Patent ID: 7250483

Claim:
In the melt transesterification process for the preparation of polycarbonate which process includes a medium viscosity reactor and a high viscosity reactor the improvement comprising adding to the process between said reactors at least one bridged ester of organic sulphur-containing acid conforming to a formula selected from the group consisting of formula (I) in which the substituents R 1 independently of one another represent hydrogen or unsubstituted or halo-substituted C 1 -C 20 -alkyl, R 2 and R 3 independently of one another represent hydrogen, C 1 -C 6 -alkyl or C 4 -C 30 -alkylcarboxyl or R 2 and R 3 represent the radical wherein R 1 has the meaning given above, m independently one of the other denotes 0 or 1, n represents an integer from 0 to 8, formula (II) in which R 1 has the meaning given above, A independently of one another represents hydrogen or C 1 -C 12 -alkyl, I represents 2 or3, formula (IV) in which R 1 and n have the meaning given above, and R 4 represents C 4 -C 30 -alkylcarboxyl, or wherein R 1 has the meaning given above formula (V) formula (VI) formula (VIIa) formula (VIIb) formulas (Ib) and (IVa) in which R 1 and n have the meaning given above, and P represents an integer from 0 to 10, R 5 and R 6 independently of one another represent hydrogen or C 1 -C 20 -alkyl and R 11 independently of one another represents hydrogen or di-(C 1 -C 4 -alkylamino, formula (VIII) in which R 1 and A have the meaning given above, formula (IX) in which R 1 and m have the meaning given above, formula (X) in which R 1 and A have the meaning given above and formula (XI) in which R 1 and A have the meaning given above.