Plastic pouches | materials
The growth in plastic pouches as a packaging material owes a great deal to innovations in both materials and machinery. Lou Reade reports
In the bag: advances in plastic pouches
Despite their thoroughly modern appearance, plastic retort pouches – which are used to package everything from coffee to catfood – were first developed by the US Army in the 1950s, as a light alternative to metal cans for field rations. Things have come a long way since then, and many of these refinements – ranging from high barrier properties to superior printability – were covered at the recent Plastic Pouches conference in Vienna, Austria, organised by Applied Market Information.
Rolf-Egbert Gruetzner, market
development manager at BASF, told delegates that a new aliphatic polyamide, Ultramid C37LC, would help to boost the barrier properties of plastic pouches. Aliphatic polyamides offer superior mechanical
properties (including puncture resistance), as well as barrier properties, resistance to heat and chemicals, and compliance with food legislation, he said – adding that the new grade offers a number of advantages including reduced crystallinity and a lower melting point. He said that there is an ongoing ‘wish list’ regarding
polyamide properties, including: more stable moisture performance; better barrier properties; handling high blow-up ratios and large bubbles; improving shrink levels; and eliminating ‘anti-curl’ effects in multi-layer structures. “The reduced crystallinity – due to better cooling efficiency during film manufacturing of Ultramid C37LC – offers advanced performance for shrink bags, asymmetric pouches and other applications,” he said. Against a benchmark co-polyamide, the new grade
showed a better cooling rate, which generated softer and more transparent films. At the same time, the reduced crystallinity enabled a higher stretch ratio
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– generating higher hot water shrink. “Slow crystallisation also helped to eliminate curl,” said Gruetzner. A reduced melting point also helps seal strength, making it appropriate for cooking bags that require high temperature resistance, as well as for breatheable vegetable and fruit packages.
Coating benefit Markus Koppers, head of the technology department at Brueckner, said that chemical coating could have advantages over corona treatment, in the inline coating of bi-oriented PET (BOPET). He said that applying a water-based coating, using a
reverse gravure kiss-coater, offered a number of benefits, including better optical properties, and better barrier properties – through a reduction in pinholes in metallised film. The technique also allowed the application of a ‘primer’ layer, to enhance metal adhesion, as well as a surface treatment to boost printing quality. “This is especially relevant for nanocomposite-based universal ink systems,” he said.
June 2017 | FILM & SHEET EXTRUSION 37
Main image: Petfood is a typical
application of stand-up pouches
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