Strategizing the Development of a Metal- and Formaldehyde-Free Tanning Process Using (3,5-Dimethyl-1H,3H,5H-oxazolo[3,4-c]oxazol-7a(7H)-yl) Methanol Heterocyclic Derivative Oxazolidine and Polyallylamine

The chrome tanning process is increasingly restricted due to severe health concerns and environmental hazards caused by chromium under certain environmental conditions. Heterocyclic derivatives evoke a huge array of interest as an alternative for the metal-free tanning process. Oxazolidine, one such saturated heterocyclic compound, is known for tanning; however, formaldehyde toxicity has been associated with it. In this current study, (3,5-dimethyl-1H,3H,5H-oxazolo[3,4-c]oxazol-7a(7H)-yl) methanol and polyallylamine have been synthesized and their potential as chrome-free and formaldehyde-free tanning agents has been explored. The synthesized oxazolidine has been characterized by ultraviolet–visible spectroscopy, nuclear magnetic resonance spectroscopy, electronspray ionization–mass spectrometry, and attenuated total reflectance–Fourier transform infrared spectroscopy. Polyallylamine has been synthesized by solution polymerization and introduced alongside oxazolidine to create additional amine binding sites to improve the functional properties of the leather. 10% oxazolidine and 2% polyallylamine have been optimized to achieve 82 °C hydrothermal stability for leathers. The BOD/COD ratio of the oxazolidine tanning process is relatively less compared to the conventional chrome tanning process. The physical strength characteristics and organoleptic properties of the oxazolidine-tanned leather have been found to be better than those of the chrome-tanned leather. Thus, the current study paves way for an eco-friendly alternative to chrome- and metal-free tanning process as a greener and cleaner leather processing system.