Method for preparing regenerated polyester by closed-loop recovery of waste polyester with typical green and low-carbon characteristics

Abstract

The invention discloses a method for preparing regenerated polyester by closed-loop recovery of waste polyester with typical green and low-carbon characteristics. The method comprises the steps: selecting a specific depolymerization catalyst to depolymerize waste polyester under a microwave condition; removing a polyol solvent from the depolymerized product, and purifying to remove byproducts to obtain a depolymerized monomer; and mixing the depolymerized monomer with dibasic acid, polyol, a polymerization catalyst and a chain extender, carrying out esterification reaction, adding a stabilizer and a catalyst, and carrying out polycondensation to obtain the regenerated polyester. According to the method, the depolymerization temperature is low, the efficiency is high, the dosage of the polyol solvent is small, and the content of the byproducts is extremely low; meanwhile, the depolymerization catalyst does not need to be separated, co-esterification of the regenerated polyester can be directly carried out, and no adverse effect is caused on the performance of the prepared regenerated polyester. The method provided by the invention can realize closed-loop recovery of waste polyester.

Description

technical field [0001] The invention relates to the technical field of chemical regeneration of polyester, and more specifically, relates to a method for preparing regenerated polyester by closed-loop recovery of waste polyester with typical green and low-carbon characteristics. Background technique [0002] With the rapid development of the polyester industry, the disposal of waste polyester products has come one after another. The huge stock of waste polyester products in the society has not only brought huge pressure to the ecological environment, but also caused a serious waste of petrochemical resources. Therefore, a large amount of waste polyester needs to be recycled and recycled. [0003] The recycling methods of waste polyester are mainly divided into two categories: physical recycling and chemical recycling. Physical recycling mainly uses the thermoplasticity of polyester to remove impurities, wash, melt and re-granulate polyester and its products to obtain second...

AI Technical Summary

Problems solved by technology

[0004] In the method of existing chemical method recycling waste polyester, mainly have the defect of the following aspects: (1) the residue that contains heavy metal depolymerization catalyst has adverse effect on the performance of regenerated polyester, as causing regenerated polyester to be easy to decompose , the viscosity is low, and the heavy metal content exceeds the standard; (2) The temperature is high during the depolymerization process of waste polyester, and the amount of depolymerization agent is high. The energy consumption is relatively large, which does not meet the current green and low-carbon technical requirements. At the same time, it is easy to produce by-products with complex components, which affects the depolymerization efficiency and leads to energy consumption and a series of environmental impacts of by-product treatment; (3) Recycled polyester is difficult Applied to the same or similar scenarios before recycling, that is, it is difficult to achieve closed-loop recycling, and currently PET is mainly used to prepare plastic bottles, fibers and fabrics after chemical recycling, while the recycling of industrially prepared degradable plastics is rarely involved, and it is currently degradable Plastic composting conditions are harsh, and it is difficult to complete effective and sufficient degradation in the natural environment. It is the general trend to realize the closed-loop recycling of degradable materials

[0005] Chinese patent application CN107266664A discloses a polyester waste recycling process, which uses zinc acetate as a catalyst to depolymerize PET waste, but the zinc ions remaining in the depolymerization product will cause regeneration due to its catalytic mechanism for carbonyl oxygen coordination. Side reactions such as thermal degradation are accelerated during the polymerization process, which limits the growth of molecular weight, and the viscosity of recycled polyester is low and the quality is poor

Chinese patent application CN102731310A discloses a method for catalyzing the alcoholysis of PET with a first transition metal ionic liquid, but the content of halogen group elements in the catalyst of this type of ionic liquid is very high, if the catalyst cannot be removed from the depolymerization product, then During the repolymerization process, the macromolecule will be decomposed due to the generation of hydrogen halide, which seriously affects the quality of the repolymerized product; and in this method, the amount of catalyst added needs to reach 10wt.% of PET, and the amount of alcoholysis solvent ethylene glycol is about PET 4 to 10 times of that, the amount of catalyst and diol is large

But on the one hand, this method can only recycle waste PET, and does not involve other types of waste polyester; on the other hand, the depolymerization temperature in the alcohol solution polymerization process of this method is 160-240 °C, and the depolymerization time is 0.5-5h , the temperature is too high and the time is too long, so that ethylene glycol is easily cyclodehydrated to form cyclized by-products, and the method uses a large amount of alcoholysis agent and the process is complicated

[0007] Existing technology (Meng Hui. The influence of process conditions on the by-product tetrahydrofuran in the esterification process in the synthesis of polybutylene succinate [D]. East China University of Science and Technology, 2011.) reported a solution for the cyclization by-product, For example, reduce the generation rate and output of the cyclization product tetrahydrofuran in the esterification process by feeding nitrogen, reducing the reaction temperature, etc.

However, for the depolymerization reaction, the polyester cannot be depolymerized at too low a reaction temperature and too short a reaction time.

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