Sometimes you can have the best of both worlds. New mineral water bottles from Germany-based Vilsa will soon hit the shelves in Germany. They use KHS’ FreshSafe PET technology that combines the advantages of polyethylene terephthalate (PET) and glass.
The technology coats the inner wall of the PET bottle with a completely transparent, wafer-thin protective layer of silicon oxide (SiOx), or chemically pure glass. The result is an effective barrier that retains aroma and carbon dioxide whilst preventing oxygen from penetrating the bottle resulting in no loss of vitamins or taste.
After preform infeed, stretch blow moulding, cooling, and transfer the PET bottles are coated following the Plasma Impulse Chemical Vapor Deposition (PICVD) method.
During this stage, the containers are turned upside down and passed on to the coating chamber where a reaction gas mixture is introduced into the bottle in a fine vacuum and subsequently transformed into a plasma state by microwaves. At this state silicon oxide is deposited on the inside of the container. Once transported to Vilsa’s facilities, the bottles are stretch blow moulded and coated at a maximum rate of 24,500 containers per hour.
Vilsa’s mineral water is a premium product extracted from deep underground in Bruchhausen-Vilsen in the German federal state of Lower Saxony. All varieties of Vilsa mineral water have been organically certified since 2021 and are thus subject to strict threshold values and sustainability standards commonly applied on the German mineral water market.
A bottle that combines the low weight and robustness of PET with the superior barrier properties of glass was thus the best solution for Vilsa. The system protects the bottle against oxygen pickup and carbon dioxide loss, which both extends the shelf life and increases flavour stability. Moreover, the material is fully recyclable. During the recycling process the glass coating is washed off by the caustic in a standard procedure. This produces pure, separated PET which can be fully recycled. The coating can also be applied to recycled PET, which can then be recycled again.
The container’s suitability for use with foods has also been officially established by the U.S. Food and Drug Administration (FDA), amongst others. At less than 0.1 micrometres thick and chemically bonded to the inside wall, the interior glass coating is flexible. KHS claims it cannot be accidentally removed or flake off when force is applied to the bottle, with the coating only separating off during the recycling process.
The cooperation between KHS and Vilsa involved an intensive development process in the runup to the launch the new container sizes from 0.25 to 1.5 litres. The designs of the 0.25-, 0.5-, 0.75 and 1-litre bottles were already suitable for coating. The 1.5 litres bottle had to undergo minor changes to ensure its vacuum stability during the process, making it the first 1.5-litre FreshSafe PET bottle on the market.
“We ran extensive simulations to effect an optimum separation behavior of the reaction gas in the coating process and thus achieve perfect distribution of the wafer-thin glass coating in the bottle,” explained Stefan Knappmann, head of Sales for Germany and Switzerland at KHS. “Our bottles and shapes specialists defined the exact recipe for each container size, product and carbon dioxide level,” he concluded.