Cold alkali refining of cellulosic pulps derived from Egyptian cotton and bagasse

A cotton linter pulp, a bagasse dissolving pulp and a bagasse paper pulp were subjected to cold sodium hydroxide refining and the resulting changes in their chemical, physical and submicroscopic characteristics were investigated. In the case of cotton linters the main change took place in the physical and submicroscopic properties and the refining resulted in better reactivity towards xanthation. The α-cellulose content of the paper and viscose pulps increased with alkali concentration until it reached a constant value which depends on the type of pulp and the concentration of alkali. The refining of the paper and viscose pulps impaired their reactivity towards xanthation. The presence of the more hydrophilic hemicellulose increased the swelling ability of the fibres and made them more reactive towards xanthation. The undesirable effects of drying after refining with high alkali concentration could be overcome if the DP is sufficiently lowered. In this case the resulting shorter chain macromolecules dissolve more readily during xanthation.