Lignin-derived non-toxic aldehydes for ecofriendly tannin adhesives for wood panels

An adhesive based on the reaction of a very fast reacting procyanidin-type condensed tannin, namely purified pine bark tannin, and food-grade non-toxic slow-reacting aldehydes derived from lignin was shown to satisfy well the relevant standards for bonding wood particleboard. Vanillin and a dialdehyde derivative of vanillin were the aldehydes used. The oligomers obtained and their distribution have been determined by matrix assisted laser ionization desorption time-of-flight (MALDI-TOF) mass spectrometry for the reactions with catechin used as a model compound and with the pine tannin itself, and by cross polarization magic angle spinning 13C nuclear magnetic resonance (CP MAS 13C NMR) for the reaction with pine tannin.