Selection criteria of Eucalyptus globulus Labill. for production of chemithermomechanical pulps (CTMP)

摘要

Utilization of rapidly growing trees, such as eucalypts, for high-yield mechanical pulps is limited by low brightness owing to high contents of alkali and neutral extractives. Wood supply problems have developed in many areas of the world and new sources of high-yield pulp are needed. Ten Eucalyptus globulus trees were selected from two plantation sites to evaluate suitability as raw material for high-quality and high-yield pulp. Chemithermomechani-cal pulp (CTMP) was prepared from tree chips pretreated with sodium sulfite prior to refining. Characteristics of the CTMP were correlated with chemical and physical prop-erties of the wood. There was a linear relationship between the content of alcohol-benzene extractives in wood and CTMP brightness. Klason lignin content in wood was inversely correlated with pulp sheet density, which is an important characteristic affecting the physical properties of pulp. The content of alkali extractives were inversely correlated with pulp yields. Color reversion was tested by exposing CTMP sheets to heat and light. Heat-induced yellowing of CTMP was of a low level and satisfied requirements for printing paper. The rate of yel-lowing was inversely associated with extractives and can be reduced by antioxidants.