Preparation of a syntan containing active chlorine groups for chrome-free tanned leather

In this research, a syntan containing active chlorine groups (SACG) was synthesized by the condensation of phenol sulfonic acid condensation product (PSAC) and cyanuric chloride (TCT). The structure and composition of as-received syntans were characterized by Fourier transform infrared spectrometer (FT-IR), nuclear magnetic resonance spectroscopy (1H-NMR), and gel permeation chromatography (GPC). The thermal properties and morphology of the tanned leather were analyzed using thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The results indicated that the multi-point active chlorine groups in syntans had an excellent cross-linking effect on collagen fibers, which increased the shrinkage temperature of leather to 81.6 °C. The tensile strength, the tearing strength, and the thickening rate of the tanned leather were 14.26 MPa, 42.56 N/mm, and 78.3%, respectively. The tanned leather exhibited flat and fine grain. The collagen fibers showed uniform dispersion. Besides, the SACG had remarkable environmental benefits compared with the traditional chrome tanning system by significantly reducing the content of chemical oxygen demand (COD), total solids (TS), dissolved solids (DS), suspended solids (SS), chloride, and total chromium analyses (TCr) in tannery wastewater and thus could be applied to non-pickling tanning system. Moreover, the SACG tanning technology is a promoting chrome-free tanning technology because of the facile, cost-effective, and environment-friendly performance, suggesting that this technology has great potential to be widely applied in leather manufacturing.