An encapsulating adhesive film for photovoltaic modules, a preparation method and a photovoltaic module

Abstract

The application discloses a kind of encapsulation adhesive film for photovoltaic module, preparation method and photovoltaic module, the encapsulation adhesive film for photovoltaic module includes the following raw material components by weight parts: first POE resin: 90-95 parts;POE grafting modified resin: 5-8 parts;Nano silicon dioxide: 2-4 parts;Crosslinking agent: 0.6-1 part;Crosslinking aid: 0.3-0.6 parts;Light stabilizer: 0.3-0.5 parts;Ultraviolet absorber: 0.2-0.4 parts;Rheological aid: 0.08-0.15 parts.The encapsulation adhesive film for photovoltaic module has flexibility and mechanical properties, simultaneously realizes high flexibility, high bonding strength, low thermal shrinkage, high water vapor barrier performance and excellent damp heat aging resistance, meets the corresponding long-term bending service of photovoltaic module and the use requirement of high reliable long-term packaging, reduces the appearance of microcrack and delamination and the problem of packaging failure caused by defect.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module encapsulation technology, and in particular to an encapsulation film for photovoltaic modules, a preparation method thereof, and a photovoltaic module. Background Technology

[0002] Flexible lightweight photovoltaic modules, with their advantages of light weight, bendability, adaptability to curved surfaces, and mobile energy applications, represent the mainstream development direction of the photovoltaic module industry. These flexible lightweight photovoltaic modules often employ ultra-thin glass, flexible backsheets, or glass-free structures. Due to their unique structure and operating conditions, the requirements for the comprehensive performance of the encapsulating film are far higher than those for conventional double-glass modules.

[0003] Currently, the mainstream encapsulating films for flexible lightweight photovoltaic modules use POE or EVA as the matrix, prepared through physical blending of nanofillers, thermal cross-linking of a single peroxide, and ordinary casting processes. However, this system suffers from fundamental structural defects: the nanofillers and resin are only physically mixed, making coupling agents prone to migration and precipitation; it only has a single cross-linked network and lacks internal stress relief design. These multiple problems result in an inability to simultaneously achieve both mechanical strength and flexibility in the encapsulating film. It exhibits low tensile strength, insufficient elongation at break, low interfacial adhesion strength, low peel strength to the flexible backsheet, and rapid performance degradation after humid heat aging (e.g., adhesion strength retention rate <65% after 1000 hours in a humid heat aging environment of 85℃ / 85% relative humidity). Simultaneously, it suffers from high thermal shrinkage (e.g., thermal shrinkage rate >2.5%), insufficient moisture barrier capacity, and is prone to microcracks and delamination after repeated bending, making it unsuitable for the long-term bending service and high-reliability, long-lasting encapsulation requirements of flexible lightweight photovoltaic modules. Summary of the Invention

[0004] This invention provides an encapsulating film for photovoltaic modules, a preparation method thereof, and a photovoltaic module, to solve the problem that existing encapsulating films for photovoltaic modules cannot simultaneously achieve high flexibility, high adhesive strength, low shrinkage, high moisture barrier properties, and excellent damp heat aging resistance.

[0005] In a first aspect, embodiments of the present invention provide an encapsulating film for photovoltaic modules, comprising the following raw material components in parts by weight: First POE resin: 90-95 parts; POE grafted modified resin: 5-8 parts; Nano silica: 2-4 parts; Crosslinking agent: 0.6-1 part; Co-crosslinking agent: 0.3-0.6 parts; Light stabilizer: 0.3-0.5 parts; Ultraviolet absorber: 0.2-0.4 parts; Rheology modifier: 0.08-0.15 parts.

[0006] Optionally, the POE grafted modified resin is a maleic anhydride grafted POE resin. The maleic anhydride-grafted POE resin comprises a second POE resin and maleic anhydride, and the grafting rate of the maleic anhydride-grafted POE resin ranges from 0.8% to 1.2%.

[0007] Optionally, the crosslinking agent is tert-butyl peroxide; and / or, the co-crosslinking agent is trimethylolpropane tris(3-mercaptopropionate); and / or, the light stabilizer is HALS-944; and / or, the ultraviolet absorber is UV-123; and / or, the rheology modifier is a fluoropolymer.

[0008] Secondly, embodiments of the present invention also provide a method for preparing an encapsulating film for photovoltaic modules, used to prepare an encapsulating film for photovoltaic modules as described in any one of the first aspects, the method comprising: According to the weight proportions, the first POE resin, POE grafted modified resin, nano silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber and rheology modifier are mixed to obtain a homogeneous mixture. The mixture is uniformly mixed and melt-extruded through an extruder, and the extruded melt is sequentially subjected to calendering, internal stress relief, cross-linking curing, and corona activation to obtain the encapsulating film for photovoltaic modules.

[0009] Optionally, the first POE resin, POE graft-modified resin, nano-silica, crosslinking agent, co-crosslinking agent, light stabilizer, UV absorber, and rheology modifier are mixed in parts by weight to obtain a homogeneous mixture comprising: The first POE resin, the POE grafted modified resin, and the nano-silica are added to a mixing device to obtain a first mixed powder. An alkenyl silane coupling agent is added to the first mixed powder to obtain a second mixed powder; The light stabilizer, the ultraviolet absorber and the rheology modifier are added to the second mixed powder to obtain a third mixed powder; The crosslinking agent and the co-crosslinking agent are added to the third mixed powder to obtain the mixture.

[0010] Optionally, before adding the first POE resin, the POE grafted modified resin, and the nano-silica into the mixing device to obtain the first mixed powder, the method further includes: The first POE resin, the POE grafted modified resin, and the nano silica are dried to reduce the water content of the first POE resin, the POE grafted modified resin, and the nano silica to less than 0.05%.

[0011] Optionally, the mixture is uniformly mixed and melt-extruded using an extruder, and the extruded melt is sequentially subjected to calendering, internal stress relief, cross-linking curing, and corona activation to obtain the encapsulating film for photovoltaic modules, comprising: The mixture is uniformly mixed and melt-extruded through an extruder to achieve uniform dispersion and interfacial bonding of the mixture; The extruded melt is cast into a calendering and cooling device; wherein the temperature of each cooling roller in the calendering and cooling device is different, and the temperature of the cooling roller gradually decreases with the casting direction; The film material after casting is heated using an infrared annealing device to reduce the internal stress of the film material. The heat-treated film material is then subjected to cross-linking and curing treatment. One surface of the cross-linked and cured film material is subjected to corona activation treatment.

[0012] Optionally, the heat-treated film material is subjected to a cross-linking and curing treatment, including: The heat-treated film material was subjected to electron beam irradiation under a nitrogen protective atmosphere. The film material after electron beam irradiation is subjected to stepped heating treatment in a segmented drying oven.

[0013] Optionally, the thickness of the film material after casting is in the range of 250-350 μm.

[0014] Thirdly, embodiments of the present invention also provide a photovoltaic module, including an encapsulating film for photovoltaic modules as described in any one of the first aspects.

[0015] This invention provides an encapsulating film for photovoltaic modules, a preparation method thereof, and a photovoltaic module. The encapsulating film for photovoltaic modules comprises the following raw material components by weight: a first POE resin: 90-95 parts; a POE graft-modified resin: 5-8 parts; nano-silica: 2-4 parts; a crosslinking agent: 0.6-1 parts; a co-crosslinking agent: 0.3-0.6 parts; a light stabilizer: 0.3-0.5 parts; a UV absorber: 0.2-0.4 parts; and a rheology modifier: 0.08-0.15 parts. This encapsulation film for photovoltaic modules can be a reinforced film for flexible and lightweight photovoltaic modules. It uses a first POE resin as the matrix and is combined with POE grafted modified resin to improve the compatibility of nano-silica. This encapsulation film has both flexibility and mechanical properties, and simultaneously achieves high flexibility, high adhesive strength, low thermal shrinkage, high water vapor barrier performance and excellent damp heat aging resistance. It meets the requirements of long-term bending service and high-reliability long-term encapsulation of corresponding photovoltaic modules, and reduces the occurrence of defects such as microcracks and delamination and the resulting encapsulation failure.

[0016] Compared with the prior art, the present invention also has the following significant advantages: 1. Mechanical strength and flexibility are achieved simultaneously. Due to the use of in-situ interface grafting, the nano-silica forms chemical bonds with the first POE resin and the POE grafted modified resin, rather than physical blending. There is no agglomeration or precipitation. As a result, the tensile strength of the encapsulation film can reach 28MPa, the elongation at break can reach 750%, and there are no microcracks or delamination after repeated bending 1000 times. This fundamentally solves the problem of the incompatibility between mechanical strength and flexibility. 2. Significantly improved dimensional stability: Due to the use of gradient cooling and online infrared annealing to eliminate internal stress, and combined with electron beam pre-crosslinking and shaping, the thermal shrinkage rate of the encapsulation film is less than or equal to 1.3% in the longitudinal direction and less than or equal to 1.1% in the transverse direction. The lamination does not shift or overflow, and the encapsulation accuracy and consistency are significantly improved. Moreover, the elimination of internal stress can achieve ultra-low shrinkage. 3. Excellent interfacial adhesion and resistance to humid heat aging: Due to the synergistic effect of enhanced adhesion from POE grafted modified resin and single-sided corona activation, the adhesion reliability is improved. The migration and precipitation of crosslinking agents and coupling agents are prevented. As a result, the peel strength of the encapsulation film to the flexible backing plate reaches 87 N / cm. After 1000 hours of humid heat aging at 85℃ / 85% relative humidity, the adhesion strength retention rate is greater than or equal to 85%. It does not delaminate or bulge during long-term use. 4. The dual cross-linking structure brings high gel rate and high reliability, taking into account both high gel rate and high flexibility. By constructing a network structure of electron beam pre-cross-linking and thermal cross-linking curing, controllable cross-linking is achieved. The final gel rate of the encapsulation film is greater than or equal to 90%, and the creep resistance, dimensional stability and aging resistance are improved simultaneously, meeting the requirements of long-term bending and reliable service under wind and snow loads of flexible and lightweight photovoltaic modules. 5. High thickness accuracy and process compatibility for mass production: Due to the use of precision casting technology combined with online thickness measurement, the thickness of the encapsulation film formed is stable at 250-350μm, with tolerance controlled within ±3μm. The production process is stable and controllable, without complex multi-layer co-extrusion, with moderate cost, and can be continuously mass-produced.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for preparing an encapsulating film for photovoltaic modules according to an embodiment of the present invention; Figure 2 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided in an embodiment of the present invention; Figure 3 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided in an embodiment of the present invention; Figure 4 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided in an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] This invention provides an encapsulating film for photovoltaic modules, comprising the following raw material components by weight: first POE resin: 90-95 parts; POE grafted modified resin: 5-8 parts; nano silica: 2-4 parts; crosslinking agent: 0.6-1 parts; co-crosslinking agent: 0.3-0.6 parts; light stabilizer: 0.3-0.5 parts; ultraviolet absorber: 0.2-0.4 parts; rheology modifier: 0.08-0.15 parts.

[0023] Specifically, the first POE resin, as the main matrix of the encapsulating film, provides basic flexibility, low-temperature bending resistance, and light transmittance. The POE-grafted modified resin improves the interfacial bonding between the resin and nano-silica, enhances the compatibility of nano-silica, prevents filler agglomeration, improves adhesion, and inhibits the migration and precipitation of related additives. Nano-silica improves the water vapor barrier properties and dimensional stability of the prepared encapsulating film, reduces thermal shrinkage, enhances mechanical strength, and does not compromise the bending toughness of the prepared encapsulating film. Furthermore, the first POE resin, the POE-grafted modified resin, and nano-silica form chemical bonds during the mixing process, rather than simple physical blending, avoiding filler agglomeration and coupling agent precipitation. The coupling agent can be understood as a solvent for crosslinking agents, enabling in-situ interfacial grafting. The crosslinking agent and crosslinking agent facilitate the subsequent construction of a dense double-crosslinked network, increasing crosslinking density, enhancing heat resistance, aging resistance, and adhesive strength, and achieving a balance between mechanical strength and flexibility, making it less prone to aging and debonding. Light stabilizers and UV absorbers work synergistically to block UV light, delay aging, maintain adhesion and mechanical properties over the long term, improve long-term weather resistance, and do not affect light transmittance. Rheology modifiers can improve melt flowability, eliminate molding internal stress, reduce the risk of bending cracks, and are suitable for long-term repeated bending conditions.

[0024] In the technical solution of this invention embodiment, the encapsulating film for photovoltaic modules can be a flexible and lightweight reinforced encapsulating film for photovoltaic modules. It uses a first POE resin as the matrix and is combined with POE grafted modified resin to improve the compatibility of nano-silica. The encapsulating film has both flexibility and mechanical properties, and simultaneously achieves high flexibility, high bonding strength, low thermal shrinkage rate, high water vapor barrier performance and excellent damp heat aging resistance. It meets the long-term bending service and high reliability long-term encapsulation requirements of the corresponding photovoltaic modules, and reduces the occurrence of defects such as microcracks and delamination and the resulting encapsulation failure.

[0025] For example, the first POE (polyolefin elastomer) resin includes metallocene. For example, the melt index of the first POE resin can be in the range of 8-12 g / 10 min, and it has good flexibility and aging resistance.

[0026] For example, the POE grafting modified resin can be a maleic anhydride-grafted POE resin (POE-g-MAH); the maleic anhydride-grafted POE resin includes a second POE resin and maleic anhydride, and the grafting rate of the maleic anhydride-grafted POE resin ranges from 0.8% to 1.2%. For example, the second POE resin includes metallocene.

[0027] For example, the nano-silica is hydrophobic. For example, the particle size of the nano-silica ranges from 15 to 25 nm.

[0028] For example, the crosslinking agent may be tert-butyl peroxide (THEBP).

[0029] For example, the co-crosslinking agent may be trimethylolpropane tris(3-mercaptopropionate) (TMMP).

[0030] For example, the light stabilizer may be HALS-944.

[0031] For example, the ultraviolet absorber may be UV-123.

[0032] For example, the rheology modifier can be a fluoropolymer.

[0033] Based on the same inventive concept, this invention also provides a method for preparing an encapsulating film for photovoltaic modules. Figure 1 This is a schematic flowchart illustrating a method for preparing an encapsulating film for photovoltaic modules according to an embodiment of the present invention. This method is used to prepare an encapsulating film for photovoltaic modules as described in any of the embodiments of the present invention, such as... Figure 1 As shown, the preparation method includes: S110. According to the weight parts, the first POE resin, POE grafted modified resin, nano silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber and rheology modifier are mixed to obtain a homogeneous mixture.

[0034] Specifically, according to defined weight proportions, the first POE resin, POE grafted modified resin, and nano-silica are weighed sequentially, and then a crosslinking agent, co-crosslinking agent, light stabilizer, UV absorber, and rheology modifier are precisely added and placed into a mixing device for thorough mixing. For example, continuous shearing and stirring can break up the agglomerated particles of nano-silica, allowing these inorganic fillers to be uniformly dispersed in the corresponding POE resin matrix. Various functional additives exhibit no localized enrichment or stratification, forming a mixture with uniform component distribution. This uniform mixture ensures stable melt performance during subsequent casting, and after molding, the degree of crosslinking, barrier properties, and weather resistance of the entire film remain consistent across regions, guaranteeing the overall uniformity of the encapsulation film for photovoltaic modules and improving the reliability of the encapsulated photovoltaic modules.

[0035] S120. The mixture is mixed evenly through an extruder and melted and extruded. The extruded melt is then subjected to calendering, internal stress relief, cross-linking and curing, and corona activation treatment in sequence to obtain an encapsulating film for photovoltaic modules.

[0036] Specifically, the mixture is fed into an extruder for high-temperature melt blending to further refine filler dispersion, eliminate component offset precipitation, and obtain a homogeneous melt. The extruded melt is first calendered to control thickness and surface smoothness; then internal stress is eliminated to release residual molding stress and prevent bending shrinkage and cracking of the prepared encapsulating film; subsequently, cross-linking and curing are performed to build a stable cross-linking network, improving mechanical properties and resistance to damp heat and aging; finally, corona activation is performed to improve the surface adhesion and bonding performance of the prepared encapsulating film. These multiple processes work together to prepare an encapsulating film that combines low shrinkage, high toughness, strong interfacial adhesion, and long-term weather resistance, making it suitable for the long-term encapsulation conditions of flexible and lightweight photovoltaic modules that are subject to repeated bending.

[0037] The technical solution in this embodiment of the invention firstly involves mixing a first POE resin, a POE graft-modified resin, nano-silica, a crosslinking agent, a co-crosslinking agent, a light stabilizer, a UV absorber, and a rheology modifier according to their weight proportions to obtain a homogeneous mixture. This mixture is then uniformly mixed and melt-extruded using an extruder. The extruded melt undergoes sequential calendering, internal stress relief, crosslinking curing, and corona activation to obtain an encapsulating film for photovoltaic modules. Using this method, the first POE resin is used as the matrix, combined with a POE graft-modified resin to improve the compatibility of nano-silica. The resulting encapsulating film possesses both flexibility and mechanical properties, simultaneously achieving high flexibility, high adhesive strength, low thermal shrinkage, high moisture barrier performance, and excellent damp heat aging resistance. This meets the requirements of long-term bending service and high-reliability, long-lasting encapsulation for photovoltaic modules, reducing the occurrence of defects such as microcracks and delamination, and preventing encapsulation failures.

[0038] Figure 2 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided by an embodiment of the present invention. This embodiment is an optimization based on the above embodiment. Optionally, according to parts by weight, the first POE resin, POE grafted modified resin, nano-silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber and rheology modifier are mixed to obtain a homogeneous mixture, comprising: The first POE resin, the POE grafted modified resin and nano silica are added to a mixing device to obtain the first mixed powder. An alkenylsilane coupling agent is added to the first mixed powder to obtain a second mixed powder; A light stabilizer, a UV absorber, and a rheology modifier are added to the second mixed powder to obtain a third mixed powder; A crosslinking agent and a co-crosslinking agent are added to the third mixed powder to obtain a mixture.

[0039] For details not covered in this embodiment, please refer to the above embodiments. Figure 2 As shown, the preparation method includes: S210. The first POE resin, the POE grafted modified resin and the nano silica are added to the mixing equipment to obtain the first mixed powder.

[0040] Specifically, the first POE resin, the POE grafted modified resin, and nano-silica are added to a mixing device. For example, this mixing device can be a high-speed mixer, capable of low-speed mixing at 300 r / min for 3 minutes. The POE grafted modified resin can improve the dispersion effect of the nano-silica, reduce particle agglomeration, and avoid uneven dispersion of inorganic fillers after the addition of subsequent functional additives, laying the foundation for subsequent uniform mixing.

[0041] Optionally, before adding the first POE resin, the POE grafted modified resin and the nano silica into the mixing device to obtain the first mixed powder, the method further includes: drying the first POE resin, the POE grafted modified resin and the nano silica so that the water content in the first POE resin, the POE grafted modified resin and the nano silica is less than 0.05%.

[0042] Specifically, this method can eliminate the moisture inherent in the raw material components such as the first POE resin, the POE grafted modified resin, and nano-silica, preventing moisture from causing bubbles and pinholes in the film during processing. It also avoids moisture reducing crosslinking efficiency and damaging interfacial adhesion, ensuring the film's moisture barrier and aging resistance, and improving the yield of flexible photovoltaic encapsulation products. For example, the first POE resin and the POE grafted modified resin can be dried in a 50°C hot air drying oven for 1 hour, cooled, and sealed for later use; that is, they can be added to the mixing equipment only after cooling. Similarly, nano-silica can be dried in a 110°C vacuum oven for 3 hours, cooled, sealed, and stored for later use; that is, it can be added to the mixing equipment only after cooling.

[0043] S220. Add an alkenyl silane coupling agent to the first mixed powder to obtain a second mixed powder.

[0044] The alkenyl silane coupling agent can be understood as part of the crosslinking aid. Specifically, an alkenyl silane coupling agent is added to the first mixed powder. The two ends of this coupling agent can respectively bind to nano-silica and POE resin, further strengthening the interfacial bonding and achieving in-situ interfacial grafting between the inorganic filler and the matrix resin, reducing the agglomeration of the inorganic filler. Simultaneously, the alkenyl structure can participate in the subsequent crosslinking and curing reaction, improving the overall strength and moisture barrier effect of the prepared encapsulating film, resulting in a more stable second mixed powder. For example, the temperature range for preparing the second mixed powder can be 65-75℃, the stirring speed can be 1000-1200 r / min, and the processing time can be 10 min.

[0045] S230. Add a light stabilizer, an ultraviolet absorber and a rheology modifier to the second mixed powder to obtain a third mixed powder.

[0046] Specifically, a light stabilizer, a UV absorber, and a rheology modifier are added to the second mixed powder, and then mixed uniformly at a low speed to obtain a third mixed powder. This step-by-step addition avoids the agglomeration and precipitation of the functional additives, and the uniform dispersion ensures that the prepared encapsulating film possesses long-lasting UV aging resistance, while also optimizing melt processing fluidity and reducing molding internal stress. For example, the processing time for preparing the third mixed powder can be 4 minutes.

[0047] S240. Add a crosslinking agent and a co-crosslinking agent to the third mixed powder to obtain a mixture.

[0048] Specifically, adding a crosslinking agent and a co-crosslinking agent to the third mixed powder helps to improve the mechanical strength, heat resistance, and adhesive properties of the prepared encapsulating film. For example, after adding the crosslinking agent and the co-crosslinking agent, the mixture can be stirred at low speed for 2 minutes to achieve uniformity. Adding the crosslinking agent and the co-crosslinking agent last can also prevent the crosslinking agent from decomposing and becoming ineffective due to heat.

[0049] S250. The mixture is mixed evenly through an extruder and melted and extruded. The extruded melt is then subjected to calendering, internal stress relief, cross-linking and curing, and corona activation treatment in sequence to obtain an encapsulating film for photovoltaic modules.

[0050] Figure 3 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided by an embodiment of the present invention. This embodiment is an optimization based on the above embodiment. Optionally, the mixture is uniformly mixed and melt-extruded through an extruder, and the extruded melt is sequentially subjected to calendering, internal stress relief, crosslinking and curing, and corona activation to obtain an encapsulating film for photovoltaic modules, comprising: The mixture is homogenized by an extruder and melt-extruded to achieve uniform dispersion and interfacial bonding of the mixture; The extruded melt is cast into a calendering and cooling equipment; the temperature of each cooling roller in the calendering and cooling equipment is different, and the temperature of the cooling roller gradually decreases with the direction of casting. Infrared annealing equipment is used to heat-treat the film material after casting to reduce the internal stress of the film material; The heat-treated film material is then subjected to cross-linking and curing treatment. One surface of the cross-linked and cured film material is subjected to corona activation treatment.

[0051] For details not covered in this embodiment, please refer to the above embodiments. Figure 3 As shown, the preparation method includes: S310. According to the weight parts, the first POE resin, POE grafted modified resin, nano silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber and rheology modifier are mixed to obtain a homogeneous mixture.

[0052] S320. The mixture is mixed evenly through an extruder and melt-extruded to achieve uniform dispersion and interfacial bonding of the mixture.

[0053] Specifically, the mixture is fed into an extruder for high-temperature melting and shear mixing, further breaking up filler agglomerations and ensuring highly uniform dispersion of all components. Simultaneously, it promotes full interfacial bonding between the first POE resin, the POE-grafted modified resin, and nano-silica, strengthening the bond between the resin and the inorganic filler, and providing a melt with uniform properties and stable interfacial bonding for subsequent molding. For example, the extruder can be a parallel twin-screw extruder, with the temperatures set as follows: Zone 1 90℃, Zone 2 105℃, Zone 3 115℃, Zone 4 120℃, and the die temperature 122℃. For example, the main extruder speed ranges from 200-220 r / min, the feed rate is 15-18 kg / h, and the vacuum degree is controlled at -0.08 to -0.09 MPa to fully remove volatile moisture. Furthermore, the screw assembly includes a strong shear section and a reaction homogenization section to achieve uniform dispersion and interfacial bonding between the resin matrix and the inorganic filler.

[0054] S330, the extruded melt is cast into a calendering and cooling device; wherein, the temperature of each cooling roller in the calendering and cooling device is different, and the temperature of the cooling roller gradually decreases with the direction of casting.

[0055] Specifically, the melt obtained from high-temperature melting is directly conveyed to the calendering and cooling equipment after flowing out of the extruder head. The thickness and surface flatness of the film are precisely controlled through roller pressing, while simultaneous and rapid cooling and shaping are achieved. This process also fixes the uniformly dispersed structure within the melt, reducing delamination and precipitation defects, and initially releasing the stress generated during film formation, resulting in a film material with a smooth surface and uniform thickness. For example, the melt obtained from high-temperature melting can be cast to a three-roll mirror cooling system through a coat hanger-type die, with the die opening range being 0.12-0.25mm. For example, the temperature settings of each cooling roller in the calendering and cooling equipment can be: upper roller 30℃, middle roller 22℃, and lower roller 18℃. For example, the speed range of the casting line can be 4-5m / min, and the traction tension is controlled at 10-12N to avoid excessive stretching.

[0056] By adjusting the thickness in real time using an online thickness gauge, the thickness of the film material after casting can be stabilized within the range of 250-350μm, with a thickness tolerance of ±3μm.

[0057] S340. The film material after casting is heated using infrared annealing equipment to reduce the internal stress of the film material.

[0058] Specifically, after casting, the film material enters the infrared annealing zone to gently release the stress accumulated during the calendering process, thereby significantly reducing internal residual stress, decreasing thermal shrinkage, and alleviating the bending and warping problems of the film material. For example, the infrared annealing equipment can be used at a processing temperature of 80°C for 30 seconds.

[0059] S350, Perform cross-linking and curing treatment on the heat-treated film material.

[0060] Optionally, the heat-treated film material is subjected to cross-linking and curing treatment, including: electron beam irradiation treatment of the heat-treated film material under a nitrogen protective atmosphere; and step-by-step heat treatment of the electron beam irradiated film material in a segmented oven.

[0061] Specifically, the infrared-annealed stress-relieved film material is subjected to low-dose electron beam irradiation under a nitrogen protective atmosphere. Nitrogen isolates oxygen, preventing resin oxidative degradation during irradiation and ensuring the stability of the film matrix. Furthermore, the electron beam excites the crosslinking components in the system to generate active free radicals, initially establishing a crosslinked structure. For example, the electron beam accelerating voltage can be 180kV, the electron beam irradiation dose range can be 5-10kGy, and the electron beam irradiation velocity range can be 8-18m / min, thus achieving mild pre-crosslinking and improving the dimensional stability of the laminate. Afterward, it is sent to a segmented oven for step-by-step heating and curing, i.e., step-by-step crosslinking. The crosslinking reaction is mild and thorough, forming a dense and uniform double-crosslinked network. For example, the step-by-step crosslinking process involves preheating at 125°C for 5 minutes, then crosslinking at 140°C for 8 minutes, and finally slow cooling at 90°C for 2 minutes, resulting in a final film gel rate greater than or equal to 90%.

[0062] This process avoids the severe thermal shrinkage and surface wrinkling defects caused by one-time high temperature, and greatly improves the mechanical strength, interfacial adhesion stability and weather resistance of the prepared encapsulation film, making it suitable for the long-term bending service and high reliability requirements of flexible and lightweight photovoltaic modules.

[0063] S360. One surface of the cross-linked and cured film material is subjected to corona activation treatment.

[0064] Specifically, the surface of the cross-linked and cured film material that subsequently adheres to and contacts the solar cell array undergoes corona activation treatment. High-voltage ionized air generates polar groups on the surface of the film material, improving surface properties. For example, it enhances the adhesion between the film and glass or backsheet, suppresses delamination during long-term use, and meets the encapsulation and bonding requirements of photovoltaic modules. For instance, the power range of the corona activation treatment can be 1-1.2kW, resulting in a surface tension of 40-42mN / m, improving interfacial adhesion without damaging the structure of the other surface.

[0065] Figure 4 This is a schematic flowchart of another method for preparing an encapsulating film for photovoltaic modules provided in an embodiment of the present invention, as shown below. Figure 4As shown, the raw materials are first pretreated by drying. The first POE resin and the POE grafted modified resin are placed in a hot air drying oven at 50°C and dried for 1 hour, controlling the moisture content of the first POE resin and the POE grafted modified resin to be less than 0.05%. After cooling, they are sealed and stored for later use, i.e., added to the mixing equipment after cooling. Then, the nano-silica is placed in a vacuum oven at 110°C and dried for 3 hours, controlling the moisture content of the nano-silica to be less than 0.05%. After cooling, it is sealed and stored for later use, i.e., added to the mixing equipment after cooling. Next, reactive high-speed mixing and in-situ grafting are performed. The dried first POE resin, POE grafted modified resin, and nano-silica are added to a high-speed mixer and mixed at a low speed of 300 r / min for 3 min. Subsequently, an alkenyl silane coupling agent is added dropwise, the temperature is raised to 65-75°C, and the mixture is stirred at a high speed of 1000-1200 r / min for 10 min to achieve in-situ interfacial grafting between the inorganic filler and the matrix resin. Then add the light stabilizer, UV absorber, and rheology modifier, and continue mixing for 4 minutes. Next, add the crosslinking agent and co-crosslinking agent, and stir at low speed for 2 minutes to mix thoroughly.

[0066] Then, reactive twin-screw extrusion blending is performed. The mixture is fed into a parallel twin-screw extruder, with the temperatures set as follows: Zone 1 90℃, Zone 2 105℃, Zone 3 115℃, Zone 4 120℃, and the die temperature 122℃. For example, the main extruder speed ranges from 200-220 r / min, the feed rate is 15-18 kg / h, and the vacuum degree is controlled at -0.08 to -0.09 MPa to fully remove volatile moisture. Furthermore, the screw assembly includes a high-shear section and a reaction homogenization section to achieve uniform dispersion and interfacial bonding of the resin matrix and inorganic fillers. Afterward, precision casting and gradient cooling are performed. The melt obtained from the high-temperature melting can be cast through a coat hanger-type die to a three-roll mirror cooling system. The die opening range can be 0.12-0.25 mm. For example, the temperature settings of each cooling roller in the calendering cooling equipment can be: upper roller 30℃, middle roller 22℃, and lower roller 18℃. For example, the speed range of the casting line can be 4-5 m / min, and the traction tension can be controlled at 10-12 N to avoid excessive stretching.

[0067] Then, online infrared annealing is performed to eliminate internal stress. The film material after casting enters the infrared annealing zone at a temperature of 80°C for 30 seconds. This gently releases the stress accumulated in the film material during calendering, significantly reducing internal residual stress and decreasing thermal shrinkage.

[0068] Following this, electron beam pre-crosslinking curing is performed. Under a nitrogen protective atmosphere, the infrared-annealed stress-relieved film material undergoes low-dose electron beam irradiation treatment. The electron beam accelerating voltage can be 180kV, the electron beam irradiation dose range can be 5-10kGy, and the electron beam irradiation velocity range can be 8-18m / min, achieving mild pre-crosslinking and improving the dimensional stability of the laminate. Then, segmented thermal crosslinking curing is performed. The film is sent to a segmented oven for step-by-step heating and curing, i.e., step-by-step crosslinking. The step-by-step crosslinking process is as follows: first, preheating at 125℃ for 5 minutes, then crosslinking at 140℃ for 8 minutes, and then slow cooling at 90℃ for 2 minutes. The final film gel rate is greater than or equal to 90%.

[0069] Following this, single-sided corona activation is performed, applying the corona activation treatment only to the side of the film material that will subsequently adhere to and contact the solar cell array. The power range for corona activation is 1-1.2 kW, resulting in a surface tension of 40-42 mN / m, improving interfacial adhesion without damaging the structure of the other surface. Finally, trimming, winding, and finished product inspection are performed. The prepared encapsulation film undergoes automatic trimming and constant tension winding. Inspection items include appearance, thickness uniformity, peel strength, tensile properties, heat shrinkage rate, and damp heat aging reliability. After passing inspection, the film is sealed and packaged.

[0070] Example 1 In this embodiment, the encapsulating film for the photovoltaic module comprises the following raw material components by weight: 92 parts of first POE resin, 6 parts of POE grafted modified resin (POE-g-MAH), 3 parts of nano-silica, 0.8 parts of crosslinking agent (THEBP), 0.4 parts of co-crosslinking agent (TMMP), 0.4 parts of light stabilizer (HALS-944), 0.3 parts of ultraviolet absorber (UV-123), and 0.1 parts of rheology modifier. The thickness of the prepared encapsulating film is 300 μm. The relevant properties are as follows: tensile strength 28 MPa, elongation at break 750%, longitudinal heat shrinkage 1.3%, transverse heat shrinkage 1.1%, peel strength to flexible backsheet 87 N / cm, adhesive strength retention rate greater than or equal to 85% after 1000 hours of humid heat aging at 85℃ / 85% relative humidity, and no cracks or delamination after 1000 repeated bending cycles.

[0071] Example 2 In this embodiment, the encapsulating film for the photovoltaic module comprises the following raw material components by weight: 94 parts of first POE resin, 5 parts of POE graft-modified resin (POE-g-MAH), 2.5 parts of nano-silica, 0.8 parts of crosslinking agent (THEBP), 0.4 parts of co-crosslinking agent (TMMP), 0.4 parts of light stabilizer (HALS-944), 0.3 parts of ultraviolet absorber (UV-123), and 0.1 parts of rheology modifier. This embodiment emphasizes higher flexibility, adapting to high curvature bending scenarios.

[0072] Comparative Examples In this embodiment, the encapsulating film for the photovoltaic module is made by physical blending of ordinary POE resin and inorganic filler, followed by thermal crosslinking with a single peroxide, without annealing or electron beam pre-crosslinking steps, and the other functional additives are similar. However, the tensile strength of the prepared encapsulating film is low, the thermal shrinkage rate is greater than 2.5%, and the adhesive strength retention rate is less than 65% after 1000 hours in a humid heat aging environment of 85℃ / 85% relative humidity, and microcracks easily appear when bent.

[0073] Based on the same inventive concept, embodiments of the present invention also provide a photovoltaic module. This photovoltaic module includes an encapsulating film for photovoltaic modules as described in any of the embodiments of the present invention. Exemplarily, the encapsulating film for photovoltaic modules can be disposed on the light-receiving surface of the cell array in the photovoltaic module, and on a backlighting surface opposite to the light-receiving surfaces. Therefore, the photovoltaic module possesses the beneficial effects corresponding to the encapsulating film for photovoltaic modules, which will not be elaborated further here.

[0074] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0075] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An encapsulating film for photovoltaic modules, characterized in that, Includes the following raw material components by weight: First POE resin: 90-95 parts; POE grafted modified resin: 5-8 parts; Nano silica: 2-4 parts; Crosslinking agent: 0.6-1 part; Co-crosslinking agent: 0.3-0.6 parts; Light stabilizer: 0.3-0.5 parts; UV absorber: 0.2-0.4 parts; Rheology modifier: 0.08-0.15 parts.

2. The encapsulating film for photovoltaic modules according to claim 1, characterized in that, The POE grafted modified resin is maleic anhydride grafted POE resin. The maleic anhydride-grafted POE resin comprises a second POE resin and maleic anhydride, and the grafting rate of the maleic anhydride-grafted POE resin ranges from 0.8% to 1.2%.

3. The encapsulating film for photovoltaic modules according to claim 1, characterized in that, The crosslinking agent is tert-butyl peroxide; and / or, the co-crosslinking agent is trimethylolpropane tris(3-mercaptopropionate); and / or, the light stabilizer is HALS-944; and / or, the ultraviolet absorber is UV-123; and / or, the rheology modifier is a fluoropolymer.

4. A method for preparing an encapsulating film for photovoltaic modules, characterized in that, The method for preparing an encapsulating film for photovoltaic modules as described in any one of claims 1-3 comprises: According to the weight proportions, the first POE resin, POE grafted modified resin, nano silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber and rheology modifier are mixed to obtain a homogeneous mixture. The mixture is uniformly mixed and melt-extruded through an extruder, and the extruded melt is sequentially subjected to calendering, internal stress relief, cross-linking curing, and corona activation to obtain the encapsulating film for photovoltaic modules.

5. The preparation method according to claim 4, characterized in that, According to parts by weight, the first POE resin, POE grafted modified resin, nano-silica, crosslinking agent, co-crosslinking agent, light stabilizer, ultraviolet absorber, and rheology modifier are mixed to obtain a homogeneous mixture, comprising: The first POE resin, the POE grafted modified resin, and the nano-silica are added to a mixing device to obtain a first mixed powder. An alkenyl silane coupling agent is added to the first mixed powder to obtain a second mixed powder; The light stabilizer, the ultraviolet absorber and the rheology modifier are added to the second mixed powder to obtain a third mixed powder; The crosslinking agent and the co-crosslinking agent are added to the third mixed powder to obtain the mixture.

6. The preparation method according to claim 5, characterized in that, Before adding the first POE resin, the POE grafted modified resin, and the nano-silica into a mixing device to obtain the first mixed powder, the process further includes: The first POE resin, the POE grafted modified resin, and the nano silica are dried to reduce the water content of the first POE resin, the POE grafted modified resin, and the nano silica to less than 0.05%.

7. The preparation method according to claim 4, characterized in that, The mixture is homogenized and melt-extruded using an extruder. The extruded melt is then subjected to calendering, stress relief, cross-linking curing, and corona activation treatments to obtain the encapsulating film for photovoltaic modules, comprising: The mixture is uniformly mixed and melt-extruded through an extruder to achieve uniform dispersion and interfacial bonding of the mixture; The extruded melt is cast into a calendering and cooling device; wherein the temperature of each cooling roller in the calendering and cooling device is different, and the temperature of the cooling roller gradually decreases with the casting direction; The film material after casting is heated using an infrared annealing device to reduce the internal stress of the film material. The heat-treated film material is then subjected to cross-linking and curing treatment. One surface of the cross-linked and cured film material is subjected to corona activation treatment.

8. The preparation method according to claim 7, characterized in that, The heat-treated film material is subjected to cross-linking and curing treatment, including: The heat-treated film material was subjected to electron beam irradiation under a nitrogen protective atmosphere. The film material after electron beam irradiation is subjected to stepped heating treatment in a segmented drying oven.

9. The preparation method according to claim 7, characterized in that, The thickness of the film material after casting is in the range of 250-350 μm.

10. A photovoltaic module, characterized in that, Including the encapsulating film for photovoltaic modules as described in any one of claims 1-3.

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