Patent ID: 8334327

Claim:
A breathable film having a base layer comprising first filler particles and second filler particles dispersed within a biodegradable polymer matrix that includes an aliphatic-aromatic copolyester, the first filler particles constituting from about 25 wt. % to about 75 wt. % of the base layer and the second filler particles constituting from about 0.1 wt. % to about 10 wt. % of the base layer, wherein the ratio of the average size of the first filler particles to the average size of the second filler particles is from about 2 to about 100, and wherein the film exhibits a water vapor transmission rate of about 2,000 g/m 2 /24 hours or more and a peak load in the machine direction of about 800 grams-force per inch or more, further wherein the base layer has a pore structure that includes first pores and second pores, the second pores being smaller than the first pores, wherein the first pores have an average length of from about 5 to about 100 micrometers and the second pores have an average length of from about 0.5 to about 5 micrometers.