Paper and cardboard are porous, fibrous and natural materials which, without the application of one or more barrier layers, are of limited suitability for the packaging of e.g. foodstuffs, cosmetics or medicines. Sufficient barrier properties against various media and substances, such as oxygen, water vapor, aromas, fatty and oily substances, are an important factor in successfully using paper as a packaging material in a broader range of applications. Therefore, paper and board are often (extrusion)coated with synthetic (petrochemical) polymers that are non-biodegradable and difficult to recycle. In recent years, there has been intensive research to use bio-based materials as a functional barrier in the production of paper and board, thereby partially or completely replacing petroleum-based materials. This has mostly involved the use of existing coating technologies for paper and board, such as a film press (for water-based coatings) or extrusion (for thermoplastic coatings). These efforts have had limited success because, on the one hand, biobased coating materials are currently only available on the market to a limited extent and, on the other hand, it has often been technically and technologically impossible to process biopolymers in the same way as the conventionally used synthetic materials.
In this project, barrier coating with biopolymers using spray technology is investigated to explore a new way of paper surface functionalization.The working hypothesis, based on an extensive literature review and our own preliminary work, is that spray coating of paper and board with biopolymers is an economical, flexible and easy-to-integrate process into paper production and processing that can enable the production of plastic-free, paper-based and sustainable packaging materials, and in this respect is superior to currently used production processes. The objectives of the project are to scientifically investigate spray coating technology as a versatile coating process for the functional surface coating of paper and board with biopolymers and to explore the behavior of bio-based barrier materials in this process. In order to systematically explore the applicability of spray coating technology as a potential coating process for biobased barrier materials, important process parameters, such as droplet formation, droplet impact, homogeneity of the spray jet and wetting of the paper surface with the droplets, will be investigated as a function of the material used, rheology and solids content. Due to the possibility of application of biopolymers in addition to existing coating processes, multiple surface-coated concepts will also be investigated, which could markedly improve barrier properties (water vapor, grease, oxygen...). In addition to a comprehensive analysis of barrier and processing properties, the packaging materials produced in this way will also be evaluated in terms of recyclability and compostability, thus enabling the further development of completely plastic-free packaging materials purely from renewable and natural raw materials.