Polymer granulates with a high percentage of additives, higher than in the end use, are called masterbatch. In later production steps, such as injection moulding, film or fibre production, those granulates are mixed with the raw polymer for colouring or the targeted modification of certain properties.
Advantages: In comparison to pastes, powders or fluid additives, using masterbatch increases the process stability. The reason lies in the exactly defined pigment quantity in each granulate. Additionally, Since there is no handling of large powder masses and therefore the environment and the work station are not being polluted, masterbatch is regarded to be a very good processing material.
3 method is used in plastic masterbatch production:
1. Pre- mix, most widely spread production process, a premix consisting of polymer, pigment and dispersion additives is fed to the extruder. Normally, these premixes are produced in batches in a previous mixing step. Great importance must be given to this premix process. If a mistake happens here, unfortunately, oftentimes it is very difficult to make corrections during the extrusion step. Due to the usage of volumetric feeders, there is a high operational reliability, handling is quite uncomplicated, and the process is very popular as well as low priced.
2. Split-feed version of masterbatch production, the polymer is plastified first. Then the other formulation components (pigments, fillers and if needed dispersion aids) are added via one or two side stuffers (hot melt extrusion). Feeding is done via separate gravimetric feeders. The handling of the formulation via the extruder or feed control is relatively uncomplicated and does not need elaborate premixing. This makes big scale masterbatch production much easier.
3. Custom Colouring uses an exact mixture of standard colours (monobatches) to produce the required colour match. Via a multi-component gravimetric feed system (generally 5 to 8 components) and predefined standard colours, the colour required by the customer is produced. The setup of the extrusion line is similar to the premix system.