Chemimechanical pulping of New Zealand-grown Eucalyptus regnans

Plantation grown Eucalyptus regnans was evaluated for its chemimechanical p ulping potential using the cold soda and alkaline peroxide mechanical pulpi ng (APMP) processes. A wide range of sodium hydroxide application rates (1. 2 to 9.5%) were used with bulked tree samples, and a single sodium hydroxid e application rate was used with individual tree samples, selected for a wi de range of wood density (365 to 509 kg/m(3)), to provide a comparison of t he relative effects of process conditions and wood properties. The sodium h ydroxide application was the most important factor affecting pulp freeness, shive content, sheet density, strength and brightness. Wood density affect ed the absorption of sodium hydroxide during impregnation, and can result i n large differences in pulp freeness, sheet density and strength at a given sodium hydroxide liquor concentration. The light scattering coefficient an d opacity were largely affected by wood density, as a result of changes in the fibre wall thickness.