Designing Coating Systems for Multilayer Curtain Coating

Presented during TAPPICon, April 26-29 in Columbus, Ohio

As demand for paper-based packaging grows, waterborne coating systems offer a widespread solution for providing necessary barrier and converting properties to a paper substrate. While some applications require a barrier to a single substance (eg. Oil and Grease), other applications, such as long shelf-life flexible packaging, need a degree of multifunctionality that can only come from the use of two or more materials, often in the form of a multilayer coating solution. Multilayer curtain coating is an interesting technique for applying such systems because multiple layers are transferred to the paper substrate in the liquid state and in a single pass. This allows for high line speeds and excellent coating coverage and contouring at low coat weights. Designing multi-layer systems for curtain coating, however, often requires consideration of properties not traditionally considered in the paper coatings space, such as dynamic surface tension, interlayer compatibility, and extensional viscosity, to name a few. This presentation focuses on developing design rules for surface tension in multi-layer curtain-coated systems.