Synthesis of Photoactive Compounds from Tall Oil Fatty Acids

Photocurable systems are more effective, faster and require less energy than conventional thermal curing methods. To facilitate the ongoing transition toward a biobased economy, photoactive compounds were synthesized from tall oil fatty acids (TOFA) which is a by-product from wood pulping. In this study, photoactive monomers were synthesized by two different chemical pathways using oleic acid and TOFA as raw materials. Firstly, double bonds present in TOFA were epoxidized, followed by epoxy ring-opening with acrylic acid which introduced photoactive functional groups into the fatty acid backbone. Intermediates and final products were analysed using titration methods (acidic value, epoxy value, iodine value) and FTIR. The preferred final product (3-acxyloyloxy-2-hydroxypropyl)-9-hydroxy-10-acryoyloxystearate (Acr-St) was synthesized by both pathways. In the case of oleic acid, a compound of Acr-St was yielded, while in case of TOFA, the Acr-St was present in mixture along with TOFA acryloyloxy derivates (TOFA-acr.der.). The final products were photopolymerized using UV irradiation (396 nm) and as a photoinitiator 3 wt% solution of TPO (2,4,6-trimethylbenzoyl diphenylphosphine oxide) was used. However, only the synthesis using oleic acid yielded a photocurable compound.