Method for recovering solar backsheet

Abstract

The present invention belongs to the field of the recovery of high polymer materials. Disclosed is a method for recovering a solar backsheet. The method uses a specific extraction-depolymerization process to treat a solar backsheet, and can not only effectively remove an adhesive component from the raw material, but can also effectively obtain a PET depolymerization oligomer and a recovered material of an outer layer.

Description

A recycling method of a solar cell backboard TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer material recycling, in particular to a recycling method of a solar cell backboard. BACKGROUND

[0002] Solar cells are a relatively popular new energy device, and their environmental protection lies not only in the fact that they do not cause pollution problems of traditional energy devices during operation, but also in the fact that they have high recyclability after retirement.

[0003] In the recycling process of existing solar cells, key photovoltaic materials are generally recycled by physical crushing, high-temperature pyrolysis, chemical purification and other methods, but for typical high molecular materials such as solar cell backboards, they need to be separated and then treated, otherwise they may produce pollution sources during the recycling process or cannot effectively recycle the materials.

[0004] The solar cell backboard is generally a TPT structure, i.e., a layer structure of PP / adhesive / PET / adhesive / PP or PVDF / adhesive / PET / adhesive / PVDF. After long-term use, the molecular chains of this structure material may have partially fused, and the composition is relatively complex. In the existing process, the solar cell backboard is separated by using an organic solvent, the adhesive is dissolved by using an organic solvent to separate the layers, and then the separated PET layer and the peripheral layer (PVDF, PP) are recycled. However, the recycled layer itself has low purity, and there is still a lot of adhesive residue, and the available field is very small, and even additional processes are needed for purification. If a solvent with strong solubility is used for recycling, the PET layer and the peripheral layer may also be dissolved, resulting in a low recycling rate.

[0005] SUMMARY

[0006] Based on the defects of the prior art, the purpose of the present application is to provide a recycling method of a solar cell backboard, which uses a specific extraction-depolymerization process to treat the solar cell backboard, which can effectively remove the adhesive components in the raw material, and can effectively obtain PET depolymerization oligomers and peripheral layer recycled materials with high purity and high recycling rate. The recycled material can be reused without additional treatment, and has high practicality.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] A recycling method of a solar cell backboard, comprising the following steps:

[0009] (1) The solar cell backsheet is cut, broken and treated into fragments, then placed in acetone and ultrasonically treated for 50-70 min under 80-120 W power, filtered, dried to obtain a residue A;

[0010] (2) The residue A is placed in a polyol containing depolymerization catalyst and microwave heated to 170-200℃ for 10-20 min of depolymerization reaction, filtered to obtain a depolymerization liquid B and insoluble C;

[0011] (4) The insoluble C is subjected to inorganic phase separation, filtration and drying to obtain a peripheral layer recovery material.

[0012] Taking a solar cell backsheet with the structure of PVDF / adhesive / PET / adhesive / PVDF as an example, the adhesive in the product is mainly EVA. In the existing recycling technology, strong acid, strong alkali and high solubility organic solvent are often used to prepare a dissolution solution to corrode and dissolve the adhesive, so as to obtain a PET layer plate and a PVDF plate. However, since the PET material itself has poor chemical resistance and is easy to hydrolyze and oxidize, the PET layer in the backsheet has been hydrolyzed and degraded to a certain extent during the service of the solar cell. If the above high-polarity dissolution solution is used for treatment, the materials in the PET layer may also be dissolved, the recovered PET layer plate has high impurity content, the mechanical strength of the product is poor, and the product cannot be directly recycled and used. If a low-polarity dissolution solution is used for treatment, the adhesive component cannot be effectively removed, and the recovered product needs to be further purified and separated from EVA, which is complicated.

[0013] Based on this technical dilemma, the inventors creatively use a segmented extraction-depolymerization treatment step to recycle the solar cell backsheet. First, the material is pretreated with acetone under specific ultrasonic conditions. Under this treatment condition, the impurities produced by the degradation and hydrolysis of the adhesive and some high molecular materials in the material can be separated to the maximum extent, and the PET material and the peripheral layer (PVDF / PP) material can maintain the minimum loss rate. After removing the small molecular adhesive, the obtained residue is depolymerized into oligomers under specific conditions, and the peripheral layer material is not affected. After further separation of the solution, the obtained PET depolymerization oligomer (i.e. bis-hydroxyethyl terephthalate) has high purity and high recovery rate. According to actual requirements, it can be directly re-polymerized into regenerated PET, PBAT or PBET. The insoluble material left after depolymerization can be easily separated from the high molecular material (PVDF / PP) and inorganic filler in the peripheral layer plate after further treatment. The recovery rate of the high molecular material is higher than that of the directly recycled peripheral layer plate recovery material, and the utilization range is significantly improved.

[0014] Meanwhile, the inventors have found through experiments that the adhesive (usually EVA or acrylate), PET and peripheral layer material in the backsheet of a solar cell are all soluble in different organic solvents, and the degree of solubility varies depending on the difference in the dissolution conditions. If the pre-extraction solvent (for example, methanol, tetrahydrofuran, etc. with similar solubility of each material) and the pre-extraction conditions (for example, microwave conditions or oil bath conditions) are not appropriate, not only can the adhesive not be completely separated, but the recovered material can also be greatly dissolved and lost. In the depolymerization process, since the PET in the recovered material is not a new material, the reaction temperature needs to be strictly controlled and the constant temperature state needs to be controlled in real time to ensure that the PET is completely depolymerized and the peripheral layer material is not dissolved in the organic solvent. If the operation is not proper, the desired technical effect cannot be achieved.

[0015] Preferably, in step (1), the mass of the solar cell backsheet crushed material to the volume of acetone is 10 g:(80-120) mL.

[0016] More preferably, in step (1), the power of the ultrasonic treatment is 90-110 W, and the time is 55-65 min.

[0017] As described above, each material in the solar cell backsheet crushed material can be dissolved in the acetone without strong corrosive components described in the present application. Under ultrasonic conditions, the dissolution of each material is different. When the treatment power and time are within the preferred range, the adhesive can be separated to the greatest extent, and the loss rate of the recovered material is minimized.

[0018] Preferably, in step (2), the depolymerization catalyst is at least one of titanium nanotubes, butyl titanate, zinc acetate, and titanium dioxide.

[0019] More preferably, the mass ratio of the depolymerization catalyst to the raffinate A is (0.0005-0.015):1.

[0020] Preferably, in step (2), the polyol is at least one of ethylene glycol, propylene glycol, butanediol, and pentanediol.

[0021] More preferably, the polyol is ethylene glycol.

[0022] When ethylene glycol is selected as the solvent for the depolymerization reaction, the PET can be more efficiently and completely depolymerized, the impact on the peripheral layer recovered material is small, the purity of the final recovered material is higher, the recovery rate is higher, the amount of polyol used is less, and the cost performance is higher.

[0023] More preferably, the volume of the polyol to the mass of the raffinate A is (0.5-5) mL:1 g.

[0024] Preferably, the step (3) of freezing crystallization and filtration treatment is as follows: mixing the depolymerization liquid B with water, then cooling to 3-5℃, and filtering the crystallized solid after the complete crystallization of the obtained mixture.

[0025] Preferably, the inorganic phase separation in the step (4) is carried out by organic solvent extraction, and the organic solvent is at least one of methanol, dimethylformamide, tetrahydrofuran and dimethylbenzene.

[0026] Since the insoluble substance C only contains the peripheral layer high molecular material (PVDF / PP) and inorganic rigid filler such as titanium white after the previous extraction-depolymerization and subsequent separation, a high-purity peripheral layer recovery material can be obtained by using a conventional high-solubility organic solvent for organic-inorganic separation treatment, but the organic solvent is not limited to the above-mentioned types, and the extraction process can be carried out under various conditions such as normal pressure, inert atmosphere protection, heating treatment, microwave treatment, ultrasonic treatment, etc., and is not limited to the above-mentioned preferred scheme.

[0027] Preferably, in the step (2), the temperature variation amplitude is controlled to be ≤2℃ during the depolymerization reaction.

[0028] The present application has the beneficial effect that the present application provides a recycling method of solar cell backsheet, which uses a specific extraction-depolymerization process to treat the solar cell backsheet, which can effectively remove the adhesive component in the raw material, and can effectively obtain a high-purity, high-recovery-rate PET depolymerization oligomer and peripheral layer recovery material, which can be reused without additional treatment, and has high practicability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 is a flowchart of the recycling method of the solar cell backsheet according to the present application.

[0030] Fig. 2 is an infrared diagram of the adhesive component separated from the solar cell backsheet after ultrasonic extraction in the method according to the embodiment 1 of the present application.

[0031] Fig. 3 is an infrared diagram of the depolymerization liquid B and the insoluble substance C in the method according to the embodiment 1 of the present application.

[0032] Fig. 4 is an infrared diagram of the adhesive component separated from the solar cell backsheet after ultrasonic extraction in the method according to the embodiment 2 of the present application.

[0033] Fig. 5 is an infrared diagram of the depolymerization liquid B and the insoluble substance C in the method according to the embodiment 2 of the present application. DETAILED DESCRIPTION

[0034] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples and comparative examples, the purpose of which is to understand the content of the present application in detail, rather than to limit the present application. All other examples obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present application. The experimental reagents and instruments involved in the implementation of the present application are all common ordinary reagents and instruments unless otherwise specified.

[0035] The solar cell backsheet 1 described in the present application is a PVDF / EVA / PET / EVA / PVDF structure recycling product recovered by Dongyue Blue Sky New Energy Co., Ltd.;

[0036] The solar cell backsheet 2 described in the present application is a PP / acrylate / PET / acrylate / PP structure recycling product recovered by Dongyue Blue Sky New Energy Co., Ltd.;

[0037] Example 1

[0038] One embodiment of the recycling method of the solar cell backsheet described in the present application, the specific step flow is shown in FIG. 1, which comprises the following steps:

[0039] (1) 10 g of solar cell backsheet 1 is cut and crushed into fragments, then placed in 100 mL of acetone and ultrasonically treated at 100 W for 60 min, filtered, dried, and 9.86 g of residue A is obtained;

[0040] (2) The residue A is placed in 20 mL of ethylene glycol containing 10 mg of butyl titanate and heated to 180℃ by 500 W microwave for 15 min of depolymerization reaction, filtered, and 10 mL of depolymerization liquid B and insoluble C are obtained; the temperature change amplitude is controlled to be ≤2℃ during the depolymerization reaction;

[0041] (3) The depolymerization liquid B is mixed with water and then cooled to 4℃ to start freezing crystallization, and after the crystallization is completed, the crystalline solid is filtered, and the PET depolymerization oligomer is obtained;

[0042] (4) The insoluble C is placed in 50 mL of tetrahydrofuran and treated by 100 W ultrasonic for 60 min to separate the inorganic phase contained therein, filtered and dried, and the peripheral layer recycling material is obtained.

[0043] Example 2

[0044] One embodiment of the recycling method of the solar cell backsheet described in the present application comprises the following steps:

[0045] (1) 50 g of solar cell backsheet 2 is cut and crushed into fragments, then placed in 400 mL of acetone and ultrasonically treated at 100 W for 60 min, filtered, dried, and 48.25 g of residue A is obtained;

[0046] (2) The residue A is put into 60 mL ethylene glycol containing 50 mg butyl titanate and heated to 190℃ by microwave with 500W for 10 min, and filtered to obtain the depolymerization liquid B and the insoluble C; the temperature variation is controlled to be less than 2℃ during the depolymerization reaction;

[0047] (3) The depolymerization liquid B is mixed with water and then cooled to 4℃ to start the freeze crystallization, and the crystallized solid is filtered after the crystallization is completed, to obtain the PET depolymerization oligomer.

[0048] (4) The insoluble C is put into 50 mL dimethylbenzene and treated by ultrasonic with 100W for 30 min to separate the inorganic phase contained in the insoluble C, and the insoluble C is filtered and dried to obtain the outer layer recovery material.

[0049] Example 3

[0050] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 120W and the time is 60 min.

[0051] Example 4

[0052] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 110W and the time is 60 min.

[0053] Example 5

[0054] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 90W and the time is 60 min.

[0055] Example 6

[0056] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 80W and the time is 60 min.

[0057] Example 7

[0058] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 105W and the time is 50 min.

[0059] Example 8

[0060] The difference between the embodiment of the recycling method of the solar cell backboard and the embodiment 1 is only that the power of the ultrasonic treatment in the step (1) is 95W and the time is 70 min.

[0061] Example 9

[0062] One embodiment of the recycling method of the solar cell backsheet according to the present application differs from Example 1 only in that the ethylene glycol in step (2) is replaced with an equal mass of propylene glycol.

[0063] Example 10

[0064] One embodiment of the recycling method of the solar cell backsheet according to the present application differs from Example 1 only in that the ethylene glycol in step (2) is replaced with an equal mass of butylene glycol.

[0065] Example 11

[0066] One embodiment of the recycling method of the solar cell backsheet according to the present application differs from Example 2 only in that the ethylene glycol in step (2) is replaced with an equal mass of pentylene glycol.

[0067] Comparative Example 1

[0068] A recycling method of a solar cell backsheet differs from Example 1 only in that the acetone is replaced with a mixture of water, sodium hydroxide, and acetone in a mass ratio of 2:5:6.

[0069] Comparative Example 2

[0070] A recycling method of a solar cell backsheet differs from Example 2 only in that the acetone is replaced with a mixture of water, sodium hydroxide, and acetone in a mass ratio of 10:5:6.

[0071] Comparative Example 3

[0072] A recycling method of a solar cell backsheet differs from Example 1 only in that the acetone is replaced with methanol.

[0073] Comparative Example 4

[0074] A recycling method of a solar cell backsheet differs from Example 2 only in that the acetone is replaced with dimethylformamide.

[0075] Comparative Example 5

[0076] A recycling method of a solar cell backsheet differs from Example 1 only in that the acetone is replaced with tetrahydrofuran.

[0077] Comparative Example 6

[0078] A recycling method of a solar cell backsheet differs from Example 1 only in that the ultrasonic treatment in step (1) is replaced with a blank treatment, i.e., no ultrasonic treatment is performed, and the treatment duration remains unchanged.

[0079] Comparative Example 7

[0080] A recycling method of a solar cell back sheet, which differs from Example 1 only in that the step (1) ultrasonic treatment is replaced by 70℃ oil bath treatment, and the treatment time is unchanged.

[0081] Comparative Example 8

[0082] A recycling method of a solar cell back sheet, which differs from Example 1 only in that the step (1) ultrasonic treatment is replaced by microwave heating to 70℃ holding treatment, and the treatment time is unchanged.

[0083] Comparative Example 9

[0084] A recycling method of a solar cell back sheet, which differs from Example 1 only in that the power of the ultrasonic treatment in the step (1) is 50W, and the time is 80min.

[0085] Comparative Example 10

[0086] A recycling method of a solar cell back sheet, which differs from Example 1 only in that the power of the ultrasonic treatment in the step (1) is 180W, and the time is 40min.

[0087] Comparative Example 11

[0088] A recycling method of a solar cell back sheet, comprising the following steps:

[0089] (1) 10g of a solar cell back sheet 1 is cut and crushed into fragments, and then placed in 20mL of ethylene glycol containing 10mg of butyl titanate and heated to 180℃ by 100W microwave for 15min of depolymerization reaction, filtered to obtain a depolymerization liquid B and insoluble matter C; the temperature change amplitude during the depolymerization reaction is controlled to be ≤2℃;

[0090] (2) The depolymerization liquid B is mixed with water and then cooled to 4℃ to start freezing crystallization, and after the crystallization is complete, the crystalline solid is filtered to obtain a PET depolymerization oligomer;

[0091] (3) The insoluble matter C is placed in 50mL of tetrahydrofuran and treated by 100W ultrasonic for 60min to separate the inorganic phase contained therein, filtered and dried to obtain a peripheral layer recycling material.

[0092] Example 1

[0093] In order to verify the recycling effect of the recycling method of the solar cell backsheet according to the present application, the purity and the recycling rate of the PET depolymerized oligomer and the peripheral layer recyclate obtained in each example and the comparative example were determined and counted, wherein the purity test method of the PET depolymerized oligomer was as follows: using high performance liquid chromatography (HPLC): Waters liquid chromatograph (E2695-2998)-DAD detector, the depolymerized oligomer was dissolved in a methanol / dichloromethane (mass ratio 1:1) solution for testing. The test conditions were as follows: the chromatographic column used was a Discovery C-18 column (4.6 mm x 250 mm, 5 μm), acetonitrile and water were used as the mobile phase, the elution mode was isocratic elution; the injection amount was 2 μL, the column temperature was 30°C, the flow rate was 1 mL / min, and the ultraviolet detection wavelength was 254 nm.

[0094] The recycling rate calculation method of the PET depolymerized oligomer was as follows: PET depolymerized oligomer mass / theoretical PET depolymerized oligomer mass x 100%;

[0095] The theoretical PET depolymerized oligomer mass was calculated according to the thickness and the proportion of the PET layer determined by taking a photograph of the solar cell backsheet section by a microscope or a scanning electron microscope (SEM), in combination with the density of each material to obtain the theoretical PET mass in the solar cell, and then the theoretical PET depolymerized oligomer mass was calculated by a depolymerization reaction equation;

[0096] The recycling rate calculation method of the peripheral layer recyclate was as follows: peripheral layer recyclate mass / theoretical peripheral layer recyclate mass x 100%;

[0097] The theoretical peripheral layer recycling rate mass was calculated according to the thickness and the proportion of the peripheral layer determined by taking a photograph of the solar cell backsheet section by a microscope or a scanning electron microscope (SEM), in combination with the density of each material to obtain the theoretical peripheral layer mass in the solar cell;

[0098] The test results are shown in Table 1.

[0099] Table 1

[0100] As can be seen from Table 1, the material is recycled by using the recycling method of the solar cell backsheet described in the application, and the material TPT structure system is PVDF or PP, and high-purity PET depolymerization oligomer and peripheral layer recycled material can be effectively obtained, the recycling interference of the adhesive is effectively removed, and the material loss caused by the problem of the dissolving reagent is also avoided, the purity of the PET depolymerization oligomer can reach more than 98.5%, the recovery rate can reach more than 94%, and the recovery rate of the peripheral layer recycled material can reach more than 94.5%. Taking Examples 1 and 2 as examples, in Example 1, the solar cell backsheet of the PVDF system is extracted by the extraction process of the method described in the application, and the residue of the extract liquid after solvent removal is detected by infrared detection, and it is found that the main component is the adhesive EVA, as shown in Figure 2, and when the material is depolymerized, the mixture obtained is detected by infrared detection, and only PET depolymerization oligomer, peripheral layer recycled material PVDF and inorganic filler titanium dioxide are found, as shown in Figure 3; similarly, in Example 2, the residue of the extract liquid after solvent removal is detected by infrared detection, and the components are as shown in Figure 4, that is, acrylate, and the mixture after depolymerization is detected, and only PET depolymerization oligomer, peripheral layer recycled material PP and inorganic filler titanium dioxide are found, as shown in Figure 5. In contrast, Comparative Example 1 uses a solvent liquid containing a corrosive component to dissolve the solar cell backsheet scrap, although the component can also effectively separate the adhesive, but obviously it will also greatly increase the loss rate of the recycled material, and even cause the purity of the final product to be reduced, especially in the early dissolution process, a large amount of peripheral layer recycled material is also dissolved and lost, so in the subsequent insoluble C, the content of the peripheral layer recycled material is small, and the yield of the final product is low. The results of Comparative Example 2 are similar to those of Comparative Example 1, indicating that the adverse results of Comparative Example 1 are not only present in the recycling of one type of solar cell backsheet. As can be seen from Examples 1-2 and Comparative Examples 3-5, although there are not a few solvents similar to acetone in solubility of PET, adhesive and peripheral layer recycled material in the prior art, but after these solvents are used to replace acetone, the recycling condition is significantly worse, indicating that in the recycling method described in the application, the organic solvent in the extraction process can only be acetone, otherwise it is difficult to realize the selective dissolution of the adhesive in the recycled material.However, after selecting acetone as the organic solvent, appropriate extraction conditions also need to be adopted for matching, as shown in Comparative Examples 6-8, the oil bath and microwave heating processes often used in some existing impurity removal and recovery processes are not suitable for the adhesive pretreatment separation of the recovery method described in the present application. Such a separation process can cause the separation body to change from the adhesive to the PET and even the peripheral layer material, resulting in low purity and low yield of the final product. As can be seen from Example 1, Examples 3-6 and Comparative Examples 9-10, in the acetone extraction process under ultrasonic conditions, if the extraction conditions are too mild, such a low-polarity solvent is difficult to effectively separate the adhesive, and the adhesive will be depolymerized with the PET and mixed in the finally prepared PET depolymerized oligomer, thereby affecting the purity of the PET depolymerized oligomer. However, if the extraction conditions are too severe, the materials to be recovered other than the adhesive can also be dissolved therein, ultimately resulting in low recovery rates of both the PET oligomer and the peripheral layer recovery material. Therefore, the extraction conditions need to be strictly controlled. When the preferred extraction conditions are an ultrasonic power of 90-110 W, the adhesive can be fully dissolved and separated during the treatment process, and the PET and the peripheral layer material are not significantly dissolved and separated, which ensures the purity and recovery rate of the product during subsequent depolymerization, crystallization and peripheral layer material recovery. The recovery efficiency of the method is the highest and the purity of the recovered material is higher. As can be seen from the recovery results of Comparative Example 11, if the adhesive is not separated in advance before the depolymerization process, although the adhesive will be separated with the PET depolymerized oligomer after depolymerization, the adhesive cannot be effectively separated from the PET depolymerized oligomer after the PET depolymerized oligomer is recrystallized, resulting in a significant decrease in the purity of the PET depolymerized oligomer. As can be seen from Examples 1-2 and Examples 9-11, for the recovery methods of different types of solar cell backplanes, the depolymerization effect of using ethylene glycol as the solvent is the best in the depolymerization process, the purity and yield of the PET oligomer are high, and the recovery rate of the peripheral layer recovery material is the highest.

[0101] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and do not limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for recycling a solar cell backsheet, characterized in that: The following steps are involved: (1) Cutting and crushing the solar cell backsheet into pieces, placing them in acetone and ultrasonically treating them at a power of 80 to 120 W for 50 to 70 minutes, filtering them, and drying them to obtain a residue A; (2) placing the raffinate A in a polyol containing a depolymerization catalyst and heating the mixture to 170-200° C. by microwave heating for 10-20 min, followed by filtration to obtain a depolymerization solution B and an insoluble substance C; (3) After the depolymerization liquid B is frozen, crystallized, and filtered, PET depolymerized oligomers are obtained; (4) The insoluble matter C is separated from the inorganic phase, filtered, and dried to obtain the outer layer recycled material.

2. The method for recycling a solar cell back sheet according to claim 1, wherein: In the step (1), the ratio of the mass of the solar cell backsheet scraps to the volume of acetone is 10 g: (80-120) mL.

3. The method for recycling a solar cell backsheet according to claim 1, wherein: In the step (1), the power of the ultrasonic treatment is 90 to 110 W, and the time is 55 to 65 minutes.

4. The method for recycling a solar cell backsheet according to claim 1, wherein: The depolymerization catalyst in step (2) is at least one of titanate nanotubes, butyl titanate, zinc acetate, and titanium dioxide; and the mass ratio of the depolymerization catalyst to the raffinate A is (0.0005-0.015):

1.

5. The method for recycling a solar cell back sheet according to claim 1, wherein: In the step (2), the polyol is at least one of ethylene glycol, propylene glycol, butylene glycol, and pentanediol; and the ratio of the volume of the polyol to the mass of the raffinate A is (0.5-5) mL:1 g.

6. The method for recycling a solar cell back sheet according to claim 1, wherein: In the step (2), the temperature variation of the depolymerization reaction device is controlled to be ≤2°C.

7. The method for recycling a solar cell back sheet according to claim 1, wherein: The freezing crystallization and filtration treatment steps of step (3) are as follows: adding water to the depolymerization liquid B and mixing, then cooling to 3-5° C., and filtering the crystallized solid after the obtained mixed liquid is completely crystallized.

8. The method for recycling a solar cell back sheet according to claim 1, wherein: The inorganic phase separation in step (4) is performed by extraction with an organic solvent, wherein the organic solvent is at least one of methanol, dimethylformamide, tetrahydrofuran, and xylene.

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