Thermoplastic polyphosphonatophenyl ester carbonate from aryloxycarbonyloxy-benzoic acid aryl ester and preparation thereof

A process for the preparation of thermoplastic aromatic polyphosphonatophenyl ester carbonates comprising

• (i) reacting a hydroxy benzoic acid with a molar excess of diaryl carbonate of the structure ##STR16## wherein Ar is an aryl radical, in the presence of an alkaline or neutral transesterification catalyst, to obtain a aryloxycarbonyloxybenzoic acid aryl ester of the structure ##STR17## wherein Ar is as defined above, and (ii) transesterifying said (1) with phosphonic acid diaryl ester of the structure ##STR18## wherein Ar' is a substituted or an unsubstituted aromatic radical and R is selected from the group consisting of at least one of C.sub.1 -C.sub.12 alkyl, C.sub.2 -C.sub.12 alkenyl, C.sub.6 -C.sub.30 cycloalkenyl, C.sub.6 -C.sub.30 aryl, C.sub.7 -C.sub.30 arylalkyl or C.sub.8 -C.sub.30 arylalkenyl and (3) a diphenol reactant in continuous contact with said catalyst, at a temperature of about 80.degree. to 400.degree. C. under vacuum, with the proviso that the molar amount of said diphenol equals the total molar amount of said (1) and said (2).