EFFECT OF DIFFERENT TREE AGES OF JAPANESE LARCHES ON THE PULP AND PAPER PROPERTIES

摘要

Japanese larches are introduced and cultivated widely in high-altitude mountainous areas in Hubei and Hunan provinces in China and have a great potential for pulp and paper industry. In this study, some Japanese larches with different tree ages were obtained as raw materials', and the effects of different tree ages of Japanese larches are investigated on the biomass production, chemical compositions, fiber morphology, and pulping properties. The objectives are to determine the proper rotation of Japanese larches as pulpwoods, and to establish a method as well to evaluate the pulp and paper properties by measuring the chemical components and fiber morphology of Japanese larches. The results show that the growth rate, fiber length and fiber coarseness of Japanese larch increase as the tree age increases from 12 years to 29 years. Their increments are relatively quick for the larches with tree ages from 12 to 21 years; while they are relatively slow for the larches with tree ages from 21 to 29 years. The 1% NaOH extractive content decreases first, then increases with the increase of tree ages; it is the lowest when the tree age is about 20 years. The pulp yield increases first, then decreases a little; while the kappa number decreases first, then increases a little. As the tree age increases, the density and the tensile strength of handsheets made of larch kraft pulp decrease; however, the tearing strength increases obviously. Therefore, the suitable rotation for the pulpwoods of Japanese larch is 15-20 years. There is a negative correlation between the 1% NaOH extractive content and the pulp yield. The fiber length and fiber coarseness are inversely proportional to the density and tensile strength of handsheets, however directly proportional to the tearing strength. It is possible to forecast the pulp yield and physical properties according to the measurements of the 1% NaOH extractive content and fiber morphology of Japanese larch raw material.