SUPPORTED TRANSITION METAL COMPOSITION

A supported transition metal composition is obtained by suspending a support material in an inert liquid medium, spraying the suspension, collecting a solid material and contacting the sprayed solid with a transition metal compound. The support material may be a metal halide such as magnesium chloride or an inorganic oxide such as silica or alumina. In addition to being contacted with the transition metal compound, the support material may be contacted either before or after the spraying step with other reagents such as oregano metallic compounds, halogen compounds, or Lewis Base compounds. The product obtained after contacting with the transition metal compound may be used as a component of a polymerisation catalyst system to polymerise an unsaturated monomer such as ethylene or propylene.