Some properties of kraft and kraft-borate pulps of different wood species.

APPLICATION: With no detrimental effects observed for maple, spruce, and birch pulps, autocausticizing with sodium metaborate added in the white liquor appears to be an easy way for a causticizing-limited mill to increase its capacity without new equipment.

Research has brought us a better understanding of the efficiency of autocausticizing reactions, proving that the amount of sodium metaborate needed to produce sodium hydroxide is only half that previously perceived to be necessary. With less borate required, pulping should proceed with less pronounced side effects, such as an increase in the boiling point and an increase in the viscosity of black liquor. What is really important, though, is the effect that autocausticizing will have on the pulp properties.

These researchers carried out analyses on the properties of birch, maple, and spruce pulps to determine how conventional kraft pulping compares with kraft pulping with sodium metaborate added. The purpose was to simulate autocausticizing and find out if there are any detrimental effects on the pulp produced.

They found that sodium borate has no effect on the pulp properties of birch and maple. In their experiments, sodium borate did not change the brightness nor the contents of extractives and hexenuronic acid groups of the kraft pulps studied. For spruce, they noticed an increase in the total yield at kappa numbers lower than 50. According to these results, autocausticizing should have no deleterious effects on the properties of pulps derived from maple, spruce, and birch. View this paper online at http://www.tappi.org/index.asp?pid=29475

Biljana Bujanovic and John Cameron are with the Dept. of Paper and Printing Science and Engineering, Western Michigan University, Kalamazoo, MI 49008. Nural Yilgor is with the Faculty of Forestry, Istanbul University, Istanbul, Turkey. Email Bujanovic at [e-mail].