Where colouring agents are concerned, a differentiation is made between dyes and pigments, with the latter being of much greater importance in the plastics sector. Pigment particles – as they are usually generated in manufacture – have strong forces of attraction, due to their extremely small particle sizes. Consequently, primary particles gather to form so-called aggregates.
In powder pigments, aggregates invariably form agglomerates. During colouring, the agglomerates need to be broken up, wetted by the polymers, and distributed homogeneously. These steps – which take place simultaneously – are called dispersion. From the aspect of machine technology, dispersion is a difficult and complex process. Dyes undergo a solution process, with molecularly dissolved dyes as the outcome. Solubility depends on the individual dye, the polymer material, and processing conditions.
Plastic colour masterbatches contain colouring agents in dispersed or dissolved form. Colours or shades serve, inter alia, as characteristics for certain products, protection components or functional additives.
Pigments need to be 'handled with care' as to not destroy their leaf structure. Quite often, this is not reliably ensured in processing together with standard pigments. High shear forces in extruders should be avoided.
Masterbatches contain effect pigments, such as e.g. perlescent pigments, metal pigments, colour-variable pigments, fluorescent pigments/dyes, glitter, mica, glass or fibres.