VERFAHREN ZUR HERSTELLUNG VON THERMOPLASTISCHEN, AROMATISCHEN POLYPHOSPHATEN MIT GERINGEN ANTEILEN AN CARBONATSTRUKTUREN

1. Process for the preparation of polyphosphonates containing carbonate structures in quantities of 0.3 to 4.5 mol-%, relative to the sum of phosphonate and carbonate structural units, which is characterised in that diphenols are reacted with phosphonic acid diaryl esters in a molar ratio of 1.03 to 0.97, in the presence of neutral transesterification catalysts, at temperatures of 230 to 320 degrees C, and the volatile monohydroxyaryls are distilled off over a period of 1.5 to 2.5 hours, at a pressure falling from 500 to not less than 2 mbars, and then the reaction is completed over a period of 1 to 2 hours by adding diaryl carbonate in quantities of 0.5 mol-% to 8.5 mol-%, relative to the molar sum of phosphonic acid diaryl ester and diaryl carbonate used, at temperatures of 250 to 320 degrees C and at a pressure falling from 300 to not less than 1 mbar to 0.2 mbar.