MATERIALS | MULTILAYER PACKAGING
Armed with this research, the company has
moved from lab to pilot scale – with an eye on a commercial launch for the multilayer bags. One potential all-compostable design uses PBAT, PLA and PHA. The next steps are to test the line speed and the barrier properties of the new bags prior to full commercialisation.
Barrier boost Kuraray has developed a range of EVOH grades aimed at a variety of packaging formats. Its Eval SC range can be used for thermoforming
Above: NaturTec says compostable plastics could be used to create effective freezer bags
Last year, over a 72-hour period, it demonstrat-
ed the production of 18-micron MDO PE film in collaboration with LG Chem. The new 18-micron film reduces the amount of
material used by around 25% compared to previous thicknesses of 25 microns. This makes production much more economical. Despite the low thickness, there are no compromises in optical or mechanical properties, he said. The film has a modulus of elasticity exceeding 1,400 MPa (MD) and exceeding 1,100 MPa (TD). Its haze, of below 5%, exceeds that of current prod- ucts (6-7%), he said. At Drupa, it exhibited an 18-micron film that combined 59% HDPE, 39% mLLDPE-C6 and 2% additives – made on an Evo five-layer line with MDO Evo Ultra Stretch. “The 18-micron film will come closer to the
standard PET weight per metre, and get more competitive,” said DeSpain.
Cold comfort NaturTec says it is using its ‘reactive extrusion’ technique to create freezer bags from compostable bioplastics. Anthony Keyes, senior formulations engineer at
NaturTec, told delegates that reactive extrusion blends polymers and modifiers in a way that increases miscibility – and thus prevents phase separation. “The controlled molecular architecture can
generate new material properties,” he said. He pointed to the example of freezer bags – and the concept of ‘freezer burn’, in which food deteriorates in the freezer due to water vapour loss. The company created and tested many formula- tions, using a compostable bioplastic in place of traditional PE.
“Both thickness and formulation play a role in
water loss,” he said. “While WVTR is higher, compostable bags still can stave off freezer burn.”
26 FILM & SHEET EXTRUSION | September 2025
films, biax film and triple-bubble shrink bags. The main benefit of the material is its high oxygen barrier – which complements the water barrier of PE. Edgard Chow, director of TSD at Kuraray Ameri-
ca, and Takeshi Sakano, Eval R&D leader at Kuraray in Japan, said that EVOH helps keep oxygen, off-flavours and odous out of packaging – while retaining flavour, aroma and MAP gases within. As well as being mechanically recyclable – typi- cally up to amounts of 5-6% – it has also undergone a proof of concept with chemical recycling, with “no adverse effect in the pyrolysis process at ExxonMobil”, they said. They added that Eval SC has “improved orient- ability without sacrificing oxygen barrier” com- pared to ‘conventional’ EVOH. In one study, Kuraray compared ‘legacy’ designs (containing polyamide and EVOH) with new ‘all-polyolefin’ designs that include an Eval SC barrier layer. Here, it created a 7-layer thermoform- able film (of both types) and carried out a single- batch forming study. In one case, the amount of Eval needed to create a satisfactory barrier – and have high transparency – was just 2.1% (compared to 18.2% for the original PA/Eval structure). For tenter frame biax film, it ran on a 7-layer BOPP pilot line. The 20-30 micron film, which included an Eval layer of 1-4 microns, was aimed at formats such as lidding film and flow pack film for applications such as processed meat and cheese. Another format is to incorporate both Eval and metallised layers for even higher barrier properties. Here, several polyolefin layers are combined with a co-extruded and oriented Eval layer, plus a metallised layer. The overall structure is recyclable, said Kuraray. “The structure has high mechanical strength due to orientation, and an ultra-high barrier due to dense metal-EVOH bonding,” said the presenters. Eval SC was also used to create vacuum packag- ing for meat, as an alternative to a PVDC-based structure. It was created using the triple-bubble
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IMAGE: SHUTTERSTOCK
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