Tanning Process Study Using Chestnut and Acacia Tannin Associated with Acrylic Resin

Abstract

Chromium is the most commonly used tanning agent in the leather industry worldwide due to the good characteristics it adds to the leather. However, it is known that chromium III may oxidize to chromium VI and damage the environment. Based on this context, the industry has vegetable tanning as one of the options that provide leather with different characteristics when compared to the characteristics provided by tanning with salts of chromium. Thus, this study intends to develop a product which is combined with vegetable tanning and brings better characteristics to chrome-free leather. This process raises the quality of the final product, that is, it improves the tanning by combining tannins (acacia and chestnut) with acrylic resin. The methodology consisted of employing six different tanning processes. Firstly, the tanning agents were used alone; secondly, there was the addition of acrylic resin; and, finally, the use of the acrylic resin with tannins. Organoleptic properties, light fastness, shrinkage temperature, and physical mechanical tests were performed in order to test the quality of the leathers obtained. In the residual baths, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen, and total solids were evaluated. Based on the results obtained, it was possible to conclude that the best results were found with the use of chestnut tannin and acrylic resin separately and with the use of acacia mixed with chestnut tannin, which demonstrated that combined vegetable tanning can be an alternative to the production of chrome-free leather with good properties.