Polymer formulation and irrigation pipe comprising the same

Abstract

Embodiments of polyethylene formulations and articles comprising the polyethylene formulations are disclosed. The polyethylene formulation may comprise: 45 wt.% to 90 wt.% of MDPE having a density of 0.930 g / cc to 0.950 g / cc and a melt index (I2) of 0.05 g / 10 min to 0.5 g / 10 min; 10 wt.% to 50 wt.% of a polyethylene composition having a density of 0.910 g / cc to 0.936 g / cc and a melt index (I2) of 0.7 g / 10 min to 1.0 g / 10 min; and 0.5 wt.% to 5% of a masterbatch composition. The polyethylene composition may include a first polyethylene fraction area of an elution curve obtained by an improved comonomer composition distribution (iCCD) analysis method in a temperature range of 45°C to 87°C and a second polyethylene fraction area of the elution curve obtained by iCCD in a temperature range of 95°C to 120°C.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 030,471, filed on May 27, 2020, the entire disclosure of which is hereby incorporated by reference. Technical Field

[0003] Embodiments described herein relate generally to polyethylene formulations, and more particularly to articles, such as irrigation pipes, comprising the polyethylene formulations. Background Art

[0004] Irrigation pipes are used by the agricultural industry as an economical and effective means of watering crops. Irrigation pipes include drip tapes and pipes that may be made of polymeric materials. Irrigation pipes may include perforations in the wall of the pipe to allow water (or other liquids) to drain through the perforations as it flows through the pipe. Summary of the invention

[0005] The irrigation pipe market has been searching for solutions to allow thinner pipes to be produced without compromising stiffness and burst strength. It would therefore be advantageous for polymer drip tapes and pipes to exhibit adequate stiffness and burst strength properties while allowing for reduced material costs, for example by downsizing (i.e., using thinner film thicknesses) or by reducing or eliminating relatively expensive materials. There is therefore a need for polymer formulations that can be used in irrigation pipe applications that exhibit stiffness and burst strength properties that meet customer and industry requirements while allowing for reduced material costs.

[0006] Embodiments of the present disclosure meet these needs by providing a polyethylene formulation comprising a medium density polyethylene, a polyethylene composition, and a masterbatch composition. When used in irrigation pipes, the polyethylene formulation can provide a desired combination of burst strength without compromising stiffness even when the thickness is reduced by 15%. Thus, embodiments of the present disclosure can provide a polyethylene formulation that provides an improved balance of stiffness and burst strength properties when used in irrigation pipes while allowing for reduced material costs.

[0007] According to one or more embodiments, a polyethylene formulation is provided. The polyethylene formulation may include: 45 wt.% to 90 wt.% of a medium density polyethylene (MDPE) having a density of 0.930 g / cc to 0.950 g / cc and a melt index (I2) of 0.05 g / 10 min to 0.5 g / 10 min; 10 wt.% to 50 wt.% of a polyethylene composition having a density of 0.910 g / cc to 0.936 g / cc and a melt index (I2) of 0.25 g / 10 min to 2.0 g / 10 min; and 0.5 wt.% to 5% of a masterbatch composition. The polyethylene composition may include a first polyethylene fraction area in a temperature range of 45°C to 87°C of an elution curve obtained by an improved comonomer composition distribution (iCCD) analysis method and a second polyethylene fraction area in a temperature range of 95°C to 120°C of an elution curve obtained by an improved comonomer composition distribution (iCCD) analysis method. The first polyethylene fraction area may account for at least 50% of the total area of ​​the elution curve. The second polyethylene fraction area may account for less than or equal to 23% of the total area of ​​the elution curve. The ratio of the first polyethylene fraction area to the second polyethylene fraction area may be 2.9 to 12.5.

[0008] According to one or more embodiments, a product is provided. The product may be an irrigation pipe. The product may include the above polyethylene formulation. These and embodiments are described in more detail in the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following detailed description of certain embodiments of the present disclosure may be best understood when taken in conjunction with the following drawings, in which like reference numerals are used to indicate like structures and in which:

[0010] Figure 1 graphically depicts an elution curve of a polyethylene composition according to one or more embodiments presently described; and

[0011] Figure 2 Graphically depicted are elution curves for exemplary embodiments of polyethylene compositions according to one or more embodiments presently described. DETAILED DESCRIPTION

[0012] Specific embodiments of the present application will now be described. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the claimed subject matter to those skilled in the art.

[0013] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different types. Thus, the generic term polymer encompasses the terms "homopolymer," which generally refers to polymers prepared from only one type of monomer, and "copolymer," which refers to polymers prepared from two or more different monomers. As used herein, the term "interpolymer" refers to a polymer prepared by the polymerization of at least two different types of monomers. Thus, the generic term interpolymer encompasses copolymers or polymers prepared from two or more different types of monomers, such as terpolymers.

[0014] "Polyethylene" or "ethylene-based polymer" shall mean a polymer comprising greater than 50 mole % of units derived from ethylene monomers. This includes ethylene-based homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of ethylene-based polymers known in the art include, but are not limited to: low density polyethylene (LDPE); linear low density polyethylene (LLDPE); ultra low density polyethylene (ULDPE); very low density polyethylene (VLDPE); single-site catalyzed linear low density polyethylene, which includes both linear low density resins and substantially linear low density resins (m-LLDPE); medium density polyethylene (MDPE); and high density polyethylene (HDPE).

[0015] The term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean a polymer that is partially or completely homopolymerized or copolymerized in an autoclave or tubular reactor at pressures above 14,500 psi (100 MPa) using a free radical initiator such as a peroxide (see, e.g., U.S. Pat. No. 4,599,392, which is incorporated herein by reference in its entirety). The density of LDPE resins is typically 0.916 g / cm 3 Up to 0.940g / cm 3 within the range.

[0016] The term "LLDPE" includes resins made using a Ziegler-Natta catalyst system and resins made using single-site catalysts, including but not limited to dimetallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimines, constrained geometry catalysts; and resins made using post-metallocene molecular catalysts, including but not limited to bis(biphenylphenoxy) catalysts (also known as polyvalent aryloxyether catalysts). LLDPE includes linear, substantially linear or heterogeneous ethylene-based copolymers or homopolymers. LLDPE contains less long chain branching than LDPE and includes: substantially linear ethylene polymers, which are further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923 and U.S. Pat. No. 5,733,155, each of which is incorporated herein by reference in its entirety; homogeneously branched linear ethylene polymer compositions, such as those described in U.S. Pat. No. 3,645,992, which is incorporated herein by reference in its entirety; heterogeneously branched ethylene polymers, such as those prepared according to the process disclosed in U.S. Pat. No. 4,076,698, which is incorporated herein by reference in its entirety; and blends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 and U.S. Pat. No. 5,854,045), which are incorporated herein by reference in their entirety. The LLDPE resin may be prepared via gas phase, solution phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0017] As used herein, the term "MDPE" refers to a polyethylene having a density of 0.930 g / cm 3 Up to 0.950g / cm 3 MDPE is typically prepared using chromium or Ziegler-Natta catalysts or using single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (commonly referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyvalent aryloxyether catalysts (commonly referred to as bisphenylphenoxy).

[0018] The term "HDPE" refers to polyethylene with a density greater than 0.950 g / cm 3 and at most 0.980g / cm 3 MDPE is typically prepared using Ziegler-Natta catalysts, chromium catalysts, or single-site catalysts, including but not limited to substituted mono- or bis-cyclopentadienyl catalysts (commonly referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyvalent aryloxyether catalysts (commonly referred to as bisphenylphenoxy).

[0019] The term "ULDPE" refers to a polyethylene having a density of 0.855 g / cm 3 Up to 0.912g / cm 3 Polyethylenes of the type described herein are generally prepared using Ziegler-Natta catalysts, chromium catalysts or single-site catalysts (including but not limited to substituted mono- or di-cyclopentadienyl catalysts (commonly referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts and polyvalent aryloxyether catalysts (commonly referred to as bisphenylphenoxy). ULDPE includes but is not limited to polyethylene (ethylene-based) plastomers and polyethylene (ethylene-based) elastomers. Polyethylene (ethylene-based) elastomer plastomers generally have a molecular weight of 0.855 g / cm 3 Up to 0.912g / cm 3 density.

[0020] "Blends," "polymer blends," and similar terms mean components of two or more polymers. Such blends may or may not be miscible. Such blends may or may not be phase separated. Such blends may or may not contain one or more domain configurations as determined by transmission electron spectroscopy, light scattering, x-ray scattering, and any other method known in the art. A blend is not a laminate, but one or more layers of a laminate may contain a blend. Such blends may be prepared as dry blends, formed in situ (e.g., in a reactor), melt blends, or using other techniques known to those skilled in the art.

[0021] The terms "comprising," "including," "having," and derivatives thereof are not intended to exclude the presence of any additional components, steps, or procedures, whether or not specifically disclosed. For the avoidance of any doubt, all compositions claimed through use of the term "comprising" may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term "consisting essentially of excludes from the scope of any subsequently recited component, step, or procedure, except those that are not essential to operability. The term "consisting of excludes any ingredient, step, or procedure not specifically recited or listed.

[0022] Embodiments of polyethylene formulations will now be described. When used for drip irrigation applications, embodiments of the polyethylene formulations currently described can provide a balance of improved rigidity and improved burst strength properties. Additionally, embodiments of the polyethylene formulations currently described can also provide such a balance of improved rigidity and improved burst strength properties even at reduced thicknesses (reduced specifications). In one or more embodiments, the polyethylene formulation can include medium density polyethylene, polyethylene compositions, and masterbatch compositions.

[0023] In one or more embodiments, the polyethylene formulation may comprise a medium density polyethylene (MDPE). Without being bound by theory, it is believed that having at least 45 wt.% MDPE may impart sufficient stiffness properties to the polyethylene formulation. MDPE may typically be prepared using chromium or Ziegler-Natta catalysts or using single-site catalysts including but not limited to substituted mono- or bis-cyclopentadienyl catalysts (commonly referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyvalent aryloxyether catalysts (commonly referred to as bisphenylphenoxy). In an embodiment, the density of the MDPE may be 0.930 g / cm when measured according to ASTM D792. 3 Up to 0.950g / cm 3 In an embodiment, the density of the MDPE may be: 0.930 g / cm 3 Up to 0.945g / cm 3 , 0.930g / cm 3 Up to 0.940g / cm 3 , 0.930g / cm 3 Up to 0.935g / cm 3 , 0.935g / cm 3 Up to 0.950g / cm 3 , 0.935g / cm 3 Up to 0.945g / cm 3 , 0.935g / cm 3 Up to 0.940g / cm 3 , 0.940g / cm 3 Up to 0.950g / cm 3 , 0.940g / cm 3 Up to 0.945g / cm 3 or 0.945g / cm 3 Up to 0.950g / cm 3 .

[0024] In one or more embodiments, the MDPE may have a melt index (I2) of 0.05 g / 10 minutes (g / 10 min) to 0.5 g / 10 min when measured according to ASTM D-1238 at 190° C. and 2.16 kg. In an embodiment, the MDPE may have a melt index (I2) of 0.05 g / 10 min to 0.4 g / 10 min, 0.05 g / 10 min to 0.3 g / 10 min, 0.05 g / 10 min to 0.2 g / 10 min, 0.05 g / 10 min to 0.1 g / 10 min, 0.1 g / 10 min to 0.5 g / 10 min, 0.1 g / 10 min to 0.4 g / 10 min, 0.1 g / 10 min to 0.6 g / 10 min, 0.1 g / 10 min to 0.7 g / 10 min, 0.1 g / 10 min to 0.8 g / 10 min, 0.1 g / 10 min to 0.9 g / 10 min, 0.1 g / 10 min to 0.10 g / 10 min, 0.1 g / 10 min to 0.2 g / 10 min, 0.05 g / 10 min to 0.1 g / 10 min, 0.1 g / 10 min to 0.5 g / 10 min, 0.1 g / 10 min to 0.4 g / 10 min, 0.1 g / 10 min to 0.5 ... / 10min to 0.3g / 10min, 0.1g / 10min to 0.2g / 10min, 0.2g / 10min to 0.5g / 10min, 0.2g / 10min to 0.4g / 10min, 0.2g / 10min to 0.3g / 10min, 0.3g / 10min to 0.5g / 10min, 0.3g / 10min to 0.4g / 10min, 0.4g / 10min to 0.5g / 10min, or any combination of these ranges.

[0025] In one or more embodiments, the polyethylene formulation can include up to 90 wt% MDPE, based on the total weight of the polyethylene formulation. In some embodiments, the polyethylene formulation can include 45 wt.% to 80 wt.%, 45 wt.% to 70 wt.%, 45 wt.% to 60 wt.%, 45 wt.% to 50 wt.%, 50 wt.% to 90 wt.%, 50 wt.% to 80 wt.%, 50 wt.% to 70 wt.%, 50 wt.% to 60 wt.%, 60 wt.% to 90 wt.%, 60 wt.% to 80 wt.%, 60 wt.% to 70 wt.%, 70 wt.% to 90 wt.%, 70 wt.% to 80 wt.%, or 80 wt.% to 90 wt.% MDPE, based on the total weight of the polyethylene formulation.

[0026] In one or more embodiments, the polyethylene formulation may include a masterbatch composition. In an embodiment, the masterbatch composition may include carbon black. In an embodiment, carbon black may be used to impart UV absorption and stability properties to the polyethylene formulation. In one or more embodiments, the polyethylene formulation may include at least 0.5 wt % of a masterbatch composition based on the gross weight of the polyethylene formulation. In some embodiments, the polyethylene formulation may comprise 0.5 wt.% to 5 wt.%, 0.5 wt.% to 4 wt.%, 0.5 wt.% to 3 wt.%, 0.5 wt.% to 2 wt.%, 0.5 wt.% to 1 wt.%, 1 wt.% to 5 wt.%, 1 wt.% to 4 wt.%, 1 wt.% to 3 wt.%, 1 wt.% to 2 wt.%, 2 wt.% to 5 wt.%, 2 wt.% to 4 wt.%, 2 wt.% to 3 wt.%, 3 wt.% to 5 wt.%, 3 wt.% to 4 wt.%, or 4 wt.% to 5 wt.%, based on the total weight of the polyethylene formulation.

[0027] The masterbatch composition may include a carrier resin. In an embodiment, the carrier resin may be a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), a medium density polyethylene (MDPE), a high density polyethylene (HDPE), or a combination thereof. In some embodiments, the carrier resin is LDPE. In some embodiments, the second polyethylene is LLDPE. In other embodiments, the second polyethylene is MDPE or HDPE. The density of the carrier resin may be between 0.860 g / cm 3 Up to 0.980g / cm 3 The melt index can be in the range of 0.01 g / 10 min to 100 g / 10 min. 3 Up to 0.970g / cm 3 All individual values ​​and subranges of density in the range of and melt index in the range of 0.01 g / 10 min to 100 g / 10 min are included and disclosed herein. In an embodiment, the density of the carrier resin may be: 0.860 g / cm 3 Up to 0.970g / cm 3 、0.860g / cm 3 Up to 0.960g / cm 3 、0.860g / cm 3 Up to 0.940g / cm 3 、0.860g / cm 3 Up to 0.920g / cm 3 、0.860g / cm 3 Up to 0.900g / cm 3, 0.900g / cm 3 Up to 0.970g / cm 3 , 0.900g / cm 3 Up to 0.960g / cm 3 , 0.900g / cm 3 Up to 0.940g / cm 3 , 0.900g / cm 3 Up to 0.920g / cm 3 , 0.920g / cm 3 Up to 0.970g / cm 3 , 0.920g / cm 3 Up to 0.960g / cm 3 , 0.920g / cm 3 Up to 0.940g / cm 3 , 0.940g / cm 3 Up to 0.970g / cm 3 , 0.940g / cm 3 Up to 0.960g / cm 3 、0.960g / cm 3 Up to 0.970g / cm 3 or any combination of these ranges. In an embodiment, the carrier resin may have a melt index of 0.05 g / 10 min to 30 g / 10 min, 0.1 g / 10 min to 30 g / 10 min, 0.1 g / 10 min to 25 g / 10 min, 0.1 g / 10 min to 20 g / 10 min, 0.1 g / 10 min to 18 g / 10 min, 0.1 g / 15 min to 30 g / 10 min, 0.25 g / 10 min to 15 g / 10 min, 0.25 g / 10 min to 12 g / 10 min, 0.25 g / 10 min to 10 g / 10 min, 0.25 g / 10 min to 8 g / 10 min, 0.25 g / 10 min to 5 g / 10 min.

[0028] In an embodiment, the polyethylene formulation may include a polyethylene composition. As used herein, the presently disclosed polyethylene composition may be composed of ethylene and a comonomer such as C3-C 12 The polymerization of olefins forms. Contemplated comonomers include C6-C9 olefins, such as 1-octene and 1-hexene. In one or more embodiments, the comonomer is 1-octene.

[0029] In one or more embodiments, the polyethylene composition may have a density of 0.910 g / cm2 when measured according to ASTM D792. 3 Up to 0.936g / cm 3In an embodiment, the density of the presently disclosed polyethylene composition may be: 0.910 g / cm 3 Up to 0.930g / cm 3 、0.910g / cm 3 Up to 0.925g / cm 3 、0.910g / cm 3 Up to 0.920g / cm 3 、0.910g / cm 3 Up to 0.915g / cm 3 、0.915g / cm 3 Up to 0.936g / cm 3 、0.915g / cm 3 Up to 0.930g / cm 3 、0.915g / cm 3 Up to 0.925g / cm 3 、0.915g / cm 3 Up to 0.920g / cm 3 , 0.920g / cm 3 Up to 0.936g / cm 3 , 0.920g / cm 3 Up to 0.930g / cm 3 , 0.920g / cm 3 Up to 0.925g / cm 3 , 0.925g / cm 3 Up to 0.936g / cm 3 、0.925g / cm 3 Up to 0.930g / cm 3 , 0.930g / cm 3 Up to 0.936g / cm 3 or any combination of these ranges.

[0030] In one or more embodiments, the polyethylene composition may have a melt index (I2) of 0.25 g / 10 minutes (g / 10 min) to 2.0 g / 10 min when measured according to ASTM D-1238 at 190°C and 2.16 kg. In an embodiment, the polyethylene composition may have a melt index (I2) of 0.25 g / 10 min to 1.75 g / 10 min, 0.25 g / 10 min to 1.50 g / 10 min, 0.25 g / 10 min to 1.25 g / 10 min, 0.25 g / 10 min to 1.0 g / 10 min, 0.25 g / 10 min to 0.75 ... g / 10min to 0.50 g / 10min, 0.50 g / 10min to 2.0 g / 10min, 0.50 g / 10min to 1.75 g / 10min, 0.50 g / 10min to 1.50 g / 10min, 0.50 g / 10min to 1.25 g / 10min, 0.50 g / 10min to 1.0 g / 10min, 0.50 g / 10min to 0.75 g / 10min, 0.75 g / 10min to 2.0 g / 10min / 10min, 0.75g / 10min to 1.75g / 10min, 0.75g / 10min to 1.50g / 10min, 0.75g / 10min to 1.25g / 10min, 0.75g / 10min to 1.0g / 10min, 1.0g / 10min to 2.0g / 10min, 1.0g / 10min to 1.75g / 10min, 1.0g / 10min to 1.50g / 10min, 1. g / 10min, 1.50 g / 10min to 2.0 g / 10min, 1.50 g / 10min to 1.75 g / 10min, 1.75 g / 10min to 2.00 g / 10min, or any combination of these ranges.

[0031] In one or more embodiments, the polyethylene composition may include a melt index ratio (I 10 / I2)∶I 10 / I2≥7.0-1.2×log(I2). In an embodiment, the melt index ratio I of the polyethylene composition is 10 / I2 can be: 5.5 to 8.5, 5.5 to 8.0, 5.5 to 7.5, 5.5 to 7.0, 5.5 to 6.5, 5.5 to 6.0, 6.0 to 8.5, 6.0 to 8.0, 6.0 to 7.5, 6.0 to 7.0, 6.0 to 6.5, 6.5 to 8.5, 6.5 to 8.0, 6.5 to 7.5, 6.5 to 7.0, 7.0 to 8.5, 7.0 to 8.0, 7.0 to 7.5, 7.5 to 8.5, 7.5 to 8.0, or 7.5 to 8.0. In an embodiment, the I2 of the polyethylene composition is 10 / I2 can be between 7.7 and 8.1.

[0032] According to one or more embodiments, the polyethylene composition may have a zero shear viscosity ratio of 1.2 to 3.0. In embodiments, the polyethylene composition may have a zero shear viscosity ratio of 1.2 to 2.8, 1.2 to 2.6, 1.2 to 2.4, 1.2 to 2.2, 1.2 to 2.0, 1.2 to 1.8, 1.2 to 1.6, 1.2 to 1.4, 1.4 to 3.0, 1.4 to 2.8, 1.4 to 2.6, 1.4 to 2.4, 1.4 to 2.2, 1.4 to 2.0, 1.4 to 1.8, 1.4 to 1.6, 1.6 to 3.0, 1.6 to 2.8, 1.6 to 2.4, 1.6 to 2.6. from 2.2, 1.6 to 2.0, 1.6 to 1.8, 1.8 to 3.0, 1.8 to 2.8, 1.8 to 2.6, 1.8 to 2.4, 1.8 to 2.2, 1.8 to 2.0, 2.0 to 3.0, 2.0 to 2.8, 2.0 to 2.6, 2.0 to 2.4, 2.0 to 2.2, 2.2 to 3.0, 2.2 to 2.8, 2.2 to 2.6, 2.2 to 2.4, 2.4 to 3.0, 2.4 to 2.8, 2.4 to 2.6, 2.6 to 0.3, 2.6 to 2.8, or 2.8 to 3.0.

[0033] In embodiments, the polyethylene composition may have a z-average molecular weight (Mz) of 200,000 to 400,000 g / mol when measured by conventional GPC techniques as described herein. According to one or more embodiments, the polyethylene composition can have an Mz of 200,000 g / mol to 350,000 g / mol, 200,000 g / mol to 300,000 g / mol, 200,000 g / mol to 250,000 g / mol, 250,000 g / mol to 400,000 g / mol, 250,000 g / mol to 350,000 g / mol, 250,000 g / mol to 300,000 g / mol, 300,000 g / mol to 400,000 g / mol, 300,000 g / mol to 350,000 g / mol, or 350,000 g / mol to 400,000 g / mol, when measured by light scattering GPC techniques as described herein. Without being bound by theory, higher Mz may generally be associated with stronger mechanical properties; however, in embodiments of the present disclosure, the polyethylene composition may exhibit improved mechanical properties while having a z-average molecular weight (Mz) of 200,000 to 400,000 g / mol.

[0034] In an embodiment, the number average molecular weight (Mn) of the polyethylene composition can be in the range of 10,000 g / mol to 50,000 g / mol as determined by conventional GPC. For example, the number average molecular weight can be from a lower limit of 10,000 g / mol, 20,000 g / mol, or 25,000 g / mol to an upper limit of 35,000 g / mol, 40,000 g / mol, 45,000 g / mol, or 50,000 g / mol.

[0035] In one embodiment, the melt viscosity ratio Eta*0.1 / Eta*100 of the polyethylene composition may be in the range of 2.2 to 7.0. For example, the number average molecular weight may be from a lower limit of 2.2, 2.3, 2.4 or 2.5 to an upper limit of 6.0, 6.2, 6.5 or 7.0.

[0036] In an embodiment, the weight average molecular weight (Mw) of the polyethylene composition can be in the range of 70,000 g / mol to 200,000 g / mol as determined by conventional GPC. For example, the number average molecular weight can be from a lower limit of 70,000 g / mol, 75,000 g / mol, or 78,000 g / mol to an upper limit of 120,000 g / mol, 140,000 g / mol, 160,000 g / mol, 180,000 g / mol, or 200,000 g / mol.

[0037] According to an embodiment, as determined by conventional GPC, the molecular weight distribution of the polyethylene composition expressed as the ratio of weight average molecular weight to number average molecular weight (Mw / Mn) can be in the range of 2.0 to 5.0. In an embodiment, the molecular weight distribution of the polyethylene composition can be: 2.0 to 4.5, 2.0 to 4.0, 2.0 to 3.5, 2.0 to 3.0, 2.0 to 2.5, 2.5 to 5.0, 2.5 to 4.5, 2.5 to 4.0, 2.5 to 3.5, 2.5 to 3.0, 3.0 to 5.0, 3.0 to 4.5, 3.0 to 4.0, 3.0 to 3.5, 3.5 to 5.0, 3.5 to 4.5, 3.5 to 4.0, 4.0 to 5.0, 4.0 to 4.5, 4.5 to 5.0 or any combination of these ranges. As currently described, molecular weight distribution can be calculated according to gel permeation chromatography (GPC) technology as described herein.

[0038] In an embodiment, the polyethylene composition may have a ratio of z-average molecular weight to weight average molecular weight (Mz / Mw) of 1.5 to 3.5 when measured by conventional GPC techniques as described herein. According to one or more embodiments, the polyethylene composition may have a ratio of z-average molecular weight to weight average molecular weight (Mz / Mw) of 1.5 to 3.0, 1.5 to 2.5, 1.5 to 2.0, 1.5 to 1.8, 1.8 to 3.5, 1.8 to 3.0, 1.8 to 2.5, 1.8 to 2.0, 2.0 to 3.5, 2.0 to 3.0, 2.0 to 2.5, 2.5 to 3.5, 2.5 to 3.0, or 3.0 to 3.5 when measured by light scattering GPC techniques as described herein.

[0039] In an embodiment, the polyethylene composition comprises a molecular weighted comonomer distribution index (MWCDI) value from 0.9 to 10.0. According to one or more embodiments, the MWCDI value of the polyethylene composition can be from 0.9 to 9.0, 0.9 to 8.0, 0.9 to 7.0, 0.9 to 6.0, 0.9 to 5.0, 0.9 to 4.0, 0.9 to 3.0, 0.9 to 2.0, 0.9 to 1.0, 1.0 to 10.0, 1.0 to 9.0, 1.0 to 8.0, 1.0 to 7.0, 1.0 to 6.0, 1.0 to 5.0, 1.0 to 4.0, 1.0 to 3.0, 1.0 to 2.0, 2.0 to 10.0, 2.0 to 9.0, 2.0 to 8.0, 2.0 to 7.0, 2.0 to 6.0, 2.0 to 5.0, 2.0 to 4.0, 2.0 from 3.0 to 10.0, 3.0 to 9.0, 3.0 to 8.0, 3.0 to 7.0, 3.0 to 6.0, 3.0 to 5.0, 3.0 to 4.0, 4.0 to 10.0, 4.0 to 9.0, 4.0 to 8.0, 4.0 to 7.0, 4.0 to 6.0, 4.0 to 5.0, 5.0 to 10.0, 5.0 to 9.0, 5.0 to 8.0, 5.0 to 7.0, 5.0 to 6.0, 0.9 to 10.0, 0.9 to 9.0, 0.9 to 8.0, 0.9 to 7.0, 7.0 to 10.0, 7.0 to 9.0, 7.0 to 8.0, 8.0 to 10.0, 8.0 to 9.0, or 9.0 to 10.0. Without being bound by theory, the molecular weighted comonomer distribution index (MWCDI) value is related to the comonomer distribution which affects the strength of the polymer. A negative MWCDI value may reflect that the comonomer is not optimally distributed and therefore the copolymer may not exhibit adequate mechanical properties.

[0040] In one embodiment, the polyethylene composition has vinyl unsaturation greater than 10 vinyl groups per 1,000,000 total carbons, for example greater than 20 vinyl groups per 1,000,000 total carbons, or greater than 50 vinyl groups per 1,000,000 total carbons, or greater than 70 vinyl groups per 1,000,000 total carbons, or greater than 100 vinyl groups per 1,000,000 total carbons.

[0041] As described herein, a polyethylene "fraction" refers to a portion of the total composition of a multimodal polyethylene composition. The presently disclosed embodiments comprise at least a "first polyethylene fraction" and a "second polyethylene fraction". The various fractions contained in the polyethylene composition can be quantified by their temperature ranges in the elution curves obtained via an improved comonomer composition distribution (iCCD) analysis method. Unless otherwise stated, any elution curve referred to herein is an elution curve observed by iCCD. Embodiments of such fractions will be better understood in view of the examples provided herein. Typically, a first fraction may include a peak within the temperature range of the first fraction, and a second fraction may include a peak within the temperature range of the second fraction. The polyethylene compositions described herein may be referred to as "multimodal", meaning that they include at least two peaks in their elution curves.

[0042] Referring to the iCCD distribution described, Figure 1 A sample iCCD distribution 100 and a cumulative weight fraction curve 200 are schematically depicted. Figure 1 Several features of the iCCD curves of the presently described polyethylene compositions discussed in detail herein are generally depicted, such as the first fraction, the second fraction, the half peak width, etc. Thus, Figure 1 Can be used as a reference to the disclosure related to the iCCD curves provided herein. Specifically, a first fraction 102 and a second fraction 106 are depicted. The first fraction 102 has a peak 104 and the second fraction 106 has a peak 108. Each fraction has a half-peak width 110 and a half-peak width 112. It should be understood that Figure 1 The curves are not derived from experiments or observations but are provided for informational purposes to describe specific features of the iCCD elution curves.

[0043] In one or more embodiments, the polyethylene composition can have a first polyethylene fraction area in the temperature range of 45° C. to 87° C. of an elution curve obtained by an improved comonomer composition distribution (iCCD) analysis method. As used herein, the first polyethylene fraction area can be defined as the area under the single peak of the first polyethylene fraction between 45° C. and 87° C. in the elution curve. The first polyethylene area fraction can correspond to the total relative mass of the polymer fraction in the multimodal polyethylene composition.

[0044] In an embodiment, the first polyethylene fraction may have a single peak in the elution curve obtained by iCCD in the temperature range of 45°C to 87°C. As used herein, "single peak" refers to an iCCD in which a particular fraction includes only one peak. That is, in some embodiments, the iCCD of the first polyethylene fraction includes only an upward sloping region, followed by a downward sloping region to form a single peak. In one or more embodiments, the single peak of the first polyethylene fraction may be in the temperature range of 60°C to 80°C, such as 65°C to 75°C.

[0045] It should be understood that the peak in the first polyethylene fraction may not be formed by a local minimum in the corresponding polyethylene fraction under a defined temperature boundary. That is, the peak must be a peak within the entire spectral range, rather than a peak formed by a threshold temperature of the polyethylene fraction. For example, if there is a single peak in the polyethylene fraction, followed by a single valley (upward slope, then downward slope, then upward slope), there will only be a single peak in such a polyethylene fraction.

[0046] In one or more embodiments, the first polyethylene fraction area can account for at least 50% of the total area of ​​the elution curve (e.g., at least 52%, at least 54%, at least 56%, at least 58%, and at least 60% of the total area of ​​the elution curve). For example, the first polyethylene fraction area can account for 50% to 70% of the total area of ​​the elution curve, such as 50% to 65%, 50% to 60%, or 50% to 55% of the total area of ​​the elution curve. Without being bound by theory, the first polyethylene fraction area is related to the comonomer incorporation amount and therefore may affect the properties of the entire polyethylene composition. In embodiments, having a first polyethylene fraction area of ​​at least 50% of the total area of ​​the elution curve can allow the entire polyethylene composition to exhibit sufficient secant modulus properties, burst strength properties, or both.

[0047] In one or more embodiments, the polyethylene composition can have a second polyethylene fraction area in the temperature range of 95° C. to 120° C. of an elution curve obtained by an improved comonomer composition distribution (iCCD) analysis method. As used herein, the second polyethylene fraction area can be defined as the area below the third polyethylene fraction between 95° C. and 110° C. in the elution curve. The first polyethylene area fraction can correspond to the total relative mass of the polymer fraction in the polyethylene composition.

[0048] In one or more embodiments, the second polyethylene fraction may have a single peak in the temperature range of 95°C and 120°C in the elution curve obtained by iCCD. It should be understood that the peak in the second polyethylene fraction may not be formed by a local minimum in the corresponding polyethylene fraction under a defined temperature boundary. That is, the peak must be a peak within the entire spectral range, rather than a peak formed by the threshold temperature of the polyethylene fraction. For example, if there is a single peak in the polyethylene fraction, followed by a single valley (sloping upward, then tilted downward, then tilted upward), there will only be a single peak in such a polyethylene fraction. The temperature range of the second polyethylene fraction of 95°C to 120°C may be desirable because the low molecular weight, high density components at 95°C and 120°C can allow the polyethylene to achieve a higher overall density while maintaining a lower density fraction.

[0049] According to one or more embodiments, the second polyethylene fraction area can account for less than or equal to 23% of the total area of ​​the elution curve (e.g., less than 15% or less than 10% of the total area of ​​the elution curve). For example, the first polyethylene fraction area can account for 6% to 23%, 6% to 20%, 6% to 16%, 6% to 12%, 6% to 8%, 8% to 23%, 8% to 16%, 8% to 12%, 12% to 23%, 12% to 16% or 16% to 23% of the total area of ​​the elution curve.

[0050] According to some embodiments, the ratio of the area of ​​the first polyethylene fraction to the area of ​​the second polyethylene fraction can be 2.9 to 12.5, 2.9 to 12.0, 2.9 to 10.0, 2.9 to 8.0, 2.9 to 6.0, 2.9 to 4.0, 2.9 to 3.0, 3.0 to 12.5, 3.0 to 12.0, 3.0 to 10.0, 3.0 to 8.0, 3.0 to 6.0, 3.0 to 4.0, 4.0 to 12.5, 4.0 to 12.0, 4.0 to 10.0, 4.0 to 8.0, 4.0 to 6.0, 6.0 to 12.5, 6.0 to 12.0, 6.0 to 10.0, 6.0 to 8.0, 8.0 to 12.5, 8.0 to 12.0, 8.0 to 10.0, 10.0 to 12.5, 10.0 to 12.0, 12.0 to 12.5, or any combination of these ranges.

[0051] In embodiments, the polyethylene formulation may also include HDPE, LDPE, and combinations thereof.

[0052] In an embodiment, the polyethylene formulation may include LDPE. In one or more embodiments, the melt index of the LDPE may be 0.1 g / 10 min to 10.0 g / 10 min when measured according to ASTM D1238 at a load of 2.16 kg and a temperature of 190° C. In an embodiment, the melt index of the LDPE may be 0.1 g / 10 min to 5.0 g / 10 min or 0.5 g / 10 min to 5.0 g / 10 min or 0.5 g / 10 min to 2.0 g / 10 min. In an embodiment, the density of the LDPE may be 0.916 g / cm 3 Up to 0.935g / cm 3 In another embodiment, the density of the LDPE may be 0.916 g / cm 3 Up to 0.925g / cm 3 .

[0053] In one or more embodiments, the polyethylene formulation can include up to 20 wt% LDPE based on the total weight of the polyethylene formulation. In some embodiments, each skin layer can include 0 wt.% to 20 wt.%, 0 wt.% to 15 wt.%, 0 wt.% to 10 wt.%, 0 wt.% to 5 wt.%, 5 wt.% to 20 wt.%, 5 wt.% to 15 wt.%, 5 wt.% to 10 wt.%, 10 wt.% to 20 wt.%, 10 wt.% to 15 wt.%, or 15 wt.% to 20 wt.% LDPE based on the total weight of the polyethylene formulation.

[0054] In an embodiment, the polyethylene formulation may comprise a high density polyethylene (HDPE) having a density of 0.950 g / cm2 when measured according to ASTM D792. 3 Up to 0.980g / cm 3 In another embodiment, the density of the HDPE may be: 0.950 g / cm 3 Up to 0.980g / cm 3 、0.950g / cm 3 Up to 0.970g / cm 3 、0.950g / cm 3 Up to 0.960g / cm 3 、0.960g / cm 3 Up to 0.980g / cm 3 、0.960g / cm 3 Up to 0.970g / cm 3 or 0.970g / cm 3 Up to 0.980g / cm3 .

[0055] In one or more embodiments, the polyethylene formulation may include HDPE having a melt index (I2) of 0.1 grams per 10 minutes (g / 10 min) to 10.0 g / 10 min when measured according to ASTM D1238 at a load of 2.16 kg and a temperature of 190° C. It is also contemplated that the melt index (I2) of the high density polyethylene may be 0.1 g / 10 min to 5.0 g / 10 min, 0.1 g / 10 min to 1.0 g / 10 min, or 1.0 g / 10 min to 10.0 g / 10 min, 1.0 g / 10 min to 5.0 g / 10 min, or 5.0 g / 10 min to 10.0 g / 10 min.

[0056] Various methods are contemplated for producing high density polyethylene. For example, HDPE resins can be prepared using a Ziegler-Natta catalyst system, a chromium catalyst, or a single site catalyst (including but not limited to dual metallocene catalysts and constrained geometry catalysts).

[0057] In one or more embodiments, the polyethylene formulation can include up to 20 wt% HDPE based on the total weight of the polyethylene formulation. In some embodiments, each skin layer can include 0 wt.% to 20 wt.%, 0 wt.% to 15 wt.%, 0 wt.% to 10 wt.%, 0 wt.% to 5 wt.%, 5 wt.% to 20 wt.%, 5 wt.% to 15 wt.%, 5 wt.% to 10 wt.%, 10 wt.% to 20 wt.%, 10 wt.% to 15 wt.%, or 15 wt.% to 20 wt.% HDPE based on the total weight of the polyethylene formulation.

[0058] It should be understood that the polyethylene formulation may also include one or more additives known to those skilled in the art, such as plasticizers, stabilizers (including viscosity stabilizers, hydrolysis stabilizers), primary and secondary antioxidants, UV absorbers, antistatic agents, dyes, pigments or other colorants, inorganic fillers, flame retardants, lubricants, reinforcing agents (such as glass fibers and glass flakes), synthetic (e.g., aramid) fibers or pulp, foaming or foaming agents, processing aids, slip additives, anti-caking agents (such as silica or talc), release agents, tackifying resins, or a combination of two or more thereof. Inorganic fillers such as calcium carbonate may also be incorporated into the polyethylene formulation. In some embodiments, the polyethylene formulation may include up to 5% by weight of such additional additives based on the total weight of the polyethylene formulation. In an embodiment, the total amount of additives in the polyethylene formulation can be 0.5 wt.% to 5 wt.%, 0.5 wt.% to 4 wt.%, 0.5 wt.% to 3 wt.%, 0.5 wt.% to 2 wt.%, 0.5 wt.% to 1 wt.%, 1 wt.% to 5 wt.%, 1 wt.% to 4 wt.%, 1 wt.% to 3 wt.%, 1 wt.% to 2 wt.%, 2 wt.% to 5 wt.%, 2 wt.% to 4 wt.%, 2 wt.% to 3 wt.%, 3 wt.% to 5 wt.%, 3 wt.% to 4 wt.%, or 4 wt.% to 5 wt.%, based on the total weight of the polyethylene formulation. The incorporation of additives can be carried out by any known method, for example, by dry blending, by extruding a mixture of the various ingredients, by conventional masterbatch technology, etc.

[0059] Polymerization of polyethylene compositions

[0060] The polymerization method includes, but is not limited to, a solution polymerization method using one or more conventional reactors, such as loop reactors, isothermal reactors, adiabatic reactors, stirred tank reactors, autoclave reactors and / or any combination thereof in parallel or in series. The polyethylene composition can be produced, for example, by a solution phase polymerization method using one or more loop reactors, adiabatic reactors and combinations thereof.

[0061] Typically, the solution phase polymerization process occurs in one or more well-mixed reactors, such as one or more loop reactors and / or one or more adiabatic reactors, at a temperature in the range of 115°C to 250°C (e.g., 135°C to 200°C) and a pressure in the range of 300 psig to 1000 psig (e.g., 450 psig to 750 psig).

[0062] In one embodiment, the polyethylene composition can be produced in two loop reactors configured in series, wherein the first reactor temperature is in the range of 115°C to 200°C, such as 135°C to 165°C, and the second reactor temperature is in the range of 150°C to 210°C, such as 185°C to 200°C. In another embodiment, the polyethylene composition can be produced in a single reactor, and the reactor temperature is in the range of 115°C to 200°C, such as 130°C to 190°C. The residence time in the solution phase polymerization process is generally in the range of 2 minutes to 40 minutes, such as 5 minutes to 20 minutes. Ethylene, solvent, one or more catalyst systems, optionally one or more cocatalysts and optionally one or more comonomers are continuously fed to one or more reactors. Exemplary solvents include, but are not limited to, isoparaffins. For example, such solvents can be commercially available from ExxonMobil Chemical under the name ISOPAR E. The resulting mixture of the polyethylene composition and the solvent is then removed from the one or more reactors and the polyethylene composition is separated. The solvent is typically recovered via a solvent recovery unit (ie, heat exchangers and separator vessels) and then recirculated back into the polymerization system.

[0063] In one embodiment, the polyethylene composition can be produced by a solution polymerization process in a dual reactor system, such as a dual loop reactor system, wherein ethylene and optionally one or more alpha-olefins are polymerized in one reactor in the presence of one or more catalyst systems to produce a first ethylene-based polymer, and ethylene and optionally one or more alpha-olefins are polymerized in a second reactor in the presence of one or more catalyst systems to produce a second ethylene-based polymer. In addition, one or more cocatalysts may be present.

[0064] In another embodiment, the polyethylene composition can be produced by a solution polymerization process in a single reactor system, such as a single loop reactor system, wherein ethylene and optionally one or more alpha-olefins are polymerized in the presence of one or more catalyst systems. In addition, one or more cocatalysts may be present.

[0065] The method may include: polymerizing ethylene and optionally at least one comonomer in solution in the presence of a catalyst system comprising a metal-ligand complex of Structure I to form a first ethylene-based polymer; and polymerizing ethylene and optionally at least one comonomer in the presence of a catalyst system comprising a Ziegler / Natta catalyst to form a second ethylene-based polymer; and wherein Structure I is as follows:

[0066]

[0067] wherein: M is titanium, zirconium or hafnium, each independently in a formal oxidation state of +2, +3 or +4; and n is an integer from 0 to 3, and wherein when n is 0, X is absent; and each X is independently a neutral, monoanionic or dianionic monodentate ligand; or two Xs taken together form a neutral, monoanionic or dianionic bidentate ligand; and X and n are selected in such a way that the metal-ligand complex of formula (I) is neutral overall; and each Z is independently O, S, N (C1-C 40 ) alkyl or P(C1-C 40 ) alkyl; and wherein the ZLZ fragment comprises formula (1):

[0068]

[0069] R 1 To R 16 are each independently selected from the group consisting of: substituted or unsubstituted (C1-C 40 )alkyl, substituted or unsubstituted (C1-C 40 ) heteroalkyl, Si(R C )3、Ge(R C )3. P(R P )2、N(R N )-2, OR C , SR C 、NO2、CN、CF3、R C S(O)-、R C 5(O)2-、(R C )2C=N-、R C C(O)O-、R C OC(O)-、R C C(O)N(R)-、(R C )2NC(O)-, a halogen atom, a hydrogen atom; and wherein each R C are independently (C1-C30) hydrocarbon groups; RP is (C1-C30) hydrocarbon group; and R N is a (C1-C30) hydrocarbon group; and wherein optionally two or more R groups (R 1 To R 16 ) can be combined together into one or more ring structures, such ring structures each independently having 3 to 50 atoms in the ring excluding any hydrogen atoms.

[0070] In one embodiment, the method comprises: polymerizing ethylene and optionally at least one α-olefin in solution in the presence of a catalyst system comprising a metal-ligand complex of structure I to form a first ethylene-based polymer; and polymerizing ethylene and optionally at least one α-olefin in the presence of a catalyst system comprising a Ziegler / Natta catalyst to form a second ethylene-based polymer; in other embodiments, each α-olefin is independently a C1-C8 α-olefin.

[0071] In one embodiment, R 9 To R 13 or R 4 To R 8 Optionally two or more R groups may be combined together into one or more ring structures, wherein such ring structures each independently have from 3 to 50 atoms in the ring(s) excluding any hydrogen atoms.

[0072] In one embodiment, M is hafnium.

[0073] In one embodiment, R 3 and R 14 Each is independently an alkyl group, and further is a C1-C3 alkyl group, and further is a methyl group.

[0074] In one embodiment, R 1 and R 16 They are as follows:

[0075]

[0076] In one embodiment, aryl, heteroaryl, alkyl, heteroalkyl, Si(R C )3、Ge(R C )3. P(R P )2、N(R N )-2, OR C , SR C , R C S(O)-、R C S(O)2-、(R C )2C=N-、R C C(O)O-、R C OC(O)-、R C C(O)N(R)-、(R C Each of )2NC(O)-, alkylene and heteroalkylene is independently unsubstituted or substituted with one or more R 5 Substituents; and each R S are independently halogen atoms, polyfluorinated, perfluorinated, unsubstituted (C1-C 18)alkyl, F3C-, FCH2O-, F2HCO-, F3CO-, R3Si-, R3Ge-, RO-, RS-, RS(O)-, RS(O)2-, R2P-, R2N-, R2C=N-, NC-, RC(O)O-, ROC(O)-, RC(O)N(R)- or R2NC(O)-, or two R S Together they form an unsubstituted (C1-C 18 )alkylene, wherein each R is independently an unsubstituted (C1-C 18 )alkyl.

[0077] In one embodiment, R 1 To R 16 Two or more of them do not combine to form one or more ring structures.

[0078] In one embodiment, a catalyst system suitable for producing the first ethylene-based polymer is a catalyst system comprising bis((2-oxo-3-(dibenzo-1H-pyrrol-1-yl)-5-(methyl)phenyl)-2-phenoxymethyl)-methylene-1,2-cyclohexanediylhafnium(IV)dimethyl, represented by the following structure: IA:

[0079]

[0080] Ziegler / Natta catalysts suitable for use in the present invention are typical supported Ziegler-type catalysts that are particularly useful at the high polymerization temperatures of the solution process. Examples of such compositions are compositions derived from organomagnesium compounds, alkyl halides or aluminum halides or hydrogen chloride and transition metal compounds. Examples of such catalysts are described in U.S. Pat. Nos. 4,612,300; 4,314,912; and 4,547,475, the teachings of which are incorporated herein by reference.

[0081] Particularly suitable organomagnesium compounds include, for example, hydrocarbon-soluble dihydrocarbylmagnesiums, such as dialkylmagnesiums and diarylmagnesiums. Exemplary suitable dialkylmagnesiums specifically include n-butyl-sec-butylmagnesium, diisopropylmagnesium, di-n-hexylmagnesium, isopropyl-n-butylmagnesium, ethyl-n-hexylmagnesium, ethyl-n-butylmagnesium, di-n-octylmagnesium, etc., wherein the alkyl group has 1 to 20 carbon atoms. Exemplary suitable diarylmagnesiums include diphenylmagnesium, dibenzylmagnesium and ditolylmagnesium. Suitable organomagnesium compounds include alkoxides and phenolates of alkylmagnesiums and arylmagnesiums and halides of arylmagnesiums and alkylmagnesiums, more preferably halogen-free organomagnesium compounds.

[0082] Halide sources include active non-metallic halides, metal halides and hydrogen chloride. Suitable non-metallic halides are represented by the formula R'X, wherein R' is hydrogen or an active monovalent organic group, and X is a halogen. Particularly suitable non-metallic halides include, for example, hydrogen halides and active organic halides, such as tertiary alkyl halides, allyl halides, benzyl halides and other active hydrocarbon halides. By active organic halides is meant hydrocarbon halides containing unstable halogens, which are at least as active as the halogens of sec-butyl chloride, i.e., are easily lost to another compound, preferably as active as tert-butyl chloride. In addition to organic monohalides, it should be understood that organic dihalides, trihalides and other polyhalides having the activity defined above can also be suitably used. Examples of preferred active non-metal halides include hydrogen chloride, hydrogen bromide, tert-butyl chloride, tert-amyl bromide, allyl chloride, benzyl chloride, butenyl chloride, methylvinylcarbinylchloride, α-phenylethyl bromide, benzhydryl chloride, etc. Most preferred are hydrogen chloride, tert-butyl chloride, allyl chloride and benzyl chloride.

[0083] Suitable metal halides include those represented by the formula MRy-aXa, wherein: M is a metal of Group IIB, Group IIIA or Group IVA in Mendeleev's periodic Table of Elements; R is a monovalent organic group; X is a halogen; the value of y corresponds to the valence of M; and the value of "a" is 1 to y. Preferred metal halides are of the formula AlR 3-a X a Aluminum halides, wherein each R is independently a hydrocarbon group, such as an alkyl group; X is a halogen; and a is a number from 1 to 3. Most preferably, alkylaluminum halides are such as ethylaluminum sesquichloride, diethylaluminum chloride, ethylaluminum dichloride, and diethylaluminum bromide, with ethylaluminum dichloride being particularly preferred. Alternatively, a metal halide such as aluminum trichloride or a combination of aluminum trichloride and an alkylaluminum halide or a trialkylaluminum compound may be suitably employed.

[0084] Any of the conventional Ziegler-Natta transition metal compounds can be usefully used as the transition metal component in preparing the supported catalyst component. Typically, the transition metal component is a compound of a Group IVB, Group VB, or Group VIB metal. The transition metal component is typically represented by the formula: TrX′ 4-q (OR1)q、TrX′ 4-q (R2)q, VOX′3 and VO(OR)3.

[0085] Tr is a Group IVB, Group VB or Group VIB metal, preferably a Group IVB or Group VB metal, preferably titanium, vanadium or zirconium; q is 0 or a number equal to or less than 4; X′ is a halogen, and R1 is an alkyl group, an aryl group or a cycloalkyl group having 1 to 20 carbon atoms; and R2 is an alkyl group, an aryl group, an aralkyl group, a substituted aralkyl group, etc.

[0086] Aryl, aralkyl and substituted aralkyl contain 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. When the transition metal compound contains a hydrocarbyl R2, the hydrocarbyl is an alkyl, cycloalkyl, aryl or aralkyl group, and the hydrocarbyl group will preferably not contain an H atom in the position β to the metal carbon bond. Illustrative but non-limiting examples of aralkyl groups are methyl, neopentyl, 2,2-dimethylbutyl, 2,2-dimethylhexyl; aryl groups such as benzyl; cycloalkyl groups such as 1-norbornyl. If desired, mixtures of these transition metal compounds can be used.

[0087] Illustrative examples of transition metal compounds include TiCl4, TiBr4, Ti(OC2H5)3Cl, Ti(OC2H5)Cl3, Ti(OC4H9)3Cl, Ti(OC3H7)2Cl2, Ti(OC6H 13 )2Cl2、Ti(OC8H 17 )2Br2 and Ti(OC 12 H 25 )Cl3, Ti(O-iC3H7)4, and Ti(O-nC4H9)4. Illustrative examples of vanadium compounds include VCl4, VOCl3, VO(OC2H5)3, and VO(OC4H9)3. Illustrative examples of zirconium compounds include ZrCl4, ZrCl3(OC2H5), ZrCl2(OC2H5)2, ZrCl(OC2H5)3, Zr(OC2H5)4, ZrCl3(OC4H9), ZrCl2(OC4H9)2, and ZrCl(OC4H9)3.

[0088] Inorganic oxide supports can be used in the preparation of the catalyst, and the support can be any particulate oxide or mixed oxide that has been thermally or chemically dehydrated so that it is substantially free of adsorbed moisture. See U.S. Pat. Nos. 4,612,300; 4,314,912; and 4,547,475; the teachings of which are incorporated herein by reference.

[0089] Co-catalyst component

[0090] The catalyst system described above can be rendered catalytically active by contacting it with an activating cocatalyst, or by combining it with an activating cocatalyst, or by using an activation technique, such as an activation technique known in the art for metal-based olefin polymerization reactions. Activating cocatalysts suitable for use herein include alkylaluminums; polymeric or oligomeric aluminoxanes (also known as aluminoxanes); neutral Lewis acids; and non-polymeric, non-coordinating, ion-forming compounds (including the use of such compounds under oxidizing conditions). A suitable activation technique is bulk electrolysis. Combinations of one or more of the foregoing activating cocatalysts and techniques are also contemplated. The term "alkylaluminum" means a monoalkylaluminum dihydride or monoalkylaluminum dihalide, a dialkylaluminum hydride or dialkylaluminum halide, or a trialkylaluminum. Aluminoxanes and their preparation are known, for example, in U.S. Pat. No. 6,103,657. Examples of preferred polymeric or oligomeric aluminoxanes are methylaluminoxane, triisobutylaluminum-modified methylaluminoxane, and isobutylaluminoxane.

[0091] Exemplary Lewis acid activating cocatalysts are Group 13 metal compounds containing 1 to 3 hydrocarbyl substituents as described herein. In some embodiments, exemplary Group 13 metal compounds are tri(hydrocarbyl)substituted aluminum compounds or tri(hydrocarbyl)-boron compounds. In some other embodiments, exemplary Group 13 metal compounds are tri(hydrocarbyl)substituted aluminum, or tri(hydrocarbyl)-boron compounds are tri((C1-C 10 )alkyl)aluminum or tri((C6-C 18 In some other embodiments, the exemplary Group 13 metal compound is tri(fluoro-substituted phenyl)borane, and in other embodiments, tri(pentafluorophenyl)borane. In some embodiments, the activating cocatalyst is tri((C1-C 20 )alkyl) borate (e.g., trityl tetrafluoroborate) or tris((C1-C 20 )alkyl)ammonium tetra((C1-C 20 )alkyl)borane (e.g., bis(octadecyl)methylammoniumtetra(pentafluorophenyl)borane). As used herein, the term "ammonium" refers to a nitrogen cation that is ((C1-C 20 )alkyl)4N + 、((C1-C 20 )alkyl)3N(H) + 、((C1-C 20 )alkyl)2N(H)2 + 、(C1-C 20 )Hydrocarbon N(H)3 + or N(H)4 + , where (C1-C 20 ) The hydrocarbon groups may be the same or different.

[0092] Exemplary combinations of neutral Lewis acid activating cocatalysts include those comprising tri((C1-C4)alkyl)aluminum and tri((C6-C 18 )aryl)boron compounds, especially tris(pentafluorophenyl)borane. Other exemplary embodiments are combinations of such neutral Lewis acid mixtures with polymeric or oligomeric aluminoxanes, and single neutral Lewis acids, especially tris(pentafluorophenyl)borane with polymeric or oligomeric aluminoxanes. Exemplary embodiments of the molar ratio of (metal-ligand complex):(tris(pentafluorophenylborane):(aluminoxane) [e.g., (Group 4 metal-ligand complex):(tris(pentafluorophenylborane):(aluminoxane)] are 1:1:1 to 1:10:30, and other exemplary embodiments are 1:1:1.5 to 1:5:10.

[0093] A number of activating cocatalysts and activation techniques have been previously taught for different metal-ligand complexes in the following U.S. patents: U.S. 5,064,802; U.S. 5,153,157; ​​U.S. 5,296,433; U.S. 5,321,106; U.S. 5,350,723; U.S. 5,425,872; U.S. 5,625,087; U.S. 5,721,185; U.S. 5,783,512; U.S. 5,883,204; U.S. 5,919,983; U.S. 6,696,379; and U.S. 7,163,907. Examples of suitable hydrocarbyl oxides are disclosed in U.S. 5,296,433. Examples of Bronsted acid salts suitable for use as addition polymerization catalysts are disclosed in US 5,064,802, US 5,919,983, US 5,783,512. Examples of suitable salts of cationic oxidants and non-coordinating compatible anions as activating cocatalysts for addition polymerization catalysts are disclosed in US 5,321,106. Examples of carbon ion salts suitable for use as activating cocatalysts for addition polymerization catalysts are disclosed in US 5,350,723. Examples of silyl salts suitable for use as activating cocatalysts for addition polymerization catalysts are disclosed in US 5,625,087. Examples of suitable complexes of alcohols, thiols, silanols and oximes with tris(pentafluorophenyl)borane are disclosed in US 5,296,433. Some of these catalysts are also described in a portion of US 6,515,155 Bl starting at column 50, line 39 through column 56, line 55, only the portion described therein being incorporated herein by reference.

[0094] In embodiments, the catalyst system described above can be activated by combining with one or more cocatalysts, such as a cation forming cocatalyst, a strong Lewis acid, or a combination thereof to form an active catalyst composition. Suitable cocatalysts include polymeric or oligomeric aluminoxanes, particularly methylaluminoxane, and inert compatible non-coordinating ion forming compounds. Exemplary suitable cocatalysts include, but are not limited to, modified methylaluminoxane (MMAO), bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate (1-)amine, triethylaluminum (TEA), and any combination thereof.

[0095] In some embodiments, one or more of the aforementioned activating cocatalysts are used in combination with one another. In one embodiment, a combination of a mixture of tri((C1-C4)hydrocarbyl)aluminum, tri((C1-C4)hydrocarbyl)borane or ammonium borate and an oligomeric or polymeric aluminoxane compound may be used.

[0096] Products

[0097] Embodiments of the present disclosure also relate to articles formed by the polyethylene formulations of the present disclosure, such as irrigation pipes. Such articles can be formed by any polyethylene formulation of the present disclosure described herein. The irrigation pipe can include perforations on the wall of the pipe to allow water (or other liquids) to be discharged through the perforations and flow through the pipe. The irrigation pipe can include one or more pipes, the one or more pipes including an internal (or "supply") pipe and an external (or "discharge") pipe, each of which can include perforations. The irrigation pipe of the present disclosure may be particularly useful in applications requiring a balance of stiffness and burst strength properties. Examples of such irrigation pipes may include drip irrigation tapes and pipes. Such plastic irrigation pipes have significant benefits, especially in arid climates. The lightweight nature of the pipe can allow the pipe to be easily buried in the soil at a convenient depth by hand or advantageously by using a concealed pipe plastic hole plow, a line laying plow or similar equipment.

[0098] Irrigation pipes may be formed from films comprising the polyethylene formulations described herein, wherein two films are perforated, aligned in a face-to-face relationship, folded, and heat sealed to form a seal at the edges where the two films meet.

[0099] In use, by maintaining a water pressure through the irrigation pipe (i.e., of the order of several pounds per square inch), a continuous supply of moisture can be fed into the soil. Thus, the irrigation pipe can provide an efficient irrigation system that can be relatively inexpensive to install. In some embodiments, the irrigation pipe can be installed in such a way that its height remains reasonably constant, otherwise the flow rate in the lower portion will be greater than the flow rate in the higher portion.

[0100] Conventional polyolefin compositions suitable for drip irrigation applications may include blends of linear low density polyethylene (LLDPE) with medium density polyethylene (MDPE), high density polyethylene (HDPE), low density polyethylene (LDPE), or combinations thereof. However, in embodiments of the present disclosure, providing a polyethylene formulation comprising MDPE, the polyethylene composition described herein, and the masterbatch composition can provide a desired combination of burst strength without compromising stiffness, even with a 15% reduction in thickness. Thus, embodiments of the present disclosure can provide a polyethylene formulation that provides an improved balance of stiffness and burst strength properties when used in irrigation pipes while allowing for reduced material costs.

[0101] The irrigation pipes of the present disclosure may have a variety of thicknesses. The thickness of the irrigation pipe may depend on many factors, including, for example, the composition of the polyethylene formulation, the desired properties of the irrigation pipe, the desired end use application of the irrigation pipe, the manufacturing process of the irrigation pipe, etc. In an embodiment, the thickness of the irrigation pipe may be: 5 mils to 50 mils, 5 mils to 40 mils, 5 mils to 30 mils, 5 mils to 20 mils, 5 mils to 10 mils, 10 mils to 50 mils, 10 mils to 40 mils, 10 mils to 30 mils, 10 mils to 20 mils, 20 mils to 50 mils, 20 mils to 40 mils, 20 mils to 30 mils, 30 mils to 50 mils, 30 mils to 40 mils, or 40 mils to 50 mils.

[0102] In an embodiment, the article may be a drip tape having a thickness of 16 mils to 18 mils and a burst strength greater than 6.5 bar when measured according to NBR ISO 9261. According to one or more embodiments, the article may be a drip tape having a thickness of 16 mils to 18 mils and a burst strength greater than or equal to 6.5 bar, greater than or equal to 7.0 bar, or greater than or equal to 7.5 bar when measured according to NBR ISO 9261. According to one or more embodiments, the article can be a drip tape having a thickness of 16 mils to 18 mils and a burst strength of 6.5 bar to 9.0 bar, 6.5 bar to 8.5 bar, 6.5 bar to 8.0 bar, 6.5 bar to 7.5 bar, 6.5 bar to 7.0 bar, 7.0 bar to 9.0 bar, 7.0 bar to 8.5 bar, 7.0 bar to 8.0 bar, 7.0 bar to 7.5 bar, 7.5 bar to 9.0 bar, 7.5 bar to 8.5 bar, 7.5 bar to 8.0 bar, 8.0 bar to 9.0 bar, 8.0 bar to 8.5 bar, or 8.5 bar to 9.0 bar when measured according to NBR ISO 9261.

[0103] In an embodiment, the article may be a drip tape having a thickness of 16 mils to 18 mils and a 2% secant modulus in the longitudinal direction greater than 150 MPa when measured according to ASTM D882. According to one or more embodiments, the article may be a drip tape having a thickness of 16 mils to 18 mils and a 2% secant modulus in the longitudinal direction greater than 150 MPa, greater than or equal to 155 MPa, greater than or equal to 160 MPa, or greater than or equal to 165 MPa when measured according to ASTM D882. According to one or more embodiments, the article may be a drip tape having a thickness of 16 mils to 18 mils and a 2% secant modulus in the longitudinal direction greater than 150 MPa, 150 MPa to 170 MPa, 150 MPa to 160 MPa, 160 MPa to 180 MPa, 160 MPa to 170 MPa, or 170 MPa to 180 MPa when measured according to ASTM D882.

[0104] In an embodiment, the article can be a drip tape having a thickness of 16 mils to 18 mils and a yield stress of at least 6.8 MPa when measured according to ASTM D882. According to one or more embodiments, the article can be a drip tape having a thickness of 16 mils to 18 mils and a yield stress greater than or equal to 6.8 MPa, greater than or equal to 7.0 MPa, or greater than or equal to 7.5 MPa when measured according to ASTM D882. According to one or more embodiments, the article can be a drip tape having a thickness of 16 mils to 18 mils and a yield stress of 6.8 MPa to 10.0 MPa, 6.8 MPa to 9.0 MPa, 6.8 MPa to 8.0 MPa, 6.8 MPa to 7.0 MPa, 7.0 MPa to 10.0 MPa, 7.0 MPa to 9.0 MPa, 7.0 MPa to 8.0 MPa, 8.0 MPa to 10.0 MPa, 8.0 MPa to 9.0 MPa, or 9.0 MPa to 10.0 MPa when measured according to ASTM D882.

[0105] In an embodiment, the article can be a drip tape having a thickness of 16 mils to 18 mils and a stress at break of at least 10.5 MPa when measured according to ASTM D882. According to one or more embodiments, the article can be a drip tape having a thickness of 16 mils to 18 mils and a stress at break greater than or equal to 10.5 MPa, greater than or equal to 11.0 MPa, greater than or equal to 11.5 MPa, or greater than or equal to 12.0 MPa when measured according to ASTM D882.

[0106] According to one or more embodiments, the article may be a drip tape having a thickness of 16 mils to 18 mils and a stress at break of 10.5 MPa to 14.0 MPa, 10.5 MPa to 13.5 MPa, 10.5 MPa to 13.0 MPa, 10.5 MPa to 12.5 MPa, 10.5 MPa to 12.0 MPa, 10.5 MPa to 11.5 MPa, 10.5 MPa to 11.0 MPa, 11.0 MPa to 14.0 MPa, 11.0 MPa to 13.5 MPa, 11.0 MPa to 13.0 MPa, 11.0 MPa to 12.5 MPa, 11.0 MPa to 12 ...5 MPa 0MPa to 11.5MPa, 11.5MPa to 14.0MPa, 11.5MPa to 13.5MPa, 11.5MPa to 13.0MPa, 11.5MPa to 12.5MPa, 11.5MPa to 12.0MPa, 12.0MPa to 14.0MPa, 12.0MPa to 13.5MPa, 12.0MPa to 13.0MPa, 12.0MPa to 12.5MPa, 12.5MPa to 14.0MPa, 12.5MPa to 13.5MPa, 12.5MPa to 13.0MPa, 13.0MPa to 14.0MPa, 13.0MPa to 13.5MPa, 13.5MPa to 14.0MPa.

[0107] Various methods of producing embodiments of articles such as irrigation pipes from the polyethylene formulations disclosed herein are familiar to those of ordinary skill in the art. Various methods are contemplated for producing embodiments of irrigation pipes. In one or more embodiments, the method of making the irrigation pipe may include cast film extrusion or blown film extrusion.

[0108] Test Method

[0109] The test methods include the following:

[0110] Melt Index

[0111] The melt index I2 (or I2) and I 10 (or I10) is measured according to ASTM D-1238 at 190°C and under 2.16kg and 10kg loads, respectively. Their values ​​are reported in g / 10min. The fraction of a polymer sample is measured by collecting the product polymer from a reactor that produces a specific fraction or portion of a polymer composition. For example, a first polyethylene fraction can be collected from a reactor to produce a lower density, higher molecular weight component of a polymer composition. Prior to melt index measurement, the polymer solution is dried under vacuum.

[0112] density

[0113] Samples for density measurement were prepared according to ASTM D4703. Measurements were made according to ASTM D792, Method B within one hour of pressing the sample.

[0114] Creep Zero Shear Viscosity Measurement Method

[0115] Zero shear viscosity was obtained by creep testing, which was performed at 190°C on an AR-G2 stress-controlled rheometer (TAInstruments; New Castle, Del) using 25 mm diameter parallel plates. The rheometer oven was set to the test temperature for at least 30 minutes before the fixture was zeroed. The compression-molded sample disk was inserted between the plates at the test temperature and allowed to equilibrate for 5 minutes. The upper plate was then lowered to 50 μm above the desired test gap (1.5 mm). Any excess material was trimmed off and the upper plate was lowered to the desired gap. The measurements were performed under a nitrogen purge at a flow rate of 5 L / min. The default creep time was set to 2 hours.

[0116] A constant low shear stress of 20 Pa was applied to all samples to ensure that the steady-state shear rate was low enough to be in the Newtonian region. For the samples in this study, the steady-state shear rate was 10 -3 Up to 10 -4 s -1 The steady state is determined by performing a linear regression of all data points in the last 10% time window of a plot of log(J(t)) versus log(t), where J(t) is the creep compliance and t is the creep time. If the slope of the linear regression is greater than 0.97, steady state is considered to be reached and the creep test is stopped. In all cases in this study, the slope met the criterion within 2 hours. The steady-state shear rate is determined by the slope of the linear regression of all data points in the last 10% time window of a plot of ε versus t, where ε is the strain. The zero shear viscosity is determined by the ratio of the applied stress to the steady-state shear rate.

[0117] To determine if a sample has degraded during creep testing, a small amplitude oscillatory shear test from 0.1 to 100 rad / sec is performed on the same sample before and after creep testing. The complex viscosity values ​​from the two tests are compared. If the difference in viscosity values ​​is greater than 5% at 0.1 rad / sec, the sample is considered to have degraded during creep testing and the result is discarded.

[0118] Gel Permeation Chromatography (GPC)

[0119] The chromatographic system consists of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infrared detector (IR5). The autosampler oven chamber is set to 160 degrees Celsius, and the column chamber is set to 150 degrees Celsius. The columns used are 4 Agilent "Mixed A" 30cm 20 micron linear mixed bed columns and 20um pre-columns. The chromatographic solvent used is 1,2,4 trichlorobenzene and contains 200ppm of butylated hydroxytoluene (BHT). The solvent source is nitrogen sparged. The injection volume used is 200 microliters, and the flow rate is 1.0 ml / min.

[0120] The GPC column set was calibrated with 21 narrow molecular weight distribution polystyrene standards ranging from 580 to 8,400,000 molecular weights and arranged in 6 "cocktail" mixtures with at least ten times intervals between individual molecular weights. Standards were purchased from Agilent Technologies. For molecular weights equal to or greater than 1,000,000, 0.025 grams of polystyrene standards were prepared in 50 milliliters of solvent, and for molecular weights less than 1,000,000, 0.05 grams of polystyrene standards were prepared in 50 milliliters of solvent. The polystyrene standards were dissolved at 80 degrees Celsius and gently stirred for 30 minutes. The polystyrene standard peak molecular weight was converted to polyethylene molecular weight using equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., Vol. 6, p. 621 (1968)):

[0121] M 聚乙烯 =A×(M 聚苯乙烯 ) B (EQ1)

[0122] Where M is the molecular weight, A has a value of 0.4315, and B equals 1.0.

[0123] A fifth order polynomial was used to fit the calibration points to the corresponding polyethylene equivalents.A small adjustment (approximately 0.375 to 0.445) was made to A to correct for column resolution and band broadening effects such that a linear homopolymer polyethylene standard was obtained at 120,000 Mw.

[0124] Plate counts for the GPC column set were performed using decane (prepared as 0.04 g in 50 mL TCB and dissolved for 20 minutes under slow stirring). Plate counts (Equation 2) and symmetry (Equation 3) were measured at 200 μL injection according to the following equations:

[0125]

[0126] where RV is the retention volume in milliliters, peak width is in milliliters, peak maximum is the maximum height of the peak, and 1 / 2 height is 1 / 2 the height of the peak maximum.

[0127]

[0128] Where RV is the retention volume in milliliters, and peak width is in milliliters, peak maximum is the maximum position of the peak, tenth height is 1 / 10 of the height of the peak maximum, and where post-peak refers to the tail of the peak with a retention volume later than the peak maximum, and where pre-peak refers to the front of the peak with a retention volume earlier than the peak maximum. The plate count of the chromatographic system should be greater than 18,000, and the symmetry should be between 0.98 and 1.22.

[0129] The samples were prepared semi-automatically using the PolymerChar "Instrument Control" software, where the target weight of the sample was set to 2 mg / ml and the solvent (containing 200 ppm BHT) was added to a septum-capped vial previously sparged with nitrogen by the PolymerChar high temperature autosampler. The samples were dissolved at 160 degrees Celsius for 2 hours under "slow" shaking.

[0130] Based on the GPC results, using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR spectrometer, according to equations 4-6, the PolymerChar GPCOne TM The software was used to calculate the Mn value of the baseline-subtracted IR chromatogram at each equidistant data collection point (i) and the polyethylene equivalent molecular weight obtained from the narrow standard calibration curve at point (i) according to Equation 1. (GPC) 、Mw (GPC) and Mz (GPC) Calculation.

[0131]

[0132]

[0133]

[0134] To monitor deviations over time, a flow rate marker (decane) was introduced into each sample via a micropump controlled by the PolymerChar GPC-IR system. This flow rate marker (FM) was used to linearly correct the pump flow rate (flow rate (nominal)) for each sample by comparing the RV of the corresponding decane peak in the sample (RV (FM sample)) with the RV of the alkane peak in the narrow standard calibration (RV (calibrated by FM)). It was then assumed that any changes in the decane marker peak time were related to linear changes in the flow rate (flow rate (effective)) throughout the run. In order to facilitate the highest accuracy measured for the RV of the flow marker peak, a least squares fitting procedure was used to fit the peak of the flow marker concentration chromatogram to a quadratic equation. The first derivative of the quadratic equation was then used to solve for the true peak position. After calibrating the system based on the flow marker peak, the effective flow rate (relative to the narrow standard calibration) was calculated as Equation 7. By PolymerCharGPCOne TM The software completes the processing of the flow marker peaks. An acceptable flow rate correction is such that the effective flow rate should be within + / - 0.5% of the nominal flow rate.

[0135] Flow rate (effective) = flow rate (nominal) * (RV (FM calibrated) / RV (FM sample)) (EQ 7)

[0136] Improved comonomer content analysis method (iCCD)

[0137] An improved method for comonomer content analysis (iCCD) was developed in 2015 (Cong and Parrott et al., WO2017040127A1). The iCCD test was performed with a Crystallization Elution Fractionator (CEF) (PolymerChar, Spain) equipped with an IR-5 detector (PolymerChar, Spain) and a two-angle light scattering detector model 2040 (Precision Detectors, now Agilent Technologies). A 5 cm or 10 cm (length) X 1 / 4" (ID) stainless steel guard column filled with 20-27 micron glass (MoSCi Corporation, USA) was installed just before the IR-5 detector in the detector oven. Ortho-dichlorobenzene (US ODCB, 99% anhydrous or technical grade) was used. From the EMD Chemicals obtained silica gel 40 (particle size 0.2-0.5 mm, catalog number 10181-3) (previously used to dry ODCB solvent). The CEF instrument was equipped with an autosampler with N2 sweep function. ODCB was bubbled with dry nitrogen (N2) for one hour before use. Sample preparation was performed with an autosampler at a concentration of 4 mg / ml (unless otherwise specified) at 160°C, under shaking, for 1 hour. The injection volume was 300 μl. The temperature profile of the iCCD was: crystallization from 105°C to 30°C at 3°C / min, thermal equilibrium at 30°C for 2 minutes (including the elution time of the soluble fraction set to 2 minutes), and elution from 30°C to 140°C at 3°C / min. The flow rate during crystallization was 0.0 ml / min. The flow rate during elution was 0.50 ml / min. Data were collected at a rate of one data point per second.

[0138] The iCCD column was filled with gold-plated nickel particles (Bright7GNM8-NiS, Nippon Chemical Industrial Co.) in a stainless steel tube of 15 cm (length) X 1 / 4" (ID). The column was filled and conditioned using a slurry method according to references (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. WO2017040127A1). The final pressure of the TCB slurry filling was 150 bar.

[0139] The column temperature calibration was performed by using a reference material linear homopolymer polyethylene (with zero comonomer content, melt index (I2) of 1.0, polydispersity Mw / Mn of approximately 2.6 by conventional gel permeation chromatography, 1.0 mg / ml) and a mixture of ODCB containing eicosane (2 mg / ml). The iCCD temperature calibration consisted of four steps: (1) calculation of the delay volume, which was defined as the temperature offset between the measured peak elution temperature of eicosane minus 30.00°C; (2) subtraction of the temperature offset of the elution temperature from the iCCD raw temperature data. It should be noted that this temperature bias is a function of experimental conditions, such as elution temperature, elution flow rate, etc.; (3) Create a linear calibration line to convert the elution temperature in the range of 30.00°C to 140.00°C, so that the linear homopolymer polyethylene reference has a peak temperature at 101.0°C and eicosane has a peak temperature at 30.0°C; (4) For the soluble fraction measured isothermally at 30°C, according to reference (Cerk and Cong et al., US9,688,795), the elution temperature below 30.0°C is linearly extrapolated by using an elution heating rate of 3°C / min.

[0140] The relationship between comonomer content and elution temperature of iCCD was constructed by using 12 reference materials (ethylene homopolymers and ethylene-octene random copolymers made with single-site metallocene catalysts with ethylene equivalent weight average molecular weights ranging from 35,000 to 128,000). All of these reference materials were analyzed in the same manner as the previously specified 4 mg / mL. The reported elution peak temperatures were linearly fitted to the linear equation y = -6.3515x. + 101.00, where y represents the elution temperature of iCCD, and x represents the octene mole %, and R 2 It is 0.978.

[0141] The molecular weight of the polymer and the molecular weight of the polymer fractions were determined directly from the LS detector (90 degree angle) and the concentration detector (IR-5) by assuming a shape factor of 1 and all virial coefficients equal to zero according to the Rayleigh-Gans-Debys approximation (Striegel and Yau, Modern Size Exclusion Liquid Chromatogram, pp. 242 and 263). The integration window was set to integrate the entire chromatogram over the elution temperature range (temperature calibration specified above) from 23.0°C to 120°C.

[0142] Calculation of molecular weight (Mw) from iCCD involves the following four steps:

[0143] (1) Measure the bias between detectors. The bias is defined as the geometric volume bias between the LS detector and the concentration detector. It is calculated as the difference in elution volume (mL) of the polymer peak between the concentration detector and the LS chromatogram. This is converted to a temperature bias using the elution heat rate and the elution flow rate. The polydispersity M of a linear high density polyethylene (0 comonomer content, melt index (I2) of 1.0, and a conventional gel permeation chromatography method) is used. w / M n The same experimental conditions as the normal iCCD method described above were used, except for the following parameters: crystallization from 140°C to 137°C at 10°C / min, 1 minute of thermal equilibrium at 137°C as the soluble fraction elution time, soluble fraction (SF) time of 7 minutes, elution from 137°C to 142°C at 3°C / min. The flow rate during crystallization was 0.0 ml / min. The flow rate during elution was 0.80 ml / min. The sample concentration was 1.0 mg / ml.

[0144] (2) Prior to integration, each LS data point in the LS chromatogram was shifted to correct for inter-detector bias.

[0145] (3) Integrate the baseline-subtracted LS and concentration chromatograms over the entire elution temperature range of step (1). The MW detector constant is calculated by using known MW HDPE samples in the range of 100,000 to 140,000 Mw and the area ratio of the LS and concentration integrated signals.

[0146] (4) The Mw of the polymer is calculated by using the ratio of the integrated light scattering detector (90 degree angle) to the concentration detector and using the MW detector constant.

[0147] The calculation of the half-peak width is defined as the temperature difference between the front temperature and the back temperature at half the maximum peak height, searching from 35.0°C forward for the front temperature at half the maximum peak and from 119.0°C backward for the back temperature at half the maximum peak.

[0148] Zero Shear Viscosity Ratio (ZSVR)

[0149] ZSVR is defined as the ratio of the zero shear viscosity (ZSV) of a branched polyethylene material to the ZSV of a linear polyethylene material at equivalent weight average molecular weight (Mw-gpc) according to the following equations (EQ) 8 and 9:

[0150]

[0151]

[0152] The ZSV value is obtained by creep testing at 190°C by the method described above. The Mw-gpc value is determined by the conventional GPC method (Equation 5 in the conventional GPC method). Based on a series of linear polyethylene reference materials, a correlation between the ZSV of linear polyethylene and its Mw-gpc is established. A description of the ZSV-Mw relationship can be found in the following literature, ANTEC Conference: Karjala, Teresa P., Sammler, Robert L., Mangnus, Marc A., Hazlitt, Lonnie G., Johnson, Mark S., Hagen, Charles M.Jr., Huang, Joe WL, Reichek, Kenneth N., "Detection of low levels of long-chain branching in polyolefins", Annual Technical Conference-Society of Plastics Engineers (2008), No. 66, pp. 887-891.

[0153] Dynamic rheological analysis

[0154] In order to characterize the rheological behavior of essentially linear ethylene polymers, S Lai and GW Knight introduced (ANTEC'93 Proceedings, Insite(TM) Technology Polyolefins (ITP) - New Rules in the Structure / Rheology Relations of Ethylene & -Olefin Copolymers, New Orleans, La., May 1993) a new rheological measurement, the Dow Rheological Index (DRI), which represents the "normalized relaxation time as a result of long chain branching" of a polymer. S. Lai et al.; (ANTEC'94, Dow Rheology Index (DRI) for Insite(TM) Technology Polyolefins (ITP): Unique structure-Processing Relationships, pp. 1814-1815) defines DRI as the degree to which the rheology of ethylene-octene copolymers incorporating long chain branches into the polymer backbone, known as ITP (Dow Insite Technology Polyolefins), deviates from conventional linear homogeneous polyethylenes reported to have no long chain branches (LCBs) by the following normalized equation:

[0155] DRI=[3650000×(τ0 / η0)-1] / 10 (EQ 10)

[0156] Where τ0 is the characteristic relaxation time of the material and is the zero shear rate complex viscosity of the material. The DRI is calculated by least squares fitting the rheological curve described in U.S. Pat. No. 6,114,486 (dynamic complex viscosity η*(ω) versus applied frequency (ω), e.g., 0.01-100 rad / sec) using the following generalized crossover equation:

[0157] η*(ω)=η0 / [1+(ω·τ0) n ] (EQ 11)

[0158] where n is the power law index of the material, η*(ω) and ω are the measured complex viscosity and applied frequency data, respectively.

[0159] Dynamic rheology measurements are performed in dynamic mode on a dynamic rheometer (e.g., ARES rheometer from TA Instruments) with 25 mm diameter parallel plates under an inert atmosphere according to ASTM D4440. For all experiments, the rheometer is thermally stabilized at 190°C for at least 30 minutes, and then a properly stabilized (using antioxidant additives) compression molded sample is inserted onto the parallel plates. The plate is then closed with a positive normal force recorded on the instrument to ensure good contact. After approximately 5 minutes at 190°C, the plate is gently compressed and excess polymer is trimmed from the periphery of the plate. Thermal stability is allowed to remain for another 10 minutes and the normal force is reduced back to zero. That is, all measurements are performed after the sample has been equilibrated at 190°C for approximately 15 minutes and are run under complete nitrogen protection.

[0160] Two strain sweep (SS) experiments were initially performed at 190°C to determine the linear viscoelastic strain that would produce a torque signal greater than 10% of the lower scale of the sensor over the full frequency range (e.g., 0.01 rad / sec to 100 rad / sec). The first SS experiment was performed at a low applied frequency of 0.1 rad / sec. This test was used to determine the sensitivity of torque at low frequencies. The second SS experiment was performed at a high applied frequency of 100 rad / sec. This ensured that the selected applied strain was completely within the linear viscoelastic region of the polymer so that the oscillatory rheological measurements would not cause structural changes in the polymer during the test. In addition, a time sweep (TS) experiment was performed at a low applied frequency of 0.1 rad / sec at the selected strain (determined by the SS experiment) to check the stability of the sample during the test.

[0161] The values ​​of storage (or elastic) modulus, loss (or viscous) modulus (G"), complex modulus (G*), complex viscosity (η*), and tan δ (the ratio of loss modulus to storage modulus, G'VG') are obtained as functions of frequency (ω) at a given temperature (e.g., 190°C).

[0162] ASTM D882 MD and CD, 1% and 2% secant modulus

[0163] Film MD (machine direction) and CD (cross direction) secant modulus were determined according to ASTM D 882. The reported secant modulus values ​​are the average of five measurements.

[0164] Bursting strength

[0165] The bursting strength of the pipe samples was measured according to NBR ISO 9261. The values ​​are reported in bar.

[0166] Molecular Weighted Comonomer Distribution Index (MWCDI)

[0167] The GPC-IR high temperature chromatography system from Perimocha (Valencia, Spain) was equipped with a precision detector (Amherst, MA), a 2040 2-angle laser light scattering detector, and an IR5 infrared detector (GPC-IR) and a 4-capillary viscometer, all from Perimocha. The "15 degree angle" of the light scattering detector was used for calculation purposes. Data collection was performed using the Instrument Control software and data collection interface from Perimocha. The system was equipped with an online solvent degasser and pumping system from Agilent Technologies (Santa Clara, CA).

[0168] The injection temperature was controlled at 150°C. The columns used were four 20 micron "Mixed-A" light scattering columns from Polymer Laboratories (Shropshire, UK). The solvent was 1,2,4-trichlorobenzene. The samples were prepared at a concentration of "0.1 g polymer in 50 ml solvent". The chromatography solvent and the sample preparation solvent each contained "200 ppm butylated hydroxytoluene (BHT)". Both solvent sources were sparged with nitrogen. The ethylene-based polymer samples were gently stirred at 160 degrees Celsius for three hours. The injection volume was "200 microliters" and the flow rate was "1 ml / min".

[0169] The GPC column set was calibrated with 21 "narrow molecular weight distribution" polystyrene standards with molecular weights ranging from 580 g / mol to 8,400,000 g / mol. These standards were arranged in six "mixed liquor" mixtures with at least ten times spacing between individual molecular weights. The standards were purchased from Polymer Laboratories (Shropshire, UK). The polystyrene standards were prepared as follows: for molecular weights equal to or greater than 1,000,000 g / mol, they were prepared as "0.025 g in 50 ml of solvent", and for molecular weights less than 1,000,000 g / mol, they were prepared as "0.050 g in 50 ml of solvent". The polystyrene standards were dissolved at 80 degrees Celsius with gentle stirring for 30 minutes. The narrow standards mixture was run first, and degradation was minimized in the order of decreasing "highest molecular weight component". The polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 12 (as described by Williams and Ward, J. Polym. Sci. Polym. Lett., Vol. 6, p. 621 (1968)):

[0170] Mpolyethylene=A×(Mpolystyrene) B (Equation 12),

[0171] Where M is the molecular weight, the value of A is approximately 0.40 and B equals 1.0. The value of A is adjusted between 0.385 and 0.425 (depending on the specific column set efficiency) so that the NBS 1475A (NIST) linear polyethylene weight average molecular weight corresponds to 52,000 g / mole as calculated by the following equation 14:

[0172]

[0173]

[0174] In Equation 13 and Equation 14, RV is the column retention volume (linearly spaced) collected at "1 point / second". IR is the baseline-subtracted IR detector signal from the measurement channel of the GPC instrument, in volts, and M PE is the polyethylene equivalent MW determined from Equation 12. Data calculations were performed using "GPC One Software (Version 2.013H)" from Perimozza.

[0175] Using the known short chain branching (SCB) frequencies (as discussed above) 13 The IR5 detector ratio calibration was performed with at least ten ethylene-based polymer standards (polyethylene homopolymers and ethylene / octene copolymers; narrow molecular weight distribution and uniform comonomer distribution) measured by C NMR method, ranging from homopolymer (0 SCB / 1000 total C) to about 50 SCB / 1000 total C, where total C = carbon in the backbone + carbon in the branches. The weight average molecular weight of each standard was 36,000 g / mole to 126,000 g / mole, as determined by the GPC-LALS processing method described above. The molecular weight distribution (Mw / Mn) of each standard was 2.0 to 2.5, as determined by the GPC-LALS processing method described above. The SCB standard terpolymer properties are shown in Table A.

[0176] Table A: "SCB" Standards

[0177] Wt% comonomer IR5 Area Ratio SCB / 1000Total C M Mw / Mn 23.1 0.2411 28.9 37,300 2.22 14.0 0.2152 17.5 36,000 2.19 0.0 0.1809 0.0 38,400 2.20 35.9 0.2708 44.9 42,200 2.18 5.4 0.1959 6.8 37,400 2.16 8.6 0.2043 10.8 36,800 2.20 39.2 0.2770 49.0 125,600 2.22 1.1 0.1810 1.4 107,000 2.09 14.3 0.2161 17.9 103,600 2.20 9.4 0.2031 11.8 103,200 2.26

[0178] For each of the "SCB" standards, the "IR5 Area Ratio" (or "IR5 Area Response of the IR5 Methyl Channel Sensor Subtracted Baseline") was calculated as the "IR5 Area Response of the IR5 Measurement Channel Sensor Subtracted Baseline". 甲基通道面积 / IR5 测量通道面积 ”)” (such as the standard filter and filter wheel supplied by PolymerChar: Part No. IR5_FWM01 included as part of the GPC-IR instrument). A linear fit of SCB frequency to “IR5 area ratio” was constructed in the form of the following formula 4B:

[0179] SCB / 1000 Total C = A0 + [A1 × (IR5 甲基通道面积 / IR5 测量通道面积 )](Equation 4B), where A0 is the "SCB / 1000 Total C" intercept at "IR5 Area Ratio" of zero, and A1 is the slope of "SCB / 1000 Total C" versus "IR5 Area Ratio" and represents the increase of "SCB / 1000 Total C" as "IR5 Area Ratio" changes.

[0180] A series of "linear baseline-subtracted chromatogram heights" of the chromatogram produced by the "IR5 methyl channel sensor" is established as a function of the column elution volume to produce a baseline-corrected chromatogram (methyl channel). A series of "linear baseline-subtracted chromatogram heights" of the chromatogram produced by the "IR5 measurement channel" is established as a function of the column elution volume to produce a baseline-corrected chromatogram (measurement channel).

[0181] At each column elution volume index (each equally spaced index represents 1 data point per second at 1 ml / min elution) at both ends of the sample integration limit, the "IR5 Height Ratio" of the "Baseline Corrected Chromatogram (Methyl Channel)" to the "Baseline Corrected Chromatogram (Measurement Channel)" is calculated. The "IR5 Height Ratio" is multiplied by the factor A1, and the factor A0 is added to this result to produce the predicted SCB frequency for the sample. The result is converted to comonomer mole percentage in Equation 5B as follows:

[0182] Comonomer mole percentage = {SCB f / [SCB f +((1000-SCB f * comonomer length) / 2)]}*100 (Equation 5B), where "SCB f " is SCB per 1000 total C", and "comonomer length" = 8 for octene, 6 for hexene, etc.

[0183] Each elution volume index was converted to a molecular weight value (Mw) using the method of Williams and Ward. i ) (as described above; Equation 1). Plot "Mole Percent Comonomer (y-axis)" as a function of Log(Mwi) and calculate the Mw of 15,000 g / mol i With Mw of 150,000 g / mol iThe slope between Mwi of 15,000 g / mol and 150,000 g / mol (end group correction on the chain end was omitted for this calculation). EXCEL linear regression was used to calculate the slope between Mwi of 15,000 g / mol and 150,000 g / mol (and including the end point). This slope is defined as the molecular weighted comonomer distribution index (MWCDI = molecular weighted comonomer distribution index).

[0184] The following examples illustrate features of the present disclosure but are not intended to limit the scope of the present disclosure.The following experiments analyze the performance of embodiments of the polyethylene formulations described herein.

[0185] Example 1: Preparation of polyethylene composition 1

[0186] Polyethylene Composition 1 is discussed in conjunction with Examples 3-5 below. Polyethylene Composition 1 contains an ethylene-octene copolymer. The composition was prepared using the catalyst system described subsequently under the polymerization conditions reported in Table 1.

[0187] The polyethylene composition 1 was prepared by solution polymerization in a dual series loop reactor system according to US Pat. No. 5,977,251 as described below in the presence of a first catalyst system in the first reactor and a second catalyst system in the second reactor.

[0188] The first catalyst system comprises bis((2-oxo-3-(dibenzo-1H-pyrrol-1-yl)-5-(methyl)phenyl)-2-phenoxymethyl)-methylene-1,2-cyclohexanediylhafnium(IV)dimethyl represented by the following formula (Catalyst 1):

[0189]

[0190] The molar ratios of the metal of Catalyst 1 to the metal of Cocatalyst 1 (modified methylaluminoxane) or Cocatalyst 2 (bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate(1-)amine) added in situ to the polymerization reactor are shown in Table 1.

[0191] The second catalyst system comprises a Ziegler-Natta type catalyst (Catalyst 2). A heterogeneous Ziegler-Natta type catalyst premix was prepared essentially according to U.S. Pat. No. 4,612,300 by sequentially adding a slurry of anhydrous magnesium chloride in ISOPAR E, a solution of EtAlCl2 in heptane, and a solution of Ti(O-iPr)4 in heptane to a volume of ISOPAR E to obtain a composition containing a magnesium concentration of 0.20 M and a Mg / Al / Ti ratio of 40 / 12.5 / 3. An aliquot of this composition was further diluted with ISOPAR-E to give a final concentration of Ti in the slurry of 500 ppm. Upon feeding into the polymerization reactor and prior to entering the polymerization reactor, the catalyst premix was contacted with a dilute solution of Et3Al at the molar ratio of Al to Ti specified in Table 1 to obtain an active catalyst.

[0192] The polymerization conditions for Polyethylene Composition 1 are reported in Table 1. As shown in Table 1, Cocatalyst 1 (modified methylaluminoxane (MMAO)); and Cocatalyst 2 (bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate (1-)amine) were each used as a cocatalyst for Catalyst 1. Polyethylene Composition 1 was stabilized with a small amount (ppm) of a stabilizer.

[0193] Table 1. Polymerization conditions of polyethylene composition 1 .

[0194]

[0195]

[0196] *Solvent=ISOPAR E

[0197] Example 2: Comparative Composition A

[0198] Comparative composition A is a linear low density polyethylene DOWLEX commercially available from The Dow Chemical Company. TM 2045.

[0199] Example 3: Comparison of Polyethylene Composition 1 and Comparative Composition A

[0200] The properties of Polyethylene Composition 1 and Comparative Composition A were measured according to the test methods described herein and are reported in Table 2.

[0201] Table 2. Comparison of properties of Sample A and Sample 1 .

[0202]

[0203] Example 4: Comparison of sample tube A and sample

[0204] Preparation of Tubes 1-3

[0205] In Example 4, four irrigation pipe samples were produced from the polyethylene formulation of Table 3 using the following extrusion parameters: The irrigation pipe samples were made using a profile extruder with a circular die, a subsequent vacuum system (to control the pipe diameter) and a water cooling bath. The extrusion speed was 170 m / min; the extrusion temperature profile was 220° C. / 220° C. / 230° C. / 240° C. / 250° C.; the melt pressure was 193 bar, and the melt temperature was 260° C.

[0206] Table 3. Comparison of formulations of Sample Tube A, Sample Tube 1, Sample Tube 2, and Sample Tube 3 .

[0207]

[0208]

[0209] Example 5: Comparison of sample tube A and sample

[0210] Comparison of tubes 1-3

[0211] The properties of Comparative Sample Tube A and Sample Tubes 1-3 were measured according to the test methods described herein and are reported in Table 4.

[0212] Table 4. Comparison of properties of sample pipe A, sample pipe 1, sample pipe 2, and sample pipe 3 .

[0213] Comparison sample tube A Sample tube 1 Sample tube 2 Sample tube 3 2% secant modulus (MPa) 162.1 150.2 157.4 169.2 Fracture stress (MPa) 11.04 10.83 12.16 12.42 Yield stress (MPa) 6.8 6.8 7.9 7.5 Bursting strength (bar) 6.5 7.5 6.9 6.9

[0214] As shown in Table 4, Sample Tube 1 exhibited higher burst strength than Comparative Sample Tube A at the same thickness (18 mils). In addition, Polyethylene Formulation 1 in Sample Tubes 2 and 3 allowed for reduced thickness tubes (17 mils and 16 mils for Sample Tubes 2 and 3, respectively) to provide better burst strength than Comparative Sample Tube A. Thus, embodiments of the present disclosure may provide a polyethylene formulation (such as Polyethylene Formulation 1) that provides a balance of comparable or improved stiffness and burst strength properties when used in irrigation pipes while allowing for reduced material costs.

[0215] Obviously, modifications and variations are possible without departing from the scope of the present disclosure as defined in the appended claims.More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

1. A polyethylene formulation, comprising: 45 wt.% to 90 wt.% of a medium density polyethylene having a density of 0.930 g / cc to 0.950 g / cc and a melt index I2 of 0.05 g / 10 min to 0.5 g / 10 min; 10 wt.% to 50 wt.% of a polyethylene composition having a density of 0.910 g / cc to 0.936 g / cc and a melt index I2 of 0.25 g / 10 min to 2.0 g / 10 min; as well as 0.5 wt.% to 5% of a masterbatch composition; The polyethylene composition comprises: A first polyethylene fraction area in the temperature range of 45°C to 87°C of an elution curve obtained by an improved comonomer composition distribution iCCD analysis method, wherein the first polyethylene fraction area accounts for at least 50% of the total area of ​​the elution curve; A second polyethylene fraction area in the temperature range of 95°C to 120°C of an elution curve obtained by an improved comonomer composition distribution iCCD analysis method, wherein the second polyethylene fraction area accounts for less than or equal to 23% of the total area of ​​the elution curve; wherein the ratio of the area of ​​the first polyethylene fraction to the area of ​​the second polyethylene fraction is 2.9 to 12.5, wherein the density is measured according to ASTM D792, and the melt index I2 is measured according to ASTM D1238 at a load of 2.16 kg and a temperature of 190° C., and The total weight percentage of the medium-density polyethylene, the polyethylene composition and the masterbatch composition is 100%.

2. The formulation according to claim 1, wherein the masterbatch composition is a carbon black masterbatch composition.

3. The formulation according to any one of claims 1-2, wherein the polyethylene composition has a molecular weight distribution Mw / Mn of 2.0 to 5.0, wherein Mn is determined by conventional GPC, and Mw is determined by conventional GPC.

4. The formulation of any one of claims 1-2, wherein the polyethylene composition has a Mz / Mw of 1.5 to 3.5, wherein Mz is determined by conventional GPC and Mw is determined by conventional GPC.

5. The formulation of any one of claims 1-2, wherein the polyethylene composition has an Mz of 200,000 g / mol to 400,000 g / mol, wherein the Mz is determined by conventional GPC.

6. The formulation of any one of claims 1-2, wherein the polyethylene composition has 10 / I2 is 5.5 to 8.5, where the melt index I 10 It is measured according to ASTM D1238 at a load of 10 kg and a temperature of 190°C.

7. The formulation of any one of claims 1-2, wherein the first polyethylene fraction area is 50% to 80% of the total area of ​​the elution curve of the polyethylene composition.

8. The formulation of any one of claims 1-2, wherein the second polyethylene fraction area is 6% to 23% of the total area of ​​the elution curve of the polyethylene composition.

9. The formulation of any one of claims 1-2, wherein the ratio of the first polyethylene fraction area to the second polyethylene fraction area is 3.0 to 6.

0.

10. The formulation of any one of claims 1-2, wherein the polyethylene composition has a molecular weighted comonomer distribution index MWCDI of 1.0 to 10.

0.

11. An article comprising the polyethylene formulation according to any one of claims 1-10.

12. The article of claim 11, wherein the article is a drip tape.

13. The article of claim 12 wherein the drip tape has a thickness of 16 to 18 mils and a burst strength greater than 6.5 bar when measured according to NBR ISO 9261.

14. The article of claim 12, wherein the drip tape has a thickness of 16 to 18 mils and a 2% secant modulus in the machine direction greater than 150 MPa when measured according to ASTM D882.

15. The article of claim 12, wherein the drip tape has a thickness of 16 to 18 mils and a yield stress of at least 6.5 MPa when measured according to ASTM D882.

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