Patent ID: 6855390

Claim:
Polycarbonate characterized by its stability to blue laser light of more than 123 seconds when irradiated at 0.2 GW/m 2 prepared by the phase boundary process comprising (i) reacting at least one dihydroxydiarylalkane in the form of its alkali metal salt with phosgene in the heterogeneous phase in the presence of sodium hydroxide solution and an organic solvent wherein the concentration of Fe, Cr, Ni, Zn, Ca, Mg, Al metals or their homologues in the feedstock is no more than 2 ppm, to form an aqueous phase and an organic polycarbonate phase, (ii) separating the aqueous phase, (iii) washing the organic polycarbonate phase, optionally following filtration, with an aqueous wash liquid, to obtain a washed organic polycarbonate phase, (iv) separating the washed organic polycarbonate phase from the wash liquid, optionally followed by filtering, to obtain a separated washed organic polycarbonate phase, (v) heating the separated washed organic polycarbonate phase to obtain a heated phase, (vi) filtering the heated phase at least once, to obtain a filtered organic solvent and polycarbonate, (vii) separating the organic solvent, and (viii) working up the polycarbonate.