A method for evaluating long-term durability of a resin for piping is provided. Unlike the conventional FNCT evaluation method requiring a long period of time, the method disclosed herein is capable of predicting long-term durability of a resin for piping in a short time, by a simple calculation using a content of tie molecules, an entanglement molecular weight (M.sub.e) and a content of ultrahigh molecular weight components. In addition, the olefinic polymer is configured to have a predetermined relationship in relation to the content of tie molecules, the entanglement molecular weight (M.sub.e) and the content of ultrahigh molecular weight components, whereby the polymer of the present application can be used in the manufacture of a heating pipe requiring excellent long-term durability.

Apparatuses and processes that produce multimodal polyolefins, and in particular, polyethylene resins, are disclosed herein. This is accomplished by using two reactors in series, where one of the reactors is a multi-zone circulating reactor that can circulate polyolefin particles through two polymerization zones optionally having two different flow regimes so that the final multimodal polyolefin has improved product properties and improved product homogeneity.

Apparatuses and processes that produce multimodal polyolefins, and in particular, polyethylene resins, are disclosed herein. This is accomplished by using two reactors in series, where one of the reactors is a multi-zone circulating reactor that can circulate polyolefin particles through two polymerization zones optionally having two different flow regimes so that the final multimodal polyolefin has improved product properties and improved product homogeneity.

Embodiments provide bimodal polymerization catalyst systems comprising metallocene olefin polymerization catalysts and biphenylphenol polymerization catalysts made from biphenylphenol polymerization precatalysts of Formula I.

Embodiments are directed towards the use of a supported biphenylphenol polymerization catalyst made from a biphenylphenol polymerization precatalyst of Formula I via a gas-phase or slurry-phase polymerization process under gas-phase or slurry-phase polymerization conditions to make a polymer.

Embodiments are directed towards the use of a supported biphenylphenol polymerization catalyst made from a biphenylphenol polymerization precatalyst of Formula I via a gas-phase or slurry-phase polymerization process under gas-phase or slurry-phase polymerization conditions to make a polymer.

A reactor for the polymerization of olefins comprising a first inlet for introducing a first stream comprising monomer(s), catalyst(s) and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof, at least one outlet for withdrawing a product stream, characterized in that the reactor further comprises at least one second inlet for introducing a second stream comprising monomer(s), catalyst(s) and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof; and a process for polymerizing olefins in a reactor according to the present invention, comprising the steps of introducing monomer(s), catalyst(s), and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof as the first stream via the first inlet into the reactor forming a reaction mixture; polymerizing a polymer from the reaction mixture; withdrawing the product stream via the at least one outlet from the reactor; characterized in that the process comprises a further step of introducing a second stream comprising monomer(s), catalyst(s), and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof into the reactor via the at least one second inlet into the reactor.

A reactor for the polymerization of olefins comprising a first inlet for introducing a first stream comprising monomer(s), catalyst(s) and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof, at least one outlet for withdrawing a product stream, characterized in that the reactor further comprises at least one second inlet for introducing a second stream comprising monomer(s), catalyst(s) and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof; and a process for polymerizing olefins in a reactor according to the present invention, comprising the steps of introducing monomer(s), catalyst(s), and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof as the first stream via the first inlet into the reactor forming a reaction mixture; polymerizing a polymer from the reaction mixture; withdrawing the product stream via the at least one outlet from the reactor; characterized in that the process comprises a further step of introducing a second stream comprising monomer(s), catalyst(s), and optionally hydrogen, solvent or comonomer(s) and/or mixtures thereof into the reactor via the at least one second inlet into the reactor.

Provided are methods for producing bimodal polyolefins comprising the steps of contacting α-olefin monomers with a catalyst in slurry polymerization conditions in the presence of zero to minimum hydrogen to produce a high molecular weight polyolefin and contacting additional α-olefin monomers in gas phase polymerization conditions and the high molecular weight polyolefin and the catalyst to produce bimodal polyolefin having high stiffness and broad molecular weight distribution. An additional step of polymerizing the bimodal polyolefin with a comonomer in a second gas phase can provide a bimodal impact copolymer having high stiffness and broad molecular weight distribution. Among the advantages of the present methods, bimodal polyolefins can be produced in a continuous process between a slurry polymerization reactor and a gas phase polymerization reactor without a venting step in between and with minimal hydrogen in the slurry polymerization reactor.

Provided are methods for producing bimodal polyolefins comprising the steps of contacting α-olefin monomers with a catalyst in slurry polymerization conditions in the presence of zero to minimum hydrogen to produce a high molecular weight polyolefin and contacting additional α-olefin monomers in gas phase polymerization conditions and the high molecular weight polyolefin and the catalyst to produce bimodal polyolefin having high stiffness and broad molecular weight distribution. An additional step of polymerizing the bimodal polyolefin with a comonomer in a second gas phase can provide a bimodal impact copolymer having high stiffness and broad molecular weight distribution. Among the advantages of the present methods, bimodal polyolefins can be produced in a continuous process between a slurry polymerization reactor and a gas phase polymerization reactor without a venting step in between and with minimal hydrogen in the slurry polymerization reactor.