Effects of kappa number variability on pulp properties

Documented pulp uniformity issues are available for the pulp and paper industry, but no clear understanding exists for the effect of nonuniformity on pulp properties. The project examines effects of nonuniformity by comparing pulp with variable kappa number distributions for bleachability and mechanical properties. Two mixtures with different kappa number distributions were compared with a uniform control pulp with the same average kappa number with analysis for brownstock strength and fiber morphology. The pulps were also bleached using ECF and TCF bleaching sequences. The pulps in this study did not show significant differences in strength or bleachability compared with the control pulp. Some limited differences existed in brownstock strength. The laboratory pulping and bleaching conditions were too mild to produce the negative effects that traditionally affect fiber strength. The pulps in this study therefore showed limited differences compared with the control pulp. Intrinsic fiber strength was maintained. Even with kappa number variability, all the pulps behaved similarly. Application : no differences in brownstock strength or bleach ability for the mixtures tested occurred when mechanical factors in a pulp are minimized. Lignin content alone does not have a negative impact on fiber performance.