High speed process for producing polyester filaments

A high speed process for producing polyester filaments comprising melt spinning polyester filaments at a taking-up speed of at least 3,000 m/minute, while an aqueous emulsion of an oiling agent is applied to the polyester filaments, wherein the oiling agent comprises:

• (A) at least 50% by weight of a principal component consisting of at least one member selected from monobasic acid esters of aliphatic monocarboxylic acids with 10 to 18 carbon atoms with aliphatic monohydric alcohols with 4 to 18 carbon atoms and having an average molecular weight of 300 to 500;
• and
• (B) an additional component comprising:
• (a) 1 to 10% by weight of at least one copolymer of oxytetramethylene units and oxyethylene units and having an average molecular weight of 1,000 to 7,000 and
• (b) 0.1 to 3% by weight of at least one member selected form the group consisting of organic siloxane compounds and fluoroalkyl group-containing compounds in which the fluoroalkyl group has 3 to 18 carbon atoms.