Increased Demand for Filtration Systems
At the last „K" show in 2016, Gneuss presented new generations of their Rotary Melt Filtration Systems. Since then, the demand for the Gneuss process - and pressure - constant Melt Filtration Systems has increased dramatically. The demand has come from all sectors of the industry, from not only recycling industry but also from sheet (including foam sheet) and film producers. The number of Melt Filtration Systems supplied for compounding has also seen a major increase.
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Fig.1: Pressure and process constant |
In the compounding industry, there has been a trend to ever more different colours and material formulations with shorter production runs. This requirement for increased flexibility means that fast material changes become an important economic factor. The Gneuss Rotary Filtration Systems are especially well- suited to such applications. In addition to process constant operation, they offer streamlined melt flow paths. A special version of the process - constant, automatic KF screen changer is available, which in addition to having extremely efficient flow paths, is designed to be individually customised for the specific requirements of compounders with short production runs and drastic material grade changes – and thermally/ residence – time sensitive materials.
Permanent pressure- and process-constant melt filtration is important in the manufacture of sheet and foam sheet. Parallel to the requirement for every higher quality, manufacturers of such sheet are constantly striving to reduce material costs, which usually means higher contamination levels, thus increasing the importance of melt filtration. For such applications, Gneuss has seen a surge in interest for the RSFgenius screen changer, which permits filtration fineness of for example 56 μm whilst maintaining constant running conditions and automatically cleaning its filter elements in situ. Constant pressure is an important added bonus for foam sheet manufacturers, for whom constant pressure means a constant foam structure.
MRS-Extruder with exceptional decontamination performance
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| Fig.2: Gneuss Processing Unit (GPU) with MRS-Extruder, Rotary Filtration System RSFgenius and Online Viscometer VIS |
The MRS Extruder (a single screw extruder with an innovative multiple screw devolatilising section) provides excellent devolatilisation of the polymer melt. The multiple satellite screws (which rotate in the opposite direction to the main screw) ensure a rapid surface area exchange of the polymer melt under vacuum, thereby achieving a huge improvement in the diffusion process. The system is therefore ideally suited to the processing of heavily contaminated polymers.
The high polymer melt exchange rate by means of the Multi Rotation System is achieved during an extremely short residence time, with low shear and temperature stress for the polymer. At the same time, additives can efficiently and homogeneously be introduced into the melt.
As a result, the polymer decontaminated on the Gneuss MRS extruder fulfils the strict requirements of food contact application standards such as FDA, EFSA and Invima without restrictions.
Odour- Free Products
„Decontamination" refers to harmful volatiles such as oils, solvents etc.. These need not necessarily be harmful but can nevertheless be a problem if the volatiles create an unwanted odour. This is especially often a problem when recycling polymers. Under temperature, the polymer can absorb residues from the washing process and other contaminants can decompose and create strong unwanted odours. Additionally, polymers, with simple molecular structures can already have absorbed odours from their first "life" as packaging materials. Typical cases are films (e.g. LDPE) which have been used for packaging meat or fish.
The high diffusion rate in the MRS extruder reliably removes such odours and enables the production of odour- neutral products.
Technology Leader in PET Recycling
Gneuss has been at the forefront of polymer recycling technology for over 30 years now and offers a range of innovative solutions for the processing and recycling of polymers. Gneuss´ systems are optimised for the challenges of PET recycling. They are perfectly harmonised with one another and can their modular design can be configured flexibly. The Gneuss- Processing-Unit, consisting of the unique Gneuss MRS Extruder, Rotary Filtration Systems and Online Viscometer represent are the heart of the Gneuss recycling systems.
With the MRS Multi Rotation System, Gneuss provides a processing system which can handle a wide range of input materials with different qualities and properties. It can process 100 % recycled material without pre-drying or crystallising. In addition to the unmatched devolatilisation performance of this extruder (for example input material with up over 1 % residual moisture level) the decontamination performance is so good, that the extruder matches EFSA and FDA requirements without restrictions or compromises.
The especially gentle direct processing without pre-drying, crystallisation and above all without the need for frictional heat makes the processing of materials and mixtures of materials with differing melt temperatures possible and eliminates steps in the processing chain.
Polymer purification takes place not only in the MRS extruder but also in the Gneuss Rotary Melt Filtration Systems which ensure a purified polymer melt, without foreign particles or specks. Gneuss has continued to develop the Rotary Filtration Systems and introduced new generations with a host of detailed enhancements last year.
The Online Viscometer from Gneuss completes the Gneuss- Processing-Unit. With its sophisticated control system, it ensures that the IV value of the melt matches the setpoint. (The vacuum setting of the extruder is automatically adjusted to compensate for variations in the input material IV). Different IV values can be set for different applications, ensuring excellent flexibility.
PET Foam – new at the Fakuma
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| Fig.3: Examples of food containers made from foamed PET sheet |
At the Fakuma, Gneuss will present its latest development in PET sheet: the manufacture of PET foam sheet. The sheet lines from Gneuss are characterised by their extremely flexible operation with regard to the input material and the sheet manufactured. These sheet extrusion lines can be quickly and flexibly switched to foam sheet. The MRS foam sheet module enables a weight / density reduction of over 50 %, and this from input materials of up to 100 % post consumer material, regrind, virgin or blends of these materials. With equivalent mechanical product properties, a wide range of PET foam products for food packaging can be manufactured cost efficiently.
Thanks to the excellent low shear mixing properties of the MRS extruder, both the nucleating and the blowing agent are completely dispersed and homogenously distributed in the polymer melt. After extrusion and filtration, the polymer melt is conditioned so that it has the optimum viscosity and ductility so that material foams with the required density as it emerges from the die.
