A method for removing ethylene-vinyl acetate copolymer from solar panels using an organic solvent system

Abstract

The present invention belongs to the technical field of solid waste resource recovery, and in particular to a method for removing ethylene-vinyl acetate copolymer from solar panels using an organic solvent system. The present invention is carried out by placing a sample to be processed containing ethylene-vinyl acetate copolymer (EVA) in a heating reactor, adding an organic solvent system of a certain volume ratio, and heating the sample to make the EVA lose viscosity. By using the method described in the present invention to process waste solar panels, the EVA in the waste solar panels can be effectively made to lose viscosity, thereby achieving an unsealing effect, and the internal battery chip of the solar panel is not damaged, and will not cause a large amount of metal to be leached and lost. The whole process of the technical solution of the present invention is green and efficient, no secondary pollution is generated, and the economic benefit is remarkable, with wide application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource recovery and more specifically relates to a method for degrading ethylene-vinyl acetate copolymer in solar panels using an organic solvent system. Background Art

[0002] Among the rapidly developing energy sources globally, solar energy is the cleanest and most promising emerging alternative. Solar photovoltaic power generation is currently the most mature technology for utilizing solar energy. Solar panels, the core components that convert solar energy into electricity through the photovoltaic effect, have long dominated the photovoltaic market. However, with the expiration of the service life of first-generation crystalline silicon solar panels and the upgrading and retirement of second- and third-generation solar panels, a large number of solar panels have been discarded. Solar panels contain a wealth of metal elements and organic resources. If not utilized, they will harm the environment and inevitably result in the waste of large quantities of these resources. Therefore, recycling the precious metal and organic resources contained in solar panels is extremely valuable.

[0003] When recycling solar panels, the photovoltaic panel components must first be separated. The key and first step is to use a certain method to make the ethylene vinyl acetate polymer (EVA) encapsulant lose its viscosity. Currently, there are publicly available technologies for decapsulating EVA from waste solar panels. For example, Taiwan patent application TW107201031U discloses a steam degumming system for waste solar photovoltaic panel modules. This method heats a solvent to its boiling point to convert it into steam, and then uses the solvent vapor to repeatedly act on the various components of the solar panel. This method can remove EVA from waste solar photovoltaic panel modules while using a relatively small amount of solvent. However, this method is energy-intensive and costly. CN115591540A discloses a method for recycling waste solar panels to prepare a hydrolysis hydrogen production catalyst. This method removes the EVA and PET encapsulation by heating to 350-450°C. However, this method is prone to metal element loss during the thermal decomposition process, reducing the recovery value. Furthermore, the heating temperature is too high, resulting in high energy consumption. Chinese patent application CN106883939A discloses a chemical decomposition and removal agent for EVA resin stains. This application uses a large number of different chemical substances to remove EVA, generating a large amount of organic wastewater and toxic vapors during use.

[0004] Therefore, in order to achieve low-cost, green and efficient EVA decapsulation process, an efficient waste solar panel EVA decapsulation solvent system is urgently needed. Summary of the Invention

[0005] The technical problem addressed by the present invention is to overcome the drawbacks and shortcomings of the existing EVA wet decapsulation process in waste solar panel recycling, such as high cost, high energy consumption, and the risk of secondary pollution. This method provides a method for decapsulating ethylene-vinyl acetate copolymer using an organic solvent system. The organic solvent system of the present invention produces no secondary pollution during the decapsulation process, is low-cost, and does not physically or chemically damage other components of the solar panel, such as the glass and battery chips, thereby fully preserving the recyclable metal and glass resources in the panels.

[0006] The object of the present invention is to provide an application of the method of the present invention in the field of solar panel recycling.

[0007] Another object of the present invention is to provide an application of an organic solvent system in the field of desealing products containing ethylene-vinyl acetate copolymers.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A method for depolymerizing ethylene-vinyl acetate copolymer using an organic solvent system comprises the following steps: placing a sample to be processed in an organic solvent system and heating the sample at 60-150° C. to depolymerize the ethylene-vinyl acetate copolymer;

[0010] The organic solvent system is composed of N,N-dimethylpropionamide, N,N-dimethylacetamide and N,N-diethylformamide in a volume ratio of (1-3):(1-3):(1-3).

[0011] Preferably, in the present invention, the ethylene-vinyl acetate copolymer is ethylene-vinyl acetate copolymer (EVA) glue for solar panel encapsulation.

[0012] N,N-dimethylacetamide and N,N-diethylformamide stretch the ethylene-vinyl acetate copolymer (EVA) structure through the action of dispersion forces. The stretched structure facilitates the diffusion of solvent molecules, ultimately causing the EVA to swell and lose viscosity, resulting in an unblocking effect. N,N-dimethylpropionamide can undergo a grafting reaction with EVA, adding functional groups such as NH and C=O to the molecular structure, destroying the EVA cross-linking bridge structure. At the same time, N,N-dimethylpropionamide also produces dispersion forces with the uncrosslinked side chains of EVA, causing the EVA structure to stretch. Solvent molecules diffuse into the gaps in the EVA structure, exacerbating the swelling of the EVA and losing its viscosity, thus causing unblocking.

[0013] There are two effects of increasing the temperature: one is to promote the movement of solvent molecules, increase the reaction rate, and facilitate faster deblocking effect; the other is to promote the grafting of organic solvents and EVA.

[0014] Preferably, the organic solvent system consists of N,N-dimethylpropionamide, N,N-dimethylacetamide and N,N-diethylformamide in a volume ratio of (2-3):1:1.

[0015] More preferably, the organic solvent system consists of N,N-dimethylpropionamide, N,N-dimethylacetamide and N,N-diethylformamide in a volume ratio of 3:1:1.

[0016] Furthermore, the temperature of the heating treatment is 90-150°C; preferably, the temperature of the heating treatment is 150°C.

[0017] Furthermore, the heating treatment time is 0.5 to 3 hours; preferably, the heating treatment time is 2 to 3 hours; more preferably, the heating treatment time is 2 hours.

[0018] Furthermore, the organic solvent system submerges the sample to be processed.

[0019] Furthermore, the sample to be processed is a product containing ethylene-vinyl acetate copolymer.

[0020] Preferably, the product containing ethylene-vinyl acetate copolymer is a solar panel.

[0021] More preferably, the solar panel is a crystalline silicon solar panel or a copper indium gallium selenide solar panel.

[0022] Furthermore, the crystalline silicon solar panel is a disassembled waste solar panel module, which is cut into 4 cm×4 cm samples.

[0023] Specifically, solar modules are constructed from solar panels connected in series and parallel, heat-pressed and sealed with tempered glass, EVA (ethylene vinyl acetate copolymer), and PET (polyethylene terephthalate). From top to bottom, the typical structure of a solar module is: tempered glass, EVA, solar cells, EVA, and PET. To recycle intact waste solar panel chips, the EVA encapsulant between the two layers must be removed, while minimizing damage to the solar panel chips and preserving their inherent metal components.

[0024] At the same time, the present invention also protects the application of the method in the field of solar panel recycling.

[0025] Additionally, the invention protects the use of said method in the field of decapsulation of products containing ethylene-vinyl acetate copolymers.

[0026] The present invention has the following beneficial effects:

[0027] The present invention provides a method for deblocking ethylene-vinyl acetate copolymer using an organic solvent system. This method involves placing a sample containing EVA to be processed in a heated reactor and allowing the organic solvent system to heat and react, thereby deblocking the EVA in the sample. Compared to traditional heating methods for removing EVA, this organic solvent deblocking process does not significantly damage the cell chips inside the solar panel, nor does it significantly leach and lose metals, thus providing a very high recycling value. The entire process of the technical solution of the present invention is environmentally friendly and efficient, without generating secondary pollution, with significant economic benefits and broad application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the desealing effect of the crystalline silicon solar panel after treatment in Example 1.

[0029] Figure 2 This is a microstructure diagram of the unsealed crystalline silicon solar panel observed under a scanning electron microscope after treatment in Example 1.

[0030] Figure 3 This is the desealing effect of the crystalline silicon solar panel after treatment in comparative example 1. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0032] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0033] Example 1 A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0034] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0035] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor. An organic solvent system (volume ratio of N, N-dimethylacetamide: N, N-diethylformamide: N, N-dimethylpropionamide = 1:1:3) totaling 30 mL was added to the heated reactor, and then reacted at 150°C for 2 h to decapsulate the EVA.

[0036] The unblocking effect is as follows Figure 1 As shown, the glass falls off by itself during the unsealing process, the silicon layer and the PET layer are completely separated, the solar panel is completely unsealed, and the unsealing effect is excellent; Figure 2 This is an electron microscope image of the cross-section of the solar panel. It can be seen that the EVA is in a strip shape after desealing, with complete loss of viscosity and complete separation from the glass layer, indicating an excellent desealing effect.

[0037] Example 2 A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0038] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0039] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:1:2) was added to the heated reactor, and then reacted at 150°C for 2 h to decapsulate the EVA.

[0040] The glass fell off by itself during the unsealing process, and the silicon layer and the PET layer were completely separated. The unsealing effect was the same as that in Example 1.

[0041] Example 3: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0042] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0043] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:1:1) was added to the heated reactor. The reaction was then carried out at 150°C for 2 h to decapsulate the EVA.

[0044] Most of the glass fell off by itself during the unsealing process, the solar panels were basically unsealed completely, and the unsealing effect was good.

[0045] Example 4: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0046] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0047] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor. A total of 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:2:1) was added to the heated reactor, and then the reaction was carried out at 150°C for 2 h to decapsulate the EVA.

[0048] Most of the glass fell off by itself during the unsealing process, and the solar panel was basically unsealed completely. The unsealing effect was the same as that of Example 3.

[0049] Example 5: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0050] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0051] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:3:1) was added to the heated reactor. The reaction was then carried out at 150°C for 2 h to decapsulate the EVA.

[0052] Most of the glass fell off by itself during the unsealing process, and the solar panel was basically unsealed completely. The unsealing effect was the same as that of Example 3.

[0053] Comparative Example 1: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0054] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0055] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 4:1:1) was added to the heated reactor. The reaction was then carried out at 150°C for 2 h to decapsulate the EVA.

[0056] The experimental results show that the unblocking effect is as follows Figure 3 As shown, only a small part of the glass fell off and only a small part of the solar panel was unsealed, and the unsealing effect was poor.

[0057] Comparative Example 2: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0058] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0059] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:1:4) was added to the heated reactor, and then reacted at 150°C for 2 h to decapsulate the EVA.

[0060] The experimental results show that only a very small part of the glass falls off and only a small part of the solar panel is unsealed, and the unsealing effect is poor.

[0061] Comparative Example 3: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0062] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0063] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:4:1) was added to the heated reactor. The reaction was then carried out at 150°C for 2 h to decapsulate the EVA.

[0064] After the reaction was completed, the treated solar panel was taken out and it was found that the solar panel had not been unsealed and the solvent and the components of the solar panel had not changed.

[0065] Comparative Example 4: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0066] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0067] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of N,N-dimethylacetamide:N,N-diethylformamide:N,N-dimethylpropionamide = 1:1:8) was added to the heated reactor, and then reacted at 150°C for 2 h to decapsulate the EVA.

[0068] After the reaction was completed, the treated solar panel was taken out and it was found that the solar panel had not been unsealed and the solvent and the components of the solar panel had not changed.

[0069] Comparative Example 5: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0070] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0071] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heating reactor. A total of 30 mL of an organic solvent system (volume ratio of N, N-diethylformamide: N, N-dimethylpropionamide = 1:1) was added to the heating reactor, and then the reaction was carried out at 150°C for 2 h to decapsulate the EVA.

[0072] After the reaction was completed, the treated solar panel was taken out and it was found that the solar panel had not been unsealed and the solvent and the components of the solar panel had not changed.

[0073] Comparative Example 6: A method for removing EVA packaging from waste crystalline silicon solar panels using an organic solvent system

[0074] A method for removing EVA packaging of waste crystalline silicon solar panels using an organic solvent system, specifically comprising the following steps:

[0075] A 4 cm × 4 cm waste crystalline silicon solar panel encapsulated with EVA was placed in a heated reactor, and 30 mL of an organic solvent system (volume ratio of acetamide: N, N-dimethylacetamide: N, N-diethylformamide: N, N-dimethylpropionamide = 1:1:1:3) was added to the heated reactor, and then reacted at 150°C for 2 h to decapsulate the EVA.

[0076] After the reaction was completed, the treated solar panel was taken out and it was found that the solar panel had not been unsealed and the solvent and the components of the solar panel had not changed.

[0077] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for depolymerizing ethylene-vinyl acetate copolymer using an organic solvent system, characterized in that: The specific steps include: The sample to be treated is placed in an organic solvent system and heated at 60-150° C. for 0.5-3 hours to remove the ethylene-vinyl acetate copolymer in the sample to be treated; The organic solvent system is composed of N,N-dimethylpropionamide, N,N-dimethylacetamide and N,N-diethylformamide in a volume ratio of (1-3):(1-3):(1-3).

2. The method according to claim 1, characterized in that The organic solvent system consists of N,N-dimethylpropionamide, N,N-dimethylacetamide and N,N-diethylformamide in a volume ratio of (2-3):1:

1.

3. The method according to claim 1, characterized in that The temperature of the heating treatment is 90-150°C.

4. The method according to claim 1, characterized in that The heating treatment time is 2 to 3 hours.

5. The method according to claim 1, characterized in that: The organic solvent system submerges the sample to be processed.

6. The method according to claim 1, characterized in that The sample to be processed is a product containing ethylene-vinyl acetate copolymer.

7. The method according to claim 6, characterized in that The product containing ethylene-vinyl acetate copolymer is a solar panel.

8. The method according to claim 7, characterized in that: The solar panel is a crystalline silicon solar panel or a copper indium gallium selenide solar panel.

9. Application of the method according to any one of claims 1 to 8 in the field of solar panel recycling.

10. Use of the method according to any one of claims 1 to 8 in the field of desealing products containing ethylene-vinyl acetate copolymers.

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