machinery feature | Mixers
three stokes for every 360˚ revolution of the screw, to broaden mixing flexibility. The screw can be configured with up to 12 in-
termeshing flights to modify mixing. Stationary pins inside the barrel create what Lazorchak describes as a “slalom effect” on the melt as it undergoes shearing, decompression, folding and elongational mixing. “The stroke of the machine is not adjustable, but the geometry is,” he explains. A compounder tailors mixing parameters by adjusting elements on the screw. “You can configure units according to the process you run.” Moreover, kneading and splitting of the
melt, caused by the screw and stationary pins as it travels down the barrel, opens and exposes material to grafts and reactive processing. It also facilitates venting moisture and volatile gases. This is useful for com- pounds that contain natural fibres, which typically have high moisture content. In addition to producing a high-quality melt, the
Promixon’s TRX container mixer is designed for a range of materials including masterbatches, additives and polymers
process minimizes the heat and energy in mixing. As B&P explains, the mechanical energy used for melting and mixing does not come from aggressive shear-induc- ing devices but from elongational mixing that takes place in the intermeshing areas between the stationary pins and reciprocating screw flights. There is, as a result, less material degradation, as well as cost savings. Six models are in the TriVolution line, with screw
diameters of 30 to 160 mm and L/D ratios of 12, 16 and 20:1 for each.
The Speedy Mixer from Mixaco uses an optional PE liner (shown in blue) to minimize clean-up during product changeovers
Batch benefits When it comes to mixing colorants, “everyone fights the clean-up afterwards,” says Markus Frantzen, general manager of the US division of Germany’s Mixaco Maschinenbau. How rapidly a compounder cleans and preps a mixer for changeover is clearly vital to machine uptime and productivity. As a result, Mixaco continues to promote a system it
unveiled several years ago called Speedy Mixer. The vertical system mixes masterbatches and other material in a double-walled stainless steel vessel with an optional high-density polyethylene liner. The liner ranges in volume from 50 to 100 litres, and a drum option is available up to 200 litres. The system is designed to eliminate the need for post-processing clean-up of a dedicated mixing vessel, thus speeding changeover. The liner resembles a blow moulded jerry can. It
stands by itself and has a round base, which eliminates dead spaces during mixing and prevents material from accumulating in corners. The liner can be put on a weigh station and loaded with resin, colorant and other additives prior to mixing, or secured by vacuum in the Speedy Mixer and charged with raw materials. Processing occurs when the system’s mixing tool
drops into place and is activated. After processing, the tool is raised and the liner used for storage or to transport material to a compounding line. The process is used with an array of materials, including polyolefins, PVC, polyamides, styrenics, TPEs and dry colour. Mixaco says that it is a simple concept, but it works and keeps production, storage and shipping operations moving smoothly, while reducing downtime
60 COMPOUNDING WORLD | November 2014
www.compoundingworld.com
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