machinery | Pelletizers Working with micropellets
Typical pellet sizes are in the 3.0mm to 5.0mm range, but micropellets in the range of 0.4mm to 1.0mm are growing in popularity. In rotational moulding, for example, micropellets can be used instead of powder, eliminating the additional step of grinding pellets into powder. Micropellets eliminate dust, have a better bulk density and higher pourabil- ity than powder, and can also improve rotomolding cycle times, says Mark Tate, technical manager at Gala, whose pelletizers can produce 0.4mm micropel- lets for rotomolding applications. “The shape of the micropellet has as much influence on the rotomolding process as the size of the pellet,” he says. Gala also produces 1.0mm “minipellets” for
masterbatch applications, where they are said to offer quicker and better disper- sion.
At last year’s Compounding World
Forum, Michael Forstner, area manager for Econ, described a project for produc- tion of 0.5-1.0mm PP micropellets for rotomolding. Grinding PP into a powder requires sophisticated nitrogen cooling systems, said Forstner, and this limits the use of PP in rotomolding. One of the key requirements for
processing very small pellet sizes is to prevent die freeze off. Econ’s pelletizers feature a die insulation system, including a patented airgap, that eliminates freeze-off. For micropellet applications, Econ has designed multi-hole nozzles
elaborately equipped, higher-cost, underwater pelletizing lines,” says Adam Cowart, business development manager. For PET and PLA resins, Nordson has developed its
CrystallCut system, which pelletizes and crystallizes in one step. The CrystallCut system saves energy by using latent heat from the polymer melt in the pelletizing step to crystallise the pellets at a later stage in an integrated process. In December of 2014, a CrystallCut system was commissioned as part of Lotte Chemical UK’s 200,000 tonne PET plant at Wilton in the UK. “For a modern, world-scale PET plant operating
Right: Nordson BKG’s belt
filter option allows
Master-Line
systems to be upgraded to offer finer
filtration and self-cleaning
‘24/7,’ we estimate that the CrystallCut system can save millions of Euros per year in energy costs by combining pelletizing and crystallising into a single integrated process without a cooling step,” says Ralf Simon, Nordson BKG managing director. “And because the latent heat causes pellets to crystallise from the inside out, the result is an improved crystalline structure that requires less energy for re-melting.” Underwater pelletizing
technology can handle an increasingly broad range of polymers and some difficult compounds that could previously only be strand cut can now be taken on using die-face pelletizers. Nordson
34 COMPOUNDING WORLD | January 2016
with up to 22 holes. At the company’s lab in Austria, it has produced PP, PA, PEEK, and PET micropellets and is testing them in-house. Researchers are also working on reducing die hole size even further, to 0.2 mm, says Forstner. Beyond rotomolding, smaller pellets
also result in higher dosing accuracy, according to Asmuss at Nordson. With the industry trend toward more highly loaded masterbatches and lower dosing levels in the final product, a smaller pellet diameter can be a real advantage.
Click on the links for more information: ❙
www.gala-industries.com ❙
www.econ.eu ❙
www.nordson-k.com
continues to work on processing of low viscosity products, which can be challenging because a high melting point is required to prevent the polymer from freezing and thus blocking the holes in the die. The company is currently developing a die plate material that will improve insulation and reduce the tendency of polymer to freeze in the die channels. Nordson also reports increasing demand for special
pelletizers. The increasing use of expanded polystyrene (EPS) as a building insulation, for example, has seen demand grow for systems for cutting EPS. As pentane is used in EPS production, these pelletizers must be designed for suitability for use in hazardous (potentially explosive) environments. Econ, opened subsidiaries in India and the US in 2013 and commissioned a test lab at its US technical centre at Monroe in Michigan in March last year. The lab houses an EUP 150 underwater pelletizing system, EWA 50 pelletizer that is interchangeable for water or air cooling, and an EUP 10 laboratory-sized under- water pelletizing system. The Austrian-headquarte-
red company recently introduced a simplified control system for its
pelletizers with an improved human-machine interface (HMI). The system, using either a Siemens or Allen Bradley PLC, provides a programmable, auto-
www.compoundingworld.com
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