Effect of Pulping Conditions on Stickies Behavior in Office Waste Deinking Systems, 1994 Recycling Symposium Proceedings

T. F. Ling, F. J. Sutman, S. K. Richmann, M. K. Letscher

Utilization of office waste paper (OWP) as a fiber source for printing and writing grades can be limited by its high content of non-impact or “laser print” inks. Chemical aggregation and densification of non-impact inks is one option for the deinking of OWP. OWP typically contains a variety of stickies contaminants. Successful use of OWP as a furnish source requires an understanding of how pulping conditions, chemistry, and interaction with ink affect the behavior of stickies.

OWP containing stickie contaminants was deinked under “mild” and “harsh” pulping conditions and then contaminants were removed using cleaning and screening. The same furnish was also deinked using the chemistry and “harsh” pulping conditions required for aggregation and densification of non-impact inks. The effects of pulping conditions and chemistry on the size of stickies, efficiency of stickies removal by cleaning and screening, and the nature of the stickies in the finished stock were investigated.

Under the pulping chemistry and conditions required for aggregation and densification of non-impact inks, the majority of stickies associated with the ink in the pulper. The combined stickies and ink particles were separable from the fiber by mechanical systems, particularly forward cleaning. These contaminants were less prone to deposition than stickies formed under the same “harsh” pulping conditions without chemical treatment. The deposition potential of the chemically-treated contaminants was no greater than stickies formed under mild pulping conditions without chemical treatment.