Polyester resins formed by recurring units X=[O-(CH2)n-OCO-(CH2)m-CO] and/or Y=[O-(CH2)k-CO], where the half-sum of n+m is equal to or greater than 6 and k is a number equal to or greater than 6, or by copolymers comprising units and/or sequences having the formula xi[O-(CH2)ni-OCO-(CH2)mi-CO]； yj[O-(CH2)kj-CO] where: i,j=1-5； ni=2-22； mi=0-20； kj=1=21； (Formula (1)) and xi and yj vary between 0 and 1 and are molar fractions of the various units such that (Formula (2)), are used for the preparation of products in which a permeability to water vapour of less than 350 gx30 mum/m<；2 >；per day, measured at 38° C. and 90% RH and good biodegradability are required.
