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Two suppliers of extrusion and material handling technology have come together to develop an extrusion line for the production of highly filled compounds with up to 85% CaCo3 content. Partners Leistritz Extrusionstechnik and AZO have developed a system that, with slight adjustments, can run other applications such as talc, titanium dioxide and barium sulfate filler. In the field of flame retardants, meanwhile, materials such as aluminum hydroxide and magnesium hydroxide can be processed.

PlasticsToday Staff

November 7, 2013

2 Min Read
K 2013: High-tech extrusion plant for highly filled compounds

Two suppliers of extrusion and material handling technology have come together to develop an extrusion line for the production of highly filled compounds with up to 85% CaCo3 content. Partners Leistritz Extrusionstechnik and AZO have developed a system that, with slight adjustments, can run other applications such as talc, titanium dioxide and barium sulfate filler. In the field of flame retardants, meanwhile, materials such as aluminum hydroxide and magnesium hydroxide can be processed.

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Leistritz had daily video link-up with its Nuernberg plant at K to demonstrate compounding of highly filled materials.

The Leistritz ZSE MAXX extruder employed in the system has a specific volume/torque ratio (OD/ID = 1.66 and 15.0 Nm/cm³) for maximum throughput, but also facilitating highly energy efficient production. Leistritz and AZO were supported by GALA Kunststoff- und Kautschukmaschinen, Maag Pump Systems, Reverte Mineralprodukte, Ultrapolymers Deutschland and BYK-Chemie in their development.

Production of this type is very challenging for compounders according to Anton Fürst, Managing Director at Leistritz. Transport of material from the big bag stations/silos to the extruder plays a crucial role: This has to be done with minimum dust, granting enough settling time and minimum air content in the material. A particular focus in this process was paid to the stable feeding of the dosing units, which is accomplished by means of pneumatic suction conveyors.

The collective feeding system used here, is designed in a very energy efficient way and thus, works with optimum conveying speed. If necessary, the polymer can be combined from various feeding points. Each component is sucked in according to its formula, accurately weighed and homogenously mixed by the AZO Mixomat. Colors and additives are also fed into the process directly above the extruder. Since the dosing unit is pivotable, material can be fed into the extruder from two positions.

"The art of producing highly filled compounds lies definitively in the optimum distribution of the material streams," explains Fürst. "You need proven expertise in process technology to incorporate a large quantity of filler homogenously into a polymer matrix. Particularly, one needs to control the air streams that are brought in with the material feeding."

Another challenge is material moisture which can complicate the process. Therefore, the processing unit and the screw geometry have to be designed according to the task. In this plant Leistritz used a ZSE 75 MAXX twin screw extruder with a processing length of 48 L/D. Polymer, additives and calcium carbonate (provided by Ultrapolymers, Reverte and BYK) are fed into the process via the main feed opening and two side feeders. Leistritz implemented the downstream equipment with long-standing partners Maag (gear pump screen changer) and GALA: (underwater pelletizer). Last but not least the pellets are gently conveyed to the filling station by means of a suction conveyor.

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