A filler distribution factor and its relationship with the critical properties of mineral-filled paper

Abstract

The use of mineral fillers in the paper industry has attracted much attention due to its low cost and ability to improve optical properties and printability. Besides the filler characteristics, paper properties, such as bulk, tensile, and opacity, are greatly affected by filler distribution in the z-direction. Therefore, optimization of filler distribution is an effective way to maximize the value of fillers. In this work, a filler distribution factor (Fc) was proposed to quantitatively describe the concentrated degree of filler distribution in the z-direction. The reduction in Fc resulted in an increase in paper bulk, porosity, and opacity, due to the generation of more interfaces between fibers and fillers. When filler particles were concentrated in one layer (Fc = 1), the tensile strength of the filled paper increased between 26 to 40% in comparison to the paper with various Fc values. For a given Fc, better tensile and opacity properties were achieved by increasing filler concentration on the surface layer of paper.