Is deinkability of inkjet prints an issue?

Abstract

In the fast-growing digital printing market, a noteworthy development is the introduction of com¬mercial inkjet web presses for on-demand newspapers and various publications and business forms. Despite the enthusiasm brought about by these new inkjet technologies, a number of deinking studies carried out in Europe have raised serious issues about the deinkability of inkjet prints. Some representatives of the digital printing indus¬try question the validity of these conclusions. We carried out deinkability tests with different ratios of inkjet-printed newsprint at alkaline and near-neutral deinking chemistries, with fresh and aged papers. A representative pigmented inkjet formulation was used for the deinking tests and well-proven protocols were used to follow the fate of ink in pulping, flotation, and thickening. Under these conditions, our results were similar to those obtained by European researchers. Pigmented inkjet inks do not have the physicochemical attributes to be effectively collected by air bub¬bles during flotation. Causes for this poor deinkability of inkjet inks are discussed, as well as the potential means to enhance their deinkability.