Dimensional Stability Issues of Lightweight and New Paper Grades: Causes and Remedies

摘要

As the market for paper and paperboard grades become more competitive, many mills are looking into market diversification and production of new grades with growth potential, while for many others cost reduction and lightweighting remains the key priority. For either of these initiatives, most of the mills are restricted to use their actual paper machine with minimal capital investment on equipment and rebuilds, thus they push the paper machine operation near to or beyond its design limits. Avoiding dimensional stability issues is one of the many challenges that are associated with grade change and lightweighting. Common dimensional stability problems associated with such changes are curl, web shrinkage/expansion, bad stacking & waviness, leading to costly rejects due to poor converting or end-use performance. In addition to the need for in-depth understanding of the root cause, mills need to identify the key operation changes to control these issues. This paper will first focus on describing different dimensional stability issues that mills could face with new grades development, then will present the techniques developed to understand the fundamental mechanisms behind these issues. Few field studies are also presented to demonstrate how the expertise can be put to work in close collaboration with the mills to provide optimal solutions to dimensional stability issues.