Recycling of End-of-Life Poly(bisphenol A carbonate) via Alkali Metal Halide-Catalyzed Phenolysis

Abstract

The chemical recycling of end-of-life plastic waste streams can contribute to a resource-conserving and sustainable society. This matter of recycling is composed of a sequence of depolymerization and subsequent polymerization reactions. In this regard, we have studied the chemical recycling of end-of-life poly(bisphenol A carbonate) applying phenol as depolymerization reagent. In the presence of catalytic amounts of alkali metal halides as products bisphenol A and diphenyl carbonate were obtained in excellent turnover frequencies of up to 1392 h^-1 and short reaction times. These depolymerization products offer the straightforward possibility to close the cycle by producing new poly(bisphenol A carbonate) and as second product phenol, which can be reused for further depolymerizations.

Keywords: catalysis; depolymerization; green chemistry; polymers; recycling.

Scheme 1

PBPAC production and concept for the chemical recycling of poly(bisphenol A carbonate).

Figure 1

Depolymerization of poly(bisphenol A carbonate) 1  a originated from DVDs with phenol‐time vs. yield of 2 [Reaction conditions: conventional heating: 1  a (1.35 mmol, based on the monomeric unit), phenol (47.3 equiv.), KF (0.5 mol %, based on the monomeric unit), 180 °C, yield determined by ¹H NMR].

Scheme 2

Depolymerization of poly(bisphenol A carbonate) 1 originated from DVDs with phenol [Reaction conditions: 1  b/1  c (1.35 mmol, based on the monomeric unit), phenol (47.3 equiv.), KF (2 mol %), 180 °C, 30 min; yield determined by ¹H NMR.