A bimodal poly(ethylene-co-1-alkene) copolymer comprising a higher molecular weight poly(ethylene-co-1-alkene) copolymer component and a lower molecular weight poly(ethylene-co-1-alkene) copolymer component. The copolymer is characterized by a unique combination of features comprising, or reflected in, its density; molecular weight distributions; component weight fraction amount; and viscoelastic properties; and at least one of environmental stress-cracking resistance and resin swell. Additional inventive embodiments include a method of making the copolymer, a formulation comprising the copolymer and at least one additive that is different than the copolymer, a method of making a manufactured article from the copolymer or formulation; the manufactured article made thereby, and use of the manufactured article.

Provided herein are polyethylene compositions with unimodal molecular weight distribution exhibiting an excellent balance of physical properties. The polyethylene compositions may have density of 0.935 to 0.975 g/cm.sup.3 and Melt Index (I.sub.2.16) of 0.1 to 1 g/10 min. Polyethylene compositions of certain embodiments may exhibit environmental stress crack resistance (ESCR, 10% Igepal, ASTM D1693 Cond. B) within the range from 45 to 80 hours, and/or (ESCR, 100% igepal, ASTM D1693 Cond. B) within the range from 70 to 250 hours. Such ESCR outperforms other unimodal resins of similar melt index and density, approaching ESCR performance of more expensive and complex resins with bimodal molecular weight distribution. The polyethylene compositions of certain embodiments may have two distinct crystalline fractions as shown by temperature rising elution fractionation (TREF).

Provided herein are polyethylene compositions with unimodal molecular weight distribution exhibiting an excellent balance of physical properties. The polyethylene compositions may have density of 0.935 to 0.975 g/cm.sup.3 and Melt Index (I.sub.2.16) of 0.1 to 1 g/10 min. Polyethylene compositions of certain embodiments may exhibit environmental stress crack resistance (ESCR, 10% Igepal, ASTM D1693 Cond. B) within the range from 45 to 80 hours, and/or (ESCR, 100% igepal, ASTM D1693 Cond. B) within the range from 70 to 250 hours. Such ESCR outperforms other unimodal resins of similar melt index and density, approaching ESCR performance of more expensive and complex resins with bimodal molecular weight distribution. The polyethylene compositions of certain embodiments may have two distinct crystalline fractions as shown by temperature rising elution fractionation (TREF).

This invention relates to a supported catalyst system comprising: (i) at least one first catalyst component comprising a group 4 bis(phenolate) complex; (ii) at least one second catalyst component comprising a 2,6-bis(imino)pyridyl iron complex; (iii) activator; and (iv) support. The catalyst system may be used for preparing polyolefins, such a bimodal polyethylene, typically in a gas phase polymerization.

This invention relates to a supported catalyst system comprising: (i) at least one first catalyst component comprising a group 4 bis(phenolate) complex; (ii) at least one second catalyst component comprising a 2,6-bis(imino)pyridyl iron complex; (iii) activator; and (iv) support. The catalyst system may be used for preparing polyolefins, such a bimodal polyethylene, typically in a gas phase polymerization.

Disclosed are ethylene polymer compositions containing a homogeneously-branched first ethylene polymer component and 15-35 wt. % of a homogeneously-branched second ethylene polymer component of higher density than the first ethylene polymer component. The ethylene polymer composition can be characterized by a density from 0.912 to 0.925 g/cm.sup.3, a ratio of Mw/Mn from 2 to 5, a melt index less than 2 g/10 min, and a CY-a parameter at 190° C. from 0.35 to 0.7. These polymer compositions have the excellent dart impact strength and optical properties of a metallocene-catalyzed LLDPE, but with improved machine direction tear resistance, and can be used in blown film and other end-use applications. Further, methods for improving film Elmendorf tear strength also are described.

Disclosed are ethylene polymer compositions containing a homogeneously-branched first ethylene polymer component and 15-35 wt. % of a homogeneously-branched second ethylene polymer component of higher density than the first ethylene polymer component. The ethylene polymer composition can be characterized by a density from 0.912 to 0.925 g/cm.sup.3, a ratio of Mw/Mn from 2 to 5, a melt index less than 2 g/10 min, and a CY-a parameter at 190° C. from 0.35 to 0.7. These polymer compositions have the excellent dart impact strength and optical properties of a metallocene-catalyzed LLDPE, but with improved machine direction tear resistance, and can be used in blown film and other end-use applications. Further, methods for improving film Elmendorf tear strength also are described.

A composition, such as a catalyst precursor or a catalyst comprising a Cr coated silica support with particularly defined levels of Na and Al, such that the resulting Cr/Silica catalyst has an increased MI potential is disclosed. In an embodiment, the disclosed catalyst composition comprises a silica-containing substrate made using a base-set gel and comprising a catalytically active metal consisting of Cr, with Al impurities of less than 50 ppm and Na in an amount of less than 800 ppm of the catalyst composition. The disclosed composition has an increased MI potential over a catalyst having higher Al content, a lower Na:Al ratio, or both. Methods of making the disclosed composition, and methods of using it to prepare a polyethylene are also disclosed.

A composition, such as a catalyst precursor or a catalyst comprising a Cr coated silica support with particularly defined levels of Na and Al, such that the resulting Cr/Silica catalyst has an increased MI potential is disclosed. In an embodiment, the disclosed catalyst composition comprises a silica-containing substrate made using a base-set gel and comprising a catalytically active metal consisting of Cr, with Al impurities of less than 50 ppm and Na in an amount of less than 800 ppm of the catalyst composition. The disclosed composition has an increased MI potential over a catalyst having higher Al content, a lower Na:Al ratio, or both. Methods of making the disclosed composition, and methods of using it to prepare a polyethylene are also disclosed.

A bimodal copolymer comprises on average at least 90 weight-percent units derived from ethylene and at least 0.05 weight percent units derived from an α-olefin comonomer having from 4 to 10 carbon atoms, wherein the copolymer has the properties described herein.