New Flexibility for Print-Surface Design from 100% Natural Ground Calcium Carbonate, 1998 Coating Conference Proceedings

With the continuing trend toward higher brightness coatings the proportion of calcium carbonate in the coating formulation has steadily increased. In effect, this has meant that no longer is calcium carbonate simply the whitening agent in the pigment blend but is rapidly becoming the dominating coating structure-determining component. For the papermaker, it is important that the tools for print structure control are readily available and the progress toward 100% calcium carbonate in the printing surface requires that the flexibility of design must come from the carbonate itself. To achieve this necessary power of fine tuning, a new approach has been taken to product design for natural calcium carbonate. A new generation of pigments with the potential for developing a continuously variable range of designed coating structures has been developed. These high solids materials operate through pore structure and surface chemistry factors to create the dynamic relationship between ink tack build, pore size distribution and total pore volume required for print runnability, ink acceptance and print gloss. The new flexibility offered by these developments caters well for the broad range of structures created in a variety of paper and board applications. Examples are given of high gloss coating including the most recent design requirements for achieving good printability from the highly compressive mechanism of hot extended nip calendering.