VERFAHREN ZUR HERSTELLUNG VON POLYCARBONATEN

Polycarbonate can be obtained using a multistep continuous phase boundary process, a special pump reactor and a tubular reactor, special reaction conditions, and a specific ratio of metered starting components to the amount of reaction emulsion remaining in the pump reactor. Polycarbonate can be obtained using a multistep continuous phase boundary process, a special pump reactor and a tubular reactor, special reaction conditions, and a specific ratio of metered starting components to the amount of reaction emulsion remaining in the pump reactor. The method includes the following steps: (A) continuous mixing of an organic and aqueous phase in a specially designed pump reactor, where the organic phase is a solvent for the polycarbonate, contains phosgene, and the aqueous phase consists of a mixture of alkali hydroxide and phenolic components (bisphenol A and optionally monophenol as chain splitter); (B) by means of a heat exchanger, a mean temperature of less than 60 degrees C is established in the pump reactor, and part of the emulsion obtained over a period of 2 minutes is removed continuously from the reactor via an intermediate vessel (IV); (C) the emulsion portion is pumped through tubular reactors provided with mixing dwell zones, providing 2 and 40 minute dwell times, where: (1) the ratio (in moles per mole) of the metered amount of phosgene to the theoretical amount required to react all the phenol and bisphenol is 1:12 to 1:22; (2) the phosgene and bisphenol solutions in the pump reactor are metered directly downstream of (IV) into the pump circuit, and the chain splitter is fed into the pump circuit or optionally directly into the tubular reactors; (3) alkali hydroxide is metered into the pump reactor on the pump suction side in amount 15-40% of the total amount to be metered; (4) inside the pump reactor in the pump circuit in accordance with (2) above bisphenol A and phosgene are metered so that the ratio of their total amounts measured as the throughput over the pump circuit cross section (the sum of both solutions measured in cubic meters per hour) to the pumped emulsion is 1:3 to 1:12, and the amount fed to the IV corresponds to the total amount of metered solutions (sic); (5) immediately before feeding to the tubular reactor, more alkali solution (85-60% of the total metered alkali solution) is fed into the amount removed from (IV), and if required a chain splitter is added; and (6) after a further 1-20 minutes dwell time in the tubular reacto