Our grandparents made metal-free leathers, tanned skins only with vegetable tannins, and fattened them with natural fats, made real “vacchetta” which did not contain any type of metal, it was beautiful and smelled of leather, but did not have the product features and the performance of modern chrome tanned leather, those performances of fastness to light, sweat, PVC and aging, basically to everything…. requested by the main fashion brands.
Today the term Metal Free is one of the most recurring themes in the communication of the tanning industry as it is a prerequisite required by the brands for the leather they use, becoming now an integral part of their strategy for the sustainability of the chain, it is a logo used in proposing new articles for fairs and events. For the R&D team of FGL International SpA, this has necessarily become a priority theme in the research and development planning to find innovative solutions through products/processes that allow the creation of metal free leather with product features comparable to traditional chrome items but according to sustainability criteria of the supply chain.
The request for metal free articles was not always accompanied by a precise definition of what was meant by it, that is what metals were involved and the required limits. Among the numerous specifications/MRSL that provide for limits, ZDHC in its 2.0 version is now a reference for the sector.
The research activities were planned according to the procedures of the certified FGL Quality/Safety system having as reference the principles of the ECHA guidelines that aim to promote safer products and processes that have less impact on the environment by developing an adequate ability to communicate along the supply chain, identifying adequate technical support and professionalism to make effective replacements.
The activity of FGL’s R&D team was set up defining as a priority the context in which it was to develop by identifying legislative, technical and environmental aspects considering feasibility, operating limits and eco-friendliness using as reference the European Standard UNI EN 15987 which reports the following definition: (metal free) leather – Animal skin converted to leather, where the total content of all tanning metals (Cr, Al, Ti, Zr, Fe) is less than or equal to 0.1% (mass of all metals/total dry weight of leather).
The input of the FGL research that started from this definition led to the consideration that the tanning treatment and the choice of the tanning agent is the basis for the development of a proposal for a metal free leather.
This consideration, together with a deep and intimate knowledge of the mechanisms of organic tanning deriving from dozens of years of experience of the Lapi Group on vegetable tanning, has therefore led FGL’s R&D team to evaluate the types of tanning on which to intervene with innovative ideas to arrive to the “Metal Free” goal. The technological knowledge acquired over the years on the potential of tanning agents has been refined by evaluating the chemical-physical features that they are able to give to the leather, highlighting potential and critical issues for obtaining versatile leather items suitable for as many uses as possible. In the past, innovative FGL proposals have led to the realisation of the RELEASYS® process that is still applied and proposed today with optimised management aspects.
The recent activities of FGL’s R&D team have focused on a new proposal of organic tanning which finds its innovative inspiration in a re-modulated use of an oxazolidine derivative making the best use of the characteristics and potential of the molecular structure to build the “metal free leather” offer with a good degree of cross-linking, good fullness and softness, great operational versatility for items with performances similar to chrome tanned leather.
Research has identified the tanning agent with the highest stabilising potential, understood the best application conditions, identified the most suitable application rates and the most suitable products to be used after the tanning process to increase and optimise leather features without compromising the “metal free” characteristics.
The analytical results achieved with the Metal Free FGL proposal are as follows:
Total metals – UNI EN ISO 17072-2 :2011 < 500 ppm
Free formaldehyde – UNI EN ISO 17226-1:2019 < 20 ppm
Good colour fastness to light – UNI EN ISO 105-B02:2014
FGL research continues anyway to offer processes that are increasingly less impactful on the environment by focusing on the concept of circular economy and green growth.
by Franca Nuti, R&D Manager of FGL International