The behavior of on-site synthesized precipitated calcium carbonates and other calcium carbonate fillers on paper properties

With the advent of on-site precipitated calcium carbonate (PCC), a flexibility now exists for the alkaline papermaker that has never existed before. Various products can be custom-made to provide the specific properties for each grade of paper manufactured at each site. For example, a paper mill which produces high opacity printing and writing grades along with merchant bond grades with lower opticals and different physical specifications may find it advantageous to have more than one type of filler produced upon demand from an on-site precipitated calcium carbonate plant. With this scenario in mind, a pilot paper machine study was conducted to investigate what effect different calcium carbonate fillers-PCC, ground limestone and chalk-had on paper properties. Results from the study revealed that PCC fillers produce significantly higher scattering coefficients and opacity than ground limestone or chalk fillers. It was found that the opacity/tensile strength performance of scalenohedral PCC fillers was superior to that of natural ground limestone or chalk. Control over stiffness, caliper, porosity and sizing can be obtained by altering the particle size and surface area of scalenohedral PCC fillers to achieve various paper specifications. Also, abrasion problems (wire wear and converting operations) can be minimized by the use of scalenohedral or rhombohedral PCC fillers.