| 摘要 |
<p>Prodn. of thermoplastic, aromatic, polycarbonates by interfacial polycondensation of phosgene, a bisphenol, chain stopper and opt. a chain branching agent, includes phosgenation of an aq. alkali soln. of the bisphenol in presence of a solvent (mixt.) in which the oligo-, aromatic polycarbonate is soluble, and which is not miscible with water. Reaction is at pH 4-8, in the presence of a polycondensation catalyst and in three, series-connected, reactors. The resulting aq. phase is mixed with further starting materials and fed back to the phosgenation reactor. An oil-in-water emulsion is formed directly and maintained in the three reactors for the entire reaction time. Pref., in a first step the aq. alkali soln. of the bisphenol is reacted with phosgene in presence of the recycled aq. reaction phase and the organic solvent and extra alkali. In a second step the intermediate prod. is further reacted with further caustic soda. In a third step the intermediate prod. is polycondensed into polycarbonate in the presence of the polycondensation catalyst. The alkali soln. contains 10-40 wt.% of bisphenol. The recycled aq. reaction phase contains 2.5-15 wt.% of bisphenol. The recycled aq. phase is cooled to such an extent that no further cooling is necessary to ensure that the b.pt. of the organic solvent is not exceeded in the three reactors. Alternatively, the b.pt. of the solvent is chosen so that no cooling is necessary. The first step lasts 10 seconds-30 minutes, the second step lasts 1-30 minutes and the third step lasts 2-30 minutes. ADVANTAGE - Good yields and reproducibility of MW for the polymers produced.</p> |
