Effects of Material and Sealing Process Parameters on the Tightness of the Layer Transition Area of Pouch Packaging Made From Functional Papers

ABSTRACT Functional papers with a minimum weight proportion of barrier and heat‐seal coating are one alternative to difficult‐to‐recycle plastic‐based multilayer composite films. Due to the low amount of thermoplastic polymer coating compared to the base paper material, the meltable material alone is not sufficient to close the channel leak at the transition between cross and fin seals when producing pouch packaging. Therefore, this paper focuses on the influence of the thermomechanical material properties of the seal coating, the paper layer structure and process parameters of the heat‐sealing process to reduce the channel leak at the layer transition area. Regarding the technologically based measures, the focus of the study is on the application of a deformable layer on the sealing jaws and the localization of sealing pressure by profiled sealing jaws. It is shown that the amount of thermoplastic material flowing into the channel leak highly depends on the thickness of seal coating and the melting behaviour of the applied coating. For the selection of suitable heat‐sealing parameters, sealing pressure on the paper material and temperature of the jaws must be considered. By applying a deformable material layer on one side of the sealing jaws, the closure of the channel leak at layer transition area is significantly reduced. Finally, with the use of certain deformable materials, a complete closing of the channel leak at the layer transition area is achieved on a laboratory scale.