BLACK AND WHITE | PIGMENTS
When it comes to black and white pigments, there are a whole range of new options designed to target sustainability and regulatory concerns. Peter Mapleston find out more
New moves in black and white
Regulatory issues are bringing about change in the use of the pigments that make plastics compounds black or white. Not so long ago, the choice was straightforward: carbon for black and titanium dioxide (TiO2
) for white. Today, it is not so simple.
Carbon black is facing issues around its compli- ance with some current sorting techniques used in the recycling sector, for example, while European regulators have taken aim at TiO2
. The choice is
becoming more difficult. High volume recycling of plastics packaging
starts with collection and then sorting of mixed plastic waste into separate mono-material streams at recovery facilities. This sorting step frequently makes use of near-infrared (NIR) optical sensors to differentiate different polymers. However, prob- lems can arise with carbon black pigmented products such as films, trays, and bottles because the pigment does not reflect sufficient signal. As a result, material can end up in the residual fraction, which typically goes to landfill or the incinerator. For this reason, numerous companies producing pigments or colour masterbatches have been developing alternatives that contain no carbon
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black. In the majority of cases, these are not quite as black as carbon but they are often an acceptable compromise for customers needing to improve the sortability — and ultimately the sustainability — of their products. “With our latest black pigment, we can help to
increase the recycling rate for plastic packaging, which is still far too low around the world,” says Stefano Bartolucci, Global Market Segment Manager for Plastics in the Inorganic Pigments (IPG) business unit at Lanxess. Several months ago the company introduced Bayferrox 303 T, an iron-manganese mixed oxide black pigment for plastics that reflects 20% of NIR and has a Colour Index classification of PBk 33. Carbon black is the pigment that has been most
frequently used for black packaging materials as it is relatively inexpensive and exhibits high colour strength. “Complex inorganic coloured pigments (CICPs) and manganese ferrites, of which the latter are far more cost-effective, are high-quality alterna- tives to carbon black thanks to their property profiles – because they reflect infrared light,” according to Lanxess. “Bayferrox 303 T also offers colour strength
November 2021 | COMPOUNDING WORLD 17
Main image: Sustainability and regulation are driving developments of alternatives to traditional black and
white pigments for plastics
IMAGE: SHUTTERSTOCK
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