Roll-to-roll processed cellulose nanofiber coatings

Current environmental concerns have encouraged the food packaging industry to search for biobased barriers produced from renewable material sources. One candidate for renewable barrier applications is nanocellulose which has been found to possess excellent barrier properties, especially against grease and oxygen. However, most of the research presented so far has been based on small, batch-produced films or coatings of nanocellulose. Reports on continuous processing of nanocellulose into films or coatings, which is required for large-scale, low-cost production, are few. The current work presents a roll-to-roll coating process of cellulose nanofiber (CNF) suspensions on paperboard for renewable barrier applications. The coating apparatus used herein provides a low effective viscosity to enable the processing of the highly viscous nanocellulose suspensions into a coating on a paper web. The impact of various process parameters on the coating quality and runnability are discussed. Strength (tensile and burst) and barrier properties (air permeability, water and heptane vapor transmission rate, and mineral oil and grease barrier) of the CNF-coated paperboards are promising and mostly superior to what has previously been reported.