Growth opportunities in blown film extrusion
Market and consumer demands on blown films are increasing, and more and more functions have to be integrated in the product. In many cases, this can only be achieved by increasing the number of layers in the film.
This summer, US packaging specialist General Films, plans to increase its production capabilities with a line for nine layer blown film. The company hopes this investment will give it a competitive advantage on overseas markets, especially as the film types are grades with a particularly high barrier effect. The new line, to be supplied by Battenfeld Gloucester, will allow it to produce more complex structures for a range of customers. It can be used to process various PA, PE and EVOH materials, as well as opening up opportunities such as in-line production of bags and the manufacture of tubular films.
The demands placed on plastics films used for food packaging have risen constantly in recent years and have now reached a level which can only be met by employing a variety of measures. Whereas in the past, three and later five layer films were enough to meet specific packaging criteria, today films with in some cases seven or even nine layers are needed. Lines which can blow 11 layers simultaneously have been on the horizon for some time now and are already said to be available as lab prototypes. These multiple layers are essential to ensure the whole range of functions such as protection from sunlight and oxygen, guaranteed taste and aroma, effective barrier properties, sealability and printability.
As the number of film layers increases, so too do the organizational demands on the production line. To maintain the flexibility of the overall operation, most suppliers favour modular design. Another major aspect is control of the system: reliable and fast acting controls are essential for continuous reproducibility of film properties.
According to Reifenhäuser, the large raw material capacities in the Gulf and Asia Pacific regions, as well as the desire for high film quality and high cost efficiency, require new line concepts. The company has tested new components, various processes and raw materials of different formulations under real production conditions in its own technology centre. Use of the recently developed Rei2cool cooling system in combination with an optimized blown film die and low temperature screws is said to have achieved performance increases of 20-35 per cent.
Another way of improving the cost efficiency of blown film lines is to replace the conventional three layer with five layer films. Reifenhäuser has developed a special die for this with spiral mandrels designed to produce very thin layers. This offers great flexibility in the production of polyolefin films and processing of barrier materials such as EVOH, PA and CoPET. For the user, it opens up new opportunities and paves the way to reduce raw material costs and improve the mechanical properties of the film.
According to Battenfeld, advancing globalization will result in increasing mergers and take-overs among converters. It will also increase worldwide pressure on prices and result in further price falls. Companies’ strategies will differ. Some will want to reduce their own engineering within a leaner organization, others will want to intensify their already significant technological know-how.
Windmöller & Hölscher recently unveiled a five layer blown film die – the Maxicone – that could eventually replace conventional three layer dies. W&H also supplies a nine-layer Maxicone die whose patented conical spiral mandrel, it claims, offers extreme layer ratios, perfect distribution of the individual layers, short residence times and high output rates.
Kiefel says it sees major growth opportunities in multilayer film extrusion. Lines for the manufacture of barrier films with up to nine layers are one speciality of the company, which was recently bought by the Brückner group. Last year, it unveiled a module to upgrade its Kirion systems. The Machine Direction Orientation technology allows targeted monoaxial stretching of films and film structures.
According to Kiefel, this is an easy and effective way to endow both blown and cast films with special properties. An MDO line consisting of heating zone, stretch zone, temperature control and cooling zone will support converters in their efforts to reduce film thicknesses and save raw materials, and ultimately costs, the company states. Monoaxial orientation of the film also increases the barrier effect against gas and water vapour, and improves the optical properties of the film.
All of these developments can be checked out at K 2007 next month (see our show preview in the Exhibitions section).