A tackifier comprising a resin with repeating units of formula (I) wherein R1 is a linear or branched alkylen group with 1 to 10 carbon atoms and R2 is a linear or branched, saturated or unsaturated aliphatic hydrocarbon group with up to 20 carbon atoms and a non-aromatic compound which consists to at least 50% by weight of one or more linear or branched, saturated or unsaturated aliphatic hydrocarbon groups with at least 4 carbon atoms.