Patent ID: 6376032
Filing Date: 2002-04-23
Classification: B32B,B65D,C08J,Y10T

Abstract:
A gas-permeable membrane which is useful in the packaging of respiring biological materials and which comprises(a) a microporous polymeric film comprising a network of interconnected pores such that gases can pass through the film, and (b) a crystalline polymeric coating on the microporous film, wherein (1) the pores in the microporous film have an average pore size of less than 0.24 micron; (2) at least 70% of the pores in the microporous film have a pore size of less than 0.24 micron; and (3) the polymeric coating (a) comprises a crystalline polymer having a peak melting temperature Tp of âˆ’5 to 40Â° C., an onset of melting temperature To such that (Tpâˆ’To) is less than 10Â° C., and a heat of fusion of at least 5 J/g; and (b) has a thickness such that the membrane (i) has a P10 ratio, over at least one 10Â° C. range which includes Tp, of at least 1.3; (ii) has an oxygen permeability (OTR), at all temperatures between 20 and 25Â° C., of at least 775,000 ml/m2.atm.24 hrs (50,000 cc/100 inch2.atm.24 hrs); and (iii) has a CO2/O2 permeability ratio(R) at 20Â° C. of at least 1.5; the P10, OTR and R values being measured at a pressure of 0.035 kg/cm2 (0.5 psi).