PREPARATION OF OLEFINIC POLYMER

PURPOSE:To profitably provide the subject polymer such as PE or PP in a greatly high catalytic activity state by polymerizing an olefin in the presence of a catalyst comprising a specific aluminoxane and a group IV transition metal compound as main components. CONSTITUTION:An olefin is polymerized in the presence of a catalyst to provide the objective polymer, the catalyst comprising (A) an aluminoxane prepared by the reaction of normal alkyl aluminum [preferably a compound of formula I (R and R are 1-20C normal alkyl; R is 1-20C normal alkyl, halogen or H)], a branched alkyl aluminum [preferably a compound of formula II (R and R are 3-20C branched alkyl; R is 3-20C branched alkyl, halogen or H)] and water and (B) a group IV transition metal compound {preferably a compound of formula III [R is (substituted) cyclopentadienyl; R is R , 1-20C alkyl, H, etc.; R and R are 1-20C alkoxy, 1-20C alkyl, H, etc.; M is Ti, Zr or Hf]} as main components.