A novel tool for studying the yellowing phenomenon during delignification and bleaching of pulp

摘要

The notion yellowing tendency is introduced to describe the ability of a pulp to yellow under certain well-defined conditions,as opposed to the natural yellowing occurring in a pulp bale after leaving the dryer and on its way to the paper mill.In order to provide more information about the origin to the yellowing,a powerful new tool,referred to as the Almquist method is utilised.In the method the yellowing tendency is plotted versus the ISO brightness throughout the delignification and bleaching.Expanding the measurement of the yellowing tendency this way provides a more complete picture also of the yellowing tendency of a fully bleached pulp.Small differences in the yellowing tendency of a fully bleached pulp could then more easily be confirmed as true and real or vice versa.