Multilayer composite efficient protection solar cell backboard polyester film and application thereof

Abstract

The invention relates to the technical field of solar cell backboard films, in particular to a multi-layer composite efficient protection solar cell backboard polyester film. The reinforced polyester film is divided into a weather-proof coating, a PET layer and a waterproof layer; the weather-proof coating is arranged on the upper layer, the PET layer is arranged on the middle layer, and the waterproof layer is arranged on the lower layer; the preparation raw materials of the weather-resistant coating comprise one or more of polytetrafluoroethylene, ethylene, polyvinylidene fluoride, modified polyvinylidene fluoride, a modifier, a dispersion medium and an initiator; the waterproof layer is prepared from one or more of polyethylene glycol terephthalate slices, a hydrolysis-resistant agent, a water-blocking agent and nano-zinc oxide. The polyester film provided by the invention has good weather resistance and high water resistance, and can prolong the service life of the solar backboard and improve economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell backsheet films, and particularly relates to a multi-layer composite highly protective polyester film for solar cell backsheets and its application. Background Art

[0002] Solar energy is the most important basic energy source among various renewable energy sources. It contains no chemicals and is the cleanest and most reliable huge energy treasure house. The energy radiated to the ground each year alone reaches 3.8×10²⁴ joules, which is equivalent to eight thousand times the energy consumption of the whole world in 2009, and is known as the source of all things. Solar energy is a form of radiant energy, and it must be converted into electrical energy with the help of an energy converter. This energy converter that converts light energy into electrical energy is a solar cell (also known as a photovoltaic cell). Solar cells are mainly composed of materials such as glass, cell wafers, EVA film, backsheet film, aluminum frame, and junction box. The backsheet film of a solar cell, as a packaging material for photovoltaic cell modules, is an important part of a solar cell. The backsheet film is the material used to encapsulate the back of the solar cell and plays a role in protecting and supporting the cell wafers. The service life requirement for commercial solar cells is 25 years. As a photovoltaic packaging material that is directly in large-area contact with the external environment, the backsheet film must possess excellent properties such as resistance to aging (humid heat, dry heat, ultraviolet), electrical insulation, water vapor barrier, and dimensional stability.

[0003] Currently, many backsheets of solar panels cannot withstand the tests of diverse and harsh environments. For example, problems such as delamination, cracking, blistering, and yellowing occur, leading to phenomena such as the detachment of the battery module, the slippage of the cell wafers, and the reduction of the effective output power of the battery. The reliability, stability, and durability of solar cells cannot be guaranteed, and even greater accidents may be caused. Summary of the Invention

[0004] The first aspect of the present invention provides a multi-layer composite highly protective polyester film for solar cell backsheets, which is characterized in that: the reinforced polyester film is divided into a weather-resistant coating, a PET layer, and a waterproof layer; the positional relationship of the weather-resistant coating, the PET layer, and the waterproof layer is that the weather-resistant coating is on the upper layer, the PET layer is in the middle layer, and the waterproof layer is on the lower layer; the preparation raw materials of the weather-resistant coating include one or more of polytetrafluoroethylene, ethylene, polyvinylidene fluoride, modified polyvinylidene fluoride, modifier, dispersion medium, and initiator; the preparation raw materials of the waterproof layer include one or more of polyethylene terephthalate chips, hydrolysis-resistant agent, water-blocking agent, and nano-zinc oxide.

[0005] The present invention is further configured as follows: the preparation raw materials of the weather-resistant coating include modified polyvinylidene fluoride, nano-titanium dioxide, modifier, dispersion medium, and initiator. The modifier is a fluorine-containing compound, the dispersion medium is an alcohol solvent, and the initiator is an azo compound.

[0006] The present invention is further configured that: the modifier is hexafluoropropylene oxide, the dispersion medium is isopropyl alcohol, and the initiator is azobisisobutyronitrile; the thickness of the weather-resistant coating is 12 - 18 μm, and the thickness of the weather-resistant coating accounts for 4 - 10% of the total thickness of the reinforced polyester film.

[0007] The present invention is further configured that: the raw materials for preparing the PET layer are a mixture of polyethylene terephthalate chips and polyethylene naphthalate chips, and the mass ratio of the two is (3 - 5):1; the thickness of the PET layer is 220 - 320 μm, and the thickness of the PET layer accounts for 75 - 95% of the total thickness of the reinforced polyester film.

[0008] The present invention is further configured that: the hydrolysis-resistant agent is one of carbodiimide polymers and epoxy group silane coupling agents.

[0009] The present invention is further configured that: the water-blocking agent is one of organic bentonite and ethylene-vinyl acetate copolymer.

[0010] The present invention is further configured that: the hydrolysis-resistant agent is a carbodiimide polymer.

[0011] The present invention is further configured that: the water-blocking agent is organic bentonite.

[0012] The present invention is further configured that: the thickness of the waterproof layer is 12 - 18 μm, and the thickness of the waterproof layer accounts for 4 - 10% of the total thickness of the reinforced polyester film.

[0013] The present invention also provides an application of a multilayer composite high-efficiency protective solar cell backplane polyester film, which is characterized in that: the above-mentioned reinforced polyester film is applied to a solar cell backplane.

[0014] The polyester film provided by the present invention has good weather resistance and high water-blocking property, can extend the service life of the solar backplane, and improve economic benefits. Detailed embodiments

[0015] To solve the above problems, the present invention provides a multilayer composite high-efficiency protective solar cell backplane polyester film. The first aspect of the present invention provides a multilayer composite high-efficiency protective solar cell backplane polyester film, which is characterized in that: the reinforced polyester film is divided into a weather-resistant coating, a PET layer, and a waterproof layer; the positional relationship of the weather-resistant coating, the PET layer, and the waterproof layer is that the upper layer is the weather-resistant coating, the middle layer is the PET layer, and the lower layer is the waterproof layer; the raw materials for preparing the weather-resistant coating include one or more of polytetrafluoroethylene, ethylene, polyvinylidene fluoride, modified polyvinylidene fluoride, modifier, dispersion medium, and initiator; the raw materials for preparing the waterproof layer include one or more of polyethylene terephthalate chips, hydrolysis-resistant agent, water-blocking agent, and nano-zinc oxide.

[0016] The present invention further provides that the raw materials for preparing the weather-resistant coating include modified polyvinylidene fluoride, nano-titanium dioxide, a modifier, a dispersion medium, and an initiator. The modifier is a fluorine-containing compound, the dispersion medium is an alcohol solvent, and the initiator is an azo compound.

[0017] The present invention further provides that the modifier is hexafluoropropylene oxide, the dispersion medium is isopropyl alcohol, and the initiator is azobisisobutyronitrile; the thickness of the weather-resistant coating is 12 - 18 μm, and the thickness of the weather-resistant coating accounts for 4 - 10% of the total thickness of the reinforced polyester film.

[0018] The present invention further provides that the raw materials for preparing the PET layer are a mixture of polyethylene terephthalate chips and polyethylene naphthalate chips, and the mass ratio of the two is (3 - 5):1; the thickness of the PET layer is 220 - 320 μm, and the thickness of the PET layer accounts for 75 - 95% of the total thickness of the reinforced polyester film.

[0019] The present invention further provides that the hydrolysis-resistant agent is one of carbodiimide polymers and epoxy group silane coupling agents.

[0020] The present invention further provides that the water-blocking agent is one of organic bentonite and ethylene-vinyl acetate copolymer.

[0021] The present invention further provides that the hydrolysis-resistant agent is a carbodiimide polymer.

[0022] The present invention further provides that the water-blocking agent is organic bentonite.

[0023] The present invention further provides that the thickness of the waterproof layer is 12 - 18 μm, and the thickness of the waterproof layer accounts for 4 - 10% of the total thickness of the reinforced polyester film.

[0024] The present invention also provides an application of a multi-layer composite high-efficiency protective solar cell backplane polyester film, which is characterized in that the reinforced polyester film is applied to a solar cell backplane.

[0025] The polyester film provided by the present invention has good weather resistance and high water-blocking property, can extend the service life of the solar backplane, and improve economic benefits.

[0026] In the present invention, ethylene-tetrafluoroethylene copolymer and nano-titanium dioxide are added: ethylene-tetrafluoroethylene copolymer has good weather resistance and chemical stability, and can further improve the comprehensive performance of the weather-resistant coating. Nano-titanium dioxide has photocatalytic activity and ultraviolet shielding ability, can enhance the coating's resistance to ultraviolet rays, and improve weather resistance.

[0027] Change modifiers, dispersion media, and initiators: Using fluorine-containing compounds (such as hexafluoropropylene oxide) as modifiers can endow the coating with better chemical corrosion resistance and weather resistance; alcohol solvents (such as isopropyl alcohol) as dispersion media have good solubility and volatility; azo compounds (such as azobisisobutyronitrile) as initiators have good initiation effects and relatively mild reaction conditions.

[0028] Adjust the thickness range: Appropriately expand the thickness range of the weather-resistant coating to meet the requirements of weather resistance performance in different application scenarios.

[0029] PET layer

[0030] Add polyethylene naphthalate slices: Polyethylene naphthalate slices have higher strength, heat resistance, and barrier properties. When mixed with polyethylene terephthalate slices, the comprehensive performance of the PET layer can be improved.

[0031] Adjust the thickness range: Corresponding adjust the thickness range of the PET layer, considering the possible impact on the overall performance and thickness ratio after adding new components.

[0032] Waterproof layer

[0033] Add nano-zinc oxide: Nano-zinc oxide has good waterproof and antibacterial properties, which can enhance the waterproof effect and durability of the waterproof layer.

[0034] Change hydrolysis-resistant agents and water-blocking agents: Carbodiimide polymers as hydrolysis-resistant agents have better hydrolysis stability; organic bentonite as a water-blocking agent has good water absorption and swelling properties, which can effectively prevent water penetration.

[0035] Adjust the thickness range: Similarly, appropriately adjust the thickness range of the waterproof layer to ensure the balance of overall performance.

[0036] Among them, Experimental Example 1

[0037] Preparation of weather-resistant coating: Add 20 g of modified polyvinylidene fluoride and 5 g of nano-titanium dioxide to 200 g of isopropyl alcohol, and stir evenly. Introduce 5 g of hexafluoropropylene oxide as a modifier and add 3 g of azobisisobutyronitrile as an initiator, and react at 60 °C for 3 hours to obtain a weather-resistant coating slurry. Coat the slurry on the PET layer to form a weather-resistant coating with a thickness of 12 μm, and its thickness accounts for 4% of the total thickness of the reinforced polyester film.

[0038] Preparation of PET layer: Mix 150 g of polyethylene terephthalate slices and 50 g of polyethylene naphthalate slices, and melt-extrude them at 280 °C in a twin-screw extruder to make a PET layer with a thickness of 220 μm, and its thickness accounts for 80% of the total thickness of the reinforced polyester film.

[0039] Preparation of waterproof layer: 100 g of polyethylene terephthalate chips, 3 g of carbodiimide polymer, 5 g of organic bentonite, and 2 g of nano-zinc oxide were mixed and melt-extruded at 260 °C in a twin-screw extruder to form a waterproof layer with a thickness of 12 μm, which accounted for 4% of the total thickness of the reinforced polyester film.

[0040] Performance test data: After 1000 hours of ultraviolet aging test, there was no obvious discoloration or powdering on the film surface, and the gloss retention rate reached 85%. When placed in an environment of 85 °C and 85% relative humidity for 1000 hours, the water vapor transmission rate was 0.5 g / (m 2 ·24 h), and the tensile strength retention rate was 90%, effectively proving its good weather resistance, waterproofness, and mechanical property stability.

[0041] Experimental Example 2:

[0042] Preparation of weather-resistant coating: 30 g of modified polyvinylidene fluoride and 8 g of nano-titanium dioxide were dissolved in 250 g of isopropanol, 7 g of hexafluoropropylene oxide and 5 g of azobisisobutyronitrile were added, and the reaction was carried out at 70 °C for 4 hours to obtain a slurry, which was coated to form a 15-μm weather-resistant coating, accounting for 6% of the total thickness.

[0043] Preparation of PET layer: 200 g of polyethylene terephthalate chips and 50 g of polyethylene naphthalate chips were mixed and melt-extruded at 290 °C to form a 250-μm thick PET layer, accounting for 85% of the total thickness.

[0044] Preparation of waterproof layer: 120 g of polyethylene terephthalate chips, 5 g of carbodiimide polymer, 8 g of organic bentonite, and 3 g of nano-zinc oxide were mixed and melt-extruded at 270 °C to form a 15-μm waterproof layer, accounting for 6% of the total thickness.

[0045] Performance test data: After 1500 hours of ultraviolet aging test, the film surface was slightly discolored, and the gloss retention rate was 80%. When placed in an environment of 85 °C and 85% relative humidity for 1500 hours, the water vapor transmission rate was 0.4 g / (m 2 ·24 h), and the tensile strength retention rate was 88%. All performance indicators were excellent, showing good comprehensive performance.

[0046] Experimental Example 3:

[0047] Preparation of weather-resistant coating: 40 g of modified polyvinylidene fluoride and 10 g of nano-titanium dioxide were dispersed in 300 g of isopropanol, 10 g of hexafluoropropylene oxide and 7 g of azobisisobutyronitrile were added, and the reaction was carried out at 80 °C for 5 hours to obtain a slurry, which was coated to obtain an 18-μm weather-resistant coating, accounting for 10% of the total thickness.

[0048] Preparation of PET layer: 250 g of polyethylene terephthalate chips and 50 g of polyethylene naphthalate chips were mixed and melt-extruded at 300 °C to form a PET layer with a thickness of 320 μm, accounting for 80% of the total thickness.

[0049] Preparation of waterproof layer: 150 g of polyethylene terephthalate chips, 8 g of carbodiimide polymer, 10 g of organic bentonite, and 5 g of nano-zinc oxide were mixed and melt-extruded at 280 °C to form a waterproof layer with a thickness of 18 μm, accounting for 10% of the total thickness.

[0050] Performance test data: After 2000 hours of ultraviolet aging test, only very slight discoloration occurred on the film surface, and the gloss retention rate was 78%. When placed in an environment of 85 °C and 85% relative humidity for 2000 hours, the water vapor transmission rate was 0.3 g / (m 2 ·24 h), and the tensile strength retention rate was 85%. It could still maintain good performance under long-term harsh environments, demonstrating the reliability and stability of the product.

[0051] Description of test standards

[0052] Ultraviolet aging test: According to ASTM G154 standard, a fluorescent ultraviolet lamp was used to simulate the ultraviolet radiation in sunlight to irradiate and age the film. The weather resistance was evaluated by observing the discoloration and chalking of the film surface and measuring the gloss retention rate. The formula for calculating the gloss retention rate is: (gloss after aging / gloss before aging) × 100%.

[0053] Water vapor transmission rate test: According to GB / T 1037-1988 standard, the cup method for measuring water vapor transmission was adopted. Under the specified temperature (85 °C) and relative humidity (85%) conditions, the amount of water vapor passing through a unit area of the film per unit time was measured.

[0054] Tensile strength retention rate test: According to GB / T 1040.3-2006 standard, tensile tests were carried out on the film before and after the aging test respectively to measure the tensile strength. The formula for calculating the tensile strength retention rate is: (tensile strength after aging / tensile strength before aging) × 100%.

[0055] The above is only a preferred embodiment of the present invention, and it is not a limitation of the invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or equivalent changes to equivalent embodiments, but as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A multi-layer composite high-efficiency protective polyester film for a solar cell backsheet, characterized in that: The reinforced polyester film is divided into a weather-resistant coating, a PET layer, and a waterproof layer; the positional relationship of the weather-resistant coating, the PET layer, and the waterproof layer is that the upper layer is the weather-resistant coating, the middle layer is the PET layer, and the lower layer is the waterproof layer; the preparation raw materials of the weather-resistant coating include one or more of polytetrafluoroethylene, ethylene, polyvinylidene fluoride, modified polyvinylidene fluoride, modifier, dispersion medium, and initiator; the preparation raw materials of the waterproof layer include one or more of polyethylene terephthalate chips, hydrolysis-resistant agent, water-blocking agent, and nano-zinc oxide.

2. The polyester film for a multi-layer composite highly efficient protective solar cell backplane according to claim 1, wherein: The preparation raw materials of the weather-resistant coating include modified polyvinylidene fluoride, nano-titanium dioxide, modifier, dispersion medium, and initiator. The modifier is a fluorine-containing compound, the dispersion medium is an alcohol solvent, and the initiator is an azo compound.

3. The polyester film for a multi-layer composite highly efficient protective solar cell backplane according to claim 2, wherein: The modifier is hexafluoropropylene oxide, the dispersion medium is isopropyl alcohol, and the initiator is azobisisobutyronitrile; the thickness of the weather-resistant coating is 12-18 μm, and the thickness of the weather-resistant coating accounts for 4-10% of the total thickness of the reinforced polyester film.

4. A polyester film for a multi-layer composite high-efficiency protective solar cell backplane according to claim 1, characterized in that: The preparation raw materials of the PET layer are a mixture of polyethylene terephthalate chips and polyethylene naphthalate chips, and the mass ratio of the two is (3-5):1; the thickness of the PET layer is 220-320 μm, The thickness of the PET layer accounts for 75-95% of the total thickness of the reinforced polyester film.

5. A multilayer composite high-efficiency protective solar cell backsheet polyester film according to claim 1, wherein: The hydrolysis-resistant agent is one of carbodiimide polymers and epoxy-based silane coupling agents.

6. A multilayer composite high-efficiency protective solar cell backsheet polyester film according to claim 1, wherein: The water-blocking agent is one of organic bentonite and ethylene-vinyl acetate copolymer.

7. A multilayer composite high-efficiency protective solar cell backsheet polyester film according to claim 5, wherein: The hydrolysis-resistant agent is a carbodiimide polymer.

8. A multilayer composite high-efficiency protective solar cell backsheet polyester film according to claim 6, wherein: The water-blocking agent is organic bentonite.

9. A multilayer composite high-efficiency protective solar cell backsheet polyester film according to claim 1, wherein: The thickness of the waterproof layer is 12-18 μm, and the thickness of the waterproof layer accounts for 4-10% of the total thickness of the reinforced polyester film.

10. Application of a multi-layer composite highly protective polyester film for a solar cell backsheet, characterized in that: Apply the reinforced polyester film according to any one of claims 1-9 to a solar cell backsheet.