Process for producing polyethylene

Abstract

According to some embodiments, a method for forming an ethylene-based polymer can comprise: introducing a catalyst into a loop reactor through at least two catalyst injection points, wherein: the loop comprises a first half and a second half, and a first catalyst injection point is in the first half of the loop and a second catalyst injection point is in the second half of the loop; and polymerizing the ethylene and a comonomer with the catalyst under control of one or more polymerization conditions such that: a ratio of an amount of polymerization in the first half to an amount of polymerization in the second half is 0.7 to 1.3; a ratio of heat of polymerization in the first half to heat of polymerization in the second half is 0.7 to 1.3; or both, thereby forming an ethylene-based polymer.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 575,922, filed April 8, 2024, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The embodiments of this disclosure generally relate to the production of ethylene-based polymers, and more specifically, to the production of ethylene-based polymers in a loop reactor. Background Technology

[0004] When polyethylene copolymers are produced in a loop reactor, the relative concentrations of monomers and comonomers vary around the loop. This results in variations in the comonomer content of the polymer produced in different sections of the loop. This variation is known as short-chain branching. Higher variations in the amount of comonomer incorporated can degrade polymer properties (e.g., leading to sticky pellets, sticky films, lower dart impact resistance, and reduced tear strength). Therefore, it is desirable to reduce the variation in the amount of monomers and comonomers incorporated into the polymer. Summary of the Invention

[0005] It was subsequently discovered that catalyst deactivation plays a much more significant role in the broader short-chain branching profile than previously thought. Previously, it was believed that the catalyst half-life in a loop reactor was at least equal to the catalyst recycling time; therefore, a single catalyst injector was used. Surprisingly, it was found that the catalyst half-life could be 50% or less of the catalyst recycling time. It is believed that this short half-life, relative to the recycling time, leads to excessive catalyst activity in the first half of the loop and insufficient catalyst activity in the second half, resulting in an excessively broad short-chain branching profile. Therefore, there is a need for a method for producing ethylene-based polymers that mitigates the problems of excessive short-chain branching and a relatively short catalyst half-life.

[0006] Embodiments of this disclosure meet this need by providing a loop reactor comprising a first catalyst injection point in a first half of the loop and a second catalyst injection point in a second half of the loop. The embodiments then control one or more polymerization conditions (e.g., the ratio of catalyst introduced at the second catalyst injection point to catalyst introduced at the first catalyst injection point) such that the ratio of the amount of polymerization in the first half of the loop to the amount of polymerization in the second half is controlled, such as 0.7 to 1.3; the ratio of the heat of polymerization in the first half to the heat of polymerization in the second half is 0.7 to 1.3; or both. It is believed that controlling the polymerization conditions brings polymerization equilibrium around the reactor, resulting in a reduced concentration gradient of monomers and comonomers and a narrower distribution of short-chain branching.

[0007] In some implementations, the controlled polymerization conditions are the ratio of catalyst injected at the second catalyst injection point to catalyst injected at the first catalyst injection point. It is believed that controlling the polymerization by controlling the ratio of catalyst introduced at the two injection points in this manner is a particularly effective and cost-efficient method for controlling the polymerization rate.

[0008] Another embodiment of this disclosure addresses this need by providing a loop reactor in which the number of catalyst injection points equals the number of feed injection points. While loop reactors with two feed injection points have been operating for decades and the need to narrow the short-chain branching distribution is known, it has not been understood that increasing the number of catalyst injection points to equal the number of feed injection points could be a feasible way to narrow the short-chain branching distribution. Previous attempts to narrow the short-chain branching distribution have focused on reducing production rates, which has adverse consequences for process economics.

[0009] According to some embodiments, a method for forming an ethylene-based polymer may include: introducing a catalyst into a loop reactor through at least two catalyst injection points, wherein: the loop includes a first half and a second half, and the first catalyst injection point is in the first half of the loop and the second catalyst injection point is in the second half of the loop; and polymerizing the ethylene and copolymer under controlled polymerization conditions such that: the ratio of the amount of polymerization in the first half to the amount of polymerization in the second half is 0.7 to 1.3; the ratio of the heat of polymerization in the first half to the heat of polymerization in the second half is 0.7 to 1.3; or both, thereby forming an ethylene-based polymer.

[0010] These and other embodiments are described in more detail in the detailed description. It should be understood that both the foregoing general description and the following detailed description present embodiments of the technology disclosed in this invention and are intended to provide an overview or framework for understanding the nature and characteristics of the technology as claimed. Attached Figure Description

[0011] The following detailed description of specific embodiments of this disclosure is best understood in conjunction with the following drawings, in which similar reference numerals indicate similar structures and in the drawings:

[0012] Figure 1 The operation of a loop reactor according to one or more embodiments described herein is schematically depicted;

[0013] Figure 2 It is used to determine the HT-TGIC spectrum of short-chain branching;

[0014] Figure 3 These are the HT-TGIC spectra of Example 1 and Comparative Example 1;

[0015] Figure 4 These are the HT-TGIC spectra of Example 2 and Comparative Example 2; and

[0016] Figure 5 These are the HT-TGIC spectra of Example 3 and Comparative Example 3.

[0017] 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

[0018] definition

[0019] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Therefore, the general term polymer encompasses the term "homopolymer," which is typically used to refer to a polymer prepared from only one type of monomer; and "copolymer," which refers to a polymer prepared from two or more different types of monomers.

[0020] "Polyethylene" or "ethylene-based polymer" should mean a polymer comprising more than 50% by weight of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more monomer types). Common forms of polyethylene known in the art include low-density polyethylene (LDPE); linear low-density polyethylene (LLDPE); ultra-low-density polyethylene (ULDPE); very low-density polyethylene (VLDPE); single-point catalytic linear low-density polyethylene, including both linear and substantially linear low-density resins (m-LLDPE); medium-density polyethylene (MDPE); and high-density polyethylene (HDPE).

[0021] The term "LDPE" can also be referred to as "high-pressure ethylene polymer" or "highly branched polyethylene," and is defined as meaning that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at pressures above 14,500 psi (100 MPa) using a free radical initiator, such as a peroxide (see, for example, U.S. Patent No. 4,599,392, which is incorporated herein by reference in its entirety)). LDPE resin typically has a viscosity of 0.916 g / cm³. 3 Up to 0.930 g / cm 3 The density within the range.

[0022] The term "LLDPE" includes: resins produced using Ziegler-Natta catalyst systems and resins produced using single-site catalysts, including but not limited to bismetallocene catalysts (sometimes referred to as "m-LLDPE"), phosphine imides, and geometry-restricted catalysts; and resins produced using post-metallocene molecular catalysts, including but not limited to bis(biphenylphenoxy) catalysts (also known as polyaryloxy ether catalysts). LLDPE includes linear, substantially linear, or heterogeneous ethylene-based copolymers. LLDPE contains fewer long-chain branchings than LDPE and comprises substantially linear ethylene polymers, further defined in U.S. Patent Nos. 5,272,236, 5,278,272, 5,582,923, and 5,733,155, each of which is incorporated herein by reference in its entirety; homogeneous branched linear ethylene polymer compositions, such as those described in U.S. Patent No. 3,645,992, which is incorporated herein by reference in its entirety; heterogeneous branched ethylene polymers, such as those prepared according to the method disclosed in U.S. Patent No. 4,076,698, which is incorporated herein by reference in its entirety; and blends thereof (such as those disclosed in U.S. Patent Nos. 3,914,342 and 5,854,045), which are incorporated herein by reference in their entirety. LLDPE resins can be prepared via gas-phase, solution-phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0023] Loop reactor

[0024] Now for reference Figure 1 In some embodiments, the loop reactor 100 may include a continuous pipe extending within a loop 102. Ethylene and the copolymer may be polymerized within the continuous pipe loop 102 via a solution-phase polymerization process in the presence of a catalyst. The loop 102 may include a first half 104 and a second half 110.

[0025] exist Figure 1 In some embodiments depicted, the first half 104 is the space between the outlet 106b of the second heat exchanger 106 and the outlet 108b of the first heat exchanger 108; and the second half 110 is the space between the outlet 108b of the first heat exchanger 108 and the outlet 106b of the second heat exchanger 106.

[0026] The catalyst can be introduced into the loop reactor 100 via a first catalyst injection point 112. Ethylene and comonomer can be introduced into the loop reactor 100 via a first feed injection point 114. In some embodiments, ethylene and comonomer can be introduced through a single injection point. In another embodiment, ethylene and comonomer can be introduced through separate injection points. In either case, ethylene and comonomer can be introduced into the first half 104 at the first feed injection point 114. It should be understood that each of ethylene, comonomer, and catalyst can be introduced into the first half 104 through more than one injection point (e.g., there may be 1, 2, 3, or 4 ethylene injection points in the first half 104; there may be 1, 2, 3, or 4 comonomer injection points in the first half 104; and / or there may be 1, 2, 3, or 4 catalyst injection points in the first half 104). Furthermore, the locations of the first feed injection point 114 and the first catalyst injection point 112 within the first half 104 are not particularly restricted, so that the first feed injection point 114 and the first catalyst injection point 112 do not necessarily need to be located near the heat exchanger. In some embodiments not depicted in the figures, ethylene, comonomer, and catalyst can be introduced into the first half 104 using a single combined injector. In such embodiments, the first feed injection point 114 can also be the first catalyst injection point 112.

[0027] The catalyst, ethylene, and comonomer can be polymerized within loop 102 to form an ethylene-based polymer and release heat. Still within loop 102, the catalyst, ethylene, comonomer, and ethylene can be conveyed to a first heat exchanger 108. Within the first heat exchanger 108, heat can be transferred from loop 102 to the first heat exchanger cold feed 116, thereby forming the first heat exchanger hot effluent 118. The catalyst, ethylene, and comonomer can then be conveyed to a second half 110, which begins at the outlet 108b of the first heat exchanger 108.

[0028] In the second half 110, additional catalyst may be introduced into the loop 102 via a second catalyst injection point 120. Additional ethylene and comonomer may be introduced into the loop 102 via a second feed injection point 122. In some embodiments, ethylene and comonomer may be introduced through a single injection point. In another embodiment, ethylene and comonomer may be introduced through separate injection points. In either case, ethylene and comonomer may be introduced into the second half 110 at the second feed injection point 122. It should be understood that each of the ethylene, comonomer, and catalyst may be introduced into the second half 110 through more than one injection point (e.g., there may be 1, 2, 3, or 4 ethylene injection points in the second half 110; there may be 1, 2, 3, or 4 comonomer injection points in the second half 110; and / or there may be 1, 2, 3, or 4 catalyst injection points in the second half 110). Furthermore, the locations of the second feed injection point 122 and the second catalyst injection point 120 within the second half 110 are not particularly restricted, so that the second feed injection point 122 and the second catalyst injection point 120 need not be located near the heat exchanger. In some embodiments not depicted in the figures, ethylene, comonomer, and catalyst can be introduced into the second half 110 using a single combined injector. In such embodiments, the second feed injection point 122 can also be the second catalyst injection point 120.

[0029] In implementation schemes, the number of feed injection points can be equal to the number of catalyst injection points. For example, the loop reactor 100 may include two feed injection points and two catalyst injection points, three feed injection points and three catalyst injection points, four feed injection points and four catalyst injection points, or even five feed injection points and five catalyst injection points. In implementation schemes, the number of ethylene injection points can be equal to the number of catalyst injection points. For example, the loop reactor 100 may include two ethylene injection points and two catalyst injection points, three ethylene injection points and three catalyst injection points, four ethylene injection points and four catalyst injection points, or even ethylene feed injection points and five catalyst injection points.

[0030] The produced ethylene-based polymer can be removed from the loop reactor 100 via reactor outlet 124.

[0031] Methods for producing ethylene-based polymers

[0032] Embodiments of this disclosure relate to methods for forming ethylene-based polymers. Still refer to Figure 1The method may include introducing a catalyst into a loop reactor 100 through at least two catalyst injection points 112, 120. The loop reactor 100 may include a first half 104 and a second half 110. The first catalyst injection point 112 may be located in the first half 104, and the second catalyst injection point 120 may be located in the second half 110.

[0033] The method may further include introducing ethylene and comonomer into the loop reactor 100 through at least two feed injection points 114, 122. The first feed injection point 114 may be located in the first half 104 of the loop 102, and the second feed injection point 122 may be located in the second half 110 of the loop 102.

[0034] Comonomers may include olefins, such as C3-C 14 Alkenes, such as C3-C 14 α-olefins. Contemplated comonomers include, by way of example and not limitation, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetracene, and 1-tetradecene.

[0035] Catalysts may include conventional solution polyethylene polymerization catalysts. By way of example, and not limitation, catalysts may include Ziegler-Natta catalysts, metallocene catalysts, and post-metallocene catalysts.

[0036] The method may include polymerizing ethylene and comonomers to form an ethylene-based polymer. In an embodiment, the method may include polymerizing ethylene and comonomers under controlled polymerization conditions (e.g., the ratio of catalyst injected at the second catalyst injection point 120 to the catalyst injected at the first catalyst injection point 112), such that the ratio of the amount of polymerization in the first half 104 to the amount of polymerization in the second half 110 is 0.7 to 1.3, such as 0.8 to 1.2, 0.9 to 1.1, 0.95 to 1.05, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.1, 1.1 to 1.2, 1.2 to 1.3, or any combination of two or more of these ranges. Without being bound by theory, it is believed that controlling the amount of catalyst injected into each half of the loop reactor 100, such as 0.7 to 1.3, results in a relatively uniform polymerization amount in the first half 104 and the second half 110, leading to a narrower distribution of short-chain branching in the resulting ethylene-based polymer and improved material properties.

[0037] In an embodiment, the method may include controlling one or more polymerization conditions (e.g., the ratio of catalyst injected at the second catalyst injection point 120 to the catalyst injected at the first catalyst injection point 112) such that the ratio of the heat of polymerization in the first half 104 to the heat of polymerization in the second half 110 is 0.7 to 1.3, such as 0.8 to 1.2, 0.9 to 1.1, 0.95 to 1.05, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.1, 1.1 to 1.2, 1.2 to 1.3, or any combination of two or more of these ranges. Without being theoretically limited, it is believed that controlling the amount of catalyst in each half of the loop reactor 100 such that the heat of polymerization in the first half 104 and the second half 110 is relatively uniform, such as 0.7 to 1.3, results in a narrower distribution of short-chain branching and improved material properties in the resulting ethylene-based polymer.

[0038] The ratio of the amount of polymerization and / or heat of polymerization in the first half 104 to the amount of polymerization and / or heat of polymerization in the second half 110 can be controlled by controlling the amount of catalyst fed into each of the first half 104 and the second half 110. In an embodiment, the ratio of catalyst injected at the second catalyst injection point 120 to catalyst injected at the first catalyst injection point 112 is 0.7 to 1.3, such as 0.8 to 1.2, 0.9 to 1.1, 0.95 to 1.05, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.1, 1.1 to 1.2, 1.2 to 1.3, or any combination of two or more of these ranges.

[0039] In one embodiment, the method may include measuring the heat of polymerization in the first half 104 and the second half 110. The method may then include controlling the amount of catalyst to the first catalyst injection point 112 and the second catalyst injection point 120 based on the ratio of the heat generated in the first half 104 to the heat generated in the second half 110. In one embodiment, if the ratio of the heat of polymerization in the first half 104 to the heat of polymerization in the second half 110 is greater than 1.2, the method may include increasing the proportion of catalyst to the second catalyst injection point 120. In one embodiment, if the ratio of the heat of polymerization in the first half 104 to the heat of polymerization in the second half 110 is less than 0.8, the method may include decreasing the proportion of catalyst to the second catalyst injection point 120.

[0040] It has been found that a wider distribution of comonomers is partly related to catalyst deactivation, as quantified by measuring the catalyst half-life. Catalyst half-life refers to the time required for 50% of the catalyst to deactivate in the reactor. Without theoretical constraints, when only one catalyst injector is used in the loop reactor 100, more material is produced in the first half 104 (closest to the catalyst injection) and less in the second half 110 due to catalyst deactivation. This is believed to lead to over-conversion of ethylene in the first half 104, where the catalyst is most active. When ethylene is over-converted, a polymer with a high comonomer content is produced. This high comonomer content is the cause of sticky pellets and sticky films. In embodiments, the catalyst half-life in the loop reactor 100 is less than 80% of the catalyst recycling time in the loop reactor 100, such as less than 70%, less than 60%, or less than 50%. Generally, the importance of multiple injection points increases when the catalyst half-life is shorter relative to the recycling time.

[0041] In the embodiments, the polymerization of ethylene and comonomers can occur at temperatures ranging from 180°C to 210°C, such as 180°C to 185°C, 185°C to 190°C, 190°C to 195°C, 195°C to 200°C, 200°C to 205°C, 205°C to 210°C, or any combination of two or more of these ranges. Generally, polymerization at excessively low temperatures (such as below 180°C) is believed to result in lower production rates and an undesirable increase in polymer solution viscosity. Generally, polymerization at excessively high temperatures (such as above 210°C) is believed to result in reduced catalyst activity and increased costs. In the embodiments, the polymerization of ethylene and comonomers can occur in the presence of a solvent. Contemplated solvents include linear or alkane solvents.

[0042] like Figure 1 As shown, the loop reactor 100 may include a first heat exchanger 108 and a second heat exchanger 106. A first catalyst injection point 112 and a first feed injection point 114 may be located upstream of the first heat exchanger 108 and downstream of the second heat exchanger 106. A second catalyst injection point 120 and a second feed injection point 122 may be located upstream of the second heat exchanger 106 and downstream of the first heat exchanger 108.

[0043] In an implementation scheme, the method may include controlling the ratio of catalyst injected at the first catalyst injection point 112 to catalyst injected at the second catalyst injection point 120, such that the ratio of heat extracted at the second heat exchanger to heat extracted at the first heat exchanger can be 0.7 to 1.3, such as 0.8 to 1.2, 0.9 to 1.1, 0.95 to 1.05, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.1, 1.1 to 1.2, 1.2 to 1.3, or any combination of two or more of these ranges. Generally, controlling the ratio of catalyst injected at the first catalyst injection point 112 to catalyst injected at the second catalyst injection point 120 based on the ratio of heat extracted at the two heat exchangers allows for easy and cost-effective monitoring of the reaction without the need for additional monitoring equipment or simulation.

[0044] The ratio of the catalyst injected at the second catalyst injection point 120 to the catalyst injected at the first catalyst injection point 112 can be a mass flow rate ratio or a volume flow rate ratio. The catalyst injected at the second catalyst injection point 120 can be the same as the catalyst injected at the first catalyst injection point 112.

[0045] Ethylene-based polymers

[0046] In the embodiments, less than 8% by weight of the polymer has a high-temperature thermal gradient interaction chromatography (also known as "HT-TGIC" or "TGIC") elution temperature of less than 80°C. For example, less than 7% by weight, less than 6.5% by weight, less than 6.0% by weight, less than 5.5% by weight, less than 5.3% by weight, less than 5.0% by weight, less than 4.8% by weight, less than 4.6% by weight, or even less than 4.3% by weight of the polymer can have a TGIC elution temperature of less than 80°C.

[0047] In the embodiments, the ethylene-based polymer has a density of 0.85 g / cc to 0.94 g / cc, such as 0.85 g / cc to 0.87 g / cc, 0.87 g / cc to 0.89 g / cc, 0.89 g / cc to 0.91 g / cc, 0.91 g / cc to 0.93 g / cc, 0.93 g / cc to 0.94 g / cc, or any combination of two or more of these ranges.

[0048] In the embodiments, the ethylene-based polymer has a melt index (I2) of 0.2 dg / min to 2000 dg / min, such as 0.2 dg / min to 0.5 dg / min, 0.5 dg / min to 5 dg / min, 5 dg / min to 20 dg / min, 20 dg / min to 50 dg / min, 50 dg / min to 200 dg / min, 200 dg / min to 500 dg / min, 500 dg / min to 1000 dg / min, 1000 dg / min to 2000 dg / min, or any combination of two or more of these ranges.

[0049] Test methods

[0050] TGIC

[0051] The high-temperature thermal gradient interaction chromatography (HT-TGIC) is determined according to the method disclosed in U.S. Patent No. 9,902,791,B2, the entire contents of which are incorporated herein by reference.

[0052] SCBD

[0053] The TGIC chromatogram is related to the comonomer content and its distribution. According to the Stockmeyer equation, the distribution broadens with increasing comonomer content. It can also be related to the number of catalyst active sites (Soares et al., Polyolefin reaction engineering Wiley-VCH, Polyolefin Microstructural modeling, Chapter 6) or process conditions. (For general information, see Stregel et al., "Modern size-exclusion liquid chromatography, Wiley, 2nd ed., Chapter 3".)

[0054] The width of the chemical composition distribution can be quantified by the ratio of the TGIC spectrum width at different maximum heights, such as the ratio of the TGIC spectrum width at 1 / 4 of the maximum height to the TGIC spectrum width at 1 / 4 of the maximum height.

[0055] The procedure for setting the TGIC spectrum width (@1 / 4 of the maximum height) is as follows:

[0056] 1. Following the TGIC method described above, run the sample and the eicosane / iPP / homopolymer polyethylene mixture in the same run queue. If not in the same run queue, the samples can be run in the same TGIC instrument for a very short period of time (to minimize variability in IR detector response and width). In this case, the peak width of HDPE in the eicosane / iPP / homopolymer polyethylene mixture at 1 / 4 must be <1% RSD to allow for comparison of the TGIC spectrum width of the target sample.

[0057] 2. Generate TGIC chromatograms dWi / dT relative to elution temperature (T);

[0058] 3. For each sample, the maximum height of the TGIC chromatogram (dWi / dTi) was obtained by searching for the highest intensity at each data point between 35.0℃ and 170.0℃. The corresponding elution temperature at the maximum height of the TGIC chromatogram was defined as the curve temperature (Tp). The chromatogram width (1 / 4) was defined as the temperature difference between the preceding and following temperatures at the 1 / 4 maximum height, with the preceding temperature at the 1 / 4 maximum height searched forward from 35.0℃ and the following temperature at the 1 / 4 maximum height searched backward from 170.0℃.

[0059] 4. Calculate the peak width of HDPE at 1 / 4 HDPE peak height from eicosane / iPP / HDPE (peak width @ 1 / 4th) (see...) Figure 2 The peak elution temperature for homopolymer polyethylene (HDPE) was set at 150°C.

[0060] 5. The TGIC spectrum width at 1 / 4 of the maximum height is defined as:

[0061]

[0062] density

[0063] Samples for density measurement were prepared according to ASTM D 1928. The polymer sample was pressed for three minutes at 190°C and 30,000 psi, followed by one minute at 21°C and 207 MPa. Measurements were performed within one hour of sample pressing using ASTM D792, Method B.

[0064] Melt index (I2) and (I 10 )

[0065] According to ASTM D 1238, under conditions of 190°C / 2.16 kg, measure the melt index or I² (g / 10 min or dg / min) using procedure B. 10 (g / 10min or dg / min).

[0066] Example

[0067] The following examples illustrate the features of this disclosure, but are not intended to limit the scope of this disclosure. The following experiments analyze the performance of embodiments of the methods described herein for forming ethylene-based polymers.

[0068] The experiments were conducted in a continuously operating 40-gallon loop reactor containing two shell-and-tube exchangers to remove the heat of polymerization. Ethylene, octene, hydrogen, and Isopar-E solvent were added to the reactor at 40°C at the first feed injection point in the first half and the second feed injection point in the second half. The levels of these four substances were varied to produce the final polymer at a rate of 450 lb / hr, a melt index of 1.0 dg / min, and a density of 0.870 g / cc, with a reactor polymer concentration of 29%. Catalysts and co-catalysts were added to convert 91% of the ethylene added to the reactor. The catalyst was added either at a single injection point or distributed between the first catalyst injection point in the first half and the catalyst injection point in the second half. The reactor temperature was controlled by adjusting the temperature of the cooling water used in the two exchangers. All these experiments were conducted with a recirculation time of 98 seconds in the reactor loop.

[0069] When catalyst A is used, the process conditions are given in Table 1. Catalyst A is a bisphenylphenoxy catalyst, as described in Formula I below. Catalyst A is activated with 1.2 equivalents of a co-catalyst (amine, bis(hydrogenated tallow alkyl)methyl, tetra(pentafluorophenyl)borate (1-)) (CAS# 200644-82-2).

[0070]

[0071] Table 1

[0072]

[0073] TGIC spectra of C-1 and E-1 are provided Figure 3 The TGIC spectra of C-2 and E-2 are provided in [the original text]. Figure 4 From Table 1, Figure 3 and Figure 4 It can be seen that the addition of the second catalyst injector narrows the branching distribution of the short polymer chains, as indicated by both polymer broadening and a decrease in the fraction of materials with a TGIC temperature <80°C. When the reactor temperature increases from 190°C to 200°C, the catalyst half-life shortens, and the effect of the second catalyst injector becomes more pronounced.

[0074] The experiment was repeated using catalyst B. Catalyst B is a bisphenylphenoxy catalyst, as described in Formula II below. Catalyst B was activated with 1.2 equivalents of a co-catalyst (amine, bis(hydrogenated tallow alkyl)methyl, tetra(pentafluorophenyl)borate (1-)) (CAS#200644-82-2). The process conditions are given in Table 2.

[0075]

[0076] Table 2

[0077]

[0078] TGIC spectra of C-3 and E-3 are provided. Figure 5 From Figure 5 As can be seen from Table 2, the addition of the second catalyst injector narrows the branching distribution of the short polymer chains, as indicated by both polymer broadening and a decrease in the fraction of materials with a TGIC temperature <80°C. The effect of the second catalyst injector is relatively significant due to the relatively short half-life of catalyst B.

Claims

1. A method for forming an ethylene-based polymer, the method comprising: The catalyst is introduced into the loop reactor through at least two catalyst injection points, wherein: The loop reactor includes a loop, which comprises a first half and a second half, and The first catalyst injection point is in the first half of the loop and the second catalyst injection point is in the second half of the loop. Ethylene and comonomer are introduced into the loop reactor through at least two feed injection points, wherein a first feed injection point is in the first half of the loop and a second feed injection point is in the second half of the loop; and The ethylene and copolymer are polymerized under controlled polymerization conditions such that: The ratio of the amount of polymerization in the first half of the loop to the amount of polymerization in the second half of the loop is 0.7 to 1.3; The ratio of the heat of polymerization in the first half of the loop to the heat of polymerization in the second half of the loop is 0.7 to 1.3; or Both, thus forming the ethylene-based polymer.

2. The method of claim 1, wherein the controlled polymerization conditions are the ratio of catalyst injected at the second catalyst injection point to catalyst injected at the first catalyst injection point.

3. The method according to claim 2, wherein the ratio of the catalyst injected at the second catalyst injection point to the catalyst injected at the first catalyst injection point is 0.7 to 1.

3.

4. The method according to any one of claims 1 to 3, wherein the one or more polymerization conditions are controlled such that the ratio of the heat of polymerization in the first half to the heat of polymerization in the second half is 0.7 to 1.

3.

5. The method according to any one of claims 1 to 4, wherein the number of catalyst injection points is equal to the number of feed injection points.

6. The method according to any one of claims 1 to 5, wherein: The loop reactor includes a first heat exchanger and a second heat exchanger. The first catalyst injection point and the first feed injection point are located upstream of the first heat exchanger and downstream of the second heat exchanger, and The second catalyst injection point and the second feed injection point are located upstream of the second heat exchanger and downstream of the first heat exchanger.

7. The method according to claim 6, wherein the ratio of heat extracted at the second heat exchanger to heat extracted at the first heat exchanger is 0.7 to 1.

3.

8. The method according to any one of claims 1 to 7, wherein the half-life of the catalyst in the loop reactor is less than 80% of the recirculation time of the catalyst in the loop reactor.

9. The method according to any one of claims 1 to 8, wherein the polymerization conditions of the ethylene and copolymer are controlled such that: The ratio of the amount of polymerization in the first half of the loop to the amount of polymerization in the second half of the loop is 0.9 to 1.1; The ratio of the heat of polymerization in the first half of the loop to the heat of polymerization in the second half of the loop is 0.9 to 1.1; or both.

10. The method according to any one of claims 1 to 9, wherein less than 4.8% by weight of the polymer has a TGIC elution temperature of less than 80°C.

11. The method according to any one of claims 1 to 10, wherein the loop reactor has an operating temperature of 180°C to 210°C.

12. The method of any one of claims 1 to 11, wherein the comonomer comprises a C3-C 14 olefin.

13. The method according to any one of claims 1 to 12, wherein the ethylene-based polymer has a density of 0.85 g / cc to 0.94 g / cc.

14. The method according to any one of claims 1 to 13, wherein the ethylene-based polymer has a melt index of 0.2 dg / min to 2000 dg / min.

15. The method according to any one of claims 1 to 14, wherein polymerizing the ethylene and copolymer under controlled polymerization conditions comprises: Determine the ratio of the heat of polymerization in the first half of the loop to the heat of polymerization in the second half of the loop; as well as If the ratio of the heat of polymerization in the first half of the loop to the heat of polymerization in the second half of the loop is greater than 1.2, then the proportion of catalyst injected at the second catalyst injection point is increased, or If the ratio of the heat of polymerization in the first half of the loop to the heat of polymerization in the second half of the loop is less than 0.8, then the proportion of catalyst injected at the second catalyst injection point is reduced.

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