Inhibition of catalytically active impurities in polycarbonate by the melt transesterification process
View Patent ↗An improvement to the melt transesterification process for the preparation of polycarbonate is disclosed. The improvement entails adding to the process between its medium viscosity reactor and a high viscosity reactor at least one bridged ester of organic sulphur-containing acid.
1. 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.
2. The process according to claim 1 , wherein the amount of ester is a positive amount up to 100 ppm relative to the weight of the polycarbonate.
3. A method of using the bridged ester of claim 1 for inhibiting catalytically active impurities in the melt transesterification process for preparing polycarbonate.