High pressure free radical tubular reactor configuration for improving LDPE product capability and plant capacity

Abstract

A process for producing ethylene-based polymers in the presence of at least one freeradical includes polymerizing a mixture containing ethylene in a tubular reactor having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymerization effluent comprising the ethylene-based polymers. Each each of ethylenecontaining feed streams includes ethylene and chain transfer agents (CTAs). A first ethylenecontaining feed stream passed to a first reaction zone has from 20% to 35% by mole of the total molar flow rate of the four ethylene feed streams introduced to the tubular reactor. Each reaction zone can have a CTA activity ratio that can be adjusted to produce the ethylene-polymers having broader molecular weight distributions compared to existing tubular reactor systems. The process is flexible and can be modified to change the CTA activity ratios to also produce polymers with narrow molecular weight distributions.

Description

HIGH PRESSURE FREE RADICAL TUBULAR REACTOR CONFIGURATION FOR IMPROVING LDPE PRODUCT CAPABILITY AND PLANT CAPACITYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 586,465 filed September 29, 2023, the contents of which are incorporated by reference in their entirety herein.BACKGROUNDField

[0002] The present disclosure generally relates to systems and processes for producing ethylene-based polymers, more specifically, to systems and process for increasing process capabilities of high pressure free radical tubular reactors for producing ethylene-based polymers.Technical Background

[0003] Low Density Poly Ethylene (LDPE) and other ethylene-based polymers are produced in an autoclave reactors and / or tubular reactors at high pressure and temperature. High pressure, free-radical polymerizations are disclosed in the following references: U.S. Pat. Nos. 8,445,606, 4,135,044, and 7,582,709, and Japanese Patent No. JP050534422 (Abstract). High-pressure tubular reactors have been used in industry for making LDPE products for over 40 years. High- pressure tubular reactors offer flexible technology development and high ethylene conversion per pass, in addition to enabling greater production rates with less capital investment compared to autoclave-based processes. However, due to the plug-flow characteristics of the high-pressure tubular reactors, such as but not limited to large gradient temperature, pressure, polymer / ethylene concentration, and shorter residence times along the reactor, the ethylene-based polymers produced from the high-pressure tubular reactors typically exhibit narrower molecular weight distributions and lower melt strength compared to the broader molecular weight distribution polymers made in autoclave reactors, which include well-mixed flow and long residence times. The narrow molecular weight distribution and lower melt strength of the ethylene-based polymers produced in conventional high-pressure tubular reactors limit the use of the high-pressure tubular reactors for producing ethylene-based polymers for extrusion coatings and big bubble fdms.SUMMARY

[0004] Therefore, there is an ongoing need for systems and processes for using high-pressure tubular reactors to produce ethylene-based polymers that are suitable for extrusion coatings andbig bubble films, in order to take advantage of the greater production capacity and reduced capital costs of the tubular reactors. The present disclosure is directed to systems and processes that include a tubular reactor configuration that broadens the operating window of the tubular reactor to enable the production of ethylene -based polymers having broader molecular weight distribution, greater level of long chain branching, and increased melt strength. The systems and processes disclosed herein may enable the high-pressure tubular reactors to be able to produce ethylene-based polymers having characteristics similar to those produced in autoclave reactor systems and being suitable for extrusion coating applications fulfilling FDA food contact requirement. The systems and processes disclosed herein may further enable greater process flexibility to change operation of the tubular reactors between producing broad molecular weight distribution polymers and narrow molecular weight distribution polymers.

[0005] According to an aspect disclosed herein, a process for producing ethylene-based polymers in the presence of at least one free-radical may include polymerizing a mixture comprising ethylene in a tubular reactor having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymerization effluent comprising the ethylene-based polymers. Each of the at least four ethylene-containing feed streams may comprise ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers. The at least four reaction zones may comprise a first reaction zone, a second reaction zone downstream of the first reaction zone, a third reaction zone downstream of the second reaction zone, and at least one fourth reaction zone downstream of the third reaction zone. A first ethylene-containing feed stream passed to the first reaction zone may comprise from 20% to 35% by mole of the total molar flow rate of the at least four ethylene feed streams introduced to the tubular reactor. A CTA activity ratio (Z2 / Z1) for the second reaction zone may be from 0.2 to 2.0, or more preferably from 0.3 to 1.9, or most preferably from 0.5 to 1.8; a CTA activity ratio (Z3 / Z1) for the third reaction zone may be from 0.12 to 1.5, more preferably from 0.15 to 1.4, or most preferably from 0.2 to 1.3; and a CTA activity ratio (Z4 / Z1) for the fourth reaction zone may be from 0.0 to 0.7, more preferably from greater than 0.0 to 0.7, or most preferably from 0.05 to 0.6.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0007] FIG. 1 schematically depicts a process for producing ethylene-containing polymers, according to one or more embodiments shown and described herein;

[0008] FIG. 2 graphically depicts melt strength of the ethylene-based polymers (y-axis) as a function of reactor technology (x-axis), according to one or more embodiments shown and described herein;

[0009] FIG. 3 graphically depicts reactor temperature (y-axis) as a function of relative distance along the tubular reactor (x-axis) for producing ethylene-based polymers having broad molecular weight distribution, according to one or more embodiments shown and described herein;

[0010] FIG. 4 graphically depicts reactor temperature (y-axis) as a function of relative distance along the tubular reactor (x-axis) for producing ethylene-based polymers having a narrower molecular weight distribution, according to one or more embodiments shown and described herein; and

[0011] FIG. 5 schematically depicts another process for producing ethylene-containing polymers, according to one or more embodiments shown and described herein.

[0012] Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.DETAILED DESCRIPTION

[0013] Embodiments of the present disclosure are directed to systems and processes for producing ethylene-based polymers. In particular, one or more embodiments of the present disclosure are directed to systems and processes for producing ethylene-based polymers having broad molecular weight distributions and for providing additional process flexibility to make ethylene-based polymers with narrow or broad molecular weight distributions. Referring now to FIG. 1, the reactor systems 100 disclosed herein comprise a tubular reactor 110 having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymerization effluent 130 comprising the ethylene-based polymers. Each of the at least four ethylene-containing feed streams may comprise ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers. The at least four reaction zones may comprise a first reaction zone, a second reaction zone downstream of the first reaction zone, a third reaction zone downstream of the second reaction zone, and at least one fourth reaction zone downstream of the third reaction zone. A first ethylene-containing feed stream passed to the first reaction zone may comprise from 20% to 35% by mole of the total molar flow rate of the at least four ethylenefeed streams introduced to the tubular reactor. A CTA activity ratio (Z2 / Z1) for the second reaction zone may be from 0.2 to 2.0, or more preferably from 0.3 to 1.9, or most preferably from 0.5 to 1.8; a CTA activity ratio (Z3 / Z1) for the third reaction zone may be from 0.12 to 1.5, more preferably from 0.15 to 1.4, or most preferably from 0.2 to 1.3; and a CTA activity ratio (Z4 / Z1) for the fourth reaction zone may be from 0.0 to 0.7, more preferably from greater than 0.0 to 0.7, or most preferably from 0.05 to 0.6. The CTA activity ratios are as defined herein.

[0014] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percentages are based on weight, and all test methods are current as of the filing date of this application.

[0015] As used herein, the terms "ethylene feed stream," or "ethylene based feed," or "ethylene based feed stream," or "ethylene feed," or "ethylene-containing feed stream," as used herein, refer to a feed stream to a reaction zone, and which contains a majority amount of ethylene, based on the molar amount of all of the components in the feed stream. Optionally, one of more chain transfer agents (CTA), comonomers, other process components (e.g., lubrication oil, solvent, antioxidant(s), ethane, methane, inhibitors, etc.) and / or impurities (e.g., initiator degradation products) might be present in the feed stream.

[0016] As used herein, the term "ethylene conversion" refers to a weight fraction of the ethylene fed to the reactor that is incorporated in the final polymer produced. In other words, the "ethylene conversion" refers to the amount of ethylene incorporated in the final ethylene-based polymer divided by the total amount of ethylene fed to the reactor.

[0017] As used herein, the term "composition" refers to a mixture of materials which comprise the compositions, as well as reaction products and decomposition products formed from the materials of the composition.

[0018] As used herein, the term "polymer" refers to a compound prepared by polymerizing monomers, whether of the same or a different type. The generic term "polymer" thus embraces the term "homopolymer" (which refers 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 "interpolymer," as defined below. Trace amounts of impurities may be incorporated into and / or within the polymer. Trace amount of impurities can include initiator residues and other components showing chain transfer activity, such as for instance lubrication oils, antioxidants, solvents, ethane, methane and / or initiator dissociation products, or other additives. The term "interpolymer" refers to polymers prepared by the polymerization of at least two different types of monomers. The generic term "interpolymer" includes copolymers (which refers to polymersprepared from two different monomers), and polymers prepared from more than two different types of monomers.

[0019] As used herein, the term "ethylene-based polymer" refers to a polymer that comprises a majority amount of polymerized ethylene, based on the weight of the polymer, and, optionally, at least one comonomer. As used herein, the term "ethylene-based interpolymer" refers to an interpolymer that comprises a majority amount of polymerized ethylene, based on the weight of the interpolymer, and at least one comonomer. The term "ethylene-based copolymer" refers to a copolymer that comprises a majority amount of polymerized ethylene, based on the weight of the interpolymer, and a comonomer as the only monomer types.

[0020] As used herein, the term "high pressure polymerization process" refers to a free radical polymerization process carried out at an elevated pressure (inlet pressure) of at least 1000 bar (i.e., greater than or equal to 100 MPa).

[0021] As used herein, the terms "inlet stream" or "reaction zone inlet stream" refer to the total mass flow or total molar flow at the inlet of a reaction zone, and consists of the mass flow or molar flow transferred from the previous reaction zone plus optional ethylene-rich feed streams, plus optionally CTA feed stream, plus optionally initiator feed stream fed optionally alone or together with another feed stream.

[0022] As used herein, the terms "side stream" or "side feed stream" refer to the ethylene-based feed stream, CTA system feed stream, and / or initiator system, to sequential reaction zones.

[0023] As used herein, the term "reactor system" refers to the devices used to polymerize and isolate a polymer. Such devices include, but are not limited to, one or more reactors, reactor preheaters), ethylene based feed-reactor cooling device(s), Hyper-compressor(s), Primary compressor(s), and / or Booster compressor(s).

[0024] As used herein, the term "reactor configuration" refers to one or more reactors, and optionally one or more reactor pre-heaters, used to polymerize a polymer.

[0025] As used herein, the term "inlet pressure" or "reactor inlet pressure" refers to the pressure level at the inlet of the first reaction zone.

[0026] As used herein, the term "reaction zone" refers to a zone in a reactor, in which zone a polymerization reaction is initiated or reinitiated by the addition of free radicals or components which dissociate into and / or generate free radicals. Typically, a reaction medium is heated and / or cooled by a heat transfer medium flowing through a jacket around the reactor. A reaction zone may also start with the addition of fresh and / or recycled ethylene, and / or free radicals or components, which dissociate into and / or generate free radicals.

[0027] As used herein, the term "first reaction zone" refers to the first reactor zone where the polymerization is initiated by the addition of radicals and / or components which dissociate into and / or generate radicals. The first reaction zone ends at the point where there is a new feed of radicals, and / or components, which dissociate into and / or generate radicals, and, optionally, fresh, recycled ethylene and / or comonomer(s).

[0028] As used herein, the phrase "maximum temperature for a reaction zone" refers to the highest temperature measured in a reaction zone, for example, in a tubular reaction zone.

[0029] As used herein, the terms "Hyper compressor," or "Secondary compressor" refer to a device that compresses one or more of the following: a) the compressed fresh ethylene stream coming from the first primary compressor; b) the compressed low pressure ethylene stream coming from the second primary compressor; and / or c) the high pressure ethylene recycle stream from the high pressure separator, each to a pressure level required to feed the reactor at its inlet pressure. This compression can take place in one or multiple compression stages, and can be combined with intermediate cooling. The Hyper compressor comprises a reciprocating plunger compressor, and can consist of single or multiple compressor frame(s).

[0030] As used herein, the term "fresh," in reference to an ethylene-based feed component (i.e., "fresh ethylene," "fresh CTA," etc.), refers to reactant provided from an external source(s), and not provided internally from a recycled source(s), such as but not limited to a high-pressure recycle stream, a low-pressure recycle stream, or other recycle stream. For example, in embodiments, fresh ethylene can be used as "make-up ethylene" required to compensate for the ethylene consumed by the polymerization and / or lost through, for example, ethylene purge from the process and residual ethylene in the polymer.

[0031] As used herein, the term "recycled," when used in reference to a reactant (i.e., "recycled ethylene," "recycled CTA," etc.), refers to unreacted reactants separated from the polymer in the high pressure separator(s) and / or the low pressure separator(s), and returned to the reactor and / or to the compressors upstream of the reactor.

[0032] As used herein, the terms "feed," "feed flow," or "feed stream," as used herein, refers to fresh and / or recycled components (for example, ethylene, initiator, CTA, and / or solvent) added to a reaction zone at an inlet.

[0033] As used herein, the term "mole fraction" refers to the molar ratio of one component in a mixture to the total moles of the components of the mixture. Mole fraction can be determined by calculating the ratios of molar amounts or molar flows.

[0034] As used herein, the phrase "mole fraction of fresh ethylene fed to the first reaction zone (RZ1)" refers to the molar amount of fresh ethylene fed (via a front stream) to the first reaction zone divided by the molar amount of ethylene plus optional comonomer(s) plus optional CTA(s) fed (via a front stream) to the first reaction zone.

[0035] As used herein, the phrase "mole fraction of fresh ethylene fed to the nth reaction zone (RZn)" refers to the molar amount of fresh ethylene fed (via a side stream) to the nth reaction zone divided by the molar amount of ethylene plus optional comonomer(s) plus optional CTA(s) fed (via a side stream) to the nth reaction zone.

[0036] As used herein, the term "CTA system" includes a single CTA, or a mixture of CTAs, added to the polymerization process, typically to control the melt index. A CTA system includes a component able to transfer a hydrogen atom to a growing polymer molecule containing a radical, by which a radical is formed on the CTA molecule, which can then initiate a new polymer chain. CTA is also known as telogen or telomer.

[0037] As used herein, the terms "CTA activity" or "chain transfer activity coefficient (Cs value)" refer to the ratio between the "rate of chain transfer" to the "rate of ethylene propagation." See Mortimer references: P. Ehrlich, G. A. Mortimer, Fundamentals of the free radical polymerization of ethylene, Adv. Polymer Sci., Vol. 7, 386-448 (1970); G. Mortimer, Journal of Polymer Science: Part A-l; Chain transfer in ethylene polymerization,- Vol. 4, p 881-900 (1966); G. Mortimer, Journal of Polymer Science: Part A-l, Chain transfer in ethylene polymerization. Part IV. Additional study at 1360 atm and 130° C. ; Vol. 8, p 1513-1523 (1970); G. Mortimer, Journal of Polymer Science: Part A-l, Chain transfer in ethylene polymerization. Part V. The effect of temperature,- Vol. 8, p 1535-1542 (1970); G. Mortimer, Journal of Polymer Science: Part A-l, Chain transfer in ethylene polymerization Part V. The effect of pressure, Vol. 8, p 1543-1548 (1970); and G. Mortimer, Journal of Polymer Science: Part A-l, Chain transfer in ethylene polymerization VII. Very reactive and depleteable transfer agents, Vol. 10, p 163-168 (1972). See EDPE simulation model in S. Goto et al., Journal of Applied Polymer Science: Applied Polymer Symposium, 36, 21-40, 1981 (Title: Computer model for commercial high pressure polyethylene reactor based on elementary reaction rates obtained experimentally).

[0038] As used herein, the terms "Z1 and Zi" as used herein is determined as follows: The "reactor zone molar concentration of a CTAj in a reactor zone i ([CTA]ji)" is defined as the "total molar amount of that CTA fed (excluding a transfer from a previous reaction zone) into reactor zones k=l to k=I" divided by the "total molar amount of ethylene fed (excluding a transfer froma previous reaction zone) into reactor zones 1 to i." Note i>l. This relationship is shown below in Equation AC (EQU. AC).In EQU. AC, j>l, nciAjk is the "amount of moles of the jth CTA freshly injected to the kth reactor zone (where k=l to i)," and neth k is the "amount of moles of ethylene freshly injected to the kth reactor zone (where k=l to i) . "

[0039] As used herein, the "chain transfer activity of a CTA (system) in a reactor zone I (Zi)" is defined as the "sum of the reactor zone molar concentration of each CTA in the reactor zone" multiplied with its chain transfer activity constant (Cs) — see Equation BC (EQU. BC). The chain transfer activity constant (Cs) is the ratio of reaction rates Ks / Kp, at a reference pressure (1360 atm) and a reference temperature (130 °C). This relationship is shown below in EQU. BC, where nComPiis the total number of CTAs in reactor zone i. Note i>l, and nComPi>l .

[0040] The chain transfer constant (Cs) values for some chain transfer agents are shown below in Table 1, showing chain transfer constants (Cs) derived by Mortimer at 130 °C and 200 °C, and at 1360 atm, for the shown chain transfer agents.Table 1

[0041] As used herein, the term "Rn=RZl / RZn" refers to, for reaction zone n, the ratio of the "mole fraction of fresh ethylene fed to the first reaction zone (RZ1)" to the "mole fraction of fresh ethylene fed to reaction zone n (RZn)." For the polymerization of ethylene homo-polymers, theRZ1 and RZn values are determined according to the following Equations AE and BE (EQU. AE and EQU. BE).In EQU. AE, nfresh.eth.i is molar flow of fresh ethylene (from Primary) fed to reaction zone 1 [mol / hr], nrresh cth ii is molar flow of fresh ethylene (from Primary) fed to reaction zone n [mol / hr], neth,i is molar flow of ethylene from the high pressure recycle stream fed to reaction zone 1[mol / hr], neth, n is molar flow of ethylene from high pressure recycle stream fed to the reaction n.

[0042] As used herein, the term "initiator system" includes a single initiator, or a mixture of initiators, each typically dissolved in a solvent (for example, a hydrocarbon solvent) added to the polymerization process.

[0043] As used herein, the term "injection point" refers to the inlet location of a device (used in a polymerization process) where a feed stream is added into the device.

[0044] As used herein, the term "feed conditions" refers to the flows in moles of the components fed to the reactor, for instance ethylene, CTA, initiators and / or co-monomer(s).

[0045] As used herein, the terms "upstream" and "downstream" are relative to the direction of flow of materials through the process or reactor system components. For example, a first reactor system component is upstream of a second reactor system component if one or more material streams encounter the first reactor system component before encountering the second reactor system component.

[0046] Referring now to FIG. 1, the process disclosed herein for producing ethylene-based polymers in the presence of at least one free-radical may comprise polymerizing a mixture comprising at least ethylene in a tubular reactor system 100 to produce a polymerization effluent 130 comprising the ethylene-based polymers. The tubular reactor system 100 has at least four reaction zones in series and at least four ethylene-containing feed streams. The tubular reactor system 100 comprises a tubular reactor 110. The tubular reactor 110 include at least a first reaction zone 112. In embodiments, the tubular reactor system 100 may further include at least a second reaction zone 114 downstream of the first reaction zone 112, a third reaction zone 116 disposed downstream of the second reaction zone 114, and a fourth reaction zone 118 disposed downstream of the third reaction zone 116.

[0047] Each of the at least four ethylene-containing feed streams comprise ethylene, optionally one or more comonomers, and optionally one or more chain transfer agents (CTAs). The at least four ethylene-containing feed streams may comprise at least a first ethylene-containing feed stream 122 introduced to the first reaction zone 112. The first ethylene-containing feed stream is from 20% to 35% by mole of the total of the at least four ethylene feed streams introduced to the tubular reactor 110. The concentration of the CTAs in each of the ethylene-containing feed streams may be varied along a length of the tubular reactor 110. In particular, a concentration of the CTAs in the first ethylene-containing feed stream 112 is different from concentrations of the CTAs in each of the other of the at least four ethylene-containing feed streams. In embodiments, the CTA activity ratio in each of the at least four reaction zones may be modified to produce ethylene-based polymers with broader molecular weight distribution and / or higher melt index. In embodiments, the concentrations of the CTAs in each of the at least four ethylene-containing feed stream may be adjusted to change the CTA activity ratio for each reaction zone, and thus change the molecular weight distribution, melt index, or both of the ethylene-based polymers in the polymerization effluent 130.

[0048] Referring again to FIG. 1, the reactor system 100 may include a first heat exchanger 140 disposed upstream of the first reaction zone 112 of the tubular reactor 110. The first heat exchanger 140 may be operable to heat the first ethylene-containing feed stream 122 to an inlet temperature of at least 140 °C. The reactor system 100 may include a second ethylene-containing feed stream 124 introduced to the second reaction zone 114. The reactor system 100 may further include a second heat exchanger 150 upstream of the second reaction zone 114, wherein the second heat exchanger 150 is operable to control a temperature of the second ethylene-containing feed stream 124. The reactor system 100 may further include a third ethylene-containing feed stream 126 introduced to the third reaction zone 116 and a fourth ethylene-containing feed stream 128 introduced to the fourth reaction zone 118. The system 100 may further include a third heat exchanger 160 upstream of the third reaction zone 116, wherein the third heat exchanger 160 may be operable to control a temperature of the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both. The polymerization reaction is an exothermic reaction. In embodiments, the second heat exchanger 150, the third heat exchanger 160, or both may be operable to cool the second ethylene-containing feed stream 124, third ethylene-containing feed stream 126, fourth ethylene-containing feed stream 128, or combinations of these to temperatures of less than or equal to 90 °C prior to introducing these streams to their respectivereaction zone, to provide cooling to each of the reaction zones downstream of the first reaction zone 112.

[0049] In embodiments, the reactor system 100 comprises at least one tubular reactor 110, and each tubular reactor may have one or more cooling zones (not shown). In embodiments, the reactor system 100 may comprises at least one tubular reactor 110, and each tubular reactor may be equipped with multiple heat transfer zones (not shown), and where heat is exchanged between the process side and a heat transfer medium. In embodiments, the reactor system 100 comprises the at least one tubular reactor 100, and the cooling and / or heating to each reactor may be provided by pressurized liquid water operating in a co-current mode and / or counter current mode, in multiple cooling zones surrounding the tubular reactor 110. In embodiments, the reactor system may comprise the at least one tubular reactor 110, and the cooling and / or heating to each reactor may be provided by a liquid heat transfer fluid (for example, a silicon oil and / or a polyglycol (e.g., DOWTHERM fluids)) (not shown), operating in a co-current mode and / or counter current mode, in multiple cooling zones surrounding the tubular reactor 110. In embodiments, the tubular reactor 110 may be typically equipped with a heat transfer jacket (not shown) to allow heat transfer with the help of heat transfer medium flowing through the heat transfer jacket.

[0050] In embodiments, the reactor system 100 comprises the at least one tubular reactor 110, and each tubular reactor 110 may be equipped with multiple jackets, and wherein each jacket has one inlet and one outlet, and wherein the respective inlets and outlets of all of the jackets are connected in series, to each other, to form one heat transfer zone. In embodiments, the inlet temperatures of the heat transfer zones are uniform, and each inlet temperature is from 20 °C to 330 °C, such as from 20 °C to 300 °C or from 20 °C to 250 °C. In embodiments, at least two inlet temperatures of the heat transfer zones are uniform, and wherein each inlet temperature is from 20 °C to 330 °C, such as from 20 °C to 300 °C or from 20 °C to 250 °C. In embodiments, each inlet temperature of a heat transfer zone is different from the inlet temperatures of the other heat transfer zones, and each inlet temperature is from 20 °C to 330 °C, such as from 20 °C to 300 °C or from 20 °C to 250 °C.

[0051] Referring again to FIG. 1, as previously discussed, the reactor system 100 may comprise at least four reaction zones, such as 4, 5, 6, 7, or more than 7 reaction zones. In embodiments, the total number of reaction zones equals i, and wherein i is greater than, or equal to 4, or >5, or >6, or >7, or >8, or >9, or >10, or >20. In embodiments, the reactor system 100 may comprise at least the first reaction zone 112, the second reaction zone 114 downstream of the first reaction zone 112, the third reaction zone 116 downstream of the second reaction zone 114, andthe fourth reaction zone 118 downstream of the third reaction zone 116. In embodiments, the reactor system 100 may comprise one or more fifth reaction zones 120 downstream of the fourth reaction zone 114.

[0052] In embodiments, the reactor system 100 may comprise a single tubular reactor 110 comprising each of the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, and optionally the one or more fifth reaction zones 120. In embodiments, the reactor system 100 may comprise a plurality of tubular reactors 110 in series, wherein each of the tubular reactors 110 comprises one of the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, and the optional one or more fifth reaction zones 120.

[0053] Referring again to FIG. 1, as previously discussed, the reactor system 100 includes at least 4 ethylene-containing feed streams, such as 4, 5, 6, 7, or more than 7 ethylene-containing feed streams. In embodiments, the reactor system 100 may comprise the first ethylene-containing feed stream 122 introduced to the first reaction zone 112, the second ethylene-containing feed stream 124 introduced to the second reaction zone 114, the third ethylene-containing feed stream 126 introduced to the third reaction zone 116, and at least one fourth ethylene-containing feed stream 128 introduced to at least one fourth reaction zone 118.

[0054] Each of the ethylene-containing feed streams (e.g., first ethylene-containing feed stream 122, second ethylene-containing feed stream 124, third ethylene-containing feed stream 126, fourth ethylene-containing feed stream 128, other ethylene-containing feed streams downstream of stream 128, or combinations thereof) may include ethylene, which may be fresh ethylene or recycled ethylene. One or more of the ethylene-containing feed streams may also include CTA, which may be fresh or recycled. In embodiments, the ethylene-containing feed streams may comprise a solvent (fresh and / or recycled), comonomer(s) (fresh and / or recycled), and / or other components. Other components may include, but are not limited to fresh and / or recycled lubrication oil(s), antioxidant(s), ethane, methane, and / or initiator dissociation products, and the like. In embodiments, one or more of the ethylene-containing feed streams may include ethylene, CTA, solvent, and optionally one or more comonomers, and optionally one or more other components (e.g., lubricant oils, antioxidants, ethane, methane, initiator dissociation additives, etc.)

[0055] In embodiments, the total flow rate of ethylene to the reactor system 100 from the ethylene-based feed streams combined may be from 30 tons per hour to 400 tons per hour, or from 50 tons per hour to 400 tons per hour, or from 75 tons per hour to 400 tons per hour, or from 100tons per hour to 400 tons per hour. In embodiment, the total ethylene based feed flow to the reactor system 100 may be from 40 to 350 tons per hour, or from 50 to 300 tons per hour. In embodiments, the first ethylene-containing feed stream 122, second ethylene-containing feed stream 124, third ethylene-containing feed stream 126, fourth ethylene-containing feed stream 128, other ethylenecontaining feed streams downstream of stream 128, or combinations thereof, may comprise makeup ethylene added to maintain the total flow rate of ethylene to the reactor system 100 to make up for ethylene consumed, lost through purge, and / or trapped in the ethylene-based polymer.

[0056] In embodiments, the ethylene-containing feeds streams (e.g., streams 122, 124, 126, 128, or combinations thereof) include ethylene as the only monomer. In embodiments, the ethylene-containing feed streams may comprise ethylene and one or more comonomers. Comonomers may include, but are not limited to, a-olefins, acrylates, acetates, methacrylates and anhydrides, each typically having no more than 20 carbon atoms. The a-olefin comonomers, which have a combined monomer and CTA functionality, may have 3 to 10 carbon atoms, or in the alternative, the a-olefin comonomers may have 3 to 8 carbon atoms. Exemplary a-olefin comonomers include, but are not limited to, propylene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 1 -nonene, 1 -decene, and 4 methyl- 1 -pentene and combinations thereof. In embodiments, make-up comonomer may be added to one or more of the ethylene-containing feed streams to make up for conomomer consumed, lost through purge, and / or trapped in the polymer.

[0057] As previously discussed, one or more of the ethylene-containing feed streams (e.g., streams 122, 124, 126, 128, or other ethylene-containing feed streams downstream of stream 128,) may include at least one CTA, which may be selected from an aldehyde, an alkane, a ketone, an alcohol, an acetate, an ester, a mercaptan, a phosphine, a phosgene, an alpha-olefin, or a combination thereof. In embodiments, one or more of the ethylene-containing feed streams may comprise at least one CTA selected from an aldehyde, an alkane, a ketone, an alcohol, an acetate, an ester, an alpha-olefin, or a combination thereof. In embodiments, make-up CTA may be added to one or more of the ethylene-containing feed streams (e.g., stream 122, 124, 126, 128, or combinations thereof), to make up for CTA consumed, lost through purge, and / or trapped in the ethylene-based polymer.

[0058] In embodiments, one or more of the ethylene-containing feed streams (streams 122, 124, 126, 128, other stream, or combinations thereof) may further include a branching agent, such as but not limited to polybutadiene. In embodiments, one or more of the ethylene-containing feed streams 122, 124, 126, 128 may comprise one or more hydrocarbon solvents, such as but not limited to C9-C30 normal paraffins, C9-C30 isoparaffins, or a combinations thereof. Inembodiments, one or more of the ethylene-containing feed streams may further comprise an inhibitor, such as but not limited to oxygen. Other inhibitors are contemplated.

[0059] The tubular reactor 110 may be operated at a pressure and temperature sufficient to carry out the polymerization reactions at an economically advantageous reaction rate. In embodiments, the tubular reactor 110 may be operated at a pressure of greater than or equal to 1000 bar (100 MPa), such as from 1000 bar to 4000 bar (400 MPa). Each of the ethylenecontaining feed streams (e.g., streams 122, 124, 126, 128) may be introduced to each of the reaction zones at a pressure of greater than or equal to 1000 bar, such as from 1000 bar to 4000 bar.

[0060] Referring again to FIG. 1, the reactor system 100 may include a plurality of initiator feed streams for introducing a free radical initiator composition to each of the reaction zones. In embodiments, the reactor system 100 may comprise a first initiator feed stream 131 introducing the free radical initiator composition to the first reaction zone 112, a second initiator feed stream 132 introducing the free radical initiator composition to the second reaction zone 114, a third initiator feed stream 133 introducing the free radical initiator composition to the third reaction zone 116, and a fourth initiator feed stream 134 introducing the free radical initiator composition to the fourth reaction zone 118. In embodiments, the reactor system 100 may include a fifth initiator feed stream 135 introducing the free radical initiator composition to the fifth reaction zones 129. The reactor system 100 may include additional initiator feed streams for any subsequent reaction zones downstream of the fifth reaction zone 129.

[0061] Free radical initiators are generally used to assist in producing the ethylene-based polymers. A free radical initiator, as used herein, refers to a free radical generated by chemical and / or radiation methods. Exemplary free radical initiators include organic peroxides including, but not limited to, cyclic peroxides, diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxycarbonates, peroxydicarbonates, peroxyesters, and peroxyketals. In embodiments, the free radical initiators may include, but are not limited to t-butyl peroxy pivalate, di-t-butyl peroxide, t- butyl peroxy acetate, t-butyl peroxy-2 -hexanoate, or any mixtures thereof. Furthermore, oxygen can be used as initiator. In embodiments, the free radical initiators include organic peroxide initiators in an amount from 0.001 wt.% to 0.2 wt %, based upon the total weight of polymerizable monomers. Further information on free radial initiators can be found in U.S. Patent 10,494,456, which has been incorporated by reference herein in its entirety.

[0062] In embodiments, a free radical initiator is added to at least one reaction zone, and the initiator has a half-life temperature, at one second, greater than 255 °C, preferably greater than260 °C. In embodiments, such free radical initiators are used at a peak polymerization temperature from 300 °C to 350 °C, such as from 320 °C to 350 °C. In embodiments, the free radical initiator comprises at least one peroxide group incorporated in a ring structure. Examples of such initiators include, but are not limited to, TRIGONOX 301 (3,6,9-triethyl-3,6,9-trimethyl-l,4,7- triperoxonaan) and TRIGONOX 311 (3,3,5,7,7-pentamethyl-l,2,4-trioxepane), both available from Akzo Nobel, and HMCH-4-AL (3,3,6,6,9,9-hexamethyl-l,2,4,5-tetroxonane) available from United Initiators. See also International Publication Nos. WO 02 / 14379 and WO 01 / 68723. In embodiments, each of the initiator feed streams (e.g., streams 131, 132, 133, 134, 135, etc.) may comprise the free radical initiator and a solvent. The free radical initiator and the solvent may be mixed to produce each of the initiator feed streams upstream of the reaction zones.

[0063] Referring again to FIG. 1 , during operation of the reactor system 100, the first ethylenecontaining ethylene feed stream 122 may passed to the first heat exchanger 140 and heated to a temperature of from 140 °C to 160 °C. The first ethylene-containing feed stream 122 and the first initiator feed stream 131 are then passed to the first reaction zone 112. The monomers (ethylene, and any optional comonomers), CTA, and free radical initiator undergo polymerization reactions in the first reaction zone 112. The reaction mixture then passes from the first reaction zone 112 to the second reaction zone 114.

[0064] The second ethylene-containing feed stream 124 is passed to the second heat exchanger 150 and temperature adjusted to a temperature of less than or equal to 90 °C, such as from 40 °C to 90 °C. The second ethylene-containing feed stream 124 is then passed from the second heat exchanger 150 to the second reaction zone 114 and the second initiator feed stream 132 is also passed to the second reaction zone 114. The reaction mixture from the first reaction zone 112, the second ethylene-containing feed stream 124, and the second initiator feed stream 132 undergo further polymerization in the second reaction zone 112.

[0065] The reaction mixture from the second reaction zone 114 is passed to the third reaction zone 116. An ethylene-containing feed stream is passed to the third heat exchanger 160 and temperature adjusted to a temperature of less than or equal to 90 °C, such as from 40 °C to 90 °C. The ethylene-containing feed stream may then be divided into the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128. The third ethylene-containing feed stream 126 and the third initiator feed stream 133 are then passed to the third reaction zone 116. The reaction mixture from the second reaction zone 114, the third ethylene-containing feed stream 126, and the third initiator feed stream 133 undergo further polymerization in the third reaction zone 112.

[0066] The reaction mixture from the third reaction zone 116 is passed to the fourth reaction zone 118. The fourth ethylene-containing feed stream 128 and the fourth initiator feed stream 134 are also passed to the fourth reaction zone 118. The reaction mixture from the third reaction zone 116, the fourth ethylene-containing feed stream 128, and the fourth initiator feed stream 134 may undergo further polymerization in the fourth reaction zone 118. The reaction mixture from the fourth reaction zone 118 may be passed through one or more additional reaction zones and combined with additional initiator feed streams to further polymerize the reaction mixture to produce the polymerization effluent 130 containing the ethylene-based polymers. In embodiments, the reaction mixture from the fourth reaction zone 118 may be passed to one or more reaction zones downstream of the fourth reaction zone 118, such as fifth reaction zone 120. Optionally, an initiator feed stream may be passed to the fifth reaction zone 120 to facilitate further polymerization of the reaction mixture from the fourth reaction zone 118.

[0067] In embodiments, each reaction zone, independently, may be operated at a maximum temperature that is less than 400 °C, such as from 225 °C to 400 °C, and an inlet pressure greater than or equal to 1000 bar (100 MPa), greater than or equal to 1400 bar (140 MPa), or even greater than or equal to 1800 bar (180 MPa). In embodiments, the polymerization pressure as measured at the first inlet of the first reaction zone 112 of the tubular reactor 110 may be from 1000 bar (100 MPa) to 4000 bar (400 MPa), or from 1400 bar (140 MPa) to 3600 bar (360 MPa), or from 1800 bar (180 MPa) to 3200 bar (320 MPa).

[0068] The polymerization effluent 130 may comprise the ethylene-based polymers produced through the polymerization of the monomers in the tubular reactor 110. The ethylene-based polymers in the polymerization effluent 130 may have any of the features, properties or characteristics described herein for the ethylene-based polymers. The polymerization effluent 130 may also include unreacted ethylene, CTA, and any optional monomers. The polymerization effluent 130 may further include solvents, other components (e.g., lubricating oils, antioxidants, ethane, methane, branching agents, and / or initiator dissociation products, etc.), free radical initiators, or any combinations of these. The polymerization effluent 130 exiting the tubular reactor 110 may have a pressure of from 1000 bar (100 MPa) to 4000 bar (400 MPa), or from 1400 bar (140 MPa) to 3600 bar (360 MPa), or from 1800 bar (180 MPa) to 3200 bar (320 MPa). The polymerization effluent 130 exiting the tubular reactor 110 may have a temperature of from 220 °C to 400 °C, such as from 220 °C to 350 °C.

[0069] The at least four ethylene-containing feed streams may be configured to produce a wide range of molecular weight distributions of the ethylene-based polymers in the polymerizationeffluent 130, which enables the production of ethylene-based polymers with broader molecular weight distributions and higher melt strength. Referring now to FIG. 2, the melt strength as a function of technology is graphically depicted. Reference A in FIG. 2 indicates a tubular reactor system in which all the reactants are introduced to the front of the reactor (i.e., to the first reaction zone) with no side streams introduced to any of the downstream reaction zones. The reactor system of reference A of FIG. 2 produces a specific melt strength and does not offer much flexibility in the melt strength of the resulting ethylene-based polymers. The next iteration of the polymerization technology is shown by Reference B, which refers to a tubular reactor with three reaction zones, where the ethylene-containing feed stream to the first reaction zone is 50% of the total feed flow to the tubular reactor, the ethylene-containing feed stream to the second reaction zone is 30% of the total feed flow to the tubular reactor, and the ethylene-containing feed stream to the third reaction zone is 20% of the total feed flow to the tubular reactor. As shown in FIG. 2, the prior tubular reactor system increases the process window for melt strength of the resulting ethylene-based polymers. However, the process capability range for the prior tubular reactor systems is still limited and does not allow for the production of broad molecular weight distribution polymers having high melt strength, which is required for extrusion coating and big bubble films.

[0070] The reactor system 100 disclosed herein with the at least four reaction zones and at least four ethylene-containing feed streams, which is indicated by Reference C in FIG. 2, is capable of producing a wider range of ethylene-based polymers and can produce ethylene-based polymers with broad molecular weight distribution and / or high melt strength suitable for extrusion coating and big bubble films. The molecular weight distribution and melt strength of the resulting ethylene-based polymers produced by the reactor system 110 disclosed herein can be modified by changing the amounts and compositions of each of the ethylene-based feed streams introduced to the reaction zones.

[0071] Referring again to FIG. 1, the reactor system 100 comprises at least four ethylenecontaining feed streams, which include at least the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128. The first ethylene-containing feed stream 122 may introduce from 20% to 35% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, first ethylene-containing feed stream 122 may introduce from 20% to 30%, from 20% to 25%, from 25% to 35%, from 25% to 30%, or about 25% by mole of the total ethylene, and optionally oneor more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, first ethylene-containing feed stream 122 may introduce from 20% to 35%, from 20% to 30%, from 20% to 25%, from 25% to 35%, from 25% to 30%, or about 25% by mole of the total ethylene introduced to the tubular reactor 110.

[0072] In embodiments, the second ethylene-containing feed stream 124 may introduce from 20% to 35% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, the second ethylenecontaining feed stream 124 may introduce from 20% to 30%, from 20% to 25%, from 25% to 35%, from 25% to 30%, or about 25% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, the second ethylene-containing feed stream 124 may introduce from 20% to 35%, from 20% to 30%, from 20% to 25%, from 25% to 35%, from 25% to 30%, or about 25% by mole of the total ethylene introduced to the tubular reactor 110.

[0073] In embodiments, an amount of ethylene, and optionally the one or more comonomers, and the optionally the one or more CTAs, introduced to the tubular reactor 110 by the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 combined may comprise from 40% to 70% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110, such as from 40% to 65%, from 40%, to 60%, from 40% to 55%, from 40% to 50%, from 45% to 70%, from 45% to 65%, from 45%, to 60%, from 45% to 55%, from 45% to 50%, from 50% to 70%, from 50% to 65%, from 50%, to 60%, or from 50% to 55% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110. In embodiments, an amount of ethylene introduced to the tubular reactor 110 by the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 combined may comprise from 40% to 70%, from 40% to 65%, from 40%, to 60%, from 40% to 55%, from 40% to 50%, from 45% to 70%, from 45% to 65%, from 45%, to 60%, from 45% to 55%, from 45% to 50%, from 50% to 70%, from 50% to 65%, from 50%, to 60%, or from 50% to 55% by mole of the total ethylene introduced to the tubular reactor 110. In embodiments, the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may each introduce 25% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110.

[0074] Referring again to FIG. 1, an amount of ethylene, and optionally the one or more comonomers, and the optionally the one or more CTAs, introduced to the tubular reactor 110 bythe third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 combined may comprise from 30% to 60% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110, such as from 30% to 55%, from 30%, to 50%, from 30% to 45%, from 30% to 40%, from 35% to 60%, from 35% to 55%, from 35%, to 50%, from 35% to 45%, from 40% to 60%, from 40% to 55%, or from 40% to 50% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110. In embodiments, an amount of ethylene introduced to the tubular reactor 110 by the third ethylenecontaining feed stream 126 and the fourth ethylene-containing feed stream 128 combined may comprise from 30% to 60%, from 30% to 55%, from 30%, to 50%, from 30% to 45%, from 30% to 40%, from 35% to 60%, from 35% to 55%, from 35%, to 50%, from 35% to 45%, from 40% to 60%, from 40% to 55%, or from 40% to 50% by mole of the total ethylene introduced to the tubular reactor 110.

[0075] In embodiments, an amount of the ethylene, the optional one or more CTAs, and the optional one or more comonomers in the third ethylene-containing feed stream 126 may be greater than or equal to the amount of ethylene, the optional one or more CTAs, and the optional one or more comonomers in the fourth ethylene-containing feed stream 128. In embodiments, a molar ratio of the third ethylene-containing feed stream 126 to the fourth ethylene-containing feed stream 128 may be from 1 to 4, such as from 1 to 3, from 2 to 4, or even from 2-3.

[0076] In embodiments, the third ethylene-containing feed stream 126 may introduce from 25% to 40% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110, such as from 25% to 35%, from 25% to 30%, from 30% to 40%, or from 35% to 40% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, the third ethylene-containing feed stream 126 may introduce from 25% to 40%, from 25% to 35%, from 25% to 30%, from 30% to 40%, or from 35% to 40% by mole of the total ethylene introduced to the tubular reactor 110.

[0077] In embodiments, the fourth ethylene-containing feed stream 128 may introduce from 10% to 25% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110, such as from 10% to 20%, from 10% to 15%, from 15% to 25%, from 15% to 20%, or from 20% to 25% by mole of the total ethylene, and optionally one or more CTAs, and optionally one or more comonomers introduced to the tubular reactor 110. In embodiments, the fourth ethylene-containing feed stream 128 mayintroduce from 10% to 20%, from 10% to 15%, from 15% to 25%, from 15% to 20%, or from 20% to 25% by mole of the total ethylene introduced to the tubular reactor 110.

[0078] The proportion (e.g., molar ratio) of the third ethylene-based feed stream 126 and the fourth ethylene-containing feed stream 128 introduced to the third reaction zone 116 and the fourth reaction zone 118, respectively, may be controlled with a control system comprising one or a plurality of control valves. Referring again to FIG. 1, the reactor system 100 may include a third ethylene feed control valve 170 disposed in the third ethylene-containing feed stream 126 upstream of the third reaction zone 116. The reactor system 100 may further include a fourth ethylene feed control valve 172 disposed in the fourth ethylene-containing feed stream 128 upstream of the fourth reaction zone 118. The third ethylene feed control valve 170 and the fourth ethylene feed control valve 172 may be adjusted in concert to change the molar ratio of the third ethylene-containing feed stream 126 to the fourth ethylene-containing feed stream 128. Controlling the molar ratio of the third ethylene-containing feed stream 126 to the fourth ethylenecontaining feed stream 128 may change the molecular weight distribution and / or the melt strength of the ethylene -based polymers produced from the reaction system 100.

[0079] The molecular weight distribution and / or the melt strength of the ethylene-based polymers may also be controlled by controlling the amount and / or type of CTAs in each of the ethylene-containing feed streams. In embodiments, a concentration of the CTAs in the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, and the third ethylene-containing feed stream 126 may be different from one another. As shown in FIG. 1, in embodiments, the third ethylene-containing feed stream 126 and the fourth ethylenecontaining feed stream 128 may be derived from a common stream that is divided into the two streams, and, therefore, the CTA concentration in the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 may be the same. In embodiments, a supplemental CTA stream may be added to the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both to further adjust the CTA concentrations in either or both of these two ethylene-containing feed streams.

[0080] The first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may each have concentrations of CTAs so that a CTA activity ratio for the second reaction zone 114 (Z2 / Z1) is from 0.2 to 2.0, or from 0.3 to 1.9, or from 0.5 to 1.8, wherein the CTA activity ratio in the second reaction zone (Z2 / Z1) is equal to the chain transfer activity of the CTA in the second reaction zone (Z2) divided by the chain transfer activity of the CTA in the first reaction zone (Zl). The third ethylene-containing feed stream 126 may have a concentration ofCTAs and flow rate so that a CTA activity ratio for the third reaction zone 116 (Z3 / Z1) is from 0.12 to 1.5, such as from 0.15 to 1.4, or from 0.2 to 1.3, wherein the CTA activity ratio in the third reaction zone (Z3 / Z1) is equal to the chain transfer activity of the CTA in the third reaction zone (Z3) divided by the chain transfer activity of the CTA in the first reaction zone (Z 1 ). The fourth ethylene-containing feed stream 128 may have a concentration of CTAs and flow rate so that a CTA activity ratio for the fourth reaction zone 118 (Z4 / Z1) is from 0.0 to 0.7, such as from 0.05 to 0.6, wherein the CTA activity ratio in the fourth reaction zone (Z4 / Z1) is equal to the chain transfer activity of the CTA in the fourth reaction zone (Z4) divided by the chain transfer activity of the CTA in the first reaction zone (Zl). Zl, Z2, Z3, and Z4 can all be determined using the relationship previously provided in EQU. BC.

[0081] The molecular weight distribution of the ethylene-based polymers in the polymerization effluent 130 may be modified by changing the CTA activity ratios for the second reaction zone 114 (Z2 / Z1), the third reaction zone 116 (Z3-Z1), the fourth reaction zone 118 (Z4 / Z1), or combinations of these. In embodiments, the reactor system 100 may be configured to produce ethylene-based polymers with broad MWD and the CTA activity ratio for the second reaction zone (Z2 / Z1) may be from 0.5 to 2.0, such as from 0.7 to 2.0, or from 1.0 to 2.0. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the third reaction zone (Z3 / Z1) may be from 0.5 to 1.5, such as from 0.5 to 1.4, from 0.6 to 1.3, from 0.7 to 1.25, or from 0.8 to 1.2. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the fourth reaction zone (Z4 / Z1) may be from 0.1 to 0.7, such as from 0.2 to 0.6, or from 0.3 to 0.6.

[0082] In embodiments, the reactor system 100 may be configured to produce ethylene-based polymers with a narrow MWD, and the CTA activity ratio for the second reaction zone (Z2 / Z1) may be from 0.2 to 0.5, or from 0.2 to 0.4. When configured to produce ethylene-based polymers with narrow MWD, the CTA activity ratio for the third reaction zone (Z3 / Z1) may be from 0.12 to less than 0.5, such as from 0.12 to 0.4. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the fourth reaction zone (Z4 / Z1) may be less than 0.1, such as less than or equal to 0.09 or even less than or equal to 0.08.

[0083] In embodiments, the concentration of CTA in the ethylene-containing feed streams may increase with increasing distance from the inlet 111 of the first reaction zone 112 of the tubular reactor 110 to produce ethylene-based polymers with broader molecular weight distribution and / or greater melt strength. In embodiments, the concentration of the CTAs in the second ethylenecontaining feed stream 124 may be greater than the concentration of the CTAs in the first ethylene-containing feed stream 122. In embodiments, a concentration of the CTAs in the third ethylenecontaining feed stream 126, the fourth ethylene-containing feed stream 128, or both may be greater than the concentration of the CTAs in the second ethylene-containing feed stream 124. In embodiments, each ethylene-containing feed stream to each reaction zone may comprise the same CTA system. In embodiments, the CTA system of each feed contains a single CTA. In embodiments, no fresh CTA is distributed to the third reaction zone and the fourth reaction zone.

[0084] In embodiments, the first ethylene-containing feed stream 122 may comprise a fresh ethylene feed stream. In embodiments, the ethylene-containing feed stream 122 may not include a recycled ethylene stream. The fresh ethylene does not contain a chain transfer agent other than one or more residual compounds originating from the ethylene production / fractionation process. In embodiments, make-up CTA may be added to the first ethylene-containing feed stream 122 upstream of the first reaction zone 112. In embodiments, the first ethylene-containing feed stream 122 may include at least a portion of an ethylene recycle stream comprising recycled ethylene and recycled CTAs. In embodiments, the first ethylene-containing feed stream 122 may comprise a fresh ethylene stream in combination with a recycled ethylene stream, such as but not limited to a low-pressure ethylene recycle stream, a high-pressure ethylene recycle stream, or both.

[0085] The second ethylene-containing feed stream 124 may comprise a recycled ethylene stream, such as but not limited to a low-pressure ethylene recycle stream, a high-pressure ethylene recycle stream, or both. In embodiments, the second ethylene-containing feed stream 124 may comprise a portion of a low-pressure ethylene recycle stream. The third ethylene-containing feed stream 126 may comprise a recycled ethylene stream, such as but not limited to a low-pressure ethylene recycle stream, a high-pressure ethylene recycle stream, or both. In embodiments, the third ethylene-containing feed stream 126 may comprise a portion of a high-pressure ethylene recycle stream. The fourth ethylene-containing feed stream 128 may comprise a recycled ethylene stream, such as but not limited to a low-pressure ethylene recycle stream, a high-pressure ethylene recycle stream, or both. In embodiments, the fourth ethylene-containing feed stream 128 may comprise a portion of a high-pressure ethylene recycle stream. In embodiments, the fourth ethylene-containing feed stream 128 may have the same composition as the third ethylenecontaining feed stream 126.

[0086] The molecular weight distribution and / or the melt strength of the ethylene-based polymers may be further manipulated by controlling the peak temperature in each of the reaction zones of the tubular reactor. Referring again to FIG. 1, the reactor system 100 can comprise the first heat exchanger 140, the second heat exchanger 150, and the third heat exchanger 160. Thereactor system 100 may include additional heat exchangers for further ethylene-containing feed streams in excess of the first through fourth ethylene-containing feed streams.

[0087] In embodiments, the reactor systems 100 and processes may be configured to produce the ethylene-based polymers having a broader molecular weight distribution and / or greater melt strength and each of the plurality of reaction zones may be operated at a maximum temperature of from 300 °C to 330 °C, more preferably from 300 °C to 325 °C, or most preferably from 300 °C to 320 °C. Referring now to FIG. 3, the temperature 302 in the tubular reactor (y-axis) as a function of relative position in the tubular reactor (x-axis) is graphically depicted. The reactions zones are numbered 1-5. For FIG. 3, the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 each introduced 25% by mole of the total ethylene to the tubular reactor, the third ethylene-containing feed stream 126 introduced 30% of the ethylene to the tubular reactor, and the fourth ethylene-containing feed stream 128 introduced 20% of the ethylene to the tubular reactor. The tubular reactor was operated at a maximum polymerization temperature of from 300 °C to 325 °C in each of the first three reaction zones. The cooling water temperature for cooling each of the reaction zones is indicated by reference 404 in FIG. 4. The resulting ethylene-based polymers exhibited broad molecular weight distribution, such as a relative molecular weight distribution greater than or equal to about 7.

[0088] In embodiments, the reactor systems and process may be configured to configured to produce the ethylene-based polymers having a narrow MWD distribution and / or greater density, and the reaction zones may be maintained at temperatures such that the maximum temperature of each of the reaction zones is less than or equal to 260 °C, more preferably less than or equal to 255 °C, even more preferably less than or equal to 250 °C, or most preferably less than or equal to 245 °C. In embodiments, the maximum polymerization temperature in reaction zone 1, reaction zone 2, or both may be less than or equal to 260 °C, less than or equal to 255 °C, less than or equal to 250 °C, or less than or equal to 245 °C, such as from 200 °C to 260 °C. Referring now to FIG. 4, the temperature 402 in the tubular reactor (y-axis) as a function of relative position in the tubular reactor (x-axis) is graphically depicted. The reactions zones are numbered 1-5. For FIG. 4, the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 each introduced 25% by mole of the total ethylene to the tubular reactor, the third ethylene-containing feed stream 126 introduced 40% of the ethylene to the tubular reactor, and the fourth ethylenecontaining feed stream 128 introduced 10% of the ethylene to the tubular reactor. The initiator was not passed to the fourth reaction zone 118 in FIG. 4. The tubular reactor was operated at a maximum polymerization temperature of about 260 °C in each of the first three reaction zones.The resulting ethylene-based polymers exhibited narrower molecular weight distribution and greater density compared to the ethylene-based polymers produced by the process represented in FIG. 3. Thus, FIGS. 3 and 4 show that the molecular weight distribution of the ethylene-based polymers can be modified by changing the operating temperatures of the reactions zones, optionally in conjunction with changing the molar ratio of the third ethylene-containing feed stream to the fourth ethylene-containing feed stream.

[0089] Referring again to FIG. 1 , the process of producing ethylene-based polymers using the reactor systems 100 disclosed herein may include controlling a temperature of each of the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 126. In embodiments, the process may include heating the first ethylene-containing feed stream 122 to a temperature of from 140 °C to 160 °C upstream of the first reaction zone 112. The first ethylenecontaining feed stream 122 may be heated by passing the first ethylene-containing feed stream 122 through the first heat exchanger 140.

[0090] The processes may further include cooling the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof to a temperature less than or equal to 90 °C, such as from 40 °C to 90 °C, from 40 °C to 80 °C, from 40 °C to 70 °C, or even from 40 °C to 55 °C. When the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof to a temperature less than or equal to 90 °C, such as from 40 °C to 90 °C, introducing these streams to the second reaction zone 114, third reaction zone 116, and fourth reaction zone 118, respectively, quenches the reaction mixture passing into the reaction zone, thereby reducing the temperature at the inlet of each of the second reaction zone 114, third reaction zone 116, and fourth reaction zone 118, as shown in FIG. 3.

[0091] Referring again to FIG. 1, as previously discussed, cooling the second ethylenecontaining feed stream 124 may include passing the second ethylene-containing feed stream 124 through the second heat exchanger 150. Cooling the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both may include passing one or both of these streams through the third heat exchanger 160. Modifying the temperature of each of the reaction zones may include changing the temperatures of the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 126, or combinations thereof.

[0092] Referring now to FIG. 5, another embodiment of the reactor system 100 for producing ethylene-based polymers is schematically depicted. In embodiments, the reactor system 100 comprises the tubular reactor 110, as previously described herein. The reactor system 100 may further include a fresh ethylene feed 202, an inhibitor stream 204, a first primary compressor 210, a make-up CTA stream 214, a make-up additive stream 216, a second primary compressor 220, a booster compressor 230, a first hyper compressor 240, a second hyper compressor 240, a high pressure separator 260, a high pressure ethylene recycle stream 262, a low pressure separator 270, and a low pressure ethylene recycle stream 272. Each of these additional components will be described in further detail with respect to FIG. 5.

[0093] The fresh ethylene feed 202 may be passed to the reactor system 100 to make up for ethylene consumed during the polymerization reaction in the tubular reactor 110, purged from the reactor system 100, and / or retained as free ethylene in the ethylene-based polymers. The fresh ethylene feed 202 does not contain a chain transfer agent other than one or more residual compounds originating from the ethylene production / fractionation process. The fresh ethylene feed 202 may make up at least a portion of the first ethylene-containing feed stream 122. In embodiments, the fresh ethylene feed 202 may also be introduced as a component of the second ethylene-containing feed stream 124. The fresh ethylene feed 202 may be passed to the first primary compressor 210, which may be disposed upstream of the first reaction zone 112 and upstream of the first heat exchanger 140. The first primary compressor 210 may be operable to increase the pressure of the fresh ethylene feed 202 to produce a compressed fresh ethylene stream 212 having a pressure greater than the fresh ethylene feed 202.

[0094] Referring again to FIG. 5, in embodiments, the second ethylene-containing feed stream 124 may comprise a portion of the low pressure ethylene recycle stream 272. The reactor system 100 may comprise the second primary compressor 220 disposed upstream of the second reaction zone 114 of the tubular reactor 110 and upstream of the second heat exchanger 150. The second primary compressor 220 may be operable to compress the low pressure ethylene recycle stream 272 to produce a compressed low pressure ethylene stream 222 having a pressure greater than the low pressure ethylene recycle stream 272.

[0095] In embodiments, the compressed low pressure ethylene stream 222 may have a composition that is the same as the low pressure ethylene recycle stream 272. In embodiments, a portion of the fresh ethylene feed 202 may be added to the low pressure ethylene recycle stream 272 upstream of the second primary compressor 220 so that the compressed low pressure ethylenestream 222 has a greater concentration of ethylene compared to the low pressure ethylene recycle stream 272.

[0096] In embodiments, the processes disclosed herein may include compressing the second ethylene-containing feed stream 124 in the second primary compressor 220 upstream of the second reaction zone 114, wherein the second ethylene-containing feed stream 124 comprises a low pressure ethylene-containing recycle stream 272. In embodiments, the reactor system 100 may comprise a booster compressor 230 disposed upstream of the second primary compressor 220. The booster compressor 230 may be operable to compress the low pressure ethylene recycle stream 272 to increase the pressure upstream of the second primary compressor 220.

[0097] Referring again to FIG. 5, the reactor system 100 may comprise the first hyper compressor 240, which may be disposed upstream of the tubular reactor 110. In embodiments, the first hyper compressor 240 may be disposed downstream of the first primary compressor 210 and the second primary compressor 220 and upstream of the first heat exchanger 140 and the second heat exchanger 150. The compressed fresh ethylene stream 212 and the compressed low pressure ethylene stream 222 may each be passed independently to the first hyper compressor 240.

[0098] The first hyper compressor 240 may be configured to increase the pressure of the compressed fresh ethylene stream 212 to produce the first ethylene-containing feed stream 122. The first hyper compressor 240 may be configured to increase the pressure of the compressed low pressure ethylene stream 222 to produce the second ethylene-containing feed stream 124, without mixing the compressed fresh ethylene stream 212 with the compressed low pressure ethylene stream 222. The first hyper compressor 240 may be operable to modify the temperature of the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, or both upstream of the first heat exchanger 140 and the second heat exchanger 150, respectively. The first hyper compressor 240 is designed to be able to split the desired ethylene-based feed flows upstream of the hyper suction portion of the first hyper compressor 240. Splitting the ethylenebased feed flows upstream of the hyper suction portion of the first hyper compressor 240 may affect the CTA concentration ratios in each of the reaction zones.

[0099] The reactor system 100 may comprise the second hyper compressor 250. The high pressure recycle stream 262 may be passed to the second hyper compressor 250. The second hyper compressor 250 may be disposed upstream of the tubular reactor 110 and upstream of the third heat exchanger 160. In embodiments, the high pressure recycle stream 262 may be divided into two streams upstream of the second hyper compressor 250. In embodiments, the two streamspassed through the second hyper compressor 250 may be recombined into a single stream downstream of the second hyper compressor 250.

[0100] The second hyper compressor 250 may be configured to increase the pressure of the high pressure ethylene recycle stream 262 to produce the ethylene stream 252, which may then be divided into the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128. The second hyper compressor 250 may be operable to modify the temperature of the recycled ethylene stream 252 upstream of the third heat exchanger 160 and the second heat exchanger 150, respectively. The second hyper compressor 250 is designed to be able to split the desired ethylene-based feed flows upstream of the hyper suction portion of the first hyper compressor 240. Further description of hyper compressor systems suitable for the first hyper compressor 240 and / or the second hyper compressor 250 can be found in U.S. Patent No. 11,078,301, granted on August 3, 2021, and entitled "HIGH PRESSURE FREE RADICAE POEYMERIZATION TO PRODUCE ETHYEENE-BASED POEYMERS," the entire contents of which are incorporated by reference herein.

[0101] Referring again to FIG. 5, the reactor system 100 may further include the high pressure separator 260 disposed downstream of the tubular reactor 110. The high pressure separator 260 may be in fluid communication with an outlet of the tubular reactor 110 to receive the polymerization effluent 130 from the last reaction zone of the tubular reactor 110. The high pressure separator 260 may be operable to separate the polymerization effluent 130 to produce the high pressure ethylene recycle stream 262 and a bottom stream 264. The high pressure separator 260 may separate the polymerization effluent 130 at a pressure of from 200 bar (20 MPa) to 400 bar (40 MPa).

[0102] The high pressure ethylene recycle stream 262 comprises at least unreacted ethylene and CTAs. The high pressure ethylene recycle stream 262 may also include unreacted comonomers, when the polymerization reaction includes the addition of comonomers. In embodiments the high pressure ethylene recycle stream 262 may further include any of the other constituents (e.g., additives such as but not limited to lubricating oils, antioxidants, solvents, branching agents, etc.). The high pressure ethylene recycle stream 262 may comprise at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, or even at least 90% by mole of the ethylene, CTAs, and optional comonomers present in the polymerization effluent 130. At least a portion of the high pressure ethylene recycle stream 262 may be passed back to the reactor system 100 as at least a portion of one or more of the ethylene-containing feed streams (e.g.,streams 122, 124, 126, 128). In embodiments, a high pressure ethylene purge 266 may be passed out of the reactor system 100 to prevent buildup of contaminants in the recycle loop.

[0103] The bottom stream 264 may comprise the ethylene-based polymers produced in the tubular reactor 110 and passed out in the polymerization effluent 130. The bottom stream 264 may further comprise any ethylene, CTAs, and / or optional comonomers not separated out into the high pressure ethylene recycle stream 262. In embodiments, the bottom stream 264 may further comprise any other constituents (e.g., additives such as but not limited to lubricating oils, antioxidants, solvents, branching agents, etc.) not separated out into the high pressure ethylene recycle stream 262.

[0104] Referring again to FIG. 5, the bottom stream 264 may be passed to the low pressure separator 270, which may be disposed downstream of the high pressure separator 260. The low pressure separator 270 may be in fluid communication with the high pressure separator 260 to pass the bottom stream 264 from the high pressure separator 260 to the low pressure separator 270. The low pressure separator 279 may be operable to separate the bottom stream 264 to produce the low pressure ethylene recycle stream 272 and a product stream 274. In embodiments, the low pressure separator 270 may operate at a gauge pressure of from 0 bar (0 kPa) to 1 bar (100 kPa). In embodiments, the process may comprise separating the bottom stream 264 in the low pressure separator 270 to produce the low pressure ethylene recycle stream 272 and the product stream 274. The product stream 274 may comprise the ethylene-based polymers produced in the tubular reactor 110. In embodiments, the product stream 274 may include at least 95%, at least 98%, at least 99%, or at least 99.9% of the ethylene-based polymers from the polymerization effluent 130.

[0105] The low pressure ethylene recycle stream 272 may comprise ethylene, CTAs, and optionally one or more comonomers. The low pressure ethylene recycle stream 272 may further include some of the other constituents (e.g., additives such as lubricating oils, antioxidants, branching agents, solvents, etc.). At least a portion of the low pressure ethylene recycle stream 272 may be passed back to the reactor system 100 as at least a portion of one or more of the ethylene-containing feed streams 122, 124, 126, 128, such as but not limited to a portion of or all of the second ethylene-containing feed stream 124.

[0106] Referring again to FIG. 5, in embodiments, the first ethylene-containing feed stream 122 may comprise the fresh ethylene feed 202, and the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 126 may each comprise a recycled ethylene stream. In embodiments, the second ethylenecontaining feed stream 124 may comprise a portion of the low pressure ethylene recycle stream272, and the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both may include a portion of the high pressure ethylene recycle stream 262. In embodiments, the high pressure ethylene recycle stream 262 may be divided into the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128.

[0107] In embodiments, the second ethylene-containing feed stream 124 comprising the low pressure ethylene recycle stream 272 may have CTA concentration greater than the CTA concentration of the first ethylene-containing feed stream 122 comprising the fresh ethylene feed 202. In embodiments, the third ethylene-containing feed stream 126 and the fourth ethylenecontaining feed stream 128 each may have a CTA concentration greater than the CTA concentration in the second ethylene-containing feed stream 124.

[0108] Referring again to FIG. 5, in embodiments, make-up ethylene may be supplied to one or more of the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof. The make-up ethylene may be the fresh ethylene feed 202. In embodiments, the fresh ethylene feed 202 may be added as make-up ethylene to the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof, in addition to comprising the first ethylene-containing feed stream 122. Along with make-up ethylene, an inhibitor stream 204 may be added to the fresh ethylene feed 202 upstream of the first primary compressor 210, to the low pressure ethylene recycle stream 272 upstream of the second primary compressor 220, or both. In embodiments, the initiator stream 204 may be an oxygen stream.

[0109] In embodiments, a make-up CTA stream 214 may be combined with the compressed fresh ethylene stream 212, the compressed low pressure ethylene stream 222, or both upstream of the first hyper compressor 240. Additionally or alternatively, in embodiments, the make-up CTA stream 214 may be combined with the high pressure ethylene recycle stream 262 upstream of the second hyper compressor 250. The make-up CTA may be included to account for the CTAs consumed during the polymerization reaction, passed out of the system in one or more purge streams, and / or mechanically entrained within the branches of the ethylene-based polymers. In embodiments, make-up CTA from the make-up CTA stream may be added to each of the ethylene streams (e.g., the compressed fresh ethylene stream 212, the compressed low pressure ethylene stream 222, the high pressure ethylene recycle stream 262, or combinations thereof) upstream of the tubular reactor 110. In embodiments, no CTAs are added to the compressed fresh ethylenestream 212. In embodiments, the make-up CTA is only added to the compressed low pressure ethylene stream 222, the high pressure ethylene recycle stream 262, or combinations thereof.

[0110] In embodiments, the make-up CTA may be introduced to the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, or combinations thereof. In embodiments, the make-up CTA may be introduced to the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, and the fourth reaction zone 118.

[0111] The reactor system 100 may further include one or more make-up additive streams 216, which may include make-up additives / other components (e.g., lubricating oils, antioxidants, ethane, methane, branching agents, and / or initiator dissociation products, etc.). Although shown as one stream, the make-up additive streams 216 can include multiple streams with each stream introducing a separate constituent. The make-up additive streams 216 may be added to the compressed fresh ethylene stream 212, the compressed low pressure ethylene stream 222, the high pressure ethylene recycle stream 262, or combinations thereof.

[0112] Referring again to FIG. 5, in operation of the reactor system 100, the fresh ethylene feed 202 may be passed to the first primary compressor 210 that compresses the fresh ethylene feed 202 to produce the compressed fresh ethylene stream 212. The compressed fresh ethylene stream 212, with or without make-up CTA and / or make-up additives added thereto, may be passed to the first hyper compressor 240 that further compresses the compressed fresh ethylene stream 212 to produce the first ethylene-containing feed stream 112. The first ethylene-containing feed stream 112 may be passed through the first heat exchanger 140 to heat the first ethylene-containing feed stream 112 to a temperature of from 140 °C to 160 °C. The first ethylene-containing feed stream 112 may then be introduced to the first reaction zone 112 of the tubular reactor 110.

[0113] In parallel, the low pressure recycle stream 272 may be passed to the booster compressor 230 and then the second primary compressor 240. The booster compressor 230 and the second primary compressor 240 may compress the low pressure recycle stream 272 to produce the compressed low pressure ethylene stream 222. The compressed low pressure ethylene stream 222, with or without make-up CTA and / or make-up additives added thereto, may be passed to the first hyper compressor 240 that further compresses the compressed low pressure ethylene stream 122 to produce the second ethylene-containing feed stream 114. The second ethylene-containing feed stream 114 may be passed through the second heat exchanger 150 to change the temperature of the second ethylene-containing feed stream 114 to a temperature of from 40 °C to 90 °C. Thesecond ethylene-containing feed stream 114 may then be introduced to the second reaction zone 114 of the tubular reactor 110.

[0114] Further in parallel, the high pressure ethylene recycle stream 262 may be divided into two streams and then the two streams may be passed through the second hyper compressor 250. The second hyper compressor may further compress the two streams to the operating pressure of the tubular reactor 110 greater than or equal to 1000 bar (100 MPa). The two compressed streams may be combined to produce ethylene stream 252. The ethylene stream 252 may be passed through the third heat exchanger 160 to modify the temperature of the ethylene stream 252 to a temperature of from 40 °C to 90 °C. The ethylene stream 252 may then be divided into the third ethylenecontaining feed stream 126 and the fourth ethylene-containing feed stream 128. The third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 may then be introduced to the third reaction zone 116 and the fourth reaction zone 118, respectively.

[0115] The initiator streams 131, 132, 133, 134, 135 may be introduced to each of the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, and optionally the fifth reaction zone 120. The ethylene, CT As and free radical initiators undergo polymerization reactions in the tubular reactor 110 to produce the polymerization effluent 130 comprising the ethylene-based polymers and unreacted components of each of the ethylenecontaining streams.

[0116] The polymerization effluent 130 may be passed to the high pressure separator 260, which separates the polymerization effluent 130 into the high pressure ethylene recycle stream 262 and the bottom stream 264. The high pressure ethylene recycle stream 262 may be recycled back to the reactor system 100, such as back to the second hyper compressor 250. The bottom stream 264 may be passed to the low pressure separator 270, which separates the bottom stream 264 into the low pressure ethylene recycle stream 272 and the product stream 274 comprising the ethylene-based polymers produced during polymerization. The low pressure ethylene recycle stream 272 may be passed back to the reactor system 100, such as back to the booster compressor 220. The produce stream 274 may be passed out of the reactor system 100 to one or more downstream processes, such as downstream separation, purification, and / or recovery processes.

[0117] As previously discussed, the molecular weight distribution and / or melt strength of the ethylene-based polymers produced from the reactor system 100 can be modified by changing the amount of the CTAs introduced to each of the reaction zones 112, 114, 116, 118, 120. In embodiments, the amount of CTA introduced to each of the reaction zones 112, 114, 116, 118, 120 can be modified by changing an amount of the make-up CTA stream 214 added to each ofthe first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof. Additionally or alternatively, in embodiments, the amount of the CTA introduce to each of the reaction zones 112, 114, 116, 118, 120 can be modified by changing the distribution of the high pressure ethylene recycle stream 262, the low pressure ethylene recycle stream 272, or both to each of the first ethylene-containing feed stream 122, the second ethylenecontaining feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylenecontaining feed stream 128, or combinations thereof.

[0118] Referring again to FIG. 5, in embodiments, the reactor system 100 may include a control system comprising a plurality of control valves for distributing the high pressure ethylene recycle stream 262, the low pressure ethylene recycle stream 272, or both to each of the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof. The process conducted using the reactor system 100 may include controlling a composition of each of the at least four ethylene-based feed streams (i.e., the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof) with a control system comprising one or more control valves. The plurality of control valves may include a first control valve 280, a second control valve 282, a third control valve 284, a fourth control valve 286, and a fifth control valve 288. The control system having the plurality of control valves may provide greater process flexibility for producing ethylene-based polymers using the reactor system 100.

[0119] The first control valve 280 may be disposed in the compressed fresh ethylene stream 212 downstream of the first primary compressor 210 and upstream of the first hyper compressor 240. The first control valve 280 may be operable to control the flow of the compressed fresh ethylene stream 212 to the first hyper compressor 240. Thus, the first control valve 280 may be operable to control the proportion of the compressed fresh ethylene stream 212 in the first ethylene-containing feed stream 122 or completely stop the flow of the compressed fresh ethylene stream 212 into the first ethylene-containing feed stream 122.

[0120] The second control valve 282 may be disposed in the compressed low pressure ethylene stream 222 downstream of the second primary compressor 210 and upstream of the first hyper compressor 240. The second control valve 282 may be operable to control the flow of the compressed low pressure ethylene stream 222 to the first hyper compressor 240. Thus, the secondcontrol valve 282 may be operable to control the proportion of the compressed low pressure ethylene stream 222 in the second ethylene-containing feed stream 124 or completely stop the flow of the compressed low pressure ethylene stream 222 into the second ethylene-containing feed stream 124.

[0121] In embodiments, the reactor system 100 may comprise a compressed low pressure ethylene distribution line 290 fluidly connecting the compressed low pressure ethylene stream 222 to the compressed fresh ethylene stream 212. The compressed low pressure ethylene distribution line 290 may enable distribution of the compressed low pressure ethylene stream 222 to the first reaction zone 112 as part of or all of the first ethylene-containing feed stream 122. The compressed low pressure ethylene distribution line 290 may include the third control valve 284, which may be operable to control the proportion of the compressed low pressure ethylene stream 222 in the first ethylene-containing feed stream 122 or completely stop the flow of the compressed low pressure ethylene stream 222 into the first ethylene-containing feed stream 122.

[0122] In embodiments, the reactor system 100 may include a first high pressure ethylene distribution line 292 fluidly connecting the high pressure ethylene recycle stream 262 to the compressed low pressure ethylene stream 222. The first high pressure ethylene distribution line 292 may enable distribution of the high pressure ethylene recycle stream 262 to the second reaction zone 114 as part of or all of the second ethylene-containing feed stream 124. The first high pressure ethylene distribution line 290 may include the fourth control valve 286, which may be operable to control the proportion of the high pressure ethylene recycle stream 262 in the second ethylene-containing feed stream 124 or completely stop the flow of the high pressure ethylene recycle stream 262 into the second ethylene-containing feed stream 124.

[0123] In embodiments, the reactor system 100 may comprise a second high pressure ethylene distribution line 294 fluidly connecting the high pressure ethylene recycle stream 262 to the compressed fresh ethylene stream 212. The high pressure ethylene distribution line 294 may enable distribution of the high pressure ethylene recycle stream 262 to the first reaction zone 112 as part of or all of the first ethylene-containing feed stream 122. The high pressure ethylene distribution line 294 may include the fifth control valve 288, which may be operable to control the proportion of the high pressure ethylene recycle stream 262 in the first ethylene-containing feed stream 122 or completely stop the flow of the high pressure ethylene recycle stream 262 into the first ethylene-containing feed stream 122.

[0124] Referring again to FIG. 5, the process of making the ethylene-based polymers using the reactor system 100 may include adjusting the molecular weight distribution of the ethylene-basedpolymers in the polymerization effluent 130 by controlling the amounts of the high-pressure ethylene recycle stream 262, the low-pressure ethylene recycle stream 272, or both to the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations of these. Controlling the amounts of the high-pressure ethylene recycle stream 262, the low-pressure ethylene recycle stream 272, or both to the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations of these may include controlling one or more of the first control valve 280, the second control valve 282, the third control valve 284, the fourth control valve 286, the fifth control valve 288, or combinations thereof.

[0125] Referring again to FIG. 5, in embodiments, the reactor system 100 may be configured in a broad molecular weight distribution (MWD) configuration to produced ethylene-based polymers having broad molecular weight distribution and / or greater melt index. In the broad MWD configuration, the reactor system 100 may be configured to reduce or eliminate the CTA in the first ethylene-containing feed stream 122 fed to the first reaction zone 112 and to provide increasing concentrations of CTAs in each of the subsequent ethylene-containing feed streams (i.e., the second ethylene-containing feed stream 124 and the third ethylene-containing feed stream 126). In embodiments, when the reactor system 100 is in the broad MWD configuration, no CTA may be added to the first ethylene-containing feed stream 122. In embodiments, when the reactor system 100 is in the broad MWD configuration, the first ethylene-containing feed stream 122 may comprise a concentration of the CTAs less than the concentration of CTAs in the second ethylenecontaining feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128. For the broadest molecular weight distribution, the reactor system 100 may be configured, such as by adjusting the third ethylene feed control valve 170 and / or the fourth ethylene feed control valve 172, so that the molar flow rate of the third ethylenecontaining feed stream 126 and the molar flow rate of the fourth ethylene-containing feed stream 128 are equal.

[0126] In embodiments, when the reactor system 100 is in the broad MWD configuration, the first control valve 280 and second control valve 282 may be open, and the third control valve 284, the fourth control valve 286, and the fifth control valve 288 may be closed. In embodiments, when the reactor system 100 is in the broad MWD configuration, the third control valve 284 and the fourth control valve 286 may be open or controlled to add at least some of the compressed lowpressure ethylene stream 222 to the first ethylene-containing feed stream 112 and to add at least some of the high pressure ethylene recycle stream 262 to the second ethylene-containing feed stream 124. In embodiments, when the reactor system 100 is in the broad MWD configuration, the first control valve 280, the second control valve 282, the third control valve 284, and the fourth control valve 286 may be open and the fifth control valve 288 may be closed to prevent the flow of the high pressure ethylene recycle stream 262 to the first ethylene-containing feed stream 122.

[0127] Referring again to FIG. 5, in embodiments, the reactor system 100 may be configured in a narrow MWD configuration to produce ethylene-based polymers with narrow molecular weight distribution. In the narrow MWD configuration, the concentration of the CTAs in the first ethylene-containing feed stream 122 may be increased to introduce a greater concentration of the CTAs to the first reaction zone 112. In the narrow MWD configuration, the reactor system 100 may be configured to introduce decreasing amounts of the CTAs to the subsequent reaction zones, such as the second reaction zone 114, the third reaction zone 116, and the fourth reaction zone 118. In other words, each successive reaction zone may have a concentration of CTAs less than the previous reaction zone.

[0128] In embodiments, the narrow MWD configuration to produce ethylene -based polymers having narrow MWD may include increasing the concentration of CTA in the first reaction zone 112 compared to the broad MWD configuration. In embodiments, increasing the concentration of the CTAs in the first reaction zone 112 may include increasing the flow rate of the make-up CTA stream 214 added to the first ethylene-containing feed stream 122. In embodiments, increasing the concentration of the CTAs in the first reaction zone 112 may include distributing or shifting a portion of the high pressure ethylene recycle stream 262 to the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, or both. In embodiments, the control system comprising the plurality of valves may be configured to introduce at least a portion of the high pressure ethylene recycle stream 262 to the first reaction zone 112 as the first ethylenecontaining feed stream 122. In embodiments, in the narrow MWD configuration, the first control valve 280, the second control valve 282, and the third control valve 284 may be closed, and the fourth control valve 286 and the fifth control valve 288 may be open to pass the high pressure ethylene recycle stream 262 to the first reaction zone 112 and the second reaction zone 114.

[0129] In embodiments, in the narrow MWD configuration, the decreasing CTA gradient with increasing number of reaction zone may include increasing the molar ratio of the third ethylenecontaining feed stream 126 to the fourth ethylene-containing feed stream 128. As previously discussed, changing the molar ratio of the third ethylene-containing feed stream 126 to the fourthethylene-containing feed stream 128 may include changing the relative positions of the third ethylene feed control valve 170, the fourth ethylene feed control valve 172, or both (for ref. nos. 170 and 172, the terms "third" and "fourth" are intended to modify ethylene feed, such that the third ethylene feed control valve refers to the control valve for the third ethylene-containing stream 126).

[0130] In embodiments, the fourth ethylene feed control valve 172 may be completely closed to close off the flow of the fourth ethylene-containing feed stream 128 to the fourth reaction zone 118. In this configuration, no ethylene or CTA is added to the fourth reaction zone 118, effectively allowing the reaction mixture to pass through the fourth reaction zone 118. In embodiments, no initiator feed is introduced to the fourth reaction zone 118 either. In embodiments, the fourth ethylene-containing feed stream 128 may be introduced to the fourth reaction zone 118 and no initiator may be added to the fourth reaction zone 118.

[0131] A process for producing ethylene-based polymers in the presence of at least one free- radical using the reactor system 100 described herein is also disclosed. The process may comprise polymerizing a mixture comprising ethylene in the tubular reactor 110 having the at least four reaction zones in series and the at least four ethylene-containing feed streams to produce the polymerization effluent 130 comprising the ethylene -based polymers. The at least four reaction zones may comprise a first reaction zone, a second reaction zone downstream of the first reaction zone, a third reaction zone downstream of the second reaction zone, and at least one fourth reaction zone downstream of the third reaction zone. A first ethylene-containing feed stream passed to the first reaction zone may comprise from 20% to 35% by mole of the total molar flow rate of the at least four ethylene feed streams introduced to the tubular reactor. A CTA activity ratio (Z2 / Z1) for the second reaction zone may be from 0.2 to 2.0, or more preferably from 0.3 to 1.9, or most preferably from 0.5 to 1.8; a CTA activity ratio (Z3 / Z1) for the third reaction zone may be from 0.12 to 1.5, more preferably from 0.15 to 1.4, or most preferably from 0.2 to 1.3; and a CTA activity ratio (Z4 / Z1) for the fourth reaction zone may be from from 0.0 to 0.7, more preferably from greater than 0.0 to 0.7, or most preferably from 0.05 to 0.6.

[0132] In embodiments, the at least four ethylene-containing feed streams may further comprise the second ethylene-containing feed stream 124 introduced to the second reaction zone 114 downstream of the first reaction zone 112, the third ethylene-containing feed stream 126 introduced to the third reaction zone 116 downstream of the second reaction zone 114, and at least one fourth ethylene-containing feed stream 128 introduced to at least one fourth reaction zone 118 downstream of the third reaction zone 116.

[0133] In embodiments, an amount of ethylene, and optionally the one or more comonomers, and the optionally the one or more CTAs, introduced to the tubular reactor 110 by the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may comprise from 40% to 70% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110.

[0134] In embodiments, the second ethylene-containing feed stream 124, the third ethylenecontaining feed stream 126, and the fourth ethylene-containing feed stream 128 each comprise ethylene, CTAs, and optionally one or more comonomers; a concentration of the CTAs in the second ethylene-containing feed stream 124 is greater than the concentration of the CTAs in the first ethylene-containing feed stream 122; and a concentration of the CTAs in the third ethylenecontaining feed stream 126, the fourth ethylene-containing feed stream 128, or both is greater than the concentration of the CTAs in the second ethylene-containing feed stream 124.

[0135] In embodiments, the reactor system 100 may be configured to produce ethylene-based polymers with broad MWD and the CTA activity ratio for the second reaction zone (Z2 / Z1) may be from 0.5 to 2.0, such as from 0.7 to 2.0, or from 1.0 to 2.0. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the third reaction zone (Z3 / Z1) may be from 0.5 to 1.5, such as from 0.6 to 1.4, from 0.7 to 1.3, or from 0.8 to 1.2. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the fourth reaction zone (Z4 / Z1) may be from 0.1 to 0.7, such as from 0.2 to 0.6, or from 0.3 to 0.6.

[0136] In embodiments, the reactor system 100 may be configured to produce ethylene-based polymers with a narrow MWD, and the CTA activity ratio for the second reaction zone (Z2 / Z1) may be from 0.2 to 0.5. When configured to produce ethylene-based polymers with narrow MWD, the CTA activity ratio for the third reaction zone (Z3 / Z1) may be from 0.12 to less than 0.5, such as from 0.12 to 0.4. When configured to produce ethylene-based polymers with broad MWD, the CTA activity ratio for the fourth reaction zone (Z4 / Z1) may be less than 0.1, such as less than or equal to 0.09, less than or equal to 0.08, from 0.0 to 0.1, or from greater than 0.0 to 0.1.

[0137] In embodiments, the processes disclosed herein may include adjusting the molar ratio of the third ethylene-containing feed stream 126 to the fourth ethylene-containing feed stream 128, wherein the molar ratio of the third ethylene- containing feed stream 126 to the fourth ethylene-containing feed stream 128 is from 1 to 4. In embodiments, the proportion of the third ethylene-based feed stream 126 and the fourth ethylene-containing feed stream 128 introduced to the third reaction zone 116 and the fourth reaction zone 128, respectively, is controlled with a control system comprising at least one control valve.

[0138] In embodiments, the processes disclosed herein may include controlling a composition of each of the at least four ethylene-based feed streams with a control system comprising one or more control valves. In embodiments, the first ethylene-containing feed stream 122 may comprise the fresh ethylene feed 202, and the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128 each comprise a recycled ethylene stream.

[0139] In embodiments, the processes disclosed herein may further include separating the polymerization effluent 130 in the high pressure separator 260 to produce the high pressure ethylene recycle stream 262 and the bottom stream 264, wherein the high pressure ethylene recycle stream 262 comprises ethylene, CTAs, and optionally one or more comonomers. The processes may further include separating the bottom stream 264 in the low pressure separator 270 to produce the low pressure ethylene recycle stream 272 and the product stream 274, wherein the low pressure ethylene recycle stream 272 comprises ethylene, CTAs, and optionally one or more comonomers. In embodiments, the second ethylene-containing feed stream 124 may comprise at least a portion of the low pressure ethylene recycle stream 272, and the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both may comprise at least a portion of the high pressure ethylene recycle stream 262.

[0140] In embodiments, the processes disclosed herein may further include adjusting a molecular weight distribution of the ethylene-based polymers in the polymerization effluent 130 by controlling the amounts of the high-pressure ethylene recycle stream 262, the low-pressure ethylene recycle stream 272, or both to the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations of these.

[0141] In embodiments, the first ethylene-containing feed stream 122 and the second ethylenecontaining feed stream 124 may each introduce 25% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor 110.

[0142] In embodiments, the processes disclosed herein may further include controlling a temperature of each of the first ethylene-containing feed stream 122, the second ethylenecontaining feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128. In embodiments, the processes disclosed herein may comprise cooling the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or combinations thereof to atemperature less than or equal to 90 °C, such as from 40 °C to 90 °C, from 40 °C to 80 °C, from 40 °C to 70 °C, or from 40 °C to 55 °C. In embodiments, the process may be configured to produce the ethylene-based polymers having a broad molecular weight distribution, and each of the plurality of reaction zones are operated at a maximum temperature of from 300 °C to 330 °C, such as from 300 °C to 325 °C, or from 300 °C to 320 °C. In embodiments, the process may be configured to produce the ethylene-based polymers having a narrow MWD distribution, and the reaction zones may be maintained at temperatures such that the maximum temperature of each of the reaction zones is less than or equal to 260 °C, such as less than or equal to 255 °C, less than or equal to 250 °C, or even less than or equal to 245 °C.

[0143] In embodiments, the processes disclosed herein may include compressing the first ethylene-containing feed stream 122 in the first primary compressor 210 upstream of the first reaction zone 112, wherein the first ethylene-containing feed stream 122 comprises the fresh ethylene feed 202. The processes may further include compressing the second ethylene-containing feed stream 124 in the second primary compressor 220 upstream of the second reaction zone 114, wherein the second ethylene-containing feed stream 124 comprises at least a portion of the low pressure ethylene-containing recycle stream 272.

[0144] In embodiments, the processes disclosed herein may further include passing the first ethylene-containing feed stream 122 and the second ethylene containing feed stream 124 to the first hyper compressor 240, wherein the first hyper compressor 240 is configured to split each of the ethylene-containing streams at the hyper suction. The processes disclosed herein may further include passing the high pressure ethylene recycle stream 262 to the second hyper compressor 250, wherein the second hyper compressor 250 is configured to split the high pressure ethylene recycle stream 262 at the hyper suction. The processes disclosed herein may further include dividing the stream from the second hyper compressor into the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128.

[0145] In embodiments, the processes disclosed herein may further comprising introducing an initiator stream to each of the at least four reaction zones, wherein each initiator stream comprises at least one free radical initiator and a solvent. In embodiments, the processes disclosed herein may further include mixing the at least one free radical initiator and the solvent upstream of a high-pressure initiator injection pump prior to produce the initiator stream.

[0146] The reactor system 100 and processes disclosed herein are used to produce ethylenebased polymers. The present disclosure is also directed to the ethylene-based polymers produced by the processes disclosed herein. In embodiments, the ethylene-based polymer produced by thereactor system 100 and processes disclosed herein is a polyethylene homopolymer, and further a LDPE. In embodiments, the ethylene-based polymer is a low density polyethylene (LDPE).

[0147] In embodiments, the ethylene-based polymer is an ethylene-based interpolymer comprising at least one comonomer. In embodiments, the ethylene-based polymer comprises ethylene and one or more comonomers, and preferably one comonomer. Comonomers include, but are not limited to, a-olefins, acrylates, acetates, methacrylates and anhydrides, each typically having no more than 20 carbon atoms. The a-olefin comonomers, which may have a combined monomer and CTA functionality, may have 3 to 10 carbon atoms, or in the alternative, the etale fin comonomers may have 3 to 8 carbon atoms. Exemplary a-olefin comonomers include, but are not limited to, propylene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 1 -nonene, 1- decene, and 4 methyl- 1 -pentene and combinations thereof. In embodiments, the a-olefin comonomers are selected from propylene, 1 -butene and combinations thereof.

[0148] In embodiments, the ethylene-based polymers may have a broad molecular weight distribution. In embodiments, the ethylene -based polymers may have a relative molecular weight distribution of greater than or equal to 200%, such as from 200% to 400%, or from 300% to 400%, where the relative molecular weight distribution is defined as 100 times the Mw / Mn of the ethylene-based polymer divided by the Mw / Mn of an ethylene-based polymer made by introducing 100% of the ethylene, CTAs, optional comonomers, and optional additives to the first reaction zone. Mw and Mn are determined through conventional GPC according to the test methods described herein. In embodiments, the ethylene-based polymers may have a narrow MWD, such as having a relative MWD of from about 125% to about 200%, such as from about 150% to about 190%, where the relative MWD is defined hereinabove.

[0149] In embodiments, the ethylene-based polymer may have a density from 0.910 to 0.940 g / cm3. The ethylene -based polymer may have a melt index (E) from 0.10 g / 10 min to 40.0 g / 10 min. In embodiments, the ethylene-based polymer may have a melt index from 0.10 g / 10 min to 20 g / 10 min, from 0.15 to 20 g / 10 min, or from 0.15 to 15 g / 10 min. In embodiments, the ethylenebased polymer has a melt index from 0.2 to 20 g / 10 min, or from 0.20 to 15 g / 10 min, or from 0.2 to 10 g / 10 min.

[0150] In embodiments, a polymer composition may comprise the ethylene-based polymers disclosed herein and one or more additives. Additives may include, but are not limited to, stabilizers, plasticizers, antistatic agents, pigments, dyes, nucleating agents, fdlers, slip agents, fire retardants, processing aids, smoke inhibitors, viscosity control agents, anti-blocking agents, or combinations thereof. The polymer composition may comprise less than 10% of the combinedweight of one or more additives, based on the total weight of the polymer composition. In embodiments, the ethylene-based polymers disclosed herein may be treated with one or more stabilizers, for example, antioxidants, such as IRGANOX 1010, IRGANOX 1076 and IRGAFOS 168. In general, the ethylene-based polymers may be treated with one or more stabilizers before extrusion or other melt processes.

[0151] In embodiments, the polymer composition may comprise the ethylene -based polymers disclosed herein and at least one other polymer. Suitable polymers for blending with the ethylenebased polymers disclosed herein may include natural and synthetic polymers. Examples of the at least one other polymer for blending with the ethylene-based polymers disclosed herein may include, but are not limited to propylene-based polymers (both impact modifying polypropylene, isotactic polypropylene, atactic polypropylene, and random propylene / ethylene copolymers), various types of other ethylene-based polymers, including high-pressure, free-radical LDPE, heterogeneously branched LLDPE (typically via Ziegler-Natta catalysis), homogeneously branched linear or substantially linear PE (typically via single-site, including metallocene catalysis), including multiple reactor PE ("in-reactor" compositions of heterogeneously branched PE and homogeneously branched PE, such as products disclosed in U.S. Pat. No. 6,545,088 (Kolthammer et al.); U.S. Pat. No. 6,538,070 (Cardwell, et al.); U.S. Pat. No. 6,566,446 (Parikh, et al.); U.S. Pat. No. 5,844,045 (Kolthammer et al.); U.S. Pat. No. 5,869,575 (Kolthammer et al.); and U.S. Pat. No. 6,448,341 (Kolthammer et al.)), ethylene-vinyl acetate (EVA), ethylene / vinyl alcohol copolymers, polystyrene, impact modified polystyrene, ABS, styrene / butadiene block copolymers and hydrogenated derivatives thereof (SBS and SEBS), and thermoplastic polyurethanes. The other ethylene-based polymers include homogeneous polymers, such as olefin plastomers and elastomers (for example, polymers available under the trade designations AFFINITY Plastomers and ENGAGE Elastomers (The Dow Chemical Company) and EXACT (ExxonMobil Chemical Co.)). Propylene-based copolymers (for example, polymers available under the trade designation VERSIFY Plastomers & Elastomers (The Dow Chemical Company) and VISTAMAXX (ExxonMobil Chemical Co.) can also be useful as components in blends comprising the ethylene-based polymers made by the reactor system 100 and processes disclosed herein.

[0152] The ethylene-based polymers disclosed herein and polymer compositions containing these ethylene-based polymers may be employed in a variety of conventional thermoplastic fabrication processes to produce useful articles, including extrusion coating onto varioussubstrates; monolayer and multilayer films; molded articles, such as blow molded, injection molded, or rotomolded articles; coatings; fibers; and woven or non-woven fabrics.

[0153] The ethylene-based polymers made by the reactor system 100 and processes disclosed herein may be used in a variety of films, including but not limited to, clarity shrink films, collation shrink films, cast stretch films, silage films, stretch hood, sealants, and diaper back sheets. Other suitable applications include, but are not limited to, wires and cables, gaskets and profiles, adhesives; footwear components, and auto interior parts.

[0154] The present disclosure also provides an article comprising at least one component formed from the ethylene-based polymers disclosed herein. In embodiments, the article is an extrusion coating resin. In embodiments, the article is a film. In embodiments, the article is an insulation material and / or a protection layer around a metal wire. In embodiments, the article is foam. The article may comprise the combination of two or more embodiments as described herein.TEST METHODS

[0155] Melt Index

[0156] The melt index, or h, is measured in accordance by ASTM D 1238, at conditions of 190 °C and a load of 2.16 kg. The melt index (I2) is reported in grams eluted per 10 minutes. The melt index (I10) is measured in accordance with ASTM D 1238, at conditions of 190 °C and a load of 10 kg. The melt index (I10) is reported in units of g / 10 min.

[0157] Normalized Molecular Weight Distribution (MWD)

[0158] Molecular Weight Distribution (representing the relationship between (dw / d log M) and log M) is an important parameter used in the polymerization designs, process development, improvement and operation. It is necessary to determine the types of polymer produced (narrow or broad MWD) which provide the desired product properties. Normalized MWD data can be obtained by using PREDICI commercial software package (licensed by Dr. M. Wulkow, Computing in Technology, GmbH, Paler-Klbe-Slrafie 7, D-26180 Rastede, Germany), to construct MWD from polymerization kinetics (Goto kinetics in this study), through solving polymer population balance equations. The required inputs for PREDICI are the used Goto kinetics, and the monomer and / or co-monomer, initiator and CTA flows, temperature and pressure profdes, as well as elapsed time, all of which can be obtained from the process simulation. PREDICI software package can be used to generate normalized MWD data. The MWD of each ethylene-based polymer in Comparative Examples 2 and 3 and Examples 4 and 5 is calculated and subsequently normalized with the MWD of the ethylene-based polymer of ComparativeExample 1 (comparative — 100 / 0 / 0 / 0), using Equation 1 (EQU. 1). Likewise, the MWD of each ethylene-based polymer in Comparative Examples 7 and 8 and Examples 9 and 10 is calculated and subsequently normalized with the MWD of the ethylene-based polymer of Comparative Example 6 (comparative — 100 / 0 / 0 / 0), using EQU. 1.EXAMPLES

[0159] Embodiments of the present disclosure will be further clarified by the following examples, which should not be construed as limiting on the disclosed and / or claimed embodiments presently described.

[0160] The following prophetic examples are based on polymerization simulations. A polymerization simulation model with applied reaction scheme and kinetics is described by Goto et al. (Goto et al; Journal of Applied Polymer Science: Applied Polymer Symposium, 36, 21-40, 1981 (Title: Computer model for commercial high pressure polyethylene reactor based on elementary reaction rates obtained experimentally. Other reactor and product modeling frameworks are available through ASPEN PLUS of Aspen Technology, Inc., Burlington, Mass., USA; and PREDICI of Dr. Wulkow, Computing in Technology GmbH (CiT), Rastede, Germany. Process and product responses predicted by these model frameworks are determined by the reactor parameters, the applied reaction scheme, and kinetic parameters. The applied reaction scheme and kinetic parameters are described below.

[0161] The polymerization simulations were achieved with Goto, LDPE simulation model, as discussed above. The kinetic data used by Goto et al. was derived from high pressure, free radical polyethylene polymerization experiments, performed at varying temperature, pressure and polymer concentration, as described in the following references: K. Yamamoto, M. Sugimoto; Rate constant for long chain-chain branch formation in free-radical polymerization of ethylene; J. Macromol. Science-Chem., A13 (8), pp. 1067-1080 (1979). The elementary reaction steps are described by Goto et al. as follows: i) propagation of ethylene, ii) termination of radicals, iii) backbiting or SCB formation, iv) transfer to polymer or LCB formation, v) beta elimination of secondary radicals leading to vinyl formation, and vi) beta elimination of tertiary radicals leading to vinylidene formation.

[0162] Kinetic data for main reactions are shown in Table 2, where ko is the pre-exponential or frequency factor; Ea is the activation energy, reflecting the temperature dependence; and AV isthe activation volume, reflecting the pressure dependence. All kinetic constants are from Goto et al., except the ko, Ea and AV values for backbiting, which have been optimized to better reflect the level of methyl branches (as analyzed by C13 NMR technique) in high pressure polyethylene, as a function of pressure and temperature conditions.Table 2

[0163] Further information on the methods for carrying out the polymerization simulations can be found in the methods discussed in detail in the Examples section ofU.S. Patent No. 10,494,456, the entire contents of which are incorporated by reference herein.

[0164] For the Examples and Comparative Examples, the process configuration of FIG. 5 is assumed and the various valves and make-up streams are manipulated to obtain the reactor configurations and CTA activity ratios set forth in each of the Examples and Comparative Examples herein.

[0165] Comparative Example 1 : Single ethylene-containing feed stream to first reaction zone

[0166] For Comparative Example 1, the reactor system in FIG. 5 with only the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, and the fourth reaction zone 118 (no fifth reaction zone 120) is modeled with valves 270, 272, 282, and 286 in the closed position and valves 280, 282, and 288 in the open position so that 100% of the ethylene and CTA are passed to the front of the reactor (e.g., to the first reaction zone 112) and no side streams are introduced to any of the other reaction zones. An oxygen inhibitor is added to the feed to the first reaction zone 112. The initiator streams comprising peroxide are added to each of the four reaction zones. The maximum reaction temperatures in each of the reaction zones was increased above 300 °C to make ethylene-based polymers with as broad an MWD as possible. The maximum reaction temperature for each reaction zone, the reactor pressure, and the total ethylene conversion for the modeling of Comparative Example 1 are provided in Table 3. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 1 are also provided in Table 3.

[0167] Comparative Example 2: Two ethylene-containing feed streams - broad MWD

[0168] In Comparative Example 2, the reactor system of FIG. 5 with only four of the reaction zones is modeled (no fifth reaction zone) and two ethylene-containing feed streams for making ethylene-based polymers with as broad an MWD as possible. For Comparative Example 2, valves 270 and 272 in FIG. 5 are closed and valves 280, 282, 284, 286, and 288 are configured to introduce 50% by mole of the ethylene and CTAs to the first reaction zone 112 and 50% by mole of the ethylene and CTAs to the second reaction zone 114. No ethylene-containing side streams are introduced to the third and fourth reaction zones 116, 118. An oxygen inhibitor is added to the ethylene-containing feed streams to the first reaction zone 112 and the second reaction zone 114. The initiator streams comprising peroxide are added to each of the four reaction zones. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, and the total ethylene conversion for the modeling of Comparative Example 2 are provided in Table 3. The melt index, density, and relative molecular weight distribution of the resulting ethylenebased polymer of Comparative Example 2 are also provided in Table 3.

[0169] Comparative Example 3: Three ethylene-containing feed streams - broad MWD

[0170] Comparative Example 3, the reactor system of FIG. 5 with only four of the reaction zones is modeled (no fifth reaction zone) and three ethylene-containing feed streams for making ethylene-based polymers with as broad an MWD as possible. For Comparative Example 3, valve 272 in FIG. 5 is closed and valves 270, 280, 282, 284, 286, and 288 are configured to introduce 25% by mole of the ethylene and CTAs to the first reaction zone 112, 25% by mole of the ethylene and CTAs to the second reaction zone 114, and 50% by mole of the ethylene and CTAs to the third reaction zone 116. No ethylene-containing side stream is introduced to the fourth reaction zones 116, 118. An oxygen inhibitor is added to the ethylene-containing feed streams to the first reaction zone 112, the second reaction zone 114, and the third reaction zone 116. The initiator streams comprising peroxide are added to each of the four reaction zones. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, the Z3 / Z1 ratio, and the total ethylene conversion for the modeling of Comparative Example 3 are provided in Table 3. Make up ethylene, make up CTAs, or both are introduced to one or more of the ethylenecontaining feed streams to obtain the Z2 / Z1 and Z3 / Z1 ratios in Table 3. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 3 are also provided in Table 3.

[0171] Examples 4 and 5: Five reaction zones and four ethylene-containing feed streams - Broad MWD ethylene-based polymers.

[0172] In Examples 4 and 5, the reactor system of FIG. 5 is modeled having all five reaction zone (i.e., the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 116, and the fifth reaction zone 118) to make ethylene-based polymers with broad MWD. For each of Examples 4 and 5, make-up ethylene, make-up CTAs, and valves 270, 271, 280, 282, 284, 286, and 288 are configured to introduce 25% by mole of the total ethylene and CTAs to the first reaction zone 112, 25% by mole of the total ethylene and CTAs to the second reaction zone 114, 30% by mole of the total ethylene and CTAs to the third reaction zone 116, and 20% by mole of the total ethylene and CTAs to the fourth reaction zone 118. The valves, make-up CTAs, and make-up ethylene are adjusted to obtain the Z2 / Z1, Z3 / Z1, and Z4 / Z1 ratios in Table 3. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, the Z3 / Z1 ratio, the Z4 / Z1 ratio, and the total ethylene conversion for the modeling of Examples 4 and 5 are provided in Table 3. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymers of Examples 4 and 5 are also provided in Table 3.

[0173] Comparison of Examples 4 and 5 with Comparative Examples 1 -3

[0174] Table 3 provides the reaction conditions and properties of the ethylene -based polymers resulting from the modeling conducted in Comparative Examples 1-3 and Examples 4 and 5. As shown in Table 3 the modeling for Examples 4 and 5 having the five reactions and the ethylenebased feed to the first four reaction zones increased the overall ethylene conversion and decreased the density compared to Comparative Examples 1-3. Additionally, the modeling of Examples 4 and 5 indicated a broader relative MWD for the ethylene-based polymers compared to the ethylene-based polymers resulting from Comparative Examples 1-3.Table 3

[0175] Comparative Example 6

[0176] Comparative Example 6 is the same as Comparative Example 1 except that the maximum reactor temperatures are decreased to 290 °C to narrow the molecular weight distribution of the resulting ethylene-based polymers. The maximum reaction temperature for each reaction zone, the reactor pressure, and the total ethylene conversion for the modeling are provided in Table 4. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer are also provided in Table 4. The maximum reaction temperature for each reaction zone, the reactor pressure, and the total ethylene conversion for the modeling of Comparative Example 6 are provided in Table 4. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 6 are also provided in Table 4.

[0177] Comparative Example 7: Two eth lene-containing feed streams - narrow MWD

[0178] Comparative Example 7 is similar to Comparative Example 2 except that the Z2 / Z1 ratio was 0.27 meaning less CTA introduced to the second reaction zone compared to Comparative Example 2, and the maximum temperatures in each of the reaction zones was maintained at 290 °C. The smaller 2I 2 and lower max temperatures are selected to produce ethylene-based polymers with narrower MWD. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, and the total ethylene conversion for the modeling of Comparative Example 7 are provided in Table 4. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 7 are also provided in Table 4.

[0179] Comparative Example 8: Three ethylene-containing feed streams - narrow MWD

[0180] Comparative Example 8 is similar to Comparative Example 3 except that the Z2 / Z1 ratio was 0.35 and Z3 / Z1 was 0.23 meaning less CTA introduced to the second reaction zone 114and the third reaction zone 116 compared to Comparative Example 2, and the maximum temperatures in each of the reaction zones was maintained at 290 °C. The smaller 2I 2 and lower max temperatures are selected to produce ethylene-based polymers with narrower MWD. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, the Z3 / Z1 ratio, and the total ethylene conversion for the modeling of Comparative Example 8 are provided in Table 3. Make up ethylene, make up CTAs, or both are introduced to one or more of the ethylene-containing feed streams to obtain the Z2 / Z1 and Z3 / Z1 ratios in Table 4. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 8 are also provided in Table 4.

[0181] Examples 9 and 10: Five reaction zones and four eth lene-containing feed streams - Narrow MWD ethylene-based polymers

[0182] In Examples 9 and 10, the reactor system of FIG. 5 is modeled having all five reaction zone (i.e., the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 116, and the fifth reaction zone 118), but is configured to make ethylenebased polymers with narrow MWD. For each of Examples 9 and 10, make-up ethylene, make-up CTAs, and valves 270, 271, 280, 282, 284, 286, and 288 are configured to introduce 25% by mole of the total ethylene and CTAs to the first reaction zone 112, 25% by mole of the total ethylene and CTAs to the second reaction zone 114, 40% by mole of the total ethylene and CTAs to the third reaction zone 116, and 10% by mole of the total ethylene and CTAs to the fourth reaction zone 118. For Example 10, no initiator was added to the fifth reaction zone 120, thereby, effectively skipping the fifth reaction zone 120. The valves, make-up CTAs, and make-up ethylene are adjusted to obtain the Z2 / Z1, Z3 / Z1, and Z4 / Z1 ratios in Table 4. The maximum reaction temperature for each reaction zone, the reactor pressure, the Z2 / Z1 ratio, the Z3 / Z1 ratio, the Z4 / Z1 ratio, and the total ethylene conversion for the modeling of Examples 9 and 10 are provided in Table 4. The melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymers of Examples 9 and 10 are also provided in Table 4.

[0183] Comparison of Examples 9 and 10 with Comparative Examples 6-8

[0184] Table 4 provides the reaction conditions and properties of the ethylene -based polymers resulting from the modeling conducted in Comparative Examples 6-8 and Examples 9 and 10. As shown in Table 4 the modeling for Examples 9 and 10 having the five reactions and the ethylenebased feed to the first four reaction zones increased the overall ethylene conversion and slightly decreased the density compared to Comparative Examples 1-3. Additionally, the modeling of Examples 9 and 10 demonstrate that the reactor system of FIG. 5 can be configured to producenarrow MWD ethylene-based polymers by decreasing the Z2 / Z1, Z3 / Z1, and the Z4 / Z1 ratios and decreasing the maximum reaction temperature in each of the reaction zones. Thus, the reactor systems disclosed herein can provided greater flexibility to produce ethylene -based polymers with broad MWD and ethylene-based polymers with narrow MWD.Table 4

[0185] It is noted that one or more of the following claims utilize the term "wherein" as a transitional phrase. For the purposes of defining the present invention, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term "comprising."

[0186] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, theinvention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

Claims1. A process for producing ethylene-based polymers in the presence of at least one free- radical, the process comprising polymerizing a mixture comprising ethylene in a tubular reactor having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymerization effluent comprising the ethylene-based polymers, wherein: each of the at least four ethylene-containing feed streams comprise ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers; the at least four reaction zones comprise a first reaction zone, a second reaction zone downstream of the first reaction zone, a third reaction zone downstream of the second reaction zone, and at least one fourth reaction zone downstream of the third reaction zone; a first ethylene-containing feed stream passed to the first reaction zone comprises from 20% to 35% by mole of the total molar flow rate of the at least four ethylene feed streams introduced to the tubular reactor; and a CTA activity ratio (Z2 / Z1) for the second reaction zone is from 0.2 to 2.0, or more preferably from 0.3 to 1.9, or most preferably from 0.5 to 1.8, wherein the CTA activity ratio of the second reaction zone is equal to the CTA activity in the second reaction zone (Z2) divided by the CTA activity in the first reaction zone (Zl); a CTA activity ratio (Z3 / Z1) for the third reaction zone is from 0.12 to 1.5, more preferably from 0.15 to 1.4, or most preferably from 0.2 to 1.3, wherein the CTA activity ratio of the third reaction zone is equal to the CTA activity in the third reaction zone (Z3) divided by the CTA activity in the first reaction zone (Zl); and a CTA activity ratio (Z4 / Z1) for the fourth reaction zone is from 0.0 to 0.7, more preferably from greater than 0.0 to 0.7, or most preferably from 0.05 to 0.6, wherein the CTA activity ratio of the fourth reaction zone is equal to the CTA activity in the fourth reaction zone (Z4) divided by the CTA activity in the first reaction zone (Zl).

2. The process of claim 1, wherein the at least four ethylene-containing feed streams further comprise a second ethylene-containing feed stream introduced to the second reaction zone, athird ethylene-containing feed stream introduced to the third reaction zone, and at least one fourth ethylene-containing feed stream introduced to the at least one fourth reaction zone.

3. The process of claim 2, wherein a concentration of the CTAs in the first ethylenecontaining feed stream is different from concentrations of the CTAs in each of the other of the at least four ethylene-containing feed streams.

4. The process of either one of claims 2 or 3, wherein an amount of ethylene, and optionally the one or more comonomers, and the optionally the one or more CTAs, introduced to the tubular reactor by the first ethylene-containing feed stream and the second ethylene-containing feed stream comprises 40% to 70% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor.

5. The process of any one of claims 2-4, wherein: the second ethylene-containing feed stream, the third ethylene-containing feed stream, and the fourth ethylene-containing feed stream each comprise ethylene, CTAs, and optionally one or more comonomers; a concentration of the CTAs in the second ethylene-containing feed stream is greater than the concentration of the CTAs in the first ethylene-containing feed stream; and a concentration of the CTAs in the third ethylene-containing feed stream, the fourth ethylene-containing feed stream, or both is greater than the concentration of the CTAs in the second ethylene-containing feed stream.

6. The process of any one of claims 2-5, further comprising adjusting a molar ratio of the third ethylene-containing feed stream to the fourth ethylene-containing feed stream, wherein a molar ratio of the third ethylene-containing feed stream to the fourth ethylene-containing feed stream is from 1 to 4, and the proportion of the third ethylene-based feed stream and the fourth ethylene-containing feed stream introduced to the third reaction zone and the fourth reaction zone is controlled with a control system comprising at least one control valve.

7. The process of any one of claims 2-6, further comprising controlling a composition of each of the at least four ethylene -based feed streams with a control system comprising one or more control valves.

8. The process of any one of claims 2-7, wherein the first ethylene-containing feed stream comprises a fresh ethylene feed stream and the second ethylene-containing feed stream, the third ethylene-containing feed stream, and the fourth ethylene-containing feed stream each comprise a recycled ethylene stream.

9. The process of any one of claims 2-8, further comprising: separating the polymerization effluent in a high pressure separator to produce a high pressure ethylene recycle stream and a bottom stream, wherein the high pressure ethylene recycle stream comprises ethylene, CTAs, and optionally one or more comonomers; and separating the bottom stream in a low pressure separator to produce a low pressure ethylene recycle stream and a product stream, wherein the low pressure ethylene recycle stream comprises ethylene, CTAs, and optionally one or more comonomers.

10. The process of claim 9, wherein the second ethylene-containing feed stream comprises at least a portion of the low pressure ethylene recycle stream, and the third ethylene-containing feed stream, the fourth ethylene-containing feed stream, or both comprises at least a portion of the high pressure ethylene recycle stream.

11. The process of either one of claims 9 or 10, comprising adjusting a molecular weight distribution of the ethylene-based polymers in the polymerization effluent by controlling amounts of the high-pressure ethylene recycle stream, the low-pressure ethylene recycle stream, or both to the first ethylene-containing feed stream, the second ethylene-containing feed stream, the third ethylene-containing feed stream, the fourth ethylene-containing feed stream, or combinations of these.

12. The process of any one of claims 2-11, wherein the first ethylene-containing feed stream and the second ethylene-containing feed stream each introduce 25% by mole of the total ethylene, and optionally the one or more comonomers, and optionally the one or more CTAs, introduced to the tubular reactor.

13. The process of any one of claims 2-12, further comprising controlling a temperature of each of the first ethylene-containing feed stream, the second ethylene-containing feed stream, the third ethylene-containing feed stream, and the fourth ethylene-containing feed stream.

14. The process of any one of claims 2-13, comprising cooling the second ethylenecontaining feed stream, the third ethylene-containing feed stream, the fourth ethylene-containingfeed stream or combinations thereof to a temperature less than or equal to 90 °C, preferably from 40 °C to 90 °C, more preferably from 40 °C to 80 °C, more preferably from 40 °C to 70 °C, or most preferably from 40 °C to 55 °C.

15. The process of any one of claims 2-14, further comprising: compressing the first ethylene-containing feed stream in a first primary compressor upstream of the first reaction zone, wherein the first ethylene-containing feed stream comprises a fresh ethylene feed stream; and compressing the second ethylene-containing feed stream in a second primary compressor upstream of the second reaction zone, wherein the second ethylene-containing feed stream comprises a low pressure ethylene-containing recycle stream.

16. The process of any one of claims 2-15, further comprising: passing the first ethylene-containing feed stream and the second ethylene containing feed stream to a first hyper compressor, wherein the first hyper compressor is configured to split each of the first ethylene-containing feed stream and the second ethylene-containing feed stream at a hyper suction of the first hyper compressor; passing a high pressure ethylene recycle stream to a second hyper compressor operable to split the high pressure ethylene recycle stream at a hyper suction of the second hyper compressor; and dividing an outlet stream from the second hyper compressor into the third ethylenecontaining feed stream and the fourth ethylene-containing feed stream.

17. The process of any one of claims 1-16, wherein: the process is configured to make ethylene-based polymers with broad molecular weight distribution and the CTA activity ratio (Z2 / Z1) for the second reaction zone is from 1.0 to 2.0, the CTA activity ratio (Z3 / Z1) for the third reaction zone is from 0.5 to 1.5, and the CTA activity ratio (Z4 / Z1) for the fourth reaction zone is from 0.1 to 0.7; or the process is configured to make ethylene-based polymers with narrow molecular weight distribution and the CTA activity ratio (Z2 / Z1) for the second reaction zone is from 0.2 to 0.5, the CTA activity ratio (Z3 / Z1) for the third reaction zone is from 0.12 to less than 0.5, and the CTA activity ratio (Z4 / Z1) for the fourth reaction zone is less than 0.1.

18. The process of any one of claims 1-17, wherein the process is configured to produce the ethylene-based polymers having a broad molecular weight distribution and each of the plurality of reaction zones are operated at a maximum temperature of from 300 °C to 330 °C, more preferably from 300 °C to 325 °C, or most preferably from 300 °C to 320 °C.

19. A process for producing ethylene-based polymers in the presence of at least one free- radical, the process comprising: polymerizing a mixture comprising ethylene in a tubular reactor having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymerization effluent comprising the ethylene-based polymers, wherein each of the at least four ethylene-containing feed streams comprise ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers, and wherein the at least four reaction zones comprise a first reaction zone, a second reaction zone downstream of the first reaction zone, a third reaction zone downstream of the second reaction zone, and at least one fourth reaction zone downstream of the third reaction zone; and changing a molecular weight distribution of the ethylene-based polymers between a narrow molecular weight distribution and a broad molecular weight distribution, wherein changing the molecular weight distribution of the ethylene -based polymers may comprise: modifying a CTA activity in one or more of the at least four reaction zones, changing a maximum reaction temperature in one or more of the at least four reaction zones, or a combination thereof.

20. The process of claim 19, wherein: the process further comprises separating the polymerization effluent into at least a high pressure ethylene recycle, a low pressure ethylene recycle, and a product stream and passing the high pressure ethylene recycle, the low pressure ethylene recycle or both back to the tubular reactor; changing the molecular weight distribution of the ethylene-based polymers comprises modifying a CTA activity in one or more of the at least four reaction zones, which comprises: changing a proportion of the high pressure ethylene recycle, the low pressure ethylene recycle, a fresh ethylene feed, or combinations thereof to one or more of the at least four ethylene-containing feed streams;changing an amount of make-up CTAs introduced to one or more of the at least four ethylene-containing feed streams; or combinations thereof.

21. The process of either one of claims 19 or 20, comprising configuring the tubular reactor in a broad molecular weight configuration to produce the ethylene-based polymers having a broad molecular weight distribution, wherein in the broad molecular weight configuration: a CTA activity ratio (Z2 / Z1) for the second reaction zone is from 1.0 to 2.0, more preferably from 1.04 to 2.0, or most preferably from 1.1 to 2.0, wherein the CTA activity ratio of the second reaction zone is equal to the CTA activity in the second reaction zone (Z2) divided by the CTA activity in the first reaction zone (Zl); a CTA activity ratio (Z3 / Z1) for the third reaction zone is from 0.5 to 1.5, more preferably from 0.6 to 1.4, more preferably from 0.7 to 1.3, or most preferably from 0.8 to 1.2, wherein the CTA activity ratio of the third reaction zone is equal to the CTA activity in the third reaction zone (Z3) divided by the CTA activity in the first reaction zone (Zl); and a CTA activity ratio (Z4 / Z1) for the fourth reaction zone is from 0.1 to 0.7, more preferably from 0.2 to 0.6, or most preferably from 0.3 to 0.6, wherein the CTA activity ratio of the fourth reaction zone is equal to the CTA activity in the fourth reaction zone (Z4) divided by the CTA activity in the first reaction zone (Zl).

22. The process of either one of claims 19 or 20, comprising configuring the tubular reactor in a narrow molecular weight configuration to produce the ethylene-based polymers having a narrow molecular weight distribution, wherein in the narrow molecular weight configuration: a CTA activity ratio (Z2 / Z1) for the second reaction zone is from 0.2 to 0.5, more preferably from 0.2 to 0.4, wherein the CTA activity ratio of the second reaction zone is equal to the CTA activity in the second reaction zone (Z2) divided by the CTA activity in the first reaction zone (Zl); a CTA activity ratio (Z3 / Z1) for the third reaction zone is from 0.12 to less than 0.5, or more preferably from 0.12 to 0.4, wherein the CTA activity ratio of the third reaction zone is equal to the CTA activity in the third reaction zone (Z3) divided by the CTA activity in the first reaction zone (Zl); anda CTA activity ratio (Z4 / Z1) for the fourth reaction zone is less than 0.1, more preferably less than or equal to 0.09, or most preferably less than or equal to 0.08, wherein the CTA activity ratio of the fourth reaction zone is equal to the CTA activity in the fourth reaction zone (Z4) divided by the CTA activity in the first reaction zone (Zl).

Images