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A new "clean" process for leather tanning

   
 
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Faced with strict Community regulations on environmental protection, European tanneries are sustaining high costs for the processing of their waste and are also suffering from the unfair competition of Asian countries. The chemical industry is offering them a new technique for pre-processing hides which eliminates pollution and makes it possible to guarantee the production of very high quality leather with lower manufacturing costs

Researchers in the French branch of the European group Hoechst, a major supplier of chemical products for the tanning industry, were the source of this initiative. "The challenge facing our customers was clear," say the Hoechst representatives. "Faced with their Asian competitors, these industrialists needed new technologies which would meet European standards on the environment and guarantee quality leather while preferably reducing production costs."

The French laboratories of Hoechst, in partnership with an Italian tannery and a German company, launched their R&D project in 1991 with the support of the European Commission.

Silica enters the fray

Hides are tanned in order to render them rot-proof and amenable to the cutting treatments which they must subsequently undergo for the manufacture of clothing or other leather goods. The chemical agents traditionally used in this process are chrome-based products and other metal salts and it is these, in fact, which are the source of the serious damage caused to the environment by this industry.

It was by conducting bibliographical research that the Hoechst team found a lead which was to guide this project. In the 1940s, tanneries had tried replacing chrome-based compounds with silica, a mineral found abundantly in sand, grit and flint. The results then had been disappointing, leading to the production of poor-quality leather on account of the instability of the tanning properties in the silica solutions used. The non-pollutant features of silica, however, justified new and more detailed investigations.

Taking advantage of recent technological advances, the researchers attempted once again to use silica in what are known as colloidal forms (in which extremely small particles are suspended in liquid solutions), which are much more stable. The results proved to be particularly worthwhile at the pre-tanning phase, which is the rapid processing of fresh hides which must be carried out initially to guarantee their preservation before they are later transformed into finished leather.

An environmental solution

It quickly became clear that the new pre-processing was in fact even more advantageous because, during the actual tanning, the chrome-based products used in this phase were then almost entirely absorbed by the leather. As a result, the amount of chrome present in the final waste dropped by a factor of almost 100. Additional, not inconsiderable advantages were that the fixing and quality of the leather were improved, while the overall processing cost was reduced.

Uses in addition to tanning

What is more, this new process is not just of interest to tanners. The German company involved in the project became interested in using the non-toxic silica extracted from pre-tanning waste to manufacture gelatine for use in the food, pharmaceutical and cosmetics industries.

"We have filed a European patent application for the "FELIDERM W®" silica, which is now part of our product range," the Hoechst representative explains. "But its use means revolutionising the practices of tanneries. If they want to take advantage of this new process, which could increase their overall profitability by 30%, industrialists must review how they organise their production. But on top of this, this pre-processing would enable them to obtain a worthwhile quality-price ratio. This is particularly important in view of the competition from Asian tanneries which are not subject to any anti-pollution rules."

 

 

Project Title:
New colloidal silicas for white stabilised skin immediate development leading to improved ecological tanning

Programme: Industrial technologies and materials - BRITE/EURAM 1
Contract Reference: BREU 0296

Cordis Database For more information on this project,
go to the CORDIS Database Record

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