Slot die coating of nanocellulose on paperboard

Abstract

Constantly growing interest in nanocellulose usage and applications is pushing the scientific community to search for suitable production and processing techniques. One example is use of nanocellulose as a barrier material in packaging applications, which requires processing of nanocellulose into films and coatings. It is challenging to coat nanocellulose suspensions using conventional pigment coating techniques due to their yield stress behavior and very high viscosity, even at low solids concentration. This work demonstrates a novel roll-to-roll coating method of nanocellulose on paperboard using slot die geometry. The rheology of nanocellulose suspensions in pressure-driven flow is found to play a critical role in enabling their coating using the said process. In this work, the slot die is used in an unconventional manner where the shearing and metering elements are combined to aid wet film formation and application of nanocellulose suspension onto the paperboard. Barrier performance of the nanocellulose coated paperboards against air, water, heptane vapor, grease, and oils was found to be reasonable and warrants further research on the subject. Application: The modified slot die coating method reported here could be utilized for roll-to-roll coating of web materials with a large variety of highly viscous materials such as cellulose