A polyethylene composition for producing blow-molded hollow articles, having the following features: 1) density from 0.940 to 0.955 g/cm.sup.3, determined according to ISO 1183 at 23° C.; 2) ratio MIF/MIP from 12 to 40; 3) Mz from 500,000 to 3,500,000 g/mol; 4) η.sub.0.02 from 80,000 to 300,000 Pa.Math.s; 5) HMWcopo index from 1 to 15; and 6) Mz/Mw*LCBI lower than 6.4.

A polyethylene composition for producing blow-molded hollow articles, having the following features: 1) density from 0.940 to 0.955 g/cm.sup.3, determined according to ISO 1183 at 23° C.; 2) ratio MIF/MIP from 12 to 40; 3) Mz from 500,000 to 3,500,000 g/mol; 4) η.sub.0.02 from 80,000 to 300,000 Pa.Math.s; 5) HMWcopo index from 1 to 15; and 6) Mz/Mw*LCBI lower than 6.4.

Metallocene complexes represented by the structure below are useful for alpha olefin oligomerization in the presence of an activator to generate polyalphaolefins having a high percentage of vinylidene termination and relatively low Mn values. ##STR00001##
M is a group 4 transition metal. A is a bridging group having one bridging atom extending between a first indenyl ring and a second indenyl ring. Each X is independently an anionic ligand, or two Xs are joined and bound to M to form a metallocycle ring, or two Xs are joined to form a chelating ligand, a diene ligand, or an alkylidene ligand. R.sup.1, R.sup.1′, R.sup.3, R.sup.3′, R.sup.4, R.sup.4′, R.sup.7 and R.sup.7′ are hydrogen. R.sup.5, R.sup.5′, R.sup.6, and R.sup.6′ are independently a C.sub.1-C.sub.10, optionally substituted, hydrocarbyl group, or R.sup.5 and R.sup.6 and/or R.sup.5′ and R.sup.6′ are bonded together to form an optionally substituted hydrocarbyl ring structure.

Metallocene complexes represented by the structure below are useful for alpha olefin oligomerization in the presence of an activator to generate polyalphaolefins having a high percentage of vinylidene termination and relatively low Mn values. ##STR00001##
M is a group 4 transition metal. A is a bridging group having one bridging atom extending between a first indenyl ring and a second indenyl ring. Each X is independently an anionic ligand, or two Xs are joined and bound to M to form a metallocycle ring, or two Xs are joined to form a chelating ligand, a diene ligand, or an alkylidene ligand. R.sup.1, R.sup.1′, R.sup.3, R.sup.3′, R.sup.4, R.sup.4′, R.sup.7 and R.sup.7′ are hydrogen. R.sup.5, R.sup.5′, R.sup.6, and R.sup.6′ are independently a C.sub.1-C.sub.10, optionally substituted, hydrocarbyl group, or R.sup.5 and R.sup.6 and/or R.sup.5′ and R.sup.6′ are bonded together to form an optionally substituted hydrocarbyl ring structure.

The polymerization process comprises polymerizing an olefin monomer and a comonomer in the presence of a polymerization catalyst in a polymerization step conducted in a polymerization reactor in a solvent to produce a solution comprising a polymer of the olefin monomer and the comonomer.

The polymerization process comprises withdrawing an exhaust stream of the solution from the polymerization reactor in a withdrawing step.

The polymerization process comprises separating the exhaust stream to a first primary stream and a primary concentrated solution stream in a first primary separation step, wherein the first primary stream comprises hydrocarbons and polymer.

The polymerization process comprises separating the first primary stream to a second primary stream and a third primary stream in a second primary separation step, wherein the second primary stream comprises dissolved polymer and the third primary stream comprises majority of the hydrocarbons.

The polymerization process comprises cooling the third primary stream to a temperature of −80 to 20° C. in a primary cooling step to obtain a cooled third primary stream.

The polymerization process comprises separating the cooled third primary stream to a fourth primary stream and a fifth primary stream in a third primary separation step, wherein the fourth primary stream comprises hydrocarbons in vapour phase and the fifth primary stream comprises liquid hydrocarbons.

The polymerization process comprises returning the fourth primary stream and the fifth primary stream independently in a primary returning step to a location upstream of the polymerization reactor.

The polymerization process comprises polymerizing an olefin monomer and a comonomer in the presence of a polymerization catalyst in a polymerization step conducted in a polymerization reactor in a solvent to produce a solution comprising a polymer of the olefin monomer and the comonomer.

The polymerization process comprises withdrawing an exhaust stream of the solution from the polymerization reactor in a withdrawing step.

The polymerization process comprises separating the exhaust stream to a first primary stream and a primary concentrated solution stream in a first primary separation step, wherein the first primary stream comprises hydrocarbons and polymer.

The polymerization process comprises separating the first primary stream to a second primary stream and a third primary stream in a second primary separation step, wherein the second primary stream comprises dissolved polymer and the third primary stream comprises majority of the hydrocarbons.

The polymerization process comprises cooling the third primary stream to a temperature of −80 to 20° C. in a primary cooling step to obtain a cooled third primary stream.

The polymerization process comprises separating the cooled third primary stream to a fourth primary stream and a fifth primary stream in a third primary separation step, wherein the fourth primary stream comprises hydrocarbons in vapour phase and the fifth primary stream comprises liquid hydrocarbons.

The polymerization process comprises returning the fourth primary stream and the fifth primary stream independently in a primary returning step to a location upstream of the polymerization reactor.

Cyclic organosilicon compounds having a structure represented by the general formula

##STR00001##

and a method for using thereof as a component of catalysts for producing propylene polymer having a very high melt-flowability are disclosed. The cyclic organosilicon compounds are employed as external electron donors in Ziegler-Natta catalyst systems to dramatically improve the hydrogen response, and therefore the catalyst systems can be used to prepare polymer having high melt-flowability and high isotacticity at high yield.

Cyclic organosilicon compounds having a structure represented by the general formula

##STR00001##

and a method for using thereof as a component of catalysts for producing propylene polymer having a very high melt-flowability are disclosed. The cyclic organosilicon compounds are employed as external electron donors in Ziegler-Natta catalyst systems to dramatically improve the hydrogen response, and therefore the catalyst systems can be used to prepare polymer having high melt-flowability and high isotacticity at high yield.

Cyclic organosilicon compounds having a structure represented by the general formula

##STR00001##

and a method for using thereof as a component of catalysts for producing propylene polymer having a very high melt-flowability are disclosed. The cyclic organosilicon compounds are employed as external electron donors in Ziegler-Natta catalyst systems to dramatically improve the hydrogen response, and therefore the catalyst systems can be used to prepare polymer having high melt-flowability and high isotacticity at high yield.

The present invention provides a transition metal compound, a catalyst composition comprising same, and a method for producing an olefin polymer using the catalyst composition. A transition metal compound having a specific functional group at a specific position, according to the present invention, has high solubility and catalytic activity, and thus a method for producing an olefin polymer by using said transition metal compound can produce an olefin polymer having excellent physical properties through a simple process.