Substitution of Hardwood Bleached Kraft Pulp with Aspen High-Yield Pulp in LWC Wood-Free Papers, Part 2: Impact on Coated Paper Quality

Abstract

The effect of high-yield pulp (HYP) substitution on the properties of basestock, coat-ed, and calendered sheets are examined, specifically in lightweight coated (LWC) wood-free papers. Part 1 (TAPPI JOURNAL, March 2006, p. 21) focused on the impact on basestock properties. Part 2 presents results on coated paper properties including surface quality, coating coverage, and print-ability. The increased bulk created by HYP substitution is partially preserved after coating and soft-nip calendering. There is no significant effect on roughness and gloss at a HYP substitution of below 20%. Above 20%, a higher roughness and lower gloss are observed, but the effect can be minimized with a higher calendering load. Coated sheets containing HYP have a slightly poorer coating coverage, which can be attributed to the slight increase in roughness. Coating coverage is unaffected at HYP substitution ranging from 10%-30%. There is no significant effect on printability at low HYP substitution levels (e.g., 10%). A higher ink demand found at a high HYP substitution level (e.g., 30%) is attributed to the higher surface roughness.