Investigation of production of good quality paper pulp from sisal fibres

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University of Dar es Salaam
In this work, production of good quality paper pulp from sisal fibres was investigated. Sisal fibres obtained from Tanga, Arusha, and Morogoro were pulped using sodium sulfite buffered with sodium hydroxide, sodium sulfite buffered with sodium carbonate, and ethanol. Major parameters investigated are: chemical concentration, fibre to chemical ratio, ratio of Na2S03 to NaOH or Na2C03, cooking time and cooking temperature. Minor parameters investigated after obtaining suitable cooking parameters include: soaking of the fibres, presence of pulping additive and originality of the fibres. The effect of these parameters on pulp yield, Kappa number, brightness, freeness and strength properties have been reported. Sodium sulfite buffered with sodium carbonate at a ratio of 7:1 was found to be a better cooking chemical compared to sodium sulfite buffered with sodium hydroxide at the same ratio. The observed suitable pulping conditions were: Na2S03/Na2C03 at a ratio of 7:1, pH 10.20, fibre to chemical ratio: 1:6, chemical concentration: 95.0 g/1, cooking time: 6 hours at 168°C and 6% w/w MgC12 as additive. With these cooking conditions, following pulp properties have been obtained: pulp yield: 69.98 % , Kappa number : 16.44, pulp viscosity: 13.31 [mPa. s], pulp brightness: 78.4 [%ISO] and freeness: 725 [CSF]. The maximum strength indices obtained were : tensile index: 75.6 [Nm/g], burst index: b.05 [kPa.m2/g] and tear index: 19.30 [Nm2/kg]. These values were relatively higher than those reported for bleached and unbleached kraft pulp produced by Southern Paper Mills. A decrease in Kappa number to 12.64 was observed after soaking the fibres in cooking chemical for 21 days. Pulp yield slightly increased to 70.01 % and viscosity increased to 24.52 mPa.s. However, brightness reduced to 62.10% ISO. Ethanol produced dark brown pulp, which was weaker in strength compared to pulp obtained using the other two chemicals. Further studies are recommended to establish kinetics of lignin removal during sisal pulping, development of the rate equation and its temperature dependency. Also, effects of organic additives such as soluble anthraquinone (SAQ) and 1,10 phenanthraline need to be investigated. If bleaching of pulp is required, then investigation of bleaching characteristics and bleaching chemicals is very important.
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Paper industry, Paper making, Sisal hemp, Supplies, Tanzania
Ntalikwa, J W. (1994) Investigation of production of good quality paper pulp from sisal fibres, Masters’ dissertation, University of Dar es Salaam. Available at (