Title
Soda pulp cooked from rapeseed straw
Authors
FRANTISEK POTUCEK and MARTINA RIHOVA

Published Volume 50 Issue 5-6 May-June
Keywords rapeseed straw, soda-anthraquinone pulping, degree of polymerisation, colour properties, tensile strength

Abstract
The paper deals with batch soda cooking of pulp from rapeseed straw. Preliminary runs were focused on determining the effect of active alkali charge and liquor-to-straw ratio upon the delignification degree of pulp. Then, further investigation was carried out under the established optimum cooking parameters, viz. active alkali charge of 19%, liquor-to-straw ratio of 5:1 and anthraquinone charge of 0.1%, to determine the effect of the delignification degree, which is directly proportional to the H-factor, upon the total yield, kappa number and amount of rejects in the H-factor interval from 800 to 2,800 h. For soda-AQ cooks of straw, stalks and silique valves, the total pulp yield, kappa number and amount of rejects decreased with an increasing H-factor. The highest total yield and degree of delignification were found for soda-AQ pulp cooked from stalks only. On the contrary, the silique valves gave the lowest total yield. The degree of polymerisation of the pulp cooked from straw, stalks and silique valves increased with an increasing H-factor, the greatest values being measured for the pulp from stalks. The colour properties of the pulps from straw and stalks, including brightness, which ranged between 30 and 34, were found not to differ significantly between the pulps. However, the tensile strength of the handsheets made from once dried and repulped pulp was found to be markedly lower in comparison with that of never dried pulp.