LAB COMPOUNDERS | MACHINERY Developments in the lab
Flexibility is a prime requirement for any laboratory compounding
system.Peter Mapleston looks at how manufacturers are meeting that need in their newest introductions
The latest developments in equipment for com- pound and process development laboratories span extruders designed to process the smallest amounts of micro-pellets, through twin-screw extruders intended to handle both PVC and other thermoplastics, to machines that can easily double as small-series production lines. Lab-scale compounding extruders for product and/or process development have evolved along with production-scale twin-screw machines in terms of torque density and maximum screw speed. According to Adam Dreiblatt, Director of Process Technology for CPM Extrusion Group, this means that for scale-up purposes, laboratory extruders need to operate at high output to duplicate the melt history in the production-scale machines. “Most lab-scale extruders have enough power and speed - but not enough open area for feeding and venting,” he says. With a 35kW water-cooled motor, the company’s CXE26 machine (which with a 26mm screw diameter is well suited to develop- ment work) has enough power to compound up to 150 kg/hr, which drove the design for larger feed and vent ports. The i:o diameter ratio of lab machines should be the same as the production machines to facilitate scale-up, which means a 26mm machine with 1.55 do
geometry provides the smallest channel depth which can easily accept pelletised resin. “The larger feed and vent openings on our CXE26 has proven to be a solution for companies running recycled resin or bioplastics, since these materials tend to have larger particle size and/or lower bulk densities and can utilise the full available torque that the CXE26 can deliver,” Dreiblatt says. He explains that small-scale compounding of
/di Scaling concepts
recycled plastics and bio-based fibres also imposes substantially higher degassing requirements than
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At Italian compounding systems producer ICMA San Giorgio, CEO Giorgio Colombo says the company’s small 25mm extruders are based on the same concepts as its larger units and hence are highly suited to scaling-up laboratory develop- ments to commercial production. In common with its larger equipment, the smaller model can be extensively customised according to customer requirements. He says that its slightly larger 30mm
December 2020 | COMPOUNDING WORLD 41
other types of compound production, and this can become a problem with small extruders having relatively small vent openings. When laboratory extruders are required to fulfil small-lot production orders, Dreiblatt says the company’s larger diameter CXE32 and RXT35 models are often specified. These higher torque machines can still operate at low capacity for formulation development when not in production mode, he says, adding that the extensive portfolio of screw element designs, side feeders and vacuum vent stuffers available from CPM “enables robust compounding at any scale.”
Main image: This 18mm Leistritz laboratory system was installed in a cleanroom at the Aimplas institute in Spain this summer for medical compound development
IMAGE: AIMPLAS
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