The Influence of Electrolytes and Certain Substantive Azo-Dyes on the Rate of Beating

Abstract

From the results of beating experiments on several pulps in the presence of electrolytes and water soluble substantive azo-dyes, it has been possible to draw the following conclusions –

1. Generally speaking, the presence of various electrolytes causes a decrease of the beating rate of the cellulose fibres in comparison with beating in distilled water. In some few instances, there has been noted a slight increase of the beating rate. This fact could be explained on the basis that the additive acts as a sequestrant of the cations present in water. In fact, this seems to be more realistic than the hypothesis of specific action of the electrolytes on the fibre during the beating process.
2. Some substantive azo-dyes belonging to the benzidine class cause outstanding acceleration in beating, together with a remarkable improvement in the mechanical characteristics of the corresponding paper sheets.
3. When the same dyes are added to beaten pulp, an increase of beating degree (°S.R.) is obtained without any remarkable change in the strength.
4. When the dye is extracted from the beaten pulp, a decrease of beating degree (°S.R.) is observed. If compared with paper sheets prepared from unextracted pulps, those prepared from the extracted pulps show an increased folding endurance. The other strength characteristics do not present any noticeable variation.

The results of these experiments are discussed on the hypothesis of the lamellar cleavage of cellulose fibres during beating and the interaction between dye molecules and cellulose macromolecules.