“Covercarb”(Hydrocarb CC)

A New Coating GCC for Enhanced Optical Properties

Abstract

Almost unknown 25 years ago, ground calcium carbonate is today the most used coating pigmentworld-wide in several applications.
Significant technical and economical benefits like high brightness, lower binder demand, excellentcoater runnability and improved off-set printability are well known to the Industry.
In a number of applications however, conventional GCC pigments have the limitation of lower hidingpower and reduced opacity. Therefore it is common practice to add opacifying pigments to the coatingcolor for reaching the required opacity.
The theories of light scattering on small particle can be used to explain this phenomenon. Pigmentswith the high brightness, broad particle size distribution and fine particle size of the GCC's presentlyused are not optimal for opacity.
We have focused on particle size and particle size distribution to design a GCC pigment for improvedopacity. We realised that a narrow particle size distribution (steep curve) would optimise opacitybut at the same time many of the advantages of the present pigments would be reduced. Therewould be significant negative influence on coater runnability, binder demand and solids content of thecoatings using the “ideal opacifying GCC”.
Therefore a compromise was decided upon by which, as much as possible, the present advantagesof GCC would be retained in the new pigment, while particle size distribution and average particle sizewould be shifted towards that of the ideal opacifying pigment.
The manufacture of this pigment is possible by use of a modified grinding technology.The presentation describes the new coating pigment and gives a number of examples where conventional GCC pigments were substituted by the new type.