FILMS HAVING IMPROVED SEALING PROPERTIES

摘要

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 film having at least two layers for use as a sealant component in a multi-layer film or as a sealant film in packaging comprising a surface sealing layer and a hot tack strength boosting layer, the surface sealing layer being a single-site catalyst (SSC) interpolymer of ethylene and one or more C3 - C20 alpha -olefins having a density in the range of about 0.87 to about 0.930 gm/cc and a melt index of from about 0.2 to about 10 dg/minute; and the hot tack strength boosting layer which substantially increases the hot tack strength of the surface sealing layer being selected from single-site catalyst and non-single-site catalyst copolymers, homopolymers and terpolymers of ethylene and blends thereof having a density of from at least about 0.945 to about 0.960 gm/cc and a melt index of from about 0.2 to about 20 dg/minute; wherein the density difference between the SSC layer and the boosting layer ranges from at least about 0.03 gm/cc to about 0.075 gm/cc.