Ammonia modified bis(cyclopentadienyl) chromium (II) catalyst - for polymerisation of ethylene with improved toughness and impact strength

摘要

Ethylene polymers, of improved toughness and impact strength, are prepd. by contacting the monomer with an inorg. oxide - supported bis(cyclopentadienyl) chromium (II) which is treated with ammonia prior to or during contact with monomer. 0.01 - 12 mol. NH3 are used per 1 mol. organo-Cr cpd. of formula:- (where n and n' are each 1-5; and R and R' are each 1-20 C hydrocarbon). The inorg. oxide has high surface area and is selected from silica, alumina, thoria and/or zirconia. Opt., = one other 3-12 C-olefin may be copolymerised with the ethylene.