PIGMENTS | BLACK AND WHITE


Figure 1: This graph from UK-based Colour Tone Masterbatch shows percentage reflectance over the 300-2,500 nm wavelength spectrum for a carbon black pigment (red line) and NIR-reflective black (blue line). UV extends to 380nm, VIS from 380-780nm, IR >780nm. Image: Colour Tone Masterbatch


does not inhibit NIR sorting. He says that the overall absorbance in the NIR range of a combination of pigments (each of which considered NIR-sortable on their own) can reduce reflectance more than would be expected.


Sorting problems Although it is true that NIR spectroscopy can have difficulty sorting plastics containing carbon black, some commercial-scale recycling facilities use technologies other than NIR, according to Dominique Strässler, Global Segment Manager Plastics, Cabot Corporation. “For example, so-called ‘mid-infrared (MIR) scanners’ offer significant advantages for positive identification of, among others, carbon black-containing black plastics,” he says. “We [Cabot] believe that the value provided by carbon black will result in carbon black remaining as the black pigment of choice in packaging applications,” says Strässler. “The use of carbon black pigment is the best way to colour the mixed colour fraction of recycled plastic. Black plastic has been popular among packaging producers because it enables the use of skeletal waste, factory scrap and recycled plastics in products without creating a colour that is considered unattractive to consumers.” Strässler also expects carbon black to continue to dominate in black plastics where high tint strength and other properties, such as UV and weathering protection, are important, including automotive, electronics and consumer goods, plastic pressure pipes, agricultural films, wire and cable, and conductive plastics.


30 COMPOUNDING WORLD | November 2022 He also says that plastics customers are looking


for increased “sustainable content” in products and reductions in environmental footprint. “As a result of this, we are working both on exploring options to make and formulate our products with recycled and/or renewable content and on assessing our greenhouse gas (GHG) footprint, with the main goal of reducing it,” he explains. The company has already published GHG emissions intensity (Scope 1 and 2) and has initiated a cradle-to-gate life cycle analysis of its carbon black products. “Once this analysis is complete, we expect to be able to provide Scope 1, 2 and 3 GHG emission estimates and other environmental aspects for various carbon black product grades.” (Learn more about the GHG Protocol and the Scope 1, 2 and 3 emissions HERE.)


Recycled options Cabot also offers carbon black masterbatches, including masterbatches made from recycled materials, through Cabot Specialty Compounds. It is building a new specialty compounds facility in Cilegon, Indonesia. Expected to start up by the end of this year, it will add 20,000 tonnes of annual global capacity for specialty compounds. The company says the facility is being designed to reduce environmental impact. It will, for example, use recovered waste-heat energy from Cabot’s existing carbon black manufacturing facility that is located on the same site. Other carbon black suppliers are also expand- ing manufacturing supply, with Birla Carbon adding facilities in China, India and Hungary to come online in 2024 and Orion Engineered


www.compoundingworld.com


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