Twin screw extruders enable direct up-cycling

In the lead-up to K 2022, the German Mechanical Engineering Industry Association, VDMA has been conducting a series of interviews with leading businesspersons in the industry, under the title Way2K. Here, Daniel Nagl, Managing Director of Leistritz Extrusionstechnik GmbH talks about how ‘Twin screw extruders enable direct up-cycling’.

Mr. Nagl, what role does the extruder play in the recycling process?

Large quantities of plastic waste still end up in landfills, are incinerated or simply thrown away. The extruder helps to turn something that is considered waste into a plastic again, be it for a superior, equivalent or inferior application. There are different approaches to recycling: mechanical, physical and chemical recycling. There is still a considerable amount of development taking place.

What advantage does a twin-screw extruder offer here?

Its big advantage is that it’s a very good mixing machine. Other machines can also melt materials, but the twin screw can incorporate additives at the same time. In mechanical recycling, this is how you shift from pure re-cycling to up-cycling. In other words, you can produce higher quality material. In physical recycling, a solvent is added to a plastic melt to extract a plastic. In this process, degassing is very important. Again, the twin screw is the best choice because it can degas very well. At Leistritz, we see it as our task to further develop all these processes and technologies to make recycling even more efficient and better. This is a very dynamic field, which is constantly generating new tasks.

Does recycling drive the demand at Leistritz?

We’re noticing that this topic is moving increasingly into focus, which is pleasing to us. Plastic waste from production has been recycled for a long time, for reasons of cost efficiency. What is new is that consumer pressure is growing, which, among other things, is leading to large consumer goods manufacturers voluntarily imposing recyclate quotas on themselves. In this situation, our extruders are increasingly in demand.

However, the premise is that there are sufficient quantities, isn't it?

That is the critical point. With recycling, it depends on who controls the material flows. With PET, the material flow is already relatively well established thanks to the deposit system in Germany. But this is not the case in many other areas. So first of all, you have to get the material flow and then, if possible, a high quality one. There is great potential here to increase the recycling quota, and therefore a holistic solution is urgently needed.

Where else is the twin-screw extruder important besides recycling?

For the extruder, besides recycling plastics, lightweight construction is the second major sustainability issue. In the automotive, in the aviation industry, everywhere plastic components contribute to weight loss and thus to the reduction of CO2 emissions. For example, to further expand our expertise in this area, we entered into a development partnership with the Johannes Kepler University in Linz back in 2018, through which we conduct research on process engineering in plastic processing together with other well-known companies. Starting with the use of fibre-reinforced plastics for lightweight construction, and digitalisation to the recycling of plastics; the entire value chain, from the material via component development, to automated processing. In this context, recycling activities focus on mechanical recycling and upcycling to improve properties.

But the energy turnaround in our country isn’t feasible without plastics, either. For example, a lot of PET is used in wind turbines. We have always made extruders for plastics, but people can identify much more easily with applications such as lightweight construction and recycling. Our employees can tell their families that we’re contributing towards something good.

The demand for plastics is increasing. What needs to be done to ensure that this development is perceived as positive?

We need to inform people and show that a lot of good can be achieved through plastics, and that the extruder is necessary for that purpose, which is something people need to understand. We need to tell them that they must use a cotton bag in the vegetable department at least 1000 times before it pays off from an eco-balance perspective compared to a plastic bag. The problem is that plastic is often misrepresented. We intend to do this educational work as part of our trade fair presence at the K, and are therefore focusing on the topic of sustainability, recycling, and efficiency.

On the Leistritz website, there is a project called "Plastics 2050". What is it about?

We started the project at the beginning of 2021. We inform people about plastics there, presenting questions, but also solutions – and visions. Among other things, we ask ourselves how the increasing demand for plastics can be met without harming the environment, and what options are available to optimally combine technologies, efficiency, and sustainability with the help of digitalisation.