Study on Neutral Sulphite CGP

Abstract

Using Japanese birch, alder and oak, respectively, neutral sulphite CGP pulping was conducted to evaluate the effects of wood species, pulp yields, cooking conditions, refining and bleachina on the properties of CGP. The major results were as follows :(1) Wood species had great influence on the properties of CGP. Under the same conditions, the pulp made from birch was stronger and brighter than the pulp from alder, and the pulp from oak which was dense and dark was poorest in strength and unbleached brightness. The opacity of bleached oak CGP treated by hypochlorite was lower than that of unbleached alder or birch CGP, when their brightmess was the same.(2) At the same freeness, the strengths (e.g. breaking length) of pulps were closely related with yields and other properties of pulps. Each correlation was found to be approximately linear regardless of cooking variables. With increasing breaking length, yield, unbleached brightness and opacity decreased and sheet dencity, oil penetration and wet web strength increased. In case of oak CGP, bleach requirement increased and the opacity of bleached pulp decreased at the same brightness.(3) Lowering the freeness of pulps, the strength developed and the opacity increased in case of alder CGP having yields above 83%, and decreased in case of the lower yields pulp. At the same breaking length, the pulps of higher yield and lower freeness were superior in brightness and opacity to those of lower yield and higher freeness.(4) Bleaching developed the strength and increased the sheet density.(5) The effects of several cooking variables on the cooking rate were discussed.