Polymer composition blends and films made therefrom

Abstract

A polymer composition for producing gel extrusion articles is described. The polymer composition contains at least three different polyethylene polymers, namely a lower molecular weight polyethylene polymer, a medium molecular weight polyethylene polymer, and a high molecular weight polyethylene polymer. Combining different ratios of different polyethylene polymers can not only optimize mechanical properties but also improve processability.

Description

[Technical field]

[0001] Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 322,468, having a filing date of March 22, 2022, which is incorporated by reference herein. [Background technology]

[0002] Polyethylene polymers have a wide variety of uses and applications. For example, high density polyethylene polymers are valuable engineering plastics that have a unique combination of abrasion resistance, surface lubricity, chemical resistance and impact strength. They find use in the production of high strength fibers for use in ropes and anti-ballistic shaped articles, and in the production of other elongated articles, such as membranes for electronic devices. However, the flowability of these materials in the molten state decreases as the molecular weight increases, so they are not always processable by conventional techniques such as melt extrusion.

[0003]

[0003] One alternative method for producing fibers and other elongated elements from polyethylene polymers is by gel processing, in which the polymer is combined with a solvent. The resulting gel can be extruded into fibers or films and stretched in one or two directions while removing a substantial portion of the solvent.

[0004]

[0004] Membranes made from polyethylene polymers via gel processing can be formed to have many beneficial properties. For example, membranes with micropores can be formed. Microporous polyethylene membranes formed via gel processing are particularly well suited for use as separators in batteries, such as lithium ion batteries. Microporous membranes can, for example, separate the anode from the cathode and prevent short circuits between active battery components. At the same time, microporous membranes allow the passage of ions due to the porous nature of the material. Due to the ion permeability characteristics of microporous polyethylene membranes, this material is particularly well suited for regulating electrochemical reactions within batteries.

[0005]

[0005] In addition to the microporous nature of polyethylene membranes, their chemical resistance and other physical properties, polyethylene membranes also provide what is referred to in the industry as an effective "shutdown action". The shutdown action refers to the automatic closing of the microscopic pores in the polyethylene separator once a certain temperature is exceeded. When the pores in the polyethylene membrane close when a certain temperature is reached, ions cannot pass through the membrane and the electrochemical function of the battery ceases. This action provides an important safety mechanism for the battery to prevent the thermal runaway reaction from continuing and the battery from overheating, creating a potentially harmful situation. Summary of the Invention [Problem to be solved by the invention]

[0006] In addition to chemical resistance and shutdown properties, polymer membranes should also have very good mechanical properties. For example, microporous membranes should have relatively high puncture strength, tensile strength, and tensile modulus, especially when used as separators in battery applications. In this regard, there is a constant need to improve the above membrane properties. The present disclosure is directed to improving at least one of the above properties using a specific polymer formulation. [Means for solving the problem]

[0007]

[0007] In general, the present disclosure is directed to a polymer composition that is particularly well suited for gel processing applications, for producing various articles such as fibers and membranes. The polymer composition of the present disclosure contains a blend of different polymers, such as at least three different polyethylene polymers, that when blended together result in an excellent combination of mechanical and physical properties. For example, membranes having excellent puncture and / or pin strengths in combination with an optimal amount of porosity can be produced according to the present disclosure. The membranes are particularly well suited for use as membranes in lithium ion batteries to separate the anode from the cathode.

[0008] In one embodiment, the present disclosure is directed to a polymer composition for producing a gel extrusion article comprising a plasticizer in combination with polymer particles. The polymer particles include a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer. The first polyethylene polymer may have a molecular weight of about 300,000 g / mol to about 1 million g / mol. The first polyethylene polymer may be present in the polymer composition in an amount of about 3% to about 25% by weight of the polymer particles. The second polyethylene polymer may have a molecular weight of about 1 million g / mol to about 2.9 million g / mol. The second polyethylene polymer may be present in an amount of about 25% to about 85% by weight, based on the weight of the polymer particles. The third polyethylene polymer may have a molecular weight of about 2 million g / mol to about 10 million g / mol and may be present in the polymer composition in an amount of about 5% to about 48% by weight, based on the weight of the polymer particles.

[0009] In one form, the polymers present in the polymer composition include only the first polyethylene polymer, the second polyethylene polymer, and the third polyethylene polymer. The polymer composition may be formulated to be free of polypropylene. The polymer particles contained in the composition may be made from only one of the polyethylene polymers or may be made from a blend of two or three of the polyethylene polymers.

[0010] In one embodiment, the first polyethylene polymer may have a molecular weight of about 500,000 g / mol to about 700,000 g / mol and may be present in the polymer composition in an amount of about 5% to about 15% by weight of the polymer particles. Meanwhile, the second polyethylene polymer may have a molecular weight of about 1.5 million g / mol to about 2.1 million g / mol and may be present in the polymer composition in an amount of about 50% to about 75% by weight of the polymer particles. The third polyethylene polymer may have a molecular weight of about 4 million g / mol to about 8 million g / mol and may be present in the polymer composition in an amount of about 20% to about 40% by weight of the polymer particles. Although particle sizes may vary, the polymer particles may have a median diameter based on volume of about 70 micrometers to about 210 micrometers, for example, about 110 micrometers to about 170 micrometers. The polymer particles may be present in the polymer composition in an amount up to about 50% by weight.

[0011]

[0011] In general, any suitable plasticizer may be present in the polymer composition. The plasticizer may include, for example, mineral oil, paraffinic oil, hydrocarbon, alcohol, ester, ether, or mixtures thereof. Specific examples of plasticizers include decalin, paraffin oil, white oil, mineral oil, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, monochlorobenzene, camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or mixtures thereof.

[0012]

[0012] The present disclosure is also directed to a process for producing a polymeric article. The process includes forming a gel-like composition from the polymeric composition described above. The gel-like composition is then extruded through a die to form a polymeric article. The polymeric article may include, for example, a film or may include a fiber. The process may further include removing at least a portion of the plasticizer from the polymeric article. For example, greater than 90% by weight, such as greater than about 95% by weight, of the plasticizer may be removed. An extraction solvent may be present in the gel-like composition to facilitate removal of the plasticizer. The extraction solvent may include dichloromethane, acetone, chloroform, an alkane, hexene, heptene, an alcohol, or a mixture thereof.

[0013]

[0013] The present disclosure is also directed to a porous membrane particularly well suited for use as a separator in a battery. The porous membrane comprises a polymer blend including a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer. The first polyethylene polymer may have a molecular weight of about 400,000 g / mol to about 1 million g / mol. The second polyethylene polymer may have a molecular weight of about 1.1 million g / mol to about 2.9 million g / mol. The third polyethylene polymer may have a molecular weight of about 3 million g / mol to about 10 million g / mol. The first polyethylene polymer may be present in the porous membrane in an amount of about 3% to about 18% by weight. The second polyethylene polymer may be present in the porous membrane in an amount of about 34% to about 85% by weight. The third polyethylene polymer may be present in the porous membrane in an amount of about 12% to about 48% by weight.

[0014]

[0014] Membranes made according to the present disclosure may have a tensile strength of greater than about 155 MPa. The porous membranes may have a puncture strength of greater than about 1,450 mN / micrometer and a tensile strength of greater than about 252 gf / g / cm 2 It may have a greater pin strength. The above physical properties can be achieved when the membrane has a porosity of about 35% to about 38%.

[0015] When the membrane has a porosity of about 45% to about 50%, the membrane has a puncture strength of greater than about 340 mN / micrometer and a porosity of about 72 gf / g / cm 2 It may have a greater pin strength.

[0016]

[0016] The membrane may be biaxially stretched and may have a thickness of about 5 micrometers to about 20 micrometers, for example, about 6 micrometers to about 15 micrometers. The membrane may have a Gurley air permeability of greater than about 105 sec / 100 ml.

[0017]

[0017] Other features and aspects of the present disclosure are discussed in greater detail below.

[0018] The present disclosure can be better understood with reference to the following drawings. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view of an electronic device, such as a battery, incorporating a porous membrane made in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. definition

[0020] As used herein, puncture strength is measured according to ASTM test D3763 and measures the ability of a membrane to resist the creation of holes or defects caused by foreign particles. The test is performed on a testing device such as an Instron CEAST 9340 device. The drop height is 0.03 to 1.10 m. The impact velocity is 0.77 to 4.65 m / sec. The maximum drop mass is 37.5 kg and the maximum potential energy is 405 J. Puncture strength is measured in a slow velocity puncture mode at 1.67 mm / sec.

[0020]

[0021] The melt flow rate of a polymer or polymer composition is measured according to ISO test 1133 at 190° C. and a load of 21.6 kg.

[0022] The density of the polymer is measured in g / cm according to ISO test 1183. 3 It is measured in units of.

[0021]

[0023] The average particle size (d50) is measured using laser diffraction / light scattering, for example using a suitable Horiba light scattering device.

[0024] The average molecular weight of a polymer is determined using the Margolies equation.

[0022]

[0025] Tensile modulus, tensile stress at yield, tensile strain at yield, tensile stress at 50% break, tensile stress at break, and nominal tensile strain at break are all measured according to ISO test 527-2 / 1B.

[0023]

[0026] Gurley air permeability can be measured according to the Gurley test using a Gurley air permeability tester, for example, a Gurley air permeability tester, model KRK2060c, commercially available from Kumagai Riki Kogyo Co., LTD. The test is performed according to ISO test 5636. The Gurley test measures air permeability as a function of the time required for a specified amount of air to pass through a specified area under a specified pressure. Units are reported in seconds / 100 ml.

[0024]

[0027] The porosity (%) is measured according to the following procedure, during which the following ASTM standards are used as reference: D622 Standard Test Method for Apparent Density of Rigid Cellular Plastics 1; and D729 Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement 1. The following equipment is used: a calibrated analytical balance (0.0001 grams); a Lorentzen & Wettre Micrometer, code 251 (0.1 um); and a Deli 2056 art knife.

[0025] procedure: 1.1. Samples and sample preparation Using a specimen art knife, cut each sample material into a minimum of three 60 mm ± 0.5 x 60 mm ± 0.5 specimens. 1.2. Equipment and Measurements 3.2.1 Using the L&W micrometer, take five readings of the thickness of each 60 mm x 60 mm sample (average of the five readings). Record this value as the thickness of the sample.

[0026] 3.2.2 Weigh the sample directly on the balance and record this value as the weight of the sample. 3.2.3 Place three specimens of the same sample together and repeat steps 2.2.1 and 3.2.2 to obtain the [bulk] thickness and [bulk] weight.

[0027] Calculate the density to three significant figures as follows:

[0028]

number

[0029] Dfilm = density of sample, mg / mm3 Wt = weight of sample, mg THK = sample thickness, mm Square = area of ​​sample, (mm2) bD polymer = density (polymer) 0.95 (g / cm3) D Polymer: Density of raw material without pores. c. Porosity = (1-D film / D polymer) x 100%

[0030] Detailed Description

[0028] Those skilled in the art will understand that the discussion of the present invention is merely a description of exemplary embodiments, and is not intended to limit the broader aspects of the present disclosure.

[0031]

[0029] In general, the present disclosure is directed to a polymeric composition well suited for producing gel extrusion articles such as fibers and films, including porous membranes. The polymeric composition includes a plurality of polyethylene resins, such as high density polyethylene particles, in combination with a plasticizer that is used to facilitate the formation of the article. When the article is formed, the plasticizer can be evaporated and removed, leaving an extruded article with improved mechanical properties.

[0032]

[0030] In accordance with the present disclosure, gel extrusion articles are formed using at least three different types of polyethylene polymers. All of the polyethylene polymers may be high density polyethylene polymers. In one form, the article is formed from a first polyethylene polymer having a relatively low molecular weight, a second polyethylene polymer having a medium molecular weight, and a third polyethylene polymer having a relatively high molecular weight. The second polyethylene polymer may be present in the composition or article in an amount greater than the first and third polyethylene polymers.

[0033] Combining the first and third polyethylene polymers with the second polyethylene polymer may produce various advantages and benefits. For example, the porous membrane formed from the combination of polymers may have improved mechanical properties. For example, a membrane made from a blend of three different polyethylene polymers may have an increase in puncture strength of more than about 2%, such as more than about 5%, such as more than about 8%, such as more than about 12%, such as more than about 15%, such as more than about 20%, at the same porosity level, compared to a membrane made only from the second polyethylene polymer, and generally have an increase in puncture strength of less than about 80%. A membrane made according to the present disclosure may also have an increase in pin strength of more than about 3%, such as more than about 5%, such as more than about 8%, such as more than about 10%, such as more than about 15%, such as more than about 17%, and generally have an increase in pin strength of less than about 70%, compared to a membrane made only from the second polyethylene polymer at the same porosity level.

[0034]

[0032] The tensile strength in the machine direction and cross direction of membranes made according to the present disclosure may also be improved as compared to membranes made only from the second polyethylene polymer at the same porosity level and thickness. For example, the tensile strength in either direction may be increased by more than about 2%, such as more than about 4%, such as more than about 5%, such as more than about 10%, and typically by less than about 50%.

[0035] In addition to improved mechanical properties, it has also been found that combining lower and higher molecular weight polyethylenes with medium molecular weight polyethylene dramatically improves the ability of the resulting composition to be melt processed into articles. Additionally, the ratios and amounts of the different polyethylene polymers can be adjusted and controlled to optimize one or more resulting properties in the final product, which is not possible when producing articles from a single polyethylene polymer.

[0036] In one embodiment, each of the polyethylene polymers incorporated in the polymer composition is optionally a high density polyethylene polymer. For example, each of the polyethylene polymers has a density of about 0.92 g / cm 3 or greater, e.g., about 0.93 g / cm 3 or greater, e.g., about 0.94 g / cm 3 or greater, typically about 1 g / cm 3 Less than about 0.97 g / cm 3 It may have a density of less than 1000 nm.

[0037] The polyethylene polymer may be made up of more than 90% ethylene derived units, for example greater than 95% ethylene derived units, or it may be made up of 100% ethylene derived units. The polyethylene may be a homopolymer or a copolymer with other monomer units, for example a terpolymer.

[0038] The first polyethylene polymer, the second polyethylene polymer, and the third polyethylene polymer each have a range of molecular weights. In one embodiment, the first polyethylene polymer may be a high molecular weight polyethylene polymer, the second polyethylene polymer may be a very high molecular weight polyethylene polymer, and the third polyethylene polymer may be an ultra high molecular weight polyethylene polymer. "High molecular weight polyethylene" refers to a polyethylene having a molecular weight of at least about 3×10 5 "Molecular weight" refers to a polyethylene composition having an average molecular weight in g / mol, and as used herein is intended to include very high molecular weight polyethylene and ultra-high molecular weight polyethylene. For purposes of this specification, molecular weights referred to herein are determined according to the Margolies equation ("Margolies molecular weight").

[0039] "Very high molecular weight polyethylene" is about 1×10 6g / mol ~ approx. 3×10 6 In some embodiments, the molecular weight of the very high molecular weight polyethylene composition is about 2×10 6 g / mol to about 3 × 10 6 is less than g / mol.

[0040] "Ultra-high molecular weight polyethylene" refers to polyethylene having a molecular weight of at least about 3×10 6 In some embodiments, the molecular weight of the ultra high molecular weight polyethylene composition is about 3×10 6 g / mol ~ approx. 30×10 6 g / mol, or approximately 3 × 10 6 g / mol ~ approx. 20×10 6 g / mol, or approximately 3 × 10 6 g / mol ~ approx. 10×10 6 g / mol, or approximately 3 × 10 6 g / mol ~ approx. 6×10 6 g / mol.

[0041] In one embodiment, the high density polyethylene polymer is a homopolymer of ethylene. In another embodiment, the high density polyethylene polymer may be a copolymer. For example, the high density polyethylene polymer may be a copolymer of ethylene and another olefin containing 3 to 16 carbon atoms, such as 3 to 10 carbon atoms, such as 3 to 8 carbon atoms. These other olefins include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, and the like. Also usable herein are polyene comonomers such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene, and 5-vinyl-2-norbornene. The amount of non-ethylene monomers in the one or more copolymers, if present, may be less than about 10 mol.%, such as less than about 5 mol.%, for example less than about 2.5 mol.%, for example less than about 1 mol.%, where mol.% is based on the total molar amount of monomers in the polymer.

[0042] In one embodiment, the high density polyethylene polymer may have a monomodal molecular weight distribution. Alternatively, the high density polyethylene polymer may exhibit a bimodal molecular weight distribution. For example, a bimodal distribution generally refers to a polymer having a separate higher molecular weight and a separate lower molecular weight (e.g., two separate peaks) in a size exclusion or gel permeation chromatography curve. In another embodiment, the high density polyethylene polymer may exhibit more than two molecular weight distribution peaks such that the polyethylene exhibits a multimodal (e.g., trimodal, tetramodal, etc.) distribution. Alternatively, the high density polyethylene polymer may exhibit a broad molecular weight distribution. In this case, the polyethylene is composed of a blend of higher and lower molecular weight components such that the size exclusion or gel permeation chromatography curve does not exhibit at least two separate peaks, but instead exhibits one individual peak that is broader than the peaks of the individual components.

[0043]

[0041] Any method known in the art can be used to synthesize polyethylene polymers. Polyethylene powders are typically produced by catalytic polymerization of ethylene monomer, or ethylene monomer and optionally one or more other 1-olefin comonomers, with the 1-olefin content in the final polymer being less than or equal to 10% ethylene content, using heterogeneous catalysts and organoaluminum or magnesium compounds as cocatalysts. Ethylene is usually polymerized in gas or slurry phase at relatively low temperatures and pressures. The polymerization reaction may be carried out at temperatures between 50°C and 100°C, and pressures ranging from 0.02 to 2 MPa.

[0044]

[0042] The molecular weight of the polyethylene can be adjusted by adding hydrogen. Varying the temperature and / or the type and concentration of the cocatalyst can also be used to fine-tune the molecular weight. In addition, the reaction may be carried out in the presence of an antistatic agent to avoid fouling and contamination of the product.

[0045] Suitable catalyst systems include, but are not limited to, Ziegler-Natta type catalysts. Typically, Ziegler-Natta type catalysts are obtained by the combination of a transition metal compound from Groups 4 to 8 of the Periodic Table with an alkyl or hydride derivative of a metal from Groups 1 to 3 of the Periodic Table. The transition metal derivatives typically used include metal halides or esters or combinations thereof. Exemplary Ziegler-Natta catalysts include those based on organoaluminum or magnesium compounds, such as, but not limited to, reaction products of aluminum or magnesium alkyls with titanium, vanadium or chromium halides or esters. Heterogeneous catalysts can be either unsupported or supported on porous particulate materials such as silica or magnesium chloride. Such supports may be added during the synthesis of the catalyst or may be obtained as a chemical reaction product of the catalyst synthesis itself.

[0046] In one embodiment, a suitable catalyst system can be obtained by reacting a titanium(IV) compound with a trialkylaluminum compound in an inert organic solvent at a temperature ranging from -40°C to 100°C, preferably from -20°C to 50°C. The concentration of the starting materials is in the range of 0.1-9 mol / L, preferably 0.2-5 mol / L, for the titanium(IV) compound, and in the range of 0.01-1 mol / L, preferably 0.02-0.2 mol / L, for the trialkylaluminum compound. The titanium component is added to the aluminum component over a period of 0.1 min to 60 min, preferably 1 min to 30 min, and the molar ratio of titanium and aluminum in the final mixture is in the range of 1:0.01-1:4.

[0047] In another embodiment, a suitable catalyst system is obtained by one or two step reaction of a titanium(IV) compound with a trialkylaluminum compound in an inert organic solvent at a temperature ranging from -40°C to 200°C, preferably from -20°C to 150°C. In the first step, the titanium(IV) compound is reacted with the trialkylaluminum compound at a temperature ranging from -40°C to 100°C, preferably from -20°C to 50°C, using a molar ratio of titanium to aluminum ranging from 1:0.1 to 1:0.8. The concentration of the starting materials is in the range of 0.1 to 9.1 mol / L, preferably 5 to 9.1 mol / L, for the titanium(IV) compound and 0.05 to 1 mol / L, preferably 0.1 to 0.9 mol / L, for the trialkylaluminum compound. The titanium component is added to the aluminum compound over a period of 0.1 min to 800 min, preferably 30 min to 600 min. In the second step, if applicable, the reaction product obtained in the first step is treated with a trialkylaluminum compound at a temperature in the range of -10°C to 150°C, preferably 10°C to 130°C, using a molar ratio of titanium to aluminum in the range of 1:0.01 to 1:5.

[0048] In yet another embodiment, a suitable catalytic system is obtained by a procedure in which in a first reaction stage magnesium alcoholate is reacted with titanium chloride in an inert hydrocarbon at a temperature between 50° C. and 100° C. In a second reaction stage the reaction mixture formed is subjected to a heat treatment at a temperature between 110° C. and 200° C. for a period of about 10 to 100 hours, which is accompanied by the evolution of alkyl chlorides, and when no further alkyl chlorides are evolved the solids are removed from the soluble reaction product by washing several times with a hydrocarbon.

[0049] In a further embodiment, silica supported catalysts such as the commercially available catalyst system Sylopol 5917 can also be used.

[0048] Using such a catalyst system, the polymerization is usually carried out in suspension, at low pressure and temperature, in one or several steps, continuously or batchwise. The polymerization temperature is typically in the range of 30°C to 130°C, preferably in the range of 50°C to 90°C, and the ethylene partial pressure is typically less than 10 MPa, preferably 0.05 to 5 MPa. Trialkylaluminums, such as, but not limited to, isoprenylaluminum and triisobutylaluminum, are used as cocatalysts such that the ratio of Al:Ti (cocatalyst:catalyst) is in the range of 0.01 to 100:1, more preferably in the range of 0.03 to 50:1. The solvent is typically an inert organic solvent such as those used for Ziegler-type polymerizations. Examples are butane, pentane, hexane, cyclohexene, octane, nonane, decane, their isomers and mixtures thereof. The molecular weight of the polymer is controlled by feeding hydrogen. The ratio of hydrogen partial pressure to ethylene partial pressure is in the range of 0-50, preferably 0-10. The polymer is isolated and dried under nitrogen in a fluidized bed dryer. The solvent may be removed via steam distillation in case of using high boiling point solvents. As stabilizers, salts of long chain fatty acids may be added. Typical examples are calcium stearate, magnesium stearate, and zinc stearate.

[0050] Optionally, other catalysts such as Phillips catalysts, metallocenes, and post-metallocenes may be employed. In general, cocatalysts such as alumoxanes or alkylaluminum or alkylmagnesium compounds may be employed. Other suitable catalyst systems include Group 4 metal complexes of phenolate ether ligands.

[0051] In one embodiment, one or more of the polyethylene polymers present in the polymer composition of the present disclosure have a relatively low bulk density, as measured according to DIN 53466. For example, in one embodiment, the bulk density of one or more of the polyethylene polymers is generally less than about 0.5 g / cm. 3 For example, less than about 0.4 g / cm 3 Less than about 0.35 g / cm 3 Less than about 0.33 g / cm 3 Less than about 0.28 g / cm 3 Less than about 0.26 g / cm 3 The bulk density is generally less than about 0.1 g / cm 3 Larger, for example about 0.15 g / cm 3 Greater than.

[0052] As mentioned above, each of the polyethylene polymers contained in the composition of the present disclosure has a different molecular weight, specifically a different average molecular weight. The average molecular weight is determined according to the Margolies equation. The molecular weight can be determined by first measuring the viscosity number according to DIN EN ISO test 1628. The dry powder flow is measured using a 25 mm nozzle. The molecular weight is then calculated from the viscosity number using the Margolies equation.

[0053]

[0052] The first polyethylene polymer contained in the polymer composition of the present disclosure generally has a lower molecular weight than the second polyethylene polymer and the third polyethylene polymer. The first polyethylene polymer may, for example, generally have a molecular weight of about 300,000 g / mol to about 1 million g / mol, including all 50 g / mol increments therebetween. For example, the molecular weight may be greater than about 400,000 g / mol, such as greater than about 500,000 g / mol, such as greater than about 550,000 g / mol, such as greater than about 580,000 g / mol. The molecular weight may be less than about 900,000 g / mol, such as less than about 800,000 g / mol, such as less than about 700,000 g / mol, such as less than about 650,000 g / mol.

[0054]

[0053] The amount of the first polyethylene polymer present in the polymer composition may vary depending on various factors, including the desired outcome. In one embodiment, the first polyethylene polymer can be added to the polymer composition in an amount sufficient to improve the processing of the composition, particularly during a gel extrusion process. In one embodiment, the first polyethylene polymer is present in the polymer composition in an amount greater than about 3 wt%, such as greater than about 5 wt%, such as greater than about 7 wt%, such as greater than about 9 wt%, based on the total amount of polyethylene polymer present in the polymer composition, and generally in an amount less than about 25 wt%, such as less than about 22 wt%, such as less than about 18 wt%, such as less than about 15 wt%, such as less than about 12 wt%. For example, the above weight percentages are based on the total amount of the first polyethylene polymer present, the second polyethylene polymer present, and the third polyethylene polymer present.

[0055] The second polyethylene polymer present in the polymer composition generally has a molecular weight of from about 1,000,000 g / mol to about 2,900,000 g / mol, including all 50,000 g / mol increments therebetween. For example, the second polyethylene polymer may have a molecular weight greater than about 1,100,000 g / mol, such as greater than about 1,300,000 g / mol, for example greater than about 1,500,000 g / mol, such as greater than about 1,700,000 g / mol, for example greater than about 1,800,000 g / mol, for example greater than about 1,900,000 g / mol, and generally less than about 2,500,000 g / mol, such as less than about 2,300,000 g / mol, for example less than about 2,200,000 g / mol, for example less than about 2,100,000 g / mol, for example less than about 2,050,000 g / mol.

[0056] The second polyethylene polymer may be present in the polymer composition in an amount greater than the first polyethylene polymer and the third polyethylene polymer. For example, the second polyethylene polymer may be the predominant polymer contained in the polymer composition. However, in other embodiments, the third polyethylene polymer may be present in an amount greater than the second polyethylene polymer. The second polyethylene polymer may be present in the polymer composition in an amount greater than about 25% by weight, such as greater than about 30% by weight, such as greater than about 34% by weight, such as greater than about 38% by weight, such as greater than about 42% by weight, such as greater than about 48% by weight, such as greater than about 53% by weight, such as greater than about 58% by weight, such as greater than about 62% by weight, such as greater than about 68% by weight, such as greater than about 73% by weight. The second polyethylene polymer is generally present in the polymer composition in an amount less than about 85%, such as less than about 70%, for example less than about 65%, such as less than about 60%, for example less than about 55% by weight, for example less than about 50%, based on the total amount of polyethylene polymer present in the composition.

[0057] The third polyethylene polymer having the highest molecular weight may generally have a molecular weight of about 2 million g / mol to about 10 million g / mol, including all 50,000 g / mol increments therebetween. For example, the third polyethylene polymer may have a molecular weight of greater than about 3 million g / mol, such as greater than about 4 million g / mol, such as greater than about 4.5 million g / mol, such as greater than about 4.8 million g / mol. The molecular weight of the third polyethylene polymer is generally less than about 9 million g / mol, such as less than about 8 million g / mol, such as less than about 7 million g / mol, such as less than about 6 million g / mol, such as less than about 5.5 million g / mol.

[0058]

[0057] The third polyethylene polymer may be present in the polymer composition in an amount generally between about 5% and about 60% by weight, based on the total weight of the polyethylene polymers present in the composition. For example, the third polyethylene polymer may be present in the polymer composition in an amount greater than about 12% by weight, such as greater than about 14% by weight, such as greater than about 16% by weight, such as greater than about 18% by weight, such as greater than about 22% by weight, such as greater than about 25% by weight, such as greater than about 28% by weight, such as greater than about 30% by weight, such as greater than about 35% by weight. The third polyethylene polymer is generally present in an amount less than about 50% by weight, such as less than about 48% by weight, such as less than about 45% by weight, such as less than about 42% by weight, such as less than about 38% by weight, such as less than about 35% by weight, such as less than about 33% by weight, such as less than about 30% by weight, based on the total weight of the polyethylene polymers present in the composition.

[0059]

[0058] Prior to forming an article from the polymer composition of the present disclosure, each of the polyethylene polymers may be present in the form of particles. For example, in one embodiment, the polymer composition contains particles formed only from the first polyethylene polymer, particles formed only from the second polyethylene polymer, and particles formed only from the third polyethylene polymer blended together. Alternatively, two or more of the polyethylene polymers may be pre-blended or compounded together. For example, the polymer particles may contain at least two of the polyethylene polymers. Each particle may contain, for example, a combination of the second polyethylene polymer and the third polyethylene polymer, a combination of the first polyethylene polymer and the second polyethylene polymer, a combination of the first polyethylene polymer and the third polyethylene polymer, or a combination of the first polyethylene polymer, the second polyethylene polymer, and the third polyethylene polymer.

[0060]

[0059] In one embodiment, the polyethylene particles may be a free-flowing powder. Such particles may have a median diameter (d50) based on volume of less than 210 micrometers. For example, the median diameter (d50) of the polyethylene particles may be less than about 170 micrometers, such as less than about 150 micrometers. The median diameter (d50) is generally greater than about 20 micrometers, such as greater than about 70 micrometers, such as greater than about 110 micrometers. The particle size of the powder may be measured using a laser diffraction method according to ISO 13320.

[0061] In one embodiment, 90% of the polyethylene particles may have a particle size less than about 250 micrometers. In another embodiment, 90% of the polyethylene particles may have a particle size less than about 200 micrometers, such as less than about 170 micrometers.

[0062]

[0061] Each of the polyethylene polymers may have a viscosity number, measured according to ISO 1628 Part 3, utilizing a concentration in decahydronaphthalene of 0.0002 g / mL, of at least 100 mL / g, such as at least 500 mL / g, such as at least 700 mL / g, such as at least 900 mL / g, such as at least 1,000 mL / g, to less than about 6,000 mL / g, such as less than about 5,000 mL / g, such as less than about 4,000 mL / g, such as less than about 3,000 mL / g, such as less than about 1,800 mL / g.

[0063] The high density polyethylene polymer may have a crystallinity of at least about 40%-85%, such as 45%-80%. In one embodiment, the crystallinity may be greater than about 50%, such as greater than about 55%, such as greater than about 60%, such as greater than about 65%, such as greater than about 70%, and typically less than about 80%.

[0064]

[0063] In forming a gel extrusion article, the polyethylene particles containing the first polyethylene polymer, the second polyethylene polymer, and the third polyethylene polymer can be combined with a plasticizer to form a polymer composition, which is well suited for producing a gel extrusion article such as a porous membrane. Generally, the polyethylene particles are present in the polymer composition in an amount of up to about 50% by weight. For example, the high density polyethylene particles may be present in the polymer composition in an amount of less than about 45% by weight, such as less than about 40% by weight, such as less than about 35% by weight, such as less than about 30% by weight, such as less than about 25% by weight, such as less than about 20% by weight, such as less than about 15% by weight. The polyethylene particles may be present in the composition in an amount of more than about 5% by weight, such as more than about 10% by weight, such as more than about 15% by weight, such as more than about 20% by weight, such as more than about 25% by weight. During gel processing, a plasticizer is combined with the high density polyethylene particles, which can be substantially or completely removed during formation of the polymeric article. For example, in one embodiment, the resulting polymeric article may contain polyethylene polymer in an amount greater than about 70% by weight, such as greater than about 80% by weight, such as greater than about 85% by weight, such as greater than about 90% by weight, such as greater than about 95% by weight.

[0065]

[0064] Generally, any suitable plasticizer can be combined with the various polyethylene polymers. The plasticizer may include, for example, a hydrocarbon oil, an alcohol, an ether, an ester such as a diester, or a mixture thereof. For example, suitable plasticizers include mineral oil, paraffinic oil, decalin, and the like. Other plasticizers include xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, and the like. In one embodiment, the plasticizer may include a halogenated hydrocarbon such as monochlorobenzene. Cycloalkanes and cycloalkenes such as camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, and the like may also be used. Similarly, the plasticizer may include mixtures and combinations of any of the above.

[0066]

[0065] The plasticizer is generally present in the composition used to form the polymeric article in an amount greater than about 50% by weight, such as greater than about 55% by weight, such as greater than about 60% by weight, such as greater than about 65% by weight, such as greater than about 70% by weight, such as greater than about 75% by weight, such as greater than about 80% by weight, such as greater than about 85% by weight, such as greater than about 90% by weight, such as greater than about 95% by weight, such as greater than about 98% by weight. In practice, the plasticizer may be present in an amount up to about 99.5% by weight.

[0067] The polyethylene particles are blended with a plasticizer to form a homogeneous gel-like material. To form a polymeric article according to the present disclosure, the polyethylene particles are combined with a plasticizer and extruded through a die of desired shape. In one embodiment, the composition may be heated in the extruder. For example, the plasticizer may be combined with the particle mixture and fed to the extruder. To form a polymeric article that is largely free of impurities, according to the present disclosure, the plasticizer and particle mixture form a homogenous gel-like material before leaving the extruder.

[0068] In one embodiment, the elongated article is formed in a gel spinning or extrusion process. The polymer article may be in the form of, for example, a fiber or a film, such as a membrane.

[0069] During the process, at least a portion of the plasticizer is removed from the final product. If a relatively volatile plasticizer is used, the plasticizer removal process may occur by evaporation. Alternatively, an extraction liquid may be used to remove the plasticizer. The extraction liquid may include, for example, a hydrocarbon solvent. An example of an extraction liquid is, for example, dichloromethane. Other extraction liquids include acetone, chloroform, alkanes, hexenes, heptenes, alcohols, or mixtures thereof.

[0070] If necessary, the resulting polymeric article can be stretched at an elevated temperature below the melting point of the polymer mixture to increase strength and modulus. Suitable temperatures for stretching are within the range of about ambient temperature to about 155°C. The stretch ratio can generally be greater than about 4, such as greater than about 6, such as greater than about 8, such as greater than about 10, such as greater than about 15, such as greater than about 20, such as greater than about 25, such as greater than about 30. In certain embodiments, the stretch ratio can be greater than about 50, such as greater than about 100, such as greater than about 110, such as greater than about 120, such as greater than about 130, such as greater than about 140, such as greater than about 150. The stretch ratio is generally less than about 1,000, such as less than about 800, such as less than about 600, such as less than about 400. In one embodiment, a lower stretch ratio is used, such as a stretch ratio of about 4 to about 10. The polymeric article may be uniaxially or biaxially stretched.

[0071]

[0071] The polymeric articles made according to the present disclosure have a variety of uses and applications. For example, in one embodiment, the process is used to produce a membrane. The membrane can be used, for example, as a battery separator. Alternatively, the membrane can be used as a microfilter. When producing fibers, the fibers can be used to produce nonwovens, ropes, netting, and the like. In one embodiment, the fibers can be used as a filler material in ballistic apparel.

[0072]

[0072] Referring to FIG. 1, one embodiment of a lithium ion battery 10 made according to the present disclosure is shown. Battery 10 includes an anode 12 and a cathode 14. Anode 12 may be made of, for example, lithium metal, while cathode 14 may be made of sulfur or intercalated lithium metal oxide. In accordance with the present disclosure, battery 10 further includes a porous membrane 16 or separator located between anode 12 and cathode 14. Porous membrane 16 minimizes electrical shorting between the two electrodes while allowing the passage of ions, such as lithium ions. As shown in FIG. 1, in one embodiment, porous membrane 16 is a single layer polymeric membrane and does not include a multilayer structure. In one embodiment, the single layer polymeric membrane may also include a coating. The coating may be an inorganic coating, for example, an inorganic coating made of aluminum oxide or titanium oxide. Alternatively, the single layer polymeric membrane may also include a polymeric coating. The coating may provide increased thermal resistance.

[0073]

[0073] Porous membranes made according to the present disclosure may generally have a thickness of greater than about 5 micrometers, such as greater than about 6 micrometers, such as greater than about 7 micrometers, such as greater than about 8 micrometers, such as greater than about 9 micrometers, such as greater than about 10 micrometers, such as greater than about 11 micrometers. The thickness of the membrane is generally less than about 20 micrometers, such as less than about 16 micrometers, such as less than about 14 micrometers, such as less than about 12 micrometers, such as less than about 10 micrometers, such as less than about 8 micrometers.

[0074]

[0074] Membranes made according to the present disclosure may have excellent physical properties. For example, a membrane having a porosity of about 35% to about 38% may have a puncture strength of greater than about 1,450 mN / micrometer, such as greater than about 1,475 mN / micrometer, such as greater than about 1,500 mN / micrometer, such as greater than about 1,525 mN / micrometer, such as greater than about 1,550 mN / micrometer, such as greater than about 1,575 mN / micrometer, such as greater than about 1,600 mN / micrometer, such as greater than about 1,625 mN / micrometer, such as greater than about 1,650 mN / micrometer, and generally less than about 3,000 mN / micrometer. Pin strength is about 252 gf / g / cm 2 It may be larger, for example about 254 gf / g / cm 2 It may be larger, for example about 256 gf / g / cm 2 It may be larger, for example about 258 gf / g / cm 2 It may be larger, for example about 260 gf / g / cm 2 It may be larger, for example about 262 gf / g / cm 2 Can be much larger, but typically less than about 300 gf / g / cm 2 may be also possible.

[0075] At a membrane porosity of about 45% to about 50%, the membrane may have a puncture strength of greater than about 340 mN / micrometer, such as greater than about 350 mN / micrometer, such as greater than about 360 mN / micrometer, such as greater than about 370 mN / micrometer, such as greater than about 380 mN / micrometer, such as greater than about 390 mN / micrometer, such as greater than about 400 mN / micrometer, and typically less than about 600 mN / micrometer, and generally less than about 72 gf / g / cm 2 Larger, for example about 74 gf / g / cm 2 Larger, for example about 76 gf / g / cm 2 Larger, for example about 78 gf / g / cm2 Larger, for example about 80gf / g / cm 2 Larger, for example about 82 gf / g / cm 2 It may have a higher pin strength, typically about 150 gf / g / cm 2 The pin strength may be less than 1.

[0076]

[0076] Membranes made according to the present disclosure may also have excellent tensile strength properties in either the machine or cross-machine direction. For example, in either direction, the membrane may have a tensile strength greater than about 155 MPa, such as greater than about 160 MPa, such as greater than about 162 MPa, such as greater than about 164 MPa, such as greater than about 166 MPa, such as greater than about 168 MPa, such as greater than about 170 MPa, and generally less than about 250 MPa.

[0077] Polymeric membranes made according to the present disclosure may have a viscosity of greater than about 105 sec / 100 ml, greater than about 150 sec / 100 ml, greater than about 200 sec / 100 ml, greater than about 225 sec / 100 ml, greater than about 250 sec / 100 ml, greater than about 275 sec / 100 ml, greater than about 300 sec / 100 ml, greater than about 325 sec / 100 ml, greater than about 350 sec / 100 ml, greater than about 375 sec / 100 ml, greater than about 400 sec / 100 ml, greater than about 400 sec / 100 ml, greater than about 45 ... It may have a Gurley air permeability of greater than 100 ml, greater than about 425 sec / 100 ml, greater than about 450 sec / 100 ml, greater than about 475 sec / 100 ml, greater than about 500 sec / 100 ml, greater than about 525 sec / 100 ml, greater than about 550 sec / 100 ml, greater than about 575 sec / 100 ml, greater than about 600 sec / 100 ml, and typically has a Gurley air permeability of less than about 1,000 sec / 100 ml.

[0078]

[0078] The polymer compositions and polymer articles made according to the present disclosure may contain various other additives, such as nucleating agents, heat stabilizers, light stabilizers, UV absorbers, acid scavengers, flame retardants, lubricants, colorants, and the like.

[0079] Examples of nucleating agents include phosphate esters. Examples of nucleating agents that can be used include methylene-bis(4,6-di-t-butylphenyl)phosphate sodium salt and aluminum hydroxy-bis[2,4,8,10-tetrakis(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphocin-6-oxidate]. Other examples of nucleating agents include nonitol, 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene], or 3,4-dimethylbenzylidenesorbitol (e.g. sorbitol). Another nucleating agent that can be used in the composition is, for example, N-[3,5-bis-(2,2-dimethyl-propionylamino)-phenyl]-2,2-dimethylpropionamide.

[0080]

[0080] One or more nucleating agents may be present in the polymer composition in an amount greater than about 100 ppm, such as greater than about 300 ppm, such as greater than about 500 ppm, such as greater than about 600 ppm, and generally in an amount less than about 20,000 ppm, such as less than about 10,000 ppm, such as less than about 4000 ppm, such as less than about 2000 ppm, such as less than about 1500 ppm, such as less than about 1000 ppm.

[0081] In one embodiment, a heat stabilizer may be present in the composition, including, but not limited to, a phosphite, an amine-based antioxidant, a phenolic antioxidant, or any combination thereof.

[0082] In one embodiment, an antioxidant may be present in the composition, including, but not limited to, secondary aromatic amines, benzofuranones, sterically hindered phenols, or any combination thereof.

[0083] In one embodiment, a light stabilizer may be present in the composition, including, but not limited to, 2-(2'-hydroxyphenyl)-benzotriazole, 2-hydroxy-4-alkoxybenzophenone, nickel-containing light stabilizer, 3,5-di-tert-butyl-4-hydroxybenzoate, sterically hindered amines (HALS), or any combination thereof.

[0084] In one embodiment, instead of or in addition to a light stabilizer, a UV absorber may be present in the composition, including, but not limited to, a benzotriazole, a benzoate, or a combination thereof, or any combination thereof.

[0085] In one embodiment, a halogenated flame retardant may be present in the composition, including, but not limited to, tetrabromobisphenol A (TBBA), tetrabromophthalic anhydride, decachloropentacyclooctadecadiene (dechlorane), hexabromocyclodecane, chlorinated paraffins, or any combination thereof.

[0086] In one embodiment, non-halogenated flame retardants may be present in the composition. Non-halogenated flame retardants include, but are not limited to, resorcinol diphosphate tetraphenyl ester (RDP), ammonium polyphosphate (APP), phosphinic acid derivatives, triaryl phosphates, trichloropropyl phosphate (TCPP), magnesium hydroxide, aluminum trihydroxide, and antimony trioxide.

[0087] In one embodiment, a lubricant may be present in the composition, including, but not limited to, silicone oil, wax, molybdenum disulfide, or any combination thereof.

[0088] In one embodiment, colorants may be present in the composition. Colorants include, but are not limited to, inorganic and organic based color pigments.

[0089] In one embodiment, an acid scavenger may be present in the polymer composition. The acid scavenger may include, for example, an alkali metal salt or an alkaline earth metal salt. Such salts may include salts of fatty acids, such as stearates. Other acid scavengers include carbonates, oxides, or hydroxides. Specific acid scavengers that may be incorporated into the polymer composition include metal stearates, such as calcium stearate. Still other acid scavengers include zinc oxide, calcium carbonate, magnesium oxide, and mixtures thereof.

[0089]

[0090] These additives may be used alone or in any combination thereof. Generally, each additive may be present in an amount of at least about 0.05 wt%, such as at least about 0.1 wt%, such as at least about 0.25 wt%, such as at least about 0.5 wt%, such as at least about 1 wt%, and generally may be present in an amount of less than about 20 wt%, such as less than about 10 wt%, such as less than about 5 wt%, such as less than about 4 wt%, such as less than about 2 wt%. When present in the polymer composition, the sum of the weight percentages of all components, including all additives utilized, equals 100 wt%.

[0090]

[0091] The present disclosure may be better understood with reference to the following examples, which are provided by way of illustration only and not by way of limitation. The following experiments were carried out to demonstrate some of the benefits and advantages of the present invention. EXAMPLES

[0091] Example 1

[0092] A variety of different polyethylene polymer compositions were compounded, formed into films, and tested for various physical properties. More specifically, three different polyethylene polymers were blended together to form films, and compared to films made from a single polyethylene polymer. The resin compositions were conventionally prepared into films via gel extrusion, biaxial stretching, and solvent extraction.

[0092]

[0093] The following polyethylene polymers were used: A first polyethylene polymer: molecular weight of 600,000 g / mol, D50 particle size of 115 micrometers A second polyethylene polymer: molecular weight of 1,700,000 g / mol, D50 particle size of 135 micrometers A third polyethylene polymer: molecular weight of 5,000,000 g / mol, D50 particle size of 155 micrometers.

[0093]

[0094] Each of the formulations in the table below was combined with a plasticizer and gel extruded to form a film. The plasticizer was almost completely removed from the final product. The following results were obtained:

[0094] [Table 1]

[0095] Example 2

[0095] The process described in Example 1 was repeated to produce additional polymeric membranes (sample numbers 10-13).

[0096] The following polyethylene polymers were used: A first polyethylene polymer: molecular weight of 600,000 g / mol, D50 particle size of 115 micrometers A second polyethylene polymer: molecular weight of 1,700,000 g / mol, D50 particle size of 135 micrometers (sample numbers 10-12); molecular weight of 2,000,000 g / mol, D50 particle size of 115 micrometers (sample number 13) A third polyethylene polymer: molecular weight of 5,000,000 g / mol, D50 particle size of 155 micrometers.

[0097]

[0097] Samples Nos. 11 and 12 also contained a nucleating agent at a concentration of 700 ppm. The nucleating agent was sodium 2,2'-methylenebis-(4,6-di-tert-butylphenyl) phosphate.

[0098] Each of the formulations set forth in the table below was combined with a plasticizer and gel extruded to form a film. The plasticizer was almost completely removed from the final product. The following results were obtained:

[0099] [Table 2]

[0100] [Table 3]

[0101]

[0099] As shown above, membranes made in accordance with the present disclosure have increased pin puncture strength and are easier to process, a combination of properties that is dramatic and unexpected.

[0102]

[0100] These and other modifications and variations to the present invention may be implemented by those skilled in the art without departing from the spirit and scope of the present invention, which is more particularly described in the appended claims. In addition, it will be understood that forms of the various embodiments may be interchanged both in whole or in part. Furthermore, those skilled in the art will appreciate that the foregoing description is merely exemplary and is not intended to further limit the invention as set forth in such appended claims.

Claims

1. a plasticizer; and polymer particles A polymer composition for producing a gel extruded article, comprising: the polymer particles comprise a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer; the first polyethylene polymer has a molecular weight of about 300,000 g / mol to about 1 million g / mol, and the first polyethylene polymer is present in an amount of about 3% to about 25% by weight of the polymer particles; the second polyethylene polymer has a molecular weight of about 1 million g / mol to about 2.9 million g / mol, and the second polyethylene polymer is present in an amount of about 25% to about 85% by weight of the polymer particles; The polymer composition, wherein the third polyethylene polymer has a molecular weight of about 2 million g / mol to about 10 million g / mol, and the third polyethylene polymer is present in an amount of about 5% to about 48% by weight of the polymer particles.

2. 2. The polymer composition of claim 1, wherein the polymer particles comprise polymer particles made only from the first polyethylene polymer, polymer particles made only from the second polyethylene polymer, and polymer particles made only from a third polyethylene polymer.

3. 10. The polymer composition of claim 1, wherein said polymer particles comprise particles comprising at least two of said polyethylene polymers.

4. 4. The polymer composition of claim 1, wherein the first polyethylene polymer has a molecular weight of about 500,000 g / mol to about 700,000 g / mol, the second polyethylene polymer has a molecular weight of about 1.5 million g / mol to about 2.1 million g / mol, and the third polyethylene polymer has a molecular weight of about 4 million g / mol to about 8 million g / mol.

5. 4. The polymer composition of claim 1, wherein the first polyethylene polymer is present in an amount of about 5% to about 15% by weight of the polymer particles, the second polyethylene polymer is present in an amount of about 50% to about 75% by weight of the polymer particles, and the third polyethylene polymer is present in an amount of about 20% to about 40% by weight of the polymer particles.

6. The membrane has a porosity of about 35% to about 38%, a puncture strength of greater than 1450 mN / micrometer, and a tensile strength of about 252 gf / g / cm ２ The polymer composition of any one of claims 1 to 3, having greater pin strength.

7. The membrane has a porosity of about 38% to about 50%, a puncture strength of greater than 340 mN / micrometer, and a puncture strength of about 72 gf / g / cm ２ The polymer composition of any one of claims 1 to 3, having greater pin strength.

8. The polymer composition of any one of claims 1 to 3, having a viscosity number of about 1000 to about 1800.

9. The polymer composition of any one of claims 1 to 3, having a median size by volume of from about 70 micrometers to about 210 micrometers, for example from about 110 micrometers to about 170 micrometers.

10. The polymer composition of any one of claims 1 to 3, wherein the polymer particles are present in the composition in an amount of up to about 50% by weight.

11. The polymer composition of any one of claims 1 to 3, wherein the plasticizer comprises a mineral oil, a paraffinic oil, a hydrocarbon, an alcohol, an ether, an ester, or a mixture thereof.

12. 4. The polymer composition of any one of claims 1 to 3, wherein the plasticizer comprises decalin, paraffin oil, white oil, mineral oil, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetralin, monochlorobenzene, camphene, methane, dipentene, methylcyclopentadiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or a mixture thereof.

13. The polymer composition according to any one of claims 1 to 3, which is free of polypropylene.

14. 1. A process for producing a polymeric article, comprising: forming the polymer composition of any one of claims 1 to 3 into a gel-like composition; extruding the gel-like composition through a die to form a polymeric article. wherein the polymeric article comprises a film.

15. 15. The process of claim 14, further comprising the step of removing at least a portion of the plasticizer from the polymeric article.

16. 16. The process of claim 15, wherein an extraction solvent is added to the polymer composition during the process to facilitate removal of the plasticizer from the polymer article.

17. 17. The process of claim 16, wherein the extraction solvent comprises dichloromethane, acetone, chloroform, an alkane, hexene, heptene, an alcohol, or a mixture thereof.

18. 1. A porous membrane comprising a polymer blend comprising a first polyethylene polymer, a second polyethylene polymer, and a third polyethylene polymer, the first polyethylene polymer has a molecular weight of about 400,000 g / mol to about 1 million g / mol, and the first polyethylene polymer is present in an amount of about 3% to about 18% by weight; the second polyethylene polymer has a molecular weight of about 1.1 million g / mol to about 2.9 million g / mol, and the second polyethylene polymer is present in an amount of about 34% to about 85% by weight; the third polyethylene polymer has a molecular weight of about 3 million g / mol to about 10 million g / mol, and the third polyethylene polymer is present in an amount of about 12% to about 48% by weight; The porous membrane has a tensile strength in the machine direction of greater than about 155 MPa.

19. A porosity of about 35% to about 38%, a puncture strength of greater than 1450 mN / micrometer, and a viscosity of about 252 gf / g / cm ２ 20. The porous membrane of claim 18 having greater pin strength.

20. A porosity of about 45% to about 50%, a puncture strength of greater than 340 mN / micrometer, and a viscosity of about 72 gf / g / cm ２ 20. The porous membrane of claim 18 having greater pin strength.

21. 20. The porous membrane of claim 18, having a thickness of about 5 micrometers to about 20 micrometers, for example about 6 micrometers to about 15 micrometers, and containing a nucleating agent.

22. 20. The porous membrane of claim 18 having a Gurley air permeability greater than about 105 seconds / 100 ml.

23. 20. The porous membrane of claim 18, which is biaxially oriented.

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