Coperion celebrates 60 year anniversary of ZSK Extruders

Coperion, a German builder of extrusion systems, is celebrating 60 years of its ZSK twin screw extruder, the ‘forefather’ of all twin screw extruders.  

In 1957, Werner und Pfleiderer, now known as Coperion, delivered the first co-rotating, closely intermeshing ZSK twin screw extruder.

Since then, the ZSK extruders have evolved from relatively simplistic co-kneaders with a throughput rate of 170 kg/h, to sophisticated, high-performance processing machines for a variety of applications in the plastics, chemicals, food and pharmaceutical industries. They are manufactured with screw diameter sizes ranging from 18 to 420 mm and achieve throughput rates from 200g to 125 t/h for polyolefins.

Werner und Pfleiderer acquired an exclusive license from Bayer in Leverkusen, Germany, in 1953. Work was started by Rudolf Erdmenger and Walter Meskat at the IG plant in Wolfen in 1943. In 1945 Erdmenger continued the work as part of the ‘High-Viscosity Technology’ group and developed the fully self-wiping profile for co-rotating intermeshing screws. This was the inception of the ZSK twin screw extruder, which remains functional over a wide range of viscosities or frictional properties of the processed material. The prototype of this machine invented by Erdmenger was still equipped with vertically arranged screws, unlike the ZSK twin screw extruder of today. Werner und Pfleiderer undertook an additional four years of development work in order to make the first machines fit for production.

Today, the ZSK twin screw extruder is distinguished by a performance level considered revolutionary at the time of its market launch and for a long time afterwards. For a machine of the same shaft centre distance, the throughput rate today is 35 times higher than it was 60 years ago. At the same time, today’s compounding machines handle a considerably higher number of processing tasks. Today, the process section can be extended up to 80 screw diameter, from an original figure of 6. While the first ZSKs featured a specific torque Md/a³ of 3.7 Nm/cm³, today’s ZSK high-performance extruders boast torques of 18 Nm/cm³ on the ZSK Mc18 and 11.3 Nm/cm³ on the ZSK Mv PLUS. Together with a significant increase in speed from 150 min^-1 to 1,200 min^-1 or 1,800 min^-1 – which some experts initially viewed with scepticism – the current ZSK range can achieve incredibly high throughput rates.

The developers at Coperion already have their sights set on the machines of tomorrow – with an even wider spectrum of applications for new tasks in a vast range of industrial sectors. Energy efficiency, the conservation of resources and the integration of ZSK high-performance extruders into companies’ digital environments are the current hot topics that are shaping the future of the ZSK.

Frank Lechner, Head of Process Technology at Coperion, said: “Current examples of our innovative strength are the changeover from batch processes to continuous processes, which are increasingly in demand by customers in the chemical and pharmaceutical industries in particular. We have already been able to achieve impressive results with our ZSK extruders when producing products such as sealants or cleaning agents. In many processes, we are also able to increase the throughput rates and the product quality many times over with our latest development, the recently introduced involute screw elements, thus contributing to more efficient use of the systems and resources. We are also equipped for the future requirements of the ‘Circular Economy’ as far as both extruder technology and our decades of processing know-how are concerned.”