Condebelt drying and linerboard performance

摘要

Condebelt drying has been studied and implemented as a process for improving the mechanical properties of paper. The aim of this work was to clarify the role of shrinkage and density and other mechanisms on the properties of Condebelt dried papers. Laboratory- and machine-made papers made of recycled pulps from old corrugated containers (OCC) and never-dried unbleached kraft pulp was studied. Several properties were investigated, including creep under constant and cyclic moisture conditions, hygroexpansion, fracture toughness, tensile properties, compression strength and the strength in the thickness direction. With Condebelt drying, compared to conventional drying, it is possible to increase strength properties in CD dramatically mainly due to a reduction in shrinkage. Additionally, an increased density will add to the property increase in this direction. In MD, the contribution due to a higher density will be dominating. The effect of density will be dependent on the type of furnish, where the smallest effects are likely to occur for never-dried, well-beaten thin-walled fibers. Paper made of recycled, less beaten and thick-walled fibers are expected to have the highest effect due to the densification. The effect of the Condebelt drying on fracture toughness and moisture dependent properties such as creep and hygroexpansion indicates that no other type of mechanism, apart from shrinkage and density effects, are needed to explain the results. The Condebelt linerboards in corrugated boards are likely to produce containers with much higher BCT and lifetime during stacking in high humidity climates and should not be prone to excessive cracking during converting operations.