Preparation method of POE (Polyolefin Elastomer) packaging adhesive film with high crosslinking degree and photovoltaic module

Abstract

The invention relates to the field of photovoltaic packaging adhesive films, and discloses a preparation method of a high-crosslinking-degree POE packaging adhesive film and a photovoltaic module. The preparation method comprises the following steps: mixing an ethylene-alpha olefin copolymer with an initiator, and reacting at a temperature higher than the initiation temperature of the initiator to obtain modified polyolefin resin, the initiator being at least one of dicumyl peroxide, methyl ethyl ketone peroxide and di-tert-butyl peroxide; the preparation method comprises the following steps: taking raw materials including modified polyolefin resin, a cross-linking agent and an assistant cross-linking agent, wherein the cross-linking agent is at least one of tert-amyl peroxy (2-ethylhexyl) carbonate, dicyclohexyl peroxy dicarbonate and azodiisobutyronitrile; all the raw materials are blended, extruded and molded at the temperature higher than the initiation temperature of the cross-linking agent and not higher than 110 DEG C. By adopting the preparation method disclosed by the invention, the POE packaging adhesive film can have relatively high crosslinking degree and crosslinking speed, relatively good PID (Potential Induced Degradation) resistance and long-term stability, and also can be endowed with relatively high light transmittance and relatively low haze.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic encapsulation adhesive films, and in particular to a preparation method of a high-crosslinking POE encapsulation adhesive film and a photovoltaic module. Background Art

[0002] In the photovoltaic industry, encapsulation film is one of the key materials to ensure the long-term stable operation of solar cell modules. It not only needs to protect the cells from external environmental damage, such as humidity, oxygen and extreme weather conditions, but also ensure the electrical insulation and mechanical strength between the cells, while maximizing the transmittance of sunlight to improve the overall photoelectric conversion efficiency.

[0003] Polyolefin elastomer (POE) has become one of the mainstream materials in photovoltaic encapsulation films due to its excellent weather resistance, high light transmittance and good adhesive properties. However, with the continuous advancement of photovoltaic technology and increasingly stringent market demand, the performance of traditional POE films has gradually revealed limitations, especially in terms of lower cross-linking degree than ethylene-vinyl acetate copolymer (EVA) and slower cross-linking speed.

[0004] In recent years, in order to improve the cross-linking speed and degree of cross-linking of POE encapsulation films, the industry has developed some new technical solutions. These solutions, without changing the cross-linking agent and the auxiliary cross-linking agent, introduce modified resins containing active groups, etc., so that the film can cross-link more quickly during the lamination process, thereby reducing the lamination time and improving the production efficiency of components (such as patent CN110713798A). However, this method has the problem of poor compatibility between high-active group resins and α-olefin copolymers, which limits the further improvement of the cross-linking speed and is not conducive to the improvement of the cross-linking degree. Summary of the invention

[0005] In order to solve the above technical problem, that is, the existing methods for improving the crosslinking degree and crosslinking speed of POE encapsulation film have limited effects, the present invention provides a preparation method of a high-crosslinking POE encapsulation film and a photovoltaic module. The preparation method of the present invention can make the prepared POE encapsulation film have a high crosslinking degree and crosslinking speed, give it good anti-potential induced degradation (PID) performance and long-term stability, and also make it have a high light transmittance and a low haze.

[0006] The specific technical scheme of the present invention is: In a first aspect, the present invention provides a method for preparing a high-crosslinked POE encapsulation film, comprising the following steps: S1: mixing an ethylene-α-olefin copolymer and an initiator, and reacting them at a temperature higher than the initiation temperature of the initiator to obtain a modified polyolefin resin; the initiator is at least one of dicumyl peroxide, methyl ethyl ketone peroxide and di-tert-butyl peroxide; S2: taking raw materials including a modified polyolefin resin, a crosslinking agent and a co-crosslinking agent; the crosslinking agent is at least one of tert-amyl peroxy (2-ethylhexyl) carbonate, dicyclohexyl peroxy dicarbonate and azobisisobutyronitrile; S3: All the raw materials in step S2 are blended and extruded at a temperature higher than the initiation temperature of the crosslinking agent and not higher than 110° C., and then molded to obtain a high-crosslinking POE encapsulation film.

[0007] Before the ethylene-alpha olefin copolymer is blended with a crosslinking agent and a crosslinking aid and extruded, the ethylene-alpha olefin copolymer is first reacted under the action of an initiator to form a modified polyolefin resin with a long-chain branched structure, which can increase the degree of entanglement and overlap between molecular chains, thereby facilitating further crosslinking under the action of a crosslinking agent, so that the prepared POE encapsulation film has a higher degree of crosslinking, can achieve better anti-PID performance and long-term stability, and can have a wider processing window, and improve its crosslinking speed during lamination. In addition, the use of an initiator to modify the ethylene-alpha olefin copolymer can also destroy the original crystallization of the ethylene-alpha olefin copolymer, thereby making the POE encapsulation film have a higher light transmittance and a lower haze.

[0008] The present invention adopts specific initiators and crosslinking agents in the ethylene-α-olefin copolymer modification stage and the subsequent co-blending extrusion molding stage, respectively, and can produce the following effects: in the ethylene-α-olefin copolymer modification stage (step S1), the initiator used is at least one of dicumyl peroxide, methyl ethyl ketone peroxide and di-tert-butyl peroxide, and these initiators need to be at a relatively high temperature to quickly initiate the reaction, and have a long half-life, so that the obtained modified polyolefin resin can have a lightly crosslinked and branched structure, which ensures that the POE encapsulation film has a high degree of crosslinking, and is conducive to achieving sufficient mixing at a lower temperature during the subsequent step S3 co-blending extrusion, so that the crosslinking agent, the crosslinking aid and the crosslinking agent can be effectively bonded to the ethylene-α-olefin copolymer. The crosslinking agent and other auxiliary agents contained in the raw materials can better play their roles; in the subsequent co-mixing and extrusion molding stage (step S3), the crosslinking agent used is at least one of tert-amyl peroxy (2-ethylhexyl) carbonate, dicyclohexyl peroxy dicarbonate and azobisisobutyronitrile. These crosslinking agents can initiate reactions at lower temperatures and have shorter half-lives. With the lower co-mixing and extrusion temperature in step S3 (not higher than 110°C), they can not only initiate further crosslinking reactions during the co-mixing and extrusion process in step S3, but also avoid the self-polymerization or vaporization of the auxiliary agents due to excessively high extrusion temperatures, and the failure after escaping, as well as the obstruction of the extrusion process and the impact on the product appearance after the resin undergoes gel curing. Through the above effects, the POE encapsulation film can achieve high crosslinking degree and crosslinking speed while having better anti-PID performance and long-term stability.

[0009] Preferably, step S1 comprises the following process: mixing an initiator, an ethylene-α-olefin copolymer and a solvent, and reacting them at 120-200° C. for 0.5-2 h to obtain a modified polyolefin resin.

[0010] Furthermore, during the reaction, the stirring speed is 200-500 rpm.

[0011] Furthermore, the solvent includes at least one of n-hexane, cyclohexane, n-heptane, n-octane, n-decane, benzene, toluene, xylene, methyl ethyl benzene and chlorobenzene.

[0012] Preferably, step S1 includes the following process: mixing the initiator and the ethylene-α-olefin copolymer at 150-200° C. and extruding to obtain a modified polyolefin resin.

[0013] Furthermore, the mixing and extruding process is carried out using a twin-screw extruder with a screw speed of 20-80 rpm.

[0014] Preferably, in step S1, the mass ratio of the ethylene-α-olefin copolymer to the initiator is 100:0.1-0.3.

[0015] In step S1, the above-mentioned reaction in a solvent, or mixing and extrusion can be used to achieve the modification of the ethylene-alpha olefin copolymer under the action of the initiator. During the modification process, as the amount of initiator increases and the reaction temperature increases, the degree of entanglement and overlap between the molecular chains of the modified polyolefin resin obtained can be increased, thereby increasing the crosslinking degree and crosslinking speed of the POE encapsulation film finally obtained; but when the amount of initiator is too large or the reaction temperature is too high, the modified polyolefin resin will form a crosslinked network structure with a high degree of crosslinking, which is not conducive to the subsequent step S3 co-extrusion process to achieve full mixing at a lower temperature. Based on this, the present invention controls the mass ratio of ethylene-alpha olefin copolymer to initiator at 100:0.1~0.3, and when the solvent system is used for reaction, the temperature is controlled at 120~200℃, and when the mixing and extrusion method is used for reaction, the temperature is controlled at 150~200℃, which can make the prepared POE encapsulation film better take into account the performance of crosslinking degree, crosslinking speed, light transmittance, haze, anti-PID performance and long-term stability.

[0016] Preferably, in step S2, the raw materials include the following components in parts by weight: 90-100 parts of modified polyolefin resin, 0.6-0.8 parts of cross-linking agent, and 0.5-0.7 parts of auxiliary cross-linking agent.

[0017] Furthermore, in step S2, the raw materials further include the following components in parts by weight: 1 to 10 parts of functional masterbatch and 0.1 to 0.4 parts of auxiliary agent; the auxiliary agent includes a silane coupling agent; the functional masterbatch includes a POE silane graft masterbatch and / or a POE blended light stabilizer masterbatch.

[0018] Furthermore, step S3 includes the following process: after shearing and dispersing the modified polyolefin resin, the crosslinking agent, the auxiliary crosslinking agent and the auxiliary agent, mixing with the functional masterbatch, blending and extruding at a temperature higher than the crosslinking agent initiation temperature and not higher than 110°C, and molding to obtain a high crosslinking degree POE encapsulation film.

[0019] Preferably, in step S1, the ethylene-α-olefin copolymer includes at least one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-butadiene copolymer, ethylene-isoprene copolymer, ethylene-isobutylene copolymer and ethylene-norbornene copolymer.

[0020] Preferably, in step S3, the temperature of the co-extrusion is 70-110°C.

[0021] Preferably, in step S3, the forming method is tape casting or calendering.

[0022] In a second aspect, the present invention provides a photovoltaic module, comprising a high-crosslinking POE encapsulation film prepared by the preparation method.

[0023] Preferably, the photovoltaic module comprises glass, a first packaging film, a battery cell array, a second packaging film and glass stacked in sequence; the first packaging film and / or the second packaging film is the high-crosslinking POE packaging film.

[0024] Compared with the prior art, the present invention has the following advantages: (1) The present invention first uses an initiator to modify the ethylene-α-olefin copolymer to form a modified polyolefin resin with a long-chain branched structure, which can promote further cross-linking between polyolefin molecular chains under the action of a cross-linking agent when it is subsequently blended with other raw materials for extrusion and molding, thereby making the prepared POE encapsulation film have the characteristics of high cross-linking degree, wide processing window, fast cross-linking speed, good anti-PID performance and long-term stability, and at the same time can also give it higher light transmittance and lower haze; (2) The present invention uses specific initiators and crosslinking agents in the ethylene-α-olefin copolymer modification stage and the subsequent co-blending extrusion molding stage, respectively, so that the POE encapsulation film can achieve high crosslinking degree and crosslinking speed while having better anti-PID performance and long-term stability; (3) By controlling the ratio between the ethylene-α-olefin copolymer and the initiator, as well as the reaction temperature during the modification process of the ethylene-α-olefin copolymer, the present invention can make the prepared POE encapsulation film better balance the performance of crosslinking degree, crosslinking speed, light transmittance, haze, anti-PID performance and long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Cole-Cole plot of modified polyolefin resin and ethylene-butene copolymer. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the embodiments.

[0027] A method for preparing a high-crosslinked POE encapsulation film comprises the following steps: S1: mixing an ethylene-α-olefin copolymer and an initiator, and reacting them at a temperature higher than the initiation temperature of the initiator to obtain a modified polyolefin resin; the initiator is at least one of dicumyl peroxide, methyl ethyl ketone peroxide and di-tert-butyl peroxide; S2: taking raw materials including a modified polyolefin resin, a crosslinking agent and a co-crosslinking agent; the crosslinking agent is at least one of tert-amyl peroxy (2-ethylhexyl) carbonate, dicyclohexyl peroxy dicarbonate and azobisisobutyronitrile; S3: All the raw materials in step S2 are blended and extruded at a temperature higher than the initiation temperature of the crosslinking agent and not higher than 110° C., and then molded to obtain a high-crosslinking POE encapsulation film.

[0028] As a specific embodiment, in step S1, the ethylene-α-olefin copolymer includes at least one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-butadiene copolymer, ethylene-isoprene copolymer, ethylene-isobutylene copolymer and ethylene-norbornene copolymer.

[0029] As a specific implementation, step S1 includes the following process: mixing an initiator, an ethylene-α-olefin copolymer and a solvent, reacting at 120-200° C. and 200-500 rpm for 0.5-2 hours to obtain a modified polyolefin resin; the solvent includes at least one of n-hexane, cyclohexane, n-heptane, n-octane, n-decane, benzene, toluene, xylene, methyl ethyl benzene and chlorobenzene.

[0030] As another specific implementation, step S1 includes the following process: adding an initiator and an ethylene-α-olefin copolymer into a twin-screw extruder, mixing and extruding at 150-200° C. and a screw speed of 20-80 rpm to obtain a modified polyolefin resin.

[0031] As a specific implementation, in step S1, the mass ratio of the ethylene-α-olefin copolymer to the initiator is 100:0.1-0.3.

[0032] As a specific implementation, in step S2, the raw materials include the following components in parts by weight: 90-100 parts of modified polyolefin resin, 0.6-0.8 parts of cross-linking agent, and 0.5-0.7 parts of auxiliary cross-linking agent.

[0033] As a specific implementation, in step S2, the raw materials also include the following components in parts by weight: 1 to 10 parts of functional masterbatch and 0.1 to 0.4 parts of auxiliary agent; the auxiliary agent includes a silane coupling agent; the functional masterbatch includes a POE silane graft masterbatch and / or a POE blended light stabilizer masterbatch; step S3 includes the following process: after shearing and dispersing the modified polyolefin resin, the cross-linking agent, the auxiliary cross-linking agent and the auxiliary agent, mixing them with the functional masterbatch, blending and extruding at a temperature higher than the cross-linking agent initiation temperature and not higher than 110°C, and molding, to obtain a high-cross-linking POE encapsulation film.

[0034] As a specific implementation, in step S3, the temperature of the co-extrusion is 70-110°C.

[0035] As a specific implementation, in step S3, the forming method is tape casting or calendering.

[0036] A photovoltaic component comprises a high-crosslinking POE packaging adhesive film prepared by the preparation method.

[0037] As a specific implementation, the photovoltaic module includes glass, a first packaging film, a battery cell array, a second packaging film and glass stacked in sequence; the first packaging film and / or the second packaging film is the high-crosslinking POE packaging film.

[0038] The present invention is described below by specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and the attached claims and any equivalents thereof are the protection scope of the present invention.

[0039] Example 1 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of diisopropylbenzene peroxide (half-life at 117°C is 10 hours), 50 parts of ethylene-butene copolymer, 50 parts of ethylene-octene copolymer and 1000 parts of xylene were weighed and added into a 500L closed reactor, and stirred at 150°C and 300rpm for 1 hour. Then, the xylene was evaporated and removed at a pressure of 60Pa to obtain a modified polyolefin resin.

[0040] (2) Preparation of materials: According to weight parts, 95 parts of modified polyolefin resin, 5 parts of POE silane grafted masterbatch, 0.6 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 hour), 0.5 parts of triallyl cyanurate and 0.3 parts of trimethylallyloxy silane were weighed.

[0041] (3) Preparation of premix: The modified polyolefin resin, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxy silane were added into a high-speed disperser and sheared and dispersed for 20 minutes to obtain a premix.

[0042] (4) Preparation of compound materials: The premix and the POE silane grafted masterbatch were mixed at a rotation speed of 300 rpm for 45 minutes to obtain a composite material.

[0043] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, co-extruded at 90°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.5 mm.

[0044] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0045] Example 2 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of dicumyl peroxide (half-life at 117° C. is 10 hours) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 165° C. for blending and extrusion to obtain a modified polyolefin resin.

[0046] (2) Preparation of materials: According to weight parts, 90 parts of modified polyolefin resin, 10 parts of POE silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 hour), 0.7 parts of triallyl cyanurate and 0.1 parts of trimethylallyloxy silane were weighed.

[0047] (3) Preparation of premix: The modified polyolefin resin, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxysilane were added into a high-speed disperser and sheared and dispersed for 30 minutes to obtain a premix.

[0048] (4) Preparation of compound materials: The premix and the POE silane grafted material masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0049] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, co-extruded at 95°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.4 mm.

[0050] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0051] Example 3 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of methyl ethyl ketone peroxide (half-life at 105°C is 10 hours), 50 parts of ethylene-propylene copolymer, 50 parts of ethylene-butadiene copolymer and 500 parts of n-octane were weighed and added into a 500L closed reactor, and stirred at 120°C and 500 rpm for 2 hours. Then, the n-octane was evaporated and removed at a pressure of 60 Pa to obtain a modified polyolefin resin.

[0052] (2) Preparation of materials: According to weight parts, 98 parts of modified polyolefin resin, 2 parts of POE blended light stabilizer masterbatch, 0.7 parts of benzoyl peroxide (half-life at 120° C. is 5 minutes), 0.6 parts of ethylene glycol dimethacrylate and 0.4 parts of vinyl trimethoxy silane were weighed.

[0053] (3) Preparation of premix: Add modified polyolefin resin, benzoyl peroxide, ethylene glycol dimethacrylate and vinyl trimethoxysilane into a high-speed disperser, and shear and disperse for 40 minutes to obtain a premix.

[0054] (4) Preparation of compound materials: The premix and the POE light stabilizer masterbatch were mixed at a rotation speed of 500 rpm for 45 minutes to obtain a composite material.

[0055] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 80°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is cut and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.6 mm.

[0056] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0057] Example 4 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of methyl ethyl ketone peroxide (half-life at 105° C. is 10 hours) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 160° C. for blending and extrusion to obtain a modified polyolefin resin.

[0058] (2) Preparation of materials: According to weight parts, 97 parts of modified polyolefin resin, 1 part of POE silane graft masterbatch, 2 parts of POE blended light stabilizer masterbatch, 0.6 parts of dicyclohexyl peroxydicarbonate (half-life at 110°C is 1 min), 0.6 parts of diethylene glycol dimethacrylate and 0.1 parts of vinyl trimethoxy silane were weighed.

[0059] (3) Preparation of premix: Add the modified polyolefin resin, dicyclohexyl peroxydicarbonate, diethylene glycol dimethacrylate and vinyl trimethoxysilane into a high-speed disperser, and shear and disperse for 30 minutes to obtain a premix.

[0060] (4) Preparation of compound materials: The premix and the POE silane grafted material masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0061] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, blended and extruded at 88°C, and cast into a film, and then pulled into an embossing roller and pressed to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.4 mm.

[0062] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0063] Example 5 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of methyl ethyl ketone peroxide (half-life at 105°C is 10 hours), 50 parts of ethylene-hexene copolymer, 50 parts of ethylene-norbornene copolymer and 600 parts of n-decane were weighed and added into a 500L closed reactor, and stirred at 200°C and 200rpm for reaction for 1 hour, and then the n-decane was evaporated and removed at a pressure of 60Pa to obtain a modified polyolefin resin.

[0064] (2) Preparation of materials: According to parts by weight, 100 parts of modified polyolefin resin, 0.6 parts of azobisisobutyronitrile (half-life at 100° C. is 10 min), 0.5 parts of triallyl isocyanurate and 0.2 parts of γ-methacryloxypropyltrimethoxysilane were weighed.

[0065] (3) Preparation of mixed materials: Add modified polyolefin resin, azobisisobutyronitrile, triallyl isocyanurate and γ-methacryloxypropyltrimethoxysilane into a high-speed disperser, and shear and disperse for 1 hour to obtain a mixture.

[0066] (4) Extrusion molding: The mixed material is injected into a single-screw extruder through a feeding system, blended and extruded at 100°C, and cast into a film, and then pulled into an embossing roller and pressed to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.3 mm.

[0067] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0068] Example 6 The POE encapsulation film of this embodiment is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.3 parts of di-tert-butyl peroxide (half-life at 115° C. is 34 hours) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 150° C. for blending and extrusion to obtain a modified polyolefin resin.

[0069] (2) Preparation of materials: According to weight parts, 97 parts of modified polyolefin resin, 1 part of POE silane graft masterbatch, 2 parts of POE blended light stabilizer masterbatch, 0.6 parts of azobisisobutyronitrile (half-life at 120°C is 2 minutes), 0.6 parts of diethylene glycol dimethacrylate and 0.1 parts of vinyltrimethoxysilane were weighed.

[0070] (3) Preparation of premix: Add modified polyolefin resin, azobisisobutyronitrile, diethylene glycol dimethacrylate and vinyltrimethoxysilane into a high-speed disperser, and shear and disperse for 30 minutes to obtain a premix.

[0071] (4) Preparation of compound materials: The premix, POE silane grafted masterbatch and POE blended light stabilizer masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0072] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, blended and extruded at 85°C, and cast into a film, and then pulled into an embossing roller and pressed to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this embodiment with a thickness of 0.4 mm.

[0073] The POE encapsulation film prepared in this embodiment is used to assemble a photovoltaic module with the following structure: glass, a first encapsulation film, a battery cell array, a second encapsulation film and glass are stacked in sequence, and both the first encapsulation film and the second encapsulation film are made of the POE encapsulation film prepared in this embodiment.

[0074] Comparative Example 1 This comparative example is an EVA encapsulation film, which differs from Example 2 only in that the modified polyolefin resin is replaced by ethylene-vinyl acetate copolymer in this comparative example, and the rest of the raw materials and steps are the same as those in Example 2. Specifically, the EVA encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of materials: According to weight parts, 90 parts of ethylene-vinyl acetate copolymer, 10 parts of EVA silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 h), 0.7 parts of triallyl cyanurate and 0.1 parts of trimethylallyloxy silane were weighed.

[0075] (2) Preparation of premix: Ethylene-vinyl acetate copolymer, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxy silane were added into a high-speed disperser and sheared and dispersed for 30 minutes to obtain a premix.

[0076] (3) Preparation of compound materials: The premix and the EVA silane grafted masterbatch were mixed at a rotation speed of 400 rpm for 50 min to obtain a composite material.

[0077] (4) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, co-extruded at 95°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the EVA packaging film of this comparative example with a thickness of 0.4 mm.

[0078] Comparative Example 2 The difference between this comparative example and Example 2 is that the modified polyolefin resin is replaced by ethylene-butene copolymer in this comparative example, and the other raw materials and steps are the same as those in Example 2. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of materials: According to weight parts, 90 parts of ethylene-butene copolymer, 10 parts of POE silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 hour), 0.7 parts of triallyl cyanurate and 0.1 parts of trimethylallyloxy silane were weighed.

[0079] (2) Preparation of premix: Ethylene-butene copolymer, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxysilane were added into a high-speed disperser and sheared and dispersed for 30 minutes to obtain a premix.

[0080] (3) Preparation of compound materials: The premix and the POE silane grafted material masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0081] (4) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 95°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.4 mm.

[0082] Comparative Example 3 The difference between this comparative example and Example 1 is that the modified polyolefin resin is replaced by ethylene-butene copolymer and ethylene-octene copolymer in this comparative example, and the other raw materials and steps are the same as those in Example 1. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of materials: According to weight parts, 47.5 parts of ethylene-butene copolymer, 47.5 parts of ethylene-octene copolymer, 5 parts of POE silane grafted masterbatch, 0.6 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116°C is 1h), 0.5 parts of triallyl cyanurate and 0.3 parts of trimethylallyloxy silane were weighed.

[0083] (2) Preparation of premix: Ethylene-butene copolymer, ethylene-octene copolymer, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxy silane were added into a high-speed disperser and sheared and dispersed for 20 minutes to obtain a premix.

[0084] (3) Preparation of compound materials: The premix and the POE silane grafted masterbatch were mixed at a rotation speed of 300 rpm for 45 minutes to obtain a composite material.

[0085] (4) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 90°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.5 mm.

[0086] Comparative Example 4 The difference between this comparative example and Example 1 is that the modified polyolefin resin is replaced by ethylene-butene copolymer and ethylene-octene copolymer, and the amount of crosslinking agent and auxiliary crosslinking agent is increased, and the rest of the raw materials and steps are the same as those in Example 1. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of materials: According to weight parts, 47.5 parts of ethylene-butene copolymer, 47.5 parts of ethylene-octene copolymer, 5 parts of POE silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116°C is 1h), 0.7 parts of triallyl cyanurate and 0.3 parts of trimethylallyloxy silane were weighed.

[0087] (2) Preparation of premix: Ethylene-butene copolymer, ethylene-octene copolymer, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxy silane were added into a high-speed disperser and sheared and dispersed for 20 minutes to obtain a premix.

[0088] (3) Preparation of compound materials: The premix and the POE silane grafted masterbatch were mixed at a rotation speed of 300 rpm for 45 minutes to obtain a composite material.

[0089] (4) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 90°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.5 mm.

[0090] Comparative Example 5 The difference between this comparative example and Example 2 is that the initiator diisopropylbenzene peroxide is replaced by tert-amyl peroxy (2-ethylhexyl) carbonate in this comparative example, and the remaining raw materials and steps are the same as those in Example 2. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 h) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 160° C. for blending and extrusion to obtain a modified polyolefin resin.

[0091] (2) Preparation of materials: According to weight parts, 90 parts of modified polyolefin resin, 10 parts of POE silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 hour), 0.7 parts of triallyl cyanurate and 0.1 parts of trimethylallyloxy silane were weighed.

[0092] (3) Preparation of premix: The modified polyolefin resin, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxysilane were added into a high-speed disperser and sheared and dispersed for 30 minutes to obtain a premix.

[0093] (4) Preparation of compound materials: The premix and the POE silane grafted material masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0094] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 95°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.4 mm.

[0095] Comparative Example 6 The difference between this comparative example and Example 5 is that the reaction temperature in step (1) is increased in this comparative example, and the remaining raw materials and steps are the same as those in Example 5. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of methyl ethyl ketone peroxide (half-life at 105°C is 10 hours), 50 parts of ethylene-hexene copolymer, 50 parts of ethylene-norbornene copolymer and 600 parts of n-decane were weighed, added into a 500L closed reactor, and stirred at 250°C at a speed of 200 rpm for 1 hour to obtain a modified polyolefin resin.

[0096] (2) Preparation of materials: According to parts by weight, 100 parts of modified polyolefin resin, 0.6 parts of azobisisobutyronitrile (half-life at 100° C. is 10 min), 0.5 parts of triallyl isocyanurate and 0.2 parts of γ-methacryloxypropyltrimethoxysilane were weighed.

[0097] (3) Preparation of mixed materials: Add modified polyolefin resin, azobisisobutyronitrile, triallyl isocyanurate and γ-methacryloxypropyltrimethoxysilane into a high-speed disperser, and shear and disperse for 1 hour to obtain a mixture.

[0098] (4) Extrusion molding: The mixed material is injected into a single screw extruder through a feeding system, blended and extruded at 100°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.3 mm.

[0099] Comparative Example 7 The difference between this comparative example and Example 2 is that the reaction temperature in step (1) is increased in this comparative example, and the other raw materials and steps are the same as those in Example 2. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.1 parts of dicumyl peroxide (half-life at 117° C. is 10 hours) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 230° C. for blending and extrusion to obtain a modified polyolefin resin.

[0100] (2) Preparation of materials: According to weight parts, 90 parts of modified polyolefin resin, 10 parts of POE silane grafted masterbatch, 0.8 parts of tert-amyl peroxy (2-ethylhexyl) carbonate (half-life at 116° C. is 1 hour), 0.7 parts of triallyl cyanurate and 0.1 parts of trimethylallyloxy silane were weighed.

[0101] (3) Preparation of premix: The modified polyolefin resin, tert-amyl peroxy (2-ethylhexyl) carbonate, triallyl cyanurate and trimethylallyloxysilane were added into a high-speed disperser and sheared and dispersed for 30 minutes to obtain a premix.

[0102] (4) Preparation of compound materials: The premix and the POE silane grafted material masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0103] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 95°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.4 mm.

[0104] Comparative Example 8 The difference between this comparative example and Example 6 is that the amount of initiator used in step (1) is increased in this comparative example, and the remaining raw materials and steps are the same as those in Example 6. Specifically, the POE encapsulation film of this comparative example is prepared according to the following steps: (1) Preparation of modified polyolefin resin: According to weight parts, 0.6 parts of di-tert-butyl peroxide (half-life at 115° C. is 34 hours) and 100 parts of ethylene-butene copolymer are weighed and added into a twin-screw extruder. The screw speed is set to 50 rpm and the temperature is set to 150° C. for blending and extrusion to obtain a modified polyolefin resin.

[0105] (2) Preparation of materials: According to weight parts, 97 parts of modified polyolefin resin, 1 part of POE silane graft masterbatch, 2 parts of POE blended light stabilizer masterbatch, 0.6 parts of azobisisobutyronitrile (half-life at 120°C is 2 minutes), 0.6 parts of diethylene glycol dimethacrylate and 0.1 parts of vinyltrimethoxysilane were weighed.

[0106] (3) Preparation of premix: Add modified polyolefin resin, azobisisobutyronitrile, diethylene glycol dimethacrylate and vinyltrimethoxysilane into a high-speed disperser, and shear and disperse for 30 minutes to obtain a premix.

[0107] (4) Preparation of compound materials: The premix, POE silane grafted masterbatch and POE blended light stabilizer masterbatch were mixed at a rotation speed of 400 rpm for 50 minutes to obtain a composite material.

[0108] (5) Extrusion molding: The compound material is injected into a single screw extruder through a feeding system, extruded at 85°C, cast into a film, and then drawn into an embossing roller to form a pattern. After cooling and shaping, it is slit and rolled to obtain the POE encapsulation film of this comparative example with a thickness of 0.4 mm.

[0109] Test Example 1: Rheological Analysis of Modified Polyolefin Resin The modified polyolefin resins in Examples 1 to 6 (respectively referred to as modified polyolefin resins 1 to 6) and the ethylene-butene copolymer in Comparative Example 2 were subjected to rheological analysis in the following manner: a rotational rheometer (HAAKE MARS40, ThermoFisher) was used to perform frequency sweeps on each sample at 100°C. The test results are shown in Figure 1 .

[0110] In the Cole-Cole diagram, linear polymers form a semicircular curve. The more they deviate from the semicircular curve, the higher the proportion of long-chain branches in the polymer. Figure 1 It can be seen that modified polyolefin resins 1 to 6 all contain long-chain branched structures.

[0111] Test Example 2: Encapsulation Film Performance Test The encapsulation films prepared in the embodiments and comparative examples were tested for performance, including: (1) Melting point and melting enthalpy of encapsulation film: It was measured by differential scanning calorimeter (DSC 25, TA Instruments) in the following way: under nitrogen atmosphere, the sample was first heated to 100°C and kept for 2 min to eliminate the thermal history, then cooled to 0°C at a rate of 10°C / min and kept for 2 min, and the sample was heated to 100°C again at a rate of 10°C / min. The DSC curve of the heating process was recorded, and the melting temperature and melting enthalpy of the polymer and its fractions were obtained based on the curve of the second heating process.

[0112] (2) Vulcanization properties of encapsulation films (TC10, TC90, ML and MH): The vulcanization curve was obtained by testing the vulcanization curve at 145°C for 15 min using a vulcanizer (RPA elite, TA Instruments).

[0113] (3) Degree of cross-linking of encapsulation film: Refer to national standard GB / T 29848-2013 and measure by xylene extraction method.

[0114] (4) Transmittance of packaging film: The results were measured by UV-Vis spectrophotometer (Cary 5000, Agilent Technologies).

[0115] (5) Haze of packaging film: It was measured by a high-precision haze meter (SGH-2, Beijing Aobotai Technology Co., Ltd.).

[0116] (6) Power attenuation after PID test of photovoltaic modules: Tested in accordance with IEC TS 62804-1:2015.

[0117] The performance test results are shown in Table 1 and Table 2.

[0118] Table 1

[0119] Table 2

[0120] From Table 1 and Table 2, we can see that: (1) Comparing Comparative Example 1, Comparative Example 2 and Example 2, it can be seen that: ① Compared with directly using ethylene-α-olefin copolymer and cross-linking agent and other materials to blend for film preparation (Comparative Example 2), the method of the present invention, i.e. first modifying the ethylene-α-olefin copolymer under the action of an initiator and then blending it with cross-linking agent and other materials to form a film (Example 1), can effectively improve the cross-linking degree of the POE encapsulation film, and to a certain extent improve the problem that the cross-linking degree of the POE encapsulation film is significantly lower than that of the EVA encapsulation film (Comparative Example 1); ② The melting point, melting enthalpy, TC10 and TC90 of Example 2 are significantly lower than those of Comparative Example 2, indicating that the method of the present invention can make the processing window of the POE encapsulation film wider, easier to process, and can accelerate the cross-linking speed, which will be beneficial to shorten the lamination time and improve production efficiency; ③ Compared with directly using polyolefin copolymers and cross-linking agents and other materials to blend for film making (Comparative Example 2), the method of the present invention (Example 1) can also effectively reduce the haze of the POE encapsulation film, improve its light transmittance and anti-PID performance, and is significantly better than EVA encapsulation film in these properties (especially anti-PID performance).

[0121] (2) Comparison of Comparative Example 3, Comparative Example 4 and Example 1 shows that: when ethylene-α-olefin copolymer is directly blended with materials such as a crosslinking agent for film preparation, by increasing the amount of the crosslinking agent and the auxiliary crosslinking agent, the crosslinking degree, processing window, crosslinking speed and anti-PID performance of the encapsulation film can be improved to a certain extent, but the effect is limited. The method of the present invention can improve the above performance to a greater extent and reduce the haze of the film. The reason for this is that: the present invention first reacts the ethylene-α-olefin copolymer under the action of an initiator to form a modified polyolefin resin with a long-chain branched structure, which can increase the degree of entanglement and overlap between molecular chains, thereby facilitating further crosslinking under the action of a crosslinking agent, and is beneficial to improving the crosslinking degree, crosslinking speed and anti-PID performance of the film, and making it have a wider processing window; and, by modifying the ethylene-α-olefin copolymer with an initiator, the original crystallization of the ethylene-α-olefin copolymer can be destroyed, which is beneficial to reducing the haze of the film.

[0122] (3) Comparing Comparative Example 5 with Example 2, it can be seen that: in the process of pre-modifying the ethylene-α-olefin copolymer using an initiator, compared with the use of an initiator with a shorter half-life (Comparative Example 5), the present invention uses an initiator with a longer half-life (Example 2), which can make the prepared encapsulation film have lower haze, better anti-PID performance and long-term stability. The reason for this is that the use of an initiator with a longer half-life can make the obtained modified polyolefin resin have a slightly cross-linked and branched structure, which ensures that the POE encapsulation film has a high degree of cross-linking, and can make the subsequent modified polyolefin resin and other materials blended and extruded in a low temperature to achieve sufficient mixing, so that the cross-linking agent, auxiliary cross-linking agent, functional masterbatch and silane coupling agent can better play their role.

[0123] (4) Comparison of Comparative Example 6 with Example 5, Comparative Example 7 with Example 2, and Comparative Example 8 with Example 6 shows that when the reaction temperature is too high (Comparative Example 6, Comparative Example 7) or the amount of initiator used (Comparative Example 8) is too large, the haze and anti-PID performance of the encapsulation film will be negatively affected. The reason is that when the reaction temperature is too high or the amount of initiator used is too large, the modified polyolefin resin forms a cross-linked network structure with a high degree of cross-linking, which is not conducive to achieving sufficient mixing at a lower temperature during the co-extrusion of the modified polyolefin resin with other materials.

[0124] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meanings as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. Unless otherwise specified, the raw materials and equipment used in the present invention are conventional raw materials and equipment in the field and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in the present invention are conventional methods in the field.

[0125] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high cross-linked POE encapsulation film, characterized in that: The following steps are involved: S1: mixing an ethylene-α-olefin copolymer and an initiator, and reacting them at a temperature higher than the initiation temperature of the initiator to obtain a modified polyolefin resin; the initiator is at least one of dicumyl peroxide, methyl ethyl ketone peroxide and di-tert-butyl peroxide; S2: taking raw materials including a modified polyolefin resin, a crosslinking agent and a co-crosslinking agent; the crosslinking agent is at least one of tert-amyl peroxy (2-ethylhexyl) carbonate, dicyclohexyl peroxy dicarbonate and azobisisobutyronitrile; S3: All the raw materials in step S2 are blended and extruded at a temperature higher than the initiation temperature of the crosslinking agent and not higher than 110° C., and then molded to obtain a high-crosslinking POE encapsulation film.

2. The preparation method according to claim 1, characterized in that: Step S1 includes the following process: mixing an initiator, an ethylene-α-olefin copolymer and a solvent, and reacting them at 120-200° C. for 0.5-2 hours to obtain a modified polyolefin resin.

3. The preparation method according to claim 2, characterized in that: During the reaction, the stirring speed is 200-500 rpm.

4. The preparation method according to claim 1, characterized in that: Step S1 includes the following process: mixing an initiator and an ethylene-α-olefin copolymer at 150-200° C. and extruding the mixture to obtain a modified polyolefin resin.

5. The preparation method according to claim 4, characterized in that: The mixing and extruding process is carried out using a twin-screw extruder with a screw speed of 20-80 rpm.

6. The preparation method according to claim 1, 2 or 4, characterized in that: In step S1, the mass ratio of the ethylene-α-olefin copolymer to the initiator is 100:0.1-0.

3.

7. The preparation method according to claim 1, characterized in that: In step S2, the raw materials include the following components in parts by weight: 90-100 parts of modified polyolefin resin, 0.6-0.8 parts of cross-linking agent, and 0.5-0.7 parts of auxiliary cross-linking agent.

8. The preparation method according to claim 7, characterized in that: In step S2, the raw materials further include the following components in parts by weight: 1 to 10 parts of functional masterbatch and 0.1 to 0.4 parts of auxiliary agent; the auxiliary agent includes a silane coupling agent; the functional masterbatch includes a POE silane graft masterbatch and / or a POE blended light stabilizer masterbatch.

9. The preparation method according to claim 1, characterized in that: In step S3, the temperature of the co-extrusion is 70-110°C.

10. A photovoltaic module, characterized in that: It comprises a high cross-linking POE encapsulation film prepared by the preparation method according to any one of claims 1 to 9.

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