COLOUR | PIGMENTS
IMAGE: HEUBACH
Above: PCR resins display a considerable variation in colour
consistency and require powerful colorants
PE 69-1501 or Microlen Green 8745 LW MCN pigment preparations, are important for enhancing uniform processing behaviour across several batch- es of recyclate. It is also important to consider the purity of raw
materials used to make pigments, according to Heubach’s Lazerme. He says that materials that are less pure, as well as materials processed on poorly cleaned equipment, can result in non-intentionally added substance (NIAS) content in pigments. NIAS are restricted in sensitive end-use applications such as food packaging and toys. As recycling of plastics grows, there is also an
increasing focus on degradation of consituent materials that can occur each time material is reprocessed. “We are working on a range of pigments that can withstand several recycling loops. Those pigments that will not generate any NIAS after multiple recycling cycles can then be recommended for recycling,” says Lazerme. He says that it is important for pigments selected
in a “design for recycling” process to have been thoroughly analysed, because even pigments with the same colour index can vary in composition and purity. Research at Heubach has investigated the stability of pigments through 10 successive recycling loops, where the colour compounds were analysed to identify NIAS. Heubach says its PV Fast pigments did not show any NIAS after 10 cycles but a different compound containing a yellow pigment showed an unexpect-
ed peak in the chromatograph after the 10th cycle. “This [test] underlines the importance of selecting the right pigments when designing new packaging that will be recycled,” says Lazerme. Compostable solutions The market for plastics that can be composted — either in industrial composting or home composting — is
growing, particularly in the packaging segment, where the ability to put a package with food waste into the organic recycle stream can be desirable. To be labeled as compostable, however, com- pounds (and the pigments used in them) must meet test requirements and comply with regulatory restrictions. European standard EN 13432, for example, defines compostability and restricts heavy metals and the concentration of pigment that can be used. Pigment suppliers have introduced a range of pigments that are certified for compostability, including “OK compost” certification by TÜV-Aus- tria. Lazerme says Heubach has nine pigments with OK Compost certification covering the full colour spectrum.
Dumont says a new pigment from Sun Chemical
will provide a good option for compostable plastics in the bluish colour space. “Our soon to be launched Microlen Blue 7460 ECO significantly extends the workable colour space for composta- ble plastics,” he says. “Metals such as zinc, copper and chromium must be avoided [in biodegradable and composta- ble plastics],” says Llado at Vibrantz. “Ultramarines and iron oxides are good candidates to be used in these materials due to their chemical composition, regulatory profile and colour properties.” Lars Schulze, Head of Colour Development and
Material Sciences at Grafe, says EN 13432 includes maximum contents of metals in the final product
Study calculates carbon cost of pigments
Eurocolour, an umbrella trade organisation representing colorant manufacturers in Europe, published some estimated product carbon footprint (PCF) numbers for several broad groups of pigments in May this year. The association says it found that CF values for starting materials were difficult to source. However, it was able to determine and estimate CF
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from “cradle” (raw materials) to “gate” (of the manufacturing facility) using published greenhouse gas emissions for various production processes. It estimated that production of inor- ganic pigments and fillers results in a PCF of 2.3 (±30%) kg CO2
equiv/kg of
product. Production of organic pigments
results in 11 (±30%) kg CO2 COMPOUNDING WORLD | September 2022 equiv/kg of product using single stage synthe- sis and 24 (±10%) kg CO2 equiv/kg
using multi-stage synthesis. The association’s data is not specific to the plastics industry, but the report points out that the contri- bution of pigments is “almost negligi- ble in comparison to the [end] product lifecycle”. �
https://eurocolour.org/media/ eurocolour_flyer_carbon_foot- print_05.2022.pdf
www.compoundingworld.com
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