Response of Lightly-Filled Groundwood Paper to Calendering, 1995 Finishing and Converting Conference Proceedings

M.F. Gratton

Pulp and Paper Research Institute of Canada

The effect of conventional machine calendering and temperature-gradient calendering on the physical properties of a lightly filled commercial groundwood paper were studied. The effect of filler was also studied. The filler contents were approximately 1% and 8%, and the two papers were fabricated on the same paper machine. Temperature-gradient calendering yielded lower bulks and roughnesses, higher gloss, less strength losses and lower optical properties than conventional machine calendering. The level of fillers in each paper also had a significant effect on the physical properties. Compared at the same bulk, paper with the higher filler content had higher roughness, proportionately lower gloss, better strength, and similar optical properties. The results also show the effect of the mechanical action of a calender on the surface and strength properties of paper. The use of fillers for enhancing the surface properties of paper is discussed. It should provide the papermaker with a better understanding of the role of fillers in paper and give him a means to optimize his product through a choice of calendering technique and filler content in the sheet.