Process for producing recycled polyester from waste polyester materials

Abstract

This invention relates to a process for preparing recycled polyester from waste polyester materials, belonging to the field of waste polyester recycling technology. This invention effectively reduces residual impurities in waste polyester materials through a two-stage chemical cleaning process, improving the purity of the polyester fragments. The polyester fragments and ethylene glycol undergo rapid depolymerization via microwave heating under the catalysis of tetrabutyl titanate, significantly improving reaction efficiency and product controllability. During the polycondensation stage, the addition of epoxy chain extenders and modified nano-silica further enhances the molecular structure of the recycled polyester, improving its mechanical properties and thermal stability. Furthermore, the addition of an antistatic agent, prepared by grafting polyester compatible monomers onto polyurethane-coated carbon nanotubes as the core, effectively improves the electrical properties of the recycled polyester and enhances the fiber's application stability.

Description

Technical Field

[0001] This invention belongs to the field of waste polyester recycling technology, and relates to a process for preparing recycled polyester using waste polyester materials. Background Technology

[0002] Waste polyester materials, especially waste PET bottles, are abundant due to their widespread use in beverage packaging. Polyester possesses excellent physical and chemical properties, including high strength, heat resistance, chemical resistance, and good transparency, making it an important engineering plastic. Simultaneously, polyester, as a synthetic fiber, is widely used in the textile industry. Polyester exhibits excellent abrasion resistance, wrinkle resistance, and heat resistance, and is soft to the touch and brightly colored, holding an important position in clothing, home textiles, and other fields. However, with the continuous growth in demand for polyester, the recycling and reuse of waste polyester materials has become increasingly prominent. How to transform waste polyester materials into high-quality recycled polyester has become one of the current research hotspots.

[0003] Utilizing waste polyester materials to produce recycled polyester offers significant environmental and economic benefits. Firstly, recycling waste polyester reduces environmental pollution. Polyester materials are difficult to degrade under natural conditions, and large quantities of discarded polyester bottles can severely impact the ecological environment. Recycling waste polyester bottle flakes can effectively reduce the accumulation of plastic waste and lessen the environmental burden. Secondly, using waste polyester materials to produce recycled polyester helps conserve resources and energy. Producing virgin polyester requires a large amount of petroleum resources, while the production of recycled polyester significantly reduces dependence on petroleum resources, lowering production costs and energy consumption. Furthermore, recycled polyester can maintain properties similar to virgin polyester, meeting the needs of the textile industry and representing a sustainable raw material choice.

[0004] However, existing waste polyester recycling technologies still have some shortcomings. First, traditional physical recycling methods, such as mechanical crushing and melt spinning, cannot completely remove impurities from waste polyester, resulting in low-quality and unstable recycled polyester. Second, although chemical recycling methods can depolymerize polyester into monomers, conventional chemical depolymerization processes are time-consuming, energy-intensive, and require large amounts of chemical reagents, posing certain environmental risks. Furthermore, the poor antistatic properties of polyester fibers limit their application in certain high-end applications. Therefore, it is necessary to develop efficient, environmentally friendly, and economical processes for preparing recycled polyester from waste polyester materials to improve the quality and performance of recycled polyester and promote its widespread application in the textile industry. Summary of the Invention

[0005] This invention relates to a process for preparing recycled polyester from waste polyester materials, belonging to the field of waste polyester recycling technology. This invention effectively reduces residual impurities in waste polyester materials through a two-stage chemical cleaning process, improving the purity of the polyester fragments. The polyester fragments and ethylene glycol undergo rapid depolymerization via microwave heating under the catalysis of tetrabutyl titanate, significantly improving reaction efficiency and product controllability. During the polycondensation stage, the addition of epoxy chain extenders and modified nano-silica further enhances the molecular structure of the recycled polyester, improving its mechanical properties and thermal stability. Furthermore, the addition of an antistatic agent, prepared by grafting polyester compatible monomers onto polyurethane-coated carbon nanotubes as the core, effectively improves the electrical properties of the recycled polyester and enhances the fiber's application stability.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A process for preparing recycled polyester using waste polyester materials includes the following steps:

[0008] (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments.

[0009] (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 30-40 min;

[0010] (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 260-270℃ under vacuum of 20-50Pa to obtain recycled polyester material;

[0011] (4) The recycled polyester material is spun by a twin-screw extruder with a microporous spinneret, a traction ratio of 3.5-4.5, and a heat setting temperature of 180-200℃.

[0012] As a preferred technical solution of the present invention, the two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 50-70℃ using ultrasonic cleaning for 20-30 minutes, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes; the alkaline cleaning solution consists of 3-7wt% NaOH, 0.3-0.7wt% sodium dodecylbenzenesulfonate surfactant, and the remainder being deionized water.

[0013] As a preferred technical solution of the present invention, the mass ratio of polyester fragments, ethylene glycol and tetrabutyl titanate in step (2) is 1:1.2-1.8:0.003-0.008.

[0014] As a preferred embodiment of the present invention, the epoxy chain extender in step (3) is ADR-4370, and the addition amount is 0.3-0.8wt%.

[0015] As a preferred technical solution of the present invention, the amount of modified nano-silica added in step (3) is 1-3 wt%;

[0016] The preparation of the modified nano-silica includes the following steps:

[0017] A1. Disperse nano-silica in a 3 mol / L hydrochloric acid solution, sonicate for 1-3 h, then wash and dry to obtain pretreated nano-silica;

[0018] A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a mass ratio of 3-5 times, stir evenly, add 3-7% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 5-7h, wash and vacuum dry to obtain aminated nano-silica.

[0019] A3. Polyethylene terephthalate and aminated nano-silica are mixed at a mass ratio of 1:0.5-1.5, and under nitrogen protection, the mixture is melted and stirred at 230-250℃ for 40-80 minutes. After cooling and grinding, modified silica is obtained.

[0020] As a preferred technical solution of the present invention, the antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted on the surface; the amount of antistatic agent added is 1-3 wt%.

[0021] As a preferred embodiment of the present invention, the preparation of the antistatic agent includes the following steps:

[0022] B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 70-90℃ for 3-5 hours, and then wash and dry.

[0023] B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 20-40 min.

[0024] B3. Add ammonium persulfate dropwise and stir at 0-4℃ for 10-14h to obtain polyaniline-coated carbon nanotubes;

[0025] B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate are mixed at a mass ratio of 1:0.5-1.5, and 0.05-0.2wt% tetrabutyl titanate is added. The mixture is reacted at 230-250℃ for 1-3 hours under nitrogen protection to obtain an antistatic agent.

[0026] As a preferred embodiment of the present invention, the mass ratio of the multi-arm carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:2-4:2-4:0.3-0.7:0.3-0.7.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention employs a two-stage chemical cleaning process, utilizing an alkaline cleaning solution and an ethanol-acetone mixture to thoroughly remove impurities from waste polyester bottle flakes, ensuring the high purity of the raw materials. Microwave-assisted depolymerization technology, under the action of tetrabutyl titanate catalyst, rapidly and efficiently depolymerizes polyester fragments into monomers. This process not only significantly shortens the reaction time but also reduces energy consumption. The addition of epoxy chain extenders and modified nano-silica during the polycondensation stage further enhances the molecular structure of the recycled polyester, improving its mechanical properties and thermal stability.

[0029] (2) This invention uses multi-arm carbon nanotubes and, through a series of chemical treatments and reactions, produces polyurethane-coated carbon nanotubes with an outer layer grafted with polyethylene terephthalate oligomers. This antistatic agent not only has excellent antistatic properties but also good compatibility with recycled polyester materials, significantly reducing the surface resistance of the fiber, reducing static electricity accumulation, and improving the safety and comfort of the fiber. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0031] In the following examples and comparative examples, the polyethylene terephthalate was purchased from Shenzhen Hansen Plastic Technology Co., Ltd.; the multi-arm carbon nanotubes were purchased from Beijing Tanyang Technology Co., Ltd.; and the nano-silica was purchased from Hubei Huifu Nanomaterials Co., Ltd.

[0032] Example 1

[0033] A process for preparing recycled polyester using waste polyester materials includes the following steps:

[0034] (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments.

[0035] (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 35 min;

[0036] (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 265°C under vacuum of 35Pa to obtain recycled polyester material;

[0037] (4) The recycled polyester material is spun by a twin-screw extruder with a microporous spinneret, a traction ratio of 4, and a heat setting temperature of 190℃.

[0038] The two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 60°C for 25 minutes using ultrasonic cleaning, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes. The alkaline cleaning solution consists of 5 wt% NaOH, 0.5 wt% sodium dodecylbenzenesulfonate surfactant, and the remainder is deionized water.

[0039] The mass ratio of polyester fragments, ethylene glycol, and tetrabutyl titanate in step (2) is 1:1.5:0.005.

[0040] The epoxy chain extender mentioned in step (3) is ADR-4370, and the addition amount is 0.5wt%.

[0041] The amount of modified nano-silica added in step (3) is 2 wt%.

[0042] The preparation of the modified nano-silica includes the following steps:

[0043] A1. Disperse nano-silica in a 3 mol / L hydrochloric acid solution, sonicate for 2 h, then wash and dry to obtain pretreated nano-silica;

[0044] A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a mass ratio of 4, stir evenly, add 5% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 6h, wash and vacuum dry to obtain aminated nano-silica.

[0045] A3. Polyethylene terephthalate and aminated nano-silica were mixed at a mass ratio of 1:1, and stirred at 240°C for 60 minutes under nitrogen protection. Modified silica was then obtained by cooling and grinding.

[0046] The antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted onto the surface; the amount of antistatic agent added is 2 wt%.

[0047] The preparation of the antistatic agent includes the following steps:

[0048] B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 80°C for 4 hours, and then wash and dry.

[0049] B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 30 min.

[0050] B3. Add ammonium persulfate dropwise and stir at 2°C for 12 hours to obtain polyaniline-coated carbon nanotubes;

[0051] B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate were mixed at a mass ratio of 1:0.5-1.5, and 0.1 wt% tetrabutyl titanate was added. The mixture was reacted at 240°C for 2 hours under nitrogen protection to obtain an antistatic agent.

[0052] The mass ratio of the multi-arm carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:3:3:0.5:0.5.

[0053] Example 2

[0054] A process for preparing recycled polyester using waste polyester materials includes the following steps:

[0055] (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments.

[0056] (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 30-40 min;

[0057] (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 260°C under vacuum of 20Pa to obtain recycled polyester material.

[0058] (4) The recycled polyester material is spun by a twin-screw extruder with a microporous spinneret, a traction ratio of 3.5, and a heat setting temperature of 180℃.

[0059] The two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 50°C for 20 minutes using ultrasound, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes. The alkaline cleaning solution consists of 3wt% NaOH, 0.3wt% sodium dodecylbenzenesulfonate surfactant, and the remainder is deionized water.

[0060] The mass ratio of polyester fragments, ethylene glycol, and tetrabutyl titanate in step (2) is 1:1.2:0.003.

[0061] The epoxy chain extender mentioned in step (3) is ADR-4370, and the addition amount is 0.3wt%.

[0062] The amount of modified nano-silica added in step (3) is 1 wt%.

[0063] The preparation of the modified nano-silica includes the following steps:

[0064] A1. Disperse nano-silica in a 3 mol / L hydrochloric acid solution, sonicate for 1 h, then wash and dry to obtain pretreated nano-silica;

[0065] A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a mass ratio of 3, stir evenly, add 3% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 5h, wash and vacuum dry to obtain aminated nano-silica.

[0066] A3. Polyethylene terephthalate and aminated nano-silica were mixed at a mass ratio of 1:0.5, and the mixture was melted and stirred at 230°C for 40 minutes under nitrogen protection. After cooling and grinding, modified silica was obtained.

[0067] The antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted onto the surface; the amount of antistatic agent added is 1 wt%.

[0068] The preparation of the antistatic agent includes the following steps:

[0069] B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 70°C for 3 hours, and then wash and dry.

[0070] B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 20 min.

[0071] B3. Add ammonium persulfate dropwise and stir at 0°C for 10 h to obtain polyaniline-coated carbon nanotubes;

[0072] B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate were mixed at a mass ratio of 1:0.5, and 0.05wt% tetrabutyl titanate was added. The mixture was reacted at 230℃ for 1 hour under nitrogen protection to obtain an antistatic agent.

[0073] The mass ratio of the multi-armed carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:2:2:0.3:0.3.

[0074] Example 3

[0075] A process for preparing recycled polyester using waste polyester materials includes the following steps:

[0076] (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments.

[0077] (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 40 min;

[0078] (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 270°C under vacuum of 50Pa to obtain recycled polyester material;

[0079] (4) The recycled polyester material is spun by a twin-screw extruder with a microporous spinneret, a traction ratio of 4.5, and a heat setting temperature of 200℃.

[0080] The two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 70°C using ultrasound for 30 minutes, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes. The alkaline cleaning solution consists of 7wt% NaOH, 0.7wt% sodium dodecylbenzenesulfonate surfactant, and the remainder is deionized water.

[0081] The mass ratio of polyester fragments, ethylene glycol, and tetrabutyl titanate in step (2) is 1:1.8:0.008.

[0082] The epoxy chain extender mentioned in step (3) is ADR-4370, and the addition amount is 0.8wt%.

[0083] The amount of modified nano-silica added in step (3) is 3 wt%.

[0084] The preparation of the modified nano-silica includes the following steps:

[0085] A1. Pretreated nano-silica was obtained by dispersing nano-silica in a 3 mol / L hydrochloric acid solution, sonicating for 3 h, washing and drying.

[0086] A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a 5:5 ratio, stir evenly, add 7% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 7h, wash and vacuum dry to obtain aminated nano-silica.

[0087] A3. Polyethylene terephthalate and aminated nano-silica were mixed at a mass ratio of 1:1.5, and the mixture was melted and stirred at 250°C for 80 minutes under nitrogen protection. After cooling and grinding, modified silica was obtained.

[0088] The antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted onto the surface; the amount of antistatic agent added is 3 wt%.

[0089] The preparation of the antistatic agent includes the following steps:

[0090] B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 90°C for 5 hours, and then wash and dry.

[0091] B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 40 min.

[0092] B3. Add ammonium persulfate dropwise and stir at 4°C for 14 hours to obtain polyaniline-coated carbon nanotubes.

[0093] B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate were mixed at a mass ratio of 1:1.5, and 0.2 wt% tetrabutyl titanate was added. The mixture was reacted at 250°C for 3 hours under nitrogen protection to obtain an antistatic agent.

[0094] As a preferred embodiment of the present invention, the mass ratio of the multi-arm carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:4:4:0.7:0.7.

[0095] Example 4

[0096] A process for preparing recycled polyester using waste polyester materials includes the following steps:

[0097] (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments.

[0098] (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 32 min;

[0099] (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 262°C under vacuum of 35Pa to obtain recycled polyester material;

[0100] (4) The recycled polyester material is spun by a twin-screw extruder with a microporous spinneret, a traction ratio of 3.8, and a heat setting temperature of 185℃.

[0101] The two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 55°C for 22 minutes by ultrasonication, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes. The alkaline cleaning solution consists of 4 wt% NaOH, 0.6 wt% sodium dodecylbenzenesulfonate surfactant, and the remainder is deionized water.

[0102] The mass ratio of polyester fragments, ethylene glycol, and tetrabutyl titanate in step (2) is 1:1.4:0.006.

[0103] The epoxy chain extender mentioned in step (3) is ADR-4370, and the addition amount is 0.4wt%.

[0104] The amount of modified nano-silica added in step (3) is 3 wt%.

[0105] The preparation of the modified nano-silica includes the following steps:

[0106] A1. Disperse nano-silica in a 3 mol / L hydrochloric acid solution, sonicate for 2 h, then wash and dry to obtain pretreated nano-silica;

[0107] A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a 5:5 ratio, stir evenly, add 7% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 5h, wash and vacuum dry to obtain aminated nano-silica.

[0108] A3. Polyethylene terephthalate and aminated nano-silica were mixed at a mass ratio of 1:0.8, and the mixture was melted and stirred at 235°C for 48 minutes under nitrogen protection. After cooling and grinding, modified silica was obtained.

[0109] The antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted onto the surface; the amount of antistatic agent added is 1 wt%.

[0110] The preparation of the antistatic agent includes the following steps:

[0111] B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 78°C for 3-5 hours, and then wash and dry.

[0112] B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 25 min.

[0113] B3. Add ammonium persulfate dropwise and stir at 1°C for 11 h to obtain polyaniline-coated carbon nanotubes;

[0114] B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate were mixed at a mass ratio of 1:0.7, and 0.08 wt% tetrabutyl titanate was added. The mixture was reacted at 235°C for 3 hours under nitrogen protection to obtain an antistatic agent.

[0115] The mass ratio of the multi-armed carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:2:2:0.7:0.7.

[0116] Comparative Example 1

[0117] Based on Example 1, the two-stage chemical cleaning is omitted, and the rest remains the same as in Example 1.

[0118] Comparative Example 2

[0119] Based on Example 1, the nano-silica was not modified, and the rest remained the same as in Example 1.

[0120] Comparative Example 3

[0121] Based on Example 1, carbon nanotubes were added directly as an antistatic agent, and the rest remained the same as in Example 1.

[0122] Performance testing:

[0123] The elongation at break and tensile strength of Examples 1-4 and Comparative Examples 1-3 were tested according to GB / T 14344-2008; the surface resistivity of Examples 1-4 and Comparative Examples 1-3 was tested according to GB / T 14342-1993, the experimental method for resistivity of synthetic short fibers.

[0124]

[0125] The test results show that this invention effectively reduces residual impurities in waste polyester materials through two-stage chemical cleaning. The addition of epoxy chain extender and modified nano-silica enhances the molecular structure of recycled polyester and improves its mechanical properties. The addition of an antistatic agent, obtained by using polyurethane-coated carbon nanotubes as the core and grafting polyester compatible monomers onto the outer layer, effectively improves the electrical properties of recycled polyester.

[0126] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for preparing recycled polyester using waste polyester materials, characterized in that: Includes the following steps: (1) After crushing the waste polyester bottle flakes, two-stage chemical cleaning is carried out to obtain polyester fragments. (2) Mix polyester fragments with ethylene glycol, add tetrabutyl titanate catalyst, and microwave-assisted depolymerize for 30-40 min; (3) Add epoxy chain extender, modified nano silica and antistatic agent, and heat to 260-270℃ under vacuum of 20-50Pa to obtain recycled polyester material; (4) The recycled polyester material is spun by a twin-screw extruder with a traction ratio of 3.5-4.5 and a heat setting temperature of 180-200℃; The two-stage chemical cleaning in step (1) involves cleaning the waste polyester bottle flakes with an alkaline cleaning solution at 50-70℃ using ultrasonic cleaning for 20-30 minutes, followed by soaking in a 1:1 volume ratio ethanol-acetone mixture for 30 minutes. The alkaline cleaning solution consists of 3-7 wt% NaOH, 0.3-0.7 wt% sodium dodecylbenzenesulfonate surfactant, and the remainder is deionized water. The epoxy chain extender mentioned in step (3) is ADR-4370, and the addition amount is 0.3-0.8wt%. The amount of modified nano-silica added in step (3) is 1-3 wt%. The preparation of the modified nano-silica includes the following steps: A1. Disperse nano-silica in a 3 mol / L hydrochloric acid solution, sonicate for 1-3 h, then wash and dry to obtain pretreated nano-silica; A2. Disperse the pretreated nano-silica in a 5wt% ethanol solution at a mass ratio of 3-5 times, stir evenly, add 3-7% KH-550 silane coupling agent of the pretreated nano-silica, reflux at 80℃ for 5-7h, wash and vacuum dry to obtain aminated nano-silica. A3. Polyethylene terephthalate and aminated nano-silica are mixed at a mass ratio of 1:0.5-1.5, and under nitrogen protection, the mixture is melted and stirred at 230-250℃ for 40-80 minutes. After cooling and grinding, modified silica is obtained. The antistatic agent in step (3) is polyurethane-coated carbon nanotubes with ethylene glycol phthalate oligomer grafted onto the surface; the amount of antistatic agent added is 1-3 wt%. The preparation of the antistatic agent includes the following steps: B1. Place the multi-armed carbon nanotubes in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid with a volume ratio of 1:3, reflux at 70-90℃ for 3-5 hours, and then wash and dry. B2. Disperse the acidified multi-arm carbon nanotubes in a 1 mol / L hydrochloric acid solution, add aniline and sonicate for 20-40 min. B3. Add ammonium persulfate dropwise and stir at 0-4℃ for 10-14h to obtain polyaniline-coated carbon nanotubes; B4. Polyaniline-coated carbon nanotubes and polyethylene terephthalate are mixed at a mass ratio of 1:0.5-1.5, and 0.05-0.2wt% tetrabutyl titanate is added. The mixture is reacted at 230-250℃ for 1-3 hours under nitrogen protection to obtain an antistatic agent.

2. The process for preparing recycled polyester using waste polyester materials according to claim 1, characterized in that: The mass ratio of polyester fragments, ethylene glycol, and tetrabutyl titanate in step (2) is 1:1.2-1.8:0.003-0.

008.

3. The process for preparing recycled polyester using waste polyester materials according to claim 1, characterized in that: In the preparation of the antistatic agent, the mass ratio of multi-arm carbon nanotubes, mixed acid solution, hydrochloric acid solution, aniline, and ammonium persulfate is 1:2-4:2-4:0.3-0.7:0.3-0.7.

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