Nano-fibrillated cellulose as a coating agent to improve print quality of synthetic fiber sheets, 2010 TAPPI Advanced Coating Fundamentals Symposium

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Nano-fibrillated cellulose (NFC) has the potential to be produced from wood fibers at low costs. To determine the potential of NFC to be used as a coating material, the characteristics of several NFC coated samples on a synthetic fiber sheet are reported. Two water-based printing methods were used to characterize the change in print quality. Two types of NFC were prepared by two different physical treatment methods. Various coat weights were applied onto synthetic fiber sheets. The printability of the coated sheets was evaluated by ink absorption rates and print density. Ink pigment penetration is characterized with a Confocal Laser Scanning Microscope and a Scanning Electron Microscope with chemical analysis with Focused Ion Beam to prepare samples. The contact angle and the ink penetration rates decreased with increasing the coat weight of NFC. This result is the opposite of what the Lucas-Washburn equation would predict; a decrease of contact angle should increase capillary pressure and absorption rate. The ink pigments were captured by the NFC layer and held near the surface, increasing the resistance to fluid penetration. For pigment based flexographic inks, ink pigments were captured at the NFC layer. For dye based inks, the ink components penetrated and moved through the NFC coated layer. For the ink-jet printing, the print quality improved with the NFC coating. The pigments in ink-jet ink were captured near the surface, even though the pigments are nanometer in size. Synthetic fiber sheets coated with NFC did improve in terms of printing resolution and ink density, especially for pigment type inks.