:Behaviors of Carboxymethylated Carbohydrate and Lignin toward Hot Water Treatment

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The water-insoluble fraction (I<SUB>1</SUB>) of carboxymethylated refiner mechanical pulp (Fig. 1) could be dissolved by hot water treatment in an autoclave. The extents of dissolution of carbohydrates and lignin increased with the increase of heating temperature and time, and with the decrease of pH (Fig. 2, 3 and 4).<BR>Molecular weight distribution of carbohydrates and lignin dissolved by hot water treatment at 150°C were measured by the use of gel filtration. The carboxymethylated carbohydrates (CM-carbohydrates) were obviously hydrolyzed during the heating process, while a large portion of dissolved lignin remained almost unchanged in high molecular weight fractions (Fig. 5). The existence of carboxymethylated lignin, which is insoluble in water, in high molcecular weight fractions suggests that this part of lignin might be linked to carbohydrates. The hot water treatment at 170°C resulted in remarkable hydrolysis of lignin (Fig. 6). Thus it may be concluded that the dissolution of CM-carbohydrates by hot water treatment is caused by hydrolysis of lignin, which prevents the dissolution of CM-carbohydrates, as well as by the hydrolysis of CM-carbohydrates themselves.
紙パルプ技術協会の論文