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10-05-2016

Cutting Costs, Improving Flexibility and Productivity

Efficient Purging with HPC Compounds

Companies wish to reduce costs – but how can they achieve it? This question is growing increasingly important to many plastics producers. Most of all, frequent and fast changes in color and material lead to high expenses. These changes are often necessary during compounding/production as well as processing of plastics, which is mainly done on screw compounders.

Efficient cleaning of the plasticizing unit is one of the possible measures to reduce costs. In many cases, however, companies have their own individual strategies to clean screws and barrels. They apply different kinds of purging techniques or a combination of these methods: natural-colored polymers are often used to rinse the unit, or the screw is purged mechanically or by pyrolysis. Machine cleaning leads to downtimes, which mean additional costs.

Time evaluation: Purging tests were carried out on Acano HPC compounds as well as commercial compounds (© SKZ)

Time evaluation: Purging tests were carried out on Acano HPC compounds as well as commercial compounds (© SKZ)

Prevent Delays and Downtimes

Purging of polycarbonate (PC) and high-temperature thermoplastics has proven extremely challenging, with many purging compounds coming to their limits. As a result, in many cases, the operator must dismount the screw and clean it mechanically in a time-consuming process. This leads to significant delays and downtimes, especially with large plants.

In a joint project, the SKZ - Das Kunststoff-Zentrum, Würzburg, Germany, investigated various methods to clean extruders or injection molding units. Machines that had previously processed PC were purged with high performance cleaning compounds by Acano and with commercial granules. Other test were carried out on alternative purging techniques such as combined cleaning by sandblasting/ultrasonic bath and pyrolysis/ultrasonic bath, respectively, determining the times and energies required. Based on the results, the engineers eventually evaluated the methods under ecological aspects, too.

No Temperature Change or Exposure Time Necessary

Generating only small amounts of process waste, mechanical cleaning causes very little harm to the environment, other than purging compounds. However, considering the life cycle cost analysis, purging compounds are clearly superior to conventional methods, because cleaning only takes a short period of time, leading to low costs of machine and personnel. Thanks to the co-operation with SKZ, the field of high-temperature thermoplastics such as PPS, PPSU and PEEK could also be investigated, in addition to PC. According to producer Acano from Groß-Umstadt in Germany, HPC purging compounds are suited for application within a temperature range of 160°C to 380°C. Acano emphasizes that cleaning with these purging compounds requires no exposure time or change in temperature.

Company profile

SKZ - KFE gGmbH

Frankfurter Straße 15-17
DE 97082 Würzburg
Tel.: 0931 4104-235
Fax: 0931 4104-707

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