Linerboard fines - effects and composition

The fines component of a pulp has a significant effect (positive and negati ve) on the production and quality of linerboard. A typical linerboard can c ontain between 5% fines, for a relatively unrefined kraft furnish, up to 30 % fines or more in a waste based (recycle fibre) liner furnish. All fines c ause some loss of drainage on the wire that limits production, decreases th e refining able to be given to the pulp, lowers first pass retention and in crease headbox consistency. Good quality fines, however, can also make a si gnificant contribution to sheet strength, smoothness and printability. Conv ersely, lower quality fines can reduce strength as well as drainage. It is deduced that the fibrillar rather than particulate material in the fi nes develops sheet strength. Fibrillar material is more common in the fines within pure refined kraft pulp and particulate fines material dominates in recycled fibre pulp. The chemical composition of the strength-reducing par ticulates was found to be higher in ash and aluminium and to be insoluble i n 72% sulphuric acid. Filler clay was likely to be a large part of the part iculate make up although probably not the only strength reducing component. Considerable potential exists to manipulate linerboard quality by separati on and then treatment of fibrillar and particulate fractions of the fines c ontents of some of the pulp components. Alternatively, manipulation is poss ible by simply removing some fractions from the furnish. A technical soluti on of how to achieve this, practically, is required.