Reimelt Henschel MischSysteme: First compounder for the processing of WPC now in operation

The first compounding line (Photo) specially developed by Reimelt Henschel MischSysteme (www.reimelt-henschel.com) for the processing of highly filled wood-plastic composites (WPCs) has now gone into regular production. eco-Profil N.V., a Belgian manufacturer of special structural elements for outdoor applications, is now using this compounder for the extrusion of inline-compounded, wood flour-filled PE-HD into terrace deckings. This Belgian company now belongs to the Ideal Automotive GmbH group of companies which is based nearby Bamberg/Germany.

Installed at eco-Profil´s production facility in Burgebrach, Upper Franconia, Germany, the production line consists of an RHC 95 compounder with co-rotating twin screws and an ESE 180 single-screw melt extruder. The closely intermeshing screws have a diameter of 95 mm and ensure an output of 1,500 kg/h. With an outer to inner diameter ratio of 1.66, the twin-screw extruder is distinguished by its large free volume, permitting high output even at low screw speeds and with an optimum residence time for gentle, homogeneous compounding of the material. The single-screw extruder is equipped with a 180 mm diameter screw and ensures a constant build-up of pressure upstream of the extrusion die. The pre-dried wood flour is fed via a twin-screw side feeder into the melting zone of the compounder, which for this purpose is equipped with special, newly developed screw elements. A degassing unit removes the residual moisture from the natural fibres, thus ensuring the complete absence of air bubbles in the wood-plastic composite.

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The delivery of the compounder was preceded by comprehensive trials with an RHC 55 compounder (55 mm screw diameter) in Reimelt Henschel´s Technology Centre in Kassel, the aim being to process wood flour with a particle size of up to 500 µm and to incorporate a wood flour content of well over 60% w/w into polyolefins.

The trials were particularly challenging as regards the actual process, both on account of the moisture content of the natural fibres and on account of the fluctuating viscosity of the thermoplastic melt, this being due to the fact that the compounder also had to process different grades of reclaim of varying melt viscosity. Added to this was the extremely limited heat resistance of the filler.
In the course of these trials, Reimelt Henschel developed screw elements specially tailored for the processing of WPC. These new screw elements permit extreme flexibility when it comes to configuring the screws, not least when the focus is on consistently high product quality and high output rates. The results obtained during commissioning of the compounder at the production facility again showed that the calculated upscaling of a production line proves itself in practice.
For the production of compounds, blends and masterbatches, the RHC series of compounders from Reimelt Henschel MischSysteme comprises a total of 6 machine sizes with screw diameters ranging from 25 to 120 mm and output rates ranging from 5 to 5,000 kg/h.

Reimelt Henschel MischSysteme GmbH, Kassel, Germany

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