Improving the smoothness/bulk relationship through a pure fines layer on the paper surface

One of the most desired targets of papermakers in recent decades has been to produce smooth papers with high bulk. This study reveals the potential of a layered sheet structure for improving the smoothness/bulk -relationship. The aim was to determine how paper properties develop when fines are increasingly taken from the base layer and redistributed on the paper surface. The study was performed using TMP (Thermo Mechanical Pulp) as the raw material. Sheets with a layer of fines deployed on the surface were prepared with a dynamic sheet former. Laboratory scale studies showed that paper smoothness, bulk, surface density and print density simultaneously increased by deploying some of the fines fraction of a mechanical pulp on the paper surface once the fibrous backbone has been formed using the same mechanical pulp with reduced fines content. Reduction of internal bonding was a drawback of the method. Optical properties were retained at least the same level as the reference sheets.