Extrusion visbreaking

Abstract

A visbreaking method can include: extrusion visbreaking at a temperature of at least 250 DEG C of at least one basic post consumer recycle (PCR) ethylene-based polymer resin having a density of 0.900 g / cc to 0.975 g / cc and a melt index (I2) of less than 3 dg / min to produce a visbreaking PCR ethylene-based polymer, the viscosity-reduced PCR ethylene-based polymer has an I2 that is at least 3 times the I2 of the at least one base PCR ethylene-based polymer resin. The extrusion visbreaking of at least one base PCR ethylene-based polymer resin may be performed at a screw speed of at least 350 revolutions per minute (RPM), at a specific energy input (SEI) of 0.4 kW-hr / kg to 2.0 kW-hr / kg, or both.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 579,105, filed on January 30, 2023, the contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to polymer treatment, and more specifically to polymer viscosity reduction. Background Technology

[0003] Recycling plastic waste is one of the most important sustainability issues of our time. Nonwoven materials are an important application for recycled plastic packaging, such as post-consumer recycled (PCR) resins. However, current PCRs are unsuitable for producing food-grade products due to the limited availability of food-grade PCRs. Those available food-grade PCRs are typically 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 for producing nonwoven materials requires a significantly higher melt index. Similarly, the melt index of these PCRs is too low for injection-molded or stretch packaging production.

[0004] Therefore, a method is needed to convert low melt index PCR into high melt index PCR. Summary of the Invention

[0005] Embodiments of this disclosure meet this need by providing a viscosity reduction method comprising extruding and reducing the viscosity of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin at a temperature of at least 250°C and a screw speed of at least 350 rpm and / or a specific energy input (SEI) of 0.4 kW-hr / kg polymer to 2.0 kW-hr / kg polymer to produce a viscous PCR ethylene-based polymer.

[0006] Embodiments of this disclosure relate to a viscosity reduction method, which may include: extruding and reducing viscosity of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin having a density of 0.900 g / cc to 0.975 g / cc and a melt index (I2) of less than 3 dg / min at a temperature of at least 250°C and a screw speed of at least 350 rpm to produce a viscous PCR-based polymer, wherein the I2 of the viscous PCR-based polymer is at least 3 times that of the I2 of at least one basic PCR-based polymer resin.

[0007] Embodiments of this disclosure relate to a viscosity reduction method, which may include: extruding and reducing viscosity of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin having a density of 0.900 g / cc to 0.975 g / cc and a melt index (I2) of less than 3 dg / min at a temperature of at least 250°C and a specific energy input (SEI) of 0.4 kW-hr / kg to 2.0 kW-hr / kg to produce a viscosity-reduced PCR ethylene-based polymer, wherein the I2 of the viscosity-reduced PCR ethylene-based polymer is at least 3 times that of the I2 of at least one basic PCR ethylene-based polymer resin.

[0008] These and other embodiments are described in more detail in the detailed description. It should be understood that both the foregoing general description and the following detailed description present embodiments of the technology disclosed in this invention and are intended to provide an overview or framework for understanding the nature and characteristics of the technology as claimed. Detailed Implementation

[0009] "Polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Therefore, the term polymer encompasses the term homopolymer (used to refer to a polymer prepared from only one type of monomer, where it should be understood that trace impurities may be incorporated into the polymer structure) and the terms copolymer and interpolymer. Trace impurities (e.g., catalyst residues) may be incorporated into and / or within the polymer. A polymer can be a single polymer or a polymer blend.

[0010] A "copolymer" is a polymer formed by the polymerization of at least two monomers with different structures. The term "copolymer" includes terpolymers. For example, ethylene copolymers (such as ethylene-propylene copolymers) comprise at least two structurally different monomers (e.g., an ethylene-propylene copolymer comprises copolymer units of at least ethylene monomers and propylene monomers) and may optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride functional groups. In other words, copolymers described herein contain at least two structurally different monomers, and although copolymers may consist of only two structurally different monomers, they are not necessarily composed of only two structurally different monomers and may contain additional monomers, functional materials, or modifiers.

[0011] "Ethylene-based polymers" (also referred to herein as "polyethylene" or "polyethylene-based polymers") mean polymers containing more than 50% by weight of units derived from ethylene monomers. 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-point catalytic 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 conventional Ziegler-Natta catalyst systems as well as resins made using single-center catalysts (such as metallocenes) (sometimes referred to as "m-LLDPE"). LLDPE contains less long-chain branching than LDPE and comprises: substantially linear ethylene polymers, which are further defined in U.S. Patent Nos. 5,272,236, 5,278,272, 5,582,923, and 5,733,155; homogeneously branched linear ethylene polymer compositions, such as those in U.S. Patent No. 3,645,992; non-homogeneously branched ethylene polymers, such as those prepared according to the method disclosed in U.S. Patent No. 4,076,698; and / or blends thereof (such as those disclosed in U.S. Patent Nos. 3,914,342 or 5,854,045). LLDPE can be prepared by 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-phase and solution-phase reactors).

[0013] The term “LDPE” can also be referred to as “high-pressure ethylene polymer” or “highly branched polyethylene”, and is defined to mean that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at pressures above 14,500 psi (100 MPa) using a free radical initiator (e.g., peroxide (see, for example, U.S. Patent No. 4,599,392, which is incorporated herein by reference)).

[0014] "HDPE" typically refers to a density greater than approximately 0.930 g / cm³. 3 And at most about 0.970 g / cm³ 3Polyethylene is generally prepared using Ziegler-Natta catalysts, chromium catalysts, or single-point catalysts (including but not limited to substituted mono- or di-cyclopentadienyl catalysts (commonly known as metallocenes), confined geometry catalysts, phosphine imine catalysts, and polyvalent aryloxy ether catalysts (commonly known as bisphenylphenoxy).

[0015] "Recycled resin" refers to resin that is incorporated into a product and subsequently remelted to form a recycled resin. The term "recycled resin" specifically refers to mechanically recycled resin, where the resin is melted and re-incorporated into a new product. "Recycled resin" does not include chemically recycled resin, where the polymer is broken down into constituent monomers and incorporated into a new virgin polymer. The term "recycled resin" encompasses both pre-consumer recycled polymers and post-consumer resins. Recycled resin is defined in ISO 14021 7.8.1.1.

[0016] The terms "pre-consumer recycled polymer" and "post-industrial recycled polymer" refer to polymers including blends of polymers recovered from pre-consumer materials as defined by ISO 14021. Therefore, the general term "pre-consumer recycled polymer" includes blends of polymers recovered from materials transferred from waste streams during the manufacturing process. The general term "pre-consumer recycled polymer" does not include the reuse of materials generated in the process and capable of being recovered in the same process in which they are generated, such as reprocessing, regrinding, or waste. Pre-consumer recycled polymers are defined in ISO 14021 7.8.1.1.

[0017] As used herein, the term "post-consumer resin" (or "PCR") refers to polymeric materials that include materials previously used in consumer or industrial applications; that is, pre-consumer recycled polymers and post-industrial recycled polymers. PCRs are typically collected from recycling programs and recycling plants. PCRs may include one or more of ethylene-based polymers (such as LDPE, LLDPE, HDPE, polyethylene), polypropylene, polyester, polyvinyl chloride, polystyrene, acrylonitrile butadiene styrene, polyamide, ethylene vinyl alcohol, ethylene vinyl acetate, or polyvinyl chloride. PCRs may contain one or more contaminants. Contaminants may be the result of the polymeric material being used before it is reused. For example, contaminants may include paper, ink, food scraps, or other recycled materials other than polymers that can be generated from the recycling process. PCRs differ from virgin polymeric materials. Virgin polymeric materials (such as virgin polyethylene resin) do not include materials previously used in consumer or industrial applications. Virgin polymeric materials have not undergone, or have not otherwise undergone, a heating or molding process after the initial polymer manufacturing process. PCR resins have different physical, chemical, and flow properties compared to virgin polymeric resins, which in turn may present challenges in incorporating PCRs into commercial-use formulations. Post-consumer resins are defined in ISO 14021 7.8.1.1.

[0018] As used herein, the term "devolatiles" refers to the process of removing unwanted volatile contaminants (e.g., dissolved gases, solvents, unreacted monomers, etc.) from a polymer melt or solution.

[0019] Viscosity reduction methods may include extruding and reducing the viscosity of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin to produce a reduced-viscosity PCR ethylene-based polymer. Extrusion viscosity reduction is a thermal cracking process performed under shear in an extruder to reduce the viscosity of the polymer resin.

[0020] Basic PCR-based ethylene polymer resins may contain at least 51% by weight of post-consumer materials, such as at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, or even at least 99% by weight of post-consumer materials. Generally, PCR resins have been found to be more susceptible to extrusion tackification than virgin resins. Without being theoretically limited, this is believed to be due to the more complex thermal history of PCR resins, the additional thermal history of PCR resins, differences in antioxidants, and differences in the amount of unsaturated compounds.

[0021] The ethylene-based polymer resin for basic PCR may include LDPE, HDPE, LLDPE, or blends thereof. In an embodiment, the ethylene-based polymer resin for basic PCR may contain at least 50% by weight, at least 75% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, or even at least 99% by weight of LDPE, HDPE, LLDPE, or blends thereof.

[0022] The ethylene-based polymer resin for basic PCR can have a density of 0.900 g / cc to 0.975 g / cc. In embodiments, the ethylene-based polymer resin for basic PCR can have densities of 0.900 g / cc to 0.970 g / cc, 0.900 g / cc to 0.960 g / cc, 0.900 g / cc to 0.950 g / cc, 0.900 g / cc to 0.940 g / cc, 0.900 g / cc to 0.930 g / cc, 0.910 g / cc to 0.975 g / cc, 0.920 g / cc to 0.975 g / cc, 0.930 g / cc to 0.975 g / cc, 0.930 g / cc to 0.970 g / cc, or any subset thereof.

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

[0024] At least one basic PCR-based ethylene-based polymer resin can have a melt index (I) of less than 50 dg / min. 10 In the implementation scheme, at least one basic PCR-based ethylene-based polymer resin may have a melt index (I0) 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, 5 dg / min to 50 dg / min, 5 dg / min to 40 dg / min, 5 dg / min to 30 dg / min, 5 dg / min to 20 dg / min, 5 dg / min to 15 dg / min, 5 dg / min to 12 dg / min, 8 dg / min to 50 dg / min, 8 dg / min to 30 dg / min, 8 dg / min to 15 dg / min, or any subset thereof. 10 ).

[0025] At least one basic PCR-based 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, 5 to 40, 5 to 30, 5 to 20, 10 to 40, 10 to 30, 10 to 20, 15 to 20, or any subset thereof.

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

[0027] The viscosity reduction of a base PCR-based ethylene-based polymer resin is achieved through extrusion in an extruder. The extruder can be a tandem system, a single-screw extruder, a twin-screw extruder, etc. The extruder can be equipped with multi-layer annular dies, flat dies and feed blocks, multi-layer feed blocks, multi-blade or multi-manifold dies such as a three-layer blade die. In one embodiment, the viscosity reduction is achieved using a twin-screw extruder. Based on the total polymer weight introduced into the extruder, at least one base PCR-based ethylene-based polymer resin may contain at least 80% by weight, such as at least 90% by weight, at least 95% by weight, at least 99% by weight, or even at least 99.9% by weight of the polymer introduced into the extruder. At least one base PCR-based ethylene-based polymer resin may contain at least 80% by weight of the material introduced into the extruder, such as at least 90% by weight, at least 95% by weight, at least 99% by weight, at least 99.9% by weight, or even at least 99.99% by weight of all the material introduced into the extruder.

[0028] Unrestricted by theory, extrusion de-viscosity processes can introduce thermal and mechanical energy (via an extruder) into at least one basic PCR ethylene-based polymer resin. Generally, this energy induces chain scission in the ethylene-based polymer within the resin. Chain scission is believed to lead to an increase in the resin's melt index and a decrease in molecular weight and Mw / Mn. The total mechanical energy input can be referred to as specific energy input (SEI). SEI can be calculated according to the equation... Calculation. The unit of SEI is kW-hr / kg.

[0029] Specific energy input (SEI) can range from 0.4 kW-hr / kg polymer to 2.0 kW-hr / kg polymer. Without theoretical limitations, it is believed that SEI below this range may not induce sufficient chain scission to adequately increase the melt index of ethylene-based polymers. Conversely, SEI above this range may cause excessive chain scission and impair the mechanical properties of ethylene-based polymers. In the implementation plan, the SEI can be 0.4 kW-hr / kg polymer to 1.8 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 1.6 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 1.4 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 1.2 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 1.0 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 0.8 kW-hr / kg polymer, 0.4 kW-hr / kg polymer to 0.6 kW-hr / kg polymer, 0.6 kW-hr / kg polymer to 2.0 kW-hr / kg polymer, 0.8 kW-hr / kg polymer The polymers are in the range of 2.0 kW-hr / kg, 1.0 kW-hr / kg, 1.2 kW-hr / kg, 1.4 kW-hr / kg, 1.6 kW-hr / kg, 1.8 kW-hr / kg, 0.6 kW-hr / kg, 0.8 kW-hr / kg, 1.6 kW-hr / kg, 1.0 kW-hr / kg, or any subset thereof.

[0030] Extrusion tapering can be performed at a temperature of at least 250°C. Without theoretical limitations, it is believed that if the tapering temperature is too low, such as below 250°C or below 290°C, the extruder motor may have difficulty applying sufficient energy to the resin to complete the tapering. In embodiments, extrusion tapering can occur at temperatures of at least 275°C, at least 285°C, at least 290°C, at least 295°C, 250°C to 350°C, 275°C to 350°C, 285°C to 350°C, 295°C to 350°C, 275°C to 325°C, 285°C to 325°C, 295°C to 325°C, 295°C to 315°C, 295°C to 305°C, or any subset thereof.

[0031] Extrusion viscosity reduction can occur in extruders such as twin-screw extruders at screw speeds of at least 350 rpm. Without theoretical limitations, it is believed that screw speeds below this range may not induce sufficient chain breakage to adequately increase the melt index of ethylene-based polymers. Extrusion viscosity reduction can occur at screw speeds of at least 400 RPM, at least 500 RPM, at least 600 RPM, at least 700 RPM, at least 800 RPM, 400 RPM to 1100 RPM, 500 RPM to 1100 RPM, 600 RPM to 1100 RPM, 700 RPM to 1100 RPM, 800 RPM to 1100 RPM, 900 RPM to 1100 RPM, 350 RPM to 1000 RPM, 500 RPM to 1000 RPM, 700 RPM to 1000 RPM, 800 RPM to 1000 RPM, or any subset thereof.

[0032] Extrusion viscosity reduction can have residence times ranging from 30 seconds to 200 seconds. Without being theoretically limited, the amount of energy input to the resin is a function of temperature, extruder motor power (as defined by screw speed), and the amount of time the resin is exposed to these conditions (residence time). Extrusion viscosity reduction can have residence times of 30 to 180 seconds, 30 to 160 seconds, 30 to 140 seconds, 30 to 120 seconds, 30 to 100 seconds, 30 to 80 seconds, 30 to 60 seconds, 50 to 200 seconds, 70 to 200 seconds, 90 to 200 seconds, 110 to 200 seconds, 130 to 200 seconds, 150 to 200 seconds, 170 to 200 seconds, 50 to 180 seconds, 70 to 160 seconds, 90 to 140 seconds, 110 to 130 seconds, or any subset thereof.

[0033] Extrusion viscosity reduction can occur in the absence of oxygen. Without being theoretically limited, it is believed that extrusion viscosity reduction in the absence of oxygen results in a decrease in the percentage of aldehydes in ethylene-based polymers compared to extrusion viscosity reduction in the presence of oxygen. Aldehydes are sensory detectable and can cause taste and odor problems in many applications, including food storage containers. Generally, the oxygen concentration can be reduced by using a vacuum or by replacing oxygen with another gas such as an inert gas (e.g., nitrogen, helium, argon, krypton, neon, or xenon). The gas in the extruder can 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. Based on the total moles of gas in the extruder, the gas in the extruder can be at least 80 mol% 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% inert gas.

[0034] In some embodiments, the viscosity reduction process may include at least one volatile matter removal step. This volatile matter removal can be carried out using any conventional volatile matter removal apparatus and methods, including, in non-limiting embodiments, the use of extruder reactors and / or kneader reactors, and methods including, for example, direct separation, main evaporation bulk evaporation, steam stripping, and / or direct volatile matter removal. In embodiments, at least one volatile matter removal step may occur in an extruder during the extrusion viscosity reduction step or in a separate extruder after the extrusion viscosity reduction step. In embodiments, the volatile matter removal process is driven by overheating the volatile components of the polymer melt and then subsequently exposing the melt to rapid decompression. Volatilization can be carried out on a screw extruder (including a single-screw extruder or a multi-screw extruder). A typical volatile matter removal zone in a screw extruder consists of a partially filled portion of the screw, separated by two zones filled with melt / solution. A stripping agent may be used in the extruder. In various aspects, the stripping agent used may be selected from the group consisting of water, carbon dioxide, nitrogen, and hydrocarbon gases. The stripping agent used in an extruder can be selected from the group consisting of water and carbon dioxide. Water can also be used as the stripping agent in an extruder.

[0035] Devolatileization of a viscous PCR-based ethylene polymer can produce a viscous PCR-based ethylene polymer with devolatiles. When the viscous PCR-based ethylene polymer leaves the extrusion viscous reduction process, the viscous PCR-based ethylene polymer with devolatiles can have a volatile organic compound (VOC) concentration that is at least 50% lower than that in the viscous PCR-based ethylene polymer, such as at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or even at least 99%. In an embodiment, during the devolatiles removal process, changes in other properties of the viscous PCR-based ethylene polymer, other than VOC concentration, do not exceed 10%, such as exceeding 5%, exceeding 3%, or exceeding 1%.

[0036] Extrusion viscosity reduction can occur in the absence of reaction aids such as catalysts, peroxides, or free radical initiators. Reaction aids can 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, their carboxylates, their chlorides, and their oxides. Based on the total polymer weight of at least one basic PCR-based ethylene-based polymer resin, the concentration of the reaction aid can be 0 wt% to 1 wt%, 0 wt% to 0.5 wt%, 0 wt% to 0.1 wt%, 0 wt% to 0.01 wt%, 0 wt% to 0.001 wt%, 0 wt% to 0.0001 wt%, 0 wt% to 0.000001 wt%, or even 0 wt% to 0.0000000001 wt%.

[0037] The I2 of the ethylene-based polymer used in de-viscosity PCR can be at least 3 times that of the I2 of at least one basic ethylene-based polymer resin used in PCR. In embodiments, the I2 of the ethylene-based polymer used in de-viscosity PCR can be at least 4 times, at least 5 times, at least 7 times, at least 8 times, at least 10 times, at least 12.5 times, at least 15 times, at least 17.5 times, at least 20 times, 3 to 50 times, 5 to 50 times, 7 to 50 times, 10 to 50 times, 15 to 50 times, 18 to 50 times, or any subset thereof.

[0038] The I2 of the ethylene-based polymer used in de-viscosity PCR can be at least 2 dg / min. In embodiments, the I2 of the ethylene-based polymer used in de-viscosity PCR can 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, 2 dg / min to 50 dg / min, 2 dg / min to 25 dg / min, 2 dg / min to 15 dg / min, 6 dg / min to 15 dg / min, 8 dg / min to 15 dg / min, 10 dg / min to 20 dg / min, or any subset thereof.

[0039] Anti-viscosity PCR based on ethylene polymers I 10 It can be an I of at least one basic PCR-based ethylene polymer resin 10 At least 5 times. In the implementation scheme, the de-viscosity PCR is based on the polymer of ethylene. 10 It can be an I of at least one basic PCR-based ethylene polymer resin 10 At least 6 times, at least 7 times, at least 8 times, at least 9 times, 5 to 20 times, 8 to 20 times, 5 to 15 times, 8 to 15 times, or any subset thereof.

[0040] The viscosity-reducing PCR based on ethylene polymers can have a viscosity 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, 20 dg / min to 200 dg / min, 40 dg / min to 200 dg / min, 80 dg / min to 200 dg / min, 90 dg / min to 200 dg / min, 40 dg / min to 160 dg / min, 80 dg / min to 150 dg / min, 90 dg / min to 120 dg / min, 95 dg / min to 110 dg / min, or any subset thereof. 10 .

[0041] The viscosity-reducing PCR-based ethylene polymer may have a yellowness index (YI) that is 1 / 4 of that of the YI of at least one basic PCR-based ethylene polymer resin. In embodiments, the YI of the viscosity-reducing PCR-based ethylene polymer may be 1 / 3, 1 / 2, 1 / 1.5, or even greater than that of the YI of at least one basic PCR-based ethylene polymer resin.

[0042] The viscosity-reducing PCR based on ethylene polymers can 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 viscosity-reducing ethylene-based polymer can have a color coordinate (L) value that is less than that of at least one basic PCR-based ethylene-based polymer resin, such as 100%, 95%, 90%, 85%, 80%, or 75% smaller than the L value of at least one basic PCR-based ethylene-based polymer resin.

[0044] The viscosity-reducing PCR based on ethylene polymers can have color coordinate (L) values ​​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 viscous-reducing ethylene-based polymer may have a lower Mw / Mn than that of at least one basic PCR-based ethylene-based polymer resin. Generally, viscous reduction results in a lower Mw / Mn of the polymer. In embodiments, the viscous-reducing ethylene-based polymer may have an Mw / Mn that is 100%, 97.5%, 95%, 90%, 85%, 80%, 70%, 60%, or even less than 50% lower than that of at least one basic PCR-based ethylene-based polymer resin.

[0046] The viscosity-reducing PCR based on ethylene polymers can have Mw / Mn values ​​less than 10, such as less than 8, less than 6, less than 4, or even less than 2.

[0047] The articles may include ethylene-based polymers used in reduced-viscosity PCR. In some embodiments, the articles may be cast stretch films or blown films. In other embodiments, the articles may be food packaging.

[0048] Test methods

[0049] Melt Flow Index

[0050] Melt flow index (also referred to herein as “melt index”) (I2) was measured at 190 degrees Celsius and 2.16 kg according to ASTM D 1238-10 Method B and expressed as grams eluted per 10 minutes (dg / min).

[0051] Melt index (I) 10 The values ​​are measured according to ASTM D 1238-10 Method B at 190 degrees Celsius and 10 kg, and are expressed as grams eluted per 10 minutes (dg / min).

[0052] density

[0053] Density was measured according to ASTM D792.

[0054] Yellowness Index (YI)

[0055] The yellowness index (YI) value of granules was determined using ASTM D6290-05 (Method title: Standard Test Method for the Determination of Color in Plastic Granules). The yellowness index (YI) is an instrumental measurement of the yellowness (or yellowness variation) of homogeneous, non-fluorescent, nearly colorless transparent or nearly white translucent or opaque plastics under sunlight illumination using a BYK-Gardner 9000 spectrophotometer equipped with a sample rotator. The granules (250 g) were measured based on the values ​​obtained from the colorimeter. This test method is applicable to the color analysis of plastic granules. The color in polymers is primarily due to organic impurities. Inorganic impurities can also affect color.

[0056] Color coordinates (L)

[0057] The color coordinate (L) value of the pellets was determined using ASTM D6290-05 (Method title: Standard test method for color determination of plastic pellets).

[0058] Gel permeation chromatography

[0059] The chromatographic system utilized a PolymerChar GPC-IR (Valencia, Spain) high-temperature GPC chromatograph equipped with an internal IR5 infrared detector. The autosampler oven chamber was set to 160°C, and the column chamber to 150°C. Four Agilent "Mixed A" 30cm 20µm linear mixed-bed columns were used. The chromatographic solvent was 1,2,4-trichlorobenzene containing 200 ppm butylated hydroxytoluene (BHT). The solvent source was nitrogen injection. The injection volume was 200 μL, and the flow rate was 1.0 mL / min.

[0060] The GPC column assembly was calibrated using 21 polystyrene standards with narrow molecular weight distributions, ranging from 580 to 8,400,000, arranged in six “cocktail” mixtures, with individual molecular weights spaced at least tenfold apart. The standards were purchased from Agilent Technologies. For molecular weights equal to or greater than 1,000,000, 0.025 g of polystyrene standard was prepared in 50 mL of solvent; for molecular weights less than 1,000,000, 0.05 g of polystyrene standard was prepared in 50 mL of solvent. The polystyrene standards were pre-dissolved at 80 °C with gentle stirring for 30 min, then cooled, and the room temperature solution was transferred to a 160 °C autosampler dissolution oven for 30 min. The peak molecular weights of the polystyrene standards were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).

[0061]

[0062] Where M is the molecular weight, A has a value of 0.4049, and B equals 1.0.

[0063] A fifth-order polynomial is used to fit the calibration point for the corresponding polyethylene equivalent.

[0064] Total plate counts of the GPC column assembly were performed using decane, which was introduced into the blank sample via a micropump controlled by a PolymerChar GPC-IR system. For four Agilent "Mixed A" 30 cm 20 μm linear mixed-bed columns, the plate count of the chromatographic system should be greater than 18,000.

[0065] Samples were prepared semi-automatically using PolymerChar "Instrument Control" software, with a target sample weight of 2 mg / ml. Solvent (containing 200 ppm BHT) was added to a pre-bubbled, diaphragm-capped vial via a PolymerChar high-temperature autosampler. The sample was then dissolved at 160°C for 2 hours with "low-speed" shaking.

[0066] Based on the GPC results, using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph, according to Equation 2-4, the PolymerChar GPCOne was used. ™The software calculates Mn, Mw, and Mz using baseline-subtracted IR chromatograms at each equidistant data collection point (i) and polyethylene equivalent molecular weights obtained from the narrow standard calibration curve at point (i) according to Equation 1.

[0067]

[0068] To monitor deviations over time, a flow rate marker (decane) was introduced into each sample via a micropump controlled by a PolymerChar GPC-IR system. This flow rate marker (FM) was used to linearly correct the pump flow rate (nominal flow rate) for each sample by comparing the RV (RV(FM sample)) of the corresponding decane peak within the sample with the RV (RV(FM calibrated)) of the decane peak within the narrow standard calibration. It was then assumed that any variation in the decane marker peak time was linearly related to the flow rate (effective flow rate) throughout the run. The effective flow rate (relative to the narrow standard calibration) was calculated according to Equation 5 after calibration based on the flow marker peak system. (via PolymerChar GPCOne) ™ The software processes the flow marker peaks. Acceptable flow rate correction ensures that the effective flow rate is within + / - 0.5% of the nominal flow rate.

[0069]

[0070] DSC

[0071] Differential scanning calorimetry (DSC) results were determined using a TAI Q1000 DSC equipped with an RCS cooling accessory and an autosampler. A nitrogen purge flow of 50 ml / min was used. The sample was pressed into a thin film and melted in a press at approximately 175 °C, then air-cooled to room temperature (25 °C). 3 mg to 10 mg of material was then cut into 6 mm diameter discs, accurately weighed, placed in a lightweight aluminum disc (approximately 50 mg), and then rolled up. The thermal behavior of the sample was investigated using the following temperature profiles. The sample was rapidly heated to 180 °C and held isothermally for 3 minutes to remove any prior thermal history. The sample was then cooled to -40 °C at a cooling rate of 10 °C / min and held at -40 °C for 3 minutes. The sample was then heated to 150 °C at a heating rate of 10 °C / min. The cooling and heating profiles were recorded.

[0072] The DSC melting peak is measured as the maximum heat flow rate (W / g) relative to a linear baseline plotted between -30°C and the end of melting. The heat of fusion is measured as the area under the melt curve between -30°C and the end of melting using a linear baseline.

[0073] Unless otherwise stated, the melting point (T) of each polymer is determined according to the second heating curve obtained by DSC as described above. m (Peak Tm). The crystallization temperature (T) is measured based on the first cooling curve. c (peak T) C ).

[0074] Antioxidant levels

[0075] To determine antioxidant levels, approximately 0.5 g of sample (accurately recorded to 0.0001 g) was weighed and placed in a 125 mL glass vial. Using Gerstel MPS, a PTFE-coated stir bar and 25 mL of a 0.04% triethyl phosphite solution in o-xylene were added to the vial. The vial was placed on a heated stirrer and stirred at 130 °C for 30 minutes. After 30 minutes, the vial was removed, and the solution was allowed to cool to room temperature while stirring for at least 2 hours. The polymer was further precipitated by adding 50 mL of methanol to the vial using Gerstel MPS. The solution was stirred during this addition. The solution was stirred for another 2 hours. After stirring for 2 hours, the stirrer was turned off, and the solids were allowed to settle. Aliquots of the solution were transferred to 2 mL glass autosampler vials. The vials were analyzed using liquid chromatography. The sample and standard solutions were analyzed using reversed-phase liquid chromatography with a UV / Vis absorbance detector. The concentrations in the extracts were determined using an external standard calibration procedure. Data on AO in the resin are reported in parts per million (ppm; µg / g).

[0076] DMS viscosity

[0077] For preparation, the test sample is initially placed in a 1.5-inch diameter groove with a thickness of 3.10 mm and compressed using a hydraulic press at 190°C with a pressure of 25,000 lb for 6.5 min. After cooling to room temperature, the sample is removed and awaits dynamic mechanical spectroscopy.

[0078] Dynamic mechanical spectroscopy (DMS) frequency scans were performed using 25 mm parallel plates at frequencies ranging from 0.1 rad / s to 100 rad / s. The test gap separating these plates was 1.8 mm. Strain satisfying the linear viscoelastic condition was used. Each test was performed under a nitrogen atmosphere and isothermal conditions at 190 °C. To initiate the DMS test, the rheometer oven was first equilibrated at the desired test temperature for at least 30 min, and then the sample was loaded into the test geometry. The sample was then equilibrated in the oven with the door closed for 1 min. The test gap was then set to 1.8 mm, and the sample was distributed for 5 min to release the generated normal force. Afterward, the oven was quickly opened, and the sample was trimmed to eliminate any bulging. The DMS measurement was then initiated after the oven was closed again. During the test, the shear modulus (G'), viscous modulus (G''), and complex viscosity were measured.

[0079] All DMS frequency tests were performed on either an ARES-G2 or DHR-3 rheometer, both manufactured by TA Instruments. Data analysis was performed using TA Instruments' TRIOS software.

[0080] aldehyde

[0081] use 1 H NMR was used to measure aldehyde content.

[0082] Samples were prepared as follows: Approximately 0.1 g of the sample was added to 3.25 g (by weight) of 50 / 50 1,1,2,2-tetrachloroethane-d2 / perchloroethylene (TCE / PCE) containing 0.001 M Cr(AcAc)3 relaxant and approximately 75 ppm butylated hydroxytoluene (BHT) as an antioxidant in a Norell 1001-7 10 mm NMR tube. The solvent mixture was stored on a 4A molecular sieve. The sample was capped, sealed with Teflon tape, and then heated and vortexed at approximately 120°C to 140°C to dissolve and ensure homogeneity.

[0083] Each sample was acquired at 120°C using a 10mm cryogenic probe on a Bruker AVANCE 600MHz spectrometer. 1 1H NMR spectroscopy. Two experiments were performed to measure aldehydes: a control experiment and a double-presaturation experiment. The control spectrum was obtained using the zg pulse sequence NS=16 for quantitative analysis. 1 H-spectrum. In the control spectrum, the residue from TCE-d2 1The H signal was set to 100, and the integral from approximately -0.5 ppm to 3 ppm was used as the signal from the entire polymer. This integral was divided by 2 to obtain the total amount of carbon in the polymer. Double presaturated spectra were obtained using 64 scans, and the residual from TCE-d2 was also analyzed. 1 The H signal was also set to 100. The aldehyde peaks in the 9.5 ppm to 10 ppm region were integrated, and the aldehyde per 100,000 polymer carbons was calculated (using the total carbon measured in the control spectrum).

[0084] Volatile substances

[0085] The total concentration of volatile organic compounds (VOCs) was determined using the total evaporation headspace gas chromatography (FE-HS / GC) method.

[0086] VOC concentrations in polyethylene were determined using headspace gas chromatography with a flame ionization detector. One resin pellet (0.04 g ± 0.02 g) and 0.005 g of Irganox 1330 were placed in a headspace vial and sealed. VOCs were sampled using a headspace analyzer, with the sample equilibrated at 190 °C for 120 min. A calibration solution was prepared using the process solvent in dichloromethane. 10 µL aliquots of the calibration solution were transferred to headspace vials using an electronic digital injector, and the vials were immediately sealed with a cap using a crimping tool. The peak areas of the solvent peaks in the sample and calibration solution were summed. Quantification was performed using an external standard calibration procedure. Data are reported in parts per million (ppm; µg / g).

[0087] Example

[0088] Material :

[0089] The following materials are used in the embodiments.

[0090] DMDA ™ 6200 is HDPE with a density of 0.953 g / cc and a melt index (I2) of 0.38 dg / min, and is commercially available from Dow Inc., Midland MI.

[0091] DMDA ™ 6400 is HDPE with a density of 0.961 g / cc and a melt index (I2) of 0.80 dg / min, and is commercially available from Dow Chemical Company, Midland, Michigan.

[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 / min, commercially available from KW Plastics, Troy, AL, Alabama.

[0093] Envision Ecoprime ™ It is a food-safe recyclable resin with a density of 0.961 g / cc and a melt index (I2) of 0.6, and is 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 / min, and is commercially available from Avangard Innovative.

[0095] Irganox ™ 1010 is a sterically hindered primary phenolic antioxidant stabilizer, commercially available from BASF Corporation.

[0096] Irganox ™ 1076 is a sterically hindered primary phenolic antioxidant stabilizer, commercially available from BASF.

[0097] Irgafos ™ 168 is a tris(2,4-di-tert-butylphenyl) phosphite antioxidant stabilizer.

[0098] MEK stands for methyl ethyl ketone.

[0099] Example 1

[0100] Four samples were subjected to extrusion tack reduction. The base resins CE-A to CE-D are described in Table 1. As shown in Table 1, each of these samples includes a base resin (described as “material”) and residues of processing aids that introduce the base resin into its primary application (e.g., Irganox 1010, Irganox 1076, Irgafos 168, oxidized I-168).

[0101] Table 1

[0102]

[0103] The base samples were then extruded and viscous-reduced using a TPV screw in a ZSK 26mm twin-screw extruder. The base samples were viscous-reduced at 300°C, 900 RPM, 10 lbs / hr feed, an average residence time of 81 s, and specific energy input (SEI) ranging from 1.55 kW-hr / kg to 1.77 kW-hr / kg. Note that CE-E is viscous-reduced CE-A, CE-F is viscous-reduced CE-B, EX-1 is viscous-reduced CE-C, and EX-2 is viscous-reduced CE-D. The melt index (I2) of the base and viscous-reduced samples is shown in Table 2.

[0104] Table 2

[0105]

[0106] Example 2

[0107] Yellowness tests were performed on all samples in Table 2 as described in the Test Methods section. The results are given in Table 3.

[0108] Table 3

[0109]

[0110] The samples were subjected to rheological tests using the same method as those used for CE-A to CE-I. The results are shown in Table 4.

[0111] Table 4

[0112]

[0113] The samples were then subjected to conventional gel permeation chromatography. The results are shown in Table 5.

[0114] Table 5

[0115]

[0116] Example 3

[0117] CE-D (Envision Ecoprime) was used as the base post-consumption recycling (PCR) ethylene-based polymer resin for extrusion viscosity reduction to investigate the effects of oxygen removal and additives on the viscosity reduction process. Process conditions, reactants, and characterization results are shown in Table 6.

[0118] Table 6

[0119]

[0120] As can be seen in Table 6, even without the use of antioxidants, nitrogen sealing reduced aldehyde production by nearly 50%.

[0121] The study was repeated using Avangard 100 to investigate the effects of oxygen removal and additives on the viscosity reduction process. Process conditions, reactants, and characterization results are shown in Table 7.

[0122] Table 7

[0123]

[0124] Example 4

[0125] Other samples of Envision Ecoprime and AV100 were extruded and viscous-reduced in a ZE-42 x 48D BluePower twin-screw extruder. PCR samples were viscous-reduced at 300°C under different treatment conditions described in Table 8. The results are shown in Table 9. The melt index (I2) of the starting and viscous-reduced samples is shown in Table 2.

[0126] Table 8

[0127]

[0128] Table 9

[0129]

Claims

1. A method for reducing viscosity, the method comprising: Extrusion de-tackification of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin having a density of 0.900 g / cc to 0.975 g / cc and a melt index (I2) of less than 3 dg / min at a temperature of at least 250°C and a screw speed of at least 350 rpm produces a de-tackified PCR ethylene-based polymer, wherein the I2 of the de-tackified PCR ethylene-based polymer is at least 3 times that of the at least one basic PCR ethylene-based polymer resin.

2. A method for reducing viscosity, the method comprising: Extrusion de-tackification of at least one basic post-consumption recycling (PCR) ethylene-based polymer resin having a density of 0.900 g / cc to 0.975 g / cc and a melt index (I2) of less than 3 dg / min at a temperature of at least 250 °C and a specific energy input (SEI) of 0.4 kW-hr / kg to 2.0 kW-hr / kg produces a de-tackified PCR ethylene-based polymer, wherein the I2 of the de-tackified PCR ethylene-based polymer is at least 3 times that of the at least one basic PCR ethylene-based polymer resin.

3. The method according to claim 1, wherein the screw speed is 450 RPM to 1100 RPM.

4. The method according to any of the preceding claims, wherein the extrusion viscosity reduction utilizes a twin-screw extruder.

5. The method according to any of the preceding claims, wherein the viscosity reduction method comprises at least one devolatileization step.

6. The method according to any of the preceding claims, wherein the extrusion detack reduction occurs in the absence of oxygen.

7. The method according to any of the preceding claims, wherein the extrusion detackification has a residence time of 30 seconds to 200 seconds.

8. The method according to any one of claims 1 to 7, wherein the extrusion tack reduction has a specific energy input of 0.4 kW-hr / kg to 2.0 kW-hr / kg.

9. The method according to any of the preceding claims, wherein the at least one basic PCR-based ethylene polymer resin comprises LDPE, HDPE, LLDPE, or blends thereof.

10. The method according to any of the preceding claims, wherein the melt index (I2) of the at least one basic PCR-based ethylene polymer resin is less than 1 dg / min, and the density of the at least one basic PCR-based ethylene polymer resin is from 0.940 g / cc to 0.970 g / cc.

11. The method of claim 10, wherein the melt index (I2) of the ethylene-based polymer used in the anti-viscosity PCR is at least 2 dg / min, and the melt index (I2) of the ethylene-based polymer used in the anti-viscosity PCR is at least 2 dg / min. 10 The concentration should be at least 16 dg / min.

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

13. The method of claim 12, wherein the melt index (I2) of the ethylene-based polymer used in the anti-viscosity PCR is at least 5 dg / min, and the melt index (I2) of the ethylene-based polymer used in the anti-viscosity PCR is at least 5 dg / min. 10 The concentration should be at least 30 dg / min.

14. The method according to any of the preceding claims, wherein the ethylene-based polymer of the reduced viscosity PCR has a yellowness index (YI) of less than 40 when measured according to ASTM D6290-05.

15. The method according to any of the preceding claims, wherein the viscosity-reducing PCR-based polymer has a Mw / Mn ratio of less than 8, as measured by GPC.

16. A viscosity-reducing PCR-based ethylene polymer, said viscosity-reducing PCR-based ethylene polymer being produced by the method according to any of the preceding claims.

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