Recycling of Rigid Plastics
Cluster Project on Technology and Efficiency
Recycling the waste from plastics processing (post-industrial waste stream) has become a standard application today. According to the Austrian plastics cluster, the optimum has not been achieved yet in the area of recovering post-consumer waste (e.g. from the centers collecting secondary materials). A recent project by four cluster enterprises shows that knowledge as well as processes to recover these plastics are in fact at hand. However, the oil price significantly determines the extent of application.
At present only few plants are available to recycle this kind of material goods in Austria, after the end of their service lives. This is why the fraction of rigid plastics from the collection centers is frequently recovered only thermally. In some of the collection centers, waste separation had been difficult to introduce. The plastics cluster says that this lack of recycling options may eventually lead to the end of separation for these types of plastics.
From Waste Stream to Final Product
To make better use of the fallow raw material resources, four partner enterprises* of the plastics cluster decided to work together on finding a useful process of material recovery and recycling for the fraction of rigid plastics. The project was finished in spring 2016, leading to the following result: the entire process chain, starting from cleaning, compounding and formulation up to producing new, high-quality products by injection molding was described in technical terms and optimized. The quality of the regranulate produced in this way finally turned out to be only slightly lower than that of virgin material, which makes it perfectly suited as a substitute for virgin material.
The rigid plastic was shredded and polyolefins (approx. 65% of this fraction) were separated and washed in a float/sink process. The partners employed different plant concepts and filter techniques to generate regranulate material from these polyolefins, on recycling test units. The recycled material was used to produce different components by injection molding. The parts were then compared to components made of virgin material, with regard to properties. The material was frequently characterized in terms of mechanical, thermal and rheological properties, and modified by additions, if necessary.
A Small Downer
However, efficiency is unambiguously linked to the cost of virgin material. According to the plastics cluster, the current low price of oil makes it virtually impossible to reuse this fraction – despite the newly acquired knowledge and optimized technique. This is why one of the project partners continues to work on the project, looking into the utilization of the fraction’s polystyrene share. Should they be successful in re-using this share, too, in addition to the polyolefins, efficiency would be secured, in times of low oil price.
* TCKT Transfercenter für Kunststofftechnik GmbH (Wels), Innplast Kunststoffe GmbH (Waldzell), Erema Engineering Recycling Maschinen und Anlagen Ges.m.b.H. (Ansfelden), Katzengruber Kunststofftechnik GmbH (Dimbach)