PAPER INK INTERACTIONS. The effect of coating pore structure and geometry on the drying efficiency of heatset web-offset ink solvent

Abstract

Abstract This work examines the effect of coating pore structure on the evaporation behaviour of mineral oil, as a typical heatset web-offset ink solvent. Two different kinds of coating pigments are compared, a standard ground calcium carbonate (GCC) and a highly porous modified calcium carbonate (MCC) with fine intraparticle pores. The aim is to identify relevant pore structure parameters and their effect on the drying rate. Two internal stages of drying were identified for both structures : a rising drying rate period and a falling rate period. In the rising rate period, the effect of film tlow was of particular relevance for the case of GCC based structures : binder, filling the pore structure decreases the detail of geometry and thus reduces the film flow tendency, progressively depressing the drying rate. At the onset of the falling rate period the liquid phase is in the form of disconnected liquid clusters. Therefore, the diffusion resistance becomes a dominant factor. Because of the high permeability of MCC systems the evaporation rate proofed to be largely unsusceptible to the binder concentration. However, the GCC pigment systems exhibited an extended peak of the drying rate as a result of the increasing diffusion resistance with increasing binder content.