| 摘要 |
<FORM:1039547/C3/1> Solid polycarbonates are recovered from their solutions by introducing a polycarbonate solution into a shearing device having an operating speed sufficient to cut the polycarbonate particles as they are precipitated, while concurrently maintaining in the shearing device a turbulent stream of polycarbonate non-solvent having a Reynolds number of at least 1500 and while maintaining the temperature in the shearing device at at least the boiling point of the polycarbonate solvent. The shearing device preferably operates at a speed of 2000 to 20,000 r.p.m. The polycarbonate solvent may be a chlorinated aliphatic hydrocarbon, thiophene, dioxan, tetrahydrofuran, acetophenone, anisole, cyclohexanone, benzonitrile, dimethyl formamide or nitrobenzene. The non-solvent may be water, a hydrocarbon, acetone, ethyl acetate, trichloroethylene, carbon tetrachloride, 1,1-dichloroethane, nitromethane, acetonitrile or a dialkyl carbonate. Polycarbonate solution is sprayed into a shearing device 5 also fed with a stream of hot water from a pump 4. The output from the shearing device flows to a tank 1, the temperature of which is maintained at above the boiling point of the polycarbonate solvent by spurging live steam into it. Volatilized solvent is removed from the top of the tank whilst hot water is removed from the bottom via a screen 2. Polycarbonate particles collect above the valve 3 and are removed and passed to a dryer. In place of the valve, a star feed or a de-watering screw conveyer may be used. In an alternative, the screen 2 may be removed and the solids recirculated via pump 4 with controlled removal of slurry at 7. In examples, the polycarbonate solution used is one obtained by phosgenating bisphenol A in the presence of methylene chloride.
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