2. Polyester carbonate and phosgene-free processes

Polyester carbonate is a by-product with superior characteristics to PC, intermediate between polysulfones and polyarylates. Like PC, the product is obtained from bisphenol A and TMC bisphenol, trimethylcyclohexanone-bisphenol. Both products can be condensed in any mixing ratio, with thermal resistance increasing with the proportion of bisphenol TMC. The carbonic acid in PC is partly replaced by terephthalic acid. If it were entirely replaced, the result would be aromatic polyester, such as polyarylate. Bayer was the first to offer polyester carbonate on the market, at the end of 1983. Mitsubishi Chemical has a plant in Japan with an Allied patent. PPC (polyphthalate carbonate) resins, launched in 1984 by General Electric, are a similar development, aimed at adding greater resistance to higher temperatures, while retaining all the other characteristics of PCs.

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