Extrusion visbreaking

Abstract

A visbreaking process may comprise: extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene-based polymer resin having a density of 0.900 to 0.975 g / cc and a melt index (I2) less than 3 dg / min at a temperature of at least 250 °C to produce a visbroken PCR ethylene-based polymer having an I2 at least 3 times greater than the at least one base PCR ethylene-based polymer resin. The at least one base PCR ethylene-based polymer resin may be extrusion visbroken at a screw speed of at least 350 revolutions per minute (RPM), a specific energy input (SEI) of from 0.4 kW-hr / kg to 2.0 kW-hr / kg, or both.

Description

85545-WO-PCT / DOW 85545 WO EXTRUSION VISBREAKING CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 579,105 filed January 30, 2023, the contents of which are incorporated in their entirety herein. FIELD

[0002] The present disclosure relates to polymer processing, and more specifically to polymer visbreaking. BACKGROUND

[0003] Recycling of plastic waste is one of the most important sustainability issues of our time. Non-woven materials are an important application for recycled plastic packaging, such as post- consumer recycled (PCR) resins. However, present PCRs are not suitable for producing food grade products as food grade PCRs are of limited availability. Those food grade PCRs, which are available are generally obtained from recycled, blow molded milk jugs. These blow molded materials have a melt index (MI) of less than 1 dg / min while fiber spinning, which is used to produce non-woven materials, requires a significantly higher melt index. Similarly, the melt index of these PCRs is too low for use in injection molding or stretch wrap production.

[0004] Accordingly, methods of converting low melt index PCRs into high melt index PCRs are desired. BRIEF SUMMARY

[0005] Embodiments of the present disclosure meet this need by providing a visbreaking process comprising extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene-based polymer resin at a temperature of at least 250 °C and a screw speed of at least 350 revolutions per minute (RPM) and / or a specific energy input (SEI) of from 0.4 kW-hr / kg polymer to 2.0 kW- hr / kg polymer to produce a visbroken PCR ethylene-based polymer.

[0006] Embodiments of the present disclosure are directed to a visbreaking process which may comprise: extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene-85545-WO-PCT / DOW 85545 WO based polymer resin having a density of 0.900 to 0.975 g / cc and a melt index (I2) less than 3 dg / min at a temperature of at least 250 °C and a screw speed of at least 350 revolutions per minute (RPM) to produce a visbroken PCR ethylene-based polymer having an I2 at least 3 times greater than the at least one base PCR ethylene-based polymer resin.

[0007] Embodiments of the present disclosure are directed to a visbreaking process which may comprise: extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene- based polymer resin having a density of 0.900 to 0.975 g / cc and a melt index (I2) less than 3 dg / min at a temperature of at least 250 °C and specific energy input (SEI) of from 0.4 kW- hr / kg to 2.0 kW-hr / kg to produce a visbroken PCR ethylene-based polymer having an I2 at least 3 times greater than the at least one base PCR ethylene-based polymer resin.

[0008] 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. DETAILED DESCRIPTION

[0009] "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.

[0010] “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 anhydride functional groups. Put another way, the copolymers described herein comprise at least two structurally different85545-WO-PCT / DOW 85545 WO 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.

[0011] "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).

[0012] 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.

[0013] The term “LDPE” may also be referred to as “high pressure ethylene polymer” or “highly branched polyethylene” and is defined to mean that the polymer is partly or entirely homopolymerized or copolymerized in autoclave or tubular reactors at pressures above 14,500 psi (100 MPa) with the use of free-radical initiators, such as peroxides (see for example U.S. Pat. No. 4,599,392, incorporated herein by reference).

[0014] “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,85545-WO-PCT / DOW 85545 WO 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).

[0015] “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 140217.8.1.1.

[0016] 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.

[0017] 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, 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) does not include materials previously used in a consumer or industry85545-WO-PCT / DOW 85545 WO 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. Post-consumer resin is defined in ISO 140217.8.1.1.

[0018] 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.

[0019] A visbreaking process may comprise extrusion visbreaking at least one base post- consumer recycled (PCR) ethylene-based polymer resin to produce a visbroken PCR ethylene- based polymer. Extrusion visbreaking is a thermal cracking process conducted in an extruder under shear to reduce the viscosity of a polymer resin.

[0020] The base PCR ethylene-based polymer resin may comprise at least 51 wt. % of post- consumer material, such as at least 75 wt. %, at least 80 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of post-consumer material. Generally, it has been found that PCR resins are more susceptive to extrusion visbreaking than virgin resins. Without being limited by theory, this is believed to be due to the more complex thermal histories of PCR resins, the additional thermal histories of PCR resins, differences in anti-oxidants, and differences in the quantity of unsaturated compounds.

[0021] The base PCR ethylene-based polymer resin may comprise an LDPE, an HDPE, an LLDPE, or a blend thereof. In embodiments, the base PCR ethylene-based polymer resin may comprise at least 50 wt. %, at least 75 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of an LDPE, an HDPE, an LLDPE, or a blend thereof.

[0022] The base PCR ethylene-based polymer resin may have a density of 0.900 g / cc to 0.975 g / cc. In embodiments, the base PCR ethylene-based polymer resin may have a density of from 0.900 g / cc to 0.970 g / cc, from 0.900 g / cc to 0.960 g / cc, from 0.900 g / cc to 0.950 g / cc, from 0.900 g / cc to 0.940 g / cc, from 0.900 g / cc to 0.930 g / cc, from 0.910 g / cc to 0.975 g / cc, from 0.920 g / cc to 0.975 g / cc, from 0.930 g / cc to 0.975 g / cc, from 0.930 g / cc to 0.970 g / cc, or any subset thereof.85545-WO-PCT / DOW 85545 WO

[0023] The base PCR ethylene-based polymer resin may have a melt index (I2) of less than 3 dg / min. In embodiments, the base PCR ethylene-based polymer resin may have a melt index (I2) of less than 2.8 dg / min, less than 2.6 dg / min, less than 2.4 dg / min, less than 2 dg / min, less than 1.5 dg / min, less than 1 dg / min, less than 0.8 dg / min, less than 0.6 dg / min, from 0.1 dg / min to 3 dg / min, from 0.1 dg / min to 1 dg / min, from 0.3 dg / min to 0.8 dg / min, from 2 dg / min to 3 dg / min, from 2.2 dg / min to 2.5 dg / min, or any subset thereof.

[0024] The at least one base PCR ethylene-based polymer resin may have a melt index (I10) of less than 50 dg / min. In embodiments, the at least one base PCR ethylene-based polymer resin may have a melt index (I10) of less than 40 dg / min, less than 30 dg / min, less than 20 dg / min, less than 15 dg / min, less than 12 dg / min, from 5 dg / min to 50 dg / min, from 5 dg / min to 40 dg / min, from 5 dg / min to 30 dg / min, from 5 dg / min to 20 dg / min, from 5 dg / min to 15 dg / min, from 5 dg / min to 12 dg / min, from 8 dg / min to 50 dg / min, from 8 dg / min to 30 dg / min, from 8 dg / min to 15 dg / min, or any subset thereof.

[0025] The at least one base PCR ethylene-based polymer resin may have a yellowness index (YI) of less than 40, such as less than 30, less than 20, less than 15, less than 5, from 5 to 40, from 5 to 30, from 5 to 20, from 10 to 40, from 10 to 30, from 10 to 20, from 15 to 20, or any subset thereof.

[0026] In embodiments, the at least one base PCR ethylene-based polymer resin may have an Mw / Mn, measured by GPC in the “Test Methods” section, of less than 20, such as less than 15, less than 10, less than 8, less than 5, from 1 to 20, from 1 to 15, from 1 to 10, from 1 to 5, from 3 to 20, from 3 to 15, from 3 to 10, from 3 to 5, from 8 to 10, or any subset thereof..

[0027] The base PCR ethylene-based polymer resin is subjected to extrusion visbreaking 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 feedblocks, multi-layer feedblocks, multi-vaned or multi-manifold dies such as a 3-layer vane die. In embodiments, the extrusion visbreaking utilizes a twin screw extruder. The at least one 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 at least one base PCR ethylene-based polymer resin may comprise at least 80 wt. % of the material introduced into85545-WO-PCT / DOW 85545 WO 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.

[0028] Without being limited by theory, the extrusion visbreaking process may introduce heat and mechanical energy (through the extruder) into the at least one base PCR ethylene-based polymer resin. Generally, this energy may cause chain scission of the ethylene-based polymers in the at least one 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 may be calculated according to the equation ^^ ^^ ^^ ൌ units ofkW-hr / kg.

[0029] 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 a SEI below this range may not cause sufficient chain scission to sufficiently increase the melt indices of the base ethylene-based 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-hr / 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.

[0030] 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 35085545-WO-PCT / DOW 85545 WO °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.

[0031] 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 cause sufficient chain scission to sufficiently increase the melt indices of the base ethylene-based 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.

[0032] 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 110 sec to 200 sec, from 130 sec to 200 sec, from 150 sec to 200 sec, from 170 sec to 200 sec, from 50 sec to 180 sec, from 70 sec to 160 sec, from 90 sec to 140 sec, from 110 sec to 130 sec, or any subset thereof.

[0033] 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 including food storage containers 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, such85545-WO-PCT / DOW 85545 WO 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.

[0034] In some embodiments, the visbreaking process may comprise at least one devolatization step. This devolatilization may be carried out using any conventional devolatilization 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 devolatilization. In embodiments, the at least one 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 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.

[0035] 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 ethylene-based 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.

[0036] 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,85545-WO-PCT / DOW 85545 WO 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 base PCR ethylene- based polymer resin.

[0037] The visbroken PCR ethylene-based polymer may have an I2at least 3 times greater than the I2of the at least one base PCR ethylene-based polymer resin. In embodiments, the visbroken PCR ethylene-based polymer may have an I2 at least 4 times greater, at least 5 times greater, at least 7 at least 8 times greater, at least 10 times greater, at least 12.5 times greater, at least 15 times greater, at least 17.5 times greater, at least 20 times greater, from 3 times to 50 times greater, from 5 times greater to 50 times greater, from 7 times greater to 50 times greater, from 10 times greater to 50 times greater, from 15 times greater to 50 times greater, from 18 times greater to 50 times greater, or any subset thereof greater than the I2of the at least one base PCR ethylene-based polymer resin.

[0038] The I2 of the visbroken PCR ethylene-based polymer may be at least 2 dg / min. In embodiments, the I2of the visbroken PCR ethylene-based polymer may be at least 3 dg / min, at least 4 dg / min, at least 5 dg / min, at least 8 dg / min, at least 10 dg / min, a from 2 dg / min to 50 dg / min, from 2 dg / min to 25 dg / min, from 2 dg / min to 15 dg / min, from 6 dg / min to 15 dg / min, from 8 dg / min to 15, from 10 dg / min to 20 dg / min, or any subset thereof.

[0039] The visbroken PCR ethylene-based polymer may have an I10at least 5 times greater than the I10 of the at least one base PCR ethylene-based polymer resin. In embodiments, the visbroken PCR ethylene-based polymer may have an I10at least 6 times greater, at least 7 times greater, at least 8 times greater, at least 9 times greater, from 5 times greater to 20 times greater, from 8 times greater to 20 times greater, from 5 times greater to 15 times greater, from 8 times greater to 15 times greater, or any subset thereof greater than the I10 of the at least one base PCR ethylene-based polymer resin.

[0040] The visbroken PCR ethylene-based polymer may have an I10 of at least 16 dg / min, such as at least 20 dg / min, at least 30 dg / min, at least 50 dg / min, at least 75 dg / min, at least 80 dg / min, at least 90 dg / min, at least 95 dg / min, at least 100 dg / min, from 20 dg / min to 200 dg / min, from85545-WO-PCT / DOW 85545 WO 40 dg / min to 200 dg / min, from 80 dg / min to 200 dg / min, from 90 dg / min to 200 dg / min, from 40 dg / min to 160 dg / min, from 80 dg / min to 150 dg / min, from 90 dg / min to 120 dg / min, from 95 dg / min to 110 dg / min, or any subset thereof.

[0041] The visbroken PCR ethylene-based polymer may have a Yellowness index (YI) less than 4 times a YI of the at least one base PCR ethylene-based polymer resin. In embodiments, the YI of the visbroken PCR ethylene-based polymer may be less than 3 times, less than 2 times, less than 1.5 times, or even less than the YI of the at least one base PCR ethylene-based polymer resin.

[0042] The visbroken PCR ethylene-based polymer may have a YI of less than 50, such as less than 40, less than 30, less than 20, less than 15, or even less than 10.

[0043] The visbroken ethylene-based polymer may have a color coordinate (L) value of less than the L value of the at least one base PCR ethylene-based polymer resin, such as less than 100 %, less than 95 %, less than 90 %, less than 85 %, less than 80 %, or less than 75 % of the L value of the at least one base PCR ethylene-based polymer resin.

[0044] The visbroken PCR ethylene-based polymer may have a color coordinate (L) value of less than 100, such as less than 90, less than 80, less than 75, less than 70, less than 65, or less than 60.

[0045] The visbroken ethylene-based polymer may have an Mw / Mn of less than the Mw / Mn of the at least one base PCR ethylene-based polymer resin. Generally, visbreaking results in a decrease of the Mw / Mn of the polymer. In embodiments, the visbroken ethylene-based polymer may have an Mw / Mn of less 100 %, less than 97.5 %, less than 95 %, less than 90 %, less than 85 %, less than 80 %, less than 70 %, less than 60 %, or even less than 50 % of an Mw / Mn of the at least one base PCR ethylene-based polymer resin.

[0046] The visbroken PCR ethylene-based polymer may have an Mw / Mn of less than 10, such as less than 8, less than 6, less than 4, or even less than 2.

[0047] An article may comprise the visbroken PCR ethylene-based polymer. In embodiments, the article may be a cast stretch film or a blown film. In embodiments, the article may be a food package. TEST METHODS85545-WO-PCT / DOW 85545 WO

[0048] Melt Flow Index

[0049] Melt Flow Index (also referred to herein as “melt index”) (I2) is measured in accordance with ASTM D 1238-10 at 190 Celsius and 2.16 kg, Method B, and is expressed in grams eluted / 10 minutes (dg / min).

[0050] Melt Index (I10) is measured in accordance with ASTM D 1238-10 at 190 Celsius and 10 kg, Method B, and is expressed in grams eluted / 10 minutes (dg / min).

[0051] Density

[0052] Density is measured according to ASTM D792.

[0053] Yellowness Index (YI)

[0054] Yellowness Index (YI) values were determined on pellets using ASTM D6290-05 (Method Title: Standard Test Method for Color Determinations of Plastic Pellets). The yellowness index (YI) is an instrumental measurement, using a BYK-Gardner Model 9000 spectrophotometer with sample rotator of the degree of yellowness (or change of degree of yellowness) under daylight illumination of homogeneous, nonfluorescent, nearly-colorless transparent or nearly-white translucent or opaque plastics. The measurement was made on pellets (250 g) and based on values obtained with a colorimeter. The test method is applicable to the color analysis of plastic pellets. Color in the polymer was primarily due to organic impurities. Inorganic impurities may also affect the color.

[0055] Color Coordinate (L)

[0056] Color coordinate (L) values were determined on pellets using ASTM D6290-05 (Method Title: Standard Test Method for Color Determinations of Plastic Pellets).

[0057] Gel Permeation Chromatography

[0058] 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 160º Celsius and the column compartment was set at 150º 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 contained85545-WO-PCT / DOW 85545 WO 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.

[0059] 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 for molecular weights less than 1,000,000. The polystyrene standards were pre-dissolved at 80 ºC with gentle agitation for 30 minutes then cooled and the room temperature solution is transferred cooled into the autosampler dissolution oven at 160ºC 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)).:

[0060] ^^^^^^௬^௧^௬^^^^ൌ ^^ ൈ ൫ ^^^^^௬^௧௬^^^^൯ (EQ1)

[0061] where M is the molecular weight, A has a value of 0.4049 and B is equal to 1.0.

[0062] A fifth order polynomial was used to fit the respective polyethylene-equivalent calibration points.

[0063] 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.

[0064] 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 160º Celsius under “low speed” shaking.85545-WO-PCT / DOW 85545 WO

[0065] 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.

[0069] 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.

[0070] Flowrate(effective) = Flowrate(nominal) * (RV(FM Calibrated) / RV(FM Sample)) (EQ 5)

[0071] DSC

[0072] Differential Scanning Calorimetry results are determined using a TAI model Q1000 DSC equipped with an RCS cooling accessory and an autosampler. A nitrogen purge85545-WO-PCT / DOW 85545 WO gas flow of 50 ml / min is used. The sample is pressed into a thin film and melted in the press at about 175° C. and then air-cooled to room temperature (25° C.) 3-10 mg of material is then cut into a 6 mm diameter disk, accurately weighed, placed in a light aluminum pan (ca 50 mg), and then crimped shut. The thermal behavior of the sample is investigated with the following temperature profile. The sample is rapidly heated to 180° C. and held isothermal for 3 minutes in order to remove any previous thermal history. The sample is then cooled to −40° C. at 10° C. / min cooling rate and held at −40° C. for 3 minutes. The sample is then heated to 150° C. at 10° C. / min. heating rate. The cooling and second heating curves are recorded.

[0073] The DSC melting peak is measured as the maximum in heat flow rate (W / g) with respect to the linear baseline drawn between −30° C. and end of melting. The heat of fusion is measured as the area under the melting curve between −30° C. and the end of melting using a linear baseline.

[0074] Unless otherwise stated, melting point(s) (Tm) of each polymer is determined from the second heat curve obtained from DSC, as described above (peak Tm). The crystallization temperature (Tc) is measured from the first cooling curve (peak TC).

[0075] Antioxidant Levels

[0076] To determine antioxidant levels, about 0.5 grams of sample is weighed (and recorded to the nearest 0.0001-g) into a 125 mL glass bottle. A PTFE-coated stir bar is added to the bottle and 25 mL of 0.04% triethyl phosphite in o-xylene using a Gerstel MPS. The bottle is placed on a heated stirrer for 30 minutes at 130°C with stirring. After 30 minutes, the bottle is removed to cool the solution at room temperature with stirring for at least 2 hours. The polymer is further precipitated with addition of 50 mL of methanol to the bottle using a Gerstel MPS. The solution is stirred during this addition. The solution is stirred for an additional 2 hours. After 2 hours of stirring, the stirrer is turned off and the solids are allowed to settle. An aliquot of solution is transferred into a 2 mL glass autosampler vial. The vial is placed on the liquid chromatograph for analysis. The samples and standard solutions are analyzed using a reversed phase liquid chromatographic method with a UV / Vis absorbance detector. Concentrations in extracts are determined using an external standard calibration procedure. The data for AOs in resin are reported in parts per million (ppm; µg / g).85545-WO-PCT / DOW 85545 WO

[0077] DMS Viscosity

[0078] For preparation, test samples are initially placed into a 1.5 in. diameter chase of thickness 3.10 mm and compression 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.

[0079] The DMS (dynamic mechanical spectroscopy) frequency sweep is conducted using 25mm 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.

[0080] 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.

[0081] Aldehydes

[0082] Aldehyde content is measured using1H NMR.

[0083] Samples were prepared by adding ~0.1 g of sample to 3.25 g of 50 / 50 by weight 1,1,2,2-tetrachlorethane-d2 / perchloroethylene (TCE / PCE) containing 0.001 M Cr(AcAc)3 relaxation agent and about 75 ppm butylated hydroxytoluene (BHT) as an antioxidant, in a Norell 1001-7 10mm NMR tube. The solvent mixture is stored over 4A Molecular Sieve. The samples were capped, sealed with Teflon tape and then heated and vortexed at about 120 to 140 °C to dissolve and ensure homogeneity.

[0084] Each1H NMR spectrum was acquired with a 10 mm cryoprobe, at 120 °C, on a Bruker AVANCE 600 MHz spectrometer. Two experiments are run to measure aldehydes: a85545-WO-PCT / DOW 85545 WO control and a double presaturation experiment. The control spectrum is a quantitative1H spectrum acquired with the zg pulse sequence, NS=16. In the control spectrum, the signal from residual1H of TCE-d2 is set to 100 and the integral from about -0.5 to 3 ppm is used as the signal from the whole polymer. This integral divided by 2 provides the total number of polymer carbons. The double presaturation spectrum is acquired with 64 scans, and the signal from residual1H of TCE-d2 is also set to 100. The aldehydes peak(s) in the region from 9.5 to 10 ppm are integrated, and aldehydes per 100,000 polymer carbons (using the total carbons measured in the control spectrum) are calculated.

[0085] Volatiles

[0086] Total concentration of volatile organic compounds (VOCs) are determined using a full evaporation head space gas chromatography (FE-HS / GC) process.

[0087] VOC concentrations are determined in polyethylene using headspace gas chromatography with a flame ionization detector. One pellet of resin, which weighs 0.04 ± 0.02 g, and 0.005 g of Irganox 1330 are placed into a headspace vial and sealed. The VOCs are sampled using a headspace analyzer with the sample equilibrated at 190 °C for 120 min. A calibration solution is prepared with process solvent in methylene chloride. A 10- µL aliquot of the calibration solution is transferred using an electronic digital syringe into the headspace vial and the vial is immediately sealed with a cap using the crimping tool. The sum of peak area for the solvent peak in sample and calibration solution is summed. Quantitation is performed using an external standard calibration procedure. The data are reported as parts per million (ppm; µg / g). EXAMPLES

[0088] Materials:

[0089] The following materials were used in the examples.

[0090] DMDATM6200 is an HDPE with a density of 0.953 g / cc and a melt index (I2) of 0.38 dg / min, commercially available from Dow Inc., Midland MI.

[0091] DMDATM6400 is an HDPE with a density of 0.961 g / cc and a melt index (I2) of 0.80 dg / min, commercially available from Dow Inc., Midland MI.85545-WO-PCT / DOW 85545 WO

[0092] KWR101-150 is a recycled HDPE resin with a density of 0.960 g / cc and a melt index (I2) of 0.6 dg / minutes, commercially available from KW Plastics, Troy, AL.

[0093] Envision EcoprimeTMis a food safe, recycled resin with a density of 0.961 g / cc and a melt index (I2) of 0.6, commercially available from Envision Plastics.

[0094] Avangard 100 is a recycled resin with a density of 0.917 g / cc and a melt index (I2) of 2.32 dg / minutes, commercially available from Avangard Innovative.

[0095] IrganoxTM1010 is a sterically hindered primary phenolic antioxidant stabilizer, commercially available from BASF Corporation.

[0096] IrganoxTM1076 is a sterically hindered primary phenolic antioxidant stabilizer, commercially available from BASF Corporation.

[0097] IrgafosTM168 is a tris(2,4-di-tert-butylphenyl)phosphite antioxidant stabilizer.

[0098] MEK refers to methyl ethyl ketone.

[0099] Example 1

[0100] Four samples were subjected to extrusion visbreaking. The base resins CE-A to CE-D are described in Table 1. As is shown in table 1, each of the samples included the base resin (described as “material”) and residues of processing aids introduced to the base resins in their primary applications (e.g. Irganox 1010, Irganox 1076, Irgafos 168, oxidized I-168). Table 1

[0101] The base samples were then subjected to extrusion visbreaking in a ZSK 26 mm twin screw extruder using a TPV screw. The base samples were visbroken at 300 °C, 900 RPM, 1085545-WO-PCT / DOW 85545 WO lbs / hr feed, an average residence time of 81s, and a specific energy input (SEI) of 1.55 – 1.77 kW- hr / kg. It should be noted that CE-E is visbroken CE-A, CE-F is visbroken CE-B, EX-1 is visbroken CE-C, and EX-2 is visbroken CE-D. The melt indices (I2) of the base and visbroken samples are shown in Table 2. Table 2

[0102] Example 2

[0103] All samples in Table 2 were subjected to the yellowness testing as described in the Test Methods section. Results are given in Table 3. Table 3

[0104] The samples were subjected to rheology testing according to the same methods as CE- A to CE-I. The results are shown in Table 4.85545-WO-PCT / DOW 85545 WO Table 4

[0105] The samples were then subjected to conventional gel permeation chromatography. Results are shown in Table 5. Table 5

[0106] Example 3

[0107] CE-D (Envision Ecoprime) was used as the base post-consumer recycled (PCR) ethylene-based polymer resin for extrusion visbreaking to study the impact of oxygen removal and additives on the visbreaking process. Process conditions, reactants, and characterization results are shown in Table 6. Table 685545-WO-PCT / DOW 85545 WO

[0108] As can be seen in Table 6, nitrogen blanketing reduced the production of aldehydes by nearly 50 %, even without the use of antioxidants.

[0109] The study was repeated with Avangard 100 to study the impact of oxygen removal and additives on the visbreaking process. Process conditions, reactants, and characterization results are shown in Table 7. Table 785545-WO-PCT / DOW 85545 WO 22

[0110] Example 4

[0111] Further samples of the Envision Ecoprime and AV100 were subjected to extrusion visbreaking in a ZE-42 x 48D BluePower twin screw extruder. The PCR samples were visbroken at 300 °C, under different processing conditions described in Table 8. The results are shown in Table 9. The melt indices (I2) of the starting and visbroken samples are shown in Table 2.85545-WO-PCT / DOW 85545 WO Table 8Table 9

Claims

85545-WO-PCT / DOW 85545 WO CLAIMS 1. A visbreaking process comprising: extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene-based polymer resin having a density of 0.900 to 0.975 g / cc and a melt index (I2) less than 3 dg / min at a temperature of at least 250 °C and a screw speed of at least 350 revolutions per minute (RPM) to produce a visbroken PCR ethylene-based polymer having an I2 at least 3 times greater than the at least one base PCR ethylene-based polymer resin.

2. A visbreaking process comprising: extrusion visbreaking at least one base post-consumer recycled (PCR) ethylene-based polymer resin having a density of 0.900 to 0.975 g / cc and a melt index (I2) less than 3 dg / min at a temperature of at least 250 °C and specific energy input (SEI) of from 0.4 kW-hr / kg to 2.0 kW-hr / kg to produce a visbroken PCR ethylene-based polymer having an I2at least 3 times greater than the at least one base PCR ethylene-based polymer resin.

3. The process of claim 1, wherein the screw speed is 450 RPM to 1100 RPM.

4. The process of any preceding claim, wherein the extrusion visbreaking utilizes a twin screw extruder.

5. The process of any preceding claim, wherein the visbreaking process includes at least one devolatilization step.

6. The process of any preceding claim, wherein the extrusion visbreaking occurs in the absence of oxygen.

7. The process of any preceding claim, wherein the extrusion visbreaking has a residence time of from 30 sec to 200 sec.

8. The process of any one of claims 1 or 3-7, wherein the extrusion visbreaking has a specific energy input of from 0.4 kW-hr / kg to 2.0 kW-hr / kg.

9. The process of any preceding claim, wherein the at least one base PCR ethylene-based polymer resin comprises an LDPE, an HDPE, an LLDPE, or a blend thereof.

10. The process of any preceding claim, wherein the melt index (I2) of the at least one base PCR ethylene-based polymer resin is less than 1 dg / min, and the density of the at least one base PCR ethylene-based polymer resin is from 0.940 to 0.970 g / cc.85545-WO-PCT / DOW 85545 WO 11. The process of claim 10, wherein the melt index (I2) of the visbroken PCR ethylene-based polymer is at least 2 dg / min, and a melt index (I10) of the visbroken PCR ethylene-based polymer is at least 16 dg / min.

12. The process of any of claims 1-9, wherein the melt index (I2) of the at least one base PCR ethylene-based polymer resin is from 1 to 3 dg / min, and the density of the at least one base PCR ethylene-based polymer resin is from 0.900 to 0.930 g / cc.

13. The process of claim 12, wherein the melt index (I2) of the visbroken PCR ethylene-based polymer is at least 5 dg / min, and the melt index (I10) of the visbroken PCR ethylene-based polymer is at least 30 dg / min.

14. The process of any preceding claim, wherein the visbroken PCR ethylene-based polymer has a Yellowness index (YI) of less than 40, when measured according to ASTM D6290-05.

15. The process of any preceding claim, wherein the visbroken PCR ethylene-based polymer has an Mw / Mn, as measured by GPC, of less than 8.

16. A visbroken PCR ethylene-based polymer produced from the process of any preceding claim.

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