Abstract: A textile fiber lubricant, namely random copolymers of polyoxyethylene polyoxypropylene glycol monoester produced by the condensation reaction of an aliphatic fatty acid, or acids having from about 8 to about 22 carbons in the chain, with a mixture of ethylene oxide and propylene oxide, in the presence of an alkali catalyst. These fatty esters are water soluble, biodegradable and exhibit superior lubricating properties when applied to synthetic fibers.The esters have the empirical formula: ##STR1## wherein R is an aliphatic chain having from about 7 to about 21 carbon atoms and M is a random mixture of oxyethylene [--CH.sub.2.CH.sub.2.O--] and oxypropylene [--CH.sub.2.CH(CH.sub.3).O--] groups.