STUDIES ON THE NEUTRAL SULPHITE SEMI-CHEMICAL PULP OF BEECH
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概要
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Neutral sulphite semi-chemical pulps of beech (Fagus crenata Blume) were made with yields ranging from 60 to 72%. The cooking liquors used in this test were : sodium sulphite liquor with no buffer and sodium sulphite liquors with such buffering agents as sodium carbonate, sodium bicarbonate and calcium hydroxide. The results of these digestions were compared with each other in point of physical and chemical properties of pulps, and then the effects of these buffering agents on pulp properties were closely studied. The results obtained were as follows : <BR>(1) The value of buffering agent in cooking increased as its alkalinity became stronger.<BR>(2) As yields of crude pulps increased total cellulose contained in the pulps decreased and the lignin contents increased.<BR>(3) With respect to the affection of buffers on values of total cellulose per lignin (each based on the wood), it was indicated that when calcium hydroxide, sodium bicarbonate and no added buffer were used, the pulps were more or less similar, but the use of sodium carbonate buffer resulted in a lower value at the similar yield of crude pulp. And these values derceased according to the rate of increase in pH values of the spent liquor.<BR>(4) The brightest pulps were obtained when pH value of the spent liquor was somewhere from 7.2 to 7.7 with the aid of the abovementioned buffering agents.The highest brightness of the pulp was attained when no buffer was added to the cooking liquor. The addition of a limited quantity of calcium hydroxide and sodium bicarbonate proved next best, while sodium carbonate brought forth the lowest in the brightness of the pulp.<BR>(5) Unbuffered pulps would be considered advantageous for fully bleaching because of the lowest chlorine number, considering the relations between crude pulp yields or lignin contents and chlorine number.<BR>(6) When several pulps were treated by the one-stage calcium hypochlorite bleaching process, the bleached pulp yields were from 66 to 68%, as against the quantity of wood used. The brightness of the pulp obtained therefrom 55 to 65%.<BR>In conclusion, considering total cellulose, lignin contents, chlorine number, brightness, extracted resin and the pulp strength, I found out that the uubuffered pulp was the best and that those pulps obtained with calcium hydroxide, sodium bicarbonate and sodium carbonate fell off in point of properties in the order mentioned.
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