Long-chain branched ethylene copolymers with novel composition distribution and films formed therefrom

Abstract

Disclosed are Ziegler-Natta catalyzed ethylene and α-olefin LLDPE copolymers having a unique composition distribution and long-chain branching. The polymers of the present invention inherently exhibit outstanding melt strength, good bubble stability, sufficient flexibility, excellent gel performance, and desirable mechanical properties, such as balanced toughness and stiffness, which are desirable for thick-gauge film applications. In particular, the polymers of the present invention.

Description

Technical Field

[0001] The present invention relates to Ziegler-Natta catalyzed ethylene-α-olefin copolymers, methods for their preparation, and articles made from the novel compositions, wherein the copolymers have a unique composition distribution and desirable long chain branching (LCB) and a density in the range of about 0.900 to 0.930 g / cc. Background Art

[0002] In various thick gauge polyethylene film applications such as geomembranes, high melt strength and bubble stability during film processing are very important. Attempts to extrude thick geomembrane sheets (i.e., about 100 mils) of pure linear low density polyethylene (LLDPE) through casting or blow molding lines are challenging due to the lack of sufficient melt strength. Conventionally, the bottom and sides of geomembrane-lined land areas (e.g., leachate ponds and municipal landfills) are lined with high-density polyethylene (HDPE) sheets, which are strong, non-biodegradable, impermeable to air and water, and effectively serve as a barrier against toxic waste leaks into the soil. However, when this material is used to cover the top of the often irregularly shaped material below, it is too hard and lacks the flexibility and stretchability to form an effective leak-proof barrier.

[0003] Typical LLDPE has low melt strength, which adversely affects bubble stability during blown film extrusion and is prone to melt fracture at commercial shear rates. It is well known that improved melt strength can be achieved through blending strategies (U.S. Patent Publication Nos. 2014 / 0260016 and 2014 / 0364545). In the past, various levels of low-density polyethylene (LDPE) or high-density polyethylene (HDPE) with long-chain branching prepared in high-pressure polymerization processes have been blended with LLDPE to increase melt strength, improve shear response, and reduce the tendency to melt fracture. However, these blends generally have poor mechanical properties compared to pure LLDPE. Improving the processability of LLDPE without sacrificing physical properties is a challenge.

[0004] It is well known that the processing characteristics of LLDPE can be improved by including a desired level of long-chain branching (LCB) during the polymerization process (U.S. Publication No. 2017 / 0015768 and U.S. Patent No. 8,541,519) or by post-reactor tailoring. The formation of LCB helps to increase the melt strength of the LLDPE resin and provide good bubble stability, especially for the manufacture of thick geomembrane sheets. U.S. Publication Nos. 2013 / 0,131,297 and 2015 / 0125645 and U.S. Patent No. 8,629,217 disclose that chemically modified polyethylene compositions with dendritic hydrocarbons show excellent melt strength and bubble stability in blown film applications (e.g., thick films for geomembranes). U.S. Patent No. 6,187,423 discloses post-reactor modified Ziegler-Natta catalyzed LLDPE with a relatively broad comonomer distribution for geomembrane applications with desired melt strength. U.S. Patent No. 9,346,897 discloses peroxide-treated, metallocene-catalyzed LLDPE for thick-gauge film applications. It is well known that the compositional distribution of the base polymer will influence branch formation. The key is to select an LLDPE resin with the optimal molecular structure as the base polymer for subsequent post-reactor chemical tailoring to achieve the desired long-chain branching (LCB).

[0005] Various types of LLDPE resins with varying molecular structures are known in the art. Conventional Ziegler-Natta-catalyzed ethylene-α-olefin LLDPE copolymers exhibit both a relatively broad molecular weight distribution and a relatively broad comonomer distribution; the comonomer is primarily incorporated into low-molecular-weight polymer molecules or short polyethylene chains, while long polyethylene chains or high-molecular-weight polymer molecules lack comonomer. This lack of compositional uniformity is associated with several drawbacks, such as "feel" issues and suboptimal impact strength resulting from low-molecular-weight materials. In contrast, single-site catalysts typically produce resins with narrow composition and molecular weight distributions; the comonomer is typically evenly distributed between polymer chains of varying molecular weights. However, this uniform structure comes with some drawbacks in processability and properties. Most single-site-catalyzed LLDPEs exhibit weak machine direction tear strength in films and may exhibit unfavorable processability at the machine direction (MD) for geomembranes. Selecting LLDPE with a unique structure other than those described above as the base resin and tailoring it to the optimal reactor inherently results in polymers with good melt strength, adequate flexibility, and outstanding physical properties due to optimal composition distribution and long-chain branching.

[0006] For applications in thick gauge films or sheets made of polyethylene materials by melt extrusion, it is also crucial that the polymer has as low a gel content as possible. Gel is a problem often encountered in the production of polyolefin film products. In the worst case, gel can cause the film to break or lose bubble stability. The term gel usually refers to structural inhomogeneities visible to the naked eye or a microscope, which appear as imperfections on the product or interrupt processing (in the worst case). Gels can be polymers with densities or molecular weights different from those of the matrix, highly branched or cross-linked domains of oxidation origin, clusters of foreign matter, etc. They can be thermally cross-linked gels, highly oxidized gels, unmixed gels, or contaminants. The presence of such gel domains may lead to defects in the film material itself. Therefore, it is highly desirable to reduce the occurrence of such gels, particularly to reduce relatively large-sized gels.

[0007] Thus, the LLDPE resins of the present invention have unique composition distribution, chain branching, and post-reactor tailoring. The polymers of the present invention inherently exhibit outstanding melt strength, good bubble stability, sufficient flexibility, excellent gel performance, and desirable mechanical properties, such as balanced toughness and stiffness, for use in a variety of thick-gauge film applications. Summary of the Invention

[0008] The present invention discloses a high melt strength Ziegler-Natta catalyzed ethylene and alpha-olefin copolymer, a method for preparing the same, and articles made from the same, wherein the copolymer has a unique composition distribution and long chain branching and has excellent physical properties.

[0009] In one embodiment, the LLDPE resin of the present invention exhibits a unique comonomer distribution across its entire molecular weight, wherein the comonomer is uniformly incorporated into the high molecular weight polymer chains. The resin of the present invention elutes at least 15 wt.% of the ethylene copolymer component in TREF at a temperature of 35°C or less. The molecular weight distribution of the 35°C fraction is nearly identical to the total molecular weight distribution, while the distribution of the comonomer (albeit at a much higher level) is uniform across the molecular weight. Furthermore, the molecular weight (Mw) of the copolymer resin of the present invention is essentially constant across all TREF fractions. As an indicator of this unique composition, the Mw of the copolymer satisfies the following formula:

[0010] (Mw at 100°C) / (Mw at 35°C) = 1.0 - 1.5 (1)

[0011] The polymers of the present invention prepared with C3-C8 α-olefin comonomers have a molecular weight distribution (Mw / Mn) of 3.0-5.0, a melt index of 0.3-0.8 dg / min, and a density of 0.910-0.930 g / cc. The zero shear viscosity (η0) is 6×10 4 to 6×10 6The base copolymer is polymerized by reacting ethylene and an α-olefin comonomer in the presence of a titanium-based Ziegler-Natta catalyst in a gas phase reactor process at a temperature in the range of about 50° C. to about 100° C.

[0012] In another embodiment, the LLDPE polymers of the present invention exhibit outstanding gel properties, which are important for thick film applications. In addition, when the melt index is from about 0.45 to about 0.50 dg / min, the zero shear viscosity (η) of the polymers of the present invention at 190°C is 0 ) in 6×10 4 to 5×10 5 Within the range of Pa*s.

[0013] In yet another embodiment, the high melt strength LLDPE of the present invention has an oxidative induction time (OIT) of at least 150 minutes as measured according to ASTM D3895, an ESCR of a resin compressed plaque of at least 3000 hours according to ASTM D1693, a tensile elongation of at least 700% according to ASTM D638, and a tensile strength at yield of at least 1500 psi according to ASTM D638. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The novel short chain branching distribution (SCBD) of the copolymers of the present invention is depicted.

[0015] Figure 2 Depicted are the TREF fractions eluting below 35°C for the copolymers of the present invention.

[0016] Figure 3 Similar molecular weight distribution and uniform comonomer distribution are depicted for the 35°C TREF fraction of the inventive copolymer.

[0017] Figure 4 The copolymers of the present invention exhibit essentially constant molecular weight across all TREF fractions.

[0018] Figure 5 The dynamic rheological curves (viscosity versus shear rate) of the copolymers according to the invention at 190° C. are plotted. DETAILED DESCRIPTION

[0019] The present invention relates to Ziegler-Natta catalyzed ethylene-alpha olefin copolymers having desirable long chain branching (LCB) and novel composition distribution. The LLDPE resin used in the present invention is polymerized in a gas phase fluidized bed reactor using an advanced Ziegler-Natta catalyst prior to post-reactor modification.

[0020] Catalyst systems and polymerization processes

[0021] The catalyst used herein is an advanced Ziegler-Natta catalyst modified with a non-single-site catalyst ligand and / or an interior having a strong Lewis base (e.g., an aromatic compound containing a nitrogen atom). Examples of such catalysts are described in U.S. Patent Nos. 6,992,034 and 7,618,913, which are incorporated herein by reference.

[0022] The LLDPE copolymers of the present invention from ethylene and α-olefins are produced in a commercial BP gas phase polymerization process. The copolymers of the present invention can be ethylene with one or more C3-C 10 Copolymers of alpha-olefins. Preferred comonomers include 4-methyl-1-pentene, 1-hexene, 1-octene and 1-butene. Typically, in gas phase polymerization processes, continuous circulation is adopted, wherein a portion of the reactor system circulation (circulating gas stream, also referred to as circulating stream or fluidizing medium) is heated in the reactor by the heat of polymerization. This heat is removed from the recirculating composition of the other portion of the circulation by a cooling system outside the reactor. Typically, in a gas fluidized bed process for producing polymers, a gas stream containing one or more monomers is continuously circulated through a fluidized bed in the presence of a catalyst or prepolymer under reaction conditions. The gas stream is extracted from the fluidized bed and recycled back into the reactor. Simultaneously, the polymer product is extracted from the reactor and fresh monomers are added to replace the monomers that have been polymerized.

[0023] The ethylene partial pressure should vary between 10 and 250 psi, preferably between 65 and 150 psi, more preferably between 75 and 140 psi, and most preferably between 90 and 120 psi. More importantly, the comonomer to ethylene ratio in the gas phase should vary between 0.0 and 0.50, preferably between 0.005 and 0.25, more preferably between 0.05 and 0.20, and most preferably between 0.10 and 0.15. The reactor pressure typically varies between 100 psig and 500 psi. In one aspect, the reactor pressure is maintained in the range of 200 psig to 500 psi. In another aspect, the reactor pressure is maintained in the range of 250 psig to 350 psi.

[0024] Utilizing the unique catalysts used in the resins of the present invention, molecular weight can be suitably controlled with hydrogen when polymerization is conducted at temperatures of about 20°C to about 300°C. This control of molecular weight can be demonstrated by a measurable positive change in melt index (I2). The molecular weight distribution (MWD) of the base polymers prepared in the presence of the catalysts of the present invention, as indicated by MFR values, varies from about 10 to about 40. MFR is a measure of the high load melt index (HLMI or I2). 21 ) to the melt index (MI or I2) of a given resin (MFR = I21 In a preferred embodiment, the melt index ratio (I2) of the ethylene / 1-hexene copolymer having a density of 0.910 g / cc to 0.930 g / cc is 21 / I2) is greater than about 20 and less than about 30. The copolymer resin produced according to the present invention preferably contains at least about 75% by weight of ethylene units. Most preferably, the copolymer resin of the present invention contains at least 0.5% by weight, such as 0.5 to 25% by weight, of an α-olefin.

[0025] Structure and properties of high melt strength LLDPE

[0026] Geomembranes are synthetic membranes, liners or barriers of very low permeability, commonly used to control fluid migration in man-made projects. The use of polyethylene copolymers in geomembranes is well known to those skilled in the art. Polyethylene resins suitable for thick gauge films include conventional linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE) and medium density polyethylene (MDPE), which can be homopolymers, copolymers or terpolymers of ethylene and alpha-olefins. In the copolymers, the weight percent of alpha-olefins is about 4-15 weight percent, preferably 6-12 weight percent. Suitable alpha-olefin comonomers include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-pentene and 1-octene. The range of alpha-olefins is about C3 to C 20 , preferably C3 to C 10 , more preferably C3 to C8. The resin melt index is typically 0.2 to 10 dg / min, preferably 1 to 5 dg / min, and more preferably 1 to 2 dg / min. The resin density will be between 0.860 and 0.940 g / cc, preferably between 0.900 and 0.930 g / cc. It is generally desirable to have an LLDPE with a hexane extractable level of less than about 4% by weight to minimize the possibility of film plugging, high unwinding noise, roll telescoping, roll softness, and mold buildup.

[0027] Geomembranes are typically made by film blowing with large bubble sizes or casting with wide widths, and require resins with sufficient melt strength. Therefore, long-chain branching is generally a desirable structure for a resin because it contributes to melt strength (e.g., U.S. Patent No. 9,346,897). The long-chain branched (LCB) LLDPE resins of the present invention are chemically tailored based on reactor resins, which are Ziegler-Natta catalyzed LLDPE copolymers having unique molecular compositions, as described in U.S. Patent Nos. 8,993,693 and 6,992,034, which are incorporated by reference in their entireties. The reactor ethylene copolymers used in the present invention are produced by reacting ethylene and α-olefin comonomers in the presence of a titanium-based Ziegler-Natta catalyst in a gas phase process at a reaction temperature of about 50°C to about 100°C. This ethylene copolymer resin has a unique composition distribution and a unique molecular structure. The LLDPE copolymers of the present invention exhibit a unique comonomer distribution because the comonomers preferentially bind to high molecular weight polymer chains. The resins of the present invention have at least 15 weight percent ethylene copolymer components eluting in TREF at temperatures below 35° C. The weight average molecular weight (Mw) of the copolymer resins of the present invention is substantially constant across the TREF fraction distribution. The resins of the present invention prepared with C3 to C8 α-olefin compositions have a controlled molecular weight distribution (Mw / Mn) of 2.5 to 5.0, a melt index of 0.5 to 5 dg / min, and a density of 0.910 to 0.930 g / cc.

[0028] The LLDPE copolymers of the present invention are polymerized using advanced Ziegler-Natta catalysts modified with non-single-site catalyst ligands and / or with an internal strong Lewis base (e.g., an aromatic compound containing a nitrogen atom). The α-olefin comonomer is selected from 1-hexene and 1-butene. Typically, ethylene and other α-olefins are copolymerized in a gas phase polymerization process in the presence of a titanium-based Ziegler-Natta catalyst and an alkylaluminum cocatalyst at an ethylene partial pressure of 10 psi to 350 psi and a comonomer to ethylene ratio of 0.01 to 0.50. Examples of such catalysts and polymerization conditions are described in U.S. Patent Nos. 6,992,034 and 7,618,913, which are incorporated herein by reference in their entireties.

[0029] The resins of the present invention have less than about 2.5% hexane extractables by weight, a beneficial feature for film extrusion processability. There are concerns about including high hexane extractable polymers in the outermost layer because high hexane extractables are believed to cause die buildup issues during extrusion and the accumulation of low molecular weight olefinic materials on manufacturing equipment. The accumulation of low molecular weight olefinic materials is undesirable because the film surface can be negatively impacted during film extrusion, which can lead to inconsistent film physical properties.

[0030] Chemical modification after the reactor can be carried out in batch reactor or continuous reaction extrusion process.The modification using batch reactor is discontinuous.It can allow the high conversion of reactant and the good control of reaction.Yet, it is unrealistic to use in most large-scale polyolefin productions usually.By contrast, the modification carried out by reaction extrusion is more difficult to control, can be incorporated into the extrusion finishing (extrusion finishing) stage in the polyolefin production simultaneously.

[0031] For the present invention, under the temperature that is applicable to commercial polyolefin extrusion pelletizing, selected base polymer with unique structure is carried out extrusion modification with peroxide compound.The selection of peroxide initiator, auxiliary additive and extrusion condition allows to produce peroxide free radical.The peroxide compound can be any compound containing one or more peroxide groups, and its suitable example can include but not limited to dicumyl peroxide and dimethyl peroxide two (tert-butyl peroxy) hexane etc.

[0032] Several techniques in the prior art have been proposed to reduce the amount of gel in polyethylene film materials. U.S. Patent No. 5,508,319 claims to utilize irradiation of polyethylene materials by gamma radiation or electron beam radiation to reduce gel, but such treatment affects the resin melt flow characteristics. Another option in U.S. Patent No. 5,015,693 proposes adding certain fluoropolymers to the polymer melt in a melt extruder. However, the disadvantage is that the use of such fluoropolymers leads to limitations in use in certain applications. Another technique in U.S. Patent No. 6,485,662 proposes to reduce gel in polyethylene by applying a melt filter in a melt extruder. However, this has the disadvantage that the pressure buildup through the screen leads to a loss of productivity. Therefore, there is a need to develop polyethylene film products with reduced gel content in a simple and effective manner without the need for additional complex treatments.

[0033] Melt flow ratio, which is the ratio of high melt flow index (HLMI) to melt flow index (MI), is used as a measure of melt fluidity and a measure of polymer molecular weight distribution. Melt flow ratio is considered to be an indication of polymer molecular weight distribution, and the higher the value, the wider the molecular weight distribution. The composition distribution or short chain branching distribution and the comonomer content and molecular weight in each fractionated fraction are measured by TREF and GPC-FTIR with TCB solvent. Unless otherwise stated, all molecular weights are weight average molecular weight. Molecular weight is measured by gel permeation chromatography (GPC), including weight average molecular weight (Mw), number average molecular weight (Mn) and Z average molar mass (Mz).

[0034] Vicat softening temperature was determined according to ASTM D 1525. Peak melting point was determined according to ASTM D3418 using differential scanning calorimetry (DSC) with a heating rate of 10°C / minute.

[0035] Film of the present invention is usually produced by traditional blown film process. According to the polymer of the present invention's formulation, it is easily extruded into blown film. There is the example of various extruders of blown film die, air ring and continuous take-out equipment (including but not limited to LabTech blown film production line) can be used to produce film of the present invention. Example

[0036] The ethylene / 1-hexene copolymers of this invention are polymerized in a gas phase fluidized bed reactor using an advanced Ziegler-Natta catalyst prior to post reactor tailoring. More detailed resin polymerization information is described in our US Patent Nos. 8,993,693 and 6,992,034.

[0037] In order to provide a better understanding of the foregoing discussion, the following non-limiting examples are provided. Although the examples may be directed to specific embodiments, they should not be construed as limiting the invention in any particular respect.

[0038] The melt flow index (MI) of the polymer is measured at 190°C according to ASTM D1238. Density is measured according to ASTM D1505. Unless otherwise stated, all molecular weights are weight average molecular weights. Molecular weights (weight average molecular weight (Mw), number average molecular weight (Mz)) are measured by gel permeation chromatography (GPC). The composition distribution or short chain branching of the polymer, as well as the comonomer content and molecular weight in each fractionated fraction are determined by temperature rising elution fractionation (TREF) and GPC-FTIR at a high temperature of 145°C, a flow rate of 0.9 mL / min, a solvent of TCB, and a solution concentration of 2.5 mg / mL.

[0039] Melt rheology characterization was performed by frequency sweep on a TA Instruments ARES G2 rheometer. All tests were run at 190°C with a strain amplitude of 5% and a frequency of 100 rad / sec to 0.01 rad / sec at intervals of 5 points / decade. The dynamic viscosity as a function of frequency was fit to the Carreau-Yasuda (CY) viscosity model (PJ Carreau, PhD thesis, University Wisconsin, 1968) to obtain the zero shear viscosity (η0). The rate exponent was fixed to 0.1818 to minimize the uncertainty of the curve fit. The flow of polymers with long branching (i.e., branches long enough to entangle with other polymer chains) is significantly different from their linear counterparts. The presence of long chain branching (LCB) can profoundly affect processing and crystallization. It is generally desirable to incorporate a certain amount of long chain branching into polyethylene resins to achieve certain advantages in processability and physical properties. The LCB level in the polyethylene resin sample was calculated according to Janzen and Colby (J. Mol. Struct. 485, 589, 1999) from the zero shear viscosity (η 0 ) and the GPC weight average molecular weight (M w ), and is expressed as JC-α.

[0040] The short chain branching distribution (SCBD) of the copolymers of the present invention is as follows: Figure 1 Compared to comparative examples of competitive resins (which are also Ziegler-Natta catalyzed LLDPE copolymers), the copolymers have a unique composition distribution in which the comonomer is almost uniformly incorporated throughout the molecular weight distribution.

[0041] Temperature Rising Elution Fractionation (TREF) is performed to characterize the molecular structure of the resin eluting from a TREF column at a given low temperature. Figure 2 The TREF results in FIG. 3 show that the resin of the present invention exhibits a TREF fraction content of up to 16% eluted at a low temperature of 35° C., which is a significant difference from mLLDPE. Figure 3 The molecular weight (Mw) of the TREF low temperature soluble fraction was found to be comparable to the bulk composition. Figure 4 As shown, the molecular weight of the copolymer of the present invention is substantially constant throughout the TREF fraction distribution, wherein the Mw of the copolymer satisfies the following formula:

[0042] (Mw at 100) / (Mw at 35°C) = 1.0 - 1.5 (1)

[0043] The polymers of the present invention have a temperature rising elution fractionation (TREF) fraction of at least 15% at an elution temperature below 35°C. Generally, the high melt strength polymers of the present invention are Ziegler-Natta catalyzed copolymers of ethylene and α-olefins having a unique composition distribution and desired long chain branching (LCB). The unique compositional characteristics include, but are not limited to, a uniform short chain branching distribution according to GPC-FTIR and a substantially constant weight average molecular weight across the TREF fraction.

[0044] Figure 5 The dynamic rheological curves (viscosity versus shear rate) of the resins of the present invention at 190°C are shown with various MIs. Examples of polymer molecular parameters in terms of molecular weight, molecular weight distribution, zero shear viscosity (η0), and LCB (JC-α) are provided in Table 1. The zero shear viscosity of the polymer at any given MI is significantly higher than that of the linear control. In one embodiment, the zero shear viscosity follows a simple function of the MI and LCB level:

[0045] η0 = k0*MI^[n0*(1+z*α)] (2)

[0046] Where: k0=13017 Pa*s, n0=-1.3884, z = 0.062014.

[0047] The zero shear viscosity of the inventive resin sample at 0.35 MI is about 20 times that of its competitive counterpart. The higher η0 of the inventive resin at a given MI is an advantage in achieving higher throughput while meeting the melt strength requirements of the process. Typically, the long chain branching (LCB) level of the ethylene copolymers of the present invention is from about 5 to about 100, from about 5 to 50, or from about 10 to about 30 LCBs per million total carbon atoms.

[0048] Table 1

[0049]

[0050] Table 2 shows examples of the physical properties of high melt strength resins of the present invention with desired LCB levels. The physical properties of the resins were tested according to ASTM procedures. The resins of the present invention exhibited desired physical properties, such as desired stiffness and flexibility, as well as outstanding thermal stability. The flexural modulus of the resin compression plate was at least 55 kpsi according to ASTM D790. The OIT was at least 150 min, measured according to ASTM D3895. The tensile elongation and tensile strength of the resin compression plate at yield were at least 700% and at least 1500 psi, respectively, according to ASTM D638. The hardness of the resin compression plate was at least 50 Shore-D according to ASTM D2240. The ESCR was at least 3000 hours under both Condition B and Condition C, according to ASTM D1693.

[0051] Table 2

[0052]

[0053] In addition, the high melt strength resins of the present invention exhibit outstanding gel properties, which are crucial for geomembrane applications. According to ASTM D7310, the gel counts of less than 425 μm in size are 0.1% per 100 cm 2 Gels smaller than 20 and larger than 425 μm are counted per 100 cm 2 Less than 5.

[0054] Therefore, the present invention is well suited to achieve the purposes and advantages mentioned and inherent therein. The specific embodiments disclosed above are illustrative only, as the present invention can be modified and practiced in different but equivalent ways that are obvious to those skilled in the art, and benefit from the teachings therein. In addition, except as described in the appended claims, the details of construction or design shown herein are intended to be without any limitation. Therefore, it is obvious that the specific illustrative embodiments disclosed above can be changed or modified, and all such changes are considered to be within the scope and spirit of the present invention. Unless otherwise stated, all numbers representing the amounts of components, properties, reaction conditions, etc. used in the specification and claims should be understood as approximate values based on the desired properties and measurement errors sought to be obtained by the present invention, and should at least be interpreted according to the number of reported significant figures and by applying conventional rounding techniques. Whenever a numerical range with a lower limit and an upper limit is disclosed, the numbers falling within the range are explicitly disclosed. In addition, the indefinite articles "a" or "an" used in the claims are defined herein to mean one or more than one element introduced therein.

Claims

1. Ziegler-Natta catalyzed ethylene and α-olefin LLDPE copolymers comprising: a) a density within the range of 0.910 g / cc to 0.930 g / cc; b) a melt index (I2) in the range of 0.2 dg / min to 0.8 dg / min; c) Melt index ratio (I 21 / I2) in the range of 25 to 45; d) a polydispersity index (Mw / Mn) within the range of 3.0 to 5.0; e) polydispersity index (Mz / Mw) greater than 2.5; f) a peak melting point in the range of 123°C to 127°C; g) at least 15% of the temperature rising elution fractionation (TREF) fraction when the elution temperature is below 35°C; h) a weight average molecular weight (Mw) that is constant throughout the TREF fraction distribution, wherein the Mw at 100°C divided by the Mw at 35°C is in the range of 1.0 to 1.5; i) Zero shear viscosity at 190°C (η 0 ) in 2×10 4 to 1×10 7 within the range of Pa·s; j) long chain branching (LCB) levels in the range of 5 to 50 per million total carbon atoms; wherein the number of gels smaller than 425 μm in size is measured per 100 cm according to ASTM D7310. 2 Less than 20, and the number of gels larger than 425 μm is per 100 cm 2 Less than 5; The TREF is measured at a high temperature of 145°C, a flow rate of 0.9 mL / min, a solvent of TCB and a solution concentration of 2.5 mg / mL; and the copolymer is ethylene and one or more C3-C 10 Copolymers of α-olefins.

2. The copolymer of claim 1 , wherein the polymer zero shear viscosity (η 0) is a function of the melt index (I 2 ) and the level of long chain branching (LCB) as follows: η0≥k0*I2^[n0*(1+z*α)] where k0 = 13017 Pa·s, n0 = -1.3884, and z = 0.062014, and α is the long chain branching (LCB) level.

3. The copolymer of claim 1, wherein when the melt index (I2) is in the range of 0.30 to 0.60 dg / min, the zero shear viscosity (η0) at 190°C is in the range of 3×10 4 to 5×10 5 within the range of Pa·s.

4. The copolymer of claim 1 , wherein the Mw is in the range of 80,000 to 200,000 g / mil; wherein the number average molecular weight (Mn) is in the range of 30,000 to 70,000 g / mol; and wherein the Z average molar mass (Mz) is in the range of 300,000 to 400,000 g / mol.

5. The copolymer of claim 1, wherein the ratio (Mz / Mw) is in the range of 2.5 to 3.

8.

6. The copolymer of claim 1, wherein the ratio (Mz / Mw) is in the range of 2.5 to 3.

5.

7. The copolymer of claim 1, wherein the ratio (Mz / Mw) is in the range of 2.5 to 3.

0.

8. The copolymer of claim 1, wherein the copolymer has a homopolymer content of less than 10%.

9. The copolymer of claim 1, wherein the polydispersity index (Mw / Mn) of the TREF soluble fraction eluting at 35°C is in the range of 3.0 to 5.

0.

10. The copolymer of claim 1, wherein the alpha-olefin comonomer is selected from 1-hexene, 1-octene, or 1-butene.

11. The copolymer of claim 1 , wherein the copolymer has an OIT of at least 120 minutes as measured according to ASTM D3895.

12. The copolymer of claim 1, wherein the resin plaque has a tensile elongation at break of at least 700% according to ASTM D638.

13. The copolymer of claim 1, wherein the resin plaque has a tensile strength at yield of at least 1500 psi according to ASTM D638.

14. The copolymer of claim 1, wherein the resin plaque has an ESCR of at least 3000 hours according to ASTM D1693 for both Conditions B and C.

15. The copolymer of claim 1, wherein the resin plaque has a hardness of at least 50 Shore-D according to ASTM D2240.

16. The copolymer of claim 1, wherein the resin plaque has a flexural modulus of at least 55 kpsi according to ASTM D790.

17. The copolymer of claim 1, wherein the copolymer is produced by reacting ethylene and an alpha-olefin comonomer in the presence of a titanium-based Ziegler-Natta catalyst at a reaction temperature of 50°C to 100°C.

18. The copolymer of claim 17, wherein the titanium-based Ziegler-Natta catalyst comprises: a. Magnesium; b. With formula R 1 m Si(OR 2 ) n A compound wherein R 1 and R 2 It is C1-C 20 carbon atoms, m=0-3, n=1-4, and m+n=4, and wherein each R 1 and each R 2 Can be the same or different; c. With formula R 3 x SiX y A compound wherein R 3 It is C1-C 20 A carbon atom, X is a halogen, x=0-3, y=1-4, and x+y=4, and wherein each X and each R 3 Can be the same or different; d. With the formula MX4 and M(OR 4 )X4, wherein M is titanium, wherein R 4 It is C1-C 20 a carbon atom, X is a halogen, and each R 4 Can be the same or different; e. substituted aromatic nitrogen compounds; and f. having formula R 5 X is an alkyl halide or aromatic halide compound, wherein R 5 is an alkyl group containing 3 to 20 carbon atoms or an aryl group containing 6 to 18 carbon atoms, and X is selected from chlorine and bromine.

19. A blown film comprising the copolymer of claim 1 wherein the film has a thickness in the range of 10 to 150 mils.

20. A cast film comprising the copolymer of claim 1 wherein the film has a thickness in the range of 10 to 150 mils.

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