Project 15: Mechanical pulp
Mechanical pulp fibres have a very heterogeneous structure, and the surface
structure and composition depends on both the wood species and the processing
method adopted. The quality of mechanical pulps is determined by the inherent
properties of the pulp fibres, such as surface ultrastructure and chemical
composition, as well as physical characteristics like shape. Project 15 aims at
studying the fibre-surface structure and chemistry, fibre collapsibility, and
their subsequent effects on final paper quality.
Fig. 1. Part of a compression wood fibre selected from a Norway spruce mechanical pulp and observed using scanning electron microscopy. The white arrow indicates the abrupt transition from the outer (i.e. S1) to the middle (i.e. S2) secondary cell wall layers. The cell corners (CC) are smooth due to the presence of intercellular spaces in native compression wood (from Brändström 2004).
pectin on mechanical pulp surface.
Fig. 3. Fibre fibrillation by the initiation of splits near sites of weakness (arrows) within the cell wall of pulp fibres such as cross-field (a, b.) and bordered pits (c.).
part of the Ph.D. work, industrial practice was commenced in collaboration with
Kappa Kraftliner, Piteå where there is a considerable problem with printed top
birch kraftliner paper, which is thought to be due to wood extractives
responsible for pitch problems in the pulp and paper.
A study has been conducted on birch aimed at localizing the extractives involved in pitch deposition in the native wood raw materials and at different stages of the kraft pulping process to understand the nature and behavior of its redistribution using variety of microscopical methods (LM, FM, SEM and TEM) in combination with chemical analysis.
results have shown that the polyene antibiotic Filipin can be successfully
applied for localizing sterols in both wood raw materials and the pulps at
different stages during the pulping process as well to understand the
redistribution of wood extractives. Other major birch wood extractive
constituents, i.e. fats (neutral fats and fatty acids) that are also thought to
be substantially responsible for the above problem, were successfully localized
and their redistribution studied during different stages of the pulping process
using both osmium tetroxide and Nile blue histochemical staining techniques.
group: Dinesh Fernando (Ph.D
student), Jonas Brändström (project leader), Jonas Hafrén (project leader),
Geoffrey Daniel (project leader), Hans Höglund (scientific advisor), Peter
Sandström (industrial representative), Lennart salmén (STFI), Lars Ödberg
(Sveaskog), Erik Persson (Holmen) and Magnus Paulsson (Stora-Enso).
1Brändström, J. 2004. Ultrastructure of compression wood fibres in
fractions of a thermomechanical pulp. Nord. Pulp Paper Res. J., 19, 13-18
J. 2004. Microfibril angle of the
S1 cell wall layer of Norway spruce compression wood tracheids. IAWA J. In
J. and G. Daniel. 2003. Distribution of methyl-esterified galacturonan in
chemical and mechanical pulp fibers. Journal of Wood Science 49, 361-365.
J. and G. Daniel. 2003. A bioassay for methylated galacturonan on pulp-fiber
surfaces. Biotechnology Letters 25, 859-862.
J. and G. Daniel. 2004. Chemoenzymatic modifications of charge in
chemithermomechanical wood pulp (submitted to Journal of Biotechnology).
J. 2004. Antibody-based assay for galacturonan de-esterification on wood-pulp
fibers during bleaching (manuscript).
D. and G. Daniel. 2004. Micro-morphological observations on spruce TMP fibre
fractions with emphasis on fibre cell wall fibrillation and splitting.
Nord. Pulp Paper Res. J. (In