The effect of mannan on physical properties of ECF bleached softwood kraft fibre handsheets

The role of surface mannan in ECF bleached softwood kraft pulp fibres was investigated by altering the mannan content of fibres by combined extensive enzymatic removal and chemical sorption methods. The effect of amount, structure and location of mannan in the fibres on physical properties of fibres was measured. Mannanase treatment was able to remove both native fibre galactoglucomannan and sorbed, enzymatically modified locust bean gum galactomannan from the fibres. Extensive chemical sorption of galactomannan seemed to occur preferably on the native galactoglucomannan present on the fibre surfaces. The amount, structure, composition and location of mannan in the fibres were found to influence the handsheet properties. The native fibre surface galactoglucomannan affected mainly the density of the fibres and thus the binding properties of the fibres. The sorption of modified galactomannan increased the WRV of fibres as expected and clearly increased the air resistance of the handsheets. Of the bonding strength properties, Scott Bond values correlated well with the amount of mannan located on the fibre surfaces whereas tensile strength was mostly affected by the total amount of mannan in the fibres.