Canadian Co-Operative Permanent Paper Research Project: The Impact Of Lignin On Paper Performance, 1998 Process & Product Quality Conference Proceedings

The Canadian co-operative research project has examined the impact of air pollutants on the permanence of handsheets from six pulp types and four alkaline commercial papers. An automated environmental chamber is designed and constructed to study the effect of air pollutants. A protocol that includes an exposure of paper to 10 ppm SO and 20 2 ppm NO for four days (at 23°C and 50% RH), followed by accelerated aging at 80°C and 65% RH for up to 50 days x is used. The pollution results confirm that sheets from mechanical pulps absorb more air pollutants and show a greater brightness loss than lignin-free sheets. However, this does not necessarily result in greater deterioration of strength properties. A four-day exposure to 10 ppm SO and 20 ppm NO causes a significant acidification and degradation of 2 x all papers containing no alkaline reserve. The addition of calcium carbonate as an alkaline reserve is very effective in reducing the negative effect of air pollutants on both lignin-containing and lignin-free sheets. This study further confirms that lignin does not have any negative impact on the mechanical permanence of paper.