DE1520656

An a -olefine is polymerized by introducing into a reaction zone an a -olefine and at least 5% by weight, preferably 5 to 10% by weight, of an inert diluent, both in liquid form, and a catalyst formed from a reducible halide of a Group IVa, Va or VIa metal (Mendeleeff Table) and a reducing compound of a Group Ia or IIa metal or aluminium, withdrawing from the reaction zone a slurry of a -olefine polymer in liquid olefine and inert diluent, separating the polymer from the unreacted a -olefine and inert diluent and recycling the unreacted a -olefine and inert diluent to the reaction zone. Preferably the inert diluent is a normally gaseous material liquefiable under the conditions existing in the reaction zone. In the Figure, liquid propylene and inert diluent are introduced via line 10 to reactor 11, a chain transfer agent or molecular weight control agent such as hydrogen via line 12, one component of the catalyst, e.g. TiCl3 via line 13 and the other component of the catalyst, e.g. diethyl aluminium monochloride, via line 14 to reactor 11. Alternatively, the catalyst components may be premixed. A slurry of the polymer in liquid propylene and inert diluent is withdrawn from the reactor and passed to cyclone 17 where the propylene and diluent are flashed off and the polymer recovered is then worked up. From cyclone 17 the propylene and inert diluent are flashed off to filter 34 and part then passes to recycle compressor 37, the other part being diverted via line 38, blower 39 and heater 40 to cyclone 17 to aid in the separation of volatiles in cyclone 17. From compressor 37 the recycle stream passes to condenser 41 and accumulator 42 from where a proportion of the recycle stream may be vented through line 431, the rest passing to driers 45, storage tank 47 and drier 51 and then to reactor 11. Fresh propylene may be introduced via line 50. Specification 810,023 is referred to.