A 1-butene polymer optionally containing from 0 to 30% by mol of derived units of ethylene, propylene or alpha-olefin of formula CH2═CHZ, wherein Z is a C3-C20 linear or branched alkyl radical, having the following features: a) distribution of molecular weight (Mw/Mn) lower than 4; b) Melt flow rate (MFR) measured according to ISO 1133 (190° C., 2.16 kg); c) Intrinsic viscosity (IV) measured in tetrahydronaftalene (THN) at 135° C. lower than 0.8 dl/g; d) melting point higher than 100° C.; e) isotactic pentads (mmmm) measured with 13C-NMR operating at 100.61 MHz higher than 90%; f) 4,1 insertions not detectable at a C13-NMR operating at 100.61 MHz; and g) a yellowness index lower than 0.