Thermally cross-linked ethylene-based polymer

Abstract

Embodiments are directed to a thermally cross-linked ethylene-based polymer comprising an ethylene-based polymer formed by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules. Each of the one or more hydrocarbon-based molecules comprises three or more terminal alkene groups. The thermally cross-linked ethylene-based polymer, thermally cross-linked in the presence of oxygen, has a greater melt elongation relative to an ethylene-based polymer not subjected thermal crosslinking in the presence of oxygen. Further embodiments are directed to a process for making the thermally cross-linked ethylene-based polymer.

Description

86132-WO-PCT / DOW 86132 WO1THERMALLY CROSS-LINKED ETHYLENE-BASED POLYMERCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application Serial No. 63 / 725,665 filed November 27, 2024, the entire disclosure of which is hereby incorporated by reference.TECHNICAL FIELD

[0002] Embodiments of the present disclosure generally relate to ethylene-based polymers and specifically relate to thermally cross-linked ethylene-based polymers.BACKGROUND

[0003] High-pressure reactors have been used in industry for making low density polyethylene (LDPE) products for many years. The level of branching in LDPE at given melt index correlates to melt elongation, with higher branching correlating to a higher melt elongation. The level of branching in LDPE is affected by the reactor design and the polymerization conditions used to make the LDPE. But the process conditions required to achieve LDPE with a high level of branching, and thus high melt elongation may result in a final product with a lower crystallinity and with a higher content of a low molecular weight extractable fraction. Branching agents have been used to increase the level of branching in an LDPE under conditions that maintain desirable polymer properties. However, due to processing limitations, only a limited amount of branching agent may be added, thereby limiting the melt elongation increase that may be achieved.

[0004] Accordingly, there is a need for a modified LDPE having relatively higher branching levels corresponding to a relatively higher melt elongation as compared to a LDPE formed utilizing a branching agent.SUMMARY

[0005] The embodiments of the present disclosure meet this need by utilizing thermal crosslinking in the presence of oxygen. This resulted in a thermally cross-linked ethylene-based polymer having a greater melt elongation (e.g., at least 5% greater) relative to an ethylene-based polymer not subjected thermal crosslinking in the presence of oxygen.

[0006] In one embodiment, a thermally cross-linked ethylene-based polymer comprises an ethylene-based polymer formed by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-86132-WO-PCT / DOW 86132 WO2 based molecules. Each of the one or more hydrocarbon-based molecules comprises three or more terminal alkene groups. The thermally cross-linked ethylene-based polymer, thermally cross-linked in the presence of oxygen, has a greater melt elongation relative to an ethylenebased polymer not subjected thermal crosslinking in the presence of oxygen.

[0007] In another embodiment, a process for making a thermally cross-linked ethylene-based polymer comprises producing an ethylene-based polymer by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules and crosslinking the ethylene-based polymer with heat in the presence of oxygen for a duration of at least 10 minutes to form the thermally cross-linked ethylene-based polymer. Each of the one or more hydrocarbon-based molecules comprises three or more terminal alkene groups. The thermally cross-linked ethylene-based polymer has a greater melt elongation relative to an ethylene-based polymer not subjected thermal crosslinking.

[0008] Additional features and advantages will be set forth in the detailed description, which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows and the claims.

[0009] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter.DETAILED DESCRIPTION

[0010] Specific embodiments of the present application will now be described. The disclosure may be embodied in different forms and should not be construed as limited to the embodiments set forth in this disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0011] DEFINITIONS

[0012] Unless stated to the contrary, implicit from the context, or customary in the art, all test methods are current as of the filing date of this disclosure.

[0013] Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from86132-WO-PCT / DOW 86132 WO3 the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0014] The terms “comprising”, “including”, “having”, and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, "consisting essentially of’ excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term "consisting of’ excludes any component, step or procedure, not specifically delineated or listed.

[0015] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight.

[0016] The term "ethylene monomer," as used herein, refers to a chemical unit having two carbon atoms with a double bond there between, and each carbon bonded to two hydrogen atoms, wherein the chemical unit polymerizes with other such chemical units to form an ethylene-based polymer composition.

[0017] 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 high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa) with the use of free-radical initiators, such as peroxides (see, for example, U.S. Patent No. 4,599,392, which is hereby incorporated by reference in its entirety). LDPE resins typically have a density in the range of 0.916 g / cm3to 0.930 g / cm3.

[0018] The term “hydrocarbon-based molecules comprising three or more terminal alkene groups,” (or interchangeably referred to as “hydrocarbon-based molecules”) as used herein, refers to a chemical component that is a polymer chain composed of only carbon atoms and hydrogen atoms, the polymer chain being branched and having three or more terminal alkene groups.86132-WO-PCT / DOW 86132 WO4

[0019] The term “mixture of hydrocarbon-based molecules,” as used herein, refers to two or more hydrocarbon-based molecules, wherein at least two of the molecules differ in structure, property, and / or composition.

[0020] The term “terminal double bond,” as used herein, refers to a double bond between two carbon atoms in a polymer chain, wherein one of the carbons in the double-bond is a =CH? group. Terminal double bonds are located at terminal ends of polymer chains and / or at branched ends of polymer chains.

[0021] The term “thermally cross-linked ethylene-based polymer,” as used herein, refers to a polymer that has been thermally cross-linked in the presence of oxygen.

[0022] The terms “crosslinking,” “thermal crosslinking,” and “thermal treatment,” as used herein, refer to crosslinking with heat in the presence of oxygen.

[0023] EMBODIMENTS

[0024] Embodiments of the present disclosure are directed to thermally cross-linked ethylenebased polymers comprising an ethylene-based polymer formed by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules.

[0025] Ethylene-based Polymer

[0026] The ethylene-based polymer is the polymerization reaction product of ethylene and one or more hydrocarbon-based molecules. Each hydrocarbon-based molecule comprises three or more terminal alkene groups.

[0027] In embodiments, each of the hydrocarbon-based molecules (i.e., one or more of the hydrocarbon-based molecules) may comprise Structure I:Structure I

[0028] In Structure I, R = H or OH n may be from 3 to 160, such as from 3 to 60, from 3 to 30, from 5 to 160, from 10 to 160, from 20 to 160, from 30 to 160, or from 40 to 160, from 5 to 100, or from 9 to 40; m may be from 0 to 50, such as from 0 to 30, from 1 to 50, from 1 to 40, from 1 to 30, from 1 to 20, from 2 to 20, from 2 to 10, or any subset thereof.86132-WO-PCT / DOW 86132 WO5

[0029] In embodiments, each of the hydrocarbon-based molecules (i.e., one or more of the hydrocarbon-based molecules) may comprise Structure II: s,ruc,ure"

[0030] In Structure II, R = H or OH, n may be from 3 to 160, and m may be from 0 to 50; x may be from 0 to 160, and y may be from 0 to 50. For example, n may be from 3 to 160, such as from 3 to 100, from 3 to 30, from 5 to 160, from 10 to 160, from 20 to 160, from 30 to 160, or from 40 to 160, from 5 to 100, or from 9 to 40; m may be from 0 to 50, such as from 0 to 30, from 1 to 50, from 1 to 40, from 1 to 30, from 1 to 20, from 2 to 20, from 2 to 10, or any subset thereof, x may be from 0 to 160, such as from 0 to 140, from 0 to 120, from 0 to 100, from 0 to 80, from 0 to 60, from 0 to 40, from 0 to 20, from 1 to 20, from 1 to 60, from 1 to 100, from 1 to 160, from 10 to 150, from 20 to 140, from 40 to 120, from 60 to 100, or any subset thereof, y may be from 0 to 40, from 0 to 30, from 0 to 20, from 0 to 10, from 1 to 50, from 5 to 50, from 10 to 60, from 20 to 50, from 30 to 50, from 40 to 50, from 10 to 40, or any subset thereof.

[0031] The hydrocarbon-based molecules of Structure I, the hydrocarbon-based molecules of Structure II, and / or the overall mixture of hydrocarbon-based molecules may have a molecular weight distribution (MWD = Mw / Mn) from 1.2 to 20, such as from 1.2 to 10, from 1.2 to 5, from 1.2 to 3, from 1.3 to 20, from 1.4 to 20, from 1.5 to 20, from 2 to 20, from 5 to 20, from 10 to 20, from 2 to 18, from 6 to 16, from 8 to 14, or any subset thereof.

[0032] In Structure I and Structure II, it should be understood that the hydrocarbon-based molecules may be random copolymers or block copolymers. The individual monomers may, but need not, be arranged in the same order as is shown in Structure I and Structure II. Any polymer which includes both the monomers shown in Structure I (and only those two monomers) is defined by Structure I. Any polymer which includes all four of the monomers shown in Structure II (and only those monomers) is defined by structure II, regardless of the order of the monomers.

[0033] In embodiments, a mixture of hydrocarbon-based molecules having the Structure I and / or the Structure II, with differing molecular weights, may be used. The mixture of hydrocarbon-based molecules may comprise hydrocarbon-based molecules of Structure I, Structure II, or a combination thereof. Suitable hydrocarbon-based molecules include those described in detail in U.S. Patent Application Publication Number 2022 / 0017666, the entirety of which is incorporated by reference86132-WO-PCT / DOW 86132 WO6 herein; and include polybutadiene available from Nippon Soda Co., Ltd under the names PB B-1000 (polybutadiene with a number average molecular weight (Mn) of 1200 and at least 85% 1,2-vinyl content), and Poly vest 110, available from Evonik Industries (polybutadiene with a number average molecular weight (Mn) of 2600 and only about 1% of 1,2-vinyl content), Poly vest EP MV, available from Evonik Industries (polybutadiene with a number average molecular weight (Mn) of 2000 and only about 61% of 1,2-vinyl content).

[0034] In embodiments, the ethylene-based polymer may comprise, in polymerized form, from 95 wt% to 99.95 wt%, from 95 wt% to 99.90 wt%, from 96 wt% to 99.95 wt%, from 96 wt% to 99.0- wt%, from 97 wt% to 99.95 wt%, from 97 wt% to 99.90 wt%, from 98 wt% to 99.95 wt%, from 98 wt% to 99.90 wt%, or any subset thereof, of ethylene, and a reciprocal amount of the mixture of hydrocarbon-based molecules, or from 0.05 wt% to 5 wt%, from 0.05 wt% to 4 wt%, from 0.05 wt% to 3 wt%, from 0.05 wt% to 2 wt%, from 0.1 wt% to 5 wt%, from 0.1 wt% to 4 wt%, from 0.1 wt% to 3 wt%, from 0.1 wt% to 2 wt%, from 0.5 wt% to 5 wt%, from 0.5 wt% to 4 wt%, from 0.5 wt% to 3 wt%, from 0.5 wt% to 2 wt%, from 1 wt% to 5 wt%, from 1 wt% to 4 wt%, from 1 wt% to 3 wt%, from 1 wt% to 2 wt%, or any subset thereof. Weight percent is based on total weight of the ethylenebased polymer.

[0035] In embodiments, the ethylene-based polymer may have a density from 0.910 g / cc to 0.940 g / cc, from 0.910 g / cc to 0.935 g / cc, from 0.910 g / cc to 0.930 g / cc, from 0.910 g / cc to 0.925 g / cc, from 0.914 g / cc to 0.940 g / cc, from 0.914 g / cc to 0.935 g / cc, from 0.914 g / cc to 0.930 g / cc, from 0.914 g / cc to 0.925 g / cc, or any subset thereof.

[0036] In embodiments, the ethylene-based polymer may have a melt index (h), prior to thermal crosslinking, from 0.05 g / 10 min to 200 g / 10 min, from 0.10 g / 10 min to 150 g / 10 min, from 0.10 g / 10 min to 50 g / 10 min, from 0.1 g / 10 min to 10 g / 10 min, from 0.15 g / 10 min to 150 g / 10 min, from 0.15 g / 10 min to 10 g / 10 min, from 0.25 g / 10 min to 150 g / 10 min, from 0.25 g / 10 min to 10 g / 10, or any subset thereof.

[0037] In embodiments, the ethylene-based polymer may have an alkenes content from 0.05 / 1000 carbons to 3.0 / 1000 carbons, from 0.05 / 1000 carbons to 2.0 / 1000 carbons, from 0.05 / 1000 carbons to 1.0 / 1000 carbons, from 0.15 / 1000 carbons to 3.0 / 1000 carbons, from 0.15 / 1000 carbons to 2.0 / 1000 carbons, from 0.15 / 1000 carbons to 1.0 / 1000 carbons, from 0.3 / 1000 carbons to 3.0 / 1000 carbons, from 0.3 / 1000 carbons to 2.0 / 1000 carbons, from 0.3 / 1000 carbons to 1.0 / 1000 carbons, from 0.4 / 1000 carbons to 3.0 / 1000 carbons, from 0.4 / 1000 carbons to 2.0 / 1000 carbons, from 0.4 / 1000 carbons to 1.0 / 1000 carbons, or any subset thereof.86132-WO-PCT / DOW 86132 WO7

[0038] In embodiments, the ethylene-based polymer may be a low density polyethylene comprising, in polymerized form, ethylene monomer and the hydrocarbon-based molecules.

[0039] The ethylene-based polymer is produced via in-reactor high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules. An exemplary process of making the ethylenebased polymer is described in International Patent Application Publication No. WO 2020 / 112873, which is incorporated herein by reference in its entirety.

[0040] Thermally Cross-linked Ethylene-based Polymer

[0041] As described herein, the thermally cross-linked ethylene-based polymer has a greater melt elongation relative to the ethylene-based polymer not subjected to thermal crosslinking.

[0042] In embodiments, the melt elongation of the of the thermally cross-linked ethylene-based polymer may be at least 5% greater, at least 10% greater, at least 25% greater, at least 50% greater, at least 75% greater, or even at least 100% greater than the ethylene-based polymer not subjected to thermally crosslinking in the presence of oxygen.

[0043] In embodiments, the melt elongation of the of the thermally cross-linked ethylene-based polymer may be at least 2 nm greater, at least 5 nm greater, at least 10 nm greater, at least 25 nm greater, at least 50 nm greater, at least 75 nm greater, or even at least 100 nm greater than the ethylene-based polymer not subjected to thermally crosslinking in the presence of oxygen.

[0044] In embodiments, the thermally cross-linked ethylene-based polymer may have a melt elongation greater than or equal to 20 mN, greater than or equal to 25 mN, greater than or equal to 30 mN, greater than or equal to 35 mN, greater than or equal to 40 mN, greater than or equal to 45 mN, greater than or equal to 50 mN, greater than or equal to 55 mN, greater than or equal to 60 mN, greater than or equal to 65 mN, or even greater than or equal to 70 mN.

[0045] While not wishing to be bound by theory, relatively greater melt elongation is indicative of enhanced mechanical properties, dimensional stability, and heat resistance. For example, higher melt elongation may indicate better molecular alignment and packing during the molding process, leading to improved mechanical properties, such as tensile strength, impact resistance, and rigidity. Moreover, rigid articles may need to maintain their shape and dimensions under various conditions. Increased melt elongation may help in achieving a better dimensional stability, reducing warping and deformation. Furthermore, rigid applications may rely on materials that can withstand higher temperatures without losing structural integrity. Increased86132-WO-PCT / DOW 86132 WO8 melt elongation may contribute to better heat resistance, making the material more suitable for demanding environments.

[0046] One skilled in the art should appreciate that melt index (I2) correlates to melt elongation, lower melt index (I2) corresponding to greater the melt elongation. However, while not wishing to be bound by theory, after a given thermal crosslinking, the melt index (I2) of the thermally cross-linked, ethylene-based polymer may begin to increase.

[0047] The thermally cross-linked ethylene-based polymer may be used to form various articles, including monolayer and multilayer films; molded articles, such as blow molded, injection molded, or rotomolded articles; coatings; fibers; and woven or non- woven fabrics, cables, pipes, green house films, silo bag films, collation shrink films, food packaging films, or foams.

[0048] Process for Making Thermally Cross-linked Ethylene-based Polymer

[0049] In embodiments, a process for making a thermally cross-linked ethylene-based polymer comprises producing an ethylene-based polymer and crosslinking the ethylene-based polymer with heat in the presence of oxygen for a duration and at a temperature

[0050] The ethylene-based polymer may be produced by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules, as described herein.

[0051] In embodiments, the crosslinking may comprise heating the ethylene-based polymer in the presence of oxygen. Heat and oxygen promote crosslinking, thereby achieving the desired increase in melt elongation. In embodiments, the ethylene-based polymer may be formed into an article (e.g., polymer pellets) prior to thermal treatment. In embodiments, the crosslinking may occur in ambient air (i.e. 21% oxygen). In embodiments, the crosslinking may occur in little to no light, such as in a dark convection oven.

[0052] In embodiments, the crosslinking may occur at a temperature greater than or equal to 40 °C, greater or equal to 60 °C, greater or equal to 80 °C, or even greater or equal to 100 °C.

[0053] In embodiments, the crosslinking may occur for a duration greater than or equal to 10 minutes, greater than or equal to 20 minutes, greater than or equal to 30 minutes, or even greater or equal to 60 min.86132-WO-PCT / DOW 86132 WO9

[0054] One skilled in the art would appreciate that temperature and / or duration may be altered to effect crosslinking. Relatively higher temperatures for relatively short durations or relatively low temperature for relatively long durations may both produce the desired crosslinking.

[0055] In embodiments, the crosslinking does not include any additional reagents or catalysts, such as silane or peroxide crosslinker.

[0056] TEST METHODS

[0057] Melt Elongation

[0058] “Melt elongation,” as used herein, refers to the measure of the maximum tension applied to a polymer in a melted state, before the polymer breaks. Melt elongation is measured using a GOTTFERT D-Melt instrument (GOTTFERT Werkstoff-Prufmaschinen GmbH, SiemensstraBe 2, 74722 Buchen, Germany). A molten polymer strand is extruded from a standard plastometer barrel at a constant temperature (190 °C) through a standard ASTM D1238 MFR die orifice (height (8.000 ± 0.025 mm) and diameter (2.0955 ± 0.005 mm)) using a weighted piston. The extrudate is pulled through 2 free spinning rollers onto a drum driven by a stepper motor which is ramped over a velocity range during the analysis. The force of the polymer strand pulling up on the force sensor platform mounted tension roller is recorded by the integrated control computer. From a curve fitting function of the acquired force data, the final reported melt elongation value is determined based on a constant velocity ratio of the polymer strand speed versus the die exit speed. Measurement results are reported as melt elongation in milli-Newton (mN). After the melt elongation measurement, the melt index measurement at ASTM conditions as described below is performed with the same charge.

[0059] Melt Index

[0060] The terms "melt index," or “h,” as used herein, refer to the measure of how easily a thermoplastic polymer flows when in a melted state. Melt index (H) is measured in accordance with ASTM D 1238, Condition 190 °C / 2.16 kg, and is reported in grams eluted per 10 minutes (g / 10 min).

[0061] EXAMPLES

[0062] By way of example, and not limitation, some embodiments of the present disclosure will now be described in detail by the following examples.Materials86132-WO-PCT / DOW 86132 WO10

[0063] Polybutadienes (Additive A: Polyvest 110 and Additive B: Polyvest EP MV) were supplied from Evonik Industries. Polybutadiene (Additive C: B-1000) was supplied from Nippon Soda, Co.Polymerization: Autoclave Reactor

[0064] Inventive Examples IE1-IE3

[0065] For Inventive Examples IE1-IE3, Additive A, B, or C was loaded into a 316 stainless steel supply vessel and diluted with Isopar™ E to produce a final concentration of 1.7 wt%. This vessel was purged with nitrogen for three hours before use and kept under 70 psig nitrogen pad during operation.

[0066] Peroxide initiator tert-butyl peroxy acetate (TP A, 20% by weight solution in ISOPAR™ H) and peroxide initiator di-tert-butyl peroxide (DTBP, 20% by weight solution in ISOPAR™ H) were combined with ISOPAR E in a second 316 stainless steel supply vessel to produce 1500 mass ppm TPA and 415 mass ppm DTBP (a ratio of 4:1 mole TPA / mole DTBP). The vessel was padded and de-padded five times with 70 psig nitrogen before use and kept under nitrogen pad during operation.

[0067] Ethylene was injected at 5500 gm / hr and at a pressure of 193 MPa into an agitated (1600 rpm) 300 mL high pressure CSTR reactor with an external heating jacket set to control the internal reactor temperature at 220 °C. Propylene (CTA) was added to the ethylene stream at a pressure of 6.2 MPa and controlled at a rate to produce a final product with a MI of about 4 g / 10 min before the mixture was compressed to 193 MPa and injected into the reactor. The solution of the appropriate additive solution was pumped at a pressure of 193 MPa directly into the reactor via a high-pressure pump. The peroxide initiator solution was added directly to the reactor, through the sidewall, at a pressure of 193 MPa at a rate to control the ethylene conversion near 12%.

[0068] Comparative Sample CSA

[0069] For Comparative Sample CSA, all process conditions were the same as for Inventive Examples IE1-IE3, except for the Comparative Sample CSA, no additives were added.

[0070] Polymerization: Tubular Reactor

[0071] Comparative Sample CSB

[0072] For Comparative Sample CSB, the polymerization was carried out in a tubular reactor with three reaction zones. In each reaction zone, pressurized water was used for cooling and / or86132-WO-PCT / DOW 86132 WO11 heating the reaction medium, by circulating this water through the jacket of the reactor. The inlet-pressure was 222 MPa. Each reaction zone had one inlet and one outlet. Each inlet stream consisted of the outlet stream from the previous reaction zone and / or an added ethylene-rich feed stream. The non-converted ethylene and other gaseous components in the reactor outlet were recycled through a high pressure recycle and a low pressure recycle and were compressed and distributed through a booster and a primary and a hyper (secondary) compressor. Organic peroxides (tert-butyl peroxy-2-ethyl hexanoate and di-tert-butyl peroxide) were fed into each reaction zone. Propionaldehyde (PA) was used as a chain transfer agent (CTA) and it was present in each reaction zone inlet, originating from the low pressure and high pressure recycle flows. The fresh PA was added only to the second and third reactions zones in the ratio equivalent to 0.8 and 0.2, respectively. Fresh ethylene was directed towards the first reaction zone.

[0073] After reaching the first peak temperature (maximum temperature) in reaction zone 1, the reaction medium was cooled with the aid of the pressurized water. At the outlet of reaction zone 1, the reaction medium was further cooled by injecting cold, ethylene-rich feed and the reaction was re-initiated by feeding an organic peroxide system. This process was repeated at the end of the second reaction zone to enable further polymerization in the third reaction zone. The polymer was extruded and pelletized (about 30 pellets per gram), using a single screw extruder at a melt temperature around 230-250°C. The weight ratio of the ethylene-rich feed streams to the three reaction zones was 1.00:0.80:0.20. The internal process velocity was approximately 12.5, 9, and 11 m / sec, respectively, for the first, second, and third reaction zones.

[0074] Inventive Example IE4

[0075] For Inventive Example IE4, the polymerization was carried out in a tubular reactor with three reaction zones, as discussed above for Comparative Sample B. All process conditions were the same as for Comparative Sample B, except for Inventive Example IE4, Additive C was added to the first zone.

[0076] Thermal crosslinking in the presence of air

[0077] Inventive Examples IE1-4 and Comparative Samples CSA and CSB were heated in a dark convection oven at 100 °C in ambient conditions for various durations as indicated. The oven was the UT 6060 model of Heraeus Instruments, with valve to control air flow fully open. The pellets were introduced in an aluminum bucket, evenly distributed over the surface in a single layer, and placed in the center of the oven.86132-WO-PCT / DOW 86132 WO12

[0078] The melt elongations (in mN) of Inventive Examples IE1-4 and Comparative Samples CSA and CSB, after thermal treatment for the time indicated and the melt elongation increase (in percentage and change), as compared to non-exposure (i.e., time = 0 hours) are shown in Tables 1 and 2. The melt indexes (in g / 10 min) of Inventive Examples IE1-IE4, Comparative Samples CSA and CSB and corresponding change of melt index, as compared to non-exposure are also shown in Tables 1 and 2.

[0079] Table 11Reliable measurement capabilities of machine limited to 200 mN.86132-WO-PCT / DOW 86132 WO13

[0080] Table 2

[0081] Table 2 cont.

[0082] As shown in Tables 1 and 2, after thermal treatment, Inventive Examples IE1-IE4, thermally cross-linked ethylene-based polymers including polybutadiene, had greater melt86132-WO-PCT / DOW 86132 WO14 elongations as compared to the samples not exposed to thermal treatment. Moreover, the melt elongations of Inventive Examples IE1-IE4 continued to increase as thermal treatment duration increased. After a certain duration, melt elongations were so high that they could not be measured.

[0083] As also shown in Tables 1 and 2, after thermal treatment, Inventive Examples IE1-IE4, thermally cross-linked ethylene-based polymers including polybutadiene, had greater melt elongation increases as compared to Comparative Samples CSA and CSB, thermally crosslinked ethylene-based polymers lacking polybutadiene, after the same duration of exposure.

[0084] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.

Claims

86132-WO-PCT / DOW 86132 WO15CLAIMS1. A thermally cross-linked ethylene-based polymer comprising: ethylene-based polymer formed by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules, each of the one or more hydrocarbon-based molecules comprising three or more terminal alkene groups, wherein the thermally cross-linked ethylenebased polymer, thermally cross-linked in the presence of oxygen, has a greater melt elongation relative to an ethylene-based polymer not subjected thermal crosslinking in the presence of oxygen.2 The thermally cross-linked ethylene-based polymer of claim 1, wherein each of the one or more hydrocarbon-based molecules comprise Structure I:Structure Iwherein R = H or OH, n is from 3 to 160, and m is from 0 to 50.3 The thermally cross-linked ethylene-based polymer of claims 1 or 2, wherein each of the one or more hydrocarbon-based molecules comprise Structure II:Structure IIwherein R = H or OH, n is from 3 to 160, and m is from 0 to 50; x is from 0 to 50, and y is from 0 to 160.4 The thermally cross-linked ethylene-based polymer of claims 2 or 3, wherein a mixture of the one or more hydrocarbon-based molecules based on Structures I or II has a molecular weight distribution (MWD = Mw / Mn) from 1.2 to 20.86132-WO-PCT / DOW 86132 WO165. The thermally cross-linked ethylene-based polymer of any one of claims 1 to 4, wherein the ethylene-based polymer has an alkenes content from 0.05 / 1000 carbons to 3.0 / 1000 carbons, or from 0.07 / 1000 carbons to 2.0 / 1000 carbons, or from 0.1 / 1000 carbons to 1.2 / 1000 carbons.6 The thermally cross-linked ethylene-based polymer of any one of claims 1 to 5, wherein the ethylene-based polymer composition is a low density polyethylene comprising, in polymerized form, ethylene monomer and the one or more hydrocarbon-based molecules.7 The thermally cross-linked ethylene-based polymer of any one of claims 1 to 6, wherein the melt elongation of the thermally cross-linked ethylene-based polymer is at least 5% greater than the ethylene-based polymer not subjected to thermal crosslinking in the presence of oxygen.8 The thermally cross-linked ethylene-based polymer of any one of claims 1 to 7, wherein the melt elongation of the thermally cross-linked ethylene-based polymer is at least 2 mN greater than the ethylene-based polymer not subjected to thermal crosslinking in the presence of oxygen.9 The thermally cross-linked ethylene-based polymer of any one of claims 1 to 8, wherein the melt elongation of the thermally cross-linked ethylene-based polymer is greater than or equal to 20 mN.10 An article comprising the thermally cross-linked ethylene-based polymer of any one of claims 1 to 9.11 A process for making a thermally cross-linked ethylene-based polymer comprising: producing an ethylene-based polymer by high pressure (greater than or equal to 100 MPa and less than or equal to 400 MPa), free-radical polymerization of ethylene and one or more hydrocarbon-based molecules, each of the one or more hydrocarbon-based molecules comprising three or more terminal alkene groups; and crosslinking the ethylene-based polymer with heat in the presence of oxygen for a duration of at least 10 minutes to form the thermally cross-linked ethylene-based polymer, wherein the thermally cross-linked ethylene-based polymer has a greater melt elongation86132-WO-PCT / DOW 86132 WO17 relative to an ethylene-based polymer not subjected to thermal crosslinking in the presence of oxygen.

12. The process of claim 11, wherein the crosslinking does not include silane or peroxide crosslinker.

13. The process of claim 11 or claim 12, wherein the crosslinking occurs at a temperature greater than or equal to 40 °C.

14. The process of any one of claims 11 to 13, wherein the melt elongation of the thermally cross-linked ethylene-based polymer is at least 5% greater than the ethylene-based polymer not subjected to thermal crosslinking in the presence of oxygen.

15. The process of any one of claims 10 to 14, wherein the melt elongation of the thermally cross-linked ethylene-based polymer is at least 2 mN greater than the ethylene-based polymer not subjected to thermal crosslinking in the presence of oxygen.

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