Development of a Novel Method to Distinguish Poor-recyclable Prints and the Application of the Method for Field Survey

Abstract

In recent years, the quality of recovered paper has been deteriorated due to an increase of materials to be avoided, such as prints with Ultra Violet(UV)curable ink. The aim of this paper is to develop a method which can easily and promptly distinguish those poor-recyclable prints from recovered paper, and to put the method into practical use in deinked pulp(DIP)mills. In order to achieve this purpose, first, the spectrum data of several kinds of prints were obtained by using the attenuated total reflection infrared spectroscopy (ATR-IR) . Second, the recyclability of those prints was evaluated by lab-experiments. Third, a database was made by correlating the spectrum data and their recyclability, so as to develop the ATR-IR method. Finally, the ATR-IR method was applied to inspection of bales in DIP mills. By examining each print with ATR-IR apparatus, characteristic peaks were detected which helped to determine the type of ink. From the results of lab-experiments, the numbers of dirt speckles in DIPs from UV, UV varnish over coated, and polystyrene over coated prints, respectively, were much higher than those of conventional prints(oil-based ink) . In case of using the ATR-IR method, those prints were distinguished more precisely compared with the conventional solvent detection method used in DIP mills. As for the application of the method for incoming inspection in the mills, it has turned out that there was a certain tendency to decrease incidence rate of dirt troubles in DIP production after the application.