Carbonate in the Manufacturing of Polycarbonates

Diphenyl carbonate (DPC) is a carbonate ester of formula (QH50)2C0. The principal use of DPC is as a critical comonomer in the manufacture of polycarbonate resin, an engineering thermoplastic with high impact resistance and excellent optical properties. It is widely used as a heat-resistant and flame-retardant insulator in electronics, a construction material, and an optical material for data storage (CD and DVD disks) and in manufacturing transparent parts in automotive and aerospace industries [1]. 

Originally, polycarbonate was produced by interfacial (organic/aqueous) polycondensation of phosgene (COClj) with disodium salt of a bisphenol, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A or BPA). Initially, the reaction produces an intermediate chloroformate R0C(0)C1 (Eq. (12.1)), which subsequently reacts with another phenoxide molecule, growing a polymer chain 

Liquid Phase Aerobic Oxidation Catalysis Industrial Applications mid Academic Perspectives, 

First Edition. Edited by Shannon. Stahl and Paul L. Alsters. 

However, a phosgene-free route was desired because of environmental hazards and governmental restrictions associated with the production and storage of extremely toxic phosgene (and chlorine used to synthesize it) and the use of chlorinated solvents. An important phosgene-free, so-called melt process, for the DPC synthesis involving transesterification of DPC in the absence of solvents was independently developed by GE, Bayer, Asahi/Chi Mei, and Mitsubishi. 

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