Why is Precipitated Calcium Carbonate (PCC) Preferred in Paper?
There are four popular minerals used in paper filling and coating: kaolin clay, calcium carbonate (available as ground or precipitated), titanium dioxide and talc. Both titanium dioxide and talc, however, are consumed in small quantities for special applications where extreme whiteness and opacity, or pitch control are required. Hence, the workhorse minerals employed in the paper industry today are precipitated and ground calcium carbonates and kaolin clay.
PCC differs from ground calcium carbonate (GCC) and kaolin clay in a very basic way. PCC is manufactured, while GCC and clay are mined from large natural deposits of ore. This fundamental difference gives rise to a number of advantages for precipitated calcium carbonate. When Specialty Minerals manufactures PCC, we can control the chemical and physical properties of the particles. This allows us to optimize PCC properties like particle size, particle size distribution, surface area, particle shape and surface chemistry to meet our customer’s specifications. This manufacturing freedom allows us to produce PCC in various crystal habits, each with unique properties and advantages. Synthesized PCC is also inherently whiter and brighter than kaolin clay or many GCCs. Manufacturing flexibility also allows us to prepare precipitated calcium carbonate on-site at the paper mill in our own nearby PCC satellite plant. PCC is thus readily available with little or no transportation. By contrast, GCC and kaolin clay must be mined and processed at specific locations then transported to the paper mill. Precipitated calcium carbonate is the most cost-effective mineral for producing high quality paper and paperboard via substitution of more expensive wood pulp, additives or other minerals.
The use of PCC as a filler has been growing at a phenomenal rate since Specialty Minerals’ first satellite facility was installed in 1986. Demand for filler PCC in uncoated papers has grown from about 275,000 metric tons in 1986 to more than 4 million metric tons. In coated papers, quality creep continually increases performance standards toward brighter papers with better printing surfaces. Within the carbonates, coating PCC has advantages over GCC due to its greater gloss and opacity.