In this invention, the starting polyester is comprised of repeating units corresponding to the formula where R is a divalent alicyclic radical having 4 to 20 carbon atoms, a divalent aliphatic radical having 1 to 40 carbon atoms or a divalent aromatic radical having 6 to 16 carbon atoms with the carbonyl linkages separated by at least 3 carbon atoms, and R is a divalent aliphatic radical of 2 to 4