This invention relates to a process for the production of a polymer film or fibre wherein a polymer composition comprising a propylene homo- or copolymer is formed into a film or fibre, and wherein said propylene homo or copolymer is produced in a process which comprises the polymerization of propylene monomers or propylene monomers and one or more types of comonomers in the presence of a high yield Ziegler-Natta olefin polymerization catalyst, which catalyst comprises a component in the form of particles having a predetermined size range which has been produced in a process comprising: a) preparing a solution of a complex of a Group 2 metal and an electron donor by reacting a compound of said material with said electron donor or a precursor thereof in an organic liquid reaction medium, b) reacting said complex in solution with a compound of a transition metal to procedure an emulsion the dispersed phase of which containing more than 50 mol % of the Group 2 metal in said complex, c) maintaining the particles of said dispersed phase within the average size range of 5 to 200 microns by agitation in the presence of an emulsion stabilizer and d) solidifying said particles, and recovering, optionally washing said particles to obtain said catalyst component. The invention further relates to polpropylene products obtainable by this process and to the use of polypropylene products in the production of films and fibres.