Man-made urushi Preparation of crosslinked polymeric firms from renewable resources via air-oxidation processes

"Man-made (artificial) urushi" has been prepared by laccase-catalyzed curing of new urushiol analogues, which were facilely synthesized by lipase-catalyzed regioselscive acylathin of catechol drivatives having a primary alcohoi with unsaturated fatty acide derived from plant oils,one of the most inportant renewable resources. The curing of the catechol derivative having twe or three unsaturated group proceeded under mild reaction conditions to conditions to produce the crosslinked ("man-made urushi") with high hardness and gloss surface, which are comparable with those of natural urushi coating. Similar urushiol analogues from 4-hydroxyphenetyl alchol and unsaturated fatty acids were subjected to an oxidative prlymerization by Fe-salen catalyst,yielding soluble polyphenols having the unsaturated group in the side chain.Garganal, a phenol derivative mainly having a C15 unsaturated hydrocarbon chain with 1-3 double bonds at m-position, is obtained from cashew nut shell liquid. Oxidative polymerization of cardanol by peroxidase or Fe-salen catalst gave the crosslinkable polyphenol. These prepolymers were subjected to harddening by thermal treatment or cobalt naphthenate catalyst to give a crosslinked film (also,"man-made urushi") with good hardness.