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Content archived on 2024-06-18

Development of a selective, green solvent-based recovery process for waste polystyrene and polycarbonate

Periodic Report Summary 2 - POLY-SOLVE (Development of a selective, green solvent-based recovery process for waste polystyrene and polycarbonate)

Project Context and Objectives:
Polystyrene and Polycarbonate are two important polymer types for which recycling is possible today but still lagging behind compared to the recycling of polyolefins and PET. Novel technologies are needed to deal with more difficult-to-recycle fractions of the waste streams, such as expanded polystyrene and polycarbonate with glassfibre and/or polycarbonate coming from electric and electronic waste.
Expanded polystyrene is widely used as packaging for foodstuffs and for shipping. Several hundred Thousand tonnes of polystyrene are sent unnecessarily to landfill every year in Europe, where it does not biodegrade but persists for hundreds of years. Meanwhile, oil-derived feed stocks are being consumed in the production of new polystyrene. Recycling systems for polystyrene are underdeveloped compared to those in existence for many other plastics, owing to the unfavorable economics of collecting and recycling low density material.
The proposed project will develop a new process by which an environmentally friendly and selective solvent is used to dissolve and recycle polystyrene waste into a high purity product comparable to virgin material. A novel thermoplastic recovery system is under development in the form of a modular, scalable recycling process. This will facilitate:
• Reduced pressure on oil feed stocks for virgin polystyrene production
• High value-added product manufactured from effectively zero-value waste, to be sold by the end user.
At the end of the project POLYSOLVE technology has been demonstrated through the operation of a pilot plant for the recycling of waste expanded polystyrene (EPS) and polycarbonate (PC). The POLYSOLVE technology provides a solution by achieving a high grade product that is suitable for industrial applications.

Project Results:
The project has started with a detailed exploration of the potential for solvent-based technology on EPS and PC. Initial brainstorming and road mapping have supported this process. The consortium is aware of the cost-price issue on solvent-based techniques, but the dynamics in the legal environment determining the future of certain industries, call for new technologic development. The circular economy package proposed to ban landfilling by 2025. This is a threat for the EPS industry, as due to the high volume recycling is in many cases not economical. EPS from building and construction is not a readily available stream, but will become in the future. Recycling is impossible without removal of HBCD, a flame retardant which is subject to current and future restrictions.
On the other hand, fish boxes from EPS are a readily available waste stream, in order to deal with the volume solvent decentralized tanks could be interesting to dissolve the EPS. Solvent screenings have been performed, to determine the best candidate solvents for the recycling processes. Based on the criteria on safety and environment. Subsequently tests have been performed on selected input material, to verify both options for polymer/solvent recovery in the initial step: precipitation and/or evaporation.
Prototype recovery processes have been tested and evaluated. In the solvent recovery process, values of 92% have been reached, but not the required 99%. Materials recovered from solvent-based processes have been tested mechanically and by means of FTIR, to verify their nature. Improvements in solvent removal should improve mechanical properties of the recovered material.
Fish boxes have been obtained via the BPF EPS group. They have been used as substrate for solvent prototype processes, based on the established solvent selection tool. The tool is very interesting because it allows to deal with more complex waste streams and to determine the best solvent compositions. This is particularly the case for PC-WEEE, which often contains 15 or more other polymers, and often blends such as PC/ABS. PC as such is already recycled from pure streams, such as PC bottles.
Mechanical recycling will always be cheaper than solvent mechanical, therefore waste fractions have been identified which cannot be readily recycled without problems nowadays. PC composites belong to this category, as glass fibres cause a lot of abrasion to the tooling for extrusion of the recyclate. Although long-fibre PC applications are not that common, for these applications in particular solvent based techniques can provide novel routes.
Solvent prototypes for both PC and EPS have been tested, and the material obtained has undergone initial material parametrization (tests). LCA-methodology has also been established for the processes, giving more insights in the economic and ecologic feasibility of the processes. Throughout the activities, a lot of validation work has been performed. In the meanwhile, advanced road mapping with several experts once more underlined the need for novel technology which can decontaminate plastics from so-called legacy additives, those which are currently banned but will show up in waste streams.
POLYSOLVE technology has been demonstrated through the operation of a pilot plant for the recycling of waste expanded polystyrene (EPS) and polycarbonate (PC). Results from both the POLYSOLVE PS and PC indicate that the pilot plant is sufficient at producing material with a realistic industrial application and market. For some mechanical properties of the POLYSOLVE plastics, they are comparable or superior to the present commercial materials, whilst other parameters are within or close to the optimal range.
Therefore it is likely that the POLYSOLVE generated material feedstock will provide a suitable product quality for some plastics manufacturers. With no thermal degradation occurring to the PS polymer, after multiple cycles through the POLYSOLVE plant, suggests that at vast amount of energy and raw materials could be saved with the circular behaviour of PS when utilising the POLYSOLVE technology.
Field production indicated that POLYSOLVE processes are a reliable technology. However, PS drying turned out not to be sufficient in the batch used for production of test specimen. However, larger scale vacuum extrusion lines apply usually more than one vacuum port (mostly 2-4) and have been shown to be more effective in previous trials. It is therefore expected, that the issue of performing a suitable final drying has been treated sufficiently and do not require further optimisation.
Results for recycling PC are also very promising. However, drying has been found to be time consuming which increase the size of suitable drying aggregates. Therefore, optimisation (acceleration) of the drying technology will remain a future issue.

Potential Impact:
Polysolve will have to yield an economical recycling route for EPS via decentralized systems (e;g. for fish box collection) and for PC filled with fibres and/or coming from WEEE-fractions Polysolve will directly feed in the European Resource Efficiency Roadmap and the strategy released by DG ENV, have named the Green Paper for Plastics. Currently, too little fraction of the plastics are recycled.

This is the case, especially for WEEE streams and for Building & Construction. Also, the EPS-recycling posing the volumetric problem (the large jumbo-trucks can only load up to 700 kg of EPS without compaction) needs solutions. Maybe short-term economic benefits of solvent based technology will not be that high, numeric examples of the CREASOLVE process have shown for other solvent-based processes that especially the solvent removal contributes to the costs.

Those same analysis have however shown as well that when the scale is big enough, the process would become economically feasible. Certain streams, such as WEEE, are special because first of all the recycling rates will double or even tripple by 2020, because of more strict requirements, and the stream is financed.

The WEEE directive foresees that the producer pays for the waste collection. Additionaly many manufacturers such as SIEMENS, PHILIPS, HP among others, have launched product stewardship initiatives to increase recycling rates and to come up with a closed loop approach. As mentioned in the deliverables, WEEE streams are problematic because of legacy additives.

These additives are maybe not that much in polycarbonate but their presence in other plastics fractions and in the dust generated during shredding. They jeopardize the options for recyclers to make compliant recyclates out of it. Another phenomenon is that much of the waste is shipped to Africa and South-East Asia, eventually leading to hazards for human health and even re-import of potentially contaminated recyclates used in E&E devices, leading to exposure of customers in Europe. Solvent based technologies are the only option we have at this moment to decontaminate plastics.

Polysolve demonstrate the power of solvent-based technology in the current industrial climate, where f.e. also the PVC industry is looking for options to remove DEHP from waste fractions and where many of the engineering plastics (polycarbonate is also an engineering plastics) and composite materials are mainly studied in an approach of incineration or chemical feedstock recycling, which are as confirmed by the best experts in the field, not sustainable from an economic and/or ecologic point of view.

The European Framework Programmes have the goal of uniting important innovation partners, and in this perspective the POLYSOLVE consortium will do everything - in spite of difficulties with the initial partnership - to give the project a maximum impact.

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