Sustainable utilization of corn starch resources: A novel soluble starch-based functional chrome-free tanning agent for the eco-leather production

Tanning is an important procedure in the leather making process. Currently, chrome tanning is still mainly used for leather processing both domestically and internationally, resulting in chrome-containing wastewater, chrome-containing sludge and chrome-containing solid waste. In this study, a new soluble starch-based chrome-free tanning agent (SCT) with abundant terminal epoxy groups was synthesized by grafting triglycidyl isocyanurate (TGIC) onto soluble starch (ST). In addition, structure characterization and performance test of the obtained SCT tanning agent were conducted, which was subsequently used as a chrome-free tanning agent for ecological leather processing and manufacturing. NMR and FTIR spectra revealed typical peaks for the TGIC functional groups in the SCT molecular structure, indicating that ST was successfully crosslinked with TGIC. After the prepared SCT was used for the chrome-free tanning process of sheepskin, the moisture and heat stability of the tanned leather were significantly increased, and the shrinkage temperature (Ts) exceeded 84.2 °C. Furthermore, SCT-tanned leather exhibited good collagen fiber dispersion, yellowing resistance, mechanical properties, softness and thickening compared with those of commercially available chrome-free tanning agent. Therefore, keeping with the trend of eco-leather processing development, SCT as a green chrome-free tanning agent demonstrates broad application prospects for the sustainable industrial processing of leather.