Multilayer packaging (MLP) is good for mankind as it preserves and protects the content. MLP is the mainstay of the FMCG industry, combining functionalities of dissimilar materials, such as excellent barrier against water, vapor and gases like oxygen, carbon dioxide, along with good mechanical and ability to withstand low-temperature environments. Thereby, increasing the shelf life of the product considerably and potentially helps in significantly reducing the carbon footprint throughout the food supply chain.
However, due to lack of efficient collection and processing or safe disposal system, MLP poses several challenges. In India, the system of primary waste collection is practically non-existent. Door-to-door collection of wastes from household, shops and establishments is insignificant and unorganized. As a result, most of the waste MLP is difficult to collect and dispose in a proper manner to reduce adverse impact on environmental and public health. Moreover, it is widely believed by various stakeholders that the MLP waste being generated is “non-recyclable” because the polymers involved in different layers have different rheology points.
As of today however, the technology does exist to recycle MLP that renders Multi-layer packaging recyclable in spite of the fact that multilayered polymers have different functionalities and together act to provide the durability that MLP’s offer. The “myth-buster” technology has the capacity to convert MLP waste into granules which are fit to be used for making a variety of products ranging from furniture road dividers, bottle caps, trays, crates, stools, benches and much more across a large range of industrial, domestic & other applications.
1. Multilayer Packaging: An introduction
Multilayer packaging is a composite material consists of more than one layer of different materials (polymers, aluminum foil etc.), where the components are layered in a variety of ways to create flexible structures. Figure 1 shows a typical three-layer structure of a multilayer film architecture.
Figure 1: Three layer structure of a multi-layer flexible packaging film structure.
Each layer of a flexible multi-layer packaging has a specific role and responsibility within the application, for example:-
Outer layer: This layer provides a printing surface, and is usually made of BOPP or PET.
Barrier layer: This layer prevents oxygen and moisture from infiltrating the packaging, which is essential for preserving the freshness of packed food. EVOH, Nylon, METPET, METBOPP and Aluminum-foil offers superior barrier performance in flexible packaging.
Sealing layer: Polymers with a low melting point are typically used as the sealant layer because they readily melt and fuse together when heat is applied, creating a strong bond between different layers of the packaging material. Polyethylene is the most common inner sealing film layer in flexible packaging.
2. Multi-layer Packaging: Recycling Hurdles
a. As already discussed above, multi-layer packaging is a composite material consists of more than one layer of different materials having different rheology points and chemical composition. During recycling, different polymers or sometimes incompatible polymers (e.g., PE and PET) do not blend well, reducing the quality of recycled products.
b. Polymers used in multi-layer packaging have unique processing characteristics, like melt flow rate, thermal stability and processing temperature. These differences necessitate specific recycling processes and conditions, making it difficult to develop a “one-size-fits-all” ideal approach.
c. The lack of detection systems for multi-layer films. Current recycling facilities often rely on manual sorting or obsolete technologies that cannot differentiate small-sized contaminants such as dirt and stones, scrap metal, glass, papers, non-ferrous metals and polymer contaminants.
d. The current waste management infrastructure lacks specialized collection systems for multi-layer films, leading to their frequent disposal in landfills or incineration.
3. Multi-layer packaging: The Recycling Technology
The post-consumer multi-layer flexible packaging bales are sourced from the recognized MRFs. Since, incoming bales may be contaminated with foreign particles/ materials that need to be removed before processing, therefore, multi-layer flexible packaging materials are passed through trommel, vibrating screen and eddy current separator to remove dirt, glass, papers, stones, ferrous and non-ferrous materials. The packaging materials are then washed with water and moved through a vibrator shaker to remove the excess water. In the next step, the packaging materials are passed through AI sorters (UV-Visible light, near-infrared (NIR), X-ray, fluorescence, laser, hyper-spectral and metal detectors) to remove non-polymer contamination. The next step involves wet grinding of the packaging material followed by a hot caustic pre-washing at 60°C for a duration of 4–10 min. This is followed by a high speed hot washing step at approx. 60°C, where the material remains for about 6–12 min. after being squeezed.
The squeezed material then passes through two stage extrusion and vacuum degassing for better removal of volatiles and non-targeted polymers. The first stage involves melt filtration using a laser filter of 200µm, followed by atmospheric degassing of the polymer melt. Whereas, the second stage involves feeding of degassed polymer melt into the extruder, adding odor remover additives followed by very fine filtration using mesh disc filters of 150µm. After that, the polymer melt exits the extruder through the die holes, pellets are cut by rotating blades and are solidified by the process water flowing across the die face inside the cutting.
Figure 2: Flowchart, showing the complete recycling process of the MLP.
Technology offers many advantages, including:-
a. Sorting and separation process: Trommel, Vibrator shaker. Magnetic separator, Eddy-current separator.
b. AI-based auto-sorting technology: UV-Visible light, near-infrared (NIR), X-ray, fluorescence, laser, hyper-spectral and metal detectors.
c. Multi-stage washing: Dry wash, Augur washing, centrifugation, hot washing with alkali, cold wash, High speed hot washing and cold washing.
d. Two- stage extrusion decontamination process: Vacuum drying, Double-stage vacuum degassing, and continuous polymer filtration using laser-disk filter technology etc.
4. End Products
It is recommended to use post-consumer recycled (PCR)-MLP granules in certain proportions into wide range of applications (Figure 3), for example:-
a. Decorative - PCR to Virgin shall be of ratio up to 60:40.
b. Functional components like Furniture, Road Dividers, Bottle caps, Trays, Crates, etc. shall be up to 40: 60
c. High-strength applications like core plugs, Floor tiles, etc. shall be 25:75
In addition to the above, the recycled granulates can be mixed and used in applications like Pipe extrusion for agriculture, Sheet Extrusions for ACP panels & Roto-Molding for Tanks in the regulated mix.
Figure 3: Different applications of PCR-MLP granules
For more details, please contact Plastics Packaging Research and Development Centre
Addressed to: Dr. Amit Singh, amit.singh@pprdc.in
Report Published by Plastics Packaging Research and Development Centre
19-Oct-24 
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