SETTING RATES OF OIL-RESIN SYSTEMS, PaperCon 2010 Conference

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The rate of ink setting on coated papers can influence the final product quality as well as press operation. Much of the past research on this topic has focused on the coating layer structure; for example, fine pores have been found to set ink more rapidly than large pores. Little has been reported on the influence of ink composition.

Two alkyl resins were dispersed in a mineral oil and a linseed oil at elevated temperatures at various concentrations. A composite ceramic plate, with pores around half a micron on the top layer, was used to simulate a porous layer similar to a paper coating. The absorption rate of the resin/oil mixture into the plate was characterized gravimetrically. The viscosity change of the mixture after contact with the ceramic plate was characterized by a controlled stress rheometer. The predicted absorption rate and the change in viscosity were compared by various models in the literature.

The absorption rate is reduced by the presence of the resin. This reduction in absorption does correlate to the steady viscosity rise of the mixture after accounting for the increasing resin concentration. However, a filtercake based model also predicts a reduction in the absorption rate and shows the best fit with the experimental results. The increase in viscosity due to absorption is predicted by the various models, but the thickening and the phase model seem to best predict the viscosity increase in a resin mineral oil system and resin linseed oil respectively.