processing feature | Kneaders
the screw, it oscillates three times. The company cites improved com- pounding capabilities thanks to superior melt flow elongation created by up to 12 times the number of axial flow splitting regions found on typical kneaders and twin-screw extruders (which it also makes). A higher number of pins and flights than on other kneaders is claimed to create a high degree of break-up necessary to finely disperse additives
without excessive shear or heat
generation. “The TriVolution has 12 rows of
B&P says its TriVolution offers excel- lent com- pounding thanks to
superior melt flow elongation
pins and our elements go up to 24 flights,” says Midwest territory manager Aaron Anderson. “This allows us to run at slower screw speeds, create less wear on the components, use less Specific Mechanical Energy (SME), but get more throughput.” Target applications are very much in line with those
of rival kneaders, but B&P also points out that several aspects to the TriVolution design enable very efficient devolatilization and reactive extrusion. “Smaller channels and quick multiplication of flow splitting for a given throughput result in thinner material thickness-
es,” the company notes. “This creates shorter diffusion paths for volatiles to escape from the melt. A narrow residence time distribution, coupled with excellent surface area renewal, promote efficient temperature control. Volatiles can therefore be efficiently removed. In grafting processes, the flow-splitting and high renewable surface features create an increased number of [available] grafting sites.” Since the concept was first shown at K2010, B&P has been busy developing the TriVolution for industrial applications. Anderson says that it currently has six units in the field, operating from food products to chemical applications, all in North America. “We are currently trialling for customers in other countries with some coming from as far as Australia. For dispersive and distributive mixing continuously, this is the best machine on the market,” he claims. Michael Lazorchak stepped down earlier this year as
global product manager for mixing systems at B&P Process Equipment and Systems. Before he left, he told Compounding World that the company had matured its ability to fine tune TriVolution during test trials. “Customers are reporting both product quality improve- ments (tensile strength gains etc.) as well as the established production efficiency gains,” he said. “Our customers are running in mastics and reactive extru- sion for over a year now and we are beginning to run TriVolution in glass-filled, mineral-filled and natural- fibre reinforced compounds.”
Polycompound – making the most of kneaders
Independent toll compounder Polycom- pound, founded by ex-Buss employees in Switzerland in 1988, has relied on kneader technology for processing challenging compounds from the beginning – the company originated as an in-house division of Buss producing compounds before being spun-off. Stefan Rohr, head of process technol-
ogy at Polycompound, says that a special feature of the kneader enables exact scale-up: shear gap is proportional to machine size as defined by outer shaft diameter D. “This makes the kneader unique in as much as the shear gradient is independent of machine size,” he says. “It depends only on the screw speed, which decisively simplifies scale-up and process transferability to various machine sizes. So it is quite common for the
42 COMPOUNDING WORLD | August 2015
laboratory model machine (D = 46mm) and full size production lines (D = 100 and 200 mm) to have identical kneading shaft geometries. Elaborate entry and transfer phases can often be omitted altogether, thus avoiding loss of valuable material.” Rohr further notes that kneader
technology provides benefits in applications beyond the well-known shear- and temperature-sensitive products. Examples include: reinforced engineering plastics containing glass fibres, glass beads, carbon fibres, nanofillers etc; complex formula- tions with a wide range of ingredients; reactive compounding; electrically- or thermally-conductive compounds contain- ing carbon black, carbon fibres, graphite etc; and new applications in nanotechnol- ogy and bio-feedstock areas. “Aware of these strengths and
opportunities, we have increased our capacity almost ten-fold over the years to 12,500 tonnes/year,” says Rohr. “Kneader technology shows more than ever its advantages compared to other com- pounding technologies. In my opinion, three-flight technology is more flexible in processing, while four-flight is ideal to optimize the throughput.” Until now, Polycompound has stayed
with three-flight machines, from Buss. Polycompound will soon install a new line from X-Compound that can be switched from a three-flight to four-flight format in just a few hours. Raul Friedrich, X-Com- pound managing director, says the company offers this option only on its lab kneaders. “We do not intend to extend this system to the big machines,” he says. ❙
www.polycompound.ch
www.compoundingworld.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84