EPC Engineering & Technologies GmbH from Arnstadt, in cooperation with Coperion GmbH from Stuttgart, has developed a one-step direct compounding process for polycarbonate (PC) melt. The technology is based on non-phosgene polymerization and links the outlet of the final polymerization reactor directly to a compounding step, where PC melt is combined with other polymers, such as ABS, and with additives. By eliminating separate downstream compounding lines and intermediate material handling, the process is designed to increase energy efficiency, lower operating and investment costs and simplify the overall production of PC compounds for a broad range of applications.
Integration of polymerization and compounding
At the core of the concept is the direct compounding of the PC melt immediately after it leaves the final polymerization reactor. Instead of cooling, pelletizing and storing PC granules and then feeding them to a separate compounding plant, the melt is transferred straight to a dedicated direct compounding extruder. In this extruder the polycarbonate is mixed with other polymers, such as ABS, as well as with functional additives according to the target formulation.
The extruder used in this setup is a Coperion ZSK twin screw machine, which homogenizes the ready-made PC compound melt before pelletizing. This machine configuration is intended to provide intensive mixing combined with controlled residence time to achieve uniform distribution of additives and blend partners in a single continuous step. The one-step approach replaces the conventional sequence of polymerization, chip production, storage, conveying and second-step extrusion compounding.
Energy efficiency and operating cost impact
According to the developers, one of the key advantages of the one-step process is the substantial reduction in energy consumption. In conventional PC compounding routes, solid PC chips or granules must be stored, conveyed and then reheated and remelted in a second extrusion stage before compounding. The new process eliminates this intermediate solid phase and the related thermal cycle.
The PC melt is conveyed directly from the final polymerization reactor to the extruder together with the additional polymers and additives. This removes the need for intermediate PC granule storage systems, conveying equipment and a separate compounding extrusion line. By avoiding reheating and remelting in a second step, the overall energy demand of the PC compounding process is reduced.
The companies report that, depending on the product mix, these changes can result in operating cost savings of up to 1 million USD per 100 kta of production capacity. The savings potential is attributed mainly to lower energy consumption and to the reduction or elimination of handling and conveying systems that are otherwise required between polymerization and compounding.
Capital expenditure and plant layout
In addition to operating cost effects, the integrated concept is aimed at reducing capital expenditure. Because compounding is carried out directly on the polymer melt, there is no requirement for separate, full-scale compounding plants or associated supporting infrastructure. Storage silos for PC chips, conveying lines to downstream compounding extruders and additional extrusion lines themselves can be reduced or omitted in plants that adopt the one-step approach.
The entire production chain can be implemented within one integrated direct compounding process step and its associated machine setup. This simplifies the overall layout, potentially reduces the footprint and lowers the complexity of project engineering. For new PC capacity, this can translate into lower initial investment, while for existing sites the concept offers a route to debottlenecking or modernization by linking polymerization more tightly with downstream value-adding steps.
Formulation flexibility and market responsiveness
Beyond cost and energy aspects, EPC Engineering & Technologies and Coperion emphasize the flexibility of the new process. Because the compounding step is directly connected to polymerization, producers can adjust formulations more rapidly in response to market demand. Changes in the type or ratio of blend partners such as ABS, as well as in additives, can be implemented at the compounding extruder without modifying the upstream polymerization chemistry.
This flexibility is intended to support short reaction times to customer requirements and frequent product changeovers. It enables producers to widen their portfolio of PC compounds by tailoring impact strength, optical properties, heat resistance or other performance parameters through controlled addition of polymers and additives in the direct compounding step. As a result, the technology is positioned as a tool for increasing product diversity while maintaining an efficient, integrated process chain.
According to the companies, the combination of non-phosgene PC polymerization with direct melt compounding provides a platform for long-term competitiveness. By coupling high energy efficiency, reduced capital intensity and agile formulation capabilities, the process addresses both economic and operational drivers for producers of polycarbonate compounds.
EPC and Coperion have worked closely together to develop an innovative process for the direct compounding of polycarbonate (PC) melt, which is characterized by both its high flexibility and cost efficiency.
