Sesbania Bispinosa - A New Source of Raw Material for High Yield Pulping, 1997 Pulping Conference Proceedings

Sesbania bispinosa, syn. Sesbania aculeata, is a semi-annual leguminous plant, widely utilized for hundreds of years by farmers in South East Asia as green manure in its immature form and as a fuel when mature. The plant grows in many tropical and subtropical regions of the world. Until recently, its potential as a fibre raw material resource for pulp production has been neglected and this paper is an attempt to shed some light on the potential of this fibre resource as a raw material for high yield pulping.

Sesbania bispinosa, syn. Sesbania aculeata, is a semi-annual leguminous plant, widely utilized for hundreds of years by farmers in South East Asia as green manure in its immature form and as a fuel when mature. The plant grows in many tropical and subtropical regions of the world. Until recently, its potential as a fibre raw material resource for pulp production has been neglected and this paper is an attempt to shed some light on the potential of this fibre resource as a raw material for high yield pulping.

High yield pulping trials have been carried out to determine the response of this raw material to sodium hydroxide and sodium sulphite impregnation followed by a two stage refining treatment with interstage washing. Three different levels of sodium hydroxide were applied in the impregnator to produce a series of unbleached pulps covering the freeness range 60 - 250 ml.CSF to assess their potential for use in newsprint and board grade applications. Peroxide bleaching was also carried out on one of the pulps from each set of refining trials, not only to determine the bleaching response but also to determine whether the density and strength gains achieved during the bleaching operation would be adequate to permit the bleached pulp to be used in printing and writing grades.

The results were encouraging and indicated that with the exception of tear strength, which was low due to the short fibre length of the raw material, the physical property profiles of the unbleached pulps were comparable with the quality characteristics of high yield pulps produced from wood species such as Aspen and Eucalyptus. The unbleached pulps also responded well to peroxide bleaching, bleached brightness levels in the range 75-80% ISO brightness being achieved at reasonable peroxide consumption levels. As in the case of most common hardwood species, the peroxide bleached pulps exhibited significantly improved density and bonding properties compared to the unbleached pulps, due to the effect of caustic swelling during peroxide bleaching. These improvements in physical properties appear to be sufficient to permit the pulps to be used in the manufacture of printing grades.