MATERIALS | MASTERBATCH
These can impart shades with a hint of every-
thing from ‘red’ (including brown) to ‘blue’ (in various degrees) by using two specific pigments – known as Pigment Brown 29 (PBr29) and Pigment Green 17 (PG17). A 1% loading of one of these special grades –
rather than a ‘standard’ carbon black – lowered surface temperature by around 10°C, said the company. There are grades for thin films that combine these two pigments – and a third, Ultramarine Blue
Masterbatches can be ‘seen’ using NIR
UK-based Colour Tone has launched a new generation of ‘competitively-priced’ near- infrared (NIR) detectable masterbatches that meet recyclability concerns for single- use black plastic tubs, trays and films. Plastics coloured with carbon black cannot be ‘seen’ by the NIR technology used in commer- cial waste sorting operations. These new masterbatches overcome this problem. The first two grades are targeted primar- ily at polypropylene (PP) but can be applied to other polymers. The company said NIR black 958884 meets EU food contact legislation requirements. NIR black 95893 supports applications that meet the US FDA Code of Federal Regulations’ criteria at up to 10% dosage. Colour Tone director Tony Gaukroger said price has been a barrier to wide adoption of NIR-detectable black masterbatches. �
www.colourtone-masterbatch.co.uk
(PB29) – but higher loadings are needed to ensure visible and NIR opacity. For more moderate performance, manganese ferrite black oxides are a more cost-effective option, said the company. Palad Sopanakijkosol, a technical services manager at Birla Carbon in India, explained the importance of particle size in carbon black master- batches: while larger particles are relatively easy to disperse, and impart a ‘grey’ colour to products, smaller particles have a more intense colour effect – but are harder to disperse. For this reason, the company has studied the
factors affecting dispersion – including compound- ing conditions (such as mixing time and tempera- ture) as well as other factors like polymer proper- ties and the presence of other additives. “Complete letdown of masterbatch into the final
product is essential for the best performance of carbon black,” he told delegates. Different factors that affect letdown include: a viscosity mismatch between masterbatch and letdown resin; inadequate compounding time and shear; and the presence of other fillers in the polymer matrix. He showed a range of blown film samples –
where a good letdown showed a darker film, while poor letdown resulted in black spots caused by undispersed masterbatch.
Size selection At the other end of the colour spectrum – white rather than black – particle size is also important. Jörg Hocken, global application manager at Venator Materials in Germany, said that titanium
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