Multilayer polymeric films

A process for the manufacture of an opaque, tear-resistant film having a tear toughness in at least one dimension of the film of at least 0.3 kg/mm2 measured as the area beneath the curve in a graphical plot of stress versus strain in accordance with ASTM D1004-94A, said process comprising the steps of providing a plurality of layers of polymeric material, wherein said plurality of layers comprises at least two layers of filled polymeric material containing therein at least 5% by weight of opacifying agent and at least two layers of unfilled polyester material substantially devoid of opacifying agent, and forming a composite film of said plurality of layers wherein the filled and unfilled layers alternate.

A method of using a multilayer film structure comprising at least two unfilled layers of polymeric material substantially devoid of opacifying agent and at least two filled layers of polymeric material wherein said filled layers comprise at least 5% by weight of opacifying agent for providing improved tear-resistance in an opaque polymeric film such that said film has a tear toughness in at least one dimension of the film of at least 0.3 kg/mm2 measured as the area beneath the curve in a graphical plot of stress versus strain in accordance with ASTM D1004-94A.

A method for improving the tear-resistance of an opaque multilayer polymeric film comprising at least two filled layers of polymeric material wherein said filled layers comprise at least 5% by weight of opacifying agent, said method comprising incorporating into the film at least two unfilled layers of polymeric material substantially devoid of opacifying agent, such that said film has a tear toughness in at least one dimension of the film of at least 0.3 kg/mm2 measured as the area beneath the curve in a graphical plot of stress versus strain in accordance with ASTM D1004-94A.

A method of using two or more layers of unfilled polymeric material substantially devoid of opacifying agent to improve the tear-resistance of an opaque multilayer film comprising at least two filled layers of polymeric material wherein said filled layers comprise at least 5% by weight of opacifying agent, such that said film has a tear toughness in at least one dimension of the film of at least 0.3 kg/mm2 measured as the area beneath the curve in a graphical plot of stress versus strain in accordance with ASTM D1004-94A.