Development of formaldehyde-free leathers in the perspective of retanning: part II. Combination of formaldehyde-free retanning syntans

There is a growing demand for the formaldehyde-free leathers in global leather market due to increasing awareness towards eco-labelling. The first part of this work described the optimisation of formaldehyde-free syntans in their applications as single syntans in making leathers with desired properties. In this work the use of formaldehyde-free syntans in combination to produce leathers with desired properties has been attempted. Three combination-retanning systems have been chosen using formaldehyde-free resin, acrylic and protein syntans. The performance of leathers in terms of bulk and strength properties is shown to be comparable or even better for all the combination-retanning systems chosen compared to the control system. In particular, Experiment “C” (resin syntan 3%, acrylic syntan 4% and protein syntan 2%) provides leathers with improved bulk, strength and colour properties as well as reduced COD and TS loads, besides not having free formaldehyde. Scanning electron microscopic study reveals that the extent of filling in all the three combination-retanning systems is similar.