Lignocellulosic Nanofibers (LCNF) combined with Polyelectrolyte Complexes (PECs) as a Strength Additive for Packaging Papers.

CARLA N. SCHNELL; MARÍA V. GALVÁN; PAULINA MOCCHIUTTI; JOAQUÍN TARRES; MARC DELGADO-AGUILAR; MIGUEL A. ZANUTTINI

Montevideo

Workshop; Workshop on Insights and Strategies Towards a Bio-based Economy (I&S).; 2016

Facultad de Química. Universidad de la República. Uruguay

The use of synthetic polyelectrolyte complexes (PECs) was evaluated as a retention aid for the application of lignocellulosic nanofibers (LCNF) in the production of packaging papers. The cationic complexes of (poly(allylamine hydrochloride - PAH)/(polyacrylic acid - PAA) are strongly adsorbed on cellulosic surfaces and are useful to increase papermaking strength properties. These complexes, with 50% of free charge, were formed by adding solution of the anionic polyelectrolyte (PAA) on a solution of the cationic polyelectrolyte (PAH). A controlled addition rate of PAA solution onto PAH solution under continuous stirring (300 rpm) at ionic strength of 0.01N NaCl and pH 7.5 was applied for complex formation. Mechanical LCNF were obtained from unbleached softwood pulp (Kappa N° 25) using a pressure homogenizer. LCNF were observed by Atomic Force Microscopy (AFM) and with Scanning Electron Microscopy (SEM). The addition of 0.3; 0.5; 0.75 and 1.0% of PECs and 3% of LCNF on a lignified recycling pulp, were considered. Britt Dynamic Drainage Jar (BDDJ) was used to evaluate the total retention of LCNF and fines. The colloidal titration ratio method (CTR) was employed to determinate the total colloidal charge of materials. The results show a maximum retention when 0.75% of PEC was added on LCNF-fibre suspension. In concordance, under these conditions log CTR showed a null value, indicating that this level correspond to an optimum balance between negative and positive colloidal materials. The best drainability result (18°SR) was obtained for the same dosage of PECs (0.75% on pulp). The evaluation of handsheets showed that, in comparison to the reference pulp, all the additions led to an increase in mechanical properties. Using LCNF, the higher increase in tensile strength (+48%) was obtained for a PEC dosage of 0.75%. For this level of addition, a remarkable increase in compressive strength CMT (+72%) was achieved. The presence of LCNF in lyophilized handsheets samples were observed by Scanning Electron Microscopy (SEM). Results indicate that these PECs are a possible alternative to assist the application of mechanical nanocelluloses in papermaking.