Innovative Interplay: ZSK FilCo Filtration Compounder and ZS-B MEGAfeed Side Feeder

The demands put on recycled plastic are very high. In fact, recycled plastic often competes directly with new plastic in many areas, since recyclates are increasingly being used in various sectors such as the automotive industry, food applications and numerous other products used in everyday life. This means the quality of the recyclate is of utmost importance.

Mechanical recycling has become a prevalent method for repurposing used plastic into raw material for new products. In order to fully satisfy the high quality standards, this process must be as gentle as possible on the plastic. 

The ZSK FilCo filtration compounder and the ZS-B MEGAfeed side feeder are two of the range of solutions we have developed to optimize mechanical plastics recycling processes. The interplay of these technologies ensures both superior recompound quality and a cost-effective recycling process. 

Conventional Mechanical Recyclate Processing Requires Two Process Steps

Plastic waste contains impurities that must be eliminated through melt filtration, a process that subjects the waste plastic to mechanical and thermal stress. After filtration, the plastic is granulated. 

The next step involves compounding with additives to imbue the plastic with the desired mechanical properties. This involves melting the plastic again and mixing it with additives such as glass fibers, fillers or color pigments, subjecting the plastic to a second round of mechanical and thermal stress.

This conventional approach to recycling plastics involves two separate steps and requires two processing machines, significantly increasing not only the complexity of the equipment but also the space requirements. 

ZSK FilCo Filtration Compounder: Single-Step Processing

Coperion has engineered the ZSK FilCo filtration compounder to achieve the filtering and compounding of post-consumer recyclate (PCR) and other heavily contaminated polymers in a single production step. 

Waste plastic – in the form of regrind, fiber pellets, film flakes or agglomerate – is fed into a ZSK twin screw extruder where it is melted with all components (any polymers: PE, PP, PA, PS, PC/ABS, etc.), homogenized, and devolatilized. The melt is then discharged out of the ZSK extruder and an integrated filter removes all contaminants. The cleaned melt is reintroduced into the ZSK extruder, where reinforcing materials such as fiberglass, wood, and carbon fibers, or fillers such as talc, CaCo₃ or ground PEX are added. The recompound is then pelletized.

This single-step recycling process using the Coperion ZSK FilCo is characterized by its extremely streamlined machine set-up. Filtration and compounding are possible in just one processing machine. This results in a more than 50% reduction in energy consumption for the extrusion process and significantly lower emissions in comparison to the two-step process. 

The plastification process is very stressful for the plastic. The deformation and subsequent transition into the melt phase can mechanically and thermally stress the molecular chains, potentially causing them to break down. However, with the ZSK FilCo, the plastic is only subjected to this stress once, maintaining its chemical structure as much as possible. Consequently, the quality of recompounds produced using the ZSK FilCo is exceptionally high. 

Interplay of ZSK FilCo and ZS-B MEGAfeed: High Profitiability in Plastics Recycling

To maximize the cost-effectiveness of the ZSK FilCo, it is crucial to maintain a steady feed rate of raw materials with no intake limitation. This can be accomplished either by pelletizing the waste plastic or regrind, or by using a compacting process. Both methods are highly energy-intensive and increase the recycling process costs. 

Using the ZS-B MEGAfeed side feeder, plastic recyclate with bulk densities as low as 20 kg/m³, which had previously been considered intake-limited and thus not economically recyclable, can be reliably fed in large quantities into the ZSK FilCo for recycling and compounding at high throughputs. This allows the high performance of the ZSK FilCo to be fully utilized, even with lightweight, high-volume fibers and flakes from various plastics (e.g. PA, PE, PET, PP), achieving very high throughputs. 

ZS-B MEGAfeed Side Feeder: Throughput Increase in Numbers

The full potential of the increased throughput possible with the the ZS-B MEGAfeed becomes very clear when used with a ZSK 58 Mc¹⁸ twin screw extruder. For example, when recycling PA fibers with a bulk density of ~40-50 kg/m³, conventional equipment achieves throughputs of 70 kg/h. In contrast, when the PS fibers are processed using a ZSK extruder via the ZS-B MEGAfeed, throughputs increase about fourteenfold to 1000 kg/h. Results are even more impressive in carbon fiber recycling, where throughputs increase from 50 kg/h to 2500 kg/h using the ZS-B MEGAfeed. When recycling PCR flakes, throughputs increase from 50 kg/h to 700 kg/h, and from 80 kg/h to 1300 kg/h with multilayer film flakes. 

Innovative Technologies Are Key to Economical Recycling of Various Plastics

The ZSK FilCo filtration compounder and the ZS-B MEGAfeed side feeder complement each other perfectly. Together, they significantly increase both product quality and plastic recycling efficiency. 

The ZS-B MEGAfeed side feeder revolutionizes the mechanical recycling process by completely eliminating the need for process steps such as compacting and agglomeration. Using this innovative side feeder, flakes and fibers can be fed directly into the ZSK FilCo, where they are melted, devolatilized, filtered and compounded in a single production step. This not only reduces investment costs and energy consumption but also significantly improves the efficiency of the production process. Moreover, it reduces both mechanical and thermal stress on the product. As a result, the quality of the recyclate is exceptionally high.