A1 Journal article (refereed), original research

Fractionation of pulp and precipitated CaCO3–pulp composites: effects on sheet properties of selective CaCO3 precipitation onto fiber size fractions

Open Access hybrid publication

Publication Details
Authors: Laukala Teija, Backfolk Kaj, Heiskanen Isto
Publisher: Springer Verlag (Germany)
Publication year: 2021
Language: English
Related journal or series: Cellulose
Volume number: 28
Issue number: 9
Start page: 5807
End page: 5826
Number of pages: 20
ISSN: 0969-0239
JUFO level of this publication: 2
Open Access: Open Access hybrid publication


CaCO3-pulp composite was prepared via precipitation of calcium hydroxide in
the presence of pulp. In order to investigate the precipitation selectivity and
mechanism, the substrate pulps and the obtained composites were fractionated
(R30, R100, R200, R400 and a sedimented fraction that passed the 400 mesh wire)
using a Bauer-McNett unit. The main fractionation criterion was therefore fiber
length. The pulp used was CTMP (chemithermomechanical pulp), yielding a precipitated
calcium carbonate-chemithermomechanical pulp (PCC-CTMP) composite with a targeted
PCC-to-CTMP ratio of 1:1. The PCC consisted primarily of nano-sized primary
particles which formed aggregates and clusters on the fibers. When the fiber
morphology, zeta potential and surface charge density of the fractions were
determined, a correlation was found between the surface charge density of the CTMP
and the ash content of the corresponding PCCCTMP fractions. This supports the
hypothesis that the precipitation on the CTMP fiber is driven by the charge
interparticle interaction. The use of refined CTMP furnishes and fractionation
of the PCC-CTMP furnishes demonstrates that PCC is preferably fixed on fines
and fibrils since it appears at a higher content in the fines fractions. Fiber
activation via fiber split, removal of primary wall and surface defibrillation enhanced
the affinity of the PCC for the fibrils. The laboratory handsheets prepared
from the material demonstrated the importance of controlling the substrate fiber
properties for the mineral-fiber composite, e.g. via refining, as differences
between the refining levels and fractions were found to lead to differences in
both optical properties and bonding.

Last updated on 2021-14-06 at 15:32