CUT! ITS A WRAP
Most label converters are unfamiliar with film wrap-around labelling. Yet, as a recent conference showed, the technology has much potential in many branded end-use applications, not least for plastic bottles and even beverage cans using shrinkable labels.
With 360˚ exposure, wrap-around film labels are proving popular with a growing number of end-users, striving to create instant brand recognition for their products. The labels are versatile enough for applying to glass jars and bottles, metal or cardboard cans and many types and shapes of plastic containers. One particularly growing application is labelling plastic bottles for branded carbonated drinks as replacements for paper labels.
Adhesion between film label and container is usually effected by a narrow hot-melt strip transferred to the label’s leading and trailing edges. The label is then tightly wrapped around the container, which rotates constantly at a controlled speed on high-speed rotary machines. Shrinkable types of film wraps are being developed. They are seen to have a large potential for labelling smaller volumes of beverage cans and certain aerosols as an alternative to direct decoration.
A Cowise conference held in Amsterdam – Developments in Wrap-Around Film Labelling – gave the subject its first public airing. Delegates learnt that as one of 15 adhesive and non-adhesive labelling methods, wrap-arounds have the highest annual growth at around 25 per cent. The closely-related in-mould labelling technology has 15 per cent, while shrink sleeving has 20 per cent. However, these levels stem from an extremely small base and collectively they have only about 5-6 per cent of the total labelling market.
Nevertheless, it is an important niche sector that also thrives on the back of the phenomenal growth of plastics in packaging. In fact the fastest growing sectors in all labelling technologies are all non-paper (notably filmic pressure-sensitives) with a double-figure growth rate that almost correlates with that of plastic containers. By contrast growth for glass containers is only some 1.5 per cent annually in Europe.
The growth of PET containers linked to end-use globalization and the evolution of oriented polypropylene (OPP) films technology are driving forces for roll-fed film labels. This was the theme of a comprehensive paper by Rob Carter of AET Films (the formerly spent many years promoting OPP in Europe with Mobil’s Films Division).
PET resins are readily available and benefit from pricing stability. World capacity is expected to exceed 8 million tonnes by 2000 – up from 5.7 million tonnes in 1997 – with the Asia Pacific region accounting for most growth. Consumers in Western Europe and North America accept containers made from PET: they do not break like glass and unlike metal cans are reclosable. Their lighter weight saves freight costs for packagers. New resins and barrier coatings give improved temperature resistance and better oxygen and carbon dioxide characteristics for selected ‘hot fill’ applications.
While recognising that glass bottles were the prime choice for premium beers, Carter said PET containers were emerging as a real threat to refillable glass. Again, the new coatings could make a huge difference to how the beer industry viewed these containers, which could concern producers of steel and aluminium. ‘In any event, whether we label their plastic containers or cans, roll-fed labelling of these products could emerge as a significant new and important end-use for films.’
He added that this technique accorded with modern patterns of shorter manufacturing cycles, increased promotional activity and moves to keep inventories to a minimum. Container decoration increasingly had to be compatible with shorter runs and the need to change graphics frequently.
Wrap-around labelling began as an extension of the paper label market: cut labels fed from a magazine. But applied with hot-melt adhesives. From the early 1970s in the USA, glass gave way to unbreakable PET and transparent OPP films laminated to paper superseded coated paper labels. Eventually white and mould-free OPP films became the mainstay of the US market, backed by new types of roll-fed machines.
He acknowledged that converter-friendly PVC films have also had exceptional growth. A propensity to shrink and conform to containers, while also including tamper-evident features, had led to the significant sleeve labelling sector. Clear and opaque polyethylenes had also emerged as paper and OPP substitutes, while cast polypropylenes, special opaque PEs and white foamed polystyrene had entered the roll-fed film labelling market.
Famous brands, notably Coca Cola and Pepsi Cola, boosted the transition from paper and successful evolution of OPPs in carbonated soft drinks (CSD). This market alone accounted for an estimated 31 million tonnes of OPP for roll-fed labelling in 1996; some 85 per cent consumed in Western Europe and North America. Improved opacity has eliminated the need for white ink, while label converters have learnt to print and/or laminate the material at high speeds, while maintaining the tight repeat-length tolerances essential for high-speed labelling.
Gravure is favoured for printing wrap-around labels in Europe, but following the US pattern high-quality flexo was an emerging trend here and in the Middle East and Pacific Rim. White opaque and transparent films were in demand for both processes.
According to Carter, one of the most significant trends is roll-fed shrinkable labelling since it embraces all kinds of containers, from glass to beverage cans. AET and its predecessor, Hercules Film Group, had pioneered shrinkable labels films. By early 1990 it had a range of transparent and opaque films suitable for various contoured containers. Mobil introduced a line of shrinkable OPP films in October 1996. Between them they have helped establish this method’s creditability to embrace beverage cans, aerosols and glass containers as cost-effective alternatives to direct decoration or other labelling methods.
He acknowledged that the shrink film decorated can still had some way to go in operations where labelling before filling was mandatory; a dearth of proven pasteurisable hot-melts was one reason. Anheuser Busch had successfully used an adapted Krones Contiroll Can machine in a pre-fill shrink label operation and the Warstein Brewery in Germany was testing a similar machine with shrinkable OPP.
He concluded a fact-packed presentation by forecasting a phase of even greater innovation, with continuous evolution in machinery and substrates. ‘We know that container shapes are set to undergo radical changes and that we will need films of far higher specification to decorate them – in part or completely. Emerging polymer technology will realise resins and films to allow the total shrouding of containers at high speed on new generation shrink machinery. This will ease the adoption of films for beer and soft drinks cans and containers, whether of metal or plastic.’
Also waving the OPP flag was Richard Britton of Hoechst Trespaphan UK, which makes the extruded films under the Eticourt name. He described the latest extrusion methods that produced four or five-layer films. These ‘engineered’ films offered more flexibility to meet specific demands, including two new 35 and 40-micron non-coated wrap-around films.
Britton also noted that while gravure dominated high-volume orders, there was a noticeable increase in the use of UV flexo and rotary offset for medium-volume runs. They could also produce the high-quality graphics needed for this market. Another application was for cut-and-stack OPP labels, applied to the glass or plastic container from a magazine like paper types and also printed sheet-fed offset. They would suit smaller application, while the global activities of the larger players will continue to drive forward usage of 35-40 micron films for rotary applications.
Dr David Tidmarsh of Applied Holographics related the mixed fortunes of holograms in wrap-around films. Several projects involving major brand names have been tried in collaboration with packaging designers, usually involving 2-litre PET containers. Problems have included the need to register print with holography, or vice versa, and the need to decide technical aspects of production.
‘We proved that the idea works. Statistics showed that on one occasion it boosted supermarket sales of a soft drink by 15 per cent. The anti-counterfeiting factor could provide an added incentive for holography usage as a joint promotional device.’ He added that at present holograms were less effective with shrink wrap-around film, since the image disappeared at the label’s extremes.
Delegates quickly appreciated that wrap-around labelling requires particularly close co-operation between all concerned, from design to application, Franck Steverlynck of B & H Labelling Systems, which pioneered the idea of applying web-fed labels, touched on this point. New types of containers in different materials and produced with different processes required new types of labelling machinery. The various film labels became part of the manufacturing process and defined the technology to use. That is why companies like his had to work closely with the printer and end-user, he said.
Designers played a key role in ensuring effective labelling. Johan Michiels of Barco Graphics showed how they could compensate for image distortions in shrinkable labelling, using electronic origination and grid-type warp tables. He also described Barco’s Kaleidoscope Plus colour management system, based on the reflective and transmissive characteristics of the ink not the print process.
Nothing the shift from gravure to flexo in packaging printing, he said the DuPont/BG Cyrel Digital Imager gave a fully digitised approach to platemaking. The latest Compact version, again with a laser ablation imaging process, opened narrow-web CTP for flexo.
Later, Helger Neumann of BASF was to cover similar ground by describing the Digiflex system, which can use various types platesetters including those from Barco. It uses similar photopolymer plates with a protected black exposure layer on a relief layer. Film-less processing obviously reduces this expense, but it also obviates vacuum drawdown and scattered light while reducing the risk of dust and static. As mentioned in previous issues, flexo CTP can give marked increases in platemaking quality, including an 8-10 per cent reduction in mid-tone dot gain for sharper results. BASF also offers a thin-plate sleeve version of Digiflex, which reduces mounting time and offers more accurate colour register.
Wrap-around labels are printable by all the main processes on paper and different films (involving either reverse printing or surface printing and laminating). This gave Niklas Olsson of Akzo Nobel plenty of scope to describe the various UV-curable and conventional ink types. Even UV-curable gravure inks are possible, although demand remains small.
A crucial property of UV curing of thin unsupported films was to formulate inks that adhered to the surface, but at curing speeds that did not create too much shrinkage. The ink molecules of cured ink were more tightly-packed then in a wet form, which could cause curling and slow the feeding process.
Other demands included good colour strength, opacity, printability and adhesion to non-corona treated PE, PP and PS. The inks should not crack following stretching or wrapping, have a resistance to moisture and various liquids, be free of odour and not cost too much. ‘Don’t take risks that may jeopardise the end-products and image, Work closely with your supplier to be on the safe side.’
One session dealt with the intricacies of both roll-fed and cut-and-stack applications. Oliver Rebours of Trine Labelling explained how his firm had developed a glueless leading edge method as an option for one of its hot-melt machines. Josef Wolf of Krones described the latest techniques possible on its Contiroll machines. The fact that rectangular labels are produced more economically in reel format than in the traditional pre-cut method was encouraging interest in reel-fed labelling. Reels of either paper or film labels are also easier to handle compared with packaged lots of pre-cut labels.
Wolf reiterated the popularity of film labelling. ‘Its real benefit have become apparent during the last few years, following the development of high-quality materials printed with suitable printing techniques. Also, in application procedures capable of decorating non-cylindrical containers, such as beverage and aerosol cans. In these cases, the labels are thermally treated to shrink and conform to the curvature of the containers. Compared with using pre-printed cans, the benefits of this method are obvious. Besides drastically reduced warehouse space, labelling of cans increases flexibility when reacting to market requirements or changing the looks of a product in response to consumer behaviour.’
Like other speakers, Wolf felt that wrap-around labelling was attuned to the changing needs of changing markets. It depended, however, upon closer liaison down the line between all parties to achieve the innovation required to meet new challenges. Applications will increase in volume and new materials will be employed to satisfy the needs of bottlers and canners worldwide.
At present around 1,200 packaging plants in Europe use some form of wrap-around labelling, with 2,000 machines in use. During an earlier open forum, Rob Carter said, unequivocally, that 48 plants in Europe were producing wrap-around labels. Some 60 per cent were gravure printers, the rest were conventional flexo with some narrow-web presses involved. Rotary UV offset was an unknown commodity. Some sheet-fed offset printers with in-mould label experience had moved into the cut-and-stack market.
European film printers usually converted reverse-printed single webs, whereas North American plants favoured higher gloss laminated webs. They had more experience in using dedicated films with in-built consistency. Apparently, this factor was less of a problem for end-users seven years ago. Now many more more label converters source film from different suppliers with variable results.
Where will wrap-around labelling be in five years time? The consensus is that there is still much untapped growth. Film manufacturers are particularly aware of the potential in South East Asia and Latin America.
They expect to take market share from paper, while anticipating many completely new markets.