MBM takes the stress out of recycling

The ICM system shreds the waste which is then fed to a single screw extruder (L/D ratio 14). The smaller parts are then melted and mixed with reinforcing fibres. This material passes into a non-intermeshing twin-screw extruder (L/D ratio 20-25), where additives and additional fibres and fillers can be added if required.

Finally, using the force of a piston, the melt is fed through a single nozzle injection point into a partly closed mould. The finished parts are injection-compression moulded at a low pressure, typically 250-300 bar.

Aside from the advantage of exposure to only one heating process and without intermediate cooling, as in a conventional re-granulation process, the clamping force is only 1,500 tonnes. This is much lower than the typical 3,000-3,500 tonnes needed to mould standard size palettes in a conventional injection moulding process, says MBM research manager Peter Naday.

Naday says that the melt flow is laminar, not turbulent, and that the low shear rate and shear stress combines with a short flow path to ensure low stress in finished mouldings. The final mouldings retain glass fibres of 24mm, which benefits the product’s mechanical properties, he adds.

The process is suitable for recycling thermoplastics with a wide range of fibre reinforcements, including glass fibres, natural fibres and carbon fibres. The CFK carbon valley cluster in Stade, Germany, has already shown interest in the ICM process, says Naday.

The most productive ICM 15050 duplex version has two melt lines and two moulding machines, each equipped with two full size palette moulds. The machine processes up to 1,000 kg to produce 50-60 palettes in one hour. The palette moulds are designed by MBM and manufactured by external mouldmakers.

The process makes palettes which are very strong because it can process highly compact materials, says Naday, who

A feature of the process is its ability to compact materials, which enhances the strength of the final product. Naday said that the machines increases density by 14% for natural fibre reinforced plastics and by around 38% in the case of honeycomb reinforced output, for which density has increased from 0.956 grams/cm³ to 1.403 grams/cm³.

The first part-to-part recycling system was constructed by MBM in 2003. The company then sent five machines to Japan for assembly, the first of which process plastic film waste, says managing director Dr Wolfgang Friedrich.

Friedrich says the ICM system can help the plastic palette industry sell its wares in Europe.

In Europe, “as wood is relatively cheap, so plastics palettes have difficulty in competing”, he says, adding: “But they can compete by using a closed loop plastics recycling process such as the MBM’s ICM system.”

The company has so far been mostly successful on the global market, where use of plastic palettes is more widespread. One reason for this is that wood palettes sold in the US need costly certification to show they are free from bacteria, Friedrich points out.

Naday adds: “We have a big advantage that our entire process complies with the REACH chemicals legislation, as it is one process. In comparison, chemical recycling has problems because it involves a mixture of oligomers derived from undefined polymers.”

Continuing, Naday adds: “We have developed as many as 1,700 formulations, but when we supply the machinery the customer is obliged to use the formulation supplied with it and so it is always known what the finished palettes contain.”

Aside from recycled plastics, trials have also been made by MBM with virgin plastics, with a suitable compatibilising agent enabling production of parts reinforced to a 65% level in a combination of glass fibres and Twintex glass/thermoplastic commingled fibres from Owens Corning Vetrotex.