Determination of Lignin Distribution in Pulps by MIR ATR Spectroscopy, 2002 International Pulp Bleaching Conference Proceedings

Anna-Stiina Jääskeläinen, Mari Nuopponen, Patrik Axelsson, Mari Halttunen, Mia Löijä, and Tapani Vuorinen

Kappa number variation in pulp sheets was determined by MIR ATR spectroscopy. The effect of pulping and successive delignification and bleaching processes on the homogeneity of the laboratory pulps was evaluated. MIR ATR spectroscopy combined with the multivariate data analysis provides information on both the surface and bulk chemical structure of the fibres. The variation in the laboratory hardwood pulps was similar to that in the mill-scale hardwood pulp from the continuous digester. The kappa distribution of the softwood Super Batch mill pulp became more even after the oxygen delignification. In the case of the laboratory and mill-scale hardwood pulps, the distribution after the bleaching stages was as inhomogenous as after cook, although the average and measured kappa values were decreased. The inhomogeneous lignin distribution was not found to be responsible for the poor bleachability of the laboratory pulp.