Abstract: A film-forming composition comprising a copolymer of propylene with an alpha-olefin containing from 4 to 10 carbon atoms, the copolymer containing from 80 to 95% by weight of propylene, and from 25 to 90% by weight of the composition of a second homo- or co-polymer of a similarly defined alpha-olefin. The composition is particularly suitable for the production of heat-sealable, multiple-layer films having a polypropylene core.

Abstract: A multiple-layer film having a substrate layer of high density polyethylene or a propylene homo- or co-polymer, and, on at least one surface of the substrate, a heat-sealable layer of a propylene co-polymer containing from 80 to 95% of propylene, the balance being a C.sub.4 to C.sub.10 olefin. The substrate and surface layers exhibit a monoclinic crystalline structure.

Abstract: An olefine polymerisation catalyst comprises a titanium trichloride component of high surface area, an organo-metallic component, a Lewis Base component and optionally a polyene. The TiCl.sub.3 component which may have a high porosity is conveniently obtained by the reaction of TiCl.sub.4 and an organo-aluminium compound, treating the reaction product with a complexing agent and then contacting this product with TiCl.sub.4. The organo-metallic component is preferably aluminium triethyl, the Lewis Base component hexamethylphosphoric triamide and the polyene is cycloheptatriene. This system has high polymerisation activity combined with good stereospecificity. Polypropylene can be obtained in high yield thereby giving low catalyst residues and the polymer has a high stiffness modulus.