Process for producing polycarbonates

Abstract

A continuous process for producing polycarbonates by the transesterification of didiaryl carbonates with dihydroxyaryl compounds in the presence of quaternary onium compounds is disclosed. The polycarbonates thus produced are suitable for preparing a variety of articles.

What is claimed is:  
     
         1 . A continuous process for producing polycarbonate comprising transesterifying didiaryl carbonate with dihydroxyaryl compound, and condensing in the presence of a quaternary onium compound catalyst, said condensing including a final stage, said process characterized in the absence of additional catalyst from said final stage.  
     
     
         2 . A continuous process for producing polycarbonate according to  claim 1 , wherein a essentially readily decomposable onium compound is used as a catalyst and in which after a precondensation without removing the released monohydroxyaryl compound an oligocarbonate is formed in subsequent evaporation steps by stepwise reduction of pressure and stepwise rise of temperature removing the released monohydroxyaryl compound, which is then further condensed to the final product in one or more basket-type reactors without adding further catalysts again by evaporating the monohydroxyaryl compound using a stepwise reduction of pressure and stepwise rise of temperature.  
     
     
         3 . The polycarbonate prepared by the the process according to  claim 1 .  
     
     
         4 . The polycarbonate of according to  claim 2 , characterized in being substantially free of electrolytes.  
     
     
         5 . A storage medium comprising the polycarbonate of  claim 2 .  
     
     
         6 . Optical storage medium comprising the polycarbonate of  claim 2 .  
     
     
         7 . Magneto-optic storage medium comprising the polycarbonate of  claim 2 .  
     
     
         8 . The process of  claim 1  wherein onium compound is tetraphenylphosphonium phenolate.  
     
     
         9 . The process of  claim 1  wherein catalyst is used in an amount of 10 −8  to 10 −3  mol per one mol bisphenol.  
     
     
         10 . The process of  claim 9  wherein the catalyst is used in an amount of 10 −8  to 10 −3  mol per one mol bisphenol.  
     
     
         11 . The process of  claim 1  wherein the catalyst is added dissolved in phenol.  
     
     
         12 . The process of  claim 1  wherein the apparatuses, reactors, pipelines, pumps and fittings which are used at process temperatures of up to about 290° C. are made of stainless steels of type Cr Ni (Mo) 18/10 and the ones used at process temperatures of higher than about 290° C. are made of Ni base alloys of type C.