Additives: NIR-Detectable Black Masterbatch Technology Make Dark Colors More Recyclable

In its continued quest to develop new technology that improves the recyclability of plastics while offering packaging and product developers more color options, Clariant (U.S. office in Charlotte, N.C.) has launched a family of proprietary deep, dark colorants that typically would require use of carbon black pigments that makes them undetectable by the near-infrared (NIR) sensors used in automated polymer sorting systems at recycling centers.

However, the new Clariant colorants developed in its ColorWorks design and technology center near Milan, Italy, now makes it possible to explore a darker and more mysterious color space entirely without the use of carbon black. Development is well underway for  PET, HDPE and PP in both virgin and post-consumer recycled (PCR) forms for use in all the various packaging applications, including trays, bottles and caps.

In most automatic sortation systems, infrared light is beamed onto plastic materials and, because different polymers reflect that light differently, the system can sort the different materials. Unfortunately, carbon black pigments typically used to make black and other deeply dark colors absorb all or most of the NIR light shone at them and, as a result, the sensors cannot even “see” the black packaging, much less sort one polymer from another.

In late 2019, Clariant introduced Cesa IR, a masterbatch range that makes black plastics visible to NIR radiation. This effect was confirmed by testing conducted by TOMRA Sorting Recycling, a Norwegian company that is a leader in the field of instrumentation for recycling solutions.

But designers want more choices than pure black, according to Roberto Romanin, a Clariant ColorWorks designer, “There are very definite trends in this direction. Some exclusive, high-end facial treatments, nutrient serums and oils are being packaged in these rich dark colors. However, most of them still use carbon black and so they have recyclability problems.” To address this issue, the ColorWorks team undertook a project, to use Cesa-IR technology to develop colors that could be dark without the use of carbon black. Three colors – a dark umber, a deep velvety green, and a regal dark blue – have been created initially. All three are really saturated so they are almost black but the colors come through, bringing to mind elegance, exclusivity, heritage and boldness.