An EPE photovoltaic film and its preparation process and application

Abstract

The present invention belongs to the field of photovoltaic technology and provides an EPE photovoltaic film and its preparation process and application. The preparation process includes: selecting EVA particles with a melt index of 4-10g / 10min as low melt index EVA particles; adding an appropriate amount of low melt index EVA particles to EVA layer particles, mixing, adding an auxiliary agent, and mixing to obtain EVA layer raw materials; and adding an appropriate amount of low melt index EVA particles and a compatibilizer to POE layer particles, mixing, adding an auxiliary agent, and mixing to obtain POE layer raw materials; EVA layer raw materials, POE layer raw materials and EVA layer raw materials are co-extruded to prepare EPE photovoltaic film. The preparation process can effectively enhance the interlayer interface adhesion of the EPE photovoltaic film and prevent the auxiliary agent in the POE layer from precipitating and migrating; the EPE photovoltaic film has both high crosslinking stability, PCT aging peel strength and wet heat aging resistance, and low cost, and is suitable for double-glass or single-glass photovoltaic modules.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to an EPE photovoltaic adhesive film and a preparation process and application thereof. Background Art

[0002] EPE photovoltaic film is a three-layer composite of EVA (ethylene-vinyl acetate copolymer), POE (polyolefin elastomer), and EVA. EPE photovoltaic film is currently gaining increasing market share, effectively addressing the adhesion issues of POE film and the PID problem of EVA film, while being more affordable than pure POE film. However, due to the significant difference in polarity between POE and EVA, polar additives in the POE layer easily migrate into the EVA layer, resulting in poor interfacial adhesion and a decrease in crosslinking, impacting the performance of the EPE photovoltaic film and the lifespan of photovoltaic modules.

[0003] Currently, there are usually two solutions to the above problems of EPE photovoltaic film: one is to add silane-coupling agent grafting material to the EVA layer or POE layer, but this method will increase the cost and affect the uniformity of the additive distribution; the other is to add macromolecular additives to the EVA layer or POE layer, but this will bring problems such as the macromolecular additives being difficult to disperse in the matrix.

[0004] For example, publication number CN117487463A discloses an EPE photovoltaic film and its preparation method, which uses EVA resin grafted with a coupling agent as a base material, or EVA resin grafted with a coupling agent and EVA resin as a base material, and adds an auxiliary agent to the base material as the EVA layer raw material in the EPE photovoltaic film; the EVA layer raw material and the POE layer raw material are mixed, co-extruded, and cast to obtain the EPE photovoltaic film. In this method of adding a grafting material to the EVA layer, although the grafted coupling agent on the outer surface of the EVA layer is not easy to migrate to the interface between the EVA layer and the POE layer or into the POE layer; the auxiliary agent in the POE layer will still migrate to the EVA layer, resulting in uneven distribution of the auxiliary agent, resulting in a decrease in the degree of cross-linking and a decrease in the interfacial viscosity between the EVA layer and the POE layer. Therefore, this method cannot solve the fundamental problem of interface delamination of the EPE photovoltaic film. Therefore, there is an urgent need to find a new solution to the delamination problem of the EPE photovoltaic film. Summary of the Invention

[0005] The purpose of the present invention is to provide an EPE photovoltaic film and its preparation process and application in view of the deficiencies in the prior art.

[0006] Based on this, the present invention discloses a preparation process of EPE photovoltaic film, which includes the following process steps:

[0007] S1 material selection: EVA particles with a melt index of 4-10g / 10min are selected as low melt index EVA particles;

[0008] S2 mixing: adding low melt index EVA particles to EVA layer particles, mixing evenly, adding additives, and mixing evenly to obtain EVA layer raw materials; wherein the mass percentages of low melt index EVA particles and additives in the EVA layer raw materials are 1-50% and 0.1-5%, respectively;

[0009] The low melt index EVA particles and the compatibilizer are sequentially added to the POE layer particles, mixed evenly, and then the additives are added and mixed evenly to obtain a POE layer raw material; wherein the mass percentages of the low melt index EVA particles, the compatibilizer and the additives in the POE layer raw material are 1-10%, 0.1-20% and 0.1-5%, respectively;

[0010] S3: Co-extrusion molding: EVA layer raw material, POE layer raw material and EVA layer raw material are co-extruded to prepare EPE photovoltaic film.

[0011] Preferably, in step S1, the VA content of the low melt index EVA particles is 20-30%;

[0012] Step S1 further includes: selecting photovoltaic-grade EVA particles with a VA content of 20-30% and a melt index of 23-28 g / 10 min as EVA layer particles.

[0013] Preferably, step S1 further comprises: selecting photovoltaic-grade POE particles with a melt index of 4-15 g / 10 min as POE layer particles.

[0014] Preferably, in step S2, the melt index of the low melt index EVA particles added to the POE layer raw material is greater than or equal to the melt index of the low melt index EVA particles added to the EVA layer raw material.

[0015] Further preferably, in step S2, the content of the low melt index EVA particles added to the POE layer raw material is less than or equal to the content of the low melt index EVA particles added to the EVA layer raw material.

[0016] More preferably, in step S2, the mass percentage content of the low melt index EVA particles in the EVA layer raw material is 10-20%, and the mass percentage content of the low melt index EVA particles in the POE layer raw material is 5-10%.

[0017] Preferably, in step S2, the auxiliary agent includes 0.2-2% of a peroxide initiator (such as tert-butyl peroxy-2-ethylhexyl carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, etc.), 0.1-1% of a silane coupling agent (such as KH550, KH560, KH570, etc.), 0.05-3% of a light stabilizer (such as UV622, UV944, UV292, UV770, etc.) and 0.05-3% of an antioxidant (such as antioxidant 1010, antioxidant 1076, etc.);

[0018] The compatibilizer is a POE graft, and the POE graft is at least one of maleic anhydride grafted POE, POE-methyl methacrylate and acrylonitrile grafted copolymer, glycidyl methacrylate grafted POE, and acrylate grafted POE.

[0019] Preferably, in step S3, a film forming machine is used for co-extrusion molding; the extrusion temperature of the EVA layer raw material and the POE layer raw material are both controlled between 85-90°C.

[0020] The present invention also discloses an EPE photovoltaic film, which is prepared by the preparation process of the EPE photovoltaic film described above in the present invention. The film comprises an EVA layer, a POE layer and an EVA layer, and the thicknesses of the three layers are 120-200 μm, 120-200 μm and 120-200 μm respectively.

[0021] The present invention also discloses an application of an EPE photovoltaic adhesive film, wherein the EPE photovoltaic adhesive film is used as an encapsulating adhesive film in a photovoltaic module.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] Adding an appropriate amount of low melt index EVA particles to the POE layer particles and the EVA layer particles respectively, and adding a compatibilizer (such as a POE graft with a polar group) to the POE layer particles can effectively enhance the interfacial adhesion between the EVA layer and the POE layer in the prepared EPE photovoltaic film, prevent the precipitation and migration of the additives in the POE layer, improve the crosslinking stability of the EPE photovoltaic film, stabilize the interfacial adhesion between the EVA layer and the POE layer, and increase the cohesive force of the EPE photovoltaic film. Furthermore, after PCT48H aging, the retention rate of the peel strength between the EPE photovoltaic film and the photovoltaic glass is high, and after long-term wet and hot aging, the EPE photovoltaic film will not delaminate, and the bubbles applied to the photovoltaic module are also greatly reduced. Therefore, the EPE photovoltaic film prepared by the preparation process of the present invention has both high crosslinking stability, PCT48H aging peeling strength and wet and hot aging resistance, and its cost is low. The EPE photovoltaic film is suitable for double-glass or single-glass photovoltaic modules. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific embodiments.

[0025] Example 1

[0026] The preparation process of an EPE photovoltaic film of this embodiment includes the following process steps:

[0027] Step S1: Material selection: select conventional photovoltaic-grade EVA particles with a VA content of 28% and a melt index of 25 g / 10 min as EVA layer particles; select conventional photovoltaic-grade POE particles with a melt index of 14 g / 10 min as POE layer particles; and select EVA particles with a VA content of 28% and a melt index of 10 g / 10 min as low melt index EVA particles.

[0028] Step S2: Mixing: 20% (i.e., the mass percentage of the low melt index EVA particles in the EVA layer raw material is 20%, the same below) of the low melt index EVA particles prepared in step S1 are added to the EVA layer particles, and after mixing evenly, 1.5% of initiator TBEC (tert-butyl peroxy-2-ethylhexyl carbonate), 0.8% of silane KH570, 1% of antioxidant 1010, and 1% of light stabilizer UV622 are added and mixed evenly to obtain the EVA layer raw material;

[0029] 10% of the low melt index EVA particles in step S1 and 5% of the acrylate-grafted POE were added to the POE layer particles, mixed evenly, and then 1.5% of the initiator TBEC, 0.8% of the silane KH570, 1% of the antioxidant 1010, and 1% of the light stabilizer UV622 were added and mixed evenly to obtain the POE layer raw material.

[0030] Step S3 co-extrusion molding: The EPE photovoltaic film of this embodiment is prepared by co-extrusion of the EVA layer raw material, the POE layer raw material and the layered structure of the EVA layer raw material using a film machine (which includes a 160 μm thick EVA layer, a 140 μm thick POE layer and a 160 μm thick EVA layer formed by co-extrusion). The extrusion temperature of the EVA layer in the film machine is between 85°C and the extrusion temperature of the POE layer is between 87°C.

[0031] An application of the EPE photovoltaic film of this embodiment is to use the EPE photovoltaic film of this embodiment as an encapsulation film in a photovoltaic module.

[0032] Example 2

[0033] The EPE photovoltaic film and its preparation process and application in this embodiment are all referred to Example 1. The difference between this embodiment and Example 1 is that:

[0034] In the mixing step S2 of this embodiment, 10% (i.e., the mass percentage content of the low melt index EVA particles in the EVA layer raw material is 10%, the same below) of the low melt index EVA particles of step S1 is added to the EVA layer particles. The subsequent preparation process of the EVA layer raw material of this embodiment refers to that of Example 1.

[0035] Instead, 5% of the low melt index EVA particles prepared in step S1 and 5% of the acrylate-grafted POE were added to the POE layer particles. The subsequent preparation process of the POE layer raw materials in this embodiment was similar to that in Example 1.

[0036] Example 3

[0037] The EPE photovoltaic film and its preparation process and application in this embodiment are all referred to Example 2, and the difference between this embodiment and Example 2 is that:

[0038] In step S1 of this embodiment, EVA particles with a VA content of 28% and a melt index of 8 g / 10 min are selected as low melt index EVA particles.

[0039] Comparative Example 1

[0040] The preparation process of an EPE photovoltaic film in this comparative example refers to Example 1, and the difference between this comparative example and Example 1 is that:

[0041] In the preparation process of the EPE photovoltaic film of this comparative example, low melt index EVA particles are not added, and the rest are referred to Example 1.

[0042] Comparative Example 2

[0043] The preparation process of an EPE photovoltaic film in this comparative example refers to Example 1, and the difference between this comparative example and Example 1 is that:

[0044] In the preparation process of the EPE photovoltaic film of this comparative example, only the low melt index EVA particles described in Example 1 are added to the EVA layer particles, while no low melt index EVA particles are added to the POE layer particles of this comparative example.

[0045] Comparative Example 3

[0046] The preparation process of an EPE photovoltaic film in this comparative example refers to Example 1, and the difference between this comparative example and Example 1 is that:

[0047] In the preparation process of the EPE photovoltaic film of this comparative example, only the low melt index EVA particles described in Example 1 are added to the POE layer particles, and no low melt index EVA particles are added to the EVA layer particles of this comparative example.

[0048] Comparative Example 4

[0049] The preparation process of an EPE photovoltaic film in this comparative example refers to Example 1, and the difference between this comparative example and Example 1 is that:

[0050] In the preparation process of the EPE photovoltaic film of this comparative example, the content of low melt index EVA particles added to the EVA layer particles is 10%, and the content of low melt index EVA particles added to the POE layer particles is 20% (that is, the content of low melt index EVA particles added to the EVA layer particles is less than the content of low melt index EVA particles added to the POE layer particles).

[0051] Performance Testing

[0052] The EPE photovoltaic adhesive films prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the test results are shown in Table 1. The degree of crosslinking (xylene method) was tested in accordance with standard GB / T 29848-2018, the peel strength with photovoltaic glass was tested in accordance with standard GB / T 2790-1995, the PCT aging test (48 h) was tested in accordance with standard JEAS22-A102-D, and the damp heat aging test was tested in accordance with standard IEC 61215-2:2023.

[0053] Table 1

[0054]

[0055] Combined with the test data in Table 1, we can see that:

[0056] (1) Compared with Comparative Example 1, the crosslinking degree of the EPE photovoltaic film of Example 1 is still higher than 82% after six months of storage. This shows that after adding low melt index EVA particles to the preparation process of the EPE photovoltaic film of Example 1, the crosslinking degree of the EPE photovoltaic film prepared is relatively stable and the precipitation of the additive is weak.

[0057] (2) Compared with Example 1, after PCT48H aging treatment, the retention rate of the peel strength between the EPE photovoltaic film of Comparative Example 1 and the photovoltaic glass is significantly lower than that of Example 1; moreover, after wet heat aging treatment, the EPE photovoltaic film of Comparative Example 1 exhibits delamination and a small amount of bubbles. This indicates that after adding low melt index EVA particles to the preparation process of the EPE photovoltaic film of Example 1, the resulting EPE photovoltaic film also has excellent PCT48H aging peel strength and wet heat aging resistance, and its layers are not easily delaminated. The external environment, such as humidity and temperature, has little effect on the EPE photovoltaic film of Example 1; therefore, the EPE photovoltaic film prepared in Example 1 can increase the service life of the EPE photovoltaic film and delay the power attenuation of the photovoltaic module.

[0058] (3) The crosslinking degree of the EPE photovoltaic film of Comparative Example 2 after six months of storage is lower than that of Comparative Example 1, and the PCT48H aging peeling strength and wet heat aging resistance of the EPE photovoltaic film of Comparative Example 2 are worse than those of Comparative Example 1. This shows that compared with the EPE photovoltaic film of Comparative Example 1, in which low melt index EVA particles are not added to the EVA layer particles and the POE layer particles in the preparation process, the EPE photovoltaic film of Comparative Example 2 adds low melt index EVA particles to the EVA layer particles, but does not add low melt index EVA particles to the POE layer particles in the preparation process, which will aggravate the precipitation of the POE layer additive in the prepared EPE photovoltaic film; therefore, the PCT48H aging peeling strength and wet heat aging resistance of the EPE photovoltaic film of Comparative Example 2 are worse, and the EPE photovoltaic film delaminates and produces more bubbles after wet heat aging.

[0059] (4) The cross-linking degree of the EPE photovoltaic film of Comparative Example 3 after six months of storage is higher than that of Comparative Example 1, but still lower than that of Example 1; moreover, the retention rate of the peeling strength between the EPE photovoltaic film of Comparative Example 3 and the photovoltaic glass after PCT48H is higher than that of Comparative Example 1, but lower than that of Example 1; the resistance to wet heat aging of the EPE photovoltaic film of Comparative Example 3 is also higher than that of Comparative Example 1, but lower than that of Example 1. This shows that, compared with the preparation process of the EPE photovoltaic film of Comparative Example 1, in which low melt index EVA particles are not added to the EVA layer particles and the POE layer particles, the preparation process of the EPE photovoltaic film of Comparative Example 3 only adds low melt index EVA particles to the POE layer particles, which is beneficial to preventing the precipitation of the POE layer additive in its EPE photovoltaic film, but its effect is still inferior to that of Example 1 (in which an appropriate amount of low melt index EVA particles are added to both the EVA layer particles and the POE layer particles).

[0060] (5) Compared with Comparative Examples 1-3, the crosslinking degree of the EPE photovoltaic film of Comparative Example 4 after six months of storage is relatively high, but still lower than that of Example 1; however, the retention rate of the peeling strength of the EPE photovoltaic film of Comparative Example 4 with photovoltaic glass after PCT48H is lower than that of Comparative Examples 1-3, and significantly lower than that of Example 1; the wet heat aging resistance of the EPE photovoltaic film of Comparative Example 3 is also lower than that of Example 1. This indicates that, compared with Comparative Examples 1-3, in the preparation process of the EPE photovoltaic film of Comparative Example 4, the content of low melt index EVA particles added to the EVA layer particles is less than the content of low melt index EVA particles added to the POE layer particles, although it can delay the precipitation of the POE layer additive; however, after PCT48H, when the EPE photovoltaic film of Comparative Example 4 is tested for peeling strength with photovoltaic glass, the EPE photovoltaic film has a tendency to break, indicating that adding too many low melt index EVA particles to the POE layer particles will greatly affect the peeling strength of the EPE photovoltaic film.

[0061] In addition, the melt index of photovoltaic-grade POE particles is generally lower than 15g / 10min, while the melt index of high-melt-index EVA particles is generally higher than 20g / 10min; the higher the melt index of the particles, the better the fluidity. In the preparation process of EPE photovoltaic film, if step S2 replaces low-melt-index EVA particles with high-melt-index EVA particles to add to the POE layer particles and EVA layer particles; then in the co-extrusion molding process of step S3, the EVA layer raw material and the POE layer raw material will cause the EVA layer raw material with high-melt-index EVA particles to have a faster casting rate at a certain processing temperature. The casting rates of the EVA layer raw material and the POE layer raw material will differ more greatly. At the same time, the processing temperature of the POE layer raw material is higher, and the high-melt-index EVA particles may react with the additives, generating crystal points and holes that clog the extrusion die head, affecting the processing performance of the EPE photovoltaic film, increasing the processing difficulty of the EPE photovoltaic film, and affecting the overall performance of the EPE photovoltaic film.

[0062] In addition, compared with low melt index EVA particles, the processing temperature of low melt index POE particles is higher. If low melt index POE particles are added to EVA layer particles, it will affect the processing process of EVA layer particles, increase the processing difficulty of EPE photovoltaic film, and affect the comprehensive performance of EPE photovoltaic film.

[0063] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0064] The technical solution provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A process for preparing an EPE photovoltaic film, characterized in that: The process steps include: S1 Material Selection: Select EVA particles with a melt index of 4-10g / 10min as low melt index EVA particles; select photovoltaic grade EVA particles with a melt index of 23-28g / 10min as EVA layer particles; S2 mixing: adding low melt index EVA particles to EVA layer particles, mixing evenly, adding additives, and mixing evenly to obtain EVA layer raw materials; wherein the mass percentages of low melt index EVA particles and additives in the EVA layer raw materials are 1-50% and 0.1-5%, respectively; The low melt index EVA particles and the compatibilizer are sequentially added to the POE layer particles, mixed evenly, and then an auxiliary agent is added and mixed evenly to obtain a POE layer raw material; wherein the mass percentages of the low melt index EVA particles, the compatibilizer and the auxiliary agent in the POE layer raw material are 1-10%, 0.1-20% and 0.1-5%, respectively; wherein the content of the low melt index EVA particles added to the POE layer raw material is less than or equal to the content of the low melt index EVA particles added to the EVA layer raw material; and the compatibilizer is a POE graft having a polar group; S3: Co-extrusion molding: EVA layer raw material, POE layer raw material and EVA layer raw material are co-extruded to prepare EPE photovoltaic film.

2. The preparation process of an EPE photovoltaic film according to claim 1, characterized in that: In step S1, the VA content of the low melt index EVA particles is 20-30%; The VA content of the EVA layer particles is 20-30%.

3. The preparation process of an EPE photovoltaic film according to claim 1, characterized in that: Step S1 also includes: selecting photovoltaic-grade POE particles with a melt index of 4-15 g / 10 min as POE layer particles.

4. The preparation process of an EPE photovoltaic film according to claim 1, characterized in that: In step S2, the melt index of the low melt index EVA particles added to the POE layer raw material is greater than or equal to the melt index of the low melt index EVA particles added to the EVA layer raw material.

5. The preparation process of an EPE photovoltaic film according to claim 1, characterized in that: In step S2, the mass percentage content of the low melt index EVA particles in the EVA layer raw material is 10-20%, and the mass percentage content of the low melt index EVA particles in the POE layer raw material is 5-10%.

6. The process for preparing an EPE photovoltaic film according to any one of claims 1 to 5, characterized in that: In step S2, the auxiliary agent includes 0.2-2% of a peroxide initiator, 0.1-1% of a silane coupling agent, 0.05-3% of a light stabilizer, and 0.05-3% of an antioxidant.

7. The process for preparing an EPE photovoltaic film according to any one of claims 1 to 5, characterized in that: The compatibilizer is a POE graft, and the POE graft is at least one of maleic anhydride grafted POE, POE-methyl methacrylate and acrylonitrile grafted copolymer, glycidyl methacrylate grafted POE, and acrylate grafted POE.

8. The preparation process of an EPE photovoltaic film according to claim 1, characterized in that: In step S3, a film forming machine is used for co-extrusion molding; the extrusion temperature of the EVA layer raw material and the POE layer raw material are both controlled between 85-90°C.

9. An EPE photovoltaic film, characterized in that: The photovoltaic film is prepared by the preparation process of the EPE photovoltaic film according to any one of claims 1 to 8.

10. The use of the EPE photovoltaic film according to claim 9, characterized in that: The EPE photovoltaic film is used as an encapsulation film in photovoltaic modules.

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