Multilayer composite anti-aging functional master batch, preparation method thereof and photovoltaic adhesive film

Abstract

The application belongs to the technical field of photovoltaic adhesive film, and particularly relates to a multi-layer composite anti-aging functional master batch, a preparation method thereof and a photovoltaic adhesive film. The master batch adopts an inner layer, a middle layer and an outer layer structure which are sequentially compounded from inside to outside. The inner layer comprises a first polymer resin and an ultraviolet shielding material, the middle layer comprises a second polymer resin and a microcapsule-coated antioxidant, and the outer layer comprises a third polymer resin and a fluorine-containing organic substance. Through the synergistic design of ultraviolet shielding of the inner layer, slow release of the middle layer and protection of the outer layer, the outer layer effectively improves the processing fluidity and inhibits the migration of the antioxidant, the middle layer realizes the intelligent slow release and long-acting effect of the antioxidant, and the inner layer shields ultraviolet light from the source to reduce the aging inducement. The application significantly improves the weather resistance and service life of the photovoltaic adhesive film, overcomes the problems of easy migration of the antioxidant, easy failure of the light stabilizer and weak interface combination of the traditional master batch, and is suitable for the packaging of photovoltaic modules in complex environments.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic encapsulant technology, specifically relating to a multilayer composite anti-aging functional masterbatch, its preparation method, and a photovoltaic encapsulant film. Background Technology

[0002] As the photovoltaic industry develops towards longer lifespan and higher reliability, the weather resistance of photovoltaic encapsulating films has become one of the key factors determining the lifespan of modules. To improve the anti-aging ability of encapsulating films, the industry typically employs the method of adding anti-aging functional masterbatches to the base resin (such as EVA, POE). These functional masterbatches are usually made by melt blending and extrusion granulation of antioxidants, light stabilizers, and other functional additives with the carrier resin.

[0003] However, this traditional homogeneous anti-aging masterbatch has the following technical problems in practical applications: First, antioxidants are prone to migration and premature consumption. During the high-temperature process of film preparation, small-molecule antioxidants in the masterbatch migrate from the interior of the masterbatch to the surface of the film and are consumed in large quantities in the early stages of processing. Studies have shown that the migration rate of antioxidants in traditional masterbatches can be as high as 30% or more, leading to the loss of protective components inside the masterbatch. This results in the inability to achieve long-term and stable protection for the film, causing the tensile strength retention rate of the film to be generally low after long-term humid heat aging, typically only 60% to 70%.

[0004] Secondly, the light-stabilizing system is inefficient and prone to failure. Traditional masterbatches often directly add light stabilizers such as UV absorbers. These substances undergo photodecomposition under long-term, intense UV irradiation, losing their protective function. At the same time, due to the premature migration and consumption of antioxidants, the encapsulant system cannot effectively quench free radicals induced by UV light, accelerating the aging and yellowing process of the encapsulant, leading to decreased light transmittance and power degradation of photovoltaic modules.

[0005] Third, the interfacial bonding is weak and the functional synergy is poor. Traditional single-layer masterbatch and film matrix are only physically blended, resulting in weak interfacial bonding. Under environmental stress, microcracks are easily formed, becoming channels for aging propagation. More importantly, all functional additives are randomly distributed in the masterbatch, failing to achieve synergistic effects and limiting further improvement in overall anti-aging performance.

[0006] Therefore, there is an urgent need in this field for a novel anti-aging masterbatch design that can solve problems such as antioxidant migration, light stabilizer failure, and weak interfacial bonding, providing a more durable and reliable long-term protection solution for photovoltaic films.

[0007] It should be noted that this part of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or known technology. Summary of the Invention

[0008] This invention provides a multilayer composite anti-aging functional masterbatch, its preparation method, and a photovoltaic encapsulant film. It at least solves the technical problems in the prior art where the antioxidants in traditional anti-aging masterbatches are prone to migration, the light stabilizers are prone to failure, and there is a lack of synergistic effect among the components, thus making it impossible to achieve long-term protection for photovoltaic encapsulant films.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a multilayer composite anti-aging functional masterbatch, comprising an inner layer, a middle layer, and an outer layer sequentially composited from the inside out; the inner layer comprises a first polymer resin and an ultraviolet shielding material; the middle layer comprises a second polymer resin and an antioxidant encapsulated in microcapsules; and the outer layer comprises a third polymer resin and a fluorinated organic compound.

[0010] Preferably, the masterbatch has a cylindrical structure with a cross-section of three concentric circles; the inner layer is a solid structure with a radius of 0.05 mm to 0.1 mm; the middle layer is an annular structure with a radial thickness of 0.1 mm to 0.5 mm; and the outer layer is an annular structure with a radial thickness of 0.1 mm to 0.3 mm.

[0011] Preferably, the first polymer resin, the second polymer resin, and the third polymer resin are each independently selected from ethylene-vinyl acetate copolymer or polyolefin elastomer.

[0012] Preferably, the inner layer comprises, by weight percentage: 70% to 90% of the first polymer resin and 10% to 30% of the ultraviolet shielding material.

[0013] Preferably, the ultraviolet shielding material is nano-titanium dioxide, which is nano-titanium dioxide with a surface modified by a silane coupling agent, and the particle size of the nano-titanium dioxide is no greater than 20 nm.

[0014] Preferably, by weight percentage, the middle layer comprises: 55% to 80% of the second polymer resin and 20% to 45% of the antioxidant encapsulated in microcapsules.

[0015] Preferably, the microcapsules have a particle size of 5μm to 10μm, and the wall material of the microcapsules includes at least one of polylactic acid and polyurethane.

[0016] Preferably, the antioxidants include hindered amine antioxidants and thioester antioxidants, and the mass ratio of hindered amine antioxidants to thioester antioxidants is (2~4):1.

[0017] Preferably, the outer layer comprises 70% to 80% of a third polymer resin and 20% to 30% of a fluorinated organic compound, by weight percentage.

[0018] Preferably, the fluorinated organic compound is a fluorinated polymer processing aid.

[0019] Secondly, the present invention provides a method for preparing a multilayer composite anti-aging functional masterbatch according to the first aspect, the preparation method comprising: The first polymer resin and the ultraviolet shielding material are melt-blended and extruded at 145℃~155℃ to obtain inner layer particles. The second polymer resin and the antioxidant encapsulated in microcapsules are melt-blended at 155℃~165℃, extruded and granulated to obtain middle-layer particles; The third polymer resin and fluorinated organic compound are melt-blended at 175℃~185℃, extruded and granulated to obtain outer layer particles; The inner, middle, and outer granules are co-extruded together using a three-layer co-extrusion die, cooled, and then granulated to obtain a multi-layer composite anti-aging functional masterbatch.

[0020] Preferably, the temperature zone control of the three-layer co-extrusion die is as follows: inner layer zone 145℃~155℃, middle layer zone 155℃~165℃, and outer layer zone 175℃~185℃.

[0021] Thirdly, the present invention provides a photovoltaic encapsulant film, which includes a matrix resin and a multilayer composite anti-aging functional masterbatch prepared by the method of the first aspect or the method of the second aspect.

[0022] Preferably, the multilayer composite anti-aging functional masterbatch is dispersed in the matrix resin of the photovoltaic film in discrete individual form, and the multilayer composite anti-aging functional masterbatch accounts for 0.5% to 3% of the total mass of the photovoltaic film.

[0023] The beneficial effects of this invention are as follows: This invention designs a multi-layered composite anti-aging functional masterbatch, employing a three-layer structure of inner UV shielding, middle slow-release, and outer protection, significantly improving the anti-aging performance and long-term reliability of photovoltaic films. The outer layer, containing fluorinated organic matter, effectively improves processing flowability, reduces the migration and loss of antioxidants during high-temperature processes, and ensures processing stability. The middle layer's microcapsule slow-release system enables long-term release and control of antioxidants, avoiding the rapid consumption and deactivation of antioxidants in traditional masterbatches. The inner layer's nano-UV shielding material works synergistically with the microcapsule slow-release system; the inner layer reduces photoaging factors and antioxidant consumption at the source, while the middle layer slowly releases antioxidants, effectively enhancing UV shielding and long-term antioxidant capabilities. Overall, this structure achieves gradient protection and functional synergy, overcoming the technical defects of traditional masterbatches such as antioxidant migration, light stabilizer failure, and weak interfacial bonding, providing photovoltaic films with more durable and stable weather-resistant protection, suitable for photovoltaic module applications in complex environments. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the cross-sectional structure of the multilayer composite anti-aging functional masterbatch provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the photovoltaic encapsulant film provided in an embodiment of the present invention.

[0026] Figure 3 This is an optical microscope image showing the distribution of the multilayer composite anti-aging functional masterbatch provided in Embodiment 1 of the present invention in a photovoltaic film.

[0027] Figure 4 This is a physical image of the multilayer composite anti-aging functional masterbatch provided in Embodiment 1 of the present invention.

[0028] Figure 5 The image shows an axial longitudinal section of the multilayer composite anti-aging functional masterbatch provided in Embodiment 1 of the present invention.

[0029] Explanation of reference numerals in the attached figures: 100. Multi-layer composite anti-aging functional masterbatch; 10. Inner layer; 20. Middle layer; 30. Outer layer; 200. Photovoltaic encapsulant film. Detailed Implementation

[0030] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" are generally understood in conjunction with the accompanying drawings and the directions shown in actual applications.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0034] In a first aspect, the present invention provides a multilayer composite anti-aging functional masterbatch, comprising an inner layer, a middle layer and an outer layer sequentially composited from the inside out; the inner layer comprises a first polymer resin and an ultraviolet shielding material; the middle layer comprises a second polymer resin and an antioxidant encapsulated in microcapsules; and the outer layer comprises a third polymer resin and a fluorinated organic compound.

[0035] Understandably, the three-layer composite structure employed in this invention differs substantially from traditional single-layer homogeneous masterbatches. Traditional masterbatches simply blend various functional additives with resin, leading to the easy migration and precipitation of antioxidants at high processing temperatures, the easy decomposition and inactivation of light stabilizers under ultraviolet irradiation, and a lack of synergy among the components, resulting in limited functional synergy. This invention, by strictly defining a specific structural order from the inside out as inner layer, middle layer, and outer layer, and endowing each layer with unique functional components, constructs a synergistic system in which the inner layer reduces free radicals at the source, the middle layer provides intelligent slow-release antioxidants, and the outer layer protects the preparation process.

[0036] Specifically, because the outer layer is in direct contact with the extrusion equipment (screw, die) and the external environment (moisture and dust during storage), there are issues with stability and primary protection during processing. This invention effectively solves these problems by adding fluorinated organic compounds to the outer layer. Fluorinated organic compounds effectively reduce melt viscosity, ensuring good flowability of the masterbatch during subsequent processing (such as co-extrusion with the film matrix), preventing premature release of antioxidants due to shear force rupture of the middle layer microcapsules during high-viscosity extrusion, and reducing the agglomeration of the inner layer UV-shielding material during extrusion. Furthermore, the dense surface it forms can block the intrusion of the external environment (such as moisture and oxygen) to prevent hydrolysis of the microcapsule wall material. The low surface energy of the fluorinated organic compounds also reduces dust adhesion, providing physical protection for the middle layer. Without this outer layer, the active ingredients in the middle layer are easily damaged or migrated away by high-temperature shear during the initial stages of processing.

[0037] The middle layer of this invention uses microencapsulated antioxidants, which is the core of achieving long-lasting and intelligent protection. Microencapsulation technology encapsulates easily migratable and consumed small-molecule antioxidants, keeping them stable during masterbatch processing and storage, and allowing for controlled release at specific lamination temperatures and times during the photovoltaic module lamination process. This mechanism avoids the premature consumption of antioxidants in traditional masterbatches, significantly extending the effective protection time. If the middle layer does not use microencapsulation, the antioxidants may still suffer from easy migration and rapid deterioration.

[0038] The inner layer of this invention incorporates an ultraviolet (UV) shielding material, which intervenes at the source of aging induction. When UV light irradiates a photovoltaic film containing this masterbatch, the UV shielding material in the inner layer of the masterbatch efficiently absorbs the incident UV light before it causes molecular chain breakage in the localized film substrate surrounding any masterbatch. This design is equivalent to constructing numerous dispersed UV absorption points within the film, reducing the direct irradiation of the film substrate by UV light at the source, thereby lowering the overall aging reaction initiation rate.

[0039] It is understandable that the middle and inner layers constitute a synergistic effect of passive defense and active scavenging. The essence of this synergistic effect lies in constructing a local protective microenvironment centered on the individual masterbatch at the microscale, achieving a match between ultraviolet protection and free radical scavenging in the spatial and temporal dimensions. Specifically, when ultraviolet light irradiates the film, the ultraviolet shielding material of the inner layer located at the geometric center of the masterbatch efficiently intercepts ultraviolet photons in the 280~400nm band, converting light energy into heat energy for dissipation, significantly reducing the ultraviolet light flux transmitted to the periphery of the masterbatch and the surrounding film substrate. Since the inner layer, as a solid absorber located at the center of the masterbatch, ultraviolet light incident from any direction undergoes optical path absorption when penetrating the inner layer, making the masterbatch as a whole a local ultraviolet energy attenuation source. The ultraviolet irradiation intensity of the surrounding film region is significantly lower than that of the region farther from the masterbatch, and the initial free radical generation rate decreases accordingly.

[0040] Simultaneously, the middle-layer microcapsules rupture under lamination conditions, releasing antioxidant molecules that diffuse spherically along the polymer interpenetrating network towards the surrounding film matrix, using the masterbatch as a diffusion source, forming an antioxidant concentration gradient field centered on the masterbatch. More importantly, the inner-layer UV absorption and the middle-layer antioxidant diffusion are spatially highly coupled within the same microfunctional region. The film region surrounding the masterbatch is under low UV irradiation due to inner-layer absorption, while maintaining a high antioxidant concentration due to the sustained release from the middle layer. This synergy results in a significantly lower steady-state free radical concentration in this region compared to traditional homogeneous systems, leading to a substantial increase in the antioxidant scavenging efficiency per unit mass.

[0041] If the two single-layer masterbatches (high reflectivity masterbatch and antioxidant masterbatch) in the existing technology are simply physically mixed and dispersed in the film, since they are completely separated in space, it is impossible to guarantee that the film area around any reflectivity masterbatch can maintain an effective contact distance with the nearest antioxidant masterbatch, and it is impossible to guarantee that there is an effective concentration of antioxidant around any UV shielding point. Furthermore, the reaction rate of free radicals is much higher than their diffusion efficiency. The chain oxidation reaction initiated by free radicals can cause local polymer backbone breakage in a very short time. The time for antioxidants to diffuse from other locations to the free radicals is much longer than the free radical reaction time. Locally generated free radicals have already completed the chain oxidation reaction before the antioxidants diffuse in, leading to irreversible damage. This invention spatially couples and matches the UV shielding function and the slow-release function on a small scale, so that each masterbatch can constitute a complete protective unit, fundamentally avoiding the protection blind spots caused by statistical distribution.

[0042] It is understood that the specific inner layer absorption and middle layer sustained-release structure of this invention have a strict order, and reversing the order will lead to a serious decrease in protective efficacy. This order stems from the matching requirements of the spatial distribution of the ultraviolet light shielding center and the antioxidant diffusion source. When the inner layer is an ultraviolet shielding layer and the middle layer is a sustained-release layer, the inner layer ultraviolet shielding material efficiently absorbs ultraviolet light in the central region of the masterbatch, reducing the amount transmitted to the surrounding film matrix; while the middle layer microcapsules are located in the annular region outside the geometric center. The antioxidants released during the lamination process diffuse spherically in all directions along the polymer interpenetrating network with this annular region as the diffusion source. The high concentration region exactly covers the irradiated area around the masterbatch, thus simultaneously satisfying the conditions of low irradiation and high antioxidant concentration, which significantly reduces the steady-state concentration of free radicals and correspondingly slows down the antioxidant consumption rate, thereby maintaining an effective antioxidant concentration for a long time. The central position of the middle layer allows antioxidants to diffuse freely in both directions, acting on the substrate area of ​​the film adjacent to the inner layer and replenishing the consumption on the surface of the film, resulting in a balanced spatial distribution of antioxidants.

[0043] If the order of the two layers is reversed, with the UV shielding layer in the middle and the antioxidant layer in the inner layer, the center of the UV shielding will deviate from the geometric center of the masterbatch, located in a ring-shaped region outside the center. This causes the spatial attenuation distribution of UV irradiance to lose its spherical symmetry, and the area near the geometric center of the masterbatch becomes a relatively high-irradiance zone. Meanwhile, the inner layer antioxidant is located at the geometric center of the masterbatch, and this high-irradiance zone will rapidly deplete the antioxidant content. More critically, the inner layer antioxidant needs to diffuse outward through the high-density UV shielding material in the middle layer. This layer significantly hinders the diffusion of small molecules, severely reducing the diffusion coefficient and resulting in insufficient antioxidant migration rate. This prevents timely replenishment of antioxidants consumed in the outer, low-irradiance regions. Ultimately, this leads to the rapid depletion of antioxidants in the high-irradiance inner layer, while the low-irradiance outer layer will still undergo oxidative aging due to a lack of antioxidant replenishment.

[0044] Preferably, the masterbatch has a cylindrical structure with a cross-section of three concentric circles; the inner layer is a solid structure with a radius of 0.05mm to 0.1mm, which can be 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm and any value between them; The middle layer has a ring structure with a radial thickness of 0.1mm to 0.5mm, which can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or any value between them. The outer layer has a ring structure with a radial thickness of 0.1mm to 0.3mm, which can be 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, or any value between them.

[0045] It should be noted that the above-mentioned radius is the average radius, specifically calculated by selecting at least five cross-sections at equal intervals along the axial direction of the masterbatch, measuring the distance from the outer edge of the inner layer of each cross-section to the geometric center, and then taking the arithmetic mean. The above-mentioned radial thickness is the average radial thickness, specifically calculated by selecting at least five cross-sections at equal intervals along the axial direction of the masterbatch, measuring the difference in radial distance between the outer and inner edges of the layer of each cross-section, and then taking the arithmetic mean. The above dimensional definition method takes into account the axial thickness fluctuations caused by factors such as melt flow fluctuations and cooling shrinkage differences in the three-layer co-extrusion process, and conforms to the actual industrial production.

[0046] Understandably, controlling the average radius of the inner layer within a suitable range helps to ensure the uniform distribution density of the UV shielding material, forming an effective UV shielding network and significantly reducing the UV irradiation intensity of the film substrate around the masterbatch. If the average radius of the inner layer is less than 0.05 mm, the distribution density of the UV shielding material is too low, the center-to-center distance of the UV shielding increases, resulting in blind spots in local UV protection. If the average radius of the inner layer is greater than 0.1 mm, due to the significant difference in elastic modulus and thermal expansion coefficient between the inner layer UV shielding material and the film substrate, stress concentration is likely to occur at the interface during temperature cycling, inducing the formation of microcracks and unnecessarily increasing material costs. Maintaining the average radial thickness of the intermediate layer within a suitable range helps to accommodate an appropriate amount of microcapsules and maintain a proper spacing between them, preventing wall material damage due to localized stress concentration during the three-layer co-extrusion process. When the average thickness of the intermediate layer is less than 0.2 mm, the microcapsule distribution density is too high, and the spacing between adjacent microcapsules is too small, making them prone to collision and extrusion under melt shearing, leading to premature wall material rupture. When the average thickness of the intermediate layer exceeds 0.5 mm, the overall diameter of the masterbatch is too large, resulting in decreased dispersion uniformity in the film matrix and a tendency to form localized agglomerations. Furthermore, an excessively high proportion of the intermediate layer will dilute the concentration of functional components per unit volume, reducing the sustained-release efficiency. Controlling the average radial thickness of the outer layer within a suitable range helps form a continuous fluoropolymer enrichment layer on the masterbatch side surface, effectively reducing melt viscosity and significantly delaying water vapor penetration. If the average outer layer thickness is less than 0.1 mm, the fluoropolymer component cannot form a continuous phase on the masterbatch side surface, significantly weakening the lubrication and barrier effects. If the average outer layer thickness is greater than 0.3 mm, the fluoropolymer component excessively dilutes the functional components of the inner and middle layers, and the excessively high proportion of the outer layer leads to a decrease in the overall functional density of the masterbatch, reducing its economic efficiency. The synergistic design of the three layers' average dimensions facilitates the formation of a diffusion field with a reasonable concentration gradient of antioxidants released from the microcapsules around the masterbatch, precisely matching the low UV radiation zone constructed in the inner layer in space, thereby optimizing the protective efficacy.

[0047] It should be noted that since the masterbatch is made into a short cylindrical shape through the pelletizing process, the axial cross-sections at both ends inevitably expose the interface between the middle layer and the inner layer. Therefore, the protective function of the outer layer is mainly manifested in reducing the shear stress of the contact surface between the melt and the equipment during the extrusion process, preventing the middle layer microcapsules from rupturing due to the strong shearing effect of the high viscosity melt, and delaying the penetration of environmental moisture into the middle layer during the storage stage.

[0048] Preferably, the particle distribution density of the ultraviolet shielding material in the inner layer is 1×10⁻⁶. 6 pcs / mm 3 ~5×10 6 pcs / mm 3 It can be 1×10 6 pcs / mm 3 2×10 6 pcs / mm 3 3×10 6 pcs / mm 3 4×10 6 pcs / mm 3 5×10 6 pcs / mm 3 and any values ​​in between; The particle density of the antioxidants encapsulated in the middle layer is 100 particles / mm². 3 ~150 pieces / mm 3 It can be 100 pieces / mm 3 110 pieces / mm 3 120 pieces / mm 3 130 pieces / mm 3 140 pieces / mm 3 150 pieces / mm 3 and any values ​​in between; The particle density of fluorinated organic matter in the outer layer is 500 particles / mm². 3 ~800 pieces / mm 3 It can be 500 pieces / mm 3 550 pieces / mm 3 600 pieces / mm 3 650 pieces / mm 3 700 pieces / mm 3 750 pieces / mm 3 800 pieces / mm 3 And any values ​​in between.

[0049] It is understood that the "particle distribution density" mentioned in this invention refers to the unit volume (mm²) of any specified functional layer (inner layer, middle layer, or outer layer) of the multilayer composite anti-aging functional masterbatch. 3Within a given range, the number of distributed units that can function independently, formed by the key functional components it carries.

[0050] The particle distribution density can be determined using the following optional methods, without any particular limitation in this invention. Specifically, the cross-sectional sample of the masterbatch can be observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Under at least five different fields of view, the number of specific functional dispersion units per unit cross-sectional area is counted, and then combined with the known observation thickness during sample preparation, the number of dispersion units per unit volume, i.e., the particle distribution density, is calculated. For the middle layer (microcapsules) and outer layer (fluorinated organic compounds), the dispersion unit size is relatively large, and can be directly counted through SEM image analysis; for the inner layer (nano-titanium dioxide), the dispersion unit size is relatively small, and can be observed and analyzed using high-magnification TEM images.

[0051] This invention rationally sets the particle distribution density of each layer, matching the functional requirements of each layer and achieving a balance between functional efficiency and structural stability. The high particle distribution density of the inner layer forms a continuous UV shielding network, ensuring no blind spots in UV shielding. When the particle distribution density of the inner layer is too low, UV light can penetrate through the gaps between particles, leading to localized aging; conversely, if the particle distribution density of the inner layer is too high, the increased interaction between UV shielding materials can lead to agglomeration, reducing UV shielding efficiency and affecting dispersibility. The rational particle distribution density of the middle layer in this invention can effectively utilize the functional characteristics of microcapsules, providing sufficient space between them to avoid premature rupture caused by mutual compression. When the particle distribution density of the middle layer is too high, the probability of collision between microcapsules during extrusion increases significantly, making the wall material prone to damage; if the particle distribution density of the middle layer is too low, it cannot provide a sufficient total amount of antioxidants, failing to maintain long-term protection requirements. The rational particle distribution density of the outer layer ensures both uniformity of lubrication and avoids compatibility issues due to localized enrichment.

[0052] Furthermore, the particle size and thickness of each layer in this invention are matched to ensure the effective dispersion, stable existence, and efficient functioning of each functional component. Specifically, the particle size of the fluorinated organic matter in the outer layer is 1~3μm, much smaller than the outer layer thickness (0.1mm~0.3mm), thus enabling uniform dispersion in the resin matrix. This fully utilizes the lubricating effect while maintaining the continuity of the outer layer structure, preventing the penetration of environmental media such as water vapor due to point defects. The particle size of the microcapsules in the middle layer is 5~10μm, smaller than the middle layer thickness (0.1mm~0.5mm), and their size is much larger than the inner layer UV shielding material. This design effectively prevents the microcapsules from penetrating the inner layer and entering the film matrix during processing or use, thereby avoiding excessive local release of antioxidants. The particle size of the inner layer UV shielding material is controlled to ≤20nm, much smaller than the inner layer thickness (0.05mm~0.1mm). This particle size range enables it to effectively shield ultraviolet light in the 280~400nm wavelength band (the wavelength that most easily leads to aging of photovoltaic modules). By matching the particle size and layer thickness as described above, the present invention ensures the independence and synergy of the functions of each layer in terms of microstructure, and avoids functional failure or performance degradation caused by size mismatch.

[0053] Preferably, the first, second, and third polymer resins are each independently selected from ethylene-vinyl acetate copolymer (EVA) or polyolefin elastomer (POE). This design provides flexibility in material selection to adapt to different process conditions and cost requirements while ensuring interfacial compatibility of the three-layer structure. EVA and POE are commonly used matrix resins for photovoltaic films, exhibiting good compatibility and similar melt processing windows. When the three layers use the same resin system, it ensures strong interfacial bonding and avoids interfacial delamination due to thermal stress during subsequent film processing or module use. When different resins are selected for each layer according to actual production conditions, since EVA and POE are both vinyl copolymers with similar polarities, a gradual transition layer with interdiffusion of molecular chains can be formed at the interface during the co-extrusion process of the three layers. It is important to note that when the inner UV shielding material is nano-titanium dioxide modified with a silane coupling agent, its surface has been organically modified, exhibiting good interfacial compatibility with both EVA and POE, enabling uniform dispersion. The protection of the middle layer microcapsules primarily relies on the outer fluorinated organic material to reduce melt shear stress, rather than a specific resin type. The outer fluorinated polymer processing aid exhibits good compatibility with both EVA and POE, effectively fulfilling lubrication and barrier functions. Therefore, this invention allows for flexible selection of resins within the EVA and POE range. A unified resin system can be used to simplify process control, or differentiated configurations can be made based on raw material supply, cost control, or specific performance requirements, without affecting the realization of the masterbatch's core function and the stability of the three-layer structure. This flexibility significantly enhances the adaptability and economy of this invention in actual production.

[0054] Preferably, by weight percentage, the inner layer comprises: 70% to 90% of a first polymer resin, which can be 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, or any value between therewith; and 10% to 30% of an ultraviolet shielding material, which can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any value between therewith. This formulation ensures a balance between ultraviolet shielding and interface reinforcement in the inner layer. The first polymer resin, within a reasonable content range, provides flexibility and compatibility as a matrix, while the ultraviolet shielding material, within a reasonable content range, achieves effective ultraviolet shielding.

[0055] Optionally, the ultraviolet shielding material is an inorganic nanoparticle capable of shielding ultraviolet light in the 280-400nm wavelength band, which may include, but is not limited to, nano-zinc oxide, nano-cerium oxide, and nano-titanium dioxide. Preferably, the ultraviolet shielding material is nano-titanium dioxide, which possesses excellent ultraviolet shielding performance and chemical stability in the 280-400nm wavelength band (the band where photovoltaic modules are most prone to aging).

[0056] The particle size of nano-titanium dioxide is no larger than 20 nm, and can be 20 nm, 18 nm, 15 nm, 12 nm, 10 nm, 8 nm, 5 nm, smaller, or any value in between. Controlling the particle size to no larger than 20 nm is more conducive to improving ultraviolet performance. The electronic band gap of titanium dioxide is approximately 3.2 eV (corresponding to an absorption edge wavelength of 387 nm). When the particle size is reduced to below 20 nm, short-wave ultraviolet absorption is effectively optimized, while visible light scattering is reduced. The absorption coefficient of short-wave ultraviolet light in the 280~350 nm range is significantly improved. The shielding mechanism is dominated by electronic band gap absorption, supplemented by weak Rayleigh scattering. At the same time, the nanoscale particle size is much smaller than the visible light wavelength (400~800 nm), and the monodisperse state is maintained through surface modification, effectively avoiding particle agglomeration to form micron-sized scattering centers. Thus, while achieving efficient ultraviolet shielding, visible light scattering is minimized, ensuring that the film transmittance remains at a high level. If the particle size is too large, although the scattering contribution is enhanced, it is easy to form local agglomerates, which leads to increased visible light haze and decreased light transmittance, directly affecting the power generation efficiency of the module. If the particle size is too small, the specific surface area increases sharply and the surface energy is too high. Even with surface modification, it is still difficult to completely suppress the agglomeration tendency. Moreover, the excessively high interface area may cause interface defects and reduce the bonding strength with the resin matrix.

[0057] It should be noted that the "ultraviolet shielding" mentioned in this invention refers to the functional effect of preventing ultraviolet light from penetrating and causing polymer chain breakage through physical mechanisms such as absorption and scattering. The ultraviolet shielding material is preferably nano-titanium dioxide with a particle size of no more than 20 nm, which is dominated by ultraviolet absorption and supplemented by Rayleigh scattering.

[0058] In this invention, the function of the inner UV shielding material is not only UV shielding, but also to intervene at the source of the photoaging chain reaction, constructing the first passive protective barrier. Specifically, when this inner UV shielding function is not provided, UV light in the 280~400nm band will directly penetrate and act on the film matrix, causing the C-C bonds and CO bonds in its polymer molecular chain to break, thereby generating a large number of hydroxyl radicals (…). OH) and alkyl radicals ( These highly reactive free radicals (R) rapidly initiate and accelerate the yellowing and embrittlement process of the film. However, by introducing highly efficient UV-shielding materials such as nano-titanium dioxide into the inner layer, the total amount of free radicals generated by UV irradiation within the film matrix is ​​significantly reduced. This mechanism of reducing the load at the source greatly alleviates the scavenging pressure on the mid-layer antioxidants, providing a foundation for the slow, long-lasting release of antioxidants and maintaining their effective concentration in the mid-layer.

[0059] Preferably, the nano-titanium dioxide is nano-titanium dioxide surface-modified with a silane coupling agent. Optionally, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, allyltrimethoxysilane, and vinyltrimethoxysilane; preferably, the silane coupling agent is γ-aminopropyltriethoxysilane. In this invention, the surface modification with the silane coupling agent mainly addresses the issues of dispersion and interfacial bonding of nano-inorganic fillers in an organic polymer matrix. Unmodified nano-titanium dioxide contains a large number of hydroxyl groups on its surface, exhibiting strong hydrophilicity. It easily aggregates in non-polar first polymer resins, forming stress concentration points and becoming the initiation sites of microcracks. This invention uses a silane coupling agent (such as γ-aminopropyltriethoxysilane) to surface-treat nano-titanium dioxide, forming an organic molecular layer on the particle surface through a hydrolysis-condensation reaction. Specifically, the siloxane groups of the silane coupling agent react with the hydroxyl groups on the surface of the nanoparticles, while the organic functional groups (amino, epoxy, etc.) form chemical bonds or strong interactions with the first polymer resin. This molecular bridging effect not only significantly improves the dispersion uniformity of nano-titanium dioxide in the first polymer resin, but also greatly enhances the interfacial bonding strength and effectively improves the interlayer shear strength. More importantly, the surface of the nano-titanium dioxide modified by the silane coupling agent changes from hydrophilic to lipophilic, greatly improving its compatibility with the first polymer resin and avoiding the phase separation phenomenon caused by interfacial tension differences during the melt processing of traditional unmodified nanofillers.

[0060] Furthermore, after surface modification with a silane coupling agent, the particle morphology of the nano-titanium dioxide was optimized, resulting in a near-spherical shape, thus controlling its specific surface area within a suitable range. On one hand, the near-spherical structure ensures excellent UV shielding efficiency; on the other hand, compared to needle-like or plate-like particles with sharp edges, the near-spherical particles effectively avoid stress concentration at the interface between the masterbatch and the film matrix, thereby significantly reducing the risk of microcrack initiation and ensuring the long-term integrity of the film structure.

[0061] In this invention, the nano-titanium dioxide is nano-titanium dioxide surface-modified with a silane coupling agent. The modification method can refer to existing technologies, and this invention does not limit it. Preferably, this invention provides a modification method that helps to better achieve the modification of nano-titanium dioxide. Specifically, it includes activating nano-titanium dioxide and a silane coupling agent at a mass ratio of (5~10):1 in a high-speed mixer, controlling the rotation speed at 1000~2000 rpm, and the treatment time at 5~20 minutes.

[0062] Preferably, by weight percentage, the middle layer comprises: 55% to 80% of a second polymer resin, which can be 55%, 60%, 65%, 70%, 75%, 80%, or any value between therewith; and 20% to 45% of an antioxidant encapsulated by microcapsules, which can be 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, or any value between therewith. This formulation ensures that the middle layer has sufficient resin matrix to support the microcapsules while also guaranteeing an effective concentration of antioxidant. The second polymer resin provides flexibility and thermal stability, and the microcapsule-encapsulated antioxidant achieves long-term release within a reasonable content range.

[0063] Preferably, the particle size of the microcapsules is 5μm to 10μm, and can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm and any value between them; The wall material of the microcapsules includes at least one of polylactic acid and polyurethane.

[0064] The microcapsules described in this invention can be prepared using composite agglomeration or other common existing technologies, and this invention does not limit them.

[0065] It should be noted that this invention does not strictly limit the specific chemical composition of the microcapsule wall material. The selection principle is that it can maintain structural integrity during a short residence time (≤30 seconds) at the masterbatch preparation temperature (155℃~165℃) to ensure that the microcapsules do not rupture prematurely during the three-layer co-extrusion process; at the same time, it needs to undergo controllable degradation or softening under photovoltaic module lamination conditions (140℃~160℃, pressure 0.10MPa~0.12MPa, time 15 minutes~20 minutes) to achieve timely release of antioxidants. Wall materials that meet this functional requirement include, but are not limited to, polylactic acid, thermoplastic polyurethane with a specific soft segment content, polycaprolactone and its copolymers, and other biodegradable polymers with appropriate glass transition temperatures and thermal degradation sensitivities. This invention utilizes the stability difference of the wall material under different thermal histories as a release trigger mechanism. That is, the wall material can withstand short-term high-temperature shear during extrusion processing, but under the long-term high-temperature and high-pressure action of the lamination process, its molecular chain thermal motion intensifies and the accumulated heat energy exceeds the structure maintenance threshold, thereby releasing antioxidants. Those skilled in the art can select a suitable wall material system within the above functional framework based on actual production process conditions and cost requirements, without affecting the implementation and effect of the technical solution of the present invention.

[0066] Understandably, a suitable particle size range for microcapsules is beneficial for balancing structural stability and sustained-release efficiency during the three-layer co-extrusion process. When the particle size is less than 5 μm, the ratio of wall thickness to core volume increases, resulting in insufficient antioxidant loading and difficulty in supporting continuous release over a longer aging period. When the particle size is greater than 10 μm, the microcapsules are prone to wall damage due to localized stress concentration under melt shear conditions at 155~165℃, and excessively large particle sizes reduce the number density of microcapsules per unit volume, affecting the spatial uniformity of antioxidant distribution in the film.

[0067] Understandably, polylactic acid (PLA), as a preferred wall material, has a melting point of 170-180℃ and a glass transition temperature of approximately 60℃. During the masterbatch preparation process, it undergoes a short-term thermal shock of 160℃ (material residence time in the die ≤30 seconds), primarily resulting in reversible chain segment movement without significant chemical bond breakage, thus maintaining good wall material integrity. However, under the long-term lamination process conditions of photovoltaic modules (140℃-160℃, pressure 0.10MPa-0.12MPa, time 15-20 minutes), PLA molecular chains undergo thermal degradation or viscoelastic failure under the synergistic effect of sustained high temperature and pressure, leading to a significant increase in wall material porosity or the formation of microcracks, thereby achieving controlled release of antioxidants. The thermal degradation of PLA exhibits a clear time dependence; short-term high temperatures are insufficient to trigger significant degradation, but long-term heat accumulation can lead to a significant decrease in molecular weight. Furthermore, the environmental pressure within the lamination cavity further promotes the expansion of micro-defects in the wall material; additionally, a small amount of water vapor may be present in the lamination environment, further accelerating ester bond breakage. In summary, the microcapsules of this invention are mainly degraded by thermo-coupling caused by prolonged high temperature and high pressure, thereby ensuring that the microcapsule function is activated at the appropriate time.

[0068] Preferably, the microcapsules of the present invention are spherical. This spherical structure has the smallest specific surface area for a given volume. On the one hand, during the extrusion process of the masterbatch, the frictional resistance between the spherical microcapsules and the second polymer resin matrix is ​​minimized, significantly reducing the risk of wall material damage caused by shear stress, thereby effectively preventing premature release of antioxidants. On the other hand, the geometric symmetry of the sphere ensures uniform wall material thickness, making the sustained-release kinetics more stable and controllable, avoiding local stress concentration and weak points in the wall material caused by irregular shapes such as sharp edges, thereby preventing unexpected burst release of antioxidants in certain areas and ensuring a long-lasting and uniform protective effect.

[0069] Preferably, the antioxidant includes hindered amine antioxidants and thioester antioxidants, and the mass ratio of hindered amine antioxidants to thioester antioxidants is (2~4):1, which can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1 and any value between them.

[0070] Preferably, the hindered amine antioxidant (HALS) is selected from at least one of Tinuvin 770, Tinuvin 622, and Chimassorb 944, more preferably Tinuvin 770. The thioester antioxidant is selected from at least one of dilauryl thiodipropionate (DLTDP), distearate thiodipropionate (DSTDP), and di(tridecyl) thiodipropionate (DTDTDP), more preferably distearate thiodipropionate (DSTDP).

[0071] Hindered amine antioxidants, as primary antioxidants, function by efficiently scavenging free radicals through a capture-regeneration cycle mechanism. Firstly, the amine groups in their molecular structure can capture reactive free radicals generated by factors such as ultraviolet light (e.g., free radicals produced by UV radiation). OH、 R, and convert it into relatively stable nitrogen oxide free radicals (NO). Subsequently, the nitroxide free radical can continue to capture other reactive free radicals, thereby achieving a multiplier effect of HALS molecular cycle scavenging multiple free radicals, greatly improving the free radical quenching efficiency. The compounded thioester auxiliary antioxidant's main function is to decompose hydroperoxides, converting them into stable alcohol compounds, thus effectively cutting off the initiation source of free radical chain reactions. The two work synergistically in this specific ratio, effectively inhibiting the entire process of free radical generation and propagation. More importantly, this invention uses microencapsulation technology to encapsulate the above-mentioned composite antioxidant system, allowing for slow and controllable release, thus ensuring that the concentration of key active ingredients such as HALS remains stable at a high level throughout the entire service life of the film, ultimately achieving a long-lasting protective lifespan.

[0072] Preferably, by mass percentage, the outer layer comprises 70% to 80% of a third polymer resin, which can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any value between thereof; and 20% to 30% of a fluorinated organic compound, which can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any value between thereof. This outer layer formulation design reasonably balances the functionality and structure of the material.

[0073] The third polymer resin, as the main matrix, ensures sufficient continuous phase and mechanical strength in the outer layer, forming a complete and dense protective shell. Simultaneously, the appropriate amount of fluorinated organic compounds incorporated into the third polymer resin primarily reduces melt viscosity at processing temperatures, significantly improving processing fluidity. Furthermore, the low-viscosity melt effectively reduces the shearing force of the screw and die on the masterbatch, thus protecting the shear-sensitive microcapsules within the middle layer structure and preventing them from rupturing due to high shear forces during processing, which would lead to premature release of antioxidants. It also helps maintain the uniform dispersion of the inner layer of nano-titanium dioxide, inhibiting its agglomeration under high stress. In addition, the fluorinated organic compounds distributed on the surface endow the outer layer of the masterbatch with extremely low surface energy. This characteristic effectively delays the intrusion of moisture from the environment and reduces the adhesion of dust and other contaminants, providing a stable and clean storage and working environment for the internal functional layers.

[0074] Preferably, the fluorinated organic compound is a fluoropolymer processing aid (fluorinated PPA), which mainly functions to reduce melt viscosity, improve processing fluidity, and delay the intrusion of environmental media in the outer layer of the masterbatch. This type of aid has extremely low surface energy and excellent shear-thinning properties in the polymer melt. When added at a concentration of 20%~30%, it can accumulate on the outer surface of the masterbatch to form a continuous fluorinated phase, significantly reducing the coefficient of friction between the melt and the die wall during the three-layer co-extrusion process, greatly reducing the extrusion pressure, and thus effectively preventing the wall material of the middle layer microcapsules from cracking due to high shear stress. Simultaneously, the dense surface layer formed by this fluorinated phase has excellent barrier properties against moisture and oxygen, protecting the middle layer microcapsules from environmental moisture erosion during masterbatch storage and transportation, maintaining their structural integrity until the component lamination stage. Preferred fluoropolymer processing aids of this invention include perfluoropolyethers (PFPE) and their derivatives. These substances have excellent thermal stability, good compatibility with the EVA / POE matrix, and stable lubrication performance at processing temperatures of 155-185°C.

[0075] Secondly, the present invention provides a method for preparing a multilayer composite anti-aging functional masterbatch according to the first aspect, the preparation method comprising: The first polymer resin and the ultraviolet shielding material are melt-blended and extruded at 145℃~155℃ to obtain inner layer particles. The second polymer resin and the antioxidant encapsulated in microcapsules are melt-blended at 155℃~165℃, extruded and granulated to obtain middle-layer particles; The third polymer resin and fluorinated organic compound are melt-blended at 175℃~185℃, extruded and granulated to obtain outer layer particles; The inner, middle, and outer granules are co-extruded together using a three-layer co-extrusion die, cooled, and then granulated to obtain a multi-layer composite anti-aging functional masterbatch.

[0076] The preparation method of the multilayer composite anti-aging functional masterbatch of the present invention ensures that the functions of each layer are independent and the interface is tightly bonded by preparing each layer of particles in steps and then co-extruding them together.

[0077] The selection of preparation temperatures for each layer of particles is based on a synergistic match between the thermal stability of the functional components and the melting characteristics of the resin. The inner layer temperature is controlled at 145℃~155℃, which is sufficient to allow EVA or POE to fully melt and plasticize, while avoiding the reduction of UV shielding efficiency due to crystal transformation caused by overheating of nano-titanium dioxide. The middle layer temperature is set at 155℃~165℃, which is slightly higher than the inner layer to compensate for the increase in melt viscosity caused by microcapsule filling, ensuring material flowability, while being controlled within the short-term tolerance limit of polylactic acid wall material. The outer layer temperature is increased to 175℃~185℃, mainly based on the dispersion requirements of fluoropolymer processing aids. At this temperature, the fluoropolymer components have sufficient molecular chain mobility to rapidly migrate in the melt to the polymer-air interface for enrichment, forming a continuous lubricating layer. At the same time, this temperature is still lower than the thermal degradation initiation temperature of EVA / POE, avoiding resin yellowing.

[0078] Preferably, the temperature zone control of the three-layer co-extrusion die is as follows: the inner layer zone is 145℃~155℃, which can be 145℃, 146℃, 147℃, 148℃, 149℃, 150℃, 151℃, 152℃, 153℃, 154℃, 155℃ and any value between them; The middle zone is 155℃~165℃, and can be 155℃, 156℃, 157℃, 158℃, 159℃, 160℃, 161℃, 162℃, 163℃, 164℃, 165℃ and any value between them; The outer region is 175℃~185℃, and can be 175℃, 176℃, 177℃, 178℃, 179℃, 180℃, 181℃, 182℃, 183℃, 184℃, 185℃ and any value between them.

[0079] The temperature zones of the three-layer co-extrusion die correspond to the particle preparation temperatures of each layer. The gradient design of 145℃~155℃ for the inner layer, 155℃~165℃ for the middle layer, and 175℃~185℃ for the outer layer aims to create a melt viscosity distribution that increases from the inside to the outside. This viscosity gradient can effectively suppress interface disturbances and interlayer entrainment caused by flow rate differences in the three-layer melt at the die junction area, ensuring the accurate forming of the concentric circular cross-section structure. At the same time, the higher temperature of the outer layer gives it lower melt elasticity at the die exit, allowing it to cool and solidify preferentially to form a stable outer shell, providing forming support for the inner and middle layers and preventing cross-sectional deformation.

[0080] It is worth noting that although the middle-layer microcapsules undergo two thermal processes during particle preparation and co-extrusion, the integrity of the wall material can be maintained because the heat exposure time is controlled within a short period of time each time, and the thermal degradation rate of polylactic acid wall material under short-term conditions of 160℃ is extremely low. In the subsequent photovoltaic module lamination process (140℃~160℃, pressure 0.10MPa~0.12MPa, time 15 minutes~20 minutes), under the long-term action of high temperature and high pressure during lamination, the heat energy accumulated inside the wall material exceeds its structural stability threshold, the free volume of the polymer increases and the molecular chains undergo thermal breakage, allowing antioxidant molecules to diffuse through the wall material, thereby ensuring that the microcapsule function is activated at the appropriate time.

[0081] This stepwise preparation and co-extrusion composite process ensures the uniform dispersion of functional components in each layer during the premixing stage, and achieves molecular-level bonding of the three-layer interface through one-time composite in the die head. This avoids the degradation problem of functional components in traditional multi-step composite processes, and ultimately obtains a multi-layer composite anti-aging functional masterbatch with stable structure and synergistic function.

[0082] Thirdly, the present invention provides a photovoltaic encapsulant film, which includes a matrix resin and a multilayer composite anti-aging functional masterbatch prepared by the method of the first aspect or the method of the second aspect.

[0083] The photovoltaic encapsulant film provided by this invention incorporates functional masterbatches with a specific multilayer structure as functional units into the film matrix resin. Each functional masterbatch does not simply release its functional components within the film, but rather functions as a complete and independent unit. Compared to traditional homogeneous systems, this design effectively enhances the protective function both spatially and temporally. Spatially, the functions of inner layer UV shielding, middle layer slow-release antioxidant, and outer layer providing physical protection are integrated into a single micro-unit, forming a synergistic protective local microenvironment around it. This effectively solves the problem of uneven distribution and localized failure of functional additives caused by diffusion and migration within the macroscopic encapsulant film. Temporally, thanks to the microencapsulation slow-release design of the middle layer and the protection of the outer layer, the release and consumption rate of the antioxidant can be regulated, matching its protective lifespan with the aging process of the encapsulant film.

[0084] Preferably, the base resin of the photovoltaic film is ethylene-vinyl acetate copolymer (EVA) or polyolefin elastomer (POE).

[0085] Preferably, the complete formulation of photovoltaic encapsulant film as a thermosetting encapsulation material typically includes crosslinking agents, crosslinking aids, and conventional processing aids, in addition to the matrix resin and functional masterbatch.

[0086] The crosslinking agent can be selected from organic peroxides (such as 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane) or silane coupling agent crosslinking systems, with an addition amount of 0.3~1.0 wt%, used to initiate the crosslinking reaction of the matrix resin during the lamination process, forming a three-dimensional network structure to improve heat resistance and mechanical strength; The crosslinking aid can be selected from triallyl isocyanurate and trimethylolpropane trimethacrylate, with an addition amount of 0.5~2.0 wt%, to improve crosslinking efficiency and improve the uniformity of the crosslinking network; In addition, the film may contain conventional processing stabilizers (such as hindered phenolic antioxidant 1010 and phosphite auxiliary antioxidant 168) and silane coupling agents (such as vinyltrimethoxysilane) to improve processing stability and interfacial adhesion performance.

[0087] Preferably, the multilayer composite anti-aging functional masterbatch is dispersed in the matrix resin of the photovoltaic film in discrete individual form, and the multilayer composite anti-aging functional masterbatch accounts for 0.5% to 3% of the total mass of the photovoltaic film, which can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3% and any value between them.

[0088] It can be further understood that the core of the present invention, which describes "multilayer composite anti-aging functional masterbatch dispersed in discrete individual form in the matrix resin of photovoltaic film," lies in the fundamental difference between the distribution state of functional components in the matrix resin and that of traditional masterbatches. In traditional masterbatches, functional additives are often uniformly dispersed after melt blending, resulting in excessively low local concentrations and easy migration and loss. In the present invention, although melt extrusion is performed during the photovoltaic film preparation process, the low surface energy barrier and viscosity regulation effect formed by the outer fluorinated organic material effectively suppress excessive miscibility between the masterbatch and the matrix resin of the film, as well as the instantaneous complete diffusion of functional components. Therefore, in the final photovoltaic film, the masterbatch does not completely form a homogeneous system, but rather forms locally functionally enriched micro-regions centered on the original location of the masterbatch. Within these micro-regions, the inner layer of UV shielding material and the middle layer of antioxidants maintain a relatively concentrated distribution, allowing each masterbatch to function as a relatively independent functional unit in the film, thereby achieving spatial gradient protection and temporal slow-release synergy.

[0089] In this invention, the appropriate amount of multilayer composite anti-aging functional masterbatch added helps to construct an efficient and economical dot-like protective network. Within this preferred range, the functional masterbatch can be uniformly dispersed in the film matrix at an appropriate spatial density, allowing the local protective areas of each masterbatch to connect with each other, thereby forming a continuous, seamless protective coverage throughout the three-dimensional space of the film. This design ensures that even in harsh environments such as high humidity and strong ultraviolet radiation, the weak areas of the film can be effectively protected, significantly improving the uniformity and reliability of the protection. Simultaneously, this ratio balances the relationship between functionality and the basic performance of the film, providing excellent long-term weather resistance while avoiding problems such as transmittance loss, deterioration of interfacial compatibility, and uneconomical costs caused by excessive masterbatch addition.

[0090] Fourthly, this invention provides a method for preparing a photovoltaic encapsulant film, comprising: premixing a matrix resin, a multilayer composite anti-aging functional masterbatch, and conventional components such as a crosslinking agent and crosslinking aid under low-temperature conditions (80℃~100℃) for 3~5 minutes at a speed of 800~1200 rpm to ensure that the functional masterbatch is uniformly dispersed under controllable shear force and to prevent the intermediate microcapsules from prematurely rupturing due to high temperature or strong shear; feeding the premixed material into a casting extruder and melting and extruding it into a film at a processing temperature of 140℃~160℃, wherein the lower limit of the temperature (140℃) ensures that the EVA / POE matrix resin is fully melted and plasticized to achieve good film-forming properties, and the upper limit of the temperature (160℃) is strictly controlled within the short-term tolerance limit of the polylactic acid wall material (the material residence time in the extruder is ≤60 seconds) to ensure that the microcapsules maintain structural integrity during the film preparation stage; and then rapidly cooling the extruded melt to below 40℃ by a cooling roller and winding it up to obtain a photovoltaic encapsulant film roll. This preparation process, through the synergistic control of low-temperature premixing and appropriate extrusion temperature, effectively maintains the sustained-release function of microcapsules while ensuring the quality of film formation, which helps to release antioxidants during subsequent lamination.

[0091] Fifthly, the present invention provides a method for using the above-mentioned photovoltaic encapsulant film, the method comprising: stacking the photovoltaic encapsulant film, solar cell, glass and backsheet in sequence and feeding them into a laminator, laminating them at 140℃~160℃ and 0.10MPa~0.12MPa pressure for 15~20 minutes, and then naturally cooling them to room temperature to obtain a fully encapsulated photovoltaic module.

[0092] The lamination temperature of 140℃~160℃ and the pressure conditions are within the thermo-coupling degradation activation window of polylactic acid wall materials. Under the long-term high temperature and high pressure of lamination, the thermal motion of the wall material molecular chains intensifies and the accumulated heat energy exceeds the structural maintenance threshold. At the same time, the environmental pressure promotes the expansion of micro-defects, resulting in a significant increase in the porosity of the wall material or the generation of microcracks, thus achieving the controlled release of antioxidants. Meanwhile, this temperature is also conducive to the free radical cross-linking reaction between the EVA / POE matrix resin and the peroxide cross-linking agent. The antioxidants released by the microcapsules diffuse into the matrix during the formation of the cross-linking network of the film, thus timely clearing the free radicals caused by the cross-linking reaction and ultraviolet irradiation.

[0093] This preparation method is not only simple to operate, but also capable of large-scale production, providing a reliable guarantee for the industrial application of the technical solution of this invention.

[0094] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0095] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available, and all proportions, percentages, etc., mentioned in this invention are mass proportions or mass percentages unless otherwise specified. The POE resin is a commercially available polyolefin elastomer, and the EVA resin is a commercially available ethylene-vinyl acetate copolymer.

[0096] Example 1 This embodiment provides a multilayer composite anti-aging functional masterbatch 100 and its photovoltaic film 200.

[0097] The multi-layer composite anti-aging functional masterbatch 100 has a cylindrical structure, and its cross-section has a three-layer concentric circle structure, consisting of an inner layer 10, a middle layer 20, and an outer layer 30 from the inside out: The inner layer 10 is a solid structure with a radius of 0.1 mm. Its composition, by mass percentage, is: 80 wt% EVA resin and 20 wt% nano-titanium dioxide (particle size ≤ 20 nm) surface-modified with γ-aminopropyltriethoxysilane. The particle size distribution density of the nano-titanium dioxide in the inner layer is 3 × 10⁻⁶. 6 pcs / mm 3 .

[0098] The middle layer 20 has a ring-shaped structure with a radial thickness of 0.1 mm. Its composition, by mass percentage, is: 60 wt% POE resin and 40 wt% microcapsule-encapsulated antioxidant. The microcapsule wall material is polylactic acid with a particle size of 8 μm; the antioxidant is a compound of hindered amine antioxidant Tinuvin 770 and thioester antioxidant DSTDP in a mass ratio of 3:1. The particle size distribution density of the antioxidant encapsulated in the middle layer is 120 particles / mm². 3 .

[0099] The outer layer 30 has a ring-shaped structure with a radial thickness of 0.3 mm. Its composition, by mass percentage, is: 75 wt% POE resin and 25 wt% fluorinated PPA (perfluoropolyether type). The particle density of the fluorinated organic matter in the outer layer is 600 particles / mm². 3 .

[0100] The preparation method of multilayer composite anti-aging functional masterbatch 100 includes: Inner layer particle preparation: Nano-titanium dioxide and γ-aminopropyltriethoxysilane (mass ratio 9:1) were activated in a high-speed mixer at 1500 rpm for 10 minutes, and then melt-blended with EVA resin at 150℃ and extruded into granules to obtain inner layer particles.

[0101] Preparation of intermediate particles: The antioxidants encapsulated in microcapsules are melt-blended with POE resin at 160°C and extruded and granulated to obtain intermediate particles.

[0102] Outer layer particle preparation: POE resin and PPA are melt-blended at 180°C and extruded and granulated to obtain outer layer particles.

[0103] Multi-layer co-extrusion composite: The inner, middle, and outer layer particles are integrally formed using a spiral flow channel type three-layer co-extrusion round die. The die temperature is controlled in zones: 150℃ for the inner layer, 160℃ for the middle layer, and 180℃ for the outer layer. After co-extrusion, cooling, and pelletizing, particles with a diameter of approximately 1mm are finally obtained. Figure 1 The multi-layer composite anti-aging functional masterbatch 100 shown is shown.

[0104] The preparation method of photovoltaic encapsulant film 200 includes: The matrix resin EVA, the multilayer composite anti-aging functional masterbatch 100 prepared in this embodiment (added at 1.0 wt%), and conventional components such as crosslinking agents and crosslinking aids were premixed at 90°C for 4 minutes at a speed of 1000 rpm. The premixed material was fed into a casting extruder and melt-extruded into a film at a processing temperature of 150°C. The extruded melt was rapidly cooled to below 40°C by cooling rollers and then wound up to obtain the desired film. Figure 2 The photovoltaic film 200 shown.

[0105] like Figure 3 As shown in the figure, the white bright spots are the multilayer composite anti-aging functional masterbatch. As can be seen from the figure, the multilayer composite anti-aging functional masterbatch is dispersed in the matrix resin of the photovoltaic film in a discrete individual form and irregularly. The functional components form locally enriched protective micro-regions in the film.

[0106] like Figure 4 As shown, the multilayer composite anti-aging functional masterbatch obtained in Example 1 of this invention has a short cylindrical shape with a diameter of approximately 1.0 mm, a smooth and dense surface, and a uniform milky white color. This shape is obtained by extruding continuous strips through a three-layer co-extrusion die and then performing a rotary pelletizing process. Its side surface is composed of an outer layer of fluoropolymer-enriched phase, exhibiting low surface energy characteristics. This short cylindrical structure is beneficial for achieving uniform dispersion of the masterbatch during subsequent blending with the film matrix resin. At the same time, its size design balances the formation of an effective protective microenvironment in the film with the avoidance of optical defects caused by excessively large particles.

[0107] like Figure 5 The image shown is an electron microscope (EM) image of the longitudinal section obtained by cutting the multilayer composite anti-aging functional masterbatch along the axial direction according to Embodiment 1 of the present invention. As can be seen from the image, the masterbatch exhibits a clear three-layer concentric cylindrical structure: the innermost layer 10 is a solid cylindrical inner layer; the middle layer 20 is a ring-shaped middle layer surrounding the inner layer; and the outermost layer 30 is a ring-shaped outer layer, tightly covering the middle layer, with uniform thickness. It should be noted that the longitudinal section image reflects the layered distribution characteristics along the axial direction of the masterbatch, while the cross-section of the masterbatch (perpendicular to the axial direction) presents a standard three-layer concentric circular structure. The interfaces of each layer in the image are tightly bonded, with no obvious pores or debonding, indicating that the melt flow is well matched in the three-layer co-extrusion process, forming a stable interlayer bond. This structural feature confirms that the present invention successfully achieves stable molding of a multilayer composite structure by controlling the melt viscosity of the three-layer material and the die temperature gradient, laying a structural foundation for its synergistic anti-aging function in photovoltaic films.

[0108] Example 2 This embodiment is the same as Embodiment 1, except that the thickness of each layer is: The inner radius is 0.05 mm.

[0109] The radial thickness of the middle layer is 0.5 mm.

[0110] The outer layer has a radial thickness of 0.1 mm.

[0111] Example 3 This embodiment is the same as Embodiment 1, except that the thickness of each layer is: The inner radius is 0.05 mm.

[0112] The radial thickness of the middle layer is 0.2 mm.

[0113] The outer layer has a radial thickness of 0.2 mm.

[0114] Example 4 This embodiment is the same as Embodiment 1, except that the thickness of each layer is: The inner radius is 0.05 mm.

[0115] The radial thickness of the middle layer is 0.2 mm.

[0116] The outer layer has a radial thickness of 0.3 mm.

[0117] Example 5 This embodiment is the same as Embodiment 1, except that the thickness of each layer is: The inner radius is 0.05 mm.

[0118] The radial thickness of the middle layer is 0.2 mm.

[0119] The outer layer has a radial thickness of 0.1 mm.

[0120] Example 6 This embodiment is the same as Embodiment 3, except that the component content of each layer is: The inner layer composition is changed to: 70wt% EVA resin and 30wt% nano titanium dioxide.

[0121] The middle layer composition is changed to: 55wt% POE resin and 45wt% microcapsule-encapsulated antioxidant.

[0122] The outer layer composition changed to: 70wt% POE resin and 30wt% fluorinated PPA.

[0123] Example 7 This embodiment is the same as Embodiment 3, except that the component content of each layer is: The inner layer composition is changed to: 90wt% EVA resin and 10wt% nano titanium dioxide.

[0124] The middle layer composition is changed to: 80wt% POE resin and 20wt% microcapsule-encapsulated antioxidant.

[0125] The outer layer composition is changed to: 80wt% POE resin and 20wt% fluorinated PPA.

[0126] Comparative Example 1 60 wt% POE resin and 40 wt% antioxidant were directly melt-blended and extruded and granulated at 170°C to obtain homogeneous monolayer masterbatch. The antioxidant was a compound of hindered amine antioxidant Tinuvin 770 and thioester antioxidant DSTDP in a mass ratio of 3:1.

[0127] The masterbatch was blended with EVA matrix resin at a ratio of 1.0 wt%, and photovoltaic films were prepared using the same process as in Example 1.

[0128] Comparative Example 2 Referring to the formulation and process of Example 3, a double-layer masterbatch without an inner layer was prepared. Its structure consisted of an outer layer (0.2 mm, same as the outer layer in Example 3) directly coating a middle layer (0.2 mm, same as the middle layer in Example 3). This masterbatch was then used to prepare a photovoltaic film at a ratio of 1.0 wt%.

[0129] Comparative Example 3 Referring to the formulation and process of Example 3, a double-layer masterbatch without an outer layer was prepared. Its structure consisted of a middle layer (0.2 mm, the same as the middle layer in Example 3) directly covering an inner layer (0.05 mm, the same as the inner layer in Example 3). This masterbatch was then used to prepare a photovoltaic film at a ratio of 1.0 wt%.

[0130] Comparative Example 4 Referring to the formulation and process of Example 3, a three-layer masterbatch with interchangeable inner and middle layers was prepared. The masterbatch, from the inside out, consists of: Inner layer: The composition is the middle layer of Example 3, which contains 60wt% POE resin and 40wt% microcapsule-encapsulated antioxidant with a radius of 0.05mm.

[0131] Middle layer: The composition is the inner layer of Example 3, namely containing 80wt% EVA resin and 20wt% surface-modified nano titanium dioxide, with a radial thickness of 0.2mm.

[0132] Outer layer: The composition is the outer layer of Example 3, which contains 75wt% POE resin and 25wt% fluorinated PPA, with a radial thickness of 0.2mm.

[0133] The masterbatch was used to make a photovoltaic film at a ratio of 1.0 wt%.

[0134] Comparative Example 5 This comparative example is the same as Example 3, except that its intermediate particles are prepared using antioxidants and POE resin that are not encapsulated in microcapsules.

[0135] Test case The photovoltaic films prepared in Examples 1-7 and Comparative Examples 1-5 were subjected to performance testing in accordance with the IEC 61215 standard. Specific testing methods may include: Tensile strength retention rate: After aging the standard sample in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for 1000 hours, the tensile strength before and after aging is tested using a universal tensile testing machine, and the retention rate is obtained by calculating the percentage of the strength after aging to the strength before aging.

[0136] Yellowing Index: The L value of samples before and after aging at 85℃ and 85% relative humidity for 1000 hours was measured using a colorimeter. a b The value is calculated, and the overall color difference ΔE is calculated based on the CIELAB color difference formula.

[0137] Adhesive film-glass peel force: After the prepared adhesive film-glass laminate (25mm wide) has been aged at 85℃ and 85% relative humidity for 1000 hours, the peel force is tested at a peel angle of 180° and a speed of 50mm / min, and the average value is taken.

[0138] Photovoltaic module power degradation rate: The photovoltaic encapsulant film, solar cells, glass, and backsheet are stacked in sequence and then fed into a laminator. Lamination is performed at 150℃ and 0.10MPa pressure for 20 minutes, followed by natural cooling to room temperature to obtain the encapsulated photovoltaic module. The maximum output power of the photovoltaic module is measured under standard test conditions before and after DH2000h aging, and the percentage of power degradation is calculated.

[0139] The results are shown in Table 1 below.

[0140] Table 1

[0141] Test results show that the multilayer composite anti-aging functional masterbatch provided in this invention significantly outperforms the traditional single-layer masterbatch (Comparative Example 1) in all aspects of performance. Comparative Example 2, lacking an inner layer for UV shielding, experienced accelerated yellowing of the film and a significant decrease in its UV aging resistance. Comparative Example 3, lacking an outer layer providing processing protection and external barrier, experienced accelerated antioxidant migration and consumption, resulting in significantly lower tensile strength retention and peel strength compared to the complete structure embodiment, indicating insufficient long-term protection. Comparative Example 4 (a three-layer structure with interchangeable inner and middle layers) also performed significantly worse than the embodiments of this invention. This fully demonstrates that simply possessing a three-layer structure does not necessarily yield superior results; the specific functional sequence of inner UV shielding, middle slow-release, and outer protection is key to achieving synergistic effects. Comparative Example 4 placed the easily consumed antioxidant in the inner layer, leading to rapid consumption in the early stages of aging; while placing the UV shielding layer in the middle layer significantly reduced the protection efficiency and failed to effectively reduce the initial generation of free radicals in the film matrix. This fully demonstrates the necessity, functional independence, and synergy of the three-layer structure design of the present invention: inner layer UV shielding, middle layer sustained release, and outer layer protection. Comparative Example 5 uses the same three-layer structure as Example 3, but its middle layer uses an antioxidant that is not microencapsulated. Its test results show that, despite the three-layer structure, because the antioxidant is not microencapsulated, it is prone to migration and premature consumption during the high-temperature processes of masterbatch preparation and film processing, resulting in significantly lower anti-aging performance than Example 3.

[0142] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A multilayer composite anti-aging functional masterbatch, characterized in that, It comprises an inner layer, a middle layer, and an outer layer, which are sequentially composited from the inside out; the inner layer comprises a first polymer resin and an ultraviolet shielding material; the middle layer comprises a second polymer resin and an antioxidant encapsulated in microcapsules; and the outer layer comprises a third polymer resin and a fluorinated organic compound. The wall material of the microcapsules is polylactic acid; The masterbatch has a cylindrical structure with a cross-section of three concentric circles. The inner layer is a solid structure, and the radius of the inner layer is 0.05mm to 0.1mm; The middle layer has a ring structure, and the radial thickness of the middle layer is 0.1mm to 0.5mm; The outer layer has a ring structure and a radial thickness of 0.1 mm to 0.3 mm.

2. The multilayer composite anti-aging functional masterbatch according to claim 1, characterized in that, The inner layer comprises, by weight percentage: 70% to 90% of a first polymer resin and 10% to 30% of an ultraviolet shielding material.

3. The multilayer composite anti-aging functional masterbatch according to claim 2, characterized in that, The first polymer resin is selected from ethylene-vinyl acetate copolymer or polyolefin elastomer; The ultraviolet shielding material is nano-titanium dioxide, which is nano-titanium dioxide with a surface modified by a silane coupling agent, and the particle size of the nano-titanium dioxide is no greater than 20 nm.

4. The multilayer composite anti-aging functional masterbatch according to claim 1, characterized in that, The middle layer comprises, by weight percentage: 55% to 80% of a second polymer resin and 20% to 45% of an antioxidant encapsulated in microcapsules.

5. The multilayer composite anti-aging functional masterbatch according to claim 4, characterized in that, The second polymer resin is selected from ethylene-vinyl acetate copolymer or polyolefin elastomer; The microcapsules have a particle size of 5μm to 10μm; The antioxidants include hindered amine antioxidants and thioester antioxidants, and the mass ratio of the hindered amine antioxidants to the thioester antioxidants is (2~4):

1.

6. The multilayer composite anti-aging functional masterbatch according to claim 1, characterized in that, By weight percentage, the outer layer comprises 70% to 80% of a third polymer resin and 20% to 30% of a fluorinated organic compound.

7. The multilayer composite anti-aging functional masterbatch according to claim 6, characterized in that, The third polymer resin is selected from ethylene-vinyl acetate copolymer or polyolefin elastomer; The fluorinated organic compound is a fluorinated polymer processing aid.

8. A method for preparing a multilayer composite anti-aging functional masterbatch as described in any one of claims 1 to 7, characterized in that, The preparation method includes: The first polymer resin and the ultraviolet shielding material are melt-blended and extruded at 145℃~155℃ to obtain inner layer particles. The second polymer resin and the antioxidant encapsulated in microcapsules are melt-blended at 155℃~165℃, extruded and granulated to obtain middle-layer particles; The third polymer resin and fluorinated organic compound are melt-blended and extruded and granulated at 175℃~185℃ to obtain outer layer particles; The inner layer particles, middle layer particles, and outer layer particles are co-extruded together through a three-layer co-extrusion die, cooled, and then granulated to obtain the multi-layer composite anti-aging functional masterbatch. The temperature zone control of the three-layer co-extrusion die head is as follows: inner layer zone 145℃~155℃, middle layer zone 155℃~165℃, and outer layer zone 175℃~185℃.

9. A photovoltaic encapsulant film, characterized in that, The photovoltaic film contains a matrix resin and a multilayer composite anti-aging functional masterbatch as described in any one of claims 1 to 7 or a multilayer composite anti-aging functional masterbatch prepared by the preparation method described in claim 8. The multilayer composite anti-aging functional masterbatch is dispersed in the matrix resin of the photovoltaic film in discrete individual form, and the mass of the multilayer composite anti-aging functional masterbatch accounts for 0.5% to 3% of the total mass of the photovoltaic film.

Images