Motan and Greiner Packaging come together to produce sustainable coffee capsules

Greiner Packaging has produced a sustainable coffee capsules solution to help protect coffee beans from the oxidative ageing process.

As coffee is an organic product, it is subject to an oxidative ageing process when exposed to air and moisture.

With coffee in particular this can be a major issue, as the flavouring substances released when roasting and the unsaturated fatty acids in the coffee bean oil can oxidise very quickly, which is perceptible by the change in taste and aroma.

The coffee can become sour and rancid, and this applies to both whole roasted beans and ground coffee.

With whole roasted beans, the process is incredibly quick, and can mean it loses up to 60 per cent of its aroma after just 15 minutes.

The only way to stop this process is to stop the oxidation reaction as quickly and completely as possible, by packaging it in air-tight and water-tight containers, such as coffee capsules.

These capsules usually consist of either aluminium or plastic, both made from deep-drawn foils.

However, there is a significant difference between the two alternatives.

While aluminium foil is a good barrier against almost all external influences, there are very few plastics which are gas-tight and aroma-tight.

EVOH, an ethylene vinyl alcohol copolymer, offers the best barrier properties against both oxygen and steam.

EVOH is just as water-tight as an LDPE layer, which is over 10,000 times thicker.

As it is comparatively expensive, it is used centrally as a thin barrier layer with a compound foil together with other plastics.

Production concept

At Greiner Packaging, a seven-layer compound foil is used to produce coffee capsules.

As traditional coffee capsules are produced from the compound foil by deep-drawing and punching, more than 50 per cent of the film remains as a punched frame.

As this quantity of waste cannot be disposed of logistically or economically due to the projected mass production, Greiner Packaging has developed a concept for the complete recycling of the punching waste during ongoing production together with the long-term partners motan and Luger.

For the multi-layer foil to be produced, it must be adapted in such a way that up to 60 per cent of it can consist of the regrind of the original foil.

The punched frame and waste parts are ejected directly from the deep-drawing machine and fed into a mill.

The regrind either goes into a storage silo or into an FIBC, and is fed from there into the main extrusion plant, where it is made into a mixed polymer which provides the two main layers of the compound foil.

Therefore, including the addition of the new material, 70 per cent of the total material throughput of the projected conveying and dosing unit is provided by the recycling circuit.

The comparatively small material throughputs of the additional four extruders represent the remaining 30 per cent.

These four extruders are arranged on two levels around the central regrind extruder, which is on the base level, and is flanked by the extruders for the central barrier levels and the adhesion promoter layers.

Compared to the complex dosing and mixing technology, the design of the pipeline system is simple and direct, with fixed piping to each material trap, as well as having no coupling station or intermediate material drying.

Dosing precision lies in the detail

Most of the material throughput is from the regrind layers, which are supplied via gravimetric dosing units and a downstream mixing system due to possible fluctuations in the bulk density.

Helmut Reckzeigel, Head of Business Using Capsules, said: “In this regard it is worth noting that the regrind fed back into the multi-layer foil as filler materials consists of the seven-layer foil and is therefore composed of the five different viscosity materials which this contains. It was our joint objective to achieve stable mixing and flow properties for this five-material mixture. An unstable material composition, whether due to fluctuating bulk density or a

change in material proportions, leads to reductions in the quality of the extrudate, in particular when seven layers have to harmonise with each other. As we wanted to install a control option for this, we provided for the addition of virgin PP material to the regrind. Therefore, the continual enrichment of the concentrations of the percentage of EVOH and the adhesion promoter in the total foil, triggered by the return of the stamping grid, can be stabilised at 14 and 12 per cent respectively and consequently the melt flow index.”

Also, due to the shortest possible return of the regrind, it does not cool down completely, and therefore a large part of the heat energy contained therein can be used for faster melting in the extruder, which leads to an improvement in the energy balance in view of a material throughput on the regrind extruder of approximately 500 kg/hr.

All other material properties are added volumetrically as virgin material in constant quality.

The throughput quantities for the barrier material and the adhesion promoter are a maximum of 60kg/hr.

The throughput of PP layers, which are additionally mixed with a white or brown colour masterbatch, is around 110kg/hr.

Process helped by motan’s LINKnet

All machine components are activated and operated by via the remote-controlled electronic modules specifically developed by motan.

These are GRAVInet for gravimetric dosing units, and VOLUnet for volumetric dosing units, which are connected to a ControlNet of the central machine control, and this can be extended to LINKnet, a comprehensive plant management system.

It is therefore possible with LINKnet 2.0 to collect and log the process sequences and application data and to operate all connected controls up to device level.

All motan controls with communication capability can be connected, which means batch tracking is continuously possible.

Reckzeigel concluded: “In view of the introduction to a new dimension of mass production, it was important for us to keep the technical risk at a small, manageable level. It is not least for this reason that we continued to work with our long-standing, proven partnerships. We have been working with Luger, the systems technology partner of motan, for more than 40 years already. We knew from similar machine projects in the past that the motan components would not call into question the availability of the complete system of 90 per cent required by us around the clock. Likewise, we assumed that the necessary dosing accuracy and the full integration of all setting and performance specifications would also be given in our ‘big data concept’ for the logging of quality data.”