Studies on Beating of Pulp (II)

Effect of Ultrasonic Treatment on Chemical Pulps

Abstract

Softwood sulphite and sulphate pulps were beaten by lampén mill and 25 kc and 400 kc ultrasonic waves, and dissolution of hemicellulose during the beating and fractional dissolution of the nitrated pulps were studied. The results are summarized as follows :
(1) The freeness change by lampén mill beating and 25 kc ultrasonic treatment proceeded in a similar manner, while 400 kc ultrasonic treatment gave only a slight freeness decrease after 6 hours treatment. The 25 kc ultrasonic treatment gave the highest water retention value when compared at the same treating time.
(2) The amount of the dissolved hemicellulose varied depending on the kind of treatment ; 400 kc ultrasonic treatment gave higher dissolution than lampén mill beating and 25 kc ultrasonic treatment when compared at the same water retention value. No monosaccharides could be found in the dissolved parts. The main portion of the dissolved hemicellulose was xylan, and a small amount of glucomannan was found. In the case of 400 kc ultrasonic treatment, however, the proportion of xylan and glucomannan was almost 1 : 1.
(3) The fractional dissolution of nitrated sulphite and sulphate pulps were carried out in ethyl acetate-ethanol mixture. The solubility of the nitrated sulphite pulp was higher than that of nitrated sulphate pulp, and cellulose framework of the nitrated sulphite pulp started to dissolve at lower ethyl acetate concentration. The beating of pulps prior to the nitration increased the solubility of the cellulose framework, but no quantitative relationship between solubility and beating degree could be found.