Natural polyelectrolyte complex as a novel retention agent for cellulose micro/nanofibers. Influence on the drainability and physical properties of recycled paper.

BASTIDA, G.A.; ZANUTTINI, M.A. ; GALVÁN, M.V.; DELGADO-AGUILAR, M.

Buenos Aires

Congreso; WCCE11 ? 11th WORLD CONGRESS OF CHEMICAL ENGINEERING.; 2023

Asociación Argentina de Ingenieros Químicos, Confederación Interameticana de Ingeniería Química, WCEC

Recycling of paper and paper related products are very important for sustainable global economic growth. Some underlying trends are creating new technical challenges for paper industry. For instance, the addition of cellulose nanofiber (CNF) is useful to improve the physical properties of recycled paper. But due to the small size of CNFs, it is a challenge to retain them in the fiber network, achieving a homogeneous distribution to maximize their action without affecting the drainage rate during papermaking process. For this, retention agents are used. The objective of this work is to analyze the use of natural hemicellulose-based polyelectrolyte complex (PEC) as retention agent of cellulose micro/nanofibrillar (CMNFs), to achieve a proper drainage and retention and simultaneously, to maximize the physical properties of the paper. For this, PECs were formed by adding a solution of xylan (Xyl) from sugar cane bagasse to a solution of commercial chitosan (Ch), considering a Xyl/Ch of 80/20 mass ratio. In addition, the production of the CMNFs was carried out from a bleached commercial pulp of eucalyptus, through a mechanical pre-treatment with a PFI mill refiner and a chemical pre-treatment with 25 wt% and 50 wt% of oxalic acid solution. Finally, mechanical fibrillation was performed with a pressurized homogenizer at different pressures. The colloidal interaction between CMNF and PEC was analyzed by means of z-potential measurements, thus determining the level of PEC addition corresponding to anionic (An), neutral (Ne) and cationic (Cat) PEC-CMNF systems. On the other hand, in a Dynamic Jar, the retention of fines of recycled pulp and CMNF was studied. Then, 3% of CMNFs and the corresponding dosage of PEC were added to recycled pulp and the drainage speed was analyzed. Finally, sheets were prepared, and the physical properties were determined. The results shows that the highest retention of CMNF and fines were achieved for the neutral PEC-CMNF system. A significant improve in drainability is observed when only PEC was added to the untreated pulp. Furthermore, as the dosage of PEC increases, the drainability increase. This improvement indicates that PEC favors filtering through the controlled flocculation of fines and fibers. On the other hand, the addition of CMNFs slightly decreased this property with respect to pulps treated only with PEC. The air permeability decreased with the increase in addition of PEC. However, when CMNFs are introduced, this property increased, especially when anionic or neutral formulation was considered. In neutral system, the Tensile Index increased (up to 28%) and excellent results were obtained in Scott Bond (up to 253%). In the compressive strength increases of 30% (SCT) and 73% (CMT) were achieved for some cases. This suggests that these systems are a promising alternative for their application in packaging paper.