MATERIALS | PIGMENTS
moulding applications where it can help solve dispersion problems and improve colouring of thin wall-section parts. Lanxess, which is the world’s largest manufac-
turer of iron-oxide pigments and a leading pro- ducer of chrome oxide pigments, is also active in developing colours with improved thermal resistance. Its Colortherm brand features a range of synthetic red iron-oxide pigments that are said to provide better thermal stability than comparable pigments. The company attributes this to its proprietary Laux production process, which involves heating the pigments to temperatures as high as 800°C to force traces of water that could cause a colour shift out of the crystal lattice. As a result, the pigments can be processed at tempera- tures well in excess of 300°C without problem. Development of a portfolio of pigments for high
temperature applications has also been a priority at BASF Colors & Effects (at the time of writing part of BASF but it is in the process of being acquired by Sun Chemical parent, DIC). Its latest product launches include Sicopal pigments in the red, turquoise and green colour space, as well as Cinquasia Rubine K 4370 FK, which is optimised for use in Unfilled and glass reinforced PA compounds.
Below: Clariant is one of several pigment suppliers offering black products suitable for automated NIR recycling sorting systems
Sustainability matters Aside from the thermal challenges, many new developments in colorants are addressing environ- mental concerns and the growth of the Circular Economy. “The organic pigment market will face various challenges driven by the acceleration of the plastics sustainability agenda,” says Philippe Laz- erme, Head of Marketing in the Business Unit Pigments at Clariant. “Everything indicates that the
packaging market will be the most impacted. The largest brand owners and packaging producers have committed themselves to use less plastic packaging. Those who continue using plastic packaging will potentially increase the amounts of recycled polymers to up to 70% within the next decade.” The challenges faced with recycled polymers are manifold and most definitely extend to colour, says Andreas Buder, Global Technical Marketing Manager Plastics in the Clariant pigments business. “First of all, the ground tone is greyish and ex- tremely inconsistent. It will be a particular chal- lenge for packaging designers and masterbatch producers to create and match a specific color which should still be visually appealing.” Lazerme and Buder say that to support both designer and colour matcher, Clariant Pigments has worked with Konica Minolta and Matchmycolor (owner of the Colibri colour communication, matching, and quality control software tools) to prove the suitability of its “Clariant pigment calibra- tion set” to match recycled polyolefins. The pair say that using this calibration set and the Konica software “it becomes increasingly easy to match a strong and appealing colour in just a few steps.” The company currently offers the calibration set to its customers and to downstream companies that may need it. The other important challenge, they say, is the
safety, not only of the recycled polymers, but also of the workers compounding and processing the recycled polymers. “To avoid the release of harmful substances after a certain number of recycling loops the use of particular stable pigments is essential. The chemical structure of a pigment doesn’t allow any conclusions about its suitability for recycling,” Buder says. Potential pigment-related NIAS (Non-Intentional-
ly Added Substances) can originate from reactants used for synthesis or the pigment itself as they differ in their stability, he says. “Depending on process conditions, exposure during product life, and reprocessing conditions during recycling, some materials might be less stable and migrate or evaporate more easily. Therefore, it is essential to rely on pigments that have been accurately tested under recycling conditions.”
Alternative blacks For post-consumer recycling to succeed, effective high speed sorting of plastics into different polymer types is critical. To this end, Clariant Pigments has developed a black colorant — Graph- tol Black CLN — and two black polymer soluble dyes — Solvaperm Black PCR and Polysynthren Black H — for sorting of black polymers by NIR
34 COMPOUNDING WORLD | September 2020
www.compoundingworld.com
IMAGE: CLARIANT
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