Deinking of Laser-Printed Stock Using Chemical Densification and Forward Cleaning, 1992 Papermakers Conference Proceedings

Mixed office waste is receiving considerable interest as a source of recycled fiber, particularly in printing and writing grades. The major problem in using mixed office waste (and the reason why it is currently underutilized) is that it contains from 50 to 80% non-impact printed material (commonly referred to as “laser” or “xero-graphic”) which is difficult to deink. The current approach to deinking this furnish involves mechanical dispersion followed by mechanical removal and requires significant capital investment.

A new process for deinking non-impact printed waste has been developed. The process involves chemically enhanced densification of the toner particles to facilitate their removal by forward cleaning. Using this technology, a stock preparation/deinking system can provide clean pulp at substantially reduced capital investment.

This paper discusses the development of the chemical technology, the physical and chemical mechanisms by which densification is achieved, and key cleaning operating parameters. The results of 12 production-scale trials are reviewed. Ink removal efficiencies of 95-97% are demonstrated to be practical with the proper chemistry and correctly designed and balanced forward cleaning systems.