Laboratory High Consistency Dispersion Studies of Laser Printed Office Copy Paper, Part II, 1997 Recycling Symposium Proceedings

This paper presents the second part of a laboratory study of high consistency dispersion using a bench scale hand fed 12 inch refiner. The influence of dispersion consistency, temperature, and specific energy input is investigated. Dispersion trials were conducted at three consistencies, 21,28 and 36%, and at two plate gap widths. Dispersion consistency has a very strong influence of toner particle break down and size reduction, especially at 36% consistency. Microscopic visual examination of the toner particles reveals, however, that very little change in the ratio of clean (no fiber retained on particle after repulping) to hairy (unde-tached fiber retained on particle) particles takes place as a result of dispersion. High temperature trials were conducted at 58, 69 and 75° . Higher temperatures lead to less particle size reduction with the production of fewer small particles compared to trials at 25°C. There is some evidence, however, that high temperature dispersion somewhat enhances fiber detachment from toner, although considerable deformation of toner particles is shown to occur. The temperature studies are interpreted in terms of the physical state of the thermoplastic toner above or below its softening point. Specific energy input was investigated over a wide range from about 10 to 225 kWhr/ton. Increased spe-cific energy input leads to greater particle break down and size reduction, as expected. However, for a given specific energy input, increased dispersion consistency is seen to greatly enhance particle break down.