Methods for improving gas phase polymerization

Abstract

Disclosed is a process to polymerize olefins in a gas phase polymerization reactor. The process comprises adding ethylene, a comonomer, hydrogen, and a polymerization catalyst to a reaction zone of the gas phase polymerization reactor under first polymerization conditions to produce a first polyethylene having a first density and a first melt index. The first polymerization conditions comprise a first hydrogen addition rate (HA1), a first ethylene addition rate (EA1), and a first comonomer addition rate (CA1). A first comonomer addition ratio (C AR1) is defined as CA1 / EA1, a first total hydrogen ratio (THR1) is defined as (HA1+HG1) / EA1, and HG1 is a first rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CA1. In some embodiments, the process further comprises implementing second polymerization conditions to produce a second polyethylene having a second density and a second melt index while reducing off-spec material produced when transitioning from first to second polymerization conditions.

Description

METHODS FOR IMPROVING GAS PHASE POLYMERIZATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U. S. Provisional Application No.63 / 719,848 having a filing date of November 13, 2024, the disclosure of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure relates to systems and methods for operating a polyolefin polymerization reactor with improved production rates. More specifically, this disclosure provides for improved hydrogen control to reduce production of off-spec polymer during grade transitions.BACKGROUND OF THE INVENTION

[0003] Polyolefins may be produced using gas phase polymerization processes. If the process is a gas-phase fluidized bed polymerization process, the process may include a gas stream including one or more monomers continuously passed through a fluidized bed of catalyst and growing polymer particles. As polymerization occurs, a portion of the monomers are consumed and the gas stream is heated in the reactor by the heat of polymerization. A portion of the gas stream exits the reactor and may be recycled back to the reactor with additional monomers and additives.

[0004] Polyethylene properties, in particular density and melt index for any particular catalyst system, are controlled by feed rates and / or ratios of ethylene, comonomer, and hydrogen to the reactor. Polyethylene grade slates have expanded in recent years to provide a broader array of polyethylene products for various end uses. Current polyethylene grade slates include a broad variety of combinations of density and melt index.

[0005] Polyethylene reactor transitions between grades using metallocene catalysts, particularly transitions that involve large density changes, have historically proven difficult to maintain on-spec melt index, leading to significant quantities of off-spec material. In some instances, hydrogen flow to a polyethylene gas phase reactor to control melt index (i.e., molecular weight) is based on a measured hydrogen concentration ratio in the reactor cycle gas and an ethylene feed rate to the reactor. While this control scheme is sufficient during steady state operation, it may be less so when reactor operations are in a transitional state.

[0006] For example, cycle gas composition after a process change such as a change in density (i.e., change in comonomer feed rate) does not accurately reflect steady state operation of thereaction zone potentially for hours after the change. Additionally, prior to achieving steady state operations, the lag time between taking cycle gas samples and receiving laboratory results in delays in responding to reactor conditions that may need to be modified. For at least these reasons, hydrogen addition rate calculated based on cycle gas composition and ethylene addition rate can result in extended delays between on-spec operations when transitioning from one polymer grade to another.

[0007] Even within the constraints of safe operation, real-time control of gas phase polymerization reactors is complex. The complexity of reactor control adds further to the difficulty and uncertainty of experimentation if one wishes to alter operating conditions during grade transitions. Large-scale gas phase plants are expensive and highly productive. Risks associated with experimentation in such plants are high because any time period when a reactor is producing off-spec material is costly. Therefore, exploring design and operating boundaries experimentally is difficult in view of the costs and risks.

[0008] There remains a need for methods of controlling the gas phase polymerization process to more accurately estimate the optimum hydrogen addition rate changes to more quickly achieve a desired melt index target, particularly during grade transitions, thereby reducing the production of off-spec polymer. Ideally, such process improvements could be implemented in retrofitted or newly built facilities with commonly used equipment and familiar techniques.SUMMARY OF THE INVENTION

[0009] This disclosure provides processes for polymerizing olefins at increased effective production rates by reducing the amount of time a gas phase polymerization reactor produces off-spec polymer, especially during grade transitions. Disclosed herein is a process to polymerize olefins in a gas phase polymerization reactor, the process comprising adding ethylene, a comonomer, hydrogen, and a polymerization catalyst to a reaction zone of the gas phase polymerization reactor under first polymerization conditions to produce a first polyethylene having a first density and a first melt index, wherein the first polymerization conditions comprise a first hydrogen addition rate (HAi), a first ethylene addition rate (EAi), and a first comonomer addition rate (CAi). A first hydrogen addition ratio (HARi) is defined as HAi / EAi. A first comonomer addition ratio (CARi) is defined as CAi / EAi. A first total hydrogen ratio (THRi) is defined as (HAi+HGi) / EAi. HGi is a first rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CAi and is defined as HGi = a x CARi; wherein a is an empirically determined constant associated with the catalyst and the comonomer.

[0010] In some embodiments of the process, the first melt index (MIi) can be calculated according to Equation 1: MIi = exp(b + (c * HARi) + (d x CARi)), wherein b, c, and d are empirically determined constants associated with the catalyst and the comonomer. In further embodiments, the first density (Di) can be calculated according to Equation 2: Di = 0.97 - (e x CAi / (CAi + EAi)) + (f x MIi), wherein e and f are empirically determined constants associated with the catalyst and the comonomer, wherein e and f are empirically determined constants associated with the catalyst and the comonomer.

[0011] In some embodiments, the process further comprises implementing second polymerization conditions to produce a second polyethylene having a second density and a second melt index, wherein second polymerization conditions comprise a second hydrogen addition rate (HA2), a second ethylene addition rate (EA2), and a second comonomer addition rate (CA2). A second hydrogen addition ratio (HAR2) is defined as HA2 / EA2. A second comonomer addition ratio (CAR2) is defined as CA2 / EA2. A second total hydrogen ratio (THR2) is defined as (HA2+HG2) / EA2. HG2 is a second rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CA2 and is defined as HG2 = a x CAR2, wherein a is an empirically determined constant associated with the catalyst and the comonomer

[0012] In some embodiments of the process, the first melt index (MIi) can be calculated according to Equation la: MIi = exp(Z> + (c x HARi)+ (d x CARi)), and the second melt index (MI2) can be calculated according to Equation lb: MIi = exp(Z> + (c x HAR2)+ (d x CAR2)), wherein b, c, and d are empirically determined constants associated with the catalyst and the comonomer. In further embodiments, the first density (Di) can be calculated according to Equation lb: Di = 0.97 - (e x CAi / (CAi +EAi)) + (f x MIi), and the second density (D2) can be calculated according to Equation 2b: D2 = 0.97 - (t? x CA2 / CA2 + EA2)) + (fxMI2), wherein e and / are empirically determined constants associated with the catalyst and the comonomer.

[0013] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject matter of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other catalyst compositions and / or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as setforth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its compositions and methods, together with further objects and advantages will be better understood from the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The claimed subject matter may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

[0015] FIG. 1 is a schematic diagram of a gas phase polymerization system;

[0016] FIG. 2 is a diagram of a control system for controlling a gas phase polymerization process;

[0017] FIG. 3 shows a simplified control scheme of a gas phase polymerization system, wherein hydrogen addition is controlled based on cycle gas composition and ethylene feed rate;

[0018] FIG. 4 shows a simplified control scheme of a gas phase polymerization system, wherein hydrogen addition is controlled based on ethylene and comonomer feed rates, according to embodiments of the disclosure;

[0019] FIGs. 5A and 5B show overlaid graphs of gas phase polymerization reactor process parameters with respect to time showing a comparison of a comparative process to an inventive process according to an embodiment of the disclosure;

[0020] FIG. 6 shows overlaid graphs of gas phase polymerization reactor process parameters with respect to time for comparative Example 2;

[0021] FIG. 7 shows overlaid graphs of gas phase polymerization reactor process parameters with respect to time for comparative Example 4;

[0022] FIG. 8 shows overlaid graphs of gas phase polymerization reactor process parameters with respect to time for inventive Example 7, according to an embodiment of the disclosure; and

[0023] FIGs. 9A and 9B show the relationship of hydrogen addition to polymer density changed demonstrated by examples of the improved process disclosed herein.

[0024] While the disclosed process and system are susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments and / or aspects herein described in detail by way of example. It should be understood, however, that the description herein of a specific embodiment is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.DETAILED DESCRIPTION OF THE INVENTION

[0025] Illustrative embodiments of the subject matter claimed below will now be disclosed. In the interest of clarity, some features of some actual implementations may not be described in this specification. It will be appreciated that in the development of any such actual embodiments, numerous implementation-specific decisions must be made to achieve the developer’s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking forthose of ordinary skill in the art having the benefit of this disclosure.

[0026] The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended tobe implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than the broadest meaning understood by skilled artisans, such a special or clarifying definition will be expressly set forth in the specification in a definitional manner that provides the special or clarifying definition for the term or phrase.

[0027] For example, the following discussion contains a non-exhaustive list of definitions of several specific terms used in this disclosure (other terms may be defined or clarified in a definitional manner elsewhere herein). These definitions are intended to clarify the meanings of the terms used herein. It is believed that the terms are used in a manner consistent with their ordinary meaning, but the definitions are nonetheless specified here for clarity.Definitions

[0028] As used herein, “iCf’ and “isobutane” refer to 2-methylpropane.

[0029] As used herein, “nCf’ and “n-butane” refer to normal-butane.

[0030] As used herein, “iCs” and “isopentane” refer to 2-methylbutane.

[0031] As used herein, “nCs” and “n-pentane” refer to normal-pentane.

[0032] As used herein, “neoCs” and “neo-pentane” refer to 2,2-dimethylpropane.

[0033] As used herein, “nCe” and “n-hexane” refer to normal-hexane.

[0034] As used herein, “Ce inerts” refers to various hexane isomers that are inert to reaction conditions and may include nCe, 2-methylpentane, 3 -methylpentane, 2,2-dimethyl butane, 2,3-dimethylbutane, 2-hexene, and / or 3 -hexene.

[0035] As used herein, “comprising” is to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps, or components, or groups thereof. Moreover, each of the terms “by”, “comprising,” “comprises”, “comprised of’ “including,” “includes,” “included,” “involving,” “involves,” “involved,” and “such as” are used in their open, non-limiting sense and may be used interchangeably. Further, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of’ and “consisting of.” Similarly, the term “consisting essentially of’ is intended to include examples encompassed by the term “consisting of.”

[0036] As used herein, “ICA” refers to a condensing agent. “ICAs” refers to condensing agents. “ICA composition” refers to the total condensing agent in the reactor and encompasses compositions with two ormore condensing agents. ICAs suitable for use in methods of the present disclosure may include C3-C6 hydrocarbons or combinations thereof. For example, ICAs suitable for use may include n-butane, isobutane, n-pentane, isopentane, neo-pentane, hexane, isohexane, Ce inerts, and other hydrocarbon compounds that are similarly non-reactive in the polymerization process. A “binary ICA composition” is an ICA composition that includes two ICAs, and a “ternary ICA composition” is an ICA composition that includes three ICAs.

[0037] As used herein, “linear low density polyethylene” (LLDPE) refers to polyethylene having a density in the range of from 0.900 g / cm3to 0.945 g / cm3, from 0.901 g / cm3to 0.940 g / cm3, from 0.902 g / cm3to 0.935 g / cm3, from 0.903 g / cm3to 0.930 g / cm3, from 0.904 g / cm3to 0.925, or from 0.905 g / cm3to 0.920 g / cm3. In some embodiments, LLDPE herein can be produced with one ormore Ziegler-Natta catalysts, one ormore single-site transition metal catalysts, such as, but not limited to, metallocene catalysts, or a combination thereof. In some embodiments, LLDPE herein can be produced in one or more gas phase reactors.

[0038] As used herein, “melt index” or “MI” or “I2” refers to a measure of the flow of the melt of the thermoplastic polymer. Melt index may be measured according to ASTM D1238-13 at suitable weight and temperature. Generally, the melt index of polyolefins is measured at 2.16 kg at 190°C, 5 kg at 190°C, or 21.6 kg at 190°C. Examples herein were performed using 12 (2.16 kg, 190°C), but numerical relationships between melt index and other process parameters using other types of melt index as well.

[0039] As used herein, “polyethylene” denotes a polymer of ethylene and optionally one or more C3-C18 alpha-olefins, while the term “polyolefin” denotes a polymer of one ormore C2-C18alpha-olefins and optionally one or more comonomers. An “olefin” is an unsaturated hydrocarbon that contains at least one carbon-carbon double bond. An alpha-olefin is a hydrocarbon that contains at least one carbon-carbon double bond at one end of a carbon chain (e.g., 1-butene, vinyl-cyclohexane). For the purposes of this disclosure, ethylene shall be considered an a-olefin.

[0040] As used herein, “real-time” means data processed, and systems adjusted, without intentional delay, given the processing limitations of the system and the time to accurately measure the data.

[0041] As used herein, Mnis number average molecular weight, Mwis weight average molecular weight, and Mzis z average molecular weight, wt % is weight percent, and mol % is mole percent. Molecular weight distribution (MWD), also referred to as polydispersity index (PDI), is defined to be Mw divided by Mn. Unless otherwise noted, all molecular weights (e.g., Mw, Mn, Mz) are reported in units of g / mol.Reducing Off-spec Material

[0042] The present disclosure relates to processes for production of polyolefins in a gas phase reactor wherein transitions between grades can be made from a first polyethylene having a first density and a first melt index to a second polyethylene having a second density and a second melt index, wherein less off-spec material is produced in the transition between the first polyethylene and the second polyethylene than has previously been possible.

[0043] In some embodiments, the first and second densities are the same, and the first and second melt indexes are different. In some embodiments, the first and second densities are different, and the first and second melt indexes are the same. In some embodiments, the first and second densities are different, and the first and second melt indexes are different.

[0044] In some embodiments, when the densities are different, the first density is greater than the second density. In some embodiments, when the densities are different, the first density is less than the second density.

[0045] In some embodiments, when the melt indexes are different, the first melt index is greater than the second melt index. In some embodiments, when the melt indexes are different, the first melt index is less than the second index.

[0046] In the past, hydrogen feed rate to a gas phase polymerization reactor has been controlled as function of the composition of the cycle gas in the cycle gas recycle line, wherein the overhead gas from the gas phase polymerization reactor is cooled and reinjected in the base of the reactor to help fluidize the bed of catalyst and polymer particles. When transitioning between polyethylenegrades, one or more of the hydrogen feed rate, the ethylene feed rate, or the comonomer feed rate to the gas phase polymerization reactor are changed. When one or more of the hydrogen feed rate, the ethylene feed rate, or the comonomer feed rate are changed relative to one another, here is a lag time before kinetics in the reaction zone reach an equilibrium. Before such equilibrium is reached, instantaneous measurements of the composition of the cycle gas will not provide accurate long term targets for adjustment of the hydrogen addition rate to the gas phase polymerization reactor.

[0047] In some embodiments, the improvements to the processes disclosed herein are accomplished by controlling the hydrogen feed rate to a gas phase polymerization reactor as a function of the ethylene feed rate and the comonomer feed rate to the gas phase polymerization reactor. With operating knowledge regarding polymerization systems using selected catalyst and a selected comonomer, controlling hydrogen feed rate based on the ethylene and comonomer feed rates permits changing the hydrogen feed rate directly to the long-term target, thereby minimizing production of off-spec material during the transition.Polymerization Reactor

[0048] The methods described may be used in pilot plant or commercial size reactors including a variety of designs. For example, the model can be used in commercial-scale reactions, such as gas-phase fluidized-bed polymerization reactions, that can be monitored and optionally also controlled. Some such reactions can occur in a reactor having the geometry of the fluidized bed reactor 101 discussed with respect to FIG. 1. In other embodiments, a reactor is monitored and optionally also controlled while operating to perform polymerization using any of a variety of different processes (e.g., slurry or gas phase processes).

[0049] Generally, in a gas-phase fluidized-bed process used forproducing polymers, a gaseous stream containing one or more monomers is continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. The gaseous stream is withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product is withdrawn from the reactor and fresh monomer is added to replace the polymerized monomer. (See, for example, U. S. Pat. Nos. 4,543,399; 4,588,790; 5,028,670; 5,317,036; 5,352,749; 5,405,922; 5,436,304; 5,453,471; 5,462,999; 5,616,661; and 5,668,228; all of which are incorporated by reference.)

[0050] FIG. 1 is a schematic diagram of a polymerization system 100 that can be monitored and controlled in accordance with embodiments described. The polymerization system 100includes a fluidized bed reactor 101. The fluidized bed reactor 101 has a bottom end 103, a straight section 105, a top expanded section 107, and a distributor plate 109 within the straight section 105.A fluidized bed 111 of granular polymer (once formed) and catalyst particles is contained within the straight section 105 and may optionally extend slightly into the top expanded section 107. The bed is fluidized by the steady flow of recycle gas through the distributor plate 109. The recycle gas enters fluidized bed reactor through line 113, additional reaction and inert gases (including ICAs) may be added in adjustable ratios through line 115. Aluminum alkyl (optional) may be added through line 117. The flow rate of the recycle gas is regulated to maintain circulation of fluidized bed 111. In some embodiments, a recycle gas velocity of from about 1 ft / sec to about 3 ft / sec, such as from about 2 ft / sec to about 3 ft / sec, or from about 2.4 ft / sec to about 2.8 ft / sec is used to maintain a fluidized bed 111 in the reactor 101 while operating the reactor 101 at a total pressure of about 4200 kPa or less, about 700 kPa to about 4200 kPa, about 1300 kPa to about 2800 kPa, or about 1700 kPa to about 2500 kPa.

[0051] The polymerization system 100 has one or more catalyst lines 119 for controlling the addition of polymerization catalyst to a reaction zone (not shown) within fluidized bed 111, and generally within straight section 105. Within the reaction zone, the catalyst particles react with reaction gases including an olefin monomer (e.g., ethylene) and optionally a comonomer and other reaction gases (e.g., hydrogen) to produce the granular polymer particles. As new polymer particles are produced, other polymer particles are continually withdrawn from the fluidized bed 111 through a product discharge line 121 to product recovery system 123. The fluidized bed 111 may be maintained at a constant height by withdrawing a portion of the fluidized bed 111 at a rate equal to the rate of formation of particulate product. The product may be removed continuously or nearly continuously via a series of valves (not shown) into a fixed volume chamber (not shown), which is simultaneously vented back to the reactor. The fixed volume chamber and venting back to the reactor allows for highly efficient removal of the product, while recycling a large portion of the unreacted gases back to the reactor.

[0052] Unreacted olefins and ICA composition within the product recovery system may be removed via line 125, compressed in compressor 127, and travel via line 129 to heat exchanger 131 to be cooled before being recycled (e.g., via line 133) to line 113. The particles within product recovery system 123 may be degassed (or “purged”) with a flow of inert gas such as nitrogen through line 135 to remove substantially all of the dissolved hydrocarbon materials. In some instances, the polymer granules may be treated with a small stream of humidified nitrogen todeactivate trace quantities of residual catalyst. The purge gas may be removed via line 137 to be vented to flare or recycled with further processing.

[0053] The polymerization system 100 also has a cooling loop which includes a first recycle gas line 139, compressor 141, a second recycle gas line 143, and cooling system 145 (such as a circulating gas cooler), coupled with the fluidized bed reactor 101. Cooling system 145 may accept cooling water via line 147 and expel heated water via line 149. Cooling of the recycle gas is a method used to cool polymerization system 100 to reduce or eliminate issues that may arise from exothermic polyolefin production. During operation, the cooled circulating gas from cooling system 145 flows via line 113 through inlet 151 into the fluidized bed reactor 101, then propagates upward through fluidized bed 111 and out from the fluidized bed reactor 102 via outlet 153.

[0054] The top expanded section 107 may also be known as a “velocity reduction zone,” and is designed to reduce the quantities of particle entrainment in therecycle gas line from the fluidized bed. The diameter of the top expanded section 107 generally increases with the distance from straight section 105. The increased diameter causes a reduction in the speed of the gas stream, which allows most of the entrained particles to settle back into the fluidized bed 111, thereby minimizing the quantities of solid particles that are “carried over” from the fluidized bed 111 through the recycle gas line 139. In some instances, a screen (not shown) may be included upstream of the compressor 141 to remove larger material.

[0055] To maintain a reactor temperature, the temperature of the recycle gas may be continuously adjusted up or down to accommodate changes in the rate of heat generation due to the polymerization reaction. One or more temperature sensors 155 may be located in the fluidized bed and used with a control system and the cooling loop to control the temperature of the fluidized bed 111 near the process set -point. Heated reactor gas, which carries heat energy from the fluidized bed reactor 101, is withdrawn from the outlet 153 and is pumped by the compressor 141 via line 143 to cooling system 145 where the temperature of the heated reactor gas is reduced and at least a portion of the ICA composition present is condensed to a liquid. The recycle gas from the cooling system 145, including condensed liquids, flows via line 113 to the reactor inlet 151 to cool the fluidized bed 111. Temperature sensors (not shown) near the inlet and outlet of thecooling system 145 may provide feedback to a control system (not shown) to regulate the amount by which cooling system 145 reduces the temperature of the recycle gas entering the fluidized bed reactor 101.-10-

[0056] The fluidized bed reactor 101 may also include skin temperature sensors 157, mounted in positions along a wall of the straight section 105 of the fluidized bed reactor 101 so as to protrude into the bed from the reactor wall by a small amount (e.g., about one eighth to one quarter of an inch (3-6 mm)). The skin temperature sensors 157 may be configured and positioned to sense the temperature of the resin near the wall of the fluidized bed reactor 101 during operation.

[0057] The temperature sensors 155 in the fluidized bed 111 can include a resistance temperature sensor positioned and configured to sense bed temperature during reactor operation at a location within the fluidized bed reactor 101 away from the reactor wall. The resistance temperature sensor can be mounted so as to protrude into the bed more deeply than the skin temperature sensors 157 (e.g., about 8 to 18 inches (20-46 cm) away from the reactor wall).

[0058] Other sensors and other apparatuses may be employed to measure other reaction parameters during a polymerization reaction. The reaction parameters may include instantaneous and bed-averaged resin product properties (e.g., melt index and density of the polymer resin product being produced by the polymerization system 100 during a polymerization reaction). Resin product properties may be measured by periodically sampling the resin when exiting the reactor (e.g., about once per hour), and performing the appropriate tests in a quality control laboratory.

[0059] Other measured reaction parameters may include reactor gas composition (e.g., concentrations and partial pressures of reactant gases, ICA, and other inert gases, such as nitrogen, inert hydrocarbon, and the like). The reactor gas composition may be measured by removal of gas from upper portion 107 via line 159 to a gas chromatograph (“GC”) system 161. GC system 161 may also be connected by lines (not shown) other than line 159 to other parts of polymerization system 100, such as recycle gas line 139, compressor 141, line 143 or any combination thereof.

[0060] The process control variables may be controlled to obtain the desired productivity for the polymerization system 100 and properties for the resin. For example, the parameters used to control gas phase composition within the fluidized bed reactor 101 can include the concentration (partial pressure) and composition of the ICA composition and comonomer, the partial pressure of monomer, the type and properties of catalysts, and the temperature of the reaction process. For example, a polymerization reaction during a transition from production of a certain grade of polyolefin to a different grade may be controlled by controlling process control variables to ensure that the product (e.g., the granular resin) has properties compliant with an initial specification set at the start of the transition, the product produced during the transition ceases to comply with theinitial specification set at a first time, and the product has properties compliant with a final specification set at the end of the transition. In the processes described herein, stickiness of the resin during the reaction may be controlled by a control system adjusting (or regulating) the temperature in the reaction zone and / or the concentration (partial pressure) of the IC A composition used in the reaction.

[0061] FIG. 2 is a block diagram of a control system 200 that can be used to control the polymerization system 100. The control system 200 may be a distributed control system (DCS), a direct digital controller (DDC), a programmable logic controller (PLC), or other suitable systems or combination of systems. The control system 200 has a processor 201 that implements machine readable instructions from a storage system 203. Illustrative processors may include a single core processor, a multiple core processor, a virtual processor, a virtual processor in a cloud implementation, an application specific integrated circuit (ASIC), or a combination of these systems. Illustrative storage systems 203 can include random access memory (RAM), read only memory (ROM), hard drives, virtual hard drives, RAM drives, cloud storage systems, optical storage systems, physically encoded instructions (for example, in an ASIC), or a combination of these systems.

[0062] Adjustments to control settings may be determined based on the input of data from temperature sensors 155 and 157, the GC 161, and lab data 205, among others. After determining new control settings, the control system 200 may make in real time, or recommend, adjustments, for example, to the process cooling systems 207, the ICA addition and recycling systems 209, flow control systems 211 (e.g., hydrogen addition, ethylene additions, comonomer addition, etc.), and termination systems 213, among others.

[0063] The reactor and associated methods may be an element of a staged reactor employing two or more reactors in series, where one reactor may produce, for example, a high molecular weight polyolefin and another reactor may produce a low molecular weight polyolefin.Polyolefin Production

[0064] Polyolefin polymerization may be performed by contacting in a reactor (such as the fluidized bed reactor 101 of FIG. 1) an olefin monomer (optionally with a comonomer) with one or more catalysts (supported or not) in the presence of ICA composition and optionally hydrogen. The individual flow rates of olefin monomer, optional comonomer, optional hydrogen, and ICA composition (or individual components thereof) may be controlled to maintain fixed gas composition targets. The concentration of all gases may be measured with a chromatograph. Asolid catalyst, a catalyst slurry, or liquid solution of the catalyst(s) may be injected directly into the reactor using a carrier gas (e.g., purified nitrogen), where the feed rate of catalyst(s) may be adjusted to change or maintain the catalyst inventory in the reactor.

[0065] In some embodiments, the polymerization reaction may be performed at a reactor pressure of about 4,200 kPa or less, about 700 kPa to about 4,200 kPa, about 1,300 kPa to about 2,800 kPa, or about 1,700 kPa to about 2,500 kPa.

[0066] Generally, the olefin monomer concentration is controlled and monitored by the olefin monomer partial pressure. In some embodiments, the olefin partial pressure may be at about 4200 kPa or less, such as about 500 kPa to about 2,000 kPa, about 1,000 kPa to about 1,800 kPa, about 1,200 kPa to about 1,700 kPa, or about 1,400 kPa to about 1,600 kPa.

[0067] The comonomer concentration may be controlled and monitored by a comonomer to olefin monomer mole ratio (or alternatively, the flow rates of comonomer and olefin monomer are held at a fixed ratio). When present, the comonomer may be at a relative concentration to the olefin monomer that will achieve the desired weight percent incorporation of the comonomer into the finished polyolefin. In some embodiments, the comonomer may be present with the olefin monomer in a mole ratio in the gas phase of from about 0.0001 to about 50 (comonomer to olefin monomer), from about 0.0001 to about 5, from about 0.0005 to about 1.0, or from about 0.001 to about 0.5.

[0068] The olefin monomer or comonomers, for example, may be a C2-C18 alpha-olefin. In some embodiments, the olefin monomer is ethylene, and a comonomer is a C3-C12 alpha olefin. In some embodiments, the olefin monomer may be ethylene or propylene, and a comonomer may include C4-C10 alpha-olefins. For example C2-C18 alpha-olefins that may be utilized as a comonomer in embodiments described may include: ethylene, propylene, 1 -butene, 1 -pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-l-ene, 1-decene, 1-dodecene, 1-hexadecene, and the like, and a combination thereof. Additionally, a polyene may be used as a comonomer according to some embodiments described. For example, polyenes may include: 1,3 -hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-l-ene, methyloctadiene, 1-methyl-l,6-octadiene, 7-methyl-l,6-octadiene, 1,5-cyclooctadiene, norbomadiene, ethylidene norbomene, 5-vinylidene-2-norbomene, 5-vinyl-2-norbomene, and olefins formed in situ in the polymerization medium. When olefins are formed in situ in the polymerization medium, the formation of polyolefins containing long chain branching may occur. Additional examples ofcomonomers may include isoprene, styrene, butadiene, isobutylene, chloroprene, acrylonitrile, and cyclic olefins. Combinations of the foregoing may be utilized in the methods described.

[0069] Examples of polymers that can be produced in accordance with the method described may include the following: homopolymers and copolymers of C2-C18 alpha olefins; polyvinyl chlorides, ethylene propylene rubbers (EPRs); ethylene-propylene diene rubbers (EPDMs); polyisoprene; polystyrene; polybutadiene; polymers of butadiene copolymerized with styrene; polymers of butadiene copolymerized with isoprene; polymers of butadiene with acrylonitrile; polymers of isobutylene copolymerized with isoprene; ethylene butene rubbers and ethylene butene diene rubbers; polychloroprene; norbomene homopolymers and copolymers with one or more C2-C18 alpha olefin; and terpolymers of one or more C2-C18 alpha olefins with a diene. In some embodiments, the polyolefin produced by the method described may include olefin homopolymers (e.g., homopolymers of ethylene or propylene). In some instances, the polyolefin produced may be copolymers, terpolymers, and the like of the olefin monomer and the comonomer.

[0070] In some embodiments, the polyolefin produced may be a polyethylene or a polypropylene. Exemplary polyethylenes produced by the methods described may be homopolymers of ethylene or copolymers of ethylene (or terpolymers of ethylene) having at least one alpha-olefin (comonomer) where the ethylene content may be at least about 50% by weight of the total monomers involved. Exemplary polypropylenes produced by the methods described may be homopolymers of propylene or interpolymers of propylene and at least one alpha-olefin (comonomer) where the propylene content may be at least about 50% by weight of the total monomers involved.

[0071] Hydrogen gas is often used in olefin polymerization to control the final properties of the polyolefin. For some types of catalyst systems, increasing concentrations (or partial pressures) of hydrogen may alter the molecular weight or melt index of the polyolefin generated. The melt index can thus be influenced by the hydrogen concentration. Generally, the amount of hydrogen in the polymerization is expressed as a mole ratio relative to the total polymerizable monomer (e g., relative to ethylene or relative to a blend of ethylene and hexene or propylene). The amount of hydrogen used in some polymerization processes is an amount necessary to achieve the desired melt index (or molecular weight) of the final polyolefin resin. In some embodiments, the mole ratio in the gas phase of hydrogen to total polymerizable monomer (H2 to monomer) may be about 0.00001 or greater, about 0.0005 or greater, about 0.001 or greater, about 10 or less, about 5 orless, about 3 or less, or about 0.10 or less, where a range may include a combination of an upper mole ratio with a lower mole ratio described.Catalyst

[0072] Exemplary catalysts suitable for use in the embodiments described may include: Ziegler Natta catalysts, chromium based catalysts, vanadium based catalysts (e.g., vanadium oxychloride and vanadium acetylacetonate), metallocene catalysts and other single-site or singlesite-like catalysts, cationic forms of metal halides (e g., aluminum trihalides), anionic initiators (e.g., butyl lithiums), cobalt catalysts and mixtures thereof, nickel catalysts and mixtures thereof, rare earth metal catalysts (i.e., those containing a metal having an atomic number in the Periodic Table of 57 to 103), such as compounds of cerium, lanthanum, praseodymium, gadolinium and neodymium. A single catalyst may be used, or a mixture of catalysts may be employed, if desired. The catalyst may be soluble or insoluble, supported or unsupported. Further, the catalyst may be a prepolymer, spray dried with or without a filler, a liquid, or a solution, slurry / suspension, or dispersion.Ziegler-Natta Catalyst

[0073] Traditional Ziegler-Natta catalysts are transitional metal catalysts that are well known in the art. Examples of transition metal catalysts are discussed in U. S. Pat. Nos. 4,115,639, 4,077,904, 4,482,687, 4,564,605, 4,721,763, 4,879,359 and 4,960,741, the disclosures of which are hereby fully incorporated herein by reference. The transition metal catalyst compounds that may be used in the present invention include transition metal compounds from Groups 3 to 17, preferably 4 to 12, more preferably 4 to 6 of the Periodic Table of Elements.

[0074] Transition metal catalyst compounds based on magnesium / titanium electron-donor complexes that are useful in the invention are described in, for example, U. S. Pat. Nos. 4,302,565 and 4,302,566, the disclosures of which are hereby fully incorporated herein by reference.

[0075] British Patent Application No. 2,105,355 and U. S. Pat. No. 5,317,036, the disclosures of which are hereby incorporated herein by reference, describe various vanadium catalyst compounds.

[0076] Still other transition metal catalyst compounds and catalyst systems suitable for use in the present invention are disclosed in U. S. Pat. Nos. 4,124,532, 4,302,565, 4,302,566, 4,376,062, 4,379,758, 5,066,737, 5,763,723, 5,849,655, 5,852,144, 5,854,164 and 5,869,585 and publishedEP-A2 0416815 A2 and EP-A1 0420436, the disclosures of which are hereby fully incorporated herein by reference.

[0077] Other catalysts may include cationic catalysts such as A1C1 3, and other cobalt, iron, nickel and palladium catalysts well known in the art. See for example U. S. Pat. Nos. 3,487,112, 4,472,559, 4,182,814 and 4,689,437, the disclosures of which are hereby fully incorporated herein by reference.

[0078] For more details on Ziegler-Natta catalysts, see for example, U. S. Pat. Nos. 3,687,920, 4,086,408, 4,376,191, 5,019,633, 4,482,687, 4,101,445, 4,560,671, 4,719,193, 4,755,495, 5,070,055, the disclosures of which are hereby incorporated herein by reference.

[0079] Also or instead, a catalyst compound of the present disclosure can be a chromium or chromium-based catalyst. Such catalysts and polymerization processes have been described, for example, in U. S. Patent Application Publication No. 2011 / 0010938 and U. S. Pat. Nos. 7,915,357, 8,129,484, 7,202,313, 6,833,417, 6,841,630, 6,989,344, 7,504,463, 7,563,851, 8,420,754, and 8,101,691.- Metallocene Catalyst

[0080] In some embodiments processes disclosed herein utilize single-site transition metal catalysts. Exemplary single-site transition metal catalysts suitable for use in the embodiments described may include metallocene catalysts and other single-site or single-site-like catalysts. A single catalyst may be used, or a mixture of catalysts may be employed, if desired. The catalyst may be soluble or insoluble, supported or unsupported. Further, the catalyst may be a prepolymer, spray dried with or without a filler, a liquid, or a solution, slurry / suspension, or dispersion.

[0081] Metallocenes may include “half sandwich” and “full sandwich” compounds having one or more pi-bonded ligands (e.g., cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to at least one Group 3 to Group 12 metal atom (Including the Lanthanide series and Actinide series elements), and one or more leaving groups bound to the at least one metal atom. The metallocene may be supported on a support material and may be supported with or without another catalyst component.

[0082] The structure of the metallocene catalyst compound may take on many forms, such as those disclosed in, for example, U. S. Pat. Nos. 5,026,798, 5,703,187, and 5,747,406, including a dimer or oligomeric structure, such as disclosed in, for example, U. S. Pat. Nos. 5,026,798 and 6,069,213. Others include those catalysts described in U. S. Patent Application Publication Nos. US2005 / 0124487A1, US2005 / 0164875A1, and US2005 / 0148744. In some embodiments, themetallocene may be formed with a hafnium metal atom (e.g., bis(n-propylcyclopentadienyl) hafnium Xn, bis(n-butylcyclopentadienyl) hafnium Xn, or bis(n-pentylcyclopentadienyl) hafnium Xn, where X is one of chloride or fluoride and n is 2), such as is described in U. S. Pat. Nos.6,242,545 and 7,157,531.

[0083] A catalyst compound of the present disclosure can be a chromium or chromium-based catalyst. Chromium-based catalysts include chromium oxide (CrO3) and silylchromate catalysts. Chromium catalysts have been the subject of much development in the area of continuous fluidized -bed gas-phase polymerization for the production of polyethylene polymers. Such catalysts and polymerization processes have been described, for example, in U. S. Patent Application Publication No. 2011 / 0010938 and U. S. Pat. Nos. 7,915,357, 8,129,484, 7,202,313, 6,833,417, 6,841,630, 6,989,344, 7,504,463, 7,563,851, 8,420,754, and 8,101,691.

[0084] Other catalysts for use in processes of the present disclosure include “non-metallocene complexes” that are defined to be transition metal complexes that do not feature a cyclopentadienyl anion or substituted cyclopentadienyl anion donors (e.g., cyclopentadienyl, fluorenyl, indenyl, methylcyclopentadienyl). Examples of families of non-metallocene complexes that may be suitable can include late transition metal pyridylbisimines (e.g., U. S. Pat. No. 7,087,686), group 4 pyridyldiamidos (e.g., U. S. Pat. No. 7,973,116), quinolinyldiamidos (e.g., U. S. Pub. No.2018 / 0002352 Al), pyridylamidos (e.g., U. S. Pat. No. 7,087,690), phenoxyimines (e.g., Accounts of Chemical Research 2009, 42, 1532-1544), and bridged bi-aromatic complexes (e.g., U. S. Pat. No. 7,091,292), the substance of which are fully incorporated herein by reference.Hydrogen Addition to Gas phase polymerization

[0085] Polyethylene reactor transitions using metallocene catalysts that involve large density changes have historically proven difficult to maintain on-spec melt index, leading to significant quantities of off-spec material. A new approach has been discovered that avoids melt index excursions by controlling the effective hydrogen flow ratio by accounting for hydrogen generated in-reactor via a previously poorly characterized kinetic pathway. Implementation of this control scheme can significantly reduce transition losses caused by melt index spec excursions.

[0086] FIG. 3 shows an embodiment of a comparative control scheme 300 for inputs to a gas phase polymerization reactor. Hydrogen feed 310 is controlled by flow control valve 312, ethylene feed 320 is controlled by flow control valve 322, and comonomer feed 330 is controlled by flow control valve 332, to a gas phase polymerization reactor 340 are shown as inputs to the cycle gas line 350 in this simplified flow diagram. Analyzer 352 measures a hydrogen concentration (HC)and a C2H4 concentration (EC) of the cycle gas in cycle gas line 350. The H2 / C2 Concentration Ratio (HCR) is the ratio of the mole percentage of H2 in the cycle gas to the mole percentage of C2H4 in the cycle gas. The measured HCR value from analyzer 352 is sent to HC controller 354 to produce a signal to flow control valve 312. HC target or set point (SP) underthis process control system is:HCSP = HCR x ECwherein:HCSP is the hydrogen concentration target;HCR is the hydrogen to ethylene molar ratio; andEC is the ethylene concentration.

[0087] If measured HC is above the HCSP set point, the signal to flow control valve 312 will be to decrease H2 flow to cycle gas line 350. If measured HC is below the HCSP set point, the signal to flow control valve 312 will be to increase H2 flow to cycle gas line 350. If measured HC matches the HCSP set point, the signal to flow control valve 312 will be to maintain H2 flow to cycle gas line 350.

[0088] This control scheme is adequate for maintaining hydrogen feed rate or making minor adjustments as required to maintain a constant melt index of the polymer product. However, when significant changes are made to change polymer product grade, such as significantly increasing comonomer feed 330 through control valve 332 to decrease the density of the polymer product, it was originally believed that the increase in comonomer incorporated into the polymer backbone would decrease melt index and thus require an increase in in hydrogen feed 310 in order to maintain a constant melt index. Although it was correct that a higher hydrogen concentration is required to maintain a desired melt index after increasing comonomer feed, it has been discovered that fresh hydrogen addition is not the only significant source of hydrogen in the polymerization system. A second source of hydrogen supplied to the polymerization system is a kinetic pathway wherein hydrogen is generated from the comonomer.

[0089] FIG. 5A graphically represents density versus time for a density reduction from 0.935 g / cm3to 0.920 g / cm3. Line 1 shows the density set point, wherein the drop in the density at about 17:30 hours equates to a corresponding drop in the comonomer feed rate. Density measured by the laboratory is shown on line 3. The “steps” in line 2 indicate the time between tested polymer product samples. Line 2 shows density predicted by the control model:D2= 0.97 - (e x CA2 / (CA2+ EA2)) + ( / ’x MI2)wherein:D is density in g / cm3;0.97 is the density of polyethylene homopolymer;CA is the comonomer addition rate;EA is the ethylene addition rate;MI is the melt index (calculation shown below); ande and f are empirically determined constants associated with the catalyst and the comonomer.Good correlation between lines 2 and 3 indicates that the density model provides a good prediction of density changes in response to changes in comonomer addition rate. Further, good correlation between all of lines 1-3 at the right-hand side of the graph indicates that the density model provides a good prediction of steady state density as well as transitional density.

[0090] FIG. 5B graphically represents melt index versus time corresponding to the reduction from 0.935 g / cm3to 0.920 g / cm3as shown in FIG. 5A. Line 1 shows the melt index set point of 0.5 dg / min. At about 17:00 hours to 19:00 hours, melt index drops along with the drop in density shown in FIG. 5A. The “recipe” for higher density polymer at the same melt index was believed to be operation at a higher HCR. The response was to increase hydrogen addition to decrease molecular weight and increase melt index. However, this results in an apparent overcorrection with melt index spiking to over 0.7 dg / min. as compared to the set point of 0.5 dg / min. Melt index does not approach the set point level until about 07:30 hours. Therefore, in the scenario depicted by line 2 in FIG. 5B, use of the control scheme wherein hydrogen addition is based on cycle gas composition results in over 15 hours of production of off-spec material.

[0091] A new approach has been developed that avoids melt index excursions by controlling the “effective” hydrogen flow ratio by accounting for hydrogen generated in-reactor via a previously poorly characterized kinetic pathway. This has resulted in significantly reduced transition losses caused by melt index deviations from specification.

[0092] FIG. 4 shows an embodiment of an inventive control scheme 400 for inputs to a gas phase polymerization reactor. Hydrogen feed 410 is controlled by flow control valve 412, ethylene feed 420 is controlled by flow control valve 422, and comonomer feed 430 is controlled by flow control valve 432, to a gas phase polymerization reactor 440 are shown as inputs to the cycle gas line 450 in this simplified flow diagram. In control scheme 400, hydrogen addition 410 iscontrolled based on the ethylene addition 420 and the comonomer addition 430 instead of analyzer 452 measuring the composition of the cycle gas in cycle gas line 450.

[0093] The process to polymerize olefins in a gas phase polymerization reactor comprises adding ethylene, a comonomer, hydrogen, and a polymerization catalyst to a reaction zone of the gas phase polymerization reactor under first polymerization conditions to produce a first polyethylene having a first density and a first melt index (2.16 kg@190°C), wherein the first polymerization conditions comprise a first hydrogen addition rate (HAi) 410, a first ethylene addition rate (EAi) 420, and a first comonomer addition rate (CAi) 430;wherein:a first comonomer addition ratio (CARi) is defined as CAi / EAi;a first total hydrogen ratio (THRi) is defined as (HAi+HGi) / EAi;HGi is a first rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CAi;HGi = α x CARi; anda is an empirically determined constant associated with the catalyst and the comonomer.

[0094] In some embodiments, the first melt index (MIi) can be calculated according to Equation 1:MIi = exp(b + (c x HARi) + (d x CARi)) Eq. 1wherein:a first hydrogen addition ratio (HARi) is defined as HAi / EAi; and b, c, and d are empirically determined constants associated with the catalyst and the comonomer.

[0095] In some embodiments, the first density (Di) can be calculated according to Equation 2:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f x MIi) Eq. 2wherein:e and / are empirically determined constants associated with the catalyst and the comonomer.

[0096] In some embodiments, in addition to production of the first polyethylene, the process further comprises implementing second polymerization conditions to produce a second polyethylene having a second density and a second melt index, wherein second polymerizationconditions comprise a second hydrogen addition rate (HA2), a second ethylene addition rate (EA2), and a second comonomer addition rate (CA2);wherein:a second comonomer addition ratio (CAR2) is defined as CA2 / EA2;a second total hydrogen ratio (THR2) is defined as (HA2+HG2) / EA2;HG2 is a second rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CA2;HG2 = a x CAR2; anda is an empirically determined constant associated with the catalyst and the comonomer.

[0097] In some embodiments, in addition to production of the first and second polyethylenes, the first melt index (MIi) can be calculated according to Equation la, and the second melt index (MI2) can be calculated according to Equation lb:MIi = exp(A + (c x HARi) + d x CARi)) Eq. la MI2= exp(b + (c x HAR2) + (d x CAR2)) Eq. lb wherein:a first hydrogen addition ratio (HARi) is defined as HA1 / EA1;a second hydrogen addition ratio (HAR2) is defined as HA2 / EA2; and b, c, and d are empirically determined constants associated with the catalyst and the comonomer.

[0098] In some embodiments, in addition to production of the first and second polyethylenes, the first density (Di) can be calculated according to Equation lb, and the second density (D2) can be calculated according to Equation 2b:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f x MIi) Eq. 2a D2= 0.97 - (e x CA2 / (CA2+ EA2)) + ( / x Ml2) Eq. 2b wherein:e and / are empirically determined constants associated with the catalyst and the comonomer.

[0099] In some embodiments of the process producing a first polyethylene and transitioning to producing a second polyethylene, the second melt index is equal to the first melt index, and the second hydrogen addition rate is: i) greater than the first hydrogen addition rate when the seconddensity is greater than the first density; or ii) less than the first hydrogen addition rate when the second density is less than the first density.

[0100] In some embodiments of the process producing a first polyethylene and transitioning to producing a second polyethylene, the second hydrogen addition ratio is less than the first hydrogen addition ratio when the second density is greater than the first density, or the second hydrogen addition ratio is greater than the first hydrogen addition ratio when the second density is less than the first density.

[0101] In some embodiments of the process producing a first polyethylene and transitioning to producing a second polyethylene, the second comonomer addition ratio is less than the first comonomer addition ratio when the second density is greater than the first density, or the second comonomer addition ratio is greater than the first comonomer addition ratio when the second density is less than the first density.

[0102] In some embodiments of the processes disclosed herein, the comonomer is one or more C2-C18 alpha-olefins. In some embodiments of the processes disclosed herein, the one or more C2-Cis alpha-olefins are selected from 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 4-methylpent-l-ene, or a combination thereof.

[0103] In some embodiments of the processes disclosed herein, the first polyethylene and / or the second polyethylene has a density in the range of from 0.900 g / cm3to 0.945 g / cm3. In some embodiments of the processes disclosed herein, the first polyethylene and the second polyethylene each have a density in the range of from 0.900 g / cm3to 0.945 g / cm3.

[0104] In some embodiments of the processes disclosed herein, the difference between the first density and the second density is at least 0.005 g / cm3, at least 0.010 g / cm3, or at least 0.015 g / cm3. In some embodiments of the processes disclosed herein, the difference between the first density and the second density is no greater than 0.035 g / cm3, is no greater than 0.040 g / cm3, or no greater than 0.045 g / cm3.

[0105] In some embodiments of the processes disclosed herein, the first polyethylene has a melt index in the range of from density in the range of from 0.10 dg / min. to 20.0 dg / min. In some embodiments of the processes disclosed herein, the first polyethylene and the second polyethylene each have a melt index in the range of from density in the range of from 0.20 dg / min. to 10.0 dg / min.

[0106] In some embodiments of the processes disclosed herein, the polymerization catalyst comprises a Ziegler-Natta catalyst, a metallocene catalyst, or a combination thereof. In someembodiments of the processes disclosed herein, the metallocene catalyst comprises: a) an unbridged bis-cyclopentadienyl Group 4 and substituted versions thereof (Type 1); b) a bridged bis-cyclopentadienyl Group 4 and substituted versions thereof (Type 2); c) a substituted bulky ligand hafnium transition metal metallocene-type catalyst compound and substituted versions thereof (Type 3); d) a dual catalyst system comprising a bridged bis-cyclopentadienyl Group 4 metal catalyst and an unbridged bis-cyclopentadienyl Group 4 metal catalyst (Type 4); or e) a combination thereof.

[0107] In some embodiments, in processes producing a first polyethylene and / or processes producing a first polyethylene and transitioning to a second polyethylene, the first and / or second polyethylene comprises: a) a narrow-CD mLLDPE; b) a LCB-mLLDPE; c) a narrow MWD BOCD-mLLDPEs; d) a broad MWD BOCD-mLLDPE; or e) a combination thereof.

[0108] In some embodiments, in processes producing a first polyethylene and / or processes producing a first polyethylene and transitioning to a second polyethylene, the process further comprises adding an induced condensing agent (ICA) composition to the reaction zone. In further embodiments, the ICA composition comprises n-butane, isobutane, n-pentane, isopentane, neopentane, hexane, isohexane, or a combination thereof.

[0109] In some embodiments, in processes producing a first polyethylene, the first polymerization conditions are implemented by a control system. In further embodiments comprising transitioning to producing a second polyethylene, the second polymerization conditions are implemented by a control system. Infurther embodiments of either of the foregoing, the control system comprises a distributed control system (DCS), a direct digital controller (DDC), a programmable logic controller (PLC), or a combination thereof.Total Allowable Condensing Agent Composition

[0110] A fluidized bed process is performed where the velocity of the gaseous recycle stream is sufficient to maintain the reaction zone in a fluidized state. In a fluidized bed polymerization process, the amount of fluid circulated to remove the heat of polymerization may be greater than the amount of fluid needed for support of the fluidized bed and for adequate mixing of the solids in the fluidized bed. The excess velocity provides additional gas flow to (and through) the fluid bed for additional cooling capacity and more intensive mixing of the reactor bed. However, to prevent excessive entrainment of solids in a gaseous stream withdrawn from the fluidized bed, the velocity of the gaseous stream may be regulated.[OHl] A fluidized bed within a gas phase reactor may include reactive components, other reagents (anti-slip, anti-static), and inert components including inert gas and ICAs. The combination of all these components can make up 100% of the flow (e.g., of volume or mass balance) of gas in and through a gas phase reactor. The total allowable ICA composition (Z) is the amount of the combination of ICAs that is subject to the concentration of other components in the fluidized bed.

[0112] Therefore, in order to increase Z, a portion of another component of the gas stream may be decreased. An increase in Z may allow for greater cooling of the reactor and therefore increased production rates, but is limited by reactor volume and venting. Substantially all (e g., 100%) of the components entering the reactor leave the reactor either in the product stream or the recycle stream. Z is increased by decreasing another component. For example, an increase in Z may be accomplished by lower quantities of other inert compounds including nitrogen. Alternatively, Z may be increased by using monomer and comonomer feeds with fewer inert impurities, a higher purity feed may allow for increased addition of ICA composition.

[0113] The ratio of inert components can be varied, but may be limited by reactor venting. In order to maintain the mass balance for a given inert gas concentration, the inert gas flow into the reactor must equal the inert gas vented from the reactor. Reducing the concentration of inert gas in the reactor may result in more total vent flow. An increased vent flow may result in greater material loss and may also be limited by reactor design. For a given reactor producing a particular grade of polyolefin, the minimum inert gas can be ascertained based on a cost analysis balancing the reactor design including limits on vent flow and raw material loss associated with increased production rates related to improved cooling from a greater quantity of ICA composition. Because the reactive components and other components that aid in product formation may be specific to one embodiment of a desired product, they may be kept constant. Alternatively, Z may be increased by lowering the concentration of monomers or comonomers. Without being limited by theory, reduction of pressures of monomer and comonomer may decrease the catalyst activity, but it is possible that the cost associated with a decrease in catalyst activity is overcome by the improved production rates that accompany increased cooling from additional Z.

[0114] Furthermore, Z may be increased by increasing the overall reactor pressure. For example, if the individual components are at a specific partial pressure increasing the total pressure in the reactor would therefore increase pressure available to an ICA composition. An increase in pressure of the reactor may be limited by reactor design, feedstock pressures and compressioncosts, changes in the solubility and stickiness of the products and reactants. Therefore, the total allowable ICA composition may be a cost benefit analysis of individual options for increasing Z including, but not limited to removal of portions of other components or reactor pressurization. The cost analysis may take into account many factors including the catalyst activity, feedstock purity and availability, reactor design (in pressure, volume, and venting), product grades, and flow rates sufficient to fluidize the bed. The cost of any of these factors may be balanced by increased production rate resulting from improved cooling due to additional volume (or pressure) allotted to ICA composition.

[0115] In some embodiments, the total allowable amount of ICA composition is increased through use of a mixture of IC As, such as, but not limited to, isopentane and isobutane, isobutane and n-butane, n-hexane and iso-pentane, isobutane and propane, isopentane and neo-pentane, or neo-pentane and isobutane. Methods for optimizing mixtures of ICAs are disclosed in US 2022 / 0098332, the substance of which is fully incorporated by reference herein.Polyolefin Products

[0116] In some embodiments, the polyolefin products comprise polyethylene produced with a metallocene catalyst system. Metallocene catalysts produce in the gas phase polymerization process produce linear low density polyethylene (LLDPE). LLDPEs made using one or more metallocene catalysts are labeled herein as mLLDPE. The mLLDPE can include copolymers of 80 to 99.9 wt% ethylene-derived units, with the balance of units derived from one or more C3 to C12 a-olefin comonomers (and in particular one or more of butene, hexene, octene; and more preferably hexene). Metallocene catalysts include, but are not limited to: Type 1: an unbridged bis-cyclopentadienyl Group 4 and substituted versions thereof; Type 2: a bridged bis-cyclopentad ienyl Group 4 and substituted versions thereof; Type 3: a substituted bulky ligand hafnium transition metal metallocene-type catalyst compound and substituted versions thereof; and Type 4: a dual catalyst system comprising a bridged bis-cyclopentadienyl Group 4 metal catalyst and an unbridged bis-cyclopentadienyl Group 4 metal catalyst.Type 1 Metallocene Catalyst

[0117] In some embodiments, the metallocene catalyst is an unbridged bis-cyclopentadienyl Group 4 and substituted versions thereof. Such Type 1 catalysts produce polyethylene grades having a narrow composition distribution (i.e., a move uniform distribution of comonomer among polymer chains) and are referred to herein as narrow-CD mLLDPE.

[0118] In some embodiments, a narrow-CD mLLDPE comprises a flat composition distribution metallocene-catalyzed LLDPE (mLLDPE) that is a copolymer of 80 to 99.9 wt% ethylene-derived units, with the balance of units derived from one or more C3 to C12 a-olefin comonomer (and in particular one or more of butene, hexene, octene; preferably one of those; and more preferably hexene). The wt% is based on total mass of ethylene-derived units plus comonomer-derived units in the polyethylene. Such polyethylenes are referred to as “flat composition distribution” in recognition that comonomer is incorporated in relatively equal amounts (by wt%) in shorter vs. longer molecular-weight chains within the polymer. These also may be referred to as “narrow-CD” or “narrow-composition-distribution” polyethylenes; or, equivalently, high-CDBI mLLDPEs. Composition distribution refers to the distribution of comonomer among polymer chains of different length (different molecular weight), and CDBI refers to Composition Distribution Breadth Index, which is defined as the weight percent of the copolymer molecules (chains) having a comonomer content within 50% of the median total molar comonomer content, and it is described in U. S. Patent 5,382,630, which is hereby incorporated by reference. The CDBI of a copolymer is readily determined utilizing well known techniques for isolating individual fractions of a sample of the copolymer. One such technique is Temperature Rising Elution Fraction (TREF), as described in Wild, etal., J. Poly. Sci., Poly. Phys. Ed., vol. 20, p. 441 (1982) and U. S. PatentNo. 5,008,204, which are incorporated herein by reference. Thus, a higher value of CDBI indicates a narrow composition distribution (meaning that comonomer is distributed relatively evenly across polymer chains of different molecular weight).

[0119] The narrow-CD polyethylene may have CDBI of at least 50%, more preferably at least 60%, such as within the range from 50 to 90%, or 60 to 80%.

[0120] A narrow-CD polyethylene may more particularly have ethylene-derived content within the range from a low of any one of 80, 85, 86, 87, 87.5, 88, 90, 91, 92, 93, 94 or 95 wt%to a high of any one of 88, 90, 93, 94, 95, 96, 97, 98, 99, or 99.9 wt%; with ranges from any foregoing low to any foregoing high contemplated, provided the high end is greater than the low end (e.g., 85 to 95 wt%, such as 86 to 92 wt% ethylene-derived units; or 94 to 99 wt% ethylene-derived units). The balance is comprised of the C3to C12a-olefin comonomer-derived units (e.g., hexene).

[0121] The narrow-CD mLLDPE can provide reduced softening point relative to formation processes, and furthermore provide excellent sealing, optical, and mechanical properties to a film made therefrom. The narrow-CD mLLDPE preferably also has one or more, preferably all, of the following further properties:• Peak melting temperature within the range from 105°C to 120°C, preferably 110°C or 111°C to 115°C or 116°C. Peak melting temperature, also referred to herein by the shorthand “melting point” is determined by using a differential scanning calorimeter (DSC). DSC measurements can be carried out with a TA DSC8000 instrument under N2 atmosphere with a heating / cooling rate of 10 K / min. The samples are heated from -50 to 300°C., held for 5 minutes in order to remove the previous thermal history, then cooled down to -50°C, and then heated again to 300°C.• Vicat softening temperature (ASTM D 1525) within the range from softening point within the range from 70°C to 130°C, preferably 90°C to 110°C, such as from a low of any one of 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100°C to a high of any one of 100, 101, 102, 103, 104, 105, 110, 115, 120, 125, or 130°C (with ranges from any foregoing low to any foregoing high contemplated, provided the high is greater than the low, e.g., 90°C to 110°C or97°C to 103°C).• Melt index (MI, also referred to as I2 or I2. I6 in recognition of the 2.16 kg loading used in the test) within the range from 0.1 to 5.0 g / 10 min (ASTM D1238, 190°C, 2.16 kg load), such as from alow of any one of 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, or 0.8 g / 10 min to a high of any one of 1.0, 1.1, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 g / 10 min; with ranges from any foregoing low end to any foregoing high end also contemplated.• Long chain branching index (LCB Index, also referred to herein as g'vlsor g' index) greater than 0.95, preferably greater than or equal to 0.96 or 0.97.[0122 J The narrow-CD mLLDPE can also have one or more, preferably all of the following:• Weight average molecular weight (Mw) within the range from 45,000 to 120,000 g / mol, such as from 50,000 to 115,000 g / mol or 60,000 to 110,000 g / mol (with ranges from any foregoing low end to any foregoing high end also contemplated, e.g., 45,000 to 110,000 g / mol);• Number average molecular weight (Mn) within the range from 20,000 to 55,000 g / mol, such as within the range from 25,000; 30,000; 35,000; or 40,000 to a high of 30,000; 35,000; 40,000; 45,000; 50,000; or 55,000 g / mol, with ranges from any foregoing low end to any foregoing high end also contemplated (provided the high end is greater than the low end), e.g., from 35,000 to 55,000 g / mol;• Molecular weight distribution (MWD) within the range from 1.5 or 2.0 to 3.5 or 4; and• Density (ASTM DI 505) within the range from 0.905 to 0.940 g / cm3, such as within the range from a low end of any one of 0.905, 0.910, 0.911, 0.912, or 0.915 g / cm3to a high end of any one of 0.913, 0.914, 0.915, 0.920, 0.925, 0.926, 0.928, 0.930, 0.935, or 0.940 g / cm3, with ranges from any foregoing low end to any foregoing high end contemplated (provided the high end is greater than the low end), e.g., 0.910 to 0.915 g / cm3.

[0123] Examples of suitable polyethylenes for the narrow-CD mLLDPE include Exceed™ performance polyethylenes available from ExxonMobil Chemical Company, as well as other commercially available mLLDPEs such asEvolue™ SP1510, available from Prime Polymer Co., Ltd.

[0124] In some embodiments of the method disclosed herein, the catalyst is a Type 1 metallocene catalyst and the first polyethylene is a first narrow-CD mLLDPE and the second polyethylene is a second narrow-CD mLLDPE. The first narrow-CD mLLDPE and the second narrow-CD mLLDPE can be the same or different narrow-CD mLLDPEs.

[0125] In some embodiments, where a Type 1 metallocene catalyst is employed, the first polyethylene is a first narrow-CD mLLDPE, and the second polyethylene is a second narrow-CD mLLDPE. The first narrow-CD mLLDPE has a first density in the range of from 0.910 g / cm3to 0.930 g / cm3, and a first melt index (I2) is in the range of from 0.80 dg / min. to 5.0 dg / min. The second narrow-CD mLLDPE has a second density is in the range of from 0.910 g / cm3to 0.930 g / cm3, and a second melt index (I2) is in the range of from 0.80 dg / min. to 5.0 dg / min.; or a combination thereof.Type 2 Metallocene Catalyst

[0126] In some embodiments, the metallocene catalyst is a bridged bis-cyclopentadienyl Group 4 and substituted versions thereof, as disclosed in one or more of U. S. Pat. No. 6,255,426 and 6,476,171, the contents of which are fully incorporated by reference herein. Such Type 2 catalysts produce polyethylene grades having some long-chain branching (as compared to the highly linear structure of most mLLDPEs), and are referred to herein as “LCB-mLLDPE.”

[0127] Long chain branched mLLDPEs (“LCB mLLDPE”) are considered long-chain-branched as compared to other linear low-density polyethylenes, and in particular as compared to other metallocene LLDPEs; whereas their total long-chain branching will still be less than LDPEs with very high degrees of long-chain branching.) This small amount of LCB can be evidenced through, e.g., a high melt index ratio (MIR) and / or particular rheology characteristics as shown through data obtained by small angle oscillatory shear (SAGS) experiments (for instance, ratio ofη0.01 / η100, the complex viscosity recorded at shear rates of 0.01 and 100 rad / s, respectively). Another useful parameter for indicating the presence of LCB is illustrated in Figure 4: Van Gurp Palmen (VGP) plots. In particular, polyethylene copolymers (even LLDPE) with some LCB will exhibit an inflection point in their V GP curve, while LLDPE without any LCB present show no such inflection point. See, for example, the Enable™ brand LLDPEs, examples of LCB-mLLDPEs, in FIG. 4, as compared to the XP8318, which is an example of the narrow -MWD BOCD-mLLDPEs discussed below.

[0128] Y et another useful parameter illustrating presence of some LCB can be seen in the melt index ratio. Melt index ratio (MIR) is the ratio of high load melt index (HLMI, ASTM D1238 at 190 °C, 21.6 kg) to melt index (MI2, ASTMD1238 at 190°C, 2.16 kg).

[0129] Accordingly, LCB-mLLDPEs useful for the present compositions can have one or more of the following properties (which can be useful indicia of moderate LCB):• MIR within the range from a low of any one of 20, 25, 26, 27, 28, 29, 30, or 31 to a high of any one of 40, 35, 34, 33, 32, 31, or 30 with ranges from any of the foregoing lows to any of the foregoing highs contemplated herein (e.g., 27 to 33, such as 28 to 32, or 29 to 31).• Complex shear viscosity (r|*) @ 0.01 rad / sec and 190° C in the range of 5,000 to 12,000 Pa s; or from a low of anyone of 5,000; 6,000; 7,000; 8,000; 9,000; 10,000; or 11,000 Pa s, to a high of any one of 12,000; 11,000; 10,000; 9,000; 8,000; 7,000; or 6,000 Pa s, with ranges from any low end to any high end contemplated (e.g., 6,000 to 8,000 Pa s).• Complex shear viscosity (r|*) @ 100 rad / sec and 190° C within the range from 900 to 2000 Pa s; such as from a low end of any one of 900; 1,000; 1,100; or 1,200 Pa s to a high end of any one of 1,200; 1,300; 1,400; 1,500; or 2,000 Pa s, with ranges from any foregoing low to any foregoing high also contemplated (e.g., 1,100 to 1,300 Pa s).• Shear thinning ratio (r|* @ 0.01 / 100) less than 15, or in the range of 3 to 15, or 4 to 12, or 5 to 10, or 5.5 to 8.• An inflection point in a Van Gurp Palmen plot of phase angle vs. complex modulus (Pa) of the LCB-mLLDPE.

[0130] Finally, yet another indicator of LCB can be seen in the LCB index (g1or alternatively g'vis), which for LCB-mLLDPE could be less than 1, such as within the range from 0.9 to 0.99 or 0.94 to 0.98, although still substantially higher than g' for heavily-LCB polyethylene, such as LDPE made using free radical polymerization.

[0131] Suitable mLLDPEs with the aforementioned moderate LCB are preferably copolymers of 80, 85, 88, 90, 92, 93, 94, or 95 to 96, 97, 98, or 99 wt% ethylene-derived units, with the balance derived from one or more C3 to C12 a-olefins (and in particular one or more of butene, hexene, octene; preferably one of those; and more preferably hexene). The wt% is based on total mass of ethylene-derived units plus comonomer-derived units in the polyethylene.

[0132] Suitable LCB mLLDPEs can also have a CDBI greater than or equal to 60%, preferably greater than or equal to 70%, such as within the range from a low of any one of 60, 70, or 75% to a high of 80, 85, 90, 95, or 99%, with ranges from any foregoing low end to any foregoing high end contemplated. Composition Distribution Breadth Index (" CDBI") is defined as the weight percentage of the copolymer molecules having a comonomer content within 50% of the median total molar comonomer content. The CDBI of a copolymer is readily determined utilizing well known techniques for isolating individual fractions of a sample of the copolymer. One such technique is Temperature Rising Elution Fraction (TREF), as described in Wild, et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, p. 441 (1982) and U. S. Patent No. 5,008,204, which are fully incorporated herein by reference.

[0133] Suitable LCB mLLDPEs can also have a MWD (Mw / Mn) within the range of 2.5 to 5.5, such as within the range of 3 or 3.5 to 4.5 or 5.

[0134] Suitable LCB mLLDPEs can further have a Melt Index (I2, determined per ASTM DI 238 at 190°C, 2.16 kg load) within the range of 0.1 to 3.0 g / 10 min, or can range from a low of any one of 0.1, 0.15, 0.2, or 0.22 to a high of any one of 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.5, 2.0, 2.2, 2.5, 2.7, or 3.0 g / 10 min; with ranges from any foregoing low end to any foregoing high end also contemplated (provided the high end is greater than the low end), e.g., from 0.1 to 2.5 g / 10 min; 0.15 to 1.0 g / 10 min; or 0.2 to 0.50 g / 10 min.

[0135] High load melt index (HLMI, or I21, determined per ASTM D1238 at 190°C, 21.6 kg load) can be within the range from 10 to 75 g / 10 min, such as from 12 to 70 g / 10 min.• Density of the LCB-mLLDPE can be within the range from 0.900 to 0.940 g / cm3, such as from a low of any one of 0.905, 0.910, 0.920, or 0.925 g / cm3to a high of any one of 0.930, 0.932, 0.933, 0.934, 0.935, or 0.940 g / cm3, with ranges from any forgoing low to any foregoing high contemplated herein (e g., 0.910 to 0.935 g / cm3).

[0136] These LCB-mLLDPEs can be referred to as a “first mLLDPE” in compositions described herein. Some particular examples of such first mLLDPEs having the foregoing unique combination of properties include certain Enable™ and Exceed™ XP brand polyethylenes fromExxonMobil Chemical Company, such as Exceed™ XP 6026, Enable™ 2010, Enable™ 2703, Enable™ 3505, Enable™ 4002, and Enable™ 4009 performance polyethylenes. Other commercial examples include Dow Innate™ ST70, Dow Agility™ 2001, Dow Elite™ 5940, Dowlex™ 2038.68G, Dow Elite™ AT 6401, Dow Attane™ 4701G, Marlex™ TR130, and Nova Surpass™ 117 / 116.- Type 3 Metallocene Catalyst

[0137] In some embodiments, the metallocene catalyst is a substituted bulky ligand hafnium transition metal metallocene-type catalyst compound and substituted versions thereof, as disclosed in one or more of U. S. Pat. Nos. US 9,181,362, 6,242,545, 7,078,467, RE40751 11,214.659, and 9,695,290; and U. S. Pub. Nos. 2015 / 240000, 2015 / 259445, and 2015 / 284523, the contents of which are fully incorporated by reference herein. Such Type 3 catalysts produce polyethylene grades having narrow MWD with a broad orthogonal comonomer distribution (“BOCD”), which may be referred to herein as Narrow MWD BOCD-mLLDPEs.

[0138] As mentioned above, a suitable mLLDPE can have a narrow molecular weight distribution (MWD) with broad orthogonal composition distribution (BOCD). The molecular weight distribution (MWD) or (Mw / Mn) can range from about 2.0 to about 4.5, from about 2.2 to about 4.5, from about 3.0 to about 4.0, or from about 2.5 to about 4.0. The weight average molecular weight (Mw) can range from about 15,000 to about 400,000 g / mol, from about 20,000 to about 250,000 g / mol, from about 20,000 to about 200,000 g / mol, from about 25,000 to about 150,000 g / mol, from about 150,000 to about 400,000 g / mol, from about 200,000 to about 400,000 g / mol, or from about 250,000 to about 350,000 g / mol. The z-average molecular weight (Mz) to weight average molecular weight (Mw) ratio can be greater than about 1.5, or greater than about 1.7, or greater than about 2.0. In some embodiments, this ratio is from about 1.7 to about 3.5, from about 2.0 to about 3.0, or from about 2.2 to about 3.0.

[0139] The term "orthogonal comonomer distribution" is used herein to mean across the molecular weight range of the polymer, comonomer contents for the various polymer fractions are not substantially uniform and a higher molecular weight fraction thereof generally has a higher comonomer content than that of a lower molecular weight fraction. The term "substantially uniform comonomer distribution" is used herein to mean that comonomer content of the polymer fractions across the molecular weight range of the ethylene-based polymer vary by < 10.0 wt%. In some embodiments, a substantially uniform comonomer distribution may refer to < 8.0 wt%, < 5.0 wt%, or < 2.0 wt%. Both a substantially uniform and an orthogonal comonomer distributionmay be determined using fractionation techniques such as gel permeation chromatographydifferential viscometry (GPC-DV), temperature rising elution fraction-differential viscometry (TREF-DV) or cross-fractionation techniques.

[0140] The broadness of the composition distribution of the polymer may be characterized by T75-T25. TREF is measured using an analytical size TREF instrument (Polymerchar, Spain), with a column of the following dimensions: inner diameter (ID) 7.8 mm, outer diameter (OD) 9.53 mm, and column length of 150 mm. The column may be filled with steel beads. 0.5 mL of a 4 mg / ml polymer solution in orthodichlorobenzene (ODCB) containing 2 g BHT / 4 L were charge onto the column and cooled from 140°C to -15°C at a constant cooling rate of 1.0°C / min Subsequently, ODCB may be pumped through the column at a flow rate of 1.0 ml / min, and the column temperature may be increased at a constant heating rate of 2°C / min to elute the polymer. The polymer concentration in the eluted liquid may then be detected by means of measuring the absorption at a wavenumber of 2941 cm⁻¹ using an infrared detector. The concentration of the ethylene-a-olefin copolymer in the eluted liquid may be calculated from the absorption and plotted as a function of temperature. As used herein, T75-T25 values refer to where T25 is the temperature in degrees Celsius at which 25% of the eluted polymer is obtained and T75 is the temperature in degrees Celsius at which 75% of the eluted polymer is obtained via a TREF analysis.

[0141] By “broad orthogonal comonomer distribution” or BOCD, it is meant that a substantially higher degree of short chain branching is present on longer molecular-weight polymer chains than on shorter molecular-weight polymer chains within the copolymer. Suitable narrow-MWD mLLDPEs with BOCD can have a T75-T25 value from 5 to 10, alternatively, a T75-T25 value from 5.5 to 10, and alternatively, a T75-T25 value from 5.5 to 8, alternatively, a T75-T25 value from 6 to 10, and alternatively, a T75-T25 value from 6 to 8, where T25 is the temperature in degrees Celsius at which 25% of the eluted polymer is obtained and T75 is the temperature in degrees Celsius at which 75% of the eluted polymer is obtained via temperature rising elution fractionation (TREF).

[0142] These mLLDPEs can have a CDBI of less than about 40%, or less than about 35%, or less than about 30%, or less than about 25%. The CDBI can also range from a low of about 15%, 20%, or 25% to a high of about 30%, 35%, or 40%, and it is further noted that composition distribution is such that higher molecular weight chains of these mLLDPEs have greater wt% of comonomer than lower molecular weight chains of the mLLDPEs.

[0143] These mLLDPEs can have 70.0 wt% to 100.0 wt% of units derived from ethylene. The lower limit on the range of ethylene content may be from 70.0 wt%, 75.0 wt%, 80.0 wt%, 85.0 wt%, 90.0 wt%, 92.0 wt%, 94.0 wt%, 95.0 wt%, 96.0 wt%, 97.0 wt%, 98.0 wt%, or 99.0 wt% based on the wt% of polymer units derived from ethylene. These mLLDPEs can also have an upper ethylene limit of 80.0 wt%, 85.0 wt%, 90.0 wt%, 92.0 wt%, 94.0 wt%, 95.0 wt%, 96.0 wt%, 97.0 wt%, 98.0 wt%, 99.0 wt%, 99.5 wt%, or 100.0 wt%, based on polymer units derived from ethylene. Less than 30.0 wt% of polymer units can be derived from a C3- C20 olefin, preferably, an alpha-olefin, e.g., hexene or octene. The lower limit on the range of C3-C20 olefin-content can be 25.0 wt%, 20.0 wt%, 15.0 wt%, 10.0 wt%, 8.0 wt%, 6.0 wt%, 5.0 wt%, 4.0 wt%, 3.0 wt%, 2.0 wt%, 1.0 wt%, or 0.5 wt%, based on polymer units derived from the C3-C20 olefin. The upper limit on the range of C3-C20 olefin-content can be 20.0 wt%, 15.0 wt%, 10.0 wt%, 8.0 wt%, 6.0 wt%, 5.0 wt%, 4.0 wt%, 3.0 wt%, 2.0 wt%, or 1.0 wt%, based on polymer units derived from the C3 to C20 olefin.

[0144] These mLLDPEs can have a density in accordance with ASTM D-4703 and ASTM D-1505 / ISO 1183 of from about 0.900 g / cm3to about 0.940 g / cm3, from about 0.910 g / cm3to about 0.935 g / cm3, from about 0.900 g / cm3to about 0.930 g / cm3, from about 0.900 g / cm3to about 0.925 g / cm3, from about 0.900 g / cm3to about 0.923 g / cm3, from about 0.900 g / cm3to about 0.920 g / cm3, from about 0.912 g / cm3to about 0.919 g / cm3, from about 0.912 g / cm3to about 0.918 g / cm3, from about 0.914 g / cm3to about 0.918 g / cm3, or from about 0.915 g / cm3to about 0.918 g / cm3.

[0145] These mLLDPEs can have a melt index (MI) or (I2. I6) as measured by ASTM D-1238-E (190°C / 2.16 kg) of about 0.1 g / 10 min to about 5.0 g / 10 min, about 0.1 g / 10 min to about 3.0 g / 10 min, about 0.1 g / 10 min to about 2.0 g / 10 min, about 0.1 g / 10 min to about 1.2 g / 10 min, about 0.2 g / 10 min to about 1.5 g / 10 min, about 0.2 g / 10 min to about 1.1 g / 10 min, about 0.3 g / 10 min to about 1.0 g / 10 min, about 0.4 g / 10 min to about 1.0 g / 10 min, about 0.5 g / 10 min to about 1.0 g / 10 min, about 0.6 g / 10 min to about 1.0 g / 10 min, about 0.7 g / 10 min to about 1.0 g / 10 min, or about 0.75 g / 10 min to about 0.95 g / 10 min.

[0146] These mLLDPEs can have a melt index ratio (MIR) (I21.6 / I2. I6) (as defined below) of from about 20.0 to about 35.0, from about 22 to about 38, from about 20 to about 32, from about 25 to about 32 or from about 28 to about 31.

[0147] These mLLDPEs can also have at least a first peak and a second peak in a comonomer distribution analysis, wherein the first peak has a maximum at a log(Mw) value of from 4.0 to 5.4, or from 4.3 to 5.0, or from 4.5 to 4.7; and aTREF elution temperature of from 70.0°C to 100.0°C,or from 80.0°C to 95.0°C, or from 85.0°C to 90.0°C. The second peak in the comonomer distribution analysis has a maximum at a log(Mw) value of 5.0 to 6.0, 5.3 to 5.7, or 5.4 to 5.6; and a TREF elution temperature of 40.0°C to 60.0°C, 45.0°C to 60.0°C, or 48.0°C to 54.0°C.

[0148] In any of the embodiments described above, a suitable mLLDPE can have a narrow MWD with broad orthogonal composition distribution with one or more of the following properties: a melt index (MI) (190°C / 2.16 kg) of from about 0.1 g / 10 min to about 5.0 g / 10 min; a melt index ratio (MIR) of from about 25 to about 32; a Mwof from about 20,000 to about 200,000 g / mol; a Mw / Mnof from about 2.0 to about 4.5; and a density of from about 0.900 g / cm3to about 0.940 g / cm3. These narrow MWD BOCD-mLLDPEs may be referred to as a “second mLLDPE” in recycled resin compositions of the present disclosure.

[0149] Commercially available examples of such second mLLDPEs having the foregoing unique combination of properties include Exceed XP™ resins from ExxonMobil Chemical Company.- Type 4 Metallocene Catalyst

[0150] In some embodiments, the metallocene catalyst is a dual catalyst system comprising a bridged bis-cyclopentadienyl Group 4 metal catalyst and an unbridged bis-cyclopentadienyl Group 4 metal catalyst, as disclosed in one or more of U. S. Pat. Nos. 10,611,867, 10,808,053, and 11,274,196; WIPO Publication WO2019 / 108327; and U. S. Pub. No. 2021 / 0238321, the contents of which are fully incorporated by reference herein (and which further include description of relevant mLLDPEs). Such Type 4 catalysts produce polyethylene grades having broad MWD with a broad orthogonal comonomer distribution (“BOCD”), which are referred to herein as a “Broad-MWD BOCD-mLLDPE.”

[0151] As mentioned above, other suitable mLLDPEs can have a broad molecular weight distribution (MWD) with a broad orthogonal composition distribution (BOCD). The MWD of these mLLDPEs can range, for example, from about 6.0 to about 10.0, from about 6.4 to about 9.5, from about 6.0 to about 9.0, from about 6.5 to about 10.0, or from 7.0 to 8.5.

[0152] These mLLDPEs can have a density in accordance with ASTM D-4703 and ASTM D-1505 / ISO 1183 of from about 0.900 g / cm3to about 0.940 g / cm3, from about 0.910 to about 0.935 g / cm3, from about 0.910 g / cm3to about 0.930 g / cm3, from about 0.900 g / cm3to about 0.925 g / cm3, from about 0.900 g / cm3to about 0.933 g / cm3, from about 0.900 g / cm3to about 0.920 g / cm3, from about 0.912 g / cm3to about 0.919 g / cm3, from about 0.912 g / cm3to about 0.938 g / cm3, from about 0.914 g / cm3to about 0.928 g / cm3, or from about 0.915 g / cm3to about 0.938 g / cm3.

[0153] These mLLDPEs can have a branching index (as defined herein) of g'vis > 0.95, > 0.96, > 0.97, > 0.98, > 0.99 or 1.0, for example, from 0.95 to 1.0, from 0.96 to 1.0, from 0.97 to 0.995, from 0.98 to 0.998, from 0.98 to 0.99, from 0.99 to 1.0. Preferably, the g'vis is > 0.98 or > 0.995.

[0154] Suitable Broad MWD BOCD-mLLDPEs can have a BOCD characterized in that the T75-T25 value is 15°C or greater, 17.5°C or greater, 20°C or greater, 25°C or greater, 30°C or greater, 35°C or greater, 40°C or greater, or 45°C or greater, wherein T25 is the temperature (°C) at which 25% of the eluted polymer is obtained and T75 is the temperature (°C) at which 75% of the eluted polymer is obtained in a TREF experiment. For instance, the T75-T25 value for these Broad MWD BOCD-mLLDPEs can be within the range from 30°C or 35°C to 55°C, 55°C, 60°C, or 65°C (with ranges from any foregoing low end to any foregoing high end contemplated).

[0155] These mLLDPEs can have a CDBI of less than about 40%, or less than about 35%, or less than about 34%, or less than about 33%. The CDBI can also range from a low of about 15%, 20%, or 25% to a high of about 35%, 37%, or 40%, and the composition distribution (or comonomer distribution) is such that the mLLDPE has a greater amount (wt%) of comonomer incorporated in its longer (higher molecular weight) polymer chains than the amount (wt%) of comonomer incorporated in its shorter (lower molecular weight) polymer chains. As noted already, GPC analytical methods are suitable for determining relative amounts of comonomer incorporation at high and low polymer chains. For an example of some such polymers and discussion of the incorporation of comonomer along their chains, see, e.g., PCT / US2021 / 072552, filed 22 Nov 2021, entitled “Medium Density Polyethylene Compositions with Broad Orthogonal Composition Distribution”, and hereby incorporated by reference. These broad-MWD BOCD-mLLDPEs can be referred to as “third mLLDPEs” in recycled resin compositions of the present disclosure.

[0156] In any of the embodiments described above, a suitable third mLLDPE can have a broad MWD (e.g., Mw / Mn from about 6.0 to about 10) with broad orthogonal CD and a density of from about 0.900 to about 0.940 g / cm3.

[0157] In some embodiments of the method disclosed herein, the catalyst is a Type 4 metallocene catalyst and the first polyethylene is a first broad MWD BOCD-mLLDPE and the second polyethylene is a second broad MWD BOCD-mLLDPE. The first broad MWD BOCD-mLLDPE and the second broad MWD BOCD-mLLDPE can be the same or different broad MWD BOCD-mLLDPE.

[0158] In some embodiments of the method disclosed herein, the catalyst is a Type 4 metallocene catalyst and the first polyethylene is a first broad MWD BOCD-mLLDPE and thesecond polyethylene is a second broad MWD BOCD-mLLDPE. The first broad MWD BOCD-mLLDPE and the second broad MWD BOCD-mLLDPE can be the same or different broad MWD BOCD-mLLDPE.

[0159] In some embodiments, where a Type 4 metallocene catalyst is employed, the first polyethylene is a first broad MWD BOCD-mLLDPE, and the second polyethylene is a second broad MWD BOCD-mLLDPE. The first broad MWD BOCD-mLLDPE has a first density in the range of from 0.915g / cm3to 0.930 g / cm3, and a first melt index (I2) is in the range of from 0.60 dg / min. to 2.5 dg / min. The second broad MWD BOCD-mLLDPE has a second density is in the range of from 0.915g / cm3to 0.930 g / cm3, and a second melt index (I2) is in the range of from 0.60 dg / min. to 2.5 dg / min.; or a combination thereof.Certain Embodiments

[0160] Disclosed herein is a process to polymerize olefins in a gas phase polymerization reactor, wherein the hydrogen addition to the reactor is controlled based on the feed rate of ethylene and the feed rate of comonomer. The process comprises adding ethylene, a comonomer, hydrogen, and a polymerization catalyst to a reaction zone of the gas phase polymerization reactor under first polymerization conditions to produce a first polyethylene having a first density and a first melt index (2.16 kg@190°C), wherein the first polymerization conditions comprise a first hydrogen addition rate (HAi), a first ethylene addition rate (EAi), and a first comonomer addition rate (CAi). A first comonomer addition ratio (CARi) is defined as CA1 / EA1. A first total hydrogen ratio (THRi) is defined as (HAi+HGi) / EAi. HGi is a first rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CAi. HGi = a x CARi, wherein a is an empirically determined constant associated with the catalyst and the comonomer. In some embodiments, the control set point is then based on the ratio of the hydrogen addition rate to the ethylene addition rate. In some embodiments, the process further comprises adding an induced condensing agent (ICA) composition to the reaction zone, wherein in further embodiments, the ICA composition comprises n-butane, isobutane, n-pentane, isopentane, neo-pentane, hexane, isohexane, or a combination thereof.

[0161] In some embodiments, in addition to the limitations of any one of the foregoing embodiments of the process, the process is further characterized by one of more of the following:a) the first melt index (MIi) can be calculated according to Equation 1:MIi = exp(b + (c x HARi) + (d x CARi)) Eq. 1wherein:a first hydrogen addition ratio (HARi) is defined as HA1 / EA1; and / ?, c, and d are empirically determined constants associated with the catalyst and the comonomer;b) the first density (Di) can be calculated according to Equation 2:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f× MI1) Eq. 2 wherein e and fare empirically determined constants associated with the catalyst and the comonomer; orc) a combination thereof.

[0162] In some embodiments, in addition to the limitations of each of the foregoing embodiments, the process further comprises implementing second polymerization conditions to produce a second polyethylene having a second density and a second melt index, wherein second polymerization conditions comprise a second hydrogen addition rate (HA2), a second ethylene addition rate (EA2), and a second comonomer addition rate (C A2). A second comonomer addition ratio (CAR2) is defined as CA2 / EA2. A second total hydrogen ratio (THR2) is defined as (HA2+HG2) / EA2. HG2 is a second rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CA2. HG2 = a x CAR2. a is an empirically determined constant associated with the catalyst and the comonomer.

[0163] In some embodiments of the process comprising first polymerization conditions followed by implementing second polymerization conditions, the process is further characterized by one of more of the following:a) the first melt index (MIi) can be calculated according to Equation la, and the second melt index (MI2) is calculated according to Equation lb:MIi = exp(b + (c x HARi) + (d x CARi)) Eq. 1a MI2 = exp(b + (c x HAR2) + (d x CAR2)) Eq. 1b wherein:a first hydrogen addition ratio (HARi) is defined as HA1 / EA1;a second hydrogen addition ratio (HAR2) is defined as HA2 / EA2; and b, c, and d are empirically determined constants associated with the catalyst and the comonomer;b) the first density (Di) can be calculated according to Equation lb, and the second density (D2) can be calculated according to Equation 2b:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f× MIi) Eq. 2aD2= 0.97 - (e x CA2 / (CA2+ EA2)) + (fx MI2) Eq. 2b wherein e and / are empirically determined constants associated with the catalyst and the comonomer; andc) a combination thereof.

[0164] In some embodiments of the process comprising first polymerization conditions followed by implementing second polymerization conditions, the process is further characterized by one of more of the following:a) the second melt index is equal to the first melt index; and the second hydrogen addition rate is: i) greater than the first hydrogen addition rate when the second density is greater than the first density; or ii) less than the first hydrogen addition rate when the second density is less than the first density;b) the second hydrogen addition ratio is less than the first hydrogen addition ratio when the second density is greater than the first density; or the second hydrogen addition ratio is greater than the first hydrogen addition ratio when the second density is less than the first density;c) the second comonomer addition ratio is less than the first comonomer addition ratio when the second density is greater than the first density; or the second comonomer addition ratio is greater than the first comonomer addition ratio when the second density is less than the first density; ord) a combination thereof.

[0165] In some embodiments of the process, in addition to the limitations of any one of the foregoing embodiments, the process is further characterized by one or more of the following: a) the comonomer is one or more C2-C18alpha-olefins, wherein in further embodiments, the one or more C2-C18alpha-olefins are selected from 1-butene, 1-pentene, 1-hexene, 1 -heptene, 1 -octene, 4-methylpent-l-ene, or a combination thereof;b) the first polyethylene and the second polyethylene, where applicable, each have a density in the range of from 0.900 g / cm3to 0.945 g / cm3;c) the difference between the first density and the second density, where applicable, is at least 0.005 g / cm3, at least 0.010 g / cm3, or at least 0.015 g / cm3.d) the first polyethylene and the second polyethylene, where applicable, each have a melt index in the range of from density in the range of from 0.10 dg / min. to 20.0 dg / min.e) the polymerization catalyst comprises a Ziegler-Natta catalyst, a metallocene catalyst, or a combination thereof, wherein in further embodiments, the metallocene catalyst comprises:i) an unbridged bis-cyclopentad ienyl Group 4 and substituted versions thereof; ii) a bridged bis-cyclopentadienyl Group 4 and substituted versions thereof; ii) a substituted bulky ligand hafnium transition metal metallocene-type catalyst compound and substituted versions thereof;iv) a dual catalyst system comprising a bridged bis-cyclopentadienyl Group 4 metal catalyst and an unbridged bis-cyclopentadienyl Group 4 metal catalyst; or v) a combination thereof;f) the first polyethylene and the second polyethylene, where applicable, comprises: i) a narrow-CD mLLDPE;ii) a LCB -mLLDPE;iii) a narrow MWD BOCD-mLLDPEs;iv) a broad MWD BOCD-mLLDPE; orv) a combination thereof; andg) the first polymerization conditions and the second polymerization conditions, where applicable, are implemented by a control system, wherein in further embodiments, the control system comprises a distributed control system (DCS), a direct digital controller (DDC), a programmable logic controller (PLC), or a combination thereof.Test Method s / Polymer Characterization

[0166] Density (g / cm3): Density measurements were made following ASTMD-1505.

[0167] Gel permeation chromatography (“GPC”) 4D Methodology:a) Unless otherwise indicated, the distribution and the moments of molecular weight (Mw, Mn, Mz, Mw / Mn, etc.), the comonomer content (C2, C3, Ce, etc.), the branching index (g'), and CCDI (Mw-specific, 5-95, and Mn-Mz) are determined by using a high temperature Gel Permeation Chromatography (Polymer Char GPC-IR) equipped with a multiple-channel bandfilter based Infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10-pm Mixed -B LS columns are used to provide polymer separation. Aldrich reagent grade 1,2,4- trichlorobenzene (“TCB”) with 300 ppm antioxidant butylated hydroxy toluene (“BHT”) is used as the mobile phase. The TCB mixture is filtered through a 0.1-pm Teflon filter and degassed with an online degasserbefore entering the GPC instrument.The nominal flow rate is 1.0 ml / min. and the nominal injection volume is 200 pl. The whole system including transfer lines, columns, and detectors are contained in an oven maintained at 145°C. Given amount of polymer sample is weighed and sealed in a standard vial with 80-pl flow marker (heptane) added to it. After loading the vial in the autosampler, polymer is automatically dissolved in the instrument with 8 ml added TCB solvent. The polymer is dissolved at 160°C with continuous shaking for about 1 hour for most polyethylene samples or 2 hours for polypropylene samples. The TCB densities used in concentration calculation are 1.463 g / ml at room temperature and 1.284 g / ml at 145°C. The sample solution concentration is from 0.2 to 2.0 mg / ml, with lower concentrations being used for higher molecular weight samples. The concentration (c), at each point in the chromatogram is calculated from the baseline-subtracted IR5 broadband signal intensity (7), using the following equation: c = βI, where β is the mass constant. The mass recovery is calculated from the ratio of the integrated area of the concentration chromatography over elution volume and the injection mass which is equal to the pre-determined concentration multiplied by injection loop volume. The conventional molecular weight (IR MW) is determined by combining universal calibration relationship with the column calibration which is performed with a series of monodispersed polystyrene (PS) standards ranging from 700 to 10M g / mole. The MW at each elution volume is calculated with following equation:log M = (a_PS / (a+1)) log M_PS + log(K_PS / K)×(1 / (a+1))° a+1 a-i-1 °where the variables with subscript “PS” stand for polystyrene while those without a subscript are forthe test samples. In this method, aps=0.67 and Kps=0.000175, while a and K for other materials are as calculated and published in literature (Sun, T. et al. Macromolecules 2001, 34, 6812), except that for purposes of this invention and claims thereto, a=0.695 and K=0.000579 for linear ethylene polymers, a=0.705 and K = 0.0002288 for linear propylene polymers, a=0.695 and K=0.000181 for linear butene polymers, a is 0.695 and K is 0.000579 x (1 -0.0087 x w2b + 0.000018 x (w2b)2) for ethylene-butene copolymer where w2b is a bulk weight percent of butene comonomer, a is 0.695 and K is 0.000579 x (1 - 0.0075 x w2b) for ethylenehexene copolymer where w2b is a bulk weight percent of hexene comonomer, and a is 0.695 and K is 0.000579 x (1 - 0.0077 x w2b) for ethylene-octene copolymer where w2b is a bulk weight percent of octene comonomer. Concentrations are expressed in g / cm3, molecularweight is expressed in g / mole, and intrinsic viscosity (hence K in the Mark-Houwink equation) is expressed in dl / g unless otherwise noted.b) The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CH2 and CH3 channel calibrated with a series of PE and PP homo / copolymer standards whose nominal value are predetermined by NMR or FUR. In particular, this provides the methyls per 1000 total carbons (“CH3 / 1000TC”) as a function of molecular weight. The short-chain branch (“SCB”) content per 1000TC (“SCB / 1000TC”) is then computed as a function of molecular weight by applying a chain-end correction to the CH3 / 1000TC function, assuming each chain to be linear and terminated by a methyl group at each end. The weight % comonomer is then obtained from the following expression in which is 0.3, 0.4, 0.6, 0.8, and so on for C3, C4, Ce, Cs, and so on co-monomers, respectively:w2 = * SCB / 1000TC.c) The bulk composition of the polymer from the GPC-IR and GPC-4D analyses is obtained by considering the entire signals of the CH3 and CH2 channels between the integration limits of the concentration chromatogram. First, the following ratio is obtainedArea of CH₃ signal within integration limitsBulk 1R ratioArea of CH₂ signal within integration limitsd) Then the same calibration of the CH2 and CH3 signal ratio, as mentioned previously in obtaining the CH3 / 1000TC as a function of molecular weight, is applied to obtain the bulk CH3 / 1000TC. A bulk methyl chain ends per 1000TC (“bulk CH3end / 1000TC”) is obtained by weight- averaging the chain-end correction over the molecular-weight range. Thenw2' b ~ * bulk CH3 / 1000TC,bulk SCB / 1000TC = bulk CH3 / 1000TC ~ bulk CH3end / 1000TC,and bulk SCB / 1000TC is converted to bulk w2 in the same manner as described above. e) The LS detector is the 18-angle Wyatt Technology High Temperature DAWN HELEOSII. The LS molecular weight (M) at each point in the chromatogram is determined by analyzing the LS output using the Zimm model for static light scattering (Light Scattering from Polymer Solutions, Huglin, M. B., Ed.; Academic Press, 1972.):Kc / AR(θ) = 1 / MP(θ) + 2A₂cAR(e) MP(e)2Here, AR(9) is the measured excess Rayleigh scattering intensity at scattering angle 0, c is the polymer concentration determined from the IR5 analysis, A2 is the second virial coefficient,P(0) is the form factor for a monodisperse random coil, and Ko is the optical constant for the system:K₀ = 4π²n²(dn / dc)²72 ’X4NAwhere NA is Avogadro’s number, and (dn / dc) is the refractive index increment forthe system. The refractive index, n=1.500 for TCB at 145°C and = 665 nm. For analyzing polyethylene homopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, dn / dc=0.1048 ml / mg and A2=0.0015; for analyzing ethylene-butene copolymers, dn / dc=0.1048*(1-0.00126*w2) ml / mg and A2= 0.0015 where w2 is weight percent butene comonomer.f) A high temperature Agilent (or Viscotek Corporation) viscometer, which has four capillaries arranged in a Wheatstone bridge configuration with two pressure transducers, is used to determine specific viscosity. One transducer measures the total pressure drop across the detector, and the other, positioned between the two sides of the bridge, measures a differential pressure. The specific viscosity, rp, for the solution flowing through the viscometer is calculated from their outputs. The intrinsic viscosity, ηs, at each point in the chromatogram is calculated from the equation [η]= ηS / C, where c is concentration and is determined from the IR5 broadband channel output. The viscosity MW at each point is calculated as M = KpsMaPs+1 / [r|], where apsis 0.67 and Kpsis 0.000175.g) The branching index (g'vis) is calculated using the output of the GPC-IR5-LS-VIS method as follows. The average intrinsic viscosity, [η]avg, of the sample is calculated by:[η]avg = Σ[η]ᵢcᵢ / Σcᵢwhere the summations are over the chromatographic slices, i, between the integration limits. h) The branching indexg'vis is defined as g'vis = (|j|]avg) / (KMv“), where Mvis the viscosityaverage molecular weight based on molecular weights determined by LS analysis and the K and a are for the reference linear polymer, which are, for purposes of this invention and claims thereto, a = 0.695 and K = 0.000579 for linear ethylene polymers, a = 0.705 and K = 0.0002288 for linear propylene polymers, a = 0.695 and K=0.000181 for linear butene polymers, a = 0.695 and K is 0.000579 x ( 1- 0.0087 w2b + 0.000018 x (w2b)2) for ethylene-butene copolymer where w2b is a bulk weight percent of butene comonomer, a is 0.695 and K is 0.000579*(1 -0.0075 x w2b) for ethylene-hexene copolymer where w2b is a bulk weight percent of hexenecomonomer, and a is 0.695 and K is 0.000579*(1 - 0.0077 x w2b) for ethylene-octene copolymer where w2b is a bulk weight percent of octene comonomer. Concentrations are expressed in g / cm3, molecular weight is expressed in g / mole, and intrinsic viscosity (hence K in the Mark- Houwink equation) is expressed in dl / g unless otherwise noted. Calculation of the w2b values is as discussed above.

[0168] Melt index (g / 10 min. or dg / min.): MI, also referred to as I2 or I2.16 in recognition of the 2.16 kg loading used in the test, was measured according to ASTM D-1238, 190°C, 2.16 kg.EXAMPLES

[0169] The following examples are included to demonstrate some embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

[0170] Table 1 below shows the results of examples performed using a commercial sized gas phase polymerization reactor while producing an ethylene-hexene copolymers. Pl and P2 were LCB-mLLDPE produced with a bridged bis-cyclopentad ienyl Group 4 (Type 2) metallocene catalyst. Pl had a density of 0.920 g / cm3and a melt index (I2) of 0.5 dg / min. P2 had a density of 0.935 g / cm3and a melt index (I2) of 0.5 dg / min.TABLE 1Ex. Off-Spec PE Off-Spec Transition FIG.(klb) PE (tonne) Method1 2,131 967 Comparative - 2 1,864 845 Comparative 63 1,631 740 Comparative - 4 1,878 852 Comparative 75 258 117 Inventive - 6 300 136 Inventive -7 470 213 Inventive 8

[0171] Comparative Examples 1-4 show the amount of off-spec material produced where hydrogen addition was controlled by analysis of the composition of the cycle gas in the cycle gas line as previously discussed.

[0172] In FIGs.6-8, the upper graph lines, where the y-axis is shown with values ranging from 0.30 to 0.80, show predicted and measured melt index values in dg / min. (I2; 2.16 kg @190°C)versus time. In FIGs. 6-8, the lower graph lines show the trends of H2 / C2H4 concentration ratio, H2 / C2H4 addition ratio, and comonomer (hexene-l) / C2H4 concentration ratio versus time, corresponding to the melt index graphs. These trend lines are normalized and unitless as they are just intended to show how these parameters are changing with respect to one another as discussed in more detail below.

[0173] Comparative Example 2 is shown graphically in FIG.6. Predicted melt index 1 by the comparative model. Modification of density starts at approximately time A and ends at approximately time B. Although the lab-measured melt index 2 time lags the predicted melt index 1. H2 added 3 to the process is decreased after time B as compared to before time A.H2 / C2H4 concentration 4 is shown to increase after time B as compared to before time A.Comonomer additions shown to decrease after time B as compared to before time A. A high degree of disagreement between predicted melt index 1 and lab-measured melt index 2 continues off the right-hand side of the graph indicating continued production of off-spec material.

[0174] Comparative Example 4 is shown graphically in FIG.7. Modification of density starts at approximately time A and ends at approximately time B. Although the lab-measured melt index 2 time lags the predicted melt index 1. H2 added 3 to the process is decreased after time B as compared to before time A. H2 / C2H4 concentration 4 is shown to increase after time B as compared to before time A. Comonomer addition 5 shown to decrease after time B as compared to before time A. A high degree of disagreement between predicted melt index 1 and lab-measured melt index 2 continues off the right-hand side of the graph indicating continued production of off-spec material.

[0175] Inventive Examples 5-7 show a significant reduction in the amount of off-spec material produced where hydrogen addition was controlled based on ethylene and comonomer feed rates as described herein.

[0176] Inventive Example 7 is shown graphically in FIG.8. Modification of density starts at approximately time A and ends at approximately time B. Although the lab-measured melt index 2 time lags the predicted melt index 1. H2 added 3 to the process is decreased after time B as compared to before time A. H2 / C2H4 concentration 4 is shown to increase after time B as compared to before time A. Comonomer addition 5 shown to decrease after time B as compared to before time A. Unlike FIG. 6 and FIG. 7, a time shift of lab-measured melt index 2 to the left shows good agreement between predicted melt index 1 and lab-measured melt index 2 after time A.

[0177] FIG. 9A and FIG. 9A show a compilation of numerous data points of hydrogen concentration ratio (HAR) and hydrogen added (HA) versus time using the inventive method for hydrogen control. All HAR and HA data points for times after time=0 are normalized for comparison to a value of 1 and time =0.

[0178] FIG. 9A shows thatwhen the transition is from lower to higher density at constant melt index, HA increases after time=0, and HAR decreases after time=0. This shows that the requirement for fresh hydrogen increases when comonomer is decreased, thus indicating that comonomer is responsible for some amount of hydrogen generation.

[0179] FIG. 9B shows that when the transition is from higher to lower density at constant melt index, HA decreases after time=0, and HAR increases after time=0. This shows that the requirement for fresh hydrogen decreases when comonomer is increased, thus indicating that comonomer is responsible for some amount of hydrogen generation.

[0180] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, in addition to recited ranges, any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0181] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the processes, machines, means, processes, and / or steps described in the specification. As one of the ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, means, processes, and / or steps, presently existing or later tobe developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein, may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, means, processes, and / or steps.

Claims

CLAIMSWhat is claimed is:

1. A process to polymerize olefins in a gas phase polymerization reactor, the process comprising adding ethylene, a comonomer, hydrogen, and a polymerization catalyst to a reaction zone of the gas phase polymerization reactor under first polymerization conditions to produce a first polyethylene having a first density and a first melt index, wherein:the first polymerization conditions comprise a first hydrogen addition rate (HAi), a first ethylene addition rate (EAi), and a first comonomer addition rate (CAi); a first comonomer addition ratio (CARi) is defined as CA1 / EA1;a first total hydrogen ratio (THRi) is defined as (HAi+HGi) / EAi;HGi is a first rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CAi;HGi = a x CARi; anda is an empirically determined constant associated with the catalyst and the comonomer.

2. The process of claim 1, wherein the first melt index (MI₁) can be calculated according to Equation 1:MIi = exp(b + (c x HARi) + (d x CARi)) Eq. 1 wherein:a first hydrogen addition ratio (HARi) is defined as HAi / EAi; and b, c, and d are empirically determined constants associated with the catalyst and the comonomer.

3. The process of claim 1 or claim 2, wherein the first density (Di) can be calculated according to Equation 2:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f* MIi) Eq. 2 wherein:e and / are empirically determined constants associated with the catalyst and the comonomer.

4. The process of claim 1 or any of claims 2-3, further comprising implementing second polymerization conditions to produce a second polyethylene having a second density and a second melt index, wherein:second polymerization conditions comprise a second hydrogen addition rate (HA2), a second ethylene addition rate (EA2), and a second comonomer addition rate (CA2); a second comonomer addition ratio (CAR2) is defined as CA2 / EA2;a second total hydrogen ratio (THR2) is defined as (HA2+HG2) / EA2;HG2 is a second rate of hydrogen generated in the reaction zone from a kinetic pathway associated with CA2; andHG2 = a x CAR2.

5. The process of claim 4, wherein the first melt index (MIi) can be calculated according to Equation la, and the second melt index (MI2) is calculated according to Equation lb:MI₁ = exp(b + (c x HAR₁) + (d x CAR₁)) Eq. 1a MI₂ = exp(b + (c x HAR₂) + (d x CAR₂)) Eq. 1b wherein:a first hydrogen addition ratio (HARi) is defined as HA1 / EA1;a second hydrogen addition ratio (HAR2) is defined as HA2 / EA2; and b, c, and d are empirically determined constants associated with the catalyst and the comonomer.

6. The process of claim 4 or claim 5, wherein the first density (Di) can be calculated according to Equation lb, and the second density (D2) can be calculated according to Equation 2b:Di = 0.97 - (e x CAi / (CAi + EAi)) + (f× MIi) Eq. 2a D2= 0.97 - (e x CA2 / (CA2+ EA2)) + f* MI2) Eq. 2b wherein:e and / are empirically determined constants associated with the catalyst and the comonomer.

7. The process of claim 4 or any of claims 5-6, wherein:a) the second melt index is equal to the first melt index; andb) the second hydrogen addition rate is:i) greater than the first hydrogen addition rate when the second density is greater than the first density; orii) less than the first hydrogen addition rate when the second density is less than the first density.

8. The process of claim 4 or any of claims 5-7, wherein:a) the second hydrogen addition ratio is less than the first hydrogen addition ratio when the second density is greater than the first density; orb) the second hydrogen addition ratio is greater than the first hydrogen addition ratio when the second density is less than the first density.

9. The process of claim 4 or any of claims 5-8, wherein:a) the second comonomer addition ratio is less than the first comonomer addition ratio when the second density is greater than the first density; orb) the second comonomer addition ratio is greater than the first comonomer addition ratio when the second density is less than the first density.

10. The process of claim 1 or any of claims 2-9, wherein the comonomer is one or more C2-C18 alpha-olefins.

11. The process of claim 10, wherein the one or more C2-C18 alpha-olefins are selected from 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 4-methylpent-l-ene, or a combination thereof.

12. The process of claim 1 or any of claims 2-11, wherein the first polyethylene has a density in the range of from 0.900 g / cm3to 0.945 g / cm3.

13. The process of claim 4 or any of claims 5-9, wherein the first polyethylene and the second polyethylene each have a density in the range of from 0.900 g / cm3to 0.945 g / cm3.

14. The process of claim 4 or any of claims 5-9, wherein the difference between the first density and the second density is at least 0.005 g / cm3.

15. The process of claim 1 or any of claims 2-14, wherein the first polyethylene has a melt index in the range of from density in the range of from 0.10 dg / min. to 20.0 dg / min.

16. The process of claim 1 or any of claims 2-15, wherein the polymerization catalyst comprises:a) an unbridged bis-cyclopentadienyl Group 4 and substituted versions thereof; b) a bridged bis-cyclopentadienyl Group 4 and substituted versions thereof;c) a substituted bulky ligand hafnium transition metal metallocene-type catalyst compound and substituted versions thereof;d) a dual catalyst system comprising a bridged bis-cyclopentadienyl Group 4 metal catalyst and an unbridged bis-cyclopentadienyl Group 4 metal catalyst; or e) a combination thereof.

17. The process of claim 1 or any of claims 2-16, wherein the first polyethylene comprises: a) a narrow-CD mLLDPE;b) a LCB-mLLDPE;c) a narrow MWD BOCD-mLLDPEs;d) a broad MWD BO CD -mLLDPE; ore) a combination thereof.

18. The process of claim 1 or any of claims 2-17, further comprising adding an induced condensing agent (ICA) composition to the reaction zone.

19. The process of claim 4 or any of claims 2-9, wherein the first polymerization conditions and the second polymerization conditions are implemented by a control system.

20. The process of claim 19, wherein the control system comprises a distributed control system (DCS), a direct digital controller (DDC), a programmable logic controller (PLC), or a combination thereof.

Images