Effect of Alum Consumption Levels in Alum-Rosin Sizing on Multilayered Paperboard Properties

Sizing of paperboard has a distinctive position in packaging grade paperboard material. Optimization of sizing by alum-rosin at neutral pH in 4 layered paperboard (330 g/m2) wereevaluated in this study to find the optimum ratio of alum- rosin loading in the process. fixed amount of 1% cationic dispersed rosin together with alum as a fixing agent at 5 different levels of 1, 1.5, 2, 3, and 4% (based on OD weight of pulp) were used. Water absorption of top and back layers of the sized paperboard (Cobb test) and the paperboard strength and surface properties weredetermined. According to the results performance of rosin sizing system was improved by increasing the loading of alumledand led to a decrease in water absorption at top and back layers of the paperboard. Also, regarding to the unique improving features of alum in retention, bonding ability and charge neutralization of pulp ingredients, the strength properties such as ply bond, tensile and bending stiffness were improved, too. The results revealed that strength properties of cardboard are more affected by alum and rosin consumption levels than alum to rosin ratio and the best ratio of alum-rosin at the neutral pH, revealed as 2:1.