Variables affecting the thermal yellowing of TCF-bleached birch kraft pulps

摘要

The purpose of this investigation was to identify the most important variables influencing ht ethermal yellowing of TCF-bleached kraft pulps. The variables studied were: hexe- nuronic acid content, dry content, temperature, time, pH, and iron content. All these variables influence the process of colour rever- sion. It was shown that there is a strong relationship between hexenuronic acid content and the magnitude of the colour rever- sion. Of the conditions investigated, long time (6 days), high temperature (80 deg. C), slightly acidic conditions (pH 4.5) and a moist environment (92/100 dry content) caused the greatest bright- ness reversion.