Substituted silanes as chain transfer agents for polyolefin production.

Abstract

Some embodiments relate to a method for producing an olefin-based polymer by free radical polymerization in a reactor system. The method includes initiating free radical polymerization of an olefin-based monomer, propagating growth of the olefin-based polymer while the free radical polymerization of the olefin-based monomer continues, and adding a chain transfer agent to the reactor system to terminate the growth of the olefin-based polymer. The chain transfer agent includes a silane. Examples of suitable silanes are triethylsilane, diethylmethylsilane, tris(trimethylsilyl)silane, n-butylsilane, dimethylphenylsilane, phenylsilane, chlorodimethylsilane, diisopropylaminosilane, 1,2-bis(dimethylsilyl)benzene, 1,3-bis(dimethylsilyl)benzene, 1,4-bis(dimethylsilyl)benzene, 1,1,3,3-tetramethyldisiloxane, trimethylsilane, (trimethylsilyl)dimethylsilane, and bis(trimethylsilyl)methylsilane.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 002,636, filed March 31, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to olefin polymerization chain transfer agents and processes, and more specifically to methods for making olefin-based polymers by free radical polymerization using substituted silanes as chain transfer agents. [Background technology]

[0003] Chain transfer agents (CTAs) or "telogens" are used in free-radical polymerization processes to control the melt index. "Chain transfer" refers to the termination of growing polymer chains, thus limiting the final molecular weight of the polymeric material. Chain transfer agents are typically hydrogen atom donors that react with growing polymer chains and terminate the chain polymerization reaction. Known CTAs include many types of hydrogen atom donor compounds, such as saturated or unsaturated hydrocarbons, aldehydes, ketones, and alcohols. Manipulating the concentration and type of chain transfer agent used in the process can affect the average length of the polymer chains and the molecular weight distribution. This, in turn, affects the melt index (I2 or MI), which is related to molecular weight.

[0004] After donating a hydrogen atom, the CTA can form a radical that can initiate a new polymer chain. As a result, the original CTA is incorporated into a new or existing polymer chain, thereby introducing a new functional group into the polymer chain associated with the original CTA. The CTA may introduce a new functional group into a polymer chain that is not normally the result of monomer / comonomer polymerization.

[0005] Low density olefin-based polymers produced in the presence of a CTA exhibit modified processability, film optical properties such as haze, gloss, and clarity, and many physical properties such as density, stiffness, yield point, film elongation, and tear strength. For example, the α-olefin acting as a CTA may also introduce short chain branching into the polymer chain upon incorporation.

[0006] Known CTAs fall into one of two categories: low-activity CTAs and high-activity CTAs. Low-activity CTAs typically have a chain transfer constant (Cs) less than 1 and are typically saturated or unsaturated hydrocarbons, aldehydes, or ketones. High-activity CTAs typically have a Cs greater than or equal to 1 and contain sulfur or phosphorus. While high-activity CTAs tend to be more efficient in olefin polymerization, they also result in the inclusion of sulfur or phosphorus in the resulting polymer. When such polymers are included in food applications, for example, degradation of the polymer over time can result in unpleasant odors and tastes. Therefore, there is a need for high-activity CTAs and methods for producing low-density olefin-based polymers by free-radical polymerization that do not incorporate sulfur and phosphorus into the resulting polymer. Summary of the Invention

[0007] According to some embodiments, a method for making an olefin-based polymer by free radical polymerization in a reactor system includes initiating free radical polymerization of an olefin-based monomer, propagating growth of the olefin-based polymer while the free radical polymerization of the olefin-based monomer continues, and adding a chain transfer agent to the reactor system to terminate growth of the olefin-based polymer, the chain transfer agent comprising a silane of formula (1): [ka] In the formula, R 1 , R 2 , R 3 , and R 4are independently a hydrogen atom, a (C1-C40) hydrocarbyl, -N(R 5 )2, -Si(R 5 )3, -OSi(R 5 )3, -OR 5 , and -R 6 -Si(R 5 )3, and each R 5 are independently selected from a hydrogen atom and a (C1-C40) hydrocarbyl, and each R 6 is (C1-C40) hydrocarbylene, and optionally R 1 , R 2 , R 3 , and R 4 or any two R bonded to the same nitrogen atom 5 , or any two R bonded to the same silicon atom 5 are joined to form a ring having 3 to 50 atoms in the ring, excluding any hydrogen atoms. [Brief explanation of the drawings]

[0008] The Summary and Detailed Description will be better understood when read in conjunction with the accompanying drawings. It should be understood, however, that the scope of the invention as claimed is not limited to the precise arrangements and instrumentalities shown. The components in the drawings are not necessarily to scale. In the drawings, like reference numerals indicate corresponding parts throughout the several views.

[0009] [Figure 1] FIG. 1 is a process diagram illustrating elements of the disclosed tubular reactor system 100. [Figure 2] 1 is a concentration-normalized light scattering (LS) chromatographic curve of a conventionally calibrated logarithmic GPC molecular weight range and a portion thereof of a GPC-LS characterization analysis for an exemplary system described herein. [Figure 3] 1 is a concentration-normalized light scattering (LS) chromatographic curve of a conventionally calibrated logarithmic GPC molecular weight range and a portion thereof of a GPC-LS characterization analysis for an exemplary system described herein. DETAILED DESCRIPTION OF THE INVENTION

[0010] According to some embodiments, CTAs can be used to make low density olefin-based polymers, such as low density ethylene-based polymers with narrow molecular weight distributions, which can be used in blown and cast films, and can be used alone or in blends with other polymers.

[0011] A high-activity CTA may have sufficiently high activity during free radical polymerization that the growing monomer chain will preferentially accept a hydrogen atom donated by the CTA over the course of its propagation with another monomer molecule. A CTA is considered a high-activity CTA if its chain transfer constant (Cs) is greater than 1. As the reaction progresses, the high-activity CTA in the process fluid is consumed so that the relative concentration of the CTA decreases relative to the concentration of the monomer. If the reaction continues and no additional CTA is provided, the high-activity CTA may become depleted so that the amount of CTA in the reaction system is insufficient to control molecular weight near the end of the reaction.

[0012] By using a high activity CTA at the beginning of the process, the formation of high molecular weight polymer chains is suppressed at the beginning of the process, and the resulting polymer has a narrower molecular weight distribution. This suppression prevents the formation of hyperbranched high molecular weight polymer chains that form in later stages of the process. Furthermore, this suppression improves the overall conversion of the single-pass process by improving the performance of the process system.

[0013] However, it is difficult to effectively use a high-activity CTA by itself in a free-radical polymerization process. To compensate, additional high-activity CTAs may be added later in the process. Alternatively, a combination of at least one high-activity CTA and at least one low-activity CTA may be incorporated at the beginning of the process. In such a process, as the reaction progresses from initiation to completion, the high-activity CTA is preferentially consumed during periods of relatively high monomer concentration, particularly in tubular reactor systems with two or more reaction zones (i.e., initiator injection points). The low-activity CTA is not preferentially consumed early in the process because its concentration relative to the monomer and its reaction rate with the monomer are both lower than those of the high-activity CTA. Later in the process, both the monomer and the high-activity CTA are substantially consumed, and the low-activity CTA has less reaction with the forming polymer chains, so it has a greater impact on the process by supporting chain transfer to control molecular weight.

[0014] According to embodiments, a method for making an olefin-based polymer by free radical polymerization in a reactor system can include initiating free radical polymerization of an olefin-based monomer, propagating growth of the olefin-based polymer while the free radical polymerization of the olefin-based monomer continues, and adding a chain transfer agent to the reactor system to terminate growth of the olefin-based polymer. The chain transfer agent comprises a silane. In embodiments, the free radical polymerization can be high-pressure peroxide-initiated free radical polymerization.

[0015] In embodiments of the method of making an olefin-based polymer, the CTA can include a silane of formula (1): [ka] In the formula, R 1 , R 2 , R 3 , and R 4 are independently a hydrogen atom, a (C1-C40) hydrocarbyl, -N(R 5 )2, Si(R 5)3, -OSi(R 5 )3, -OR 5 , and -R 6 -Si(R 5 ) 3. Each R 5 are independently selected from hydrogen atoms and (C1-C40) hydrocarbyl. 6 is (C1-C40) hydrocarbylene. 1 , R 2 , R 3 , and R 4 or any two R bonded to the same nitrogen atom 5 , or any two R bonded to the same silicon atom 5 are linked to form a ring having 3 to 50 atoms, excluding any hydrogen atoms, in some embodiments, the silane of formula (1) is not triethylsilane or diethylmethylsilane.

[0016] When used to describe a chemical group containing specific carbon atoms, parenthetical expressions having the form "(Cx-Cy)" mean that the unsubstituted form of the chemical group has from x carbon atoms to y carbon atoms, inclusive, x and y. For example, (C1-C50) alkyl is an alkyl group having from 1 to 50 carbon atoms in its unsubstituted form. In some embodiments and general structures, the specific chemical group can be represented by R S R defined using parenthetical "(Cx-Cy)" may be substituted by one or more substituents such as S The substituted chemical group can be any group R S may contain more than y carbon atoms depending on the identity of the group. For example, "R S is phenyl (-C6H5), then exactly one group R S A "(C1-C50) alkyl substituted with" can contain 7 to 56 carbon atoms. Thus, in general, a chemical group defined using the bracketed "(Cx-Cy)" can contain one or more substituents R containing carbon atoms. S When substituted by x and y, the minimum and maximum total number of carbon atoms in the chemical group are the substituents R containing all carbon atoms in both x and y. SIt is determined by adding the total number of carbon atoms from

[0017] The term "substituted" refers to the replacement of at least one hydrogen atom (-H) bonded to a carbon or heteroatom or functional group of the corresponding unsubstituted compound with a substituent (e.g., R S The term "hypersubstituted" means that all hydrogen atoms (H) bonded to carbon atoms or heteroatoms of the corresponding unsubstituted compound or functional group are replaced by a substituent (e.g., R S ) The term "polysubstituted" means that at least two, but fewer than all, hydrogen atoms bonded to a carbon atom or heteroatom of the corresponding unsubstituted compound or functional group are replaced by substituents. The term "-H" means a hydrogen or hydrogen radical covalently bonded to another atom. "Hydrogen" and "-H" are interchangeable and have the same meaning unless otherwise specified.

[0018] The term "(C1-C40)hydrocarbyl" means a hydrocarbon radical having from 1 to 40 carbon atoms, and the term "(C1-C40)hydrocarbylene" means a hydrocarbon diradical having from 1 to 40 carbon atoms, wherein each hydrocarbon radical and each hydrocarbon diradical is aromatic or non-aromatic, saturated or unsaturated, straight or branched chain, cyclic (having 3 or more carbons, including monocyclic and polycyclic, fused and non-fused polycyclic, and bicyclic) or acyclic, and wherein each hydrocarbon radical and each hydrocarbon diradical is a cyclic or non-cyclic hydrocarbon radical having from 1 to 40 carbon atoms, and ... S is or is not substituted by

[0019] In the present disclosure, the (C1-C40)hydrocarbyl can be unsubstituted or substituted (C1-C40)alkyl, (C3-C40)cycloalkyl, (C3-C20)cycloalkyl-(C1-C20)alkylene, (C6-C40)aryl, or (C6-C20)aryl-(C1-C20)alkylene (benzyl (—CH2—C6H5)).

[0020] The term "(C1-C40) alkyl" refers to an alkyl group that is unsubstituted or has one or more R S

[0033] The term "(C45) alkyl" refers to a saturated straight-chain or branched-chain hydrocarbon radical of 1 to 40 carbon atoms, substituted with (C1-C40) alkyl. Examples of unsubstituted (C1-C20) alkyl are unsubstituted (C1-C10) alkyl, unsubstituted (C1-C5) alkyl, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methylpropyl, 1,1-dimethylethyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-nonyl, and 1-decyl. Examples of substituted (C1-C40) alkyl are substituted (C1-C20) alkyl, substituted (C1-C10) alkyl, trifluoromethyl, and [C45] alkyl. The term "(C45) alkyl" refers to a radical in which there are up to 45 carbon atoms in the radical, including the substituents, e.g., one R, each of which is (C1-C5) alkyl. S Each (C1-C5) alkyl can be methyl, trifluoromethyl, ethyl, 1-propyl, 1-methylethyl, or 1,1-dimethylethyl.

[0021] The term "(C6-C40)aryl" refers to an unsubstituted or (one or more R S"(C6-C40)aryl" refers to a monocyclic, bicyclic, or tricyclic aromatic hydrocarbon radical substituted with at least 6 to 14 of the carbon atoms, wherein at least 6 to 14 of the carbon atoms are aromatic ring carbon atoms. A monocyclic aromatic hydrocarbon radical contains one aromatic ring, a bicyclic aromatic hydrocarbon radical has two rings, and a tricyclic aromatic hydrocarbon radical has three rings. When a bicyclic or tricyclic aromatic hydrocarbon radical is present, at least one of the rings of the radical is aromatic. The other ring or rings of the aromatic radical may independently be fused or non-fused, and aromatic or non-aromatic. Examples of unsubstituted (C6-C40)aryl include unsubstituted (C6-C20)aryl, unsubstituted (C6-C18)aryl, 2-(C1-C5)alkyl-phenyl, phenyl, fluorenyl, tetrahydrofluorenyl, indacenyl, hexahydroindacenyl, indenyl, dihydroindenyl, naphthyl, tetrahydronaphthyl, and phenanthrene. Examples of substituted (C6-C40)aryl include substituted (C1-C20)aryl, substituted (C6-C18)aryl, 2,4-bis([C20]alkyl)-phenyl, polyfluorophenyl, pentafluorophenyl, and fluoren-9-on-1-yl. The term "[C20]alkyl" refers to groups having up to 20 carbon atoms in the radical, including the substituents, e.g., one R, each of which is (C1-C5)alkyl. S It means that the alkyl group is (C2-C15) alkyl substituted with

[0022] The term "(C-C)cycloalkyl" refers to an alkyl group that is unsubstituted or has one or more R S Other cycloalkyl groups (e.g., (Cx-Cy)cycloalkyl) have x to y carbon atoms and are unsubstituted or substituted with one or more R Sand substituted by . Examples of unsubstituted (C3-C40)cycloalkyl are unsubstituted (C3-C20)cycloalkyl, unsubstituted (C3-C10)cycloalkyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl. Examples of substituted (C3-C40)cycloalkyl are substituted (C3-C20)cycloalkyl, substituted (C3-C10)cycloalkyl, cyclopentanon-2-yl, and 1-fluorocyclohexyl.

[0023] Examples of (C1-C40)hydrocarbylene include unsubstituted or substituted (C6-C40)arylene, (C3-C40)cycloalkylene, and (C1-C40)alkylene (e.g., (C1-C20)alkylene). The diradicals can be on the same carbon atom (e.g., —CH2—) or adjacent carbon atoms (i.e., 1,2-diradicals), or separated by one, two, or three or more intervening carbon atoms (e.g., 1,3-diradicals, 1,4-diradicals, etc.). Some diradicals include 1,2-, 1,3-, 1,4-, or α,ω-diradicals, while others include 1,2-diradicals. α,ω-diradicals are diradicals with the greatest carbon backbone spacing between the radical carbons. Some examples of (C2-C20) alkylene α,ω-diradicals include ethane-1,2-diyl (i.e., -CH2CH2-), propane-1,3-diyl (i.e., -CH2CH2CH2-), 2-methylpropane-1,3-diyl (i.e., -CH2CH(CH3)CH2-). Some examples of (C6-C40) arylene α,ω-diradicals include phenyl-1,4-diyl, naphthalene-2,6-diyl, or naphthalene-3,7-diyl.

[0024] In embodiments, the CTA does not contain sulfur or phosphorus.

[0025] In embodiments, the CTA comprises a silane of Formula (1) selected from triethylsilane, diethylmethylsilane, tris(trimethylsilyl)silane, n-butylsilane, dimethylphenylsilane, phenylsilane, chlorodimethylsilane, diisopropylaminosilane, 1,2-bis(dimethylsilyl)benzene, 1,3-bis(dimethylsilyl)benzene, 1,4-bis(dimethylsilyl)benzene, and bis(dimethylsilyl)ether. In embodiments, the CTA comprises a silane of Formula (1) selected from trimethylsilane, (trimethylsilyl)dimethylsilane, bis(trimethylsilyl)methylsilane, and tris(trimethylsilyl)silane. In embodiments, the CTA comprises tris(trimethylsilyl)silane.

[0026] In the method of making an olefin-based polymer herein, when the CTA is a high activity CTA comprising a silane of formula (1), about 0.90 g / cm 3 ~Approx. 0.94g / cm 3 density, molecular weight distribution M of about 2 to about 30 w / M n A low-density olefin-based polymer having a melt index I2 of 0.1 grams per 10 minutes to about 50 grams per 10 minutes can be obtained. In some embodiments, the olefin-based polymer can comprise an ethylene-based polymer. In some embodiments, the olefin-based polymer can consist essentially of an ethylene-based polymer. In some embodiments, the olefin-based polymer can consist of an ethylene-based polymer.

[0027] Low-density olefin-based polymers can be homopolymers of olefins, such as ethylene, or can be olefin-based interpolymers composed of olefins and at least one comonomer.For example, in addition to ethylene in ethylene / α-olefin interpolymers, useful comonomers for incorporation into olefin-based interpolymers include, but are not limited to, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 1-octene, non-conjugated dienes, polyenes, butadiene, isoprene, pentadiene, hexadiene (for example, 1,4-hexadiene), octadiene, styrene, halo-substituted styrenes, alkyl-substituted styrenes, tetrafluoroethylene, vinylbenzocyclobutene, naphthenes, cycloalkenes (for example, cyclopentene, cyclohexane, cyclooctene), and mixtures thereof.Ethylene is often used in combination with at least one C3-C6 alkyl ester, such as propene, 1-butene, 1-hexene, and 1-octene. 20 It is copolymerized with α-olefins.

[0028] The silicon-containing low density olefinic polymers have conventionally calibrated molecular weights M, both in grams / mol, as determined by the triple detector gel permeation chromatography method described below. w,GPC and absolute molecular weight M w,Abs and a zero shear viscosity η (Pascal-seconds) at 190°C measured by the zero shear viscosity method described below. Additionally, the silicon-added low-density olefin-based polymers can exhibit a zero shear viscosity relationship indicative of long chain branching characterized by a conventionally calibrated molecular weight, an absolute molecular weight, and a gpcBR value of greater than 0.05 as determined by the gpcBR branching index by 3D-GPC.

[0029] Concentration-normalized light scattering (LS) response and conventionally calibrated molecular weight M w,GPCThe present invention discloses low-density olefin-based polymers further comprising silicon, which are different from other low-density olefin-based polymers in that the relationship between the logarithm of the GPC-LS characteristic value and the GPC-LS characteristic value (Y) is captured in a relationship called the GPC-LS characteristic value (Y). The GPC-LS characteristic value (Y) is measured by the GPC-LS characterization method described below. The present invention discloses olefin-based polymers having a GPC-LS characteristic value (Y) greater than 2.1 and having long-chain branching. Long-chain branching is characterized by a gpcBR value greater than 0.05, as determined by the gpcBR branching index using the 3D-GPC method described below. The present invention also discloses olefin-based polymers having a GPC-LS characteristic value (Y) greater than 2.3 or greater than 2.4. The present invention also discloses olefin-based polymers having a given GPC-LS characteristic value (Y) within the range of 2.1 to 10.

[0030] A method according to embodiments can be a high-pressure free-radical reactor process for polymerizing an olefin, such as ethylene, and optionally at least one comonomer to produce a low-density olefin-based polymer and by-product heat. In embodiments, the free-radical polymerization is a peroxide-initiated free-radical polymerization, such that a peroxide-based initiator can be used. In embodiments, the free-radical polymerization is a high-pressure peroxide-initiated free-radical polymerization. In embodiments, a metal catalyst can be included in addition to the peroxide initiator. In other embodiments, a metal catalyst may not be included.

[0031] As used herein, the term "high pressure" means a pressure greater than 100 MPa, greater than 110 MPa, greater than 120 MPa, greater than 130 MPa, greater than 140 MPa, or greater than 150 MPa. In embodiments, the pressure can be in the range of 100 MPa to 400 MPa, 110 MPa to 390 MPa, 120 MPa to 380 MPa, 130 MPa to 370 MPa, 140 MPa to 360 MPa, 150 MPa to 350 MPa, 160 MPa to 340 MPa, 170 MPa to 330 MPa, 180 MPa to 320 MPa, 190 MPa to 310 MPa, or 200 MPa to 300 MPa. The process according to embodiments can include at least one high-activity CTA, and optionally a mixture of at least one high-activity CTA and at least one low-activity CTA, as defined above, to aid in the formation of low-density olefin-based polymers with narrower molecular weight distributions compared to polymers produced by conventional processes.

[0032] In some embodiments, the reactor system may include a reactor having one or more reaction zones. The reactor may be an autoclave reactor, a tubular reactor, or a combination of an autoclave reactor and a tubular reactor. The two types of reactors allow for two different types of high-pressure, free-radical initiated polymerization processes. In the first type of process, a stirred autoclave reactor having one or more reaction zones is charged with initiator or monomer feed, or both, through at least one injection point. In the second type of process, the tubular reactor is a jacketed tube having one or more reaction zones. Suitable reactor lengths may be, but are not limited to, 100 meters to 3000 meters, or 1000 meters to 2000 meters. The beginning of the reaction zone in either type of reactor is typically defined by a side injection of either the initiator, olefin, CTA, comonomer(s), or a combination thereof. The high pressure process can be carried out in an autoclave reactor or a tubular reactor having one or more reaction zones, or in a combination of autoclave and tubular reactors each containing one or more reaction zones.

[0033] In some embodiments, a method for making an olefin-based polymer can include injecting an initiator into a high-pressure feed upstream of a reaction zone where free radical polymerization is to be induced. Accordingly, initiating the free radical polymerization can include adding a peroxide initiator to the reactor system. Examples of free radical initiators include oxygen-based initiators such as organic peroxides (PO). Exemplary initiators can include, but are not limited to, t-butyl peroxypivalate, di-t-butyl peroxide, t-butyl peroxyacetate, t-butyl peroxyoctanoate, and t-butyl peroxy-2-ethylhexanoate, and mixtures thereof. These organic peroxy initiators can be injected into the reactor system in an exemplary initiator amount of 0.0001 wt % to 0.01 wt %, based on the total weight of the high-pressure feed.

[0034] For tubular reactors, in addition to feeding the olefin and optionally at least one comonomer to the tubular reactor, other components can be fed to the reactor to initiate and support the free radical reaction as the olefin polymer is formed. Additional components can include, but are not limited to, a reaction initiator, a catalyst, and a CTA. In embodiments, the tubular reactor is a multi-zone tubular reactor with alternative locations for feeding fresh olefin to control the olefin to CTA ratio and, therefore, the polymer properties. Fresh olefin monomer can be added simultaneously at multiple locations to achieve a desired olefin monomer to CTA ratio. Fresh CTA can be added simultaneously at multiple locations to achieve a desired CTA to olefin monomer ratio. Non-limiting examples of suitable tubular polymerization reactors include the tubular reactors and polymerization conditions disclosed in WO 2013059042 (A1) and WO 2013078018 (A2), the entire contents of each reference being incorporated herein by reference.

[0035] In one embodiment, the free radical polymerization reactor system includes a tubular reactor having multiple reactor zones (3 to 6 reactor zones). The maximum temperature in each reactor zone is 150°C to 360°C, or 170°C to 350°C, or 200°C to 340°C. The pressure in each reactor zone is 100 MPa to 380 MPa, or 110 MPa to 340 MPa, or 110 MPa to 300 MPa.

[0036] In some embodiments, the free-radical polymerization reactor system includes a tubular polymerization reactor in which a process fluid consisting partially of olefins undergoes free-radical polymerization, resulting in a highly exothermic reaction. The reaction occurs under high operating pressures (e.g., 100 MPa to 400 MPa) in a turbulent process fluid stream, with an initial reaction start temperature of 120°C to 200°C, but a maximum reactor temperature of 160°C to 360°C (hence, low-density olefin-based polymers are also referred to as "high-pressure" polymers). At certain points along the tube, a portion of the heat generated during free-radical polymerization can be removed through the tube wall. Typical single-pass conversion values ​​for tubular reactors range from about 20% to 40%. Tubular reactor systems also typically include at least one monomer recycle loop to improve conversion efficiency.

[0037] A typical tubular polymerization reaction system is shown in Figure 1. The tube reactor system 100 typically has a tube 2 with a length of about 250 meters to about 2000 meters. The length and diameter of the tube affect the residence time and velocity of the process fluids and the heat addition / removal capacity of the tube 2. Suitable reactor lengths can be, but are not limited to, 100 meters to 3000 meters, and some are 500 meters to 2000 meters. The tube 2 also has a working internal diameter of about 30 mm to about 100 mm, based on the desired system throughput, operating pressure range, and degree of turbulence for mixing and reaction. The working internal diameter may widen or narrow at points along the tube 2 to accommodate different portions of the process, such as turbulent mixing, initiator and feed injection, and process fluid throttling (i.e., accelerating process fluid velocity at the expense of pressure drop).

[0038] In some embodiments, the average velocity of the process fluid is at least 10 meters per second, or up to 25 meters per second. The process fluid velocity can affect overall process throughput, olefin conversion, heat removal capacity, and, for processes with several reaction zones, local reaction initiation temperatures and control of CTA and process initiator injection rates.

[0039] Referring to FIG. 1 and tubular reactor system 100, a first compressor 4, which may be a multi-stage compressor or two or more compressors operating in parallel, is connected on its intake side to a source of fresh monomer / comonomer feed, i.e., fresh feed conduit 6, and to a low pressure system recycle conduit 8.

[0040] Continuing with reference to FIG. 1, a second compressor, e.g., hyper compressor 5, which may be a multi-stage compressor, is connected on its intake side to the discharge of primary compressor 4 and to the second of the two recycle streams, i.e., high-pressure system recycle conduit 26.

[0041] After compression by hyper-compressor 5, the process fluid is supplied to line 2 via conduit 12 as an upstream process feed stream. In some disclosed processes, the process fluid is split and supplied to line 2 at different feed locations. In such processes, a portion of the process fluid is supplied to line 2 via conduit 12 as an upstream process feed stream to a first reaction zone, and then another portion (depending on the number of splits made in the process fluid) may be supplied to line 2 via various conduits 14 as a downstream process feed stream to another reaction zone.

[0042] In some embodiments, the reactor system of the present process may include several reaction zones to which fresh feed may be added, including a first reaction zone and at least one other reaction zone. Having multiple reaction zones may improve overall olefin conversion by removing heat within the system through the introduction of a feed stream (e.g., initiator, monomer) that is cooler than the process fluid in tube 2 downstream of the first reaction zone. A tubular reactor system with multiple reaction and feed zones may allow the tube reactor to operate at an overall lower average peak reactor temperature. This assumes that conversion remains the same between a multiple reactor or feed zone and a similar non-multiple reaction or feed zone tubular reactor. While not intending to be bound by any particular theory, downstream process feeds passing through conduit 14 may be cooled prior to injection into the reaction system, or the downstream process feeds may be inherently cooler, thereby lowering the overall temperature of the reaction process fluids prior to (re)initiation of polymerization. Cooling the process may allow for the addition of additional initiator, thereby improving single-pass monomer / comonomer conversion. In some embodiments, the temperature of the downstream process feedstream(s) is preferably less than 120°C, or less than 50°C, or even less than 30°C. Lower average reactor temperatures may reduce the overall level of long chain branching, thereby producing a product with a narrower molecular weight distribution. Additionally, the use of multiple feed locations along the line may produce resins with narrow molecular weight distributions for use in applications such as film resins where optical properties may be an important criteria. Multiple feed locations may also result in narrower molecular weight distributions compared to similar systems without multiple reaction zones.

[0043] In some embodiments, the reactor system includes a reactor having two or more reaction zones. In such reactors, one or more free radical initiator or catalyst conduits 7 deliver initiator or catalyst to tube 2 near or at the beginning of each reaction zone.

[0044] The free radical polymerization reactions that result in the disclosed olefin-based polymers occur in each reaction zone in the presence of an initiator or catalyst. The reactions are exothermic, generating large amounts of heat. Without cooling, the adiabatic temperature rise in the process fluid and the olefin-based polymer (which absorbs and retains heat) would result in undesirable reactions. Such reactions may include olefin cracking (olefins and polyolefins are cracked to base products in a reaction that does not involve combustion) or excessive long-chain branching, which results in broadening of the molecular weight distribution.

[0045] In conventional processes, high molecular weight polymer chains form and "plate out" to the inside of the reactor tube walls, insulating the process and preventing heat removal. However, in some embodiments involving the use of a high activity CTA and process fluid velocities greater than 10 meters per second, the degree to which this insulating layer forms is reduced. This improves the heat removal process relative to a comparable process without a high activity CTA.

[0046] Without intending to be bound by any particular theory, it is believed that polymerization processes including high-activity CTAs offer several advantages over polymerization processes in which high-activity CTAs are not used. For example, when a high-activity CTA is added to a process instead of a low-activity CTA, the ability to remove heat from a tubular reactor during steady-state operation appears to have the following effects: (a) at least 1% more heat, and possibly at least 3% more heat, can be removed from at least one reaction zone; and / or (b) the average temperature difference between the inlet and outlet temperatures (temperature "Δ") of a heat removal medium used in a heat exchanger that removes heat from a reaction system can be statistically significantly higher (i.e., greater than three times the standard deviation of temperature Δ over a period of time) than that of a similar heat removal medium used in a similar heat exchanger in a similar process; and / or (c) the difference in outlet temperature of a heat removal medium used in a heat exchanger that removes heat from a reaction system can be at least 1° C. higher over a period of time than that of a similar heat removal medium used in a similar heat exchanger in a similar process.

[0047] In some embodiments, adding a CTA to the reactor system can include adding at least one high activity CTA to the process fluid. In some embodiments, adding a CTA to the reactor system can include adding at least two CTAs, for example, one high activity CTA and one low activity CTA, to the process fluid. Two or more CTAs can be used to take advantage of their relative properties during free radical polymerization in line 2.

[0048] In some embodiments, the CTA is added so as to be blended as uniformly as possible with the process fluid before being introduced into tube 2. Depending on the physical layout of the tubular reactor system 100 and the chemical properties of the process fluid and CTA, such blending can be achieved by injecting the CTA at the inlet of the booster compressor 21 for the low pressure system recycle conduit 8, in the inlet of the primary compressor 4, in the inlet of the hyper compressor 5, at the outlet of the hyper compressor 5, at the inlet of tube 2, or with the first peroxide injection.

[0049] Although not shown in FIG. 1 , selective feeding of CTA to tube reactor 2 is possible. In such cases, the CTA can be fed to tube 2 by selective injection into conduit 12 or conduit 14 instead of using CTA source 23 as shown in FIG. 1 . In certain cases, the CTA can be injected only into the upstream process feedstream from CTA source 23 via conduit 12. This flexibility in the disclosed process with respect to injection of CTA from CTA source 23 allows for selective injection of the CTA only into the first reaction zone, or only into a different reaction zone, or into some or all of the reaction zones. It also allows for injection of different CTAs, including CTAs with different Cs characteristics, into different zones from CTA source 23 (e.g., a high-activity CTA injected into the first reaction zone and a low-activity CTA injected into at least one other reaction zone) to optimize reaction system performance and olefin-based polymer properties.

[0050] In embodiments in which two or more CTAs are added to the reactor system, one of the CTAs may have a Cs<1 and the other CTA may have a Cs>1. In such processes, the CTAs may be fed to the system at different feed rates or amounts to customize effectiveness in different parts of the process or to optimize olefin-based polymer properties. In embodiments, the feed rate of the low-activity CTA may be adjusted depending on the amount of recycled low-activity CTA detected in either or both of recycle stream 26 and recycle stream 8. The CTA feed rates, the ratio of CTAs to each other, and the relative amount of CTA to the amount of olefin in fresh feed conduit 6 vary depending on several factors, including, but not limited to, the configuration of line 2 and reactor system 100, the production rate, the relative activity of the CTAs, and the overall residence time in line 2. The CTA feed rates and ratios may also be adjusted based on final olefin-based polymer properties such as melt viscosity, overall production, target molecular weight distribution, desired melt index, first zone peak temperature, residual CTA or CTA by-products, and line process fluid velocity.

[0051] In embodiments, the concentration of the CTA in the process fluid is from about 1 molar ppm to about 600 molar ppm, or from about 1 molar ppm to about 200 molar ppm. In embodiments, the disclosed CTA concentrations are found in an upstream process feed stream, such as conduit 12. In embodiments, the concentration of the high activity CTA in the upstream process feed stream is from about 1 molar ppm to about 600 molar ppm, or from about 1 molar ppm to about 200 molar ppm. In embodiments using both high activity and low activity CTAs, the CTA molar flow ratio, which is the ratio of high activity CTA in moles / hour to low activity CTA in moles / hour in the process fluid, is from about 0.01 to about 100, or from about 0.05 to about 5, or from about 0.05 to about 0.5.

[0052] Referring to FIG. 1 , the mixture of olefin-based polymer formed from the reaction, unreacted monomer (and comonomer, if applicable), and unused feeds such as solvent and CTA, or cracking and by-products, passes through line outlet 16 to the separation section of the process. The separation and recycle section of the process in the tube reactor system 100 includes a high-pressure separator (HPS) 18, which receives the mixture of product polymer and process fluids from the outlet of line 2. The tail of HPS 18 transfers the polymer, as well as any remaining unreacted monomer / comonomer and other unused feeds that may be dissolved in the polymer, to a low-pressure separator (LPS) 20. The higher-pressure lighter stream containing unreacted monomer passes through a high-pressure system recycle conduit 26, which may include a purification system 24 to cool and purify the stream and purge inert gases, and recombines the process fluids passing from the primary compressor 4 to the hypercompressor 5.

[0053] When the heat removal medium is a liquid, the reactor may include a heat exchanger 30 to provide heat transfer and cooling of the process fluid and the olefin-based polymer.

[0054] In embodiments, there is an overall improvement in olefin conversion. The overall improvement is due to reduced formation of high molecular weight polymer chains early in the process, improved heat transfer, and the ability to use more free radical initiator. Under comparable steady-state conditions, the olefin conversion of the disclosed process in which at least one CTA having a Cs greater than 1 is added to the reactor system can be at least 0.3% higher than the olefin conversion of a similar process lacking a CTA having a Cs greater than 1.

[0055] End use

[0056] End-use products made using the disclosed olefin-based polymers include all types of films (e.g., blown, cast, and extrusion coatings (single or multilayer)), molded articles (e.g., blown and rotationally molded articles), wire and cable coatings and formulations, crosslinking applications, foams (e.g., open-cell or closed-cell blown), and other thermoplastic applications. The disclosed olefin-based polymers are also useful as blend components with other polyolefins.

[0057] The types of films that can be produced as end-use products from embodiments of the disclosed olefin-based polymers include silage films, sealants, silo bags, stretch films, display packaging, shrink films, and heavy-duty shipping bags. In addition, blow coatings, cast coatings, and extrusion coatings (single layer or multilayer) can also be produced using the disclosed olefin-based polymers.

[0058] definition

[0059] As used herein, the term "blend" or "polymer blend" refers to a blend of two or more polymers. A blend may or may not be miscible (not phase separated at the molecular level). A blend may or may not be phase separated. A blend may or may not contain one or more domain configurations as determined from transmission electron spectroscopy, light scattering, x-ray scattering, and other methods known in the art.

[0060] The term "composition" includes a mixture of materials that comprise the composition, as well as reaction products and decomposition products formed from the interaction and reaction between the materials of the composition.

[0061] The term "olefin-based polymer" refers to a polymer formed from greater than 50 mole percent polymerized olefin monomers (based on the total amount of polymerizable monomers) and optionally at least one comonomer. Homopolymers of olefins are also olefin-based polymers.

[0062] The term "ethylene-based polymer" refers to a polymer formed from greater than 50 mole percent polymerized ethylene monomer (based on the total amount of polymerizable monomers), and optionally at least one comonomer. Homopolymers of ethylene are also ethylene-based polymers.

[0063] The term "ethylene / α-olefin interpolymer" refers to an interpolymer formed from greater than 50 mole percent polymerized ethylene monomer and at least one α-olefin comonomer (based on the total amount of polymerizable monomers).

[0064] The term "homopolymer" refers to a polymer formed from only a single type of monomer, such as ethylene.

[0065] The term "interpolymer" refers to a polymer prepared by the polymerization of at least two different types of monomers. The term interpolymer is inclusive of copolymers, which are typically used to refer to polymers prepared from two different monomers, and polymers prepared from three or more different types of monomers, such as terpolymers.

[0066] The term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean that the polymer is partially or fully polymerized in an autoclave or tubular reactor at pressures greater than 100 MPa using a free radical initiator such as peroxide (see, for example, U.S. Pat. No. 4,599,392 (McKinney, et al.)).

[0067] The term "polymer" refers to a compound prepared by polymerizing one or more monomers, whether of the same or different types. The term polymer encompasses the terms "homopolymer" and "interpolymer."

[0068] Test Method

[0069] Density: Samples for polymer density measurements are prepared according to ASTM D1928. Measurements are made within 1 hour of pressing the sample using ASTM D792, Method B.

[0070] Melt Index: The melt index or I2 of an ethylene-based polymer is measured in accordance with ASTM D1238, condition 190°C / 2.16 kg.

[0071] Melt Strength: Melt strength measurements were performed on a Gottfert Rheotens 71.97 (Goettfert Inc.; Rock Hill, SC) attached to a Gottfert Rheotester 2000 capillary rheometer. The polymer melt is extruded through a capillary die with a flat incidence angle (180 degrees) with a capillary diameter of 2.0 mm and an aspect ratio (capillary length / capillary radius) of 15. After equilibrating the sample at 190°C for 10 minutes, the piston is operated at a constant piston speed of 0.265 mm / sec. The standard test temperature is 190°C. The sample is then forced into an accelerating nip set 100 mm below the die at a rate of 2.4 mm / sec. 2 The strand is uniaxially stretched at an acceleration of 0.265 mm / s. The tensile force is recorded as a function of the take-up speed of the nip rolls. The melt strength is reported as the plateau force (cN) before the strand breaks. The following conditions are used in the melt strength measurement: plunger speed = 0.265 mm / s, wheel acceleration = 2.4 mm / s 2 , capillary diameter = 2.0 mm, capillary length = 30 mm, barrel diameter = 12 mm.

[0072] Dynamic mechanical spectroscopy (DMS): Dynamic oscillatory shear measurements were performed at 190 °C under an inert nitrogen atmosphere using a 25 mm parallel plate ARES system from TA Instruments (New Castle, Del.) at a 2.0 mm gap and a constant strain of 10%. The frequency interval was 0.03 to 300 rad / s with 5 points / decimal logarithmic spacing. The stress response was analyzed in terms of amplitude and phase, from which the storage modulus (G'), loss modulus (G''), and complex modulus (G * ), tan δ, phase angle δ, and complex viscosity (η * ) is calculated. * are complex numbers whose real component is G' and whose imaginary component is G'', respectively (G * =G'+iG''). G * The magnitude of |G * |=(G' 2 +G'' 2 ) 1 / 2 Both tan δ and the phase angle δ are related to the relative elasticity of a material. Tan δ is the ratio of the loss modulus to the storage modulus, i.e., tan δ=G' / G', and the phase angle δ is reported as δ=tan -1 (G'' / G') * is also a complex number whose real component is η' and whose imaginary component is η''. * The magnitude of is reported as follows:

number

[0073] DSC: Differential scanning calorimetry (DSC) can be used to measure the crystallinity of a sample at a given temperature over a wide temperature range. For example, a TA Instruments Q1000 DSC equipped with an RCS (refrigerated cooling system) and an autosampler module is used to perform this analysis. A nitrogen purge gas flow of 50 mL / min is used during testing. Each sample is pressed into a thin film and melted in the press at approximately 175°C. The molten sample is then air-cooled to room temperature (approximately 25°C). A 3-10 mg, 6 mm diameter specimen is extracted from the cooled polymer, weighed, placed in a lightweight aluminum pan (approximately 50 mg), and crimped shut. The specimen is then analyzed to determine its thermal properties. The thermal behavior of the sample is determined by generating a heat flow vs. temperature profile as the sample temperature is increased or decreased. To remove the thermal history, the sample is first rapidly heated to 180°C and held isothermal for 3 minutes. The sample is then cooled to -40°C at a cooling rate of 10°C / min and isothermally held at -40°C for 3 minutes. The sample is then heated to 150°C at a heating rate of 10°C / min (this is the "second heating" gradient). The cooling curve and the second heating curve are recorded. The cooling curve is analyzed by setting a baseline endpoint from the onset of crystallization to -20°C. The heating curve is analyzed by setting a baseline endpoint from -20°C to the end of melting. The value determined is the peak melting temperature (T m ), peak crystallization temperature (T c ), heat of fusion (H f ) (in Joules per gram), and the % crystallinity of the polyethylene sample calculated using Equation 1.

number

[0074] Triple-detector gel permeation chromatography: A triple-detector gel permeation chromatography (3D-GPC or TD-GPC) system consists of a Waters (Milford, Mass.) 150°C high-temperature chromatograph. (Other suitable high-temperature GPC instruments include Polymer Laboratories (Shropshire, UK) Models 210 and 220 equipped with an onboard refractive index detector (RI). Additional detectors include an IR4 infrared detector manufactured by Polymer ChAR (Valencia, Spain), a two-angle laser light scattering (LS) detector Model 2040 manufactured by Precision Detectors (Amherst, Mass.), and a 150R4-capillary solution viscometer manufactured by Viscotek (Houston, Tex.). GPCs equipped with the latter two independent detectors and at least one of the former detectors are sometimes referred to as "3D-GPC" or "TD-GPC," although the term "GPC" alone generally refers to conventional GPC. Depending on the sample, either a 15° or 90° angle of the light scattering detector is used for calculations. Data collection is performed using Viscotek TriSEC software, Version 3, and a 4-channel Viscotek Data Manager DM400. The system is also equipped with an online solvent degassing device from Polymer Laboratories (Shropshire, United Kingdom).

[0075] Suitable high-temperature GPC columns may be used, including, but not limited to, four 30 cm long Shodex HT803 13 micrometer columns or four 30 cm Polymer Labs columns with 20 micrometer mixed pore size packing (MixA LS, Polymer Labs). The sample carousel compartment is operated at 140°C, and the column compartment is operated at 150°C. Samples were prepared at a concentration of 0.1 grams of polymer in 50 milliliters of solvent. The chromatographic and sample preparation solvents contain 200 ppm butylated hydroxytoluene (BHT) in trichlorobenzene (TCB). Both solvents were sparged with nitrogen. The polyethylene samples were gently stirred at 160°C for 4 hours. The injection volume was 200 microliters. The flow rate through the GPC was set at 1 mL / min.

[0076] The GPC column set is calibrated by running 21 narrow molecular weight distribution polystyrene standards. The molecular weights (MW) of the standards range from 580 to 8,400,000, and the standards are contained in six "cocktail" mixtures. Each standard mixture has at least a 10-fold interval between individual molecular weights. The standard mixtures are purchased from Polymer Laboratories. The polystyrene standards are prepared at 0.025 g in 50 mL of solvent for molecular weights ≥ 1,000,000 and 0.05 g in 50 mL of solvent for molecular weights < 1,000,000. The polystyrene standards are dissolved at 80 °C for 30 minutes with gentle agitation. The narrow standard mixtures are run first and in order of decreasing highest molecular weight components to minimize degradation. Polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 2 (as described by Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)),

number

[0077] A systematic approach to determining multi-detector offsets was performed in a manner consistent with that published by Balke, Mourey, et al. (Mourey and Balke, Chromatography Polym., Chapter 12, (1992)) (Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym., Chapter 13, (1992)), by optimizing triple-detector logarithmic (MW and intrinsic viscosity) results from Dow 1683 broad-dispersion polystyrene (American Polymer Standards Corp.; Mentor, Ohio) or its equivalent to narrow-dispersion standard column calibration results from a narrow-dispersion polystyrene standard calibration curve. Molecular weight data were obtained using methods consistent with those published by Zimm (Zimm, BH, J. Chem. Phys., 16, 1099 (1948)) and Kratochvil (Kratochvil, P., Classical Light Scattering from Polymer Solutions, Elsevier, Oxford, NY (1987)). The overall injected concentration used in determining molecular weights is obtained from the mass detector area and mass detector constant derived from a suitable linear polyethylene homopolymer or one of the polyethylene standards of known weight-average molecular weight. Calculated molecular weights are obtained using the light scattering constant derived from one or more of the aforementioned polyethylene standards and a refractive index concentration coefficient d / dc of 0.104. Generally, the mass detector response and light scattering constant should be determined from a linear standard having a molecular weight greater than about 50,000 daltons. Calibration of the viscometer can be accomplished using methods described by the manufacturer or using published values ​​of suitable linear standards such as Standard Reference Materials (SRM) 1475a, 1482a, 1483, or 1484a. Chromatographic concentrations are assumed to be low enough to eliminate consideration of second viral coefficient effects (concentration effects on molecular weight).

[0078] gpcBR branching index by 3D-GPC: In a 3D-GPC setup, the Mark-Houwink constants K and α can be measured independently for two polymers, polystyrene and polyethylene, using polyethylene standards and these can be used to refine the Williams and Ward polyethylene equivalent molecular weight using the following method.

[0079] The gpcBR branching index is determined by first calibrating the light scattering, viscosity, and concentration detectors as described above. Baselines are then subtracted from the light scattering, viscometer, and concentration chromatograms. An integration window is then set to ensure full integration of the low molecular weight retention volume range in the light scattering and viscometer chromatograms, which indicates the presence of detectable polymer from the refractive index chromatogram. Linear polyethylene standards are then used to establish the Mark-Houwink constants for polyethylene and polystyrene as described above. Once the constants are obtained, the two values ​​are used to construct two linear reference conventional calibrations of polyethylene molecular weight and polyethylene intrinsic viscosity as a function of elution volume, as shown in Equations 3 and 4.

number

[0080] The gpcBR branching index is a robust method for characterizing long chain branching as described in Yau, Wallace W., "Examples of Using 3D-GPC-TREF for Polyolefin Characterization," Macromol. Symp., 2007, 257, 29-45. This index avoids the slice-by-slice 3D-GPC calculations traditionally used in determining g' values ​​and calculating branching frequency in favor of the entire polymer detector area. From the 3D-GPC data, the absolute weight average molecular weight (M) of the sample bulk can be determined by the light scattering (LS) detector using the peak area method. w;Abs ) can be obtained.

[0081] By 3D-GPC, the weight average molecular weight (M w;Abs ") and intrinsic viscosity are also obtained using Equations 5 and 6, respectively.

number

number

[0082] The area calculation of Equation 5 provides greater accuracy because the overall sample area is less susceptible to detector noise and fluctuations caused by GPC settings to the baseline and integration limits. More importantly, the peak area calculation is not affected by detector volume offsets. Similarly, high-precision sample intrinsic viscosity (IV) can be obtained by the area method shown in Equation 6,

number

[0083] To determine the gpcBR branching index, the light scattering elution area of ​​the sample polymer is used to determine the molecular weight of the sample. The viscosity detector elution area for the sample polymer is used to determine the intrinsic viscosity (IV or [η]) of the sample.

[0084] First, the molecular weight and intrinsic viscosity of a linear polyethylene standard sample, such as SRM1475a or equivalent, are determined using conventional calibrations ("cc") for both molecular weight and intrinsic viscosity as a function of elution volume per Equations 7 and 8.

number

[0085] Equation 9 is used to determine the gpcBR branching index,

number

[0086] All statistics with the subscript "cc" refer to the respective elution volume, the corresponding conventional calibration as described above, and the concentration (C) derived from the retention volume molecular weight calibration. i ) are determined using the K. Values ​​without subscripts are measurements based on the mass detector, LALLS, and viscometer area. PE The value of is iteratively adjusted until the linear reference sample has a gpcBR measurement of zero. For example, in this particular case, the final values ​​of α and Log K for determining gpcBR are 0.725 and −3.355, respectively, for polyethylene, and 0.722 and −3.993, respectively, for polystyrene.

[0087] Once the K and α values ​​have been determined using the procedure described above, the procedure is repeated using the branched sample. Analyze the branched sample using the final Mark-Houwink constant as the best "cc" calibration value and apply Equations 5-8.

[0088] The interpretation of gpcBR is as follows: For linear polymers, the values ​​measured by LS and viscometer will be close to the conventional calibration standards, so the gpcBR calculated from Equation 9 will be close to zero. For branched polymers, the measured polymer molecular weight will be close to the calculated M w,cc Higher than the calculated IV ccis higher than the measured polymer IV, so gpcBR is greater than zero, especially at high levels of long chain branching. In effect, the gpcBR value represents the fractional change in IV due to the molecular size contraction effect as a result of polymer branching. gpcBR values ​​of 0.5 or 2.0 represent a molecular size contraction effect on IV at levels of 50% and 200%, respectively, relative to an equivalent weight of linear polymer molecules.

[0089] In these particular examples, the advantage of using gpcBR over traditional "g' index" and branching frequency calculations is due to the higher precision of gpcBR. All parameters used in the gpcBR index determination are obtained with good precision and are not adversely affected by the low 3D-GPC detector response at high molecular weights from the concentration detector. Errors in detector volume alignment should also not affect the precision of the gpcBR index determination.

[0090] Zero Shear Viscosity: Specimens for creep measurements are prepared on a programmable tetrahedron benchtop press. The program is 177°C for 5 minutes, 10 7 The melt is held at a pressure of 1.8 Pa. The chase is then removed to the bench and allowed to cool to room temperature. Circular specimens are then die cut from the plaque using a punch press and a hand-held die with a diameter of 25 mm. The specimens are approximately 1.8 mm thick.

[0091] Zero-shear viscosity was obtained from creep tests conducted on an AR-G2 stress-controlled rheometer (TA Instruments; New Castle, Del.) using 25 mm diameter parallel plates at 190 °C. Each sample was stabilized before compression molding by adding 2000 ppm of an antioxidant, a 2:1 mixture of IRGAFOS 168 and IRGANOX 1010 (Ciba Specialty Chemicals; Glattbrugg, Switzerland). Before zeroing, the rheometer oven was set to the test temperature of 190 °C for at least 60 minutes. At this test temperature, a disk of the compression-molded sample was inserted between the plates and allowed to equilibrate for 5 minutes. The upper plate was then lowered 50 μm above the desired test gap (1.5 m). Any excess material was trimmed, and the upper plate was lowered to the desired gap. Measurements were performed under a nitrogen purge at a flow rate of 5 L / min. The initial creep time was set to 6 hours.

[0092] A low shear stress of 5 Pa to 20 Pa was applied to all samples to ensure that the steady-state shear rate was low enough to be in the Newtonian region. Steady-state was determined by taking a linear regression of all data within the last 10% time window of a plot of log(J(t)) vs. log(t), where J(t) is creep compliance and t is creep time. If the slope of the linear regression is greater than 0.97, steady-state was considered reached, and the creep test was then stopped. In all cases in this test, the samples reached steady-state within 6 hours. The steady-state shear rate was determined from the slope of all linear regressions of all data within the last 10% time window of a plot of ε vs. t (ε is strain). Zero-shear viscosity was determined from the ratio of the applied stress to the steady-state shear rate.

[0093] Before and after the creep test, the same specimen is subjected to a dynamic oscillatory shear test at 10% strain from 0.1 rad / s to 100 rad / s. The complex viscosity values ​​of the two tests are compared. If the difference in viscosity at 0.1 rad / s is greater than 5%, the specimen is considered to have deteriorated during the creep test and the results are discarded.

[0094] Surface Haze and Internal Haze: Samples measured for internal haze and total haze are sampled and prepared according to ASTM D1003. Azegard Plus (BYK-Gardner USA; Columbia, Md.) is used for testing. Surface haze is determined as the difference between total haze and internal haze. Surface haze tends to be related to the surface roughness of the film, and surface haze increases with increasing surface roughness. The ratio of surface haze to internal haze is the surface haze value divided by the internal haze value.

[0095] Blown Film Production Conditions: Sample films were extruded blown films produced on a 45 mm COVEX monolayer blown film line (Barcelona, ​​Spain) using the conditions in Table 1. [Table 1]

[0096] GPC-LS Characterization: Analyzing the concentration-normalized LS chromatogram response curve of a particular sample using a predetermined molecular weight range is useful for distinguishing the polymers of the embodiments from similar and commercially available ethylene-based polymers with relatively low densities. The "GPC-LS Characterization" parameter Y is designed to capture the unique combination of a particular material's molecular weight distribution (MWD) and GPC-LS profile. Important properties are melt index (I2), MWD, long-chain branching, and haze. Desirable attributes for polymers with low haze are a higher melt index (I2), a narrower MWD, and a lower long-chain branching value. This GPC-LS characterization value is designed to capture the features of low long-chain branching, narrow MWD, and high melt index (I2). Figure 2 provides examples and guidance for using GPC-LS.

[0097] Characterization Method for Identifying Embodiments of the Invention: Ethylene-based polymers with long chain branching, such as low-density ethylene-based polymers, can be distinguished by using an analytical technique called "GPC-LS characterization." In the GPC-LS characterization method, this determination is made using the light scattering (LS) detector response for samples processed by conventionally calibrated 3D-GPC ("cc-GPC") over the sample's molecular weight range. The sample's molecular weight is converted to a logarithmic value for scaling purposes. The LS response is "concentration-normalized" so that LS responses can be compared between samples, since it is known in the art that unnormalized LS signals can vary widely from sample to sample without normalization. When plotted, the logarithmic and concentration-normalized LS values ​​for a range of cc-GPC molecular weights form a concentration-normalized LS chromatogram curve, as shown in Figure 2.

[0098] Once the concentration-normalized LS chromatogram curve is available, the determination of the GPC-LS characterization value is straightforward. In the GPC-LS characterization method, the GPC-LS characterization value (Y) is determined using Equation 10:

number

[0099] The GPC-LS characterization value is the relationship between the two associated areas (A and B) between two points on the concentration-normalized LS chromatogram curve at the logarithm of two specified cc-GPC molecular weight values ​​and the slope of the exponential line (x). A particular cc-GPC molecular weight value attempts to bracket the molecular weight fraction known to contain polymer chains with long chain branches.

[0100] The first step in the analysis is the generation of a concentration-normalized LS chromatogram curve representing the concentration-normalized LS response value versus the logarithm of the cc-GPC molecular weight for the polymer being tested.

[0101] The second step is to connect two points on the concentration-normalized LS chromatogram curve with a straight line. The line and point provide the basis for determining area A and area B. Two points, the first point and the second point, are located on the concentration-normalized LS chromatogram curve and represent concentration-normalized LS response values ​​(the first concentration-normalized LS response value and the second concentration-normalized LS response value) at logarithmic values ​​for two cc-GPC molecular weight values ​​(the first logarithmic cc-GPC molecular weight value and the second logarithmic cc-GPC molecular weight value). The first point (point 1 on FIG. 2 ) is defined as being on the concentration-normalized LS chromatogram curve (representing the first concentration-normalized LS response value) corresponding to the logarithmic value (representing the first logarithmic cc-GPC molecular weight value) of a cc-GPC molecular weight of 350,000 grams / mole, and its value is approximately 5.54. A second point (point 2 on Figure 2) is defined as being along the concentration-normalized LS chromatogram curve at the concentration-normalized LS response value (representing the second concentration-normalized LS response value) corresponding to the logarithmic cc-GPC molecular weight of 1,150,000 grams / mole (representing the second logarithmic cc-GPC molecular weight value), which is approximately 6.06. It is known in the art that differentiation in long chain branching typically occurs near a cc-GPC molecular weight of 1 million grams / mole.

[0102] The third step is to determine the area A between the line between the two logarithmic cc-GPC molecular weight values ​​and the concentration-normalized LS chromatogram curve. Area A is defined as A1 minus A2. In some embodiments, area A is defined for a range of values ​​between the logarithmic value of a cc-GPC molecular weight of 350,000 g / mole and the logarithmic value of a cc-GPC molecular weight of 1,150,000 g / mole.

[0103] A1 is defined as the area enclosed between a straight line and a normalized LS chromatogram curve, where the concentration-normalized LS response value of the straight line is greater than the concentration-normalized LS response value of the concentration-normalized LS chromatogram curve between two logarithmic cc-GPC molecular weight values.

[0104] As can be seen from Figure 2, the area defined as A1 fills the entire range between the two logarithmic cc-GPC molecular weights, and therefore A = A1. In many cases, the line is "above" the concentration-normalized LS chromatogram curve for the logarithmic cc-GPC molecular weight range and does not intersect the concentration-normalized LS chromatogram curve except at points 1 and 2. In these cases, A = A1 and A2 = 0. However, in some embodiments, A does not equal A1. The concentration-normalized LS chromatogram curve shown in Figure 3 provides an example of when this can occur.

[0105] In some embodiments, as can be seen in Figure 3, the line may intersect the concentration-normalized LS chromatogram curve at at least one point other than points 1 and 2 (see "Line Intersection" in Figure 3). In such a situation, A1 is determined as previously defined. For the example shown in Figure 3, A1 would be the area between the concentration-normalized LS chromatogram curve and the line from a log cc-GPC molecular weight value of approximately 5.8 to a log cc-GPC molecular weight of 1,150,000 grams / mole.

[0106] A2 is defined as the inverse of A1. A2 is the area enclosed between the line and the concentration-normalized LS chromatogram curve, where the concentration-normalized LS response of the line is less than the concentration-normalized LS response of the concentration-normalized LS chromatogram curve between two logarithmic cc-GPC molecular weight values. For the example shown in Figure 3, A2 is the area between the concentration-normalized LS response curve and the line from a logarithmic cc-GPC molecular weight value of approximately 5.8 to a logarithmic cc-GPC molecular weight of 350,000 grams / mol.

[0107] In calculating the total value of A, A is again defined as area A minus area A. In some embodiments, A can be a negative value, reflecting that the line subtends more area below than above the concentration-normalized LS response curve, as can be seen in the graph of FIG.

[0108] The fourth step is to determine the area under the concentration-normalized LS chromatogram curve for the logarithmic cc-GPC molecular weight range, B. B is defined as the area under the concentration-normalized LS chromatogram curve between two logarithmic cc-GPC molecular weight values. Area B is independent of the analysis of area A.

[0109] The fifth step is to determine the value of x, the slope index value. The value of x takes into account the slope of the line established to determine area A and area B. The value of x is not the slope of the line; however, it represents a value that reflects the difference between point 1 and point 2. The value of x is defined by Equation 11:

number

[0110] Finally, once x, A, and B are established, the GPC-LS characterization value (Y) is determined using Equation 10 shown above.

[0111] When examining an LS chromatogram response curve, it is known that the magnitude of the LS peak at approximately log MW 6 is related to the degree of long-chain branching of the polymer. The smaller the log MW 6 LS peak, the steeper the angle of the line, and therefore the more negative the value of the slope of the line segment in the LS plot. This results in a more negatively exponential slope of the line (x) value. From the relationship in Equation 10, more negative x values ​​contribute to a more positive value of Y.

[0112] Another term that contributes to Y in Equation 10 is the area ratio of A / B. The higher the A / B ratio, the larger the Y value. This ratio is influenced by the polymer's melt index (I2) and MWD values. These two values, in turn, affect how far the main polymer peak is separated from the LS pre-peak, which is located near a LogMW of 6 in the high MW region. A higher melt index (I2) value means a lower MW and indicates a more pronounced separation between the two response peaks. This will result in a deeper valley between the high and low MW portions. A deeper valley creates a larger area under the line, designated "A." A narrower MWD means the LS response curve is less wide, which has the similar effect of creating a deeper valley in the plot and a larger A.

[0113] Extrusion Multi-Pass: A relative measure of the atmospheric stability (resistance to oxidative attack and degradation) of two or more resins can be tested by passing a polymer sample through a heated extruder under atmospheric conditions several times, then testing physical properties such as melt index (I2) after each pass.

[0114] Polymer samples are processed through a LEISTRIZ micro-18 twin-screw extruder (obtained from American Leistritz Extruder Corporation, Somerville, NJ). The extruder is controlled and driven by a HAAKE™ PolyLab System (Thermo Fischer Scientific; Waltham, Mass.) computer system. The extruder consists of six heating zones, each 90 mm long, and a heated die with a 3 mm strand hole. The first zone is the feed port and is jacket-cooled with flowing water to prevent crosslinking of the polymer feed. The first zone is equipped with an open cone to receive the polymer feed from a K-TRON KV2T20 twin-auger feeder (Pitman, NJ). The five heating zones are set at 135°C, 165°C, 200°C, 220°C, and 220°C, respectively. The die at the end of the extruder is heated to 220°C.

[0115] Each screw has an 18 mm diameter and a length of 540 mm, resulting in an L / D ratio of 30. The first five-zone screw stack consists of an open forward design with a 30-degree (non-vertical) slope. The final zone of the screw stack has a slightly narrower forward slope with a 20-degree (non-vertical) slope. The overall screw design imparts little shear to the polymer, with the material moving primarily through the heated barrel section. The molten polymer is compressed near the end of the screw through a tighter slope element to provide sufficient back pressure to force the molten material into the die.

[0116] During processing, the screw rotates at 250 revolutions per minute (rpm), and the polymer is fed into the extruder by a feeder, providing enough polymer to process as many passes as required, while allowing a sample, preferably about 50 g, to be taken after each pass for analysis.

[0117] The resulting molten polymer strands are sent into a cold water bath where they solidify. After solidification, the polymer strands are passed through an air knife to remove the water and then chopped into polymer pellets by a strand chopper. Once pelletized, a sample is obtained for analysis, and the remainder is then returned to the feeder for further processing, if desired.

[0118] One or more features of the present disclosure will be illustrated in light of the following examples. [Example]

[0119] Example 1: Polymerization - Autoclave Reactor

[0120] Additive A is tris(trimethylsilyl)silane obtained from Gelest, Inc.

[0121] Initiator: In a second 316 stainless steel feed vessel, the peroxide initiators tert-butyl peroxyacetate (TPA, a 20 wt % solution in ISOPAR™ H) and tert-butyl peroxyoctoate (TPO) were combined with ISOPAR E to produce 3000 ppm by weight TPA and 5000 ppm by weight TPO (a 1:1 molar TPA / molar TPO ratio). The vessel was padded and unpadded five times with 70 psig nitrogen prior to use and kept under the nitrogen pad during operation.

[0122] Ethylene was injected at 5500 gm / h at 193 MPa into a stirred (1600 rpm) 300 mL high-pressure CSTR reactor, with the external heating jacket set to control the internal reactor temperature at 215 °C. Various chain transfer agents were added sequentially to determine their chain transfer effectiveness. First, propylene (CTA) was added to the ethylene stream at 6.2 MPa pressure at a controlled rate to produce a final product with an MI of 2 g / 10 min. The mixture was then compressed to 193 MPa and injected into the reactor. A solution of the appropriate additive solution was pumped directly into the reactor at 193 MPa via a high-pressure pump. A peroxide initiator solution was added directly to the reactor through the sidewall at 193 MPa pressure at a rate that controlled the ethylene conversion to near 12%. In all experiments shown in Table 2 below, ISOPAR E was added at a rate of 40.7 grams / hour, TPA was added at a rate of 0.123 grams / hour, and TPO was added at a rate of 0.202 grams / hour. Comparative chain transfer agents were run to determine the relative Cs of the materials. Comparative Example 1 (ISOPAR E) was run at multiple concentrations to determine the Cs at the relevant temperature and pressure. This was found to be 0.030. This value was used in subsequent calculations.

[0123] To determine the Cs of Additive A, it had to be diluted in ISOPAR E before being fed to the reactor. To account for the effect of additional chain transfer, the combined Cs of ISOPAR E and Additive A was determined from the relationship between the molar feed rates of all CTAs and the molar feed rate of ethylene. The determined Cs of ISOPAR E was then subtracted to obtain the Cs of Additive A alone.

[0124] The polymerization procedures for each experiment are detailed in the table below. [Table 2] [Table 3] [Table 4]

[0125] Cs is derived according to the Mayo formula (Mayo, F.R., Chain Transfer in the Polymerization of Styrene: The Reaction of Solvents with Free Radicals. J. Am. Chem. Soc. 1943, 65, 2324-2329),

number

number

[0126] Example 2: Polymerization - Autoclave reactor in the presence of triethylsilane

[0127] Chemicals: CTA triethylsilane (CAS number: 617-86-7) had a purity of >95%, the solvent was n-heptane, and the initiator was TBPA (Tx-F).

[0128] Methods: Run 1: A solution of 100 g of silane in 200 g of n-heptane was prepared. The initiator solution contained 9 g of Trigonox F (t-butyl peroxyacetate) 35 wt% per 500 mL of n-heptane. Run 2: The silane was used pure as received. The initiator solution concentration was 2.8 g of Trigonox F (t-butyl peroxyacetate) 35 wt% per 500 mL of n-heptane.

[0129] Triethylsilane was used as the CTA in a 54 mL continuous stirred-tank reactor. CTA injection via an HPLC pump was performed at approximately 250 bar on the suction side of the compressor's third stage. The initiator solution reservoir was purged with nitrogen and then charged with the peroxide high-pressure pump. The CTA feed tank was maintained under an air atmosphere. The capillary between the reactor and the pressure relief valve was heated to 140 °C. The bottom of the magnetically driven stirrer was water-cooled using tap water at ambient temperature. Ethylene was fed completely through the stirrer, and the peroxide and CTA were fed into the ethylene before entering the reactor. The experiment was conducted at 2000 bar. The reactor temperature was controlled to approximately 200 °C to approximately 220 °C using a heating mantle outside the reactor. The conversion rate in the reactor was controlled by the flow rate of a peroxide mixture of Trigonox F (t-butyl peroxyacetate) diluted with n-heptane. The melt index was adjusted by adjusting the flow rate of the pure compound being studied as a potential CTA or by adjusting the flow rate of a mixture of the compound in n-heptane, methyl ethyl ketone, isopropanol, or ethyl acetate.

[0130] The table below summarizes the polymerization conditions and the properties of the resulting polymers. [Table 5] [Table 6]

[0131] For the experiments summarized in the table, Cs is calculated according to the Mayo formula (Eq. 12), n was derived as described above with respect to Example 1.

[0132] Example 3: Polymerization of vinyl acetate

[0133] Chemicals: All chemicals were purchased from either Aldrich or Strem. Vinyl acetate was distilled daily before use. Azobisisobutyronitrile (AIBN) initiator solution in toluene was made fresh daily.

[0134] Method: In a glovebox, samples were prepared by mixing 10 mL of vinyl acetate, an appropriate amount of chain transfer agent, and 25 microliters of a 0.25 M solution of AIBN in toluene in a vial. Each vial was then sealed and placed in a reflux shaker at 60 °C. Each vial was monitored, and when a clear increase in viscosity was observed, the reaction mixture was poured into 20 mL of n-hexane containing 0.02 g of di-tert-butylmethylphenol inhibitor. The resulting polymer was collected by filtration and dried at 130 °C for 1 hour. The final polymer was analyzed by GPC to determine the molecular weight.

[0135] The chain transfer constant was determined by running experiments with different levels of chain transfer agent and measuring the molecular weight of the resulting polymer, using the Mayo equation (Equation 12).

[0136] The Cs of ethylene was predicted using the following equation:

number

[0137] The measured Cs values ​​for vinyl acetate and the predicted Cs values ​​for ethylene based on Equation 14 are shown in Table 7. [Table 7]

[0138] Aspects According to one embodiment, alone or in combination with any other embodiment, a method for making an olefin-based polymer by free radical polymerization in a reactor system includes initiating free radical polymerization of an olefin-based monomer, propagating growth of the olefin-based polymer while the free radical polymerization of the olefin-based monomer continues, and adding a chain transfer agent to the reactor system to terminate growth of the olefin-based polymer, the chain transfer agent comprising a silane of formula (1): [ka] In the formula, R 1 , R 2 , R 3 and R 4 are independently a hydrogen atom, a (C1-C40) hydrocarbyl, -N(R 5 )2, -Si(R 5 )3, -OSi(R 5 )3, -OR 5 , and -R 6 -Si(R 5 )3, and each R 5 are independently selected from a hydrogen atom and a (C1-C40) hydrocarbyl, and each R 6 is (C1-C40) hydrocarbylene, and optionally R 1 , R 2 , R 3 , and R 4 or any two R bonded to the same nitrogen atom 5 , or any two R bonded to the same silicon atom 5 are joined to form a ring having 3 to 50 atoms in the ring, excluding any hydrogen atoms.

[0139] According to a second aspect, alone or in combination with any other aspect, the chain transfer agent does not contain sulfur or phosphorus.

[0140] According to a third aspect, alone or in combination with any other aspect, the silane of formula (1) is selected from the group consisting of triethylsilane, diethylmethylsilane, tris(trimethylsilyl)silane, n-butylsilane, dimethylphenylsilane, phenylsilane, chlorodimethylsilane, diisopropylaminosilane, 1,2-bis(dimethylsilyl)benzene, 1,3-bis(dimethylsilyl)benzene, 1,4-bis(dimethylsilyl)benzene, and 1,1,3,3-tetramethyldisiloxane.

[0141] According to a fourth aspect, alone or in combination with any other aspect, the silane of formula (1) is selected from the group consisting of trimethylsilane, (trimethylsilyl)dimethylsilane, bis(trimethylsilyl)methylsilane, and tris(trimethylsilyl)silane.

[0142] According to a fifth aspect, alone or in combination with any other aspect, the silane of formula (1) comprises tris(trimethylsilyl)silane.

[0143] According to a sixth aspect, alone or in combination with any other aspect, the reactor system comprises at least one tubular reactor, or at least one autoclave reactor, or a combination of at least one tubular reactor and at least one autoclave reactor.

[0144] According to a seventh aspect, alone or in combination with any other aspect, the reactor system comprises at least one tubular reactor, or at least one autoclave reactor, or a combination of at least one tubular reactor and at least one autoclave reactor, and the silane of formula (1) comprises tris(trimethylsilyl)silane.

[0145] According to an eighth aspect, alone or in combination with any other aspect, the reactor system comprises at least one tubular reactor.

[0146] According to a ninth aspect, alone or in combination with any other aspect, the reactor system comprises at least one tubular reactor, and the silane of formula (1) comprises tris(trimethylsilyl)silane.

[0147] According to a tenth embodiment, alone or in combination with any other embodiment, the reactor system comprises a pressure of 100 MPa or greater during propagation of the olefin polymer growth.

[0148] According to an eleventh aspect, alone or in combination with any other aspect, the olefinic monomer comprises ethylene.

[0149] According to a twelfth embodiment, alone or in combination with any other embodiment, the olefin-based polymer consists of ethylene.

[0150] According to a thirteenth aspect, alone or in combination with any other aspect, the (C1-C40)hydrocarbylene is selected from ethane-1,2-diyl, propane-1,3-diyl, 2-methylpropane-1,3-diyl, phenyl-1,4-diyl, naphthalene-2,6-diyl, and naphthalene-3,7-diyl.

[0151] According to a fourteenth aspect, alone or in combination with any other aspect, the (C1-C40)hydrocarbylene is phenyl-1,4-diyl.

[0152] According to a fifteenth aspect, alone or in combination with any other aspect, the free radical polymerization is a high pressure peroxide initiated free radical polymerization.

[0153] According to a sixteenth embodiment, alone or in combination with any other embodiment, the initiating the free radical polymerization comprises adding a peroxide initiator to the reactor system.

[0154] According to a seventeenth aspect, alone or in combination with any other aspect, the initiating free radical polymerization comprises adding a peroxide initiator to the reactor system, the peroxide initiator being selected from t-butyl peroxypivalate, di-t-butyl peroxide, t-butyl peroxyacetate, t-butyl peroxyoctanoate, and t-butyl peroxy-2-ethylhexanoate, and mixtures thereof.

[0155] It will be apparent to those skilled in the art that various modifications can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover modifications and variations of the described embodiments provided that such modifications and variations come within the scope of the appended claims and their equivalents. Examples of the invention of this application include the following. [1] A method for making an olefin-based polymer by free radical polymerization in a reactor system, said method comprising: initiating free radical polymerization of olefinic monomers in said reactor system; propagating growth of the olefin-based polymer during the continuation of the free radical polymerization of the olefin-based monomer; adding a chain transfer agent to the reactor system to terminate the growth of the olefin-based polymer; The chain transfer agent comprises a silane of formula (1): [ka] During the ceremony, R 1 、R 2 、R 3 , and R 4 are independently a hydrogen atom, a (C1-C40) hydrocarbyl, -N(R 5 ) 2 , -Si(R 5 ) 3 , -OSi(R 5 ) 3 , -OR 5 , and -R 6 -Si(R 5 ) 3 is selected from Each R 5 are independently selected from a hydrogen atom and a (C1-C40) hydrocarbyl; Each R 6 is (C1-C40) hydrocarbylene, Optionally, R 1 、R 2 、R 3 , and R 4 or any two R bonded to the same nitrogen atom 5 , or any two R bonded to the same silicon atom 5 are linked to form a ring having 3 to 50 atoms in the ring, excluding any hydrogen atoms. [2] The method according to [1] above, wherein the chain transfer agent does not contain sulfur or phosphorus. [3] The method according to [1] or [2] above, wherein the silane of formula (1) is selected from the group consisting of triethylsilane, diethylmethylsilane, tris(trimethylsilyl)silane, N-butylsilane, dimethylphenylsilane, phenylsilane, chlorodimethylsilane, diisopropylaminosilane, 1,2-bis(dimethylsilyl)benzene, 1,3-bis(dimethylsilyl)benzene, 1,4-bis(dimethylsilyl)benzene, and 1,1,3,3-tetramethyldisiloxane. [4] The method according to any one of the above [1] to [3], wherein the silane of formula (1) is selected from the group consisting of trimethylsilane, (trimethylsilyl)dimethylsilane, bis(trimethylsilyl)methylsilane, and tris(trimethylsilyl)silane. [5] The method according to any one of the above [1] to [4], wherein the silane of formula (1) includes tris(trimethylsilyl)silane. [6] The method according to any one of the above [1] to [5], wherein the reactor system comprises at least one tubular reactor, or at least one autoclave reactor, or a combination of at least one tubular reactor and at least one autoclave reactor. [7] The method according to [6] above, wherein the silane of formula (1) comprises tris(trimethylsilyl)silane. [8] The method according to any one of [1] to [7] above, wherein the reactor system comprises at least one tubular reactor. [9] The method according to [8] above, wherein the silane of formula (1) comprises tris(trimethylsilyl)silane.

[10] The method according to any one of the above [1] to [9], wherein the reactor system contains a pressure of 100 MPa or more during propagation of the olefin polymer growth.

[11] The method according to any one of the above [1] to

[10] , wherein the (C1-C40) hydrocarbylene is selected from ethane-1,2-diyl, propane-1,3-diyl, 2-methylpropane-1,3-diyl, phenyl-1,4-diyl, naphthalene-2,6-diyl, and naphthalene-3,7-diyl.

[12] The method according to any one of the above [1] to

[11] , wherein the (C1-C40) hydrocarbylene is phenyl-1,4-diyl.

[13] The method according to any one of the above [1] to

[12] , wherein the free radical polymerization is a high-pressure peroxide-initiated free radical polymerization.

[14] The method according to any one of [1] to

[13] above, wherein initiating the free radical polymerization comprises adding a peroxide initiator to the reactor system.

[15] The method of

[14] above, wherein the peroxide initiator is selected from t-butyl peroxypivalate, di-t-butyl peroxide, t-butyl peroxyacetate, t-butyl peroxyoctanoate, and t-butyl peroxy-2-ethylhexanoate, and mixtures thereof.

Claims

1. 1. A method for making an ethylene-based polymer by free radical polymerization in a reactor system, the method comprising: initiating free radical polymerization of ethylenic monomers in said reactor system; propagating the growth of the ethylene-based polymer at a temperature of 150°C to 360°C under a pressure of 100 MPa to 400 MPa during the free radical polymerization of the ethylene-based monomer; terminating the growth of the ethylene-based polymer with a chain transfer agent comprising (trimethylsilyl)dimethylsilane, bis(trimethylsilyl)methylsilane, or tris(trimethylsilyl)silane; A method comprising:

2. The method of claim 1, wherein the chain transfer agent comprises tris(trimethylsilyl)silane.

3. 10. The method of claim 1, wherein the reactor system comprises at least one tubular reactor, or at least one autoclave reactor, or a combination of at least one tubular reactor and at least one autoclave reactor.

4. The method of claim 3, wherein the chain transfer agent comprises tris(trimethylsilyl)silane.

5. The method of any one of claims 1 to 4, wherein the reactor system comprises at least one tubular reactor.

6. The method of any one of claims 1 to 5, wherein initiating the free radical polymerization comprises adding a peroxide initiator to the reactor system.

7. 7. The method of claim 6, wherein the peroxide initiator is selected from t-butyl peroxypivalate, di-t-butyl peroxide, t-butyl peroxyacetate, t-butyl peroxyoctanoate, and t-butyl peroxy-2-ethylhexanoate, and mixtures thereof.

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