Abstract
To determine the factor, on which the dissolution of hemicellulose at the steeping process depends, molecular weight distribution and chemical composition of dissolved hemicellulose (acidprecipitable cellulose) were studied.
The results are as follows:
(1) Dissolution of hemicellulose depends chiefly on the swelling degree of the pulp in the case of sheet, and on the molecular weight of the hemicellulose in the case of slurry steeping.
(2) As mannan and xylan dissolves preferentially in steeping lye, the chemical composition of pulp also affects on dissolution of hemicellulose.
(3) The solubility of hemicellulose shows a minimum with steeping temparature but various pulps show different curves. The solubility of hemicellulose decreases over the whole molecular weight range similarly, and the solubility of mannan and xylan also decreases at minimum.
(4) The solubility of hemicellulose decreasses with increase in concentration of hemicellulose and alkali (from 18% to 20%) of steeping liquor over the whole molecular weight range.
