Preparation method and application of white fluorine-free photovoltaic coating

Abstract

The application relates to the technical field of silicone coating preparation, and discloses a preparation method and application of white fluorine-free photovoltaic coating. 1 )4, R 2 Si(OR 3 )3, R 4 2Si(OR 5 )2, R 6 Si(OR 3 )3 and R 4 Si(OR 5 )3 are hydrolyzed and polycondensated in mixed acid solution to obtain a silicone resin; 100 parts of the silicone resin is mixed with 20-100 parts of an organic silicon modified hydroxyl acrylic resin coating prepared according to a specific ratio and 50-200 parts of titanium white paste prepared according to a specific ratio, and the white fluorine-free photovoltaic coating is obtained. The white fluorine-free photovoltaic coating has good adhesion and adhesion force to a photovoltaic substrate, high hardness, good scratch resistance and aging resistance, and high light reflectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone coating preparation, in particular to a preparation method and application of white fluorine-free photovoltaic coating. BACKGROUND

[0002] It is predicted that tens to hundreds of GW of photovoltaic components will be retired each year in the future. Harmless treatment, waste gas, waste liquid, waste collection and treatment during the recycling of photovoltaic components are all difficult points. The fluorine-containing photovoltaic backboard brings new problems to the recycling of photovoltaic components. Fluoride is highly toxic. If incineration is used for treatment, hydrogen fluoride and other toxic gases will be generated. In addition, after the photovoltaic power station catches fire, the operation and rescue personnel are also prone to fluoride poisoning. In the face of increasingly stringent safety and environmental protection requirements, photovoltaic enterprises need to balance the long-term use reliability and green environmental protection requirements of the material to truly realize the sustainable development of the photovoltaic industry. Therefore, in recent years, fluorine-free photovoltaic products (such as organic silicon photovoltaic products) have been widely promoted.

[0003] However, although the existing silicone resin (such as CN110144044A) is outstanding in terms of weather resistance, hardness and other properties, it also has defects that cannot be ignored. The flexibility of this type of silicone resin is very poor, and the deformation of the photovoltaic substrate can easily cause the silicone resin coating coated on the photovoltaic substrate to peel off and crack. Without the aid of a catalyst or curing agent, the curing speed of the silicone coating prepared from the silicone resin on the photovoltaic substrate used in the photovoltaic backboard is slow, and it is difficult to achieve surface drying in a short time, resulting in a long process cycle. In addition, the adhesion of the silicone coating prepared from the silicone resin on the photovoltaic substrate (especially the adhesion after PCT aging and the water boiling resistance) is poor, and the friction resistance also needs to be improved.

[0004] Based on this, CN111621228A provides an easy-to-clean coating with high hardness and high toughness. The coating simultaneously adds a tough silicone resin (such as an organic silicon modified hydroxyl acrylate resin) and a brittle silicone resin (such as a methyl silicone resin), and by adjusting the ratio of the tough silicone resin and the brittle silicone resin, the coating has high toughness and high hardness, and the scratch resistance of the coating is also improved, and the coating also has easy-to-clean performance. However, this coating still has defects such as slow curing speed, poor adhesion after PCT aging and water boiling resistance, and the reflectivity of the coating in the 400-780 nm light wave band is poor, which makes it difficult to be applied to the preparation of high-quality coated white photovoltaic backboards. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a preparation method and application of white fluorine-free photovoltaic coating.

[0006] Based on this, the application discloses a preparation method of white fluorine-free photovoltaic coating, which comprises the following preparation steps:

[0007] S1, preparation of the organic silicon resin:

[0008] S11, mixing tetraalkoxysilane of Si(OR 1 )4, alkyl trialkoxysilane of R 2 Si(OR 3 )3, phenyl trialkoxysilane of R 4 2Si(OR 5 )2, dialkyl dialkoxysilane of R 6 Si(OR 3 )3, chloroalkyl trialkoxysilane of R 4 Si(OR 5 )3 and epoxy alkyl trialkoxysilane of R 1 in a weight ratio of 10-20:30-40:10:5:5:10, stirring uniformly to obtain an organic silicon solution; mixing water, acetic acid and propylene glycol methyl ether in a weight ratio of 18:2:2-10, stirring uniformly to obtain a mixed acid solution;

[0009] wherein, R 1 , R 3 and R 5 are hydrogen or C1-4 alkyl, R 2 and R 4 are C1-8 alkyl, C1-8 unsaturated alkyl, cycloalkyl or phenyl, and R 6 is C1-4 chloroalkyl;

[0010] S12, slowly dropping the mixed acid solution into the organic silicon solution while stirring, continuing to stir, so that the organic silicon solution is subjected to hydrolysis and polycondensation reaction, thereby obtaining the organic silicon resin;

[0011] S2, mixing the organic silicon modified hydroxyl acrylic resin, isocyanate curing agent, dispersant, defoaming agent, leveling agent and solvent in a mass ratio of 30-40:15-35:0.5:0.2:0.6:20-30, stirring uniformly to obtain the organic silicon modified hydroxyl acrylic resin coating;

[0012] S3, mixing titanium white powder, polyester resin, dispersant and solvent in a mass ratio of 100-200:200:10:120, grinding, filtering to obtain the titanium white powder color paste;

[0013] S4, mixing 100 parts of the organic silicon resin, 20-100 parts of the organic silicon modified hydroxyl acrylic resin coating and 50-200 parts of the titanium white powder color paste, stirring uniformly to obtain the white fluorine-free photovoltaic coating.

[0014] Preferably, in step S11, Si(OR1 )4 of tetraalkoxysilane uses tetraethyl orthosilicate, R 2 Si(OR 3 )3 of alkyltrialkoxysilane uses methyl triethoxysilane, R 2 Si(OR 3 )3 of phenyltrialkoxysilane uses phenyltrimethoxysilane, R 4 2Si(OR 5 )2 of dialkyldialkoxysilane uses dimethyldiethoxysilane, R 6 Si(OR 3 )3 of chloroalkyltrialkoxysilane uses chloropropyl triethoxysilane, R 4 Si(OR 5 )3 of epoxyalkyltrialkoxysilane uses KH560.

[0015] Further preferably, in step S11, the tetraethyl orthosilicate, methyl triethoxysilane, phenyltrimethoxysilane, dimethyldiethoxysilane, chloropropyl triethoxysilane, KH560 are mixed in a weight ratio of 10-20:30:10:5:5:10.

[0016] More preferably, in step S11, the tetraethyl orthosilicate, methyl triethoxysilane, phenyltrimethoxysilane, dimethyldiethoxysilane, chloropropyl triethoxysilane, KH560 are mixed in a weight ratio of 20:30:10:5:5:10.

[0017] The water, acetic acid and propylene glycol methyl ether are mixed in a weight ratio of 18:2:10.

[0018] Preferably, in step S12, the time for dropping is 30-60 minutes, and the time for continuing stirring is 3-6 hours.

[0019] In step S1 of the present application, the basic principle of obtaining the silicone resin by hydrolysis and condensation of the organosiloxane in the silicone solution is as follows:

[0020] For example, the dialkyldialkoxysilane (such as dimethyldiethoxysilane) is hydrolyzed to obtain a silicon diol, and further condensation can produce linear polymers in various forms. Take dimethyldimethoxysilane as an example, the reaction is as follows:

[0021]

[0022] For example, the alkyltrialkoxysilane (such as methyl triethoxysilane, phenyltrimethoxysilane) is hydrolyzed to obtain a silicon triol, and further condensation can produce three-dimensional cross-linked polymers in various forms. Take methyltrimethoxysilane as an example, the reaction is as follows:

[0023]

[0024] For example, the hydrolysis of tetraethyl orthosilicate yields silanetetrol, which can then undergo polycondensation to produce nano-silica aggregates, resulting in nanostructures that provide higher hardness to organosilicon resins.

[0025] Thus, the polycondensation between silicon polyols can produce various forms of cross-linked polymers. Generally, cross-linked polymers of siloxanes substituted with short-chain alkyl (such as methyl, ethyl, propyl) or phenyl segments are relatively hard and brittle. The brittleness can be adjusted by introducing different intermediates for copolymerization modification. In step S1 of this invention, through blending, hydrolysis, and co-condensation of various organosiloxanes with different functional groups, an organosilicon resin with active groups such as chloroalkyl and silanol groups can be obtained.

[0026] In step S1 of this invention, multiple organosiloxanes are compounded using various active groups to adjust the hardness, gloss, toughness, curing rate, and thermal stability of the organosilicon resin. Experiments have shown that these organosiloxanes, in addition to tetraethyl orthosilicate, must also contain chloroalkyl groups, resulting in a novel organosilicon resin with chloroalkyl side chains. This is mainly because: the introduced chloroalkyl functionalized groups can undergo cross-linking reactions with other resins or photovoltaic substrate surfaces during curing, making the coating more stable; and the introduction of nano-silica through tetraethyl orthosilicate can increase the hardness of the organosilicon resin.

[0027] Preferably, in step S2, the silicone-modified hydroxyl acrylic resin, isocyanate curing agent, dispersant, defoamer, leveling agent, and solvent are mixed in a mass ratio of 40:25:0.5:0.2:0.6:20.

[0028] The dispersant is an alkyl-modified polysiloxane dispersant, the defoamer is a polysiloxane defoamer or a polyether-modified silicone oil defoamer, the leveling agent is an organosilicon leveling agent, and the solvent is a mixed solution of isopropanol, ethylene glycol butyl ether, and propylene glycol methyl ether acetate.

[0029] Preferably, in step S3, the titanium dioxide, polyester resin, dispersant and solvent are mixed in a mass ratio of 200:200:10:120.

[0030] Preferably, in step S3, the grinding is carried out using a ball mill, and the grinding time is 2-4 hours.

[0031] Preferably, in step S4, 100 parts of the organosilicon resin, 40-80 parts of organosilicon-modified hydroxyl acrylic resin coating and 100-150 parts of titanium dioxide paste are mixed.

[0032] More preferably, in step S4, 100 parts of the organosilicon resin, 50 parts of organosilicon-modified hydroxyl acrylic resin coating, and 150 parts of titanium dioxide paste are mixed.

[0033] This invention also discloses an application of a white fluorine-free photovoltaic coating, which is applied to the preparation of a coated white photovoltaic backsheet. The white fluorine-free photovoltaic coating is prepared by the preparation method of the white fluorine-free photovoltaic coating described above in this invention.

[0034] The application method is as follows: the white fluorine-free photovoltaic coating is applied to the front and back of the photovoltaic substrate and cured in an oven at 100-190℃ for 2-10 minutes to obtain the coated white photovoltaic backsheet.

[0035] Preferably, the photovoltaic substrate is a polypropylene terephthalate film, a polycarbonate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyethylene terephthalate film, or a polymethyl methacrylate film, and the photovoltaic substrate is a semi-transparent or white substrate.

[0036] The thickness of the photovoltaic substrate is 100-320μm, more preferably 265-300μm; the thickness of the white fluorine-free photovoltaic coating formed by curing is 8-25μm.

[0037] Preferably, the coating is performed using a roller coating method, employing a roll-to-roll processing technique to apply the white fluorine-free photovoltaic coating to the front and back sides of the photovoltaic substrate.

[0038] The organosilicon resin prepared in step S1 of this invention has the following characteristics:

[0039] 1. Low molecular weight: Organosilicon resins mostly exist as bimolecular oligomers with a molecular weight of 1000-3000 (e.g., 1500). The low molecular weight of organosilicon resins gives them higher reactivity and lower curing temperature, making them suitable for producing coated photovoltaic backsheets.

[0040] 2. High reactivity: Organosilicon resins have many active groups (such as chloroalkyl and silanol groups). Organosilicon resins have a large number of silanol groups (these silanol groups can enable organosilicon resins to self-crosslink, and other active groups, such as chloroalkyl groups, can also rapidly crosslink with other resins, increasing the reactivity). Without the need for catalysts or curing agents, they can rapidly crosslink and polymerize at a certain temperature, allowing the formed organosilicon coating to quickly reach surface dryness and shorten the process cycle.

[0041] 3. New properties: The synthesized organosilicon resin contains chloroalkyl groups. These chloroalkyl groups can undergo cross-linking reactions with other resins or photovoltaic substrate surfaces, increasing reactivity and forming cross-linked structures. This makes the coating more stable and the adhesion between the coating and the photovoltaic substrate surface is stronger. For example, after self-polymerization (such as self-condensation), the remaining Cl atoms and OH groups in the chloroalkyl-containing organosilicon resin... - Dechlorination reactions can occur, such as X3-Si-CH2-CH2-Cl+OH - It can generate X3-Si-OH, X3-Si-CH2-CH2-OH or X3-Si-CH=CH2. The newly generated hydroxyl groups can further undergo polymerization with the isocyanate curing agent; the generated vinyl groups can undergo self-polymerization or react with polyesters via free radicals.

[0042] 4. This silicone resin introduces nano-silica through tetraethyl orthosilicate, which gives the silicone resin high hardness and high gloss. When used in white fluorine-free photovoltaic coatings, it can make the resulting white photovoltaic backsheet have a higher 400-780nm reflectivity.

[0043] 5. The silicone resin has both soft segments (such as KH560, a type of silane coupling agent) and hard segments (such as tetraethyl orthosilicate), which makes the coating suitable for both softness and hardness, and can promote the adhesion of the coating on photovoltaic substrates.

[0044] Therefore, in this invention, the organosilicon resin prepared in step S1, combined with the tough organosilicon resin coating (i.e., organosilicon-modified hydroxyl acrylic resin coating) prepared in step S2 at a specific weight ratio, and further combined with the titanium dioxide paste prepared in step S3 at a specific weight ratio, can greatly improve the adhesion and bonding strength of the obtained white fluorine-free photovoltaic coating on photovoltaic substrates (such as PET film) (especially the adhesion after PCT aging and the water-resistant adhesion). Moreover, when this white fluorine-free photovoltaic coating is applied to photovoltaic substrates, it can quickly achieve surface drying of the coating, and also has excellent scratch resistance, environmental friendliness, weather resistance and UV+DH aging resistance, high hardness, and high 400-780nm reflectivity. It is especially suitable for preparing high-quality coated white photovoltaic backsheets, which can increase the reflection and utilization rate of sunlight and improve battery efficiency.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] The white fluorine-free photovoltaic coating of the present invention, through the combination of the above-prepared organosilicon resin, organosilicon-modified hydroxyl acrylic resin coating and titanium dioxide paste in specific weight ratios, and by controlling the weight ratio of each organosiloxane in the organosilicon resin, and by adding an appropriate amount of chloropropyltriethoxysilane to the base of tetraethyl orthosilicate, can greatly improve the adhesion and bonding strength of the obtained white fluorine-free photovoltaic coating on photovoltaic substrates (such as PET film), especially the adhesion and water-resistant adhesion after PCT aging are significantly improved. Moreover, the white fluorine-free photovoltaic coating is fluorine-free, environmentally friendly and non-toxic. When applied to photovoltaic substrates, the coating can achieve rapid surface drying and also has high hardness and excellent scratch resistance, environmental friendliness, weather resistance and aging resistance. The organosilicon resin also has high gloss and a large flash cross section. When used in the white fluorine-free photovoltaic coating, it can make the coating have a higher 400-780nm reflectivity, which can increase the reflection and utilization of sunlight and improve battery efficiency. It is particularly suitable for the preparation of high-quality coated white photovoltaic backsheets. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] The preparation method of a white fluorine-free photovoltaic coating in this embodiment includes the following preparation steps:

[0050] S1. Preparation of organosilicon resin:

[0051] S11. Tetraethyl orthosilicate, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldiethoxysilane, chloropropyltriethoxysilane, and KH560 are mixed sequentially in a weight ratio of 10:30:10:5:5:10 and stirred until homogeneous to obtain an organosilicon solution; water, acetic acid, and propylene glycol methyl ether are mixed in a weight ratio of 18:2:10 and stirred until homogeneous to obtain a mixed acid solution.

[0052] S12. While stirring, slowly add the mixed acid solution dropwise to the organosilicon solution over 30 minutes. Then continue stirring for 6 hours to allow the organosilicon alkane in the organosilicon solution to undergo hydrolysis and condensation in sequence, thus obtaining the organosilicon resin.

[0053] S2. Preparation of organosilicon-modified hydroxyl acrylic resin coatings:

[0054] The silicone-modified hydroxyl acrylic resin, isocyanate curing agent, alkyl-modified polysiloxane dispersant, polyether-modified silicone oil defoamer, silicone leveling agent, and solvent are mixed in a weight ratio of 40:25:0.5:0.2:0.6:20 and stirred evenly to obtain a silicone-modified hydroxyl acrylic resin coating.

[0055] The solvent is a mixed solution of isopropanol, ethylene glycol butyl ether, and propylene glycol methyl ether acetate.

[0056] S3. Preparation of titanium dioxide powder paste:

[0057] Titanium dioxide, polyester resin, BYK160 dispersant and ethyl acetate were mixed in a weight ratio of 200:200:10:120, and then ground in a ball mill for 2 hours. After that, the mixture was filtered through gauze to obtain a titanium dioxide slurry.

[0058] S4. Preparation of white fluorine-free photovoltaic coating:

[0059] 100 parts of the silicone resin from step S1, 100 parts of the silicone-modified hydroxyl acrylic resin coating from step S2, and 100 parts of titanium dioxide paste were mixed and stirred evenly to obtain the white fluorine-free photovoltaic coating of this embodiment.

[0060] The application of the white fluorine-free photovoltaic coating obtained in this embodiment is to apply the white fluorine-free photovoltaic coating to the preparation of a coated white photovoltaic backsheet. The specific application method is as follows:

[0061] A white fluorine-free photovoltaic coating is applied to the front and back of a photovoltaic substrate using a roller coating method and a roll-to-roll processing technique. The coating is then cured in segmented drying tunnels at 100℃, 140℃, 160℃, and 190℃ for 2 minutes at a linear speed of 90 meters per minute, to form a white fluorine-free photovoltaic coating with a thickness of 8-25μm (e.g., 13μm) on both the front and back of the photovoltaic substrate. This results in a white photovoltaic backsheet, which serves to bond and protect the photovoltaic module.

[0062] The photovoltaic substrate is a polyethylene terephthalate film with a thickness of 100-320μm (e.g., 270μm).

[0063] Example 2

[0064] The preparation method of the white fluorine-free photovoltaic coating in this embodiment is the same as that in Example 1, except that:

[0065] In step S4, instead of mixing, 100 parts of the silicone resin from step S1, 80 parts of the silicone-modified hydroxyl acrylic resin coating from step S2, and 100 parts of titanium dioxide paste are mixed and stirred evenly to obtain the white fluorine-free photovoltaic coating of this embodiment.

[0066] The application of the white fluorine-free photovoltaic coating prepared in this embodiment is specifically described in Example 1, which yields the white photovoltaic backsheet of this embodiment.

[0067] Example 3

[0068] The preparation method of the white fluorine-free photovoltaic coating in this embodiment is the same as that in Example 1, except that:

[0069] In step S4, instead of mixing 100 parts of the silicone resin from step S1 and 60 parts of the silicone-modified hydroxyl acrylic resin coating from step S2 with 100 parts of titanium dioxide paste, stir evenly to obtain the white fluorine-free photovoltaic coating of this embodiment.

[0070] The application of the white fluorine-free photovoltaic coating prepared in this embodiment is specifically described in Example 1, which yields the white photovoltaic backsheet of this embodiment.

[0071] Example 4

[0072] The preparation method of the white fluorine-free photovoltaic coating in this embodiment is the same as that in Example 1, except that:

[0073] In step S4, instead of mixing 100 parts of the silicone resin from step S1 and 40 parts of the silicone-modified hydroxyl acrylic resin coating from step S2 with 100 parts of titanium dioxide powder paste, stir evenly to obtain the white fluorine-free photovoltaic coating of this embodiment.

[0074] The application of the white fluorine-free photovoltaic coating prepared in this embodiment is specifically described in Example 1, which yields the white photovoltaic backsheet of this embodiment.

[0075] Example 5

[0076] The preparation method of the white fluorine-free photovoltaic coating in this embodiment is the same as that in Example 1, except that:

[0077] In step S4, instead of mixing 100 parts of the silicone resin from step S1, 50 parts of the silicone-modified hydroxyl acrylic resin coating from step S2, and 150 parts of titanium dioxide paste, stir evenly to obtain the white fluorine-free photovoltaic coating of this embodiment.

[0078] The application of the white fluorine-free photovoltaic coating prepared in this embodiment is specifically described in Example 1, which yields the white photovoltaic backsheet of this embodiment.

[0079] Example 6

[0080] The preparation method of the white fluorine-free photovoltaic coating in this embodiment is the same as that in Example 1, except that:

[0081] In step S11, the following steps are changed: Tetraethyl orthosilicate, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldiethoxysilane, chloropropyltriethoxysilane, and KH560 are mixed sequentially in a weight ratio of 20:30:10:5:5:10 and stirred until homogeneous to obtain an organosilicon solution.

[0082] The application of the white fluorine-free photovoltaic coating prepared in this embodiment is specifically described in Example 1, which yields the white photovoltaic backsheet of this embodiment.

[0083] Comparative Example 1

[0084] The preparation method of the white fluorine-free photovoltaic coating in this comparative example is the same as that in Example 1, except that:

[0085] Step S1, which involves preparing the silicone resin, is omitted. In step S4, 100 parts of commercially available methyl silicone resin (CAS: 67763-03-5), 100 parts of the silicone-modified hydroxyl acrylic resin coating from step S2, and 100 parts of titanium dioxide powder paste (i.e., replacing the silicone resin with commercially available methyl silicone resin) are stirred evenly to obtain the white fluorine-free photovoltaic coating of this comparative example.

[0086] The application method of the white fluorine-free photovoltaic coating prepared in this comparative example is as described in Example 1, which yields the white photovoltaic backsheet of this comparative example.

[0087] Comparative Example 2

[0088] The preparation method of the white fluorine-free photovoltaic coating in this comparative example is the same as that in Example 1, except that:

[0089] Step S2, which involves preparing the silicone-modified hydroxyl acrylic resin coating, is omitted. In step S4, instead, 100 parts of silicone resin, 100 parts of hydroxyl acrylic resin coating, and 100 parts of titanium dioxide powder paste are mixed (i.e., the silicone-modified hydroxyl acrylic resin coating is replaced with hydroxyl acrylic resin coating), and stirred evenly to obtain the white fluorine-free photovoltaic coating of this comparative example.

[0090] The application method of the white fluorine-free photovoltaic coating prepared in this comparative example is as described in Example 1, which yields the white photovoltaic backsheet of this comparative example.

[0091] Comparative Example 3

[0092] This comparative example uses existing fluorocarbon coatings to fabricate white photovoltaic backsheets, wherein the weight percentage of titanium dioxide in the existing fluorocarbon coating is the same as the weight percentage of titanium dioxide in the white fluorine-free photovoltaic coating of Example 1.

[0093] Comparative Example 4

[0094] The preparation method of the white fluorine-free photovoltaic coating in this comparative example is the same as that in Example 1, except that:

[0095] In step S11, chloropropyltriethoxysilane is replaced with propyltriethoxysilane, and the weight ratio of each organosiloxane used in the mixture is the same as in Example 1, so as to obtain the mixed acid solution of this comparative example.

[0096] The application method of the white fluorine-free photovoltaic coating prepared in this comparative example is as described in Example 1, which yields the white photovoltaic backsheet of this comparative example.

[0097] Performance testing

[0098] Performance tests were conducted on the white photovoltaic backsheets of Examples 1-6 and Comparative Examples 1-4, and the test results are shown in Table 1 below:

[0099] Table 1

[0100]

[0101] In Table 1, taking Example 1 as an example, its scratch resistance data of 20N means that the white photovoltaic backsheet can be scratched with a steel needle with a force of 20 Newtons without breaking.

[0102] As can be seen from Table 1:

[0103] Compared with Example 1, the white fluorine-free photovoltaic coatings of Examples 2-4, based on 100 parts of silicone resin and 100 parts of titanium dioxide paste, with an appropriate reduction in the weight of the added silicone-modified hydroxyl acrylic resin coating, can further improve the hardness and 400-780nm reflectivity of the white fluorine-free photovoltaic coating on the white photovoltaic backsheet, and can reduce the yellowing value after UV+DH aging.

[0104] Compared with Example 1, the white fluorine-free photovoltaic coating of Example 5, based on 100 parts of silicone resin, appropriately reduces the weight of the added silicone-modified hydroxyl acrylic resin coating and appropriately increases the weight of titanium dioxide paste, which can further improve the 400-780nm reflectance of the white fluorine-free photovoltaic coating on the white photovoltaic backsheet and further reduce the yellowing value after UV+DH aging.

[0105] Compared with Example 1, by appropriately changing the weight ratio of each organosiloxane in the organosilicon resin of Example 6 (such as increasing the weight ratio of tetraethyl orthosilicate to 20), the coating hardness and 400-780nm reflectivity of the obtained white fluorine-free photovoltaic coating can be further improved, and the yellowing value after UV+DH aging can be further reduced.

[0106] Compared to Example 1, the adhesion, boiling water resistance, 400-780nm reflectance, scratch resistance, and UV+DH aging resistance of the white fluorine-free photovoltaic coating of Comparative Example 1 (where the silicone resin was replaced with commercially available methyl silicone resin) decreased after PCT aging. The initial adhesion, PCT aging adhesion, boiling water resistance, 400-780nm reflectance, scratch resistance, and UV+DH aging resistance of the white fluorine-free photovoltaic coating of Comparative Example 2 (where the silicone-modified hydroxyl acrylic resin coating was replaced with hydroxyl acrylic resin coating) also showed a significant decrease. Therefore, the white fluorine-free photovoltaic coating of the present invention achieves high hardness and high 400-780nm reflectance, as well as excellent initial adhesion, PCT aging adhesion, boiling water resistance, scratch resistance, and UV+DH aging resistance through the synergistic combination of a specific silicone resin, silicone-modified hydroxyl acrylic resin coating, and titanium dioxide pigment.

[0107] Compared with existing white photovoltaic backsheets made of fluorocarbon coatings (Comparative Example 3), the adhesion, hardness, 400-780nm reflectance and scratch resistance of the white photovoltaic backsheets in Examples 1-4 after PCT aging are significantly improved, and the yellowing value after UV+DH aging is significantly reduced.

[0108] Compared with Example 1, after replacing chloropropyltriethoxysilane with propyltriethoxysilane in the silicone resin of Comparative Example 4, the adhesion, 400-780nm reflectivity, scratch resistance and UV+DH aging resistance of the resulting white fluorine-free photovoltaic coating decreased after PCT aging.

[0109] In summary, the white fluorine-free photovoltaic coating of the present invention, through the combination of the above-mentioned organosilicon resin, the above-mentioned organosilicon-modified hydroxyl acrylic resin coating and the above-mentioned titanium dioxide paste in a specific weight ratio, and by controlling the weight ratio of each organosiloxane in the organosilicon resin and adding an appropriate amount of chloropropyltriethoxysilane, results in a white fluorine-free photovoltaic coating that, when applied to a photovoltaic substrate, exhibits excellent initial adhesion, adhesion after PCT aging, water-resistant adhesion, scratch resistance, and UV+DH aging resistance. It also has high hardness and high reflectivity (400-780nm), making it particularly suitable for preparing coated white photovoltaic backsheets to increase the reflection and utilization of sunlight and improve battery efficiency.

[0110] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0111] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A process for the preparation of a white fluorine-free photovoltaic coating, characterized in that, The preparation method comprises the following steps: S1, preparation of the silicone resin: S11, Si(OR) 1 )4 tetraalkoxysilane, R 2 Si(OR 3 )3 alkyltrialkoxysilanes and phenyltrialkoxysilanes, R 4 2Si(OR 5 )2 dialkyldialkoxysilane, R 6 Si(OR 3 )3 Chloroalkyltrialkoxysilane, R 4 Si(OR 5 )3 epoxyalkyltrialkoxysilanes are mixed and stirred evenly to obtain an organosilicon solution; water, acetic acid and propylene glycol methyl ether are mixed in a weight ratio of 18:2:2-10 and stirred evenly to obtain a mixed acid solution; wherein the tetraalkoxysilane of Si(OR 1 )4 uses tetraethyl orthosilicate, R 2 the alkyltrialkoxysilane of Si(OR 3 )3 uses methyl triethoxysilane, R 2 the phenyltrialkoxysilane of Si(OR 3 )3 uses phenyl trimethoxysilane, R 4 the dialkyldialkoxysilane of 2Si(OR 5 )2 uses dimethyl diethoxysilane, R 6 the chloroalkyltrialkoxysilane of Si(OR 3 )3 uses chloropropyl triethoxysilane, R 4 the epoxyalkyltrialkoxysilane of Si(OR 5 )3 uses KH560; The tetraethyl orthosilicate, methyl triethoxysilane, phenyl trimethoxysilane, dimethyl diethoxysilane, chloropropyl triethoxysilane and KH560 are mixed in a weight ratio of 10-20:30:10:5:5:10; S12, slowly drop the mixed acid liquid into the silicone solution while stirring, continue to stir, and make the silicone solution undergo hydrolysis and polycondensation reaction, to obtain the silicone resin; S2, mix the silicone modified hydroxyl acrylic resin, isocyanate curing agent, dispersant, defoaming agent, leveling agent and solvent in a mass ratio of 30-40:15-35:0.5:0.2:0.6:20-30, stir uniformly, to obtain the silicone modified hydroxyl acrylic resin coating; S3, mix the titanium white powder, polyester resin, dispersant and solvent in a mass ratio of 100-200:200:10:120, grind, filter, to obtain the titanium white powder color paste; S4, mix 100 parts of the silicone resin, 20-100 parts of the silicone modified hydroxyl acrylic resin coating and 50-200 parts of the titanium white powder color paste, stir uniformly, to obtain the white fluorine-free photovoltaic coating.

2. A process for the preparation of a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S11, the tetraethyl orthosilicate, methyl triethoxysilane, phenyl trimethoxysilane, dimethyl diethoxysilane, chloropropyl triethoxysilane and KH560 are mixed in a weight ratio of 20:30:10:5:5:10; The water, acetic acid and propylene glycol methyl ether are mixed in a weight ratio of 18:2:

10.

3. A process for the preparation of a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S12, the dropping time is 30-60 minutes, and the continuous stirring time is 3-6 hours.

4. The method for preparing a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S2, the silicone modified hydroxyl acrylic resin, isocyanate curing agent, dispersant, defoaming agent, leveling agent and solvent are mixed in a mass ratio of 40:25:0.5:0.2:0.6:20; The dispersant is an alkyl modified polysiloxane dispersant, the defoaming agent is a polysiloxane defoaming agent or a polyether modified silicone oil defoaming agent, the leveling agent is a silicone leveling agent, and the solvent is a mixed solution of isopropyl alcohol, ethylene glycol butyl ether and propylene glycol methyl ether acetate.

5. The method for preparing a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S3, the titanium white powder, polyester resin, dispersant and solvent are mixed in a mass ratio of 200:200:10:

120.

6. The method for preparing a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S3, the grinding is performed by using a ball mill, and the grinding time is 2-4 hours.

7. The method for preparing a white fluorine-free photovoltaic coating according to claim 1, characterized in that, In step S4, 100 parts of the silicone resin, 40-80 parts of the silicone modified hydroxyl acrylic resin coating and 100-150 parts of the titanium white powder color paste are mixed.

8. Use of a white fluorine-free photovoltaic coating, characterized in that, The white fluorine-free photovoltaic coating is applied to prepare a coated white photovoltaic backboard, wherein the white fluorine-free photovoltaic coating is prepared by using the preparation method of the white fluorine-free photovoltaic coating in any one of claims 1-7; The application method is that the white fluorine-free photovoltaic coating is coated on the front and back surfaces of a photovoltaic substrate, and is cured in a 100-190℃ baking tunnel for 2-10 minutes, to obtain the coated white photovoltaic backboard.

9. Use of a white fluorine-free photovoltaic coating according to claim 8, characterized in that, The photovoltaic substrate is a polytrimethylene terephthalate film, a polycarbonate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyethylene terephthalate film or a polymethyl methacrylate film, and the photovoltaic substrate is a semi-transparent or white substrate; The thickness of the photovoltaic substrate is 100-320 μm; and the thickness of the white fluorine-free photovoltaic coating formed by curing is 8-25 μm.

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