Evaluation of a new sustainable continuous system for processing bovine leather

The aim of the present work is to evaluate a new sustainable continuous system for processing bovine leather. By means of a prototype described in the international patent WO, 2010/070571 (A2) of the technological centre AIICA, a dehydration process for bovine hides is carried out. What is obtained through this new process is a dehydrated leather with the optimal physical and chemical characteristics that will allow its subsequent tanning by immersion processes in aqueous solutions of chemical products. When compared to existing traditional processes, there are economic and environmental advantages resulting from the use of this new system. More specifically, the new process results in reductions of 30.6% in water use, 50.2% in chemical use and 16.4% in process time. In addition, a reduction of 27.3% in wastewater and a reduction of 47.5% of thermal energy consumption are obtained. However, this new system presents an increase in electricity consumption of 63.03% and an increase in gaseous emissions of 75% due to the use of acetone in the dehydration process and the 0.5% losses of acetone during the process. In order to better assess the environmental impact of this new tanning system, life cycle analysis methodology has been chosen to perform calculations on the Global Warming Potential (CO2 equivalent emissions) and the energy consumption comparing both traditional and new tanning processes

Synthesis of polyurethanes with low volatile organic Compounds content for upholstery and automotive Articles

The manufacture of upholstery and automotive articles is linked to the release of Volatile Organic Compounds (hereinafter VOCs) during their manufacture, which have short and long-term effects on the health of users and the environment. In the leather sector, around 40 kg of VOCs are generated per 1000 kg of raw skin. This research work has focused on the synthesis of new and more sustainable urethane-based polymers that, in turn, allow the quality requirements of the finish to be met, which vary depending on the leather article manufactured. The main objective of the study is to minimize the content of VOCs in the different aliphatic polyurethanes synthesized in a pilot-scale reactor, making small modifications to the synthesis formulations. The synthesis route developed is based on the preparation of polymers of ionomeric polyurethanes and their subsequent dispersion in water. In the synthesis processes developed, the content of coalescing solvents and neutralizing agents, which directly contribute to the concentration of VOCs of the urethane polymers, is eliminated and / or minimized as much as possible. The new urethane-based polymers obtained have been analyzed according to the parameters of pH, viscosity, density and percentage of solids in the resin. Likewise, organoleptic tests (color, transparency, hardness, touch and tacking) and physical tests (tensile strength, water absorption, hardness and color change at 100°C for 24 hours) have been carried out on the film corresponding to each synthesized polyurethane resin. These products will be introduced in finishing formulations designed to obtain high-performance upholstery and automotive leather with minimal impact in terms of VOC content at the pilot level. Tests of fastness and physical resistance have been carried out to evaluate the performance of these leathers.This research work has been developed within the framework of the NoVOCs project (RTC-2016-4575-5) within the Collaboration Challenges program (2016-2018) approved by the Ministry of Economy and Competitiveness of Spain

Formaldehyde scavengers for cleaner production: A case study focused on the leather industry

Due to its carcinogenic character, the presence of formaldehyde in leather continues to be a subject of great concern. By using formaldehyde scavengers, it is possible to reduce the formaldehyde content in leather. In this work, the potential ability of three different compounds (ethylene urea, pyrogallol and gallic acid) to reduce the formaldehyde content in splits leathers treated with formaldehyde resins (melamine-formaldehyde and dicyandiamide-formaldehyde) is assessed. This capacity is compared with that of a fourth scavenger (hydroxylamine sulphate) already used in tanneries. The evolution of the formaldehyde content with time is also considered, as well as the potential coadjuvant effect of other compounds such as mimosa extract and an acid dye (Acid Black 234). Hydroxylamine sulphate initially showed the highest ability to reduce formaldehyde content. However, after a certain time, this ability proved to be inferior to the ability of other compounds due to the reversibility of the reaction between hydroxylamine and formaldehyde. Pyrogallol showed a higher ability than gallic acid when used in the final wash of leather processing. However, the treatment with pyrogallol results in a darkening of the leather; this darkening limits its use. Gallic acid may be a good alternative to formic acid as the final fixing agent in leather processing when the presence of formaldehyde in leathers is suspected. The use of gallic acid in the final wash or as a fixing agent fulfils the formaldehyde content limit (65–75 mg/kg) of the major brands in leather goods in direct contact with the skin. The addition of 2% of gallic acid in the final wash of leather processing resulted in formaldehyde content reductions that varied from 65% to 85%. However, further experiments are required to assess the influence of gallic acid on the fastness properties and the coloration acquired by the treated leathers. The joint effect of gallic acid in the final wash or as a fixing agent and mimosa extract as a retanning agent in formaldehyde content reduction is even enhanced by subsequently using a dye with amino groups in its chemical structure. Reducing the formaldehyde content by using scavengers can contribute to the achievement of a cleaner production in those sectors (leather, textile, wood) that use formaldehyde resins