Method for the preparation of ethylene polymer compositions

Claim 1

A method for the preparation of an ethylene polymer composition, having a density of 0.86-0.94 g/cm³ and an intrinsic viscosity [η] of 1-6 dl/g, using an olefin polymerization catalyst [I] comprising a transition metal compound [A], which contains a ligand having a cycloalkadienyl skeleton, and an organoaluminum oxy-compound [B], wherein the method comprises carrying out a multi-stage process comprising a polymerization step (a): wherein ethylene is homopolymerized or ethylene and another α-olefin are copolymerized to form an ethylene polymer [I] having a density greater than 0.88 g/cm³ and an intrinsic viscosity [η] of 0.3-3 dl/g, and a polymerization step (b): wherein ethylene and another α-olefin are copolymerized to form an ethylene copolymer [II] having a density no higher than that of the ethylene polymer [I] and having an intrinsic viscosity of at least 1.5 times that of the ethylene polymer [I] and from 1 to 10 dl/g, wherein the polymerization steps (a) and (b) are carried out such that step (a) is carried out first and step (b) is carried out in the presence of the ethylene polymer [I] or step (b) is carried out first and step (a) is carried out in the presence of the ethylene copolymer [II] so that the ethylene copolymer [II] amounts to 10-1000 parts by weight based on 100 parts by weight of the ethylene polymer [I].

Claim 3

A method for the preparation of an ethylene polymer composition having a density of 0.87-0.93 g/cm³ and an intrinsic viscosity [η] of 0.5-6 dl/g, which comprises carrying out a multi-stage process comprising a polymerization step (c): wherein ethylene and another α-olefin are copolymerized using an olefin polymerization catalyst [II], which comprises a transition metal compound [A] containing a ligand having a cycloalkadienyl skeleton and an organoaluminum oxy-compound [B], to form an ethylene copolymer [III] having a density of lower than 0.91 g/cm³ and an intrinsic viscosity [η] of 0.5-6 dl/g, and a polymerization step (d): wherein ethylene is homopolymerized or ethylene and another α-olefin are copolymerized using an olefin polymerization catalyst [III], which comprises a titanium catalyst component [C] containing titanium, magnesium and halogen as its essential ingredients, an organoaluminum compound [D] and/or an organoaluminum oxy-compound [E] to form an ethylene copolymer [IV] having a density greater than that of the ethylene copolymer [III] and an intrinsic viscosity [η] of 0.5-6 dl/g, wherein the polymerization steps (c) and (d) are carried out such that step (c) is carried out first and step (d) is carried out in the presence of the ethylene copolymer [III] or step (d) is carried out first and step (c) is carried out in the presence of the ethylene polymer [IV] so that the ethylene polymer [IV] amounts to 10-1000 parts by weight based on 100 parts by weight of the ethylene copolymer [III].

Claim 6

A method according to any one of the preceding claims wherein the transition metal of the transition metal compound [A] is zirconium, titanium, hafnium, chromium or vanadium.