Abstract: High molecular weight linear condensation polyesters are stabilized against deterioration by heat by reacting the polyester in molten form with an epoxy compound having 5 to 25 carbon atoms in the molecule and selected from the group consisting of ##STR1## where R represents the radical remaining after removal of the carboxyl group from a monocarboxylic acid, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 represent hydrogen or hydrocarbon radicals, and n is an integer that can be 0 to 3.

Abstract: In a process for the preparation of high molecular weight linear polyesters of terephthalic acid which comprises partially esterifying terephthalic acid with an alkylene glycol under direct esterification conditions and then further esterifying and polycondensing the partially esterified product, the molecular weight distribution of the polyester is narrowed by correlating the carboxyl conversion with the reacted glycol to terephthalic acid mol ratio in various steps of a multistep process.

Abstract: The esterification of an aromatic dicarboxylic acid with an alkylene glycol containing 2 to 10 carbon atoms is described under conditions of direct esterification wherein the resultant polyester has low ether content. The dicarboxylic acid is esterified with the alkylene glycol in the presence of a compound of the formula ##STR1## wherein M is H, an alkali metal selected from the group consisting of lithium, sodium and potassium or an alkaline earth metal selected from the group calcium and magnesium.

Abstract: In a continuous process for production of polyester polymers, polymer additives are added to the process stream at a point where the polymer is molten by injecting a stable liquid dispersion formed from a liquid polyisobutene and the requisite polymer additives. The process is particularly useful in production of thermally stabilized polyesters wherein a stabilizing amount of a copper complex compound is incorporated therein.

Abstract: An improved polyamide characterized by resistance to thermal-oxidative degradation consisting essentially of a polyamide having a stabilizing amount of copper II dichloro bis (pyridine) or copper II dichloro bis (quinoline) incorporated therein. In a continuous process, the stabilizing compound is preferably added as a dispersion in an inert carrier liquid.CROSS-REFERENCE TO RELATED APPLICATIONSThis application is related to U.S. application Ser. No. 752,483 filed Dec. 20, 1976.BACKGROUND OF THE INVENTIONThis invention relates to improved polyamides and to methods for their preparation. More particularly, the invention relates to improvement in the preparation of fibers, filaments and yarns from polyamides modified for enhanced resistance to thermal-oxidative degradation.The polyamide synthetic resins have many valuable properties that have resulted in their well known wide-spread use in industry and in the arts.