Removal of Oligomers from Poly(ethylene terephthalate) Resins by Hydrothermal Extraction

Abstract

In this study, hydrothermal extraction experiments were performed in a semibatch apparatus at varying temperatures and different extraction times to determine the optimum operating conditions for the removal of oligomers from poly(ethylene terephthalate) (PET) resins. High-molecular-weight PET in pellet form (M w: 100 kDa) was used as the raw material. The results obtained suggest that hydrothermal treatment enables partial extraction of oligomers from PET resins. Using theoretical methods and the experimental data, we calculated the maximum reaction time at each temperature, considering the potential for application in plastic processing. A maximum extraction efficiency of 16% was achieved by hydrothermal extraction at 200 °C for 10 minutes. This novel technique is a promising tool for the development of a next-generation, low-oligomer, eco-friendly method in a short time.

Purification of Polybutylene Terephthalate by Oligomer Removal Using a Compressed CO2 Antisolvent

“…A number of research groups have investigated the removal of oligomers from polyesters [5,6,7,8]. The extraction of oligomers from a similar thermoplastic, poly(ethylene terephthalate) (PET), using a liquid–solid Soxhlet extractor resulted in the removal of oligomers but required the use of a possibly carcinogenic solvent, 1,4-dioxan, and extremely long extraction times because of the nonporous nature of the materials [7,8].…”

“…The extraction of oligomers from a similar thermoplastic, poly(ethylene terephthalate) (PET), using a liquid–solid Soxhlet extractor resulted in the removal of oligomers but required the use of a possibly carcinogenic solvent, 1,4-dioxan, and extremely long extraction times because of the nonporous nature of the materials [7,8]. Inagaki et al [6] used subcritical water to extract soluble oligomers from PET at 5 MPa and 200 °C in 10 min, which reduced the oligomer content by 16%. Weijers et al [5] proposed the use of supercritical CO 2 to extract cyclic oligomers from PBT.…”

Material Separation from Polyester/Cotton Blended Fabrics Using Hydrothermal Treatment

“…These fluids enable the easy decomposition of polymers into monomers without a catalyst. Many studies have been conducted on the decomposition of polyesters into the constituent monomer, terephthalic acid (TPA), using sub/supercritical water for chemical recycling. − Notably, alcohols are used as supercritical fluids, and many studies have investigated their application in the decomposition of polyesters for chemical recycling. − …”