THE EFFECT OF COOKING TO DIFFERENT KAPPA NUMBERS ON REFINING AND PAPER SHEET PROPERTIES

摘要

This study examines the fibre properties induced by cooking to different kappa numbers (~10, 20 and 26), cooking procedures, ECF bleaching and refining of bamboo pulps in relation to the properties of the resulting paper sheet. Two different cooking methods were applied: a high temperature with a short cooking time and a low temperature with a prolonged cooking time. The unbleached pulps, with kappa numbers 20 and 26, required less energy to reach a certain Schopper Riegler value, and exhibited much higher strength properties (tensile index, burst and tear at a given SR value), than the low kappa number pulp (~10). Cooking to a high kappa number also gave paper sheets with a density that was between 10 and 15% lower at a given tensile index. No major differences in the final properties of the paper could be ascertained between the two cooking procedures. The response of the bleached pulps to refining was similar to that of the unbleached pulps. Although the high kappa number pulps had been subjected to more extensive bleaching to reach the same brightness as the pulps with low kappa number, they still required less energy to reach a certain SR value and had greater strength properties. A main conclusion reached was that the properties of the bleached pulps were dependent on the initial fibre properties of the unbleached fibres. Thus, the cooking conditions, washing and handling of the pulp is of the utmost importance for producing pulps of high quality. This investigation may help mills to find the optimum link between cooking and bleaching when bamboo is used as the raw material.