Extended Delignification of Southern Pine with Polysulfide and Anthraquinone, 1993 Pulping Conference Proceedings

Extended modified cooking of southern pine with polysulfide (PS) and anthraquinone (AQ) to a Kappa number as low as eight was conducted in the laboratory. The effects of addition of AQ and PS on pulp yield and strength properties were investigated.

In the range of Kappa numbers studied, addition of 0.1% AQ resulted in a marginal (<= 0.5%)="" increase="" in="" pulp="" yield.="" charging="" 2%="" ps="" to="" extended="" modified="" cooking="" was="" found="" to="" increase="" pulp="" yield="" by="" about="" 1.5%="" on="" wood.="" a="" 3%="" ps="" charge="" increased="" the="" screened="" pulp="" yield="" by="" about="" 3%,="" from="" about="" 42%="" to="" 45%="" (on="" wood)="" at="" kappa="" 12.="" applying="" both="" 0.1%="" aq="" and="" 2%="" ps="" resulted="" in="" a="" yield="" increase="" of="" about="" 2.5%,="" considerably="" higher="" than="" additive.="">

Addition of AQ to extended modified cooking appeared to decrease the pulp tear strength. At the presence of PS, no detrimental effect on tear was found. Up to 3% addition of polysulfide showed no significant effect on pulp tear strength in cooking to a Kappa number as low as 12.

This study shows that tear strength improvement from extended modified cooking and yield improvement from PS or AQ+PS pulping can be achieved simultaneously in such a combined pulping process.