Understanding the Roughening Light Weight Coated Papers Containing Mechanical Pulp, 2007 Coating & Graphic Arts Conference

ABSTRACT ONLY

Mechanical pulp gives the advantage of high bulk, good opacity and printability. Moreover, mechanical pulp is generally more cost effective than chemical pulp. For these reasons, it is desirable to replace chemical pulp with mechanical pulp in lightweight coated (LWC) papers. However, mechanical pulp roughens more when coated. As a result, this work focused on the understanding the roughness changes that occurs when chemical pulp is replaced with mechanical pulp under laboratory conditions.

Hand sheets with base weights 60 ± 3 g/m2 were prepared using 70% hardwood Eucalyptus and 30% softwood kraft. The Eucalyptus kraft was replaced with up to 20% aspen 325/85 high yield pulp (HYP). The hardwood and softwood kraft pulps were refined to a freeness of approximately 400 mL. The samples were coated with 15 g/m2 of mixture of kaolin clay and SB latex at 60% solids. The coated samples were then calendered to 50 ± 2.5 Tappi gloss. The variables investigated were precalendering, multiple coating, % coating solids and sizing.

It is expected that high precalendering temperatures, high % coating solids will limit the roughening of LWC containing mechanical pulp.