Polyolefin films

A self-supporting multiple-layer film comprising:

• a substrate layer of a polymer of a mono-alpha-olefin containing from 2 to 8 carbon atoms in its molecule, a modulus improver incorporated in the substrate layer,
• wherein said modulus improver is a resin, of natural or synthetic origin, which is (I) amorphous, hard, brittle, and solid at ambient temperature, (II) has a softening range at elevated temperature, (III) has a drop softening point of at least 70.degree. C., and (IV) is sufficiently compatible with the film-forming olefin polymer to yield a composition from which may be formed a drawn, self-supporting transparent film exhibiting a modulus exceeding that of a film formed from an identical olefin polymer in the absence of the improver resin,
• a polymeric heat-sealable layer adhered to at least one surface of the substrate layer, and, on the surface of the heat-sealable layer remote from the substrate, an antistatic medium comprising a quaternary ammonium of general formula ##STR4## wherein each of R.sup.1, R.sup.2, and R.sup.3, which may be the same or different, is a hydrogen atom or a lower alkyl radical containing from 1 to 6 carbon atoms, or R.sup.1 and R.sup.2 are each methylene groupings within a common five- or six-membered saturated heterocyclic ring, R.sup.4 is a hydrogen atom or an acyl radical containing up to 15 carbon atoms, Z is a methylene group or a carbonyl group when R.sup.4 is a hydrogen atom, or Z is a methylene group when R.sup.4 is said acyl radical, and X is a univalent anion or an equivalent of a multivalent anion.