By using different material concepts, manufacturers can make an important contribution to meeting the current market demands with regard to sustainable packaging solutions.
By utilising innovative packaging concepts and new pack shapes, packaging volume can be reduced and plastic waste curbed.
One very promising approach is to develop pack concepts based on materials, for which closed recycling loops already exist. One example of this are paper fibre-based packaging solutions, since the paper fibre can be fed back into the existing recycling loop, after it has been used. Even if the material is disposed of in the normal packaging waste rather than in the recycling bin, it can be detected in today's modern recycling centers, where it is removed and fed into the proper recycling loop.
MULTIVAC's PaperBoard offers a range of solutions for producing packs made from paper fibre-based materials. The packaging materials, which were developed in conjunction with leading manufacturers, can be run on standard machines and meet the requirements of the food industry as regards barrier properties and protective functions. The PaperBoard range includes solutions for producing MAP or skin packs on thermoforming packaging machines and traysealers. Both types of packaging machine can be individually designed to meet the particular output requirements of customers.
When it comes to traysealers, it is possible to run either trays or pre-cut sheets made of board or cardboard composites, which can be separated by the consumer after use into their constituent parts. MULTIVAC offers three different solutions for producing paper fibre-based packs on thermoforming packaging machines. Where vacuum skin packs are produced, formable paper composites can be used, which are available in various grammages and with different functional layers. Cardboard composites from the roll can also be used as carrier materials for vacuum skin packs. Both types of carrier material can be separated by the consumer after use into their constituent parts.
In addition to this, we have also developed a machine concept for running cardboard trays made of mono board on thermoforming packaging machines. A suitable plastic sealing layer is applied in the forming die, which enables the appropriate skin film to be sealed. This concept also enables the consumer to separate the packaging materials into their constituent parts.
When it comes to developing sustainable packaging materials, so-called biopolymers are also being considered as an alternative. The term “biopolymers” comprises two classes of materials: firstly those polymers which are manufactured from renewable raw materials, such as PLA or PHA. These polymers are biodegradable. The second class of materials includes those polymers which can be manufactured entirely or partially from renewable resources, but which are not biodegradable, examples being PET or PE.
Based on current knowledge, thermoplastic PLA is the most practical alternative for producing thermoformed packs made of biopolymers from renewable resources. Due to its low barrier properties and impact resistance, the applications for thermoformed packs made of this material are limited however. It is often used in the fresh fruit and vegetable sectors. If one is going to evaluate biopolymers overall, it is important to consider not just the economic aspects such as price and availability, but also the recyclability of these materials at the end of their life cycle. In the absence of sufficient consumer education about these materials, as well as the lack of integrated disposal systems, it is not yet practical to completely separate these materials into their constituent parts. This could lead to situations where biodegradable polymers are fed into the recycling stream for conventional plastics instead of industrial composting facilities.
Another approach is the development of packs, which consist of just one material, i.e. so-called mono materials. These can then simply be fed back into the particular closed-loop system. From today's perspective, prime candidates for this solution are PP (polypropylene) and APET (amorphous polyethylene terephthalate).
When using mono materials for packing food products, it is important to take into account the change in barrier properties compared with composite materials, which may have been used previously, as well as the effects of this on the packed product. It should also be noted that a reduction in the functional layers, such as the sealing layer, can also alter the parameter window of the materials. This means the running parameters on the machine have to be adjusted.
PP film is a standard plastic material frequently used for packs. The material is characterised by its good barrier properties, heat resistance, and stability. PP also has the lowest density of all standard plastics. Packs made of PP therefore have a lower weight compared to those made of other materials - an important aspect in terms of sustainability and environmental protection. However, running this material on thermoforming packaging machines is more challenging than with other plastic materials.
The highly transparent APET material is also impressive in its very good water vapour and gas barrier properties. It is resistant to oils and fats and it can be used in a temperature range between -40 °C and +70 °C. Currently packs and trays made from APET and other mono materials are already being used instead of composite materials for packing fresh products. In order to achieve reliable packaging results, upper webs with a thin sealing medium are used, such as sealing lacquers.
The shape and size of every pack should basically be matched as ideally as possible to the particular product. MULTIVAC's concepts for format change make it quick and easy to match the individual format to the pack size that is actually required. This enables overpackaging with smaller products to be avoided and thereby saving packaging material.
The volume of packaging material can also be reduced by the use of thinner thermoformable films. Materials can be used, which have comparable barrier properties despite their reduced thickness, and these provide the same product protection as thicker materials. By using a suitable pack design, the same rigidity and pack functionality as with thicker materials can be achieved. These design features include the use of stabilising ribs on the side walls of the pack, as well as modifying the shape in the corners and on the pack base.
Another aspect is the forming process used during thermoforming packaging. By using alternative forming methods, the material flow in the forming die can be optimised, which means that again thinner materials can be used without compromising product protection. Examples of this are so-called plug assist forming or explosive forming. In the case of explosive forming, better forming can be achieved by rapid pressure build-up in the forming die, since the film material is distributed more quickly and evenly than with a standard forming system. By combining explosive forming with plug assist, this positive effect can be amplified even more, enabling up to 20 percent thinner films to be used while maintaining the same forming quality.
When producing vacuum skin packs, the materials used have the optimum barrier properties despite the thinness of the materials, which means they provide the optimum shelf life, as well as reducing packaging volume. If the skin film is used in conjunction with a carrier material made of paper fibre, a large part of the pack can be put into the recycling stream, after the PE sealing layer has been separated from the cardboard backing.
If one looks at the so-called folded pack, this can be an attractive alternative to the traditional thermoformed pack made of rigid film, if one is for example packing sliced sausage or cheese - and it has a significantly smaller packaging volume. Another possibility for reducing packaging material is to run foamed materials, which have a much smaller use of plastic due to their lower density. Today mechanically foamed APET films are available, which only have a weight of around 25 percent of that for compacted films.
When producing thermoformed packs, there has to be film trim by the nature of the process, but this can be reduced to a minimum by using innovative die technology, which has a positive effect on the consumption of packaging material and on the cost-effectiveness of the process.
The edge strips in the thermoforming process ensure the thermoformable film is guided accurately through the machine, and that the filled and finished packs are supported as far as the end of the process. In order to ensure a high level of output and pack quality is achieved, the edge strips must have a minimum width, so the evacuation cross sections in the sealing die are also large enough to guarantee the minimum evacuation and gas flushing times.
In the case of the new X-tools die generation for the RX 4.0 thermoforming packaging machine, the edge strips required for guiding the thermoformable film through the machine are reduced from 19.5 to 15 mm without compromising the packaging procedure.
The seal seam width for thermoformed packs is usually 5 mm. By reducing this to 3 mm, significant material savings can be made in the area of film required to produce the pack. Innovative dies ensure maximum seal seam quality is achieved.
It is also possible to further reduce the width of the sealing flanges across the machine running direction by using servo-operated shifting units for the sealing and cutting stations.
When producing packs with larger radii, the use of a strip punch is unavoidable. It is for this reason that a 5 mm strip of land at right angles to the machine running direction has to be provided for standard strip punch dies.
However, a segmented cutting tool can be used to reduce the strip of land to 3 mm at right angles to the machine running direction. By combining the segmented cutting tool with the other technology mentioned above, it is possible to further optimise material consumption, and the necessary investment is very quickly amortised by the significant material savings.
When it comes to producing shaped contour packs, MULTIVAC can offer innovative cutting tools, which ensure the packs are cut with virtually no trim, as well as other cutting systems such as the BAS 20 shaped contour cutter, where the trim is reduced considerably. MULTIVAC's complete cutting tools also contribute to virtually halving the punch waste produced by cutting out shaped contour packs.