Polymer‐ and wax‐based monoconcentrate predispersed pigments in the colouring of plastics

Over the past few decades, masterbatch production has been increasing year by year. Pigments are used primarily in masterbatches because of their ability to impart colour or opacity to a matrix. The effectiveness of pigments depends not only on their intrinsic ability to absorb or scatter light, but also, importantly, on the dispersiblity and distribution of the pigments that can be achieved in plastics. Nowadays, stringent environmental as well as excellent quality controls are making inevitable the use of non‐dusty monoconcentrated predispersed pigments for the production of masterbatches for the colouring of plastics. Commercially, for the most part, two types of monoconcentrated predispersed pigments are being used for the colouring of thermoplastic masterbatches. These are polymer‐ and wax‐based predispersed pigments. This study has been undertaken to provide a comparison of the colouring properties of polymer‐ and wax‐based monoconcentrated predispersed pigments. Four commercially used organic pigments have been selected. Both types of monoconcentrate predispersed pigments have been developed on a co‐rotating twin‐screw compounding extruder with a length/diameter ratio of 44. A detailed analysis on the comparison of the colouring properties is presented. Results indicate that good colour properties are achieved when operating conditions are optimised.