of 2.5, they are usually combined with SiO2 nanoparticles to adjust the refractive index and construct different microstructures. But the cross-linking degree between nanoparticles is too weak, usually requiring high temperatures to achieve good adhesion between the particles and the substrate. These high temperatures make it difficult to apply to existing photovoltaic panels. To solve these problems, researchers have conducted a great deal of innovative research:

[0005] Chinese patent CN110093050A describes a modified SiO2 / TiO2 composite coating prepared by a solid-state sol-gel method, which forms a superhydrophilic coating on a glass substrate at room temperature through a coating process. This coating exhibits excellent superhydrophilicity and photocatalytic performance. However, the coating prepared by the sol-gel method has weak adhesion to the glass substrate and poor stability in an aqueous environment. Furthermore, the manual coating method requires highly skilled operators, easily leading to uneven coating preparation and a decrease in superhydrophilicity. Additionally, the manual coating method is inefficient, hindering large-scale application.

[0006] Chinese patent CN114772942A utilizes organic-inorganic doping technology to form a three-dimensional cross-linked network structure and simultaneously construct SiO2 / TiO2 nanoparticles with a core-shell microstructure, achieving the preparation of a superhydrophilic self-cleaning interface. However, because the organic aqueous polyurethane encapsulates the core-shell structured SiO2 / TiO2 nanoparticles, the microstructure of the nanoparticles is difficult to function effectively. Furthermore, the preparation process of the core-shell structured SiO2 / TiO2 nanoparticles is complex, making large-scale industrial production difficult. In addition, the coating has poor UV resistance, leading to polyurethane resin degradation and powdering, causing intrinsic contamination.

[0007] In summary, the self-cleaning and durability properties of current technologies are not ideal, and the preparation process is complex, often requiring high temperatures to prepare the superhydrophilic self-cleaning coating. Therefore, it is both necessary and meaningful to research and develop an organic-inorganic composite superhydrophilic self-cleaning coating with excellent superhydrophilic properties, wear resistance, weather resistance, and water environment stability, prepared using an ultra-micro dual-spray method that is simple, low-cost, and applicable to existing photovoltaic systems. Summary of the Invention

[0008] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0009] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0010] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide an organic-inorganic composite superhydrophilic self-cleaning coating.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution: the organic-inorganic composite superhydrophilic self-cleaning coating is composed of an organic layer and an inorganic layer, with a thickness of 1-10 μm;

[0012] The organic layer material is a water-based transparent polyurethane resin prepared from a modified hydroxyl resin; the inorganic layer material is a zinc oxide sol modified with a silane coupling agent.

[0013] As a preferred embodiment of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, the waterborne transparent polyurethane resin prepared by the modified hydroxyl resin is composed of a main agent and a curing agent in a mass ratio of 10:2.8-3.0, wherein the main agent, by mass parts, comprises,

[0014] 10.0–30.0 parts deionized water, 0.4–3 parts defoamer, 0.1–2 parts multifunctional additive, 4.0–10.0 parts propylene glycol methyl ether, 2.0–8.0 parts dipropylene glycol methyl ether, 40.0–60.0 parts hydroxyl resin, 20.0–35.0 parts bio-based modified hydroxyl resin, 0.5–2.0 parts leveling agent.

[0015] As a preferred embodiment of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, wherein: the curing agent comprises, by weight parts,

[0016] 24.0–52.0 parts of propylene glycol methyl ether acetate, 48.0–76.0 parts of Bayhydur XP.

[0017] As a preferred embodiment of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, wherein: the bio-based modified hydroxyl resin, wherein the bio-based includes one of dopamine or citric acid.

[0018] As a preferred embodiment of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, wherein:

[0019] The silane coupling agent modified zinc oxide sol comprises, by weight parts,

[0020] 45.0–60.0 parts anhydrous ethanol, 45.0–60.0 parts deionized water, 1.8–9.0 parts silane coupling agent KH560, 0.6–3.0 parts silane coupling agent GPTMS, 4–20.0 parts ZnO sol;

[0021] The ZnO sol comprises, by mass parts,

[0022] 30.0–40.0 parts deionized water, 5.0–20.0 parts zinc acetate, 0.4–2.0 parts triammonium citrate surfactant, 48.0–68.0 parts anhydrous ethanol, and 4.0–10.0 parts oxalic acid.

[0023] Another object of the present invention is to provide a method for preparing an organic-inorganic composite superhydrophilic self-cleaning coating, wherein the organic-inorganic composite superhydrophilic self-cleaning coating is prepared by an ultra-micro dual-spray process, comprising,

[0024] The organic layer material is diluted and placed in spray gun I, and the inorganic layer material is diluted and placed in spray gun II. The nozzle is perpendicular to the surface of the sample to be sprayed, and spray guns I and II are moved simultaneously parallel to the sample to be sprayed. After rapid film formation on the surface of the sample, curing treatment is performed to obtain an organic-inorganic composite super-hydrophilic self-cleaning coating.

[0025] As a preferred embodiment of the preparation method of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, the organic layer material is diluted with deionized water, wherein the weight of the deionized water is 10-30% of the organic layer material.

[0026] The inorganic layer material is diluted with acetone, with the weight of acetone being 85-95% of the inorganic layer material.

[0027] As a preferred embodiment of the preparation method of the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, the spraying pressure is 0.2-0.6 MPa, the spraying distance is 10-30 cm, and the coating thickness is 1-10 μm.

[0028] In a preferred embodiment of the method for preparing the organic-inorganic composite superhydrophilic self-cleaning coating of the present invention, the curing temperature is 20-30°C and the curing time is 12-36 hours.

[0029] Another objective of this invention is to provide an application of an organic-inorganic composite superhydrophilic self-cleaning coating on a photovoltaic panel.

[0030] Beneficial effects of this invention:

[0031] (1) Compared with the prior art, the organic coating of the present invention uses water-based transparent polyurethane resin. Its raw material hydroxyl resin is modified with bio-based properties, which can improve the hydrophilicity of water-based transparent polyurethane resin, and at the same time improve the adhesion between the coating and the glass substrate and the stability of the coating in the water environment.

[0032] (2) The inorganic nanomaterial used in this invention is zinc oxide. On the one hand, zinc oxide can photocatalytically induce superhydrophilic properties, which is beneficial for water rinsing and self-cleaning. On the other hand, zinc oxide provides hardness to the coating film, increasing its wear resistance. In addition, compared with the traditional material silicon dioxide, the energy level transition of zinc oxide can provide UV protection, preventing the degradation and powdering of organic resins from causing intrinsic contamination of the coating film. At the same time, nano zinc oxide can inhibit bacteria, preventing the growth of microorganisms from causing surface contamination of the coating film, thereby preventing the coating film from losing its superhydrophilic properties.

[0033] (3) The organic-inorganic composite superhydrophilic coating of the present invention adopts a dual-spray process, which overcomes the problem that the organic-inorganic composite coating prepared by the original single-spray process cannot reflect the microstructure and roughness of inorganic particles. Two spray guns are used for simultaneous spraying. One ultra-fine spray gun sprays polyurethane atomized material with extremely high volatility and atomization, while the other ultra-fine nozzle spray gun sprays zinc oxide sol gel. The solvent evaporates and mixes with the coating in the atomized and fluidized state, which accelerates the mass transfer reaction, cross-links and forms a film, and quickly forms a superhydrophilic film with high roughness.

[0034] (4) The coating preparation process of the present invention is economical, simple, environmentally friendly, and easy to scale up for industrial production. Moreover, the present invention achieves room temperature curing, and the formation of the cross-linked network can be carried out at room temperature, which breaks through the limitations of traditional products that require high temperature conditions to cross-link and cure the functional groups. It also breaks through the limitations of traditional curing methods on practical application fields, and is easier to apply to photovoltaic panels that are already in operation compared with traditional products. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 The figure shows the water contact angle test results of the coating obtained in Example 1 of the present invention.

[0037] Figure 2 The figure shows the water contact angle test results of the coating obtained in Comparative Example 2 of this invention.

[0038] Figure 3 The figure shows the water contact angle test results of the coating film prepared in Comparative Example 4 of this invention. Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] Unless otherwise specified, all raw materials used in this invention are commercially available analytical grade materials commonly used in the field.

[0043] The coating performance testing method in this invention is as follows:

[0044] The water contact angle of the coating was tested according to standard GB / T 23764-2009;

[0045] The light transmittance of the coating was tested in accordance with the standard GB / T 29501-2013;

[0046] The adhesion of the coating was tested in accordance with the standard GB / T 29501-2013;

[0047] The waterproofness of the coating was tested in accordance with the standard GB / T 31815-2015;

[0048] The weather resistance of the coating was tested in accordance with the standard GB / T 31815-2015;

[0049] Example 1

[0050] This embodiment provides a method for preparing an organic-inorganic composite superhydrophilic self-cleaning coating:

[0051] 1) Preparation of waterborne transparent polyurethane resin based on organic layer material - modified hydroxyl resin:

[0052] Main agent formulation (by weight):

[0053] 10 parts deionized water, 3 parts defoamer, 2 parts multifunctional additive AMP-95, 10 parts propylene glycol methyl ether, 8 parts dipropylene glycol methyl ether, 60 parts hydroxyl resin, 35 parts dopamine-modified hydroxyl resin, 2 parts leveling agent TEGO 450.

[0054] Hardener formulation by parts by weight:

[0055] 24 parts propylene glycol methyl ether acetate, 76 parts Bayhydur XP;

[0056] Weigh the raw materials according to the above formula:

[0057] After adding deionized water to the stirred tank, add defoamer, multifunctional additive AMP-95, propylene glycol methyl ether, and dipropylene glycol methyl ether in sequence. After stirring for 10 minutes, add hydroxyl resin, dopamine-modified hydroxyl resin, and leveling agent TEGO 450 in sequence. After stirring for 10-20 minutes, stop stirring, filter, and let stand for 24 hours to complete the preparation of the main agent.

[0058] Propylene glycol methyl ether acetate and Bayhydur XP were added sequentially to a stirred tank and stirred for 20-30 minutes until the mixture was evenly dispersed, thus completing the preparation of the curing agent.

[0059] The main agent and curing agent were mixed at a weight ratio of 10:3 and stirred for 2 minutes to obtain an aqueous transparent polyurethane resin prepared by organic layer material-modified hydroxyl resin.

[0060] 2) Preparation of inorganic layer material - silane coupling agent modified zinc oxide sol:

[0061] The formulation of zinc oxide sol, by parts by weight:

[0062] 4 parts oxalic acid, 68 parts anhydrous ethanol, 40 parts deionized water, 5 parts zinc acetate, and 0.4 parts triammonium citrate surfactant;

[0063] The formulation of inorganic layer material - silane coupling agent modified zinc oxide sol, by mass parts:

[0064] 60 parts anhydrous ethanol, 60 parts deionized water, 1.8 parts silane coupling agent KH560, 0.6 parts silane coupling agent GPTMS, 4 parts zinc oxide sol;

[0065] Weigh the raw materials according to the above formula:

[0066] Oxalic acid was dissolved in anhydrous ethanol to prepare an anhydrous oxalic acid ethanol solution. Deionized water, zinc acetate, and triammonium citrate surfactant were poured into a stirred tank in sequence. The stirred tank was placed in a water bath at 80°C and stirred for 90 min. The zinc acetate solution was slowly added dropwise to the anhydrous oxalic acid ethanol solution and placed in a water bath for reaction for 30 min. After filtration, the preparation of ZnO sol was completed.

[0067] Anhydrous ethanol, deionized water, silane coupling agent KH560, silane coupling agent GPTMS, and zinc oxide sol were added sequentially to a stirred tank. After stirring for 16 hours, stirring was stopped, and the resulting solution was filtered to obtain inorganic layer material-silane coupling agent modified zinc oxide sol.

[0068] 3) Spraying of organic-inorganic composite superhydrophilic self-cleaning coating:

[0069] The waterborne transparent polyurethane resin prepared by organic layer material - modified hydroxyl resin was diluted with 20% by weight of deionized water and placed in spray gun I.

[0070] The inorganic layer material - zinc oxide sol modified with silane coupling agent was diluted with 90% by weight acetone solution and then placed in spray gun II;

[0071] The glass substrate was ultrasonically cleaned in acetone and deionized water in sequence as a sample to be sprayed.

[0072] The nozzles of the two spray guns were perpendicular to the glass substrate and 20 cm away from it. Spray guns I and II were moved simultaneously parallel to the glass substrate for spraying. The spraying pressure was 0.4 MPa. Spraying was performed simultaneously with both ultra-fine spray guns, and spraying was stopped when the coating thickness reached 5 μm. The coating was cured at room temperature (25°C) for 24 hours, forming an organic-inorganic composite coating on the glass substrate surface. The water contact angle test results are as follows: Figure 1 As shown.

[0073] Example 2

[0074] The difference between this embodiment and Embodiment 1 is that the formulation of the inorganic layer material in step 2) is adjusted, specifically as follows:

[0075] The formulation of zinc oxide sol, by parts by weight:

[0076] 10 parts oxalic acid, 48 parts anhydrous ethanol, 30 parts deionized water, 20 parts zinc acetate, and 2 parts triammonium citrate surfactant.

[0077] The formulation of inorganic layer material - silane coupling agent modified zinc oxide sol, by mass parts:

[0078] 45 parts anhydrous ethanol, 45 parts deionized water, 9 parts silane coupling agent KH550, 3 parts silane coupling agent GPTMS, 20 parts zinc oxide sol.

[0079] The remaining steps and processes are the same as in Example 1, and the organic-inorganic composite coating of this example is obtained.

[0080] Example 3

[0081] The difference between this embodiment and Embodiment 2 is that the formulation of the organic layer material is adjusted, specifically:

[0082] Main agent formulation (by weight):

[0083] 30 parts deionized water, 0.4 parts defoamer, 0.1 parts multifunctional additive AMP-95, 4 parts propylene glycol methyl ether, 2 parts dipropylene glycol methyl ether, 40 parts hydroxyl resin, 20 parts dopamine-modified hydroxyl resin, 0.5 parts leveling agent TEGO 450;

[0084] Hardener formulation by parts by weight:

[0085] 52 parts propylene glycol methyl ether acetate, 48 parts Bayhydur XP;

[0086] The remaining steps and processes are the same as in Example 2, and the organic-inorganic composite coating of this example is obtained.

[0087] Example 4

[0088] The difference between this embodiment and Embodiment 1 is that the formulation of the organic layer material is adjusted, specifically as follows:

[0089] Main agent formulation (by weight):

[0090] 30 parts deionized water, 0.4 parts defoamer, 0.1 parts multifunctional additive AMP-95, 4 parts propylene glycol methyl ether, 2 parts dipropylene glycol methyl ether, 40 parts hydroxyl resin, 20 parts dopamine-modified hydroxyl resin, 0.5 parts leveling agent TEGO 450;

[0091] Hardener formulation by parts by weight:

[0092] 52 parts propylene glycol methyl ether acetate, 48 parts Bayhydur XP;

[0093] The remaining steps and processes are the same as in Example 1, and the organic-inorganic composite coating of this example is obtained.

[0094] The performance of the coatings prepared in Examples 1 to 4 was tested according to the above test methods, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] As can be seen from Table 1, the coatings prepared within the range of Examples 1-4 of this invention all exhibit excellent superhydrophilicity, weather resistance, and stability in aquatic environments, and the adhesion between the coating and the substrate meets the requirements. This is superior to the organic coating of this invention, which uses waterborne transparent polyurethane resin modified with bio-based technology to improve the hydrophilicity of the waterborne transparent polyurethane resin, while also improving the adhesion between the coating and the glass substrate and the stability of the coating in aquatic environments; while the inorganic nanomaterial selected is zinc oxide. On the one hand, zinc oxide can photocatalytically induce superhydrophilicity, which is beneficial for water rinsing and self-cleaning; on the other hand, zinc oxide provides hardness to the coating, increasing the wear resistance of the coating. The organic and inorganic components work synergistically to improve the overall performance of the coating.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 1 is that only an inorganic coating is prepared, specifically:

[0101] 1) Preparation of inorganic layer material - silane coupling agent modified zinc oxide sol:

[0102] The formulation of zinc oxide sol, by parts by weight:

[0103] 4 parts oxalic acid, 68 parts anhydrous ethanol, 40 parts deionized water, 5 parts zinc acetate, and 0.4 parts triammonium citrate surfactant;

[0104] The formulation of inorganic layer material - silane coupling agent modified zinc oxide sol, by mass parts:

[0105] 60 parts anhydrous ethanol, 60 parts deionized water, 1.8 parts silane coupling agent KH550, 0.6 parts silane coupling agent GPTMS, 4 parts zinc oxide sol;

[0106] Weigh the raw materials according to the above formula:

[0107] Oxalic acid was dissolved in anhydrous ethanol to prepare an anhydrous oxalic acid ethanol solution. Deionized water, zinc acetate, and triammonium citrate surfactant were poured into a stirred tank in sequence. The stirred tank was placed in a water bath at 80°C and stirred for 90 min. The zinc acetate solution was slowly added dropwise to the anhydrous oxalic acid ethanol solution and placed in a water bath for reaction for 30 min. After filtration, the preparation of ZnO sol was completed.

[0108] Anhydrous ethanol, deionized water, silane coupling agent KH550, silane coupling agent GPTMS, and zinc oxide sol were added sequentially to a stirred tank. After stirring for 16 hours, stirring was stopped, and the resulting solution was filtered to obtain inorganic layer material-silane coupling agent modified zinc oxide sol.

[0109] 2) Spraying of inorganic coatings:

[0110] Inorganic layer material - silane coupling agent modified zinc oxide sol is diluted with 90% by weight acetone solution and then placed in a spray gun;

[0111] The glass substrate was ultrasonically cleaned in acetone and deionized water in sequence as a sample to be sprayed.

[0112] The nozzle of the spray gun is perpendicular to the glass substrate and 20cm away from the glass substrate. Spray gun I and spray gun II are moved parallel to the glass substrate for spraying. The spraying pressure is 0.4MPa. The two ultra-fine spray guns spray simultaneously. Spraying ends when the spray thickness is 5μm. After spraying, it is cured at 25℃ for 24h to form an inorganic coating on the surface of the glass substrate.

[0113] Comparative Example 2

[0114] The difference between this comparative example and Example 1 is that only an organic coating is prepared, specifically:

[0115] 1) Preparation of waterborne transparent polyurethane resin based on organic layer material - modified hydroxyl resin:

[0116] Main agent formulation (by weight):

[0117] 30 parts deionized water, 0.4 parts defoamer, 0.1 parts multifunctional additive AMP-95, 4 parts propylene glycol methyl ether, 2 parts dipropylene glycol methyl ether, 40 parts hydroxyl resin, 20 parts dopamine-modified hydroxyl resin, 0.5 parts leveling agent TEGO 450;

[0118] Hardener formulation by parts by weight:

[0119] 52 parts propylene glycol methyl ether acetate, 48 parts Bayhydur XP;

[0120] Weigh the raw materials according to the above formula:

[0121] After adding deionized water to the stirred tank, add defoamer, multifunctional additive AMP-95, propylene glycol methyl ether, and dipropylene glycol methyl ether in sequence. After stirring for 10 minutes, add hydroxyl resin, dopamine-modified hydroxyl resin, and leveling agent TEGO 450 in sequence. After stirring for 10-20 minutes, stop stirring, filter, and let stand for 24 hours to complete the preparation of the main agent.

[0122] Propylene glycol methyl ether acetate and Bayhydur XP were added sequentially to a stirred tank and stirred for 20-30 minutes until the mixture was evenly dispersed, thus completing the preparation of the curing agent.

[0123] The main agent and curing agent were mixed at a weight ratio of 10:3 and stirred for 2 minutes to obtain an aqueous transparent polyurethane resin prepared by organic layer material-modified hydroxyl resin.

[0124] 2) Spraying of organic coatings:

[0125] The waterborne transparent polyurethane resin prepared by organic layer material - modified hydroxyl resin was diluted with 20% by weight of deionized water and then placed in a spray gun;

[0126] The glass substrate was ultrasonically cleaned in acetone and deionized water in sequence as a sample to be sprayed.

[0127] The spray gun nozzles were perpendicular to the glass substrate and 20 cm away. Spray guns I and II were moved parallel to the glass substrate for spraying. The spraying pressure was 0.4 MPa. Both ultra-fine spray guns sprayed simultaneously, stopping when the coating thickness reached 5 μm. After spraying, the coating was cured at 25°C for 24 hours, forming an organic coating film on the glass substrate surface. The water contact angle test results are as follows: Figure 2 As shown.

[0128] Comparative Example 3

[0129] The difference between this comparative example and Example 1 is that the double-spray process is not used. Instead, an organic layer is sprayed first, followed by an inorganic layer, to obtain the organic-inorganic layer of this comparative example.

[0130] Comparative Example 4

[0131] The difference between this comparative example and Example 1 is that the bio-based modified hydroxyl resin in step 1) is changed to a hydroxyl resin, while the rest of the preparation process is the same as in Example 1. The resulting organic-inorganic coating film of this comparative example has the following water contact angle test results: Figure 3 As shown.

[0132] The performance of the coatings prepared in Comparative Examples 1 to 4 was tested according to the above test method and compared with that in Example 1. The results are shown in Table 2.

[0133] Table 2

[0134]

[0135] As shown in Table 2, the overall performance of the coating film prepared in Example 1 of this invention is significantly improved compared to Comparative Examples 1-4. This indicates that for waterborne transparent polyurethane with insufficient hydrophilicity, it is necessary to modify it to give it excellent superhydrophilic properties and weather resistance. In addition, compared with the traditional material silica, zinc oxide energy level transitions can provide UV protection, preventing organic resin degradation and powdering that leads to intrinsic contamination of the coating film. At the same time, nano zinc oxide can inhibit bacteria, preventing microbial growth and surface contamination of the coating film, thereby preventing the coating film from losing its superhydrophilicity. The use of a dual-spray process can overcome the problem that the organic-inorganic composite coating film prepared by the original single-spray process cannot reflect the microstructure and roughness of inorganic particles. The improved adhesion of the organic-inorganic composite coating film after sequential spraying is mainly because sequential spraying makes it difficult for the organic coating to react with the inorganic coating after room temperature curing, resulting in poor adhesion. Moreover, the double-layer coating results in poor refractive index matching, which actually reduces the original transparency.

[0136] In summary, the coating preparation process of this invention is economical, simple, environmentally friendly, and easy to scale up for industrial production. Furthermore, this invention achieves room-temperature curing, allowing the cross-linking network to form at room temperature. This overcomes the limitations of traditional curing methods that require high temperatures for functional group cross-linking and curing, thus overcoming the practical application limitations of traditional curing methods. Compared to traditional products, this invention is more easily applied to photovoltaic panels already in operation.

[0137] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An organic-inorganic composite superhydrophilic self-cleaning coating, characterized in that: The organic-inorganic composite superhydrophilic self-cleaning coating is composed of an organic layer and an inorganic layer, and is applied to the surface of a photovoltaic panel with a thickness of 1~10 μm. The organic layer material is a water-based transparent polyurethane resin prepared by modifying hydroxyl resin; the inorganic layer material is zinc oxide sol modified by silane coupling agent. The organic-inorganic composite superhydrophilic self-cleaning coating adopts a dual-spray process. The organic layer material is diluted and placed in spray gun I, and the inorganic layer material is diluted and placed in spray gun II. The two spray guns are sprayed simultaneously. One ultra-fine spray gun sprays water-based transparent polyurethane resin atomized material, and the other ultra-micro nozzle spray gun sprays silane coupling agent modified zinc oxide sol. The coatings are mixed in the atomized and fluidized state to form a superhydrophilic film. The waterborne transparent polyurethane resin prepared by the modified hydroxyl resin is composed of a main agent and a curing agent in a mass ratio of 10:2.8~3.0, wherein the main agent, by mass parts, includes, 10.0–30.0 parts deionized water, 0.4–3 parts defoamer, 0.1–2 parts multifunctional additive, 4.0–10.0 parts propylene glycol methyl ether, 2.0–8.0 parts dipropylene glycol methyl ether, 40.0–60.0 parts hydroxyl resin, 20.0–35.0 parts dopamine-modified hydroxyl resin, 0.5–2.0 parts leveling agent; The silane coupling agent modified zinc oxide sol comprises, by weight parts, 45.0–60.0 parts anhydrous ethanol, 45.0–60.0 parts deionized water, 1.8–9.0 parts silane coupling agent KH550, 0.6–3.0 parts silane coupling agent GPTMS, 4–20.0 parts ZnO sol; The ZnO sol comprises, by mass parts, 30.0–40.0 parts deionized water, 5.0–20.0 parts zinc acetate, 0.4–2.0 parts triammonium citrate surfactant, 48.0–68.0 parts anhydrous ethanol, and 4.0–10.0 parts oxalic acid.

2. The organic-inorganic composite superhydrophilic self-cleaning coating as described in claim 1, characterized in that: The curing agent comprises, by weight parts, 24.0–52.0 parts of propylene glycol methyl ether acetate, 48.0–76.0 parts of Bayhydur XP.

3. The method for preparing the organic-inorganic composite superhydrophilic self-cleaning coating as described in claim 1, characterized in that: The organic-inorganic composite superhydrophilic self-cleaning coating is prepared by an ultra-micro dual-spray process, comprising, The organic layer material is diluted and placed in spray gun I, and the inorganic layer material is diluted and placed in spray gun II. The nozzle is perpendicular to the surface of the sample to be sprayed, and spray guns I and II are moved simultaneously parallel to the sample to be sprayed. After rapid film formation on the surface of the sample, curing treatment is performed to obtain an organic-inorganic composite super-hydrophilic self-cleaning coating.

4. The method for preparing the organic-inorganic composite superhydrophilic self-cleaning coating as described in claim 3, characterized in that: The organic layer material is diluted with deionized water, wherein the weight of the deionized water is 10-30% of the organic layer material. The inorganic layer material is diluted with acetone, with the weight of acetone being 85-95% of the inorganic layer material.

5. The method for preparing the organic-inorganic composite superhydrophilic self-cleaning coating as described in claim 3, characterized in that: The spraying pressure is 0.2~0.6 MPa, the spraying distance is 10~30 cm, and the coating thickness is 1~10 μm.

6. The method for preparing the organic-inorganic composite superhydrophilic self-cleaning coating as described in claim 3, characterized in that: The curing temperature is 20~30℃, and the curing time is 12~36 h.

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