TECHNOLOGY | RECYCLING LINES
Above: Coperion ZSK extruder with side-degassing unit ZS-EG and side-feeder ZS-B with Feed Enhancement Technology to provide high quality product at the highest throughput rates for recycling processes
moisture build-up is also common, and the economics of the PVC market require high produc- tion rates to be profitable. In recent work, recycled PVC was compounded along with fly ash and plasticiser. The objective was to run an acceptable final compound with low melt temperature and process stability for a carpet back- ing application. Four recycle streams were run, including clear film, luxury vinyl tile (LVT), window profile and vinyl siding. By utilising a standard Compact Processor set-up, a 15/7 rotor configura- tion run at 300 rpm, dam inserted and orifice 60% open, the mixer was able to run a stable process and produced good quality material for each of the four recycle streams. The continuous mixer was able to process the
recycled PVC with a temperature range of 147- 187°C. This is due to multiple temperature control zones that allow for processing the recycled PVC within its ideal temperature range, as well as an effective atmospheric venting feature that allows air, volatiles and residual moisture to escape. There are rotor cooling features as well, however, they were not utilised in this test. A production range of 250–450 kg/h was achieved during testing and within the nominal production range for the CP550 model that was used. Based on substantial experi- ence processing PVC and verified factory perfor- mance of the machine, significantly higher produc- tion rates are expected, says the company. Another area where Farrel Pomini has seen
increased interest in recycled materials is wood plastic composite (WPC), particularly in the deck board sector. WPC is the combination of natural wood flour and plastic. Approximately 65% wood flour is mixed with a corresponding amount of plastic, such as HDPE and PVC, along with a coupling agent. The recipe increases the durability
30 PLASTICS RECYCLING WORLD | October 2021
and moisture resistance for both indoor and outdoor applications. In recent work, the company completed compounding trials of 60-70% wood flour, with a 5% moisture concentration and recycled polyethylene. The objective was to achieve a benchmark throughput rate for scale-up purposes with a range of wood flour fill rates. One trial utilised the standard Compact Proces- sor set-up with a 15/15 rotor configuration, dam inserted and orifice 60% open; the mixer was able to run 300 kg/h with 70% wood flour loading. The mixer melt temperature was 170-190°C and acceptable for this application. The moisture level of the final compound was reduced to less than 1% by using a twin-screw vent stuffer to promote consistent venting and minimise mixer vent flow. No pre-drying of the wood flour was required. The Compact Processor with continuous mixing technology was able to process the WPC decking due to the adiabatic nature of the technology and effective atmospheric venting of residual moisture with a twin-screw vent stuffer. Nominal scale up rates could be established depending on formula- tion, demonstrating economical processing on an industrial scale. Farrel Pomini plans further work with recycled
materials. “One of our primary development areas relates to feeding recycled streams to the continu- ous mixer,” says Lloyd. “We are actively looking to enable feeding the machine with minimally processed materials, mainly post-consumer plastics such as film. In addition, we are being challenged to find processes for several new feed streams, or filling materials that include the addition and processing of thermosetting materials.” Coperion is observing a number of trends in the
recycling and recompounding market. “Plastic waste is often a mixture with a high degree of contamination and recycling is frequently difficult because sorting and cleaning the plastic waste is in many cases not economically viable or technically feasible,” says Marina Matta, Team Leader Process Technology Engineering Plastics. “However, we are currently seeing many new developments that significantly improve the sorting and washing quality of waste. We see this as a very important step in meeting this challenge. At the same time, end-of-life waste, in particular, is increasingly being chemically recycled. The pyrolysis process most commonly used in this process has also recently been significantly enhanced, so that this recycling process can be carried out in a much more energy-efficient way. The aim of all recycling process solutions and technologies is to optimise the properties of plastic recyclate to such an extent
www.plasticsrecyclingworld.com
IMAGE: COPERION
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