Industrial polyester yarn

Claim 1

A polyester filament, essentially free of unreacted carbodiimide and having a carboxyl end group concentration ranging from 2-10 equivalents per 10 6 grams, prepared by melt extrusion of a reaction mixture consisting of A. a polyester resin having a free carboxyl group concentration ranging from 0 to 30 equivalents per 10 6 grams and an intrinsic viscosity of at least 0.75 as measured in a 60/40 phenol/tetrachloroethane mixed solvent at 30° C. and B. at least one carbodiimide selected from the group consisting of mono- and bis-carbodiimides corresponding to the formulae R--N=C=N--R' and R--N=C=N--R"--N=C=N--R' where R, R' and R" are substituted and unsubstituted radicals selected from the group consisting of C 4 -C 20 alkyl radicals, cycloalkyl radicals and aryl radicals, said substitution being selected from the group consisting of halogen atoms, nitro groups, amino groups, sulfonyl groups, hydroxyl groups and alkyl and alkoxy radicals, wherein said carbodiimide, (B), is present in said reaction mixture in an amount equivalent to the free carboxyl group concentration of the polyester resin, (A), before the melt extrusion thereof plus an amount equivalent to the free carboxyl group concentration generated by the polyester resin, (A), during the melt extrusion thereof in the absence of the carbodiimide, (B).