Abstract: Cyclic polycarbonate (or thiol analog) oligomer mixtures are prepared by the reaction of bishaloformates or their thio analogs, or mixtures thereof with dihydroxy or dimercapto compounds, with alkali metal hydroxides and various amines. The oligomer mixtures may be converted to polycarbonates or their thiol analogs by a method which is particularly adaptable to integration with polycarbonate processing operations. Polymerization may be conducted simultaneously with molding, extrusion and the like. The oligomer mixtures are adaptable to the preparation of filled prepregs.

Abstract: Cyclic polycarbonate mixtures containing units derived from spirobiindane bisphenols, preferably 6,6'-dihydroxy-3,3,3',3'-tetramethylspirobiindane, are prepared from the corresponding bischloroformates or mixtures thereof with bisphenols. They may be homopolymeric or copolymeric; cyclic oligomer mixtures are preferred. Such oligomers may be converted to linear polycarbonates having high glass transition temperatures.

Abstract: Cyclic polycarbonate (or thiol analog) oligomer mixtures are prepared by the reaction of bishaloformates or their thio analogs, or mixtures thereof with dihydroxy or dimercapto compounds, with alkali metal hydroxides and various amines. The oligomer mixtures may be converted to polycarbonates or their thiol analogs by a method which is particularly adaptable to integration with polycarbonate processing operations. Polymerization may be conducted simultaneously with molding, extrusion and the like. The oligomer mixtures are adaptable to the preparation of filled prepregs.

Abstract: A method is provided for determining the stoichiometric end point of phosgenation reactions which produce polycarbonates and chloroformates, respectively, by monitoring the rate of heat generated by the reaction mixture per unit of phosgene utilized.

Abstract: Cyclic heterocarbonates containing linkages such as ester, urethane, imide, ether sulfone, ether ketone or amide may be prepared from the corresponding bishaloformates. They may be converted to linear copolycarbonates.

Abstract: A method is provided for reducing the reflux temperatures of methylene chloride in phosgenation reactions by introducing a second inert vaporizable component to the reaction medium. This second inert vaporizable component has a lower vaporization temperature than the methylene chloride so as to reduce the temperature of vaporization of the mixture. More efficient use of phosgene is obtained when polymerizing aromatic dihydroxy compounds to polycarbonates and higher yields of monomeric and dimeric bischloroformates are obtained.

Abstract: Cyclic polycarbonate (or thiol analog) oligomer mixtures are prepared by the reaction of bishaloformates or their thio analogs or mixtures thereof with dihydroxy or dimercapto compounds, with alkali metal hydroxides and various amines. The oligomer mixtures may be converted to polycarbonates or their thiol analogs by a method which is particularly adaptable to integration with polycarbonate processing operations.

Abstract: Chloroformate compositions, particularly bischloroformate compositions, are prepared by the reaction of phosgene with a hydroxy compound, preferably a dihydroxy compound such as bisphenol A, in a heterogeneous mixture, while adding a hydrogen chloride scavenger comprising aqueous base as necessary and maintaining a pH of 0.5-8 during the phosgene addition. When a polyhydroxy compound is employed and the temperature is above 30.degree. C., the phosgene addition rate is maintained at a level high enough to effect rapid and complete reaction with dissolved hydroxy compound. This method uses substantially less phosgene than methods involving a higher pH.

Abstract: Bischloroformate compositions are prepared by passing gaseous phosgene into an agitated aqueous solution of a di-(alkali metal) salt of an organic dihydroxy compound such as bisphenol A, while maintaining said solution at a temperature within the range of about 0.degree.-50.degree. C. Phosgene passage and agitation are continued until the bischloroformate composition has precipitated. The reaction is typically complete when the pH of the aqueous phase drops below 7.