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 (primary 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.
Colour masterbatches contain colouring agents in dispersed or dissolved form. Colours or shades serve, inter alia, as characteristics for companies or certain products, protection components or functional additives. Amorphous polymers (polystyrene, polycarbonate, polymethyl methacrylate etc) – which are intended to remain transparent – necessitate the use of polymer-soluble dyes.
Mono-concentrates or Single Pigment Concentrates (SPCs) consist of only one colouring agent in a substrate. PE, PP, PS etc. are used as substrate. The concentration of the colouring agent in the substrat depends on the type of colouring agent (inorganic pigments up to 70 %, organic pigments up to 60 %, dyes up to 25 %). They are distributed directly to plastic processors (e.g. compounders, extruders, injection moulding companies or other producer of masterbatches). Internally, they are used for tailor-made masterbatches, according to customer requirements – as an alternative to powder pigments.
Tailor-made (Colour) Masterbatches are tailor-made, according to customer requirements (colour, matrix, function). Combinations of pigments, dyes, effect pigments and further materials are needed, in order to meet certain requirements. Powder colourants or SPCs are used for this purpose.
Effect Pigment Masterbatches:
Effect 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.
image: Masterbatch with fibres
Some processors want combinations of colouring agents and functional additives. The advantages are obvious: customers can work with only one product. Mistakes are avoided; there is no need to store several products.
Combinations of colouring agents, UV stabilizers and anti-oxidants are commonly found, as the required concentrations are possible in masterbatches.
Further variations: mixtures of colouring agents and flame retardants, including nucleating agents, lubricants, antistatic agents, anti-repellents, laser pigments, etc.
Compounds are granular or powder preparations, which contain all ingredients of the end-product and are processed directly into the end-product.
Compounds are ready-for-use preparations for end-product manufacturers.
Difficult profiles of requirements, for example conductive compounds, necessitate compounds.
Universal uses for all polymers.
A dream for all users. only very few colouring agents can be used universally in polymers.
Detailed studies identify problematic (rheological, mechanical) influences.
Differences in colour shade through own colour of substrate systems.