Dispersive Mixing Using Polymeric Waxes

A technique enabling single screw extruders to achieve good dispersion of pigments in colour masterbatches has been describe in the past by polymer wax manufacturers. 

An advantage of this process is that a number of small single screw extruders which are of relatively low cost, can economically produce small orders for specialised colours. They can he easily cleaned between batches or maybe dedicated to a single colour. The attraction of this approach has probably declined over more recent years following the introduction of very small twin screw compounding extruders. 

As explained in Chapter 2, the medium into which pigments are to be dispersed should ideally have a low viscosity such that it can easily wet powders and penetrate between particles, preventing agglomeration should small particles be pressed together during mixing. The reality with plastics extrusion, is that the opposite situation is normally the case. 

An example taken from a Luwax brochure [12] is as follows  

1) The polymer wax melts to become a low viscosity liquid which wets and coats the pigment particles 

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