Abstract
We report synthesis and utilization of epoxy resin derived from lignin (L), which is classified as a plant biomass with a polyphenol structure. L is considered to be a suitable alternative to petroleum-derived phenolic resins used for preparation of epoxy resins. Thus, we synthesized epoxidized lignin (EL) by the reaction of L with epichlorohydrin and cured the resulting EL by using phenol novolac (PN) as a curing agent. At first, the effect of phase-transfer catalysts on epoxidization was examined by model reaction using coniferyl alcohol (CA). CA was allowed to react with epichlorohydrin by a two-step process in the presence of the catalysts, and it was found that the catalysts composed of ammonium cations with alkyl chains longer than ethyl group were suitable for epoxidization. Then, L was epoxidized by using tetraethylammonium chloride as a phase-transfer catalyst. As a result of optimization of synthetic conditions, EL with low epoxy equivalent weight and with softening point was obtained in good yield. The resulting EL was cured with PN to give a cured resin containing about 75wt% of biomass-derived component.
