Heat stabilization of polyesters with built-in stabilizers

Claim 1

A FIBER FORMING LINEAR POLYESTER WHICH IS STABLE AGANST OXIDATIVE DETERIORATION UNDER THE INFLUENCE OF HEAT COMPRISING A HIGHLY POLYMERIC CONDENSATION POLYMER OF THREE CLASSES OF CONSTITUENTS WHEREIN THE PRESENCE OF PHENOLIC HYDROXY GROUPS IS LIMITED TO CLASS (C), SAID CLASSES BEING (A) AT LEAST ONE BIFUNCTIONAL DIBASIC ACID HAVING CARBOXY RADICALS AS THE SOLE FUNCTIONAL GROUPS, (B) AT LEAST ONE BIFUNCTIONAL GLYCOL HAVING HYDROXY RADICALS AS THE SOLE FUNCTIONAL GROUPS, AND (C) .01-5 MOLE PERCENT OF A RING SUBSTITUTED HYDROQUINONE COMPOUND HAVING RING-SUBSTITUTED THEREON AT LEAST ONE ESTER-FORMING GROUP IN ADDITION TO THE TWO PHENOLIC HYDROXY GROUPS OF SAID HYDROQUINONE COMPOUND, EACH OF SAID ESTER-FORMING GROUPS HAVING A TERMINAL RADICAL SELECTED FROM THE GROUP OF RADICALS CONSISTING OF CARBOXY, CARBALKOXY AND HYDROXYALKYL RADICALS, SAID HYDROQUINONE COMPOUND BEING CHEMICALLY COMBINED THROUGH THE SAID ESTER-FORMING GROUPS NTO A LINEAR POLYESTER OF CONSTITUENTS CONSISTING ESSENTIALLY OF SAID CLASSES (A), (B), AND (C), SAID PHENPHENOLIC HYDROXY GROUPS OF SAID CLASS (C) CONSTITUENT REMAINING ESSENTIALLY UNCOMBINED.