An enzymatic approach to develop a lignin-based adhesive for wool floor coverings

This work describes a novel enzymatic approach to develop a lignin-based adhesive aimed at replacing the synthetic latex in wool floor coverings. The adhesive production consisted of a lignin pre-activation step to oxidise it by a laccase-enhancer system followed by a phenolation step where natural phenolic compounds were copolymerised with lignin in order to increase its content of quinone structures reactive towards wool. The electrochemical behaviour of the adhesive precursors and the influence of process conditions on the adhesive characteristics suggested that the phenolic compounds were able to auto-polymerise and copolymerise between themselves and with lignin during the enzymatic reaction. Consequently, the flexibility and bonding strength of the adhesive increased. The latter showed strength performance similar to that of the traditional latex-based adhesive. A satisfactory level of flexibility was obtained using polyethylene glycol as an external plasticizer of lignin.