Date of Award

4-1995

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

This thesis involved the study of the effects of calcium carbonate on gloss. The variables investigated were different types and levels of calcium carbonate in the coating color. Four different calcium carbonates, three ground and one precipitated, were used. The calcium carbonate/clay ratio changes from 0% carbonate/100% clay to 75% carbonate/25% clay in increments of 25. The coat weight target was 12 +/- 1 g/m2. The coating colors containing higher levels of calcium carbonate had better low shear viscosities; therefore, these coatings were able to run at the 62% solids target.

It was found that calcium carbonate decreases gloss in comparison to the 100% clay coating, and the larger the particle size of the CaCO3 the greater the decrease. However, the coarsest calcium carbonate (GCC-60) did produce the greatest gains in gloss after supercalendering. The GCC-Hg which had the smallest average particles size did not significantly change the gloss at higher substitution levels. The GCC-90 had no significant effect on gloss until the 75% substitution level, when a decrease occurred.

The narrow particle size distribution of the PCC was detrimental to gloss, and it was also a factor in the brightness loss due to Ink absorption.

The brightness loss of the coatings due to K&N ink absorption corresponded to the gloss results, except for the PCC trend. PCC had the most dramatic decrease in brightness.

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