Process for preparing copolycarbonates

Transparent copolycarbonate can be obtained containing more than 35 mole% 4,4'-dihydroxydiphenyl when it is prepared after a melt ester interchange process when the mean viscosity in the reaction vessel is maintained for a maximum of 40 minutes during the heating phase. A process for preparation of transparent copolycarbonates via a melt ester interchange process and consisting of 35-60 mole % of compounds of formula (I) and complimentary amounts (i.e. 65-40 mole%) of compounds of formula (II): R to R = H, 1-4C alkyl, phenyl, or halogen ; R to R = H, Me, Cl, or Br; and X = 1-5C alkylene 2-5C alkylidene, 5-6C cycloalkylene, 5-10C cycloalkylidene. The compound of formula (II) is synthesized as a bisphenol A molecule, where the final temperature is maintained at 270-330 degrees C for less than 40 minutes, with a starting temperature of 220-240 degrees C. Independent claims are also included for: (1) a transparent copolycarbonate containing more than 35 mole% 4,4'-dihydroxydiphenyl (DOD); and (2) a shaped body and extrudate obtained from the copolycarbonates