Repeated curing skin membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photovoltaic packaging composite materials, in particular to a multi-time curing skin film and a preparation method and application thereof. The multi-curing skin film comprises a film covering layer and a bearing layer which are arranged in a stacked mode. The coating layer comprises EVA resin, a cross-linking agent, an assistant cross-linking agent, a first silane coupling agent and a first antioxidant; the bearing layer is prepared from epoxy modified POE resin, maleic anhydride modified POE resin, POE resin, a cross-linking agent, an assistant cross-linking agent, a second silane coupling agent, an accelerant and a second antioxidant. The multi-time curing skin film meets the requirements of an 0BB battery for accurate pressing and rigid fixing of the adhesive film, and when the multi-time curing skin film is used in the 0BB battery, the welding strip displacement can be effectively prevented, and delamination and the like can be avoided.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulation composite materials technology, and in particular to a multi-cured skin film, its preparation method, and its application. Background Technology

[0002] Zero Busbar (0BB) cells, as one of the core technologies for the high-efficiency development of crystalline silicon photovoltaic cells, rely on the removal of the main grid lines on the surface of traditional cells, using only fine grid lines for current collection. Compared to traditional grid-based cell technologies (such as MBB and shingled cells), 0BB technology reduces the shading area by 3%–5% by eliminating the main grid structure, thereby improving cell conversion efficiency by 0.5%–1%. Simultaneously, the fine grid lines are directly connected to the solder ribbon, reducing the contact points between the main grid and the fine grid, which helps to reduce series resistance. Furthermore, this technology eliminates the main grid printing process, further reducing silver paste consumption.

[0003] However, the application of OBB technology also brings new challenges. Because the main busbars are eliminated, the solder ribbons need to be directly soldered to fine busbars with a diameter of only 30–50 μm. During module lamination, traditional encapsulating films exhibit high fluidity after heating, easily leading to displacement or incomplete soldering of the fine solder ribbons, severely impacting module performance and long-term reliability. Therefore, OBB cell technology places far higher demands on the "precise bonding and rigid fixation" capabilities of the encapsulating film compared to traditional cells. The encapsulating film needs to achieve initial positioning and fixation of the solder ribbons before lamination and provide sufficient support strength through self-hardening after lamination, thereby effectively preventing solder ribbon displacement.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-cured skin membrane, its preparation method, and its application. The multi-cured skin membrane of this invention can fix the solder strips immediately in the early stage of lamination by relying on low fluidity. The increased hardness during the lamination process can further press the solder strips together, ensuring that no displacement or incomplete soldering occurs.

[0006] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a multi-cured skin membrane, comprising a coating layer and a carrier layer stacked together; The coating layer comprises the following components by weight: 100 parts EVA resin, 0.5 to 1 part crosslinking agent, 0.2 to 0.8 parts co-crosslinking agent, 0.2 to 0.8 parts first silane coupling agent, and 0.05 to 0.2 parts first antioxidant; The supporting layer comprises the following components by weight: 10-20 parts epoxy-modified POE resin, 10-20 parts maleic anhydride-modified POE resin, 60-80 parts POE resin, 0.4-0.8 parts crosslinking agent, 0.4-0.8 parts co-crosslinking agent, 0.2-0.8 parts second silane coupling agent, 0.5-2 parts accelerator, and 0.05-0.2 parts second antioxidant.

[0007] In a specific embodiment of the present invention, the epoxy-modified POE resin is mainly prepared from POE resin, initiator, epoxy group-containing substance and third antioxidant.

[0008] In a specific embodiment of the present invention, the amount of the initiator is 0.05% to 0.5% of the POE resin; the amount of the epoxy group-containing substance is 1% to 5% of the POE resin.

[0009] In a specific embodiment of the present invention, the substance containing an epoxy group includes at least one selected from glycidyl methacrylate, glycidyl triacrylate, 1,4-butanediol glycidyl ether, ethylene glycol diglycidyl ether, ethylene oxide polyethylene glycol ethylene oxide, 1,4-bis[(glycidyloxy)methyl]cyclohexane, and 1,1,3,3-tetramethyl-1,3-bis[3-(epoxyethylmethoxy)propyl]disiloxane.

[0010] In a specific embodiment of the present invention, the content of maleic anhydride groups in the maleic anhydride modified POE resin is 0.5wt% to 2wt%.

[0011] In a specific embodiment of the present invention, the promoter includes at least one of sebacic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, and adipate dihydrazide.

[0012] In a specific embodiment of the present invention, the mass ratio of the epoxy-modified POE resin to the maleic anhydride-modified POE resin is 1:(0.8-1.2).

[0013] In a specific embodiment of the present invention, the thickness of the coating layer is 50-150 μm, and the thickness of the bearing layer is 50-150 μm.

[0014] The second aspect of the present invention provides a method for preparing the multi-cured skin membrane of the first aspect of the present invention, comprising the following steps: distributing materials according to the composition of the coating layer and the carrier layer, performing multi-layer co-extrusion; and then subjecting one side of the coating layer to electron beam irradiation treatment to obtain the multi-cured skin membrane.

[0015] In a specific embodiment of the present invention, the electron beam irradiation treatment is performed with a voltage of 100-500 kV, a beam current of 20-50 mA, and a linear velocity of 20-50 m / min.

[0016] The third aspect of the present invention provides the application of the repeatedly cured skin membrane of the first aspect of the present invention in a gridless battery.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The skin membrane of the present invention includes a coating layer and a support layer. The coating layer can effectively fix the solder ribbon through its low fluidity in the initial stage of lamination without excessive pre-crosslinking. This can not only reduce the irradiation dose and increase the irradiation line speed, thereby improving production efficiency, but also avoid the decrease in adhesion caused by excessive pre-crosslinking, reducing the risk of delamination between the adhesive film and the battery cell. The support layer introduces epoxy-modified POE resin, maleic anhydride-modified POE resin and acylhydrazine accelerator. During the low-temperature (100-120°C) lamination process, the acylhydrazine accelerator reacts with the anhydride groups in the maleic anhydride-modified POE resin to form an imide-acylhydrazine intermediate. After the intermediate decomposes, free amino groups are introduced into the POE main chain. The amino groups react chemically with the epoxy groups in the epoxy-modified POE resin to achieve bridging between the maleic anhydride-modified POE resin and the epoxy-modified POE resin, forming a basic crosslinked structure network. The remaining amino groups react chemically with maleic anhydride groups and epoxy groups, further increasing the crosslinking density and perfecting the three-dimensional network structure. The three-dimensional crosslinking network formed during the low-temperature lamination stage increases the hardness of the film and reduces its fluidity in the molten state. This allows for precise pressing of the OBB ultrafine solder ribbon during lamination, limiting the slippage of the solder ribbon during the molten flow of the film and fundamentally preventing solder ribbon misalignment and incomplete soldering. During the high-temperature (140-160℃) lamination process, the unreacted amino and epoxy groups remaining in the carrier layer can react with the ester groups in the EVA resin in the coating layer to generate stable crosslinking points. This transforms the physical bond between the POE carrier layer and the EVA coating layer into a chemical bond, further enhancing the interlayer adhesion and effectively solving the risk of EVA and POE delamination during long-term use of the module.

[0018] (2) In the low-temperature lamination stage, the cross-linking network of the multi-cured skin film of the present invention is first completed and shaped inside the film, which improves the hardness of the film and solves the core pain points of solder strip misalignment and solder strip poor soldering. In the high-temperature lamination stage, the cross-linking network is further improved and the interlayer bonding is strengthened, which solves the long-term reliability pain point of EVA and POE interlayer delamination and meets the requirements of OBB battery for precise pressing and rigid fixation of the film. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0020] The first aspect of the present invention provides a multi-cured skin membrane, comprising a coating layer and a carrier layer stacked together; The coating layer comprises the following components by weight: 100 parts EVA resin, 0.5 to 1 part crosslinking agent, 0.2 to 0.8 parts co-crosslinking agent, 0.2 to 0.8 parts first silane coupling agent, and 0.05 to 0.2 parts first antioxidant; The support layer comprises the following components by weight: 10-20 parts epoxy-modified POE resin, 10-20 parts maleic anhydride-modified POE resin, 60-80 parts POE resin, 0.4-0.8 parts crosslinking agent, 0.4-0.8 parts co-crosslinking agent, 0.2-0.8 parts second silane coupling agent, 0.5-2 parts accelerator, and 0.05-0.2 parts second antioxidant.

[0021] The total amount of epoxy-modified POE resin, maleic anhydride-modified POE resin, and POE resin in the support layer is 100 parts by weight.

[0022] The skin membrane of this invention includes a coating layer and a support layer. The coating layer effectively fixes the solder ribbon during the initial lamination stage due to its low fluidity, without requiring excessive pre-crosslinking. This not only reduces the irradiation dose and increases the irradiation linear velocity, thereby improving production efficiency, but also avoids the decrease in adhesion caused by excessive pre-crosslinking, reducing the risk of delamination between the film and the battery cell. The support layer incorporates epoxy-modified POE resin, maleic anhydride-modified POE resin, and hydrazide-based accelerators. During low-temperature (100–120°C) lamination, the hydrazide-based accelerators react with the anhydride groups in the maleic anhydride-modified POE resin to form an imide-hydrazide intermediate. After the intermediate decomposes, free amino groups are introduced onto the POE backbone. These amino groups chemically react with the epoxy groups in the epoxy-modified POE resin, achieving bridging between the maleic anhydride-modified POE resin and the epoxy-modified POE resin, forming a basic crosslinked network structure. The remaining amino groups react chemically with maleic anhydride groups and epoxy groups, further increasing the crosslinking density and perfecting the three-dimensional network structure. The three-dimensional crosslinking network formed during the low-temperature lamination stage increases the hardness of the film and reduces its fluidity in the molten state. This allows for precise pressing of the OBB ultrafine solder ribbon during lamination, limiting the slippage of the solder ribbon during the molten flow of the film and fundamentally preventing solder ribbon misalignment and incomplete soldering. During the high-temperature (140-160℃) lamination process, the unreacted amino and epoxy groups remaining in the carrier layer can react with the ester groups in the EVA resin in the coating layer to generate stable crosslinking points. This transforms the physical bond between the POE carrier layer and the EVA coating layer into a chemical bond, further enhancing the interlayer adhesion and effectively solving the risk of EVA and POE delamination during long-term use of the module.

[0023] In some embodiments, the amount of crosslinking agent in the coating layer is 0.5 to 1 part, based on 100 parts of EVA resin. Specifically, it can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, or any combination thereof.

[0024] In some embodiments, the crosslinking agent includes at least one selected from tert-amyl peroxy(2-ethylhexyl)carbonate, tert-butyl peroxycarbonate-2-ethylhexyl, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-bis(tert-butyl peroxy)hexane.

[0025] In some embodiments, the amount of crosslinking agent in the coating layer is 0.2 to 0.8 parts, based on 100 parts of EVA resin. Specifically, it can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or any combination thereof.

[0026] In some embodiments, the co-crosslinking agent includes at least one of trimethylolpropane triacrylate, propane trimethylolpropane trimethacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, glyceryl trihydroxypropyl ether triacrylate, propoxylated glyceryl triacrylate, and diallyl phthalate.

[0027] In some embodiments, the amount of the first silane coupling agent in the coating layer is 0.2 to 0.8 parts, based on 100 parts of EVA resin. Specifically, it can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or any combination thereof.

[0028] In some embodiments, the first silane coupling agent includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, triacetoxyvinylsilane, vinyltris(2-methoxyethoxy)silane, γ-glycidoxypropyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane.

[0029] In some embodiments, the amount of the first antioxidant in the coating layer is 0.05 to 0.2 parts, based on 100 parts of EVA resin. Specifically, it can be 0.05 parts, 0.08 parts, 0.1 parts, 0.15 parts, 0.2 parts, or any combination thereof.

[0030] In some embodiments, the first antioxidant includes at least one of antioxidant 1035, antioxidant 168, antioxidant 1010, and antioxidant 1098.

[0031] In some embodiments, the amount of epoxy-modified POE resin used in the carrier layer is 10 to 20 parts, specifically 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, or any combination thereof.

[0032] In some embodiments, the epoxy-modified POE resin is mainly prepared from POE resin, an initiator, a substance containing epoxy groups, and a third antioxidant.

[0033] In some embodiments, in the preparation of epoxy-modified POE resin, the amount of initiator is 0.05% to 0.5% of the POE resin, specifically it can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or any combination thereof; the amount of the substance containing epoxy groups is 1% to 5% of the POE resin, specifically it can be 1%, 2%, 3%, 4%, 5% or any combination thereof.

[0034] In some embodiments, in the preparation of epoxy-modified POE resin, the amount of the third antioxidant is 0.01% to 0.1% of the POE resin. The type of the third antioxidant is the same as that of the first antioxidant mentioned above.

[0035] In some embodiments, the preparation method of epoxy-modified POE resin includes: weighing POE resin, initiator, epoxy-containing substance, and third antioxidant in proportion; mixing the initiator, epoxy-containing substance, and third antioxidant uniformly at room temperature to obtain a blend; and extruding and granulating the POE resin and the blend. In the extrusion granulation, the blend is added via an additive pump.

[0036] In some embodiments, the temperature settings for each zone of the extrusion granulation process in the preparation of epoxy-modified POE resin include: granulation temperature of 100-160°C, feeding zone temperature of 100-120°C, reaction zone temperature of 140-160°C, and homogenization zone temperature of 100-120°C.

[0037] In some embodiments, the epoxy group-containing substance includes at least one selected from glycidyl methacrylate, glycidyl triacrylate, 1,4-butanediol glycidyl ether, ethylene glycol diglycidyl ether, ethylene oxide polyethylene glycol ethylene oxide, 1,4-bis[(glycidyloxy)methyl]cyclohexane, and 1,1,3,3-tetramethyl-1,3-bis[3-(epoxyethylmethoxy)propyl]disiloxane.

[0038] In some embodiments, the amount of maleic anhydride modified POE resin in the carrier layer is 10 to 20 parts, specifically 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, or any combination thereof.

[0039] In some embodiments, the content of maleic anhydride groups in the maleic anhydride-modified POE resin is 0.5wt% to 2wt%, specifically 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, or any combination thereof.

[0040] In some embodiments, the mass ratio of epoxy-modified POE resin to maleic anhydride-modified POE resin is 1:(0.8–1.2), specifically within the range of 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, or any combination thereof. This is more advantageous in balancing the bonding performance and peel strength of the solder strip.

[0041] In some embodiments, the amount of POE resin used in the carrier layer is 60 to 80 parts, specifically 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, or any combination thereof.

[0042] In some embodiments, the type of POE resin used in the carrier layer and the type of POE resin used to prepare the epoxy-modified POE resin are not limited; any POE resin that can be conventionally used to prepare photovoltaic films can be used.

[0043] In some embodiments, the amount of crosslinking agent in the carrier layer is 0.4 to 0.8 parts, specifically 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or any combination thereof. The type of crosslinking agent in the carrier layer can refer to, but is not limited to, the type of crosslinking agent in the coating layer.

[0044] In some embodiments, the amount of the co-crosslinking agent in the carrier layer is 0.4 to 0.8 parts, specifically 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or any combination thereof. The type of co-crosslinking agent in the carrier layer can refer to, but is not limited to, the type of co-crosslinking agent in the coating layer.

[0045] In some embodiments, the amount of accelerator in the carrier layer is 0.5 to 2 parts, specifically 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, or any combination thereof.

[0046] In some embodiments, the accelerator is an acylhydrazine accelerator, specifically including at least one of sebacylhydrazine, phthalic acid dihydrazine, isophthalic acid dihydrazine, and adipate dihydrazine.

[0047] In some embodiments, the amount of the second silane coupling agent in the support layer is 0.2 to 0.8 parts, specifically 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or any combination thereof. The type of the second silane coupling agent is the same as that of the first silane coupling agent described above.

[0048] In some embodiments, the amount of the second antioxidant in the carrier layer is 0.05 to 0.2 parts, specifically 0.05 parts, 0.08 parts, 0.1 parts, 0.15 parts, 0.2 parts, or any combination thereof. The type of the second antioxidant is the same as that of the first antioxidant described above.

[0049] In some embodiments, the thickness of the coating layer is 50 to 150 μm, specifically it can be a range of 50 μm, 80 μm, 100 μm, 120 μm, 150 μm or any two of these; the thickness of the carrier layer is 50 to 150 μm, specifically it can be a range of 50 μm, 80 μm, 100 μm, 120 μm, 150 μm or any two of these.

[0050] The second aspect of the present invention provides a method for preparing the multi-cured skin membrane of the first aspect of the present invention, comprising the following steps: distributing materials according to the composition of the coating layer and the carrier layer, performing multi-layer co-extrusion; and then subjecting one side of the coating layer to electron beam irradiation treatment to obtain the multi-cured skin membrane.

[0051] In some embodiments, in multilayer co-extrusion, the extrusion temperature range of both the coating layer and the carrier layer is 50–90°C, and the co-extrusion die temperature is 90–95°C.

[0052] In some embodiments, during electron beam irradiation, the voltage is 100–500 kV, specifically 100 kV, 200 kV, 300 kV, 400 kV, 500 kV, or any combination thereof; the beam current is 20–50 mA, specifically 20 mA, 30 mA, 40 mA, 50 mA, or any combination thereof; and the linear velocity is 20–50 m / min, specifically 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, or any combination thereof.

[0053] A third aspect of the present invention provides the application of the repeatedly cured skin film of the first aspect of the present invention in a gridless battery. In use, the coating layer faces the battery.

[0054] The material information used in the following specific embodiments of the present invention may be as follows, but is not limited thereto: EVA resin: Sirbon Corporation, UE2806; POE resin: LG Corporation, LF675, LF575; Maleic anhydride modified POE resin: Fine-Blend® FB521A, manufactured by Jiayirong Polymer (Shanghai) Co., Ltd.

[0055] Example 1 This embodiment provides a multi-cured skin membrane, comprising a laminated coating layer and a carrier layer. The thickness of the coating layer is 100 μm, and the thickness of the carrier layer is 100 μm.

[0056] The raw materials for preparing the coating layer include the following components in parts by weight: 100 parts of EVA resin UE2806, 0.6 parts of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.6 parts of propane trimethylol ester, 0.8 parts of γ-(methacryloyloxy)propyltrimethoxysilane, and 0.1 parts of antioxidant 1010.

[0057] The raw materials for preparing the support layer include the following components in parts by weight: 10 parts epoxy-modified POE resin, 10 parts Fine-Blend® FB521A, 80 parts POE resin LF675, 0.6 parts tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.6 parts propane trimethylol ester, 0.8 parts γ-(methacryloyloxy)propyltrimethoxysilane, 0.6 parts sebacic acid dihydrazide, and 0.1 parts antioxidant 1010.

[0058] The preparation of epoxy-modified POE resin includes: weighing POE resin LF675, dicumyl peroxide, glycidyl methacrylate, and antioxidant 1010 in a mass ratio of 100:0.1:1.42:0.05; then mixing dicumyl peroxide, glycidyl methacrylate, and antioxidant 1010 uniformly at room temperature to obtain a blend; then adding POE resin LF675 to a granulator, and adding the blend through an additive pump; the blend reacts directly with the POE resin during the high-temperature shearing process of the screw compressor to obtain epoxy-modified POE resin. The temperature settings for each zone in the preparation of epoxy-modified POE resin include: granulation temperature 100–160℃, feeding zone temperature 100–120℃, reaction zone temperature 140–160℃, and homogenization zone temperature 100–120℃.

[0059] The method for preparing the multiple-curing skin film in this embodiment includes the following steps: (1) After preparing the coating layer and the carrier layer of the multi-cured skin film according to the composition of the coating layer and the carrier layer, multi-layer co-extrusion is carried out; wherein, the extrusion temperature range of the coating layer and the carrier layer is set to 50~90℃; the co-extrusion die temperature is 90~95℃.

[0060] (2) Electron beam irradiation treatment is performed on one side of the coating layer of the film obtained by co-extrusion in step (1) to obtain a multi-cured skin film; wherein, in the electron beam irradiation treatment, the voltage is 500kV, the beam current is 49mA, and the linear velocity is 35m / min.

[0061] Example 2 group This embodiment group refers to the multiple-curing skin film and its preparation method in Example 1, with the only difference being the amount of epoxy-modified POE resin, Fine-Blend® FB521A, and POE resin used in the carrier layer. The specific differences are as follows: Example 2a: 20 parts epoxy-modified POE resin, 20 parts Fine-Blend® FB521A, and 60 parts POE resin LF675; Example 2b: 15 parts epoxy-modified POE resin, 15 parts Fine-Blend® FB521A, and 70 parts POE resin LF675; Example 2c: 10 parts epoxy-modified POE resin, 20 parts Fine-Blend® FB521A, and 70 parts POE resin LF675; Example 2d: 20 parts epoxy-modified POE resin, 10 parts Fine-Blend® FB521A, and 70 parts POE resin LF675.

[0062] Example 3 Group This embodiment group refers to the multiple-curing skin film and its preparation method in Example 1, with the only difference being the amount of glycidyl methacrylate used in the preparation of the epoxy-modified POE resin. The specific differences are as follows: Example 3a: The amount of glycidyl methacrylate used was 1% of the POE resin; Example 3b: The amount of glycidyl methacrylate used was 5% of the POE resin.

[0063] Example 4 group This embodiment group refers to the multiple-curing skin film and its preparation method in Example 1, with the only difference being the amount of acylhydrazine accelerator used in the carrier layer. The specific differences are as follows: Example 4a: The amount of sebacic acid dihydrazide used was 0.5 parts; Example 4b: The amount of sebacic acid dihydrazide used was 2 parts.

[0064] Example 5 group This embodiment group refers to the multiple-curing skin membrane and its preparation method in Example 1, with the only difference being the linear velocity of the electron beam irradiation treatment. The specific differences are as follows: Example 5a: Voltage 500kV, beam current 49mA, line speed 15m / min; Example 5b: Voltage 500kV, beam current 49mA, line speed 55m / min.

[0065] Comparative Example 1 This comparative example group refers to the multiple-curing skin film and its preparation method in Example 1, with the only difference being the amount of epoxy-modified POE resin, Fine-Blend® FB521A, and POE resin used in the carrier layer. The specific differences are as follows: Comparative Example 1a: 25 parts epoxy-modified POE resin, 25 parts Fine-Blend® FB521A, and 50 parts POE resin LF675; Comparative Example 1b: 0 parts epoxy-modified POE resin, 0 parts Fine-Blend® FB521A, and 100 parts POE resin LF675; Comparative Example 1c: 20 parts epoxy-modified POE resin, 0 parts Fine-Blend® FB521A, and 80 parts POE resin LF675; Comparative Example 1d: 0 parts epoxy-modified POE resin, 20 parts Fine-Blend® FB521A, and 80 parts POE resin LF675.

[0066] Comparative Example 2 This comparative example group refers to the multiple-curing skin film and its preparation method in Example 1, with the only difference being the amount of hydrazide-based accelerator used in the carrier layer. The specific differences are as follows: Comparative Example 2a: The amount of sebacic acid dihydrazide used was 0 parts; Comparative Example 2b: The amount of sebacic acid dihydrazide used was 4 parts.

[0067] Comparative Example 3 The skin membrane provided in Comparative Example 3 includes a coating layer and a support layer stacked together. The coating layer has a thickness of 100 μm, and the support layer has a thickness of 100 μm.

[0068] The raw materials for preparing the coating layer include the following components by weight: 100 parts of EVA resin UE2806, 0.6 parts of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.6 parts of propane trimethylol ester, 0.8 parts of γ-(methacryloyloxy)propyltrimethoxysilane, and 0.1 parts of antioxidant 1010.

[0069] The raw materials for preparing the support layer include the following components in parts by weight: 100 parts of POE resin LF675, 0.6 parts of tert-butyl peroxycarbonate-2-ethylhexyl ester, 0.6 parts of propane trimethylol ester, 0.8 parts of γ-(methacryloyloxy)propyltrimethoxysilane, and 0.1 parts of antioxidant 1010.

[0070] The preparation method of the skin membrane in Comparative Example 3 includes the following steps: (1) After the ingredients are prepared according to the composition of the coating layer and the carrier layer of the skin membrane, multi-layer co-extrusion is carried out; wherein, the extrusion temperature range of the coating layer and the carrier layer is set to 50~90℃; the co-extrusion die temperature is 90~95℃.

[0071] (2) Electron beam irradiation is performed on one side of the coating layer of the co-extruded film obtained in step (1) to obtain a skin film; wherein, in the electron beam irradiation treatment, the voltage is 500kV, the beam current is 49mA, and the linear velocity is 15m / min.

[0072] Experimental Example The performance of the skin membranes in different embodiments and comparative examples was tested. The test methods are as follows, and the test results are shown in Table 1.

[0073] 1. Pre-crosslinking degree and crosslinking degree test Preparation of pre-crosslinking degree test samples: Take the skin films prepared in different examples and comparative examples, cut them into small particles with a size of less than 3mm×3mm, weigh them between 0.2020 and 0.2050g, and prepare test samples; Preparation of crosslinking degree test samples: Skin films prepared in different examples and comparative examples were taken and placed in a vacuum laminator according to the test method of GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation". The temperature of the first chamber was 120°C, the vacuum time was 360s, the first stage pressure was -70kPa for 5s, the second stage pressure was -50kPa for 5s, and the third stage pressure was -30kPa for 110s to obtain test sample one; the crosslinking degree of test sample one was then tested.

[0074] The pre-crosslinking degree and crosslinking degree tests are performed according to the following steps: a) Take a clean, dried 120-mesh stainless steel mesh and cut it into a rectangle of 35mm × 70mm. Fold it in half once to make it 35mm × 35mm. Then fold the two open edges twice at 2-2.5mm intervals to make an open mesh bag of 30mm × 35mm. Weigh the bag and record the weight as W1.

[0075] b) Weigh 0.2020 to 0.2050 g of the cut film, put it into a stainless steel mesh bag, and record the weight as W2.

[0076] c) Fold the opening of the mesh bag, seal it with wire, and mark each group of samples. Insert the mesh bag into the side opening of the three-necked flask, ensuring that the mesh bag does not touch the inner wall or bottom of the flask. Seal the flask opening with a rubber stopper. Add 2 / 3 volume of xylene solvent to the flask, ensuring that the sample pack is immersed in the solvent. Install a reflux condenser in the middle of the flask, heat to approximately 145°C until the xylene boils, and start timing for 5 hours, maintaining a reflux rate of 20–40 drops / min.

[0077] d) After reflux, remove the sample and place it in a vacuum oven at 140℃ until it reaches constant weight. Remove the sample package from the oven, remove the iron wire, and place it in a desiccator to cool for 30 minutes before weighing it and recording the weight as W3.

[0078] Calculate the pre-crosslinking degree and crosslinking degree using the following formula, and retain the results to two decimal places. Take the average value of the test results. D=(W3-W1) / (W2-W1)×100% In the formula: D: Pre-crosslinking degree and crosslinking degree, expressed as a percentage (%). W1: Mass of the empty stainless steel wire mesh bag, in grams (g). W2: Mass of the stainless steel mesh bag containing the sample, in grams (g). W3: Mass of the sample package after solvent extraction and drying, in grams (g).

[0079] 2. Peel strength test Peel strength from glass: Skin films prepared in different implementations and comparative proportions were placed in a vacuum laminator in the order of "tempered glass / skin film (carrier layer facing the glass) / backsheet" according to the test method of GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation" and "tempered glass / skin film (carrier layer facing the glass) / backsheet". First, the temperature of the first chamber was 120℃, the vacuum time was 360s, the first pressure was -70kPa for 5s, the second pressure was -50kPa for 5s, and the third pressure was -30kPa for 110s. Then, the temperature of the second chamber was 145℃, the vacuum time was 20s, the first pressure was -70kPa for 5s, the second pressure was -50kPa for 5s, and the third pressure was -30kPa for 570s to obtain test sample three.

[0080] Peel strength from solar cells: Skin films prepared in different embodiments and comparative proportions were tested according to the test methods in GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation". Skin film samples were taken at 20cm × 10cm glass dimensions, and two 2cm × 20cm samples were taken from the backsheet. A 1cm × 15cm strip was cut off from the corresponding position of the 20cm × 10cm release film. The test was conducted according to the sequence: "Tempered glass / Skin film (coating layer facing solar cell) / Solar cell / Release film / Skin film (coating layer facing solar cell) / Backsheet". The samples were placed into a vacuum laminator in sequence. First, the first chamber was evacuated at a temperature of 120℃ for 360s, followed by lamination at a pressure of -70kPa for 5s, a pressure of -50kPa for 5s, and a pressure of -30kPa for 110s. Then, the second chamber was evacuated at a temperature of 145℃ for 20s, followed by lamination at a pressure of -70kPa for 5s, a pressure of -50kPa for 5s, and a pressure of -30kPa for 570s, resulting in test sample four.

[0081] 3. High temperature and high humidity aging DH1000h test Test samples three and four were subjected to high temperature and high humidity aging for 1000 hours in accordance with the test method of high temperature and high humidity aging performance in GB / T 29848-2018 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation". Then, the peel strength between the skin film and the glass, the peel strength between the skin film and the cell, and the appearance phenomenon after aging were measured.

[0082] 4. Test of pressed weld strip Align the solder ribbon with the main grid position on the OBB solar cell. Cover the surface of the solar cell with skin films prepared in different embodiments and comparative proportions. Place the films into a vacuum laminator in the following order: tempered glass / skin film (coating layer facing the solar cell) / solar cell / skin film (coating layer facing the solar cell) / glass. First, perform lamination at a chamber temperature of 120℃ for 360s, followed by a first-stage pressure of -70kPa for 5s, a second-stage pressure of -50kPa for 5s, and a third-stage pressure of -30kPa for 110s. Then, perform lamination at a chamber temperature of 145℃ for 20s, followed by a first-stage pressure of -70kPa for 5s, a second-stage pressure of -50kPa for 5s, and a third-stage pressure of -30kPa for 570s to obtain the test sample. Observe the solder ribbon misalignment and air bubbles.

[0083] Table 1 Performance test results of different skin films

[0084] As can be seen from the above test results, the multi-cured skin film of the present invention meets the requirements of precise pressing and rigid fixation of the adhesive film for OBB batteries. When used in OBB batteries, it can effectively prevent solder strip displacement and avoid delamination.

[0085] Based on the results of Examples 1 and 2, and Comparative Example 1a, it can be seen that with the increase of the amount of epoxy-modified POE resin and Fine-Blend® FB521A added, the pre-crosslinking degree of the film does not change much, while the crosslinking degree of the film after lamination at 120°C is significantly improved. However, excessive addition leads to an excessively fast crosslinking rate of the film, making it difficult for air bubbles in the battery grid lines to be expelled. Based on the results of Examples 1 and 3, it can be seen that in Example 3a, the amount of glycidyl methacrylate added to prepare the epoxy-modified POE resin was reduced, resulting in a decrease in the number of crosslinking sites that can be formed in the film and a decrease in the degree of crosslinking. In Example 3b, the addition of excessive glycidyl methacrylate resulted in the residue of some unreacted epoxy groups, leading to an uneven crosslinking network. Moreover, the free epoxy may slowly hydrolyze during subsequent use, destroying the crosslinking network, resulting in a decrease in the adhesive strength of the film and delamination. The results from Examples 1 and 4 show that a decrease in the amount of sebacic acid dihydrazide added results in incomplete anhydride group reaction, less intermediate formation, and insufficient free amino groups, leading to a decrease in the crosslinking degree of the POE layer. Conversely, an increase in the amount of sebacic acid dihydrazide added promotes the reaction of the anhydride groups in the POE layer, accelerates the crosslinking efficiency of the POE layer, and improves the degree of crosslinking. The test data from Examples 1 and 5 show that a decrease in irradiation linear velocity increases the irradiation dose received per unit area of ​​the film, increases the pre-crosslinking degree of the film, and leads to a decrease in the peel strength between the film and the battery cell, making delamination more likely during aging. Conversely, an increase in irradiation linear velocity reduces the pre-crosslinking degree, making the solder ribbon more prone to poor solder joint misalignment. Based on the experimental results of Example 1 and Comparative Example 1, Comparative Example 1b, without the addition of epoxy-modified POE resin and maleic anhydride-modified POE resin, had a low degree of crosslinking, excessive film fluidity, and insufficient rigidity after curing, resulting in slight solder ribbon misalignment and poor interfacial adhesion. Comparative Example 1c, without maleic anhydride-modified POE resin, and Comparative Example 1d, without epoxy-modified POE resin, had a slower crosslinking rate of the POE layer at 120°C, leading to a reduced degree of crosslinking and making the solder ribbon prone to misalignment. Furthermore, a large amount of residual active anhydride and epoxy groups made the film prone to delamination and bubbling. Based on the results of Example 1 and Comparative Example 2, Comparative Example 2a, without sebacic acid dihydrazide, could not form an effective crosslinking network in the POE layer, preventing the film from pressing the solder ribbon and causing severe misalignment. Comparative Example 2b, with the addition of excessive sebacic acid dihydrazide, had some unreacted hydrazide residues that easily migrated to the interface under high temperature and humidity, damaging the adhesion and causing delamination and bubbling. The experimental results from Example 1 and Comparative Example 3 show that, without adding epoxy-modified POE resin and maleic anhydride-modified POE resin, to achieve the effect of press-bonded ribbon, the irradiation line speed needs to be significantly reduced, which greatly affects the production capacity of the adhesive film, and the adhesive film is prone to delamination and bubbling.

[0086] 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 skin film that has been cured multiple times, characterized in that, Includes a laminated coating layer and a carrier layer; The coating layer comprises the following components by weight: 100 parts EVA resin, 0.5 to 1 part crosslinking agent, 0.2 to 0.8 parts co-crosslinking agent, 0.2 to 0.8 parts first silane coupling agent, and 0.05 to 0.2 parts first antioxidant; The supporting layer comprises the following components by weight: 10-20 parts epoxy-modified POE resin, 10-20 parts maleic anhydride-modified POE resin, 60-80 parts POE resin, 0.4-0.8 parts crosslinking agent, 0.4-0.8 parts co-crosslinking agent, 0.2-0.8 parts second silane coupling agent, 0.5-2 parts accelerator, and 0.05-0.2 parts second antioxidant.

2. The repeatedly cured skin film according to claim 1, characterized in that, The epoxy-modified POE resin is mainly prepared from POE resin, initiator, epoxy group-containing substance and third antioxidant. Preferably, the amount of the initiator is 0.05% to 0.5% of the POE resin; Preferably, the amount of the epoxy group-containing substance is 1% to 5% of the POE resin.

3. The repeatedly cured skin film according to claim 2, characterized in that, The epoxy group-containing substances include at least one of glycidyl methacrylate, epoxy glyceryl triester, 1,4-butanediol glycidyl ether, ethylene glycol diglycidyl ether, ethylene oxide polyethylene glycol ethylene oxide, 1,4-bis[(glycidyloxy)methyl]cyclohexane, and 1,1,3,3-tetramethyl-1,3-bis[3-(epoxyethylmethoxy)propyl]disiloxane.

4. The repeatedly cured skin film according to claim 1, characterized in that, The content of maleic anhydride groups in the maleic anhydride modified POE resin is 0.5wt% to 2wt%.

5. The repeatedly cured skin film according to claim 1, characterized in that, The accelerator includes at least one of sebacic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, and adipate dihydrazide.

6. The repeatedly cured skin film according to claim 1, characterized in that, The mass ratio of the epoxy-modified POE resin to the maleic anhydride-modified POE resin is 1: (0.8 to 1.2).

7. The repeatedly cured skin film according to claim 1, characterized in that, The thickness of the coating layer is 50–150 μm, and the thickness of the bearing layer is 50–150 μm.

8. The method for preparing the multiple-curing skin film according to any one of claims 1 to 7, characterized in that, The process includes the following steps: dispensing materials according to the composition of the coating layer and the carrier layer, and performing multi-layer co-extrusion; then subjecting one side of the coating layer to electron beam irradiation treatment to obtain a multi-cured skin film.

9. The preparation method according to claim 8, characterized in that, In the electron beam irradiation treatment, the voltage is 100-500kV, the beam current is 20-50mA, and the linear velocity is 20-50m / min.

10. The application of the multi-cured skin membrane according to any one of claims 1 to 7 or the multi-cured skin membrane prepared by the preparation method according to any one of claims 8 to 9 in a gridless cell.

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