Powder coating for white photovoltaic backsheet, and method for preparing white photovoltaic backsheet

Abstract

Provided in the present disclosure are a powder coating for a white photovoltaic backsheet, and a method for preparing a white photovoltaic backsheet. The powder coating comprises the following components in percentages 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 absorber: 0-3%; a light stabilizer: 0-2%; and a flow aid: 0-1%. In the present disclosure, a high-reflectivity white photovoltaic backsheet is prepared by adding titanium dioxide to the formula for the powder coating. For example, titanium dioxide is added in the synthesis stage of the selected resin, or titanium dioxide and the resin are pre-mixed by means of extrusion to achieve uniform mixing of titanium dioxide and the resin in advance, thereby reducing the influence of titanium dioxide in the powder coating formula on the overall viscosity of the powder coating. In this way, the powder coating prepared will have a better dispersion effect and can better impregnate glass fiber cloth, thereby achieving a higher reflectivity.

Description

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

[0001] This disclosure is based on and claims priority to Chinese Patent Application No. 202510465145.7, filed on April 15, 2025, entitled "White Photovoltaic Backsheet Powder Coating and Method for Preparing White Photovoltaic Backsheet", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to, but is not limited to, a powder coating and a method for preparing a photovoltaic backsheet. Background Technology

[0003] In related technologies, lightweight backsheets mainly include three categories: adhesive-coated backsheets, coated backsheets, and resin-fiberglass composite backsheets. The first type, adhesive-coated backsheets, are mainly prepared by bonding fluoropolymer films such as PVF (Polyvinyl Fluoride), PVDF (Polyvinylidene Fluoride), or ETFE (Ethylene Tetrafluoroelastomer) with PET (Polyethylene Terephthalate) substrates using adhesives. The second type, coated backsheets, are prepared by coating PET substrates with a coating based on polytetrafluoroethylene (PTFE) or chlorotrifluoroethylene (CTFE) resin. Both of these backsheet solutions have the problem of high cost. The third type, resin-fiberglass composite backsheets, are made by bonding coatings or powder coatings with fiberglass cloth.

[0004] Category 1 and Category 2: Fluoropolymers such as polyvinylidene fluoride (PVF) and polyvinylidene fluoride (PVDF) are inherently expensive, resulting in high raw material costs for fluorinated backsheets. The production process involves bonding a pre-manufactured fluoropolymer film onto a PET substrate to form a "sandwich" structure, a complex process. To obtain a durable laminated backsheet, a primer or adhesive layer must be pre-coated onto the substrate, and lamination is completed through heat and pressure, further increasing the complexity and cost of the production process. Fluorocarbons have a robust chemical structure and are difficult to degrade even after long periods of landfill disposal, potentially becoming a new form of white pollution, further restricting the future use of fluorine. Furthermore, these two categories lack fiberglass support, resulting in poor mechanical properties in terms of hardness, impact resistance, and tensile strength. They typically require a photovoltaic frame, and during subsequent photovoltaic module lamination, the backsheet's softness and low hardness lead to numerous wrinkles on the back side, affecting both appearance and performance. The third type, although the addition of fiberglass provides good support, some coatings contain volatile organic compounds (VOCs), which will evaporate into the air during construction and use, causing air pollution. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail in this disclosure. This overview is not intended to limit the scope of the claims.

[0006] This disclosure provides a white photovoltaic backsheet powder coating and a method for preparing a white photovoltaic backsheet.

[0007] In a first aspect of this disclosure, a white photovoltaic backsheet powder coating is provided, comprising the following components by weight percentage: titanium dioxide-resin mixture or titanium dioxide-modified resin: 66-95%; curing agent: 3-27%; catalyst: 0-2%; defoamer: 0-2%; leveling agent: 0-2%; antioxidant: 0.2-1.5%; ultraviolet light absorber: 0-3%; light stabilizer: 0-2%; and flow aid: 0-1%.

[0008] In some exemplary embodiments, the preparation method of the titanium dioxide-resin mixture is as follows:

[0009] Titanium dioxide and resin are premixed, melt-extruded in a twin-screw extruder, and then crushed into flakes.

[0010] In some exemplary embodiments, the twin-screw extruder has a length-to-diameter ratio of (15-50):1, an extrusion temperature of 30-100°C, and a screw speed of 600-1500 rpm.

[0011] In some exemplary embodiments, the preparation method of the titanium dioxide modified resin is as follows:

[0012] Before the distillation stage of resin synthesis, add titanium dioxide and stir at 1000-1500 rpm for 15-30 minutes. After stirring and mixing evenly, remove the solvent and pulverize.

[0013] In some exemplary embodiments, the resin is a glycidyl methacrylate acrylic resin or a carboxylated polyester resin. The glycidyl methacrylate acrylic resin has an epoxy equivalent of 300–600 g / eq, for example, 350–420 g / eq, a glass transition temperature of 40–60°C, for example, 45–55°C, a viscosity of 2000–8000 mPa·s / 180°C, for example, 3000–6000 mPa·s / 180°C, and a softening point temperature of 95–115°C. The carboxylated polyester resin has an acid value of 20–80 mgKOH / g, for example, 30–55 mgKOH / g, a viscosity of 1500–4000 mPa·s / 200°C, and a glass transition temperature of 60–70°C.

[0014] In some exemplary embodiments, when the resin is GMA acrylic resin, the titanium dioxide-resin mixture or titanium dioxide-modified resin accounts for 66-85% by weight in the white photovoltaic backsheet powder coating, the amount of titanium dioxide is 5-10% of the total weight of the resin and titanium dioxide, the curing agent accounts for 12-27% by weight in the white photovoltaic backsheet powder coating, and the curing agent is a long-chain diacid carboxylic acid, such as at least one of sebacic acid, undecanoic acid, dodecanoic acid, and tridecanoic acid, further for example, dodecanoic acid; when the resin is carboxylated polyester resin, the titanium dioxide-resin mixture or titanium dioxide-modified resin accounts for 81-95% by weight in the white photovoltaic backsheet powder coating, the amount of titanium dioxide is 4-9% of the total weight of the resin and titanium dioxide, the curing agent accounts for 3-9% by weight in the white photovoltaic backsheet powder coating, and the curing agent is triglycidyl isocyanurate or hydroxyalkylamide.

[0015] In some exemplary embodiments, the median particle size of the titanium dioxide is no more than 1 μm, for example, the median particle size of the titanium dioxide is 0.4 to 0.8 μm, and the crystal form is rutile or anatase, for example, rutile.

[0016] In some exemplary embodiments, the titanium dioxide is produced by, for example, the chloride process, or by using titanium dioxide with a silicon-aluminum composite coating, because titanium dioxide has better weather resistance and better dispersibility after surface treatment.

[0017] In some exemplary embodiments, the catalyst is a catalyst capable of catalyzing the reaction between carboxyl-COOH and epoxy-CH(O)CH2, such as a quaternary ammonium salt catalyst, a phosphorus-based catalyst, or an imidazole catalyst. The quaternary ammonium salt catalyst is tetrabutylammonium bromide, the phosphorus-based catalyst is triphenylphosphine or triphenylphosphine bromide, and the imidazole catalyst is dimethylimidazole. The defoamer is benzoin and its modified products, polyamide wax, or polyolefin wax. The modified benzoin product, for example, is selected from products manufactured by Tianwo Company. D900 low-temperature degassing agent; the leveling agent is an acrylate leveling agent, a polyether leveling agent, or an organosilicon leveling agent; the antioxidant is one or a mixture of two hindered phenolic and phosphite antioxidants, wherein the hindered phenolic antioxidant is the main antioxidant and the phosphite antioxidant is the auxiliary antioxidant; the ultraviolet light absorber is benzophenone, benzotriazole, or 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, alumina, fumed silica, and organic wax powder.

[0018] In a second aspect of this disclosure, a method for preparing a white photovoltaic backsheet powder coating as described above is provided, comprising the following steps:

[0019] After the raw materials are premixed evenly, they are transferred to a twin-screw extruder for melt extrusion to obtain molten material;

[0020] The molten material is compressed and cooled to obtain a sheet-like material;

[0021] After the flake material is crushed, it is ground into powder, sieved, and set aside. The median particle size of the obtained powder coating is 60-200 μm, for example, the median particle size of the powder coating is 100-150 μm.

[0022] The twin-screw extruder has an aspect ratio of (15-50):1, an extrusion temperature not exceeding 100℃ (e.g., a base temperature of 60-90℃), and a screw speed of 1000-1500 rpm.

[0023] In a third aspect of this disclosure, a method for preparing a white photovoltaic backsheet is provided, comprising the following steps:

[0024] The aforementioned white photovoltaic backsheet powder coating is spread onto fiberglass cloth and heated at 100-150°C to melt the powder coating and bond it to the fiberglass cloth. Then, cold pressing is performed to ensure that the powder coating and fiberglass cloth are evenly impregnated and composited. Finally, after cutting, the powder fiberglass composite backsheet, i.e., the white photovoltaic backsheet, is obtained.

[0025] In some exemplary embodiments, the glass fibers used in the fiberglass cloth are E-glass fibers with a single filament diameter ranging from 5 to 10 μm, and the selected glass fiber basis weight is ≤200 g / m². 2 For example, the selected glass fiber has a basis weight of 100–200 g / m². 2 The powder coating powder application rate shall not exceed 600g / m². 2 For example, the powder coating powder application rate is 350–450 g / m². 2 .

[0026] Compared to existing technologies, this disclosure offers the following advantages: By adding titanium dioxide to the powder coating formulation to prepare a high-reflectivity white photovoltaic backsheet, and by either adding titanium dioxide during the resin synthesis stage or pre-mixing the titanium dioxide and resin using an extruder, the impact of titanium dioxide on the overall viscosity of the powder coating is reduced. This results in a powder coating with better dispersion and better wetting of the fiberglass cloth, leading to higher reflectivity. This innovative approach not only significantly improves the performance of the backsheet but also increases the power output of the photovoltaic module. Furthermore, eliminating the white adhesive film avoids the problem of insufficient adhesion between the white adhesive film and the backsheet material under harsh environments, effectively reducing costs. Attached Figure Description

[0027] Other features, objects, and advantages of this disclosure will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0028] Figure 1 shows a structural comparison between photovoltaic modules in the prior art and photovoltaic modules prepared using white photovoltaic backsheets in this disclosure.

[0029] In the image: 1. Transparent front panel; 2. Solar cell; 3. Transparent back panel; 4. Transparent film; 5. White film; 6. White photovoltaic back panel. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0031] Among related technologies, the first type of adhesive-coated backsheet and the second type of coated backsheet have high raw material costs and complex production steps. Furthermore, due to the lack of fiberglass support, their mechanical properties are poor. The third type of resin-fiberglass composite backsheet, due to the presence of volatile organic compounds in the coating, easily causes air pollution. While powder coatings do not have these environmental problems and use weather-resistant resins such as acrylic, ultra-weather-resistant polyester, and fluorocarbon resins, these backsheets are typically transparent, preventing sunlight penetrating the solar cells from being reflected back, thus wasting some sunlight. To overcome this drawback, a white POE or EVA film is usually added in front of the backsheet, which undoubtedly increases costs. In addition, under harsh environmental conditions such as high temperature, high humidity, and strong ultraviolet radiation, the adhesion between the white film and the backsheet material will decrease to varying degrees. This may not only cause loosening of the internal structure of the module but also lead to short circuits and other problems, posing a hidden danger to the safe and stable operation of the photovoltaic system.

[0032] This disclosure provides an exemplary white photovoltaic backsheet powder coating comprising the following components by weight percentage: titanium dioxide-resin mixture or titanium dioxide-modified resin: 66-95%; curing agent: 3-27%; catalyst: 0-2%; defoamer: 0-2%; leveling agent: 0-2%; antioxidant: 0.2-1.5%; ultraviolet light absorber: 0-3%; light stabilizer: 0-2%; and flow aid: 0-1%.

[0033] This disclosure provides an exemplary method for preparing a white photovoltaic backsheet.

[0034] I. Example 1

[0035] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, including:

[0036] Titanium dioxide (rutile type, median particle size 0.4 μm) was added before the synthesis and distillation of GMA acrylic resin (viscosity 4500~5000mPa·s / 180℃, epoxy equivalent 400g / eq, glass transition temperature 55℃, softening point 95~105℃). The mixture was stirred at 1200rpm for 30 minutes to form a homogeneous mixture. After distillation to remove the solvent, titanium dioxide modified GMA acrylic resin was obtained (the epoxy equivalent of titanium dioxide modified GMA acrylic resin is slightly higher than that of GMA acrylic resin, but it does not affect the achievement of the technical effect, and the glass transition temperature, softening point and viscosity are almost unchanged). The amount of titanium dioxide added was 6% of the total weight of titanium dioxide and GMA resin.

[0037] The ingredients are formulated according to the following weight percentages: titanium dioxide modified GMA acrylic resin: 75%, dodecanoic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, phosphite ester (CHINOX 626): 0.5%, triazine UV absorber. 405: 1.0%, hindered amine light stabilizer 622:0.5%, then mix well to obtain a mixture;

[0038] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zone is set to 65 / 70 / 75 / 80℃ (four-stage temperature control), the screw speed is 1200 rpm, and the mixture is extruded to obtain molten material.

[0039] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0040] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 120 μm.

[0041] The white photovoltaic backsheet was prepared using the powder coating prepared in this embodiment. The specific method is as follows: 160 g / m³ powder coating was selected. 2 Fiberglass cloth, with a single filament diameter of 7μm and a powder application rate of 350g / m. 2 The powder coating is applied to fiberglass cloth using a powder spreader or similar equipment. The cloth is then heated in an oven at 120°C for 60 seconds. The powder melts and adheres to the fiberglass cloth, becoming pre-impregnated. After being cold-pressed at the end of the oven using a cold roller, the powder coating and fiberglass cloth are uniformly pre-impregnated and bonded together. The final cutting process allows it to be cut into the required shape and size.

[0042] II. Example 2

[0043] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0044] GMA acrylic resin (viscosity 4500~5000mPa·s / 180℃, epoxy equivalent 400g / eq, glass transition temperature 55℃, softening point 95~105℃) and titanium dioxide (rutile type, median particle size 0.4μm) were premixed and then transferred to a twin-screw extruder (length-to-diameter ratio 36:1). The temperature zones were set to 30 / 70 / 90 / 80℃ (four-stage temperature control) and the speed was 1200rpm for melt extrusion and pulverization into flakes to obtain a titanium dioxide-GMA acrylic resin mixture. The amount of titanium dioxide added was 6% of the total weight of titanium dioxide and GMA acrylic resin.

[0045] The ingredients are formulated according to the following weight percentages: titanium dioxide-GMA acrylic resin mixture: 75%, dodecanoic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, phosphite ester (CHINOX 626): 0.5%, triazine UV absorber. 405: 1.0%, hindered amine light stabilizer 622:0.5%, then mix well to obtain a mixture;

[0046] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zone is set to 65 / 70 / 75 / 80℃ (four-stage temperature control), the screw speed is 1200 rpm, and the mixture is extruded to obtain molten material.

[0047] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0048] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 120 μm.

[0049] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this embodiment is the same as that in Example 1.

[0050] III. Example 3

[0051] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0052] The ingredients are formulated according to the following weight percentages: GMA resin: 70.5%, titanium dioxide: 4.5%, dodecanoic acid: 21.3%, tetrabutylammonium bromide: 0.2%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, phosphite (CHINOX 626): 0.5%, triazine UV absorber. 405 1.0%, hindered amine light stabilizer 6220.5%, then mix well to obtain a mixture;

[0053] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zone is set to 65 / 70 / 75 / 80℃ (four-stage temperature control), the screw speed is 1200 rpm, and the mixture is extruded to obtain molten material.

[0054] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0055] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 120 μm.

[0056] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this embodiment is the same as that in Example 1.

[0057] IV. Example 4

[0058] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0059] Titanium dioxide (rutile type, median particle size 0.4 μm) was added before the synthesis distillation of GMA acrylic resin (viscosity 5000~5500mPa·s / 180℃, epoxy equivalent 300g / eq, glass transition temperature 60℃, softening point 100~105℃). The mixture was stirred at 1000rpm for 30 minutes to form a homogeneous mixture. After distillation to remove the solvent, titanium dioxide modified GMA acrylic resin was obtained. The amount of titanium dioxide added was 5% of the total weight of titanium dioxide and GMA resin.

[0060] The ingredients are formulated according to the following weight percentages: titanium dioxide modified GMA acrylic resin: 66%, tridecanoic acid: 26.5%, benzoin: 1.5%, acrylic leveling agent: 1.5%, hindered phenolic antioxidant (CHINOX 1076): 1%, phosphite ester (CHINOX 626): 0.5%, benzophenone UV absorber. 81:1.0%, hindered amine light stabilizer 622: 0.5%, polyamide wax defoamer: 1.0%, flow aid alumina C: 0.5%, then mix well to obtain a mixture;

[0061] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 15:1), the temperature zone is set to 30 / 70 / 75 / 65℃ (four-stage temperature control), the screw speed is 1000 rpm, and the mixture is extruded to obtain molten material.

[0062] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0063] After the sheet material is crushed, it is ground and sieved to obtain a powder coating for photovoltaic backsheets, the median particle size of which is 60 μm.

[0064] The white photovoltaic backsheet was prepared using the powder coating prepared in this embodiment. The specific method is as follows: 100 g / m³ powder coating was selected. 2 Fiberglass cloth with a monofilament diameter range of 7μm and a powder application rate of 350g / m. 2The powder coating is applied to the fiberglass using a powder spreader or similar equipment. The fiberglass is then heated in an oven at 100°C for 80 seconds. The powder melts and bonds with the fiberglass. After being cold-pressed at the end of the oven using a cold roller, the powder coating and fiberglass are uniformly pre-impregnated and bonded together. The fiberglass can then be cut into the required shape and size after a final cutting process.

[0065] V. Example 5

[0066] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0067] Titanium dioxide (rutile type, median particle size 0.4 μm) was added before the synthesis and distillation of GMA acrylic resin (viscosity 5000~5500mPa·s / 180℃, epoxy equivalent 300g / eq, glass transition temperature 60℃, softening point 100~105℃). The mixture was stirred at 1500rpm for 15 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified GMA acrylic resin was obtained. The amount of titanium dioxide added was 5% of the total weight of titanium dioxide and GMA resin.

[0068] The ingredients are formulated according to the following weight percentages: titanium dioxide modified GMA acrylic resin: 71%, tridecanoic acid: 27%, benzoin: 0.5%, hindered phenolic antioxidant (CHINOX 1076): 0.2%, and ultraviolet absorber. 405: 0.5%, hindered amine light stabilizer 622: 0.5%, polyolefin wax defoamer: 0.3%, then mix well to obtain a mixture;

[0069] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 24:1), the temperature zone is set to 30 / 70 / 75 / 65℃ (four-stage temperature control), the screw speed is 1200 rpm, and the mixture is extruded to obtain molten material.

[0070] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0071] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 150 μm.

[0072] The white photovoltaic backsheet was prepared using the powder coating prepared in this embodiment. The specific method is as follows: 200 g / m³ powder coating was selected... 2 Fiberglass cloth with a monofilament diameter ranging from 5 to 9 μm and a powder application rate of 450 g / m. 2The powder coating is applied to the fiberglass using a powder spreader or similar equipment. The fiberglass is then heated in an oven at 150°C for 30 seconds. The powder melts and bonds with the fiberglass. After being cold-pressed at the end of the oven using a cold roller, the powder coating and fiberglass are uniformly pre-impregnated and bonded together. The fiberglass can then be cut into the required shape and size after a final cutting process.

[0073] VI. Example 6

[0074] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0075] Titanium dioxide (rutile type, median particle size 0.4 μm) was added before the synthesis distillation of GMA acrylic resin (viscosity 2000~2500mPa·s / 180℃, epoxy equivalent 600g / eq, glass transition temperature 45℃, softening point 95~100℃). The mixture was stirred at 1300rpm for 15 minutes to form a homogeneous mixture. After distillation to remove the solvent, titanium dioxide modified GMA acrylic resin was obtained. The amount of titanium dioxide added was 10% of the total weight of titanium dioxide and GMA resin.

[0076] The ingredients are formulated according to the following weight percentages: titanium dioxide modified GMA acrylic resin: 80%, sebacic acid: 12%, dimethylimidazole: 0.3%, benzoin: 1%, silicone leveling agent: 2%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, phosphite antioxidant (CHINOX 626): 0.2%, benzotriazole UV absorber. 928: 2.0%, hindered amine light stabilizer 622: 0.5%, polyolefin wax defoamer: 1%, flow aid silicone: 0.5%, then mix well to obtain a mixture;

[0077] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 36:1), the temperature zone is set to 60 / 90 / 100 / 70℃ (four-stage temperature control), the screw speed is 1500 rpm, and the mixture is extruded to obtain molten material.

[0078] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0079] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 200 μm.

[0080] The white photovoltaic backsheet was prepared using the powder coating prepared in this embodiment. The specific method is as follows: 160 g / m³ powder coating was selected. 2 Fiberglass cloth, with a monofilament diameter ranging from 5-9μm and a powder application rate of 400g / m. 2The powder coating is applied to the fiberglass using a powder spreader or similar equipment. The fiberglass is then heated in an oven at 120°C for 70 seconds. The powder melts and bonds with the fiberglass. After being cold-pressed at the end of the oven using a cold roller, the powder coating and fiberglass are uniformly pre-impregnated and bonded together. The fiberglass can then be cut into the required shape and size after a final cutting process.

[0081] VII. Example 7

[0082] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0083] Titanium dioxide (rutile type, median particle size 0.4 μm) was added before the synthesis distillation of GMA acrylic resin (viscosity 3000~3500mPa·s / 180℃, epoxy equivalent 600g / eq, glass transition temperature 40℃, softening point 95~100℃). The mixture was stirred at 1300rpm for 25 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified GMA acrylic resin was obtained. The amount of titanium dioxide added was 10% of the total weight of titanium dioxide and GMA resin.

[0084] The ingredients are formulated according to the following weight percentages: titanium dioxide modified GMA acrylic resin: 85%, sebacic acid: 13.3%, benzoin: 0.5%, hindered phenolic antioxidant (CHINOX 1076): 0.2%, and ultraviolet absorber. 405: 0.5%, hindered amine light stabilizer 144:0.5%, then mix well to obtain a mixture;

[0085] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 50:1), the temperature zone is set to 60 / 90 / 90 / 70℃ (four-stage temperature control), the screw speed is 1500 rpm, and the mixture is extruded to obtain molten material.

[0086] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0087] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 100 μm.

[0088] The white photovoltaic backsheet was prepared using the powder coating prepared in this embodiment. The specific method is as follows: 160 g / m³ powder coating was selected. 2 Fiberglass cloth, with a monofilament diameter ranging from 5-9μm and a powder application rate of 600g / m². 2The powder coating is applied to the fiberglass using a powder spreader or similar equipment. The fiberglass is then heated in an oven at 140°C for 60 seconds. The powder melts and bonds with the fiberglass. After being cold-pressed at the end of the oven using a cold roller, the powder coating and fiberglass are uniformly pre-impregnated and bonded together. The fiberglass can then be cut into the required shape and size after a final cutting process.

[0089] VIII. Example 8

[0090] This embodiment provides a method for preparing a white photovoltaic backsheet powder coating, specifically including the following steps:

[0091] Titanium dioxide (rutile type, median particle size of 0.6 μm) was added before the synthesis and distillation of carboxylated polyester resin (acid value 35 mg KOH / g, viscosity 1500~2000 mPa·s / 200℃, glass transition temperature 65℃). The mixture was stirred at high speed of 1300 rpm for 25 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified carboxylated polyester resin was obtained. The amount of titanium dioxide added was 5% of the total weight of titanium dioxide and carboxylated polyester resin.

[0092] The ingredients are formulated according to the following weight percentages: titanium dioxide modified carboxylated polyester resin: 88%, triglycidyl isocyanurate (TGIC): 6.5%, triphenylphosphine bromide (ADDITOL P964): 2%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 1.0%, and ultraviolet absorber. 405: 1.0%, hindered amine light stabilizer 622:0.5%, then mix well to obtain a mixture;

[0093] The mixture is fed into a twin-screw extruder (length-to-diameter ratio of 28:1), the temperature zone is set to 65 / 70 / 75 / 80℃ (four-stage temperature control), the screw speed is 1200 rpm, and the mixture is extruded to obtain molten material.

[0094] The extruded molten material is pressed and cooled using a cooling roller press to obtain sheets;

[0095] After the sheet material is crushed, it is ground and sieved to obtain a photovoltaic backsheet powder coating with a median particle size of 120 μm.

[0096] The method for preparing a white photovoltaic backsheet using the powder coating prepared in this embodiment is the same as that in Example 1.

[0097] IX. Example 9

[0098] Titanium dioxide (rutile type, median particle size of 0.5 μm) was added before the synthesis and distillation of carboxylated polyester resin (acid value 55 mg KOH / g, viscosity 3500~4000 mPa·s / 200℃, glass transition temperature 70℃). The mixture was stirred at 1500 rpm for 25 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified carboxylated polyester resin was obtained. The amount of titanium dioxide added was 4% of the total weight of titanium dioxide and carboxylated polyester resin.

[0099] The ingredients are formulated according to the following weight percentages: titanium dioxide modified carboxylated polyester resin: 81%, triglycidyl isocyanurate (TGIC): 8.5%, catalyst P964: 1%, silicone leveling agent: 1%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 1.0%, phosphite antioxidant (CHINOX 626): 0.5%, and ultraviolet absorber. 405: 3.0%, hindered amine light stabilizer 622:1%, polyamide wax defoamer:1.0%, flow aid aluminum hydroxide 1.0%, then mix well to obtain a mixture;

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

[0101] 10. Example 10

[0102] Titanium dioxide (rutile type, median particle size of 0.8 μm) was added before the synthesis and distillation of carboxylated polyester resin (acid value 20 mg KOH / g, viscosity 2000~2500 mPa·s / 200℃, glass transition temperature 60℃). The mixture was stirred at 1000 rpm for 20 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified carboxylated polyester resin was obtained. The amount of titanium dioxide added was 9% of the total weight of titanium dioxide and carboxylated polyester resin.

[0103] The ingredients are formulated according to the following weight percentages: titanium dioxide modified carboxylated polyester resin: 95%, hydroxyalkylamide (HAA): 3%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, and ultraviolet absorber. 405: 0.5%, hindered amine light stabilizer 622: 0.5%, polyamide wax defoamer: 0.5%, then mix well to obtain a mixture;

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

[0105] XI. Example 11

[0106] Titanium dioxide (anatase type, median particle size of 0.5 μm) was added before the synthesis distillation of carboxylated polyester resin (acid value 50 mg KOH / g, viscosity 2500~3000 mPa·s / 200℃, glass transition temperature 68℃). The mixture was stirred at high speed of 1300 rpm for 20 minutes to form a homogeneous mixture. After the solvent was removed by distillation, titanium dioxide modified carboxylated polyester resin was obtained. The amount of titanium dioxide added was 6% of the total weight of titanium dioxide and carboxylated polyester resin.

[0107] The ingredients are formulated according to the following weight percentages: titanium dioxide modified carboxylated polyester resin: 86%, triglycidyl isocyanurate (TGIC): 9%, benzoin: 1.0%, hindered phenolic antioxidant (CHINOX 1076): 0.5%, phosphite antioxidant (CHINOX 626): 0.5%, and ultraviolet absorber. 405: 1.0%, hindered amine light stabilizer 622:2%, then mix well to obtain a mixture;

[0108] The rest is the same as in Example 8.

[0109] XII. Example 12

[0110] This embodiment provides a method for assembling a photovoltaic power generation module using a white photovoltaic backsheet prepared in Example 1, specifically including the following steps:

[0111] The white photovoltaic backsheet, along with the front sheet material, adhesive film, solar cells, and other necessary materials, are stacked according to the predetermined design structure of the module. Then, they are transferred to a laminator for lamination and curing to obtain the target photovoltaic power generation module. Figure 1 shows a structural comparison between this photovoltaic power generation module and existing photovoltaic power generation modules. Both the transparent front sheet 1 and the solar cells 2 are bonded together with transparent adhesive film 4. The difference is that in existing photovoltaic modules, the other side of the solar cells 2 is bonded to the transparent backsheet 3 with a white adhesive film 5. However, in the photovoltaic module prepared in this embodiment, the other side of the solar cells 2 is directly bonded to the white photovoltaic backsheet 6, eliminating the need for the white adhesive film and avoiding the problem of insufficient adhesion between the white adhesive film and the backsheet material under harsh environments.

[0112] XIII. Comparative Example 1

[0113] The rest of the techniques in this comparative example are the same as in Example 4, except that the content of titanium dioxide in the GMA acrylic resin is 4%.

[0114] XIV. Comparative Example 2

[0115] The rest of the techniques in this comparative example are the same as in Example 7, except that the content of titanium dioxide in the GMA acrylic resin is 11%.

[0116] 15. Comparative Example 3

[0117] The rest of the techniques in this comparative example are the same as in Example 1, except that the GMA acrylic resin used does not contain titanium dioxide and is used to make a transparent backing plate, wherein the resin accounts for 74.5% and the curing agent DDDA accounts for 21.8%.

[0118] The high-reflectivity white photovoltaic backsheets prepared in Examples 1-11 and Comparative Examples 1-3 were subjected to the following testing requirements after lamination and curing at 150°C for 20 minutes:

[0119] 1. Appearance: The powder coating exhibits excellent wetting effect with the fiber material, and no poor wetting occurred;

[0120] 2. Diagonal flow, refer to GB / T 21782.11, greater than 150mm;

[0121] 3. Mechanical properties, referring to GB / T 13542.2, tensile strength greater than 100 MPa;

[0122] 4. Breakdown voltage, referring to GB / T 1408.1, >16KV;

[0123] 5.48 hPCT test, 2 standard atmospheres (absolute pressure), 121℃, 100% RH, surface does not delaminate, does not bubble, yellowing <3, reflectivity attenuation <3%;

[0124] 6. Constant humidity and heat test for 1000h: 85℃, 85%RH, no surface delamination, no blistering, yellowing <3;

[0125] 7. Reflectance, test wavelength 400-1100nm, ultraviolet spectrophotometer, reflectance >75%.

[0126] Compared with Comparative Example 2, increasing the titanium dioxide content in the resin increases the reflectivity. However, when it exceeds 10% (Comparative Example 2), the oblique flow is significantly shortened, affecting the wetting effect.

[0127] Compared with Comparative Example 1 and Example 4, the total titanium dioxide content in the formulation was 2.64%, which is less than 3.3% (4% × 66%), and the backplate reflectivity could not reach 75%.

[0128] Comparing Examples 1-3, with the same amount of titanium dioxide added, for example, adding titanium dioxide directly during the resin synthesis stage and mixing it evenly with the resin in advance, the resulting powder coating will have better dispersion and higher reflectivity.

[0129] Finally, it should be noted that in this disclosure, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0130] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure. Industrial applicability

[0131] This disclosure discloses a method for preparing high-reflectivity white photovoltaic backsheets by adding titanium dioxide to the powder coating formulation. Titanium dioxide is added during the resin synthesis stage or pre-mixed with the selected resin using an extruder. This pre-mixing process minimizes the impact of titanium dioxide on the overall viscosity of the powder coating, resulting in better dispersion and impregnation of the fiberglass cloth, thus achieving higher reflectivity. This innovative approach not only significantly improves the performance of the backsheet but also increases the power output of the photovoltaic module. Furthermore, eliminating the white adhesive film avoids insufficient adhesion between the white adhesive film and the backsheet material under harsh environments and effectively reduces costs.

Claims

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

2. The white photovoltaic backsheet powder coating according to claim 1, wherein,the resin is GMA acrylic resin or carboxyl polyester resin;when the resin is GMA acrylic resin, the titanium dioxide-resin mixture or the titanium dioxide modified resin accounts for 66%-85% by weight of the white photovoltaic backsheet powder coating, and an amount of the titanium dioxide is 5%-10% of a total weight of the resin and the titanium dioxide;when the resin is carboxyl polyester resin, the titanium dioxide-resin mixture or the titanium dioxide modified resin accounts for 81%-95% by weight of the white photovoltaic backsheet powder coating, and the amount of the titanium dioxide is 4%-9% of the total weight of the resin and the titanium dioxide.

3. The white photovoltaic backsheet powder coating according to claim 2, wherein the titanium dioxide-resin mixture is prepared by the following method:premixing the titanium dioxide and the resin, then performing melt extrusion on the mixture in a twin-screw extruder and crushing the mixture into flakes;the titanium dioxide modified resin is prepared by the following method:adding the titanium dioxide before a distillation stage of resin synthesis, stirring at a rotation speed of 1000 rpm -1500 rpm for 15 min -30 min until uniform mixing, removing the solvent, and crushing the mixture.

4. The white photovoltaic backsheet powder coating according to claim 3, wherein the twin-screw extruder has a length-diameter ratio of (15-50):1, an extrusion temperature of 30°C -100°C, and a screw speed of 600 rpm -1500 rpm.

5. The white photovoltaic backsheet powder coating according to claim 3, wherein the GMA acrylic resin has an epoxy equivalent of 300 g / eq -600 g / eq, a glass transition temperature of 40°C -60°C, a viscosity of 2000 mPa-s / 180°C -8000 mPa-s / 180°C, and a softening point temperature of 95°C -115°C; the carboxyl polyester resin has an acid value of 20 mgKOH / g -80 mgKOH / g, a viscosity of 1500 mPa-s / 200°C -4000 mPa-s / 200°C, and a glass transitiontemperature of 60°C -70°C.

6. The white photovoltaic backsheet powder coating according to claim 5, wherein the GMA acrylic resin has the epoxy equivalent of 350 g / eq -420 g / eq, the glass transition temperature of 45°C -55°C, the viscosity of 3000 mPa-s / 180°C -6000 mPa-s / 180°C, and the carboxyl polyester resin has the acid value of 30 mgKOH / g -55 mgKOH / g.

7. The white photovoltaic backsheet powder coating according to claim 2, wherein, when the resin is the GMA acrylic resin, the curing agent accounts for 12%-27% by weight of the white photovoltaic backsheet powder coating, and the curing agent is long-chain dicarboxylic acid; when the resin is carboxyl polyester resin, the curing agent accounts for 3%-9% by weight of the white photovoltaic backsheet powder coating, and the curing agent is triglycidyl isocyanurate or hydroxyalkyl amide.

8. The white photovoltaic backsheet powder coating according to claim 7, wherein the long-chain dicarboxylic acid is at least one of sebacic acid, undecanedioic acid, dodecanedioic acid and tridecanedioic acid.

9. The white photovoltaic backsheet powder coating according to claim 1, wherein the titanium dioxide has a median particle size of no more than 1 pm, and a crystal form is rutile type or anatase type.

10. The white photovoltaic backsheet powder coating according to claim 1, wherein, the catalyst is a catalyst capable of catalyzing a reaction between carboxyl -COOH and epoxy -CH(O)CH2-, and the catalyst is a quaternary ammonium salt catalyst, a phosphorus-based 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 one or a mixture of a hindered phenol antioxidant and a phosphite antioxidant, wherein the hindered phenol antioxidant is a primary antioxidant, and the phosphite antioxidant is an auxiliary antioxidant; the ultraviolet light absorber is of benzophenone type, benzotriazole type or triazine type; the light stabilizer is a hindered amine light stabilizer; the flow promoter is a dry powder flow promoter selected from one or more of aluminum hydroxide, alumina, fumed silica and organic wax powder.

11. A preparation method of the white photovoltaic backsheet powder coating according to any one of claims 1-10, comprising the following steps:premixing all raw materials uniformly, then pouring mixed raw materials into a twin-screw extruder for melt extrusion, and obtaining a molten material;tabletting and cooling the molten material, and obtaining a flaky material;crushing the flaky material, grinding into powder, and sieving the powder;the twin-screw extruder has a length-diameter ratio of (15-50):1, an extrusion temperature of no more than 100°C, and a screw speed of 1000 rpm -1500 rpm.

12. A preparation method of a white photovoltaic backsheet, comprising the following steps:sprinkling the white photovoltaic backsheet powder coating according to any one of claims 1-10 on glass fiber fabric, heating at 100°C -150°C for 30 s -80 s to melt the powder coating, and bond and pre-impregnate the powder coating with the glass fiber fabric, then performing cold pressing with a pressure roller to impregnate and compound the powder coating and the glass fiber fabric, finally cutting the glass fiber fabric compounded with the powder coating, and obtaining the white photovoltaic backsheet.

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