Changes of Strength Properties of Wood Pulps with Cellulase Treatment

III Changes of Strength Properties of Semi-Chemical Pulp

Abstract

Unbleached semi-chemical market pulp from coniferous wood (USCP) and bleached one prepared from the former (BSCP) were hydrolyzed with powdered cellulase, and the changes of the strength characteristics of paper sheets as well as some variables assumed to affect the strength were studied. Tensile and tear strength of the pulps decreased with the time of cellulase treatment.
From the changes of characteristics including that of yield of pulps with the cellulase treatment, water retention value (WRV), fine content, specific volume of web, pentosan content, number-average fiber length and lignin content, the following facts were inferred :
(1) Changes in tensile strength of BSCP with cellulase treatment were caused by the decrease in interfiber hydrogen bonding and interfiber friction because of the decrease in fiber length, fine content and pentosan content ; the results were similar to those obtained in our previous study made with kraft pulps.
(2) In spite of the fact that fine content and WRV of USCP increased considerably with cellulase treatment, specific volume of the web increased definitely ; the web became bulky as the lignin content in USCP increased with the cellulase treatment, and the tensile strength decreased.
(3) Changes in tear strength with cellulase treatment were considered as the results of lowering of fiber length both in USCP and BSCP as well.