Use of cellulose nanofibrils (CNF) in coating colors

Cellulose nanofibrils (CNF) have been tested as a substitute for synthetic latex binders and different thickeners in board coating colors in the laboratory scale. Partial replacement of latex with nanofibrillated cellulose increased viscosity of the coating colors especially at low shear. CNF grades of this study increased the viscosity efficiently even at very low dosage. Water retention results indicate similar effect as with CMC. Tested CNFs induced stronger influence on e.g. water retention and viscosity for calcium carbonate based coating colors than for clay based coating colors. Our results indicate that CNFs might not be suitable to be used as binders because of too strong thickening effect. It was also found that dry surface strength of laboratory coated board was clearly lower when part of latex was replaced with CNFs. However, they could be used as a thickener since even at a very low dosage level they thicken coating colors properly.