The new masterbatches from Clariant are intended to help increase the recycling rates in Europe and elsewhere

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Image: Clariant Innovation Center in Frankfurt. Photo: Courtesy of Clariant.

Swiss speciality chemicals company Clariant has developed CESA-IR additive masterbatches to make dark-coloured plastics visible to the near-infrared (NIR) sensors that are used in automated polymer sorting systems.

Even though several companies use black packaging to brand their products, problems posed by the packaging in recycling systems has prompted calls for the phasing out of black from the palette.

The new masterbatches are intended to help resolve the issue and allow increased recycling rates in Europe and elsewhere.

Clariant masterbatches support the ‘Design for Recycling’ programme

The new masterbatches product range supports the company’s ‘Design for Recycling’ programme. The solutions can be used for numerous polymers and applications.

To ensure a higher percentage of plastic packaging is recycled, Clariant Masterbatches and its packaging market group are mobilising resources across the packaging value chain.

In automatic sortation systems, infrared light is beamed onto packaging materials. As different polymers reflect that light differently, NIR sensors can discriminate between polyethylene, polypropylene, polyester and other polymers used in packaging.

However, the carbon black pigments used in black plastics absorb all or most of the NIR light. Consequently, the sorting sensors cannot even ‘see’ the black packaging, making them useless to sort one polymer from another.

Clariant Masterbatches global head of packaging Alessandro Dulli said: “As a result of this phenomon, much of the dark-colored materials entering the recycling stream has not been recovered. For that reason, many brand owners have been pressured to move away from black for environmental reasons.

“In close collaboration with these brand companies and as a leader in sortation technology, Clariant has developed a way to achieve a persuasive black color in plastics without compromising the essential detectability during recycling process.”

The company has developed CESA-IR formulations to allow IR-detectability of black HDPE and LDPE in injection and extrusion blow-moulded products; black polypropylene in films and injection-moulded products; and black PET and C-PET in sheets and film.

During tests conducted by Norwegian company Tomra Systems, polypropylene containing carbon black was not indistinguishable under NIR radiation from surfaces such as a conveyor belt.

However, the same material made using another colouring system, including CESA-IR additive masterbatches, was readily detectable.