Oxidative unhairing with hydrogen peroxide: Development of an industrial scale process for high-quality upper leather

As an alternative to the traditional process based on the use of sulfides, an unhairing process in drum by hydrogen peroxide was developed for the production of high-quality bovine upper leather. A preliminary investigation at laboratory scale has allowed us to set out the optimal process conditions, in terms of H2O2 dosage and pH, in order to achieve an effective unhairing and a compatible swelling of the hide. The pilot and industrial scale runs have assessed the industrial feasibility of the process that allows the production of a versatile base for different final applications of the leather (either chrome or vegetable tanned), and appear practical to implement as well as compatible with existing machinery. The finished leather obtained by the innovative unhairing process shows good physical-mechanical and technical properties comparable with those of the traditional process, and the leather was technically assessed as satisfactory and suitable for use in the production of high quality upper leathers. The major pollutants of the oxidative unhairing, either as absolute concentrations or if normalized with respect to the salted weight of hide processed, appear quite similar to those from the traditional process. The evident advantage is obviously the complete absence of dissolved sulfides in the exhaust baths of the oxidative process. Scanning electron microscopy was used as investigation method to better understand the mechanism of the oxidative unhairing in comparison with the traditional.