Following the launch of a universal adhesive for beverage cans in mid-2023, KHS is now offering this same Nature Multipack technology for plastic bottles. This has increased the possible uses of this technology, one of the most environmentally-friendly forms of secondary packaging currently available on the beverage market.
KHS universal adhesive joins beverage containers with just a few dots of adhesive without the use of any shrink film. It can be used on practically any shape, size or material thickness. This is facilitated by a special process where the adhesive is foamed during application to the containers. According to Dr. Matthias Caninenberg, Head of Nature MultiPack Technology at KHS, “This is a principally proven technology that’s been used for many years in the production of foam for mattresses or seals in car manufacture, for example. In our case we face 2 challenges. One of these lies in the process technology, the aim of which is to reconcile 3 different objectives: protection of the container wall against damage, simple handling and safe transportation of the pack.”
3 objectives: a triangle of tension
In order to effect the perfect balance in this “triangle of tension”, as Dr. Caninenberg calls it, nitrogen is added to the adhesive on the KHS Innopack Kisters NMP packaging machine before this is applied to the full PET bottle. During application, the previously pressurized gas expands and foams the adhesive. This gives the glue a higher elasticity that has 3 benefits:
Firstly, it is easier for consumers to separate the bottles from one another. Instead of containers suddenly snapping apart, the adhesive is compressed and peeled off much more slowly during opening. This gives people the impression that even less strength is required to unstick the containers – even though very little was needed before. Practical application is thus as simple as with the previous pack.
Secondly, the outer wall of the PET container is subjected to less stress when the pack is opened, meaning that even with lightweight bottles with a very low wall thickness overload and damage are more or less totally ruled out.
Thirdly, as the adhesive and thus the pack are more flexible, the forces applied along the logistics chain can be better absorbed and compensated for without the pack being damaged.
The second challenge concerns the machine technology. “The gas/adhesive mixture must be homogenous in its distribution to the applicators. To this end, we’ve developed an optimized pressure nozzle with the help of modern production facilities. What’s more, our machine operates within an extremely narrow tolerance range in order to perfectly maintain the aforementioned triangle of tension. The very first shot has to hit the tolerance window,” said Dr. Caninenberg. “The machine and process technology must of course function reliably for this to be the case.”
Meanwhile, the new setup has two further pluses to offer when it comes to the recycling of the PET containers. When separated from the container, the dots of adhesive do not leave any notable sticky residue behind and thus do not cause any disruptions when fed into bottle deposit machines. Moreover, the density of the adhesive is greatly reduced by foaming, enabling it to rise to the surface much better when washed off during the actual recycling process. This makes it even easier to remove this material from the recycling loop.
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