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CN-121974799-A - Technology for degrading colored waste PET fabric and recycling BHET

CN121974799ACN 121974799 ACN121974799 ACN 121974799ACN-121974799-A

Abstract

The invention relates to the technical field of fabric recycling, in particular to a process for recycling BHET by degrading colored waste PET fabric, which comprises the following steps of S1, mixing a composite catalyst, colored waste PET fabric and ethylene glycol, adding the mixture into a reaction kettle, heating the mixture to 150-165 ℃, controlling the pressure in the kettle to be 0-0.2 MPa for degradation reaction, filtering after the degradation reaction is finished for 2-6 hours, removing insoluble impurities to obtain alcoholysis liquid, S2, decolorizing the alcoholysis liquid obtained in the step S1 through a multi-stage resin tank to obtain a mixture containing ethylene glycol and a product, S3, mixing the mixture obtained in the step S2 with deionized water, heating the mixture to 95-100 ℃, cooling the mixture to 70-80 ℃ after the mixture is completely dissolved, continuing stirring for 1-3 hours, performing hot filtration to obtain filtrate A and solid A, continuing cooling the filtrate A to-10 to-5 ℃ after the degradation reaction, stirring for 8-12 hours, filtering to obtain filtrate B and solid B, and drying the solid B to obtain BHET. The process disclosed by the invention has good decoloring efficiency on the colored waste PET, the yield of BHET is high, and meanwhile, the solvent can be efficiently recycled, so that the resource waste is reduced.

Inventors

  • SHEN JUEFENG
  • REN XUHUA
  • ZHAO DONG

Assignees

  • 浙江蓝德能源科技发展有限公司

Dates

Publication Date
20260505
Application Date
20260224

Claims (10)

  1. 1. The process for degrading the colored waste PET fabric and recycling the BHET is characterized by comprising the following steps of: S1, mixing a composite catalyst, colored waste PET fabric and ethylene glycol, adding the mixture into a reaction kettle, heating the mixture to 150-165 ℃, controlling the pressure in the kettle to be 0-0.2 MPa, carrying out degradation reaction for 2-6 hours, and filtering after the degradation reaction is finished to remove insoluble impurities to obtain alcoholysis liquid; s2, decolorizing the alcoholysis solution obtained in the step S1 by a multi-stage resin tank to obtain a mixture containing glycol and a product; S3, mixing the mixture obtained in the step S2 with deionized water, heating to 95-100 ℃, cooling to 70-80 ℃ after all the mixture is dissolved, continuously stirring for 1-3 hours, hot filtering to obtain filtrate A and solid A, continuously cooling to-10 to-5 ℃ after the filtrate A is cooled, stirring for 8-12 hours, filtering to obtain filtrate B and solid B, and drying the solid B to obtain BHET; the yield of the BHET is not less than 85%; the decoloring rate of the process is not less than 90%.
  2. 2. The process for recycling BHET by degrading colored waste PET fabric according to claim 1, wherein the composite catalyst is a mixture of an iron-based catalyst and a zinc-based catalyst.
  3. 3. The process for recycling BHET by degrading colored waste PET fabrics according to claim 2, wherein the mass ratio of the iron-based catalyst to the zinc-based catalyst is (2-4): 1.
  4. 4. The process for recycling BHET by degrading colored waste PET fabric according to claim 1, wherein the disperse dye in the colored waste PET fabric has a conjugated structure.
  5. 5. The process for recycling BHET from degraded colored waste PET fabrics according to claim 1, wherein the multistage resin tank comprises a cation exchange resin and a modified anion exchange resin, and the alcoholysis liquid passes through the cation exchange resin and then the modified anion exchange resin.
  6. 6. The process for recycling BHET from degraded colored waste PET fabrics according to claim 5, wherein the preparation method of the modified anion exchange resin comprises the steps of: S21, mixing, stirring and dispersing styrene, divinylbenzene, epoxybutene and toluene, then adding an initiator, heating to 70-80 ℃, stirring for 10-12 hours at a constant temperature, centrifugally filtering, and drying to constant weight to obtain a resin matrix; S22, adding the resin matrix obtained in the step S21 into N, N-dimethylformamide, stirring and dispersing, then adding bromoacetic acid, stirring at room temperature for 20-24 hours, filtering after finishing, washing, then mixing the filtered product with triphenylphosphine, adding N, N-dimethylformamide, heating to 80-85 ℃, stirring at constant temperature for 12-14 hours, filtering after finishing, washing with toluene and deionized water in sequence, and drying to constant weight to obtain the modified anion exchange resin.
  7. 7. The process for recycling BHET by degrading colored waste PET fabrics according to claim 6, wherein the molar ratio of styrene to epoxybutene is 1 (0.3-0.5).
  8. 8. The process for recycling BHET by degrading colored waste PET fabrics according to claim 6, wherein the molar ratio of bromoacetic acid to epoxybutene is (1-1.3): 1.
  9. 9. The process for recycling BHET by degrading colored waste PET fabrics according to claim 6, wherein the molar ratio of triphenylphosphine to bromoacetic acid is (1-1.5): 1.
  10. 10. The process for recycling BHET from degraded colored waste PET fabrics according to claim 1, wherein said solid a is put into step S1 for continuous alcoholysis; And purifying and separating deionized water and ethylene glycol from the filtrate B through rectification for recycling.

Description

Technology for degrading colored waste PET fabric and recycling BHET Technical Field The invention relates to the technical field of fabric recycling, in particular to a process for recycling BHET by degrading colored waste PET fabric. Background In the context of continuous and rapid growth of the global textile industry and plastic consumption, waste PET fabrics have become an important research object in the fields of environmental remediation and resource recycling. According to statistics, the waste PET fabric produced in each year in the world exceeds 5000 ten thousand tons, wherein the proportion of the blended fabric exceeds 60 percent, and the materials are difficult to realize high-efficiency separation and high-value utilization due to the components such as spandex, cotton and the like in the traditional recovery technology. The treatment of the colored waste PET fabric is particularly troublesome, and the additives such as dye, auxiliary agent and the like not only affect the purity of the recovered material, but also generate toxic byproducts in the chemical degradation process, thereby restricting the closed loop construction of the circular economy industrial chain. The traditional recovery technology faces double dilemma that the mechanical recovery causes performance degradation due to fiber breakage, and the chemical recovery causes high energy consumption and poor selectivity, so that the technical bottleneck is difficult to break through. By taking physical melting regeneration as an example, the method can realize the reutilization of fiber forms, but the strength loss rate of regenerated fibers is as high as 30% -50%, and blending components cannot be separated, so that the product can only be used for low-end filling materials. Although the chemical degradation technology can depolymerize PET as a monomer, the prior art has the remarkable defects that the methanol hydrolysis method needs to be carried out under the high-temperature and high-pressure condition of 260-300 ℃, the equipment investment and the operation cost are high, the ethylene glycol hydrolysis method has mild condition, but dye impurities can lead to the purity of BHET (dihydroxyethyl terephthalate) to be less than 90 percent and difficult to meet the high-end application requirement, so that in order to solve the problem of decoloring polyester fiber, the patent No. CN111607956B discloses a method for decoloring the dyed polyester fiber, which comprises the steps of providing an alcohol ether solvent and the dyed polyester fiber, heating the alcohol ether solvent to the boiling point to continuously generate steam, wherein the temperature of the steam is between 90-200 ℃ and the glass transition temperature of the polyester fiber, and forming an extraction condensate with the dye after the dye is extracted by utilizing the steam of the solvent, and the extraction condensate with the dye is returned to the solvent, and the method can effectively decolor the polyester fiber by repeating the steps. However, this process is suitable for the decolorization of polyester fibers and does not provide for how to recover BHET from the removal of dye during the alcoholysis of polyester fibers. As further disclosed in patent No. CN119286057a, a method for separating, recovering and synchronously decolorizing a colored waste polyester-cotton blended fabric uses the synergistic effect of the combination of a decolorizing agent and a low-cost green good solvent organic acid to promote the decolorizing and separating processes of the polyester-cotton blended fabric, synchronously improves the decolorizing and separating efficiency, but the decolorizing capacity of sodium hypochlorite is limited, and researchers find that when sodium hypochlorite is applied to batch recovery of colored PET textiles, the method has the problems of large demand and low decolorizing efficiency. Therefore, development of a process which is green and environment-friendly, can degrade the colored waste PET fabric to recycle BHET and has high decoloring efficiency is needed. Disclosure of Invention The invention aims to provide a process for degrading colored waste PET fabric and recycling BHET, which aims to solve the problems of poor decoloring effect and non-environment-friendly process in the existing PET fabric recycling process. In order to achieve the above purpose, the present invention adopts the following technical scheme: The invention provides a process for degrading colored waste PET fabric and recycling BHET, which comprises the following steps: S1, mixing a composite catalyst, colored waste PET fabric and ethylene glycol, adding the mixture into a reaction kettle, heating the mixture to 150-165 ℃, controlling the pressure in the kettle to be 0-0.2 MPa, carrying out degradation reaction for 2-6 hours, and filtering after the degradation reaction is finished to remove insoluble impurities to obtain alcoholysis liquid; s2, decolorizing the alcoh