- Water quenched & bi-oriented film technology
- High level of molecular orientation due to biaxial stretching
- Surlyn as shrink layer, and also sealing layer
- Up to 13 layers / 1 tonne per hour
- Applications: multilayer shrink & lidding film
At Interpack 2014, Kuhne Anlagenbau presented its TripleBubble1 water quenched and bi-oriented film technology to show new ways to save material in multilayer shrink and lidding film applications. Cooperation partner DuPont developed suitable Surlyn grades which can be used either as a shrink layer or sealing layer.
TripleBubble1 shrink films typically consist of a PET or PA based outer layer, a structural layer based on DuPont Surlyn and a PE based seal layer, and can be enhanced with an EVOH or PVDC based barrier structure. Here, the partially crosslinked thermoplastic ionomer Surlyn allows high shrink, softness and perforation resistance. In general, the TripleBubble1 technology enhances the mechanical properties of such films due to the high level of molecular orientation brought about by biaxial stretching. Thermal relaxation which occurs in the third bubble of the process, where film shrinkage is reduced to a controlled value, is a particular challenge. Here, the effectiveness of the tie layer, which bonds incompatible functional layers of the structure together, is of major significance for producing high tear and puncture resistant films.
The most advanced and most widespread application of such shrink films is the production of shrink bags, used to transport meat on the bone from the slaughterhouse to retailers or restaurants. A new trend is to use shrink bags for supermarket consumer packaging. Such films adhere tightly to the meat without any protruding edges and improve colour, odour and meat texture. In addition, compared to tray-and-lid solutions, which weigh around 14g, shrink bags for retail applications only weigh 4g. To address this trend, DuPont and Kuhne have recently focused their joint development on using new, dedicated Surlyn grades to further optimize the shrinking and sealing performance of TripleBubble1 shrink bag and barrier shrink bag structures. Used not only as shrink layer but also as sealant layer, these new grades provide a good balance of puncture resistance, flexibility, softness, seal performance, transparency, and shrink behaviour.
A standard feature of all TripleBubble1 systems is quenching of the first bubble using water chilled to 4 to 6°C. This water quench technology was developed for the TripleBubble1 process by Kuhne in 1996 to permit significantly higher cooling rates compared to other production processes, so preventing the development of crystallinity in the film and enabling a uniform downstream orientation process. In 2008, this concept for the production of water quenched blown films was extended to produce films of up to eleven layers. Moreover, TripleBubble1 technology has recently been further developed to include up to 13 layers and large film widths and outputs of over 1 tonne per hour and to convert all common raw materials including PE, PP, PET, PS, PA, EVOH, COC, EVA, EMA, ionomers, among others.
