Coating & Laminating
oneBARRIER FibreCycle W
A high barrier fibre-based solution from Bobst.
hen looking at global market trends for sustainable flexible packaging, the trends can be grouped into three pillars of sustainability: mono-material polyolefins, compostable, biodegradable and bio-based and paper/fibre-based. Bobst has been actively working with different industry partners along the value chain to support the industry meeting flexible packaging’s sustainability challenges.
Within the oneBARRIER family of solutions which target the three pillars, Bobst has already launched oneBARRIER PrimeCycle, an EVOH-free, top-coat free mono-material solution for full PE barrier as a viable alternative to metallised polyester film.
Now, working on a joint end-to-end project developed with partners UPM and Michelman, Bobst has presented a high barrier, recycle- ready, fibre-based solution named oneBARRIER FibreCycle which is the successful outcome of extensive test trials aimed at enabling the solution’s characterisation and validation at every process stage – paper production, processing for high barrier functionalities, machinability, tenure of barrier and optical properties.
THE ONEBARRIER FIBRECYCLE CREATION Paper processing presents different challenges from filmic substrates: it is hydroscopic and absorbs moisture, its surface is very rough and offers poor barrier properties. So, to create high barrier paper-based material, a thin layer of primer is required to make the surface ready for metallization. Starting of course with selecting a paper that would offer maximized functionality in hight barrier packaging, in this case UPM Solide Lucent specialty kraft paper. After understanding the paper substrate, the right chemistry was selected for the paper primer by Michelman that would provide the correct barrier and good adhesion before metal deposition. This is strictly connected with the identification of the correct coating method and drying profile needed to enhance the paper coating and ensure careful web handling due to the brittle nature of the paper substrate. Over the past three years, Bobst has carried out intensive paper coating tests, conducting over 300 trials using various paper thicknesses (from 32gsm to 100gsm) and testing various chemistries (PVOH, PU, Acrylic etc) and optimized coating weight for both the primer and top coating, and building extensive experience and know-how related to paper coating technology.
The creation of the structure involves two phases of coating: primer coating before metallization and a heat-sealable topcoat afterwards. Both coating phases were carried out in Bobst Italia on the LEONARDO pilot coating line, whilst metallization was carried out in Bobst Manchester on an EXPERT K5 vacuum metallizer.
After the primer is applied and tested for pinholes, vacuum metallization is performed. This layer can either by opaque (produced using Bobst AluBond process) or transparent (produced using Bobst AlOx process). After metallization, the paper is again tested for pinholes. Tests have also been conducted on the durability of the paper using a fold test. This test is to simulate the production of packaging such as a three-side sealed pouch with a bottom fold.
The test was conducted before and after the application of a heat seal coating on top of the metallized layer. Without heat seal, the OTR after folding various greatly, this shows that the OTR can be drastically impacted by folding; the WVTR which is mainly associated with the metallization layer is less impacted by folding. Once the heat seal is applied, OTR and WVTR are maintained after folding which demonstrates that the heat seal coating enhances fold resistance of the metallized paper structure.
A VIABLE SOLUTION ON ALL COUNTS The oneBARRIER FibreCycle structure was also assessed in terms of recyclability using the PTS method. Two criteria were assessed: the disintegrateability and the undisturbed sheet formation. The test showed that the structure is easy to disintegrate and that no stickies or optical inhomogeneities were found meaning that the structure is recyclable.
oneBARRIER FibreCycle utilizes the synergies between wet dispersion coating and dry vacuum coating to achieve high-performance packaging solution. FibreCycle delivers a high barrier paper-based solution with barrier performance of OTR < 1 cm³/(m² d) & WVTR < 1 g /(m² d), hence it offers a mono-material paper based alterative to plastic-based flexible packaging, which is also recyclable in current recycling infrastructures for paper and board.
Xwww.bobst.com
16
July /August 2022
www.convertermag.com
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