Novel EVA (Ethylene Vinyl Acetate Copolymer) adhesive film capable of resisting potential-induced degradation and preparation method thereof

Abstract

According to the novel anti-potential-induced-degradation EVA adhesive film and the preparation method thereof provided by the invention, the alkaline fragment is grafted into the EVA resin to play a role in absorbing acetic acid, and the EVA adhesive film prepared by using the method can solve the problems that the light transmittance is reduced and the like due to the addition of an inorganic salt type anti-potential-induced-degradation auxiliary agent in a traditional adhesive film. The preparation process comprises the following steps: a) under the action of an initiator, grafting EVA resin and an amino-containing olefin derivative to obtain modified EVA resin; and b) mixing and curing the modified EVA resin, an initiator, an assistant crosslinker, an antioxidant, an anti-ultraviolet aid and the like, and carrying out casting extrusion to obtain the packaging adhesive film. The test result shows that the vulcanization performance, the mechanical property and the optical property of the light conversion adhesive film all meet the industrial standard, the basic group is connected into the resin in a chemical bonding mode, an anti-potential-induced-degradation auxiliary does not need to be additionally added, and the light conversion adhesive film does not migrate and is easy to process.

Description

Technical Field

[0001] The invention relates to the technical field of EVA photovoltaic adhesive films, in particular to the technical field of EVA adhesive films resistant to potential induced attenuation, and belongs to the category of photovoltaic packaging materials. Background Art

[0002] In recent years, the photovoltaic industry has developed rapidly in the world, and my country has developed particularly rapidly. Since 2008, the output has ranked first in the world. However, the current industrialized photovoltaic conversion efficiency of solar cells has stagnated at 24% to 25%, and it is difficult to continue to improve. How to improve the photovoltaic conversion efficiency of photovoltaic cells has become one of the focuses of the world photovoltaic industry. According to theoretical calculations, the power generation efficiency of solar cells can reach 26.8% to 30%. These losses are partly due to the natural limitations of photovoltaic conversion. In addition to factors such as pn junction dark current loss and temperature (the efficiency of the cell decreases linearly with temperature), the most prominent are two interrelated factors: ① the inherent spectrum of the sun; ② the inherent bandgap width of the semiconductor material. These two factors jointly determine that the wavelength of light waves less than the minimum absorption limit, the part of its photon energy greater than the bandgap width is generally released through thermal vibration, that is, heat is generated rather than photoelectric conversion, and the wavelength of light waves greater than the maximum absorption limit is completely ineffective for photovoltaic power generation. At present, although the ultraviolet rays with a wavelength of 300 to 400nm in the cell can be partially absorbed and converted, the efficiency is not ideal.

[0003] However, the long-term reliable and stable operation of crystalline silicon solar cell modules faces a severe challenge, namely the PID effect (potential induced decay). The PID effect can cause the output power of solar cell modules to decay by 20%, and in severe cases, by more than 50%. The real cause of the PID effect is still inconclusive. It is generally believed that it is related to batteries, glass, film, temperature, humidity and voltage. Under the PID test environment of 85°C, RH85%, and bias 1000V, when using EVA film, moisture penetrates and diffuses into the encapsulation film, causing the ester bonds in the EVA molecules to hydrolyze and produce free-moving acetic acid (CH 3 COOH), acetic acid reacts with sodium compounds on the surface of glass containing silicate components to precipitate sodium ions. Under the action of an external electric field, the sodium ions move to the surface of the battery and are enriched in the anti-reflection layer, increasing the leakage current and causing the Voc, Isc, FF and Pmax of the component to decay.

[0004] In order to reduce the occurrence of PID and its impact on component performance, adding acid-absorbing components to the film to inhibit the PID phenomenon is the mainstream solution in the industry. Inorganic substances such as magnesium salts or alkaline organic substances are often used in reports, but they are all added to the formula by external addition. Although inorganic particles can effectively absorb acetic acid, they will significantly affect the transmittance of the film, thereby affecting the battery power. Multiple reports show that when more than 0.1% of inorganic salts are added, the transmittance of the film in the long-wave region will decrease by 1-2%, and the decrease will be more obvious when more is added. In other words, the anti-PID performance must be improved by sacrificing battery power, which is something the industry does not want to see. Therefore, it is of great significance to develop a type of EVA film that takes into account both high anti-PID characteristics and high transmittance. Summary of the invention

[0005] The present invention provides an EVA film resistant to potential induced decay and a preparation method thereof. The photovoltaic film prepared by the method can solve the problem that a large amount of anti-PID additives are added to the traditional EVA film, resulting in increased cost and decreased light transmittance, while not affecting key indicators such as vulcanization efficiency, mechanical properties, and aging properties.

[0006] The preparation process comprises: a) grafting EVA resin with an olefin derivative containing an amino group under the action of a grafting initiator to obtain a modified EVA resin; b) mixing and aging the modified EVA resin with a cross-linking initiator, a co-cross-linking agent, an antioxidant, a coupling agent, an anti-ultraviolet auxiliary agent, etc., and then casting and extruding to obtain an EVA film resistant to potential induced decay.

[0007] The test results show that the vulcanization properties, mechanical properties and aging properties of the light-converting adhesive film all meet industry standards. The acid-absorbing groups are connected to the resin through chemical bonding, do not migrate, have long-term anti-PID properties, and are low in cost.

[0008] An EVA film resistant to potential induced decay, wherein the EVA resin is characterized in that it is a random or block polymer obtained by polymerization of ethylene and vinyl acetate, has a molecular weight Mw between 30,000 and 250,000, a PDI of 1.5-3, an MFR of 1 to 50 g / 10 minutes, preferably 10 to 30 g / 10 minutes, measured under the conditions of 190°C and 2.16 kg load, and a density of 0.85 to 0.95 g / cm 3 ; Vinyl acetate content 10-45wt%, preferably vinyl acetate content 20-35%; body resistance 10 13 -10 16 Ω·cm.

[0009] The olefin derivatives containing amine groups further include the following structures:

[0010]

[0011] It should be pointed out that for ordinary technicians in this field, without departing from the method of the present invention, appropriate derivation of the above structure should also be regarded as within the scope of protection of the present invention.

[0012] The added amounts of the substances in the grafting reaction are as follows: 100 parts of EVA resin; 1-5 parts of amine-containing olefin derivatives; and 0.1-1 parts of grafting initiator.

[0013] The cross-linking initiator in the EVA film further described as being resistant to potential induced degradation is a peroxide compound, including but not limited to one or more of the following: 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxycarbonic acid-2-ethylhexyl ester, 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-amyl peroxy 2-ethylhexyl carbonate, tert-amyl peroxy carbonate, tert-butyl peroxy 3,3,5-trimethylhexanoate, tert-butyl peroxy isopropyl carbonate, and tert-butyl peroxy 2-ethylhexyl carbonate. Based on 100 parts by weight of the base resin, the amount of the crosslinking agent is 0.1-5 parts by weight, preferably 0.5-2 parts by weight.

[0014] Further, the auxiliary crosslinking agent is one or more of multifunctional acrylate substances, including but not limited to one or more of the following: trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanuric acid triacrylate, ethoxylated trimethylolpropane triacrylate, 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, 2-butyl-2-ethyl-1,3-propanediol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate. Based on 100 parts by weight of the base resin, the amount of the auxiliary crosslinking agent is 0.1-5 parts by weight, preferably 0.1-2 parts by weight.

[0015] Further, the coupling agent is a silane coupling agent, including but not limited to one or more of the following: γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidyloxypropyltrimethoxysilane, 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate, anilinemethyltriethoxysilane, octyltrimethoxysilane. Based on 100 parts by weight of the base resin, the amount of the coupling agent is 0.1-3 parts by weight, preferably 0.1-0.6 parts by weight.

[0016] Furthermore, the antioxidant is one or more of the hindered phenol or phosphate antioxidants, including but not limited to one or more of the following: β-[3,5-di-tert-butyl-4-hydroxyphenyl] propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, bis(3,5-di-tert-butyl-4-hydroxypropionyl)hydrazine, 2,2'-oxalyl-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)] propionate, N,N'-hexamethylenebis(3,5-di-tert-butyl The antioxidant is preferably selected from the group consisting of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylpropionamide), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione, triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 4,6-bis(octylthiomethyl)-o-cresol, 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 diphosphate. Based on 100 parts by weight of the base resin, the amount of the antioxidant is 0.01-1 parts by weight, preferably 0.05-0.5 parts by weight.

[0017] Compared with the preparation process of traditional anti-PID EVA film, the present invention introduces acid-absorbing groups into the resin by chemical bonding, without the need to add external anti-PID additives, thereby solving the problem of decreased light transmittance caused by the addition of anti-PID additives. The light conversion agent is introduced into the resin by chemical bonding, does not migrate, and has a long service life. The vulcanization performance, mechanical properties, and aging properties of the film all meet industry standards. DETAILED DESCRIPTION

[0018] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0019] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. In this application, "parts" and "%" are by weight unless otherwise specified.

[0020] Preparation Example 1

[0021] A method for preparing a novel EVA film resistant to potential induced degradation is carried out according to the following steps: EVA resin, an olefin derivative A containing an amino group and a grafting initiator are mixed in a mixer according to a proportion for 120 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain grafted EVA-1.

[0022] The antioxidant, coupling agent, anti-ultraviolet additive, crosslinking initiator and co-crosslinking agent are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to the grafted EVA-1 and mixed at a high speed for 6-12 hours until the additives are completely absorbed.

[0023] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0024] Preparation Example 2

[0025] A preparation method of a novel EVA film resistant to potential induced degradation is carried out according to the following steps: EVA resin, an olefin derivative B containing an amino group and a grafting initiator are mixed in a mixer according to a proportion for 120 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain grafted EVA-2.

[0026] The antioxidant, coupling agent, anti-ultraviolet additive, crosslinking initiator and auxiliary crosslinking agent are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to the grafted EVA-2 and mixed at a high speed for 6-12 hours until the additives are completely absorbed.

[0027] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0028] Preparation Example 3

[0029] A method for preparing a novel EVA film resistant to potential induced degradation is carried out according to the following steps: EVA resin, an olefin derivative C containing an amino group and a grafting initiator are mixed in a mixer according to a proportion for 120 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain grafted EVA-3.

[0030] The antioxidant, coupling agent, anti-ultraviolet additive, crosslinking initiator and co-crosslinking agent are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to the grafted EVA-3 and mixed at a high speed for 6-12 hours until the additives are completely absorbed.

[0031] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0032] Preparation Example 4

[0033] A preparation method of a novel EVA film resistant to potential induced degradation is carried out according to the following steps: EVA resin, an olefin derivative D containing an amino group and a grafting initiator are mixed in a mixer according to a proportion for 120 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain grafted EVA-4.

[0034] The antioxidant, coupling agent, anti-ultraviolet additive, crosslinking initiator and auxiliary crosslinking agent are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to the grafted EVA-4 and mixed at a high speed for 6-12 hours until the additives are completely absorbed.

[0035] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0036] Comparative Example 1

[0037] The antioxidant, coupling agent, anti-ultraviolet additive, cross-linking initiator, co-cross-linking agent and anti-PID additive are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to conventional photovoltaic EVA resin and mixed at high speed for 6-12 hours until the additives are completely absorbed.

[0038] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0039] Comparative Example 2

[0040] The antioxidant, coupling agent, anti-ultraviolet additive, cross-linking initiator, co-cross-linking agent and anti-PID additive are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed additives to 1-300 mPa·s; the mixed additives are added to the conventional photovoltaic POE resin and mixed at a high speed for 6-12 hours until the additives are completely absorbed.

[0041] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-120℃, and the film is pulled into the embossing roller for pressing to form patterns. After cooling and shaping, it is slit and rolled up, and packaged into finished products as required.

[0042] Test results:

[0043]

[0044]

[0045] Through characterization data and application data, it can be found that the anti-potential induced decay EVA film prepared by this technology can achieve high anti-PID effect by connecting acid-absorbing fragments without adding anti-PID additives, solving the problem of decreased absorbance caused by adding PID additives, improving battery power, and has excellent anti-PID performance, even close to the level of POE; the film's peel strength, tensile strength and other mechanical performance indicators are excellent and stable.

Claims

1. A method for preparing a novel EVA film resistant to potential induced degradation, Features: The steps include: a) using EVA resin and an olefin derivative containing an amine group as raw materials, and obtaining an EVA grafted resin under the action of a grafting initiator; b) mixing the EVA grafted resin with a cross-linking initiator, a co-cross-linking agent, an antioxidant, a coupling agent, an anti-ultraviolet additive, etc., and aging the mixture, and then casting and extruding the mixture to obtain a packaging film.

2. The method for preparing the novel EVA film resistant to potential induced degradation as claimed in claim 1, Features: The EVA resin is a random or block polymer obtained by polymerization of ethylene and vinyl acetate, with a molecular weight Mw between 30,000 and 250,000, a PDI of 1.5-3, an MFR of 1 to 50 g / 10 minutes measured at 190°C and a load of 2.16 kg, and a density of 0.85-0.95 g / cm 3 , vinyl acetate content 10-45wt%.

3. The method for preparing the novel EVA film resistant to potential induced degradation as claimed in claim 1, Features: The olefin derivatives containing amine groups include the following structures:

4. The method for preparing the novel EVA film resistant to potential induced degradation as claimed in claim 1, Features: a) The addition amounts of the substances in step a) are as follows: 100 parts of EVA resin; 1-5 parts of olefin derivatives containing amino groups; Grafting initiator 0.1-1 part.

5. The method for preparing the novel EVA film resistant to potential induced degradation as claimed in claim 1, Features: b) The antioxidant in step is one or more of an ultraviolet absorber and an anti-thermal aging decomposition agent, preferably one or more of antioxidant 1010, antioxidant 770 and antioxidant 4720; The coupling agent is an organic silicon compound containing two groups of different chemical properties in the molecule, preferably including one or more of vinyl triacetoxysilane and γ-methacryloxypropyl trimethoxysilane; The cross-linking initiator includes one or more of diisopropylbenzene peroxide, tert-butyl peroxy-2-ethylhexyl carbonate and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; the auxiliary cross-linking agent includes one or more of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate.

6. The method for preparing the novel EVA film resistant to potential induced degradation as claimed in claim 1, Features: b) The addition amount of each component in the step is as follows:

7. The method for preparing the novel EVA film resistant to potential induced degradation according to claim 1, Features: The following steps are involved: The raw materials are pre-mixed and allowed to stand before entering a tape casting machine, where they are extruded, cast into film, cooled, slit, and rolled up to form an adhesive film for photovoltaic modules.

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