紙の空げき構造，とくに水銀の圧入・退出挙動の解析

Abstract

An attempt to approach better understanding on porous structure of paper, particularly on interconnected fiber to fiber channels occupied large part of total pore volume of paper, was made by applying the conception of porous model in packings of uniform spheres to the penetration and retraction curves obtained by mercury porosimetry. The experimental data for a series of handsheets prepared from a bleached softwood kraft pulp with variety of wet pressure and beating degree are presented.The mercury penetration into the channels between fibers and the retraction from those are completed within narrow pressure range and further, in handsheets of unbeaten fibers, almost all mercury penetrated are retracted at the reduced pressure. It may be reasonably considered from these behavior of mercury on handsheets from unbeaten or lightly beaten fibers that the channels between fibers having complicated structures in practic are similar to the interconnected pore-space of packed spheres. However, the tendency is ound that the total mercury retraction volume expressed as the percentage to the total mercury penetration volume decreases with decreasing the total penetration volume. These facts seem to indicate that the pores occupied by mercury after the reduced pressure are formed within the sheets as the effects of wet pressing or beating operations.The penetration and retraction curves concretely represent the actual change in porous structure of handsheets. In addition to the tendency mentioned above, the apparent breakthrough pressure obtained form penetration curves and the apparent withdrawal pressure from retraction curves increase meaningfully with decreasing the total volume of mercury penetrated.