The invention relates to hydrophilic additives for synthetic fibres containing polyolefin; said additives are represented by general formula (I): A--B--C--B--A wherein A is a radical R--COO, wherein R represents a saturated, cross-linked or non-cross-linked alkyl radical having 7 21 C atoms, B represents a group (C.sub.nH.sub.2nO).sub.k, wherein n is a whole number from 2 4 and k can have a value of 1 15, C represents a linear or cross-linked alkylene radical having at least 2 and at the most 6 C atoms and the radical C can be, optionally, interrupted by oxygen atoms.