Adsorption of cationic starch on typical furnishes used in the Portuguese paper industry

摘要

This paper deals with the adsorption behaviour of cationic starch (CS) onto the surface of fibres from bleached kraft pulps of Eucalyptus globulus and Pinus sylvestris, a mixture of both species (85% E. globulus and 15% P. sylvestris) and unbleached P. pinaster kraft pulp. Three cationic starches (CSs) with three degrees of substitution (DSs), namely 0.017, 0.034 and 0.06, were investigated. The retention of CS as a function of the addition level was studied and it was shown that the maximum retention values of CS were 30 mg/g o.d. pulp for bleached pulps from E. globulus and P. sylvestris as well as for the mixed species furnish, and 40 mg/g o.d. pulp for unbleached P. pinaster kraft pulp. The influence of suspension electrical conductivity on the adsorption of CS was also investigated and it was shown that for all starches the adsorption decreased drastically when the electrical conductivity reached a range of 3 to 4 mS/cm: the retention of CS for the four furnishes studied decreased from 95% to 20%.