MACHINERY | ALTERNATIVE COMPOUNDERS
Right: The conical twin-screw discharge unit is a new option for the Buss Compeo kneader range
intensity mixing and to handle compounds with high filler contents while maintaining precise temperature control. Assembled from standardised modules, they are claimed to enable cost-effective configuration of specifically-optimised compounding lines for a wide range of processing tasks and temperatures. The company says one of the great
flexibilities of the Compeo series is its ability to combine conventional three or four-flight kneading elements with new elements comprising of two or six flights and to put them to use in any desired position within the process section. “Combined with an increase in specific torque, this permits longer mixing zones without any additional increase in energy input,” it says. Dino Kudrass is a Design & Development Engineer at Buss. He says the company has run a variety of compounds on the Compeo 55, including highly filled engineering plastics, masterbatches, natural fibre filled polymers, elastomers and PVC. “The machine proved to have an extremely wide application spectrum and set a new standard for data acquisition and operating simplicity,” he says.
Learning curve “We have experienced a steep learning curve with higher processing temperatures (400°C), the new powerful heating/cooling system, and a larger variety of screw elements to choose from,” Kudrass adds. “We have also gained new insights into the advantages of our newly-developed conical twin-screw discharge extruder. We are developing different screw geometries and continuing to learn
X-Compound’s Continuous Kneader CK225 for recycling of flooring products
more about the effects of the discharge unit’s compression ratio, control system and pelletiser feed character- istics. We have seen more stable pressure output and gentle melt processing due to low shaft speeds, resulting in lower shear velocities.” Kudrass says the new conical twin-screw
discharge unit aims to provide a wide application spectrum for pressurising the finished compound as it exits the kneader. “Previously we have mostly worked with either melt pumps, which have closed gear chambers, or single screw extruders, which have an open helical chamber. One provides higher pressures and is more compact, while the latter is gentler on the compound and can be a low complexity solution, especially for PVC processing. The conical twin screw is in some ways the best of both worlds while introducing new advantages, such as being able to gelate PVC during start-up.” The conical design allows for a greater screw diameter in the gearbox, which means more torque, and provides a larger volume in the intake zone. It features active de-gassing, reduces the shear velocity in the stressed discharge zone due to its lower screw diameter, makes disassembling the screws easier, and allows for both screws to be heated/cooled, Kudrass says.
Success on the tiles
Another Swiss company making kneaders is X-Compound. It points to successes for its equip- ment in production of Luxury Vinyl Tiles (LVTs), including systems that use recyclate. “Demand for good looking, easy to maintain floors is constantly growing,” says Karsten Kretschmer, responsible for new machinery sales at the firm. “The market for LVTs as well as SPC (Stone Plastic Tiles) is develop- ing exceptionally well.” One of the key features of these tiles is the
application of a click-down system, which makes for quick and easy installation. Kretschmer says that during the production of the several layers of the floor tiles – as well as during the manufactur- ing of the click-down profiles – various amounts of
80 COMPOUNDING WORLD | October 2019
www.compoundingworld.com
PHOTO: X-COMPOUND
PHOTO: BUSS
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