CN116200131B - Modified polyvinyl butyral adhesive film, preparation method thereof and solar cell module - Google Patents

Abstract

The invention provides a modified polyvinyl butyral adhesive film, a preparation method and a solar cell module. The modified polyvinyl butyral film comprises a polyvinyl butyral film layer and a grafted modified polyolefin thermoplastic elastomer film layer arranged on the surface of the polyvinyl butyral film layer; the grafted modified polyolefin thermoplastic elastomer comprises the following preparation raw materials in parts by weight: 90-110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 part of cross-linking agent; 2.0 to 6.0 portions of maleic anhydride. The modified polyvinyl butyral adhesive film has good transparency, adhesion and weather resistance. The solar cell module has the advantages of tight adhesion of each layer, good sealing and good aging performance.

Description

Modified polyvinyl butyral film and preparation method thereof, and solar cell module

Technical Field

The invention relates to the technical field of solar cells, and in particular to a modified polyvinyl butyral film and a preparation method thereof, and a solar cell assembly.

Background technique

In the packaging process of solar cell modules, it is usually necessary to set a polymer packaging film in the solar cell module to provide protection for the solar cell string. Currently, the commonly used polymer packaging film materials mainly include POE (polyolefin thermoplastic elastomer) film, EVA (Ethylene Vinyl Acetate Copolymer) film and PVB (PolyVinyl Butyral Film) film.

Among them, the electrical insulation of POE film is good, but the adhesion of the film to glass and backplane is poor, and it is easy to slip during the preparation process of solar cell modules, resulting in a decrease in the qualified rate. During the use of the encapsulated components, the additives in the POE film will migrate to the bonding interface, causing the bonding performance to further deteriorate, the film to delaminate or be peeled off; at the same time, due to the precipitation of the additives, the aging performance, light transmittance, and insulation sealing performance of the film will deteriorate, thereby affecting the service life and efficiency of the components. EVA film-encapsulated solar cell modules will produce acetic acid during the aging process, which will corrode the solar cells. Traditional PVB film has a hydrocarbon structure on the molecule and is easy to absorb water when exposed to the air, resulting in poor electrical insulation and poor anti-PID (Potential Induced Degradation) performance.

Therefore, developing an adhesive film with good adhesion and aging properties to improve the service life and efficiency of solar cell modules has become one of the important research directions in this field.

Summary of the invention

Based on this, it is necessary to provide a modified polyvinyl butyral film with good adhesion and aging performance, a preparation method, and a solar cell module.

The technical solution proposed by the present invention is as follows:

According to a first aspect of the present invention, a modified polyvinyl butyral film is provided, comprising a polyvinyl butyral film layer and a grafted modified polyolefin thermoplastic elastomer film layer arranged on the surface of the polyvinyl butyral film layer; the grafted modified polyolefin thermoplastic elastomer comprises the following preparation raw materials in parts by weight: 90 to 110 parts of a polyolefin thermoplastic elastomer; 0.05 to 1.0 parts of a cross-linking agent; and 2.0 to 6.0 parts of maleic anhydride.

In some embodiments, the graft-modified polyolefin thermoplastic elastomer comprises the following raw materials by weight: 90 to 110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 parts of cross-linking agent; 2.0 to 4.0 parts of maleic anhydride, preferably 4.0 parts.

In some embodiments, the graft-modified polyolefin thermoplastic elastomer film layer is disposed on two opposite surfaces of the polyvinyl butyral film layer.

In some embodiments, the graft-modified polyolefin thermoplastic elastomer film layer has a thickness of 50 μm to 100 μm.

In some embodiments, the polyvinyl butyral film layer has a thickness of 200 μm to 300 μm.

In some embodiments, the graft-modified polyolefin thermoplastic elastomer film layer has a thickness of 70 μm to 100 μm.

In some embodiments, the polyvinyl butyral film layer has a thickness of 200 μm to 260 μm.

In some embodiments, the polyolefin thermoplastic elastomer has a hydroxyl value of 10% to 22% and a melt index of 4 g/10 min to 8 g/10 min.

In some embodiments, the crosslinking agent is one or more of dicumyl peroxide, di(2,4-dichlorobenzoyl) peroxide, di(tert-butylperoxyisopropyl)benzene and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

According to a second aspect of the present invention, there is provided a method for preparing the modified polyvinyl butyral film according to the first aspect of the present invention, comprising the following steps:

The graft-modified polyolefin thermoplastic elastomer, the silane coupling agent, the antioxidant, and the ultraviolet light stabilizer are melt-blended to form a mixture I;

Melt-blending polyvinyl butyral, a plasticizer, an antioxidant, and an ultraviolet light stabilizer to form a mixture II; and

The mixture I and the mixture II are co-extruded into a blown film.

In some embodiments, the method for preparing the graft-modified polyolefin thermoplastic elastomer comprises the following steps: mixing the polyolefin thermoplastic elastomer, the crosslinking agent and the maleic anhydride according to a proportion, and performing melt grafting at a temperature of 180° C. to 190° C.

According to a third aspect of the present invention, there is provided a solar cell assembly, comprising: a front cover plate, a front modified polyvinyl butyral film, a solar cell, a back modified polyvinyl butyral film, a back cover plate and a side sealing adhesive layer;

The front cover plate, the front modified polyvinyl butyral film, the solar cell, the back modified polyvinyl butyral film and the back cover plate are stacked in sequence;

The side sealing adhesive layer seals the side surfaces of the solar cell, the front modified polyvinyl butyral adhesive film and the back modified polyvinyl butyral adhesive film;

The front modified polyvinyl butyral film and the back modified polyvinyl butyral film are both modified polyvinyl butyral films of the first aspect of the present invention, and the front cover plate is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer in the front modified polyvinyl butyral film, and the back cover plate is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer in the back modified polyvinyl butyral film.

In some embodiments, at least one of the front cover plate and the back cover plate is a glass cover plate.

In some embodiments, the front modified polyvinyl butyral film and the back modified polyvinyl butyral film both include the polyvinyl butyral film layer, and the grafted modified polyolefin thermoplastic elastomer film layer is provided only on one surface of the polyvinyl butyral film layer.

In some embodiments, the front modified polyvinyl butyral film and the back modified polyvinyl butyral film both include the polyvinyl butyral film layer, and the grafted modified polyolefin thermoplastic elastomer film layer is provided on two opposite surfaces of the polyvinyl butyral film layer.

Compared with the prior art, the present invention has the following beneficial effects:

The modified polyvinyl butyral film of the present invention can increase the chemical bonding force between the film and the cover plate in the solar cell module by arranging a grafted modified polyolefin thermoplastic elastomer film layer on the surface of the polyvinyl butyral film layer and controlling the grafting amount of maleic anhydride, thereby increasing the adhesion between the film and the cover plate; and can increase the compatibility between POE and the auxiliary agent, avoiding the migration of the auxiliary agent to the bonding interface during use; and can also increase the interlayer compatibility and adhesion between the grafted modified polyolefin thermoplastic elastomer film layer and the polyvinyl butyral film layer in the film, solving the interlayer peeling and delamination problems; and can reduce the crystallinity of POE, increase the light transmittance of the grafted modified polyolefin thermoplastic elastomer film layer, and increase the efficiency of the solar cell module. The modified polyvinyl butyral film of the present invention has lower cost than pure PVB, and has good transparency, impact resistance and excellent weather resistance.

The solar cell module of the present invention adopts the modified polyvinyl butyral film of the present invention, so that the layers of the solar cell module can be tightly bonded into a whole, which can effectively prevent PVB from contacting water in the air and reduce the PID effect of the module during use. The layers in the solar cell module are tightly bonded, well sealed, have good aging performance, and have a long service life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a modified polyvinyl butyral film according to an embodiment of the present invention;

FIG2 is a schematic structural diagram of a modified polyvinyl butyral film according to another embodiment of the present invention;

FIG3 is a schematic structural diagram of a solar cell assembly according to an embodiment of the present invention;

FIG4 is a schematic structural diagram of a solar cell assembly according to another embodiment of the present invention;

FIG5 is a schematic structural diagram of a solar cell assembly according to another embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a solar cell assembly according to another embodiment of the present invention.

Description of reference numerals:

10. Modified polyvinyl butyral film; 11. Polyvinyl butyral film layer; 12. Graft-modified polyolefin thermoplastic elastomer film layer; 20. Front cover plate; 30. Solar cell; 40. Back cover plate; 50. Side sealing adhesive layer; 100. Solar cell module.

Detailed ways

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and/or" used herein includes any and all combinations of one or more related listed items.

Referring to FIG. 1 and FIG. 2 , one embodiment of the present invention provides a modified polyvinyl butyral film 10. The modified polyvinyl butyral film 10 includes a polyvinyl butyral film layer 11 and a grafted modified polyolefin thermoplastic elastomer film layer 12 disposed on the surface of the polyvinyl butyral film layer 11. In addition, the grafted modified polyolefin thermoplastic elastomer in the grafted modified polyolefin thermoplastic elastomer film layer 12 includes the following raw materials by weight: 90 to 110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 parts of cross-linking agent; and 2.0 to 6.0 parts of maleic anhydride.

The present invention forms a modified polyvinyl butyral adhesive film 10 by arranging a specific grafted modified polyolefin thermoplastic elastomer film layer 12 on the surface of a polyvinyl butyral film layer 11; wherein the raw materials for preparing the grafted modified polyolefin thermoplastic elastomer include a specific amount of polyolefin thermoplastic elastomer (POE), maleic anhydride and a crosslinking agent; by grafting and modifying POE with a specific amount of maleic anhydride, a carboxyl group can be introduced into the POE molecule, and the introduction of a strongly polar carboxyl group can increase the chemical bonding force between the POE film layer and the cover plate in the solar cell module, thereby increasing the adhesion between the grafted modified polyolefin thermoplastic elastomer film layer 12 and the cover plate; the introduction of a strongly polar carboxyl group can also increase The compatibility between POE and additives (silane coupling agent, antioxidant, ultraviolet light stabilizer, etc.) can prevent the above-mentioned additives in the grafted modified polyolefin thermoplastic elastomer film layer 12 from migrating to the bonding interface during use; in addition, the introduction of carboxyl groups can also increase the interlayer compatibility and adhesion between the grafted modified polyolefin thermoplastic elastomer film layer 12 and the polyvinyl butyral film layer 11 in the modified polyvinyl butyral film 10, effectively solving the interlayer peeling and delamination problems; furthermore, the grafted carboxyl groups destroy the regularity of the POE molecular chain, reduce the crystallinity of POE, and can increase the light transmittance of the grafted modified polyolefin thermoplastic elastomer film layer 12, thereby increasing the efficiency of the solar cell module.

The modified polyvinyl butyral film 10 of the present invention has lower cost than PVB (polyvinyl butyral) film of the same volume and has good transparency; the grafted modified POE molecules have random and flexible ether bonds, and the free volume of the molecular chain is large, so that the modified polyvinyl butyral film 10 has good impact resistance; the hydroxyl groups and ether bonds in the grafted modified POE molecular chain are extremely stable, and it is difficult to undergo oxidative degradation under the action of ultraviolet light, oxygen and water, so that the modified polyvinyl butyral film 10 has excellent weather resistance.

The modified polyvinyl butyral film 10 is used for the encapsulation of solar cell modules, so that the layers in the solar cell modules can be tightly bonded into a whole, and the polyvinyl butyral film layer 11 (PVB film layer) can be effectively prevented from contacting the air, so that the PVB film layer can be protected and insulated, and the PID effect of the solar cell module during use can be reduced. At the same time, the layers of the entire solar cell module are tightly bonded, which reduces the possibility of silver streaks when the module is impacted by the outside world, and can improve the impact resistance of the solar cell module and extend the service life of the module.

In some of the embodiments, the graft-modified polyolefin thermoplastic elastomer includes the following raw materials in parts by weight: 90 to 110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 parts of a cross-linking agent; and 2.0 to 4.0 parts of maleic anhydride.

The inventors have found that appropriately increasing the amount of maleic anhydride grafted in the grafted modified POE (i.e. increasing the amount of maleic anhydride in the raw material) within the scope of the present invention helps to increase the peeling force of the modified polyvinyl butyral film 10 and reduce the volume resistivity of the film. The main reason is that the increase in the content of polar groups enhances the bonding force between the film and the cover plate surface and reduces the dielectric constant of the film material. When the amount of maleic anhydride increases from 2.0 parts to 4.0 parts, the peel strength of the film increases, the volume resistivity decreases, and the transmittance increases. The reason is that when the amount of maleic anhydride is small, its grafting points are more dispersed, which increases the irregularity of the system molecules, thereby reducing the crystallinity of the system.

When the amount of maleic anhydride is increased to 6.0 parts, the grafting sites of maleic anhydride will be partially concentrated, so that a strong conjugated structure is formed within or between the molecular chains, resulting in a rapid decrease in the transmittance of the adhesive film. In addition, with the increase in the amount of maleic anhydride grafted, the yellowing index (ΔYI) of the solar cell module after ultraviolet aging gradually increases, and the aging performance decreases. The main reason is that with the further increase of polar groups in POE, more ultraviolet light will be absorbed during the aging process, accelerating the aging of the adhesive film. Therefore, considering the various aspects of the performance of the adhesive film and the solar cell module, it is preferred in the present invention that the amount of maleic anhydride is controlled at 2.0 to 4.0 parts, wherein 4.0 parts of maleic anhydride is a more optimal grafting amount.

Please refer to Fig. 1, in one specific example, a grafted modified polyolefin thermoplastic elastomer film layer 12 is disposed only on one surface of a polyvinyl butyral film layer 11. When the modified polyvinyl butyral film 10 of this structure is used for solar cell module packaging, the grafted modified polyolefin thermoplastic elastomer film layer 12 in the modified polyvinyl butyral film 10 needs to be directly bonded to the cover plate.

Please refer to Fig. 2, in another specific example, grafted modified polyolefin thermoplastic elastomer film layers 12 are provided on two opposite surfaces of the polyvinyl butyral film layer 11. When the modified polyvinyl butyral film 10 of this structure is used for solar cell module packaging, the grafted modified polyolefin thermoplastic elastomer film layer 12 on one surface of the modified polyvinyl butyral film 10 can be directly attached to the cover plate at will.

In some embodiments, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 on one side of the modified polyvinyl butyral film 10 is 50 μm to 100 μm. Studies have shown that the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 has an important influence on the weather resistance of the solar cell module. If the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 is too small, the UV aging test Pmax attenuation, the damp heat aging Pmax attenuation, and the anti-PID performance Pmax attenuation of the solar cell module will be large, and the aging performance will be poor.

The present invention can make the solar cell module have better aging performance by controlling the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 to 50 μm to 100 μm. It can be understood that the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 can be but not limited to 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm.

In some of the embodiments, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 is 70 μm to 100 μm. Experimental studies have found that when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 gradually increases from 50 μm to 70 μm, the power attenuation of the component in the UV aging test, the wet heat aging test and the PID test gradually decreases, indicating that the aging performance of the component gradually improves. When the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 exceeds 70 μm, its film thickness has little effect on the power attenuation of the component.

The possible reason is that the molecular chain of the grafted POE resin does not contain a branched structure, and has good fluidity after lamination and melting during component packaging. However, PVB has poor fluidity after melting due to its branched structure, and its molecular chain is softer, so the thermal shrinkage during the lamination process is relatively large. During the shrinkage process, the external pressure can press the POE melt into the shrinkage holes of PVB; when the grafted POE layer is thin, the POE layer solidifies relatively quickly during the lamination process, and the micro-holes left by the shrinkage of PVB are not filled in time, resulting in a large power Pmax attenuation during wet heat aging, ultraviolet aging and PID testing of the component. Considering the improvement of component aging performance, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 is preferably 70μm to 100μm in the present invention. Comprehensive consideration is further preferred to 70μm.

In some embodiments, the thickness of the polyvinyl butyral film layer 11 in the modified polyvinyl butyral film 10 is 200 μm to 300 μm. It is understood that the thickness of the polyvinyl butyral film layer 11 can be, but is not limited to, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, or 300 μm.

Further, in some embodiments, the thickness of the polyvinyl butyral film layer 11 is 200 μm to 260 μm. It should be noted that the thickness of the polyvinyl butyral film layer 11 can be adjusted according to the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12. For example, when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 is large, the thickness of the polyvinyl butyral film layer 11 can be reduced accordingly; when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 is small, the thickness of the polyvinyl butyral film layer 11 can be increased accordingly, so that the overall thickness of the modified polyvinyl butyral film 10 is basically the same.

In some embodiments, the hydroxyl value of POE in the grafted modified polyolefin thermoplastic elastomer film layer 12 is 10% to 22%, and the melt index of POE is 4 g/10min to 8 g/10min. It is understood that the hydroxyl value of POE can be, but not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%; the melt index of POE can be, but not limited to, 4 g/10min, 5 g/10min, 6 g/10min, 7 g/10min, 8 g/10min.

In some embodiments, the cross-linking agent may be one or more of dicumyl peroxide, di(2,4-dichlorobenzoyl) peroxide, di(tert-butylperoxyisopropyl)benzene and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

An embodiment of the present invention further provides a method for preparing a modified polyvinyl butyral film 10 , and the method comprises the following steps S100 to S300 .

Step S100: adding the grafted modified polyolefin thermoplastic elastomer, the silane coupling agent, the antioxidant, and the ultraviolet light stabilizer into a high-speed mixer for melt blending to form a mixture I.

In some of the embodiments, the antioxidants used include a primary antioxidant and a secondary antioxidant; wherein the primary antioxidant is 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester; the secondary antioxidant can be any one of tris(2,4-di-tert-butylphenyl) phosphite, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester and tris(2,4-di-tert-butylphenyl) phosphite, or a combination of more.

In some of the embodiments, the UV stabilizer used is any one of bis-2,2,6,6-tetramethylpiperidinol sebacate, N,N-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine, 2,4,6-trichloro-1,3,5-triazine and bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate or a combination of more than one thereof.

In one specific example, the mass ratio of the grafted modified polyolefin thermoplastic elastomer, the silane coupling agent, the antioxidant, and the ultraviolet light stabilizer is 100:0.5:0.5:0.5.

Step S200: adding polyvinyl butyral, plasticizer, antioxidant and ultraviolet light stabilizer into a high-speed mixer for melt blending to form a mixture II.

In some of the embodiments, the plasticizer used is any one of di(2-ethylbutyrate) triethylene glycol ester (3GH for short), diisobutyl phthalate, di(2-ethylhexyl) phthalate and diisononyl phthalate, or a combination of multiple thereof.

In some of the embodiments, the antioxidants used include a primary antioxidant and a secondary antioxidant; wherein the primary antioxidant is 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester; the secondary antioxidant can be any one of tris(2,4-di-tert-butylphenyl) phosphite, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester and tris(2,4-di-tert-butylphenyl) phosphite, or a combination of more.

In some of the embodiments, the UV stabilizer used is any one of bis-2,2,6,6-tetramethylpiperidinol sebacate, N,N-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine, 2,4,6-trichloro-1,3,5-triazine and bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate or a combination of more than one thereof.

In one specific example, the mass ratio of polyvinyl butyral, plasticizer, antioxidant, and ultraviolet light stabilizer is 100:30:0.5:0.5.

Step S300: putting the mixture I prepared in step S100 and the mixture II prepared in step S200 into a co-extrusion film blowing machine for co-extrusion film blowing to obtain a modified polyvinyl butyral film 10.

In some embodiments, the co-extrusion blown film obtains a two-layer structure of modified polyvinyl butyral film 10. As shown in FIG1 , the two-layer structure of modified polyvinyl butyral film 10 includes a polyvinyl butyral film layer 11 and a grafted modified polyolefin thermoplastic elastomer film layer 12 disposed on one surface of the polyvinyl butyral film layer 11.

In some embodiments, the co-extrusion blown film obtains a three-layer structure of a modified polyvinyl butyral film 10. As shown in FIG2 , the three-layer structure of the modified polyvinyl butyral film 10 includes a polyvinyl butyral film layer 11, and a grafted modified polyolefin thermoplastic elastomer film layer 12 is disposed on two opposite surfaces of the polyvinyl butyral film layer 11. In some specific examples, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer 12 on the two opposite surfaces of the polyvinyl butyral film layer 11 is controlled to be consistent during the co-extrusion blown film process.

In some embodiments, the preparation method of the graft modified polyolefin thermoplastic elastomer in step S100 is as follows: according to the raw material ratio of the graft modified polyolefin thermoplastic elastomer in the present invention, the polyolefin thermoplastic elastomer, the crosslinking agent and the maleic anhydride are mixed, and melt grafting is performed at a temperature of 180°C to 190°C to obtain the graft modified polyolefin thermoplastic elastomer. Maleic anhydride is grafted into the polyolefin thermoplastic elastomer molecules by melt grafting to modify them. It is understood that the temperature of melt grafting can be but is not limited to 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 190°C.

3 to 6 , some embodiments of the present invention further provide a solar cell module 100. The solar cell module 100 includes a front cover plate 20, a front modified polyvinyl butyral film, a solar cell 30, a back modified polyvinyl butyral film, a back cover plate 40 and a side sealant layer 50.

Among them, the front cover plate 20, the front modified polyvinyl butyral film, the solar cell 30, the back modified polyvinyl butyral film and the back cover plate 40 are stacked in sequence; the side sealing layer 50 seals the sides of the solar cell 30, the front modified polyvinyl butyral film and the back modified polyvinyl butyral film.

The front modified polyvinyl butyral film and the back modified polyvinyl butyral film both adopt the modified polyvinyl butyral film 10 of the present invention. In addition, the front cover plate 20 is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer 12 in the front modified polyvinyl butyral film; the back cover plate 40 is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer 12 in the back modified polyvinyl butyral film.

The above-mentioned solar cell module 100, by arranging a front modified polyvinyl butyral film between the solar cell 30 and the front cover plate 20, and arranging a back modified polyvinyl butyral film between the solar cell 30 and the back cover plate 40; and making the front cover plate 20 directly contact with the grafted modified polyolefin thermoplastic elastomer film layer 12 in the front modified polyvinyl butyral film, and the back cover plate 40 directly contact with the grafted modified polyolefin thermoplastic elastomer film layer 12 in the back modified polyvinyl butyral film, can effectively improve the impact resistance and aging performance of the solar cell module 100, and extend the service life of the solar cell module 100; and can make the solar cell module 100 have good transparency performance, thereby improving the module efficiency.

Please refer to FIG. 3 and FIG. 4. In some embodiments, the front modified polyvinyl butyral film and the back modified polyvinyl butyral film in the solar cell module 100 both adopt the modified polyvinyl butyral film 10 of the two-layer structure of the present invention. In the solar cell modules 100 of these structures, the grafted modified polyolefin thermoplastic elastomer film layer 12 on the front modified polyvinyl butyral film is in direct contact with the front cover plate 20; the grafted modified polyolefin thermoplastic elastomer film layer 12 on the back modified polyvinyl butyral film is in direct contact with the back cover plate 40.

Please refer to FIG. 5 and FIG. 6 , in some embodiments, the front modified polyvinyl butyral film and the back modified polyvinyl butyral film in the solar cell module 100 both adopt the three-layer structure modified polyvinyl butyral film 10 of the present invention. In the solar cell modules 100 of these structures, the grafted modified polyolefin thermoplastic elastomer film layer 12 on any surface of the front modified polyvinyl butyral film can be in direct contact with the front cover plate 20; the grafted modified polyolefin thermoplastic elastomer film layer 12 on any surface of the back modified polyvinyl butyral film can be in direct contact with the back cover plate 40.

In the solar cell module 100 of the present invention, at least one of the front cover plate 20 and the back cover plate 40 is a glass cover plate. That is, the front cover plate 20 and the back cover plate 40 can be glass cover plates at the same time, or only one of them can be a glass cover plate. When the front cover plate 20 and the back cover plate 40 are both glass cover plates, the solar cell module 100 is a double-glass solar cell module; when one of the front cover plate 20 and the back cover plate 40 is a glass cover plate, the solar cell module 100 is a single-glass solar cell module.

Please refer to Figures 3 and 5. In some embodiments, both the front cover plate 20 and the back cover plate 40 are glass cover plates, and the solar cell module 100 is a double-glass solar cell module. Please refer to Figures 4 and 6. In some embodiments, the front cover plate 20 is a glass cover plate, and the back cover plate 40 is a CPC structure cover plate (a transparent back plate with functional layers coated on both sides of a PET substrate), and the solar cell module 100 is a single-glass solar cell module.

In some embodiments, the solar cell 30 in the solar cell assembly 100 is a solar cell string formed by connecting a plurality of solar cell sheets in series, wherein the solar cell sheet may be a TOPcon cell (Tunnel Oxide Passivated Contact solar cell).

The preparation method of the solar cell assembly 100 of the present invention is as follows:

The layers of the solar cell module 100 are stacked in the following order: front cover 20, front modified polyvinyl butyral film, solar cell 30, back modified polyvinyl butyral film, back cover 40, and polyisobutylene tape is placed 5 cm away from the edge of the front cover 20 and the back cover 40 to seal to form a side sealing adhesive layer 50.

The stacked solar cell module 100 is placed under a temperature condition of 135° C. to 145° C. and heated for 5 to 10 minutes. At the same time, vacuum is drawn and pressure is applied for hot pressing. The vacuum degree is 200 Pa to 300 Pa and the applied pressure is 70 kPa to 80 kPa.

The solar cell module 100 after hot pressing is heated to 160° C. to 180° C. for lamination. The lamination pressure is 1.0 MPa to 1.5 MPa. The lamination time is 10 min to 15 min.

The laminated solar cell module 100 is cooled to 20° C. to 30° C. to obtain a finished solar cell module 100 having a modified polyvinyl butyral film 10 .

In general, in the modified polyvinyl butyral film 10 of the present invention, a grafted modified polyolefin thermoplastic elastomer film layer 12 is disposed on the surface of the polyvinyl butyral film layer 11 . By grafting modified polyolefin thermoplastic elastomer with maleic anhydride, the chemical bonding force between the grafted modified polyolefin thermoplastic elastomer film layer 12 and the cover plate in the solar cell module 100 can be increased, thereby increasing the adhesion between the grafted modified polyolefin thermoplastic elastomer film layer 12 and the cover plate; and the compatibility between POE (polyolefin thermoplastic elastomer) and additives (silane coupling agent, antioxidant, ultraviolet light stabilizer) can be increased to avoid the migration of additives to the bonding interface during use; the interlayer compatibility and adhesion between the grafted modified polyolefin thermoplastic elastomer film layer 12 and the polyvinyl butyral film layer 11 in the film can also be increased, effectively solving the interlayer peeling and delamination problems; and the crystallinity of POE can be reduced, and the transmittance of the grafted modified polyolefin thermoplastic elastomer film layer 12 can be increased, thereby increasing the efficiency of the solar cell module 100.

The present invention adopts polyvinyl butyral (PVB) and grafted modified polyolefin thermoplastic elastomer to co-extrude and blow film to prepare a layered co-extruded adhesive film, which has lower cost than pure PVB and has good transparency, impact resistance and excellent weather resistance.

The solar cell module 100 of the present invention adopts the modified polyvinyl butyral film 10 of the present invention, so that the layers of the solar cell module 100 can be tightly bonded into a whole, and then the four sides of the module are sealed by the side sealing adhesive layer 50, which can effectively prevent PVB from contacting with water in the air, thereby protecting and insulating PVB and reducing the PID effect of the module during use. The layers of the entire solar cell module 100 are tightly bonded and well sealed, which can reduce the possibility of silver streaks when the module is impacted by the outside, improve the impact resistance of the module, and extend the service life of the module.

The present invention will be further described below in conjunction with specific embodiments and comparative examples, but they should not be construed as limiting the scope of protection of the present invention.

Embodiment 1:

1. Preparation of grafted modified polyolefin thermoplastic elastomer:

The raw materials for preparing the graft modified polyolefin thermoplastic elastomer are as follows: 100 parts of POE resin, 0.1 parts of dicumyl peroxide, and 2.0 parts of maleic anhydride by weight; the above raw materials are melt grafted at 185° C. to prepare the graft modified polyolefin thermoplastic elastomer.

2. Preparation of modified polyvinyl butyral film:

(1) Add the graft-modified polyolefin thermoplastic elastomer prepared above, silane coupling agent, antioxidant, and ultraviolet light stabilizer into a high-speed mixer at a mass ratio of 100:0.5:0.5:0.5, and melt-blend to form a uniform mixture I.

(2) PVB, plasticizer, antioxidant and ultraviolet light stabilizer are added into a high-speed mixer at a mass ratio of 100:30:0.5:0.5, and melt-blended to form a uniform mixture II.

(3) Put the mixture I obtained in step (1) and the mixture II obtained in step (2) into a co-extrusion film blowing machine, and co-extrude and blow the film to obtain a three-layer modified polyvinyl butyral film. The three-layer co-extruded film is a grafted modified polyolefin thermoplastic elastomer film layer-polyvinyl butyral film layer-grafted modified polyolefin thermoplastic elastomer film layer from top to bottom, wherein the thickness of the upper and lower grafted modified polyolefin thermoplastic elastomer film layers is controlled to be consistent, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is 100 μm, and the thickness of the polyvinyl butyral film layer is 200 μm. The ultraviolet light stabilizer is bis-2,2,6,6-tetramethylpiperidinol sebacate. The antioxidant is: 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester: tris(2,4-di-tert-butylphenyl) phosphite: 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid distearyl ester=3:1:1 (mass ratio).

3. Preparation of solar cell modules:

The modified polyvinyl butyral film is used to prepare solar cell modules:

(1) Stack the layers in the following order: front glass, modified polyvinyl butyral film, N-type battery string, modified polyvinyl butyral film, CPC backplane, and place polyisobutylene glue 5 cm away from the edge of the front glass for sealing.

(2) The solar cell assembly sealed in step (1) was heated at 140° C. for 8 min, and simultaneously evacuated to a vacuum degree of 250 Pa and subjected to a pressure of 75 kPa for hot pressing.

(3) The temperature of the hot-pressed assembly in step (2) was raised to 170° C. and the assembly was laminated. The lamination pressure was 1.2 MPa and the lamination time was 12 min.

(4) Cool the laminated solar cell module to 25° C. to obtain a finished solar cell module.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 1.

Embodiment 2:

This embodiment is substantially the same as embodiment 1, except that in the step of preparing the graft-modified polyolefin thermoplastic elastomer, the amount of maleic anhydride used is 4.0 parts.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 1.

Embodiment 3:

This embodiment is substantially the same as embodiment 1, except that in the step of preparing the graft-modified polyolefin thermoplastic elastomer, the amount of maleic anhydride used is 6.0 parts.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 1.

Comparative Example 1:

This comparative example is basically the same as Example 1, except that the preparation of the graft-modified polyolefin thermoplastic elastomer is not performed, and the graft-modified polyolefin thermoplastic elastomer is replaced with a conventional polyolefin thermoplastic elastomer in the preparation step of the polyvinyl butyral film.

The volume resistivity, visible light transmittance and peel strength with glass of the polyvinyl butyral film prepared in this comparative example, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 1.

Table 1

experimental project Example 1 Example 2 Example 3 Comparative Example 1 Test standard or method Film volume resistivity/(Ω.cm) 8.5×10 ¹⁵ 6.0×10 ¹⁵ 5.6×10 ¹⁴ 9.4×10 ¹⁵ GB/T 1410-1989 Film visible light transmittance 91.5 92 86.5 90.5 380-800nm Peel strength between film and glass (N/cm) 158.5 167.2 170.6 126.2 ASTM D903-98 Component UV aging test Pmax attenuation 1.45% 1.95% 3.15% 1.20% 180kwh/ ^m2 Component heat aging Pmax attenuation 5.60% 3.20% 4.80% 10.30% RH85%,85℃,2000h Component anti-PID performance Pmax attenuation 2.20% 1.50% 3.60% 2.50% -1500V,192h

By comparing the test data of Examples 1 to 3 and Comparative Example 1, it can be seen that increasing the grafting amount of maleic anhydride in the graft-modified polyolefin thermoplastic elastomer film layer helps to increase the peeling force of the film and reduce the volume resistivity of the product. This is mainly due to the increase in the content of polar groups (carboxyl groups) that enhances the bonding force between the film and the glass surface and reduces the dielectric constant of the material. When the amount of maleic anhydride is less than or equal to 4.0 parts (such as Examples 1 and 2), the transmittance of the film increases; and when the amount of maleic anhydride reaches 6.0 parts, its transmittance decreases rapidly. The reason may be that when the amount of maleic anhydride is small, its grafting points are more dispersed, increasing the irregularity of the system molecules, thereby reducing the crystallization of the system; when the amount of maleic anhydride increases to 6.0 parts, its grafting points are partially concentrated, resulting in the formation of a strong conjugated structure within or between the molecular chains, causing the transmittance to decrease rapidly.

As the amount of maleic anhydride grafted increases, the yellowing index of the component after ultraviolet aging gradually increases. This is mainly due to the increase in polar groups in POE, which absorbs more ultraviolet light during the aging process and accelerates the aging of the film. After the components are subjected to wet heat aging, the attenuation rate of comparative example 1 is relatively large. This is mainly because there are no polar groups in conventional POE, which will cause the additive to transfer between layers during the aging process. The anti-PID performance of the component is greatly enhanced, among which Example 2 has the best anti-PID performance; in Example 3, due to the large amount of grafted maleic anhydride, the carboxyl group ionizes hydrogen ions under the action of water vapor and migrates rapidly under the action of voltage, which reduces the anti-PID performance. Based on the above test results, 4.0 parts of maleic anhydride is the optimal grafting amount.

Embodiment 4:

This embodiment is basically the same as embodiment 2, except that in the step of preparing the modified polyvinyl butyral film, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is controlled to be 50 μm, and the thickness of the polyvinyl butyral film layer is controlled to be 300 μm.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 2.

Embodiment 5:

This embodiment is basically the same as embodiment 2, except that in the step of preparing the modified polyvinyl butyral film, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is controlled to be 60 μm, and the thickness of the polyvinyl butyral film layer is controlled to be 280 μm.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 2.

Embodiment 6:

This embodiment is basically the same as embodiment 2, except that in the step of preparing the modified polyvinyl butyral film, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is controlled to be 70 μm, and the thickness of the polyvinyl butyral film layer is controlled to be 260 μm.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 2.

Embodiment 7:

This embodiment is basically the same as embodiment 2, except that in the step of preparing the modified polyvinyl butyral film, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is controlled to be 80 μm, and the thickness of the polyvinyl butyral film layer is controlled to be 240 μm.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 2.

Embodiment 8:

This embodiment is basically the same as embodiment 2, except that in the step of preparing the modified polyvinyl butyral film, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is controlled to be 90 μm, and the thickness of the polyvinyl butyral film layer is controlled to be 220 μm.

The volume resistivity, visible light transmittance and peel strength with glass of the modified polyvinyl butyral film prepared in this embodiment, as well as the ultraviolet aging performance, wet heat aging performance and anti-PID performance of the solar cell module were tested. The test results and test methods are shown in Table 2.

Table 2

Examples 4 to 8 investigated the effect of the thickness of the grafted modified polyolefin thermoplastic elastomer film layer on the performance of the co-modified film and its components. The performance test data showed that the thickness of the grafted modified polyolefin thermoplastic elastomer film layer had little effect on the resistivity, transmittance and peel strength of the film. However, after being prepared into a solar cell module, the thickness of the grafted modified polyolefin thermoplastic elastomer film layer had an important effect on the weather resistance of the module.

It can be seen from the test data in Table 2 that: when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer gradually changes from 50μm to 70μm, the power attenuation of the component UV aging test, heat aging test and anti-PID test gradually decreases; and when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer exceeds 70μm, the film thickness has little effect on the aging performance of the component.

The possible reasons are as follows: the molecular chain of the grafted modified polyolefin thermoplastic elastomer does not contain a branched structure and has good fluidity after lamination and melting. However, PVB has poor fluidity after melting due to its branched structure, and its molecular chain is softer. Therefore, the thermal shrinkage during the lamination process is relatively large. During the shrinkage process, the external pressure can press the POE melt into the shrinkage holes of PVB; when the thickness of the grafted modified polyolefin thermoplastic elastomer film layer is thin, the POE layer solidifies relatively quickly during the lamination process, and the tiny holes left by the shrinkage of PVB cannot be filled in time, resulting in the power Pmax attenuation of the component during wet heat aging, UV aging and PID testing.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description and drawings can be used to interpret the content of the claims.

Claims (14)

1. The modified polyvinyl butyral film is characterized by comprising a polyvinyl butyral film and a grafted modified polyolefin thermoplastic elastomer film layer arranged on the surface of the polyvinyl butyral film; the grafted modified polyolefin thermoplastic elastomer comprises the following preparation raw materials in parts by weight: 90-110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 part of cross-linking agent; 2.0 to 6.0 portions of maleic anhydride.

2. The modified polyvinyl butyral film according to claim 1, wherein the graft modified polyolefin thermoplastic elastomer comprises the following preparation raw materials in parts by weight: 90-110 parts of polyolefin thermoplastic elastomer; 0.05 to 1.0 part of cross-linking agent; 2.0 to 4.0 parts of maleic anhydride.

3. The modified polyvinyl butyral film according to claim 1, wherein the graft modified polyolefin thermoplastic elastomer film layer is provided on both of opposite surfaces of the polyvinyl butyral film layer.

4. The modified polyvinyl butyral film according to any one of claims 1 to 3, wherein the thickness of the graft modified polyolefin thermoplastic elastomer film layer is 50 μm to 100 μm.

5. The modified polyvinyl butyral film according to claim 4, wherein the thickness of the graft modified polyolefin thermoplastic elastomer film layer is 70 μm to 100 μm.

6. The modified polyvinyl butyral film according to any one of claims 1 to 3, 5, wherein the thickness of the polyvinyl butyral film layer is 200 to 300 μm.

7. The modified polyvinyl butyral film according to claim 6, wherein the polyvinyl butyral film layer has a thickness of 200 μm to 260 μm.

8. The modified polyvinyl butyral film according to any one of claims 1 to 3, 5, 7, wherein the modified polyvinyl butyral film satisfies at least one of the following (1) to (2):

(1) The hydroxyl value of the polyolefin thermoplastic elastomer is 10-22%, and the melt index is 4-8 g/10min;

(2) The cross-linking agent is one or more of dicumyl peroxide, di (2, 4-dichlorobenzoyl peroxide), di (tert-butyl isopropyl peroxide) benzene and 2, 5-dimethyl-2, 5-bis (tert-butyl peroxy) hexane.

9. A method of making the modified polyvinyl butyral film of any one of claims 1 to 8, comprising the steps of:

melt blending the grafted modified polyolefin thermoplastic elastomer, a silane coupling agent, an antioxidant and an ultraviolet stabilizer to form a mixture I;

Melt blending polyvinyl butyral, a plasticizer, an antioxidant and an ultraviolet stabilizer to form a mixture II; and

And carrying out coextrusion film blowing on the mixture I and the mixture II.

10. The method for preparing a modified polyvinyl butyral film according to claim 9, wherein the method for preparing a graft modified polyolefin thermoplastic elastomer comprises the steps of:

mixing the polyolefin thermoplastic elastomer, the cross-linking agent and the maleic anhydride according to the proportion, and carrying out melt grafting at the temperature of 180-190 ℃.

11. A solar cell module, comprising: the solar cell comprises a front cover plate, a front modified polyvinyl butyral adhesive film, a solar cell, a back modified polyvinyl butyral adhesive film, a back cover plate and a side sealing adhesive layer;

The front cover plate, the front modified polyvinyl butyral adhesive film, the solar cell, the back modified polyvinyl butyral adhesive film and the back cover plate are sequentially laminated;

The side surface sealing glue layer seals the side surfaces of the solar cell, the front surface modified polyvinyl butyral glue film and the back surface modified polyvinyl butyral glue film;

Wherein the front side modified polyvinyl butyral film and the back side modified polyvinyl butyral film are both the modified polyvinyl butyral films of any one of claims 1 to 8, and the front side cover plate is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer in the front side modified polyvinyl butyral film, and the back side cover plate is in direct contact with the grafted modified polyolefin thermoplastic elastomer film layer in the back side modified polyvinyl butyral film.

12. The solar cell assembly of claim 11, wherein at least one of the front cover plate and the back cover plate is a glass cover plate.

13. The solar module of claim 11 or 12, wherein the front side modified polyvinyl butyral film and the back side modified polyvinyl butyral film each comprise the polyvinyl butyral film layer with the graft modified polyolefin thermoplastic elastomer film layer disposed on only one of the surfaces of the polyvinyl butyral film layer.

14. The solar module of claim 11 or 12, wherein the front side modified polyvinyl butyral film and the back side modified polyvinyl butyral film each comprise the polyvinyl butyral film having the grafted modified polyolefin thermoplastic elastomer film layers on opposite surfaces of the polyvinyl butyral film.