Polycarbonate with phenolic building blocks and low chlorine content

A process for preparing a polycarbonate comprising at least 30 wt-% of structural units of formula (1), wherein the wt.-% is based on the total weight of the polycarbonate,

• wherein in formula (1)
• each X independently represents a single bond, —O—, —S—, —S(O)—, —S(O)2—, —C(O)—, or an organic group having 1 to 18 carbon atoms, wherein the organic group having 1 to 18 carbon atoms is linear, branched or cyclic, aromatic or non-aromatic, and can further comprise heteroatoms,
• each of R1 and R3 independently represents a monovalent hydrocarbon group,
• each of R2 and R4 independently represents a hydrogen atom, an alkoxy group, or a monovalent hydrocarbon group, and
• each of p and q independently is 1 or 2, and
• n represents the average number of repeating units,
• the process comprising
• (a) dissolving at least one diol of formula (I) in an aqueous alkali solution
• wherein in formula (I)
• each X independently represents a single bond, —O—, —S—, —S(O)—, —S(O)2—, —C(O)—, or an organic group having 1 to 18 carbon atoms, wherein the organic group having 1 to 18 carbon atoms is linear, branched or cyclic, aromatic or non-aromatic, and can further comprise heteroatoms,
• each of R1 and R3 independently represents a monovalent hydrocarbon group,
• each of R2 and R4 independently represents a hydrogen atom, an alkoxy group, or a monovalent hydrocarbon group, and
• each of p and q independently is 1 or 2, and
• optionally adding at least one chain terminator,
• optionally adding at least one catalyst and
• optionally adding additional aqueous alkali solution,
• to result in a solution,
• (b) adding an organic solvent suitable for dissolving polycarbonate to the solution of step (a) and thereby obtaining a mixture,
• (c) adding phosgene to the mixture of step (b) and optionally adding additional aqueous alkali solution,
• (d) reacting the mixture of step (c) for 2 to 30 minutes,
• (e) optionally adding at least one chain terminator to the mixture of step (d) with the proviso that in case in step (a) no chain terminator was added, the addition of at least one chain terminator in step (e) is mandatory and
• optionally adding at least one catalyst,
• optionally adding additional aqueous alkali solution,
• and in case at least one chain terminator and/or at least one catalyst is added in this step reacting the resulting mixture for 2 to 60 minutes,
• (f) optionally adding at least one catalyst to the mixture of step (d) or step (e), whichever step is carried out last, with the proviso that in case neither in step (a) nor in step (e) a catalyst was added, the addition of at least one catalyst in step (f) is mandatory,
• and in case at least one catalyst is added in this step reacting the resulting mixture for 2 to 60 minutes,
• (g) determining the pH of the mixture obtained after step (d), (e) or (f), whichever step is carried out last, and if required adjusting the pH by the addition of additional aqueous alkali solution so that the resulting pH is at least 10.0
• and in case additional aqueous alkali solution is added in this step reacting the mixture for 2 to 30 minutes.