Breathable microporous film
AssigneeHercules Incorporated
InventorsMitchell K. Antoon, Jr., David J. Hill
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Abstract
A soft, flexible, microporous film is provided having high tensile strength and good air and water vapor transmission rates therethrough while being substantially impenetrable to liquid water. This film is prepared by stretching a casting of a composition of a polyolefin and high levels of CaCO.sub.3 or glass beads and calcium stearate in two directions from 1.5-7 times in each direction to produce a film having a Gurley porosity of from 0.1 to 85 seconds. This film is especially useful for disposable items such as feminine panty liners, diapers, bed sheets, and hospital gowns. When glass beads are substituted for the CaCO.sub.3, the film is useful for battery separators.
Claims7
A breathable film composition comprising:
- 20 to 37% by weight of a polymer or copolymer of an .alpha.-olefin having 2-8 carbons or mixtures thereof,
- 60 to 75% by weight of calcium carbonate or glass beads having particle sizes of 10 to 25 micrometers,
- 0.1 to 3.0% by weight of calcium stearate, and
- optionally, 0 to 2% by weight of a UV light, oxygen, and heat stabilizer,
- wherein the moisture level in the blended composition is maintained below 700 ppm prior to forming a casting and then, based on the polymer or copolymer used, stretching the casting to produce oriented film in 2 directions from about 1.5 to 7 times in each direction in a temperature range of from about 20.degree. to about 160.degree. C. and each oriented film having a Gurley porosity (method B, ASTM D-726) of 0.1 second to 85 seconds so that the film has good air and water vapor transmission rates but is substantially impenetrable by liquid water.
Dependencies are inferred from the claim text.