Mark Stewart

PVC is a thermoplastic resin that cannot be processed on its own due to its very low thermal stability and high melt viscosity. Therefore, it is necessary to prepare an intermediate product where a variety of additives are mixed with the PVC resin to form a “dry-blend” that can be later melt-compounded or processed into a finished article. The unit operations present in the compounding of PVC involve delivering and storage of raw materials, feeding and spraying of all ingredients into a special mixer, mixing and heating the materials to create a dry-blend, then cooling and transferring the dry-blend to storage or to a conversion process such as molding, extrusion or calendering.

The goal of a compounding plant is economical production! Among other things, this means as little waste as possible and minimum reconfiguration time. The Coperion K-Tron feeding system makes this possible. An important factor is the adherence to the recipe during ramping up of the extruder and naturally also during large setpoint changes. The short-term accuracy of a high-performance extruder is a key factor for quality of the end product. In order to even be able to speak of adhering to recipes with changing operating data, one condition must be fulfilled: the mass flow must adapt to the setpoint as quickly as possible. This is only possible with advanced gravimetric control and the high sampling rate and resolution offered by Coperion K-Tron’s Smart Force Transducer weighing technology.