Current developments in chemical recycling of post-consumer polyethylene terephthalate wastes for new materials production: A review

Beyond Mechanical Recycling: Giving New Life to Plastic Waste

“…As mentioned in Section 1.4.1, solvolysis is ap otentially more selective way to recover monomers from polyesters and polyamides employing lower temperatures compared to those used in pyrolysis.The solvolysis processes hydrolysis,alcoholysis (glycolysis and methanolysis), phosphorolysis,ammonolysis,and aminolysis cleave ether, ester,and acid amide bonds and therefore are limited to polymers with these bonds.Much R&D focusses on PET [112][113][114][115][116] and PU [117,118] and to al esser extent on PA ,polycarbonate (PC) [119] and PLA [120] depolymerization. Thea dvantage of these processes lies in the possibility to obtain monomers that can be further purified, filtering out additives and colorants,allowing for re-polymerization to virgin-grade quality.T his is especially interesting for PU,w hich cannot be recycled mechanically.I ft he purity or quality of the recovered monomers is not as good as the monomers initially used, they can also be mixed with conventionally obtained monomers for the polymer synthesis.Afew commercial plants exist for methanolysis of PET [121] and glycolysis of PET and PU.…”

“…[136] Re:2 )T he small contact area between liquid and solid plastic pieces retards the reaction, which is why the reaction proceeds much faster at temperatures exceeding the plastic melting point. [115] An approach to lower the reaction temperature is reactive extrusion, which also decreases reaction times from hours to minutes. [124,137] Theglycolysis of PET via reactive extrusion led to low molecular weight oligoesters, [124,138] which could be used to make PU.H owever, more research effort is needed to make this process more selective to BHET.A nother approach uses ap hase-transfer catalysts that was shown to transport sodium anions from NaOH to the plastic surface of different nylons and PET in basic hydrolysis.…”

Recycling of Bioplastics: Routes and Benefits

“…The optimum parameters for PET glycolysis are: a temperature range of 180-240 °C, pressures of 0.1-0.6 MPa, a transesterification catalyst, a high EG/PET ratio and 0.5-8 h for completion, product formation is mostly BHET with very little oligomers [132,136,142]. The reaction follows first order kinetics with respect to PET, and second order with respect to EG concentration [143]. A higher ratio of EG:PET (≥ 5:1) favors the formation of BHET instead of oligomers [143].…”

Die nächste Generation des Recyclings – neues Leben für Kunststoffmüll

“…Deshalb ist die Anwendung dieser Verfahren auch auf Polymere beschränkt, in denen diese Bindungen vorkommen. Zahlreiche Forschungs-und Entwicklungsarbeiten beschäftigen sich mit PET [110][111][112][113][114] und PU, [115,116] weniger mit PA ,P olycarbonat (PC) [117] und PLA. [118] All diese Verfahren zeichnet aus,dass Monomere erzeugt werden, die noch weiter aufgereinigt und gefiltert werden kçnnen, wobei Zusatz-und Farbstoffe entfernt werden kçnnen.…”

“…[134] Ad 2) Die kleine Kontaktfläche zwischen Flüssigkeit und den Kunststoffstücken verlangsamt die Reaktion, weshalb die Solvolyseprozesse viel schneller bei Te mperaturen über dem Schmelzpunkt ablaufen. [113] Mit reaktiver Extrusion kann der Prozess auch bei niedrigerer Te mperatur gefahren und die Reaktionszeit von Stunden auf Minuten verkürzt werden. [122,135] Die Glykolyse von PET mit reaktiver Extrusion führte zu Oligoestern mit niedriger Molekülmasse, [122,136] die zur PU-Herstellung genutzt werden konnten.…”