Low-additive migration multilayer packaging adhesive film, preparation method thereof and packaging adhesive film cross-linked cured product

Abstract

The invention belongs to the technical field of photovoltaic module packaging materials, and particularly relates to a low-additive migration multilayer packaging adhesive film, a preparation method thereof and a packaging adhesive film cross-linked cured product. The multi-layer packaging adhesive film provided by the invention comprises a POE layer and an EVA / POE blending layer arranged on the surface of one side or two sides of the POE layer, the POE layer comprises the following components: POE resin, a main cross-linking agent, an auxiliary cross-linking agent and a silane coupling agent; the EVA / POE blending layer comprises the following components: EVA resin, POE resin, acrylate, a compatilizer, a main cross-linking agent, an auxiliary cross-linking agent, a silane coupling agent and an antioxidant. The multi-layer packaging adhesive film provided by the invention has excellent comprehensive performance under the condition of keeping low additive migration.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic module encapsulation material technology, and particularly relates to a low-additive migration multilayer encapsulation film, its preparation method, and the cross-linked cured product of the encapsulation film. Background Technology

[0002] As a clean, low-carbon, environmentally friendly, and efficient green energy source, photovoltaic (PV) solar energy is rapidly transforming into a primary energy source. PV encapsulation film, placed between the glass of a PV module and the solar cells, or between the backsheet and the solar cells, is used to encapsulate and protect the solar cells. It is one of the key materials for PV modules and plays a crucial role in improving and ensuring the quality of PV modules.

[0003] Currently, the mainstream adhesive films on the market are mainly EVA films, POE films, and EPE films formed by multi-layer co-extrusion of EVA and POE. EPE films combine the low water vapor permeability and better anti-PID performance of POE with the high adhesion of EVA, solving the technical challenges of slippage and bubble formation in pure POE films, and the high water vapor permeability and potential-induced degradation (PID) caused by the hydrolysis of acetate ions within EVA, which severely affects battery output power. However, because POE has a saturated molecular weight and does not contain polar monomers, while EVA is a polar molecule with good compatibility with additives, polar additives in the POE layer tend to migrate to the EVA layer during long-term use. This reduces the cross-linking degree of the intermediate POE layer, leading to excessively rapid aging of the EPE film and delamination between the EVA and POE layers, resulting in a decline in film performance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a low-additive-migration multilayer encapsulating film, a method for preparing the same, and a cross-linked cured encapsulating film. The multilayer encapsulating film provided by the present invention has excellent comprehensive performance while maintaining low additive migration.

[0005] This invention provides a low-additive migration multilayer encapsulating film, comprising a POE layer and an EVA / POE blend layer disposed on one or both sides of the POE layer;

[0006] The POE layer comprises POE resin, primary crosslinking agent, secondary crosslinking agent, and silane coupling agent;

[0007] The components of the EVA / POE blend layer include EVA resin, POE resin, acrylate, compatibilizer, main crosslinking agent, co-crosslinking agent, silane coupling agent and antioxidant;

[0008] The POE resin is copolymerized from ethylene and an α-olefin, wherein the α-olefin is one or more selected from 1-butene, 1-octene, and 1-hexene; the α-olefin insertion rate of the POE resin is 10-30 wt%; the melt index of the POE resin measured at 190°C and a load of 2.16 kg is 2-20 g / 10 min; the number-average molecular weight of the POE resin is 100,000-250,000 g / mol; the molecular weight distribution index of the POE resin is 2-4; and the density of the POE resin is 0.6-0.9 g / cm³. 3 .

[0009] Preferably, the acrylate is one or more selected from 1,6-hexanediol diacrylate, ethoxylated 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, 2-methyl-1,3-propanediol diacrylate, ethoxylated 2-methyl-1,3-propanediol diacrylate, and ethoxylated trimethylolpropane triacrylate.

[0010] Preferably, the compatibilizer is one or more of the following: styrene-grafted polyethylene, styrene-grafted polypropylene, maleic anhydride-grafted acrylonitrile-butadiene-styrene polymer, maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyolefin elastomer, glycidyl methacrylate-grafted polyolefin elastomer, and ethylene-acrylic acid copolymer.

[0011] Preferably, the main crosslinking agent is one or more selected from tert-butylperoxy-2-ethylhexane carbonate, tert-amylperoxy-2-ethylhexane carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide, bis-tert-butylperoxyisopropylbenzene, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane;

[0012] And / or, the co-crosslinking agent is one or more of triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and diallyl 1,2-phthalate.

[0013] Preferably, the silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(2-methoxyethoxy)silane.

[0014] Preferably, the antioxidant is one or more selected from the following: β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxyanisole, dilauryl thiodipropionate, 1,6-hexanediol-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate diester, triethylene glycol-bis-3-(2-tert-butyl-4-hydroxy-5-methyl-phenyl)acrylic acid, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dodecanol thiodipropionate, triphenyl phosphite, pentaerythritol phosphate, trinonylphenyl phosphite, and diphenyl-octyl phosphite.

[0015] Preferably, the POE layer comprises, by weight, the following components:

[0016] 100 parts of POE resin;

[0017] 0.3-1 part of the main crosslinking agent;

[0018] 0.5-1.1 parts of crosslinking agent;

[0019] 0.3 to 0.8 parts of silane coupling agent.

[0020] Preferably, the composition of the EVA / POE blend layer, by weight, includes:

[0021] 100 parts of EVA resin;

[0022] 1-20 parts of POE resin;

[0023] Acrylic ester 0.6~0.8 parts;

[0024] 1-20 parts compatibilizer;

[0025] 0.6 to 1 part of main crosslinking agent;

[0026] 0.5-1.1 parts of crosslinking agent;

[0027] 0.6-0.8 parts of silane coupling agent;

[0028] Antioxidant 0.05~3 parts.

[0029] This invention provides a method for preparing the low-additive migration multilayer encapsulating film described in the above technical solution, comprising the following steps:

[0030] POE layer mixture and EVA / POE blend layer mixture were prepared separately.

[0031] Using the POE layer mixture and the EVA / POE blend mixture as raw materials, a multilayer structure is prepared to obtain a low-additive migration multilayer encapsulation film.

[0032] This invention provides a cross-linked cured encapsulating film, wherein the cross-linked cured encapsulating film is the product of cross-linking treatment of the low-additive migration multilayer encapsulating film described in the above technical solution or the low-additive migration multilayer encapsulating film prepared by the preparation method described in the above technical solution.

[0033] Compared with the prior art, the present invention provides a low-additive migration multilayer encapsulating film, its preparation method and the cross-linked cured product of the encapsulating film. The multilayer encapsulating film provided by this invention includes a POE layer and an EVA / POE blend layer disposed on one or both sides of the POE layer. The POE layer comprises POE resin, a primary crosslinking agent, a secondary crosslinking agent, and a silane coupling agent. The EVA / POE blend layer comprises EVA resin, POE resin, acrylate, a compatibilizer, a primary crosslinking agent, a secondary crosslinking agent, a silane coupling agent, and an antioxidant. The POE resin is copolymerized from ethylene and an α-olefin, wherein the α-olefin is one or more selected from 1-butene, 1-octene, and 1-hexene. The α-olefin insertion rate of the POE resin is 10-30 wt%. The melt index of the POE resin measured at 190°C and a load of 2.16 kg is 2-20 g / 10 min. The number-average molecular weight of the POE resin is 100,000-250,000 g / mol. The molecular weight distribution index of the POE resin is 2-4. The density of the POE resin is 0.6-0.9 g / cm³. 3 This invention introduces a portion of POE resin into the EVA layer, forming an EVA / POE blend layer. This reduces the polarity of the EVA layer, thereby decreasing its absorption capacity for POE layer additives. Furthermore, by regulating the physical properties and molecular structure of POE, the retention capacity of the POE layer for additives is improved, further mitigating the additive migration problem in the POE layer. In addition, through the above component design, this invention not only enables multilayer encapsulating films to exhibit low additive migration but also high light transmittance, peel strength, volume resistivity, and crosslinking degree, resulting in excellent overall performance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of the low-additive migration double-layer encapsulation film provided in an embodiment of the present invention;

[0036] Figure 2This is a schematic diagram of the structure of the low-additive migration three-layer encapsulation film provided in an embodiment of the present invention.

[0037] Explanation of reference numerals in the attached figures: 1 represents the POE layer, and 2 represents the EVA / POE blend layer. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a low-additive migration multilayer encapsulating film, the structure of which is as follows: Figures 1-2 As shown, it includes a POE layer 1 and an EVA / POE blend layer 2 disposed on one or both sides of the POE layer 1.

[0040] In the multilayer encapsulating film provided by the present invention, the POE layer 1 comprises POE resin, a primary crosslinking agent, a secondary crosslinking agent, and a silane coupling agent.

[0041] In the multilayer encapsulating film provided by this invention, in the POE layer 1, the POE resin is copolymerized from ethylene and α-olefin, wherein the α-olefin is one or more of 1-butene, 1-octene, and 1-hexene, preferably 1-butene; the α-olefin insertion rate (α-olefin content) of the POE resin is 10~30wt%, preferably 11~20wt%, specifically 17.2wt%, 18.3wt%, and 19.5wt%; the melt index of the POE resin measured at 190℃ and 2.16kg load is 2~20g / 10min, preferably... The POE resin has a molecular weight distribution of 4~16 g / 10 min, specifically 4.5 g / 10 min, 5 g / 10 min, or 5.3 g / 10 min; the number average molecular weight of the POE resin is 100,000~250,000 g / mol, preferably 110,000~230,000 g / mol, specifically 175,000 g / mol, 184,000 g / mol, or 192,000 g / mol; the molecular weight distribution index of the POE resin is 2~4, preferably 2~3.5, specifically 2; the density of the POE resin is 0.6~0.9 g / cm³. 3 The preferred concentration is 0.7~0.8 g / cm³. 3 Specifically, it can be 0.876 g / cm³. 3 .

[0042] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, the main crosslinking agent is preferably one or more of tert-butylperoxy-2-ethylhexane carbonate, tert-amylperoxy-2-ethylhexane carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide, bis-tert-butylperoxyisopropylbenzene, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0043] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, based on 100 parts by weight of POE resin, the content of the main crosslinking agent is preferably 0.3 to 1 part by weight, specifically 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, or 1 part by weight.

[0044] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, the co-crosslinking agent is preferably one or more of triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and diallyl 1,2-phthalate.

[0045] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, based on 100 parts by weight of POE resin, the content of the crosslinking agent is preferably 0.5 to 1.1 parts by weight, specifically 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, or 1.1 parts by weight.

[0046] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, the silane coupling agent is preferably one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(2-methoxyethoxy)silane, more preferably γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane, and the mass ratio of γ-methacryloxypropyltrimethoxysilane to vinyltrimethoxysilane is preferably 1:(0.5~5), more preferably 1:3.

[0047] In the multilayer encapsulating film provided by the present invention, in the POE layer 1, based on 100 parts by weight of POE resin, the content of the silane coupling agent is preferably 0.3 to 0.8 parts by weight, specifically 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight or 0.8 parts by weight.

[0048] In the multilayer encapsulating film provided by the present invention, the basis weight of POE layer 1 is preferably 100~300 g / m². 2 Specifically, it can be 100g / m 2 130g / m2 150g / m 2 170g / m 2 200g / m 2 230g / m 2 250g / m 2 270g / m 2 Or 300g / m 2 .

[0049] In the multilayer encapsulating film provided by the present invention, the components of the EVA / POE blend layer 2 include EVA resin, POE resin, acrylate, compatibilizer, main crosslinking agent, co-crosslinking agent, silane coupling agent and antioxidant.

[0050] In the multilayer encapsulating film provided by this invention, in the EVA / POE blend layer 2, the melt index of the EVA resin measured under conditions of 190°C and 2.16 kg load is 15~40 g / 10 min, preferably 20~30 g / 10 min, and specifically 25 g / 10 min; the VA content of the EVA resin is preferably 20~35 wt%, more preferably 25~30 wt%, and specifically 28 wt%; the density of the EVA resin is preferably 0.9~1 g / cm³. 3 More preferably, it is 0.93~0.97 g / cm³. 3 Specifically, it can be 0.952 g / cm³. 3 .

[0051] In the multilayer encapsulating film provided by this invention, in the EVA / POE blend layer 2, the POE resin is copolymerized from ethylene and α-olefins, wherein the α-olefin is one or more of 1-butene, 1-octene, and 1-hexene, preferably 1-butene; the α-olefin insertion rate (α-olefin content) of the POE resin is 10~30wt%, preferably 11~20wt%, specifically 17.2wt%, 18.3wt%, and 19.5wt%; the melt index of the POE resin measured at 190℃ and 2.16kg load is 2~20g / 10min. The preferred concentration is 4~16 g / 10 min, specifically 4.5 g / 10 min, 5 g / 10 min, or 5.3 g / 10 min; the number-average molecular weight of the POE resin is 100,000~250,000 g / mol, preferably 110,000~230,000 g / mol, specifically 175,000 g / mol, 184,000 g / mol, or 192,000 g / mol; the molecular weight distribution index of the POE resin is 2~4, preferably 2~3.5, specifically 2; the density of the POE resin is 0.6~0.9 g / cm³. 3 The preferred concentration is 0.7~0.8 g / cm³. 3Specifically, it can be 0.876 g / cm³. 3 .

[0052] In the multilayer encapsulation film provided by the present invention, in the EVA / POE blend layer 2, the content of POE resin is preferably 1 to 20 parts by weight, based on 100 parts by weight of EVA resin, specifically 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 15 parts by weight, 17 parts by weight or 20 parts by weight.

[0053] In the multilayer encapsulating film provided by the present invention, the acrylate in the EVA / POE blend layer 2 is preferably one or more of 1,6-hexanediol diacrylate, ethoxylated 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, 2-methyl-1,3-propanediol diacrylate, ethoxylated 2-methyl-1,3-propanediol diacrylate, and ethoxylated trimethylolpropane triacrylate.

[0054] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, based on the content of EVA resin as 100 parts by weight, the content of acrylate is preferably 0.6 to 0.8 parts by weight, specifically 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight or 0.8 parts by weight.

[0055] In the multilayer encapsulating film provided by this invention, in the EVA / POE blend layer 2, the compatibilizer is styrene-grafted polyethylene (PE-g-ST), styrene-grafted polypropylene (PP-g-ST), maleic anhydride-grafted acrylonitrile-butadiene-styrene polymer (ABS-g-MAH), maleic anhydride-grafted polyethylene (PE-g-MAH), maleic anhydride-grafted polypropylene (PP-g-MAH), maleic anhydride-grafted polyolefin elastomer (POE-g-MAH), glycidyl methacrylate grafted... One or more of grafted polyolefin elastomer (POE-g-GMA) and ethylene-acrylic acid copolymer (EAA); wherein the grafting rate of the grafted polymer is preferably 1-5 wt%, more preferably 1.5-3 wt%, and specifically 2 wt%; the melt index of the grafted polymer measured at 190°C and 2.16 kg load is preferably 5-15 g / 10 min, more preferably 8-12 g / 10 min, and specifically 10 g / 10 min; the number average molecular weight of the grafted polymer is preferably 10 × 10⁻⁶. 4 ~20×10 4 g / mol, more preferably 13 × 10 g / mol 4 ~17×10 4 g / mol, specifically 15 × 10 4 g / mol.

[0056] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, the content of the compatibilizer is preferably 1 to 20 parts by weight, based on 100 parts by weight of EVA resin, specifically 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 10 parts by weight, 12 parts by weight, 15 parts by weight, 17 parts by weight or 20 parts by weight.

[0057] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, the main crosslinking agent is preferably one or more of tert-butylperoxy-2-ethylhexane carbonate, tert-amylperoxy-2-ethylhexane carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide, bis-tert-butylperoxyisopropylbenzene, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0058] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, based on 100 parts by weight of EVA resin, the content of the main crosslinking agent is preferably 0.6 to 1 part by weight, specifically 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight or 1 part by weight.

[0059] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, the co-crosslinking agent is preferably one or more of triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and diallyl 1,2-phthalate.

[0060] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, based on 100 parts by weight of EVA resin, the content of the crosslinking agent is preferably 0.5 to 1.1 parts by weight, specifically 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, or 1.1 parts by weight.

[0061] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, the silane coupling agent is preferably one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris(2-methoxyethoxy)silane, more preferably γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane, and the mass ratio of γ-methacryloxypropyltrimethoxysilane to vinyltrimethoxysilane is preferably 1:(0.5~5), more preferably 1:1.

[0062] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, based on 100 parts by weight of EVA resin, the content of the silane coupling agent is preferably 0.6 to 0.8 parts by weight, specifically 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight or 0.8 parts by weight.

[0063] In the multilayer encapsulating film provided by the present invention, the antioxidant in the EVA / POE blend layer 2 is preferably one or more of the following: β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxyanisole, dilauryl thiodipropionate, 1,6-hexanediol-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate diester, triethylene glycol-bis-3-(2-tert-butyl-4-hydroxy-5-methyl-phenyl)acrylic acid, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dodecanol thiodipropionate, triphenyl phosphite, pentaerythritol phosphate, trinonylphenyl phosphite, and diphenyl-octyl phosphite.

[0064] In the multilayer encapsulating film provided by the present invention, in the EVA / POE blend layer 2, based on 100 parts by weight of EVA resin, the content of the antioxidant is preferably 0.05 to 3 parts by weight, specifically 0.05 parts by weight, 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight or 0.3 parts by weight.

[0065] In the multilayer encapsulating film provided by the present invention, the basis weight of one side of the EVA / POE blend layer 2 is preferably 100~300 g / m³. 2 Specifically, it can be 100g / m 2 130g / m 2 150g / m 2 170g / m 2 200g / m 2 230g / m 2 250g / m 2 270g / m 2 Or 300g / m 2 .

[0066] The present invention also provides a method for preparing the low-additive migration multilayer encapsulating film described in the above technical solution, comprising the following steps:

[0067] POE layer mixture and EVA / POE blend layer mixture were prepared separately.

[0068] Using the POE layer mixture and the EVA / POE blend mixture as raw materials, a multilayer structure is prepared to obtain a low-additive migration multilayer encapsulation film.

[0069] In the preparation method provided by the present invention, the POE layer mixture is preferably prepared according to the following steps: mixing POE resin, main crosslinking agent, co-crosslinking agent and silane coupling agent to obtain POE layer mixture; wherein, the mixing temperature is preferably 40~50℃; the mixing speed is preferably 70~80rpm; and the mixing time is preferably 2~3h.

[0070] In the preparation method provided by the present invention, the EVA / POE blend layer mixture is preferably prepared according to the following steps: EVA resin, POE resin, acrylate, compatibilizer, main crosslinking agent, co-crosslinking agent, silane coupling agent and antioxidant are mixed to obtain the EVA / POE blend layer mixture; wherein, the mixing temperature is preferably 40~50℃; the mixing speed is preferably 70~80rpm; and the mixing time is preferably 2~3h.

[0071] In the preparation method provided by the present invention, the preparation of the multilayer structure is preferably carried out by melt co-extrusion or coating; wherein, the temperature of melt co-extrusion is preferably 80~110℃; and the rotation speed is preferably 60~80rpm.

[0072] The present invention also provides a cross-linked cured encapsulating film, wherein the cross-linked cured encapsulating film is the product of cross-linking treatment of the low-additive migration multilayer encapsulating film described in the above technical solution or the low-additive migration multilayer encapsulating film prepared by the preparation method described in the above technical solution.

[0073] In the cross-linked cured encapsulating film provided by the present invention, the temperature of the cross-linking treatment is preferably 120~180℃, more preferably 130~150℃, and specifically 148℃; the time of the cross-linking treatment is preferably 200~800s, more preferably 300~600s, and specifically 400s.

[0074] The technical solution provided by this invention introduces a portion of POE resin into the EVA layer, forming an EVA / POE blend layer. This reduces the polarity of the EVA layer, thereby decreasing its absorption capacity for POE layer additives. Furthermore, by regulating the physical properties and molecular structure of POE, the retention capacity of the POE layer for additives is improved, further mitigating the additive migration problem in the POE layer. In addition, through the above-mentioned component design, this invention not only enables the multilayer encapsulating film to have low additive migration but also high light transmittance, peel strength, volume resistivity, and crosslinking degree, resulting in excellent overall performance.

[0075] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0076] Example 1

[0077] A low-additive migration multilayer encapsulating film, the structure of which is as follows: Figure 2 As shown, it includes a POE layer 1 and an EVA / POE blend layer 2 disposed on both sides of the POE layer 1;

[0078] The basis weight of POE layer 1 is 130 g / m². 2 The product comprises the following components by weight: 100 parts POE resin, 0.4 parts tert-butylperoxy-2-ethylhexane carbonate, 0.8 parts triallyl isocyanurate, 0.1 parts γ-methacryloyloxypropyltrimethoxysilane, and 0.3 parts vinyltrimethoxysilane.

[0079] The POE resin in POE layer 1 is an ethylene-butene copolymer; the number average molecular weight of this POE resin is 18.4 × 10⁻⁶. 4 g / mol, molecular weight distribution index of 2.0, density of 0.876 g / cm³ 3 The melt index is 5 g / 10 min (190℃, 2160 g), and the content of comonomer (1-butene) is 17.2 wt%.

[0080] The weight per side of the EVA / POE layer 2 is 130 g / m². 2 The product comprises the following components by weight: 100 parts EVA resin, 3 parts POE resin, 3 parts glycidyl methacrylate grafted polyolefin elastomer, 0.6 parts tert-butylperoxy-2-ethylhexane carbonate, 0.7 parts triallyl isocyanurate, 0.3 parts γ-methacryloyloxypropyltrimethoxysilane, 0.3 parts vinyltrimethoxysilane, 0.6 parts ethoxytrimethylolpropane triacrylate, and 0.05 parts triphenyl phosphite.

[0081] The EVA resin in the EVA / POE layer 2 has a melt index of 25 g / 10 min (190℃, 2160 g), a VA content of 28 wt%, and a density of 0.952 g / cm³. 3 The POE resin is the same as in POE layer 1; the glycidyl methacrylate-grafted polyolefin elastomer has a grafting rate of 2%, a melt index of 10 g / 10 min (190℃, 2160 g), and a number-average molecular weight of 15 × 10⁻⁶. 4 g / mol.

[0082] The preparation method of the low-additive migration multilayer encapsulating film is as follows:

[0083] According to the formula, the raw materials of each layer of the low migration multilayer encapsulating film are added to the mixer for mixing. The mixture is stirred for 2-3 hours at a temperature of 40-50℃ and a speed of 70-80rpm to obtain the mixed raw materials. Co-extrusion: The raw materials of each layer are placed in different hoppers of a twin-screw extruder and co-extruded at a temperature of 80-110℃ and a speed of 60-80rpm to form a film, which is then cast to obtain the low additive migration multilayer encapsulating film.

[0084] Comparative Example 1

[0085] A low-additive migration multilayer encapsulating film, which differs from Example 1 in that the number-average molecular weight of the POE resin is 17.5 × 10⁻⁶. 4 g / mol, melt index 5.3 g / 10 min; all other conditions were the same as in Example 1.

[0086] Comparative Example 2

[0087] A low-additive migration multilayer encapsulating film, which differs from Example 1 in that the number-average molecular weight of the POE resin is 19.2 × 10⁻⁶. 4 g / mol, melt index 4.5 g / 10 min; all other conditions were the same as in Example 1.

[0088] Comparative Example 3

[0089] A low-additive migration multilayer encapsulating film differs from Example 1 in that the POE resin has a comonomer (1-butene) content of 18.3 wt%; all other conditions are the same as in Example 1.

[0090] Comparative Example 4

[0091] A low-additive migration multilayer encapsulating film differs from Example 1 in that the POE resin comonomer (1-butene) content is 19.5 wt%; all other conditions are the same as in Example 1.

[0092] Comparative Example 5

[0093] A low-additive migration multilayer encapsulating film differs from Example 1 in that the POE resin in the EVA / POE layer 2 is 0 parts and the glyceryl methacrylate-grafted polyolefin elastomer is 0 parts; all other conditions are the same as in Example 1.

[0094] Comparative Example 6

[0095] A low-additive migration multilayer encapsulating film differs from Example 1 in that the EVA / POE layer contains 10 parts of POE resin and 10 parts of glyceryl methacrylate-grafted polyolefin elastomer; all other conditions are the same as in Example 1.

[0096] Comparative Example 7

[0097] A low-additive migration multilayer encapsulating film, differing from Example 1 in that the POE resin in the EVA / POE blend layer 2 is replaced with HDPE resin (density 0.949 g / cm³). 3 The melt flow index was 6 g / 10 min (230℃, 2.16 kg), meaning the blended layer was an EVA / HDPE blended layer; all other conditions were the same as in Example 1.

[0098] Performance testing

[0099] The multilayer encapsulating films prepared in Example 1 and Comparative Examples 1-7 of this invention were subjected to relevant performance tests, and the test methods are as follows:

[0100] (1) Light transmittance: Take a multi-layer encapsulation film with a size of 50mm×50mm, and stack it from bottom to top in the following order: front panel material, non-adhesive film, adhesive film, non-adhesive film, and back panel material. Place the front panel down into the vacuum laminator and cure and crosslink it according to the curing temperature and time required by the product. Then take it out and place it in a desiccator to cool to room temperature for later use. The sample taken from the non-adhesive film should have flat upper and lower surfaces and uniform thickness. There should be no less than 3 samples in each group. Test the samples according to the spectrophotometer method of GB / T2410-2008. Set the wavelength range of the spectrophotometer to 290nm~1100nm. Calculate the average light transmittance of the wavelength ranges of 290nm~380nm and 380nm~1100nm respectively. Test at least 3 samples in each group and take the average value of the test results.

[0101] (2) Crosslinking degree: The film is subjected to hot-press crosslinking (hot-pressing temperature 148℃, hot-pressing time 400s). After the crosslinking reaction occurs, xylene extraction is used to determine the crosslinking degree. The film is cut into 1mm pieces, weighed as m0, placed in a stainless steel mesh bag, and immersed in boiling xylene for 4h. The uncrosslinked film will be extracted into xylene, and the undissolved part is the crosslinked film m1. Crosslinking degree = crosslinked film m1 / total weight of film m0 × 100%.

[0102] (3) Peel force test:

[0103] Sample preparation: ① Prepare two pieces of adhesive film, one piece of glass, and one flexible backing plate, each with a size of 300mm×100mm; ② Stack the glass / adhesive film (two pieces) / flexible backing plate in sequence, place them in a vacuum laminator, and laminate them according to the temperature and time required by the product. The adhesive film in the laminated sample should be free of air bubbles. Prepare 3 samples; ③ Cut the flexible backing plate / adhesive film layer into samples with a width of 10mm±0.5mm every 5mm in the width direction for testing the peel force between the adhesive film and the glass.

[0104] Test procedure: The peel force F between the glass and the film was measured on a tensile testing machine at a tensile speed of 100 mm / min ± 10 mm / min, according to the test method of GB / T2790-1995.

[0105] (4) Volume resistivity test:

[0106] Take a piece of adhesive film with a size of 100mm×100mm and cure it for cross-linking at the curing temperature (148℃) and time (400s) required by the product. The surface of the cured adhesive film should be flat and free of bubbles and impurities. Prepare 3 samples. Test the volume resistivity of the samples according to the provisions of GB / T1410-2006. Test 3 samples and take the average value of the results.

[0107] (5) Maximum torque value (MH value) test

[0108] Sample preparation: Remove the POE layer of the film, take two 10cm×10cm sample films, cut them into several pieces of prototype sample film with a radius of 1.5cm (the film weight is about 3.0g), and place a high temperature resistant film on the top and bottom of the sample film.

[0109] Test procedure: The sample was placed in a non-transfer self-vulcanizing instrument and tested at a test temperature of 145℃ for 900s.

[0110] The test results are shown in Table 1:

[0111] Table 1 Performance characterization data of multilayer encapsulating films

[0112]

[0113] The comparison of the effects of Example 1 and Comparative Examples 1-4 shows that, under the same formulation system, the POE layer with low additive migration rate has a larger MH value. The MH value change rate of the POE layer after optimization of parameters such as POE resin molecular weight and insertion rate is significantly reduced compared with the unoptimized one. Therefore, the method provided by the present invention has a good improvement on the additive migration problem of multilayer films.

[0114] A comparison of the effects of Example 1 and Comparative Examples 5-7 shows that the rate of change of MH value of the multilayer film with an outer layer of EVA / POE blend and compatibilizer is significantly lower than that of the POE layer films without compatibilizer or with other blended materials. Furthermore, the laminated film exhibits higher peel strength, crosslinking degree, light transmittance, and volume resistivity.

[0115] In summary, this invention improves the problem of additive migration while ensuring the overall performance of the encapsulant film, providing a more reliable material selection solution for photovoltaic module encapsulation.

[0116] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-additive migration multilayer encapsulating film, characterized in that, Includes a POE layer and an EVA / POE blend layer disposed on one or both sides of the POE layer; The POE layer comprises POE resin, primary crosslinking agent, secondary crosslinking agent, and silane coupling agent; The components of the EVA / POE blend layer include EVA resin, POE resin, acrylate, compatibilizer, main crosslinking agent, co-crosslinking agent, silane coupling agent and antioxidant; The POE resin is copolymerized from ethylene and an α-olefin, wherein the α-olefin is one or more selected from 1-butene, 1-octene, and 1-hexene; the α-olefin insertion rate of the POE resin is 10-30 wt%; the melt index of the POE resin measured at 190°C and a load of 2.16 kg is 2-20 g / 10 min; the number-average molecular weight of the POE resin is 100,000-250,000 g / mol; the molecular weight distribution index of the POE resin is 2-4; and the density of the POE resin is 0.6-0.9 g / cm³. 3 .

2. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The acrylate is one or more of the following: 1,6-hexanediol diacrylate, ethoxylated 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, 2-methyl-1,3-propanediol diacrylate, ethoxylated 2-methyl-1,3-propanediol diacrylate, and ethoxylated trimethylolpropane triacrylate.

3. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The compatibilizer is one or more of the following: styrene-grafted polyethylene, styrene-grafted polypropylene, maleic anhydride-grafted acrylonitrile-butadiene-styrene polymer, maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyolefin elastomer, glycidyl methacrylate-grafted polyolefin elastomer, and ethylene-acrylic acid copolymer.

4. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The main crosslinking agent is one or more of the following: tert-butylperoxy-2-ethylhexane carbonate, tert-amylperoxy-2-ethylhexane carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, dicumyl peroxide, bis-tert-butylperoxyisopropylbenzene, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. And / or, the co-crosslinking agent is one or more of triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and diallyl 1,2-phthalate.

5. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltri(2-methoxyethoxy)silane.

6. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The antioxidant is one or more of the following: β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxyanisole, dilauryl thiodipropionate, 1,6-hexanediol-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate diester, triethylene glycol-bis-3-(2-tert-butyl-4-hydroxy-5-methyl-phenyl)acrylic acid, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dodecanol thiodipropionate, triphenyl phosphite, pentaerythritol phosphate, trinonylphenyl phosphite, and diphenyl-octyl phosphite.

7. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The POE layer comprises, by weight, the following components: 100 parts of POE resin; 0.3-1 part of the main crosslinking agent; 0.5-1.1 parts of crosslinking agent; 0.3 to 0.8 parts of silane coupling agent.

8. The low-additive migration multilayer encapsulating film according to claim 1, characterized in that, The composition of the EVA / POE blend layer, by weight, includes: 100 parts of EVA resin; 1-20 parts of POE resin; Acrylic ester 0.6~0.8 parts; 1-20 parts compatibilizer; 0.6 to 1 part of main crosslinking agent; 0.5-1.1 parts of crosslinking agent; 0.6-0.8 parts of silane coupling agent; Antioxidant 0.05~3 parts.

9. A method for preparing a low-additive migration multilayer encapsulating film according to any one of claims 1 to 8, characterized in that, Includes the following steps: POE layer mixture and EVA / POE blend layer mixture were prepared separately. Using the POE layer mixture and the EVA / POE blend mixture as raw materials, a multilayer structure is prepared to obtain a low-additive migration multilayer encapsulation film.

10. A cross-linked cured encapsulating film, characterized in that, The cross-linked cured encapsulating film is the product of cross-linking treatment of the low-additive migration multilayer encapsulating film according to any one of claims 1 to 8 or the low-additive migration multilayer encapsulating film prepared by the preparation method according to claim 9.

Images