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An (almost) perfect couple
Key requirements for an optimal balance between recyclates and trendy designs
Sustainable products and packaging (made of recycled plastic, for example) are becoming more and more important to consumers. This was confirmed, for instance, by a study published in 2022 by the Norwegian inspection, certification and consultancy company DNV. At the same time, aesthetics and design continue to be a decisive sales factor at the point of sale as the brand's calling card. Many packaging manufacturers therefore need to ask themselves the following question: Which colour can be achieved with which PCR type using which base materials with which properties? And can the colour be achieved in each case without making compromises in terms of packaging design?
We have noticed a significant increase in the number of inquiries that we as a masterbatch manufacturer receive regarding colours produced for recycled materials. The associated projects are very complex due to the different recyclate types on the market and their various intrinsic colours and requirements. Using single-variety (unmixed) plastic for the same reproduction process leads to a comparatively smoother and simpler recycling procedure. Within the framework of the DSD system (Duales System Deutschland – the Green Dot), this only works at the moment with PET, which can be used to reproduce bottles from a recyclate material.
The situation is more difficult in the case of old multicoloured plastics. That’s because the most important factor in colouring is the actual colour of the recyclate itself. Regranulates are a conglomerate of collected recycled products that have been coloured to either a large or small extent. These products already have colour in them – i.e. they have a high proportion of intrinsic colour. “There is no process in mechanical recycling that can remove the colour from the mixtures”, says Marco Meixner, Head of Research and Development at Lifocolor in Lichtenfels (Germany). “This means that recyclates always have to be overcoloured.” The recyclates have different intrinsic colours, ranging from light to dark and from grey to brighter colours. The colourants therefore need to display a high degree of colour intensity in order to achieve maximum colour brilliance and quality in the masterbatch and in the colouring process. Colourants that are highly stable are used here because the polymers themselves need to be able to withstand a large number of reproduction cycles.
Easy to work with, but hard to procure
Light-coloured recycled polymers offer numerous benefits. For one thing, they are easier to colour and thus enable more diverse product designs. Lighter-coloured recyclates are also more economical, as the masterbatch dosages needed for them are usually in a moderate range of less than five per cent. Such polymers are a good option for companies that pride themselves on manufacturing 100% recycled products, as they enable full recyclate content in the final product. There is a downside here, however, as the effort and expense associated with the production of such polymers makes for a lower level of availability on the market as compared to other polymers. Lighter-coloured recyclate mixtures can also be more expensive.
At the same time, initial advances have already been made in terms of addressing such challenges associated with the circular economy, as recyclers and sorting facility manufacturers are now optimising sorting and reprocessing systems in order to increase the availability of light-coloured recycled plastics.
Compromises in colouring
The situation is different with darker recyclates. Here, the effort and expense associated with colouring is much more extensive, as higher dosages are usually needed. In addition, the colour variety that can be achieved in the final product is more limited. A compromise can be made here by using a proportion of 20%-70% virgin material as an additive in order to maintain cost efficiency in production and achieve a moderate colour result.
Additives and combi batches
Additives have a major impact on recyclate quality. Additives that are added to products in the first processing cycle must be able to complete that cycle without suffering any damage. Ideally, the additives used should actually support the process and ensure high-quality recycling. A good example of how colour quality can be stabilised is offered by our Lifocycle Clear product, which can balance out green or yellow tinges in PET recyclates. The goal here must be to manufacture recyclates with reproducible quality. Impurities and pre-existing damage in materials also influence recyclate quality in a major way. In the case of pre-existing material damage, it is advisable to replace stabilisers that were lost during the recycling process, or even increase the amount of stabilisers used if damage is too extensive.
“In many application cases, it’s enough to use the additives that have already been mixed into the recyclate”, Meixner explains. “We haven’t observed any greater demand for combi batches – a combination of colour and additive batches. In special cases, for example in connection with engineering polymers, it may, however, be necessary to additionally stabilise the recyclates. Demoulding aids are often used in such situations.”
Design4Recycling is on the rise
Standard products from the LifoCycle product portfolio are an important foundation for the individual development of recyclable masterbatches. These solutions support various process steps in the circular economy – everything from collection and separation to sorting, classification, qualification and preparation. Among other things, the product portfolio includes NIR-detectable masterbatches to support sorting. The range is supplemented by recyclable masterbatches for polyolefins and PET that are based on a high-quality selection and combination of highly temperature resistant and stable colourants. Recyclable additives are also used for process stabilisation and the preparation of recyclates.
2024 trend colours with a high-quality (recycling) design
When utilising recyclates, plastics processors shouldn’t have to choose between high-quality design and a recyclable product. The fact that a circular economy and colour innovations are not mutually exclusive is demonstrated by our interpretations of the trend colour line for everyday products in the Colour Road series, as well as by our own Shades of Beauty & Care cosmetic line. “Our masterbatches designed as ‘Eternity Colours’ point the way towards good recyclability as early as the processing and colouring stages”, says Andrea Hanke, Head of Technikum (Technical Centre) at Lifocolor. “They are equipped with the selected colourants and display high temperature stability and migration resistance. That makes them perfect for multiple cycles.” This applies to both virgin material from the first cycle and to recycled material for subsequent and repeated cycles. Depending on the recyclate type, the colour result may differ only slightly from that of the virgin material, and it will still remain economical. Even if it seems to literally be a contradiction at first, temporary trend colours can also be “Eternity Colours” in terms of the way they develop.