Performance of Brazilian Clay in Coated Paper, 1997 Coating Conference Proceedings

During the past year, naturally platy kaolins from Brazil have been introduced to paper coaters worldwide. This presentation will briefly describe the mineralogy of the deposit, basic physical properties and performance data in a variety of coated grades. Included will be data from laboratory CLC studies and pilot coater evaluations. Incorporation of these clays into coating formulations has shown that their use results in, improved brightness, opacity and smoothness, a more porous coating layer and the capability to run at higher coating solids relative to current commercial clays. The good coverage and runnability obtained makes them ideal for use in low coatweight applications. These quality improvements offer the opportunity to eliminate or partially replace costly prime pigments such as TiO2 , calcined clay and plastic pigment. Due to the narrow particle size distribution of these clays, the binder demand is also lower, allowing possible reduction in binder level in certain grades. Printability enhancement that results with the use of these novel Brazilian kaolins offers great benefits to North American paper coaters. Improvements in rotogravure printability have been demonstrated using Image Analysis. These Brazilian clays have consistently shown the ability to produce higher print gloss while maintaining sheet gloss levels. Surface strength enhancement related to the lower surface area of these pigments offers improved pick resistance on press, often at lower binder level.