Bonding Between Vegetable Oil Inks and Cellulose.

Many workers have shown that the longer the delay after printing, the more difficult it is to recycle inks with ingredients that cross-link with time. In this work, we show that inks containing linseed oil or soya oil form covalent bonds with cellulose, via oxidative polymerization. Printed cellulose films were aged for different times at different temperatures. Ink that could not be extracted with a good solvent for linseed oil films, chloroform, was considered to have reacted with the cellulose surface. Ink films printed onto polyethylene were always extractable, showing that no reaction had occurred with the polyethylene. The amount of non-extractable ink increased with both time and temperature, as well as with the content of Mn drier catalyst. An induction time was observed before the non-extractable ink started to build up. The induction time decreased with increasing temperature or with increasing Mn content. The reaction follows pseudo-first order kinetics, with an activation energy of 55 kJ/mol. It is difficult to fully remove the vegetable oil without degrading the cellulose.