WO2021154442A1

WO2021154442A1 - Polyethylene films having high tear strength

Info

Publication number: WO2021154442A1
Application number: PCT/US2020/067400
Authority: WO
Inventors: Arnold Lustiger; Jevan Furmanski
Original assignee: Exxonmobil Research And Engineering Company
Priority date: 2020-01-31
Filing date: 2020-12-30
Publication date: 2021-08-05

Abstract

Blends of ethylene α-olefin copolymers, the films of which possess high tear strength, particularly high machine direction (MD) tear strength, are described. The blends contain mixtures of high and low density ethylene α-olefin copolymers prepared using catalysts containing bulky ligand transition metal compounds.

Description

POLYETHYLENE FILMS HAVING HIGH TEAR STRENGTH FIELD OF THE INVENTION

[0001] This disclosure relates to blends of ethylene α-olefins copolymers the films of which possess high tear strength, particularly high machine direction (MD) tear strength. The blends contain mixtures of high and low density ethylene α-olefins copolymers prepared using single site olefin polymerization catalysts containing bulky ligand transition metal compounds.

BACKGROUND OF THE INVENTION

[0002] Machine direction (MD) tear strength is an important performance metric in the evaluation of polyethylene films. Generally, ethylene α-olefins copolymers synthesized via single site bulky ligand transition metal catalysts have relatively poor tear strength, believed to be related to the narrow distribution of comonomer in these materials.

[0003] The advent of single site catalysis for the production of linear low density polyethylene film grade material as a replacement for Ziegler-Natta catalyzed material resulted in many improved product attributes, including organoleptics and transparency. However, one property in which single site catalyzed polyethylene is deficient is machine direction (MD) tear strength, an important attribute that may limit the use of these materials in numerous film applications.

[0004] It is recognized that there is a strong relationship between MD tear strength, the molecular weight distribution (MWD), and where the comonomer resides within this distribution, as determined by cross-fractionation. Single site catalyst derived polyethylene typically has a relatively narrow molecular weight and comonomer (composition) distribution, and this narrowness is related to its relatively poor tear strength.

[0005] In contrast, Ziegler-Natta catalyst derived polyethylene has a broad molecular weight distribution in which a high comonomer rubbery component resides among the lower molecular weight chains. These materials generally outperform similar products made with a single site catalyst in terms of MD tear strength, potentially due to their broader composition distribution. [0006] It would be desirable to identify polyethylene compositions that have improved MD tear strength and which are prepared from polyethylenes derived from single site olefin polymerization catalysts. The present disclosure addresses this desire.

[0007] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

SUMMARY OF THE INVENTION [0008] The present disclosure provides polyethylene blends comprising two or more bulky ligand transition metal catalyst derived ethylene α-olefins copolymers. Films blown from the blends have very high MD tear strength, along with other desirable attributes.

[0009] In one aspect the present disclosure provides a polyolefin blend, said polyolefin blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: from about 10% to about 80% by weight of a first ethylene α-olefins copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; and from about 20% to about 90% by weight of a second ethylene α-olefins copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; wherein both the first and second ethylene α-olefins copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

[0010] In certain embodiments the bulky ligand transition metal compound is a metallocene, preferably a metallocene comprising Ti, Zr or Hf.

[0011] In some embodiments the density of the polyolefin blend is from about 0.913 g/cm3 to about 0.923 g/cm3, or from about 0.915 g/cm3 to about 0.921 g/cm3, or from about 0.917 g/cm3 to about 0.919 g/cm3.

[0012] In some embodiments the melt index of the polyolefin blend is from about 0.7 g/10min to about 1.5 g/10min.

[0013] In certain preferred embodiments the polyolefin blend comprises from about 15% to about 75% by weight of the first ethylene α-olefins copolymer, or from about 20% to about 70%, or from about 25% to about 65%, or from about 30% to about 60%.

[0014] In certain preferred embodiments the polyolefin blend comprises from about 25% to about 85% by weight of the second ethylene α-olefins copolymer, or from about 30% to about 80%, or from about 35% to about 75%, or from about 40% to about 70%.

[0015] The density of the first ethylene α-olefins copolymer may be from about 0.940 g/cm3 to about 0.960 g/cm3, or from about 0.942 g/cm3 to about 0.958 g/cm3.

[0016] The melt index of the first ethylene α-olefins copolymer may be from about 0.2 g/1 Omin to about 0.9 g/10min, or from about 0.3 g/10min to about 0.8 g/10min.

[0017] The density of the second ethylene α-olefins copolymer may be from about 0.860 g/cm3 to about 0.905 g/cm3, or from about 0.870 g/cm3 to about 0.905 g/cm3. [0018] The melt index of the second ethylene α-olefins copolymer may be from about 0.8 g/10min to about 4 g/10min, or from about 1.0 g/10min to about 3.0 g/10min.

[0019] In preferred embodiments the first and second ethylene α-olefins copolymers are prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

[0020] Preferably, the first ethylene α-olefins copolymer is prepared in a gas phase polymerization process.

[0021] Preferably, the second ethylene α-olefins copolymer is prepared in a solution process. [0022] Advantageously, both the first and second ethylene α-olefins copolymers may be prepared in single reactor processes. Furthermore, both the first and second ethylene α-olefins copolymers may be prepared using catalyst systems comprising a single bulky ligand transition metal compound, for example a single metallocene compound.

[0023] In another aspect the present disclosure provides a film comprising a polyolefin blend, said polyolefin blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: from about 10% to about 80% by weight of a first ethylene α-olefins copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; and from about 20% to about 90% by weight of a second ethylene α-olefins copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; wherein both the first and second ethylene α-olefins copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

[0024] In some embodiments the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

[0025] In some embodiments the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil.

[0026] In another aspect of the present disclosure there is provided a polyolefin blend, said polyolefin blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: from about 10% to about 80% by weight of a first ethylene α-olefins copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; from about 20% to about 90% by weight of a second ethylene α-olefins copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; and a third ethylene α-olefins copolymer having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, wherein the first, second and third ethylene α-olefins copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

[0027] In some embodiments the bulky ligand transition metal compound is a metallocene comprising Ti, Zr or Hf.

[0028] In some embodiments the density of the third ethylene α-olefins copolymer is from about

0.910 g/cm3 to about 0.926 g/cm3, or from about 0.912 g/cm3 to about 0.924 g/cm3, or from about 0.914 g/cm3 to about 0.922 g/cm3, or from about 0.916 g/cm3 to about 0.920 g/cm3 [0029] In some embodiments the melt index of the third ethylene α-olefins copolymer is from about 0.7 g/10min to about 1.6 g/10min, or from about 0.8 g/10min to about 1.2 g/10min.

[0030] In certain embodiments the polyolefin blend comprises: from about 10% to about 80% by weight of the first ethylene α-olefins copolymer; from about 20% to about 90% by weight of the second ethylene α-olefins copolymer; and from about 10% to about 50% by weight of the third ethylene α-olefins copolymer. [0031] In some preferred embodiments the amount of second ethylene α-olefins copolymer in the blend does not exceed about 50% by weight of the total blend.

[0032] Preferably, the third ethylene α-olefins copolymer is prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

[0033] Preferably, the third ethylene α-olefins copolymer is prepared in a gas phase polymerization process.

[0034] Advantageously, the third ethylene α-olefins copolymer may be prepared in a single reactor process. Furthermore, the third ethylene α-olefins copolymer may be prepared using a catalyst system comprising a single bulky ligand transition metal compound, for example a single metallocene compound. [0035] In another aspect the present disclosure provides a film comprising a polyolefin blend, said blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: from about 10% to about 80% by weight of a first ethylene a-olefin copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; from about 20% to about 90% by weight of a second ethylene a-olefin copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; and a third ethylene a-olefin copolymer having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, wherein the first, second and third ethylene a-olefin copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

[0036] In some embodiments the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

[0037] In some embodiments the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil.

[0038] There is also provided an article of manufacture comprising any one or more of the herein disclosed films.

[0039] The present disclosure also provides a method of preparing a polyolefin blend comprising melt blending a mixture of the first ethylene a-olefin copolymer according to any one of the herein disclosed embodiments and the second ethylene a-olefin copolymer according to any one of the herein disclosed embodiments.

[0040] The present disclosure further provides a method of preparing a polyolefin blend comprising melt blending a mixture of the first ethylene a-olefin copolymer according to any one of the herein disclosed embodiments, the second ethylene a-olefin copolymer according to any one of the herein disclosed embodiments and the third ethylene a-olefin copolymer according to any one of the herein disclosed embodiments.

[0041] Further features and advantages of the present disclosure will be understood by reference to the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS [0042] Figure 1 illustrates the heat seal curves of Exceed™ 1018 and two polyolefin blends prepared according to embodiments of the present disclosure.

[0043] Figure 2 illustrates the variation of MD tear strength of trimodal blends containing varying proportions of Exceed™ 1018.

[0044] Figure 3 illustrates the variation of dart drop impact of trimodal blends containing varying proportions of Exceed™ 1018.

DET AIL ED DESCRIPTION OF THE EMBODIMENTS

[0045] The following is a detailed description of the disclosure provided to aid those skilled in the art in practicing the present disclosure. Those of ordinary skill in the art may make modifications and variations in the embodiments described herein without departing from the spirit or scope of the present disclosure.

[0046] Although any compositions, blends, methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred compositions, blends, methods and materials are now described.

[0047] It must also be noted that, as used in the specification and the appended claims, the singular forms ‘a’, ‘an’ and ‘the’ include plural referents unless otherwise specified. Thus, for example, reference to ‘α-olefins’ may include more than one α-olefins, and the like.

[0048] Throughout this specification, use of the terms ‘comprises’ or ‘comprising’ or grammatical variations thereon shall be taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof not specifically mentioned.

[0049] Unless specifically stated or obvious from context, as used herein, the term ‘about’ is understood as within a range of normal tolerance in the art, for example within two standard deviations of the mean. ‘About’ can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein in the specification and the claim can be modified by the term ‘about’.

[0050] Any processes provided herein can be combined with one or more of any of the other processes provided herein.

[0051] Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,

17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,

43, 44, 45, 46, 47, 48, 49, or 50. [0052] The following definitions are included to provide a clear and consistent understanding of the specification and claims. As used herein, the recited terms have the following meanings. All other terms and phrases used in this specification have their ordinary meanings as one of skill in the art would understand. Such ordinary meanings may be obtained by reference to technical dictionaries, such as Hawley's Condensed Chemical Dictionary 14th Edition, by R. J. Lewis, John Wiley & Sons, New York, N.Y., 2001.

[0053] The ethylene α-olefins copolymers utilized to prepare the blends of the present disclosure are ethylene-based polymers derived from ethylene and one or more C₃to C₂₀ α-olefins comonomers, preferably C₃to C₁₀α-olefins, and more preferably C₄to C₈ α-olefins. The α-olefm comonomer may be linear, branched, cyclic and/or substituted, and two or more comonomers may be used, if desired. Examples of suitable comonomers include propylene, butene, 1-pentene; 1- pentene with one or more methyl, ethyl, or propyl substituents; 1 -hexene; 1 -hexene with one or more methyl, ethyl, or propyl substituents; 1-heptene; 1-heptene with one or more methyl, ethyl, or propyl substituents; 1-octene; 1-octene with one or more methyl, ethyl, or propyl substituents; 1-nonene; 1-nonene with one or more methyl, ethyl, or propyl substituents; ethyl, methyl, or dimethyl-substituted 1-decene; 1-dodecene; and styrene. Particularly suitable comonomers include 1 -butene, 1 -hexene, and 1-octene, 1 -hexene, and mixtures thereof.

[0054] The ethylene α-olefins copolymers may be prepared by any suitable polymerization method including solution polymerization, slurry polymerization, gas phase polymerization using supported or unsupported catalyst systems. The catalyst systems may comprises bulky ligand transition metal compounds, sometimes referred to as “single site” catalyst systems. In some embodiments the catalyst systems comprise one or more metallocene catalysts. It is preferred that the ethylene α-olefins copolymers of the present disclosure are not prepared from a Ziegler-Natta catalyst system or a Chromium (Phillips) catalyst system.

[0055] As used herein, the term “metallocene catalyst” is defined to comprise at least one transition metal compound containing one or more substituted or unsubstituted cyclopentadienyl moiety (Cp) (typically two Cp moieties) in combination with a Group 4, 5, or 6 transition metal, such as, zirconium, hafnium, and titanium.

[0056] Metallocene catalysts generally require activation with a suitable co-catalyst, or activator, in order to yield an “active metallocene catalyst”, i.e., an organometallic complex with a vacant coordination site that can coordinate, insert, and polymerize olefins. Active catalyst systems generally include not only the metallocene complex, but also an activator, such as an alumoxane or a derivative thereof (preferably methyl alumoxane), an ionizing activator, a Lewis acid, or a combination thereof. Alkylalumoxanes (typically methyl alumoxane and modified methylalumoxanes) are particularly suitable as catalyst activators. The catalyst system may be supported on a carrier, typically an inorganic oxide or chloride or a resinous material such as, for example, polyethylene or silica.

[0057] Zirconium transition metal metallocene-type catalyst systems are particularly suitable. Non-limiting examples of metallocene catalysts and catalyst systems useful in practicing the present invention include those described in, U.S. Pat. Nos. 5,466,649; 6,476,171; 6,225,426; and 7,951,873; and in the references cited therein, all of which are fully incorporated herein by reference. Particularly useful catalyst systems include supported dimethylsilyl bis(tetrahydroindenyl) zirconium dichloride.

[0058] Supported polymerization catalyst may be deposited on, bonded to, contacted with, or incorporated within, adsorbed or absorbed in, or on, a support or carrier. In another embodiment, the metallocene is introduced onto a support by slurrying a presupported activator in oil, a hydrocarbon such as pentane, solvent, or non-solvent, then adding the metallocene as a solid while stirring. The metallocene may be finely divided solids. Although the metallocene is typically of very low solubility in the diluting medium, it is found to distribute onto the support and be active for polymerization. Very low solubilizing media such as mineral oil (e.g., Kay do™ or Drakol™) or pentane may be used. The diluent can be filtered off and the remaining solid shows polymerization capability much as would be expected if the catalyst had been prepared by traditional methods such as contacting the catalyst with methylalumoxane in toluene, contacting with the support, followed by removal of the solvent. If the diluent is volatile, such as pentane, it may be removed under vacuum or by nitrogen purge to afford an active catalyst. The mixing time may be greater than 4 hours, but shorter times are suitable.

[0059] Typically in a gas phase polymerization process, a continuous cycle is employed where in one part of the cycle of a reactor, a cycling gas stream, otherwise known as a recycle stream or fluidizing medium, is heated in the reactor by the heat of polymerization. This heat is removed in another part of the cycle by a cooling system external to the reactor. (See e.g., U.S. Pat. Nos.

4,543,399; 4,588,790; 5,028,670; 5,317,036; 5,352,749; 5,405,922; 5,436,304; 5,453,471;

5,462,999; 5,616,661; and 5,668,228 all of which are fully incorporated herein by reference.) [0060] Generally, in a gas fluidized bed process for producing polymers, a gaseous stream containing one or more monomers is continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. The gaseous stream is withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product is withdrawn from the reactor and fresh monomer is added to replace the polymerized monomer. The reactor pressure may vary from 100 psig (680 kPag)-500 psig (3448 kPag), or in the range of from 200 psig (1379 kPag)-400 psig (2759 kPag), or in the range of from 250 psig (1724 kPag)-350 psig (2414 kPag). The reactor may be operated at a temperature in the range of 60° C. to 120° C., 60° C. to 115° C., 70° C. to 110° C., 75° C. to 95° C., or 80° C. to 95° C. The productivity of the catalyst or catalyst system is influenced by the main monomer partial pressure. The mole percent of the main monomer, ethylene, may be from 25.0-90.0 mole percent, or 50.0-90.0 mole percent, or 70.0-85.0 mole percent, and the monomer partial pressure may be in the range of from 75 psia (517 kPa)-300 psia (2069 kPa), or 100-275 psia (689-1894 kPa), or 150-265 psia (1034-1826 kPa), or 200-250 psia (1378-1722 kPa).

[0061] Other gas phase processes contemplated by the process of the invention include those described in U.S. Pat. Nos. 5,627,242; 5,665,818; 5,677,375; 6,255,426; and European published patent applications EP-A-0794200; EP-A-0802202; and EP-B-0634421; all of which are herein fully incorporated by reference.

[0062] Additionally, the use of a process continuity aid, while not required, may be desirable in any of the foregoing processes. Such continuity aids are well known to persons of skill in the art and include, for example, metal stearates.

Films

[0063] The polyethylene blends of the present disclosure may be fabricated into many types of films. The films may be monolayer or multilayer films. The polyethylene blends of the present disclosure may comprise one or more layers of the film and be used in combination with other polymers, such as, other polyolefin polymers, functionalized polymers, elastomers, plastomers, etc.

Polymer Blends

[0064] The polymer blends of the present disclosure may be blended with other polymers, such as polyolefin polymers, including others types of polyethylene polymers, to produce end-use articles, such as, films.

[0065] Suitable blown film and cast film processes are described in detail in “Plastics Films” by John H. Briston, Longman Scientific and Technical, 1986.

[0066] The density of the herein disclosed ethylene a-olefin copolymers and blends is measured according to ASTM D1505-10 using a density-gradient column on a compression- molded specimen that has been slowly cooled to room temperature (i.e., over a period of 10 minutes or more) and allowed to age for a sufficient time that the density is constant within +/-0.001 g/cm³. Compression molded specimens for density measurements are made according to ASTM D4703- 10a. Unless otherwise indicated, the specimens are typically made from pelleted polymers and conditioned for 40 hours at 23 °C before the density measurement. In the case of specimens made from reactor granule samples, an accelerated conditioning of 2 hours at 23°C is used. [0067] The melt index (12) of the herein disclosed ethylene α-olefins copolymers and blends is measured according to ASTM D1238 (190° C, 2.16 kg weight).

Test Methods

[0068] The properties cited below were determined in accordance with the following test procedures. Where any of these properties is referenced in the appended claims, it is to be measured in accordance with the specified test procedure.

[0069] Where applicable, the properties and descriptions below are intended to encompass measurements in both the machine and transverse directions. Such measurements are reported separately, with the designation “MD” indicating a measurement in the machine direction, and “TD” indicating a measurement in the transverse direction.

[0070] Gauge, reported in mils, was measured using a Measuretech Series 200 instrument. The instrument measures film thickness using a capacitance gauge. For each film sample, ten film thickness datapoints were measured per inch of film as the film was passed through the gauge in a transverse direction. From these measurements, an average gauge measurement was determined and reported.

[0071] Elmendorf Tear, reported in grams (g) or grams per mil (g/mil), was measured as specified by ASTM D-1922.

[0072] Tensile Strength at Yield, reported in pounds per square inch (lb/in2 or psi), was measured as specified by ASTM D-882.

[0073] Tensile Strength at Break, reported in pounds per square inch (lb/in2 or psi), was measured as specified by ASTM D-882.

[0074] Elongation at Yield, reported as a percentage (%), was measured as specified by ASTM D-882.

[0075] Elongation at Break, reported as a percentage (%), was measured as specified by ASTM D-882.

[0076] 1% Secant Modulus (M), reported in pounds per square inch (lb/int or psi), was measured as specified by ASTM D-882.

[0077] Haze, reported as a percentage (%), was measured as specified by ASTM D-1003.

[0078] Gloss, reported as a percentage (%), was measured as specified by ASTM D-2457.

[0079] Dart F50, or Dart Drop Impact or Dart Drop Impact Strength (DIS), reported in grams (g) and/or grams per mil (g/mil), was measured as specified by ASTM D-1709, method A.

[0080] Where any of the above properties are reported in pounds per square inch, grams per mil, or in any other dimensions that are reported per unit area or per unit thickness, the ASTM methods cited for each property have been followed except that the film gauge was measured based on ASTM D-374, method C.

EXAMPLES Copolymer resins

[0081] Table 1 collects the details of the ethylene α-olefins copolymer resins utilized to prepare the blends of the present disclosure. All the resins were commercially available, except for resins 1 and 2 which were prepared in house. The Exact™ plastomers, Exceed™ LLDPE, Paxon™ high density resin and HD 9856 blow molding resin were all obtained from ExxonMobil Chemical Company. Paxon™ AD 60-003 is produced in a slurry polymerization process using a chromium catalyst system. HD 9856 is produced in a slurry polymerization process using a Ziegler-Natta catalyst system.

Preparation of copolymer resins 1 and 2

[0082] The two high density copolymer resins 1 and 2 were prepared in a continuous gas phase fluidized bed reactor having a straight section of 24 inch (61 cm) diameter with a length of approximately 11.75 feet (3.6 m) and an expanded section of 10.2 feet (3.1 m) length and 4.2 feet (1.3 m) diameter at the largest width. The fluidized bed is made up of polymer granules. The gaseous feed streams of ethylene and hydrogen together with liquid 1 -hexene were mixed together in a mixing tee arrangement arid introduced below the reactor bed into the recycle gas line. The individual flow rates of ethylene, hydrogen and 1 -hexene were controlled to produce copolymers 1 and 2. The ethylene concentration was controlled to maintain a constant ethylene partial pressure. The hydrogen was controlled to maintain a constant hydrogen to ethylene mole ratio. The concentrations of ail gasses were measured by an on-line gas chromatograph to ensure relatively constant composition in the recycle gas stream.

[0083] Solid XCAT™ HP-100 catalyst (ExxonMobil Chemical Company) was injected directly into the fluidized bed using purified nitrogen as a carrier. Its rate of injection was adjusted to maintain a constant production rate of the polymer. The reacting bed of growing polymer particles was maintained m a fluidized state by continually flowing the makeup feed and recycle gas through the reaction zone at a superficial gas velocity 1-3 ft/sec (0.3 to 0.9 rn/sec). The reactor w as operated at a total pressure of 300 psig (2068 kPa gauge). To maintain a constant reactor temperature, the temperature of the recycle gas was continuously adjusted up or down to accommodate any changes in the rate of heat generation due to the polymerization.

[0084] The fluidized bed was maintained at a constant height by withdrawing a portion of the bed at a rate equal to the rate of formation of particulate product. The product was removed semi- continuously via a series of valves into a fixed volume chamber winch was simultaneously vented back to the reactor to allow highly efficient removal of the product, while at the same time recycling a large portion of the unreacted gases back to the reactor. Tins product w as purged to remove entramed hydrocarbons and treated with a small stream of humidified nitrogen to deactivate any trace quantities of residual catalyst and cocatalyst.

Example 1

[0085] Each of the two high density copolymer resins 1 and 2 were blended with commercial EXACT™ 4056 plastomer (ethylene/1 -hexene polymer). By blending in the relevant proportions, film grade resins of 0.918 g/cm³ density and a melt index between 0.7 and 1.5 were produced. The blends were compounded, pelletized, and fabricated into films on a small film blowing line with a two inch diameter die (Little Giant).

[0086] 1 mil thick films were produced using a 3:1 blow up ratio at a rate of 10 lb/linear die inch and a die temperature of 375° C. The extruder screw was run at 76 rpm and the cooling air temperature was held at 10° C.

[0087] The characterization of these films appear in Table 2.

[0088] The tear strength of the films blown from the blends dramatically increased relative to that of the film blown from Exceed™ 1018.

[0089] The data also indicates that film stiffness (as represented by secant modulus), yield strength and elongation to break all increased in the films blown from the blends. The films also have the advantage of greatly reduced heat seal initiation temperature, as illustrated in Figure 1, where squares represent Exceed™ 1018, stars represent Blend 9 and triangles Blend 10.

Example 2

[0090] Each of the high-density resins 1 and 2 were blended with resins 5 and 6 to yield 0.918 g/cm³ density, approximately 1 MI blends as shown in Table 3.

[0091] It was considered that the improved MD tear was a result of the presence of an immiscible rubbery component in the blend and that immiscibility increased when the difference in density between the two components was maximized. Therefore it was expected that the MD tear would be improved in those blends with the highest

. Yet, significantly improved MD tear was found only from Blend 13 (Table 3), a blend with a lower

than Blends 11 and 12. Furthermore, Blend 10 (Table 2) containing Exact 4056 blended with BCT 181258 - a blend with an outstanding tear strength of 401 g/mil - had a of 0.062, very close to the 0.060 of Blend

11 which showed modest MD tear improvement relative to Exceed™ 1018.

[0092] The results suggested another factor aside from density difference may be contributing to MD tear performance. Referring to Table 3, the Exact™ plastomers 4151 and 3132 all constituted the majority component in each blend. The blends were each chosen to provide a final blend density of 0.918 g/cm³ and therefore, of necessity, blends containing higher density plastomer (resin 9) needed to be added at higher concentrations to meet the final blend density target of 0.918 g/cm³. However, note that the blend with the highest tear strength (Blend 13) also contained the least amount of plastomer compared to the other three.

[0093] To examine the supposition that the plastomer must not constitute a substantial majority component to attain improved MD tear strength, trimodal blends containing the same higher density Exact™ resins 5 or 6, the same high density copolymers 1 and 2 as in Table 3, but also containing Exceed™ 1018 were prepared. These trimodal blends enabled the ratio of high density copolymer 1 or 2 to plastomer (5 or 6) to be kept the same, while reducing the amount of plastomer in each blend to below 50%, but still maintaining the overall density at 0.918 g/cm³, since the density of the Exceed™ 1018 was already at the target 0.918 g/cm³.

Example 3

[0094] Trimodal blends were prepared by further blending blends 11, 13 and 14 with 25% by weight Exceed™ 1018, such that the ratio of resin 1 or 2 with resin 5 or 6 in blends 11, 13 and 14 was maintained. Details are collected in Table 4.

[0095] The bimodal blend 11 resulted in a modest MD tear of 304 g/mil, while the addition of 25% Exceed™ 1018, a material which itself typically displays an MD tear of only 250 g/mil, increases MD tear of the trimodal blend to 409 g/mil. Blend 16, which corresponds to Blend 14 in Table 3, showed a more modest improvement in MD tear from 311 to 339 g/mil. These results suggested a synergistic effect between the three components in the blend, as the final result could not be predicted from a mixture rule of the bimodal blend and Exceed™ 1018.

Example 4

[0096] Additional blends were prepared by further blending blends 9 and 10 with 25% by weight Exceed™ 1018, such that the ratio of resin 1 or 2 with resin 3 in blends 9 and 10 was maintained. Details are collected in Table 5.

[0097] No improvement in MD tear was observed and MD tear was, in fact, reduced from 422 g/mil in the bimodal blend 10, to 379 and 397 g/mil respectively in the trimodal blends, with the higher value corresponding to the blend with the lesser amount of Exceed™ 1018. The MD tear results from trimodal blends 18 and 19 suggest that for the plastomer blend concept to result in high MD tear values, the plastomer component should preferably not exceed about half of the entire blend composition by weight.

[0098] In the case of the blends containing the higher density Exact™ plastomers (Exact™ 4151 or 3132) higher MD tear was only attained when the blend was diluted with Exceed™ 1018, thus changing the plastomer from the majority to the minority component. In contrast, in the Exact™ 4056 blends (Tables 2 and 5), the Exact™ 4056 was already a minority component in the bimodal blend. Presumably, for this reason, further dilution in the trimodal blend via the addition of Exceed™ 1018 did not result in improved tear.

[0099] It was also established that in the trimodal blends, the MD tear values did not substantially change when the Exceed™ 1018 component was varied in the blend from 20% to 45% by weight (see Figure 2).

[0100] For the trimodal blends containing the higher density Exact™ 4151 and 3132 plastomers, the dart impact values were relatively high even without added talc and erucamide for lubrication. The trimodal blends containing Exact™ 4056 were lower in dart drop, although not as low as the bimodal blends containing 4056.

[0101] Blend 15 had a dart drop impact of 424 g/mil and Blend 18 a dart drop impact of 364 g/cm³.

[0102] The higher density plastomers Exact™ 4151 and 3132 (with densities of 0.895 g/cm³ and 0.900 g/cm³ respectively), likely do not impart the same degree of tackiness to the film surface as does lower density Exact™ 4056 (0.882 g/cm³). The result is reflected in higher drop dart numbers. For trimodal blend 17, the dart drop values did not vary significantly (within the data variability) when the Exceed™ 1018 content was varied between 20% and 45% (see Figure 3).

Example 5: Comparative Example

[0103] Blends 20 and 21 were prepared using different high density components and the results are collected in Table 6. It is important to note that using either of two commercial high density polyethylenes as substitutes for either of the high density polyethylenes 1 and 2 in Table 2 resulted in dramatically decreased MD tear strength. The two commercial HDPE resins tested were Paxon AD60-003 (0.963 g/cm³ density, 0.3 MI) and HD 9856 (0.957 g/cm³ density, 0.46 MI).

Certain Embodiments

[0104] Certain embodiments of the blends, films and methods according to the present disclosure are presented in the following paragraphs.

[0105] Embodiment 1 provides a polyolefin blend, said polyolefin blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: a) from about 10% to about 80% by weight of a first ethylene a-olefin copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; and b) from about 20% to about 90% by weight of a second ethylene a-olefin copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; wherein both the first and second ethylene a-olefin copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

[0106] Embodiment 2 provides a polyolefin blend according to embodiment 1, wherein the bulky ligand transition metal compound is a metallocene comprising Ti, Zr or Hf. [0107] Embodiment 3 provides a polyolefin blend according to embodiment 1 or embodiment

2, wherein the density of the blend is from about 0.913 g/cm3 to about 0.923 g/cm3, or from about 0.915 g/cm3 to about 0.921 g/cm3, or from about 0.917 g/cm3 to about 0.919 g/cm3.

[0108] Embodiment 4 provides a polyolefin blend according to any one of embodiments 1 to

3, wherein the melt index of the blend is from about 0.7 g/10min to about 1.5 g/10min.

[0109] Embodiment 5 provides a polyolefin blend according to any one of embodiments 1 to

4, wherein said blend comprises from about 15% to about 75% by weight of the first ethylene a- olefin copolymer, or from about 20% to about 70%, or from about 25% to about 65%, or from about 30% to about 60%.

[0110] Embodiment 6 provides a polyolefin blend according to any one of embodiments 1 to

5, wherein said blend comprises from about 25% to about 85% by weight of the second ethylene α-olefins copolymer, or from about 30% to about 80%, or from about 35% to about 75%, or from about 40% to about 70%.

[0111] Embodiment 7 provides a polyolefin blend according to any one of embodiments 1 to

6, wherein the density of the first ethylene α-olefins copolymer is from about 0.940 g/cm3 to about 0.960 g/cm3, or from about 0.942 g/cm3 to about 0.958 g/cm3.

[0112] Embodiment 8 provides a polyolefin blend according to any one of embodiments 1 to

7, wherein the melt index of the first ethylene α-olefins copolymer is from about 0.2 g/10min to about 0.9 g/10min, or from about 0.3 g/10min to about 0.8 g/10min.

[0113] Embodiment 9 provides a polyolefin blend according any one of embodiments 1 to 8, wherein the density of the second ethylene α-olefins copolymer is from about 0.860 g/cm3 to about 0.905 g/cm3, or from about 0.870 g/cm3 to about 0.905 g/cm3.

[0114] Embodiment 10 provides a polyolefin blend according to any one of embodiments 1 to

9, wherein the melt index of the second ethylene α-olefins copolymer is from about 0.8 g/10min to about 4 g/10min, or from about 1.0 g/10min to about 3.0 g/10min.

[0115] Embodiment 11 provides a polyolefin blend according to any one of embodiments 1 to

10, wherein the first and second ethylene α-olefins copolymers are prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

[0116] Embodiment 12 provides a polyolefin blend according to any one of embodiments 1 to

11 , wherein the first ethylene α-olefins copolymer is prepared in a gas phase polymerization process. [0117] Embodiment 13 provides a polyolefin blend according to any one of embodiments 1 to

12, wherein the first ethylene α-olefins copolymer is prepared in a single reactor polymerization process. [0118] Embodiment 14 provides a polyolefin blend according to any one of embodiments 1 to

13, wherein the first ethylene α-olefins copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

[0119] Embodiment 15 provides a polyolefin blend according to any one of embodiments 1 to

14, wherein the second ethylene α-olefins copolymer is prepared in a solution process.

[0120] Embodiment 16 provides a polyolefin blend according to any one of embodiments 1 to

15, wherein the second ethylene α-olefins copolymer is prepared in a single reactor polymerization process.

[0121] Embodiment 17 provides a polyolefin blend according to any one of embodiments 1 to

16, wherein the second ethylene α-olefins copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

[0122] Embodiment 18 provides a film comprising the polyolefin blend according to any one of embodiments 1 to 17.

[0123] Embodiment 19 provides a film according to embodiment 18, wherein the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

[0124] Embodiment 20 provides a film according to embodiment 18 or embodiment 19, wherein the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil.

[0125] Embodiment 21 provides an article of manufacture comprising a film according to any one of embodiments 18 to 20.

[0126] Embodiment 22 provides a polyolefin blend according to any one of embodiments 1 to

17, further comprising a third ethylene α-olefins copolymer having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, wherein the third ethylene α-olefins copolymer is prepared in the presence of a catalyst comprising a bulky ligand transition metal compound

[0127] Embodiment 23 provides a polyolefin blend according to embodiment 22, wherein the bulky ligand transition metal compound is a metallocene comprising Ti, Zr or Hf.

[0128] Embodiment 24 provides a polyolefin blend according to embodiment 22 or 23, wherein the density of the third ethylene α-olefins copolymer is from about 0.910 g/cm3 to about 0.926 g/cm3, or from about 0.912 g/cm3 to about 0.924 g/cm3, or from about 0.914 g/cm3 to about 0.922 g/cm3, or from about 0.916 g/cm3 to about 0.920 g/cm3 [0129] Embodiment 25 provides a polyolefin blend according to any one of embodiments 22 to 24, wherein the melt index of the third ethylene α-olefins copolymer is from about 0.7 g/10min to about 1.6 g/10min, or from about 0.8 g/10min to about 1.2 g/10min.

[0130] Embodiment 26 provides a polyolefin blend according to any one of embodiments 22 to 25 , said polyolefin blend comprising: a) from about 10% to about 80% by weight of the first ethylene α-olefins copolymer; b) from about 20% to about 90% by weight of the second ethylene α-olefins copolymer; and c) from about 10% to about 50% by weight of the third ethylene α-olefins copolymer. [0131] Embodiment 27 provides a polyolefin blend according to any one of embodiments 22 to 26, wherein the amount of second ethylene α-olefins copolymer in the blend does not exceed about 50% by weight of the total blend.

[0132] Embodiment 28 provides a polyolefin blend according to any one of embodiments 22 to 27, wherein the third ethylene α-olefins copolymer is prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

[0133] Embodiment 29 provides a polyolefin blend according to any one of embodiments 22 to 28, wherein the third ethylene α-olefins copolymer is prepared in a gas phase polymerization process.

[0134] Embodiment 30 provides a polyolefin blend according to any one of embodiments 22 to 29, wherein the third ethylene α-olefins copolymer is prepared in a single reactor polymerization process.

[0135] Embodiment 31 provides a polyolefin blend according to any one of embodiments 22 to 30, wherein the third ethylene α-olefins copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

[0136] Embodiment 32 provides a film comprising the polyolefin blend according to any one of embodiments 22 to 31.

[0137] Embodiment 33 provides a film according to embodiment 32, wherein the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

[0138] Embodiment 34 provides a film according to embodiment 32 or embodiment 33, wherein the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil. [0139] Embodiment 35 provides an article of manufacture comprising a film according to any one of embodiments 32 to 34.

[0140] Embodiment 36 provides a method of preparing a polyolefin blend according to any one of embodiments 1 to 17 comprising the step of melt blending a mixture of the first ethylene a- olefin copolymer and the second ethylene a-olefin copolymer.

[0141] Embodiment 37 provides a method of preparing a polyolefin blend according to any one of embodiments 22 to 31 comprising the step of melt blending a mixture of the first ethylene a-olefin copolymer, the second ethylene a-olefin copolymer and the third ethylene a-olefin copolymer.

[0142] All patents, patent applications and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

[0143] Various modifications or changes in light thereof will be suggested to persons skilled in the art and are included within the spirit and purview of this application and are considered within the scope of the appended claims. For example, the relative quantities of the ingredients may be varied to optimize the desired effects, additional ingredients may be added, and/or similar ingredients may be substituted for one or more of the ingredients described. Additional advantageous features and functionalities associated with the systems, methods, and processes of the present disclosure will be apparent from the appended claims. Moreover, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the disclosure described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

1. A polyolefin blend, said polyolefin blend having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, said polyolefin blend comprising: a) from about 10% to about 80% by weight of a first ethylene α-olefins copolymer having a density from about 0.935 g/cm3 to about 0.965 g/cm3 and a melt index from about 0.1 g/10min to about 1.0 g/10min; and b) from about 20% to about 90% by weight of a second ethylene α-olefins copolymer having a density from about 0.850 g/cm3 to about 0.905 g/cm3 and a melt index from about 0.5 g/10min to about 5.0 g/10min; wherein both the first and second ethylene α-olefins copolymers are prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

2. A polyolefin blend according to claim 1, wherein the bulky ligand transition metal compound is a metallocene comprising Ti, Zr or Hf.

3. A polyolefin blend according to claim 1 or claim 2, wherein the density of the blend is from about 0.913 g/cm3 to about 0.923 g/cm3, or from about 0.915 g/cm3 to about 0.921 g/cm3, or from about 0.917 g/cm3 to about 0.919 g/cm3.

4. A polyolefin blend according to any one of claims 1 to 3, wherein the melt index of the blend is from about 0.7 g/10min to about 1.5 g/10min.

5. A polyolefin blend according to any one of claims 1 to 4, wherein said blend comprises from about 15% to about 75% by weight of the first ethylene α-olefins copolymer, or from about 20% to about 70%, or from about 25% to about 65%, or from about 30% to about 60%.

6. A polyolefin blend according to any one of claims 1 to 5, wherein said blend comprises from about 25% to about 85% by weight of the second ethylene α-olefins copolymer, or from about 30% to about 80%, or from about 35% to about 75%, or from about 40% to about 70%.

7. A polyolefin blend according to any one of claims 1 to 6, wherein the density of the first ethylene α-olefins copolymer is from about 0.940 g/cm3 to about 0.960 g/cm3, or from about 0.942 g/cm3 to about 0.958 g/cm3.

8. A polyolefin blend according to any one of claims 1 to 7, wherein the melt index of the first ethylene α-olefins copolymer is from about 0.2 g/10min to about 0.9 g/10min, or from about 0.3 g/10min to about 0.8 g/10min.

9. A polyolefin blend according any one of claims 1 to 8, wherein the density of the second ethylene α-olefins copolymer is from about 0.860 g/cm3 to about 0.905 g/cm3, or from about 0.870 g/cm3 to about 0.905 g/cm3.

10. A polyolefin blend according to any one of claims 1 to 9, wherein the melt index of the second ethylene α-olefins copolymer is from about 0.8 g/10min to about 4 g/10min, or from about 1.0 g/10min to about 3.0 g/10min.

11. A polyolefin blend according to any one of claims 1 to 10, wherein the first and second ethylene α-olefins copolymers are prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

12. A polyolefin blend according to any one of claims 1 to 11, wherein the first ethylene a- olefin copolymer is prepared in a gas phase polymerization process.

13. A polyolefin blend according to any one of claims 1 to 12, wherein the first ethylene a- olefin copolymer is prepared in a single reactor polymerization process.

14. A polyolefin blend according to any one of claims 1 to 13, wherein the first ethylene a- olefin copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

15. A polyolefin blend according to any one of claims 1 to 14, wherein the second ethylene α-olefins copolymer is prepared in a solution process.

16. A polyolefin blend according to any one of claims 1 to 15, wherein the second ethylene α-olefins copolymer is prepared in a single reactor polymerization process.

17. A polyolefin blend according to any one of claims 1 to 16, wherein the second ethylene α-olefins copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

18. A film comprising the polyolefin blend according to any one of claims 1 to 17.

19. A film according to claim 18, wherein the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

20. A film according to claim 18 or claim 19, wherein the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil.

21. An article of manufacture comprising a film according to any one of claims 18 to 20.

22. A polyolefin blend according to any one of claims 1 to 17, further comprising a third ethylene α-olefins copolymer having a density from about 0.908 g/cm3 to about 0.928 g/cm3 and a melt index from about 0.5 g/10min to about 2.0 g/10min, wherein the third ethylene α-olefins copolymer is prepared in the presence of a catalyst comprising a bulky ligand transition metal compound.

23. A polyolefin blend according to claim 22, wherein the bulky ligand transition metal compound is a metallocene comprising Ti, Zr or Hf.

24. A polyolefin blend according to claim 22 or 23, wherein the density of the third ethylene α-olefins copolymer is from about 0.910 g/cm3 to about 0.926 g/cm3, or from about 0.912 g/cm3 to about 0.924 g/cm3, or from about 0.914 g/cm3 to about 0.922 g/cm3, or from about 0.916 g/cm3 to about 0.920 g/cm3.

25. A polyolefin blend according to any one of claims 22 to 24, wherein the melt index of the third ethylene α-olefins copolymer is from about 0.7 g/10min to about 1.6 g/10min, or from about 0.8 g/10min to about 1.2 g/10min.

26. A polyolefin blend according to any one of claims 22 to 25, said polyolefin blend comprising: a) from about 10% to about 80% by weight of the first ethylene α-olefins copolymer; b) from about 20% to about 90% by weight of the second ethylene α-olefins copolymer; and c) from about 10% to about 50% by weight of the third ethylene α-olefins copolymer.

27. A polyolefin blend according to any one of claims 22 to 26, wherein the amount of second ethylene α-olefins copolymer in the blend does not exceed about 50% by weight of the total blend.

28. A polyolefin blend according to any one of claims 22 to 27, wherein the third ethylene α-olefins copolymer is prepared by polymerizing ethylene in the presence of an α-olefins selected from the group consisting of 1 -butene, 1 -hexene, 1-octene and mixtures thereof.

29. A polyolefin blend according to any one of claims 22 to 28, wherein the third ethylene α-olefins copolymer is prepared in a gas phase polymerization process.

30. A polyolefin blend according to any one of claims 22 to 29, wherein the third ethylene α-olefins copolymer is prepared in a single reactor polymerization process.

31. A polyolefin blend according to any one of claims 22 to 30, wherein the third ethylene α-olefins copolymer is prepared with a catalyst system comprising a single bulky ligand transition metal compound, preferably a metallocene.

32. A film comprising the polyolefin blend according to any one of claims 22 to 31.

33. A film according to claim 32, wherein the film has a machine direction (MD) tear strength of greater than 300 g/mil, or greater than 325 g/mil, or greater than 350 g/mil, or greater than 375 g/mil, or greater than 400 g/mil.

34. A film according to claim 32 or claim 33, wherein the film has a dart drop impact of greater than 200 g/mil, or greater than 250 g/mil, or greater than 300 g/mil, or greater than 350 g/mil, or greater than 400 g/mil.

35. An article of manufacture comprising a film according to any one of claims 32 to 34.

36. A method of preparing a polyolefin blend according to any one of claims 1 to 17 comprising the step of melt blending a mixture of the first ethylene a-olefin copolymer and the second ethylene a-olefin copolymer.

37. A method of preparing a polyolefin blend according to any one of claims 22 to 31 comprising the step of melt blending a mixture of the first ethylene a-olefin copolymer, the second ethylene a-olefin copolymer and the third ethylene a-olefin copolymer.