ECTFE transparent front sheet for photovoltaics

Abstract

The application discloses a kind of ECTFE transparent front panel for photovoltaic, the ECTFE transparent front panel for photovoltaic includes ECTFE film layer, ultraviolet blocking layer, water vapor barrier layer, fiber reinforced layer in turn, the ultraviolet blocking layer is the copolymer of fluorinated acrylate, acrylate containing ultraviolet absorption group and hydroxyl-containing acrylate and aliphatic isocyanate crosslinking curing material.The visible light transmittance of the ECTFE transparent front panel for photovoltaic is greater than or equal to 90%, ultraviolet blocking rate is greater than or equal to 95%, water vapor transmission rate is less than 0.01g / m 2 24h.

Description

Technical Field

[0001] This invention relates to the field of polymer processing applications, specifically to an ECTFE transparent front panel for photovoltaic applications. Background Technology

[0002] With the increasing global demand for renewable energy, photovoltaic installations have grown rapidly. In recent years, in addition to large-scale ground-mounted power plants, distributed photovoltaics have also developed rapidly. Application scenarios such as industrial and commercial rooftops, mobile portable components, and curtain walls have driven the continuous development of components towards lightweight and flexible designs. Lightweight and flexible components, due to their flexibility and lightweight properties, will usher in a broad market development space.

[0003] Currently, the mainstream solution for flexible photovoltaic modules is to replace the traditional photovoltaic glass used for encapsulation with transparent polymer materials to achieve the characteristics of lightweight and partially flexible modules. The polymer material is particularly useful as the outer protective layer on the front of the module, and it needs to withstand 2000 kWh / m². 2 In addition to ultraviolet irradiation, the system must also be able to prevent microcracks in solar cells, delamination and yellowing of encapsulation materials in complex environments such as hail and rain and snow, while avoiding PID phenomenon and ensuring high power generation efficiency of the module for more than 25 years. This poses a challenge to the selection of key materials and the design of the structure of polymer encapsulation materials.

[0004] Due to their characteristics, polymer encapsulation materials generally suffer from yellowing, failure, and delamination caused by long-term aging. Modules using polymer encapsulation materials have low mechanical strength, which can lead to microcracks in the cells during icy and snowy weather, resulting in a decrease in module power generation efficiency. At the same time, their low water vapor barrier properties can cause PID (Polyhydraulic Inertia) in the modules.

[0005] To address the aforementioned technical challenges, some research and exploration have been conducted regarding the packaging structure and material selection of flexible components:

[0006] CN210167364U discloses a lightweight flexible photovoltaic module. The photovoltaic module includes, from top to bottom, a TFB film layer, a water-blocking film layer, a composite fiberglass layer, a battery string, and an FFC double-sided fluorinated back film layer. The TFB film layer is connected to the water-blocking film layer, the water-blocking film layer is connected to the composite fiberglass layer, the composite fiberglass layer is connected to the battery string, and the battery string is connected to the FFC double-sided fluorinated back film layer through an EVA film. A coating liquid is sprayed on the side of the TFB film layer away from the water-blocking film layer. The water-blocking film layer includes, from top to bottom, an EVA adhesive layer, a PET film layer, a high barrier layer, a PE protective layer, and an EVA adhesive layer. The key TFB layer adopts a PVF / PET / fluorinated adhesive structure. Due to its low fluorine content and lack of ultraviolet absorption function, the PVF film cannot meet the weather resistance requirements of the front panel for up to 25 years of ultraviolet irradiation.

[0007] CN112420864A discloses a lightweight shingled photovoltaic module based on a glass fiber prepreg process. The photovoltaic module is composed of a transparent flexible front film, a first layer of high-transparency EVA film, a high-transparency glass fiber prepreg, a second layer of high-transparency EVA film, shingled cell strings, a first layer of high-cutoff EVA film, a rear layer of glass fiber prepreg, a second layer of high-cutoff EVA film, and a photovoltaic backsheet, which are sequentially laid and encapsulated by a lamination process. The module has a high water vapor permeability, which makes the EVA prone to hydrolysis, causing the module to exhibit PID phenomenon and reducing the module's power generation efficiency.

[0008] Both of the above solutions use glass fiber reinforcement to increase the impact resistance of the modules. Therefore, neither of these solutions is sufficient to make the flexible modules meet the long-term high power generation efficiency requirements of the photovoltaic industry in terms of UV resistance and water vapor barrier performance. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention uses a high-weather-resistant ECTFE membrane as the substrate. A UV-blocking layer, made by cross-linking and curing a copolymer of fluorinated acrylate, acrylate containing UV-absorbing groups, and hydroxyl-containing acrylate with an aliphatic isocyanate, achieves a UV blocking rate of over 95%. A water vapor barrier layer ensures a water vapor transmittance of <0.01 g / m². 2 24 hours.

[0010] The technical solution of the present invention is as follows:

[0011] This invention provides a photovoltaic ECTFE transparent front panel, which sequentially comprises an ECTFE film layer, an ultraviolet blocking layer, a water vapor blocking layer, and a fiber reinforcement layer. The ultraviolet blocking layer is a material that is cross-linked and cured with aliphatic isocyanate, a copolymer of fluorinated acrylate, acrylate containing ultraviolet absorbing groups and hydroxyl-containing acrylate.

[0012] The thickness of the ECTFE film layer only needs to meet the photovoltaic requirements. Preferably, the thickness is 10-100 μm, and more preferably, it is 15-50 μm.

[0013] The ECTFE film is prepared by granulating ECTFE resin, antioxidants, heat stabilizers and other processing aids using a twin-screw extruder, followed by single-screw extrusion casting or extrusion blow molding.

[0014] The thickness of the ultraviolet blocking layer should meet the photovoltaic requirements. Preferably, the thickness is 1 to 10 μm, and more preferably, it is 2 to 5 μm.

[0015] The copolymer of the fluorinated acrylate, the acrylate containing ultraviolet absorbing groups, and the hydroxyl-containing acrylate is shown in formula (1).

[0016]

[0017] Among them, R1 is selected from H and CH3.

[0018] R2 is Where n is an integer from 1 to 3,

[0019] R3 is selected from -CH2CH2- and -CH2CH2CH2-.

[0020] x+y+z=1, x=0.5~0.8, y=0.1~0.3, z=0.1~0.2.

[0021] Furthermore, the fluoroacrylate is selected from at least one of trifluoromethyl acrylate and trifluoromethyl methacrylate; the hydroxyl-containing acrylate is selected from at least one of methyl hydroxypropyl acrylate and methyl hydroxyethyl acrylate.

[0022] The aliphatic isocyanate is selected from at least one of hexamethylene diisocyanate (HDI), isoflurane diisocyanate (IPDI), and dicyclohexylmethane-4,4'-diisocyanate (HMDI).

[0023] The cross-linking curing temperature of the compound shown in formula (1) with the aliphatic isocyanate is 100-120°C for 0.5-2 min, and the curing temperature is 50-90°C for 24-72 h.

[0024] Because the ultraviolet barrier layer is a cross-linked and cured material, substances with ultraviolet absorption properties are not easily released, and the ultraviolet barrier performance can be maintained for a long time.

[0025] The thickness of the water vapor barrier layer should meet the photovoltaic requirements; preferably, the thickness is 10–100 μm.

[0026] The water vapor barrier layer is selected from at least one of silicon oxide, silicon nitride, and aluminum oxide.

[0027] The areal density of the fiber reinforcement layer should meet the requirements for lightweight photovoltaic applications, preferably 40–400 g / m². 2 .

[0028] The method for preparing the fiber reinforcement layer includes mixing a hydroxyl-terminated acrylic resin, a reactive ultraviolet absorber, a reactive light stabilizer, and an aliphatic isocyanate into a uniform first solution, and immersing a transparent glass fiber cloth in the first solution. The hydroxyl-terminated acrylic resin has a molecular weight of 10,000 to 500,000 and a hydroxyl value of 20 to 60.

[0029] The reactive UV absorber is selected from at least one of 2-[4-[2-hydroxy-3-tetrazoxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and 2-[2-hydroxy-4-[3-(2-ethylhexyloxy)-2-hydroxypropoxy]phenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and the reactive light stabilizer is 2,4-bis[N-butyl-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine.

[0030] The photovoltaic transparent front panel of the present invention comprises, in sequence, an ECTFE film layer, an ultraviolet blocking layer, a water vapor blocking layer, and a fiber reinforcement layer;

[0031] The ultraviolet blocking layer is coated and bonded to the ECTFE film to obtain the first film. The coating liquid is prepared by fully mixing the compound shown in formula (1), aliphatic isocyanate and solvent.

[0032] After the ECTFE film is coated with an ultraviolet blocking layer, the side with the ultraviolet blocking layer is facing upwards, and the water vapor barrier layer material is bonded to the ultraviolet blocking layer using one of the following methods: vacuum evaporation, atomic deposition, magnetron sputtering, or PECVD, to obtain a second thin film.

[0033] The method for preparing the fiber reinforcement layer includes mixing hydroxyl-terminated acrylic resin, reactive ultraviolet absorber, reactive light stabilizer and aliphatic isocyanate into a uniform first solution, immersing transparent glass fiber cloth in the first solution, and after the transparent glass fiber cloth comes out of the first solution, it is laminated with the second film, pre-cured and aged to obtain the photovoltaic ECTFE transparent front panel.

[0034] The aliphatic isocyanate is selected from at least one of hexamethylene diisocyanate (HDI), isoflurane diisocyanate (IPDI), and dicyclohexylmethane-4,4'-diisocyanate (HMDI).

[0035] The photovoltaic ECTFE transparent front panel described in this invention has a visible light transmittance ≥90%, an ultraviolet blocking rate ≥95%, and a water vapor transmittance <0.01g / m². 2 24h.

[0036] The photovoltaic ECTFE transparent front panel of this invention is subjected to 2000 kWh / m of ultraviolet irradiation. 2 The yellowness value after aging is <0.5, and the yellowness value after aging at 121℃ and 100%RH for 96 hours is <0.5.

[0037] The technical solution of the present invention has the following technical advantages compared with the prior art:

[0038] Using ECTFE membrane as the substrate, its good water vapor barrier properties ensure that the acrylate structure in the UV barrier layer is not hydrolyzed and destroyed, while avoiding wear of the UV barrier layer.

[0039] By combining the fiber-reinforced layer with an ECTFE membrane layer loaded with an ultraviolet barrier layer and a water vapor barrier layer, the use of EVA / POE is avoided, enabling continuous production and improving production efficiency. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the thin film composite of the embodiments and comparative examples of the present invention, wherein 1 is a glass fiber cloth roll, 2-5 are transition rollers, 6 is solution A tank, 7 is a transition roller, 8 is an ECTFE film roll, 9 is release film unwinding, 10 is release film rewinding, 11-12 are pressure rollers, 13-16 are transition rollers, 17 is a heating drying tunnel, and 18 is an ECTFE photovoltaic panel. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0042] Example 1

[0043] (1) 100 parts of ECTFE resin, 0.1 parts of antioxidant 1790, and 0.4 parts of antioxidant 9228 were mixed evenly at high speed. The mixed material was granulated by a twin-screw extruder. The ECTFE granules were then extruded and cast by a single screw extruder to obtain an ECTFE film with a thickness of 25 μm.

[0044] Extrusion casting process parameters

[0045] 265℃ 260℃ 270℃ 150℃ 50rpm 20m / min

[0046] (2) Dissolve 112g of trifluoromethyl acrylate, 15g of hydroxyethyl methyl methacrylate, and 35g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate in 800mL of xylene, add the solution to a 5L glass reactor with mechanical stirring, and after three nitrogen purgings, heat the solution to 70℃, add 1.5g of azobisisobutyronitrile, react for 6h, and then cool the solution to obtain a fluoromethyl acrylate copolymer solution.

[0047] 2g of HDI (hexamethylene diisocyanate), 100g of methyl fluorinated acrylate copolymer solution, and 0.01g of dibutyltin dilaurate were thoroughly mixed and then slit-coated onto a 25µm ECTFE film. After drying in a 120℃ oven for 0.5min, the film was placed in a 60℃ oven for 48h to obtain Film1 with a UV blocking layer thickness of 2µm.

[0048] (3) Magnetron sputtering was performed on the ultraviolet barrier layer of Film1, with SiO2 as the target material and an inorganic sputtering layer (water vapor barrier layer) of 50 nm thickness to obtain Film2.

[0049] (4) Add 35g of UV absorber 2-[4-[2-hydroxy-3-tetrazoloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 25g of UV absorber 2,4-bis[N-butyl-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, 4g of HDI, and 1700g of hydroxyl-terminated acrylic resin. Solution A is obtained by thoroughly mixing 587 (molecular weight 17,000) and 5L of ethyl acetate. A pre-woven glass fiber cloth is then immersed in solution A and online laminated with unwound Film 2 and unwound release film. After heating at 100℃ for 0.5 min in an oven, it is online cut to the specified size and cured at 60℃ for 48 h to obtain the photovoltaic ECTFE transparent front panel Sheet 1.

[0050] Example 2

[0051] Same as Example 1, except that the thickness of the ultraviolet blocking layer is 5 μm.

[0052] Example 3

[0053] Same as Example 1, except that the thickness of the water vapor barrier layer is 100nm.

[0054] Example 4

[0055] Same as Example 1, except that: 98g of trifluoromethyl acrylate, 15g of hydroxyethyl methyl acrylate, and 70g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate were dissolved in 20 parts of xylene and added to a 5L glass reactor with mechanical stirring. After three nitrogen purgings, the temperature was raised to 70°C, and 0.05 parts of AIBN were added. After reacting for 6 hours, the temperature was lowered to obtain a fluoromethyl acrylate copolymer solution.

[0056] Example 5

[0057] Same as Example 1, except that the target material is Al2O3 and the thickness of the water vapor barrier layer is 50nm.

[0058] Comparative Example 1: No UV blocking layer

[0059] A 25µm ECTFE thin film was magnetron sputtered with a SiO2 target and an inorganic sputtering layer (water vapor barrier layer) of 50nm thickness to obtain Film1.

[0060] 35g of UV absorber 2-[4-[2-hydroxy-3-tetrazoloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 25g of UV absorber 2,4-bis[N-butyl-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, 4g of HDI, and 1700g of hydroxyl-terminated acrylic resin were added. Solution A is obtained by thoroughly mixing 587 (molecular weight 17,000) and 5L of ethyl acetate. A pre-woven glass fiber cloth is immersed in solution A and then online laminated with unwound Film 1 and unwound release film. After heating at 100°C for 0.5 min in an oven, it is online cut to the specified size and cured at 60°C for 48 h to obtain a photovoltaic ECTFE transparent front panel.

[0061] Comparative Example 2: Without a water vapor barrier layer

[0062] 112g of trifluoromethyl acrylate, 15g of hydroxyethyl methyl methacrylate, and 35g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate were dissolved in 800mL of xylene and added to a 5L glass reactor equipped with a mechanical stirrer. After three nitrogen purgings, the temperature was raised to 70℃, and 1.5g of azobisisobutyronitrile was added. After reacting for 6 hours, the temperature was lowered to obtain a fluoromethyl acrylate copolymer solution.

[0063] 2g of HDI (hexamethylene diisocyanate), 100g of methyl fluorinated acrylate copolymer solution, and 0.01g of dibutyltin dilaurate were thoroughly mixed and then slit-coated onto a 25µm ECTFE film. After drying in a 120℃ oven for 0.5min, the film was placed in a 60℃ oven for 48h to obtain Film1 with a UV blocking layer thickness of 2µm.

[0064] 35g of UV absorber 2-[4-[2-hydroxy-3-tetrazoloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 25g of UV absorber 2,4-bis[N-butyl-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, 4g of HDI, and 1700g of hydroxyl-terminated acrylic resin were added. Solution A is obtained by thoroughly mixing 587 (molecular weight 17,000) and 5L of ethyl acetate. A pre-woven glass fiber cloth is then immersed in solution A and online laminated with unwound Film 1 and unwound release film. After heating at 100°C for 0.5 min in an oven, it is online cut to the specified size and cured at 60°C for 48 h to obtain a photovoltaic ECTFE transparent front panel.

[0065] Comparative Example 3: The reinforcing layer is PET

[0066] 112g of trifluoromethyl acrylate, 15g of hydroxyethyl methyl methacrylate, and 35g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl 2-methacrylate were dissolved in 800mL of xylene and added to a 5L glass reactor equipped with a mechanical stirrer. After three nitrogen purgings, the temperature was raised to 70℃, and 1.5g of azobisisobutyronitrile was added. After reacting for 6 hours, the temperature was lowered to obtain a fluoromethyl acrylate copolymer solution.

[0067] 2g of HDI (hexamethylene diisocyanate), 100g of methyl fluorinated acrylate copolymer solution, and 0.01g of dibutyltin dilaurate were thoroughly mixed and then slit-coated onto a 25µm ECTFE film. After drying in a 120℃ oven for 0.5min, the film was placed in a 60℃ oven for 48h to obtain Film1 with a UV blocking layer thickness of 2µm.

[0068] Film1 was obtained by magnetron sputtering of the ultraviolet barrier layer with SiO2 target material and an inorganic sputtering layer (water vapor barrier layer) with a thickness of 50 nm.

[0069] Film2 and 250um PET are dry-laminated to obtain ECTFE transparent front panel for photovoltaic applications.

[0070] The photovoltaic ECTFE transparent front panels prepared in Examples 1-5 and Comparative Examples 1-3 were compared for their ultraviolet blocking rate, visible light transmittance, water vapor transmittance, yellowness after 96 hours of accelerated damp heat aging, and ultraviolet irradiation at 2000 kWh / m². 2 The yellowness and component power loss (35mm hail impact test) were tested afterward, and the test results are detailed in Table 2.

[0071] The testing method is as follows:

[0072] UV blocking rate: tested according to ASTM G173.

[0073] Visible light transmittance: Tested according to GB / T 18830.

[0074] Water vapor transmission rate: tested according to GB / T 1037.

[0075] Yellowing value: According to GB / T 7921, the initial state L0, a0, b0 is read, and the final state L1, a1, b1 is read. The yellowing value db = b1 - b0.

[0076] Accelerate damp heat aging: Place at a temperature of 121℃ and a humidity of 100% for 96 hours.

[0077] Ultraviolet irradiation: Irradiation intensity 1.55 W / m 2 @340nm, blackboard temperature 65℃, continuous illumination, cumulative irradiance 2000kWh / m 2 .

[0078] Component power loss (35mm hail impact test): Tested according to IEC 61215.

[0079] Table 2 Performance data of ECTFE transparent front panel for photovoltaic applications

[0080]

[0081] The data in Table 2 shows that:

[0082] Data from Examples 1-5 shows that the transparent front panel prepared by combining an ultraviolet (UV) barrier layer, a moisture barrier layer, and a fiber reinforcement layer exhibits excellent performance, meeting the 25-year service life requirements of lightweight photovoltaic modules. Data from Comparative Example 1 shows that in the scheme without a UV barrier layer, the resin in the fiber reinforcement layer yellows, affecting the module's appearance. Comparative Example 2 shows that the scheme without a moisture barrier layer allows moisture to pass through, leading to yellowing of the glass fiber reinforcement layer. Comparative Example 3 shows that using PET instead of the fiber reinforcement layer reduces the impact resistance of the transparent front panel, resulting in a decrease in module power generation efficiency.

Claims

1. A photovoltaic ECTFE transparent front panel, characterized in that: The photovoltaic ECTFE transparent front panel comprises, in sequence, an ECTFE film layer, an ultraviolet blocking layer, a water vapor blocking layer, and a fiber reinforcement layer. The ultraviolet blocking layer is a material cross-linked and cured with fluorinated acrylate, acrylate containing ultraviolet absorbing groups and hydroxyl-containing acrylate, and aliphatic isocyanate. The copolymer of the fluorinated acrylate, the acrylate containing ultraviolet absorbing groups, and the hydroxyl-containing acrylate is shown in formula (1). Equation (1) Among them, R1 is selected from H and CH3. R2 is Where n is an integer from 1 to 3, R3 is -CH2CH2- or -CH2CH2CH2-. x+y+z=1,x=0.5~0.8,y=0.1~0.3,z=0.1~0.2, The moisture barrier layer is selected from at least one of silicon oxide, silicon nitride, and aluminum oxide. The method for preparing the fiber reinforcement layer includes the steps of mixing hydroxyl-terminated acrylic resin, reactive ultraviolet absorber, reactive light stabilizer and aliphatic isocyanate to form a first solution, and immersing transparent glass fiber cloth in the first solution.

2. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The aliphatic isocyanate is selected from at least one of hexamethylene diisocyanate, isoflurane diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

3. The photovoltaic ECTFE transparent front panel according to any one of claims 1-2, characterized in that: The thickness of the ultraviolet blocking layer is 1~10um.

4. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The thickness of the water vapor barrier layer is 10~100nm.

5. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The hydroxyl-terminated acrylic resin has a molecular weight of 10,000 to 500,000 and a hydroxyl value of 20 to 60.

6. The photovoltaic ECTFE transparent front panel according to claim 5, characterized in that: The reactive UV absorber is selected from at least one of 2-[4-[2-hydroxy-3-tetrazoxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and 2-[2-hydroxy-4-[3-(2-ethylhexyloxy)-2-hydroxypropoxy]phenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and the reactive light stabilizer is 2,4-bis[N-butyl-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine.

7. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The thickness of the ECTFE film is 10–100 μm.

8. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The photovoltaic ECTFE transparent front panel has a visible light transmittance ≥90%, an ultraviolet blocking rate ≥95%, and a water vapor transmittance <0.01g / m². 2 24 hours.

9. The photovoltaic ECTFE transparent front panel according to claim 1, characterized in that: The photovoltaic ECTFE transparent front panel is subjected to 2000 kWh / m² ultraviolet irradiation. 2 The yellowing value after aging is <0.5, and the yellowing value after aging at 121℃ and 100%RH for 96 hours is <0.5.

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