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Effects of metal ions and wood pitch on retention and physical properties of TMP

Authors
  • Lu, Xiaomin1
  • Sundberg, Anna2
  • Strand, Anders3
  • Hubbe, Martin A.1
  • 1 North Carolina State University, USA , (United States)
  • 2 Åbo Akademi University, Porthaninkatu 3 , (Finland)
  • 3 Mirka Ltd, Pensalavägen 210 , (Finland)
Type
Published Article
Journal
Nordic Pulp & Paper Research Journal
Publisher
De Gruyter
Publication Date
Sep 24, 2020
Volume
35
Issue
4
Pages
649–659
Identifiers
DOI: 10.1515/npprj-2020-0036
Source
De Gruyter
Keywords
License
Yellow

Abstract

The influence of metal ions, Ca2+{\mathrm{Ca}^{2+}} and Mg2+{\mathrm{Mg}^{2+}}, on wood pitch retention at pH 8 was studied by investigating the pitch content of TMP-papers using both short- and long-column gas chromatography (GC). The effects of two different drying methods, air-drying and freeze-drying, on pitch retention were also compared in this work. The pitch emulsion was prepared with fatty acids, resin acids, and triglycerides at a certain ratio to simulate the pitch composition in closed water system in paper mill. At increasing pH, some of the resin and fatty acids will dissolve into the water phase as metal soaps. In this work, the retention of colloidal pitch in TMP-papers by metal ions at pH 8 was determined. The amount of 5 mM metal ions was found to retain more pitch. The tensile index decreased by the addition of metal ions, and the decrease became more pronounced as the increase of the metal ions concentration. Besides, the hydrophobicity of handsheets was found being changed only a little, which might because the morphology and pitch retained on the surface both affected the hydrophobicity.

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