Some Properties of Chlorinated Lignosulfonic Acid
On the Mechanism of Pulp Bleaching X
1963 Volume 17 Issue 10 Pages 647-650
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1963 Volume 17 Issue 10 Pages 647-650
Barium lignosulfonate was treated with chlorine water and chlorinated material was isolated as barium salt with PAN and inspected for acidic groups and molecular weight.
1) The conductometric and potentiometric titration curves of the chlorinated material are shown in Fig. 1. The titration curves are divided in strong acidic part, medium acidic part and weakly acidic part and these acidic groups are considered as sulfonic acid group, carboxyl group and phenolic hydroxyl group respectively.
2) As is evidient from Fig. 2, the molar ratio of Ba/S in the barium salt of chlorinated lignosulfonic acid increased to 1.25, when about 4 mol Cl2/CH3O was consumed. If no carboxyl group are formed, the ratio of Ba/S must not exceed 0.5, in so far as no barium salt is formed in the phenolic group. It may be considered that the excess Ba/S of 0.75 are due to carboxyl group.
3) When the lignosulfonic acid is chlorinated to the degree of the condition used in the technical pulp bleaching process (Cl2/CH3O_??_4), the yield of chlorinated lignosulfonic acid isolated with PAN are only half of lignosulfonic acid which was applied in the chlorination. (Fig. 3).
4) The diffusion coefficient of the chlorinated lignosulfonic acid measured by means of the Mc-Carthy's method has a tendency to increase together with the increase of Cl2/CH3O. This fact may suggest that the molecular of the lignin was ruptured with the treatment of the chlorine water.
