Fireproof polyester composition

A fireproof polyester composition comprising a blend of (1) a copolymerized polyester comprising a polyalkylene terephthalate containing in the main chain thereof binding units of the formula:

• ##STR23## wherein Y denotes an oxygen atom, an alkylidene radical having 1 to 6 carbon atoms or a cycloalkylidene radical having 3 to 6 carbon atoms, the bromine content in said copolymerized polyester being from 2 to 12% by weight, with (2) a high molecular weight organic phosphorus compound of the formula:
• ##STR24## wherein R.sub.1 denotes a monovalent hydrocarbon radical of 1 to 18 carbon atoms which is unsubstituted or substituted with one or more substituents, R.sub.2 denotes a divalent hydrocarbon radical of 2 to 20 carbon atoms which is unsubstituted or substituted with one or more substituents, x and z each denote 0 or 1 and n is an integer of 5 to 100, the amount of organic phosphorus compound in said blend being such as to correspond to 0.1 to 0.8% by weight of phosphorus atoms.