Mixers for PVC | machinery feature The orifice is adjustable to control melt


residence time. The device opens to whatever degree is necessary to increase or decrease work to the material prior to discharge.


Free rotor


Another supplier of continu- ous mixers, Technical Process & Engineering Inc (TPEI) continues to upgrade and expand a design it commercialized several years ago – its Free Rotor (FR) machines. FR rotors are three-piece


constructions that are installed without opening a machine’s driveshaft bearing block. This is possible because the rotor shafts are separate from the rotor body. The rotor itself is installed with couplings, says engineer Jim Hower. This facilitates installation and doesn’t expose bearings to contaminants. FR models also come in extended FRE versions,


which lengthen the rotor body by 1 L/D. Hower says this permits an extension of the feed chamber, which improves the feeding and processing of lightweight and other hard-to-feed materials such as recyclate. Eight models of the FR and FRE mixers are available


– two in FR configurations and six in FRE versions. Hower points out that TPEI’s rotors evenly disperse


highly loaded materials such as colour concentrates. Some formulations have an 85/15 ratio of concentrate and base material. One continuous mixer that utilizes innovative


technology to optimize process capabilities is the TriVolution line of single-screw machines from B&P Process Equipment. The system achieves dispersive and distributive mixing. It also allows controlled shear mixing with high surface area regeneration for devolati- zation and reactive processing of materials. The unit performs these and other capabilities by


blending the mixing features of a reciprocating kneader with those of a twin-screw extruder, says Michael Lazorchak, global product manager for mixing systems. But there is a twist. Whereas reciprocating kneaders allow one stroke (a forward and backward movement) per screw revolution, the TriVolution mixer generates 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


www.pipeandprofile.com March 2015 | PIPE & PROFILE EXTRUSION 27


“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 compounds that contain natural fibres,


which typically have high moisture content. In addition to producing a high-quality melt, the


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.


Batch benefits Promixon of Italy reports developments in equipment and product distribution. The company has made a number of upgrades to its batch mixing systems and components, and in September inaugurated a venture with US-based Exline to distribute custom mixing


Promixon has upgraded


mixing tools to improve material


distribution, reduce wear


and save energy


B&P says that its TriVolution combines the mixing features of a reciprocat- ing kneader with those of a twin-screw machine


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