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09. April 2010

Thinner films and more functional packages

Packages may not be able to speak yet. But if they were, they would tell the consumer when their contents have reached their sell-by date, where and at what temperature the packaged product has to be stored and the applications it is intended for. All the same, modern packages already come with all this information. Intelligent packages that satisfy many criteria in addition to supplying the necessary consumer information are on the advance – and not only where foods are concerned. The plastic film industry has therefore been hit much less hard by the 2009 economic crisis than other branches of the plastics industry.

It’s flexible packages, i.e. film packages, that are in particularly strong demand because of the low cost of materials and production and their broad range of applications. Low in weight, they help to conserve resources while also offering plenty of scope for recycling. Film packages are replacing their rigid counterparts in many applications and conquering new market segments thanks to their constantly growing functionality. Even today, plastic films meet about three quarters of global demand for flexible packages and with a growing trend at the expense of paper and aluminium foil. According to a study by the US Freedonia Group, global demand for flexible packages will rise by an average of about 3.5% per annum in the coming years from a good 16milliont in 2008 to ultimately almost 19.5 million t in 2013. The market researchers are forecasting the fastest growth in the developing regions of Asia, Latin America, Eastern Europe and Africa as well as in the Middle East. The biggest volume growth, Freedonia anticipates, can be expected in China – the country that has meanwhile overtaken Japan and is now, after the USA, the second biggest market for flexible packages. The growth expected in India, Russia and Indonesia is also strong. However, the already saturated markets in the USA, Western Europe and Japan will temper a global boom in film, Freedonia claims. Furthermore, the technical scope for achieving the same applicational properties with increasingly thin films will also check the increase in the processed volume. For instance, a nappy film weighed 30g/m² a few years ago; today, at 14g/m², it now weighs less than half. The use of flexible packages in the food and beverages industry and in the pharmaceutical and cosmetics industry is encouraged by the materials’ hygienic qualities and long shelf life. The further development of breathable films, microwave- and freezer-safe films, and biodegradable films is also spurring their growing use.

Industrial films usually three-layer

“Industrial films” is the term usually given to those films that are employed, for example, as shrink film hoods, stretch films or as packaging for industrial goods; and to films sold by the film producer to industry as raw stock for converting. For the production of industrial films, polyolefins are mainly used and chiefly grades of PE. While monofilms are still widely used for certain products such as shrink film hoods – and this is unlikely to change – three-layer film composites have become established among industrial films. By combining two or three different types of polymer, it is often possible to save on material while enhancing functionality at the same time. Particularly when it comes to the production of blown and cast films, it is the cost of the raw materials employed that are the key to the cost-effectiveness of the overall production line and thus to the profit made by the producer. Plastics processors specialising in the production of industrial films operate their production lines around the clock. Product changeovers therefore tend to be rare. For such applications, many makers of machines today sell standardised three-layer installations at attractive investment prices. The Troisdorf-based OEM Reifenhäuser GmbH has had an inexpensive three-layer blown film line from its Chinese plant in Suzhou in its portfolio for several years now. Since autumn 2009, Windmöller & Hölscher KG (W&H) from Lengerich has also had in its product range a three-layer line by the name of Optimex with which it hopes to appeal to manufacturers of standard products.

Consumer packages defy the crisis

Unlike companies in the industrial film value chain, who have been affected, though not seriously, by the crisis, manufacturers of consumer packages cannot complain. More and more products are being packaged in flexible and semi-rigid rather than rigid packages and a growing number in plastic rather than paper, cardboard or metal. This applies to both the non-food and the fast-growing food sector. In the industrialised nations, the reasons for the increasing use of flexible food packages made of plastic are not only ecological and economic, but can also be found above all in changing consumer habits. There is constant growth in the consumption of ready-to-serve meals, a trend due not only to the growing number of single-person households, but also to more and more women working and a certain aversion to cooking. Convenience is the magic word. The consumer wants a healthy and balanced diet with minimum preparation effort – and without having to make a time commitment. New trends are also resulting from the fast-expanding range of foods. Irrespective of the season and local harvest, fresh vegetables, salads, and domestic and exotic fruits have become daily fare. Finally, there is a growing desire for an appealing exterior with a highly transparent, glossy or also colourfully printed package and an if possible distinctive shape. Obviously these changes are imposing growing demands on the package itself and hence on raw materials producers, machine makers and packaging material manufacturers and call for a maximum of flexibility.

Good die technology boosts efficiency

Extrusion line manufacturers are attempting to give the processor this flexibility by enabling him to produce as many different products as possible with a single line. Kuhne GmbH in St.Augustin, for example, is marketing a five-layer coextrusion line with which both conventional three-layer standard films and five-layer barrier films can be produced without retooling. This has been made possible by using five extruders, all of which are equipped with a barrier screw suitable for any type of material. In connection with extruders, two decisive innovations ought to be mentioned. In both cast and blown film lines, virtually all machine makers today use energy-saving and maintenance-free AC motors or, in some cases for reasons for space, direct drives instead of conventional motor-gearbox versions. Especially for cast film lines, some companies have in their portfolios so-called high-speed extruders that achieve high throughput by virtue not of their size, but of their elevated speed of rotation. Battenfeld Extrusionstechnik GmbH in Bad Oeynhausen is making its mark with a 75mm extruder. With its installed power of 440kW and 1,500 rpm, it achieves an extruder rate of 2t/h in the processing of PP and as much as 2.4t/h with PS. Always a crucial element in the production of blown films is the blow head. Together with suitable film cooling and gauge control, it ensures a high extruder rate and film quality. Most recently, the improvement of film cooling has been the goal of many refinements. For instance, K-Design in Königswinter has introduced a novel air ring that works on the counter-flow principle. One air current counter to the direction of film feed pre-cools the film, while upward air currents handle the rest of the cooling like a traditional dual-lip air ring. Compared to conventional air rings, this new approach permits markedly superior line performance and, thanks to its improved bubble control, optimises the film’s mechanical properties. W&H recently unveiled its new single-deck Opticool air ring system whose cooling performance is said to surpass that of a double air ring system. Extremely rapid cooling can also be achieved with the Aquarex, which is also from W&H. In this upside-down wet three-layer blown film line, the film bubble is cooled with the aid of a film of water. This way, films of exceptionally high transparency can be produced, such as those in demand for pharmaceutical applications. Overall, it can be concluded that film composites have become established for consumer packages and particularly food packages. Five-layer films are standard, and seven- and nine-layer composites are by no means rare today. Extrusion Dies Industries LLC, Chippewa Falls, WI, and Cloeren Inc., Orange, TX, both from the USA, have even developed systems capable of producing cast films in an almost unlimited numbers of layers. While Cloeren markets what it calls a nanolayer feedblock for up to 27 layers, EDI presented a flat die system with layer multiplication at the last NPE. It converts a typical sandwich structure from a conventional coextrusion feedblock into a sandwich in which one or more layers in turn consist of several microlayers. Both systems help to improve film characteristics and particularly impact resistance, stretch and barrier properties against oxygen and moisture. The range of applications of such systems extends from industrial films to barrier packages. At K2010 from 27 October to 3 November in Düsseldorf, Germany, many of these new developments will be on show.

Bio- and recycled materials conquer food packages

While grades of polyolefin combined with barrier materials such as polyamides and EVOH are usually employed on a blown film line for the production of food films, PET has long established itself as the “mass plastic” for cast films. This is explained by its good mechanical properties and above all by its outstanding transparency and high amenability to further processing techniques such as thermoforming. The endeavors of many companies to efficiently recycle PET came to fruition some time back in the form of successful recovery processes. One obstacle, however, continues to be the approval of grades of so-called rPET (recycled PET) for repeat use in direct contact with foods. Already established are many processes for the production of multi-layer film composites in which rPET is employed as the middle layer. Thanks to ongoing improvements in machine technology, rPET can now be used in direct food contact. The British company Sharp Interpack in Aylesham, for example, operates a production line with a capacity of 1,500 kg/h on which it produces packaging films from post-consumer wastes. Thanks to the use of a V-type screen changer from Kreyenborg GmbH in Münster, Germany, which removes even the finest impurities, the manufacturer has obtained PIRA certification of its film for the food sector. The films produced from ground PET bottles on a Vacurema inline sheet line by the Austrian companies Erema GmbH, Ansfelden, and SML Maschinengesellschaft mbH, Lenzing, have also received a food approval. This approval was recently extended to rPET from Erema’s Vacurema recycling lines and now even applies to packages for deep-frozen ready-to-serve meals. Biomaterials have been on the advance for some time now, but only recently in connection with food packages. As the world’s first film maker in the packaging sector, Alesco GmbH & Co. KG from Langerwehe has been including carbon-neutral film products made of PE and from renewable resources in its product range since the beginning of 2009. The company has since launched a biofilm printed with solvent-free waterborne inks and a compostable shopping bag made from renewable raw materials. And, in time for Drinktec 2009 – again a first – it presented a compostable shrink film made from renewable raw materials. The driving force behind the expanding use of biomaterials is the desire for resource conservation and compostability. Although the concept of sustainability is closely associated with biomaterials, it still has to be settled in each case whether a biodegradable material or a material based on biological raw materials is in fact greener and more sustainable than a conventional plastic. Biomaterials’ frequently hailed carbon-neutrality only really holds, says RWE SE, Frankenthal, if the manufacturers include purchased emission certificates or the installation of wind farms in the calculation. A drawback of film packages made of biomaterials is their higher weight compared to conventional PE, a fact due to their up to 30% higher density. Furthermore, biomaterials call for a higher input of energy in production. Growing environmental awareness and the discussion of the pros and cons of various categories of materials have at any rate accelerated innovation in packaging made of plastics. It goes without saying that the goal is a sensible and resource-conserving treatment of all raw materials.

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