Mono material film structures is the name of the modern solution for all packaging applications that require both high performance and environmental friendliness. However, the production of full PO films poses challenges for plastics processors: they have to adapt and expand their manufacturing equipment and meet all the requirements of the food industry. With its Triple Bubble® technology, Kuhne Anlagenbau GmbH from St. Augustin, Germany, now offers an ideal solution to all film manufacturers for the economical production of uniformly oriented mono-material films that are both high quality and directly sealable.
“We have been building Triple Bubble® blown film lines for over 20 years and thus have an enormous wealth of experience both in terms of machine technology and formulation development,” emphasizes Jürgen Schiffmann, Managing Director of Kuhne Anlagenbau GmbH. “We have now transferred this know-how advantage to five-layer full polyolefin film structures and are thus offering an alternative that has many advantages over conventional blown film lines with MDO stretching units”.
Kuhne Anlagenbau carried out these developments in its in-house technical center, which has a modern but small 13-layer triple-bubble R&D line with an output of around 250 – 300 kg / h for a maximum double film width of 900 mm. During the extensive tests, the machine technology for manufacturing the five-layer structures was optimized and suitable formulations were tried out. The result is a uniformly oriented film, optionally as a full PE or full PP barrier film structure. The main advantages of these film structures are their sealability and their waste-free, and thus more efficient and environmentally friendly, production.
Nowadays there are only a few packaging solutions without a barrier function, especially when it comes to the packaging of food or pet food. “The term mono-material structures is somewhat misleading,” explains Jürgen Schiffmann, “because all commercially available full PO films contain up to five percent foreign material in order to achieve the desired barrier properties.” In detail, this is what the Kuhne solution looks like: The sealing layer consists of commercially available sealing materials such as metallocene PE or plastomers, the inner EVOH barrier layer is enclosed by two PE-based tie layers and an HDPE blend is used for the outer layer. “With the same line configuration, we can also produce a mono PP film without any modification,” emphasizes Jürgen Schiffmann. The technology is just as flexible in terms of the film thickness, which can vary between 15 and 150 µm, and in terms of the film properties. Film shrinkage is also adjustable, depending on whether the film is to be used for stand-up pouches, coffee and snack packaging, which require non-shrinkable films or for lid films, which require slightly shrinkable films. For bottom web film in the food packaging sector, the films can also be designed to be thermoformable and even deep-drawable and shrinkable for form-shrink applications.
Since the films are produced using the Triple Bubble® technology they have the same properties and thickness over the entire circumference, so that neither a neck-in nor an edge trim occur. In the first bubble the film tube is rapidly quenched with water in order to achieve ideal amorphous properties, in the second bubble simultaneous biaxial orientation is imparted and in the third bubble the annealing takes place.
An ecological solution! The solution from Kuhne Anlagenbau also eliminates the need to laminate an MDO film with a sealing layer, which is usually necessary. “Our films are directly sealable and can be processed further,” says Jürgen Schiffmann, adding another economic and ecological argument for the production of mono-material film structures with Triple Bubble® technology.