Functional filler for photovoltaic encapsulation adhesive film, preparation method thereof and photovoltaic encapsulation adhesive film

Abstract

The application provides a functional filler for a photovoltaic encapsulating adhesive film, a preparation method of the functional filler and the photovoltaic encapsulating adhesive film, and relates to the technical field of functional fillers. The functional filler is formed by grafting a bifunctional organic molecule to the surface of an inorganic filler through a covalent bond. The bifunctional organic molecule contains a phosphate group and a phenolic hydroxyl group. The inorganic filler is a hydroxide and / or an oxide with a surface rich in hydroxyl groups. The application solves the technical problems of easy migration or consumption of functional substances, functional dispersion and lack of molecular-level synergistic linkage in the photovoltaic encapsulating adhesive film, and achieves the technical effects of excellent and long-term anti-PID performance, persistent anti-aging performance and high comprehensive reliability.

Description

Technical Field

[0001] This invention relates to the technical field of functional fillers, and in particular to a functional filler for photovoltaic encapsulation films, its preparation method, and photovoltaic encapsulation films. Background Technology

[0002] In photovoltaic module encapsulation, the vinyl acetate copolymer (EVA) film undergoes irreversible hydrolysis with water under prolonged humid and hot conditions, continuously generating small-molecule acetic acid. This process triggers a chain reaction of failures: acetic acid corrodes the cell grid lines and glass surface, causing sodium ions to precipitate from the glass. Under the influence of the bias electric field inside the module, these free sodium ions migrate to and accumulate on the cell surface, forming leakage current channels and leading to severe potential-induced degradation (PID) effects.

[0003] To address the aforementioned problems, existing technologies typically involve physically incorporating two types of functionally independent additives into the EVA film formulation to specifically target the two key destructive factors: acid and sodium ions. The first category is alkaline substances: adding inorganic bases (such as Mg(OH)2) or organic bases, whose role is to neutralize the acetic acid produced, thereby slowing down the corrosion of glass and batteries by eliminating acidic substances, and indirectly reducing the release of sodium ions; The second category is inorganic salts: adding specific inorganic salts (such as phosphates and silicates) can capture free sodium ions that are already migrating through chemical adsorption or ion exchange, blocking their path to the battery surface.

[0004] In addition, to improve the weather resistance (resistance to light, heat and oxygen aging) of the film itself, existing technologies usually also physically incorporate a third type of additive into the formulation, namely antioxidants and light stabilizers.

[0005] However, existing technologies have the following problems: First, functional substances are prone to migration or consumption: anti-acid and anti-PID additives, as small molecules added physically, are prone to migration, volatilization, or consumption due to continuous reaction during long-term use of the film, resulting in a sharp decline in the protective effect over time; additional antioxidants and light stabilizers also face the problem of easy migration. Second, the functions are fragmented and lack synergy: alkaline substances aim to neutralize the acetic acid that has been generated, inorganic salts aim to intercept the sodium ions that have been precipitated and migrated, and antioxidants and light stabilizers deal with photothermal aging on their own. The three functions work independently and lack synergy and linkage at the molecular level, failing to address the three interrelated failure factors of "acetic acid production", "sodium ion migration" and "matrix aging" from the root.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One of the objectives of this invention is to provide a functional filler for photovoltaic encapsulation films, which enables the films to possess excellent and long-lasting anti-PID performance and durable anti-aging performance, thereby improving the overall reliability of the films.

[0008] The second objective of this invention is to provide a method for preparing a functional filler for photovoltaic encapsulation films, which can permanently fix functional groups on the surface of inorganic fillers, thereby integrating acid neutralization, sodium ion capture and interfacial anti-aging functions into one, forming a non-migrating stable structure.

[0009] The third objective of this invention is to provide a photovoltaic encapsulation film that possesses excellent and long-lasting anti-PID performance, durable anti-aging performance, and high overall reliability.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: Firstly, a functional filler for photovoltaic encapsulation films is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule contains a phosphate ester group and a phenolic hydroxyl group; The inorganic filler is a hydroxide and / or oxide with a surface rich in hydroxyl groups.

[0011] Furthermore, the bifunctional organic molecule includes at least one of dimethyl 4-hydroxybenzylphosphonate and diphenyl 4-hydroxyphenyl phosphate.

[0012] Furthermore, the inorganic filler includes at least one of magnesium hydroxide, aluminum hydroxide, layered double hydroxide, and silicon dioxide.

[0013] Secondly, a method for preparing the functional filler described in any one of the above claims includes the following steps: Bifunctional organic molecules are grafted onto the surface of inorganic fillers in the form of covalent bonds to obtain the functional fillers.

[0014] Furthermore, the preparation method includes the following steps: (a) Hydroxymethylation reaction of bifunctional organic molecules to convert phenolic hydroxyl groups into hydroxymethyl groups, and obtain hydroxymethylated derivatives; (b) The hydroxymethyl group of the hydroxymethylated derivative is reacted with the active hydroxyl group on the surface of the inorganic filler to undergo a dehydration condensation reaction to obtain the functional filler.

[0015] Furthermore, in step (a), the hydroxymethylation reaction is carried out under alkaline conditions; Preferably, the reagent used in the hydroxymethylation reaction includes formaldehyde.

[0016] Furthermore, in step (a), the hydroxymethylation reaction temperature is 60℃-100℃, and the reaction time is 1h-10h.

[0017] Furthermore, in step (b), the dehydration condensation reaction temperature is 60℃-100℃, and the reaction time is 2h-8h.

[0018] Thirdly, a photovoltaic encapsulating film includes a matrix resin and any of the functional fillers described above; The functional filler is distributed in the matrix resin.

[0019] Furthermore, the matrix resin includes at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, and polyvinyl butyral.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: The functional filler for photovoltaic encapsulation films provided by this invention can, on the one hand, endow the film with excellent and long-lasting anti-PID performance. The filler body can continuously neutralize acetic acid, and the phosphate ester groups are tightly arranged on the filler surface through chemical bonds, which can form stable and high-density sodium ion coordination sites in the film. Compared with randomly dispersed small molecules, this ordered arrangement can more efficiently chelate migrating sodium ions. More importantly, the chemical bonding completely eliminates the pathway for additive migration and loss, so that the anti-PID performance can be maintained throughout the entire life cycle of the module. On the other hand, it can endow the film with long-lasting anti-aging performance. The grafted phenolic hydroxyl structure is an excellent free radical scavenger. When exposed to ultraviolet light, these firmly anchored phenolic hydroxyl groups can effectively quench free radicals and interrupt the oxidative degradation process of polymer chains. Since the phenolic hydroxyl groups are linked by covalent bonds, they do not become ineffective due to migration like traditional small molecule antioxidants. This provides more durable protection for the film, especially the filler-resin interface region, inhibiting yellowing and embrittlement. At the same time, the organic modification of the filler surface can improve the dispersibility of the filler in the film matrix and reduce the internal stress caused by filler agglomeration. This helps to maintain or even improve the mechanical strength (tensile strength, elongation at break) and adhesion reliability (peel strength) of the film, reducing the risk of delamination.

[0021] The method for preparing functional fillers for photovoltaic encapsulation films provided by this invention can permanently fix functional groups on the surface of inorganic fillers, thereby integrating acid neutralization, sodium ion capture and interfacial anti-aging functions into one, forming a non-migrating stable structure.

[0022] The photovoltaic encapsulation film provided by this invention has excellent and long-lasting anti-PID performance, durable anti-aging performance, and high overall reliability. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] According to a first aspect of the present invention, a functional filler for photovoltaic encapsulation films is provided, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; Bifunctional organic molecules contain phosphate ester groups and phenolic hydroxyl groups; Inorganic fillers are hydroxides and / or oxides with hydroxyl-rich surfaces.

[0025] This invention provides a functional filler for photovoltaic encapsulation films. On one hand, it imparts excellent and long-lasting anti-PID performance to the film. The filler itself can continuously neutralize acetic acid, and the phosphate ester groups are tightly arranged on the filler surface through chemical bonds, forming stable and high-density sodium ion coordination sites in the film. Compared to randomly dispersed small molecules, this ordered arrangement can more efficiently chelate migrating sodium ions. More importantly, the chemical bonding completely eliminates the pathway for additive migration and loss, ensuring that the anti-PID performance is maintained throughout the entire life cycle of the module. On the other hand, it also imparts durable anti-aging performance to the film. The grafted phenolic hydroxyl structure is an excellent free radical scavenger. When the film is subjected to... When ultraviolet light irradiation generates free radicals, these firmly anchored phenolic hydroxyl groups can effectively quench the free radicals and interrupt the oxidative degradation process of the polymer chain. Since the phenolic hydroxyl groups are linked by covalent bonds, they will not become ineffective due to migration like traditional small molecule antioxidants. This provides more durable protection for the film, especially the filler-resin interface region, inhibiting yellowing and embrittlement. At the same time, the organic modification of the filler surface can improve the dispersibility of the filler in the film matrix and reduce the internal stress caused by filler agglomeration. This helps to maintain or even improve the mechanical strength (tensile strength, elongation at break) and adhesion reliability (peel strength) of the film, reducing the risk of delamination.

[0026] In a preferred embodiment, the bifunctional organic molecule includes, but is not limited to, at least one of 4-hydroxybenzylphosphonate dimethyl ester and 4-hydroxyphenyl phosphate (diphenyl) ester, which simultaneously possesses phenolic hydroxyl groups (anti-aging source) and phosphate ester groups (sodium ion capture source), and has both free radical quenching and ion coordination capabilities.

[0027] The phosphate ester group can be replaced with a phosphonic acid group, a phosphate monoester group, or their salts, which may enhance the ability to capture sodium ions; the phenolic hydroxyl group can be replaced with other groups with anti-aging effects, such as partially hindered phenolic structures, aminophenols, etc.; the molecular skeleton can be adjusted, such as by using polyphenolic compounds (tannic acid derivatives) for grafting, to provide more capture sites and antioxidant sites.

[0028] In a preferred embodiment, the inorganic filler includes, but is not limited to, at least one of magnesium hydroxide, aluminum hydroxide, layered double hydroxides, and silicon dioxide, which has acetic acid neutralization capability. As a functional platform, a bifunctional organic molecule with both free radical quenching and ion coordination capabilities is covalently grafted onto its surface to construct a non-migrating stable structure that integrates acid neutralization, sodium ion capture, and interfacial anti-aging functions. This not only achieves the purpose of multifunctional synergy but also overcomes the inherent defects of small molecule additives in traditional physical blending processes, such as easy migration and precipitation and unsustainable function.

[0029] According to a second aspect of the present invention, a method for preparing the functional filler described in any one of the above claims is provided, comprising the following steps: Bifunctional organic molecules are grafted onto the surface of inorganic fillers in the form of covalent bonds to obtain functional fillers.

[0030] The method of the present invention can permanently fix functional groups on the surface of inorganic fillers, thereby integrating acid neutralization, sodium ion capture and interfacial anti-aging functions into one, forming a non-migrating stable structure.

[0031] In a preferred embodiment, the preparation method of the present invention includes the following steps: (a) Hydroxymethylation reaction of bifunctional organic molecules to convert phenolic hydroxyl groups into hydroxymethyl groups, and obtain hydroxymethylated derivatives; (b) The hydroxymethyl group of the obtained hydroxymethylated derivative undergoes a dehydration condensation reaction with the active hydroxyl group on the surface of the inorganic filler to obtain the functional filler.

[0032] In a preferred embodiment, in step (a), the hydroxymethylation reaction can be carried out under alkaline conditions, and the reagent used in the hydroxymethylation reaction can be formaldehyde, which is more conducive to converting the inert phenolic hydroxyl group into the highly reactive hydroxymethyl group.

[0033] A typical method for preparing a functional filler includes the following steps: (a) Under alkaline conditions, the phenolic hydroxyl group of a bifunctional organic molecule undergoes a hydroxymethylation reaction with formaldehyde, converting the inert phenolic hydroxyl group into a highly reactive hydroxymethyl group, thus yielding a hydroxymethylated derivative. (b) The obtained hydroxymethylated derivative is mixed with inorganic filler and reacted. The hydroxymethyl group on the hydroxymethylated derivative undergoes a dehydration condensation reaction with the active hydroxyl group on the surface of the inorganic filler to form a strong covalent bond, thus obtaining the functional filler product.

[0034] In summary, this invention permanently fixes the functional groups of bifunctional organic molecules onto the surface of an inorganic filler with acetic acid neutralization capability through hydroxymethylation and dehydration condensation reactions, thereby achieving the goals of non-migratory, highly dispersible, and long-lasting effects of the functional components.

[0035] In a preferred embodiment, in step (a), the hydroxymethylation reaction temperature can be 60℃-100℃ and the reaction time can be 1h-10h, which is more conducive to a complete hydroxymethylation reaction.

[0036] In a preferred embodiment, in step (b), the dehydration condensation reaction temperature can be 60℃-100℃ and the reaction time can be 2h-8h, which is more conducive to a complete dehydration condensation reaction.

[0037] According to a third aspect of the present invention, a photovoltaic encapsulating film is provided, comprising a matrix resin and the functional filler described in any one of the preceding claims; This functional filler is distributed within the matrix resin.

[0038] The photovoltaic encapsulation film of this invention has excellent and long-lasting anti-PID performance, durable anti-aging performance, and high overall reliability.

[0039] Functional fillers are blended with the matrix resin as key additives to obtain masterbatch, which is then added to the matrix resin and compounded with functional additives such as crosslinking agents and silane coupling agents through processes such as mixing and extrusion. Ultimately, inside the film, each filler particle becomes a micro-site that is chemically anchored and has both sodium ion capture and interfacial anti-aging functions.

[0040] In a preferred embodiment, the matrix resin may be selected from ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE) and / or polyvinyl butyral (PVB), or other thermoplastic or thermosetting polymers suitable for photovoltaic encapsulation.

[0041] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0042] Example 1 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is dimethyl 4-hydroxybenzylphosphonate, and the inorganic filler is magnesium hydroxide.

[0043] Example 2 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is dimethyl 4-hydroxybenzylphosphonate, and the inorganic filler is aluminum hydroxide.

[0044] Example 3 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is dimethyl 4-hydroxybenzylphosphonate, and the inorganic filler is silica.

[0045] Example 4 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is 4-hydroxyphenyl phosphate (diphenyl) ester, and the inorganic filler is magnesium hydroxide.

[0046] Example 5 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is 4-hydroxyphenyl phosphate (diphenyl) ester, and the inorganic filler is aluminum hydroxide.

[0047] Example 6 This embodiment provides a functional filler product for photovoltaic encapsulation films, which is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule is 4-hydroxyphenyl phosphate (diphenyl) ester, and the inorganic filler is silicon dioxide.

[0048] Example 7 This embodiment describes the preparation method of the functional filler products of Examples 1-6, including the following steps: (a) Mix bifunctional organic molecules with formaldehyde at a mass ratio of 1:0.1-1:0.5, add an alkaline catalyst, adjust the pH to 8-11, and stir the reaction at 60℃-100℃ for 1h-10h. After the reaction is completed, separate the hydroxymethylated derivative by distillation, precipitation and other methods. (b) The obtained hydroxymethylated derivative is added to the water slurry of inorganic filler particles. The mass ratio of hydroxymethylated derivative to inorganic filler particles is 1:5-1:30. The mixture is stirred and reacted at 60℃-100℃ for 2h-8h. After the reaction is completed, the mixture is washed and dried in a spray dryer to obtain the functional filler product.

[0049] Comparative Example 1 This comparative example provides a filler product, which is magnesium hydroxide.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that the bifunctional organic molecule did not undergo hydroxymethylation; instead, it was directly mixed with the inorganic filler to obtain the filler product.

[0051] Test case Performance tests were conducted on the packing products of Examples 1-6 and Comparative Examples 1-2: The filler products of Examples 1-6 and Comparative Examples 1-2 were used as additives to prepare corresponding photovoltaic encapsulation films for performance testing. The formulations of the photovoltaic encapsulating films corresponding to the examples and comparative examples are shown in Table 1; The test results are shown in Tables 2, 3 and 4.

[0052] The preparation method of photovoltaic encapsulation film includes the following steps: EVA matrix resin, filler and additives are premixed in a stirring tank at a stirring temperature of 30℃-50℃ for 5h-10h. The mixture is then fed into an extruder and cast and extruded into a film at 70℃-90℃ to obtain photovoltaic encapsulation film.

[0053] Table 1. Formulations of photovoltaic encapsulating films corresponding to the examples and comparative examples.

[0054] Table 2. Conventional performance test results of the photovoltaic encapsulating films corresponding to the examples and comparative examples.

[0055] Table 3. Material test results of the photovoltaic encapsulating films corresponding to the examples and comparative examples.

[0056] Table 4. Component reliability test results of the photovoltaic encapsulating films corresponding to the examples and comparative examples.

[0057] In summary, this invention uses an inorganic filler with acetic acid neutralization capability as a carrier. Through surface chemical modification, it simultaneously loads sodium ion capturing groups (phosphate esters) and free radical quenching groups (phenolic hydroxyl groups), integrating multiple stabilizing functions on a single filler particle. Furthermore, the functional components are fixed by chemical bonds, making them difficult to migrate. A two-step chemical reaction of hydroxymethylation and surface condensation is employed to covalently graft bifunctional organic molecules onto the filler surface, ensuring the long-term stability of the functional groups within the polymer matrix and preventing their physical migration or loss. The filler-resin interface is directionally modified to possess both ion capturing and anti-aging capabilities, which, combined with the acid neutralization function of the filler itself, form a multi-mechanism synergistic stabilization network within the film. This helps suppress PID and aging phenomena from different stages, thereby improving the long-term reliability of the film.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A functional filler for photovoltaic encapsulation films, characterized in that it is It is composed of bifunctional organic molecules grafted onto the surface of inorganic fillers via covalent bonds; The bifunctional organic molecule contains a phosphate ester group and a phenolic hydroxyl group; The inorganic filler is a hydroxide and / or oxide with a surface rich in hydroxyl groups.

2. The functional filler according to claim 1, characterized in that, The bifunctional organic molecule includes at least one of dimethyl 4-hydroxybenzylphosphonate and diphenyl 4-hydroxyphenyl phosphate.

3. The functional filler according to claim 2, characterized in that, The inorganic filler includes at least one of magnesium hydroxide, aluminum hydroxide, layered double hydroxide, and silicon dioxide.

4. A method for preparing the functional filler according to any one of claims 1-3, characterized in that, Includes the following steps: Bifunctional organic molecules are grafted onto the surface of inorganic fillers in the form of covalent bonds to obtain the functional fillers.

5. The preparation method according to claim 4, characterized in that, The preparation method includes the following steps: (a) Hydroxymethylation reaction of bifunctional organic molecules to convert phenolic hydroxyl groups into hydroxymethyl groups, and obtain hydroxymethylated derivatives; (b) The hydroxymethyl group of the hydroxymethylated derivative is reacted with the active hydroxyl group on the surface of the inorganic filler to undergo a dehydration condensation reaction to obtain the functional filler.

6. The preparation method according to claim 5, characterized in that, In step (a), the hydroxymethylation reaction is performed under alkaline conditions; Preferably, the reagent used in the hydroxymethylation reaction includes formaldehyde.

7. The preparation method according to claim 6, characterized in that, In step (a), the hydroxymethylation reaction temperature is 60℃-100℃ and the reaction time is 1h-10h.

8. The preparation method according to claim 5, characterized in that, In step (b), the dehydration condensation reaction temperature is 60℃-100℃ and the reaction time is 2h-8h.

9. A photovoltaic encapsulating film, characterized in that, Includes the matrix resin and the functional filler as described in any one of claims 1-3; The functional filler is distributed in the matrix resin.

10. The photovoltaic encapsulating film according to claim 9, characterized in that, The matrix resin includes at least one of ethylene-vinyl acetate copolymer, polyolefin elastomer, and polyvinyl butyral.

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