Preparation method of photovoltaic packaging adhesive film with good compatibility with auxiliaries and potential-induced degradation resistance

Abstract

The invention discloses a preparation method of a photovoltaic package with good compatibility with auxiliaries and resistance to potential-induced degradation. The preparation method comprises the following steps: grafting low-density polyethylene with a melting point range of 80-110 DEG C with polyvinyl ether or polyallyl ether to form adhesive film matrix resin; and then the matrix resin and an adhesive film auxiliary agent are subjected to the processes of premixing, melt extrusion, film casting, cooling, slitting, rolling and the like to prepare the adhesive film. According to the invention, the polar fragments are connected into the polyolefin resin, so that the absorption efficiency and the migration resistance of the auxiliary agent are improved, the peel strength and the light transmittance are improved, the polar fragments cannot be decomposed to generate acid, the content of acetic acid and the ion mobility are reduced from the source, the passivation phenomenon caused by an anti-reflection layer of a battery piece is weakened or even eliminated, and the service life of the battery piece is prolonged. And the adhesive film has excellent potential-induced degradation resistance.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic adhesive films, and in particular to a photovoltaic encapsulation adhesive film with good compatibility with auxiliary agents and resistance to potential induced attenuation, belonging to the category of photovoltaic encapsulation materials. Background Art

[0002] Solar energy is an inexhaustible renewable energy source with excellent characteristics such as cleanliness, high efficiency, green environmental protection and pollution-free. It uses the photovoltaic effect to convert solar energy into electrical energy, benefiting human life and economic development. The long-term reliable and stable operation of solar panels has long-term strategic significance for sustainable development.

[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, preventing water vapor from entering photovoltaic modules through packaging materials and reducing the mobility of sodium ions at a high temperature of 85°C are effective solutions. People began to use polyolefin materials such as POE as adhesive films, which can solve the various problems of EVA to a certain extent. However, due to the limitations of polymer structure, polyolefin materials bring new problems, such as poor absorption of additives, low processing efficiency, and low peel strength. Therefore, it is of great significance to develop a type of packaging material that can take into account the advantages of EVA and POE adhesive films and avoid most of their shortcomings.

[0005] A patent discloses that EVA and POE or other vinyl polymers are blended or grafted to prepare a film, which can take into account the advantages of both to a certain extent. However, there are still EVA fragments in this type of resin, which fails to completely solve the problem. There are also reports proposing the use of DuPont ionic polymers to prepare PID protective films. The PID protective film is prepared based on ionic polymer technology that has been verified by the performance of crystalline silicon modules for more than 15 years. It is used to replace the POE film and placed between the EVA film and the glass. It can effectively block the migration of sodium ions to the surface of the battery and completely solve the PID problem. However, the material is expensive, which limits its promotion in the market. Therefore, current solutions are difficult to achieve large-scale industrial application. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a photovoltaic encapsulation film with good compatibility with additives and resistance to potential induced decay. Polar fragments are introduced into polyethylene through a grafting process, and at the same time, groups that are easily hydrolyzed and produce acid are not contained. The encapsulation film prepared by this method can take into account the good adjuvant absorption and processing performance of EVA film and the anti-PID performance of POE film, while avoiding the problems of easy acid precipitation of EVA film and poor processing performance of POE film, and also has good light transmission and vulcanization performance. Its preparation process includes: a) using low-density polyethylene with a melting point range of 80 to 110°C and polyvinyl ether or polyallyl ether as raw materials, grafting under the action of an initiator to obtain a film matrix resin; b) mixing and aging the film matrix resin with an initiator, a co-crosslinking agent, a silane coupling agent, an antioxidant, etc., and then casting and extruding to obtain a film. The test results show that the film additive has high absorption efficiency, easy processing, fast vulcanization speed, low water permeability, and its mechanical and optical properties meet industry standards. It also has good anti-PID performance and takes into account the characteristics of both EVA and POE.

[0007] A photovoltaic encapsulation adhesive film with good compatibility with additives and resistance to potential induced degradation, wherein the low-density polyethylene is a polymer obtained by a high-pressure process of ethylene and comonomers such as butene-1, pentene-1, and hexene-1, and has a molecular weight Mw of 50,000 to 150,000, a PDI of 1.5 to 3, and 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; a comonomer content of 5 to 20 wt%, preferably 5 to 10%; and a density of 0.90 to 0.95 g / cm 3 , body resistance is 10 16 -10 18 Ω·cm.

[0008] The polyvinyl ether or polyallyl ether further includes polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl butyl ether, polyvinyl tert-butyl ether, polyallyl methyl ether, polyallyl ethyl ether, polyallyl butyl ether and polyallyl tert-butyl ether.

[0009] The molecular weight Mw of the polyvinyl ether or polyallyl ether is between 10,000 and 150,000, the PDI is 1.5-4, the MFR measured at 190°C and 2.16 kg load is 1-50 g / 10 minutes, and the density is 0.85-1.0 g / cm 3 .

[0010] Furthermore, the added amounts of various substances in the grafting reaction are respectively: 60-85 parts of low-density polyethylene, 15-40 parts of polyvinyl ether or polyallyl ether, and 0.1-1 parts of grafting initiator, in parts by mass.

[0011] The crosslinking initiator in the photovoltaic encapsulation film with good compatibility of the auxiliary agent and resistance to potential induced degradation is a peroxide compound, including but not limited to one or more of the following: 1,1-bis (tert-butyl peroxy) -3,3,5-trimethylcyclohexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 1,1-bis (tert-amyl peroxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5- (bis-tert-butyl peroxy) )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 carbonate isopropyl, tert-butyl peroxy 2-ethylhexyl carbonate. The amount of the crosslinking initiator is 0.1-5 parts by weight. Preferably, it is 0.5-2 parts by weight.

[0012] 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.

[0013] Further, the coupling agent is a silane coupling agent, including but not limited to one or more of the following: vinyl trimethoxysilane, γ-chloropropyl methoxysilane, vinyl ethoxysilane, vinyl tri(β-methoxyethoxy) silane, γ-methacryloxypropyl trimethoxysilane, vinyl triacetoxysilane, γ-glycidyl ether oxypropyl trimethoxysilane, 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate, aniline methyl triethoxysilane, octyl trimethoxysilane. The amount of the coupling agent is 0.1-3 parts by weight, preferably 0.1-0.6 parts by weight.

[0014] Furthermore, the antioxidant is one or more of hindered phenol or phosphate antioxidants, including but not limited to one or more of the following: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, N,N'-di-sec-butyl-1,4-phenylenediamine, β-[3,5-di-tert-butyl-4-hydroxyphenyl]propionic acid n-octadecyl ester, tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester, bis(3,5-di-tert-butyl-4-hydroxypropionyl)hydrazine, 2,2'-oxalyl-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionic acid Acid ester, N,N'-hexamethylenebis(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, 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.

[0015] The preparation of the photovoltaic encapsulation film with good compatibility of the additive and resistance to potential induced degradation further comprises the following steps: the raw materials are pre-mixed, placed in a static state, and then enter a casting machine, and are prepared into a film for photovoltaic modules through extrusion, casting film, cooling, slitting and winding processes. Compared with the traditional film, the present invention improves the absorption efficiency and migration resistance of the additive by introducing polar fragments into the polyolefin resin, and at the same time improves the peel strength and light transmittance. Such polar fragments will not decompose to produce acid, which reduces the acetic acid content and ion mobility from the source, weakens or even eliminates the passivation phenomenon caused by the anti-reflection layer of the battery cell, and the film has excellent resistance to potential induced degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the molecular formula structure of polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl butyl ether, polyvinyl tert-butyl ether, polyallyl methyl ether, polyallyl ethyl ether, polyallyl butyl ether and polyallyl tert-butyl ether. DETAILED DESCRIPTION

[0017] The technical scheme in the embodiments of the present invention is further described in detail below in conjunction with the accompanying drawings. The present invention is further described below through specific embodiments, which are only used as illustrations of the present invention and do not limit the scope of the present invention.

[0018] 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.

[0019] Preparation Example 1

[0020] A method for preparing a photovoltaic encapsulation film with good compatibility of auxiliary agents and resistance to potential induced degradation is carried out according to the following steps: low-density polyethylene with a melting point of 100°C, polyvinyl ethyl ether, and a grafting initiator are mixed in a mixer according to a proportion for 90 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain a film matrix resin-1.

[0021] The auxiliary cross-linking agent, silane coupling agent, antioxidant and cross-linking initiator are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed auxiliary agents to 1-300 mPa·s; the mixed auxiliary agents are added to the film matrix resin-1 and mixed at a high speed for 6-12 hours until the auxiliary agents are completely absorbed.

[0022] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-110℃, 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.

[0023] Preparation Example 2

[0024] A method for preparing a photovoltaic encapsulation film with good compatibility of auxiliary agents and resistance to potential induced degradation is carried out according to the following steps: low-density polyethylene with a melting point of 105°C, polyvinyl butyl ether, and a grafting initiator are mixed in a mixer according to a proportion for 90 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain a film matrix resin-2.

[0025] The auxiliary cross-linking agent, silane coupling agent, antioxidant and cross-linking initiator are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed auxiliary agents to 1-300 mPa·s; the mixed auxiliary agents are added to the film matrix resin-2 and mixed at a high speed for 6-12 hours until the auxiliary agents are completely absorbed.

[0026] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-110℃, 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.

[0027] Preparation Example 3

[0028] A method for preparing a photovoltaic encapsulation film with good compatibility of additives and resistance to potential induced degradation is carried out according to the following steps: low-density polyethylene with a melting point of 110° C., polyallyl butyl ether, and a grafting initiator are mixed in a mixer according to a proportion for 90 minutes until they are uniform; and the mixture is put into a twin-screw extruder for grafting reaction and then granulated to obtain a film matrix resin-3.

[0029] The auxiliary cross-linking agent, silane coupling agent, antioxidant and cross-linking initiator are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed auxiliary agents to 1-300 mPa·s; the mixed auxiliary agents are added to the film matrix resin-3 and mixed at a high speed for 6-12 hours until the auxiliary agents are completely absorbed.

[0030] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-110℃, 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.

[0031] Preparation Example 4

[0032] A method for preparing a photovoltaic encapsulation film with good compatibility of auxiliary agents and resistance to potential induced degradation is carried out according to the following steps: low-density polyethylene with a melting point of 80° C., polyallyl ether, and a grafting initiator are mixed in a mixer according to a proportion for 90 minutes until they are uniform; and a twin-screw extruder is used for grafting reaction and then granulated to obtain a film matrix resin-4.

[0033] The auxiliary cross-linking agent, silane coupling agent, antioxidant and cross-linking initiator are sheared for 30 minutes by a high-speed disperser to reduce the viscosity of the mixed auxiliary agents to 1-300 mPa·s; the mixed auxiliary agents are added to the film matrix resin-4 and mixed at a high speed for 6-12 hours until the auxiliary agents are completely absorbed.

[0034] The mixed ingredients are added into the casting machine through the feeding system, extruded at 80-110℃, 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.

[0035] Test results:

[0036]

[0037] Through characterization data and application data, it can be found that the grafted resin prepared by this technology has high efficiency in absorbing additives, and the additives are not easy to precipitate. The film processing parameters are consistent with those of conventional films, and there is no need to make significant changes to the production line. Due to the addition of polyvinyl ether or polyallyl ether fragments, the mechanical properties such as peel strength are excellent and far better than conventional EVA or POE films. Under the same formula, the vulcanization speed is fast, which is consistent with EVA film and better than POE film. The anti-PID performance is consistent with that of POE film and significantly better than EVA, which takes into account the advantages of EVA and POE.

Claims

1. A method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance to potential induced degradation, Features: The steps include: a) using low-density polyethylene with a melting point range of 80 to 110° C. and polyvinyl ether or polyallyl ether as raw materials, grafting under the action of a grafting initiator to obtain a film matrix resin; b) mixing the film matrix resin with a cross-linking initiator, a co-cross-linking agent, a silane coupling agent, an antioxidant, etc., and aging the mixture, and then casting and extruding the mixture to obtain a film.

2. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance to potential induced degradation as claimed in claim 1, Features: The low-density polyethylene is a polymer obtained by high-pressure process of ethylene and butene-1, pentene-1, hexene-1, etc., with a molecular weight Mw between 50,000 and 150,000, 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 0.90-0.95 g / cm 3 .

3. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance to potential induced degradation as claimed in claim 1, Features: The polyvinyl ether or polyallyl ether includes polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl butyl ether, polyvinyl tert-butyl ether, polyallyl methyl ether, polyallyl ethyl ether, polyallyl butyl ether and polyallyl tert-butyl ether.

4. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance to potential induced degradation as claimed in claim 1, Features: The molecular weight Mw of the polyvinyl ether or polyallyl ether is between 10000 and 150000, the PDI is 1.5-4, the MFR measured at 190°C and 2.16kg load is 1-50g / 10min, and the density is 0.85-1.0g / cm 3 .

5. The method according to claim 1, wherein the amounts of the substances added in step a) are respectively: 60-85 parts of low-density polyethylene, 15-40 parts of polyvinyl ether or polyallyl ether, and 0.1-1 parts of grafting initiator, in parts by mass.

6. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance 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 silane coupling agent is an organic silicon compound containing two groups of different chemical properties in the molecule, preferably including one or more of silane coupling agent A-171 and silane coupling agent A-174; The cross-linking initiator includes one or more of diisopropylbenzene peroxide, tert-butyl peroxide-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.

7. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance to potential induced degradation as claimed in claim 1, Features: b) The addition amount of each component in the step is as follows:

8. The method for preparing a photovoltaic encapsulation film having good compatibility with additives and resistance 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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