FRACTIONAL DISSOLUTION CURVES OF NITRATED PULTS WITH ETHYL ACETATE-ETHANOL MIXTUTES

Abstract

Ranby et al. had extracted nitrated pulp fibers with ethyl acetate-ethanol mixtures of increased ethyl acetate concentration, and found that the solubility curve thus obtained shows a level (Fig. 1). This fact means the carbohydrates are deposited in the plant fibers as two fractions differing markedly in solubility after nitration. In their investigation, two fractions were denitrated, hydrolyzed to monosaccharides and then analyzed by paper chromatography. This solvent-nonsolvent system gives a swelling of the fibers without destroying the fiber structure, until the concentration of ethyl acetate in mixture becomes about 60% (in volume). Therefore, the shape of this solubility curve can be effected not only by the amounts of easily soluble carbohydrates, but also the fiber structures, mainly outer layer of the cell wall and fine structure.The purpose of this investigation has been to establish what effect the fiber structurs and average degree of polymerization of pulp could have on the shape of the fractional dissolution curve. The following samples were prepared for determining the solubility curve:1. F-pulp fibers, which had been immersed in water, frozen and thawed, were prepared. This can be seen as destroyed of outer layer of cell wall or loosen fiber framework without the degradation of cellulose chain and the change of crystalline region.2. Acid hydrolyzed pulp fibers were prepared under the mild conditions. This can be seen as degradated of cellulose chain and as destroyed of outer layer of cell wall without any change in crystalline region.Two kinds of acid were used for hydrolysis of pulp fibers, namely sulfuric acid and lignosulfonic acid. According to the investigation by Samuelson, the latter had “screen effect”, then the outer layer of cell wall can be attacked more severely with lignosulfonic acid than with sulfuric acid.3. Mercerized pulp fibers were prepared. This can be seen as disordered of the crystalline region without degradation of cellulose chain. A part of easily soluble carbohydrates goes into solution during mercerization treatment.4. Linters pulp (Li. P), dissolving sulfite pulp (DSP), dissolving sulfate pulp (DKP), bleached paper sulfite pulp (BSP) and bleached paper sulfate pulp (BKP) were also used as original pulps.Mitchell's mixture was used for nitration of pulp fibers and the fractional dissolution was performed in the way Ranby did. The shape of solubility curve has been expressed by l, h, α and s (Fig. 1).As a result, it was found that l and α are effected by fiber structure, namely outer layer of cell wall and fine structure. When the outer layer of cell wall was destroyed or lateral order of cellulose was lowered, I decreased. In the case of DKP, the recrystallization had occured during freezing or acid hydrolysis and l increased. h shows the amounts of easily soluble carbohydrates in the fiber, and the shape s depends on the corelation between h and character of outer layer of cell wall. And the effect of average degree of polymerization of cellulose chain on the shape of fractional dissolution curve can be seen as subordinated to the fiber structure.