Cumapol: Recycling and upcycling PET polymers

In 2010, Cumapol acquired the production lines in Emmen where chemical company Akzo used to make PET from petrochemicals. Half of these were converted to process recycled PET flakes from post-consumer bottles. ‘We now produce some 25 kilotons of PET pellets per year, which we can upcycle or adapt to the different specifications of our customers’, says Technical Director Marco Brons.

Continuous chemical recycling process

By extrusion, the flakes are heated and the viscous melt is filtered to remove solid contaminants, while volatile substances are removed by a vacuum. After regranulation, the polymer can be extended by solid state polymerization. ‘We can bring the polymers up to their original strength, or make them even stronger’, explains Brons. ‘And in the extruder phase, additives can be added to produce custom made polymers.’ To assist this custom production process, Cumapol is installing a tumble-drier in which batches of 20 tons can be upcycled. ‘Up until now, we have two continuous processes with a minimum batch size of one hundred tons.’

This mechanical recycling is successful, but it still leaves a lot of polyester waste unused. Heavy colored materials or mixed plastics are not suitable as feedstock for this process. That is why Cumapol has developed a continuous chemical recycling process. ‘We depolymerize the PET by adding a certain amount of glycol. Polymerization is an equilibrium reaction, and this way we shift it.’ The result is a low viscosity fluid, from which the dyes and other contaminants can be removed using activated carbon and/or distillation and crystallization.

‘We can bring the polymers up to their original strength, or make them even stronger.’

Pilot plant

‘This process works well in the lab, so now we are building a pilot plant to test it on a kilogram scale.’ The plant, a scaled down and adapted version of their PET production line, will be installed in the Cumapol premises in Emmen. When this is successful, the aim is to convert the production lines that are not used for the mechanical recycling. ‘So we will have a capacity of another 25 kilotons of PET from chemical recycling.’

Using this new technology, Cumapol can use different sources of recycled PET. ‘Food safety regulations mean we have to use 95 percent PET from food packaging for mechanical recycling. However, for chemical recycling we can use every kind of starting material including colored PET.’ And there is another option: during chemical recycling, the polymers are broken down to monomers. At that stage, bio based monomers could be added.

Together with BioBTX

‘We are working with chemical company BioBTX from Groningen, who developed a process to produce these bio based monomers. And the glycol we use for depolymerization can be produced by Avantium, who just opened a biorefinery pilot plant in Delfzijl.’ This is going a long way towards the ultimate goal set by Cumapol: to make polymers from bio based building blocks and recycle them, creating a fully bio based and circular process.

Of course, recycling is limited to almost pure PET, only a few percent contamination by other plastics is allowed. ‘Again, BioBTX has a solution, they developed a process to break down mixed plastics into the basic building blocks, and use these to make monomers for PET production.’ So, Cumapol will use mechanical recycling for clean PET from post-consumer bottles, chemical recycling for colored and non-food PET products, while mixed plastics could be converted by BioBTX and then used to make PET.

‘It is important to have a network of contacts, as provided by Chemport Europe.’

Network of contacts

The chemical recycling process was developed by Cumapols own the R&D department, with assistance of two Universities of Applied Science (NHL Stenden and Windesheim). Polymer scientists of the University of Groningen are involved in BioBTX. ‘It is important to have a network of contacts, as provided by Chemport Europe’, says Brons. Local and provincial governments and regional development organization SNN are also important. ‘They can provide subsidies which speeds up development.’

In about two years’ time, Brons expects his company is ready to convert the remaining PET production lines for chemical recycling. This will bring total production to 50 kilotons per year. Compared to the 400 kilotons an average PET bottle factory uses, this may seem small. ‘Our niche is production of custom made polymers, for the national and international market. But we do hope that our technology will be adopted by larger producers.’

Cumapol proves that for polymer innovations Emmen is the place to be.