INVESTIGATION UPON DISSOLVING PULP

Abstract

The influence of the variation in average D. P. of unbleached pulps upon the change of the molecular weight distribution of wood cellulose during pulping and ageing process was investigated by using the same samples described in Parts V and VI. From each unbleached pulp with various average D. P., were prepared the bleached pulp with approximately same average D. P. level (ca. 900) and same α-cellulose content (ca. 92%), from which were prepared also their alkali cellulose with approximately same average D. P. level (ca. 400) respectively (cf Parts V. VI). The clogging constant (Kw) of the viscose from each alkali cellulose was determined by normal method (cf. Part V), and also the reactivity of each bleached pulp in emulsion xanthation, i.e. “Resistance to Mercerization”, (cf. Part III), and “Resistance to Xanthation”, (NaOH: 140g/l, CS2 added on the basis of cellulose 40%, 70%, 100%, 140%) were determined by modification of Bartunek's method.The results were as follows:1, Sulfite cooking, hot caustic purification, hypochlorite bleaching and alkali-ageing, these four stages have all contributed to the uniformity of the molecular weight distribution of wood cellulose. The influence of the variation in average D. P. of unbleached pulp upon the polymolecularity of the bleached pulp and also their alkali cellulose with approximately same average D. P. level respectively, was found comparatively small, however, under more detailed observation, it was found that the content of higher molecule weight portion in each bleached and also aged samples had increased with increase in the average D. P. of original unbleached pulp.2, The influence of the variation in average D. P. of unbleached pulp upon the reactivity in emulsion xanthation of each bleached pulp with approximately same average D. P. level, was found so little, that both “Resistance to Mercerization” and “Resistance to Xanthation” were only dependent upon the average D. P. of bleached pulp. These results were quite similar with that previously reported. (cf Part III).3, On the other hand, the clogging constants of the viscose prepared from each alkali cellulose with same D. P. level (ca. 400) have increased more or less proportionally with the increase in average D. P. of original unbleached pulp.Therefore it is dangerous to estimate directly the suitability of bleached pulp for viscose, only by Bartunek's method. It could be thought more advisable to use, besides emulsion xanthation method, the method of morphlogical investigation upon the behavior of wood cellulose by modification of Heide's method under specialized xanthation condition, e. g. under the addition of insufficient amount of CS2 to the normally prepared alkali cellulose.