NexKemia Petrochemicals Inc., a manufacturer of expandable polystyrene (EPS), has relied on ZSK twin screw extruders from Coperion since 2020. With a focus on innovative manufacturing processes and sustainability, the company supplies EPS products for the packaging industry as well as for building insulation. In addition to white EPS, NexKemia produces EPS mixed with graphite, referred to as graphite-enhanced polystyrene (GPS), and grades containing up to 30% recyclate. For both manufacturing and product development, NexKemia uses Coperion ZSK twin screw extruders, which enable environmentally oriented production, gentle handling of white and grey EPS and the incorporation of recycled materials on a single production line.
Twin screw technology simplifies EPS production
Conventional white expandable polystyrene is typically manufactured discontinuously via suspension polymerization, where the styrene monomer is polymerized in a batch process. Alternative continuous manufacturing routes exist, in which processing is carried out with the feeding of additives and pentane in several successive process steps. These solutions generally combine various units such as twin screw extruders, single screw extruders or static cooling mixers.
Coperion offers a different approach based on a simplified, single-step process using the ZSK twin screw extruder for EPS production. In suspension polymerization, maintaining the chemical balance during the reaction is critical, since even small impurities or foreign materials can upset this balance and destabilize the process. In contrast, no chemical reaction takes place in the ZSK extruder. The substances are mixed rather than polymerized, so this sensitivity does not arise in this manufacturing route.
All ingredients are metered into the Coperion ZSK extruder via high-accuracy Coperion K-Tron feeders and are processed into a homogeneous melt using precisely adjusted shear input and short residence times. According to the description, this approach ensures low thermal stress on the material. Micropellets are then produced via an underwater pelletizer downstream of the extruder, generating very small pellets of up to 1 mm with a narrow particle size distribution.
With the Coperion ZSK twin screw extruder efficient production of EPS microbeads is possible on a single machine.
Production of GPS and EPS with recyclate
Beyond the single-step EPS process, the ZSK twin screw extruder enables the production of graphite-enhanced polystyrene and EPS grades containing recycled material. For GPS, free graphite, among other ingredients, is added to the formulation. The graphite reflects heat radiation and provides higher thermal insulation performance compared with white EPS. NexKemia reports that its GPS products achieve a very low lambda value, indicating reduced thermal conductivity and high insulating capacity.
Together with Coperion, NexKemia has implemented the integration of recycled material into EPS manufacturing on one production line. Purified and compacted regrind can be fed directly into the ZSK extruder. Depending on quality requirements, the micropellets and the availability and properties of the discharge material, recycling contents of up to 30% or higher can be achieved. According to the information provided, the final EPS product exhibits physical properties comparable to those of virgin-based products.
The process is also described as having environmental advantages compared with alternative technologies. It is associated with markedly lower airborne emissions and a significant reduction in wastewater generation.
Focusing on innovative manufacturing processes and sustainability, NexKemia provides products for the packaging industry and for building insulation: white EPS, EPS mixed with graphite and products containing up to 30% recyclate.
Cooperation between NexKemia and Coperion
The collaboration between NexKemia and Coperion focuses on process technology for specialized EPS products. Michael Hays, President of Integreon, the parent company of NexKemia, commented on the cooperation: "Using Coperion twin screw extruders, we have the ability to manufacture specialized products for various applications. Thanks to the excellent collaboration and process-technical support, we were able to realize new and environmentally friendly processes together for EPS manufacturing. This allows us to be true to our values of customer focus, innovation and sustainability".
