Structural changes of amorphous cellulose by alkaline pulping treatments

Structural changes of cellulose molecules in amorphous region in wood during alkaline pulping treatments were studied by using new amorphous cellulose samples. Changes in yields, molecular mass, and X-ray diffraction patterns of samples during alkaline, alkalineanthraquinone, and kraft pulping treatments were examined. Decrease in yields of treated samples was remarkable within the initial 30 min of pulping treatments. This phenomenon can be explained in terms of crystallization and solubilization of hydrolyzed cellulose molecules in alkaline solutions. Cellulose molecules in amorphous samples were primarily crystallized to cellulose IV with depolymerization under alkaline conditions at 170°C. Temperature of the cooking liquor had a greater influence on crystallization of amorphous cellulose samples than alkalinity and additives. Thus, alkaline pulps such as kraft pulp probably have mixed crystal structure, cellulose I and IV. The former is originally present in wood state, and the latter is formed from cellulose molecules in amorphous region during pulping treatments.