Ethylene-based polymers having a reverse comonomer distribution

Abstract

An ethylene-based polymer exhibits a density of 0.905 g / cc to 0.960 g / cc as measured according to ASTM D792 and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing. The ethylene-based polymer is made in a single reactor using a single catalyst of Structure (I) wherein R1 and R2 are each independently selected from an unbranched C3 to C8 hydrocarbyl, wherein R1 and R2 are not the same, and each X is independently selected from a C1 to C4 alkyl, a halide, an aryl or a benzyl.

Description

[0001] ETHYLENE-BASED POLYMERS HAVING A REVERSE COMONOMER DISTRIBUTION BACKGROUND

[0002] Field of the disclosure

[0003] The disclosure generally relates to ethylene-based polymers and more specifically to ethylene-based polymers having a reverse comonomer distribution.

[0004] Introduction

[0005] Copolymers are polymers made of two or more monomers that are produced under polymerization conditions. In polyolefins with a majority of ethylene monomers, a comonomer may be an alpha olefin such as butene, hexene, octene or other monomers. While in theory the comonomers should have a random distribution across various molecular weight fractions of the polymer, in reality polymerization catalysts often concentrate the comonomer in lower molecular weight fractions of the polymer. Generally, a “reverse comonomer distribution” or “broad orthogonal composition distribution” (“BOCD”) occurs when a comonomer is distributed across more than just the low molecular weight fractions. In other words, a reverse comonomer distribution occurs when there is an increase in comonomer incorporation to the high molecular weight fractions of polymers as opposed to just the low molecular weight fractions. One method of quantifying the level of reverse comonomer distribution is through the molecular weight composition distribution index (“MWCDI”). The MWCDI is the slope of a linear regression of a comonomer distribution taken from a triple detector compositional gel permeation chromatography measurement. A reverse comonomer distribution is defined as an MWCDI greater than 0 and a normal comonomer distribution is defined as an MWCDI less than 0. Having a reverse comonomer distribution is advantageous as it improves a variety of polymer properties but is hard to achieve given that predicting reverse comonomer distribution based on the catalyst structure is difficult. Even more difficult is to achieve reverse comonomer distribution across a range of densities because composition distributions and comonomer contents all decrease with increasing density. Taking into account the above, with BOCD being a rare case at low densities it becomes even more scarce with increasing density.Conventional approaches to achieving such a distribution usually include a dual reactor configuration or dual catalyst process. In a dual reactor process, a single catalyst can be used to make a high molecular weight, lower density component (i.e., having higher wt% comonomer) and a low molecular weight high density (i.e., lower wt% comonomer) component in separate reactors via independent process controls in the two reactors. The result is a bimodal resin that has a BOCD. In the case of a dual catalyst single reactor process, one catalyst makes a high molecular weight low density component, while the other catalyst makes a low molecular weight high density component, resulting in a bimodal product having a reverse comonomer distribution. Running two reactors or a dual catalyst system can be complicated and costly. In addition, such bimodal polymers tend to have a broader molecular weight distribution(“MWD”) from combining two polymers at different molecular weights so a narrower MWD with BOCD is difficult or impossible to achieve by these methods.

[0006] A more desirable way to achieve polymers exhibiting a reverse comonomer distribution is with a single catalyst in a single reactor. One example of such a catalyst is VP- 100 (from the metallocene bis( / 7-propylcyclopentadienyl)hafnium dimethyl, which is commercially available from Univation. While VP- 100 is able to produce a reverse comonomer distribution across low density resins, it is unable to generate a reverse comonomer distribution in medium and high-density resins. For example, United States patent number 11,193,008 (“the ‘008 patent”) is concerned with making a high melt strength (a property enhanced by reverse comonomer distribution) polymer using a dual catalyst system in the manner described above. The claims and examples of the ‘008 patent disclose use of the metallocene VP- 100 on its own and in addition to biphenyl phenol catalysts as catalyst systems to produce improved melt strength polymers with low densities. Claim 3 also discloses the replacement of VP- 100 with the catalyst (n-propyl cyclopentadienyl) (n-butyl cyclopentadienyl) hafnium dichloride or dimethyl in the dual catalyst system, but it is not used in the examples so its effect on BOCD is heretofore unknown.

[0007] In view of the foregoing, it would be surprising to discover a resin exhibiting a MWCDI > 0 over a variety of density ranges from a single catalyst in a single reactor system.

[0008] SUMMARY OF THE DISCLOSURE

[0009] The inventors of the present disclosure have surprisingly discovered a resin exhibiting a MWCDI > 0 over a variety of density ranges from a single catalyst in a single reactor system.The invention is the result of discovering that the catalyst of claim 1 can produce resins exhibiting a MWCDI > 0 over a variety of density ranges. Such a result is surprising because bis (n-propylcyclopentadienyl)hafnium dimethyl), which is structurally similar to the catalyst of claim 1, does not exhibit this same behavior as evidenced by the ‘008 patent’s inclusion of it in dual catalyst systems to improve melt strength (i.e., a property reliant on reverse comonomer distribution).

[0010] According to a first aspect of the present disclosure, an ethylene-based polymer, comprises a density of 0.905 g / cc to 0.960 g / cc as measured according to ASTM D792 and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing, wherein the ethylene-based polymer is made in a single reactor using a single catalyst of Structure (I) wherein Ri and R2 are each independently selected from an unbranched C3 to Cs hydrocarbyl, wherein Ri and R2 are not the same, and each X is independently selected from a Ci to C4 alkyl, a halide, an aryl or a benzyl.

[0011] According to another aspect of the present disclosure, the ethylene-based polymer comprises one or more of the following features: a density of 0.905 g / cc to 0.930 g / cc as measured according to ASTM D792; a density of 0.930 g / cc to 0.940 g / cc as measured according to ASTM D792; a density of 0.940 g / cc to 0.960 g / cc as measured according to ASTM D792; and a density of 0.925 g / cc to 0.960 g / cc as measured according to ASTM D792.

[0012] According to another aspect of the present disclosure, the ethylene-based polymer comprises one or more of the following features: a melt flow ratio (I21 / I2) of 30 or less; a melt flow ratio (I21 / I2) of 25 or less; and a melt flow ratio (I21 / I2) of 20 or less.

[0013] According to another aspect of the present disclosure, the ethylene-based polymer exhibits a molecular weight composition distribution index according to the following equation: MWCDI > 0.662(wt% comonomer') — 0.8144 or a molar molecular weight composition distribution index according to the following equation: MWCDIn> 0.7309(mo / % comonomer) — 0.3154.

[0014] According to another aspect of the present disclosure, the ethylene-based polymer has a broad orthogonal comonomer distribution ratio according to the following equations: BOCD Ratio = -MWCDI- 100an ;QRR Ratio > 15.632(moles comonomer) +

[0015] (wt% comonomer)

[0016] 10.289.

[0017] According to another aspect of the present disclosure, each X of Structure (I) is a halide.According to another aspect of the present disclosure, each X of Structure (I) is a methyl group.

[0018] According to another aspect of the present disclosure, the catalyst is one or more of (n-butylcyclopentadienyl)(?7-propylcyclopentadienyl)hafnium dichloride and (n-butylcyclopentadienyl)(?r-propylcyclopentadienyl)hafnium dimethyl.

[0019] According to another aspect of the present disclosure, a method comprises the steps of: contacting ethylene and an alpha olefin comonomer with a catalyst in the presence of molecular hydrogen gas, wherein the catalyst comprises Structure (I) wherein Ri and R2 are each independently selected from an unbranched C3 to Cx hydrocarbyl, wherein Ri and R2 are not the same, and each X is independently selected from a Ci to C4 alkyl, a halide, or a benzyl; and generating an ethylene-based polymer exhibiting a density of 0.905 g / cc to 0.970 g / cc as measured according to ASTM D792 and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing.

[0020] According to another aspect of the present disclosure, the ethylene-based polymer exhibits a molecular weight composition distribution index of 0.25 to 2.25 over a comonomer content of 1 wt% to 3 wt%.

[0021] According to another aspect of the present disclosure, the steps of contacting the ethylene and the alpha olefin and generating an ethylene-based polymer are performed within a single gas phase polymerization reactor containing a fluidized resin bed at a temperature from 70 °C to 110 °C.

[0022] DETAILED DESCRIPTION

[0023] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0024] All ranges include endpoints unless otherwise stated.

[0025] Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number as a hyphenated two-digit number. References to test methods contain both a reference to the testing society and the test methodnumber. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); EN refers to European Norm; DIN refers to Deutsches Institut fur Normung; and ISO refers to International Organization for Standards.

[0026]

[0027] One feature of the present disclosure is an ethylene-based polymer. As used herein, “ethylene-based” polymers are polymers in which greater than 50 wt% of the monomers are ethylene though other co-monomers may also be employed. Ethylene-based polymers include ethylene and one or more C3-C20 a-olefin comonomers such as propylene, 1 -butene, 1 pentene, 4- methyl-1 -pentene, 1 -hexene, and 1 -octene. The ethylene-based polymer may be produced in a gas phase polymerization reactor or in a solution or slurry phase reactor.

[0028] The ethylene-based polymer may comprise 50 wt% or greater, 60 wt% or greater, 70 wt% or greater, 80 wt% or greater, 85 wt% or greater, 90 wt% or greater, or 91 wt% or greater, or 92 wt% or greater, or 93 wt% or greater, or 94 wt% or greater, or 95 wt% or greater, or 96 wt% or greater, or 97 wt% or greater, or 97.5 wt% or greater, or 98 wt% or greater, or 99 wt% or greater, or 99.5 wt% or greater, or 99.8 wt% or greater, while at the same time, 99.9 wt% or less, or 99.5 wt% or less, or 99 wt% or less, or 98 wt% or less, or 97 wt% or less, or 96 wt% or less, or 95 wt% or less, or 94 wt% or less, or 93 wt% or less, or 92 wt% or less, or 91 wt% or less, or 90 wt% or less, or 85 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less of ethylene monomers as measured using Nuclear Magnetic Resonance (NMR) or Fourier-Transform Infrared (FTIR) Spectroscopy.

[0029] The density of the ethylene-based polymer may be from 0.905 g / cc to 0.970 g / cc as measured according to ASTM D792. For example, the density of the ethylene-based polymer may be 0.905 g / cc or greater, or 0.910 g / cc or greater, or 0.915 g / cc or greater, or 0.918 g / cc or greater, or 0.920 g / cc or greater, 0.922 g / cc or greater, or 0.924 g / cc or greater, or 0.926 g / cc or greater, or 0.928 g / cc or greater, or 0.930 g / cc or greater, or 0.932 g / cc or greater, or 0.934 g / cc or greater, or 0.936 g / cc or greater, or 0.938 g / cc or greater, or 0.940 g / cc or greater, or 0.942 g / cc or greater, or 0.944 g / cc or greater, or 0.946 g / cc or greater, or 0.948 g / cc or greater, or 0.950 g / cc or greater, or 0.952 g / cc or greater, or 0.954 g / cc or greater, or 0.956 g / cc or greater, or 0.958 g / cc or greater, or 0.960 g / cc or greater, or 0.962 g / cc or greater, or 0.964 g / cc or greater, or 0.966 g / cc or greater, or0.968 g / cc or greater, while at the same time, 0.970 g / cc or less, or 0.968 g / cc or less, or 0.966 g / cc or less, or 0.964 g / cc or less, or 0.952 g / cc or less, 0.960 g / cc or less, or 0.958 g / cc or less, or 0.956 g / cc or less, or 0.954 g / cc or less, or 0.952 g / cc or less, or 0.950 g / cc or less, or 0.948 g / cc or less, or 0.946 g / cc or less, or 0.944 g / cc or less, or 0.942 g / cc or less, or 0.940 g / cc or less, 0.940 g / cc or less, or 0.938 g / cc or less, or 0.936 g / cc or less, or 0.934 g / cc or less, or 0.932 g / cc or less, or 0.930 g / cc or less, or 0.928 g / cc or less, or 0.926 g / cc or less, or 0.924 g / cc or less, or 0.922 g / cc or less, or 0.920 g / cc or less, or 0.918 g / cc or less, or 0.916 g / cc, or 0.914 g / cc, or 0.912 g / cc, or 0.910 g / cc, or 0.908 g / cc, or 0.906 g / cc or less as measured according to ASTM D792. In specific examples, the ethylene-based polymer may exhibit any one of the following density ranges: a density of 0.905 g / cc to 0.930 g / cc as measured according to ASTM D792; a density of 0.930 g / cc to 0.940 g / cc as measured according to ASTM D792; a density of 0.940 g / cc to 0.960 g / cc as measured according to ASTM D792; and a density of 0.925 g / cc to 0.960 g / cc as measured according to ASTM D792.

[0030] The ethylene-based polymer may have a melt index (I2) of 0.1 g / 10 min to 75 g / 10 min. as measured according to ASTM D1238 (190 °C, 2.16 kg). For example, the ethylene-based polymer may have a melt index (I2) of 0.1 g / 10 min or greater, or 1.0 g / 10 min or greater, or 2.0 g / 10 min or greater, or 3.0 g / 10 min or greater, or 4.0 g / 10 min or greater, or 5.0 g / 10 min or greater, or 10 g / 10 min or greater, or 20 g / 10 min or greater, or 30 g / 10 min or greater, 40 g / 10 min or greater, or 50 g / 10 min or greater, or 60 g / 10 min or greater, or 70 g / 10 min or greater, while at the same time, 75 g / 10 min or less, or 60 g / 10 min or less, or 50 g / 10 min or less, or 40 g / 10 min or less, or 30 g / 10 min or less, or 20 g / 10 min or less, or 10 g / 10 min or less, or 5.0 g / 10 min or less, or 1.0 g / 10 min or less as measured according to ASTM D1238.

[0031] The ethylene-based polymer may have a melt index (I5) of 0.1 g / 10 min to 160 g / 10 min. as measured according to ASTM D1238 (190 °C, 5 kg). For example, the ethylene-based polymer may have a melt index (I5) of 0.1 g / 10 min or greater, or 1.0 g / 10 min or greater, or 2.0 g / 10 min or greater, or 3.0 g / 10 min or greater, or 4.0 g / 10 min or greater, or 5.0 g / 10 min or greater, or 10 g / 10 min or greater, or 20 g / 10 min or greater, or 40 g / 10 min or greater, 60 g / 10 min or greater, or 80 g / 10 min or greater, or 100 g / 10 min or greater, or 120 g / 10 min or greater, or 140 g / 10 min or greater, while at the same time, 160 g / 10 min or less, or 140 g / 10 min or less, or 120 g / 10 min or less, or 100 g / 10 min or less, or 80 g / 10 min or less, or 60 g / 10 min or less, or 40 g / 10 min orless, or 20 g / 10 min or less, or 10 g / 10 min or less, or 1.0 g / 10 min or less as measured according to ASTM D1238.

[0032] The ethylene-based polymer may have a melt index (I21) of 0.1 g / 10 min to 700 g / 10 min. as measured according to ASTM D1238 (190 °C, 21.6 kg). For example, the ethylene-based polymer may have a melt index (I21) of 0.1 g / 10 min or greater, or 1.0 g / 10 min or greater, or 10 g / 10 min or greater, or 50 g / 10 min or greater, or 100 g / 10 min or greater, or 200 g / 10 min or greater, or 400 g / 10 min or greater, or 500 g / 10 min or greater, or 600 g / 10 min or greater, while at the same time, 700 g / 10 min or less, or 600 g / 10 min or less, or 500 g / 10 min or less, or 400 g / 10 min or less, or 300 g / 10 min or less, or 200 g / 10 min or less, or 100 g / 10 min or less, or 50.0 g / 10 min or less, or 10.0 g / 10 min or less as measured according to ASTM D1238.

[0033] The ethylene-based polymer may exhibit a melt flow ratio (I21 / I2) of 1 to 30. For example, the ethylene-based polymer may have exhibit a melt flow ratio (I21 / I2) of 1 or greater, or 2 or greater, or 5 or greater, or 10 or greater, or 15 or greater, or 20 or greater, or 25 or greater, while at the same time. 30 or less, or 25 or less, or 20 or less, or 15 or less, or 10 or less, or 5 or less.

[0034] The ethylene-based polymer may exhibit a melt flow ratio (I21 / I2) when the I2 is less than 40 from 15 to 30. For example, the ethylene-based polymer may exhibit a I21 / I2 of 15 or greater, or 17 or greater, or 20 or greater, or 22 or greater, or 25 or greater, or 30 or greater, while at the same time, 30 or less, or 25 or less, or 22 or less, or 20 or less, or 17 or less.

[0035] The ethylene-based polymer may exhibit a molecular weight composition distribution index greater than 0 as measured according to GPC Testing. The ethylene-based polymer may exhibit a MWCDI according to equation A.

[0036] MWCDI > 0.662(wt% comonomer) — 0.8144 Eq. A

[0037] For equation A, the weight percent of comonomer in the ethylene-based polymer is determined according to Gel Permeation Chromatography as explained in greater detail below. In specific examples, the ethylene-based polymer may exhibit a MWCDI of 0.1 or greater, or 0.2 or greater, or 0.4 or greater, or 0.6 or greater, or 0.8 or greater, or 1.0 or greater, or 1.2 or greater, or 1.4 or greater, or 1.6 or greater, or 1.8 or greater, or 2.0 or greater, or 2.2 or greater, or 2.4 or greater, or 2.6 or greater, or 2.8 or greater, or 3.0 or greater, or 3.2 or greater, or 3.4 or greater, or 3.6 or greater, or 3.8 or greater, or 4.0 or greater, or 4.2 or greater, or 4.4 or greater, or 4.6 or greater, or 4.8 orgreater, or 5.0 or greater, or 5.2 or greater, or 5.4 or greater, or 5.6 or greater, or 5.8 or greater, or 6.0 or greater, or 6.2 or greater, or 6.4 or greater, or 6.6 or greater, or 6.8 or greater, or 7.0 or greater, or 7.2 or greater, or 7.4 or greater, or 7.6 or greater, or 7.8 or greater, or 8.0 or greater, or 8.2 or greater, or 8.4 or greater, or 8.6 or greater, or 8.8 or greater, or 9.0 or greater, or 9.2 or greater, or 9.4 or greater, or 9.6 or greater, or 9.8 or greater, or 10.0 or greater as measured according to GPC Testing. The ethylene-based polymer may exhibit a molecular weight composition distribution index of 0.25 to 2.25 over a comonomer content of 1 wt% to 3 wt%. For example, molecular weight composition distribution index of 0.25 or greater, or 0.50 or greater, or 0.75 or greater, or 1.00 or greater, or 1.25 or greater, or 1.50 or greater, or 1.75 or greater, or 2.0 or greater, while at the same time, 2.25 or less, or 2.00 or less, or 1.75 or less, or 1.50 or less, or 1.25 or less, 1.00 or less, or 0.75 or less, or 0.50 or less over a comonomer content of 1 wt% to 3 wt%.

[0038] Additionally or alternatively, the ethylene-based polymer may exhibit a molar molecular weight composition distribution index (“MWCDIU”) according to equation B.

[0039] MWCDIn> 0.7309(moZ% comonomer) — 0.3154 Eq. B

[0040] For MWCDIn the mol% comonomer is also determined according to Gel Permeation Chromatography as explained in detail below and the mol% may be determined from the wt% of a specific comonomer and vice versa. In specific examples, the ethylene-based polymer may exhibit a MWCDL of 0.1 or greater, or 0.2 or greater, or 0.4 or greater, or 0.6 or greater, or 0.8 or greater, or 1.0 or greater, or 1.2 or greater, or 1.4 or greater, or 1.6 or greater, or 1.8 or greater, or 2.0 or greater, or 2.2 or greater, or 2.4 or greater, or 2.6 or greater, or 2.8 or greater, or 3.0 or greater, or 3.2 or greater, or 3.4 or greater, or 3.6 or greater, or 3.8 or greater, or 4.0 or greater, or 4.2 or greater, or 4.4 or greater, or 4.6 or greater, or 4.8 or greater, or 5.0 or greater as measured according to GPC Testing.

[0041] MWCDI and MWCDInboth quantify the BOCD of the ethylene-based polymer. However, comparisons of the BOCD of ethylene-based polymers exhibiting different densities (i.e., having different comonomer contents) is most appropriately performed by normalizing the MWCDI to the comonomer content of the polymer. The BOCD Ratio, in essence, provides the comonomer content normalized MWCDI. The ethylene-based polymer may exhibit a broad orthogonal comonomer distribution ratio as calculated by equation C. 100 Eq. C

[0042]

[0043] The ethylene-based polymer may exhibit a BOCD ratio as governed by equation D.

[0044] BOCD Ratio > 15.632(moZ% comonomer) + 10.289 Eq. D

[0045] Generally, the ethylene-based polymer may exhibit a BOCD ratio of 20 to 80. For example, the ethylene-based polymer may exhibit a broad orthogonal comonomer distribution ratio of 20 or greater, or 25 or greater, or 30 or greater, or 35 or greater, or 40 or greater, or 45 or greater, or 50 or greater, or 55 or greater, or 60 or greater, or 65 or greater, or 70 or greater, or 75 or greater, while at the same time, 80 or less, 75 or less, 70 or less, or 65 or less, or 60 or less, 55 or less, or 50 or less, 45 or less, or 40 or less, 35 or less, or 30 or less, 25 or less.

[0046] The ethylene-based polymer may exhibit a unimodal molecular weight distribution as defined by having a single peak maxima. The ethylene-based polymer may exhibit a molecular weight distribution (Mw / Mn) from 2 to 5. For example, the ethylene-based polymer may exhibit a Mw / Mn of 2.0 or greater, or 2.5 or greater, or 2.7 or greater, or 3.0 or greater, or 3.2 or greater, or 3.5 or greater, or 4.0 or greater, or 4.5 or greater, while at the same time, 5.0 or less, or 4.5 or less, or 4.0 or less, or 3.5 or less, or 3.2 or less, or 3.0 or less, or 2.7 or less, or 2.5 or less.

[0047] Catalyst

[0048] The ethylene-based polymer is made in a single reactor using a single catalyst of Structure (I):

[0049]

[0050] Structure (I)wherein Ri and R2 are each independently selected from an unbranched C3 to Cx hydrocarbyl, wherein Ri and R2 are not the same, and each X is independently selected from a Ci to C4 alkyl, a halide, an aryl, or a benzyl. As used herein, the term "hydrocarbyl " refers to a moiety comprising carbon and hydrogen atoms. Exemplary hydrocarbyl moieties include n-propyl, n-butyl, n-pentyl, n-hexyl. N-heptyl, n-octyl straight chain or aromatic compounds. Each X is independently selected from a Ci, or a C2, or a C3, or a C4 alkyl, or a halide or a benzyl. For example, each of the X of Structure (I) may be a methyl group. Exemplary halides include fluorine, chlorine, bromine, iodine, and astatine. As used herein the term benzyl means refers to a molecular fragment or substituent that consists of a benzene ring attached to a methylene group. In specific example, the catalyst may be (n-butylcyclopentadienyl)(w-propylcyclopenatdienyl)hafnium dichloride or may be ( / i-butylcyclopentadienyl)( / i-propylcyclopenatdienyl)hafnium dimethyl.

[0051] Method

[0052] The present disclosure is also directed to a method of making the ethylene-based polymer. The method may comprise steps of contacting ethylene and an alpha olefin comonomer with a catalyst in the presence of molecular hydrogen gas, wherein the catalyst comprises Structure (I) and generating an ethylene-based polymer exhibiting a density of 0.905 g / cc to 0.970 g / cc as measured according to ASTM D792 and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing. The steps of contacting the ethylene and the alpha olefin and generating an ethylene-based polymer may be performed within a single gas phase polymerization reactor containing a fluidized resin bed at a temperature from 70 °C to 110 °C.

[0053] Examples

[0054] Test Methods

[0055] Melt Index: Melt index (I2) was determined according to ASTM D1238 (190 °C. 2.16 kg), melt index (I5) was determined according to ASTM D1238 (190 °C, 5 kg), melt index (I21) was determined according to ASTM D1238 (190 °C, 21.6 kg).

[0056] Melt Temperature (Tm): Melt temperatures were determined using Differential Scanning Calorimetry according to ASTM D 3418-08, with a scan rate of 10 °C / min on a sample of 10 mg and the second heating cycle was used to determine Tm.GPC Testing: A chromatographic system consisted of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5). The autosampler oven compartment was set at 160 °C and the column compartment was set at 150 °C. 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.

[0057] Calibration of the GPC column set was performed with 21 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 g / mol and were arranged in 6 cocktail mixtures with at least a decade of separation between individual molecular weights. The standards were purchased from Agilent Technologies. The polystyrene standards were prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000, and 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000.000. The polystyrene standards were pre-dissolved at 80 °C with gentle agitation for 30 minutes then cooled and the room temperature solution is transferred cooled into the autosampler dissolution oven at 160 °C for 30 minutes. The polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).:

[0058]

[0059] where M is the molecular weight, A has a value of 0.4061 and B is equal to 1.0. A fifth order polynomial was used to fit the respective polyethylene-equivalent calibration points.

[0060] 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” 30 cm 20-micron linear mixed-bed columns.

[0061] 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 thePolymerChar high temperature autosampler. The samples were dissolved for 2 hours at 160 °C under low speed shaking.

[0062] The calculations of MU(GPC), MW(GPC). and MZ(GPC) were based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 2-4, using PolymerChar GPCONE software, the baseline-subtracted IR chromatogram at each equally-spaced data collection point (i). and the polyethylene equivalent molecular weight obtained from the narrow standard calibration curve for the point (i) from Equation 1.

[0063]

[0064] 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 flowmarker peak was done via the PolymerChar GPCONE Software. Acceptable flowrate correction is such that the effective flowrate should be within + / -0.5% of the nominal flowrate.

[0065] Flowrate(effective) = Flowrate(nominal) * (RV(FM calibrated) I RV(FM sample)) (EQ5) IR5 GPC Octene Composition Calibration is discussed as follows.

[0066] A calibration for the IR5 detector rationing was performed using at least ten ethylene-based polymer standards (Octene as comonomer) made by single-site metallocene catalyst from a single reactor in solution process (polyethylene homopolymer and ethylene / octene copolymers) of a narrow SCB distribution and known comonomer content (as measured by13C NMR Method, Qiu et al., Anal. Chem.2009, 81, 8585-8589), ranging from homopolymer (0 SCB / 1000 total C) to approximately 40 SCB / 1000 total C, where total C = carbons in backbone + carbons in branches. Each standard had a weight-average molecular weight from 36,000 g / mole to 126,000 g / mole measured by GPC. Each standard had a molecular weight distribution (Mw / Mn) from 2.0 to 2.5. Polymer properties for the SCB standards are shown in Table A.

[0067] Table A: Copolymer Standards

[0068]

[0069] The “IR5 Area Ratio (or “IR5 Methyl Channel Area / IR5 Measurement Channel Area ’)” of “the baseline-subtracted area response of the IR5 methyl channel sensor” to “the baseline-subtracted area response of IR5 measurement channel sensor” (standard filters and filter wheel as supplied by PolymerChar: Part Number IR5 FWM01 included as part of the GPC-IR instrument) was calculated for each of the “Copolymer” standards. A linear fit of the Wt% Comonomer frequency versus the “IR5 Area Ratio” was constructed in the form of the following Equation 6:Wt% Comonomer = Ao + [Ai x (IR5 Methyl Channel Area / IR5 Measurement Channel Area)] (EQ 6)

[0070] where Ao is the “Wt% Comonomer” intercept at an “IR5 Area Ratio” of zero, and Ai is the slope of the “Wt% Comonomer” versus “IR5 Area Ratio” and represents the increase in the Wt% Comonomer as a function of “IR5 Area Ratio.” The IR5 area ratio is equal to the IR5 height ratio for narrow PDI and narrow SCBD standard materials.

[0071] The comonomer distribution in an ethylene / a- olefin copolymer can be characterized as either normal (also referred to as having a Zeigler-Natta distribution), reverse, or flat. Several reported methods are utilized to quantify a Broad Orthogonal Composition Distribution (BOCD). Herein, a simple line fit is utilized such that the normal or reverse nature of the comonomer distribution can be quantified by the molecular weight composition distribution index (MWCDI), which is the slope of the linear regression of the comonomer distribution in weight precent comonomer taken from a compositional GPC measurement, wherein the x-axis is Log(MW) and the y-axis is weight percent of comonomer. The molar MWCDI, or MWCDL, is similarly the slope of the linear regression of the in mole precent comonomer taken from a compositional GPC measurement, wherein the x-axis is Log(MW) and the y-axis is weight percent of comonomer. A reverse comonomer distribution is defined when the MWCDI > 0 and a normal comonomer distribution is defined when the MWCDI < 0. When the MWCDI = 0 the comonomer distribution is said to be flat. Additionally, the MWCDI quantifies the magnitude of the comonomer distribution. Comparing two polymers that have MWCDI > 0, the polymer with the greater MWCDI value is defined to have a greater, i.e., increased, BOCD; in other words, the polymer with the greater MWCDI value has a greater reverse comonomer distribution. Similar is true for MWCDL. Polymers with a relatively greater MWCDI, i.e., BOCD, can provide one or more improved physical properties, as compared to polymers having a relatively lesser MWCDI. Data used for the MWCDI calculation excluded data according to SCBf x MW signal < 0.5, where SCBf is the short chain branching frequency and MW signal is the detect response of the MW signal in the GPC measurement. Additionally, a cut-off criteria of MW signal < 0.009 was used for the GPC parameters reported including Mn, Mw, Mz, and Mp.

[0072]

[0073] Inventive Example 1 (“IE1”): Synthesis of (n-butylcylopentadienylO?-propylcylopentadienyl))hafnium dichloride. To a 40 mL vial containing (n-propylcyclopentadienyl)hafnium trichloride dimethoxyethane adduct (reported previously) (0.200 g, 0.51 mmol) in THF (5 mL) was slowly added lithium n-butylcyclopentadienide (obtained from Boulder Scientific Company) (0.065 g, 0.51 mmol) in THF (5 mL). The mixture was allowed to stir at ambient temperature overnight. The following day, solvent was removed in vacuo, reaction crude was re-dissolved in toluene (10 mL), filtered through a syringe filter and solvent was removed in vacuo overnight to afford Example 1 as off-white powder (0.230 g, 94%). ’H NMR (400 MHz, Benzene-d6) 55.81 (m, J = 7.2, 2.4 Hz, 4H), 5.69 -5.59 (m, 4H), 2.67 (t, J = 7.8 Hz, 2H), 2.62 (t, J = 7.7 Hz, 2H), 1.43 (ddt, J= 15.6, 10.4, 5.1 Hz, 4H), 1.22 (dq, J= 14.6, 7.3 Hz, 2H), 0.83 (dt, J= 11.0, 7.4 Hz, 6H).

[0074] The catalyst of IE1 was formed into a spray dried and supported catalyst according to the following procedure. In a nitrogen-purged glovebox, slurry 0.98 g Cabosil TS-610 hydrophobic fumed silica in 26 g toluene until well dispersed. Then add 8 g of a 10 wt% solution of MAO in toluene. Stir the mixture for 15 minutes. Then add 0.041 g of Example 1. Stir the mixture for 30 to 60 minutes. Spray-dry the mixture using a Biichi Mini Spray Dryer B-290 with the following operating parameters: set temperature 140° C, outlet temperature 100° C, aspirator 50%, and pump speed 150 rotations per minute (rpm) to give spray dried Inventive Example 3 (IE2).

[0075] Comparative Example 1 (“CE1”): CE1 is a supported spray dried catalyst from the comparative metallocene bis(n-propylcyclopentadienyl)hafnium dimethyl. The catalyst was supported and spray dried as follows. In a nitrogen-purged glovebox, slurry 1.56 g Cabosil TS-610 hydrophobic fumed silica in 37 g toluene until well dispersed. Then add 9.9 g of a 10 wt% solution of MAO in toluene. Stir the mixture for 15 minutes. Then add 0.047 g of bis(n-propylcyclopentadienyl)hafnium dimethyl (which was obtained from the Boulder Scientific Company). Stir the mixture for 30 to 60 minutes. Spray-dry the mixture using a Biichi Mini Spray Dryer B-290 with the following operating parameters: set temperature 140° C., outlet temperature 100° C., aspirator 50%, and pump speed 150 rotations per minute (rpm) to give spray dried Comparative Example 5 (CE5).

[0076] Gas-Phase Batch Reactor Test: IE2 and CE5 were used for ethylene / 1 -hexene copolymerizations conducted in the gas-phase autoclave polymerization reactor. Gas-phase batch reactor catalyst testing procedure: The gas phase reactor employed is a 2 liter, stainless steelautoclave equipped with a mechanical agitator. For the experimental runs, the reactor was first dried for 1 hour, charged with 200 g of NaCl and dried by heating at 100 °C under nitrogen for 30 minutes. After baking out the reactor, 3g of SMAO (supported methylaluminoxane) was introduced as a scavenger under nitrogen pressure. After adding SDMAO, the reactor was sealed and components were stirred. The reactor was then charged with hydrogen and 1 -hexene pressurized with ethylene. Once the system reached a steady state, the catalyst was charged into the reactor at 80°C to start polymerization. The reactor temperature was brought to the desired reaction temperature and maintained at this temperature, and at the ethylene, 1 -hexene, and hydrogen feed ratios throughout the 1 hour run. At the end of the run, the reactor was cooled down, vented and opened. The resulting product mixture was washed with water and methanol, then dried. Polymerization Activity (grams polymer / gram catalyst-hour) was determined as the ratio of polymer produced to the amount of catalyst added to the reactor.

[0077] Results

[0078] Tables 1 provides the individual run conditions of the inventive and comparative examples. Table 2 provides GPC Characterization data of the ethylene-based polymers. Table 3 provides rheological and MWCDI data for the ethylene-based polymer. Table 4 provides the molar molecular weight composition distribution index of the inventive and comparative examples.

[0079] Table 1

[0080]

[0081]

[0082] Table 2.

[0083]

[0084] Table 3.

[0085]

[0086]

[0087] Uptake wt% is the comonomer content as determined by the total amounts of ethylene and 1 -hexene consumed during the polymerization reaction, n.m. = not measured.

[0088] Table 4.

[0089]

[0090] Table 1 shows the process conditions (i.e. temperature, comonomer to ethylene ratio, hydrogen to ethylene molar ratio, and ethylene partial pressure) each polymer sample was made at. IE2 have good to excellent productivities. These conditions provided a range of polymer Mw or I2 values at different densities, represented here by comonomer content (Tables 2-4). These polymers are unimodal with narrow Mw / Mn from 2.39 to 3.17 and hi / 12 from 15.77 to 27.54. Note example 7 hit the limit of the melt detector used and thus the I21 / I2 is lower than actual which is supported by the Mw / Mn of 2.55. MWCDI of the inventive polymer is greater than zero in all cases. While it is similar to the comparative at high comonomer content (examples 1, 4 and 12), the MWCDI is significantly higher for the inventive catalyst at low comonomer (i.e. higher density) such as for examples 2, 3. 5-8 compared to examples 10 and 11. Equations A, B and D provided above provide linear demarcations between the inventive and comparative examples are and derived from the data of Tables 1-4. While both catalysts have similar MWCDI at highercomonomer content (i.e., 8 wt% to 10 wt% 1 -hexene) the inventive catalyst maintains a higher MWCDI at lower values of 1-hexene content in the polymer.(i.e., < 4 wt% 1-hexene). Lower 1-hexene content corresponds to higher density polymers. The inventive catalyst offers improved MWCDI at higher densities, which is advantaged for medium and higher density applications while being versatile enough to offer advantaged MWCDI at lower densities as well.

Claims

CLAIMSWhat is claimed is1. An ethylene-based polymer, comprising:a density of 0.905 g / cc to 0.960 g / cc as measured according to ASTM D792; and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing;wherein the ethylene-based polymer is made in a single reactor using a single catalyst of Structure (I)Structure (I) wherein Ri and R2 are each independently selected from an unbranched C3 to Cs hydrocarbyl, wherein Ri and R2 are not the same, and each X is independently selected from a Ci to C4 alkyl, a halide, an aryl or a benzyl.

2. The ethylene-based polymer of claim 1, wherein the ethylene-based polymer comprises one or more of the following features:a density of 0.905 g / cc to 0.930 g / cc as measured according to ASTM D792;a density of 0.930 g / cc to 0.940 g / cc as measured according to ASTM D792;a density of 0.940 g / cc to 0.960 g / cc as measured according to ASTM D792; and a density of 0.925 g / cc to 0.960 g / cc as measured according to ASTM D792.

3. The ethylene-based polymer of any one of claims 1 and 2, wherein the ethylene-based polymer comprises one or more of the following features:a melt flow ratio (I21 / I2) of 30 or less;a melt flow ratio (I21 / I2) of 25 or less; anda melt flow ratio (I21 / I2) of 20 or less.

4. The ethylene-based polymer of any one of claims 1-3, wherein the ethylene-based polymer exhibits a molecular weight composition distribution index according to the following equation:MWCDI > 0.662(wt% comonomer) — 0.8144or a molar molecular weight composition distribution index according to the following equation:MWCDIn> 0.7309(mol% comonomer) — 0.31545. The ethylene-based polymer of claim 4, wherein the ethylene-based polymer has a broad orthogonal comonomer distribution ratio according to the following equations:MWCDI BOCD Ratio = - - -X 100(wt% comonomer)and:BOCD Ratio > 15.632(moZes comonomer) -I- 10.2896. The ethylene-based polymer of any one of claims 1-5, wherein each X of Structure (I) is a halide.

7. The ethylene-based polymer of any one of claims 1-5, wherein each X of Structure (I) is a methyl group.

8. The ethylene-based polymer of any one of claims 1-5, wherein the catalyst is one or more of (zi-butylcyclopentadienyl)(n-propylcyclopenatdienyl)hafnium dichloride and (n-butylcyclopentadienyl)(?i-propylcyclopenatdienyl)hafnium dimethyl.

9. A method of making an ethylene-based polymer, the method comprising the steps of:contacting ethylene and an alpha olefin comonomer with a catalyst in the presence of molecular hydrogen gas, wherein the catalyst comprises Structure (I):Structure (T) wherein Ri and R2 are each independently selected from an unbranched C3 to Cs hydrocarbyl, wherein Ri and R2 are not the same, and each X is independently selected from a Ci to C4 alkyl, a halide, or a benzyl; andgenerating an ethylene-based polymer exhibiting a density of 0.905 g / cc to 0.970 g / cc as measured according to ASTM D792 and a molecular weight composition distribution index greater than 0 as measured according to GPC Testing.

10. The method of claim 9, wherein the ethylene-based polymer exhibits a molecular weight composition distribution index of 0.25 to 2.25 over a comonomer content of 1 wt% to 3 wt%.

11. The method of claim 9, wherein the steps of contacting the ethylene and the alpha olefin and generating an ethylene-based polymer are performed within a single gas phase polymerization reactor containing a fluidized resin bed at a temperature from 70 °C to 110 °C.

Images