Patent ID: 7858727

Claim:
A process for preparing polycarbonate by the phase boundary process and processing at least a part of the resulting alkali metal chloride-containing solution in a downstream alkali metal chloride electrolysis, comprising: a) preparing phosgene by reacting chlorine with carbon monoxide; b) reacting the phosgene of a) with at least one bisphenol in the presence of at least one base, optionally at least one basic catalyst, and optionally at least one organic solvent, to give a polycarbonate and an alkali metal chloride-containing solution; c) separating the polycarbonate and alkali metal chloride-containing solution of b) and subsequently washing the polycarbonate at least once with water; d) separating the alkali metal chloride-containing solution of c) from solvent residues and optionally separating the alkali metal chloride-containing solution from catalyst residues via treatment with an adsorbent, wherein prior to treatment with an adsorbent, the alkali metal chloride-containing solution is adjusted to a pH of less than or equal to 8; and e) electrochemically oxidating at least a part of the alkali metal chloride-containing solution of d) to form chlorine, alkali metal hydroxide solution, and optionally hydrogen; wherein f) at least a part of the chlorine prepared in e) is recycled to a); and/or g) at least a part of the alkali metal hydroxide solution prepared in e) is recycled to b).