A kind of transparent self-cleaning coating, the preparation method of transparent self-cleaning coating for solar photovoltaic panel

Abstract

The application provides a transparent self-cleaning coating, and a preparation method of the transparent self-cleaning coating for solar photovoltaic panels, and belongs to the technical field of self-cleaning materials, and aims to solve the technical problems of low light transmittance and poor mechanical properties of the self-cleaning film.The preparation method of the transparent self-cleaning coating comprises the following steps: (1) uniformly mixing a silicon source, a hydrophobic modifier, a solvent I and water, and then aging to prepare a hydrophobically modified silicon sol; (2) dissolving a hydroxyl acrylic resin, a crosslinking agent and a hydrophobic resin into a solvent II to obtain a composite resin sol; and (3) diluting the hydrophobically modified silicon sol, and then uniformly mixing the dilution liquid with the composite resin sol to obtain the transparent self-cleaning coating.The self-cleaning film prepared by the application has high light transmittance, excellent mechanical properties and a high hydrophobic angle, and can achieve the effect of a coating that is not stained and self-cleaning.Moreover, the nano-particles are modified by using a fluorine-free modifier, and are mixed with a fluorine-free resin, so that the coating has high weather resistance and wear resistance, has almost no influence on the environment, and is a green, environmentally-friendly and pollution-free self-cleaning coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of self-cleaning materials, and particularly relates to a transparent self-cleaning coating and a preparation method of the transparent self-cleaning coating for solar photovoltaic panels. BACKGROUND

[0002] With the rapid development of the photovoltaic industry, many problems are left behind, especially the cleaning problem of photovoltaic panels, which is difficult to be properly solved. The economic loss caused by dust to the photovoltaic industry exceeds several billion yuan per year, and the cleaning technology for photovoltaic panels is high in cost and difficult to operate. Therefore, a new type of nano self-cleaning protective coating for solar photovoltaic glass has gradually appeared on the market to solve this problem. However, photovoltaic components are exposed to the outside for a long time and are eroded by rain, sand and other factors, the protective coating degrades, and the self-cleaning effect is reduced. Therefore, what is needed is a coating that reduces or even prevents dust accumulation, can perform self-cleaning in harsh working environments for a long time without human intervention, and does not affect the light transmittance of the photovoltaic glass and thus the power generation efficiency of the photovoltaic component.

[0003] Patent CN 108358469A discloses a wear-resistant self-cleaning anti-reflection film for solar cells. The wear-resistant self-cleaning anti-reflection film takes photovoltaic packaging glass as a substrate, and from the side close to the glass outward, there are a magnesium fluoride film layer, an inorganic anti-reflection film layer and a high-transparency self-cleaning coating. The anti-reflection film can improve the light transmittance of the packaging material, has high material adhesion, good wear resistance and corrosion resistance, and has certain self-cleaning performance. However, the glass substrate is coated with a fluorinated magnesium layer by evaporation, which contains a large amount of fluorine element, is difficult to operate, high in cost and not environmentally friendly. The use of the evaporation method can only be used on photovoltaic glass that is about to be shipped, and cannot be used on existing photovoltaic glass, greatly reducing the use value.

[0004] Patent CN 104530852A discloses a preparation method of a high-hydrophobic fluorocarbon coating for a photovoltaic component backboard, which provides a preparation process simple, and the nano-silicon dioxide is uniformly dispersed in the main resin after being hydrophobically modified by a coupling agent, and forms a micro-nano rough texture structure after being coated on the substrate, which, in combination with the low surface energy of the fluorocarbon resin itself, makes the surface have high hydrophobicity of 'lotus effect', and avoids the adhesion of dew, rain and water vapor on the surface of the backboard, improves the hydrolysis resistance of the backboard, and has good anti-fouling effect. However, the patent uses hydrophobic particles mixed with fluorocarbon resin, which is difficult to mix, and the uniformity of the coating cannot be guaranteed, which has an adverse effect on the light transmittance and mechanical properties. And the use of fluorocarbon resin as the main resin contains a large amount of fluorine element, and a variety of organic substances are used, which is not environmentally friendly and high in cost. SUMMARY

[0005] In order to solve the technical problems of low light transmittance and poor mechanical property of the self-cleaning film, the application provides a transparent self-cleaning coating and a preparation method of the transparent self-cleaning coating for solar photovoltaic panels. The self-cleaning film prepared by the method has high light transmittance, excellent mechanical property and high hydrophobic angle, and achieves the effect of self-cleaning without dust. Moreover, the nano-particles are modified by using a fluorine-free modifier and mixed with a fluorine-free resin, so that the self-cleaning coating has high weather resistance and wear resistance and almost no influence on the environment, and is a green and environmentally-friendly self-cleaning coating without pollution.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0007] A preparation method of a transparent self-cleaning coating comprises the following steps:

[0008] (1) uniformly mixing a silicon source, a hydrophobic modifier, a solvent I and water, and then aging to prepare a hydrophobic modified silicon sol;

[0009] (2) dissolving a hydroxyl acrylic resin, a crosslinking agent and a hydrophobic resin into a solvent II to obtain a composite resin sol;

[0010] (3) diluting the hydrophobic modified silicon sol, and then uniformly mixing the dilution, the composite resin sol and a silane coupling agent I to obtain the transparent self-cleaning coating.

[0011] The silicon source is one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, methyl triethoxysilane, phenyl trimethoxysilane, n-octyl triethoxysilane, octadecyl triethoxysilane, methoxysilane, ethoxysilane, propoxysilane and butoxysilane; the hydrophobic modifier is hexamethyldisilazane; and the solvent I is one or more of ethanol, methanol, ethyl acetate, toluene, xylene and n-hexane.

[0012] The volume ratio of the silicon source, the hydrophobic modifier, the solvent I and water is 1:(0.5-2):(10-15):(1-2).

[0013] The aging temperature is 35-45 DEG C, and the aging time is 3-14 days.

[0014] The crosslinking agent is an amino resin; the hydrophobic resin is one or more of silicone resin, MQ methyl silicone resin, methyl phenyl silicone resin and methyl vinyl silicone resin; the solvent II is one or more of ethanol, methanol, ethyl acetate, toluene, xylene and n-hexane; and the silane coupling agent I is gamma-aminopropyl triethoxysilane (KH-550).

[0015] The mass ratio of the hydroxyl acrylic resin, the crosslinking agent and the hydrophobic resin is 1:(0.5-1):(0.5-3), and the ratio of the hydroxyl acrylic resin to the solvent II is 10-50 g / mL.

[0016] The diluent used for diluting the hydrophobic modified silica sol in the step (3) is the solvent I, and the volume ratio of the diluent to the hydrophobic modified silica sol is (3-5):1; the mass ratio of the diluent, the composite resin sol and the silane coupling agent I is 1:(0.8-1.2):(0.005-0.01).

[0017] A preparation method of a transparent self-cleaning coating for a solar photovoltaic panel, comprising the following steps:

[0018] (1) mixing a silane coupling agent II, octadecylamine, polyethylene glycol, ethanol and water to prepare an anti-reflective sol;

[0019] (2) coating the anti-reflective sol on a substrate, and then performing annealing treatment to prepare an anti-reflective layer on the substrate;

[0020] (3) coating a transparent self-cleaning coating on the anti-reflective layer of the step (2), and performing calcination to prepare a transparent self-cleaning coating.

[0021] The mass ratio of the silane coupling agent II, octadecylamine, polyethylene glycol, ethanol and water is 1:0.1:2:20:0.3.

[0022] The silane coupling agent II is gamma-glycidoxypropyltrimethoxysilane (KH-560).

[0023] The substrate is a glass substrate, which is treated with an otocinclus solution before use, and is dried with nitrogen and then used.

[0024] The otocinclus solution is prepared by mixing strong acid and 30% hydrogen peroxide in a ratio of 7:3, wherein the strong acid is one or more of concentrated sulfuric acid and concentrated hydrochloric acid; the treatment step is that the cleaned glass substrate is placed in the otocinclus solution and shaken for 5 min, and then is placed at a temperature of 60-80 DEG C for 1-2 h, and then is washed with a large amount of distilled water.

[0025] The annealing temperature in the step (2) is 450 DEG C-550 DEG C; and the calcination temperature in the step (3) is 200 DEG C-250 DEG C.

[0026] The beneficial effects of the present application are:

[0027] (1) the fluorine-free modifier in the present application is used to modify the silanol hydrolyzed from TEOS, and the hydrophobic modified silica sol is used to replace the traditional silica powder, so that the agglomeration in the coating is avoided, and the light transmittance of the transparent self-cleaning coating can reach 85%;

[0028] (2) The double-layer composite structure is adopted, the anti-reflective layer of the bottom layer has a positive influence on the transmittance of the transparent self-cleaning coating, the bottom layer is combined with the substrate by covalent bond, the connection is tight, and meanwhile the adhesion of the transparent self-cleaning coating to the substrate is increased;

[0029] (3) The three kinds of resins are combined, the -COOH in the hydroxyl acrylic resin and the -NH3 in the amino resin are cross-linked and polymerized, the hydrophobic MQ methyl silicone resin is introduced to form the composite resin substrate, the cross-linking reaction occurs between the resins, the three-dimensional network structure is formed, and the hydrophobic groups in the MQ methyl silicone resin improve the wetting performance of the coating. In addition, the hydroxyl acrylic resin and the hydrophobic modified silica sol can further react, the composite resin wraps the hydrophobic nanoparticles, and the weather resistance and durability of the coating are greatly increased. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0031] Figure 1 XPS comparison curve of the anti-reflective layer before and after calcination.

[0032] Figure 2 Scanning electron microscope photo of the anti-reflective layer.

[0033] Figure 3 Water contact angle of the transparent self-cleaning coating.

[0034] Figure 4 Transmittance spectrum of the transparent self-cleaning coating.

[0035] Figure 5 White light interference image of the transparent self-cleaning coating.

[0036] Figure 6 FT-IR spectrum of the transparent self-cleaning coating.

[0037] Figure 7 Scanning electron microscope photo of the transparent self-cleaning coating.

[0038] Figure 8 (a) P-V curve of the transparent self-cleaning coating, (b) I-V curve of the transparent self-cleaning coating.

[0039] Figure 9 (a) P-V curve of the coated film photovoltaic module after dusting and the blank photovoltaic module, (b) I-V curve of the coated film photovoltaic module after dusting and the blank photovoltaic module. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0041] Embodiment 1

[0042] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0043] (1) 8.4 mL of tetraethyl orthosilicate is dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then a mixture of 8 mL of hexamethyldisilazane and 12 mL of high-purity water is added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2 sol is obtained after aging for one week, and all the reactions are carried out at 40°C;

[0044] (2) 0.88 g of a hydroxy acrylic resin, 0.56 g of an amino resin and 0.4 g of an MQ methyl silicone resin are dispersed in 30 ml of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0045] (3) the hydrophobic modified sol is diluted with ethanol at a ratio of 1:4, 10 g of the diluted solution is uniformly mixed with 10 g of the composite resin sol, and then 0.1 g of γ-aminopropyl triethoxysilane is added, and a transparent self-cleaning coating is prepared after full reaction for standby.

[0046] Embodiment 2

[0047] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0048] (1) 8.4 mL of tetraethyl orthosilicate is dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then a mixture of 8 mL of hexamethyldisilazane and 12 mL of high-purity water is added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2 sol is obtained after aging for one week, and all the reactions are carried out at 40°C;

[0049] (2) 0.88 g of a hydroxy acrylic resin, 0.56 g of an amino resin and 0.4 g of an MQ methyl silicone resin are dispersed in 30 ml of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0050] (3) the hydrophobic modified sol is diluted with ethanol at a ratio of 1:4, 10 g of the diluted solution is uniformly mixed with 10 g of the composite resin sol, and then 0.1 g of γ-aminopropyl triethoxysilane is added, and a transparent self-cleaning coating is prepared after full reaction for standby.

[0051] Example 3

[0052] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0053] (1) 8.4 mL of tetraethyl orthosilicate was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 8 mL of hexamethyldisilazane and 12 mL of high-purity water were added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2 sol was obtained after aging for one week, and all the reactions were carried out at 40°C;

[0054] (2) 0.88 g of hydroxy acrylic resin, 0.56 g of amino resin and 1.2 g of MQ methyl silicone resin were dispersed in 30 ml of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0055] (3) The hydrophobic modified sol was diluted with ethanol at a ratio of 1:4, 10 g of the diluted solution was uniformly mixed with 10 g of the composite resin sol, and then 0.1 g of γ-aminopropyl triethoxysilane was added, and a transparent self-cleaning coating was prepared after fully reacting.

[0056] Example 4

[0057] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0058] (1) 8.4 mL of tetraethyl orthosilicate was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 8 mL of hexamethyldisilazane and 12 mL of high-purity water were added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2 sol was obtained after aging for one week, and all the reactions were carried out at 40°C;

[0059] (2) 0.88 g of hydroxy acrylic resin, 0.56 g of amino resin and 1.2 g of MQ methyl silicone resin were dispersed in 30 ml of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0060] (3) The hydrophobic modified sol was diluted with ethanol at a ratio of 1:4, 10 g of the diluted solution was uniformly mixed with 10 g of the composite resin sol, and then 0.1 g of γ-aminopropyl triethoxysilane was added, and a transparent self-cleaning coating was prepared after fully reacting.

[0061] Comparative Example 1

[0062] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0063] (1) 8.4 mL of tetraethyl orthosilicate was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 8 mL of hexamethyldisilazane and 12 mL of high-purity water were added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2sol was obtained after aging for one week, and all the reactions were carried out at 40°C;

[0064] (2) 0.88 g of hydroxy acrylic resin, 0.56 g of amino resin were dispersed in 30 mL of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0065] (3) The hydrophobic modified sol was diluted with ethanol at a ratio of 1:4, 10 g of the diluted solution was uniformly mixed with 10 g of the composite resin sol, and then 0.1 g of γ-aminopropyl triethoxysilane was added, and a transparent self-cleaning coating was prepared after fully reacting.

[0066] Comparative Example 2

[0067] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0068] (1) 8.4 mL of tetraethyl orthosilicate was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 8 mL of hexamethyldisilazane and 12 mL of high-purity water were added and fully reacted in the stirring process for 2 h, and a hydrophobic modified SiO2sol was obtained after aging for one week, and all the reactions were carried out at 40°C; the hydrophobic modified sol was centrifuged, washed with ethanol, and centrifuged 3 times, and the obtained gel was placed in a drying box at 80°C, and finally ground, sieved, and hydrophobic modified SiO2particles were prepared.

[0069] (2) 0.88 g of hydroxy acrylic resin, 0.56 g of amino resin and 0.8 g of MQ methyl silicone resin were dispersed in 30 mL of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0070] (3) 0.35 g of hydrophobic modified nano-SiO2was uniformly dispersed in 30 mL of ethanol, 10 g of nano-SiO2dispersion liquid was uniformly mixed with 10 g of composite resin sol, and 0.1 g of KH-550 was added and fully reacted to prepare a transparent self-cleaning coating.

[0071] Example 5

[0072] A transparent self-cleaning coating for solar photovoltaic panels, the preparation method comprising the following steps:

[0073] (1) 5.75 mL of silane coupling agent KH-560 was added dropwise to 92 mL of anhydrous ethanol, stirred at 35°C for 1 h, then 2.3 mL of high-purity water and 0.69 g of octadecylamine were added and stirred for 0.5 h, and finally 10 g of polyethylene glycol 1500 was added and stirred for two hours to obtain an antireflection sol.

[0074] (2) Put the glass sheet into the piranha solution (98% concentrated sulfuric acid: 30% hydrogen peroxide = 3:1), heat to keep the temperature at 70℃, after 1h reaction, take out and rinse with plenty of distilled water, finally blow off the surface residual water with nitrogen, and place in the 40℃ oven for standby;

[0075] (3) Apply the anti-reflective sol on the treated glass sheet substrate to obtain the anti-reflective layer substrate after high temperature annealing, and uniformly apply the transparent self-cleaning coating prepared in Example 1 on the bottom layer to form a transparent self-cleaning coating layer after high temperature calcination, and the prepared sample is marked as a.

[0076] Technical mechanism:

[0077] The present application first uses the piranha solution to hydroxylate the glass surface, so that the surface is rich in -OH functional groups; the anti-reflective layer is further calcined at high temperature, and the PEG is cracked and volatilized to form a pore structure, which increases the light transmittance of the coating; at the same time, the KH-560 and ODA undergo ring opening and then react to form a three-dimensional network structure, which increases the stability of the coating; the -OH after ring opening and the -OH group on the glass surface undergo dehydration condensation, which increases the adhesion between the coating and the glass; the -COOH in the hydroxy acrylic resin in the top layer reacts with the -NH3 in the amino resin to produce crosslinking polymerization, and the terminal hydroxyl in the hydroxy acrylic resin condenses with the -OH in the silanol produced by the hydrolysis of TEOS to produce covalent bonds, so that the nano-SiO2 particles are better coated and have excellent stability; the introduction of hydrophobic MQ methyl silicone resin forms a compatible resin substrate, and the neutralization of the resin composite produces more hydrophilic properties of the hydroxyl and amino groups, so that the hydrophobicity of the coating is increased. The three resins jointly play a positive role in the stability, mechanical properties and self-cleaning properties of the coating. Under the action of KH-550, the organic and inorganic materials are better combined to form a self-cleaning coating material for solar photovoltaic panels.

[0078] Example 6

[0079] The difference from Example 5 is that the transparent self-cleaning coating uses the transparent self-cleaning coating prepared in Example 2, and the other conditions are the same, and the prepared sample is marked as b.

[0080] Example 7

[0081] The difference from Example 5 is that the transparent self-cleaning coating uses the transparent self-cleaning coating prepared in Example 3, and the other conditions are the same, and the prepared sample is marked as c.

[0082] Example 8

[0083] The difference from Example 5 is that the transparent self-cleaning coating was prepared using the transparent self-cleaning coating prepared in Example 4, with other conditions being the same, and the prepared sample is denoted as d.

[0084] Comparative Example 3

[0085] The difference from Example 5 is that the transparent self-cleaning coating was prepared using Comparative Example 1, with other conditions being the same. The prepared sample is denoted as e.

[0086] Comparative Example 4

[0087] The difference from Example 5 is that the transparent self-cleaning coating was prepared using Comparative Example 2, with other conditions being the same. The prepared sample is denoted as f.

[0088] The samples af prepared in Examples 5-8 and Comparative Examples 3 and 4 were characterized and compared with bare glass.

[0089] 1. XPS analysis of the antireflection layer

[0090] XPS tests were performed on the antireflective layer in Example 5 before and after calcination. PEG-1500 was used as a pore-forming agent in the underlying antireflective solution. Calcination of the coated sample at 500°C caused the carbon chain structure of PEG to break down and volatilize into gas. Figure 1 It can be seen that the C content was greater than that of Si and O before calcination. After calcination, the C content was greatly reduced and the O content increased. This indicates that C was oxidized and volatilized into gas during calcination. The remaining elements continued to react with KH-560 and ODA, thus forming a dense three-dimensional network structure with a large number of pores.

[0091] 2. Scanning electron microscopy analysis of the antireflection layer

[0092] In Example 5, after the antireflection layer is annealed, by Figure 2 SEM images of the antireflective coating reveal a large number of porous structures. These porous structures increase the refractive index of light, thereby reducing reflectivity and increasing transmittance. This is a key reason why the transmittance of the antireflective coating is higher than that of bare glass. Therefore, using an antireflective coating to improve the transmittance of a hydrophobic coating is highly effective.

[0093] 3. Wetting properties of self-cleaning coating surface

[0094] In order to explore the hydrophobic properties of the self-cleaning coating, the contact angle measuring instrument was used to measure the contact angle of water droplets on the coating with different proportions. Specifically, three positions on the sample surface were selected and a drop of deionized water was dropped from a needle tube, and the average value of the contact angle was taken. By observing and analyzing the contact angle of water droplets on the coating surface, the performance of the hydrophobic coating on the sample surface was characterized. Figure 3 As shown in FIG. 8, the contact angles of different contents of MQ methyl silicone resin are different. With the increase of the content of MQ methyl silicone resin, the contact angle of the coating reaches a maximum of 133.1° when the content is 0.8 g. Then, with the continuous increase of the content of the resin, the contact angle gradually decreases. This is because when the content of the resin increases to a certain extent, the spreading speed of the water droplets on the coating surface is accelerated, and at the same time, with the increase of the content, the surface roughness of the coating is reduced, thereby reducing the contact angle. Using traditional nano-SiO2 particles, the contact angle of the coating decreases, as shown in sample f in FIG. 6, indicating that the nanoparticles are unstable in further dispersion and agglomeration occurs, and the resin cannot exhibit its hydrophobic properties when it is wrapped. Figure 3

[0095] 4. Analysis of the light transmittance of the self-cleaning coating

[0096] In this test, the UV-visible-near infrared spectrophotometer was used to measure the light transmittance of a series of hydrophobic coatings with different proportions at room temperature. The wavelength range used was 300-1100 nm, and the instrument was calibrated with air as the reference with a light transmittance of 100%. Figure 4 is the transmittance spectrum of the hydrophobic coating with different contents of MQ methyl silicone resin. This experiment mainly prepared a hydrophobic coating on a photovoltaic glass substrate to study its light transmittance. During the test, special attention was paid to the influence of different contents of MQ methyl silicone resin on the light transmittance of the coating in the visible light range, and the sample with good light transmittance was selected.

[0097] The influence of different contents of MQ methyl silicone resin on the transmittance of the coating is shown in FIG. 8. As shown in FIG. 8, Figures 3-5 Figure 4 ​​As can be seen, the light transmittance of the coating containing 0.8 g, 1.2 g, 1.6 g of MQ methyl silicone resin is only about 80%, which is 10% lower than that of bare glass. When the content of MQ methyl silicone resin is 0.4 g, the light transmittance is about 85%, and when there is no MQ methyl silicone resin, the light transmittance reaches the best, which is 90%, close to that of bare glass. Since the addition of MQ methyl silicone resin improves the adhesion of the coating, it will affect the light transmittance, thereby causing the light transmittance of the coating to decrease to a certain extent. The light transmittance of the coating containing 0.4 g of MQ methyl silicone resin and the coating containing 0.8 g of MQ methyl silicone resin reaches 85% and 80% respectively, which achieves the effect of considering both the hydrophobicity and the light transmittance.

[0098] 5. Surface roughness analysis

[0099] As Figure 5 shown are the planar and 3D images of the roughness of the coating, and the coating with the addition of 0 g, 0.4 g, 0.8 g, 1.2 g, 1.6 g of MQ methyl silicone resin is tested. This method uses the principle of Michelson interference, uses white light as the light source, and uses a white light interferometer to test the roughness of the coating. As shown in the figure, there are micro-nano level bumps in the a-b figures, and from the 3D image of the sample, it can be seen that the surface of the sample has tight bumps, so the coating has a certain rough structure, thereby making the coating have water-repellent property to liquid drops. As can be seen from the figure, the roughness (Ra) value of a is 29 nm, and the Ra value of c is 64 nm. From the discussion of the contact angle above, it can be seen that the water contact angle of c is greater than that of a, thereby further verifying that the roughness has a positive effect on the contact angle of the sample. However, when the content of MQ-Me continues to increase, the contact angle of the coating decreases. From the WLI image, it can also be seen that the Ra values of samples d and e are 56 nm and 27 nm respectively, and the roughness value decreases, which affects the wettability of the sample to water. In summary, the Ra value of c is the highest, and the contact angle is the best, which shows that the roughness is proportional to the hydrophobicity of the coating to a certain extent.

[0100] 6. Infrared spectrum analysis of self-cleaning coating

[0101] The transparent self-cleaning coating prepared in Example 6 was measured by infrared, and as shown in Figure 6 , the chemical composition of the surface of each sample was analyzed by FT-IR spectrum. From the curve, the peaks appearing near 2966 cm -1 and 1400 cm -1 are caused by the bending vibration of the -CH3 group in the Si-CH3 bond, and the peak appearing near 804 cm -1 is caused by the rocking and asymmetric deformation vibration of the -CH3 group in the Si-CH3 bond. The peak appearing near 1022 cm -1and 700 cm -1 The peaks appearing near 800 cm"1and 700 cm"1are the result of the stretching motion of Si-O-Si bond and Si-C of the silicone resin, respectively. These results show that the Si02 hydrolyzed from the hydrophobic sol is mostly modified by the fluoride-free modifier HMDS, and at the same time, the introduced resin is firmly coated in it, making the coating more robust.

[0102] 7. SEM analysis of self-cleaning coating

[0103] To further prove the mechanical properties of the coating, we took a scanning electron microscope photo of sample b, as shown in Figure 6. Figure 7 The nanoparticles are evenly distributed in the flat composite resin, indicating that cross-linking, bonding and coating between the nanosilica and the resin have occurred. The resin plays a protective role for the fragile inorganic nanosilica particles, and when subjected to external forces, the coating can exhibit excellent mechanical properties, thereby improving the durability and weather resistance of the coating.

[0104] 8. Pencil hardness of self-cleaning coating

[0105] According to the standard test method for coating performance, the hardness of the hydrophobic coating is evaluated by whether the pencil mark can scratch the coating, and the highest hardness of the pencil core (from soft to hard, 6B-6H) that the coating can withstand is tested. The hardness of the coating prepared with different contents of MQ methyl silicone resin is shown in Table 1. When the content of MQ methyl silicone resin is 0 g, the pencil hardness of the coating is 2B. With the increase of the content of the adhesive MQ methyl silicone resin, the pencil hardness of the coating shows an upward trend. When the content of MQ methyl silicone resin reaches 0.8 g, the pencil hardness of the hydrophobic coating on the surface reaches 2H. At this time, the pencil hardness of the coating reaches the highest, which indicates that when the content of MQ methyl silicone resin in the coating reaches 0.8 g, the adhesion of the coating is the best. The pencil hardness of the comparative example f is HB, indicating that the redissolution of the nanoparticles has occurred with large agglomeration, making the resin coating uneven, and thus the mechanical properties decrease.

[0106] Table 1 Pencil hardness value of transparent self-cleaning coating

[0107] Sample No. a b c d e f Pencil Hardness Value HB 2H 3B 4B 2B HB

[0108] 9. Performance test of self-cleaning coating on photovoltaic modules

[0109] Figure 8P-V (a) and I-V curves (b) of different content of MQ-Me coating. As can be seen from the figure, the open circuit voltage of bare glass and sample e is 5.85V and 5.9V respectively, indicating that the open circuit voltage will increase by 0.8% after the hydrophobic coating is coated. While the short circuit current of bare glass and e is 0.186A and 0.1863A, and the maximum output power is 0.825W and 0.83W, it can be seen that after the hydrophobic coating is coated, the short circuit current, open circuit voltage and maximum output power are increased to a certain extent. The main reason is that the anti-reflective coating coated increases the light transmittance due to its anti-reflective property, which enables the module to receive more light source, thereby generating more photo-generated carriers to increase the current. Because the coating has a weak effect on the output voltage, the output current is increased, and the output power of the module is also increased.

[0110] As can be seen from Figure 8 , with the increase of the content of MQ methyl silicone resin, the short circuit current, open circuit voltage and maximum output power of the coating are all slightly reduced, especially S5, the open circuit voltage is reduced by 4.2% compared with S1, so it can be known that the MQ methyl silicone resin has a certain influence on the light transmittance of the coating, which leads to the decrease of the light source received by the solar cell. Therefore, the fewer photo-generated carriers result in the corresponding decrease of the current and power.

[0111] In addition, the coating with sample number b is selected to coat the photovoltaic glass plate and the blank photovoltaic glass plate with dust to study the effect of dust on the photovoltaic module. As Figure 9 indicated, it can be found by comparison that after the photovoltaic module is coated with dust, the maximum output power of the coated photovoltaic module is 0.95247W, while the maximum output power of the blank photovoltaic module is 0.94369W, and the short circuit current of the coated photovoltaic module is higher than that of the blank glass module at this time. This shows that after the hydrophobic coating is coated, the photovoltaic glass has obvious dust-repellent property, which is due to the rough micro-nano structure on the surface of the coating, which reduces the adhesion between the dust and the coating, and the dust is more easily removed by gravity or wind. At the same time, the surface of the coating has low surface energy, and the dust is more difficult to stay on the surface of the photovoltaic module, so that the light transmittance of the coating can still be maintained, so that more sunlight can be absorbed to generate more photo-generated carriers, so that the output power is higher than that of the blank photovoltaic module.

[0112] Example 9

[0113] A kind of transparent self-cleaning coating, the preparation method comprises the following steps:

[0114] (1) 10 mL of methyl triethoxysilane was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 5 mL of hexamethyldisilazane and 10 mL of high-purity water were added and reacted for 2 h under stirring, and a hydrophobic modified SiO2 sol was obtained after aging for two weeks, all the reactions were carried out at 35°C;

[0115] (2) 1 g of hydroxy acrylic resin, 0.5 g of amino resin and 0.5 g of methyl phenyl silicone resin were dispersed in 10 mL of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0116] (3) The hydrophobic modified sol was diluted with ethanol at a ratio of 1:5, 10 g of the diluted solution was uniformly mixed with 10 g of the composite resin sol, then 0.1 g of γ-aminopropyl triethoxysilane was added, and a transparent self-cleaning coating was prepared after sufficient reaction.

[0117] Example 10

[0118] A transparent self-cleaning coating, the preparation method comprising the following steps:

[0119] (1) 10 mL of methyl triethoxysilane was dissolved in 120 mL of anhydrous ethanol and ultrasonically dispersed for 0.5 h, then 5 mL of hexamethyldisilazane and 10 mL of high-purity water were added and reacted for 2 h under stirring, and a hydrophobic modified SiO2 sol was obtained after aging for two weeks, all the reactions were carried out at 35°C;

[0120] (2) 1 g of hydroxy acrylic resin, 0.5 g of amino resin and 0.5 g of methyl phenyl silicone resin were dispersed in 10 mL of anhydrous ethanol by high-speed stirring to obtain a composite resin sol;

[0121] (3) The hydrophobic modified sol was diluted with ethanol at a ratio of 1:5, 10 g of the diluted solution was uniformly mixed with 10 g of the composite resin sol, then 0.1 g of γ-aminopropyl triethoxysilane was added, and a transparent self-cleaning coating was prepared after sufficient reaction.

[0122] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for the preparation of a transparent self-cleaning coating for solar photovoltaic panels, characterized by, The method comprises the following steps: (1) mixing silane coupling agent II, octadecylamine, polyethylene glycol, ethanol and water to prepare a reflection-reducing sol; (2) coating the reflection-reducing sol on a substrate, and then performing annealing treatment to prepare a reflection-reducing layer on the substrate; (3) coating a transparent self-cleaning coating on the reflection-reducing layer prepared in step (2) and performing calcination to prepare a transparent self-cleaning coating layer; The calcination temperature in step (3) is 200-250°C; The preparation method of the transparent self-cleaning coating comprises the following steps: S1 uniformly mixing a silicon source, a hydrophobic modifier, a solvent I and water, and then performing aging to prepare a hydrophobically modified silica sol; S2 dissolving a hydroxyl acrylic resin, a crosslinking agent and a hydrophobic resin into a solvent II to obtain a composite resin sol; S3 diluting the hydrophobically modified silica sol, and then uniformly mixing the dilution, the composite resin sol and a silane coupling agent I to prepare the transparent self-cleaning coating; The silane coupling agent II is γ-glycidoxypropyltrimethoxysilane; The silicon source is one or more of methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, n-octyltriethoxysilane, octadecyltriethoxysilane, propylsilane and butoxysilane; The aging temperature is 35-45°C, and the aging time is 3-14 days; The diluent used for diluting the hydrophobically modified silica sol in S3 is the solvent I, the volume ratio of the diluent to the hydrophobically modified silica sol is (3-5):1; the mass ratio of the dilution, the composite resin sol and the silane coupling agent I is 1:(0.8-1.2):(0.005-0.01).

2. The method for preparing a transparent self-cleaning coating for solar photovoltaic panels according to claim 1, characterized in that, The mass ratio of the silane coupling agent II, octadecylamine, polyethylene glycol, ethanol and water is 1:0.1:2:20:0.

3.

3. The method for the preparation of a transparent self-cleaning coating for solar photovoltaic panels according to claim 2, characterized by the fact that, The annealing temperature in step (2) is 450-550°C.

4. The method for preparing a transparent self-cleaning coating for solar photovoltaic panels according to claim 1, characterized in that, The hydrophobic modifier is hexamethyldisilazane; the solvent I is one or more of ethanol, methanol, ethyl acetate, toluene, xylene and n-hexane.

5. The method for the preparation of a transparent self-cleaning coating for solar photovoltaic panels according to claim 4, characterized by the fact that, The volume ratio of the silicon source, the hydrophobic modifier, the solvent I and water is 1:(0.5-2):(10-15):(1-2).

6. The method for the preparation of a transparent self-cleaning coating for solar photovoltaic panels according to claim 5, characterized by the fact that, The crosslinking agent is an amino resin; the hydrophobic resin is one or more of MQ methyl silicone resin, methylphenyl silicone resin and methylvinyl silicone resin; the solvent II is one or more of ethanol, methanol, ethyl acetate, toluene, xylene and n-hexane; and the silane coupling agent I is γ-aminopropyltriethoxysilane.

7. The method for the preparation of a transparent self-cleaning coating for solar photovoltaic panels according to claim 6, characterized by the fact that, The mass ratio of the hydroxyl acrylic resin, the crosslinking agent and the hydrophobic resin is 1:(0.5-1):(0.5-3), and the ratio of the hydroxyl acrylic resin to the solvent II is 10-50 g / mL.

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