Eighty-seven percent of this pulp is produced with the kraft process, using sodium hydroxide and sodium sulfide to produce unbleached pulp, which is bleached with chlorine and chlorine dioxide. Only alkaline pulping with sodium hydroxide is a potential pulping process for hemp woody core, and a basis for alkaline-oxygen and alkaline peroxide processes. I found that strong and smooth paper can be produced from hemp woody core, as treated with sodium hydroxide. It seemed sensible to study further the kinetics and mechanisms of alkaline pulping of hemp woody core, to support the development and optimization of alkaline pulp production for printing and writing grades. I modeled degradation kinetics in relation to literature data on lignin and carbohydrate degradation.
Sodium hydroxide promotes swelling and expansion of hemicellulose.
This suppresses cross-fibre fragmentation during mechanical treatment and promotes fibrillation and formation of interfibre bonding during paper making, resulting in better mechanical properties of the paper. This facilitates disintegration of wood in fibrous components and eliminates the colouring substances. For my experiments I used a 80 ml flow-through reactor, which was designed at the university, in which woody core chips can be heated up from room temperature to reaction temperature within 6 minutes. The concentration of NaOH appeared to be of major importance. As elaboration of the modeling procedure and reaction kinetics is beyond the scope of this article, I refer to our articles in Holzforschung.