Basf Aktiengesellschaft

Wolfgang Rau

Wolfgang Lenart

Hubertus Baron

Peter Hennenberger

Karl Wisseroth

Hans-Georg Trieschmann

Karl-Heinz Ambil

Helmut Klamann

The disclosure is directed to an improvement in the gas phase polymerization of propylene using a Ziegler-Natta catalyst in the presence of hydrogen wherein the gaseous propylene is withdrawn from the reactor, cooled and condensed and returned as a liquid to the reactor in order to regulate the polymerization temperature. The amount of the gaseous phase in the condenser-cooler-accumulator system is kept constant by regulating the amount of gaseous phase returned to the reactor.

Preparation of propylene homopolymers or copolymers

In a self-supporting stirrer for mixing a bed of free-flowing solids, the lower end of the stirring device, facing the bottom of the stirred vessel, passes into a hub. The hub is located on a vertical drive shaft which extends through the bottom of the stirred vessel and consists of shaft sections detachably joined to one another. The drive shaft itself is carried in a cage attached to the bottom of the stirred vessel and can be adjusted vertically by means of a lifting device. This opens or closes an annular gap between a centering cone, provided at the bottom of the stirred vessel, and a conically recessed ring, inserted in the hub. In this way, the need to empty the vessel, for example when carrying out maintenance or repair work, is avoided.

Self-supporting stirrer for mixing a bed of free-flowing solids

A spiral stirrer unsupported at one end, for mixing and stirring free-flowing solids, especially in continuous gas phase polymerization. The stirrer comprises a plurality of turns formed from hollow profiles. The botton end of the spiral, facing the bottom of the stirred vessel, is attached to a hub seated on a drive shaft. In the vicinity of the transition from the hub to the first turn of the spiral, a distributor spiral is provided to avoid flowless zones in the hub region. Uniform distribution of the gas entering at the bottom of the vessel is also achieved.

Spiral stirrer unsupported at one end

An improved method of removing heat from polymerization reactions of normally gaseous monomers in the gas phase comprising feeding the monomer in liquid form to a polymerization zone, immediately after entering said zone, removing a portion of said gaseous monomer from the polymerization zone, liquefying said portion of monomer by cooling it at the same pressure as that prevailing in the polymerization zone, recycling the liquefied monomer to the polymerization zone together with fresh monomer in liquid form and causing said liquid monomer to change to the gaseous form immediately after entering said zone. The improvement consists in not only condensing the monomer outside the polymerization zone but also storing the same, in keeping the temperature in the polymerization zone constant by regulating the rate at which liquid monomer is fed to the zone, and in keeping the temperature and pressure in the polymerization zone within limits conducive to the gaseous state of the monomer.

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Heidelberg, Germany

Wolfgang Rau