Process for sizing textile fibers for use on water jet looms

In a process for weaving textile fibers into fabric on a water jet loom wherein the fibers are sized prior to weaving, the improvement which comprises (a) depositing on the fibers a sizing amount of an inherently water dispersible copolymer of an aliphatic .alpha.-olefin and an ammoniated .alpha., .beta.-ethylenically unsaturated carboxylic acid, (b) drying the resulting textile fibers such that the copolymer forms a tough, adherent water-insensitive coating on the textile fibers, and (c) weaving the resulting sized fibers on a water jet loom.