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On the chemical processes occurring during thermal yellowing of a TCF-bleached birch kraft pulp
KTH, Superseded Departments, Pulp and Paper Technology.
2002 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 17, no 4, 427-433 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this investigation was to survey the reactions taking place during heat-induced yellowing of a TCF-bleached birch kraft pulp bleached according to the sequence O Q P Q (PO). This was done by determining the metal profiles in pulp and aqueous pulp extracts before and after accelerated ageing of pulp. It was concluded that low-molecular substances were formed during heat treatment of the pulp. It was further shown that hexenuronic acid (HexA) groups were hydrolysed during the ageing and that the destruction of HexA significantly lowered the chelating properties of the pulp, implying a liberation of metal ions. Two different procedures to isolate the coloured compounds in an aqueous extract of aged pulp are reported. Analysis of the separated strongly coloured material revealed that manganese and iron as well as some dicarboxylic acids were enriched. It was also concluded that if iron ions were removed without hydrolysing HexA, the brightness stability could be improved. Finally some observations and conclusions from previous work are discussed.

Place, publisher, year, edition, pages
2002. Vol. 17, no 4, 427-433 p.
Keyword [en]
brightness reversion, dicarboxylic acids, discoloration, hexenuronic acid, metal profile, metal complexes, thermal yellowing, brightness reversion, hexenuronic acid
URN: urn:nbn:se:kth:diva-22207ISI: 000180616600012OAI: diva2:340905
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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