KR20260003679A - Linear high-density polyethylene compositions and rotational molded products - Google Patents

Abstract

A solution phase polymerization process using a metallocene catalyst in a first reactor and a Ziegler-Natta catalyst in a second reactor provides a polyethylene composition having a density of ≥ 0.940 g/cm ³ and a melt index, I ₂ , of less than 3.0 g/10 min. When formed into plaques, the polyethylene composition has an excellent combination of environmental stress cracking resistance, IZOD impact strength, and stiffness. Furthermore, the polyethylene composition comprising the first ethylene copolymer and the second ethylene copolymer also has an excellent processing window when forming rotationally molded specimens.

Description

Linear high-density polyethylene compositions and rotational molded products

The present invention relates to a polyethylene composition suitable for use in rotationally molded parts. The present invention also relates to a solution polymerization process for producing the polyethylene composition. The present invention also relates to rotationally molded parts, particularly, but not limited to, large, thick rotationally molded parts for use in large tanks and the like.

Rotational molding, also known as rotomolding, is used to manufacture hollow plastic parts. The process is often described as a four-step process: (1) loading the polymer, often in solid powder form; (2) slowly rotating the mold biaxially while heating the powder to form a uniform melt; (3) cooling and solidifying the melt; and (4) removing the plastic part from the mold. Biaxial rotation of the mold is essential in steps (2) and (3) of the process. During the rotational molding process, the material is exposed to high temperatures for a relatively long period of time, resulting in the deposition of the melt and the complete densification of the powder particles. Melt solidification is gradual and non-uniform throughout the thickness of the molded part. Resin design needs to take into account the rapid sintering and densification capabilities of the material, demonstrate excellent thermal stability, and exhibit optimal crystallization behavior in terms of mechanical properties and dimensional stability (see Rao et al ., Polymer Engineering and Science [1972], vol. 12, no. 4, pg. 237-264).

The mold typically rotates at relatively low speeds, typically in the range of 4 to 30 rpm. This process involves the gradual melting of the plastic powder, starting in the layer adjacent to the mold surface and progressing toward the inner free surface that will become the hollow plastic part. Once the particle layers adhere to the mold surface and undergo a melt transition, they undergo a coalescence process (sintering) driven by surface energy. During the powder deposition process, air pockets become trapped between the particles, eventually forming bubbles. These bubbles are then slowly dissipated by gas dissolution into the melt. To ensure the formation of a bubble-free molded part, it is important to minimize the size of the bubbles that form initially during powder compaction. This is achieved by ensuring rapid coalescence between individual particles. Coalescence is driven by surface energy, but is slower for resins with high viscosity and relative modulus. During this transition, the polymer experiences very low strain rates. Therefore, the most relevant rheological properties are low-shear viscosity (zero-shear viscosity), viscosity temperature dependence, especially in the temperature range above but near the melting transition temperature, and the relative elastic modulus of the material.

Suitable rheological parameters for rotational molding are described, for example, in (a) Bellehumeur et al ., Polymer Engineering and Science [1996], vol. 36., no. 17, pg. 2198-2207; (b) Bellehumeur et al ., Rheologica Acta [1998], vol. 37, pg. 270-278; and (c) Wang et al ., Polymer Engineering and Science [2004], vol. 44, no. 9, pg. 1662-1669.

The assessment of the relative modulus is based on measurements performed at low frequencies, which are most appropriate for conditions associated with powder sintering and densification in rotational molding. The relative modulus can be assessed based on the ratio of G' to G" at a frequency of 0.05 rad/s in DMA frequency sweep measurements performed at 190°C. Data reported in the literature show that resin compositions with high relative moduli tend to present difficulties in processing in terms of slow powder densification. Wang et al. [2004] reported adequate rotational moldability for blend compositions characterized by relative moduli as high as 0.125. The study investigated the effect of plastomer content on the rotational moldability of polypropylene. Further analysis of the results published by Wang et al. showed that compositions with high plastomer content had increased relative moduli (G'/G" > 0.13), which in turn increased the difficulty in achieving full densification during rotational molding.

Some key considerations when developing a thermoplastic suitable for use in the manufacture of molded parts, such as rotationally molded parts, include resistance to environmental stresses over time (e.g., environmental stress cracking resistance [ESCR]), impact resistance (e.g., Izod impact test performance), and processability (rheology suitable for rotational molding applications).

Although several polyethylene resins suitable for use in molded parts have been developed, improvements are still needed, particularly for those resins used in the production of large and/or thick rotationally molded parts, such as those for large tanks.

For example, US 7022770 discloses the ESCR performance of polyethylene compositions suitable for use in molded articles, but does not teach how to achieve a balance between ESCR performance and processability.

Meanwhile, US 10808053 teaches that a reverse comonomer distribution is advantageous for molding applications, and discloses examples containing long-chain branching. However, these examples are limited to compositions having a density of less than 0.930 g/cm ³ , and performance is observed only in film applications.

US 8076421 discloses a composition based on molecular fractions having very low molecular weight (GPC-RI) and very high molecular weight (GPC-LC), but this example is also limited to film applications.

US 8101687 describes a multimodal ethylene copolymer, specifying that one low-molecular-weight component is a heterogeneous ethylene copolymer. This composition exhibits excellent stress cracking resistance and is suitable for pipe applications. However, the upper limit of the melt flow index is 1.0 g/10 min.

Resins with low melt flow rates (less than 1.5 g/10 min) are also described in US 9169337, which describes bimodal compositions with improved ESCR, particularly for blow molding applications. These compositions have relatively high molecular weights and relatively broad molecular weight distributions.

Furthermore, US 8492498 discloses compositions with high ESCR, but is limited to compositions having a primary structural parameter (PSP2) greater than 8.9. There remains a need for new polyethylene resins that can be used in rotational molding applications, while simultaneously exhibiting excellent stiffness and toughness, as well as environmental resistance, while maintaining good processability.

The present invention has been conceived with the above considerations in mind.

A first aspect of the present invention is a polyethylene composition comprising:

(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm³, a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;

(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm³, a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;

Here, the ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;

The polyethylene composition has a density of at least 0.940 g/cm³, a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;

The weight percentage of the first or second ethylene copolymer is defined as the weight of the first or second copolymer, respectively, divided by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100.

The present invention provides polyethylene compositions having a density of at least 0.940 g/cm³ and a melt index of from 1.0 to 3.0 g/10 min, or less than 3.0 g/10 min, which are suitable for molding applications (particularly rotational molding) having high toughness and ESCR properties. The compositions are advantageous for the fabrication of large and/or thick rotational molded parts, such as those used in large tanks, because they provide a unique combination of performance (toughness, stiffness, ESCR) and processability (rheology). The compositions have a high comonomer content and a reverse comonomer distribution. In addition, the compositions contain a limited amount of long chain branching, which results in higher zero-shear viscosity and higher flow resistance at low strain rates. This is advantageous in preventing excessive flow during the fabrication of large and/or thick rotational molded parts, especially since the heating cycles of such parts can be long, which increases the risk of the resin developing excessive melt flow limitations.

A second aspect of the present invention is a solution polymerization process for producing a polyethylene composition, wherein the polymerization process comprises:

A step of polymerizing ethylene and alpha-olefin using a metallocene catalyst in a first reactor; and

A step of polymerizing ethylene and alpha-olefin using a Ziegler-Natta catalyst in a second reactor;

Here, the first and second reactors are configured in series with each other; the polyethylene composition comprises:

(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm ³ , a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;

(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm ³ , a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;

Here, the ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;

The polyethylene composition has a density of at least 0.940 g/cm³, a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;

The weight percentage of the first or second ethylene copolymer is defined as the weight of the first or second copolymer, respectively, divided by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100.

Accordingly, the second aspect provides a solution polymerization process for producing the polyethylene composition of the first aspect.

Appropriately, the process on the second side is a dual reactor process.

A third aspect of the present invention is a rotationally molded article manufactured from a polyethylene composition, wherein the polyethylene composition comprises:

(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm ³ , a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;

(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm ³ , a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;

Here, the ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;

The polyethylene composition has a density of at least 0.940 g/cm ³ , a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;

The weight percentage of the first or second ethylene copolymer is defined as the weight of the first or second copolymer, respectively, divided by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100.

Accordingly, the third aspect provides a rotationally molded article manufactured from the polyethylene composition of the first aspect.

The present invention encompasses combinations of the described aspects and preferred features, except where such combinations are expressly disallowed or expressly avoided.

Embodiments and experiments illustrating the principles of the present invention will now be discussed with reference to the accompanying drawings:
Figure 1 shows the temperature rising elution fraction profiles obtained from TREF-CEF for Examples 1 to 3 of the present invention and Comparative Examples 7, 12 and 13.
Figure 2 shows the molecular weight distribution and comonomer distribution from GPC-FTIR measurements (Examples 1 to 3 of the present invention and Comparative Examples 15 and 16 are presented in Graph A, and Example 3 of the present invention and Comparative Examples 7 and 10 to 13 are presented in Graph B).
Figure 3 shows complex viscosity profiles obtained from DMA frequency sweeps at 190°C (graphs A, B, and C) and Ellis model estimated zero shear viscosity versus weight average molecular weight (graph D) for examples of the present invention and several comparative examples.
Figure 4 shows the ESCR results for the A100 condition (Graph A) and Izod impact (Graph B) plotted against the bending secant modulus, respectively.
Figure 5 shows the results of tests performed on rotationally formed specimens - specifically, the ARM impact average fracture energy at -40°C (graphs A and B), the ductility at -40°C (graphs C and D), and the difference between the rotationally formed as-is density and the plaque density (graphs E and F).

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying drawings. Additional aspects and embodiments will be apparent to those skilled in the art. All documents cited herein are incorporated herein by reference.

Definition of terms

Unless otherwise stated in the examples or otherwise, all numbers or expressions expressing quantities of ingredients, preparation conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained in various embodiments. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. The numerical values set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors that inevitably result from the standard deviation found in corresponding testing and measurements.

Any numerical range set forth herein should be understood to include all subranges subsumed therein. For example, a range of "1 to 10" includes all subranges therebetween, including the listed minimum value of 1 and the listed maximum value of 10; that is, the minimum value is greater than or equal to 1 and the maximum value is less than or equal to 10. The disclosed numerical ranges are continuous and therefore include all values between the minimum and maximum values. Unless explicitly stated otherwise, the various numerical ranges set forth herein are approximations.

All compositional ranges expressed in this specification are limited to a total of 100% (vol% or wt%) and will not actually exceed 100%. If multiple components are present in a composition, the sum of the maximum amounts of each component may exceed 100%, provided that those skilled in the art will recognize that the actual amounts of the components used will be at most 100%.

To facilitate a more complete understanding of the present disclosure, the following terms are defined and should be used in conjunction with the accompanying drawings and the general description of the various embodiments.

As used herein, the term “monomer” refers to a small molecule that can chemically react to form a polymer by chemically combining with itself or with other monomers.

As used herein, the term "α-olefin" or "alpha-olefin" is used to describe a monomer having a linear hydrocarbon chain containing 3 to 20 carbon atoms with a double bond at one end of the chain; an equivalent term is "linear α-olefin".

As used herein, the term "polyethylene" or "ethylene polymer" refers to a macromolecule produced from ethylene monomer and optionally one or more additional monomers; and is independent of the specific catalyst or specific process used to prepare the ethylene polymer.

The term "ethylene homopolymer" or "polyethylene homopolymer" means that the polymer referred to is the product of a polymerization process in which ethylene is intentionally added or intentionally present as the only polymerizable monomer.

The term "ethylene copolymer" or "polyethylene copolymer" means that the polymer referred to is the product of a polymerization process in which ethylene and one or more α-olefins are intentionally added or intentionally present as polymerizable monomers.

So-called "long-chain branching" or "long-chain branching" is distinguished from short-chain branching in that it is macromolecular in nature and may be, for example, similar in length to the polymer backbone (to which the long-chain branch is attached).

As used herein, the term "unsubstituted" means that a hydrogen radical is bonded to the molecular group following the term unsubstituted. The term "substituted" means that the group following the term bears one or more moieties (non-hydrogen radicals) that replace one or more hydrogen radicals at any position within the group; non-limiting examples of moieties include halogen radicals (F, Cl, Br), hydroxyl groups, carbonyl groups, carboxyl groups, silyl groups, amine groups, phosphine groups, alkoxy groups, phenyl groups, naphthyl groups, C ₁ to C ₃₀ alkyl groups, C ₂ to C ₃₀ alkenyl groups, and combinations thereof. Non-limiting examples of substituted alkyl and aryl radicals include acyl radicals, alkylsilyl radicals, alkylamino radicals, alkoxy radicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyl radicals, alkyl- and dialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals, arylamino radicals, and combinations thereof.

As used herein, the term "hydrocarbyl", "hydrocarbyl radical" or "hydrocarbyl group" refers to a linear or cyclic, aliphatic, olefinic, acetylenic and aryl (aromatic) radical containing hydrogen and carbon and lacking one hydrogen.

As used herein, the term "alkyl radical" includes linear, branched, and cyclic paraffin radicals lacking one hydrogen radical; non-limiting examples include methyl (-CH ₃ ) and ethyl (-CH ₂ CH ₃ ) radicals. The term "alkenyl radical" refers to linear, branched, and cyclic hydrocarbons containing at least one carbon-carbon double bond lacking one hydrogen radical.

As used herein, the term "aryl" group includes phenyl, naphthyl, pyridyl and other radicals whose molecules have an aromatic ring structure; non-limiting examples include naphthylene, phenanthrene and anthracene. An "arylalkyl" group is an alkyl group having an aryl group suspended therefrom; non-limiting examples include benzyl, phenethyl and tolylmethyl; and an "alkylaryl" is an aryl group having one or more alkyl groups suspended therefrom; non-limiting examples include tolyl, xylyl, mesityl and cumyl.

As used herein, the phrase "heteroatom" includes any atom other than carbon and hydrogen that can be bonded to carbon. A "heteroatom-containing group" is a hydrocarbon radical that contains a heteroatom and may contain one or more identical or different heteroatoms. In some embodiments, the heteroatom-containing group is a hydrocarbyl group containing one to three atoms selected from the group consisting of boron, aluminum, silicon, germanium, nitrogen, phosphorus, oxygen, and sulfur. Non-limiting examples of heteroatom-containing groups include radicals such as imines, amines, oxides, phosphines, ethers, ketones, oxoazoline heterocyclics, oxazolines, and thioethers. The term "heterocyclic" refers to a ring system having a carbon skeleton that includes one to three atoms selected from the group consisting of boron, aluminum, silicon, germanium, nitrogen, phosphorus, oxygen, and sulfur.

The present disclosure provides a polyethylene composition comprising two components: (i) a first ethylene copolymer; and (ii) a second ethylene copolymer different from the first ethylene copolymer.

In some embodiments, the polyethylene composition is useful for making molded articles.

In some embodiments, the polyethylene composition is useful for making rotationally molded articles.

In some embodiments, the polyethylene composition is useful for making compression molded or injection molded articles.

In some embodiments, the polyethylene composition is useful for the manufacture of blown films.

first ethylene copolymer

In some embodiments, the first ethylene copolymer comprises both polymerized ethylene and at least one polymerized α-olefin comonomer, wherein the polymerized ethylene is the predominant species.

In some embodiments, the α-olefin copolymerizable with ethylene to prepare the first ethylene copolymer can be selected from the group consisting of 1-propene, 1-butene, 1-pentene, 1-hexene, and 1-octene, and mixtures thereof.

In some embodiments, the first ethylene copolymer is prepared using a single-site catalyst, non-limiting examples of which include phosphinimine catalysts, metallocene catalysts, and constrained geometry catalysts, all of which are well known in the art.

In some embodiments, the first ethylene copolymer is prepared using a single-site polymerization catalyst in a solution phase polymerization process.

In some embodiments, the first ethylene copolymer is prepared with a single-site catalyst having hafnium (Hf) as the active metal center.

In some embodiments, the first ethylene copolymer is an ethylene/1-octene copolymer.

In some embodiments, the first ethylene copolymer is prepared with a metallocene catalyst.

In some embodiments, the first ethylene copolymer is prepared with a crosslinked metallocene catalyst.

In some embodiments, the first ethylene copolymer is prepared with a crosslinked metallocene catalyst having the following formula (I):

In formula (I): M is a Group 4 metal selected from titanium, zirconium or hafnium; G is a Group 14 element selected from carbon, silicon, germanium, tin or lead; R ₁ is a hydrogen atom, a C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _6-10 aryl oxide radical; R ₂ and R ₃ are independently selected from a hydrogen atom, a C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _6-10 aryl oxide radical; R ₄ and R ₅ are independently selected from a hydrogen atom, an unsubstituted C _1-20 hydrocarbyl radical, a substituted C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _6-10 aryl oxide radical; Q is an independently activatable leaving ligand.

In some embodiments, G is carbon.

In some embodiments, R ₄ and R ₅ are independently aryl groups.

In some embodiments, R ₄ and R ₅ are independently a phenyl group or a substituted phenyl group.

In some embodiments, R ₄ and R ₅ are phenyl groups.

In some embodiments, R ₄ and R ₅ are independently substituted phenyl groups.

In some embodiments, R ₄ and R ₅ are substituted phenyl groups, wherein the phenyl groups are substituted with substituted silyl groups.

In some embodiments, R ₄ and R ₅ are substituted phenyl groups, wherein the phenyl groups are substituted with trialkyl silyl groups.

In some embodiments, R ₄ and R ₅ are substituted phenyl groups, wherein the phenyl group is substituted with a trialkylsilyl group at the para position. In one embodiment, R ₄ and R ₅ are substituted phenyl groups, wherein the phenyl group is substituted with a trimethylsilyl group at the para position. In one embodiment, R ₄ and R ₅ are substituted phenyl groups, wherein the phenyl group is substituted with a triethylsilyl group at the para position.

In some embodiments, R ₄ and R ₅ are independently an alkyl group.

In some embodiments, R ₄ and R ₅ are independently an alkenyl group.

In some embodiments, R ₁ is hydrogen.

In some embodiments, R ₁ is an alkyl group.

In some embodiments, R ₁ is an aryl group.

In some embodiments, R ₁ is an alkenyl group.

In some embodiments, R ₂ and R ₃ are independently a hydrocarbyl group having 1 to 30 carbon atoms.

In some embodiments, R ₂ and R ₃ are independently aryl groups.

In some embodiments, R ₂ and R ₃ are independently an alkyl group.

In some embodiments, R ₂ and R ₃ are independently an alkyl group having 1 to 20 carbon atoms.

In some embodiments, R ₂ and R ₃ are independently a phenyl group or a substituted phenyl group.

In some embodiments, R ₂ and R ₃ are tert-butyl groups.

In some embodiments, R ₂ and R ₃ are hydrogen.

In some embodiments, M is hafnium (Hf).

In some embodiments, the first ethylene copolymer is prepared using a crosslinked metallocene catalyst having the following formula (I):

In formula (I): G is a Group 14 element selected from carbon, silicon, germanium, tin or lead; R ₁ is a hydrogen atom, a C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _6-10 aryl oxide radical; R ₂ and R ₃ are independently selected from a hydrogen atom, a C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _{6-10 aryl} oxide radical; R ₄ and R ₅ are independently selected from a hydrogen atom, an unsubstituted C _1-20 hydrocarbyl radical, a substituted C 1-20 hydrocarbyl radical, a C _1-20 alkoxy radical or a C _6-10 aryl oxide radical; Q is an independently activatable leaving group ligand.

As used herein, the term "activatable" means that the ligand Q can be cleaved from the metal center M via a protonolysis reaction, or abstracted from the metal center M, respectively, by a suitable acidic or electrophilic catalyst activator compound (also called a "cocatalyst" compound), examples of which are described below. The activatable ligand Q can also be converted to another ligand that is cleaved or abstracted from the metal center M (e.g., a halide can be converted to an alkyl group). Without wishing to be bound by any single theory, it is believed that the protonolysis or abstraction reaction creates an active "cationic" metal center capable of polymerizing olefins.

In some embodiments, the activatable ligand Q is independently selected from the group consisting of a hydrogen atom; a halogen atom; a C _1-20 hydrocarbyl radical, a C _1-20 alkoxy radical, and a C _6-10 aryl or aryloxy radical, wherein each of the hydrocarbyl, alkoxy, aryl, or aryl oxide radicals may be unsubstituted or further substituted with one or more halogens or other groups; a C _1-8 alkyl; a C _1-8 alkoxy; a C _6-10 aryl or aryloxy; an amido or phosphido radical, provided that Q is not cyclopentadienyl. Two Q ligands may also be joined to each other to form, for example, a substituted or unsubstituted diene ligand (e.g., 1,3-butadiene); It may also form a delocalized heteroatom-containing group such as an acetate or acetamidinate group. In a convenient embodiment of the present disclosure, each Q is independently selected from the group consisting of a halide atom, a C _1-4 alkyl radical, and a benzyl radical. Particularly suitable activatable ligands Q are monoanionic, such as halides (e.g., chlorides) or hydrocarbyls (e.g., methyl, benzyl).

In some embodiments, the single-site catalyst used to prepare the first ethylene copolymer is diphenylmethylene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dichloride having the molecular formula: [(2,7-tBu ₂ Flu)Ph ₂ C(Cp)HfCl ₂ ].

In some embodiments, the single-site catalyst used to prepare the first ethylene copolymer is diphenylmethylene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dimethyl having the molecular formula: [(2,7-tBu ₂ Flu)Ph ₂ C(Cp)HfMe ₂ ].

In addition to the single-site catalyst molecule itself, the active single-site catalyst system may further comprise one or more of the following: an alkylaluminoxane cocatalyst and an ionic activator. The single-site catalyst system may also optionally comprise a hindered phenol.

Although the exact structure of alkylaluminoxanes is uncertain, experts in the field generally agree that they are oligomeric species containing repeating units of the following general formula:

(R) ₂ AlO-(Al(R)-O) _n -Al(R) ₂

Here, the R group can be a linear, branched or cyclic hydrocarbyl radical containing 1 to 20 identical or different carbon atoms, and n is 0 to about 50. A non-limiting example of an alkylaluminoxane is methylaluminoxane (or MAO), wherein each R group is a methyl radical.

In some embodiments, R of the alkylaluminoxane is a methyl radical and m is 10 to 40.

In some embodiments, the co-catalyst is modified methylaluminoxane (MMAO).

It is well known in the art that alkylaluminoxanes can play a dual role as alkylating agents and activators. Therefore, alkylaluminoxane cocatalysts are often used in combination with activatable ligands such as halogens.

Typically, ionic activators consist of a cation and a bulky anion, where the anion is substantially non-coordinating. A non-limiting example of an ionic activator is a boron ionic activator, which is tetracoordinated with four ligands bonded to the boron atom. Non-limiting examples of boron ionic activators include the following chemical formulas:

[R ⁵ ] ⁺ [B(R ⁷ ) ₄ ] ^-

wherein B represents a boron atom, R ⁵ is an aromatic hydrocarbyl (e.g., triphenyl methyl cation), each R ⁷ is a phenyl radical which is unsubstituted or substituted with 3 to 5 substituents selected from a fluorine atom, a C _1-4 alkyl or alkoxy radical which is unsubstituted or substituted with a fluorine atom; and a silyl radical of the formula -Si(R ⁹ ) ₃ , wherein each R ⁹ is independently selected from a hydrogen atom and a silyl radical which is independently selected from a C _1-4 alkyl radical, and

[(R ⁸ ) _t ZH] ⁺ [B(R ⁷ ) ₄ ] ^-

Wherein B is a boron atom, H is a hydrogen atom, Z is a nitrogen or phosphorus atom, t is 2 or 3, R ⁸ is selected from a C _1-8 alkyl radical, a phenyl radical which is unsubstituted or substituted by up to three C _1-4 alkyl radicals, or one R ⁸ may form an anilinium radical together with the nitrogen atom, and R ⁷ is as defined above.

A non-limiting example of R ⁷ in both formulas is a pentafluorophenyl radical. Generally, boron ionic activators can be described as salts of tetra(perfluorophenyl)boron; non-limiting examples of which include anilinium, carbonium, oxonium, phosphonium, and sulfonium salts of tetra(perfluorophenyl)boron with anilinium and trityl (or triphenylmethylium). Additional non-limiting examples of ionic activators include: triethylammonium tetra(phenyl)boron, tripropylammonium tetra(phenyl)boron, tri(n-butyl)ammonium tetra(phenyl)boron, trimethylammonium tetra(p-tolyl)boron, trimethylammonium tetra(o-tolyl)boron, tributylammonium tetra(pentafluorophenyl)boron, tripropylammonium tetra(o,p-dimethylphenyl)boron, tributylammonium tetra(m,m-dimethylphenyl)boron, tributylammonium tetra(p-trifluoromethylphenyl)boron, tributylammonium tetra(pentafluorophenyl)boron, tri(n-butyl)ammonium tetra(o-tolyl)boron, N,N-dimethylanilinium tetra(phenyl)boron, N,N-diethylanilinium tetra(phenyl)boron, N,N-Diethylanilinium tetra(phenyl)n-butylboron, N,N-2,4,6-pentamethylanilinium tetra(phenyl)boron, di-(isopropyl)ammonium tetra(pentafluorophenyl)boron, dicyclohexylammonium tetra(phenyl)boron, triphenylphosphonium tetra(phenyl)boron, tri(methylphenyl)phosphonium tetra(phenyl)boron, tri(dimethylphenyl)phosphonium tetra(phenyl)boron, tropylium tetrakispentafluorophenyl borate, triphenylmethylium tetrakispentafluorophenyl borate, benzene(diazonium)tetrakispentafluorophenyl borate, tropylium tetrakis(2,3,5,6-tetrafluorophenyl)borate, triphenylmethylium tetrakis(2,3,5,6-tetrafluorophenyl)borate, benzene(diazonium) Tetrakis(3,4,5-trifluorophenyl)borate, tropylium tetrakis(3,4,5-trifluorophenyl)borate, benzene(diazonium) tetrakis(3,4,5-trifluorophenyl)borate, tropylium tetrakis(1,2,2-trifluoroethenyl)borate, triphenylmethylium tetrakis(1,2,2-trifluoroethenyl)borate, benzene(diazonium) tetrakis(1,2,2-trifluoroethenyl)borate, tropylium tetrakis(2,3,4,5-tetrafluorophenyl)borate, triphenylmethylium tetrakis(2,3,4,5-tetrafluorophenyl)borate, and benzene(diazonium) tetrakis(2,3,4,5-tetrafluorophenyl)borate. Readily available commercial ionic activators include N,N-dimethylanilinium tetrakispentafluorophenyl borate and triphenylmethylium tetrakispentafluorophenyl borate.

Non-limiting examples of hindered phenols include butylated phenol antioxidants, butylated hydroxytoluene, 2,6-di-tert-butyl-4-ethyl phenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate.

To produce an active metallocene-based catalyst system, the amounts and molar ratios of three or four components, i.e., metallocene single-site catalyst, alkylaluminoxane, ionic activator, and optional hindered phenol, are optimized.

In some embodiments, the single site catalyst used to prepare the first ethylene copolymer produces long chain branches, and the first ethylene copolymer will contain long chain branches, hereinafter referred to as 'LCBs'.

LCB is a well-known structural phenomenon in ethylene copolymers and is well known to those skilled in the art. Traditionally, three methods have been used to analyze LCB: nuclear magnetic resonance spectroscopy (NMR), see, e.g., J.C. Randall, J Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, 29, 201; triple-detection SEC with a DRI, viscometer, and low-angle laser light scattering detector, see, e.g., W.W. Yau and D.R. Hill, Int. J. Polym. Anal. Charact. 1996; 2:151; and rheology, see, e.g., W.W. Graessley, Acc. Chem. Res. 1977, 10, 332-339. In embodiments of the present disclosure, the long chain branches are macromolecular in nature, i.e., sufficiently long to be observed in NMR spectra, triple detector SEC experiments, or rheological experiments.

In some embodiments, the first ethylene copolymer contains long chain branching characterized by a long chain branching factor (LCBF) as disclosed herein. In embodiments of the present disclosure, the upper limit of the LCBF of the first ethylene copolymer can be 0.5000, or 0.4000, or 0.0375, or 0.3000 (dimensionless). In embodiments of the present disclosure, the lower limit of the LCBF of the first ethylene copolymer can be 0.0010, 0.0015, 0.0020, 0.0050, 0.0070, 0.0100, 0.0500, or 0.1000 (dimensionless).

In embodiments of the present disclosure, the LCBF of the first ethylene copolymer is at least 0.0010, or at least 0.0020, or at least 0.0050, or at least 0.0070, or at least 0.0100.

The first ethylene copolymer may contain catalyst residue reflecting the chemical composition of the catalyst formulation used to prepare it. Those skilled in the art will appreciate that, for example, if the metal present in the first ethylene copolymer (or polyethylene composition; see below) originates from the metal of the catalyst formulation used to prepare it, the catalyst residue is typically quantified in parts per million of the metal. Non-limiting examples of metal residues that may be present include Group 4 metals, titanium, zirconium, and hafnium. In embodiments of the present disclosure, the upper limit for the ppm of the metal in the first ethylene copolymer may be about 3.0 ppm, in other cases about 2.0 ppm, and in other cases about 1.5 ppm. In embodiments of the present disclosure, the lower limit for the ppm of the metal in the first ethylene copolymer may be about 0.03 ppm, in other cases about 0.09 ppm, and in other cases about 0.15 ppm.

In some embodiments, the first ethylene copolymer has from 0.03 to 3.0 ppm of metal, or from 0.09 to 3.0 ppm of metal, or from 0.15 to 3.0 ppm of metal, or from 0.03 to 2.0 ppm of metal, or from 0.09 to 2.0 ppm of metal, or from 0.15 to 2.0 ppm of metal, or from 0.03 to 1.5 ppm of metal, or from 0.09 to 1.5 ppm of metal, or from 0.15 to 1.5 ppm of metal.

In some embodiments, the first ethylene copolymer has at least 1, at least 2, at least 3, at least 4, at least 5, at least 7, at least 8.5, or at least 10 short chain branches (SCB1) per 1,000 carbon atoms.

In some embodiments, the first ethylene copolymer has at most 100, or at most 75, or at most 50, or at most 30, or at most 25, or at most 20 short chain branches (SCB1) per 1,000 carbon atoms.

In some embodiments, the first ethylene copolymer has from 1 to 100 short chain branches per 1,000 carbon atoms (SCB1). In some embodiments, the first ethylene copolymer has from 2 to 100 short chain branches (SCB1) per 1,000 carbon atoms, or from 3 to 100 short chain branches (SCB1) per 1,000 carbon atoms, or from 4 to 100 short chain branches (SCB1) per 1,000 carbon atoms, or from 2 to 75 short chain branches (SCB1) per 1,000 carbon atoms, or from 3 to 75 short chain branches (SCB1) per 1,000 carbon atoms, or from 4 to 75 short chain branches (SCB1) per 1,000 carbon atoms, or from 2 to 50 short chain branches (SCB1) per 1,000 carbon atoms, or from 3 to 50 short chain branches (SCB1) per 1,000 carbon atoms, or from 4 to 75 short chain branches (SCB1) per 1,000 carbon atoms. 50 short chain branches (SCB1), or 2 to 30 short chain branches (SCB1) per 1,000 carbon atoms, or 3 to 30 short chain branches (SCB1) per 1,000 carbon atoms, or 4 to 30 short chain branches (SCB1) per 1,000 carbon atoms, or 5 to 30 short chain branches (SCB1) per 1,000 carbon atoms, or 7 to 30 short chain branches (SCB1) per 1,000 carbon atoms, or 2 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 3 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 4 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 5 to 25 short chain branches (SCB1), or 7 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 8.5 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 10 to 25 short chain branches (SCB1) per 1,000 carbon atoms, or 2 to 20 short chain branches (SCB1) per 1,000 carbon atoms, or 3 to 20 short chain branches (SCB1) per 1,000 carbon atoms, or 4 to 20 short chain branches (SCB1) per 1,000 carbon atoms, or 5 to 20 short chain branches (SCB1) per 1,000 carbon atoms, or 7 to 20 short chain branches (SCB1) per 1,000 carbon atoms It has 8.5 to 20 short chain branches (SCB1), or 10 to 20 short chain branches (SCB1) per 1,000 carbon atoms.

In some embodiments, the first ethylene copolymer has from 2 to 30 short chain branches per 1,000 carbon atoms.

In some embodiments, the first ethylene copolymer has from 4 to 25 short chain branches per 1,000 carbon atoms.

In some embodiments, the first ethylene copolymer has from 4 to 20 short chain branches per 1,000 carbon atoms.

Short-chain branching (i.e., short chain branches per thousand backbone carbon atoms, SCB1) is branching due to the presence of an α-olefin comonomer in the ethylene copolymer, for example, 2 carbon atoms for 1-butene comonomer, 4 carbon atoms for 1-hexene comonomer, or 6 carbon atoms for 1-octene comonomer, etc.

In an embodiment of the present disclosure, the number of short chain branches (SCB1) per 1,000 carbon atoms in the first ethylene copolymer is greater than the number of short chain branches (SCB2) per 1,000 carbon atoms in the second ethylene copolymer.

In some embodiments, the density of the first copolymer is lower than the density of the second ethylene copolymer.

The density of the first ethylene copolymer is from 0.880 to 0.930 g/cm³, including any narrower range therein and any value subsumed therein. For example, in some embodiments, the first ethylene copolymer has a viscosity of from 0.880 to 0.925 g/cm ³ , or from 0.880 to 0.922 g/cm ³ , or from 0.880 to 0.920 g/cm ³ , or from 0.880 to 0.918 g/cm ³ , or from 0.890 to 0.930 g/cm ³ , or from 0.890 to 0.925 g/cm ³ , or from 0.890 to 0.922 g/cm ³ , or from 0.890 to 0.920 g/cm ³ , or from 0.890 to 0.918 g/cm ³ , or from 0.900 to 0.930 g/cm ³ , or from 0.900 to 0.925 g/cm ³ , or 0.900 to 0.922 g/cm ³ , or 0.900 to 0.920 g/cm ³ , or 0.900 to 0.918 g/cm ³ , or 0.905 to 0.930 g/cm ³ , or 0.905 to 0.925 g/cm ³ , or 0.905 to 0.922 g/cm ³ , or 0.905 to 0.920 g/cm ³ , or 0.905 to 0.918 g/cm ³ , or 0.910 to 0.930 g/cm ³ , or 0.910 to 0.925 g/cm ³ , or 0.910 to 0.922 g/cm ³ , or 0.910 to 0.920 g/cm ³ , or a density of 0.910 to 0.918 g/cm ³ .

In some embodiments, the first ethylene copolymer has a density of less than 0.880 to 0.925 g/cm ³ .

In some embodiments, the first ethylene copolymer has a density of 0.890 to 0.925 g/cm ³ .

In some embodiments, the first ethylene copolymer has a density less than 0.920 g/cm ³ or less than 0.918 g/cm ³ .

In some embodiments, the first ethylene copolymer has a density greater than 0.900 g/cm ³ , or greater than 0.905 g/cm ³ .

In some embodiments, the melt index (I ₂ ) of the first ethylene copolymer is lower than the melt index (I ₂ ) of the second ethylene copolymer.

In some embodiments, the first ethylene copolymer has a melt index (I ₂ ) of ≤ 10 g/10 min, or ≤ 5.0 g/10 min, or ≤ 2.5 g/10 min, or ≤ 1.0 g/10 min, or ≤ 0.7 g/10 min, or ≤ 0.5 g/10 min, or < 0.5 g/10 min.

In some embodiments, the first ethylene copolymer has a melt index (I ₂ ) of at most 1.0 g/10 min.

In some embodiments, the first ethylene copolymer has a melt index (I ₂ ) from 0.001 to 10.0 g/10 min, including any narrower range therein and any value subsumed therein. For example, in some embodiments, the melt index (I ₂ ) of the first ethylene copolymer is from 0.001 to 7.5 g/10 min, or from 0.001 to 5.0 g/10 min, or from 0.001 to 2.5 g/10 min, or from 0.001 to 1.0 g/10 min, or from 0.001 to 0.7 g/10 min, or from 0.001 to 0.5 g/10 min, or from 0.01 to 10.0 g/10 min, or from 0.01 to 7.5 g/10 min, or from 0.01 to 5.0 g/10 min, or from 0.01 to 2.5 g/10 min, or from 0.01 to 1.0 g/10 min, or from 0.01 to 0.7 g/10 min, or from 0.01 to 0.5 g/10 min, or 0.05 to 10.0 g/10 min, or 0.05 to 7.5 g/10 min, or 0.05 to 5.0 g/10 min, or 0.05 to 2.5 g/10 min, or 0.05 to 1.0 g/10 min, or 0.05 to 0.7 g/10 min, or 0.05 to 0.5 g/10 min, or less than 0.05 to 0.5 g/10 min.

In some embodiments, the first ethylene copolymer has a melt index (I ₂ ) of from 0.001 to 0.7 g/10 min.

In some embodiments, the first ethylene copolymer has a melt flow ratio (I ₂₁ /I ₂ ) of less than 25, or less than 23, or less than 20.

The first ethylene copolymer has a weight average molecular weight (M _w ) of from 130,000 to 275,000 g/mol, including any narrower ranges therein and any subsumed therein. For example, in some embodiments, the first ethylene copolymer has a weight average molecular weight (M _w ) of from 130,000 to 260,000 g/mol, or from 130,000 to 250,000 g/mol, or from 130,000 to 240,000 g/mol, or from 140,000 to 260,000 g/mol, or from 140,000 to 250,000 g/mol, or from 140,000 to 240,000 g/mol.

In some embodiments, the first ethylene copolymer has a weight average molecular weight (M _w ) of at least 125,000 g/mol, or at least 130,000 g/mol, or at least 135,000 g/mol, or at least 140,000 g/mol, or at least 145,000 g/mol.

In some embodiments, the first ethylene copolymer has a weight average molecular weight (M _w ) of at most 275,000 g/mol, or at most 265,000 g/mol, or at most 260,000 g/mol, or at most 255,000 g/mol, or at most 250,000 g/mol, or at most 245,000 g/mol, or at most 240,000 g/mol.

In some embodiments, the upper limit of the molecular weight distribution (M _w /M _n ) of the first ethylene copolymer is about 2.7, or about 2.5, or about 2.4, or about 2.3. In some embodiments, the lower limit of the molecular weight distribution (M _w /M _n ) of the first ethylene copolymer is about 1.7, or about 1.8, or about 1.9.

The first ethylene copolymer has a molecular weight distribution (M _w /M _n ) from 1.7 to 2.7, including any narrower ranges therein and any subsumed therein. For example, in some embodiments, the first ethylene copolymer has a molecular weight distribution (M _w /M _n ) from 1.8 to 2.7, or from 1.8 to 2.5, or from 1.8 to 2.4, or from 1.8 to 2.3, or from 1.9 to 2.7, or from 1.9 to 2.5, or from 1.9 to 2.4, or from 1.9 to 2.3.

In some embodiments, the upper limit of the CDBI ₅₀ of the first ethylene copolymer can be about 98 wt%, in other cases about 95 wt%, and in still other cases about 90 wt%. In some embodiments, the lower limit of the CDBI ₅₀ of the first ethylene copolymer can be about 70 wt%, in other cases about 75 wt%, and in still other cases about 80 wt%.

In some embodiments, a single-site catalyst that provides an ethylene copolymer having at least 65 wt%, or at least 70 wt%, or at least 75 wt%, or at least 80 wt%, or at least 85 wt% CDBI ₅₀ when solution-phase polymerized in a single reactor is used in the preparation of the first ethylene copolymer.

In some embodiments, the first ethylene copolymer is an ethylene copolymer having a CDBI ₅₀ of greater than about 60 wt%, or greater than about 65 wt%, or greater than about 70 wt%, or greater than about 75 wt%, or greater than about 80 wt%, or greater than about 85 wt%.

The weight percentage (wt %) of the first ethylene copolymer in the polyethylene composition (i.e., the weight percentage of the first ethylene copolymer based on the total weight of the first ethylene copolymer and the second ethylene copolymer) can be from about 10 wt % to about 60 wt %, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the weight percentage (wt%) of the first ethylene copolymer in the polyethylene copolymer composition can be from about 10 wt% to about 55 wt%, or from about 10 wt% to about 50 wt%, or from about 10 wt% to about 45 wt%, or from about 10 wt% to about 40 wt%, or from about 15 wt% to about 55 wt%, or from about 15 wt% to about 50 wt%, or from about 15 wt% to about 40 wt%, or from about 15 wt% to about 35 wt%, or from about 20 wt% to about 45 wt%, or from about 20 wt% to about 40 wt%, or from about 20 wt% to about 35 wt%, or from about 25 wt% to about 50 wt%, or from about 25 wt% to about 40 wt%, or from about 25 wt% to about 35 wt%.

Second ethylene copolymer

In some embodiments, the second ethylene copolymer is prepared using a multi-site catalyst system, non-limiting examples of which include Ziegler-Natta catalysts and chromium catalysts, both of which are well known in the art.

In some embodiments, the alpha-olefin that can be copolymerized with ethylene to produce a second ethylene copolymer is selected from the group comprising 1-propene, 1-butene, 1-pentene, 1-hexene, and 1-octene, and mixtures thereof.

In some embodiments, the second ethylene copolymer is a heterogeneously branched ethylene copolymer.

In some embodiments, the second ethylene copolymer is an ethylene/1-octene copolymer.

In some embodiments, the second ethylene copolymer is prepared using a Ziegler-Natta catalyst system.

Ziegler-Natta catalyst systems are well known to those skilled in the art. Ziegler-Natta catalysts can be in-line or batch Ziegler-Natta catalyst systems. The term "in-line Ziegler-Natta catalyst system" refers to the continuous synthesis of a small quantity of active Ziegler-Natta catalyst system and the immediate injection of this catalyst into at least one continuously operating reactor, where the catalyst polymerizes ethylene and one or more optional α-olefins to form ethylene polymers. The term "batch Ziegler-Natta catalyst system" or "batch Ziegler-Natta procatalyst" refers to the synthesis of a much larger quantity of catalyst or procatalyst in one or more mixing vessels external to or separate from the continuously operating solution polymerization process. Once produced, the batch Ziegler-Natta catalyst system or batch Ziegler-Natta procatalyst is transferred to a catalyst storage tank. The term "procatalyst" refers to an inert catalyst system (inert to ethylene polymerization); the procatalyst is converted to an active catalyst by the addition of an alkyl aluminum cocatalyst. Optionally, the procatalyst is pumped from a storage tank to at least one continuously operating reactor, where the active catalyst polymerizes ethylene and one or more optional α-olefins to form an ethylene copolymer. The procatalyst may be converted to an active catalyst within the reactor, outside the reactor, or on its way to the reactor.

A wide variety of compounds can be used to synthesize active Ziegler-Natta catalyst systems. The following describes various compounds that can be combined to produce active Ziegler-Natta catalyst systems. Those skilled in the art will appreciate that the embodiments of the present disclosure are not limited to the specific compounds disclosed.

An active Ziegler-Natta catalyst system can be formed from a magnesium compound, a chloride compound, a metal compound, an alkyl aluminum cocatalyst, and an aluminum alkyl. As will be appreciated by those skilled in the art, the Ziegler-Natta catalyst system can contain additional components; non-limiting examples of additional components include electron donors, such as amines or ethers.

A non-limiting example of an active in-line (or batch) Ziegler-Natta catalyst system can be prepared as follows. In a first step, a solution of a magnesium compound is reacted with a solution of a chloride compound to form a magnesium chloride support suspended in the solution. A non-limiting example of the magnesium compound includes Mg(R ¹ ) ₂ , wherein the R ¹ groups can be linear, branched, or cyclic hydrocarbyl radicals containing 1 to 10 carbon atoms, which may be the same or different. A non-limiting example of the chloride compound includes R ² Cl , wherein R ² represents a hydrogen atom or a linear, branched, or cyclic hydrocarbyl radical containing 1 to 10 carbon atoms. In the first step, the magnesium compound solution may also contain an aluminum alkyl. Non-limiting examples of aluminum alkyls include Al(R ³ ) ₃ , wherein the R ³ groups can be linear, branched or cyclic hydrocarbyl radicals containing 1 to 10 carbon atoms, which may be the same or different. In the second step, a solution of the metal compound is added to the magnesium chloride solution and the metal compound is supported on the magnesium chloride. Non-limiting examples of suitable metal compounds include M(X) _n or MO(X) _n , wherein M represents a metal selected from groups 4 to 8 of the periodic table or a mixture of metals selected from groups 4 to 8; O represents oxygen; X represents chloride or bromide; and n is an integer from 3 to 6 that satisfies the oxidation state of the metal. Additional non-limiting examples of suitable metal compounds include metal alkyls of Groups 4 to 8, metal alkoxides (which may be prepared by reacting metal alkyls with alcohols), and mixed ligand metal compounds containing a mixture of halide, alkyl, and alkoxide ligands. In the third step, an alkyl aluminum cocatalyst solution is added to the metal compound supported on magnesium chloride. A wide variety of alkyl aluminum cocatalysts are suitable, including those represented by the following chemical formulas:

Al(R ⁴ ) _p (OR ⁹ ) _q (X) _r

Here, the R ⁴ groups can be the same or different, hydrocarbyl groups having 1 to 10 carbon atoms; the OR ⁹ groups can be the same or different, alkoxy or aryloxy groups, wherein R ⁹ is a hydrocarbyl group having 1 to 10 carbon atoms bonded to oxygen; X is chloride or bromide; and (p+q+r) = 3, provided that p is greater than 0. Non-limiting examples of commonly used alkyl aluminum cocatalysts include trimethyl aluminum, triethyl aluminum, tributyl aluminum, dimethyl aluminum methoxide, diethyl aluminum ethoxide, dibutyl aluminum butoxide, dimethyl aluminum chloride or bromide, diethyl aluminum chloride or bromide, dibutyl aluminum chloride or bromide, and ethyl aluminum dichloride or dibromide.

The process for synthesizing the active in-line (or batchwise) Ziegler-Natta catalyst system described in the above paragraph can be carried out in a variety of solvents; non-limiting examples of solvents include linear or branched C ₅ to C ₁₂ alkanes or mixtures thereof.

In some embodiments, the short chain branching of the second ethylene copolymer can be from about 0.05 to about 10.0 short chain branches per 1,000 carbon atoms (SCB2/1000C). In some embodiments, the short chain branching of the second ethylene copolymer can be from 0.05 to 7.5, or from 0.05 to 5.0, or from 0.05 to 3.0, or from 0.05 to 1.5, or from 0.05 to 1.0, or from 0.08 to 7.5, or from 0.08 to 5.0, or from 0.08 to 3.0, or from 0.08 to 1.5, or from 0.08 to 1.0, or from 0.10 to 7.5, or from 0.10 to 5.0, or from 0.10 to 3.0, or from 0.10 to 1.5, or from 0.10 to 1.0 branches per 1,000 carbon atoms (SCB2/1000C).

In some embodiments, the second ethylene copolymer has from 0.05 to 3 short chain branches per 1000 carbon atoms (SCB2/1000C).

Short-chain branching (i.e., short chain branches per 1,000 backbone carbon atoms, SCB2) is branching due to the presence of an α-olefin comonomer in the ethylene copolymer, for example, 2 carbon atoms for 1-butene comonomer, 4 carbon atoms for 1-hexene comonomer, or 6 carbon atoms for 1-octene comonomer.

In embodiments of the present disclosure, the number of short chain branches per 1,000 carbon atoms (SCB2) in the second ethylene copolymer is less than the number of short chain branches per 1,000 carbon atoms (SCB1) in the first ethylene copolymer.

In some embodiments, the density of the second copolymer is greater than the density of the first ethylene copolymer.

The density of the second ethylene copolymer is from 0.940 to 0.975 g/cm³, including any narrower range therein and any value subsumed therein. For example, in some embodiments, the second ethylene copolymer has a viscosity of from 0.940 to 0.970 g/cm ³ , or from 0.940 to 0.965 g/cm ³ , or from 0.945 to 0.975 g/cm ³ , or from 0.945 to 0.970 g/cm ³ , or from 0.945 to 0.965 g/cm ³ , or from 0.950 to 0.975 g/cm ³ , or from 0.950 to 0.970 g/cm ³ , or from 0.950 to 0.965 g/cm ³ , or from 0.955 to 0.975 g/cm ³ , or from 0.955 to 0.972 g/cm ³ , or from 0.955 to 0.970 g/cm ³ , or It has a density of 0.955 to 0.967 g/cm ³ or 0.955 to 0.965 g/cm ³ .

In some embodiments, the melt index (I ₂ ) of the second ethylene copolymer is greater than the melt index (I ₂ ) of the first ethylene copolymer.

In some embodiments, the second ethylene copolymer has a melt index (I ₂ ) of at least 2.0 g/10 min.

In some embodiments, the second ethylene copolymer has a melt index (I ₂ ) from 2.0 to 500 g/10 min, including any narrower range therein and any value subsumed therein. For example, in some embodiments, the melt index (I ₂ ) of the second ethylene copolymer is from 2 to 250 g/10 min, or from 2 to 100 g/10 min, or from 2 to 75 g/10 min, or from 2 to 50 g/10 min, or from 2 to 40 g/10 min, or from 2 to 30 g/10 min, or from 2 to 25 g/10 min, or from 2 to 20 g/10 min, or from 5 to 250 g/10 min, or from 5 to 100 g/10 min, or from 5 to 75 g/10 min, or from 5 to 50 g/10 min, or from 5 to 40 g/10 min, or from 5 to 30 g/10 min, or from 5 to 25 g/10 min, or from 5 to 20 g/10 min, or from 10 to 250 g/10 min, or 10 to 100 g/10 min, or 10 to 75 g/10 min, or 10 to 50 g/10 min, or 10 to 40 g/10 min, or 10 to 30 g/10 min, or 10 to 25 g/10 min, or 10 to 20 g/10 min.

In some embodiments, the melt index (I ₂ ) of the second ethylene copolymer is from 2.0 to 50 g/10 min.

The second ethylene copolymer has a weight average molecular weight (M _w ) of from 20,000 to 90,000 g/mol, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the first ethylene copolymer has a weight average molecular weight (M _w ) of from 20,000 to 80,000 g/mol, or from 20,000 to 70,000 g/mol, or from 20,000 to 65,000 g/mol, or from 30,000 to 90,000 g/mol, or from 30,000 to 80,000 g/mol, or from 30,000 to 70,000 g/mol, or from 30,000 to 65,000 g/mol, or from 40,000 to 90,000 g/mol, or from 40,000 to 80,000 g/mol, or from 40,000 to 70,000 g/mol, or from 40,000 to 65,000 g/mol.

In some embodiments, the second ethylene copolymer has a weight average molecular weight (M _w ) of at least 20,000 g/mol, or at least 30,000 g/mol, or at least 40,000 g/mol.

In some embodiments, the second ethylene copolymer has a weight average molecular weight (M _w ) of at most 90,000 g/mol, or at most 80,000 g/mol, or at most 70,000 g/mol, or at most 65,000 g/mol.

The weight average molecular weight (M _w ) of the second ethylene copolymer is lower than the weight average molecular weight (M _w ) of the first ethylene copolymer.

In some embodiments, the second ethylene copolymer has an upper limit for the molecular weight distribution (M _w /M _n ) of about 4.0, or about 3.5, or about 3.3, or about 3.1, or about 2.9, or about 2.8, or about 2.7. In some embodiments, the lower limit for the molecular weight distribution (M _w /M _n ) of the second ethylene copolymer is about 2.0, or about 2.2, or about 2.4, or about 2.5.

In an embodiment, the second ethylene copolymer has a molecular weight distribution (M _w /M _n ) from 2.0 to 4.5, including any narrower range therein and any value encompassed by the range. For example, in some embodiments, the second ethylene copolymer has a molecular weight distribution (M _w /M _n ) of from 2.0 to 4.0, or from 2.0 to 3.5, or from 2.0 to 3.1, or from 2.0 to 2.9, or from 2.0 to 2.8, or from 2.0 to 2.7, or from 2.2 to 3.3, or from 2.2 to 3.1, or from 2.2 to 2.9, or from 2.2 to 2.8, or from 2.2 to 2.7, or from 2.4 to 3.3, or from 2.4 to 3.1, or from 2.4 to 2.9, or from 2.4 to 2.8, or from 2.4 to 2.7, or from 2.5 to 3.3, or from 2.5 to 3.1, or from 2.5 to 2.9, or from 2.5 to 2.8, or 2.5 to 2.7.

In some embodiments, a multi-site catalyst that provides an ethylene copolymer having less than 60 wt% or less than 50 wt% CDBI ₅₀ when solution-phase polymerized in a single reactor is used to prepare the second ethylene copolymer.

The weight percentage (wt%) of the second ethylene copolymer in the polyethylene composition (i.e., the weight % of the second ethylene copolymer based on the total weight of the first ethylene copolymer and the second ethylene copolymer) is from 90 wt% to 40 wt%, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the weight percentage (wt%) of the second ethylene copolymer in the polyethylene copolymer composition is from about 90 wt% to about 45 wt%, or from about 90 wt% to about 50 wt%, or from about 90 wt% to about 55 wt%, or from about 90 wt% to about 60 wt%, or from about 85 wt% to about 45 wt%, or from about 85 wt% to about 50 wt%, or from about 85 wt% to about 60 wt%, or from about 85 wt% to about 65 wt%, or from about 80 wt% to about 55 wt%, or from about 80 wt% to about 60 wt%, or from about 80 wt% to about 65 wt%, or from about 75 wt% to about 50 wt%, or from about 75 wt% to about 60 wt%, or from about 75 wt% to about 65 wt%.

polyethylene composition

The polyethylene composition comprises a first ethylene copolymer and a second ethylene copolymer, each defined above.

The polyethylene compositions disclosed herein can be prepared using any technique known in the art, including but not limited to melt blending, solution blending, or in-reactor blending to combine the first ethylene copolymer and the second ethylene copolymer.

In some embodiments, the polyethylene composition of the present disclosure is prepared using a single-site catalyst in a first reactor to provide a first ethylene copolymer and a multi-site catalyst in a second reactor to provide a second ethylene copolymer.

In some embodiments, the polyethylene composition of the present disclosure is prepared by polymerizing ethylene and an α-olefin using a single-site catalyst in a first reactor to form a first ethylene copolymer; and polymerizing ethylene and an α-olefin using a multi-site catalyst in a second reactor to form a second ethylene copolymer.

In some embodiments, the polyethylene composition of the present disclosure is prepared by polymerizing ethylene and an α-olefin using a single-site catalyst in a first solution phase polymerization reactor to form a first ethylene copolymer; and polymerizing ethylene and an α-olefin using a multi-site catalyst in a second solution phase polymerization reactor to form a second ethylene copolymer.

In some embodiments, the polyethylene composition of the present disclosure is prepared by polymerizing ethylene and an α-olefin using a single-site catalyst in a first solution phase polymerization reactor to form a first ethylene copolymer; and polymerizing ethylene and an α-olefin using a multi-site catalyst in a second solution phase polymerization reactor to form a second ethylene copolymer, wherein the first and second solution phase polymerization reactors are configured in series with each other.

In some embodiments, the polyethylene composition of the present disclosure is prepared by polymerizing ethylene and an α-olefin using a single-site catalyst in a first solution phase polymerization reactor to form a first ethylene copolymer; and polymerizing ethylene and an α-olefin using a multi-site catalyst in a second solution phase polymerization reactor to form a second ethylene copolymer, wherein the first and second solution phase polymerization reactors are configured in parallel with each other.

In some embodiments, the solution phase polymerization reactor used as the first solution phase reactor is a continuous stirred tank reactor or a tubular reactor.

In some embodiments, the solution phase polymerization reactor used as the second solution phase reactor is a continuous stirred tank reactor or a tubular reactor.

In solution polymerization, the monomer is dissolved/dispersed in a solvent before being fed to the reactor (or, in the case of gaseous monomers, the monomer may be fed to the reactor so that it is dissolved in the reaction mixture). Prior to mixing, the solvent and monomer are typically purified to remove potential catalyst poisons such as water, oxygen, or metallic impurities. Feedstock purification follows standard practices in the relevant art; for example, molecular sieves, alumina beds, and oxygen scavenging catalysts are used to purify the monomer. The solvent itself (e.g., methylpentane, cyclohexane, hexane, or toluene) is preferably treated in a similar manner.

The feedstock may be heated or cooled before being fed into the reactor. Typically, the catalyst components may be premixed with the reaction solvent or fed to the reactor as a separate stream. In some cases, premixing the catalyst components may be desirable to provide reaction time for the catalyst components before entering the polymerization reaction zone. This "inline mixing" technique is well known to those skilled in the art.

Solution polymerization processes for the polymerization or copolymerization of ethylene are well known in the art (see, e.g., U.S. Patent Nos. 6,372,864 and 6,777,509). These processes are carried out in the presence of an inert hydrocarbon solvent. In a solution phase polymerization reactor, a variety of solvents can be used as process solvents; non-limiting examples include linear, branched, or cyclic C ₅ to C ₁₂ alkanes. Suitable catalyst component solvents include aliphatic and aromatic hydrocarbons. Non-limiting examples of aliphatic catalyst component solvents include linear, branched, or cyclic C _5-12 aliphatic hydrocarbons, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, cyclopentane, methylcyclohexane, hydrogenated naphtha, or combinations thereof. Non-limiting examples of aromatic catalyst component solvents include benzene, toluene (methylbenzene), ethylbenzene, o-xylene (1,2-dimethylbenzene), m-xylene (1,3-dimethylbenzene), p-xylene (1,4-dimethylbenzene), a mixture of xylene isomers, hemelitene (1,2,3-trimethylbenzene), pseudocumene (1,2,4-trimethylbenzene), mesitylene (1,3,5-trimethylbenzene), a mixture of trimethylbenzene isomers, prehenythene (1,2,3,4-tetramethylbenzene), durene (1,2,3,5-tetramethylbenzene), a mixture of tetramethylbenzene isomers, pentamethylbenzene, hexamethylbenzene, and combinations thereof.

In a typical solution process, the polymerization temperature can be from about 80° C. to about 300° C. In some embodiments, the polymerization temperature in the solution process is from about 120° C. to about 250° C. The polymerization pressure in the solution process can be a "medium pressure process," meaning that the pressure within the reactor is less than about 6,000 psi (about 42,000 kilopascals or kPa). In some embodiments, the polymerization pressure in the solution process can be from about 10,000 to about 40,000 kPa, or from about 14,000 to about 22,000 kPa (i.e., from about 2,000 psi to about 3,000 psi).

Suitable comonomers (i.e., α-olefins) for copolymerization with ethylene in a solution phase polymerization process include C _3-20 monoolefins and diolefins. In some embodiments, comonomers copolymerizable with ethylene include C _3-12 α-olefins optionally substituted with up to two C _1-6 alkyl radicals, C 8-12 vinyl aromatic monomers optionally substituted with up to two substituents selected from the group consisting of C _1-4 alkyl radicals, and C _4-12 straight chain or cyclic diolefins optionally substituted with C _{1-4 alkyl} radicals. In a further embodiment, the α-olefin copolymerizable with ethylene is one or more of constrained-ring cyclic olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 1-decene, styrene, alpha methyl styrene, and cyclobutene, cyclopentene, dicyclopentadiene norbornene, alkyl-substituted norbornene, alkenyl-substituted norbornene, and the like (e.g., 5-methylene-2-norbornene and 5-ethylidene-2-norbornene, bicyclo-(2,2,1)-hepta-2,5-diene).

In some embodiments, the polyethylene composition comprises ethylene and one or more alpha olefins selected from the group consisting of 1-butene, 1-hexene, 1-octene, and mixtures thereof.

In some embodiments, the polyethylene composition comprises ethylene and one or more alpha olefins selected from the group consisting of 1-hexene, 1-octene, and mixtures thereof.

In some embodiments, the polyethylene composition comprises ethylene and 1-octene.

In some embodiments, the polyethylene composition has from 0.1 to 7.5 mole percent of one or more α-olefins, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has from 0.1 to 5.0 mole percent of one or more α-olefins, or from 0.1 to 3.0 mole percent of one or more α-olefins, or from 0.5 to 5.0 mole percent of one or more α-olefins, or from 0.5 to 3 mole percent of one or more α-olefins, or from 0.1 to 2.5 mole percent of one or more α-olefins, or from 0.1 to 2.0 mole percent of one or more α-olefins, or from 0.5 to 2.0 mole percent of one or more α-olefins.

In some embodiments, the polyethylene composition has from 0.1 to 5.0 mol % 1-octene, or from 0.1 to 3.0 mol % 1-octene, or from 0.5 to 5.0 mol % 1-octene, or from 0.5 to 3 mol % 1-octene, or from 0.1 to 2.5 mol % 1-octene, or from 0.1 to 2.0 mol % 1-octene, or from 0.5 to 2.0 mol % 1-octene.

A polyethylene composition comprising a first ethylene copolymer and a second ethylene copolymer (as defined above) has a ratio of the number of short chain branches per 1,000 carbon atoms (i.e., SCB1) in the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms (i.e., SCB2) in the second ethylene copolymer (SCB1/SCB2) of at least 5.0 (i.e., SCB1/SCB2 ≥ 5.0). In some embodiments, the ratio of short chain branches (SCB1) in the first ethylene copolymer to short chain branches (SCB2) in the second ethylene copolymer is at least 7.5 or greater than 7.5. In some embodiments, the ratio of short chain branches (SCB1) in the first ethylene copolymer to short chain branches (SCB2) in the second ethylene copolymer is at least 10.0 or greater than 10.0. In some embodiments, the ratio of short chain branching (SCB1) in the first ethylene copolymer to short chain branching (SCB2) in the second ethylene copolymer is at least 12.5 or greater than 12.5. In some embodiments, the ratio of short chain branching (SCB1) in the first ethylene copolymer to short chain branching (SCB2) in the second ethylene copolymer is at least 15.0 or greater than 15.0.

In some embodiments, the ratio of the number of short chain branches per 1,000 carbon atoms in the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms in the second ethylene copolymer (SCB1/SCB2) is at least 10.

In one embodiment of the present disclosure, the polyethylene composition comprising the first ethylene copolymer and the second ethylene copolymer (as defined above) will have a ratio of the number of short chain branches per 1000 carbon atoms (i.e., SCB1) in the first ethylene copolymer to the number of short chain branches per 1000 carbon atoms (i.e., SCB2) in the second ethylene copolymer (SCB1/SCB2) of from 5.0 to 100, or from 5.0 to 80.0, or from 10.0 to 100.0, or from 10.0 to 80.0.

In some embodiments, the polyethylene composition is characterized by a short chain branching frequency at M _z (SCB-M _z ), a short chain branching frequency at M _w (SCB-M _w ), and a short chain branching frequency at M _n (SCB-M _n ), wherein the short chain branching frequency is the number of short chain branches per 1,000 polymer backbone carbons at M _z , M _{w ,} and M _{n ,} respectively, as determined by GPC-FTIR analysis.

In some embodiments, the polyethylene composition has a short chain branching content satisfying: SCB-M _z > SCB-M _w > SCB-M _n .

In some embodiments, the polyethylene composition has an SCB-M _z of greater than 2.0 short chain branches per 1,000 polymer backbone carbon atoms. In some embodiments, the polyethylene composition has an SCB-M _z of from 2.0 to 7.5 short chain branches per 1,000 polymer backbone carbon atoms.

In some embodiments, the polyethylene composition has an SCB-M _w of from 0.5 to 5.0 short chain branches per 1,000 polymer backbone carbon atoms. In some embodiments, the polyethylene composition has an SCB-M _w of from 0.5 to 3.5 short chain branches per 1,000 polymer backbone carbon atoms.

In some embodiments, the polyethylene composition has an SCB-M _n of less than 2.0 short chain branches per 1,000 polymer backbone carbon atoms, or less than 1.0 short chain branches per 1,000 polymer backbone carbon atoms.

In some embodiments, the polyethylene composition has a density of ≥ 0.940 g/cm ³ , or > 0.940 g/cm ³ , or ≥ 0.942 g/cm ³ , or > 0.942 g/cm ³ , or ≥ 0.944 g/cm ³ , or > 0.944 g/cm ³ , or ≥ 0.945 g/cm ³ , or > 0.945 g/cm ³ , or ≥ 0.946 g/cm ³ , or > 0.946 g/cm ³ , or ≥ 0.947 g/cm ³ , or > 0.947 g/cm ³ .

In some embodiments, the polyethylene composition has a density of > 0.942 g/cm ³ . In some embodiments, the polyethylene composition has a density of > 0.947 g/cm ³ .

In some embodiments, the polyethylene composition has a density from 0.940 g/cm ³ to 0.965 g/cm ³ , including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a density of from 0.940 to 0.960 g/cm ³ , or from 0.940 to 0.957 g/cm ³ , or from 0.940 to 0.955 g/cm ³ , or from 0.940 to 0.953 g/cm ³ , or from 0.940 to 0.950 g/cm ³ , or from 0.942 to 0.960 g/cm ³ , or from 0.942 to 0.957 g/cm ³ , or from 0.942 to 0.955 g/cm ³ , or from 0.942 to 0.953 g/cm ³ , or from 0.942 to 0.950 g/cm ³ , or from 0.944 to 0.960 g/cm ³ , or 0.944 to 0.957 g/cm ³ , or 0.944 to 0.955 g/cm ³ , or 0.944 to 0.953 g/cm ³ , or 0.944 to 0.950 g/cm ³ , or 0.945 to 0.960 g/cm ³ , or 0.945 to 0.957 g/cm ³ , or 0.945 to 0.955 g/cm ³ , or 0.945 to 0.953 g/cm ³ , or 0.945 to 0.950 g/cm ³ , or 0.946 to 0.960 g/cm ³ , or 0.946 to 0.957 g/cm ³ , or 0.946 to 0.955 g/cm ³ , or 0.946 to 0.953 g/cm ³ , or 0.946 to 0.950 g/cm ³ , or 0.947 to 0.960 g/cm ³ , or 0.947 to 0.957 g/cm ³ , or 0.947 to 0.955 g/cm ³ , or 0.947 to 0.953 g/cm ³ , or 0.947 to 0.950 g/cm ³ .

In some embodiments, the polyethylene composition has a density of 0.942 g/cm ³ to 0.957 g/cm ³ .

In some embodiments, the polyethylene composition has a density of 0.945 g/cm ³ to 0.955 g/cm ³ .

In some embodiments, the polyethylene composition has a density of 0.947 g/cm ³ to 0.955 g/cm ³ .

In some embodiments, the polyethylene composition has a weight average molecular weight (M _w ) of ≤ 130,000 g/mol, or ≤ 120,000 g/mol, or ≤ 110,000 g/mol, or ≤ 105,000 g/mol, or < 130,000 g/mol, or < 120,000 g/mol, or < 110,000 g/mol, or < 105,000 g/mol.

In some embodiments, the polyethylene composition has a weight average molecular weight (M _w ) of from 30,000 to 150,000 g/mol, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a weight average molecular weight (M _w ) of 50,000 to 150,000 g/mol, or 50,000 to 130,000 g/mol, or 50,000 to 120,000 g/mol, or 70,000 to 150,000 g/mol, or 70,000 to 130,000 g/mol, or 70,000 to 120,000 g/mol, or 70,000 to 110,000 g/mol, or 70,000 to 105,000 g/mol, or 75,000 to 130,000 g/mol, or 75,000 to 120,000 g/mol, or 75,000 to 110,000 g/mol, or 75,000 to 105,000 g/mol.

In some embodiments, the polyethylene composition has a weight average molecular weight (M _w ) of 70,000 to 120,000 g/mol.

In some embodiments, the polyethylene composition has a number average molecular weight (M _n ) of ≤ 60,000 g/mol, or ≤ 50,000 g/mol, or < 50,000 g/mol, or ≤ 45,000 g/mol, or < 45,000 g/mol, or ≤ 40,000 g/mol, or < 40,000 g/mol, or ≤ 35,000 g/mol, or < 35,000 g/mol.

In some embodiments, the polyethylene composition has a number average molecular weight (M _n ) of from 5,000 to 60,000 g/mol, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a number average molecular weight (M _n ) of 5,000 to 50,000 g/mol, or 10,000 to 50,000 g/mol, or 10,000 to 45,000 g/mol, or 15,000 to 45,000 g/mol, or 20,000 to 45,000 g/mol, or 10,000 to 40,000 g/mol, or 15,000 to 40,000 g/mol, or 20,000 to 40,000 g/mol, or 10,000 to 35,000 g/mol, or 15,000 to 35,000 g/mol, or 20,000 to 35,000 g/mol.

In some embodiments, the polyethylene composition has a number average molecular weight (M _n ) of 20,000 to 40,000 g/mol.

In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) of ≤ 400,000 g/mol, or ≤ 350,000 g/mol, or ≤ 310,000 g/mol, or ≤ 275,000 g/mol, or ≤ 250,000 g/mol, or < 400,000 g/mol, or < 350,000 g/mol, or < 310,000 g/mol, or < 275,000 g/mol, or < 250,000 g/mol.

In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) of <400,000 g/mol. In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) of <310,000 g/mol.

In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) from 100,000 to 400,000 g/mol, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a molecular weight of from 100,000 to 350,000 g/mol, or from 125,000 to 350,000 g/mol, or from 150,000 to 350,000 g/mol, or from 160,000 to 350,000 g/mol, or from 200,000 to 350,000 g/mol, or from 100,000 to 310,000 g/mol, or from 125,000 to 310,000 g/mol, or from 150,000 to 310,000 g/mol, or from 160,000 to 310,000 g/mol, or from 200,000 to 310,000 g/mol, or from 100,000 to Has a Z-average molecular weight (M z ) of 275,000 g/mol, or 125,000 to 275,000 g/mol, or 150,000 to 275,000 g/mol, or 160,000 to 275,000 g/mol, or 200,000 to 275,000 g/mol, or 100,000 to 250,000 g/mol, or 125,000 to 250,000 g/mol, or 150,000 to 250,000 g/mol, or 160,000 to 250,000 g/ _mol .

In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) of 100,000 to 350,000 g/mol.

In some embodiments, the polyethylene composition has a Z-average molecular weight (M _z ) of 100,000 to 250,000 g/mol.

In some embodiments, the polyethylene composition has a bimodal profile (i.e., a bimodal molecular weight distribution) in gel permeation chromatography (GPC) analysis.

In some embodiments, the polyethylene copolymer composition has a bimodal profile in a gel permeation chromatograph generated according to the method of ASTM D6474-99.

In some embodiments, the polyethylene composition has a unimodal profile (i.e., a unimodal molecular weight distribution) in gel permeation chromatography (GPC) analysis.

In some embodiments, the polyethylene copolymer composition has a unimodal profile in a gel permeation chromatograph generated according to the method of ASTM D6474-99.

The term "unimodal" is defined herein to mean that there will be only one significant peak or maximum apparent in a GPC curve. Conversely, the use of the term "bimodal" is intended to convey that in addition to the first peak, there will be a second peak or shoulder representing higher or lower molecular weight components (i.e., the molecular weight distribution can be said to have two maxima in the molecular weight distribution curve). Alternatively, the term "bimodal" means that there are two maxima in a molecular weight distribution curve generated according to the method of ASTM D6474-99. The term "multimodal" means that there are two or more maxima in a molecular weight distribution curve generated according to the method of ASTM D6474-99, typically more than two maxima.

In some embodiments, the polyethylene composition has a molecular weight distribution (M _w /M _n ) of ≤ 6.0, or < 6.0, or ≤ 5.5, or < 5.5, or ≤ 5.0, or < 5.0, or ≤ 4.5, or < 4.5, or ≤ 4.0, or < 4.0, or ≤ 3.5, or < 3.5, or ≤ 3.0, or < 3.0. In some embodiments, the polyethylene composition has a molecular weight distribution (M _w /M _n ) of 2.0 to 6.5, including any narrower ranges therein and any subsumed therein. For example, in some embodiments, the polyethylene composition has a molecular weight distribution (M _w /M _n ) of from 2.0 to 6.0, or from 2.0 to 5.5, or from 2.0 to 5.0, or from 2.0 to 4.5, or from 2.0 to 4.0, or from 2.0 to 3.5, or from 2.3 to 6.0, or from 2.3 to 5.5, or from 2.3 to 5.0, or from 2.3 to 4.5, or from 2.3 to 4.0, or from 2.3 to 3.5.

In some embodiments, the polyethylene composition has a molecular weight distribution (M _w /M _n ) of less than 4.5. In some embodiments, the polyethylene composition has a molecular weight distribution (M _w /M _n ) of from 2.0 to 4.0.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of at most 3.0 g/10 min, or at most 2.8 g/10 min, or at most 2.6 g/10 min, or at most 2.4 g/10 min, or at most 2.2 g/10 min, or at most 2.0 g/10 min, or at most 1.8 g/10 min, or less than 3.0 g/10 min, or less than 2.8 g/10 min, or less than 2.6 g/10 min, or less than 2.4 g/10 min, or less than 2.2 g/10 min, or less than 2.0 g/10 min, or less than 1.8 g/10 min.

In embodiments, the polyethylene composition has a melt index (I ₂ ) from 1.0 to 3.0 g/10 min, or from 1.0 to less than 3.0 g/10 min, or less than 3.0 g/10 min, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a melt index (I ₂ ) of from 1.0 to 2.8 g/10 min, or from 1.0 to 2.6 g/10 min, or from 1.0 to 2.4 g/10 min, or from 1.0 to 2.2 g/10 min, or from 1.0 to 2.0 g/10 min, or from 1.0 to 1.8 g/10 min, or from 1.3 to 3.0 g/10 min, or from 1.3 to 2.8 g/10 min, or from 1.3 to 2.6 g/10 min, or from 1.3 to 2.4 g/10 min, or from 1.3 to 2.2 g/10 min, or from 1.3 to 2.0 g/10 min, or from 1.3 to 1.8 g/10 min, or from 1.5 to 3.0 g/10 min, or 1.5 to 2.8 g/10 min, or 1.5 to 2.6 g/10 min, or 1.5 to 2.4 g/10 min, or 1.5 to 2.2 g/10 min, or 1.5 to 2.0 g/10 min, or 1.5 to 1.8 g/10 min.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of 1.3 to 3.0 g/10 min.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of less than 1.3 to less than 3.0 g/10 min.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of 1.5 to 3.0 g/10 min.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of less than 1.5 to less than 3.0 g/10 min.

In some embodiments, the polyethylene composition has a melt index (I ₂ ) of 1.3 to 2.6 g/10 min.

In some embodiments, the polyethylene composition has a high load melt index (I ₂₁ ) of at least 20 g/10 min, or at least 25 g/10 min, or at least 30 g/10 min, or at least 35 g/10 min, or at least 40 g/10 min, or greater than 20 g/10 min, or at least 25 g/10 min, or at least 30 g/10 min, or at least 35 g/10 min, or at least 40 g/10 min.

In some embodiments, the polyethylene composition has a high load melt index (I ₂₁ ) of at least 30 g/10 min.

In some embodiments, the polyethylene composition has a high load melt index (I ₂₁ ) of from 20 to 150 g/10 min, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the high load melt index (I ₂₁ ) of the polyethylene composition is from 20 to 125 g/10 min, or from 20 to 100 g/10 min, or from 20 to 80 g/10 min, or from 20 to 70 g/10 min, or from 20 to 60 g/10 min, or from 25 to 150 g/10 min, or from 25 to 125 g/10 min, or from 25 to 100 g/10 min, or from 25 to 80 g/10 min, or from 25 to 70 g/10 min, or from 25 to 60 g/10 min, or from 30 to 150 g/10 min, or from 30 to 125 g/10 min, or from 30 to 100 g/10 min, or from 30 to 80 g/10 min, or from 30 to 70 g/10 min, or 30 to 60 g/10 min, or 35 to 150 g/10 min, or 35 to 125 g/10 min, or 35 to 100 g/10 min, or 35 to 80 g/10 min, or 35 to 70 g/10 min, or 35 to 60 g/10 min, or 40 to 150 g/10 min, or 40 to 125 g/10 min, or 40 to 100 g/10 min, or 40 to 80 g/10 min, or 40 to 70 g/10 min, or 40 to 60 g/10 min.

In some embodiments, the polyethylene composition has a high load melt index (I ₂₁ ) of 30 to 100 g/10 min.

In some embodiments, the polyethylene composition has a melt flow ratio (I ₂₁ /I ₂ ) of ≤ 60, or < 60, or ≤ 50, or < 50, or ≤ 40, or < 40. In some embodiments, the polyethylene composition has a melt flow ratio (I ₂₁ /I ₂ ) of from 15 to 60, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a melt flow ratio (I ₂₁ /I ₂ ) of from 15 to 50, or from 15 to 40, or from 20 to 60, or from 20 to 50, or from 20 to 40, or from 25 to 60, or from 25 to 50, or from 25 to 40.

In some embodiments, the polyethylene composition has a melt flow ratio (I ₂₁ /I ₂ ) of from 20 to 50.

In some embodiments, the polyethylene composition will have a reversed or partially reversed comonomer distribution profile as measured using GPC-FTIR. If the comonomer incorporation decreases with molecular weight as measured using GPC-FTIR, the distribution is described as "normal." If the comonomer incorporation is approximately constant with molecular weight as measured using GPC-FTIR, the comonomer distribution is described as "flat" or "uniform." The terms "reverse comonomer distribution" and "partially reverse comonomer distribution" mean that the GPC-FTIR data obtained for the copolymer has a higher comonomer incorporation in one or more of the higher molecular weight components than in one or more of the lower molecular weight components. The term "inverted (or inverted) comonomer distribution" is used herein to mean that the comonomer contents of the various polymer fractions are not substantially uniform across the molecular weight range of the ethylene copolymer, with the higher molecular weight fractions having a proportionally higher comonomer content (i.e., when comonomer incorporation increases with molecular weight, the distribution is described as "inverted" or "inverted"). If comonomer incorporation rises and then decreases with increasing molecular weight, the comonomer distribution is still considered "inverted", but may also be described as "partially inverted". A partially inverted comonomer distribution will exhibit a peak or maximum.

In some embodiments, the polyethylene composition has an inverted comonomer distribution profile as measured using GPC-FTIR.

In some embodiments, the polyethylene composition has a partially inverted comonomer distribution profile as measured using GPC-FTIR.

In some embodiments, the polyethylene composition comprises about 20 to 75 wt%, or about 20 to 65 wt%, or about 20 to about 60 wt% of CDBI ₅₀ .

In some embodiments, the upper limit for parts per million (ppm) by weight of hafnium in the polyethylene composition is about 3.0 ppm, or about 2.5 ppm, or about 2.4 ppm, or about 2.0 ppm, or about 1.5 ppm, or about 1.0 ppm, or about 0.75 ppm, or about 0.5 ppm. In some embodiments, the lower limit for parts per million (ppm) of hafnium in the polyethylene composition is about 0.0015 ppm, or about 0.0050 ppm, or about 0.0075 ppm, or about 0.010 ppm, or about 0.015 ppm, or about 0.030 ppm, or about 0.050 ppm, or about 0.075 ppm, or about 0.100 ppm, or about 0.150 ppm, or about 0.175 ppm, or about 0.200 ppm.

In some embodiments, the polyethylene composition has at least 0.0015 ppm hafnium, or at least 0.005 ppm hafnium, or at least 0.0075 ppm hafnium, or at least 0.015 ppm hafnium, or at least 0.030 ppm hafnium, or at least 0.050 ppm hafnium, or at least 0.075 ppm hafnium, or at least 0.100 ppm hafnium, or at least 0.125 ppm hafnium, or at least 0.150 ppm hafnium, or at least 0.175 ppm hafnium, or at least 0.200 ppm hafnium, or at least 0.300 ppm hafnium, or at least 0.350 ppm hafnium.

In some embodiments, the polyethylene composition comprises 0.0015 to 2.4 ppm of hafnium, or 0.0050 to 2.4 ppm of hafnium, or 0.0075 to 2.4 ppm of hafnium, or 0.010 to 2.4 ppm of hafnium, or 0.015 to 2.4 ppm of hafnium, or 0.050 to 3.0 ppm of hafnium, or 0.050 to 2.4 ppm of hafnium, or 0.075 to 2.4 ppm of hafnium, or 0.075 to 2.0 ppm of hafnium, or 0.075 to 1.5 ppm of hafnium, or 0.075 to 1.0 ppm of hafnium, 0.075 to 0.75 ppm of hafnium, or 0.100 to 2.0 ppm of hafnium, or 0.100 to 1.5 ppm of hafnium, or 0.100 to 1.0 ppm of hafnium, or 0.100 to 0.75 ppm of hafnium, or 0.20 to 2.0 ppm of hafnium, or 0.20 to 1.5 ppm of hafnium, or 0.20 to 1.0 ppm of hafnium, or 0.20 to 0.75 ppm of hafnium, or 0.35 to 2.0 ppm of hafnium, or 0.35 to 1.5 ppm of hafnium, or 0.35 to 1.0 ppm of hafnium, or 0.35 to 0.75 ppm of hafnium.

In some embodiments, the polyethylene composition has from 0.0015 ppm to 2.4 ppm of hafnium.

In some embodiments, the polyethylene composition contains long chain branching characterized by a long chain branching factor (LCBF) as disclosed herein. In embodiments of the present disclosure, the upper limit of the LCBF of the polyethylene composition is 0.0400 (dimensionless).

In some embodiments, the LCBF of the polyethylene composition is at most 0.0375, or at most 0.0370, or at most 0.0350, or at most 0.0330, or at most 0.0300, or at most 0.0270, or at most 0.0250. In some embodiments, the LCBF of the polyethylene composition is less than 0.0400, or less than 0.0370, or less than 0.0350, or less than 0.0330, or less than 0.0300, or less than 0.0270, or less than 0.0250.

In some embodiments, the LCBF of the polyethylene composition is at least 0.0010, or at least 0.0030, or at least 0.0050, or at least 0.0060, or at least 0.0070, or at least 0.0080. In some embodiments, the LCBF of the polyethylene composition is greater than 0.0010, or greater than 0.0030, or greater than 0.0050, or greater than 0.0060, or greater than 0.0070, or greater than 0.0080.

In some embodiments, the LCBF of the polyethylene composition is from 0.0010 to 0.0400, or from 0.0030 to 0.0400, or from 0.0050 to 0.0400, or from 0.0050 to 0.0375, or from 0.0060 to 0.0400, or from 0.0070 to 0.0400, or from 0.0010 to 0.0370, or from 0.0030 to 0.0370, or from 0.0050 to 0.0370, or from 0.0060 to 0.0370, or from 0.0070 to 0.0370, or from 0.0010 to 0.0350, or from 0.0030 to 0.0350, or from 0.0050 to 0.0350, or 0.0060 to 0.0350, or 0.0070 to 0.0350, or 0.0010 to 0.0330, or 0.0030 to 0.0330, or 0.0050 to 0.0330, or 0.0060 to 0.0330, or 0.0070 to 0.0330, or 0.0010 to 0.0300, or 0.0030 to 0.0300, or 0.0050 to 0.0300, or 0.0060 to 0.0300, or 0.0070 to 0.0300, or 0.0010 to 0.0270, or 0.0030 to 0.0270, or 0.0050 to 0.0270, or 0.0060 to 0.0270, or 0.0070 to 0.0270, or 0.0010 to 0.0250, or 0.0030 to 0.0250, or 0.0050 to 0.0250, or 0.0060 to 0.0250, or 0.0070 to 0.0250.

In some embodiments, the polyethylene composition has an LCBF of 0.0050 to 0.0375.

In some embodiments, the polyethylene composition has an LCBF of 0.0050 to 0.0350.

In some embodiments, the polyethylene composition has an LCBF of 0.0080 to 0.0350.

In some embodiments, the polyethylene composition has a fraction that elutes above 95°C in CTREF analysis.

In some embodiments, the polyethylene composition has a fraction that elutes below 90°C in CTREF analysis.

In some embodiments, the polyethylene composition has a fraction that elutes above about 95°C and a fraction that elutes below about 90°C in a CTREF analysis.

In some embodiments, the polyethylene composition has a rheological width parameter (a) of less than 0.450, or at most 0.450, or less than 0.425, or at most 0.425, or less than 0.400, or at most 0.400, or less than 0.375, or at most 0.375, as measured by the Carreau-Yasuda model.

In some embodiments, the polyethylene composition has a rheological width parameter (a) of at least 0.200, or greater than 0.200, or at least 0.225, or greater than 0.225, or at least 0.250, or greater than 0.250, as measured by the Carreau-Yasuda model.

In some embodiments, the polyethylene composition has a rheological width parameter (a) of from 0.200 to 0.450, or from 0.200 to 0.425, or from 0.200 to 0.400, or from 0.200 to 0.375, or from 0.225 to 0.450, or from 0.225 to 0.425, or from 0.225 to 0.400, or from 0.225 to 0.375, or from 0.250 to 0.450, or from 0.250 to 0.425, or from 0.250 to 0.400, or from 0.250 to 0.375, as measured by the Carreau-Yasuda model.

In some embodiments, the polyethylene composition has a rheological breadth parameter (a) of less than 0.450 as measured by the Carreau-Yasuda model. In some embodiments, the polyethylene composition has a rheological breadth parameter (a) of less than 0.400 as measured by the Carreau-Yasuda model. In some embodiments, the polyethylene composition has a rheological breadth parameter (a) of from 0.200 to 0.400 as measured by the Carreau-Yasuda model.

In some embodiments, the polyethylene composition or plaques made from the ^polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 500 hours, or greater than 600 hours, or greater than 700 hours, or greater than 800 hours, or greater than 900 hours, or greater than 1000 hours, or greater than 1100 hours, or greater than 1200 hours as determined by ASTM D1693 under Condition A of 100% IGEPAL ® CO-630.

In some embodiments, the polyethylene composition or a plaque made of the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 500 hours as determined by ASTM D1693 under Condition A at 100% IGEPAL CO-630. In some embodiments, the polyethylene composition or a plaque made of the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 1000 hours as determined by ASTM D1693 under Condition A at 100% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 500 hours, or greater than 600 hours, or greater than 700 hours, or greater than 800 hours, or greater than 900 hours, or greater than 1000 hours, or greater than 1100 hours, or greater than 1200 hours as determined by ASTM D1693 under Condition B on 100% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 500 hours, or greater than 600 hours, or greater than 700 hours, or greater than 800 hours, or greater than 900 hours, or greater than 1000 hours, or greater than 1100 hours, or greater than 1200 hours as determined by ASTM D1693 under both Condition A and Condition B of 100% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 500 hours, or greater than 600 hours, or greater than 700 hours, or greater than 800 hours, or greater than 900 hours, or greater than 1000 hours, or greater than 1100 hours, or greater than 1200 hours as determined by ASTM D1693 under Condition A or Condition B of 100% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 50 hours, or greater than 60 hours, or greater than 100 hours, or greater than 150 hours, or greater than 200 hours, or greater than 400 hours, or greater than 600 hours, or greater than 700 hours, or greater than 800 hours, or greater than 900 hours as determined by ASTM D1693 under Condition A in 10% IGEPAL CO-630.

In some embodiments, the polyethylene composition or a plaque made from the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 50 hours as determined by ASTM D1693 under Condition A at 10% IGEPAL CO-630. In some embodiments, the polyethylene composition or a plaque made from the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 100 hours as determined by ASTM D1693 under Condition A at 10% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 30 hours, or greater than 40 hours, or greater than 50 hours, or greater than 60 hours, or greater than 100 hours, or greater than 150 hours, or greater than 200 hours, or greater than 400 hours as determined by ASTM D1693 under Condition B in 10% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an environmental stress cracking resistance (ESCR) of greater than 50 hours, or greater than 60 hours, or greater than 100 hours, or greater than 150 hours, or greater than 200 hours, or greater than 400 hours as determined by ASTM D1693 under both Condition A and Condition B of 10% IGEPAL CO-630.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 50 hours, or greater than 60 hours, or greater than 100 hours, or greater than 150 hours, or greater than 200 hours, or greater than 400 hours as determined by ASTM D1693 under Condition A or Condition B of 10% IGEPAL CO-630.

In some embodiments, the polyethylene composition has a zero shear viscosity (η ₀ ) at 190° C. of from about 4,000 Pa.s to about 20,000 Pa.s, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition has a zero shear viscosity (η ₀ ) at 190° C. of from about 4,000 Pa.s to about 16,000 Pa.s, or from about 4,000 Pa.s to about 14,000 Pa.s, or from about 4,000 Pa.s to about 13,000 Pa.s, or from about 6,000 Pa.s to about 20,000 Pa.s, or from about 6,000 Pa.s to about 16,000 Pa.s, or from about 6,000 Pa.s to about 14,000 Pa.s, or from about 6,000 Pa.s to about 13,000 Pa.s, or from about 7,000 Pa.s to about 20,000 Pa.s, or from about 7,000 Pa.s to about 16,000 Pa.s, or From about 7,000 Pa.s to about 14,000 Pa.s, or from about 7,000 Pa.s to about 13,000 Pa.s, or from about 8,000 Pa.s to about 20,000 Pa.s, or from about 8,000 Pa.s to about 16,000 Pa.s, or from about 8,000 Pa.s to about 14,000 Pa.s, or from about 8,000 Pa.s to about 13,000 Pa.s, or from about 10,000 Pa.s to about 20,000 Pa.s, or from about 10,000 Pa.s to about 16,000 Pa.s, or from about 10,000 Pa.s to about 14,000 Pa.s, or from about 10,000 Pa.s to about 13,000 Pa.s.

In some embodiments, the polyethylene composition has a relative modulus (elasticity ratio G'/G") at 0.05 rad/s of at most 0.30, or at most 0.27, or at most 0.25, or at most 0.22, or at most 0.20. In some embodiments, the polyethylene composition has a relative modulus (elasticity ratio G'/G") at 0.05 rad/s of at most 0.25.

In some embodiments, the polyethylene composition has a melt strength of at least 0.75 cN, or at least 1.00 cN, or at least 1.25 cN, or at least 1.50 cN, or at least 1.75 cN, or at least 2.00 cN, or at least 2.25 cN, or at least 2.50 cN, or at least 2.75 cN.

In some embodiments, the polyethylene composition has a melt strength of from 2.0 to 5.0 cN, or from 2.0 to 4.0 cN, or from 2.5 to 4.0 cN.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has a 1% flexural modulus of at least 900 MPa, or greater than 900 MPa, or at least 950 MPa, or greater than 950 MPa, or at least 1000 MPa, or greater than 1000 MPa, or at least 1050 MPa, or greater than 1050 MPa, or at least 1100 MPa, or greater than 1100 MPa.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have a 1% flexural modulus of from 900 to 1400 MPa, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition or plaque made of the polyethylene composition has a 1% flexural secant modulus of from 900 to 1300 MPa, or from 900 to 1200 MPa, or from 900 to 1150 MPa, or from 950 to 1400 MPa, or from 950 to 1300 MPa, or from 950 to 1200 MPa, or from 950 to 1150 MPa, or from 1000 to 1400 MPa, or from 1000 to 1300 MPa, or from 1000 to 1200 MPa, or from 1000 to 1150 MPa, or from 1050 to 1400 MPa, or from 1050 to 1300 MPa, or from 1050 to 1200 MPa, or from 1050 to 1150 MPa, or 1100 to 1400 MPa, or 1100 to 1300 MPa, or 1100 to 1200 MPa, or 1100 to 1150 MPa.

In some embodiments, the polyethylene composition or a plaque made of the polyethylene composition has a 1% bending secant modulus of at least 1000 MPa, in some embodiments, the polyethylene composition or a plaque made of the polyethylene composition has a 1% bending secant modulus of from 1000 to 1300 MPa.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has a 1% tensile secant modulus of at least 900 MPa, or greater than 900 MPa, or at least 950 MPa, or greater than 950 MPa, or at least 1000 MPa, or greater than 1000 MPa, or at least 1050 MPa, or greater than 1050 MPa, or at least 1100 MPa, or greater than 1100 MPa.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have a 1% tensile secant modulus of from 900 to 1500 MPa, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition or plaque made of the polyethylene composition has a 1% tensile secant modulus of from 900 to 1400 MPa, or from 900 to 1300 MPa, or from 900 to 1250 MPa, or from 950 to 1500 MPa, or from 950 to 1400 MPa, or from 950 to 1300 MPa, or from 950 to 1250 MPa, or from 1000 to 1500 MPa, or from 1000 to 1400 MPa, or from 1000 to 1300 MPa, or from 1000 to 1250 MPa, or from 1050 to 1500 MPa, or from 1050 to 1400 MPa, or from 1050 to 1300 MPa, or from 1050 to 1250 MPa, or 1100 to 1500 MPa, or 1100 to 1400 MPa, or 1100 to 1300 MPa, or 1100 to 1250 MPa.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has an Izod impact strength value (also known as Izod impact value or Izod impact strength) of ≥ 4.0 ft. lbs/inch, or > 4.0 ft. lbs/inch, or ≥ 5.0 ft. lbs/inch, or > 5.0 ft. lbs/inch, or ≥ 6.0 ft. lbs/inch, or > 6.0 ft. lbs/inch, or ≥ 6.5 ft. lbs/inch, or > 6.5 ft. lbs/inch.

In some embodiments, the polyethylene composition or a plaque made from the polyethylene composition has an Izod impact strength value of at least 4.0 ft. lbs./inch. In some embodiments, the polyethylene composition or a plaque made from the polyethylene composition has an Izod impact strength value of at least 6.0 ft. lbs./inch.

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an Izod impact strength value of from 4.0 to 20.0 ft. lbs./inch, including any narrower ranges therein and any values subsumed therein. For example, in some embodiments, the polyethylene composition or plaques made from the polyethylene composition have an Izod impact strength value of from 4.0 to 18.0 ft. lbs/inch, or from 4.0 to 16.0 ft. lbs/inch, or from 4.0 to 14.0 ft. lbs/inch, or from 4.0 to 13.0 ft. lbs/inch, or from 5.0 to 20.0 ft. lbs/inch, or from 5.0 to 18.0 ft. lbs/inch, or from 5.0 to 16.0 ft. lbs/inch, or from 5.0 to 14.0 ft. lbs/inch, or from 5.0 to 13.0 ft. lbs/inch, or from 6.0 to 20.0 ft. lbs/inch, or from 6.0 to 18.0 ft. lbs/inch, or from 6.0 to 16.0 ft. lbs/inch, or from 6.0 to 14.0 ft. lbs/inch, or 6.0 to 13.5 ft. lbs/inch, or 6.5 to 20.0 ft. lbs/inch, or 6.5 to 18.0 ft. lbs/inch, or 6.5 to 16.0 ft. lbs/inch, or 6.5 to 14.0 ft. lbs/inch, or 6.5 to 13.0 ft. lbs/inch.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has an Izod impact strength value of from 4.0 to 13.0 ft. lbs./inch.

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has a tensile impact strength value (also known as tensile impact value or tensile impact strength) of ≥ 150 ft. lbs/inch², or ≥ 175 ft. lbs/inch², or ≥ 200 ft. lbs/inch², or ≥ 215 ft. lbs/inch², or ≥ 230 ft. lbs/inch², or ≥ 240 ft. lbs/inch².

In some embodiments, the polyethylene composition or plaque made from the polyethylene composition has a tensile impact strength value of at least 230 ft. lbs./inch².

In some embodiments, the polyethylene composition or plaques made from the polyethylene composition have a tensile impact strength value of from 150 to 500 ft. lbs./in. ² , or from 150 to 450 ft. lbs./in. ² , or from 150 to 400 ft. lbs./in. ² , or from 150 to 375 ft. lbs./in. ² , or from 175 to 500 ft. lbs./in. ² , or from 175 to 450 ft. lbs./in. ² , or from 175 to 400 ft. lbs./in. ² , or from 175 to 375 ft. lbs./in. ² , or from 200 to 500 ft. lbs./in. ² , or from 200 to 450 ft. lbs./in. ² , or from 200 to 400 ft. lbs./in. ² , or from 200 to 375 ft. lbs./in. ² , or 215 to 500 ft. lb/in. ² , or 215 to 450 ft. lb/in. ² , or 215 to 400 ft. lb/in. ² , or 215 to 375 ft. lb/in. ² , or 230 to 500 ft. lb/in. ² , or 230 to 450 ft. lb/in. ² , or 230 to 400 ft. lb/in. ² , or 230 to 375 ft. lb/in. ² , or 240 to 500 ft. lb/in. ² , or 240 to 450 ft. lb/in. ² , or 240 to 400 ft. lb/in. ² , or 240 to 375 ft. lb/in. ² .

Optionally, additives may be added to the polyethylene composition. The additives may be added to the polyethylene composition during the extrusion or compounding step, although other suitable known methods will be apparent to those skilled in the art. The additives may be added as is or as part of a separate polymer component (i.e., other than the first or second ethylene polymer described above) added during the extrusion or compounding step. Suitable additives are known in the art and include, but are not limited to, antioxidants, phosphites and phosphonites, nitrones, antacids, UV stabilizers, UV absorbers, metal deactivators, dyes, fillers and reinforcing agents, nanoscale organic or inorganic materials, antistatic agents, lubricants such as calcium stearate, slip additives such as erucamide, and nucleating agents (including nucleating agents, pigments, or any other chemical capable of providing a nucleating effect to the polyethylene composition). Optional additives are typically added in an amount of up to 20 weight percent (wt%).

One or more nucleating agents can be introduced into the polyethylene composition by kneading a mixture of the polymer, typically in powder or pellet form, with the nucleating agent, which may be utilized alone or in the form of a concentrate containing additional additives such as stabilizers, pigments, antistatic agents, UV stabilizers, and fillers. The nucleating agent must be a material that is wettable or absorbed by the polymer, is insoluble in the polymer, has a melting point higher than the melting point of the polymer, and can be uniformly dispersed in the polymer melt in as fine a form as possible (1 to 10 μm). Compounds known to have nucleating ability for polyolefins include salts of aliphatic monobasic or dibasic acids or arylalkyl acids, such as sodium succinate or aluminum phenylacetate; and alkali metal or aluminum salts of aromatic or cycloaliphatic carboxylic acids, such as sodium β-naphthoate. Another compound known to have nucleating ability is sodium benzoate. The nucleation effect can be monitored microscopically by observing the degree of reduction in the size of the spheroids into which the crystal grains aggregate.

Examples of commercially available nucleating agents that can be added to the polyethylene composition include dibenzylidene sorbital esters (e.g., those sold under the trade name MILLAD ^® 3988 by Milliken Chemical and those sold under the trade name IRGACLEAR ^® by Ciba Specialty Chemicals). Other examples of nucleating agents that can be added to the polyethylene composition include the cyclic organic structures disclosed in U.S. Pat. No. 5,981,636 (and salts thereof, e.g., disodium bicyclo[2.2.1]heptene dicarboxylate); saturated forms of the structures disclosed in U.S. Pat. No. 5,981,636 (which is disclosed in U.S. Pat. No. 6,465,551; Zhao et al., assigned to Milliken); Salts of certain cyclic dicarboxylic acids having a hexahydrophthalic acid structure (or "HHPA" structure) as disclosed in U.S. Patent No. 6,599,971 (Dotson et al., assigned to Milliken); and phosphoric acid esters as disclosed in U.S. Patent No. 5,342,868, and those sold by Asahi Denka Kogyo under the trade names NA-11 and NA-21, cyclic dicarboxylates and salts thereof, such as divalent metal or metalloid salts (particularly calcium salts) of the HHPA structure disclosed in U.S. Patent No. 6,599,971. To be clear, the HHPA structure generally comprises a ring structure having six carbon atoms in the ring and two carboxylic acid groups which are substituents on adjacent atoms of the ring structure. As disclosed in U.S. Patent No. 6,599,971, the other four carbon atoms in the ring may be substituted. An example is 1,2-cyclohexanedicarboxylic acid, calcium salt (CAS registration number 491589-22-1). Other examples of nucleating agents that can be added to the polyethylene composition include those disclosed in WO 2015042561, WO 2015042563, WO 2015042562, and WO 2011050042.

Many of the nucleating agents described above can be difficult to mix with the polyethylene composition being nucleated, and the use of dispersing aids such as zinc stearate is known to alleviate this problem.

In some embodiments, the nucleating agent is well dispersed within the polyethylene composition.

In some embodiments, the amount of nucleating agent used is relatively small (5 to 3,000 ppm by weight (based on the weight of the polyethylene composition)), and those skilled in the art will appreciate that some care must be taken to ensure that the nucleating agent is well dispersed. In some embodiments, the nucleating agent is added to the polyethylene composition in a finely divided form (less than 50 microns, particularly less than 10 microns) to facilitate mixing. This type of "physical blend" (i.e., a mixture of the resin and the nucleating agent in solid form) is generally preferred over the use of a "masterbatch" of the nucleating agent (wherein the term "masterbatch" refers to the practice of first melt mixing the additive [in this case, the nucleating agent] with a small amount of the polyethylene composition resin, and then melt mixing the "masterbatch" with the remainder of the bulk of the polyethylene composition resin).

In some embodiments, additives such as nucleating agents may be added to the polyethylene composition via a "masterbatch," wherein the term "masterbatch" refers to the practice of first melt mixing the additive (e.g., nucleating agent) with a small amount of the polyethylene composition, and then melt mixing the "masterbatch" with the remainder of the bulk of the polyethylene composition.

In some embodiments, the polymer composition further comprises a nucleating agent or a mixture of nucleating agents.

In some embodiments, the polyethylene composition is used to form molded articles. For example, articles formed by rotational molding, continuous compression molding, and injection molding are contemplated. Such articles include, for example, tanks manufactured by rotational molding, and bottle caps, screw caps, and bottle closures manufactured by compression or injection molding. However, those skilled in the art will readily appreciate that the compositions described above can also be used in other applications, including, but not limited to, film, injection blow molding, blow molding, and sheet extrusion applications.

In some embodiments, the polyethylene compositions disclosed herein can be converted into molded articles.

In some embodiments, the polyethylene compositions disclosed herein can be used to manufacture articles by a rotational molding process.

In some embodiments, the polyethylene compositions disclosed herein can be converted into rotationally molded articles.

In some embodiments, and as an alternative to rotational molding, the polyethylene compositions of the present disclosure can be used to manufacture articles by an extrusion molding process, a compression molding process, or an injection molding process.

In some embodiments, and as an alternative to rotational molding, the polyethylene compositions of the present disclosure can be used to manufacture articles by a blown film process.

Rotational molding products

Typically, polyethylene compositions for use in rotational molding are manufactured in powder or pellet form. The rotational molding process may further comprise a process step for manufacturing the polyethylene composition. Powders are preferably used in rotational molding, and the particle size may be no greater than 35 US mesh. If necessary, milling may be performed at cryogenic temperatures. The polymer powder is then placed into a hollow mold and heated within the mold as it rotates. The mold is typically a dual-axis mold, meaning it rotates simultaneously about two perpendicular axes. The mold is typically heated externally (typically in a forced-air oven). Typically, the rotational molding process steps involve tumbling, heating, and melting the polymer powder, followed by coalescence, fusion, or sintering, and removal of the molded article through cooling.

The polyethylene composition of the present disclosure can be processed in a commercial rotational molding machine in certain embodiments of the present disclosure. The time and temperature used will vary depending on factors including the thickness of the part being rotationally molded, and those skilled in the art can readily determine appropriate processing conditions. By way of non-limiting example, the oven temperature during the heating step can range from 400°F to 800°F (204°C to 427°C), or from about 500°F to about 700°F (260°C to 371°C), or from about 575°F to about 650°F (302°C to 343°C).

After the heating step, the mold is cooled. The part must be cool enough to be easily removed from the mold and maintain its shape. The mold can be removed from the oven while continuing to rotate. First, cool air is blown into the mold. The air can be at ambient temperature. After the air begins to cool the mold for a controlled period of time, water spray can be used. The water cools the mold more quickly. The water used can be cold tap water, for example, at about 40°F (4°C) to about 60°F (16°C). After the water cooling step, another air cooling step can be used. This step can be a short one, during which the equipment is dried due to heat removal while the water evaporates.

The heating and cooling cycle times will vary depending on the equipment used and the article being molded. Specific factors include the thickness of the part within the mold material. As a non-limiting example, conditions for a ⅛-inch thick part in a steel mold might be to heat the mold in an oven with air at about 316°C (600°F) for about 15 minutes; the part could then be cooled in forced air at ambient temperature for about 8 minutes, followed by spraying with tap water at about 10°C (50°F) for about 5 minutes; optionally, the part could be cooled in forced air at ambient temperature for an additional 2 minutes.

During the heating and cooling stages, the mold containing the molded article is preferably rotated continuously. Typically, this is done along two perpendicular axes. The rotational speed of the mold along each axis is limited by the machine performance and the shape of the article being molded. A typical, non-limiting operating range that can be used with the present disclosure is a rotation ratio of the major axis to the minor axis of about 1:8 to 10:1, or about 1:2 to 8:1.

Non-limiting examples of articles that can be manufactured using the rotational molding process include custom tanks, water tanks, carts, transport cases and containers, coolers, as well as sports and recreational equipment (e.g., boats, kayaks), toys, and playground equipment.

The desired physical properties of rotationally molded parts vary depending on the application. Non-limiting examples of desired properties include: flexural modulus (1% and 2% secant modulus), environmental stress cracking resistance (ESCR), Shore hardness, heat deflection temperature (HDT), VICAT softening point, Izod impact strength, ARM impact resistance, and color (whiteness and/or yellowness index).

In some embodiments, a polyethylene composition having a melt index (I ₂ ) of from 1.0 to 3.0 g/10 min, or less than 3.0 g/10 min, is used to produce a rotationally molded article having an internal volume of at least about 2,500 liters, or at least about 5,000 liters, or at least about 10,000 liters, or at least about 20,000 liters, or at least about 50,000 liters, or at least about 100,000 liters.

In some embodiments, the rotomolded article is a tank. In some embodiments, the rotomolded article is a large tank.

In some embodiments, a polyethylene composition having a melt index (I ₂ ) of from 1.0 to 3.0 g/10 min, or less than 3.0 g/10 min, is used to produce a rotationally molded article having an internal volume of less than about 1,000,000 liters or less than about 500,000 liters.

In some embodiments, a process for manufacturing a rotationally molded article comprises the steps of: (i) filling a mold with a polyethylene composition; (ii) heating the mold in an oven to a temperature greater than 280° C.; (iii) rotating the mold about at least two axes; (iv) cooling the mold while the mold is rotating; and (v) opening the mold to eject the rotationally molded article.

Additives and Auxiliaries - Rotational Molding

The polyethylene compositions described and the resulting rotationally molded articles may optionally include additives and auxiliaries, depending on the intended use. The additives may be added to the polyethylene composition during the extrusion or compounding step, although other suitable known methods will be apparent to those skilled in the art. The additives may be added as is or as part of a separate polymer component added during the extrusion or compounding step. Non-limiting examples of additives and auxiliaries include anti-blocking agents, antioxidants, heat stabilizers, slip agents, processing aids, antistatic additives, colorants, dyes, fillers, light stabilizers, heat stabilizers, light absorbers, lubricants, pigments, plasticizers, nucleating agents, and combinations thereof. Non-limiting examples of suitable primary antioxidants include IRGANOX ^® 1010 [CAS Reg. No. 6683-19-8] and IRGANOX 1076 [CAS Reg. No. 2082-79-3]; Both are available from BASF Corporation, Florham Park, NJ, USA. Non-limiting examples of suitable secondary antioxidants include IRGAFOS ^® 168 [CAS Reg. No. 31570-04-4], available from BASF Corporation, Florham Park, NJ, USA; Weston 705 [CAS Reg. No. 939402-02-5], available from SI Group, The Woodlands, Texas, USA; and DOVERPHOS ^® LGP-11 [CAS Reg. No. 1227937-46-3], available from Dover Chemical Corporation, Dover, Ohio, USA. Optional additives are typically added in amounts of up to 20 weight percent (wt%).

One or more nucleating agents can be introduced into the polyethylene composition by kneading a mixture of the nucleating agent, which may be used alone or in the form of a concentrate containing additional additives such as stabilizers, pigments, antistatic agents, UV stabilizers, and fillers, with the polymer, typically in powder or pellet form. The nucleating agent must be a material that is wettable or absorbed by the polymer, is insoluble in the polymer, has a melting point higher than that of the polymer, and can be uniformly dispersed in the polymer melt in as fine a form as possible (1 to 10 μm). Compounds known to have nucleating ability for polyolefins include salts of aliphatic monobasic or dibasic acids or arylalkyl acids, such as sodium succinate or aluminum phenylacetate; and alkali metal or aluminum salts of aromatic or cycloaliphatic carboxylic acids, such as sodium β-naphthoate. Another compound known to have nucleating ability is sodium benzoate. The nucleation effect can be monitored microscopically by observing the degree of reduction in the size of the spheres into which the crystal grains aggregate.

In some embodiments, the polyethylene compositions and the resulting rotationally molded articles may include additives selected from the group consisting of antioxidants, phosphites and phosphonites, nitrones, antacids, UV stabilizers, UV absorbers, metal deactivators, dyes, fillers and reinforcing agents, nanoscale organic or inorganic materials, antistatic agents, release agents such as zinc stearate, and nucleating agents (which include nucleating agents, pigments, or any other chemical capable of providing a nucleating effect to the polyethylene composition).

In some embodiments, the additive may be added in an amount of up to 20 weight percent (wt%).

Additives may be added to the polyethylene composition during the extrusion or compounding step, although other suitable known methods will be apparent to those skilled in the art. Additives may be added as is or as part of a separate polymer component added during the extrusion or compounding step.

A more detailed list of additives that may be added to the polyethylene composition of the present disclosure and used in rotational moldings is as follows:

phosphites (e.g., aryl monophosphites)

The term aryl monophosphite, as used herein, refers to a phosphite stabilizer containing (1) only one phosphorus atom per molecule; and (2) at least one aryloxide (which may also be referred to as phenoxide) radical bonded to the phosphorus.

In some embodiments, the aryl monophosphite contains three aryloxide radicals - for example, trisphenyl phosphite is the simplest member of this preferred group of aryl monophosphites.

In some embodiments, the aryl monophosphite contains a C ₁ to C ₁₀ alkyl substituent on at least one aryloxide group. Such substituents may be linear (as in the case of a nonyl substituent) or branched (e.g., an isopropyl or tertiary butyl substituent).

Non-limiting examples of aryl monophosphites that can be used in embodiments of the present disclosure include those selected from triphenyl phosphite; diphenyl alkyl phosphites; phenyl dialkyl phosphites; tris(nonylphenyl) phosphite [WESTON 399, available from SI Group]; tris(2,4-di-tert-butylphenyl) phosphite [IRGAFOS 168, available from Ciba Specialty Chemicals Corp.]; and bis(2,4-di-tert-butyl-6-methylphenyl)ethylphosphite [IRGAFOS 38, available from BASF Corp.]; and 2,2',2"-nitrilo[triethyltris(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite [IRGAFOS 12, available from BASF Corp.].

In some embodiments, the amount of aryl monophosphite added to the polyethylene composition is from 200 to 2,000 ppm (based on polymer weight), or from 300 to 1,500 ppm, or from 400 to 1,000 ppm.

Phosphites, phosphonites (e.g., diphosphite, diphosphonite)

As used herein, the term diphosphite refers to a phosphite stabilizer containing at least two phosphorus atoms per phosphite molecule (similarly, the term diphosphonite refers to a phosphonite stabilizer containing at least two phosphorus atoms per phosphonite molecule).

Non-limiting examples of diphosphites and diphosphonites that may be used in embodiments of the present disclosure include distearyl pentaerythritol diphosphite, diisodecyl pentaerythritol diphosphite, bis(2,4 di-tert-butylphenyl) pentaerythritol diphosphite [ULTRANOX ^® 626, available from SI Group]; bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite; bisisodecyloxy-pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-biphenylene-diphosphonite [HOSTANOX P-EPQ ^® , available from Clariant] and bis(2,4-dicumylphenyl)pentaerythritol diphosphite [DOVERPHOS S9228-T or DOVERPHOS S9228-CT] and one example of a commercially available diphosphonite is PEP-Q (CAS No. 119345-01-06).

In some embodiments, the diphosphite and/or diphosphonite added to the polyethylene composition is added in an amount of from 200 ppm to 2,000 ppm (based on polymer weight), or from 300 ppm to 1,500 ppm, or from 400 ppm to 1,000 ppm.

In some embodiments, the use of diphosphite is preferred over the use of diphosphonite.

In some embodiments, the most preferred diphosphites are those available under the trade names DOVERPHOS S9228-CT and ULTRANOX 626.

Disability phenol antioxidants

The hindered phenolic antioxidant may be any of the molecules commonly used as primary antioxidants for stabilizing polyolefins. Suitable examples include 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, 2-(1-methylcyclohexyl)-4,6-dimethylphenol, 2,6-di-octadecyl-4-methylphenol, 2,4,6-tricyclohexyphenol, and 2,6-di-tert-butyl-4-methoxymethylphenol.

Two (non-limiting) examples of suitable hindered phenolic antioxidants that may be used in embodiments of the present disclosure are sold by BASF Corporation under the trade names IRGANOX 1010 (CAS Reg. No. 6683-19-8) and IRGANOX 1076 (CAS Reg. No. 2082-79-3).

In some embodiments, the amount of hindered phenolic antioxidant added to the polyethylene composition is from 100 to 2,000 ppm, or from 400 to 1,000 ppm (based on polymer weight).

Long-term stabilizer

Plastic parts intended for long-term use may, in some embodiments of the present disclosure, contain at least one hindered amine light stabilizer (HALS). HALS are well known to those skilled in the art.

When used, HALS may in some embodiments be commercially available materials and may be used in conventional manners and in conventional amounts.

Commercially available HALS that may be used in embodiments of the present disclosure include those sold by BASF Corporation under the trademarks CHIMASSORB ^® 119; CHIMASSORB 944; CHIMASSORB 2020; TINUVIN ^® 622 and TINUVIN 770, and those sold by Solvay under the trademarks CYASORB ^® UV 3346, CYASORB UV 3529, CYASORB UV 4801 and CYASORB UV 4802. In some embodiments of the present disclosure, TINUVIN 622 is preferred. In other embodiments of the present disclosure, the use of mixtures of more than one HALS is also contemplated.

In some embodiments, suitable HALS are bis(2,2,6,6-tetramethylpiperidyl)-sebacate; bis-5(1,2,2,6,6-pentamethylpiperidyl)-sebacate; n-butyl-3,5-di-tert-butyl-4-hydroxybenzyl malonic acid bis(1,2,2,6,6-pentamethylpiperidyl)ester; condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidine and succinic acid; condensation product of N,N'-(2,2,6,6-tetramethylpiperidyl)-hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1,3,5-s-triazine; tris-(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate, tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane-tetra-arvonic acid; and 1,1'(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone).

Hydroxylamine

Hydroxylamine and its derivatives (including amine oxides) are known for use as additives in polyethylene compositions used to manufacture rotationally molded parts, as disclosed, for example, in U.S. Patent No. 6,444,733, and embodiments of the present disclosure may also include the hydroxylamines and derivatives disclosed therein.

In some embodiments, the hydroxylamine useful for inclusion in the polyethylene composition may be selected from N,N-dialkylhydroxylamines, a commercially available example of which is N,N-di(alkyl)hydroxylamine sold as IRGASTAB FS 042 (BASF), which is reported to be prepared by direct oxidation of N,N-di(hydrogenated) tallow amine.

Additive package

In some embodiments, the polyethylene composition contains an additive package comprising at least one additional additive selected from the group consisting of hindered monophosphites, diphosphites, hindered amine light stabilizers, and hindered phenols and hydroxylamines.

In some embodiments, the additive package comprises hydroxylamine.

In some embodiments, the hydroxylamine is an N,N-dialkylhydroxylamine.

In some embodiments, the hydroxylamine is IRGASTAB FS 042 (BASF).

In some embodiments, the hydroxylamine is present in a concentration of at least about 400 ppm, or at least about 500 ppm, or at least about 600 ppm, or at least about 700 ppm, or at least about 750 ppm, or at least about 800 ppm by weight.

In some embodiments, the hydroxylamine is present in a concentration of at least about 750 ppm by weight.

In some embodiments, the hydroxylamine is present at a concentration of about 400 ppm, or about 500 ppm, or about 600 ppm, or about 700 ppm, or about 750 ppm, or about 800 ppm by weight.

In embodiments of the present disclosure, the amount of hydroxylamine added to the polyethylene composition is from 100 to 2,000 ppm, or from 400 to 1,000 ppm, or from 600 to 1,000 ppm, or from 700 to 1,000 ppm, or from 800 to 1,000 ppm, by weight.

The features disclosed in the above description, the claims below, or the accompanying drawings, when expressed in terms of a specific form or means for performing the disclosed function, or a method or process for obtaining the disclosed result, can be utilized, individually or in any combination of these features, to realize the present invention in various forms, as needed.

While the present invention has been described with reference to the exemplary embodiments described above, many equivalent modifications and variations will readily occur to those skilled in the art, given the present disclosure. Therefore, the exemplary embodiments of the present invention presented above are intended to be illustrative, not limiting. Various modifications to the described embodiments may be made without departing from the spirit and scope of the present invention.

For the avoidance of doubt, any theoretical explanations provided herein are provided solely to aid the reader's understanding. The inventors do not intend to be bound by any such theoretical explanations.

All section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter discussed.

Throughout this specification, including the claims hereafter, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprises," "comprising," and "including" should be understood to imply the inclusion of a stated integer, step, or group of integers or steps, but not the exclusion of any other integer, step, or group of integers or steps.

It should be noted that the singular forms "a," "an," and "the" as used in this specification and the appended claims include plural references unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, it will be understood that the particular value forms another embodiment by use of the antecedent "about." The term "about" in connection with a numerical value is optional and means, for example, +/- 10%.

Additional non-limiting details of the present disclosure are provided in the following examples. These examples are presented for the purpose of illustrating selected embodiments of the present disclosure and should not be construed as limiting the claims presented.

Example

General Testing Procedures

Prior to testing, each polymer specimen was conditioned for at least 24 hours at 23±2°C and 50±10% relative humidity, and testing was then performed at 23±2°C and 50±10% relative humidity. The term "ASTM conditions" herein refers to a laboratory maintained at 23±2°C and 50±10% relative humidity; the specimens to be tested were conditioned in this laboratory for at least 24 hours prior to testing. ASTM refers to the American Society for Testing and Materials.

density

Polyethylene composition density was determined using ASTM D792-13 (November 1, 2013).

Melting index

The melt index of polyethylene compositions was determined using ASTM D1238 (August 1, 2013). Melt indices I ₂ , I ₆ , I ₁₀ , and I ₂₁ were measured at 190°C using weights of 2.16 kg, 6.48 kg, 10 kg, and 21.6 kg, respectively. As used herein, the term "stress index" or its abbreviation "S.Ex." is defined by the relationship: S.Ex. = log (I ₆ /I ₂ )/log(6480/2160), where I ₆ and I ₂ are the melt flow rates measured at 190°C using loads of 6.48 kg and 2.16 kg, respectively. In the present disclosure, melt indices may be expressed in units of g/10 min or g/10 min or dg/min or dg/min - which units are equivalent.

Gel Permeation Chromatography (GPC)

The molecular weights, M _n , M _w , and M _z , as well as the polydispersity (M _w /M _n ) of the polyethylene compositions were determined using ASTM D6474-12 (December 15, 2012). Polymer sample solutions (1 to 2 mg/mL) were prepared by heating the polymer in 1,2,4-trichlorobenzene (TCB) and then rotating it on a wheel in an oven at 150°C for 4 h. An antioxidant, 2,6-di-tert-butyl-4-methylphenol (BHT), was added to the mixture to stabilize the polymer against oxidative degradation. The BHT concentration was 250 ppm. The sample solution was chromatographed at 140°C on a PL 220 high-temperature chromatography instrument equipped with four SHODEX ^® columns (HT803, HT804, HT805, and HT806) using TCB as the mobile phase at a flow rate of 1.0 mL/min and differential refractive index (DRI) as the concentration detector. To prevent oxidative degradation of the GPC column, BHT was added to the mobile phase at a concentration of 250 ppm. The sample injection volume was 200 μL. The GPC raw data were processed using CIRRUS ^® GPC software. The GPC column was calibrated using narrow-distribution polystyrene standards. The polystyrene molecular weight was converted to the polyethylene molecular weight using the Mark-Houwink equation described in ASTM D6474-12 (December 15, 2012).

Triple detection size exclusion chromatography (3D-SEC)

Polyethylene composition sample (polymer) solutions (1 to 3 mg/mL) were prepared by heating the polymer in 1,2,4-trichlorobenzene (TCB) and rotating it on a wheel in an oven at 150°C for 4 h. An antioxidant (2,6-di-tert-butyl-4-methylphenol (BHT)) was added to the mixture to stabilize the polymer against oxidative degradation. The BHT concentration was 250 ppm. The sample solutions were chromatographed at 140°C on a PL 220 high-temperature chromatography apparatus equipped with a differential refractive index (DRI) detector, a dual-angle light scattering detector (15 degrees and 90 degrees), and a differential viscometer. The SEC columns used were four SHODEX columns (HT803, HT804, HT805, and HT806) or four PL Mixed ALS or BLS columns. TCB was the mobile phase at a flow rate of 1.0 mL/min, and BHT was added to the mobile phase at a concentration of 250 ppm to protect the SEC column from oxidative degradation. The sample injection volume was 200 μL. The raw SEC data were processed with CIRRUS GPC software to produce absolute molar mass and intrinsic viscosity ([η]). The term “absolute” molar mass was used to distinguish the absolute molar mass determined by 3D-SEC from the molar mass determined by conventional SEC. The viscosity-averaged molar mass (M _v ) determined by 3D-SEC was used in the calculation to determine the long-chain branching factor (LCBF).

GPC-FTIR

Polyethylene composition (polymer) solutions (2 to 4 mg/mL) were prepared by heating the polymer in 1,2,4-trichlorobenzene (TCB) and rotating it on a wheel in an oven at 150°C for 4 h. 2,6-Di-tert-butyl-4-methylphenol (BHT), an antioxidant, was added to the mixture to stabilize the polymer against oxidative degradation. The BHT concentration was 250 ppm. The sample solutions were chromatographed at 140°C on a Waters GPC 150C chromatography instrument equipped with four SHODEX columns (HT803, HT804, HT805, and HT806) using TCB as the mobile phase at a flow rate of 1.0 mL/min, and a heated FTIR flow cell and FTIR spectrometer coupled to the chromatography instrument via a heated transfer line were used as the detection system. To protect the SEC column from oxidative degradation, BHT was added to the mobile phase at a concentration of 250 ppm. The sample injection volume was 300 μL. The raw FTIR spectra were processed with OPUS FTIR software, and the polymer concentration and methyl content were calculated in real time using the OPUS-integrated Chemometric Software (PLS technique). The polymer concentration and methyl content were then acquired and baseline-corrected using CIRRUS GPC software. The SEC column was calibrated using narrow-distribution polystyrene standards. The polystyrene molecular weight was converted to polyethylene molecular weight using the Mark-Houwink equation described in ASTM Standard Test Method D6474. The comonomer content was calculated based on the polymer concentration and methyl content predicted by the PLS technique described in Paul J. DesLauriers, Polymer 43, pages 159-170 (2002), which is incorporated herein by reference.

The GPC-FTIR method measures the total methyl content, including the methyl groups located at the end of each macromolecular chain, i.e., methyl end groups. Therefore, the raw GPC-FTIR data must be corrected by subtracting the contribution of methyl end groups. More specifically, the raw GPC-FTIR data overestimates the amount of short-chain branching (SCB), and this overestimation increases as the molecular weight (M) decreases. In the present disclosure, the raw GPC-FTIR data were corrected using the 2-methyl correction. The number of methyl end groups (N _E ) at a given molecular weight (M ) was calculated using the following equation: N _E = 28000/M , and the SCB/1000C (2-methyl corrected) GPC-FTIR data was generated by subtracting N _E (M dependent) from the raw GPC-FTIR data.

Unsaturated content

The amount of unsaturation, i.e., double bonds, in the polyethylene composition was determined according to ASTM D3124-98 (vinylidene unsaturation, published March 2011) and ASTM D6248-98 (vinyl and trans unsaturation, published July 2012). Polymer samples were a) first extracted with carbon disulfide to remove additives that could interfere with the analysis; b) the samples (in the form of pellets, films, or granules) were pressed into plaques of uniform thickness (0.5 mm); and c) the plaques were analyzed by FTIR.

Comonomer content: Fourier transform infrared (FTIR) spectroscopy

The amount of comonomer in the polyethylene composition was determined by FTIR and reported as the short-chain branching (SCB) content, which has a dimension of CH ₃ #/1000C (the number of methyl branches per 1000 carbon atoms). The test was completed using compression-molded polymer plaques according to ASTM D6645-01 (2001) and a Thermo-Nicolet 750 Magna-IR spectrophotometer. The polymer plaques were manufactured using a compression-molding machine (Wabash-Genesis series press) according to ASTM D4703-16 (April 2016).

Composition Distribution Branching Index (CDBI) by CTREF

The "Composition Distribution Branching Index" or "CDBI" of the disclosed and comparative examples was determined using a crystal-TREF apparatus ("CTREF" apparatus) commercially available from Polymer Char (Valencia, Spain). The acronym "TREF" stands for Temperature Rising Elution Fractionation. A polyethylene composition sample (80 to 100 mg) was placed in the reactor of the Polymer Char crystal-TREF apparatus, the reactor was filled with 35 mL of 1,2,4-trichlorobenzene (TCB), heated to 150°C, and maintained at that temperature for 2 hours to dissolve the sample. An aliquot of the TCB solution (1.5 mL) was then loaded onto a Polymer Char TREF column packed with stainless steel beads, and the column was equilibrated at 110°C for 45 minutes. The TREF column was then slowly cooled from 110°C to 30°C at a cooling rate of 0.09°C/min to crystallize the polyethylene composition from the TCB solution. The TREF column was then equilibrated at 30°C for 30 minutes. The crystallized polyethylene composition was eluted from the TREF column by passing pure TCB solvent through the column at a flow rate of 0.75 mL/min while the column temperature was slowly increased from 30°C to 120°C at a heating rate of 0.25°C/min. As the polyethylene composition eluted from the TREF column, a TREF distribution curve was generated using Polymer Char software. That is, the TREF distribution curve is a plot that shows the amount (or intensity) of the polymer material eluted from the column as a function of the TREF elution temperature. The CDBI ₅₀ was calculated from the TREF distribution curve for each polyethylene composition analyzed. "CDBI ₅₀ " is defined as the percentage of polymer whose composition is within 50% of the median comonomer composition (25% on either side of the median comonomer composition); it is calculated from the TREF composition distribution curve and the normalized cumulative integral of the TREF composition distribution curve. Those skilled in the art will recognize that a calibration curve is required to convert TREF elution temperature to comonomer content, i.e., the amount of comonomer in the polyethylene composition fraction that elutes at a particular temperature. The generation of such calibration curves is described in the prior art, for example, in Wild et al., J. Polym. Sci., Part B, Polym. Phys., Vol. 20 (3), pages 441-455.

Crystallization elution fraction (CEF)

Crystallization elution fraction (CEF) is also referred to as TREF-CEF in the text. Polymer samples (20 to 25 mg) were weighed into sample vials and loaded onto the autosampler of a Polymer Char CEF apparatus. The vials were filled with 6 to 7 mL of 1,2,4-trichlorobenzene (TCB) and heated to the desired dissolution temperature (e.g., 160°C) for 2 h at a shaking speed of level 3. The solution (0.5 mL) was then loaded onto a CEF column (two CEF columns purchased from Polymer Char and installed in series). After equilibrating at a given stabilization temperature (e.g., 115°C) for 5 min, the polymer solution was crystallized by decreasing the temperature from the stabilization temperature to 30°C. After equilibrating at 30°C for 10 min, the crystallized sample was eluted with TCB by increasing the temperature from 30°C to 110°C. The CEF column was washed at 150°C for 5 min after the run. Other CEF run conditions were as follows: cooling rate 0.5°C/min, crystallization flow rate 0.02 mL/min, heating rate 1.0°C/min, and elution flow rate 2.0 mL/min. Data were processed using an Excel spreadsheet.

Hexane extract

Hexane extractables were determined according to Code of Federal Registration 21 CFR §177.1520 Para (c) 3.1 and 3.2; where the amount of hexane extractable in a sample is determined gravimetrically.

Neutron Activation Analysis (NAA)

Neutron activation analysis, hereafter NAA, was used to determine catalyst residues in polyethylene compositions and was performed as follows. Polymer samples were filled into radiation vials (consisting of ultrapure polyethylene, internal volume 7 mL) and the sample weight was recorded. The samples were placed in a SLOWPOKE™ reactor (Atomic Energy of Canada Limited, Ottawa, Ontario, Canada) using a pneumatic transfer system and irradiated for 30 to 600 seconds for short half-life elements (e.g., Ti, V, Al, Mg, and Cl) or 3 to 5 hours for long half-life elements (e.g., Zr, Hf, Cr, Fe, and Ni). The average thermal neutron flux in the reactor was 5×10 ¹¹ /cm²/s. After irradiation, the samples were removed from the reactor and aged to allow the radioactivity to decay; short half-life elements were aged for 300 seconds or long half-life elements were aged for several days. After aging, the gamma-ray spectra of the samples were recorded using a germanium semiconductor gamma-ray detector (Ortec model GEM55185, Advanced Measurement Technology Inc., Oak Ridge, TN, USA) and a multichannel analyzer (Ortec model DSPEC Pro). The amount of each element in the sample was calculated from the gamma-ray spectra and reported as parts per million relative to the total weight of the polymer sample. The NAA system was calibrated with Specpure standards (1,000 ppm solutions of the desired element (>99% purity)). 1 mL of the solution (element of interest) was pipetted onto a 15 mm × 800 mm rectangular filter paper and air-dried. The filter paper was then placed in a 1.4 mL polyethylene irradiation vial and analyzed with the NAA system. The standards are used to determine the sensitivity (in counts/μg) of the NAA procedure.

Dynamic Mechanical Analysis (DMA)

Oscillatory shear measurements under small strain amplitudes were performed in a nitrogen atmosphere at 190°C with a strain amplitude of 10% and a frequency range of 0.02 to 126 rad/s at 5 points per decade to obtain linear viscoelastic functions. Frequency sweep experiments were performed on a TA Instruments DHR3 stress-controlled rheometer using a cone-and-plate geometry with a cone angle of 5°, a truncated surface area of 137 μm, and a diameter of 25 mm. In these experiments, sinusoidal strain waves were applied, and the stress response was analyzed as a linear viscoelastic function. Zero-shear rate viscosity (η ₀ ) based on DMA frequency sweep results was predicted using the Ellis model (see R. B. Bird et al. "Dynamics of Polymer Liquids. Volume 1: Fluid Mechanics" Wiley-Interscience Publications (1987) p. 228) or the Carreau-Yasuda model (see K. Yasuda (1979) Ph.D. thesis, IT Cambridge). Dynamic rheological data were analyzed using rheometer software (i.e., Rheometrics RHIOS V4.4 or Orchestrator Software) to determine the melt modulus G'(G"=500) from a reference melt viscoelasticity (G") value of G"=500 Pa. When necessary, values were obtained by interpolation between available data points using Rheometrics software. The term "storage modulus"G'(co), also known as the "elastic modulus", is defined as the stress divided by the strain in phase with the strain during sinusoidal deformation as a function of the applied oscillation frequency co; whereas the term "viscous modulus"G"(ω), also known as the "loss modulus", is defined as the stress divided by the strain at 90 degrees out of phase with the strain as a function of the applied oscillation frequency ω. These two moduli, and other linear viscoelastic and dynamic rheological parameters, are well known in the art, as discussed, for example, by G. Marin in Chapter 10 "Oscillatory Rheometry" in the book on rheological measurements edited by A. A. Collyer and D. W. Clegg, Elsevier, 1988.

The shear thinning index, SHI _(1,100) , was calculated as the ratio of the complex viscosity estimated at 1 kPa of shear stress to the complex viscosity estimated at 100 kPa of shear stress. The shear thinning index SHI _(1,100) provides information on the shear thinning behavior of polymer melts. High values indicate a strong dependence of viscosity on changes in strain (shear or frequency).

The assessment of relative modulus is based on measurements performed at low frequencies, which are most appropriate for the conditions associated with powder sintering and densification in rotational molding. The relative modulus is evaluated based on the ratio of G' to G" at a frequency of 0.05 rad/s (or 0.5 rad/s) in DMA frequency sweep measurements performed at 190°C. Data reported in the literature show that resin compositions with high relative moduli tend to present processing difficulties in terms of slow powder compaction. Wang and Kontopoulou (2004) reported adequate rotomoldability for blend compositions characterized by relative moduli as high as 0.125. In that study, the effect of plastomer content on the rotomoldability of polypropylene was investigated (W.Q. Wang and M. Kontopoulou (2004) Polymer Engineering and Science, vo. 44, no 9, pp 1662-1669). Further analysis of the results published by Wang and Kontopoulou showed that compositions with high plastomer content have an increased relative modulus (G'/G">0.13), which in turn leads to a decrease in the ability to achieve full densification during rotomolding. It shows that the difficulty increases.

In this disclosure, the long chain branching factor (LCBF) was determined using η ₀ determined in DMA (see U.S. Patent No. 10,442,921).

Melt strength

Melt strength was measured at 190°C using a Rosand RH-7 capillary rheometer (barrel diameter = 15 mm) with a flat die of 2 mm diameter and L/D ratio of 10:1. Pressure transducer: 10,000 psi (68.95 MPa). Piston speed: 5.33 mm/min. Haul-off angle: 52°. Haul-off incremental speed: 50 to 80 m/min² or 65±15 m/min². The polymer melt was extruded through a capillary die at a constant rate and then drawn at increasing haul-off speeds until the polymer strands broke. The maximum steady-state force in the plateau region of the force versus time curve was defined as the melt strength of the polymer. Melt strength elongation was defined as the ratio of the pulley speed to the die exit speed.

Long-chain branching factor (LCBF)

LCBF (dimensionless) was determined for polyethylene compositions using the method described in U.S. Patent No. 10,442,921, which is incorporated herein by reference.

Calculation of the long-chain branching factor ("LCBF") requires the polydispersity-corrected zero-shear viscosity (ZSV _c ) and the short-chain branching ("SCB")-corrected intrinsic viscosity (IV _c ), which are described in detail in the following paragraphs.

The correction for the zero-shear viscosity, ZSV _c , with poise dimension was performed as given in equation (1):

Here, the zero shear viscosity (Poise) η ₀ was measured by DMA as described above; Pd was the dimensionless polydispersity (M _w /M _n ) measured using conventional GPC as described above; and 1.8389 and 2.4110 are dimensionless constants.

The correction for the intrinsic viscosity IV _c with dimension dL/g was performed as given in equation (2):

Here, the intrinsic viscosity [η] (dL/g) was measured using 3D-SEC as described above; SCB has the dimension of (CH ₃ #/1000C) and was determined using FTIR as described above; M _v , the viscosity-average molar mass (g/mol), was determined using 3D-SEC as described above; A was a dimensionless constant that depended on the α-olefin of the ethylene/α-olefin copolymer samples, i.e., A was 2.1626, 1.9772 or 1.1398 for 1-octene, 1-hexene and 1-butene α-olefins, respectively. For ethylene homopolymers, no correction for the Mark-Houwink constant was necessary, i.e., SCB was zero.

“Linear” ethylene copolymers (or linear ethylene homopolymers) that contain no LCBs or contain undetectable levels of LCBs fall within the baseline defined by equation (3):

LCBF calculations were based on horizontal shifts (S _h ) and vertical shifts (S _v ) from a linear baseline defined by the following equations:

In equations (4) and (5), ZSV _c and IV _c are required to have dimensions of poise and dL/g, respectively.

The horizontal shift (S _h ) is the shift of the ZSV _c at constant intrinsic viscosity (IV _c ). Eliminating the logarithmic function makes its physical meaning clear, namely, the ratio of two zero-shear viscosities, namely the ZSV _c of the sample under test to the ZSV _c of a linear ethylene copolymer (or linear ethylene homopolymer) having the same IV _c . The horizontal shift (S _h ) is dimensionless.

The vertical shift (S _v ) is the shift in IV _c at constant zero-shear viscosity (ZSV _c ). Eliminating the logarithmic function makes its physical meaning clear, namely, the ratio of two intrinsic viscosities, namely the IV _c of the sample under test to the IV _c of a linear ethylene copolymer (or linear ethylene homopolymer) having the same ZSV _c . The vertical shift (S _v ) is dimensionless.

The dimensionless long-chain branching factor (LCBF) is defined by equation (6):

In some embodiments of the present disclosure, an ethylene polymer (e.g., a polyethylene composition) having an LCB is characterized by an LCBF ≥ 0.0010 (dimensionless); whereas an ethylene polymer without an LCB (or having an undetectable LCB) is characterized by an LCBF less than 0.0010 (dimensionless).

Impact characteristics

Izod impact performance was determined according to ASTM D256. Izod impact specimens were notched to promote stress concentrations that induce brittle rather than ductile fracture.

Tensile impact performance was determined according to ASTM D1822.

Tensile properties

The following tensile properties were determined using ASTM D 638: yield elongation (%), yield strength (MPa), ultimate elongation (%), ultimate strength (MPa), and 1% and 2% secant modulus (MPa).

Bending characteristics

Flexural properties, i.e., 2% bending modulus, were determined using ASTM D790-10 (issued April 2010).

Environmental Stress Cracking Resistance (ESCR)

Plaques molded from polyethylene compositions were tested according to the following ASTM method: Bent Strip Environmental Stress Cracking Resistance (ESCR), ASTM D1693; ESCR testing under "B" condition of ASTM D1693 (temperature 50°C) was performed using a 100% solution of IGEPAL CO-630 (nonylphenoxy poly(ethyleneoxy)ethanol, branched, chemical formula: 4-(branched-C ₉ H ₁₉ )-phenyl-[OCH ₂ CH ₂ ] _n -OH, where the subscript n is 9-10) and a 10% solution of IGEPAL CO-630. The skilled practitioner will recognize that the test using the 10% solution ("B ₁₀ ") is more stringent than the test using the 100% solution ("B ₁₀₀ "); i.e., the B ₁₀ value is typically lower than the B ₁₀₀ value.

Plaques molded from polyethylene compositions were tested according to the following ASTM method: Bent Strip Environmental Stress Cracking Resistance (ESCR), ASTM D1693; ESCR testing under "A" condition of ASTM D1693 (temperature 50°C) was performed using a 100% solution of IGEPAL CO-630 (nonylphenoxy poly(ethyleneoxy)ethanol, branched, chemical formula: 4-(branched-C ₉ H ₁₉ )-phenyl-[OCH ₂ CH ₂ ] _n -OH, where the subscript n is 9-10), and a 10% solution of IGEPAL CO-630. The skilled practitioner will recognize that the test using the 10% solution ("A ₁₀ ") is more stringent than the test using the 100% solution ("A ₁₀₀ "); i.e., the A ₁₀ value is typically lower than the A ₁₀₀ value.

Preparation of polyethylene compositions

A polyethylene composition was prepared using a mixed dual catalyst system in a "series" dual reactor solution polymerization process. As a result, the polyethylene composition comprised a first ethylene copolymer prepared with a single-site catalyst and a second ethylene copolymer prepared with a multi-site catalyst. A "series" dual reactor solution polymerization process, including a process utilizing a mixed dual catalyst, is described in U.S. Patent Application Publication No. 2018/0305531. Essentially, in the "series" dual reactor system, the outlet stream from the first polymerization reactor (R1) flows directly into the second polymerization reactor (R2). The pressure in R1 was between about 14 MPa and about 18 MPa, while R2 was operated at a lower pressure to facilitate continuous flow from R1 to R2. Both R1 and R2 were continuous stirred tank reactors (CSTRs) and were stirred to ensure good mixing of the reactor contents. The process was operated continuously by feeding fresh process solvent, ethylene, 1-octene, and hydrogen to the reactors and removing the products. In particular, in this embodiment of the present invention, although no comonomer was directly fed to the downstream second reactor, R2 (i.e., fresh 1-octene was fed only to the first reactor, R1), ethylene copolymer was nevertheless formed due to the presence of unreacted 1-octene flowing from the first reactor to the second reactor, where it was copolymerized with ethylene. Methylpentane was used as the process solvent (a commercial blend of methylpentane isomers). The volume of the first CSTR reactor (R1) was 3.2 gallons (12 L) and the volume of the second CSTR reactor (R2) was 5.8 gallons (22 L). The monomer (ethylene) and comonomer (1-octene) were purified using a conventional feed preparation system (e.g., by contact with various absorption media to remove impurities such as water, oxygen, and polar contaminants) before being added to the reactor. The reactor feed was pumped into the reactor at the rates presented in Table 1. The average residence time in the reactor is calculated by dividing the average flow rate by the reactor volume and is primarily influenced by the amount of solvent passing through each reactor and the total amount of solvent passing through the solution process.

In the first reactor R1, the first ethylene copolymer was prepared using the following single-site catalyst (SSC) components: diphenylmethylene(cyclopentadienyl)(2,7-di-t-butylfluorenyl)hafnium dimethide [(2,7-tBu ₂ Flu)Ph ₂ C(Cp)HfMe ₂ ]; methylaluminoxane (MMAO-07); trityl tetrakis(pentafluoro-phenyl)borate (trityl borate), and 2,6-di-t-butyl-4-ethylphenol (BHEB). Methylaluminoxane (MMAO-07) and 2,6-di-tert-butyl-4-ethylphenol are premixed in-line and then combined with diphenylmethylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)hafnium dimethide and trityl tetrakis(pentafluorophenyl)borate immediately before entering the polymerization reactor (R1). Suitable solvents used to deliver the single-site catalyst components to the reactor include solvents such as methyl pentane and o-xylene. The efficiency of the single-site catalyst formulation was optimized by adjusting the molar ratio of the catalyst components and the R1 catalyst inlet temperature.

A second ethylene copolymer was prepared in a second reactor R2 using the following Ziegler-Natta (ZN) catalyst components: butyl ethyl magnesium; tert-butyl chloride; titanium tetrachloride; diethyl aluminum ethoxide; and triethyl aluminum. Methylpentane was used as a catalyst component solvent, and the in-line Ziegler-Natta catalyst formulation was prepared through the following steps and then injected into the second reactor (R2). In step 1, a solution of triethyl aluminum and butyl ethyl magnesium (Mg:Al = 20, mol:mol) was combined with a tert-butyl chloride solution and reacted for about 30 seconds to produce a MgCl ₂ support. In step 2, a titanium tetrachloride solution was added to the mixture formed in step 1, reacted for about 14 seconds, and then injected into the second reactor (R2). The in-line Ziegler-Natta catalyst was activated in the reactor by injecting a diethyl aluminum ethoxide solution into R2. The amount of titanium tetrachloride added to the reactor is presented in Table 1. The efficiency of the inline Ziegler-Natta catalyst formulation was optimized by adjusting the molar ratio of the catalyst components.

In the continuous solution polymerization process, polymerization was terminated by adding a catalyst deactivator to the outlet stream of the second reactor. The catalyst deactivator used was octanoic acid (caprylic acid), commercially available from P&G Chemicals, Cincinnati, Ohio, USA. The catalyst deactivator was added in such a way that the moles of fatty acid added were 50% of the total moles of hafnium, titanium, and aluminum added to the polymerization process; for clarity, moles of octanoic acid added = 0.5 x (moles of hafnium + moles of titanium + moles of aluminum).

A two-stage devolatilization process was used to recover the ethylene copolymer product from the process solvent, i.e., two vapor/liquid separators were used, and the second bottom stream (from the second V/L separator) was passed through a gear pump/pelletizer combination. DHT- ^4V® (hydrotalcite) [supplied by Clariant] was used as a passivating agent or acid scavenger in the continuous solution process. A slurry of DHT-4V in the process solvent was added prior to the first V/L separator.

Prior to pelletizing, the polyethylene composition was stabilized by adding approximately 500 ppm of IRGANOX 1076 (primary antioxidant) and approximately 500 ppm of IRGAFOS 168 (secondary antioxidant), based on the weight of the polyethylene composition. The antioxidants were dissolved in the process solvent and added between the first and second V/L separators.

Table 1 shows the reactor conditions used to prepare the polymer compositions of the present invention, Examples 1 to 6, as well as the comparative polyethylene compositions, Examples 10, 11, 15, and 16.

Examples 1 to 6 of the present invention and Comparative Examples 15 and 16 are ethylene-octene copolymers produced in a pilot plant under similar conditions, using a series dual solution polymerization mode using a single-site hafnocene catalyst ("metallocene" in the table) in the first reactor (R1) and a Ziegler-Natta catalyst ("ZN" in the table) in the second reactor (R2). Comparative Examples 15 and 16 have a melt flow ratio (I ₂₁ /I ₂ ) of greater than 60 (greater than the examples of the present invention).

As can be seen, Examples 4 to 6 of the present invention were prepared using slightly different manufacturing conditions compared to Example 3 of the present invention, demonstrating the robustness of product performance even with changes in manufacturing conditions, which is important for commercial operation (easier process control, better product quality).

Comparative Examples 10 and 11 are prepared using a phosphinimine catalyst (“phosphinimine” in the table) in the first reactor (R1) instead of the hafnocene catalyst.

Additionally, comparative examples 7 to 9 and 12 to 14 are also described herein.

Comparative Example 7: Commercial rotomolding grade SURPASS ^® RMs245-U (single site catalyst, dual reactor AST technology), NOVA Chemicals.

Comparative Example 8: US 9321865, substantially prepared according to Example 1.

Comparative Example 9: Prepared substantially according to US 9321865, Example 3.

Comparative Example 10: Prepared substantially according to US 9695309, Example 73.

Comparative Example 11: Prepared substantially according to US 9695309, Example 71.

Comparative Example 12: US 2022/0396690, substantially prepared according to Example 1.

Comparative Example 13: Prepared substantially according to US 2022/0396690, Example 2.

Comparative Example 14: Prepared substantially according to WO 2021/250520, Example 1. This is a blend of two commercially available products, namely SURPASS RMs245 and CCs154.

Comparative Example 15: Prepared substantially according to WO 2022/195513, Example 3.

Comparative Example 16: Prepared substantially according to WO 2022/195513, Example 4.

The properties of the polyethylene compositions of Examples 1 to 6 and Comparative Examples 7 to 16 of the present invention are presented in Table 2.

As shown in Table 2, the CTREF profiles of the embodiments of the present invention are characterized by at least two peaks, specifically a first peak eluting at a temperature above 95° C. and a second peak eluting at a temperature below 90° C. Figure 1 shows the temperature rising elution fraction profiles obtained from REF-CEF for Examples 1 to 3 of the present invention and Comparative Examples 7, 12, and 13.

Table 3 shows the key performance indicators and rheological properties of the exemplified polyethylene compositions in tests on plaques made from the exemplified polyethylene compositions. It is noteworthy that Example 6 of the present invention demonstrates maintained ESCR performance despite having a higher melt flow index I ₂ (1.98 g/10 min) and lower average molecular weights (M _n , M _w , M _z ) compared to Examples 3 to 5 of the present invention (since a higher melt flow index I ₂ or lower molecular weight is known to result in a loss of ESCR performance).

The results are discussed in more detail below in relation to the drawings.

Estimation of zero-shear viscosity and rheological width parameters

The viscosity data can be fitted with the Ellis model (equation 7) and the Carreau-Yasuda (C-Y) model (equation 8) below:

In equation 7, η ( ω ) is the complex viscosity as a function of angular frequency ω , C ₁ is the zero-shear viscosity, C ₂ is the characteristic relaxation time, and C ₃ is the power law exponent.

In Equation 8, η ( ω ) is the complex viscosity, C ₁ is the zero-shear viscosity, C ₂ is the characteristic relaxation time, C ₃ is the width of the transition between the Newtonian plateau and the power-law regime, and C ₄ is the power-law exponent. C ₃ , referred to as the "rheological width parameter" or "parameter" in some literature, is proportional to the polydispersity index or molecular weight distribution width. A steeper transition will indicate a narrower molecular weight distribution.

Dow Rheological Index (DRI)

DRI estimates the deviation from the estimated zero-shear viscosity and characteristic relaxation time due to the presence of long-chain branching. For resins with a narrow molecular weight distribution and no long-chain branching, values close to zero are expected. If the material has a narrow molecular weight distribution, a high DRI value may be due to the presence of LCB.

References: S. Lai, T.A. Plumley, T.I. Butler, G.W. Knight, and C.I. Kao, Dow Rheology Index (DRI) for Insite Technology Polyolefins (ITP): Unique Structure-Processing Relationships, ANTEC (San Francisco) May 1-5, 1994: 1814-1815.

RSI (Relaxation Spectrum Index)

The chain mobility of polymer molecules can be characterized by relaxation time spectra. Union Carbide introduced the Relaxation Spectrum Index (RSI) based on discrete relaxation spectra. The RSI is sensitive to changes in molecular weight, molecular weight distribution, and long-chain branching.

References:

M. Baumgaertel, H.H. Winter, Interrelation between continuous and discrete relaxation time spectra, Journal of Non-Newtonian Fluid Mechanics, 1992, 44: 15-36.

GPC-FTIR results

Figure 2 shows the molecular weight distribution and comonomer distribution of the GPC-FTIR measurement results. Examples 1 to 3 of the present invention and Comparative Examples 15 and 16 are presented in Graph A, and Example 3 of the present invention and Comparative Examples 7 and 10 to 13 are presented in Graph B.

Embodiments of the present invention are characterized in that the branching frequency of the high molecular weight component is greater than 2 per 1000 carbon atoms, preferably greater than 4 per 1000 carbon atoms.

Rheological behavior results

Figure 3 shows the rheological behavior results. Specifically, graphs A, B, and C in Figure 3 show complex viscosity profiles obtained through DMA frequency sweeps at 190°C. Meanwhile, graph D shows zero-shear viscosity (estimated using the Ellis model) versus weight-average molecular weight. The labels indicate the example numbers, and the dashed lines indicate the trends for each data set.

Additionally, the data were fitted to a rheological model to obtain various parameters, which are summarized in Table 3 above.

In the examples produced using the hafnocene catalyst (inventive examples 1 to 6 and comparative examples 15 and 16), the presence of long chain branches is most evident by the characteristic width of the transition between the Newtonian plateau and the power law regime, which spans a longer frequency range compared to resins having a linear molecular structure (i.e., no long chain branches). In the inventive examples, the transition width is less pronounced than in comparative examples 15 and 16 (which have a higher long chain branch content). In the present disclosure, the transition is quantified using the rheological width parameter, a (Carreau-Yasuda model).

The relaxation spectrum index (RSI) and Dow rheological index (DRI) values also suggest long chain branching in the examples of the present invention, although the effect is not as pronounced as in comparative examples 15 and 16.

The embodiments of the present invention contain a small amount of long-chain branching, which is believed to result in higher zero-shear viscosities and, therefore, higher melt strengths compared to resins with a linear structure and otherwise similar molecular weight distribution (see graph D in FIG. 3 ). The presence of long-chain branching is indicated by relatively low values of the rheological width parameter a (typically less than about 0.040). Higher zero-shear viscosities (i.e., higher flow resistance at low deformation frequencies) are advantageous for the fabrication of large rotationally molded parts (e.g., large tanks) where longer heating cycles may be required and the resin is at greater risk of developing excessive melt flow limitations.

ESCR, Izod Impact, and Stiffness - Discussion and Results

Environmental stress cracking occurs when a chemical agent penetrates a material, reducing its ductility and disrupting the intermolecular forces that bind polymer chains. This chemical penetration reduces the energy required for disentanglement, leading to a shift from yielding to fracture mode.

ESCR is a performance appropriate for applications containing chemical formulations (including containers such as intermediate bulk containers), ranging from household applications (e.g., detergents) to many industrial applications (e.g., agricultural and chemical). The ESCR performance of polyethylene resins with densities exceeding 0.940 g/cm³ tends to decrease with increasing density, resulting in increased stiffness. The increased amount of crystalline structure can further restrict mobility associated with amorphous regions. However, for higher-density resins, a decrease in comonomer content also reduces the amount of molecules that bind the crystalline domains together. The concept of tie molecules relates to crack initiation resistance by reducing chain mobility in the amorphous region, thus increasing the resistance to chain dissociation when the specimen is exposed to stress.

The concept of binding molecules also relates to the efficiency of energy transfer and dissipation when a specimen is subjected to impact. Izod impact resistance and tensile impact resistance generally decrease with increasing density (stiffness) when other resin properties are similar. Izod measures a resin's resistance to bending impact, while tensile impact measurements, performed at higher strain rates, are useful for further differentiating resins.

The ESCR and impact performance of Examples 1 to 6 of the present invention are compared with several comparative examples and are presented in FIG. 4 (and Table 3 above). In FIG. 4, Graph A shows the results at ESCR condition A100 in IGEPAL CO-630, while Graph B shows Izod impact, both plotted against flexural modulus (1%).

The high performance of the embodiments of the present invention is primarily attributed to the high comonomer incorporation into the high molecular weight component of these polymer compositions. This follows the general guidelines for enhancing ESCR and toughness based on the concept of binding molecules. The formation of binding molecules is advantageous as molecular weight increases along with increasing comonomer incorporation.

Izod impact generally decreases with increasing density (stiffness) when other resin properties are similar. For rigid molding applications, a similar trend is observed between ESCR and stiffness within the density range considered herein. As shown in Figure 4, the Izod impact versus stiffness trend shifts toward higher values in the examples produced using the hafnocene catalyst (Examples 1 to 6 of the present invention and Comparative Examples 15 and 16).

Embodiments of the present invention demonstrate an excellent combination of ESCR, Izod impact, and stiffness compared to the comparative examples. In general, higher Izod impact performance is observed in other cases with similar stiffness (e.g., see Comparative Examples 7, 13, and 14).

Rotational molding parts manufacturing

The powdered polyethylene composition was converted into rotationally molded parts using a rotational molder, specifically a Rotospeed RS160 from Ferry Industries Inc. (Stowe, Ohio). The Rotospeed has two arms that rotate about a central axis in a sealed oven. The arms are equipped with plates that rotate about an axis that is approximately perpendicular to the arms' axes of rotation. Each arm is equipped with six cast aluminum molds to produce cubic hollow rotationally molded parts measuring 12.5 in. (31.8 cm) x 12.5 in. x 12.5 in. The arm rotation was set to approximately 8 revolutions per minute (rpm) and the plate rotation was set to approximately 2 rpm. Rotationally molded parts having a nominal thickness of approximately 0.250 in. (0.64 cm) were produced using a standard charge of approximately 3.7 kg of powdered polyethylene composition; Here, the powder had a 35 US mesh size (0.0197 in (500 μm) mesh opening). The temperature inside the sealed oven was maintained at 560°F (293°C). The mold and its contents were heated in the oven for 18, 20, 22, 24, and 26 minutes to achieve complete powder densification. The mold was then cooled using an air fan for approximately 30 minutes before being removed from the mold. After removing the plastic part from the mold, the part was allowed to stand at room temperature for at least 24 hours before being cut and specimens collected for subsequent testing. Specimens were collected from the molded part for density evaluation and ARM impact testing.

ARM impact test

The ARM impact test was performed at a test temperature of -40°C according to ASTM D5628. This test was adapted from the Low Temperature Impact Test, Version 4.0, July 2003 edition of the Association of Rotational Molders International. The purpose of this test was to determine the impact properties of rotationally molded parts. Five-inch x five-inch (12.7 cm x 12.7 cm) ARM impact test specimens were cut from the sidewalls of cuboid rotationally molded parts. The test specimens were thermally equilibrated in a refrigerated test chamber maintained at -40°F ± 3.5°F (-40°C ± 2°C) for at least 24 hours prior to impact testing. The testing technique used is commonly referred to as the Bruceton Staircase Method or Up-and-Down Method. This procedure established a specific dart height at which 50% of the specimens would fail, i.e., the test (dart dropping on the specimen) was performed for at least 10 passes and 10 failures. Each failure was characterized as either ductile or brittle. Ductile failure was characterized by the dart penetrating the specimen and the impact zone becoming elongated and tapered, leaving a hole with thread-like fibers at the point of failure. Brittle failure was evident when cracks developed in the test specimen, where the cracks formed radially outward from the point of failure and the sample exhibited little or no elongation at the point of failure. The "ARM Ductility %" was calculated as: 100% × [(number of ductile failures) / (total number of all failures)].

Samples were impact tested using a drop weight impact tester; the available impact darts consisted of 10 pound (4.54 kg), 15 pound (6.80 kg), 20 pound (9.07 kg), or 30 pound (13.6 kg) darts. All impact darts had a round dart tip with a diameter of 1.0 ± 0.005 inches (2.54 cm), the dart tip transitioned to a lower cylindrical shaft (1.0 inch in diameter), and the lower cylindrical shaft had a length (to the dart tip) of 4.5 inches (11.4 cm). The impact darts included an upper cylindrical shaft with a diameter of 2.0 inches (5.08 cm), the length of which varied depending on the desired dart weight, for example, 10.5 inches (26.7 cm) or 16.5 inches (41.9 cm) for 10- or 20-pound darts, respectively. Preferably, the dart weight is selected such that the drop height is between 2.5 ft and 7.5 ft (0.8 m to 2.3 m). The test specimens were oriented in the impact tester so that the dropping dart impacted the surface of the part that was in contact with the mold (when formed). If the sample did not fail at a given height and weight, the height or weight was incrementally increased until part failure occurred. If failure occurred, the height or weight was decreased by the same increment and the process was repeated. The "ARM Average Failure Energy (ft lb)" was calculated by multiplying the drop height (ft) by the nominal dart weight (lb). After impact, both the upper and lower surfaces of the specimen were examined for fracture. For the polyethylene composition disclosed herein, ductile fracture was the preferred fracture mode.

Rotational Forming Processability and Performance Window Results

Excellent rotational molding performance is characterized by parts exhibiting a combination of high average fracture energy (>100 ft lb) and high ductility (>50%). The processability and processing window is defined as the width of the oven residence time range that provides excellent performance under consistent molding conditions (mold, part thickness, oven temperature).

Figure 5 presents the results of tests performed on rotationally molded specimens (1/4 inch thick specimens collected from test cubes rotationally molded at an oven temperature of 293°C (560°F); see above for further details on the fabrication of rotationally molded parts). Graphs A and B in Figure 5 show the ARM impact average fracture energy at -40°C; graphs C and D show the ductility at -40°C; and graphs E and F show the difference between as-is rotationally molded density and plaque density (ASTM D792-13).

It can be seen that Examples 1 to 3 of the present invention exhibit a process window similar to or better than that of a commercial rotational molding grade (Comparative Example 7). Examples 1 to 3 of the present invention exhibit a process window better than Comparative Examples 15 and 16. This may be due to the more favorable rheology (low zero-shear viscosity) of the examples of the present invention. Low zero-shear viscosity is beneficial for neck growth (sintering) between powder particles during the melt densification process. Better sintering leads to the formation of smaller bubbles, which dissolve at a faster rate in the melt. Faster sintering and bubble dissolution are important for ensuring that melt densification is completed within the molding cycle. If melt densification is not completed, bubbles remain in the molded part and act as defects, resulting in deteriorated mechanical performance.

Embodiments of the present invention maintain excellent performance even when bubbles are present in the molded part (even with short oven times). The presence of bubbles is inferred if the current density of the molded specimen is significantly lower than the plaque density (ASTM D792-13). Interestingly, the disclosed embodiments exhibit superior impact performance (average fracture energy and ductility) despite slower densification than Comparative Example 7. This result suggests that the embodiments of the present invention can withstand a higher level of defects within the molded part, thereby providing superior toughness.

For Examples 1 and 2 of the present invention, the additive package formulation for the rotational molding tests contained 384 ppm by weight of hydroxylamine IRGASTAB FS 042. Example 3 of the present invention was formulated using two levels of IRGASTAB FS 042. As shown for the results of Example 3 of the present invention in FIG. 5 , changing the additive package, specifically increasing the hydroxylamine content from 384 ppm by weight (labeled “regular additive”) to 800 ppm by weight (labeled “alternative additive”), resulted in significant improvements in performance and powder densification. This can be seen in the profiles of average fracture energy, ductility, and current density versus oven residence time in FIG. 5 . A significant shift was observed toward achieving higher ductility and fracture energy, as well as higher densification.

Some additives were added in masterbatch form, while others were added in powder form. The masterbatch additives were melt compounded in Examples 1 and 2 using a Coperion ZSK26 twin-screw extruder. In Example 3, the additives were added using a Leistritz LSM 30.34 twin-screw extruder. The standard additive formulations were prepared by melt compounding the additives in masterbatch form. The alternative additive formulations used masterbatch combinations supplemented with selected additives in powder form. When adding the powder additives, the powdered additives were first combined with a portion of the base resin, also in powder form, to ensure the correct additive weight throughout the sample.

Deconvolution of polyethylene compositions

For Examples 1 to 6 of the present invention, mathematical deconvolution was performed to determine the relative amounts of each of the first and second ethylene copolymers (and the third ethylene copolymer, if present in the comparative examples) present in the polyethylene composition, as well as the molecular weights (M _w , M _n , M _z ) and comonomer contents (SCB frequency per 1000 polymer backbone carbon atoms) of each copolymer. For the deconvolution calculations, the single-site catalyzed ethylene copolymer components were assumed to follow the Flory molecular weight distribution function and have a uniform comonomer distribution over the entire molecular weight range. The ethylene copolymer components produced using Ziegler-Natta type catalysts were modeled as a combination of four catalytic sites, each of which follows the Flory molecular weight distribution function. For the comparative examples (Examples 10 and 11), the data provided in Table 4 are as previously reported in US 9695309.

The estimates were first obtained from predictions obtained through a basic kinetic model using kinetic constants specific to each catalyst formulation as well as feed and reactor conditions. The simulations were based on the configuration of a solution pilot plant as described above and were used to produce the polyethylene compositions disclosed herein. The kinetic model predictions were used to establish estimates of the short-chain branching distribution within the first and second ethylene copolymer components. The estimates of short-chain branching content were also validated against experimental results obtained from GPC-FTIR for the comonomer distribution. The fit between the simulated molecular weight distribution profiles and the actual data obtained from GPC chromatography was improved by modeling the molecular weight distribution as a sum of components whose molecular weight distributions were described using a multi-site ideal Flory distribution.

During deconvolution, the overall Mn, Mw, and Mz are calculated using the following relationships:

Here, i represents the ith component and wi represents the relative weight fraction of the ith component in the composition.

The density and melt index (I ₂ ) of each ethylene copolymer component were calculated using the following equations:

Equation (9)

Equation (10)

Equation (11)

Here, Mn, Mw, Mz, and SCB/1000C are the deconvoluted values of the individual ethylene polymer components obtained from the deconvolution results described above, while ρ is the density of the entire polyethylene composition and is determined experimentally. Equations (9) and (10) were used to estimate the densities ρ1 and ρ2 of the first and second ethylene copolymers, respectively. Equation (11) was used to estimate the melt index (I ₂ ) of the first and second ethylene copolymers, respectively. See, e.g., Alfred Rudin, in The Elements of Polymer Science and Engineering , 2nd edition, Academic Press, 1999, and U.S. Patent No. 8,022,143.

Molecular weight deconvolution results are provided in Table 4, which shows Examples 1 to 6 of the present invention and comparative examples (Examples 10 and 11) with the most similar compositions.

Industrial applicability

A polyethylene composition suitable for use in rotationally molded plastic articles is disclosed. When manufactured into plaques, the polyethylene composition exhibits an excellent combination of environmental stress cracking resistance, Izod impact strength, and rigidity.

Claims (46)

As a polyethylene composition,
(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm³, a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;
(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm³, a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;
The ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;
The polyethylene composition has a density of at least 0.940 g/cm ³ , a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;
A polyethylene composition, wherein the weight % of the first or second ethylene copolymer is defined as the value obtained by dividing the weight of the first or second copolymer by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100. A polyethylene composition in claim 1, wherein the polyethylene composition has an LCBF of 0.0050 to 0.0375. A polyethylene composition according to claim 1 or 2, wherein the polyethylene composition has a melt flow ratio (I ₂₁ /I ₂ ) of 20 to 50. A polyethylene composition according to any one of claims 1 to 3, wherein the polyethylene composition has a molecular weight distribution (M _w /M _n ) of less than 4.5. A polyethylene composition in claim 4, wherein the polyethylene composition has a molecular weight distribution (M _w /M _n ) of 2.0 to 4.0. A polyethylene composition according to any one of claims 1 to 5, wherein the polyethylene composition has a unimodal profile in GPC analysis. A polyethylene composition according to any one of claims 1 to 6, wherein the density of the first ethylene copolymer is 0.890 to 0.925 g/cm ³ . A polyethylene composition according to any one of claims 1 to 7, wherein the melt index (I ₂ ) of the first ethylene copolymer is at most 1.0 g/10 min. A polyethylene composition in claim 8, wherein the melting index (I ₂ ) of the first ethylene copolymer is 0.001 to 0.7 g/10 min. A polyethylene composition according to any one of claims 1 to 9, wherein the melt index (I ₂ ) of the second ethylene copolymer is at least 2.0 g/10 min. A polyethylene composition in claim 10, wherein the melting index (I ₂ ) of the second ethylene copolymer is 2.0 to 50 g/10 min. A polyethylene composition according to any one of claims 1 to 11, wherein the polyethylene composition has a density of 0.942 to 0.957 g/cm ³ . A polyethylene composition according to claim 12, wherein the polyethylene composition has a density of 0.945 to 0.955 g/cm ³ . A polyethylene composition according to any one of claims 1 to 13, wherein the polyethylene composition has a melt index (I ₂ ) of 1.0 to 2.6 g/10 min. A polyethylene composition according to any one of claims 1 to 14, wherein the polyethylene composition has a high load melt index (I ₂₁ ) of at least 30 g/10 min. A polyethylene composition according to claim 15, wherein the polyethylene composition has a high load melt index (I ₂₁ ) of 30 to 100 g/10 min. A polyethylene composition according to any one of claims 1 to 16, wherein the polyethylene composition has a weight average molecular weight (M _w ) of 70,000 to 120,000 g/mol. A polyethylene composition according to any one of claims 1 to 17, wherein the polyethylene composition has a number average molecular weight (M _n ) of 20,000 to 40,000 g/mol. A polyethylene composition according to any one of claims 1 to 18, wherein the polyethylene composition has a Z-average molecular weight (M _z ) of less than 400,000 g/mol. A polyethylene composition according to claim 19, wherein the polyethylene composition has a Z-average molecular weight (M _z ) of 100,000 to 350,000 g/mol. A polyethylene composition according to any one of claims 1 to 20, wherein the polyethylene composition has an M _z /M _w of less than 3.3. A polyethylene composition according to claim 21, wherein the polyethylene composition has an M _z /M _w of 1.5 to 3.0. A polyethylene composition according to any one of claims 1 to 22, wherein the polyethylene composition has 0.0015 to 2.4 ppm of hafnium. A polyethylene composition according to any one of claims 1 to 23, wherein the first ethylene copolymer has 2 to 30 short-chain branches per 1,000 carbon atoms (SCB1/1000C). A polyethylene composition according to claim 24, wherein the first ethylene copolymer has 4 to 25 short-chain branches per 1,000 carbon atoms (SCB1/1000C). A polyethylene composition according to any one of claims 1 to 25, wherein the second ethylene copolymer has 0.05 to 3 short-chain branches per 1,000 carbon atoms (SCB2/1000C). A polyethylene composition according to any one of claims 1 to 26, wherein the ratio of the number of short-chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short-chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 10. A polyethylene composition according to any one of claims 1 to 27, wherein the polyethylene composition has a fraction that elutes above 95°C in CTREF analysis. A polyethylene composition according to any one of claims 1 to 28, wherein the polyethylene composition has a fraction that elutes at less than 90°C in CTREF analysis. A polyethylene composition according to any one of claims 1 to 29, wherein the polyethylene composition has a rheological width parameter (a) of less than 0.400 as measured by the Carreau-Yasuda model. A polyethylene composition according to any one of claims 1 to 30, wherein the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 500 hours as determined under condition A at 100% IGEPAL CO-630 according to ASTM D1693. A polyethylene composition according to claim 31, wherein the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 1000 hours as determined under condition A at 100% IGEPAL CO-630 according to ASTM D1693. A polyethylene composition according to any one of claims 1 to 32, wherein the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 50 hours as determined under condition A at 10% IGEPAL CO-630 according to ASTM D1693. A polyethylene composition according to claim 33, wherein the polyethylene composition has an environmental stress cracking resistance (ESCR) of greater than 100 hours as determined under condition A at 10% IGEPAL CO-630 according to ASTM D1693. A polyethylene composition according to any one of claims 1 to 34, wherein the polyethylene composition has an Izod impact value of at least 4.0 ft. lbs./inch. A polyethylene composition in claim 35, wherein the polyethylene composition has an Izod impact value of 4.0 to 13.0 ft. lbs./inch. A polyethylene composition according to claim 35 or 36, wherein the polyethylene composition has an Izod impact value of at least 6.0 ft. lbs./inch. A polyethylene composition according to any one of claims 1 to 37, wherein the polyethylene composition has a tensile impact value of at least 230 ft. lbs./inch ² . A polyethylene composition according to any one of claims 1 to 38, wherein the polyethylene composition has a 1% bending modulus of at least 1000 MPa. A polyethylene composition according to claim 39, wherein the polyethylene composition has a 1% bending modulus of elasticity of 1000 to 1300 MPa. A polyethylene composition according to any one of claims 1 to 40, wherein the polyethylene composition has an elasticity ratio (G'/G") of at most 0.25 at 0.05 rad/s. A solution phase polymerization process for producing a polyethylene composition,
The above solution phase polymerization process
A step of polymerizing ethylene and alpha-olefin using a metallocene catalyst in a first reactor; and
A step of polymerizing ethylene and alpha-olefin using a Ziegler-Natta catalyst in a second reactor;
The first and second reactors are configured in series with each other;
The above polyethylene composition
(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm³, a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;
(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm³, a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;
The ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;
The polyethylene composition has a density of at least 0.940 g/cm ³ , a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;
A solution phase polymerization process, wherein the weight % of the first or second ethylene copolymer is defined as the value obtained by dividing the weight of the first or second copolymer by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100. A rotationally molded article manufactured from a polyethylene composition, wherein the polyethylene composition
(i) 10 to 60 wt% of a first ethylene copolymer having a density of 0.880 to 0.930 g/cm³, a molecular weight distribution (M _w /M _n ) of 1.7 to 2.7, and a weight average molecular weight (M _w ) of 140,000 to 250,000 g/mol;
(ii) 90 to 40 wt% of a second ethylene copolymer having a density of 0.940 to 0.975 g/cm³, a molecular weight distribution (M _w /M _n ) of 2.0 to 3.3, and a weight average molecular weight (M _w ) of 20,000 to 90,000 g/mol;
The ratio of the number of short chain branches per 1,000 carbon atoms of the first ethylene copolymer to the number of short chain branches per 1,000 carbon atoms of the second ethylene copolymer (SCB1/SCB2) is at least 5.0;
The polyethylene composition has a density of at least 0.940 g/cm ³ , a melt index (I ₂ ) of less than 3.0 g/10 min, a melt flow ratio (I ₂₁ /I ₂ ) of at most 60, and a long chain branching factor (LCBF) of at most 0.0400;
A rotationally molded product, wherein the weight % of the first or second ethylene copolymer is defined as the value obtained by dividing the weight of the first or second copolymer by the sum of the weights of the first ethylene copolymer and the second ethylene copolymer, multiplied by 100. A rotationally molded article according to claim 43, wherein the polyethylene composition contains an additive package comprising at least one additional additive selected from the group consisting of a hindered monophosphite; a diphosphite; a hindered amine light stabilizer; and a hindered phenol and a hydroxylamine. A rotationally molded product in claim 44, wherein the hydroxylamine of the additive package is N,N-dialkylhydroxylamine, preferably IRGASTAB FS 042. A rotationally molded article in claim 45, wherein the hydroxylamine is present in a concentration of at least about 750 ppm by weight.