(116g) Screening Investigations for the Development of a Back to Monomer Recycling Method for PET Containing Composite Materials

In the last decade recycling has moved into the focus of our society because of the awareness of finite resources and the resulting need for a circular economy. However, state-of-the-art recycling technology is capable to recycle homogenous plastic waste such as PET (poly(ethylene terephthalate)) at the penalty of progressive downgrading but still no technology is available for the recycling of PET composite materials. The research project revolPET®[1] addresses this issue and develops a new recycling technology to close the loop for PET material.

As a first feasibility and screening test, an innovative quasi solid-solid kneading reaction has been investigated. The hydrolysis of PET with a strong base represents the key step of the recycling technology to produce the monomers terephthalic acid (TA) and ethylene glycol. In traditional solvent based hydrolysis reactions high temperatures and long residence times are necessary for the quantitative depoly­merization of PET [2].

In this study the depolymerization has been conducted in a laboratory kneader, see Fig 1 a). The influence of various process and reaction parameters on the yield in TA has been examined. High yields of TA were obtained in very short reaction and kneading time, e.g. 5 min, with and without the use of additional solvent. The color index of the obtained TA was measured and used to evaluate the influence of the process parameters on the TA quality, Fig 1 b).

The high yields of TA at very short reaction times which are achieved with this novel approach of quasi solid/solid reaction are promising results for the development of a new chemical recycling technology for PET composite materials which addresses a major challenge of this decade.

[1] www.revolpet.eu

[2] A. Oku, L.-C. Hu, E. Yamada, J. Appl. Polym. Sci. 1997, 63, 595-601.