GB1376693A - Polymerization of olefins - Google Patents

Abstract

1376693 Olefin polymerization NAPHTACHIMIE 1 Dec 1972 [2 Dec 1971] 55652/72 Heading C3P A solid polymer having a molecular weight of over 50,000 is obtained from one or more C 2 -C 10 α-olefins by a gas phase reaction in a fluidized bed of a prepolymer containing 500- 10,000 p.p.m. of a transition metal of Group IVA, VA or VIA, the prepolymer being formed by polymerization of propylene, optionally mixed with a lesser amount of ethylene or 1- butene, in a liquid medium in the presence of a slightly stereospecific catalyst (i.e. one forming a polymer containing 10-40% of amorphous material) formed from a compound of the transition metal and an organometallic compound of a metal of Group II or III. The amorphous component of the prepolymer is removed, by discarding the prepolymerization medium and preferably extracting the residue with additional solvent, before the main polymerization. The prepolymer is then activated by addition of fresh organometallic compound. In the examples ethylene is polymerized in the presence of a prepolymer of propylene, copolymerized in some cases with a small proportion of 1-butene or ethylene. The prepolymer is activated with (i-butyl) 3 Al or (n-octyl) 3 Al and is prepared in the presence of Et 2 AlCl and TiCl 3 or TiCl 2À75 (O-n-C 3 H 7 ) (prepared from the corresponding tetravalent compounds by reduction with Et 3 AlCl, and not modified by any subsequent heat treatment).