GB963982A - Process for the production of homogeneous copolymers - Google Patents

Abstract

A process for the copolymerization of two or more alpha-olefins, at least one of which polymerizes at a different rate from another of the olefins, comprises initiating the copolymerization with a first feed containing a ratio of monomers selected to produce a copolymer of desired composition and continuing the copolymerization while maintaining the monomer ratio constant by introducing a second feed containing the monomers in a ratio corresponding to the relative rates of consumption or reaction of said monomers and at a rate sufficient to maintain a constant concentration of monomers in the reaction zone. Specified monomers are ethylene, propylene, butene, pentene, heptene, octene, dodecene, tetradecene, hexadecene, methylbutene, methylpentene, methylhexene, butadiene, isoprene, piperylene, and cyclopentadiene and minor amounts of tetrafluoroethylene and fluoro-chloro-ethylene as comonomers. The catalysts suitable for the copolymerization are preformed transition metals as elements or oxides on high surface area supports (e.g. nickel on charcoal or chromia on silica-alumina), promoted transition oxide catalyst (e.g. chromia-alumina and aluminium trialkyl), solid catalysts precipitated in situ from transition metal salts and organo metallics (e.g. titanium tetrachloride + aluminium trialkyl), and pretreated precipitated catalysts in combination with organometallic compounds (e.g. titanium trichloride + aluminium trialkyl). Many catalysts are listed and in the examples there is used sodium promoted molybdena/alumina in a mineral spirits medium. The polymerization may be continuous or semi-batch, and the second feed may be in correct proportion in response to a monitored reaction zone composition analysis. The examples illustrate initial and second feeds for ethylene/propylene and ethylene/butene copolymerizations. The products have macroscopic and microscopic homogeneity.