The 3-layer film has a bio-based content (minimum C14 content) >95% and heat-sealability and barrier properties against oxygen and water vapour (OTR <1 cc/m2/day; 23°C, 0% RH, WVTR <2 g/m2/day; 38°C, 90% RH).
It has been produced at VTT by combining a traditional extrusion coating technology to a recently patented cellulose nanofibrils (CNF) film production method (WO2013/060934).
Jari Vartiainen, senior scientist, Packaging and Coating Technology, VTT Technical Research Centre of Finland, told FoodProductionDaily.com it studied and produced single layer CNF films for many years starting from cast films on Petri dishes and then made roll-to-roll films with its pilot-scale coating equipment.
He said as single layer films have inadequate moisture resistance and sealability it decided to move on towards multi-layered films. Because it is bio-based, it can replace existing synthetic multilayer films containing EVOH and PVDC.
“VTT has a strong background in the study of CNF. The Finnish Centre for Nanocellulosic Technologies, founded by VTT, the Aalto University and UPM, began operations already in 2008,” added Vartiainen.
“The research relates to the whole production chain of CNF – from the selection of raw materials to the development of the production processes and the modification of CNF materials according to the needs of various applications.
Single layer films
“The method for CNF film production (WO2013/060934) was patented recently. However, we realized single layer films have inadequate technical properties, mostly due to high moisture sensitivity and zero-sealability.
“As single layer CNF films were lacking the competitive edge against synthetic films, the combination of bio-based layers to multilayer structures was necessary.”
Vartiainen said the bio-based multilayer films development project started at the beginning of 2014.
“One of the most promising outcomes of the project was a fully bio-based 3-layer film for modified atmosphere packaging applications: bio-HDPE/CNF/bio-LDPE. Bio-PE (grades SGE7252 and SPB681) were obtained from Braskem and CNF was produced at VTT,” he added.
Dry food items
The film can be used as a packaging material for dry food items such as snacks, dried fruits, nuts and spices.
By multilayer structures, the overall performance of bio-based films was dramatically improved.
In addition, the material concepts consisting of several layers are closer to real-life applications and more valuable for the customer.
According to Vartiainen, the bio-based 3-layer film was produced three months ago and it has not been sold to anyone yet.
“We are actively looking for industrial partners and collaborators for further developing and finally commercializing this new technology. The results will be published in scientific journals and marketed at conferences and fairs. Further development will be done with our partners,” he added.
VTT is a globally networked multitechnological applied research organization. It has expertise in food and packaging technologies, including engineering of novel fibre-based and other biomaterials.