Importance

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Abstract

This invention provides a film structure and a method of making it, as well as packages formed therefrom, wherein the sealing properties of a single-site catalyst, SSC or metallocene polymer surface sealing layer are substantially increased as compared with a monolayer film of such a polymer. This invention provides in one embodiment a sealant film having at least two layers comprising a surface sealing layer and an adjacent hot tack strength boosting layer, the surface sealing layer being selected from single-site catalyst (SSC) interpolymers of ethylene and one or more C.sub.4-C.sub.8 .alpha.-olefins having a density in the range of about 0.87 to about 0.915 gm/cc and a melt index of from about 0.2 to about 10 dg/minute, and a CDBI of greater than 30%; and the adjacent hot tack strength boosting layer increases the hot tack strength of the sealing layer by an amount of at least 1.5 times the unboosted hot tack strength value of the sealing layer over a broad sealing temperature range, and the sealing layer is selected from single-site and non-single-site catalyst copolymers, homopolymers and terpolymers of ethylene and blends thereof; wherein the density difference for the sealing layer to the adjacent hot tack strength boosting layer is at least about 0.015 gm/cc.

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First Claim