Role of Deinking Agent and Its Challenge

The basic deinking process for old newspapers, the role of the deinking agent, the science and the condition for good deinking are reviewed based on the results in our laboratory first. Then, by using this typical deinking process, the deinkability of the pigment―based inkjet printings was examined. In commercial printings, the transition to on―demand printings is in progress, because the on―demand printings enable to print many various lots and even small lots. Among them, the ink―jet printing has attracted attention in terms of printing speed. Therefore, it is thought that the waste papers printed by ink―jet printers will be used as raw materials in pulp manufacturing in near future. In deinking of pigment―based inkjet printings, there were no problems in the ink―releasing process. But, inks released from the waste papers were too small to be rejected out in the flotation process. For increasing the efficiency of the flotation, it was found that the weakened shear in the ink―releasing process and the combined use of the aggregating agents such as fatty acids in the flotation process were effective. However, by this method, it is considered that ink―releasing will be not enough in the deinking of old newspapers and electrophotography printings. It is necessary to establish the deinking method of mixed waste of ink―jet printings, electrophotography printings and old newspapers by adopting the suitable deinking systems and deinking agents and/or improving the ink―jet inks.