JAPAN TAPPI JOURNAL
Online ISSN : 1881-1000
Print ISSN : 0022-815X
ISSN-L : 0022-815X
Research Report (Original Paper)
Preparation of Dissolving Pulp by Totally Chlorine-free Bleaching:Roles of Hardwood Syringyl and Guaiacyl Lignins
Ayyoub SalaghiAgusta Samodra PutraRoni MaryanaMikio KajiyamaHiroshi Ohi
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2018 Volume 72 Issue 10 Pages 1167-1175

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Abstract

Dissolving pulp was produced from four diff erent hardwoods by prehydrolysis-kraft cooking and totally chlorine-free (TCF) bleaching using oxygen (O),peroxymonosulfuric acid (Psa),and alkali extraction with hydrogen peroxide (Ep) in an O-Psa-Ep-Psa-Ep sequence. The hardwood lignin structures were characterized by the nitrobenzene oxidation method, which provided syringaldehyde (Sa) to vanillin (Va) molar ratios (S/V ratios) of the lignin. Eucalyptus globulus wood had the highest S/V ratio of 5.81 and a combined yield of Sa and Va of 3.04 mmol/g-lignin, while the Acacia hybrid wood exhibited the lowest S/V ratio and the combined yield. The E. globulus wood provided a fi nal pulp with an acceptable level of viscosity 7.0 mPa·s, a weight-average molecular weight (Mw) 3.04 × 105 g/mol, a number-average molecular weight (Mn) 5.56 × 104 g/mol, polydispersity (Mw/Mn) 5.47, a high brightness of 90.1% ISO, and an α-cellulose content of 94.2%. It is attributed to the high S/V ratio and the high combined Sa and Va yield, which is suggestive of a less-condensed lignin structure compared to the other hardwoods tested. No signifi cant diff erences in the cellulose crystallinities of the bleached pulp produced from the four hardwoods were observed.

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© 2018 Japan Technical Association of the Pulp and Paper lndustry
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