Masterbatch is a concentrated mixture of pigments and / or additives encapsulated during a heating process in a carrier resin, afterwards cooled and cut into a granular form. The Masterbatch allows the manufacturer to economically color natural polymers during the plastics manufacturing process.
The masterbatch use alternatives are composite raw materials (which may imply) a cost increase and less flexibility, such as product color variability), or on-site raw materials mixing (a potentially problematic process, with regard to the total dispersion of dyes and additives and prone to mandatory acquisition of materials in excess of the necessary). Compared to pure pigments, masterbatches require more storage space with longer delivery times.
As masterbatches are already pre-mixed compositions, their use avoids additive and dispersion problems or dyes agglomeration. The use of masterbatches allows the manufacturer to acquire a smaller number of polymer degrees, thus providing conditions for the purchase of raw material in scale.
Masterbatches can be highly concentrated (compared to the final blend), with high “reduction rates”. A 25 kg bag can process a ton of raw material. The relatively diluted nature of masterbatches, when compared to raw additives, allows greater precision in the dosing of small quantities of high-cost components. The compact nature of the solid masterbatch grains eliminates dust problems, which are inherent in refined solid additives.
Solid masterbatches do not contain solvents and subsequently tend to have a longer service life considering their non-evaporation characteristics. The masterbatch usually contains 40 to 65% of additive, but in extreme cases, the range can reach values between 15 to 80%.
The masterbatch carrier can be based on a wax (universal vehicle) or on a specific polymer, identical or compatible with the polymer to be transformed. For example, EVA or LDPE can be used as a carrier for polyolefins and nylon, polystyrene can be used as a carrier for ABS, SAN and sometimes polycarbonates.
When a carrier of the masterbatch is incompatible with the raw material, the masterbatch can modify the properties of the transformed material, so whenever necessary, the manufacturer must specify the characteristics of the raw material.
The masterbatches percentage use in relation to the raw material is between 1 and 5%. Several masterbatches (color and additive) can be combined. The transformation equipment is usually fed with raw material and masterbatch. The homogenization of both materials is verified at the end of the machine’s spindle stroke.
Sometimes the system is prone to adverse effects such as the masterbatch separation from the raw material in the machine hopper. The masterbatch can also be added directly to the machine’s spindle, as a free-flowing solid or, in a liquid masterbatch case, via a peristaltic pump. The use of liquid masterbatch allows obtaining highly accurate dosages in addition to rapid color changes between productions.
Masterbatches can be used in most processes, except rotational molding, Plastisol and other liquid resin systems.