Application of Advanced Wet-End System Using Carboxymethyl Cellulose to Mixed Pulp Slurries for Wood-Containing Paper Production

A pulp modification technique using carboxymethyl cellulose (CMC) at the wet end was applied to mixed pulp slurries containing softwood bleached kraft pulp (SBKP), deinked pulp (DIP), and hydrogen peroxide-bleached thermomechanical pulp (TMP). Introduction of anionic sites by adsorption of the added CMC molecules on the fibers was confirmed by an increase in negative charge of the mixed pulp fibers. Sizing degree of the handsheets prepared with 2% aluminum sulfate and 0.2% rosin dispersion size was clearly improved by 0.1% CMC addition. On the other hand, we observed no significant differences in rosin size content between the handsheets prepared with and without CMC. These results indicate that some mechanisms other than enhancement of rosin size retention may have brought about the clear improvement of sizing performance by the CMC addition. Changes in distribution of rosin size components or some structural changes of rosin size components in the handsheets by the CMC addition may be candidates for sizing development. The CMC addition technique at the wet end is, therefore, also applicable to mixed pulps containing DIP and TMP.