Study of the dehydration and rehydration capacity of microfibrillated cellulose (MFC)

GONZÁLEZ, G.; COLMENAREZ LOZADA, O.; EHMAN, N.; FELISSIA, F.E.; AREA, M.C.; VALLEJOS, M.E.

Conferencia; XXV TECNICELPA ? International Forest, Pulp and Paper Conference and XI CIADICYP ? Iberoamerican Congress on Pulp and Paper Research; 2021

TECNICELPA

Thefibrillation process to produce microfibrillated cellulose (MFC) involves largequantities of water, and the final product has low consistency (1-2%), whichleads to problems associated to transport costs. This study analyzes the effectof reducing MFC water content using coagulation/flocculation commercialreagents and evaluates the eventual changes in MFC performance as a drystrength additive of paper and paperboard. MFC was obtained from unbleachedsoftwood kraft pulp using a disk refiner at 1% consistency during 60 min.Combinations of commercial retention reagents conventionally used in the paperindustry were mass-applied using different aggregation mechanisms(coagulation/flocculation). Then, the samples were filtered using a filtercloth. Transmittance, turbidity, and consistency after centrifugation weremeasured to compare the behavior of the suspension before and after thethickening. Optical, scanning, and transmission electron microscopy were alsoapplied. MFC was added at 3wt.% to an old corrugated container OCC pulp toproduce handsheets. Physical-mechanical properties such as permeability,tensile index (TI), elongation, tensile energy absorption (TEA), burst index(BI), and tear index were measured. Besides, the typical mechanical test ofpaperboard as ring crush test (RCT), short-span compressive test (SCT), cóncoracorrugating medium test (CMT), and Taber stiffness, were performed. Theobtained transmittance (at 800 nm) and turbidity of MFC were 33.3% and 427 NTU,respectively. A dual flocculation system combining patch and bridge modelsproduced the highest water removal (from 0.89% to 4.82% consistency, reachingup to 15.88% when filtered in fabric). Higher doses of reagents did not resultin consistency increases. The application of both initial and thickened MFCimproves paper and paperboard properties. Nevertheless, results are better inthe first case (except permeability and stiffness), demonstrating the value ofwater-MFC links on its performance as paper and paperboard reinforcement.