Biodegradable tapes and design for recycling

 Afera explored “markets, applications and regulations” in 4th Session of TechSem 2021

Afera’s 6 May online Session, part of our 4-part 9th TechSem, was moderated by Afera Technical Committee Member Gert-Jan van Ruler, who is also technical support and business development manager at DRT, and included 2 presentations followed by a Q&A section. During Afera’s 90-minute webinar, Tobias Winkler, laboratory manager at tesa SE, discussed biodegradable carton sealing tapes as sustainable end-of-life options, and Mikko Rissanen, director of technology at UPM Specialty Papers, delved into improving sustainability in release liner recycling. Below, each presenter has contributed an abstract and supporting information on his subject:

Sustainable end-of-life options: biodegradable carton sealing tapes
by Dr. Tobias Winkler, laboratory manager at tesa SE

With growing concern about the environment, sustainable products are gaining recognition, which is especially pronounced within the packaging industry. Amongst others, sustainable end-of-life scenarios for packaging products, like biodegradability and enabling of a more efficient circular economy, are required. Nevertheless, there are only few examples of biodegradable PSA tapes so far that support these packaging developments.

Promising solutions include natural-rubber-based and polyurethane-based adhesives. Biodegradability was proven in accordance with EN 13432 for a first generation of PU-based adhesive and is shown in graph 1. This adhesive shows excellent shear strength but did not completely fulfil the requirement regarding the peel adhesion of carton sealing tapes. A second generation of a PU-based adhesive was developed by changing the polymer composition leading to improved adhesive properties. Furthermore, the disintegration according to EN ISO 20200 was faster, and the adhesive is stable even under elevated temperatures and high humidity. In addition, a PSA system based on natural rubber is being developed. In a first set of disintegration tests, this composition showed a very promising performance (fig. 2). One major finding was that the disintegration behaviour can be strongly influenced by additives.

About Dr. Tobias Winkler
After obtaining a diploma in chemistry from the University of Hamburg and a PhD focussing on surface modification and biosensors from the Institute of Inorganic and Applied Chemistry at the same university, Dr. Tobias Winkler worked for 4 years as manager of laboratory customer support at Krüss GmbH. For the past 9 years he has worked at tesa SE based in Norderstedt, first as a laboratory manager for silicone technology and presently as a laboratory manager for repairing and packaging.

Design for recycling: improving sustainability in release liner recycling
by Mikko Rissanen, director of technology at UPM Specialty Papers Oy

Advances in responsible end-of-life for packaging products and awareness in resource efficiency is appearing as an opportunity for many to contribute to a better future of the one planet we have. UPM, as a leader in the new bioeconomy, has set up a collection and reuse system for spent paper release liner waste.

Recycling of silicone-coated paper has triggered very high interest within the industries that make use of these materials as carrier materials for both label stock and other adhesive handling technologies. For tape and industrial sectors using liner, the shade/colours of liner materials have traditionally been very colourful and dark. With the recycling infrastructure set up to treat mainly lighter shade yellow and white glassine, darker colours have needed to be directed to lower value-added end uses or left outside collection programmes, thus ending up in landfill or incineration plants.

1. Circular economy in UPM
Our vision is that every single wood fibre is used innovatively and efficiently. We do this to create value for our stakeholders and societies by:

• Avoiding generation of waste
• Reusing materials and products
• Replacing fossil-based fuels and raw materials with renewable alternatives
• Creating added value through smart solutions.

2. Release liner recycling in UPM

About Mikko Rissanen
With a master’s degree from the Helsinki University of Technology, Mikko Rissanen has had a 23-year career with UPM, having spent the last 9 years in various leadership roles, primarily dealing with strategy and business development, product offering management and its development. He has also previously been deeply involved in improvements of release base paper grades, production line and project management, and growth initiatives. Mr. Rissanen is also the inventor listed in a number of UPM’s paper patents.

Q&A section

Biodegradable carton sealing tapes as sustainable end-of-life options

On slide 16, you showed the results for the adhesive with or without the backing? It is with the backing, but for these tests we wanted to look at the behaviour and disintegration of the adhesive, so we used a 100% disintegratable thin film backing.

If composting requires heat energy and degrades plastic to carbon dioxide and water, how is it advantageous when compared to using any plastics as fuel as combustion, giving equal quantities of CO₂ in addition to heat energy? This is a common discussion. You could incinerate the materials, forming CO₂ and water. The composting process does the same without releasing heat which can be used in other processes. Here the question is how to treat these available options. In some cases, people prefer to incinerate materials and utilise the heat. In other processes, they prefer to go the composting route. Nevertheless, depending on local waste collection and disposal systems, composting may be preferred over incineration in certain regions.

Does that also mean that compostable products offer an advantage in terms of CO₂ emission? No, the CO₂ emission will be similar, maybe slightly less because some of the material is converted into biomass, but in total the CO₂ emission will be very comparable. So composting does not offer significant advantage in terms of CO₂ emission.

You presented interesting first results on PLA tape, but I did not understand whether the carrier or the adhesive is made of PLA, or both? The carrier is PLA. For the PSAs, we use other chemistries. In principle, PLA chemistry is also thinkable in a PSA, but in our tests, we did not use it. Unfortunately I cannot discuss the PSA chemistry in detail, as it is part of our current development activities.

Packaging tape will most likely end up on cardboard disposed for recycling. How does the biodegradable tape work in the paper and cardboard recycling process? Can it still be biodegraded upon separation from cardboard? What is the advantage of biodegradable tapes versus repulpable tapes in this regard? Yes, it can be sorted out of the cardboard recycling process. We have tapes for which we certify that as “recycling friendliness”. This means that the tape can be separated from the cardboard and the cardboard recycling process, and afterwards, it can be composted. The product group for which we are developing these compostable tapes is heavy-duty packaging tapes, which require a stable, non-repulpable polymer backing. We also have sustainable paper carton-sealing tapes in our assortment, for which repulpability could be an option, but these products use less stable paper backings and are intended for use with light-weight packaging. For this reason, for the heavy-duty packaging tapes, repulpability is not an option for the time being; however, perhaps Mr. Rissanen will have a stronger paper option for this at some stage?

Have you found any solution for biodegradable or “non-toxic” release systems? What is allowed in compostable tapes is the use of organic non-compostable materials at a concentration below 1%. So if we talk about release systems, even silicone would be possible. We currently use non-silicone release coatings in our prototypes that are tolerated by the microorganisms, although we would not consider them to be compostable materials. But because of the 1% threshold defined in compostability standards, you can use many release solutions.

How does the compostability of the tape affect its stability before you want to compost it? For example, what happens to it as a courier is delivering a package on a rainy day? This is especially challenging for home-compostable tapes, because in these types of products, you need to involve materials which are very easily compostable. This means that they are very prone to microbial attack. If we talk of backings and materials such as PLA, then already the fact that you need to expose it to industrial composting conditions at elevated temperatures shows that composting is not that easily set into motion. For industrial compostable materials, the stability of a typical carton sealing tape application is comparable to the well-established standards like PP or PVC. A rainy day would not affect the tape, and for normal transport conditions, you would not expect the durability or stability of the tape to be an issue.

Is the shelf life of biodegradable tapes similar to that of standard tapes? Yes, as long as you store them dry.

From a commercial perspective, would you expect that your invention will be comparable to standard packaging tapes? No, they will be more expensive, because we are focussed on special raw materials, which currently are often not produced in sizeable volumes. We do expect these materials to become less expensive in the future when volumes increase. But for the time being, those products cost more, but this is acceptable, because certain target markets are increasingly focussing on this technology.

How do you expect packaging tapes to reach the composting installation? People are not likely to separate tapes after unpackaging. That is true. For consumer applications, a collection system needs to be implemented in the future. For the industrial waste stream, these tapes would be collected and then sent to the disposal facilities by the cardboard recyclers.

Improving sustainability in release liner recycling

If 50 million trees are planted by UPM per year, how does this compare to the number of trees being harvested by UPM? All UPM products are based on wood being harvested from legally harvested forests, and most of the production is already third-party-verified—FSC-certified for wood. So within our industry, a leading principle is that we can provide customers with FSC-certification if needed. This brings a third-party element into the discussion. Then I would not need to be worried about, for example, deforestation. The dialogue is very active around biodiversity at the moment. We are very actively trying to pursue solutions in line with this issue.

How do you tackle the stigma around recycled materials being somewhat less consistent in quality and specification compared to standard materials? In the case of glassine recycling, we hold a lot of control over the supply side. It is not post-consumer waste we use. In most cases, the materials come from very controlled sources, so we know what to expect and have a consistent supply. Alongside the recycled material we use to make our products, some or a majority of the raw material base is made up of virgin fibre. This limits any inconsistencies in the incoming feedstock.

There are really good ways to control the quality of the feedstock, and now that we have an offline process to do the siliconising, we can measure the quality of the synchronisation process at intermediate stages and take this into account when we are feeding it back into our production process. So far, the performance of this pulp has been quite promising in terms of quality. It even looks to be more consistent than material based on virgin pulp, because it has already been used once, and from a dimensional stability point of view, it has upside potential compared to virgin fibre. So to some extent, recycled raw materials can actually be seen as a benefit in terms of quality and specification.

Is UPM today only able to take back its own materials, or are you also able to recycle competitive materials? We recycle material from the value chain, irrespective of the original supplier. We can collaborate within the value chain. I am happy to say that with the CELAB initiative, the representation of suppliers across the value chain is quite broad, so we can collaborate on the technical side of things, as well as with the label stock OEMs.

Do you think that replacing PE in PCKs with cellulose or a PLA-type plastic would improve their ease of recycling? We are looking for opportunities in graphic applications, for example, on the delivery side with such constructions in which kraft paper has been traditionally used. And I think the results look promising in the sense of potentially offering a replacement for plastics. This use of this technology is not so prevalent in Europe yet as it is in the U.S. and APAC regions. I am pretty confident, however, that we can find many end uses where we can use a clay-coated, kraft-dyed paper instead of a polycoated Kraft and get equal performance in terms of silicone holdout, release values and other product characteristics. Once we move forward with the barrier-type packaging grades, there will be synergies between those 2, because packaging constructions often share a similar construction with polycoated on paper. This combination of products or complex materials should be avoided, according to the regulatory push by the E.U. Like Dr. Winkler referred to the definition of plastics, most likely you will not be getting rid of this with a composite structure with a polyolefin on paper if the coating is not considered sustainable or a mono-material.

Do I understand correctly that the recycling process will be far easier if there are no dark-coloured liners like Havana? Yes, definitely. The reason we think this is that the fibres have received so much dye in those products in the initial process of making the paper that it is very difficult to remove it from the fibres hereafter. Mixing those darker-coloured fibres in the stream will give the appearance of impure fibres or fibre lumps of a darker colour, and then the final product will exhibit these spots. If we wanted to use Topaz or Havana shade glassine, it would be a complicated process of either bleaching or another method of removing the dark fibres, but at the moment, this is not technically feasible. It is also an unnecessary burden if we have to work with the dark colour. Moreover, it takes away some of the yield in the cleaning process. We need to start using very effective bleaching or other cleaning methods.

Can you comment on how the release liner acts as a contaminant in the recycling of paper and cardboard? Is a certain amount of siliconised liner allowed in a mixed waste paper stream? That is very much dependent on the type of end product you are making out of it. Some cardboard grades, for example fluting, which has no huge requirements for quality, seems to allow less than 5% of liner waste in them without the de-siliconising process. As a very low-polarity substance, silicone easily attracts some hydrophobic colloidal substances which cause deposits to build up in the paper-making process, specifically in the wet end of the paper-making machine, creating sticky issues. Furthermore, in certain board mills, you have to have rather strong pulpers to break the release liner into small enough pieces to use in the process, so it does not get screened away in a comingled feedstock stream. Some value chain participants performing trials with very high proportions of liner waste as a feedstock without the de-siliconising process have met with serious issues with even starting to break the fibres or the web into pieces and defibrillate it. From a paper-making weight and chemistry point of view, silicone is quite sensitive but much easier if you take it away before using it.

Is there any incentive for your customers to work with your recyclable grades over non-recyclable grades? I think with the overall sentiment of both brand owners and consumers valuing recycled content in the products they use and also the very strong regulatory push to make use of these kinds of ecological recycling systems, as well as avoiding the cost associated with the heavier EPR fees if you do not have a responsible system for maintaining your end-of-life, are a very strong set of drivers for making this happen, even if it were not already here. I expect to speak more about this with the rest of the value chain in the very near future. Furthermore, I can see that the frequency with which we talk of sustainability is increasing. It will not be going away. It is a critical business contributor. We are taking care of the waste we generate, and the more this improves, the better business becomes for all of us. I find a lot of incentive for getting this going.

Especially for the big raw material suppliers in Afera’s audience, is there anything—any specific product attributes which you expect from raw material suppliers that will facilitate your development towards higher recyclable or compostable, biodegradable end products? Mr. Rissanen said that from a supplier and receiving-end standpoint, consistency and predictability are key, as well co-creation. We are encouraging building this up, involving everyone in the value chain. Our expectation of this audience is that you will collaborate to the best of your ability, not work in silos. This will get us far.

What do we expect from market suppliers in order to speed up development or to be more successful? Dr. Winkler said that he thinks, and he has already seen it happening, that you need to think in new material class groups. We have been using polyolefin or fossil-based materials for years now. The world is changing and new requirements are evolving, and especially if we are talking about biodegradability, we, along with our suppliers, have to look into a new material classes, make new material classes which offer advantages for moving in an ecological direction available at an acceptable price. The price issue is always important, because it is a facilitator. But he is confident in positive developments because sustainability and biodegradability are gaining traction in the tape industry value chain, and he is looking forward to what will come next.

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