Ionic liquids: new age materials for eco-friendly leather processing

Abstract

The manufacture of leather is a challenging and complicated process, which converts natural biomaterial to various high end applications. There are several stringent regulations in processing this natural biomaterial skin due to the discharge of effluent and impact on environment. In this study, an attempt has been made to use ionic liquids to remove inter-fibrillary materials from the skin. Cleaner leather processing is a new avenue to explore the existing pollution complications during leather manufacture. Herein, an ionic liquid, 1-butyl-3-methylimidazolium chloride, is used as a fiber opening agent. Conventional reliming process was avoided by the treatment of molten salt. Enzymatic unhairing methods have been adopted for the removal of hairs from the skin. After the complete removal of hair, the pelts are treated with various concentrations of molten salts by the drum method. The pelts treated with low concentrations of molten salts showed better appearance and there was no damage to the pelts. After the fiber opening process, the pelts were subjected to conventional chrome tanning and post tanning processes. The shrinkage temperature of the experimental leathers is around 108–116 °C. The physical strength characteristics like tensile strength, tear strength and grain crack index of crust leathers meet the standard norms. Morphological studies ascertain that there was no grain damage and coalescence of fibers. These results show a promising venture for the use of ionic liquid for leather manufacture. This study signifies the role of ionic liquid in the tanning industry and gives a new dimensional approach to existing cleaner processing systems.