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Posted: Mar 09, 2013
Nanotechnology improves leather and tanning process
(Nanowerk News) Humanity’s interest in preserving animal skins dates to prehistory, but in the 21st century leather goods have become ubiquitous. Leather shoes, belts, jackets and handbags are part of many people’s everyday attire. The material is also commonly found in our homes and vehicles, for example in the form of leather upholstery.
To produce leather, animal skins must be tanned to stop the natural process of decomposition. This is achieved by applying a chemical treatment that acts on collagen fibres in the skin and stabilises the proteins. Currently, this chemical change is brought about using vegetable, synthetic, and, most frequently, mineral agents; chromium salts are now used in the tanning of 90% of the leather produced in Europe. Tanning also includes mechanical processes that complement the treatments applied to skins. When the tanning process is completed, products are added in the finishing stage to give the leather the desired physical and aesthetic properties.
Contemporary leather producers have overcome the medieval stigma that associated the industry with filth and foul smells. In recent decades, the number of craft workshops has declined. Small-scale operations have been replaced by industrial producers that take full advantage of technology and are constantly innovating. These modern tanneries face the challenge of purifying the large volume of wastewater they produce and disposing of chemical by-products. In more developed countries, industrial producers rely on R&D to make their processes as environmentally friendly as possible and produce high-quality products.
The Igualada School of Engineering is an internationally recognised teaching and research centre that specialises in tanning.
Global production of tanned leather is concentrated in some twenty countries, led by China, with Spain ranking eighth. More than half of Spain’s production is based in Catalonia, and much of this activity is concentrated in a tanning cluster in Igualada. The capital of the county of Anoia is home to the Igualada School of Engineering (EEI), a school associated with the Universitat Politècnica de Catalunya · BarcelonaTech (UPC) that is internationally recognised in the sector. The EEI and the University of North Hampton are the only schools in Europe that offer university-level studies in tanning. The expertise of EEI researchers plays a key role in driving innovation in tanneries.
The team led by Anna Bacardit and Lluís Ollé—members of the UPC’s Engineering and Biotechnology Research Group (ENGIBIO) and of the A³ Chair in Leather Innovation—participates in national and international projects. Environmental improvement of tanning processes and products is one of their main lines of research.
In the Chrome-Free project, supported by the Centre for the Development of Industrial Technology (CDTI), the team is working on processes that use chrome-free tanning agents to produce high-end leathers. Chromium(III) is the chemical agent used in tanning. If chromium(III) is oxidised, it turns into its toxic cousin chromium(IV), so researchers are looking for alternative products for stabilising collagen proteins.
The large-scale use of vegetable agents such as tannins, which are extracted from chestnut trees and other trees and shrubs, has many drawbacks, including the risk of deforestation. This explains the team’s involvement in another European project, known as Lowest. “In this project, we’re developing synthetic agents that are economically competitive and work at least as well as the tanning agents currently in use,” says Anna Bacardit.
Research is also paving the way for leather producers to make leather of higher quality and with properties previously unimaginable—possible thanks to nanotechnology, which allows scientists to explore the properties of materials at the nanoscale.
The A³ Chair in Leather Innovation is developing new nanostructured materials that are applied in the finishing stage of the tanning process to improve the functional properties of leather products. In the Nanopelltech project, researchers are working closely with a number of companies to improve the upholstery used on seating for public spaces and vehicles. The project is part of a programme of technological innovation clusters funded by ACC1Ó, the agency that supports innovation in Catalan firms and their internationalisation efforts.
The A³ Chair is the technology partner of the five companies involved in the project. The team has developed new nanomaterials that add antibacterial, flame-retardant and self-cleaning properties to leather and fabric for seating.
“By creating nanostructured surfaces that repel dirt, we make seating easier to maintain and more hygienic,” says Lluís Ollé. This improves the health safety of users, who also benefit from better fire-retardant treatments. The conventional approach is to apply such treatments directly to the leather or fabric, but thanks to nanotechnology, encapsulated products can now be applied. “These products are only activated if there’s a fire, so under normal conditions people don't come in contact with them,” says Anna Bacardit.
The leather used in seating also incorporates nanocapsules that perform a self-repairing function. If a small scratch is made on the upholstery, they release a product that covers the damaged spot.
These nanostructured products were developed in collaboration with two companies: Colorantes Industriales, which conducted the formulation study, and Eco Poltech, which synthesised the nanomaterials. Bacardit stresses that “the project has taken advances in nanotechnology beyond the lab and helped companies incorporate nanomaterials in their production processes—an essential step if the research is to benefit society.” The researchers have worked with Curtits Aqualata, which has produced the leather for upholstery; Figueras International Seating, a company that has made a prototype seat for use in public spaces; and Aunde, which has produced a seat for buses. The prototype made by Aunde has been installed on two buses and is being tested to validate its functional characteristics.
Research on tanning is adding value in many areas beyond the fashion industry. The knowledge investigators are gaining about collagen materials opens up the possibility of applying biotechnology techniques in sectors such as cosmetics and pharmaceuticals. Relationships are also being developed with the paper industry, the graphic arts sector, the chemical industry, and even cultural industries.
The A³ Chair research team is currently studying how leather ages in order to improve its restoration. The research is being carried out within the framework of a European project aimed at creating a tool for assessing damage and deterioration in leather and parchment items held by museums and in other historical collections. Launched by the European platform Eureka, the ADAS project brings together organisations and companies based in Romania and Spain, including Curtits Aqualata.
The Spanish company has commissioned the research team to simulate the aging processes that leather undergoes. The information obtained will be entered into a database to facilitate the study and dating of historical items. The research results will also be made available to companies that make facsimiles and reproductions of documents. “The research will make it possible to reproduce original items—the leather cover of an ancient manuscript, for example—more quickly, more economically, and with better quality results. At present, reproductions of this kind are generally made using traditional methods that don't give consistent results," says Ollé.
R&D and industry: the A³ Chair in Leather Innovation
Links between researchers at the Igualada School of Engineering (EEI) and the tanning industry have been strengthened thanks to the establishment of the A³ Chair in Leather Innovation in early 2012. The Chair is a joint initiative of the UPC (through the EEI), the Igualada City Council, the Association for Research in Leather and Related Industries (AIICA) and the Spanish Chemical Association for the Leather Industry (AQEIC). A total of 175 companies—from SMEs to multinationals like Louis Vuitton, Loewe, Tous, Kemira, BASF, Munich and Inditex—have requested research-related services from the A³ Chair team.