THE CHANGE IN MORPHOLOGICAL AND FINE STRUCTURE OF PULP FIBERS DURING HOT ALKALINE REFINING

Abstract

In the previous paper (Japanese Tappi, 14, 745, 15, 122), the effects of temperature and concentration of the alkaline solution used in the hot alkaline refining process were discussed. In the present paper, an attempt is made to study the effect of hot alkaline refining on the morphological and fine structure of pulp fibers, and the following resulte are obtained:(1) The outer-layer of the cell wall of pulp fibers was not ruptured by the hot alkaline solution under conditions which ordinarily exist during the conventional refining.(2) Comparison of data for unbeaten and fibrillated pulp indicated that penetration of alkaline solution into the cell wall was not a controlling factor in the rate of refining.(3) Hot alkaline refinning did not affect the degree of crystallinity of the cellulose, as measured by X-ray diffraction.(4) A small increase in the receptivity of pulp fibers to dye was observed during the alkaline refining. Moisture contents above 3% had no effect on the dye absorption. Below 3%, the dye absorption was markedly reduced.(5) The size of the cellulose micelles, measured by water vapor absorption and limiting D. P., was reduced by hot alkaline treatment. The decrease in both D. P. and absorption were noted and this suggests that the change in both the length and lateral dimensions of the crystallites occured.