Controlled retention and drainage of microfibrillated cellulose in continuous paper production

In the current study an attempt has been made to scale up the microfibrillated cellulose (MFC) reinforced paper using pilot scale Experimental Paper Machine (XPM) in continuous mode. Complete retention of MFC (≈2 nm - 10 µm in diameter) on XPM (using 150 wire mesh, 100 µm pour size) was not possible. Consequently, a “mix/hybrid” approach was followed using pulp fibers (≈25 µm diameter) as supportive phase. Produced dense network (≈ 3 µm pour size) of long pine fibers on wire mesh (100 µm pour size) might be responsible for holding of MFC by introducing hydrogen bonds in continuous production of paper on XPM. Thereafter, increase in MFC retention was further observed using additives (cationic starch and anionic silica microparticles) and maximum 23.4 wt% of MFC in final paper was calculated. Highest retention (73%), adequate water drainage time (< 1 min) and improved formation was recorded using mixture of 65 wt% long pine fibers, 35 wt% MFC, 1.2 wt% cationic starch and 0.3 wt% silica microparticles at the machine speed of 1.4 m/min. Produced paper showed aligned fibers towards machine direction (supported by SEM images and tensile strength). Furthermore, compacted micro/nano morphology after addition of MFC and decrease in average pore size was recorded after addition of additives. The 11% and 17% increase in density was recorded after introduction of MFC and additives, respectively. Improved tensile strength of paper (≈3 fold) compared to reference paper was recorded. The β-radiogram analysis confirms improved formation in paper after addition of MFC and additives. Therefore, machine trials confirm the possibility to produce MFC reinforced paper in tons using roll-to-roll approach in continuous mode with high retention of MFC and improved properties.