Hairy cationic nanocrystalline cellulose as retention additive in recycled paper.

Hairy cellulose nanocrystalloids (HNC) are a brand new family of nanocellulose characterized by having functionalized amorphous poles joined by a crystalline shaft. In this paper we hypothesize that cationic HNC (CNCC) could be used as an effective retention agent in papermaking. To investigate this, we first flocculated a suspension of only fillers, namely kaolinite and CaCO₃, and second, a suspension of recycled fibers, with CNCC. It was monitored by photometric dispersion analysis and laser focused beam reflectance. The flocculation mechanism was assessed by means of zeta potential, reflocculation efficiency, flocculation stability and optical microscopy. Finally, the effect of CNCC on drainage, retention and paper mechanical properties was studied. CNCC were found to heteroflocculate fillers at a wide range of dosages, finding a maximum floc size at a dosage of 30 mg/g. On the other hand, the maximum floc size when flocculating the pulp suspension, was found at a lower CNCC dosage (20 mg/g). In this case, fillers were being attached to the exterior surface of the fibers. In both systems, the maximum size increment was observed at the isoelectric point, so a charge neutralization mechanism was proposed. The addition of CNCC not only improved filler retention, but also pulp drainage by reducing these times. Moreover, although mechanical properties of the handsheets were affected by the presence of CNCC, this effect was much lighter than that caused by traditionally used retention systems. Hence, CNCC could replace many additives used in the wet-end of a paper machine, thus simplifying its operation. [ABSTRACT FROM AUTHOR]