Optimising CMC sorption in order to improve tensile stiffness of hardwood pulp sheets

SUMMARY: An ECF-bleached hardwood pulp was treated with carboxymethyl cellulose (CMC) under specified conditions. This paper studies the combined effect of CMC modification, drying conditions and DDJ-fractionation of hardwood pulp on fibre and strength properties of paper. The drying effect was investigated by drying the sheets in a drum (free drying) or on a plate (restrained drying). The CMC-treatment increased markedly the tensile stiffness index of the handsheets dried under restraint. Moreover, all strength properties were significantly increased after the CMC modification. The effects of the fines were investigated in the second part by fractionating the pulp by a Super DDJ. Fines affected internal and tensile strength positively.