Packaging adhesive film and preparation method thereof

Abstract

The invention discloses a packaging adhesive film and a preparation method thereof. The packaging adhesive film comprises a middle layer, an upper surface layer and a lower surface layer, wherein the upper surface layer and the lower surface layer are located on two sides of the middle layer. Through ultraviolet irradiation, the middle layer is pre-crosslinked, and the thickness stability of the middle layer is improved. Meanwhile, the adhesive film prepared by the invention does not use peroxide, so that the adhesive film can be processed and used at a relatively low temperature, and the requirements on high-temperature sensitivity, water resistance, creep resistance and the like of light-emitting battery materials, especially perovskite batteries and the like are met.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic applications, and particularly relates to a packaging adhesive film and a preparation method thereof, which are especially suitable for the packaging of perovskite solar cells. Background Art

[0002] With the gradual improvement of the power generation efficiency of crystalline silicon solar cells in the photovoltaic industry and the gradual perfection of the process, the engineering power generation efficiency has gradually reached the limit of the theoretical power generation efficiency. In order to continuously reduce the LCOE (levelized cost of electricity), perovskite solar cells with higher power generation efficiency have developed rapidly in the past two years. Whether it is a single-layer perovskite solar cell or a perovskite-silicon tandem solar cell, the power generation efficiency has continuously refreshed records. Although perovskite solar cells have higher power generation efficiency than traditional crystalline silicon solar cells, their perovskite layer itself belongs to organic materials, and the perovskite material structure will decompose under high temperature, ultraviolet light, and water vapor conditions. Therefore, for the packaging of perovskite solar cells, four major requirements are put forward for the packaging materials: water resistance, chemical inertness, low-temperature packaging, and weather resistance.

[0003] At present, the perovskite solar cell technology has initially entered the GW era, and the problems of large-area stability of components, improvement of power generation efficiency, and improvement of battery life still need to be solved urgently. The improvement of the power generation efficiency of components is inseparable from the protection of packaging materials. The generally recognized packaging materials in the industry are packaging adhesive films based on polyolefin elastomers, but the technical routes have not been unified. For example, CN117165194A discloses a low-temperature lamination thermoplastic high-water resistance packaging adhesive film and a preparation method thereof. The adhesive film includes a water-resistant layer in the middle and adhesive layers on both sides. By selecting TPO resins with appropriate softening points, low-temperature packaging and processing are achieved, and the water resistance effect is achieved. However, the initial peel strength of the adhesive film is not high, and due to the absence of cross-linking components, its high-temperature and long-term aging problems need to be investigated. CN109503934B discloses a thermoplastic adhesive film and a preparation method thereof. The adhesive film contains a second resin with a high melting point. Although it can improve the creep resistance to a certain extent, it is necessary to add a nucleating agent to reduce the haze, which increases the cost, and the initial peel strength of the adhesive film is not high. Its high-temperature and long-term aging problems also need to be verified. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a packaging adhesive film and a preparation method thereof. The packaging adhesive film can have high water resistance, high initial peel strength under low-temperature lamination conditions, especially excellent peel retention and yellowing resistance after high-temperature and long-term aging, and protect the stability of the power generation power of perovskite solar cell components during long-term operation.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A packaging adhesive film comprises an intermediate layer and upper and lower surface layers located on both sides of the intermediate layer;

[0007] The intermediate layer comprises the following components in parts by mass:

[0008]

[0009] The upper and lower surface layers comprise the following components in parts by mass:

[0010]

[0011] Further, the resin component A is a vinyl thermoplastic elastomer modified with an acrylate monomer containing at least two double bonds.

[0012] Further, the resin component B is a vinyl resin with a melting peak temperature of 80 - 130°C.

[0013] Further, the resin component C is a vinyl thermoplastic elastomer modified with silane.

[0014] Further, the preparation method of the resin component A comprises the following steps: mixing a vinyl thermoplastic elastomer, an initiator, and an acrylate monomer containing at least two double bonds in a mass ratio of 100:0.01 - 5:0.5 - 10, performing melt grafting, with a processing temperature of 120 - 190°C, a screw speed of 50 - 80 r / min for a screw with a diameter of 35 - 65 mm, and pelletizing through a twin-screw extruder to obtain the resin component A.

[0015] Further, the vinyl thermoplastic elastomer includes one or more of ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-1-decene copolymer; its melt index is 1 - 30 g / 10 min, the number average molecular weight is 30000 - 150000 g / mol, the comonomer mass insertion rate is 10 - 50 wt%, and the melting peak temperature is 35 - 80°C.

[0016] Further, the vinyl resin is one or more of LDPE, HDPE, POP (polyolefin plastomer), LLDPE, OBC (olefin block copolymer), EMA (ethylene-methyl acrylate copolymer), EMMA (ethylene-methyl methacrylate copolymer), EVA (ethylene-vinyl acetate copolymer), EBA (ethylene-butyl acrylate copolymer), EAA (ethylene-acrylic acid copolymer); its melt index is 1 - 30 g / 10 min, and the melting peak temperature is 80 - 130°C.

[0017] Further, the functional additive C is a linear, cyclic or three-dimensional monomer containing at least two polythiol groups, with a molecular weight of 60-1000 g / mol, preferably one or more of 1,2-ethanedithiol, 1,2-propanedithiol, 1,2-butanedithiol, 2,3-dithio(2-mercapto)-1-propanethiol, bis(3-mercaptopropionic acid) ethylene ester, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate).

[0018] Further, the acrylate monomer containing at least two double bonds has a molecular weight of 100-2000 g / mol, preferably one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, dipropylene glycol diacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, bis-trimethylolpropane tetraacrylate, bis-trimethylolpropane tetramethacrylate, propoxylated pentaerythritol tetraacrylate, tricyclodecane dimethanol diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate.

[0019] Further, the initiator is a peroxide initiator, preferably one or more of dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide, tert-butyl peroxy-2-ethylhexyl carbonate.

[0020] Further, the silane monomer used in the silane-modified vinyl thermoplastic elastomer is a silane coupling agent, preferably one or more of 3-methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(methoxyethoxy)silane, tetramethyltetravinylcyclotetrasiloxane, vinyltriacetoxime silane.

[0021] Further, the preparation method of the silane-modified vinyl thermoplastic elastomer includes the following steps: mixing the vinyl thermoplastic elastomer, the initiator, and the silane monomer in a mass ratio of 100:0.05-1:1-8, performing melt grafting, with a processing temperature of 140-200 °C, a screw rotation speed of 50-80 r / min for a screw with a diameter of 35-65 mm, and granulating through a twin-screw extruder to obtain the silane-modified vinyl thermoplastic elastomer.

[0022] Further, the antioxidant includes but is not limited to one or more of tris(2,4 - di - tert - butylphenyl) phosphite, n - octadecyl 3,5 - di - tert - butyl - 4 - hydroxyphenylpropionate, distearyl pentaerythritol diphosphite, tris(nonylphenyl) phosphite, 2,2'-methylenebis(4 - methyl - 6 - tert - butylphenol), triethylene glycol bis(3 - tert - butyl - 4 - hydroxy - 5 - methylphenyl) propionate, 1,3,5 - trimethyl - 2,4,6 - tris(3,5 - di - tert - butyl - 4 - hydroxybenzyl) benzene, tris(2,4 - di - tert - butylphenyl) phosphite, bis(2,4 - di - tert - butylphenyl) pentaerythritol diphosphite, and bis(2,6 - di - tert - butyl - 4 - methylphenyl) pentaerythritol diphosphite.

[0023] Further, the light stabilizer is a hindered amine light stabilizer, including but is not limited to one or more of bis(2,2,6,6 - tetramethyl - 4 - piperidyl) sebacate, mono(2,2,6,6 - tetramethyl - 4 - piperidyl) sebacate, bis(1,2,2,6,6 - pentamethyl - 4 - piperidyl) sebacate, and polybutanedioic acid (4 - hydroxy - 2,2,6,6 - tetramethyl - 1 - piperidylethanol) ester.

[0024] The present invention also provides a method for preparing the encapsulation film, comprising the following steps: fully mixing the upper surface layer, lower surface layer and intermediate layer formulation materials, melting and extruding through three single - screw extruders, the extrusion temperature is 70 - 90 °C, the screw speed of a 25 - 40 mm diameter screw is 5 - 15 r / min, and casting into a three - layer film through a die head distributor in the order of upper surface layer / intermediate layer / lower surface layer by a traction roller, the thickness of the film surface layer is 0.05 - 0.3 mm, and the thickness of the intermediate layer is 0.1 - 0.6 mm.

[0025] Further, the cross - linking degree of the encapsulation film measured under the lamination conditions of 120 °C for 12 min is > 30%, the shrinkage rate is < 2%, and the initial peel strength with glass is greater than 120 N / cm.

[0026] The beneficial effects of the present invention are as follows: The obtained encapsulation film of the present invention is a non - peroxide system film, avoiding the corrosion phenomenon of battery chips caused by the residue of auxiliaries such as peroxides. Through the molecular structure and formulation design of the intermediate layer and surface layer, resin component A in the intermediate layer undergoes a thiol - double bond addition reaction with the monomer containing a polythiol group at high temperature, generating a certain cross - linking degree, reducing the fluidity of the intermediate layer during lamination, and ensuring that the shrinkage rate of the film meets the performance requirements; meanwhile, the addition of resin component B can enhance the anti - deformation ability of the film at high temperature and protect the battery module during long - term outdoor use. Specific Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Example 1

[0029] Intermediate layer formulation:

[0030] Resin component A: 100 parts by mass of ethylene-1-octene copolymer (Dow 8669), 0.25 part by mass of dicumyl peroxide DCP, and 3.0 parts by mass of trimethylolpropane triacrylate are mixed evenly and granulated by a twin-screw extruder with a diameter of 40 mm to obtain resin component A. The extrusion temperature is 170 °C and the screw speed is 60 r.

[0031] Resin component B: EMA (Dow 1125AC)

[0032] Functional additive C: 1,2-propanedithiol

[0033] Antioxidant: n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

[0034] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate

[0035] Surface layer formulation:

[0036] Resin component B: EMA (Dow 1125AC)

[0037] Resin component C: 100 parts by mass of ethylene-1-butene copolymer (Dow 38688), 0.8 part by mass of tert-butyl peroxy-2-ethylhexyl carbonate TBEC, and 2.5 parts by mass of vinyltrimethoxysilane are mixed evenly and granulated by a twin-screw extruder with a diameter of 40 mm to obtain resin component C. The extrusion temperature is 180 °C and the screw speed is 40 r.

[0038] Antioxidant: n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

[0039] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate

[0040] After the upper and lower surface layer and intermediate layer formulation materials are fully mixed evenly, absorbed completely, and melt-extruded through three single-screw extruders. The extrusion temperature is 85 °C, the screw speed of the 35 mm diameter screw is 8 r / min, and it is cast into a three-layer film through a die head distributor according to the upper surface layer / intermediate layer / lower surface layer by a traction roller. The thickness of the surface layer of the adhesive film is 0.15 mm, and the thickness of the intermediate layer is 0.4 mm, denoted as H1.

[0041] Example 2

[0042] In the middle layer formulation, the acrylate monomer is selected as triethylene glycol dimethacrylate, and the remaining steps are the same as in Example 1 to obtain resin component A. Resin component B is selected as POP (Dow 1880G). Functional additive C is selected as ethylene glycol bis(3-mercaptopropionate).

[0043] In the surface layer formulation, resin component B is selected as POP (Dow 1880G). The remaining steps are the same as in Example 1 to obtain the encapsulation film denoted as H2.

[0044] Example 3

[0045] In the middle layer formulation, the acrylate monomer is selected as pentaerythritol tetraacrylate, and the remaining steps are the same as in Example 1 to obtain resin component A. Resin component B is selected as LDPE (Dow 722). Functional additive C is selected as dipentaerythritol hexakis(3-mercaptopropionate).

[0046] In the surface layer formulation, resin component B is selected as LDPE (Dow 722). The remaining steps are the same as in Example 1 to obtain the encapsulation film denoted as H3.

[0047] Example 4

[0048] In the middle layer formulation, the acrylate monomer is selected as ethoxylated trimethylolpropane trimethacrylate, and the remaining steps are the same as in Example 1 to obtain resin component A. Resin component B is selected as EVA (Lotte VS430). Functional additive C is selected as trimethylolpropane tris(3-mercaptopropionate).

[0049] In the surface layer formulation, resin component B is selected as EVA (Lotte VS430). The remaining steps are the same as in Example 1 to obtain the encapsulation film denoted as H4.

[0050] Example 5

[0051] In the middle layer formulation, the acrylate monomer is selected as dipropylene glycol diacrylate, and the remaining steps are the same as in Example 1 to obtain resin component A. Resin component B is selected as EAA (ExxonMobil 5050). Functional additive C is selected as pentaerythritol tetrakis(3-mercaptopropionate).

[0052] In the surface layer formulation, resin component B is selected as EAA (ExxonMobil 5050). The remaining steps are the same as in Example 1 to obtain the encapsulation film denoted as H5.

[0053] Comparative Example

[0054] Three comparative examples are listed and denoted as W1-3. In W1, the intermediate layer does not contain functional additive C. In W2, resin component B is selected as a vinyl resin (LG675) with a melting peak temperature of less than 80 °C. In W3, a small amount of resin component C is used.

[0055] The formulations of Examples 1-5 and the comparative examples are listed in Table 1.

[0056] Table 1 Formulations of Examples 1-5 and Comparative Examples

[0057]

[0058] Performance Testing

[0059] The encapsulation adhesive films obtained from the above examples and comparative examples are applied to the encapsulation of solar cell modules and evaluated by the following test methods. The evaluation results are listed in Table 2.

[0060] 1. Crosslinking Degree

[0061] The test method refers to the China Photovoltaic Industry Association standard T / CPIA0006—2017 "Copolyolefin Adhesive Films for Photovoltaic Module Encapsulation".

[0062] Sample Preparation: After taking two adhesive films and laminating them, weigh 0.5 g ± 0.01 g, cut them into small pieces of adhesive film with dimensions less than 3 mm × 3 mm, and prepare 3 specimens for each group.

[0063] Extract with xylene at 140 °C for 5 h, then place it in a vacuum oven at 140 °C and dry to constant weight.

[0064] 2. Glass / Encapsulation Adhesive Film Bonding Strength

[0065] The test method refers to the national standard GB / T2790 "Test Method for 180° Peel Strength of Adhesives - Flexible Materials to Rigid Materials".

[0066] Sample Preparation: Take 3.2 mm thick ultra-white embossed tempered glass, double-layer encapsulation adhesive film, and TPT backsheet, and place them in a vacuum laminator in the order of glass / adhesive film / backsheet. Laminating and curing at 120 °C for 18 min.

[0067] Test on a tensile machine at a tensile speed of 100 mm / min and record the tensile strength value.

[0068] 3. Shrinkage Rate

[0069] The test method refers to the China Photovoltaic Industry Association standard T / CPIA0006—2017 "Copolyolefin Adhesive Films for Photovoltaic Module Encapsulation".

[0070] Sample preparation: Take an uncured adhesive film and cut the specimen according to the longitudinal length of 200 mm and the transverse width of 100 mm of the adhesive film. Take one specimen in the middle of the wide-width direction of the adhesive film and one specimen at about 50 mm from the edge on both sides, and a total of three specimens are prepared.

[0071] First, place the smooth surface of the embossed glass with a thickness of 3.2 mm facing up on the surface of the hot plate of the laminator preheated to 120 °C, and control its temperature at 120 °C ± 5 °C. Then place the specimen flat on the glass surface, heat it for 3 min, and then take it out and cool it to room temperature. Measure the length (L, mm) at the minimum distance. The longitudinal shrinkage rate C MD =(200 - L) / 200 × 100%.

[0072] 4. Creep resistance

[0073] Cut the adhesive film into a size of 50 mm × 50 mm. Clamp it with the rough surfaces of two pieces of embossed glass with a width of 50 mm and a length of 100 mm and a thickness of 3.2 mm, and laminate them in a way that the bonding area is 50 mm × 50 mm at 120 °C for 14 min. Grasp one end of the obtained bonded body with a clip and let it sag in the length direction, place it in an oven at 105 °C, and let it stand for 48 h. Measure the offset of the glass after taking it out as the creep resistance index.

[0074] The performance of the encapsulation adhesive films prepared in the examples and comparative examples is shown in Table 2:

[0075] Table 2 Performance of the encapsulation adhesive films prepared in the examples and comparative examples

[0076]

[0077] It can be seen from the performance data of the above examples and comparative examples that the encapsulation adhesive film of the present invention can meet the requirements of perovskite batteries for the bonding, high-temperature sensitivity, mechanical properties, etc. of the adhesive film through the design of the structure and formula.

Claims

1. A packaging film, comprising a middle layer and upper and lower surface layers located on both sides of the middle layer; The intermediate layer comprises the following components by weight: The upper and lower surface layers include the following components by weight:

2. The packaging film according to claim 1, characterized in that: The resin component A is a vinyl thermoplastic elastomer modified by an acrylic ester monomer containing at least two double bonds.

3. The packaging film according to claim 1 or 2, characterized in that: The resin component B is a vinyl resin having a melting peak temperature of 80 to 130°C. Preferably, the vinyl resin is one or more of LDPE, HDPE, POP, LLDPE, OBC, EMA, EMMA, EVA, EBA, and EAA; its melt index is 1 to 30 g / 10 min, and its melting peak temperature is 80 to 130°C.

4. The packaging film according to any one of claims 1 to 3, characterized in that: The resin component C is a vinyl thermoplastic elastomer modified by silane.

5. The packaging film according to any one of claims 1 to 4, characterized in that: The preparation method of the resin component A comprises the following steps: mixing a vinyl thermoplastic elastomer, an initiator, and an acrylic ester monomer containing at least two double bonds in a mass ratio of 100:0.01-5:0.5-10, performing melt grafting, processing at a temperature of 120-190°C, a screw speed of 35-65 mm in diameter at 50-80 r / min, and granulating through a twin-screw extruder to obtain the resin component A.

6. The packaging film according to any one of claims 1 to 5, characterized in that: The vinyl thermoplastic elastomer includes one or more of ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and ethylene-1-decene copolymer; its melt index is 1-30g / 10min, the number average molecular weight is 30000-150000g / mol, the comonomer mass insertion rate is 10-50wt%, and the melting peak temperature is 35-80℃.

7. The packaging film according to any one of claims 1 to 6, characterized in that: The functional auxiliary agent C is a linear, cyclic or stereogenic monomer containing at least two polythiol groups, and its molecular weight is 60-1000 g / mol, preferably one or more of 1,2-ethanedithiol, 1,2-propylenethiol, 1,2-butanethiol, 2,3-dithio(2-mercapto)-1-propanethiol, bis(3-mercaptopropionic acid)ethylene glycol, trimethylolpropane tris(3-mercaptopropionic acid), tetrakis(3-mercaptopropionic acid)pentaerythritol ester, and hexa(3-mercaptopropionic acid)dipentaerythritol ester.

8. The packaging film according to any one of claims 1 to 7, characterized in that: The acrylic ester monomer containing at least two double bonds has a molecular weight of 100-2000 g / mol, and is preferably one or more of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanuric acid triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, tripropylene glycol diacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, ditrimethylolpropane tetraacrylate, ditrimethylolpropane tetramethacrylate, propoxylated pentaerythritol tetraacrylate, tricyclohexane dimethanol diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, diethylene glycol dimethacrylate, and triethylene glycol dimethacrylate.

9. The encapsulation film according to claims 1-8, characterized in that: The preparation method of the silane-modified vinyl thermoplastic elastomer comprises the following steps: mixing a vinyl thermoplastic elastomer, an initiator and a silane monomer in a mass ratio of 100:0.05 to 1:1 to 8, performing melt grafting, the processing temperature is 140 to 200°C, the speed of a 35-65mm diameter screw is 50 to 80r / min, and granulating through a twin-screw extruder to obtain the silane-modified vinyl thermoplastic elastomer; preferably, the silane monomer is a silane coupling agent, preferably one or more of 3-methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, tetramethyltetravinylcyclotetrasiloxane and vinyltributanoximosilane.

10. A method for preparing the encapsulation film according to any one of claims 1 to 9, comprising the following steps: The upper and lower surface layer and middle layer formula materials are fully mixed, melt-extruded through three single-screw extruders, the extrusion temperature is 70-90°C, the 25-40mm diameter screw speed is 5-15r / min, and the three-layer film is cast through the die head distributor according to the upper surface layer / middle layer / lower surface layer through the traction roller. The surface layer thickness of the film is 0.05-0.3mm, and the middle layer thickness is 0.1-0.6mm.

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