Oligomer Removal From Polyester Fiber Surfaces by Surfactants in Nonaqueous Dyeing Systems

ABSTRACT Due to the low solubility of oligomers in nonaqueous medium, these oligomers would influence the uniformity of dyeing. In this investigation, the solubilization and dispersion effects of surfactants on oligomers in nonaqueous medium, as well as their influences on the oligomer removal efficiency were investigated. Oligomers predominantly adhere to the fiber surfaces during the cooling processes, which exhibit significant differences from the conventional water‐bathed dyeing. Through the screening of oil‐soluble surfactants with a hydrophilic–lipophilic balance value below 10 and their combination with isopropyl myristate, fatty alcohol polyoxyethylene ether, sorbitan tristearate, monooleate, trioleate, and nonylphenol polyethylene glycol ether were determined to be suitable for the nonaqueous medium system. The blending of isopropyl myristate significantly improves the solubility of surfactants and the removal efficiency of oligomers. A multi‐component surfactant (SANI) was prepared. At a dosage of 2 g/L, the oligomer removal efficiency was improved by approximately 40% compared with pure nonaqueous medium cleaning. Dyeing performance tests demonstrated that SANI cleaning not only effectively removes oligomers but also improves washing fastness by 0.5–1 grade, with negligible impact on fiber color. Fiber surface observations further confirmed that the fiber surfaces become significantly smoother, indicating that this cleaning process has promising application prospects.