Manufacture of polyesters

Claim 1

In a continuous process for melt-spinning yarn from a high molecular weight polyethylene terephthalate polymer, the improvement which consists of continuously incorporating in said polymer a stabilizing amount of a copper compound selected from the group consisting of copper II dichloro 2,2'-dipyridyl, copper II dichloro bis(2,2'-dipyridyl), copper II dichloro oxamide, copper II dichloro 1,10-phenanthroline, and copper II dichloro ethylene diamine, said process being further characterized in that said copper compound is incorporated in said polymer when said polymer is in the molten state immediately prior to spinning, by forming a stable dispersion comprising a liquid polyisobutene and said copper compound and injecting the dispersion with mixing into said molten polymer, said liquid polyisobutene having a viscosity of 3 to 70 poises at 20° C., and said dispersion containing 10 to 60 weight percent of said copper compound, whereby said yarn has an intrinsic viscosity of 0.90 to 0.95 dl. per gram and less than 12 equivalents of carboxyl end groups per 10 6 grams of yarn, said yarn being particularly useful to make fabric for tire building.