BOBST, Brückner, and Mitsui Chemicals have teamed up to develop a mono-material recyclable retort solution for food packaging, featuring high barrier properties achieved through opaque metallization. Anrika Heermant, Senior Specialist at Mitsui Chemicals Europe, explains that maintaining a high barrier in retort solutions has traditionally required a composite layer structure made up of polyester, aluminum foil, and other materials.

Source: PackagingEurope

The primary challenge in creating a mono-material solution is preserving the barrier qualities during the retorting process, which occurs at very high temperatures. Willi Lindemann, a specialist in inline coating and New Technologies at Brückner, adds that transitioning to mono-material polypropylene poses another challenge due to the risk of shrinkage, which could adversely affect the barrier properties.

Nick Copeland, R&D director of Barrier Solutions at BOBST, notes that the goal of the companies was to develop an “ultra-thin, stretchable, heat-resistant” barrier primer combined with advanced opaque metallization. Brückner supplied the inline coating technology to stretch the primers and create very thin layers, focusing on achieving the appropriate hardness of the coating material to ensure it remains stretchable and can endure retort conditions.

The Bobst Expert K5 vacuum metallizer, featuring AluBond technology, was utilized to enhance barrier performance, adhesion, and maintain surface energy over time. Mitsui contributed its water-based Takelac polyurethane dispersion and top coating grade to further improve barrier performance and protect the AluBond layer. The company also introduced a newly developed Takelac Primer grade designed for heat resistance.

The partners have reportedly reached proof of concept for the solution and have conducted tests on the Oxygen Transmission Rate (OTR), Water Vapour Transmission Rate (WVTR), and adhesion levels before and after the retort process, yielding “excellent” results. Additional partners may be brought on board in the future to ensure the solution is robust, repeatable, and ready for production.

Related Developments in Sustainable Packaging

In other news, Siegwerk, Borouge, and TPN Food Packaging (TPN) have collaborated to create a fully recyclable, mono-material barrier stand-up pouch designed to offer robust protection and superior functionality. This solution aims to fulfill the requirements of converters, brand owners, and consumers seeking sustainable, high-performance packaging for oxygen-sensitive, dry products such as nuts and pet food.

Last month, Coveris unveiled its new resealable mono-material tray for refrigerated food applications, intended to replace non-recyclable, mixed-material packaging while ensuring extended shelf life and consumer convenience. This solution is ideally suited for processed meats, sausages, dairy products, cheese, and other chilled or refrigerated items.