Process for the manufacture of stabilized polyester-polycarbonate copolymers

Claim 1

An improved process for the manufacture of thermoplastic polyesters containing carbonate groups and a stabilizer containing phosphorus from linear polyester precondensates which still contain hydroxyl groups, characterized in that linear polyesters containing hydroxyl groups and having a relative viscosity of at least 1.30, measured at 30° C on a 1% strength solution in equal parts of phenol and tetrachloroethane, are allowed to react with 0.01 to 45% by weight, based on the total amount, of a polycarbonate built up from diols of which the hydroxyl groups are bonded to one or different aromatic radicals and which polycarbonate has a degree of polycondensation of at least 10, in the melt phase or solid phase, at a temperature of 170° to 320° C and in vacuo, in a stream of inert gas, or in vacuo and a stream of inert gas wherein the improvement comprises increasing the relative viscosity of said thermoplastic polyesters by adding 1 to 15% by weight, based on the polyester precondensate, of a stabilizer containing phosphorus simultaneously with the addition of the polycarbonate.