Nanofibrillated Cellulose with Fine Clay as a Coating Agent to Improve Print Quality, PaperCon 2010 Conference

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Nano-fibrillated cellulose (NFC) may be produced from wood fibers at low costs. To determine the potential of NFC as a coating material, the characteristics of several coated sheets formulated with NFC were investigated. Several coating formulations with NFC used as a pigment or used as a binder were compared; the distinction being related to the amount of the NFC compared to the fine clay. A water based ink suitable for flexographic printing was used. The printability of the coated sheets was evaluated by ink absorption rates and print density of flexographic printing. The ink absorption rates were predicted by a model based on Darcy`s law. Ink penetrated is characterized with a Confocal Laser Scanning Microscope. The sheets coated with NFC and fine clay cause low ink absorption rates and high print density. The pigments in the flexographic ink are captured on the coating surfaces and do not penetrate into the base paper because the pigments are larger than the pores. The sheets coated with NFC as a binder show higher print density than when NFC is used as a pigment. The predictions of the ink absorption rates by Darcy`s law showed a high correlation with experimental data for most conditions.