Elastomeric polymer, outer transparent self-healing coating for photovoltaic transparent backsheet

Abstract

The present invention belongs to the technical field of photovoltaic backplanes, and specifically relates to an outer transparent self-repairing coating for a photovoltaic transparent backplane and a preparation method thereof. The self-repairing coating for a photovoltaic backplane comprises: 45 to 150 parts of an elastomeric polymer; 10 to 50 parts of a fluororesin; 0.3 to 0.5 parts of a leveling agent; 2 to 8 parts of a powder; 0.02 to 0.10 parts of a dispersant; 0.18 to 0.70 parts of an antioxidant; 4 to 10 parts of a UV additive; 25 to 50 parts of a polyisocyanate curing agent; and 20 to 60 parts of a solvent; wherein the elastomeric polymer has a terminal hydroxyl polybutadiene or a hydrogenated terminal hydroxyl polybutadiene as the main chain, hexamethylene diisocyanate as the middle segment, and sorbitol polyglycidyl ether as the end caps at both ends of the molecular chain. The self-repairing coating for a photovoltaic backplane of the present invention has a self-repairing property through the synthetic application and formula design of the self-repairing material, and the wear resistance of the outer layer coating of the transparent backplane is improved without reducing the weather resistance of the transparent backplane.

Description

[0001] This application is a divisional application with application number 202111529514.2, application date December 14, 2021, and invention name “Outer transparent self-healing coating for photovoltaic transparent backplane and preparation method thereof”. Technical Field

[0002] The present invention belongs to the technical field of photovoltaic backboards, and in particular relates to an outer transparent self-repairing coating for a photovoltaic transparent backboard and a preparation method thereof. Background Art

[0003] In recent years, with the gradual promotion of solar photovoltaics, the application of bifacial battery modules has become more and more widespread.

[0004] As the name implies, bifacial solar panels are panels that can generate electricity on both the front and back sides. When sunlight hits a bifacial panel, part of the light will be reflected by the surrounding environment to the back of the bifacial panel. This part of light can be absorbed by the back of the cell, thereby improving the efficiency of the cell's use of light and increasing the panel's power generation by 20-40%.

[0005] The current conventional double-sided double-glass battery module is composed of two pieces of glass, EVA or POE film and solar cell silicon wafers, which are laminated at high temperature by a laminator to form a composite layer. The solder strips and bus bars between the battery cells collect electrons to the lead ends to form a double-glass module.

[0006] Compared with double-glass modules, the application of transparent backplane in bifacial battery modules has irreplaceable advantages, such as lighter weight, low freight cost, lower module finished product fragmentation rate, and returnability. Summary of the invention

[0007] The invention provides an outer transparent self-repairing coating for a photovoltaic transparent back plate and a preparation method thereof.

[0008] In order to solve the above technical problems, the present invention provides a self-healing coating for a photovoltaic backplane, comprising the following components in parts by mass: an elastomeric polymer: 45 to 150 parts; a fluororesin: 10 to 50 parts; a leveling agent: 0.3 to 0.5 parts; a powder: 2 to 8 parts; a dispersant: 0.02 to 0.10 parts; an antioxidant: 0.18 to 0.70 parts; a UV additive: 4 to 10 parts; a polyisocyanate curing agent: 25 to 50 parts; and a solvent: 20 to 60 parts; wherein the elastomeric polymer has a terminal hydroxyl polybutadiene or a hydrogenated terminal hydroxyl polybutadiene as the main chain, hexamethylene diisocyanate as the middle segment, and both ends of the molecular chain are capped with sorbitol polyglycidyl ether.

[0009] On the other hand, the present invention also provides a method for preparing a self-healing coating for a photovoltaic backplane, comprising the following steps: first, mixing a solvent and a dispersant, and then sequentially adding a powder and an inorganic UV additive and stirring and dispersing them, so that the powder is stably suspended without precipitation, to obtain a dispersion slurry; mixing an elastomeric polymer, a fluororesin, a leveling agent, an antioxidant, and an organic UV additive, and adding the dispersion slurry, stirring and dispersing them, to obtain a semi-finished coating product; adding a polyisocyanate curing agent to the semi-finished coating product, stirring and dispersing them, to obtain a finished coating product; applying the finished coating product to the surface of a corona-treated PET single-coated product, baking and curing it into a film, and then performing a corona treatment, and after aging, obtaining a self-healing transparent backplane outer coating.

[0010] The beneficial effect of the present invention is that the self-repairing coating for the photovoltaic backplane of the present invention has self-repairing properties through the synthetic application and formula design of the self-repairing material, thereby improving the wear resistance of the outer layer coating of the transparent backplane.

[0011] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practicing the present invention.

[0012] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 It is a process flow chart of the preparation of the self-repairing coating for the photovoltaic back panel of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Since the double-glass module uses glass as the outermost layer of the module, when the glass is damaged, it cannot be repaired, resulting in high costs and poor recyclability. The present invention provides an outer transparent coating for a transparent backplane, which can realize the self-repair function of the outer transparent coating of the transparent backplane, so as to improve the service life and light utilization rate of the double-sided battery module.

[0017] The invention provides a self-repairing coating for a photovoltaic back panel, comprising the following components in parts by mass: 45 to 150 parts of an elastomeric polymer; 10 to 50 parts of a fluororesin; 0.3 to 0.5 parts of a leveling agent; 2 to 8 parts of a powder; 0.02 to 0.10 parts of a dispersant; 0.18 to 0.70 parts of an antioxidant; 4 to 10 parts of a UV additive; 25 to 50 parts of a polyisocyanate curing agent; and 20 to 60 parts of a solvent. The elastomeric polymer has a main chain of hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene, a middle segment of hexamethylene diisocyanate, and both ends of the molecular chain are capped with sorbitol polyglycidyl ether.

[0018] Specifically, the elastomeric polymer is the main film-forming material of the coating of the present invention. Through synthetic modification, the compatibility of terminal hydroxyl polybutadiene or hydrogenated terminal hydroxyl polybutadiene in the system can be improved, the adhesion of the coating to the PET substrate can be enhanced, and the self-healing property and wear resistance of the coating can also be greatly improved.

[0019] Among them, optionally, the elastomeric polymer includes the following components in parts by mass: 80 to 106 parts of terminal hydroxyl polybutadiene or hydrogenated terminal hydroxyl polybutadiene; 23 to 45 parts of hexamethylene diisocyanate; 18 to 39 parts of sorbitol polyglycidyl ether; 0.1 to 0.4 parts of organic bismuth catalyst; and 88 to 120 parts of propylene glycol methyl ether acetate.

[0020] The elastomeric polymer provided by the present invention is a polymer formed by polyurethane reaction of hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene, hexamethylene diisocyanate, sorbitol polyglycidyl ether, organic bismuth catalyst and propylene glycol methyl ether acetate under certain conditions.

[0021] Optionally, the molecular weight Mn of the hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene is 1000-4500.

[0022] Optionally, the fluororesin is one or more of tetrafluoroethylene-vinyl ether resin, tetrafluoroethylene-vinyl ester resin, trifluorochloroethylene-vinyl ether, trifluorochloroethylene-vinyl ester resin; and the hydroxyl value of the fluororesin is 50-80 mgKOH / g, such as Dongfu Chemical ZHM-2 or HLR-6 fluororesin, Changxing 41011 fluororesin, Daikin GK-570 fluororesin, etc.; the addition of fluororesin can cross-link with the elastomeric polymer under the action of the curing agent to form a tight network structure, further improving the weather resistance of the coating and allowing the self-healing property of the coating to be maintained for a long time.

[0023] Optionally, the powder is one or more of PTFE micropowder, PVDF micropowder, and silicon micropowder. Adding the powder into the coating can avoid the problem of anti-sticking after the finished product is rolled up.

[0024] Optionally, the solvent is one or more of butyl acetate, xylene, ethyl acetate, and propylene glycol methyl ether acetate. The solvent can dissolve the organic reactants to form a homogeneous system, so that each component in the coating is fully and evenly reacted and cross-linked. Solvents with different boiling points are selected according to the baking temperature to ensure that the coating is not sticky and has sufficient cross-linking and curing time.

[0025] Optionally, the leveling agent is one or more of an acrylic leveling agent, a silicone leveling agent, a fluorosilicone leveling agent and a high-boiling point solvent, such as BYK-300; the leveling agent migrates to the wet film surface through limited compatibility, affects the surface tension of the paint film, and promotes the coating to form a smooth and uniform coating during the drying process, improves the permeability of the coating to the substrate, and reduces spots, marks and other appearance defects produced during painting.

[0026] Optionally, the dispersant is one or more of anionic wetting dispersants, cationic wetting dispersants, nonionic wetting dispersants, amphoteric wetting dispersants, polymeric hyperdispersants, and controlled free radical hyperdispersants, such as Efka PU 4010. The addition of the dispersant can improve the surface properties of the powder particles, adjust the mobility of the powder particles, thereby improving the stability of the powder and avoiding flocculation and sedimentation.

[0027] Optionally, the antioxidant is one or more of hindered amines, hindered phenols, phosphites, thiodipropionates, and thiols, such as 1010 or 168 antioxidants. Since photovoltaic backsheets are used outdoors under high temperature conditions for a long time, the addition of antioxidants can delay or inhibit thermal oxidative decomposition of elastomeric polymers, delay polymer aging and extend their service life.

[0028] Optionally, the UV additives are divided into two types: organic and inorganic. The organic type is one or more of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines; organic UV additives can absorb ultraviolet rays and stabilize the generated free radicals to prevent the organic components in the coating from being damaged and degraded by ultraviolet rays; inorganic UV additives are one or more of nano zinc oxide and nano titanium dioxide; inorganic UV additives can shield ultraviolet rays, and the size between nanoparticles is comparable to or smaller than the light wave. Due to the size effect, the spacing between the conduction band and the valence band increases, so the light absorption is significantly enhanced. The addition of UV additives can effectively protect the molecular chains of the elastomeric polymer and other components in the coating, making the molecular chains less likely to break, avoiding problems such as yellowing, cracking, and stickiness of the coating, so as to further improve the self-healing property of the coating.

[0029] Optionally, the polyisocyanate curing agent is one or more of HDI trimer, H6XDI adduct, and XDI adduct; each molecule of the polyisocyanate curing agent carries two or more -NCO active groups, which can react with the -OH functional groups carried by the elastomeric polymer, fluororesin, etc. in the coating components to form a network cross-linked structure. At the same time, part of the -NCO will also form chemical bonds with the polar functional groups on the substrate to enhance the adhesion of the coating. The reaction cross-linking characteristics of the curing agent enable the self-healing property of the coating to be maintained stably for a long time.

[0030] On the other hand, Figure 1 As shown, the present invention provides a method for preparing a self-repairing coating for a photovoltaic backplane, comprising the following steps: firstly mixing a solvent and a dispersant, and then sequentially adding a powder and an inorganic UV additive and stirring and dispersing them, so that the powder is stably suspended without precipitation, to obtain a dispersion slurry; after mixing an elastomeric polymer, a fluororesin, a leveling agent, an antioxidant, and an organic UV additive, adding the dispersion slurry, stirring and dispersing them, to obtain a semi-finished coating product; adding a polyisocyanate curing agent to the semi-finished coating product, stirring and dispersing them, to obtain a finished coating product; applying the finished coating product to the surface of a corona-treated PET single-coated product, baking and curing it into a film, performing a corona treatment, and after aging, obtaining a self-repairing transparent backplane outer coating.

[0031] The preparation method of the elastomeric polymer comprises the following steps: adding propylene glycol methyl ether acetate into a reaction container, heating it to 90-100° C., sequentially adding hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene and an organic bismuth catalyst, stirring and dispersing, and obtaining a pre-dispersion liquid; adding hexamethylene diisocyanate into the pre-dispersion liquid, and reacting at a temperature of 105-110° C., adding sorbitol polyglycidyl ether, and reacting by stirring to obtain an elastomeric polymer.

[0032] Specifically, the reaction mechanism for preparing the elastomeric polymer is as follows:

[0033]

[0034] Example 1

[0035] Nitrogen was continuously introduced into the reactor to exclude air and water vapor, 93 parts of propylene glycol methyl ether acetate were added into the reactor, the temperature was raised to 95°C, 89 parts of terminal hydroxyl polybutadiene and 0.3 parts of organic bismuth catalyst were added in sequence, and the mixture was stirred at 300r / min for 0.5h to make it evenly dispersed; after the temperature of the reactor was stable, 31 parts of hexamethylene diisocyanate were added into the reactor at one time, the stirring speed and reaction temperature were maintained to react for 1.5h to make it fully react; the temperature was further raised to 110°C, 21 parts of sorbitol polyglycidyl ether were added into the reactor at one time, the stirring speed and reaction temperature were maintained for 2.5h; sampling was performed, and the NCO content was tested by titration (di-n-butylamine), and the reaction end point was considered when the NCO content was ≤0.1%, and the mixture was discharged and packaged for use after natural cooling.

[0036] Example 2

[0037] Nitrogen is continuously introduced into the reactor to exclude air and water vapor, 88 parts of propylene glycol methyl ether acetate are added into the reactor, the temperature is raised to 90°C, 89 parts of hydrogenated hydroxy-terminated polybutadiene and 0.2 parts of organic bismuth catalyst are added in sequence, and the mixture is stirred at 400r / min for 0.5h to make it evenly dispersed; after the temperature of the reactor is stable, 35 parts of hexamethylene diisocyanate are added into the reactor at one time, the stirring speed and reaction temperature are maintained to react for 1h to make it fully react; the temperature is further raised to 103°C, 18 parts of sorbitol polyglycidyl ether are added into the reactor at one time, the stirring speed and reaction temperature are maintained for 2h; sampling is performed, and the NCO content is tested by titration (di-n-butylamine), and the reaction end point is considered when the NCO content is ≤0.1%, and the mixture can be discharged and packaged for use after natural cooling.

[0038] Example 3

[0039] Nitrogen is continuously introduced into the reactor to exclude air and water vapor, 120 parts of propylene glycol methyl ether acetate are added into the reactor, the temperature is raised to 100°C, 89 parts of hydrogenated hydroxy-terminated polybutadiene and 0.4 parts of organic bismuth catalyst are added in sequence, and the mixture is stirred at 200r / min for 0.5h to make it evenly dispersed; after the temperature of the reactor is stable, 45 parts of hexamethylene diisocyanate are added into the reactor at one time, the stirring speed and reaction temperature are maintained to react for 2h to make it fully react; the temperature is further raised to 108°C, 39 parts of sorbitol polyglycidyl ether are added into the reactor at one time, the stirring speed and reaction temperature are maintained for 3h; sampling is performed, and the NCO content is tested by titration (di-n-butylamine), and the reaction end point is considered when the NCO content is ≤0.1%, and the mixture can be discharged and packaged for use after natural cooling.

[0040] Example 4

[0041] Nitrogen was continuously introduced into the reactor to exclude air and water vapor, 115 parts of propylene glycol methyl ether acetate were added into the reactor, the temperature was raised to 93°C, 89 parts of terminal hydroxyl polybutadiene and 0.1 parts of organic bismuth catalyst were added in sequence, and the mixture was stirred at 500r / min for 0.5h to make it evenly dispersed; after the temperature of the reactor was stable, 23 parts of hexamethylene diisocyanate were added into the reactor at one time, the stirring speed and reaction temperature were maintained to react for 1.8h to make it fully react; the temperature was further raised to 105°C, 27 parts of sorbitol polyglycidyl ether were added into the reactor at one time, the stirring speed and reaction temperature were maintained for 2.7h; sampling was performed, and the NCO content was tested by titration (di-n-butylamine), and the reaction end point was considered when the NCO content was ≤0.1%, and the mixture was discharged and packaged for use after natural cooling.

[0042] Example 5

[0043] 45 parts of butyl acetate solvent and 0.05 parts of polymer superdispersant are mixed and stirred evenly, and 2.25 parts of PVDF micropowder, 2.25 parts of silicon micropowder and 0.15 parts of nano zinc oxide are added in sequence; during the feeding process, the stirrer speed is gradually increased to 2000 rpm and maintained for 20 minutes to ensure that the powder is evenly dispersed and stably suspended without precipitation, thereby completing the preparation of the dispersion slurry.

[0044] 140 parts of the elastomeric polymer prepared in Example 1, 36 parts of fluororesin, 0.45 parts of acrylic leveling agent, 0.3 parts of hindered phenol antioxidant, 3.375 parts of triazines and 1.125 parts of benzotriazole organic UV additives were mixed and dispersed at a high speed of 1000 rpm for 10 minutes, and then the above dispersion slurry was added and dispersed at a high speed of 2000 rpm for 45 minutes to obtain a semi-finished coating.

[0045] Add 38 parts of polyisocyanate curing agent to the semi-finished coating, stir at 1000 rpm for 10 min and adjust the viscosity to obtain the finished coating; apply the finished coating to the surface of the corona-treated PET single-coated product, bake in an oven at 150°C for 2 min, perform corona treatment at a corona intensity of 4.5 kW, and then mature at 60°C for 48 h.

[0046] Example 6

[0047] 24 parts of butyl acetate and 24 parts of PMA are used as solvents, 0.1 parts of polymer hyperdispersant are added, mixed and stirred evenly, and 1.875 parts of PVDF micropowder, 1.875 parts of PTFE micropowder and 3.75 parts of silicon micropowder and 0.12 parts of nano zinc oxide are added in sequence; during the feeding process, the speed of the stirrer is gradually increased to 2000 rpm and maintained for 10 minutes to make the powder dispersed evenly and stably suspended without precipitation, thereby completing the preparation of the dispersion slurry.

[0048] 122 parts of the elastomeric polymer prepared in Example 2, 29 parts of fluororesin, 0.5 parts of acrylic leveling agent, 0.45 parts of hindered phenol antioxidant, and 6 parts of triazine organic UV additive were mixed and dispersed at a high speed of 1000 rpm for 30 minutes, and then the above dispersion slurry was added and dispersed at a high speed of 2000 rpm for 60 minutes to obtain a semi-finished coating.

[0049] Add 42 parts of polyisocyanate curing agent to the semi-finished coating, stir at 1000 rpm for 10 min and adjust the viscosity to obtain the finished coating; apply the finished coating to the surface of the corona-treated PET single-coated product, bake in an oven at 160°C for 2 min, perform corona treatment at a corona intensity of 4.5 kW, and then mature at 60°C for 48 h.

[0050] Example 7

[0051] 32 parts of PMA solvent and 0.07 parts of polymer hyperdispersant were mixed and stirred evenly, and 2.17 parts of PTFE micropowder, 4.33 parts of silicon micropowder and 0.1 part of nano titanium dioxide were added in sequence; during the feeding process, the stirrer speed was gradually increased to 2000 rpm and maintained for 30 minutes to ensure that the powder was evenly dispersed and stably suspended without precipitation, thereby completing the preparation of the dispersion slurry.

[0052] 132 parts of the elastomeric polymer prepared in Example 3, 25 parts of fluororesin, 0.4 parts of silicone leveling agent, 0.36 parts of hindered phenol antioxidant, 4.58 parts of triazines and 0.92 parts of salicylate organic UV additives were mixed and dispersed at a high speed of 1000 rpm for 30 minutes, and then the above dispersion slurry was added and dispersed at a high speed of 2000 rpm for 30 minutes to obtain a semi-finished coating.

[0053] Add 38 parts of polyisocyanate curing agent to the semi-finished coating, stir at 1000 rpm for 10 min and adjust the viscosity to obtain the finished coating; apply the finished coating to the surface of the corona-treated PET single-coated product, bake in an oven at 160°C for 2 min, perform corona treatment at a corona intensity of 4.5 kW, and then mature at 60°C for 48 h.

[0054] Example 8

[0055] Mix 20 parts of butyl acetate solvent and 0.03 parts of polymer superdispersant and stir evenly, then add 1 part of PVDF micropowder, 1 part of silicon micropowder and 0.6 part of nano zinc oxide in sequence; during the addition process, gradually increase the stirrer speed to 2000 rpm and maintain it for 20 minutes to make the powder dispersed evenly and stably suspended without precipitation, thus completing the preparation of the dispersion slurry.

[0056] 45 parts of the elastomeric polymer prepared in Example 4, 10 parts of fluororesin, 0.3 parts of acrylic leveling agent, 0.2 parts of hindered phenol antioxidant, 2.1 parts of triazines and 1.3 parts of benzotriazole organic UV additives were mixed and dispersed at a high speed of 1000 rpm for 10 minutes, and then the above dispersion slurry was added and dispersed at a high speed of 2000 rpm for 45 minutes to obtain a semi-finished coating.

[0057] Add 25 parts of polyisocyanate curing agent to the semi-finished coating, stir at 1000 rpm for 10 min and adjust the viscosity to obtain the finished coating; apply the finished coating to the surface of the corona-treated PET single-coated product, bake in an oven at 150°C for 2 min, perform corona treatment at a corona intensity of 4.5 kW, and then mature at 60°C for 48 h.

[0058] The coatings prepared in the above embodiments were tested for relevant properties, and the data are summarized in Table 1.

[0059] Table 1 Summary of performance data of the coatings prepared in each embodiment

[0060]

[0061] It can be seen from the data in Table 1 that in terms of light transmittance, the light transmittance of the transparent backplane prepared in each embodiment is basically the same as that of glass, and slightly higher than that of the coated and composite backplanes; in terms of self-repair, the transparent backplane prepared in each embodiment has thermal repair properties, while ordinary backplanes do not have self-repair properties. The present invention can perform thermal repair on scratches caused by outdoor use and workers' installation operations.

[0062] In summary, the self-repairing coating for photovoltaic backplane provided by the present invention has self-repairing properties through the synthetic application and formula design of self-repairing materials, thereby improving the wear resistance of the outer coating of the transparent backplane.

[0063] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A self-repairing coating for photovoltaic backsheet, characterized in that: The composition comprises the following components in parts by weight: Elastomer polymer: 45-150 parts; Fluororesin: 10-50 parts; Leveling agent: 0.3-0.5 parts; Powder: 2-8 parts; Dispersant: 0.02-0.10 parts; Antioxidant: 0.18-0.70 parts; UV additive: 4-10 parts; Polyisocyanate curing agent: 25-50 parts; Solvent: 20-60 parts; The elastomeric polymer has hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene as the main chain, hexamethylene diisocyanate as the middle segment, and both ends of the molecular chain are capped with sorbitol polyglycidyl ether; The preparation method of the elastomeric polymer comprises the following steps: Propylene glycol methyl ether acetate is added into a reaction container, the temperature is raised, and terminal hydroxyl polybutadiene or hydrogenated terminal hydroxyl polybutadiene and an organic bismuth catalyst are added in sequence, and the mixture is stirred and dispersed to prepare a pre-dispersion liquid; Adding hexamethylene diisocyanate to the pre-dispersed liquid and reacting at a temperature keeping warm to obtain a pre-reaction liquid; The pre-reaction solution is heated to 105-110° C., sorbitol polyglycidyl ether is added, and stirred for reaction to obtain an elastomeric polymer; The elastomeric polymer comprises the following components in parts by weight: Hydroxyl-terminated polybutadiene or hydrogenated hydroxy-terminated polybutadiene: 80-106 parts; Hexamethylene diisocyanate: 23-45 parts; Sorbitol polyglycidyl ether: 18-39 parts; Organic bismuth catalyst: 0.1-0.4 parts; Propylene glycol methyl ether acetate: 88-120 parts.

2. The self-repairing coating according to claim 1, characterized in that: The molecular weight Mn of the hydroxyl-terminated polybutadiene or hydrogenated hydroxyl-terminated polybutadiene is 1000-4500.

3. The self-repairing coating according to claim 1, characterized in that: The fluororesin is one or more of tetrafluoroethylene-vinyl ether resin, tetrafluoroethylene-vinyl ester resin, chlorotrifluoroethylene-vinyl ether, and chlorotrifluoroethylene-vinyl ester resin; and The fluororesin has a hydroxyl value of 50 to 80 mgKOH / g.

4. The self-repairing coating according to claim 1, characterized in that The powder material is one or more of PTFE micropowder, PVDF micropowder and silicon micropowder.

5. The self-repairing coating according to claim 1, characterized in that: The solvent is one or more of butyl acetate, xylene, ethyl acetate, and propylene glycol methyl ether acetate.

6. A method for preparing a self-repairing coating for a photovoltaic backsheet according to any one of claims 1 to 5, characterized in that: The following steps are involved: First, mix the solvent and dispersant, then add the powder and inorganic UV additive in sequence, stir and disperse, so that the powder is stably suspended without precipitation, and obtain a dispersion slurry; After mixing the elastomeric polymer, fluororesin, leveling agent, antioxidant and organic UV additive, adding the dispersion slurry, stirring and dispersing, a semi-finished coating product is obtained; Adding a polyisocyanate curing agent to the semi-finished coating, stirring and dispersing, and obtaining a finished coating; The finished coating product is applied to the surface of the corona-treated PET single-coating product, baked and cured to form a film, and then corona-treated and aged to obtain the outer coating of the self-repairing transparent backplane; The UV additives are divided into two types: organic and inorganic. The organic additives are one or more of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines.

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