The key role of lignin in the production of low-cost lignocellulosic nanofibres for papermaking applications

Abstract

The use of cellulose nanofibres (CNF) for the enhancement of paper’s mechanical properties has beenreported by many authors. Concretely, the available literature is mainly focused on TEMPO-oxidizedcellulose nanofibres. However, recent industrial research projects, in which LEPAMAP group has beeninvolved, have demonstrated that this type of nanocellulose has unaffordable production costs for thepapermaking industry. In this sense, the present work aims to produce low-cost lignocellulosic nanofi-bres (LCNF), finding some strong alternatives to TEMPO-mediated oxidation. For that, lignocellulosicnanofibres (LCNF) were produced from stone groundwood pulp (SGW) from pine after a chemical pulp-ing process (sodium hydroxide and antraquinone). The effect of lignin content was studied and controlledthrough bleaching steps and quantified. It was found that high lignin content makes nanofibrillation dif-ficult. The reinforcing effect of CNF was mechanically characterized by the addition of 3 wt% of CNF intodifferent papermaking pulps. The results showed that it is possible to obtain low-cost LCNF that providethe same increase in mechanical properties than TEMPO-oxidized CNF when they are used for paperreinforcement. It was also found that lignin plays an important role in the obtaining of LCNF by fullymechanical treatments, where lower lignin contents expedite the nanofibrillation