Processing of Kenaf Bast and Core TCF Pulp for Paper Making Applications, 1997 Pulping Conference Proceedings

In recent years, the North American pulp and paper industry has focused its attentions towards the utilization of alternative, non-wood fiber sources. The impetus behind such efforts is largely due to two factors. First, there is an ever-growing concern in North America regarding environmental preservation and the conservation of North American forestlands. Secondly, the presence of an emerging foreign competition, stemming from the rapid expansion of fiber supplies on such continents as Asia and South America, has placed a strain on North America’s once dominant position. In order to remain competitive, North American manufactures have aggressively sought out fast growing non-wood fiber sources that could be grown domestically and used to produce various grades of quality paper. In this vane, the tropical plant Kenaf has been studied as a possible non-wood fiber source and its viability as a quality fiber source has proved promising. Presently, three pulping methods have proven suitable for cooking Kenaf fibers: Kraft, Soda-AQ, and low temperature Soda-AQ processes. The focus of this study involved the cooking of Kenaf core and bast fibers along with softwood and hardwood fibers utilizing a Soda-AQ process. The cooked fibers were then subjected to an OQPQP bleaching sequence. After bleaching, the four fiber types were blended in 50:50 ratios in order to assess the strength characteristics of sheets produced from core and bast and hardwood / softwood blends. Burst index, tensile strength and tear strength tests were performed. In addition, viscosity and brightness tests were performed in order to determine the suitability of Kenaf to be used as a non-wood fiber source in conjunction with or in lieu of softwood and hardwood fibers. The bleached fibers yielded promising results. Initial viscosity values for the cooked pulp of 23.74 cp for the core fibers and 35.08 cp for the bast fibers decreased to 7.96 cp and 8.39 cp for the core and bast, respectively, after bleaching. This is in comparison to initial viscosity values of 10.27 cp and 19.31 cp for the hardwood and softwood fibers, respectively, decreasing to 5.76 cp and 3.72 cp. These values demonstrate that bleached Kenaf retains sufficient strength for subsequent papermaking applications that is comparable to softwood and hardwood fibers. In complement to promising final viscosity values, the bleached Kenaf also exhibited a considerable increase in brightness. The core and bast fibers yielded final brightness values of 87.03 ISO and 84.16 ISO, respectively, in comparison to initial brightness values of 26.04 ISO and 28.68 ISO as seen with the unbleached pulp. These values compare favorably with hardwood and softwood initial brightness values of 25.06 ISO and 33.55, respectively, increasing to post bleaching brightness levels of 86.53 ISO and 84.15 ISO, for the hardwood and softwood fibers, respectively. From these results, it can be concluded that bast fibers exhibit a superior level of brightness and superior viscosity in comparison to core fibers when subjected to the same chemical treatments. It is also supported that Kenaf can be used to produce paper products from an environmentally friendly soda AQ pulping process. Since it possesses viscosity and brightness values comparable to bleached softwoods and hardwoods, Kenaf can be used as a viable non-wood alternative fiber source. Finally, based on strength testing results, it can be inferred that bast fibers are best suited for blending with softwood fibers and that core fibers are best suited for blending with hardwood fibers.