パルプ製造中間規模試驗に就いて

Abstract

A number of studies on pulp and its associates, done by us hitherto on laboratory scale, are going to be tested on semi-commercial scale by a pilot plant which is now under construction at the Institute for Chemical Research, Kyoto University. Of various important subjects to be tested, we will explain this time "The Manufacture of Dissolving pulp by Sulfate Process". A series of our researches on this subject2) revealed that the normal bleached sulfate fibers show very peculiar character when subjected to the viscose process. In spite of the very high alpha celullose content, they could not be converted into usable viscose, since individual fibers are dissolved very poorly in alkaline liquor even if they were elaborately xanthated. Many photomicrographical investigations concerning the course of dissolution could reveal that the primary lamella, or possibly the outer layer of the secondary lamella also prevented the complete dissolution of xanthated fibers (ref. Fig.1). The treatment of fibers with caustic soda solution 5% in strength enhanced the solubility of fibers. It could be ascertained that 95% of the extracted substances was pentosan, and the microstracture of fibers was altered by this caustic treatment (ref. Fig.2, 3, 4 and 5). In order to remove pentosan before cooking, we treated the chips preliminarily with dilute sulfuric acid. This pre-treatment, as had been expected, was very effective to improve the dissolving property of the sulfate pulp resulted. To simplify the process we further modified the process, and cooked the chips with water before subjecting them to the normal sulfate cooking. By the action of several organic acids such as acetic and formic acid which were extracted by hot water, the medium became acidic enough to hydrolyse the harmful pentosan. The possibility of the re-use of the precooked liquor was also recognized. The pulp thus obtained has very high alpha cellulose content, 95% or higher, and posseses many other excellent properties of dissolving pulp. This process has a general availability and can be applied to pine, larch and hardwoods, to which the sulfite cooking is unsuitable or unavailable.