Effect of Coating Components and Fillers in the Deinking of Paper. Image Analysis and Microscopic Investigations, 1995 Recycling Symposium Proceedings

J. Heimonen

Helsinki University

T. Oksanen

VTT/BEL

Image analysis is widely used and perhaps the most promising method to evaluate the effect of deinking processes. However, it is known that the user of image analysis faces many problems and restrictions. The objective of the experiments was to test the use of image analysis method as a method of obtaining a better understanding of the chemistry of complete flotation model systems.

Test samples containing different ratios of mechanical (TMP) and chemical pulp (bleached birch kraft), dispersed coldset-offset news print ink and ground calcium carbonate (GCC) were analyzed. The effect of different analysis variables (equipment, sample form, transmitted/reflected light, constant/constant optimized/manual gray value settings) was studied. Then, the model systems containing dispersed coldset-offset news print ink, six different pigments used as fillers and coating pigments, other coating components and mechanical pulp (TMP) were flotated in fixed conditions.

Flotation results were studied with image analysis and by microscopic investigation.

The results showed that pulp composition affects the gray value setting and therefore the accuracy of the measurement. It was also shown that the flotation chemistry of the system must be well understood, (e.g. Ca-concentration) and taken into account when estimating the amount of ink in pulp sample from image analysis results.