High solid coatings

For high solid glossy top coats it is necessary to use a micronized Gemme Micron or Gemme Fine grade of a particle size of around 0.5-1um. With larger grades top gloss is not available. Smaller grades are determined by a higher specific surface area and therefore by a higher binder demand. As a result high filling rates and high solid contents would be nearly impossible. Apart from the basic formulation some modifications with increased amounts of Gemme Fine and decreased amount of titanium dioxide are mentioned. Gemme Micron of a particle size in the range of 0.5um is able to deflocculate and space titanium dioxide. As replacement ratios ten percent titanium dioxide to ten or twenty percent of Gemme Micron are well know.

Apart from white or bright colored coatings, it is worth mentioning, that the white powder Gemme Micron can also be used in pure blank coatings without affecting the blank color. This has to do with the refractive index of Gemme Micron, which is close to that of usual resins. Thus incorporated in a system, Gemme Micron is not white, it is transparent. Therefore it will not create a light gray color in carbon black coatings. Also in black coatings Gemme Micron can be used to reduce the VOC. The major effect here is the large difference in the binder demand or specific surface area respectively of carbon black versus that of Gemme Micron. If the effectiveness of carbon black can be increased only slightly by deflocculation, a lot of carbon black can be replaced by Gemme Micron, resulting in a reduced overall binder demand, viscosity and therefore VOC.