White photovoltaic backsheet powder coating and preparation method of white photovoltaic backsheet

Abstract

The present invention discloses a white photovoltaic backsheet powder coating and a method for preparing the same. The powder coating comprises the following components, by weight: a titanium dioxide-resin mixture or a titanium dioxide-modified resin: 66-95%; a curing agent: 3-27%; a catalyst: 0-2%; a defoamer: 0-2%; a leveling agent: 0-2%; an antioxidant: 0.2-1.5%; an ultraviolet light absorber: 0-3%; a light stabilizer: 0-2%; and a flow aid: 0-1%. The present invention prepares a high-reflectivity white photovoltaic backsheet by adding titanium dioxide to the powder coating formula. Preferably, the titanium dioxide is added during the synthesis of the selected resin, or the titanium dioxide and resin are premixed by extrusion and uniformly mixed with the resin in advance. This reduces the effect of the titanium dioxide in the powder coating formula on the overall viscosity of the powder coating. The resulting powder coating has a better dispersion effect and can better wet the fiberglass cloth, thereby achieving a higher reflectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic materials, and in particular to a white photovoltaic backboard powder coating and a preparation method of the white photovoltaic backboard. Background Art

[0002] Existing lightweight backsheets mainly include three categories: laminated backsheets, coated backsheets and resin glass fiber cloth composite backsheets; the first category is mainly prepared by bonding fluorine films such as PVF, PVDF or ETFE with PET substrates through adhesives to prepare laminated backsheets; the second category is coated backsheets developed by coating with polytetrafluoroethylene resin PTFE or trifluorochloroethylene resin CTFE as the main resin and compounding it with PET substrates; the above two backsheet solutions have the problem of high costs; the third category is a composite material obtained by compounding coatings or powder coatings with glass fiber cloth as the backsheet material solution for photovoltaic modules.

[0003] Category 1 and Category 2: Fluoropolymers such as polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF) are inherently expensive, leading to high raw material costs for fluorinated backsheets. Traditional backsheet production involves laminating prefabricated fluoropolymer films onto a PET substrate to form a "sandwich" structure, a complex process. To achieve a durable laminated backsheet, a primer or adhesive layer may need to be pre-coated on the substrate before lamination is completed under heat and pressure, adding complexity and cost to the production process. Fluorocarbons have a strong chemical structure and are difficult to degrade over long periods of time in landfills, becoming a new source of white pollution. Fluorine's future use will be increasingly restricted. Furthermore, most of these two categories lack fiberglass support, resulting in poor mechanical properties such as stiffness, impact resistance, and tensile strength. They often require the addition of a photovoltaic frame. Furthermore, during subsequent lamination of the photovoltaic module, their softness and low stiffness can lead to significant wrinkles on the back of the backsheet, impacting both appearance and performance. The third type of backsheet, while glass fiber provides excellent support, contains volatile organic compounds (VOCs) in some coatings, which can evaporate into the air during construction and use, causing air pollution. Powder coatings do not present these environmental issues and are made from weather-resistant resins such as acrylics, super-weather-resistant polyesters, and fluorocarbons. However, these backsheets are typically transparent, preventing sunlight from penetrating the cells from being reflected back, wasting some of the sunlight. To overcome this drawback, a white POE or EVA film is typically applied to the backsheet, which undoubtedly increases costs. Furthermore, under harsh environmental conditions such as high temperature, high humidity, and strong ultraviolet light, the adhesion between the white film and the backsheet material can decrease to varying degrees. This can not only cause loosening of the module's internal structure but also lead to circuit shorts and other problems, compromising the safe and stable operation of the photovoltaic system. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a white photovoltaic backsheet powder coating and a method for preparing the white photovoltaic backsheet.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A white photovoltaic backplane powder coating comprises the following components in percentage by weight: a titanium dioxide-resin mixture or a titanium dioxide-modified resin: 66-95%; a curing agent: 3-27%; a catalyst: 0-2%; a defoaming agent: 0-2%; a leveling agent: 0-2%; an antioxidant: 0.2-1.5%; an ultraviolet light absorber: 0-3%; a light stabilizer: 0-2%; and a flow aid: 0-1%.

[0007] As a preferred embodiment, the preparation method of the titanium dioxide-resin mixture is:

[0008] After titanium dioxide and resin are premixed, they are melt-extruded in a twin-screw extruder and crushed into flakes.

[0009] As a preferred solution, the aspect ratio of the twin-screw extruder is (15-50):1, the extrusion temperature is 30-100°C, and the screw speed is 600-1500 rpm.

[0010] As a preferred embodiment, the preparation method of the titanium dioxide modified resin is:

[0011] Before the distillation stage of resin synthesis, add titanium dioxide and stir at a speed of 1000-1500 rpm for 15-30 minutes. After stirring and mixing evenly, remove the solvent and crush it.

[0012] As a preferred embodiment, the resin is a glycidyl methacrylate acrylic resin or a carboxyl polyester resin. The glycidyl methacrylate acrylic resin has an epoxy equivalent of 300-600 g / eq, preferably 350-420 g / eq, a glass transition temperature of 40-60°C, preferably 45-55°C, a viscosity of 2000-8000 mPa·s / 180°C, preferably 3000-6000 mPa·s / 180°C; and a softening point of 95-115°C. The carboxyl polyester resin has an acid value of 20-80 mgKOH / g, preferably 30-55 mgKOH / g, a viscosity of 1500-4000 mPa·s / 200°C, and a glass transition temperature of 60-70°C.

[0013] As a preferred embodiment, when the resin is GMA acrylic resin, the weight percentage of the titanium dioxide-resin mixture or the titanium dioxide modified resin in the white photovoltaic backplane powder coating is 66~85%, the amount of the titanium dioxide is 5~10% of the total weight of the resin and titanium dioxide, the weight percentage of the curing agent in the white photovoltaic backplane powder coating is 12~27%, and the curing agent is a long-chain diacid carboxylic acid, preferably at least one of sebacic acid, undecane dioic acid, dodecanedioic acid, and tridecanedioic acid, and further preferably dodecanedioic acid; when the resin is a carboxyl polyester resin, the weight percentage of the titanium dioxide-resin mixture or the titanium dioxide modified resin in the white photovoltaic backplane powder coating is 81~95%, the amount of the titanium dioxide is 4~9% of the total weight of the resin and titanium dioxide, the weight percentage of the curing agent in the white photovoltaic backplane powder coating is 3~9%, and the curing agent is triglycidyl isocyanurate or hydroxyalkylamide.

[0014] As a preferred solution, the median particle size of the titanium dioxide does not exceed 1 μm, preferably 0.4-0.8 μm, and the crystal form is rutile or anatase, preferably rutile.

[0015] As a further preferred solution, the production method of the titanium dioxide is preferably chloride process titanium dioxide, and further preferred is titanium dioxide treated with silicon-aluminum composite coating, because titanium dioxide has better weather resistance and better dispersibility after surface treatment.

[0016] As a preferred embodiment, the catalyst is a catalyst capable of catalyzing the reaction of carboxyl group -COOH and epoxy group -CH(O)CH2, preferably a quaternary ammonium salt catalyst, a phosphorus catalyst or an imidazole catalyst, wherein the quaternary ammonium salt catalyst is tetrabutylammonium bromide, the phosphorus catalyst is triphenylphosphine or triphenylphosphine bromide, and the imidazole catalyst is dimethylimidazole; the defoaming agent is benzoin and its modified products, polyamide wax or polyolefin wax, wherein the modified benzoin product is preferably PowderAdd® produced by Tianwo Company. D900 low-temperature degassing agent; the leveling agent is an acrylic leveling agent, a polyether leveling agent or a silicone leveling agent; the antioxidant is one or a mixture of hindered phenol and phosphite antioxidants, wherein the hindered phenol antioxidant is the main antioxidant and the phosphite antioxidant is the auxiliary antioxidant; the ultraviolet light absorber is a benzophenone, a benzotriazole or a triazine; the light stabilizer is a hindered amine light stabilizer; the flow aid is a dry powder flow aid selected from one or more of aluminum hydroxide, aluminum oxide, fumed silica, and organic wax powder.

[0017] A method for preparing the white photovoltaic backsheet powder coating as described above comprises the following steps:

[0018] After premixing the raw materials evenly, transfer them into a twin-screw extruder for melt extrusion to obtain a molten material;

[0019] The molten material is pressed and cooled to obtain a flake material;

[0020] The flake material is crushed, ground into powder, sieved, and set aside. The median particle size of the obtained powder coating is 60-200 μm, and most preferably 100-150 μm;

[0021] The aspect ratio of the twin-screw extruder is (15-50):1, the extrusion temperature does not exceed 100°C, preferably 60-90°C, and the screw speed is 1000-1500 rpm.

[0022] A method for preparing a white photovoltaic backsheet comprises the following steps:

[0023] The aforementioned white photovoltaic backplane powder coating is sprinkled on the glass fiber cloth, heated at 100-150°C to melt the powder coating and bond it to the glass fiber cloth for pre-impregnation, then cold pressed to evenly infiltrate and composite the powder coating and glass fiber cloth, and finally cut to obtain a powder glass fiber composite backplane, i.e., a white photovoltaic backplane.

[0024] As a preferred solution, the glass fiber used in the glass fiber cloth is E glass fiber, the diameter of the monofilament ranges from 5 to 10 μm, and the selected glass fiber weight is ≤200g / m 2 , preferably 100~200g / m 2 , powder coating powder amount does not exceed 600 g / m 2 , preferably 350~450g / m 2 .

[0025] Compared to existing technologies, the present invention offers the following advantages: High-reflectivity white photovoltaic backsheets are prepared by adding titanium dioxide to the powder coating formula. Titanium dioxide can be added during the resin synthesis stage or pre-mixed with the selected resin in an extruder, allowing for uniform mixing with the resin in advance. This reduces the effect of titanium dioxide on the overall viscosity of the powder coating. The resulting powder coating has better dispersion and can better wet the fiberglass cloth, resulting in higher reflectivity. This innovative approach not only significantly improves the performance of the backsheet but also increases the power of the photovoltaic module. Furthermore, the removal of the white adhesive film avoids the problem of insufficient adhesion between the white adhesive film and the backsheet material in harsh environments, effectively reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0027] Figure 1 The structure of the photovoltaic module in the prior art is compared with the photovoltaic module prepared using a white photovoltaic backsheet according to the present invention.

[0028] In the figure: 1. Transparent front panel; 2. Solar cell; 3. Transparent back panel; 4. Transparent adhesive film; 5. White adhesive film; 6. White photovoltaic back panel. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0030] 1. Example 1

[0031] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0032] Titanium dioxide (rutile type, median particle size of 0.4 μm) was added to a GMA acrylic resin (viscosity of 4500-5000 mPa·s / 180°C, epoxy equivalent weight of 400 g / eq, glass transition temperature of 55°C, and softening point of 95-105°C) before distillation during synthesis. The mixture was stirred at 1200 rpm for 30 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified GMA acrylic resin (the epoxy equivalent weight of the titanium dioxide-modified GMA acrylic resin was slightly higher than that of the GMA acrylic resin, but this did not affect the technical effect, and the glass transition temperature, softening point, and viscosity remained almost unchanged). The amount of titanium dioxide added was 6% of the total weight of the titanium dioxide and GMA resin.

[0033] The following ingredients were prepared according to weight percentage: titanium dioxide modified GMA acrylic resin: 75%, dodecanedioic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX 1076): 0.5%, phosphite (CHINOX 626): 0.5%, triazine UV absorber Tinuvin® 405: 1.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and then mixed to obtain a mixture.

[0034] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zones were set at 65 / 70 / 75 / 80°C (four-stage temperature control), the screw speed was 1200 rpm, and extrusion was performed to obtain a molten material;

[0035] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0036] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 120 μm.

[0037] The powder coating prepared in this example is used to prepare a white photovoltaic backsheet. The specific method is as follows: 160g / m² glass fiber cloth with a single filament diameter of 7μm is selected, and a powder coating amount of 350g / m² is applied to the glass fiber cloth using a powdering machine or similar equipment. The powder coating is then applied to the glass fiber cloth using a drying oven set at 120°C for 60 seconds. The powder melts and then pre-impregnates the glass fiber cloth. At the end of the drying oven, cold rollers are used to cold-press the powder coating and glass fiber cloth, evenly pre-impregnating the powder coating and pre-impregnating the cloth. The powder coating can then be cut into desired shapes and sizes through a cutting process at the end.

[0038] 2. Example 2

[0039] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0040] GMA acrylic resin (viscosity of 4500-5000 mPa·s / 180°C, epoxy equivalent weight of 400 g / eq, glass transition temperature of 55°C, softening point of 95-105°C) and titanium dioxide (rutile type, median particle size of 0.4 μm) were pre-mixed and then transferred into a twin-screw extruder (length-to-diameter ratio of 36:1) with temperature zones set at 30 / 70 / 90 / 80°C (four-stage temperature control) and a speed of 1200 rpm for melt extrusion. The mixture was then crushed into flakes to obtain a titanium dioxide-GMA acrylic resin mixture, wherein the amount of titanium dioxide added was 6% of the total weight of the titanium dioxide and GMA acrylic resin.

[0041] The following ingredients are prepared according to weight percentage: titanium dioxide-GMA acrylic resin mixture: 75%, dodecanedioic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX 1076): 0.5%, phosphite (CHINOX 626): 0.5%, triazine UV absorber Tinuvin® 405: 1.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and then mixed to obtain a mixture.

[0042] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zones were set at 65 / 70 / 75 / 80°C (four-stage temperature control), the screw speed was 1200 rpm, and extrusion was performed to obtain a molten material;

[0043] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0044] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 120 μm.

[0045] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this example is the same as that in Example 1.

[0046] 3. Example 3

[0047] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0048] The following ingredients are prepared according to weight percentage: GMA resin: 70.5%, titanium dioxide: 4.5%, dodecanedioic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX 1076): 0.5%, phosphite (CHINOX626): 0.5%, triazine UV absorber Tinuvin® 405: 1.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and then mixed to obtain a mixture.

[0049] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zones were set at 65 / 70 / 75 / 80°C (four-stage temperature control), the screw speed was 1200 rpm, and extrusion was performed to obtain a molten material;

[0050] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0051] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 120 μm.

[0052] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this example is the same as that in Example 1.

[0053] 4. Example 4

[0054] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0055] Titanium dioxide (rutile type, median particle size of 0.4 μm) was added to a GMA acrylic resin (viscosity of 5000-5500 mPa·s / 180°C, epoxy equivalent weight of 300 g / eq, glass transition temperature of 60°C, and softening point of 100-105°C) before distillation during synthesis. The mixture was stirred at 1000 rpm for 30 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified GMA acrylic resin. The amount of titanium dioxide added was 5% of the total weight of the titanium dioxide and the GMA resin.

[0056] The following ingredients were prepared according to weight percentage: titanium dioxide modified GMA acrylic resin: 66%, tridecanedioic acid: 26.5%, benzoin: 1.5%, acrylic leveling agent: 1.5%, hindered phenol antioxidant (CHINOX 1076): 1%, phosphite (CHINOX 626): 0.5%, benzophenone UV absorber Chimassorb® 81: 1.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, polyamide wax defoamer: 1.0%, and flow aid aluminum oxide C: 0.5%, and then mixed to obtain a mixture.

[0057] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 15:1), the temperature zones were set to 30 / 70 / 75 / 65°C (four-stage temperature control), the screw speed was 1000 rpm, and extrusion was performed to obtain a molten material;

[0058] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0059] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 60 μm.

[0060] The powder coating prepared in this example is used to prepare a white photovoltaic backsheet. The specific method is as follows: 100g / m² glass fiber cloth with a single filament diameter of 7μm is selected, and a powder coating amount of 350g / m² is applied to the glass fiber using a powder coating machine or similar equipment. The powder coating is then applied to the glass fiber using a drying oven set at 100°C for 80 seconds. The powder melts and then pre-impregnates the glass fiber. At the end of the drying oven, cold rollers are used to cold-press the powder coating and glass fiber, evenly pre-impregnating the powder coating and pre-impregnating the glass fiber. The powder coating can then be cut into desired shapes and sizes through a cutting process at the end.

[0061] V. Example 5

[0062] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0063] Titanium dioxide (rutile type, median particle size of 0.4 μm) was added to a GMA acrylic resin (viscosity of 5000-5500 mPa·s / 180°C, epoxy equivalent weight of 300 g / eq, glass transition temperature of 60°C, and softening point of 100-105°C) before distillation. The mixture was stirred at 1500 rpm for 15 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified GMA acrylic resin. The amount of titanium dioxide added was 5% of the total weight of the titanium dioxide and the GMA resin.

[0064] The following ingredients are prepared according to weight percentage: titanium dioxide modified GMA acrylic resin: 71%, tridecanedioic acid: 27%, benzoin: 0.5%, hindered phenol antioxidant (CHINOX 1076): 0.2%, ultraviolet absorber Tinuvin® 405: 0.5%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and polyolefin wax defoamer: 0.3%, and then mixed to obtain a mixture.

[0065] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 24:1), the temperature zones were set at 30 / 70 / 75 / 65°C (four-stage temperature control), the screw speed was 1200 rpm, and extrusion was performed to obtain a molten material;

[0066] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0067] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 150 μm.

[0068] The powder coating prepared in this example is used to prepare a white photovoltaic backsheet. The specific method is as follows: 200g / m² glass fiber cloth with a single filament diameter ranging from 5 to 9μm is selected, and a powder coating amount of 450g / m² is applied to the glass fiber using a powder coating machine or similar equipment. The powder coating is then applied to the glass fiber using a drying oven set at 150°C for 30 seconds. The powder melts and then pre-impregnates the glass fiber. After cold pressing with cold rollers at the end of the drying oven, the powder coating and glass fiber are evenly pre-impregnated and composited. The finished product can then be cut into desired shapes and sizes through a cutting process at the end.

[0069] VI. Example 6

[0070] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0071] Titanium dioxide (rutile type, median particle size of 0.4 μm) was added to a GMA acrylic resin (viscosity of 2000-2500 mPa·s / 180°C, epoxy equivalent weight of 600 g / eq, glass transition temperature of 45°C, and softening point of 95-100°C) before distillation during synthesis. The mixture was stirred at 1300 rpm for 15 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified GMA acrylic resin. The amount of titanium dioxide added was 10% of the total weight of the titanium dioxide and the GMA resin.

[0072] The following ingredients were prepared according to weight percentage: titanium dioxide modified GMA acrylic resin: 80%, sebacic acid: 12%, dimethylimidazole: 0.3%, benzoin: 1%, silicone leveling agent: 2%, hindered phenol antioxidant (CHINOX 1076): 0.5%, phosphite antioxidant (CHINOX 626): 0.2%, benzotriazole UV absorber Tinuvin® 928: 2.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, polyolefin wax defoamer: 1%, and flow aid gas silica: 0.5%, and then mixed to obtain a mixture.

[0073] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 36:1), the temperature zones were set at 60 / 90 / 100 / 70°C (four-stage temperature control), the screw speed was 1500 rpm, and extrusion was performed to obtain a molten material;

[0074] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0075] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 200 μm.

[0076] The powder coating prepared in this example is used to prepare a white photovoltaic backsheet. The specific method is as follows: 160g / m² glass fiber cloth with a single filament diameter range of 5-9μm is selected, and a powder coating amount of 400g / m² is applied to the glass fiber using a powder coating machine or similar equipment. The powder coating is then applied to the glass fiber using a drying oven set at 120°C for 70 seconds. At this point, the powder melts and bonds with the glass fiber, forming a pre-impregnated bond. At the end of the drying oven, cold rollers are used to cold-press the powder coating and glass fiber, evenly pre-impregnating the bond. The finished product can then be cut into desired shapes and sizes through a cutting process at the end.

[0077] VII. Example 7

[0078] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0079] Titanium dioxide (rutile type, median particle size of 0.4 μm) was added to a GMA acrylic resin (viscosity of 3000-3500 mPa·s / 180°C, epoxy equivalent weight of 600 g / eq, glass transition temperature of 40°C, and softening point of 95-100°C) before distillation during synthesis. The mixture was stirred at 1300 rpm for 25 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified GMA acrylic resin. The amount of titanium dioxide added was 10% of the total weight of the titanium dioxide and the GMA resin.

[0080] The following ingredients were prepared according to weight percentage: titanium dioxide modified GMA acrylic resin: 85%, sebacic acid: 13.3%, benzoin: 0.5%, hindered phenol antioxidant (CHINOX 1076): 0.2%, ultraviolet absorber Tinuvin® 405: 0.5%, hindered amine light stabilizer Tinuvin® 144: 0.5%, and then mixed to obtain a mixture.

[0081] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 50:1), the temperature zones were set at 60 / 90 / 90 / 70°C (four-stage temperature control), and the screw speed was 1500 rpm for extrusion to obtain a molten material;

[0082] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0083] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 100 μm.

[0084] The powder coating prepared in this example is used to prepare a white photovoltaic backsheet. The specific method is as follows: 160g / m² glass fiber cloth with a single filament diameter range of 5-9μm is selected, and a powder coating amount of 600g / m² is applied to the glass fiber using a powder coating machine or similar equipment. The powder coating is then applied to the glass fiber using a drying oven set at 140°C for 60 seconds. At this point, the powder melts and bonds with the glass fiber, forming a pre-impregnated bond. At the end of the drying oven, cold rollers are used to cold-press the powder coating and glass fiber, evenly pre-impregnating the bond. The finished product can then be cut into desired shapes and sizes through a cutting process at the end.

[0085] 8. Example 8

[0086] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, which specifically includes the following steps:

[0087] Titanium dioxide (rutile type, median particle size of 0.6 μm) was added to a carboxyl polyester resin (acid value 35 mgKOH / g, viscosity 1500-2000 mPa·s / 200°C, glass transition temperature 65°C) before distillation. The mixture was stirred at 1300 rpm for 25 minutes to form a uniform mixture. The solvent was removed by distillation to obtain a titanium dioxide-modified carboxyl polyester resin. The amount of titanium dioxide added was 5% of the total weight of the titanium dioxide and the carboxyl polyester resin.

[0088] The following ingredients are prepared according to weight percentage: titanium dioxide modified carboxyl polyester resin: 88%, triglycidyl isocyanurate TGIC: 6.5%, triphenyl phosphonium bromide (ADDITOL P964): 2%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX1076): 1.0%, ultraviolet absorber Tinuvin® 405: 1.0%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and then mixed to obtain a mixture.

[0089] The mixed material was put into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zones were set at 65 / 70 / 75 / 80°C (four-stage temperature control), the screw speed was 1200 rpm, and extrusion was performed to obtain a molten material;

[0090] The molten material after extrusion is compressed and cooled using a cooling roller machine to obtain a sheet;

[0091] The flakes are crushed, ground and sieved to obtain a powder coating for a photovoltaic backsheet, wherein the median particle size of the powder coating for a photovoltaic backsheet is 120 μm.

[0092] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this example is the same as that in Example 1.

[0093] IX. Example 9

[0094] Titanium dioxide (rutile type, median particle size of 0.5 μm) was added to a carboxyl polyester resin (acid value of 55 mgKOH / g, viscosity of 3500-4000 mPa·s / 200°C, glass transition temperature of 70°C) before distillation, and the mixture was stirred at 1500 rpm for 25 minutes to form a uniform mixture. After distillation to remove the solvent, a titanium dioxide-modified carboxyl polyester resin was obtained, wherein the amount of titanium dioxide added was 4% of the total weight of the titanium dioxide and the carboxyl polyester resin;

[0095] The following ingredients are prepared according to weight percentage: titanium dioxide modified carboxyl polyester resin: 81%, triglycidyl isocyanurate TGIC: 8.5%, catalyst P964: 1%, silicone leveling agent: 1%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX1076): 1.0%, phosphite antioxidant (CHINOX 626): 0.5%, ultraviolet absorber Tinuvin® 405: 3.0%, hindered amine light stabilizer Tinuvin® 622: 1%, polyamide wax defoamer: 1.0%, and flow aid aluminum hydroxide: 1.0%, and then mixed to obtain a mixture.

[0096] The rest is the same as Example 8.

[0097] 10. Example 10

[0098] Titanium dioxide (rutile type, median particle size of 0.8 μm) was added to a carboxyl polyester resin (acid value of 20 mgKOH / g, viscosity of 2000-2500 mPa·s / 200°C, glass transition temperature of 60°C) before distillation, and the mixture was stirred at 1000 rpm for 20 minutes to form a uniform mixture. After distillation to remove the solvent, a titanium dioxide-modified carboxyl polyester resin was obtained, wherein the amount of titanium dioxide added was 9% of the total weight of the titanium dioxide and the carboxyl polyester resin;

[0099] The following ingredients are prepared according to weight percentage: titanium dioxide modified carboxyl polyester resin: 95%, hydroxyalkylamide HAA: 3%, hindered phenol antioxidant (CHINOX 1076): 0.5%, ultraviolet absorber Tinuvin® 405: 0.5%, hindered amine light stabilizer Tinuvin® 622: 0.5%, and polyamide wax defoamer: 0.5%, and then mixed to obtain a mixture;

[0100] The rest is the same as Example 8.

[0101] 11. Example 11

[0102] Titanium dioxide (anatase type, median particle size of 0.5 μm) was added to a carboxyl polyester resin (acid value of 50 mgKOH / g, viscosity of 2500-3000 mPa·s / 200°C, glass transition temperature of 68°C) before distillation, and the mixture was stirred at 1300 rpm for 20 minutes to form a uniform mixture. After distillation to remove the solvent, a titanium dioxide-modified carboxyl polyester resin was obtained, wherein the amount of titanium dioxide added was 6% of the total weight of the titanium dioxide and the carboxyl polyester resin;

[0103] The following ingredients are prepared according to weight percentage: titanium dioxide modified carboxyl polyester resin: 86%, triglycidyl isocyanurate TGIC: 9%, benzoin: 1.0%, hindered phenol antioxidant (CHINOX 1076): 0.5%, phosphite antioxidant (CHINOX 626): 0.5%, ultraviolet absorber Tinuvin® 405: 1.0%, hindered amine light stabilizer Tinuvin® 622: 2%, and then mixed to obtain a mixture;

[0104] The rest is the same as Example 8.

[0105] 12. Example 12

[0106] This embodiment provides a method for assembling a photovoltaic power generation assembly using the white photovoltaic backsheet prepared in Example 1, specifically comprising the following steps:

[0107] The white photovoltaic backsheet is stacked together with the front sheet material, adhesive film, solar cells and other required materials according to the predetermined design structure of the component, and then transferred to the laminator for lamination and curing to obtain the target photovoltaic power generation component. The structure of this photovoltaic power generation component is compared with the photovoltaic power generation component in the prior art. Figure 1 As shown, the transparent front panel 1 and the battery cell 2 are both bonded by a transparent adhesive film 4. The difference is that in the photovoltaic module of the prior art, the other side of the battery cell 2 is bonded to the transparent back panel 3 by a white adhesive film 5, while in the photovoltaic module prepared in this embodiment, the other side of the battery cell 2 is directly bonded to the white photovoltaic back panel 6, eliminating the white adhesive film and avoiding the problem of insufficient bonding between the white adhesive film and the back panel material in harsh environments.

[0108] 13. Comparative Example 1

[0109] The rest of the technology of this comparative example is the same as that of Example 4, except that the content of titanium dioxide in the GMA acrylic resin is 4%.

[0110] 14. Comparative Example 2

[0111] The rest of the technology in this comparative example is the same as that in Example 7, except that the content of titanium dioxide in the GMA acrylic resin is 11%.

[0112] 15. Comparative Example 3

[0113] The rest of the technology of this comparative example is the same as that of Example 1, except that the GMA acrylic resin used does not contain titanium dioxide and is used to make a transparent backplane, in which the resin accounts for 74.5% and the curing agent DDDA accounts for 21.8%.

[0114] The high-reflectivity white photovoltaic backsheets prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to the following test requirements after lamination and curing at 150°C for 20 minutes:

[0115] 1. Appearance: The powder coating and fiber material have excellent wetting effect, and no poor wetting occurs;

[0116] 2. Oblique flow, refer to GBT 21782.11, greater than 150mm;

[0117] 3. Mechanical properties, refer to GB / T 13542.2, tensile strength greater than 100Mpa;

[0118] 4. Breakdown voltage, refer to GB / T 1408.1, >16KV;

[0119] 5. 48h PCT test, 2 standard atmospheres (absolute pressure), 121°C, 100% RH, no surface delamination, no blistering, yellowing less than 3, and reflectivity reduction less than 3%;

[0120] 6. Constant humidity test for 1000h: 85℃, 85%RH, no delamination or blistering on the surface, yellowing less than 3;

[0121] 7. Reflectivity, test wavelength 400-1100nm, UV spectrophotometer, reflectivity > 75%.

[0122]

[0123] Comparing Example 7 with Comparative Example 2, increasing the content of titanium dioxide in the resin increases the reflectivity. When the content exceeds 10% (Comparative Example 2), the oblique flow is significantly shortened, affecting the wetting effect.

[0124] Compared with Example 4 and Comparative Example 1, the content of titanium dioxide in the total formula is 2.64%. When it is lower than 3.3% (4%×66%), the reflectivity of the backplane cannot reach 75%.

[0125] Comparing Examples 1 to 3, with the same amount of titanium dioxide added, it is preferred to add titanium dioxide directly during the resin synthesis stage and mix it evenly with the resin in advance. The powder coating prepared in this way will have a better dispersion effect and higher reflectivity.

[0126] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A white photovoltaic backsheet powder coating, characterized in that: The invention comprises the following components by weight percentage: titanium dioxide-resin mixture or titanium dioxide modified resin: 66-95%; curing agent: 3-27%; catalyst: 0-2%; defoaming agent: 0-2%; leveling agent: 0-2%; Antioxidant: 0.2-1.5%; UV absorber: 0-3%; Light stabilizer: 0-2%; flow aid: 0-1%; The preparation method of the titanium dioxide-resin mixture is: After premixing titanium dioxide and resin, they are melted and extruded in a twin-screw extruder and crushed into flakes; The preparation method of the titanium dioxide modified resin is: Before the distillation stage of resin synthesis, add titanium dioxide, stir at 1000-1500 rpm for 15-30 minutes to mix evenly, remove the solvent, and crush. The resin is GMA acrylic resin or carboxyl polyester resin; When the resin is GMA acrylic resin, the titanium dioxide-resin mixture or titanium dioxide modified resin is in white light. The weight percentage of the powder coating of the back panel is 66-85%, and the amount of the titanium dioxide is 5-10% of the total weight of the resin and the titanium dioxide; When the resin is a carboxyl polyester resin, the weight percentage of the titanium dioxide-resin mixture or the titanium dioxide-modified resin in the white photovoltaic backsheet powder coating is 81-95%, and the amount of the titanium dioxide is 4-9% of the total weight of the resin and titanium dioxide; The twin-screw extruder has an aspect ratio of (15-50):1, an extrusion temperature of 30-100°C, and a screw speed of 600-1500 rpm; The median particle size of the titanium dioxide is 0.4 to 0.8 μm.

2. The white photovoltaic backsheet powder coating according to claim 1, characterized in that: The resin is a GMA acrylic resin or a carboxyl polyester resin. The epoxy equivalent of the GMA acrylic resin is 300 to 600 g / eq, the glass transition temperature is 40 to 60°C, the viscosity is 2000 to 8000 mPa·s / 180°C, and the softening point is 95 to 115°C. The acid value of the carboxyl polyester resin is 20 to 80 mgKOH / g, the viscosity is 1500 to 4000 mPa·s / 200°C, and the glass transition temperature is 60 to 70°C.

3. The white photovoltaic backsheet powder coating according to claim 2, characterized in that: The epoxy equivalent of the GMA acrylic resin is 350-420 g / eq, the glass transition temperature is 45-55° C., and the viscosity is 3000-6000 mPa·s / 180° C. The acid value of the carboxyl polyester resin is 30-55 mgKOH / .

4. The white photovoltaic backsheet powder coating according to claim 1, characterized in that: When the resin is GMA acrylic resin, the weight percentage of the curing agent in the white photovoltaic backplane powder coating is 12 to 27%, and the curing agent is a long-chain diacid carboxylic acid; when the resin is carboxyl polyester resin, the weight percentage of the curing agent in the white photovoltaic backplane powder coating is 3 to 9%, and the curing agent is triglycidyl isocyanurate or hydroxyalkylamide.

5. The white photovoltaic backsheet powder coating according to claim 4, characterized in that: The long-chain diacid carboxylic acid is at least one of sebacic acid, undecanedioic acid, dodecanedioic acid, and tridecanedioic acid.

6. The white photovoltaic backsheet powder coating according to claim 1, characterized in that: The crystal form of the titanium dioxide is rutile or anatase.

7. The white photovoltaic backsheet powder coating according to claim 1, characterized in that: The catalyst is a catalyst capable of catalyzing the reaction of carboxyl group -COOH and epoxy group -CH(O)CH2, and the catalyst is a quaternary ammonium salt catalyst, a phosphorus catalyst or an imidazole catalyst; the defoaming agent is benzoin, polyamide wax or polyolefin wax; the leveling agent is an acrylate leveling agent, a polyether leveling agent or an organosilicon leveling agent; the antioxidant is a mixture of one or two of a hindered phenol antioxidant and a phosphite antioxidant, wherein the hindered phenol antioxidant is the main antioxidant and the phosphite antioxidant is the auxiliary antioxidant; the ultraviolet light absorber is a benzophenone, a benzotriazole or a triazine; the light stabilizer is a hindered amine light stabilizer; and the flow aid is a dry powder flow aid, selected from one or more of aluminum hydroxide, aluminum oxide, fumed silica and organic wax powder.

8. A method for preparing a white photovoltaic backsheet powder coating according to claim 1, characterized in that: The steps include: After premixing the raw materials evenly, pour them into a twin-screw extruder for melt extrusion to obtain a molten material; The molten material is pressed and cooled to obtain a flake material; The flaky material is crushed, ground into powder, sieved and set aside; The length-to-diameter ratio of the twin-screw extruder is (15-50):1, the extrusion temperature does not exceed 100° C., and the screw speed is 1000-1500 rpm.

9. A method for preparing a white photovoltaic backsheet, characterized in that: The steps include: The powder coating for the photovoltaic backsheet according to claim 1 is sprinkled on the glass fiber cloth, and heated at 100-150° C. for 30-80 seconds to melt the powder coating and bond it to the glass fiber cloth for pre-impregnation. The powder coating is then cold-pressed with a roller to uniformly infiltrate and compound the powder coating and the glass fiber cloth. Finally, the powder glass fiber composite backsheet, i.e., a white photovoltaic backsheet, is obtained by cutting.

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