Abstract: A process is disclosed for preparing shaped or preformed polyester material for coloring with acid type dyes, which comprises impregnating the shaped or preformed polyester material, preferably but not necessarily continuously, at a temperature between 90.degree. C. and 250.degree. C. at ordinary atmospheric pressure with a mixture of (a) an organic nitrogen compound and (b) a glycol, an alcohol, a ketone, an ether, or water; then cooling the treated material with cold water or a mixture of a carboxylic acid with cold water whereby to impart affinity for acid dyes to the treated polyester material. Coloring the treated polyester material is then effected such as by padding, printing or cascading the treated polyester material with an acid dye from an aqueous solution or a printing paste whereby to effect fixation of said acid dye on the treated polyester material with substantially uniform distribution thereof within the polyester material.

Abstract: A process is disclosed for coloring a polyester material, which comprises impregnating the same by padding, printing or cascading with an aqueous solution or printing paste of one or more acid dyes incorporated with both (a) an organic nitrogen compound and (b) an organic carboxylic acid, drying the impregnated polyester material and then exposing same to dry heat at a temperature between 150.degree.C. and 230.degree.C. for a period of 5 to 60 seconds, thereby effecting fixation of said acid dye or dyes on the polyester material and uniform distribution thereof within the polyester material. The organic nitrogen compound with which the polyester material is treated is an alkyleneamine, an alkanolamine, or an alkylamine.