Provided is a hybrid catalyst composition including a first transition metal compound represented by Formula 1 and a second transition metal compound represented by Formula 2, the compounds being different from each other in the Formulae. The hybrid catalyst composition including the first and second transition metal compounds may exhibit high catalytic activity and may prepare a polyolefin having processability and mechanical properties.

A polyethylene homopolymer composition comprises: a first ethylene homopolymer having a density, d.sup.1 of from 0.943 to 0.975 g/cm.sup.3, a melt index, I.sub.2.sup.1 of from 0.01 to 10 g/10 min, and a molecular weight distribution, Mw/Mn of less than 3.0; and a second ethylene homopolymer having a density, d.sup.2 of from 0.950 to 0.985 g/cm.sup.3, a melt index, I.sub.2.sup.2 of at least 500 g/10 min, and a molecular weight distribution, M.sub.w/M.sub.n of less than 3.0; wherein the ratio of the melt index, I.sub.2.sup.2 of the second ethylene homopolymer to the melt index, I.sub.2.sup.1 of the first ethylene homopolymer is at least 50. The polyethylene homopolymer compositions which may be nucleated have a weight average molecular weight, M.sub.w of ≤75,000, a high load melt index, I.sub.21 of at least 200 g/10 min, a molecular weight distribution, M.sub.w/M.sub.n of from 4.0 to 12.0 and may be usefully employed in molding applications, such as, for example, in compression molded closures.

A polyethylene homopolymer composition comprises: a first ethylene homopolymer having a density, d.sup.1 of from 0.943 to 0.975 g/cm.sup.3, a melt index, I.sub.2.sup.1 of from 0.01 to 10 g/10 min, and a molecular weight distribution, Mw/Mn of less than 3.0; and a second ethylene homopolymer having a density, d.sup.2 of from 0.950 to 0.985 g/cm.sup.3, a melt index, I.sub.2.sup.2 of at least 500 g/10 min, and a molecular weight distribution, M.sub.w/M.sub.n of less than 3.0; wherein the ratio of the melt index, I.sub.2.sup.2 of the second ethylene homopolymer to the melt index, I.sub.2.sup.1 of the first ethylene homopolymer is at least 50. The polyethylene homopolymer compositions which may be nucleated have a weight average molecular weight, M.sub.w of ≤75,000, a high load melt index, I.sub.21 of at least 200 g/10 min, a molecular weight distribution, M.sub.w/M.sub.n of from 4.0 to 12.0 and may be usefully employed in molding applications, such as, for example, in compression molded closures.

Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

Ethylene-based polymers are characterized by a melt index less than 1 g/10 min, a density from 0.94 to 0.965 g/cm.sup.3, a Mw from 100,000 to 250,000 g/mol, a relaxation time from 0.5 to 3 sec, and an average number of long chain branches (LCBs) per 1,000,000 total carbon atoms in a molecular weight range of 300,000 to 900,000 g/mol that is greater than that in a molecular weight range of 1,000,000 to 2,000,000 g/mol, or an average number of LCBs per 1,000,000 total carbon atoms in a molecular weight range of 1,000,000 to 2,000,000 g/mol of less than or equal to about 5 and a maximum ratio of η.sub.E/3η at an extensional rate of 0.1 sec.sup.−1 from 1.2 to 10. These polymers have substantially no long chain branching in the high molecular weight fraction of the polymer, but instead have significant long chain branching in a lower molecular weight fraction, such that polymer melt strength and parison stability are maintained for the fabrication of blow molded products and other articles of manufacture. These ethylene polymers can be produced using a dual catalyst system containing a single or two atom bridged metallocene compound with two indenyl groups, and a single atom bridged metallocene compound with a fluorenyl group and a cyclopentadienyl group.

Ethylene-based polymers are characterized by a melt index less than 1 g/10 min, a density from 0.94 to 0.965 g/cm.sup.3, a Mw from 100,000 to 250,000 g/mol, a relaxation time from 0.5 to 3 sec, and an average number of long chain branches (LCBs) per 1,000,000 total carbon atoms in a molecular weight range of 300,000 to 900,000 g/mol that is greater than that in a molecular weight range of 1,000,000 to 2,000,000 g/mol, or an average number of LCBs per 1,000,000 total carbon atoms in a molecular weight range of 1,000,000 to 2,000,000 g/mol of less than or equal to about 5 and a maximum ratio of η.sub.E/3η at an extensional rate of 0.1 sec.sup.−1 from 1.2 to 10. These polymers have substantially no long chain branching in the high molecular weight fraction of the polymer, but instead have significant long chain branching in a lower molecular weight fraction, such that polymer melt strength and parison stability are maintained for the fabrication of blow molded products and other articles of manufacture. These ethylene polymers can be produced using a dual catalyst system containing a single or two atom bridged metallocene compound with two indenyl groups, and a single atom bridged metallocene compound with a fluorenyl group and a cyclopentadienyl group.

A process for preparation of an ethylene polymer in a gas-phase polymerization unit comprising a gas-phase polymerization reactor by homopolymerizing ethylene or copolymerizing ethylene and one or more C.sub.4-C.sub.12-1-alkenes in a reaction gas made from or containing propane as polymerization diluent in the presence of a pre-activated polymerization catalyst, wherein a purified propane feed stream made from or containing at least 99 mol % propane and from 0.1 to 100 ppm mol propylene is fed to the gas-phase polymerization unit.

A process for preparation of an ethylene polymer in a gas-phase polymerization unit comprising a gas-phase polymerization reactor by homopolymerizing ethylene or copolymerizing ethylene and one or more C.sub.4-C.sub.12-1-alkenes in a reaction gas made from or containing propane as polymerization diluent in the presence of a pre-activated polymerization catalyst, wherein a purified propane feed stream made from or containing at least 99 mol % propane and from 0.1 to 100 ppm mol propylene is fed to the gas-phase polymerization unit.

Provided are various bimodal polyethylene, including but not limited to a bimodal polyethylene for a pipe having a density of from 0.9340 to 0.9470 gram/cubic centimeters (g/ccm), a melt index (12) of from 0.1 to 0.7 gram/10 minute, a melt flow ratio (121/12) of from 20 to 90. The bimodal polyethylene includes a high molecular weight polyethylene component and a low molecular weight polyethylene component which are a reaction product of a polymerization process performed in a single reactor and that employs a bimodal polymerization catalyst system. The bimodal polymerization catalyst system includes a bimodal catalyst system of bis(2-pentamethylphenylamido)ethyl)amine Zirconium dibenzyl and either (tetramethylcyclopentadienyl)(n-propylcyclopentadienyl)Zirconium dichloride or (tetramethylcyclopentadienyl)(n-propylcyclopentadienyl)zirconium dimethyl in a 3.0:1 molar ratio; and a trim catalyst of (tetramethylcyclopentadienyl)(n-propylcyclopentadienyl)Zirconium dichloridedimethyl in heptane added to adjust melt.