EVA resin molecular structure
By joining small molecules with light-transformed functions in the EVA resin molecular structure, such as benzotriazole compounds, the problem of additive migration in the EVA film is solved, and the stable retention of additives is achieved, ensuring the performance of the film is maintained.
Patent Information
- Application Number
- CN202311807665.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-26
- Publication Date
- 2025-06-27
AI Technical Summary
The additives added to the EVA film easily migrate to the surface of the film due to polarity, resulting in the loss of the expected efficacy of the packaging film during storage and use.
In the molecular structure of the EVA resin, small molecules with light-transforming function, such as benzotriazole compounds, are selectively bonded to the main chain and branch chain of the EVA molecular structure to form a modified EVA molecular structure to prevent the migration of the light-transforming agent.
Through this method, the light converter is kept tightly inside the EVA film, avoiding migration and ensuring that the film maintains the expected performance during storage and use.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of encapsulation adhesive films, and particularly to an EVA resin molecular structure. Background Art
[0002] EVA resin is ethylene-vinyl acetate copolymer, and generally the content of vinyl acetate (VA) is 5% - 40%. Compared with polyethylene, since vinyl acetate monomer is introduced into the molecular chain of EVA, the high crystallinity is reduced, and the flexibility, impact resistance, filler compatibility and heat sealing performance are improved. It is widely used in fields such as foamed shoe materials, functional greenhouse films, packaging films, hot melt adhesives, wires and cables, and toys. Generally speaking, the performance of EVA resin mainly depends on the content of vinyl acetate on the molecular chain.
[0003] In the photovoltaic industry, according to different product structures, encapsulation adhesive films are divided into EVA adhesive films (ordinary transparent EVA films, white EVA films), POE adhesive films, EPE adhesive films, etc.
[0004] In order to further improve the performance of the encapsulation adhesive film, various additives have been successfully added to the EVA adhesive film through the efforts of researchers. Through the various additives added, the performance of the EVA adhesive film has been improved to a higher level again. However, there is an unavoidable problem, that is, the EVA adhesive film itself has polarity. As a result, during the period when the EVA adhesive film is extruded and formed in the adhesive film factory and transported to the component factory for encapsulating the battery, the additives added to the EVA adhesive film to improve the performance of the EVA encapsulation adhesive film often migrate to the surface of the adhesive film due to polarity factors. However, these additives are not like additives such as slip agents and anti-sticking agents... etc. used to improve the surface performance of the adhesive film, but must remain inside the encapsulation adhesive film.
[0005] In order to achieve this goal, the industry has developed various different technologies to keep the added additives inside the encapsulation adhesive film. These different technologies include, for example: changing the single-layer structure into a multi-layer structure to delay the migration of additives. These different methods can indeed achieve the expected purpose to a certain extent. However, if the encapsulation adhesive film is stored for a slightly longer time, the above methods still cannot effectively prevent the additives from migrating to the surface of the adhesive film. As a result, after the encapsulation adhesive film is assembled with the battery, due to the migration of the additives added, it will more or less lose the originally expected efficacy. Summary of the Invention
[0006] The main object of the present invention is to provide an EVA resin molecular structure in view of the above problems and deficiencies:
[0007] The composition of the molecular structure of the EVA resin includes a main chain and side chains, wherein the main chain and the side chains are selectively attached with a molecule having a light conversion function.
[0008] Another object of the present invention is that the small molecule having a light conversion function is a benzotriazole compound, and the general structural formula of the benzotriazole compound is as follows:
[0009]
[0010] R1 and R2 are each independently selected from any one or more of H, C1-C20 alkyl, and C1-C20 alkyl in which at least one methylene group is substituted by a polyether segment, R3 is a substituent at the 2nd nitrogen position of the benzotriazole nucleus, and this substituent is selected from one of α-olefins, acrylate esters, and methacrylate esters containing a carbon-carbon unsaturated double bond, and the carbon-carbon unsaturated double bond is located at the end of the substituent.
[0011] Another object of the present invention is that the structure of the main chain attached with a molecule having a light conversion function includes the following molecular formula:
[0012]
[0013] Wherein, n and m are both natural numbers not equal to 0.
[0014] Another object of the present invention is that the structure of the side chain attached with a molecule having a light conversion function includes the following molecular formula:
[0015]
[0016] Wherein, n and m are both natural numbers not equal to 0. Detailed implementation mode
[0017] In order to more clearly understand the technical content of the present invention, the following specific examples are hereby given for detailed illustration. The present invention will be further described below in conjunction with specific examples. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.
[0018] In the specific embodiments provided by the present invention, mainly a molecular structure of ethylene-vinyl acetate copolymer (EVA) is provided. A well-known fact is that ethylene-vinyl acetate copolymer itself is a large molecular group with a loose structure, so that the additives (light conversion agents) for improving the performance of EVA can easily flow (migrate) through the gaps between the molecular structures, resulting in that even if additives are added to EVA, its performance in functions such as light absorption and light conversion cannot meet the expectations.
[0019] In order to keep the light conversion agent added inside EVA within the VA film, the technical means adopted by the present invention is to directly add a light conversion agent that can bind to EVA molecules into the molecular structure of the original ethylene-vinyl acetate copolymer (EVA) to form a modified EVA molecular structure. During implementation, peroxides are used to generate free radicals in the EVA molecular structure and benzotriazole compounds; subsequently, the benzotriazole compounds are used to combine with the EVA molecular structure.
[0020] The general structural formula of the benzotriazole compounds is as follows:
[0021]
[0022] R1 and R2 are each independently selected from any one or more of H, C1-C20 alkyl groups, and C1-C20 alkyl groups in which at least one methylene group is substituted by a polyether chain segment. Among them, R3 is a substituent at the second nitrogen position of the benzotriazole nucleus, and this substituent is selected from one of α-olefins containing carbon-carbon unsaturated double bonds, acrylate esters, and methacrylate esters, and the carbon-carbon unsaturated double bond is located at the end of the substituent.
[0023] The following examples illustrate the possible reactions of the EVA resin molecular structure in the present invention under the action of a crosslinking agent.
[0024]
[0025] From the above reactions, it can be found that when free radicals are generated in the molecular structure of ethylene-vinyl acetate copolymer under the action of peroxides, these free radicals may appear on the main chain of the EVA molecular structure or on the side chain of the EVA molecular structure. Whether on the main chain or on the side chain, the free radicals can combine with the light conversion agent, which thus forms the following various different molecular structures:
[0026] Example:
[0027] The structure of an EVA main chain linked with a molecule having a light conversion function includes the following molecular formula:
[0028]
[0029] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment
[0030]
[0031] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment.
[0032] The structure of the main chain of EVA with a molecule having a light conversion function includes the following molecular formula:
[0033]
[0034] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment.
[0035] The structure of the side chain of EVA with a molecule having a light conversion function includes the following molecular formula:
[0036]
[0037] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment.
[0038] The structure of the side chain of EVA with a molecule having a light conversion function includes the following molecular formula:
[0039]
[0040] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment.
[0041] The structure of the side chain of EVA with a molecule having a light conversion function includes the following molecular formula:
[0042]
[0043] Among them, both n and m are natural numbers not equal to 0, and R4 can be any one or more of C1-C15 alkyl groups, C1-C15 alkyl groups in which at least one methylene group is substituted by a polyether chain segment.
[0044] The molecular structure of the modified EVA is directly combined with the original, unmodified EVA macromolecular chain by the benzotriazole compound used as a light conversion agent, which results in the inability of the light conversion agent to migrate any further. From this result, it can be known that the benzotriazole compound used as a light conversion agent is tightly retained inside the EVA. By this way of retaining the light conversion agent inside the EVA through grafting, the phenomenon of light conversion agent migration is solved once and for all.
[0045] In this specification, the invention has been described with reference to specific embodiments thereof. However, it is obvious that various modifications and variations can still be made without departing from the spirit and scope of the invention. Therefore, the specification should be regarded as illustrative rather than restrictive.
Claims
1. An EVA resin molecular structure, characterized in that, The composition of the molecular structure of the EVA resin includes a main chain and side chains, wherein a small molecule with a light conversion function is selectively attached to the main chain and the side chains.
2. The molecular structure of the EVA resin according to claim 1, wherein, The small molecule with a light conversion function is a benzotriazole compound, and the structural general formula of the benzotriazole compound is as follows: R1 and R2 are each independently selected from any one or more of H, C1-C20 alkyl groups, and C1-C20 alkyl groups in which at least one methylene group is substituted by a polyether chain segment. R3 is a substituent at the second nitrogen position of the benzotriazole nucleus, and this substituent is selected from one of α-olefins containing carbon-carbon unsaturated double bonds, acrylate esters, and methacrylate esters, and the carbon-carbon unsaturated double bond is located at the end of the substituent.
3. The molecular structure of the EVA resin according to claim 2, characterized in that, The structure of the main chain attached with a molecule having a light conversion function includes the following molecular formula: Among them, both n and m are natural numbers not equal to 0.
4. The molecular structure of the EVA resin according to claim 3, characterized in that, The structure of the side chain attached with a molecule having a light conversion function includes the following molecular formula: Among them, both n and m are natural numbers not equal to 0.