Regeneration of polyester from waste polyester-spandex textiles by ethylene glycolysis

To address the challenges of poor quality in recycled products from post-consumer polyester blended textiles due to complex fiber composition and additives like dyes, we developed an ethylene glycol (EG) extraction decolorization technique based on the solubility difference of dyes and fibers in EG. The decolorization rate of waste polyester-spandex blended textiles reached 99.8%, achieving efficient separation of polyester-spandex fibers and dyes. The decolorized textiles were further subjected to glycolysis. Utilizing the phase transition characteristics of the glycolysis product, bis(2-hydroxyethyl) terephthalate (BHET), a reduced-pressure phase transition purification technique was developed, yielding purified rBHET with a purity of 98.2% and color values of L* = 99.7, a* = −1.5, b* = 0.1. The rBHET was polycondensed to produce regenerated PET (rPET), which was successfully converted into regenerated polyester fibers through melt spinning and drawing. The rPET exhibited an intrinsic viscosity of 0.692 dL g−1, a carboxyl end-group content of 16.1 mol t−1, and a melting point of 254 °C, meeting all standards for fiber-grade polyester chips. The recycled polyester fibers demonstrated quality (color values, mechanical properties, etc.) comparable to petroleum-based polyester, confirming the feasibility and industrial potential of this recycling route. This work provides a theoretical reference for achieving green, closed-loop recycling throughout the lifecycle of polyester.