GB873020A - Process for carrying out low pressure polymerization - Google Patents

Abstract

A method of polymerizing a -olefins with a catalyst system comprising a halide of a metal of Group IV(A), V(A), VI(A) or VIII of the Mendeleef Periodic System reduced from a higher to a lower valency state and a metal-containing compound capable of reducing said halide, in a hydrocarbon diluent in a reactor at 0 DEG -100 DEG C., comprises circulating the reaction mixture containing catalyst, diluent and monomer at a velocity of 5-25 feet per second through a confined mixing zone in the reactor, passing the reaction mixture through a plurality of further tubes in an annular portion of the reactor about the mixing zone, the tubes being externally cooled, discharging the reaction mixture into an annular zone beyond said tubes, said annular zone having a volume larger than that of said mixing zone, recirculating at least a portion of the reaction mixture through the mixing zone and withdrawing a product mixture comprising polymer, diluent and unreacted monomer from the reactor. The monomer may be ethylene, propylene, butene-1, heptene-1, dodecene-1, butadiene, isoprene, piperylene, vinylcyclohexene, cyclopentadiene or 1, 4-pentadiene. The diluent may be isopentane, n-heptane or xylene. Catalyst residues may be deactivated and removed by washing the product with alcohols, e.g. methyl alcohol, isopropyl alcohol or n-butyl alcohol, preferably together with a chelating agent, e.g. acetylacetone, followed by washing with water, alcohol or hydrochloric acid. In an example the polymerization of propylene in xylene in the presence of a catalyst comprising titanium trichloride and aluminium triethyl is described, and a reactor for carrying out the process is described and illustrated. Belgian Specification 538,782 is referred to.