Deionized Clay: Properties And Improvements In Coated Sheet Properties, 1996 Coating Conference Proceedings

A deionized clay, a clay with significantly improved colloidal dispersion and stability, offers improved rheology of pigment and coating and greatly improved glossability. Because of the increased supercalenderability of the deionized clay, the polystyrene pigment level was reduced from 8 parts in the control to 3.5 parts in the deionized clay formulation. High Speed pilot coater trials were conducted to produce C2S rolls that were supercalendered on pilot scale equipment. The coating color was a high clay content web publication grade formulation. In the first pilot coater trial, the coated rolls were supercalendered at equal calendering conditions. Even with a greater than 50% reduction in polystyrene pigment, the formulation containing deionized clay had 4 points higher gloss, 2-3 points increased ink gloss, improved smoothness, slightly increased opacity and brightness and equal high pressure porosity. When rolls were supercalendered to equal gloss, smoothness and ink gloss were also equal. Substantial increases in opacity and brightness were obtained as well as a 20% increase in porosity. These results were obtained using a fine clay but comparable results can be obtained for other clays including delaminated clays.