Rotary Melt Filtration Systems for highly corrosive materials
Thanks to intensive research and development work Gneuss Kunststofftechnik in Bad Oeynhausen, Germany have been successfully able to optimise their SFXmagnus and RSFgenius range of pressure and process-constant Melt Filtration Systems for foam insulation board, as used in the building industry. Thanks to a special surface treatment and the completely encapsulated design, corrosion resistance has been increased greatly.
„Manufacturers of products such as foam sheet for food trays and cups as well as foam boards for various insulating uses were convinced of the decisive advantages of our Filtration 
Systems from the very beginning” explained Daniel Gneuss. For over 20 years, Gneuss Rotary Filtration Systems have gained widespread acceptance in this industry as in addition to the reliable filtration of foreign particles, the pressure constant operation also ensures an absolutely constant foam structure in the final product. This consistent foam structure is of major advantage in downstream processes and is therefore a “must”. The manufacture of extruded foam insulation boards (XPS) for the building industry is also an interesting application for these high quality systems. However in contrast to other foam processes, there is in this case the issue of corrosion caused by the flame retardants, which places specific requirements on the design of the screen changers.
Matching the design to the specifics of the application…..
Thanks to their better mechanical and insulating properties, XPS insulation boards are used increasingly in the building industry as a replacement for EPS boards. The XPS boards are usually manufactured on an extrusion line with two extruders in cascade orientation. The first or primary extruder principally plasticises the material and disperses additives and the blowing agent whilst the secondary extruder cools the material efficiently. In this configuration, the location of the Melt Filtration System in the transfer section between the primary and secondary extruders has been found to be best suited for this application.
…and at the same time fulfilling the requirements
Because of the specifics of the foam extrusion process, the screen changer must fulfil several requirements at the same time:
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In spite of the low viscosity of the polymer / blowing agent mix and melt pressures of up to 300 bar at the exit of the primary extruder, the Filtration System must operate leak free.
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Fully automatic operation and the avoidance of operating errors is as important as the uninterrupted, consistent melt pressure, even during filter element changes in order to ensure that no changes in the foam structure take place.
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Short residence times are essential, in order to prevent activation of the flame retardants, which are added to the polymer melt in order to comply with building industry standards.
Both the well–known SFXmagnus and RSFgenius Melt Filtration Systems from Bad Oeynhausen, with their pressure and process constant operation ensure the removal of foreign particles from the melt, without negatively influencing the sensitive foam extrusion process. Additionally, the RSFgenius ensures a time span between screen changes of several months, (even on highly contaminated material) thanks to its integrated self–cleaning system.
Now Gneuss can offer these systems with long term corrosion protection thanks to a special anti corrosion treatment of the steel used for the manufacture of the screen changers. In this way, all the advantages of the Rotary Filtration Systems are available for the building industry suppliers, even where highly corrosive materials are processed.
In Russia for example, a market with a strong demand for foam insulation board 14 Filtration Systems have been installed alone in this market sector in recent years.
The success of the Gneuss Melt Filtration Systems is largely due to their process- and pressure-constant operation, which ensures the processor a constant, uniform product quality coupled with a high level of automation. These advantages are particularly important, when recycled material is used, which is due to the growing cost pressure increasingly the case.
In many cases, highly flammable gases are used as blowing agents: the Gneuss Filtration Systems offer a further advantage compared with conventional systems. With the Gneuss systems, there is no sudden, large scale and uncontrolled foaming of the material and correspondingly no sudden, large scale and uncontrolled gas release during screen changes. This provides a major improvement in operating safety.
For further information, please contact: Andrea Kossmann, gneuss@gneuss.com