Depolymerisation offers viable recycling route for PMMA

A European project aimed at developing an economically feasible method to successfully recycle PMMA  is currently testing a solution based on thermal depolymerisation. The technology being used was originally developed and patented by Japan Steel Works.

The project, called MMAtwo was launched in 2018 and has 13 participants. The first contact with JSW was in 2017, when, interested in JSW’s patent, PMMA-manufacturer Arkema contacted the company.

JSW soon joined the newly-established consortium as the key technology provider for depolymerisation. Its Düsseldorf-based Europe Extrusion Technical Centre, equipped with a modified TEX44αIII twin-screw extruder, is now being used to run a series of PMMA depolymerisation tests. The first trial set-up was at the Technical Centre in June 2020.

PMMA, also known as acrylic glass, has excellent optical and physical properties. It is used for glazing applications in, for example, caravans, facades, furniture, and vehicle taillights, but is also found in flat screens, neon signs, jewellery and more. Around 300,000 tonnes of PMMA are produced in Europe alone each year of which just 10% cent is being collected for recycling.

Recycling PMMA waste is not that easy, explained Makoto Tojo, technical manager at Germany-based JSW-EU. His colleague, Hayato Hobo, a JSW-EU sales representative, agreed.

“Most of plastics recycling, not just PMMA, is done by mechanical recycling. In this process, the quality of plastic material becomes lower and lower every time the material is submitted to recycling,“ he said.

Using a thermal depolymerisation route, through which the PMMA polymer is converted back into the monomer state, however, changes the game.

“Mind you: we cannot say that thermal depolymerisation can be applied to all plastic materials. For example, polycarbonate is one of the competitors of PMMA from the optical properties point of view, but it cannot be depolymerised back to the monomer at all. Polystyrene can also be recycled by the same way but the yield is lower,” said Hayato Hobo.

Unlike other processes that have been attempted, the depolymerisation process using JSW’s TEX twin screw extruder can handle a wide range of PMMA waste materials including end-of-life scraps containing inorganic contamination substances and with a relatively high yield. If the MMAtwo project proves to be a success, waste which currently goes to landfill, is incinerated or exported will be able to recycled and used again and again.

Next to developing second-generation MethylMethAcrylate (MMA) raw material, the aim is to establish a second value chain for the product.

Much has already been achieved. After first processing relatively pure PMMA waste in the initial tests, the next step was contaminated PMMA waste material, which was more challenging. Ultimately the required level of purity was achieved, and the rMMA was delivered to consortium partner members Speichim and Arkema for further processing and application.

Further testing was carried out in November 2020, which ‘provided excellent yields of regenerated crude MMA’, according to the newsletter published by the project organisation. In spring 2021, a fourth test series will take place.

“We are getting closer and closer to the industrial, commercially highly interesting implementation of our PMMA depolymerisation project. The personnel requirements are significantly lower compared to the competing conventional process. The ecological advantage, sustainability and operator safety are unquestionable,” concluded Makoto Tojo.

The project ends in September 2022. If all goes as expected, the first commercial plant will go into operation, shortly after the end of the project.

The project has received €6.6 million in funding from the EU Horizon 2020 Research and Innovation Programme.