Bleached Softwood Kraft Research Articles

Chlorinated phenolics of bleached kraft mill origin: An olfactory evaluation

Biologically treated effluent samples from 9 Canadian bleached softwood kraft mills were analyzed for chlorinated phenolics content. Odour thresholds were determined for selected chlorinated phenolics and for a synthetic mixture of these compounds at concentrations typical of a biologically-treated bleached kraft mill effluent. Results indicate that chlorinated phenolics present in effluent discharged from bleached kraft mills are not expected to contribute an off-odour to recipient waters.

紙の空げき構造，とくに水銀の圧入・退出挙動の解析

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.

The water absorbency of hydrolyzed polyacrylonitrile‐grafted cellulose fibers

AbstractThe water absorbency of a bleached softwood kraft pulp, as measured by its water retention value (WRV), was increased up to 30 times by graft polymerizing polyacrylonitrile (PAN) and subsequently hydrolyzing it to sodium polyacrylate–polyacrylamide copolymer. WRV was found to be related to the initial PAN graft level rather than to the final sodium polyacrylate content, and was independent of the grafting process used. However, the ceric ion process was found superior to both the cellulose xanthate–H2O2 and ferrous ion–H2O2 redox systems in that it occasioned only a minor loss during the hydrolysis stage and the WRV was less affected by drying. The WRV remained constant as pH was lowered from 9 to 5 but dropped to the level of unmodified pulp at pH 3.5 where the sodium salt is fully converted to poly(acrylic acid). Retention of 1% aqueous NaCl was about 60% of the WRV. The swelling properties of the grafted fibers under various conditions appear to be explained by considering the grafting to act in two ways: (a) the introduction of a potentially hydrophilic component capable of generating swelling pressures and (b) the reduction in the cohesion of the fiber by the interposition of graft polymer chains in the fiber structure.