Method for grading and recycling photovoltaic adhesive film scrap and white photovoltaic packaging adhesive film

Abstract

This invention provides a method for graded reuse of photovoltaic encapsulant film and a white photovoltaic encapsulant film, relating to the technical field of photovoltaic encapsulant film. The method for graded reuse of photovoltaic encapsulant film includes the following steps: (a) granulating the recycled granulated material obtained from waste photovoltaic encapsulant film into difficult-to-recycle granulated material and conventionally recycled granulated material; (b) preparing a three-layer white photovoltaic encapsulant film, wherein the upper, middle, and lower layers of the white photovoltaic encapsulant film all contain white filler, adding the difficult-to-recycle granulated material to the middle layer, and adding the conventionally recycled granulated material to the upper and / or lower layers. This invention adds the high-risk difficult-to-recycle granulated material to the middle layer of the three-layer white encapsulant film, and distributes the low-risk conventionally recycled granulated material to the upper and / or lower layers. By utilizing the fact that the middle layer is wrapped by the upper and lower layers, combined with the high hiding power design of each layer containing white filler, it can cover up defects such as crystal points, holes, and bluish light that may occur.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulant technology, and in particular to a method for graded reuse of recycled photovoltaic encapsulant materials and a white photovoltaic encapsulant film. Background Technology

[0002] In the manufacturing process of photovoltaic films (such as EVA, POE, EPE, etc.), a large amount of adjustment material or waste film is generated during start-up, specification switching, or production anomalies. To reduce costs and achieve green manufacturing, the industry generally adopts physical granulation to recycle these waste films, making them into granulated material, which is then added back into the production of new films. The traditional recycling method usually involves directly mixing the granulated material with virgin material and extruding it into a single-layer film.

[0003] However, the aforementioned simple mixed recycling model reveals significant process compatibility defects and quality risks when dealing with recycled materials of different quality characteristics, specifically manifested as follows: 1. Difficulty in recycling special membrane types: For OBB carrier membranes (typically extremely thin, approximately 0.1mm-0.5mm), due to their large specific surface area, intense shear friction occurs between membranes and between the membrane and the screw during granulation, leading to excessively high local temperatures. This causes irreversible partial cross-linking (gelling) of the recycled material. Directly adding this to transparent films or ordinary single-layer films easily results in defects such as crystal points, holes, and white spots during subsequent module lamination, severely affecting module yield and appearance.

[0004] 2. Hue and appearance issues of recycled functional film materials: Recycled materials of light-converting films contain light-converting agents (organic or inorganic phosphors). Directly adding them to conventional films will cause uneven bluish light to appear on the finished film under natural light, affecting the product's appearance and optical consistency.

[0005] 3. Compatibility issues of low-flow adhesive films: Some recycled adhesive films with high cross-linking degree or low flow rate do not match the melt index of high-flow virgin materials. Direct addition can easily lead to uneven casting during extrusion and surface defects.

[0006] 4. Limited reuse ratio of conventional recycled materials: For conventional recycled materials of good quality (such as transparent EVA adjustment materials, scraps, etc.), existing technologies can usually only mix and add them with new materials at a low ratio (generally no more than 10%), which fails to maximize the use ratio of recycled materials while ensuring the appearance and performance of the product, and the room for cost reduction is limited. Summary of the Invention

[0007] One of the objectives of this invention is to provide a method for the graded reuse of photovoltaic encapsulant film, so as to at least solve one of the technical problems existing in the prior art.

[0008] The second objective of this invention is to provide a white photovoltaic encapsulation film.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for graded reuse of photovoltaic encapsulant film, comprising the following steps: (a) The recycled granulated material obtained from the granulation of waste photovoltaic encapsulant film is divided into difficult-to-recycle granulated material and conventionally recycled granulated material; (b) Prepare a three-layer white photovoltaic encapsulating film, wherein the upper, middle and lower layers of the white photovoltaic encapsulating film each contain white filler, the difficult-to-recycle granulated material is added to the middle layer, and the conventionally recycled granulated material is added to the upper and / or lower layers.

[0010] Furthermore, the criteria for determining the difficult-to-recycle granulated material are that it meets at least one of the following: (A) The gel content is 5-10%; (B) The melt flow index decreases by 10-50% compared to the original sheet; (C) Contains functional additives that cause abnormal color in the finished film under natural light; (D) The granulated product appears yellow or black or contains impurities visible to the naked eye; Preferably, the difficult-to-recycle granulated material includes at least one of OBB carrier film granulated material, light-converting film granulated material, and low-flow-rate adhesive film granulated material.

[0011] Furthermore, the criteria for determining whether the conventional recycled granulated material is acceptable are that it meets at least one of the following: (A) Gel content < 5%; (B) Melt flow index retention rate compared to the original sheet ≥ 90%; (C) Contains no functional additives, or contains functional additives but has no significant effect on the color of the finished film; (D) The granules have a uniform appearance and no impurities visible to the naked eye; Preferably, the conventional recycled granulation material includes at least one of transparent film granulation material and scrap granulation material.

[0012] Furthermore, the white filler includes one or more of titanium dioxide, talc, barium sulfate, calcium carbonate, and magnesium hydroxide; Preferably, the content of white filler in the upper, middle and lower layers is 5%-25% of the total mass of the corresponding layer.

[0013] Furthermore, the amount of the difficult-to-recycle granulated material added to the intermediate layer is 5%-50% of the total mass of the intermediate layer.

[0014] Furthermore, the amount of conventional recycled granulated material added to the upper and / or lower surface layers is 5%-50% of the total mass of the corresponding layers.

[0015] Furthermore, the matrix materials of the upper, middle, and lower layers are each one or more of the following: ethylene-vinyl acetate copolymer, polyvinyl butyral, polyolefin elastomer, polyurethane, ionomer, ethylene-acrylic acid copolymer, and ethylene-ethyl acrylate copolymer; or are co-extruded composite systems composed of any two or more of the above materials.

[0016] Furthermore, the thickness of the upper surface layer is 100-300 μm; the thickness of the middle layer is 30-180 μm; and the thickness of the lower surface layer is 100-300 μm. Preferably, the white photovoltaic encapsulating film is prepared using a three-layer co-extrusion process.

[0017] Secondly, the present invention provides a white photovoltaic encapsulating film, which is prepared by the graded reuse method of the photovoltaic encapsulating film recycled material.

[0018] Furthermore, the white photovoltaic encapsulating film comprises a lower surface layer, an intermediate layer, and an upper surface layer stacked sequentially.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a graded reuse method for photovoltaic encapsulant film. This method categorizes the risk of defects caused by recycled granulated materials in the photovoltaic encapsulation process. High-risk, difficult-to-recycle granulated materials are added to the middle layer of a three-layer white encapsulant film, while low-risk, conventionally recycled granulated materials are distributed to the upper and / or lower layers. The middle layer is encased by the upper and lower layers, and the high-coverage design of each layer containing white filler masks potential defects such as crystal points, voids, and bluish tint. This invention achieves spatially differentiated adaptation of recycled materials and physical shielding against defects, thereby significantly increasing the overall reuse rate of various recycled granulated materials while ensuring the appearance quality and lamination reliability of the encapsulant film. Detailed Implementation

[0020] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 are within the scope of protection of the present invention.

[0022] The first aspect of this invention provides a method for the graded reuse of photovoltaic encapsulant film, comprising the following steps: (a) The recycled granulated material obtained from the granulation of waste photovoltaic encapsulant film is divided into difficult-to-recycle granulated material and conventionally recycled granulated material; (b) Prepare a three-layer white photovoltaic encapsulating film, wherein the upper, middle and lower layers of the white photovoltaic encapsulating film each contain white filler, the difficult-to-recycle granulated material is added to the middle layer, and the conventionally recycled granulated material is added to the upper and / or lower layers.

[0023] The present invention provides a graded reuse method for photovoltaic encapsulant film, which classifies the recycled material into difficult-to-recycle material and conventional recycled material according to its impact on the manufacturing process, and establishes clear quantitative distinction standards. It adopts a three-layer co-extruded white photovoltaic encapsulant film structure, with all three layers containing white filler. The difficult-to-recycle material is added only to the middle layer. The middle layer is wrapped by the upper and lower layers, and the white filler has high opacity to cover up defects such as crystal points, holes, and blue light. At the same time, conventional recycled material (i.e., recycled material that has no significant impact on the manufacturing process) is added to the upper and / or lower layers to further increase the amount of recycled material used and reduce raw material costs.

[0024] Further explanation: This invention achieves graded utilization, maximizing the use of each component. It proposes a strategy of graded addition based on the quality of recycled materials and provides clear quantitative grading standards. The lowest quality, difficult-to-recycle materials are confined to the middle layer, where their physical and optical defects are concealed by the high opacity of the white filler and the double-layer encapsulation structure. Higher-quality, conventionally recycled materials are added to the outer layer, avoiding appearance problems caused by adding excessively poor-quality recycled materials. Simultaneously, it maximizes the utilization rate of recycled materials and significantly reduces costs: In traditional solutions, difficult-to-recycle materials are often discarded or disposed of at low prices, and the proportion of conventionally recycled materials added is usually no more than 15%. This invention, through graded addition, allows for a high proportion of reuse of difficult-to-recycle materials (20%-30% can be added to the middle layer), while a large amount of conventionally recycled materials can be added to the outer layer (up to 50%). The total proportion of recycled materials added to the entire film can be significantly increased to over 30%-50%, significantly reducing raw material procurement costs. In addition, the present invention has excellent process stability, all three layers contain white filler, good interlayer compatibility, and because the outer layer uses conventional recycled material with more stable quality, the appearance of the membrane surface (smoothness, gloss) is better than the scheme of concentrating all recycled material in one layer.

[0025] In some preferred embodiments, the criteria for determining the difficult-to-recycle granulated material are that it meets at least one of the following: (A) The gel content is 5-10% (based on the mass percentage of residue after filtration through a 100-mesh sieve). (B) The melt flow index (MFI) decreases by 10-50% compared to the original sheet; (C) The presence of functional additives (including but not limited to light-converting agents, anti-PID additives, UV absorbers, etc.) causes the finished film to exhibit obvious color abnormalities (such as bluish light, yellowish light, etc.) under natural light. (D) The granulated product appears yellow or black or contains impurities visible to the naked eye.

[0026] Preferably, the difficult-to-recycle granulated material includes at least one of OBB carrier film granulated material, light-converting film granulated material, and low-flow-rate adhesive film granulated material.

[0027] In some preferred embodiments, the criteria for determining the conventional recycled granulated material are that it meets at least one of the following: (A) Gel content < 5% (based on the mass percentage of residue after filtration through a 100-mesh sieve); (B) Melt Flow Index (MFI) retention rate compared to the original sheet ≥ 90% (or can be described as a decrease of < 10%); (C) Contains no functional additives, or contains functional additives but has no significant effect on the color of the finished film; (D) The granules have a uniform appearance and no impurities visible to the naked eye.

[0028] Preferably, the conventional recycled material includes at least one of transparent film granulation material and scrap granulation material.

[0029] This invention can effectively mask various defects in difficult-to-recycle materials: For partial cross-linking (crystal points, holes) in 0BB carrier film granules: the white filler in the middle layer and the wrapping of the upper and lower surface layers doubly mask the defects in terms of both visual appearance and physical structure; for the bluish tint in light-converting film granules: the high reflectivity of the white middle layer blocks the optical color development of the light-converting agent; for the poor flowability of low-flow adhesive film granules: the good flowability of the upper and lower surface layers wraps the middle layer, avoiding extrusion defects.

[0030] In some preferred embodiments, the white filler includes one or more of titanium dioxide, talc, barium sulfate, calcium carbonate, and magnesium hydroxide; Preferably, the content of white filler in the upper, middle and lower layers is 5%-25% of the total mass of the corresponding layer, for example, 5%, 10%, 15%, 20% and 25%.

[0031] In some preferred embodiments, the amount of the difficult-to-recycle material added to the intermediate layer is 5%-50% of the total mass of the intermediate layer, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0032] In some preferred embodiments, the amount of conventional recycled granulated material added to the upper and / or lower surface layers is 5%-50% of the total mass of the corresponding layers, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0033] In some preferred embodiments, the matrix material of the upper, middle and lower layers is a thermoplastic resin for photovoltaic encapsulation, each of which is one or more of ethylene-vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), polyolefin elastomer (POE), polyurethane (TPU), ionomer, ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), or a two-layer or multi-layer co-extruded composite system of the above materials.

[0034] Specifically, the method of the present invention is not only applicable to EVA-based white films, but can also be extended to other photovoltaic encapsulation thermoplastic resin-based white film systems such as PVB, POE, TPU, ionomer, EAA, and EEA, as well as co-extruded composite systems such as EPE, and has broad application prospects.

[0035] In some preferred embodiments, the thickness of the upper surface layer is 100-300 μm; the thickness of the middle layer is 30-180 μm; and the thickness of the lower surface layer is 100-300 μm.

[0036] Preferably, the white photovoltaic encapsulating film is prepared using a three-layer co-extrusion process.

[0037] A second aspect of the present invention provides a white photovoltaic encapsulating film, which is prepared by the graded reuse method of the photovoltaic encapsulating film recycled material.

[0038] In some preferred embodiments, a lower surface layer, an intermediate layer, and an upper surface layer are stacked sequentially.

[0039] Specifically, the raw material composition of the three-layer white photovoltaic encapsulation film is as follows: Top layer: Contains matrix resin (thermoplastic resin for photovoltaic encapsulation), white filler, and conventional recycled granules (optional); Intermediate layer: Contains matrix resin (thermoplastic resin for photovoltaic encapsulation), white filler, and difficult-to-recycle granules; Bottom layer: Contains matrix resin (thermoplastic resin for photovoltaic encapsulation), white filler, and conventional recycled granules (optional); At least one of the upper and lower surface layers contains conventional recycled granulated material.

[0040] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0041] Example 1 This embodiment provides a method for the graded reuse of photovoltaic encapsulant film, the specific process of which is as follows: Step 1: Grading and Granulation of Recycled Materials Waste films generated during the production of photovoltaic encapsulant films are collected and classified into difficult-to-recycle materials and conventionally recyclable materials according to grading standards. The two types of waste films are crushed, melted, extruded, and granulated to produce difficult-to-recycle granulated materials (specifically OBB carrier film granulated materials and light-converting film granulated materials) and conventionally recyclable granulated materials (specifically transparent encapsulant film granulated materials). The criteria for determining the difficult-to-recycle granulated material are that it meets at least one of the following: (A) The gel content is 5-10% (based on the mass percentage of residue after filtration through a 100-mesh sieve). (B) The melt flow index (MFI) decreases by 10-50% compared to the original sheet; (C) Contains functional additives; (D) The granulated product appears yellow or black or contains impurities visible to the naked eye; Among them, the gel content of the 0BB carrier film granule is 5%, and the MFI is reduced by 10% compared with the original film; the gel content of the light conversion film granule is 5%, and the MFI is reduced by 10% compared with the original film.

[0042] The criteria for determining conventional recycled granulated materials are that they meet at least one of the following: (A) Gel content < 5% (based on the mass percentage of residue after filtration through a 100-mesh sieve); (B) Melt Flow Index (MFI) retention rate compared to the original wafer ≥ 90%; (C) Contains no functional additives, or contains functional additives but has no significant effect on the color of the finished film; (D) The granules have a uniform appearance and no impurities visible to the naked eye.

[0043] The gel content of the transparent film granules is 1%, and the MFI is 1% lower than that of the original film.

[0044] Step 2: Layered addition and three-layer co-extrusion molding A white photovoltaic encapsulating film is prepared using a three-layer co-extrusion process. The film includes an upper surface layer, a middle layer, and a lower surface layer. All three layers contain white filler (titanium dioxide, with a content of 15% of the total mass of each layer). The base film of all three layers is ethylene-vinyl acetate copolymer (EVA).

[0045] The upper surface layer contains conventional recycled granulated material, which accounts for 5% of the total mass of the upper surface layer, and the thickness of the upper surface layer is 200um. The intermediate layer contains difficult-to-recycle granules, with an addition amount of 5% of the total mass of the intermediate layer (the ratio of 0BB carrier film granules to light-converting film granules is 1:1), and the thickness of the intermediate layer is 90um. The lower surface layer contains conventional recycled granulated material, which accounts for 5% of the total mass of the lower surface layer, and the thickness of the lower surface layer is 200 μm.

[0046] Example 2 This embodiment provides a graded reuse method for photovoltaic encapsulant film, which differs from Embodiment 1 in that it uses difficult-to-recycle granulated material (specifically, low-flow-rate encapsulant film granulated material) and conventionally recycled granulated material (specifically, scrap granulated material). The low-flow-rate encapsulant film granulated material has a gel content of 7%, resulting in a 15% decrease in MFI compared to the original film; the scrap granulated material has a gel content of 4%, resulting in a 3% decrease in MFI compared to the original film. The matrix material of the three-layer structure is ethylene-ethyl acrylate copolymer (EEA); the white filler of the three-layer structure is talc.

[0047] Example 3 This embodiment provides a graded reuse method for photovoltaic encapsulant film, which differs from Embodiment 1 in that: the thickness of the upper surface layer is 100 μm; the thickness of the middle layer is 30 μm; and the thickness of the lower surface layer is 100 μm.

[0048] Example 4 This embodiment provides a graded reuse method for photovoltaic encapsulant film, which differs from Embodiment 1 in that: the thickness of the upper surface layer is 300 μm; the thickness of the middle layer is 180 μm; and the thickness of the lower surface layer is 300 μm.

[0049] Example 5 This embodiment provides a method for graded reuse of photovoltaic encapsulant film recycled material, which differs from Embodiment 1 in that: conventional recycled granulated material is added to the upper surface layer, and the amount added is 10% of the total mass of the upper surface layer; The intermediate layer contains difficult-to-recycle granulated material, with an addition amount of 20% of the total mass of the intermediate layer; The lower surface layer contains conventional recycled granulated material, which accounts for 50% of the total mass of the lower surface layer.

[0050] Example 6 This embodiment provides a method for graded reuse of photovoltaic encapsulant film recycled material, which differs from Embodiment 1 in that: conventional recycled granulated material is added to the upper surface layer, and the amount added is 50% of the total mass of the upper surface layer; The intermediate layer contains difficult-to-recycle granulated material, with an addition amount of 30% of the total mass of the intermediate layer; The lower surface layer contains conventional recycled granulated material, which accounts for 10% of the total mass of the lower surface layer.

[0051] Example 7 This embodiment provides a graded reuse method for photovoltaic encapsulant film, which differs from Embodiment 1 in that all three layers contain white filler (titanium dioxide, with a content of 5% of the total mass of each layer). The intermediate layer contains difficult-to-recycle granulated material, and the amount added is 5% of the total mass of the intermediate layer.

[0052] Example 8 This embodiment provides a graded reuse method for photovoltaic encapsulant film, which differs from Embodiment 1 in that all three layers contain white filler (titanium dioxide, with a content of 25% of the total mass of each layer). The intermediate layer contains difficult-to-recycle granulated material, and the amount added is 50% of the total mass of the intermediate layer.

[0053] Example 9 This embodiment provides a graded reuse method for photovoltaic encapsulant film recycled materials. The difference from Embodiment 1 is that the gel content of the OBB carrier film granules is 10%, and the MFI is reduced by 50% compared to the original film; the gel content of the light conversion film granules is 10%, and the MFI is reduced by 50% compared to the original film.

[0054] Example 10 This embodiment provides a graded reuse method for photovoltaic encapsulant film recycled materials. The difference from Embodiment 1 is that the gel content of the OBB carrier film granules is 20%, and the MFI is reduced by 55% compared to the original film; the gel content of the light conversion film granules is 20%, and the MFI is reduced by 55% compared to the original film.

[0055] Comparative Example 1 This comparative example provides a graded reuse method for photovoltaic encapsulant film recycled materials. The difference from Example 1 is that the same batch of OBB carrier film granules, light-converting film granules, and transparent encapsulant film granules from Example 1 are uniformly added to a single-layer white EVA encapsulant film at a mass ratio of 30%. The white filler is titanium dioxide, with a content of 15% and a thickness of 490um.

[0056] Comparative Example 2 This comparative example provides a graded reuse method for photovoltaic encapsulant film recycled materials. The difference from Example 1 is that: the three-layer co-extrusion is maintained and each layer contains titanium dioxide (15%), but difficult-to-recycle materials are added to the upper surface layer (25%) and the lower surface layer (25%). The upper and lower surface layers also contain conventional recycled granulated materials, and the middle layer does not contain difficult-to-recycle materials.

[0057] Comparative Example 3 This comparative example provides a graded reuse method for photovoltaic encapsulant film, which differs from Example 1 in that: no titanium dioxide is added to the intermediate layer (the intermediate layer contains difficult-to-recycle materials, and the remainder is the matrix).

[0058] Comparative Example 4 This comparative example provides a graded reuse method for photovoltaic encapsulant film recycled materials. The difference from Example 1 is that it involves two-layer co-extrusion, eliminating the lower surface layer.

[0059] Test case The white photovoltaic encapsulating films prepared in the above embodiments and comparative examples were used as samples for testing.

[0060] Test method: Statistically analyze the data from the online defect detection instrument at the film casting manufacturing end, pull the data of the whole roll 400m / roll, observe the number of holes, crystal points, and curing fastness of the 400m / roll, and use a UV spectrophotometer to test the reflectance of the laminated film in the 400-1100nm wavelength band.

[0061] The test results are shown in Table 1.

[0062] Table 1

[0063] As shown in Table 1, the photovoltaic encapsulating film prepared in this embodiment of the invention has better quality and performance than all comparative examples, fully demonstrating the synergistic effectiveness of the overall technical concept of three-layer co-extrusion + full-layer white filler + confined intermediate layer of difficult-to-recycle material. Data shows that the lower the proportion of recycled material added, the better the quality. Example 1 (with 5% recycled material added to each layer, gel content ≤5%, and MFI reduction ≤10%) achieved zero voids, zero crystal points, and high reflectivity (92.3%), representing the optimal parameter ratio. However, when the amount of difficult-to-recycle material added to the intermediate layer is greater than or close to 50% (as in Example 8), a 400mm... 2The above findings regarding holes and rapid curing confirm that 50% is the critical upper limit; the optimal ratio of titanium dioxide content in each layer is 15%, as too high a ratio increases material costs, while too low a ratio reduces product reflectivity. Crucially, four comparative examples verified the irreplaceability of this invention's technical solution from different perspectives: Comparative Example 1 (single-layer blend) showed 36 holes; Comparative Example 2 (difficult-to-recycle material placed in the outer layer) showed significant outward leakage of defects; Comparative Example 3 (no titanium dioxide in the middle layer) had no holes but the lowest reflectivity (90.3%) and defects could not be visually shielded; Comparative Example 4 (double-layer structure) reproduced the problems of holes and rapid curing. This demonstrates that only a three-layer co-extruded white film structure can enable the large-scale utilization of difficult-to-recycle materials; any structural adjustment or component reduction leads to a decline in quality or performance.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for graded reuse of photovoltaic encapsulant film recycled materials, characterized in that, Includes the following steps: (a) The recycled granulated material obtained from the granulation of waste photovoltaic encapsulant film is divided into difficult-to-recycle granulated material and conventionally recycled granulated material; (b) Prepare a three-layer white photovoltaic encapsulating film, wherein the upper, middle and lower layers of the white photovoltaic encapsulating film each contain white filler, the difficult-to-recycle granulated material is added to the middle layer, and the conventionally recycled granulated material is added to the upper and / or lower layers.

2. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The criteria for determining the difficult-to-recycle granulated material are that it meets at least one of the following: (A) The gel content is 5-10%; (B) The melt flow index decreases by 10-50% compared to the original sheet; (C) Contains functional additives that cause abnormal color in the finished film under natural light; (D) The granulated product appears yellow or black or contains impurities visible to the naked eye; Preferably, the difficult-to-recycle granulated material includes at least one of OBB carrier film granulated material, light-converting film granulated material, and low-flow-rate adhesive film granulated material.

3. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The criteria for determining conventional recycled granulated material are that it meets at least one of the following: (A) Gel content < 5%; (B) Melt flow index retention rate compared to the original sheet ≥ 90%; (C) Contains no functional additives, or contains functional additives but has no significant effect on the color of the finished film; (D) The granules have a uniform appearance and no impurities visible to the naked eye; Preferably, the conventional recycled granulation material includes at least one of transparent film granulation material and scrap granulation material.

4. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The white filler includes one or more of titanium dioxide, talc, barium sulfate, calcium carbonate, and magnesium hydroxide; Preferably, the content of white filler in the upper, middle and lower layers is 5%-25% of the total mass of the corresponding layer.

5. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The amount of the difficult-to-recycle granulated material added to the intermediate layer is 5%-50% of the total mass of the intermediate layer.

6. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The amount of conventional recycled granulated material added to the upper and / or lower surface layers is 5%-50% of the total mass of the corresponding layers.

7. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The matrix materials of the upper, middle and lower layers are each one or more of the following: ethylene-vinyl acetate copolymer, polyvinyl butyral, polyolefin elastomer, polyurethane, ionomer, ethylene-acrylic acid copolymer, and ethylene-ethyl acrylate copolymer; or a co-extruded composite system composed of any two or more of the above materials.

8. The method for graded reuse of photovoltaic encapsulant film recycled material according to claim 1, characterized in that, The thickness of the upper surface layer is 100-300 μm; the thickness of the middle layer is 30-180 μm; and the thickness of the lower surface layer is 100-300 μm. Preferably, the white photovoltaic encapsulating film is prepared using a three-layer co-extrusion process.

9. A white photovoltaic encapsulating film, characterized in that, It is prepared by the graded reuse method of photovoltaic encapsulant material according to any one of claims 1-8.

10. The white photovoltaic encapsulating film according to claim 9, characterized in that, It includes a bottom layer, a middle layer, and a top layer that are stacked in sequence.

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