Patent ID: 6881695

Claim:
A method for producing a modified methylaluminoxane preparation which comprises hydrolyzing a) an organoaluminum compound represented by the following formula (I): R 1 m AlX 3-m (I) wherein R 1 represents a straight-chained or branched hydrocarbon group selected from the group consisting of alkyl, alkenyl, and aryl groups having 2 to 20 carbon atoms; X represents a hydrogen atom, halogen atom, alkoxy group, or allyloxy group; and 0<m≦3 with b) trimethyl aluminum, by adding said trimethyl aluminum to said organoaluminum compound of formula (I) in the presence of water; and repeating the step of adding said trimethyl aluminum as many times as necessary, whereby in said modified inethylaluminoxane, a mole fraction of methyl group of the modified aluminoxane unit with respect to a total number of moles of the hydrocarbon group having 2 to 20 carbon atoms and methyl group present in the modified methylaluminoxane preparation is 65% or greater.