PROCESSING | MULTI-LAYER PACKAGING
Above: Oben creates a number of mono-material films, including those made from BOPA
materials such as BOPP, BOPET and blown PE, in both Europe and North America – with replace- ment of blown PE film applications in the US likely to be most prevalent.
Mono-material film Peter Malmros, business development manager at US-based Baystar, said the company had used Borealis’ Borstar material to create various products – including stand-up pouches (SUPs), sachets and heavy-duty shipping sacks. In one case, it combined two ‘enhanced’ grades
of Borstar – FB1350 and FB2230 – to create a three-layer film structure. Benefits of the grades include: better processability; more bubble stability; and higher sealability, yield stress and tensile strength. “The melt strength of FB1350 supports the
sealing layer and avoids deformation during the sealing process,” he said. Similarly, a three-layer SUP featured an inner
layer of PE lamination film, an adhesive layer, plus an MDO PE outer/surface layer – offering high stiffness, good flatness and printability and good sealability. “It is fully recyclable due to the all-PE material mix,” said Malmaros. Similarly, Michelle Tsui – associate TS&D scientist
at Dow, told delegates that using various Dow grades allowed the creation of mono-material, multi-layer films. “Most flexible packaging must be designed for recyclability,” she said. While multiple layers remain, they need to be
converted mainly to PE to be eligible for recycling using store drop-off collection method, she added. However, extra sustainability brings new challeng- es, she said – such as the need for the machinability of mono-material PE films to be optimised in order to broaden the packaging window. PE cannot be used as a direct replacement for other materials such as PP or PET – and if this is done, it may lead to more pouch failures and higher scrap rates.
14 FILM & SHEET EXTRUSION | September 2023
Dow has teamed up with Mespack to create an all-PE packaging line. It involves pairing the right resin with the right equipment technologies, optimising sealants and assessing the impact of MDO on printing. Dow has a large number of resins, include its
Innate and Elite grades, plus Affinity sealant. One important factor was the effect of sealant density on the packaging window – and the project studied the use (or non-use) of triple-point sealer. Tsui said that combining Dow resins with Mespack’s all-PE line showed that mono-material PE films could have a packaging window of 27°-37°C – similar to PET-laminate films – at reasonable pouch speeds (of 30-60 bags per minute).
Recycled content Oriented film manufacturer Oben presented details of many of its mono-material films – includ- ing many with recycled content. Omar Gonzalez, regional development manager
at Oben, told delegates: “There is no universal polymer that can provide all properties by itself. Polymers need to be mixed in a single structure [for multi-layer packaging].” This is because different layers have different functions. He described a typical three-layer structure – with an outer ‘printable’ layer, a middle barrier layer and an inner layer that comes into contact with the product. However, he said it is possible to combine variants of the same polymer – such as PE – within a multi-layer package. An example was a PE-based SUP, made from bi-oriented HDPE – with enhanced mechanical and thermal properties, as well as good haze and gloss – for the outer layer. He pointed out that bi-oriented film typically has superior properties to standard blown film, in areas such as mechanical strength. Oben also offers mono-material, high-barrier cast PP pouches, for applications such as coffee or
www.filmandsheet.com
IMAGE: OBEN
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