The need to expand the debate on near-infrared (NIR) sorting of post-consumer plastics away from just black packaging waste is one of the aims of a new EU-funded project.
UK-based technical compounder Luxus is leading the two-year project called NIRSort, which also involves Nordic polymer processing partner Polykemi and global plastics manufacturer One51. The commercialisation project aims to replace the carbon black pigment (see box) and others with alternative NIR detectable pigments that would allow for end-of-life plastics to be sorted with NIR sorting equipment. These new colourants will be tested in a wide range of applications beyond packaging, such as automotive plastics and consumer durables like home appliances and electronics. The idea is that if these new pigments can be successfully used in the aforementioned applications and then separated into individual plastic polymer streams using NIR sorting equipment, manufacturers could adopt the use of such colourants to ensure that the products they produce and put on the market can be effectively sorted and then recycled at the end of their lives. The first trials are expected to start after Christmas.
Colour Tone Masterbatch, which was acquired by Luxus in March, was involved in a previous WRAP funded project published in 2011 that aimed to develop the materials technology required to substitute the carbon black pigment commonly used in black food packaging with an infra-red reflection (IRR) black pigment. The project validated that IRR pigments could allow NIR spectroscopy to sort black plastic packaging waste, and it reproduced as near as possible the shade and opacity of the carbon black pigment currently used in such packaging.
Since the original NIR project, new masterbatch with the same NIR sortable IRR pigment is being devised for numerous applications, which provides the opportunity to shape the technical properties of thermoplastics used for auto interior components including steering wheels, seats and instrument panels for example.
According to Luxus, black plastics represent around 30% of the waste electrical and electronic equipment (WEEE) and vehicle polymers waste streams. This waste material – around two million tonnes – is unrecyclable because it cannot be effectively sorted at present. On top of that, it believes a further million tonnes of coloured plastic waste is lost to landfill or incineration in the UK each year. The NIRSort project aims to find a solution to allow for this current disposal stream to be diverted to recycling and used again in new products.
Tony Gaukroger, director at Colour Tone Masterbatch, explains that the project is a first attempt to look at non-packaging polymers, and to look at coloured plastics other than black, as most coloured plastics also include carbon black, which absorbs the infrared and affects the ability to sort them using NIR technology. “Essentially, [the project is asking] can we sort every polymer in every application, and then potentially reclaim them? It is looking at plastics that haven’t been looked at. It is looking at applications that haven’t been considered in this manner and hopefully marrying the two things together to create new opportunities. Nobody is looking currently at the post-use sorting of automotive plastics automatically or even electrical appliances automatically.”
Gaukroger explains the project is a natural extension of the work that has been done on plastic packaging, and it is now time to broaden its scope. “From my point of view, and what I find most frustrating, is that the drive has been around black plastic in a couple of polymers, which is fine, you have got to start somewhere, but we need to expand that debate. We need to expand it into other polymer types, other colours, things other than packaging,” he says.
“The first thing is, we now have kerbside collection which is wonderful and we have got all of these unpaid recycling waste sorters who will quite happily fill bags, bins and boxes with all of this potentially recyclable waste.
“If we assume it can be collected and it can be recycled, we then have the interesting concept that you [currently] have one set of plastic going into a recycling network which is up and running and you have other [plastic] things which are going straight to landfill. From a domestic point of view that could be something as simple as your old washing up bowl.
“It strikes me as absolutely ludicrous that you have these two things happening when you can actually expand the kerbside collection to take all plastic items. I would have thought that longer term that is really where we should be aiming: it is reducing landfill, it is utilising a resource that we have already got and a process that we have partially in place, and hopefully will be in place, and that is a complete change in thinking.
“The situation at the moment is you walk out the back door and you go: ‘I have this plastic bottle – that goes in the recycling’, and ‘I have this old [plastic] soap dish which is broken, I put that in the non-recyclable bin’.”
In addition to this, Gaukroger says legislation in the UK such as the End of Life Vehicles directive and WEEE directive are designed to drive up recycling rates, yet the initial focus of achieving these targets has been on recovering the metals rather than the plastics, as they are easier to separate and heavier, thus more useful in meeting weight-based targets. However, to further increase recycling rates, focus will have to turn to recovering and recycling more of their plastic components.
As Gaukroger explains, the question of recyclability orientates around the ability to separate out polymers, “and if we can do that the world is our oyster”.
But he says a shift in thinking is required from the design stage of a product, so that ‘end of life’ and recyclability is one of the parameters that designers consider from the outset. This would mean factoring in whether materials can be effectively sorted when they become waste.
“That requires a lot of repositioning of ideas and I don’t expect that a lot of this is going to happen overnight by any means at all,” he adds.
What will the main challenges of the project be? “From a material point of view we have to produce colour and packages that are aesthetically correct, and that is not quite as simple as it sounds. In the case of mixed plastic components, for instance, on the interior of an automobile, the chances are that one component you are working with has to match another one. So because you are using different colourant systems there is a potential metamerism issue – that will have to be addressed.”
One of the issues is that the colourants that are NIR detectable may not cover as well as carbon black, which could affect applications which have a strong colour base. “From a colour point of view, obviously, it has got to be NIR sortable, but it has also got to be aesthetically acceptable, and it has got to meet the criteria that the original colour did.”
Anette Munch Elmer, plastics application and material specialist at Polykemi, which develops and produces tailor-made thermoplastic compounds, explains its role in the project will mainly be in polymer characterisation. She explains: “We will get the materials for this new pigment that allow details to be NIR sorted. Then we can evaluate them: do they function as normal black or coloured parts do?
“Then we will measure the material properties, like the chemical properties, aging properties, thermal properties – to evaluate whether, if we use this new pigment we can expect changes in material properties.”
The first part of the project will be to make the material, then analyse it and make parts, before trying to sort it. Elmer explains that Polykemi has a subsidiary called Rondo which procures recycled materials. Currently it easier for it to buy post-industrial rather than post-consumer material, due to the sorting difficulty. “But if we could also use post-consumer material that would be really beneficial for a recycling company,” she says. The main challenges to Elmer are whether the new IRR pigment will be as effective as the commonly used carbon pigment? If it is, she foresees that the research could give the likes of automotive producers and electrical and electronics producers the opportunity to take more responsibility for their products.
Gaukroger believes now is the time to take on this mantle of responsibility: “I know it sounds harsh, but if we don’t [take responsibility for waste plastics], it is no different to the mentality of unwrapping your bar of chocolate and throwing your wrapper out of the car. We need to be a little more responsible. What we are saying is, we need to address this in more detail and if you want the plastics to be recyclable, the first issue is that we have to sort them.”
Box – The Carbon black issue
Carbon black is the name of a common black pigment. Black plastics that are coloured with carbon black colourants present a problem for NIR detectors as carbon black strongly absorbs infrared radiation as well as visible light, so the NIR light is not reflected into the detectors. This means that the items remain undetected and end up in the residual fraction from the sorting processes and are disposed of to landfill if this sorting method is used.
Source: WRAP: Final report, Development of NIR detectable black plastic packaging
Box – The question of cost: should recycled material be cheaper?
There is a historic belief that recycled materials should be cheaper than their virgin counterparts, but should it? Tony Gaukroger, director at Colour Tone Masterbatch says: “If it is a recycled material that has been sorted and then put back into a specification as near as where it started its life in the first place, then surely the cost should become part of it. Even if it is an increased cost then so be it, it is part and parcel of disposing of another problem.”