BUSS Four-Flight Kneaders for Plastic Compounders on Show at K 2010

BUSS four-flight Kneaders MX are setting new throughput benchmarks for compounding heat and shear sensitive plastics. The remarkable progress of these machines since market launch at the K 2007 is now exemplified by three compounding lines for various products, each incorporating a BUSS Kneader MX with 140 mm screw shaft diameter. One of these BUSS Kneader MX 140 lines, for masterbatch compounding, can be seen at the K 2010 in Düsseldorf (October 27 to November 3) on BUSS stand A59 in hall 16.

HFFR cable compound throughput tripled A leading European cable manufacturer recently took delivery of a BUSS Kneader MX 140 line for HFFR cable compounds with up to 3000 kg/h throughput. That is double the capacity of the largest existing line for halogen free flame retardant cable compounds, and almost three times more than the preceding BUSS Kneader MKS of the same size. This breakthrough in compounding throughput is attributable to the four-flight kneading screw, lower cut and operating at a higher speed of 750 rpm.

The result is also outstandingly good mixing to ensure a perfectly homogeneous product. Thanks to less heat generation per kneading screw revolution, the compound temperature stays well below the maximum limit of 190 °C for ATH flame retardant, even at speeds up to 750 rpm. The single-shaft discharge screw flanged on to the BUSS Kneader MX smoothly builds up extrusion pressure without harming the product, and is easily cleaned - an ideal combination for high-fill HFFR compounds in particular. This is followed by water-mist pelletizing with the advantages not only of lower pressure requirement and good startup behaviour: since the pelletizing die plate is not in contact with water, its holes cannot freeze up and cause production problems. Both the discharge screw and the pelletizer are mounted on rails for separate retraction and easy access.

World record line for semiconductives compounding Throughputs up to 3000 kg/h are now attained by the world's largest compounding line for semiconductive polyolefins, recently commissioned by a leading European supplier to the cable industry. The compounding technology challenges conquered here by the BUSS Kneader MX include dependably feeding and intensively mixing the special carbon black (with extremely low bulk density) into the melt, without destroying the microstructure on which its conductivity depends. Downstream of the BUSS Kneader MX 140 on this line a melt pump builds up the necessary pressure for pelletizing, which is by the versatile underwater method. Here again, the discharge unit and pelletizer are mounted on rails for separate retraction to enable easy cleaning and maintenance access.

Quantum leap in black masterbatch quality for piping compounds Compounding black masterbatch for piping materials is particularly challenging, because the viscosity of the HDPE or LLDPE substrate must be high enough for compatibility with the equally high-viscosity piping material. Trials in the BUSS test facility showed much higher compounding quality with the BUSS Kneader MX than with conventional three-flight kneaders, and higher throughput as well. This is thanks to extremely efficient distributive mixing by the four-flight Kneader MX, which ensures absolutely consistent distribution of carbon black in the high viscosity melt even at up to 50% content by weight.

The BUSS Kneader MX 140 sold to a globally active carbon black producer after completing these pilot trials has a length/diameter ratio L/D of 22 at 140 mm screw shaft diameter. Designed for compounding polymers with a melt index of 2 to 20 g/10min, its throughput capacity for black masterbatch is up to 3000 kg/h. At this throughput, the main drive power consumption is nearly 1000 kW. The BUSS Kneader MX has three feed metering ports and a degassing port. Downstream pelletizing pressure is built up by a gear pump. Thanks to the excellent mixing and high quality of the black masterbatch, no melt filtration is required. Even with critical formulations, the kneading chamber temperature remains so low that the heat history is improved - the overall thermal loading on the plastic through all processing stages. A BUSS Kneader MX 140 for black masterbatch compounding to this specification can be seen on the BUSS stand during the K 2010 in Düsseldorf.

Market supremacy both in throughput and product quality BUSS CEO Beat Sturzenegger attributes this success as follows: "Ever since launching our high-performance MX Kneader at the International Trade Fair for Plastics and Rubber three years ago, we have systematically worked on applications development. And that is the secret of our success: we already sold well over a dozen MX Kneader lines. Because they meet all demands for gentle and homogeneous compounding of heat and shear sensitive plastics. Whatever the application, BUSS engineers team up with our customers to assure them of a truly optimized Kneader line".