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, 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, it is possible to dramatically increase strength properties in the cross-direction mainly due to a reduction in shrinkage, as compared to conventional drying. Additionally, the increase in density will add to the increase in properties in the CD. 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 lignin-richand thick-walled fibers are expected to be affected the most 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.