Low Temperature Deinking of Non-Impact Printed Office Waste. Results of Laboratory, Pilot and Commercial Trials of a New 'Laser' Deinking Program, 1994 Recycling Symposium Proceedings

C. S. Greer, Ph.D., D. R. Cosper, Ph.D.

Recycled office waste papers are potentially an excellent source of low cost, high quality fiber for the papermaking industry. However, office waste papers typically contain a high percentage of photocopier and laser printed papers, which are printed with inks that are literally fused to the paper surface. In the pulper, these inks, or toners, are released from the fibers in the form of flat flakes. Most of these flakes are too large to be removed by washing or flotation, and too small and flat to be removed by fine screening or centrifugal cleaning. Without chemical treatment, the toner flakes stay with the pulp and end up in the finished sheet as visible dirt specks. Therefore, many papermakers must purchase more costly, “laser-free” grades of postconsumer waste papers in

order to meet their recycling needs. A chemical pulper program has been developed which provides the papermaker with a way to effectively recycle photocopier and laser printed papers. Benefits of the program include: low pulping temperatures, moderate pulping times, the ability to handle variable impact/non-impact furnish blends, broad pulp consistency range, and no tendency to deposit toners/inks on equipment surfaces. This chemical program transforms the toner flakes into solid, three-dimensional toner aggregates which are readily removed from the

pulp with fine screening and forward centrifugal cleaning. Results of developmental laboratory, pilot and commercial trials of this new “laser” deinking program are the subject of this paper.