Process for preparing propylene polymer composition and propylene polymer composition

A process for preparing a propylene polymer composition comprises:

• conducting multistage polymerization including the following steps (a), (b), (d) and (e) in the presence of
• (A) a transition metal compound containing a ligand having a cyclopentadienyl skeleton represented by the following formula (III) ##STR5## wherein M.sup.2 is a transition metal atom of group IVB to group VIB of the periodic table;
• R.sup.5, R.sup.6 and R.sup.8 to R.sup.10, which may be the same or different, are each a hydrogen, a halogen, a hydrocarbon group of 1 to 20 carbon atoms, a halogenated hydrocarbon group of 1 to 20 carbon atoms, a silicon-containing group, an oxygen-containing group, a sulfur-containing group, a nitrogen-containing group or a phosphorus-containing group;
• R.sup.7 is an aryl group of 6 to 16 carbon atoms;
• y.sup.2 is a divalent hydrocarbon group of 1 to 20 carbon atoms, a divalent halogenated hydrocarbon group of 1 to 20 carbon atoms, a divalent silicon-containing group or a divalent germanium-containing group;
• and
• X.sup.3 and X.sup.4 are each a hydrogen, a halogen, a hydrocarbon group of 1 to 20 carbon atoms, a halogenated hydrocarbon group of 1 to 20 carbon atoms, an oxygen-containing group or a sulfur-containing group, and
• (B) a compound activating the transition metal compound (A),
• in which the steps (a), (b), (d) and (e) are carried out in any order, and each of the second and subsequent stage polymerizations is carried out in the presence of a polymer or polymers obtained in the preceding stage or stages, respectively, to produce a propylene polymer composition comprising 20 to 85% by weight of a propylene (co)polymer (a) obtained in the step (a), 5 to 75% by weight of a propylene/olefin copolymer (b) obtained in the step (b), 5 to 75% by weight of an ethylene/olefin copolymer (d) obtained in the step (d) and 5 to 30% by weight of an ethylene/olefin copolymer (e) obtained in the step (e), said composition having a melt flow rate, as measured at 230.degree. C. under a load of 2.16 kg, of 0.01 to 500 g/10 min;
• the step (a):
• (i) homopolymerizing propylene or (ii) copolymerizing propylene and at least one olefin selected from ethylene and olefins of 4 to 20 carbon atoms to prepare a propylene (co)polymer (a) comprising not less than 80 mol % of constituent units derived from propylene, said propylene (co)polymer (a) having a melting point, as measured by a differential scanning calorimeter, of not lower than 100.degree. C. and a melt flow rate, as measured at 230.degree. C. under a load of 2.16 kg, of 0.01 to 1,000 g/10 min;
• the step (b):
• copolymerizing propylene and at least one olefin selected from ethylene and olefins of 4 to 20 carbon atoms to prepare a propylene/olefin copolymer (b) comprising more than 50 mol % of constituent units derived from propylene, said propylene/olefin copolymer (b) having an intrinsic viscosity (.eta.), as measured in decahydronaphthalene at 135.degree. C., of 0.1 to 20 dl/g;
• the step (d):
• copolymerizing ethylene and at least one olefin selected from olefins of 3 to 20 carbon atoms to prepare an ethylene/olefin copolymer (d) comprising more than 50 mol % and less than 90 mol % of constituent units derived from ethylene, said ethylene/olefin copolymer (d) having an intrinsic viscosity (.eta.), as measured in decahydronaphthalene at 135.degree. C., of 0.1 to 20 dl/g;
• and
• the step (e):
• copolymerizing ethylene and at least one olefin selected from olefins of 3 to 20 carbon atoms to prepare an ethylene/olefin copolymer (e) comprising not less than 90 mol % of constituent units derived from ethylene, said ethylene/olefin copolymer (e) having an intrinsic viscosity (.eta.), as measured in decahydronaphthalene at 135.degree. C., of 0.1 to 20 dl/g.