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Mono-material structure a clear trend in circular packaging
Source:CPRJ Editorial Team    Author:By Sofie Chong    Date:17.Dec.2019

Awareness of the need for more sustainable packaging has become increasingly acute in recent years. There is widespread support for the shift to mono-material packaging solutions.

The followings are the reasons why mono-material structure enables higher circularity:

  • Different materials have diverse characteristics and recycling properties. Packaging made of mixed materials cannot be directly recycled.
  • It is difficult to separate mixed-material packaging in post-processing. For example, packaging made of mixed materials such as PET, PA, EVOH or OPP is difficult to separate one by one and is not easy to recycle.
  • Mixed packaging, even if it can be recycled, is more costly and requires more processes, yet the recovery rate may be unsatisfactory.
  • Mono-material can be easily classified for recycling. It is also possible to achieve 100% recovery rate based on the recycling properties of the mono-material.

Solutions already available in the market

Material suppliers, packaging producers and brands have joined forces to develop and launch numerous mono-material solutions to the market successfully, not just for environmental reasons but also to lower the total cost of packaging.

PP-based food packaging

Borealis and Mondi recently collaborated to introduce more easily recyclable, PP-based food packaging.

Borealis has developed a breakthrough application based on its proprietary Borstar Nucleation Technology (BNT) that enhances the circularity of plastic food packaging.

Using Borealis BC918CF, a special BNT-modified copolymer, Mondi, a global leader in packaging and paper, is producing new mono-material packaging solutions for meat and dairy products. These offer the same performance characteristics as conventional multi-material packaging, while also increasing yields for mechanical recycling plants.

Innovative PP solutions based on Borealis BC918CF and Borealis RB707CF are viable mono-material substitutes for multi-material plastics. In addition to offering a high moisture barrier, their use enables material cost savings thanks to downgauging, as well as efficient processing on film conversion and packaging lines.

The combination of both copolymers in production helps achieve performance, including both thermal resistance and high transparency, a key combination for efficient packaging.

Besides, Mondi also cooperated with Jindal Films and Unilever to develop a new mono-material “PP-rich” film barrier laminate, which can run on high speed horizontal pouch machinery to fill sensitive dehydrated powder soups for the famous global Knorr brand.

This mono-material recycle-ready barrier laminate (OPP/Met-OPP/Seal OPP) is considered by the three parties as a breakthrough innovation, as it is said as the first large volume dehydrated soup pouch application in the market to resort to only OPP films.

It is considered an achievement for a traditional market segment typically using paper, aluminum foil, PET and PE based high barrier laminates, which are considered today unrecyclable according to the pending CEFLEX guidelines.

The pack is the first recyclable Knorr branded dehydrated soup pack at Unilever globally. The use of new high barrier and high seal performance technologies from Jindal Films was instrumental in the success of the project.

For the high barrier applications, Jindal Films has assessed with partners such as Tomra that the Knorr barrier OPP laminate developed is easily sortable, which means detectable by near IR techniques and diverted to the PP fraction during sorting.

Jindal Films has further on-going work with partners such as Axion Polymers to demonstrate the mechanical recyclability of this type of all-PP high barrier laminates for injection molded applications.

PE-based dry pet food packaging

Answering the market demand for recyclable flexible packaging, Coveris has introduced different types of materials that share the same goal – increasing product shelf life, while minimizing material waste.

The first development is Monoflex E, a mono-material alternative for dry pet food packaging, including snacks and treats. Designed using 100% PE, it works for both form-fill-seal and pre-made bags.

Monoflex E stands out on the shelf with its high gloss finish and improved printing options (suitable for both gravure and flexo printing), ensuring the graphics catch the customer’s eye.

Moreover, the increased stiffness of the material, and the equivalent machinability as standard PET/PE, make introducing Monoflex E to existing production lines a straightforward procedure. Additionally, Monoflex E maintains the best features of standard Coveris films, including enhanced convenience for opening and reclosing, as well as an attractive, premium look at point-of-sale.

These strengths, combined with 100% recyclability thanks to its mono-material base, meet the growing market need for more flexible and sustainable solutions in the pet food market. Future expansions are planned for other markets, including consumer products and long shelf-life items.

Simply plastic, reusable container

The single-material container from Jokey is free of foreign materials, such as paper.Jokey has launched its fourth generation of Jokey Euro Tainer Box JETB 12. The small bucket has proved its worth particularly in the food industry. Its strength is its optimal recyclability thanks to mono-material. In terms of sustainability, it also convinces due to its reusability.

Less is more” is also shown by the material savings. Wall thicknesses, design details and production technology of the container were subjected to a feasibility study so that the small bucket could be trimmed to an optimum volume.

The operating weight could be reduced by almost 15% compared to the previous generation, and by more than 40% less compared to the first generation.

Furthermore, the model upgrade is decorated and refined with a material-homogeneous PP label. This ensures that the bucket can be recycled without any problems, even with a label. 

There is also the option of secondary use. By using removable peel-off labels, the original packaging can be transformed into a neutral utility container and then fulfill many new tasks in the household and workshop. 

Manufacturing technologies keep pace with new needs

Along the entire value chain, developments must go hand in hand. A close exchange between brands, material suppliers and machinery manufacturers is necessary to innovate and prevent possible shortfall. The machinery manufacturers need to evolve their technologies more rapidly to enable or facilitate the switch to mono-material structure applications.

Stretching film lines for keeping barrier functions

In conventional composite packaging, PET provides stability and barrier properties. On the downside, its recyclability is very restricted. Stretched PE produced with Reifenh?user technology can fully replace PET with no loss of quality.

The patented Reifenh?user Ultra Stretch process produces PE film with mechanical properties that meet all the requirements of the packaging industry in terms of high-performance packaging and its conversion: heat-sealing, high stiffness in the machine direction, good flatness and printability.

The process involves stretching the film from initial heat to 10 times its surface area. Due to its patented positioning in the haul-off, the EVO Ultra Stretch features low energy consumption and high process stability.

A major advantage is that the PE film can be converted on existing conversion lines with no adaptation required. This makes the switchover to packaging made from PE mono-material considerably easier.

Brückner aims to produce films with the highest possible recycling capabilities on film stretching lines.Meanwhile, Brückner Maschinenbau, a member of the Brückner Group, is working on a means to make films with the highest possible recycling capabilities producible on film stretching lines. The focus is on mono-material film with superior mechanical and optical properties.

Brückner has introduced two completely new line concepts for the production of BOPE films. Film producers can choose between a working width of 6.6 m and an output of 3t/h, or a working width of 8.7 m and an output of 5t/h. These are 5 layer concepts for an extended range of films. The new lines also have the flexibility to produce BOPP films.

Even if recycling stands at the forefront of a circular economy, new mono-material structures must fulfill the highest demands and must not be inferior to previous packaging films.

This is why Brückner has developed a new inline coater for all BOPE and BOPP lines, installed in the line before the transversal stretching, which makes the production of extremely thin functional layers within the nano-range possible.

Due to the extreme thinness, the layers do not disrupt the sorting and recycling, but cater, for example, for an improved adherence during metallizing and barriers in combination with the equally thin but effective aluminium oxide coating.

MDO technology for high-performance PE products

The MDO (Machine Direction Orientation) technology from Hosokawa Alpine has been used for niche products. It is drawing more attention due to circular economy as it can be applied in manufacturing high-performance mono-material PE products.

By using monoaxial orientation, film characteristics such as stiffness, oxygen permeability or appearance can be specifically adapted and the film thickness reduced. Hosokawa Alpine has been dealing with monoaxial stretching for more than 20 years and has continuously optimized the flatness of the films in recent years.

In addition, the patented TRIO “Trim Reduction for Inline Orientation” technology also ensures savings in materials when trimming the boundary strips.

Hosokawa Alpine’s new MDO 04 orientation line in combination with TRIO technology therefore fulfills high demands in terms of quality in film production and allows lamination and printing of full PE material composites.

Thermoforming technology for heat insulating foamed sheets

Hot fill cups made of foamed PET.SML has developed foamed sheet for hot fill applications with new features in terms of heat resistance, insulation and recyclability in a joint R&D program together with its partner KIEFEL. The basis for these new products is a 3-layer PET (or PP) sheet with a physically foamed central layer.

Mono-material foamed PET or PP sheet produced from SML’s new systems have product features that can help to replace difficult-to-recycle hot fill applications made of expanded PS.

The foamed sheet from SML’s new lines has an A/B/A structure, in which the central B layer is foamed while the two outer layers are rigid. The central layer is physically-foamed with the injection of nitrogen or simple carbon dioxide gas which is widely available.

Mono-material structures facilitate recycling while the foamed layer reduces weight up to 50% compared to PET sheet with the same properties. No special additives are required to enhance the heat stability of the sheet which is thus suitable for the economic production of low-weight cups with excellent insulation properties.

In a new joint R&D project, KIEFEL and SML are exploring and further developing the potentials and opportunities this type of foamed sheet is offering. In addition to end products with very specific mechanical and thermal properties, the optimization of the manufacturing processes and the research on new recycling methods are in the focus of this research program.

The first outcomes are cups boasting heat resistance of up to 100°C created form standard APET. The sheet for such cups can have an overall density of about 0.65 kg/dm3, which saves material and increases the insulating properties, so that it is possible to hand-hold these cups filled with extremely hot liquids.

Unlike PS, mono-material foamed sheet, especially from PET, is straight-forward to recycle as the relevant infrastructure already exists in many places. Hot fill applications made of foamed PET sheet can be easily processed with other single use products from PET.



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