Process for the purification of polycarbonates

Abstract From the Canadian patent

The free and bonded residual phenol content of oligocarbonates prepared by transesterification between a diol and a diphenyl carbonate is substantially reduced by a process comprising (i) introducing water into the oligocarbonate in the liquid state at an elevated temperature under reduced pressure and (ii) purging the mixture with an inert gas to effect degassing. The purified oligocarbonates are particularly resistant to yellowing and are useful in the preparation of polyurethane elastomers which are resistant to hydrolysis.