Differences in the chemical composition and properties of unbleached grey and black alder kraft pulps

The content of the main chemical components in mature grey (Alnus incana Mo ench.) and black alder (Alnus glutinosa Gaertn.) woods was elucidated. Comp arative kraft cookings of grey and black alder woods were performed. It has been established that the pulp yield from grey alder wood is lower by 2-5% . Differences in the residual lignin content in grey and black alder pulps at a degree of delignification over 94% are not essential. The hemicellulos es content in grey alder pulp at similar delignification process parameters is considerably higher than for black alder pulp. Higher values of tensile strength and folding endurance have been also observed.