Characteristics of eucalyptus woods from plantations in South Africa for kraft cooking

Abstract

Eucalyptus woods (E. nitens, E. smithii, E. grandis, and E. macarthurii) grown in South Africa as pulp and paper grade hardwoods, which are expected to be raw materials used in a Japanese pulp mill, were investigated to clarify their characteristics for kraft-anthraquinone (AQ) cooking and totally chlorine-free (TCF) bleaching. E. smithii wood had the highest density (0.665 g/cm3) next to E. macarthurii wood. It was shown that E. smithii wood was most easily delignified and had the best response to cooking and bleaching. The Klason lignin content of E. smithii wood was 22.8%. It was a little higher than that of E. nitens, but much lower than that of E. grandis and E. macarthurii. Furthermore, E. smithii wood gave the highest syringaldehyde to vanillin ratio (S/V ratio, 4.18) by alkaline nitrobenzene oxidation analysis. Therefore, E. smithii wood should show good delignification during cooking and bleaching. All eucalyptus full bleached pulps gave high brightness, E. smithii showed the highest brightness (86.7% ISO).