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

Abstract

A process for producing an ethylene-based polymer in the presence of at least one free radical includes polymerizing an ethylene-containing mixture in a tubular reactor having at least four in-series reaction zones and at least four ethylene-containing feed streams to produce a polymerization effluent comprising the ethylene-based polymer. Each of the ethylene-containing feed streams includes ethylene and a chain transfer agent (CTA). The first ethylene-containing feed stream passed to the first reaction zone comprises from 20 mol% to 35 mol% 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 ethylene-polymers with a wider molecular weight distribution compared to existing tubular reactor systems. The process is flexible and can be modified to alter the CTA activity ratio, thereby also producing polymers with narrow molecular weight distribution.

Description

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

[0002] Background technology. Technical Field

[0003] This disclosure generally relates to systems and methods for producing ethylene-based polymers, and more specifically, to systems and methods for increasing the process capacity of high-pressure free radical tubular reactors for producing ethylene-based polymers. Background Technology

[0004] Low-density polyethylene (LDPE) and other ethylene-based polymers are produced under high pressure and high temperature in autoclave reactors and / or tubular reactors. High-pressure free radical polymerization is disclosed in the following references: U.S. Patents 8,445,606, 4,135,044, and 7,582,709, and Japanese Patent JP050534422 (abstract). High-pressure tubular reactors have been used industrially to produce LDPE products for over 40 years. Compared to autoclave-based methods, high-pressure tubular reactors offer flexible technology development and high ethylene single-pass conversion, and also enable higher productivity with less capital investment. However, due to the plug flow characteristics of high-pressure tubular reactors, such as, but not limited to, large gradient temperatures, pressures, polymer / ethylene concentrations, and shorter residence times along the reactor, ethylene-based polymers produced by high-pressure tubular reactors typically exhibit narrower molecular weight distributions and lower melt strengths compared to polymers produced in autoclave reactors, which include well-mixed flow and a wider molecular weight distribution with longer residence times. The narrow molecular weight distribution and low melt strength of ethylene-based polymers produced in conventional high-pressure tubular reactors limit their use for producing ethylene-based polymers for extrusion coatings and large bubble films. Summary of the Invention

[0005] Therefore, there remains a continued need for systems and methods using high-pressure tubular reactors to produce ethylene-based polymers suitable for extrusion coatings and large bubble films, leveraging the greater production capacity and reduced investment costs of tubular reactors. This disclosure relates to systems and methods including a tubular reactor configuration that widens the operating window of the tubular reactor to enable the production of ethylene-based polymers with a wider molecular weight distribution, higher levels of long-chain branching, and increased melt strength. The systems and methods disclosed herein enable high-pressure tubular reactors to produce ethylene-based polymers with similar properties to those produced in autoclave reactor systems and suitable for extrusion coating applications that meet FDA food contact requirements. The systems and methods disclosed herein also allow for greater process flexibility, enabling the operation of the tubular reactor to be varied between the production of polymers with wide and narrow molecular weight distributions.

[0006] According to one aspect disclosed herein, a method for producing an ethylene-based polymer in the presence of at least one free radical may include polymerizing an ethylene-containing mixture in a tubular reactor having at least four tandem reaction zones and at least four ethylene-containing feed streams to produce a polymeric effluent containing an ethylene-based polymer. Each of the at least four ethylene-containing feed streams may contain ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers. The at least four reaction zones may include 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. The first ethylene-containing feed stream delivered to the first reaction zone may account for 20 mol% to 35 mol% of the total molar flow rate of the at least four ethylene feed streams introduced into the tubular reactor. The CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.2 to 2.0, more preferably 0.3 to 1.9, or most preferably 0.5 to 1.8; the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.12 to 1.5, more preferably 0.15 to 1.4, or most preferably 0.2 to 1.3; and the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be 0.0 to 0.7, more preferably greater than 0.0 to 0.7, or most preferably 0.05 to 0.6. Attached Figure Description

[0007] The following detailed description of specific embodiments of this disclosure is best understood in conjunction with the accompanying drawings, in which similar reference numerals indicate similar structures and in the drawings: Figure 1 A method for producing an ethylene-containing polymer is schematically depicted according to one or more embodiments shown and described herein; Figure 2The melt strength (y-axis) of ethylene-based polymers according to one or more embodiments shown and described herein is graphically depicted as a function of reactor technology (x-axis). Figure 3 The reactor temperature (y-axis) for producing ethylene-based polymers with a wide molecular weight distribution, according to one or more embodiments shown and described herein, is depicted graphically as a function of the relative distance (x-axis) along the tubular reactor. Figure 4 The reactor temperature (y-axis) for producing ethylene-based polymers with a narrow molecular weight distribution, according to one or more embodiments shown and described herein, is graphically depicted as a function of the relative distance (x-axis) along the tubular reactor; and Figure 5 Another method for producing ethylene-containing polymers according to one or more embodiments shown and described herein is illustrated schematically.

[0008] Reference will now be made in more detail to various embodiments, some of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. Detailed Implementation

[0009] Embodiments of this disclosure relate to systems and methods for producing ethylene-based polymers. Specifically, one or more embodiments of this disclosure relate to systems and methods for producing ethylene-based polymers having a broad molecular weight distribution and for providing additional process flexibility to prepare ethylene-based polymers having a narrow or broad molecular weight distribution. Reference is now made to... Figure 1The reactor system 100 disclosed herein includes a tubular reactor 110 having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymeric effluent 130 comprising an ethylene-based polymer. Each of the at least four ethylene-containing feed streams may contain ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers. The at least four reaction zones may include 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. The first ethylene-containing feed stream delivered to the first reaction zone may account for 20 mol% to 35 mol% of the total molar flow rate of the at least four ethylene feed streams introduced into the tubular reactor. The CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.2 to 2.0, more preferably 0.3 to 1.9, or most preferably 0.5 to 1.8; the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.12 to 1.5, more preferably 0.15 to 1.4, or most preferably 0.2 to 1.3; and the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be 0.0 to 0.7, more preferably greater than 0.0 to 0.7, or most preferably 0.05 to 0.6. The CTA activity ratio is as defined herein.

[0010] Unless stated to the contrary, implied by the context or customary in the art, all parts and percentages are by weight, and all test methods are current methods as of the filing date of this application.

[0011] As used herein, the terms "ethylene feed stream" or "ethylene-based feed" or "ethylene-containing feed stream" or "ethylene feed" or "ethylene-containing feed stream" as used herein refer to the feed stream entering the reaction zone and containing a substantial amount of ethylene in the molar amounts of all components in the feed stream. Optionally, the feed stream may contain one or more chain transfer agents (CTAs), comonomers, other process components (e.g., lubricants, solvents, antioxidants, ethane, methane, inhibitors, etc.) and / or impurities (e.g., initiator degradation products).

[0012] As used herein, the term "ethylene conversion" refers to the weight fraction of ethylene in the final polymer resulting from the incorporation into the reactor. In other words, "ethylene conversion" is the amount of ethylene incorporated into the final ethylene-based polymer divided by the total amount of ethylene fed into the reactor.

[0013] As used herein, the term "composition" means a mixture of materials constituting the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0014] As used herein, the term "polymer" refers to a compound prepared by polymerizing monomers of the same or different types. Therefore, the general term "polymer" encompasses the terms "homopolymer" (which refers to a polymer prepared from only one type of monomer, and it should be understood that trace impurities may also be incorporated into the polymer structure) and "interpolymer" as defined below. Trace impurities may be incorporated into and / or within a polymer. Trace impurities may include initiator residues and other components exhibiting chain transfer activity, such as, for example, lubricants, antioxidants, solvents, ethane, methane, and / or initiator dissociation products or other additives. "Interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. The general term "interpolymer" includes copolymers (which refer to polymers prepared from two different monomers) and polymers prepared from more than two different types of monomers.

[0015] As used herein, the term "ethylene-based polymer" refers to a polymer that, by weight of the polymer, comprises a majority amount of polymeric ethylene and optionally at least one comonomer. As used herein, the term "ethylene-based interpolymer" refers to an interpolymer that, by weight of the interpolymer, comprises a majority amount of polymeric ethylene and at least one comonomer. The term "ethylene-based copolymer" refers to a copolymer that, by weight of the interpolymer, comprises a majority amount of polymeric ethylene and a comonomer as the sole monomer type.

[0016] As used herein, the term "high-pressure polymerization method" refers to a free radical polymerization method carried out at an elevated pressure (inlet pressure) of at least 1000 bar (i.e., greater than or equal to 100 MPa).

[0017] As used herein, the term “inlet flow” or “reaction zone inlet flow” refers to the total mass flow rate or total molar flow rate at the inlet of the reaction zone, and consists of the mass flow rate or molar flow rate transferred from the previous reaction zone plus an optional ethylene-rich feed flow, an optional CTA feed flow, and an optional initiator feed flow that is optionally fed alone or together with another feed flow.

[0018] As used herein, the term “side stream” or “side feed stream” refers to the ethylene-based feed stream, CTA system feed stream, and / or initiator system entering the sequential reaction zone.

[0019] As used herein, the term "reactor system" refers to an apparatus for polymerizing and separating polymers. Such apparatus includes, but is not limited to, one or more reactors, reactor preheaters, ethylene-based feed-reactor cooling systems, ultra-high pressure compressors, main compressors, and / or booster compressors.

[0020] As used herein, the term “reactor configuration” refers to one or more reactors used to polymerize a polymer, and optionally one or more reactor preheaters.

[0021] As used herein, the term “inlet pressure” or “reactor inlet pressure” refers to the pressure level at the inlet of the first reaction zone.

[0022] As used herein, the term "reaction zone" refers to a region within a reactor where a polymerization reaction is initiated or re-initiated by the addition of radical- and / or radical-dissociating components. Typically, the reaction medium is heated and / or cooled by a heat transfer medium flowing through a jacket surrounding the reactor. The reaction zone may also be initiated by the addition of fresh and / or recycled ethylene and / or radical- or radical-dissociating components.

[0023] As used herein, the term "first reaction zone" refers to the first reactor zone in which polymerization is initiated by the addition of free radicals and / or components that dissociate into and / or generate free radicals. The first reaction zone ends at the presence of free radicals and / or components that dissociate into and / or generate free radicals, as well as, optionally, a fresh, recycled feed of ethylene and / or comonomers.

[0024] As used in this article, the phrase “highest temperature in the reaction zone” refers to the highest temperature measured in the reaction zone, such as in a tubular reaction zone.

[0025] As used herein, the term "ultra-high pressure compressor" or "secondary compressor" refers to an apparatus for compressing one or more of the following substances: a) a compressed fresh ethylene stream from a first primary compressor; b) a compressed low-pressure ethylene stream from a second primary compressor; and / or c) a high-pressure ethylene recirculation stream from a high-pressure separator, each reaching the pressure level required for the reactor feed at its inlet pressure. This compression may take place in one or more compression stages and may be combined with intercooling. Ultra-high pressure compressors include reciprocating plunger compressors and may consist of a single or multiple compressor frames.

[0026] As used herein, the term "fresh" in relation to ethylene-based feed components (i.e., "fresh ethylene," "fresh CTA," etc.) refers to reactants supplied from an external source, rather than internally supplied from a recycling source such as, but not limited to, high-pressure recycling streams, low-pressure recycling streams, or other recycling streams. For example, in embodiments, fresh ethylene can be used as "supplementary ethylene" to compensate for ethylene consumed during polymerization and / or lost through, for example, purging ethylene from the process, as well as residual ethylene in the polymer.

[0027] As used herein, the term “recycled” when used with respect to reactants (i.e., “recycled ethylene”, “recycled CTA”, etc.) refers to unreacted reactants that have been separated from the polymer in a high-pressure separator and / or a low-pressure separator and returned to the reactor and / or a compressor upstream of the reactor.

[0028] As used herein, the terms “feed,” “feed flow,” or “feed stream” refer to fresh and / or recycled components (e.g., ethylene, initiator, CTA, and / or solvent) added to the reaction zone at the inlet.

[0029] As used herein, the term "mole fraction" refers to the molar ratio of one component in a mixture to the total number of moles of the components in the mixture. The mole fraction can be determined by calculating the ratio of molar quantity or molar flow rate.

[0030] As used herein, the phrase “molar fraction of fresh ethylene fed into the first reaction zone (RZ1)” refers to the molar amount of fresh ethylene fed into the first reaction zone (via the front flow) divided by the molar amount of ethylene fed into the first reaction zone (via the front flow) plus optional comonomers plus optional CTA.

[0031] As used herein, the phrase “molar fraction of fresh ethylene fed into the nth reaction zone (RZn)” refers to the molar amount of fresh ethylene fed into the nth reaction zone (via side flow) divided by the molar amount of ethylene fed into the nth reaction zone (via side flow) plus optional comonomers plus optional CTA.

[0032] As used herein, the term "CTA system" includes a single CTA or a mixture of CTAs added to the polymerization process to typically control the melt index. A CTA system comprises components capable of transferring hydrogen atoms to growing polymer molecules containing free radicals, thereby forming free radicals on the CTA molecules, which can then initiate new polymer chains. CTAs are also known as telomeres or telomeres.

[0033] As used herein, the terms “CTA activity” or “chain transfer activity coefficient (Cs value)” refer to the ratio between the “chain transfer rate” and the “ethylene growth rate”. See Mortimer’s references: P. Ehrlich, GA 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-1; Chain transfer in ethylene polymerization Volume 4, pp. 881-900 (1966); G. Mortimer, Journal of Polymer Science: Part A-1 Chain transfer in ethylene polymerization. part IV. Additional study at 1360 atm and 130 ° C.Volume 8, pp. 1513-1523 (1970); G. Mortimer, Journal of Polymer Science: Part A-1 Chain transfer in ethylene polymerization. part V. The effect of temperature Volume 8, pp. 1535-1542 (1970); G. Mortimer, Journal of Polymer Science: Part A-1 Chain transfer in ethylene polymerization part V. The effect of pressure Volume 8, pp. 1543-1548 (1970); and G. Mortimer, Journal of Polymer Science: Part A-1 Chain transfer in ethylene polymerization VII.Very reactive and depleteable transfer agents Volume 10, pp. 163-168 (1972). See also LDPE 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 ).

[0034] As used herein, the terms "Z1" and "Zi" are defined as follows: "the reactor zone molar concentration of CTAj in reactor zone i ([CTA])". ji ")" is defined as "the total molar amount of CTA fed into reactor zones k=1 to k=I (excluding the amount transferred from the previous reaction zone)" divided by "the total molar amount of ethylene fed into reactor zones 1 to i (excluding the amount transferred from the previous reaction zone)". Note that i ≥ 1. This relationship is shown in the following equation AC (EQU.AC). In EQU.AC, j≥1, n CTA,jk It is "the molar amount of the j-th type of CTA freshly injected into the k-th reactor zone (where k = 1 to i)," ​​and n eth k It is "the molar amount of ethylene freshly injected into the k-th reactor zone (where k = 1 to i)".

[0035] As used herein, the chain transfer activity (Zi) of the CTA (system) in reactor zone I is defined as the sum of the reactor zone molar concentrations of each CTA in the reactor zone multiplied by its chain transfer activity constant (Cs) – see Equation BC (EQU.BC). The chain transfer activity constant (Cs) is the reaction rate ratio Ks / Kp at a reference pressure (1360 atm) and a reference temperature (130 °C). This relationship is shown in EQU.BC below, where n compi This represents the total number of CTAs in reactor zone i. Note that i ≥ 1, and n compi ≥1. The chain transfer constant (Cs) values ​​of some chain transfer agents are shown in Table 1 below, which shows the chain transfer constant (Cs) of the chain transfer agents shown, derived by Mortimer at 130 °C and 200 °C and at 1360 atm. As used herein, the term “Rn = RZ1 / RZn” refers to the ratio, for reaction zone n, “the mole fraction of fresh ethylene fed into the first reaction zone (RZ1)” to “the mole fraction of fresh ethylene fed into reaction zone n (RZn)”. For the polymerization of ethylene homopolymers, the RZ1 and RZn values ​​are determined according to the following equations AE and BE (EQU.AE and EQU.BE). In EQU.AE, n fresh,eth,1 It is the molar flow rate [mol / h] of fresh ethylene (from the main reactor) fed into reaction zone 1, n fresh,eth,n It is the molar flow rate [mol / h] of fresh ethylene (from the main reactor) fed into reaction zone n, n eth,1 n is the molar flow rate [mol / h] of ethylene from the high-pressure recirculated flow fed into reaction zone 1. eth,n It is the molar flow rate of ethylene from the high-pressure recirculated flow fed into reaction zone n.

[0036] As used herein, the term "initiator system" includes a single initiator or a mixture of initiators, each of which is typically dissolved in a solvent (e.g., a hydrocarbon solvent) added to the polymerization process.

[0037] As used herein, the term "injection point" refers to the inlet location of the apparatus (used in polymerization methods) in which the feed stream is added to the apparatus.

[0038] As used herein, the term “feed conditions” refers to the molar flow rate of the components fed into the reactor (e.g., ethylene, CTA, initiator, and / or comonomer).

[0039] As used herein, the terms “upstream” and “downstream” are relative to the direction of material flow through a process or reactor system component. For example, if one or more material flows encounter a first reactor system component before encountering a second reactor system component, then the first reactor system component is upstream of the second reactor system component.

[0040] Now for reference Figure 1 The method disclosed herein for producing ethylene-based polymers in the presence of at least one free radical may include polymerizing a mixture containing at least ethylene in a tubular reactor system 100 to produce a polymeric effluent 130 containing an ethylene-based polymer. 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 includes a tubular reactor 110. The tubular reactor 110 includes 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.

[0041] Each of at least four ethylene-containing feed streams contains ethylene, optionally one or more comonomers, and optionally one or more chain transfer agents (CTAs). The at least four ethylene-containing feed streams may include at least a first ethylene-containing feed stream 122 introduced into the first reaction zone 112. The first ethylene-containing feed stream is 20 mol% to 35 mol% of the total amount of the at least four ethylene-containing feed streams introduced into the tubular reactor 110. The CTA concentration in each ethylene-containing feed stream may vary along the length of the tubular reactor 110. Specifically, the CTA concentration in the first ethylene-containing feed stream 112 differs from the CTA concentration in each of the other ethylene-containing feed streams among the at least four ethylene-containing feed streams. In embodiments, the CTA activity ratio in each of the at least four reaction zones can be modified to produce ethylene-based polymers with a wider molecular weight distribution and / or a higher melt index. In the implementation scheme, the CTA concentration in each of at least four ethylene-containing feed streams can be adjusted to change the CTA activity ratio in each reaction zone, and thus change the molecular weight distribution, melt index, or both of the ethylene-based polymer in the polymer effluent 130.

[0042] Refer again Figure 1The reactor system 100 may include a first heat exchanger 140 disposed upstream of a first reaction zone 112 of the tubular reactor 110. The first heat exchanger 140 is operable to heat a 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 into a second reaction zone 114. The reactor system 100 may also include a second heat exchanger 150 upstream of the second reaction zone 114, wherein the second heat exchanger 150 is operable to control the temperature of the second ethylene-containing feed stream 124. The reactor system 100 may also include a third ethylene-containing feed stream 126 introduced into a third reaction zone 116 and a fourth ethylene-containing feed stream 128 introduced into a fourth reaction zone 118. The system 100 may also include a third heat exchanger 160 upstream of the third reaction zone 116, wherein the third heat exchanger 160 is operable to control the 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 the implementation, the second heat exchanger 150, the third heat exchanger 160, or both are operable to cool these streams to a temperature of less than or equal to 90°C before introducing the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or a combination thereof into their respective reaction zones, in order to provide cooling to each reaction zone downstream of the first reaction zone 112.

[0043] In one embodiment, reactor system 100 includes at least one tubular reactor 110, and each tubular reactor may have one or more cooling zones (not shown). In another embodiment, reactor system 100 may include at least one tubular reactor 110, and each tubular reactor may be equipped with multiple heat transfer zones (not shown), wherein heat exchange occurs between the reactor and a heat transfer medium on the process side. In another embodiment, reactor system 100 includes at least one tubular reactor 100, and cooling and / or heating of each reactor may be provided by pressurized liquid water operating in co-current and / or counter-current modes in multiple cooling zones surrounding the tubular reactor 110. In another embodiment, reactor system may include at least one tubular reactor 110, and cooling and / or heating of each reactor may be provided by a liquid heat transfer fluid (e.g., silicone oil and / or polyethylene glycol (e.g., DOWTHERM fluid)) (not shown) operating in co-current and / or counter-current modes in multiple cooling zones surrounding the tubular reactor 110. In an embodiment, the tubular reactor 110 may typically be equipped with a heat transfer jacket (not shown) to allow heat transfer by means of a heat transfer medium flowing through the heat transfer jacket.

[0044] In one embodiment, reactor system 100 includes at least one tubular reactor 110, and each tubular reactor 110 may be equipped with multiple jackets, wherein each jacket has an inlet and an outlet, and wherein the respective inlets and outlets of all jackets are connected in series to form a heat transfer zone. In another embodiment, the inlet temperature of the heat transfer zone is uniform, and each inlet temperature is between 20°C and 330°C, such as 20°C to 300°C or 20°C to 250°C. In yet another embodiment, at least two inlet temperatures of the heat transfer zone are uniform, and each inlet temperature is between 20°C and 330°C, such as 20°C to 300°C or 20°C to 250°C. In yet another embodiment, each inlet temperature of the heat transfer zone differs from the inlet temperatures of other heat transfer zones, and each inlet temperature is between 20°C and 330°C, such as 20°C to 300°C or 20°C to 250°C.

[0045] Refer again Figure 1 As previously discussed, reactor system 100 may include at least four reaction zones, such as 4, 5, 6, 7, or more than 7 reaction zones. In an embodiment, the total number of reaction zones is equal to i, and i is greater than or equal to 4, or ≥ 5, or ≥ 6, or ≥ 7, or ≥ 8, or ≥ 9, or ≥ 10, or ≥ 20. In an embodiment, reactor system 100 may include at least a first reaction zone 112, a second reaction zone 114 downstream of the first reaction zone 112, a third reaction zone 116 downstream of the second reaction zone 114, and a fourth reaction zone 118 downstream of the third reaction zone 116. In an embodiment, reactor system 100 may include one or more fifth reaction zones 120 downstream of the fourth reaction zone 114.

[0046] In one embodiment, reactor system 100 may include a single tubular reactor 110, which includes each of a first reaction zone 112, a second reaction zone 114, a third reaction zone 116, a fourth reaction zone 118, and optionally one or more fifth reaction zones 120. In another embodiment, reactor system 100 may include a plurality of tubular reactors 110 connected in series, wherein each tubular reactor 110 includes one of the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, and optionally one or more fifth reaction zones 120.

[0047] Refer again Figure 1As previously discussed, reactor system 100 includes at least four ethylene-containing feed streams, such as four, five, six, seven, or more than seven ethylene-containing feed streams. In an embodiment, reactor system 100 may include a first ethylene-containing feed stream 122 introduced into a first reaction zone 112, a second ethylene-containing feed stream 124 introduced into a second reaction zone 114, a third ethylene-containing feed stream 126 introduced into a third reaction zone 116, and at least one fourth ethylene-containing feed stream 128 introduced into at least one fourth reaction zone 118.

[0048] Each of the ethylene-containing feed streams (e.g., 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, 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 contain solvents (fresh and / or recycled), comonomers (fresh and / or recycled), and / or other components. Other components may include, but are not limited to, fresh and / or recycled lubricants, antioxidants, ethane, methane, and / or initiator dissociation products. In embodiments, one or more of the ethylene-containing feed streams may include ethylene, CTA, solvents, and optionally one or more comonomers, as well as optionally one or more other components (e.g., lubricants, antioxidants, ethane, methane, initiator dissociation additives, etc.).

[0049] In the implementation scheme, the total ethylene flow rate entering reactor system 100 from the combined ethylene-based feed streams can be 30 tons / hour to 400 tons / hour, or 50 tons / hour to 400 tons / hour, or 75 tons / hour to 400 tons / hour, or 100 tons / hour to 400 tons / hour. In the implementation scheme, the total ethylene-based feed flow rate entering reactor system 100 can be 40 tons / hour to 350 tons / hour, or 50 tons / hour to 300 tons / hour. In the implementation scheme, 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, other ethylene-containing feed streams downstream of stream 128, or combinations thereof may contain supplemental ethylene. Supplemental ethylene is added to maintain the total ethylene flow rate entering reactor system 100 to compensate for ethylene consumed, lost through purging, and / or trapped in the ethylene-based polymer.

[0050] In embodiments, the ethylene-containing feed stream (e.g., streams 122, 124, 126, 128, or combinations thereof) contains ethylene as the sole monomer. In embodiments, the ethylene-containing feed stream may contain ethylene and one or more comonomers. Comonomers may include, but are not limited to, α-olefins, acrylates, acetates, methacrylates, and anhydrides, each typically having no more than 20 carbon atoms. α-olefin comonomers with combined monomer and CTA functionality may have 3 to 10 carbon atoms, or alternatively, α-olefin comonomers may have 3 to 8 carbon atoms. Exemplary α-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, supplementary comonomers may be added to one or more of the ethylene-containing feed streams to replenish comonomers consumed, lost through purging, and / or trapped in the polymer.

[0051] 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 selected from: aldehydes, alkanes, ketones, alcohols, acetates, esters, thiols, phosphine, phosgene, α-olefins, or combinations thereof. In an embodiment, one or more of the ethylene-containing feed streams may contain at least one CTA selected from: aldehydes, alkanes, ketones, alcohols, acetates, esters, α-olefins, or combinations thereof. In an embodiment, supplemental CTA may be added to one or more of the ethylene-containing feed streams (e.g., streams 122, 124, 126, 128, or combinations thereof) to replenish CTA consumed, lost through purging, and / or trapped in the ethylene-based polymer.

[0052] In the embodiments, one or more of the ethylene-containing feed streams (streams 122, 124, 126, 128, other streams, or combinations thereof) may also contain a branching agent, such as, but not limited to, polybutadiene. In the embodiments, one or more of the ethylene-containing feed streams 122, 124, 126, 128 may contain one or more hydrocarbon solvents, such as, but not limited to, C9-C30 n-chain alkanes, C9-C30 iso-chain alkanes, or combinations thereof. In the embodiments, one or more of the ethylene-containing feed streams may also contain an inhibitor, such as, but not limited to, oxygen. Other inhibitors have been considered.

[0053] The tubular reactor 110 can be operated at pressures and temperatures sufficient to allow polymerization to proceed at economically advantageous reaction rates. In embodiments, the tubular reactor 110 can be operated at pressures greater than or equal to 1000 bar (100 MPa), such as 1000 bar to 4000 bar (400 MPa). Each of the ethylene-containing feed streams (e.g., streams 122, 124, 126, 128) can be introduced into each reaction zone at pressures greater than or equal to 1000 bar, such as 1000 bar to 4000 bar.

[0054] Refer again Figure 1 The reactor system 100 may include multiple initiator feed streams for introducing a radical initiator composition into each reaction zone. In one embodiment, the reactor system 100 may include a first initiator feed stream 131 introducing a radical initiator composition into a first reaction zone 112, a second initiator feed stream 132 introducing a radical initiator composition into a second reaction zone 114, a third initiator feed stream 133 introducing a radical initiator composition into a third reaction zone 116, and a fourth initiator feed stream 134 introducing a radical initiator composition into a fourth reaction zone 118. In another embodiment, the reactor system 100 may include a fifth initiator feed stream 135 introducing a radical initiator composition into a fifth reaction zone 129. The reactor system 100 may include additional initiator feed streams for any subsequent reaction zones downstream of the fifth reaction zone 129.

[0055] Free radical initiators are generally used to help generate ethylene-based polymers. As used herein, a free radical initiator 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 initiator may include, but is not limited to, tert-butyl peroxypentanoate, di-tert-butyl peroxy, tert-butyl peracetate, tert-butyl peroxy-2-hexanoate, or any mixture thereof. Additionally, oxygen may be used as an initiator. In embodiments, the free radical initiator comprises an organic peroxide initiator in an amount of 0.001% to 0.2% by weight of the total weight of the polymerizable monomers. More information about free radical initiators can be found in U.S. Patent 10,494,456, which is incorporated herein by reference in its entirety.

[0056] In one embodiment, a free radical initiator is added to at least one reaction zone, and the initiator has a 1-second half-life temperature greater than 255°C, preferably greater than 260°C. In another embodiment, such a free radical initiator is used at a peak polymerization temperature of 300°C to 350°C, such as 320°C to 350°C. In yet another embodiment, the free radical initiator comprises at least one peroxide group incorporated into the ring structure. Examples of such initiators include, but are not limited to, TRIGNOX 301 (3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane) and TRIGNOX 311 (3,3,5,7,7-pentamethyl-1,2,4-trioxacycloheptane), both available from Akzo Nobel, and HMCH-4-AL (3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclononane), available from United Initiators. See also international publications WO 02 / 14379 and WO 01 / 68723. In an embodiment, each of the initiator feed streams (e.g., streams 131, 132, 133, 134, 135, etc.) may contain a radical initiator and a solvent. The radical initiator and solvent may be mixed to generate each of the initiator feed streams upstream of the reaction zone.

[0057] Refer again Figure 1 During operation of reactor system 100, a first ethylene-containing feed stream 122 can be passed to a first heat exchanger 140 and heated to a temperature of 140°C to 160°C. The first ethylene-containing feed stream 122 and the first initiator feed stream 131 are then passed to a first reaction zone 112. Monomers (ethylene and any optional comonomers), CTA, and a free radical initiator undergo polymerization in the first reaction zone 112. The reaction mixture is then passed from the first reaction zone 112 to a second reaction zone 114.

[0058] A second ethylene-containing feed stream 124 is passed to a second heat exchanger 150, and the temperature is adjusted to less than or equal to 90°C, such as 40°C to 90°C. The second ethylene-containing feed stream 124 is then passed from the second heat exchanger 150 to a second reaction zone 114, and a 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.

[0059] The reaction mixture from the second reaction zone 114 is transferred to the third reaction zone 116. An ethylene-containing feed stream is then transferred to a third heat exchanger 160, and the temperature is adjusted to less than or equal to 90°C, such as 40°C to 90°C. This ethylene-containing feed stream can then be split into a third ethylene-containing feed stream 126 and a fourth ethylene-containing feed stream 128. The third ethylene-containing feed stream 126 and the third initiator feed stream 133 are then transferred 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.

[0060] The reaction mixture from the third reaction zone 116 is passed to the fourth reaction zone 118. A fourth ethylene-containing feed stream 128 and a 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 can undergo further polymerization in the fourth reaction zone 118. The reaction mixture from the fourth reaction zone 118 can be passed through one or more additional reaction zones and combined with additional initiator feed streams to further polymerize the reaction mixture to produce a polymeric effluent 130 containing an ethylene-based polymer. In an embodiment, the reaction mixture from the fourth reaction zone 118 can be passed to one or more reaction zones downstream of the fourth reaction zone 118, such as a fifth reaction zone 120. Optionally, an initiator feed stream can be passed to the fifth reaction zone 120 to promote further polymerization of the reaction mixture from the fourth reaction zone 118.

[0061] In the implementation scheme, each reaction zone can operate independently at a maximum temperature of less than 400°C, such as 225°C to 400°C, and an inlet pressure of 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 the implementation scheme, the polymerization pressure measured at the first inlet of the first reaction zone 112 of the tubular reactor 110 can 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).

[0062] Polymerization effluent 130 may contain ethylene-based polymers produced by monomer polymerization in tubular reactor 110. The ethylene-based polymers in polymerization effluent 130 may have any of the characteristics, properties, or characteristics described herein for ethylene-based polymers. Polymerization effluent 130 may also contain unreacted ethylene, CTA, and any optional monomers. Polymerization effluent 130 may also contain solvents, other components (e.g., lubricants, antioxidants, ethane, methane, branching agents, and / or initiator dissociation products, etc.), free radical initiators, or any combination thereof. Polymerization effluent 130 exiting tubular reactor 110 may have a pressure of 1000 bar (100 MPa) to 4000 bar (400 MPa), or 1400 bar (140 MPa) to 3600 bar (360 MPa), or 1800 bar (180 MPa) to 3200 bar (320 MPa). The polymer effluent 130 exiting the tubular reactor 110 may have a temperature of 220°C to 400°C, such as 220°C to 350°C.

[0063] At least four ethylene-containing feed streams can be configured to produce ethylene-based polymers with a wide molecular weight distribution in the polymer effluent 130, enabling the production of ethylene-based polymers with a broad molecular weight distribution and high melt strength. (See now for reference.) Figure 2 The melt strength varies with technology, as depicted graphically. Figure 2 Reference mark A indicates a tubular reactor system in which all reactants are introduced into the front of the reactor (i.e., into the first reaction zone), with no sideflow introduced into any downstream reaction zone. Figure 2 The reactor system, denoted by reference numeral A, produces a specific melt strength and offers little flexibility in terms of the melt strength of the resulting ethylene-based polymer. The next iteration of the polymerization technology, shown by reference numeral B, refers to a tubular reactor with three reaction zones, where the ethylene-containing feed stream entering the first reaction zone is 50% of the total feed flow into the tubular reactor, the ethylene-containing feed stream entering the second reaction zone is 30% of the total feed flow into the tubular reactor, and the ethylene-containing feed stream entering the third reaction zone is 20% of the total feed flow into the tubular reactor. For example... Figure 2 As shown, existing tubular reactor systems increase the process window for the melt strength of the resulting ethylene-based polymers. However, the process capacity range of existing tubular reactor systems remains limited and does not allow for the production of polymers with a wide molecular weight distribution and high melt strength, which is required for extrusion coatings and large bubble films.

[0064] The reactor system 100 disclosed herein has at least four reaction zones and at least four ethylene-containing feed streams (in... Figure 2(Indicated by reference numeral C) It is capable of producing a wider range of ethylene-based polymers, and can produce ethylene-based polymers with a wide molecular weight distribution and / or high melt strength, suitable for extrusion coating and large 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 amount and composition of each of the ethylene-based polymer feed streams introduced into the reaction zone.

[0065] Refer again Figure 1 The reactor system 100 includes at least four ethylene-containing feed streams, including at least a first ethylene-containing feed stream 122, a second ethylene-containing feed stream 124, a third ethylene-containing feed stream 126, and a fourth ethylene-containing feed stream 128. The first ethylene-containing feed stream 122 may introduce 20 mol% to 35 mol% of total ethylene, optionally one or more CTAs, and optionally one or more comonomers into the tubular reactor 110. In an embodiment, the first ethylene-containing feed stream 122 may introduce 20 mol% to 30 mol%, 20 mol% to 25 mol%, 25 mol% to 35 mol%, 25 mol% to 30 mol% or about 25 mol% of total ethylene, optionally one or more CTAs, and optionally one or more comonomers into the tubular reactor 110. In the implementation scheme, the first ethylene-containing feed stream 122 may introduce 20 mol% to 35 mol%, 20 mol% to 30 mol%, 20 mol% to 25 mol%, 25 mol% to 35 mol%, 25 mol% to 30 mol%, or about 25 mol% of the total ethylene introduced into the tubular reactor 110.

[0066] In one embodiment, the second ethylene-containing feed stream 124 may introduce 20 mol% to 35 mol% of total ethylene, optionally one or more CTAs, and optionally one or more comonomers introduced into the tubular reactor 110. In another embodiment, the second ethylene-containing feed stream 124 may introduce 20 mol% to 30 mol%, 20 mol% to 25 mol%, 25 mol% to 35 mol%, 25 mol% to 30 mol% or about 25 mol% of total ethylene introduced into the tubular reactor 110. In another embodiment, the second ethylene-containing feed stream 124 may introduce 20 mol% to 35 mol%, 20 mol% to 30 mol%, 20 mol% to 25 mol%, 25 mol% to 35 mol%, 25 mol% to 30 mol% or about 25 mol% of total ethylene introduced into the tubular reactor 110.

[0067] In the implementation scheme, the amount of ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110 by the combined first ethylene-containing feed stream 122 and second ethylene-containing feed stream 124 may be from 40 mol% to 70 mol% of the total ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110, such as 40 mol% to 65 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, 40 mol% to 50 mol%, 45 mol% to 70 mol%, 45 mol% to 65 mol%, 45 mol% to 60 mol%, 45 mol% to 55 mol%, 45 mol% to 50 mol%, 50 mol% to 70 mol%, 50 mol% to 65 mol%, 50 mol% to 60 mol%, or 50 mol% to 55 mol%. In one embodiment, the amount of ethylene introduced into the tubular reactor 110 by the combined first ethylene-containing feed stream 122 and second ethylene-containing feed stream 124 can be 40 mol% to 70 mol%, 40 mol% to 65 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, 40 mol% to 50 mol%, 45 mol% to 70 mol%, 45 mol% to 65 mol%, 45 mol% to 60 mol%, 45 mol% to 55 mol%, 45 mol% to 50 mol%, 50 mol% to 70 mol%, 50 mol% to 65 mol%, 50 mol% to 60 mol%, or 50 mol% to 55 mol%. In another embodiment, the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 can each introduce 25 mol% of the total ethylene introduced into the tubular reactor 110, and optionally one or more comonomers and optionally one or more CTAs.

[0068] Refer again Figure 1The amount of ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110 by the combined third ethylene-containing feed stream 126 and fourth ethylene-containing feed stream 128 may be 30 mol% to 60 mol% of the total ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110, such as 30 mol% to 55 mol%, 30 mol% to 50 mol%, 30 mol% to 45 mol%, 30 mol% to 40 mol%, 35 mol% to 60 mol%, 35 mol% to 55 mol%, 35 mol% to 50 mol%, 35 mol% to 45 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, or 40 mol% to 50 mol%. In the implementation scheme, the amount of ethylene introduced into the tubular reactor 110 by the combined third ethylene-containing feed stream 126 and fourth ethylene-containing feed stream 128 can be 30 mol% to 60 mol%, 30 mol% to 55 mol%, 30 mol% to 50 mol%, 30 mol% to 45 mol%, 30 mol% to 40 mol%, 35 mol% to 60 mol%, 35 mol% to 55 mol%, 35 mol% to 50 mol%, 35 mol% to 45 mol%, 40 mol% to 60 mol%, 40 mol% to 55 mol%, or 40 mol% to 50 mol% of the total ethylene introduced into the tubular reactor 110.

[0069] In an embodiment, the amount of ethylene, optionally one or more CTAs, and optionally one or more comonomers in the third ethylene-containing feed stream 126 may be greater than or equal to the amount of ethylene, optionally one or more CTAs, and optionally one or more comonomers in the fourth ethylene-containing feed stream 128. In an embodiment, the molar ratio of the third ethylene-containing feed stream 126 to the fourth ethylene-containing feed stream 128 may be 1 to 4, such as 1 to 3, 2 to 4, or even 2-3.

[0070] In one embodiment, the third ethylene-containing feed stream 126 may introduce 25 mol% to 40 mol% of the total ethylene and optionally one or more CTAs and optionally one or more comonomers introduced into the tubular reactor 110, such as 25 mol% to 35 mol%, 25 mol% to 30 mol%, 30 mol% to 40 mol%, or 35 mol% to 40 mol% of the total ethylene and optionally one or more CTAs and optionally one or more comonomers introduced into the tubular reactor 110. In another embodiment, the third ethylene-containing feed stream 126 may introduce 25 mol% to 40 mol%, 25 mol% to 35 mol%, 25 mol% to 30 mol%, 30 mol% to 40 mol%, or 35 mol% to 40 mol% of the total ethylene introduced into the tubular reactor 110.

[0071] In one embodiment, the fourth ethylene-containing feed stream 128 may introduce 10 mol% to 25 mol% of the total ethylene and optionally one or more CTAs and optionally one or more comonomers introduced into the tubular reactor 110, such as 10 mol% to 20 mol%, 10 mol% to 15 mol%, 15 mol% to 25 mol%, 15 mol% to 20 mol%, or 20 mol% to 25 mol% of the total ethylene and optionally one or more CTAs and optionally one or more comonomers introduced into the tubular reactor 110. In another embodiment, the fourth ethylene-containing feed stream 128 may introduce 10 mol% to 20 mol%, 10 mol% to 15 mol%, 15 mol% to 25 mol%, 15 mol% to 20 mol%, or 20 mol% to 25 mol% of the total ethylene introduced into the tubular reactor 110.

[0072] The ratio (e.g., molar ratio) of the third ethylene-based feed stream 126 and the fourth ethylene-containing feed stream 128 introduced into the third reaction zone 116 and the fourth reaction zone 118, respectively, can be controlled by a control system including one or more control valves. (See again...) Figure 1 The reactor system 100 may include a third ethylene feed control valve 170 disposed in a third ethylene-containing feed stream 126 upstream of the third reaction zone 116. The reactor system 100 may also include a fourth ethylene feed control valve 172 disposed in a 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 can be uniformly adjusted 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 ethylene-containing feed stream 128 can change the molecular weight distribution and / or melt strength of the ethylene-based polymer produced by the reaction system 100.

[0073] The molecular weight distribution and / or melt strength of ethylene-based polymers can also be controlled by controlling the amount and / or type of CTA in each of the ethylene-containing feed streams. In an embodiment, the CTA concentrations in the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, and the third ethylene-containing feed stream 126 can be different from each other. Figure 1 As shown, in the embodiment, the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 can originate from a common stream split into two streams, and therefore, the CTA concentrations in the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 can be the same. In the embodiment, a supplemental CTA stream can be added to the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both, to further adjust the CTA concentration in either or both of these ethylene-containing feed streams.

[0074] The first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may each have a CTA concentration such that the CTA activity ratio (Z2 / Z1) in the second reaction zone 114 is 0.2 to 2.0, or 0.3 to 1.9, or 0.5 to 1.8, wherein the CTA activity ratio (Z2 / Z1) in the second reaction zone is equal to the chain transfer activity (Z2) of the CTA in the second reaction zone divided by the chain transfer activity (Z1) of the CTA in the first reaction zone. The third ethylene-containing feed stream 126 may have a CTA concentration and flow rate such that the CTA activity ratio (Z3 / Z1) in the third reaction zone 116 is 0.12 to 1.5, such as 0.15 to 1.4 or 0.2 to 1.3, wherein the CTA activity ratio (Z3 / Z1) in the third reaction zone is equal to the chain transfer activity (Z3) of the CTA in the third reaction zone divided by the chain transfer activity (Z1) of the CTA in the first reaction zone. The fourth ethylene-containing feed stream 128 may have a CTA concentration and flow rate such that the CTA activity ratio (Z4 / Z1) of the fourth reaction zone 118 is 0.0 to 0.7, such as 0.05 to 0.6, wherein the CTA activity ratio (Z4 / Z1) in the fourth reaction zone is equal to the chain transfer activity (Z4) of the CTA in the fourth reaction zone divided by the chain transfer activity (Z1) of the CTA in the first reaction zone. Z1, Z2, Z3, and Z4 can all be determined using the relationships previously provided in EQU.BC.

[0075] The molecular weight distribution of the ethylene-based polymer in the polymer effluent 130 can be modified by changing the CTA activity ratio of the second reaction zone 114 (Z2 / Z1), the third reaction zone 116 (Z3-Z1), the fourth reaction zone 118 (Z4 / Z1), or a combination thereof. In an embodiment, the reactor system 100 can be configured to produce an ethylene-based polymer with a wide MWD, and the CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.5 to 2.0, such as 0.7 to 2.0, or 1.0 to 2.0. When configured to produce an ethylene-based polymer with a wide MWD, the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.5 to 1.5, such as 0.5 to 1.4, 0.6 to 1.3, 0.7 to 1.25, or 0.8 to 1.2. When configured to produce an ethylene-based polymer with a wide MWD, the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be 0.1 to 0.7, such as 0.2 to 0.6, or 0.3 to 0.6.

[0076] In an embodiment, reactor system 100 can be configured to produce ethylene-based polymers with a narrow MWD, and the CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.2 to 0.5 or 0.2 to 0.4. When configured to produce ethylene-based polymers with a narrow MWD, the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.12 to less than 0.5, such as 0.12 to 0.4. When configured to produce ethylene-based polymers with a wide MWD, the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be less than 0.1, such as less than or equal to 0.09 or even less than or equal to 0.08.

[0077] In one embodiment, the CTA concentration in the ethylene-containing feed stream may increase with increasing distance from the inlet 111 of the first reaction zone 112 of the tubular reactor 110 to produce an ethylene-based polymer with a wider molecular weight distribution and / or higher melt strength. In one embodiment, the CTA concentration in the second ethylene-containing feed stream 124 may be greater than the CTA concentration in the first ethylene-containing feed stream 122. In one embodiment, the CTA concentration in the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both may be greater than the CTA concentration in the second ethylene-containing feed stream 124. In one embodiment, each ethylene-containing feed stream entering each reaction zone may contain the same CTA system. In one embodiment, each feed CTA system contains a single CTA. In one embodiment, no fresh CTA is allocated to the third and fourth reaction zones.

[0078] In one embodiment, the first ethylene-containing feed stream 122 may comprise a fresh ethylene feed stream. In another embodiment, the ethylene-containing feed stream 122 may not include a recycled ethylene stream. The fresh ethylene is free of chain transfer agents other than one or more residual compounds derived from the ethylene production / fractionation process. In another embodiment, supplemental CTA may be added to the first ethylene-containing feed stream 122 upstream of the first reaction zone 112. In another embodiment, the first ethylene-containing feed stream 122 may include at least a portion of an ethylene recirculation stream comprising recycled ethylene and recycled CTA. In yet another embodiment, the first ethylene-containing feed stream 122 may comprise a combination of a fresh ethylene stream and a recycled ethylene stream, such as, but not limited to, a low-pressure ethylene recirculation stream, a high-pressure ethylene recirculation stream, or both.

[0079] The second ethylene-containing feed stream 124 may include a recirculated ethylene stream, such as, but not limited to, a low-pressure ethylene recirculated stream, a high-pressure ethylene recirculated stream, or both. In an embodiment, the second ethylene-containing feed stream 124 may include a portion of a low-pressure ethylene recirculated stream. The third ethylene-containing feed stream 126 may include a recirculated ethylene stream, such as, but not limited to, a low-pressure ethylene recirculated stream, a high-pressure ethylene recirculated stream, or both. In an embodiment, the third ethylene-containing feed stream 126 may include a portion of a high-pressure ethylene recirculated stream. The fourth ethylene-containing feed stream 128 may include a recirculated ethylene stream, such as, but not limited to, a low-pressure ethylene recirculated stream, a high-pressure ethylene recirculated stream, or both. In an embodiment, the fourth ethylene-containing feed stream 128 may include a portion of a high-pressure ethylene recirculated stream. In an embodiment, the fourth ethylene-containing feed stream 128 may have the same composition as the third ethylene-containing feed stream 126.

[0080] The molecular weight distribution and / or melt strength of ethylene-based polymers can be further manipulated by controlling the peak temperature in each reaction zone of the tubular reactor. (See again...) Figure 1 The reactor system 100 may include a first heat exchanger 140, a second heat exchanger 150, and a third heat exchanger 160. The reactor system 100 may also include additional heat exchangers for additional ethylene-containing feed streams beyond the first to fourth ethylene-containing feed streams.

[0081] In the embodiments, reactor system 100 and method can be configured to produce ethylene-based polymers with a broad molecular weight distribution and / or high melt strength, and each of the plurality of reaction zones can be operated at a maximum temperature of 300°C to 330°C, more preferably 300°C to 325°C, or most preferably 300°C to 320°C. Reference now is made to... Figure 3 The temperature 302 in the tubular reactor is graphically depicted as a function of the relative position (x-axis) within the reactor (y-axis). Reaction zones are numbered 1-5. For Figure 3 The first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 each introduce 25 mol% of the total ethylene into the tubular reactor, the third ethylene-containing feed stream 126 introduces 30% of the ethylene into the tubular reactor, and the fourth ethylene-containing feed stream 128 introduces 20% of the ethylene into the tubular reactor. In each of the first three reaction zones, the tubular reactor operates at the highest polymerization temperature of 300°C to 325°C. The cooling water used to cool each reaction zone is at a temperature of... Figure 4 The reference numeral 404 indicates the molecular weight distribution. The resulting ethylene-based polymers exhibit a broad molecular weight distribution, such as a relative molecular weight distribution greater than or equal to about 7.

[0082] In embodiments, the reactor system and method can be configured to produce ethylene-based polymers with a narrow MWD distribution and / or a high density, and the reaction zones can be maintained at temperatures such that the highest temperature in each reaction zone 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 highest polymerization temperature in reaction zone 1, reaction zone 2, or both can 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 200°C to 260°C. Reference now. Figure 4 The temperature 402 in the tubular reactor is graphically depicted as a function of the relative position (x-axis) within the reactor (y-axis). Reaction zones are numbered 1-5. For Figure 4 The first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 each introduce 25 mol% of the total ethylene into the tubular reactor, the third ethylene-containing feed stream 126 introduces 40% of the ethylene into the tubular reactor, and the fourth ethylene-containing feed stream 128 introduces 10% of the ethylene into the tubular reactor. No initiator transfer is performed. Figure 4 The fourth reaction zone, 118, is located within the reactor. In each of the first three reaction zones, the tubular reactor operates at the highest polymerization temperature of approximately 260°C. (The last sentence appears to be incomplete and possibly refers to a different process.) Figure 3 Compared to the ethylene-based polymers produced by the method shown, the resulting ethylene-based polymers exhibit a narrower molecular weight distribution and a higher density. Therefore, Figure 3 and Figure 4 The molecular weight distribution of ethylene-based polymers can be modified by changing the operating temperature of the reaction zone, optionally in combination with changing the molar ratio of the third ethylene-containing feed stream to the fourth ethylene-containing feed stream.

[0083] Refer again Figure 1 A method for producing ethylene-based polymers using the reactor system 100 disclosed herein may include controlling the temperature of each of a first ethylene-containing feed stream 122, a second ethylene-containing feed stream 124, a third ethylene-containing feed stream 126, and a fourth ethylene-containing feed stream 126. In an embodiment, the method may include heating the first ethylene-containing feed stream 122 to a temperature of 140°C to 160°C upstream of the first reaction zone 112. The first ethylene-containing feed stream 122 may be heated by passing it through a first heat exchanger 140.

[0084] The method 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 40°C to 90°C, 40°C to 80°C, 40°C to 70°C, or even 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 reach a temperature less than or equal to 90°C, such as 40°C to 90°C, these streams are introduced into the second reaction zone 114, the third reaction zone 116, and the fourth reaction zone 118, respectively, to quench the reaction mixture delivered to the reaction zones, thereby reducing the temperature at the inlet of each reaction zone in the second reaction zone 114, the third reaction zone 116, and the fourth reaction zone 118, such as... Figure 3 As shown.

[0085] Refer again Figure 1 As previously discussed, cooling the second ethylene-containing 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 reaction zone may include changing the temperature 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.

[0086] Now for reference Figure 5 This illustration schematically depicts another embodiment of a reactor system 100 for producing ethylene-based polymers. In this embodiment, reactor system 100 includes a tubular reactor 110 as previously described herein. Reactor system 100 may also include a fresh ethylene feed 202, an inhibitor stream 204, a first main compressor 210, a supplemental CTA stream 214, a supplemental additive stream 216, a second main compressor 220, a booster compressor 230, a first ultra-high pressure compressor 240, a second ultra-high pressure compressor 240, a high-pressure separator 260, a high-pressure ethylene recirculation stream 262, a low-pressure separator 270, and a low-pressure ethylene recirculation stream 272. Each of these additional components will be referenced in reference to... Figure 5 Further detailed description.

[0087] Fresh ethylene feed 202 may be delivered to reactor system 100 to replenish ethylene consumed during polymerization in tubular reactor 110, purged from reactor system 100, and / or retained as free ethylene in ethylene-based polymers. Fresh ethylene feed 202 is free of chain transfer agents other than one or more residual compounds derived from ethylene production / fractionation processes. Fresh ethylene feed 202 may supplement at least a portion of the first ethylene-containing feed stream 122. In an embodiment, fresh ethylene feed 202 may also be introduced as a component of a second ethylene-containing feed stream 124. Fresh ethylene feed 202 may be delivered to a first main compressor 210, which may be disposed upstream of the first reaction zone 112 and upstream of the first heat exchanger 140. The first main compressor 210 is operable to increase the pressure of fresh ethylene feed 202 to produce a compressed fresh ethylene stream 212 with a pressure greater than that of fresh ethylene feed 202.

[0088] Refer again Figure 5 In one embodiment, the second ethylene feed stream 124 may include a portion of the low-pressure ethylene recirculation stream 272. The reactor system 100 may include a second main compressor 220 disposed upstream of the second reaction zone 114 and the second heat exchanger 150 of the tubular reactor 110. The second main compressor 220 is operable to compress the low-pressure ethylene recirculation stream 272 to produce a compressed low-pressure ethylene stream 222 with a pressure greater than that of the low-pressure ethylene recirculation stream 272.

[0089] In one embodiment, the compressed low-pressure ethylene stream 222 may have the same composition as the low-pressure ethylene recirculation stream 272. In another embodiment, a portion of the fresh ethylene feed 202 may be added to the low-pressure ethylene recirculation stream 272 upstream of the second main compressor 220, such that the compressed low-pressure ethylene stream 222 has a higher ethylene concentration compared to the low-pressure ethylene recirculation stream 272.

[0090] In one embodiment, the method disclosed herein may include compressing a second ethylene-containing feed stream 124 in a second main compressor 220 upstream of the second reaction zone 114, wherein the second ethylene-containing feed stream 124 includes a low-pressure ethylene-containing recirculation stream 272. In another embodiment, the reactor system 100 may include a booster compressor 230 disposed upstream of the second main compressor 220. The booster compressor 230 is operable to compress the low-pressure ethylene recirculation stream 272 to increase the pressure upstream of the second main compressor 220.

[0091] Refer again Figure 5The reactor system 100 may include a first ultra-high pressure compressor 240 that can be arranged upstream of the tubular reactor 110. In an embodiment, the first ultra-high pressure compressor 240 may be arranged downstream of the first main compressor 210 and the second main compressor 220 and upstream of the first heat exchanger 140 and the second heat exchanger 150. Compressed fresh ethylene stream 212 and compressed low-pressure ethylene stream 222 may be independently delivered to the first ultra-high pressure compressor 240.

[0092] The first ultra-high pressure compressor 240 can be configured to increase the pressure of a compressed fresh ethylene stream 212 to produce a first ethylene-containing feed stream 122. The first ultra-high pressure compressor 240 can also be configured to increase the pressure of a compressed low-pressure ethylene stream 222 to produce a second ethylene-containing feed stream 124 without mixing the compressed fresh ethylene stream 212 with the compressed low-pressure ethylene stream 222. The first ultra-high pressure compressor 240 is 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 ultra-high pressure compressor 240 is designed to be able to divert the desired ethylene-based feed stream upstream of the ultra-high pressure suction section of the first ultra-high pressure compressor 240. Diverting the ethylene-based feed stream upstream of the ultra-high pressure suction section of the first ultra-high pressure compressor 240 can affect the CTA concentration ratio in each reaction zone.

[0093] Reactor system 100 may include a second ultra-high pressure compressor 250. A high-pressure recirculation flow 262 may be delivered to the second ultra-high pressure compressor 250. The second ultra-high pressure compressor 250 may be arranged upstream of tubular reactor 110 and upstream of third heat exchanger 160. In one embodiment, the high-pressure recirculation flow 262 may be split into two flows upstream of the second ultra-high pressure compressor 250. In another embodiment, the two flows delivered through the second ultra-high pressure compressor 250 may be recombined into a single flow downstream of the second ultra-high pressure compressor 250.

[0094] The second ultra-high pressure compressor 250 can be configured to increase the pressure of the high-pressure ethylene recirculation stream 262 to produce an ethylene stream 252, which can then be split into a third ethylene-containing feed stream 126 and a fourth ethylene-containing feed stream 128. The second ultra-high pressure compressor 250 is operable to modify the temperature of the recirculated ethylene stream 252 upstream of the third heat exchanger 160 and the second heat exchanger 150, respectively. The second ultra-high pressure compressor 250 is designed to be able to split the desired ethylene-based feed stream upstream of the ultra-high pressure suction section of the first ultra-high pressure compressor 240. Further description of the ultra-high pressure compressor system suitable for the first ultra-high pressure compressor 240 and / or the second ultra-high pressure compressor 250 can be found in U.S. Patent No. 11,078,301, issued August 3, 2021, entitled “HIGH PRESSURE FREE RADICAL POLYMERIZATION TO PRODUCE ETHYLENE-BASED POLYMERS,” the entire contents of which are incorporated herein by reference.

[0095] Refer again Figure 5 The reactor system 100 may further include a high-pressure separator 260 disposed downstream of the tubular reactor 110. The high-pressure separator 260 may be in fluid communication with the 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 is operable to separate the polymerization effluent 130 to produce a high-pressure ethylene recirculation stream 262 and a bottom stream 264. The high-pressure separator 260 can separate the polymerization effluent 130 at pressures ranging from 200 bar (20 MPa) to 400 bar (40 MPa).

[0096] The high-pressure ethylene recirculation stream 262 contains at least unreacted ethylene and CTA. When the polymerization reaction involves the addition of comonomers, the high-pressure ethylene recirculation stream 262 may also contain unreacted comonomers. In embodiments, the high-pressure ethylene recirculation stream 262 may also contain any other components (e.g., additives, such as, but not limited to, lubricants, antioxidants, solvents, branching agents, etc.). The high-pressure ethylene recirculation stream 262 may contain at least 50 mol%, at least 60 mol%, at least 70 mol%, at least 75 mol%, at least 80 mol%, at least 85 mol%, or even at least 90 mol% of ethylene, CTA, and optionally comonomers present in the polymerization effluent 130. At least a portion of the high-pressure ethylene recirculation stream 262 may be returned to 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, high-pressure ethylene purge material 266 may be discharged from reactor system 100 to prevent the accumulation of contaminants in the recirculation loop.

[0097] The bottom stream 264 may contain ethylene-based polymers generated in the tubular reactor 110 and delivered in the polymer effluent 130. The bottom stream 264 may also contain any ethylene, CTA, and / or optional comonomers that have not been separated from the high-pressure ethylene recirculation stream 262. In embodiments, the bottom stream 264 may also contain any other components (e.g., additives, such as, but not limited to, lubricants, antioxidants, solvents, branching agents, etc.) that have not been separated from the high-pressure ethylene recirculation stream 262.

[0098] Refer again Figure 5 The bottom stream 264 can be passed to a low-pressure separator 270, which can be arranged downstream of the high-pressure separator 260. The low-pressure separator 270 can 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 can be operated to separate the bottom stream 264 to produce a low-pressure ethylene recirculation stream 272 and a product stream 274. In an embodiment, the low-pressure separator 270 can operate at a gauge pressure of 0 bar (0 kPa) to 1 bar (100 kPa). In an embodiment, the method can include separating the bottom stream 264 in the low-pressure separator 270 to produce a low-pressure ethylene recirculation stream 272 and a product stream 274. The product stream 274 may contain an ethylene-based polymer produced in the tubular reactor 110. In an implementation scheme, product stream 274 may contain at least 95%, at least 98%, at least 99%, or at least 99.9% of an ethylene-based polymer from polymer effluent 130.

[0099] The low-pressure ethylene recirculation stream 272 may contain ethylene, CTA, and optionally one or more comonomers. The low-pressure ethylene recirculation stream 272 may also include other components (e.g., additives, such as lubricants, antioxidants, branching agents, solvents, etc.). At least a portion of the low-pressure ethylene recirculation stream 272 may be returned to reactor system 100 as part of one or more of the ethylene-containing feed streams 122, 124, 126, 128, such as, but not limited to, part or all of the second ethylene-containing feed stream 124.

[0100] Refer again Figure 5 In one embodiment, the first ethylene-containing feed stream 122 may contain 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 contain a recycle ethylene stream. In another embodiment, the second ethylene-containing feed stream 124 may contain a portion of a low-pressure ethylene recycle stream 272, and the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both may contain a portion of a high-pressure ethylene recycle stream 262. In yet another embodiment, 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.

[0101] In one embodiment, the CTA concentration of the second ethylene-containing feed stream 124, which includes the low-pressure ethylene recirculation stream 272, may be greater than the CTA concentration of the first ethylene-containing feed stream 122, which includes the fresh ethylene feed 202. In another embodiment, the CTA concentrations of the third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 may each be greater than the CTA concentration in the second ethylene-containing feed stream 124.

[0102] Refer again Figure 5 In this embodiment, supplemental ethylene can 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 supplemental ethylene can be fresh ethylene feed 202. In this embodiment, in addition to including the first ethylene-containing feed stream 122, fresh ethylene feed 202 can also be added as supplemental 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. Along with the supplemental ethylene, an inhibitor stream 204 can be added to the fresh ethylene feed 202 upstream of the first main compressor 210, to the low-pressure ethylene recirculation stream 272 upstream of the second main compressor 220, or both. In this embodiment, the initiator stream 204 can be an oxygen stream.

[0103] In one embodiment, supplemental CTA stream 214 may be combined with a compressed fresh ethylene stream 212, a compressed low-pressure ethylene stream 222, or both upstream of the first ultra-high pressure compressor 240. Alternatively, in another embodiment, supplemental CTA stream 214 may be combined with a high-pressure ethylene recirculation stream 262 upstream of the second ultra-high pressure compressor 250. Supplemental CTA may be included to account for CTA consumed during the polymerization reaction, discharged from the system in one or more purge streams, and / or mechanically entrained in the ethylene-based polymer streams. In one embodiment, supplemental CTA from this supplemental CTA stream may be added to each of the ethylene streams upstream of the tubular reactor 110 (e.g., compressed fresh ethylene stream 212, compressed low-pressure ethylene stream 222, high-pressure ethylene recirculation stream 262, or combinations thereof). In one embodiment, no CTA is added to the compressed fresh ethylene stream 212. In one embodiment, supplemental CTA is added only to the compressed low-pressure ethylene stream 222, the high-pressure ethylene recirculation stream 262, or combinations thereof.

[0104] In the implementation scheme, supplemental CTA may be introduced into the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, or a combination thereof.

[0105] The reactor system 100 may also include one or more supplementary additive streams 216, which may include supplementary additives / other components (e.g., lubricants, antioxidants, ethane, methane, branching agents, and / or initiator dissociation products, etc.). Although shown as a single stream, supplementary additive stream 216 may include multiple streams, each introducing a separate component. Supplementary additive stream 216 may be added to a compressed fresh ethylene stream 212, a compressed low-pressure ethylene stream 222, a high-pressure ethylene recirculation stream 262, or a combination thereof.

[0106] Refer again Figure 5 In the operation of reactor system 100, fresh ethylene feed 202 can be passed to a first main compressor 210, which compresses the fresh ethylene feed 202 to produce a compressed fresh ethylene stream 212. The compressed fresh ethylene stream 212, with or without supplemental CTA and / or supplemental additives, can be passed to a first ultra-high pressure compressor 240, which further compresses the compressed fresh ethylene stream 212 to produce a first ethylene-containing feed stream 112. The first ethylene-containing feed stream 112 can be passed through a first heat exchanger 140 to heat it to a temperature of 140°C to 160°C. The first ethylene-containing feed stream 112 can then be introduced into the first reaction zone 112 of tubular reactor 110.

[0107] In parallel, the low-pressure recirculation stream 272 can be passed to the booster compressor 230, and then to the second main compressor 240. The booster compressor 230 and the second main compressor 240 can compress the low-pressure recirculation stream 272 to produce a compressed low-pressure ethylene stream 222. The compressed low-pressure ethylene stream 222, with or without supplemental CTA and / or supplemental additives, can be passed to the first ultra-high pressure compressor 240, which further compresses the compressed low-pressure ethylene stream 122 to produce a second ethylene-containing feed stream 114. The second ethylene-containing feed stream 114 can be passed through the second heat exchanger 150 to change its temperature to 40°C to 90°C. The second ethylene-containing feed stream 114 can then be introduced into the second reaction zone 114 of the tubular reactor 110.

[0108] Further in parallel, the high-pressure ethylene recirculation stream 262 can be split into two streams, and these two streams can then be passed through a second ultra-high pressure compressor 250. The second ultra-high pressure compressor can further compress the two streams to an operating pressure of greater than or equal to 1000 bar (100 MPa) for the tubular reactor 110. The two compressed streams can be combined to produce ethylene stream 252. Ethylene stream 252 can be passed through a third heat exchanger 160 to modify the temperature of ethylene stream 252 to a temperature of 40°C to 90°C. Ethylene stream 252 can then be split into a third ethylene-containing feed stream 126 and a fourth ethylene-containing feed stream 128. The third ethylene-containing feed stream 126 and the fourth ethylene-containing feed stream 128 can then be introduced into the third reaction zone 116 and the fourth reaction zone 118, respectively.

[0109] Initiator streams 131, 132, 133, 134, and 135 can be introduced into each of the first reaction zone 112, the second reaction zone 114, the third reaction zone 116, the fourth reaction zone 118, and an optional fifth reaction zone 120. Ethylene, CTA, and a free radical initiator undergo polymerization in a tubular reactor 110 to produce a polymer effluent 130 containing an ethylene-based polymer and unreacted components from each ethylene-containing stream.

[0110] The polymerization effluent 130 can be passed to a high-pressure separator 260, which separates the effluent 130 into a high-pressure ethylene recirculation stream 262 and a bottom stream 264. The high-pressure ethylene recirculation stream 262 can be recycled back to reactor system 100, such as back to the second ultra-high-pressure compressor 250. The bottom stream 264 can be passed to a low-pressure separator 270, which separates the bottom stream 264 into a low-pressure ethylene recirculation stream 272 and a product stream 274 containing ethylene-based polymers generated during polymerization. The low-pressure ethylene recirculation stream 272 can be passed back to reactor system 100, such as back to the booster compressor 220. The product stream 274 can be passed from reactor system 100 to one or more downstream processes, such as downstream separation, purification, and / or recovery processes.

[0111] As previously discussed, the molecular weight distribution and / or melt strength of the ethylene-based polymer produced by reactor system 100 can be modified by changing the amount of CTA introduced into each of reaction zones 112, 114, 116, 118, and 120. In an embodiment, the amount of CTA introduced into each of reaction zones 112, 114, 116, 118, and 120 can be modified by changing the amount of supplementary CTA stream 214 added 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. Alternatively or in an alternative embodiment, the amount of CTA introduced into each of the reaction zones 112, 114, 116, 118, 120 can be modified by altering the distribution of the high-pressure ethylene recirculation stream 262, the low-pressure ethylene recirculation 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.

[0112] Refer again Figure 5 In an embodiment, reactor system 100 may include a control system comprising a plurality of control valves for distributing high-pressure ethylene recirculation stream 262, low-pressure ethylene recirculation stream 272, or both, to each of a first ethylene-containing feed stream 122, a second ethylene-containing feed stream 124, a third ethylene-containing feed stream 126, a fourth ethylene-containing feed stream 128, or combinations thereof. Methods using reactor system 100 may include controlling the composition of each of 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) using 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 can provide greater process flexibility for producing ethylene-based polymers using reactor system 100.

[0113] A first control valve 280 may be disposed downstream of the first main compressor 210 and upstream of the first ultra-high pressure compressor 240 in the compressed fresh ethylene stream 212. The first control valve 280 is operable to control the flow of the compressed fresh ethylene stream 212 to the first ultra-high pressure compressor 240. Therefore, the first control valve 280 is operable to control the proportion of the compressed fresh ethylene stream 212 in the first ethylene-containing feed stream 122 or to completely stop the flow of the compressed fresh ethylene stream 212 to the first ethylene-containing feed stream 122.

[0114] A second control valve 282 may be disposed downstream of the second main compressor 210 and upstream of the first ultra-high pressure compressor 240 in the compressed low-pressure ethylene stream 222. The second control valve 282 is operable to control the flow of the compressed low-pressure ethylene stream 222 to the first ultra-high pressure compressor 240. Therefore, the second control valve 282 is operable to control the proportion of the compressed low-pressure ethylene stream 222 in the second ethylene-containing feed stream 124 or to completely stop the flow of the compressed low-pressure ethylene stream 222 to the second ethylene-containing feed stream 124.

[0115] In one embodiment, the reactor system 100 may include a compressed low-pressure ethylene distribution line 290 that fluidly connects a compressed low-pressure ethylene stream 222 to a compressed fresh ethylene stream 212. The compressed low-pressure ethylene distribution line 290 may enable the compressed low-pressure ethylene stream 222 to be distributed as part or entirely to the first ethylene-containing feed stream 122 into the first reaction zone 112. The compressed low-pressure ethylene distribution line 290 may include a third control valve 284 operable to control the proportion of the compressed low-pressure ethylene stream 222 in the first ethylene-containing feed stream 122 or to completely stop the flow of the compressed low-pressure ethylene stream 222 into the first ethylene-containing feed stream 122.

[0116] In one embodiment, reactor system 100 may include a first high-pressure ethylene distribution line 292 that fluidly connects a high-pressure ethylene recirculation stream 262 to a compressed low-pressure ethylene stream 222. The first high-pressure ethylene distribution line 292 allows the high-pressure ethylene recirculation stream 262 to be distributed as part or entirely to the second ethylene-containing feed stream 124 into the second reaction zone 114. The first high-pressure ethylene distribution line 290 may include a fourth control valve 286 operable to control the proportion of the high-pressure ethylene recirculation stream 262 in the second ethylene-containing feed stream 124 or to completely stop the flow of the high-pressure ethylene recirculation stream 262 into the second ethylene-containing feed stream 124.

[0117] In one embodiment, the reactor system 100 may include a second high-pressure ethylene distribution line 294 that fluidly connects the high-pressure ethylene recirculation stream 262 to the compressed fresh ethylene stream 212. The high-pressure ethylene distribution line 294 may allow the high-pressure ethylene recirculation stream 262 to be distributed as part or entirely to the first ethylene-containing feed stream 122 into the first reaction zone 112. The high-pressure ethylene distribution line 294 may include a fifth control valve 288 operable to control the proportion of the high-pressure ethylene recirculation stream 262 in the first ethylene-containing feed stream 122 or to completely stop the flow of the high-pressure ethylene recirculation stream 262 into the first ethylene-containing feed stream 122.

[0118] Refer again Figure 5A method for preparing an ethylene-based polymer using reactor system 100 may include adjusting the molecular weight distribution of the ethylene-based polymer in the polymer effluent 130 by controlling the amount of high-pressure ethylene recirculation stream 262, low-pressure ethylene recirculation stream 272, or both, entering 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 a combination thereof. Controlling the amount of high-pressure ethylene recirculation stream 262, low-pressure ethylene recirculation stream 272, or both, entering 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 a combination thereof may include controlling one or more of a first control valve 280, a second control valve 282, a third control valve 284, a fourth control valve 286, a fifth control valve 288, or a combination thereof.

[0119] Refer again Figure 5 In one embodiment, reactor system 100 can be configured in a wide molecular weight distribution (MWD) configuration to produce ethylene-based polymers having a wide molecular weight distribution and / or a large melt index. In a wide MWD configuration, reactor system 100 can be configured to reduce or eliminate CTA in the first ethylene-containing feed stream 122 fed into the first reaction zone 112, and to provide an increasing CTA concentration in each of subsequent ethylene-containing feed streams (i.e., the second ethylene-containing feed stream 124 and the third ethylene-containing feed stream 126). In one embodiment, when reactor system 100 is in a wide MWD configuration, CTA may not be added to the first ethylene-containing feed stream 122. In another embodiment, when reactor system 100 is in a wide MWD configuration, the CTA concentration that the first ethylene-containing feed stream 122 may include is less than the CTA concentration in the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128. For the widest molecular weight distribution, reactor system 100 can be configured, for example, by adjusting the third ethylene feed control valve 170 and / or the fourth ethylene feed control valve 172, such that the molar flow rate of the third ethylene-containing feed stream 126 is equal to the molar flow rate of the fourth ethylene-containing feed stream 128.

[0120] In one embodiment, when the reactor system 100 is in a wide MWD configuration, the first control valve 280 and the second control valve 282 can be opened, and the third control valve 284, the fourth control valve 286, and the fifth control valve 288 can be closed. In another embodiment, when the reactor system 100 is in a wide MWD configuration, the third control valve 284 and the fourth control valve 286 can be opened or controlled to add at least some of the compressed low-pressure ethylene stream 222 to the first ethylene-containing feed stream 112, and to add at least some of the high-pressure ethylene recirculation stream 262 to the second ethylene-containing feed stream 124. In yet another embodiment, when the reactor system 100 is in a wide MWD configuration, the first control valve 280, the second control valve 282, the third control valve 284, and the fourth control valve 286 can be opened, and the fifth control valve 288 can be closed to prevent flow of the high-pressure ethylene recirculation stream 262 into the first ethylene-containing feed stream 122.

[0121] Refer again Figure 5 In one embodiment, reactor system 100 can be configured with a narrow molecular weight distribution (MWD) to produce ethylene-based polymers with a narrow molecular weight distribution. In a narrow MWD configuration, the CTA concentration in the first ethylene-containing feed stream 122 can be increased to introduce a higher concentration of CTA into the first reaction zone 112. In a narrow MWD configuration, reactor system 100 can be configured to introduce decreasing amounts of CTA into subsequent reaction zones, such as a second reaction zone 114, a third reaction zone 116, and a fourth reaction zone 118. In other words, each successive reaction zone can have a lower CTA concentration than the preceding reaction zone.

[0122] In an embodiment, a narrow MWD configuration for producing ethylene-based polymers with a narrow MWD, compared to a wide MWD configuration, may include increasing the CTA concentration in the first reaction zone 112. In an embodiment, increasing the CTA concentration in the first reaction zone 112 may include increasing the flow rate of supplemental CTA stream 214 added to the first ethylene-containing feed stream 122. In an embodiment, increasing the CTA concentration in the first reaction zone 112 may include distributing or transferring a portion of the high-pressure ethylene recirculation stream 262 to the first ethylene-containing feed stream 122, the second ethylene-containing feed stream 124, or both. In an embodiment, a control system including multiple valves may be configured to introduce at least a portion of the high-pressure ethylene recirculation stream 262 as the first ethylene-containing feed stream 122 into the first reaction zone 112. In an embodiment, 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 opened to deliver the high-pressure ethylene recirculation stream 262 to the first reaction zone 112 and the second reaction zone 114.

[0123] In an implementation scheme, in a narrow MWD configuration, reducing the CTA gradient as the number of reaction zones increases may include increasing the molar ratio of the third ethylene-containing 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 fourth ethylene-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 reference numerals 170 and 172, the terms "third" and "fourth" are intended to modify the ethylene feed, such that the third ethylene feed control valve refers to the control valve used for the third ethylene-containing feed stream 126).

[0124] In one embodiment, the fourth ethylene feed control valve 172 can be completely closed to shut 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, thereby effectively allowing the reaction mixture to pass through the fourth reaction zone 118. In another embodiment, no initiator feed is introduced into the fourth reaction zone 118. In yet another embodiment, the fourth ethylene-containing feed stream 128 can be introduced into the fourth reaction zone 118, and no initiator may be added to the fourth reaction zone 118.

[0125] A method for producing ethylene-based polymers in the presence of at least one free radical is also disclosed using the reactor system 100 described herein. The method may include polymerizing an ethylene-containing mixture in a tubular reactor 110 having at least four reaction zones in series and at least four ethylene-containing feed streams to produce a polymeric effluent 130 containing an ethylene-based polymer. The at least four reaction zones may include 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. The first ethylene-containing feed stream delivered to the first reaction zone may account for 20 mol% to 35 mol% of the total molar flow rate of the at least four ethylene feed streams introduced into the tubular reactor. The CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.2 to 2.0, more preferably 0.3 to 1.9, or most preferably 0.5 to 1.8; the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.12 to 1.5, more preferably 0.15 to 1.4, or most preferably 0.2 to 1.3; and the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be 0.0 to 0.7, more preferably greater than 0.0 to 0.7, or most preferably 0.05 to 0.6.

[0126] In the implementation scheme, the at least four ethylene-containing feed streams may further include a second ethylene-containing feed stream 124 introduced into a second reaction zone 114 downstream of the first reaction zone 112, a third ethylene-containing feed stream 126 introduced into a third reaction zone 116 downstream of the second reaction zone 114, and at least one fourth ethylene-containing feed stream 128 introduced into at least one fourth reaction zone 118 downstream of the third reaction zone 116.

[0127] In the implementation scheme, the amount of ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110 via the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may be 40 mol% to 70 mol% of the total ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110.

[0128] In the implementation scheme, the second ethylene-containing feed stream 124, the third ethylene-containing feed stream 126, and the fourth ethylene-containing feed stream 128 each contain ethylene, CTA, and optionally one or more comonomers; the CTA concentration in the second ethylene-containing feed stream 124 is greater than the CTA concentration in the first ethylene-containing feed stream 122; and the CTA concentration in the third ethylene-containing feed stream 126, the fourth ethylene-containing feed stream 128, or both is greater than the CTA concentration in the second ethylene-containing feed stream 124.

[0129] In an embodiment, reactor system 100 can be configured to produce ethylene-based polymers with a wide MWD, and the CTA activity ratio (Z2 / Z1) of the second reaction zone can be 0.5 to 2.0, such as 0.7 to 2.0, or 1.0 to 2.0. When configured to produce ethylene-based polymers with a wide MWD, the CTA activity ratio (Z3 / Z1) of the third reaction zone can be 0.5 to 1.5, such as 0.6 to 1.4, 0.7 to 1.3, or 0.8 to 1.2. When configured to produce ethylene-based polymers with a wide MWD, the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be 0.1 to 0.7, such as 0.2 to 0.6, or 0.3 to 0.6.

[0130] In an embodiment, reactor system 100 can be configured to produce ethylene-based polymers with a narrow MWD, and the CTA activity ratio (Z2 / Z1) of the second reaction zone can be from 0.2 to 0.5. When configured to produce ethylene-based polymers with a narrow MWD, the CTA activity ratio (Z3 / Z1) of the third reaction zone can 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 a wide MWD, the CTA activity ratio (Z4 / Z1) of the fourth reaction zone can be less than 0.1, such as less than or equal to 0.09, less than or equal to 0.08, 0.0 to 0.1, or greater than 0.0 to 0.1.

[0131] In an embodiment, the method disclosed herein may include adjusting the molar ratio of a third ethylene-based feed stream 126 to a fourth ethylene-based feed stream 128, wherein the molar ratio of the third ethylene-based feed stream 126 to the fourth ethylene-based feed stream 128 is 1 to 4. In an embodiment, the ratio of the third ethylene-based feed stream 126 and the fourth ethylene-based feed stream 128 introduced into the third reaction zone 116 and the fourth reaction zone 128, respectively, is controlled by a control system including at least one control valve.

[0132] In an embodiment, the method disclosed herein may include controlling the composition of each of the at least four ethylene-based feed streams using a control system comprising one or more control valves. In an embodiment, the first ethylene-containing feed stream 122 may comprise 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.

[0133] In embodiments, the method disclosed herein may further include separating the polymerization effluent 130 in a high-pressure separator 260 to produce a high-pressure ethylene recirculation stream 262 and a bottom stream 264, wherein the high-pressure ethylene recirculation stream 262 comprises ethylene, CTA, and optionally one or more comonomers. The method may further include separating the bottom stream 264 in a low-pressure separator 270 to produce a low-pressure ethylene recirculation stream 272 and a product stream 274, wherein the low-pressure ethylene recirculation stream 272 comprises ethylene, CTA, and optionally one or more comonomers. In embodiments, a second ethylene-containing feed stream 124 may contain at least a portion of the low-pressure ethylene recirculation stream 272, and a third ethylene-containing feed stream 126, a fourth ethylene-containing feed stream 128, or both may contain at least a portion of the high-pressure ethylene recirculation stream 262.

[0134] In the implementation scheme, the method disclosed herein may further include adjusting the molecular weight distribution of the ethylene-based polymer in the polymer effluent 130 by controlling the amount of high-pressure ethylene recirculation stream 262, low-pressure ethylene recirculation stream 272, or both entering 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 a combination thereof.

[0135] In the implementation scheme, the first ethylene-containing feed stream 122 and the second ethylene-containing feed stream 124 may each introduce 25 moles of total ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor 110.

[0136] In embodiments, the method disclosed herein may further include controlling the 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 128. In embodiments, the method disclosed herein may 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 40°C to 90°C, 40°C to 80°C, 40°C to 70°C, or 40°C to 55°C. In embodiments, the method may be configured to produce an ethylene-based polymer having a broad molecular weight distribution, and each of the plurality of reaction zones operates at a maximum temperature of 300°C to 330°C, such as 300°C to 325°C or 300°C to 320°C. In an implementation, the method can be configured to produce an ethylene-based polymer with a narrow MWD distribution, and the reaction zones can be maintained at a temperature such that the highest temperature of each reaction zone 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.

[0137] In embodiments, the method disclosed herein may include compressing a first ethylene-containing feed stream 122 in a first main compressor 210 upstream of a first reaction zone 112, wherein the first ethylene-containing feed stream 122 comprises fresh ethylene feed 202. The method may also include compressing a second ethylene-containing feed stream 124 in a second main compressor 220 upstream of a second reaction zone 114, wherein the second ethylene-containing feed stream 124 comprises at least a portion of a low-pressure ethylene-containing recirculated stream 272.

[0138] In the implementation scheme, the method disclosed herein may further include passing a first ethylene-containing feed stream 122 and a second ethylene-containing feed stream 124 to a first ultra-high pressure compressor 240, wherein the first ultra-high pressure compressor 240 is configured to split each of the ethylene-containing streams at an ultra-high pressure suction section. The method disclosed herein may further include passing a high-pressure ethylene recirculation stream 262 to a second ultra-high pressure compressor 250, wherein the second ultra-high pressure compressor 250 is configured to split the high-pressure ethylene recirculation stream 262 at an ultra-high pressure suction section. The method disclosed herein may further include splitting the stream from the second ultra-high pressure compressor into a third ethylene-containing feed stream 126 and a fourth ethylene-containing feed stream 128.

[0139] In embodiments, the method disclosed herein may further include introducing an initiator stream into each of the at least four reaction zones, wherein each initiator stream comprises at least one radical initiator and a solvent. In embodiments, the method disclosed herein may further include mixing the at least one radical initiator and solvent upstream of a high-pressure initiator injection pump prior to generating the initiator stream.

[0140] The reactor system 100 and method disclosed herein are used to produce ethylene-based polymers. This disclosure also relates to ethylene-based polymers produced by the methods disclosed herein. In embodiments, the ethylene-based polymer produced by the reactor system 100 and methods disclosed herein is a polyethylene homopolymer, and more specifically, LDPE. In embodiments, the ethylene-based polymer is low-density polyethylene (LDPE).

[0141] 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 comprises one comonomer. The comonomer includes, but is not limited to, α-olefins, acrylates, acetates, methacrylates, and anhydrides, each typically having no more than 20 carbon atoms. α-olefin comonomers, which may have a combination of monomers and CTA functionality, may have 3 to 10 carbon atoms, or alternatively, α-olefin comonomers may have 3 to 8 carbon atoms. Exemplary α-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 α-olefin comonomer is selected from propylene, 1-butene, and combinations thereof.

[0142] In the embodiments, the ethylene-based polymer may have a wide molecular weight distribution. In the embodiments, the relative molecular weight distribution of the ethylene-based polymer may be greater than or equal to 200%, such as 200% to 400%, or 300% to 400%, wherein the relative molecular weight distribution is defined as 100 multiplied by the Mw / Mn of the ethylene-based polymer divided by the Mw / Mn of the ethylene-based polymer prepared by introducing 100% ethylene, CTA, optional comonomers, and optional additives into the first reaction zone. Mw and Mn are determined by conventional GPC according to the test methods described herein. In the embodiments, the ethylene-based polymer may have a narrow MWD, such as having a relative MWD of about 125% to about 200%, such as about 150% to about 190%, wherein the relative MWD is as defined above.

[0143] In the implementation scheme, the ethylene-based polymer may have a content of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 The density. Ethylene-based polymers may have a melt index (I2) of 0.10 g / 10 min to 40.0 g / 10 min. In embodiments, the melt index of the ethylene-based polymer may be 0.10 g / 10 min to 20 g / 10 min, 0.15 g / 10 min to 20 g / 10 min, or 0.15 g / 10 min to 15 g / 10 min. In embodiments, the melt index of the ethylene-based polymer may be 0.2 g / 10 min to 20 g / 10 min, or 0.20 g / 10 min to 15 g / 10 min, or 0.2 g / 10 min to 10 g / 10 min.

[0144] In embodiments, the polymer composition may comprise the ethylene-based polymer disclosed herein and one or more additives. Additives may include, but are not limited to, stabilizers, plasticizers, antistatic agents, pigments, dyes, nucleating agents, fillers, slip agents, flame retardants, processing aids, smoke suppressants, viscosity control agents, anti-caking agents, or combinations thereof. The polymer composition may comprise less than 10% by weight of one or more additives based on the total weight of the polymer composition. In embodiments, the ethylene-based polymer disclosed herein may be treated with one or more stabilizers, such as antioxidants like IRGANOX 1010, IRGANOX 1076, and IRGAFOS 168. Typically, the ethylene-based polymer may be treated with one or more stabilizers prior to extrusion or other melt processing.

[0145] In embodiments, the polymer composition may comprise an ethylene-based polymer disclosed herein and at least one other polymer. Suitable polymers for blending with the ethylene-based 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-modified polypropylene, isotactic polypropylene, atactic polypropylene, and atactic propylene / ethylene copolymers), various types of other ethylene-based polymers, including high-pressure radical LDPE, non-uniformly branched LLDPE (typically produced via Ziegler-Natta catalysis), uniformly branched linear or substantially linear PE (typically produced via single-point catalysis, including metallocene catalysis) (including multi-reactor PE (“in-reactor” compositions of non-uniformly branched PE and uniformly branched PE, such as U.S. Patent 6,545,088 (Kolthamm)). Products disclosed in (e.g., Cardwell et al.); U.S. Patent 6,538,070 (Cardwell et al.); U.S. Patent 6,566,446 (Parikh et al.); U.S. Patent 5,844,045 (Kolthammer et al.); U.S. Patent 5,869,575 (Kolthammer et al.); and products disclosed in U.S. Patent 6,448,341 (Kolthammer et al.); ethylene-vinyl acetate (EVA), ethylene / vinyl alcohol copolymers, polystyrene, impact-modified polystyrene, ABS, styrene / butadiene block copolymers and their hydrogenated derivatives (SBS and SEBS), and thermoplastic polyurethanes. Other ethylene-based polymers include homogeneous polymers, such as olefin plastomers and elastomers (e.g., polymers available under trade names AFFINITY Plastomers and ENGAGE Elastomers (The Dow Chemical Company) and EXACT (ExxonMobil Chemical Co.). Propylene-based copolymers (such as polymers available under trade names like VERSIFY Plastomers & Elastomers (The Dow Chemical Company) and VISTAMAXX (ExxonMobil Chemical Co.)) can also be used as components in blends containing ethylene-based polymers prepared by the reactor system 100 and methods disclosed herein.

[0146] The ethylene-based polymers and polymer compositions containing these ethylene-based polymers disclosed herein can be used in a variety of conventional thermoplastic manufacturing processes to produce useful articles, including extrusion coatings onto a variety of substrates; single-layer and multi-layer films; molded articles, such as blow-molded, injection-molded, or rotationally molded articles; coatings; fibers; and woven or nonwoven fabrics.

[0147] The ethylene-based polymers produced using the reactor system 100 and methods disclosed herein can be used in a variety of membranes, including but not limited to transparent shrink films, finished shrink films, cast stretch films, silage films, stretch covers, sealants, and diaper backing sheets. Other suitable applications include, but are not limited to, wires and cables, gaskets and profiles, adhesives; footwear components and automotive interior components.

[0148] This disclosure also provides an article comprising at least one component formed from an ethylene-based polymer disclosed herein. In an embodiment, the article is an extruded coated resin. In an embodiment, the article is a film. In an embodiment, the article is an insulating material and / or protective layer around a metal wire. In an embodiment, the article is a foam. The article may comprise a combination of two or more embodiments as described herein.

[0149] Test methods Melt index According to ASTM D 1238, the melt index, or I2, is measured at 190°C and a load of 2.16 kg. The melt index (I2) is reported as grams eluted per 10 minutes. According to ASTM D 1238, the melt index (I2) is measured at 190°C and a load of 10 kg. 10 Report the melt index (I) in g / 10 minutes. 10 ).

[0150] Normalized molecular weight distribution ( MWD ) Molecular weight distribution (represented by the relationship between (dw / d log M) and log M) is an important parameter used in polymerization design, process development, improvement, and operation. The type of polymer (narrow or wide MWD) produced must be determined to provide the desired product properties. Normalized MWD data can be obtained using the PREDICI commercial software package (licensed by Dr. M. Wulkow). Computing in Technology, GmbH, Pater - Klbe - Straβe 7 , D-26180 Rastede, Germany), to construct the MWD from polymerization kinetics (Goto kinetics in this study) by solving the polymer population equilibrium equations. The inputs required to PREDICI are the Goto kinetics used, as well as monomer and / or comonomer, initiator and CTA flow rates, temperature and pressure profiles, and elapsed time, all of which can be obtained from process simulations. The 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, was calculated and then normalized using Equation 1 (EQU.1) with the MWD of the ethylene-based polymer in Comparative Example 1 (Comparative -100 / 0 / 0 / 0). Similarly, the MWD of each ethylene-based polymer in Comparative Examples 7 and 8, and Examples 9 and 10, was calculated and then normalized using EQU.1 with the MWD of the ethylene-based polymer in Comparative Example 6 (Comparative -100 / 0 / 0 / 0). Example The following examples will further illustrate embodiments of this disclosure and should not be construed as limiting the disclosed and / or claimed embodiments described herein.

[0151] The following illustrative examples are based on polymerization simulations. Goto et al. described the polymerization simulation model with the applied reaction scheme and kinetics (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 from ASPEN PLUS of Aspen Technology, Inc., Burlington, Mass., USA; and PREDICI of Dr. Wulkow, Computingin Technology GmbH (CiT), Rastede, Germany. The process and product responses predicted by these model frameworks are determined by reactor parameters, the applied reaction scheme, and kinetic parameters. The applied reaction scheme and kinetic parameters are described below.

[0152] As discussed above, the polymerization simulation was performed using the Goto LDPE simulation model. The kinetic data used by Goto et al. were derived from high-pressure, free-radical polyethylene polymerization experiments conducted at different temperatures, pressures, and polymer concentrations, 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). Goto et al. described the elementary reaction steps as follows: i) ethylene growth, ii) radical termination, iii) backbiting or SCB formation, iv) transfer to polymer or LCB formation, v) β-elimination of secondary radicals causing vinyl formation, and vi) β-elimination of tertiary radicals causing vinylidene formation.

[0153] The kinetic data for the main reactions are shown in Table 2, where ko refers to the pre-exponential factor or frequency factor; Ea is the activation energy, reflecting temperature dependence; and ΔV is the activation volume, reflecting pressure dependence. All kinetic constants are from Goto et al., except for the ko, Ea, and ΔV values ​​for bite-off, which have been optimized to better reflect the varying levels of methyl branching in high-pressure polyethylene under pressure and temperature conditions (e.g., as analyzed by C13 NMR). Further information regarding the methods for performing aggregation simulations can be found in the methods discussed in detail in the Embodiments section of U.S. Patent No. 10,494,456, the entire contents of which are incorporated herein by reference.

[0154] For the embodiments and comparative examples, the following methods are adopted: Figure 5 The process configuration and manipulation of various valves and make-up flows are used to obtain the reactor configuration and CTA activity ratio described in each embodiment and comparative example herein.

[0155] Comparative example 1 A single ethylene-containing feed stream enters the first reaction zone. For Comparative Example 1, Figure 5The reactor system, consisting only of reaction zones 112, 114, 116, and 118 (excluding reaction zone 120), was modeled with valves 270, 272, 282, and 286 in the closed position and valves 280, 282, and 288 in the open position, such that 100% of the ethylene and CTA were transferred to the front of the reactor (e.g., to reaction zone 112) and no side flow was introduced into any other reaction zone. An oxygen inhibitor was added to the feed to reaction zone 112. An initiator stream containing peroxide was added to each of the four reaction zones. The maximum reaction temperature in each reaction zone was increased to above 300°C to prepare an ethylene-based polymer with the widest possible MWD. ​​Table 3 provides the maximum reaction temperature, reactor pressure, and total ethylene conversion for each reaction zone used in the modeling of Comparative Example 1. Table 3 also provides the melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer from Comparative Example 1.

[0156] Comparative example 2 Two ethylene-containing feed streams - Width MWD In Comparative Example 2, for Figure 5 A reactor system with only four reaction zones (no fifth reaction zone) was modeled, and two ethylene-containing feed streams were used to prepare ethylene-based polymers with the widest possible MWD. ​​For Comparative Example 2, Figure 5 Valves 270 and 272 were closed, and valves 280, 282, 284, 286, and 288 were configured to introduce 50 mol% ethylene and CTA into the first reaction zone 112 and 50 mol% ethylene and CTA into the second reaction zone 114. No ethylene-containing side stream was introduced into the third reaction zone 116 and the fourth reaction zone 118. An oxygen inhibitor was added to the ethylene-containing feed streams entering the first reaction zone 112 and the second reaction zone 114. An initiator stream containing peroxide was added to each of the four reaction zones. Table 3 provides the highest reaction temperature, reactor pressure, Z2 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Comparative Example 2. Table 3 also provides the melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer from Comparative Example 2.

[0157] Comparative example 3 Three ethylene-containing feed streams - Width MWD In Comparative Example 3, for Figure 5 A reactor system with only four reaction zones (without a fifth reaction zone) was modeled, and three ethylene-containing feed streams were used to prepare ethylene-based polymers with the widest possible MWD. ​​For Comparative Example 3, Figure 5Valve 272 is closed, and valves 270, 280, 282, 284, 286, and 288 are configured to introduce 25 mol% ethylene and CTA into the first reaction zone 112, 25 mol% ethylene and CTA into the second reaction zone 114, and 50 mol% ethylene and CTA into the third reaction zone 116. No ethylene-containing side stream is introduced into the fourth reaction zones 116 and 118. An oxygen inhibitor is added to the ethylene-containing feed streams entering the first reaction zone 112, the second reaction zone 114, and the third reaction zone 116. An initiator stream containing peroxide is added to each of the four reaction zones. Table 3 provides the maximum reaction temperature, reactor pressure, Z2 / Z1 ratio, Z3 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Comparative Example 3. Supplemental ethylene, supplemental CTA, or both are introduced into one or more of the ethylene-containing feed streams to obtain the Z2 / Z1 ratio and Z3 / Z1 ratio shown in Table 3. Table 3 also provides the melt index, density, and relative molecular weight distribution of the ethylene-based polymer obtained in Comparative Example 3.

[0158] Example 4 and Examples 5 Five reaction zones and four ethylene-containing feed streams - Width MWD Ethylene-based polymerization things.

[0159] In Examples 4 and 5, Figure 5 The reactor system was modeled with all five reaction zones (i.e., first reaction zone 112, second reaction zone 114, third reaction zone 116, fourth reaction zone 116, and fifth reaction zone 118) to prepare ethylene-based polymers with a wide MWD. ​​For each of Examples 4 and 5, ethylene supplementation, CTA supplementation, and valves 270, 271, 280, 282, 284, 286, and 288 were configured to introduce 25 mol% of total ethylene and CTA into the first reaction zone 112, 25 mol% of total ethylene and CTA into the second reaction zone 114, 30 mol% of total ethylene and CTA into the third reaction zone 116, and 20 mol% of total ethylene and CTA into the fourth reaction zone 118. The valves, CTA supplementation, and ethylene supplementation were adjusted to obtain the Z2 / Z1, Z3 / Z1, and Z4 / Z1 ratios in Table 3. Table 3 provides the highest reaction temperature, reactor pressure, Z2 / Z1 ratio, Z3 / Z1 ratio, Z4 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Examples 4 and 5. Table 3 also provides the melt index, density, and relative molecular weight distribution of the ethylene-based polymers obtained in Examples 4 and 5.

[0160] Example 4 and Examples 5 Comparative example 1-3 Comparison Table 3 provides the reaction conditions and properties of the ethylene-based polymers generated by modeling in Comparative Examples 1-3 and Examples 4 and 5. As shown in Table 3, compared to Comparative Examples 1-3, the modeling of Examples 4 and 5, which have five reaction zones and ethylene-based feeds entering the first four reaction zones, increased the overall ethylene conversion and decreased the density. Furthermore, the modeling of Examples 4 and 5 indicates that these ethylene-based polymers have a wider relative MWD compared to the ethylene-based polymers generated by Comparative Examples 1-3. Comparative example 6 Comparative Example 6 was identical to Comparative Example 1, except that the maximum reactor temperature was reduced to 290°C to narrow the molecular weight distribution of the resulting ethylene-based polymer. Table 4 provides the maximum reaction temperature, reactor pressure, and total ethylene conversion for each reaction zone used in the modeling. Table 4 also provides the melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer.

[0161] Comparative example 7 Two ethylene-containing feed streams - narrow MWD Comparative Example 7 is similar to Comparative Example 2, except that the Z2 / Z1 ratio is 0.27, which means that less CTA is introduced into the second reaction zone compared to Comparative Example 2, and the maximum temperature in each reaction zone is maintained at 290°C. A smaller Z2 / Z2 ratio and a lower maximum temperature were chosen to produce an ethylene-based polymer with a narrower MWD. ​​Table 4 provides the maximum reaction temperature, reactor pressure, Z2 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Comparative Example 7. Table 4 also provides the melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 7.

[0162] Comparative example 8 Three ethylene-containing feed streams - narrow MWD Comparative Example 8 is similar to Comparative Example 3, except that the Z2 / Z1 ratio is 0.35 and the Z3 / Z1 ratio is 0.23. This means that less CTA is introduced into the second reaction zone 114 and the third reaction zone 116 compared to Comparative Example 2, and the maximum temperature in each reaction zone is maintained at 290°C. A smaller Z2 / Z2 ratio and a lower maximum temperature are chosen to produce an ethylene-based polymer with a narrower MWD. ​​Table 3 provides the maximum reaction temperature, reactor pressure, Z2 / Z1 ratio, Z3 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Comparative Example 8. Supplemental ethylene, supplemental CTA, or both are introduced into one or more of the ethylene-containing feed streams to obtain the Z2 / Z1 ratio and Z3 / Z1 ratio in Table 4. Table 4 also provides the melt index, density, and relative molecular weight distribution of the resulting ethylene-based polymer of Comparative Example 8.

[0163] Example 9 and Examples 10 Five reaction zones and four ethylene-containing feed streams - narrow MWD Ethylene-based polymerization thing In Examples 9 and 10, Figure 5 The reactor system was modeled as having all five reaction zones (i.e., first reaction zone 112, second reaction zone 114, third reaction zone 116, fourth reaction zone 116, and fifth reaction zone 118), but configured to prepare ethylene-based polymers with a narrow MWD. ​​For each of Examples 9 and 10, the supplementation of ethylene, supplementation of CTA, and valves 270, 271, 280, 282, 284, 286, and 288 were configured to introduce 25 mol% of total ethylene and CTA into the first reaction zone 112, 25 mol% of total ethylene and CTA into the second reaction zone 114, 40 mol% of total ethylene and CTA into the third reaction zone 116, and 10 mol% of total ethylene and CTA into the fourth reaction zone 118. For Example 10, no initiator was added to the fifth reaction zone 120, thus effectively skipping the fifth reaction zone 120. The control valves, supplemental CTA, and supplemental ethylene were used to obtain the Z2 / Z1, Z3 / Z1, and Z4 / Z1 ratios shown in Table 4. Table 4 provides the maximum reaction temperature, reactor pressure, Z2 / Z1 ratio, Z3 / Z1 ratio, Z4 / Z1 ratio, and total ethylene conversion for each reaction zone used in the modeling of Examples 9 and 10. Table 4 also provides the melt index, density, and relative molecular weight distribution of the ethylene-based polymers obtained in Examples 9 and 10.

[0164] Example 9 and Examples 10 Comparative example 6-8 Comparison Table 4 provides the reaction conditions and properties of the ethylene-based polymers derived from the modeling performed in Comparative Examples 6-8 and Examples 9 and 10. As shown in Table 4, compared to Comparative Examples 1-3, the modeling in Examples 9 and 10, which have five reaction zones and ethylene-based feed entering the first four reaction zones, increased the overall ethylene conversion and slightly reduced the density. Furthermore, the modeling in Examples 9 and 10 demonstrates that… Figure 5 The reactor system can be configured to produce ethylene-based polymers with narrow MWD by reducing the Z2 / Z1, Z3 / Z1, and Z4 / Z1 ratios and lowering the maximum reaction temperature in each reaction zone. Therefore, the reactor system disclosed herein can provide greater flexibility to produce both ethylene-based polymers with wide MWD and ethylene-based polymers with narrow MWD. It should be noted that one or more of the appended claims utilize the term "wherein" as a transitional expression. For the purposes of defining the invention, it should be noted that this term is introduced in the claims as an open transitional phrase used to introduce a series of features of the structure and should be interpreted in the same manner as the more commonly used open leading term "comprising".

[0165] It will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its spirit and scope. Because modifications, combinations, sub-combinations, and variations of the disclosed embodiments can be made by those skilled in the art that incorporate the spirit and essence of the invention, the invention should be construed as including everything within the scope of the appended claims and their equivalents.

Claims

1. A method for producing an ethylene-based polymer in the presence of at least one free radical, the method comprising polymerizing a mixture containing ethylene in a tubular reactor having at least four tandem reaction zones and at least four ethylene-containing feed streams to produce a polymeric effluent containing the ethylene-based polymer, wherein: Each of the at least four ethylene-containing feed streams comprises ethylene, one or more chain transfer agents (CTAs), and optionally one or more comonomers; The at least four reaction zones include 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. The first ethylene-containing feed stream delivered to the first reaction zone accounts for 20 mol% to 35 mol% of the total molar flow rate of the at least four ethylene feed streams introduced into the tubular reactor; and The CTA activity ratio (Z2 / Z1) of the second reaction zone is 0.2 to 2.0, more preferably 0.3 to 1.9, or most preferably 0.5 to 1.8, wherein the CTA activity ratio of the second reaction zone is equal to the CTA activity (Z2) in the second reaction zone divided by the CTA activity (Z1) in the first reaction zone. The CTA activity ratio (Z3 / Z1) of the third reaction zone is 0.12 to 1.5, more preferably 0.15 to 1.4, or most preferably 0.2 to 1.3, wherein the CTA activity ratio of the third reaction zone is equal to the CTA activity (Z3) in the third reaction zone divided by the CTA activity (Z1) in the first reaction zone; and The CTA activity ratio (Z4 / Z1) of the fourth reaction zone is 0.0 to 0.7, more preferably greater than 0.0 to 0.7, or most preferably 0.05 to 0.6, wherein the CTA activity ratio of the fourth reaction zone is equal to the CTA activity (Z4) in the fourth reaction zone divided by the CTA activity (Z1) in the first reaction zone.

2. The method according to claim 1, wherein the at least four ethylene-containing feed streams further include a second ethylene-containing feed stream introduced into the second reaction zone, a third ethylene-containing feed stream introduced into the third reaction zone, and at least one fourth ethylene-containing feed stream introduced into the at least one fourth reaction zone.

3. The method of claim 2, wherein the concentration of CTA in the first ethylene-containing feed stream is different from the concentration of CTA in each of the other ethylene-containing feed streams among the at least four ethylene-containing feed streams.

4. The method according to any one of claims 2 or 3, wherein the amount of ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor via the first ethylene-containing feed stream and the second ethylene-containing feed stream is 40 mol% to 70 mol% of the total ethylene and optionally one or more comonomers and optionally one or more CTAs introduced into the tubular reactor.

5. The method according to any one of claims 2 to 4, wherein: The second ethylene-containing feed stream, the third ethylene-containing feed stream, and the fourth ethylene-containing feed stream each contain ethylene, CTA, and optionally one or more comonomers; The concentration of CTA in the second ethylene-containing feed stream is greater than the concentration of CTA in the first ethylene-containing feed stream; and The concentration of CTA in the third ethylene-containing feed stream, the fourth ethylene-containing feed stream, or both is greater than the concentration of CTA in the second ethylene-containing feed stream.

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

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

8. The method according to any one of claims 2 to 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 method according to any one of claims 2 to 8, further comprising: The polymer effluent is separated in a high-pressure separator to produce a high-pressure ethylene recirculation stream and a bottom stream, wherein the high-pressure ethylene recirculation stream comprises ethylene, CTA, and optionally one or more comonomers; The bottom stream is separated in a low-pressure separator to produce a low-pressure ethylene recirculation stream and a product stream, wherein the low-pressure ethylene recirculation stream comprises ethylene, CTA, and optionally one or more comonomers.

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

11. The method according to any one of claims 9 or 10, the method comprising adjusting the molecular weight distribution of the ethylene-based polymer in the polymer effluent by controlling the amount of the high-pressure ethylene recirculation stream, the low-pressure ethylene recirculation stream, or both entering 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 a combination thereof.

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

13. The method according to any one of claims 2 to 12, the method further comprising controlling the 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 method according to any one of claims 2 to 13, the method comprising cooling the second ethylene-containing feed stream, the third ethylene-containing feed stream, the fourth ethylene-containing feed stream, or a combination thereof to a temperature below or equal to 90°C, preferably 40°C to 90°C, more preferably 40°C to 80°C, even more preferably 40°C to 70°C, or most preferably 40°C to 55°C.

15. The method according to any one of claims 2 to 14, further comprising: The first ethylene-containing feed stream is compressed in a first main compressor upstream of the first reaction zone, wherein the first ethylene-containing feed stream includes a fresh ethylene feed stream; The second ethylene-containing feed stream is compressed in a second main compressor upstream of the second reaction zone, wherein the second ethylene-containing feed stream includes a low-pressure ethylene-containing recirculated stream.

16. The method according to any one of claims 2 to 15, further comprising: The first ethylene-containing feed stream and the second ethylene-containing feed stream are passed to a first ultra-high pressure compressor, wherein the first ultra-high pressure compressor is configured to split each of the first ethylene-containing feed stream and the second ethylene-containing feed stream at the ultra-high pressure suction section of the first ultra-high pressure compressor; The high-pressure ethylene recirculation stream is passed to a second ultra-high pressure compressor, which is operable to split the high-pressure ethylene recirculation stream at the ultra-high pressure suction section of the second ultra-high pressure compressor. and The outlet flow from the second ultra-high pressure compressor is divided into the third ethylene-containing feed flow and the fourth ethylene-containing feed flow.

17. The method according to any one of claims 1 to 16, wherein: The method is configured to prepare an ethylene-based polymer with a wide molecular weight distribution, wherein the CTA activity ratio (Z2 / Z1) of the second reaction zone is 1.0 to 2.0, the CTA activity ratio (Z3 / Z1) of the third reaction zone is 0.5 to 1.5, and the CTA activity ratio (Z4 / Z1) of the fourth reaction zone is 0.1 to 0.7; or The method is configured to prepare an ethylene-based polymer with a narrow molecular weight distribution, wherein the CTA activity ratio (Z2 / Z1) of the second reaction zone is 0.2 to 0.5, the CTA activity ratio (Z3 / Z1) of the third reaction zone is 0.12 to less than 0.5, and the CTA activity ratio (Z4 / Z1) of the fourth reaction zone is less than 0.

1.

18. The method according to any one of claims 1 to 17, wherein the method is configured to produce the ethylene-based polymer having a wide molecular weight distribution, and each of the plurality of reaction zones operates at a maximum temperature of 300°C to 330°C, more preferably 300°C to 325°C, or most preferably 300°C to 320°C.

19. A method for producing an ethylene-based polymer in the presence of at least one free radical, the method comprising: A mixture comprising ethylene is polymerized in a tubular reactor having at least four tandem reaction zones and at least four ethylene-containing feed streams to produce a polymeric effluent comprising the ethylene-based polymer, wherein each of the at least four ethylene-containing feed streams comprises 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 The molecular weight distribution of the ethylene-based polymer can be changed between a narrow molecular weight distribution and a wide molecular weight distribution, wherein changing the molecular weight distribution of the ethylene-based polymer may include: modifying the CTA activity in one or more of the at least four reaction zones, changing the highest reaction temperature in one or more of the at least four reaction zones, or a combination thereof.

20. The method of claim 19, wherein: The method further includes separating the polymer effluent into at least a high-pressure ethylene recycle, a low-pressure ethylene recycle, and a product stream, and transferring 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 polymer includes modifying the CTA activity in one or more of the at least four reaction zones, including: The proportion of the high-pressure ethylene recycle, the low-pressure ethylene recycle, the fresh ethylene feed, or a combination thereof, to one or more of the at least four ethylene-containing feed streams is changed. Change the amount of supplemental CTA introduced into one or more of the at least four ethylene-containing feed streams; Or a combination thereof.

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

22. The method according to any one of claims 19 or 20, the method comprising configuring the tubular reactor in a narrow molecular weight configuration to produce the ethylene-based polymer having a narrow molecular weight distribution, wherein in the narrow molecular weight configuration: The CTA activity ratio (Z2 / Z1) of the second reaction zone is 0.2 to 0.5, more preferably 0.2 to 0.4, wherein the CTA activity ratio of the second reaction zone is equal to the CTA activity (Z2) in the second reaction zone divided by the CTA activity (Z1) in the first reaction zone. The CTA activity ratio (Z3 / Z1) of the third reaction zone is 0.12 to less than 0.5, or more preferably 0.12 to 0.4, wherein the CTA activity ratio of the third reaction zone is equal to the CTA activity (Z3) in the third reaction zone divided by the CTA activity (Z1) in the first reaction zone; and The CTA activity ratio (Z4 / Z1) of 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 (Z4) in the fourth reaction zone divided by the CTA activity (Z1) in the first reaction zone.

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