Influence of Engineered Kaolin on Web Offset Blister Resistance, 1996 Coating Conference Proceedings

A comparison was made of the blister tendency for coating formulations containing a standard fine coating clay with commercially available latexes of distinct glass transition temperatures, calcined clay, or engineered kaolin. The engineered kaolin high glass transition latex, and calcined clay were found to increase the resistance to blister as compared to the fine coating clay formulation. Examination of the respective coating structures with air flow porosity, mercury porosimetry, and water interference mottle suggest both the engineered kaolin and calcined clay create a pore network which is characterized as having larger pore diameters than the standard clay. The associated larger pore diameters provide a structural porosity which is thought to allow water vapor to escape during the drying phase of web offset printing. Furthermore, the shift in pore size was correlated with an increase in opacity. A unique feature of the engineered kaolin was an increase in print gloss as compared to the other coatings. The pore structure found with the use of the engineered kaolin not only allowed water vapor to escape but was able to achieve better ink hold out which led to improved print gloss.