Enzymatic synthesis of epoxy resins from bio-sourced tannins.

Edited on 09/05/2013
The French National Institute for Agricultural Research (INRA) and the chemical engineering school ENSCM Montpellier are conducting research on a new process that will make it possible to avoid using Bisphenol A in the synthesis of epoxy resins, through the use of bio-sourced tannins. The process also makes it possible to substitute epichlorohydrin (which is classed as a carcinogen) with an enzyme when synthesising the resin.
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Various types of polyphenols deriving from wine-making waste and pine bark are being studied by INRA and ENSCM Montpellier as possible substitutions for BPA in epoxy resins. The potential substitutes for BPA are catechin, which has a simple polymerised-tannin structure, gallic acid from gallotannins and vanillic acid from lignins.

INRA and ENSCM Montpellier have conducted research on a new way of synthesising epoxy resin using these polyphenols. The synthesis of epoxy resins normally uses epichlorohydrin during the monomer epoxidation phase, even though this compound is classed as a CMR substance. The recent advance in INRA's research lies in the substitution of epichlorohydrin by oxygenated water in the presence of an enzyme (lipase B from the yeast Candida Antarctica). Enzymatic synthesis yields good results with gallic and vanillic acids, but does not work with catechin. Catechin is, however, easier to extract than gallic and vanillic acid, making it more readily available. Furthermore, the quality of the epoxy resins obtained with catechin makes them suitable for use in food tins. The resins obtained with gallic and vanillic acids are currently too rigid, but studies on these two monomers are ongoing.

The main possible sources of tannins are the bark of pine trees (Douglas Pine, Picea Abies) and waste from wine-making (grape pomace, etc.), which is abundant in France. "Industrial tests will be carried out, but first of all we need to create the tannin production network," explains Hélène Fulcran, who is leading the research at INRA. With this in mind, a Single Inter-ministerial Fund (Fond Unique Interministériel or FUI), bringing together industry players and a sawmill cooperative from the Tarn in the south of France, is set to be established some time in 2014.

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