Separable and detachable photovoltaic packaging adhesive film and preparation method thereof

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a photovoltaic packaging adhesive film capable of being separated and disassembled. The packaging adhesive film prepared by adopting 1, 1 '-[(1, 4-phenyl bis (1, 3, 2-dioxaborolane-2, 4-diyl)) bis (methylene)] bis (1H-pyrrole-2, 5-diketone) containing dynamic boron ester bonds as a cross-linking agent is colorless and transparent, can be used in the photovoltaic field, and can be disassembled during recovery, so that green recovery is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a separable and disassemblable photovoltaic encapsulation film based on dynamic crosslinking and a preparation method thereof. Background Art

[0002] In recent years, China's photovoltaic industry has achieved leapfrog development. It has not only become the world's largest producer of photovoltaic modules but also taken the lead in the field of photovoltaic power generation applications. However, due to the specific service life of photovoltaic modules, they will face the severe challenge of large-scale retirement of photovoltaic modules in the future. As a typical representative of clean energy, the green development of the photovoltaic industry is not only reflected in the energy production link but also in building a complete photovoltaic module recycling system to achieve a green closed-loop of the industrial chain.

[0003] Currently, the core technical bottleneck in photovoltaic module recycling lies in the effective removal of the encapsulation film. Photovoltaic modules adopt a multi-layer composite structure of "glass-encapsulation film-crystalline silicon cell layer-encapsulation film-backplane". Among them, the encapsulation film undergoes a crosslinking reaction during the encapsulation process, playing a key protective role for the crystalline silicon cell layer. However, during the disassembly and recycling process, due to the inability to achieve the de-crosslinking of the permanently crosslinked encapsulation film, it remains tightly adhered to the backplane and the glass layer, making it a major technical challenge to achieve the complete separation and efficient recycling of each material.

[0004] Therefore, developing a separable and disassemblable photovoltaic encapsulation film to achieve the efficient peeling and material recycling of photovoltaic modules is of great strategic significance for promoting the green circular development of the photovoltaic industry and facilitating the efficient utilization of resources. Summary of the Invention

[0005] The purpose of the present invention is to provide a separable and disassemblable photovoltaic encapsulation film based on dynamic crosslinking for the problem that the photovoltaic encapsulation film in the prior art cannot be efficiently and completely separated after being discarded due to its permanently crosslinked structure, which hinders the recycling of photovoltaic modules. By designing a crosslinking agent containing dynamic bonds and compounding and using it through formula design, the above problems can be effectively solved, and the colorless transparency of the encapsulation film can be maintained, having a broad application space. The encapsulation film of the present invention has good adhesion to the battery module, and maintains the light transmittance of the encapsulation film. After being discarded, the complete separation of the film can be achieved under heating conditions.

[0006] The present invention first provides a separable and disassemblable photovoltaic encapsulation film. The separable and disassemblable photovoltaic encapsulation film is prepared from raw materials comprising the following parts by weight: 100 parts of POE resin, 0.01-2 parts of initiator, 0-3 parts of crosslinking agent I, 0.5-5 parts of crosslinking agent II, 0.01-1 part of antioxidant, 0.05-1 part of light stabilizer; wherein, the crosslinking agent II is 1,1'-[(1,4-phenylbis(1,3,2-dioxaborolane-2,4-diyl))bis(methylene)]bis(1H-pyrrole-2,5-dione).

[0007] Further, in the separable and disassemblable photovoltaic encapsulation film, the octene content in the POE (ethylene-α-octene) resin is 20-35 wt%.

[0008] Further, in the separable and disassemblable photovoltaic encapsulation film, the initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, tert-amyl peroxybenzoate, tert-butyl peroxybenzoate, di-tert-butyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl peroxyisopropyl carbonate, tert-amyl peroxyacetate, tert-amyl peroxy(2-ethylhexyl) carbonate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,1-di-tert-butylperoxycyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxy-tert-amyl carbonate, 1,1-di(tert-amylperoxy)cyclohexane, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane. More preferably, the initiator is tert-amyl peroxy(2-ethylhexyl) carbonate.

[0009] Further, in the separable and disassemblable photovoltaic encapsulation film, the crosslinking agent I is selected from at least one of triallyl cyanurate, trimethylolpropane trimethacrylate, triallyl isocyanurate, ethoxylated pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate. More preferably, the crosslinking agent I is triallyl isocyanurate.

[0010] Further, in the separable and disassemblable photovoltaic encapsulation film, the antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1-2.

[0011] Furthermore, in the above-mentioned separable and disassemblable photovoltaic encapsulation film, the hindered phenol antioxidant is selected from at least one of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, and 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid ester. More preferably, the hindered phenol antioxidant is pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0012] Furthermore, in the above-mentioned separable and disassemblable photovoltaic encapsulation film, the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyldiphosphite, and dipentaerythritol diphosphite diisodecyl ester. More preferably, the phosphite antioxidant is tris(2,4-di-tert-butylphenyl)phosphite.

[0013] Further, in the above-mentioned separable and disassemblable photovoltaic encapsulation film, the light stabilizer is a mixture of a hindered amine light stabilizer and an ultraviolet absorber in a mass ratio of 1:1 to 2.

[0014] Furthermore, in the above-mentioned separable and disassemblable photovoltaic encapsulation film, the hindered amine light stabilizer is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-dialdehyde hexanediamine. More preferably, the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate.

[0015] Furthermore, in the above-mentioned separable and disassemblable photovoltaic encapsulation film, the ultraviolet absorber is selected from at least one of ethylhexyl methoxycinnamate, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, ethylhexyl triazone, N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)oxamide, ethyl 2-cyano-3,3-diphenylacrylate, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-(octyloxy)phenol, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2,4-dihydroxybenzophenone. More preferably, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone.

[0016] The present invention also provides a preparation method of the above-mentioned separable and disassemblable photovoltaic encapsulation film. The preparation method includes the following steps: mixing each raw material, then melting and blending the mixed raw materials, discharging through a coextrusion casting die head, pulling, and stretching; measuring the thickness, pressing the edge, shaping, then trimming the edge, and winding, to obtain the separable and disassemblable photovoltaic encapsulation film.

[0017] Furthermore, in the preparation method of the above-mentioned separable and disassemblable photovoltaic encapsulation film, the POE extrusion process is as follows: the barrel temperature is 85-110°C, and the rotation speed is 45-50 rpm.

[0018] Furthermore, in the preparation method of the above-mentioned separable and disassemblable photovoltaic encapsulation film, the mixed raw materials are placed in a twin-screw extruder for melting and blending.

[0019] Advantages of the present invention:

[0020] (1) In the encapsulation film of the present invention, since the crosslinking agent II used contains a dynamic covalent bond structure, when the temperature rises, the exchange reaction of the dynamic chemical bond can be activated, and the exchange reaction of the dynamic covalent bond enables the crosslinked network to undergo topological rearrangement, thereby realizing the separation and disassembly of the film. However, traditional static crosslinked films cannot achieve de-crosslinking and have the characteristics of being insoluble and infusible. During the disassembly process of the module, they remain tightly adhered to the backplane and the glass layer and cannot be separated.

[0021] (2) In the encapsulation film of the present invention, since the crosslinking agent II contains a dynamic borate bond, no color change is brought about by the introduction of polar groups after the crosslinking reaction, so it does not affect the transparency of the POE encapsulation film and meets the application requirements of the photovoltaic module encapsulation film. Specific embodiments

[0022] The information of some components in the following examples and comparative examples of the present invention is as follows:

[0023] POE resin: The octene content is 25 wt%; Initiator: tert-Amyl peroxy(2-ethylhexyl) carbonate; Crosslinking agent I: Triallyl isocyanurate; Crosslinking agent II: 1,1'-[(1,4-phenylbis(1,3,2-dioxaborolane-2,4-diyl))bis(methylene)]bis(1H-pyrrole-2,5-dione); Antioxidant: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite are added in a mass ratio of 1:2; Light stabilizer: Bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2-hydroxy-4-n-octyloxybenzophenone are added in a mass ratio of 1:2.

[0024] Among them, the preparation process of crosslinking agent II is as follows:

[0025] 1) Add furan (18.5 g), maleic anhydride (20 g), and ethyl acetate (30 mL) to a round-bottom flask, stir at room temperature for 24 h, and filter to obtain 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride. The reaction formula is shown in (1):

[0026]

[0027] 2) Add 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride (20 g) and ethanol (30 mL) to a round-bottom flask, and then dropwise add (±)-3-amino-1,2-propanediol (11.25 g). Reflux and react at 85 °C for 5 h, cool overnight, and filter to obtain 2-(2,3-dihydroxypropyl)-3a,4,7,7a-tetrahydro-4,7-epoxyisoindole-1,3-dione. The reaction formula is shown in (2):

[0028]

[0029] 3) Add 2-(2,3-dihydroxypropyl)-3a,4,7,7a-tetrahydro-4,7-epoxyisoindole-1,3-dione (10.9 g), 1,4-benzenediboronic acid (4 g), toluene (150 mL), and water (3 mL) to a round-bottom flask, reflux at 130 °C for 16 h, cool, remove the solvent under reduced pressure, wash with ethanol, filter, and dry to obtain crosslinking agent II. The reaction formula is shown in (3):

[0030]

[0031] Example 1

[0032] The specific formulation is shown in Table 1, and the preparation method is as follows: Mix each component according to the ratio, place the mixed raw materials in a twin-screw extruder for melt blending, discharge through a co-extrusion cast film die head, draw, and stretch; the extrusion process is that the temperature of the first zone of the barrel is 90 °C, the temperature of the second zone is 100 °C, the temperature of the third zone is 105 °C, the die head temperature is 108 °C, and the rotation speed is 50 rpm; after thickness measurement, edge pressing, and shaping, and then through edge trimming and winding, the separable and disassemblable POE encapsulation film is obtained.

[0033] Example 2

[0034] The difference from Example 1 is only that the weight parts of each component are different, as shown in Table 1 specifically.

[0035] Example 3

[0036] The difference from Example 1 is only that the weight parts of each component are different, as shown in Table 1 specifically.

[0037] Example 4

[0038] The difference from Example 1 is only that the weight parts of each component are different, as shown in Table 1 specifically.

[0039] Comparative Example 1

[0040] The difference from Example 1 is that it does not contain crosslinking agent II, as shown in Table 1 specifically.

[0041] Comparative Example 2

[0042] The difference from Example 1 is that crosslinking agent II is replaced by bis(2,2,6,6-tetramethyl-4-piperidyl methacrylate) disulfide, as shown in Table 1 specifically.

[0043] Table 1 Specific formulations (weight parts) of examples and comparative examples

[0044]

[0045] The physical properties of the POE films prepared in the examples and comparative examples of the present invention were measured respectively, and the results are shown in Table 2.

[0046] Table 2 Physical test properties of examples and comparative examples

[0047]

[0048] As can be seen from Table 2, Examples 1-4 and Comparative Example 1 of the present invention, the POE film based on dynamic crosslinking has excellent bonding strength compared with the traditional static crosslinked POE, can maintain the colorless transparency of the POE encapsulation film, and can be completely separated under the heating condition of 95 °C.

[0049] As can be seen from Examples 1-4 and Comparative Example 2 in Table 2, compared with other dynamically crosslinked POE films achieved by disulfide bond dynamic exchange reactions, the dynamically crosslinked POE film of the present invention realized by borate bond dynamic exchange reactions can maintain the colorless transparency of the encapsulation film.

[0050] In summary, the POE encapsulation film based on dynamic crosslinking of the present invention has good adhesion to the battery module, maintains the light transmittance of the encapsulation film, and can achieve complete separation of the film under heating conditions after being discarded.

[0051] The test methods are as follows:

[0052] (1) Light transmittance: Tested by an ultraviolet / visible / near-infrared spectrophotometer (PerkinElmer Lambda 750S), and the test range is 400 - 800 nm.

[0053] (2) Peel strength test:

[0054] Specimen preparation:

[0055] 1) Prepare two pieces of raw film with a size of 300 mm × 150 mm, one piece of glass, and one piece of flexible backplane;

[0056] 2) Stack them in the order of glass / film (two pieces) / flexible backplane, put them into a vacuum laminator, and laminate according to the temperature and time required by the product. There should be no bubbles in the film in the laminated sample. Prepare 3 specimens.

[0057] 3) Cut the flexible backplane / film layer into specimens with a width of 10 mm ± 0.5 mm every 5 mm in the width direction for the peel strength test between the film and the glass.

[0058] Test process: According to the test method of GB / T 2790-1995, measure the peel strength F between the glass and the film on a tensile testing machine at a tensile speed of 100 mm / min ± 10 mm / min.

[0059] Test results: The peel strength is calculated according to the following formula, and take the arithmetic mean of 3 specimens, accurate to 0.1 N / cm.

[0060] σ = F / B

[0061] Where: σ—180° peel strength, N / cm; F—peel force, N; B—specimen width, cm.

[0062] (3) UV aging: The obtained POE film is subjected to ultraviolet irradiation aging test according to the requirements of the International Electrotechnical Commission standard IEC61345. Test conditions: The surface temperature of the test piece is 60 ± 5 °C, the ultraviolet wavelength range is 280 - 400 nm, and the irradiation intensity is 15 kW·h / m2 The ultraviolet irradiation test time is 2000 hr.

[0063] The yellowing index (ΔYI) before and after the test is measured according to GB 2409.

[0064] (4) Separation and disassembly of the adhesive film:

[0065] Specimen preparation:

[0066] 1) Prepare two pieces of raw adhesive film with dimensions of 300 mm × 150 mm, one piece of glass, and one piece of flexible backplane.

[0067] 2) Stack them in the order of glass / adhesive film (two pieces) / flexible backplane, put them into a vacuum laminator, and laminate them at the temperature and time required by the product. There should be no bubbles in the adhesive film in the laminated sample. Prepare 3 specimens.

[0068] 3) Cut the flexible backplane / adhesive film layer into specimens with a width of 10 mm ± 0.5 mm at intervals of 5 mm in the width direction.

[0069] Separation process: Heat the specimen in an oven at 95°C for 10 min, and perform the separation and disassembly of the adhesive film through a tensile testing machine.

[0070] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A separable and disassemblable photovoltaic encapsulation film, characterized in that: It is prepared from the following raw materials in parts by weight: 100 parts of POE resin, 0.01 - 2 parts of initiator, 0 - 3 parts of crosslinking agent I, 0.5 - 5 parts of crosslinking agent II, 0.01 - 1 part of antioxidant, and 0.05 - 1 part of light stabilizer; wherein, the crosslinking agent II is 1,1'-[(1,4-phenylbis(1,3,2-dioxaborolane-2,4-diyl))bis(methylene)]bis(1H-pyrrole-2,5-dione).

2. The separable and disassemblable photovoltaic encapsulation film according to claim 1, wherein: The octene content in the POE resin is 20 - 35 wt%.

3. The separable and disassemblable photovoltaic encapsulation film according to claim 1 or 2, characterized in that: The initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, tert-amyl peroxybenzoate, tert-butyl peroxybenzoate, di-tert-butyl peroxide, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl peroxyisopropyl carbonate, tert-amyl peroxyacetate, tert-amyl peroxy(2-ethylhexyl) carbonate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,1-di-tert-butylperoxycyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxy-tert-amyl carbonate, 1,1-di(tert-amylperoxy)cyclohexane, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane; preferably, the initiator is tert-amyl peroxy(2-ethylhexyl) carbonate.

4. The separable and disassemblable photovoltaic encapsulation film according to any one of claims 1-3, characterized in that: The crosslinking agent I is selected from at least one of triallyl cyanurate, trimethylolpropane trimethacrylate, triallyl isocyanurate, ethoxylated pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate; preferably, the crosslinking agent I is triallyl isocyanurate.

5. The separable and disassemblable photovoltaic encapsulation adhesive film according to any one of claims 1-4, characterized in that: The antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1 - 2.

6. The separable and disassemblable photovoltaic encapsulation adhesive film according to claim 5, wherein: The hindered phenol antioxidant is selected from at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid ester; preferably, the hindered phenol antioxidant is pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the phosphite antioxidant is selected from at least one of tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, tetra(2,4-di-tert-butylphenyl)-4,4'-biphenyldiphosphite, dipentaerythritol diphosphite diisodecyl ester; preferably, the phosphite antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

7. The separable and disassemblable photovoltaic encapsulation film according to any one of claims 1-6, characterized in that: The light stabilizer is a mixture of a hindered amine light stabilizer and an ultraviolet absorber in a mass ratio of 1:1 - 2.

8. The separable and disassemblable photovoltaic encapsulation adhesive film according to claim 7, wherein: The hindered amine light stabilizer is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-N,N'-diformylhexanediamine; preferably, the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate; the ultraviolet absorber is selected from at least one of ethylhexyl methoxycinnamate, 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, ethylhexyl triazone, N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)oxalamide, ethyl 2-cyano-3,3-diphenylacrylate, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)phenol, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2,4-dihydroxybenzophenone; preferably, the ultraviolet absorber is 2-hydroxy-4-n-octyloxybenzophenone.

9. The preparation method of the separable and disassemblable photovoltaic encapsulation adhesive film according to any one of claims 1-8, characterized in that: Comprising the following steps: Mixing each raw material, then melt-blending the mixed raw materials and discharging through a co-extrusion casting die head, followed by traction and stretching; After thickness measurement, edge pressing, and shaping, and then through edge trimming and winding, the separable and disassemblable photovoltaic encapsulation adhesive film is obtained.

10. The preparation method of the separable and disassemblable photovoltaic encapsulation adhesive film according to claim 9, wherein: The extrusion process is as follows: the barrel temperature is 85-110 °C and the rotation speed is 45-50 rpm.

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