Bad odours – this is an issue many recyclers of post-consumer plastic scrap have to deal with. The input material they are processing often contains migrated substances from food, cosmetics or cleaners, which cause an unpleasant smell during the recycling process. But also residues of monomers, oxidation or hydrolysis, as well as decomposition products (VOCs – volatile organic compounds) can be the reason for unwanted smells in recycled granulate. Solid contaminants and foreign matter, e.g. paper or wood, cannot be removed to 100 % even in intense washing processes and thus can cause odour development in the extrusion process.
Measures for odour reduction can be taken during the different stages of plastic production and processing. Usually, additives are added to achieve a reduction of unwanted odours. The use of additives, however, causes additional production costs with questionable results – an additive does not actually remove the odour, it only blankets it. This means that the original odour might return during the following process steps or in the final product. To avoid that, Starlinger recycling technology has developed a recycling process with odour reduction that does not require additives and has a permanent effect.
Odour reduction in 3 steps
Starlinger adapts the recycling and odour reduction process individually according to the needs of the recycler, i. e. depending on the polymer type, source or type of the odour, its intensity, and the specifications of the produced regranulate. The recycling and odour reduction process consists of the following steps:
- Material preparation in the SMART feeder – the input material is heated and homogenised until the ideal operating point is reached. Highly volatile odours are already extracted during this process.
- C-VAC degassing module – increases the melt surface by 300 %, thus achieving an extremely high degassing efficiency. This results in permanently removing also deeply embedded odours.
- Smell extraction unit – gives the regranulate the finishing touches. In this final unit, the most persistent odours are reliably extracted and removed permanently.
The result is high-quality, permanently odour-free regranulate that can be used up to 100 % in many applications.
Starlinger’s recoSTAR dynamic recycling line has proven to be the ideal choice for processing a wide range of plastic scrap with strong odours. The integrated “Dynamic Automation Package” allows highly automatized production as well as continuous process adaptions. It does not only increase productivity and machine uptime, but also reduces energy consumption. The automatic temperature control ensures unchanging high product quality even when processing input materials with varying bulk densities and humidity levels – including materials with more than 10 % moisture content.
An opportunity for recyclers
With Starlinger’s odour reduction technology, recyclers of post-consumer plastic scrap have the opportunity to turn their input material into a high-grade secondary resource: excellent and homogenous regranulate quality and permanent odour reduction ensure reuse of the regranulate to up to 100 % also in demanding applications.
Starlinger recycling technology has been working on the issue of odour reduction for many years and officially presented the developments and results during the last K fair in Düsseldorf. The interest in odour reduction continues to be enormous even months after the K fair, and the Starlinger Technical Center in Weissenbach, Austria, is busy with trials. The high effectiveness of the Starlinger odour reduction process evidenced in the trials also was the reason that a customer placed a repeat order already before the previously ordered odour reduction equipment had been installed at his premises.