POST INDUSTRIAL RECYCLING | TECHNOLOGY
injection into two mutually tuned but independent steps. In the first stage, the raw material is melted in a conventional plasticising screw. The melt is then transferred to a second screw for injection into the mould cavity. “Depending on the material and application, a melt filter and a degassing unit can be integrated into the process between the plasticising and injection units. This means that high-quality products can be created, even from contaminated plastic waste,” says Engel. The process is designed to run on Engel’s legacy injection moulding machines. However, it did develop two special features for the two-stage process. One feature is that the plasticising unit used in the first step also has the task of buffering the raw material to achieve a continuous process that supports the use of smaller plasticising screws, which ensures further cost savings. Developers at Engel also focused on the degassing unit’s design and operation to achieve high product quality. Residual moisture and volatile substances originat- ing from material degradation or ink residues can pass through the melt filter, but if these com- pounds are not removed before the melt is injected it can impair the visual appeal of the final product, with pores forming on the inside and defects appearing on the surface of the part. In addition, the volatile substances can reduce the mechanical load bearing capacity of the part. Integrated degassing extends the usage spectrum of the process to applications in the technical moulding and automotive sectors. Engel said the new process is focused on
large-volume moulded parts, some of which are already made from recycled materials, such as pallets, transport boxes and waste containers. Engel demonstrated the new two-stage process at last year’s K show, where an Engel Duo 12060H/80Z/900 two-platen servo-hydraulic
IMAGE: ENGEL
injection moulding press manufactured dolly pallets from a blend of post-industrial polyolefins. Project partners for the tradeshow presentation
included AVK Plastics, which produces pallets on an Engel Duo moulding machine at its facility in Balk, the Netherlands. Some of the Engel presses installed at AVK Plastics are producing parts using the new process. Other partners include Haidlmair, which designed and supplied the mould, Ettlinger, which supplied the high-performance melt filter for effective removal of solid and elastomer contami- nation, and IPP of Ennepetal, Germany, a specialist in logistics solutions for supply chains. Alpha XS, a compact, energy efficient and cost competitive recycling extruder designed for inline reprocessing of film scrap, is the latest develop- ment from Plasmac, the recycling division of Syncro Group that manufactures inline and offline repelletising machinery for industrial waste applica- tions. Erema Group has a 60% share of Plasmac. The Alpha XS unit is designed to process 45-50
kg/hr of edge film scrap inline with the manufactur- ing process. The intake of the film is via a trim basket. An optional rollfed unit can be used to feed off-spec reels or scrap reels. The unit can also be used with a supatrim device to automatically feed tacky or stretch films, or used with a flake feeder to feed pre-sized reduced flakes or chips into the extruder. In-house industrial waste material is directly fed into Plasmac’s recycling extruder, which incorpo- rates a dual-diameter, 8:1 L/D ratio screw based on the company’s Short Screw Technology (SST). The extruder is designed to run at low melt tempera- tures and ensures low shearing to minimise material degradation. The direct extrusion design minimises material dwell time, with heated and melted material extruded through a multi-hole die face. The unit can be fitted with an inline manual screen changer if required. The Alpha XS unit incorporates a new air-cooled pelletising system in which the cooling capacity has been increased by over 50%. The cutting system is updated with an improved cutting blades that deliver better pellet cutting and a longer operating
www.plasticsrecyclingworld.com
Above: Engel’s two-step process makes it possible to process
post-industrial or post-con- sumer plastic waste as flakes in an injection moulding machine directly after grinding
Left: Plasmac’s Alpha XS unit can inline process 45-50 kg/hr of edge film scrap
May/June 2023 | PLASTICS RECYCLING WORLD 51
IMAGE: PLASMEC
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