A chemical regeneration method for waste PET-PBT and regenerated fiber

Abstract

The present invention relates to a chemical regeneration method and regenerated fiber of waste PET-PBT. The regeneration method comprises: dissolving the waste PET-PBT at 170-190°C by a solvent and a co-solvent; then reacting ethylene glycol and 1,4-butanediol as depolymerizing agents at 170-190°C for 10-30 minutes to obtain a depolymerization liquid mainly composed of ethylene terephthalate or butylene terephthalate; decolorizing, purifying, and drying the depolymerization liquid, and then polymerizing it to obtain recycled PET-PBT copolyester chips rich in PET or PBT; the two copolyester chips are subjected to composite spinning processing to obtain a recycled product whose thermal performance meets the performance requirements of petroleum-based virgin PET-PBT elastic fibers. Compared with the prior art, the present invention can achieve closed-loop recovery and high-quality regeneration of waste PET-PBT, with high recovery rate and recovery efficiency, and can effectively avoid side reactions such as cyclization of 1,4-butanediol at high temperatures, thus making up for the shortcomings of the prior art.

Description

Technical Field

[0001] The present invention relates to a chemical regeneration technology for waste PET-PBT, and in particular to a method for achieving low-temperature homogeneous depolymerization of a mixture of PET and PBT by dissolving the mixture, and regenerating the mixture into PET-PBT parallel composite elastic fibers with high added value. Background Art

[0002] PET-PBT textiles combine the advantages of both PET and PBT and are widely used in elastic textiles. However, PET-PBT textiles are a polymer material that is difficult to degrade in the natural environment, and their raw materials are all derived from non-renewable petroleum. With the development of the PET-PBT textile industry, waste disposal has become a pressing issue. Currently, polyester recycling in the market primarily focuses on PET, while research on PET-PBT recycling is relatively limited.

[0003] Currently, the main methods for regenerating waste PET-PBT include physical and chemical methods. Physical methods, which can be further categorized as melt regeneration and mechanical crushing regeneration, result in products with poor mechanical and dyeing properties, requiring downgrading. Chemical regeneration, however, allows for high-value utilization of waste PET-PBT and is a major research area in the textile industry.

[0004] Patent CN 114805766A first melt-processes a waste PET-PBT mixture, then depolymerizes it with ethylene glycol / 1,4-butanediol. The resulting monomer undergoes an ester exchange reaction with methanol to produce dimethyl terephthalate, achieving the recycling of waste PET-PBT. The depolymerization reaction temperature ranges from 190 to 240°C, the reaction pressure is 101 to 201 kPa, and the residence time is 1 to 2 hours.

[0005] Patent CN 105088410A melt-recycles waste PET bottle flakes to produce recycled PET chips. These chips are then modified and extruded into pellets through a twin-screw extruder. These pellets are then mixed with PBT to produce PBT-modified recycled PET particles. The PBT-modified recycled PET stretch yarn is then melt-spun at a spinning temperature of 240°C to 280°C and a spinning speed of 1000 to 1500 m / min.

[0006] In summary, current chemical regeneration technologies for waste PET-PBT are mostly based on high-temperature, heterogeneous depolymerization of PBT / PET, resulting in low depolymerization efficiency and recovery rates. Furthermore, during the high-temperature depolymerization process, 1,4-butanediol undergoes side reactions such as cyclization, which reduces the quality of the recycled product. Furthermore, the production of dimethyl terephthalate via an ester exchange reaction with methanol is a long and costly process. Therefore, the development of a low-temperature, homogeneous depolymerization technology for waste PET-PBT and a direct polymerization technology for the depolymerization products is urgently needed to reduce / avoid the cyclization of 1,4-butanediol during the reaction, thereby improving recovery rates, depolymerization efficiency, and the quality of the recycled product. This is of great scientific significance and practical value. Summary of the Invention

[0007] In response to the above problems, the present application provides a chemical regeneration of waste PET-PBT and regenerated fibers, which adopts low-temperature homogeneous depolymerization technology and direct polymerization technology of depolymerization products to reduce / avoid the cyclization reaction of 1,4-butanediol during the reaction process, improve the recovery rate, depolymerization efficiency and quality of regenerated products, and has important scientific significance and practical value. The thermodynamic properties of the regenerated PET-PBT fibers prepared based on the process method of the present invention meet the performance requirements of petroleum-based virgin products.

[0008] The present application first provides a chemical regeneration method for waste PET-PBT, comprising the following steps:

[0009] Step 1: Add 100 parts of waste PET-PBT, 100-600 parts of solvent, and 50-400 parts of co-solvent to an autoclave, heat to 170-190°C, and stir at 15-50 rpm for 10-30 minutes. Then, add 50-400 parts of ethylene glycol and 0.5-5 parts of a first catalyst, and continue the reaction for 10-30 minutes to produce a first crude depolymerization liquid. This first crude depolymerization liquid is decolorized, purified, and dried to produce a first refined depolymer. The mass ratio of waste PET-PBT, solvent, co-solvent, ethylene glycol, and first catalyst is 100:100-600:50-400:0.5-5:50-400:0.5-5.

[0010] Step 2: 100 parts of the first refined depolymer and 0.5 parts of the second catalyst are placed in an autoclave and polymerized to produce the first recycled PET-PBT copolyester chips. The mass ratio of the first refined depolymer to the second catalyst is 100:0.5.

[0011] Step 3: Add 100 parts of waste PET-PBT, 100-600 parts of solvent, and 50-400 parts of co-solvent to an autoclave, raise the temperature to 170-190°C, and stir at 15-50 rpm for 10-30 minutes. Then, add 50-400 parts of 1,4-butanediol and 0.5-5 parts of the first catalyst, and continue the reaction for 10-30 minutes to produce a second crude depolymerization liquid. This second crude depolymerization liquid is decolorized and purified to produce a second refined depolymer. The mass ratio of PET-PBT, solvent, co-solvent, ethylene glycol, and first catalyst is 100:100-600:50-400:0.5-5:50-400:0.5-5.

[0012] Step 4: 100 parts of the second refined depolymer obtained in Step 3 and 0.5 parts of the second catalyst are placed in an autoclave and polymerized to produce a second recycled PBT-PET copolyester chip. The mass ratio of the second refined depolymer to the second catalyst is 100:0.5.

[0013] Step 5: placing the first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips in the feed hopper of a parallel composite spinning machine respectively, and producing the regenerated elastic fiber through composite spinning.

[0014] The parts per unit mass in each of the above steps may not be the same.

[0015] Preferably, the waste PET-PBT is one or more of waste mixed fabrics, waste PET-PBT composite fibers, and PET and PBT mixed plastics.

[0016] Preferably, the solvent in the depolymerization step is one or more of dimethyl sulfoxide, N-methylpyrrolidone, aniline, and nitrobenzene.

[0017] Preferably, the co-solvent in the depolymerization step is one or more of acetonitrile, anisole, and dichloromethane.

[0018] Preferably, the first catalyst in the depolymerization step is one or more of an ionic liquid, a deep eutectic solvent and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0019] Preferably, the ionic liquid is one or more of 1,3-dimethylimidazolium chloride, 1,3-dimethylimidazolium bromide, and 1,3-dimethylimidazolium acetate.

[0020] Preferably, the deep eutectic solvent is one or more of 1,3-dimethylurea / zinc acetate and choline chloride / urea.

[0021] Preferably, in the chemical regeneration of waste PET-PBT and its fiber, the first refined depolymer is a mixture of ethylene terephthalate, butylene terephthalate, and hydroxyethyl (hydroxybutyl) terephthalate, wherein the content of ethylene terephthalate is higher than 80%.

[0022] Preferably, the chemical regeneration of waste PET-PBT and its fiber are characterized in that the PET content in the first regenerated PET-PBT copolyester chips is higher than 80wt%, and the intrinsic viscosity of the first regenerated PET-PBT copolyester chips is not higher than 0.6dl / g.

[0023] Preferably, the second catalyst of PET-PBT is one or more of tetrabutyl titanate, isopropyl titanate, antimony trioxide, and antimony glycol.

[0024] Preferably, the second refined depolymer of PET-PBT is a mixture of ethylene terephthalate, butylene terephthalate and hydroxyethyl (hydroxybutyl) terephthalate, wherein the content of butylene terephthalate is higher than 80 wt%.

[0025] Preferably, the content of PBT in the second recycled PBT-PET copolyester chips of PET-PBT is higher than 80 wt % and the intrinsic viscosity is not lower than 0.9 dl / g.

[0026] Preferably, the regenerated elastic fiber of PET-PBT is a side-by-side composite, wherein the content of the first regenerated PET-PBT copolyester is 30wt% to 80wt%, and the content of the second regenerated PBT-PET copolyester is 70wt% to 20wt%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The present invention uses ethylene glycol and 1,4-butanediol as depolymerization agents, respectively, to degrade PET-PBT into depolymerization solutions primarily composed of ethylene terephthalate and butylene terephthalate via a low-temperature homogeneous depolymerization reaction. This depolymerization process exhibits virtually no side reactions, such as cyclization of 1,4-butanediol, and features a rapid depolymerization rate, high recovery rate, and superior quality of the regenerated product, thus overcoming the shortcomings of existing technologies.

[0029] 2) The present invention uses depolymerization solutions composed primarily of ethylene terephthalate and butylene terephthalate as raw materials to produce PET-PBT copolyesters primarily composed of PET and PBT-PET copolyesters primarily composed of PBT. Furthermore, through composite spinning, high-value-added parallel composite elastic fibers are produced, achieving closed-loop recycling and high-value-added reuse of PET-PBT. DETAILED DESCRIPTION

[0030] Overall, this technical solution provides a chemical regeneration method for waste PET-PBT and regenerated fibers. This application achieves low-temperature and efficient alcoholysis of waste PET-PBT under the action of solvents and co-solvents, and directly polycondenses the depolymerization products of ethylene glycol and 1,4-butanediol into PET-PBT copolyesters with different contents after decolorization, purification, and drying, thereby solving the problem of difficult monomer separation after depolymerization of waste PET-PBT. The recycled PET-PBT copolyester chips are then melt-spun. The mechanical properties of the recycled PET-PBT parallel composite fibers prepared by the process of the present invention, such as breaking strength and elongation at break, meet the requirements of the original fibers.

[0031] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0032] Any features such as preparation methods, materials, structures or composition ratios that are not clearly described in this technical solution shall be deemed to be common technical features disclosed in the prior art.

[0033] Unless otherwise specified, the number of portions described in the present invention refers to the value under the condition of equal unit mass. The unit mass is the mass of each portion. If each portion is 1g, the unit mass is 1g / portion, and 100 portions are equal to 100g.

[0034] The testing steps for the intrinsic viscosity in each embodiment of the present invention are as follows:

[0035] Dissolve 0.25±0.005g of sample in 96.00±0.2% concentrated sulfuric acid and measure its viscosity at 25°C using an Ubbelohde viscometer. Specific test principles and methods are described in GBT 12006.1-2009. The intrinsic viscosity is calculated using the following formula:

[0036]

[0037] Where [η] is the intrinsic viscosity, η sp is the specific viscosity, η r is the relative viscosity, C is the sample concentration, and the unit is g / dl.

[0038] Example 1

[0039] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0040] Step 1: Add 1 kg of waste PET-PBT, 1 kg of dimethyl sulfoxide (DMSO) solvent, and 0.5 kg of acetonitrile co-solvent to a 5L autoclave. Heat to 170°C and stir at 15 rpm for 10 minutes. Then, add 0.5 kg of ethylene glycol and 5 g of 1,3-dimethylimidazolium chloride catalyst. Stir at 100 rpm for 10 minutes to produce depolymerization solution 1, which contains 82.9% BHET monomer. The crude depolymerization solution is decolorized, purified, and dried to produce the refined depolymerization product.

[0041] Step 2: 0.84 kg of the first refined depolymerized product and 4.2 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.55 dl / g. The PET content was 82.9%.

[0042] Step 3: 1 kg of waste PET-PBT, 1 kg of dimethyl sulfoxide (DMSO) solvent, and 0.5 kg of acetonitrile co-solvent were added to a 5L autoclave. The temperature was raised to 170°C and stirred at 15 rpm for 10 minutes. 0.5 kg of 1,4-butanediol and 5 g of 1,3-dimethylimidazolium chloride catalyst were then added. The reaction was stirred at 100 rpm for 10 minutes to produce depolymerization solution 2, which contained 80.7% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0043] Step 4: 0.84 kg of the second refined depolymerized product and 4.2 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.95 dl / g. The PBT content was 80.7%.

[0044] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 25.8% and a fiber strength of 2.56 cN / dtex.

[0045] Example 2

[0046] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0047] Step 1: 0.8 kg of waste PET-PBT, 0.8 kg of N-methylpyrrolidone solvent, and 0.8 kg of acetonitrile co-solvent were added to a 5L autoclave. The temperature was raised to 175°C and stirred at 30 rpm for 15 minutes. 0.8 kg of ethylene glycol and 8 g of 1,3-dimethylurea / zinc acetate catalyst were then added. The reaction was stirred at 100 rpm for 15 minutes to produce depolymerization solution 1, which contained 83.3% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0048] Step 2: 0.8 kg of the first refined depolymerized product and 4 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.57 dl / g. The PET content was 83.3%.

[0049] Step 3: 0.8 kg of waste PET-PBT, 0.8 kg of N-methylpyrrolidone solvent, and 0.8 kg of acetonitrile co-solvent were added to a 5-liter autoclave. The temperature was raised to 175°C and stirred at 30 rpm for 15 minutes. 0.8 kg of 1,4-butanediol and 8 g of 1,3-dimethylurea / zinc acetate catalyst were then added. The reaction was stirred at 100 rpm for 15 minutes to produce depolymerization solution 2, which contained 81.2% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0050] Step 4: 0.8 kg of the second refined depolymerized product and 4 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.91 dl / g. The PBT content was 81.2%.

[0051] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.2% and a fiber strength of 2.51 cN / dtex.

[0052] Example 3

[0053] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0054] Step 1: 0.4 kg of waste PET-PBT, 1.2 kg of dimethyl sulfoxide (DMSO) solvent, and 1.2 kg of acetonitrile co-solvent were added to a 5-liter autoclave. The temperature was raised to 180°C and stirred at 50 rpm for 30 minutes. 1.2 kg of ethylene glycol and 6 g of choline chloride / urea catalyst were then added, and the mixture was stirred at 100 rpm for 10 minutes to produce depolymerization solution 1, which contained 83.6% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerized product.

[0055] Step 2: 0.4 kg of the first refined depolymerized product and 2 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.58 dl / g. The PET content was 83.6%.

[0056] Step 3: 0.4 kg of waste PET-PBT, 1.2 kg of dimethyl sulfoxide (DMSO) solvent, and 1.2 kg of acetonitrile co-solvent were added to a 5L autoclave. The temperature was raised to 180°C and stirred at 50 rpm for 30 minutes. 1.2 kg of 1,4-butanediol and 6 g of choline chloride / urea catalyst were then added. The mixture was stirred at 100 rpm for 10 minutes to produce depolymerization solution 2, which contained 82.5% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0057] Step 4: 0.4 kg of the second refined depolymerized product and 2 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 1.12 dl / g. The PBT content was 82.5%.

[0058] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT side-by-side composite fibers had an elongation at break of 26.4% and a fiber strength of 2.59 cN / dtex.

[0059] Example 4

[0060] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0061] Step 1: 0.3 kg of waste PET-PBT, 1.8 kg of aniline solvent, and 1.2 kg of anisole co-solvent were added to a 5L autoclave. The temperature was raised to 185°C and stirred at 50 rpm for 30 minutes. 1.2 kg of ethylene glycol and 15 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst were then added and stirred at 100 rpm for 30 minutes to produce depolymerization solution 1, which contained 84.8% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0062] Step 2: 0.32 kg of the first refined depolymerized product and 1.6 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.59 dl / g. The PET content was 84.8%.

[0063] Step 3: 0.3 kg of waste PET-PBT, 1.8 kg of aniline solvent, and 1.2 kg of anisole co-solvent were added to a 5L polymerization reactor. The temperature was raised to 185°C and stirred at 50 rpm for 30 minutes. Then, 1.2 kg of 1,4-butanediol and 15 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst were added and stirred at 100 rpm for 30 minutes to produce depolymerization solution 2, which contained 83.9% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce a second refined depolymerization product.

[0064] Step 4: 0.32 kg of the second refined depolymerized product and 1.6 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 1.09 dl / g. The PBT content was 83.9%.

[0065] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.7% and a fiber strength of 2.61 cN / dtex.

[0066] Example 5

[0067] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0068] Step 1: 0.6 kg of waste PET-PBT, 3.6 kg of aniline solvent, and 0.6 kg of anisole co-solvent were added to a 5L autoclave. The temperature was raised to 190°C and stirred at 40 rpm for 30 minutes. 0.6 kg of ethylene glycol and 6 g of 1,3-dimethylimidazolium bromide catalyst were then added. The reaction was stirred at 100 rpm for 10 minutes to produce depolymerization solution 1, which contained 83.2% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0069] Step 2: 0.6 kg of the first refined depolymerized product and 3 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.52 dl / g. The PET content was 83.2%.

[0070] Step 3: 0.6 kg of waste PET-PBT, 3.6 kg of aniline solvent, and 0.6 kg of anisole co-solvent were added to a 5L polymerization reactor. The temperature was raised to 190°C and stirred at 40 rpm for 30 minutes. 0.6 kg of 1,4-butanediol and 6 g of 1,3-dimethylimidazolium bromide catalyst were then added. The reaction was stirred at 100 rpm for 10 minutes to produce depolymerization solution 2, which contained 82.6% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0071] Step 4: 0.6 kg of the second refined depolymerized product and 3 g of antimony trioxide catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.99 dl / g. The PBT content was 82.6%.

[0072] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.8% and a fiber strength of 2.69 cN / dtex.

[0073] Example 6

[0074] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0075] Step 1: 0.5 kg of waste PET-PBT, 2 kg of aniline solvent, and 1 kg of dichloromethane co-solvent were added to a 5-liter autoclave. The temperature was raised to 170°C and stirred at 30 rpm for 20 minutes. 1 kg of ethylene glycol and 0.5 g of 1,3-dimethylurea / zinc acetate catalyst were then added. The reaction was stirred at 100 rpm for 20 minutes to produce depolymerization solution 1, which contained 84.6% BHET monomer. The crude depolymerization solution was then decolorized, purified, and dried to produce the refined depolymerization product.

[0076] Step 2: 0.5 kg of the first refined depolymerized product and 2.5 g of the catalyst, antimony ethylene glycol, were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.58 dl / g. The PET content was 84.6%.

[0077] Step 3: 0.5 kg of waste PET-PBT, 2 kg of aniline solvent, and 1 kg of dichloromethane co-solvent were added to a 5-liter autoclave. The temperature was raised to 170°C and stirred at 30 rpm for 20 minutes. Then, 1 kg of 1,4-butanediol and 0.5 g of 1,3-dimethylurea / zinc acetate catalyst were added and stirred at 100 rpm for 20 minutes to produce depolymerization solution 2, which contained 80.5% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0078] Step 4: Place 0.5 kg of the second refined depolymerized product and 2.5 g of the catalyst, antimony ethylene glycol, in an autoclave. The temperature is gradually raised to 255°C and the pressure is gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.97 dl / g. The PBT content is 80.5%.

[0079] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.3% and a fiber strength of 2.55 cN / dtex.

[0080] Example 7

[0081] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0082] Step 1: 0.7 kg of waste PET-PBT, 2.1 kg of aniline solvent, and 2.1 kg of dichloromethane co-solvent were added to a 5L autoclave. The temperature was raised to 175°C and stirred at 50 rpm for 15 minutes. 2.1 kg of ethylene glycol and 3.5 g of choline chloride / urea catalyst were then added and stirred at 100 rpm for 30 minutes to produce depolymerization solution 1, which contained 84.3% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0083] Step 2: 0.7 kg of the first refined depolymerized product and 3.5 g of the catalyst, antimony ethylene glycol, were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.53 dl / g. The PET content was 84.3%.

[0084] Step 3: 0.7 kg of waste PET-PBT, 2.1 kg of aniline solvent, and 2.1 kg of dichloromethane co-solvent were added to a 5L autoclave. The temperature was raised to 175°C and stirred at 50 rpm for 15 minutes. 2.1 kg of 1,4-butanediol and 3.5 g of choline chloride / urea catalyst were then added and stirred at 100 rpm for 30 minutes to produce depolymerization solution 2, which contained 81.8% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0085] Step 4: 0.7 kg of the second refined depolymerized product and 3.5 g of the catalyst antimony glycolate were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.96 dl / g. The PBT content was 81.8%.

[0086] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT side-by-side composite fibers had an elongation at break of 27.1% and a fiber strength of 2.65 cN / dtex.

[0087] Example 8

[0088] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0089] Step 1: 0.6 kg of waste PET-PBT, 1.2 kg of nitrobenzene solvent, and 1.2 kg of acetonitrile co-solvent were added to a 5L autoclave. The temperature was raised to 180°C and stirred at 20 rpm for 10 minutes. 1.8 kg of ethylene glycol and 3 g of 1,3-dimethylimidazolium chloride catalyst were then added. The reaction was stirred at 100 rpm for 30 minutes to produce depolymerization solution 1, which contained 85.2% BHET monomer. The crude depolymerization solution was then decolorized, purified, and dried to produce the refined depolymerization product.

[0090] Step 2: 0.6 kg of the first refined depolymerized product and 3 g of ethylene glycol antimony catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.54 dl / g. The PET content was 85.2%.

[0091] Step 3: 0.6 kg of waste PET-PBT, 1.2 kg of nitrobenzene solvent, and 1.2 kg of acetonitrile co-solvent were added to a 5L polymerization autoclave. The temperature was raised to 180°C and stirred at 20 rpm for 10 minutes. 1.8 kg of 1,4-butanediol and 3 g of 1,3-dimethylimidazolium chloride catalyst were then added. The reaction was stirred at 100 rpm for 30 minutes to produce depolymerization solution 2, which contained 84.1% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0092] Step 4: Place 0.6 kg of the second refined depolymerized product and 3 g of the catalyst, antimony ethylene glycol, in an autoclave. The temperature is gradually raised to 255°C and the pressure is gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips. The chips have an intrinsic viscosity of 0.93 dl / g and a PBT content of 84.1%.

[0093] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.3% and a fiber strength of 2.53 cN / dtex.

[0094] Example 9

[0095] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0096] Step 1: 0.4 kg of waste PET-PBT, 0.4 kg of N-methylpyrrolidone solvent, and 1.6 kg of acetonitrile co-solvent were added to a 5L autoclave. The temperature was raised to 185°C and stirred at 30 rpm for 20 minutes. 1.6 kg of ethylene glycol and 1.2 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst were then added. The reaction was stirred at 100 rpm for 30 minutes to produce depolymerization solution 1, which contained 83.4% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0097] Step 2: 0.4 kg of the first refined depolymerized product and 2 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.58 dl / g. The PET content was 83.4%.

[0098] Step 3: 0.4 kg of waste PET-PBT, 0.4 kg of N-methylpyrrolidone solvent, and 1.6 kg of acetonitrile co-solvent were added to a 5L polymerization reactor. The temperature was raised to 185°C and stirred at 30 rpm for 20 minutes. Then, 1.6 kg of 1,4-butanediol and 1.2 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst were added and stirred at 100 rpm for 30 minutes to produce depolymerization solution 2, which contained 82.7% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce a second refined depolymerization product.

[0099] Step 4: 0.4 kg of the second refined depolymerized product and 2 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 1.08 dl / g. The PBT content was 82.7%.

[0100] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 27.4% and a fiber strength of 2.68 cN / dtex.

[0101] Example 10

[0102] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0103] Step 1: 0.8 kg of waste PET-PBT, 0.8 kg of dimethyl sulfoxide (DMSO) solvent, and 0.4 kg of anisole co-solvent were added to a 5-liter autoclave. The temperature was raised to 185°C and stirred at 40 rpm for 30 minutes. 3.2 kg of ethylene glycol and 2 g of choline chloride / urea catalyst were then added, and the mixture was stirred at 100 rpm for 20 minutes to produce depolymerization solution 1, which contained 82.5% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0104] Step 2: 0.8 kg of the first refined depolymerized product and 4 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.59 dl / g. The PET content was 82.5%.

[0105] Step 3: 0.8 kg of waste PET-PBT, 0.8 kg of dimethyl sulfoxide (DMSO) solvent, and 0.4 kg of anisole co-solvent were added to a 5-liter autoclave. The temperature was raised to 185°C and stirred at 40 rpm for 30 minutes. 3.2 kg of 1,4-butanediol and 2 g of choline chloride / urea catalyst were then added. The mixture was stirred at 100 rpm for 20 minutes to produce depolymerization solution 2, which contained 81.5% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0106] Step 4: 0.8 kg of the second refined depolymerized product and 4 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 1.16 dl / g. The PBT content was 81.5%.

[0107] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 25.9% and a fiber strength of 2.66 cN / dtex.

[0108] Example 11

[0109] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0110] Step 1: 0.3 kg of waste PET-PBT, 1.8 kg of dimethyl sulfoxide (DMSO) solvent, and 1.2 kg of dichloromethane co-solvent were added to a 5L autoclave. The temperature was raised to 190°C and stirred at 50 rpm for 10 minutes. 1.2 kg of ethylene glycol and 1.5 g of 1,3-dimethylimidazolium bromide catalyst were then added. The reaction was stirred at 100 rpm for 10 minutes to produce depolymerization solution 1, which contained 85.3% BHET monomer. The crude depolymerization solution was decolorized, purified, and dried to produce the refined depolymerization product.

[0111] Step 2: 0.3 kg of the first refined depolymerized product and 1.5 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.51 dl / g and a PET content of 85.3%.

[0112] Step 3: 0.3 kg of waste PET-PBT, 1.8 kg of dimethyl sulfoxide (DMSO) solvent, and 1.2 kg of dichloromethane co-solvent were added to a 5L autoclave. The temperature was raised to 190°C and stirred at 50 rpm for 10 minutes. 1.2 kg of 1,4-butanediol and 1.5 g of 1,3-dimethylimidazolium bromide catalyst were then added. The reaction was stirred at 100 rpm for 10 minutes to produce depolymerization solution 2, which contained 83.7% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce the second refined depolymerization product.

[0113] Step 4: 0.3 kg of the second refined depolymerized product and 1.5 g of isopropyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.98 dl / g and a PBT content of 83.7%.

[0114] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 26.9% and a fiber strength of 2.57 cN / dtex.

[0115] Example 12

[0116] In this embodiment, a chemical regeneration method for waste PET-PBT is described, and the specific steps are as follows:

[0117] Step 1: Add 0.5 kg of waste PET-PBT, 0.5 kg of N-methylpyrrolidone solvent, and 2 kg of anisole co-solvent to a 5 L polymerization reactor. Heat to 170°C and stir at 50 rpm for 25 minutes. Then, add 2 kg of ethylene glycol and 2.5 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst. Stir at 100 rpm for 25 minutes to produce depolymerization solution 1, which has a BHET monomer content of 85.1%. The resulting first crude depolymerization solution is decolorized, purified, and dried to produce the first refined depolymerization product.

[0118] Step 2: 0.5 kg of the first refined depolymerized product and 2.5 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.56 dl / g and a PET content of 85.1%.

[0119] Step 3: 0.5 kg of waste PET-PBT, 0.5 kg of N-methylpyrrolidone solvent, and 2 kg of anisole co-solvent were added to a 5-L autoclave. The temperature was raised to 170°C and stirred at 50 rpm for 25 minutes. Then, 2 kg of 1,4-butanediol and 2.5 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene catalyst were added and stirred at 100 rpm for 25 minutes to produce depolymerization solution 2, which contained 83.2% BHBT monomer. The resulting second crude depolymerization solution was decolorized, purified, and dried to produce a second refined depolymerization product.

[0120] Step 4: 0.5 kg of the second refined depolymerized product and 2.5 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.93 dl / g and a PBT content of 83.2%.

[0121] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT parallel composite fibers had an elongation at break of 25.8% and a fiber strength of 2.63 cN / dtex.

[0122] Comparative Example 1

[0123] A chemical regeneration method for waste PET-PBT in this comparative example comprises the following steps:

[0124] Step 1: 1 kg of waste PET-PBT, 2 kg of ethylene glycol, and 5 g of zinc acetate catalyst were added to a 5 L polymerization reactor. The temperature was raised to 200°C and the reaction was carried out at a stirring speed of 100 r / min for 2 hours to produce depolymerization solution 1, in which the BHET monomer content was 78.9%. The first crude depolymerization solution was decolorized, purified, and dried to produce the first refined depolymerization product.

[0125] Step 2: 1 kg of the first refined depolymerized product and 5 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 275°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the first recycled PET-PBT copolyester chips with an intrinsic viscosity of 0.53 dl / g and a PET content of 78.9%.

[0126] Step 3: 1 kg of waste PET-PBT, 2 kg of 1,4-butanediol, and 5 g of zinc acetate catalyst were added to a 5 L polymerization reactor. The temperature was raised to 200°C and the reaction was carried out at a stirring speed of 100 r / min for 2 hours to produce depolymerization solution 2, in which the BHBT monomer content was 74.6%. The second crude depolymerization solution was decolorized, purified, and dried to produce the first refined depolymerization product.

[0127] Step 4: 0.5 kg of the second refined depolymerized product and 2.5 g of tetrabutyl titanate catalyst were placed in an autoclave. The temperature was gradually raised to 255°C and the pressure in the autoclave was gradually reduced to below 50 Pa for 4 hours to allow for polycondensation to produce the second recycled PBT-PET copolyester chips with an intrinsic viscosity of 0.92 dl / g and a PBT content of 74.6%.

[0128] Step 5: The first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips were subjected to a two-component composite spinning process. The first recycled PET-PBT copolyester chips were spun at a temperature of 280°C, and the second recycled PBT-PET copolyester chips were spun at a temperature of 265°C. The resulting recycled PET-PBT side-by-side composite fibers had an elongation at break of 25.2% and a fiber strength of 2.49 cN / dtex.

[0129] Analysis of Comparative Example 1 and Examples of the present invention shows that:

[0130] In Comparative Example 1, the depolymerization reaction of waste PET-PBT was carried out at 200°C, while in the Examples of the present invention, the depolymerization reaction temperature ranged from 170°C to 190°C, employing a lower reaction temperature. The depolymerization reaction time in Comparative Example 1 was 2 hours, while the depolymerization reaction times in the Examples of the present invention ranged from 10 minutes to 30 minutes, demonstrating that the Examples of the present invention may have a faster reaction rate.

[0131] In Comparative Example 1, the BHET monomer recovery rate was 78.9%, and the BHBT monomer recovery rate was 74.6%. However, in the embodiments of the present invention, the BHET monomer recovery rate ranged from 82.5% to 85.3%, and the BHET monomer recovery rate ranged from 80.7% to 84.1%, indicating that the embodiments of the present invention have a higher monomer recovery rate.

[0132] The recycled PET-PBT parallel composite fibers obtained in Comparative Example 1 had an elongation at break of 25.2% and a fiber strength of 2.49 cN / dtex. In contrast, the regenerated PET-PBT parallel composite fibers in the present invention exhibited elongation at break ranging from 25.8% to 27.4%, and fiber strength ranging from 2.51 cN / dtex to 2.69 cN / dtex. The strength and elongation at break of the regenerated PET-PBT parallel composite fibers more closely matched the required ranges for virgin PET-PBT parallel composite fibers.

[0133] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A chemical regeneration method for waste PET-PBT, characterized in that: The following steps are involved: Step 1: adding waste PET-PBT, solvent, and co-solvent into a high-pressure reactor, heating to 170-190° C., treating at a stirring speed of 15-50 r / min for 10-30 minutes, then adding ethylene glycol and a first catalyst, and continuing the reaction for 10-30 minutes to obtain a first crude depolymerization liquid, and decolorizing, purifying, and drying the obtained first crude depolymerization liquid to obtain a first refined depolymer, wherein the mass ratio of waste PET-PBT, solvent, co-solvent, ethylene glycol, and first catalyst is 100:100-600:50-400:50-400:0.5-5; Step 2: placing the first refined depolymerized product and the second catalyst obtained in step 1 in a high-pressure reactor, and preparing a first recycled PET-PBT copolyester chip by polymerization, wherein the mass ratio of the first refined depolymerized product to the second catalyst is 100:0.5; Step 3: adding waste PET-PBT, solvent, and co-solvent into a high-pressure reactor, heating to 170-190° C., treating at a stirring speed of 15-50 r / min for 10-30 min, then adding 1,4-butanediol and the first catalyst, and continuing the reaction for 10-30 min to obtain a second crude depolymerization liquid, and decolorizing and purifying the obtained second crude depolymerization liquid to obtain a second refined depolymer, wherein the mass ratio of PET-PBT, solvent, co-solvent, 1,4-butanediol, and the first catalyst is 100:100-600:50-400:50-400:0.5-5; Step 4: placing the second refined depolymerized product and the second catalyst obtained in step 3 into a high-pressure reactor, and preparing a second recycled PBT-PET copolyester chip by polymerization, wherein the mass ratio of the second refined depolymerized product to the second catalyst is 100:0.5; Step 5: placing the first recycled PET-PBT copolyester chips and the second recycled PBT-PET copolyester chips into the feed hopper of a parallel composite spinning machine, respectively, and producing the regenerated elastic fiber through composite spinning; In step 1 and step 3, the solvent is one or more of dimethyl sulfoxide, N-methylpyrrolidone, aniline, and nitrobenzene; The co-solvent is one or more of acetonitrile, anisole and dichloromethane.

2. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In step 1 and step 3, the waste PET-PBT is one or more of waste mixed fabrics, waste PET-PBT composite fibers, and waste PET and PBT mixed plastics.

3. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In step 1 and step 3, the first catalyst is one or more of an ionic liquid, a deep eutectic solvent and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

4. The chemical regeneration method for waste PET-PBT according to claim 3, characterized in that: The ionic liquid is one or more of 1,3-dimethylimidazolium chloride, 1,3-dimethylimidazolium bromide, and 1,3-dimethylimidazolium acetate; The deep eutectic solvent is one or more of 1,3-dimethylurea / zinc acetate and choline chloride / urea.

5. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In the steps 1 and 2, the first refined depolymer is a mixture of ethylene terephthalate, butylene terephthalate, hydroxyethyl terephthalate, and hydroxybutyl terephthalate, wherein the content of ethylene terephthalate is higher than 80 wt%.

6. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In steps 2 and 5, the PET content in the first recycled PET-PBT copolyester chips is higher than 80 wt %, and the intrinsic viscosity of the first recycled PET-PBT copolyester chips is not higher than 0.6 dl / g.

7. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In step 2 and step 4, the second catalyst is one or more of tetrabutyl titanate, isopropyl titanate, antimony trioxide, and antimony ethylene glycol.

8. The chemical regeneration method for waste PET-PBT according to claim 1, characterized in that: In steps 3 and 4, the second refined depolymer is a mixture of butylene terephthalate, ethylene terephthalate, hydroxyethyl terephthalate, and hydroxybutyl terephthalate, wherein the content of butylene terephthalate is higher than 80 wt%; In steps 4 and 5, the PBT content in the second recycled PBT-PET copolyester chips is higher than 80 wt %, and the intrinsic viscosity is not lower than 0.9 dl / g.

9. A regenerated fiber prepared by the method according to any one of claims 1 to 8, characterized in that the regenerated elastic fiber is a parallel composite fiber, wherein: The content of the first recycled PET-PBT copolyester is 30 wt % to 80 wt %, and the content of the second recycled PBT-PET copolyester is 70 wt % to 20 wt %.

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