Polyethylene composition

A polyethylene composition characterized in that:

• (1) said composition is produced by a multistage polymerization process in which in the presence of a Ziegler-type catalyst formed from (A) a highly active titanium catalyst component comprising magnesium, titanium and halogen as essential components and (B) an organoaluminum compound catalyst component, ethylene or ethylene and a small amount of an alpha-olefin are polymerized in at least one polymerization step to form ultrahigh-molecular-weight polyethylene having an intrinsic viscosity of at least 12 dl/g, and ethylene or ethylene and a small amount of an alpha-olefin are polymerized in the presence of hydrogen in another.polymerization step to form low-molecular-weight to high-molecular-weight polyethylene having an intrinsic viscosity of 0.1 to 5 dl/g,
• (2) said ultrahigh-molecular-weight polyethylene has an intrinsic viscosity, measured in decalin at 135.degree. C., of at least 12 dl/g, and said low-molecular-weight to high-molecular-weight polyethylene has an intrinsic viscosity, measured in decalin at 135.degree. C., of 0.1 to 5 dl/g,
• (3) the proportion of said ultrahigh-molecular-weight polyethylene is in the range of 20 to 95% by weight based on the total weight of said ultrahigh-molecular-weight polyethylene and said low-molecular-weight to high-molecular-weight polyethylene, and
• (4) said polyethylene composition consists substantially of said ultrahigh-molecular-weight polyethylene and said low-molecular-weight to high-molecular-weight polyethylene and has an intrinsic viscosity [.eta.]c, measured in decalin at 135.degree. C., of 10 to 50 dl/g.