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The Precipitated Calcium Carbonate (PCC) Advantage for Coated Woodfree (Freesheet) Papers

Five major particle parameters affect a pigment’s performance on the surface of paper: shape, size, size distribution, surface chemistry, and surface area. Manipulation of these variables makes it possible to control the structure and brightness of the coating layer.

Specialty Minerals Inc.’s (SMI’s) crystal-engineered precipitated calcium carbonate (PCC) pigments can adjust the above properties to support whiter and brighter papers across a wide range of paper grades. We are unique in our ability to design and produce many different shapes of crystals. Working together with the papermaker, our scientists create not only coating formulations, but—more importantly—also provide the ability to meet the demands of tomorrow’s paper markets for brighter, high-quality papers. 

SMI’s PCC is a tool for quality enhancement and cost reduction with the following advantages as a surface coating:

  • Optical Properties—SMI’s coating pigments offer high light scattering due to control of coating pore volume. This delivers significant brightness advantages compared to competing pigments. Optimum size, uniformity, and pore volume bring increased opacification in comparison to kaolin and ground calcium carbonate (GCC). Paper benefits include increased opacity, easy gloss development upon calendering, and potential titanium dioxide (TiO2) replacement. Crystal engineered particles allow an increase of five to eight units of gloss over GCCs. Furthermore, synthetic glossing additives can be reduced or omitted from formulations.
  • Smoothness—The narrow particle size distribution and its resultant high pore volume of PCC produces a bulky coating, which contributes to improved fiber coverage and sheet smoothness.
  • Printability—The ability to control coating layer pore size and volume allows in turn for control of fountain solution acceptance, better ink trapping, more predictable ink setting and reduced blister potential on drying.
  • Bulk and Stiffness—The unique particle size and steep distribution curve of PCC improves the physical properties of the coated sheet.
  • Rheology—SMI’s PCC have been applied in coatings at up 3,000 meters per minute. Our coating pigments exhibit outstanding rheology.