A method for upgrading recycled waste photovoltaic backsheet polyester by click-dynamic crosslinking

Abstract

The application discloses a kind of click-dynamic crosslinking upgrade recycling waste photovoltaic backboard polyester method, and specifically relates to new energy photovoltaic module recycling field.The method comprises the following steps: waste photovoltaic backboard separation PET polyester board is crushed, then mixed with dihydric alcohol and catalyst, and the partial degradation of PET and hydroxyl end-capping are realized by glycolysis reaction through temperature rising.Using the carbon-carbon double bond introduced in the polymerization process and the reaction of dynamic crosslinking agent to carry out curing process, the regenerated polyester product has excellent mechanical properties and outstanding reprocessing performance.The method disclosed in the application does not produce any waste in the polymerization process, the reaction is green and efficient, the product performance is close to the performance of commercially available PET plastic and easy to reprocess, the crack can be quickly healed at 80 DEG C for 15 min, and the sheet can be reprocessed into powder at 100 DEG C for 2 h, which greatly reduces the energy consumption of recycling, and is expected to partially replace commercial polyester materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photovoltaic module recycling, and particularly relates to a method for upgrading and recycling waste photovoltaic backboard polyester through click-dynamic crosslinking. BACKGROUND

[0002] Resource recycling of waste polymer materials is an important part of developing green low-carbon circular economy. With the large increase in demand for green energy, China's new energy industry has developed rapidly and has become the world's largest photovoltaic application market. The service life of a photovoltaic module is generally 20-25 years.

[0003] The polymer backboard is an important component of a photovoltaic module, generally having a composite structure, with a PET film as a base film and a fluorine film or other plastic film adhered to both sides of the base film through an adhesive. The high-proportion intermediate layer PET polyester mainly plays the roles of electrical insulation, chemical barrier and mechanical support. The fluorine-containing multilayer co-extrusion photovoltaic backboard is difficult to separate and recycle. The existing recycling methods mainly include thermal, chemical and physical recycling methods. The pyrolysis method has high energy consumption and produces toxic gases to pollute the environment. The chemical depolymerization method usually has problems such as low recycling rate, high cost, harsh conditions and poor performance of regenerated products.

[0004] Therefore, it is urgent to provide a simple, efficient and environmentally friendly method for recycling photovoltaic backboard polyester, to fill the last link of green low-carbon circular development of the photovoltaic industry chain and promote the healthy development of the photovoltaic recycling industry and efficient use of resources. SUMMARY

[0005] The application provides a method for upgrading and recycling waste photovoltaic backboard polyester through click-dynamic crosslinking, aiming to solve the problems of low resource utilization, environmental pollution and poor performance of regenerated products in the existing recycling schemes. The method has the following characteristics:

[0006] The method uses partially degraded and hydroxyl-terminated PET oligomers and bio-based unsaturated diacids to introduce carbon-carbon double bonds into the polyester main chain during the repolymerization process. The material is cured through a thiol-ene click reaction under the treatment of a borate dynamic crosslinking agent. No waste is generated during the polymerization process. The reaction is green and efficient. The prepared regenerated polyester has excellent mechanical properties and is easy to reprocess, greatly reducing the recycling energy consumption and being expected to partially replace commercial polyester materials.

[0007] The application discloses a method for upgrading and recycling waste photovoltaic backboard polyester through click-dynamic crosslinking, which comprises the following steps:

[0008] (1) The waste photovoltaic backboard is stirred in a renewable and environmentally friendly solvent at a stirring speed of 60-80 DEG C for 0.5-1 h to completely swell the adhesive layer, and then the PET layer is peeled off and crushed;

[0009] (2) Add the above material to a certain amount of glycolysis catalyst and glycol solvent, heat to 190-220℃ and stir at a certain stirring rate for 2-6h until the PET is converted into white slurry, then stop the reaction;

[0010] (3) Wash the white slurry with excess water to remove glycol, then filter to obtain the mixture, dry at 30℃ for 12-24h, then grind into powder;

[0011] (4) Mix the powder with bio-based unsaturated diacid at a molar ratio of 1:1 and a certain amount of catalyst, put into a three-necked flask, introduce nitrogen and heat to 180℃ for 4-6h to obtain polyester with carbon-carbon double bond in the main chain;

[0012] (5) Add a certain amount of dynamic crosslinking agent and photoinitiator to the polyester with carbon-carbon double bond in the main chain, stir until uniform, then pour into a mold, treat under ultraviolet lamp for 15-30min to fully crosslink to obtain regenerated polyester material.

[0013] Further, the renewable and environmentally friendly solvent in step (1) is (R)-(+)-limonene; the stirring conditions are: stirring temperature 60-80℃, stirring time 0.5-1h, stirring rate 400r / min;

[0014] Further, the glycolysis catalyst in step (2) is selected from one of tetrabutyl titanate, zinc acetate or cobalt acetate; the glycol is selected from ethylene glycol or propylene glycol.

[0015] Further, the addition amount of the glycolysis catalyst in step (2) is 0.5-1% of the total mass of the first intermediate material and glycol solvent; the certain stirring rate is 400r / min.

[0016] Further, the mass ratio of the first intermediate material to glycol in step (2) is 1:1-2.

[0017] Further, the bio-based unsaturated diacid in step (4) is selected from any one of fumaric acid, maleic acid or muconic acid; the catalyst is selected from any one of tetrabutyl titanate, zinc acetate or cobalt acetate, and the addition amount is 0.5-1% of the total mass of the powder and diacid.

[0018] Further, the dynamic crosslinking agent in step (5) is 2,2'-(1,4-phenylene) bis[1,3,2-dioxaborane-4-methylthiol]; the photoinitiator is selected from 2,2-diethoxyacetophenone or benzoin dimethyl ether.

[0019] Further, the molar equivalent ratio of the dynamic crosslinking agent, photoinitiator in step (5) to the unsaturated diacid in step (4) is 0.5-1:0.1-0.2:1.

[0020] The application also discloses a regenerated polyester material prepared by a method for recycling waste photovoltaic backboard polyester through click-dynamic crosslinking upgrading.

[0021] Compared with the prior art, the click-dynamic crosslinking upgrading method for recycling waste photovoltaic backboard polyester has the following effects:

[0022] (1) The application first applies simple and green efficient click chemistry reaction to recycling of waste polyester, and introduces dynamic borate ester bond between PET molecular chains to endow the waste polyester with excellent mechanical properties and reworkability.

[0023] (2) By controlling the degradation reaction time and temperature, the molecular weight of the partially degraded waste can be adjusted, the crystallinity of the regenerated polyester product can be controlled by adjusting the cooling rate during solidification, the performance can be adjusted, the reprocessing energy barrier of the final product is low, the recycling energy consumption is greatly reduced, and the commercial polyester material can be partially replaced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a chemical change process in the material preparation method according to the embodiment of the application.

[0025] Figure 2 is a photovoltaic backboard separation diagram according to the embodiment 1 of the application.

[0026] Figure 3 is a GPC diagram of the degraded waste PET polyester according to the embodiment 1 of the application. DETAILED DESCRIPTION

[0027] The application will be specifically described through the following embodiments. It is necessary to point out that the following embodiments only further illustrate the application, and cannot be understood as a limitation on the protection scope of the application. Those skilled in the art can make some non-essential improvements and adjustments to the application according to the above content.

[0028] Embodiment 1:

[0029] The 30 g of waste photovoltaic backboard was taken out after the adhesive layer was completely swelled by stirring at 400 r / min stirring rate at 60°C for 0.5 h in limonene, the PET layer was peeled off and crushed. 10 g of the above material was mixed with 0.15 g of tetrabutyl titanate and 20 g of ethylene glycol, then heated to 200°C and stirred at 400 r / min for 2 h until the PET was converted into a white slurry. The reaction was stopped. The white slurry was washed with excess water to remove ethylene glycol, then filtered to obtain the mixture. The precipitate was dried at 30°C for 24 h, then ground into powder. The powder was mixed with maleic acid at a molar ratio of 1:1 and 0.5 wt% tetrabutyl titanate, placed in a three-necked flask, purged with nitrogen and heated to 180°C for 6 h to obtain a polyester with carbon-carbon double bonds in the main chain. The maleic acid content was set to 1 mole equivalent, 0.5 mole equivalent of dynamic crosslinking agent and 0.2 mole equivalent of benzoin dimethyl ether were added to the three-necked flask, stirred until evenly mixed, then poured into a mold, treated under a UV lamp for 30 min to fully crosslink to obtain a regenerated polyester material. Based on the low-energy reversible reconstruction characteristics of the dynamic borate ester bond, the regenerated polyester can quickly heal after being cut at 80°C for 15 min. The crushed product can be reprocessed into a sheet at 100°C for 2 h.

[0030] According to the results of Figure 2 It can be known that the photovoltaic backboard treated by the renewable and environmentally friendly solvent limonene can be easily separated, which lays the foundation for the preparation of the first intermediate material.

[0031] According to the results of Figure 3 It can be known that the product obtained by degrading for 4 hours under the condition of the first intermediate material: ethylene glycol solvent = 1:2 has a uniform molecular weight distribution, Mw = 753, PDI = 1.056336, which is preliminarily determined as a trimer of BHET, providing a basis for subsequent repolymerization with bio-based unsaturated diacid.

[0032] Example 2:

[0033] After 30 g of waste photovoltaic backsheet was completely swelled by stirring at 400 r / min for 0.5 h at 60℃ in limonene, the PET layer was peeled off and crushed. 10 g of the above material was mixed with 0.3 g of zinc acetate and 20 g of ethylene glycol, and then heated to 220℃ and stirred at 400 r / min for 2 h until the PET was converted into a white slurry. The reaction was stopped, and the white slurry was washed with excess water to remove ethylene glycol, and then filtered to obtain a mixture. The mixture was dried at 30℃ for 24 h, and then ground into powder. The powder was mixed with fumaric acid at a molar ratio of 1:1 and 0.5 wt% of tetrabutyl titanate, and then placed in a three-necked flask, and then nitrogen was introduced and heated to 180℃ for 4 h to obtain a polyester with carbon-carbon double bonds in the main chain. The fumaric acid content was set to 1 molar equivalent, and 0.7 molar equivalents of a dynamic crosslinking agent and 0.15 molar equivalents of benzpinacol were added to the three-necked flask, and then stirred until uniform, and then poured into a mold, and then treated under a UV lamp for 20 min to fully crosslink to obtain a regenerated polyester material. Based on the low-energy reversible reconstruction characteristics of the dynamic borate ester bond, the regenerated polyester can be quickly healed after being cut at 90℃ for 20 min, and the crushed product can be reprocessed into a sheet at 120℃ for 2 h.

[0034] The above are only preferred embodiments of the present application, and do not limit the patent scope of the present application, and any equivalent structure or equivalent flow transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied to other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking, comprising: (1) stirring the waste photovoltaic backsheet in a renewable and environmentally friendly solvent until the adhesive layer is completely swollen, then taking it out, peeling off the PET layer and crushing it to obtain a first intermediate material for standby; (2) adding the first intermediate material to a glycolysis catalyst and a glycol solvent, then heating to 190-220℃ and stirring at a certain stirring rate for 2-6h until the first intermediate material is converted into a white slurry, then stopping the reaction; (3) washing the white slurry with excess water to remove the glycol, then filtering, and grinding the obtained mixture into powder after drying at 30℃ for 12-24h; (4) mixing the powder with a bio-based unsaturated diacid in a molar ratio of 1:1 and a certain amount of catalyst in a three-necked flask, purging with nitrogen and heating to 180℃ for polymerization for 4-6h to obtain a polyester with carbon-carbon double bonds in the main chain; (5) adding a certain amount of dynamic crosslinking agent and photoinitiator to the polyester with carbon-carbon double bonds in the main chain, stirring until uniformly mixed, then pouring into a mold, treating under a UV lamp for 15-30min to fully crosslink to obtain a regenerated polyester material; wherein: the renewable and environmentally friendly solvent is (R) - (+) -limonene; the bio-based unsaturated diacid is selected from any one of fumaric acid, maleic acid or muconic acid; the dynamic crosslinking agent is 2, 2' - (1, 4-phenylene) bis [1, 3, 2-dioxaborane-4-methylthiol]. 2.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the stirring conditions in step (1) are: stirring temperature 60-80℃, stirring time 0.5-1h, stirring rate 400r / min. 3.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the glycolysis catalyst in step (2) is selected from one of tetrabutyl titanate, zinc acetate or cobalt acetate; the glycol is selected from ethylene glycol or propylene glycol. 4.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the amount of glycolysis catalyst added in step (2) is 0.5-1% of the total mass of the first intermediate material and the glycol solvent; the certain stirring rate is 400r / min. 5.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the mass ratio of the first intermediate material to the glycol in step (2) is 1:1-2. 6.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the catalyst in step (4) is selected from any one of tetrabutyl titanate, zinc acetate or cobalt acetate, and the amount added is 0.5-1% of the total mass of the powder and the diacid. 7.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: the photoinitiator in step (5) is selected from 2, 2-diethoxyacetophenone or benzoin dimethyl ether. 8.The method for recycling waste photovoltaic backsheet polyester by click-dynamic crosslinking according to claim 1, wherein: The molar equivalent ratio of the dynamic crosslinking agent, the photoinitiator and the unsaturated dibasic acid of step (4) described in step (5) is 0.5-1:0.1-0.2:

1.

9. A recycled polyester material prepared by the method of upgrading and recycling waste photovoltaic backsheet polyester according to any one of claims 1-8.

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