Multimodal polyethylene compositions

Abstract

Disclosed herein are multimodal polyethylene compositions, processes for making the same, and pipes made from the same. The multimodal polyethylene composition includes a first component and a second component. The composition according to embodiments disclosed herein has a density from 0.940 g / cm3 to 0.955 g / cm3; a melt index (I2) of at least 0.30 g / 10 min; and a Tp MW of greater than 145,000 g / mol at an elution temperature range of 90.0°C to 95.0°C. Pipes made from the composition can have a desirable balance of properties, including slow growth crack and hydrostatic pressure properties.

Description

[0001] MULTIMODAL POLYETHYLENE COMPOSITIONS

[0002] FIELD

[0003] Embodiments of the present disclosure relate to multimodal polyethylene compositions, and processes for making the same, as well as pipes comprising multimodal polyethylene compositions.

[0004] INTRODUCTION

[0005] Polyethylene compositions can be formed into useful articles from molding and extrusion processes. Such articles include containers, conduits, and pipes. When making higher density polyethylene compositions and extruding them to form articles like a pipe, it can be difficult to achieve a balance of target properties for the article, including, for example, strain hardening modulus, hydrostatic strength, creep resistance, cracked round bar performance, melt strength, environmental stress crack resistance (ESCR), and processability. For instance, increasing the density of polyethylene compositions can result in desirable hydrostatic strength and creep resistance properties but significantly comprises cracked round bar, ESCR, and flexibility. The interplay between density, molecular weight, and branching can also present challenges and undesirable trade-offs, where branching can decrease density while at the same time can negatively impact processability and ESCR, and where increasing melt index (12) aids processability but can diminish ESCR and hydrostatic strength.

[0006] While polyethylene compositions can have worse performance than other materials like polybutylene or polypropylene in terms of hydrostatic strength, such materials can be difficult to process, cost-prohibitive, or fail to meet industry standards. For example, many pipes and fittings are classified as “PE 100” ready, meaning they are able to hold fluid for an extended time at a pressure of 10 bar (10.0 MPa) without bursting. Similarly, many pipe and fittings are classified as “PE-RT” ready, meaning they are able to hold fluid under pressure for an extended time at raised temperatures such as 80°C or more. Existing materials often fail to meet these standard as well as updated standards, and so a need exists for a polyethylene compositions having a desirable balance of strain hardening modulus, hydrostatic strength, creep resistance, cracked round bar performance, melt strength, environmental stress crack resistance (ESCR), and processability.

[0007] SUMMARY

[0008] In a first aspect, a multimodal polyethylene is disclosed. The multimodal polyethylene composition according to the first aspect comprises a first component and a second component. The first component consists of a first ethylene / a-olefin copolymer and the second component consists of a second ethylene / a-olefin copolymer or homopolymer; wherein the first component has a higher weight average molecular weight (Mw) than the second composition. The composition according to the first aspect has a density from 0.940 g / cm3to 0.955 g / cm3; a melt index (I2) of at least 0.30 g / 10 min; and a TPMW of greater than 145,000 g / mol at an elution temperature range of 90.0°C to 95.0°C.

[0009] In a second aspect, a process for making a multimodal polyethylene composition according to the first aspect is disclosed. The process comprises: (a) polymerizing a first polyethylene component by solution polymerization from ethylene and a comonomer selected from 1 -hexene, 1 -heptene or 1 -octene, wherein the monomer mix feed in the first component polymerization comprises at least 90 weight percent of the ethylene and comprises at most 9 weight percent comonomer, in the presence of a catalyst system comprising a primary catalyst that meets Formula below:

[0010]

[0011] under conditions to produce the first component; and

[0012] (b) polymerizing a second polyethylene component by solution polymerization to from ethylene and a comonomer selected from 1 -hexene, 1 -heptene or 1 -octene in the presence of a Ziegler-Natta catalyst system, wherein the monomer mix fed into the first component polymerization comprises at least 1 weight percent more comonomer than the monomer mix fed into the second component polymerization, to produce the second polyethylene component having a molecular weight distribution of greater than 2.50; and

[0013] wherein M is titanium, zirconium, or hafnium, each independently being in a formal oxidation state of +2, +3, or +4; and n is an integer of from 0 to 3, and wherein when n is 0, X is absent; and each X independently is a monodentate ligand that is neutral, monoanionic, or dianionic; or two Xs are taken together to form a bidentate ligand that is neutral, monoanionic, or dianionic; and X and n are chosen in such a way that the metal-ligand complex of formula (IA) is, overall, neutral; and each Z independently is O, S, N(Cl-C40)hydrocarbyl, or P(C1-C40)hydrocarbyl; and the Z-L-Z fragment comprises a transition metal and ligand; and

[0014] R1-16are selected from the group consisting of a (Ci-C4o)hydrocarbyl, (C1-C40)heterohydrocarbyl, Si(Rc)3, Ge(Rc)3, P(Rp)2, N(RN)2, ORC, SRC, NO2, CN, CF3, RCS(O)-, RCS(O)2-, (RC)2C=N-, RCC(O)O-, RCOC(O)-, RCC(O)N(R)-, (RC)2NC(O)-, halogen atom, hydrogen atom, and combinations thereof.

[0015] In a third aspect, a pipe is disclosed. The pipe is made from the composition of the first aspect.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 shows the molecular weight profiles of examples.

[0018] Figure 2 shows iCCD analysis of examples.

[0019] Figure 3 shows the dynamic viscosity of examples.

[0020] DETAILED DESCRIPTION

[0021] The term “composition,” as used herein, refers to a mixture of materials which comprises the composition, as well as reaction products and decomposition products formed from the materials of the composition. For example, a multimodal copolymer having two components is an example of a composition.

[0022] The term “polymer” means a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term polymer thus embraces the term homopolymer as defined hereafter, and the term interpolymer as defined hereinafter. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and / or within a polymer such as the ethylene / alpha-olefin copolymers disclosed herein. A polymer may be a single polymer, a polymer blend or a polymer mixture, including mixtures of polymers that are formed in situ during polymerization.

[0023] The term “copolymer”, as used herein, refers to a polymer made from two or more monomers.

[0024] The term, “ethylene / a-olefin copolymer,” as used herein, refers to a copolymer that comprises, in polymerized form, a majority amount (>50 mol%) of ethylene monomer, and an a-olefin, as monomer types. Typical a-olefins used in forming ethylene / a-olefin interpolymers are C3-C10 alkenes.

[0025] The term “alpha-olefin” or “a-olefin”, as used herein, refers to an alkene having a double bond at the primary or alpha (a) position. “Polyethylene” or “ethylene-based polymer” shall mean polymers comprising a majority amount (>50 mol %) of units which have been derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m-LLDPE); ethylene-based plastomers (POP) and ethylene-based elastomers (POE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

[0026] The term “HDPE” or “high density polyethylene” refers to polyethylene having densities greater than about 0.935 g / cm3and up to about 0.980 g / cm3. HDPE can be prepared with Ziegler-Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis -cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, pyridylamine catalysts, phosphinimine catalysts & polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).

[0027] The term “multimodal” refers to a composition that can be characterized by having at least two (2) polymer components or subcomponents with different in molecular weights and / or different comonomer contents. In one embodiment, multimodal may be defined by having at least two distinct peaks in an Absolute Gel Permeation Chromatography (GPC) chromatogram showing the molecular weight distribution of the composition. The term “bimodal” refers to a composition that can be characterized by having two (2) polymer components or subcomponents with different molecular weights and / or different comonomer contents. In one embodiment, bimodal may be defined by having two distinct inflections or peaks in an Absolute Gel Permeation Chromatography (GPC) chromatogram showing the molecular weight distribution of the composition. All GPC measurement values (e.g., Mw, Mn, Mz) recited herein are Absolute GPC measurements provided in accordance with the test methods described below.

[0028] The terms “comprising,” “including,” “having,” and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of” excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term “consisting of’ excludes any component, step or procedure not specifically delineated or listed.

[0029] Disclosed herein is a multimodal polyethylene composition, referred herein as the “composition.” The composition comprises a first component and a second component. The first component has a higher weight average molecular weight (Mw) than the second component. The first component can be referred to as the high molecular weight component (HMW component) and the second component can be referred to as the low molecular weight component (LMW component). The first component consists of a first ethylene / a-olefin copolymer, and the second component consists of a second ethylene / a-olefin copolymer or homopolymer. In some embodiments, the second component consists of a second ethylene / a-olefin copolymer. In some embodiments, the second component consists of a second homopolymer.

[0030] The multimodal polyethylene composition can be made in a two-step solution polymerization of ethylene and one or more comonomers selected from 1 -hexene, 1 -heptene and 1-octene. In this two-step process, one step of the process polymerizes the first component, and another step of the process polymerizes the second component. In some embodiments, the first component polymerization and the second component polymerization are carried out in separate reactors. In some embodiments, the first component polymerization is performed first reactor, and then the second component polymerization is performed second reactor.

[0031] The multimodal polyethylene can be made where the polymerization steps use solution polymerization. In embodiments disclosed herein, monomers are polymerized in a high-boiling organic solvent in the presence of an appropriate catalyst system and optionally hydrogen and / or other chain transfer agents. In some embodiments, the polymerization is carried out in continuously stirred reactors (CSTR), and in some embodiments the reaction is carried out in loop reactors. In some embodiments, the weight ratio of monomers to solvent in the solution polymerization is at least 8 percent or at least 10 percent or at least 12 percent or at least 14 percent. In some embodiments, the weight ratio of monomers to solvent in the solution polymerization is at most 30 percent or at most 25 percent or at most 20 percent or at most 16 percent.

[0032] The temperature in each reactor can promote polymerization and maintain desired viscosity without degrading the reagents or products. In some embodiments, the reactor temperature is at least 115°C or at least 125°C or at least 135°C or at least 145°C or at least 150°C or at least 155°C or at least 160°C. In some embodiments, the reactor temperature is at most 250°C or at most 230°C or at least most 210°C or at most 190°C or at most 180°C or at most 170°C or at most 165°C or at most 160°C. The pressure in each reactor can maintain a stable reaction solution at reaction temperatures and to encourage the reaction. In some embodiments, the reactor pressure is at least 300 psi (2 MPa) or at least 350 psi (2.4 MPa) or at least 375 psi (2.6 MPa) or at least 400 psi (2.8 MPa). In some embodiments, the reactor pressure is at most 1000 (6.9 MPa) psi or at most 900 psi (6.2 MPa) or at most 800 psi (5.5 MPa) or at most 750 psi (5.2 MPa).

[0033] Catalyst systems used on solution polymerization of polyethylene contain a primary catalyst that is sometimes called a procatalyst, and in many embodiments the catalyst system further contains one or more cocatalysts or activators, which activate and / or reinforce the activity of the primary catalyst. The descriptions of the components, below, describe catalysts that can be used in polymerizations to form the composition.

[0034] Common cocatalysts include a cation-forming co-catalysts, Lewis acid cocatalysts, and combinations thereof. Some embodiments of cocatalysts contain organometallic compounds of Group 13 metals, such as boron or aluminum.

[0035] Examples of aluminum-containing co-catalysts include alkyl aluminums or polymeric or oligomeric alumoxanes (also known as aluminoxanes). The term “alkyl aluminum” includes a monoalkyl aluminum dihydride or a monoalkylaluminum dihalide, a dialkyl aluminum hydride or dialkyl aluminum halide, or a trialkylaluminum such as tri-ethyl aluminum (TEA). Examples of polymeric or oligomeric alumoxanes include methylalumoxane (MAO), modified methylalumoxane (MMAO), and isobutylalumoxane.

[0036] Examples of boron-containing cocatalysts include tri(hydrocarbyl)-boron compounds, tri(aryl)boron compounds, and halogenated (including perhalogenated) derivatives thereof. Other examples of boron-containing co-catalysts include organoborates such as tetrakis-hydrocarbyl borate and halogenated variations such as tetrakis(pentaflourophenyl)borate.

[0037] When cocatalyst is used, its quantity should be sufficient to activate the primary catalyst. In some embodiments, the molar ratio of cocatalyst to primary catalyst is at least 0.5:1 or at least 0.8: 1 or at least 0.9: lor at least 1:1. In some embodiments, the molar ratio of primary catalyst to cocatalyst is at most 10:1 or at most 5:1 or most 3:1 or most 2:1 or most 1.5:1 or most 1.2:1.

[0038] The first component polymerization can be carried out using from 90 to 96 weight percent ethylene and from 4 to 10 weight percent comonomers selected from 1 -hexene, 1 -heptene, and 1-octene. In some embodiments, the first ethylene / a-olefin copolymer and / or second ethylene / a-olefin copolymer consists essentially of 1 -hexene. In some embodiments, the comonomer of consist essentially of 1 -heptene. In some embodiments, the comonomer consist essentially of 1- octene. In some embodiments, the comonomer comprises a mixture of two or more comonomers selected from 1 -hexene, 1 -heptene and 1 -octene.

[0039] In some embodiments, the monomer mix fed into in the first component polymerization comprises at least 90 weight percent ethylene (based on the total weight of monomers) or at least 91 weight percent or at least 92 weight percent or at least 93 weight percent or at least 94 weight percent. In some embodiments, the monomer mix in the first component polymerization comprises at most 96 weight percent ethylene (based on the total weight of monomers) or at most 94 weight percent. In some embodiments, the monomer mix in the first component polymerization comprises at least 5 weight percent comonomer (based on the total weight of monomers) or at least 6 weight percent. In some embodiments, the monomer mix in the first component polymerization comprises at most 9 weight percent comonomer, or at most 8 weight percent or at most 7 weight percent or at most 6 weight percent.

[0040] In some embodiments, the monomer mix fed into the first component polymerization comprises at least 1 weight percent more comonomer than the monomer mix fed into the second component polymerization (based on the total weight of monomers), or at least 2 weight percent more or at least 3 weight percent more or at least 4 weight percent more. In some embodiments, the monomer mix fed into the first component polymerization comprises up to 10 weight percent more comonomer than the monomer mix fed into the second polymerization (based on the total weight of monomers), or up to 9 weight percent more or up to 8 weight percent more or up to 7 weight percent more or up to 6 weight percent more.

[0041] The monomer mix can contain a small quantity of ethylenically-unsaturated comonomers other than 1 -hexene, 1 -heptene and 1 -octene. Examples of other comonomers include other a-olefins such as propylene, 1 -butene, 1 -pentene, 1 -nonene and 1 -decene. In some embodiments, the quantity of other comonomers is less than 3 weight percent (based on the total weight of monomers) or less than 2 weight percent or less than 1 weight percent or as low as 0 weight percent.

[0042] The first component can be formed via polymerization in the presence of catalyst system in which the primary catalyst is a single site catalyst that meets Formula I

[0043]

[0044] wherein: M is titanium, zirconium, or hafnium, each independently being in a formal oxidation state of +2, +3, or +4; and n is an integer of from 0 to 3, and wherein when n is 0, X is absent; and each X independently is a monodentate ligand that is neutral, monoanionic, or dianionic; or two Xs are taken together to form a bidentate ligand that is neutral, monoanionic, or dianionic; and X and n are chosen in such a way that the metal-ligand complex of formula (I) is, overall, neutral; and each Z independently is O, S, N(Cl-C40)hydrocarbyl, or P(Cl-C40)hydrocarbyl; and the Z-L-Z fragment comprises a transition metal and ligand; R1-16are selected from the group consisting of a (Ci-C4o)hydrocarbyl, (C Ci-C4o)heterohydrocarbyl, Si(Rc)3, Ge(Rc)3, P(Rp)2, N(RN)2, ORC, SRC, NO2, CN, CF3, RCS(O)-, RCS(O)2-, (RC)2C=N-, RCC(O)O-, RcOC(O)-, RcC(O)N(R)-, (RC)2NC(O)-, halogen atom, hydrogen atom, and combinations thereof.

[0045] In some embodiments, the Z-L-Z fragment is in accordance with the following formula (II)

[0046]

[0047] Optionally two or more R groups (from R9 13or R4 s) can combine together into ring structures, with such ring structures having from 3 to 50 atoms in the ring excluding any hydrogen atoms.

[0048] Each of the aryl, heteroaryl, hydrocarbyl, heterohydrocarbyl, Si(Rc)3, Ge(Rc)3P(RP)2, N(RN)2, ORC, SRC, RCS(O)-, RCS(O)2-, (RC)2C=N-, RCC(O)O-, RCOC(O)-, RCC(O)N(R)-, (RC)2NC(O)-, hydrocarbylene, and heterohydrocarbylene groups independently is unsubstituted or substituted with one or more RS substituents; and each RS independently is a halogen atom, polyfluoro substitution, perfluoro substitution, unsubstituted (Ci-Cis)alkyl, F3C-, FCH2O-, F2HCO-, F3CO-, R3Si-, R3Ge-, RO-, RS-, RS(O)-, RS(O)2-, R2P-, R2N-, R2C=N-, NC-, RC(O)O- , ROC(O)-, RC(O)N(R)-, or R2NC(O)-, or two of the RS are taken together to form an unsubstituted (Ci-Cis)alkylene, wherein each R independently is an unsubstituted (Ci-Ci8)alkyl.

[0049] In some embodiments, M is titanium. In some embodiments, M is zirconium. In some embodiments, M is hafnium.

[0050] In some embodiments, X is hydrocarbyl. In some embodiments, X is an alkyl group. In some embodiments, X comprises an aryl or alkaryl group. In some embodiments, each X group contains on average at most 10 carbon atoms or at most 8 carbon atoms or at most 6 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms or 1 carbon atom.

[0051] In some embodiments, one or both of R1and R16comprise sterically hindering groups with a molecular weight of at least 50 Da or at least 75 Da or at least 100 Da or at least 125 Da or at least 150 Da. In some embodiments, the sterically hindering groups at R1and / or R16have a molecular weight of at most 350 or at most 300 or at most 250 or at most 200 or at most 175. In some embodiments, the sterically hindering groups at R1and / or R16comprise at least one aromatic ring system. In some embodiments, the aromatic ring system comprises a single aromatic ring. In some embodiments, the aromatic ring system comprises two or more unfused aromatic rings. In some embodiments, the aromatic ring system comprises two or more fused aromatic rings. In some embodiments, the aromatic rings are carbocyclic, meaning they contain only carbon atoms in the ring structure. In some embodiments, the aromatic rings are heterocyclic, meaning they contain at least one atom in the ring structure that is not carbon; in some embodiments, the heterocyclic ring structures contain one or more nitrogen atoms in the ring structure. In some embodiments, one or both of R1and R16comprise a substituted or unsubstituted N-carbazole moiety, which is illustrated in Formula 3:

[0052]

[0053] and is bonded to the 1 or 16 position via the nitrogen atom.

[0054] In some embodiments, each of R2through R15are hydrogen, a halogen atom or an alkyl group comprising up to 12 carbon atoms. In some embodiments, at least 7 of R2through R15is hydrogen, or at least 8 or at least 9 or at least 10 or at least 11 or at least 12 or at least 13. In some embodiments, all of R2through R15are hydrogen. In some embodiments, no more than 4 of R2through R15are halogen, or no more than 3 or no more than 2 or no more than 1. In some embodiments, none of R2through R15are halogen. In some embodiments, the halogen is selected from chlorine or fluorine, and in some embodiments the halogen is fluorine. In some embodiments, no more than 4 of R2through R15are alkyl, or no more than 3 or no more than 2 or no more than 1. In some embodiments, none of R2through R15are alkyl. In some embodiments, at least 1 of R2through R15are alkyl or at least 2. In some embodiments, one or both of R3and R14are alkyl. In some embodiments, each alkyl group in R2through R15contains on average at most 10 carbon atoms or at most 8 carbon atoms or at most 6 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms or 1 carbon atom.

[0055] In some embodiments when they are present, each of R17through R24are hydrogen, a halogen atom or an alkyl group comprising up to 12 carbon atoms. In some embodiments, at least 4 of R17through R24are hydrogen, or at least 5 or at least 5 or at least 7 or at least 8. In some embodiments, all of R17through R24are hydrogen. In some embodiments, no more than 2 of R17through R24are halogen, or no more than 1. In some embodiments, none of R17through R24are halogen. In some embodiments, the halogen is selected from chlorine or fluorine, and in some embodiments the halogen is fluorine. In some embodiments, no more than 2 of R17through R24are alkyl, or no more than 1. In some embodiments, none of R17through R24are alkyl. In some embodiments, one or both of R19and R22are alkyl. In some embodiments, each alkyl group in R17through R24contains on average at most 10 carbon atoms or at most 8 carbon atoms or at most 6 carbon atoms or at most 4 carbon atoms or at most 3 carbon atoms or at most 2 carbon atoms or 1 carbon atom. Alkyl groups in R17through R24necessarily contain at least 1 carbon atom. In some embodiments, each alkyl group in R17through R24contains on average at least 2 carbon atoms or at least 3 carbon atoms or at least 4 carbon atoms or at least 6 carbon atoms or at least 8 carbon atoms.

[0056] In one embodiment, the catalyst system for the first component polymerization comprises a primary catalyst that meets Catalyst Formula IV. Some embodiments of the primary catalyst may comprise one or more adjacent homologs of the catalyst in Formula IV:

[0057]

[0058] (Catalyst Formula IV)

[0059] In some embodiments, the catalyst system used in the first component polymerization has a reactivity ratio for ethylene over the comonomer that is no more than 50 or no more than 40 or no more than 30 or no more than 20 or no more than 18 or no more than 16. In some embodiments, the catalyst system used in the first component polymerization has a reactivity ratio for ethylene over the comonomer that is at least 1 or at least 5 or at least 8 or at least 10 or at least 12 or at least 14.

[0060] The product of the first component polymerization can be a solution containing the first component dissolved in the solvent. In some embodiments, the solution further contains unreacted ethylene, unreacted comonomers, unreacted hydrogen and / or active catalysts and cocatalysts, in addition to the first component.

[0061] The Second Component Polymerization

[0062] The second component polymerization process produces the second component having a lower molecular weight than the first component and lower levels of comonomer incorporation than the first component.

[0063] The second component polymerization can be carried out using from 96 to 100 weight percent ethylene and from 0 to 4 weight percent comonomers selected from 1 -hexene, 1 -heptene and 1-octene. In some embodiments, the comonomers consist essentially of 1-hexene. In some embodiments, the comonomers consist essentially of 1-heptene. In some embodiments, the comonomers consist essentially of 1-octene. In some embodiments, the comonomers contain a mixture two or more comonomers selected from 1-hexene, 1-heptene and 1-octene. In some embodiments, the comonomer(s) are the same as in the first component polymerization. In some embodiments, the comonomer(s) are different from the first component polymerization. Where the second component is a homopolymer, the second component can be polymerized in the presence of 0 weight percent comonomer. In some embodiments, when there is a carry-over or connection in a dual-reactor process, for example, the second component can comprise a detectable level of comonomer even if it is polymerized without the presence, injection, or flow of comonomer into the reactor where the second component is being polymerized.

[0064] In some embodiments, the monomer mix fed into the second component polymerization contains at least 97 weight percent ethylene (based on the total weight of monomers) or at least 98 weight percent. In some embodiments, the monomer mix in the second component polymerization contains at most 100 weight percent ethylene (based on the total weight of monomers) or at most 99 weight percent or at most 98 weight percent. In some embodiments, the monomer mix fed into the second component polymerization contains 0 weight percent comonomer (based on the total weight of monomers) or at least 1.0 weight percent or at least 1.5 weight percent or at least 2.0 weight percent. In some embodiments, the monomer mix in the second component polymerization contains at most 3 weight percent comonomer, or at most 2 weight percent.

[0065] The monomer mix may optionally contain a small quantity of ethylenically-unsaturated comonomers other than 1 -hexene, 1 -heptene and 1 -octene. Examples of other comonomers include other a-olefins such as propylene, 1 -butene, 1 -pentene, 1 -nonene and 1 -decene. In some embodiments, the quantity of other comonomers is less than 2 weight percent (based on the total weight of monomers in the second component polymerization) or less than 1.5 weight percent or less than 1 weight percent or as low as 0 weight percent.

[0066] It should be noted that, when the second component polymerization comes after the first component polymerization, the reaction mixture flowing from the first component polymerization to the second component polymerization may contain unreacted ethylene and comonomer from the first component polymerization, as well as unreacted hydrogen and active catalyst from the first component polymerization.

[0067] The second component polymerization can be formed in the presence of a Ziegler-Natta catalyst system. Ziegler-Natta catalysts are well-known and commercially available, such as under the UCAT™ trademark.

[0068] Some embodiments of Ziegler-Natta catalyst system useful in the second component polymerization comprise: a porous support; a layer of magnesium chloride deposited on the support; and a titanium chloride compound and tri-alkyl aluminum deposited on the layer of magnesium chloride. Trialkyl aluminum in the Ziegler-Natta catalyst can act as a cocatalyst for the titanium chloride compound. Primary catalysts in the second component polymerization may be activated with an activator and / or cocatalyst. The cocatalysts and activators can be as previously described.

[0069] The product of the second component polymerization can be a solution containing the second component of the composition. In some embodiments, a solution with the second component further contains unreacted ethylene, unreacted comonomers, unreacted hydrogen and / or active catalysts and cocatalysts.

[0070] Product Recovery:

[0071] After the first component polymerization and the second component polymerization, polymerization can be terminated, and the composition can be recovered.

[0072] In some embodiments, the molten copolymer is pelletized according to known means, such as by extruding strands of molten polymer into a cooling water bath and chopping the strands into pellets.

[0073] Multimodal Polyethylene Composition

[0074] The composition has a density from 0.940 g / cm3to 0.955 g / cm3; a melt index (I2) of at least 0.30 g / 10 min; and a TpMw of greater than 145,000 g / mol at an elution temperature range of 90.0°C to 95.0°C.

[0075] The composition comprises a first component and a second component. The first component is or consists of a first ethylene / a-olefin copolymer and the second component is or consists of a second ethylene / a-olefin copolymer or homopolymer. In some embodiments, the second component makes up at least 45 weight percent of the composition (based on the total weight of composition) or at least 48 weight percent or at least 50 weight percent or at least 51 weight percent or at least 53 weight percent or at least 55 weight percent. In some embodiments, the second component makes up at most 65 weight percent of the blend (based on the total weight of composition) or at most 63 weight percent or at most 61 weight percent or at most 59 weight percent or at most 57 weight percent or at most 55 weight percent. In some embodiments, the first component makes up at least 35 weight percent of the blend (based on the total weight of first component) or at least 37 weight percent or at least 39 weight percent or at least 41 weight percent or at least 43 weight percent or at least 45 weight percent. In some embodiments, the first component makes up at most 55 weight percent of the blend (based on the total weight of PE polymer) or at most 52 weight percent or at most 50 weight percent or at most 49 weight percent or at most 47 weight percent or at most 45 weight percent.

[0076] The composition has a density from 0.940 g / cc to 0.955 g / cc. In some embodiments, the composition has a density of at least 0.941 g / cc or at least 0.942 g / cc or at least 0.943 g / cc or at least 0.944 g / cc or at least 0.945 g / cc. In some embodiments, the composition has a density of at most 0.953 g / cc or at most 0.951 g / cc or at most 0.950 g / cc or at most 0.949 g / cc or at most 0.948 g / cc or at most 0.947 g / cc or at most 0.946 g / cc or at most 0.945 g / cc.

[0077] The composition has a melt index (12) of at least 0.30 g / 10 min. In some embodiments, the composition has a melt index (12) of at least 0.35 g / 10 min or at least 0.40 g / 10 min, at least 0.42 g / 10 min or at least 0.44 g / 10 min or at least 0.46 g / 10 min or at least 0.48 g / 10 min or at least 0.50 g / 10 min or at least 0.52 g / 10 min or at least 0.54 g / 10 min or at least 0.55 g / 10 min or at least 0.56 g / 10 min or at least 0.57 g / 10 min. In some embodiments, the composition has a melt index (12) of at most 2.00 g / 10 min or at most 1.50 g / 10 min or at most 1.40 g / 10 min or at most 1.00 g / 10 min or at most 0.80 g / 10 min or at most 0.70 g / 10 min or at most 0.60 g / 10 min.

[0078] The composition has a TpMW of greater than 145,000 g / mol at an elution temperature range of 90.0°C to 95.0°C. In some embodiments, the composition has a TPMW of greater than 147,000 g / mol, or greater than 148,000 g / mol, or greater than 149,000 g / mol, or greater than 150,000 g / mol at an elution temperature range of 90.0°C to 95.0°C. The TpMW is measured in accordance with the test methods described below. Without being bound by theory, the multimodal compositions combination of two components and overall density, melt flows, and TPMW deliver the compositions desirable balance of properties, including, for example, the CRB, PENT, and hydrostatic strength.

[0079] In some embodiments, the composition has a number average molecular weight (Mn) of at least 10,000 g / mol or at least 11,000 g / mol or at least 12,000 g / mol or at least 13,000 g / mol or at least 14,000 g / mol or at least 15,000 g / mol. In some embodiments, the composition has a number average molecular weight of at most 30,000 g / mol or at most 25,000 g / mol or at most 22,000 g / mol or at most 20,000 g / mol or at most 18,000 g / mol or at most 16,000 g / mol.

[0080] The composition in some embodiments has a weight average molecular weight (Mw) from 100,000 g / mol to 200,000 g / mol. In some embodiments, the composition has a weight average molecular weight (Mw) of at least 105,000 g / mol or at least 110,000 g / mol or at least 115,000 g / mol or at least 118,000 g / mol or at least 120,000 g / mol. In some embodiments, the composition has a weight average molecular weight (Mw) of at most 190,000 g / mol or at most 170,000 g / mol or at most 150,000 g / mol or at most 140,000 g / mol or at most 130,000 g / mol.

[0081] In some embodiments, the composition has a z-average molecular weight (Mz) of at least 250,000 g / mol or at least 300,000 g / mol or at least 320,000 g / mol or at least 340,000 g / mol or at least 360,000 g / mol or at least 380,000 g / mol or at least 400,000 g / mol. In some embodiments, the composition has a z-average molecular weight of at most 1,000,000 g / mol or at most 800,000 g / mol or at most 600,000 g / mol or at most 500,000 g / mol or at most 450,000 g / mol.

[0082] The composition in some embodiments has a molecular weight distribution (Mw / Mn) from 4.0 to 12.0. In some embodiments, the composition has molecular weight distribution (Mw / Mn) of at least 4.0 at least 5.0 at least 5.5 at least 6.2 or at least 6.4 or at least 6.6 or at least 6.8 or at least 7.0 or at least 7.2 or at least 7.4 or at least 7.6 or at least 7.8 or at least 8.0 or at least 8.1. Tn some embodiments, the composition has a molecular weight distribution (Mw / Mn) of at most 12.0 or at most 11.0 or at most 10.0 or at most 9.5 or at most 9.3 or at most 9.1 or at most 8.9 or at most 8.7 or at most 8.5 or at most 8.3.

[0083] In some embodiments, the composition has a dynamic viscosity (T|) at 0.01 rad / s of at least 18,000 Pa»s or at least 20,000 Pa»s or at least 21,000 Pa»s or at least 22,000 Pa»s or at least 23,000 Pa»s or at least 24,000 Pa*s or at least 24,000 Pa»s. In some embodiments, the bimodal PE copolymer has a dynamic viscosity (η) at 0.01 rad / s of at most 80,000 Pars or at most 35,000 Pa»s or at most 33,000 Pa*s or at most 31,000 Pa*s or at most 30,000 Pa*s or at most 29,000 Pa*s or at most 28,000 Pa»s or at most 27,000 Pa»s or at most 26,000 Pa»s.

[0084] In some embodiments, the composition has a dynamic viscosity (η) at 100 rad / s of at least 900 Pa*s or at least 1000 Pars or at least 1100 Pa»s or at least 1200 Pa*s or at least 1300 Pars or at least 1400 Pa»s or at least 1500 Pa»s. In some embodiments, the bimodal PE copolymer has a dynamic viscosity (η) at 100 rad / s of at most 3000 Pa*s or at most 2800 Pa*s or at most 2600 Pa»s or at most 2400 Pa»s or at most 2200 Pa»s or at most 2000 Pa»s or at most 1800 Pa»s or at most 1700 Pa»s or at most 1600 Pa»s.

[0085] In some embodiments, the composition has a shear thinning ratio (r| o.oi / i] 100) from 12 to 30. In some embodiments, the composition has a shear thinning ratio (T| O. OI / h IOO) of at least 12.5 or at least 13.0 or at least 13.5 or at least 14.0 or at least 14.5 or at least 15.0 or at least 15.5 or at least 16.0. In some embodiments, the composition has a shear thinning ratio (T| O. OI / n ioo) of at most 35 or at most 30 or at most 28 or at most 26 or at most 24 or at most 22 or at most 20 or at most 19 or at most 18 or at most 17 or at most 16.

[0086] Cong et al., PCT Patent Application W02017 / 040127 Al (9 Mar 2017) describes an improved method to measure comonomer content and distribution of polyolefins (iCCD), which is adapted from temperature rising elution fractionation (TREF). The Test Methods describe specific implementation of the iCCD analysis. In iCCD analysis, a polymer can be divided into a fraction that elutes at different temperatures. The Test Methods describe specific implementation of the iCCD analysis. In some embodiments, the composition has an elution of at least 4.0 weight percent of polymer between 35.0°C and 90.0°C or at least 5.0 weight percent or at least 6.0 weight percent or at least 7.0 weight percent or at least 8.0 weight percent or at least 10.0 weight percent, when measured in accordance with the iCCD test method below. In some embodiments, the composition has an elution of at most 15.0 weight percent of polymer between 35°C and 90.0°C or at most 14.0 weight percent or at most 13.0 weight percent or at most 12.5 weight percent or at most 12.0 weight percent or at most 11.0 weight percent, when measured in accordance with the iCCD test method below.

[0087] In some embodiments, the composition has an elution of at least 85.0 weight percent of polymer above 90.0°C, or at least 86.0 weight percent or at least 88.0 weight percent, when measured in accordance with the iCCD test method in the description. In some embodiments, the composition has an elution of at most 96.0 weight percent of polymer above 90.0°C or at most 95.0 weight percent or at most 94.0 weight percent or at most 92.0 weight percent or at most 91.0 weight percent, when measured in accordance with the iCCD test method in the description.

[0088] In some embodiments, the composition can blended with one or more additives, such as during pelletizing or when it is formed into a finished product or both. Examples of common additives include antistatic agents, dyes, lubricants, fillers, pigments, primary antioxidants, secondary antioxidants, processing aids, UV stabilizers, nucleators, slip agents such as erucamide, antiblock agents such as talc, and combinations thereof.

[0089] The multimodal polyethylene composition comprises a first component and a second component. The first component consists of a first ethylene / a-olefin copolymer. The second component consists of a second ethylene / a-olefin copolymer or homopolymer. In some embodiments, the composition comprises less than 48 wt.% of the first component and greater than 52 wt.% of the second component. In some embodiments, the composition comprises less than 47 wt.% of the first component, and greater than 53 wt.% of the second component. In some embodiments, the first component has a Mw greater than 200,000 g / mol, or greater than 225,000 g / mol; a Mn of greater than 60,000 g / mol, or greater than 70,000 g / mol, or greater than 80,000 g / mol; a Mz of greater than 375,000 g / mol, or greater than 400,000 g / mol, or greater than 425,000 g / mol. In some embodiments, the second component has a Mw of less than 50,000 g / mol, or less than 40,000 g / mol; a Mn of less than 20,000 g / mol, or less than 15,000 g / mol; a Mz of less than 120,000 g / mol, less than 100,000 g / mol, less than 90,000 g / mol. The molecular weight split along with the comonomer or density split of the components can contribute to the desirable properties discussed herein. Pipe and Other Shaped Articles

[0090] The composition according to embodiments disclosed herein can be formed into articles, such as blow molded articles and pipes. The compositions may be particularly useful in extruded pipes and conduits.

[0091] Extrusion of a polyethylene to form a pipe is well known. In a pipe extrusion line, polyethylene is melted in an extruder and extruded through an annular die to form a tubular melt. The molten pipe then passes through a sizing or calibration device (which gives its dimensions) and into a cooling trough. The cooled pipe may be coiled or cut to desired lengths. Printing devices in the line may mark the extruded pipes for identification.

[0092] Extruded pipes may be subject to a number of specifications and testing requirements. Good strain hardening modulus can be desirable in resins used for pipes. In some embodiments, the composition has a strain hardening modulus of at least 50 MPa or at least 52 MPa or at least 54 MPa or at least 56 MPa or at least 58 MPa or at least 59 MPa. Good hydrostatic strength (e.g., resistance to bursting from water pressure) can be desirable for pipes, both at room temperature and at higher temperatures. A pipe comprising the composition according to embodiments disclosed herein can have a pipe hydrostatic strength, determined according to ISO 1167, of greater than 10,000 hours at 20°C. and 10.8 MPa as specified in ISO 22391-2. In some embodiments, a pipe comprising the composition can have a a pipe hydrostatic strength, determined according to ISO 1167, of greater than 10,000 hours at 95°C. and 3.9 MPa as specified in ISO 22391-2. Good Pennsylvania Notch Test (PENT) and Cracked Round Bar (CRB) Test can be desirable for pipes. In some embodiments, the composition has a PENT of greater than 2,000 hours (when molded into a plaque). The composition can have a PENT of greater than 3,000 hours, or 4,000 hours, or 5,000 hours. A pipe comprising the composition according to embodiments disclosed herein can have a CRB at 12.5 MPa test for at least 500,000 cycles or at least 600,000 cycles or at least 650,000 cycles or at least 700,000 cycles or at least 750,000 cycles.

[0093] Test Methods

[0094] Unless stated otherwise, measurements discussed above and listed in this application are made using the following test methods:

[0095]

[0096] Gel Permeation Chromatography (GPC)

[0097] The chromatographic system consisted of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5) and 4-capillary viscometer (DV) coupled to a Precision Detectors (Now Agilent Technologies) 2-angle laser light scattering (LS) detector Model 2040. For all absolute Light scattering measurements, the 15 degree angle is used for measurement. The autosampler oven compartment was set at 160° Celsius and the column and detector compartment were set at 150° Celsius. The columns used were 4 Agilent “Mixed A” 30cm 20-micron linear mixed-bed columns. The chromatographic solvent used was 1,2,4 trichlorobenzene and contained 200 ppm of butylated hydroxytoluene (BHT). The solvent source was nitrogen sparged. The injection volume used was 200 microliters and the flow rate was 1.0 milliliters / minute.

[0098] The total plate count of the GPC column set was performed with decane which was introduced into blank sample via a micropump controlled with the PolymerChar GPC-IR system. The plate count for the chromatographic system should be greater than 18,000 for the 4 Agilent “Mixed A” 30cm 20-micron linear mixed-bed columns.

[0099] Samples were prepared in a semi-automatic manner with the PolymerChar “Instrument Control” Software, wherein the samples were weight-targeted at 2 mg / ml, and the solvent (contained 200ppm BHT) was added to a pre nitrogen-sparged septa-capped vial, via the PolymerChar high temperature autosampler. The samples were dissolved for 2 hours at 160° Celsius under “low speed” shaking.

[0100] In order to monitor the deviations over time, a flowrate marker (decane) was introduced into each sample via a micropump controlled with the PolymerChar GPC-IR system. This flowrate marker (FM) was used to linearly correct the pump flowrate (Flowrate(nominal)) for each sample by RV alignment of the respective decane peak within the sample (RV(FM Sample)) to that of the decane peak within the narrow standards calibration (RV(FM Calibrated)). Any changes in the time of the decane marker peak are then assumed to be related to a linear-shift in flowrate (Flowrate(effective)) for the entire run. After calibrating the system based on a flow marker peak, the effective flowrate (with respect to the narrow standards calibration) is calculated as Equation 5. Processing of the flow marker peak was done via the PolymerChar GPCOne™ Software. Acceptable flowrate correction is such that the effective flowrate should be within + / - O.5% of the nominal flowrate.

[0101] Flowrate(effective) = Flowrate(nominal) * (RV(FM Calibrated) / RV(FM Sample)) (EQI)

[0102] Triple Detector GPC (TDGPC)

[0103] For the determination of the viscometer and light scattering detector offsets from the IR5 detector, the Systematic Approach for the determination of multi-detector offsets is done in a manner consistent with that published by Balke, Mourey, et. al. (Mourey and Balke, Chromatography Polym. Chpt 12, (1992)) (Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym. Chpt 13, (1992)), optimizing triple detector log (MW and IV) results from a linear homopolymer polyethylene standard (3.5 > Mw / Mn > 2.2) with a molecular weight in the range of 115,000 to 125,000 g / mol to the narrow standard column calibration results from the narrow standards calibration curve using PolymerChar GPCOne™ Software.

[0104] The absolute molecular weight data was obtained in a manner consistent with that published by Zimm (Zimm, B. H., J. Chem. Phys., 16, 1099 (1948)) and Kratochvil (Kratochvil, P., Classical Light Scattering from Polymer Solutions, Elsevier, Oxford, NY (1987)) using PolymerChar GPCOne™ software. The overall injected concentration, used in the determination of the molecular weight, was obtained from the mass detector area and the mass detector constant, derived from a suitable linear polyethylene homopolymer, or one of the polyethylene standards of known weight-average molecular weight. The calculated molecular weights (using GPCOne™) were obtained using a light scattering constant, derived from one or more of the polyethylene standards mentioned below, and a refractive index concentration coefficient, dn / dc, of -0.104. Generally, the mass detector response (IR5) and the light scattering constant (determined using GPCOne™) should be determined from a linear standard with a molecular weight in excess of about 50,000 g / mole. The viscometer calibration (determined using GPCOne™) can be accomplished using the methods described by the manufacturer, or, alternatively, by using the published values of suitable linear standards, such as Standard Reference Materials (SRM) 1475a (available from National Institute of Standards and Technology (NIST)). A viscometer constant (obtained using GPCOne™) is calculated which relates specific viscosity area (DV) and injected mass for the calibration standard to its intrinsic viscosity. The chromatographic concentrations are assumed low enough to eliminate addressing 2nd viral coefficient effects (concentration effects on molecular weight).

[0105] The absolute weight average molecular weight (MW(Abs)) is obtained (using GPCOne™) from the Area of the Light Scattering (LS) integrated chromatogram (factored by the light scattering constant) divided by the mass recovered from the mass constant and the mass detector (IR5) area. The molecular weight and intrinsic viscosity responses are linearly extrapolated at chromatographic ends where signal to noise becomes low (using GPCOne™). Other respective moments, Mn(Abs) and Mz(Abs) are be calculated according to equations 2-4 as follows:

[0106]

[0107] Deconvolution of GPC Chromatogram - The fitting of the chromatogram into a high molecular weight (HMW) and low molecular weight (LMW) component fraction was accomplished using a Flory distribution which was broadened with a normal distribution function as follows: For the log M axis, 601 equally-spaced Log(M) points, spaced by 0.01, were established between 2 and 8 representing the molecular weight range between 100 and 100,000,000 where Log is the logarithm function to the base 10. At any given Log (M), the population of the Flory distribution was in the form of Eq. 5:

[0108]

[0109] where Mw is the weight- average molecular weight of the Flory distribution and M is the specific x-axis molecular weight point, (10A[Log(M)]). The Flory distribution weight fraction was broadened at each 0.01 equally-spaced log(M) index according to a normal distribution function, of width expressed in Log(M), □; and current M index expressed as Log(M), >, as shown in Eq.

[0110] 6:

[0111]

[0112] It should be noted that before and after the spreading function has been applied that the area of the distribution (dWf / dLogM) as a function of Log(M) is normalized to unity. Two weight-fraction distributions, dWf i and dWf 2, for LMW and HMW components or components 1 and 2 were expressed with two unique Mw target values, Mwi and Mw2 and with overall component compositions Ai and A2, where each composition wt% is determined by the reactor process. Both distributions were broadened with the same width,,v. The two distributions were summed as follows in Eq. 7:

[0113] dWf / dLogM = ArdW^ / dLogM + A2dWf2 / dLogM Eq. 7 where: A1+A2 = 1

[0114] The weight fraction result of the measured (from Absolute GPC) GPC molecular weight distribution was interpolated along 601 log M points using a 2nd-order polynomial. Microsoft Excel™ 2010 Solver was used to minimize the sum of squares of residuals for the equally-spaces range of 601 LogM points between the interpolated chromatographically determined molecular weight distribution and the two broadened Flory distribution components (s1and s2), weighted with their respective component compositions, Ai and A2. The iteration starting values for the components are as follows:

[0115] Component 1: Mwi = 28,000, s = 0.200

[0116] Component 2: Mwi = 210,000, s = 0.200 (Note 5i = 52 and Ai + Az= 1)

[0117] The bounds for components 1 and 2 are such that 5 is constrained such that 5 > 0.001, yielding an Mw / Mn of approximately 2.00 and 5 < 0.450, yielding a Mw / Mn of approximately 5.71. The composition, Ai, is constrained between 0.000 and 1.000. The Mwi is constrained between 2,500 and 2,000,000. The composition, Ao, is constrained between 0.000 and 1.000. The Mw2 is constrained between 2,500 and 2,000,000. The “GRG Nonlinear” engine was selected in Excel Solver™ and precision was set at 0.00001 and convergence was set at 0.0001. The solutions were obtained after convergence (in all cases shown, the solution converged within 60 iterations).

[0118] ICCD

[0119] Improved method for comonomer content analysis (iCCD) was developed in 2015 (Cong and Parrott et al., W02017040127A1). iCCD test was performed with Crystallization Elution Fractionation instrumentation (CEF) (PolymerChar, Spain) equipped with IR-5 detector (PolymerChar, Spain) and two angle light scattering detector Model 2040 (Precision Detectors, currently Agilent Technologies). Ortho-dichlorobenzene (ODCB, 99% anhydrous grade or distilled) was used. Silica gel 40 (particle size 0.2~0.5 mm, catalogue number 10181-3) from EMD Chemicals was obtained (can be used to dry ODCB solvent before). The CEF instrument is equipped with an autosampler with N2 purging capability. ODCB is sparged with dried nitrogen (N2) for one hour before use. Sample preparation was done with autosampler at 4 mg / ml (unless otherwise specified) under shaking at 160°C for 1 hour. The injection volume was 300pl. The temperature profile of iCCD was: crystallization at 3°C / min from 105°C to 30°C, the thermal equilibrium at 30°C for 2 minute (including Soluble Fraction Elution Time being set as 2 minutes), elution at 3°C / min from 30°C to 140°C. The flow rate during crystallization is 0.0 ml / min. The flow rate during elution is 0.50 ml / min. The data was collected at one data point / second.

[0120] The iCCD column was packed with gold coated nickel particles (Bright 7GNM8-NiS, Nippon Chemical Industrial Co.) in a 15cm (length)Xl / 4” (ID) stainless tubing. The column packing and conditioning were with a slurry method according to the reference (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. W02017040127A1). The final pressure with TCB slurry packing was 150 Bars.

[0121] Column temperature calibration was performed by using a mixture of the Reference Material Linear homopolymer polyethylene (having zero comonomer content, Melt index (I2) of 1.0, poly dispersity Mw / Mnapproximately 2.6 by conventional gel permeation chromatography, l. Omg / ml) and Eicosane (2mg / ml) in ODCB. iCCD temperature calibration consisted of four steps: (1) Calculating the delay volume defined as the temperature offset between the measured peak elution temperature of Eicosane minus 30.00° C; (2) Subtracting the temperature offset of the elution temperature from iCCD raw temperature data. It is noted that this temperature offset is a function of experimental conditions, such as elution temperature, elution flow rate, etc.; (3) Creating a linear calibration line transforming the elution temperature across a range of 30.00° C and 140.00° C so that the linear homopolymer polyethylene reference had a peak temperature at 101.0°C, and Eicosane had a peak temperature of 30.0° C; (4) For the soluble fraction measured isothermally at 30° C, the elution temperature below 30.0° C is extrapolated linearly by using the elution heating rate of 3° C / min according to the reference (Cerk and Cong et al., US9,688,795).

[0122] The comonomer content versus elution temperature of iCCD was constructed by using 12 reference materials (ethylene homopolymer and ethylene-octene random copolymer made with single site metallocene catalyst, having ethylene equivalent weight average molecular weight ranging from 35,000 to 128,000 g / mol). All of these reference materials were prepared at 4 mg / mL and analyzed the same way as specified previously. The mathematical fit of the reported elution peak temperatures as a function of octene mol% using linear regression resulted in Equation 1 (EQI) for which R2was greater than 0.97.

[0123] (Elution Temperature in Degrees C) = — 6.3515 x (Octene Mol%) + 101.0 (EQI) A linear baseline is calculated by selecting two data points: one before the polymer elutes, at temperature of 28°C or below, and another one after the polymer elutes, at 120°C or above. For each data point, the detector signal is subtracted from the baseline before integration.

[0124] Molecular weight of polymer and the molecular weight of the polymer fractions was determined directly from LS detector (90 degree angle) and concentration detector (IR-5) according Rayleigh-Gans-Debys approximation (Striegel and Yau, Modem Size Exclusion Liquid Chromatogram, Page 242 and Page 263) by assuming the form factor of 1 and all the virial coefficients equal to zero. Baselines were subtracted from LS, and concentration detector chromatograms. Integration windows are set to integrate all the chromatograms in the elution temperature (temperature calibration is specified above) range from 23.0 to 120°C.

[0125] The calculation of Molecular Weight (MW) from iCCD includes the following steps:

[0126] (1) Measuring the interdetector offset. The offset is defined as the geometric volume offset between LS with respect to concentration detector. It is calculated as the difference in the elution volume (mL) of polymer peak between concentration detector and LS chromatograms. It is converted to the temperature offset by using elution thermal rate and elution flow rate. A linear high density polyethylene homopolymer (having non-measurable comonomer content, Melt index (L) of 1.0, polydispersity Mw / Mnin the range of 2.2 to 3.5 by conventional gel permeation chromatography) is used. Same experimental conditions as the normal iCCD method above are used except the following parameters: crystallization at 10°C / min from 140°C to 137°C, the thermal equilibrium at 137°C for 1 minute as Soluble Fraction Elution Time, soluble fraction (SF) time of 7 minutes, elution at 3°C / min from 137°C to 142°C. The flow rate during crystallization is 0.0 ml / min. The flow rate during elution is 0.80 ml / min. Sample concentration is l. Omg / ml.

[0127] (2) Each LS datapoint in LS chromatogram is shifted to correct for the interdetector offset before integration.

[0128] (3) Baseline subtracted LS and concentration chromatograms are integrated for the whole eluting temperature range of the Step (1). The MW detector constant (K) is calculated by using the same linear high density polyethylene homopolymer sample as described above with a Mw in the range of 100,000 to 140,000 g / mol and the area ratio of the LS and concentration integrated signals.

[0129] (4) Molecular weight, MW, at each retention temperature, i, is calculated as the baseline subtracted LS signal / the baseline subtracted IR5 signal / MW detector constant (K).

[0130] (5) The weight average molecular weight, Mw, of the polymer was calculated by using the ratio of the baseline subtracted integrated light scattering detector (90 degree angle) area to the baseline subtracted integrated concentration detector area and using the MW detector constant (K). With the measured MW detector constant (K), NIST NBS 1475a analyzed with same method specified in (1) above gave molecular weight of 58,000 g / mol.

[0131] (6) The white noise level of the LS detector (90 degree) is calculated from the LS chromatogram prior to the polymer eluting. The LS chromatogram is first corrected for the baseline correction to obtain the baseline subtracted signal. The white noise of the LS is calculated as the standard deviation of the baseline subtracted LS signal by using 40 data points prior to the polymer eluting. Typical white noise for LS is 0.20 to 0.35 mV while the whole polymer has a baseline subtracted peak height typically around 170 mV for the linear high density polyethylene homopolymer with non-measurable comonomer, 12 of 1.0, polydispersity Mw / Mn in the range of 2.2 to 3.5, which is used in the interdetector offset measurements. The requirement for calculating MW is that the signal to noise ratio (the peak height of the whole polymer to the white noise) is at least 500 for the high density polyethylene GPCOne™ software (available from PolymerChar) is used to generate a SCBD distribution curve, dWf / dT, where Wf is the mass fraction at each elution temperature after calibration, T. The temperature increments are equally spaced at 0.2°C.

[0132] Within the elution temperature zone of 90.0-95.0°C, the existence of a peak is found in the SCBD distribution curve, whereby a peak is defined as the point having both the maximum signal (dWf / dT) and a first derivative value of zero, is given a corresponding temperature value, Tp. The MW at this peak temperature point, Tp, is assigned to be the TP, MW. Where the signal to noise ratio, at Tp, of the LS (90 degree) baseline subtracted signal to the white noise of the baseline subtracted LS (calculated as the standard deviation using at least 100 data points prior to the polymer eluting) is at least 500.

[0133] Examples

[0134] The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention. The materials in Table 1 are used for the Examples:

[0135] Table 1

[0136]

[0137] Inventive Example 1 (IE1) Polymer Synthesis:

[0138] A multimodal composition is made by polymerizing ethylene and 1 -octene using solution polymerization in a dual-loop reactor. The solvent is Isopar E fluid from ExxonMobil. Reactor 1 makes a first component (High Molecular Weight Component) ethylene / 1 -octene copolymer of the composition, and the reaction mixture feeds to Reactor 2, which makes second component (Low Molecular Weight Component) of the composition.

[0139] The ethylene monomer and 1-octene comonomer are dissolved in the solvent in the ratios shown in Table 2 for Reactor 1 feeds to make a first solution. The catalyst system listed in Table 2 for Reactor 1 feeds is dissolved in solvent to make a first catalyst solution. The first solution and first catalyst solution and hydrogen are fed into Reactor 1 to achieve the flows shown in Table 2 for Reactor 1 feeds. An exothermic reaction occurs, and Reactor 1 is cooled to the temperature shown in Table 2. Pressure in Reactor 1 is about 600 psi. After an average residence time of 20 mins, the reaction solution flows from Reactor 1 to Reactor 2.

[0140] The ethylene monomer and 1-octene comonomer are dissolved in the solvent in the ratios shown in Table 2 for Reactor 2 feeds to make a second solution. The catalyst system listed in Table 2 for Reactor 2 feeds is dissolved in solvent to make a second catalyst solution. The second solution and second catalyst solution and hydrogen are fed into Reactor 2 with the effluent from Reactor 1 to achieve the flows shown in Table 2 for Reactor 2 feeds. An exothermic reaction occurs, and Reactor 2 is cooled to the temperature shown in Table 2. Pressure in Reactor 2 is about 600 psi. After an average residence time of about 20 mins, the solution contains finished bimodal copolymer dissolved in solvent. The copolymer solution flows from Reactor 2 to a devolatilization step.

[0141] In the devolatilization step, any remaining catalyst in the solution is neutralized. Volatile components such as solvent and unreacted monomers and hydrogen are flash distilled off, leaving the composition. The molten composition is pelletized.

[0142] Table 2: Reaction Conditions

[0143]

[0144]

[0145] Comparative Example 1 (CE1) Polymer Synthesis: The product is a bimodal HDPE copolymer having the properties shown in Table 3.

[0146] Comparative Example 2 (CE2) Polymer Synthesis: Sample CE2 was produced using a Ziegler Natta catalyst system, UCAT™ J (commercially available from Univation Technologies, LLC, Houston, TX), and a cocatalyst, triethylaluminum (TEAL), in a dual reactor gas phase polymerization process. The product is a bimodal HDPE copolymer having the properties shown in Table 3.

[0147] Comparative Example 3 (CE3) is made in accordance with the procedures provided for Inventive Example 1 in WO2017151358A1

[0148] The compositions are tested according to the Test Methods. The pellets are extruded into test pipes according to the Test Methods, and the pipes are subjected to hydrostatic strength testing, according to the Test Methods. Results of the tests and analyses are listed in Table 3.

[0149] The molecular weight distribution profiles for IE1, CE1 and CE2 are shown in Figure 1. The iCCD elution profiles for IE1, CE1 and CE2 are shown in Figure 2. The molecular weight distribution profiles for IE1, CE1 and CE3 are shown in Figure 1. The iCCD elution profiles for IE1, CE1 and CE3 are shown in Figure 2. The dynamic viscosity curves measured for IE1, CE1 and CE3 are shown in Figure 3.

[0150]

[0151]

Claims

CLAIMS:We claim:

1. A multimodal polyethylene composition comprising a first component and a second component, wherein the composition has:(a) a density from 0.940 g / cm3to 0.955 g / cm3;(h) a melt index (I2) of at least 0.30 g / 10 min; and(c) a TpMW of greater than 145,000 g / mol at an elution temperature range of 90.0°C to 95.0°C;wherein the first component consists of a first ethylene / a-olefin copolymer and the second component consists of a second ethylene / a-olefin copolymer or homopolymer; wherein the first component has a higher weight average molecular weight (Mw) than the second component.

2. The multimodal polyethylene composition of claim 1, wherein the second component has a comonomer content at least 2 wt.% less than the comonomer content of the first component.

3. The multimodal polyethylene composition of any one of the preceding claims, wherein the second component has a molecular weight distribution (Mw / Mn) of greater than 2.50.

4. The multimodal polyethylene composition of any one of the preceding claims, wherein the composition has an elution of at least 4.0 weight percent of polymer between 35.0°C and 90.0°C, and an elution of at most 96.0 weight percent of polymer above 90.0°C, when measured in accordance with the iCCD test method in the description.

5. The multimodal polyethylene composition of any one of the preceding claims, wherein the second component comprises greater than 52 wt.% of the composition, based on the total weight of the composition.

6. The multimodal polyethylene composition of any one of the preceding claims, wherein the composition has a weight average molecular weight (Mw) from 100,000 g / mol to 200,000 g / mol.

7. The multimodal polyethylene composition of any one of the preceding claims, wherein the copolymer has a molecular weight distribution (Mw / Mn) of 4.0 to 12.0.

8. The multimodal polyethylene composition of any one of the preceding claims, wherein the composition has a shear thinning ratio (η0.01 / η100) in the range of from 12.0 to 30.

09. The multimodal polyethylene composition of any one of the preceding claims, wherein the TpMW of is greater than 150,000 g / mol at an elution temperature range of 90.0°C to 95.0°C.

10. The multimodal polyethylene composition of any one of the preceding claims, wherein the first component has a weight average molecular weight distribution (Mw) of greater than 200,000 g / mol, and the second component has a weight average molecular weight distribution (Mw) of less than 50,000 g / 10 mol, and wherein the composition comprises less than 48 wt.% of the first component, and greater than 52 wt.% of the second component.

11. The multimodal polyethylene composition of any one of the preceding claims, wherein the first ethylene / a-olefin copolymer and the second ethylene / a-olefin copolymer consist of ethylene and a comonomer selected from the group consisting of 1 -hexene, 1 -heptene, and 1-octene.

12. The multimodal polyethylene composition of any one of the preceding claims, wherein the copolymer has a strain hardening modulus of at least 50 MPa.

13. The multimodal polyethylene composition of any one of the preceding claims, wherein the multimodal polyethylene composition has a dynamic viscosity (η) at 0.01 rad / s of greater than 20,000 Pa.s.

14. The multimodal polyethylene composition of any one of the preceding claims, wherein the multimodal polyethylene copolymer has a Mz of greater than 250,000 g / mol.

15. The multimodal polyethylene composition of any one of the preceding claims, wherein the composition has a PENT of greater than 2,000 hours.

16. A pipe comprising the multimodal polyethylene composition of claims 1 to 15.

17. The pipe of claim 16, wherein the pipe has a pipe hydrostatic strength, determined according to ISO 1167, of greater than 10,000 hours at 20°C. and 10.8 MPa as specified in ISO 22391-2.

18. The pipe of claim 16 or 17, wherein the pipe has a pipe hydrostatic strength, determined according to ISO 1167, of greater than 10,000 hours at 95°C. and 3.9 MPa as specified in ISO 22391-2.

19. The pipe of claim 16, 17, or 18, wherein the pipe has a CRB at 12.5 MPa of at least 500,000 cycles.

20. A process for making a multimodal polyethylene composition comprising:(a) polymerizing a first polyethylene component by solution polymerization from ethylene and a comonomer selected from 1 -hexene, 1 -heptene or 1 -octene, wherein the monomer mix feed in the first component polymerization comprises at least 90 weight percent of the ethylene and comprises at most 9 weight percent comonomer, in the presence of a catalyst system comprising a primary catalyst that meets Formula below:under conditions to produce the first component; and(b) polymerizing a second polyethylene component by solution polymerization to from ethylene and a comonomer selected from 1 -hexene, 1 -heptene or 1 -octene in the presence of a Ziegler-Natta catalyst system, wherein the monomer mix fed into the first component polymerization comprises at least 1 weight percent more comonomer than the monomer mix fed into the second component polymerization, to produce the second polyethylene component having a molecular weight distribution of greater than 2.50; andwherein M is titanium, zirconium, or hafnium, each independently being in a formal oxidation state of +2, +3, or +4; and n is an integer of from 0 to 3, and wherein when n is 0, X is absent; and each X independently is a monodentate ligand that is neutral, monoanionic, ordianionic; or two Xs are taken together to form a bidentate ligand that is neutral, monoanionic, or dianionic; and X and n are chosen in such a way that the metal-ligand complex of formula (IA) is, overall, neutral; and each Z independently is O, S, N(Cl-C40)hydrocarbyl, or P(C1-C40)hydrocarbyl; and the Z-L-Z fragment comprises a transition metal and ligand; andR1-16are selected from the group consisting of a (Ci-C4o)hydrocarbyl, (C1-C40)heterohydrocarbyl, Si(Rc)3, Ge(Rc)3, P(Rp)2, N(RN)2, ORC, SRC, NO2, CN, CF3, RCS(O)-, RCS(O)2-, (RC)2C=N-, RCC(O)O-, RCOC(O)-, RCC(O)N(R)-, (RC)2NC(O)-, halogen atom, hydrogen atom, and combinations thereof.

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