US chemicals giant DuPont (Wilmington, Delaware; www.dupont.com) and thermoforming and film extrusion specialist Kuhne Anlagenbau (St. Augustin / Germany; www.kuhne-anlagenbau.de) have improved the performance of their “TripleBubble” shrink films for food applications. The companies say the new grades have better shrink and lidding structures, allowing cost- and material-savings.

The new shrink film and bag structures, which are based on using DuPont’s “Surlyn” thermoplastic ionomer, provide advantages including advanced meat adhesion and good puncture resistance, extending shelf life and minimising food waste caused by packaging failure during transportation. In particular, the use of Surlyn for food contact layers in shrink bag applications has resulted in improved transparency, meat adhesion and colour as well as reduced drip and odour development, the companies claim.

TripleBubble shrink films typically consist of a PET or PA based outer layer, a structural layer based on Surlyn and a PE based seal layer, and can be enhanced with an EVOH or PVDC based barrier structure. Surlyn provides the high shrink, softness and perforation resistance, the companies say. A new development is the combination of conventional shrink film technology using Surlyn as shrink layer with an advanced sealing technology, where Surlyn is used also as sealant.

The new developments support the trend towards the use of such shrink films to produce shrink bags for supermarket consumer packaging of meat. The films are already used widely to produce bags for transporting meat on the bone from the slaughterhouse to retailers or restaurants. Shrink bags for consumer packaging applications weigh considerably less than the tray-and-lid solutions, as well as helping to improve the meat’s colour and texture.

Another area of development is the downgauging of strong coextruded and bi-oriented high performance films with controlled thermal stability for lidding applications. Tests from new lidding film solutions using DuPont’s “Appeel” resins as the sealing layer and “Bynel” adhesive resins as the tie layer indicate that raw materials savings of up to 50% can be achieved compared with conventional laminate structures, depending on the application, the companies say.

The TripleBubble technology has recently been developed to include up to 13 layers and to convert all common raw materials including PE, PP, PET, PS, PA, EVOH, COC, EVA, EMA and ionomers.