Combined effect of sodium carboxymethyl cellulose, cellulose nanofibers and drainage aids in recycled paper production process.

The present work shows the suitability of using recovered cardboard boxes for the development of high-performance papers through the use of cellulose nanofibers (CNF) and sodium carboxymethyl cellulose (CMC-Na). CNF were prepared by enzymatic hydrolysis using bleached kraft hardwood pulp, while a commercial grade of CMC-Na was used. Both were added in bulk together with polyethylenimine (PEI) as wet-end additive to improve pulp drainability. The combination of 3 wt% CNF and 7.5 wt% CMC-Na double the breaking length of paper. In addition, the use of 0.4 wt% of PEI significantly decreased the Schopper - Riegler degree, while mechanical properties remained almost at the same level. It was found that it is possible to recover and even increase the properties of recycled papers, with the added advantage that no structural damages were caused on the fibres, increasing the life span and recyclability of paper products.