Polyolefin film exhibiting heat resistivity, low hexane extractives and controlled modulus

A film comprising a polymer mixture, wherein the polymer mixture comprises

• (A) from 15 to 60 weight percent, based on the total weight of the mixture, of at least one first ethylene/cc-olefin polymer which is a substantially linear ethylene polymer having a density in the range of 0.850 to 0.920 g/cc, wherein the substantially linear ethylene polymer is further characterized as having
• i. a melt flow ratio, I.sub.10 /I.sub.2 .gtoreq.5.63,
• ii. a molecular weight distribution, M.sub.w /M.sub.n, as determined by gel permeation chromatography and defined by the equation:
• (M.sub.w /M.sub.n).ltoreq.(I.sub.10 /I.sub.2)-4.63,
• iii. a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene/.alpha.-olefin polymer, wherein the substantially linear ethylene polymer and the linear ethylene/.alpha.-olefin polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an I.sub.2, M.sub.w /M.sub.n and density within ten percent of the substantially linear ethylene polymer and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene/.alpha.-olefin polymer are measured at 190.degree. C. and nitrogen pressures between 250 to 5500 psig using a gas extrusion rheometer equipped with a 20:1 L/D die having a 0.0754 mm diameter and an 180.degree. entrance angle,
• iv. a single differential scanning calorimetry, DSC, melting peak between -30.degree. and 150.degree. C.;
• v. a short chain branching distribution index equal to or greater than 50 percent;
• and
• vi. 0.01 to 3 long chain branches/1000 carbons, and
• (B) from 40 to 85 weight percent, based on the total weight of the mixture, of at least one second ethylene polymer which is a homogeneously branched ethylene/.alpha.-olefin polymer or heterogeneously branched linear ethylene/.alpha.-olefin polymer having a density between 0.890 and 0.942 g/cc;
• wherein the polymer mixture is characterized as having a density of from 0.890 to 0.930 g/cc, a differential between the densities of the first ethylene/.alpha.-olefin polymer and the second ethylene polymer of at least 0.015 g/cc,with the proviso that where the density of the first ethylene polymer is less than 0.870 g/cc, the density of the second ethylene polymer is greater than 0.920 g/cc, a compositional hexane extractive level of less than 10 percent or less than 30 percent lower than the expected extractive amount for the mixture based on the total weight of the mixture and a Vicat softening point of at least 75.degree. C.;
• and wherein
• (a) a 0.038 mm thick coextruded sealant layer fabricated from the polymer mixture has a heat seal initiation temperature equal to or less than 100.degree. C. and an ultimate hot tack strength of at least 2.56 N/cm, and
• (b) the Vicat softening point of the polymer mixture is more than 6.degree. C. higher than the heat seal initiation temperature of the coextruded sealant layer;
• wherein the I.sub.2 melt index is measured in accordance with ASTM D-1238, Condition 190.degree. C./2.16 kilogram, the I.sub.10 melt index is measured in accordance with ASTM D-1238, Condition 190.degree. C./10 kilogram, density is measured in accordance with ASTM D-792 and hexane extractive is determined according the Food and Drug Administration test method set forth under 21 C.F.R. .sctn. 177.1520 (d)(3)(ii).