Volgare, Michela (2025) ECOTAN new sustainable process for the leather industry. [Tesi di dottorato]

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• Diagnostica e trattamento chirurgico delle lesioni non palpabili della mammella. (deposited 10 Lug 2008)
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Abstract

In the leather manufacturing industry, the transformation process of animal hide into leather involves several complex steps to create a stable substrate ready for further processing. However, the tanning process is associated with significant environmental concern, primarily due to the high water consumption and the extensive use of chemicals, which generate both liquid and solid waste. Traditional tanning process consume only 54-57% of the chemicals used, with the remaining solution discharged as waste. In addition, tanning agents are delivered using large quantities of water (30-50 Liters per kilogram of treated hide, and in some cases up to 140-150 L/kg). These environmental challenges underscore the need for innovative technologies in the tanning industry. The present research aims to develop a set of modifications designed to reduce the environmental impact of leather tanning industry. The tanning process relies on three main components: the animal hide, water, and tanning agents that acts as a cross-linker for collagen fibers, strengthening and preserving the leather. Based on this consideration, the ultimate goal of the present work is to substantially modify the tanning process in three ways: 1) by changing the starting material, the hide; 2) by replacing the conventional aqueous tanning bath with micronized droplets; 3) by substituting traditional tanning agents with environmentally friendly molecules. The common objective of these changes is to reduce environmental impact, placing this Project within the framework of the PON 2014 – 2020 Research and Innovation PhD programs, with a specific focus on green themes. The first step in this project was the implementation of an innovative sustainable process that allowed the elimination of the water as the vehicle for tanning agent (water-free process) or a significantly reduction of water consumption throughout the process (water-less process), while simultaneously minimizing chemical use. The implementation of an innovative tanning process could lead to a cleaner and punctual cross-linking process between the chemicals and the collagen, thus avoiding excess of wastes of water and tanning agents typically generated in traditional methods. The starting point was an in-depth analysis of the structure of collagen to better understand and properly manipulate the properties of animal dermis. With thorough understanding of the dermal collagen matrix collagen matrix, a dehydration process was developed to obtain anhydrous substrates. The displacement of water and fats from the collagen structure played a key role to develop a green and clean technology, surpassing the aqueous baths currently used in the tanning process. The use of an anhydrous substrate enabled the development of a process in which chemicals and nanomaterials could be delivered in the loose collagen matrix. The core principle of this project was indeed the use of anhydrous substrates, free from water and fats, which were characterized from a morphological, thermal, and mechanical perspective. Subsequently, the study involved a detailed study of the traditional tanning process. Recognizing the complexity and multi-stage nature of the conventional method, the research activity focused on the examination of some phenomena to identify areas for improvement. An alternative and innovative tanning system was developed during the second phase of the project. In details, an aerosol process was explored in which the tanning agents were nebulized. The fine-tuning of the process began with an aerosol tanning process conducted with chromium in water, to ensure that the new method performed comparably to the traditional tanning process. The results of these experiments were compared to those obtained using traditional “wet blue” leathers and key performance characteristics were assessed. With confidence in the efficacy of the innovative tanning process, prototypes were realized using water-less and water-free, approaches, employing both conventional tanning agents in solvents, and subsequently exploring innovative cross-linker that are completely unexplored in the tanning field, to realize a process that was totally metal-free and water-free. In addition, this project is focused on the identification of macromolecular compounds and microparticle to confers technological properties to the leather, giving it three-dimensional and surface-specific characteristics. Surface treatments and "three-dimensional" treatments open the way to the realization of natural leather with unique features, similar or superior to those of technical textiles This project was conducted in collaboration with two Companies, CHIME S.p.A. and Leather Plus S.r.l., located in Solofra (AV), important centres of tanning process and leather manufacturing in Italy and Europe, in which we developed innovative formulations for the realization of a sustainable tanning, as well as the study of the spongelike substrates for a precise and stoichiometric tanning suitable to reduction of consumption and environmental pollution.

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