Forming and Dewatering of a Microfibrillated Cellulose Composite Paper

Abstract

An approach is demonstrated for the manufacturing of a microfibrillated cellulose (MFC) composite paper. A key element in the manufacturing paradigm is the use of high consistency suspensions to improve retention and minimize the need for water removal after forming. The rheological characterization of the composite furnish, which contained 70% structured pigment, 20% MFC, and 10% pulp fibers, revealed a gel-like shear thinning behavior of the suspension, which differs greatly from traditional fiber-based papermaking furnishes. The results from laboratory and pilot scale studies show that the headbox consistency range from 5 to 10% offers the best combination of processing, forming characteristics, retention, and dewatering. While the furnish dewatering in laboratory scale was very problematic, under suitable dynamic conditions the wire section dewatering was excellent. The results of this study suggest that the MFC composite can be manufactured on a modified paper machine and that the final product will have an attractive cost structure.

Gel structure phase behavior in micro nanofibrillated cellulose containing in situ precipitated calcium carbonate

“…The high level of filler, unusual for paper and board manufacture, is to represent the target of a filler–fiber composite material, which is considered as a realistic sustainable natural polymer composite replacement . The sample labels follow the notation: consistency/MFC grade/ratio of total pigment precipitated on MFC.…”

“…The network level swelling of MFC and NFC was evaluated with a water retention value test (WRV, ISO/DIS 23714). The WRV test was slightly modified to suit the measurement of the nanocellulosic materials . This was done by mixing quantities of the nanocellulose in the range 0–6% with an unrefined Kraft pulp and then centrifuging the mixture under normal WRV test conditions.…”

“…3ITT measurement can be expected to provide information on the dynamic elastic structure recovery of MFC containing furnish after high shear deformation, say, in a head box and/or during fluidization. It is desirable that the initially high dynamic viscosity of MFC can be reduced at the head box slit and during application on a wire, in order to be in a reduced viscosity “flowing state” for application, and then to recover when forming the fiber mat . Initially, in the first low shear interval, samples were subjected to low shear rate (0.1 s −1 ), then subsequently high shear rate (500 s −1 ) and finally once again low shear rate “recovery” (0.1 s −1 ).…”

“…Initially, in the first low shear interval, samples were subjected to low shear rate (0.1 s −1 ), then subsequently high shear rate (500 s −1 ) and finally once again low shear rate “recovery” (0.1 s −1 ). Structure recovery was traced with respect to recovery of dynamic transient viscosity (η + ) in the third interval, expressed as percentage (%) of ratio η + /η 0 after 300 s of measurements, where η 0 is the low shear viscosity value at the beginning of the first interval …”

“…In this research we contribute further to the rheological evaluation of different grades of MNFC, obtained with enzymatic pretreatment of pulp, by controlling the level of postfluidizing . This enzymatically pretreated MFC is studied as an additive in high consistency high filler load furnish . Of novel importance in this work is the as yet not studied effect on rheology and dewatering of the inclusion of in situ calcium carbonate precipitation onto MFC ( in situ PCC‐MFC costructure) when added to fiber furnish .…”