K 2007 Trade press conference
July 3 and 4, 2007 in Frankenthal, Germany
Soft drinks in designer clothing or
shrinkage the easy way
Styrolux HS 70: a new SBC block copolymer for shrink film
used in packaging
Presentation by Dr. Daniel Wagner,
Technical Product Manager Styrolux,
BASF Aktiengesellschaft, Ludwigshafen, Germany
Under the brand name Styrolux® HS 70, BASF is now providing the packaging market throughout the world with a novel product that has been optimized especially with an eye towards the requirements made of high-grade shrink film. Shrink film can give beverage bottles a particularly attractive design, thus making them appealing to the senses and enhancing their selling power. This novel extrusion grade on the basis of styrene-butadiene block copolymer (SBC) expands the Styrolux range by one more specialty that comes on the heels of the introduction of Styrolux 3G 46 in 2006. The development of this new grade was triggered by global market trends in the packaging industry as well as by the increasing demands being made by film producers and final consumers. Styrolux HS 70 was developed in close cooperation with leading manufacturers of machinery and films.
High market growth and driving forces
The current global market volume of 2.4 million square meters of film and projected growth rates of well over 10 percent in the coming years means that shrink films constitute an extremely attractive segment of the packaging market for consumer goods. Today, more than 80 percent of the shrink films go into upscale sleeve packaging for food such as dairy products, soft drinks and alcoholic beverages. Aside from this, more and more household articles, cosmetics and pharmaceuticals are being packaged in sleeve films.
The driving forces behind this dynamic evolution of the shrink film market are the rising expectations in terms of product differentiation and branding as well as the desire for ever more sophisticated presentations of the final-consumer products on the shelves. But regulations – which vary from one region to another – concerning the product information are also raising expectations in terms of the printing quality and the visual appearance of packaging with sleeve films. Additional benefits are provided by special, integrated functionalities: Completely shrink-wrapped packaging provides protection against manipulation such as unauthorized opening. In the final analysis, shrink films are a very cost-effective alternative to directly printing on bottles and they allow a wide variety of looks along with a standardization of the containers, which further cuts costs.
Advantages of the new plastic
The new product stands out especially for its optimized shrinkage behavior. Until now, SBC/PS blends could only be employed for films having an average final shrinkage of about 50 percent within the relevant processing window ranging from about 80°C to 95°C [176°F to 203°F]. Thanks to a novel product design, BASF has now succeeded in markedly increasing the final shrinkage. Styrolux® HS 70 allows shrinkage values of 70% to 80%, which is a relative improvement of more than 50%. Only this high final shrinkage allows form-fitting sheathing (also called “sleeves”) of bottles having complex geometries or large radius differences such as, for example, champagne bottles. This optimized product also exhibits a steady but not overly steep increase in the shrinkage as the temperature rises, thus offering a wide processing window. BASF delivers this plastic as a ready-to-use product: it no longer needs to be mixed with standard polystyrene, and this is very convenient for film producers. Besides, Styrolux HS 70 is even more transparent than its predecessors, it offers an improved stiffness and can be easily printed on.
In comparison to others
Aside from the SBC/PS blends, for the most part, the transparent packaging materials PET-G (glycol-modified PET) and PVC are employed nowadays for shrink films. Whereas conventional SBC/PS blends have about the same shrinkage level as PVC, Styrolux® HS 70 now yields final shrinkage values that are close to those of today’s industry standard, PET-G. Another advantage of Styrolux HS 70 is its high efficiency. Thanks to its lower density, approximately 30 percent more film per kilogram can be produced in comparison to PVC or PET-G. Processors benefit from the fact that this product lends itself very well to machine-processing and also that the tough-rigid nature of the styrene-butadiene block copolymers give the sleeves the soft and more pleasant feel that is so appreciated by final customers.
Processing: from plastic granules to the bottle with the sleeve
When shrink film is manufactured, the plastic granules are first melted in an extruder, then extruded through a cast film extrusion die and, usually, the film is then stretched transversally to the extrusion direction to several times its original width so as to reach the desired high final shrinkage. The new Styrolux® is not only very well-suited for this classic transversal direction orientation (TDO), but also for the machine direction orientation (MDO) for films. This degree of stretching, which is a co-determining factor for the final shrinkage, can be “frozen” by cooling off at the end of the line. Over the course of additional process steps, the sheet of film is cut, printed, shaped into a tube and glued at the seam. The continuous tube thus created is cut to the length of each bottle and then slipped over the bottle. In a shrink tunnel, the sheathed bottles are exposed to steam, hot air or IR radiation and thus absorb sufficient heat to cause the film to contract and wrap tightly around the contour of the bottle.
Photo: BASF, 2007
How can you quickly and efficiently turn a bare bottle into an individualized object that appeals to the senses? Shrink film made of BASF’s new plastic, Styrolux® HS 70, a styrene-butadiene block copolymer (SBC), can be used to completely wrap bottles, even those with odd shapes. BASF developers have given this new material precisely the temperature behavior that is needed for this type of packaging.