The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of lowgrammage handsheets

Abstract

ABSTRACT:The effect of increasing the pulp yield by the addition of sodium borohydride (NaBH 4 ) or polysulfide (PS) in softwood kraft cooking, i.e. enhancing the retention of glucomannan, on the physical properties of low-grammage handsheets was studied. In addition to the yield improvement, an increase in tensile index was observed, especially at lower degrees of beating. These higher yield pulps showed an increase in pore volume, indicating an increased degree of swelling of the fibres. Presumably, the increased flexibility of the fibres affects the bonding strength and leads to the higher tensile index observed.

Evaluation of Kraft-PS Cooking for Eucalypt and Pine Wood Chip Mixtures

“…This result may be explained by the higher hemicelluloses contents of the pulps derived from kraft-PS cooking. Our results corroborated with those from Rahman et al, [10] which observed an increasing in tensile index for spruce pulp due to the use of PS as additive in kraft cooking, especially at lower refining degrees. It is worth noting that the well-known correlation between tensile and burst strength did not hold true when the proportion of pine fibers in the furnish increased.…”

“…[13,34] Nevertheless, there are also chemical aspects of carbohydrate preservation by PS, especially hemicelluloses, which need to be considered. [8][9][10] The results in Table 2 shows that there is, in general, a greater preservation of the hemicelluloses in the pulps for the PS assisted cooking, although this trend is not so clear when the charge of PS is increased from 1.5 to 3.0%. The PS brought more significant benefits for the wood chip mixture containing larger proportion of pine chips, which is explained by the PS protection of the mannans, which are labile during kraft pulping and exist in larger quantities in the softwoods.…”

“…In the early 1970, a class of additives called polysulfides (PS) were introduced and have been widely studied ever since. [2][3][4][5][6][7][8][9][10] In fact, there are a reasonable number of pulp mills worldwide currently using PS as additives to their cooking processes. The PS action in kraft cooking is well-documented and their positive effect on yield is largely attributable to minimization of the endwise depolymerization reaction that occurs on cellulose and hemicellulose polymer chains.…”

“…The PS action in kraft cooking is well-documented and their positive effect on yield is largely attributable to minimization of the endwise depolymerization reaction that occurs on cellulose and hemicellulose polymer chains. [8][9][10] By oxidizing the reducing end group on these polymer chains, to stable carboxylic acid groups (aldonic acids), the PS minimize pulp yield losses during kraft cooking. [2,11] The increase in yield caused by PS is affected by its concentration in the impregnation and cooking liquors and the pulping process conditions, [12] and it results from minimized peeling reaction of polysaccharides.…”

On-Site X-ray Fluorescence Spectrometry Measurement Strategy for Assessing the Sulfonation to Improve Chemimechanical Pulping Processes

“…An unbeaten low grammage handsheet of 20 gm/m 2 was measured for single line scanning in this setup. The low grammage handsheet 20 gm/m 2 was prepared by mixing CTMP and BSWK at different percentages according to the ISO 5269-2:2004 standard with tap water using a conventional sheet former with a surface area of 0.021 m 2 at the SCA R&D Centre in Sundsvall, Sweden . For the study of sulfonation degree, four different proportions as 100% CTMP, 50% CTMP + 50% BSWK, 30% CTMP + 70% BSWK, and 20% CTMP + 80% BSWK were used.…”