Right: TPEI says continuous mixers are attracting attention for their high efficiency and uptime

according to Technical Processing and Engineering (TPEI). “Companies that can shift their capabilities to follow market demand are going to have an advantage in a more volatile market place,” says Slayton Altenburg, responsible for Sales, Logistics and Research at the company. “Continuous mixers improve that ability, being able to process a wide variety of resins and additives efficiently without costly reconfigurations. For instance, if your core business is compounding for the automotive industry and yet you have the ability to produce materials for PPE and the medical industry while avoiding large capital expenditure, it is possible to take advantage of market opportunities.” Altenburg says continuous mixers are attracting

attention for their efficiency and uptime. “These qualities make the technology attractive to mature, as well as growth, sectors. While commodity compounding still commands the largest segment of the industry, high performance resins and additives are growing at the highest rate. High performance resins for lightweighting and metal replacement are being implemented in new end uses daily,” he says. “In addition, new additives such as graphene and other nano-materials offer incredible performance benefits. As their applications expand, demand for end-use specific compounds and masterbatches will increase as well.” However, TPEI says new solutions are still sought for specific mixing problems as cutting-edge additives also bring challenges, such as low bulk density, slip, shear sensitivity and thermal boundaries. In addition, some high temperature materials, such as crystalline resins, are difficult to mix using frictional melt dissipation, which has made their processing on continuous mixers difficult in the past.

TPEI claims it has developed technologies that meet a number of these mixing issues. “Continuous

60 COMPOUNDING WORLD | November 2020

mixers can convey 70 times the volume of material they are capable of mixing,” says Altenburg. “By doubling the cross-sectional area of the feed opening of our mixer, we can feed low bulk density materials efficiently and consistently. The addition of a mixing dam will further enhance the dispersion by restricting the free volume and forcing those additives into the resin before it exits the machine.” For high temperature resins and additives that induce slip, he says the company has designed a new high temperature mixing chamber (HTMC). “Our standard chamber with 6 kW of heat can run at temperatures of around 475°F (246°C), while the HTMC provides 16 kW of heat and can process materials at around 750°F (399°C). This lowers the mechanical energy required to melt the resin and allows that energy to be utilised for dispersion and distribution of the additives,” he says. TPEI recently supplied an HTMC system to long-standing US customer Color-Master, which produces colour and additive concentrates and PVC and specialty compounds. “The company undertook a project that demonstrated the improved efficiency of the HTMC over the standard mixing chamber with the same formulation,” Altenburg adds. “They are also helping us develop best practice for the compounding of ultra-high- performance resin systems, which to our knowledge had only been previously possible in single and twin-screw extruders.”



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