Process for the isolation of polycarbonates based on 4,4'-dihydroxydiphenyl sulphones

Claim 1

A process for the isolation of a polycarbonate containing 18 to 45 mol % of structural units of the general formula ##STR5## in which R 1 denotes a hydrogen atom or a C 1 to C 3 alkyl group, relative to the sum of polycarbonate structural units of the formula (I)+(Ia) in a polycarbonate of the general formula ##STR6## in which X denotes a direct bond, a C 1 to C 8 alkylene, C 2 to C 8 alkylidene, cyclohexylene or cyclohexylidene radical, S, O or CO, each R independently denotes a hydrogen, chlorine or bromine atom or an alkyl group having 1 to 3 carbon atoms, and m is 0, 1 or 2, comprising reacting, by the phase-boundary process, 18 to 45 mol % of a sulphone-bisphenol of the general formula ##STR7## in which R 1 has the meaning given above, with 82 to 55 mol % of a bisphenol of the general formula ##STR8## in which X, R and m have the meanings given above, said mol percentages in each case being relative to the total molar amount of the bisphenols of formula (IIA)+(II) used, in which reaction the bisphenol of the formula (II) is phosgenated to give an oligocarbonate containing chloroformic acid ester end groups and the oligocarbonate is then subjected to a polycondensation reaction with the sulphone-bisphenols of the formula (IIa) using an amine catalyst, separation of the phases in a separating vessel after the polycondensation has ended, and washing of the organic phase with phosphoric acid and water until the washings are neutral, and after further separation of the phases, isolation of the sulphone-bisphenol polycarbonate by precipitation or evaporation of the organic solvent.