Polyethylene blends comprising PCR and multimodal virgin resins

Abstract

A polyethylene blend may comprise: (a) 35 wt. % to 75 wt. % of a multimodal virgin polyethylene resin and (b) 25 wt. % to 65 wt. % of a visbroken polyethylene PCR. The multimodal virgin polyethylene resin may have a density from 0.940 g / cc to 0.950 g / cc and may comprise from 45 wt. % to 60 wt. % of a high molecular weight (HMW) fraction and from 40 wt. % to 55 wt. % of a low molecular weight (LMW) fraction. The visbroken polyethylene PCR may have I2 between 7 dg / min and 15 dg / min. The overall polyethylene blend may have I2 from 0.7 dg / min and 3 dg / min.

Description

86190-WO-PCT / DOW 86190 WO1POLYETHYLENE BLENDS COMPRISING PCR AND MULTIMODAL VIRGIN RESINSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No.63 / 739,896 filed December 30, 2024, the contents of which are incorporated in their entirety herein.BACKGROUND

[0002] Recycling of plastic waste is one of the most important sustainability issues of our time. Caps and closures are an important application for recycled plastic, such as postconsumer resins (PCR). However, incorporation of present PCRs into caps and closures is challenging as PCR resins often have low melt indices and high density, which is not inherently suitable for caps and closure applications. Prior approaches have included blending the low melt index, high density PCR with high melt index low density virgin resins. However, while this approach may sometimes result in acceptable melt indices, it results in low environmental stress crack resistance (ESCR), an important parameter for caps and closures.

[0003] Accordingly, there is a need for polymer blends comprising PCR yet still suitable for use in caps and closures.BRIEF SUMMARY

[0004] Embodiments of this disclosure meet this need by providing polymer blends comprising a visbroken polyethylene PCR and a multimodal virgin polyethylene resin. Generally, the visbreaking process increases the melt index of the PCR, producing a visbroken polyethylene PCR with suitable processing characteristics. Additionally, the inclusion of a multimodal virgin polyethylene resin (as opposed to a unimodal virgin polyethylene resin) having particular amount of a high molecular weight (HMW) fraction (e.g., from 45 wt. % to 60 wt. %) and a particular amount of a low molecular weight (LMW) fraction (e.g., from 40 wt. % to 55 wt. %) can produce a blend which has both suitable melt index and ESCR.86190-WO-PCT / DOW 86190 WO2

[0005] According to one embodiment, a polyethylene blend may comprise: (a) 35 wt. % to 75 wt. % of the multimodal virgin polyethylene resin and (b) 25 wt. % to 65 wt. % of the visbroken polyethylene PCR. The multimodal virgin polyethylene resin may have a density from 0.940 g / cc to 0.950 g / cc. The multimodal virgin polyethylene resin may comprise from 45 wt. % to 60 wt. % of a high molecular weight (HMW) fraction and from 40 wt. % to 55 wt. % of a low molecular weight (LMW) fraction. The HMW fraction may have a density from 0.910 g / cc to 0.920 g / cc and a melt flow index (hi) from 0.5 dg / min to 1.5 dg / min. The LMW fraction may have a higher density and a lower weight average molecular weight (Mw) than the HMW. The visbroken polyethylene PCR may have a melt index (h) between 7 dg / min and 15 dg / min. The overall polyethylene blend may have h from 0.7 dg / min and 3 dg / min.

[0006] These and other embodiments are described in more detail in the Detailed Description. It is to be understood that both the foregoing general description and the following detailed description present embodiments of the presently disclosed technology, and are intended to provide an overview or framework for understanding the nature and character of the technology as it is claimed. Additionally, the descriptions are meant to be merely illustrative, and are not intended to limit the scope of the claims in any manner.DETAILED DESCRIPTION

[0007] "Polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The term polymer thus embraces the term homopolymer (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term copolymer or interpolymer. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and / or within the polymer. A polymer may be a single polymer or a polymer blend.

[0008] “Copolymer” refers to a polymer formed by the polymerization reaction of at least two structurally different monomers. The term “copolymer” is inclusive of terpolymers. For example, ethylene copolymers, such as ethylene-propylene copolymers, include at least two structurally different monomers (e.g., ethylene-propylene copolymer includes copolymerized units of at least ethylene monomer and propylene monomer) and can optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride86190-WO-PCT / DOW 86190 WO3functional groups. Put another way, the copolymers described herein comprise at least two structurally different monomers, and although the copolymers may consist of only two structurally different monomers, they do not necessarily consist of only two structurally different monomers and may include additional monomers or functional materials or modifiers.

[0009] "Ethylene-based polymer" (also referred to herein as “polyethylene” or "polyethylene-based polymers”) refers to polymers comprising greater than 50% by weight of units, which have been derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m-LLDPE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

[0010] The term “LLDPE” includes resins made using the traditional Ziegler-Natta catalyst systems as well as single-site catalysts such as metallocenes (sometimes referred to as “m-LLDPE”). LLDPEs contain less long chain branching than LDPEs and include the 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; the homogeneously branched linear ethylene polymer compositions such as those in U.S. Pat. No. 3,645,992; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Pat. No. 4,076,698; and / or blends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 or U.S. Pat. No. 5,854,045). The LLDPE can be made via gas-phase, solution-phase or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art, including, but not limited to, gas and solution phase reactors.

[0011] “HDPE” generally refers to polyethylenes having densities greater than about 0.930 g / cm3and up to about 0.970 g / cm3, which are generally prepared with Ziegler-Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).86190-WO-PCT / DOW 86190 WO4

[0012] The term “polypropylene,” as used herein, refers to a polymer that comprises, in polymerized form, greater than 50% by mole of units, which have been derived from propylene monomer. This includes propylene homopolymer, random copolymer polypropylene, impact copolymer polypropylene, propylene / a-olefin copolymer, and propylene / ot-olefin copolymer.

[0013] “Recycled resins” refers to resins, which were incorporated into products and subsequently re-melted to form a recycled resin. The term “recycled resins” refers to mechanically recycled resins, where the resin is melted and reincorporated into a new product. “Recycled resins” does not include chemically recycled resins, where the polymer is broken down into constituent monomers and incorporated into a new virgin polymer. The term “recycled resins” embraces both pre-consumer recycled polymer and post-consumer resin. Recycled resins are defined in ISO 14021 7.8.1.1.

[0014] The terms “pre-consumer recycled polymer” and “post-industrial recycled polymer” refer to polymers, including blends of polymers, recovered from pre-consumer material, as defined by ISO- 14021. The generic term pre-consumer recycled polymer thus includes blends of polymers recovered from materials diverted from the waste stream during a manufacturing process. The generic term pre-consumer recycled polymer excludes the reutilization of materials, such as rework, regrind, or scrap, generated in a process and capable of being reclaimed within the same process that generated it. Pre-consumer recycled polymer is defined in ISO 14021 7.8.1.1.

[0015] The term “post-consumer resin” (or “PCR”), as used herein, refers to a polymeric material that includes materials previously used in a consumer or industry application (i.e., pre-consumer recycled polymer and post-industrial recycled polymer). PCR is typically collected from recycling programs and recycling plants. The PCR may include one or more of an ethylene-based polymer, such as LDPE, LLDPE, HDPE, a polyethylene, a polypropylene, a polyester, a poly(vinyl chloride), a polystyrene, an acrylonitrile butadiene styrene, a polyamide, an ethylene vinyl alcohol, an ethylene vinyl acetate, or a poly-vinyl chloride. The PCR may include one or more contaminants. The contaminants may be the result of the polymeric material’s use prior to being repurposed for reuse. For example, contaminants may include paper, ink, food residue, or other recycled materials in addition to the polymer, which may result from the recycling process. PCR is distinct from virgin polymeric material. A virgin polymeric material (such as a virgin polyethylene resin) does86190-WO-PCT / DOW 86190 WO5not include materials previously used in a consumer or industry application. Virgin polymeric material has not undergone, or otherwise has not been subject to, a heat process or a molding process, after the initial polymer manufacturing process. The physical, chemical, and flow properties of PCR resins differ when compared to virgin polymeric resin, which in turn can present challenges to incorporating PCR into formulations for commercial use. Postconsumer resin is defined in ISO 14021 7.8.1.1.

[0016] As used herein, the term “devolatization” refers to a process by which undesired volatile contaminants (e.g., dissolved gasses, solvent, unreacted monomer, etc.) are removed from a polymer melt or solution.

[0017] The polyethylene blend and its constituents will now be described in more detail. A polyethylene blend may comprise from 35 wt. % to 75 wt. % of a multimodal virgin polyethylene resin and from 25 wt. % to 65 wt. % of a visbroken polyethylene PCR. In embodiments, the polyethylene blend may comprise from 35 wt. % to 40 wt. %, from 40 wt. % to 45 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, from 65 wt. % 70 to wt. %, from 70 wt. % to 75 wt. %, or any combination of two or more of these ranges of the multimodal virgin polyethylene resin; and from 25 wt. % to wt. 30 %, from 30 wt. % to 35 wt. %, from 35 wt. % to 40 wt. %, from 40 wt. % to 45 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, or any combination of two or more of these ranges of the visbroken polyethylene PCR, on the basis of the total polymer weight of the polyethylene blend.

[0018] The multimodal virgin polyethylene resin may comprise two or more fractions, such as a high molecular weight (HMW) fraction and a low molecular weight (LMW) fraction. In embodiments, the multimodal virgin polyethylene resin is bimodal (having exactly two fractions, e.g., the HMW fraction and the LMW fraction). In embodiments, each of the fractions (e.g., the HMW fraction and the LMW fraction) may be produced in separate reactors. For example, the HMW fraction may be produced in a first reactor and referred to as a 1streactor fraction, the LMW fraction may be produced in a second reactor and referred to as a 2ndreactor fraction. In embodiments, the 1streactor fraction may be passed to the second reactor, where further constituents are polymerized to form the 2ndreactor fraction, mixed with the 1streactor fraction. In embodiments, the multimodal virgin polyethylene resin comprises at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or even at86190-WO-PCT / DOW 86190 WO6least 99.9 wt. % of the combined weight of the HMW fraction and the LMW fraction. In embodiments, the multimodal virgin polyethylene resin fraction may comprise from 45 wt. % to 60 wt. %, such as from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, or any combination of two or more of these ranges of the HMW fraction, on the basis of the total weight of the multimodal virgin polyethylene resin. In embodiments, the multimodal virgin polyethylene resin may comprise from 40 wt. % to 55 wt. %, such as from 40 wt. % to 45 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, or any combination of two or more of these ranges of the LMW, on the basis of the total weight of the multimodal virgin polyethylene resin.

[0019] In embodiments, the HMW fraction may have a density from 0.910 g / cc to 0.920 g / cc, such as from 0.910 g / cc to 0.912 g / cc, from 0.912 g / cc to 0.914 g / cc, from 0.914 g / cc to 0.916 g / cc, from 0.916 g / cc to 0.918 g / cc, from 0.918 g / cc to 0.920 g / cc, or any combination of two or more of these ranges.

[0020] In embodiments, the HMW fraction may have a melt flow index (hi) from 0.5 dg / min to 1.5 dg / min, such as from 0.5 dg / min to 0.6 dg / min, from 0.6 dg / min to 0.7 dg / min, from 0.7 dg / min to 0.8 dg / min, from 0.8 dg / min to 0.9 dg / min, from 0.9 dg / min to 1.0 dg / min, from 1.0 dg / min to 1.2 dg / min, from 1.2 dg / min to 1.4 dg / min, from 1.4 dg / min to 1.5 dg / min, or any combination of two or more of these ranges.

[0021] The multimodal virgin polyethylene resin may have a density from 0.940 g / cc to 0.950 g / cc, such as from 0.940 g / cc to 0.942 g / cc, from 0.942 g / cc to 0.944 g / cc, from 0.944 g / cc to 0.946 g / cc, from 0.946 g / cc to 0.948 g / cc, from 0.948 g / cc to 0.950 g / cc, or any combination of two or more of these ranges.

[0022] The multimodal virgin polyethylene resin may have a melt index (h) from 0.1 dg / min and 1.0 dg / min, such as from 0.1 dg / min to 0.3 dg / min, from 0.3 dg / min to 0.5 dg / min, from 0.5 dg / min to 0.7 dg / min, from 0.7 dg / min to 0.9 dg / min, from 0.9 dg / min to 1.0 dg / min, or any combination of two or more of these ranges.

[0023] The multimodal virgin polyethylene resin may have a melt flow index (hi) of from 20 dg / min to 50 dg / min, such as from 20 dg / min to 25 dg / min, from 25 dg / min to 30 dg / min, from 30 dg / min to 35 dg / min, from 35 dg / min to 40 dg / min, from 40 dg / min to 45 dg / min, from 45 dg / min to 50 dg / min, or any combination of two or more of these ranges.

[0024] The multimodal virgin polyethylene resin may have an hi / h of from 70 to 150, such as from 90 to 130, from 70 to 75, from 75 to 80, from 80 to 85, from 85 to 90, from 90 to 95,86190-WO-PCT / DOW 86190 WO7from 95 to 100, from 100 to 105, from 105 to 110, from 110 to 115, from 115 to 120, from 120 to 125, from 125 to 130, from 130 to 135, from 135 to 140, from 140 to 145, from 145 to 150, or any combination of two or more of these ranges.

[0025] The multimodal virgin polyethylene resin may have an Mz (conventional) of greater than 800,000 g / mol and less than 2,000,000 g / mol, such as from greater than 800,000 g / mol to 900,000 g / mol, from 900,000 g / mol to 1,000,000 g / mol, from 1,000,000 g / mol to 1,100,000 g / mol, from 1,100,000 g / mol to 1,200,000 g / mol, from 1,200,000 g / mol to 1,300,000 g / mol, from 1,300,000 g / mol to 1,400,000 g / mol, from 1,400,000 g / mol to less than 1,500,000 g / mol, from 1,500,000 g / mol to 1,600,000 g / mol, from 1,600,000 g / mol to 1,700,000 g / mol, from 1,700,000 g / mol to 1,800,000 g / mol, from 1,800,000 g / mol to 1,900,000 g / mol, from 1,900,000 g / mol to 2,000,000 g / mol, or any combination of two or more of these ranges.

[0026] The multimodal virgin polyethylene resin may have a Mz / Mn (conventional) from 50 to 150, such as from 50 to 55, from 55 to 60, from 60 to 65, from 65 to 70, from 70 to 75, from 75 to 80, from 80 to 85, from 85 to 90, from 90 to 95, from 95 to 100, from 100 to 105, from 105 to 110, from 110 to 115, from 115 to 120, from 120 to 125, from 125 to 130, from 130 to 135, from 135 to 140, from 140 to 145, from 145 to 150, or any combination of two or more of these ranges.

[0027] The multimodal virgin polyethylene resin may have a strain hardening modulus of greater than 55 MPa, such as greater than 56 MPa, greater than 57 MPa, greater than 58 MPa, greater than 59 MPa, greater than 60 MPa, greater than 61 MPa, or greater than 62 MPa. In embodiments, the strain hardening modulus may be from 55 MPa to 90 MPa, such as from 56 MPa to 90 MPa, from 57 MPa to 90 MPa, from 58 MPa to 90 MPa, from 59 MPa to 90 MPa, from 60 MPa to 90 MPa, or any combination of two or more of these ranges.

[0028] In some embodiments, the multimodal virgin polyethylene resin may be a gas phase, Ziegler-Natta catalyzed polyethylene. Without being limited by theory, it is believed that Ziegler-Natta catalyzed polyethylenes otherwise meeting the criteria described herein provide better processability (shear thinning) than metallocene catalyzed polyethylenes otherwise meeting the criteria described herein.

[0029] As described herein, the polyethylene blend may further comprise a visbroken polyethylene PCR. The visbroken polyethylene PCR may be formed from a base PCR ethylene-based polymer by an extrusion visbreaking process. Extrusion visbreaking is a thermal cracking process conducted in an extruder under shear to reduce the viscosity of a86190-WO-PCT / DOW 86190 WO8polymer resin. Visbreaking process may produce a visbroken polyethylene PCR having a greater melt index (I2) than the base PCR ethylene-based polymer. In embodiments, the visbroken polyethylene PCR may be formed from a base PCR ethylene based polymer comprising linear low density polyethylene, high density polyethylene, or both. In embodiments, the visbroken polyethylene PCR may comprise at least 75 wt. %, at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or at least 99.9 wt. % of material formed from visbreaking the base PCR ethylene based polymer.

[0030] The visbroken polyethylene PCR may have a density of from 0.950 g / cc to 0.965 g / cc, such as from 0.950 g / cc to 0.955 g / cc, from 0.955 g / cc to 0.960 g / cc, from 0.960 g / cc to 0.965 g / cc, or any combination of two or more of these ranges.

[0031] The visbroken polyethylene PCR may have a melt index (I2) from 7 dg / min to 15 dg / min, such as from 7 dg / min to 9 dg / min, from 9 dg / min to 11 dg / min, from 11 dg / min to 13 dg / min, from 13 dg / min to 15 dg / min, or any combination of two or more of these ranges. Before visbreaking, the base PCR ethylene-based polymer may have had a melt index (I2) of less than 1 dg / min, such as from 0.3 dg / min to 1.0 dg / min.

[0032] The visbroken polyethylene PCR may have a rheology ratio (r|o i / pioo) from 3 to 20, such as from 3 to 5, from 5 to 7, from 7 to 9, from 9 to 11, from 11 to 13, from 13 to 15, from 15 to 17.5, from 17.5 to 20, or any combination of two or more of these ranted, po.i is the shear viscosity measured at 0.1 radians / second and pioo is the shear viscosity measured at 100 radians / second. In embodiments, the visbreaking process may produce a visbroken polyethylene PCR with a rheology ratio (po. i / pioo) of at most 1 / 5 of that of polyethylene PCR prior to visbreaking.

[0033] The visbroken polyethylene PCT may have an I21 / I2 of from 5 to 20, such as from 5 to 10, from 10 to 15, from 15 to 20, or any combination of two or more of these ranges.

[0034] In embodiments, the visbroken polyethylene PCR may have a tan8o 1 at least 15 times the tanSo i of the polyethylene PCR prior to visbreaking. In embodiments, the visbroken polyethylene PCR may have a tanSo i of from 5 to 90, such as from 5 to 10, 10 to 20, 20 to 30, 30 to 40, 40 to 50, 50 to 60, 60 to 70, 70 to 80, 80 to 90, or any combination of two or more of these ranges.

[0035] Suitable visbroken PCR ethylene-based polymers, and their methods of making, are disclosed in U.S. Patent Appln. No. 63 / 579,105, the entirety of which is incorporated herein by reference. A summary of the visbreaking process is provided herein.86190-WO-PCT / DOW 86190 WO9

[0036] The visbroken PCR ethylene-based polymer may be produced by extrusion visbreaking the base PCR ethylene-based polymer resin in an extruder. The extruder may be a tandem system, a single screw extruder, a twin screw extruder, or the like. The extruder may be equipped with multilayer annular dies, flat film dies and feed blocks, multi-layer feed blocks, multi-vane or multi-manifold dies such as a 3-layer vane die. In embodiments, the extrusion visbreaking utilizes a twin screw extruder. The base PCR ethylene-based polymer resin may comprise at least 80 wt. % of polymers introduced into the extruder, such as at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or even at least 99.9 wt. %, on the basis of the total polymer weight introduced into the extruder. The base PCR ethylene-based polymer resin may comprise at least 80 wt. % of the material introduced into the extruder, such as at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, at least 99.9 wt. %, or even at least 99.99 wt. % of all material introduced into the extruder.

[0037] Without being limited by theory, the extrusion visbreaking process may introduce heat and mechanical energy (through the extruder) into the base PCR ethylene-based polymer resin. Generally, this energy may cause chain scission of the ethylene-based polymers in the base PCR ethylene-based polymer resin. It is believed that the chain scission may cause the melt index of the resin to increase and the molecular weights and Mw / Mn to decrease. The total mechanical energy input may be referred to as the specific energy input (SEI). SEI maybe calculated from according to the equation SEI has unitsof kW-hr / kg.

[0038] The specific energy input (SEI) may be from 0.4 kW-hr / kg polymer to 2.0 kW-hr / kg polymer. Without being limited by theory, it is believed that an SEI below this range may not cause sufficient chain scission to sufficiently increase the melt indices of the base ethylenebased polymer. Conversely, an SEI above this range may cause excessive chain scission and damage the mechanical properties of the base ethylene-based polymer. In embodiments, the SEI may be from 0.4 kW-hr / kg polymer to 1.8 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 1.6 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 1.4 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 1.2 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 1.0 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 0.8 kW-hr / kg polymer, from 0.4 kW-hr / kg polymer to 0.6 kW-hr / kg polymer, from 0.6 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 0.8 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 1.0 kW-hr / kg polymer to 2.0 kW-86190-WO-PCT / DOW 86190 WO10hr / kg polymer, from 1.2 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 1.4 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 1.6 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 1.8 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, from 0.6 kW-hr / kg polymer to 1.8 kW-hr / kg polymer, from 0.8 kW-hr / kg polymer to 1.6 kW-hr / kg polymer, from 1.0 kW-hr / kg polymer to 1.4 kW-hr / kg polymer, or any subset thereof.

[0039] The extrusion visbreaking may occur at a temperature of at least 250 °C. Without being limited by theory, it is believed that if the visbreaking temperature is too low, such as less than 250 °C or less than 290 °C, it may be difficult for the extruder motor to add enough energy to the resin to accomplish the visbreaking. In embodiments, the extrusion visbreaking may occur at a temperature of at least 275 °C, at least 285 °C, at least 290 °C, at least 295 °C, from 250 °C to 350 °C, from 275 °C to 350 °C, from 285 °C to 350 °C, from 295 °C to 350 °C, from 275 °C to 325 °C, from 285 °C to 325 °C, from 295 °C to 325 °C, from 295 °C to 315 °C, from 295 °C to 305 °C, or any subset thereof.

[0040] The extrusion visbreaking may occur in an extruder, such as a twin screw extruder, at a screw speed of at least 350 revolutions per minute (RPM). Without being limited by theory, it is believed that a screw speed below this range may not introduce enough energy to cause sufficient chain scission to sufficiently increase the melt indices of the base ethylenebased polymer. The extrusion visbreaking may occur at a screw speed of at least 400 RPM, at least 500 RPM, at least 600 RPM, at least 700 RPM, at least 800 RPM, from 400 RPM to 1100 RPM, from 500 RPM to 1100 RPM, from 600 RPM to 1100 RPM, from 700 RPM to 1100 RPM, from 800 RPM to 1100 RPM, from 900 RPM to 1100 RPM, from 350 RPM to 1000 RPM, from 500 RPM to 1000 RPM, from 700 RPM to 1000 RPM from 800 RPM to 1000 RPM, or any subset thereof.

[0041] The extrusion visbreaking may have a residence time of from 30 seconds (sec) to 200 sec. Without being limited by theory, the amount of energy input into the resin is a function of the temperature, the extruder motor power (as is defined by screw speed), and the amount of time the resin is exposed to these conditions (the residence time). The extrusion visbreaking may have a residence time of from 30 sec to 180 sec, from 30 sec to 160 sec, from 30 sec to 140 sec, from 30 sec to 120 sec, from 30 sec to 100 sec, from 30 sec to 80 sec, from 30 sec to 60 sec, from 50 sec to 200 sec, from 70 sec to 200 sec, from 90 sec to 200 sec, from 104 sec to 200 sec, from 130 sec to 200 sec, from 150 sec to 200 sec, from 170 sec to86190-WO-PCT / DOW 86190 WO11200 sec, from 50 sec to 180 sec, from 70 sec to 160 sec, from 90 sec to 140 sec, from 104 sec to 130 sec, or any subset thereof.

[0042] The extrusion visbreaking may occur in the absence of oxygen. Without being limited by theory, it is believed that extrusion visbreaking in the absence of oxygen results in a lower percentage of aldehydes in the visbroken PCR ethylene-based polymer than extrusion visbreaking in the presence of oxygen. Aldehydes are organoleptic and can cause taste and odor issues in many applications. Accordingly, decreasing the production of aldehydes is a significant benefit. Generally, the concentration of oxygen may be reduced through the use of a vacuum or by replacing the oxygen with another gas, such an inert gas (e.g., nitrogen, helium, argon, krypton, neon, or xenon). The gas in the extruder may have an oxygen partial pressure of less than 3 psi, such as less than 2 psi, less than 1 psi, less than 0.5 psi, less than 0.1 psi, or even less than 0.01 psi. The gas in the extruder may be at least 80 mol. % of inert gas, such as at least 90 mol. %, at least 95 mol. %, at least 99 mol. %, at least 99.9 mol. %, at least 99.99 mol. %, or even at least 99.999 mol. % of inert gas, on the basis of the total moles of gas in the extruder.

[0043] In some embodiments, the visbreaking process may comprise a devolatization step. This devolatization may be carried out using any conventional devolatization means and methods, including, in non-limiting embodiments, use of extruder reactors and / or kneader reactors, and methods including, for example, direct separation, main evaporation bulk evaporation, steam stripping, and / or direct devolatization. In embodiments, the devolatization step may occur in the extruder during the extrusion visbreaking step or after the extrusion visbreaking step in a separate extruder. In embodiments, the devolatization process is driven by superheating the volatile component of the polymer melt, then subsequently exposing the melt to a rapid decompression. Devolatization may be performed on screw extruders, including single-screw or multi-screw extruders. A typical devolatization zone in a screw extruder consists of a portion of a screw that is partially filled, isolated by two sections that are filled with melt / solution. A stripping agent may be used in the extruder. In aspects, the stripping agent used in the extruder may be selected from the group consisting of: water, carbon dioxide, nitrogen, and a hydrocarbon gas. The stripping agent used in the extruder may be selected from the group consisting of water and carbon dioxide. The stripping agent used in the extruder may be water.86190-WO-PCT / DOW 86190 WO12

[0044] Devolatilizing the visbroken PCR ethylene-based polymer may produce a devolatilized visbroken PCR ethylene-based polymer. The devolatilized visbroken PCR ethylene-based polymer may have a concentration of volatile organic compounds (VOCs) at least 50 % lower, such as at least 75 %, at least 80 %, at least 85 %, at least 90 %, at least 95 %, or even at least 99 % lower than the concentration of VOCs in the visbroken PCR ethylenebased polymer as the visbroken PCR ethylene-based polymer exits the extrusion visbreaking process. In embodiments, no properties of the visbroken PCR ethylene-based polymer, other than the VOC concentration, may change by more than 10 %, such as more than 5 %, more than 3 %, or more than 1 % during the devolatization process.

[0045] The extrusion visbreaking may occur without the presence of reaction aids (such as catalysts, peroxides, or radical initiators). The reaction aids may include metal salts, carboxylates (such as metal carboxylates, such as stearates), metal halides (such as chlorides), metal oxides and zeolites. Non-limiting examples include zinc, aluminum, manganese, cobalt, chromium, iron, calcium and magnesium, carboxylates thereof, chlorides thereof, and oxides thereof. The concentration of the reaction aids may be from 0 wt. % to 1 wt. %, from 0 wt. % to 0.5 wt. %, from 0 wt. % to 0.1 wt. %, from 0 wt. % to 0.01 wt. %, from 0 wt. % to 0.001 wt. %, from 0 wt. % to 0.0001 wt. %, from 0 wt. % to 0.000001 wt. %, or even from 0 wt. % to 0.0000000001 wt. % on the basis of the total polymer weight of the at least one visbroken PCR ethylene-based polymer.

[0046] As described herein, the visbroken polyethylene PCR may be blended with the multimodal virgin polyethylene resin to produce the polyethylene blend. The polyethylene blend may have a density of from 0.950 g / cc to 0.955 g / cc, such as from 0.950 g / cc to 0.951 g / cc, from 0.951 g / cc to 0.952 g / cc, from 0.952 g / cc to 0.953 g / cc, from 0.953 g / cc to 0.954 g / cc, from 0.954 g / cc to 0.955 g / cc, or any combination of two or more of these ranges.

[0047] The polyethylene blend may have a melt index (h) from 0.7 dg / min and 3 dg / min, such as from 0.7 dg / min to 0.9 dg / min, from 0.9 dg / min to 1.1 dg / min, from 1.1 dg / min to 1.3 dg / min, from 1.3 dg / min to 1.5 dg / min, from 1.5 dg / min to 1.7 dg / min, from 1.7 dg / min to 1.9 dg / min, from 1.9 dg / min to 2.1 dg / min, from 2.1 dg / min to 2.3 dg / min, from 2.3 dg / min to 2.5 dg / min, from 2.5 dg / min to 2.7 dg / min, from 2.7 dg / min to 2.9 dg / min, and from 2.9 dg / min to 3.0 dg / min, or any combination of two or more of these ranges. The polyethylene blend may have a melt flow index (I21) from 70 dg / min to 200 dg / min, such as from 70 dg / min to 90 dg / min, from 90 dg / min to 110 dg / min, from 110 dg / min to 130 dg / min, from 13086190-WO-PCT / DOW 86190 WO13dg / min to 150 dg / min, from 150 dg / min to 170 dg / min, from 170 dg / min to 190 dg / min, and from 190 dg / min to 200 dg / min, or any combination of two or more of these ranges.

[0048] The polyethylene blend may have a I2 / I21 ratio of from 70 to 130, such as from 70 to 80, from 80 to 90, from 90 to 100, from 100 to 110, from 110 to 120, from 120 to 130, or any combination of two or more of these ranges

[0049] The polyethylene blend may have a (pooi / psoo) rheology ratio of 50 to 100, such as from 50 to 60, from 60 to 70, from 70 to 80, from 80 to 90, from 90 to 100, or any combination of two or more of these ranges. po oi is the shear viscosity at 190 °C at 0.01 rad / s and psoo is the shear viscosity at 190 °C at 500 rad / s. Generally, the rheology ratio characterizes the shear thinning behavior of the resin. A resin with a higher rheology ratio will generally flow better under high-shear rate conditions, such as during injection molding of caps.

[0050] An article may comprise the polyethylene blend. The article may have an environmental stress crack resistance (ESCR) (Cond B, 10% Igepal) F50 >150 hr, such as greater than 160 hr, greater than 170 hr, greater than 180 hr, greater than 190 hr, greater than 200 hr, greater than 210 hr, greater than 220 hr, greater than 230 hr, greater than 240 hr, or even greater than 250 hr.TEST METHODS

[0051] Density

[0052] Density is measured in accordance with ASTM D792, and expressed in grams / cubic centimeter (g / cc).

[0053] Melt Index (I2)

[0054] Melt Index (I2) is measured in accordance with ASTM D 1238-10 at 190 °C and 2.16 kg, Method B, and is expressed in dg / min eluted.

[0055] Melt Index

[0056] Melt Index (ho) is measured in accordance with ASTM D 1238-10 at 190 °C and 10 kg, Method B, and is expressed in dg / min eluted.

[0057] Melt Flow Index (I21)

[0058] Melt Flow Index (I21) is measured in accordance with ASTM D 1238-10 at 190 °C and 21.6 kg, Method B, and is expressed in dg / min eluted.

[0059] DMS Viscosity

[0060] po ol and psoo are determined according to the DMS viscosity test. For preparation, test samples are initially placed into a 1.5 in. diameter chase of thickness 3.10 mm and86190-WO-PCT / DOW 86190 WO14compression molded at a pressure of 25,000 lbs for 6.5 min. at 190 °C with a hydraulic press. After cooling to room temperature, the samples are extracted to await dynamic mechanical spectroscopy.

[0061] The DMS (dynamic mechanical spectroscopy) frequency sweep is conducted using 25 mm parallel plates at frequencies ranging from 0.1 to 100 rad / s. The test gap separating the plates is 1.8 mm. A strain that satisfies linear viscoelastic conditions is utilized. Each test is conducted under nitrogen atmosphere and isothermal conditions at 190 °C. To initiate the DMS test, the rheometer oven is first allowed to equilibrate at the desired testing temperature for at least 30 min before loading the sample into the test geometry. The sample is then equilibrated in the oven, with the door closed, for 1 min. The test gap is then set to 1.8 mm, and the sample is allotted 5 min. to relax the resulting normal force. Afterwards, the oven is quickly opened, and the sample is trimmed so that no bulge is present. The DMS measurement is then initiated after reclosing the oven. During the test, the shear elastic modulus (G’), viscous modulus (G”) and complex viscosity are measured.

[0062] All DMS frequency tests are conducted on either ARES-G2 or DHR-3 rheometers, both of which are manufactured by TA Instruments. Data analyses are conducted via TA Instruments TRIOS software.

[0063] Gel Permeation Chromatography (GPC)

[0064] Molecular weight data (e.g., Mw, Mn, and Mz) are determined by GPC. The chromatographic system utilized a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5). The autosampler oven compartment was set at 160° Celsius and the column compartment was set at 150° Celsius. The columns used were 4 Agilent “Mixed A” 30cm 20-micron linear mixed-bed columns. The chromatographic solvent used was 1,2,4 trichlorobenzene and contained 200 ppm of butylated hydroxytoluene (BHT). The solvent source was nitrogen sparged. The injection volume used was 200 microliters and the flow rate was 1.0 milliliters / minute.

[0065] Calibration of the GPC column set was performed with 21 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 and were arranged in 6 “cocktail” mixtures with at least a decade of separation between individual molecular weights. The standards were purchased from Agilent Technologies. The polystyrene standards were prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000, and 0.05 grams in 50 milliliters of solvent for86190-WO-PCT / DOW 86190 WO15molecular weights less than 1,000,000. The polystyrene standards were pre-dissolved at 80 °C with gentle agitation for 30 minutes then cooled and the room temperature solution is transferred cooled into the autosampler dissolution oven at 160 °C for 30 minutes. The polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).:

[0067] where M is the molecular weight, A has a value of 0.4049 and B is equal to 1.0.

[0068] A fifth order polynomial was used to fit the respective polyethylene-equivalent calibration points.

[0069] The total plate count of the GPC column set was performed with decane which was introduced into blank sample via a micropump controlled with the PolymerChar GPC-IR system. The plate count for the chromatographic system should be greater than 18,000 for the 4 Agilent “Mixed A” 30cm 20-micron linear mixed-bed columns.

[0070] Samples were prepared in a semi-automatic manner with the PolymerChar “Instrument Control” Software, wherein the samples were weight-targeted at 2 mg / ml, and the solvent (contained 200ppm BHT) was added to a pre nitrogen-sparged septa-capped vial, via the PolymerChar high temperature autosampler. The samples were dissolved for 2 hours at 160° Celsius under “low speed” shaking.

[0071] The calculations of Mn, Mw, and Mz were based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 2-4, using PolymerChar GPCOne™ software, the baseline-subtracted IR chromatogram at each equally-spaced data collection point (i), and the polyethylene equivalent molecular weight obtained from the narrow standard calibration curve for the point (i) from Equation 1.86190-WO-PCT / DOW 86190 WO16

[0075] In order to monitor the deviations over time, a flowrate marker (decane) was introduced into each sample via a micropump controlled with the PolymerChar GPC-IR system. This flowrate marker (FM) was used to linearly correct the pump flowrate (Flowrate(nominal)) for each sample by RV alignment of the respective decane peak within the sample (RV(FM Sample)) to that of the decane peak within the narrow standards calibration (RV(FM Calibrated)). Any changes in the time of the decane marker peak are then assumed to be related to a linear-shift in flowrate (Flowrate(effective)) for the entire run. After calibrating the system based on a flow marker peak, the effective flowrate (with respect to the narrow standards calibration) is calculated as Equation 5. Processing of the flow marker peak was done via the PolymerChar GPCOne™ Software. Acceptable flowrate correction is such that the effective flowrate should be within + / -0.5% of the nominal flowrate.

[0076] Flowrate(effective) = Flowrate(nominal) * (RV(FM Calibrated) / RV(FM Sample)) (EQ 5)

[0077] Strain Hardening Modulus

[0078] ISO 18488 standard is followed to determine strain hardening modulus. Resin pellets are compression molded and then conditioned at 120 °C for one hour followed by controlled cooling at a rate of 2 °C / min to RT. Tensile bars (dog bone shaped) are punched out of compression molded sheets. The tensile test is conducted at 80 °C and a non-contact extensometer is used to record the strain. As specified in ISO 18488, NHSM and true stress plot is used to calculate the slope between a draw ratio of 8 and 12. If failure occurred before a draw ratio of 12, then the draw ratio corresponding to the failure strain is considered as upper limit of the slope. If failure occurred before a draw ratio of 8.5, then the test is considered invalid. In the Examples, none of the samples failed before draw ratio of 8.5.

[0079] Environmental Stress Crack Resistance (ESCR)

[0080] To measure ESCR, the pellet samples were compression molded at 190 °C into a 0.075 inch sheet according to ASTM D4703 per Annex A.l Procedure C. The compression molded sheet was conditioned at 23 °C (+ / -2 °C) and 50 %RH (+ / -5 %RH) for at least 24 hours before the individual coupons were stamped out using an appropriate die. The coupon dimensions were 38 mm x 13 mm with a thickness of 1.90 mm. The coupons were further conditioned at 23 °C (+ / -2 °C) and 50 % RH (+ / -5 %RH) and tested at least 40 hours after compression molding and within 96 hours of compression molding. ESCR was measured according to ASTM-D 1693-01, Condition B. The sample thickness was measured to ensure86190-WO-PCT / DOW 86190 WO17they were within the ASTM 1693-01 specifications. Immediately prior to testing, the samples were notched to the required depth and then bent and loaded into the specimen holder. The holder was then placed in a test tube filled with a 10 percent, by volume, Tergitol NP-9 (Dow Chemical) aqueous solution, maintained at 50° C. The F50 failure time is reported.EXAMPLES

[0081] The following examples are provided to illustrate embodiments described in this disclosure and are not intended to limit the scope of this disclosure or its appended claims.

[0082] Materials:

[0083] The following materials were used in the examples.

[0084] Envision Ecoprime™ is a food safe, recycled resin with a density of 0.961 g / cc and a melt index (I?) of about 0.6, commercially available from Envision Plastics.

[0085] KWR 101-150 is a high density polyethylene PCR with a density of 0.960 g / cc and a melt index (I2) of 0.606 dg / min, commercially available from KW Plastics.

[0086] The KWR 101-150 (referred to as “PCR A)and Envision Ecoprime™ (referred to as “PCR B”) were used as starting materials for the visbreaking process. They were each visbroken in a ZSK 26 mm Twin Screw Extruder at 300 °C, 900 RPM and 10 pounds per hour of feed, resulting in PCR A -Visbroken and PCR B -Visbroken. The properties of the raw and visbroken polyethylene PCRs are provided in Table 1. PCR B was visbroken in at 600 RPM and 175 pounds per hour of feed, resulting in PCR B -Visbroken 2.Table 186190-WO-PCT / DOW 86190 WO18

[0087] Experimental resin HDPE A and comparative resin HDPE B were each used as multimodal virgin polyethylene resins. HDPE A and HDPE B can each be produced using a catalyst system including a procatalyst, UCAT™ J (commercially available from Univation Technologies, LLC, Houston, TX), and a cocatalyst, triethylaluminum (TEAL), in a gas phase polymerization process. The UCAT™ J catalyst is partially activated by contact at room temperature with an appropriate amount of a 50 percent mineral oil solution of tri-n-hexyl aluminum (TNHA). The catalyst slurry is added to a mixing vessel. While stirring, a 50 percent mineral oil solution of tri-n-hexyl aluminum (TNHA) is added at ratio of 0.17 moles of TNHA to mole of residual tetrahydro furan (THF) in the catalyst and stirred for at least 1 hour prior to use. Ethylene (C2) and 1 -hexene (Ce) are polymerized in two fluidized bed reactors. Each polymerization is continuously conducted, after equilibrium is reached, under the respective conditions, as shown below in Tables 1. Polymerization is initiated in the first reactor by continuously feeding the catalyst and cocatalyst (trialkyl aluminum, specifically tri ethyl aluminum or TEAL) into a fluidized bed of polyethylene granules, together with ethylene, hydrogen, and, 1 -hexene. The resulting polymer, mixed with active catalyst, is withdrawn from the first reactor, and transferred to the second reactor, using second reactor gas as a transfer medium. The second reactor also contains a fluidized bed of polyethylene granules. Ethylene, hydrogen and hexene are introduced into the second reactor, where the gases come into contact with the polymer and catalyst from the first reactor. Inert gases, nitrogen and isopentane, make up the remaining pressure in both the first and second reactors. In the second reactor, the cocatalyst (TEAL) is again introduced. The final product blend is continuously removed. Table 2 lists the polymerization conditions for HDPE A and HDPE B.

[0088] The product is combined with 1000 ppm calcium stearate and 1500 ppm Irgafos™ 168, and fed to a continuous mixer (Kobe Steel, Ltd. LCM-100 continuous mixer), which is closed coupled to a gear pump, and equipped with a melt filtration device and an underwater pelletizing system. The properties of these resins are provided in Table 3.Table 286190-WO-PCT / DOW 86190 WO19Table 386190-WO-PCT / DOW 86190 WO20

[0089] Polyethylene Blends

[0090] The multimodal virgin polyethylene resin described in Table 3 was then blended with the visbroken polyethylene PCRs described in Table 1 in varying ratios, as is shown in Table 4. As can be seen in Table 4, the comparative examples CE-B to CE-F are unable to meet the desired performance characteristics (processability and ESCR) for use in caps and closures applications. In contrast, examples E-l to E-2 incorporate large amounts of PCR while being highly processable and meeting required ESCR parameters.Table 4>86190-WO-PCT / DOW 86190 WO21

Claims

86190-WO-PCT / DOW 86190 WO22CLAIMS1. A polyethylene blend comprising:(a) 35 wt. % to 75 wt. % of a multimodal virgin polyethylene resin comprising from 45 wt. % to 60 wt. % of a high molecular weight (HMW) fraction and from 40 wt. % to 55 wt. % of a low molecular weight (LMW) fraction, wherein:the HMW fraction has a density from 0.910 g / cc to 0.920 g / cc and a melt flow index (I21) from 0.5 dg / min to 1.5 dg / min;the LMW fraction has a higher density and a lower weight average molecular weight (Mw) than the HMW; andthe multimodal virgin polyethylene resin has a density from 0.940 g / cc to 0.950 g / cc; and(b) 25 wt. % to 65 wt. % of a visbroken polyethylene PCR with I2 between 7 dg / min and 15 dg / min,wherein the polyethylene blend has I2 from 0.7 dg / min and 3 dg / min.

2. The polyethylene blend of claim 1, wherein the polyethylene blend has a melt flow index (I21) from 70 dg / min to 200 dg / min and a density from 0.950 g / cc to 0.955 g / cc.

3. The polyethylene blend of claim 1 or 2, wherein the multimodal virgin polyethylene resinhas a melt index (I2) from 0.1 dg / min and 1.0 dg / min and a melt flow index (I21) of from 20 dg / min to 50 dg / min.

4. The polyethylene blend of any one of claims 1 to 3, wherein the multimodal virgin polyethylene resin has an I21 / I2 of from 70 to 150.

5. The polyethylene blend of any one of claims 1 to 4, wherein the multimodal virgin polyethylene resin has 800,000 g / mol <Mz < 2,000,000 g / mol and an Mz / Mn from 50 to 150.

6. The polyethylene blend of any one of claims 1 to 5, wherein:the visbroken polyethylene PCR has a rheology ratio (r|o. I / T]IOO) from 3 to 20, wherein r|o.i is the shear viscosity measured at 0.1 radians / second and rpoo is the shear viscosity measured at 100 radians / second;86190-WO-PCT / DOW 86190 WO23(b) the visbroken polyethylene PCR has an I21 / I2 of from 5 to 20;or both.

7. The polyethylene blend of any one of claims 1 to 6, wherein the multimodal virgin polyethylene resin is a gas phase, Ziegler-Natta catalyzed polyethylene.

8. The polyethylene blend of any one of claims 1 to 8, wherein the multimodal virgin polyethylene resin has a strain hardening modulus of greater than 55 MPa.

9. The polyethylene blend of any one of claims 1 to 8, wherein the polyethylene blend has a (r|ooi / r|5oo) rheology ratio of 50 to 100 wherein r|o.oi is the shear viscosity at 190 °C at 0.01 rad / s and psoo is the shear viscosity at 190 °C at 500 rad / s.

10. An article comprising the polyethylene blend of any one of claims 1 to 9.

11. The article of claim 10, wherein the article has an environmental stress crack resistance (ESCR) F50 >150 hr.

12. A method of making the polyethylene blend of any one of claims 1 to 9 comprising:visbreaking a polyethylene PCR having a melt index (I2) of less than 1.0 dg / min to increase the melt index (I2) and thereby produce the visbroken polyethylene PCR; and blending the visbroken polyethylene PCR with virgin ethylene based polymer to produce the polyethylene blend.

13. The method of claim 12, wherein the polyethylene PCR prior to visbreaking has an I2 from 0.3 dg / min to 1.0 dg / min.

14. The method of claim 12 or 13, wherein the visbroken polyethylene PCR has a rheology ratio (po.i / pioo) of at most 20% of the polyethylene PCR prior to visbreaking.86190-WO-PCT / DOW 86190 WO2415. The method of any one of claims 12 to 14, wherein the visbroken polyethylene PCR has a tanSo i at least 15 times the tanSo i of the polyethylene PCR prior to visbreaking, and the visbroken polyethylene PCR has a tanbo i between 5 to 90.

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