Ethylene polymer, catalyst for producing thereof and method for producing thereof

摘要

A method for producing an ethylene polymer which comprises continuously polymerizing ethylene alone or copolymerizing ethylene and a C₃-C₈ alpha-olefin by multistage polymerization in a plurality of polymerization reactors connected in series in the presence of a chromium catalyst having at least a part of chromium atoms converted to hexavalent chromium carried on an inorganic oxide carrier by calcination-activating in a non-reducing atmosphere, wherein an organoaluminum compound of the formula (1): (R¹)xAl(OR²)y(OSiR³R⁴R⁵)z (1) (in the above formula, R¹ and R² may be the same or different, each represents a C₁-C₁₈ alkyl group or a C₆-C₁₈ aryl group, R³, R⁴ and R⁵ may be the same or different, each represents a C₁-C₁₈ alkyl group or a C₆-C₁₈ aryl group, R¹, OR² and OSiR³R⁴R⁵ respectively may be the same or different when each has a plurality of kinds, and x, y and z are respectively 0<=x<=3, 0<=y<3, 0<=z<3, and x+y+z=3) is introduced at least one or all of the polymerization reactors.