Potentialities of three Acacia Nilotica subspecies and kenaf for pulping with additives [Sudan]

Like most developing countries Sudan is almost entirely dependent on imports to satisfy its needs of pulp and paper. Out of the total paper consumption only 8 is locally produced. There is a need to identify the local fibrous raw materials and examine their suitability for pilping. Therefore several prospects have been carried out to evaluate the available locally raw materials as potential sources for a pulp and paper industry to meet the increasing cultural and industrial needs and to save the expenditure of foreign currency. Acacia nilotica is a widely distributed species in Sudan and easiy to grow on large areas. It a multipurpose species and it gives tannins, gum, dyes and commercial fibres for pulp and paper. To assess the potentiality for producing pulp and paper from fibrous raw materials, three wood suspecies of Acacia nilotica, namely subspecies nilotica, tomentosa and adansonii together with two agricltural residues, namelty Hibiscus cannabinus and Helianthus annus stalks, have been studie. Evaluation of physical, anatomical features, fibers morphological indices, chemical composition, soda pulping with and without anthraquinone, beating without and with guar gum addition were carried out. The wood samples studied were of moderately high density suitable for pulping. The bark-to-wood ratio for the subspecies were in the normal range for pulp wood. The Hibiscus cannabinus stalks were of low density and of acceptable woody portion. The heat value of the three wood species indicated the suitability for their logging wastes for charcoal making and fire wood. However the kenaf stalks were of lower heat value. The effect of the chemical composition of the three wood subspecies on their heat value was clearly demonstrated. The anatomical structure study carried out on cross, radial and tangential wood sections was characteristicsfor the species. Generally no difficulties were wereexpected for chemical penetration and impregnation. The fibre dimensions were evaluated by microscopic observations and by fibre classification. The fibres of Acacia nilotica subspecies studie were short (1.01 mm for ssp nilotica, 1.31 mm for ssp tomentosa, and 1.00 mm for ssp adansonii) but in the normal range of hardwoods for commercial pulping. The medium thick walls (5.23-6.12 um) were the thinnest for subspecies nilotica and thickest for subspecies tomentosa. Hibiscus cannabinus stalks were of longer fibres (2.32-0.79 um) with thin wall (4.59-4.33 um) like softwoods. The morphological indices for the A.nilotica subspecies are in the range of 40-46 for flexibility and 57-64 for felting power, and are comparable with those of the temperate hardwoods currently used in commercial pulping. The kenaf was with different morphological indices reflected later in its higher strength properties. The chemical composition of the two subspecies tomentosa and adansonii wasmore or less similar and thus they were somewhat different from the other subspecies, but all of them were typical for tropical hardwoods. The good cellulose content of the three wood subspecies predicated good pulp yields. On the other hand Hibiscus cannabinus was of different chemical composition with high ash and silica as expected for agricultural residues. Its high cellulose and low lignin content were favourable for easy pulping to high pulp yields. The overall chemical composition of the wood subspecies indicate the suitability of the alkaline methods for pulping with reasonable alkali charges and predicted good to very good yield. The subspecies were pulped easily with alkali charge of 15.5-17.4 as Na2O at 90-120 minutes cooking time at maximum temperature of 170 C to bleachable Kappa values. Addition of 0.1 anthraquinone reduced the active alkali of A.nilotica ssp by 2.1 to 3.25, highest for ssp nilotica and lowest for ssp adansonii. In the case of kenaf stalks the active alkali charges where higher than for wood subspecies in soda cooks (18) and lower than then in soda-AQ cooks (14 Na2O). The anthraquinone addition reduced the active alkali charges by 4 and increased the pulp yield by 4.78 and the bonding strength properties of the pulps were considerably improved. Guar gum (0.5 on oven-dry pulp) was added after beating of soda-AQ pupls and its effect was increased interfiber bonding reflected in improved bonding properties. Papermaking properties of the various wood pulps indicated suitability for products not requiring strength as well as for fine paper, such as printing and writing, where as high as 80 of the fibres can be used. The pulping of kenaf indicated its excellent properties as pulp raw material and its suitability for substituting woody long fibrous materials. Its addition to sunflower pulp gave much improved strength properties compared to sunflower alone, especially in a mixture of 50 to 50