| Abstract: | The presence of borax during alkali refining of pulps increased the solubility of the short-chain celluloses and hemicelluloses and thus improved their chemical characteristics. Small improvements in the chemical characteristics of cotton linters took place. A stronger effect was observed in case of the dissolving pulp and a more pronounced effect took place in case of the kraft pulp. Cold 20% NaOH refining was more effective than hot 5% NaOH refining. The physical and sub-microscopic characteristics of linters were mainly affected. Refining lowered the D.P., increased the affinities towards water and alkali, decreased the crystallinity, and improved the reactivity towards xanthation. The presence of borax resulted in a more open and accessible fine structure and better reactivity. Cold refining of the dissolving and kraft pulps resulted in lower reactivity than hot refining and the presence of borax improved the reactivity. It also increased the yield of cellulose acetate. The increase in the solubility of the short-chain celluloses and hemicelluloses resulting from the presence of borax resulted in better homogenisation of the pulp. This was reflected in better chemical and physical characteristics of the acetate. |
