Effect of ionic form on fibrillation and the development of the fibre network strength during the refining of the kraft pulps

Authors*: M arie Bäckström
Sergio Bolivar
Jouni Paltakari

The refining of unbleached kraft pulps in their Na+-form has shown
energy saving potential. In this study, the fibre network strength of
unrefined and laboratory refined samples of an unbleached neverdried
kraft pulp in different ionic forms was studied. The external
fibrillation and the fibre flexibility were also studied. The objective
was to investigate whether the improved refinability of fibres in
the Na+-form could be related to the floc network strength or to
fibrillation characteristics.

The results showed that the rheological properties may not
explain the improved refinability of fibres in the Na+-form, since
fibres showed similar rheological properties regardless of their
ionic form. Measurements using the MMS (Pulp Measuring System)
showed that fibres refined in the Na+-form have a larger amount
of external fibrillation, and microscopic investigation confirmed that
the characteristics of the fibrils are different for fibres refined in the
Na+-form from those of fibres refined in the H+- or Ca2+-forms. The
observed differences in fibrillation and improved refinability may
be explained by the co-operation of electrostatic interactions of the
fibre wall and the mechanical forces applied during refining.

References

O PAPEL vol. 73, num. 7, pp. 57 - 65 JUL 2012

*Authors’ references:
1. INNVENTIA, Box 5604, SE-114 86 Stockholm, Sweden – E-mail: marie.backstrom@innventia.com
2. UPM, Porkkalankatu 20 B, FI-00180 Helsinki, Finland - E-mail: sergio.bolivar@upm.com
3. Aalto University, Department of Forest Products Technology, Box 16300, FI-00076 Aalto, Finland –E-mail: jouni.paltakari@aalto.fi
Corresponding author: Marie Bäckström – E-mail: marie.backstrom@innventia.com