Recovery method for chemical recovery of waste pet
By using chemical recycling methods to depolymerize and regenerate waste PET, combined with antimony glycol catalyst, the problem of difficult PET material recycling has been solved, achieving efficient and low-cost recycling results.
Patent Information
- Application Number
- CN202511829639.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-10
- Publication Date
- 2026-03-17
AI Technical Summary
Existing PET materials are difficult to recycle efficiently, resulting in high production costs and low efficiency, and the waste materials cause serious environmental pollution.
A chemical recycling method is adopted, including steps such as color sorting, metal separation, twin-screw extrusion, esterification reaction, pre-condensation and final condensation, combined with antimony glycolate catalyst, to achieve efficient depolymerization and regeneration of PET materials.
It improves PET production efficiency and purity, reduces usage costs, and decreases environmental pollution.
Smart Images
Figure CN121673535A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pet recycling technology, and more particularly to a chemical recycling method for waste pet. Background Technology
[0002] Polyethylene terephthalate (PET) is the most important type of thermoplastic polyester, commonly known as polyester resin. It is produced by transesterification of dimethyl terephthalate with ethylene glycol or by esterification of terephthalic acid with ethylene glycol to synthesize diethyl terephthalate, followed by polycondensation reaction.
[0003] Existing PET production, after spinning or granulation, generally needs to produce the required products. However, after the products are used and discarded, they cause environmental pollution due to their long degradation time. Moreover, PET, as a basic material, has a wide range of applications, and it is difficult to recycle and regenerate waste PET, resulting in high production costs. Furthermore, existing production lines have many processes and low production efficiency. Summary of the Invention
[0004] The present invention aims to provide a recycling method for chemically recycling waste pet to overcome or at least partially solve the above-mentioned problems.
[0005] To achieve the above objectives, the technical solution of the present invention is specifically implemented as follows: This invention provides a chemical recycling method for waste PET, comprising the following steps: S1, waste PET material is sequentially placed into a color sorter and a metal separator for mixing, crushing and dispersing, and PET and metal impurities of different colors are removed; S2, waste PET is fed into a twin-screw extruder, where the screws extrude, melt, and transport the waste PET. At the same time, the waste PET is heated and melted by a heating device, and ethylene glycol is added into the twin-screw extruder to achieve alcoholysis between ethylene glycol and the molten waste PET, generating depolymerization product BHET, gaseous ethylene glycol, and water. S3, the depolymerization product is sent to the esterification reactor, and catalyst and stabilizer are added in proportion to carry out the esterification reaction. The reaction temperature is 250-260℃, the residence time is 0.5-1 hour, and the pressure is controlled at 50-300 kPa. The ethylene glycol and water produced are separated and recovered through the process tower. At the same time, the gaseous ethylene glycol and water are removed by vacuum equipment. S4. The depolymerization product BHET is sent to the prepolymerization reactor for further prepolymerization reaction. The reaction temperature is 260-275℃ and the reaction pressure is 20-25Kpa. At the same time, excess ethylene glycol is discharged. The reaction time lasts for 30-45 minutes. Through the reaction, further polymerization is carried out to form a prepolymer with a higher molecular weight. S5. The prepolymer is pumped to the final polycondensation reactor for further final polycondensation reaction at a temperature of 270-285℃. At the same time, the pressure is reduced to 0.11-0.15KPa to carry out the final polycondensation reaction, so as to promote the removal of residual ethylene glycol and small molecule volatiles and maintain a high stirring rate to ensure melt homogeneity. The reaction time lasts for 50-60 minutes to complete the synthesis of high molecular weight copolyester. S6, the produced high-purity PET is fed into spinning equipment for spinning and pelletizing equipment for pelletizing.
[0006] As a further aspect of the present invention, in step S4, the polycondensation catalyst used is antimony glycolate, and the amount used is 50-260 ppm of the product mass.
[0007] This invention provides a chemical recycling method for waste pet, which has the following advantages: by recycling and reusing waste pet materials, the cost of using pet is reduced. By combining pre-condensation and final condensation, the production efficiency and purity of PET have been improved. Attached Figure Description
[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0009] Figure 1 This is a flowchart of the method of the present invention.
[0010] Figure 2 This is a flowchart of the present invention.
[0011] Figure 3 This is a flowchart of a continuous polyester plant with one start and two ends.
[0012] Figure 4 This is the chemical reaction formula for the alcoholysis of PET. Detailed Implementation
[0013] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0014] See Figure 1-4The present invention provides a method for chemically recycling waste PET, comprising the following steps: S1, waste PET material is sequentially placed into a color sorter and a metal separator for mixing, crushing and dispersing, and PET and metal impurities of different colors are removed; S2, waste PET is fed into a twin-screw extruder, where the screws extrude, melt, and transport the waste PET. At the same time, the waste PET is heated and melted by a heating device, and ethylene glycol is added into the twin-screw extruder to achieve alcoholysis between ethylene glycol and the molten waste PET, generating depolymerization product BHET, gaseous ethylene glycol, and water. S3, the depolymerization product is sent to the esterification reactor, and catalyst and stabilizer are added in proportion to carry out the esterification reaction. The reaction temperature is 250-260℃, the residence time is 0.5-1 hour, and the pressure is controlled at 50-300 kPa. The ethylene glycol and water produced are separated and recovered through the process tower. At the same time, the gaseous ethylene glycol and water are removed by vacuum equipment. S4. The depolymerization product BHET is sent to the prepolymerization reactor for further prepolymerization reaction. The reaction temperature is 260-275℃ and the reaction pressure is 20-25Kpa. At the same time, excess ethylene glycol is discharged. The reaction time lasts for 30-45 minutes. Through the reaction, further polymerization is carried out to form a prepolymer with a higher molecular weight. The polycondensation catalyst used is antimony glycolate, and the dosage is 50-260ppm of the product mass. S5. The prepolymer is pumped to the final polycondensation reactor for further final polycondensation reaction at a temperature of 270-285℃. At the same time, the pressure is reduced to 0.11-0.15KPa to carry out the final polycondensation reaction, so as to promote the removal of residual ethylene glycol and small molecule volatiles and maintain a high stirring rate to ensure melt homogeneity. The reaction time lasts for 50-60 minutes to complete the synthesis of high molecular weight copolyester. S6, the high-purity PET produced is fed into spinning equipment for spinning and pelletizing equipment for pelletizing; The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A recycling method of chemically recycling waste pet, characterized by, Comprise the following steps: S1, the waste PET material is put into the color sorter and metal separator in turn, mixing, crushing and dispersing, and removing different color pet and metal impurities; S2, the waste pet is sent into the double screw extruder, the waste pet is extruded and melted by the screw, and the waste pet is heated and melted by the heating device, and the ethylene glycol is added into the double screw extruder, the alcoholysis of ethylene glycol and melted waste pet is realized, and the depolymerization product BHET, gaseous ethylene glycol and water are generated; S3, the depolymerization product is sent into the esterification kettle, the catalyst and stabilizer are added at the same time, the esterification reaction is carried out, the reaction temperature is 250-260℃, the residence time is 0.5-1 hour, the pressure is controlled at 50-300 kPa, the generated ethylene glycol and water are separated and recovered by the process tower, and the gaseous ethylene glycol and water are removed by vacuumizing equipment; S4, the depolymerization product BHET is sent into the pre-polycondensation kettle, further pre-polycondensation reaction is carried out, the reaction temperature is 260-275℃, the reaction pressure is 20-25Kpa, the excess ethylene glycol is discharged at the same time, the reaction time is 30-45 minutes, the reaction is further polymerized, and the pre-polymer with high molecular weight is formed; S5, the pre-polymer is sent to the final polycondensation kettle by the delivery pump, further final polycondensation reaction is carried out, the reaction temperature is 270-285℃, the pressure is reduced to 0.11-0.15KPa at the same time, the final polycondensation reaction is carried out to promote the removal of residual ethylene glycol and small molecule volatile substances, and high stirring speed is maintained to ensure the uniformity of the melt, the reaction time is 50-60 minutes, and the synthesis of high molecular weight copolyester is completed; S6, the high purity pet produced is sent into the spinning equipment for spinning and the pelletizing equipment for pelletizing respectively.
2. The recycling method of claim 1, wherein, In the step S4, the polycondensation catalyst used is ethylene glycol antimony, and the amount is 50-260ppm of the product mass.