Examples of such diols are: aliphatic diols such as ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol and decamethylene glycol; alicyclic diols such as 1,1-cyclohexane dimethanol, 1,4-cyclohexane dimethanol and tricyclodecane dimethanol; and diols containing aromatic group(s) such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)prop