sorting | Materials


New masterbatch enables sorting of black plastics


Colour Tone explains in this article how it is answering the problem of sorting black plastics by developing colour masterbatch that can be detected by NIR technology


Main image: Black food trays cause problems during recycling


In recent years the role of the masterbatch manufac- turer has changed. Instead of simply matching a colour, the industry is often required to enhance the physical properties of the product at the same time to deliver, for example, enhanced UV protection, flame retardance or antistatic qualities. Colour Tone has now taken this a stage further by developing the technology to allow its colourants to be detected by near infra-red (NIR) sorting systems used by plastics recyclers. Why?


Black tray recycling Each year 1.3 billion black food trays are sent to landfill, as black and other dark coloured packaging cannot be picked up by recycling sorters. This is because these packaging products contain carbon black that reflects very little or no radiation rendering it ‘invisible’ to sorting machines in recycling facilities. In response UK agency WRAP commissioned a


project called ‘Development of NIR Detectable Black Plastic Packaging’, supported by Colour Tone and plastics resource consultancy Nextek. The aim was to develop a solution to enable black plastic packaging, that is currently destined for landfill or energy recovery, to be recycled. A new NIR black product was developed as a result,


to reproduce as near as possible the same shade and opacity of carbon black (previous attempts had resulted in a less commercial brown), while still being detectable by sorters. This approach uses novel NIR-detectable black colourants and has been shown to work with


20 PLASTICS RECYCLING WORLD | June 2017


APET, CPET, PP, HDPE, PS, and PVC in both laboratory and large-scale trials at a plastic recycling facility. The initial trial proved that the technology would work in principle, but further research was required for wider adoption by the supply chain. The project achieved its original aim of devising black masterbatches to suit numerous end applications in different polymers using NIR black. In the next stage, Colour Tone’s focus was to determine how well this technology can be applied to a broader range of colours, including dark blue, grey, brown and many others used for food trays and other applications.


More colours The colours were chosen from existing matches to give a good selection of shades and included greys (light, mid and dark). A spread of concentrations of carbon black in the original formulations was used to compare their detection abilities against the performance of the new NIR formulations. The tests analysed solar reflectance and heat build-up. Once again, in each case, the reflection was higher than in previous trials, confirming that the substitution of carbon black by an NIR black delivered a significant measureable difference across a range of colours. Tony Gaukroger, Director at Colour Tone, says: “We


are therefore confident of being able to replace carbon black with NIR black in any colour to improve its suitability for sorting by NIR spectroscopy and that this


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