Preparation of Dissolving Pulp from Bamboo for Textile Applications. Part 2. Optimization of Pulping Conditions of Hydrolyzed Bamboo and Its Kinetics

Kraft pulping of hydrolyzed green bamboo (Dendrocalamopsis oldhami) chips was performed under various conditions to determine the effects of process variables (alkali charge, sulfidity, cooking temperature, and cooking time) on the dissolution of the lignocellulosic components, i.e. lignin, pentosans, and cellulose. Meanwhile, the kinetics of kraft delignification of hydrolyzed bamboo was investigated. The results showed that both an increase of alkali charge and sulfidity could result in a clear reduction in kappa number and yield, but the effect of alkali charge was more significant than that of sulfidity. Even though severe conditions were able to purify fiber, the cellulose degradation occurred intensively. Active alkali charge 23%, sulfidity 26%, cooking temperature 170°C, and cooking time 60 min were selected as the optimum conditions for the consideration of selective delignification. As a consequence, the properties of the pulp produced at optimum cooking conditions were determined to be: kappa number 6.3, pentosans 5.0%, α-cellulose 90.2%, and viscosity 30.3 mPa·s. The data analysis confirmed that the reaction order of delignification was approximate to 1.1, and the activity energy of the hydrolyzed bamboo was 53 kJ/mol.