GB1077975A - Process for preparing block polymers from alpha-olefins - Google Patents

Abstract

A vapour phase block copolymerization process comprises the steps of (a) introducing to a continuously agitated reaction zone a preformed alpha-olefin polymer powder prepared from an alpha-olefin containing at least 3 carbon atoms, and containing active catalyst residues and less than 5% by weight volatile constituents; (b) introducing in vapour form one or more alpha-olefin monomers, at least one of which differs from that which said polymer powder was prepared, into intimate contact with said preformed polymer in said reaction zone; (c) continuously moving said preformed polymer from the inlet of said reaction zone to the outlet thereof while in contact with said monomer vapour, and polymerizing said monomer on to said preformed polymer; and (d) recovering from the outlet of said reacton zone a block copolymer containing up to 40% by weight of the total copolymer of copolymerized alpha-olefin monomer. In a modification, the block polymerization is carried out in a series of two or more reactors. Suitable monomers include ethylene, propylene, butene-1, pentene-1, hexene-1, isobutene, 3-methylbutene-1 and 4-methylpentene-1; these (except ethylene) are also suitable for forming the preformed polymer, which may be obtained in powder form by polymerization in a hydrocarbon diluent and removing the solvent from the polymer slurry obtained. The catalyst may be a mixture of a Group IVa, Va or VIa (Mendeleef) metal subhalide and an alkyl aluminium, preferably titanium tri-chloride, optionally cocrystallized with aluminium chloride, in admixture with, for example, triethyl aluminium or diethyl/aluminium monochloride. A chain regulator, e.g. hydrogen, may be employed in the block polymerization. Particular forms of apparatus are described for carrying out the process in a semi-continuous batch or continuous manner.