Deinking Difficulties Related to Ink Formulation, Printing Process and Type of Paper, 1999 Recycling Symposium Proceedings

B. Carré, L. Magnin, G. Galland, Y. Vernac

Centre Technique du Papier

Domaine Universitaire

The deinking ability of several types of paper, printed with different processes and different inks has been investigated. With a conventional alkaline deinking process, some of them lead to rather good results, whereas others lead to poor deinkability : low brightness, high speck contamination or residual colour. Specific attention has been paid to deinking vegetable-oil -based newsprint offset ink, offset heat-set ink and red rotogravure ink. Deinking difficulties are clearly identified and solutions are proposed. Recent work with ink manufacturers enable them to formulate new vegetable inks which deink as well as mineral oil based inks, and also to understand more deeply the main reasons why red rotogravure ink gives a red shade to the

deinked pulp. Additional work enables the effect of some printing and paper characteristics on the deinking of offset heat-set printed papers to be determined. For all these trials, deinking ability is explained in terms of brightness, effective residual ink concentration (E.R.I.C.), attached and detached ink, specks and colour coordinates to characterise residual dye.