CN121443682A

CN121443682A - Trimodal ethylene-based polymers

Info

Publication number: CN121443682A
Application number: CN202480043152.1A
Authority: CN
Inventors: R·D·J·弗勒泽; K·卢; J·D·魏因霍尔德; C·F·J·邓都尔德; L·马丁内蒂; 侯健博; J·A·佩雷拉; J·巴津; J·克洛西
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2023-06-28
Filing date: 2024-06-12
Publication date: 2026-01-30
Also published as: WO2025006179A1

Abstract

Embodiments of the present disclosure relate to a trimodal ethylene-based polymer comprising a first polymer fraction, a second polymer fraction, and a third polymer fraction, wherein the first polymer fraction, the second polymer fraction, and the third polymer fraction each comprise a polymerization reaction product of ethylene monomer and optionally a C ₃ ₃-C₁₄ ₁₄ a-olefin comonomer, with the proviso that at least one of the first polymer fraction, the second polymer fraction, and the third polymer fraction comprises a polymerization reaction product of ethylene monomer, a polyene comonomer, and optionally a C ₃ ₃-C₁₄ ₁₄ a-olefin comonomer.

Description

Trimodal ethylene-based polymers

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional application serial No. 63/510,769, filed on 28, 6, 2023, the contents of which are incorporated herein by reference in their entirety.

Technical Field

Embodiments relate generally to multimodal ethylene-based polymers, and in particular, to trimodal ethylene-based polymers having processability and mechanical properties.

Background

Linear Low Density Polyethylene (LLDPE) made via solution or gas phase processes generally has excellent mechanical properties but has poor melt strength and processability in film manufacture. Thus, to improve processability, an amount of LDPE may be blended with LLDPE to improve the processability and melt strength of the LLDPE resin. Unfortunately, the addition of LDPE results in reduced mechanical properties of the resulting blend when compared to pure LLDPE resins.

Thus, there is a need for ethylene-based polymers suitable for providing processability and excellent mechanical properties (e.g., dart drop) without blending with LDPE.

Disclosure of Invention

The trimodal ethylene-based polymers of the present invention fulfill this need for processability and mechanical strength by including at least one polymer fraction with increased long chain branching. Without being limited by theory, such long chain branching provides the increased melt strength required in film processing while the trimodal ethylene-based polymer remains excellent in abuse resistance in the film.

According to one or more embodiments, there is provided a trimodal ethylene-based polymer comprising a first polymer fraction, a second polymer fraction, and a third polymer fraction. The first, second, and third polymer fractions each comprise a polymerization reaction product of ethylene monomer and optionally a C ₃-C₁₄ a-olefin comonomer, with the proviso that at least one of the first, second, and third polymer fractions comprises a polymerization reaction product of ethylene monomer, a polyene comonomer, and optionally a C ₃-C₁₄ a-olefin comonomer.

These and other embodiments are described in more detail in the following detailed description in conjunction with the accompanying drawings.

Drawings

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

FIG. 1 graphically depicts the molecular weight distribution of a trimodal ethylene-based polymer of the present disclosure according to one or more embodiments described herein, an

FIG. 2 graphically illustrates the relationship between melt strength and normalized dart drop strength for a trimodal ethylene-based polymer of the present disclosure, in accordance with one or more embodiments described herein.

Detailed Description

Specific examples of methods for synthesizing polymers and polymers synthesized by the methods of the present disclosure will now be described. It is to be understood that the methods of the present disclosure for synthesizing polymers may be embodied in different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

Definition of the definition

The term "polymer" refers to a polymeric compound prepared by polymerizing monomers (whether of the same type or a different type). Thus, the generic term polymer encompasses the term "homopolymer," which is generally used to refer to polymers prepared from only one type of monomer, as well as "copolymer," which refers to polymers prepared from two or more different monomer types.

"Polyethylene" or "ethylene-based polymer" shall mean a polymer comprising greater than 50 weight percent of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more monomer types). Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), ultra Low Density Polyethylene (ULDPE), very Low Density Polyethylene (VLDPE), single site catalyzed linear low density polyethylene, including both linear and substantially linear low density resins (m-LLDPE), medium Density Polyethylene (MDPE), and High Density Polyethylene (HDPE).

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 homo-or co-polymerized in an autoclave or tubular reactor at a pressure above 14,500psi (100 MPa) using a free radical initiator such as peroxide (see, e.g., U.S. patent No. 4,599,392, which is incorporated herein by reference in its entirety). The LDPE resin typically has a density in the range of 0.916g/cm ³ to 0.930g/cm ³.

The term "LLDPE" includes resins made using Ziegler-Natta (Ziegler-Natta) catalyst systems as well as resins made using single site catalysts, including but not limited to dual metallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimines, and constrained geometry catalysts, and resins made using post metallocene molecular catalysts, including but not limited to bis (biphenylphenoxy) catalysts (also referred to as polyvalent aryloxyether catalysts). LLDPE includes linear, substantially linear or heterogeneous ethylene-based copolymers. LLDPE contains less long chain branching than LDPE and comprises substantially linear ethylene polymers further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923 and U.S. Pat. No. 5,733,155, each of which is incorporated herein by reference in its entirety, homogeneously branched linear ethylene polymer compositions, such as those described in U.S. Pat. No. 3,645,992, which is incorporated herein by reference in its entirety, heterogeneously branched ethylene polymers, such as those prepared according to the methods disclosed in U.S. Pat. No. 4,076,698, which is incorporated herein by reference in its entirety, and blends thereof, such as those disclosed in U.S. Pat. No. 3,914,342 and U.S. Pat. No. 5,854,045, which are incorporated herein by reference in their entirety. The LLDPE resin can be prepared via gas phase, solution phase or slurry polymerization or any combination thereof using any type of reactor or reactor configuration known in the art.

"Blend," "polymer blend," and similar terms mean a composition of two or more polymers. Such blends may or may not be miscible. Such blends may or may not be phase separated. Such blends may or may not contain one or more domain configurations, as determined by transmission electron spectroscopy, light scattering, x-ray scattering, and any other method known in the art. The blend is not a laminate, but one or more layers of the laminate may contain the blend. Such blends may be prepared as dry blends, formed in situ (e.g., in a reactor), melt blends, or using other techniques known to those skilled in the art.

By "multilayer structure" or "multilayer film" is meant any structure having more than one layer. For example, a multilayer structure (e.g., film) may have two, three, four, five, six, seven, or more layers. The multi-layer structure may be described as having layers denoted by letters. For example, a three-layer structure designated as A/B/C may have a core layer (B) and two outer layers (A) and (C).

As used herein, "multimodal" refers to polymers produced from multiple polymer fractions, each produced from a different catalyst in a different reaction environment. Multimodal may include bimodal polymers with two polymer fractions, trimodal ethylene-based polymers with three polymer fractions, or polymers with more than three polymer fractions.

As used herein, the term "polyene" refers to a comonomer having at least two double bonds. The polyene encompasses "dienes", which are comonomers having two double bonds.

The term "gel" or "gelling" refers to a solid composed of at least two components, a first being a three-dimensionally crosslinked polymer and a second being a medium in which the polymer is not completely dissolved. When the polymer gel is not completely dissolved, the reactor may be contaminated with the polymer gel.

The term "long chain branching" refers to branches having greater than 100 carbon atoms. "branching" refers to a portion of a polymer that extends from a tertiary or quaternary carbon atom. When a branch extends from a tertiary carbon atom, there are two other branches, which together may be a polymer chain from which the branch extends. The polymer chain is a linear segment of a polymer or more specifically a copolymer, optionally linked at the ends by branched attachment points. For example, a tetrafunctional branched attachment point links the ends of four polymer chains, as opposed to a trifunctional branched attachment point, which links the ends of three polymer chains.

The terms "comprises," "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional component, step or procedure, whether or not the component, step or procedure is specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant or compound whether polymeric or otherwise. In contrast, the term "consisting essentially of excludes any other component, step, or procedure from any subsequently recited range, except for those components, steps, or procedures that are not essential to operability. The term "consisting of" excludes any component, step, or procedure not specifically recited or listed.

Trimodal ethylene-based polymers

Embodiments of the present disclosure relate to multimodal ethylene-based polymers, in particular embodiments, trimodal ethylene-based polymers comprising a first polymer fraction, a second polymer fraction, and a third polymer fraction. The first, second, and third polymer fractions each comprise a polymerization reaction product of ethylene monomer and optionally a C ₃-C₁₄ a-olefin comonomer, with the proviso that at least one of the first, second, and third polymer fractions comprises a polymerization reaction product of ethylene monomer, a polyene comonomer, and optionally a C ₃-C₁₄ a-olefin comonomer.

In one or more embodiments, the polyene can comprise an acyclic non-conjugated diene. The acyclic nonconjugated dienes may include one or more of 1, 4-pentadiene, 1, 5-hexadiene, 1, 6-heptadiene, 1, 7-octadiene, 1, 8-nonadiene, 1, 9-decadiene, 1, 10-undecadiene, 1, 11-dodecadiene, dimethyldivinyl silane, dimethyldiallyl silane, dimethylallyl vinyl silane. The polyene may not comprise cyclic polyenes or bicyclic polyenes, such as norbornene-based compounds, because these cyclic or bicyclic polyenes are not efficiently incorporated into the polymer chain to generate long chain branching.

The C ₃-C₁₄ alpha-olefin comonomer may include one or more of 1-propylene, 1-butene, 1-hexene, 1-octene, or combinations thereof.

As described above, the trimodal ethylene-based polymers of the present invention have excellent processability, which can be quantified in part by their melt strength. As further noted above, this processability and melt strength is due to the long chain branching present in the trimodal ethylene-based polymer. In one or more embodiments, the trimodal ethylene-based polymer can have a Melt Strength (MS) of 4.0cN to 25.0cN, wherein MS is the melt strength in cN (Rheotens device, 190 ℃,2.4mm/s ², 120mm from die exit to wheel center, extrusion rate 38.2s ^-1, capillary die length 30mm, diameter 2mm, and entry angle 180 °). In further embodiments, the Melt Strength (MS) is 4.0cN to 20.0cN, 4.0cN to 15.0cN, 8.0cN to 15.0cN, or 9.0cN to 14.0cN.

Further, the trimodal ethylene-based polymer can have a rheology ratio V _0.1/V₁₀₀ of 4.0 to 12.0, where V _0.1 is the viscosity of the trimodal ethylene-based polymer at 190 ℃ at an angular frequency of 0.1 rad/sec, and V ₁₀₀ is the viscosity of the trimodal ethylene-based polymer at 190 ℃ at an angular frequency of 100 rad/sec. In further embodiments, the rheology ratio V _0.1/V₁₀₀ is 4.0 to 8.0 or 4.0 to 6.5. Without being limited by theory, the rheology ratio indicates shear thinning, and increased long chain branching is associated with increased shear thinning. However, in the case of the present invention, shear thinning may be controlled in a trimodal ethylene-based polymer, for example, by producing one or more fractions in the trimodal ethylene-based polymer other than a small amount of long chain branching.

The trimodal ethylene-based polymer can have a melt index (I ₂) of 0.5dg/min to 2.0dg/min, or 0.5dg/min to 1.0dg/min, wherein I ₂ is measured according to ASTM D1238 (2.16 Kg/190 ℃). The trimodal ethylene-based polymer can have an I ₁₀/I₂ ratio of 5.0 to 15.0 or 5.0 to 10.

In one or more embodiments, the trimodal ethylene-based polymer has a density of from 0.910g/cc to 0.935g/cc, from 0.910g/cc to 0.920g/cc, or from 0.912g/cc to 0.920 g/cc.

In one or more embodiments, the trimodal ethylene-based polymer has a Molecular Weight Distribution (MWD) of 3.0 to 5.0, as measured according to conventional gel permeation chromatography, wherein MWD is defined as Mw/Mn, where Mw is the weight average molecular weight and Mn is the number average molecular weight. In addition, the trimodal ethylene-based polymer has a Mn of from 20.0kg/mol to 35.0kg/mol, or from 25.0kg/mol to 35.0 kg/mol. In addition, the trimodal ethylene-based polymer has a Mw of 100.0kg/mol to 130.0kg/mol, or 105.0kg/mol to 125.0 kg/mol.

Method of

Various processes and processing parameters are believed suitable for producing the multimodal ethylene-based polymer and trimodal ethylene-based polymer of the present disclosure. In one or more embodiments, a process for producing a multimodal ethylene-based polymer (e.g., a trimodal ethylene-based polymer) in a reactor system includes a first reactor and a second reactor. The process comprises polymerizing ethylene, one or more (C ₃-C₁₄) alpha-olefin monomers, and at least one polyene in the presence of a multi-chain catalyst and at least one single-chain catalyst in a first reactor to produce a first reactor polyethylene product comprising long chain branching. The multi-chain catalyst comprises a plurality of polymerization sites and wherein long chain branching occurs by linking the two polymer chains of the multi-chain catalyst with the polyene in a synergistic manner during polymerization. In the second reactor, ethylene and one or more (C ₃-C₁₄) alpha-olefin monomers are polymerized in the absence of an initial polyene feed and in the presence of at least one single-chain catalyst to produce a second reactor polyethylene product. The trimodal ethylene-based polymer comprises a first reactor polyethylene product and a second reactor polyethylene product.

It is contemplated that the polymerization reaction may involve solution polymerization, slurry polymerization, or gas phase polymerization. In particular embodiments, the solution polymerization is carried out in the first reactor, the second reactor, or both. The first reactor and the second reactor may be connected in parallel or in series. Such solution polymerization processes include the use of one or more conventional reactors, such as loop reactors, isothermal reactors, adiabatic reactors, fluidized bed gas phase reactors, stirred tank reactors, batch reactors, in parallel, in series, or any combination thereof.

Exemplary solvents for use in the solution polymerization process may include, but are not limited to, isoparaffins. For example, such solvents are commercially available under the name ISOPAR ^™ E from Exxon Mobil chemical company (ExxonMobil Chemical).

As described above, one or more single-chain catalysts may be in the first reactor and the second reactor. In one embodiment, both the first reactor and the single-chain catalyst may comprise one single-chain catalyst.

As used herein, a "single-chain catalyst" is a polymerization catalyst having one active polymerization site and/or reactive metal center and one active polymer chain at that site. Various single-chain catalysts are considered suitable. These may include dual metallocene catalysts, phosphinimines, constrained geometry catalysts, post-metallocene catalysts, and single site molecular catalysts, including, but not limited to, bis (biphenylphenoxy) catalysts (also known as polyvalent aryloxyether catalysts).

In one embodiment, the single-chain catalyst in the first reactor, the second reactor, or both comprises a bis (biphenylphenoxy) catalyst. According to some embodiments, the bis (biphenylphenoxy) catalyst has a structure according to formula (I):

In formula (I), M is a metal selected from titanium, zirconium or hafnium, which metal is in the formal oxidation state +2, +3 or +4. The subscript n of (X) _n is 0, 1, or 2. When subscript n is 1, X is a monodentate ligand or a bidentate ligand, and when subscript n is 2, each X is selected from a monodentate ligand. Each Z is independently selected from-O-, -S-, -N (R ^N) -or-P (R ^P)-;R¹ and R ¹⁶ are independently selected from the group consisting of: -H, (C ₁-C₄₀) hydrocarbyl, (C ₁-C₄₀) heterohydrocarbyl 、-Si(R^C)₃、-Ge(R^C)₃、-P(R^P)₂、-N(R^N)₂、-OR^C、-SR^C、-NO₂、-CN、-CF₃、R^CS(O)-、R^CS(O)₂-、-N=C(R^C)₂、R^CC(O)O-、R^COC(O)-、R^CC(O)N(R)-、(R^C)₂NC(O)-、 halogen, a radical having formula (II), a radical having formula (III) and a radical having formula (IV):

In formulas (II), (III) and (IV), each of R ^31–35、R^41–48 and R ^51–59 is independently selected from-H, (C ₁-C₄₀) hydrocarbyl, (C ₁-C₄₀) heterohydrocarbyl 、-Si(R^C)₃、-Ge(R^C)₃、-P(R^P)₂、-N(R^N)₂、-OR^C、-SR^C、-NO₂、-CN、-CF₃、R^CS(O)-、R^CS(O)₂-、(R^C)₂C=N-、R^CC(O)O-、R^COC(O)-、R^CC(O)N(R^N)-、(R^C)₂NC(O)-, or halogen, provided that at least one of R ¹ or R ¹⁶ is a group of formula (II), a group of formula (III), or a group of formula (IV).

In one or more embodiments, each X may be a monodentate ligand that, independently of any other ligand X, is a halogen, an unsubstituted (C ₁-C₂₀) hydrocarbyl group, an unsubstituted (C ₁-C₂₀) hydrocarbyl group C (O) O-or R ^KR^L N-, wherein each of R ^K and R ^L is independently an unsubstituted (C ₁-C₂₀) hydrocarbyl group.

Additional details and examples of bis (biphenylphenoxy) catalysts are provided in PCT publications WO2011/146291, WO2018/183056, WO2019/190925, and U.S. patent 7060848B2, which are incorporated herein by reference in their entirety.

In one embodiment, the single-chain catalyst in the first reactor, the second reactor, or both may comprise a phosphinimine catalyst. The phosphinimine pre-catalyst may have the structure of formula (V):

In formula (V), each Q is independently selected from (C ₁-C₅₀) hydrocarbyl, (C ₁-C₅₀) heterohydrocarbyl 、-CH₂Si(R^C)_3-Q(OR^C)_Q、-Si(R^C)_3-J(OR^C)_J、-OSi(R^C)_3-J(OR^C)_J、-CH₂Ge(R^C)_3-J(OR^C)_J、-Ge(R^C)_3-J(OR^C)_J、-P(R^C)_2-W(OR^C)_W、-P(O)(R^C)_2-W(OR^C)_W、-N(R^C)₂、-NH(R^C)、-N(Si(R^C)₃)₂、-NR^CSi(R^C)₃、-NHSi(R^C)₃、-OR^C、-SR^C、-NO₂、-CN、-CF₃、-OCF₃、-S(O)R^C、-S(O)₂R^C、-OS(O)₂R^C、-N=C(R^C)₂、-N=CH(R^C)、-N=CH₂、-N=P(R^C)_3、-OC(O)R^C、-C(O)OR^C、-N(R^C)C(O)R^C、-N(R^C)C(O)H、-NHC(O)R^C、-C(O)N(R^C)₂、-C(O)NHR^C、-C(O)NH₂、 halogen, B (R ^Y)₄、Al(R^Y)₄ or Ga (R ^Y)₄ or a monodentate ligand of hydrogen) wherein each R ^C is independently (C ₁-C₃₀) hydrocarbyl or (C ₁-C₃₀) heterohydrocarbyl, and each J is 0,1, 2 or 3, and each W is 0,1 or 2, each R ^Y is-H, (C ₁-C₃₀) hydrocarbyl or a halogen atom, wherein two X ligands may be linked to form a metalloheterocycle

In formula (V), each Y is independently a Lewis base, optionally Q and Y may be linked to form a ring. Each subscript m is 1 and 2 and each subscript n is 0, 1, and 2. The metal-ligand complex is overall electrically neutral.

In formula (V), M ₂ is titanium, zirconium, or hafnium, R ⁶⁰、R⁶¹、R⁶²、R⁶³ and R ⁶⁴ are independently (C ₁-C₅₀) hydrocarbyl, (C ₁-C₅₀) heterohydrocarbyl, wherein any one of R ⁶¹、R⁶²、R⁶³ and R ⁶⁴ is optionally linked to form a ring structure, and R ⁶⁵、R⁶⁶ and R ⁶⁷ are independently (C ₁-C₂₀) hydrocarbyl, (C ₁-C₂₀) heterohydrocarbyl, (C ₆-C₃₀) aryl, (C ₅-C₃₀) heteroaryl, wherein two of R ⁶⁵、R⁶⁶ and R ⁶⁷ are optionally linked to form a ring.

In various embodiments, in formula (V), (A) R ⁶⁰ and R ⁶¹ are linked and form a ring and are optionally substituted with one or more R ^S, or (B) R ⁵² and R ⁶³ are linked and form a ring and are optionally substituted with one or more R ^S, or (C) both (A) and (B). Thus, when (a), (B) or (C) occurs, the cyclopentadienyl group of formula (V) has a structure selected from the group consisting of:

As described above, the multi-chain catalyst produces a polymer fraction with long chain branching. A multi-chain catalyst is a metal-ligand catalyst having at least two polymeric chains that promote the growth of at least two separate polymeric chains. Suitable multi-chain catalysts and mechanisms of action are described in PCT publications WO2020/069364, WO2020/205585 and WO2021195502A1, which are incorporated herein by reference in their entirety and briefly summarized herein. At high levels, long chain branched fractions are produced by adding polyenes, particularly acyclic non-conjugated dienes, in the presence of a multi-chain catalyst. The polyene is added to the polymer chain in a similar manner to the alpha-olefin, but leaves a pendant vinyl group that can be inserted into the polymer chain a second time to create long chain branches. As described above, the multi-chain catalyst has at least two polymer sites that propagate two separate polymer chains. One olefin in the polyene is incorporated into one polymer chain, and it is believed that the second olefin in the polyene is then rapidly incorporated into the second polymer chain due to the close proximity of the growth sites, forming a bridge or step. This continuous addition of diene is known as a "synergistic" addition of diene, as distinguished from a catalyst without two proximal chains, wherein the diene addition results in a concentration of vinyl-containing polymer in the reactor that reacts at a later time. The synergistic addition of polyenes is known as a "ladder" mechanism. The term "step" refers to the joining of chains together once the diene is incorporated into two separate polymer chains. The first polymer chain and the second polymer chain continue to grow until the polymer is released from the catalyst, catalyst die, or another diene is added.

Embodiments of the present disclosure utilize minimal multi-chain and single-chain catalysts in the first reactor. Without being bound by theory, the single-chain catalyst will polymerize ethylene and optionally an alpha-olefin comonomer, but will not produce an appreciable amount of long chain branching with the polyene, particularly because the single-chain catalyst will not produce two closely spaced polymer chains with the polyene incorporated therebetween. Thus, a single chain catalyst will produce a polymer fraction that is substantially free of long chain branching, while a multi-chain catalyst produces a long chain branched polymer fraction in the same reactor without gel formation and reactor fouling. Thus, the first reactor polyethylene product comprises a first fraction having long chain branching and a second fraction substantially free of long chain branching. As used herein, "substantially free of long chain branching" means less than 0.01 long chain branches per 1000 carbon atoms (LCB/1000C) as measured by NMR. In the examples below, the first reactor is referred to as a high density reactor because the first reactor polyethylene product may have a density greater than 0.930g/cc and a melt index (I ₂) greater than 3 dg/min. In one or more embodiments, the trimodal ethylene-based polymer comprises from 35 wt.% to 55 wt.% of the first reactor polyethylene product comprising the first fraction and the second fraction.

In one or more embodiments, the first fraction, i.e., the long chain branching fraction, may comprise about 2 wt% to 10 wt% of the multimodal ethylene-based polymer (e.g., trimodal ethylene-based polymer).

The second reactor, which does not include the initial polyene feed and which also does not include a multi-chain catalyst, produces a second reactor polyethylene product that is also substantially free of long chain branching. In this case, the single-chain catalyst in the second reactor will polymerize ethylene and optionally the alpha-olefin comonomer. In one or more embodiments, the trimodal ethylene-based polymer comprises 45 wt.% to 65 wt.% of the second reactor polyethylene product comprising at least the third polymer fraction. In the examples below, the second reactor is referred to as a low density reactor because the second reactor polyethylene product may have a density of less than 0.910g/cc, a melt index (I ₂) of less than 0.8dg/min, and a MWD of less than 3.0. For a trimodal ethylene-based polymer, the combination of a first reactor (high density reactor) polyethylene product with a first fraction and a second fraction with long chain branching and a second reactor (low density reactor) with a third stage polyethylene product produces a molecular weight distribution as depicted in fig. 1.

Film and method for producing the same

Additional embodiments of the present disclosure relate to films. In some embodiments, the film may comprise a multimodal ethylene-based polymer or a trimodal ethylene-based polymer as described above.

In other embodiments, the film may comprise an ethylene-based polymer that is the polymerization reaction product of ethylene, a C ₃-C₁₄ a-olefin monomer, and optionally a polyene. In embodiments, such ethylene-based polymers may be multimodal and/or trimodal. In additional embodiments, the ethylene-based polymer of the film may comprise the polymerization reaction product of ethylene, a C ₃-C₁₄ a-olefin monomer, and a polyene. In particular embodiments, the film may comprise at least 95 wt% ethylene-based polymer, at least 97 wt% ethylene-based polymer, at least 99 wt% ethylene-based polymer, or at least 99.5 wt% ethylene-based polymer. In further embodiments, the film is substantially free of any other polymeric components.

For embodiments of these films, the films may include a normalized dart Drop Strength (DS) of greater than or equal to 400+1400/(MS-2.7), where the normalized DS is measured in grams (g) divided by the film thickness (in mils) according to ASTM 1709 method a, with the proviso that the Melt Strength (MS) is at least 4cN. This relationship between normalized dart drop strength and melt strength is depicted in fig. 2. By achieving both higher normalized dart drop strength and melt strength, the films of the present invention do not sacrifice abuse resistance for processability, which is a compromise for LLDPE/LDPE blends. In further embodiments, as also depicted in FIG. 2, the normalized DS is greater than or equal to 430+2000/(MS-2.4), greater than or equal to 400+2736/(MS-2.2), or greater than or equal to 390+3900/(MS-2.5). Further, the normalized DS of the film may be 750g/mil to 1750g/mil, or 750g/mil to 1500g/mil.

The film may comprise a single layer film or a multilayer film. The films of the present disclosure may have a variety of thicknesses. The thickness of the film may depend on a number of factors including, for example, the number of layers in the film, the composition of the layers in the multilayer film, the desired properties of the film, the desired end use application of the film, the manufacturing process of the film, and the like. In embodiments, the film may have a thickness of 0.5 mil to 5 mil, 1 mil to 4 mil, 1 mil to 3 mil, or 1.5 mil to 2.5 mil.

Various methods for producing the films of the present disclosure are contemplated. In one or more embodiments, the method of making a film can include cast film extrusion or blown film extrusion.

Additive agent

It will be appreciated that the multimodal ethylene-based polymer, trimodal ethylene-based polymer, or films produced therefrom described above may further include one or more additives as known to those skilled in the art, such as, for example, plasticizers, stabilizers (including viscosity stabilizers, hydrolytic stabilizers), primary and secondary antioxidants, ultraviolet light absorbers, antistatic agents, dyes, pigments or other colorants, inorganic fillers, flame retardants, lubricants, reinforcing agents (such as glass fibers and glass flakes), synthetic (e.g., aramid) fibers or pulp, foaming or blowing agents, processing aids, lubricant additives, antiblocking agents (such as silica or talc), mold release agents, tackifying resins, or combinations of two or more thereof. Inorganic fillers (such as calcium carbonate and the like) may also be incorporated into the blend.

Article of manufacture

Embodiments of the present disclosure also relate to articles, such as packages, formed from the films of the present disclosure. The films of the present disclosure are particularly useful in articles where good tear and dart strength is desired. Examples of such articles may include flexible packages, pouches, stand-up pouches, and pre-made packages or pouches. Various methods of producing embodiments of articles from the films disclosed herein will be familiar to those of ordinary skill in the art.

Test method

The test method comprises the following steps:

Melt index

Melt indices I ₂ and I ₁₀ of the polymer samples were measured according to ASTM D-1238 (method B) at 190℃and under a load of 2.16kg and 10kg, respectively.

Density of

Samples for density measurement were prepared according to ASTM D4703. Method B was measured within one hour of pressing the sample according to ASTM D792.

ASTM D1709 dart

The film dart test determines the energy that, under the specified impact conditions, causes the plastic film to fail under the influence of a free falling dart. The test results are energy expressed in terms of the weight of the projectile falling from a specified height (which would result in failure of 50% of the test specimen).

After the film was produced, the film was conditioned at 23 ℃ (+/-2 ℃) and 50% R.H (+/-5) for at least 40 hours according to ASTM standards. Standard test conditions were 23 ℃ (+/-2 ℃) and 50% R.H (+/-5) according to ASTM standards.

The test results are reported by method a, which uses a 1.5 "diameter dart head and a 26" drop height. The sample thickness at the center of the sample was measured and then clamped by an annular sample holder having an internal diameter of 5 inches. Darts are loaded over the center of the sample and released by pneumatic or electromagnetic mechanisms.

The test is performed according to the "ladder" method. If the sample fails, a new sample is tested with the dart reduced in weight by a known and fixed amount. If the sample does not fail, a new sample is tested with the weight of the dart increased by a known amount. After testing 20 samples, the number of failures was determined. If this number is 10, the test is complete. If the number is less than 10, the test continues until 10 failures are recorded. If the number is greater than 10, the test is continued until the sum of the non-failures is 10. Dart strength is determined from these data according to ASTM D1709 and expressed in grams as type a dart impact. All samples analyzed were 2 mil thick.

Instrumented dart impact

The instrumented dart impact method is a measurement of plastic film samples using an Instron CEAST 9350 impact tester according to ASTM D7192. The test was performed using a 12.7mm diameter domed head with a 75mm diameter clamping assembly with a rubber faced clamp. The instrument is equipped with an environmental chamber for testing at low or high temperatures. Typical sample sizes are 125mm by 125mm. The standard test speed was 200m/min.

Size Exclusion Chromatography (SEC) by gel permeation chromatography (conventional GPC)

GPC-SEC (conventional GPC) measurements were performed according to the test procedure defined in PCT publication WO2021195502A 1.

Triple detector GPC (TD) (absolute GPC)

GPC-TD (absolute GPC) measurements were performed according to the test procedure defined in PCT publication WO2021195502A 1.

MD tear

MD tear is measured according to ASTM D-1922. The force in grams required to propagate a tear across a membrane sample was measured using an erlenmeorf (Elmendorf) tear meter. The pendulum swings in an arc by gravity, thereby tearing the sample from the precut slit. The tear propagates in the transverse direction. The samples were conditioned at temperature for at least 40 hours prior to testing.

Linear viscoelastic behavior (Small amplitude Oscillating shear)

Linear Viscoelastic (LVE) behavior was measured under simple shear via a strain controlled, separate motor-sensor ARES-G2 rheometer (TA meter) equipped with 25-mm parallel plates. Measurements were performed at 190 ℃.

The geometry was contained in an insulated Forced Convection Oven (FCO) controlled to a temperature within 0.1 ℃ and a nitrogen purge gas was used to prevent oxidative damage to the material. Small Amplitude Oscillating Shear (SAOS) was used to characterize LVE material response in simple shear. The experimental procedure in simple shear is as follows. Test specimens (25-mm diameter disks) were loaded onto a base plate and centered at a test temperature of 190 ℃ in advance. Once the FCO temperature reading reached 190 ± 0.1 ℃, the top plate was slowly lowered onto the sample until contact. When trimming excess material at the edge of the parallel plate rapidly (+≤20s) with a Hyde rigid brass spatula, the normal force (+.1N to 2N) is kept small to achieve the proper disk geometry. After trimming, the gap was slightly reduced (by +.about.0.03 mm) to ensure complete filling of the parallel plate geometry. When temperature uniformity was established and residual stress was released, the residence time before testing was 180s. To determine the range of strain amplitudes associated with the LVE response in shear, the critical strain at which NLVE behavior begins is determined by an isochronous strain sweep at four angular frequencies (ω=0.1 rad/s, 1rad/s, 10rad/s, and 100 rad/s).

The sample is then subjected to SAOS excitation at a frequency in the range of 0.1rad/s to 100 rad/s. During these isothermal frequency sweeps, the angular frequency ω varies from high (100 rad/s) to low (0.1 rad/s), and the strain amplitude γ ₀ increases gradually (in the LVE regime and in the range of 0.1% to 50%) with decreasing oscillation frequency to meet the resolution of the torque sensor at low frequencies.

For each material studied, a SAOS frequency scan was performed on one test sample. The resulting data is analyzed in terms of magnitude of complex shear viscosity, |η (ω) |≡g "(ω)/ω -iG '(ω)/ω| defined in terms of two frequency dependent SAOS material functions, namely storage shear modulus G' (ω) and loss shear modulus G" (ω).

ASTM D1922 MD and CD type B Elmendorf tear

Elmendorf tear test an Elmendorf tear tester was used to determine the average force to propagate a tear through a specified length of plastic film or non-rigid sheet after the tear began.

After producing the film from the sample to be tested, the film was conditioned at 23 ℃ (+/-2 ℃) and 50% R.H (+/-5) for at least 40 hours according to ASTM standards. Standard test conditions were 23 ℃ (+/-2 ℃) and 50% R.H (+/-5) according to ASTM standards.

The force (in grams) required to propagate a tear on a film or sheet sample was measured using a precisely calibrated pendulum device. In the test, the pendulum swings into an arc under the force of gravity, tearing the sample from the pre-slit. One side of the sample is fixed by the pendulum and the other side is fixed by the fixing member. The energy loss of the pendulum is indicated by a pointer or an electronic scale. The scale indication is a function of the force required to tear the sample.

The sample specimen geometry used in the Elmendorf tear test is the "constant radius geometry" specified in ASTM D1922. Samples cut from the MD and CD directions of the film are typically tested. The thickness of the film sample was measured at the center of the sample prior to testing. A total of 15 samples were tested for each film direction and the average tear strength and average thickness were reported. The average tear strength was normalized to the average thickness.

Examples

The following examples illustrate features of the present disclosure, but are not intended to limit the scope of the present disclosure. The following experiments analyze the performance of the embodiments of the multilayer films described herein.

Polymer synthesis

The trimodal ethylene-based polymers 1-11 of the present invention were prepared by the process described below, which were produced by a double reactor having a multi-chain catalyst and two single-chain catalysts therein. Comparative example C1 is a bimodal ethylene-based polymer produced in a dual reactor system having a single chain catalyst but no multiple chain catalyst in each reactor. Comparative example C2 is a bimodal ethylene-based polymer produced in a single reactor system having a single chain catalyst and a multiple chain catalyst. Comparative example C3 is a unimodal ethylene-based polymer produced in a single reactor system with a single chain catalyst.

All raw materials (monomers and comonomers) and process solvents (narrow boiling range high purity isoparaffin solvents, isopar-E) were purified with molecular sieves prior to introduction into the reaction environment. Hydrogen was supplied under pressure at a high purity level and no further purification was performed. The reactor monomer feed stream is pressurized above the reaction pressure by a mechanical compressor. The solvent and comonomer feeds are pressurized via a pump to a pressure greater than the reaction pressure. The individual catalyst components are diluted manually in batches with the purified solvent and pressurized to a pressure above the reaction pressure. All reaction feed streams were measured with mass flowmeters and independently controlled with a computer automated valve control system.

Two reactor systems are used in a parallel configuration. Each continuous solution polymerization reactor consisted of a liquid-filled, non-adiabatic, isothermal, continuously Stirred Tank Reactor (CSTR) with heat removal. All fresh solvent, monomer, comonomer, diene, hydrogen and catalyst components can be independently controlled. The total fresh feed stream (solvent, monomer, comonomer and hydrogen) to each reactor is temperature controlled by passing the feed stream through a heat exchanger to maintain a single solution phase. The catalyst component is directly injected into the polymerization reactor. The computer controls the main catalyst component feed to maintain each reactor monomer conversion at a specified target. The cocatalyst component is fed into the main catalyst component based on the calculated specified molar ratio. The reactor feeds are shown in tables 1A and 1B. Immediately following the reactor feed injection location, the feed stream was mixed with the circulating polymerization reactor contents using a static mixing element. The reactor was surrounded by an oil jacket responsible for maintaining the isothermal reaction environment at the indicated temperature.

In a dual parallel reactor configuration, the effluent from each polymerization reactor (containing solvent, monomer, comonomer, hydrogen, catalyst components, and polymer) exits the appropriate reactor and is blended. The contents were deactivated by adding isopropanol. At this same reactor outlet location, other additives are added for polymer stabilization (typical antioxidants are suitable for stabilization during extrusion and film manufacture).

After catalyst deactivation and additive addition, the reactor effluent enters a devolatilization system where polymer is removed from the non-polymer stream. The separated polymer melt is pelletized and collected. There is no recycling in this process, but recycling can generally be achieved.

Cocatalyst A (CoCat A) was bis (hydrogenated tallow alkyl) methyl ammonium tetrakis (pentafluorophenyl) borate

Cocatalyst B (CoCat B) is MMAO-3A or a modified methylaluminoxane

The structures of CAT a, CAT B and CAT C shown in tables 1A and 1B are provided in table 2 below.

Film processing

Films were run using inventive examples 1-11, comparative example C1, and commercially available resins and blends C4-C7.

C4 comprises 80 wt% C1 and 20 wt% AGILITY ^™ 1021. AGILITY ^™ 1021, commercially available from the Dow company (Dow inc., MIDLAND MI) of midland, michigan, is an LDPE resin having a density of 0.919g/cc and a melt index (I ₂) of 1.9 dg/min.

C5 comprises 100 wt.% of a comparative bimodal polyethylene resin having a density of 0.918g/cc and a melt index (I ₂) of 0.85 dg/min. A comparative bimodal polyethylene resin was produced according to the method of inventive example 1 of PCT publication WO2015200742, incorporated herein by reference.

C6 comprises 90 wt% C5 and 10 wt% AGILITY ^™ 1021.

C7 comprises 80 wt% C5 and 20 wt% AGILITY ^™ 1021.

Specifically, a monolayer Dr. Collin blown film line was used to prepare 2 mil blown films. The production line included a 30:1L/D single screw extruder equipped with a slotted feed zone and a30 mm screw diameter. The annular die was 60mm in diameter and a double lip air ring cooling system was used. The die lip gap was 2mm and the blow-up ratio (BUR) was 2.0. The tile (lay flat) width is about 48cm. The frozen line height is 5 inches to 6 inches. The total output rate is 5 kg/hr to 8 kg/hr. The melting temperature is 200 ℃ to 220 ℃, and the mold temperature is set to 225 ℃.

Film and Polymer data

As shown in tables 3A through 3C, inventive samples 1-11 had melt strengths in the range of 4.7cN to 13.3cN and normalized dart A of 760g/mil to 1373 g/mil. These normalized dart a values are significantly higher than the C4, C6 and C7 blends (which include LDPE to increase melt strength) and C5 single resin films. This demonstrates how LDPE improves melt strength and processability, but at the cost of significantly reduced abuse resistance (i.e. normalized dart a).

Furthermore, as shown in comparative example C1, which does not contain a multi-chain catalyst or diene, the melt strength is lower (3.2 cN) due to the lack of long chain branching. Furthermore, the first reactor bimodal polymer (comparative example C2) had long chain branching present, but the melt strength (2.2 cN) of the polymer of the present invention could not be achieved due to the high melt index (I ₂ is 29.5 dg/min). Finally, unimodal comparative example C3 is essentially free of long chain branching and has a melt strength of 4.5cN, but it is achieved by having a very low melt index (I ₂) of 0.26 dg/min.

Having described the subject matter of the present disclosure in detail and by reference to specific embodiments, it should be noted that the various details disclosed in the present disclosure should not be construed as implying that such details relate to elements which are essential components of the various embodiments described in the present disclosure. Further, it will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, including but not limited to the embodiments defined in the appended claims.

Claims

1. A three-peaked ethylene-based polymer, the three-peaked ethylene-based polymer comprising a first polymer fraction, a second polymer fraction, and a third polymer fraction, wherein:

The first polymer fraction, the second polymer fraction, and the third polymer fraction each comprise the polymerization product of an ethylene monomer and an optional _C3 - _C14 α-olefin comonomer, wherein at least one of the first polymer fraction, the second polymer fraction, and the third polymer fraction comprises the polymerization product of an ethylene monomer, a polyene comonomer, and an optional _C3 - _C14 α-olefin comonomer.

2. The trimodal ethylene-based polymer of claim 1, wherein the trimodal ethylene-based polymer has a melt strength (MS) of 4.0 cN to 25.0 cN and a rheological ratio V _{0.1} /V _{100} of 4.0 to 12.0, wherein V _{0.1} is the viscosity of the trimodal ethylene-based polymer at 190°C and an angular frequency of 0.1 radians/second, and V _{100} is the viscosity of the trimodal ethylene-based polymer at 190°C and an angular frequency of 100 radians/second, and wherein MS is the melt strength in cN (Rheotens apparatus, 190°C, 2.4 mm/s ² , 120 mm from die exit to wheel center, extrusion rate of 38.2 s ^-1 , capillary die length of 30 mm, diameter of 2 mm and entry angle of 180°).

3. The trimodal ethylene-based polymer of claim 1, wherein the polyene comprises acyclic, non-conjugated dienes.

4. The trimodal ethylene-based polymer according to any of the preceding claims, wherein the rheological ratio V _{0.1} /V _100 is from 4.0 to 8.0.

5. The trimodal ethylene-based polymer according to any of the preceding claims, wherein the trimodal ethylene-based polymer has an _I₂ concentration of 0.5 dg/min to 2.0 dg/min.

6. The trimodal ethylene-based polymer according to any of the preceding claims, wherein the trimodal ethylene-based polymer has a density of 0.910 g/cc to 0.935 g/cc.

7. The three-peaked ethylene-based polymer according to any of the preceding claims, wherein the three-peaked ethylene-based polymer has a molecular weight distribution (MWD) of 3.0 to 5.0 as measured by conventional gel permeation chromatography, wherein the MWD is defined as _Mw / _Mn , where _Mw is the weight-average molecular weight and _Mn is the number-average molecular weight.

8. The three-peaked ethylene-based polymer according to any of the preceding claims, wherein the first fraction has a density of less than 0.925 g/cc, a melt index ( _I² ) of less than 0.5 dg/min, and a MWD of less than 3.0.

9. The trimodal ethylene-based polymer according to any of the preceding claims, wherein at least one of the first polymer fraction, the second polymer fraction, and the third polymer fraction is substantially free of long-chain branching.

10. The trimodal ethylene-based polymer according to any of the preceding claims, wherein the trimodal ethylene-based polymer comprises 45% to 65% by weight of a first fraction and 35% to 55% by weight of a second polymer fraction and the third polymer fraction.

11. The trimodal ethylene-based polymer according to any of the preceding claims, wherein the melt strength (MS) is 8.0 cN to 15 cN.

12. A membrane comprising a trimodal ethylene-based polymer according to any of the preceding claims.

13. The membrane according to claim 12, wherein the membrane is a single-layer membrane or a multilayer membrane.

14. The membrane according to claim 12 or 13, wherein the membrane has a normalized dart strength (DS) of 750 g/mil to 1750 g/mil as measured according to ASTM D1709.

15. The membrane according to any one of claims 11 to 14, wherein the membrane has an average transverse (CD) tear of 40 gf to 70 gf and the membrane has an average thickness of 1 mil to 3 mil.