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.

Disclosed are metallocene compounds, catalyst compositions comprising a metallocene compound, processes for polymerizing olefins, methods for making catalyst compositions, olefin polymers and articles made from olefin polymers. In an aspect, a metallocene compounds contain a fluorenyl ligand and a cyclopentadienyl ligand which are bridged by a linking group, in which the metallocene is characterized by [1] the cyclopentadienyl ligand being substituted with a C.sub.2-C.sub.18 heterohydrocarbyl group having an oxygen atom positioned 5 atoms distance or less from the cyclopentadienyl ligand and [2] the linking group having a pendant C.sub.3-C.sub.12 alkenyl group having a terminal C═C double bond. It has been discovered that a catalyst composition comprising a metallocene compound having these features can produce polyethylene having a low melt index in the absence of a second metallocene.

Disclosed are metallocene compounds, catalyst compositions comprising a metallocene compound, processes for polymerizing olefins, methods for making catalyst compositions, olefin polymers and articles made from olefin polymers. In an aspect, a metallocene compounds contain a fluorenyl ligand and a cyclopentadienyl ligand which are bridged by a linking group, in which the metallocene is characterized by [1] the cyclopentadienyl ligand being substituted with a C.sub.2-C.sub.18 heterohydrocarbyl group having an oxygen atom positioned 5 atoms distance or less from the cyclopentadienyl ligand and [2] the linking group having a pendant C.sub.3-C.sub.12 alkenyl group having a terminal C═C double bond. It has been discovered that a catalyst composition comprising a metallocene compound having these features can produce polyethylene having a low melt index in the absence of a second metallocene.

Catalyst compositions containing a metallocene compound, a solid activator, and a co-catalyst, in which the solid activator or the supported metallocene catalyst has a d50 average particle size of 15 to 50 μm and a particle size distribution of 0.5 to 1.5, can be contacted with an olefin in a loop slurry reactor to produce an olefin polymer. A representative ethylene-based polymer produced using the catalyst composition has excellent dart impact strength and low gels, and can be characterized by a HLMI from 4 to 10 g/10 min, a density from 0.944 to 0.955 g/cm.sup.3, a higher molecular weight component with a Mn from 280,000 to 440,000 g/mol, and a lower molecular weight component with a Mw from 30,000 to 45,000 g/mol and a ratio of Mz/Mw ranging from 2.3 to 3.4.

Catalyst compositions containing a metallocene compound, a solid activator, and a co-catalyst, in which the solid activator or the supported metallocene catalyst has a d50 average particle size of 15 to 50 μm and a particle size distribution of 0.5 to 1.5, can be contacted with an olefin in a loop slurry reactor to produce an olefin polymer. A representative ethylene-based polymer produced using the catalyst composition has excellent dart impact strength and low gels, and can be characterized by a HLMI from 4 to 10 g/10 min, a density from 0.944 to 0.955 g/cm.sup.3, a higher molecular weight component with a Mn from 280,000 to 440,000 g/mol, and a lower molecular weight component with a Mw from 30,000 to 45,000 g/mol and a ratio of Mz/Mw ranging from 2.3 to 3.4.

A preparation method for a copolymer includes the step(s) of contacting an olefin and an unsaturated carboxylic acid shown in Formula II or a derivative of the unsaturated carboxylic acid shown in Formula II with a catalyst and optionally a chain transfer agent for reaction in the presence of an alkane solvent to obtain the copolymer. The copolymer is a spherical and/or spherical-like copolymer.

A preparation method for a copolymer includes the step(s) of contacting an olefin and an unsaturated carboxylic acid shown in Formula II or a derivative of the unsaturated carboxylic acid shown in Formula II with a catalyst and optionally a chain transfer agent for reaction in the presence of an alkane solvent to obtain the copolymer. The copolymer is a spherical and/or spherical-like copolymer.

The present disclosure relates to a polyethylene having high pressure resistance and a crosslinked polyethylene pipe including the same. The polyethylene according to the present disclosure has high melt index and density and exhibits a sufficient degree of crosslinking, thereby exhibiting excellent strength and pressure resistance characteristics.

The present disclosure relates to a polyethylene having high pressure resistance and a crosslinked polyethylene pipe including the same. The polyethylene according to the present disclosure has high melt index and density and exhibits a sufficient degree of crosslinking, thereby exhibiting excellent strength and pressure resistance characteristics.

The invention relates to a solid catalyst system comprising a first chromium compound, a second chromium compound, a reaction product of an alkyl aluminium compound and a nitrogen containing compound and a silicon oxide support, wherein the first chromium compound is chromium trioxide or a compound convertible to chromium trioxide, the second chromium compound is a slilylchromate compound and the nitrogen containing compound is a cycloalkylamine compound having the general formula: R.sup.3—NH.sub.2, wherein R.sup.3 is selected from C3-C8 cycloalkyl groups.