Physical and mechanical properties of kraft pulps with 45 and 55 kappa numbers meant for the production of sack kraft with low grammage paper

Results of the survey presented in this study aim at evaluating the feasibility of increasing from 45 to 55 the kappa number of Pinus taeda kraft pulp meant for the production of flexible packaging with low grammage paper. The yield observed for kappa number 55 increased by 1.5[%], with consequent increase in shives content, condition that could be handled in the screening process. The tear resistance did not differ between pulps kappa 45 and 55. Tensile strength and airflow through sheet values decreased with the increased kappa number, requiring a higher re(ning action to recondition these properties. The results indicate that kappa 55 pulp can be used for the production of low weight sacks paper, being suitable for the demands associated with this class of products.