New method for the synthesis of formaldehyde-free phenolic resins from lignin-based aldehyde precursors

Abstract

Phenolic resins are mainly obtained from phenol and the highly toxic and volatile formaldehyde. In order to synthesize new formaldehyde substituents for the synthesis of resol-type phenolic resins, we designed a method to functionalize phenolic compounds with aliphatic aldehydes by a two-steps reaction: the functionalization of an acetal group on aromatic hydroxyl functions and the subsequent deprotection of theses acetal groups into aliphatic aldehyde groups. This method was used on the lignin-based aromatic aldehyde precursors i.e. 4-hydroxybenzaldehyde and vanillin to turn them into reactive and difunctional biobased aromatic aldehyde precursors. Those precursors proved to lead to formaldehyde-free and biobased phenolic resins with competitive thermal properties compared to the usual formaldehyde resins.