Abstract: Oligomeric carbonate dihydroxyaromatic-based chainstoppers are disclosed. One example of this type of chainstopper is a bisphenol A bischloroformate oligomer monocapped with phenol. These chainstoppers may be prepared by phosgenating a dihydroxyaromatic compound to terminate one or both of the terminal oxygen atoms with chlorocarbonyl groups, followed by reaction of the chlorocarbonyl-terminated material with a phenolic-type compound in the presence of an amine catalyst. The chainstoppers of the present invention are very useful in accurately controlling the molecular weight of polycarbonates formed by various processes, while also preventing the formation of undesirable by-products, such as diarylcarbonates.

Abstract: Aromatic polycarbonates having a predetermined relatively low weight average molecular weight, as well as a low molecular weight distribution, are prepared by partially capping an aromatic bischloroformate composition, preferably a bisphenol A bischloroformate composition, with a monohydroxyaromatic compound and subsequently converting the partially capped composition to a polycarbonate, using a base which provides a buffered pH in the range of about 12-13. The preferred base is calcium hydroxide, which is soluble in water in precisely the amount required to provide the desired pH.

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 polycarbonate oligomers are prepared by the reaction of a bisphenol bischloroformate (e.g. bisphenol A bischloroformate) with an amine (e.g., triethylamine) and an alkali or alkaline earth metal hydroxide in at least two back-mixed vessels and in a mixed aqueous-organic system. The liquid contents of each vessel except the last are passed to the next vessel and each vessel is simultaneously charged with reactants, with the concentration of carbonate units in the reactants being less in the first vessel than in subsequent vessels. By this method, there is obtained a cyclic product containing a minimum proportion of linear polycarbonates.

Abstract: A method is provided for making reaction products of phosgene and dihydric phenol under interfacial reaction conditions. The dihydric phenol such as BPA is introduced into the reactor in the form of a stable suspension which reduces phosgene hydrolysis, minimizes phosgene escape and effects improved BPA metering into the reactor.

Abstract: Linear polycarbonates of controlled molecular weight are prepared by first reacting a bischloroformate composition with a monohydroxyaromatic compound in a system comprising water, a base and a suitable organic liquid, and then converting the resulting partially capped bischloroformate composition to linear polycarbonate by contact with an interfacial polycarbonate formation catalyst in an alkaline medium. By this method, the efficiency of the capping agent is improved.

Abstract: Bischloroformate oligomer compositions are prepared by passing phosgene into a heterogeneous aqueous-organic mixture containing at least one dihydroxyaromatic compound, with simultaneous introduction of a base at a rate to maintain a specific pH range and to produce a specific volume ratio of aqueous to organic phase. By this method, it is possible to employ a minimum amount of phosgene. The reaction may be conducted batchwise or continuously. The bischloroformate composition may be employed for the preparation of cyclic polycarbonate oligomers or linear polycarbonate, and linear polycarbonate formation may be integrated with bischloroformate composition formation in a batch or continuous process.

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: A method is provided for making reaction products of phosgene and dihydric phenol, such as bischloroformates and polycarbonates utilizing a reactor with an overhead condenser. Reduced phosgene blow-by is achieved by using an absorber for phosgene which is connected in series to the overhead condenser.

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 oligomers are prepared by a method which is adaptable to continuous operation, by the reaction of a bisphenol bischloroformate (e.g., bisphenol A bischloroformate) with an amine (e.g., triethylamine) and an alkali metal hydroxide in a tank reactor (preferably a continuous stirred tank reactor) in a mixed aqueous-organic system, with agitation (preferably by stirring) at a rate just sufficient to prevent segregation of the aqueous and organic liquid phases. The residence time of the mixture in the reactor is preferably about 8-12 minutes.

Abstract: A method is provided for making aromatic bis(ether anhydrides) by effecting an exchange reaction between aromatic bis(ether imide) and phthalic anhydride in the presence of water and an exchange catalyst. The separation and recovery of phthalimide and aromatic bis(ether anhydride) is achieved in a stripper-reactor using a vaporous mixture of water and the exchange catalyst.