Halogen-free flame-retardant polyurethane packaging film with high refractive index and preparation method of halogen-free flame-retardant polyurethane packaging film

Abstract

The invention discloses a halogen-free flame-retardant polyurethane packaging film with high refractive index and a preparation method thereof. The halogen-free flame-retardant polyurethane packaging film with the high refractive index is prepared from the following substances in parts by mass: 100 parts of thermoplastic polyurethane, 0.5 to 5.0 parts of ammonium polyphosphate, 50 to 60 parts of phenyl vinyl silicone resin and 0.1 to 0.3 part of an initiator. The high-refractive-index halogen-free flame-retardant polyurethane packaging film provided by the invention is high in refractive index and good in weather resistance and flame retardance.

Description

Technical Field

[0001] This invention relates to the field of solar cell module encapsulation materials technology, specifically to a high refractive index halogen-free flame-retardant polyurethane encapsulation film and its preparation method. Background Technology

[0002] Currently, global warming is increasingly threatening the Earth's ecological environment, primarily due to human activities such as burning fossil fuels and emitting greenhouse gases like carbon dioxide. For sustainable development, humanity needs to adhere to energy conservation and emission reduction strategies and develop a green and low-carbon economy. Energy transition is paramount, and solar energy, being both a primary and renewable energy source, has broad development prospects. The most crucial component of a solar cell system is the solar cell module. Its structure includes a top cover typically made of photovoltaic glass; a substrate (backsheet) requiring properties such as heat insulation, electrical insulation, water resistance, and aging resistance, often composed of composite materials; and a middle layer consisting of cell layers encapsulated by a sealing film. This sealing material must possess characteristics such as transparency, moisture resistance, and good adhesion to meet the performance requirements of solar photovoltaic cell encapsulation materials.

[0003] The encapsulation film is a key factor affecting the quality and lifespan of solar cell modules. While it accounts for only about 7% of the total cost of a solar cell module, its impact on the operational lifespan is crucial. Solar cell modules are generally required to last over 25 years, and the encapsulation process is irreversible. If the encapsulation film begins to yellow or crack during its lifespan, the module will fail and be unusable. Polymer materials are widely used as encapsulation materials due to their low cost, light weight, excellent adhesion, and flexibility. Transparent thermoplastic polyurethane elastomer (TPU) is a special material between general plastics and rubber, exhibiting excellent mechanical and optical properties, making it suitable for photovoltaic module encapsulation. However, because thermoplastic polyurethane has a unique physical cross-linked structure formed by hydrogen bonds and contains water-absorbing groups, its moisture permeability is relatively high. Furthermore, its dimensional stability deteriorates under long-term use due to the effects of heat, oxygen, humidity, and sunlight. In addition, TPU itself has poor flame retardancy, which also limits its use as an encapsulation film. Therefore, it is necessary to modify TPU so that it not only has a high refractive index for use as an encapsulation film, but also has excellent flame retardant properties and weather resistance. Summary of the Invention

[0004] This invention solves the problems existing in the prior art and provides a high refractive index halogen-free flame-retardant polyurethane encapsulation film and its preparation method. The high refractive index halogen-free flame-retardant polyurethane encapsulation film proposed in this invention has high refractive index, good weather resistance and flame retardant properties, which can solve the problems of poor flame retardant properties and weather resistance of TPU encapsulation films in the prior art.

[0005] The purpose of this invention is to provide a high refractive index halogen-free flame-retardant polyurethane encapsulation film, which is prepared by means of the following substances in parts by weight: 100 parts of thermoplastic polyurethane, 0.5-5.0 parts of ammonium polyphosphate, 50-60 parts of phenyl vinyl silicone resin and 0.1-0.3 parts of initiator.

[0006] Preferably, the refractive index of the thermoplastic polyurethane is 1.52-1.54. The initiator proposed in this invention is dicumyl peroxide.

[0007] Preferably, the phenyl vinyl silicone resin is prepared by the following steps:

[0008] S1. Mix phenyltrimethoxysilane and tetramethyldivinyldisiloxane, add hydrolysis catalyst, and slowly add pure water dropwise over 1-3 hours at room temperature to carry out hydrolysis reaction. After the addition is complete, heat to 65℃-75℃ and reflux for 2-6 hours. Stop heating, cool to room temperature, separate the liquids, and take the upper resin layer to obtain the reaction mixture.

[0009] S2. Add toluene or xylene to the reaction mixture obtained in step S1, mix thoroughly, adjust the pH to 8-14, and carry out the condensation reaction at 100℃-120℃ for 1-6 h. Use a water separator to remove the distilled water until no water is produced, then stop heating and cool to room temperature to obtain the initial phenyl vinyl siloxane resin solution.

[0010] S3. Wash the phenyl vinyl siloxane resin solution obtained in step S2 with water, separate the liquids, take the upper resin layer, dehydrate, stir and filter to obtain a colorless phenyl vinyl siloxane resin solution, and dehydrate under reduced pressure to obtain the phenyl vinyl silicone resin. The refractive index of the phenyl vinyl silicone resin is 1.52-1.54.

[0011] In step S2, the pH is adjusted to 8-14 by adding KOH. In step S3, the solvent is removed by vacuum distillation at 110℃~130℃.

[0012] Further preferably, the mass ratio of phenyltrimethoxysilane to tetramethyldivinyldisiloxane in step S1 is 100:(10-30), the hydrolysis catalyst is 36.5 wt% concentrated hydrochloric acid, and the mass ratio of the hydrolysis catalyst to phenyltrimethoxysilane is 0.4-0.6:100.

[0013] Further preferably, the mass ratio of pure water to phenyltrimethoxysilane in step S1 is 30-50:100.

[0014] Further preferably, the mass ratio of toluene or xylene to phenyltrimethoxysilane in step S2 is 25-50:100.

[0015] Further preferred, in step S3, anhydrous calcium chloride is added for dehydration, wherein the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 2-5:100.

[0016] This invention also protects a method for preparing the flame-retardant polyurethane encapsulation film, comprising the following steps:

[0017] (1) The thermoplastic polyurethane, ammonium polyphosphate, phenyl vinyl silicone resin and initiator are mixed in a speed mixer, and then the mixed raw materials are placed in an extruder and granulated by melt blending extrusion to obtain a high refractive index halogen-free flame retardant polyurethane masterbatch.

[0018] (2) Dry the high refractive index halogen-free flame-retardant polyurethane masterbatch obtained in step (1) and set it aside for later use;

[0019] (3) Take the dried high refractive index halogen-free flame retardant polyurethane masterbatch and disperse it between two release films, and hot press it into a film to obtain the high refractive index halogen-free flame retardant polyurethane encapsulation film.

[0020] Preferably, the specific conditions for melt blending extrusion granulation in step (1) are: melt blending extrusion granulation at a rotation speed of 150-250 r / min and a temperature of 150℃-170℃.

[0021] Preferably, the specific steps of hot pressing to form a film in step (3) are as follows: hot pressing to form a film at 160℃-170℃ using a flatbed hot press, with a pressure of 5-20 MPa and a holding time of 60-120 s.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The polyurethane encapsulation film proposed in this invention has a high refractive index, which can better absorb solar energy and thus improve photoelectric conversion efficiency.

[0024] 2. Organosilicon has good weather resistance and certain flame retardancy, and the introduction of phenyl groups further enhances this property. When combined with phosphorus-based flame retardants, the flame retardant effect is very significant.

[0025] 3. During the melt extrusion process, the TPU matrix and phenyl vinyl silicone resin undergo cross-linking initiated by an initiator to form a well-compatible micro-cross-linked structure, thereby preparing a high-refractive-index halogen-free flame-retardant polyurethane. This modified TPU not only has a physical cross-linked structure with hydrogen bonds, but also generates a certain proportion of phenyl silicone resin grafted onto the TPU main chain to form a strong chemical cross-linked structure. Since phenyl silicone resin has good hydrophobicity and weather resistance, it can reduce the moisture permeability of TPU and improve the weather resistance of TPU. Detailed Implementation

[0026] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this technical field. In the examples below, TPU was purchased from Yantai Wanhua Co., Ltd., brand name WHT-1195, and the initiator was dicumyl peroxide (DCP), purchased from Aladdin Reagent Co., Ltd.

[0028] Preferably, in the following embodiments, the phenyl vinyl silicone resin has a refractive index of 1.52-1.54 and is prepared by the following steps:

[0029] S1. Mix phenyltrimethoxysilane and tetramethyldivinyldisiloxane, add hydrolysis catalyst, and slowly add pure water dropwise over 1-3 hours at room temperature to carry out hydrolysis reaction. After the addition is complete, heat to 65℃~75℃ and reflux for 2-6 hours. Stop heating, cool to room temperature, separate the liquids, and take the upper resin layer to obtain the reaction mixture.

[0030] S2. Toluene or xylene is added to the reaction mixture obtained in step S1. After thorough mixing, KOH is added to adjust the pH to 8-14. The mixture is concentrated at 100℃~120℃ and subjected to a condensation reaction for 1-6 h. The distilled water is removed using a water separator until no water is produced. Heating is then stopped and the mixture is cooled to room temperature to obtain the initial phenyl vinyl siloxane resin solution.

[0031] S3. After washing the above solution three times with water and separating the liquid, take the upper resin layer, add anhydrous calcium chloride to dehydrate, stir for 30 minutes, and then filter under vacuum to obtain a colorless phenyl vinyl siloxane resin solution. Remove the solvent by vacuum distillation at 110℃-130℃ to obtain phenyl vinyl silicone resin.

[0032] Further preferably, the mass ratio of phenyltrimethoxysilane to tetramethyldivinyldisiloxane in step S1 is 100:(10-30). Even more preferably, the mass ratio of phenyltrimethoxysilane to tetramethyldivinyldisiloxane in step S1 is 100:20.

[0033] Further preferably, the hydrolysis catalyst in step S1 is 36.5 wt% concentrated hydrochloric acid; the mass ratio of the hydrolysis catalyst to phenyltrimethoxysilane is 0.4-0.6:100, and the mass ratio of pure water to phenyltrimethoxysilane is (30-50):100. Even more preferably, the mass ratio of the hydrolysis catalyst to phenyltrimethoxysilane is 0.5:100, and the mass ratio of pure water to phenyltrimethoxysilane is 40:100.

[0034] Further preferably, in step S2, the mass ratio of toluene or xylene to phenyltrimethoxysilane is (25-50):100, and the mass ratio of KOH to phenyltrimethoxysilane is (0.5-1.0):100. Even more preferably, the mass ratio of toluene or xylene to phenyltrimethoxysilane is 35:100, and the mass ratio of KOH to phenyltrimethoxysilane is 0.75:100.

[0035] Further preferably, the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane in step S3 is (2.0~5.0):100. Even more preferably, the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 3.5:100.

[0036] In the following preferred embodiments, the preparation method of the high refractive index halogen-free flame-retardant polyurethane encapsulation film includes the following steps:

[0037] (1) Thermoplastic polyurethane (TPU), ammonium polyphosphate, phenyl vinyl silicone resin and initiator are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain high refractive index halogen-free flame retardant polyurethane masterbatch.

[0038] (2) The high refractive index halogen-free flame retardant polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0039] (3) Take the dried high refractive index halogen-free flame retardant polyurethane masterbatch and disperse it between two release films. Then, use a flat plate hot press to hot press the film at 160℃-170℃ with a pressure of 5-20 MPa and keep it at the temperature for 60-120 s to obtain a high refractive index halogen-free flame retardant polyurethane encapsulation film.

[0040] Example 1

[0041] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film, comprising the following components by mass: 100 parts thermoplastic polyurethane, 5 parts ammonium polyphosphate, 50 parts phenyl vinyl silicone resin, and 0.1 parts dicumyl peroxide.

[0042] The refractive index of thermoplastic polyurethane is 1.52, and the refractive index of phenyl vinyl silicone resin is 1.52.

[0043] Phenyl vinyl silicone resin is prepared by the following steps:

[0044] S1. Phenylacetoxysilane and tetramethyldivinyldisiloxane were mixed in a mass ratio of 100:20. 36.5 wt% concentrated hydrochloric acid was added, with a mass ratio of 0.5:100 between the concentrated hydrochloric acid and phenyltrimethoxysilane. At room temperature, pure water was slowly added dropwise over 2 h to carry out the hydrolysis reaction, with a mass ratio of 40:100 between the pure water and phenyltrimethoxysilane. After the addition was complete, the temperature was raised to 70 °C and refluxed for 4 h. Heating was then stopped, and the mixture was cooled to room temperature. The liquid was separated, and the upper resin layer was taken to obtain the reaction mixture.

[0045] S2. Toluene is added to the reaction mixture obtained in step S1. After thorough mixing, KOH is added to adjust the pH to 10. The mass ratio of toluene to phenyltrimethoxysilane is 35:100, and the mass ratio of KOH to phenyltrimethoxysilane is 0.75:100. The mixture is concentrated at 110°C and subjected to a condensation reaction for 3 h. The distilled water is removed using a water separator until no water is produced. Heating is then stopped, and the mixture is cooled to room temperature to obtain the initial phenylvinylsiloxane resin solution.

[0046] S3. After washing the above solution three times with water and separating the liquid, take the upper resin layer, add anhydrous calcium chloride to dehydrate it, and the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 3.5:100. After stirring for 30 minutes, filter under vacuum to obtain a colorless phenylvinylsiloxane resin solution. Remove the solvent by vacuum distillation at 120°C to obtain phenylvinylsilane resin.

[0047] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film includes the following steps:

[0048] (1) Thermoplastic polyurethane (TPU), ammonium polyphosphate, phenyl vinyl silicone resin and diisopropylbenzene peroxide are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain a high refractive index halogen-free flame-retardant polyurethane masterbatch.

[0049] (2) The high refractive index halogen-free flame retardant polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0050] (3) Take the dried high refractive index halogen-free flame retardant polyurethane masterbatch and disperse it between two release films. Then, use a flat plate hot press to hot press the film at 165°C with a pressure of 8 MPa and keep it at the temperature for 90 s to obtain the high refractive index halogen-free flame retardant polyurethane encapsulation film.

[0051] Example 2

[0052] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film, comprising the following components by mass: 100 parts thermoplastic polyurethane, 5 parts ammonium polyphosphate, 60 parts phenyl vinyl silicone resin, and 0.3 parts dicumyl peroxide. The refractive index of the thermoplastic polyurethane is 1.52, and the refractive index of the phenyl vinyl silicone resin is 1.52.

[0053] The preparation steps for phenyl vinyl silicone resin and high refractive index halogen-free flame-retardant polyurethane encapsulation film are as described in Example 1.

[0054] Example 3

[0055] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film, comprising the following components by mass: 100 parts thermoplastic polyurethane, 0.5 parts ammonium polyphosphate, 55 parts phenyl vinyl silicone resin, and 0.2 parts dicumyl peroxide. The refractive index of the thermoplastic polyurethane is 1.52, and the refractive index of the phenyl vinyl silicone resin is 1.52.

[0056] The preparation steps for phenyl vinyl silicone resin and high refractive index halogen-free flame-retardant polyurethane encapsulation film are as described in Example 1.

[0057] Example 4

[0058] Same as Example 3, except that:

[0059] The refractive index of thermoplastic polyurethane is 1.54. The refractive index of phenyl vinyl silicone resin is 1.54.

[0060] Phenyl vinyl silicone resin is prepared by the following steps:

[0061] S1. Mix phenyltrimethoxysilane and tetramethyldivinyldisiloxane at a mass ratio of 100:10. Add 36.5 wt% concentrated hydrochloric acid at a mass ratio of 0.4:100 to phenyltrimethoxysilane. Slowly add pure water dropwise over 3 hours at room temperature to carry out the hydrolysis reaction at a mass ratio of 50:100 to phenyltrimethoxysilane. After the addition is complete, heat to 65°C and reflux for 6 hours. Stop heating, cool to room temperature, separate the layers, and take the upper resin layer to obtain the reaction mixture.

[0062] S2. Add xylene to the reaction mixture obtained in step S1. The mass ratio of xylene to phenyltrimethoxysilane is 50:100. After thorough mixing, add KOH to adjust the pH to 14. Concentrate at 120°C and carry out a condensation reaction for 1 h. Use a water separator to remove the distilled water until no water is produced. Stop heating and cool to room temperature to obtain the initial phenylvinylsiloxane resin solution.

[0063] S3. After washing the above solution three times with water and separating the liquid, take the upper resin layer, add anhydrous calcium chloride to dehydrate it, and the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 5.0:100. After stirring for 30 minutes, filter under vacuum to obtain a colorless phenylvinylsiloxane resin solution. Remove the solvent by vacuum distillation at 130°C to obtain phenylvinylsilane resin.

[0064] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film includes the following steps:

[0065] (1) Thermoplastic polyurethane (TPU), ammonium polyphosphate, phenyl vinyl silicone resin and diisopropylbenzene peroxide are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain a high refractive index halogen-free flame-retardant polyurethane masterbatch.

[0066] (2) The high refractive index halogen-free flame retardant polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0067] (3) High refractive index halogen-free flame retardant polyurethane masterbatch is dispersed between two release films and hot-pressed into a film at 170°C using a flatbed hot press with a pressure of 20 MPa and a holding time of 60 s to obtain a high refractive index halogen-free flame retardant polyurethane encapsulation film.

[0068] Example 5

[0069] Same as Example 3, except that:

[0070] The refractive index of thermoplastic polyurethane is 1.52. The refractive index of phenyl vinyl silicone resin is 1.54.

[0071] Phenyl vinyl silicone resin is prepared by the following steps:

[0072] S1. Mix phenyltrimethoxysilane and tetramethyldivinyldisiloxane at a mass ratio of 100:30. Add 36.5 wt% concentrated hydrochloric acid at a mass ratio of 0.6:100 to phenyltrimethoxysilane. Slowly add pure water dropwise over 1 hour at room temperature to carry out the hydrolysis reaction at a mass ratio of 30:100 to phenyltrimethoxysilane. After the addition is complete, heat to 75°C and reflux for 2 hours. Stop heating, cool to room temperature, separate the layers, and take the upper resin layer to obtain the reaction mixture.

[0073] S2. Add xylene to the reaction mixture obtained in step S1. The mass ratio of xylene to phenyltrimethoxysilane is 25:100. After thorough mixing, add KOH to adjust the pH to 8. Concentrate at 100°C and carry out a condensation reaction for 6 h. Use a water separator to remove the distilled water until no water is produced. Stop heating and cool to room temperature to obtain the initial phenylvinylsiloxane resin solution.

[0074] S3. After washing the above solution three times with water and separating the liquid, take the upper resin layer, add anhydrous calcium chloride to dehydrate it, and the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 5.0:100. After stirring for 30 minutes, filter under vacuum to obtain a colorless phenylvinylsiloxane resin solution. Remove the solvent by vacuum distillation at 110°C to obtain phenylvinylsilane resin.

[0075] A method for preparing a high refractive index halogen-free flame-retardant polyurethane encapsulation film includes the following steps:

[0076] (1) Thermoplastic polyurethane (TPU), ammonium polyphosphate, phenyl vinyl silicone resin and diisopropylbenzene peroxide are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain a high refractive index halogen-free flame-retardant polyurethane masterbatch.

[0077] (2) The high refractive index halogen-free flame retardant polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0078] (3) High refractive index halogen-free flame retardant polyurethane masterbatch is dispersed between two release films and hot-pressed into a film at 160°C using a flatbed hot press with a pressure of 5 MPa and a holding time of 120 s to obtain a high refractive index halogen-free flame retardant polyurethane encapsulation film.

[0079] Comparative Example 1

[0080] A polyurethane encapsulation film, by weight, comprises the following components: 100 parts thermoplastic polyurethane (TPU) and 0.1 parts initiator DCP. The thermoplastic polyurethane has a refractive index of 1.52.

[0081] The method for preparing the above-mentioned polyurethane encapsulation film includes the following steps:

[0082] (1) TPU and initiator DCP are mixed in a speed mixer at 250 r / min, and then the mixed raw materials are placed in an extruder and granulated by melt blending at 200 r / min at 160℃ to obtain polyurethane masterbatch.

[0083] (2) The polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0084] (3) Disperse polyurethane masterbatch between two release films, and press them into a film at 165°C using a flatbed hot press with a pressure of 8 MPa and a holding time of 90 s to obtain a polyurethane encapsulation film.

[0085] Comparative Example 2

[0086] A polyurethane encapsulation film, by weight, comprises the following components: 100 parts thermoplastic polyurethane (TPU), 0.1 parts initiator DCP, and 55 parts phenyl vinyl silicone resin. The thermoplastic polyurethane has a refractive index of 1.52, and the phenyl vinyl silicone resin has a refractive index of 1.52. The preparation steps of the phenyl vinyl silicone resin are as described in Example 1.

[0087] The method for preparing the above-mentioned polyurethane encapsulation film includes the following steps:

[0088] (1) TPU, initiator DCP and phenyl vinyl silicone resin are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain polyurethane masterbatch.

[0089] (2) The polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0090] (3) Disperse polyurethane masterbatch between two release films, and press them into a film at 165°C using a flatbed hot press with a pressure of 8 MPa and a holding time of 90 s to obtain a polyurethane encapsulation film.

[0091] Comparative Example 3

[0092] A polyurethane encapsulation film, by weight, comprises the following components: 100 parts thermoplastic polyurethane (TPU), 0.1 parts initiator DCP, and 55 parts ammonium polyphosphate. The refractive index of the thermoplastic polyurethane is 1.52.

[0093] The method for preparing the above-mentioned polyurethane encapsulation film includes the following steps:

[0094] (1) TPU, initiator DCP and ammonium polyphosphate are mixed in a speed mixer at 250 r / min. The mixed raw materials are then placed in an extruder and granulated by melt blending at 200 r / min at 160°C to obtain polyurethane masterbatch.

[0095] (2) The polyurethane masterbatch obtained in step (1) is dried in a vacuum oven at 80°C for 3 hours, and then placed in a desiccator for later use.

[0096] (3) Disperse polyurethane masterbatch between two release films, and press them into a film at 165°C using a flatbed hot press with a pressure of 8 MPa and a holding time of 90 s to obtain a polyurethane encapsulation film.

[0097] The performance of the polyurethane encapsulation films obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to standards GB 1034-70, GB / T 16928-1997, GB 1036-70, and ASTM D-3801. The test results are shown in Table 1.

[0098] Table 1. Performance test results of each embodiment and comparative example.

[0099] The polyurethane encapsulation films obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests after 7 days of thermo-oxidative aging at 140°C, referring to standards GB 1034-70, GB / T 16928-1997, GB 1036-70, and ASTM D-3801. The test results are shown in Table 2.

[0100] Table 2 Performance test results of each embodiment and comparative example

[0101] As shown in Tables 1 and 2, compared with Comparative Examples 2-3, the synergistic effect of phenyl vinyl silicone resin and phosphorus-based flame retardant in Example 1 is significantly better. Before thermo-oxidative aging, the water absorption, moisture permeability, and linear expansion coefficient of Examples 1-3 are much lower than those of Comparative Examples 1-3, indicating that the water resistance and dimensional stability of Examples 1-3 are significantly better than those of Comparative Examples 1-3. After thermo-oxidative aging, although the water absorption, moisture permeability, and linear expansion coefficient of Examples 1-3 increase slightly, the values ​​of Comparative Examples 1-3 increase significantly, indicating that the water resistance and dimensional stability of Examples 1-3 remain good, while their weather resistance is far superior to that of Comparative Examples 1-3. The limiting oxygen index and UL-94 vertical flammability rating of Examples 1-3 do not change before and after thermo-oxidative aging, while the limiting oxygen index of Comparative Examples 1-3 decreases after thermo-oxidative aging, indicating that the flame retardant performance of Examples 1-3 remains excellent after thermo-oxidative aging.

[0102] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A high refractive index halogen-free flame-retardant polyurethane encapsulation film, characterized in that, It is prepared by means of the following substances in parts by mass: 100 parts of thermoplastic polyurethane, 0.5-5.0 parts of ammonium polyphosphate, 50-60 parts of phenyl vinyl silicone resin and 0.1-0.3 parts of initiator.

2. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 1, characterized in that, The refractive index of the thermoplastic polyurethane is 1.52-1.

54.

3. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 1 or 2, characterized in that, The phenyl vinyl silicone resin is prepared by the following steps: S1. Mix phenyltrimethoxysilane and tetramethyldivinyldisiloxane, add hydrolysis catalyst, and slowly add pure water dropwise over 1-3 hours at room temperature to carry out hydrolysis reaction. After the addition is complete, heat to 65℃~75℃ and reflux for 2-6 hours. Stop heating, cool to room temperature, separate the liquids, and take the upper resin layer to obtain the reaction mixture. S2. Add toluene or xylene to the reaction mixture obtained in step S1, mix thoroughly, adjust the pH to 8-14, and carry out the condensation reaction at 100℃-120℃ for 1-6 h. Use a water separator to remove the distilled water until no water is produced, then stop heating and cool to room temperature to obtain the initial phenyl vinyl siloxane resin solution. S3. Wash the phenyl vinyl siloxane resin solution obtained in step S2 with water, separate the liquids, take the upper resin layer, dehydrate, stir and filter to obtain a colorless phenyl vinyl siloxane resin solution, and distill under reduced pressure to obtain the phenyl vinyl siloxane resin.

4. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 3, characterized in that, In step S1, the mass ratio of phenyltrimethoxysilane to tetramethyldivinyldisiloxane is 100:(10-30), the hydrolysis catalyst is 36.5 wt% concentrated hydrochloric acid, and the mass ratio of the hydrolysis catalyst to phenyltrimethoxysilane is 0.4-0.6:

100.

5. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 3, characterized in that, The mass ratio of pure water to phenyltrimethoxysilane in step S1 is 30-50:

100.

6. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 3, characterized in that, The mass ratio of toluene or xylene to phenyltrimethoxysilane in step S2 is 25-50:

100.

7. The high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 3, characterized in that, In step S3, anhydrous calcium chloride is added for dehydration, wherein the mass ratio of anhydrous calcium chloride to phenyltrimethoxysilane is 2-5:

100.

8. The method for preparing the high refractive index halogen-free flame-retardant polyurethane encapsulation film according to claim 1 or 2, characterized in that, Includes the following steps: (1) The thermoplastic polyurethane, ammonium polyphosphate, phenyl vinyl silicone resin and initiator are mixed in a speed mixer, and then the mixed raw materials are placed in an extruder and granulated by melt blending extrusion to obtain a high refractive index halogen-free flame retardant polyurethane masterbatch. (2) Dry the high refractive index halogen-free flame-retardant polyurethane masterbatch obtained in step (1) and set it aside for later use; (3) Take the dried high refractive index halogen-free flame retardant polyurethane masterbatch and disperse it between two release films, and hot press it into a film to obtain the high refractive index halogen-free flame retardant polyurethane encapsulation film.

9. The preparation method according to claim 8, characterized in that, The specific conditions for melt blending extrusion granulation in step (1) are: melt blending extrusion granulation at a rotation speed of 150-250 r / min and a temperature of 150℃-170℃.

10. The preparation method according to claim 8, characterized in that, The specific steps of hot pressing film formation in step (3) are as follows: hot pressing film formation is carried out by flat plate hot press at 160℃-170℃, with a pressure of 5-20 MPa and a holding time of 60-120 s.

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